1.State Grid Economic and Technological Research Institute Co., Ltd., Beijing 102209, China;2.State Grid Corporation of China, Beijing 100031, China;3.State Grid Qinghai Electric Power Company, Xining 810000, China

At present, the traditional control mode is commonly used in China’s running HVDC projects, which may lead to frequent action of DC discrete voltage regulation equipment with a fluctuation of DC power and voltage, and directly affect the HVDC project operation reliability. In view of the technical requirement for reducing the action frequency of DC discrete voltage regulating equipment, this paper firstly analyzes the action influencing factors of discrete voltage regulation equipment. Based on this, the HVDC traditional constant extinction angle and constant DC voltage control modes are respectively improved considering the coordination of tap-changer, AC filter and dynamic reactive compensation. And DC operating voltage varies with DC power within selected power range is proposed. Then the impact of the proposed strategy is analyzed and the corresponding optimization suggestions are given. Finally, the above analysis is verified based on DC main loop calculation and electromagnetic transient simulation. The results show that the proposed strategy can effectively reduce the action frequency of DC discrete voltage regulating equipment.