A Similarity-Based Robust Open-Circuit Fault Diagnosis Method for Dual Pulse Rectifiers

This letter proposes a current similarity-based robust diagnosis scheme to detect open-circuit (OC) faults for insulated gate bipolar transistors (IGBTs) in dual pulse rectifiers. The similarity indicator between the ac-side currents of the two rectifiers is calculated based on the structural characteristics, which are independent of system parameters and naturally robust to voltage fluctuations and load changes. Also, it avoids modeling or additional sensors. Then a proper threshold is designed by analyzing variable behaviors under various normal and faulty operating conditions. Finally, the faulty switches are located by the integrals of the extracted dc-side current and designed time-sequence current indicators without injecting specific driving signals. The effectiveness of the proposed fault diagnosis method is demonstrated by both simulation and experimental testing.