| According to the "12th Five-year Plan" of the State Grid Corporation of China, UHV AC power transmission system has been developed rapidly in recent years, which strengthens the interconnections between regional grids on one hand, and demands amounts of reactive power due to the high-voltage and large-capacity power transmission systems on the other hand. By installing FACTS equipments at the landing points of UHV AC power transmission systems, it can realize local balance of reactive power, reduce the reactive power flowing in the grid and improve the transmission capacity and voltage stability. It is necessary to strengthen the connection of Xinjiang power grid with the China northwest master grid, and construct the second channel for this grid connection, i.e. the 750kV power transmission project, for increasing the transmission capacity of Xinjiang grid to the China northwest master grid, providing grid structure support for the Xinjiang power transmission project and ensure its safe and stable operation, solving the power shortage problem of Qinghai grid and the wind power delivery problem in the southeast of Hami during the "12th Five-year Plan" period, and also creating the favorable conditions for the development of renewable energy and economy in the region.In this article, the analysis and research have been made on the application of multiple FACTS equipments presently in China and other countries. Moreover, in conjunction with the second channel project for connecting Xinjiang grid with the China northwest master grid, the paper also researches 750kV magnetically controlled shunt reactor,66kV high-capacity SVC and the coordinated control strategy for multiple FACTS equipments, and proposes relevant plans meeting the project demand. Finally, it has been verified that these plans and equipments can well solve some problems existing in UHV AC power transmission system through theoretical calculation, simulation tests and engineering application. The main research includes:1. For 750kV magnetically controlled shunt reactor, the problems on excitation and its protection have been solved through plan formulation, test verification and engineering application, and the developed equipment has the features of high application voltage, large rated capacity and wide regulation range of effective capacity.2. For 66kV high-capacity SVC, it adopts TCR+FC type, effectively suppressing the 3rd,5th and 7th harmonics, and eliminating parallel resonance with the system. The SVC has a strong control capacity for 750kV voltage, and can effectively suppress the voltage fluctuation caused by power fluctuation in a certain range. When it is coordinated with the controlled shunt reactor, the capacity to suppress voltage fluctuation can be further increased. It also has sufficient capacity to control the voltage fluctuation caused by wind power fluctuation. Moreover, the SVC can play an obvious role in increasing the stability of transient voltage in case of a fault and restoring voltage after an accident, at the same time, it is with good effect to increase the system stability after implementing stability control measures and reduce the cost of stability control. The thyristor valve adopts pure water cooling type and parallel water circuit made of fire-proof materials. The water distribution master pipe is equipped with water electrodes rationally at the top and bottom for realizing homogeneous pressure distribution of the water circuit. The top and bottom mounting plates of valve bank are equipped with grading rings, to achieve homogeneous voltage distribution at the incoming and outgoing sides.3. It adopts the stable state voltage regulation and control strategy combining the voltage-based inner control, outer control for coping with major system disturbance and outermost layer control, to solve the problem of difficult voltage control resulted from wind power fluctuation, thus increasing the grid-connected power transmission capacity and recovery voltage level after a fault. For the SCSR's on both ends of Shazhou-Yuka Line, it adopts the electromagnetic transient control strategy with rapid linked operation, meeting the restriction requirements on power frequency overvoltage, secondary arc current, recovery voltage, and incomplete phase operation overvoltage. |
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