Table of Content

05 September 2019, Volume 52 Issue 9

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Theoretical Framework and Architecture Design of e-IoT Business Model

LI Suxiu, LIU Lin, WANG Xue, DAI Hongcai, ZHAO Liujun

2019, 52(9):  1-9.  DOI: 10.11930/j.issn.1004-9649.201907030

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Facing the challenges from the open market and fierce competition, it is urgent to establish systematic methodologies for the business model of e internet of things (e-IoT) so as to provide a realistic and feasible business logic for e-IoT constructions. Based on strategic management theory and related business model theories, considering the requirements and features of e-IoT, this paper constructed a theoretical framework and an architecture design method for e-IoT business model. In the theoretical framework the research interfaces covering macro, medium and micro perspectives are clearly defined, and then the research and design methods for the business model with the corresponding enterprise layer, business layer and project layer are put forward. The architecture design mainly focuses on medium and micro perspectives. The paper outlined and refined six fundamental elements into the basic framework, then formulated the logic framework as "Three links, One circulation" and the design principal as "elements layer-analysis layer-output layer-project layer", and eventually came up a novel business model named as e-IoT MAPPER.

Comparison of Clamping Force Distribution within Press-Pack IGBTs of Different Structures

LI Anqi, DENG Erping, REN Bin, ZHAO Yushan, ZHAO Zhibin, HUANG Yongzhang

2019, 52(9):  11-19,29.  DOI: 10.11930/j.issn.1004-9649.201906024

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The continuous development of flexible High Voltage Direct Current (HVDC) transmission system poses more requirements to the insulated gate bipolar transistor (IGBT) devices. Press Pack IGBTs (PPI) are valued for their development demand of high voltage, high current and high power in the areas of flexible HVDC transmission system. At present, two types of Press Pack IGBTs with pedestal structure represented by WESTCODE and TOSHIBA as well as Stakpak structure represented by ABB, have been successfully applied in the flexible HVDC transmission projects. These two kinds of structural models of the Press Pack IGBTs based on finite element method are established. The pressure distributions within these two kinds of Press-Pack IGBTs in normal pressurization conditions and normal working conditions are analyzed. The simulation results show that the pressure distributions within both types of Press-Pack IGBTs in normal pressurization conditions are relatively uniform, while the pressure distribution of the stakpak structure is more uniform in normal working conditions. Finally, based on the simulation results, this paper proposes possible solutions to the structural optimization of the Press Pack IGBTs.

Current-sharing Design of Press-Pack IGBT

LIU Guoyou, DOU Zechun, LUO Haihui, QIN Rongzhen, WANG Yangang

2019, 52(9):  20-29.  DOI: 10.11930/j.issn.1004-9649.201907122

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Aiming at the inner design of the press-pack IGBT devices, this paper focuses on the study and optimal design of these issues, such as multi-chip pressure contact and its pressure balancing, internal current-sharing and current balancing among sub-units. Testing results showed that the developed press-pack IGBT devices has promising capabilities of current turn-off, short-circuit current and RBSOA, which indicates their good ability of inner current sharing.

Reliability Modeling and Analysis of Press-Pack IGBTs Considering Internal Material Fatigue

LI Hui, WANG Xiao, YAO Ran, LONG Haiyang, LI Jinyuan, LI Yaosheng

2019, 52(9):  30-37.  DOI: 10.11930/j.issn.1004-9649.201907077

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The high power press-pack IGBTs (Insulated Gate Bipolar Transistor) devices are more suitable for flexible HVDC high power system. It is inevitable to meet the requirements for reliability evaluation of press-pack IGBTs. In this paper, a reliability modeling of press-pack IGBTs considering material fatigue is proposed. Firstly, the electro-thermal-mechanical multi-physics simulation model of single-chip press-pack IGBT device is established and the effectiveness of the IGBT simulation model is verified by experiments. Secondly, the reliability model of single-chip press-pack IGBT device is established considering the fatigue life of materials and the weak points of each layer of single-chip device are analyzed. Finally, the multi-physics simulation model of multi-chip press-pack IGBTs is established based on the actual structure. The stress distribution of the devices is analyzed, and the failure rates of each chip and multi-chip devices are calculated. The results show that the temperature and von Mises stress distribution inside the press-pack IGBTs are uneven. The maximum values are located at the edge of the contour of the contact between the IGBT chip and the emitter molybdenum layer. The chip current, temperature and thermal-mechanical stress distribution are uneven in the multi-chip device. The reliability level of the internal chip is obviously different because of uneven stress distribution in multi-chip devices. The chip at the corner of the device bears the maximum stress and the reliability is the lowest.

Failure Mechanisms and Evaluation Methods of Power Electronic Devices

LUO Yifei, WANG Lei, HUANG Yongle, LIU Binli

2019, 52(9):  38-47.  DOI: 10.11930/j.issn.1004-9649.201907059

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Power electronic devices are the core components of modern high power converters. With the increase of the power levels, the requirements of the reliability become more and more critical. There are still lack of efficient evaluation methods of reliability, especially for the applications which require high power and volume density. The traditional design methods can no longer satisfy the requirements. Therefore, in order to improve the power and volume density of the devices, the accurate characterizations of the working mechanism and reliability margin are of great need. Firstly, this paper analyzed the failure mechanisms of the devices and concluded the current research situations of power electronic devices combing the research results of the authors' project groups. Then, the failure mechanisms of power devices are analyzed from perspectives of outer and inner affects. Finally, from the perspective of overvoltage, overcurrent and fatigue failure, quantitative evaluation methods are proposed to evaluate the device failures, especially focusing on the physical methods, and verified the effectiveness by taking diodes and insulated gate bipolar transistors as examples. This paper gives supports to the extreme applications of power electronic devices.

High Temperature Gate Bias Test Equipment for High Voltage and High Power Devices

DENG Erping, MENG Heli, WANG Yanhao, WU Yuxuan, ZHAO Zhibin, HUANG Yongzhang

2019, 52(9):  48-53,72.  DOI: 10.11930/j.issn.1004-9649.201907093

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In order to accurately evaluate the gate oxide reliability of silicon IGBTs and silicon carbide MOSFETs under different electrical stresses and thermal stresses, a high temperature gate bias test equipment was developed, which is capable of measuring pico ampere level gate oxide leakage current in real time. Further,an on-line monitoring function of threshold voltage is integrated into the test equipment so as to better monitor the status of the tested equipment for reliability evaluation and failure analysis. With this equipment, the high temperature gate bias of commercial insulated gate bipolar transistor (IGBT) devices were tested under the same temperature stress and different electrical stresses. The leakage current gradually decreases at the initial stage of the test. The leakage current has a decent positive correlation with the voltage level at the end of the test-the larger the gate bias voltage, the larger the leakage current. Suitable for various kinds of packages, this equipment meets the test requirements of for high temperature gate bias of silicon carbide MOSFETs as well as silicon IGBTs.

Comparison and Analysis of Power Cycling and Thermal Cycling Lifetime of Power Semiconductor Modules for Vehicles

ZHANG Jin, QIU Zhijie, WANG Lei, NING Puqi

2019, 52(9):  54-60.  DOI: 10.11930/j.issn.1004-9649.201907058

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The power semiconductor module is more and more widely used in human transportation field, like electric vehicle and high-speed train. These applications in which the personnel safety is seriously concerned usually require power modules with higher reliability. In this paper, the typical automotive and industrial grade insulated gate bipolar transistors (IGBT) were selected. Both the power cycling and thermal cycling tests were carried out to compare the reliability differences. The experimental results showed that the thermal cycling lifetime of automotive IGBTs was obviously better than that of industrial grade products. However, the power cycling lifetime of automotive IGBT was worse than that of the industrial grade product.

Review of Failure Mechanism and State Monitoring Technology for IGBT Modules

WANG Xiping, DING Xiangkuan, YAO Fang, TANG Shengxue, LI Zhigang

2019, 52(9):  61-72.  DOI: 10.11930/j.issn.1004-9649.201907034

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With the continuous increasing of the performance requirements for power electronic systems, the power device IGBT modules must not only have high power density, but also have good thermo-mechanical properties to improve their reliability. In this paper, the failure mechanism of IGBT modules is introduced firstly, and the failure mechanism of bonding wires and solder layers is described in detail. The health state monitoring of IGBT modules is mainly introduced, and the research progress of health monitoring about junction temperature, bonding wire and solder layer and their quantitative evaluations are analyzed in detail. Finally, from reducing the thermal-mechanical stress for improving the reliability design of the package and the on-line monitoring development under the operating conditions, the prospects are presented.

Study on UV Aging Properties of Polymer Composite Insulators

SHEN Wei, GAO Hua, ZHANG Peng, ZUO Kun, TIAN Yi, YANG Wenbo, YUAN Zhenkang

2019, 52(9):  73-78,85.  DOI: 10.11930/j.issn.1004-9649.201809100

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The traditional HTV silicone rubber composite insulator is widely used in transmission lines at home and abroad due to its excellent hydrophobicity and hydrophobicity mobility. However, with the development of UHV, more and more transmission lines need to pass through the areas with strong ultraviolet radiation, strong wind & sand and frequent bird pecking, where the harsh climate is prone to cause the decline of the external insulation performance of traditional HTV silicone rubber insulators and the damage of materials. In view of this situation, a comparison is made between the high polymer composite insulators, which has good UV-resistance performance and stable mechanical properties, and the traditional HTV silicone rubber insulators in terms of ultraviolet aging properties. The purpose of this study is to investigate the aging characteristics of polymer composite insulators in the northwest plateau area with strong ultraviolet radiation. The results of the study show that under continuous irradiation of short wave ultraviolet light, the epoxy material has a tensile strength and hardness much better than silicone rubber, and has good toughness that meets the purpose of bird pecking-resistance and treading-resistance; it is slightly inferior to silicone rubber in hydrophobicity, but still meets the requirements of outdoor operation.

Operation Analysis of Over-Excitation Protection due to Voltage Transformer Inter-turn Short-Circuit at Generator Terminal

WANG Xing

2019, 52(9):  79-85.  DOI: 10.11930/j.issn.1004-9649.201808041

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A number of inter-turn short-circuit accidents have occurred in recent years in the primary winding of voltage transformer (TV) at generator terminal, which often causes slow fuse melting due to the large short-circuit current. In this paper, a calculation formula of TV secondary winding voltage is derived respectively for TV's primary winding inter-turn short-circuit and slow fuse melting, and it is concluded that the secondary winding voltage will decrease after a fault occurs. An analysis is made on the bugs in the TV disconnection logic in ABB Unitrol F excitation regulator, and a study is conducted on the mechanism of over-excitation protection and strong excitation of the excitation regulator caused by slow fuse melting. The theory is verified through a case study of an accident. Finally, the Matlab/Simulink simulation is used to verify the theory, and the simulation result proves the correctness of the theory.

Analysis and Application of Grading Electrodes Deposition Model

CHENG Yijie, HE Tingting, SONG Xiaoning, FENG Likui, YU Zhiyong, GAO Bing, YANG Fan, YANG Qi

2019, 52(9):  86-92.  DOI: 10.11930/j.issn.1004-9649.201805086

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The converter valve is one of the core equipment in high voltage direct current (HVDC) system, and the water cooling system is often used for heat dissipation. However, the corrosion of radiator in the cooling system and the sediment on the grading electrode will lead to fault of converter valve. It's therefore essential to study the characteristics of corrosion and deposition in the water cooling system. Based on the mechanism of radiator corrosion and sediment deposition, this paper uses the finite element method to establish a grading electrodes deposition model considering the electrode surface deposition reaction and material transfer process. The built model can investigate the growth process of the sediment, and analyze the electric field near the surface of electrodes and the distribution of the corrosion ion concentration. The deposition behavior of sediment and the distribution of sediment on grading electrodes is studied based on the proposed model, and the effect of voltage level on the thickness of sediment is discussed. The results indicated that the thickness of sediments is proportional to the voltage level, the sediment is mainly concentrated on the high-potential electrode, and the amount of sediment on the electrode tip is much larger than that on the parallel position of the electrode. In addition, the proposed model is verified by the measurement results of actual converter valve's cooling system and the sediment on the electrode.

Optimal Energy Features of Partial Discharge Signals in GIS Extracted by Fisher Linear Discriminant

TIAN Yu, LUO Sha, LI Binbin, HU Yong

2019, 52(9):  93-101.  DOI: 10.11930/j.issn.1004-9649.201806108

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The dual-tree complex wavelet transform (DT-CWT) is adopted to make a multi-scale decomposition of UHF partial discharge (PD) signals, and an optimal algorithm for solving DT-CWT decomposition is proposed. In addition, the optimal complex wavelet energy (OCWE) features are extracted from the high-layer real and imaginary parts of UHF PD signals after decomposed by DT-CWT, and the fisher linear discriminant method is adopted to select the energy features. Finally, the selected features are used for PD type recognition. The results show that the high-layer wavelet energy features can effectively recognize four typical insulation defects in GIS with a recognition accuracy reaching 94.5% or above. It is proved that the OCWE features are more suitable for PD recognition.

Parameter Identification Method of Synchronous Generator Based on Trajectory Sensitivity

ZHANG Weijun, CHEN Wenlong, HUANG Ting, SU Qingmei, LIN Fang, LIN Jikeng

2019, 52(9):  102-109.  DOI: 10.11930/j.issn.1004-9649.201803161

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In order to improve the identification accuracy of transient and sub-transient parameters of synchronous generators, a parameter identification method is proposed for synchronous generator based on trajectory sensitivity. Firstly, the method for selecting the data intervals is determined based on the trajectory sensitivity, and the measured trajectory sensitivity of the generator parameters is used as an index. According to the attenuation degree of the index, the measured data with more information of transient and sub-transient parameters are selected and used as the identification data so as to improve the identification accuracy of the corresponding parameters. And then, the robust optimization model is used as the optimization model of generator parameter identification to improve the anti-jamming ability of the parameter identification model. Case study has proved the effectiveness of the proposed method.

Research on Electricity Burn of Shorting Grounding Wires in EHV and UHV Transmission Lines

QIN Weinan, FANG Yuqun, QIAN Liqun, LIANG Jiakai, JIANG Weidong

2019, 52(9):  110-117.  DOI: 10.11930/j.issn.1004-9649.201811090

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Based on EMTP simulation, an analysis is made on the induced voltage and induced current of the 1 000 kV AC double circuit lines on the same tower of the Huainan-Wannan-Zhebei-Shanghai transmission project with one circuit blackout. According to the service condition of grounding wires, it is found that the main causes for grounding wire burns are the excessive induced voltage on the blackout line and the repeated arc discharge during installation of the grounding wires. Under the maximum induced voltage calculated by simulation, the arc produced in the process of installing grounding wires is studied through test, and the critical value of arc energy which can have impact on the wire and equipment is obtained. The burn problem is effectively solved by introducing arc suppression technology, which guarantees the safety of maintenance personnel.

Interactive Stability Analysis between Direct-Drive Wind Turbinesand Weak Power System

WAN Yuliang, ZHU Ling, XIANG Song, LIU Fusuo, CHEN Lu, WANG Jiajia

2019, 52(9):  118-125.  DOI: 10.11930/j.issn.1004-9649.201805058

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As an interface between new energy power generator units and a power grid, the grid-side converter plays an important role in maintaining the safe and stable operation of power system. Based on the grid-side converter of direct-drive wind turbines, a math model of grid-side converter and its control including the phase-locked loop (PLL) and voltage feed-forward control is established in the paper using the small disturbance mathematic modelling method, and the dynamic impedance analytical expression under dq axis is derived. It is found that the impedance has the features of negative resistance (negative real part) in the subsynchronous frequency band and is unstable in subsynchronous frequency band when connected with weak power grid. The key control parameters that influence the system stabilities are analyzed. The results indicate that the subsynchronous oscillation risks can be reduced to some extent through enhancing the power grid strength, optimizing the PLL control parameters and increasing the voltage feed-forward filtering frequency. Finally, the above analytical results were verified by electromagnetic transient simulation.

U.S. Electricity Markets Development and Its Inspirations for China

TIAN Wei, SHI Hang, CAO Yang, YONG Taiyou

2019, 52(9):  126-133.  DOI: 10.11930/j.issn.1004-9649.201811020

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Since the early 1990 s, the US electricity markets have gradually developed into stable and active ones. This paper summarizes the characteristics of the US electricity market reform in such aspects as market structure, market rules, market operation, market supervision, power grid and source planning and others, analyzes the challenges facing the US electricity market reform in terms of grid operation security, market operation technology and power company operation. And four recommendations are proposed for the construction of China's electricity markets.

Urban Energy Conservation Classification Based on Industrial Structure Upgrading

HUO Molin, QU Yao

2019, 52(9):  134-139.  DOI: 10.11930/j.issn.1004-9649.201809103

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With the energy-saving targets decomposed to every city, the energy-saving difference of each city needs to be considered for the city government to make energy-saving policies according to its local conditions and for the enterprises to develop energy-saving markets. The difference of each city is mainly affected by the optimization and upgrading stage of the city's industrial structure. Based on relevant literature and the national planning, this paper proposes a theoretical hypothesis that all cities in the country can be divided into five categories:core city, sub-center city, small-and medium-sized city, tourism-specific city and agricultural-specific city, and each category has its own type of industrial structure upgrading. 281 prefecture-level cities are used to make empirical analysis. The results show that these five types of cities have significant differences in industrial structure changes. It is proposed that attention should be paid to the differences of industrial structure and economic development stages of the five types of cities when the government decomposes energy-saving targets to cities and conducts city energy-saving benchmarking, and when enterprises carry out energy-saving marketing analysis.

Optimization of Electricity Purchasing Strategy for Electricity Retailers under the Medium and Long-Term Trading Mechanism

JIA Chen, DU Xinhui

2019, 52(9):  140-147.  DOI: 10.11930/j.issn.1004-9649.201805069

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With the continuous advancement of power system reform, as a new market entity, it is particularly important for electricity retailers to grasp the business opportunities accurately and understand market trading strategies clearly. Therefore, based on the medium-term and long-term electricity trading mechanism, by taking full account of the diversity of power market and trade, this paper introduces the contract transfer transaction and the energy deviation penalty assessment as the market power balance mechanism, then establishes the optimization decision model of electricity purchasing strategies for electricity retailers. Aiming at the maximization of the profit, a hybrid adaptive bacterial foraging method, i.e., particle swarm optimization algorithm (ABFO-PSO) is adopted to solve the problem. Finally, the validity of the model and method is verified through case studies. The study can provide the reference for electricity retailers to participate in market competition.

Coal Calorific Value Estimation Algorithm Based on Hyperspectral Image and Convolutional Neural Network

YANG Minghua, ZHANG Kehan

2019, 52(9):  148-153.  DOI: 10.11930/j.issn.1004-9649.201905023

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Thermal power generation is still the major power generation mode in China. Since the quality of coal quality directly determines the safe production and economic benefits of power plants, net calorific value as received basis has become one of the key indicators of coal quality. Regarding the current problems such as complicated measurement procedures of coal calorific value and limitations of the general method in situations where real-time monitoring is required, this paper proposes a convenient and fast calorific value estimating algorithm based on hyperspectral image and convolutional neural network. Firstly, the image data of coal is collected by the hyperspectral data acquisition system. After Gaussian low-pass filtering and principal component analysis, the noise and data redundancy between spectral channels are eliminated. Then, the smooth training and test data are obtained by using the neighborhood average filtering and a 7-layer convolutional neural network is established. Finally, the effectiveness of the proposed method is verified by experiments. The results show that the method has high prediction accuracy.

Noise Analysis and Signal Processing in the Turbine Valve Closing Test

MEI Yiming, GU Weifei, ZHU Xiangyun, ZHU Bao

2019, 52(9):  154-160.  DOI: 10.11930/j.issn.1004-9649.201903020

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The valve position signal may be contaminated by noise during the turbine valve closing test, which makes it hard to calculate the closing time accurately. As a result the reliability of turbine safety assessment will seriously be affected. In this paper, the components of the contaminated signal sampled in turbine valve closing test were first analyzed using fast Fourie transform (FFT). Then the accurate closing time was calculated by waveform comparison regarding the noise signal with single sinusoidal waveform component. Afterwards, the signal contaminated by multi-frequency sinusoidal noises was filtered by infinite impulse response (ⅡR) digital filtering method. The filtering effects of different filters were compared and the closing time after the filtering were calculated. It is suggested the waveform comparison method is very suitable for the computation of closing time with the signal contaminated by single component sinusoidal waveform. Both the Butterworth filter and Chebyshev I type filter can be used for signals contaminated by multi-frequency sinusoidal noises, while the former is slightly better than the latter regarding the accuracy of calculation results.

Experimental Study of Non-phosphorus Scale Inhibitor WS330 for the Seawater Cooling System

TANG Weifeng, ZHANG Jiaqi, LI Fei

2019, 52(9):  161-166,178.  DOI: 10.11930/j.issn.1004-9649.201812001

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The coal-fire power plant located in the coastal are autilized the technology of natural draft cooling tower with flue gas injection and takes, the sea water into its recirculating cooling system. Both the static test and the dynamic simulation test of the scale inhibitor for the recirculating water were performed to ensure the safe, reliable and economic operation of the recirculating water system. WS330 phosphate-free scale inhibitor was used as the scale inhibitor for the recirculating water. The dosage of the scale inhibitor was determined through the static test, and then the simulation tests regarding various performance indices were carried out on the dynamic stimulation device. The test result reveals that the system functions normally if the mass concentration of the WS330 scale inhibitor is maintained at 8 mg/L and the concentration ratio is less than or equivalent to 2.5. With the corrosion rate of the titanium heat exchanger 2.5×10^-5 mm/a, the average adhesion rate 0.33 mg/cm² per month and the fouling resistance 1.4×10^-5 m²·K/W, all the indices above are far below their upper limits. Considering the fluctuation of the water quality and load, it is recommended to maintain the concentration ratio of this system at the range of 1.5~2.0 under normal operations. Finally it is concluded from the analysis that the natural draft cooling tower with flue gas injection had limited impacts on the concentration ratio in the cooling system using seawater as the recirculation cooling water.

Simulation Study of the Impacts of Ultra-low Emission Implemented in Thermal Power Plants on PM_2.5 Mass Concentration in Ambient Air of Jiangsu Province

ZHAO Xiuyong, ZHU Fahua, WANG Sheng, SUN Xueli, XU Jingxin

2019, 52(9):  167-172.  DOI: 10.11930/j.issn.1004-9649.201904062

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Taking the implementation practice of ultra-low emissions in power plants of Jiangsu Province as the research object, a coupled model system consisting of mesoscale meteorological model MM5 and environmental air quality model CALPUFF was established to study the contribution of the ultra-low emission implementation in thermal power industry to the reduction of ambient air PM_2.5. The impacts as well as how much ambient air PM_2.5 mass concentration is reduced in the province were simulated and calculated respectively in 2013 and 2017, which correspond to the years before and after the ultra-low emission implementation. The results show that the average annual PM_2.5 concentration contributed by the province's thermal power plants at 13 prefecture-level cities was reduced from 8.0 μg/m³ in 2013 to 4.6 μg/m³ in 2017 with the average decrease rate of 42.5%. The environmental air quality monitoring results show that the average annual concentration of PM_2.5 in 13 prefecture-level cities in Jiangsu Province in 2017 was 24.1 μg/m³ lower than that in 2013 with a decrease rate of 32.9%, which is significantly lower than the average annual concentration reduction of PM2.5 contributed by thermal power industry. The difference of 9.6% shows that the emission reduction of pollutants in the thermal power industry has entirely exceeded the emission reduction of pollution sources generated in other industries in Jiangsu Province in the past five years. At last, the route of pollutants control is proposed for the future.

Ultrasonic Attenuation Spectrum Based Method for Measuring the Particle Size Distribution of Gypsum Slurry

XUE Minghua, XIA Duobing, HU Zijian, TIAN Chang, SU Mingxu

2019, 52(9):  173-178.  DOI: 10.11930/j.issn.1004-9649.201903033

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In order to control the particle size of desulfurization by-product gypsum and improve the quality of desulfurization gypsum, it is necessary to measure the density, concentration and particle size of gypsum slurry quickly and accurately. In this paper a non-destructive desulfurization gypsum slurry particle size measurement method using ultrasonic attenuation spectrum was designed (a.k.a ultrasonic method), and then implemented to examine and compare the contents of six samples of gypsum slurry from different power plants. Based on the ECAH theoretical model, the ultrasonic attenuation spectrum was obtained by Fast Fourier Transform (FFT) of ultrasonic time-domain pulse signal. Different inversion programs were written in MATLAB language. Then by taking advantage of the optimal regularization algorithm (ORT), projection algorithm (Projection) and non-independent genetic algorithm (GA), the gypsum slurry particle size distribution were calculated respectively, and compared with the conventional testing methods. Among them the reliability of the regularization algorithm is verified with the deviation below 20%. The present ultrasonic method for measuring the particle size of desulfurized gypsum slurry can provide reference for the upcoming development of on-line measuring instrument for the particle size distribution of desulfurized gypsum slurry.

Design for Modification of Flue Gas Temperature Adjustment Bypass for SCR Denitrification System under Low Load Operation Conditions

LEI Siyuan, LI Haihao, LI Letian, NI Guidong, KONG Fanhai, WU Guoxun, BIAN Zijun

2019, 52(9):  179-184.  DOI: 10.11930/j.issn.1004-9649.201903067

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The inlet flue gas temperature of SCR denitrification unit in the coal-fired power plant usually does not meet the requirement at low load. In some power plants the bypass heating method is applied, however, it is not effective to raise the flue gas temperature as expected and the problem of large deviation of flue gas temperature still exists. Taking a 300 MW unit in Power Plant A as an example, based on the field investigation, the problems are analyzed and diagnosed by numerical simulation as follows:(1) unreasonable structure of bypass flue due to the original structural defects; (2) lack of diversion elements installed in bypass flue duct; (3) unreasonable location of bypass access; (4) insufficient depth of bypass access. Therefore, on the basis of summarizing the highlights of design and operation of by-pass flue for denitrification and temperature regulation, the design of a 330 MW unit in Power Plant B is optimized by means of numerical simulation, and then the field tests are carried out to evaluate the effects of flue gas heating. The results demonstrate remarkable effectiveness of the retrofit project on flue gas bypass heating in Power Plant B with minor deviation of flue gas temperature.