For restraining inner circulating current in modular multilevel converter (MMC), this paper presents a novel restraint strategy for bridge arm circulating current, including improved topology of MMC, circulating current restraint method, constant voltage control of voltage correcting module (VCM). Second, for engineering applications, this paper proposes a redundancy control method of VCM, and the parameters of VCM are designed, including modular voltage and support module capacitance value. Simulation results show the reasonableness of the design of the proposed VCM parameters and verify the redundancy control scheme can maintain VCM voltage stability as well as effectively restrain bridge arm circulating current of converter. The proposed scheme applies to all MMC system and has obvious advantages in case of high voltage and large capacity like IGBT connecting MMC in series.