Linear Parameter Varying Control of Wind Energy Conversion Systems in Partial Load

Abstract

This paper is dealt with the rotor speed tracking problem of variable-speed wind turbine systems operating under the partial load condition. Singular perturbation techniques are used to characterize the two-time-scale property of the wind turbine system, and a linear parameter varying (LPV) model is formed to approximate nonlinear behaviours of a wind turbine system. Based on the slow-fast decomposition method, slow and fast subsystems are constructed: one for the mechanical dynamics and the other for the electrical dynamics. Slow and fast controls are derived, respectively, and then a local state feedback controller, sum of the slow and fast control, is formulated. A design procedure, using the linear parameter varying control to combine local controllers, is proposed to guarantee the robustness of the closed-loop nonlinear wind turbine system. Numerical examples are given to show the validity of the proposed control scheme.