A Novel Fault Detection of an Open-Switch Fault in the NPC Inverter System

In this paper, a simple fault detection scheme is proposed for improving the reliability under the open-switch fault of a three-level neutral point clamped (NPC) inverter. The fault of switching device is detected by checking the change of a pole-voltage in a NPC inverter. This method has the advantages of fast detection ability and a simple realization for fault detection, compared with existing methods. Reconfiguration is also performed by two-phase control method that used to supply the balancing three-phase power to the load continuously. This proposed method minimizes a bad influence on the load caused by a delay of fault detection. This method can also be embedded into the existing NPC inverter system as a subroutine without excessive computational effort. The proposed scheme has been verified by simulation and experimental results.