Direct adaptive control of utility scale wind turbine without wind speed measurement

The fundamental control problems associated with wind turbines consist of maximizing the power capture when the wind speed is below the rated value and regulating the rotor speed when the wind speed exceeds the rated value. In large wind turbines, another critical function of a wind turbine controller is to perform smooth transitioning of wind turbine operation between the below rated and above rated wind speed conditions so that wind turbine structural loads are not increased.;A wind turbine is a highly complex and nonlinear mechanical structure with many flexible parts. The complexity further increases with increase in size that demands more sophisticated control strategies to address these complexities. Also, the aerodynamics of wind turbines is unsteady and not well known, which makes the control problem more complex. Hence, beside the fundamental control problems in the below rated and the above rated wind speed regions, many other complex control problems exist in large flexible wind turbines. In such conditions, an adaptive control method is better suited because of its ability to adapt to the changing aerodynamic characteristics.;The main focus of this research is to use an adaptive control theory called Adaptive Disturbance Tracking Control (ADTC) to design adaptive controllers in all three regions of wind turbine operation, to assess the performance of the controllers with simulation, and to verify the stability and convergence of the controllers with theoretical analysis. Another important aspect of this research was to use the simplest model of wind turbine to design the controllers.;In this thesis, an adaptive controller is designed for maximizing power capture in a partial loading condition and then modified to incorporate a wind speed estimator with state feedback to get the wind speed information without directly measuring it. This controller is then modified for the transitioning of wind turbine operation between partial and full load conditions smoothly.;The proposed theory of adaptive control is then used to design a collective blade pitch controller to regulate the rotor speed in the full load condition. A preliminary study is also done to use this theory for floating offshore wind turbine to regulate the rotor speed and to damp the platform motions.