Comparison of cell selection methods for modular multilevel converters

Abstract

The modular multilevel-based power converters (MMC) are very interesting solutions for high power transmission over large distances. The modularity of the converter is achieved by cascading individual and low voltage rated power converters in series, until the stack built can withstand the required dc voltage. Due to the large number of those individual components in real VSC-HVdc applications, the proper management of their states become a crucial agent when the converter efficiency is discussed. This work analyses several algorithms that are present in the literature, in what concerns the average switching frequency, magnitude of the capacitor's voltage ripple and complexity of the implementation. The converter simulation over a broad range of operating conditions is presented and discussed.