In high-power direct drives for wind turbine, the control of grid-connected inverter is vital to power transporting and energy converting, and the output current with harmonic distortion is high. A filter, typically a series inductance, is adopted to reduce the switching harmonics entering the distribution network. An alternative filter is a LCL-filter, which can reduce the level of harmonic distortion. The control strategy of grid-connected inverter was used in this system based on a loop of bridge current regulator with grid voltage feed forward. A new decoupled double synchronous reference frame phase-locked loop was adopted in this system under unbalanced and distorted grid conditions. A 15kW direct drive for wind turbine system was constructed in the laboratory. The results prove that the grid-connected inverter can run stability and has good performances.