Analysis of self‑excited oscillations in standalone grid‑forming energy storage systems induced by transformer saturation characteristics

Xiaojing Li; Ze Ying; Zhishang An

Analysis of self‑excited oscillations in standalone grid‑forming energy storage systems induced by transformer saturation characteristics

Xiaojing Li

Ze Ying

Zhishang An

Vol. 25, No. 12, pp. 2262-2273, Dec. 2025

10.1007/s43236-025-01047-9

Describing function method

Grid-forming energy storage

Self-excited oscillation

Transformer saturation characteristics

Abstract

With the increasing global emphasis on energy independence and the integration of renewable energy sources, ensuring the stability of grid-forming energy storage systems in standalone networks has become a critical challenge. This study investigates self-excited oscillations observed in standalone grid-forming energy storage systems, triggered by the saturation characteristics of transformers during operation. A single-machine equivalent model of the standalone system is developed, and it is shown that traditional linearized methods, such as small-signal analysis and impedance-based analysis, fail to accurately capture the oscillation mechanisms under these nonlinear conditions. To address this, the describing function method is applied to analyze the underlying oscillation mechanisms. The root cause of the oscillations is further validated through hardware-in-the-loop experiments, demonstrating the accuracy of the proposed analysis approach. Moreover, effective suppression strategies are developed and validated, providing a practical solution to enhance system stability.

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Cite this article

[IEEE Style]

X. Li, Z. Ying, Z. An, "Analysis of self‑excited oscillations in standalone grid‑forming energy storage systems induced by transformer saturation characteristics," Journal of Power Electronics, vol. 25, no. 12, pp. 2262-2273, 2025. DOI: 10.1007/s43236-025-01047-9.

[ACM Style]

Xiaojing Li, Ze Ying, and Zhishang An. 2025. Analysis of self‑excited oscillations in standalone grid‑forming energy storage systems induced by transformer saturation characteristics. Journal of Power Electronics, 25, 12, (2025), 2262-2273. DOI: 10.1007/s43236-025-01047-9.