Pwm inverter control system and method

Abstract

A PWM inverter system having a sine (low-pass) filter. The sine filter includes a reactor and a capacitor, and is connected to the output of a PWM inverter. The instantaneous current flowing through the capacitor, and the instantaneous output current supplied from the sine filter to a load are detected. An instantaneous voltage command value is corrected on the basis of the detected current values. This makes it possible to limit oscillating waveforms involved in the output voltage of the PWM inverter without using a damping circuit which was connected in parallel with the capacitor in a conventional sine filter. The capacitor of the sine filter may be composed of a plurality of capacitors connected in parallel, and this will serve to further reduce the size of the sine filter. In a parallel operation of a plurality of PWM inverters, a cross current, that is, the difference between an instantaneous output current command value and an instantaneous capacitor current command value is reduced by correcting the instantaneous voltage command value. This makes it possible to share the current assigned to each PWM inverter with high stability.