Compared with the traditional AC transmission system, the development of HVDC transmission has been restricted by limiting the fault current. Because HVDC transmission current and voltage have no zero crossing point, the fault current limiting becomes a difficult point in the development of the HVDC system. This paper provides an idea of modeling a two-pole HVDC transmission system, mainly focuses on MMC average model construction and control method of voltage-type FCL in system level. Simulation at the end of the paper shows the universal applicability of the model introduced in this paper and a strong potential and necessity of investigation of voltage-type FCL.