Energy storage-enabled fractional-order virtual synchronous generator for DC-link voltage regulation in DC microgrid under load and renewable disturbances

This paper presents an advanced control strategy for energy storage-integrated DC microgrids to improve DC-link voltage stability and transient performance under operating uncertainties. The proposed approach emulates virtual synchronous generator (VSG) behavior through coordinated primary and secondary control layers, where virtual inertia and damping are introduced to enhance dynamic response. To improve robustness against load changes and renewable-generation fluctuations, a fractional-order control law is designed to regulate the rate of change of the DC-link voltage (RoCoV), offering additional tuning flexibility compared with conventional integer-order VSG schemes. Controller parameters are optimally selected using a metaheuristic optimization method to further enhance regulation quality and efficiency. Extensive simulations benchmark the proposed fractional-order VSG against representative integer-order, derivative-based VSG controllers. The results demonstrate improved DC-link voltage regulation during load variations and renewable power disturbances, with the proposed method achieving up to 80% reduction in DC-link voltage overshoot in some test scenarios compared with the baseline controller.