Base/gate drive suppression methods for NPC inverter legs

The base/gate drive suppression methods for the voltage source inverter leg are those which suppress base/gate drives of either of the two switching devices of the leg. These methods have the merits that they do not have the conventional dead time problem, raise the reliability of the leg, and others. In this paper, the concept of these methods is extended to the NPC inverter leg, so that two types of base/gate drive suppression methods for the NPC inverter leg are proposed. The one is the output current polarity detection type and the other is the output voltage polarity detection type. These two methods have nearly the same performance, but the latter is easier to implement than the former.