This paper proposes a control strategy to maximize the wind energy captured in a variable speed wind turbine,with an intal induction generator,at low to medium wind speeds.The proposed strategy controls the tip-speed ratio,via the rotor angular speed,to an optimum point at which the efficiency constant (or power coefficient) is maximum for a particular blade pitch angle and wind speed.This control method allows for aerodynamic rotor power maximization without exact wind turbine model knowledge.Representative numerical results demonstrate that the wind turbine can be controlled to achieve near maximum energy capture.