A Novel Pulse Width Modulation technique with active DC voltage balancing and device voltage falls compensation for High-Power Cascaded multilevel active rectifiers

This paper presents a novel dedicated PWM technique for use with single-phase (or four wire three-phase) multi-level Cascaded H-Bridge Converters. The proposed modulation strategy aims to minimize the unbalance of the DC-Link voltages, for any amplitude of the voltage reference, amongst the different converter cells in order to obtain high-quality waveforms with a low switching frequency. Moreover the device voltage drops and ON resistance, which in high-power multilevel converter have a significant impact on the quality of the produced voltage, are compensated. The technique is described in detail along with the concept of a modular converter prototype for smart grid applications and an outline of its construction. Verification of the modulation effectiveness is provided with simulation and experimental results for a 3kW seven level Cascaded Converter.