To improve the reactive power support capability of the current source controllable line commutated converter (CLCC) applied at the receiving end of a DC transmission system for a AC system

a reactive power support control strategy is proposed specifically for this CLCC. Firstly

the operation principle of CLCC against commutation failure is introduced. The reactive power characteristics of the CLCC in relation to firing angle and AC voltage were theoretically analyzed. The results verify that the converter's reactive power can be regulated by adjusting the firing angle. Based on the conventional line commutated converter control strategy

a reactive power support control strategy is proposed

and the rationality of its control logic is analyzed. Finally

the digital-physical hybrid dynamic model platform for CLCC was introduced

and validation tests of the control strategy were conducted on this platform. The experimental results demonstrate that the proposed reactive power support control strategy can reduce the reactive power absorbed by the converter to zero during a three-phase fault when the AC voltage drops by 50%

while enabling the converter station (converter and filters) to inject 0.16p.u. of reactive power into the system. This accelerates the recovery of the receiving-end AC voltage and reduces the transient fluctuations in DC voltage

DC current

and active power. Specifically

the fluctuation range of DC voltage is reduced from 0.45~0.97 pu to 0.647~0.97 pu

the DC current fluctuation range is narrowed from 0.59~1.43 pu to 0.73~1.3 pu

and the active power fluctuation range of the converter station is compressed from 0.375~0.86 pu to 0.647~0.86 pu. Under a single-phase fault

the proposed reactive power support control strategy does not accelerate AC voltage recovery or reduce the magnitude of the active power dip. The control strategy proposed in this paper can provide a valuable reference for the engineering control strategies of CLCC.