The DC grid is an important part of future grids. The power flow distribution and control of DC grids is not only related to the allocation of power resources

but also closely related to the security and stability of the system and should be considered first. Based on the development status of DC transmission technology

voltage control and current control methods are classified and arranged

the advantages and disadvantages of various control methods are pointed out

and new ideas for the control of future DC power grids are provided. In the field of node voltage control

converter models in different control modes

the voltage controller models of DC grids are elaborated

and the effect of single point voltage control method and multi-point voltage control method on system power flow distribution is treated as is the voltage deviation control and voltage droop control. In the field of branch current control

the design idea

external equivalent characteristics

topology and access methods of different DC power flow controllers are briefly summarized.