DC Short Circuit Fault Analysis and Protection of Ring Type DC Microgrid

DC fault location and protection is the key problem to be solved of DC microgrid in spite of the fact that it has become the ideal networking mode of distributed generation due to its obvious advantages. In this paper, a ring-type wind turbine-based DC microgrid is taken as the object of study and the transient characteristics of VSC as well as the system under DC line fault are analyzed based on which the protection scheme of current differential protection as the main protection and undervoltage protection as the backup one is proposed. In this method, the power supply security of the DC microgrid system is guaranteed by detecting the input and output currents of the DC transmission lines through which the corresponding differential currents can be calculated to locate and isolate the fault lines. Simulations are conducted on MATLAB/Simulink and the results show that the protection system can response rapidly to the line differential current value under short circuit fault, so as to realize the DC short circuit fault protection of DC microgrid system.