Abstract:  ABSTRACT： In recent years, the AC distribution network is facing the challenge of more and more DC power sources, DC loads and the diversification of power demand. AC and DC distribution network has gradually become the focus of research. This paper reviews current situation of domestic and foreign technologies for AC and DC distribution network and summarizes the characteristics of existing schemes. Aiming at the core challenge to distribution network, a new technology on AC and DC distribution network based on flexible substation is proposed. Flexible substation makes the power electronic equipment highly integrated with AC and DC multi-type interfaces, and can control the power flow, highly supports the utilization of new energy and individuation of electricity consumption scheme, can support the flexible operation of grid, the demand of new energy power supply and multiple loads etc. The paper builds the system model, makes the power calculation, designs automation system, strategy of control and protection. Simulation results verify the correctness of the principle and the feasibility of the project；verify that this project can improve the interactivity and coordination of source-network-load. Finally, this paper takes "Zhangbei AC and DC distribution network and flexible substation demonstration project" as an example to introduce the world's first AC and DC distribution network based on flexible substation, and sums up the demonstration significance of the AC and DC distribution network's development.   

Key words:  KEYWORDS： AC and DC distribution network, flexible substation, multifunctional AC/DC power electronic transformer, demonstration project, system scheme  ,