A novel topology of DC/DC converter is proposed

termed as un-interrupted DC Autotransformer(DC AUTO)

which has capability to ride through the DC fault on either side of the converter without de-blocking any devices. Firstly

the characteristics of the DC AUTO and its defects are analyzed. Aiming at the problem that current DC AUTO cannot ride through the DC fault

the requirements for the ability of riding through the DC fault are analyzed as well. On the basic of that

combined with the characteristics of the hybrid modular multilevel converter(hybrid-MMC)

the hybrid-MMC number of DC AUTO with the ability of riding through the DC fault without de-blocking any devices is designed. Then

an effective control strategy is proposed to enable the converter keeping in the steady operation during both normal and fault conditions. Finally

a test system is built on PSCAD/EMTDC platform to verify the technical feasibility of the proposed converter and the effectiveness of the proposed control strategy.