In this paper, a robust state-feedback control law is designed for rotor side converter of doubly fed induction generator to enhance both transient and steady-state performances of grid connected variable speed wind turbine. More explicitly, a disturbance observer-based control (DOBC) is designed to compensate for the offset caused by model uncertainties and unknown external disturbances which is not considered in the DFIG modeling. Moreover, the fast dynamic response is inherited from the state-feedback control law. The composite controller consisting of the state-feedback controller and the disturbance observer allows achieving a stable and accurate control of the stator active and reactive powers. The proposed control strategy is verified by simulations and experimental testbed. Various tests are conducted to demonstrate the effectiveness of the proposed control strategy, and satisfactory results are obtained.