Soft-switching techniques for PWM three-level converters

This paper proposes a family of modulation strategies including nine modulation strategies for PWM three-level converters. The modulation strategies can be classified into two kinds according to the turn-off sequence of the two power switches of the switches pair. The concept of the leading switches and the lagging switches is introduced to realize soft-switching for PWM three-level converters. The realization of soft-switching for both the leading switches and the lagging switches is proposed, based on which, soft-switching techniques for PWM three-level converters can be classified into two kinds: zero-voltage-switching (ZVS) and zero-voltage and zero-current-switching (ZVZCS). The modulation strategies and topologies for the two kinds of soft-switching PWM three-level converters are proposed.