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Bian X.-M.,Tsinghua University | Hui J.-F.,Shaanxi Electrical Power Corporation | Huang H.-K.,China Electric Power Research Institute | Wang L.-M.,Tsinghua University | And 2 more authors.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2010

In order to obtain the characteristics of negative DC corona under various pressure and humidity, a physical model of the inception voltage for negative DC corona was set up, and the voltage was computed with charge simulation method and based on the calculation of electron photos on the surface of electrodes. The inception voltage and corona current of negative DC corona under different air pressure and humidity conditions were measured with a point-to-plane electrode system in an artificial climate chamber. Corona-inception voltage decreased with the reduce of air pressure or the increase of humidity, for which the main causes are the expansion of ionization zone and strengthening of collisional ionization intensity respectively, resulting from the increase of effective ionization coefficient. Corona current also decreased with the falling of pressure or the rising of humidity when the ratio of DC voltage to corona-inception voltage was kept constant; furthermore, it increased with the falling of pressure or decreased with the rising of humidity under the same applied voltage. The coefficient C in the relationship among corona current, DC voltage and corona-inception voltage was concerned with the combinative state of ions and water molecules. © 2010 Chin. Soc. for Elec. Eng.

Bian X.,Tsinghua University | Wang L.,Tsinghua University | MacAlpine J.M.K.,Tsinghua University | Guan Z.,Tsinghua University | And 2 more authors.
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2010

The variation of positive dc corona characteristics with air pressure and humidity using a point/plane electrode system was studied in a perspex chamber allowing the pressure and humidity to be varied. A method of calculation was developed to determine the corona current for humid air over a range of pressures and humidities in which the effective ionization coefficient was calculated as a linear interpolation of the effective ionization coefficients for dry air and water vapor. The calculation method involved the solution of partial differential equations using a particle-in-cell algorithm. This also allowed the determination of the corona inception voltages for a range of pressures and humidities as the voltage at which the corona current first appeared. The validity of these calculations was confirmed by a series of experimental determinations of the corona inception voltages and of the variation of the corona current with the applied voltage for the same range of pressures and humidities. It was found that the corona current increased when the air pressure or humidity decreased (at constant applied voltage) mainly because of the rise in the space charge density or the positive ion mobility, respectively. The coefficient C, in the relationship between the corona current, the applied dc voltage and the corona inception voltage, declined with the increase of humidity. The rate of decrease of C with humidity became larger as the pressure was reduced. An approximately inversely proportional relationship was found to exist between C and the relative air density at constant humidity. This variation of C was principally associated with the variation in the positive ion mobility. © 2010 IEEE.

Li G.,Xi'an University of Technology | Li G.,Shaanxi Electrical Power Company | Song X.-F.,Xinjiang Electrical Power Company | Chang X.-Q.,Xinjiang Electrical Power Company
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011

An improved instantaneous symmetrical components method is applied to detect the positive sequence, negative sequence and zero sequence components of grid voltage sag, then the control method for low voltage ride-through of permanent magnet synchronous generator when grid voltage asymmetrical sags is put forward. The power of PMSG is reduced according to the ratio of grid positive sequence component and rated voltage during voltage dip. The positive and negative sequence components are controlled through respective channel. The power is transmitted in positive sequence channel while negative sequence voltage, which is equal to grid negative sequence voltage, is produced in negative sequence channel. So the inverter current does not contain negative sequence component, avoid the open-phase overload inverter, and make full use of its capacity. Simulation results show that the improved control strategy realizes LVRT in condition of asymmetrical fault and keeps symmetry of inverter three phase current.

Zeng M.,North China Electrical Power University | Lu C.,North China Electrical Power University | Tian K.,Shaanxi Electrical Power Corporation | Xue S.,North China Electrical Power University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2011

The development of smart grid and electricity market requires more accurate and faster short-term load forecasting. A least squares-support vector machine (LS-SVM) based on bacterial colony chemotaxis optimization (BCC) algorithm was proposed that improving the computing accuracy and speed through a novel category of bionic algorithm, and determining the hyper-parameters of LS-SVM through BCC optional algorithm fleetly and reasonably. It shows that the BCC-LS-SVM algorithm not only has strong global search capability, but also is easy to implement. A load forecast empirical example has shown that compared with back-propagation artificial neural networks and single LS-SVM algorithm, BCC-LS-SVM algorithm can achieve higher prediction accuracy, better computational speed, and which is more suitable for short term load forecasting in China. © 2011 Chinese Society for Electrical Engineering.

Hu X.,Northwest China Grid Company | Li P.,Shaanxi Electrical Power Corporation
Lecture Notes in Electrical Engineering | Year: 2013

Absolute dominator search is an effective topological analysis method to improve performance of computer-aided design (CAD) and automatic test pattern generation (ATPG). In this paper, we present a new algorithm for searching absolute dominators of multiple-output circuits to solve inefficient and complex computing in tradition algorithm. Compare with the tradition algorithm, the new algorithm analyzes the relations between different fanout nodes, and identifies absolute dominator for every fanout node in circuit, thus, the overall dominator graph is constructed without any changes for original circuit directly. The experimental results based on ISCAS85 and ITC99 benchmarks show a signification improvement in runtime, and it can meet the requirement of modern design and test for Very Large Scale Integration (VLSI). © 2013 Springer-Verlag London.

Tian K.,Shaanxi Electrical Power Corporation | Qiu L.,North China Electrical Power University | Zeng M.,North China Electrical Power University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012

As the growing attention being paid to climate change issues world wide, and the new emission reduction target proposed in China for the "twelfth five-year" period, the research about carbon emission price influence on transmission network planning is of vital importance. The fluctuations of carbon emission price were analyzed firstly. Exponential generalized autoregressive conditional heteroskedasticity, (EGARCH) model was used to forecast the carbon emission price and a calculation method of carbon emission was established. Then, transmission planning model based on dynamic carbon emission price was displayed. Finally, the validity of the model was tested by IEEE 24-bus system. The results show that the consideration of dynamic carbon emission price in planning model makes the optimal transmission line expansion simulation more effective in various scenarios of price fluctuations. It also meets the need of energy conservation work for future transmission planning. And the planning result it made possesses more economic benefits. © 2012 Chinese Society for Electrical Engineering.

Zhang J.,North China Electrical Power University | Zeng B.,North China Electrical Power University | Dong J.,North China Electrical Power University | Tian K.,Shaanxi Electrical Power Corporation | Liu N.,North China Electrical Power University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012

Under the situation of green urban network construction, quantifying the environmental effects in urban network planning is an important issue in decision-making process. Based on the analysis of the essence of green urban network and the mechanism of its environmental effects, a novel bilevel decision-making model for green urban power grid planning was proposed. Firstly, starting from the differences to conventional network, a bilevel-structured evaluation index system and its specific model were presented. Then, with the application of bilevel multi-objective hierarchy optimization, a coordination situation algorithm was developed for the decision-making of green urban network planning. Finally, the simulation results of a real urban network in China were presented and discussed. The proposed model is illustrated to be effective and feasible, providing useful guidance for the urban power grid going towards an eco-friendly condition. © 2012 Chin. Soc. for Elec. Eng.

Zeng M.,North China Electrical Power University | Lu C.,North China Electrical Power University | Lu C.,Shaanxi Electrical Power Corporation | Tian K.,Shaanxi Electrical Power Corporation | Dong J.,North China Electrical Power University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2011

Under the trend of low-carbon economy development worldwide and the requirement on energy saving and emission reduction during the twelfth five-year period in China, the demand for security and reliability in power system operations is very high. The environmental-friendly and economical development of electricity power system is also becoming an compelling issue. How to form a reliable and feasible low-carbon power system to cope with the changing external environment is a now serious business. From the perspective of secure and reliable power supply, the basic functions of low-carbon power system required are analyzed, and four mechanisms to realize low-carbon power system and two carbon reduction conversion methods are presented. The objective function of a smart grid is also discussed in terms of clean power generation, scheduling optimization, efficiency improvement, power consumption as well as investment optimization aspects. Finally, the specific technical paths for a smart grid to achieve low-carbon power system are proposed based on clean production, losses reduction, power consumption savings, and investment optimization. © 2011 State Grid Electric Power Research Institute Press.

Large-scale grid-integration of new energy sources such as wind power generation and so on leads to new problems in secure and stable operation of traditional power grids. For a hybrid power grid containing thermal power plants, wind farms and energy storage equipments, by means of constructing a unit commitment model and the stochastic property of wind power output uncertainty is simulated by scenario tree. Leading chaos embedded particle swarm optimization (CEPSO) into scenario reduction algorithms (SRA) the results of stochastic simulation and the ability to search the optimal solution are improved. Taking a hybrid power system composed of a wind farm and a 10-machine system as simulation example, simulation results show that the obtained unit commitment scheme can dispatch as many wind power units as possible and the operational cost of thermal generation units can be reduced to suit to the demand of energy conservation and emission reduction.

Tian K.,Shaanxi Electrical Power Company | Qiu L.,North China Electrical Power University | Zeng M.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2012

Transmission network investment is faced with many potential market risks, so it makes higher damnd on the flexibility of investors' decision-making. Considering uncertain factors in the investment for power transmission, a flexible investment project in led in, and by use of least squares Monte Carlo simulation a valuation model for investment options is built. On this basis, three kinds of option value models for investment priority of flexible transmission equipments, investment priority of transmisson lines and simultaneous investment for both flexible transmission equipments and transmisson lines are built, and taking the maximum social benefit as decision rule, the proposed method and models are verified by Garver 6-bus system and IEEE 24-bus system.

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