Evaluating the stability impact of the interconnecting tie-line between coupled neighboring microgrids

Even though microgrids are generally assumed to operate either in grid-connected or islanded modes, as a third alternative, neighboring microgrids may couple together provisionally to exchange power. This is helpful for the remote area microgrids when one of these experiences excessive loading or renewable-based generation or during faults in a section of one microgrid (MG) while no utility feeders exist. Such microgrids may also couple temporarily to lessen the overall electricity generation cost or to improve the overall reliability. To facilitate this connection, the neighboring microgrids should have an interlinking line. This paper analyzes the impact of such an interlinking line on the overall stability of those microgrids, and proposes a suitable interconnection, which can improve the stability of the system of coupled microgrids. To this end, first, a small signal stability model of the system is developed. Numerical analyses, realized in MATLAB, are performed for the interconnection of a few sample microgrids, based on which the general recommendations are derived for improving the stability of such systems.