Overload Vulnerability Based On Electric Network Theory And Control Method In Power Systems

At present, China is in a period of rapid economic and social development. Nationwide backbone UHV network of interconnected transmission network is under construction. So when the system vulnerable line failure easily triggered a cascading failure, to a serious impact on social production and people’s lives. In order to avoid blackouts and cascading failure, to reduce losses of the system caused by cascading failures, it is necessary to identified and analyzed of the vulnerable components in power system. And make an optimization control for the vulnerable branch, to make its meet the safe and stable operation condition.In this thesis, use power flow transferring relativity factor to identify the vulnerability branches in the system. At the same time, using flow control method based on graph theory, to meet the tide of branch of the safe operation of the static condition control, make it meet the static safety running condition, to improve the stability of the system. The main work and conclusions are as follows:Compared the calculating speed and precision of using the theory of electric network and the superposition principle to estimate for a branch off the rest of the branch power in the system method, and the of method power flow calculation. The results showed that using the theory of electric network and the method of superposition principle, able to quickly estimate the branch after disconnection, the tide of other branch in the system. This laid the groundwork for the vulnerability of system identification.Build a vulnerability assessment system of branch overload, and the node voltage vulnerability assessment system. Application trend of power flow transferring factor and the methods of impact factor could quickly identify vulnerable branch in the system, although not precise enough as the application of the vulnerability assessment system, but the result is acceptable. And the definition of vulnerability evaluation method, not only related with the system’s topology structure and network parameters, and is related to the running status and system. Through example analysis, the system under different running states of fragile branch is different; a cascading failure occurs branch broken path is different also.Use directed graph of the network transmission characteristics, and generator and scheduling method for power flow control, build a current control method. The method in the power system emergency accidents or a line under the condition of overload, first through the adjustment of generator active power, make the system meet the safe operation of the static state or eliminate line overload conditions. When active in regulating generator can’t meet the static safety running condition, will be adjusted to the system load, the system eventually meet the static safe operating condition. The results show that the method can well eliminate branch static security implications of open circuit on the system.