Modeling and Stability Analysis of Back-to-Back Converters in Networked Microgrids

This paper provides a small-signal model and stability analysis of interconnected AC microgrids (MGs) connected through back-to-back converters (BTBCs). The proposed modeling method of the networked microgrids (NMGs) is derived and it is generalized for any number of NMGs through BTBCs. Different BTBC control parts are analyzed to study their impact on the NMG stability. The eigenvalue analysis and participation matrix are employed to identify dynamic modes of BTBC DC voltage controller. For two NMGs, main participating state variables and corresponding parameters in the dominant low-frequency modes (LFMs) are recognized, then acceptable ranges of the parameters are calculated using the sensitivity analysis (SA). The contribution of the control BTBC parameters including PLL and DC voltage controller parameters in the small-signal stability margin are shown. In addition, to show the BTBC control impact on the NMGs stability in the time domain, simulation results are provided for the two NMGs in SimPowerSystems/Matlab environment.