In the process of China's ultra high-voltage (UHV) construction, Henan UHV power grid is the important part. Summer great load mode of Henan power gird is chosen as the typical method. In the background of completing Nanyang UHV extension project, based on single pole running and double pole running of Hami-Zhengzhou UHVDC project respectively, it is simulated and analyzed. The results indicate that power grid cannot maintain stability when single pole block fault or double pole block fault occurs. Through theoretical analysis and simulation, under UHV AC running certain limit, HVDC latching grid is stable. Under UHV DC running certain limit, HVDC latching grid is stable. Based on continuous simulation, this paper obtained the coordinated operation of area UHV AC and DC.
