NONLINEAR CONTROL DESIGN FOR MAXIMUM POWER POINT TRACKING OF A PMSG-BASED WIND TURBINE

. This paper deals with the design of nonlinear controllers for a variable speed permanent magnet synchronous generator (PMSG)-based wind turbine. In particular, the design seeks to maximize the generated power of a wind turbine operating in Region II where the wind speed is below the rated wind speed. The control design uses the maximum power point tracking (MPPT) method to maximize energy extraction. The key step in the design is the introduction of a state transformation that renders the nonlinear dynamics of the wind turbine system into a form that is suitable for a variety of control designs. Two control design schemes, a feedback linearization control and a sliding mode control (SMC), are then proposed to achieve maximum power point tracking. It is shown that the proposed controllers guarantee the asymptotic convergence of all state trajectories to their desired values, and guarantee maximum power tracking. The stability of the closed-loop system is proven through Lyapunov stability theory, and the effectiveness of the nonlinear controllers is demonstrated through simulation studies.