Diagnosis method of open-circuit fault for T-type three-level inverter based on residual voltage

Multilevel inverter topologies have been widely used in applications of wide-power range and fault diagnosis of such circuits is becoming more and more important. T-type three-level inverters have advantages in efficiency compared to common neutral-point-clamped inverters. This paper proposes a new diagnosis method of an open-circuit (OC) fault for a T-type three-level inverter. The method is implemented by measuring the phase voltage of the circuit and comparing it with the reference voltage of the circuit to obtain a residual voltage. Firstly, according to the analysis of different current conduction paths of the circuit, the voltage level changes of the circuit bridge voltage and phase voltage in different device open modes are studied. Then, based on the above analysis, a device open-circuit fault diagnosis scheme is proposed based on the residual voltage. Finally, simulation and experimental results show that the proposed method can identify the faulty switch exactly and quickly.