AbstractThis paper presents a variable speed control strategy for wind turbines in order to capture maximum wind power in region 2. Wind turbines are modeled as two-mass drive-train system with generator torque control. Based on the obtained wind turbine models, variable speed control schemes are investigated for region 2. We designed nonlinear tracking controllers to achieve asymptotic tracking control for given rotor speed reference signals so as to yield maximum wind power capture for both state feedback control and output feedback control. The proposed schemes are shown to be able to achieve smooth and asymptotic tracking and illustrated by the given simulation results.