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Zhu X.,North China Electrical Power University | Liu W.,North China Electrical Power University | Zhang J.,North China Electrical Power University | Qiu W.,National Electrical Power Dispatching and Control Center | Huang Y.,Jiangsu Electric Power Company
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2013

With the change of operating conditions especially integration of the large-scale wind power, power system state will be even more complex and changeable and higher requirements will be put forward to the grid analysis. Stochastic load flow is a powerful tool to solve the problem. Model, method, and application of stochastic load flow and security assessment of power system are reviewed comprehensively in this paper. First, the stochastic load flow models, solution method for conventional system are categorized and analyzed in detail. By analysis and comparison, the advantages and disadvantages of various modeling methods and solution thoughts of models are drawn, and then the future prospects are brought on. Secondly, the hot research point and development of research on stochastic load flow method including wind farms is illustrated considering the wind power is a nonconventional random factor. The developing tendency of model and method of stochastic load flow considering large-scale wind power integration is forecasted by discussing some of challenges to be solved urgently. Finally, the status quo related to engineering application of stochastic load flow is reviewed. Insufficiency of various network security evaluation method and uncertainty safety assessment application of stochastic load flow is pointed out and some further research is put forward to offer a scientific basis for practical technique of system security analysis under the new situations.


Qiu W.,National Electrical Power Dispatching and Control Center | Zhang J.,North China Electrical Power University | Liu N.,North China Electrical Power University | Zhu X.,North China Electrical Power University | Liu L.,National Electrical Power Dispatching and Control Center
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012

In view of the uncertainties existing in the operation of power grid and the drawback of traditional deterministic security criterion, the risk theory was introduced into the optimal generation dispatch. The operation risk index was defined based on line overload and bus voltage violation of limit, the utility function was employed to measure the severity in order to reflect relative severity among different contingencies. Risk-based multi-objective economic dispatch model was formulated, minimizing the operation risk and fuel cost was considered as objective functions, and the normal state constraints were taken into account. In order to solve the problem, improved differential evolution for multi-objective optimization was implemented to obtain the economy-security tradeoffs, then the compromise dispatch scheme was selected according to the coordination operation of power system. The proposed generation dispatch approach was tested on IEEE RTS-79 test system, the results show that the quantitative index that reflects security level can be provided, and the vulnerable parts of power grid can be identified. © 2012 Chin. Soc. for Elec. Eng.


Zhu X.,North China Electrical Power University | Zhang J.,North China Electrical Power University | Liu W.,North China Electrical Power University | Qiu W.,National Electrical Power Dispatching and Control Center | And 2 more authors.
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2013

The random fluctuation of wind power output will cause the voltage fluctuant randomly in the power grid with wind power integration. In this case, it is very necessary to search an all-round and accurate evaluating method of voltage fluctuation. In view of this condition, this article focuses on the overall and the partial two aspects of the voltage fluctuation and constructs three voltage fluctuation evaluation indexes including voltage distribution index, skewness index and retention index according to the characteristic of the voltage random distribution. Bus indexes and system indexes are defined respectively. These proposed indexes can well reflect the random distribution of the voltage in the network with wind power integration. The wind farm steady state model is built to evaluate the Voltage fluctuation. Compared with the proposed model and indexes, the evaluation method and process of the voltage fluctuation in the power grid with wind power integration based on Monte Carlo sampling is researched in this paper. The IEEE 36-bus system is taken as example to verify the effectiveness of these proposed indexes and methods and analyze the influence of some factors to voltage fluctuation in the network. These factors include the fluctuation of wind power output, the location of wind power integration and so on. The simulation results in this paper would provide reference for wind power integration to power grid reasonably. The proposed indexes and evaluation method is applied to solve the PCC optimization of wind farm and an example is given to illustrate the practicability of the indexes and evaluation method.


Liu W.,North China Electrical Power University | Zhao T.,North China Electrical Power University | Qiu W.,National Electrical Power Dispatching and Control Center | Zhang J.,North China Electrical Power University
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2013

The rapid development of renewable energy poses new challenges to the operation of the grid: wind power can not be fully used due to the lack of peak-load regulation capacity and so on. And the electric vehicle charging as controllable provides the opportunity to improve the grid operation. A two-stage control mechanism based on grid and EV users is proposed to determine the coordinated program between large-scale EV charging and wind-thermal system. At the user side, different charging strategies for different users are established to optimize EV charging. At the grid side, a dynamic environmental dispatch model including economy, emission and wind-power abandoned is proposed to optimize outputs of the thermal units. The orthogonal initialization, improved crowd distance calculation and self-adaptive parameter control are put forward due to the weakness existing in the multi-objective differential evolution. Simulations are done in a system containing 10 thermal units and large-scale wind-power system, the coordinated program is determined, and impacts of EV scale and reserve on the operation are also analyzed.


Chang N.,National Electrical Power Dispatching and Control Center | Wang B.,Tsinghua University | He G.,Tsinghua University | Xin Y.,National Electrical Power Dispatching and Control Center | Zhang Z.,National Electrical Power Dispatching and Control Center
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2014

Previous work has shown that the normal measurement rate based on measurement uncertainty is a credible evaluation index for state estimation when the true state is unknown. Then a new robust state estimation algorithm based on maximum normal measurement rate is proposed. By approximating the evaluation function, a nonlinearly continuous variable optimal model is developed, and the interior point algorithm is used to solve this model to obtain approximate results. Based on the above study, this paper proposed an improved algorithm by checking the consistency of abnormal measurements to obtain solutions with a higher normal measurement rate, and filtering the noise of normal measurements based on least square estimation with inequality constraints to obtain a more accurate solution. Numerical tests on different systems show the proposed algorithm is efficient for obtaining robust and accurate results, while the increased computing time is acceptable. ©2014 State Grid Electric Power Research Institute Press


Tao H.,National Electrical Power Dispatching and Control Center
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2015

Firstly, this paper briefly introduces the research fields, current concerns, recent activities and working groups of study committee of system operation and control (SC C2) of CIGRE 2014. The preferential subjects of SC C2 of CIGRE 2016 are also described. And then the details of discussion and the related papers of the two preferential subjects (managing new challenges in operational planning and real-time operation of electric power systems, emerging operational issues for transmission and distribution interaction) are given. Finally, a look-ahead of the development trend of system operation and control technologies and the technical issues that should be focused on is presented. ©, 2015 State Grid Electric Power Research Institute Press.


Liu H.,Central China Grid Company Ltd | Wang D.,National Electrical Power Dispatching and Control Center | Zhou Z.,China Electric Power Research Institute
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2016

The deficiency of traditional relay protection is analyzed, and the concept of flexible operation features of relay protection is proposed. That is, operation features are determined with a variety of criteria according to the fault characteristics of protection objects. Compared with the operation features using a single criterion for relay protection, flexible operation features are suitable for cases of indistinct fault characteristics. The application occasions of the protection flexible operation features are described, including transformer excitation inrush current identification, distance protection oscillation block open conditions, the rapidity and accuracy of high resistance grounding fault, and so on. Finally, the application prospects of the relay protection flexible operation features are previewed. © 2016 Automation of Electric Power Systems Press.


Xin Y.,National Electrical Power Dispatching and Control Center | Mi W.,NARI Group | Jiang G.,NARI Group | Xu D.,NARI Group | And 2 more authors.
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2013

The rapid development of power system requires that the grid models, real-time data and grid graphics information can be synchronously shared in real-time between control centers. The CIM/E standards that have overcome the drawback of low efficiency of CIM/XML and application only in offline exchange are briefly described, being capable of meeting the requirement of grid model online real-time exchange between control centers. Focus of attention is on CIM/E based grid model information integration management, realization of the application of multi-model integration management, offline and online model integration management and multi-level model integration management. Technical support is provided to dispatching business horizontal integration and vertical linkage. CIM/E as well as its associated technology has been applied to the smart grid-operation support system (SG-OSS) for solving the problem of real-time sharing of model information between multiple control centers and various professionals within control centers. © 2013 State Grid Electric Power Research Institute Press.


Lai X.,Tsinghua University | Zhong H.,Tsinghua University | Yang J.,National Electrical Power Dispatching and Control Center | Xia Q.,Tsinghua University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2013

A novel decomposed optimization method based on price response function is proposed for solving security constrained economic dispatch problem over large-scale power systems. In this method, provincial power systems are taken as basic optimization units, and the global optimization problem is decomposed into an upper-level master problem and provincial sub-problems. In the master problem, network reduction technique is imposed, and the dynamic price response function is trained based on the results of the sub-problems in order to optimize the power flow of inter-province tie-lines. In the sub-problems, power output of generating units is optimized with fixed tie-line export, with marginal pricing information corresponding to power loads of different time periods calculated and submitted to the upper-level. The proposed method fully exploits and utilizes the implicit pricing information in the sub-problem results of each iteration, thereby avoiding the oscillation from which the conventional method of Lagrange relaxation suffers much because of the monotony of pricing signal. Hence, the method is able to converge quickly in a few steps with good robustness and sufficient accuracy from the engineering point of view. Computational results of IEEE RTS and a large-scale real power system are presented to verify the effectiveness of the method. ©2013 State Grid Electric Power Research Institute Press.


Li G.,National Electrical Power Dispatching and Control Center | Pi J.,National Electrical Power Dispatching and Control Center | Wang Z.,National Electrical Power Dispatching and Control Center | Yan Y.,National Electrical Power Dispatching and Control Center
Dianwang Jishu/Power System Technology | Year: 2012

Fault interaction between AC and DC systems has become increasingly common. Commutation failure in the DC system caused by AC system failures is one of the common one. In some cases, commutation failure may lead to voltage fluctuation or power fluctuations in power grid. And in severe conditions it may lead to the DC block fault and other serious problems. This paper presented a fault event between AC and DC systems near the Three Gorges grid in the summer of 2011 during the peak load period, which was triggered by the AC system fault of east China grid. On the basis of presenting the event in detail, both DC commutation failure triggered by fault occurred in AC system at receiving end and power fluctuation in AC systems near the Three Gorges grid was reappeared by simulation and comparative analysis on power oscillation in sending system triggered by DC commutation failure was performed. Finally, related suggestions and measures for the research on interaction of faults in AC and DC system were proposed in four aspects, namely power system planning and construction, application of new technologies, operational control and configuration of secondary equipments in AC/DC system.

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