The Coordinate Control Strategies For Double Circuit HVDC Transmission System Erected On The Same Tower

In order to use the grounding electrodes and the converter stations more effectively,improve the transmission capacity per unit corridor, save the valuable transmission corridor,and reduce the construction and maintenance costs, Xiluodu right bank-Guangdong±500kVHVDC transmission project adopts the design of the double-circuit transmission line on thesame tower. This new HVDC transmission system shares the same AC field and groundelectrode.Differed from the one-circuit±500KV HVDC transmission system, Xiluodu HVDCtransmission project need to control the double-circuit power and the reactive power of thewhole station in order to make sure the double-circuit DC power can meet the requirement ofthe dispatching and the ac filters of the whole station can meet the requirement ofdouble-circuit DC transmission. Therefore, the hierarchical control structure of XiluoduHVDC transmission and the connection between every control hierarchy become morecomplex. Consequently, it is necessary to do a research on the hierarchical structures and thecoordinated control strategies of the double-circuit HVDC transmission system erected on thesame tower.Firstly, a new hierarchical structure of the double-circuit HVDC transmission system ispresented in this paper. Then, a detail research on the double-circuit power coordinate controlstrategy is put forward, as well as the power modulation strategy and low-load reactive powercontrol strategy, according to the new hierarchical structure. Based on PSCAD/EMTDC forthe system，Four typical operation modes are chosen in order to get the representativesimulation results. The results verify that the coordinate control strategy is feasible. Based onthe HVDC converter station reactive power demand characteristics, combined by the send andend of the AC system，the reactive power compensation scheme and its balance for converterstations are analyzed in-depth in this paper. Finally, increasing the firing angle, the turn-offangle and adjust the tap changers stalls measures leads to increase the converter station reactive power consumption, which is tested by simulation experiment. The results will be ofsignificance for the operation of the actual project.