Active Structural Control for Offshore Wind Turbines with Soil Effect Consideration

This paper proposes a reduced-order model-based control method for a class of offshore wind turbines with the soil-effect consideration. High-order or multi-state models are normally demanded for active structural control problem of offshore wind turbines, which would complicate the controller design. Therefore, to simplify the complexity of the obtained control strategy, this paper attempts to use a reduced-order model for the active structural control problem of offshore wind turbines, where a LQR control based on a 2 degree-of-freedom (DOFs) model is established. Considering the importance of soil effect on the stable operation of offshore wind turbines, an 11-DOFs wind turbine model including the soil effect and external loads are derived by using the Euler-Lagrange method. The accuracy of the obtained 2-DOF and 11-DOF models is verified by comparing with the well-used wind turbine simulation tool FAST. Finally, extensive simulations are performed to demonstrate the effectiveness of the proposed method, where it is shown that the 2-DOF model-based LQR control can effectively reduce the tower displacement of the wind turbine and effectively mitigate the motion of the platform.