Open-Circuit-Fault Diagnosis and Fault-Tolerant Strategy for Flying Capacitor Dual-Active-Bridge DC-DC Converter

The flying capacitor dual-active-bridge (FC-DAB) dc-dc converter is a promising dc-dc converter for medium-voltage and high-voltage applications. However, the open-circuit switching fault (OCSF) of the FC-DAB converter may result in various negative effects such as transformer voltage distortion, inductor current dc bias. Therefore, fault diagnosis and fault-tolerant control strategy are essential. Fault diagnosis merely based on the polarity of inductor current or the midpoint voltages of the bridge arms are not applicable for the FC-DAB converter. Moreover, FC-DAB converter has more working states which provides potential for fault-tolerant operation. To address these issues, this paper proposes a fault diagnosis and fault-tolerant control strategy for the FC-DAB converter. In the proposed fault diagnose strategy, the average values of the midpoint voltages of the bridge arms and the low-potential side voltages of flying capacitors are utilized to identify the faulty switch. Based on blocking the complementary switch, symmetry operational characteristics can be restored with the proposed fault-tolerant strategy. The proposed fault diagnosis and fault-tolerant control strategy are verified by simulation.