A State Estimator-Based Approach for Open-Circuit Fault Diagnosis in Single-Phase Cascaded H-Bridge Rectifiers

The reliability of single-phase cascaded H-bridge rectifiers (SPCHBR) is regarded as one of the most important factors for achieving the improvement of the stability and availability of the single-phase power electronic traction transformer in the railway traction system. Accordingly, an open-circuit fault diagnosis approach for single transistor faults in the SPCHBR is proposed in this paper. The proposed diagnostic algorithm relies on the state estimator and normalized detection variables. Moreover, fault cell detection and fault transistor location can be implemented according to the characteristics of the voltage and current residuals. The proposed method requires no additional sensors and only the information from the control system. Furthermore, the diagnostic method has a fast diagnosis speed and robustness against false alarms under different operating conditions. Test results in the hardware-in-the-loop system have illustrated the validity and feasibility of the proposed diagnostic method.