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Laury, J., Abrahamsson, L. & Bollen, M. (2019). A rotary frequency converter model for electromechanical transient studies of 16 (2/3) Hz railway systems. International Journal of Electrical Power & Energy Systems, 106, 467-476
Open this publication in new window or tab >>A rotary frequency converter model for electromechanical transient studies of 16 (2/3) Hz railway systems
2019 (English)In: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 106, p. 467-476Article in journal (Refereed) Published
Abstract [en]

Railway power systems operating at a nominal frequency below the frequency of the public grid (50 or 60 Hz) are special in many senses. One is that they exist in a just few countries around the world. However, for these countries such low frequency railways are a critical part of their infrastructure.

The number of published dynamic models as well as stability studies regarding low frequency railways is small, compared to corresponding publications regarding 50 Hz/60 Hz public grids. Since there are two main type of low frequency railways; synchronous and asynchronous, it makes the number of available useful publications even smaller. One important reason for this is the small share of such grids on a global scale, resulting in less research and development man hours spent on low frequency grids.

This work presents an open model of a (synchronous-synchronous) rotary frequency converter for electromechanical stability studies in the phasor domain, based on established synchronous machine models. The proposed model is designed such that it can be used with the available data for a rotary frequency converter.

The behaviour of the model is shown through numerical electromechanical transient stability simulations of two example cases, where a fault is cleared, and the subsequent oscillations are shown. The first example is a single-fed catenary section and the second is doubly-fed catenary section.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Low frequency railways; 16 (2/3)  Hz; Modelling; Simulations; Transient stability; Rotary frequency converter; Motor generator set; Multi machine system
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-71471 (URN)10.1016/j.ijepes.2018.10.017 (DOI)2-s2.0-85055732778 (Scopus ID)
Funder
Swedish Transport Administration
Note

Validerad;2018;Nivå 2;2018-11-07 (inah)

Available from: 2018-11-06 Created: 2018-11-06 Last updated: 2018-11-07Bibliographically approved
Abrahamsson, L., Laury, J. & Bollen, M. (2019). Evaluating a constant-current load model through comparativetransient stability case studies of a synchronous-synchronous rotary frequencyconverter fed railway. In: : . Paper presented at Proceedings of the 2019 IEEE/ASME Joint Rail Conference.
Open this publication in new window or tab >>Evaluating a constant-current load model through comparativetransient stability case studies of a synchronous-synchronous rotary frequencyconverter fed railway
2019 (English)Conference paper, Published paper (Refereed)
Abstract [en]

This paper continues the pursuit of getting a deeperunderstanding regarding the transient stability of lowfrequencyAC railway power systems operated at 162⁄3 Hzsynchronously to the public grid. The focus is set on theimpact of different load models. A simple constant-currentload model is proposed and compared to a previously proposedand studied load model in which the train’s activepower is regulated.The study and comparison is made on exactly the samecases as and grid as with the already proposed and moreadvanced load model. The railway grid is equipped witha low-frequency AC high-voltage transmission line whichis subjected to a fault. The study is limited to railwaysbeing fed by different distributions of RFC (Rotary FrequencyConverter) types. Both AT (auto transformer) andBT (booster transformer) catenaries are considered.The RFC dynamic models are essentially Anderson-Fouad models of two synchronous machines coupled mechanicallyby their rotors being connected to the same shaft.The differences in load behaviour between the proposedconstant-current load model and the previously proposedand studied voltage-dependent active power load model areanalyzed and described in the paper.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:ltu:diva-71801 (URN)
Conference
Proceedings of the 2019 IEEE/ASME Joint Rail Conference
Note

Submitted to JRC 2019. Not yet accepted. /20181205

Available from: 2018-11-28 Created: 2018-11-28 Last updated: 2018-12-05
Laury, J., Abrahamsson, L. & Bollen, M. (2019). Impact of reduced rotational inertia in a frequency-stiff low frequency AC railway: A transient stability study. In: : . Paper presented at Proceedings of the 2019 IEEE/ASME Joint Rail Conference.
Open this publication in new window or tab >>Impact of reduced rotational inertia in a frequency-stiff low frequency AC railway: A transient stability study
2019 (English)Conference paper, Published paper (Refereed)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-71798 (URN)
Conference
Proceedings of the 2019 IEEE/ASME Joint Rail Conference
Note

NOTE!: Submitted for JRC 2019 conference. Not accepted yet! /20181128

Available from: 2018-11-28 Created: 2018-11-28 Last updated: 2018-11-28
Alvarez, M., Rönnberg, S., Bollen, M., Frías, P., Cossent, R., Jabr, R. & Zhong, J. (2018). A Capacity Mechanism Design for Distribution Network Expansion Planning. In: 2018 IEEE International Conference on Environment and Electrical Engineering and 2018 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe): . Paper presented at 2018 IEEE International Conference on Environment and Electrical Engineering and 2018 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe), Palermo, Italy, 12-15 June 2018.. IEEE
Open this publication in new window or tab >>A Capacity Mechanism Design for Distribution Network Expansion Planning
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2018 (English)In: 2018 IEEE International Conference on Environment and Electrical Engineering and 2018 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe), IEEE, 2018Conference paper, Published paper (Refereed)
Abstract [en]

Capacity remuneration mechanisms have been originally oriented to ensure availability and continuity of supply on the power generation pool. Equivalent generation-based capacity mechanisms could be implemented to enhance and prolong the usability of the distribution grid. In particular, such capacity mechanisms would provide an alternative to traditional expansion options leading to investment deferral. In this work, a distribution capacity mechanism to fit within a distribution network planning methodology will be proposed and discussed. The capacity mechanism will be outlined following similar guidelines as for the design of capacity mechanisms used in the energy only market. The result of the design is a volume based capacity auction for a capacity-constrained system, oriented to both the active and the reactive power provision.

Place, publisher, year, edition, pages
IEEE, 2018
Keywords
Planning, Reactive power, Capacity planning, Contracts, Investment, Remuneration, Voltage control, Power system planning, capacity planning, power distribution
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-71392 (URN)10.1109/EEEIC.2018.8493874 (DOI)
Conference
2018 IEEE International Conference on Environment and Electrical Engineering and 2018 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe), Palermo, Italy, 12-15 June 2018.
Available from: 2018-10-31 Created: 2018-10-31 Last updated: 2018-10-31Bibliographically approved
Balouji, E., Gu, I. Y. .., Bollen, M., Bagheri, A. & Nazari, M. (2018). A LSTM-based deep learning method with application to voltage dip classification. 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), Ljubljana, Slovenia, 13-16 May 2018. Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>A LSTM-based deep learning method with application to voltage dip classification
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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, a deep learning (DL)-based method for automatic feature extraction and classification of voltage dips is proposed. The method consists of a dedicated architecture of Long Short-Term Memory (LSTM), which is a special type of Recurrent Neural Networks (RNNs). A total of 5982 three-phase one-cycle voltage dip RMS sequences, measured from several countries, has been used in our experiments. Our results have shown that the proposed method is able to classify the voltage dips from learned features in LSTM, with 93.40% classification accuracy on the test data set. The developed architecture is shown to be novel for feature learning and classification of voltage dips. Different from the conventional machine learning methods, the proposed method is able to learn dip features without requiring transition-event segmentation, selecting thresholds, and using expert rules or human expert knowledge, when a large amount of measurement data is available. This opens a new possibility of exploiting deep learning technology for power quality data analytics and classification.

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-69511 (URN)10.1109/ICHQP.2018.8378893 (DOI)000444771900082 ()2-s2.0-85049260061 (Scopus ID)978-1-5386-0517-2 (ISBN)
Conference
18th International Conference on Harmonics and Quality of Power (ICHQP), Ljubljana, Slovenia, 13-16 May 2018
Available from: 2018-06-14 Created: 2018-06-14 Last updated: 2018-10-10Bibliographically approved
Bagheri, A., Gu, I. Y. .., Bollen, M. & Balouji, E. (2018). A Robust Transform-Domain Deep Convolutional Network for Voltage Dip Classification. IEEE Transactions on Power Delivery, 33(6), 2794-2802
Open this publication in new window or tab >>A Robust Transform-Domain Deep Convolutional Network for Voltage Dip Classification
2018 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 33, no 6, p. 2794-2802Article in journal (Refereed) Published
Abstract [en]

This paper proposes a novel method for voltage dip classification using deep convolutional neural networks. The main contributions of this paper include: (a) to propose a new effective deep convolutional neural network architecture for automatically learning voltage dip features, rather than extracting hand-crafted features; (b) to employ the deep learning in an effective two-dimensional transform domain, under space-phasor model (SPM), for efficient learning of dip features; (c) to characterize voltage dips by two-dimensional SPM-based deep learning, which leads to voltage dip features independent of the duration and sampling frequency of dip recordings; (d) to develop robust automatically-extracted features that are insensitive to training and test datasets measured from different countries/regions.

Experiments were conducted on datasets containing about 6000 measured voltage dips spread over seven classes measured from several different countries. Results have shown good performance of the proposed method: average classification rate is about 97% and false alarm rate is about 0.50%. The test results from the proposed method are compared with the results from two existing dip classification methods. The proposed method is shown to out-perform these existing methods.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2018
Keywords
Power quality, Voltage dip, Machine learning, Deep learning, Convolutional Neural Network.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-70217 (URN)10.1109/TPWRD.2018.2854677 (DOI)
Note

Validerad;2018;Nivå 2;2018-12-05 (inah)

Available from: 2018-08-06 Created: 2018-08-06 Last updated: 2018-12-05Bibliographically approved
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
Nömm, J., Rönnberg, S. & Bollen, M. (2018). An Analysis of Frequency Variations and its Implications on Connected Equipment for a Nanogrid during Islanded Operation. Energies, Article ID en11092456.
Open this publication in new window or tab >>An Analysis of Frequency Variations and its Implications on Connected Equipment for a Nanogrid during Islanded Operation
2018 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, article id en11092456Article in journal (Refereed) Published
Abstract [en]

Frequency, voltage and reliability data have been collected in a nanogrid for 48 weeks during islanded operation. Frequency values from the 48 week measurements were analyzed and compared to relevant limits. During 19.5% of the 48 weeks, the nanogrid had curtailed the production due to insufficient consumption in islanded operation. The curtailment of production was also the main cause of the frequency variations above the limits. When the microgrid operated on stored battery power, the frequency variations were less than in the Swedish national grid. 39.4% of all the interruptions that occurred in the nanogrid are also indirectly caused by the curtailment of solar production. Possible solutions for mitigating the frequency variations and lowering the number of interruptions are also discussed.

Keywords
frequency variations, islanded operation, nanogrids, power quality, power system reliability
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-71121 (URN)10.3390/en11092456 (DOI)000446604500277 ()2-s2.0-85053911592 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-05 (svasva)

Available from: 2018-10-05 Created: 2018-10-05 Last updated: 2018-10-29Bibliographically approved
Nömm, J., Rönnberg, S. & Bollen, M. (2018). Harmonic Voltage Measurements in a Single House Microgrid. 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 >>Harmonic Voltage Measurements in a Single House Microgrid
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 harmonic voltage distortion have been measured in a single house microgrid in Sweden. The microgrid can operate in both islanded mode and grid connected mode. A comparison of the voltage harmonic magnitudes has been made between the two operation states and also against relevant standards. Both the 10 minute average and the 3 second average values are presented in the paper. The harmonic voltage magnitudes are higher during island mode and the difference between the 10 minute value and 3 second value is also greater compared to when the microgrid is connected to the grid. At some instances the magnitudes of both total harmonic distortion and of individual harmonics exceed the limits described in the standards.

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-69189 (URN)10.1109/ICHQP.2018.8378921 (DOI)000444771900110 ()2-s2.0-85049235767 (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: 2018-06-07 Created: 2018-06-07 Last updated: 2018-10-10Bibliographically approved
Cundeva, S., Krkoleva Mateska, A. & Bollen, M. (2018). Hosting capacity of LV residential grid for uncoordinated ev charging. 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 >>Hosting capacity of LV residential grid for uncoordinated ev charging
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 envisaged large penetration of electric vehicles (EVs) in the near future, brings new challenges to low voltage (LV) and medium voltage (MV) grids. For uncoordinated EV charging, the impact on the LV grid may be significant, due to the simultaneity between the residential power peak and the charging of EVs. The amount of EV chargers that can be connected to the grid without endangering the reliability or voltage quality for other customers is called the hosting capacity. This paper presents the analyses of the hosting capacity of a realistic LV residential network with 160 households for EV chargers. A stochastic approach is used, assuming that the EV chargers are randomly distributed over the households and the phases. For different EVs penetration rates in the network, the hosting capacity for slow chargers is determined. The results show that the EV penetration rate that the network can safely accept is 45%.

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-69555 (URN)10.1109/ICHQP.2018.8378892 (DOI)000444771900081 ()2-s2.0-85049258141 (Scopus ID)9781538605172 (ISBN)
Conference
18th International Conference on Harmonics and Quality of Power (ICHQP 2018), Ljubljana, Slovenia, May 13–16 2018
Available from: 2018-06-15 Created: 2018-06-15 Last updated: 2018-10-10Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-4074-9529

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