The occurrence mechanism and damping method of ultra-low-frequency oscillations

Peng Wang, Baohong Li*, Qin Jiang, Gang Chen, Xiaoyan Han, Tomislav Dragicevic, Tianqi Liu

*Corresponding author for this work

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The ultra-low-frequency oscillation (ULFO) problem has reappeared in China recently. Although the hydraulic generator is supposed to have a strong connection to this problem, the conditions for ULFO appearance and detailed reasons are not clear yet. In order to clarify the occurrence mechanism of ULFO, this paper studies each important part of hydraulic generator system, including the governor, exciter and power system stabiliser (PSS). The weak connection is confirmed to have an important impact on the occurrence of the ULFO. Nevertheless, by studying each device's contribution to ULFO through the complex torque coefficient method, it is shown that the negative damping effect of the hydraulic governor will cause the instability in the ultra-low-frequency band, while the exciter and the PSS have little influence on ULFO. Additionally, the proportional–integral parameters of the hydraulic governor system are also studied to clarify their influence on ULFO based on the complex torque coefficient method. Based on the above analysis, two damping methods for ULFO suppression are finally proposed. To verify theory and damping methods, the simulations are implemented in PSCAD and PSASP software.

Original languageEnglish
JournalIET Renewable Power Generation
Issue number5
Pages (from-to)1100-1115
Publication statusPublished - 6 Apr 2021

Bibliographical note

Funding Information:
This work was supported by the Science and Technology Project of State Grid Corporation of China under Grant 521999180003.

Publisher Copyright:
© 2021 The Authors. IET Renewable Power Generation published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology

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