Abstract:In order to the large-scale application of HVDC flexible technology in china southern grid, established the first distribution grid HVDC flexible demonstration project at Guizhou province. From construction and electrical engineering developed suitable rectifier, inverter, transformers, filters, and equipment control and protection system. Verify the HVDC flexible equipment, system access solutions, operation mode and witching method, transmission distance, control and protection strategies technologies. Detailed description of the project commissioning process, the ultimate test and commissioning results show that the whole system has high reliability, low loss, able to switching between single and double terminal operation. It proved the feasibility and generalizability of the technology.