A New Fault-Tolerant Scheme for Switch Failures in Dual Active Bridge DC-DC Converter

The dual active bridge (DAB) dc-dc converter is widely investigated for applications such as solid-state transformers (SSTs), battery energy storage systems, and electric vehicle (EV) chargers. Failures in active devices of the DAB can cause reduced terminal voltages or uncontrollable currents eventually leading to converter disconnection. The above-mentioned consequences cannot be corrected by disabling the complementary switches of the faulty leg or reconfiguring the full-bridge (FB) DAB to a half-bridge (HB) DAB topology. In this article, a new fault-tolerant (FT) approach is proposed that works for both short-circuit (SC) or open-circuit (OC) failures in the active devices of the DAB dc-dc converter. Parallel combination of a fault-tolerant capacitor and a fast acting fuse, known as fault-tolerant unit, is connected in series with the primary as well as secondary of the transformer. Once the fault is detected, the output voltage is boosted to its pre-fault value through the incorporation of fault-tolerant capacitors along with variation in control parameters, ensuring the continuity of operation. The proposed post-fault reconfiguration scheme is validated experimentally using a 1 kW, 250 V DAB prototype.