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

• The manuscript has been substantially revised to address the reviewers’ comments and improve clarity and completeness. The abstract has been expanded to clearly state the motivation, methodology, and main findings, including the reported improvements in damping ratio, phase margin, RoCoF, black start capability, fault recovery, and fuel savings. The introduction has been strengthened by adding a systematic comparison with existing DC bus strategies, clarifying the novelty of the proposed method compared with voltage-centric and inertia-emulation approaches, and citing the suggested recent literature. The differences between the proposed controller and previously reported methods such as hybrid energy storage or dual-side virtual inertia control are explicitly highlighted, with emphasis on its direct, fast-acting use of DC voltage deviations for power reference generation. • Details of the hardware-in-the-loop setup have been expanded to describe the load profile, DC source modeling, solver accuracy, measurement setup, and control implementation. It is now clearly explained that a constant DC source was used to validate the controller in isolation from renewable intermittency, with future work planned to investigate PV fluctuations. Additional discussion has been added regarding scalability beyond eight inverters, potential synchronization and circulating current issues, and proposed mitigation strategies. A new section also addresses cyber-physical considerations, including the impact of communication delays, packet loss, and mitigation through decentralized control and consensus algorithms. Furthermore, the real-world context is strengthened by aligning the experimental setup with the specifications of a practical island microgrid in Japan. • The results section now provides more detailed performance comparisons, showing superior black start, fault ride-through, and fuel efficiency outcomes relative to DG and VSG-based systems. Finally, the conclusion has been updated to include future directions such as adaptive AI-based parameter tuning, extension to hybrid AC/DC microgrids, and advanced coordination of distributed energy resources. 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.