Abstract：In order to further improve the power density and output performance of the transformerless

medium-voltage power quality control device，a partial submodule multiplexing modular multilevel converter

（PSM-MMC）topology and its control strategy were proposed. The PSM-MMC was composed of four groups of

arm submodules and three groups of arm switching switches. Some submodules were multiplexed by arm switching

switches to improve the utilization rate of submodules. Compared with the conventional MMC topology，the

number of submodules of the proposed PSM-MMC could be reduced by 1/3. Furthermore，a hybrid modulation

strategy with level multiplication was proposed for the PSM-MMC. Based on the nearest level modulation，two

submodules were introduced to output high-frequency PWM waveform to reduce the output voltage harmonics. In

addition，the working mode of PSM-MMC was analyzed in detail，and the control block diagram and capacitor

voltage balancing strategy of PSM-MMC were given. Finally，the effectiveness of the proposed topology and

control strategy was verified by simulation and experiment under 10 kV system.

      Key words：modular multilevel converter（MMC）；submodule multiplexing；arm switching；power quality；

voltage balancing