Abstract
Subsynchronous oscillation (SSO) is classified as subsynchronous resonance, torsional interaction, or control interaction, depending on which devices or controllers are involved. Researchers have conducted numerous studies and developed methodologies on how to analyze SSO cases in different types of power systems. For these diverse mechanisms, complicated systems, and analytical methods, the overall summary and categorization of the SSO phenomena have been crucial, and numerous reviews have been published to this end. However, with the emerging inverter-based and power-electronics-based devices, in addition to the high computational capability, more advanced analytical methods have recently been researched, and more general, up-to-date literature surveys are thus needed. This study reviews the various SSO types depending on the interaction mechanisms, before investigating a number of representative SSO events in terms of the devices. Following this, the study evaluates the existing cutting-edge methods for SSO analysis and compares them to ascertain the appropriate method for specific SSO types. The review provides distinct practical considerations for the analysis to simplify the entire procedure. Ultimately, this paper presents a summary of modern SSO-damping and mitigation methods for pragmatic insight and future perspectives for a reader when dealing with old and the latest power systems.
Highlights
P OWER system planners and operators must address the small-signal instability caused by subsynchronous oscillation (SSO)
SSO indicates an oscillation with a frequency of 5 to 55 Hz, when the fundamental frequency is 60 Hz, and is differentiated by low frequency oscillation, which occurs at around 0.5 Hz to 3 Hz [1]
Depending on where the resonances occur, the conventional power system SSO can be categorized into various types, including subsynchronous resonance (SSR), subsynchronous torsional interaction (SSTI), and subsynchronous control interaction (SSCI) [4]
Summary
The electrical resonance at 30.5 Hz excited a torsional mode at the 30.1 Hz frequency [3] Following these incidents, SSR analysis for the Navajo Project was jointly conducted by the Arizona Generating Plant, the Arizona Public Service Company, the Los Angeles Department of Water and Power, and the Nevada Power. The main cause for the oscillation was found to be the interaction between a type-3 wind farm and the series-compensated capacitors installed to increase the load-carrying capacity of the transmission line [21], [41]–[44]. C. HVDCS Five months after starting the commercial operation at Square Butte in North Dakota, SSO field tests were conducted, revealing that the HVDC converter controls (i.e., the rectifier current control loop and the frequency-sensitive power control) excited the 11.5-Hz torsional modes of the turbine generator [48]. A more precise linearized circuit with notch filters effectively eliminated these torsional oscillations, successfully allowing the unit to operate at full-load capacity
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