This paper proposes an isolated bidirectional DC-DC converter that is suitable for use in a low-voltage, large -current battery integrated photovoltaic(PV) system. The proposed converter comprises an asymmetrical half-bridge and current-driven rectification circuit with a center-tap transformer. The voltage stress of switching devices is suppressed by zero-voltage switching (ZVS) of the half-bridge circuit on the primary side, and synchronous rectification on the secondary side reduces conduction losses. In addition, the proposed circuit is capable of current boost operation by using synchronous rectifier on the secondary side. Voltage clamp circuits suppress the stray resonance and voltage surge during the battery charge and discharge mode. ZVS operation of all switching devices and the effectiveness of the voltage clamp circuits are confirmed through PSpice simulation.

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The main purpose this paper is rapid starting-up the X-ray power generators for animals such as horse and dog . X-ray is generated by making electron collide against the target in X-ray tube. The conventional control system in X-ray generator preheats the filament of the X-ray tube to speed-up the tube current Ip before it applies tube voltage Vp. However, the conventional X-ray power generator needs a few seconds as the boot time to generate X-rays by preheats , then photograph blur happen when animal moved. Therefore, rapid starting-up of the X-ray power generators is needed. It need the property of X-ray tube to achieve rapid starting-up of the X-ray power generators, but the detail of X-ray tube has never been clarified.X-ray tube has two states; the temperature limited state and the space-charge limited state. We have already found another state having characteristics of both the two states. And we have also discovered the requirement that the tube current Ip can start-up with highspeed. We proposed the new control method to rapid start-up the tube current Ip and tube voltage Vp in the X-ray tube, and explained the effectiveness of the control method from our analysis.

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We are demanded to develop high efficiency power electronic circuit for the prevention of global warming and energy depletion. Power electronic circuit has some losses for example turn-on loss, turn-off loss, diode reverse recovery loss and conduction loss. Therefore we develop Recovery assist inverter (proposal circuit) . This circuit can decrease the diode recovery loss and the turn-on loss by connecting pulse Trans with power devices in parallel and driving pulse Trans during the debt time. And in the 800V20kW inverter, it was confirmed that efficiency had improved 2.2% by simulation.

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[in Japanese]

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In this paper, novel methods of making standard sin waves for PWM converters, and novel PLL systems for STATCOM's and UPS's will be proposed. The single-phase utility voltage is transformed to a pseudo three-phase voltage, and this three-phase voltage is used for the phase detection. Standard sin and cos waves made by these methods suffer little influence from voltage unbalance and distortion of utility voltages. Therefore these methods can be used for the STATCOM to reduce the influence of unbalanced system voltage disturbances such as 2LS.

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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.

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Electric Double Layer Capacitor (EDLC) has an environment-friendly impact and it has a lasting life than the conventional rechargeable battery. However, EDLC has the disadvantage of loss voltage by charge energy. In this paper, the single phase PWM inverter for UPS using buck-boost chopper with EDLC is applied in discrete-time model following control. It is established that this method compensates for output sine waveforms all regardless of rippling voltage in EDLC. The output voltage of the buck-boost chopper substantially covers charge energy in EDLC.

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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.

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The miniaturization and higher efficiency performances of boost converter for Electric Vehicle have been required. Now multi-phase trans-linked boost chopper circuit, which can achieve downsizing of inductor and output smoothing capacitor, have been proposed. Characteristics about mutual coupling inductor used in the proposed trans-linked converter have not been analyzed yet. This paper analyzes and evaluates characteristic about the flux in the core of the proposed coupling inductor in order to verify its downsizing. From comparison of characteristics about the flux in the core between the proposed coupling inductor and the conventional non-coupling one, core size of coupling inductor in proposed circuit being smaller than non-coupling one is confirmed.

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This paper presents a novel high frequency (HF) full bridge (FB) inverter for induction heating (IH) applications. The newly proposed FB inverter can convert utility frequency (UF) AC into DC, and DC into HFAC with one-stage power conversion. Simultaneously, the proposed inverter has a PFC function so that the terminal voltage of DC-link-capacitor is boosted all the time, and the current is passed through only one diode component of the diode bridge rectifier by the work of boost-inductor. Therefore, there are some benefits such as minimizing the number of circuit components to use as well as the conduction power losses. The output power of the proposed FB inverter is controlled by Pulse Density Modulation (PDM) scheme, and each switch comprising the inverter legs achieves Zero Voltage-Switching (ZVS) . This paper verifies these beneficial characteristics of the proposed HF one-stage inverter by simulation analyses.

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A large capacity PCS applied to PMSG (permanent magnet synchronous generator) of wind turbine has been developed. This PCS is characterized by snubber-less circuit, as a result, it is accomplished miniaturize and high reliability. To obtain not only a maintenance-free but also robustness for dc over voltage at the over speed of the wind turbine, the film capacitor which possesses a high energy density is adopted for a dc-circuit. Three kinds of tests were carried out. First, the IGBT shut-off test was examined under the worst condition for this PCS. This test result showed that the IGBT surge voltage was less than an allowable limit. Second, the method of the run-back test was established, as the load which is actually same condition is given for the PCS. The PCS was operated stably during heat run test. Third, the characteristic test for the reactive power was carried out with run back test bench, and this test verified the reactive power of grid was able to control with tracking reference from the system controller. As a result of these tests, the PCS achieved satisfactory performance for the PMSG of the wind turbine.

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This paper shows new induction generation system for wind power generation. This system has the voltage source converter (VSC) exciting induction generator and the PFC converter to absorb the real power in parallel. Rating of the VSC is minimized since it supplies reactive power only. And the PFC converter absorbs all the reactive power. However, the loop current flows since the DC side of VSC and PFC converter are connected commonly. The cause and mode of the loop current are investigated by analysis and simulation. Simulation results and the experimental results show that suppression of loop current is possible by installing diodes at both the positive and the negative terminals of dc side of the PFC converter.

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A voltage sag generator that can reproduce actual voltage sags recorded past. It consists of PC, D/A converter, Power amplifier. A new program generating wave form has been developed on Visual Basic. Disturbance caused by interrupt process has been found and solved by program improvement. The developed voltage sag generator is effective to evaluate the performance of power system linkage inverter under various types of sags.

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High overload inverters were developed by using SiC devices for the first time, although its realization by using Si devices had been difficult because of Si's low maximum Tj. High resistive SiC pin diodes with heavy electron irradiation are proposed for the turn-on snubber circuit as an alternative to the conventional resistor and diode. The inverter circuit was greatly miniaturized by mounting the high resistive SiC pin diode in a SiCGT (SiC Commutated Gate turn-off Thyristor) module and using no heat sink for the resistor. The newly developed 100 kVA overload SiC inverter provides an overload capability rate of 200 % and can supply 300 kVA for up to 3 seconds.

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We have developed the new low-loss rectification circuit that needs neither external signals nor power sources for driving. This circuit creates the control power source for the circuit operation from reverse voltage. The direction of the current that flows in this circuit is detected from the voltage between the MOSFET's drain and source. The current is rectified by driving MOSFETs using this detection result. Also, the circuit has several types of MOSFETs connected in parallel. Types and numbers of MOSFETs are automatically selected to minimize the loss according to the magnitude of the current detected from the voltage between the MOSFET's drain and source. To create the power source and the signal for the rectification circuit, the circuit needs no inputs from outside like a diode. Therefore, this circuit can be easily substituted for a conventional diode. In operation tests, the minimum forward voltage drop was 0.04 [V] when the current was rectified. As a result, the forward voltage drop was less than 1/10 compared to conventional diodes, and the loss could be decreased extremely. Therefore, the miniaturization of the electric equipment that is radiation fin and fan becomes possible, too. The low-loss rectification circuit can save energies by substituting diodes for prevention of global warming.

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