Anti-windup LPV control of pitch actuators in wind turbines

Operation of wind turbines in the full-load region mandates that the produced power is kept at a rated value to minimize structural loads and thereby reduce fatigue damages. This is usually achieved by pitching the rotor blades in order to limit the aerodynamic torque in high wind speeds. The pitch actuators usually present a hard constraint in terms of the amplitude and rate of saturation. In this paper, we propose a method to address pitch actuator amplitude and rate saturation by designing the anti-windup controllers in the linear parameter varying (LPV) framework. The proposed design method guarantees the closed-loop stability and a prescribed level of performance while it decreases the pitch activity for regulating the generated power to the nominal power during sudden wind gusts. The anti-windup controller designed to minimize the H_∞ norm of the closed-loop system is gain-scheduled based on the operating condition of the turbine, as well as the states of amplitude and rate saturation of the pitch actuator. The effectiveness of the proposed control design method is demonstrated using the high-fidelity aeroelastic dynamic simulation tool FAST.