The immittance converter has the input impedance that is proportional to the admittance of the load connected across output terminals. Therefore, in this converter, the output current is proportional to the input voltage and the input current is proportional to the output voltage. Consequently, it converts a constant voltage source into a constant current source and a constant current source into a constant voltage source.
It is well known that the quarter-wavelength transmission line shows immittance conversion characteristics. However, it has very long line length for inverters switching frequency, and is not suitable for power electronics application. So we introduced five types of immittance converters that consist of lumped elements L, C and show improved immittance conversion characteristics at a resonant frequency. After that many types of immittance converter are developed and applied to some applications.

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In order to prevent global warming caused by carbon dioxide (CO₂), several improvements of efficency are requested from the viewpoint of energy conservation for products in the power electronics field. One of methods to improve the efficency of DC power supply with PFC (Power Factor Correction) is to decrease the power losses of FRD (Fast Recovery Diode). In this paper, we show the effect of FRD with high avalanche capability in a real machine of 3kW output power which has the secondary rectifier and PFC circuit, and the remarkable improvement of power losses is achieved in that real machine.

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An advanced switch between sensorless sinusoidal wave drive and rectangular wave drive has been developed for performance optimization in air-conditioner compressor. The phase difference between the voltage phase and the current phase is controlled to accelerate the frequency in sensorless sinusoidal wave drive, using flux-weakening control. The typical rectangular wave drive is applied to improve the efficiency in lower frequency. The novel drive system consists of the sensorless sinusoidal wave drive system, the rectangular wave drive system and the drive system exchanger which switches drive systems each other for performance optimization. High efficiency and the wide range of frequency have been achieved. The effectiveness of the proposal system is confirmed by simulations and experiments.

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In modern electrical power system, a lot of apparatus themselves are using or supplying dc power. However, conventional power networks are based on ac power and each apparatus has its optimal dc voltage level for better performance. Therefore, we now employ various types of converters in the network, such as ac/dc or dc/dc converters. Those power converters cannot avoid conversion loss inherently. This paper proposes a configuration of dc power network using a flying capacitor multilevel inverter. The multilevel inverter has an ac terminal and some dc terminals. It used to be considered as some applications where almost sinusoidal ac output is required without a bulk ac passive filter. The different dc voltage terminals are utilized as multiple dc terminals in the dc power supply network. It is also considered that each dc voltage level can be settled at the different value. A typical case operation is confirmed by simulation studies.

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Osaka Gas Co., Ltd has been developing technologies for energy saving in the residential sector. Especially, we concentrate our resources into the development of fuel cell cogeneration systems recently. The system has excellent ability of energy saving. However, amount of energy saving depends on how to operate the system. Patterns of residential energy consumption are more complicate than industrial use and depend on individuals. Therefore, it is not easy to develop a control method for the system that can be generally applied to wide variety of residential use. In this paper, the control method for hydrogen driven PEFC cogeneration systems for plural houses developed by Osaka Gas is presented and its effectiveness is demonstrated.

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Voltage dip, only about 10msec, can cause damages for product line of semiconductor material. So we developed high voltage momentary voltage dip compensation machine which can take countermeasure for voltage dip at high voltage part of customers' receiving end. This paper introduces the outline of the machine, the result of analysis and output voltage waveform of the product.

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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.

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A novel soft-switching Three-Level (TL) DC-DC converter with phase-shift PWM scheme is presented in this paper. This converter performs Zero Voltage and Zero Current Soft-Switching commutation (ZVZCS) with assist of the tapped inductor output filter in the secondary-side rectifier of the High-Frequency (HF) transformer. By employing the tapped-inductor, the circulating current which increases in the HF transformer in accordance with expansion of the phase-shift angle is drastically reduced, which ensures that the high conversion efficiency can be achieved for the wide range of load variation, compared to its counterpart of ZVS TL DC-DC converter. The operation characteristics and soft-swicthing operations in principle are verified by simulation results.

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This paper presents a digital current controller for zero-current transition (ZCT) converters. In order to reduce switching losses and noises, a soft-switching technique is adopted. It is suitable for the pulse-width modulation (PWM), because the resonant transition is very short and it is independent of the switching frequency. A field programmable gate array (FPGA) and a 2.5MHz analog to digital (A/D) converter can control the inductor current. From the experimental results, the current is controlled precisely even if the duty factor is more than 50%. Also, the zero-current transition operation of the main switch is confirmed and the efficiency of the converter is improved.

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Novel current mode control method for the multi-phase trans-linked boost chopper circuit which is suitable for Electric Vehicle (EV), Hybrid Electric Vehicle (HEV) and Fuel-Cell Electric Vehicle (FC-EV) is proposed in this paper. In case of the proposed digital current mode control method suitable for the multi-phase trans-linked type boost chopper circuit, the inductor current is sampled only twice in a switching period. The proposed digital current mode control method needs independent control for each phase current. Furthermore, solving the problem of the current instability effectively, a compensating ramp is required for the current control algorithm. The proposed digital current mode control algorithm and the block diagram are described in this paper. In addition to this, the condition of the compensating ramp for the multi-phase trans-linked type boost chopper circuit is shown, too. The feasible evaluations of the proposed digital current mode control are discussed with the experimental result.

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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 transfer the real power, in parallel. Rated power of the VSC is minimized by transferring all the real power into the PFC converter. However, the harmonic components in the current from the VSC has larger peak than expected for the fundamental component. This means the current rating of the VSC becomes much larger than expected one. Therefore, active filter action to eliminate these harmonic components in the current from the VSC is investigated in this paper. Simulation results show the reduction rate of 1/5 of harmonic components by the active filter action.

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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.

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This paper presents new types of digitally emulated current mode control soft switching DC-DC converters using FPGA. The proposed system can use A/D converter with few MSPS conversion rate. The A/D converter fetches only one or few points of the real reactor curent during “off-state” of main switch. Using the degitalized reactor current, both the vallery point and the reactor current during “on-state” of main switch in the next switching cycle are emulated by FPGA. Comparing the emulated current with the reference current, the coincident point of them is found out, and the main switch, which is turned on at the bigining of the switching cycle, is turned off at the same point. These porcedures are repeated in every cycle.
The implemented prototype is the soft switching DC-DC boost converter with such ratings as input voltage of dc60V, output voltage of dc200V, output current of dc2A and switching frequency of 100kHz. The applied control system is newly proposed “Fixed one point detection of reactor curent” using FPGA of Spartan 3 type XC3S400-4 and two types of AID converters.
It is demonstrated that the prototype is stably implemented without sub-harmonic oscillation by the aid of the digital slope-compensation. The output characteristics are also included the step response from 10% to full load condition with satisfactory results.

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Recently, fuel cell prevails around the world. Fuel cell is a device to convert electrochemical energy into electrical energy. However, it is difficult to understand fuel cell's electrochemical characteristics as electrically. Therefore, electrical model is needed when we design a system including fuel cells. There are some kind models of fuel cell. One of them is electric equivalent model. Electric equivalent model has some advantage. This paper proposes an electric equivalent model of fuel cell which described about electrical circuit.

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Application of a three-phase to single-phase matrix converter for a 1kW household gas engine cogeneration system, which connects a permanent magnet synchronous generator of the cogeneration system to the utility, is proposed. This system has the following advantages: (a) the generator efficiency will be improved because power factor control of the generator with the matrix converter can reduce reactive current which increases copper losses in the windings and harmonic current which causes harmonic torques of the generator. (b) The converter efficiency will be also improved because the conducting losses of switching devices can be reduced by employing reverse-blocking (RB) devices such as RB-IGBTs. However, since the matrix converter has no energy storage component inside itself, power pulsation due to single-phase power appears directly in the three-phase side. In order to treat this power pulsation, we have proposed a novel method that realizes modulation of the instantaneous three-phase power of the generator synchronized with the single-phase power, and the power pulsation is absorbed with inertia of the rotor of the generator and a gas engine, which is large enough to regard the rotor speed as constant. The proposed method was demonstrated through numerical simulation and experiments using a motor/generator set and an IGBT matrix converter. Additionally, the efficiencies of the system were estimated and the measures for their improvements were discussed.

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A novel simulation model for multiphase permanent magnet synchronous machines (PMSMs) formulated by the modified nodal analysis is proposed. The proposed model uses the voltage and torque equations on abc reference frame to formulate the multiphase PMSMs, so that it is not necessary to derive the state equations on dq reference frame corresponding to conduction modes of a power electronics circuit. Therefore, it is easy to simulate the complex systems consisting of multiphase PMSMs and power converters having many diodes or thyristors. The wind generator system consisting of a six-phase permanent magnet synchronous generator and two three-phase diode bridge rectifiers is discussed to show the effectiveness of the proposed simulation model. The simulation results show good agreements with the experimental ones. The proposed simulation model is considerably useful when the simulation of the system including multiphase PMSMs and the externally commutated power converter such as diode bridge rectifier is executed.

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