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Anpassning av småskaliga vattenkraftverk för ö-drift av lokalt elnät
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2019 (Swedish)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesisAlternative title
Adapting small hydropower plants for frequency control of power grids in island mode (English)
Abstract [en]

This master thesis examines technical requirements for small hydro power plants (HPP) to operate proximate parts of the power grid in island mode. The work examines how small hydropower can be modified and complemented with additional technologies to achieve sufficient frequency control capabilities. A case study was performed within the concession area of power grid operator Ålem Energy. One of the HPPs, located in Skälleryd, is owned by Ålem Energy and became the focal point of the study. Relevant parts of the concession area were surveyed for properties such as system inertia, electric load and available power. Furthermore, a model of Kaplan turbine 1 in Skälleryd HPP was created with the purpose of studying the benefits of bypassing regulation control from the wicket gates directly to the runner. The method was tested in an off-grid islanding test. Frequency control of the turbine was tested powering electric heaters and, using a new method, controlling a virtual power grid. Finally, a theory was developed to estimate the transient disturbance resilience (TDR) of a power grid. The theory was applied to the HPP in Skälleryd to suggest modifications for the plant to achieve sufficient islanding capabilities.

The survey of the power system revealed a promising potential for the HPPs to operate in island mode, especially at later stages when the grid spans several HPPs for more system inertia. The available power from the HPPs was however strongly seasonal which imposes flexibility on a future plan of action for engaging the grid in island mode. The method of controlling the turbine power from the runner proved to have several difficulties. Firstly, the current hydraulics system was not able to freely control the runner as the hydrodynamic forces on the runner blades were too large. Secondly, the method was found to be unstable due to inherent amplification of speed deviations. Furthermore, the low inertia at Skälleryd is likely detrimental to the lone frequency control of the turbine. Therefore other methods for improving frequency control were suggested.

The developed theory for TDR was used to create charts describing the TDR for various combinations of system inertia and regulation speed. By studying the proprieties of Skälleryd HPP in the charts the necessary modifications could be rationally chosen. A frequency regulating dummy load was found to be the simplest option. A control scheme was suggested with the dummy load performing primary frequency control and the turbines at Skälleryd performing secondary control, restoring the dummy load to its nominal state.

Place, publisher, year, edition, pages
2019. , p. 59
Series
UPTEC ES, ISSN 1650-8300 ; 19018
Keywords [en]
small hydropower, hydropower, Kaplan, turbine, transient, disturbance, resilliance, power grid, island, islanding, adapting, island mode, frequency control, dummy load
Keywords [sv]
Kaplan, Kaplanturbin, elnät, ö-nät, ö-drift, vattenkraft, småskaliga vattenkraftverk, transient störningstålighet, indexprov, kombineringsprov, lokalt elnät
National Category
Energy Systems Energy Engineering
Identifiers
URN: urn:nbn:se:uu:diva-388143OAI: oai:DiVA.org:uu-388143DiVA, id: diva2:1331952
External cooperation
Sweco Energy
Educational program
Master Programme in Energy Systems Engineering
Supervisors
Examiners
Available from: 2019-06-28 Created: 2019-06-27 Last updated: 2019-06-28Bibliographically approved

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CiteExportLink to record
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