1.State Key Laboratory of Power Transmission Equipment & System Security and New Technology (Chongqing University), Chongqing 400044, China;2.Southwest Branch of State Grid Corporation of China, Chengdu 610041, China

The results of three-tier voltage control for AC/DC interconnected power grid should satisfy the independent control mode of converter stations. Therefore, an optimization method for static reactive power of AC/DC systems considering independent control constraints of converter stations is proposed. The basic assumption of the new model is that the initial operation state of DC power and discrete voltage regulation devices remain unchanged during the period of three-tier voltage control. Based on the conventional static reactive power optimization model of AC/DC systems, the dead zone control constraints of local reactive power balancing of DC systems and the adjustable range constraints with non-fixed boundary of auxiliary power supply for DC systems are further considered. The problem is solved by the interior point method. An ultra-high voltage direct current (UHVDC) converter station with its nearby AC power grid in Northeast China is simulated to verify the effectiveness of the proposed method. The simulation results show that the proposed method can reduce the risk of frequent operation of discrete voltage regulation devices and realize the coordinated control of the transient and steady-state reactive power of converter stations.