The control and operation of a grid-connected wind-turbine with a permanent magnet syn-chronous generator have been investigated under asymmetrical voltage sags at the grid side. To deal with such conditions, a fast-acting control scheme is needed. It is shown in this paper that a sliding mode control can meet the challenge. In the proposed control scheme, the dc link voltage, and active/reactive powers are decoupled ?rst so that the asymmetrical voltage sag issues can be dealt with independently. To minimize additional stress in?icted by the asymmetrical voltage sag on the power electronic converters, a feed-forward negative sequence voltage is used in the vector current control strategy. Using the developed control scheme, the wind power generation system can remain on-line to support the grid even during the asymmetrical voltage sags. The effectiveness of the proposed control scheme has been validated by extensive simulations as well as through real-time hardware based experiments on a physical wind-turbine test platform.