ZPUC: A new configuration of single DC source for modular multilevel converter applications

Abstract

Z packed U-cell (ZPUC) converter topology is presented in this paper as a new type of multilevel converter topology that can be operated in a single phase as well as in three-phase configurations while using a single DC source. Since each U-cell includes two switches and one capacitor, in this topology, three U-cells are needed to generate 5 or 7 voltage levels. Moreover, the configuration proposed for the ZPUC is more appropriate for high-power application modular multilevel converters (MMCs) to increase the voltage levels compared to other topologies. Accurate voltage balancing on small-sized auxiliary capacitors is due to integrated modulation strategy without using additional controllers; additionally, the reduction of total harmonic distortion (THD) in AC currents for higher voltage levels is an advantage of this configuration. A full topology sequence of operation and performance analysis of ZPUC based on the 5-L inverter is investigated in Matlab-Simulink and experimentally validated on a 3 kVA prototype. The obtained results illustrate the good dynamic performance of the proposed topology and the implemented integrated switching pattern voltage balancing.