Resynchronization of inverter-based microgrids relying on multiple grid-forming converters

The widespread utilization of distributed generation highlights the appeal and feasibility of microgrids (MG). Decentralizing the electrical grid into smaller, self-sufficient segments, that facilitate localized generation and consumption, enhances system resilience and operational continuity during disruptions. These MGs with high share of inverter-based generation rely heavily on grid-forming (GFM) inverters to provide voltage and frequency reference for the conventional grid-following (GFL) inverters. For islanded operation to be feasible, the system must have the capability for autonomous resynchronization to the main grid. GFMs are ideal assets for this, as they directly control the voltage and frequency of the local grid. In our work we seek to investigate the capabilities of GFM inverters to successfully resynchronize the local grid considering (1) line impedances between inverters and the point of common coupling of the MG, (2) the share of GFM power relative to the overa ll power capacity of the MG and (3) the operating points of each individual GFM inverter. The topic was investigated both in MATLAB/Simulink simulation and in laboratory environment through Power Hardware-in-the-loop (PHIL) simulations. The laboratory setup contained multiple physical assets as well as an extensive low voltage distribution system with multiple consumers and prosumers implemented on a real-time simulator. We present a thorough investigation of multiple GFM inverters’ ability to cooperate in reconnecting a local grid based on multiple aspects.