This paper presents a high-order sliding mode control strategy that aims to optimize the power conversion efficiency of a wind energy conversion system within the partial load zone of operation. The main challenges of this control problem are related to the random variations of the wind speed, the nonlinear nature of the whole system, usual model uncertainties and external disturbances. For all these reasons, the robustness, simplicity and low computational burden of the proposed super-twisting algorithm result very attractive in this context. Simulation results that show the achievement of the desired characteristics are provided. Copyright (C) 2009 John Wiley & Sons, Ltd.