Table of Content

05 October 2019, Volume 52 Issue 10

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Malicious Attack Correlation Analysis Method of Source-Grid-Load System under Specific Attack Scenarios

ZHANG Rui, FEI Jiaxuan, SHI Congcong, ZHANG Xiaojian, HUANG Xiuli, WANG Qi

2019, 52(10):  1-10.  DOI: 10.11930/j.issn.1004-9649.201808093

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The key for the power grid to deal with cyber security threats is to make full use of cyber and electrical information to improve the self-adaptation ability and automation for identification of malicious attack event. In this paper, a malicious attack correlation analysis method of source-grid-load system under specific attack scenarios is proposed. Firstly, an attribute-based multi-source event fusion model is constructed to perform multi-source data fusion processing on abnormal events of cyber layer and electrical layer. And then, based on the neural network model, the fused events are trained and classified according to the attack scenarios. Thirdly, combined with electrical abnormal events, the genetic algorithm's initialization scheme, the selection operator and cross genetic probability are improved. The correlation rules for different attack scenarios are automatically generated based on the classification results. Fourthly, the number of events to be matched is gradually reduced through timing, business logic and IP classification, and the speed of event matching is improved based on vector calculation. A timing- and business logic-based correlation matching algorithm is proposed to realize the high-speed matching of correlation rules. Finally, the effectiveness and applicability of the proposed method is verified in the source-grid-load simulation experiment system. The proposed method utilizes comprehensively the abnormal events of the cyber layer and electrical layer to further improve the identification accuracy of cyber attacks, and automatically realizes the events classification and correlation rule generation, showing great potential for engineering application.

Information Security Protection of Distributed Energy Stations under the Environment of Energy Internet

PENG Daogang, WEI Tao, YAO Jun, ZHANG Kai, XIA Fei

2019, 52(10):  11-17,25.  DOI: 10.11930/j.issn.1004-9649.201807085

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The construction of distributed energy stations in the energy internet introduces network information technology and standard data transmission communication protocols, which will also leads to the threats and risks of information security. Information security is an important cornerstone for ensuring the development of distributed energy stations under energy internet environment, and construction of safe distributed energy stations is an inevitable trend of energy internet development. From the perspective of information security threats faced by energy and power systems, the system architecture of distributed energy stations under energy internet environment is designed in this paper, and the information security protection measures of distributed energy stations are analyzed. A distributed energy station platform is constructed to analyze the information security protection configuration and application. The study results can provide a guideline for implementation of the information security of distributed energy stations.

Security Analysis and Improvement of Modbus Message in Distribution Network Based on SM9

QIU Fan, CHEN Lanlan, LIN Nan, ZUO Liming

2019, 52(10):  18-25.  DOI: 10.11930/j.issn.1004-9649.201811094

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In order to ensure the information security in smart distribution network, more and more cryptographic algorithms are applied in the communication process. by SM2-based Modbus message security of distribution network was analyzed to find out such defects as its vulnerability to replay attack and tampering attack, and several other description errors. In order to improve this method, the authors in this paper propose a SM9-based protocol of identification algorithm suitable for Modbus TCP (transmission control protocol) message. At first, the process of SM9 digital signature is introduced, and then it is applied to Modbus TCP message communication added with the timestamp mechanism. And the security of the improved protocol is analyzed. Finally, the C language is used to realize the signature scheme, and its efficiency is compared with several other signature schemes. The results show that the improved protocol can not only resist replay attacks and tamper attacks, and ensure the data integrity and source reliability in the process of message communication, but also have a good advantage in running efficiency.

A Symmetric Encryption Method for Transmitting IEC 62351 Communicaiton Keys in Substations

FANG Fang, LI Guanghua, WANG Donghui, XUAN Xiaohua

2019, 52(10):  26-30,122.  DOI: 10.11930/j.issn.1004-9649.201811056

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With the improvement of the information level of the substation, the cyber security problem of information communication has become increasingly prominent. The authentication encryption-based network security solution, such as the IEC 62351 standard, needs to transmit the application keys through another special secure transmission channel. This paper creatively proposes a method to build a secure transmission channel of application encryption keys through communication key negotiation mechanism under symmetric encryption. Based on the advanced encryption standard algorithm and symmetric key group, this method realizes the communication key negotiation mechanism through the combination of initial key and random number. The negotiated key has the character of randomness, which solves the possible security risk caused by using the same key for all links of traditional symmetric encrypted communication. In this paper, the corresponding technical analysis is also carried out, which include anti-replay, encryption strength, and anti-key theft attack, etc. The method is good in security and convenient for use, and can provide reference for key transmission of intelligent substation cyber security system.

Blockchain-Based Transactive Method in Distributed Power Considering Security Constraints

YANG Xuanzhong, ZHANG Zhebo, ZHAO Shenyi, JIN Xiaoling, BAI Cuifen, ZHANG Ran

2019, 52(10):  31-39.  DOI: 10.11930/j.issn.1004-9649.201811048

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With the deepening of power system reform and the increase of distributed energy penetration rate, the effective allocation of distributed energy on the power generation side and the power sales side faces opportunities and challenges. The traditional centralized power transaction mode has such disadvantages as high maintenance cost, low efficiency and untimely settlement of funds, which cannot adapt to the high-frequency and small-scale distributed energy trading scenarios. The paper firstly reviews the development history of blockchain technology, and deeply explores the theory of blockchain technology. At the same time, based on an analysis of the distributed energy development, the paper summarizes some requirements for building a distributed energy trading market. Then, the distributed power trading mechanism and model are constructed with consideration of security constraints. Finally, a blockchain-based distributed power trading method is proposed to ensure the transparency and information symmetry of transactions, and the intelligent contracts for distributed power multilateral transactions are designed. As a case study of the Ethereum blockchain shows, the blockchain-based distributed power trading method proposed in this paper can realize the over-limit correction of power flow and the multilateral trading of power, as well as the digital management of electric energy.

Noise Characteristics of ±800 kV HVDC Convert Station Based on Spectrum Analysis

HAN Yu, FAN Chao, WANG Guangke, HE Qiang

2019, 52(10):  40-44,177.  DOI: 10.11930/j.issn.1004-9649.201806010

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By collecting the sound pressure signals of the aerodynamic noise of the converter transformer fans, the electric field noise of the smoothing reactors and the electric field noise of the DC/AC filter field in the 800 kV converter station, the spectrum characteristics of the sound pressure signals of different locations are analyzed under the load condition, and the low-frequency and A-weighted sound level noise values of each noise signal are given. It is concluded that the noise of HVDC convert stations covers the low-, mid- and high-frequency bands, and various types of noise signals have similar spectrum characteristics; the low-frequency energy makes up larger portion of the total noise energy, and the low-frequency noise value of the fans is much higher than that of other converter station outdoor equipment under the same test condition.

Multi-Vector Model Predictive Control for Three-Phase Four-Switch Rectifier with Capacitor Voltage Balancing

ZHANG Baoge, MA Weijie

2019, 52(10):  45-53,99.  DOI: 10.11930/j.issn.1004-9649.201809027

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Three-phase four-switch rectifier has the problem of unbalanced capacitor voltage because one phase of its AC side is directly connected between two capacitor neutral points on the DC side. In order to ensure the capacitor voltage balance and further enhance the steady-state performance of the three-phase four-switch rectifier control system, a multi-vector model predictive control (MVMPC) strategy for capacitor voltage balance is proposed. Since no zero voltage vector for three-phase four-switch rectifier, the equivalent zero vector model is derived to implement the proposed control strategy. To ensure the stability of the DC voltage, it is proposed to power compensation strategy to balance the DC-link capacitor voltage. In multi-vector model predictive control, two basic voltage vectors and one equivalent zero vector are selected for each sampling period, which makes the amplitude of the equivalent synthetic vector direction adjustable, as a result of expanding the range of the equivalent synthetic vector and improving the system's control precision. The simulation results show that the multi-vector model predictive control with capacitor voltage balancing strategy can make the three-phase four-switch rectifier operate reliably and stably, with great control effects on power, grid side current, DC side capacitor voltage. Compared with the conventional model predictive control (CMPC) strategy, the proposed control strategy has less power ripple and lower current harmonic content with a constant switching frequency.

Power Demand Side Management Policy Incentive Process Dynamic Evolutionary Game Analysis

SONG Zongyun, ZHANG Jian, ZHENG Zedong, XIAO Xinli, HE Yuankang

2019, 52(10):  54-64.  DOI: 10.11930/j.issn.1004-9649.201809029

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Power demand side management(DSM) has many advantages, including the optimization of power resource allocation, promoting energy conservation and emission reduction, realizing peak load shifting and renewable energy development, etc. However, under the current electricity market environment, there exists sever nonidentity between the cost of DSM and its expected profit, which may weaken the enthusiasm of power grid companies and terminal users. At the same time, the foremost motivation among governments, power grid companies and power users are different, which will lead to intense game. In order to better analyze the game behavior of the main participants, this paper focus on the politic environment of power demand side, and applies an dynamic evolutionary game model to analyze the game between the government and power companies, as well as the government and users. In addition, some measures of power demand side management are proposed to eliminate the restraint among power grid company and power users that caused by DSM, which is the future direction of this field.

Quantitative Evaluation Method and Application Scheme of 500 kV UPFC Applicable Scene

SHEN Xuhui, LIU Jiankun, GAO Wenman, ZHANG Xin, ZHOU Qian

2019, 52(10):  65-71,78.  DOI: 10.11930/j.issn.1004-9649.201809038

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In order to solve the problem of UPFC installation location selection at UHV level in actual grid planning, this paper first summarizes UPFC's configuration principle based on existing engineering experience. After the concept of UPFC "unit capacity control proportionality coefficient" is studied, that is, the ratio of UPFC's control effect to its own capacity. According to the reliability cost/benefit analysis, unit capacity control proportionality coefficient is standardized. Then, we derive the priority expression of UPFC points at the technical level, at the same time, the flow chart of the location selection method is given. Finally, the UPFC system-level control strategy is proposed for different application scenarios. In the study of the application, using 2~3 year rolling calculation data, 12 UPFC installation sites are selected in the whole country. Through simulation analysis and priority calculation, it is found that UPFC has good regulation ability at two locations of Jinjiang direct current arrival point and two sites of Jiangnan-Jiangbei section of eastern Hubei Province. The method proposed in this paper is feasible with certain guiding significance for the UPFC layout screening and demonstration project implementation on UHV level.

Architecture of Computer Supervisory Control System and Control & Protection System for Shanghai Yunzaobang UPFC Project

CUI Hubao, CHEN Guofu, MA Mingyuan, XU Bo

2019, 52(10):  72-78.  DOI: 10.11930/j.issn.1004-9649.201807010

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The technical level, architecture and reliability of computer supervisory control system and control & protection system are closely related to the safe and economic operation of UPFC. The architecture of the computer supervisory control system and control & protection system of Shanghai Yunzaobang UPFC project is developed from conventional AC substations based on the experience of smart substations, and consists of equipment, network architecture and communication protocol, etc. It is not only as cheap and reliable as conventional substation supervisory control system, but also compatible with electronic transformer, and can realize the power flow control and self-protection functions of UPFC. The architecture, sequential control operation, and operation experience of Yunzaobang UPFC project supervisory control system are of demonstration value to the implementation of other UPFC or FACTS projects.

Reliability Analysis and Improvement of Smart Electric Energy Meter Considering Field Verification

XIE Jinjun, ZHOU Wenbin, LIU Shifeng, JIANG Zijuan, JIN Yang, ZHAO Lei

2019, 52(10):  79-84.  DOI: 10.11930/j.issn.1004-9649.201812099

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In order to solve the problem of 8-year expiration replacement of smart electric energy meters, three schemes for electric energy meter replacement are introduced and analyzed. The improvement of the production level of smart energy meters has provided a necessary basis for extending the replacement period of electric energy meters. In view of the scheme of extending the replacement period with field verification method, a correction is made of the operation life process of the electric energy meter based on Weibull distribution analysis considering the climatic factors of different regions and the influence of the field verification result of the electric energy meters. The theoretical analysis and actual application have proved the feasibility of the proposed method, which will provide a reference for extending the replacement period of the smart electric meters.

A Fully Distributed Power Flow Algorithm with Exponentially Fast Convergence

GAO Changzheng, YAN Bo, WANG Jiarui, CHANG Xuefei, SUN Yue

2019, 52(10):  85-91.  DOI: 10.11930/j.issn.1004-9649.201809085

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In order to meet the data privacy requirements for interconnected power system power flow calculations, a fully distributed power flow algorithm is proposed. The method is composed of outer iteration and inner iteration. The outer iteration calculates the Jacobian matrix based on Newton-Raphson method, while the inner iteration uses the distributed algorithm to solve power flow correction equation for each partitioned area of interconnected power system. The proposed algorithm does not need any coordination layer to decompose and coordinate the distributed calculation, and each partitioned area in the power system only needs to exchange correction information of power flow equation with neighbor areas. The outer iteration has the same convergence behavior as global power flow, while the inner iteration can guarantee convergence with exponential rate. The numerical tests on IEEE 39- and 118-bus systems show that the proposed method has good convergence behavior and is suitable for power flow calculation without coordination layer.

Analysis and Prevention of Bird Fault Overhead Transmission Line

LI Fan, LI Yanglin, ZHANG Yu, KUANG Yanjun, HU Jing, ZOU Jianzhang, RAO Binbin, ZHOU Longwu

2019, 52(10):  92-99.  DOI: 10.11930/j.issn.1004-9649.201805079

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According to the statistics of transmission lines in China in recent years, the fault caused by bird activity has become the third major transmission line tripping after lightning and outsize destroy. In this paper, the bird species and habits related to bird faults in overhead transmission lines are studied and analyzed. The types of faults related to birds, bird species and regional distribution are confirmed. Through the statistical analysis of bird related faults, it is found that the main fault occurred in the farmland or the low altitude adjacent to the water from March to July. At the same time, the probability of the occurrence of bird fault is also related to the structure of tower, the arrangement and the phase of the transmission lines. On the basis of the bird fault test and simulation calculation, the protection range of different bird faults under different voltage levels is obtained. Besides, the performance, advantages and disadvantages of different protection devices are compared. The reasonable prevention and control opinions are proposed in the paper.

Simulation Analysis of Temperature Field of Optical Fiber Composite Overhead Ground Wire

ZHANG Lifeng, LI Xiaohua, ZHAO Wenbin

2019, 52(10):  100-107.  DOI: 10.11930/j.issn.1004-9649.201812143

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The optical fiber composite overhead ground wire (OPGW) has been widely used in high voltage transmission lines. In order to study the temperature field variation of OPGW under the conditions of steady state and lightning strike, the finite element software is used to establish a multi-physics coupling simulation model of magnetic field, fluid field and temperature field according to the fluid mechanics and heat transfer theory. The temperature fields of OPGW with different structures are analyzed under steady state, and the accuracy of the temperature fields is verified through comparing with conventional engineering algorithms. On this basis, a method is proposed to monitor the forest fire by using the influence of forest fire on the temperature field of OPGW. Finally, an analysis is made on the temperature field distribution of OPGW under lightning strike and the high temperature hazard of lightning strike.

Scheme Design and Engineering Implementation of DC Grid-Connection and Accommodation of Photovoltaic Power

YANG Zhaoxiang, LI Hongjian, CHEN Lei, CHEN Xiangyu

2019, 52(10):  108-114.  DOI: 10.11930/j.issn.1004-9649.201812014

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With the development of flexible DC technology, the construction of source-grid -load in distribution network is greatly enriched, and the new-type grid models become possible such as centralized photovoltaic DC grid-connection and DC power supply for data centers. Based on Zhangbei AC & DC distribution network and flexible substation demonstration project, the paper introduces the DC grid-connection scheme for photovoltaic power station and the way of engineering implementation. In the meantime, the connection of DC power supply system is designed for data center and the reliability of power supply is calculated. Compared with the traditional AC distribution network, the advantages of DC distribution network are demonstrated in view of power transmission efficiency, power supply reliability and power quality. The demonstration project has realized the DC integration and accommodation of photovoltaic power generation, and the design results and practical experience can provide a reference for similar projects.

Comprehensive Evaluation Indexes Framework and Evaluation Method for Transmission Planning of Wind Power Cluster

XIAO Shuai, ZHANG Yan, ZHANG De, YU Haifeng, LI Mengjiao

2019, 52(10):  115-122.  DOI: 10.11930/j.issn.1004-9649.201703082

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Wind power cluster, such as inland mountain wind power and lake wind power, has the characteristics of wide-range distribution and low power capacity of single wind farm. A comprehensive evaluation indexes framework is established for transmission planning of wind power cluster based on economy, security and adaptability of power grid. And then, with a comprehensive consideration of subjective weights and the objective weights, the moment estimation theory-based optimal combination weighting method is used to determine the optimal combination weight of each index, and an improved gray relational analysis method is proposed through combination of gray correlation analysis and cosine sorting method, to evaluate each scheme more accurately and reasonably. At last, the proposed evaluation indexes framework and evaluation method are applied to the wind power cluster transmission planning in Hunan Province, which has verified their effectiveness and feasibility.

An Energy Management Algorithm of PV-Assisted Smart Building Based on Offline Optimization and Online Decision

SHI Xuntao, LEI Jinyong, HUANG Andi, YU Lei, GUO Xiaobin, ZOU Fuqiang, LIU Nian

2019, 52(10):  123-131.  DOI: 10.11930/j.issn.1004-9649.201805167

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As an important development form of comprehensive energy, the charging demand and PV power of PV-assisted smart buildings have great uncertainty. The existing methods of energy management of PV-assisted smart buildings are not completely applicable. An energy management algorithm of PV-assisted smart building based on offline optimization and online decision is proposed in this paper. Firstly,combined with the historical operation data of photovoltaic intelligent buildings, an offline optimization model aiming at maximizing operating income is established, which provides a knowledge base for online learning through offline optimization. Then, in order to dispatch the smart building energy in real-time, under the condition of time-of-use price, the online algorithm is established combined with online learning and rule-based. The charging power of EVs and working conditions of shiftable loads can be decided using the online algorithm. Finally, taking a business building as an example, the proposed algorithm is tested. The simulation results show that the method can be operated without future information of PV power, charging demand and shiftable loads.

Application of Clean Coal-Fired Power Standard System in ‘The Belt and Road’ Countries

LUO Rusheng, ZHU Fahua, CHEN Kuixu, LOU Tong, YOU Yanqing

2019, 52(10):  132-137.  DOI: 10.11930/j.issn.1004-9649.201908066

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Since 2014, with the implementation of ultra-low emission in coal-fired power industry of China, the pollution control technology has been developed rapidly. In order to efficiently utilize these various treatment technologies in a precise and serialized way, a clean coal-fired power standard system is hence established. As one of the important technical routes in clean coal-fired power standard system, Ultra-clean Electrostatic-Fabric Integrated Precipitator technology has been widely implemented in China and then successfully applied in 2×660 MW unit of a power plant in Turkey. So far it has been working steadily for three years, with dust emission at the outlet of the precipitator less than 10 mg/m³ and the operating resistance less than 800 Pa. The successful practice of ultra-clean Electrostatic-Fabric Integrated Precipitator in Turkey has greatly promoted the application of clean coal-fired power standard system in the countries along the belt and road. There is no doubt that it will effectively boost the implementation of the "the belt and road" national strategy.

Experimental Studies and Numerical Simulation on the Injection and Spray of Activated Carbon Powder for Mercury Removal from Flue Gas

LIU Hanxiao, CHEN Zhaomei, GUO Gaofei, WANG Jianbo, CUI Ying, MENG Yincan, LIU Meiling

2019, 52(10):  138-143,170.  DOI: 10.11930/j.issn.1004-9649.201905003

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In view of the high material consumption for the present activated carbon injection process, in order to expand the diffusion area of single activated carbon injection points, the activated carbon powder injection test bench was build. Then based on the experiment results for the three types of nozzles, it was found out that the powder injection outperformed the pipe direct injection, in which the diffusion area at 750 mm away from the nozzle was expanded by 73.58%, 201.89% and 137.74% respectively compared with direct pipe injection, while no significant diffusion area improvement was observed for activated carbon powder injection with built-in swirl vane. Additionally, by means of commercial CFD software, the numerical simulation method of activated carbon dry powder injection was developed, and the effectiveness of the model was verified through experimental studies. Therefore, the activated carbon dry powder injection model can be used as a guidance in the actual engineering project to arrange injection points scientifically.

Influences of PM_2.5 Distribution Index on the Collection Efficiency of the Wire-Pipe Electrostatic Precipitator

ZHANG Jianping, CHEN Dong, JIANG Zexin

2019, 52(10):  144-149.  DOI: 10.11930/j.issn.1004-9649.201904096

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In order to figure out the way to improve the performance of the wire-pipe electrostatic precipitator (ESP) in PM_2.5 collection, it is necessary to determine the influence law of distribution index on the collection efficiency of ESP for PM_2.5 removal of slight particles. For this purpose, the theoretical and simplified models under multi-field coupling effects were established, and the dust removal performance for PM_2.5 under ionic wind and magnetic confinement was described in terms of grade efficiency and overall efficiency respectively. The results show that as the particle size decreases or the distribution index goes down, the grade efficiency of PM_2.5 will both rise significantly. The occurrence of ionic wind improves the collection efficiency for PM_2.5, which on the other hand will offset the increase of the efficiency brought by the decrease of the distribution index unfortunately. The magnetic field not only boosts the trapping performance of wire-pipe ESP for PM_2.5 effectively, but also reinforces the promotion effect of reducing the distribution index on the dust removal performance for PM_2.5.

Effect of Flue Gas Composition on Mercury Removal by Injecting Rice Husk-Derived Activated Carbon

TAO Jun, GU Xiaobing, HUANG Tianfang, LIU Shuai, HU Peng, DONG Lu, HUANG Yaji, DUAN Yufeng

2019, 52(10):  150-154,184.  DOI: 10.11930/j.issn.1004-9649.201901022

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The flue gas mercury removal experiment was carried out on a 0.3MW pilot scale circulating fluidized bed test facility by injecting biomass based activated carbon which is originally derived from rice husk and then modified by halogenated ammonium. Effects of exit temperature of the SCR and flue gas, concentration of SO₂ and NO on the injection demercuration efficiency were discussed. The ASTM Standard D 6784-02 (OHM Ontario Method) was applied to measure the concentration of mercury from the coal-fired flue gas. The results showed that both the mercury removal efficiency and elemental mercury conversion efficiency go up with the elevated flue gas temperature; The existence of NO can enhance the mercury removal effect but SO₂ will inhibit it on the other way. The mercury removal efficiency could reach about 90% with this modified type of activated carbon sprayed into flue gas under the conditions of SCR inlet temperature in the range of 351~370℃, flue gas temperature in the range of 191~210℃, SO₂ volume fraction of (293~602)×10^-6, NO volume fraction of (588~893)×10^-6, activated carbon injection quantity of 0.5 kg/h, reaction space velocity of 4 000 h^-1, and flue gas flow rate of 400~500 m³/h.

SO₃ Cooperative Control and Emission Situation in the Flue Gas of Coal-Fired Power Plant

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

2019, 52(10):  155-161.  DOI: 10.11930/j.issn.1004-9649.201808069

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The conversion rate of SO₂/SO₃ is 0.5%~5% in boiler combustion, but it can be controlled within 1% in SCR DeNO_x in coal-fired power plant. In operation, to control the consumption of SO₃ in the sub-layer of SCR catalyst and air pre-heater in operation, the condensation adsorption quantity of H₂SO₄ and NH₄HSO₄ should be reduced as much as possible, which is aimed at protecting the catalyst activity and ensuring the safety of air pre-heater operation. Theoretically, the low-low temperature electrostatic precipitator has the excellent removal efficiency for SO₃. However, the efficiency may changes from 1.8% to 96.6% in different projects. Study shows that the electrostatic-bag filter has removal efficiency about 74.3%~85.9% for SO₃. Most technologies of wet flue gas desulfurization have removal efficiency of above 50% for SO₃ except the empty absorption tower desulfurization and seawater desulfurization under ultra-low emission condition. Besides, the removal efficiency of wet electrostatic precipitator for SO₃ can be above 50% as well, although there is still a slight gap compared with the mature cases abroad. Overall, the comprehensive removal efficiency for SO₃ of the whole process environmental protection purification equipment of ultra-low emission coal-fired power plants is over 90% and the SO₃ emission concentration of most units are less than 5 mg/m³, when the sulfur content of coal is under 1.5%.

Wet Plume Removal Technologies for Coal-Fired Power Plants

WANG Lin, LIU Guangjian, CHEN Haiping

2019, 52(10):  162-170.  DOI: 10.11930/j.issn.1004-9649.201812075

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The direct discharge of wet saturated flue gas after wet flue gas desulfurization in coal-fired power plants usually causes wet plume. In this paper, four wet plume elimination techniques, i.e., flue gas heating, flue gas condensation, flue gas condensation and reheating and membrane recovery of flue gas moisture, are analyzed theoretically, and the parameters in each technique are determined through quantitative calculation using the wet plume predication model. The results show:For reheating technology, if the ambient temperature is lower than 5℃ and the relative humidity is greater than 40%, the flue gas should be heated to above 100℃; For condensation technology, if the ambient temperature is under 0℃ and the relative humidity of the environment is greater than 40%, flue gas temperature should be cooled down to below 15.5℃; For condensation and reheating technology, the lower the condensation temperature, the lower reheating temperature should be. If the ambient temperature is higher than 5℃ and flue gas condensation temperature is cooled down to below 40℃, the reheating temperature basically should not be higher than 80℃; For membrane recovery technology, with the ambient temperature greater than 15℃ and the water recovery rate higher than 40%, basically there will be negligible wet plume generated; If ambient temperature is lower than 5℃, the water recovery rate should be kept higher than 60%.

Characteristics of Power Coal and Recommendations on Dust Removal Techniques for Power Plants Based on the Database ofElectrostatic Precipitator and Coal Property

LI Xiaoyu, LONG Hui

2019, 52(10):  171-177.  DOI: 10.11930/j.issn.1004-9649.201905418

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As the environmental requirements and emission standards are getting tighter, the research on the ultra-low emission of coal-fired power plants has attracted more attentions. In this paper, a database of electrostatic precipitator (ESP) and coal property is established, which consists of the coal properties and the ESP design and operational parameters of hundreds of coal-fired power plants across all regions of China. Based on the database, the distribution of ash and sulfur contents is analyzed using the coal samples collected from hundreds of power plants. The results show that the high-ash coals are quite common in Southwest China, while in Northeast, Central and North China the coals with medium or medium-high ash content are mostly burned, and in coastal regions the coals with low or ultra-low ash content are prevalent. In terms of sulfur content, the high-sulfur coals are mostly burned in Southwest China, while in the power plants of Shandong, Shanxi, Henan and Hebei provinces of China the medium-sulfur coals are generally burned, and the coals burned in other regions of China are mostly low or ultra-low in sulfur. Moreover, through the case studies on the application of ultra-low particulate emission techniques in three power plants fueled with low-ash & low-sulfur, medium-ash & medium-sulfur and high-ash & high-sulfur content coals respectively, recommendations are provided accordingly on the technical routes of ultra-low particulate emission with regard to different kinds of coal.

Research and Application of Denitrification Optimal Control Based on Multi-Variable Generalized Predictive Control Algorithms

ZHANG Xiaodong, WANG Pengfei, LIU Le

2019, 52(10):  178-184.  DOI: 10.11930/j.issn.1004-9649.201901009

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For the denitrification control system of large thermal power unit, because of the characteristics of its controlled object, such as the large time delay and inertia, the impacts from multiple interference factors and model variations under different loads, traditional PID control strategy cannot meet the requirements. Regarding this problem, a multi-variable model of denitrification system is constructed by recursive least square method, and then an optimal control strategy for denitrification system is established based on multi-variable generalized predictive control. Meanwhile, this strategy has been applied in 330 MW subcritical unit of a power plant. From the practical results it is shown that the proposed denitration optimization control strategy based on multi-variable generalized predictive control has effectively controlled NO_x concentration at the denitration outlet and suppressed the fluctuation of NO_x concentration, whether the system is operated under steady state or complex variable load conditions. The usage of urea has also been reduced such that the stable and economic operation of the denitration system is achieved.