Evaluation of peak-to-peak current ripple of phase shifted carrier PWM multilevel cascaded H-bridge converters

The Phase Shifted Carrier Pulse Width Modulation (PSC-PWM) technique is a commonly used modulation strategy for multilevel converters. The PSC-PWM technique offers great performance advantages such as equal switch utilization, equal DC link utilization and harmonic benefits. With any PWM converters or modulation strategies, current ripple is inevitably generated and should be minimized. In particular, the peak-to-peak current ripple plays an adverse role in power converters, if ignored the current ripple would deteriorate the performance of the converter and damage the switching devices if the ripple exceeds the operating current limit of the device. This paper offers a novel approach for evaluating the peak-to-peak current ripple of a PSC-PWM Multilevel Cascaded H-Bridge (MLCHB). It is shown that the proposed method can determine the peak-to-peak current ripple of the standard PSC-PWM as well as with common-mode injected modulation. A comparison is made between two MLCHB converters with different number of H-bridge cells and modulation indexes. Lastly simulation results of the proposed method are provided.