Fault Detection and Mitigation of DC/DC Converters with Semiconductor-Based Isolation for DC-EVSEs

In larger electric vehicle (EV) charging parks supplied by a common DC bus, the galvanically isolated DC/DC converters usually used in the charging stations constitute a significant portion of the overall costs, size and losses. To reduce these costs, a DC/DC converter with semiconductor-based isolation is examined in this paper. To achieve a similar level of safety as galvanically isolated converters, faults within the converter must be detected and mitigated. A fault detection and mitigation strategy is therefore introduced, regarding always-on faults of semiconductors in order to enhance the safety aspects of this converter topology. A bidirectional 50 kW converter prototype is designed for the application of charging 400 V and 800 V EVs from an industrial 650 V DC-grid. The fault detection is validated with laboratory measurements. A comparison of the efficiency and power density of the Semiconductor-based Isolation (SCI) converter with a conventional converter is performed, revealing significant advantages of the proposed topology like a size reduction of approximately 33 %.