The "China's First" Power Station, which even relies on imported turf, has been replaced with a "domestic heart", adding a new business card of "Made in China" to Shanghai | Engineering | Business Card
Recently, the equipment renovation project for the ± 500 kV Nanqiao converter station in Shanghai has been officially completed and put into operation. Clean water and electricity from Gezhouba are continuously flowing into the Shanghai power grid, providing more reliable and abundant external clean energy for peak summer season. The project adopts the world's first controllable commutation valve technology with completely independent intellectual property rights, transforming this former "foreign substation" into a "Chinese high-end manufacturing" business card, providing continuous "green" support for Shanghai's economic development.
Domestic substitution of core components
The Ge'nan HVDC transmission project, completed and put into operation in 1989, is China's first ± 500 kV ultra-high voltage direct current transmission line, and the Nanqiao converter station, which was also put into operation at the same time, is also China's first ± 500 kV DC converter station. It is the main "foothold" for Shanghai Power Grid's external power supply to Shanghai. As an important channel for external power to enter Shanghai, this line has continuously supplied clean hydropower from Gezhouba to the Shanghai power grid for more than 30 years. Over the past 34 years of operation, it has transmitted a total of 180 billion kilowatt hours of electricity, providing important energy security for the Shanghai economy.
At the beginning of the construction of the Ge'nan DC project, China's power industry was still lagging behind, and all types of equipment inside the station were imported. With the increase of years, equipment such as converter valves are severely aging and unstable in operation. "In 1989, China's power industry was still relatively backward. The equipment at Nanqiao converter station came from different countries, and even the grass on the outdoor field and the small nuts of the assembly equipment were imported. The core of this renovation is to achieve the localization replacement from imported equipment to domestic equipment." Wang An'an, the deputy station manager who has worked at Nanqiao converter station for 34 years, introduced.
Meanwhile, due to the dense distribution of incoming DC points in the East China region and the proximity of the receiving end Nanqiao Station to numerous converter stations, the problem of multiple DC interlocking commutation failures is prominent. The original technology and equipment are no longer able to meet the needs of safe and stable operation of the project. In order to enhance the stability and reliability of the Three Gorges clean hydropower project entering Shanghai and ensure the power supply in East China, State Grid Corporation of China spent six months carrying out overall technical upgrades on the core equipment of the Nanqiao converter station.
According to State Grid Shanghai, the biggest highlight of this renovation project is the use of controllable commutation valves instead of traditional ones for the first time. This is a significant innovation in traditional ultra-high voltage direct current transmission technology and has an extremely important demonstration and leading role.
The addition of a new "aorta" to the "Chinese heart"
The converter valve is the "heart" of DC transmission engineering, and its function is to achieve the interaction between AC energy similar to "arteries" and DC energy as "veins". The traditional converter valve is composed of a semi control device that can actively conduct and cannot actively turn off. Although it has the advantages of large capacity, low loss, and high reliability, it also has the defect of being prone to "commutation failure".
The risk brought about by this defect is equivalent to the "heart arrest" of kilowatt level energy caused by small disturbances in the "arteries" of the converter valve. This "stubborn disease" brought by genes has long plagued the development of DC transmission technology, restricting the further improvement of the large-scale transmission capacity of clean energy from the central and western regions to the eastern load center.
To this end, the Smart Grid Research Institute, a subsidiary of State Grid Corporation of China, established a technology research team in 2019. After five years of continuous exploration, it creatively proposed the technology of controllable commutation converter valve. The device adopts a parallel dual branch structure with hybrid full control and semi control devices. Mao Yingke, a Shanghai craftsman and deputy director of the ultra-high voltage AC/DC operation and inspection center of State Grid Shanghai Ultra High Voltage Company, used a simple analogy to describe this new technology. "The converter valve is like the 'heart' of a large converter station. Compared to the original traditional converter valve, the controllable commutation converter valve is like setting up an auxiliary aorta on the 'heart', thereby avoiding the occurrence of 'cardiac arrest' when the aorta is abnormal."
In addition, in the upgrade and renovation of the control and protection system, "China Heart" with fully independent intellectual property rights has successfully replaced the original "Foreign Heart", further improving the reliability of the safe operation of the converter station. Controllable commutation converter valve is a high-end power equipment independently developed in China, with a large number of electronic components, high precision, and difficult assembly. The technical experience in practical application is also blank.
In order to ensure the successful demonstration of this technology in the Ge'nan DC renovation project, State Grid Shanghai Electric Power Company continuously optimizes the construction renovation operation and operation debugging plan, ultimately ensuring that the renovation task is completed ahead of schedule, the equipment is successfully connected to the electrolytic lock in one go, and demonstrates excellent fault crossing and system support capabilities in fault simulation tests.
Renovation of old power stations is like building blocks
Compared to the construction of new converter stations, old converter stations like Nanqiao Station have shorter renovation times, higher operational risks, and limited construction scope, making them a "dojo in a snail's shell". The State Grid Shanghai Power Project team has introduced advanced technologies such as building information systems, digital safety briefing, steel structure stress monitoring, and remote visual safety control systems to solve construction problems, based on their successful experience in renovating old stations. They have strengthened risk control and quality tracking from the source. "Based on the actual situation on the construction site, we have developed a total of 10 special construction plans and 25 general construction plans, refined to every aspect of the project, and strictly implemented the main responsibility." said Bai Qiang, Project Manager of the Planning and Engineering Department of State Grid Shanghai Ultra High Voltage Company.
In the installation process of controllable commutation converter valves, in order to smoothly lift the valve tower module, the construction party East China Power Transmission and Transformation Company used a suspended installation platform for operation. 12 new valve lifting beams were installed as new lifting points in the valve hall. Each level of valve tower module "rides" on a suspended installation platform and rises vertically, like building blocks. Finally, the entire assembly was completed in less than 3 months.
From April 24th to May 12th, State Grid DC Technology Center, State Grid Shanghai Electric Power Equipment Department, and State Grid Shanghai Ultra High Voltage Company organized various professional technical experts to conduct a comprehensive acceptance of the renovation project and promptly rectify any issues that affect safe operation. Subsequently, from May 14th to June 18th, the Equipment Department of State Grid Corporation of China organized various participating units and equipment manufacturers to carry out system debugging, and successively carried out Ge'nan DC short circuit test and 220 kV AC line short circuit test, fully verifying the reliability of the new equipment and ultimately ensuring the successful primary power transmission of Nanqiao converter station.
The renovation and successful operation of the Ge'nan DC transmission project have consolidated China's leading position in the field of high-voltage DC transmission technology. The successful demonstration application of controllable commutation valve technology provides a new technical solution for large-scale clean energy integration in regions such as East and South China in China. In the future, this technology will be further promoted and applied in the power planning of the 14th Five Year Plan and beyond, opening up a new path for the "West East Power Transmission" strategy.
