Hierarchical Grid-Forming Control and Hybrid Energy Management for Resilient Frequency Regulation in Low-Inertia Islanded Microgrids

The rapid penetration of converter-interfaced renewable generation has reduced effective inertia in islanded microgrids, making frequency regulation increasingly sensitive to renewable intermittency, generation outages, and storage stress. This paper proposes CMSA-OVSG–EMCS, a coordinated dual-layer control architecture for islanded PV–diesel microgrids with battery–supercapacitor hybrid energy storage. Its main novelty lies in coupling an adaptive grid-forming CMSA-OVSG layer, which updates virtual inertia and damping online according to disturbance severity, with a supervisory EMCS that coordinates multi-time-scale HESS power sharing through the common DC link. In contrast to OVSG approaches that rely on offline tuning of fixed controller parameters, the proposed framework uses physics-constrained multi-scenario optimization to jointly account for frequency response, DC-link regulation, converter operating limits, and battery stress. Nonlinear simulations under load variations, renewable intermittency, PV disconnection, and diesel-generator outage show that the proposed method consistently delivers the strongest transient performance among the tested controllers. In the worst-case diesel-generator outage scenario, it reduces the maximum ROCOF by 51.5% and the battery-stress index by 27.5% relative to the strongest benchmark controller.