Impact and mitigation of current saturation algorithms in grid-forming inverters on power swing detection
Author(s)
Niu, Yanshu
Yang, Zhe
Pal, Bikash C
Type
Journal Article
Abstract
Conventional power swing detection schemes generally rely on the assumption that the apparent impedance trajectory observed by a distance relay varies slowly and continuously during a power swing. However, this assumption may no longer hold when a grid-forming (GFM) inverter-based resource (IBR) enters current saturation. This paper theoretically derives the conditions for entering and exiting current saturation under circular, d-axis priority, and q-axis priority current saturation algorithms (CSAs), and analyses the corresponding full-cycle apparent impedance trajectories. The analysis reveals that the CSAs fundamentally reshape the impedance trajectories observed by protective relays, leading to behaviours that are qualitatively different from those of synchronous generator (SG)-based systems. Moreover, it is demonstrated that the conventional power swing detection scheme may lose functionality due to the rapid movement of the trajectory. To mitigate this issue, a current vector angle holding strategy is proposed to maintain the continuity of the apparent impedance trajectory during the transition into current saturation. The theoretical findings and the effectiveness of the proposed strategy are validated through MATLAB/Simulink simulations using a simplified grid-connected GFM IBR system and a modified IEEE 9-bus system.
Date Issued
2026-09-01
Date Acceptance
2026-09-01
Citation
IEEE Transactions on Power Delivery, 2026
ISSN
0885-8977
Publisher
Institute of Electrical and Electronics Engineers (IEEE)
Journal / Book Title
IEEE Transactions on Power Delivery
Copyright Statement
Copyright © 2026 IEEE. This is the author’s accepted manuscript made available under a CC-BY licence in accordance with Imperial’s Research Publications Open Access policy (www.imperial.ac.uk/oa-policy)
License URL
Publication Status
Published online
Date Publish Online
2026-09-01