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Ilves, Kalle
Publications (2 of 2) Show all publications
Bessegato, L., Ilves, K., Harnefors, L., Norrga, S. & Östlund, S. (2019). Control and Admittance Modeling of an AC/AC Modular Multilevel Converter for Railway Supplies. IEEE transactions on power electronics
Open this publication in new window or tab >>Control and Admittance Modeling of an AC/AC Modular Multilevel Converter for Railway Supplies
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2019 (English)In: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107Article in journal (Refereed) In press
Abstract [en]

Modular multilevel converters (MMCs) can be configured to perform ac/ac conversion, which makes them suitable as railway power supplies. In this paper, a hierarchical control scheme for ac/ac MMCs for railway power supplies is devised and evaluated, considering the requirements and the operating conditions specific to this application. Furthermore, admittance models of the ac/ac MMC are developed, showing how the suggested hierarchical control scheme affects the three-phase and the single-phase side admittances of the converter. These models allow for analyzing the stability of the interconnected system using the impedance-based stability criterion and the passivity-based stability assessment. Finally, the findings presented in this paper are validated experimentally, using a down-scaled MMC. 

Keywords
Modular multilevel converters, ac/ac converters, current control, voltage control, admittance, frequency-domain analysis, linearization techniques, stability, railway engineering.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-248130 (URN)
Note

QC 20190404

Available from: 2019-04-04 Created: 2019-04-04 Last updated: 2019-08-19Bibliographically approved
Heinig, S., Jacobs, K., Ilves, K., Bessegato, L., Bakas, P., Norrga, S. & Nee, H.-P. (2019). Implications of Capacitor Voltage Imbalance on the Operation of the Semi-Full-Bridge Submodule. IEEE transactions on power electronics, 34(10), 9520-9535, Article ID 8598807.
Open this publication in new window or tab >>Implications of Capacitor Voltage Imbalance on the Operation of the Semi-Full-Bridge Submodule
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2019 (English)In: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 34, no 10, p. 9520-9535, article id 8598807Article in journal (Refereed) Published
Abstract [en]

Future meshed high-voltage direct current grids require modular multilevel converters with extended functionality. One of the most interesting new submodule topologies is the semi-full-bridge because it enables efficient handling of DC-side short circuits while having reduced power losses compared to an implementation with full-bridge submodules. However, the semi-full-bridge submodule requires the parallel connection of capacitors during normal operation which can cause a high redistribution current in case the voltages of the two submodule capacitors are not equal. The maximum voltage difference and resulting redistribution current have been studied analytically, by means of simulations and in a full-scale standalone submodule laboratory setup. The most critical parameter is the capacitance mismatch between the two capacitors. The experimental results from the full-scale prototype show that the redistribution current peaks at 500A if the voltage difference is 10V before paralleling and increases to 2500A if the difference is 40V. However, neglecting very unlikely cases, the maximum voltage difference predicted by simulations is not higher than 20-30V for the considered case. Among other measures, a balancing controller is proposed which reduces the voltage difference safely if a certain maximum value is surpassed. The operating principle of the controller is described in detail and verified experimentally on a down-scaled submodule within a modular multilevel converter prototype. It can be concluded that excessively high redistribution currents can be prevented. Consequently, they are no obstacle for using the semi-full-bridge submodule in future HVDC converters.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2019
Keywords
AC-DC power conversion, HVDC converters, HVDC transmission, Power transmission, Fault tolerance, Power system faults
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-240824 (URN)10.1109/TPEL.2018.2890622 (DOI)000474581900016 ()2-s2.0-85068640873 (Scopus ID)
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage, CPC4
Note

QC 20190107

Available from: 2019-01-03 Created: 2019-01-03 Last updated: 2019-07-31Bibliographically approved
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