In order to further study the operation mechanism of the Central-North China AC synchronous power grid

this paper simplified this power grid into a 7-machine 48-node equivalent system. The equivalent system well retains the power flow static characteristics

tie-line power dynamic characteristics

the impact of large disturbance characteristics and short-circuit current characteristics of the original power grid. By the simulation analysis of the equivalent system

this paper preliminarily proves that the system UHV AC line splitting resulting from the serious fault occurring in Sichuan power grid is an angle instability problem. Based on this

a practical measure is proposed to improve the system stability.