Research On Micro-grid’s Grounding Method And Protection Configuration

With the large scale access of distributed generation into power networks, its influence on the stability of power networks is more and more prominent. In order to fully display the advantages of distributed generation and solve the conflicts with power networks access, working out a practical and feasible design scheme of micro-grid systems is of great significance in practical engineering applications. In this paper, first, through the analysis of the control strategies and operation modes of micro-grids, the conclusions were drew:The operation modes of micro-grids are divided into off grids and connected grids. The control strategies of the inverter are divided into P/Q and U/f. Then, by studying the connection schemes of micro-grid power generation units of different voltage levels, the topological structures of the main wiring of the micro-grids were obtained. They are divided into DC, AC and AC /DC hybrid. Next, via the analysis of the grounding schemes of conventional distribution networks, according to the grounding requirements of micro-grid systems, the neutral grounding methods of DG in different systems were proposed. At last, by analyzing the relay protection of conventional distribution networks, the relay protection configuration scheme of the distribution networks containing micro-grid access was put forward, i.e. Adopting the method of the combination of high voltage area differential protection and low voltage distance protection.