With the widespread access of distributed generators

energy storage and novel loads etc.

the DC characteristics of the distribution network are becoming more and more obvious

which gradually develops into a complex DC distribution network with multi-layer

multi-voltage level and multi-ring. Due to the existence of a large number of converters in the system

when a short-circuit fault occurs in a DC bus

the fault transient process is rapid and the fault mechanism is complex

which seriously jeopardizes the safe and stable operation of the system. This paper firstly elaborates on the network structure of multi-terminal flexible DC distribution system and the grounding method of each converter. Secondly

it also discusses the fault characteristics of typical fault scenarios of common converters in power grids

and summarizes the existing research status of DC distribution system fault identification methods from multiple perspectives. Then

this paper summarizes the research results that have been achieved by scholars at home and abroad in terms of fault section localization and fault distance measurement. Finally

it elaborates on the existing problems of the current research on fault identification and localization in multi-terminal flexible DC distribution networks

while looks forward to the future related research directions at the same time

so as to provide a reference for the subsequent research on fault identification and localization for large-scale and complex DC topologies.