Reconfiguration of Control under Unbalanced Grid Voltage Sags for DFIG Wind System Using Power Harmonic Components

This paper deals with an improved control for a variable speed wind system based on doubly fed induction generator under an unbalanced grid operation. The main goal of this control is to reduce mechanical stress by reducing electromagnetic torque oscillations. Under an asymmetrical grid sag, the conventional flux oriented control strategy is replaced by a novel control strategy based on a new calculation of reference currents using power harmonic components. A dynamic modelling of the doubly fed induction generator is proposed in both positive and negative frames. Theoretical analysis is developed to explain the proposed control. Simulation tests have been conducted under PSIM software and simulation results confirms the ability of the proposed control to mitigate the voltage sags effects.