Abstract -- With the increasing capacity and transmission distance of the power grid, HVDC technology has been more and more widely used. MTDC is an essential direction for the development of HVDC technology. At this stage, LCC is widely used in the MTDC transmission project, and there is a lot of corresponding design software, but the software development of the hybrid DC transmission is not perfect and mature enough. In this paper, the design method of the parameters of the main loop in the LCC-MMC hybrid HVDC transmission system has been studied. The corresponding design software has been compiled, and this paper presents functional modules to be accomplished in the software package. The correctness of the software calculation is verified by the actual HVDC transmission project data, and the software can be applied to the initial design of the hybrid HVDC transmission project.

Line commutated converter, modular multilevel converter, multi-terminal direct current, software design