The extended overlap alternate arm converter: a voltage source converter with DC fault ride-through capability and a compact design
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
The Alternate Arm Converter (AAC) was one of
the first modular converter topologies to feature DC-side fault
ride-through capability with only a small penalty in power
efficiency. However, the simple alternation of its arm conduction
periods (with an additional short overlap period) resulted in
(i) substantial 6-pulse ripples in the DC current waveform,
(ii) large DC-side filter requirements, and (iii) limited operating
area close to an energy sweet-spot. This paper presents a new
mode of operation called Extended Overlap (EO) based on
the extension of the overlap period to 60
◦
which facilitates a
fundamental redefinition of the working principles of the AAC.
The EO-AAC has its DC current path decoupled from the AC
current paths, a fact allowing (i) smooth DC current waveforms,
(ii) elimination of DC filters, and (iii) restriction lifting on the
feasible operating point. Analysis of this new mode and EO-
AAC design criteria are presented and subsequently verified
with tests on an experimental prototype. Finally, a comparison
with other modular converters demonstrates that the EO-AAC
is at least as power efficient as a hybrid MMC (i.e. a DC fault
ride-through capable MMC) while offering a smaller converter
footprint because of a reduced requirement for energy storage
in the submodules and a reduced inductor volume.
the first modular converter topologies to feature DC-side fault
ride-through capability with only a small penalty in power
efficiency. However, the simple alternation of its arm conduction
periods (with an additional short overlap period) resulted in
(i) substantial 6-pulse ripples in the DC current waveform,
(ii) large DC-side filter requirements, and (iii) limited operating
area close to an energy sweet-spot. This paper presents a new
mode of operation called Extended Overlap (EO) based on
the extension of the overlap period to 60
◦
which facilitates a
fundamental redefinition of the working principles of the AAC.
The EO-AAC has its DC current path decoupled from the AC
current paths, a fact allowing (i) smooth DC current waveforms,
(ii) elimination of DC filters, and (iii) restriction lifting on the
feasible operating point. Analysis of this new mode and EO-
AAC design criteria are presented and subsequently verified
with tests on an experimental prototype. Finally, a comparison
with other modular converters demonstrates that the EO-AAC
is at least as power efficient as a hybrid MMC (i.e. a DC fault
ride-through capable MMC) while offering a smaller converter
footprint because of a reduced requirement for energy storage
in the submodules and a reduced inductor volume.
Date Issued
2017-08-03
Date Acceptance
2017-06-30
Citation
IEEE Transactions on Power Electronics, 2017, 33 (5), pp.3898-3910
ISSN
1941-0107
Publisher
IEEE
Start Page
3898
End Page
3910
Journal / Book Title
IEEE Transactions on Power Electronics
Volume
33
Issue
5
Copyright Statement
© 2017 The Author(s). This work is licensed under a Creative Commons Attribution 3.0 License. For more information, see http://creativecommons.org/licenses/by/3.0/
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (E
Engineering & Physical Science Research Council (E
Grant Number
EP/I013636/1
EEZ1245616 (RMS96012)
EEZ1419554
Subjects
Science & Technology
Technology
Engineering, Electrical & Electronic
Engineering
AC-DC power conversion
active filters
capacitive energy storage
HVDC transmission
power system faults
power transmission protection
MODULAR MULTILEVEL CONVERTERS
BLOCKING CAPABILITY
HVDC APPLICATIONS
OPERATION
SYSTEMS
CELLS
MMC
0906 Electrical And Electronic Engineering
Electrical & Electronic Engineering
Publication Status
Published