Zero-voltage switching for the neutral-point-clamped (NPC) inverter

This paper proposes a transformer-assisted pulsewidth-modulation zero-voltage-switching neutral-pointclamped (NPC) inverter. With the assistance of a transformer-assisted small-rating lossless auxiliary circuit, the main switches work with zero-voltage switching without suffering from any voltage/current spikes, under simple explicit control. The technique allows for higher operating frequency and better device utilization of the NPC inverter. Operation, analysis, design, as well as testing results from a 7-kW prototype are presented in detail.