Multi-terminal hybrid ultra-high voltage direct current (UHVDC) transmission system provides a more flexible mode to meet the needs of longer distance and larger capacity renewable energy. In this paper, the hybrid system composed of the conventional UHVDC at the sending and the valve group series structure at the receiving is used. The RT-LAB real-time simulation model of bipolar hybrid system is built, the closed-loop connection with control and protection system is realized. The results verify the effectiveness of the closed-loop simulation model and the control and protection strategy. It can realize the verification of control and protection system function and dynamic performance of the hybrid system, and provide technical support for the application of multi-terminal hybrid UHVDC project.