Wind Turbine Structural Damping Control for Tower Load Reduction

Being wind a random excitation, wind turbines experience complex dynamic load conditions. This is becoming a growing challenge for designing larger, tall wind turbine towers and substructures in both onshore and offshore wind farms. In order to keep the structural integrity of multi-megawatt wind turbine, different structural damping strategies have been implemented in the past years like tuned mass dampers. Other techniques rely on the available control actions, as the generator torque control to reduce the side-to-side excitation and the blade pitch control to limit for-aft movements. All those strategies aim at limiting fatigue and buckling loads, as well as the dynamic interaction with the rotor harmonics without a parallel increase of material (i.e. of costs). It was proven that the achievable load reduction in significant design cases can be as high as 20% and the tower mass can consequently be reduced by up to 10%.