Autonomous and Distributed Synchronization and Restoration of an Islanded Network of Microgrids

The transition towards clean energy and the introduction of Inverter-Based Resources (IBRs) are leading to the formation of Microgrids (MGs) and Networks of MGs (NMGs). MGs and NMGs can operate autonomously in islanded mode, which requires Grid-Forming (GFM) IBRs that can perform black start, synchronization, restoration and regulation. However, such IBRs can face synchronization instability issues, which might be worsened by inadequate secondary level frequency and voltage regulation. Accordingly, we propose an autonomous and distributed synchronization and restoration scheme using Distributed-Averaging Proportional-Integral (DAPI) control. To validate the proposed method, we model and simulate a high-fidelity islanded and modified IEEE 123 bus system, modeled as an NMG consisting of 7 MGs. The MATLAB/Simulink simulation results demonstrate an effective autonomous soft-start, synchronization, connection and regulation procedure using DAPI control and distributed breaker operation logic.