Fault Mechanism and Protection Strategy for DC Micro-grid

This paper aims to introduce the research status about the protection technology for DC micro-grid system and summarizes the protective devices and protective methods of different DC micro-grid structures systematically. Firstly, this paper introduces composition and operation of DC microgrid. Then, this paper analyzes the short circuit fault process and proposes a general method to evaluate the fault current. Secondly, the development status of a variety of protection devices used in the DC system is presented. Thirdly, considering that the capacitor discharges instantly and power electronic devices are vulnerable to the high fault current, the various schemes about quickly cutting off or limiting the fault current are compared. Finally, this study summarizes the fault detection methods for DC microgrids. The outcome of this paper can be used as important reference for practical implementation of DC microgrid protections.