Closed loop identification of wind turbines models for pitch control

In order to design a model based controller availability of a linear model of the system to be controlled is mandatory. Open loop identification is a very well known and extended used technique which provides reliable linear models for control design purposes. However, classical open loop identification techniques can not be applied to the case of wind turbines for several reasons: operating in open loop could render the system unstable, the aerodynamics are non-linear, the wind input disturbance can not be measured and it has an important stochastic component and finally, the measured data are normally corrupted by disturbances and noise. This article presents a procedure allowing wind turbine identification in closed loop operation with time varying controllers. A set of reliable linear models for control design of the pitch loop are obtained.