Impact of Renewable Energy Sources on AC System Strength Using Inverter Interaction Level

Increasing penetration of Renewable Energy Sources (RESs) such as wind, solar plants equipped with fast-acting control systems to the weak points of a power system could be concerned about the problem from classical voltage instability to control instability and control interactions. System strength is one of the important concerns in the integration of RES. Short circuit ratio (SCR) is often used as an index of the system strength. However, when RES are installed in an adjacent location, system strength can be lower than evaluation by SCR. Weighted Short Circuit Ratio (WSCR) is an index that reflects RESs interaction by assuming a 100% influence. This paper propose Inverter Interaction Level Short Circuit Ratio (IILSCR) method using inverter-based resource's output tracing. IILSCR can accurately estimate system strength which RESs are connected in adjacent spot by reflecting the interaction between RESs.