Considerations on DC side grounding configurations of LVDC microgrids

Abstract

LVDC microgrids including renewable power generation and local loads are becoming more and more common. In such microgrids, a DC section is typically present, separated from the AC grid by a front-end converter: this is the case e.g. for PV generation and for full-converter wind power plant. One critical issue in such grids is grounding: several different options are available, according to the grounding schemes of DC and AC active parts. Each has different consequences on grid operation and fault behavior. In this paper, grounding schemes with ungrounded AC section and grounded DC section (both middle point- and single pole-grounding) are discussed. Behavior of a network with such configurations in normal working mode and under DC ground fault condition is considered, highlighting benefits and disadvantages.