The MMC-STATCOM is easy to produce power quality and control problems during itsoperation period

the operation condition of MMC-STATCOM is affected by the bridge arm circulation

and the converter’s loss is increased. The design of common circulation suppressor has accuracyrequirement to the mathematics model and

in case of light load

such issue as unable achievement ofcapacitive voltage balance of the engineering grading strategy is improved. The designed circulationsuppressor does not require accuracy model of system and has excellent circulation suppression effect. Atthe same time

the improvement of grading control solves the problem of the balance issue of capacitivevoltage under the light load condition

and the integral control strategy design for the MMC-STATCOMsystem is performed. Finally

the simulation model of MMC-STATCOM system is built in the PSCADsimulation software

and effectiveness of the control strategy mentioned in the paper is illustrated by thesimulation result.