Static equivalence method of external network in interconnected power grid

Provided is a static equivalence method of an external network in an interconnected power grid. The static equivalence method comprises a static equivalence model which is established on a boundary and provided with a non-generator node; two sensitivity equations before and after equivalence are equaled; and a virtual generator voltage, an equivalence injection current, an equivalence branch to ground and the like are deduced after static equivalence of the external network. In the aforementioned computation processes, the boundary of the static equivalence model is additionally provided with the equivalence branch to ground of the non-generator node of the boundary. A maximum safety error and a relative error of a line inactive injection power and an active injection power of an internal network are both improved, and a node maximum voltage amplitude relative error in the internal network is also improved so that higher static equivalence accuracy of the external network is obtained, and static safety analysis on the internal network can be better performed. When static safety analysis is performed on the internal network, a more accurate current value is also obtained.