Fault Diagnosis and Tolerant Control of Dual-Active-Bridge Converter With Triple-Phase Shift Control for Bidirectional EV Charging Systems

Efficiency and reliability are essential for isolated bidirectional dc-dc converters in electric vehicle (EV) battery charging systems. As one promising power interface between energy storage components and power bus, dual-active-bridge (DAB) dc-dc converters have gained wide applications due to the advantages of galvanic isolation, symmetric circuit structure, high power density, and easy control implementation. In this article, based on the triple-phase shift (TPS) control, a fast and effective fault diagnosis strategy is proposed for DAB converters to improve both the power conversion efficiency and reliability. First, the operation principle of DAB converters with TPS control is presented. Then, a fast and effective open-circuit fault (OCF) analysis under different operation modes of TPS control is presented. Based on the resonant phenomenon during the fault conditions, an OCF diagnosis strategy that uses midpoint voltage as diagnosis criteria is proposed for DAB converters under the advanced TPS control to identify the faulty devices quickly and avoid the system collapse. After the failure switches are located, fault-tolerant operation is adopted to maintain the power transmission ability of DAB converters and ensure safe operation. The experimental results are provided to validate the correctness and effectiveness of the OCF performance analysis, fault diagnosis, and tolerant method.