Research On Control Strategy Of UHV Transmission Line Reactive Power Optimization

With the Zhebei-Fuzhou 1000kV UHV AC power transmission project has been officially put into operation, three UHV transmission lines have been built in our country. The 1000kV UHV AC transmission project has broad application prospects and great economic benefits. In order to ensure the secure and economical running of UHV AC power grid, and maximize the UHV transmission capacity to achieve better network efficiency, the research on typical operating conditions of UHV power gird and analysis for reactive voltage control strategies of UHV AC transmission lines are highly necessary, for they can provide technical support for interconnected grids operation. In this thesis, the UHV AC transmission system is taken as a researching object, by referring previous studies and combining with the characteristics of UHV AC transmission system its own, a complete set of voltage and reactive power control strategies for UHV transmission line are proposed. The main works are organized as follows:The domestic and international development of UHV technology and researching status of reactive voltage control in UHV transmission line are introduced, followed by the features of reactive voltage control in UHV transmission line. Three level voltage control mode are presented and chosen as a study object which is focusing on the secondary voltage control. Based on the research above, the UHV AC power grid is taken as a study object, by combining with its reactive voltage operating characteristics and control requirements, a coordinate secondary voltage control mode for UHV AC near zone power grid is proposed, and meanwhile, its reactive power and voltage control partitioning methods are present. For the purpose of minimizing active power loss and maximizing the minimum singular value of trend Jacobian matrix, a reactive power optimization model of UHV transmission line is established. This model can optimize reactive power, reduce network loss, and increase static voltage stability of system as well.The basic principles and operations of standard genetic algorithm are studied. An improvement is made for the standard genetic algorithm by combining with the characteristics of reactive power optimization its own, then the improved adaptive genetic algorithm is proposed, including improvements of genetic coding,and selection operator. By introducing elite strategy and adaptive crossover and mutation rate, adaptive weights and evaluation function which can ensure multi-objective achieving optimum simultaneously are founded.According to the methods and ideas introduced above, a set of reactive voltage control strategies for UHV transmission line are put forward and applied in East China UHV power grid simulation. The results prove the effectiveness of those strategies.