The rapid development of renewable energy generation, now increasingly integrated through centralized new energy bases, is propelled by government strategy and enabling technologies. The demand for inverters to connect new energy sources results in a short-circuit current that is both amplitude-limited and highly non-linear. This characteristic makes traditional relay protection methods poorly adapted, introducing significant safety and stability hazards within new energy bases. Therefore, a current differential protection method based on a virtual short-circuit current is proposed in this study. The virtual short-circuit current is calculated based on the ratio of the inverter’s internal modulation coefficient, within the controller of both grid-forming (GFM) and grid-following (GFL) inverters, before and during a short-circuit fault in the grid. That is, the short-circuit current output from the inverter is the same as that output from a traditional synchronous generator with the same generation capacity. Consequently, the trip criterion based on RMS (Root Mean Square) measurement is satisfied, and the traditional differential protection method remains applicable. It is verified by simulation cases that the aforementioned differential protection method based on a virtual short-circuit current is correct and adaptable for new energy bases.
Su et al. (Thu,) studied this question.