This paper describes a manner in which the energy-reliability optimization of wind energy conversion systems' operation can be achieved by means of the sliding mode control. The proposed approach aims at designing a tradeoff between maximizing the power harvested from wind by a horizontal-axis-grid-connected variable-speed doubly-fed-induction-generator-based wind power system and minimizing its mechanical stress. An appropriate sliding surface has been found in the speed-power plane, which allows the operation more or less close to the optimal regimes characteristic. Thus, by torque controlling the generator, an energy-reliability optimization of the wind turbine behavior is performed. The proposed control law is validated by both off-line and real-time simulation; the latter on a dedicated experimental rig, based upon the hardware-in-the-loop simulation concept. The results show that the control objective is fully accomplished.