Improved output waveform quality for multi-level H-bridge chain converters using unequal cell voltages

This paper describes a set of techniques for improving the output waveform quality from an isolated H-bridge multi-level power converter by the introduction of unequal H-bridge cell voltages and the use of a high performance PWM H-bridge cell. The waveform quality improvements are quantified in terms of frequency weighted THD for a series of six circuit configurations. Both simulation and practical results are presented and the results compared in both the time and frequency domains as well as by THD