A control technique of line side converter for doubly fed induction generators under unbalanced voltages conditions

This paper presents a control technique to reduce the effect of unbalanced voltages on the line side converter of the wind energy conversion system with a doubly fed induction generator (DFIG). The unbalanced voltages produce oscillations of instantaneous active power and dc bus voltage. When the model of the unbalanced system is transformed onto the synchronously rotating reference frame, the d-q axis components of the currents and voltages are composed of dc and ac quantities. The ac components of currents can be directly controlled to minimize the fluctuation of active power and dc bus voltage without complex calculation. The simulation results show that the oscillations of both active and dc bus voltage are reduced significantly with the compensation of ac current components control method.