Fault protection of DC microgrid is a major challenge for the development of AC-DC hybrid microgrids. Thus

this paper focuses on the review and analysis of three key technologies in fault protection of DC microgrid. And the three key technologies include the fault transient characteristics analysis

fault detection and location methods

and fault isolation schemes. Firstly

the topologies

wiring forms and terminal-converters of DC microgrid are summarized. Secondly

the transient characteristics of the DC microgrid based on two-level and modular multilevel converters are analyzed

and the transient modeling methods of DC microgrid transmission lines and converters are also summarized. And then

the common methods of fault detection and fault location are sorted out respectively. The fault detection methods are divided into time-domain and frequency-domain fault detection methods. While the fault location methods are divided into passive fault location and active fault location methods. Next

four fault isolation schemes

including an AC circuit breaker scheme

a DC circuit breaker+DC fault current limiter scheme

a submodule in MMC scheme

and a multifunctional integration topology scheme

are analyzed. Finally

the research of key technologies for fault protection of DC microgrid is summarized and suggestions for the future research for fault protection of DC microgrid are given.