A SOFT-SWITCHING TECHNIQUE FOR NOVEL ZVT-PWM INVERTERS

A novel Direct Current (DC)-rail parallel resonant Zero Voltage Transition (ZVT) voltage-source Pulse Width Modulation (PWM) inverter for three-phase motor drives is proposed with two features, i.e., all power devices are switched under soft-switching conditions, and PWM can be realized easily. It has a simple control scheme. Compared with traditional soft-switching inverters, it is less dependent on the load current, and imposes fewer requirements on power ratings of the resonant components and auxiliary switches as verified by analysis and experimental results. This work analyzes and solves the unbalancing problem of neutral-point voltage with light load in the proposed inverter by presenting its generation principle and impacts on a soft-switching circuit. Compared with the hardware switching circuit, when the power of the inverter and switching frequency become higher, the power loss by using the proposed soft-switching circuit is greatly reduced and efficiency is significantly improved.