A soft commutated neutral-point-clamped (NPC) inverter: theory and experimentation

A soft commutation circuit aimed to substitute for the conventional snubber in a GTO NPC inverter is presented in this paper. The small rating lossless auxiliary branch creates soft switching conditions for the main devices without having to subject them to extra voltage/current spikes or any modulation constraints. Hence it allows for considerable extension of the power range and the frequency range of the main installation. Operation, analysis, and designing of the circuit as well as the experimental results from a prototype are detailed in the paper.