Optimization of Full-Bridge YY-MMC Through Pole-to-Pole DC Voltage, Circulating Current, and Zero-Sequence Voltage

Paper in proceeding, 2025

The Full-Bridge Double-Wye Modular Multilevel Converter (FB-YY-MMC) offers enhanced flexibility for grid applications, particularly in renewable energy integration. This paper investigates the effects of key degrees of freedom, including pole-to-pole DC voltage, second-order circulating current, and third-order zero-sequence voltage, on the converter's design. For this purpose, a cost function is introduced to combine all relevant design parameters, such as the number of submodules, power losses, semiconductor ratings, and submodule capacitor size, by assigning a weighting factor to each. The optimization process minimizes this cost function to determine the optimal design. As a result, it is shown that a 17% reduction in the overall cost of the MMC is achieved compared to a conventional design. Also, the proposed optimization approach is validated through timedomain simulation.