State-of-Grid-Based SoC Balancing and AC Coupling Control for DC Microgrids

The shift towards renewable energy has increased interest in dc microgrids as a promising integration solution. However, managing power-sharing, state-of-charge (SoC) balancing, and reliable ac coupling without communication remains challenging, necessitating advanced control methods. This article introduces a novel state-of-grid-based control for dc microgrids, enabling communication-free power-sharing and SoC balancing across battery systems, even with significant line resistances, while supporting synergistic ac coupling. Each battery locally projects its SoC into a small voltage offset around the nominal dc bus level; the resulting bus voltage therefore mirrors the average SoC of the entire microgrid. By using an analogous mapping for ac frequency, a single voltage–frequency metric unifies dc and ac domains. A small-signal Lyapunov analysis proves local exponential stability under realistic parameter spreads. The controller is implemented on a laboratory microgrid comprising two battery emulators, photovoltaic generation, programmable loads, and a Silicon Carbide interlink converter. Hardware results in islanded and grid-connected modes confirm voltage regulation, SoC equalization, and seamless power exchange.