Comparative Small-Signal Stability Analysis of Grid-Forming and Grid-Following Inverters in Low-Inertia Power Systems

Inverter-based resources (IBRs) are gradually replacing conventional fossil energy in modern power systems, which could make the systems susceptible as a result of insufficient inertia, especially when moving towards a 100% inverter-based power grid. Grid-following (GFL) control is a common grid-interactive inverter control algorithm, while grid-forming (GFM) control as an emerging inverter control function has drawn increasing awareness nowadays. Further, the corresponding stability issues along with a comparative study on low-inertia power systems should still be investigated. This paper focuses on small-signal stability and conducts a comprehensive analysis of GFM and GFL controls, with emphasis on the interactions between synchronous generators (SGs) and IBRs. The detailed modelings of GFM and GFL inverters as well as SGs are established. The coupling mechanism of IBRs and SGs is then conducted through participation factor analysis. Finally, the impacts of critical parameters on system stability are identified. The theoretical analyses are validated through time-domain simulations in MATLAB/Simulink.