Efficiency considerations of load side soft-switching inverters for electric vehicle applications

This paper critically evaluates the efficiency of load side soft-switching inverters for electric vehicle (EV) drive applications. Five types of load side soft-switching inverters are studied, including the auxiliary resonant commutated pole inverter (ARCP), the zero-current-transition (ZCT) inverter, the zero-voltage-transition (ZVT) inverter with coupled inductors (ZVTCI), the ZVT inverter with a single switch (ZVTSS), and the ZVT inverter with a single inductor (ZVTSI). Loss categorization methods are developed using simplified device models in order to reveal the mechanism of efficiency improvement. It is shown that the ZVTSI and the ZVTSS have poor efficiency performance compared to the hard-switching inverter because of the extra turn-off of main switches and the nonzero-current-switching for the auxiliary devices. The ARCP, the ZCT inverter and the ZVTCI show substantial energy savings. Besides, the variable timing soft-switching control can further increase efficiency in ZVT inverters.