Special issue on wind turbines and wave energy devices

The stability of a control system that has been tested on the Controls Advanced Research Turbine (CART) is analyzed. Focus is on adaptive generator torque control with constant blade pitch to maximize energy capture of a variable-speed wind turbine operating in region 2 wherein an adaptive strategy is shown to improve wind turbine performance. It is demonstrated that the rotor speed is asymptotically stable under the torque control law in the constant wind speed input case and L2 stable with respect to time-varying wind input. Further, a method is derived for selecting positive gain in gain adaptation law to guarantee convergence of the adaptive gain M to its optimal value M*