This paper presents the analysis and design of a Direct Torque Control (DTC) of a Doubly-Fed Induction Generator applied to a wind generation system. The aims of control are the control of reactive power interchanged between the generator and the grid and the control of active power absorbed from the wind turbine in order to track the optimum operation point. The DTC system control generator torque and flux directly, however, the response of DTC is slower during large change in load. Fuzzy control with grey prediction strategy is proposed for the implementation of DTC to improve its slow response. Simulation of the DTC system with grey-fuzzy controller is carried out to verify the control performance.

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This paper deals with the design of LQG controllers for pitch regulated, variable speed wind turbines where the controller is used primarily for controlling the pitch angle through a collective pitch angle in the high wind speed in order to guarantee the power regulation. A control sturctrue based on a linear model approach is presented to take into account system non linearities andevolutions of control objectives.LQG Control synthesis is used to design linear controller for each linearized model in response to the control problem. Index Terms -LQG controller, Pitch control,Wind Trubine I. INTRODUCEWind energy has widely grown during the last decades and nowadays is the most competitive form of renewable energy.Nonetheless, wind energy is not yet cost effective. In consequence, the development of new technology will be crucial that the wind energy penetrates into electricity market successfully. Implementation of advanced control systems is considered as a promising way to improve wind energy conversion and to decrease wind energy cost. The wind turbine control objectives are mainly to optimize wind energy conversion, and to reduce dynamic loads experienced by the plant mechanical structure.Indeed, dynamic loads hardly affect wind turbine lifetime and mainly determine mechanic components design, and consequently their cost .In this paper, a control system structure optimizing a selected trade off for the whole operating area between energy conversion maximization and reduction of mechanical loads experienced by turbine drive train is presented. The controller synthesis is based on a Takagi-Sugeno multiple linear model representation of the non linear system. Hence for each linearized model on the system reference trajectory, a multivariable LQG controller minimizing a quadratic criterion depending on the different control objectives and taking into account the stochastic properties of the wind speed, is designed. Control applied to the global system is then obtained by an interpolation of the controls calculated by the different controllers. II. WIND TURBINE MODELLINGThe structure of variable speed, pitch regulated wind energy conversion system is presented in Figure 1.The system is formed by the wind turbine, the drive train, and by a generator unit , composed by the generator and the static converter connected to the electrical grid. The control system acts on generator in order to apply the reference electromagnetic torque ref G T , and on the pitch actuator in order to control the pitch angel of the blades.Figure 1.Wind Energy Conversion System Structure A Wind ModelIn addition to the plant model, a wind model is established for the control design model. Wind velocity in a fixed point of space has known properties in the frequency range, represented by the Van der Hoven spectrum. Two main components appear in this spectrum: a slow time varying component, representing seasonal value ) (t v m of the wind speed, and a turbulent one ) (t v t . For the control synthesis purpose, a linear model of turbulent part )...

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