Publishing type：Research paper (international conference proceedings)  

Power electronics is an electric circuit technology for electric power conversion and is taught in many universities due to its importance in modern society. This technology is traditionally taught in lecture courses, which are based on the operation analysis of the power conversion circuits based on the circuit theory. However, unlike other fields regarding the electric circuit, the quality of the power conversion circuits is fundamentally dependent on the non-ideal features of the circuit elements as well as the size including the cooling system. Therefore, the practical design of the power conversion circuit profoundly relies not only on understanding the basic circuit operation but also on the knowledge of the actual circuit elements, including their non-ideal features. The traditional class based on theoretical circuit operation analysis was difficult to cover the latter knowledge, which may have resulted in insufficient educational achievement in power electronics technology. This paper proposes a teaching approach that embeds mini-experiments in the lecture to overcome this difficulty. These mini-experiments are carefully designed to be seamlessly combined with the lecture and shown to the students during the lecture by utilizing IT-based measurement instruments. According to the students' survey, the students felt the improvement of the lecture quality by the embedded experiment, although the difficulty in the time scheduling for the embedded experiment is a remaining problem to be solved in future studies.

DOI： 10.1109/ICELIE58531.2023.10313105

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/icelie55228.2022.9969423

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/icelie55228.2022.9969416

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/ecce50734.2022.9948072

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/ecce50734.2022.9947525

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Switched reluctance motors (SRMs) have recently attracted researchers' attention owing to their robust mechanical construction, high thermal tolerance, and strong cost-effectiveness, which are promising for vehicle propulsion. However, they tend to generate large ripples in the torque and input currents to the inverter; this deteriorates the driving comfort, and damages the battery lifetime. Preceding articles have investigated using the phase currents of SRMs to eliminate these ripples. However, these articles had difficulties in sufficiently eliminating these ripples in operations under magnetic saturation. This article further evolves one of these preceding articles, and proposes a derivation method for the phase-current waveform for improving the elimination of the torque and input-current ripples in operation under magnetic saturation. The proposed method analytically determines the phase-current waveform based on a nonlinear behavior model of the SRM while considering the magnetic saturation. A finite-element-method-based simulation and experiment are performed to evaluate the proposed method. These results reveal the successful reduction of the torque and input-current ripples under the magnetic saturation relative to a preceding study, supporting the appropriateness of the proposed method.

DOI： 10.1109/TIA.2022.3172898

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Publishing type：Research paper (international conference proceedings)  

The solenoid coil is a typical heating coil structure for induction heating of cylindrical heating objects. Conventionally, a bare solenoid coil without any soft-magnetic core has been commonly utilized. However, this conventional structure suffers from worse heating efficiency caused by the large coil copper loss and the low magnetic field induction at the heating object. This paper addresses these difficulties by proposing a novel heating coil structure. In addition to the solenoid coil, the proposed heating coils structure further incorporates the soft-magnetic cores that cover the outer coil periphery and the coil opening edges. These additional cores can reduce the local intense magnetic field around the coil, thus mitigating the eddy current induction inside the wire to reduce the copper loss, and also can increase the magnetic field inside the heating object, thus increasing the heat generation. The simulation was carried out to test the effectiveness of the proposed heating coil structure. The results inferred the reduction of the coil copper loss by 25% and the increase in the heat generation in the heating object by 53%, both of which suggest the promising features of the proposed heating coil structure for heating the cylindrical magnetic material. The heating operation of the proposed heating coil structure was tested by the experiment, although the current prototype was found to have larger power loss than expected from the simulation. The reason may lie in unintended eddy current generation of the metal case of the heating coil, which will be addressed in future work.

DOI： 10.1109/ISIE51582.2022.9831459

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Publishing type：Research paper (international conference proceedings)  

The data centers of the telecommunication infrastructure are recently consuming more electric power than before. This increasing electrical burden is requiring a small but high-power isolated power converter with a high step-down ratio. Conventionally, the LLC converter is regarded to be a promising candidate, although this converter needs vacant space for galvanic isolation due to extremely high voltage caused by the resonance in the primary side, i.e. high voltage side, of the isolation transformer, which hinders the compact implementation inside the server computers in high power design. The purpose of this paper is to propose a novel LLC converter topology to reduce this extremely high voltage by locating the LC resonator on the secondary side. The performance analysis revealed that the proposed converter exhibits a similar frequency-voltage characteristic enabling the boost and buck operation modes as well as the small rectifier conduction loss similar to the full-wave rectifier with a center-tapped transformer. The simulation confirmed the operating principles and reduction of the resonance voltage amplitude of the proposed LLC converter in comparison with the conventional LLC converter. Furthermore, the experiment also supported the operating principles, which suggests the usefulness of the proposed converter for a high voltage dc power supply system.

DOI： 10.23919/IPEC-Himeji2022-ECCE53331.2022.9806826

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Publishing type：Research paper (international conference proceedings)  

The LLC converter is a very effective topology for miniaturization of power supplies. However, its application is currently limited. That is because of the problem of degraded system stability when the load condition changes. This paper proposed a practical control circuit that controls the power factor cos\theta by adjusting the phase difference \theta between the inverter voltage and primary current of the LLC converter to control the output voltage to address this problem. As a result, experimental result confirm that the proposed control method has robust control characteristics against wide load impedance and shows low output impedance regardless of the output voltage.

DOI： 10.1109/SPEC55080.2022.10058371

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Publishing type：Research paper (international conference proceedings)  

Isolated DC-DC converter in data centers are now required to have a high step-down ratio and be suitable for high-power applications. As such DC-DC converters, LLC resonant converters have been attracting attention. However, the LLC resonant converter generates a large resonance voltage at the resonator, so the resonance inductor and resonance capacitor must be large in size. Recently, a previous study proposed a secondary-side resonance LLC converter to reduce the resonant voltages of the passive components. Nevertheless, this LLC converter requires a resonant capacitor in parallel with the rectifier to achieve boost mode operation, which complicates the circuit operation and design. Therefore, we have considered the use of the magnetizing inductance of the coupled transformer of the current doubler rectifier as a method to realize the boost mode operation. In this paper, we propose a new method of boost mode operation for LLC resonant converter using secondary-side resonance and the current doubler rectifier.

DOI： 10.1109/SPEC55080.2022.10058227

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Publishing type：Research paper (international conference proceedings)  

Reluctance machines such as the switched reluctance machines (SRMs) and the synchronous reluctance machines (SynRMs) are recently investigated for propulsion motors of the electrified vehicles owing to their robust mechanical construction, high thermal tolerance, and cost-competitiveness. However, practical application of the reluctance machines to the vehicle propulsion has been hindered by the fact that the conventional SRMs and SynRMs are difficult to meet all the three preferable features for the vehicular application: 1. High power density, 2. Low torque and input-current ripples, 3. Being drivable by the normal three-phase inverter. This paper addresses this issue by proposing a novel reluctance machine. The prominent features of the proposed reluctance machine are the sinusoidal reluctance profile and the delta-connected phase windings, both of which differ from conventional reluctance machines. Along with the theoretical discussion of the basic operating principles of the proposed reluctance machines, this paper presents a simple performance estimation of the proposed machine, the SRM, and the SynRM, which supported that the proposed machine can meet the three preferable features. Furthermore, the experiment successfully supported the operating principles of the proposed machine, suggesting the feasibility of the proposed machine for vehicle applications.

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Publishing type：Research paper (scientific journal)  

Multiple-receiver resonant inductive coupling wireless power transfer (RIC-WPT) technique is emerging as a promising charging method for multiple household appliances, mobile devices, and wearable devices. However, this technique often suffers from output power fluctuation owing to the cross-interference among receivers as well as the manufacturing and aging tolerance of the resonant frequency (i.e., resonant frequency tolerance). This article proposes an autonomous RIC-WPT system concept to solve this difficulty. The proposed concept addresses the cross-interference and resonant frequency tolerance by incorporating the following two functions. First, the amplitude of the transmitter current is controlled to have a constant amplitude. Second, the phase of each receiver current is controlled to be orthogonal to that of the transmitter current by using an active reactance compensator installed in each receiver. The experiment of a two-receiver RIC-WPT system successfully verified that the two functions of the proposed system concept can stabilize the output voltage against the cross-interference and resonant frequency tolerance.

DOI： 10.1109/TIA.2021.3081071

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Litz wire has been widely utilized in power transformers and inductors as a wire with low copper loss at high-frequency operation. The Litz wire is commonly made of many thin isolated strands twisted in multiple levels. Due to its complicated structure, the copper loss prediction of the Litz wire has been difficult, hindering the design optimization of the Litz wire structure. To overcome this difficulty, preceding studies have investigated the analytical copper loss models of the constituting elements of the Litz wire, i.e., the strands and the bundles of strands. The purpose of this article is to propose an analytical copper loss model of the Litz wire by utilizing these preceding knowledge. The proposed model is formulated only with parameters that can be measured by basic testing instruments. Besides, the proposed model considers the bundle structure of the Litz wire, which affects the local ac current distribution, and the twisting pitch, which causes the inclination of the Litz wire strands. The proposed model was tested by comparing the analytical prediction and experimental measurements of the ac resistance of commercially available Litz wires. As a result, the predicted ac resistance showed good agreement with the measured ac resistance, suggesting the appropriateness of the proposed model.

DOI： 10.1109/TIA.2021.3063993

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Industrial electronics (IE) covers a wide range of technologies and applications, being a key enabling technology for numerous industrial, domestic, and biomedical uses, among others. In this context, IE education has become a relevant and challenging topic for society and industry. This article covers its evolution and state-of-the-art methodologies and provides an overall view of its status around the world. Finally, future trends and challenges in IE education are discussed.

DOI： 10.1109/MIE.2020.3002488

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Reluctance motors, represented by the switched reluctance motor (SRM) and the synchronous reluctance motor (SynRM), are attractive for vehicle propulsion owing to their high thermal tolerance and simple mechanical construction. However, the SRM exhibits large torque and large input current ripples, deteriorating driving comfort and battery lifespan. Furthermore, a driving system of the SRM requires the special inverter topology with additional switching or rectifying devices, leading to the cost-up. Meanwhile, the SynRM does not have these drawbacks, although this motor tends to be difficult to cover the wide range of the torque and the rotation speed required for vehicle propulsion because of large phase flux induction. To solve the obstacles of these conventional reluctance motors, this paper proposes a novel reluctance motor. The proposed reluctance motor is based on magnetization by the sinusoidal phase flux waveform, whereby the torque and input current ripples are eliminated using a common three-leg inverter without inducing large phase magnetic flux. This paper presents the operating principles of the proposed reluctance motor as well as analysis and simulation results in comparison with the SRM and the SynRM. As a result, the proposed reluctance motor is elucidated to reduce the torque and input current ripples with the three-leg inverter. Furthermore, the proposed reluctance motor can improve the torque range and rotating speed range compared to the SynRM because of the sinusoidal flux waveform with reduced amplitude. These results imply feasibility of the proposed motor for vehicle propulsion.

DOI： 10.1109/PEMC48073.2021.9432579

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/IECON48115.2021.9589541

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Other Link： https://dblp.uni-trier.de/db/conf/iecon/iecon2021.html#HatakenakaUIHT21

Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/IECON48115.2021.9589676

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Other Link： https://dblp.uni-trier.de/db/conf/iecon/iecon2021.html#HirakiIU21

Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/ISIE45552.2021.9576373

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Other Link： https://dblp.uni-trier.de/db/conf/isie/isie2021.html#AbeIHUH21

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The resonant inductive coupling wireless power transfer technique (RIC-WPT) is emerging as a promising wireless power transfer method for small mobile devices with comparatively high-power transfer capability and good efficiency. However, the performance of the RIC-WPT system is severely deteriorated by the resonant frequency detuning of the transmitter, repeater, and receiver resonators, which can be naturally caused by the manufacturing tolerance and the aging effect of these resonators. Particularly, the detuning of the repeater resonator tends to severely affect the performance due to its high-quality factor, which should be solved for practical application of RIC-WPT technology. This paper addresses this difficulty by proposing an autonomous resonant frequency tuning controller circuit for the repeater resonator. The controller tunes the resonant frequency of the repeater resonator to the operating frequency of the inverter, driving the transmitter, without an external power supply and wireless communication with the inverter controller, which restricts the freedom of the installation location and therefore preferably be avoided in the wireless power transfer system. The operating principles of the proposed controller were confirmed by the circuit simulator, supporting the feasibility of the proposed controller.

DOI： 10.1109/ISIE45552.2021.9576268

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The LLC converter is attractive for its small volume and comparatively high efficiency. However, the application of this converter is limited to the power supply to a static load with almost constant output voltage and current because the LLC design covering a wide range in the output voltage and the load variation can deteriorate the output voltage stability and efficiency. This paper addresses this issue by proposing a novel control method. Unlike the conventional control, which adjusts the operating frequency to stabilize the output voltage, the proposed control adjusts the power factor of the transformer primary-side to achieve the same excellent dynamic performance as the buck chopper. Simulation supported the effectiveness of the proposed control at a wide load variation range.

DOI： 10.1109/ECCE47101.2021.9595420

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Resonant inductive coupling wireless power transfer (RIC-WPT) systems with multiple transmitters and multiple receivers often suffer from cross-interference among transmitters as well as among receivers. The cross-interference causes the fluctuation of the output power of the receiver and hard switching of the inverter on the transmitter. To avoid the cross-interference, controlling the amplitude and the phase of each transmitter current is an effective method. Therefore, this paper proposes a multiple-transmitter that can compensate for the cross-interference influence by implementing two controls. First, adopting the phase-shift control on the full-bridge inverter, the current amplitude is controlled to be constant. Second, applying the reactance control, each phase of the current is controlled to be in phase. In addition to the above operations, especially under a high-frequency operation, zero-voltage switching (ZVS) at a fixed operating frequency is essential for improving the power efficiency while not exceeding an allowable narrow bandwidth. Thus, the reactance control also works to ensure ZVS in all load conditions without adjusting the frequency. The RIC-WPT prototype with two transmitters and a single receiver is built to verify that the proposed multiple-transmitter can compensate for the cross-interference influence while achieving ZVS in different load conditions at a fixed operating frequency.

DOI： 10.1109/ECCE47101.2021.9595950

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Publishing type：Research paper (international conference proceedings)  

The Litz wire is utilized to wireless power transfer system and induction heating according to has small AC resistance in high frequency. Prediction of AC resistance of the Litz wire is important for design optimization of the Litz wire, hence the recent study has proposed analytical AC resistance prediction model of the Litz wire. However, verification in practical coils using the Litz wire is still insufficient. The purpose of this paper is to verify the prediction accuracy of AC resistance using a full analytical model in a practical coil. For practical coil, planer spiral coils are selected, and AC resistance of the planer spiral coil is calculated by combining with the loss model and the FEM analysis. As a result, the Litz wire loss model is found to well predict the measured AC resistance of the Litz wire planer spiral coil, supporting the appropriateness of the Litz wire loss model.

DOI： 10.23919/ICEMS50442.2020.9290802

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST ENGINEERING TECHNOLOGY-IET  

In recent decades, switched reluctance motors (SRMs) have been attracting increasing attention as a promising type of traction motors for electric vehicle propulsion, owing to their robust construction, elimination of permanent magnets. However, their phase inductance profile contains significant high-order harmonics, which generates input-current and torque ripples under SRM drive with the conventional square phase-current waveform. This study solves this problem by proposing a novel phase-current waveform in replacement of this square waveform. The proposed waveform is a predetermined waveform that can be stored as a look-up table in the inverter controller and can be magnified or attenuated to adjust the output torque, similarly as the conventional square waveform. Certainly, SRMs generally exhibit magnetic non-linearity due to magnetic saturation, which complicates the analysis. Therefore, the proposed waveform is analytically derived under the assumption that the magnetisation of the motor remains below the saturation level because vehicle propulsion tends to require a torque output far smaller than the maximum rating of the motor in normal vehicle travel. The proposed phase-current waveform is experimentally tested in comparison with the conventional square phase-current waveform. Consequently, the proposed waveform revealed smaller ripples in both the input-current and torque, supporting the effectiveness of the proposed phase-current waveform.

DOI： 10.1049/iet-pel.2019.1207

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Switched reluctance motor (SRM) is recently emerging as a cost-effective but mechanically and thermally robust motor for vehicle propulsion. However, the conventional driving method of the SRM causes a large input current and torque ripples, both of which are scarcely acceptable for vehicle application. Recently, a promising driving method has been proposed that tunes the phase current to eliminate the input current and torque ripples simultaneously, although this method suffers from large copper loss when applied to the normal SRMs. To solve this problem, this article proposes simultaneous tuning of the rotor shape in combination with the recently proposed driving method, which includes only tuning of the phase current. Tuning of the rotor shape is targeted at minimizing the copper loss. Meanwhile, the stator structure is the same as the normal SRM design. The proposed approach was revealed to reduce the effective value of the phase current by 18% in simulation and by 23% in experiment compared with the recently proposed driving method, without increasing the input current and torque ripples. This result suggests the effectiveness of tuning both the rotor shape and the phase current for applying SRMs to vehicle propulsion.

DOI： 10.1109/TIA.2020.3015446

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Series-series (SS) and series-parallel (SP) topologies are widely used in resonant inductive coupling wireless power transfer systems for various applications. However, the selection of an appropriate topology to achieve higher output power or higher efficiency is typically difficult because design optimization of the circuit parameters (e.g., characteristic impedance, load resistance, and mutual inductance) for each topology is generally separately discussed using different equivalent circuits with multiple resonance modes. Therefore, the purpose of this study involves proposing a simple strategy to select an appropriate topology. The proposed strategy is based on quasi-duality between the SS and SP topologies that are elucidated from the novel equivalent circuits derived using Lagrangian dynamics. Based on the quasi-duality, the output power and efficiency of the SP topology are calculated via the equivalent circuit of SS topology. Thus, the quasi-duality offers a simple comparison between the SS and SP topologies. The proposed strategy selects an appropriate topology by comparing only the equivalent ac load resistance, which is the ac resistance including the rectifying circuit and the load resistance, the characteristic impedance, and the ac load resistance that achieves the maximum efficiency ormaximum output power of the SS topology. Experiments verify the appropriateness and effectiveness of the proposed strategy.

DOI： 10.1109/TPEL.2019.2956732

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

It is quite often to utilize the transformer leakage inductance in the resonant tank of the LLC resonant converter to allow for a drastic reduction in the converter cost, weight, size, and volume. The effects of the secondary leakage inductance on the operation of the LLC resonant converter are not well discussed in the relevant literature, and it is the purpose of this paper to give an insight into these effects. The contribution of this paper lies in the following: first, highlighting that it is not always an accurate assumption to consider that the values of the primary and secondary leakage inductance are identical, specifically in asymmetric magnetic core structures. Second, it has been disclosed that the well-known coupling factor (k(12)) cannot properly express the unequalized leakage inductance distribution in the proposed asymmetric transformer. Therefore, the authors bring the primary coupling factor (k(1)) and secondary coupling factor (k(2)) into practice to appropriately express the unequalized leakage distribution on the primary and secondary windings, which can be controlled by the allocation of the relevant winding with respect to the air gap, utilizing the noise absorber, and changing the distance between the winding. Several transformer prototypes had been built and experimentally tested to validate these hypotheses. Third, it has been observed that the transformer voltage gain and efficiency can be improved when the transformer leakage inductance is concentrated on the secondary side to avoid the voltage drop inflicted by the relatively large value of the magnetizing current (i(m)), especially at the light load condition. Fourth, it has been reported that in a transformer structure with a concentrated value of leakage on the secondary side would decrease the resonant tank input impedance, vertically widen the voltage-gain curve of the converter, and eventually increase the frequency control bandwidth with respect to the load variation. Transformer prototypes had been constructed and tested in a 390 V/12 V-220 W LLC resonant converter to evaluate the proposed analysis.

DOI： 10.1109/TPEL.2019.2911093

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The Litz wire is widely utilized in recent high frequency switching regulators as a magnetic wire with small AC resistance. The AC resistance of the Litz wire is dependent on the twisting structure of the strands as well as the resultant cross-section geometry of the Litz wire. Therefore, optimization of the Litz wire is becoming important, although the numerical prediction of the AC resistance is difficult due to the complicated structure of the Litz wire. Certainly, a recent study has proposed an analytical AC resistance prediction method. However, this method cannot be applied to Litz wires with the rectangular cross-section, which is recently developed to improve the packing factor of the winding. This paper aims at extending this previous method to cover these Litz wires by partly utilizing a simple static magnetic field FEM analysis. The experiment revealed successful AC resistance prediction of the Litz wire with the rectangular cross-section.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Recently, a resonant inductive coupling wireless power transfer (RIC-WPT) system with multiple transmitters is emerging as a promising power supply method for household appliances, mobile devices, and wearable devices dispersedly placed in a wide area. However, the multiple-transmitter often suffers from an unstable operation of an inverter, feeding AC current to the transmitter coil, due to the cross-interference (i.e., cross-coupling) among the transmitters. When the cross-interference occurs, the inverter may not achieve high power factor and soft switching, which damages the power density and reliability of the multiple-transmitter. Therefore, this paper proposes a multiple-transmitter, including its controller, that can compensate for the effect of the cross-interference. In the proposed multiple-transmitter, each transmitter has a simple switching circuit that can automatically cancel the induced voltage due to the cross-interference with only simple control. Furthermore, the proposed multiple-transmitter also achieves a load-independent transmitter current by the control of the input voltage of the inverter, which results in a stable magnetic field regardless of load variation. Experiments verify the effectiveness and appropriateness of the proposed multiple-transmitter.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The windings of high-frequency high-current transformers are required to reduce the proximity effect loss. Therefore, the Litz wire in parallel connection of interleaved winding layers is usually used as the winding of transformers. However, this can cause unbalanced AC current distribution, hindering effective reduction of the copper loss. This paper solves this problem by optimizing the distance between the winding layers based on the analytical principle called the extremum co-energy principle. The transformers used in the experiment to verify this method consists of three parallel-connected primary winding and two parallel-connected secondary winding, PQ core, thin polypropylene sheets for adjusting the distance between the winding layers. As a result, the copper loss can be recused by homogenizing the AC current distribution, and the effectiveness of this method has been clarified by experiments.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Next-generation switching devices as GaN-FETs are recently emerging as promising switching devices capable of extremely high-speed switching. High-speed switching enables the high-frequency operation of the power converters, which can reduce the size of the passive components. However, highspeed switching can induce the resonance between the parasitic capacitance of the switching device and the parasitic inductance of the circuit board wiring, which appears as the gate voltage fluctuation at the switching. Particularly, GaN-FETs tend to have comparatively low gate threshold voltage and therefore are susceptible to the false turn-on, which is caused by the gate voltage fluctuation in the switching device just after the turn-off transition. For preventing this phenomenon, this paper analytically investigates the design requirement of these parasitic parameters to reduce the gate voltage fluctuation after the turn-off transition. As a result, the optimal ratio of the gate-drain capacitance and the common source inductance is elucidated to be the key to minimize the gate voltage fluctuation. The simulation and the experiment supported that the optimal design of this ratio can reduce the gate voltage fluctuation, supporting the usefulness of this novel insight for preventing the false turn-on.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Secondary-side center-tapped transformer is a common transformer design of the high step-down forward converters owing to its effective reduction of the copper loss. Particularly, the extremely high step-down converters tend to have one-turn secondary coils to increase the winding turn ratio. However, due to the proximity effect in the terminal and the wire connecting the secondary coils and the rectifier, this design tends to suffer from significant deterioration of the copper loss reduction effect. To mitigate this problem, this paper proposes a novel transformer's secondary-side structure that integrates the one-turn secondary coils and the rectifier. The proposed transformer structure can mitigate the proximity effect in the secondary coils and the rectifier, thus suppressing the local concentration of the current distribution. Experiments revealed effective reduction of the copper loss, supporting the effectiveness of the proposed structure.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Power conversion technology is characterized by the comparatively small variation of circuit topologies. Because product competitiveness mainly lies in the performance quality as efficiency and low noise emission, the professional skills of this technology commonly require the ability to improve the quality under the restriction of the space, the material resource, and the cost. The conventional teaching method of the power conversion technology is mainly based on the lecture classes and the hands-on classes, which teach the fixed knowledge of the circuit operation. Therefore, this conventional method tends to be insufficient to cover the various practical strategies to improve the quality. To overcome this difficulty, this paper proposes application of the competition-based learning (CBL), in which teams of the students design their power converters and compete on the efficiency. For many professional engineers, competition among companies is the basic motivation to think of strategies to improve product competitiveness. Therefore, the CBL may be effective for teaching design strategies. For promotion of sharing the know-how, the proposed teaching method introduces the events, in which each team share its design strategies with other teams and improve its design based on the know-hows of other teams These events emulate the economic activity, in which a company investigates its competitors' products to extract the know-how. Along with the basic methodology of the proposed teaching method, this paper also reports the experience of a teaching course.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST ENGINEERING TECHNOLOGY-IET  

Resonant inductive coupling wireless power transfer is widely known to be a possible convenient power supply method for the small mobile apparatus. However, the limited receiving-coil size tends to lower the efficiency and limit the output power owing to the small mutual inductance and comparatively large stray alternating current (AC) resistance of the receiving-coil. This study mitigates this issue by proposing a novel receiving-coil structure. This proposed structure comprises a coil and a drum core with a thin axis. The coil is wound on the axis to form a single winding layer. The proposed structure can reduce stray AC resistance by suppressing the proximity effect and reducing the wire length without deteriorating the mutual inductance significantly. Therefore, better efficiency and larger output power can be achieved. Simulations and experiments were performed to verify the proposed structure. Consequently, both simulations and experiments supported the reduction in AC resistance compared to the conventional structure. Furthermore, the experiment revealed improvements by the proposed structure in both efficiency and output power. These results support the effectiveness of the proposed structure for wireless power transfer to small mobile apparatus.

DOI： 10.1049/iet-pel.2018.5358

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Publishing type：Research paper (international conference proceedings)  

© 2019 The Korean Institute of Power Electronics (KIPE). The high-frequency transformers used for isolated DC-DC converters tend to have large volume compared with the other components. Therefore, increasing the power density of the transformer is indispensable for increasing the power density of the DC-DC converter. Reducing the dead space of the transformer is one of the effective solutions. It is well-known that the thinly extended core structure reduces the dead space around the transformer formed by the windings protruding to the outside of the core. However, it has not been clarified how much the thinly extended core structure affects the reducing power loss of the transformer. In this paper, the effect of introducing the thinly extended core structure into the transformer is quantified by the optimization of the convertible design parameters of the transformer with systematic round-robin calculation. The result revealed the volume reduction effect by the thinly extended core was greater than the simply dead space reduction effect.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Gallium-nitride-field-effect transistors (GaN-FETs) are promising switching devices with fast switching capability. However, they commonly have low gate threshold voltage, suffering from susceptibility to the false triggering. Particularly, the oscillatory false triggering, i.e., a self-sustaining repetitive false triggering, can occur after a fast switching, which is a severe obstacle for industrial applications. The purpose of this paper is to elucidate the design instruction for preventing this phenomenon. The oscillatory false triggering is known to be caused by the parasitic oscillator circuit formed of a GaN-FET, its parasitic capacitance and the parasitic inductance of the wiring. This paper analyzed the nonoscillatory condition of this oscillator. The result revealed an appropriate ratio between the gate-drain capacitance and the common-source inductance is a key to prevent the oscillatory false triggering. Experiment successfully verified this analysis result, supporting the effectiveness of the appropriate design of this ratio for preventing the oscillatory false triggering.

DOI： 10.1109/TIA.2018.2868272

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Secondary-side center-tapped transformers are widely utilized for high step-down forward DC-DC converters. For reducing the copper loss, optimization of the winding layer allocation can be a promising approach. However, the optimal allocation pattern has been difficult to be elucidated, particularly if the winding is formed of parallel-connected winding layers or carries the AC and DC current as in a center-tapped winding. This difficulty is addressed in this paper by proposing a copper loss analysis method applicable to parallel-connected winding layers and a center-tapped winding. The proposed analysis method utilizes the Dowell method in combination with the extremum co-energy principle, which has been recently proposed to analyze the current distribution in parallel-connected winding layers. As an example, this paper analyzes the center-tapped transformer each secondary winding of which is made of two parallel-connected winding layers. The optimal winding layer allocation pattern was elucidated by comparing the copper loss among six possible winding layer allocation patterns. Appropriateness of the analysis was verified by simulation, suggesting the effectiveness of the proposed method and the importance of optimizing winding layer allocation in the forward transformer design.

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The ability to charge to multiple receivers simultaneously with a single transmitter is one of the advantages of resonant inductive coupling wireless power transfer (RICWPT) technologies. However, in multiple-receiver RIC-WPT systems, each receiver often suffers from the magnetic coupling among receivers, i.e., cross-coupling. The cross-coupling not only complicates the control of the receivers but also significantly decreases the output power of each receiver. Hence, the purpose of this paper is to propose a compensation method of the influence due to the cross-coupling. To achieve this purpose, we first analyze the requirement to compensate for the influence of the cross-coupling. As a result, we reveal that it is necessary to control the phase of the current in all the receiver to be orthogonal to the phase of the transmitter current. Then, we propose the method to adjust the current phase of each receiver automatically to the desired phase by using only the phase information of the transmitter current, which results in the full compensation of the influence due to the cross-coupling. Furthermore, the proposed method also compensates for the influence of a detuning of the resonant frequency of each receiver due to the natural tolerance. Experiments of a two-receiver RIC-WPT system successfully verify the effectiveness of the proposed method.

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The resonant inductive coupling wireless power transfer (RTC-WPT) is a promising technique of the wireless power transfer with comparatively large power and high efficiency. However, the performance of RTC-WPT system is generally highly dependent on the fine adjustment of the resonant frequency between the transmitter, receiver, and repeater resonators, although the natural tolerance of the capacitor and inductance of the coil may easily lead to the significant detuning of the resonant frequency. Particularly, the repeater resonator is the key item that can improve the power transfer to a distantly located receiver resonator. However, the repeater resonator tends to have a high quality-factor; and therefore, its performance can be easily deteriorated by the detuning of the resonant frequency. The purpose of this paper is to propose a simple automatic resonant frequency tuning system for the repeater resonator as a remedy for the performance deterioration due to the resonant frequency detuning. The operation of the automatic resonant frequency tuning system was experimentally tested using the prototype wireless power transfer system. The result exhibited robust power transfer capability regardless of the natural tolerance of the resonant frequency.

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To estimate the core loss in SRMs, core loss estimation by equivalent circuit is preferable especially in the EV development because of its simple calculation. However, previously proposed models may limit applicable operating condition. These models refer instantaneous value, whereas hysteresis loop is a key factor to estimate core loss and the hysteresis loop directly associates with the history of magnetic flux. This paper focuses on the relation between the width of hysteresis loop and the peak to peak value of magnetic flux because the relation directly expresses the core loss. Therefore, the purpose of this paper is to propose a novel core loss model for equivalent circuit which estimates core loss in SRMs. This paper refers the peak to peak value of magnetic flux linkage and electrical angle. Along with the theoretical formulation of the model, this paper presents the model construction method. As a result, the proposed model successfully estimated core loss.

DOI： 10.1109/ICIT.2019.8754931

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Switched reluctance motors (SRMs) is beneficial in excellent cost-effectiveness and high thermal tolerance owing to their simple mechanical construction free from permanent magnets. Nevertheless, application of SRMs to vehicular propulsion is often hindered by their comparatively large input current ripple and torque ripple. For mitigating the problem, the previous study has proposed a phase current waveform that eliminates both of these ripples under the magnetization below the magnetic saturation. However, this previous technique still suffers from significant torque and input current ripples at large output torque, which tends to cause the magnetic saturation. This paper proposes an improved phase current waveform that eliminates these ripples even at large output torque. This waveform was derived analytically based on the nonlinear magnetic model of the SRM. The proposed phase current waveform was successfully verified by the experiment, suggesting the usefulness of the proposed technique for applying SRMs to vehicular propulsion.

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Placing a repeater, which relays the magnetic field from the transmitter to the receiver, is promising as a method to increase the spatial freedom of resonant inductive coupling wireless power transfer systems (RTC-WPT) working at 6.78MHz. However, the capability of the repeater is often affected by a frequency splitting phenomenon. When this phenomenon occurs, the resonance in the repeater becomes sufficiently small at a fixed operating frequency and make it difficult to improve the spatial freedom. To solve this problem, we apply an impedance matching method using simple switching circuits to the 6.78 RTC-WPT system with the repeater. Then we carry out experiments to verify the effectiveness of the impedance matching method. The experimental results show that the repeater improves the spatial freedom of the 6.78 MHz RTC-WPT regardless of the frequency splitting phenomenon.

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The Litz wire has been widely utilized as a wire with a low copper loss under high-frequency operation. However, design optimization of the Litz wire is difficult because this wire generally has a complicated structure of thin strands twisted in multiple levels, which hinders both of the analytical and numerical prediction of the copper loss. To overcome this issue, recent studies have proposed the analytical models of the copper loss in the bundle of twisted strands, which is the basic components constituting the Litz wire. This paper constructs a simple analytical copper loss model of the Litz wire based on these preceding insights. In addition to these insights, the proposed model further considers the effect of the inclination angle of the strands to the Litz wire on the proximity effect loss. The proposed model was tested in comparison with the experimentally measured AC resistance of commercially available Litz wires. As a result, the predicted AC resistance showed good agreement with the measured ac resistance, suggesting the effectiveness of the proposed model.

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Minimizing the transformer magnetizing inductance is essential for the soft switching operation of the LLC resonant converter, despite the fact that it results in higher values of magnetizing current, which deteriorates the converter efficiency. Furthermore, it is a well-known practice to utilize the transformer leakage as an inductive component in the resonant tank to improve the power destiny. This paper reveals that the transformer voltage gain can be improved when the transformer leakage inductance in concentrated on the secondary side to avoid the voltage drop inflicted by the relatively large value of the magnetizing current (i.), especially at light load condition. The theoretical discussion relies on the asymmetry of the EI core by placing the secondary winding in a close contact with the magnetic core and placing the primary winding in the vicinity of the air gap. Moreover, noise absorber had been utilized to control the leakage inductance value. The proposed transformer design maximizes the value of the secondary leakage inductance and minimizes the primary leakage inductance. Alongside with the theoretical discussion, experimental tests had been conducted to evaluate the proposed method using a 390V-12V, 220W LLC resonant converter.

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Resonant converters rely on a precise knowledge of leakage inductance of the equipped transformers. Resonant circuit topologies such as LLC usually utilize the transformer leakage as an inductive component in the resonant tank, allowing for a drastic reduction in the converter weight, size and volume. The existence of the secondary leakage inductance affects the whole operation of the LLC resonant converter. This paper reveals that placing the secondary winding near the air gap would increase the resonant tank input impedance, vertically shrink the voltage-gain curve of the converter, and consequently minimize the frequency range (i.e frequency bandwidth with respect to load variation). On contrary, placing the secondary winding in a close contact with the magnetic core would decrease the resonant tank input impedance, vertically stretches the voltage-gain curve of the converter, and widen the frequency variation range. It has been reported that the winding location with respect to the air gap has an impact on the leakage inductance value. In other words, placing the secondary winding in a close contact with the magnetic core (zero mmf position) would maximize the leakage energy storage originated from the secondary winding, and hence maximize the secondary leakage inductance and vice versa. The theoretical discussion is presented which is merely based on Ampere's law and Dowell's model. Furthermore, transformer prototypes had been constructed and tested in a 390V/12V-220W LLC converter prototype to evaluate the proposed analysis.

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All-metal type induction cookers are utilized to heating up the non-iron pans such as the copper and aluminum pans. These cookers are designed to drive the heating coil with extremely high frequency and large AC current. However, the high-frequency large current drive tends to generate a large electromagnetic force which has the direction levitating the pans to be heated and damages the safeties of the induction cooking by moving the hot pans. The purpose of this study is to propose a novel heating coil structure that can reduce the levitation force. The proposed structure coil is similar to the axial gap induction machine. This coil structure generates the electromagnetic force in parallel to the coil surface rather than perpendicular to the surface, thus mitigating the levitation force. In addition, a novel AC power supply is proposed to drive the proposed structure coil. The experiment revealed a successful reduction of the levitation force by approximately 20% compared to the conventional coil structure, supporting the effectiveness of the proposed coil structure.

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Recently, as the miniaturization and densification of the power conversion circuit, switching frequency has been increased. To accomplish the densification, it is essential to predict the losses that occur in each part for the optimization of electric components. However, switching loss which needs to consider nonlinear characteristics are difficult to predict. As a solution, considering the dependence of the gate-drain capacitance on gate-source voltage may improve the prediction accuracy of switching loss. The purpose of this study is to evaluate the improvement of prediction accuracy by considering it. First, to construct the simulation model, the wiring parameter in the circuit, static characteristics and the parasitic capacitance of the device was measured. Next, the device model provided by the manufacturer to use in the simulation was adjusted. Also, the characteristics of the gate-drain capacitance on the gate-source voltage were obtained from two types of measurement circuits. As a result, it was verified that the difference which occurred at the rise of the drain-source voltage at the turn-off tended to decrease and prediction accuracy of the turn-off loss was improved by considering the characteristics of the gate-drain capacitance on the gate-source voltage. Therefore, we concluded that this consideration has the ability to the improvement of turn-off waveforms.

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Resonant inductive coupling wireless power transfer (RIC-WPT) is the promising wireless power supply method to mobile applications. It is well-known that the efficiency and the power transfer capability of RIC-WPT systems deeply depend on the quality factor of the receiver-side resonator, which tends to decline by the conduction loss at rectifying diodes. Therefore, the synchronous rectification is one of the effective solutions. However, the unique characteristics of RIC-WPT, that is the weak magnetic coupling between the transmitter-side and the receiver-side resonator, tend to make the introduction of the synchronous rectification difficult. In order to address this issue, this paper newly proposes a self-driven synchronous rectifier controller suitable for RIC-WPT. This synchronous rectifier controller consists of basic analog elements and gate drivers, and no additional power supply is necessary for driving itself. In addition, the controller doesn't require any information from the transmitter-side resonator. Experiments successfully verified the operating principle as well as the efficiency improvement and clarified the usefulness of the synchronous rectifier with proposed controller for practical application of RIC-WPT.

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Resonant inverters are widely utilized to generate high-frequency high voltage AC power for the power supply to the plasma generator. These inverters commonly require the load impedance to be inductive for achieving soft-switching operation. However, the impedance often fluctuates to be momentarily capacitive due to the unstable state of the plasma, thus causing enormous switching loss and possibly destroying the inverters. This paper addresses this difficulty by using a recently-proposed resonant inverter that can achieve soft-switching operation under the capacitive load impedance. For this purpose, this paper proposes a novel soft-switching controller for applying this inverter for plasma generator application. The proposed controller observes the load impedance and controls the resonant inverter according to the impedance value. Because of the highfrequency AC power supply to the plasma generator, the voltage and current measurement are difficult for estimation of the load impedance. Therefore, the proposed controller estimates the load impedance based on traveling and reflected wave measurement. The experiment revealed successful control of the inverter according to the load impedance, suggesting high feasibility for applying the inverter to the plasma generator.

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Inductor winding is often comprised of parallel-connected wires to suppress copper loss. However, in high-frequency inductors, the proximity effect can cause concentrated AC current distribution, hindering the suppression of the copper loss. Therefore, optimization of the physical inductor structure requires predicting the AC current distribution caused by the proximity effect. Certainly, simulators have been commonly employed for predicting the AC current distribution. However, simple analytical methods are also required for efficient design or invention of inductor structures that have more uniform AC current distribution among the parallel-connected wires. The paper proposes a novel simple analysis method for AC current distribution in parallel-connected wires of high-frequency inductors. The proposed method is based on a novel insight that AC current is distributed to give an extremum of the magnetic co-energy contributed by the AC flux under the given total AC current. Analysis of basic inductor structures revealed that the proposed method can derive the AC current distribution by straightforward calculation. In addition, experiments supported the analysis results. Consequently, the proposed method is suggested to be promising for developing inductor structures with less copper loss.

DOI： 10.1541/ieejjia.7.35

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Litz wire is widely utilized for heating coils of the induction cookers to suppress the proximity effect. However, low space factor of the Litz wire often significantly increases the heating coil height, which may be an obstacle of wide-spread of the induction cookers. In order to overcome this problem, a preceding study has proposed a heating coil structure of the copper foil, which suppresses the proximity effect without using the Litz wire. The preceding study has proven effective suppression of the proximity effect, when the material to be heated is placed to cover the heating coil. However, this heating coil structure still suffers from large AC resistance, when the material to be heated does not exist or partially covers the heating coil. Furthermore, the ferrite walls, installed to suppress the proximity effect, need larger height than the coil, hindering effective reduction of the total heating coil height. The purpose of this paper is to propose an improved heating coil structure. The proposed heating coil structure further incorporates a thin layer of low-permeability soft-magnetic material covering the top of the coil. This layer enables elimination of the proximity effect regardless of the existence or the disposition of the material to be heated. Furthermore, this layer enables the ferrite walls to have the same height as the coil, thus further reducing the total heating coil height. The FEM based simulation was carried out to verify the operating principle of this structure. The result supported reduction of the heating coil height and effective suppression of the AC resistance regardless of the existence and the disposition of the material to be heated.

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Recently, the dual transmitting resonator wireless power transfer system (DTR-WPT) has been proposed as a promising technique for the power supply of mobile apparatus. Although this technique has been reported to be effective for increasing the output power as well as for covering a wide area during wireless power transfer, the complicated magnetic coupling among two transmitting resonators and one receiving resonator makes it difficult to develop practical design optimization methods, thus hindering practical applications of this technique. The purpose of this paper is to propose a design optimization method for the load impedance of DTR-WPT. This method is derived based on a novel simple equivalent circuit model of the DTR-WPT. The optimum impedance derived using this method as well as the appropriateness of the equivalent circuit were verified experimentally, thus validating usefulness of the proposed method for the practical application of DTR-WPT.

DOI： 10.1541/ieejjia.7.49

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Switched reluctance motors (SRMs) are promising for propulsion motors of electric vehicles (EVs) because of their robust mechanical construction and cost effectiveness. However, practical application of SRMs to vehicular propulsion is hindered by comparatively large torque ripple and radial force ripple, which cause noise vibration and acoustic noise. Previous studies have proposed phase current profiles which suppress both ripples. However, in the derivation process of phase current, these previous studies need numerical calculation hindering the EV development speed. The purpose of this paper is to propose a novel phase current profile to suppress both the torque ripple and the radial force ripple of SRMs without numerical calculation. The profile can be straightforwardly calculated using a simple analytical model of the SRMs. In addition, the profile can be determined for any reluctance profiles of actual SRMs. Experiment was carried out to verify the proposed method. The result supported suppression of the torque ripple and the acoustic noise by the proposed method.

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Switched reluctance motors (SRMs) are attractive motors for electric vehicle propulsion because of their cost-effectiveness or robust structures. However, SRMs suffer from input current ripple and torque ripple. The authors have proposed derivation method of phase current profile which suppresses input current ripple and torque ripple and experimentally verified the suppression of both ripples. However, the rms value of derived phase current was much greater than square wave current, which is implemented widely, and increased copper loss. For the EV application, the rms value should be reduced. To break through the issue, the author addressed the characteristic that phase current profiles are shaped based on each reluctance profile, which is shaped by motor configuration, and noticed that phase current profile with low rms value may be derived by a novel rotor configuration. Therefore, this paper proposes a novel rotor configuration which can reduce the copper loss. The proposed rotor configuration is designed to satisfy the reluctance profile which is derived by previously proposed derivation method of phase current. This paper also presents the experiment for the evaluation of the reduction of copper loss.

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Litz wire is commonly employed as the heating coil of induction cookers. In order to realize further low cost and profile, the solid wire with simple construction and high space factor is required. However, the solid wire is may suffer from the large copper loss increased by the skin and proximity effect. Then, the previous study proposed the novel coil structure, which can suppress these effects, only by the FEM simulation. Therefore, the purpose of this paper is to verify this structure experimentally in comparison with the Litz wire coil. The result revealed that the proposed structure can have similar AC resistance and the similar height with the same surface area and the same number of turns. Moreover, the experimental result showed a possibility to further height reduction by optimization of the magnetic and winding isolation design. Consequently, the experiment supported practical effectiveness of the proposed structure for induction heating.

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Recent progress of the semiconductor switching devices enabled the high-frequency design of the switching power converters, which successfully led to the miniaturization of the circuit elements. However, the heat sink has scarcely been miniaturized during past decades. Now, the heat sinks are one of the major obstacles that hinder further size reduction of the switching power converters. Conventionally, the heat sinks are designed to have a number of flat aluminum fins extending from the aluminum base. However, these flat fins tend to make the laminar airflow passing through the fins. This laminar airflow keeps the air contacting the fin surface to remain on the surface. As a result, the fin surface is covered with the air already heated in the upstream and the fresh open air is prevented from contacting with the fin surface, thus deteriorating the cooling performance of the heat sinks. To overcome this issue, this paper proposes a heat sink structure with a novel fin geometry. The proposed fin geometry incorporates two sizes of the louvers, which are disposed to form a fractal-like pattern. These louvers are intended to break the laminar flow on the fin surface, thus promoting the mixing of the air to improve the cooling performance. FEM simulation of the heat transfer was carried out to verify this concept. The result showed improvement in the heat transfer coefficient, implying the effectiveness of the proposed structure for miniaturization of the heat sink.

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Intermediate resonator (repeater) in resonant inductive coupling wireless power transfer (RIC-WPT) systems can increase the transmission distance between the transmitting and receiving coils. The induced current in the repeater is easily affected by the frequency splitting phenomenon because the quality factor (Q-factor) of the repeater is generally as high as several hundreds. If this phenomenon occurs, induction of large current is often difficult in the repeater because the one peak characteristic of the induced current is no longer expected and the single peak of resonance splits into multiple peaks which shift the resonant frequency corresponding to the circuit parameters. In this paper, we approach this difficulty by applying an auxiliary circuit to the RIC-WPT system with the repeater. As a result, under the fixed operating frequency, the induced current in the repeater can be kept large even if the frequency splitting phenomenon occurs. The effectiveness of proposed system was supported by the simulation and experiment.

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Intermediate resonators (repeaters) for resonant inductive coupling wireless power transfer have been widely studied as a method of improving not only the transmission distance but also the output power. For the repeater to operate effectively, it is needed to induce a large current in the repeater to enhance the magnetic field far from a transmitting resonator. However, it is often difficult to induce a large current in the repeater due to frequency splitting phenomenon. This phenomenon easily occurs when the resonator having high quality factor such as the repeater is used. The frequency characteristic of the induced current in the repeater has multiple peaks when the frequency splitting phenomenon occurs. In addition, these multiple peaks shift according to slight variation in the parameters of the coil and the capacitor that constitute the resonator. This slight variation is easily caused by production error, temperature characteristic, and aging degradation of the coil and the capacitor. The induced current in the repeater is significantly decreased by the slight variation in the parameters, namely, the slight variation in the resonance frequency. Therefore, the repeater has low robustness against variation in the resonance frequency. To address these difficulties, we apply an auxiliary circuit to the repeater. The auxiliary circuit can dynamically adjust a phase of the induced current in the repeater, namely, the resonance frequency without complicated control. As a result, a large induced current can be maintained even if the frequencies corresponding to the peaks shift. Consequently, we can provide the repeater having a stable characteristic against the variation in the resonance frequency. The effectiveness of the repeater applied the auxiliary circuit and the appropriateness of analysis results are supported with simulation and experimental results.

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Intermediate resonators (repeaters) of resonant inductive coupling wireless power transfer systems can improve the transmission distance as well as the output power. However, frequency bandwidths in which the repeater can operate effectively are very narrow because the repeater usually has a high quality-factor. Furthermore, these frequency bandwidths shift for the following two factors. The first factor is the intensity of the magnetic coupling between the repeater and the other resonator. The second factor is the variation in the natural resonance frequency of the resonators due to a production error, temperature characteristic, and aging degradation. Therefore, the repeater is not practical because the repeater requires accurate adjusting of the circuit parameters every time according to the various conditions. To address this problem, we propose an impedance matching method for the repeater. The proposed method can maximize the induced current in the repeater in wide frequency bandwidth regardless of the variations in the intensity of the magnetic coupling and the natural resonance frequency. Therefore, the proposed method can realize the repeater which can stably improve the performance of the wireless power transfer. Experiment and simulation successfully verified the effectiveness of the proposed method as well as the appropriateness of the theoretical analysis.

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Induction heating is the technique that heats the conductive material by high frequency large AC magnetic field. For efficient generation of the AC magnetic field, induction heating technique commonly utilizes the resonance between the heating coil and the resonating capacitor. The resonance is generally excited by applying the AC voltage of the resonant frequency. However, the resonant frequency is unstable because this frequency is susceptible to the disposition of the material to be heated. As a result, high efficiency high power induction heating system often suffers from unstable operation. This paper addresses this problem by proposing application of a simple automatic resonant frequency tuning circuit to the induction heating. This circuit can automatically achieve equivalent adjustment of the resonance frequency at the operating frequency without special control or the circuit sensing. In addition, this paper elucidated the control method of this tuning circuit to achieve the soft-switching operation in both of the inverter that drives the heating coil and the tuning circuit itself. The experiment revealed successful stabilization of the resonant frequency as well as satisfaction of the soft-switching condition both of the inverter and the tuning circuit, supporting effectiveness of the tuning circuit for induction heating.

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Recent progress of widebandgap semiconductor switching devices enabled extremely high-frequency operation of power converters owing to their ultrafast switching capability. Fast switching may cause large switching noise at the common source inductance, which may increase the switching loss and lead to false triggering. Therefore, measurement of the common source inductance is often intensely required in practical design of fast switching power converters. However, measurement of the common source inductance is difficult, because 1) the wiring path hidden beneath the molded package significantly contributes to this inductance, 2) the mutual inductance between the gating circuit and the power circuit also contributes to this inductance, and 3) this inductance cannot be defined as the stray inductance of a loop wiring path. These difficulties are addressed in this paper by proposing a novel measurement method of the common source inductance. The proposed method is applicable to already-mounted power circuits. In addition, the proposed method offers a straightforward measurement procedure with common instruments, such as a signal generator, an oscilloscope, and voltage and current probes. Along with the measurement principle, this paper also presents an experiment to evaluate the proposed method.

DOI： 10.1109/TIE.2017.2694411

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© 2016 The Institute of Electrical Engineers of Japan. Resonant inductive coupling wireless power transfer (RIC-WPT) is attractive as a convenient power supply method to small mobile apparatus. However, limited size of the receiving coil can limit the efficiency and the power transfer capability. This paper addresses this difficulty by proposing a novel receiving coil structure. The proposed structure has a coil wound on a drum core with a thin axis. The top and the bottom of the drum core has large surface area to effectively collect the magnetic flux for large mutual inductance. In addition, the thin axis can reduce the wire length, thus reducing the parasitic AC resistance. The AC resistance is further reduced by suppressing the proximity effect. Simulation supported probable improvement in the efficiency as well as the power transfer capability. In addition, experiment verified that the proposed structure improved the efficiency by 66% and the power transfer capability by 109%.

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© 2016 The Institute of Electrical Engineers of Japan. Litz wire has been widely utilized for heating coils of high frequency induction cookers. However, these coils often suffer from large winding height due to low space factor of Litz wire. Certainly, rectangular wire may reduce the winding height of the coil owing to its high space factor. However, the rectangular wire tends to suffer from large copper loss caused by the skin effect and the proximity effect. In the conventional coil structure of the rectangular wire, these effects cause concentrated AC current distribution, which leads to excessive copper loss. This paper addresses this issue by proposing a novel heating coil structure of the rectangular wire that can homogenize the AC current distribution. This paper also presents the simulation results that successfully verified the effectiveness of the proposed structure.

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GaN-FETs are attractive switching devices for their fast switching capability. However, they often suffer from the oscillatory false triggering, i.e. a series of self-sustaining repetitive false triggering induced after a fast switching. The purpose of this paper is to derive a design instruction to prevent this phenomenon. According to the previous study, the oscillatory false triggering was found to be caused by a parasitic oscillator circuit formed of a GaN-FET, its parasitic capacitance, and the parasitic inductance of the wiring. This paper analyzed the oscillatory condition to elucidate the design requirement to prevent the oscillatory false triggering. As a result, balancing the gate-drain parasitic capacitance and the common source inductance to achieve an appropriate ratio was found to be essential for preventing the oscillatory false triggering. Experiment successfully supported prevention of this phenomenon by balancing these two factors.

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In the LLC resonant converter, the transformer core is usually gapped to realize the designed value of magnetizing inductance that allows for soft switching. The air gap length which is in a scale of millimeters may be affected by the humidity and long working hours of the ferrite material, resulting into a variation of the core permeability. Moreover, a slight variation of the transformer core permeability may be encountered with any possible change in the core temperature. In a proper transformer design, the transformer shall operate with an optimum value of effective permeability where the sum of both copper and core losses is minimal. In this paper, the transformer optimal design is presented. Moreover, the influence of the permeability on the transformer's copper and core losses is revealed. Furthermore, with the help of newly derived equations, the effect of the transformer's effective permeability on the LLC converter conduction turn-on and turn-off losses is reported. Along with the theoretical discussion, the analysis is supported with simulation and experimental results utilizing a 250W-200kHz prototype.

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Three-phase power factor correction (PFC) converters have been widely utilized in industrial power applications to improve the power factor and reduce current harmonics in three-phase power grid. The PFC converters commonly incorporate large-sized inductors as a noise filter to suppress the noise emission to the grid. However, as many other power converters, the PFC converters are intensely required to achieve high power density by reducing the size of the inductors. The purpose of this paper is to propose a magnetic structure to miniaturize the inductors. The proposed magnetic structure consists of an integrated magnetic component and a three-phase common-mode choke. By integrating the inductors, the proposed magnetic structure can miniaturize the magnetic core volume, while keeping the saturation current level and the noise filtering capability unchanged. Experiment was carried out to evaluate the appropriateness of the proposed magnetic structure as well as possible volume reduction. As a result, 32.2% volume reduction was found in the proposed magnetic structure without deterioration of the filtering capability.

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Parallel-connected windings are widely utilized for power transformers to reduce the copper loss. However, this reduction effect is often hindered by the proximity effect, which causes concentrated current distribution in parallel-connected windings. This paper addresses this issue by proposing a design optimization method of winding turn allocation among winding layers. This optimization method is based on the recently proposed insight on the proximity effect, referred to as the extremum co-energy principle. Experiment on a planar transformer with four primary winding layers was carried out to verify the proposed method. As a result, the proposed method successfully optimized the allocation of the winding turns to minimize the AC resistance.

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SiC-MOSFETs have attracting increasing attention because of their outstanding characteristics that contributes to high efficiency and high power density of power converters. However, compared to conventional Si-IGBTs, SiC-MOSFETs are susceptible to false triggering, because they tend to generate large switching noise due to ultrafast switching capability and have a lower threshold voltage in high temperature operation. Particularly, disastrous oscillation of repetitive false triggering can occur after a fast turn-off, which is the severe issue for practical application of SiC-MOSFETs. The purpose of this paper is to give an instruction to avoid this phenomenon. This paper hypothesized that the repetitive false triggering is the parasitic oscillation caused by parasitic capacitance of SiC-MOSFET, and parasitic inductance of wiring. Based on this hypothesis, this paper analyzed the oscillatory condition of the parasitic oscillator to propose a design instruction to avoid the oscillatory false triggering. The result revealed that the parasitic inductance of the gate, drain, and source wiring should be designed so that the resonance frequency of the parasitic LC resonator in the gating circuit is far apart from that of the power circuit. This paper also presents experimental results that support appropriateness of the proposed design instruction.

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Recently, the common source inductance (CSI) is regarded as one of the most important obstacles for achieving ultrafast switching of switching converters. The CSI is pointed out to be a major cause of deterioration of the switching speed and false triggering. Therefore, many design instructions of next generation switching devices, such as GaN-FETs and SiC-MOSFETs, have pointed out the necessity to reduce the CSI. Certainly, many of the next generation switching devices are provided in surface mount packages in order to enable PCB designers to minimize the CSI by eliminating the common source path. However, the parasitic magnetic coupling between the gating circuit and the power circuit may still add the CSI, although preceding studies have scarcely reported how greatly the PCB layout can affect the CSI and the switching waveforms. This paper experimentally evaluated the impact of the parasitic magnetic coupling of the PCB layout on the CSI of the surface mount package and on the switching waveforms. As a result, the parasitic magnetic coupling was found to cause the major difference in the CSI. In addition, large difference in the turn-off switching waveforms was found to be caused by the difference in the magnetic coupling. The reason is also analyzed and discussed in this paper, suggesting importance of appropriate design of the parasitic magnetic coupling in the PCB layout.

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The common source inductance is one of the major causes of deterioration of the switching speed and susceptibility of the false triggering for semiconductor switching devices. Practical design of this inductance requires selection of an appropriate semiconductor package because this inductance is greatly dependent on the physical package structure. However, few studies have reported a list of the common source inductance of commercially available packages. In order to list and compare the common source inductance among typical semiconductor packages, this paper carried out measurement of this inductance of actual switching devices mounted on experimental PCBs. This paper employed a recently proposed straightforward measurement technique directly applicable to switching devices mounted on PCBs. As a result, a basic database of the common source inductance of typical packages was presented. The common source inductance was found to be determined mainly by the package type. However, in TO-247 and TO-220 packages, approximately one-third of the total common source inductance was found to possibly vary among the switching devices of the same package due to the dependence on the current rating. Investigation of the physical package structure implied that this dependence was caused by the stray inductance of the bonding wires connecting the semiconductor chip to the source terminal.

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Series-Series (SS) and Series-Parallel (SP) topologies are widely utilized in practical resonant inductive coupling wireless power transfer (RIC-WPT) systems owing to their simple circuit configurations. Conventionally, design optimization of the circuit parameters of these topologies were investigated separately, because these topologies are expressed by different equivalent circuits. However, analysis of these equivalent circuits is generally complicated due to the multiple resonant modes contained in the operation, which may cause difficulty in comparing the performance between the SS and SP topologies after design optimization of these topologies. This difficulty may prevent elucidating the methodology to select an appropriate topology that offers better output power or efficiency after design optimization. The purpose of this paper is to suggest a selection methodology of the SS and SP topologies by elucidating a novel insight that these topologies have the quasi-duality relation, in which the SP topology works approximately as the dual of the SS topology. This insight enables to share the analysis results between the topologies. As a result, both of these topologies were found to be expressed by a same novel equivalent circuit. Furthermore, the only difference between the SS and SP topologies were found to be the equivalent load resistance of this equivalent circuit, thus reducing the topology selection into selection of preferable load resistance. The appropriateness of the quasi-duality relation and the resultant equivalent circuit was successfully confirmed by the simulation and the experiment.

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Recently, resonant inverters have been employed to generate high voltage high frequency AC power for plasma generator of the semiconductor processing equipment. This inverter is beneficial in low switching loss owing to its natural soft switching capability under inductive load impedance. Generally, the resonant inverter for plasma generator is designed to have inductive load using an impedance matching circuit that interfaces the inverter and the plasma reactor. However, the load impedance often fluctuates according to the state of the plasma, momentarily causing the capacitive load impedance. In this case, the inverter is generally controlled to restrict the output power for circuit protection from excessive switching loss, although this will result in unstable plasma, deteriorating the quality of the semiconductor processing. This paper addressed this difficulty by applying a soft switching technique to the resonant inverter. This soft-switching technique can be utilized regardless to the capacitive or inductive load. Experiment was carried out to evaluate the effectiveness of the proposed technique. As a result, the effective reduction of the switching loss was successfully verified even under the capacitive load impedance.

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Resonant inductive coupling wireless power transfer (RIC-WPT) is attracting attention as a convenient power supply method to small mobile apparatus. The efficiency and the power transfer capability of RIC-WPT has been known to be profoundly dependent on the quality factor of the receiving resonator. However, the quality factor of the receiving resonator tends to be deteriorated because of the conduction loss at the diode rectifier, particularly for low output voltage applications. In order to improve the efficiency and the power transfer capability, this paper propose a novel simple synchronous rectifier, which can reduce the conduction loss. The proposed rectifier has simple circuit configuration, which contributes to straightforward application to the wireless power transfer to small mobile apparatus with limited installation space. Experiment was carried out to verify the operation principle of the proposed rectifier. As a result, the proposed rectifier revealed successful suppression of the conduction loss. In addition, the experimental wireless power transfer system verified successful improvement in the rectification efficiency, supporting usefulness of the proposed rectifier for practical applications of the RIC-WPT for small mobile apparatus.

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This paper proposes a simple control technique for switched reluctance motors to eliminate both the source current ripple and the torque ripple simultaneously. The proposed control is a current tracking control based on a pre-computed magnetic flux profile. This profile is derived using a simple analytical SRM model without the magnetic saturation. Conventionally, the magnetic saturation is commonly utilized for limiting excessive magnetic flux induction to improve the torque output. However, in the proposed control, the magnetic flux profile is utilized for limiting the magnetic flux by control. By controlling without the magnetic saturation, elimination of the source current ripple and the torque ripple can be achieved regardless to the output power. Along with theoretical derivation of the magnetic flux profile, an experiment is carried out to evaluate the proposed control. The results revealed suppression of the source current ripple and the torque ripple simultaneously in comparison with the conventional square-wave current control.

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Series-series (SS) topology and series-parallel (SP) topology of the electric-field coupling wireless power transfer system are widely utilised for practical applications. However, selecting the appropriate circuit topology, which maximise the output power by design optimisation, is often difficult, because these circuit topologies are generally analysed using different circuit models. This difficulty by analysing novel equivalent circuits for SS and SP topologies is addressed. As a result, the output power of SP topology is found to be approximated by that in SS topology with transformed load impedance. This result can offer a simple strategy for topology selection as well as design optimisation.

DOI： 10.1049/el.2016.1253

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Gallium nitride field-effect transistors (GaN-FETs) are attractive devices because of its low on-state resistance and fast switching capability. However, they can suffer from false triggering caused by fast switching. Particularly, a disastrous oscillation of repetitive false triggering can occur after a turn-off, which may deteriorate the reliability of power converters. To address this issue, we give a design guideline to prevent this phenomenon. We analyze a simple circuit model to derive the condition of occurrence of this phenomenon, which is then verified experimentally. Results show that the parasitic inductance of the gating circuit, L-g, and that of the decoupling circuit, L-d, should be designed so that the LC resonance frequency of L-g and the gate-source capacitance of the GaN-FET does not coincide with that of L-d and the drain-source capacitance, respectively. (c) 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

DOI： 10.1002/tee.22339

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A number of analytical models for switched reluctance motors have been proposed to promote development of control techniques that can alleviate the torque and source current ripples. However, these models can suffer from a large database of the nonlinearity as well as complicated derivation process of the torque and the voltage-current relation. The purpose of this paper is to propose a simple practical behavior model with small database and straightforward derivation of the torque and the voltage-current relation. The proposed model has a simple database of the magnetic energy as a matrix. The flux linkage and the electrical angle are chosen as the state variables. Along with theoretical formulation of the model, this paper presents a practical method of the model construction. In addition, experiments successfully predicted both torque and current waveforms, supporting appropriateness of the proposed model.

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This paper proposes a novel analysis method for the dual transmitting resonators wireless power transfer (DTR-WPT) system. The DTR-WPT is attractive for its higher efficiency and greater power transfer capability compared with the conventional single transmitting resonator wireless power transfer (STR-WPT) system. However, analytical understanding of the DTR-WPT is difficult due to its complicated operating principle caused by two transmitting resonators and a receiving resonator, which are all magnetically coupled each other. Therefore, practical applications of the DTR-WPT may be hindered by difficulty in establishing a design optimization method and a control scheme.This difficulty is addressed in this paper by proposing a novel simple equivalent circuit model of the DTR-WPT. Lagrangian dynamics is employed to derive this model. Brief analysis of this model showed improvement in the efficiency and the power transfer capability by the DTR-WPT compared with the conventional STR-WPT. In addition, the power transfer of the DTR-WPT system was found to be expressed by the same equivalent circuit model as the STR-WPT system. Therefore, similar design optimization methods and similar control schemes as for the STR-WPT are applicable to the DTR-WPT. Along with the theory, this paper presents experiments that verified appropriateness of the proposed model as well as the analysis results based on this model.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Switched reluctance motors (SRMs) are expected to be applied to propulsion systems of electric vehicles for their robust mechanical construction and cost-effectiveness. On the other hand, their large source current ripple and large torque ripple are main obstacles in practical applications of SRMs to vehicle propulsion. Certainly, a number of studies have been dedicated to address the torque ripple. However, unlike other motors driven by sinusoidal phase current waveforms, the large source current ripple of SRMs generally remains, even if the torque ripple is removed. The purpose of this paper is to propose a simple control technique of SRMs for vehicular propulsion by eliminating the source current ripple as well as the torque ripple. The proposed control is a current tracking control based on a pre-computed current profile. Because vehicular propulsion requires to instantaneously output large torque in sudden acceleration, SRMs tend to be designed to be propelled below the magnetic saturation in normal vehicle travel. Therefore, this proposed current profile is derived using a simple SRM analytical model without the magnetic saturation. In addition, the proposed current profile is determined so that the peak magnetic flux is minimized to offer high-speed current response at a high rotating velocity. Along with theoretical derivation of the proposed control, this paper also presents an experiment to verify the principle of the proposed control technique, which successfully revealed reduction of both the source current ripple and the torque ripple.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The Dowell model is widely utilized for copper loss analysis of forward transformers. However, this model is not directly applicable to transformers with parallel-connected windings. The reason is that the Dowell model requires determining the AC current of all the windings in advance of analysis, although the AC current distribution in parallel connected windings is severely affected by disposition of the windings. This issue is addressed in this paper by employing the Dowell model in combination with a novel insight that the AC current is distributed in parallel-connected windings to give an extremum of the magnetic co-energy of the transformer. Simulation and experiment were carried out; and, the results supported appropriateness of the proposed copper loss analysis method.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST ENGINEERING TECHNOLOGY-IET  

© 2015 The Institution of Engineering and Technology. Practical applications of switched reluctance motors (SRMs) require control techniques that can solve large torque ripple and large current ripple in power supply. To promote development of these techniques, a simple Lagrangian formulation for flux-based nonlinear SRM models is proposed. This formulation can be analysed in combination with Lagrangian circuit models of motor drivers. The properness of the formulation is supported by an example of the analysis of the operation of a simple SRM driving system.

DOI： 10.1049/el.2015.0950

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Electric-field coupling wireless power transfer has been commonly analyzed using the circuit model. However, the circuit behavior of this model is not necessarily apparent because their resonant modes can be far complicated than the basic LC oscillation. This issue is addressed in this paper by proposing a novel equivalent circuit for a basic wireless power transfer system. This equivalent circuit has a simpler topology than the conventional circuit model. Furthermore, the equivalent circuit allows intuitive understanding of three types of the resonant modes. Along with theoretical derivation of the proposed equivalent circuit, this paper also presents simulation results, which verified the appropriateness of the equivalent circuit. (C) 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

DOI： 10.1002/tee.22180

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

This paper proposes a novel simple reactive power control strategy for the active load balancer (ALB) in three-phase four-wire distribution systems. The proposed reactive power control strategy may be applicable for adjustment of the source-side power factor under the balanced load condition. Only dc capacitor voltage control is used in the proposed control strategy. Therefore, the calculation blocks of the active and reactive components of the load currents are not necessary. The authors, thus, offer the simplest control strategy to control reactive power under the balanced load condition on three-phase four-wire distribution feeders. The basic principle of dc-capacitor-voltage-control-based reactive power control strategy is discussed in detail and then confirmed by digital computer simulation. A prototype experimental system was constructed and tested. Experimental results demonstrate that balanced source currents with reactive power control are achieved on three-phase four-wire distribution feeders. These experimental results also demonstrate that controlling the reactive power reduces the required power rating of the ALB compared with that of the conventional unity power factor control strategy.

DOI： 10.1109/TIA.2015.2437972

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Wide-bandgap semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) are promising materials for next-generation power devices. We have fabricated a normally on GaN-based high-electron-mobility transistor (GaN HEMT) for power electronic converters. In this paper, the current collapse phenomena, which are distinctive characteristics of GaN devices, are evaluated in detail for several voltages with two switching frequencies. We also evaluate a gate drive circuit that we previously proposed for the normally on GaN HEMT with a single positive voltage source. We construct and test prototype circuits for a boost-type dc-dc converter and a single-phase full-bridge inverter with a gate drive circuit. The problems to be solved for the normally on GaN HEMT, which has a (static) voltage rating of over 600 V, are clarified on the basis of the experimental results.

DOI： 10.1109/TIA.2014.2369818

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

In this paper, we propose a new control algorithm to reduce the capacity of a previously proposed smart charger for electric vehicles (EVs) on single-phase three-wire distribution feeders with reactive power control. The basic principle of the proposed control algorithm is discussed in detail. It is shown that controlling the reactive power on the source side reduces the capacity of the previously proposed smart charger. A digital computer simulation is implemented to confirm the validity of the proposed control algorithm using PSIM software. A prototype experimental model is also constructed and tested. Experimental results demonstrate that balanced source currents with a power factor of 0.9, which is acceptable for Japanese home appliances, are obtained on the secondary side of the pole-mounted distribution transformer during both the battery charging and discharging operations in EVs. The capacity of dc capacitor C-DC is also reduced by 37% with the proposed reactive power control algorithm.

DOI： 10.1109/TIA.2014.2327156

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes a novel non-isolated high step-up converter suitable for miniaturization by high frequency design. High step-up converters with voltage multipliers are promising for high frequency design because many of them can be free from coupled inductors or transformers, which may lower the voltage gain due to the leakage inductance or may cause significant AC conduction loss in the primary winding. However, two issues can still hinder further miniaturization. One is that many multiplier stages may be needed to achieve extremely high voltage gain. The other is that high switching frequency may be restricted by severe turn-off voltage surge caused by high speed switching. The proposed converter addresses the former by applying a recently reported technique to a non-isolated boost converter. Additionally, the converter addresses the latter by proposing a simple passive regenerative turn-off snubber implementable only by two diodes and a capacitor. Experiments verified that the proposed converter achieves high voltage gain with fewer voltage multiplier stages compared to prior non-isolated high step-up converters. Additionally, the snubber successfully reduced the turn-off surge into half approximately without apparent deterioration of the efficiency.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST ELECTRICAL ENGINEERS JAPAN  

Sliding-mode control for power converters is gaining significant research interest for achieving a fast transient response to a step load change in a wide operating range. However, power converters also require better dynamic load regulation against load current fluctuations slower than the step change. This paper addresses this issue by deriving a novel control method for synchronous buck converters using Lagrangian dynamics. Simulation results verified improvement in dynamic load regulation against slow sinusoidal load current fluctuations.

DOI： 10.1541/ieejjia.4.728

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Communication relay stations often suffer from common-mode noise generated by high speed switching in a boost chopper equipped for power supply. This problem can be addressed by applying soft-switching techniques to the boost chopper, although this can lead to significant increase in the circuit volume. To address this difficulty, this paper proposes a novel passive regenerative turn-off snubber applicable to the two-phase interleaved boost chopper. The proposed snubber can add small circuit volume because it is implementable only by two diodes and a capacitor. Experiments are carried out to verify the operating principles of the proposed snubber. The results successfully verified suppression of the rising speed of the drain voltage at the turn-off in both of the phases without apparent deterioration of the efficiency.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST ELECTRICAL ENGINEERS JAPAN  

This paper proposes a reactive power control strategy for the active load balancer (ALB) in three-phase four-wire distribution systems. The proposed reactive power control strategy is based on constant DC capacitor voltage control only, which is always used in active power line conditioners. Therefore, the proposed approach does not require active and reactive calculation blocks of load currents for the reference source current calculation. The power factor of the source side currents can be adjusted under the balanced load condition using the proposed reactive power control strategy. The basic principle of the reactive power control strategy for the ALB is discussed in detail and verified via digital computer simulation using power electronic simulation (PSIM) software. A prototype experimental model is constructed and tested to demonstrate the validity and high practicability of the proposed control strategy. Simulation and experimental results indicate that balanced source currents with a predefined power factor are achieved when the proposed control strategy is applied to the three-phase four-wire distribution systems.

DOI： 10.1541/ieejjia.4.158

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The anxiety of tiny metal contamination into resin materials in the manufacturing process has become one of the serious issues. Because it may often cause of overheat in lithium-ion batteries, flat panel displays, and so on. Therefore, a study on detecting method of the tiny metals is a significant issue. The authors have been investigating the high-frequency induction heating (IH) based approach for tiny metals detection. In this paper, effective magnetic circuit design and IH conditions are discussed and demonstrated from theoretical and experimental point of view.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

In this paper, we propose the control method of a peak shaving system for an electric injection molding machine (EIMM). The peak power shaver consists of a multiphase bidirectional dc-dc converter and supercapacitors (SCs), and is connected to a dc link of the inverter fed injection motor drive system of the EIMM. In the proposed control method, electric power is stored in the SCs through the multiphase bidirectional dc-dc converter with a pulsewidth-modulation rectifier while the injection motor is at rest. When the injection motor is accelerating, the stored power in the SCs together with the power from the distribution feeders is supplied to the injection motor. Thus, the peak power can be shaved. The basic principle of the proposed control method is discussed in detail, then confirmed by digital computer simulation and experimental setup. The simulation and experimental results demonstrate that the peak power is shaved by 70% using the peak power shaving system.

DOI： 10.1109/TIA.2013.2272433

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Wireless power transmission via magnetic resonance has been attracted and interested as long range wireless power transmission method. As a consequence, high-frequency inverter operating under high power conversion efficiency is required. In this paper, power conversion efficiency and power transmission efficiency of full bridge inverter using GaN devices are evaluated and discussed from the experimental point of view.

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper proposes a new concept for a contactless power supply system (CPS) in a mechanical multi-level parking tower for plug-in hybrid vehicles (PHVs) and electric vehicles (EVs). In recent years, PHVs and EVs have been commercialized as low environmental impact vehicles, and the demand for such vehicles is spreading rapidly. To cater to this increasing demand of PHVs and EVs, battery charging systems in the parking tower are necessary. Most multi-level parking towers have movable parking pallets that are electrically isolated from the building side. Because of the poor positional accuracy of the movable pallets, a contactless power transmission system between the utility grid in the building and the movable pallet is necessary. As for the CPS in the parking tower, a power conversion stage from commercial AC to high-frequency AC is necessary for size reduction. In general, such a power conversion system consists of power factor correction (PFC) converters and high-frequency inverters. Therefore, two or more conversion stages are necessary, which increases the power losses and cost. In this paper, a simple circuit configuration of a high-frequency link AC-AC converter for a CPS in a parking tower is proposed. The proposed high-frequency link AC-AC converter can directly convert commercial AC to high-frequency AC (HFAC) and HFAC to commercial AC again. Experiments are performed to demonstrate the validity of the proposed CPS. The proposed CPS is found to have a coupling coefficient of 0.75 for a contact-less transformer with a 10mm gap, and an efficiency of 86% can be achieved.

DOI： 10.1541/ieejias.134.139

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

In this paper, a multiple-output high-frequency soft switching inverter is presented for home and business-use of IH cooking appliances. The proposed inverter is composed of parallel-connected single-switched multiresonant inverter cells. A detailed analysis indicates that the proposed inverter can control multiple-output power independently through a phase-shifted PWM scheme. The experimental results suggest that the prototype may be applied to multiple-output induction heating appliances.

DOI： 10.1541/ieejias.134.477

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Language：Japanese   Publisher：The Japan Institute of Power Electronics  

This paper proposes a novel reactive power control algorithm without load-side active power calculation for the previously proposed smart charger of Electric Vehicles (EVs) on single-phase three-wire distribution feeders. The basic principle of the proposed reactive power control algorithm is discussed in detail and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents with a power factor of 0.9, which is acceptable value in Japanese regulation, are obtained on the secondary side of the pole-mounted distribution transformer during the battery charging operation.

DOI： 10.5416/jipe.40.63

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes a novel, simple reactive power control strategy for the active load balancer (ALB) in three-phase four-wire distribution systems. The proposed reactive power control strategy is applicable for adjustment of the source-side power factor under the balanced load condition. Only DC capacitor voltage control is used in the proposed control strategy. Therefore, the calculation blocks of the active and reactive components of the load currents are not necessary. The authors, thus, offer the simplest control strategy to control reactive power under the balanced load condition on three-phase four-wire distribution feeders. The basic principle of DC capacitor voltage control based reactive power control strategy is discussed in detail, and then confirmed by digital computer simulation. A prototype experimental system was constructed and tested. Experimental results demonstrate that balanced source currents with reactive power control are achieved on three-phase four-wire distribution feeders. These experimental results also demonstrate that controlling the reactive power reduces the required power rating of the ALB compared to that of the existing control strategy, which achieves balanced source currents with unity power factor.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes a reactive power control strategy for the active load balancer (ALB) in three-phase four-wire distribution systems. The proposed reactive power control strategy is based on constant DC capacitor voltage control, which is always used in active power line conditioners. Therefore, the proposed reactive power control strategy does not require active, reactive calculation blocks of load currents for the reference source current calculation. Balanced source currents with a predefined power factor can be achieved without unbalanced active and reactive components detection of the load currents. The basic principle of the reactive power control strategy for the ALB is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested to validate the feasibility of the proposed control algorithm. Simulation and experimental results demonstrate that balanced source currents with a predefined power factor are achieved in three-phase four-wire distribution systems.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical Engineers of Japan  

Three-phase four-wire distribution systems are widely used in many countries. These distribution systems are used for both three-phase three-wire loads and single-phase two-wire consumer appliances, e.g., in South Korea and Myanmar. Because of the time-dependent load characteristics, unbalanced load conditions frequently occur, resulting in the unbalanced voltages for the three-phase and single-phase loads. In addition, these unbalanced load conditions cause more loss in the distribution transformer. This paper proposes a novel reference current generation method for active load balancer (ALB) in the three-phase four-wire distribution systems. The main advantages of the proposed method is that it uses only a constant DC capacitor voltage control for reference current generation without calculating the active and reactive currents in the three-phase four-wire distribution systems. The basic principle of the novel reference generation method in ALB is discussed and then confirmed on the basis of results of digital computer simulation using PSIM software.

DOI： 10.1541/ieejjia.3.286

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical Engineers of Japan  

This paper proposes a new control algorithm to reduce the capacity of the previously proposed smart charger for electric vehicles (EVs) on single-phase three-wire distribution feeders using reactive power control on the source side. The basic principle of the proposed reactive power control algorithm is discussed in detail. It is shown that controlling the reactive power on the source side reduces the capacity of the previously proposed smart charger. A digital computer simulation is carried out to confirm the validity of the proposed control algorithm using PSIM software. A prototype experimental model is constructed and tested. The experimental results demonstrate that balanced source currents with a power factor of 0.9, which conforms to Japanese regulations, are obtained on the secondary side of the pole-mounted distribution transformer during both the battery charging and discharging operations in EVs reducing the capacity of the smart charger by 31% in comparison to that of the smart charger with the previously proposed control algorithm.

DOI： 10.1541/ieejjia.3.437

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

This paper proposes a novel active power quality compensator (APQC) topology with a DC voltage balancer for electrified railways. The APQC is composed of a three-leg structure with two common DC capacitors. Two legs perform as two half-bridge inverters, which compensate the unbalanced active, reactive, and harmonic currents on the source side in the traction substation. The third leg controls two common DC capacitor voltages with a small amount of the output currents. Therefore, the current rating of the third leg can be reduced as compared to that of the already proposed three-leg structured APQC. In the control algorithm of the two half-bridge inverters, a strategy based on constant DC capacitor voltage control is used, which does not need any calculation blocks of the unbalanced active, reactive, and harmonic components of the load current to perform the APQC operation. Thus we offer the simplest algorithm for the proposed APQC. The basic principle of the proposed APQC topology with the DC voltage balancer is discussed in detail, and then confirmed by digital computer simulation using the PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that the proposed APQC can achieve balanced and sinusoidal source currents on the primary side of the Scott transformer in traction substations for electrified railways. (c) 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

DOI： 10.1002/tee.21907

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

In this paper, we propose a smart charger for electric vehicles with a power-quality compensator. The proposed smart charger consists of four-leg insulated-gate bipolar transistors (IGBTs). Three legs are used for a single-phase full-bridge-based pulsewidth-modulated (PWM) rectifier, which converts power from ac to dc during the battery-charging operation or from dc to ac during the battery-discharging operation. This PWM rectifier can compensate reactive and unbalanced active currents on single-phase three-wire distribution systems because the third leg is connected to the neutral line of single-phase three-wire distribution feeders. The fourth leg is used as a bidirectional dc-dc converter for battery-charging and battery-discharging operations. The three-leg PWM rectifier uses only constant dc-capacitor voltage control, which is commonly used in active power line conditioners. Thus, the authors have developed the simplest possible control method for a single-phase power-quality compensator. The basic principle of the proposed smart charger is discussed in detail and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents are obtained on the secondary side of the pole-mounted distribution transformer for battery-charging and battery-discharging operations.

DOI： 10.1109/TIA.2013.2262915

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

In recent years, induction heating (IH) cookers using a high-frequency (HF) inverter for home use have become increasingly popular because of their cleanliness, high efficiency, safety, and so on. With regard to the domestic consumer markets, effective applicability to a variety of pan materials such as low resistivity materials (aluminum and copper) and high-resistivity materials (iron and magnetic stainless steel) is one of the important issues. In this paper, a time-sharing HF inverter for IH cooking appliances that enables doubling of the output frequency of the switching operation is proposed. The proposed HF resonant inverter is able to reduce switching losses by the frequency doubler and the soft-switching operation. Furthermore, the current rating of the switching power devices is reduced because of the parallel-connected circuit configuration. The basic principle of the proposed time-sharing HF inverter is discussed in detail. The performance and effectiveness of the proposed time-sharing HF inverter are confirmed by experimental point of view.

DOI： 10.1541/ieejias.133.692

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In this paper, we propose a new control algorithm to reduce the capacity of a previously proposed smart charger for electric vehicles (EVs) on single-phase three-wire distribution feeders with reactive power control. The basic principle of the proposed control algorithm is discussed in detail. It is shown that controlling the reactive power on the source side reduces the capacity of the previously proposed smart charger. A digital computer simulation is implemented to confirm the validity of the proposed control algorithm using PSIM software. A prototype experimental model is also constructed and tested. Experimental results demonstrate that balanced source currents with a power factor of 0.9, which is acceptable for Japanese home appliances, are obtained on the secondary side of the pole-mounted distribution transformer during both the battery charging and discharging operations in EVs. This reduces the capacity of the smart charger by 32% compared with that of the smart charger with the previously proposed control algorithm.

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Wide bandgap semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), are promised materials for next-generation power devices. The authors have recently fabricated a GaN-based high-electron-mobility transistor (HEMT), which is a normally-on device, for power electronics application. However, the power consumption in the constructed gate drive circuit increases when the GaN HEMT is used under higher-frequency operation. A new gate drive circuit with lower power consumption for the normally-on GaN HEMT is strongly required. In this paper, a new resonant gate drive circuit, which is most suitable for the newly fabricated GaN HEMT, is proposed. The validity and high practicability of the proposed resonant gate drive circuit are demonstrated by simulation and experimental results.

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Wide bandgap semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) are the promising materials for next-generation power devices. A normally-on GaN-based high-electron-mobility transistor (GaN HEMT) has been fabricated for power electronic converters. In this study, the current collapse phenomena, which are distinctive characteristics of GaN devices, are evaluated in detail under several voltages with two switching frequencies. Prototype circuits for a boost-type dc-dc converter and a single-phase full-bridge inverter, which use the newly fabricated GaN HEMT, are constructed and tested. The experimental results demonstrate that the newly fabricated normally-on GaN HEMT with the previously proposed gate drive circuit is suitable for use as a next-generation power device.

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Language：Japanese   Publisher：パワーエレクトロニクス学会  

DOI： 10.5416/jipe.39.188

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This paper proposes a new current control strategy that is based on the internal model principle for a current balancer in single-phase three-wire distribution systems. The proposed current control strategy includes a sinusoidal reference input model to achieve the zero steady-state error tracking. The appropriate control gains of this control strategy can be systematically determined by using a state-feedback controller design method via linear matrix inequalities. The basic principle of the proposed control strategy is discussed in detail, and then confirmed by digital computer simulation using the PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that zero steady-state error tracking is achieved by the proposed control strategy. Also, balanced source currents are obtained on the secondary side of a pole-mounted distribution transformer while the load conditions are unbalanced. (c) 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

DOI： 10.1002/tee.21924

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, a multiple-output high-frequency soft switching inverter is presented for home and business use "all metal" IH cooking appliances. The frequency and handling power of each output can be selected and regulated individually. The proposed inverter is composed of two single high-frequency circuit cells which are connected in parallel. Therefore, the number of switching devices in the proposed inverter can be significantly reduced. The simulation and experimental results indicate that the proposed circuit is suitable for the multiple output IH concepts such as free-zone induction heating, multi burner type cooking set-up and so on.

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This paper proposes a mobile power for the Sectional Compact Emergency Shelter (SCES), which is used for the field hospitals, disaster response offices, and so on under the great disaster. The proposed mobile power consists of the fuel cells (FCs), photovoltaic cells (PVs) and lead-acid batteries. All of the power resources and necessary electrical equipments are constructed in a container car. Therefore, the constructed mobile power is easily moveable and constructive with the SCESs. The FCs can supply power continuously. The PVs are installed on the roof of SCES. The generated power from the PVs is fluctuated by weather conditions. Thus, the lead-acid batteries are installed for levering the difference between the generated power and consumed power in the SCES. The basic principle of the proposed ubiquitous power is discussed in detail, then confirmed by digital computer simulation using PLECS software. The simulation results demonstrate that the ubiquitous power can supply the power to the SCES continuously in winter in Japan. It is concluded that the proposed ubiquitous power is the good solution for power supply of SCES under the great disaster with the SCES.

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Three-phase four-wire distribution systems are widely used in many countries. These power distribution systems are used for both three-phase three-wire loads and single-phase two-wire consumer appliances in South Korea, Myanmar and other countries. Unbalanced load conditions always occur in three-phase four-wire distribution systems. These unbalanced load conditions cause unbalanced voltages for three-phase and single-phase loads, and increase the loss in the distribution transformer. In this paper, we propose an active load balancer (ALB) based on constant DC capacitor voltage control for three-phase four-wire distribution systems. Constant DC capacitor voltage control is always used in active power line conditioners. The proposed control algorithm does not require any computation blocks to calculate the active and reactive currents on the distribution system. Balanced source currents with a unity power factor are obtained without any calculation blocks of the unbalanced active and reactive components on the load sides. The basic principle of the constant DC capacitor voltage control based strategy for the ALB is discussed in detail and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is also constructed and tested to validate the feasibility of the proposed control algorithm. Simulation and experimental results demonstrate that the proposed ALB can balance the source currents with a unity power factor for a three-phase four-wire distribution system.

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The anxiety of merging tiny materials and resin materials in the manufacturing process has become one of the serious issues because it may become cause of overheat such as lithium-ion batteries, flat panel displays, and so on. Therefore, a study on detecting method of the tiny metals is a significant issue. A combination of high-frequency induction heating and thermal detection method is one of the useful approaches. In this paper, MHz-frequency GaN inverter based IH system is built and tested to verify heating size limitation of the tiny metals. Furthermore, the validity of the proposed method to detect the tiny metals by proposed IH thermal technique is evaluated and discussed in detail.

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Language：English   Publisher：The Institute of Electrical Engineers of Japan  

This paper proposes a universal large-capacity capacitor simulator. The proposed simulator consists of a main chemical capacitor and three-leg IGBTs. One leg of the IGBTs acts as a bidirectional dc-dc converter. The other two legs are used for a single-phase PWM rectifier. In the capacitor-charging operation, the bidirectional dc-dc converter is used as a boost converter. Most of the power supplied by the load is supplied to the utility through the single-phase PWM rectifier. In the capacitor-discharging operation, the bidirectional dc-dc converter acts as a buck converter. Most of the power supplied to the load is from the utility through the single-phase PWM rectifier. A new control method, which can perform as an inner-series resistor in a supercapacitor (SC), is also proposed for an SC simulator. The basic principle of the proposed capacitor simulator is discussed in detail. The validity and high applicability of the proposed large-capacity capacitor simulator are confirmed using PSIM software. A prototype experimental model is constructed and tested. The experimental results demonstrate that the proposed capacitor simulator acts both as an ideal large-capacity capacitor and as an SC with an inner-series resistor.

DOI： 10.1541/ieejjia.2.204

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This paper proposes a starting method of the harmonic current compensator using a hybrid active filter for wind power generation systems. The active filter (AF) in the proposed method of the hybrid power filter behaves as a resistor and reactive power compensator to suppress the inrush current and leading currents for the passive filter (PF) under the starting condition. The basic principle of the proposed starting method is discussed, and then confirmed by digital computer simulation using PSCAD/EMTDC. Simulation results demonstrate that the proposed starting method can overcome the inrush and leading currents for the PF, building up the DC capacitor voltage of the AF. IEEJ Trans 2011 DOI: 10.1002/tee.21815

DOI： 10.1002/tee.21815

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

This paper proposes a new topology for a current balancer with half-bridge inverters in single-phase three-wire distribution systems. Two half-bridge inverters are connected to the sources. The midpoint of the two capacitors on the DC-side is connected to a neutral line. The two half-bridge inverters function as a current balancer for single-phase three-wire distribution systems by exchanging the active and reactive power on each feeder through the two DC capacitors. The third leg functions as a DC-capacitor-voltage balancer for two DC capacitors connected to the half-bridge inverters. Thus, balanced source voltages and currents are obtained on the secondary side on the pole-mounted distribution transformer with balanced DC-capacitor voltages. The basic principle of the proposed current balancer is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results show that balanced source voltages and currents are obtained on the secondary side on the pole-mounted distribution transformer with balanced DC-capacitor voltages. (C) 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(4): 38-46, 2012; Published online in Wiley Online Library (wileyonlinelibrary. com). DOI 10.1002/eej.22277

DOI： 10.1002/eej.22277

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

We have been proposed the time-sharing high-frequency resonant soft-switching inverter for IH cooking appliances which is composed of two single-IGBT multiple-resonant inverter cells. Until now, the proposed inverter has been feasibly evaluated by the experimental point of view. In this paper, possibility of the minimization of the circuit volume by coupling of two inductors is discussed from theoretical way.

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper proposes a strategy based on constant dc-capacitor voltage control for a current balancer in single-phase three-wire distribution systems. The proposed control strategy involves the use of only the constant dc-capacitor voltage control block commonly used in active power conditioners for the calculation of the compensation current. No calculation block is required to obtain the reactive and unbalanced-active components. Thus, we provide the simplest possible control strategy for the current balancer. The basic principle of the proposed control method is discussed in detail and its validity, which is confirmed by a digital computer simulation using PSIM software, is shown. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents with a power factor of unity are obtained on the secondary side of a pole-mounted distribution transformer while unbalanced load current conditions with a lagging power factor are retained.

DOI： 10.1541/ieejias.132.581

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This paper proposes a constant DC voltage control-based strategy for an active power quality compensator (APQC) used in electrified railways. The proposed strategy consists of only an I-PD-based constant DC capacitor voltage control with an added moving-average type low-pass filter (LPF). The added LPF improves the response of the constant DC capacitor voltage control for the APQC. Thus we offer the simplest control method for the APQC used in electrified railways with improved response. The basic principle of the proposed control strategy is discussed in detail, and then confirmed by digital computer simulation using the PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents with unity power factor are obtained on the primary side of the Scott transformer in the traction substation systems, improving the response by one-fourth as compared to that of the previously proposed control method. (C) 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

DOI： 10.1002/tee.21733

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Language：Japanese   Publisher：The Japan Institute of Power Electronics  

This paper represents the practical evaluations of an improved time-sharing high-frequency resonant soft-switching inverter for all metal induction heating (IH) cooking appliances. By introducing inductor coupling technology, the number of the circuit components and a physical volume of the circuit can be reduced. A design procedure of the coupling inductor is discussed in detail. Furthermore, two IH power regulation sequences; phase shifted PWM and PAM are compared to the viewpoint of the power conversion efficiency.

DOI： 10.5416/jipe.38.141

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In tandem with the penetration of PH V as well as EV, contact-less power supply system in parking towers have become important subjects. In parking towers, EV and PHV are charged on the traveling pallets, supply power is to be transmitted from the building to travelling pallets. In this paper, high-frequency link AC-AC converter for contact-less power supply system in parking tower is newly proposed and its basic operation and performance have been demonstrated from computer aided simulation and experiment.

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In this paper, we propose a smart charger for electric vehicles (EVs) with a power quality compensator. The proposed smart charger consists of four-leg IGBTs. Three legs are used for a single-phase full-bridge-based PWM rectifier, which converts power from ac to de during the battery-charging operation, or from de to ac during the battery-discharging operation. This PWM rectifier can compensate reactive and unbalanced active currents on single-phase three-wire distribution systems because the third leg is connected to the neutral line of singlephase three-wire distribution feeders. The fourth leg is used as a bidirectional dc-de converter for battery-charging and discharging operations. The three-leg PWM rectifier uses only constant dc-capacitor voltage control, which is commonly used in active power line conditioners. Thus, the authors have developed the simplest possible control method for a single-phase power quality compensator. The basic principle of the proposed smart charger is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents are obtained on the secondary side of the pole-mounted distribution transformer for battery-charging and discharging operations.

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In this paper, we propose the control method of a peak shaving system for an electric injection molding machine (EIMM). The peak power shaver consists of a multiphase bidirectional dc-dc converter and supercapacitors (SCs), and is connected to a dc link of the inverter fed injection motor drive system of the EIMM. In the proposed control method, electric power is stored in the SCs through the multiphase bidirectional dc-dc converter with a PWM rectifier while the injection motor is at rest. When the injection motor is accelerating, the stored power in the SCs together with the power from the distribution feeders is supplied to the injection motor. Thus, the peak power can be shaved. The basic principle of the proposed control method is discussed in detail, then confirmed by digital computer simulation and experimental setup. The simulation and experimental results demonstrate that the peak power is shaved by 70% using the peak power shaving system.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In tandem with the penetration of PHV as well as EV, wire-less power supply system in parking towers have become important subjects. In parking towers, EV and PHV are charged on the traveling pallets, supply power is to be transmitted from the building to travelling pallets. In this paper, high frequency link AC-AC converter for non-contact power supply system in parking tower is newly proposed and its basic operation performance have been demonstrated from computer aided simulation and experiment.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper represents the practical evaluations of time-sharing high-frequency resonant soft-switching inverter composed of two multi-resonant sub inverter cells in parallel for common series resonant load for all metal induction heating (IH) cooking appliances. Together with a fixed switching frequency resonant current, IH power regulation is carried out by phasor angle control scheme with phase-shifted PWM scheme. In particular, this high-frequency multi-resonant inverter can efficiently operate under the conditions of load resonant frequency changing mode; frequency doubler mode (100 kHz) for low resistivity metal IH loads and fundamental switching frequency mode (50 kHz) for high resistivity metal IH loads, respectively. The feasible performance of the time-sharing high-frequencys inverter are demonstrated and discussed in detail.

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper proposes a new topology for a current balancer with half-bridge inverters in single-phase three-wire distribution systems with a three-leg inverter. Two half-bridge inverters are connected to the sources. The midpoint of two capacitors on the DC-side is connected to a neutral line. The two half-bridge inverters perform a current balancer for single-phase three-wire distribution systems by exchanging the active and reactive power on the each feeder through the two DC-capacitors. The third-leg performs a DC-capacitor-voltage balancer for the two DC-capacitors connected to the half-bridge inverters. Thus, balanced source voltages and currents are obtained on the secondary-side on the pole-mounted distribution transformer with balanced DC-capacitor voltages. The basic principle of the proposed current balancer is discussed in detail, and then, confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results show that balanced source voltages and currents are obtained on the secondary-side on the pole-mounted distribution transformer with balanced DC-capacitor voltages.

DOI： 10.1541/ieejias.131.880

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In this paper, a novel type time-sharing high-frequency resonant soft-switching inverter composed of combining two-phase multi-resonant sub inverter cells in parallel for common series resonant tank load is demonstrated originally for all metal induction heating cooking appliances, together with a fixed output frequency resonant current phasor angle control scheme by phase-shifted PWM which is suitable for high frequency power regulation. In particular, this high-frequency multiresonant inverter with lossless snubbing capacitors for ZVS can efficiently operate under the conditions of load resonant frequency changing mode; frequency doubler mode(100kHz) and switching frequency mode(50kHz) for low resistivity metal IH and high resistivity metal IH loads, respectively. The feasible operating performances of experimental setup implementation are evaluated and discussed in detail. The practical effectiveness of this high frequency resonant inverter is confirmed for all metal IH cooking appliances on the basis of simulation and experimental results.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Wide-band-gap semiconductors, such as gallium nitride (GaN) and silicon carbide (SiC), are expected to be used as materials for new switching devices with low loss and high switching speed. The authors have recently developed a GaN-based high-electron-mobility-transistor (HEMT) for application to power electronics. In this paper we present models of a GaN-based transistor and Schottky barrier diode (SBD) for a simulation program with integrated circuit emphasis (SPICE). The results of the SPICE simulation show that the static and dynamic characteristics of GaN- based devices are precisely simulated by the SPICE models. The application of a GaN-based device to a single-phase AC-AC direct converter results in a reduction of power loss of over 30% compared with a silicon-based one.

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Language：Japanese   Publisher：パワーエレクトロニクス学会  

DOI： 10.5416/jipe.36.168

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DOI： 10.5416/jipe.36.187

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DOI： 10.5416/jipe.36.190

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This paper proposes a half-bridge inverter based current balancer in single-phase three-wire distribution systems with the reduced dc capacitors. The proposed current balancer can use a 6-in-1 IGBT module. Two legs perform a half-bridge inverter based current balancer, which compensates the reactive and unbalanced active components on the source-side. The third-leg performs a power de-coupler with a dc-capacitor voltage balancer. This power de-coupler sinks the power fluctuation, which flows into the dc capacitors, caused by the unbalanced conditions of two half-bridge inverters. Thus the capacity of the dc capacitors of the half-bridge inverter based current balancer can be dramatically reduced as compared to those of the previously proposed current balancer. The basic principle of the proposed half-bridge inverter based current balancer with the reduced dc capacitors is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that the balanced source currents are obtained on the secondary-side of the pole-mounted distribution transformer, reducing the capacity of the dc capacitors of the half-bridge inverter based current balancer.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In tandem with the penetration of EV, PHV, non-contact power supply system in parking towers have become important subjects. In parking towers, EV and PHV are charged on the traveling pallets, supply power is to be transmitted from the building to travelling pallets. In this paper, high frequency link AC-AC converter for non-contact power supply system in parking tower is newly proposed and its performance have been demonstrated from computer aided simulation and experiment.

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

DOI： 10.1541/ieejias.131.NL3_4

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Language：Japanese   Publisher：The Japan Institute of Power Electronics  

In this paper, a multi output high frequency soft switching inverter topology is presented for home use IH cooking appliances. The proposed inverter system is comprised of simple power circuitry and unique control scheme. The detailed analysis shows that the proposed inverter has low harmonic distortion, low switching losses and wide output powerrange. A detailed PWM procedure is illustrated as well. Through simulation and experimental results, the proposed IH system is verified.

DOI： 10.5416/jipe.36.103

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This paper proposes a universal large-capacity capacitor simulator. The proposed simulator consists of a main electrolytic capacitor and three-leg IGBTs. One leg of the IGBTs acts as a bidirectional dc-dc converter. The other two legs are used for a single-phase PWM rectifier. In the capacitor-charging operation, the bidirectional dc-dc converter is used as a boost converter. Most of the power supplied by the load is injected to the utility through the single-phase PWM rectifier. In the capacitor discharging-operation, the bidirectional dc-dc converter acts as a buck converter. Most of the power supplied to the load is from the utility through the single-phase PWM rectifier. A new control method, which can perform an inner-series resistor in a supercapacitor (SC), is also proposed for an SC simulator. The basic principle of the proposed capacitor simulator is discussed in detail. The validity and high applicability of the proposed large-capacity capacitor simulator are confirmed using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that the proposed capacitor simulator acts both as an ideal large-capacity capacitor and as an SC with an inner-series resistor.

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This paper proposes a half-bridge inverter based Active Power Quality Compensator (APQC) with a DC voltage balancer for electrified railways. The APQC is composed of three-leg structured power devices with two common DC capacitors. The first two legs perform as two half-bridge inverters to generate compensation currents and the third-leg is used for DC voltage balancer. The first-leg is connected to β-phase and the second-leg is connected to α-phase. Two DC capacitors are connected in series and midpoint is grounded. These two half-bridge inverters exchange and balance active power for two feeders through two common DC capacitors and compensate reactive and harmonic components of the distorted load currents. The third-leg controls two common DC capacitors to balance voltage level of each other. Using proposed APQC, the primary side of Scott transformer attains balanced and sinusoidal source currents. The principle and control algorithm of proposed a half-bridge inverter based APQC is discussed in detail. The proposed APQC is confirmed by both the PSIM computer simulation software and prototype experiment system. Simulation results show that the proposed APQC can achieve balanced and sinusoidal source currents in secondary side of Scott transformer. © 2011 IEEE.

DOI： 10.1109/PEDS.2011.6147244

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This paper deals with two control strategies for the active power line conditioners in single-phase circuits. The first one is a constant dc capacitor voltage control based strategy, which is commonly used in the active power line conditioners. Any detection blocks of the fundamental active, reactive, and harmonic components are not necessary in this method. Thus we offer the simplest way to compensate the fundamental reactive and harmonic currents on the source-side. The other is a reactive power control based strategy, which is with the correlation and cross-correlation coefficients between the feeder voltage and load current. Controlling the detected fundamental reactive component with the cross-correlation coefficient on the source-side reduces the capacity of the PWM inverter, which performs the active power line conditioners. The basic principles of the proposed control strategies are discussed in detail, and then applied to the single-phase active power line conditioners in single-phase based distribution systems. These sigle-phase distributin systems are used in the single-phase three-wire systems and electrified railways. The validity and excellent practicability of the proposed control strategies are confirmed by experimental results. © 2011 IEEE.

DOI： 10.1109/ICPE.2011.5944516

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In recent years, kinetic energy storage systems with electric double layered capacitor (EDLC) bank have been widely studied and developed for the fuel cell electric vehicles(FCEV). In this paper, a full-bridge/push-pull inverter based isolated bi-directional DC-DC soft switching converter for EDLC interface is proposed. The DC-DC converter mentioned here has the great advantage that the number of the switching power devices can be reduced compared to the conventional full-bridge/full-bridge inverter based DC-DC converter. The lower conduction losses can be achieved by this advantage as well as cost reduction. Though, a non-negligible drawback of the full-bridge/push-pull inverter based DC-DC converter has been revealed that is high voltage stress caused by the voltage ringing through the lossless snubber capacitor and leakage inductance of the high frequency transformer. To eliminate this drawback, a low leakage transformer is implemented to the DC-DC converter. The computer aided simulation and the experimental results demonstrate that the adequacy of the proposed circuit and its voltage suppression technique. © 2011 IEEE.

DOI： 10.1109/PEDS.2011.6147304

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This paper proposes a mobile power for the Sectional Compact Emergency Shelter (SCES), which is used under the great disaster. The proposed mobile power consists of the Fuel Cells (FCs), photovoltaic cells (PVs) and lithium-ion rechargeable batteries. This mobile power is constructed in a container car. Therefore, the constructed mobile power is easily moveable and constructible with the SCESs. The authors have named it a "ubiquitous power". The FCs in the ubiquitous power can supply electrical power and waste-heated water. The waste-heated water can be used to the SCESs for a floor heating in winter. The lithium-ion rechargeable batteries level the difference between generated power and consumed power in the SCESs. The number of the SCESs, which proposed one ubiquitous power can supply power continuously, is decided considering both the depth of discharge (DOD) of the batteries and the thermal energy of the waste-heated water from the FCs. It is shown that proposed one ubiquitous power can supply twenty SCESs in winter in Japan. © 2011 IEEE.

DOI： 10.1109/PEDS.2011.6147285

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper proposes a new control method for the previously proposed large-capacity capacitor simulator, which can perform an inner series resistor of the EDLCs. In the proposed large-capacity capacitor simulator, one of three legs performs a bi-directional dc-dc converter. The others are used for a single-phase PWM rectifier. In the charging operation of the proposed large-capacity simulator, one-leg is used as a boost converter. Most power, which is stored in the proposed simulator, is injected to the utility through the PWM rectifier. In the discharging operation, the one-leg performs a buck converter. Most power, which is supplied to the load, is from the utility through the PWM rectifier. Thus the proposed simulator performs a large-capacity capacitor with an inner resistor in both charging and discharging operations. The basic principle of the proposed simulator is discussed in detail. The validity and excellent practicability of the proposed control method for the large-capacity capacitor simulator are confirmed using PSIM software.

DOI： 10.1541/ieejias.130.1189

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This paper deals with applying the constant dc voltage control based algorithm to the current balancer in single-phase three-wire secondary distribution systems. The power flows into a three-leg inverter, which performs the current balancer, are discussed, and then we show that only the reactive power flows into the three-leg inverter. This demonstrates that the required-capacity of the dc capacitor can be reduced as compared to that of the active power quality compensator used in the electrified railways. This reduced-capacity dc capacitor results in the rapid and stable balancing. The basic principle of the proposed method is discussed in detail, and then confirmed by digital computer simulation. Digital computer simulation results demonstrate that the balanced source currents with unity power factor are obtained remaining the unbalanced load currents conditions.

DOI： 10.1541/ieejias.130.935

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This paper presents a novel Zero Current Switching (ZCS)-PWM controlled half-bridge DC-DC converter with High-Frequency (HF)-link. The newly-proposed soft switching DC-DC converter consists of a multi-resonant half-bridge HF-isolated inverter controlled by an asymmetrical PWM scheme and a center-tapped diode rectifier with a choke input filter. In order to attain the wide range of soft-commutation under the condition of constant switching frequency, the single Active Edge-Resonant Cell (AERC) that is composed of a lossless inductor and a switched resonant capacitor is originally employed for the half-bridge inverter arm, providing and assisting ZCS operations in the switching power devices. The ZCS-PWMDC-DC converter treated here is evaluated in experiments using the 800 W-55 kHz prototype. The practical effectiveness of the proposed soft switching DC-DC converter is actually demonstrated and discussed with the experimental results under open loop and closed loop configurations. Finally, the feasibility of the DC-DC converter topology is discussed from the view points of the high efficiency and high power density.

DOI： 10.1541/ieejias.130.605

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This paper proposes a new method of starting the hybrid power filter for wind power generation systems with soft starter. In the proposed method, an active filter of the hybrid power filter behaves a resistor for the source current under the starting condition. Thus the inrush phenomena of the passive filter are perfectly suppressed. The basic principle of the proposed starting method is discussed, and then confirmed by digital computer simulation using PSCAD/EMTDC. Simulation results demonstrate that the proposed starting method can overcome the inrush currents for the passive filter, building up the dc voltage of the active filter.

DOI： 10.1541/ieejias.130.574

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In recent years, consumer induction-heating (IH) cooking appliances have grown increasingly popular because of their easy cleaning, high efficiency, safety, and controllability. IH food cooking system for consumer home use are indispensable to heat various metallic pans, such as aluminum, copper, stainless steel, and iron cast for further diffusing. Furthermore, these appliances have to satisfy the utility AC grid harmonics regulations of IEC61000-3-2. To meet these requirements, this paper proposes a two-stage soft-switching high-frequency inverter with simple PFC function that is suitable for consumer IH cooking appliances. The proposed system comprises a soft-switching chopper based boost PFC converter with passive snubber and phase-shifted PWM controlled ZVZCS high-frequency inverter. In order to satisfy the utility AC grid current harmonic regulations, a simple PFC control technique with discontinuous current mode is introduced. This technique as well as the fundamental operating performances of the proposed IH system is tested. The effectiveness of proposed IH system is substantially proved from a practical point of view on the basis of the experimental results.

DOI： 10.1541/ieejias.130.450

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

This paper presents a bidirectional DC-DC converter suitable for low-voltage super capacitor-based electric energy storage systems. The DC-DC converter presented here consists of a full-bridge circuit and a current-fed push-pull circuit with a high frequency (HF) transformer-link. In order to reduce the device-conduction losses due to the large current of the super capacitor as well as unnecessary ringing, synchronous rectification is employed in the super capacitor-charging mode. A wide range of voltage regulation between the battery and the super capacitor can be realized by employing a Phase-Shifting (PS) Pulse Width Modulation (PWM) scheme in the full-bridge circuit for the super capacitor charging mode as well as the overlapping PWM scheme of the gate signals to the active power devices in the push-pull circuit for the super capacitor discharging mode. Essential performance of the bidirectional DC-DC converter is demonstrated with simulation and experiment results, and the practical effectiveness of the DC-DC converter is discussed.

DOI： 10.6113/JPE.2010.10.1.027

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Language：Japanese   Publisher：The Japan Institute of Power Electronics  

This paper proposes a new starting method of the harmonic current compensator using the hybrid active filter for wind power generation systems. In the proposed method, an active filter of the hybrid power filter behaves a resistor and reactive power compensator to suppress the source currents oscillation and leading currents under the starting conditon. The basic principle of the proposed starting method is discussed, and then confirmed by digital computer simulation using PSCAD/EMTDC. Simulation results demonstrate that the proposed starting method can overcome the inrush and phase-leading currents, building up the dc capacitor voltage of the active filter.

DOI： 10.5416/jipe.35.129

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Harmonic currents generated from the power electric equipment such as IH cooking heaters involve harmful influences to the other equipments connected to the utility grid. As for the IH cooking appliances, adding the PFC converter to the input stage of IH cooking heater is one of the practical solutions to suppress harmonic current influences. In this paper, two operation modes; DCM and CCM for the PFC converter are compared and tested from the view points of magnetic volume and power quality to clarify the suitable operation mode for consumer IH cooking appliance.

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This paper presents performance characteristics of a novel soft switching three-phase utility frequency AC (UFAC) to high frequency AC (HFAC) direct power converter with PFC function for industrial induction heating (IH) applications. The proposed "simple three-phase system" consists of a single-phase UFAC to HFAC direct converter unit in each phase, three-phase low pass filter and three-phase IH load. This power converter can regulate the output power under a condition of the constant frequency zero voltage soft switching (ZVS) commutation principle on the basis of unique asymmetrical PWM control scheme. In this paper, high frequency IH output and utility AC current characteristics of three-phase direct converter supposed 5kW class IH system are demonstrated and evaluated from computer aided simulation with PSIM software. Furthermore, basic performance analysis of the single-phase converter unit is evaluated from an experimental point of view.

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In this paper, an energy recovery system with Electric Double-Layer Capacitor (EDLC) for motor drive systems is presented. The basic principle of the proposed control scheme and the energy losses consumed in an energy recovery system are discussed in detail. Digital computer simulation results indicate that the energy-saving effect by the injection molding machine was improved by 49%.

DOI： 10.1541/ieejias.130.713

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This paper proposes a new half-bridge based inverter for the DC micro-grid. The proposed topology consists of a three-leg inverter, which can be constructed by an intelligent power module (IPM). Using the IPM gives cost-effective inverters for the dc micro-grid. In the proposed half-bridge based topology with a three-leg inverter, two legs are used for two single-phase half-bridge inverters, where the neutral line is grounded. The third leg performs a power de-coupler balancing the mean value of two dc capacitor voltages. This power de-coupler exchanges the energies between two dc capacitors connected to two single-phase half-bridge inverters. Thus the capacity of the dc capacitors of the half-bridge inverters can be dramatically reduced as compared to those of the previously proposed half-bridge inverters for the dc micro-grid. The basic principle of the proposed half-bridge based inverter is discussed in detail, and then confirmed by digital computer simulation using PSIM software. Simulation results demonstrate that the capacity of the dc capacitors is reduced by one fortieth as compared to those of the previously proposed half-bridge based inverter used in the dc micro-grid.

DOI： 10.1109/ECCE.2010.5617983

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, a multi output high frequency soft switching inverter topology is presented for home use IH cooking appliances. The proposed inverter system is comprised of simple power circuitry and unique control scheme. The detailed analysis shows that the proposed inverter has low harmonic distortion, low switching losses and wide output power range. A detailed PWM procedure is illustrated as well. Through simulation and experimental results, the proposed IH system is verified.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Harmonic currents in the utility side generated from the power electric equipment such as IH cooking heaters involve harmful influences to the other electrical applications. To suppress harmonic influences, adding the PFC converter to the input stage of IH cooking heater is one of the practical solutions. In this paper, two operation modes; DCM and CCM for the PFC converter are compared and tested from the view points of magnetic volume of the boost and filter inductors, source current harmonics suppression, power conversion efficiency and input power factor to clarify the suitable operation mode for home-use IH cooking appliance.

DOI： 10.5416/jipe.35.114

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This paper proposes a new half-bridge inverter based active power quality compensator (APQC) for electrified railways with a three-leg inverter. The first-leg is connected to α-phase, and the second-leg is connected to β-phase. The midpoint of two capacitors on the dc side is connected to the ground line. These two half-bridge inverters exchange the active power on the each feeder each other through two dc capacitors, and compensate the negative-sequence and harmonic components of the load currents. The third-leg performs a dc voltage balancer for two dc capacitors connected to the half-bridge inverters. Thus the balanced and sinusoidal source voltages and currents factor are attained on the primary side of the Scott transformer with the balanced dc capacitor voltages. The basic principle of the proposed half-bridge inverter based APQC is discussed in detail, and then confirmed by digital computer simulation using PSIM software. Simulation results demonstrate that the balanced source currents with the unity power factor are obtained on the primary side the Scott transformer in the traction substation systems balancing two dc capacitor voltages. © 2010 IEEE.

DOI： 10.1109/IPEC.2010.5543371

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

This paper proposes a new current balancer in single-phase three-wire secondary distribution systems using the correlation coefficients. The components of the load currents correlative to the primary side voltage waveform, which correspond to the active currents, are detected in each feeder, then the nonactive and unbalanced-active components are compensated on the source side. The balanced currents with unity power factor are obtained in each feeder. The basic principle of the proposed method is discussed in detail, and then confirmed by digital computer simulation. A prototype experimental system is constructed and tested. Experimental results demonstrate that the balanced source currents with unity power factor are obtained in spite of unbalanced load currents. (C) 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(1): 50-58, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20843

DOI： 10.1002/eej.20843

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper proposes a new control method for reducing the capacity of an active power quality compensator with a three-leg inverter used in electrified railways. In the proposed control method, the fundamental reactive and unbalanced-active components of the load currents are detected. The non-active and unbalanced-active components are compensated on the source side with the fundamental reactive power control. This reactive power control reduces the capacity of the three-leg inverter, which performs the active power quality compensator. The basic principle of the proposed control method is discussed in detail, and then confirmed by digital computer simulation using the PSIM software. A reduced-scale experimental model is constructed and tested. Experimental results demonstrate that the balanced sinusoidal source currents with the power factor of 0.9 are obtained, reducing the capacity of the three-leg inverter by 13% as compared to the already proposed control method.

DOI： 10.1541/ieejias.129.907

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper proposes a large-capacity capacitor simulator consisting of a chemical capacitor and three-leg converter. One of three legs performs a bi-directional chopper. The others are used for a PWM rectifier. In the charging mode the most of the power stored in the chemical capacitor is injected to the utility through the PWM rectifier. In the discharging mode the power is supplied to the chemical capacitor side from the utility through the PWM rectifier. Thus the proposed simulator performs a large-capacity capacitor. The basic principle of the proposed simulator is discussed in detail. A prototype experimental model is constructed and tested. Experimental results demonstrate the validity and excellent practicability of the proposed simulator.

DOI： 10.1541/ieejias.129.852

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

This paper proposes a novel and simple control method for the active power quality compensators (APQCs) used in electrified railways. The proposed method uses only the constant dc capacitor voltage control block, which is commonly used in the APQCs. No detection blocks of the harmonic, reactive, and negative-sequence components are necessary. Thus we offer the simplest way to compensate the harmonic, reactive, and negative-sequence currents on the primary side of the Scott transformer in the traction substation. The basic principle of the proposed control method is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that the balanced source currents with the unity power factor are obtained on the primary side with the proposed control method, which uses only the constant dc capacitor voltage control. (C) 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

DOI： 10.1002/tee.20428

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In recent years, power electronic energy storage systems using Super capacitor bank have been widely studied and developed for the electronic vehicles. In this paper, a full-bridge/centertapped push-pull circuit with active clamp-based soft switching bidirectional DC-DC converter and its control method are presented and discussed. From the results of basic experimental demonstration, the proposed system is able to perform adequate charging and discharging operation between low-voltage high-current super capacitor side and high-voltage low-current side with drive train and main battery. In addition, RCDi snubber losses appeared in the basic circuit topology are drastically reduced by ZCS/ZVS operation with the assistance of newly added active clump circuit, as well as ZVS operation with lossless snubber capacitor in high-voltage primary side.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Harmonic currents generated from the power electric equipment such as IH cooking heaters involve harmful influences to the other equipments connected to the utility grid. As for the 111 cooking appliances, adding the PFC converter to the input stage of IH cooking heater is one of the practical solutions to suppress harmonic current influences. In this paper, two operation modes; DCM and CCM for the PFC converter are compared and tested from the view points of magnetic volume and power quality to clarify the suitable operation mode for consumer IH cooking appliance.

DOI： 10.1109/IECON.2009.5414802

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper presents performance characteristics of a novel soft switching three phase utility frequency AC (UFAC) to high frequency AC (HFAC) direct converter with PFC function for industrial induction heating and melting applications The proposed "simple three phase system" consists of single phase UFAC to HFAC direct converter in each phase, three phase low pass filter and IH load. This power converter can regulate the output power under a condition of a constant frequency zero voltage soft switching (ZVS) commutation principle on the basis of unique asymmetrical PWM control scheme. In this paper, the input and output characteristics of proposed direct power converter on the basis of computer aided simulation are illustrated and discussed. Furthermore, Y-connected 3 phi working coils for IH load with the balanced coupling coefficient in each phase is designed and evaluated from an experimental point of view.

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This paper is mainly concerned with a newly proposed stand-alone photovoltaic (PV) generation system. This system permanently drives the load with the capacity of about several W, such as the security camera devices, street light and outdoor measurement system, by the electric power by the solar cell. Its fundamentals of operating performances are illustrated and evaluated on the experimental results. Its effectiveness is proved on the basis of the experimental results from a practical point of view. Because of its possibility to drive without the electric power from the commercial power line, this system is especially effective in the out-door use where the commercial electric power line is not supported. ©2009 IEEE.

DOI： 10.1109/IECON.2009.5415035

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This paper proposes a universal large-capacity capacitor simulator consisting of a chemical capacitor and three-leg converter. One of three legs performs a bi-directional dc-to-dc converter. The others are used for a single-phase PWM rectifier. In the charging operation of the proposed large-capacity simulator, one-leg is used as a boost converter. Most power, which is stored in the proposed simulator, is injected to the utility through the PWM rectifier. In the discharging operation, the one-leg performs a buck converter. Most power, which is supplied to the load, is from the utility through the PWM rectifier. Thus the proposed simulator performs a large-capacity capacitor in both charging and discharging operations. The basic principle of the proposed simulator is discussed in detail. For an EDLC simulator operation, series resistors should be considered. A new control method, which performs the series resistor, is also proposed. The validity and excellent practicability of the proposed large-capacity capacitor simulator are confirmed using the PSIM software.

DOI： 10.1109/PEDS.2009.5385902

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes a constant dc voltage control based strategy for an active power quality compensator (APQC) used in electrified railways. The proposed strategy consists of only an I-PD based constant de capacitor voltage control with an added moving average type low-pass filter (LPF). The added LPF improves the response time of the constant dc capacitor voltage control for the APQC. Thus we offer the simplest control method for the APQC used in electrified railways with the improved response time. The basic principle of the proposed control strategy is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A proto-type experimental model is constructed and tested. Experimental results demonstrate that the balanced source currents with the unity power factor are obtained on the primary side the Scott transformer in the traction substation systems, improving the response time by one-fourth as compared to that of the previously proposed control method.

DOI： 10.1109/IECON.2009.5415311

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

This paper is mainly concerned with a high frequency soft-switching PWM inverter suitable for consumer induction heating systems. The proposed system is composed of a soft switching chopper based boost PFC converter stage with passive snubber and phase shifted PWM controlled full bridge ZVZCS high frequency inverter stage. Its fundamental operating performances are illustrated and evaluated in the experimental results. Its effectiveness is substantially proved on the basis of the experimental results from a practical point of view.

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper proposes a novel control method for the active power quality compensator used in electrified railways. In the proposed method, only the constant dc voltage control is used to compensate the non-active and unbalanced active currents on the secondary side of the Scott transformer. Any schemes to detect the reactive and harmonic currents are not needed. Thus we can provide the simplest way to improve the power quality in electrified railways. The basic principle of the proposed control method is discussed. The validity and excellent practicability are confirmed by digital computer simulation using PSIM soft ware.

DOI： 10.1541/ieejias.128.145

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper proposes a new control method of the current balancer for single-phase three-wire secondary distribution systems using the correlation and cross-correlation coefficients. The components of the load currents correlative and cross-correlative to the primary side voltage waveform, which correspond to the active and reactive currents, are detected in each feeder, then the reactive and unbalanced-active components are compensated on the source side. The balanced currents with the variable power factor are obtained in each feeder. The basic principle of the proposed method is discussed in detail, and then confirmed by digital computer simulation. A proto-type experimental system is constructed and tested. Experimental results demonstrate that the balanced source currents with the power factor of 0.9 are obtained in spite of unbalanced load currents.

DOI： 10.1541/ieejias.128.34

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This research is mainly concerned with a stand-alone photovoltaic (PV) generation system for low power DC applications placed where the commercial AC grid connection is not supported. In this paper, basic and improved circuit topologies and the control schemes of stand-alone photovoltaic generation system are proposed. To prevent battery from deep discharge, Electric Double Layer Capacitor (EDLC) is incorporated into the proposed systems as combined energy storage device in parallel with conventional lead battery. The fundamentals of operating performances and effectiveness of proposed stand-alone PV system are illustrated and evaluated on the basis of a practical point of view.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD PUBLISHING CORPORATION  

This paper presents a high-efficiency-high power density one stage ZVS-PWM single-ended push-pull (SEPP) high frequency Inverter with new PFC functional scheme. This high-frequency resonant series load resonant inverter with lossless snubbing capacitors is composed of a passive PFC converter operating at one diode conducting bridge circuit and asymmetrical ZVS-PWM high frequency resonant direct inverter without the bulky electrolytic capacitor stage for boosted DC voltage smoothing. In addition, this one stage utility frequency AC (UFAC) to high frequency AC (HFAC) conversion circuit has only one diode conducting mode in the diode bridge rectifier with boost inductor. The operating principle of the one stage UFAC to HFAC series load resonant inverter with lossless capacitors is described by using the switching mode equivalent circuits in addition to the simulated operating voltage and current waveforms. The operating performances of this high-frequency ZVS-PWM resonant direct inverter with lossless snubbing capacitors are illustrated on the basis of simulation analysis which includes its UFAC-to-HFAC power regulation characteristics, soft switching operating range, UFAC side power factor characteristics and UFAC side line current harmonics characteristics by FFT analysis. In principle, the effectiveness of this UFAC-to-HFAC direct power frequency converter using IGBTs for consumer high-frequency IH appliances is evaluated and proved on the basis of simulation results.

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This paper presents a utility frequency AC (UFAC) to high frequency AC (HFAC) direct power frequency conversion pulse modulated conditioning circuit using bidirectional power switches. This power converter can efficiently operate under a principle of active zero voltage clamped soft commutation for consumer induction heating (IH) fixing roller for copy machine and printer. This HFAC direct power frequency converter defined as resonant high frequency PWM controlled power frequency converter using bidirectional switches is developed and evaluated in this paper for consumer IH fixing heat roller using industrial HFAC power supply. Its operating principle is described on the basis of switching mode equivalent circuits during switching one cycle period. It is evaluated on the basis of its simulation and experimental results on the performances of HFAC direct power frequency converter treated here including various duty factor control variable vs. HFAC power regulation characteristics as well as zero voltage soft switching ranges.

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This paper presents a novel soft-switching PWM utility frequency AC to high frequency (HF) AC power conversion circuit incorporating boost-active clamp single stage inverter topology. This power converter is more suitable and acceptable for cost effective HF consumer induction heating (IH) applications. Its operating principle and the operation modes are presented using the switching mode equivalent circuits in addition to the operating voltage and current waveforms. The operating performances of this high frequency inverter using the latest IGBTs are illustrated, which includes HFAC power regulation ranges and actual efficiency characteristics based on zero voltage soft switching (ZVS) operation ranges and the power dissipation analysis as compared with those of the previously developed high frequency inverter. In addition, a dual mode selected control scheme of this high frequency inverter based on a constant frequency asymmetrical pulse width modulation (PWM) and pulse density modulation (PDM) control scheme is discussed in this paper in order to extend the soft switching operation ranges and to improve the power conversion efficiency at the low power settings. This power frequency converter practical effectiveness is substantially proved on the basis of experimental results from practical design example.

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In this paper, the novel circuit topology of half-bridge soft switching PWM DC-DC power converter with a high frequency planar transformer link was presented. The operating principle and switching pattern of the half-bridge soft switching PWM DC-DC power converter described for 40 kHz, 36V and 400A output were illustrated and discussed for low voltage and large current output applications such as telecommunication and automotive applications. The power loss analysis of the proposed soft switching DC-DC power converter was discussed and evaluated as compared with hard switching PWM DC-DC power converter with a high frequency link. The practical effectiveness of the proposed DC-DC power converter operation under soft switching PWM scheme was actually proved from a practical point of view and the high efficiency and power density of this converter could be achieved on the basis of experimental results for low voltage and large current power supplies.

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A high frequency soft-switching PWM inverter with PFC function suitable for consumer IH cooking appliance is presented in this paper. The proposed system is composed of a soft switching chopper based boost PFC converter with passive snubber and phase shifted PWM controlled full bridge ZVZCS high frequency inverter. In order to meet the utility AC grid current harmonic regulation, a simple PFC control technique with discontinuous current mode is introduced and tested in addition to the fundamental operating performances of the proposed system. Effectiveness of proposed IH system is substantially proved on the basis of the experimental results from a practical point of view.

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A newly-developed zero current soft-switching (ZCS)-PWM cell-assisted asymmetrical half-bridge (AHB) DC-DC converter topology with a high frequency (HF) link is presented in this paper. The soft-switching half-bridge DC-DC converter consists of a PWM-controlled single-ended half-bridge HF inverter and a center-tapped rectifier linked by a HF transformer. In order to attain the wide range of ZCS commutation in the primary-side HF inverter, the active edge resonant snubber cell composed of a switched capacitor and a lossless inductor is adopted in the half-bridge leg, providing ZCS commutation for a wide range of output power under constant switching frequency. The operation characteristics of the proposed DC-DC converter are described, and its feasibility data is demonstrated and evaluated with simulation and experimental results.

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Publisher：The Japan Institute of Power Electronics  

In this paper, multi-resonant zero current soft switching (ZCS) -PWM single ended push pull (SEPP) high frequency inverter is newly demonstrated for consumer induction heating (IH) appliances. The proposed inverter circuit has a novel ZCS cell consisting of high side main switch with lossless inductor snubber and active edge-resonant commutation cell (AERCC). The AERCC consisting of auxiliary diode, auxiliary resonant capacitor, auxiliary resonant inductor and auxiliary switch in parallel with the high side main switch arm. In the newly proposed inverter, heating power of IH cooking heater is controlled continuously during all heating power range under a principle of ZCS. The operating principle and performance analysis of the newly proposed inverter with asymmetrical pulse width modulation (PWM) control scheme are described using equivalent circuits in switching mode. This high frequency inverter can regulate heating power continuously from 0.25kW to 2.74kW in experiment with asymmetrical PWM control scheme. Finally, compared with conventional ZVS-PWM-SEPP high frequency inverter with asymmetrical PWM scheme, its power conversion efficiency of is high enough even in at low power range. The feasible effectiveness and practicability of the high frequency inverter treated here are substantially proved on the basis of experimental results for consumer IH cooking heater.

DOI： 10.5416/jipe2003.34.0_103

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Publisher：The Japan Institute of Power Electronics  

DOI： 10.5416/jipe2003.34.0_226

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Language：Japanese   Publisher：The Japan Institute of Power Electronics  

This paper deals with stand-alone photovoltaic (PV) generation systems low power DC applications, where a combined energy storage device consisting of an acid battery and Electric Double Layer Capacitor (EDLC) to avoid the deep discharge of the acid battery. Two types of the stand-alone PV generation systems, with a conventional converters and soft-switching converter, are constructed and tested. Experimental results demonstrate that the conventional type is very simple, but a large capacity EDLC is needed because of low efficiency. Efficiency of the PV generation system with soft-switching converters is high compared with that of the conventional type, and reduces the capacity of the EDLC. The PV generation system with soft-switching converters is useful for practical applications.

DOI： 10.5416/jipe2003.34.0_143

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This paper proposes a novel and simple control method for an active power quality compensator (APQC) used in electrified railways. The proposed method consists of only constant dc capacitor voltage control, which is generally used in APQCs. No detection method for harmonic, reactive and negative-sequence components is necessary. Thus we offer the simplest way to compensate the harmonic, reactive and negative-sequence currents on the primary side of the Scott transformer in the traction substation. The basic principle of the proposed control method is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents with unity power factor are obtained on the primary side with the proposed control method, which uses only constant dc capacitor voltage control.

DOI： 10.1109/IECON.2008.4758004

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST ENGINEERING TECHNOLOGY-IET  

A novel symmetrical zero current switching (ZCS)-pulse width modulation (PWM) cells-assisted high-frequency transformer link DC-DC converter using insulated gate bipolar transistor (IGBT) modules is presented. The proposed soft switching scheme is based on the switched-capacitor and inductive snubber in the high-voltage side inverter, assisted by active switching of MOSFET synchronous rectifier in the secondary-side low-voltage converter stage. By introducing the ZCS-PWM snubber cells, soft switching commutation which is less sensitive to the current level through the IGBTs can be achieved under the wide output power ranges. The converter circuit topology and the ZCS snubber cell operation are examined and evaluated with simulation results, and the feasibility of the converter topology is verified by experiments using a 1.0 kW - 25 kHz prototype system.

DOI： 10.1049/iet-epa:20060508

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

This paper proposes a novel method of detecting the active and reactive currents in single-phase circuits using the correlation and cross-correlation coefficients in the time domain. The active current is detected using the correlation coefficient between the source voltage and load current waveforms, and the reactive current is detected using the cross-correlation coefficient. The basic principle of the proposed detection method is discussed, and the proposed method is applied to a previously proposed single-phase shunt active filter for consumer electronic equipment. Simulation and experimental results demonstrate the excellent practicability of the proposed detection method.

DOI： 10.1109/TPWRD.2007.905359

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In recent years, power electronic energy storage systems using super capacitor bank have been widely studied and developed for the electronic vehicles. In this paper, a full-bridge/centertapped push-pull with active clamp circuit based soft switching bidirectional DC-DC converter and its control method are presented and discussed. From the results of basic experimental demonstration, switching losses in the active switches are drastically reduced by ZCS/ZVS operation with the assistance of newly added active clump circuit, as well as ZVS operation with lossless snubber capacitor in high-voltage primary side.

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper proposes a novel detection method of active and reactive currents in single-phase circuits. This method uses only two multipliers and LPFs for detecting active and reactive currents with a PLL circuit. In the proposed method the fundamental active-reactive component in single-phase circuits can be detected by LPFs in the time domain like the instantaneous active-reactive power theory in three-phase circuits. The basic principle of the proposed detection method is discussed in detail, and then confirmed by digital computer simulation. Digital computer simulation results demonstrate that the proposed method can detect the active-reactive current in single-phase circuits in the time domain.

DOI： 10.1541/ieejias.127.538

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Language：Japanese   Publisher：The Japan Institute of Power Electronics  

A novel prototype of a soft-switching PWM DC-DC converter is presented in this paper. This converter consists of a half-bridge circuit assisted with an active edge resonant snubber for Zero Current Soft-switching (ZCS) commutation, and a current doubles rectifier linked with a high-frequency transformer. With the ZCS scheme and the circuit topology proposed here, the soft switching operation can be achieved for the wide range of output power under a constant switching frequency. The converter operation and characteristics are demonstrated with simulation results, and its feasibility is verified with experimental results using its 1.2kW-35kHz prototype.

DOI： 10.5416/jipe2003.33.0_157

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE, ELECTRON DEVICES SOC & RELIABILITY GROUP  

In recent years, power electronic energy storage systems using super capacitor bank have been widely studied and developed for the electronic vehicles. In this paper, a full-bridge/centertapped push-pull circuit with active clamp-based soft switching bidirectional DC-DC converter and its control method are presented and discussed. From the results of basic experimental demonstration, the proposed system is able to perform adequate charging and discharging operation between low-voltage high-current super capacitor side and high-voltage low-current side with drive train and main battery. In addition, RCDi snubber losses appeared in the basic circuit topology are drastically reduced by ZCS/ZVS operation with the assistance of newly added active clump circuit, as well as ZVS operation with lossless snubber capacitor in high-voltage primary side.

DOI： 10.1109/PESC.2007.4342018

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A novel zero current soft-swithing PWM half-bridge DC-DC converter topology is proposed in this paper. The newly proposed converter consists of a PWM-controlled half-bridge inverter and a current doubler rectifier linked with a high-frequency transformer. In order to attain the wide range of soft switching operation in the high voltage/low current primary side inverter, asymmetrical lossless snubbers composed by an actively-switched capacitor and lossless inductors are employed in the half-bridge arm, providing Zero Current Switching (ZCS) that is less sensitive to the magnitude of the input current. The operation characteristics of the proposed DC-DC converter are described, and its feasibility is demonstrated with simulation and preliminary experimental results.

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A novel zero current soft-switching PWM half-bridge DC-DC converter topology is proposed in this paper. The newly proposed converter consists of a PWM-controlled half-bridge inverter and a current doubler rectifier linked with a high-frequency transformer. In order to attain the wide range of soft switching operation in the high voltage/low current primary side inverter, asymmetrical lossless snubbers composed by an actively-switched capacitor and lossless inductors are employed in the half-bridge arm, providing Zero Current Switching (ZCS) that is less sensitive to the magnitude of the input current. The operation characteristics of the proposed DC-DC converter are described, and its feasibility is demonstrated with simulation and experimental results.

DOI： 10.1109/PESC.2007.4342081

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper proposes a new current balancer in single-phase three-wire secondary distribution systems using the correlation coefficients. The components of the load currents correlative to the primary side voltage waveform, which correspond to the active currents, are detected in each feeder, then the non-active and unbalanced-active components are compensated on the source side. The balanced currents with unity power factor are obtained in each feeder. The basic principle of the proposed method is discussed in detail, and then confirmed by digital computer simulation. A proto-type experimental system is constructed and tested. Experimental results demonstrate that the balanced source currents with unity power factor are obtained in spite of unbalanced load currents.

DOI： 10.1541/ieejias.127.675

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The oscillation voltage (Ebm) is an important parameter of the characteristic constant of a high power microwave generator. When Ebm could he made hi-h. it serves so as to improve the power conversion efficiency of a magnetron. Thus, the newly developed magnetron with 7% higher oscillation cut-off voltage Than the present conventional one is manufactured by Matsushita Electric Industrial Co.Ltd, In addition to this, the utility AC power line current reduced harmonic type direct inverter AC-DC power converter suitable and acceptable for driving this Magnetron is proposed in this paper. This direct high frequency inverter type soft switching PWM AC-DC converter has the voltage-boost function based on active clamp scheme with soft switching pulse modulation strategy topology. This paper describes a novel type active clamp AC-DC power converter circuit defined as direct high frequency inverter and the switching operation of this power converter is described and discussed on the basis of simulation and experimental results. The operating characteristics of this soft switching direct high frequency inverter type AC-DC power converter using IGBTs that incorporates the harmonic current improvement as well as power factor correction are evaluated and discussed front a practical point of view as compared with the conventional AC-DC power converter.

DOI： 10.1109/IECON.2007.4459958

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This paper presents a novel phase shifted ZVS-PWM high frequency load resonant inverter for electromagnetic induction fluid heating (IH) appliances. The proposed high frequency inverter can be achieved stable and efficient zero voltage soft commutation over a widely specified power regulation range from full power to low power by using an active auxiliary quasi resonant snubber. The steady state operating performance of this inverter is evaluated and discussed on the basis of simulation and experimental results for IH dual-packs heater (DPH) of compact fluid heating appliance. Finally, the effectiveness of IH application of the proposed high frequency inverter with auxiliary active quasi-resonant snubber is demonstrated from the practical point of view.

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This paper proposes a new current balancer for single-phase three-wire distribution feeders using a three-leg voltage-source PWM inverter, which is equivalent to a three-phase voltage source inverter. Intelligent Power Modules (IPMs) can be used for the proposed current balancer. Thus we can provide a cost-effective and small-volume current balancer. A new control method for the proposed current balancer employing correlation coefficients between the source voltage and load currents is also proposed. The basic principle of the proposed current balancer with the proposed control method is discussed in detail, then confirmed by digital computer simulation with PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents with unity power factor are obtained in spite of unbalanced load currents.

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This paper proposes a new method of compensating harmonic currents for wind power generation systems with the soft starter using a hybrid active filter. The hybrid active filter consists of single-tuned LC and small-rated active filters. The single-tuned LC filter absorbs the harmonic current while behaving as a phase-leading capacitor for the fundamental component. The small-rated active filter improves the compensation characteristics of the passive filter under the soft start of the constant-speed wind turbine. The required rating of the active filter can be reduced because the active filter does not supply the fundamental reactive current. The basic principle of the proposed compensation method is discussed, and then confirmed by digital computer simulation using PSCAD/EMTDC. Simulation results demonstrate that the waveform of the source current becomes sinusoidal under the soft start. The required rating of the active filter is about 8.5% of the induction generator rating. A new calculation method of THD with the detrending algorithm is proposed for the transient state. The THD of the source current is about 7.3% using the hybrid active filter.

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This paper is mainly concerned with a high frequency soft-switching PWM inverter suitable for consumer induction heating system. Proposed system is composed of soft switching chopper based voltage boost PFC input stage and phase shifted PWM controlled full bridge ZCZVS high frequency inverter stage. Its fundamentals of operating performances are illustrated and evaluated on the experimental results. Its effectiveness is substantially proved on the basis of the experimental results from a practical point of view.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

This paper presents the newly proposed hybrid resonant commutation bridge-leg link (HRCB) snubber circuit which can achieve zero voltage and zero current soft-switching commutation for single-phase and three-phase voltage source-type inverter, along with its unique features and operation principle. The circuit parameter design approach for the HRCB snubber circuit and the determination estimating scheme of the gate pulse timing processing which is more suitable and acceptable for single-phase and space voltage vector modulated three-phase voltage source inverter using the HRCB snubber circuit are described in this paper. In particular, the three-phase voltage source soft-switching inverter associated with the proposed HRCB circuits are evaluated and discussed from simulation and experimental viewpoints. The practical effectiveness of the HRCB snubber-assisted three-phase voltage source soft-switching inverter using IGBT power modules which is based on the instantaneous space voltage vector modulation is clarified on the output voltage waveform, actual efficiency of electromagnetic noise in comparison with three-phase voltage source-type conventional hard-switching inverter. (C) 2006 Wiley Periodicals, Inc.

DOI： 10.1002/eej.20111

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This paper proposes a new method of compensating harmonic currents under the soft start in wind power generation systems using the hybrid filter, which consists of a passive and small-rated active filters. For the fundamental component, the passive filter behaves a phase-leading capacitor. The small-rated active filter compensates the harmonic currents under the soft start. The basic principle of the proposed compensator is discussed, and then confirmed by digital computer simulation using PSCAD/EMTDC. Simulation results demonstrate that the source currents become sinusoidal waveforms under the soft start.

DOI： 10.1541/ieejias.126.818

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A bidirectional DC-DC converter for supercapacitor-based energy storage systems in advanced electric vehicles is proposed in this letter. This converter consists of a half-bridge and current-fed push-pull circuit linked with a high frequency transformer, which is well applicable to the low voltage/high current charge and discharge of the supercapacitor. The experimental results of the prototype system prove the effective properties of the proposed topology in terms of a low device-conduction loss and a low switching surge.

DOI： 10.1541/ieejias.126.529

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This paper presents a new circuit topology of full-bridge soft-switching PWM inverter linked DC-DC power converter composed of conventional full-bridge high frequency PWM inverter with high frequency transformer and an active quasi-resonant snubber consisting of an additional power switching device in series with DC busline and a lossless capacitor in parallel with DC busline. Under this proposed high frequency soft-switching PWM inverter linked DC-DC converter, four power switches in the full-bridge arms and DC busline series switch can achieve ZVS at turn-off commutation. By developing the advanced soft-switching PWM high frequency inverter type DC-DC converter, although the conduction power loss of DC busline series power switch increases a little, the total turn-off switching loss of full-bridge high frequency inverter power modules can be sufficiently lowered more and more in the higher frequency range of 60kHz. As a result, when the switching frequency of high frequency inverter power stage using IGBT power modules is designed so as to be more than about 10kHz, the more the switching frequency of inverter increases, the more this high frequency soft-switching DC-DC converter has remarkable advantage as for the power conversion efficiency as compared with the conventional hard-switching PWM inverter DC-DC converter. Its practical effectiveness of high power density and high performance is actually proved for TIG arc welding equipment in industry.

DOI： 10.1541/ieejias.126.237

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper presents a soft switching duty factor controlled AC-AC direct conversion circuit for high frequency Induction Heated applications, which have unity power factor and sinewave line current shaping functions. The proposed utility frequency AC-high frequency AC direct inverter as direct step-up frequency changer for converting commercial low frequency AC (LFAC) into high frequency AC (HFAC) more than 20kHz can be composed of minimum circuit components for resonant pars filter and diodes, which is possible to implement effective miniaturization, low cost, reliability, downsizing because of the non-electrolytic capacitor (at zero voltage soft switching commutation scheme). This paper describes the operating principle and its unique features of LFAC-HFAC soft switching PWM direct conversion circuit. Its utility AC side sinewave current quality and unity power factor correction characteristics are evaluated and discussed from an experiment point of view. Its practical effectiveness of this direct frequency changer is proven for high frequency induction heated appliances in home and business usages.

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This paper proposes a new control method of the current balancer in single-phase three-wire secondary distribution systems using the correlation function. The components of the load currents correlative to the primary side voltage waveform, which correspond to the active currents, are detected in each feeder, then the non-active and unbalanced-active components are compensated on the source side. The balanced currents with unity power factor are obtained in each feeder. The basic principle of the proposed method is discussed in detail, and then confirmed by digital computer simulation. Digital computer simulation results demonstrate that the balanced source currents with unity power factor are obtained in spite of unbalanced load currents.

DOI： 10.1541/ieejias.126.84

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Language：Japanese   Publisher：The Japan Institute of Power Electronics  

A new type of soft switched bidirectional DC-DC converter for advanced automotive electric power systems is presented in this paper. This converter consists of dual half-bridge circuits linked with a high frequency transformer, which is applicable as an interface between a high-voltage DC bus line and a low-voltage power source such as Supercapacitor. In order to reduce the switching losses and expand the soft switching range, a newly developed two-lossless switched capacitor snubber-assisted Zero Current Switching (ZCS) are applied to the primary side circuit. By using this ZCS scheme, the soft switching operation can be achieved for the wide range of output power. The converter operation is demonstrated with simulation results, and its feasibility is verified with experimental results using its 1.0kW 25kHz prototype system.

DOI： 10.5416/jipe2003.32.0_113

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In recent years, energy storage systems assisted by super capacitor have been widely researched and developed to progress power systems for the electronic vehicles. In this paper, a full-bridge/push-pull circuit-based bidirectional DC-DC converter and its control methods are proposed. From the results of detailed experimental demonstration, the proposed system is able to perform adequate charge and discharge operation between low-voltage high-current super capacitor side and high-voltage low-current side with drive train and main battery. Furthermore, conduction losses and voltage/current surge are drastically reduced by ZVS operation with loss-less snubber capacitor in high voltage side as well as the synchronous rectification in low-voltage high-current super capacitor side.

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A new type of soft switched bidirectional DC-DC converter for automotive electric power systems is presented in this paper. This converter consists of dual half-bridge circuits linked with a high frequency transformer, which is applicable as an interface between a high-voltage DC bus line and a low-voltage power source such as Supercapacitor. In order to reduce the switching losses and expand the soft switching range, a newly developed two-lossless switched capacitor snubber-assisted Zero Current Switching (ZCS) are applied to the primary side circuit. By using this ZCS scheme, the soft switching operation can be achieved for the wide range of output power. The converter operation is demonstrated with simulation results, and its feasibility is verified by experimental using its 1.0kW-25kHz prototype system.

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In recent years, power electronic energy storage systems using super capacitor bank have been widely studied and developed for the electronic vehicles. In this paper, a full-bridge/centertapped push-pull circuit-based bidirectional DC-DC converter and its control method are proposed and discussed. From the results of detailed experimental demonstration, the proposed system is able to perform adequate charging and discharging operation between low-voltage high-current super capacitor side and high-voltage low-current side with drive train and main battery. Furthermore, conduction losses and voltage/current urge are drastically reduced by ZVS operation with lossless snubber capacitor in high-voltage side as well as the synchronous rectification in low-voltage high-current super capacitor side.

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A new type of bidirectional DC-DC converter for electric power systems in advanced electric vehicles is proposed in this paper. This converter consists of half-bridge circuits with a high frequency transformer, which is well applicable as an interface between a high-voltage DC bus line and a low-voltage power source. In order to reduce the switching loss, newly developed ZCS loss-less snubber cells are applied to the primary side power stage. By the proposed topology, a soft switching operation can be achieved under the wide range of load current. The converter operation is demonstrated with simulation results, and the feasibility of the new topology is discussed as well as the converter design consideration.

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Language：Japanese   Publisher：パワーエレクトロニクス学会  

DOI： 10.5416/jipe2003.32.0_192

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This paper proposes a novel method of suppressing the inrush current of transformers. A small-rated voltage-source PWM converter is connected in series to a transformer through a matching transformer. Since the connected PWM converter serves as a resistor for the source current, no inrush phenomenon occurs. The basic principle of the proposed method is discussed. Digital computer simulation is implemented to confirm the validity and excellent practicability of the proposed method using PSCAD/EMTDC. A prototype experimental model is constructed and tested. The experimental results demonstrate that the proposed method can perfectly suppress the inrush phenomena. The required-rating of the PWM converter, which acts as a damping resistor for the inrush phenomena, is about 0.25% of that of the main transformer in single-phase circuits, in the experimental results. In three-phase circuits, it is less than 0.1%. © 2005 IEEE.

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In this paper, the single-phase static VAR compensator (SVC) is applied to regulate and stabilize smoothly the generated output voltage of the single-phase self-excited induction generator (single-phase SEIG) driven by a variable-speed prime mover (VSPM) under the conditions of inductive load variations and prime mover speed changes. The conventional fixed gain PI controller-based feedback control scheme is employed to adjust the equivalent capacitance of the single-phase SVC composed of the fixed excitation capacitor (FC) in parallel with the thyristor switched capacitor (TSC) and the thyristor controlled reactor TCR. A PI closed-loop feedback voltage control scheme based on the SVC for the single-phase SEIG coupled by a VSPM prototype set-up is established. The closed-loop feedback output voltage responses in the single-phase SEIG coupled by a VSPM with different inductive load variations using the single-phase SVC with the PI controller are considered and discussed herein. Based on the SVC with the PI controller closed-loop feedback voltage regulation scheme, the experimental results for the single-phase SEIG driven by a VSPM are illustrated and proved its practical effectiveness in terms of the fast response and the high performances.

DOI： 10.1541/ieejias.125.355

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In this paper, high frequency power converter without DC smoothing electrolytic capacitor filter link which convert the 100V/200Vrms and 60Hz single phase utility frequency AC power into a high frequency AC. This proposed high frequency AC power converter without electrolytic capacitor filter can operate under a principle of soft switching PWM based on a lossless capacitor snubber is proposed and demonstrated for consumer high frequency induction heating (IH). In particular, this high frequency power converter capable of producing a high frequency AC more than 20kHz is developed for consumer IH applications as hot water producer and steamer based on the specially designed spiral type IH-Dual Packs Heater (DPH), which includes the dual mode pulse modulation control scheme based on soft switching PWM for high output power setting and commercial frequency AC zero voltage soft switching pulse density modulation (PDM) for low output power settings. This developed high frequency power frequency converter using trench gate IGBTs is clarified on the basis of experimental and simulation results for its circuit operation of the utility frequency AC to high frequency AC frequency PWM power converter without the electrolytic capacitor bank DC filter link for the IH hot water and IH steamer. These IH appliances are based upon an innovative electromagnetic IH-DPH for fluid heating as heat exchanger in consumer pipeline. Finally, its power regulation characteristics, power conversion efficiency and harmonic current components characteristics including power factor in utility AC grid side are evaluated and discussed from an experimental point of view. The practical effectiveness of this utility frequency AC to high frequency AC soft switching high power frequency converter defined conveniently as high frequency soft switching cyclo-inverter is proved as one of the important products effective for next generation IH application all electricity power utilizations.

DOI： 10.1541/ieejias.125.988

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In resent years, the soft switching commutated power converter technologies have attracted special interest in order to minimize semiconductor switching power losses and reduce conductive switching noise. This special issue deals with some schematic descriptions on application-specific quasi-resonant power converter circuits, which make use of soft switching commutation schemes.

DOI： 10.1541/ieejias.125.955

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

In this paper, we propose a single inductor type resonant AC link snubber as a technique for introducing soft-switching PWM technology into three-phase voltage source inverters and explain its circuit operation. We then explain the suitability of instantaneous space voltage vector sinewave modulation compared to sinewave-triangle wave relative modulation as the sinewave modulation technique of the soft-switching inverter introducing this resonant AC link snubber, and propose a time sharing pulse pattern based on the operating principle of this resonant AC link snubber. Furthermore, we discuss the limits on the widths of the pulses that can be output when the time sharing pulse output method is used and the soft-switching inverter performs sinewave modulation, and the need to correct narrow output pulse widths; describe in detail the relationship between the generation principle of the correction pulse pattern and the waveform distortion; and illustrate the simulation results when the minimum pulse width is corrected. Finally, we propose a new time sharing pulse pattern that does not nee the minimum pulse width correction by using the time sharing pulse pattern feature for the resonant AC link inverter and demonstrate its effectiveness from the simulation results for this output pulse pattern. (C) 2004 Wiley Periodicals, Inc.

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The paper presents a novel circuit topology of a high efficiency single-phase sinewave power conditioning and processing converter with a DC-link chemical capacitor. This power conditioner, used as a small scale stand-alone new-energy related power generation system, is composed of time-sharing operated sinewave absolute modulation boost chopper with a bypass diode in the first power processing stage and cascaded with a time-sharing sinewave pulse modulated full-bridge inverter as a second power processing stage operated by time-sharing dual mode pulse pattern control scheme. The unique operating principle of the power processing stage with the time-sharing dual mode sinewave modulation scheme is described with a simple design example. The paper provides and describes also a sinewave tracking voltage controlled soft switching PWM boost chopper with a passive auxiliary edge-resonant snubber. The new conceptual operating principle and the effectiveness of this novel one stage sinewave power conditioner related to new-energy generation system is reviewed through the experimental results.

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This paper presents a single lossless inductive snubber-assisted ZCS-PFM series resonant DC-DC power converter with a high-frequency high-voltage transformer link for industrial-use high power magnetron drive. The current flowing through the active power switches rises gradually at a turned-on transient state with the aid of a single lossless snubber inductor, and ZCS turn-on commutation based on overlapping current can be achieved in wide range pulse frequency modulation control scheme. The high-frequency high-voltage transformer primary side resonant current always becomes continuous operation mode, by electromagnetic loose coupling design of the high-frequency high-voltage transformer and the magnetizing inductance of the high-frequency high-voltage transformer. As a result, this high-voltage power converter circuit for the magnetron is possible to achieve a complete zero current soft switching under a condition of the broad width gate voltage signals. Furthermore, this high-voltage DC-DC power converter circuit can regulate the output power from zero to full over audible frequency range because of two resonant frequency circuit design. Its operating performances are evaluated and discussed on the basis of the power loss analysis simulation and the experimental results from a practical point of view.

DOI： 10.1541/ieejias.124.352

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This paper presents the newly-proposed hybrid resonant commutation bridge leg link (HRCB) snubber circuit which can achieve zero voltage and zero current soft-switching commutation for single-phase and three-phase voltage source-type inverter, along with its unique features and operation principle. The circuit parameter design approach for the HRCB snubber circuit and the determination estimating scheme of the gate pulse timing processing which is more suitable and acceptable for single-phase and space voltage vector modulated three-phase voltage source inverter using the HRCB snubber circuit are described in this paper. In particular the three-phase voltage source soft-switching inverter associated with the proposed HRCB circuits are evaluated and discussed from simulation and experimental viewpoint. The practical effectiveness of the HRCB snubber-assisted three-phase voltage source soft-switching inverter using IGBT power modules which is based on the instantaneous space voltage vector modulation is clarified on the output voltage waveform, actual efficiency and electromagnetic noises in comparison with three-phase voltage source-type conventional hard-switching inverter.

DOI： 10.1541/ieejias.124.286

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This paper presents a novel prototype of 3-level 3-phase voltage-fed soft switching commutation inverter with two Active Auxiliary Resonant DC Link (ARDCL) snubbers which can operate under a condition of Zero Voltage Switching (ZVS) transition. Its operating principle is described herein. The feasible steady-state performances of the proposed soft switching commutated inverter using the latest IGBTs such as planner type and trench type IGBTs, which is more suitable for power systems applications, are evaluated and discussed on the basis of its experimental results and simulation ones.

DOI： 10.1541/ieejias.123.1397

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Advanced development of the high frequency pulse modulated DC/DC power converters are indispensable in order to achieve smaller size, higher performances of the power supplies. In resent years the problems of the electromagnetic noise generation caused by the hard-switching pulse width modulation (PWM)&mdash;based high frequency operation of the switching power devices have been significant, including switching losses and switching surges. As result a variety of soft-switching power conversion circuit technologies have been attracted special interests for reducing switching power losses and minimizing electromagnetic interference. The soft-switching pulse modulation of DC/DC power circuit topologies can be divided into continuous current mode resonant type and quasi-resonant voltage mode type. The soft-switching DC/DC converters, a continuous current mode zero current soft-switching (ZCS) DC/DC converter with pulse frequency modulation (PFM) has been already put into a practical use. In this sort of power converters soft-switching commutation can be achieved over wide load variation ranges and high stability can be also performed, but high current peak stress through power semiconductor devices arises, however, and it causes relatively large increase of conduction power losses in the power semiconductor devices, high frequency transformers as well as rectifier diodes. As a result, the problem of a high efficiency for DC/DC power converter could not still unsolved.<br>Thereupon, in this paper, quasi-resonant voltage mode based soft-switching PWM DC/DC power converter with a high frequency transformer link is presented, which has on/off assisted synchronous rectifier in its secondary side. The PWM operation of this converter is described in comparison with conventional one. Due to using power MOSFET as on/off assisted synchronous rectifier in the secondary side of the high frequency isolated transformer, it is possible to achieve stable zero voltage soft-switching (ZVS) conditions from no load to the rated load for minimum requirement of a magnetizing current. As result of a high value of the magnetizing inductance design, the power converter actual efficiency of this converter can be designed so as to above 97% in experiment. Moreover, results of a switching losses analysis are discussed from an experimental point of views in this paper. The effectiveness of the power converter treated hare is proved from a practical point of view by using 32kHz-2.5kW breadboard setup.

DOI： 10.1541/ieejias.123.1414

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This paper presents a novel three-phase voltage source type soft-switching inverter using the main and auxiliary IGBT power module packages in order to reduce their switching power losses as well as its electromagnetic noises. A single inductor-assisted resonant AC link snubber circuit as one of some resonant snubbers to achieve the zero voltage soft-switching for the three-phase voltage source inverter (VSI) with instantaneous space voltage vector sinewave modulation strategy is originally demonstrated as compared with the other resonant AC link snubber circuit topologies. In addition to this, its operation principle and unique features are described in this paper for resistive and inductive loads. Furthermore, the practical basic operating performances of the new instananeous space vector modulated soft-switching VSI using IGBT power modules are evaluated and discussed on the basis of power conversion efficiency and electromagnetic conductive and radiative noises from an experimental point of view, as compared with those of hard-switching VSI.

DOI： 10.1541/ieejias.123.1269

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This paper deals with a digital control scheme of multiple paralleled high frequency switching current amplifier with four-quadrant chopper for generating gradient magnetic fields in MRI (Magnetic Resonance Imaging) systems. In order to track high precise current pattern in Gradient Coils (GC), the proposal current amplifier cancels the switching current ripples in GC with each other and designed optimum switching gate pulse patterns without influences of the large filter current ripple amplitude. The optimal control implementation and the linear control theory in GC current amplifiers have affinity to each other with excellent characteristics. The digital control system can be realized easily through the digital control implementation, DSPs or microprocessors. Multiple-parallel operational microprocessors realize two or higher paralleled GC current pattern tracking amplifier with optimal control design and excellent results are given for improving the image quality of MRI systems.

DOI： 10.1541/ieejias.123.894

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

In recent years, a resonant snubber to minimize switching power losses and EMI noises have attracted special interest for the voltage-fed soft switching sinewave PWM inverters and active rectifiers. The authors have discussed the performance evaluations on lower noise and high efficiency for two switch auxiliary resonant DC link snubber assisted three-phase voltage-fed soft switching PWM inverter. It was proved that cost effective three phase soft switching inverter treated here is able to improve both efficiency and EMI noise. However, some practical problems to be improved have recognized for the soft-switching three phase PWM inverter treated here from a practical point of view. This three phase soft-switching inverter with two switch type auxiliary resonant DC link snubber has significant disadvantages of DC busline link voltage reduction for the existence of the zero voltage mode transition period as well as the larger size and physical volume of electrolytic capacitor incorporated into the resonant DC link snubber. The additional technology to minimize the busline DC link zero voltage period in order to overcome the practical problems mentioned above is newly proposed in this paper. From experimental and simulation viewpoints, the modified version of this soft-switching inverter is discussed and evaluated for the DC busline voltage utilization factor as compared with the previously developed one.

DOI： 10.1541/ieejias.123.710

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

The A variety of switched-mode high voltage DC power supplies using voltage-fed type or current-fed type high-frequency transformer resonant inverters using MOS gate bipolar power transistors; IGBTs have been recently developed so far for a medical-use X-ray high power generator. In general, the high voltage high power X-ray generator using voltage-fed high frequency inverter with a high voltage transformer link has to meet some performances such as (i) short rising period in start transient of X-ray tube voltage (ii) no overshoot transient response in tube voltage, (iii) minimized voltage ripple in periodic steady-state under extremely wide load variations and filament heater current fluctuation conditions of the X-ray tube. <BR>This paper presents two lossless inductor snubber-assisted series resonant zero current soft switching high-frequency inverter using a diode-capacitor ladder type voltage multiplier called Cockcroft-Walton circuit, which is effectively implemented for a high DC voltage X-ray power generator. This DC high voltage generator which incorporates pulse frequency modulated series resonant inverter using IGBT power module packages is based on the operation principle of zero current soft switching commutation scheme under discontinuous resonant current and continuous resonant current transition modes. This series capacitor compensated for transformer resonant power converter with a high frequency transformer linked voltage boost multiplier can efficiently work a novel selectively-changed dual mode PFM control scheme in order to improve the start transient and steady-state response characteristics and can completely achieve stable zero current soft switching commutation tube filament current dependent for wide load parameter setting values with the aid of two lossless inductor snubbers. It is proved on the basis of simulation and experimental results in which a simple and low cost control implementation based on selectively-changed dual-mode PFM for high-voltage X-ray DC-DC power converter with a voltage multiplier strategy has some specified voltage pattern tracking voltage response performances under rapid rising time and no overshoot in start transient tube voltage as well as the minimized steady-state voltage ripple in tube voltage.

DOI： 10.1541/ieejias.123.649

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper deals the digital optimal current control scheme to improve MRI (Magnetic Resonant Imaging) Gradient-Magnetic Coil (GC) current control implementation. The GC current needs high precision control specifications so as to take clear images with MRI. The novel MRI-GC current control amplifier has the high-frequency PWM chopper circuit with a multi-parallel input structure. The GC current control circuit can prevent the current ripple amplitude and realize high precision GC current controls, but the control system is hard to design because the GC current control circuit has the multi-input and multi-output structure and required high precision control abilities. Therefore, the digital optimal control scheme has tried to apply for the GC current control. The optimal controller is skillful at the design of multi-input and multi-output systems. The novel controller will actualize the high precision GC current controllability because Error System newly includes the GC current error parameter so as to decide the multi-inputs. In this paper, we discuss the novel controller with computer simulations that it can expect the high precision GC current control to improve the image quality of MRI systems.

DOI： 10.1541/ieejias.123.188

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper presents a new topology of the voltage source bridge inverter circuit which proposes novel active edge resonant snubber circuits using the auxiliary power switches. This inverter is acceptable for an uninterruptible power supply, such as PFC power converter, utility-interactive bi-directional power converter. The soft switching operation principle and design procedure of the active auxiliary edge resonant snubber circuit for the high power applications are described and discussed. Both the main active switches and the auxiliary power switches achieve ZVS or ZCS for this sinewave PWM inverter. In order to minimize the switching surge related electromagnetic noise and the switching power loss of power semiconductor devices used here. This inverter does not need the sensor interfaced circuit to detect the voltage or the current and does not also required for the electrolytic chemical capacitors to make thc neutral point of the DC power supply voltage. Because the power semiconductor switches have the relation of the trade-off evaluations in the switching fall time characteristics and the conductive saturation voltage characteristics, this soft switching inverter can improve efficiency under the conditions of the low saturation voltage.

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Publisher：The Japan Institute of Power Electronics  

This paper presents two novel prototypes of the utility AC power source connected sinewave inverter using the high-frequency two-switch flyback transformer which is more suitable and acceptable for the small-scale solar photovoltaic and fuel cell generator interfaced power conditioners. The proposed sinewave soft-switching PWM power conditioner with a high-frequency AC link has a function of electrical isolation including sinewave hard-switching PWM power conditioner with a high frequency link, which is considered for solar photovoltaic power conditioner and fuel cell generator related power conditioner from the viewpoints of safety and reliability in total system. The discontinuous conduction mode (DCM) operation of the flyback transformer in this circuit system is also introduced to feature a simple, low-cost and high-efficiency topology of the sinewave inverter circuit and digital control implementation. The operating principle of the proposed sinewave soft-switching PWM inverter circuit as compared with sinewave hard-switching PWM inverter are described for the designing of circuit parameters. Moreover, the digitally controlled sinewave PWM control processing scheme is presented herein. Finally, the sinewave soft-switching PWM inverter prototype is actually built and tested to verify the validity of the proposed power conditioner for new energy generation systems.

DOI： 10.5416/jipe2003.29.2_54

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Language：Japanese   Publisher：The Illuminating Engineering Institute of Japan  

In recent years, the CCFL has been used for Liquid Crystal Backlight in Display. From an environmental recycle point of view, the Dielectric Barrier Discharge (DBD) Lamp has attracted special interest in place of the CCFL, the electric equivalent circuit of this lamp is represented by the diode bridge, voltage source, two capacitor capacitances. The measuring method to determine these circuit parameters is described. The low cost high-efficiency voltage resonance high-frequency inverter with a high frequency transformer which is composed of MOSFETs is introduced in order to drive DBD lamp. The dimming control scheme is based on the pulse density modulation technique.

DOI： 10.11515/ieijac.36.0.17.0

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Publisher：The Japan Institute of Power Electronics  

We have considered a voltage-source type series-resonant ZCS-PFM DC-DC Converter in order to drive an industrial-use magnetron for generating high power microwave in advance. This DC-DC converter can achieve a complete zero current soft switching by assist of the transformer parasitic parameter and a lossless inductive snubber. And the output power is regulated over all power ranges without audible frequency range due to the magnetizing current of the high-frequency transformer. However, this DC-DC converter has a weak point that it is easy to oscillate by the parasitic capacitance of the switching device and the lossless inductive snubber. Therefore in this paper, the new topology that can solve that weak point without hurting good characteristics of that converter is proposed and evaluated on the basis of simulation and experimental results.

DOI： 10.5416/jipe2003.29.2_48

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper presents, a novel prototype of the three-phase power module bridge package type auxiliary resonant AC link snubber circuit for the three-phase voltage source type sinwave soft switching PWM inverter using IGBT power module which operates under instantaneous space voltage vector modulation scheme. The operating principle of a novel prototype resonant AC link snubber circuit in addition to its unique features are described for current source load model during one switching period which is equivalent to the three-phase voltage source type inverter with LPF, along with its design approach based on the simulation data. The steady-state performance evaluations of space vector modulated three-phase voltage source type sinewave soft switching inverter incorporating a new prototype circuit of three-phase active auxiliary resonant AC link snubber is illustrated and discussed as compared with those of three-phase voltage source type sinewave hard switching PWM inverter with a space voltage vector modulation strategy. The power loss analysis of the three-phase soft switching PWM inverter using IGBT power modules is actually evaluated and discussed on the basis of the conduction power losses based upon the measured v-i characteristics in addition to all the switching power losses of each IGBT with antiparallel diode.

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper deals with a feasible power loss analysis simulator which can actually estimate the power losses of switching mode power converters using IGBTs. The power loss analysis simulator proposed newly is based upon the feasible measured switching power loss data tables and v-i characteristics data tables of power semiconductor power devices; IGBT and diodes. The effectiveness of practical simulation technique, which can discuss power loss evaluations for three phase PWM inverter, is confirmed from the viewpoints of the newly proposed simulation and experimental results.

DOI： 10.1541/ieejias.122.1142

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper proposes a new topology of the voltage source bridge inverter circuit, which has the novel active edge resonant snubber circuit using the auxiliary switches. This inverter is acceptable for an uninterruptible power supply, PFC power converter, utility-interactive bi-directional power converter and so on. In this paper, the soft switching operation principle and design procedure of the active auxiliary edge resonant snubber circuit for high power applications are described and discussed. Both the main active switches and the auxiliary switches achieve ZVS or ZCS in this sinewave PWM inverter. This soft switching PWM inverter can minimize the switching surge related electromagnetic noise and the switching power loss of power semiconductor devices used here. This inverter does not need the sensor interfaced circuit to detect the voltage or the current and does not also required for the electrolytic chemical capacitors to make the neutral point of the DC power supply voltage. Because of the power semiconductor switches have the relation of the trade-off evaluation in the switching fall time characteristic and the conductive saturation voltage characteristic, this soft switching inverter can improve efficiency under conditions of the low saturation voltage.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

This paper presents a novel type of phase shift ZVS-PWM controlled high frequency load resonant inverter with a single active resonant snubber for electromagnetic induction fluid heating appliances. The steady state operating performances of this inverter is evaluated and discussed on basis of simulation and experimental results for induction heater of compact moving fluid heating appliance in the pipeline.

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Language：Japanese   Publisher：ミマツコーポレーション  

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper presents a new prototype configuration of a single-phase voltage source soft switching inverter using IGBT power module packages in order to reduce switching power losses, electromagnetic noises. A single inductor-assisted resonant AC link snubber circuit as one of the resonant snubbers to achieve the zero voltage soft switching for the single-phase voltage source inverter is originally demonstrated, and its operation principle and unique features as well as the practical parameter design method of resonant AC link snubber circuit treated here is described on the basis of computer-aided simulation analysis. Furthermore, the practical operating performans of the single inductor-type resonant AC link snubber for the single-phase voltage source soft switching inverter using IGBTs are discussed and evaluated on the basis of switching power losses and electromagnetic conductive noise as compared with those of single-phase voltage source hard switching inverter from an experimental point of view.

DOI： 10.1541/ieejias.122.617

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese   Publisher：The Japan Institute of Power Electronics  

In this paper, a novel type of active auxiliary quasi resonant commutation leg link Snubber for three phase soft switching inverter circuit, which can be completely turned on and turned off with ZVS & ZCS hybrid mode transition is presented and discussed. The operating principle of this auxiliary hybrid resonant commutation leg link (AHRCLL) snubber circuit is described, and its optimum circuit parameters are determined from a simulation point of view. In addition to these, the performances of this resonant snubber-assisted three phase voltage source type soft switching inverter are evaluated and discussed on the basis of simulation analysis.

DOI： 10.14913/jipe1995.28.44

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper presents a novel active auxiliary resonant AC link snubber for soft switching sinewave PWM inverter. Its operating principle is described for current source load model during one sampling period and the circuit design method of this resonant snubber is pointed out by using the operating data. The performance evaluations of single phase zero voltage type soft switching pulse modulated inverter employing an active auxiliary resonant AC link snubber with a single power switch is illustrated as compared with those of a hard switching PWM sinewave inverter herein.

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper presents a three phase voltage source space voltage vector modulated soft switching inverter using bridge leg-side active auxiliary resonant commutation snubbers (ARCS) with a high frequency pulse current transformer which is designed for power regeneration to DC source, along with its performance evaluations under a digital servo control scheme.

DOI： 10.1541/ieejias.121.823

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper deals with a two-paralleled switch-mode PWM power amplifier using current pattern tracking scheme in order to generate a gradient magnetic field in the Magnetic Resonance Imaging (MRI) system. This power conversion circuit has 8-IGBTs at their inputs/outputs so as to realize further high-power density, and to reduce current switching ripple of the Gradient Coils (GCs) as well as to raise current responses. The modern optimal preview control implementation in 2 parallel bridge type PWM power amplifier can improve the quick and precise current pattern tracking control responses in accordance with the specified values for the magnetic field in GCs. It is clearly proven from a theoretical point of view that the proposed control software is to be enlarged highly the diagnostic target and improves the image quality of MRI systems.

DOI： 10.1541/ieejias.121.756

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper presents a novel type of 3-level 3-phase voltage-fed soft switching inverter with two new Auxiliary Resonant DC Link (ARDCL) snubbers topologies which can operate under a condition of Zero Voltage Switching (ZVS). The feasible operating performances of the proposed soft switching inverter using IGBT module which is more suitable for power systems applications is evaluated on the basis of its experimental results.

DOI： 10.1541/ieejias.121.821

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper presents a novel prototype of auxiliary resonant commutated snubber (ARCS) which incorporates a high frequency pulse current transformer with power regeneration diode loop, along with its practical design considerations.

DOI： 10.1541/ieejias.121.522

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper presents an electromagnetic induction eddy current-based continuous fluid heating appliance using voltage-fed quasi resonant high-frequency soft switching inverter with time ratio control scheme. Its power regulation characteristic are illustrated and this new consumer appliance is evaluated on the basis of its computer simulation and 4kW experimental setup.

DOI： 10.1541/ieejias.120.1088

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

This paper presents an approximate equation to evaluate the regulated output power of asymmetrical ZVS-PWM high frequency quasi resonant inverter for induction heating. Its approximate output power regulation characteristics derived from a theoretical point of view are discussed for induction heating loads as compared with the simulation results.

DOI： 10.1541/ieejias.120.1086

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

DOI： 10.1541/ieejias.117.129

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Publisher：The Japan Institute of Power Electronics  

Solar energy is more attractive and acceptable as one of available power sources in future from a view point of a clean and inexhaustible power supply. However, the electric power generated from a solar photovoltaic array largely depends on weather conditions. Therefore a constant mechanical power can not be obtained from one motor which is driven on the basis of the electric power from a solar photovoltaic array. In order to produce a stable mechanical power, the authors propose the parallel operation system using two induction machines.<br>This paper presents on the stability of the proposed system in which the machine A is related to a solar phtovoltaic array coupled with a general purpose inverter and another machine B is interconnected directly to the utility-grid AC line. It is shown that the system can generate a stable mechanical power with cooperation of the machine B even if the output power of the machine A becomes zero. Furthermore the operating frequency of the inverter is determined by utilizing the relation of the maximum power and the optimal operating voltage of a solar photovoltaic array. As a result, the output power of the machine A becomes always a maximum value under variable weather conditions.

DOI： 10.14913/jipe1995.21.91

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Other Link： http://id.ndl.go.jp/bib/031934588

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