The Beijing 2022 Winter Olympic Games will use 100 percent green electricity in all of its venues, a breakthrough in Olympic history. In this process, China has achieved brand-new technological breakthroughs within many fields.

The Zhangbei Pilot and Demonstration Project has adopted China’s original flexible direct current (DC) technology, which not only achieves 100% green power supply, but also makes 1/10 of the whole power load of Beijing clean. More importantly, the technology provides a Chinese solution for solving the world-class problem of large-scale development and utilization of new energy.

It is worth noting that with the world's first 500kV voltage grade mechanical DC circuit breaker developed by Pan Yuan, an academician from the School of Electrical Engineering, HUST, has made an irreplaceable contribution to the Zhangbei Project.

DC Circuit Breaker Research Team of HUST

Emerging in the 1990’s, Flexible DC is a new generation of DC power transmission technology that has voltage source converters at its core. It is the preferred technical route for large-capacity, long-distance and reliable power transmission, asynchronous grid interconnection, grid-connected transmission of new energy such as wind and solar, and construction of DC grids.

In recent years, the DC Circuit Breaker Research team has conducted in-depth and independent research in flexible DC technology, and a number of research results have been successfully put into operation.

DC Circuit Breaker: Empowering the "Green Winter Olympics"

With abundant wind and solar energy resources, Zhangbei is a key area for new energy development in Zhangjiakou, Hebei Province. Zhangbei Project is the world's first major science and technology demonstration project to realize the construction of a DC power grid which was officially put into operation on June 29th, 2020. The four-terminal grid was successfully established, and green electric energy was continuously injected into the Beijing power grid. It is understood that the Zhangbei Project can accept 22.5 billion degrees of clean electricity a year, which is equivalent to approximately 1/10 of Beijing's annual electricity consumption, which translates to around 7.8 million tons of standard coal. The project contributes to reducing carbon dioxide emissions by 20.4 million tons and nitrogen oxide emissions by 5800 tons, enormously increasing the proportion of clean energy consumed in Beijing effectively and demonstrating the win-win pattern of complementary advantages between Beijing and Zhangjiakou.

Upon the completion of the project, the 500kV mechanical DC circuit breaker, which was developed for three years, has been officially put into practice. Academician Pan Yuan, Professor He Junjia and their team including Yuan Zhao, Chen Lixue and Li Li worked in collaboration with Sieyuan, an electric company on the project.

This is the world's first 500kV engineering application for a mechanical DC circuit breaker based on artificial current zero of vacuum switch. With the characteristics of low operating loss, fast breaking speed, simple and reliable control and good economy, the new application innovatively shortens the fault clearance time after traditional DC circuit breakers turn off the DC.

Teachers and graduate students on the DC circuit breaker research team conduct experiments

Converter valve: assisting in major national projects

Promoting the transformation of the energy system to green and low carbon, Kunliulong DC Project was officially connected to the national grid and put into operation on December 27th, 2020, fully guaranteeing the power supply for the China Southern Power Grid in winter.

The geographical diagram of Kunliulong DC project

Kunliulong DC project has a rated voltage of about 800 kV and a rated transmission capacity of 8 million kilowatts. Three new converter stations have been built, spanning the four provinces of Yunnan, Guizhou, Guangxi, and Guangdong. With a total length of 1452 kilometers and investment of 24.26 billion yuan, it has amazingly reached the world's first level in 19 electric power technologies. The project will add 8 million kilowatts of channel power transmission capacity, which can transport about 33 billion kilowatt-hours of clean hydropower from Yunnan to the Guangdong-Hong Kong-Macao Greater Bay Area and the Guangxi load center every year. This is equivalent to reducing standard coal consumption by about 10 million tons and carbon dioxide by 26.6 million tons, with obvious emission reduction benefits.

Group photo of the core members of the DC power transmission research team of SGO Lab

The Kunliulong DC project is funded by the national key research and development program led by China Southern Power Grid Research Institute Co., Ltd., in which Professor Wen Jinyu, the head of the SGO Lab of School of Electrical Engineering, HUST, undertakes part of the project and is responsible for figuring out the problem of short-circuit faults in flexible DC lines.

Professor Wen works on site at Liubei Converter Station of Kunliulong Project

"The converter valve symbolizes the 'heart' of the flexible DC project, and the FaHS converter valve can strengthen the 'heart' and achieve self-protection." Team member, Xiang Wang, explained. Although there is no engineering precedent in the world for the self-removal technical route of flexible DC converter valve faults, the research team, which was overwhelmed by tight deadlines and a heavy workload, lack of reference and so on, concentrated on key obstacles and held multiple communication meetings to figure out major technical problems encountered in the manufacturing and testing process.

In the evaluation meeting of China’s key research and development programs, the project was evaluated by the expert group as “providing a brand new technical solution for the rapid elimination of short-circuit faults in flexible DC overhead transmission lines”, which is of great significance for China in achieving its commitment of eliminating carbon emissions and promoting its transformation into a low-carbon society.

Written by: Meng Ziyun

Edited by: He Rong, Andrew, Peng Yumeng