A Cascaded H-Bridge-Based Multilevel Converter With Low Energy Pulsation for High-Power Grid Applications

The ongoing transformation of power supply is leading to an increasing penetration of electrical grids with power converters, which are used in high-volume applications such as grid integration of renewable energy sources, energy storage systems, charging infrastructure for electric vehicles, and industrial electric drives. This results in significant and novel challenges for power quality and supply stability, which will likely result in further increasing demands on the converters used in the aforementioned applications. To address these challenges, this article presents a novel multilevel converter system for high-power grid applications, which is characterized by high output power and voltage quality, low energy pulsation, and high scalability and modularity. These characteristics are achieved by a novel concept of operation for the combination of a high-power main converter and a low-power cascaded H-bridge converter, which is derived based on the modeling and control design carried out for the proposed converter system. Simulation and experimental results verify the potential of the multilevel converter system and show that, compared to full-power multilevel converters, it allows high output voltage quality at high output power while maintaining low current load and low energy pulsation within the cells of the cascaded H-bridge converter.