In order to resolve the problem of serious over-voltage on the existing thyristor based power flow controller under faults

a modular multilevel power flow controller based on the full-bridge modular multilevel converter is proposed. First

the loop network structure of multi-terminal DC is analyzed

and then

the problem of over-voltage with the thyristor power flow controller is presented and analyzed. Through an analysis of the full-bridge sub-module operating state

the intrinsic mechanism of the over-voltage breakthrough concerning the modular multilevel power flow controller is pointed out

and the corresponding control strategies for control of the power flow are designed. Finally

the current regulation

bidirectional operation and over-voltage ride-through of the modular multilevel power flow controller are simulated via a model with PSCAD/EMTDC. The results show that the modular multilevel power flow controller has good performance on current regulation

needs a short response time

and is able to realize over-voltage ride-through whatever the fault is.