A Strength Index of Intermittent Renewable Energy Sources Linked System

With the global energy transition policies, the deployment of inverter-based resources (IBR) has been rapidly expanding. Unlike synchronous generators, IBRs have limited short-circuit current capability and negatively affect voltage stability during disturbances, thereby weakening overall system strength. In this paper, to accurately assess the robustness of power systems under the growing penetration of intermittent renewable energy sources (IRES), we introduce strength indices including SCR, CSCR, WSCR, and MIESCR. Their effectiveness is verified through application to two hybrid model systems. First, the system is equivalently reduced to perform overall screening, and then node-level assessments are carried out to reflect local characteristics and identify vulnerable nodes. Finally, MIESCR is applied to consider multi-infeed interactions, and this methodology is validated on the Jeju hybrid power system, demonstrating a more realistic framework for system strength evaluation.