Abstract: Based on full-bridge（FB）and half-bridge（HB）sub-modules（SMs），the conventional hybrid

modular multievel converter（MMC）is a typical topology of MMC with DC fault clearing ability. However，the

proportion of FB SMs in conventional hybrid MMC is usually greater than 50%，so as to increase the cost and

losses. To solve this mentioned issue，a DC fault commutated circuit based on thyristor-switched capacitor（TSC）

structure in the hybrid MMC was integrated to reduce the number of FBs，the improved TSC-hybrid MMC was

proposed in follows. In TSC-hybrid MMC，HB-MMCs and FB-MMCs were both retained their complete

commutated body，and meanwhile，they were connected by a three-winding transformer in AC side and in series

with DC side. In particularly，a thyristor-switched capacitor structure was integrated in the DC side of TSC-hybrid

MMC to clear the DC fault. According to the analysis，the proportion of FB SMs in TSC-hybrid MMC can be

reduced to 10%~25% or even lower（the AC-side voltage quality is a main limiting condition），the cost is reduced

as well as the on-state losses. Simulation results validate the correctness of analyses.

      Key words: thyristor-switched capacitor（TSC）；DC fault commutated circuit；hybrid modular multilevel

converter（MMC）；DC fault clearing strategy；series converter