Fault-Tolerant Control of a Single-Phase Bidirectional Dual Active Bridge DC-DC Converter

Single-phase voltage-fed dual active bridge (DAB) converters have emerged as a prevalent topology for high-power isolated dc-dc conversion, facilitating bidirectional power flow in electric vehicle dc fast chargers (DCFC). An open-circuit fault (OCF) in power switches brings a significant risk to the functionality and safety of power electronics interfaces (PEI). In DAB converters, the OCFs can give rise to current stress, DC bias, and capacitor voltage instability. It can also saturate the transformer magnetic core, leading to device over-current. To overcome these issues, the faulty switch needs to be identified so that a fault-tolerant control can be employed to ensure the safe operation of the DAB converter. In this paper, a fault diagnosis technique to detect the fault and identify the faulty switch is explored, followed by developing an enhanced fault-tolerant control scheme. This approach needs low-bandwidth current monitoring solely based on one side of the transformer, providing both economic and design benefits. The proposed method can be executed without requiring any hardware modifications.