Abstract : Abstract--Wind energy conversion is the fastest-growing energy source among the new power generation sources in the world and this tendency should remain for some time. Already now, wind energy is rapidly developing into a mainstream power source in many countries of the world, with over 60000 MW of installed capacity world wide. Under an advanced wind energy growth projection, coupled with ambitious energy saving, wind power could be supplying 29.1% of the world electricity by 2030 and 34.2% by 2050. Harnessing wind energy for electric power generation is an area of research interest and nowadays the emphasis is given to the cost-effective utilization of this energy aiming at quality and reliability in the electricity delivery. Currently, variablespeed wind turbines are continuously increasing their market share, since it is possible to track the changes in wind speed by adapting shaft speed and thus maintaining optimal power generation. The more these wind turbines are investigated, the more it becomes obvious that their behavior is significantly affected by the control strategy used. Typically, variable-speed wind turbines use aerodynamic controls in combination with power electronics to regulate torque, speed, and power. The aerodynamic control systems, usually variable-pitch blades or trailing-edge devices, are expensive and complex, especially when the turbines are larger. This situation provides an incentive to consider alternative control approaches. The prime objective of this PhD Thesis is to investigate nonlinear and robust control techniques leading not only to power efficiency maximization but also to improved dynamic characteristics, resulting in the reduction of the drive train mechanical stresses and output power fluctuations. For that purposes, sliding modes have been deeply investigated. These techniques have been first tested using the NREL FAST simulator and then experimentally validated on the Grenoble G2Elab 7.5-kW real-time simulator. The obtained results were consistent and very promising.