Research On Power Network Fault Diagnosis Based On Theory Of Hierarchical And Vulnerability Assessment

With the continuous expansion of the scale of the modern power system and sustainable growth of power load, the structure of the power system is also increasingly complex. Once the power system is mal-function, it is a very difficult thing to analysis and diagnostic the fault location, nature accurately and troubleshooting on time. In order to improve the reliability and safety of power grid, when the power grid is mal-function or disturbance, the power grid still can keep the normal operation and prevent large-scale blackouts. And in the natural disasters, extreme weather conditions or external damage cases, it still can ensure the grid security and stability operation. So the large-scale power grid mal-function diagnosis research base on the theory of the hierarchical has very important significance.Aiming at a large number of uncertainties problem of the large-scale power grid, which includes complexity of structural and variability of operating status of the large-scale grid, large information of power grid fault, complexity of mal-function diagnoses, and difficulty to ensure speed and accuracy of mal-function diagnosis, the thesis makes the following works:First of all, the thesis analyses the role and status of several monitoring and control systems in power grid fault diagnosis, such as the data acquisition and monitoring system, the integrated dispatching data platform, the wide area measurement system and the fault information system. These data platforms directly provides a variety of key data of electric information, switch and protection of information, the faults recorder information for power system fault diagnosis, which provides the data source for hierarchical fault diagnosis of power grid.Secondly, the thesis presents a hierarchical graph theory of grid based on graph theory and vulnerability assessments. Considering the actual situation of power grid topology and according to the optimization problem of graph theory, Laplace matrix are structured among the notes of topology of large-scale and Fiedler vector method is used to divide the large-scale power grid. Then by using the method of graph theory, simplify the vulnerable propagation model and analysis the source and direction of vulnerablility in power system, which provides a theoretical basis for the fault diagnosis of power system.Finally, the thesis stratified the large-scale power grid which puts forward the correlation value of voltage, frequency and phase angle in large power system as the optimization object and use the method of fuzzy C-mean. By this method, the large-scale power grid can be divided into several regionals, so that Fault Diagnosis can be performed for each small area. So it can greatly reduce the complexity of the grid system, make the complex problems relatively simple process, improve the efficiency of fault detection. Then according to the annlysis of threshold of the given node voltage and phase angle, which can effective reflects the importance of electric power system vulnerability.