On the transient short-circuit of RCD snubber in high power three-level IGBT inverter

Besides the imbalance between the voltages of internal and external power device, the NPC three-level inverter with the 3RCD snubber circuit has a large short-circuit current in the commutation path, which increases the current stress of the power devices, and even endangers the regular operation of the power devices. In this paper, the four kinds of short-circuits generated by 3RCD in a three-level NPC inverter are presented, and their reasons are also analyzed. Theoretical analysis is verified by the simulation and experiments. The result shows that the 3RCD snubber circuit with the above shortcomings is not enough excellent to be used in high-power NPC three-level IGBT inverters. More effective methods should be proposed to suppress the transient over-voltage of IGBT.