Aiming at the problem of power angle stability of a AC/DC outgoing transmission system which may be caused by AC fault in near area after a flexible DC is connected to a power grid in a certain area

the different power stalls and operation modes of the flexible DC are compared. The influence of equal power angle stability of different operation modes in this area is discussed

and the adoption of flexible DC different power shift and operation mode is put forward. The small hydropower network in this area and the main hydropower station start-up different stalls are taken as the grading standard. The stability of power angle under different operation strategies is analyzed

and the constraints of the flexible DC high power operation on the area AC outgoing section and the regional AC output limit on the flexible DC power are analyzed by using PSASP software. A pre-control strategy for coordinated outgoing analysis of flexible DC and regional power grids is proposed in this paper

which can improve the ability of coordinated outgoing power transmission in the region as far as possible on the basis of ensuring the security of the power grid.