In recent years

the technology of DC power system based on voltage source converter has developed rapidly and become a hot research topic. The power flow problem is the most basic in power system analysis

and the research on the power flow analysis and control technology of DC grids is the most important foundation in the research of DC grids. Firstly

we summarize the methods of DC power flow and optimal power flow calculation

and discussed convergence and computational efficiency of both methods. Secondly

aiming at the shortage problem of DC grid power flow control degrees of freedom

from two aspects of system level control and DC power flow controller

we summarize the method control of DC power flow

and discuss the control effect and economy. Finally

we summarize and prospect the development trends and key issues of analysis and control technology of DC power flow.