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Schwanz, Daphne
Publications (10 of 16) Show all publications
Schwanz, D. (2019). On Transfer Functions for Power Quality Studies in Wind Power and Solar PV Plants. (Doctoral dissertation). Luleå: Luleå University of Technology
Open this publication in new window or tab >>On Transfer Functions for Power Quality Studies in Wind Power and Solar PV Plants
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Överföringsfunktioner förElkvalitetstudier i vindkraft- och Solcellsanläggningar
Abstract [en]

As part of the decarbonisation of the energy system, wind and solar power are expected to play an important role. However, together with their growth, new challenges appear in the electric power system; this requires further research, development, and often studies before connection is possible. Two of those challenges, both impacts on the quality of power, are the subject of this dissertation: harmonic distortion and voltage unbalance.

The growing use of solar power for electricity generation, especially in distribution systems, will result in increased voltage unbalance due to single-phase photovoltaic inverters (PVIs). Regulation on power quality and potential impact on other equipment, place a limit to the number of PVIs that can be connected to the system, the so-called “hosting capacity”. To include different uncertainties in the planning stage, a stochastic method based on the transfer-impedance matrix is proposed for quantifying this hosting capacity, with respect to voltage unbalance. The method has been illustrated by applying it to two typical Swedish low-voltage networks.

Wind power plants (WPPs) consist of a collection grid and a number of wind turbines. These are known to be a harmonic source as power electronic devices are used to connect them to the power system. Earlier studies have shown that the actual emission at harmonic frequencies is low, but that the main issue is related to the spread of harmonics through the collection grid, especially the role of resonances. Regulation setting emission limits and the potential adverse impact of harmonics on equipment make that studies are needed to predict harmonic voltages and currents in and around a WPP. These studies are based on measurements performed on individual turbines under certain operating conditions. The main issue related to this determination is distinguishing the emission originating within the WPP (primary emission) from the emission originating elsewhere (secondary emission). A critical review has been performed on methods used for harmonic emission determination (i.e. distinguishing between primary and secondary emission) in WPPs. It was concluded that this determination cannot be solved without making assumptions. Transfers functions are independent of the emission from the individual turbines and can be obtained with less assumptions. These transfer functions have been used to estimate the spread of harmonics through a WPP and towards the public grid. Transfer functions were shown to be a suitable tool to quantify amplifications due to resonances and identify which harmonic orders can be an issue.

Furthermore, information on the different transfer functions allows the selection of proper mitigation methods. This application of transfer functions has been illustrated for a specific advanced mitigation method: the use of inverter control techniques to emulate a “virtual resistor”. In this way it is possible to damp resonances without increasing fundamental-frequency losses.

The ultimate aim of harmonic studies is to avoid interference between the grid and equipment connected to it, in this case between the power-electronics in the wind turbine and other equipment. However, these studies rarely address actual cases of interference, instead of this, measured or calculated harmonic voltages and/or currents are compared with limits set in regulations. These and regulations differ strongly between countries and even between individual network operators. A comparative study of regulatory methods has been performed presenting their advantages and disadvantages from the viewpoint of the network operator and from the viewpoint of the owner or operator of the WPP.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-71826 (URN)978-91-7790-278-2 (ISBN)978-91-7790-279-9 (ISBN)
Public defence
2019-02-15, A193, Hörsal A, Skellefteå, 10:00 (English)
Opponent
Supervisors
Available from: 2018-11-30 Created: 2018-11-29 Last updated: 2019-03-04Bibliographically approved
Schwanz, D., Bollen, M. & Larsson, A. (2019). Secondary Harmonic Emission in Wind Power Plants,. In: : . Paper presented at PowerTech 2019.
Open this publication in new window or tab >>Secondary Harmonic Emission in Wind Power Plants,
2019 (Swedish)Conference paper, Published paper (Refereed)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:ltu:diva-76908 (URN)
Conference
PowerTech 2019
Available from: 2019-11-28 Created: 2019-11-28 Last updated: 2019-11-28
Schwanz, D., Busatto, T., Bollen, M. & Larsson, A. (2018). A stochastic study of harmonic voltage distortion considering single-phase photovoltaic inverters. In: Proceedings of International Conference on Harmonics and Quality of Power, ICHQP: . Paper presented at 18th International Conference on Harmonics and Quality of Power (ICHQP 2018), Ljubljana, Slovenia, May 13–16 2018. Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>A stochastic study of harmonic voltage distortion considering single-phase photovoltaic inverters
2018 (English)In: Proceedings of International Conference on Harmonics and Quality of Power, ICHQP, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2018Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, the hosting capacity considering harmonic distortion is estimated for single-phase-connected photovoltaic inverters (PVIs) in low-voltage distribution networks. A stochastic approach is used to calculate the harmonic voltage distortion with each customer in the network. The method has been applied to a 6-customer network for the connection of 2.5-kW single-phase PVIs with and without harmonic voltage background. From the results, it was observed that the contribution from 2.5 kW single-phase photovoltaic inverters to the individual harmonic distortion will not cause the established limits to be exceeded. Also, that the harmonic voltage background is often dominating and should be continuously observed.

Place, publisher, year, edition, pages
Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2018
Series
International Conference on Harmonics and Quality of Power, E-ISSN 1540-6008
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-69529 (URN)10.1109/ICHQP.2018.8378889 (DOI)000444771900078 ()2-s2.0-85049249086 (Scopus ID)978-1-5386-0517-2 (ISBN)
Conference
18th International Conference on Harmonics and Quality of Power (ICHQP 2018), Ljubljana, Slovenia, May 13–16 2018
Available from: 2018-06-14 Created: 2018-06-14 Last updated: 2018-10-10Bibliographically approved
Schwanz, D., Bollen, M. & Larsson, A. (2018). Some methods for harmonic emission determination in wind power plants. In: Proceedings of International Conference on Harmonics and Quality of Power, ICHQP: . Paper presented at 18th International Conference on Harmonics and Quality of Power (ICHQP 2018), Ljubljana, Slovenia, May 13–16 2018. Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>Some methods for harmonic emission determination in wind power plants
2018 (English)In: Proceedings of International Conference on Harmonics and Quality of Power, ICHQP, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2018Conference paper, Published paper (Refereed)
Abstract [en]

The connection of new installations, as wind power plants, into the public grid requires that some conditions are fulfilled. Their aim is among others to ensure a proper power quality in the grid and to ensure a high probability of electromagnetic compatibility. The harmonic emission of individual sources is one of the power quality concerns, because they can damage and increase heating in devices. However, as there are other power electronics loads are connected, the correct assessment of the harmonic emission from one specific source is not straightforward. in this paper, a review of the most used methods for harmonic emission determination is presented and some considerations are discussed regarding their use in wind power plants harmonic contribution. Depending on the application, one method is more suitable than the other. However, assumptions are necessary with any method, especially for the harmonic impedances. For wind power plants not all the presented methods are suitable. Also, further investigations are needed to determine the harmonic impedance of the wind power plant and public grid, especially around resonant frequencies.

Place, publisher, year, edition, pages
Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2018
Series
International Conference on Harmonics and Quality of Power, E-ISSN 1540-6008
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-69528 (URN)10.1109/ICHQP.2018.8378934 (DOI)000444771900123 ()2-s2.0-85049249859 (Scopus ID)978-1-5386-0517-2 (ISBN)
Conference
18th International Conference on Harmonics and Quality of Power (ICHQP 2018), Ljubljana, Slovenia, May 13–16 2018
Available from: 2018-06-14 Created: 2018-06-14 Last updated: 2019-02-07Bibliographically approved
Schwanz, D., Rönnberg, S. & Bollen, M. (2017). Hosting capacity for photovoltaic inverters considering voltage unbalance. In: 2017 IEEE PowerTech: . Paper presented at 2017 IEEE Manchester PowerTech, Manchester, 18-22 June 2017. Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), Article ID 7981274.
Open this publication in new window or tab >>Hosting capacity for photovoltaic inverters considering voltage unbalance
2017 (English)In: 2017 IEEE PowerTech, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7981274Conference paper, Published paper (Refereed)
Abstract [en]

 In this paper the hosting capacity considering voltage unbalance is estimated for single-phase photovoltaic inverters (PVIs) in low-voltage distribution networks in Sweden. A stochastic approach is used to calculate the negative-sequence voltage unbalance for each of the possible locations in the network. The method has been applied to 6 and 28-customer networks for the connection of 6-kW single-phase PVIs. The impact of three-phase motors on the unbalance was also studied. From the results, it was observed that the contribution from single-phase photovoltaic inverters to the voltage unbalance likely exceeds 1%, but unlikely that it will reach 2% of voltage unbalance.

Place, publisher, year, edition, pages
Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-65642 (URN)10.1109/PTC.2017.7981274 (DOI)000411142500480 ()2-s2.0-85034731977 (Scopus ID)978-1-5090-4237-1 (ISBN)
Conference
2017 IEEE Manchester PowerTech, Manchester, 18-22 June 2017
Available from: 2017-09-14 Created: 2017-09-14 Last updated: 2019-02-07Bibliographically approved
Schwanz, D., Möller, F., Rönnberg, S., Meyer, J. C. & Bollen, M. (2017). Stochastic assessment of voltage unbalance due to single-phase-connected solar power. In: 2017 IEEE PowerTech: . Paper presented at 2017 IEEE Manchester PowerTech, Manchester, 18-22 June 2017. Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>Stochastic assessment of voltage unbalance due to single-phase-connected solar power
Show others...
2017 (English)In: 2017 IEEE PowerTech, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017Conference paper, Published paper (Refereed)
Abstract [en]

A stochastic method is presented in this paper to estimate the future voltage unbalance in a low-voltage distribution network with high-penetration of single-phase photovoltaic inverters (PVIs). The location and phase allocation of the PVIs are considered as input parameters for the stochastic simulation. The method has been applied to three different low-voltage networks: two in Sweden and one in Germany. In the Swedish networks, for 6-kW single-phase PVIs, it is likely that the contribution from single-phase photovoltaic inverters to the voltage unbalance exceeds 1%. The 2% value is unlikely to be exceeded. In the German network, for 4.6-kW single-phase PVIs, the voltage unbalance is between 1.35% and 2.62%. The risk of high-voltage unbalance can be reduced by a combination of controlled distribution over the phases and a reduction of the maximum size for a single-phase PVI.

Place, publisher, year, edition, pages
Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-65640 (URN)10.1109/PTC.2017.7981171 (DOI)000411142500378 ()978-1-5090-4237-1 (ISBN)
Conference
2017 IEEE Manchester PowerTech, Manchester, 18-22 June 2017
Available from: 2017-09-14 Created: 2017-09-14 Last updated: 2017-11-24Bibliographically approved
Schwanz, D., Möller, F., Rönnberg, S., Meyer, J. & Bollen, M. (2017). Stochastic Assessment of Voltage Unbalance due to Single-Phase-Connected Solar Power (ed.). IEEE Transactions on Power Delivery, 32(2), 852-861, Article ID 7488998.
Open this publication in new window or tab >>Stochastic Assessment of Voltage Unbalance due to Single-Phase-Connected Solar Power
Show others...
2017 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 32, no 2, p. 852-861, article id 7488998Article in journal (Refereed) Published
Abstract [en]

A stochastic method is presented in this paper to estimate the future voltage unbalance in a low-voltage distribution network with high-penetration of single-phase photovoltaic inverters (PVIs). Location and phase allocation of the PVIs are considered as input parameters for the stochastic simulation. The method has been applied to three different low-voltage networks: two in Sweden and one in Germany. In the Swedish networks, for 6-kW single-phase PVIs, it is likely that the contribution from single-phase photovoltaic inverters to the voltage unbalance exceeds 1%. The 2% value is unlikely to be exceeded. In the German network, for 4.6-kW single-phase PVIs the voltage unbalance is between 1.35% and 2.62%.The risk of high voltage unbalance can be reduced by a combination of controlled distribution over the phases and reduction of the maximum size for a single-phase PVI.

Place, publisher, year, edition, pages
IEEE, 2017
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-7911 (URN)10.1109/TPWRD.2016.2579680 (DOI)000398907100029 ()2-s2.0-85017651944 (Scopus ID)65608cd0-3d7c-42f3-a987-7b5aa293d825 (Local ID)65608cd0-3d7c-42f3-a987-7b5aa293d825 (Archive number)65608cd0-3d7c-42f3-a987-7b5aa293d825 (OAI)
Note

Validerad; 2017; Nivå 2; 2017-03-29 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2019-02-07Bibliographically approved
Schwanz, D., Bollen, M. & Larsson, A. (2016). A Review of Solutions for Harmonic Mitigation. In: 2016 17th International Conference on Harmonics and Quality of Power: . Paper presented at 17th International Conference on Harmonics and Quality of Power (ICHQP), Belo Horizonte, Brasil, 16-19 October 2016 (pp. 30-35). Piscataway, NJ: IEEE Computer Society, Article ID 7783422.
Open this publication in new window or tab >>A Review of Solutions for Harmonic Mitigation
2016 (English)In: 2016 17th International Conference on Harmonics and Quality of Power, Piscataway, NJ: IEEE Computer Society, 2016, p. 30-35, article id 7783422Conference paper, Published paper (Refereed)
Abstract [en]

With the increasing of non-linear equipments connected in the network, mitigation solutions are needed to avoid and solve harmonic and resonance problems that may damage equipments and avoid their connection into the grid. Several are the solutions given to this problem; however, not all them are suitable for all situations. For it, in this paper a review of the most used harmonic solutions and some new technologies are presented. The advantages and disadvantages are described and the most used passive, active and hybrid solutions are described

Place, publisher, year, edition, pages
Piscataway, NJ: IEEE Computer Society, 2016
Series
International Conference on Harmonics and Quality of Power, ISSN 1540-6008
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-60505 (URN)10.1109/ICHQP.2016.7783422 (DOI)000391424200006 ()2-s2.0-85009507997 (Scopus ID)9781509037926 (ISBN)
Conference
17th International Conference on Harmonics and Quality of Power (ICHQP), Belo Horizonte, Brasil, 16-19 October 2016
Available from: 2016-11-17 Created: 2016-11-17 Last updated: 2019-02-07Bibliographically approved
Schwanz, D., Bagheri, A., Bollen, M. & Larsson, A. (2016). Active harmonic filters: control techniques review. In: 17th International Conference on Harmonics and Quality of Power: . Paper presented at 17th International Conference on Harmonics and Quality of Power (ICHQP), Belo Horizonte, Brasil, 16-19 October 2016 (pp. 36-41). Piscataway, NJ, Article ID 7783423.
Open this publication in new window or tab >>Active harmonic filters: control techniques review
2016 (English)In: 17th International Conference on Harmonics and Quality of Power, Piscataway, NJ, 2016, p. 36-41, article id 7783423Conference paper, Published paper (Refereed)
Abstract [en]

The use of active filters for harmonic mitigation compensation is increasing together with the improvement of their control techniques. Depending on the situation, the use of one technique instead of the other makes the difference of achieving a better harmonic mitigation or not. In this paper, a review of control techniques related to harmonic filters for harmonic mitigation is presented, together with the advantages and disadvantages. From the literature review it was observed that new techniques are being used and classical ones are being improved.

Place, publisher, year, edition, pages
Piscataway, NJ: , 2016
Series
International Conference on Harmonics and Quality of Power, ISSN 1540-6008
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-60507 (URN)10.1109/ICHQP.2016.7783423 (DOI)000391424200007 ()2-s2.0-85009508817 (Scopus ID)9781509037926 (ISBN)
Conference
17th International Conference on Harmonics and Quality of Power (ICHQP), Belo Horizonte, Brasil, 16-19 October 2016
Available from: 2016-11-17 Created: 2016-11-17 Last updated: 2018-06-14Bibliographically approved
Schwanz, D., Bollen, M., Larsson, A. & Kocewiak, Ł. H. (2016). Harmonic Mitigation in Wind Parks: Active Filter Solutions. In: 2016 17th International Conference on Harmonics and Quality of Power, 2016: . Paper presented at 17th International Conference on Harmonics and Quality of Power (ICHQP), Belo Horizonte, Brasil, 16-19 October 2016 (pp. 220-225). Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>Harmonic Mitigation in Wind Parks: Active Filter Solutions
2016 (English)In: 2016 17th International Conference on Harmonics and Quality of Power, 2016, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 220-225Conference paper, Published paper (Refereed)
Abstract [en]

Passive solutions are the most used harmonic mitigation methods in wind power plants, but the use of active filters is also a suitable and attractive approach. However, the best location for the connection of these active filters needs to be studied and evaluated. In this paper, a study of the use of active harmonic filters placed at different locations inside a wind power plant is performed. The results for current and voltage harmonic distortion are compared and discussed to determine the most suitable location for placing active harmonic filters within a wind power plant

Place, publisher, year, edition, pages
Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2016
Series
International Conference on Harmonics and Quality of Power, E-ISSN 2164-0610
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-60518 (URN)10.1109/ICHQP.2016.7783321 (DOI)978-1-5090-3792-6 (ISBN)
Conference
17th International Conference on Harmonics and Quality of Power (ICHQP), Belo Horizonte, Brasil, 16-19 October 2016
Available from: 2016-11-17 Created: 2016-11-17 Last updated: 2018-06-14Bibliographically approved
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