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Expanding Application of Anti-icing and Disaster Mitigation Technology and Equipment in New Power System

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Expanding Application of Anti-icing and Disaster Mitigation Technology and Equipment in New Power System

Guizhou Province is located in the Yunnan-Guizhou Plateau. In winter, the cold air from the north and the warm and humid air climbing from the south meet here, forming a special "quasi-stationary front". In addition, the temperature often hovers below zero degrees Celsius. The unique geographical and climatic environment can easily cause ice and snow freezing disasters. According to the statistics of Guizhou Meteorological Bureau, since 1961, there have been 119 provincial freezing processes in Guizhou Province, ranking first in the country in terms of number of occurrences, long duration and high degree of harm. At the beginning of 2008, Guizhou power system suffered the most serious freezing disaster, which caused huge losses to Guizhou power system and had a great impact on the people's livelihood.

After the ice disaster in 2008, Guizhou Power Grid Company, under the unified and coordinated command of China Southern Power Grid Company, invested a huge amount of scientific research funds and developed a series of research and development.DC ice-melting deviceIn order to deal with the grid ice disaster, and large-scale promotion and application. From the first generation of DC ice-melting device with thyristor as the device, the second generation of DC ice-melting device with SVC function, and gradually developed to the third generation of new flexible DC ice-melting device with IGBT as the device. So far, 61 sets of various DC ice-melting devices have been applied in Guizhou power system, including 4 sets of the third-generation flexible DC ice-melting devices. These anti-icing technologies and equipment have greatly reduced the ice disaster losses of the Guizhou power system, but in a long period of time, the trend of global warming will not undergo a fundamental change, and the probability of extreme weather conditions is still increasing. Freezing disasters will also be a severe challenge for the Guizhou power system for a long time.

High proportion of new energy access is a new problem facing Guizhou power system

Guizhou power system thermal power as the main force, water and fire co-integration of the power grid is facing a high proportion of new energy access problems. According to the 14th Five-Year Plan for Electric Power Development in Guizhou Province, by 2025, the province's installed capacity will be 9 million kilowatts of wind power, 31 million kilowatts of photovoltaic power and 850000 kilowatts of biomass power generation, with a total installed capacity of 40.85 million kilowatts of new energy, accounting for more than 40%. It is estimated that by 2030, the province's installed capacity of wind power will be 13 million kilowatts, 47 million kilowatts of photovoltaic power generation, 2.85 million kilowatts of biomass power generation and 2.7 million kilowatts of pumped storage.

With the explosive growth of wind, light, biomass and other new energy power generation capacity, it will bring many severe challenges to the stable operation of the power grid. First of all, the wind and other new energy power generation installed is different from the traditional synchronous generator set, its steady-state characteristics and transient characteristics are very different from the traditional water and fire units, its large-scale access will have a profound impact on the frequency stability, voltage stability and transient stability of the power grid. Photovoltaic power generation relies on solar energy, which has no moment of inertia and cannot provide damping to the system. The variable speed constant frequency wind turbine uses power electronic devices to connect to the Internet, which makes the electromagnetic power and mechanical power decoupled, and cannot provide the moment of inertia to the power grid, which also has a negative impact on the frequency stability of the power grid. Secondly, the output of wind power and photovoltaic power generation are unstable and limited by meteorological environmental conditions. Although the prediction of wind power output has become more and more accurate, it is mainly based on new power systemIn China, the grid peaking and new energy consumption still face great challenges. Finally, the variable speed wind turbine in the continuous operation and switching process, will produce voltage fluctuations and flicker, bring high harmonics, but also produce power system voltage stability problems.

Functional Reuse Technology of Flexible DC Ice-melting Device

In order to solve the problems of frequency stability, voltage stability and transient stability brought about by large-scale access of new energy sources such as wind and light, it is imperative to establish a new interconnected complementary power network of "source, network, load and storage" by using flexible DC transmission and distribution technology, so as to improve the frequency stability, voltage stability and harmonic suppression capability of the local power grid at the sending end of high-proportion new energy sources. Combined with the characteristics of the western region of Guizhou power grid, which is rich in new energy and is also a heavy ice area of the power system, priority can be given to the construction of large-capacity flexible DC ice melting devices in Guizhou Bijie, Liupanshui and other new energy rich areas, while the pilot construction of centralized energy storage power stations, including grid-side energy storage regulation and new energy flexible access "one multi-use", so as to resist ice disasters and deal with large-scale new energy access ".

The third-generation new flexible DC de-icing device adopts the topology based on the full-bridge MMC, which is completely consistent with the structure of the STATCOM device, but the application scenario is different. In the existing flexible DC de-icing device of Guizhou power grid, the functional reuse of DC de-icing and dynamic reactive power compensation has been realized. With the increasing proportion of new energy access in the western region of Guizhou power grid, it is urgent to solve the problem of intermittent power supply regulation and the stability of "double high" power system. Based on the existing flexible DC ice-melting technology, its function is extended, and a new generation of general-purpose energy routing device with DC ice-melting function and power conversion function is developed. On the basis of the aforementioned DC de-icing and reactive power compensation function reuse, the device introduces a large-capacity energy storage device on the DC side, and uses the characteristics of fast transient response speed of power electronics (usually within 10 milliseconds). The large-scale energy storage station system can quickly inject active power into the system when the power grid fails, thereby improving the frequency stability of the system. At the same time, large-scale centralized substation energy storage system is also conducive to the new energy peak filling valley, reduce the probability of new energy abandoned wind and light.

Actively Tackling Key Technologies to Expand Application Scenarios of Anti-icing Equipment

Guizhou Power Grid has carried out a detailed investigation and analysis on the technical route of DC de-icing device with grid-side energy storage. Due to the rigid requirements of DC ice-melting of transmission lines, the capacity of flexible DC ice-melting devices is usually relatively large, which is very conducive to the construction of large-capacity energy storage stations with functional reuse. However, in order to realize the ice-melting of long transmission lines, the DC output voltage of the flexible DC ice-melting device is relatively high, usually greater than ± 10 kV. To this end, the DC bus of the flexible DC de-icing device is used as a common bus, and the DC voltage matching problem between the electrochemical energy storage system and the power grid needs to be solved, as well as the problem that the storage battery is connected to the medium voltage DC bus (± 10 kV, ± 20 kV). A feasible technical route is to make the battery pack into a functional sub-module by DC/DC boost, and then connect a plurality of functional sub-modules in series with a medium voltage DC bus in a cascade mode, and each series branch can be designed and manufactured in a modular manner. More modular branches are connected in parallel and converge on the same medium voltage DC bus, which can form a large energy storage station system. At present, there is no mature prototype in China, and Guizhou Power Grid is likely to achieve research breakthroughs and demonstration applications of this new technology due to the innate advantage of flexible DC de-icing device application scenarios.

The new energy-rich area of the power system in Guizhou Province is also the heavy ice area of the power system, which makes the demand for anti-icing and the demand for large-scale access of new energy highly coincide. Therefore, in the process of building a new power system in Guizhou Province, by making a good preliminary plan and coordinating the construction requirements, the newly-built substation for large-scale access of new energy can be turned into a general energy routing node with both DC ice melting function and power conversion function, thus realizing the coordination of network source, load and storage, and improving the resilience of the power grid to cope with extreme weather while improving the absorption capacity of new energy. In addition, for the dozens of sets of ice melting devices deployed in Guizhou power grid, it can be considered in the future due to aging and renovation, from the planning and design of overall consideration, to ensure the functional reuse of alternative devices in DC ice melting and power conversion. To this end, Guizhou Power Grid should make use of the South Grid anti-icing and disaster reduction joint laboratory platform, adopt the industry-university-research collaborative innovation model, deploy relevant project research, tackle key technologies and key equipment, and carry out demonstration applications, so as to lay a good foundation for the construction of a new power system with new energy as the main body with Guizhou characteristics.

Article from: Polaris power network