On-site report of high voltage ride-through test of China Electric Power Research Institute

By the end of 2018, the installed capacity of new energy in China reached 377 million kilowatts, surpassing hydropower to become the second largest power source in my country. The rapid development of new energy has played an important role in my country's energy transformation, but it has also caused problems with the development plan of the power grid, leading to the emergence of wind power abandonment and power rationing. The State Grid Corporation of China has solved the problem of wind power consumption by building ultra-high voltage transmission projects. In order to gain a deeper understanding of how to ensure the stable and safe operation of new energy power stations and ultra-high voltage power grids after wind power is connected to ultra-high voltage, the reporter followed the wind power testing team of the New Energy Research Center of China Electric Power Research Institute Co., Ltd. (hereinafter referred to as "China Electric Power Research Institute New Energy Center") to the China Electric Power Qiaowan Wind Farm in Yumen City, Gansu Province, to gain an in-depth understanding of the wind farm's grid-related performance transformation work.

Grid connection detection improves consumption capacity

The gravels in the river are as big as buckets, and the stones are scattered all over the ground with the wind. The wind resources in Yumen area are very rich, and it is known as the "world's wind outlet". If Yumen was mentioned before, people would think of the desolate and lifeless desert Gobi, but now the Gobi is accompanied by rows and rows of neatly running wind turbines. Due to the development of wind power technology, the wind that was once a "harm" has become a "treasure" today.

Unlike traditional power sources, wind power is intermittent and volatile, which will affect the stable operation of the power grid and even threaten the safety of the power grid in serious cases. In early 2011, there were many large-scale wind turbine disconnection accidents in Gansu Province. The reason was that the wind turbines did not have the ability to ride through low voltage, which magnified the power grid accidents. "In order to solve the problem of large-scale wind power disconnection, we cooperated with wind turbine manufacturers to carry out research on wind power grid connection technology and verify the modified models. After 2012, there has been no large-scale wind power disconnection accidents in Gansu Province." Chen Chen, a testing engineer at the New Energy Center, introduced to reporters.

When the reporter arrived at the wind farm, two members of the inspection team were connecting the wires in an orderly manner. They were conducting random inspections of high voltage ride-through of wind turbines. Liu Xudong, an inspection engineer at the New Energy Center, told the reporter: "The installed capacity of wind power in Gansu does not match the local consumption capacity. It is difficult to fully consume wind power locally. The surplus wind power needs to be transmitted to the central and eastern regions through UHV DC transmission projects. Wind power has the potential risk of large-scale disconnection from the grid during transient overvoltage caused by UHV DC faults. UHV DC transmission of large-scale wind power poses a safety hazard."

In order to efficiently solve the absorption problem and avoid the safety risks of UHV operation, wind power development companies, wind power manufacturing companies, China Electric Power Research Institute and other units have carried out work to improve the performance of UHV DC near-zone wind power grid-related projects to enhance the stability of the power grid.

"After the Spring Festival, we have been carrying out high-voltage random inspections in Yumen, running between various testing sites. One colleague in the team even only stayed at home for a dozen hours after the Spring Festival." Chen Chen said.

Because wind farms need to be built in places with abundant wind energy resources, which are generally located in inland wastelands or deserts, the testing work environment is very harsh. "Each member of the testing team basically travels for more than 200 days a year. Compared with the harsh environment, what we need to overcome more is the longing for home and relatives." Liu Xudong introduced to reporters.

However, since they are determined to engage in the new energy testing industry, they must stick to it. They firmly believe that with the increasing consumption of fossil energy, new energy will become the trend of world energy development because it is related to our common green home. Testing can solve a series of problems faced by the development of the wind power industry, and this is the value they stick to.

Since its establishment 13 years ago, the testing team has been conducting type tests and grid-connected tests on wind turbines to safeguard the healthy development of new energy. In recent years, the probability of large-scale grid-offline accidents has been greatly reduced, and the safety and stability of grid operation has been greatly improved.

Realizing international mutual recognition to safeguard industrial development

Conducting wind turbine testing is not an easy task. The wind turbines being tested must actually operate in wind farms or testing sites, and the testing equipment must be able to simulate various grid faults. The long testing cycle, complex wind conditions, and high equipment costs are all challenges that must be faced. In addition, a testing system must be developed to help wind turbine manufacturers conduct independent research and development.

my country's wind power testing work started relatively late, and the standards initially adopted were mainly based on the conversion of IEC international standards, which could not meet the needs of domestic wind power development. After more than ten years of research and practice, China Electric Power Research Institute established the National Energy Large Wind Power Grid-connected System R&D (Experimental) Center, and built a supporting Zhangbei Wind Power Test Base with a total area of ​​24.6 square kilometers. It independently developed all the equipment required for wind turbine testing and led the compilation of dozens of national and industry standards in the field of wind power testing. The resistor-capacitor boosting principle adopted by its independently developed high voltage ride-through capability device has also been recognized by European and American counterparts and written into the latest published IEC 61400-21-1:2019 standard.

In 2017, China Electric Power Research Institute officially obtained the certificate issued by the International Electrotechnical Commission, becoming the first accredited laboratory in the field of renewable energy in Asia. The international recognition of China's wind power testing capabilities has expanded from mutual recognition within internationally renowned institutions to mutual recognition within the IEC standard system.

With the joint efforts of all parties, the performance of my country's wind turbines has been qualitatively improved, the probability of large-scale grid-offline accidents has been greatly reduced, and the safety and stability of power grid operation has been greatly improved. The latest data from the National Energy Administration shows that in 2018, the national average wind power utilization rate was 93%, exceeding the 2018 wind power utilization rate target of 88%, and all key provinces and regions have achieved the 2018 consumption target.

Today, the test reports of China Electric Power Research Institute have become the golden signboard for my country's wind power industry to "go global". It is understood that the New Energy Center has completed fault ride-through capability test projects for manufacturers such as Goldwind Science & Technology and United Power in accordance with the grid connection standards of Australia, South Africa, the United States and other countries, and the test reports and certificates issued have been recognized by foreign authoritative certification agencies and power grid companies. In addition, the New Energy Center has also carried out power quality and low voltage ride-through capability test projects for manufacturers such as Siemens, Vestas, and GE in Spain, Denmark, Sweden, Poland and other countries. The "Chinese voice" in the international wind power market is getting louder and louder.

By the end of 2018, the New Energy Center had provided technical research and development and testing services for more than 200 types of wind turbines at home and abroad, which promoted the successful entry of many Chinese wind turbine manufacturers into the international market, and promoted the improvement of my country's wind power equipment manufacturing level and the sustainable development of my country's wind power. Today, wind turbines tested by the New Energy Center have been exported to 27 countries including the United States, Sweden, Spain, Australia, Ethiopia, Italy, Turkey, Pakistan, Bulgaria, Chile, etc.