Distributed layered control and stability analysis of islanded networked-microgrids

Networked-microgrid (NMG) system has a much more complex structure with larger control difficulties and complicated dynamic behaviors. This paper firstly proposes a layered distributed control framework for NMG system, which is comprised of two layers: individual MG control layer and NMG control layer. The NMG control layer generates the voltage/frequency reference for the MG control layer. Particularly, to improve the system transient frequency response, each MG layer controller is designed to provide virtual inertia to the whole system. Secondly, a small-signal model for a generalized single-bus NMG system is derived to analyze the impact of coupling among MGs and various parameters on NMG dynamic stability. It reveals that the coupling relationship among MGs will weaken the stability of the whole NMG system while the proper control parameters can facilitate the stability. Besides, the delay effect on NMG system stability is also analyzed. Lastly, the proposed control framework and analytical result are verified by time-domain simulations under various cases considering various cases of load change, different virtual inertia and communication delay.