The regional and multiple wind farm cascading trip-off induced by the wind farm inner fault will cause serious impacts on the power grid. Based on the demagnetizing control of low voltage ride through(LVRT)

wind farm equivalent modeling is carried out according to the generator groups divided by the switching criterion of Crowbar circuit after the fault. First

by taking the influence of rotor side converter into consideration

and with the rotor current not ignored

the stator flux during the period between the moments the fault occurs and Crowbar circuit switches in is calculated through the state equation. The demagnetizing rotor current is then obtained by combining with the switching criterion of demagnetizing control strategy. Thereby the generators of the wind farm are divided by estimating whether the Crowbar is to act or not. After analyzing the characteristics of wind farm inner fault

the original collector network need not be changed

but the access points of equivalent generators are determined by using nonlinear programming. Finally

example and simulation show that the method proposed can accurately reflect the characteristics of the wind farm before and after the fault.This work is supported by State Grid Corporation of China(No. SGSDDK00KJJS1500155).