Frequency Stability Assessment of Deloaded Wind Turbines in Spanish Island Power Systems

This paper investigates under what circumstances the provision of frequency regulation by renewable energy sources can provide technical and economic benefits to real island power systems. In order to do so, the unit commitment problem is simulated, and the frequency stability is analyzed in terms of frequency deviations and the amount of shed load when the wind turbine generator operates at a fixed and variable deloading percentage under normal conditions. The assessment is carried out for La Palma (small size) and Tenerife (medium size) island power systems by considering different wind source availability scenarios for sample weeks of different seasons in current and future years. Results show that in high wind penetration scenarios, considering a fixed deloading ratio to provide both inertia and reserve, improves the total system operating costs and the overall frequency response quality which translates into a lower under-frequency load shedding cost. A variable deloading factor, although leading to lower system operational costs, falls short of ensuring a reliable frequency response in certain scenarios after outages.