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One Dimensional Feed-Forward Modulation of a Cascaded H-Bridge Multi-Level Converter including Capacitor Balancing with Reduced Switching Frequency
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| Author(s) |
John VODDEN, Pat WHEELER, Leopoldo G. FRANQUELO, Jose I. LEON, Sergio VAZQUEZ |
| Abstract |
Multi-level converters are well suited to medium and high power applications where the priority is forhigh quality a.c. currents with low harmonic content and for low switching losses. Suitable modulationschemes must find a good compromise between these two conflicting aims.This paper relates one-dimensional feed-forward modulation (1DFFM) to carrier based modulation.1DFFM can produce high quality currents despite d.c. capacitor voltage ripple by accounting for mea-sured capacitor voltages in the modulation process and can balance capacitor voltages by eliminatingstates that cause the capacitor voltages to diverge. It is shown in this paper that this method increases thedevice switching frequency compared to carrier-based modulation with the same sampling rate.An alternative modulation method is presented which balances the capacitor voltages by assigning com-mutations to bridges during each sampling period. This approach is less likely to cause two bridges tocommutate at the same time so produces a lower device switching frequency than 1DFFM. It is shownexperimentally that the two methods produce similar a.c. current distortion and both effectively balancethe capacitor voltages. |
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| Filename: | 0108-epe2011-full-18535973.pdf |
| Filesize: | 449.5 KB |
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| Type |
Members Only |
| Date |
Last modified 2012-01-26 by System |
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