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<p>The increasing penetration of renewable energy sources has accentuated the significance of dynamic variation in power grid strength, commonly characterized by the short circuit ratio (SCR). The stability of grid-following converters (GFLCs) is often compromised under conditions of low SCR, whereas grid-forming converters (GFMCs) may experience instability when operating within strong grid environments. In this paper, frequency-decoupled single–input–single–output models are proposed for both GFMCs and GFLCs. Specifically, a sequence impedance (SI) model for GFMCs with a power synchronization loop is developed, and a sequence admittance (SA) model for GFLCs with a phase-locked loop is formulated. The Nyquist criterion is applied for interaction stability analysis, elucidating the causal mechanisms responsible for GFMC instability in strong grids and GFLC instability in weak grids. Based on insights obtained from the SI model, a virtual impedance control strategy grounded in the argument principle is devised to ensure stable operation of GFMCs across a wide range of SCRs. The validity and effectiveness of the proposed models and control strategy are extensively demonstrated through numerical simulations and hardware-in-the-loop experiments. Results verify the accuracy of the models and substantiate the robustness of the control approach in maintaining converter stability under diverse grid conditions.</p>

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Dynamic interaction analysis of grid-forming and grid-following converters in strong and weak grids using frequency-decoupled modeling

  • 期刊论文

  • 发表日期：

    2026年8月5日

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  • Jiajun Guo,
  • Libao Shi,
  • Zijian Guo

摘要

The increasing penetration of renewable energy sources has accentuated the significance of dynamic variation in power grid strength, commonly characterized by the short circuit ratio (SCR). The stability of grid-following converters (GFLCs) is often compromised under conditions of low SCR, whereas grid-forming converters (GFMCs) may experience instability when operating within strong grid environments. In this paper, frequency-decoupled single–input–single–output models are proposed for both GFMCs and GFLCs. Specifically, a sequence impedance (SI) model for GFMCs with a power synchronization loop is developed, and a sequence admittance (SA) model for GFLCs with a phase-locked loop is formulated. The Nyquist criterion is applied for interaction stability analysis, elucidating the causal mechanisms responsible for GFMC instability in strong grids and GFLC instability in weak grids. Based on insights obtained from the SI model, a virtual impedance control strategy grounded in the argument principle is devised to ensure stable operation of GFMCs across a wide range of SCRs. The validity and effectiveness of the proposed models and control strategy are extensively demonstrated through numerical simulations and hardware-in-the-loop experiments. Results verify the accuracy of the models and substantiate the robustness of the control approach in maintaining converter stability under diverse grid conditions.