The inverter-fed vector controlled induction motor with a speed sensor has been used in many industrial applications as actuating motors of variable speed servo-systems. In this paper, many speed sensorless methods which determine the rotating speed of these induction motors by using the motor parameters, the instantaneous values of phase voltages and or phase currents sensing are collected. And the point at issue of the each sensorless systems are summarized put in order.

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In this paper, the authors propose the calculation method of the active power filter compensating current, where a nonlinear load exists in the three-phase three-wire unsymmetrical voltage system. This new method has been named extension pq method. The authors have experimented with the extended pq methods and the usual pq method, using a current controlled IPM inverter for both methods. The results of the experiments proved that in the unsymmetrical voltage system, the source current was distorted in case of the pq method, but undistorted in case of the extension pq method.

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This report describes two types of parameter optimization methods in power electronics. One is an estimation method of circuit parameters of a power electronic circuit in which they are difficult to measure directly especially in high-frequency applications. From measured waveforms, they are estimated by the least-squares method in a model circuit. The other is an optimization method of circuit parameters of a power converter circuit design. For a given index function, the optimized parameters are computed by minimizing the function under given constraints. Filter examples of an AC power converter and an inverter circuit are shown. For the optimization methods, parameter sensitivities are necessary. They are computed by the direct differentiation method which is simple analysis of derived sensitivity circuits.

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In the industrial field, PM motors are widely used as a high-performance motor without maintenance. Recently Synchronous Reluctance Motor (SynRM) and Interior PM Motor (IPM) is drawing the attention. Therefore many designs of the rotor are proposed. In this paper, we make a SynRM with three slit and PM/Reluctance Hybrid Motors where the permanent magnet is inserted in the slit. We obtain four type Hybrid motors by adjusting the volume of PM in the slit. We investigate characteristic of SynRM and four type Hybrid motors experimentally. We clarify relation between magnet volume and output, especially speed v. s. output characteristics. Adjusting magnet volume, we can obtain the best motor accordinng to the object of use. At last we compare IPM with Surface PM motor (SPM).

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This paper proposes a novel harmonic suppression scheme for Uninterruptible Secondary Battery System (USBS). USBS has large capacity of secondary batteries, such as lead-acid or NaS, and it has plural operational modes including local load leveling and unintermptible power supply (UPS). In local load leveling mode, the input current of USBS is desired to be sinusoidal even when the commercial a. c. bus voltage has any harmonic distortions. But some mains circuit configurations cause the increase of harmonic distortion of the input current of USBS. In order to restrain such harmonic distortions, we propose a novel harmonic suppression scheme and the effect of the proposed control scheme is confirmed by the transfer function analysis and experiment.

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