Technical Considerations for Startup of Off-Grid Microgrids with Renewable Distributed Energy Resources

Starting up an isolated microgrid can be a complex and challenging task, particularly depending on the mix of Distributed Energy Resources (DERs) utilized in the system. In most off-grid microgrids, a grid-forming resource either a synchronous generator or an inverter-based resource serves as the anchor, providing voltage and frequency references for other DERs. Unlike electric utility sources, grid-forming DERs have limited capacity to manage load variations and faults. Therefore, analyzing load behavior and developing a load and source sequencing strategy is critical for achieving a successful black start and steady-state operation of the microgrid. This paper emphasizes the importance of maintaining adequate source capacity and establishing a source/load sequence to allow the combination of resources to serve the load without causing overloading, undervoltage, or other stability issues. This paper presents a comprehensive startup procedure for an off-grid microgrid system that includes a diesel generator, photovoltaic (PV) systems, and battery energy storage systems (BESS). Furthermore, it establishes a procedure for optimal anchor resource sizing to ensure system stability.