The Northwest Branch of State Grid Corporation of China jointly tackled the problem of improving the AC and DC transmission capacity of the high-proportion new energy power grid and improving the level of new energy consumption

China Energy Storage Network News: Dispatchers use the new energy multi-station online monitoring, early warning and auxiliary decision-making system to carry out their work.

At the end of March, the scientific and technological achievement "Key Control Technology and Application for High Proportion New Energy Power Grid AC and DC Transmission Capacity Improvement" led by the Northwest Branch of State Grid Corporation of China passed the expert appraisal organized by the China Electricity Council. The appraisal committee believes that the project has reached the international leading level in terms of time-space coordinated AC and DC transmission capacity improvement methods, new energy and other comprehensive sensitivity power distribution technology, and adaptive stability control.

The Northwest region has good endowment of new energy resources and great development space. In recent years, the Northwest Branch of State Grid has focused on the operation and control of high-proportion new energy power grids, achieved a series of innovative results, and accumulated practical experience. The branch applied innovative results to implement AC/DC coordination and mutual assistance, safety and control lean control and other measures. From 2019 to 2021, the cross-sectional capacity of the Northwest power grid was increased by 9 million kilowatts, ensuring that the utilization rate of new energy increased by 15 percentage points, and the proportion of new energy power generation increased from 16.06% to 21.17%. It is at the forefront of the country in the efficient use of new energy, laying a solid foundation for the construction of a new power system in the Northwest and promoting energy transformation.

Demand-oriented, grasp the key difficulties in the construction of new power systems

The Northwest region's exploitable wind energy accounts for one-third of the country's onshore wind energy, the exploitable solar energy technology accounts for 59% of the country's total, and the exploitable new energy capacity is as high as 1.9 billion kilowatts.

In recent years, with the rapid development of renewable energy power generation and DC transmission technology, the installed capacity of renewable energy power generation in Northwest China Power Grid has reached 143 million kilowatts, accounting for more than 40% of the total installed capacity of the entire grid. Northwest China Power Grid is asynchronously interconnected with other regional power grids through 11 DC transmission lines, with a total transmission capacity of 70.71 million kilowatts, making it the regional power grid with the highest proportion of renewable energy power generation installed capacity, the largest DC transmission scale and the strongest transmission capacity in my country.

At the same time, the characteristics of large DC and high proportion of renewable energy bring new challenges to the operation and control of the Northwest Power Grid. "The coupling degree between multiple DC and between DC and renewable energy is high, and the hidden danger of cascading failure is prominent. DC failure has a significant impact on the safety and stability of the power grid and the limit of important AC sections, which limits the AC and DC transmission capacity and the level of renewable energy consumption, and has an impact on the sustainable and healthy development of renewable energy in the Northwest." said Wang Jili, director of the System Operation Department of the Northwest Electric Power Dispatching and Control Center.

In response to the above challenges, the Northwest Branch of State Grid Corporation of China has focused on improving the AC and DC transmission capacity of high-proportion renewable energy power grids, organized Xi'an Jiaotong University, State Grid Corporation of China Nanrui Technology Co., Ltd. and other advantageous industry-university-research units, and focused on researching key technologies for high-proportion renewable energy power AC and DC transmission capacity, which took 7 years to form a series of technical achievements. After the achievements were applied to power grid control, the operation analysis and stability control capabilities of high-proportion renewable energy AC and DC transmission-end power grids were effectively improved.

Innovate and tackle key problems, and carry out a series of key technology research

On March 28, Li Wujing, a dispatcher at the Northwest Electric Power Dispatching and Control Center, clicked his mouse and used the country's first online monitoring, early warning and decision-making support system for multiple new energy stations to view real-time data on the Northwest power grid's new energy resources, output, stability level assessment indicators, and other real-time data, and optimized and adjusted the new energy output on this basis.

The online monitoring, early warning and decision-making support system for multiple renewable energy stations is one of the achievements of the project "Key Control Technologies and Applications for Improving AC and DC Transmission Capacity of High-Proportion Renewable Energy Power Grids". The system can intuitively and quantitatively evaluate the stability of renewable energy access by calculating and analyzing the voltage intensity of renewable energy stations connected to the power grid, and propose corresponding control plans and solutions for the hidden dangers found, guiding the operation mode arrangement of renewable energy and conventional units, and improving the intelligent decision-making control level of the Northwest Power Grid in terms of renewable energy operation control and operation mode arrangement.

Among synchronous power grids of the same size at home and abroad, the Northwest Power Grid is in a leading position in terms of DC transmission scale, proportion of installed capacity of new energy power generation, and many other indicators. There is no relevant experience to learn from at home and abroad on how to further improve the AC and DC transmission capacity of high-proportion new energy power grids. At the same time, the Northwest Power Grid has a relatively weak grid structure, and the situation faced by the power grid operation is complex. It is in a "no man's land" in areas such as power grid operation control. It must rely on innovative breakthroughs to fill the gaps and embark on a distinctive development path of independent innovation.

In order to continuously improve the transmission capacity of high-proportion new energy power grids and provide safe and reliable clean energy for a larger area, the Northwest Branch of State Grid organized technical experts and model workers to establish a large-scale new energy intelligent management and control and market mechanism innovation studio to lay the foundation for overcoming technical difficulties and promoting the implementation of the "dual carbon" goals in the Northwest Power Grid. The Northwest Branch of State Grid takes "strict, detailed, practical, new, high and fast" as the standard, starting from the actual needs of power grid operation, and taking the improvement of transmission capacity under high coupling of AC and DC as the research goal, and taking model research, mechanism analysis, quantitative evaluation, and control improvement as the research route, from AC and DC power grid modeling, DC-to-DC interaction analysis, DC-to-new energy interaction analysis, multi-DC transmission capacity improvement control and DC pole control and safety coordination control, etc., to carry out stability mechanism analysis and control technology research and equipment development, overcome a series of key technologies such as multi-DC mutual assistance, source-network coordination optimization, and adaptive adjustment of stability control strategies, and form a comprehensive and systematic solution for improving the AC and DC transmission capacity of high-proportion new energy power grids.

Application results to improve the transmission capacity and consumption level of new energy

After achieving technological breakthroughs, the project team actively carried out practical applications, and the relevant results were applied in the Northwest Branch of State Grid and provincial power companies such as State Grid Gansu, Qinghai, and Xinjiang Power. It significantly enhanced the stable operation and prevention and control capabilities of the Northwest power grid under DC faults, and improved the Northwest power grid's high-proportion new energy AC and DC transmission capacity and new energy consumption level.

From 2019 to 2021, the project results helped Jiquan, Tianzhong, Qingyu and other DC projects to increase their transmission capacity by a total of 4 million kilowatts in production and operation, and helped Xinjiang, Gansu and Qinghai power grids increase their new energy and DC transmission capacity by 11.02 billion kWh by improving the DC transmission capacity of Jiquan, Qishao and Tianzhong and expanding the space for new energy consumption. The project results helped the Northwest Power Grid increase its new energy power generation by a total of 5.5 billion kWh from 2019 to 2021, saving 1.758 million tons of thermal coal and reducing carbon dioxide emissions by 4.746 million tons.

Taking the Hami New Energy Base in Xinjiang as an example, Hami's installed capacity of new energy power generation exceeds 11 million kilowatts. Due to the limitation of the pressure resistance level of wind turbines, the transmission of new energy has been hindered. Since 2020, the Northwest Branch of State Grid has applied the technical results of the project and adopted innovative measures such as DC emergency control and optimized new energy power distribution to increase Hami's new energy transmission capacity by 3 million kilowatts. "The utilization rate of new energy has continued to increase in recent years. In 2021, the power generation of Hami Three Gorges Naomao Lake Wind Farm increased by 12.4% year-on-year, and the operating profit increased by 8% year-on-year." Zhang Yanan, director of the marketing department of Three Gorges Xinjiang New Energy Co., Ltd., introduced.