Dynamics and control of structural loads of wind turbines

The potential for active attenuation of structural dynamic load-oscillations, by means of continuous control of the yaw servo, is investigated. The analysis is based on a model with flexibly interconnected rigid bodies. The focus is put on the tower bending, particularly in the lateral direction. The results show the importance of the yaw stiffness for the lateral tower-bending. Furthermore, in the particular case studied here, a periodic linear quadratic controller could achieve the same lateral damping as a suspension system with a spring and damper, or PD controller, with less than 10% of the tower torsion. The results clearly indicate the importance of considering the system's periodic dependence on time in the controller design.