In this paper, the control of a variable wind energy conversion system (WECS) based on a doubly fed induction generator (DFIG) is proposed. The DFIG control structure contains rotor currents and stator powers loops where proportional-integral (PI) controllers are used. This control could be obtained by applying the DFIG’s active and reactive powers decoupling strategy based on stator flux orientation method. For the wind turbine, a nonlinear controller based on the sliding mode theory is proposed to maximize the extracted power. This controller works in the partial load region. Another control algorithm has been used to work in full load region. It controls the generator output power via the pitch angle so as not to exceed the rated power of the system. The proposed MPPT and pitch control algorithms provide good static and dynamic performances. The validity of the proposed strategies is analyzed throw simulation.

Keywords: Wind energy conversion system (WECS), Maximum power point tracking (MPPT), Doubly fed induction generator (DFIG), Sliding mode control