DC bus-controlled grid-forming inverters for enhanced stability and fuel efficiency in hybrid microgrids

Abstract

Diesel generators (DGs) have long provided inertia and stability in microgrids but face critical limitations including poor fuel efficiency, slow frequency recovery, and high carbon emissions. This paper proposes a DC Bus Controller for grid-forming inverters (GFMs) that leverages DC voltage dynamics as an active energy buffer to enhance stability and efficiency in diesel–renewable hybrid microgrids. Unlike droop or virtual synchronous generator (VSG) schemes, the controller directly translates DC voltage deviations into adaptive active power references, enabling sub-cycle response and seamless DG–GFM coordination. Comprehensive analysis and hardware-in-the-loop (HIL) validation confirm its effectiveness. Results show a 70 % increase in damping ratios, phase margin of 63°, RoCoF mitigation to –0.5 Hz/s, and black start capability within 1.3 s. The strategy also achieves fault recovery in 0.31 s and 57 % fuel savings under 100 % inverter-based operation. By integrating scalability, circulating current suppression, and fuel optimization, the proposed controller demonstrates a field-ready pathway toward diesel-free, inverter-dominant microgrids.