Analysis of Grid Forming Inverter and Grid Following Inverter Models In Simulating Power Systems With Varying Short Circuit Ratio

Abstract

The primary objective of this study is to assess the weaknesses and susceptibilities of the power grid before the inverter-based resources (IBR). The weak spots within the grid, specifically at the point-of-interconnection (POI) for photovoltaic (PV) systems, are identified by using a classic short circuit ratio (SCR) metric. The performance of grid-following (GFL) and grid-forming (GFM) inverter types is compared using a 100 MVA-rated PV facility that is connected to a transmission line network. By subjecting the system to a six-cycle three-phase to ground fault at different sites, such as the PV POI and nearby busses, SCR values of roughly 4.5, 3, and 1.5 are recorded, respectively. The analysis shows that when the SCR at the PV POI is low, the GFM inverter has faster and smoother fault recovery responses in terms of active and reactive power compared to the GFL inverter.