In AC/DC interconnected systems, the commutation failure of the DC system caused by the AC-side fault is one of the common faults of the inverter. According to the actual engineering parameters, a detailed model of ±660kV Yindong DC transmission project was built using PSCAD/EMTDC simulation tools, and at the same time, an equivalent model of Shandong power grid on the inverter side was also established using physical equivalence-based equivalent methods. On this basis, a simulation analysis was made on the operation of the Yindong DC system when there was a three-phase symmetrical fault in the AC system, providing a reliable reference for the safe and stable operation of the Yindong DC transmission system and other HVDC transmission projects.