The theory of instantaneous reactive power, or the so-called “p-q theory, ” in three-phase circuits was originated in 1982 by the author and his former colleagues. The p-q theory allows us to define the instantaneous reactive power in each phase as a unique value for arbitrary three-phase voltage and current waveforms without any restriction. In addition, the theory yields a lucid explanation of the physical meaning of the instantaneous reactive power in each phase. Since the emergence of the theory, eighteen years have passed, so that the concept of the instantaneous reactive power has become firmly established among electrical engineers, in particular, power electronics researchers and engineers. This paper describes the histrical background, emergenece, applications and developments of the p-q theory, including the personal views of the author.

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The first three-years test schedule in the Yamanashi Maglev Test Line has finished with satisfactory results at the end of March 2000. As is represented by the high speed runs at 500km/h, the test results proved the superiority of the superconducting Maglev system. This paper introduces the LSM drive system in the Yamanashi Maglev Test Line as an application of the Power Electronics Technologies.

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This paper presents a new prototype of voltage source-clamped quasi- resonant inverter, which is developed for the next-generation high-frequency high-power induction-headed (IH) Rice cooker. This application-specific high-frequency inverter using new-generation specially designed insulated gate bipolar transistors (IGBT's) can efficiently operate under a principle of zero-voltage switching pulsewidth modulation (ZVS-PWM) strategy. The ZVS operation condition on power regulation, loss analysis of new IGBT's incorporated into this inverter are discussed herein for IH Rice cooker.

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Hydraulic pump units are widely used to operate hydraulic actuators. In a typical machine shop, conventional constant speed hydraulic pump units consume more than 20% of the total electric power necessary to operate CNC machine tools. Most of that energy are wasted to run the axial piston pump at idle. This paper describes a variable speed hydraulic pump unit using a switched reluctance motor (SRM), which saves energy drastically. SRM was selected as the most suitable motor for this application. Design and control strategy of this motor are described. Application examples to machine tools shows the effectiveness of the new hybrid pump system in saving energy and in reducing acoustic noise.

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Recently, it is often observed that the harmonics interference occurs in the AC power line because switching mode inverter and converter have been widely used as power supplies of the electronic and electrical equipment. In order to prevent this harmonics interference, the guideline on the maximum limits of the harmonics distortion factor of the input current was indicated.
In this paper, we propose modified push-pull electronic ballast that can suppress input harmonic currents. The electronic ballast has partial smoothing function and charge pump function. The behavior of the proposed circuit is analyzed and experimental results will be shown. The experimental results show that the circuit can decrease the harmonic distortion of the input current. It is revealed that the harmonic distortion of the input current obtained by the proposed electronic ballast satisfies the maximum limit of IEC 1000-3-2 class C sufficiently. And the electronic ballast realized the high power factor of 0.995 and the high efficiency of 0.88.

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In recent years, development for wind power generation is growing faster in japan. We developed new wind power generation system for small island. This power supply system is consisted of line interactive inverter, chopper for battery, chopper for heater and variable speed converter. We present the performances of this power supply system.

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In recent years, the harmonics and EMI noise sent out from an electric power conversion system are getting a great deal of attenton in electromagnetic enviroment probrems. So, the considerations for mentioned above have been getting important. Therefore, there is need to do a detail frequency analysis such as trasient phenomena at the switching. So, we have proposed the analytic technique using Wavelet-transformer which is possible to chatch a phenomonon from the both sides of the time and the frequency. In this paper, we performed the analysis using Wavelet-transformer against the actual measured date at the switching interval. Then, based on obtained result, we describe the high validity of Wavelet-transformer and the application to the power electronics field.

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We have developed the new conceptional induction-heated fluid heating appliance-DUAL PACKS HEATER (DPH), which can heat various kind of fluids, in liquiud condition or in super heated steam gas condition, ranging from at room-temperature plus 1°C upto at max 1200°C, in very precisely controlled manner by 1°C. We have already delivered to our domestic customers some tens number of the DPH unit successfully and satisfactorily.
In this paper, I'd like to explain the working concept of the DPH system with actual model unit, followed by the presentation of actual successful application examples of DPH system, mainly working in the Food Processing Industry in Japan.

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The Bi-Flow Power Source that we developed can be used as a power source or an electronic load. As a power source, the output voltage is adjustable from zero to 200VDC, while its output current is adjustable from zero to 50ADC. On the other hand, as an electronic load, the consumed power is regenerated to power line. The load current as well as load voltage can be set freely. Since the bi-flow power source is working in switching mode, compact size and light weight are realized.
This bi-flow power source is very useful for power electronics and motor control experiment. It is also very good for the experiment of solar generating system and battery charge-discharge system.
In this paper, the operating principle is firstly explained. Experimental results is then presented.

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The single-phase buck PFC converter has several advantages, such as no lower-limit of the output-voltage control range and no rush-current of the input-current. However, the buck converter requires the LC-filter connected in the ac-side of the converter to absorb the switching frequency harmonics. The LC-filter causes an LC resonance in transient states. To solve this, the authors propose a suppression approach using the Band Reject Filter (BRF) for the single-phase buck PFC converter. To illustrate the validity of the theory, experimental results obtained from a 1.0 [kW] setup are shown.

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The conventional PWM scheme of the three-phase current source converter is much complicated compared with that of the three-phase voltage source type converter. This paper presents a simple PWM scheme for three-phase current source PWM PFC rectifier. This PWM scheme has been obtained through a study on the duality between three-phase PWM converters of the voltage source type and the current source type. Thus, the PWM scheme of the three-phase voltage source type PWM converter is reviewed first. Then, the simple PWM scheme of the three-phase current source converter is discussed by referring the discussion of the three-phase voltage source PWM converter. The validity of the theory is confirmed through experimental results obtained from a setups of the three-phase current source type PFC rectifier.

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The paper presents the combination of p-q theory and instantaneous positive sequence extraction of load current and utility voltage for controlling of shunt active filters. Operation of active filter using this method compensates for reactive power, current harmonics and imbalance currents of the load in 3-phase 3-wire utility. The presented method is very easy to implement and it is possible to make use of it in harmonic polluted and/or imbalance utility voltage case, successfully. Simulation and experimental results confirm the validity of control strategy to suppress the above-mentioned power quality problems with a very fast dynamic response.

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Authors previously proposed a new MPPT control scheme for PV system connected in parallel with the ac system line. The system needs no sensors or calculation for PV array power detection, but utilizes an interior control signal of dc link voltage control loop itself. For this reason, system response and stability greatly depend on the main circuit and control system parameters. This paper shows system design based on stability analysis. Response of the experimental system has been proved fast enough for practical use.

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