Robust control design of variable speed wind turbine using quantitative feedback theory

A robust control design of a three blade, horizontal axis variable speed wind turbine is developed in this paper. The variable speed wind turbine model consists of higher order nonlinear dynamics where uncertainty has been considered in the plant parameters. Quantitative feedback theory is an effective and efficient, robust control technique through which the desired specifications over a specified range of parametric uncertainty can easily be achieved in the frequency domain. The proposed robust torque and pitch control in variable speed wind turbine using quantitative feedback theory satisfy prescribed gain and phase margin, degree of tracking for the robust performance, fast convergence, noise attenuation, and input and output disturbance rejection. The advantages of the proposed robust control design are the consideration of a wide range of performance specifications and achieving effective control over an increased operating frequency range. The simulation results demonstrate the satisfactory performance of proposed quantitative feedback theory-based controller and prefilter which fulfill the necessary conditions such as robust stability and robust tracking. Further, it has been shown that the performance of the quantitative feedback theory-based controller is better than the performance with a standard wind turbine controller and also from the performance by proportional-integral controller.