Grid strength and converter power jointly set small-signal stability of GFL and GFM VSCs coupled to real generators.

Summary. The manuscript examines small-signal interactions between grid-following (GFL) and grid-forming (GFM) voltage-source converters (VSCs) and synchronous generators (SGs) in a multi-machine setting intended to capture real-grid dynamics rather than an ideal infinite bus. Using eigenvalue trajectories and participation factors, it compares GFL and GFM converters across grid-strength scenarios obtained by sweeping VSC rating power and short-circuit ratio (SCR). Linear and nonlinear time-domain simulations are then used to corroborate the modal findings. The abstract concludes that stability of VSC-dominated grids in either mode is strongly affected by both grid strength and VSC power through coupling between converter controls and SGs, and that ideal-grid assumptions are therefore limited for such studies.

Significance. If the multi-machine linearization, participation results, and linear/nonlinear agreement hold as claimed, the work would supply a concrete, simulation-backed demonstration that converter–SG coupling modes—not only converter–grid impedance interactions—govern stability margins under realistic SCR and power levels. That would be a useful, non-controversial contribution for planning and control design of hybrid SG–VSC systems, reinforcing the already recognized inadequacy of pure infinite-bus models. The methods named (eigenvalue trajectories, participation factors, dual time-domain validation) are standard and, if executed carefully, would make the claim falsifiable and reusable.