A waveform similarity based current-only differential protection technique for inverter interfaced microgrids

Developing a reliable protection system is crucial to facilitate the integration of renewable energy sources (RESs) into modern power grids, paving the way for reaching net-zero carbon emissions. The bidirectional power flow and limited fault current contribution of inverter interfaced RES units make designing an efficient protection system for inverter based microgrids challenging. To address these problems, this paper presents a differential protection technique for smart microgrids where the different behavior of fault current at two ends of a microgrid faulty line is quantified using a short-time correlation transform (STCT) based index. It has promising robustness to measurement noise, fault type, fault location, fault resistance, fault inception angle, communication delay, non-linear load, and microgrid configuration and operating mode with the need for a low sampling frequency. Test results on the Canadian urban benchmark distribution system indicate the viability of the developed STCT based differential protection technique.