In recent years, the wind energy has been reconsidered because it is clean and the many studies for the effective use of the wind energy have been done. The generation of electric power using wind turbine generators is distinguished from conventional methods of generation by the variability of the prime source of power. A matter of concern is the effect of the varing wind on the generated power of wind turbine generators. This problem is very important to the power systems with small capacity in remote areas or islands.
The purpose of this paper is to keep the generated power of wind turbine generators at a rated value under the varing wind, by changing the blade pitch angle. Here the backstepping algorithm is used to design the pitch angle controller in order to consider the non-linearity for wind turbine generator systems. The proposed controller not only locally asymptotically stabilizes the plants, but also effectively keep the gererated power of wind turbine generators at a rated value under the varing wind. Digital computer simulations using parameters of the actual windmill generator system also give good results.