The power demand increases rapidly in China; however, the areas of huge power demands are of longdistance from most areas of abundant energy resource in the country. Therefore,China put in great effort to develop ultrahigh voltage (UHV) power transmissionsystems to optimise its energy allocation. This includes (i) systematicallydeveloping key technologies such as overvoltage suppression, external insulationdesign, and electromagnetic environment control, and (ii) developing keyequipment such as UHV alternative current (UHVAC) transformers, circuitbreakers, and series compensated equipment, and UHV direct current (UHVDC)converter transformers, smoothing reactors, converter valves, and DCtransmission control and protection systems. Eight AC UHV projects and 11 DC UHVprojects have been built in China, which play an important role in the optimalallocation of energy. Plus there are one more UHVAC and three more UHVDCtransmission projects in construction, while UHVAC gas-insulated lines will beapplied in the UHVAC line crossover the Yangtze River and the ±1100 kV UHVDCpower transmission technology is in development. Here, the development andapplication of UHV power transmission technologies in China are described, somemain challenges the UHV projects encountered are discussed, and experiencesobtained from the operation of UHV systems are introduced. It is concluded thatChina obtained mature experience in developing, constructing, and operating UHVsystems and successfully realised long-distance, large-capacity powertransmission, and the UHV power transmission technology has become an importantmeasure for energy allocation in large areas.
The major problem in current online diagnosis and analysis for power system oscillation is mainly concerned with finding the oscillation source in a fast and correct way using the data collected by the Wide Area Measurement System (WAMS). This paper for the first time proposes a scheme of cut set energy based on WAMS. Independent of accurate parameters, the scheme can make full use of WAMS data based on cut set energy construction and fast calculation to locate the source during oscillation. Afterwards, a scheme of torque decomposition is proposed, based on which the controller's torque can be divided into damping torque and synchronous torque by calculation through WAMS data, and this paper puts forward the abnormal response and simulation models calibration of influential controllers. Analysis of an oscillation case shows how the cut set energy scheme and the torque decomposition scheme are applied in a real-world power system, and the schemes are proven to be reliable and practical in identifying and locating oscillation sources.
In developing power grids, setting standards is critical to its success. The development of China's power industry has proposed new requirements for power systems to ensure secure and stable operations. The principal standards for the security and stability of China's current power systems are analyzed in terms of operational control, generator-grid coordination and simulation. The shortcomings are pointed out and the directions of future development are discussed. In the end, the study highlighted the following key areas that require further research and improvement: the evaluation criteria of power system security and stability should be improved to ensure the secure and stable operation of China's power systems; the operational control standards should be constantly enhanced to increase the reliability and flexibility of operational control strategies; generator-grid coordination standards should be upgraded to improve the coordination between the generator control protection system and the grid; and the simulation methodology should be standardized in future power system security and stability research.
The Three Gorges Power Market (TGPM) is the first cross-region power market in China. In order to build efficient and high performance power markets in China, a significant problem is to determine the bulk power market hierarchical structure. In this paper, based on international experiences on power markets, common rules in power market design and operation, and real conditions of Chinese power industry, possible alternatives of power market hierarchical structures are outlined and studied. A two-level structure for the Chinese power markets is then proposed. They are national and regional power markets. Based on the two-level Chinese power market structure plan, the TGPM structure and its market participants are further suggested.
Investment for renewables has been growing rapidly since the beginning of the new century, and the momentum is expected to sustain in order to mitigate the impact of anthropogenic climate change. Transition towards higher renewable penetration in the power industry will not only confront technical challenges, but also face socio-economic obstacles. The connected between environment and energy systems are also tightened under elevated penetration of renewables. This paper will provide an overview of some important challenges related to technical, environmental and socio-economic aspects at elevated renewable penetration. An integrated analytical framework for interlinked technical, environmental and socio-economic systems will be presented at the end.
Strong DC coupling with weak AC and large-scale renewable energy integration are the two significant characteristics of ultra-high-voltage AC/DC (UHVAC/DC) hybrid power grids in China. Strong coupling between AC and DC grids and the different integration performance of renewable energy sources have profoundly changed the stability characteristics of the power system. The traditional stability control system is inadequate for the stability control of UHVAC/DC power grids. This paper analyzes the requirements for constructing an integrated defense system in a UHVAC/DC hybrid power grid (i.e. power system protection). The definition, connotation, and designing principles of power system protection are put forward. The relationship between the power system protection and the traditional three-defense lines is investigated. The design principles, general hardware structure and main functions of a power system protection are presented. Key problems and technologies are specified in the construction of the power system protection.
The application of HVDC transmission projects, the manufacture technology and its development are introduced briefly. A forecast is made for the development of HVDC transmission in China in the coming 15 years. Owing to the progress of HVDC technology and its excellent performance in grid of large scale, HVDC transmission has a bright future in China. Now the power grid in China has entered into the age of combination AC with DC.
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