Modal Analysis of Power System With High IBR Penetration Based on Impedance Models

This paper explores the modal analysis of power systems with high inverter-based resource (IBR) penetration utilizing an impedance-based modeling approach. Traditional modal analysis based on the state-space model (MASS) requires comprehensive control structures and parameters of each system element, which are challenging as the internal specifics of the increasingly integrated inverters remain largely inaccessible. Conversely, the newly proposed modal analysis based on the impedance model (MAI) leverages only the impedance port characteristics to trace back to the system elements influencing the unstable modes significantly. This study extends previous work by clarifying the similarities and differences between MASS and MAI in terms of sensitivity. A physical interpretation of MAI from the electrical distance perspective is further provided to bridge the gap between detailed theoretical modeling and practical, accessible analyses. In addition, two enhancements to improve the MAI computation accuracy are proposed. Finally, the voltage disturbance margin (VDM) is defined to quantify the influence of node voltage disturbance on IBR. Validation through numerical simulations on a modified IEEE 14-bus system underscores the efficacy of our approach. By examining the interplay between different elements and system modes in high IBR environments, this study offers insights and a foundational framework for delineating the oscillatory modes' participation and stability characteristics of power systems with substantial IBR integration.