China Southern Power Grid's independent innovation supports the construction of Kunliulong DC project

China Energy Storage Network News: The dynamic performance test of the control and protection system of the Kunliulong DC project is in full swing. A total of more than 150 problems have been found, solving a number of major key technical issues such as DC line restart coordination and flexible DC station AC fault recovery characteristics.

"Before on-site debugging, we used the advanced grid panoramic mirroring system to carry out dynamic performance tests. We will conduct a comprehensive physical examination of the core control and protection equipment of the multi-terminal DC, fully discover possible hidden dangers, research and formulate performance improvement measures, and complete the closed-loop control of the system design. We strive to complete it by the end of May." said Guo Qi, senior technical expert of China Southern Power Grid Co., Ltd. and captain of the engineering breakthrough party member assault team of China Southern Power Grid Research Institute.

China Southern Power Grid is taking the "new infrastructure" project as a starting point, and through repeated technological breakthroughs, it has mastered a number of key technologies and core technologies with independent intellectual property rights. At present, the key equipment technology research and development of the Kunliulong DC project, including ultra-high voltage flexible DC converter valves, system integration and control protection, has entered the final stage. The overcoming of technical difficulties such as ultra-high voltage flexible DC and multi-terminal hybrid DC has laid a solid foundation for the project to be put into operation on schedule in August this year.

The Kunliulong DC project integrates the most complex and cutting-edge power grid technologies, including UHV multi-terminal DC, UHV large-capacity flexible DC, UHV hybrid DC, and UHV flexible DC applied to long-distance overhead lines. It is the first time that flexible DC transmission technology has been applied to a project that integrates UHV, large-capacity, multi-terminal, hybrid DC.

From sorting out major technical issues in engineering applications to jointly developing key equipment with manufacturers, every step forward requires scientific researchers to break through the rut of thinking and solve new problems through technological innovation.

The application of new technologies and new equipment in engineering often means more challenges. "Many new equipment have to pass three levels: research and development, on-site commissioning, and long-term rigorous tests under high voltage and high current of the system. It is necessary to ensure that the equipment is technologically advanced and of reliable quality through multi-dimensional scientific and technological innovation." Hu Yulong, deputy manager of the Wudongde DC Project Department of the UHV Company, introduced that the research team solved the reliability and "black module" problems of large-capacity and large-scale power electronic devices through parameter optimization, test screening and cross-redundancy design, and made innovative breakthroughs in the "research of high-reliability power module bypass technology", achieving the goal of "single module failure does not cause system tripping".

The addition of the third terminal of the Kunliulong DC project has doubled the number of combinations of project operation modes. Guo Qi introduced that the total number of FPT/DPT test items in the Kunliulong DC project exceeds 1,600, an increase of more than 700 items compared with previous projects. When conducting tests, it is necessary to consider the coordination of multi-terminal control systems. Some test items do not have ready-made test methods, and they need to study and explore test plans on their own, which greatly increases the difficulty of the test.

"We spend a long time on the experiments and involve many test items in order to take various possibilities into consideration and eliminate problems in the laboratory through sufficient verification. However, there are many problems that are difficult to verify, such as lightning strikes. You may set a short-circuit point in the laboratory simulation, but lightning strikes in nature are very complex and these must be verified on site," said Li Yan, senior technical expert at the State Grid Corporation of China and assistant to the director of the State Grid Research Institute.

This is only a small part of the scientific research breakthroughs of the Kunliulong DC project. "Mastering key technologies and core technologies actually means that we have to independently solve all the key technical points in the complete chain, from proposing technical solutions, researching and testing equipment in the project, to solving all technical problems in the project operation," said Li Yan.

In recent years, China Southern Power Grid has achieved continuous breakthroughs in core technologies of flexible DC transmission by relying on specific projects. From the Nan'ao ±160 kV multi-terminal flexible DC demonstration project to the Luxi back-to-back project, a large number of scientific research talents have been trained, driving the development of domestic flexible DC transmission technology and equipment. Now, researchers of China Southern Power Grid will also achieve new breakthroughs in ultra-high voltage and large-capacity flexible DC transmission technology by relying on the Kunliulong DC project.

Original title: Independent innovation supports the construction of Kunliulong DC project