Research on Control Strategy for Reducing Reactive Power Exchange in ACDC Systems Under Low Power in DC Engineering

With the large-scale development of new energy, the high proportion of wind and solar renewable energy sources and power electronic devices profoundly affect the dynamic behavior of the power system, further posing challenges to the safe and stable operation of the DC system. Traditional ultra-high voltage direct current (UHVDC) engineering converter stations are equipped with a large number of AC filters. During the switching process of AC filters, there is a dead zone of reactive power in the AC/DC system, and there is always a certain amount of reactive power exchange. According to engineering experience, the dead zone range is about 0.8 times the maximum capacity of a single AC filter group. When the AC filter group is large, the reactive power exchange value between the AC/DC systems also increases. Under the continuous development of new energy in the future, the reactive power support capacity of the communication system may become increasingly limited. At the same time, there are a large number of power electronic devices in the network, and the reactive power injected into the communication system may also pose operational risks to the stability of the communication system. This article mainly proposes a control strategy to reduce the reactive power exchange in the AC/DC system in the case of a large dead zone of reactive power under low power in the Matiari-Lahore DC project. By comparing the reactive power exchange during the lifting process and the number of switching times, the possible applicable solutions and risk points of the current DC transmission system are analyzed, providing feasible solutions for the safe and stable operation of DC transmission projects in the future new power grid.