A transformer assisted zero voltage switching scheme for the neutral-point-clamped (NPC) inverter

This paper proposes a transformer assisted PWM zero voltage switching neutral-point-clamped (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, designing as well as testing results from a 7 kW prototype are presented in detail.