A dynamic simulation experimental platform for hybrid HVDC transmission is established, which adopts line commutated converters (LCCs) in rectifier station, and hybrid modular multilevel converters (FHMMCs) based on half bridge sub-module and full bridge sub-module in inverter station. In order to increase the system capacity, the FHMMC on the inverter side adopts a structure with valve groups in series. The key technologies such as valve groups deblocking and blocking and DC fault ride-through with different proportions of the full bridge sub-module are studied, and the experimental verification on the dynamic platform is carried out. The results show that the proposed control strategies can realize the valve groups deblocking and blocking and DC fault ride-through of the hybrid HVDC transmission system, and a demonstration platform for the application of hybrid HVDC transmission and voltage source converters is provided. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 52110418001W) Key Technologies Research on Flexible DC Converter Valve Reliability Upgrade.