Table of Content

25 November 2017, Volume 50 Issue 11

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Special Contribution

Discussion on the Reasonable Curtailment Problems in Highly Renewable Power System Planning

WANG Yaohua, LI Nan, YUAN Bo, ZHANG Fuqiang, FENG Junshu

2017, 50(11):  8-14.  DOI: 10.11930/j.issn.1004-9649.201703091

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In a highly renewable power system, it will have to dispatch a large amount of peaking power to accommodate the renewable energy's spike power that makes a very small proportion of the total renewable energy, which will reduce the safety and economics of the power system. If a certain amount of renewable energy is allowed to be abandoned, the system's overall demand of peaking power will decrease, and subsequently the peak power source construction can be reduced and the expensive cost of marginal accommodation can be avoided. The paper discusses for the first time the reasonable energy curtailment problem in the mid-and-long term power system expansion planning. By using the GESP power planning software, the reasonable energy curtailment rate and the system planning cost under the curtailment rate is calculated for the safety and economics of power system. It is concluded that the reasonable energy curtailment rate of the regional grids in China is 3%~10% in 2020.

Generation Technology

IMC-Based PID Controller Design for Cascade Control of Superheated Steam Temperature with Frequency Identification

LI Xiaofeng, CHEN Guangxue, ZHANG Zhengwei, WANG Yagang, GAO Ya, YOU Yi, GU Bochuan

2017, 50(11):  15-21.  DOI: 10.11930/j.issn.1004-9649.201703014

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An IMC-based-PID Controller design method for cascade control of superheated steam temperature through frequency identification is proposed in this paper. In this design method, the process model of superheated steam temperature is identified first. In the identification procedure, the set-point change tests are adopted to calculate the models based on the inputs and outputs of the inner and outer control loops. The process frequency-response matrix is estimated, and then a transform function matrix is obtained by the least squares method. The parameters of the IMC-based PID controller of the SST (steam temperature cascade control loop) are determined by using the internal model control (IMC) and improved SIMC method based on the identified model. It is shown that this strategy achieves better control performance and minimizes the effects of the external or the internal disturbances.

Evaluation on the Energy Efficiency of Electrostatic Precipitators in Coal-Fired Power Plants

LIU Hanxiao, LI Jianguo, YAO Yuping, ZHONG Jianfeng, DU Yujiang, DU Yiqian

2017, 50(11):  22-27.  DOI: 10.11930/j.issn.1004-9649.201703014

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Based on the statistical data of power consumption and specific power consumption for 197 sets of electrostatic precipitators in coal-fired power plants in China, the evaluation, testing, and calculation method of energy efficiency for electrostatic precipitator (ESP) are put forward. The ESP efficiency evaluation for the ultra-low emission project is conducted by using the proposed method. It is shown that the low-low temperature ESP has better efficiency, but with a higher operating energy consumption. The wet electrostatic precipitator (WESP) achieves steady dust ultra-low emissions, but with a higher operating cost. When the unit is in low load operation, the electric energy consumption is high. There is still room for further saving on the energy consumption of electrostatic precipitators and the research on the energy efficiency optimization technology of the electrostatic precipitator is suggested.

Design and Operation of the 260 t/h Circulating Fluidized Bed Boiler Burning Zhundong Coal

SHI Hang, YANG Yanmei, WU Yvxin, YANG Hairui, LÜ Junfu, ZHOU Liyun, LIANG Xiaoyv

2017, 50(11):  28-32.  DOI: 10.11930/j.issn.1004-9649.201701141

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The high sodium coal is the dominant type in Zhundong area, Xinjiang province. It has the characteristics of strong contamination and slagging. coal slagging and the convective heating surface fouling frenquently appear in the boiler burning Zhundong coal, which affects the normal operation of the boiler. This paper analyzes the slagging and fouling process of Zhundong coal, and suggests that reasonable arrangement and design of the heating surface by taking advantage of the combustion cycle in the circulating fluidized bed boiler will be able to solve the possible slagging and fouling problems. The engineering design and application are also carried out. The operation results have shown that the boiler can maintain long-term stability of operation when just burning Zhundong coal. After one-year operation, no fouling and slagging was found on the furnace heating surface when using Zhundong coal with 6% of Na₂O in ash. The funnel temperature maintains around 150 ℃ when the soot blower for low temperature coal economizer is in operation.

Study and Application of Frequency Adjustment on Large Scale Structure Based on Bottom Load Redistribution

WANG Jiulong, WANG Xiufeng, SHI Qingfeng, HE Dan, SI Xianguo, ZHANG Xingtian

2017, 50(11):  33-38.  DOI: 10.11930/j.issn.1004-9649.201

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Structural resonance is one of the common fault types that may induce the large scale structure vibration. Generally, the problem is solved by improving the structure to adjust its own natural frequencies. Due to the difficulty of structural modification, the damping scheme is often used to suppress the vibration. Unfortunately, the resonance property still remains unchanged. In this paper, a new technical thought is proposed, which can change the natural frequencies of the structure by virtue of bottom load adjustment without any structural alteration or extra damping addition. By using the finite element method, the generator model is established and both the static and the modal analyses are carried out. The impacts of different bottom load distribution on the nature frequencies are calculated. Then, the experimental test is conducted. With the stepped gaskets adjusted to change the bottom load distribution, the natural frequencies are obtained through vibration modal testing. Both the theoretical analysis and the experimental results indicate that by altering the bottom load distribution the natural frequencies can be adjusted effectively and kept away from the working frequency such that structural resonance is avoided. This method has been applied for the generator of Qinshan No.2 Nuclear Power Plant, where the problem of structural resonance is successfully solved.

A Method for Response Time Measurement of DEH System Overspeed Signal

LU Hua, HUANG Bo, CHENG Zhen, WANG Hui

2017, 50(11):  39-41.  DOI: 10.11930/j.issn.1004-9649.201703014

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The overspeed signal is one of the most important protection signals in the turbine protection system. As an important parameter in DEH (Digital Electro-hydraulic Control) system, the response time of overspeed is always difficult to test. By improving the signal source from the signal generator, the amplitude and the frequency of the signal source can be adjusted, and the frequency change point can be accurately identified in the testing process, therefore the accurate testing results can be obtained.

Innovation & Practice of Technical Standards

Study on the Internationalization of Global Energy Interconnection Standards

GAO Zhiyuan, CAO Yang, ZHANG Jing, YU Yijun

2017, 50(11):  42-47.  DOI: 10.11930/j.issn.1004-9649.201708179

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Standards internationalization is important for the development of global energy interconnection. It is a complex problem involving a wide range of technical areas and diversified standardization needs. Based on analysis of technical framework of global energy interconnection and its standards internationalization requirements, the overall strategy and specific deployment methods are studied. The technology framework of global energy interconnection is outlined which contains 4 specialized directions, 13 technical fields and 45 subdomains. According to actual situation of each specialty and technical field, standards internationalization demands are analyzed. Based on current practical basis of technology innovation, engineering construction and standards accumulation, an overall strategy is proposed which promotes internationalization of global energy interconnection standards through 4 ways. Prior technical fields and specific internationalization standards are selected and several specific measures are recommended.

Interpretation of Technical Specification for Realtime Supervisory Control & Early Warning of Smart Grid Operation and Control System

ZHANG Yong

2017, 50(11):  48-53.  DOI: 10.11930/j.issn.1004-9649.201703062

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Power industry standard DL/T 1709.4—2017 “Technical specifications of smart grid operation and control system-part IV: Realtime supervisory control & early warning” is formed after summarizing construction and practical results based on function study into realtime supervisory control & early warning application. The main contents, namely real-time supervisory control and smart alarm, automatic control, operation analysis and decision, and auxiliary monitor are interpreted and discussed. Functional requirements and key technical points are explained in detail. The interpretation improves specification understanding for relevant personnel to implement standard functions correctly and easily.

Revision Interpretation of Code for Operation and Administration of Power Dispatching Automation System

NING Jian

2017, 50(11):  54-58.  DOI: 10.11930/j.issn.1004-9649.201703058

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Combined with development of dispatching automation industry, a revised power industry standard DL/T 516—2017 “Code for operation and administration of power dispatching automation system” is formed after summarizing operational management requirements of power dispatching automation system operation and administration under new circumstance. Key points and revised contents are described in detail from aspects of general principle, operation interface, operation management, inspection regulation, technical management, basic data, data transmission channel, scheduling data network and power monitoring system security protection. Discussion improves understanding on code for dispatching personnel.

Optimization Research on Technical Standard System for Assembly and Erection Construction of the Steel Towers of Overhead Transmission Line

ZHANG Fuxuan, WAN Jiancheng, CHENG Gengsheng, PENG Fei, JIANG Ming, LIU Chen

2017, 50(11):  59-64.  DOI: 10.11930/j.issn.1004-9649.201702057

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With the rapid construction of UHV grid and the progress of construction technology and equipment of power transmission towers, some problems appear in the current technical standard system for assembly and erection construction of steel towers of overhead transmission line with the standard “Construction technology guidance for the assembling and erection of the steel towers of 750 kV overhead transmission line”（Q/GDW 112—2004）as the core, which include contents repetition, poor connection and poor applicability to the practical engineering. Therefore, in order to provide a technical support for assembling and erecting steel towers, it is necessary to further optimize the framework structure of existing China's electric power industry technical standard system for assembly and erection construction of steel towers of overhead transmission line, which should be carried out based on an analysis of the constitutions and problems of current standard system, and with a consideration of the features of tower types, the tower construction technology and the equipment for erecting steel tower.

Standardization Design Study on KYN28A-12 Type Middle Mounted Switchgear

FENG Ying, LV Jun, WANG Chengyu, LI Peng, LAN Jian, MO Jinlong, SHENG Hui

2017, 50(11):  65-71.  DOI: 10.11930/j.issn.1004-9649.201702197

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In order to realize the compatibility and interchange in a certain scope and period between equipment manufactured by different manufacturers, and to improve the operation and maintenance convenience of switchgear equipment, a standardization design study is made on the equipment KYN28A-12, a relatively mature and reliable type of middle mounted switchgear that has been mostly applied in power grid. The paper introduces the purpose, procedure, input conditions and the main contents of the design. The focus of the design is put on the determination of several typical solutions of KYN28A-12 middle mounted switchgear, and a detailed description is made of the standardization design principles and results for primary interface, civil work interface, secondary interface and key components. A standardized design scheme is proposed to meet both the needs of the distribution network equipment and the distribution equipment in the substation, which can provide an important support for the follow-up standardization works.

Interpretation and Application for DL/T 1527—2016 Technology Specification of Electric Power Utilization Information Security Protection

ZHAO Bing, FENG Zhancheng, CEN Wei, LIANG Xiaobing, LI Haibo

2017, 50(11):  72-77.  DOI: 10.11930/j.issn.1004-9649.201701034

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In order to enhance power information system security and to ensure information system data and network safety, the China Electric Power Research Institute organized formulation of DL/T 1527-2016 technology specification of electric power utilization information security protection. The specification provides security protection technology and management requirements for electricity information system and related components. The logical structure of electricity information system is analyzed first. Detailed interpretation on some key issues in the specification is performed. Based on standard interpretation,security encryption devices including cipher machine, security encryption module and special encryption isolation gateway are also developed. Finally, a double-deck security communication protocol is designed to guarantee safety and reliability of electricity information system.

Applicability of Heated Band Width Recommended by Post Weld Heat Treatment Standards for New 9%Cr Steel Pipes

CHEN Dongxu, HU Lei, WANG Xue, SUN Jianhua, SUN Songtao, GUO Meihua

2017, 50(11):  78-83.  DOI: 10.11930/j.issn.1004-9649.201703014

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Four domestic and aboard post weld heat treatment (PWHT) standards for 9% Cr steel pipes are compared and the applicability of these standards is investigated based on field trials of two typical specifications of power plant 9% Cr steel pipes. The results show that there are large differences in heated band width requirement under different standards. For thin-wall 9% Cr steel pipes, Chinese, EU and US standards are appropriate. However, guideline from Huaneng is too strict in this case. All four standards cannot meet stringent requirements of temperature difference for thick-wall 9% Cr steel pipes. It is necessary to improve existing PWHT standards to guide on-site installation of 9% Cr steel pipes.

Research and Application of Operational Maintenance Standard System of Integrated Disconnecting Circuit Breaker

LI Jinbin, XIA Tian, CHEN Jun, HAN Liu, FENG Ying

2017, 50(11):  84-89.  DOI: 10.11930/j.issn.1004-9649.201611087

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In order to support construction of new generation of smart substation, and to provide technical support for core equipment quality control, operational maintenance and test, technical standards for integrated disconnecting circuit breaker are established for the first time. The standard system includes one group standard and five enterprise standards. The whole process standardization of item, method, criterion and implementation of integrated disconnecting circuit breaker is realized, which provides basis for handover debugging, operation, test, evaluation and maintenance. The standard system ensures stable application of integrated disconnecting circuit breaker.

Comparative Research on Mid Span Clearances of Overhead Transmission Lines Design Between Domestic and Foreign Standards

WANG Jingyi, PAN Chunping, ZHU Yingjie

2017, 50(11):  90-95.  DOI: 10.11930/j.issn.1004-9649.201606076

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The mid span clearance has important influence on tower top geometry and reliable operation of overhead transmission lines. The existing comparison between domestic and foreign design standards mainly focus on wind load on the basis of tower structure, while research on mid span clearance between conductor and conductor or conductor and earthwire are absent. Chinese, Japanese, European and CIGRE design standards are selected to study mid span clearance calculation methods. The analysis and comparison includes different aspects such as design and check conditions, wind load, swing angle calculation and electric clearance requirements. The existing problems in standards are also discussed. An 500 kV line is taken as example to discuss different tower top geometry between phase to phase determining by mid span clearance. Influence of wind velocity, wind direction, conductor arrangement, conductor type and spans on tower top are also studied. It is proposed that, in domestic design and check of mid span clearance, normal distribution should be used for swing angel of conductors and standard deviation should be decided by line importance. Also, it is advised to perform long-term research and observation of swing characteristics of conductors in order to improve overhead lines design.

Power System

Analysis on Influence Factors of Ice-Shedding Unbalanced Tension of Transmission Tower- Line System

HUANG Xinbo, XU Guanhua, XIAO Yuan, ZHU Yongcan, CHEN Guimin

2017, 50(11):  96-102.  DOI: 10.11930/j.issn.1004-9649.201612014

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Ice-shedding can cause sharp tension change of the conductor and produce greater tension differences, which can easily cause serious electrical or mechanical accident of transmission lines. Therefore, an ice-shedding vibration mechanical model of conductors is established by the finite element transient dynamic method to analyze the influence factors of ice-shedding unbalanced tensions and to reveal the influence characteristics of various parameters on the unbalanced tensions. The results show that the unbalanced tension of ice-shedding increases with the increase of icing thickness, ice-shedding spans, ice-shedding rates and height differences of mutation; the unbalanced tension of ice-shedding tends to stabilize with the increase of the number of continuous spans; within a certain span, the unbalanced tension of ice-shedding decreases with the increase of suspended insulator length; and different ice-shedding modes has significant impacts on the unbalanced tension. The related research results can provide a reference for the subsequent structure design and formulation of scientific and reasonable ice melting and deicing measures.

Research on RMU Condensation Phenomenon Under Different Ventilation Conditions

GENG Jianghai, QIN Yuchen, GUO Qin, LIU Ruoxi, WANG Xingyue, LV Fangcheng

2017, 50(11):  103-107.  DOI: 10.11930/j.issn.1004-9649.201608106

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As one of the factors that affect the reliability of the power system, the condensation phenomenon seriously threatens the safe operation of electrical equipment. An experiment system of ring main unit (RMU) is set up in an artificial climate chamber, and the formation time of condensation on the cabinet inner wall is recorded under different conditions of full ventilation, half ventilation and non-ventilation of the RMU's shell with different ambient temperatures and relative humidity. The results show that, when the ambient humidity is constant within a certain temperature range, the formation time of condensation under ventilation is longer than that under non-ventilation, and the half ventilation has the longest condensation time. When the ambient temperature reaches a certain value, the ventilation, however, can stimulate the formation of condensation. With the increase of ambient temperatures, the formation time of condensation increases before decreasing, and the lower the relative humidity, the better the ventilation effects are. A suitable ambient temperature and ventilation area can make the better effects of anti-condensation under ventilation.

Generation Scheduling Evaluation Based on Three-Demarcation and TOPSIS Method

ZHAO Honglei, XIAN Tianchun, ZHANG Xinlun, YAO Li, LIN Jikeng, DAI Sai, WANG Xudong

2017, 50(11):  108-115.  DOI: 10.11930/j.issn.1004-9649.201705048

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Achieving a comprehensive assessment of the power generation scheduling is important for choosing power generation plans. Firstly, a complete set of indicator system is established. Then, by combining with TOPSIS method, the three-demarcation method is used to calculate the indicator weight with the idea of iteration, which can not only ensure the accuracy of calculation, but also avoid the difficulty of consistency check in the process of traditional weighting. Then the TOPSIS method is used to evaluate the scheme, in which the indicators of the scheme and the Euler distance between the positive and negative ideal solutions are used to grading the scheme, subsequently realizing the evaluation of the power generation scheduling. Finally, the effectiveness of the proposed method is demonstrated by the data of actual power grid.

Power Grid Emergency Drill Evaluation and the Index System

FAN Junjun, CHEN Zhichao, CHEN Tao, DONG Jianda, WU Hongwei

2017, 50(11):  116-120.  DOI: 10.11930/j.issn.1004-9649.20160434

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With the development of social economy, the social demand for electricity supply is becoming more and more. In the meantime, the pressure that the power grid undertook is heavier, and the possibility of disastrous safety contingency in power grid is becoming bigger. The electric power emergency management capability of our country falls considerably short of that of developed countries, so it is very necessary to promote the evaluation of electric power emergency drill, raise the efficiency of electric power emergency drill and enhance the emergency management capability of disastrous safety contingency in power grid. The index systems of site assessment and summative assessment of table-top exercise and combat exercise are established in this paper, and the verification process is carried out in a no-script drill of one province of China.

Urban Distribution System User Access Pattern Research and Application

WANG Huizhong, YANG Shiliang, LU Yufei, FANG Lixiang

2017, 50(11):  121-126.  DOI: 10.11930/j.issn.1004-9649.201606207

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In order to solve the power user access to the problems existing in the urban distribution network plan formulation, make the whole distribution network upgrade more scientific and reasonable, establish industry standard process reporting for work. First in-depth analysis for access to the region of space truss structure and user load characteristics, distribution network to determine user access to distribution network access points and connection mode, to develop a typical access solutions, accord with the actual situation of regional comprehensive evaluation on the plan of next to each access and make a choice, the access of guangxi nanning phoenix exclusive residential projects plan formulation, standard process for industry expansion reporting for work for example. The results showed that the standard working process calculation is simple, accurate and fast, can be used to guide the electric power department staff for reporting for new users and upgrade of the distribution network.

Estimation and Countermeasures of Floating Conductor Induced Voltage

LIU Lina, TAO Jiaxiang, WAN Jian, XIE Huichun, YU Jianqin

2017, 50(11):  127-133.  DOI: 10.11930/j.issn.1004-9649.201606156

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A floating conductor below the direct current (DC) transmission lines will produce certain induction voltage and the human body would be affected by transient shock when contacting the conductor. In order to estimate the induction voltage, the total electric field under DC lines is obtained by the Deutsch-based numerical calculation method, and the potential of floating fine conductors in the nominal electric field under DC lines is gotten by the charge simulation method. For the purpose of engineering simplification, a method is proposed for estimating conductor induction potential in the total field by multiplying the potential of floating fine conductors with the potential proportion coefficient. Finally measures are proposed to reduce the induced voltage of floating conductors.

Analysis on Common Faults of Phasor Measurement Unit Caused by Series-Compensation Isolation Switch

TAN Jinpeng, WEN Caiquan, LI Yuehua, CUI Zhiguo, LU Yitao

2017, 50(11):  134-138.  DOI: 10.11930/j.issn.1004-9649.20150167

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During the operation of series compensation isolating switches, repeated strikes of the contact gap will lead to very fast transient overvoltage(VFTO) with high amplitude and steepness. The arc current and arc gap voltage by operation of isolating series compensation switches is greater respectively than those by operation of isolating no-load bus switches. The similarity between the frequency of VFTO and the coupling frequency of the carrier equipment leads to the abnormity and even damage of the carrier equipment by the VFTO coupling from the capacitor voltage transformer. A theoretical analysis model is established for series compensation switches, capacitor voltage transformer and carrier equipment to find out both the coupling path of the VFTO and the cause of the carrier equipment problems. Suggestions are proposed to improve the capacity of MOV for the overvoltage protection and to increase the lead terminals for design, operation and maintenance.

Technology and Economics

Research on Ancillary Services Market Based on Inter-Regional Electricity Transactions in Central China Power Grid

ZHANG Chang, YANG Jianhua, SHUAI Hang, SHU Kang'an, AI Xiaomeng

2017, 50(11):  139-145.  DOI: 10.11930/j.issn.1004-9649.201705089

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With the large-scale development of such clean energies as wind power and hydropower in China and the rapid construction of UHV projects, the inter-provincial electricity transactions are becoming more frequent with transaction volume increasing year by year. Large-scale out-of-area electricity increases the pressure for the receiving-end power grid to shave peak and reserve power, but it is not involved in the current assessment and compensation system of the ancillary market. Firstly, the power source and load characteristics of the central China power grid (CCPG) are introduced in this paper, and then the status quo of its inter-regional power transaction is analyzed. Secondly, a mechanism is proposed for the inter-regional power transaction to participate in CCPG peak shaving and reserve ancillary service. Finally, according to the proposed mechanism, the influences of the high-voltage DC transmission lines on the peak shaving and reserve ancillary service in CCPG are computed. The model proposed in this paper is conducive to the establishment of sharing mechanism of inter-regional ancillary services, subsequently alleviating the peak shaving pressure of the thermal power units in CCPG and promoting the consumption of clean energy transmitted from the northwest and other areas to CCPG.

Relationship Research Between Coal Power Plants and Smog

DONG Bo, LIU Shiyu, DU Zhongming, ZHANG Shuguang

2017, 50(11):  146-151.  DOI: 10.11930/j.issn.1004-9649.201703014

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Although smog is closely related to coal burning, coal power plant is not the major factor of smog creation as many people mistakenly thought. Based on analysis of smog formation and development orientation of coal energy in China, the relationship between coal energy and smog is discussed in detail from aspects of coal burning mode, air pollutants emission strength and emission standard. The research shows that coal thermal plant is the cleanest and most effective way of coal consumption, and developing clean coal thermal plant is an important method to deal with smog.

Load Response Method of Air Conditioning Groups Based on Equalize Proportion Adjustment of Indoor Comfort Index

CAO Fang, GUO Peilin, WANG Ke, SUN Yujun

2017, 50(11):  152-157.  DOI: 10.11930/j.issn.1004-9649.201703014

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Shaping load curve has important significance to improve characteristics and to enhance security, stability and economical operation of power grid. It can be achieved intelligently during large-amount air-conditioners end-user adjustment in residential loads. With introduction of an indoor comfort index, air conditioning customers are formed into small groups according to user preference to temperature and humidity. The mathematical model of load response of air conditioning group is established. A method based on equalization proportion adjustment of indoor comfort index is also proposed. The method takes into account of different user groups′ preferences to adjust air conditioner operation mode. The analysis on an intelligent community user data validates correctness and effectiveness of proposed method.

Energy Conservation and Environmental Protection

Comprehensive Analysis and Related Measures on Current Situation of Water Saving of Thermal Power Generation in China

PAN Li, LIU Zhiqiang, ZHANG Bo

2017, 50(11):  158-163.  DOI: 10.11930/j.issn.1004-9649.201702015

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In recent years, China has promulgated and amended multiple laws and policies regarding the severe situation of water shortages. In particular, higher requirements are proposed for the water resource management in the aspect of the water saving of thermal power industry. In order to improve the water-saving work of thermal power industry, this paper summarizes the relevant legal requirements and analyzes the current situation of water utilization and major water saving measures of thermal power industry, investigates and compares the water consumption level of different types of generation units, and generalizes the main problems of the water saving in thermal power industry. At last, according to the requirements of “The 13th Five-Year Plan”, the paper puts forward countermeasures and suggestions for the water saving work of thermal power industry which will provide beneficial reference for promulgating related policies on water saving.

Analysis on Mercury Emission From WFGD and WESP Wastewater in Ultra-Low Air Pollutant Emission Coal-Fired Power Plants

SONG Chang, ZHANG Yi, HAO Jian, ZHANG Jinbao, WANG Jiawei, AN Liansuo, ZHANG Yongsheng

2017, 50(11):  164-167.  DOI: 10.11930/j.issn.1004-9649.201610054

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In order to achieve the goal of ultra-low flue gas emission, a series of retrofit projects have been carried out on the 300 MW subcritical natural circulation coal-fired unit of Sanhe Power Generation Co., Ltd., such as low NO_x burner modification, SCR denitration modification, low-low temperature economizer installation, high frequency power source modification for the electrostatic precipitator (ESP), efficiency improvement and tubular demister installation for the WFGD absorber, as well as the installation of wet ESP (WESP). Taking the unit as the study object to explore the changes of the mercury concentrations in the WFGD and WESP wastewater after the retrofits, the makeup water and discharge water of both the FGD absorber and WESP are sampled to analyze the mercury contents. The results show that due to the low mercury content in coal, limestone and the makeup water, the mercury concentration in WFGD and WESP wastewater is also very low which ranges between 0.140 and 0.468 μg/L and between 0.094 and 0.102 μg/L respectively. The mercury contents in the 52 m³/h WFGD discharge water increase by 1.75 to 5.50 mg while no significant changes of the mercury concentration is observed in the WESP discharge water.

Study on Process Design and Application of the Resourcfulization of Regenerated Wastewater Using Ion-Exchange Resin Method

LIAN Kunzhou, HU Teli, WANG Jing, PANG Shenglin, HE Gaoxiang, CAO Shihai, DENG Qiangqiang

2017, 50(11):  168-174.  DOI: 10.11930/j.issn.1004-9649.201703005

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According to the characteristics of the wastewater from exchange resin regeneration in power plants, a new process consisting of ammonia fixing-ultrafiltration(UF)-reverse osmosis (RO)-degassing membrane is proposed and applied in a domestic 1 000 MW generator unit. with the system design and project construction, as well as the commissioning and performance tests being carried out. The results show that in the treatment of the wastewater from exchange resin regeneration using the new technique, when the recovery rate of saline water RO system is 75% and that of seawater RO system is 50%, the desalination rate can reach up to 97% and 98%, respectively. After the condensed water of RO system is treated by the degassing membrane, the removal rate of ammonia can reach 99%. The produced condensed water can be electrolyzed to make sodium hypochlorite, The ammonium salts separated from above process can be sold or used in plant greening while the fresh water can be used in industrial water system simultaneously. The practice indicates that the treatment process is feasible and is of great environmental and social benefits.

Study on SCR Control⁺ Denitrification Injection Control System and Its Application in a 660 MW Unit

WU Baohui, LI Gang, XUE Dayu, JIA Xiaojing

2017, 50(11):  175-179.  DOI: 10.11930/j.issn.1004-9649.201703052

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Regarding the delayed response of SCR DeNO_x system due to the high inertia under large perturbations, and other problems in the operation of SCR ammonia injection control system after ultra-low emission retrofit, the SCR Control⁺ system model with state prediction algorithm is proposed based on the data accumulation of multiple denitrification optimization projects. Through the analysis of dominant factors, the state variables influencing the NO_x concentration are selected, and the change of the NO_x concentration is accurately and quickly predicted by designing the state variable predictive control module. The state variable predictive control is used to overcome the influence of delay and input perturbation, and the cascade feedback control is applied to ensure the steady state index of the control system. The practical application in a 660 MW unit shows that the DeNO_x control system based on SCR Control⁺ model can effectively maintain the control performance of SCR DeNO_x system during large fluctuations of SCR inlet NO_x concentrations under substantial load variations and only little deviations are observed from the setting values. The system can realize fast, effective and stable control over the denitrification under all loading conditions, which meets the control requirements for ultra low emissions of NO_x and ammonia escape.

Configuration and Application of Coordinated Multi-Parameter Automatic Control System for Boiler Water Phosphate Dosing

REN Zhimin, ZHU Zhiping, JIN Xuliang, LI Yongli, WANG Yinggao, ZHAO Qiang, QIAO Yue

2017, 50(11):  180-184.  DOI: 10.11930/j.issn.1004-9649.201707045

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With the ever-increasing requirements for steam and water quality in thermal power plants, manual dosing has been gradually replaced by automatic dosing. Currently in most automatic dosing systems single-parameter based simple PID control is utilized. However, limited by phosphate monitoring and control delay, this type of control cannot accomplish accurate and immediate regulation of phosphate concentration under peak modulation or variable load conditions. Regarding these problems, this paper proposes a multi-parameter automatic control system for boiler water phosphate dosing. The program introduces the phosphate concentration, pH value, and conductivity of boiler water together with the boiler feedwater flow as the control parameters. The calculation results of pH value and conductivity value of boiler water are corrected with the on-line monitored phosphate concentration. At the same time, in combination with the boiler feedwater flow changes, the intelligent PID control technique is used to adjust the dosage of phosphate. The program has been implemented in the dosing system innovation project in an Inner Mongolia power plant. The results show that since the commissioning of the multi-parameter automatic control system into operation, the phosphate content has been stabilized with the pH value maintained between 9.40 and 9.50 while the conductivity between 9.5 and 10.5 μS/cm in boiler water. Apparently, the boiler water quality is greatly improved, which ensures the safe and stable operation of the generation unit.