Influence of dead time on modular multi-level converter

In order to figure out the influence of dead time on modular multilevel converter (MMC), we established a mathematical model of MMC, which took dead time into account, and put forward the corresponding calculation expressions. Firstly, based on converter's operation principles, a general mathematical model was developed in aspects of the setting of dead time, arm current direction, sub-module state, and the number and its changing mode of inserted arm modules. Secondly, the general mathematical model was simplified from aspects of fundamental waveform and angle deviation, and the influences of inserted module numbers, modulation degree, load angle and the length of dead time on converter were discussed. Finally, the established general mathematic model was verified through matrix calculation and simulation using MATLAB/simulink. The simulation and calculation results show that the relative size of dead time influence is positively correlated to the number of submodules, dead time, and phase difference, respectively, and negatively correlated to voltage modulation degree.