Abstract: The self-commutated current source converter (SCC), which is composed of self-turn-off devices, has the characteristics of high power density, controllable power factor, no commutation failure, and flexible connection to the power grid. It has a broad application prospect in the field of high-voltage DC transmission. Aiming at the engineering application, this paper combined with the theoretical analysis and engineering requirements, analyzes and summarizes the key technologies of controllable current source HVDC transmission from five aspects: topology, modulation methods, control strategies, screening of power devices, and consistency of device voltage sharing, figure out the focus of the above five key technology research and their compatibility with engineering. Finally, the focus of SCC optimization, application prospects and problems that still need to be concerned are analyzed and summarized.