Adaptive Load Shedding Strategies for High Solar PV Penetration Conditions

With the increasing penetration of inverter-based solar photovoltaic (PV) systems, grid frequency stability becomes more vulnerable due to the loss of rotational inertia. This paper investigates adaptive load shedding strategies under high solar PV penetration using a detailed PSCAD simulation of the Sri Lankan transmission network. Solar penetration levels of 10.84 percent, 26.31 percent, and 41.78 percent were simulated, and a 706 MW generator trip was introduced to emulate severe disturbances. The system collapsed to 11.913 Hz at 41.78 percent penetration without load shedding, demonstrating the critical impact of reduced inertia. Two load shedding schemes, UnderFrequency Load Shedding (UFLS) and Rate of Change of Frequency (RoCoF)-based shedding, were evaluated. UFLS restored frequency to 49.990 Hz but disconnected up to 41.97 percent of the total load. In contrast, RoCoF-based control maintained minimum frequencies above 48.596 Hz with significantly fewer disconnections and 200 ms faster breaker activation. The results show that RoCoF-based adaptive control improves stability and reduces load loss, offering a more efficient solution for future low-inertia, solar-rich grids.