Effects of line dynamics on the stability margin to Hopf bifurcation in grid-forming inverters

Abstract

This paper studies oscillatory instability in grid-forming inverters through Hopf bifurcation analysis. An analytical expression for the parameter sensitivity of the stability margin is derived based on the normal vector to the bifurcation hypersurface. Through comprehensive analysis, we identify the most effective control parameters in counteracting the destabilizing effect due to parameter variations. In particular, the impacts of dynamic line modeling on the stability margin are investigated. It is observed that including line dynamics introduces a generally significant reduction in the stability margin across parameters. Additionally, dynamic line models introduce new bifurcations not present in the static model case. This suggests that adopting static line models may lead to overly optimistic stability assessment results.