Power System Strength Assessment with Inverter Based Resources: Case Studies

Power system strength assessment in Inverter Based Resources (IBRs) dominated power systems is important to predict the behaviour of IBRs at system level and under different system conditions. Further, it is useful in identifying any positive or negative interactions that may occur between power system components and IBRs. This paper presents an overview of power system strength assessment indices and case studies to illustrate the applicability of them in power systems with IBRs. The performance of Short Circuit Ratio (SCR), Weighted Short Circuit Ratio (WSCR) and Site Dependent Short Circuit Ratio (SDSCR) was observed on an available test system in Power systems Computer Aided Design (PSCAD) software and on the Modified Western Systems Coordinating Council (WSCC) system with Inverter Based Resources (IBRs). A comparative study of the above-mentioned methods of assessing power system strength is presented along with Electro-magnetic Transient type simulations (EMT) showing the extent to which the static power system strength indices can predict the dynamic behaviour of IBRs.