A new full-bridge loss optimization modulating strategy is proposed. The strategy is able to balance the thermal stress of each semiconductor in a sub-module and improve the device safety margin

so as to enhance the power transfer capability of the modular multilevel converter(MMC). To begin with

the topology of the sub-module of MMC is analyzed. Proceeding from the perspective of suppressing the DC fault current

a full-bridge sub-module is chosen as the object for analysis. Secondly

for various working conditions of the MMC-HVDC transmission system

the loss and the junction temperature are analyzed to identify the main factor limiting the MMC power transfer. Finally

based on a comprehensive analysis

the full-bridge loss optimization modulation strategy is proposed for the MMC-HVDC transmission system

which can improve the transmission power. Simulation analysis has verified the validity of the strategy.