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Publications (8 of 8) Show all publications
Eslamian, M., Kharezy, M. & Thiringer, T. (2019). Calculation of the leakage inductance of medium frequency transformershaving rectangular-shaped windings using an accurate analytical method. In: 2019 21st European Conference on Power Electronics and Applications (EPE '19 ECCE Europe): . Paper presented at EPE2019, 21st European Conference on Power Electronics and Applications, Genova, Italy.
Open this publication in new window or tab >>Calculation of the leakage inductance of medium frequency transformershaving rectangular-shaped windings using an accurate analytical method
2019 (English)In: 2019 21st European Conference on Power Electronics and Applications (EPE '19 ECCE Europe), 2019Conference paper, Published paper (Refereed)
Abstract [en]

To achieve the lowest loss by the Zero-Voltage Switching of a Dual Active Bridge converter, it is crucial to precisely calculate the embedded Leakage Inductance of the used Medium Frequency Transformer (MFT). An effective analytical method is proposed for calculation of the leakage inductance of the MFT with rectangular-shaped windings

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:ri:diva-42070 (URN)10.23919/EPE.2019.8915036 (DOI)2-s2.0-85076671554 (Scopus ID)
Conference
EPE2019, 21st European Conference on Power Electronics and Applications, Genova, Italy
Available from: 2019-12-13 Created: 2019-12-13 Last updated: 2020-02-07Bibliographically approved
Kharezy, M., Morteza, E. & Thiringer, T. (2019). Insulation Design of a Medium Frequency Power Transformer for a Cost-Effective Series High Voltage DC Collection Network of an Offshore Wind Farm. In: Proceedings of the 21st International Symposium on High Voltage Engineering: . Paper presented at The International Symposium on High Voltage Engineering 2019. (pp. 06-1417). Switzerland: Springer Publishing Company
Open this publication in new window or tab >>Insulation Design of a Medium Frequency Power Transformer for a Cost-Effective Series High Voltage DC Collection Network of an Offshore Wind Farm
2019 (English)In: Proceedings of the 21st International Symposium on High Voltage Engineering, Switzerland: Springer Publishing Company, 2019, p. 06-1417Conference paper, Published paper (Refereed)
Abstract [en]

DC can be used advantageously in transmission of power from offshore wind farms, utilizing series connection of the individual turbines’ outputs. Employing individual wind turbine converters, operating at high frequency, the advantage of DC can be achieved without the need for a large central converter. This solution obviates the need of expensive, bulky and heavy 50 Hz transformer or centralized DC/DC converter platforms.

Power electronic converters are among the enabling technologies to establish a series DC intertie system. The most important advantage of a DC/DC converter using a Medium Frequency Power Transformer (MFPT) is its compact size in comparison with a normal grid frequency transformer.

The function of a MFPT is to provide voltage step up and isolation between generators and the HVDC link. The need for a compact structure dictates further design constraints. A MFPT should have a high-power transmission capability from a small volume as well as minimal internal insolation distances. Furthermore, in the series DC integration circuit, DC/DC converters can experience a very high offset DC voltage depending on the converter’s position with respect to earth (in the range of one or two hundred kilovolts), while the primary side (wind turbine generator side) is only exposed to a few kV.

Due to its promising features, many research activities have been devoted to the design and optimization of MFPTs. However, only a few activities specifically addressed the insulation requirements for them.

Place, publisher, year, edition, pages
Switzerland: Springer Publishing Company, 2019
Keywords
HVDC transformer, Medium frequency power transformer, Power transformer insulation design, High-power.DC/DC converter, Oil-paper barrier insulation system
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:ri:diva-40594 (URN)10.1007/978-3-030-31680-8_134 (DOI)978-3-030-31679-2 (ISBN)
Conference
The International Symposium on High Voltage Engineering 2019.
Available from: 2019-11-01 Created: 2019-11-01 Last updated: 2019-12-04Bibliographically approved
Alikhanzadeh, B., Thiringer, T. & Kharezy, M. (2019). Optimum Leakage Inductance Determination for a Q2L-Operating MMC-DABwith Different Transformer Winding Configurations. In: 2019 20th International Symposium on Power Electronics (Ee): . Paper presented at 20th International Symposium on Power Electronics (Ee), Novi Sad, Serbia.
Open this publication in new window or tab >>Optimum Leakage Inductance Determination for a Q2L-Operating MMC-DABwith Different Transformer Winding Configurations
2019 (English)In: 2019 20th International Symposium on Power Electronics (Ee), 2019Conference paper, Published paper (Refereed)
Abstract [sv]

This paper discusses the procedure for the determination of the optimum leakage inductance of a medium frequency transformer (MFT) for a quasi-two-level (Q2L) operating three-phase modular multilevel converter dual-active bridge (MMC-DAB) considering the effects of the MFT winding configuration. Three different winding configurations-namely, Y-Y, D-D, and Y-D-are considered for the connection of the MFT windings. The optimum leakage inductance requirement of the MFT, the currents total harmonic distortion (THD), and the transformer utilization factor (TUF) are compared for the three winding configurations. It is found that the Y-Y and the D-D configurations have similar optimum leakage inductance patterns, which are different from the Y-D configuration. Furthermore, it is established that an optimized leakage inductance value for a conventional DAB, can be utilized for the Q2L-operating MMC-DAB for a wide range of transition time with the Y-Y and the D-D winding configurations if less than a 5% error could be tolerated in its value. A comparison with respect to the TUF and the currents THD revealed that the Y-Y and the D-D configurations result in a higher TUF compared to the Y-D configuration; However, the Y-D configuration has approximately two times lower currents THD compared to the other two configurations

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:ri:diva-42071 (URN)10.1109/PEE.2019.8923224 (DOI)2-s2.0-85077113379 (Scopus ID)
Conference
20th International Symposium on Power Electronics (Ee), Novi Sad, Serbia
Available from: 2019-12-13 Created: 2019-12-13 Last updated: 2020-02-04Bibliographically approved
Bahmani, A., Thiringer, T. & Kharezy, M. (2016). Optimization and Experimental Validation of Medium-Frequency High Power Transformers in Solid-State Transformer Applications (ed.). In: 2016 IEEE Applied Power Electronics Conference and Exposition (APEC): . Paper presented at 31st Annual IEEE Applied Power Electronics Conference and Exposition (APEC 2016), March 20-24, 2016, Long Beach, US (pp. 3043-3050).
Open this publication in new window or tab >>Optimization and Experimental Validation of Medium-Frequency High Power Transformers in Solid-State Transformer Applications
2016 (English)In: 2016 IEEE Applied Power Electronics Conference and Exposition (APEC), 2016, , p. 8p. 3043-3050Conference paper, Published paper (Other academic)
Abstract [en]

High power isolated DC-DC converters are likely to provide solutions for many technical challenges associated with power density, efficiency and reliability in potential applications such as offshore wind farms, inter-connection of DC grids, MVDC in data centers and in future solid state transformer applications. The high power medium frequency transformer (HPMFT) is one of the key elements of such a converter to realize the voltage adaption, isolation requirements, as well as high power density. This paper describes a design and optimization methodology taking into account the loss calculation, isolation requirements and thermal management. Incorporating this design methodology, an optimization process with a wide range of parameter variations is applied on a 50 kW, 1 / 3 kV, 5 kHz transformer to find the highest power density while the efficiency, isolation, thermal and leakage inductance requirements are all met. The optimized transformers are then manufactured and will be presented in this paper.

Publisher
p. 8
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-12604 (URN)10.1109/APEC.2016.7468297 (DOI)2-s2.0-84973661552 (Scopus ID)30661 (Local ID)978-1-4673-8393-6 (ISBN)978-1-4673-9550-2 (ISBN)30661 (Archive number)30661 (OAI)
Conference
31st Annual IEEE Applied Power Electronics Conference and Exposition (APEC 2016), March 20-24, 2016, Long Beach, US
Available from: 2016-09-13 Created: 2016-09-13 Last updated: 2020-02-04Bibliographically approved
Bahmani, A., Thiringer, T. & Kharezy, M. (2015). Design Methodology and Optimization of a Medium Frequency Transformer for High Power DC-DC Applications (ed.). In: Applied Power Electronics Conference APEC: . Paper presented at Applied Power Electronics Conference APEC March 15-19, 2015. Charlotte NC, USA. (pp. 2532-2539).
Open this publication in new window or tab >>Design Methodology and Optimization of a Medium Frequency Transformer for High Power DC-DC Applications
2015 (English)In: Applied Power Electronics Conference APEC, 2015, , p. 8p. 2532-2539Conference paper, Published paper (Other academic)
Abstract [en]

The high power medium frequency transformer (HPMFT) is one of the key elements of an isolated, bi-directional DC-DC converters in applications such as future all-DC offshore wind farms, traction and solid state transformers. This paper describes a design methodology taking into account the loss calculation, isolation requirements and thermal management. Incorporating this design methodology, an optimization process with a wide range of parameter variations is applied on a design example to find the highest power density while the efficiency, isolation, thermal and leakage inductance requirements are all met.

Publisher
p. 8
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-12445 (URN)10.1109/APEC.2015.7104707 (DOI)2-s2.0-84937937914 (Scopus ID)20448 (Local ID)20448 (Archive number)20448 (OAI)
Conference
Applied Power Electronics Conference APEC March 15-19, 2015. Charlotte NC, USA.
Available from: 2016-09-13 Created: 2016-09-13 Last updated: 2020-01-20Bibliographically approved
Kharezy, M. (2015). Reliability study of monitoring systems for power transformers in the smart grid (ed.). Paper presented at .
Open this publication in new window or tab >>Reliability study of monitoring systems for power transformers in the smart grid
2015 (English)Report (Refereed)
Abstract [en]

The project suggests appropriate methods for quality assurance of measurement processes and measuring equipment used for condition monitoring of power transformers, specifically for selection of on-line monitoring systems for: • Temperature • Partial discharge (PD) • Sound and vibration The developed methods can be developed further in subsequent projects to cover the quality of other types of measurement processes and measuring equipment as part of maintenance planning activities.

Publisher
p. 89
Series
Elforsk rapport 31181.
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-5644 (URN)20449 (Local ID)20449 (Archive number)20449 (OAI)
Available from: 2016-09-08 Created: 2016-09-08 Last updated: 2018-08-16Bibliographically approved
Elg, A. P., Bergman, A., Hällström, J., Kharezy, M. & Nieminen, T. (2015). Traceability and Characterization of a 1000 kV HVDC Reference Divider. IEEE Transactions on Instrumentation and Measurement, 64(6), 1709-1715, Article ID 7100891.
Open this publication in new window or tab >>Traceability and Characterization of a 1000 kV HVDC Reference Divider
Show others...
2015 (English)In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 64, no 6, p. 1709-1715, article id 7100891Article in journal (Refereed) Published
Abstract [en]

This paper presents the characterization of a resistive high-voltage dc (HVDC) reference divider and methods to establish traceability. The divider is designed for use as a laboratory reference for calibration of HVDC measuring systems up to 1000 kV. Targeting a measurement uncertainty of 20 μV/V at full voltage has put a focus on the temperature coefficients of the resistors, elimination of humidity dependence, and control of leakage currents in the high-voltage arm. A scale factor calibration against a 50 kV divider at 10 kV leads to an expanded uncertainty of 15 μV/V.

Keywords
High-voltage dc (HVDC) transmission, high-voltage techniques, measurement standards, uncertainty, voltage dividers, Calibration, Humidity control, HVDC power transmission, Leakage currents, Uncertainty analysis, High voltage DC (HVDC), High voltage dc (HVDC) transmissions, High voltage techniques, Measurement uncertainty, Measuring systems, Temperature coefficient
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:ri:diva-32451 (URN)10.1109/TIM.2015.2410373 (DOI)2-s2.0-85027955466 (Scopus ID)
Available from: 2017-11-03 Created: 2017-11-03 Last updated: 2019-07-09Bibliographically approved
Kharezy, M. & Lindgren, M. (1981). Fiberoptic sensors for high-voltage applications (ed.). Paper presented at .
Open this publication in new window or tab >>Fiberoptic sensors for high-voltage applications
1981 (English)Report (Refereed)
Abstract [en]

SP has experience in the field of fiberoptic communication and expertise in research in the field. Also, SP has expertise in the high-voltage field and there is currently a large interest in developing the high-voltage network in order to accommodate new small producers of electric power (wind mills, solar power, etc.) In this report we describe efforts to find areas of interest to develop fiberoptic sensors for offshore monitoring of high-voltage equipment. A large number of research papers and review articles have been collected and reviewed in order to investigate what possibilities are at hand for SP to provide support for development of new or existing fiberoptic sensor technologies.

Publisher
p. 40
Series
SP Rapport, ISSN 0284-5172
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-3978 (URN)20451 (Local ID)20451 (Archive number)20451 (OAI)
Available from: 2016-09-07 Created: 2016-09-07 Last updated: 2018-08-22Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0294-4430

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