Abstract A hybrid HVDC transmission system based on a line-commutated converter (LCC) and an alternate arm converter (AAC) is developed in this article. The basic operation principles and control methods of the proposed LCC-AAC hybrid HVDC system are demonstrated following with appropriate system design and parameter selection. In addition, this paper proposes a set of control schemes for riding through ac faults and handling dc fault. The operation and performance of both converters in such a hybrid HVDC configuration are verified through a detailed set of results based on a 3000 MVA LCC-AAC hybrid HVDC system including steady state operation, ac-grid harmonics & dc-side ripple analysis, reference tracking (active power change at LCC station, reactive power change at AAC station) and system performance under ac-grid faults without blocking converter at both terminals of the HVDC system. Also, the response of the hybrid system under dc fault presents potential dc fault handling capability compared with the hybrid system based on LCC and modular multilevel converter (MMC) with half-bridge submodules (HBSMs). The hybrid LCC-AAC HVDC transmission system lays preliminary steps for research on complex mixed converter multiterminal dc configurations in future dc super grids.