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On Energy Variations in Modular Multilevel Converters with Full-Bridge Submodules for Ac-Dc and Ac-Ac Applications
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| Author(s) |
Kalle ILVES, Staffan NORRGA, Hans-Peter NEE |
| Abstract |
The modular multilevel converter is a promising topology for high-voltage high-power applications. Bythe series-connection of submodules it can generate high-quality voltage waveforms with low harmonicdistortion at low switching frequencies. The submodules are low-voltage converters with capacitiveenergy storages. These capacitive energy storages are a driving factor of the size, weight, and cost of theconverter. For this reason it is important to ensure that the stored energy in the converter is distributedas evenly among the submodules as possible. In this paper it is found that during nominal operatingconditions, a large amount of energy is moved back and forth between the upper and lower arms inthe converter. These energy oscillations can, however, be reduced or even eliminated if an appropriatemodulation index or voltage ratio is used. It is also found that an appropriate modulation index or voltageratio can reduce the power rating of the semiconductors as well. The theoretical findings are validatedby simulating two systems with different voltage ratios for ac-ac conversion. |
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| Filename: | 0445-epe2013-full-12432193.pdf |
| Filesize: | 219.8 KB |
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| Type |
Members Only |
| Date |
Last modified 2014-02-09 by System |
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