Flexible HVDC transmission technology will be widely used in the future because of its great controllability and other advantages in the power grid

and it is necessary to standardize transmission voltage sequence.Considering this trend

the article puts forward a reasonable voltage sequence for flexible HVDC transmission on the basis of the principles of "technological prospectiveness" by drawing on the mature voltage level sequence of traditional HVDC transmission and the completed flexible HVDC transmission project.The adaptability

safety

reliability of AC-DC interconnection

economy and benefits for the proposed flexible DC projects at different voltage levels are analyzed.According to the development of device and equipment

the article obtains the transmission capacity of each voltage level.And further economical analysis can obtain corresponding economic distance range.Besides

the economic indicators such as return on investment and payback period of flexible DC projects with corresponding voltage levels are calculated.Finally

FAHP is used to evaluate the flexible HVDC transmission projects with ±660 kV and above transmission voltage levels

obtaining the comprehensive evaluation scores of flexible DC engineering under different voltage levels

which can further quantitatively illustrates the reasonable feasibility of putting forward the voltage sequence of flexible HVDC transmission.