Analysis of the Impact of Grid-Forming Control on Impedance Characteristics

With the rapid development of renewable energy and direct current (DC) transmission, stability issues have emerged in the interconnected system between the DC receiving-end and nearby renewable energy stations, necessitating research on their impedance characteristics. This paper establishes sequence impedance models for the voltage source converter (VSC)-based high-voltage direct current (HVDC) converter, wind farms, and the receiving-end system, along with an equivalent model of the receiving-end system. Using impedance analysis methods, the oscillation mechanisms of this interconnected system are investigated, and stability-influencing factors are analyzed. The results demonstrate that grid-forming control can reduce the capacitive range of the VSC-HVDC converter's impedance, thereby improving its impedance characteristics and mitigating oscillation risks in the interconnected system.