A structural overview on transformer and transformer-less multi level inverters for renewable energy applications

In general, multilevel inverters (MLIs) are regarded as advanced power conversion systems required for medium-voltage and high-power applications. The purpose of this article is to provide an overview of recently investigated MLI topologies classified into various categories based on the transformer requirement such as the transformer less (TL-MLI) and transformer-based (T-MLI) with single and multi-source topologies of symmetric, asymmetric, hybrid and single DC sources for renewable energy applications. For the previous few decades, multiple new variants of each group have been developed. The design and functioning of each topology, as well as each group, are examined in this study. T-MLI topologies of H-bridge, three-leg inverter-based, and other T-MLI configurations are discussed from a configuration standpoint. Each topology's state-of-the-art of both MLI configurations and problems are treated separately. Furthermore, the disadvantages and benefits of each topology have been thoroughly addressed. Finally, a comparison of existing topologies is conducted to determine the optimal topology based on several performance characteristics and the cost evaluation has been presented. This article provides a comprehensive overview of recently developed multilevel inverters and provides a solution for developing the MLIs for future research on renewable energy applications. (C) 2022 The Authors. Published by Elsevier Ltd.