[in Japanese]

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In this paper, a novel control system of PWM current-source inverter will be proposed. According to the duality properties of the control systems between the voltage-source inverter and the current-source inverter, a new control system of the current-source inverters having voltage minor-loop has been proposed and verified by simulation studies. Like the current-minor loop of the voltage-source inverter, the voltage-minor loop of the current-source inverter is essential for the control system of the current-source inverter.

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Since the 80MVA GTO-STATCOM has been introduced to the Inuyama switching station of the Kansai Electric Power Co., Inc. in 1991, installations of STATCOM has increased because the necessity of STATCOM came to be widely recognized due to the high demand for electric power in the world. This paper introduces the outline of the STATCOMs put into practical use.

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In this paper, a phase shift PWM controlled full bridge-type series load resonant high-frequency inverter is presented for consumer electromagnetic induction heating applications. The bridge arm side link passive capacitive snubbers in parallel with each and AC load side linked active edge inductive snubber-assisted series load resonant soft switching inverter with a phase shifted PWM control scheme is evaluated and discussed on the basis of the simulation and experimental results. It is proved from a practical point of view that the series load resonant and edge resonant hybrid high-frequency inverter, including the variable-power variable-frequency regulation function can expand zero voltage soft switching commutation area even under low output power setting ranges. Furthermore, even in the lower output power regulation mode of this high-frequency load resonant tank inverter, it is verified that this inverter can achieve ZVS with the aid of the dual mode control single auxiliary inductor snubber and active edge resonant snubber in HFAC side.

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This paper presents an improved optimum design approach based on genetic algorithm for Switched Reluctance Motor (SRM) with 0.1mm airgap. A simple nonlinear magnetic analysis and an iron loss prediction employed in the previous approach had problems in terms of their analytical accuracies for SRM with short airgap. To improve the computational accuracy, it is reconsidered that how to determine the geometry of a saturable permeance tip in the simple nonlinear magnetic analysis and the coefficients of hysteresis and eddy current losses for iron loss calculation. As a result, it is demonstrated that the computational accuracy of the improved approach is as high as that of 3D FEM. Finally, a 400W SRM with 0.1mm gap is redesigned, by which high efficiency more than 88% at the rated operating point is realized.

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In this research, novel small permanent magnet generator is proposed. The influence of the structural parameter on various characteristics is analyzed by using a finite element method. The suitable structure for high power and low Cogging torque is examined. The low cogging torque characteristics by the optimization of the auxiliary pole shape can be achieved.

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This paper proposes an inductance identification method of IPMSM using adaptive observer with high frequency current injection. Firstly, a flux model on the coordinate fixed to the stator is derived to construct the adaptive observer for inductance identification. This flux model involves just R and L_q, so that this model is superior to other model expression in terms of inductance identification. Next, the adaptive observer is constituted based on this model, and identifiability of L_q is analyzed in detail. As a result, this paper will clarify that L_q cannot be identified with only fundamental components of driving signals. This implies high frequency signal injection necessitates for identification of L_q. In this paper, high frequency current is injected into q axis for L_q identification by the proposed adaptive observer. Finally, the experimental results show feasibility of the proposed method.

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A novel DC-DC converter circuit whose step-up ratio is much larger than that of the conventional boost converter is presented in this paper. It also describes that the circuit can be modified to a bi-directional one with larger step-up and step-down ratios. These features can be obtained by charging two capacitors in parallel and discharging in series or vice versa alternately. The circuit is simple and has some significant advantages like extended output voltage, less input current ripple and output voltage ripple over the conventional converters. Hence, it may find good applications to household UPSs and power conditioners for fuel cell systems.

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In this paper, it is reported that the new type of a soft switching DC/DC boost converter is driven by the novel “analogue and digital mixed” current mode controller using FPGA. The main circuit configuration of the converter is just same as the one reported by references^{[1, 2]}. The converter is operated at 100kHz with the ratings of 100/200V, 400W and maximum efficiency of 97.0%. The generated LC resonant current makes both the main device of MOSFET in “ZVS” and auxiliary device of IGBT in “ZCS” operations. The new “analogue and digital mixed” current mode controller^{[4, 5]} is consisted of FPGA with 18 by 18bits integer multiplier, 10 bits ADC, 10bits DAC and analogue comparator. Comparing to the conventional voltage controller, the transient response characteristics are improved, that is, the output fluctuation voltage is 3V and recovery time is 34ms, when the output current is abruptly varied from 0.2A to 2A of the rated current.

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The miniaturization and higher efficiency performances of boost converter for Electric Vehicle have been required. In this paper, a novel recovery-less boost chopper circuit, which can reduce the power loss in diode and power switching devices, is presented. The proposed circuit is able to control recovery phenomenon by the additional inductor. Therefore, the current transition through the diodes is softly owing to the additional inductor. Furthermore zero current turn on soft switching operation can be achieved in active switching devices. The additional inductor is required best design to control diode recovery phenomenon. This paper describes the design method of additional inductor and transformer turn ratio. In the experimental results, controlling diode recovery and realizing zero current turn on soft switching operation is confirmed actually. As a result, the proposed circuit achieves 0.4% higher efficiency as compared with one of conventional circuit. As future trends, reverse buck topology is shown for regeneration aspect. In the simulation result, operation of the topology is confirmed.

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For various rectifier circuits such as those for consumer electronics and appliances, rectifier circuits of the capacitor input type are generally used. It is known that such rectifier generates various harmonics in the power system. To improve those harmonic problems, various PFC circuits have been proposed so far. Among these, Takahashi have proposed a PFC scheme using a LC filter without switching devices. This method makes a PFC effect by widening conduction period using the operations of capacitors and inductor. On the basis of this scheme, we propose another PFC circuit. This method attempts to improve the input current, towards satisfactory waveform by using a novel ladder type filter, whose operating mechanism is analogous to Takahashi's, but an original one. Various fundamental operations are discussed and these are confirmed by computer simulation, and experiment. Compared with the conventional circuits, the construction is a little simple, so could be expected to be easily developed to the three phase circuit.

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DC microgrid is a novel power system using dc distribution in order to provide a super high quality power. This dc system is suitable for dc output type distributed generations and energy storages. The dc power can be converted to required ac or dc voltages by load side converters, and these converters dc not require transformers by choosing proper dc voltages (±170V). This distributed scheme of load side converters also contributes to provide supplying high quality power. In this research, we assumed one type of the dc microgrids for residential houses. All residences have distributed generations such as gas engine cogenerations or fuel cells. Those generations are connected to the dc power line and the electricity from the generations can be shared among the residences. We constructed an experimental system based this concept in an experimental collective house (NEXT21). We studied the fundamental characteristics and the quality of the supplied power by using practical power line and some appliances. Experimental results demonstrated that the system could supply high quality power to the loads stably.

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This paper represents the dynamic avalanche mechanism of Fast Recovery Diode (FRD) based on failure analysis under the Un-clamped Inductive Switching (UIS) test condition and the improvement of avalanche capability by several 1000 times (from 0.1mJ to several 100mJ) by making experimentally different anode junction depth (from 5um to 10um) of 200V 10A FRD and when this avalanche energy guaranty is adopted to high frequency switching rectifier without voltage protection circuit (ex. R-C snabber) and adequate lower maximum reverse blocking voltage selected, rectifier conduction power loss is reduced by about 20%. This method will contribute to make some sort of power sources for example, communication base power, light projector, welder machine and plating power source so on, better power efficiency and better ecology machine. More over this method will make those power sources smaller and better cost effective.

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This paper presents a new DC-DC converter circuit topology using voltage source-fed soft-switching PWM high frequency inverter with half-bridge configuration. This type of DC-DC converter circuit has two semiconductor switching devices in series with high and low DC buslines, two lossless snubbing capacitors in parallel with two connected additional diode components. Under the newly proposed high frequency soft-switching PWM inverter link DC-DC converter circuit connected for utility ac 400V-rms input grid on the basis of divided smoothing capacitor type half bridge inverter. Its active power switches (IGBTs) can achieve ZCS turn-on commutation operation and ZVS turn-off commutation operation. Consequently, the total turn-off switching power losses of IGBTs can be significantly reduced for higher frequency. As a result, a high switching frequency operation for IGBTs used in this circuit can be actually implemented at a switching frequency more than about 20kHz. It is proved that the more the switching frequency of half bridge inverter increases, the more soft switching PWM DC-DC converters with a high frequency transformer have remarkable advantages for its power conversion efficiency and power density as compared with the conventional full-bridge type soft switching PWM DC-DC converter with DC rail side auxiliary edge resonant sunbbers that the authors have proposed previously. The practical effectiveness of these new converter topologies are substantially confirmed for low voltage and large current dc power supplies as high performance arc welding machine from a practical point of view.

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As an interior construction, a dismantlable adhesion method using induction heating (IH) and thermoplastic adhesive has been proposed. The method is called “the allover method”. But when a distance between an induction coil for generating EMF and heated metal is existed considerably, the conventional induction coil couldn't heat the metal sufficiently. That is, heating characteristics of the metal depend on the distance. In this paper, a new heating coil with concentrated winding having ferrate core is experimented. From experiments, an electric equivalent circuit is deduced, and heating characteristics of heated metal at the distances are analyzed. The usefulness of concentrated winding coil is cleared by analyzed characteristics.

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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.

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The high frequency voltage source can be transformed into a high frequency current source by an immittance converter. DC constant current power supply can be constituted by rectifying the high frequency current of the immittance converter output. When a rectifying circuit is connected to the output of the immittance converter, the voltage waveform becomes the square wave. The output current waveform of the immittance converter varies according to the DC load. The fundamental component of the output current of the immittance converter is constant, but the mean value of the current varies with the waveform variation. As a result, the DC output current varies with the DC load.
In this paper, it is shown that the output current waveform of the immittance converter which is connected a rectifier circuit to the output can be similar to the part of a sinusoidal wave. The approximate calculation method of the DC output current with this similar waveform is proposed, and it is compared to the simulation. The negative feedback circuit which improves the regulation of the DC output current is shown, and a good result is provided by simulation.

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We suggest a grid-connected photovoltaic (PV) system in which PV arrays and batteries are connected directly in DC side. In this system, batteries are discharged or charged under control by power-conditioner which converts the mixed output of PV arrays and batteries without a DC-DC converter for converting a battery voltage. Despite a shift of a power point of PV arrays from maximum power point, it is possible to increase power generation of PV arrays because conversion loss of the DC-DC converter can be removed. As a result of numerical simulations, it is found that the power generation ratio of this system to MPPT system reaches to 97.4%.

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The authors have developed an overhead line voltage compensation system for use by trains. The system consists of a lithium-ion battery and bi-directional converter, and has been installed for use on actual streetcars. This system supports the operation of electric trains by supplying energy from the battery when voltage from the overhead line decreases during streetcar acceleration, and is also capable of absorbing regenerated power during deceleration for re-use. This system utilizes a lithium-ion battery capable of discharging a high current, normally causing the battery to generate heat when generating current to supplement the overhead line voltage, thereby contributing to battery depletion. In order to resolve this problem, the authors have developed a fan-cooled module with an attached cooling fan and have verified the effectiveness of this module.
After operating for approximately six months, this system has proven to effectively compensate the overhead line voltage and operate with satisfactory results.

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In this research, it proposes optimization by the computer-aided to the design of LC-filter in the PWM inverter. The optimization system that applies a multipurpose genetic algorithm to the design of LC-filter is constructed.

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To increase the efficiency of a gas engine cogeneration system (GECS), a matrix converter is proposed to converter the generator output to utility directly. To investigate the interaction between the matrix converter and the GECS, the system needs to be validated before realization, so a real-time simulation will be executed about the Gas Engine Generator System with matrix converter based on MATLAB/simulink and OPAL RT-LAB.

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