Aiming at the switch fault diagnosis of diode neutral point clamped (NPC) three-level inverter, by studying the changes of circuit working conditions after the switch fault of NPC three-level inverter, a switch fault diagnosis and location strategy of NPC three-level inverter based on line voltage deviation is proposed. In this strategy, the estimated line voltage of the inverter under normal operation is obtained from the switching state of the inverter circuit, and the line voltage deviation is obtained by comparing the actual line voltage with the estimated line voltage. By judging the value of line voltage deviation, the fault flag output after inverter circuit fault is realized. Then, by studying the characteristic law of line voltage deviation after the failure of different switches, the location of specific faulty switches is realized. This method outputs the diagnosis results in real time and quickly, and there is no need to add additional sensors. The feasibility of the proposed scheme under the conditions of three-phase load balance and three-phase load imbalance is verified by simulation.

inverter; fault diagnosis; line voltage deviation; location;