| Automatic voltage control is an important means to improve the system voltage level and increase economic benefits. But the nonlinear characteristics of voltage and reactive power itself increase the complexity of realization.110 kV substations and above of Jiangxi power grid mostly access the AVC system while the access rate is 94%. The rate of the close-loop operation declined slightly, which is 85%. The rate of access and the close-loop operation is good. However, through the research of the AVC system and pressure regulators in Jiangxi’s cities,it can be found that pressure regulators move frequently in the AVC system, which is further than the number of national standard. It not only is disadvantageous to improve the intelligent level of power grid, but also increases the work intensity of the operators.Firstly, this paper studies the basic theory of Voltage Quality Control and two control strategies of AVC system which are the nine-area-chart control strategy and the seventeen-area-chart control strategy. It points out the deficiency of nine-area-chart control strategy and the improvement of seventeen-area-chart control strategy,which lay the foundation for the following analysis and modeling.Then through the daily frequency statistics of all pressure regulators of Ganzhou company and Nanchang company in Jiangxi Province in May 2015, we can obtain the operating frequency for the month of all the capacitor and the tap of main transformer as well as maximum operating frequency for the day,which proving that the AVC system of Jiangxi Province moves frequently.Next,focusing on the pressure regulators of the AVC system operate frequently in real, this paper analyses the four main reasons for this situation: control mode problem, the set range of operation problem, device problem and operations management problem.In order to solve the problem of frequent action of the AVC system in Jiangxi Province,this paper uses fuzzy logic toolbox in MATLAB to realize the simulation and modeling of the AVC control system of the transformer substation in Huangzhou, Fuzhou City, Jiangxi Province.Besides, the actual operating conditions are compared to the model,which proves the accuracy of the model. Finally, according to the reason for the frequent action of the AVC system in Jiangxi Province, this paper presents the corresponding countermeasures,and verifies the effect of the corresponding countermeasures in the simulation model. |
