The current situation and existing problems of security and stability control system(SSCS)of ultra-high voltage direct current(UHVDC)transmission are analyzed in the aspects of the system architecture

the interface between SSCS and pole control and protection system(PCP)

failure criterion of converter devices and control strategies of the grid. The engineering experience of UHVDC SSCS projects in China is summed up

the standard design schemes are proposed. The research focuses on the interface and communication protocol between SSCS and PCP

fault criterion

UHVDC power loss algorithmic

and coordination of security stability control strategies. The design scheme proposed has been applied in Fulong-Fengxian

Jinping-Suzhou

and Yibin-Jinhua UHVDC transmission projects. Also

the study has great significance for other designs

development and implementation of UHVDC SSCS.