Control of DFIG-WT under unbalanced grid voltage conditions

The voltage oriented control in the synchronous reference frame (VOC-SRF) have been extensively used for controlling wind turbines based on doubly fed induction generators (DFIG-WTs) through the rotor side converter of a back to back power processor. Although its performance is fast and accurate under balanced conditions its behaviour is not good enough when the voltage of the mains is unbalanced, unless an independent control for the positive and the negative sequence is implemented. This paper proposes a new control system able to control the DFIG-WT under unbalanced conditions using a simple algorithm, which does not need to be implemented for both symmetrical components but on the static alphabeta reference frame. The reliability of the presented system will be tested by means of PSCAD simulations under balanced and unbalanced grid conditions.