Topology Agnostic Detection and Location of Fault in DC Microgrid Using Local Measurements

Technical Summary:

The topology agnostic fault detection and location technique meets speed critical application needs to address current rises that can occur on the order of tens of microseconds in a dc circuit as a result of a fault. When a fault occurs on a feeder-section in a dc microgrid, the current contributions from the dc link capacitors associated with dc-dc converters or ac-dc rectifiers dominate the fault current first. Capacitors resist the rapid change of voltage. So, for a short period of time the capacitor will act like a constant voltage dc source while discharging through the fault. Within this time the current through the dc line will have the same response as it would have for an ideal voltage source instead of the capacitor. So, measurements from this initial period are used to determine the fault location. The method uses only local measurements, preventing delay due to communication. Furthermore, the technique has a fixed execution time due to being non-iterative. System independence allows for a simpler to implement system because the calculation of protection thresholds is based only on the feeder being protected and not on the topology of the whole system. When the rest of the system changes, when an adjacent line is out of operation for example, the thresholds do not have to be recalculated. These features of the technology are conducive to simple and efficient operation to protect vulnerable devices from quickly rising currents during fault events.