Open-Circuit Fault-Tolerant Control for Three-Phase 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. In this paper, a new fault-tolerant method for current-fed dual active bridge (CF-DAB) converters with blocking capacitors is proposed. The operation of the CF-DAB converter when an open-circuit fault occurs is comprehensively presented and 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 high-frequency transformer, which could avoid the core saturation of the transformer. Also, the DC blocking capacitors help isolate the faulty phase when a frozen-phase fault-tolerant method is applied. The proposed method is shown to be a practical, simple, low loss, and effective solution for not only open-circuit fault isolation but also for shedding capability of the multi-phase converter. The proposed concept could be applied for general multi-phase current-fed converters. The experiment of a 6-kW prototype is implemented to confirm the proposed concept.