Abstract: This paper investigates the impact of renewable energy source (RES) integration on the small-signal stability of interconnected power systems using linear modal analysis. Unlike conventional synchronous generators, inverter-based RESs are non-dispatchable and do not inherently contribute rotational inertia or governor-based damping. Their increasing penetration consequently degrades system frequency response, leading to a higher rate of change of frequency (RoCoF) and a lower frequency nadir following disturbances. Modal analysis reveals that both interarea and local electromechanical oscillation modes experience reduced damping as RES penetration levels rise. Furthermore, wind power integration introduces a distinct low-frequency interarea oscillatory mode not observed with equivalent photovoltaic (PV) integration. A modified Kundur two-area test system is employed to model these scenarios, wherein wind and solar farms progressively replace conventional synchronous generation to evaluate their influence on system dynamic stability.

Keywords: Power system stability -Rate of change of frequency - System inertia - Renewable energy sources- Voltage stability - Rotor angel stability

Pages: 133-146