Modeling and Small-Signal Stability Analysis for Time-Delayed AC Multi-Microgrid Systems in Islanded Mode

This paper develops modeling approaches and time delay margin analysis for the time-delayed multi-microgrid (MMG) system. Firstly, a distributed two-layer control framework for MMG is introduced, which is comprised of MMG layer and MG layer. On this basis, a systematic modeling process for MMG is developed considering the distributed secondary control signals delay. The MMG and MG layers are developed separately, and modeling approaches for sub-modules including distributed generators (DG), network, loads, and controllers are presented. Besides, a time delay margin determination method based on the Chebyshev discretization scheme is proposed. The time delay margin of the developed MMG small-signal model is calculated by the proposed method. Finally, the effectiveness of the developed MMG small-signal model and the accuracy of the proposed time delay margin determination method are validated in both frequency domain and time domain.