A design method for variable structure system control is presented. It is based on a differential geometric approach and it is intended to deal with the class of nonlinear systems affine in the control with uncertainties and disturbances. The main goals of the proposed method are: (i) robustness; (ii) tuning simplicity; (iii) chattering reduction; and (iv) reaching mode control. Its application to the wind subsystem of an electricity generation hybrid system is discussed in detail. Extensive simulation experiments were conducted with a comprehensive model of the plant and they are presented to illustrate the controller performance.