Pre-charging Characteristics Analysis and Control Strategy of Full Bridge MMC-HVDC

Considering the FB-MMC, a generalized pre-charging strategy is proposed for the MMC-based systems. It contains two stages, no control charging and controllable charging. The circuit model of the converter is established in the no control charging stage, and the submodule capacitance can be charged to about 37% of rated voltage. During the controllable charging stage, we proposed grouping charging strategy, the blocked and bypassed strategy of each group sub-module is formulated. According to the circuit model, the capacitance voltage of each module can be charged to the rated value through this strategy. Finally, we set up a 9 level full bridge MMC-HVDC simulation system in PSCAD/EMTDC. The charging strategies are simulated, and the results show that the proposed control strategy is feasible. (paper)