A new modulation method for multilevel converters

Abstract

This paper presents a simple method for modulation in multilevel converters, which is hardly affected with the number of levels. The method is based on a simple graph, whose x-axis is directly related to the extra degree of freedom associated with component γ (in the αβγ reference frame) of the desired reference vector. In the y-axis, the different possibilities for the phase averaged references are plotted. In this way, the degree of freedom is more explicit than in Space Vector Modulation (SVM) and it can be the basis of new algorithms to pursue additional control objectives such as voltage balancing or common-mode reduction, among others. A comparison with SVM based on examples is included, showing the benefits of the proposed modulation strategy.