The impact of railway to wind farm is introduced. An introduction about the AC/DC electric locomotive which is used widely and its tractive power supply system is made,and its wiring and structural features are introduced. The typical traction substation which uses three phase V/v connected traction transformer is chose to be studied. After that, the generation of the three-phase imbalance and the power quality problems of wind farm caused by the AC/DC electrified railway are studied. The principle of the generation of second harmonic fluctuation in direct driven turbine DC side,and a positive and negative sequence dual current control strategy is presented for direct driven wind turbine under the circumstance that the AC/DC electric locomotive is connected to wind farm. At last, the model of AC/DC electric locomotive and direct driven wind farm are established, and the power quality problems of wind farm caused by the AC/DC electrified railway is validated, also the running situation of direct driven wind turbine with positive and negative sequence dual current control strategy under three-phase imbalance is simulated.