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Alvarez Perez, M. A., Rönnberg, S., Bermúdez, J., Zhong, J. & Bollen, M. (2019). A Generic Storage Model Based on a Future Cost Piecewise-Linear Approximation. IEEE Transactions on Smart Grid, 10(1), 878-888
Open this publication in new window or tab >>A Generic Storage Model Based on a Future Cost Piecewise-Linear Approximation
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2019 (English)In: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061, Vol. 10, no 1, p. 878-888Article in journal (Refereed) Published
Abstract [en]

This work presents a generic storage model (GSM) inspired by the scheduling of hydraulic reservoirs. The model for steady state short-term (ST) operational studies interlaces with the long-term (LT) energy scheduling through a piecewise-linear Future Cost Function (FCF). Under the assumption that a Stochastic Dual Dynamic Programming (SDDP) approach has been used to solve the energy schedule for the LT, the FCF output from that study will be processed to obtain an equivalent marginal opportunity cost for the storage unit. The linear characteristic of a segment of the future cost function (FCF) will allow a linear modeling of the storage unit production cost. This formulation will help to coordinate the renewable resource along with storage facilities in order to find the optimal operation cost while meeting end-point conditions for the long-term plan of the energy storage. The generic model will be implemented to represent a battery storage and a pumped-hydro storage. A stochastic unit commitment (SUC) with the GSM will be formulated and tested to assess the day-ahead scheduling strategy of a Virtual Power Plant (VPP) facing uncertainties from production, consumption, and market prices.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2019
Keywords
Schedules, Uncertainty, Load modeling, Production, Energy storage, GSM, Stochastic processes
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-60774 (URN)10.1109/TSG.2017.2754288 (DOI)000455180900080 ()2-s2.0-85030639335 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-01-25 (inah)

Available from: 2016-11-29 Created: 2016-11-29 Last updated: 2019-01-29Bibliographically approved
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)000454377000043 ()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: 2019-01-29Bibliographically approved
Sierra-Fernández, J.-M., Rönnberg, S., De La Rosa, J.-J., Bollen, M. & Palomares-Salas, J.-C. (2019). Application of spectral kurtosis to characterize amplitude variability in power systems' harmonics. Energies, 12(1), Article ID en12010194.
Open this publication in new window or tab >>Application of spectral kurtosis to characterize amplitude variability in power systems' harmonics
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2019 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 1, article id en12010194Article in journal (Refereed) Published
Abstract [en]

The highly-changing concept of Power Quality (PQ) needs to be continuously reformulated due to the new schemas of the power grid or Smart Grid (SG). In general, the spectral content is characterized by their averaged or extreme values. However, new PQ events may consist of large variations in amplitude that occur in a short time or small variations in amplitude that take place continuously. Thus, the former second-order techniques are not suitable to monitor the dynamics of the power spectrum. In this work, a strategy based on Spectral Kurtosis (SK) is introduced to detect frequency components with a constant amplitude trend, which accounts for amplitude values' dispersion related to the mean value of that spectral component. SK has been proven to measure frequency components that follow a constant amplitude trend. Two practical real-life cases have been considered: Electric current time-series from an arc furnace and the power grid voltage supply. Both cases confirm that the more concentrated the amplitude values are around the mean value, the lower the SK values are. All this confirms SK as an effective tool for evaluating frequency components with a constant amplitude trend, being able to provide information beyond maximum variation around the mean value and giving a progressive index of value dispersion around the mean amplitude value, for each frequency component. 

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
harmonics, constant amplitude trend, fourth-order statistics, detection, spectral kurtosis
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-72718 (URN)10.3390/en12010194 (DOI)2-s2.0-85059981926 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-01-28 (svasva)

Available from: 2019-01-28 Created: 2019-01-28 Last updated: 2019-01-28Bibliographically 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: 2018-12-13
Laury, J., Abrahamsson, L. & Bollen, M. (2019). Impact of reduced share of rotary frequency converter in a low-frequency synchronous railway grid: 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 share of rotary frequency converter in a low-frequency synchronous railway grid: 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

Accepted.

Available from: 2018-11-28 Created: 2018-11-28 Last updated: 2019-01-08
Busatto, T., Larsson, A., Rönnberg, S. & Bollen, M. (2019). Including Uncertainties from Customer Connections in Calculating Low-Voltage Harmonic Impedance. IEEE Transactions on Power Delivery
Open this publication in new window or tab >>Including Uncertainties from Customer Connections in Calculating Low-Voltage Harmonic Impedance
2019 (English)In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208Article in journal (Refereed) Epub ahead of print
Abstract [en]

A method is proposed in this paper to determine the harmonic impedances in low-voltage networks in a stochastic way. The consequences of resonances for harmonic propagation and stability of power converters are summarized. By using Monte Carlo simulation, the method includes the uncertainties in customer impedances, specifically due to electronic loads and local generation. The uncertainty in customer impedance is included by considering probability distribution for the resistive, inductive and capacitive parts of the impedance. The concept of transfer impedance is used for phase-to-neutral connections. A method is developed and applied to two existing low-voltage networks in Sweden. Results show that, for these two networks, the resonant frequencies decrease around 28 % once PV panels are installed. The paper includes a discussion of some of the practical aspects of applying the proposed method.

Place, publisher, year, edition, pages
IEEE, 2019
Keywords
Power Quality, power system harmonics, resonance, stochastic processes, Monte Carlo methods
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-72659 (URN)10.1109/TPWRD.2018.2881222 (DOI)
Funder
Swedish Energy Agency
Available from: 2019-01-23 Created: 2019-01-23 Last updated: 2019-01-29
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), 12-15 June, Palermo, Italy. , Article ID 8493874.
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), 2018, article id 8493874Conference 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.

Keywords
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-72033 (URN)10.1109/EEEIC.2018.8493874 (DOI)2-s2.0-85056522960 (Scopus ID)9781538651858 (ISBN)
Conference
2018 IEEE International Conference on Environment and Electrical Engineering and 2018 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe), 12-15 June, Palermo, Italy
Available from: 2018-12-13 Created: 2018-12-13 Last updated: 2019-01-29Bibliographically 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)000451230500023 ()2-s2.0-85049802440 (Scopus ID)
Note

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

Available from: 2018-08-06 Created: 2018-08-06 Last updated: 2019-01-10Bibliographically 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
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4074-9529

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