LVDC microgrid with double ac grid interface: Protection against dc ground faults and control strategies

Recent technological advances allow us to envisage the possibility of developing DC microgrids, opening also the way for the creation of DC connections in distribution networks to make the whole system more robust. This paper deals with the study of a DC microgrid supplied by two AC grids through LVDC lines. The control strategies proposed for the Front-End Converters (FECs) interfacing with the two AC grids allows high levels of quality to be achieved in the microgrid, even in the presence of sudden perturbations on the grid. Finally, this paper analyzes the problem associated with high frequency circulation current that, in the absence of suitable measures, would be reclosed through the star centers of the two transformers thus affecting the whole system, and describes a possible solution. The study of DC side ground faults concludes this paper, proposing a possible protection strategy based on the use of residual current devices.