Coordination of RB-IGCT-based Solid-State Circuit Breakers for high-di/dt faults in DC EV microgrids

DC microgrids are increasingly becoming a popular choice for electric vehicle (EV) charging infrastructure (EVCI), as they allow the integration of EV chargers, photovoltaic (PV) panels, battery energy storage systems (BESS), etc. directly to the DC grid without an intermediate DC-to-AC conversion. Solid-state circuit breakers (SSCBs) can provide reliable protection from short-circuit events on the DC microgrids as they can respond rapidly and interrupt fast rising DC fault currents. One of the key aspects of protection reliability is limiting the zone of power interruption to a bare minimum, and this requires that multiple SSCBs in the DC grid coordinate their operation with each other as they interrupt the fault current. At low fault-di/dt levels, this can be achieved by time-offsetting the overcurrent trip curves or through using communication between SSCBs. However, at high fault-di/dt levels, the propagation delays associated with these techniques limit their effectiveness. This paper investigates the performance of a hardware-based protection scheme in improving protection coordination between SSCBs at high fault-di/dt levels. This scheme is then implemented in high current SSCBs that utilize reverse blocking IGCTs for fault interruption to explore their fault-di/dt limits for successful coordination.