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On the supraharmonics in single-phase and three-phase installations
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.ORCID iD: 0000-0001-5558-7708
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Society has increasingly started depending on the continuity of internet services, the interruption can be crucial for vital societal functions. It is therefore important to maintain continuous and reliable operations of e.g., installations housing sensitive IT (Information Technology) loads. The establishment of a data center attracts huge investments, thereby boosting the economy. The electrical load within the data center is more structured with a similar type of load, i.e., power supplies supplying the servers connected repetitively. They also use power-conditioning equipment such as an uninterruptible power supply (UPS), which ensures uninterrupted power to the servers. The power supplies use switching techniques to modulate and condition the power supplied to the IT load. The switching residues from the power supplies are often in the frequency range from 2 kHz to 150 kHz, known as supraharmonics. The switching frequency of power electronic converters and power line communication are identified as the main contributors to supraharmonics. The increase in the number of power electronic converters in the power system has sparked interest in supraharmonics. Limited standards are available on the magnitude of supraharmonics allowed in the system. For installations that house multiple power converters, prior knowledge about the propagation and consequences of the supraharmonics can be an advantage in increasing their reliability. This work is focused on supraharmonics within data centers, but the results of the study can be applied to other installations.

The data centers are usually three-phase installations where single-phase devices, i.e., servers are distributed over three phases. To understand the holistic view of the system, it is important to understand the spread of supraharmonics in phase, neutral, and protective earth conductors. A perspective on the behaviour of supraharmonics in three-phase installation is presented in this work. The focal point of the work is the summation of supraharmonics in the neutral conductor and conductor crosstalk. The behaviour of the device connected in single-phase installation and when the same devices are spread over three phases may differ depending on the design of the installation. Since the focus is on a greater number of devices, analysis for the change in the magnitude of supraharmonics in a neutral conductor with the change in the number of devices is also undertaken. The IT workload in a data center changes continuously, thus a constant unbalance in the electrical load between the three phases can exist. The thesis aims to understand the factors influencing the change in supraharmonic magnitude and propagation in phase and neutral conductors according to a balanced and unbalanced voltage supply and loading conditions. The presence of a supraharmonic emitting load in one phase can cause interference on the adjacent phase due to conductor crosstalk. Crosstalk leads to the propagation of supraharmonics between the phases. The work focuses on the parameters influencing the crosstalk phenomena for supraharmonics. Among the parameters studied, the type of cable used in an installation and the cable length is dominating. The measurement of supraharmonic emission from the device connected as single-phase and connected as three-phase would differ because of crosstalk.

A large number of servers in data centers connected close by may lead to an increased leakage current. The composite leakage current can comprise subharmonics, harmonics, and supraharmonics. This can cause unwanted tripping of the residual current device (RCD), which is installed for human protection. The work aims to understand the impact of the composite residual current on the operation of the residual current devices.

The main contributions of this work are summarized as:

• A sensitivity analysis is presented based on the parameters impacting the propagation of supraharmonics for different operating modes of a UPS.

• A characterization of supraharmonics emission from different devices according to their time and frequency varying behaviour.

• A mathematical model to predict the change in the supraharmonic emission in the neutral conductor.

• An increased understanding of the behaviour of supraharmonics for constant powerloads under voltage reduction conditions in three-phase installations.

• Introduction and definition of the terms induced primary emission and induced secondary emission to explain conductor crosstalk for supraharmonic emission.

• A mathematical model to show the factors influencing the magnitude of induced primary emission and induced secondary emission.

• The frequency response of RCDs of type AC, A, B, and F under residual currents comprising pure tones and composite currents is presented by measurements andmodeling.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2023. , p. 70
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-96668ISBN: 978-91-8048-321-6 (print)ISBN: 978-91-8048-322-3 (electronic)OAI: oai:DiVA.org:ltu-96668DiVA, id: diva2:1751854
Public defence
2023-05-30, Hörsal A, Luleå tekniska universitet, Skellefteå, 09:00 (English)
Opponent
Supervisors
Available from: 2023-04-20 Created: 2023-04-19 Last updated: 2023-09-05Bibliographically approved
List of papers
1. Supraharmonics within a Datacenter-Emission and Propagation
Open this publication in new window or tab >>Supraharmonics within a Datacenter-Emission and Propagation
2022 (English)In: 2022 20th International Conference on Harmonics & Quality of Power (ICHQP) Proceedings: “Power Quality in the Energy Transition”, IEEE, 2022Conference paper, Published paper (Refereed)
Abstract [en]

The reliability of the electrical and cooling systems is of utmost importance for the uninterrupted operation of the data center information technology (IT) load. The electrical distribution of the data center includes many subsystems starting with the utility and building transformers, uninterruptible power supply (UPS), power distribution units (PDUs), and power supplies ultimately powering the fans and the internal components of IT equipment. The various converters in data centers emit switching frequency residue due to PWM (pulse width modulation) techniques. The switching frequency range falls within the supraharmonic range, i.e., 2 to 150 kHz. This paper aims to show, with measurements, the different types of supraharmonic emissions measured in the data center, and the difference between their maximum and average magnitudes. The paper shows a method to identify the equipment emitting supraharmonic emission and possible disturbances caused by it. The paper traces the propagation of supraharmonic emission from the source through the transformer to the grid. Lastly, a comparison of measurements is made with the compatibility levels given by standard IEC 61000-2-2.

Place, publisher, year, edition, pages
IEEE, 2022
Series
International Conference on Harmonics and Quality of Power, ISSN 1540-6008, E-ISSN 2164-0610
Keywords
Data center, Information technology, Power quality, Power supplies, Pulse Width Modulation, Supraharmonics
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Energy Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-92095 (URN)10.1109/ICHQP53011.2022.9808561 (DOI)000844604500029 ()2-s2.0-85133789667 (Scopus ID)
Conference
20th International Conference on Harmonics & Quality of Power (ICHQP 2022), Naples, Italy, May 29 - June 1, 2022
Funder
Swedish Energy Agency, 43090-2
Note

ISBN för värdpublikation: 978-1-6654-1639-9

Available from: 2022-07-07 Created: 2022-07-07 Last updated: 2023-09-05Bibliographically approved
2. Propagation of supraharmonics in a data center with different operating modes of UPS
Open this publication in new window or tab >>Propagation of supraharmonics in a data center with different operating modes of UPS
2023 (English)In: IEEE Access, E-ISSN 2169-3536, Vol. 11, p. 36823-36833Article in journal (Refereed) Published
Abstract [en]

A data center is a major hub of different converters ensuring continuous power to the server loads. The pulse width modulation switching techniques with frequency emission from 2 to 150 kHz (i.e., supraharmonics) in these converters call for a study of the magnitude and propagation of this emission within data centers where UPS is one of the main contributors of supraharmonics. The paper shows, with measurements and model, the change in magnitude and propagation of supraharmonics with the change in the operating mode of the UPS. The magnitude of supraharmonics shows a non-linear dependency on the power consumed in the online mode. In bypass mode, the magnitude of supraharmonics shows a dependency on the type of load connected. The filter connected between PE-N at the input side of the UPS can cause resonance in the phase conductors. The results show that to study the emission, immunity, and electromagnetic compatibility of supraharmonics for UPS, the factors such as operating mode, the type of load connected, and the input and output impedance need to be considered.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2023
Keywords
Data center, electromagnetic compatibility, power quality, power conditioning, uninterruptible power supply, pulse width modulation, resonance, supraharmonics
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-96639 (URN)10.1109/access.2023.3266092 (DOI)000975054100001 ()2-s2.0-85153356418 (Scopus ID)
Funder
Swedish Energy Agency, 43090-2
Note

Validerad;2023;Nivå 2;2023-07-04 (hanlid)

Available from: 2023-04-17 Created: 2023-04-17 Last updated: 2023-09-05Bibliographically approved
3. Summation of Supraharmonics in Neutral for Three-Phase Four-Wire System
Open this publication in new window or tab >>Summation of Supraharmonics in Neutral for Three-Phase Four-Wire System
2020 (English)In: IEEE Open Journal of Industry Applications, E-ISSN 2644-1241, Vol. 1, p. 148-156Article in journal (Refereed) Published
Abstract [en]

Due to the increase in electronic loads such as LED lamps, power supply units for computing loads, voltage frequency drives in industries; high-frequency distortion is introduced into the power system. These high-frequency components appear due to the switching components of different power electronic converters present in the mentioned loads. The switching frequency components are most often in the range of 2 kHz to 150 kHz referred to as supraharmonics. The paper aims to show, with simulations and measurements, how supraharmonics sum in neutral and to quantify the neutral supraharmonic current as a ratio of single-phase current. This paper defines characteristics of supraharmonic emission that influence their summation in the neutral conductor through studies of devices connected in a balanced three-phase four-wire system. The paper further defines the relation of the supraharmonics emission with the number of devices connected at each phase. A mathematical model to predict the supraharmonics in a neutral conductor based on single-phase current and the number of devices further proposed.

Place, publisher, year, edition, pages
IEEE, 2020
Keywords
Power quality, Pulse width modulation, Neutral conductor, Supraharmonics
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-81005 (URN)10.1109/OJIA.2020.3026753 (DOI)001089202300012 ()2-s2.0-85104956504 (Scopus ID)
Note

Godkänd;2020;Nivå 0;2020-11-10 (alebob)

Available from: 2020-10-02 Created: 2020-10-02 Last updated: 2024-03-07Bibliographically approved
4. Analysis of supraharmonics in a three-phase frame
Open this publication in new window or tab >>Analysis of supraharmonics in a three-phase frame
2022 (English)In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 203, article id 107668Article in journal (Refereed) Published
Abstract [en]

Interaction in the supraharmonic range of 1-ϕ device connected in 1-ϕ or 3-ϕ installations will differ according to the design of the installation. Power factor corrected devices employing switched mode power supplies produce supraharmonics in the range 2–150 kHz. The impact of e.g. voltage unbalance, load unbalance and conductor crosstalk on supraharmonics from these devices connected in a 3-ϕ installation are still somewhat unknown. The paper aims to show with measurements and mathematical models the impact of voltage unbalance, load unbalance, and conductor crosstalk on supraharmonics. The impact of voltage unbalance for constant power loads was seen to increase the emission of supraharmonics. Two new terms induced primary and induced secondary emission showing the impact of conductor crosstalk have been introduced. The induced primary emission leads to an increase in the self-emission of the device. The induced secondary emission on the other hand influences the propagation of the emission. The impact of the voltage unbalance, load unbalance, and conductor crosstalk on the addition of supraharmonics emission in the neutral conductor is shown.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Load unbalance, Neutral conductor, Power quality, Supraharmonics, Switching frequency, Voltage unbalance
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-87953 (URN)10.1016/j.epsr.2021.107668 (DOI)000744268600005 ()2-s2.0-85119262879 (Scopus ID)
Funder
Swedish Energy Agency, 43090-2
Note

Validerad;2021;Nivå 2;2021-11-19 (beamah)

Available from: 2021-11-19 Created: 2021-11-19 Last updated: 2023-09-05Bibliographically approved
5. Factors influencing the induced primary emission and induced secondary emission in the frequency range of 2 to 150 kHz
Open this publication in new window or tab >>Factors influencing the induced primary emission and induced secondary emission in the frequency range of 2 to 150 kHz
2023 (English)In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 224, article id 109725Article in journal (Refereed) Published
Abstract [en]

The induced primary emission leads to changes in the primary emission of a device and the induced secondary emission leads to changes in the propagation of supraharmonics in the adjacent phase due to the connection of single-phase loads spread over three phases in an installation. The induced primary emission and induced secondary emission are shown to give a significant contribution to the total emission measured at a given point in an installation. The induction of the emission is caused by the inductive and capacitive coupling among the conductors within the cables. This paper presents an analysis of four parameters that impact the magnitude of the induced emissions. Simulations carried out in COMSOL, show that the type of cable used impacts the induced emission and studies show that shielded cable with a stranded conductor with the shield grounded will lead to a reduction in the induced emissions. Among the other parameters, i.e., the load and transformer impedance and the length of the cable, the length of the cable is dominating in deciding the magnitude of the induced emissions. Analysis is carried out using Monte Carlo simulation and varying parameters stochastically. For all investigated parameters there is a strong frequency dependency. The stochastic variation of the load impedance in one phase causes a variation of 5% whereas the change in length of the cable leads to a maximum 40% variation in the considered frequency range for induced primary emission. Measurement results are presented to validate the results.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Crosstalk, inductive coupling, power quality, supraharmonics, primary emission, secondary emission
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-96640 (URN)10.1016/j.epsr.2023.109725 (DOI)001050923700001 ()2-s2.0-85165970374 (Scopus ID)
Funder
Swedish Energy Agency, 43090-2
Note

Validerad;2023;Nivå 2;2023-08-07 (joosat);

Licens fulltext: CC BY License

This article has previously appeared as a manuscript in a thesis.

Available from: 2023-04-17 Created: 2023-04-17 Last updated: 2024-03-07Bibliographically approved
6. Measurements and modeling of the frequency behavior of residual current devices- from 4 Hz to 40 kHz
Open this publication in new window or tab >>Measurements and modeling of the frequency behavior of residual current devices- from 4 Hz to 40 kHz
2022 (English)In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 209, article id 108052Article in journal (Refereed) Published
Abstract [en]

Residual current devices (RCDs) are a common means of protection against shock due to indirect contact in low voltage (LV) systems. Due to the increasing penetration of power electronics equipment in LV systems, higher amounts of waveform distortion at a broad range of frequencies, from dc, subharmonics up to hundreds of kHz (supraharmonics), are expected to be present both during normal operation and during faults. The standardization committees and manufacturers have responded to this challenge by proposing different types of RCDs that are expected to function under given conditions of fault current waveform. However, subharmonic and supraharmonic frequency components are not considered in the standards for most of the RCD types. This article studies the effect of these frequency components on RCDs type AC, A, B and F. An assessment is made in terms of two types of RCD failure: blinding and nuisance tripping, for which both magnitude of the current and breaking time is considered. A frequency mapping of the RCDs is performed, and an assessment of these results based on the frequency-dependent response of the human body to currents is performed. Finally, a frequency model for RCDs type A, F and B is developed.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Frequency response, Harmonics, Leakage current, Power quality, Residual current devices, Supraharmonics
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electric Power Engineering
Identifiers
urn:nbn:se:ltu:diva-90583 (URN)10.1016/j.epsr.2022.108052 (DOI)000797729900001 ()2-s2.0-85129532678 (Scopus ID)
Funder
Swedish Energy Agency
Note

Validerad;2022;Nivå 2;2022-05-09 (sofila);

Funder: Energiforsk

Available from: 2022-05-09 Created: 2022-05-09 Last updated: 2023-09-05Bibliographically approved

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