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Multilevel cascaded H-Bridge converters (CHB) have been presented as a good solution for high power applications. In this way, several control and modulation techniques have been proposed for this power converter topology. In this paper the steady state power balance in the cells of the single phase two cell CHB is studied. The capability to be supplied with active power from the grid or to deliver active power to the grid in each cell is analyzed according to the dc-link voltages and the desired ac output voltage value. Limits of the maximum and minimum input active power for stable operation of the CHB are addressed. Simulation results are shown to validate the presented analysis.

This paper presents a simple and low computational cost modulation technique for multilevel cascaded H-bridge converters. The technique is based on geometrical considerations considering an unidimensional control region to determine the switching sequence and the corresponding switching times. In addition, a simple strategy to control the dc voltage ratio between the H-bridges of the multilevel cascaded converter is presented. Examples for the two-cell topology are shown but the proposed technique can be applied to develop modulation methods for a higher number of H-bridges. Experimental results are presented to validate the proposed technique.