Enhanced double flying capacitor multicell power converter controlled with a new switching pattern

Abstract

This study proposes an enhanced topology for pulse-width-modulated double flying capacitor multicell (DFCM) converter controlled with a new switching pattern in order to reduce voltage diversity and stored energy of flying capacitor (FC) to augment converter's integrity and modularity. The proposed power converter is a hybrid topology realised by cascade connection of DFCM and cascaded H-bridge (CHB) converters while combining, employing, and featuring advantages of both converters. The dc voltage sources and also power switches forming CHB converters’ structure in the proposed hybrid topology possess low voltage-ratings, hence imposing low additional costs and prices on DFCM converter whereas improving and enhancing output voltage power quality significantly by increasing the number of output voltage-levels and improving output voltage frequency spectrum. This progress results in reducing the bulky and costly FCs, their voltage ratings and stored energy. The FC voltages of DFCM topology in the proposed hybrid converter get stabilised naturally at their requisite voltage-levels because of the redundant charging/discharging states. First, experimental measurements of the three-cell-seven-level DFCM are provided. Afterward, simulation results and experimental observations of 15-level enhanced DFCM converter are presented to verify and validate the effectiveness and advantages of the proposed topology as well as its suggested control and modulation strategy.