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Sudha Letha, S., Bollen, M. H. J., Busatto, T., Espin Delgado, A., Mulenga, E., Bakhtiari, H., . . . Ravindran, V. (2023). Power Quality Issues of Electro-Mobility on Distribution Network—An Overview. Energies, 16(13), Article ID 4850.
Open this publication in new window or tab >>Power Quality Issues of Electro-Mobility on Distribution Network—An Overview
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2023 (English)In: Energies, E-ISSN 1996-1073, Vol. 16, no 13, article id 4850Article, review/survey (Refereed) Published
Abstract [en]

The journey towards sustainable transportation has significantly increased the grid penetration of electric vehicles (EV) around the world. The connection of EVs to the power grid poses a series of new challenges for network operators, such as network loading, voltage profile perturbation, voltage unbalance, and other power quality issues. This paper presents a coalescence of knowledge on the impact that electro-mobility can impose on the grid, and identifies gaps for further research. Further, the study investigates the impact of electric vehicle charging on the medium-voltage network and low-voltage distribution network, keeping in mind the role of network operators, utilities, and customers. From this, the impacts, challenges, and recommendations are summarized. This paper will be a valuable resource to research entities, industry professionals, and network operators, as a ready reference of all possible power quality challenges posed by electro-mobility on the distribution network.

Place, publisher, year, edition, pages
MDPI, 2023
Keywords
electric vehicle, harmonics, light flicker, power quality, voltage unbalance
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-99488 (URN)10.3390/en16134850 (DOI)001028620400001 ()2-s2.0-85164930081 (Scopus ID)
Funder
Swedish Energy Agency, 47904-1
Note

Validerad;2023;Nivå 2;2023-08-11 (hanlid)

Available from: 2023-08-11 Created: 2023-08-11 Last updated: 2023-09-05Bibliographically approved
Nakhodchi, N., Ravindran, V., Bollen, M. & Rönnberg, S. (2021). Application of Transfer Function Method in a Wind Park for Harmonic Study. In: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution: . Paper presented at 26th International Conference and Exhibition on Electricity Distribution (CIRED), Online, September 20-23, 2021 (pp. 723-727). Institution of Engineering and Technology, Article ID 0135.
Open this publication in new window or tab >>Application of Transfer Function Method in a Wind Park for Harmonic Study
2021 (English)In: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution, Institution of Engineering and Technology , 2021, p. 723-727, article id 0135Conference paper, Published paper (Refereed)
Abstract [en]

Harmonic emission from a wind park to the grid and the interaction between individual turbines within a wind park are among the power quality challenges that have been studied for many years, as part of the connection of wind parks to the grid. Different methods are proposed and various simulation models are developed under some assumptions. This paper presents the results from a transfer function based model for an existing wind park, and investigates the impact of LV load modelling (residential customers) and MV cable capacitance on the interaction between turbines and between turbines and the grid. It is shown that LV loads and MV cable capacitance can have significant impact on the interactions between turbines and grid while it has only limited impact on interactions between turbines.

Place, publisher, year, edition, pages
Institution of Engineering and Technology, 2021
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-96608 (URN)10.1049/icp.2021.1889 (DOI)978-1-83953-591-8 (ISBN)
Conference
26th International Conference and Exhibition on Electricity Distribution (CIRED), Online, September 20-23, 2021
Available from: 2023-04-17 Created: 2023-04-17 Last updated: 2023-09-05Bibliographically approved
Ravindran, V., Nakhodchi, N., Rönnberg, S. & Bollen, M. H. J. (2021). Assessing time-varying harmonic interactions in a wind park. IEEE Access, 9, 68151-68160
Open this publication in new window or tab >>Assessing time-varying harmonic interactions in a wind park
2021 (English)In: IEEE Access, E-ISSN 2169-3536, Vol. 9, p. 68151-68160Article in journal (Refereed) Published
Abstract [en]

The harmonic interaction mechanism in a wind park is examined in this paper. The paper investigates the feasibility of a solution to the yet challenging harmonic contribution estimation from multiple sources in a wind park with limited available information, via an extension of a simple modeling approach as well as from detailed analysis of field measurements. The paper has two distinct objectives in assessing harmonic interactions (a) one to extend the classical Norton equivalent model to a multi-measurement wind park system and to suggest potential areas for further model developments from field measurement analysis, and (b) second to draw inferences from field measurements and to develop a new independent concept of analysis from long-term field measurements in the wind park. From practical experience, a new concept of analysis with a ‘harmonic interaction break-even point’ is introduced. With the help of it, one could identify whether the primary emission (emission from considered source) or secondary emission (emission from a distant source) dominates in the analysis period. In this way, the highest responsibility between different interacting time-varying harmonic sources is evaluated. It was concluded that from long-term measurements one can define a magnitude of power production where a certain harmonic order is canceled or reaches its lowest magnitude. If one finds this cancellation point, one can define a level of secondary/primary emission or at least a feasible range. This knowledge is a step forward towards harmonic contribution analysis.

Place, publisher, year, edition, pages
IEEE, 2021
Keywords
power quality, wind power generation, power system harmonics, interharmonics
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-83418 (URN)10.1109/ACCESS.2021.3076879 (DOI)000649566600001 ()2-s2.0-85105074281 (Scopus ID)
Funder
Swedish Energy Agency, 245 110
Note

Validerad;2021;Nivå 2;2021-05-17 (alebob)

Available from: 2021-03-26 Created: 2021-03-26 Last updated: 2023-09-05Bibliographically approved
de Oliveira, R. A., Ravindran, V., Rönnberg, S. & Bollen, M. (2021). Deep Learning For Pattern Recognition Of Interharmonics In Time-Series And Spectrograms. In: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution: . Paper presented at 26th International Conference and Exhibition on Electricity Distribution (CIRED 2021), Online, September 20-23, 2021 (pp. 738-741).
Open this publication in new window or tab >>Deep Learning For Pattern Recognition Of Interharmonics In Time-Series And Spectrograms
2021 (English)In: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution, 2021, p. 738-741Conference paper, Published paper (Refereed)
Abstract [en]

This work applies an unsupervised deep feature learning to finding patterns of interharmonics. The main objectives of this work are to provide an additional graphical tool to handle two distinct data inputs: (a) individual interharmonics components in time-series; (b) broadband spectrum by employing spectrograms. Both data inputs are analysed employing an autoencoder based on convolutional neural networks followed by clustering. The application of the method results in the most common patterns in time-series or spectrograms. Two study cases are presented by applying the method to measurements from solar installations in Finland and Sweden. The results show the usefulness of the method to recognize interharmonics in a single frequency and broadband spectrum.

Keywords
Deep Learning, Power Quality, Pattern Recognition, Interharmonics
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-92470 (URN)10.1049/icp.2021.1930 (DOI)
Conference
26th International Conference and Exhibition on Electricity Distribution (CIRED 2021), Online, September 20-23, 2021
Note

ISBN för värdpublikation: 978-1-83953-591-8 (elektroniskt)

Available from: 2022-08-15 Created: 2022-08-15 Last updated: 2023-09-05Bibliographically approved
de Oliveira, R. A., Ravindran, V., Rönnberg, S. K. & Bollen, M. H. .. (2021). Deep Learning Method With Manual Post-Processing for Identification of Spectral Patterns of Waveform Distortion in PV Installations. IEEE Transactions on Smart Grid, 12(6), 5444-5456
Open this publication in new window or tab >>Deep Learning Method With Manual Post-Processing for Identification of Spectral Patterns of Waveform Distortion in PV Installations
2021 (English)In: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061, Vol. 12, no 6, p. 5444-5456Article in journal (Refereed) Published
Abstract [en]

This paper proposes a deep learning (DL) method for the identification of spectral patterns of timevarying waveform distortion in photovoltaic (PV) installations. The PQ big data with information on harmonic and/or interharmonics in PV installations is handled by a deep autoencoder followed by feature clustering. Measurements of voltage and current from four distinct PV installations are used to illustrate the method. This paper shows that the DL method can be used as a starting point for further data analysis. The main contributions of the paper include: (a) providing a novel DL method for finding patterns in spectra; (b) guiding the manual post-processing based on the patterns found by the DL method; and (c) obtaining information about the emission from four PV installations.

Place, publisher, year, edition, pages
IEEE, 2021
Keywords
power quality, power system harmonics, electric power distribution, interharmonics, pattern analysis, unsupervised learning, deep learning, solar power
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-83447 (URN)10.1109/TSG.2021.3107908 (DOI)000709090100078 ()2-s2.0-85114608265 (Scopus ID)
Funder
Swedish Energy Agency, 245 110
Note

Validerad;2021;Nivå 2;2021-11-08 (johcin)

Available from: 2021-03-30 Created: 2021-03-30 Last updated: 2023-09-05Bibliographically approved
Bollen, M. H., Rönnberg, S. K., Schwanz, D., Nakhodchi, N. & Ravindran, V. (2021). Harmonics and Wind Power Installations. In: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution: . Paper presented at 26th International Conference and Exhibition on Electricity Distribution (CIRED 2021), [DIGITAL], September 20-23,2021 (pp. 648-652). IEEE, Article ID 0028.
Open this publication in new window or tab >>Harmonics and Wind Power Installations
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2021 (English)In: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution, IEEE, 2021, p. 648-652, article id 0028Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
IEEE, 2021
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-103542 (URN)10.1049/icp.2021.1768 (DOI)2-s2.0-85166929396 (Scopus ID)
Conference
26th International Conference and Exhibition on Electricity Distribution (CIRED 2021), [DIGITAL], September 20-23,2021
Funder
Swedish Energy AgencyEnergy Research
Note

Funder:  AREVA T&D; Skellefteå Kraft;

ISBN for host publication: 978-1-83953-591-8;

Available from: 2024-01-10 Created: 2024-01-10 Last updated: 2024-02-06Bibliographically approved
Löfgren, I., Ravindran, V. & Rönnberg, S. (2021). Interharmonics under Fundamental Frequency Variations. In: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution: . Paper presented at 26th International Conference and Exhibition on Electricity Distribution (CIRED 2021), [DIGITAL], September 20-23, 2021 (pp. 658-662). IEEE, Article ID 0048.
Open this publication in new window or tab >>Interharmonics under Fundamental Frequency Variations
2021 (English)In: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution, IEEE, 2021, p. 658-662, article id 0048Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
IEEE, 2021
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Signal Processing
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-103545 (URN)10.1049/icp.2021.1787 (DOI)2-s2.0-85174648089 (Scopus ID)
Conference
26th International Conference and Exhibition on Electricity Distribution (CIRED 2021), [DIGITAL], September 20-23, 2021
Note

ISBN for host publication: 978-1-83953-591-8

Available from: 2024-01-10 Created: 2024-01-10 Last updated: 2024-02-08Bibliographically approved
Ravindran, V. (2021). Time-varying Waveform Distortion in Low voltage network. (Doctoral dissertation). Skellefteå: Luleå University of Technology
Open this publication in new window or tab >>Time-varying Waveform Distortion in Low voltage network
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The progressive advancement in new technologies has introduced new types of equipment into the grid. Some of these devices, which have gained significant popularity in the last few decades are photovoltaic (PV) systems and wind power systems from the generation side, and energy-efficient lighting i.e. LED lamps and energy-efficient transportation via electric vehicles from the consumption side. All these equipment essentially consist of different kinds of power electronic converters with their associated control systems. There is always feasibility of mutual interactions between these non-linear power electronic devices with the grid as well as with other grid-connected equipment placed electrically close to each other, where the control loops can face new system dynamics. Adverse interactions can cause interferences and in the worst-case lead to instability issues. A mapping of the potential interactions, in the form of emission is needed to understand interferences at the device level and system level. The overall aim of this work is to enhance the existing knowledge about the power quality aspects of the different non-linear power electronic devices that are being increasingly connected to the grid especially in low voltage networks. The conclusions derived from this study can be extended to a broader scale where there is the feasibility of multiple non-linear power electronic-based devices operating together at medium and high voltage levels.

The main contributions of the work are classified into three main parts: 

In the first part, an in-depth study of interharmonics in PV systems is carried out. Different sets of field measurements and measurements from controlled but realistic laboratory environments are investigated for interharmonic existence, persistence, and propagation. To ensure the genuinity of the observed interharmonics and to address the different challenges associated with their estimation, combinations of methods are applied and results compared. The possible reasons for their origin are systematically established through a comprehensive study. The potential system impacts which it could create in the grid and to other grid-connected equipment are investigated. The possibility for aggregation of interharmonics when multiple sources are connected to the same point of common coupling is explored via a statistical approach.

In the second part, initially harmonic interactions in wind parks, and between PV and LED lamps, are first discussed. The time-varying harmonic interaction phenomenon is studied in detail with the help of a mathematical model as well as with the help of analysis of field measurements at multiple locations of a wind park. The outcome of this study contributes to the yet challenging problem of harmonic contribution estimation in twofold. (a) A method is developed from long-term field measurements with which one could potentially identify which source of emission dominates in the analysis period, and (b) Limitations of the extended mathematical model are identified and inferences from field measurements are linked to further improve the mathematical model. Further, some specific cases of harmonic interactions between PV and LED lamps are illustrated. These examples could be a guidance for power electronic designers to increase individual device immunity subjected to harmonic interferences.

Additionally in the same part, the impact of PV induced voltage variations on different topologies of LED lamps are investigated. The considered voltage variations are distinguished as overvoltage, undervoltage, rapid voltage changes, and voltage steps due to fast-moving cloud transients, due to inverter operation itself, and due to voltage regulations caused by load tap changing operations of distribution transformers. Due to PV induced voltage variations, LED lamps are impacted in various ways. LED lamps are either potential victims of these voltage variations or LED lamps to act as sources of increased grid distortions. As potential victims, the studied LED lamps have shown changes in the light output, instability issues, and degradation in the driver efficiency. As potential sources of grid distortion, LED lamps have exhibited increased harmonic and interharmonic emissions. The difference in impact has been linked to the topology of the lamps.

In the third part, the application of a deep leaning based unsupervised machine learning method to extract waveform distortion patterns in big data for enhancing power quality knowledge is illustrated. Specifically, signal processing of interharmonics with precise frequency and amplitude estimation needs the processing of data of large volume for a higher resolution. Thus, the interharmonics analysis in long-term measurements evidences the need for an automatic tool to assist the experts. In this work, a deep learning method for the identification of spectral patterns of time-varying waveform distortion in photovoltaic installations is proposed. The PQ big data with information on harmonic and/or interharmonics in PV installations is handled by a deep autoencoder followed by feature clustering. Measurements of voltage and current from four distinct PV installations are used to illustrate the method. The proposed method accelerates the process of manual interpretation and is a starting point to determine how to proceed further with the data analysis.

Place, publisher, year, edition, pages
Skellefteå: Luleå University of Technology, 2021. p. 100
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
Interharmonics, Harmonic interactions, Voltage variations, Deep learning
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-83416 (URN)978-91-7790-795-4 (ISBN)978-91-7790-796-1 (ISBN)
Public defence
2021-05-26, Hörsal A, Skellefteå samt zoom, Skellefteå, 16:30 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency, 245 110
Available from: 2021-03-30 Created: 2021-03-30 Last updated: 2023-09-05Bibliographically approved
Ravindran, V., Sakar, S., Rönnberg, S. & Bollen, M. (2020). Characterization of the impact of PV and EV induced voltage variations on LED lamps in a low voltage installation. Electric power systems research, 185, Article ID 106352.
Open this publication in new window or tab >>Characterization of the impact of PV and EV induced voltage variations on LED lamps in a low voltage installation
2020 (English)In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 185, article id 106352Article in journal (Refereed) Published
Abstract [en]

Photovoltaic (PV) systems, Electric vehicles (EV) and LED lamps have gained significant popularity in our current society. It is therefore common to find customer installations with all three operating together. PV and EV are known sources of voltage variations on the grid. The impact of these voltage variations on LED lamps situated in close proximity to PV or EV in a low voltage installation, in terms of overvoltage, undervoltage, and rapid voltage changes is systematically studied in a laboratory environment in this paper. Such variations can cause malfunctioning of the lamp based on its immunity and tolerance level or be disturbing to the end-user based on the intensity of variations and rate of recurrence of being subjected to such variations. In this work, the observed impacts on LED lamps are illustrated as 15 different cases. The scope of this work is to identify the possible impacts due to voltage variations induced by PV and EV systems on LED lamps and the potential problems that could happen long term due to recurrent subjection of such voltage variations.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Electric vehicle, LED lamps, Light emitting diodes, Photovoltaic systems, Harmonic analysis, Power quality, Voltage variations
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-78984 (URN)10.1016/j.epsr.2020.106352 (DOI)000540159500007 ()2-s2.0-85085199499 (Scopus ID)
Note

Validerad;2020;Nivå 2;2020-05-26 (johcin)

Available from: 2020-05-26 Created: 2020-05-26 Last updated: 2023-09-05Bibliographically approved
Busatto, T., Ravindran, V., Larsson, A., Rönnberg, S., Bollen, M. & Meyer, J. (2020). Deviations between the commonly-used model and measurements of harmonic distortion in low-voltage installations. Electric power systems research, 180, Article ID 106166.
Open this publication in new window or tab >>Deviations between the commonly-used model and measurements of harmonic distortion in low-voltage installations
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2020 (English)In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 180, article id 106166Article in journal (Refereed) Published
Abstract [en]

Harmonic analysis studies of modern power systems commonly employ Norton and Thévenin equivalents at harmonic frequencies for the nonlinear devices. This approach neglects the so-called nonlinear interaction phenomenon. This paper addresses the difference between the results from the commonly-used model and the actual harmonic distortion measured in a low-voltage installation. A number of indices are introduced to quantify the nonlinear interaction. These indices allow a quantification of the extent to which the commonly-used model is also to predict harmonic voltages and currents in a modern low-voltage installation. The proposed model and the subsequent mathematical analysis are illustrated through measurements from different combinations of PV inverters and LED lamps using different technologies. The results show that deviation is dependent on the used technology, network impedance, and source voltage waveform. Other findings are that nonlinear interaction happens mainly in the low harmonic orders and impacts are more perceived on the harmonics phase angle. Possible explanations for these observations are discussed.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Power quality, Power system harmonics, Power electronics, Harmonic analysis, Nonlinear systems
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-77661 (URN)10.1016/j.epsr.2019.106166 (DOI)000514015200052 ()2-s2.0-85076840939 (Scopus ID)
Funder
Swedish Energy Agency
Note

Validerad;2020;Nivå 2;2020-03-03 (alebob)

Available from: 2020-02-06 Created: 2020-02-06 Last updated: 2023-09-05Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-3587-7879

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