Research On Security Risk And Vulnerability Assessment Methods Of Complicated Power System

Large-area Power Outages is always of concern to all sectors of society. However, how to prevent Large-area Power Outages makes people confused. With the expansion of China's power system, there are more and more factors, which contribute to Large-area Power Outages and are unconsidered by existing methods. These factors are often not expected among people. The snow disaster that hit Southern China in 2008 caused serious damages to southern power systems, which made Chinese government realize that the exiting methods could maintain statability of power system, though they cannot control the risk involved in power system effectively. Therefore, Chinese government should play to there strength, and it's necessary to collaborate with power enterprises in strengthening Electricity Regulation and taking countermeasures to reduce the risk of Large-area Power Outages.Traditional analysis methods of power system security are based on the system model which consists of the physical models of the component in power system. And the methods are considered more about the instability factors of the system operation, but fewer factors of the natural disaster and human.The methods based on modern risk theory consider most of the factors which could impact the security of the power system. They combine the security risk assessment and vulnerability analysis method to make a comprehensive and focused power system security assessment. Therefore, we either need to research the feasibility, necessity and framework for power system security risk and vulnerability assessment, or research indicator system of them.This paper first proposes a framework of the multi-cooperation power system security risk assessment, which is based on the complexity science research methods and the ideology of the multi-cooperation from the Comprehensive Integrated Method. The proposed framework consists of four parts, which are data information system, assessment indicator system, experts system, multi-cooperation assessment system. And the principle of the proposed framework is integrity. Based on the framework, this paper establishes an assessment system which can give full play to its advantages of multi-cooperation to resolve the issue open complex giant system, and advantages of integrated and coordinated government departments, and advantages of professional and technical expertise of experts in power enterprises, research institutions and other sectors of society related to the power system security. Meanwhile, using the workable assessment process of the framework to complete the complex power system risk assessment could provide suggestions to develop targeted measures to reduce the medium and long term risk of complex power systems for electric power companies. And it also provides the basis to monitor the electrical security for the government.Based on the systematology, both complex power system security risk assessment indicator system and algorithm method are proposed. The indicator system established by the fault tree modeling technique, we can fully consider various factors which impact the power system in the structure, technology, equipment and other aspects. We calculate the weights of the indicators by using the improved Analytic Hierarchy Process, which has strong practicability and maneuverability. The proposed method could take advantage of experts'expertise and be used in the multi-cooperation power system security risk assessment. Then a numerical example has been given to prove the effectiveness of the method.This paper gives a definition to the vulnerability of complex power system from the point of avoiding LPO, and constructs a four-layer set model of complex power system, which divides the large body of data information of complex power system into four sets (status information, defect condition, the defect status that might cause power failure, and vulnerability) and describes the correlation between the means of attack and the sets. Then based on these correlations, this paper constructs a set of objective, practical, and adaptive index assessment systems and evaluation methods, taking advantage of the information sources of the complex power system. The assessment results could reflect the current vulnerable points in complex power system; provide information of important reference value for the operation and planning of the electricity sector. The assessment results of a provincial large power grid in China validate the correctness and the effectiveness of the proposed method.Finally, from integral, practical and operational points of view, this paper proposes an integrated power system security assessment method, which combine the security risk assessment and vulnerability analysis method. The assessment results of the proposed method could reflect both the risk in macro level, but also weaknesses in the micro level, and it could assessment the medium and long term security of power system more comprehensive. An assessment example of Guizhou provincial power system is given and the assessment results are consistent with the real situation of the tested system. This paper also provides specific measures for improvement, which could be good references for developing measures to reduce the risk and vulnerability of the power system by power enterprise.