Nonlinear Systems Analysis and Control of Variable Speed Wind Turbines for Multi-Regime Operation Greg Semrau Moog Inc. Buffalo, NY Sigitas Rimkus Mech. & Aero. Engg. Dept. University of Central Florida Tuhin Das ∗ Mech. & Aero. Engg. Dept. University of Central Florida Orlando, Fl 32816 Abstract The key control problems associated with variable speed wind turbines are maximiza- tion of extracted energy when operating below the rated wind speed, and power and speed regulation when operating above the rated wind speed. In this paper, we develop a nonlin- ear systems framework to address these problems. The framework is used to visualize and analyze the equilibria of the wind turbine as its operating regimes and controllers change. For both below rated and above rated wind speeds, we adopt nonlinear controllers, analyze the stability property of the resulting equilibria, and establish the criterion for switching * Address all correspondence to this author: Tuhin.Das@ucf.edu 1