Under-Frequency Load Shedding in a Standalone Power System With Wind-Turbine Generators Using Fuzzy PSO

Under-frequency load shedding maintains a power grid resilient against a severe contingency. The under-frequency relay (such as 81L) with pre-determined settings is used to prevent blackout in the power grid by detecting a decreasing system frequency. In this work, the shed load and frequency setting at each stage for the 81L relay are determined in an offshore standalone power grid with wind power turbines. Possible scenarios including “N-2-2” outages and “N-3” outages as well as Markov models of diesel and wind generators are investigated. The total shed load is minimized and the frequency nadir is maximized using Takagi-Sugeno (TS)-based particle swarm optimization (PSO). Two sets of TS fuzzy rules are developed to tune the inertia weight and learning factors in the proposed PSO to obtain the optimal settings. A 31-bus standalone power grid with two wind turbines of 2×2 MW was studied to reveal the applicability of the proposed method.