Harmonic interactions in HVAC-connected offshore windfarms

The connection of new Offshore Wind Power Plants (OWPP) in the existing Dutch transmission system gives rise to many technical challenges. For example, it is expected that harmonic issues will occur more frequently when the number of large offshore wind farms increases. Cases have already been repor...

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Autor: Depla, Lara
Formato: tesis de maestría
Fecha de publicación:2019
País:España
Recursos:Universitat Politècnica de Catalunya (UPC)
Repositorio:UPCommons. Portal del coneixement obert de la UPC
Idioma:inglés
OAI Identifier:oai:upcommons.upc.edu:2117/167861
Acesso em linha:https://hdl.handle.net/2117/167861
Access Level:acceso abierto
Palavra-chave:Offshore wind power plants
Electric currents, Direct
High voltages
Parcs eòlics marins
Corrents continus
Alta tensió
Àrees temàtiques de la UPC::Energies
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oai_identifier_str oai:upcommons.upc.edu:2117/167861
network_acronym_str ES
network_name_str España
repository_id_str
dc.title.none.fl_str_mv Harmonic interactions in HVAC-connected offshore windfarms
title Harmonic interactions in HVAC-connected offshore windfarms
spellingShingle Harmonic interactions in HVAC-connected offshore windfarms
Depla, Lara
Offshore wind power plants
Electric currents, Direct
High voltages
Parcs eòlics marins
Corrents continus
Alta tensió
Àrees temàtiques de la UPC::Energies
title_short Harmonic interactions in HVAC-connected offshore windfarms
title_full Harmonic interactions in HVAC-connected offshore windfarms
title_fullStr Harmonic interactions in HVAC-connected offshore windfarms
title_full_unstemmed Harmonic interactions in HVAC-connected offshore windfarms
title_sort Harmonic interactions in HVAC-connected offshore windfarms
dc.creator.none.fl_str_mv Depla, Lara
author Depla, Lara
author_facet Depla, Lara
author_role author
dc.contributor.none.fl_str_mv Prieto Araujo, Eduardo
Cremers, Roger
Velitsikakis, Konstantinos
dc.subject.none.fl_str_mv Offshore wind power plants
Electric currents, Direct
High voltages
Parcs eòlics marins
Corrents continus
Alta tensió
Àrees temàtiques de la UPC::Energies
topic Offshore wind power plants
Electric currents, Direct
High voltages
Parcs eòlics marins
Corrents continus
Alta tensió
Àrees temàtiques de la UPC::Energies
description The connection of new Offshore Wind Power Plants (OWPP) in the existing Dutch transmission system gives rise to many technical challenges. For example, it is expected that harmonic issues will occur more frequently when the number of large offshore wind farms increases. Cases have already been reported in which resonances were triggered in HVDC- or HVAC-connected OWPPs and the wind farms had to be taken out of operation. Recently developed offshore wind farms contain wind turbines which are connected to the system with a full-scale back-to-back Voltage Source Converter, which is responsible for inserting harmonics into the system. The onshore grid is also responsible for injecting harmonics. Since the wind turbine converter is an active element, where the control loops actively determine its electrical behaviour, it interacts with other converters and with the background harmonics inserted from the network. The initial harmonic emissions and the harmonic interactions can lead to an excitation of a resonance frequency. The cables, transformers, capacitor banks and filters are responsible for shifting the resonance frequencies. Especially a long HV export cable can strongly alter the resonance frequencies of the system. To analyze the impact of connecting an increasing amount of wind farms to the same Point of Connection on the harmonic emission levels, a Harmonic Impact Assessment was performed for three offshore wind farms in the Dutch North Sea. Since the wind turbine converters are active elements, its electrical behaviour can be captured with an equivalent impedance, or Norton Equivalent. This Norton Equivalent was utilized in the Harmonic Impact Assessment to include the active behaviour of the converter. When comparing this novel approach to the conventional methodology, the expected peaks in the Total Harmonic Distortion (THD) are shifted. When an increasing amount of wind farms is connected, peaks in the THD shifted to lower frequencies. Then, depending on the specific profile of the background harmonics and the impedance profiles of the grid and the OWPP, this translates into the disappearance of appearance of an exceedance of the emission limits. The effect of connecting two wind farms to the same Point of Connection instead of a single wind farm on the harmonic stability, was assessed. Frequency sweeps of the two assessed wind farms made clear that the presence of an additional filter in a wind farm leads to a small shift in the series resonance points. When multiple wind farms are connected instead of solely one wind farm, series resonance frequencies are shifted to lower frequencies and less damping appears to be present in the system. Lastly, the postive-net damping criteria was applied to assess the stability of a system in which a varying number of wind farms is connected. Time-domain simulations in PSCAD were performed to varify the results. It can be concluded that a system becomes less damped, and therefore less stable, when an increasing amount of wind farms is connected. This effect arises since the various wind farms are placed in parallel and the total resistance of the wind farms becomes smaller than the sum of the resistances of each wind farm. Moreover, when less wind turbines are in operation, less damping is present in the system since the resistance of a single OWPP is then decreased.
publishDate 2019
dc.date.none.fl_str_mv 2019
2019-07-12
2019
2019-09-03
dc.type.none.fl_str_mv master thesis
http://purl.org/coar/resource_type/c_bdcc
NA
http://purl.org/coar/version/c_be7fb7dd8ff6fe43
dc.type.openaire.fl_str_mv info:eu-repo/semantics/masterThesis
format masterThesis
dc.identifier.none.fl_str_mv https://hdl.handle.net/2117/167861
url https://hdl.handle.net/2117/167861
dc.language.none.fl_str_mv Inglés
eng
language_invalid_str_mv Inglés
language eng
dc.rights.none.fl_str_mv open access
http://purl.org/coar/access_right/c_abf2

http://creativecommons.org/licenses/by-nc-sa/3.0/es/
dc.rights.openaire.fl_str_mv info:eu-repo/semantics/openAccess
rights_invalid_str_mv open access
http://purl.org/coar/access_right/c_abf2

http://creativecommons.org/licenses/by-nc-sa/3.0/es/
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.publisher.none.fl_str_mv Universitat Politècnica de Catalunya
publisher.none.fl_str_mv Universitat Politècnica de Catalunya
dc.source.none.fl_str_mv reponame:UPCommons. Portal del coneixement obert de la UPC
instname:Universitat Politècnica de Catalunya (UPC)
instname_str Universitat Politècnica de Catalunya (UPC)
reponame_str UPCommons. Portal del coneixement obert de la UPC
collection UPCommons. Portal del coneixement obert de la UPC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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spelling Harmonic interactions in HVAC-connected offshore windfarmsDepla, LaraOffshore wind power plantsElectric currents, DirectHigh voltagesParcs eòlics marinsCorrents continusAlta tensióÀrees temàtiques de la UPC::EnergiesThe connection of new Offshore Wind Power Plants (OWPP) in the existing Dutch transmission system gives rise to many technical challenges. For example, it is expected that harmonic issues will occur more frequently when the number of large offshore wind farms increases. Cases have already been reported in which resonances were triggered in HVDC- or HVAC-connected OWPPs and the wind farms had to be taken out of operation. Recently developed offshore wind farms contain wind turbines which are connected to the system with a full-scale back-to-back Voltage Source Converter, which is responsible for inserting harmonics into the system. The onshore grid is also responsible for injecting harmonics. Since the wind turbine converter is an active element, where the control loops actively determine its electrical behaviour, it interacts with other converters and with the background harmonics inserted from the network. The initial harmonic emissions and the harmonic interactions can lead to an excitation of a resonance frequency. The cables, transformers, capacitor banks and filters are responsible for shifting the resonance frequencies. Especially a long HV export cable can strongly alter the resonance frequencies of the system. To analyze the impact of connecting an increasing amount of wind farms to the same Point of Connection on the harmonic emission levels, a Harmonic Impact Assessment was performed for three offshore wind farms in the Dutch North Sea. Since the wind turbine converters are active elements, its electrical behaviour can be captured with an equivalent impedance, or Norton Equivalent. This Norton Equivalent was utilized in the Harmonic Impact Assessment to include the active behaviour of the converter. When comparing this novel approach to the conventional methodology, the expected peaks in the Total Harmonic Distortion (THD) are shifted. When an increasing amount of wind farms is connected, peaks in the THD shifted to lower frequencies. Then, depending on the specific profile of the background harmonics and the impedance profiles of the grid and the OWPP, this translates into the disappearance of appearance of an exceedance of the emission limits. The effect of connecting two wind farms to the same Point of Connection instead of a single wind farm on the harmonic stability, was assessed. Frequency sweeps of the two assessed wind farms made clear that the presence of an additional filter in a wind farm leads to a small shift in the series resonance points. When multiple wind farms are connected instead of solely one wind farm, series resonance frequencies are shifted to lower frequencies and less damping appears to be present in the system. Lastly, the postive-net damping criteria was applied to assess the stability of a system in which a varying number of wind farms is connected. Time-domain simulations in PSCAD were performed to varify the results. It can be concluded that a system becomes less damped, and therefore less stable, when an increasing amount of wind farms is connected. This effect arises since the various wind farms are placed in parallel and the total resistance of the wind farms becomes smaller than the sum of the resistances of each wind farm. Moreover, when less wind turbines are in operation, less damping is present in the system since the resistance of a single OWPP is then decreased.Universitat Politècnica de CatalunyaPrieto Araujo, EduardoCremers, RogerVelitsikakis, Konstantinos20192019-07-1220192019-09-03master thesishttp://purl.org/coar/resource_type/c_bdccNAhttp://purl.org/coar/version/c_be7fb7dd8ff6fe43info:eu-repo/semantics/masterThesisapplication/pdfhttps://hdl.handle.net/2117/167861reponame:UPCommons. Portal del coneixement obert de la UPCinstname:Universitat Politècnica de Catalunya (UPC)Inglésengopen accesshttp://purl.org/coar/access_right/c_abf2http://creativecommons.org/licenses/by-nc-sa/3.0/es/info:eu-repo/semantics/openAccessoai:upcommons.upc.edu:2117/1678612026-05-27T15:37:01Z
score 15.301629

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