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Summation of Supraharmonics in Neutral for Three-Phase Four-Wire System
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.ORCID-id: 0000-0001-5558-7708
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.ORCID-id: 0000-0001-6074-8633
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.ORCID-id: 0000-0002-4004-0352
2020 (Engelska)Ingår i: IEEE Open Journal of Industry Applications, E-ISSN 2644-1241, Vol. 1, s. 148-156Artikel i tidskrift (Refereegranskat) 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.

Ort, förlag, år, upplaga, sidor
IEEE, 2020. Vol. 1, s. 148-156
Nyckelord [en]
Power quality, Pulse width modulation, Neutral conductor, Supraharmonics
Nationell ämneskategori
Annan elektroteknik och elektronik
Forskningsämne
Elkraftteknik
Identifikatorer
URN: urn:nbn:se:ltu:diva-81005DOI: 10.1109/OJIA.2020.3026753ISI: 001089202300012Scopus ID: 2-s2.0-85104956504OAI: oai:DiVA.org:ltu-81005DiVA, id: diva2:1472588
Anmärkning

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

Tillgänglig från: 2020-10-02 Skapad: 2020-10-02 Senast uppdaterad: 2024-03-07Bibliografiskt granskad
Ingår i avhandling
1. On the supraharmonics in single-phase and three-phase installations
Öppna denna publikation i ny flik eller fönster >>On the supraharmonics in single-phase and three-phase installations
2023 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Luleå: Luleå University of Technology, 2023. s. 70
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Nationell ämneskategori
Annan elektroteknik och elektronik
Forskningsämne
Elkraftteknik
Identifikatorer
urn:nbn:se:ltu:diva-96668 (URN)978-91-8048-321-6 (ISBN)978-91-8048-322-3 (ISBN)
Disputation
2023-05-30, Hörsal A, Luleå tekniska universitet, Skellefteå, 09:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2023-04-20 Skapad: 2023-04-19 Senast uppdaterad: 2023-09-05Bibliografiskt granskad

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