The transient overvoltage problem of HVDC sending system caused by HVDC blocking fault may threaten the safety of the large-capacity and long-distance transmission across regions. At present, the configuration of synchronous condenser in converter stations is recognized as one of the means to reliably solve the above problem. In order to coordinate the planning of capacitor and synchronous condenser in converter station from the perspective of economy, this paper firstly analyzes the mechanism of suppressing transient overvoltage caused by HVDC blocking fault using synchronous condenser. Furthermore, this paper puts forward a transient overvoltage calculation method of converter bus based on sub-transient power flow, and applies this algebraic analytical cal-culation method to the coordinated planning of capacitor and synchronous condenser capacity in converter station to meet the voltage control requirements during normal steady-state operation and after HVDC blocking fault. Finally, the simulation results verify the efficiency and accuracy of the transient overvoltage calculation and the corre-sponding reactive power planning methods proposed in this paper, and at the same time illustrate the economy of voltage management and control realized by the cooperation of capacitor and synchronous condenser in converter station.