A direct digital control (DDC) system is adopted on feedback controllers of the poloidal field power supplies in the JT-60 tokamak. The system consisted of 5 CAMAC crates with each microcomputer and with some input/output modules, and their functions are instructing voltage (E_c) values calculated to phase controllers of thyristors. On upgrading of JT-60 (JT-60U), the DDC systems have been modified to fulfill the following requirements: (1) the processing time is under 0.5ms and hopefully 0.25ms to suppress intrinsic vertical instabilities of elongated plasmas; (2) in order to use resources of the power supplies effectively, new control methods which are (a) acting or stopping the circulating current and by-pass-pair operation as required and (b) changing over the current feedback control to the voltage control and vice versa have to be developed. A new system consists of a host computer which performs on-line processing such as setting the system under the discharge conditions, etc. and five microcomputers on VME-bus system. Functions of the microcomputers whose programs are written by C language are real-time processing such as calculating E_c values by new control algorithm and outputting E_c values on every 0.5ms and 0.25ms. The new VME system has been build and tested, and all requirements were accomplished. Moreover, It has controlled plasmas of JT-60U very well.

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A PWM three-phase ac-to-dc converter with unity input power factor can be approached by setting the required active power and setting reactive power zero in the instantaneous reactive power theory. The instantaneous reactive power theory is proposed by Akagi and is usually used to design reactive power and harmonic compensators. In the power distribution system, voltage unbalance and harmonics always exist. The effects of the harmonics and voltage unbalance are presented and discussed in this paper. Moreover, a low pass filter is suggested to add into the coordinate transformation in the instantaneous reactive power theory to reduce the effects of harmonics and unbalance in the power source. Finally, the theoretical results are verified both by simulated and experimental results in a laboratory prototype system.

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A new motor (ADTR-Motor: Anti-Directional Twin Rotary Motor) for electric vehicle drive was proposed. A stator in a conventional motor was reformed to be movable, and the stator (outer rotor) and the rotor (inner rotor) rotate in anti-directions. IM type ADTR-Motor and SM type ADTR-Motor are considerable, and in this paper a prototype of IM type ADTR-Motor was experimentally constructed. When ADTR-Motor is used for an EV drive, the direction of one of the rotors should be reversed, and both rotors, which rotate in the same direction, propel the two wheels of EV. The torque of wheels can be balanced without differential gear. The fundamental characteristics of ADTR-Motor are clarified, which are the structure of ADTR-Motor, the equivalent circuit parameters, the torque balance theory, the torque-speed characteristics, the rotors speed transient characteristics, and the transient response under the speed sensorless torque control.

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A method for the deadbeat flux level control of direct-field-oriented induction motor with position-control loop has been developed that employs an adaptive rotor flux observer. The observer is a full-order type and is used not only in the direct-field-oriented controller, but also to identify stator and rotor resistances of the motor. The observer reduces the sensitivity of a deadbeat controller to fluctuations in the motor parameters. The main advantage of this method is that it improves the efficiency of an induction motor without sacrificing dynamic perfromance.
This paper describes the method as well as the fundamental characteristics of the system derived from experimental and simulation results.

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We must switch from trucking to trains or ships for freight transportation in view of aggravating environ-ment destruction, depletion of fossil energy resources, and shortage of young manpower.
High power electric locomotives have been developed and are contributing an increased freight transporting capacity. But we have to restrict their power output because of voltage drop and shortage of capacity on account of long interval of traction substations. We have studied an adaptive output power control system of them to exploit their full ability with computer simulation. We propose a new method of calculating the difference between the voltage of contact wire of locomotives and its limit, and the resistance of feeding system with the position of the locomotive and traction substation, and calculating the current to be increased within the limit. Otherwise we propose to reduce output power of locomotives according to the difference between voltage of contact wire and its limit. We show that high power locomotives can be worked within the voltage limit and the standard train running time can be maintained by computer simulation proposed in the above. Thus we can introduce the high power locomotives without any large investment to expand the existing substation and can work them to the limit of their capacity.

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Automatic Train Operation (ATO) system is a system to control a train running automatically. It is required to operate a train to run satisfying some constraints concerned with distance, time, speed limit, and to run with little energy and riding comfort. The ATO system in this paper calculates how to run (running pattern) for a train concerned about these conditions before running as a reference, and controls a train to run along the running pattern while running.
Amodel predictive pattern tracking control algorithm for this type of ATO system is described in this paper. It is an algorithm to control notch switching to cancel effects of condition variances and disturbances during running, , and to make a train run tracking a reference running pattern with riding comfort.
This algorithm predicts how a train runs in future and selects times to switch notches leading smaller error between the train running and a reference running pattern. It realizes comfortable running with few times of notch switchings and accurate stopping of a train, a non-linear and discrete system, by adjusting notch switching times of the reference running pattern using Simulation-based Model Predictive Control.

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In this paper, we propose a new multi-level inverter with simple circuit configuration and control. The inverter is composed of a series connection of individual single phase inverters. The number of the output voltage levels depends on the number of the individual inverters in series and their output voltage level. The switching devices in the new circuit configuration can be reduced by using a common switching-leg for the individual inverters. In this inverter circuit, the number of the levels is equal to 2^m-1 or 2^m where m is the number of switching-legs used. In the paper, a 15 levels inverter using four switching legs (m=4) is introduced. If the number of voltage levels is increased, smoother sinusoidal waveforms can be obtained directly and it is possible to control the output voltage almost continuously from zero to maximum without generating high voltage step changes as pulse width modulation techniques.
The control principle, the circuit configuration and the characteristics of the output voltage control are discussed. The feasibility of the circuit is demonstrated by simulation and experimental results.

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Recently, many apparatus have been used for residential applications by the remarkable progress of the power electronics technology. So, harmonics and power factor problems have become important. This paper proposes the multi-functional high quality single phase power converter with a simple circuit configuration using a power module for three phase inverters. The basic operation of the proposed power converter is almost the same as the double converter by the inverter and the converter circuit. Many functions about the AC power line, the DC power source line with loads and the AC output load can be obtained by using the proposed circuit configuration. The converter also has the useful functions of the direct connecting the AC load to the AC power line and the line interrupting at the AC power line failer.
In this paper, I describe the circuit configuration, the control principle, the obtainable functions and the control methods. Then I confirm the feasibility of the system by the simulations and the experiments.

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This paper deals with the high-frequency leakage current caused by a voltage-source PWM inverter. A nonnegligible amount of leakage current would flow through stray capacitors between stator windings and a motor frame due to a, large step change of the common-mode voltage produced by the PWM inverter. An equivalent circuit for the leakage current is proposed, which is expressed by a series resonant circuit. The analysis applying the equivalent circuit gives us such a conclusion that the connection of a common-mode choke in series between the inverter and motor terminal is not effective to reduce the rms and average value of the leakage current, but effective to reduce the peak value. Furthermore, this paper shows that the modeling and analysis are valid in designing a previously proposed suppression method of the leakage current.

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