Model-Based Design for Reactors of the Modular Multilevel Converter

For complex power electronic converters, typical design approaches divide the system into multiple independent subsystems without sufficiently considering the interactions among them. In this article, a model-based approach for sizing the reactors of the modular multilevel converter (MMC) is proposed. The proposed method quantitatively considers the interactions between the reactor sizing and other design parameters, such as power ratings, protection schemes, and component-level short-circuit capabilities. Meanwhile, three deterministic factors are provided in this article for sizing reactors to ensure enough robustness during extreme situations instead of the heuristic factor in the existing work. The quantified interactions presented in this article also reveal that a proper overrating of the active components is able to reduce reactance, increase efficiency, and improve power density. The proposed method not only serves as a quantitative design tool for the MMC, but also emphasizes the significance of the modeling of the interactions in the model-based design. Finally, the effectiveness of the proposed method is validated by simulations and experiments. This article is also accompanied by software codes for reproducibility.