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Wang D.,NARI Group | Chen Z.,North China Grid Company | Tu M.,NARI Group | Yang Z.,China Electric Power Research Institute | Ding Q.,NARI Group
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012

Reserve demand is an important constraint in the optimization for daily generation scheduling, which is also important for the safe grid operation. With large-scale wind power integration, the traditional method of the reserve setting based on conventional energy resources cannot meet the demand of the grid operation security. Considering the intermittence of the wind power, and economical and security factor, an associated model between prediction error of wind farm output and varying reserve capacity is established by using clustering analysis to sift the data of wind farm output. Analysis of actual system examples shows the effectiveness of the proposed model. © 2012 State Grid Electric Power Research Institute Press.

Wu X.,North China Electrical Power University | Zhang J.,North China Electrical Power University | Qiu W.,North China Electrical Power University | Zhang H.,North China Grid Company
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012

Critical segments in power system are closely related to N-k contingency. Vulnerability evaluation has become a hot topic of preventing cascading failures. In order to identify the critical contingency paths, the method of N-k contingency path search and its failure probability model was proposed based on functional group decomposition. Utility theory was introduced to define the severity of the contingency. And a composite risk indicator for N-k contingency was obtained by integrating the various risk indicators, which was based on the entropy and the analytic hierarchy process. According to vulnerability functions of path risk and system structure, vulnerability indicators for N-k contingency were further proposed for the quantitative analysis of vulnerability on contingency paths and the whole grid. Taking a district grid in Henan for example, the vulnerable buses and lines in it were identified. The example analysis demonstrates that, compared with the vulnerability evaluation method considering risk only, the method considering risk as well as structure vulnerability is more accurate and its result is more instructive for power grid monitoring. © 2012 Chinese Society for Electrical Engineering.

Liu N.,North China Electrical Power University | Zhang J.,North China Electrical Power University | Zhang H.,North China Grid Company | Liu W.,North China Electrical Power University
IEEE Transactions on Power Delivery | Year: 2010

The security assessment is a key function that should be performed in advance of any security deployment. Since experiences of cyber attack in power control systems are still limited, a complete methodology of security assessment for communication networks of power control systems is needed. According to past research, the difficulties of security assessment include the security analysis of power control process, and the security degree of each control step. Therefore, the attack graph and multiple criteria decision-making (MCDM) are introduced to deal with these difficulties. The overall security assessment is decomposed into two parts. One is the security analysis model for power control systems using attack graph, includes the basic concepts definition, construction algorithm, vulnerability function of each control step, and connection model-based system vulnerability calculation. Another one is focused on the quantification of the security degree in each control stepa hybrid MCDM approach integrated with an analytic hierarchy process (AHP) and a technique for order preference by similarity to ideal solution (TOPSIS) are proposed to value the vulnerability factors derived by the security analysis model. Finally, an instance communication network of power control system is modeling to test the validity of security assessment. The result supports the usefulness of the security assessment. © 2010 IEEE.

Sun R.,North China Grid Company | Singh C.,Texas A&M University | Cheng L.,Tsinghua University | Sun Y.,Tsinghua University
Electric Power Systems Research | Year: 2010

Most of the reliability theory and applications are in the planning domain. When reliability concepts are applied in operations or operational planning, computational burden of the algorithms becomes a bottleneck as the speed of execution of algorithms becomes critical. This paper presents an efficient control variable based dagger sampling technique for reducing the computational effort in Monte-Carlo reliability evaluation for composite systems. The proposed variance reduction method is unique in combining the offline calculations with online computation. A large number of system states are simulated to calculate their consequences offline and stored. Short-term reliability sampling uses the information on offline computed consequences to construct a variance reduction function. In short-term reliability evaluation, the outage probability of each component is much smaller compared to long-term system reliability calculations. Dagger sampling is used to reduce the computation time under this condition. Test results on RTS show the improvement and effectiveness in convergence speed. © 2009 Elsevier B.V. All rights reserved.

Zhong J.-Q.,Yanshan University | Li Y.,North China Grid Company | Lu Z.-G.,Yanshan University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

Using attribute synthetic assessment method and combining four indexes including the probability of failure, probability of lose load, influence of severity and faults removing time, a comprehensive evaluation model of network vulnerability assessment is established. It considers not only grid anti-interference ability and affected degree but also the probability of fault and grid troubleshooting skills. It expresses the results of assessment qualitatively and quantitatively. Qualitative results show the level of vulnerability and the quantitative results express the difference of fragile routes between the same levels. It brings better recognition ability and higher precision for transmission lines vulnerability assessment. Based on the simulation of IEEE14 node systems, the results prove the reasonability and effectiveness of this method. It provides more accurate evidence for formulating measures of ensuring the safety of the power network and decreasing its vulnerability.

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