A Path-Based Switch Open Circuit Fault-Tolerant Method for Three-Phase DAB Converter

The three-phase dual active bridge (DAB3) converter achieves the bidirectional power transmission and voltage conversion in dc power grid. However, DAB3 is susceptible to switch open circuit fault (SOCF), causing transmission power loss and excessive current stress. Thus, a path-based fault-tolerant method (PFTM) for SOCF in DAB3 is proposed. First, the transferred energy of each phase is investigated by modality analysis of DAB3, thus, a path energization method is proposed for PFTM, and switching pattern reconfiguration strategy is summarized by switching functions during SOCF, enlarging maximum transmission power within maximum high-frequency-link (HFL) inductor current. Moreover, in the PFTM, the fault paths/legs are employed, reconfiguring the current path of modality, actively adjusting the
on
-time of antiparallel diode, and realizing the bidirectional transmission power improvement. Furthermore, the optimization strategy of phase shift ratio is proposed to reduce HFL current stress and keep zero-voltage switching, when SOCF is in primary and secondary sides. Compared with traditional methods, the PFTM can realize a wider power range and voltage gain, and a higher maximum transmission power, to ensure the safety and reliability of DAB3. Finally, experimental results verify the theoretical analysis.