Active clamping single-ended forward DC/DC converters are possible to realize soft-switching with simple circuit configuration. However, these converters need large magnetizing current to realize soft-switching, therefore conduction losses become problematic. In this paper, we propose new control strategy which solves this trade-off problem fundamentally. Then we show the realization conditions of soft-switching and design method to realize soft-switching on the basis of theoretical analysis.Finally, experimental results of laboratory model which applied new control strategy are presented, in which soft-switching are realized perfectly with small magnetizing current.

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A novel inverter with an improved turn-on and turn-off snubber circuit is proposed, which can suppress the maximum voltage applied on the main switches of the circuit. No additional sensor is required for control. Mitigation of the maximum voltage of the main switches and soft-switching are confirmed through circuit simulation and experiment with a 1kVA circuit. Reduction of switching losses is confirmed by experiment. Improvement of inverter loss is shown by estimation of losses of high power circuit based on experimental results.

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In this paper, a method of stability analysis is proposed for converters which are implemented on digital controllers.The transient responses of an output voltage and an inductor current are calculated by the state equations, and the stability of the converter system is analyzed with the singular perturbation methods. It is shown that the proposed analysis is good agreed with simulation results and experimental results.

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The PAM-type-PWM and the single-phase PWM method for the three-phase converter were presented. On the other hand, the author proposed a control method that combines the pulse space modulation and dc-current control on the three-phase current-fed inverter that is used for utility interactive system. These methods reduce the switching power loss under high power factor conditions to 1/8 compared to the conventional three-phase modulation method. In this paper, the author describes static characteristics of the inverter to which the proposed method was applied. The proposed method can control the output currents to sinusoidal waveforms under not only ideal line voltage but also a distorted or unbalanced line voltage waveforms.

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This paper deals with the novel soft-switching inverter topology and its capability of high frequency switching technology to be applicable to the power conversion system. To realize the switching power supply in the MHz switching application, there are some problems to be solved. In order to overcome these problems, we propose the phase-shift controlled zero current switching (ZCS) inverter and its control scheme. This circuit has soft-switching capability in the MHz switching range by the ZCS circuit topology and can control the output power by the phase-shift controlled method. In addition, effectiveness of this circuit is confirmed by comparative experimental study between the conventional hard-switching circuit and proposed circuit.

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Induction heating is an effective method for metal heating. As of the unique applications of induction heating, there is a superheated steamer. We have proposed a novel superheated steam generator having both advantages for cooling of induction coil and for warming of water in advance. However its steamer wasn’t satisfactory for temperature rising of superheated steam. In this paper, we propose a heating up method with improvement of heated metal shape and a cooling method of induction coil with air and water. Therefore the practicability of our steamer is proved.

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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.

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In conventional robot arms, one motor is placed to one joint. The human upper extremities can be simplified into three antagonistic pairs of muscles, those which are a pair of shoulder mono-articular muscles, a pair of elbow mono-articular and a pair of elbow/shoulder bi-articular muscles. In the present study, it is assumed that the bi-articular muscles have a profound effect on not only the position control but power output and rigidity of the arm tip. This study reports that the system is able to imitate the function of bi-article muscles in human uppers by using rotary motors and a planetary gear.

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A 10 MW-class high-precision power supply was developed for the electromagnets of a large proton accelerator (J-PARC) . This power supply consists of an advanced self-commutated current-source type converter (ACSC) using IEGTs and a hybrid filter. The current ripple was less than 1×10^-6, and the tracking error was less than ±0.5×10^-4. With this power supply, the proton beam was successfully accelerated to 30 GeV, which is the target energy of the first stage of J-PARC.

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The reduction of atmospheric CO₂ is the greatest subject for the organism on earth. The application of electric energy instead of fossil fuels to advanced transportation is effective for reduction of atmospheric CO₂. This paper describes some proposals of challenge of applying power electronics to advanced transportation such as recycle of thermal energy of exhaust by thermoelectric device and quick-charging system for EVs using new storage device for electricity.

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The Electric Vehicle (EV) is clean and environmental friendly vehicle. However, its power source, electricity still contains fossils. To reduce the fossil utilization, the authors established the Renewable Energy for Electric Vehicle (RE-EV) project. In this paper, two research topics are studied. One is a study of actual operation data to obtain the potential of the EV with PV electricity. An EV (i-MiEV) manufactured by Mitsubishi Motors Corporation was operated for 1 year. In this project, acharging station consisting of a 2.6 kW Photovoltaic power generation (PV) system with a 9 kWh battery system and measuring equipment was installed in Ookayama campus in Tokyo Institute of Technology. This system maximizes the PV electricity and minimizes grid electricity while charging the EV. Second is a statistical study to estimate CO₂ emissions for various kinds of driving patterns. In this paper, 6 driving patterns from statistical data and 1 actual data were studied by Life-Cycle Assessment (LCA) approach to estimate CO₂ emissions. As a result, 80% of charging electricity is from PV from actual operation data.Regarding the LCA, CO₂ emissions of EV with PV electricity are same with utility electricity at short distance driving pattern and much better at long distance driving patterns, even when the system uses lead acid battery. And CO₂ emissions of all EV driving patterns are smaller than those of a gasoline vehicle.

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[in Japanese]

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It is necessary to reduce the cost of fuel cells for the full-scale spread of them. As one of the solutions, the application of the low-voltage fuel cell stack, has small amount of cells, is promising. However the low input voltage at the power conditioner, consists of DC/DC converter and DC/AC inverter, causes the large input current and results in low conversion efficiency. In this paper, we present the development of the novel DC/DC converter which contains modulated push-pull circuit known as sound amplifier circuit for power electronics. The converter is controlled by soft-switching technique in order to improve the efficiency and also has proper power supply to suppress the input high-frequency ripple current. As the result of the developed 800W power conditioner for low-voltage fuel cell, the peak efficiency of 93.2% is achieved and the system efficiency maintains above 90.9% from 200W to 800W.

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This paper proposes a novel control method of the Maximum Power Point Tracking (MPPT) for thermoelectric generation by temperature detection. The reference value of the output voltage of the thermoelectric module is decided by the V-P characteristics and the module temperature. Therefore, the processor in this proposed method is used onlyone-chip microcomputer without complex calculation. The basic principle of the proposed method is discussed. Digital computer simulation is implemented to confirm the validity and practicability of the proposed method using the PSCAD/EMTDC. A prototype experimental-model is constructed and tested. The experimental results exhibit that the output voltage can track the maximum power point voltage by the proposed MPPT.

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