Combined Individual Pitch And Trailing Edge Flap Control For Structural Load Alleviation Of Wind Turbines

As the diameter of wind turbine rotors increases, the loads across the rotors are becoming more uneven due to the inhomogeneous wind field. Therefore more advanced passive or active load reduction techniques are introduced to mitigate the increased loads. The paper investigates different combinations of individual pitch and trailing edge flap control, to alleviate the frequency components of the flapwise blade root bending moment, which occur once-per-revolution (1P) and twice-per-revolution (2P) in the rotating frame of reference. A H-infinity loop shaping design is developed based on a simplified wind turbine model. Due to the actuator saturation the control loop is extended with a linear model recovery anti-windup scheme. Lifetime damage equivalent loads are evaluated for several wind turbine components which give a clear view of the best control combinations. It is shown that the maximum load reduction of the flapwise blade root bending moment can be achieved with the combination of individual pitch and trailing edge flap control. The alleviation of the 2P flapwise blade root bending moment leads to load reduction on other components of the wind turbine as well.