Staged Fault Tests to Validate a Fast Protection System of Low-Voltage DC Microgrids

This paper introduces staged fault tests for validating a fast protection system of low-voltage DC microgrid (LVDC MG). A real LVDC MG is used for these tests, containing photovoltaic generation system (PVS), battery energy storage system (BESS), DC load, and protective devices. A protective device uses a solid-state circuit breaker (SSCB) integrated with a DC microgrid digital relay (DCMDR) or a fast-acting fuse (FAF) to protect the microgrid. The islanded operation mode of LVDC MG is selected for doing staged fault tests at several possible faulted locations. The fast protection system of LVDC MG can detect, locate and isolate a faulted point by using multiple protection modules including derivative modules of current and voltage, overcurrent module, undervoltage module, and the
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characteristic of fuses. The obtained results of staged fault tests show that the DCMDR-integrated SSCBs can quickly trip to isolate the faulted location in a few milliseconds as well as get high selectivity of the protection system. Moreover, the FAFs can efficiently operate as the backup protection of the DCMDR-integrated SSCBs in order to not only protect the BESS and load sections in the microgrid but also still ensure the fast operation of MG protection system.