Detection method of an open-switch fault and fault-tolerant strategy for a grid-connected T-type three-level inverter system

This paper proposes diagnosis method and fault-tolerant control algorithm for a grid-connected T-type three-level inverter system. The faulty switch is identified by a normalized average phase current and a change of neutral-point voltage by injection of a negative reactive current. The fault-tolerant algorithm can be applied when the middle switches are faulty by simply modifying the conventional SVM method. The proposed methods are not require additional hardware and do not involve complex calculations. Therefore, the proposed methods are cost-effective and easy to use. The simulation results confirm the feasibility and effectiveness of the proposed fault diagnosis and fault-tolerant methods.