Reactive power compensation configuration and control strategy optimization of DC converter stations are of great significance to improve the operation economy and reliability for DC transmission projects.In view of such problem as dramatic reduction of operation life of circuit breaker due to the frequent switching of reactive power compensation device converter station at the sending end

in this paper

the influence of DC transmission power variation and AC voltage fluctuation on the switching number of reactive power unit is studied deeply in accordance with existing reactive power control scheme and the relations among DC transmission power

commutating bus voltage and reactive power exchange capacity of system which is derived by the related formula theory.The feasibility and achievement mode on improving reactive power control reference value and dead zone value is studied in accordance with the calculation principle of V-Q sensitivity and on the base of the study of reactive power compensation ability of fitted power of converter station at the typical sending end in the northwest area of China.As for such features as the limit of minimum switching number of AC filter when the power operation is reduced due to frequent switching of shunt capacitor during high power operation of DC system

the reference value and dead-time value of reactive power control are increased at high power operation of DC system

while the control mode of the original scheme is maintained at low power operation.It is shown by the simulation results in PS ASP that the strategy can reduce the switching number of reactive power unit effectively and provide the theoretical evidence for the practice and application of reactive power optimization strategy of converter station at the sending end.