Based on the complete model of the Wind Energy Conversion System (WECS), a robust nonlinear control using high order sliding modes (SM) is proposed to capture maximum wind power and to regulate the reactive stator power. First a slave current control is designed, then three schemes are considered to deal with captured power problem, (a) Control of electromagnetic torque, (b) Control of generator speed considering turbine dynamics and (c) Control of generator speed considering turbine dynamics as unmodeled. Simulation results are shown to validate designed control laws.