  Improving wind turbine efficiency is essential for reducing the costs of
energy production. The highly nonlinear dynamics of the wind turbines and their
uncertain operating conditions have posed many challenges for their control
methods. In this work, a robust control strategy based on sliding mode and
adaptive fuzzy disturbance observer is proposed for speed tracking in a
variable speed wind turbine. First, the nonlinear mathematical model that
describes the dynamics of the variable speed wind turbine is derived. This
nonlinear model is then used to derive the control methodology and to find
stability and robustness conditions. The control approach is designed to track
the optimal wind speed that causes maximum energy extraction. The stability
condition was verified using the Lyapunov stability theory. A simulation study
was conducted to verify the method, and a comparative analysis was used to
measure its effectiveness. The results showed a high tracking ability and
robustness of the developed methodology. Moreover, higher power extraction was
observed when compared to a classical control method.
