Table of Content

20 March 2017, Volume 50 Issue 3

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Special Contribution

Progress and Development Trend of Electric Power Construction Technology in China: Part Ⅰ-Power Grid

SUN Xin

2017, 50(3):  1-8.  DOI: 10.11930/j.issn.1004-9649.2017.03.001.08

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The planning and development of electric power industry is realized through engineering construction. The power construction technology has laid a solid foundation for the development of China’s power industry. This paper summarizes the power grid construction achievements in the “12th Five-Year” period (2011-2015), and introduces the latest research results and important engineering practices of both China and abroad in the technological field of the transmission and distribution network planning, engineering design and construction, distribution network construction, and power grid construction management. An analysis is made on the development trend as well as the reachable parameters and levels of those technologies in the above-mentioned fields in the“13th Five-Year” period(2016-2020) or even longer time, and some suggestions are proposed on the technologies that should be developed especially.

Ultra Low Emission Technologies for Coal-Fired Power Plants

Methodologies on Choosing Appropriate Technical Route for Ultra Low Emission of Flue Gas Pollutants from Coal-Fired Power Plants

ZHU Fahua

2017, 50(3):  11-16.  DOI: 10.11930/j.issn.1004-9649.2017.03.011.06

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Based on the in-depth study on the characteristics and adaptabilities of dust, SO₂ and NO_x control technologies and together in combination with the successful cases of ultra-low emission from domestic coal-fired power plants, the fundamental principles for ultra-low emission technical route selections are proposed, which should be in line with the coal quality, boiler type, local condition, and collaborative development. Then the optimal practical technologies are distinguished under different conditions of the coal quality, boiler type, unit capacity and pollutant control requirements. At last, the most popular and typical technical routes are presented to provide guidance for power plants to make their decisions.

Testing and Assessment on Performance of Flue Gas Ultra Low Emission Based on CFB-FGD Technology

HUANG Ru, MA Depeng, MO Hua, ZHU Jie, WU Jiayu, XU Haihong

2017, 50(3):  17-21.  DOI: 10.11930/j.issn.1004-9649.2017.03.017.05

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Taking the CFB-FGD-based ultra low emission project of a newly built 350-MW CFB unit in central China as a study case, the concentrations of conventional pollutants(e.g. SO₂, dust, etc.) and non-conventional pollutants(e.g. PM_2.5 particles, SO₃ and mercury, etc.) are tested on the field with 100% loading and 75% loading conditions respectively to evaluate the capabilities of ultra low SO₂ and dust emission by CFB furnace desulphurization +CFB-FGD sulfur and dust removal technologies. The field monitoring and evaluation results show that the combination of these technologies can not only satisfy the requirements of ultra low emission with SO₂ concentrations of less than 35 mg/m³ and dust concentrations of less than 10 mg/m³, but also has synergistic removal effects on SO₃, mercury and some other non-conventional pollutants.

Research and Application Progress of Ultra-Clean Electrostatic-Fabric Integrated Precipitator Technology

CHEN Kuixu

2017, 50(3):  22-27.  DOI: 10.11930/j.issn.1004-9649.2017.03.022.06

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To achieve the goal of ultra-low emission for coal-fired power plants, based on the conventional EFIP technology, the ultra-clean electrostatic-fabric integrated precipitator(EFIP) is developed, by upgrading the key technologies such as coupling matching between electrostatic field and fabric area, high uniform flow field distribution, high-precision filtration and particle coalescence technology. Featured by stable long-term emissions, simple technical process, high adaptability to varieties of coal, low investments, less land occupation, low maintenance costs and no waste water production, the ultra-clean EFIP technology has been rapidly popularized and widely used in coal-fired power plant ultra-low emission projects for the recent couple of years, with the total installed capacity of domestic coal-fired power plants over 30 000 MW, including eight 1 000-MW units. The emission concentrations are all below 10 mg/m³ or 5 mg/m³, and the average running resistance is around 663 Pa. The ultra-clean EFIP has become one of the mainstream technical routes to achieve ultra-low emission for coal-fired power plants, and will play an even more important role in the ultra-clean emission renovation projects for power plants burning inferior coals in western area of China.

Characteristics of Low-Low Temperature ESP Technology and Its Application in Ultra-Low Emissions for High-Ash Coal-Fueled Power Plant

LI Jianguo, HE Yuzhong, LIU Hanxiao, ZHAO Haibao

2017, 50(3):  28-33.  DOI: 10.11930/j.issn.1004-9649.2017.03.028.06

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The low-low temperature ESP achieves the goal of efficiency-enhancing and energy-saving with high SO₃ removal efficiency as well. Low-temperature corrosion will not occur given the ratio of ash to sulfur more than 100. In this paper, the authors elaborated and analyzed the topics on technical parameter settings, major problems and corresponding countermeasures, pollutant emission reduction characteristics of low-low temperature ESP, etc. A typical case of 660-MW unit of Huaibei Pingshan Power Plant is presented. The test shows that the dust removal efficiency of the ESP is 99.97%, the outlet dust and PM_2.5 concentrations of the ESP are respectively 4.47 mg/m³ and 2.4 mg/m³ while the outlet dust concentrations of WFGD are 2.3 mg/m³, which proves that the combination of low-low temperature ESP with rotating electrode type ESP can not only reduce the outlet dust concentration of the ESP to 5 mg/m³, but also realize ultra-low emission for high-ash and low quality coal.

Assessment of Ultra-Low SO₂ Emission Technology for Ultra-High Sulfur Coal

YI Yuping, ZHU Fahua, ZHANG Wenjie, LI Junzhuang, DUAN Jiuxiang, LI Xiaolong

2017, 50(3):  34-40.  DOI: 10.11930/j.issn.1004-9649.2017.03.034.04

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In this paper, the technology of single tower integrated desulphurization and dust removal purification, which has been applied in the 300 MW ultra-high sulfur coal firing power plant, is tested and evaluated. The test results are obtained using coals with 5% sulfur contents. It is observed from the testing data that the desulphurization efficiency of the system can be stabilized between 99.70% and 99.82% while the SO₂ emission concentrations are maintained between 23.4 mg/m³ and 30.8 mg/m³, which meets the ultra-low SO₂ emission requirement of less than 35 mg/m³. In addition, the dust removal efficiency ranges between 78.6%~87.8% with the particulate emission concentrations also stabilized between 4.60 mg/m³~5.76 mg/m³, which meets the ultra-low particulate matter emission requirement of less than 10 mg/m³. Compared with the single-tower double-cycle technology and the double-tower double-cycle technology, this technology is more cost-effective in the aspects of both retrofit constructions and operations.

Study on Fault Diagnosis and Operation Optimization for Power Plant SCR with Ultra-Low Emission

PAN Dong, LI Shuhong, JING Yunhui, XU Xiaotao, SHU Kai, YANG Shiji, NIU Guoping

2017, 50(3):  41-45.  DOI: 10.11930/j.issn.1004-9649.2017.03.041.05

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The operation control of SCR becomes more difficult after the ultra-emission retrofits. Some problems, such as, NO_x emission exceeding the guideline standard and extensive air pre-heater blocking, are much easier to happen. Generally, these problems are treated with diagnosis and optimization experiments of SCR(DOES for short). However, the effectiveness of DOES is directly related to the state of the SCR equipments: on the condition of no equipment defects, DOES tends to achieve good results, otherwise, if severe defects existing in the equipments, the effectiveness of DOES is poor, and the improvement on the original bad operation condition is limited. In this situation, the DOES functions is more like the fault diagnosis, which is able to find out the most possible causes for the SCR performance decreasing, and provide the technical evidence for the owner to take effective treatment to deal with the problems.

Test and Study on SO₃ Removal Performance of Different Wet Flue Gas Desulfurization Technologies at Ultra-Low Pollutants Emission

MO Hua, ZHU Jie, HUANG Zhijie, ZHU Fahua, CUI Liming

2017, 50(3):  46-50.  DOI: 10.11930/j.issn.1004-9649.2017.03.046.05

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The SO₃ test results of five power plants with ultra-low pollutants emission are analyzed, The analysis shows that the SO₃ removal performance of the wet flue gas desulfurization(WFGD) technologies used in ultra-low pollutants emission is obviously different from that in the domestic and foreign relevant research results. The SO₃ removal efficiency of the WFGD technologies, in the order of empty tower, seawater, single-pallet, double-pallet and rotating coupling, is quite different, which is from low to high. It is considered to be caused by the enhancement of gas-liquid mass transfer. The study indicates that the innovation of WFGD technologies for ultra-low pollutants emission has brought the progress of SO₃ removal performance.

A Novel Method to Improve the Stability and Accuracy of SO₂ and NO_x Analyzer

ZHANG Xidan, ZHU Fahua, TANG Guanghua, HAN Shaopeng

2017, 50(3):  51-54.  DOI: 10.11930/j.issn.1004-9649.2017.03.051.04

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As for the DOAS technology-based flue gas analyzer, wavelength drift may take place due to the impact of ambient temperature and vibration on its core part, i.e., the spectrometer. An online method to quickly calibrate the wavelength of the spectrometer is designed in this paper. By taking advantage of the characteristic absorption peaks of SO₂ standard gas in the wave bands of 202~214 nm and 280~310 nm, the three-order fitting is conducted based on the mapping relation of wave crest, trough and pixel, such that a rapid online calibration can be performed on the output wavelength of the spectrometer. The research results show that the drift can be reduced by 97.7% in the wave bands of 202~214 nm and 280~310 nm, with the indication error less than 2%, which turns out to be a significant improvement for the stability and measuring accuracy of the gas analyzer.

Cost Benefit Analysis on Coal-Fired Unit Modification with Ultra-Low Emission in Guangdong

SONG Peishan, LIANG Longni, WU Jinze

2017, 50(3):  55-59.  DOI: 10.11930/j.issn.1004-9649.2017.03.055.05

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In this paper, the investment cost, running expenses and annual benefit of 12 typical ultra-low emission technical combinations are examined based on the data collected from the 300-MW and above coal-fired power generation units in Guangdong Province. The unit cost and benefit of each combination are calculated and the cost-benefit curve is produced. The results show that the total control cost and benefit are balanced when the cumulative generation volume reaches 233.3 billion kW·h. To realize the balance, the ultra-low emission modification should be implemented by all the 300-MW and above coal-fired units in the key regions and seven 1 000-MW and above units in the general regions.

Generation Technology

Research on Improvement of the Air Duct Burner of a 600-MW Supercritical CFB Boiler

LEI Xiujian

2017, 50(3):  60-64.  DOI: 10.11930/j.issn.1004-9649.2017.03.060.05

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In the commissioning stage of the 600-MW supercritical CFB boiler, the startup burner upper duct burnout may occur due to the overheating of the startup burner upper duct and, the damage of the refractory layer lined in the duct inner surface. Aiming at this phenomenon, the root cause of the fault is analyzed and the corresponding methods for improvement are proposed, such as optimizing the structure of the duct, lengthening and strengthening the inner cylinder of the burner, increasing the strength of the duct and improving the refractory material performance. The implementation of these methods has effectively prevented the occurrence of the fault, which ensures the ignition and startup of the boiler and can provide reference for the startup burner design of subsequent supercritical CFB boilers and the retroffing of the existing CFB boiler.

Diagnosis and Treatment of an Unstable Motor Vibration Case

LI Zhen, HU Daqian

2017, 50(3):  65-70.  DOI: 10.11930/j.issn.1004-9649.2017.03.065.06

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The unstable motor vibration beyond the related standard which has happened repeatedly after adjustments during installation and commissioning is presented. The analysis on the waveforms concludes that it is due to the improper processing technique of the support, the increasing exciting force caused by the continuous stress releasing, the decrease of stiffness and the enhancement of dynamic amplification factor. Then, a modification plan of combining technique improvement, structure optimization and numerical simulation is proposed, which includes high-temperature tempering and strict processing standards to reduce the effects of stress release and installation deviation on the vibration. In addition, the support structure is optimized through calculating the nature frequencies of the motor-support system based on the finite element modeling to ensure that they keep certain distance from the resonance ranges and reduce the sensitivity of the amplification factor over stiffness. After the modification, the vibration keeps stable with the maximum amplitude of 0.6 mm/s. The modification results show that the cause analysis is basically correct and the finite element model is accurate. The trinity modification plan and the corresponding physical measures are effective for the excessive and unstable vibration treatment.

Calculation of Boiler Heat Storage Coefficient for Thermal Power Units Based on Primary Frequency Regulation Disturbance

WEI Danjing, TIAN Liang, QIAO Hong, LIU Jizhen

2017, 50(3):  71-76.  DOI: 10.11930/j.issn.1004-9649.2017.03.071.06

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The heat storage coefficient of the boiler is a key dynamic parameter of the load-pressure controlled object for thermal power units, of which the precise estimation provides important support for optimizing the coordinated control system. According to the simplified nonlinear dynamic model of the load-pressure object, the coordinated control system in the boiler following mode is established to analyze its closed-loop response characteristics using the frequency domain and the time domain methods. The results show that there are big differences in the time and frequency responses of the throttle pressure and the generation load outputs to the governor valve opening and the fuel flow inputs. It can be considered that the throttle pressure and the generation load are only affected by the governor valve opening within a small time scale. Therefore, the data under primary frequency regulation disturbance conditions in a short cycle are used to identify the boiler heat storage coefficient, which accuracy is good as that of the governor valve opening disturbance experiment. In addition, the feasibility of the methods is proved through the data identification and the field experiments in a 330 MW unit.

Impact of Coal Types and Pulverizing Methods on the Thermal Performance of Blending Coal-Fired Boilers and Their Operational Optimization

ZHOU Yonggang, WANG Huan, WANG Jing, LI Pei, ZHAO Hong

2017, 50(3):  77-82.  DOI: 10.11930/j.issn.1004-9649.2017.03.077.06

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The long-term operation with off-designed coal types brings a power plant significant safe and economic problems on its boiler operation. Aiming at solving the problem, tests are conducted to understand the operational status of the units, to analyze the coal blending problem and to optimize the combustion schemes according to the adaptability of the boiler to different coal types. The test results show that the coal blending should not only simply depend on the calorific value or the volatile contents the unit adaptability to different coal types and the influence of coal type dissimilarity on combustion characteristics should also be considered. In the new coal blending scheme, the anthracite(V_daf=9.23%) of Pulverizer C in phaseⅠproject is swapped with the lean coal of Pulverizer A in phase Ⅱ project, which increases the average volatile contents and reduces the coal type dissimilarity for the phase I project. After the optimization, the vibration of the pulverizer gets better. The average boiler efficiency of the units gets a 0.62 percent improvement and the average coal consumption for power generation gets a 0.65 g/（kW·h） decrease.

Discussion on Main Energy Saving Potential under Low Loads of Thermal Power Unit

DENG Shan, LI Jianping, LV Haitao, ZHANG Jianzhong, WU Liping

2017, 50(3):  83-87.  DOI: 10.11930/j.issn.1004-9649.2017.03.083.05

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To reduce the net coal consumption under low loads of the units, in this article, the optimizations and technical retrofits on energy saving of Huaneng Ruijin Power Plant in recent years are discussed thoroughly and the operation optimization plans and the technical retrofit items for low loading conditions are put forward. The practices indicate that when at the low loading operation, the two-mill operation, pressure curve optimization, cold-end optimization, and condensate pump optimization are more operable to achieve energy saving on the premise of ensuring the security and reliability of the units. The discussion results are valuable for popularization.

Three-Dimensional Numerical Simulation of Cooling Water Characteristics

QI Huiqing, GAO Deshen, HAN Qiang, LI Peng

2017, 50(3):  88-91.  DOI: 10.11930/j.issn.1004-9649.2017.03.088.04

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Using the three-dimensional numerical simulation method to simulate the flow field characteristics of natural draft counter-flow wet cooling tower,can provide reference for improving the design of the cooling tower.Based on the heat and mass transfer theory and the characteristics of the FLUENT software,applying Euler-Lagrange method and the standard wall function,using the standard k-ε turbulence model for closure, a three-dimensional numerical simulation platform was established. For 9 000 m² natural draft counter-flow wet cooling tower as an example, with no lateral aerodynamic field, the three-dimensional flow field of the tower was simulated. First of all,the cooling towers outlet water temperature was simulated. After validation with measured data, the calculated value is proved correctly. So the model is reasonable. Then using the platform,the cooling water distribution characteristics was simulated. it is concluded the change process curve of droplet temperature and velocity along with the time and location and the Temperature Distribution in fill layer and collecting tank .the results help to the optimization of water distribution system of tower

Research on the Differences of Hydrostatic Test for Class 1 Components of EPR and CPR1000 Nuclear Power Plants in the Phases of Manufacturing and Installations

ZHAO Weihua, FENG Huixing

2017, 50(3):  92-95.  DOI: 10.11930/j.issn.1004-9649.2017.03.092.04

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The hydrostatic test for Class 1 components in the phases of manufacturing and installations is a critical pre-requirement for subsequent commissioning and secure operations. The discrepancies of the requirements for hydrostatic testing are compared and analyzed between the different versions of French standard of Design and Construction Rules for Mechanical Components of PWR Nuclear Islands (RCC-M). Taking account of the characteristics of the system and structure of CPR1000 and EPR reactors, the differences of test pressure and test boundaries of hydrostatic test for Class 1 components in the manufacture and the installation phases are presented. The method on how to select test pressure for EPR Class 1 components in the manufacture and the installation phases is also explored and discussed. The conclusions can provide important reference for hydrostatic tests for EPR reactors.

The CFD-DEM Based Prediction Technology for Entrained Air Volume of Transfer Station

XIA Boshi, LIAO Rongfu, PAN Renhu, CAO Qiangli, LIU Zhixin

2017, 50(3):  96-100.  DOI: 10.11930/j.issn.1004-9649.2017.03.096.05

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The dust is generated during the process of bulk materials transferring, which pollutes the transfer station seriously. The entrained air arising from the material flow is the root cause of the dust generation. To precisely predict the entrained air volume during bulk materials transferring is of instructional importance for good transfer station design and dust removal equipment selection. In this paper, the computational fluid dynamics and discrete element method (CFD-DEM) is used to establish the predicting model of the entrained air caused by the material flow and study the factors that affect the entrained air volume. Moreover, the simulation is verified through an application case. The results show that the CFD-DEM method can precisely predict the entrained air volume.

Power System

A Service Restoration Strategy Considering Influence of Load Management for Distribution System with DG

JIANG Huilan, QIAN Guangchao, FAN Zhonglin, CHEN Juan

2017, 50(3):  101-106.  DOI: 10.11930/j.issn.1004-9649.2017.03.101.06

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With construction of active distribution network, load control has become a general means for power system dispatch. Based on load control flexibility, a service restoration strategy for distribution system with distributed generation(DG) is proposed, which fully considers the influence of load control. When serious failures result in large area power blackout, it is difficult to ensure that DG switches to islanding operation mode without losing stability as a result of long operation time, given numerous manual switches in current distribution system. In order to maintain power supply of important load and make full use of renewable energy sources, proposed method switch DG to islanding operation mode first using load control with adaptively selecting mathematical model. Second, for the purpose of reducing active loss and number of switching operations, the NSGA2 algorithm is adopted to perform reconfiguration of distribution network to restore non-failure power blackout area using a loop encoding strategy. The proposed restoration method is exerted on a 33-node feeder. The simulation results demonstrate validity of proposed method.

Shape Coefficient and Wind Load Calculation of Hexagonal Transmission Tower

ZHANG Hongjie, LI Zheng, YANG Fengli, HAN Junke, GONG Bo

2017, 50(3):  107-112.  DOI: 10.11930/j.issn.1004-9649.2017.03.107.06

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The hexagonal tower is rarely applied to transmission lines, and further studies are needed on the rationality of the shape coefficient of hexagonal tower represented by that of quadrilateral tower. For this purpose, two kinds of hexagonal transmission tower models with different solid ratio are established for a series of aerostatic force wind tunnel tests. Based on the test results, the change law of shape coefficient versus wind angles ranging from 0°to 120° is studied. Furthermore, the influences of shape coefficient difference between the hexagonal tower and quadrilateral tower on the calculated tower wind loads are discussed. The study shows that under the wind axis, the shape coefficient of hexagonal tower hexagonal tower presents a period of 60 degrees with the maximum value occurring at the wind angles of 10° and 45°. It is concluded that under the condition of the hexagonal tower shape coefficient being accurately measured, the traditional wind load calculation method used for quadrilateral tower is still applicable to the hexagonal transmission tower, but the calculated wind load of hexagonal transmission tower based on the code-provided shape coefficient is on the risk side with the wind angles ranging within 0~15°.

Evaluation on the Relative Effectiveness of Black Start Schemes Based on TRIS

YAN Qingyou, WANG Xu, GUO Wanwang

2017, 50(3):  113-116.  DOI: 10.11930/j.issn.1004-9649.2017.03.113.04

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In order to choose the proper black start scheme conveniently and effectively, the paper proposes the ranking technique based on the ideal schemes(TRIS) by applying the improved data envelopment analysis(DEA). Firstly, the new improved DEA model is established and the efficiencies of each black start scheme are calculated respectively under the common weights obtained through the improved DEA model. Then, the ranking indicators are constructed. The relative effectiveness ranking of each black start schemes can be obtained through the ranking of the indicators. This method keeps the advantages of the improved data envelopment analysis in terms of computational simplicity, and overcomes the disadvantages of the non-Archimedean infinitesimals. Finally, the feasibility and effectiveness of the proposed method are verified through real case studies.

A Distribution Network Partition Method Based on Total Supply Capability

LI Xiaohui, TAN Xianghong, ZHANG Yijun, ZHANG Xuan, XIAO Jun, ZU Guoqiang

2017, 50(3):  117-123.  DOI: 10.11930/j.issn.1004-9649.2017.03.117.07

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Based on total supply capability, a distribution network partition method is introduced. The definition of connection effectiveness is presented first. Based on analysis of connection effectiveness in distribution network, connections or connection- combinations that contribute less to power supply capability are located. Next, concept of optimized partition is proposed. The judgment basis and methods are also introduced. Two optimal partition schemes, TSC based method and exhaustive search method, are analyzed in detail. The two procedures are compared, and their applicable scopes are discussed. The simulation results on testing system prove the correctness and validity of proposed TSC based method in partition optimization.

Impacts of Additives on Sulfur Corrosion and Measurement Results of Dissolved Gas in Transformer Oil

HE Zhiman, WANG Jianfei

2017, 50(3):  124-127.  DOI: 10.11930/j.issn.1004-9649.2017.03.124.04

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In order to study the corrosive properties of transformer oil after dibenzyl disulfide(DBDS) antioxidants are added and the corrosion inhibiting abilities of metal deactivators, a series of thermal aging tests are carried out on Oil Samples A and B in the laboratory. First, the thermal aging test is conducted to test the corrosive sulfur compounds by ASTM D1275B method. Then the thermal aging tests are carried out on Oil Sample A after adding a certain amount of metal deactivator (Irgament 39) at 130 ℃ to analyze the change of the dissolved gas contents in the oil. The study concludes that DBDS is one of corrosive sulfur compounds, while the metal deactivation is not. Metal deactivation can effectively prevent the occurrence of sulfur corrosion. However, it also consumes itself rapidly with the thermal aging. The contents of dissolved gases in the oil, such as H₂, CO and CO₂, increase significantly as a result of adding metal deactivator in the oil. which needs more attention regarding their impacts on oil chromatographic results, It becomes particularly critical in the diagnosis of transformer faults to avoid misjudgment.

Voltage Sag Source Locating Method Based on Similarity Measure of Intuitionistic Fuzzy Rough Sets

WU Danyue

2017, 50(3):  128-132.  DOI: 10.11930/j.issn.1004-9649.2017.03.128.05

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In order to distinguish responsibility, coordinate dispute mitigation, and facilitate fault detection, diagnosis and mitigation measures, it is necessary to locate the voltage sag in system. A voltage sag source location method based on intuitionistic fuzzy rough sets is proposed. The nodal impedance matrix is obtained according to network topology and system parameters. The positive sequence voltages of monitoring points when line faults occur are calculated using impedance matrix. A database of identification information of voltage sag is established. Using measurement information collected by power quality monitoring devices, the intuitionistic fuzzy rough sets and the positive ideal intuitionistic fuzzy rough sets of each line are constructed. The similarity of the two sets of each line is calculated. Then the line with maximal similarity value is judged as the fault line. Simulation results in the standard IEEE 30-bus test system verify the validity and accuracy of proposed method. The method has clear physical meaning and easy implementation, which can be adopted in engineering practice.

Diagnosis and Treatment of Abnormal Chromatographic Transformer Oil Caused by On-Load Tap Changer Oil Leakage

LI Yuquan, KOU Xiaoshi, ZHENG Hanbo, ZHAO Lei, SHAO Yingbiao, WANG Wei, XIE Wei, ZHANG Zhen, QU Shaoping

2017, 50(3):  133-136.  DOI: 10.11930/j.issn.1004-9649.2017.03.133.04

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The transformer oil chromatogram can directly reflect whether there exists any fault in the power transformer. Aiming at the problem of abnormal C₂H₂ in the 220-kV power transformer oil exposed from the chromatographic analysis, the fault diagnosis is carried out on the transformer. However, no sign of faults such as discharge and over-heating are observed through the live line testing. Then by altering the operation conditions of on-load tap changer, the cause is preliminarily determined as the leakage in the oil tanks of both the on-load tap changer and the transformer, which is later verified by the field inspection after equipment shutdown. To explain the source of the characteristic gas in the fault, the mechanism and switching procedures of the on-load tap changer are presented, which tends to provide a new way of thought and relevant experience on the analysis of such problems for the future.

New Energy

Reactive Power Optimization of Distribution System Integrated with Wind Power under Multiple Load Levels

JIANG Fengli, ZHANG Xin, WANG Jun, PIAO Zailin

2017, 50(3):  137-142.  DOI: 10.11930/j.issn.1004-9649.2017.03.137.06

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Due to the random feature of wind power, the access of large numbers of wind turbines brings high uncertainties to the reactive power optimization of distribution network. In order to improve the adaptability of reactive power optimization to the wind turbines, this paper proposes a new model for multi-objective reactive power optimization of distribution systems integrated with wind power based on scenario analysis under multiple load levels. Two indexes, including net savings and nodes voltage deviation, are synthetically considered in the model. Through fuzzing of the two indexes, the maximum fuzzy satisfaction index method is used to transform the multi-objective optimization problem into a single objective problem, which is then solved by the adaptive genetic algorithm. By using a 33-bus testing system as an example, the capacitor switching, power loss, node voltage and net savings are analyzed with the proposed algorithm under different scenarios and three load levels, including maximum load, normal and minimum load. The case study shows that the proposed model and method can effectively improve the voltage profile of distribution system and significantly reduce the power loss, and can be applied to the reactive power optimization of distribution system integrated with wind power generators under multiple load levels.

Deformation Research and Finite Element Analysis on Pitch Bearing of Wind Turbine

ZHENG Hui, RUI Xiaoming, HUANG Zhe

2017, 50(3):  143-146.  DOI: 10.11930/j.issn.1004-9649.2017.03.143.04

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Pitch bearing is a key component of wind turbine. The stress state and deformation of pitch bearing has major impact on operation safety of wind power system. A calculation model of pitch bearing considering combined loads is proposed. The deformation of a typical pitch bearing is calculated by using Newton-Raphson method. The stress distribution and deformation of pitch bearing are simulated by implementation of a finite element model in ANSYS. The results show that the theoretical calculation model is correct and has enough accuracy, which provides a simple calculation method in pitch bearing structural design.

Optimization Research of Distribution Network Considering Distributed Generation

ZHANG Shixiang, SHAO Huizhuang

2017, 50(3):  147-153.  DOI: 10.11930/j.issn.1004-9649.2017.03.147.07

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As China’s environmental problems and energy savings become more prominent and more severe, the high pollution, high energy consumption problem of traditional thermal power is more and more obvious. Meanwhile, non-polluting green power generation process and flexible installation make distributed generation (DG) a good solution to those traditional problems. Proper DG access can also bring considerable economic value to the grid. A multi-objective optimization model including investors, state grid and user is established. With NSGA-2 algorithm, several experiments are conducted on IEEE 33 network. The experiments are focused on different configurations of DG location, capacity and types to confirm the accuracy of proposed algorithm. It provides optimized configuration scheme under different environments for decision makers.

MPPT Analysis of Photovoltaic Power Generation System Based on P&O and IC Method

QIU Gefei, ZHANG Chungang, ZHONG Zekun, YANG Xiaolong, ZI Yang

2017, 50(3):  154-160.  DOI: 10.11930/j.issn.1004-9649.2017.03.154.07

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In photovoltaic(PV) power generation systems, in order to improve battery utilization rate, fast and accurate control method of maximum power point tracking(MPPT) is very important. Among numerous MPPT control methods, perturbation and observation (P&O) method and incremental conductance(IC) method, due to simple principle and easy implementation, have been widely applied in research and engineering projects. In order to improve performance and control effect of photovoltaic cell MPPT algorithm, detailed review of recent algorithm improvement and combined use with other methods are performed. Advantages and disadvantages of different improvement are discussed and future prospects of MPPT method are introduced.

Hybrid Energy Storage Capacity Configuration Optimization in Micro Grids Considering Electric Vehicles

WANG Shuai, ZHAO Xingyong, HE Tianyun, LIU Jian

2017, 50(3):  161-167.  DOI: 10.11930/j.issn.1004-9649.2017.03.161.07

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Hybrid energy storage has significant effect in micro grid power balance, renewable energy fluctuation suppression and battery life improvement. It is one of the future development directions of energy storage in micro power grid. An optimization model of energy storage capacity is established for micro power grid containing wind power and photovoltaic power generation with consideration of coordinated charging/discharging of electric vehicle. Empirical Mode Decomposition(EDM) is used to split and stabilize charging/discharging task. The model is finally solved by Particle Swarm Optimization method(PSO). The capacity configuration is compared under different modes including no electric vehicles, uncoordinated charging and coordinated charging/discharging. The state of charge and power distribution of hybrid energy storage are analyzed through simulation. The simulation result verifies effectiveness of proposed model in energy fluctuation suppression.

Technology and Economics

Substation Engineering Cost Forecasting Method Based on Modified Firefly Algorithm and Support Vector Machine

SONG Zongyun, NIU Dongxiao, XIAO Xinli, ZHU Lin

2017, 50(3):  168-173.  DOI: 10.11930/j.issn.1004-9649.2017.03.168.06

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The cost level of substation engineering is closely related to the integrated economy of power grid projects, and the cost level forecasting is a crucial tool for controlling cost and improving cost rationality. Based on the conventional firefly algorithm, the Gaussian Disturbance is introduced into the firefly algorithm to improve the update equation, which aims to improve the searching ability and optimize the SVM parameters. By operating the Schaffer testing function, it is discovered that the Gaussian disturbance firefly algorithm has better convergence rate and searching ability. The case study of substation engineering in Guangdong Province further proves that the proposed model has higher forecasting accuracy and effectiveness

Research on Regional Electric Power Integrated Resource Strategic Planning under New Situation of Henan Province

BAI Hongkun, WANG Jiangbo, YIN Shuo, ZHENG Yanan, LIU Yongmin, LI Hujun

2017, 50(3):  174-179.  DOI: 10.11930/j.issn.1004-9649.2017.03.174.06

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In the face of increasingly strained resources and environment, and against the geographic, resources and demand characteristics of Henan province, and through construction of power constraints of transregion grid transmission lines in six areas of Henan province, a Henan province integrated resource strategic planning model (HNIRSP) considering transregion power trasmission is established to study the regional resources overall optimization path of Henan province. The scenario analysis of HNIRSP shows that after removing the efficiency power plants(EPP), the needed installed capcacity of Henan province during 2014-2030 will reach 96 950 MW, deacreasing 32 250 MW compared with the balanced results, consequently reducing the whole social investment of 10.86 billion yuan, and reducing the emissions of CO₂, SO₂ and nitrogen oxides by 116.27 million tons, 377 000 tons and 328 000 tons, respectively.

A Vision of Medium- and Long-Term Energy Demand Based on CO₂ Emission Peak Target

MA Ding, SHAN Baoguo, ZHU Fagen

2017, 50(3):  180-185.  DOI: 10.11930/j.issn.1004-9649.2017.03.180.06

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With China’s economic and social development, energy consumption and CO₂ emissions continue to increase, and the impacts of greenhouse gas emissions on the global warming are gradually intensifying. The long-term energy demand forecasting and the corresponding sustainable energy development strategies are the hotspot in present research. Following the idea of‘bottom-up’ and ‘top-down’, a medium- and long-term energy demand projection model is established by using such methods as dynamic material flow analysis, econometrics, and elastic coefficient and energy system optimization system. Based on the 2030 carbon emission peak target, the future energy demand and carbon emissions are forecasted under different carbon tax scenarios by choosing the carbon tax as the driving factor and designing three carbon tax scenarios. The result shows that China’s energy demand will reach the ceiling in 2045; the structure of primary energy demand will be dominated by non-fossil energy and the boost of renewable energy is the main driver of the transformation; electricity will become the largest final energy and play a dominant role in final energy consumption structure change.

Analysis on the Impacts of Joint Peak Shaving Optimization of Pumped Storage Power Units and Coal-Fired Power Units on Pollutant Treatment Cost

ZHANG Hongwei, ZHAO Jun

2017, 50(3):  186-192.  DOI: 10.11930/j.issn.1004-9649.2017.03.186.07

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Affected by the economic downturn, the average load rate of thermal power units continues to reach the recorded low level, and peak shaving energy consumption increases sharply. In this paper, a qualitative analysis is made on the impact of joint peak shaving of pumped storage power units and thermal power units on the pollutant treatment cost, and a joint peak shaving optimization model of pumped storage power units and thermal power units is established with consideration of pollutant treatment cost. Based on the mixed integer programming principle, the simulation calculation model is solved. The results show that during a daily peak period, the two-shift joint peak shaving operation of the pumped storage power units and thermal power units can effectively reduce the cost of denitration, desulfurization and dust processing, as well as the carbon emissions cost and the total cost of power generation. Compared with the low load peak shaving method, the proposed method can effectively avoid the problem of denitrification system to exit operation due to the too low temperature at the inlet, as a result, having more obvious cost impact. It is proved that with full consideration of pollutants treatment costs, the two-shift joint peak shaving method of the pumped storage power units and thermal power units can effectively solve the current high energy consumption problem of thermal power unit for peaking shaving. The rationality and practicability of the proposed model and method is verified, and it is also proved that the objective of ultra low pollutant emission can be reached for regional system peak shaving.