A Capacity Dimensioning Method for District Flexible Interconnected Converter Station in UHV DC Receiving End Power Grid

District flexible interconnection provides a new idea for solving the problems of insufficient UHV DC receiving end power grid voltage and reactive power reserve, limited power supply capacity, and weak mutual supply capability. This paper proposes a capacity dimensioning method for the flexible interconnected converter stations of UHV DC receiving end power grid. First of all, it analyzes the problems of the UHV DC receiving end power grid divisional operation and the advantages of flexible interconnection operation. Secondly, the definition of the maximum power supply capacity of the flexible interconnected district power grid is proposed, and a mathematical model for evaluating the power supply capacity of the interconnected power grid is established. The improved K-means clustering is used to obtain the typical load level of interconnected partitions, which improves the accuracy of the stepwise approximation method to solve the power supply capacity. Then, the active power capacity of the converter station is determined with the goal of reaching the maximum power supply capacity of the interconnected zone and eliminating the component overload; Considering the influence of the induction motor load ratio, the reactive power capacity of the converter station is determined with the goal of restoring the bus voltage to the specified level after a transient fault occurs in the zone. Finally, an UHV DC receiving-end power grid is taken as an example to verify the effectiveness of the proposed method.