Back-to-back flexible direct-current（DC）transmission technology can not only connect two or more different alternating-current（AC）systems

but also connect the power supply area of different distribution network with DC busbar. The technology makes fully use of the existed AC transmission line and explore the existed AC network ability for load transfer by the inter-connection of DC busbar so to achieve equalization distribution of the existed AC network and

at the same time and in case of fault mode

can achieve flexibly load transfer and reduce the load shed of the existed AC network. With the construction of rectifier and inverter stations in the same site

the flexible DC transmission structure with two or more ends can be formed and inter-connection of different partitions can be achieved

the back-to-back technology flexible DC transmission technology cans save the cost of DC inter-connection line between ends

save the total land area and investment. In this paper

the solution by using back-to-back flexible direct-current（DC）transmission technology to deal with the problems in Nanjing central urban area power system is proposed by way of analyzing the challenges in Nanjing central urban area power system during the 14 th-Five-Year planning period. The technical advantages and promotion prospects of this back-to-back flexible direct-current（DC）transmission technology utilized in the central-urban-area power systems is verified.