Research on voltage coordination recovery strategy of multi-outfeed and multi-infeed UHVDC transmission system with similar path

On the basis of multi-infeed at the receiving end, some of the DC grid structures in China further reduce the electrical distance between the rectifier stations, forming a multi-outfeed and multi-infeed ultra-high voltage direct current (MOMIDC) transmission system with similar path. The complex AC-DC and AC-AC coupling characteristics of the MOMIDC system increase the control difficulty of the system voltage stability. This paper proposes the multi-outfeed and multi-infeed interaction factor (MOMI_IF) by analyzing the limitations of multi-infeed interaction factor (MIIF) in the MOMIDC system, and further deduces the multi-outfeed and multi-infeed voltage recovery intensity factor (MOMI_VRIF) on this basis. In addition, this paper also proposes a multi-level low voltage dependent current order limiter (VDCOL) coordination recovery strategy, which is based on the MOMI_VRIF. After simplifying the MOMIDC system by Thevenin equivalent, the author builds an electromagnetic transient model of a typical MOMIDC transmission system based on PSCAD and uses this model to simulate and verify the strategy in this paper