Abstract: In response to the problems of large system power and voltage deviation, as well as long fluctuation duration in the implementation of control and protection strategies for large-scale new energy access multi terminal flexible DC transmission, this paper proposes a research on control and protection strategies for large-scale new energy access multi terminal flexible DC transmission. Establish a mathematical model for a multi terminal flexible DC transmission system to describe the state of large-scale new energy access to multi terminal flexible DC transmission; according to the fluctuation situation, the stable operation of large-scale new energy access multi terminal flexible DC transmission is protected through power allocation control and power smoothing control of the transmission system. Through experiments, it has been proven that the design strategy control protection can achieve a maximum deviation of ±3.5 MW and ±0.41 kV in power and voltage on the grid side of the transmission system when large-scale new energy access multi terminal flexible DC transmission is disturbed. The continuous fluctuation time of power and voltage is 0.05 s and 0.04 s, respectively, and can immediately restore to a stable state with good protection effect.