Diagnosis method of an open-switch fault for a grid-connected T-type three-level inverter system

This paper proposes a diagnosis method of an open-switch fault and fault-tolerant control algorithm for a grid-connected T-type three-level inverter. The location of the faulty switch is identified by using the changes of average phase current and the neutral-point voltage. The fault-tolerant control algorithm can be used when the open switch fault occurs in the middle switches. It is achieved by simply modifying the conventional SVM method. The proposed methods are advantageous as they do not require additional sensors and they do not involve complex calculations. Therefore, this method is cost-effective and industrial interesting. The simulation results confirm the feasibility and effectiveness of the proposed fault-diagnosis and tolerant methods.