Multi-dimensional modulation technique for cascaded multilevel converters

Multilevel cascaded H-bridge converters have found industrial application in the medium voltage high power range. In this paper, a generalized modulation technique for this type of converters based on a multi-dimensional control region is presented. Using the multi-dimensional control region, it is shown that all previous modulation techniques are particularized versions of the proposed method. Several possible solutions to develop a specific implementation of the modulation method are addressed in order to show the potential possibilities and the flexibility of the proposed technique. In addition, a feed-forward version of this technique is also introduced to determine the switching sequence and the switching times avoiding low harmonic distortion with unbalanced dc voltages. Experimental results are shown in order to validate the proposed concepts.