With large-scale new energy centralized access, power grid is in the difficulty of new energy consumption and stable operation. Firstly, the stability characteristics and risk of terminal bundled wind-thermal power grid are analyzed. A system frame of security defense system for bundled wind-thermal power transmission is proposed. The design objectives, the four-tier deployment architecture of the defense system and supporting strategies including the frequency coordination control and voltage coordination control are emphasized. The system aims to use the whole network controllable resources to reduce the frequency and voltage fluctuations caused by large-scale new energy, and to block the path of cascading failures, then hence to ensure the safe operation of power network.