Research On Network Vulnerable Line Identification Considering The Uncertainty Of New Energy Output

Global warming,air pollution,and the increasingly tight supply of fossil energy resources have become the three major problems today.Attention to environmental issues is gradually increasing.Along with the development of clean energy,the concept of promoting the sustainable development of resources has become a consensus worldwide.In recent years,new energy in China has continued to grow rapidly,and its proportion in the power grid has increased.It has gradually entered a stage of largescale development.At present,the installed capacity of wind power generator and solar energy generator is the top of the world.While the new energy reduces the grid’s dependence on fossil energy,the uncertainty of its generator also brings new challenges to the security of the traditional power system.The security and stability operation of the power system is related to the national economy and the human’s livelihood.In recent years,the vulnerability of power system is increasing because of the continuous expansion of the system scale,the increase of proportion of new energy,and the structural complexity.The vulnerability of the power system is an extension of the concept of power grid security.It’s also a new way of evaluating the security and stability of the power system from a global perspective.The identification of fragile lines in the power system is an effective static security analysis method,which can make up for the deficiencies of the existing large-scale power grid security research.As the basis of the power system defense strategy,the fragile lines identify can provide sufficient early warning for the system to prevent the occurrence of major power accidents.However,the uncertainty of new energy units brings new challenges to this traditional method.It is necessary to consider the impact of new energy access and restore the fragile lines of the grid.Therefore,this paper proposes a method for identifying network vulnerable lines that takes into account the uncertainty of new energy output.The main structure and the research content of this paper are summarized as follows:First,a random power flow calculation model using the short-term output model of new energy units is introduced.The Beta distribution is used to fit the output of new energy units in this model,which can better simulate the random characteristics of short-term output of new energy generator units.The model uses the linearized communication model of the network in the probability calculation process,which can effectively reduce the amount of calculation in the calculation process.Finally,the IEEE34 node network is taken as an example to verify the effectiveness of this model.Then,an identification method of network fragile lines which considers the failure consequences based on the improved power flow entropy method is proposed.Through the concepts of distance and betweenness in graph theory,a fault consequence model is proposed.According to this model,the Consequence Influencing Factor can be calculated.This factor can be used to calculate the consequences of line faults on the premise that only basic network parameters are known.On this basis,based on the power system structure entropy theory,an improved power flow entropy algorithm considering the consequences of faults is proposed.By calculating the vulnerability index of the line,it can judge the vulnerability of the line.Finally,the standard IEEE39 node network is taken as an example to verify the effectiveness of the identification process of vulnerable lines in the power grid proposed in this chapter.Finally,an augmented vulnerability index is proposed according to the uncertainty characteristics of new energy output.It can quantitatively calculate the uncertainty impact of new energy output on the vulnerability of network lines.In order to solve the convolution calculation problem in the traditional stochastic power flow calculation process,a semi-invariant characterized by the statistical characteristics of random variables is introduced.The augmented vulnerability index of the line is calculated,which characterizes the impact of the uncertainty of new energy output on the vulnerability of the line.influences.Due to the similarity of the uncertainty of the shortterm output of new energy,the improved IEEE39-node system with wind farms connected is used as an example to simulate the above research.The results are analyzed and researched to verify that the algorithm is effectively reducing while calculation is accurate.The simulation proves the effectiveness of the algorithm.