An improved McMurry snubber for Three-level NPC IGBT converter

Three-level neutral point clamped (NPC) converters seem to be best suitable for high power and medium voltage applications. However, owing to the special configuration of three-level NPC converters, it´s very difficult to design the snubber circuits which are necessary to ensure the appropriate switching conditions for the insulated gate bipolar transistor (IGBT). This paper firstly point out that pulse blocking process is ignored by most snubber circuit designators and introduce new overvoltage problem to the inner IGBTs. Then, detailed discuss the general design principle to avoid these overvoltage problems. Finally, propose an improved McMurry snubber circuit for three-level NPC IGBT converter. Simulation and experimental results demonstrate the validity of the above analysis and the effectiveness of the improved snubber circuit.