Abstract
A design method of an AC motor variable speed control system, which is made up of a power source, a PWM converter, a PWM inverter and an AC motor, is described. And how to decide the DC Link voltage reference is described. Main purpose of this research is to design a system which satisfies the following control objectives; motor speed control, PM motor vector control, DC voltage control and input power factor control. Optimal regulator theory is suitable for control system design such a control system with multiple control objectives.
And in this paper, one method how the DC voltage reference should be decided, the modulation ratio optimized control, is proposed. That is, the DC voltage which satisfies the condition that the PWM modulation ratio is lower than 0.95 and higher than 0.85 is obtained. By this manner, not only the quick motor speed response but also the suppression of total harmonic distortion factors (THD) in source current and losses in semi-conductor swichting devices are realized.
Simulation results of the proposed control system, are shown with discussions.
