Active power control for wind turbines via wind speed probability distribution-based equilibrium point optimization

• Segmented design of the rotor speed-pitch angle curve according to aerodynamic power change and maximum pitch action rate. • Stochastic optimization model of the rotor speed-pitch angle curve solved with the wind speed probability distribution. • Necessity of pitch angle regulation under different conditions quantified by the optimal rotor speed-pitch angle curve. • Active power control strategy to effectively reduce power drops and rotor overspeed while minimizing the pitch action. Accurately tracking power command while minimizing pitch action under safe operational constraints remains one of the key challenges in active power control (APC) research of wind turbines (WTs). This requires the WT to judge the potential over-limit risk of the rotor speed accurately and not to regulate the pitch angle when unnecessary. The APC based on passive rotor speed variation provides a feasible scheme for realizing the latter. However, the existing methods mainly rely on empirical design to judge the necessity of pitch angle regulation, which can easily lead to power drops or unnecessary pitch action. Therefore, an enhanced APC strategy via wind speed probability distribution-based equilibrium point optimization is proposed in this paper, and the rotor speed-pitch angle curve corresponding to the stable equilibrium points is segmentally designed according to the aerodynamic power change and the maximum pitch action rate. Combined with the predicted wind speed probability distribution, the necessity of pitch angle regulation under different conditions is quantitatively analyzed by constructing and solving the stochastic optimization model of the rotor speed-pitch angle curve. Based on the rotor speed range of non-pitch regulation corresponding to the optimal rotor speed-pitch angle curve, the proposed method can judge the potential over-limit risk of the rotor speed and regulate the pitch angle in time when the risk exceeds the allowable range, effectively reducing power drops and rotor overspeed while reducing the amount of pitch action. The improvement effect of the proposed method is verified through simulation on the NREL 5 MW WT model.