In order to solve the problem that terminal currents can not be measured in traditional single-ended distance measurement protection

a method of single-ended distance measurement protection based on control and protection cooperation is proposed for four-terminal ring DC micro-grid system. This method is based on the traditional R-L line model and can be adopted to achieve accurate distance measurement only by using single-ended electrical quantity. Firstly

after the system fault occurs

based on the idea of control and protection cooperation

the controllable devices are controlled first

and then the protection is implemented. Through the topological transformation of the ring DC microgrid

it becomes a single power system. Secondly

the precise solution of the terminal current can be achieved through the electrical quantity collected by the protection device

and then the precise fault location of the single terminal can be realized. Finally

a four-terminal ring DC microgrid model is built on the PSCAD/EMTDC simulation platform

which verifies the effectiveness of the distance-finding protection proposed in this paper. The simulation results show that the principle has high ranging accuracy in the simulation experiment

has a low ranging error of less than 3%

and has a certain resistance to transition resistance.