Sinusoidal waveform compensator for optimal digital control of three-phase PWM inverter

Optimal digital control method for a three-phase PWM inverter is proposed. It is based on the single-phase control method which has already reported. It utilizes the internal model principle to eliminate steady-state errors and to improve responses. Its principle is very simple that two phases are controlled as if they were independent and the other is controlled with the negative sum value of the two as long as the filter inductor and capacitor values are the same. It has a big advantage that there is no problem for unbalanced loads. It is validated for its performances through linear unbalanced and nonlinear loads theoretically by a simulator Saber and experimentally with a DSP-based digital control system