Robust T-S Fuzzy Control Design for Variable-Speed Wind Energy Conversion Systems Using Linear Matrix Inequalities

Abstract

This paper proposes a robust state feedback control strategy for variable speed wind energy conversion systems (WECS) within the Takagi-Sugeno fuzzy (TSF) modeling framework. A T-S fuzzy representation is used to approximate the nonlinear aerodynamic behavior of the wind turbine. This representation enables to design a stabilizing controller via Linear Matrix Inequalities (LMIs). An optimum tip-speed ratio-based reference model is presented to optimize power extraction under fluctuating wind conditions. The system performance is verified by comparing open-loop and closed-loop responses. The open-loop system has the bad tracking performance and the high sensitivity to the wind disturbance. The closed-loop configuration with the proposed fuzzy state feedback controller guarantees the improved dynamic response. The controller has fast convergence, less steady-state oscillations and improved robustness to wind variations. Numerical simulations confirm that, even under highly turbulent wind profiles, the closed-loop system achieves better tracking accuracy and stability than the open-loop case.