Fault-tolerant control of three-phase bidirectional current-fed dual active bridge DC-DC converter

Fault-tolerant methods have been recognized for improving the reliability of multi-phase bidirectional DC-DC converters, including current-fed and voltage-fed dual active bridge converters. Fault-tolerant research for voltage-fed dual active bridge converters has caught much attention recently. However, few fault-tolerant methods for current-fed dual active bridge (CF-DAB) converter have been developed because it becomes more challenging due to the asymmetrical structure between primary and secondary sides. In this paper, a new fault-tolerant CF-DAB converter with blocking capacitors is proposed. The operation of the converter when an open-circuit fault occurs in different fault scenarios of the CF-DAB converter is comprehensively analyzed. A frozen phase fault-tolerant method with additional blocking capacitors on both sides of the transformer is proposed. The aim of the use of blocking capacitors is to block the DC current component of the filter inductor from passing through the transformer, which could otherwise result in the saturation of the transformer. Also, the DC blocking capacitors help isolate the faulty phase when the frozen-phase fault-tolerant method is applied.