Table of Content

05 June 2013, Volume 46 Issue 6

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Generation Technology

Study on the Impact of Dry and Wet Bottom Ash Handling Systems on Boiler Efficiency

XU Hua, ZHANG Hua-lun, WANG Shi-neng, DANG Nan

2013, 46(6):  1-4.  DOI: 10.11930/j.issn.1004-9649.2013.6.1.3

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So far the impacts of air-cooling dry-type bottom ash handling system on boiler efficiency are still controversial and very few authoritative conclusions have been drawn. After three years’ research on the system, the mathematical models including boiler efficiency and cooling air volume are established. Combining with the tests conducted in two 1 000-MW boilers of one power plant, it is concluded that the dry-type bottom ash handling system does have impacts on boiler combustion and lower the boiler efficiency under most circumstances. In addition, the impacts of the dry-type bottom ash handling system are greater than those of the wet-type system. The easy-cooking coal is not a suitable choice for the boilers with dry-type system. If the coal quality of the power plant fluctuates drastically, it is critical to choose the dry-type system meticulously.

Comprehensive Application and Prospect of Hybrid Cooling for Air-Cooled Units

JING Sheng-xiang, WANG Qing

2013, 46(6):  5-5.  DOI: 10.11930/j.issn.1004-9649.2013.6.5.0

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To lower coal consumption of air-cooled units, the idea and technical points of hybrid cooling are introduced. By adopting auxiliary cooling equipment, the radiating area of the air-cooling island is increased to solve the problems of poor unit economics and load limitation due to high back pressure in summer; while in high back-pressure operation in winter, exhaust steam heating can be realized so that the efficiency of cogeneration is improved. Optimization on energy saving with multiple technologies accommodating local conditions and local resources is suggested. In addition, taking the wet peak cooler, the evaporative cooler and the heat pump for example, detailed implementation schemes on comprehensive application of hybrid cooling are presented.

Optimal Control System Based on Advanced Control Technologies

HUA Zhi-gang, HU Guang-yu, WU Zhi-gong, CUI Xi, LU Jian-hong

2013, 46(6):  10-15.  DOI: 10.11930/j.issn.1004-9649.2013.6.10.5

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Aiming at problems existing in the 700 MW ultra supercritical power units in a power plant, such as low load changing rate, low load regulation accuracy and instability of the control system caused by coal type changing, a coordinated control system and an optimal steam temperature control system are proposed through adopting the advanced control methods in the modern control theory. The practical application shows that the advanced optimal control systems have successfully improved the performance of load regulation and reduced the fluctuation of key parameters, which indicates that the operation stability and self-adaptability to coal variation of the units are greatly enhanced.

Analysis on Shaft Centering of Multi-Rotor Turbo-Generator

JU Qiang, DU Jin-wei

2013, 46(6):  16-21.  DOI: 10.11930/j.issn.1004-9649.2013.6.16.5

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The shaft centering of multi-rotor units is complicated and tedious. Repeated calculation and testing are needed in maintenance to reach the optimized result. For this situation, a complete-partial-complete cylinder adjustment scheme is proposed, and a chart-based fast calculation method is provided for turbine-generator shaft adjustment. In this paper, the N335-16.18/538/538 type turbine-generator shaft centering is taken as an example to show the standard establishment, calculation approach as well as the key issues which need to pay more attention in practice. Finally, the technological process and vector diagram method for fastening the coupling bolts of D600A type turbines are presented to provide reference for similar units.

Effects of Particle Distributions on Combustion Characteristics under Different Coal Blending Patterns

LIU Liang, YANG Zhe, ZHOU Zi-qi, LI Hong-ming, CHEN Ming-hui

2013, 46(6):  22-26.  DOI: 10.11930/j.issn.1004-9649.2013.6.22.4

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There are two blending patterns of different coals, i.e., mixing before grinding and mixing after grinding in power plants. To study the effects of the blending pattern on the distribution of coal particles and the combustion characteristics, experiments and analysis on four kinds of coal grinded under the same conditions(including the Longping anthracite, the Wanliu bituminous coal and the two coals blended with the two blending styles) were conducted by the Easysizer 20 laser particle size analyzer and the thermogracimetric analyzer respectively. The experimental results show that the particle size and the combustion characteristics of the coal sample blended before grinding are similar to that of the Wanliu bituminous coal which is composed of much more portion of small particles, while the particle size and the combustion characters of the coal blended after pulverization is close to the Longping anthracite which consists of much more large particles. The coal blended before grinding outperforms those blended after grinding in the aspects of the ignition index, combustion stability, burn-out characteristics and comprehensive combustion characteristics.

Analysis on Total Moisture Loss and Corrections during Mechanical Coal Sample Preparation

HAN Li-peng

2013, 46(6):  27-29.  DOI: 10.11930/j.issn.1004-9649.2013.6.27.2

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The total moisture loss of coal sample is quite common in the mechanical preparation process. In this paper, the factors influencing the total moisture loss are analyzed. Through the significance test, the total moisture loss of mechanical coal sample is evaluated. The results of coal sample total moisture test show that, compared with the sample from artificial preparation which is free of significant total moisture loss, certain bias are introduced into mechanical sample preparation. In order to make the coal sample from mechanical sample preparation consistent with the actual situation, the mathematical model with the correction of the total moisture loss in mechanical sampling is established and tested by one-dimensional linear regression method based on the artificial sampling datum. The model can be used for bituminous coal and anthracite coal with the total moisture of more than 6%, but the modifications of coefficients in the model are needed depending on the exact mechanical sample preparation system.

Power System

Modeling and Simulation of Tianshengqiao—Guangdong ±500 kV HVDC Transmission System

CHEN Ming, XIANG Yan-hui, GUO Qian-wen, ZHEN Tao, XIAO Ye-xiang, QUAN Jiang-tao, RUAN Ling

2013, 46(6):  30-33.  DOI: 10.11930/j.issn.1004-9649.2013.6.30.3

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Based on the parameters of Tianshengqiao—Guangdong HVDC transmission system, the model of AC system, converter transformer, rectifier, inverter, AC/DC filter, smoothing reactor and DC transmission line are built up by PSCAD/EMTDC electromagnetic transient simulation software. After modifying the control system of HVDC transmission line model on CIGRE HVDC of PSCAD, the bipolar and double 12-pulse HVDC transmission system of Tian—Guang model is built up. The simulation result shows that the model can simulate the Tian—Guang HVDC transmission system accurately and provide an effective tool for fault researches of bipolar HVDC transmission line.

Analysis of the Effects of the Control and Protection System Parameters on Zero-Load Test in Yunnan—Guangdong UHVDC Transmission Project

XU Pan-teng, SONG Shu-bo, ZHANG Zhi-chao

2013, 46(6):  34-37.  DOI: 10.11930/j.issn.1004-9649.2013.6.34.3

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Zero-load test is very different from valve group deblock in control and protection characteristics, the parameters of DC control and protection system in normal condition may result in zero-load test failure. The configuration of control and protection system in Yunnan—Guangdong UHVDC transmission project was introduced in this paper,and the factors influencing the zero-load test of control and protection system were analyzed. In order to successfully conduct the zero-load test of the Yunnan—Guangdong UHVDC transmission project, the control and protection system parameters were partly modified. Case study shows that the method adopted in Yunnan—Guangdong UHVDC transmission project can effectively ensure the successful implementation of the zero-load test.

Energy-Saving Dispatching Model and Its Applications in Guangdong Power Grid

CHEN Liang, WANG Cheng, WEI Wei, LIU Feng, MEI Sheng-wei, WANG Yi, CHEN Yu-guo

2013, 46(6):  38-43.  DOI: 10.11930/j.issn.1004-9649.2013.6.38.5

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To meet the requirements of energy saving and environment protection, the energy-saving generation dispatching policy (ESGDP) has been promulgated and implemented in power girds of China. The core of ESGDP is to establish a dispatching sequence for each of units, and then schedule and dispatch them in order. However, the ESGDP only provides general dispatching principles without comprehensive model and algorithm for energy-saving dispatching, which discourages the implementation of ESGDP in Guangdong power grid at large. To solve this engineering problem, this paper proposes a mix integer linear programming (MILP) based unit commitment (UC) and generation scheduling model considering the ESGDP. In view of a large capacity of pumped storage hydro in Guangdong power grid, the effects of pumped storage plants are further taken into account in the energy-saving dispatching model. Effectiveness of the proposed model is verified on the IEEE-39 bus power system. Using the real data of Guangdong power grid, the energy-saving dispatching strategies are determined and analyzed for different dispatching modes for minimizing the fuel cost and the electricity purchasing cost, respectively. Furthermore, some general principles are suggested for using pumped storage plants under different modes of energy-saving dispatching in Guangdong power grid.

Development and Application of Wind Power Dispatch Scheduling in Xinjiang Power Grid

LI Jing-kun, YAO Xiu-ping, HUANG Yue-hui, YAN Qing, PENG Zhong

2013, 46(6):  44-47.  DOI: 10.11930/j.issn.1004-9649.2013.6.44.3

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Xinjiang has abundant wind resources and the wind power generation there is growing rapidly in the recent years. However, the difficulties of dispatching wind power have exerted considerable impacts on the security of the power grid. A wind power scheduling mode based on wind power forecasting and acceptability assessment is developed and a wind power dispatch scheduling system considering the local wind resources and the characteristics of the power grid is established on a software platform associated with wind power forecasting and thermal unit commitments integrated together. The grid security constraints and the peak regulation limits of regular generators are weighted comprehensively. By virtue of power control measures, accurate wind power dispatch scheduling is set up ahead of time. The application outcome of the system indicates that the mode can provide perspective guidance for day-ahead generation planning and real-time dispatching.

Optimal Cutting of Power Cables Based on the Matlab and C#.net Hybrid Program

WAN Shu-ting, HAN Guo-dong

2013, 46(6):  48-51.  DOI: 10.11930/j.issn.1004-9649.2013.6.48.3

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In order to get the power cable optimal cutting in the electric power engineering, a mathematical model was established for the optimization objectives of cable segmentation to the total length of raw materials by using Matlab and C#.net hybrid programming method. The cable optimal segmentation system was developed based on B/S mode, including automatic generation of all feasible cutting programs, selection of optimal partitioning scheme, and calculation of raw material utilization. Case study and testing results indicate that the system is able to achieve good optimization of power cable cutting and the features and advantages of Matlab and C#.net hybrid programming are well testified.

Study on Optimization of Forging Flange Designing in UHV Steel Tubular Tower

LI Qing-hua, WU Jing, XING Hai-jun, ZHU Bin-rong

2013, 46(6):  52-56.  DOI: 10.11930/j.issn.1004-9649.2013.6.52.4

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The popularization of the steel tubular tower in UHV projects has raised new requirements for the tower reliability and economics. By comparing the materials for steel tubular towers and those for angle steel towers and considering the structural characteristics of the steel tube tower, a method for improving the economics of the UHV steel tube tower by reducing the joints is advanced. The application of the forging flange in UHV steel tubular towers is analyzed in detail and a new method for forging flange fine designing is developed. In addition, combined with the design of the EHV/UHV quadruple-circuit steel tubular tower, the feasibility and economics of the related methods are studied. The research shows that in UHV steel tubular tower designing, the proportion of forging flanges can be minimized through several ways, such as strength classification, distribution optimization and material selection. All these can further improve the economics of the UHV steel tubular towers.

Development and Application of High-Performance OPGW in the Qinghai-Tibet DC Power Transmission Interconnection Project

LI Wei-hua, JIA Xiao-tie, ZHU Jing, YU Jin

2013, 46(6):  57-62.  DOI: 10.11930/j.issn.1004-9649.2013.6.57.5

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The Qinghai-Tibet plateau’s odious natural environment of high altitude, extreme low temperature and great temperature difference has severe impact on the loss characteristics of OPGW, and threatens its long term safe and stable operation. This paper introduces the ultra high-performance OPGW used in the Qinghai-Tibet DC transmission interconnection project. Customized by the use of SMF-28 ULL fiber and low temperature resistant optical fiber ointment, the OPGW has low loss characteristics in the ultra low temperature of -55 ℃ and has been successfully used in the world’s highest ultra long-span optical fiber communication system which crosses over the Tang-ku-la Mountains with a distance up to 295 km. Application shows that the OPGW can operate stably in the poor natural environment of plateau area. The development and application of ultra high performance OPGW provides a good foundation for the long term safe and stable operation of the communication system of the Qinghai-Tibet DC transmission interconnection project and valuable experiences for similar projects in the future.

New Energy

Strategy on Wind Power Smoothing Subject to Target Parameters and Energy-Storage Capacity

CHEN Luan, HUANG Qi, CHEN Chi

2013, 46(6):  63-69.  DOI: 10.11930/j.issn.1004-9649.2013.6.63.6

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Considering the constraints of target parameters and energy-storage system capacity, three wind power smoothing control strategies are proposed. Their features and applicable situations are also discussed. The target-parameter based strategy smoothes the high-frequency components of the wind power by homogenizing the distribution of power fluctuation limits, while the storage-capacity based strategy can improve the efficiency of the energy-storage system significantly by taking its capacity as the smoothing control decision parameter. Further, the capacity inadequacy of energy-storage systems can be solved better by combining the two strategies mentioned above and adopting the wind curtailment and temporarily splitting techniques. Based on the established wind power smoothing control models, three related algorithms are developed and simulation analyses are provided, which proves that the new control strategies are effective.

Study on Power Regulation Scheme of Large-Capacity and Long-Distance DC Transmission for Wind Power

XIN Song-xu, ZHANG Yun-zhou, BAI Jian-hua

2013, 46(6):  70-74.  DOI: 10.11930/j.issn.1004-9649.2013.6.70.4

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Transmission of large-scale wind power from the north of China fits the future need for the wind power development. A new power regulation scheme of large-capacity and long-distance DC transmission is proposed then for wind power . Based on the analysis of the characteristics of power surplus and regulating capacity surplus of the sending end system, the principle of complementary operation between the sending end system and the DC system is studied with a testing case established in details. The results show that, in the case of bulk wind power transmission, constant and steady DC transmission as well as efficient wind power utilization can be achieved, by giving play to the regulating capabilities of the sending end system. Finally, relevant measures are put forward to safeguard the implementation of such DC transmission regulations.

Analysis and Forecast of Wind Power Fluctuation Based on Symbolized Time Series Theory

NAN Xiao-qiang, LI Qun-zhan, QIU Da-qiang

2013, 46(6):  75-79.  DOI: 10.11930/j.issn.1004-9649.2013.6.75.4

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Wind power fluctuation analysis and forecasting are one of the major research topics in wind power integration. Considering the randomness of wind power fluctuation, the symbolized time series theory is applied in forecasting analysis, and an adaptive partition method is proposed to realize the non-uniform segmentation of data sequence according to its distribution intensity, by which a region containing more information can be discovered to show the variation of the data. Furthermore, the location of the key data in the original time series can be caught by inversion processing of symbol sequence histograms, leading to the results of wind power prediction. The validity of the method is verified on a wind farm, which can provide reference for wind power dispatching.

Smart Grid

Key Object Modeling and Performance Simulation of Process Level Networks in Smart Substation

WANG Hai-zhu, CAI Ze-xiang, SHAO Xiang-chao, LI Yi-quan, ZHANG Chi

2013, 46(6):  80-84.  DOI: 10.11930/j.issn.1004-9649.2013.6.80.4

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For meeting the demand of performance assessment of process level networks and automation application system of smart substations, a substation process level network modeling and simulation method was provided based on OPNET(Optimized Network Engineering Tools）. This paper analyzed the modeling requirements of physical units, IEC 61850, scheduling strategies and networking architecture; and studied the key object modeling method of process level networks of substation. Based on a typical 220 kV substation, the performance assessment model of substation process level networks was established and the network performance was analyzed under normal and fault operations respectively. This paper provides an effective research tool for the performance assessment of process level networks and automation system of smart substations.

Exploration of Hot Issues on Demand Response in Smart Grids

ZHANG Qin

2013, 46(6):  85-90.  DOI: 10.11930/j.issn.1004-9649.2013.6.85.5

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Through price signals and incentive mechanisms, demand response programs can help construct a reliable, efficient and robust feedback mechanism for smart grid and power market operation. With the development of power markets and the upsurge of smart grids, various market-driven demand response programs have been established around the world. In this paper, the demand response theory and its application framework adapting to electricity markets and smart grids are established and studies on these topics are conducted. The relevant hot issues including program decision-making and risk management in smart grids are also explored, from which the function of demand response in improving the system security, reliability and economics is set forth from multiple aspects. The study concludes that novel demand response programs can further enhance the customers′ response capability, and are more supportive to safeguarding the system secure and economic operation.

Study on Strategies for Smart Charging of Electric Vehicles

ZHANG Zhi-wei, GU Dan-zhen

2013, 46(6):  91-95.  DOI: 10.11930/j.issn.1004-9649.2013.6.91.4

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Uncoordinated charging of electric vehicles (EVs) produces a series of negative effects on the power grid. Therefore smart charging strategies are necessary to reduce the negative impacts on the grid and minimize the charging cost to the EV users. Based on the characteristics of EVs, a new mathematical model for optimizing the object function is proposed to compute the smart charging strategy with Matlab and make decisions. The charging behavior is managed by the central self-control layer in the hierarchical partition management to solve the possible problems between the power grid and the EV users. Case calculation shows that smart charging can reduce negative impacts on the grid.

Energy Conservation and Environmental Protection

Characteristics of Distribution and Fractions of Arsenic in the Soil around a Coal-Fired Power Plant

HE Hong-ying, YUAN Chun-gang, ZHAO Yi, ZHANG Jing-hong

2013, 46(6):  96-98.  DOI: 10.11930/j.issn.1004-9649.2013.6.96.2

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The soil samples were collected from the locations near a coal-fired power plant. The atomic fluorescence spectrometry was applied in the total arsenic detection, and the arsenic in the soil samples was further fractionated into different fractions by a sequential extraction procedure. The results indicate that the arsenic content in the soil samples is below the national environmental quality standards for soil and decreases vertically with the deeper sampling spot. Taking the chimney as the origin, the arsenic content is distributed horizontally in agreement with parabola characteristics and is also related to the wind direction. The fractions of arsenic are mainly in iron and aluminum hydration oxide binding fractions and residuals, which are not easily uptaken by plants and animals.

Effect of Non-Equilibrium Plasma Characteristics on NO Removal Efficiency

CAO Chun-mei, DING Qing-wei

2013, 46(6):  99-102.  DOI: 10.11930/j.issn.1004-9649.2013.6.99.3

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The numerical simulation method is adopted to study NO removal from the flue gas by non-equilibrium plasma. The influence of two major characteristics in non-equilibrium plasma (electron number density n_e and electron average energy ) on NO removal efficiency is investigated. The simulation results show that the NO removal efficiency varies with the electron number density n_e and the electron average energy . In comparison, the electron number density plays a much more important role in NO removal efficiency. When the initial concentration of NO is 10¹⁶ cm^-3 and the electron density is high(n_e≥10¹⁷ cm^-3 ), the NO removal efficiency can get up to 99% even though the electron average energy is as low as 4 eV. Given constant density of the electron number and the average electron energy, the NO removal efficiency worsens as the initial concentration of NO rises.

Power Planning

Planning of Power Generation Systems Based on Violation Analysis of Clean Energy Resources Availabilities

HU Qing, HUANG Guo-he, LI Wei

2013, 46(6):  103-107.  DOI: 10.11930/j.issn.1004-9649.2013.6.103.4

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Reasonable plans for electric power generation systems are very critical for efficiency improvement in electric power industry. In this study, a lower-side-attainment-value-based inexact fuzzy chance-constraint programming model is developed to deal with the complexities and uncertainties in regional electric power generation system planning. Firstly, the model integrated the energy supply, conversion and consumption, the option, renovation and expansion of conversion technologies, the electricity generation and the pollutant mitigation into the planning frame, providing a foundation for optimized energy allocation. Secondly, based on probability(pi) levels, the violation of constraints on clean energy resource availabilities can be quantified, and the relationship between system costs and reliability can be reflected via the analysis on the solutions to energy supply, electricity generation, capacity expansion and emission mitigation under different pi levels, which is supportive to the security of generation side.

Study on Methods of Structure Improvement for Power Load Grey Forecasting

ZHENG Ya-nan, SHAN Bao-guo, GU Yu-gui, LIU Wei, LI Geng-yin

2013, 46(6):  108-112.  DOI: 10.11930/j.issn.1004-9649.2013.6.108.4

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With the rapid development of the electric power industry, mid- and long-term power load forecasting has become a very important fundamental work. Based on the study of a traditional mid- and long-term grey model, two methods to restructure the background values of the model are introduced and the improvement of the model structure is made based on the Markov chain and then the fitting accuracy index and the prediction accuracy index are tested to verify the modification from different aspects. Finally, through quantitive comparison between two scenarios, the effectiveness of the improved model is proved with the real power load data.