Revisiting Grid-Forming and Grid-Following Converter Stability via Subsystem Interaction

Paper in proceeding, 2026

The small-signal stability of grid-connected converters has gained increasing attention with the growing penetration of power-electronic interfaces in renewable-dominated power systems. Grid-forming (GFM) and grid-following (GFL) controls are widely adopted, making it important to understand their stability characteristics and the influence of grid strength on converter-grid interactions. The short-circuit ratio (SCR) is commonly used to quantify grid strength, and comparisons between GFM and GFL converters are conducted under different SCR conditions. However, SCR characterizes grid strength only at the fundamental frequency and does not capture frequency-dependent interaction phenomena. To complement SCR-based comparisons, this paper revisits the stability properties of GFM and GFL converters under identical SCR conditions while varying the grid characteristics. The investigation is conducted based on representative generic GFM and GFL control structures adopted in the literature. From a subsystem interaction perspective, a characterization method based on resonance-driven small-signal instability is applied to interpret interaction-related differences. The analysis reveals distinct instability risk scenarios for representative GFM and GFL converter structures considered in this study under the same SCR, providing physical insight into the interaction mechanisms of the considered representative control structures and guidance for converter control tuning to enhance system stability.