NONLINEAR DYNAMIC ANALYSIS OF TRANSFORMER SATURATION INDUCED BY SUBSYNCHRONOUS RESONANCE
DOI:
https://doi.org/10.59277/RRST-EE.2026.2.12Keywords:
Subsynchronous Resonance (SSR), Transformer saturation, Series compensation, Flux dynamics, Magnetizing current, Post-fault transientsAbstract
This paper presents a novel investigation into the influence of post-fault subsynchronous resonance (SSR) on transformer flux dynamics and saturation behavior. A theoretical framework is established to examine resonance conditions in fixed-series-compensated transmission lines using frequency-domain impedance analysis, identifying electrical resonance points that can induce subsynchronous excitation. A nonlinear flux-voltage integral model is developed and implemented in MATLAB/Simulink to simulate transformer response under fault-clearing scenarios. Results reveal that the SSR-induced voltage recovery—particularly at 10 Hz—can drive the core flux well beyond the saturation knee, reaching up to 1.89 pu. The corresponding magnetizing current exhibits 20 Hz modulation, generating intermodulation sidebands at 40 Hz, 80 Hz, 110 Hz, and 130 Hz. Comparative analysis shows that series compensation significantly amplifies flux excursions and spectral distortion, confirming the role of transformer saturation as a nonlinear resonance amplifier. These findings underscore the importance of incorporating nonlinear transformer modeling into SSR studies for accurate assessment and mitigation in modern compensated power systems.
References
(1) M. Gavrilas, R. Toma, Flexible alternating current transmission system optimization in the context of large disturbance voltage stability, Rev. Roum. Sci. Techn. – Électrotechn. et Énerg., 66, 1, pp. 21–26 (2021).
(2) A.H.A.N. Nawas, S. Sundaramoorthy, Giant trevally optimized congestion management using FACTS controller allocation in deregulated electricity markets, Rev. Roum. Sci. Techn. – Électrotechn. et Énerg., 69, 4, pp. 377–382 (2024).
(3) S. Arockiaraj, B.V. Manikandan, A. Bhuvanesh, Fuzzy logic controlled STATCOM with a series compensated transmission line analysis, Rev. Roum. Sci. Techn. – Électrotechn. et Énerg., 68, 3, pp. 307–312 (2023).
(4) N. Verma, N. Kumar, S. Gupta, H. Malik, F. Pedro, G. Márquez, Review of sub-synchronous interaction in wind integrated power systems: classification, challenges, and mitigation techniques, Prot. Control Mod. Power Syst., 8, 2, pp. 1–26 (2023).
(5) S. Rezaei, Behavior of protective relays during subsynchronous resonance in transmission line and adaptation of generator out-of-step protection, IEEE Transactions on Industry Applications, 55, 6, pp. 5687–5698 (2019).
(6) E. Hajipour, M. Vakilian, M. Sanaye-Pasand, Current-transformer saturation prevention using a controlled voltage-source compensator, IEEE Trans. Power Deliv., 32, 2, pp. 1039–1048 (2016).
(7) H. Wang, Y. Wang, X. Xiao, Z. Ma, Q. Xu, Harmonic state space based stability analysis of LCC-HVDC system with saturated transformer, IEEE Trans. Power Deliv., pp. 1–10 (2025).
(8) H. Weng, S. Wang, L. Xiangning, L. Chen, Jingshui Huang, Zhange Li, Waveform similarity-based transformer phase differential protection against current transformer saturation, Autom. Electr. Power Syst., 43, 4, pp. 132–138 (2019).
(9) J. Berge, R.K. Varma, Determination of the spectrum of frequencies generated by a saturated transformer, 2011 24th Canadian Conference on Electrical and Computer Engineering (CCECE), Canada, pp. 1272–1277 (2011).
(10) A. Dash, M.K.K. Mohanta, D. De, P. Abhishek, A. Castellazzi, Modeling and mitigation of transformer saturation in dual-active-bridge converter, 2021 IEEE 12th Energy Conversion Congress & Exposition-Asia (ECCE-Asia), Singapore, pp. 408–413 (2021).
(11) S.-F. Chou, X. Wang, F. Blaabjerg, Subsynchronous resonance analysis in multi-bus multi-VSC power system based on two-port network modeling method, 2020 IEEE Energy Conversion Congress and Exposition (ECCE), USA, pp. 5696–5702 (2020).
(12) K.R. Padiyar, Analysis of subsynchronous resonance in power systems, Springer US, pp. 1–300 (1999).
(13) N. Verma, N. Kumar, DFIG-based wind plant coupled series compensated transmission line: modeling and SSR stability analysis, J. Inst. Eng. Ser. B, 103, 6, pp. 1917–1926 (2022).
(14) C.-M. Gheorghe, I.-A. Macinic, A.-G. Gheorghe, Oblong core cross-section impact on power transformer characteristics, Rev. Roum. Sci. Techn. – Électrotechn. et Énerg., 67, 3, pp. 281–286 (2022).
(15) S. Abdulsalam, X. Wilsun, W.L.A. Neves, L. Xian, Estimation of transformer saturation characteristics from inrush current waveforms, IEEE Power Eng. Soc. Gen. Meet. PES, 21, 1, pp. 170–177 (2006).
(16) M. Dolinar, D. Dolinar, Š. Gorazd, B. Polajžer, J. Ritonja, A three-phase core-type transformer iron core model with included magnetic cross saturation, IEEE Trans. Magn., 42, 10, pp. 2849–2851 (2006).
(17) I. Daut, S. Hasan, S. Taib, Magnetizing current, harmonic content and power factor as the indicators of transformer core saturation, J. Clean Energy Technol., 1, 4, pp. 304–307 (2013).
(18) M. Fritsch, M. Wolter, Saturation of high-frequency current transformers: challenges and solutions, IEEE Trans. Instrum. Meas., 72, pp. 1–10 (2023).
(19) R. Elumalai, R. Varadhan, Intelligent controller-based dynamic voltage restorer to reduce the voltage fluctuations, Rev. Roum. Sci. Techn. – Électrotechn. et Énerg., 71, 1, pp. 21–26 (2026).
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