Abstract: Active damping control with virtual series impedance features in flexible HVDC systems is impossible to completely reshape the AC impedance of converter station into positive damping in medium-high frequency range resulting in the risk of high frequency resonance (HFR) still exists. In response to the adaptable difficulties of active damping control strategy in solving the problem of HFR under all operating conditions, a simplified model with mathematical expression of converter is used to analyze how the voltage feed forward part affects the first negative damping frequency range of high frequency segment and its minimum conductivity value. Secondly, to completely solve the problem of HFR, an active and passive coordinated suppression method and principle have been proposed. The active damping control strategy is not used to suppress HFR, but rather to improve the conductivity features of the first high frequency negative damping range for reducing the parameters of passive damping filter. Thirdly, according to the characteristic of direct voltage feed forward and principle of coordinated suppression, the inadaptability of traditional second order high-pass filter as damping controller to improve the conductivity characteristics of converter is analyzed. Therefore, a fourth order low-pass filter is proposed as the dominant form of active damping controller. Finally, the parameters of active damping controller and passive damping filter are analytically calculated and optimized based on the positive damping criterion of converter in high frequency range. The electromagnetic transient simulation models are used to validate the correctness of the studies.