Advances in renewable energy power converters: A review of multilevel topologies and design criteria

Multilevel power converters have received significant attention in renewable energy systems for their capabilities in delivering high-quality output waveforms. The multiple voltage level structure offers high efficiency and low voltage stress on power semiconductor switches in photovoltaic systems, microgrids, energy storage systems and transportation electrification. As the demand for efficient energy utilization continues to surge, there is a growing number of optimizations proposed for multilevel converter topology. This paper investigates multilevel converter topologies for applications in renewable energy systems. Five major design challenges are addressed: leakage current suppression, cost reduction, voltage control of capacitors, wide input voltage range, and fault-tolerant operation. For each challenge, the corresponding design principles are analyzed, existing strategies are reviewed and categorized, and modular topologies are proposed and discussed in detail. Subsequently, proposed structures are then summarized, illustrating their respective strengths and limitations. Finally, applications and modulation methods of multilevel converters in renewable energy systems are presented, along with a discussion of current challenges and future research opportunities.