A Compact MMC Submodule Structure With Reduced Capacitor Size Using the Stacked Switched Capacitor Architecture

Modular multilevel converters (MMCs) are being developed for the grid connection of offshore wind or tidal farms. In order to reduce the construction and maintenance costs, it is desirable to reduce the weight and volume of the system. In current MMC submodule designs, the reservoir capacitor usuall...

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Bibliographic Details
Published in:IEEE transactions on power electronics 2016-10, Vol.31 (10), p.6920-6936
Main Authors: Tang, Yuan, Chen, Minjie, Ran, Li
Format: Article
Language:English
Subjects:
Architecture
Capacitance
Capacitors
Conversion
Converters
Cost control
Design engineering
Electric power
Electronics
Harmonic analysis
Maintenance costs
Metal matrix composites
Modular
Modular multilevel converter
Reservoirs
Semiconductors
submodule capacitor
switched capacitor circuits
Switches
Topology
Wind farms
Wind power generation
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Summary:Modular multilevel converters (MMCs) are being developed for the grid connection of offshore wind or tidal farms. In order to reduce the construction and maintenance costs, it is desirable to reduce the weight and volume of the system. In current MMC submodule designs, the reservoir capacitor usually accounts for over 50% of the total volume and 80% of weight. This paper presents a new design concept and control principle for a submodule using the stacked switched capacitor (SSC) architecture that can significantly reduce the capacitor size in an MMC. Practical considerations for a high-voltage high-power SSC-based MMC submodule are presented in this paper, through the design of a 21-level, 40-kV (pole-pole dc), 19.1-MW, grid-connected system, and the concept is demonstrated experimenttally on a scaled-down 400-V, 12.3-Apeak laboratory prototype submodule. It is shown that with the proposed SSC architecture, the total volume of capacitors in each submodule can be reduced by more than 40% without significantly increasing the power loss.
ISSN:0885-8993
1941-0107
DOI:10.1109/TPEL.2015.2511189