Identification Of Critical Lines And Safety Precautions In Power Grid

Large-scale interconnected power system has become an inevitable trend in the development of power system at home and abroad,6and the network structure of system has become more and more complex. This paper focuses on how to identify critical lines on the large-scale network quickly, accurately and stably, then validates and compares the critical lines. Besides, to prevent and avoid the happening of blackout accident, this paper presents line overload prevention and control measures.First, an identification model of power grids for critical lines is established based on distribution entropy of power flow and transfer entropy of transmission line. The model considers many factors which may influence the operation of power system including generator nodes, load nodes and line. For the change of the first two factors, we can get the distribution entropy of power flow. For the change of lines in system, we can get the transfer entropy of transmission line. Then a model which can search and deal with islands in power system is built based on the breadth-first search theory. Through the IEEE 39-bus system simulation analysis, the critical lines can be determined.Then, a validated model which can validate critical lines is constructed based on the vulnerability of power grid. It mainly uses the power-law characteristics of self-organized critical theory to determine whether the system is to achieve self-organized critical state, then compares and selects some factors to determine the dependent variables of power-law characteristics, and uses the total loss of load as the dependent variable. In addition, the fast dynamic process simulation of power system is constructed considering the hidden fault protection and load shedding approach. Similarly, the identification result is verified to be correct through simulation and statistical analysis of the IEEE 39-bus system.Finally, a prevention control model of line overload is constructed based on sensitivity analysis. Correlation between node power and adjustment direction of line power is analyzed in this article, and indicator of power adjustment is proposed on basis of overall consideration of sensitivity, the trend of entropy and the bus power level. According to the theory that bus set of power adjustment and power balance can be formed with indicator of the bus power adjustment and the bus type, a model of line overload prevention control is proposed, which can quickly adjust system power flow by multiple rounds. The effectiveness of this model to relieve the threat of line overload and improve the reliability of the overall power grid operation has been verified by simulation results of IEEE 39-bus system.