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Publikasjoner (10 av 376) Visa alla publikasjoner
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
Åpne denne publikasjonen i ny fane eller vindu >>A Generic Storage Model Based on a Future Cost Piecewise-Linear Approximation
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2019 (engelsk)Inngår i: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061, Vol. 10, nr 1, s. 878-888Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
Institute of Electrical and Electronics Engineers (IEEE), 2019
Emneord
Schedules, Uncertainty, Load modeling, Production, Energy storage, GSM, Stochastic processes
HSV kategori
Forskningsprogram
Elkraftteknik
Identifikatorer
urn:nbn:se:ltu:diva-60774 (URN)10.1109/TSG.2017.2754288 (DOI)000455180900080 ()2-s2.0-85030639335 (Scopus ID)
Merknad

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

Tilgjengelig fra: 2016-11-29 Laget: 2016-11-29 Sist oppdatert: 2019-08-27bibliografisk kontrollert
Lennerhag, O. & Bollen, M. (2019). A power system model for resonance studies. In: : . Paper presented at CIRED 2019.
Åpne denne publikasjonen i ny fane eller vindu >>A power system model for resonance studies
2019 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
HSV kategori
Identifikatorer
urn:nbn:se:ltu:diva-76904 (URN)
Konferanse
CIRED 2019
Tilgjengelig fra: 2019-11-28 Laget: 2019-11-28 Sist oppdatert: 2019-11-28
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
Åpne denne publikasjonen i ny fane eller vindu >>A rotary frequency converter model for electromechanical transient studies of 16 (2/3) Hz railway systems
2019 (engelsk)Inngår i: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 106, s. 467-476Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
Elsevier, 2019
Emneord
Low frequency railways, 16 (2/3)  Hz, Modelling, Simulations, Transient stability, Rotary frequency converter, Motor generator set, Multi machine system
HSV kategori
Forskningsprogram
Elkraftteknik
Identifikatorer
urn:nbn:se:ltu:diva-71471 (URN)10.1016/j.ijepes.2018.10.017 (DOI)000454377000043 ()2-s2.0-85055732778 (Scopus ID)
Forskningsfinansiär
Swedish Transport Administration
Merknad

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

Tilgjengelig fra: 2018-11-06 Laget: 2018-11-06 Sist oppdatert: 2019-09-13bibliografisk kontrollert
Nömm, J., Rönnberg, S. & Bollen, M. (2019). An analysis of voltage quality in a nanogrid during islanded operation. Energies, 12(4), Article ID 614.
Åpne denne publikasjonen i ny fane eller vindu >>An analysis of voltage quality in a nanogrid during islanded operation
2019 (engelsk)Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, nr 4, artikkel-id 614Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Voltage quality data has been collected in a single house nanogrid during 48 weeks of islanded operation and 54 weeks of grid-connected operation. The voltage quality data contains the voltage total harmonic distortion (THD), odd harmonics 3 to 11 and 15, even harmonics 4 to 8, voltage unbalance, short-term flicker severity (Pst) and long-term flicker severity (Plt) values, and voltage variations at timescales below 10 min. A comparison between islanded and grid-connected operation values was made, were some of the parameters were compared to relevant grid standard limits. It is shown that some parameters exceed the defined limits in the grid-standards during islanded operation. It was also found that the islanded operation has two modes of operation, one in which higher values of the short circuit impedance, individual harmonic impedance, harmonic voltage distortion and voltage unbalance were reached.

sted, utgiver, år, opplag, sider
MDPI, 2019
Emneord
harmonics, islanded operation, nanogrids, power quality, voltage unbalance
HSV kategori
Forskningsprogram
Elkraftteknik
Identifikatorer
urn:nbn:se:ltu:diva-73155 (URN)10.3390/en12040614 (DOI)000460667700040 ()2-s2.0-85061970485 (Scopus ID)
Merknad

Validerad;2019;Nivå 2;2019-03-11 (johcin)

Tilgjengelig fra: 2019-03-11 Laget: 2019-03-11 Sist oppdatert: 2019-04-11bibliografisk kontrollert
Lennerhag, O., Lundquist, J., Engelbrecht, C., Karmokar, T. & Bollen, M. (2019). An Improved Statistical Method for Calculating Lightning Overvoltages in HVDC Overhead Line/Cable Systems. Energies, 12(16), Article ID 3121.
Åpne denne publikasjonen i ny fane eller vindu >>An Improved Statistical Method for Calculating Lightning Overvoltages in HVDC Overhead Line/Cable Systems
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2019 (engelsk)Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, nr 16, artikkel-id 3121Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

HVDC cable systems connected to HVDC overhead lines are subject to fast front overvoltages emanating from the line when lightning strikes a shield wire (backflashover) or a pole conductor (shielding failure). Representative fast front overvoltage levels for HVDC cable systems are usually established without considering their statistical characteristics. A statistical method to determine overvoltages related to the acceptable mean time between failure (MTBF) for the cable system was developed previously. The method accounts for the statistical distribution of lightning current magnitudes as well as the attenuation of the overvoltage wave due to corona discharges on the line, since this effect dominates for system voltages up to about ±320 kV. To make the method suitable for higher system voltages as well, this article introduces an improved statistical method which also accounts for surge attenuation through resistive effects, soil ionization, and statistical treatment of overvoltages due to shielding failures. To illustrate the improved method, it is applied to a case study for a ±525 kV DC line. 

sted, utgiver, år, opplag, sider
MDPI, 2019
Emneord
HVDC, cable, overhead line, lightning, overvoltage, MTBF
HSV kategori
Forskningsprogram
Elkraftteknik
Identifikatorer
urn:nbn:se:ltu:diva-75965 (URN)10.3390/en12163121 (DOI)000484454000084 ()2-s2.0-85071227522 (Scopus ID)
Merknad

Validerad;2019;Nivå 2;2019-09-11 (johcin)

Tilgjengelig fra: 2019-09-11 Laget: 2019-09-11 Sist oppdatert: 2019-10-01bibliografisk kontrollert
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.
Åpne denne publikasjonen i ny fane eller vindu >>Application of spectral kurtosis to characterize amplitude variability in power systems' harmonics
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2019 (engelsk)Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, nr 1, artikkel-id en12010194Artikkel i tidsskrift (Fagfellevurdert) 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. 

sted, utgiver, år, opplag, sider
MDPI, 2019
Emneord
harmonics, constant amplitude trend, fourth-order statistics, detection, spectral kurtosis
HSV kategori
Forskningsprogram
Elkraftteknik
Identifikatorer
urn:nbn:se:ltu:diva-72718 (URN)10.3390/en12010194 (DOI)000460665000194 ()2-s2.0-85059981926 (Scopus ID)
Merknad

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

Tilgjengelig fra: 2019-01-28 Laget: 2019-01-28 Sist oppdatert: 2019-04-12bibliografisk kontrollert
Ravindran, V., Busatto, T., Rönnberg, S., Bollen, M. & Meyer, J. (2019). Charactizations of interactions between PV and Energy efficient lighting (LED) in a mixed installation.. In: : . Paper presented at CIRED 2019, 25th International Conference on Electricity Distribution Madrid, 3-6 June 2019 (pp. 1-5). , -, Article ID 237.
Åpne denne publikasjonen i ny fane eller vindu >>Charactizations of interactions between PV and Energy efficient lighting (LED) in a mixed installation.
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2019 (engelsk)Konferansepaper, Oral presentation with published abstract (Fagfellevurdert)
Abstract [en]

The possible interactions between grid-tied powerelectronicbased PV systems and energy efficient LEDlighting systems in terms of current and voltage, fordifferent combinations of the inverter and LED lamp typesunder different grid conditions, are studied in a laboratoryenvironment. In this paper, the interactions arecharacterized in terms of the power quality disturbanceslike harmonics, interharmonics, supraharmonics,overvoltage, undervoltage, and rapid voltage changes.

Emneord
LED PV interactions harmonics supraharmonics interharmonics
HSV kategori
Forskningsprogram
Elkraftteknik
Identifikatorer
urn:nbn:se:ltu:diva-73887 (URN)
Konferanse
CIRED 2019, 25th International Conference on Electricity Distribution Madrid, 3-6 June 2019
Tilgjengelig fra: 2019-05-09 Laget: 2019-05-09 Sist oppdatert: 2019-05-20
Ravindran, V., Busatto, T., Rönnberg, S. & Bollen, M. (2019). Comparison of a non-parametric and parametric method for interharmonic estimation in PV systems. In: : . Paper presented at 13th IEEE PowerTech 2019.
Åpne denne publikasjonen i ny fane eller vindu >>Comparison of a non-parametric and parametric method for interharmonic estimation in PV systems
2019 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

A comparative analysis of ‘Desynchronized processing technique’ (non-parametric) and ‘Sliding window ESPRIT method’ (parametric) for interharmonic estimation in PV systems is carried out. Both methods were applied to field measurements and semi-measured signals to test their feasibility under different conditions. In Desynchronized processing technique, in the second stage of estimation, a Short-term Fourier transform was used to address the time-varying nature of interharmonics. In Sliding window ESPRIT method, the signal subspace dimension was fixed in all analysed cases. An adaptive algorithm was used to find the best rank of the Hankel matrix and apt order of the filter to ensure stability. A set of critical parameters affecting the performance of these methods in interharmonic estimation are identified. This paper emphasizes the significance of using appropriate methods for accurate interharmonic estimation and also demonstrates through the illustrated results that different inferences can be drawn for the same measurements analysed using different methods.

Emneord
Interharmonics, power system measurements, time-frequency analysis, Photovoltaic systems, Power quality.
HSV kategori
Forskningsprogram
Elkraftteknik
Identifikatorer
urn:nbn:se:ltu:diva-73360 (URN)
Konferanse
13th IEEE PowerTech 2019
Forskningsfinansiär
Swedish Energy Agency
Tilgjengelig fra: 2019-03-29 Laget: 2019-03-29 Sist oppdatert: 2019-05-20
Hajeforosh, S. F., Bollen, M. & Abrahamsson, L. (2019). Dynamic Line Rating Operational Planning: Issues and Challenges. In: Proc. of the 25th International Conference on Electricity Distribution (CIRED 2019): . Paper presented at 25th International Conference on Electricity Distribution (CIRED 2019); Madrid, Spain; 3-6 June, 2019. AIM, Article ID 1957.
Åpne denne publikasjonen i ny fane eller vindu >>Dynamic Line Rating Operational Planning: Issues and Challenges
2019 (engelsk)Inngår i: Proc. of the 25th International Conference on Electricity Distribution (CIRED 2019), AIM , 2019, artikkel-id 1957Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

Network operational planning aims to provide smart and cost effective solutions to postpone conventional transmission and sub-transmission expansion. One emerging measure of improving the efficiency of power lines utilization is Dynamic Line Rating (DLR). DLR has to deal with different uncertainties ranging from production and consumption to meteorological variabilities. This paper presents the application of DLR from operational planning viewpoints and reviews relevant works. It also addresses DLR protection and challenges that the power system has to cope with.

sted, utgiver, år, opplag, sider
AIM, 2019
Serie
CIRED Conference Proceedings, E-ISSN 2032-9644
HSV kategori
Forskningsprogram
Elkraftteknik
Identifikatorer
urn:nbn:se:ltu:diva-75400 (URN)978-2-9602415-0-1 (ISBN)
Konferanse
25th International Conference on Electricity Distribution (CIRED 2019); Madrid, Spain; 3-6 June, 2019
Prosjekter
Stochastic Models for Future Smart Electricity of Transmission Gid
Tilgjengelig fra: 2019-08-06 Laget: 2019-08-06 Sist oppdatert: 2020-02-07bibliografisk kontrollert
Ahmed, K. M., Sutaria, J., Bollen, M. & Rönnberg, S. (2019). Electrical Energy Consumption Model of Internal Components in Data Centers. In: : . Paper presented at 2019 IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe). Bucharest, Romania: IEEE
Åpne denne publikasjonen i ny fane eller vindu >>Electrical Energy Consumption Model of Internal Components in Data Centers
2019 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

In the context of modern information technology (IT) industry, cloud computing is gaining popularity for big data handling. Therefore, IT service providers like Google, Facebook and Amazon are expanding their technical resources by building data centers to improve the data processing and data storage facilities under cloud service pattern. However, data centers consume a large amount of electrical energy. In recent years, a lot of research has been done to reduce the electrical energy consumption of data centers by high performance computing. However, very few researchers have focused on the electrical energy consumption by the electrical components inside the data center. In this paper, a component based electrical energy consumption modelling approach is presented to identify the losses of different components as well as their interactions to the total electrical energy consumption of the data center. The electrical energy consumption models of servers and other components are presented as a function of server utilization.

sted, utgiver, år, opplag, sider
Bucharest, Romania: IEEE, 2019
Emneord
server utilization, component loss modelling, PDU and UPS, data center
HSV kategori
Forskningsprogram
Elkraftteknik
Identifikatorer
urn:nbn:se:ltu:diva-76858 (URN)10.1109/ISGTEurope.2019.8905595 (DOI)
Konferanse
2019 IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe)
Prosjekter
Data center innovation
Tilgjengelig fra: 2019-11-25 Laget: 2019-11-25 Sist oppdatert: 2019-11-25
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0003-4074-9529