Adaptive Fuzzy Control Scheme for Variable-Speed Wind Turbines Based on a Doubly-Fed Induction Generator

The purpose of this paper is to present a new adaptive fuzzy control scheme for grid-connected variable-speed wind turbines (WT) based on a doubly-fed induction generator (DFIG). The proposed controller simultaneously guarantees two independent control objectives: (1) DFIG torque control allowing the extraction of maximum available power from the wind, and (2) control of the stator reactive power to maintain a desirable power factor according to the grid requirements. Unlike many existing control designs developed for DFIG-based WT, the design of the proposed controller is based on nonlinear coupled models of WT, without attempting approximate linearization. To improve performance in operating conditions, the model uncertainties and the nonlinear functions appearing in the tracking errors dynamics are reasonably approximated by adaptive fuzzy systems. It is mathematically proven that the proposed adaptive fuzzy control scheme can guarantee that all signals of the closed-loop system are uniformly ultimately bounded. Simulation results show that the proposed control scheme has strong robustness against the system parameter variations and unstructured uncertainties.