Analysis and suppression of high-frequency oscillation in wind farm-MMC-HVDC interconnected system considering distribution characteristics of submarine cables

With the large-scale development of offshore wind power, modular multilevel converter-based high-voltage direct current (MMC-HVDC) has emerged as a pivotal grid integration solution, yet it is constrained by high-frequency oscillation issues in power-electronic-dominated systems. In most existing studies, the distributed parameter characteristics of submarine cables are overlooked during wind farm modeling, and the medium–high frequency impedance modeling of MMCs under voltage-frequency (VF) control remains incomplete, these deficiencies render traditional oscillation suppression measures ineffective: they not only fail to mitigate oscillations under VF control but also exacerbate phase margin degradation. To address this critical challenge, this paper establishes a precise frequency-domain model for wind farm-MMC interconnected systems, which systematically incorporates two core elements: the distributed parameter characteristics of submarine cables, and the coupling mechanisms between MMC control loops and system time delays. This model uncovers the core induction mechanism of high-frequency oscillations under VF control, explicitly elucidating how the interaction among submarine cable dynamics, converter control loops, and system time delays triggers impedance mismatch and subsequent system instability. On this basis, a novel oscillation suppression strategy is proposed, leveraging the collaborative optimization of multi-control-loop parameters. By reconstructing the dynamic interaction relationships among these control loops, the strategy targetedly optimizes the system’s impedance characteristics to weaken negative damping effects—the root cause of high-frequency oscillations. Comprehensive validations, including electromagnetic transient simulations under diverse operating conditions and impedance frequency-sweep tests, confirm the accuracy of the proposed model and the efficacy of the suppression strategy. The results demonstrate that the system achieves significant improvements in both stability margins and oscillation damping capabilities, with medium–high frequency oscillations effectively suppressed. This work provides solid technical support for ensuring the stable operation of offshore wind power grid-connected systems via MMC-HVDC.