Multiobjective h2/h∞ control of a pitch regulated wind turbine for mechanical load reduction

Abstract: The paper deals with the design of a control system for a variable-speed pitch-regulated wind turbine in the operating region correspond-ing to wind speeds above rated wind speed. The control objectives are mostly to regulate the plant output power and to reduce the mechanical fatigue of the plant components. The controller is designed from a non linear model of the system which takes into account the blades, shaft and tower flexibil-ities. A Linear Matrix Inequalities (LMI) formu-lation of the control problem permits to obtain a Linear Parameter Varying (LPV) controller op-timizing, through H2/H ∞ norm minimization, a criteria close to mechanical fatigue affecting the plant. The proposed controller performances are then compared in simulation with those of a gain scheduling Linear Quadratic Gaussian (LQG) con-troller and with a gain scheduling PI controller, and is seen to be more efficient