Abstract: In recent years， distribution network is developing rapidly from current to future advanced form. Under the tendency， this article puts forward a new AC and DC distribution network technology based on flexible substation. This technology is firstly launched in research， design， equipment manufacturing and engineering construction， etc. There is no mature design experience and complete theory. In this paper， system scheme and design method based on flexible substation are given systematically for the first time. And design of system scheme， parameters of key equipment， control and protection system are researched and discussed in depth. All of the research results above are adopted in the first demonstration project of AC and DC distribution network based on flexible substation for system design. The study results will provide theoretical and experimental experience for system design in the future AC and DC distribution network projects.

Key words: flexible substation, AC and DC distribution network, system design, system scheme, equipment parameters, control and protection