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A Submodule Implementation for Parallel Connection of Capacitors in Modular Multilevel Converters
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| Author(s) |
Kalle ILVES, Franz TAFFNER, Staffan NORRGA, Antonios ANTONOPOULOS, Lennart HARNEFORS, Hans-Peter NEE |
| Abstract |
The modular multilevel converter is a suitable converter topology for high-voltage high-power applicationsand consists of series-connected submodules. Typically, these submodules are half-bridges withdc capacitors. A voltage ripple in the submodule capacitors is inevitable due to the current flowing inthe arms. The converter should therefore be controlled in such a way that the capacitor voltages arekept balanced and close to their nominal values over time. This paper presents a new submodule circuitwhich alleviates the balancing of the capacitor voltages. The proposed submodule circuit consists of twocapacitors and eight switches, forming a three-level submodule. Ideally, the voltage and current ratingof the switches can be chosen such that the combined power rating of the semiconductors is the sameas for equivalent half-bridge submodules. The proposed submodule circuit provides the possibility ofconnecting the two capacitors in parallel when the intermediate voltage level is used. This will reducethe capacitor voltage ripple, especially at low switching frequencies and thus allow for a reduction of thesize, weight, and cost of the submodule capacitors. The proposed submodule circuit is validated by bothsimulation results and experiments on a laboratory prototype. It is found that the parallel connection ofthe submodule capacitors will, in fact, significantly improve the balancing of the capacitor voltages. |
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| Filename: | 0446-epe2013-full-12370676.pdf |
| Filesize: | 1.014 MB |
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| Type |
Members Only |
| Date |
Last modified 2014-02-09 by System |
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