Fault Detection and Isolation in Medium-Voltage DC Microgrids: Coordination Between Supply Power Converters and Bus Contactors

A fast and effective method for detecting and isolating faults in medium-voltage dc microgrids relies on rapid coordination between power supply converters and bus segmentizing contactors to limit currents and isolate faults without any need for fast communication between these active elements. The power converters independently enter current-limiting mode as soon as they recognize a fault condition and the segmentizing contactors autonomously decide whether or not to open based on their local interpretation of time-to-trip curves as functions of apparent circuit resistance. This method allows converters and contactors to use only local measurements when discerning whether or not to trip in order to isolate the faulted section. Simulation and experimental results show that low-impedance short-circuit faults can be isolated within 10-20 ms and the system can be reenergized within 40-60 ms. The method is effective for a wide range of fault and system configurations, and that range can likely be expanded by applying additional discrimination methods.