The grounding electrode current could cause many problems

such as DC bias of transformers

erosion of metal facilities underground

and so on. To restrain the bad effects of grounding current

the existing studies mainly focus on the technologies

such as increasing protection measures on the side of equipment

as well as the use of distributed DC grounding electrodes. So far

there is no control strategy of the grounding current at the source has been put forward. Therefore

this paper proposes two control strategies of the grounding current combining with the control and protection properties of double-circuit high voltage direct current(HVDC)transmission lines on the same tower. The first one is to reveal the defects when applying the function by checking the control logic of the existing grounding current limitation function and verify those defects one by one. On this basis

the optimization method of control logic is further put forward. The second one is to add a new bipolar shunt trip-ping function in one circuit in the HVDC control system. The function blocks one pole immediately after another pole is protectively blocked. Finally

these two kinds of control strategies are both tested by real-time digital simulation(RTDS)platform

and the results validate the correctness and effectiveness of the control strategies.