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

This paper presents a universal auxiliary commutation cell for pulse-width modulated (PWM) inverters termed 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 turn-off, with controlled di/dt and dv/dt. As a result, commutations of the main power devices occur without any losses. This unique characteristic is not achieved by any other soft-switching commutation cell for inverters hitherto presented in the literature, making it a strong candidate for use in low-power (MOSFET), medium-power (IGBT) or high-power applications (GTO, thyristor). Furthermore, reverse recovery losses of main diodes are minimized and auxiliary switches commutate at zero current. To demonstrate the operation of the proposed universal auxiliary commutation cell, a ZCZVT PWM full-bridge inverter is analyzed. To evaluate the operation of the auxiliary circuit in different conditions, prototypes with both IGBTs and MOSFETs for different output powers levels were implemented and their performances compared. Experimental results confirm that there is no overlap between main switch current and voltage, and that waveform ringing is practically eliminated.