Improved VSG Adaptive VDG Control Strategy for Multi-terminal Flexible Interconnected Distribution Systems

Introduction: To tackle the aforementioned challenges, this study aims to propose a novel control strategy for multi-terminal flexible interconnected distribution systems based on VSG- AVDG (Virtual synchronous generator-Adaptive Virtual DC Generator). Methods: This study establishes a virtual motor control framework featuring a fusion mechanism linking AC power and DC voltage deviations. A coordinated VSG-AVDG strategy is developed: on the AC side, enhanced Virtual Synchronous Generator (VSG) control utilizes DC-link voltage compensation to mitigate mode-shift impacts and ensure load balance. On the DC side, an adaptive Virtual DC Generator (VDG) strategy for flexible interconnected systems is proposed. By constructing a small-signal model of the buck/boost energy storage segment, the study analyzes how damping and inertia affect stability. Finally, parameter adaptive equations are formulated to dynamically integrate optimal damping and inertia, enhancing overall system robustness. Results: The simulation results verified the efficacy and accuracy of the proposed control strategy. Specifically, the strategy enhanced the stability of the DC bus voltage and accelerated the system's dynamic responsiveness. Discussion: With the increasing integration of large-scale renewable energy into distribution networks, traditional power generation methods are experiencing a growing shortage of inertia and damping. This poses escalating challenges for conventional flexible interconnection converter controls in addressing the impacts of load fluctuations, unpredictable renewable energy output, and system multi-mode operations on the power grid. Conclusion: The proposed VSG-AVDG-based control strategy demonstrates significant potential to improve the robustness and efficiency of modern power distribution networks.