Research on frequency coupling factors and stability influencing factors of grid-forming inverters

This paper proposes a matrix-based impedance visualization method that treats control matrices as circuit element matrices, ultimately deriving a unified impedance model incorporating power loops, power decoupling loops, virtual impedance, voltage loops, and current loops. Using this impedance model, the frequency coupling factors of grid-forming inverters (GFMI) are analyzed. The results demonstrate that the reactive power loop and power decoupling loop significantly influence frequency coupling. Furthermore, stability-influencing factors are examined through this model, revealing that reducing power loop gain, increasing power loop bandwidth, adding virtual inductance, and enhancing voltage loop gain contribute to improving the stability of GFMI, whereas virtual resistance degrades GFMI stability. Finally, experimental results validate the accuracy of the model and the correctness of the analysis.