Zero-current and zero-voltage soft-transition commutation cell for PWM inverters

This paper proposes a universal auxiliary commutation circuit for PWM inverters named the zero current and zero voltage transition (ZCZVT) commutation cell. It provides zero current and zero voltage commutation, simultaneously, during main power devices turn-on and turnoff, with limited di/dt and dv/dt. As a result, the commutations of the main power devices occur truly without losses. Furthermore, reverse recovery losses of main diodes are minimized, and auxiliary switches commutate at zero current. A brief review of soft switching topologies applied to inverters is presented. In this review, focussed on pole-commutated inverters, the basic operating principle of the main zero voltage transition (ZVT) and zero current transition (ZCT) inverter topologies are discussed and most important features are identified. The operation of a ZCZVT PWM full-bridge inverter is analyzed and experimental results are presented. These results confirm that there is no overlap between main switch current and voltage and the waveforms ringing are practically eliminated, which possibly reduces high frequency EMI.