For a large-scale wind farm with wind turbine driven doubly fed induction generator（DFIG）. Put forward a kind of equivalent model method by pitch angle action situation as a cluster index. The specific method is

input the feature vector can characterization the state of pitch angle action in support vector machine. The wind turbines are dynamically grouped

and the same group wind turbines are aggregated. The calculation method of equivalent wind turbine parameters has descried. Thus a wind farm model represented by multi-machine equivalent wind turbines is obtained. Through the comparison of different modeling methods

we can see the simulation time was reduced greatly in the premise of ensuring the accuracy of the simulation. And the result is more closed to the actual operating conditions of wind farm. Verified this equivalent model more accurately describes the dynamic characteristics of a wind farm at the grid connection point.