A robust multivariable strategy for pitch and torque control design of variable-speed variable-pitch wind turbines in the full load region is introduced in this paper. The pitch and torque control loops that share the tracking and active damping of drivetrain torsional mode objectives are designed simultaneously using a novel decomposition scheme. This permits the systematic design of robust multivariable controllers for wind turbines in a manner that facilitates industrial application. We achieve this by making the process of weighting function design fast, intuitive, and simple and by giving the designer a clear insight on the compromising aspects of the various control system objectives. FAST simulation is used to demonstrate application of the method. 1 Nomenclature: I G , I R , generator and rotor moment of inertia; K s , B s , torsional stiffness and damping of drivetrain; q GeAz , q RotAz , generator and rotor azimuth angles; N g , gearbox coefficient; g , r , generator and rotor angular speed; T a , T g , rotor aerodynamic and generator torque; P a , P g , rotor aerodynamic and generator power; T g 0 , g 0 , rated value of generator torque and generator angular speed; a , n a , damping ratio and natural frequency of pitch subsystem; e , n e , damping ratio and natural frequency of electrical subsystem; A, area of rotor; V, wind speed;, pitch angle; , blade tip speed ratio; , air density.
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