Optimal tracking and robust power control of the DFIG wind turbine

In the present paper, an optimal operation of a grid-connected variable speed wind turbine equipped with a Doubly Fed Induction Generator (DFIG) is presented. The proposed cascaded nonlinear controller is designed to perform two main objectives. In the outer loop, a maximum power point tracking (MPPT) algorithm based on fuzzy logic theory is designed to permanently extract the optimal aerodynamic energy, whereas in the inner loop, a second order sliding mode control (2-SM) is applied to achieve smooth regulation of both stator active and reactive powers quantities. The obtained simulation results show a permanent track of the MPP point regardless of the turbine power-speed slope moreover the proposed sliding mode control strategy presents attractive features such as chattering-free, compared to the conventional first order sliding technique (1-SM).

► A sub-synchronous operation of a grid connected wind system is described. ► An optimize wind energy capture, via a fuzzy MPPT controller. ► A (HOSM) control of statoric active and reactive powers of the DFIG. ► The supertwisting high order sliding mode controller (HOSM) is applied. ► At rated wind speed a proposed speed limitation circuit is design.