Abstarct: The control of Doubly-fed induction generators (DFIG) baxsed wind turbine, regardless of unbalanced voltage conditions cause malfunction of DFIG. If these conditions are neglected to control of the DFIG, undoubtedly occurring small unbalanced voltage in the terminals of the machine can lead to creating high unbalanced currents in the stator windings that causes the trips in the wind farms. Furthermore, occurring unbalanced voltage in the network, creates the oscillations with high amplitude at double the network frequency in the electromagnetic torque and power and DC-lixnk voltage. In this thesis, the DFIG system is modeled, under balanced conditions, and then the vector control method for controlling the converters of DFIG is analyzed. Then by modeling the DFIG system, under unbalanced voltage conditions, the unbalanced voltage effects on its performance are analyzed. Thus, a variety of control methods is presented to improve the performance of the DFIG baxsed wind turbine. In all these control strategies, the rotor side converter (RSC) and grid side converter (GSC) are controlled in two positive and negative ((dq)+ and (dq)–) reference frxames. It is worth noting that the control of these converters in the (dq)+ frxame is the same as the control of them under balanced conditions. A variety of goals can be considered for controlling the negative sequence currents by of the RSC and GSC, in the (dq)– reference frxame. Therefore, the different strategies can be applied for controlling both the RSC and GSC. In the first control strategy, the RSC is controlled in the (dq)– frxame to eliminate the electromagnetic torque oscillations. However, the GSC is controlled to cancel the oscillation of the stator active power by its output active power. But In this strategy, when the voltage unbalance is somewhat severe, the amplitude of stator active power oscillations increases and the compensation of the stator active power oscillation will not be achieved completely, due to limited capacity of the GSC. In this thesis, tow control strategies are proposed to achieve more improved performance of the DFIG under these conditions. In the first one, the rotor current pulsation is eliminated by controlling the RSC. This control target gives good attenuations of both stator active power and torque oscillations. Therefore, the GSC is easily controlled to eliminate the total active power oscillations. In the second one, the negative sequence reference rotor currents are given as the average of the reference negative sequence currents obtained for eliminating the electromagnetic torque and stator active power oscillations. These reference currents are also used for balancing the stator currents. Thus this target not only removes any stator current unbalance but also gives good attenuations of both the stator active power and torque oscillations. According to the simulation results, the amplitude of the electromagnetic torque and stator active power oscillations obtained in this strategy, are smaller than those of obtained in the first proposed control strategy. Hence the control of the GSC for eliminating the oscillation of the total active power is done easily. Furthermore, high computational error is accompanied with the estimation of the positive stator-flux space vector position, especially under unbalanced voltage conditions. Therefore, in order to achieve the accurate control of the DFIG, the proposed control strategies of the RSC and GSC are implemented in the stator-voltage oriented frxame. The simulation results obtained for a 7.5 kW DFIG baxsed wind turbine validate the enhancement of system operation using the proposed control strategies during unbalanced voltage network.