Fault Analysis in a Residential DC Microgrid

Abstract

It is well known that after the late 19th century ‘‘war of currents’’ fought between Edison and Tesla, Alternating Current (AC) systems have always been considered the cornerstone of electricity transmission. The recent diffusion of renewable energy sources and electronic loads, operating in direct current (DC), has led to a reassessment of the technical and economic viability of using DC microgrids or portions of grids. In this context, DC systems has recently found fertile ground also in low-voltage DC distribution (LVDC). It is known that its spread has been hampered by one of DC’s biggest problems: the fault protection system. DC protection coordination is the subject of several studies and, despite its complexity, it is possible to identify two main elements: the rapidity and magnitude of fault current transients; and the dependence of fault behavior on converter topology and the earthing system. Therefore, the deployment of DC must inevitably go through the resolution of the aforementioned problems and thus through a preliminary phase of fault analysis of DC networks. The aim of this article is to carry out fault analysis in DC microgrids with a focus on the contributions of electronic components to the fault. In this regard, a case study of a LVDC residential microgrid model has been taken as a reference, where all elements have been analyzed and, having defined the network topology and the earthing system, the circuit equivalents have been realized in order to carry out the operational fault analysis.