Time filter

Source Type

Yu J.,Hainan Power Grid Company | Guo Z.,Harbin Institute of Technology | Bai X.,Harbin Institute of Technology | Liu R.,Harbin Institute of Technology
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society

The traditional static security analysis based on the data of one time section can not adapt to the continuous state changing of power system appropriately. To improve the deficiency, a time process-oriented static security analysis method is presented in the paper. Firstly, the basic idea of time process-oriented method is explained. Secondly, with the abundant measurements and load forecasting information, the characteristic vector of each time section is extracted. Then the load curve is partitioned into several time sub-processes by the improved K-means clustering algorithm considering the successive time series of power load. Thirdly, the indices extracting the maximum and minimum characteristic sections of every time sub-process are defined. Then the representativeness of the characteristic sections is verified. While ensuring the static security, the time process-oriented method can improve the utilization rate of transmission lines to some extent. Finally, the calculation and analysis of IEEE 30-bus system shows the effectiveness of the method proposed in the paper. Source

Liu W.-X.,North China Electrical Power University | Jiang C.,North China Electrical Power University | Zhang J.-H.,North China Electrical Power University | Wang X.-W.,North China Electrical Power University | And 2 more authors.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control

A multistage reliability model of wind turbine is built utilizing a systematic method based on Markov chain approach, considering the drawback of the traditional wind turbine reliability model in sequential Monte Carlo Simulation. The probability of occurrence and duration of each state can be obtained using the state transition rate between each output power state of wind turbine calculated out with the regional wind regime of wind farm and operation historical data of wind turbine. On this basis, the double sampling method for the sequential Monte Carlo simulation is proposed. The simulation program for multistage reliability model of wind turbine is compiled. Then it is compared with the commonly used two-state model based on a single sampling method. Simulation results verify the feasibility of the proposed model based on Markov method. It can reflect accurately the output power of the wind turbine of any duration under fault conditions, improve the accuracy and expand the application range of the simulation model. Source

Qiu Y.,China Electric Power Research Institute | Yuan J.,Hainan Power Grid Company | Chen X.,China Electric Power Research Institute
Gaodianya Jishu/High Voltage Engineering

In order to provide references for quality control of new SF6 gas in electrical equipment, the influence of trace impurities in new SF6 gases on SF6-insulating electrical equipment was experimentally investigated. An internal default as metal point discharge on the center rod was simulated by using a straight-line isolator installment which shared gas chamber with a current transformer. Then experiments of using SF6 new gas with various qualities under 2 voltage modes, single 220 kV single voltage mode and 220 kV/3 150 A synchronous upward current-voltage mode, were performed for about 100 h. In the experiments, variations of volume concentration of each impurity in the SF6 gases were detected by a gas chromatography mass spectrometry analyzer and a DPD SF6 impurity analyzer ( made in Canada). The results show that, more by-products like SO2F2, SOF2, and SO2 will be generated when electrical equipment is filled with new SF6 gas which has mass trace impurities, including fluorinated alkane, fluorizating sulfonyl, and carbon sulfur fluoride; considering the corrosive effect of SO2 on the equipment, it is concluded that when SF6 is filled with new gas with high level impurities, the life of electrical equipment will be shortened, especially that of breaks will be shortened. Source

Liu K.,Tsinghua University | He G.,Shanghai JiaoTong University | Huang L.,Hainan Power Grid Company | Gu Z.,Hainan Power Grid Company
Dianwang Jishu/Power System Technology

Quantum particle swarm optimization (QPSO) may fall into local optimal solution when solving problems with variables with limited definition domain. In order to solve this problem, quantum particle swarm optimization based on asymmetric quantum potential (AQPSO) is proposed to improve QPSO quantum model. In this method, particles are located in asymmetric potential well. Potential well parameters are determined by current optimal location and definition domain. When solving wave-function indicating particle distribution, a method of reducing parameter number is proposed. This parameter-reducing method simplifies algorithm flow by specifying only one parameter: out-of-limit probability. Simulation results prove that global search performance of the new algorithm is improved significantly with advantage in solving complex problems with high-dimensional variables and strong interference. © 2016, Power System Technology Press. All right reserved. Source

Fu Y.,Hainan Power Grid Company | Chen Y.,Tsinghua University | Yao R.,Tsinghua University | Liu F.,Tsinghua University | And 2 more authors.
Dianwang Jishu/Power System Technology

To improve the robustness of state estimation, a state estimation approach based on maximum exponential absolute value (MEAV) is proposed. Firstly, the basic model of MEAV is given and its theoretical base and mathematical properties are given. Since the objective function of the basic model of MEAV is not differentiable, it cannot be solved by the gradient based method. For this reason, an equivalent model of the basic model of MEAV is given and an original-dual interior point algorithm based solving method for the equivalent model of MEAV is derived in detail. Results of calculation example show that MEAV can automatically suppress a lot of strongly correlated bad data during the estimation process, so it shows up that the MEAV method possesses good robustness and high calculation efficiency, therefore it has a bright prospect in engineering practice. Source

Discover hidden collaborations