Eigenanalysis-based small signal stability of the system of coupled sustainable microgrids

Until now, microgrids were assumed to operate either in grid-connected or islanded modes. As a third alternative, neighboring microgrids may interconnect to support each other during faults in a section of one MG, or in the course of overloading. They may also interconnect to reduce the cost of electricity generation in their systems. Thereby, a microgrid will experience a significant transformation in its structure, when coupled with one or more neighboring microgrids. Before the formation of the system of coupled microgrids, the stability of the new system is vital to be cautiously examined to intercept the transformation, if instability is to occur. An eigenanalysis-based small signal stability evaluation technique is developed in this paper which can be used to allow/deny the interconnection of the microgrids. The analysis also defines the suitable range of control parameters for the energy resources of the CMG to guarantee the stability of the new system, if it was determined unstable. Numerical analyses, realized in MATLAB, are performed for the interconnection of a few sample microgrids. The accuracy of the developed technique is validated by comparing its results with the time-domain performance of the similar system, realized in PSCAD/EMTDC.