A Modulation Method Suitable for AM-MMC with Small Quantities of Submodules

When the arm multiplexed modular multilevel converter (AM-MMC) is used in medium-voltage DC distribution grid, the number of sub modules is small, and the nearest level approach modulation (NLM) strategy in the DC transmission system will lead to serious current distortion, poor output voltage quality and other issues. After analyzing the existing modulation strategy of AM-MMC, the Multi half bridge modulation (MHBM) strategy suitable for AM-MMC is proposed, which can be used when the quantities of sub-modules are small. This modulation method of a small quantities of submodules divides the submodules into two types: half bridge submodule (HBSM) and multi-half bridge submodule(M-HBSM) by dividing the levels. Then the number of AM-MMC levels are increased to improve the problem of poor output voltage quality when the quantities of submodules are small. Finally, the built MATLAB/Simulink simulation verified that the AM-MMC under MHBM strategy has the potential to increase the output level, thereby reducing the output voltage harmonics and effectively improving the power quality of the DC distribution grid.