HVDC transmission is an important approach to delivery large-scale wind power for a long distance. When the commutation failure occurs, the voltage of sending end will fluctuate dramatically, which threatens the stable operation of wind farm. Meanwhile, different characteristics of wind turbines will further affect the transient voltage of sending end, so the impact of wind farm on the transient voltage must be considered, especially for the high proportion of wind power generation. Firstly, the sending end transient voltage characteristics are analyzed and the mechanism of transient overvoltage caused by commutation failure is revealed. Then, doubly-fed wind power generation systems with different control modes are modeled, and the dynamic reactive power response capabilities of them are studied, so as to analyze the influence of the doubly-fed induction generator (DFIG) control modes on the transient overvoltage. Finally, a simulation example is established which verifies the correctness of the theoretical analysis. The results show that when DFIG adopts the constant voltage control strategy with the quickly response speed of the converters, it has stronger reactive power output capability, and can suppress the transient overvoltage, which is beneficial to the safe and stable operation of the power grid.