With the framework of the modular multilevel converter (MMC), the research of control method for the voltage source converter-high voltage direct current (VSC-HVDC) systems plays an important role in the engineering application When AC system malfunctions. A new control method is designed to alleviate the challenging, i．e., the large number of the PI regulator, the difficulty of the control parameter debugging, the narrow stable work area of the system. The character of MMC is analysized when AC system occurs faults, and with the assistance of the feedback linearization theory, a dual-current control method of positive-sequence and negative-sequence is introdued, which indicates that the proposed method has perfect control performance when AC system is normal and enconter a failure. The reasons that the DC voltage and current have second-order harmonics when negative-sequence current has been suppressed are further analysized, and a DC voltage ripple suppressing controller(DCVRSC)is designed. The accuracy of the proposed method is validated by the simulation software PSCAD/EMTDC. Compared with the common cascade PI control method, the proposed method has advantages such as the parameter debugging is simple, the stability of the system is high and the direct current voltage is suppressed.