NR Electric Co., Ltd., Nanjing 211102, China

With large-scale asynchronous power supply replacing some synchronous motors in the traditional power grids, the power supply structure and grid skeleton are changing, and the power system will face the problems of the weak system, low inertia and weak voltage support. The flexible DC transmission system with grid-forming control can simulate the operation characteristics of synchronous motors and play the role of power grid support while realizing power transmission. This paper introduces the application scenario and technical framework of grid-forming control for flexible DC transmission systems and analyzes the key technologies of grid-forming control applied to the flexible DC transmission system from three perspectives of the grid-connected performance evaluation, broadband resonance stability and transient stability. This paper summarizes and analyzes the challenges in the three aspects of control parameter design, over-current capacity of primary equipment and energy sources as well as several technical directions.