Power maximization and fatigue alleviation are essential for variable speed wind turbines operating in partial load zone. It is within this framework that the present paper gives a global state of art of the application of sliding mode control (SMC) for wind turbines and proposes a new application of Terminal Integral Sliding Mode Control (TISMC) for variable speed wind turbines, described as a mechatronic system, represented by uncertain lumped mass dynamics. In order to represent a relatively exhaustive study, a stability proof is also synthesized and verified using the Lyapunov criterion. In order to evaluate the proposed solution, a numerical validation has been done on Controls Advanced Research Turbine (CART 2) using the National Renewable Energy Laboratory (NREL) simulator Fatigue, Aerodynamics, Structures and Turbulence (FAST). For more accuracy 9 DOFs (Degrees of Freedom) were enabled with a realistic turbulent wind field. The obtained results shown the effectiveness of TISMC compared to some existing linear and nonlinear controllers in term of output power maximization and loads mitigation.