To research the characteristics of hybrid HVDC systems with different structures

we designed and developed an experimental platform composed of Line Commutated Converter（LCC） and Voltage Sourced Converter（VSC） modules. By flexibly combining different modules

various hybrid HVDC structures can be constructed

and its control system framework can meet the requirements of the system control for various hybrid HVDC topologies. Firstly

we designed a main circuit and control structure of the experimental platform and constructed a general control framework composed of systematical and valve-based controllers. Then

we established a communication protocol and programmed the core control algorithm for the overall system. Finally

we conducted the DC current and voltage step-change experiments based on the hybrid HVDC structure

which adopted LCC as rectifier and VSC as inverter. The experimental results have proved the adaptability of the overall design of the experiment platform and its benign features under stable conditions

which is of great importance to related researches on hybrid DC transmission systems.