Model free adaptive control of large and flexible wind turbine rotors with controllable flaps

This paper investigates the dynamic load alleviation in large and flexible horizontal axis wind turbine rotors with trailing edge flaps, actuated through a novel proportional-derivative model-free adaptive control (PD-MFAC) system. First an aeroservoelastic wind turbine model is developed, which is the combination of a structural model for the tower and blades represented by geometrically non-linear composite beams, and an aerodynamic model for the rotors using an unsteady strip-theory airfoil model. Then three independent model-free controllers are developed to actuate the trailing-edge flaps mounted on three blades, using the blade root-bending moment (RBM) as control input. Comparison is given by an H-infinity (H_∞) reference controller and a Gain-scheduled proportional-integral (GS-PI) controller. Simulation results show that the MFAC flap controller provides more effective load alleviation performance in blade root-bending moment than the H_∞ and the GS-PI flap controllers, and it also exhibits marked reductions in blade tip deflection (BTD), in the presence of external disturbances.