In this paper

the problem and the cause of direct drive permanent magnet synchronous wind generating unit under asymmetrical fault of power grid is summarized and analyzed firstly in accordance with asymmetrical fault feature of power grid. On the basis of that

the main measures in solving the operation problem of the wing generating unit under asymmetrical fault is summarized from such three aspects as restraining fluctuation and rise of DC busbar voltage of back-to-back double PWM converter and maintaining balance of the networking current

and some ideas on assuring safe operation of the direct drive wind unit are proposed on the existing basis.