DC microgrids may bring changes in power supply methods for users

and the purpose of this article is to systematically explain the research status of its protection technology. First

we clarified the voltage level of the DC microgrids under study and the related power electronic devices. On this basis

we summarized the widely accepted wiring methods based on factors such as operating performance and cost. Then

we summarized the multiple performance indicators related to the grounding method and explained the important parts. We explained the DC microgrids grounding method from the four aspects of the AC grid side

the AC valve side

the DC system side

and the user side. Moreover

we discussed the choice of the ground afterwards and the choice of the number of grounding points on the DC side. Finally

we summarized the characteristics of bipolar faults and discussed the characteristics of various ground faults based on the grounding method. Meanwhile

we briefly introduced the existing protection schemes

and explained the protection method based on the coordinated control and protection in terms of its limitations and the controllable characteristics of power electronic devices from two aspects: device and system. Finally

the research directions of grounding methods

fault analysis and protection methods closely related to DC microgrids protection are prospected.