Abstract: To accommodate the large-scale development and power delivery of new energy in Western Sichuan in the future and reduce power grid operation risks, this paper explores and constructs a high-voltage large-capacity four-terminal VSC-HVDC planning grid within Sichuan Province. Based on the DC power transmission characteristics of the constructed multi-terminal VSC-HVDC transmission system and the operating conditions of the hybrid AC/DC system, a study on coordinated control of wide-area AC/DC systems is carried out, and a coordinated control strategy for AC/DC systems with priority given to DC power modulation of the multi-terminal VSC-HVDC system is proposed. Power system simulation results have verified the effectiveness of the proposed strategy. To quantitatively characterize the supporting effect of the multi-terminal VSC-HVDC system on improving the security and stability of the AC system, an effective support factor F of the multi-terminal VSC-HVDC system for the AC system is put forward. The proposed coordinated control strategy for wide-area AC/DC systems can facilitate the analysis of operating conditions of hybrid AC/DC power grids and improve the secure and stable operation level of power systems.