Quasi-Square-Wave Modulation Considering Dead Zone Compensation for Modular Multilevel DC-DC Converters

Modular multilevel dc-dc converters (MMdc) are becoming promising candidates in the medium-voltage dc (MVdc) power distribution systems, owing to its outstanding features, such as high scalability and control flexibility. The quasi-square wave (QSW) modulation is a commonly used modulation technique for MMdc. However, in real implementation, the drive dead zone in submodule power devices can cause a delay in the output voltage compared to the modulation signal, resulting in high overvoltage and current distortion in the MMC structure. This paper investigates the impact of dead zone in detail and proposes a dead zone compensation method on modular multilevel dc-dc converters, which reduces the voltage and current stresses, and mitigates the disturbance caused by dv/dt. Finally, the proposed method is verified by simulation and experiment.