Fault Detection and Localization in a Ring Bus DC Microgrid Using Current Derivatives

To provide more clean energy and satisfy the increasing power demand, microgrids using renewable energy sources (RES) are designed as additional power supplies. Recently, DC microgrids (DCMGs) have gained the attention for their higher power efficiency and simpler configuration compared to AC microgrids (ACMGs). Although DCMGs seem better than ACMGs, lack of protection standard is a critical problem when operating DCMGs. Since DC fault response is completely different as AC fault, AC protection methods cannot be used for DCMGs. In this paper, a ring bus DCMG model is simulated using computer software PSCAD. A combined protection scheme based on cable current derivatives is introduced. This protection scheme not only detects and localizes low resistance DC faults very fast, but also accurately handles high resistance DC faults. The reliability of this scheme is proved by the simulation results.