Numerical Analysis of Network Interface for Electromechanical Model of Grid-Forming Flexible DC Transmission System

Grid-forming control voltage source converters (VSCs) have good characteristics for flexible DC transmission in weakly inertial power systems. The main differences between grid-forming control and grid-following control systems lie in the form of power supply support, fault traversal switching measures, and current limiting methods. By changing the interface between the grid-forming VSC electromechanical transient model and the AC network from average power within one AC simulation time step to average voltage, it can better adapt to the characteristics of the voltage source support in grid-forming flexible DC transmission projects. In this paper, the electromechanical transient model of the typical Chinese new energy project Zhangbei Flexible DC Transmission Engineering is established using the average voltage interface. The operational characteristics of the two interfaces are compared, and the advantages of the average voltage interface are demonstrated.