A comparative assessment of different balancing control algorithms for modular multilevel converter (MMC)

Thanks to scalability, performance and efficiency, the Modular Multilevel Converter (MMC), since its invention, becomes an attractive topology in industrial applications such as high voltage direct current (HVDC) transmission system. To control such device, the Balancing Control Algorithm (BCA) for submodule capacitors is a key issue. Lots of papers have been written in this field, but most of them present methods without showing their associated advantages and drawbacks neither comparing with previous works. Therefore, this paper presents a comparative analysis of different BCAs based on staircase modulation technique. The obtained results show the advantages and drawbacks for each method regarding the switching frequency and the voltage ripple. Finally, some discussions and recommendations are given for MMC sizing (submodule capacitors, converter losses) and control (BCA sampling time) users.