Classification of multilevel converters with a modular reduced structure: Implementing a prominent 31-level 5 kVA class B converter

Abstract

Multilevel converters are capable of generating AC voltages with low-total harmonic distortion, applicable to power system applications such as penetration of renewable sources in an active network. These types of topologies may require large number of switches and power supplies, having complex structures along with complicated control algorithms. Recently, a branch of multilevel converters is emerged, in which their 'reduced structure' topologies use lower number of devices compared to the available topologies. This study concentrates on classification of the branched 'multilevel converters' with a 'reduced structure' (MCRS) that lowers the number of semiconductor switches as well as their gate-drivers. Then, these classified structures are compared in terms of their number of power supplies and switches, the number of gate-drivers, breaking voltages of the switches and so on. This will pave the way for the introduction of a structure named B2 in the defined class B among the available MCRS topologies with the lowest number of power electronic devices; this structure is obtained by modifying the structure A2 in the defined class A. Moreover, design and simulation of a 31-level converter is analysed under optimal number of DC sources for all named structures. A laboratory prototype was implemented that verifies operation and performance of the suggested structure B2.