Enormous changes and challenges will be brought to the traditional power distribution system operation by distribution network flexible interconnection based on flexible DC and AC/DC hybrid distribution network structure. Firstly

a typical multi-terminal DC distribution network system with large-scale new energy

centralized load and integrated AC/DC microgrid was introduced briefly

and a basic hierarchical operation controlling framework was described. For local stable control

basic DC voltage control strategy of DC distribution network was presented briefly

then the key technologies to improve DC distribution network stability were reviewed in terms of DC voltage fluctuation suppression

stability and damping control and multiple operation mode switching control. For the optimization operation of DC distribution network

a hierarchical optimization framework based on day-ahead scheduling and real-time optimization control was introduced. Then optimization scheduling problems for DC distribution network under long time scale were discussed from two main scenarios

including flexible interconnection distribution network based on soft open point（SOP） and complex AC/DC distribution network. Finally

following key technologies of DC distribution network operation control were prospected. The research indicates that

local control needs to be more flexible to meet the requirements of flexible power control of future AC/DC distribution networks

and the optimized operation control will deeply with integrate advanced information communication

measurement technology

and technologies of big data

artificial intelligence. The research can provide a reference for the operation and control of DC distribution network.