A Novel System Matrix Building Algorithm for Stability Analysis of Interconnected DC Microgrids

DC Microgrids (DCMGs) are achieving critical significance these days because of their colossal benefits as compared with the existing AC systems. However, with the high penetration of sources interfaced to the grid using various Power Electronic Converters (PECs), stability is often a crucial issue, especially during the interconnected operation of Microgrids (MGs). Hence, before the interconnection of DCMGs, the stability of the resultant system needs to be guaranteed. In this work, a novel step-by-step procedure, that does not require a complete rebuilding of the system matrix when a new DCMG is added through a distribution line to the cluster, is proposed. Furthermore, stability analysis of the individual DCMGs and the cluster is performed from a control system perspective using the eigenvalue method. From the analysis, it is seen that, even though the individual MG units operate as a stable system, the resulting clusters may not be stable. The stability issues of the cluster are resolved by tuning the controller parameters with Particle Swarm Optimization (PSO). The results reveal the importance of stability analysis and the selection of optimum controller gains for the reliable operation of DCMG clusters.