Cell capacitor sizing in multilevel converters: cases of the modular multilevel converter and alternate arm converter
Author(s)
Merlin, MMC
Green, TC
Type
Journal Article
Abstract
Multilevel converters, such as the modular multilevel converter (MMC) or the alternate arm converter (AAC), rely on charged capacitors in their cells to generate their AC voltage waveform. Since the cell capacitors are physically large and occupy approximately half the cell volume, their capacitance must be kept minimal while limiting the voltage fluctuation caused by the current passing periodically through these capacitors. This study proposes a mathematical model which estimates the energy deviation for the stacks of both the MMC and the AAC during steady‐state operation under any power factor and for AC voltage magnitude fluctuation of up to ±10%. The analysis is then used to calculate the minimum size for the cell capacitors in order to keep their voltage fluctuation within set boundaries for both topologies. The results show that the MMC requires 39 kJ/MVA of capacitive energy storage under sinusoidal modulation but this reduces with triplen injection modulation. The AAC has a lower requirement for storage in its cells of 11 kJ/MVA but the AAC has a six‐pulse DC current ripple which requires a filter estimated to have a further 33% capacitive storage.
Date Issued
2015-03-01
Date Acceptance
2014-09-07
Citation
IET Power Electronics, 2015, 8 (3), pp.350-360
ISSN
1755-4535
Publisher
Institution of Engineering and Technology
Start Page
350
End Page
360
Journal / Book Title
IET Power Electronics
Volume
8
Issue
3
Copyright Statement
This paper is a postprint of a paper submitted to and accepted for publication in IET Power Electronics and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital Library
Sponsor
Engineering & Physical Science Research Council (E
Engineering & Physical Science Research Council (EPSRC)
Identifier
https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/iet-pel.2014.0328
Grant Number
EEZ1245616 (RMS96012)
EP/G066477/1
Subjects
Science & Technology
Technology
Engineering, Electrical & Electronic
Engineering
TRANSMISSION
TOPOLOGIES
Publication Status
Published
Date Publish Online
2015-03-01