When the reactive power control(RPC) function of the ultra high voltage direct current(UHVDC) converter station swi-tches the filter

a certain capacity of reactive power exchange will occur between the converter station and the AC system.This causes voltage fluctuations in the AC system

further leading to frequent actions of the tap changer of the converter transformer and affecting the stable operation of the DC system.Synchronous condensers

with their characteristics of rapid and continuous adjustment of reactive power

can effectively smooth out the instantaneous changes in reactive power output caused by the switching of filters.After switching

adjust the reactive power exchange between the converter station and the AC system to zero to maintain the steady-state voltage of the converter station bus at the optimal level.Based on this

it proposes a coordinated control strategy for synchronous conden-sers and ultra-high voltage DC reactive power to balance the reactive power exchange between the converter station and the AC system and ensure the stable operation of the DC system.