Wudongde Hydropower Station leads the world in UHV technology

Seetao 2022-04-27 17:49
  • Wudongde Hydropower Station has realized the application of flexible DC technology in multi-terminal, UHV and other projects
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The electricity we are accustomed to may be a drop of water in a river, a gust of wind on a plateau, or a ray of light in the sun. It may come from the fission of atomic nuclei or the surging of ocean waves. However, it is a very great and arduous project to make thousands of households have access to electricity and use good electricity.

When it comes to UHV, we have to mention the great century project "West-East Power Transmission". Wudongde Hydropower Station is not only a major clean energy project in the country's "Thirteenth Five-Year Plan" plan, but also the backbone of the "West-East Power Transmission" strategy. The development task is mainly to generate electricity. The installed capacity of the power station is 10.2 million kilowatts, and a total of 12 hydro-generator units with a single unit capacity of 850,000 kilowatts are installed. The average power generation design value for many years is 38.91 billion kilowatt-hours of green electricity. It is of great and far-reaching significance for the country to achieve the dual carbon goal and promote the sustainable development of power transmission from west to east.

Wudongde Hydropower Station, located on the main stream of the Jinsha River at the junction of Luquan County in Yunnan Province and Huidong County in Sichuan Province, is the fourth largest hydropower station in China and the seventh largest in the world, and the second largest single-unit power generation in the world. The first 10,000-kilowatt world-class giant hydropower station put into operation. On December 24, 2015, the Wudongde Hydropower Station was fully constructed. At the end of 2020, the Wudongde Power Station sent power to the Guangdong-Guangxi UHV multi-terminal flexible DC demonstration project, referred to as the "Kunliulong DC Project", was successfully put into operation. The Kunliulong DC project has formed an independent intellectual property system in overcoming the "stuck neck" problem, showing the top level of China's power industry technology and the core competitiveness of the energy equipment manufacturing field, and has achieved original innovation from 0 to 1. On the morning of June 16, 2021, all units of the Jinsha River Wudongde Hydropower Station were officially put into operation.

Wudongde Dam is a concrete double-curvature arch dam, which is poured in 15 dam sections, and the total amount of concrete poured is about 2.7 million cubic meters. The dam crest elevation is 988 meters above sea level, the maximum dam height is 270 meters, the arc length of the upstream surface of the dam crest is 326.95 meters, and the thickness-to-height ratio is only 0.19. The dam is an extra-high arch dam using low-heat cement concrete. Yang Zongli, director of the Wudongde Construction Department of China Three Gorges Corporation, said that the whole dam uses low-heat cement concrete, and the other one uses an intelligent grouting system. There are also 850,000 units that are currently the largest in production in the world. Hydroelectric unit. All the raw materials and equipment of the unit have been localized, which is very meaningful for our hydropower system and our country's major power. After the on-site inspection, the expert group highly praised that the dam of Wudongde Hydropower Station has excellent concrete performance and basically no harmful cracks, which can be called a "seamless dam" in the true sense. During the construction process, world-wide technical problems such as the blocking of diversion tunnels under 100 meters of water head and the treatment of 1.3 million square meters of high slopes have been overcome successively, creating "a number of world firsts" and "industry firsts".

Wudongde Hydropower Station, as the world's first ±800 kV UHV multi-terminal flexible DC transmission project, was completed and put into operation almost at the forefront of the annual energy news list. "The commissioning of the Guangdong-Guangxi UHV multi-terminal flexible DC demonstration project for power transmission from Wudongde Power Station marks an important milestone in the development history of China's DC power transmission engineering technology. As the world's first UHV multi-terminal flexible DC project, it leads flexible DC technology into The era of ultra-high voltage." said Rao Hong, Secretary of the Party Committee and Chairman of the South Network Research Institute.

Its appearance directly means that domestic hydropower development has begun to penetrate into the southwest region. In this regard, even the United States and Europe have expressed: This is simply incredible! At the same time, many people are also beginning to wonder how the Wudongde Hydropower Station built in China transmits electricity from the west to the east, and what has it changed?

Open a new era of UHV power transmission

There are many places in China with sufficient power resources, such as wind energy and hydropower in the northwest, but how can western power be sent to the central and eastern parts of the country where the electricity load is the largest? This requires long-distance transmission, and UHV plays an extremely important role in long-distance power transmission projects. Wudongde Hydropower Station is a three-terminal flexible DC project. Electricity is sent from Wudongde Hydropower Station to Guangxi and Guangdong. One of its three converter stations is near Kunming, Yunnan, one is in Liuzhou, Guangxi, and the other is in Guangdong. Longmen. In order to transmit hydropower efficiently and ensure the safety and stability of Guangdong and Guangxi power grids when receiving huge amounts of electric energy, the Kunliulong project is the first in the world to use a UHV multi-terminal hybrid DC system. The terminal adopts flexible DC to create a "Hong Kong-Zhuhai-Macao Bridge" for flexible DC transmission. The sending end of Kunbei, Yunnan is a conventional DC, and the two receiving ends of Liubei, Guangxi and Longmen, Guangdong are flexible DC.

Liu Chunxiao, assistant manager of China Southern Power Grid's General Dispatch and Mode Office, said that after the Kunliulong DC project was fully put into operation, it greatly increased the power transmission capacity of western China, and the maximum power transmission capacity of China Southern Power Grid reached 58 million kilowatts. During the peak summer season in 2021, the Kunliulong DC project has repeatedly reached a full load of 8 million kilowatts, with a daily power delivery of up to 192 million kilowatt hours, which is equivalent to meeting the electricity consumption of about 3 million people for a month.

"This solution is both economical, technologically advanced," explained Li Lizhen, academician of the Chinese Academy of Engineering and chairman of the Expert Committee of China Southern Power Grid Corporation. The hydropower in the west is sent to Guangdong and Guangxi, which have high demand for electricity, with a distance of nearly 1,500 kilometers and long-distance large-capacity UHV DC for power transmission is the most economical and efficient; however, after the conventional DC is connected to the grid, due to its inherent characteristics such as commutation failure, it will bring a certain impact on the security and stability of the receiving-end power grid system. "Flexible DC can solve these problems. It is more flexible in regulation and can support the safe and stable operation of the system at critical moments."

The flexible DC transmission is equivalent to a water pump. The conventional DC of this pump can only flow from the beginning to the end. The flexible DC can control the flow rate, and it can also have a drop point in the middle, which is more flexible. One million kilowatts can be sent to more than 2,000 kilometers long-distance. Among them, the Kunbei converter station can transmit 33 billion kWh of electricity every year, which is equivalent to the electricity consumption of the whole society in Hainan Province for a whole year.

"This is a super project that is leading the world, marking China's UHVDC transmission technology to an unprecedented level, creating a new transmission model, and providing a lot of valuable experience for the development of the world's power grid." Li Lizhen said that its technical difficulty and complexity All of them have reached the world's highest level in the current power transmission and transformation field, and the main equipment autonomy rate is 100%, which effectively promotes the upgrading of domestic related equipment manufacturing industries.

Flexible DC transmission leads the world

According to experts from the South Grid Electric Power Research Institute, flexible DC transmission is a new generation of DC transmission technology with fully-controlled power electronic device IGBT as the core. It is equivalent to connecting a valve and power supply to the power grid, which can effectively control the electric energy passing through it and isolate the spread of power grid faults; it can also emit or absorb part of the energy quickly, flexibly and tunable according to the power grid demand, thereby optimizing the power flow of the power grid. distribution, enhance grid stability, and improve the intelligence and controllability of the grid. At the same time, the project has achieved engineering practice success in the three cutting-edge and cutting-edge fields of world power grid technology, such as UHV, multi-terminal and flexible DC, especially the "heart" of flexible DC - "flexible straight valve" has successfully achieved that the system will not be affected by the failure of a single module Stable operation greatly reduces the number of bypasses of the flexible straight valve, and the key performance indicators are a whole generation ahead of foreign counterparts. The project also pioneered the DC fault self-clearing technology of overhead lines: when it encounters a sudden short circuit due to external environmental impact, it can resume normal operation within 0.5 seconds.

The project adopts flexible DC technology with higher safety, flexibility and stability. Flexible DC is a new technology. Before that, the highest voltage level of flexible DC in the world was ±500 kV, and the engineering was upgraded to an unprecedented ±800 kV. Since then, the world's UHV transmission technology has entered the flexible DC era.

Since the line has to pass through many complex geographical and climatic environments, the project also pioneered the DC fault self-clearing technology for overhead lines. When encountering a sudden short circuit due to external environmental impact, the project can resume normal operation within 0.5 seconds, ensuring the stable transmission of this energy "artery".

Xu Zhengzhan, a professor at Zhejiang University and a member of the International Institute of Electrical and Electronic Engineers: "This is an open-circuit project. Since then, flexible DC technology will be the first choice for long-distance and large-capacity power transmission projects."

The Chinese have realized the application of flexible DC technology in projects such as multi-terminal, UHV, and flexible DC power grids, and China will have great prospects for developing flexible DC technology. China Southern Power Grid Corporation has promoted the progress of flexible DC technology by applying it in the main power grid and mastering the UHV multi-terminal flexible DC technology, which will eventually play a core role in the future development of power grid technology.

The key equipment of the flexible DC converter valve is now the world's first domestic "heart" capable of withstanding ±800 kV UHV, which has been stably "beating" in the Gantry converter station. Some of these advanced technologies will be applied to the upcoming offshore flexible DC projects and will be used for reference by foreign manufacturers; IGBT key chips have broken the monopoly of a few foreign manufacturers.

"When a power station is built, the station will drive the economy of one party, improve the environment, and benefit a group of immigrants." The construction of Wudongde Hydropower Station has always adhered to this development concept. At the moment, the Jinsha River has a line of clear water running through the dam. It seems to be quiet, but it is releasing its mighty power to let "silver lines" pass through the city. The development of comprehensive green transformation plays a huge positive role.Editor/Ma Xue