CONTROL STRATEGY OF A SOFT-SWITCHING THREE-PHASE PWM INVERTER

摘要

The influence of triangular and saw-tooth carrier wave on the action of the soft-switching inverter is described. When the triangular carrier wave is used in the soft-switching action, not only the resonance-trigger time is difficultly controlled due to the unfixed switching time, but also the DC voltage utilization is insufficient due to many resonance times, Although the positive slope saw-tooth carrier can avoid these problems above mentioned, it brings zero vector states around the vertical edges where the energy cannot be exchanged between the motor and the resonance circuit, and thus the condition of soft-switching resonance cannot be satisfied. The saw-tooth carrier wave, with alternate slopes (positive or negative) according to the motor current polarities to, complete the action of this soft-switching PWM inverter is proposed. The results of experiments indicate that this control method can obtain near-sinusoidal output line current waveforms in the inverter.