Fast Detection of Open Circuit Device Faults and Fault-Tolerant Operation of Single-Phase H-Bridge Flying Capacitor Multilevel Converters

This paper proposes a simple and fast detection technique for power device open circuit (OC) fault in single phase H-bridge flying capacitor multilevel converters (H-FCMCs). A fault mitigation technique is also proposed adding four additional switches to the H-FCMC regardless of the number of commutation cells or levels. The fault detection concept only needs to sense the voltage and direction of current at the output terminal of the HFCMC to detect and localize the fault. The algorithm compares the measured and expected terminal voltage considering the commanded switch state and the direction of the terminal current. A circuit with multiple windows detectors is utilized to track the output voltage level and current direction with high bandwidth. Once an OC fault is detected and localized, auxiliary switches operating at the fundamental output frequency will be activated to reconfigure the H-FCMC converter to the half H-FCMC with the same number of output voltage levels but with half the output switching frequency.