Variable speed control of DFIG-wind turbine under unbalanced grid voltage conditions

This paper aims to address the Doubly Fed Induction Generator (DFIG) problems integrated in the wind energy conversion system (WECS) and connected to the power network. As a result, the performance of the wind integration under unbalanced grid operations has been improved. Indeed, the main inconvenient when using DFIG, is its large sensitivity to the grid disturbances, especially in the case of voltage dips. This paper´s aim is to present an enhanced controller, implemented in both positive and negative synchronous rotating reference frames with the backstepping approach. The control objective is twofold: (i) tracking the maximum available wind power to ensure the achievement of the maximum power point (MPPT); (ii) keeping a safe DFIG operation, during unbalanced grid voltage conditions. The results validation has been performed through simulation, on a 7.5 kW DFIG wind generation system using Matlab/Simulink®.