As wind turbines get larger, with rotor diameters above 100 m, the blades will sweep a large wind field, containing different wind phenomenas such as, wakes, wind shear and tower shadow; applying a big structural load upon the wind turbine.

In this thesis, a lifted repetitive controller is developed which reduces the structural loads by the use of individual pitching. For this purpose a dynamic model of a wind turbine has been developed. The model contains an aerodynamic model, mechanical model, a structural model and a model of the pitch system. The model has been linearized and validated in accordance with simulation code FAST.

From the model a lifted repetitive controller was design, by making a lifted system description where made, and from this a reduced output-feedback formulation was found, making it possible to use LQR design to calculate the controller gain.

In an acceptance test, the lifted repetitive controller was compared to the controller from FAST which was implemented in Matlab. The results from this were, that the controller designed did not pass, even though the deflection of tower and blades were reduced. It is assumed that it is caused by a mismatch between the model and the implementation in Matlab.