Output Feedback Control for Wind Energy Systems

This paper deals with the control of wind energy systems with the doubly fed induction generator (DFIG) without recurring to any mechanical sensors. The control objective dressed here is twofold: maximum power point tracking (MPPT) and reactive power regulation in the DFIG. The designed controller is based on the nonlinear state-space representation of the controlled system, including a sliding mode controller and a high gain observer. The whole system enjoys a semi-global practical stability, proved using tools from the Lyapunov theory. These theoretical results are confirmed by simulations involving wide range variation of the wind speed.