Impedance Coupling Suppression Control Method for Offshore Wind Farms Integrated With MMC-HVDC System

With the expansion of offshore wind farms (WFs), the impedance of WFs exhibits increased negative damping and stronger impedance coupling with the modular multilevel converter (MMC). These effects result in sharper resonance peaks in the impedance of WFs, exacerbating oscillation problems. Existing oscillation suppression methods to improve the damping of individual converters are limited in effectiveness for systems with deep interaction. To address this issue, this article reveals that the negative-sequence impedance of the MMC is a crucial factor in its interaction with WFs. Based on this insight, a control method is proposed to suppress impedance coupling by blocking interaction paths. This method enables more targeted and effective improvements in system stability, especially within strong interaction frequency bands. The effectiveness of the proposed control method is validated through comprehensive simulations and experiments.