The Evolutions of Multilevel Converter Topology: A Roadmap of Topological Invention

The first multilevel converter (MLC) is more than 50 years old. However, its concept can be traced back to a much earlier era, i.e., the beginning of power electronics, which may not be well-known to our community. Even some of the trailblazing inventions are missed in the innumerable literature. In this article, attempts are made to rebuild the roadmap of MLCs, especially the topology techniques. The evolutions of MLC topology are summarized in detail based on four periods: the pre-silicon-controlled-rectifier (SCR) era (pre-1950s), classical era (1950s–1970s), developing era (1970s–2000s), and advanced era (2000s–now). In each area, some of the most important topology achievements are elaborated upon to provide detailed overall pictures of the technique. Finally, future trends of MLCs are discussed with considerations of emerging innovations in power electronics. We hope that this article can serve as a summary of MLC topologies in terms of their origins and evolutions and inspire researchers to make innovations on top of this remarkable legacy.