In recent years, reactive power controllers using power-electronics technology (Static Var Compensators) have been well researched and developed with a view to voltage control, power stabilization, power swing stabilization, power factor improvement, and suppression of voltage flicker. The remarkable characteristics of SVC are to make it possible to continuously control these properties, and to have quick response. The present paper deals with the SVC based upon reduced harmonics converter with tap changers. In addition to the foregoing characteristics, the SVC has some more ones given below: (1) This SVC, with the use of tap changers of interphase transformers, can make its main circuits so simplified. (2) SVC cuts harmonic current down into its non-fault level (3.3% distortion factor), so that it does not cause any practical problem. (3) The SVC so well responds that it makes the high-speed controlling of reactive power less than about 3Hz. (4) The SVC can control lead or lag reactive power itself, so that its whole system can be made compact and small-sized.
This paper proposes a fully digital current control method with DSP for the vector control of the induction motor. First, we present a new dead time compensation circuit, whch makes the delay time between the PWM signal and the actual output voltage constant. Therefore, the synchronous current sampling with the PWM signal can detect the accurate fundamental frequency component from the ripply current. Moreover, we discuss the current regulator which improves the response of the primary current and compensates the parameters deviation of the motor. And, we show that this control system is possible to get the quick response and the low current ripple in spite of the slow sampling rate by the experimental results.
The single-phase converter or rectifier always has a voltage ripple in the output DC voltage, because the instantaneous power of the single-phase AC line varies on the double frequency of the line. In order to obtain a smooth DC voltage, an energy storing element is necessary. The smoothing capacitor is used to reduce the ripple voltage in the DC output. Usually, it has much larger capacitance than that needed to absorb the ripple energy. This paper discusses the required capacitance to absorb the ripple energy, and represents a ripple compensation circuit with a small auxiliary capacitor controlled by a 2-quadrant chopper connected in parallel to the smoothing capacitor. The appended capacitor works under large ripple voltage and efficiently absorbs the ripple energy. The ripple compensation curcuit works as an equivalent capacitor which has a large capacitance.
In current control systems of AC/DC thyristor converters, digital PI controllers are usually used. But in case of lacking the knowledge about the parameters of the systems, it is difficult to choose appropriate values of gains. Moreover, the control characteristic of a PI controller will change when the input signal reaches its upper or lower bound. This paper presents a new controller by using MRAC (Model Reference Adaptive Control) theory. First, the unified discrete-time model for the full range of the control angle is derived. Next, based on the strict model and the approximate one respectively, two design methods of the MRAC controller are proposed. With the approximate model, the number of the identified parameters can be reduced and the convergence speed of the patameters is high. Finally, the results of computer simulation and experiment show that the MRAC controller is stable, and it's dynamic characteristic is much better than that of PI controllers.
This paper describes a method of determining parameters of PWM rectifiers based on the degrees of total harmonic distortion (THD). The inductance value of AC reactors and capacitance value of DC capacitor give a great influence on the amplitude of the harmonics in the AC input currents and DC output voltage, respectively. So far simulation-based harmonic analysis is dominant. In this paper we propose the harmonic distortion determining factor that provides a simpler and broader manner of obtaining THD values, that is, it enables us to calculate approximate THD values without conducting any simulations or experiments. Finally experiment using a DSP is carried out to confirm the usefulness. An optimal regulator theory is applied to the controller design.
This paper presents a feature indexing and case retriveal method of machine parts for computer aided design (CAD) based on case-based reasoning (CBR). CBR is a promising method for assisting knowledge acquisition of expert systems. The new method is for standardization and efficient design of sheet metal parts using the CBR. Feature indexing and similarity calculation are key techniques for feasible CBR. A new feature indexing method and a new method of calculating similarities of sheet metal parts are described in this paper. Fuzzy measure is introduced for incorporating human measure of similarities of the parts. Using the indices, case retrieval is carried out.
This paper deals with a consideration concerning materials for the movers, volume ratio of the stator and of the mover, structure of the mover in a cylindrical moving iron type linear oscillatory actuator (LOA) having a permanent magnet. Following results are obtained in this paper. (1) The static thrust characteristics are evaluated on two movers. Movers P and S are made of a permendur and a stainless steel, respectively. It is clarified that the static thrust of the mover P is 30% larger than that of the mover S. (2) It is suggested that the structure of the mover P should be improved to eliminate a “lump” in static thrust-displacement curve due to the step on the mover, which disturbs smooth motion of the LOA.
Compared wiht other synchronous motors, it is well known that the pull-out torque of the hysteresis motor is very decreased by the influence of the space higher harmonics. Two kinds of space harmonics exists in the motor. One of them (ΔH: constant) which is produced in the m. m. f., is due to the stator winding arrangement. The other (ΔB: constant) which is produced in the fluxdensity, is due to non-uniformity of the permeance in the air gap. The analysis due to the equivalent circuit of the hysteresis motor considering two kinds of the space harmonics has not been reported until now. In this paper, we derive the equivalent circuit considering influence of two kinds of the space harmonics. And, it is shown that the agreement between the calculated and the experimented values is comparatively good. Finally, we will make clear quantitativel influence of each harmonicto the pull-out torque.