Study Of Power Grid Vulnerability Based On Generalized Tellegen's Theorem

As one of the most complex and largest artificial networks in the world, power grid is bound to be vulnerability in the structure. Some unexpected events, such as system failure, load fluctuations and so on, will increase the vulnerability of the net. In this paper, power grid vulnerability assessment based on Generalized Tellegen's Theorem, is carried out from the point of sensitivity analysis.In the paper, sensitivity algorithm based on generalized Tellegen's theorem is improved. During the study of power grid vulnerability, we need the help of bus voltage sensitivity which can be calculated by the use of the generalized Tellegen's theorem. When we calculate the bus voltage sensitivity, the voltage needs to be corrected. At present, non-diagonal elements of the bus correction matrix is considered to be ignored, during the study of generalized Tellegen's theorem in the power system. However, non-diagonal elements can not be ignored arbitrarily. And a few examples included the network of IEEE 5,IEEE 14 and IEEE 30 are set to support my point. In the paper, calculation expressions of the vulnerability assessment under the rectangular coordinate system, which are based on the Tellegen's theorem generalized, are derived.During the research, method and index for the assessment of bus and branch in the grid are given. Bus vulnerability index mainly considers two factors: one is the sensitivity of bus voltage, when reactive load of the load area in network changes, the other is the relationship of current value,upper and lower limits,rated voltage of the bus. The definition of the index for the branch vulnerability assessment is accomplishment, by analyzing the relationship of branch power losses and reactive load of the load area in network, when the voltage is closed to the critical point.In the environment of Matlab 7.0, the bus and branch vulnerability assessment of the network IEEE 14 and IEEE 30 is conduct by the above-mentioned method and index. By comparison the results with the previous, the assessment method and index proposed by the paper are effective and feasible.