Table of Content

28 February 2014, Volume 47 Issue 2

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Orginal Article

Application of Time Scale Correction in Control Systems of Ultra-Supercritical Coal-Fired Generating Units

HUANG Wei-jian, ZHANG Shi-rong, ZHU Ya-qing, ZHANG Xi

2014, 47(2):  1-4.  DOI: 10.11930/j.issn.1004-9649.2014.2.1.3

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The time scale is a ruler used to describe the speed characteristics of a control system and can be used to correct the controller parameters. The structure of the control system with time scale correction and its parameter setting and tuning method are introduced in this paper. The implementation of time scale correction and the tuning procedure applied to the main steam pressure control system of a 1 000-MW ultra-supercritical coal-fired power generation unit are presented. The performance of the main steam pressure control system in terms of deep peak regulation and large load variation shows that time scale correction is a simple but effective method for variable parameter control and has the potential to reduce the working load and shorten the time of on-site commissioning.

Application of Generalized Predictive Control for 600-MW Supercritical Unit Coordinated Control and Steam Temperature Control System Optimization

CHEN Tao, WANG Heng, HU Chang-sheng, ZHONG Yi-nan, XU Chang-kai, ZHANG Qi

2014, 47(2):  5-6.  DOI: 10.11930/j.issn.1004-9649.2014.2.5.1

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In this paper, the advanced coordinated control and reheat steam temperature control strategies based on the generalized predictive control technology are proposed to solve the problems of Units 3 and 4 of Anhui Huainan Pingwei Power Generation Company, such as, the load changing rate is only 1%/min, the fluctuations of the main steam pressure and temperature are above 0.7 MPa and 15 ℃ respectively and the automatic reheat steam temperature control cannot be put into use. The practical application shows that, with the new control strategies, the load changing rate reaches up to more than 1.5%/min; in the process of load change, the maximum dynamic deviations of the main steam pressure and temperature controls are within 0.4 Mpa and 6 ℃ with the related parameters no longer oscillating. This improves the operational stability of the units. Moreover, the effective control of the reheat steam temperature by flue gas baffle is realized with the maximum dynamic deviation to be within 6 ℃ and the reheat spray amount reduced by over 20 t/h, which improves the operational economic efficiency of the units.

Comprehensive Optimization Strategies for Furnace Pressure Protection System of “W”-Flame Boilers

LIU Lin-hu, DI Ruo-bing

2014, 47(2):  11-17.  DOI: 10.11930/j.issn.1004-9649.2014.2.11.6

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The problems of furnace coking and coke falling are serious in the“W”-flame boilers of the six 350-MW units of Yangcheng Power Plant due to the coal quality and have caused the tripping of main fuel by furnace pressure protection repeatedly, which seriously affects the safe and stable operation of the units. The analysis on the operation curves of the furnace pressure protection and the problems in the furnace pressure sampling system, protection system and control system is conducted and solutions are proposed based on the actual field conditions. The effectiveness of the solutions is proven and can be used as the reference to similar problems.

Exploration on LVRT of Coal Feeder in Thermal Power Plants

YUE Jian-hua, BI Chun-hai, YUE Tao

2014, 47(2):  18-22.  DOI: 10.11930/j.issn.1004-9649.2014.2.18.4

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The paper discusses the generator shutdown events caused by coal feeder outage in instant power-off. The coal feeder outage happens either when the power supply voltage of coal feeder control circuit is lower than 310 V, or when the power voltage of coal feeder itself is below 210 V. Once the coal feeders are triggered off, the generating units are forced to stop running. Therefore, two solutions including improving the reliability of the power supply and modifying the control logics are proposed. The latter is recommended through comparison.

Analysis on Influencing Factors of Passing Rate of Primary Frequency Regulation of Thermal Power Units

WANG Gang, HAO Tao, ZHANG Jiang-nan, LIU Ke

2014, 47(2):  23-26.  DOI: 10.11930/j.issn.1004-9649.2014.2.23.3

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The factors influencing the passing rate of primary frequency regulation of thermal power units are categorized and analyzed from four aspects of signal acquisition, logical control, actuator system and signal transmission. After these factors are detected and tackled in the running units, the passing rate of primary frequency regulation is effectively improved. When meeting the requirements of the power grid, the units will be able to gain more generation opportunities.

Analysis and Pre-Control Technologies on Anti-Lightning of Outdoor I & C Equipment

ZHANG Wei-jun, YE Guo-man, DING Jun-hong, LIN Chen, ZHENG Jun-chu, FANG Ce

2014, 47(2):  27-31.  DOI: 10.11930/j.issn.1004-9649.2014.2.27.4

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The transmitter and actuator damage and measuring signal fluctuation of outdoor instrument and control (I & C) equipment caused by lightning happen frequently in the power plants of Zhejiang Province, especially in Yueqing Power Plant, which has seriously threatened the security and stability of the unit operation. The statistical analysis and investigation on the issue are carried out by the plant. Based on the risk assessment on the lightning stroke on the outdoor I & C equipment, the lightning protection components are developed and put into use. As the grounding system is being improved, the situation is changing positively. Through the analysis and treatment on the lightning stroke events, the technical measures of anti-lightning for the I & C system are proposed for reference in the industry.

Energy-Saving Generation Dispatching Optimization Model of Wind Power and Thermal Power Based on Time-of-Use Price

ZHAO Yin-hui, JU Li-wei, XU Chang-qing, CHEN Zhi-hong, TAN Zhong-fu

2014, 47(2):  32-36.  DOI: 10.11930/j.issn.1004-9649.2014.2.32.4

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In recent years, wind power digestion has become a major bottleneck in wind power large-scale development. Wind power has characteristics of little in day, much in night and anti-electricity lag. Introduction of time-of-use (TOU) price to adjust the users’ load can digest wind power effectively. Therefore, wind/thermal power joint-run optimization model is constructed based on TOU price under the background of the energy-saving generation dispatching way and the target of minimizing the cost of coal-fired cost and unit commitment. With the numerical example, it is found that the TOU price can realize the goal of peak load shifting, increasing wind-connect amount and reducing the system’s coal consumption compared with the result before the implementation of TOU price.

Analysis on Line-Loss Calculation and Influencing Factors Based on Gateway-Metering Platform

WANG Yi, LI Pei-jun, LI Zhong-cheng, HAN Ye

2014, 47(2):  37-41.  DOI: 10.11930/j.issn.1004-9649.2014.2.37.4

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To improve the operation and management efficiency of power grid enterprises, a provincially unified gateway-metering platform is established in Liaoning power grid, which can collect the gateway point data for management of electricity purchase and sale and analysis of line losses. A universal real-time line loss calculation method is proposed on the basis of existing research results and platform features and the impact and sensitivity of the model parameters is analyzed by means of the gradient and directional derivative. Moreover, a case study is used to prove the correctness and effectiveness of the method, and the results show that it is a useful reference for power grid planning and operation.

Optimal Island Search of Distribution Network with DGs Based on Recursive Sub-Problem Tree Algorithm

NI Cheng-jie, FANG Xin-yan, HU Zi-heng, HUANG Mei

2014, 47(2):  42-47.  DOI: 10.11930/j.issn.1004-9649.2014.2.42.5

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Islanding, by which single or several distributed generators(DG) can be incorporated in an island, is an important measure to keep power continuity and improve reliability of the power system when blackout occurs in vast areas. It is proposed in this paper to transform the island search problem into several precedence-constrained knapsack problems(PCKPs). A discrete load-shedding scheme is introduced directly into grid model. To solve PCKPs, a recursive algorithm based on sub-problem tree is applied to acquire initial island plan and the optimal island search scheme is presented after merger and verification. During the verification, the power flow, voltage and voltage stability restriction are considered. The algorithm combines the connectivity and optimality, and its complexity is only in linear correlation with the node number. The effectiveness of the proposed strategy is verified by the simulation results of several actual distribution grids.

Comparison of Different Modulation Methods for Modular Multilevel Converter

TU Xiao-gang, LI Hai-feng, LIU Chong-ru, LUO Hai-yun, CHENG Xiao-xuan

2014, 47(2):  48-52.  DOI: 10.11930/j.issn.1004-9649.2014.2.48.4

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A comparison is made in this paper of various modulation methods in terms of the output characteristics of the modular multilevel converter(MMC). The modulation methods can be divided into submodule unified method and carrier phase shifted method based on the necessity of sorting the capacitor voltages of submodules. For a given voltage level, the harmonic distribution and the total harmonic distortion(THD) of the MMC output are obviously affected by the modulation methods. With increasing of the voltage levels, the THD reduction is varied with different modulation methods.

Research of Current-Limiting Effect of Transformer-Based Fault Current Limiters

CHEN Lin, ZHANG Xiao-qing

2014, 47(2):  53-57.  DOI: 10.11930/j.issn.1004-9649.2014.2.53.4

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This paper introduces the basic principle of transformer fault current limiter that is composed of a capacitor in parallel with primary side of a transformer, whose second side is connected to a discharge gap. The current limiting effect is described quantitatively by analyzing the steady-state characteristics while the fault current limiter is limiting short-circuit current. The application of the fault current limiter in a 500 kV power system is simulated with PSCAD software which can create the equivalent simulation model. To verify the current-limiting effect of the fault current limiter, a practical short-circuit test circuit is given. The short-circuit test is programmed respectively based on the circuit with and without the fault current limiter. Meanwhile, by simulating short-circuit of a test circuit with PSCAD software, the waveforms of the short-circuit current will be accessed. The experimental results and simulation results show that the transformer-based fault current limiter has a good effect on limiting short-circuits current and can be used as an effective protector for restraining the short-circuit current in power systems.

Transmission Line Icing Prediction Model Under Micro-Meteorological Conditions

XU Jia-hao, ZHENG Wei, HUANG Xiao-ning, YANG Cheng-shun

2014, 47(2):  58-63.  DOI: 10.11930/j.issn.1004-9649.2014.2.58.5

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Icing as a kind of special weather condition has causing serious impacts on overhead transmission lines. A study is made in this paper on the icing characteristics of the transmission lines under mountainous micro-meteorological conditions, which shows that, under different micro-meteorological conditions, the influencing factors of transmission line icing vary with different meteorological parameters. A model is established for every micro-meteorological point according to different influencing factors, based on which a combined forecasting model of transmission line icing is proposed according to neural networks and fuzzy logic algorithm. Experiments show that: the micro-meteorological area-based forecasting model of transmission line icing has a higher precision in prediction over the previous overall model and BP neural network and has a good practical application.

Modeling and Simulation for Regions of Interest (ROI) Inspection of Transmission Lines

LIANG Kun, CHEN Yang, WANG Shi-yong, LI Shao-bin, HUANG Xiao-ning, YANG Zhong

2014, 47(2):  64-68.  DOI: 10.11930/j.issn.1004-9649.2014.2.64.4

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There exist such disadvantages as high site risk and poor visibility for UAVs in inspection of high voltage transmission lines. Modeling analysis of the regions of interest(ROI including insulators, fittings and lines) of the high-voltage transmission lines by use of a virtual three-dimensional setting can provide optimization theory data for the UAV inspection and is very significant for improving the inspection safety. Virtualization of a high voltage transmission line is achieved in a Qt environment by using the API interface provided by Google Earth interfaces. Modeling analysis is made of the attitude angle of the airborne multi-rotor UAV PTZ system used for transmission line inspection to determine the relationship between ROI and PTZ system and simulation is carried out in the software environment. The testing results have proved the correctness and effectiveness of the proposed method.

PSCAD/EMTDC-Based Simulation Research on HVDC Grounding Line Fault

WANG Cai-zhi, JIANG Ying-hui, WANG Jun-jiang, LI Jing

2014, 47(2):  69-72.  DOI: 10.11930/j.issn.1004-9649.2014.2.69.3

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Researches on grounding line fault protection have not been comprehensive enough up to now. Fault discrimination cannot be fast and reliable and the fault distance cannot be accurately measured. As a result, the requirements of system transient stability are difficult to be satisfied. A HVDC transmission system model is established in this paper by using the PSCAD/EMTDC simulation platform and a simulation is carried out on the grounding line faults that may occur in HVDC transmission system. The characteristics of the grounding line faults are analyzed and the fault location of single ended traveling waves is measured. The simulation results are consistent with theoretical analysis, which proves the practicality of the built model.

Insulation Detection and Analysis of XLPE Medium-Voltage Cables

HUANG Hao, LEI Yong, YAN Jia-jun, LI Chen

2014, 47(2):  73-77.  DOI: 10.11930/j.issn.1004-9649.2014.2.73.4

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The high frequency component characteristics of depolarization current is associated with the length of the tested cables, so large difference between the standard cable length and the aged cable length will affect the judgment of cable’s aging status. The polarization- depolarization current (PDC) method is used to detect the insulation status of medium-voltage cables and the testing data are analyzed. The low frequency component of depolarization current, which is relatively less sensitive to the cable length, is used to overcome the impact of cable length. Cable aging status is determined through analyzing the value range of the depolarization current’s low frequency components, the average discharge rate and the impact of different polarization time. Finally, this method is applied in repaired cables and it is verified that the characteristics of the repaired cable is close to that of new cable with same length, which shows that the method can be used for identification of the cable’s aging status.

Simulation Analysis of Electric Field Protection for Live-Working on 1 000 kV and 500 kV AC Four-Circuit Transmission Lines on One Tower

SU Zi-ming, PENG Yong, LIU Kai, LIU Ting, XIAO Bin, WU Tian, TANG Pan

2014, 47(2):  78-83.  DOI: 10.11930/j.issn.1004-9649.2014.2.78.5

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Electric field distribution of 1 000 kV and 500 kV AC four-circuit lines on one tower is quite different from that of single-voltage EHV/UHV transmission lines and electric field for live-working becomes more complicated. The field intensity distribution for live-working is simulated in this paper with 3D boundary element method of power frequency electric field and a human body model is established for analyzing the electric field intensity of the human body in different parts in the typical operating conditions including ground potential and equipotential, based on which the electric field protection measures for the live-workers are determined. It is concluded that the safety protection requirements can be met for the equipotential workers who wear screening clothes with 60 dB screen efficiency and screening helmet with 20 dB screen efficiency, and for the ground potential workers who wear conventional screening clothes or electrostatic shielding clothes.

Design of IED for Switch Cabinets’ Comprehensive Status Monitoring in Smart Substations

HUANG Xin-bo, WANG Lie-hua, TANG Shu-xia, ZHOU Ke-hong

2014, 47(2):  84-89.  DOI: 10.11930/j.issn.1004-9649.2014.2.84.5

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A new intelligent electronic device(IED) for switch cabinet comprehensive on-line condition monitoring based on Internet of Things and IEC 61850 standard is designed for the substation spacer layer. The device adopts double cpu structure of ARM+DSP as hardware core with VxWorks and C language for its software development platform; embedded with ICD files meeting the IEC 61850 standard, the IRIG-B code is used for synchronous clock. Through the Zigbee and RS485/RFID/CAN, the data transmission from the sensors to the monitoring units (the process layer) is realized, and the communication with the monitoring center (the substation control layer) by the optical fiber is conformed with IEC 61850. Moreover, the monitoring system framework, the IED’s hardware, software platform and IEC 61850 information modeling are designed. The practical operation shows that the IED can fulfill the functions of signal remote- collection, analysis, transmission and monitoring in all status and integrate them into the synthetical diagnosis on the information platform.

Application of Electronic Instrument Transformer in Differential Protection of Electromotor

QIAN Li-hong, WANG Wei, WANG Ying-nan, REN Zhe, JIN Peng

2014, 47(2):  90-93.  DOI: 10.11930/j.issn.1004-9649.2014.2.90.3

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The paper analyzes the causes of differential protection malfunction of electromotors through actual cases, elaborates the improved method of the traditional electromagnetic current transformer circuit, and introduces its defects. It is proposed in this paper to apply the electronic current transformer to the electromotor’s differential protection to prevent malfunction of protection caused by core saturation. Experiments show that the proposed scheme can effectively solve the malfunction of protection caused by core saturation, and improve the reliability and safety of electromotor’s protection.

Numerical Simulation of Dynamic Properties of 600-MW Wall Type Tangentially-Fired Boilers

LV Tai, LIU Wei-qi, LU Kun

2014, 47(2):  94-99.  DOI: 10.11930/j.issn.1004-9649.2014.2.94.5

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This paper presents the simulation of the dynamic performance in the furnace of a 600-MW ultra-supercritical wall type tangentially-fired boiler in Liaoning Province. The diameter of the simulated inscribed circle and the dynamic performance of the furnace are studied and the simulation results are then compared with those from cold dynamic testing, which demonstrate its high fullness of the furnace field. Additionally, part of the high-temperature gas reflows back to the base of the flame in the four corners of the furnace, which is conductive to the stability of the combustion flame. Rising rotary air flow is formed in the center of the combustion zone with no primary air jets scouring the furnace wall. These results are fully consistent with the cold dynamic tests. Due to the strong rigidity of the primary air jet, the rising rotary air still has a large amount of residual rotation at the exit of the furnace. Therefore, there exists speed difference at the furnace exit. The simulation results can reflect the exact dynamic performance in the furnace and thus provide reference datum for the design and innovation of this type of boiler.

Design and Numerical Simulation of Micro Gas Turbine Combustor Burning Syngas

CAO Chang-qing, FU Zhong-guang, LU Ke

2014, 47(2):  100-105.  DOI: 10.11930/j.issn.1004-9649.2014.2.100.5

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A new syngas combustion chamber of micro gas turbine is designed. The basic geometric dimensions of the combustion chamber, the location and area of the secondary air and the mixing cooling hole, as well as the structure of the swirl burner, are determined based on the results of the thermal calculation and related standards. Additionally, the performance of the designed combustion chamber, such as the cold and hot flow fields, the combustion stability and efficiency and the pressure losses, is studied with the computation fluid dynamics (CFD） software. Numerical calculation results show that the flow field of the designed combustion chamber is reasonable and the combustion is stable with high efficiency and low pressure losses. All these indicate that the design requirements are satisfied.

Development of Distributed Natural Gas Generation and Its Impact on Shanghai Power Grid

HUANG Bi-bin, LI Qiong-hui, SUN Li-ping, TAO Pei-jun

2014, 47(2):  106-110.  DOI: 10.11930/j.issn.1004-9649.2014.2.106.4

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Promoted by sustained incentives and adequate natural gas supply, the capacity of distributed generation by natural gas in Shanghai is predicted to grow continuously, and will impact Shanghai power grid development in the future. The electricity demand forecasting and power plant construction scheme of Shanghai grid is analyzed. Based on an analysis of the supply capability and consumption market of natural gas in Shanghai, the development prospect of distributed generation and the natural gas supply potential for it, as well as its impact on Shanghai power grid development are studied. It is concluded that the construction of distributed generation by natural gas is not restricted by construction space; and the installed capacity of this kind of distributed generation in 2015 may reach 400 MW, which will have limited impact on the balance of power supply and demand; the installed capacity in 2020, however, may reach 3.75 GW and the electricity generation will likely exceed 5% of the total power demand , which may have some influence on accommodation of imported power and the utilization-hour of conventional power generation.

Study on Modeling and Simulation of SVCs in Wind Farms Based on PSS/E Software

XIE Huan, WU Tao, SU Wei-min, LIU Hui, CAO Tian-zhi, LIANG Yu-zhi, LAN Hai-bo

2014, 47(2):  111-115.  DOI: 10.11930/j.issn.1004-9649.2014.2.111.4

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Simulation and modeling of state var compensators (SVCs) in wind farms are important for integration of large-scale wind power into a local grid. Standard models of reactive dynamic compensation devices in PSS/E software were introduced in detail in the paper, and user-defined modeling methods and skills of SVC controller were summarized. Based on an actual wind farm in northern Hebei, a user-defined model of SVC controllers with constant voltage or reactive power control objectives was established for typical wind farms. Comparison of the simulation and field testing results shows that the user-defined model is accurate and sufficient. Besides, the PSS/E customized modeling method mentioned above is equally applicable to other FACTS’ devices in power systems.

Case Study on Reinforced Concrete Foundation Damage of Wind Turbine Generator Tower with Finite Element Method

ZHOU Xin-gang, KONG Hui

2014, 47(2):  116-119.  DOI: 10.11930/j.issn.1004-9649.2014.2.116.3

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A failure case is introduced of an reinforced concrete(RC) gravity spread slab foundation for a 1.5 MW wind turbine generator tower. Under multiple load circumstances, the stress and deformation of the RC foundation are studied with finite element method (FEM) and the damage causes of the RC foundations are discussed. Investigation, testing and FEM analysis show that the bond between the embedded circular steel tube and the concrete foundation is lost when the tower is exposed to extreme loads, which leads to excessive stress in the concrete over flange plate and the shear and fatigue damage of the concrete. Under repeat loads, the damage develops and the slip between the circular steel tube and the concrete foundation become more and more obvious, which results in remarkable vibration of generator tower and even close down of the turbine generator. Based on the analysis, suggestions are made for strengthening treatment and design of the RC gravity spread slab foundations.

Comparison of GHG Emission Quantification Methods for Coal-Fired Electric Power Enterprises

DUAN Zhi-jie, ZHANG Li-xin, LI Wen-bo, CHEN Lin, WANG Zhen-yang

2014, 47(2):  120-125.  DOI: 10.11930/j.issn.1004-9649.2014.2.120.5

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GHG emissions in China are mainly from fossil fuel combustion in electrical power generation, which make it the key element of GHG management in China. Ensuring the accuracy of GHG quantification in electric power enterprises is essential to the GHG management. In this paper, through the analysis and comparison of measurement data from a coal-fired power plant, the differences between those quantification methods for typical sources of GHG emissions as well as the root cause of these differences are investigated. In combination with the general situation of the power plants in China, proposals on GHG quantification methods for electric power enterprises are put forward conforming to international practices and China’s current situation.

Diagnosis and Analysis on SCR Performance of 600-MW Units

WANG Jian-feng, WANG Feng-ji, LI Zhuang, ZHANG Yang, YANG Yong-long, ZHU Yue

2014, 47(2):  126-129.  DOI: 10.11930/j.issn.1004-9649.2014.2.126.3

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Aiming at the issue of high ammonia consumption in one 600-MW unit in Fujian Province, the SCR velocity field and ammonia slip are measured as theoretical evidences to reduce the ammonia slip volume. The flue gas velocity and ammonia slip at the SCR inlet and outlet values are measured by using micro-manometer and gas analyzer and then the measurement data are post-processed by using Tecplot. The analysis results show that the SCR inlet arrangement significantly affects the flue gas velocity distribution while the flue gas velocity field has great impacts on the ammonia slipping. The higher the NO_x capture efficiency, the higher ammonia slip rate will be reached. The SCR outlet flue gas velocity field and the ammonia slip rate indirectly reflect the activity as well as the plugging of catalysts. Moreover, piping wearing may occur due to the existence of high velocity area at the outlet.

Study on Some Key Issues in the Process of Carbon Dioxide Capture Technology for Flue Gas

LIU Lian-bo, GAO Shi-wang, NIU Hong-wei

2014, 47(2):  130-134.  DOI: 10.11930/j.issn.1004-9649.2014.2.130.4

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The carbon dioxide emission reduction is drawing increasing concerns globally. Particularly, the CO₂ capture technology applied in coal-fired power plants is one of the main methods to reduce CO₂ emissions from power plants on a large scale and the capture process is the basis of the technology. From the aspect of process design, the flue gas pretreatment and absorption processes of amine-based absorption are introduced, and the impacts of further desulfurization, flue gas cooling, absorption rate, plant adaptability, operational control and energy-saving technologies on CO₂ capture are analyzed, which can provide reference for large-scale CO₂ capture system design.

Estimation of Mercury Emissions from Coal-Fired Power Plants in China during the 12th Five-Year Period

ZHAO Yi, XUE Fang-ming, WANG Han, HAO Si-qi, QI Meng

2014, 47(2):  135-139.  DOI: 10.11930/j.issn.1004-9649.2014.2.135.4

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By way of the studies on the coal consumption, the coal mercury contents and the mercury emission correction factors of the combustion and flue gas purification facilities, and also by taking account of the operating proportion of pollution control equipment during the 12th Five-Year Period, the input and output amounts of the total mercury in coal-fired power plants are calculated for the year 2010 and 2015. It is predicted that by 2015 the mercury emissions from the flue gas of coal-fired power plants to the atmosphere will be reduced, while the mercury contained in the solid wastes will increase, and the amount of mercury in the desulfurization waste water will be kept at the same level of year 2010. Therefore, the total mercury emissions will increase. Moreover, the mercury discharged from the flue gas, the desulfurization waste water and the solid wastes will be 42.92 tons, 123.3 tons and 186.6 tons respectively. The mercury control in the future will be focused on solidification and harmless disposal of mercury in the desulfurization waste water and solid wastes.

Electrical Coal Demand Forecasting Model and Case Studies Based on Improved X-12-ARIMA

ZHU Fa-gen

2014, 47(2):  140-145.  DOI: 10.11930/j.issn.1004-9649.2014.2.140.5

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Considering the floating holiday effects of China’s Spring Festival, the Dragon Boat Festival and the Mid-Autumn Festival, the improvement and corresponding case studies are put forward on the X-12-ARIMA model developed by the U.S. Census Bureau. The case study results show that electrical coal consumption is characterized by apparent seasonal patterns. Each year the highest peak of the consumption happens in the period of “November-December” while the small peak appears in the period of “July-August”. As for January, February and March in 2013, the forecasting accuracies of the improved model based on X-12-ARIMA are 96.6%, 95.1% and 93.7%, respectively, which demonstrates its satisfactory performance in short-term forecasting.

Analysis and Forecast on Electricity Demand Trend of Henan Province

BAI Hong-kun, WANG Lei, LI Zong, LIU Yong-Min, WANG Jiang-bo, JIN Man, MA Ren-yuan

2014, 47(2):  146-151.  DOI: 10.11930/j.issn.1004-9649.2014.2.146.5

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Affected by the domestic and international macroeconomic situation from the year of 2012, the growth rate of electricity demand in Henan Province has been slowing down dramatically to 3.33% in 2012 and 1.17% in the first half of 2013, which are both far lower than the average growth rate of 11.7% during“The Eleventh Five-Year Plan”. Moreover, the growth rate for industry usage in the first half of 2013 is -0.86%, and that of energy-intensive industries hits -3.8%, which account for 54% of the electricity demand of the industry usage. Through the analysis on the inconstancies between the electric power consumption growth and the social economy growth, along with the market environment and the power consumption tendency in several typical industries in Henan Province, the electric power demand tendency of Henan Province is forecasted in this paper. In the end, this paper concludes that under the new circumstances, the slowdown of electric power demand is going to mitigate the electric power demand and supply situation. The development of electric power industry will turn to be an essential booster rather than constraints in the development of social economy.

Reactive Power Planning of Distribution Network Based on Evolutionary Strategy Theory

SHENG Si-qing, LI Xing, FAN Lin-tao

2014, 47(2):  152-155.  DOI: 10.11930/j.issn.1004-9649.2014.2.152.3

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In this paper a mathematical model for distribution network reactive power planning was established to solve the configuration capacity by taking the minimized sum of electrical energy loss at the different load operation mode and the investment for reactive power compensation equipments as the objective function. Meanwhile, the evolution strategy is improved. In order to better introduce competition mechanism and achieve population diversity, double populations and‘catastrophe’ are introduced. Different fitness functions is used respectively for the two populations to choose next generation, and the fitness is improved to ensure the diversity of population and the accuracy of the fitness values. Chaos search is introduced in the elite group to jump out of local convergence. A case study is conducted by use of improved evolution strategy method and results show that the improved algorithm has better global search capability for optimization.

Fuzzy Optimization of Distribution Network Reconfiguration Considering Uncertainty

WANG Hai-chao, ZHOU Ling, DING Xiao-qun, LU Chen

2014, 47(2):  156-160.  DOI: 10.11930/j.issn.1004-9649.2014.2.156.4

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There is uncertainty in load changes of actual distribution network leading to the difficulty of describing the distribution network reconfiguration in traditional models. This paper has built a fuzzy multi-objective distribution network reconfiguration model with the features of optimization of power supply quality and the minimization of network loss, which is based on the fuzzy speciality of the load change and used the quantum evolutionary algorithm(QEA) to find the best result in this model. By this way, it has improved the economy and power supply quality of the distribution network. The back/forward sweep method is used for getting the fuzzy interval of fitness function and balance the good points against the bad points by comparing the fuzzy interval, which is decided by the evaluation function of interval. The effectiveness of the method is verified through the simulation results of IEEE 33-node system with distributed generations.