VSC-HVDC Project with the World's Highest Voltage and Transmission Capacity Completed and Put into Operation

On August 29, the VSC-HVDC Unit of Luxi Back-to-Back Asynchronous Interconnection HVDC Project, which is of the world's highest voltage and transmission capacity, was completed and put into operation.

Luxi Back-to-Back Asynchronous Interconnection HVDC Project is one of the key projects of CSG. Located in Luoping County, Yunnan Province, it is the first back-to-back project in the world that combines both VSC DC and conventional DC. The project not only enhances the overall safety and stability of CSG's main grid and the transmission capacity of Yunnan Power Grid Company, but also provides clean, cheap and green power to Guangdong and Guangxi provinces. It promotes the development of China's equipment manufacturing industry and the optimization of power structure. Also, the completion of this VSC-HVDC project, with such high voltage and transmission capacity, has set a good example and provided significant experience for future power grid development.

It is said that, as a new HVDC technology, VSC-HVDC is more flexible in its control than conventional DC. It transmits higher quality power and requires a smaller convertor station, which is very conducive to the development of power grid in terms of energy conservation and intellectualization of equipment.

"VSC-HVDC technology does not need the support of AC voltage, so it is more flexible in its control and with higher power quality. Besides, its convertor station covers a smaller area. So it can effectively avoid commutation failures of conventional DC caused by the AC voltage instability," said Zhou Jingyu, technical management engineer of the Asynchronous Interconnection Project Department of CSG EHV Power Transmission Company, "For example, in terms of intelligence, it takes at least a few hours to reverse conventional DC power flow but only dozens of milliseconds to reverse VSC-HVDC. Besides, compared to the conventional DC at the same voltage level and with the same transmission capacity, VSC-HVDC convertor station can save a third of land occupation. Take the Luxi Converter Station as an example, it saves ​​nearly 100 mu (6.67 hectares) of land. "

"It is reported that the project claims a number of world firsts in the field. In addition to the initiative parallel running of conventional DC and VSC-HVDC units, it has a nominal capacity of 1,000 MW and a DC voltage of ± 350 kV, both of which by far have risen to the world's highest level. And the project is 100% self-reliant."

As it is the first project in the world to use high-voltage, large-capacity VSC-HVDC technology, there is no proven engineering experience to draw on. But CSG managed to overcome several world-class problems concerning the coordination and control of conventional DC and VSC-HVDC, and the limitation of multiple power modules in a single convertor. Meanwhile, CSG also organized domestic equipment suppliers to actively carry out researches, and formulates hundreds of design specifications. Through many design liaison meetings and several thousand functional and dynamic tests on power system control and protection, it has established in the field of VSC-HVDC a complete set of technical specifications and standards with intellectual property rights, and obtained more than 100 patents, topping the world record in the field of high-voltage, large-capacity VSC-HVDC.

"The success of this project promotes the development and innovation of high-voltage, large-capacity VSC-HVDC technologies, including the overall design and testing technology. It also facilitates the development of equipment manufacturing industry. VSC-HVDC will be widely applied in wind power, solar power and other renewable energy’s connection to the grid, " explained Cai Xipeng, Deputy Chief Engineer of CSG EHV Power Transmission Company.