Performance improvement of a DFIG in a wind turbine under an unbalanced grid-voltage condition

This paper presents a control method that reduces the pulsating torque and dc voltage problems of a Doubly Fed Induction Generator (DFIG)-based wind turbine system. To reduce the torque and the power ripple, a current control scheme, consisting of a proportional integral (PI) controller, is presented in a positive synchronously rotating reference frame and is capable of providing a precise current control for a rotor-side converter (RSC) with separated positive and negative components. It is demonstrated that the power theory can reduce the oscillation of the dc-link voltage in the grid-side converter (GSC). In this paper, the generator model is examined and the simulation results have been obtained with a 3kW-DFIG based wind turbine system in order to verify the proposed control strategy.