Assessment of Power System Stability Considering Multiple Time-Scale Dynamics: Insights into Hopf Bifurcations in Presence of GFL and GFM IBRs

TL;DR

This paper highlights the importance of analyzing power system stability across multiple time scales simultaneously, revealing potential instabilities missed by traditional single-scale models, especially in systems with inverter-based resources.

Contribution

It introduces a multi-time-scale stability assessment method using Hopf bifurcations and demonstrates how GFL and GFM inverters can complement each other from this perspective.

Findings

Multi-time-scale analysis uncovers instabilities missed by traditional methods.

Hopf bifurcation analysis reveals critical stability thresholds.

GFL and GFM inverters can complement each other for enhanced stability.

Abstract

Real power systems exhibit dynamics that evolve across a wide range of time scales, from very fast to very slow phenomena. Historically, incorporating these wide-ranging dynamics into a single model has been impractical. As a result, power engineers rely on time-scale decomposition to simplify models. When fast phenomena are evaluated, slow dynamics are neglected (assumed stable), and vice versa. This paper challenges this paradigm by showing the importance of assessing power system stability while considering multiple time scales simultaneously. Using the concept of Hopf bifurcations, it exemplifies instability issues that would be missed if multi-time-scale dynamics are not considered. Although this work employs both grid-following and grid-forming inverter-based resource models, it is not a direct comparison. Instead, it presents a case study demonstrating how one technology can complement the other from a multi time-scale dynamics perspective.