In recent years, PWM rectifiers, which realize high power factor and almost sinusoidal AC input current, have been proposed and some of them have already been put into practice.
In many cases the PWM rectifiers are of current type, that is, they have a smoothing reactor on the DC side. In such rectifiers, an LC filter has to be inserted on the AC side to reduce current harmonics due to the PWM operation. However, the LC filter may cause waveform distortion and transient oscillation of the AC side current.
As a solution to this problem, we propose a new control method introducing AC side current control by means of state feedback of the LC filter. In this case, both the DC output current and the AC input current controls should be achieved by the PWM operation of the rectifier. Furthermore, to obtain sufficient controllability regardless of the operating condition, the DC output and AC input current controls should be done independently. To meet these requirements, existing control methods for PWM rectifiers are not applicable directly.
In this paper, a novel control circuit configuration and a method of generating PWM pulse pattern which are suitable for the proposed control method are described in detail. From the view point of stability, feedback coefficients and circuit parameters are investigated on the basis of root locus analysis.
Some experimental results are also shown to confirm the effectiveness of the proposed control method and the validity of the analytical results. Improvement of the AC side current waveform and stability of the transient response are demonstrated by these experimental results.

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Demand for rail transportation is increasing rapidly in the big city areas. However for various reasons such as environmental concerns, it is not easy to expand capacity. In order to expand capacity and speed up service, a new system must be introduced. For the Automatic Train control (ATC) system, we peopose the on-board pattern control ATC system (referred to as A-ATC) be utilized. It achieves higher transportation efficiency through high-speed, high-dencity operation, while maintaining current levels of safety. The A-ATC system allows the deceleration control system to be set individually for each train, according to the vehicle type. By upgrading vehicle performance A-ATC upgrades performance of the ATC system as whole. We will be able to introduce the A-ATC system gradually, by minor modification of the current ATC system.

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This paper presents a new brushless three-phase synchronous motor which has no exciter. The technique applied to the motor gives an effective way for conventional brushless synchronous motors to simplify the system configuration. The stator of the motor is equipped with a double-star connected armature winding which has two neutral points. The rotor is a cylindrical one, which is equipped with a two-phase field winding. The field winding is connected with shaft-mounted rectifiers. A DC voitage is applied to the two neutral points of the armature winding to obtain the rotor excitation when the motor is operated at synchronous speed. At that time, the armature winding acts as a stator DC exciting winding while acting as a load winding. In this paper the principle and characteristics of the motor are described, and the experimental results are shown. It is confirmed that with a 2-kW experimental machine, the proposed motor has good performance. For example, by adjusting the stator DC current, this motor's power factor can be easily controlled within a wide range.

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For the purpose of the effective use of the power facilities, the control strategy for the leveling of the active power and the compensation of the reactve power is proposed based on the fuzzy logic using small capacity of the superconducting magnetic energy storage (SMES) equipped near to the consumer. The varidity of the proposed control strategy is clarified by the simulation. The summary in this paper is as follows.
(1) In the approximate reasoning, the rule for the current flowing into the SMES is added to the rules for the leveling of the active power and the energy stored in the SMES which are applied in the previous paper. Then, only PB is adopted to the membership function for this rule because of the function of the current limit.
(2) The variance of the controlled results to the sustained component is indicated in the three-dimensional expression. Then, the range of the scalling factor is shown for the good controlled results of leveling the active power.
(3) The controllable range in which the power control can be achieved in accordance with the power demand expands comparing wiht that in the previous paper.
(4) The variance of the controlled results to the sustained component becomes smaller than that in the previous paper. It is clarified that the proposed control strategy can level the fluctuating load power better.

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The necessity to make more eforts for cutting back on energy consumption and saving the energy is now keenly felt in order to cope with progressive depletion of fossil fuel resources and envionmental destruction going on our planet.
Many regenerative braked cars (205 type) with superposed field excitation control are being introducted in DC electric railway. In the case of silicon rectifier substation, under light load the feeding voltages becomes higher, but lower under heavy load. However in the case of thyristor rectifier (constant voltage dc feeding system), under light load the feeding voltage can be kept constant. So we can reduce the resistor loss in powering operation and improve the regeneration coefficient in regenarative operation.
The authors have complished a simulation program for regenerative braked cars with superposed field excitation control which considers the train diagram and demonstrated the validity of the simulation program by a test of JR Yokohama line, and shown with simulation that the constant voltage feeding system is one of the most energy saving systems.

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A new type of motor which utilizes multi-layer piezoelectric devices for electromechanical power conversion and mechanism of the strain wave gearing for generation of traveling waves and motive force is proposed in this paper. Construction and basic operation of the motor are described. The motor can be operated in variable frequency, because piezo-devices are operated in non-resonant mode. Approximate analysis is performed to clarify the operation mechanism of the motor and obtain characteristics on the rotational speed in the case of no load. Experimental results on rotational speed of the prototype motor made of metals except for the piezoelectric devices are also presented, which verifies the feasibility of the proposed motor.

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Since a superconducting generator (SCG) consists of a superconducting field winding, a nonmagnetic cryogenic rotor and an airgap armature winding, its design method differs from that of the conventional generator. Practical applications require establishment of its electrical and mechanical design methods.
A design flowchart of the SCG was shown and the basic design method was clarified. For this method, the electrical and mechanical design of a 50MVA experimental generator was carried out. Its design specifications and size were compared with a future 1, 120MVA generator and a 778MVA conventional generator. Furthermore, synthetic stress applied on the main rotor components, such as the torque tube and room temperature damper, was obtained. From the test results of generator power loss and the V curve under synchronous condenser operation, the design method was proved to be valid.

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The three-phase induction motor with solid-iron rotor has advantages in case of manufacture, in high torque per ampere at standstill, and in withstanding high rotational stresses. Recently there has been wide interest in the possible use of such a solid-rotor induction motor for ultrahigh-speed inverter drives with suitable high stator frequency. However, the copper loss of the solid-rotor induction motor becomes large, because it is designed with a high resistance rotor. Accordingly, the efficiency and the power factor of the motor are lower than those of conventional induction motor.
In this paper, it is clarified experimentally that starting and running characteristics of the solid-rotor induction motor are improved considerably by providing narrow slits and end-rings on the rotor. Then, a new equivalent circuit for the solid-rotor induction motor is derived considering the behavior of the solid-iron rotor as that of the double-cage rotor, and a method of determining the circuit constants for the motor is proposed. The starting characteristics for the solid-rotor induction motor with narrow slits and end-rings on the rotor is calculated using the proposed equivalent circuit. The results calculated for starting characteristics from the equivalent circuit method agreed satisfactorily with results obtained. from the measurement.

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