Abstract: An AC filter is mainly used to eliminate harmonics generated by the converter and compensate the reactive power of the DC system. Frequent operation of the AC filter circuit breakers may cause serious inrush current and overvoltage. In a converter station of the Northwest Power Grid, there have occurred repeatedly the faults that the pre-insertion resistors (PIR) failed to suppress the energization inrush current. According to the actual working conditions of the converter station, the influence of the pre-insertion resistors with different sizes on energization inrush current and overvoltage is analyzed theoretically, and the effect of PIR is compared with the effect of controlled switching device. The PSCAD is used to calculate the possible operating conditions. The results show that with the accuracy control by the controlled switching devices this method has a good effect on suppressing inrush current and overvoltage. Under the condition of using 400 ~ 1500Ω pre-insertion resistors, the maximum inrush current that may be caused by the resistor exiting exceeds the one that may be caused by its inputting. Using both the PIR and the controlled switching devices can effectively suppress the inrush current and have stronger anti-interference ability to control time error.