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  • 1.
    Barakou, Fani
    et al.
    Eindhoven University of Technology, The Netherlands.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Mousavi-Gargari, S.
    TenneT TSO B.V, The Netherlands.
    Lennerhag, Oscar
    STRI AB, Sweden.
    Wouters, Peter A A F
    Eindhoven University of Technology, The Netherlands.
    Steennis, E. Fred
    Eindhoven University of Technology, The Netherlands.
    Impact of Load Modeling on the Harmonic Impedance seen from the Transmission Network2016In: 17th International Conference on Harmonics and Quality of Power, Piscataway, NJ, 2016, p. 283-288, article id 7783466Conference paper (Refereed)
    Abstract [en]

    Traditionally when studying harmonics at transmis-sion system level the medium and low voltage grid is modeledwith either an equivalent short-circuit impedance or a fixed PQload (based on the powerflow) directly at the secondary side ofthe transmission transformer. However the recent replacement ofconventional loads with electronic loads as well as the extendeduse of power electronics in LV level will result in reductionof damping and increase of household capacitance which maychange the harmonic impedance seen from the upstream network(MV or HV) both in the dominant frequency and magnitude.In this paper a HV feeder is modeled in detail starting fromthe transmission transformer up to the household equipmentto investigate whether changes in the type of load affect theimpedance seen from the HV. The simulations are performedusing software package PSCAD/EMTDC.

  • 2.
    Bollen, Math
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Karlsson, Daniel E.
    STRI AB, Ludvika.
    Lennerhag, Oscar
    STRI AB, Sweden.
    Different Fault Types and Voltage Dips in relation to Shielding of Subtransmission Lines2016In: 2016 17th International Conference on Harmonics and Quality of Power, Piscataway, NJ, 2016, p. 518-523, article id 7783470Conference paper (Refereed)
    Abstract [en]

    This paper presents a method for considering the voltage-dip performance of the power system in the design of subtransmission lines. The shielding performance of the lines is expressed in terms of the number of faults for different number of phases involved in the fault. Relations between fault type and voltage dip at the terminals of sensitive equipment are used to determine the resulting number of equipment trips. The method is illustrated by applying it to three different tower designs used in the Swedish subtransmission networks. It is shown that the installation of shield wires significantly reduces the number of equipment trips, especially in combination with the installation of additional capacitance in adjustable-speed drives.

  • 3.
    Etherden, Nicholas
    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.
    Ackeby, Susanne
    STRI AB.
    Lennerhag, Oscar
    STRI AB.
    The transparent hosting-capacity approach – overview, applications and developments2015Conference paper (Refereed)
    Abstract [en]

    This paper summarizes the hosting capacity approach and gives some recent developments: including uncertainty in location and size of production units; curtailment to connect more production than according to the initial hosting capacity. For both developments it is shown that the transparency of the approach still holds but also that the results may be strongly location dependent. It is however also shown that the hosting-capacity approach can be used to obtain rough estimations, rules-of-thumbs, and to make a first assessment in case more detailed studies are not possible for example because insufficient data is available.

  • 4.
    Lennerhag, Oscar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Independent Insulation Group Sweden AB.
    Power system model for resonance studies2018Report (Other academic)
    Abstract [en]

    This report details an example grid suitable for the following studies:

    • Transients following energizing of transformers, capacitor banks, and cables.
    • Spread of harmonics, i.e. calculation of transfer impedances. Note that emission is not included in the example grid.

    The author has tried as much as possible to make the example grid realistic, and parts of the model are based on existing and/or planned transmission grids.

    The example grid is characterized by its large share of cables at 400 and 220 kV, with a first resonance frequency between 100 and 150 Hz.

  • 5.
    Lennerhag, Oscar
    et al.
    STRI AB, Ludvika.
    Ackeby, Susanne
    STRI AB, Ludvika.
    Bollen, Math
    STRI AB, Ludvika.
    Foskolos, Georgios
    MälarEnergi, Västerås.
    Gafurov, Tokhir
    MälarEnergi, Västerås.
    Using measurements to increase the accuracy of hosting capacity calculations2017In: CIRED - Open Access Proceedings Journal, E-ISSN 2515-0855, Vol. 2017, no 1, p. 2041-2044Article in journal (Refereed)
    Abstract [en]

    This study has compared five different methods for calculating the hosting capacity in a distribution grid. The results show a large difference in the obtained hosting capacity depending on the method used. It was found that the use of measurements in the calculations greatly increases the hosting capacity, compared with when using assumptions based on a ‘worst case scenario’, without increasing the risk for the network operator or other customers. It was also found that the statistical index used (i.e. 100, 99, or 95%) has a large impact on the calculated hosting capacity.

  • 6.
    Lennerhag, Oscar
    et al.
    STRI.
    Ackeby, Susanne
    STRI.
    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.
    Voltage variations due to wind power and solar power at time scales of 10 minutes and less2014Conference paper (Refereed)
  • 7.
    Lennerhag, Oscar
    et al.
    Independent Insulation Group Sweden AB.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Power system impacts of decreasing resonance frequencies2018In: 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]

    As the energy system is transitioning to a more sustainable one several of the related changes will affect the power system in different ways. Renewable electricity sources, energy efficiency measures and increased operational flexibility lead to more serious resonances in the electricity network and an increased uncertainty in terms of frequency and damping of those resonances. This could have a large impact on the spread of harmonics and on temporary overvoltages. In this paper, some examples of changes in the grid are presented and their impact on the spread of harmonics and temporary overvoltages, as a consequence of changes in resonances, is discussed.

  • 8.
    Lennerhag, Oscar
    et al.
    STRI.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ackeby, Susanne
    STRI AB.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Spänningsvariationer och intermittent produktion2014Report (Refereed)
  • 9.
    Lennerhag, Oscar
    et al.
    STRI AB.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ackeby, Susanne
    STRI AB.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Very short variations in voltage (timescale less than 10 minutes) due to variations in wind and solar power2015Conference paper (Refereed)
    Abstract [en]

    This paper presents results from a study on variations in voltage magnitude at a timescale less than 10 minutes, due to measured variations in wind and solar production. The variations are compared with the measured variations at several low and medium-voltage sites. It is concluded that individual solar panels are not a concern but that several solar panels connected to the same low-voltage feeder may lead to a noticeable increase in voltage variations at this timescale. Individual wind turbines and wind farms are not expected to lead to a significant increase in voltage variations. The voltage variations do change in character by the introduction of wind and solar power.

  • 10.
    Lennerhag, Oscar
    et al.
    STRI AB, Ludvika.
    Pinares, Gustavo
    STRI AB, Ludvika.
    Bollen, Math
    STRI AB, Ludvika.
    Foskolos, Georgios
    MälarEnergi, Västerås.
    Gafurov, Tokhir
    MälarEnergi, Västerås.
    Performance indicators for quantifying the ability of the grid to host renewable electricity production2017In: CIRED - Open Access Proceedings Journal, E-ISSN 2515-0855, Vol. 2017, no 1, p. 792-795Article in journal (Refereed)
    Abstract [en]

    This study proposes a comprehensive set of performance indicators that should be used when evaluating the hosting capacity (HC) of a system. Descriptions are given for the most relevant phenomena and how they should be quantified and measured. The suggested time resolution for the data has been 1 h, 10 min, and 3 s, based on what is available already in standard meters. The use of 100, 99, or 95 percentile values has an impact on the HC, and there is a need for further discussion with regard to the selection of statistical limits.

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