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  • 1.
    Cundeva, Snezana
    et al.
    University of Ss Cyril and Methodius, Faculty of Electrical Engineering and IT, Skopje.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Schwanz, Daphne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hosting capacity of the grid for wind generators set by voltage magnitude and distortion levels2016Conference paper (Refereed)
    Abstract [en]

    The hosting capacity, frequently defined as amount of distributed generation that can be connected to a certain location without resulting in an unacceptable quality or reliability for other customers, is limited. To know how much distributed generation can be connected in the grid it is important to define appropriate performance indicators. In this paper, the hosting capacity of the grid for wind power generation has been studied. Voltage magnitude and distortion levels are the performance indicators used to find the hosting capacity. A discussion is started on the interaction between windpower installations and the grid.

  • 2.
    Schwanz, Daphne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    On Transfer Functions for Power Quality Studies in Wind Power and Solar PV Plants2019Doctoral thesis, comprehensive summary (Other academic)
    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.

  • 3.
    Schwanz, Daphne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    On Wind Power Plants Harmonic Emissionand Single-Phase Photovoltaic Hosting Capacity2016Report (Refereed)
  • 4.
    Schwanz, Daphne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bagheri, Azam
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Larsson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Active harmonic filters: control techniques review2016In: 17th International Conference on Harmonics and Quality of Power, Piscataway, NJ, 2016, p. 36-41, article id 7783423Conference 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.

  • 5.
    Schwanz, Daphne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Larsson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    A Review of Solutions for Harmonic Mitigation2016In: 2016 17th International Conference on Harmonics and Quality of Power, Piscataway, NJ: IEEE Computer Society, 2016, p. 30-35, article id 7783422Conference 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

  • 6.
    Schwanz, Daphne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Larsson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Some methods for harmonic emission determination in wind power plants2018In: Proceedings of International Conference on Harmonics and Quality of Power, ICHQP, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2018Conference 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.

  • 7.
    Schwanz, Daphne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Larsson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kocewiak, Łukasz Hubert
    DONG Energy Wind Power, Fredericia.
    Harmonic Mitigation in Wind Parks: Active Filter Solutions2016In: 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 (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

  • 8.
    Schwanz, Daphne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Larsson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kocewiak, Łukasz Hubert
    DONG Energy Wind Power, Fredericia.
    Harmonic mitigation in wind power plants: Active filter solutions2016In: 17th International Conference on Harmonics and Quality of Power, Piscataway, NJ, 2016, p. 220-225, article id 7783321Conference 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

  • 9.
    Schwanz, Daphne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Obalans från enfasanslutna solpaneler2015Report (Refereed)
  • 10.
    Schwanz, Daphne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Busatto, Tatiano
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Larsson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    A stochastic study of harmonic voltage distortion considering single-phase photovoltaic inverters2018In: Proceedings of International Conference on Harmonics and Quality of Power, ICHQP, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2018Conference 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.

  • 11.
    Schwanz, Daphne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Möller, Friedemann
    Technische Universität Dresden.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Meyer, Jan Christian
    Technische Universität Dresden.
    Stochastic Assessment of Voltage Unbalance due to Single-Phase-Connected Solar Power2016In: 2016 17th International Conference on Harmonics and Quality of Power, Piscataway, NJ, 2016, p. 95-103, article id 7783353Conference 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). 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

  • 12.
    Schwanz, Daphne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Möller, Friedemann
    Technische Universität Dresden.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Meyer, Jan
    Institute of Electrical Power Systems and High Voltage Engineering, Technische Universitaet Dresden, Technical University Dresden, Dresden University of Technology.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Stochastic Assessment of Voltage Unbalance due to Single-Phase-Connected Solar Power2017In: 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)
    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.

  • 13.
    Schwanz, Daphne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Möller, Friedemann
    Technische Universität Dresden.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Meyer, Jan Christian
    Technische Universität Dresden.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Stochastic assessment of voltage unbalance due to single-phase-connected solar power2017In: 2017 IEEE PowerTech, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017Conference 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.

  • 14.
    Schwanz, Daphne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hosting capacity for photovoltaic inverters considering voltage unbalance2017In: 2017 IEEE PowerTech, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7981274Conference 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.

  • 15.
    Yang, Kai
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Schwanz, Daphne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Harmonic aggregation and amplification in a wind-park2015Conference paper (Refereed)
    Abstract [en]

    This paper studies the harmonic emission in a wind park,using a current transfer function. The emission of anindividual wind turbine has been measured during aperiod of a few weeks covering all output productions.The wind park harmonic emission is analyzed by theaverage spectrum at the collection point. The amount ofemission of the wind park as a whole is modeled by astochastic method, based on the Monte-Carlo Simulation.The measured harmonics at wind turbines have beenanalyzed and compared with the simulated overallemission at the collection point of the wind park. Theresults will be showed by graphs and some discussionswill be made.

1 - 15 of 15
CiteExportLink to result list
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