Comparative analysis on capacitor voltage balance control strategies for staircase modulated modular multilevel converter

Aiming at solving the equalization problem of capacitor voltage of the staircase modulated modular multilevel converter (MMC), an analysis of two typical capacitor voltage balance control methods is conducted and the comparison between the two methods is carried out. With the analysis of operation principle of staircase modulation based MMC, the switching sequence rotation method and sorting redundancy selection methods were detailed discussed. After that, the comparison results on voltage balance effect, switching frequency, algorithm structure and hardware requirements were given. According to the same main circuit parameters, both of the switching sequence rotation method and the sorting redundancy selection method were carried out on the simulation model and the physical experiment platform for staircase modulated MMC. The simulation and experimental results show that the steady-state performance of the switching sequence rotation method is excellent, while the sorting redundancy selection method exhibits a strong ability of transient regulation, and the latter consequently has good practicality and reliability. © 2016, Harbin University of Science and Technology Publication. All right reserved.