Abstract: With the growing popularity of wind power generation system, double-fed wind generator （DFWG） as one of the most commonly used wind turbines, its problems are gradually revealed. Since wind energy has the characteristics of multiple uncontrollable factors and poor stability, it has brought many uncertainties for the grid control. To study the fault protection technology of double-fed wind power generation system in a three-phase symmetrical fault, firstly, this paper used the method of mathematical analysis to construct double-fed wind generator （DFWG） model, and analyzed the running state of the generator in three-phase symmetrical fault. Then Crowbar protection circuit was built； and voltage sag was simulated by a voltage sag generator in the experimental platform for testing. Finally, the verification was carried out through simulation. The experiment and simulation results show that the Crowbar circuit has significantly inhibition effect on current surge on the rotor side. So, the method of adding the Crowbar circuit to achieve low voltage ride through（LVRT ） in three-phase symmetrical fault is feasible.

Key words: double-fed wind generator （DFWG）, three-phase symmetrical fault, Crowbar protection circuit, control strategy