An Open-Circuit Fault Diagnosis Method for Four-Wire T-Type Three-Level Rectifier

The four-wire T-type three-level rectifier (four-wire 3LT2R) has a wide range of applications because of its excellent performance. However, the open-circuit fault of transistors can lead to power loss, current harmonics, and even system crashes. A novel open-circuit fault diagnosis method for four-wire 3LT2R based on the three-phase currents and modulation voltages is proposed in this article, considering power factor regulation. At first, the relationship between the power factor and the working interval of the transistor is deeply analyzed. Then, the diagnostic method is designed based on the analysis. The “zero current” in each phase current is used to detect the faults with the different features related to the size of working intervals. After the fault is detected, the fault transistor is located according to the polarities of the currents and the modulated voltages. No additional sensors are needed. Experiments are carried out, and the results show its high effectiveness, robustness, and applicability for different power factors.