High Quality NLM Method for Medium Voltage Hybrid Bridge MMC

Medium voltage hybrid bridge multilevel converter (MMC) usually has a lower number of links. Therefore, the traditional Nearest Level Modulation (NLM) method problems low equivalent switching frequency and poor output quality. And Carrier Phase-shifted Pulse Width (CPS-PWM) modulation such as difficulty in control, redundant configuration, large amount calculation. In response to above problems, this paper proposes new high-quality NLM method. Based on method, PWM module equalization are realized through time difference between one input exit each control cycle. It achieves purpose improving power quality, at same advantages with small calculation amount, configuration modulation. This article describes three methods compares their effects. Finally, theoretical analysis is verified by PSCAD simulation.