Table of Content

18 February 2012, Volume 45 Issue 2

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Power System

An accurate DFT based power system frequency and harmonics measurement algorithm

ZHANG Yan-xia, CHEN Xu-lin

2012, 45(2):  1-4.  DOI: 10.11930/j.issn.1004-9649.2012.2.1.3

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Frequency is one of the most important parameters in power system operating characteristics assessment. The low precision of traditional frequency measurement method results in frequency leaking which influence harmonic measurement accuracy. An improved frequency measuring algorithm based on DFT （Discrete Fourier Transform） is proposed. Three sets of signal data which are separated by half cycle are used to calculate two modification coefficients, which modify phase angle of two adjacent cycles. The frequency is then measured by the phase angle change. Synchronous sampling is achieved by correcting the sampling frequency in real time in order to analyze harmonic accurately. Four different simulation results show that proposed method has better frequency tracking result and harmonic measurement accuracy.

Voltage control for the isolated operation of Maoxian electric grid in Sichuan province

PU Qian, ZHANG Yi-wei, LU Qiu-yu, HU Wei, CHEN Lei, LI Jian, ZHOU Jian, PANG Xiao-yan

2012, 45(2):  5-8.  DOI: 10.11930/j.issn.1004-9649.2012.2.5.3

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After a large disturbance, the hydropower group connected to main system through a long distance and extra-high voltage power line may split from the system and turn into isolated operation. Over-voltage phenomenon may occur in the isolated network. Based on the actual case of Maoxian hydropower group in Sichuan province, the problem of over-voltage control in the isolated network is studied. The major causes of over-voltage are analyzed and the feasibility of over-voltage suppression by generator leading phase operation is discussed. Methods to adequately and reasonably utilize generator’s leading phase operation capability through excitation control of generator are proposed to control isolated system voltage safely and effectively.

Features of future smart grids

HE Da-yu

2012, 45(2):  9-11.  DOI: 10.11930/j.issn.1004-9649.2012.2.9.2

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A brief introduction of a joint commentary by three foreign power network experts on the features of future smart grids was given. All of them have more than ten years of practical experience in smart grid construction. They do not believe that the future smart grid infrastructure will look much different physically. However, there will be new technology and methods of control. These differences may be summarized as follows: improved connectivity, real time communication, more advanced devices, self-healing and self-correction ability, increased control over the network. These cognizances will be helpful to understand future smart grids.

Application of smart AVC （S10） to Luzhou power grid

HU Hong-qiong, ZHANG Sheng-ting, WANG Zong-shan, MA Shou-guo, ZHAO Feng, CHEN Guang-yu

2012, 45(2):  12-14.  DOI: 10.11930/j.issn.1004-9649.2012.2.12.2

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The construction of smart automatic voltage control（smart AVC） is necessary as part of smart grid construction. The Smart AVC （S10）, which provides coordinated control for secure, economic and high quality voltage supply, is used to analyze online voltage reactive power optimization problem and perform closed loop control. S10 system has come into use in the Luzhou power grid. The system is smart enough to generate and execute the appropriate control strategy from data acquisition and analysis. It fully meets the need of Luzhou’s online voltage and reactive control. S10 system can increase the voltage qualification rate and reduce line loss, significantly reduce the regulating times of load tap changing transformers. It achieved good results in different areas including optimal reactive power flow, data information configuration and intelligent fault analysis.

Generation Technology

Materials in 700 ℃ advanced ultra-supercritical coal-fired units

ZHANG Yan-ping，CAI Xiao-yan，HUANG Shu-hong

2012, 45(2):  15-21.  DOI: 10.11930/j.issn.1004-9649.2012.2.15.6

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The present research and development status of advanced high-temperature materials in 700 ℃ advanced ultra-supercritical （A-USC） coal-fired units were introduced, as well as the welding, high-temperature coatings and cooling technology. The performance tests and selections on ferritic steel, austenitic steel and nickel-base alloy were carried out, and the new high-temperature materials were exploited in Europe, Japan and USA. Some research results have been achieved. The research on welding technology between nickel-base alloy and ferritic steel was developed in Europe and Japan. The welding technology of different alloy was researched in USA, and the welding procedure among different alloys was made. The research on high-temperature coatings and thermal barrier coating technology was implemented in USA and Europe. The thermal barrier coating technology will be used in turbine system of 700 ℃ A-USC coal-fired units. The technologies of steam cooling and sandwich structure for cooling were researched in Europe and Japan.

Off-design characteristics of condenser in direct air-cooling 1 000 MW unit

HAN Zhong-he, ZHENG Qing-yu, WU Zhi-quan, WANG Zhi

2012, 45(2):  22-25.  DOI: 10.11930/j.issn.1004-9649.2012.2.22.3

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Taking 1 000 MW direct air cooling units as an example, by using the method of effective energy-heat transfer units, a mathematical model of direct air cooling units under variable operating conditions has been elaborated. By considering the influence of pressure drop of the exhaust pipe and environment heat dissipation loss on the exhaust steam pressure of the last stage in the steam turbine in direct air cooling units, the curves of condenser pressure change with environment temperature, face velocity and exhaust steam flow were obtained. The linear relationship between the exhaust steam pressure of the last stage and its influence factors was analyzed, which can provide a reference for choosing the suitable exhaust steam pressure and for improving economical efficiency under off-design operation conditions in 1 000 MW air-cooling units.

Emergency treatment plan of the failure in distributed control system

LI Jian-guo, YIN Feng, LIU Wu-lin, SUN Yun, ZHANG Wei-jun, HUANG Bo

2012, 45(2):  26-30.  DOI: 10.11930/j.issn.1004-9649.2012.2.26.4

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An example was taken to analyze the reason of the expanded influence scope during the failure treatment process in the control system. The necessity of the establishment for the emergency treatment plans of the typical failure in the distributed control system was proposed. The primary coverage, the structure, the failure emergency treatment general requirement, the basic principle and the entire failure treatment flow of the plans were introduced. The emergency treatment instruction for the different failures in control system was given. The technical points and the effects of implementing the plans were introduced, which can provide a reference for making the plans of failure emergency treatment in distributed control system.

Emergy analysis method of energy-saving dispatching in coal-fired power plant

WANG Jun, LI Yong-hua, YAN Wei-ping, ZHANG Feng

2012, 45(2):  31-34.  DOI: 10.11930/j.issn.1004-9649.2012.2.31.3

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Energy-saving dispatching is a main measures of energy-saving and emission reduction of the electric power industry in China. A single indicator of power supply coal consumption can’t thoroughly reflect the energy-saving and emission reduction in coal-fired power plants. As the energy-saving dispatching index, the power supply coal consumption rate, SO₂ and NO_x emission, EAF, net loss and water resources consumption were selected. The emergy analysis method was implemented to sort the integrate index for determining the order of the dispatching. Based on the comparison of calculation data, the evaluation method was proposed. The evaluation method can reasonably reflect the situation of the energy-saving and emission reduction in the coal-fired power plants and can provides a reference for energy-saving dispatching.

Status of 300 MW circulating fluidized bed boiler unit operation

LI Bin, LI Jian-feng, SHENG Jian-hua, ZHANG Quan-sheng, YAO Guo-fu, WANG Yuan, HUANG Hai-tao

2012, 45(2):  35-39.  DOI: 10.11930/j.issn.1004-9649.2012.2.35.4

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There are 40 circulating fluidized bed（CFB） boiler units in operation in China and more than 70 CFB boiler units in building or to be built. In order to analyze the performances of large-scale domestic CFB boiler units, the operation data of 300 MW CFB boiler units for 3 years in China were investigated and analyzed. The reliability, economy and environmental protection of the CFB boiler units were summarized, analyzed and compared with 300 MW pulverized-coal fired boiler. The results of the analysis can provide a support for understanding the overall operating conditions of CFB boiler units in China. The operation data can also provide references for the optimization design and operation adjustment of larger-scale CFB boiler units in the future, and can provide guidance for the future development of domestic CFB technology.

Energy Conservation and Environment Protection

Application and research progress of seawater desulfurization technology

GUAN Yi-peng, LI Xiao-ming, ZHANG Zhao-cai, LIU Guo-chang,GUO Chun-gang, CHEN Ying

2012, 45(2):  40-44.  DOI: 10.11930/j.issn.1004-9649.2012.2.40.4

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The seawater desulfurization technology has the advantage of economic benefit, and is suitable for flue gas desulfurization in coastal thermal power plant. The domestic and overseas engineering application and application problem of seawater desulfurization technology were introduced. Research progress in membrane gas absorption for flue gas desulfurization, seawater recovery system, structured packing and packed tower were described. The performance comparison of economy and safety between seawater desulfurization, seawater desulfurization with membrane contactor and limestone-gypsum flue gas desulfurization were analyzed. The development strategy of seawater desulfurization technology in China was proposed. Finally the development prospects of flue gas treatment for China coastal coal-fired power plant were proposed.

Measurement, analysis for classification efficiency of dust removal in coal-fired power plant

ZANG Dian-zong,MEI Dong-sheng,LIANG Ding-hong,SU Jin-hai,WANG Yong,SHANG Sheng

2012, 45(2):  45-48.  DOI: 10.11930/j.issn.1004-9649.2012.2.45.3

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People pay more and more attention on the fine particle pollution in the air with the improvement of environmental protection consciousness. Coal-fired power plant is one of the fine particle pollution sources. The difference of fine particle removal from different precipitators was confirmed by testing the PM10 and PM2.5 mass concentration in the outlet of bag filter, electrostatic-fabric integrated precipitator and electrostatic precipitator in coal-fired power plants. The attention on classification efficiency of dust removal should be enhanced to choose the appropriate precipitator. Fine particles in outlet gas such as PM1.0, PM10 and PM2.5 were collected by cascade low pressure impactor. The test results show that the order of PM10 and PM2.5 removal efficiency from high to low is electrostatic-fabric integrated precipitator, bag filter, and electrostatic precipitator. The order of the dust removal efficiency from high to low is the same as above. The proportion of the fine particle in the electrostatic precipitator outlet dust is lower relatively.

New Energy

An active power-frequency control strategy of a DFIG based on subsection control

LIN Li， LI Xiao-yu， WANG Shi-qian， SHI Tian， LI Hao-jiong

2012, 45(2):  49-53.  DOI: 10.11930/j.issn.1004-9649.2012.2.49.4

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In order to relieve the impact of large-scale grid-connected wind power farms on power system frequency and improve frequency stability, an active power-frequency control strategy of a DFIG is proposed. With the consideration of generation economics, wind power generators can have similar frequency regulation characteristics as conventional generators by using the proposed strategy. The control strategy is divided into four sections: de-loaded operation, frequency regulation, maximum power operation and off-grid operation. The main control parameters in the proposed model are studied; the frequency regulatng ability of the proposed strategy is also analyzed, as well as the influence of wind power penetration and load change on the DFIG frequency regulation. The active power-frequency characteristics of the DFIG are obtained based on the analyses. The simulation result proves the feasibility and validity of the proposed method.

Parameter test and analysis for dynamic compensation devices in wind power farms

BAI Run-qing, QIN Rui, ZHI Yong, ZHOU Xi-chao, YANG Yong

2012, 45(2):  54-57.  DOI: 10.11930/j.issn.1004-9649.2012.2.54.3

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Dynamic reactive power compensation devices in Jiuquan wind power farms of 10 GW above in Gansu province include different types, Such as SVG, TCR and MCR. The lack of experimental verification for the performances is not conducive to voltage/var management and fully utilization of the compensation capacity. In order to solve the problem above, the compensation device performance test was conducted. The testing items and procedures were selected based on related national standards with the consideration of different grid structures and wind farm operation modes. The testing contents involved dynamic regulating range, active power loss, dynamic response time and harmonic voltage level. Three types of compensation devices installed in different wind farms, namely SVG, TCR and MCR, were chosen and tested. The performances were compared and analyzed according to the field test results.

Modelling of a large scale grid-connected PV system and its operation analysis

DAI Wu-chang, KONG Ling-guo, CUI Zhu

2012, 45(2):  58-63.  DOI: 10.11930/j.issn.1004-9649.2012.2.58.5

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A dynamic model for a large scale grid-connected photovoltaic （PV） generation system was proposed. The model can help to regulate power effectively and improve the capability to do the low voltage ride through （LVRT）. The perturbation and observation （P&O） algorithm based on power change rate and the double-loop decoupling control strategy of real and reactive power were adopted for the photovoltaic system. By using the STATCOM system, the reactive power compensation and system voltage stability are implemented. The simulation result on system performance of IEEE 3-machine 9-bus test system verifies the validity of the proposed model.

Forecasting system based on numerical weather prediction

LI Hong-tao, MA Zhi-yong, RUI Xiao-ming

2012, 45(2):  64-68.  DOI: 10.11930/j.issn.1004-9649.2012.2.64.4

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Along with the rapid development of wind power industry in the world, the integation of large number of wind turbines with high capacity to high voltage transmission networks is a great challenge for grid operation security and power supply quality. Wind power forecasting systems are needed for wind turbine power generation. A hybrid wind power forecasting system is proposed based on numerical weather prediction and artificial neural networks. By using historical wind speed and direction data as inputs, self-organizing maps model as the pretreatment model and radial basis function network model as the forecasting model, the forecasting system was used in a wind farm in Hebei province with the correction by historical outputs of a specific wind turbine or wind power generation field. The prediction results are acceptable, which shows the feasibility of proposed model.

Electric Power Economy

Grid project quantities management system based on bill of quantities

ZENG Ming, XU Zi-zhi, XUE Song, ZHU Xiao-li

2012, 45(2):  69-73.  DOI: 10.11930/j.issn.1004-9649.2012.2.69.4

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Grid construction management is important for national economy and development of electric power construction. Project quantities management is the core of construction project management. At present, grid project quantities management system is not perfect. Based on bill of quantities application, grid project quantities management is studied. By analyzing nation’s management status, the idea of whole process quantities management of grid company project department is proposed. The grid project quantities management system is constructed from design, construction and completion stages. Further analysis of working contents and process of each stage is performed, which give out the standard and reference for China’s power grid construction project quantities management.

Co-integration relationship between energy demand and the main influence factors on it in China

ZHANG Li-zi, HE Yong-jian, GE Ju

2012, 45(2):  74-77.  DOI: 10.11930/j.issn.1004-9649.2012.2.74.3

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The relationship between energy demand and the main influence factors on it in China was analyzed based on the co-integration theory. The long-term equilibrium equation and error correction model were established and used to forecast the future energy demand in China. The results show that the energy demand in China in the next five years will continue to grow strongly. In order to reach the goal of total energy demand control in the Twelfth National Five-Year Plan, it is necessary to optimize the industrial structure, speed up the technical advancement and renovation, and improve energy efficiency.