Despite extensive concern of researchers and wide application in direct current（DC）transmission and energy conversion，the modular multilevel converter（MMC）with a new topology is incapable of clearing the DC link faults because of its semi-bridge submodular topology.An improved hybrid topology utilizing the reverse voltage clamping of forward diodes and capacitor charge effect is designed to solve the unidirectional charge problem without the need to change the control and voltage balancing algorithm.By investigating the different current charge paths，the current blocking coefficient is defined as the ratio between arm equivalent DC voltage and alternating current（AC）voltage magnitude to indicate the blocking effect.The self-excited startup procedure is also designed according to the capacitor voltage in the uncontrollable rectifying process.The effectiveness of this topology is verified by MMC simulation results.