Table of Content

05 September 2018, Volume 51 Issue 9

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Technical and Economic Investigation of Blended Combustion with Inferior Coal on 600 MW Unit Boiler

ZHOU Lingmei, ZHANG Guanjun, ZHU Xianran, LI Haoyu, JIAO Kaiming

2018, 51(9):  1-7.  DOI: 10.11930/j.issn.1004-9649.201805205

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In order to reduce furnace slagging, optimize the blending of inferior coal and increase power plant profit, technical and economic investigation of blended combustion with inferior coal on 600 mw unit boiler was processed through on-site tests, such as the blending ratio of low-grade coal, pulverizer combination, furnace flame temperature, reducing gas distribution, sulfur dioxide concentration, slagging behavior, etc. The results show that the unit can safely operate with three coal mills blended with high-sulfur coal, he maximum mixing ratio is 37%, and there is no obvious slagging in the boiler furnace; at the maximum blending ratio, the sulfur dioxide concentration in flue gas increases significantly, but the desulfurization system still has a large margin; the economic evaluation shows that the low price of low-grade coal reduces the cost of power generation significantly, although the blending slightly increases the net coal consumption rate. The on-site tests and economic evaluations provide ways and references for the optimization of the blending inferior coal for the same type units.

Thermo-economic Analysis of a Blending Coal-fired Power Plant

YAN Xiaokun, JIAO Kaiming, XU Cheng

2018, 51(9):  8-14.  DOI: 10.11930/j.issn.1004-9649.201805172

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To improve the thermo-economic performance of the blending coal-fired power plants, this study adopted the unit coal cost as the objective and the coal characteristics as the constraint conditions, developed the models for evaluating the variations of the unit performance, and finally achieved the optimal blend coal ratio. Then the influence of the blending ratio on the boiler efficiency and the main auxiliary equipment power consumption were also analysed. Finally, the cost of using the blending coal was obtained. The results showed that, when the power plant operated with the optimal blending ratio of 0:2:5:3, the price of the blending coal can be reduced by 43 CNY/ton compared to the designed coal. The electricity consumption of the auxiliary equipment is increased by 1123.8 kW, which led to a 0.2% increase in the auxiliary power consumption rate. Also, the boiler efficiency is decreased by 0.5%. These two aspects increased the standard coal consumption rate by 2.4 g/(kW·h). Overall, the fuel cost of unit electricity of the blending coal decreased by 3%, which brought coal cost savings of 18.0 million CNY. This study will provide a reference for evaluation of the integrated performance of the power plants using the blend coals.

Model of Coal Cost for Blending Coal Combustion in Thermal Power Plant

LI Jinjing, JIAO Kaiming, ZHAO Zhenning, ZHANG Qingfeng, SUN Yongchun

2018, 51(9):  15-19.  DOI: 10.11930/j.issn.1004-9649.201704107

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Coal cost is the largest part of thermal power plant running cost. A model of critical values of standard coal as fired price deviation (CVSCPD) is built, according to the coal cost minimization principle. This model comprehensively expresses how the unit power efficiency and coal prices influence coal cost. Two questions are answered by CVSCPD respectively, whether blending coal is effective to save coal cost, and which blending rate is the best. It helps to correct two mistakes of coal blending in commonsense. One mistake is that blending cheaper coal always helps reducing coal cost. The other is that the more we blend cheaper coal, the more we earn. It is quite applicable to the decision making of coal purchase and the process management of coal blending.

Main Characteristics of Coal Blending Method and Adaptability Analysis for Blended Coal

YAO Wei, HAO Bing, LIU Jiali, FANG Shunli, ZHANG Xilai, WANG Zhichao

2018, 51(9):  20-27.  DOI: 10.11930/j.issn.1004-9649.201807113

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In order to improve the safety and economy of coal blending in power plants, this paper fully analyzes the characteristics of intermittent blending, premixed blending and mixed combustion which have been commonly used in thermal power plants through a large number of laboratory and field test results. Also the interactions between blending method and blended coal combustion performance are analyzed comprehensively in combination with boiler design, operational features and combustion characteristics of blended-coals. Finally the paper puts forward the coal quality requirements of furnace coal and blended coals from the aspect of combustion performance. At the same time, according to the combustion performance of different blended-coals, the appropriate mixing combustion mode is recommended and precautions during the operation process are proposed. Moreover, the problems which are more likely to occur and corresponding solutions under different blending modes are given with real examples. The research results can provide references for coal blending and boiler operation parameter optimization.

Key Technology Research and Application for Large-Scale Grouping-Based Coal Blending and Combustion

ZHAO Yuxin

2018, 51(9):  28-33.  DOI: 10.11930/j.issn.1004-9649.201808017

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Coal blending is the main way for thermal power enterprises to deal with the market and reduce the cost, which involves the processes of fuel procurement, transportation, acceptance, unloading, mixing, transportation, combustion, storage, settlement, statistics, accounting and so on. In order to give full play to the entire system in which each individual process is integrated effectively, by taking the advantages of grouping resources, management and technology, we innovated the management, application platform and technology measures of the process of purchasing, unloading, blending, evaluation, assessment and so on. Laterally we enhanced the grouping coal blending process reengineering, while longitudinally we also deepened the technological innovation of the systematic coal blending. Under the condition of meeting the requirements of safety, environmental protection and economy, the overall benefit of the group as well as the comprehensive benefit of each individual enterprise has been maximized. After years of practical application, it has exhibited certain significance of guidance and value for promotion.

Experimental Study on Ignition of Blended Coal in W-Flame Boiler with Swirl Burners

JIA Yonghui, LI Xin, ZHANG Yongsheng, AN Guoyin, YAN Huibo, MA Hui

2018, 51(9):  34-38,45.  DOI: 10.11930/j.issn.1004-9649.201804131

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The ignition characteristics of coal blends with lean coal, anthracite and bituminous coal are studied on a W-flame boiler in a power plant. The temperature of pulverized coal air is measured near the burners. Then the variation of axial pulverized coal airflow temperature is analyzed before and after blending the bituminous coal. The axial pulverized coal airflow temperature with respect to different proportions of the lean coal and the anthracite is also analyzed. Finally the variation of axial pulverized coal airflow temperature between side wall burner and middle burner is compared. It is found that the blended coal powder are burned twice. The lean coal which is easier to be ignited burns first. When the bituminous coal gradually burns out, the temperature of the pulverized coal airflow starts to drop down a little. Then after the anthracite with higher ignition temperature begins to burn, the pulverized coal airflow temperature rises again. If the lean coal is blended with anthracite, the temperature of pulverized coal will decrease and the ignition distance will be extended gradually with the increase of anthracite ratio. The furnace wall and mild air leakage cause the temperature decrease of the pulverized coal airflow such that more heat will be needed for the pulverized coal combustion, which eventually delays the ignition of the burner near the side wall.

Advanced Fine Combustion Operation Optimization of Boiler Subject to Complex Coal Quality

HUANG Xiaobin, TIAN Hongwei, WANG Yiwei, DING Yongsan

2018, 51(9):  39-45.  DOI: 10.11930/j.issn.1004-9649.201806167

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Blended coal combustion in power plants can effectively reduce the fuel cost, but it may cause volatility of the coal quality for the boiler as well as the quality deviation from the designed coal. It is becoming an increasingly urgent problem to be resolved regarding how to maintain safe and efficient operation of boiler. In this paper, the main bottlenecks of the current boiler combustion, such as pulverization, air distribution, design and manufacturing, are ana-lyzed, and the integrated solutions are proposed in three aspects, which consist of the optimization of fuel input, boiler combustion equipment, and the fine operation control of the combustion process. The key monitoring and optimizing operation technologies for fine control of pulverized coal and fine air distribution in furnace are emphatically studied and discussed. Since boiler combustion optimization is a complex system engineering, the scheme presented in this pa-per provides necessary design guidance and reference for the implementation of combustion optimization engineering in thermal power plants.

Study on the Impacts of Blending Lignite in Bituminous Coal Boiler on Unit Security and Economy

LIU Guifeng, HAN Xuesong

2018, 51(9):  46-52.  DOI: 10.11930/j.issn.1004-9649.201803070

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The coal-blend combustion using different types of coals in coal fired power plants is of great significance to the secure and economic operation of the unit. By taking account of the testing on the 350 MW supercritical bituminous coal boiler in a power plant, the positive impacts of lignite blending such as reducing unit price of standard coal, improving boiler efficiency and reducing NO_x emission are analyzed and verified and consequentially better economic benefits have been obtained. The optimal air distribution scheme under different loads is explored through combustion testing with blended coal. The on-line monitoring for the boiler CO concentration is proposed and the impact of burnout air flow ratio on low nitrogen combustion and boiler efficiency is also investigated, such that the CO concentration is generally maintained around 200 mg/m³ and the ratio of burnable air at the range of 7.0%~13.0%, which can be used as a reference to resolve the contradiction between low NO_x combustion and combustion efficiency. Moreover, comprehensive improvement measures have been taken such as improving the smoothness of the boiler's cold hopper, which effectively relieved the coking problem of the heating surface of the boiler and the results sound satisfactory. In summary, this paper has provided reference for coal blending as well as energy saving and emission reduction of utility boilers.

Exergy Efficiency Analysis of Heating Steam Pipeline for Cogeneration Power Plant

LI Jianfeng, GAO Shengpu, LI Yan, LYU Junfu, GAO Zhihong

2018, 51(9):  53-58.  DOI: 10.11930/j.issn.1004-9649.201706111

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In order to evaluate the energy efficiency of long-distance steam pipe, the exergy efficiency is proposed as an important evaluating indicator to determine the energy efficiency of the steam pipe. A one-dimensional model for flow through steam pipe is established. And then the thermal efficiency and exergy efficiency of the 2 km-long steam pipe are calculated. The calculation results show that under constant steam flow rate, with the increase of the pipe diameter, the steam flow rate in the pipe as well as the pressure loss and thermal efficiency of the pipe will continuously decrease. However, the exergy efficiency of the pipe will increase at first and then decrease, with a maximum value in between. If exergy efficiency of steam pipelines is prioritized as the design target, compared with the existing design specifications, the steam pressure loss in the pipeline will be reduced as a result of the flow rate decrease. As long as enough steam pressure for the user is ensured, the extraction pressure of the steam turbine is allowed to be reduced substantially. At the extraction flow of 250 t/h, the turbine can output an additional 3330 kW of electrical power due to reduced extraction pressure. Therefore, it is more reasonable to select the steam flow rate in the pipeline within the range of 0~25m/s according to the investment cost.

Multi-objective Optimization of Dynamic Back Pressure Setpoint Based on Genetic Algorithm

WANG Qi, QU Yan, BAI Jianyun, HOU Pengfei, LI Yongmao, FENG Geng

2018, 51(9):  59-64.  DOI: 10.11930/j.issn.1004-9649.201803122

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Aiming at existing defects in backpressure value setting of most air-cooled units in China, by taking advantage of the parameters obtained during the operation of a 300MW direct air-cooled unit, a multi-objective optimization genetic algorithm (GA) was used to establish a specific mathematical model for back pressure and air cooler fan power consumption, and then solve the optimal solution for back pressure and minimum air cooler fan power consumption under certain constraints. Through this dynamic setting method, the backpressure setting of air-cooled units are optimized dynamically under variable load and AGC conditions, which is of great practical significance for the operating parameter adjustment of air-cooled units as well as the control strategy optimizations. It is also beneficial for the safe and economical operation of air-cooled units.

Application of Unified Power-Regulating System of Auxiliary Equipment on a 660 MW Unit

MU Chunhua, LV Kai, XU Pengjiang, SUN Dawei, WU Pengyue, MA Tingshan, JU Wenping, LI Dongquan

2018, 51(9):  65-72.  DOI: 10.11930/j.issn.1004-9649.201705052

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The unified power-regulating system of auxiliary equipment (UPRS), which is mainly composed of variable-high-speed turbine and variable-frequency generator, adjusts the main auxiliary equipment with the same optimum operating frequency. It reduces the throttle loss of the system and improves the transmission efficiency, while the system is more centralized, simple and easy to maintain. A power source system of boiler fan driven by frequency conversion is adopted in a 660MW unit. The operating characteristics of the system are figured out through performance tests, and the optimal operating modes under different loads are also obtained. The best operating frequencies under THA, 75%THA and 50%THA operating conditions are 47Hz, 41Hz and 41Hz, respectively. Within the range of frequency 41~50Hz, the coal consumption of the unit when the power source system is operated under the optimal frequency is slightly less than or basically equal to that under the operation frequency before the transformation, and is slightly more than that with the variable frequency operation state, but the power consumption rate of the unit decreases significantly, and the net power supply capacity is also significantly improved. With the decrease of operating frequency, the efficiency of induced fan, primary fan and blower are improved to some extent. The total power consumption of the three blower fans is approximately linear with the operating frequency. The operating frequency is reduced from 50Hz to the optimal point, the total energy consumption is reduced by 308kW/816kW and 868kW respectively under the condition of 75THA and 50%THA.

Discussion on Critical Technologies of Double-Reheat Ultra-supercritical Boiler with Higher Steam Parameters

MO Chunhong, LIU Yugang, WANG Dongping, YANG Huachun, PAN Shaocheng, YI Guangzhou

2018, 51(9):  73-77,157.  DOI: 10.11930/j.issn.1004-9649.201804047

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The research on double-reheat boilers with the reheat steam temperature high up to 630℃ is being carried out in China. To resolve the difficulties in the development of the boilers, a series of key technologies have been studied and corresponding solutions are proposed, such as the boiler general layout optimization, application of new materials, reheat steam temperature adjustment, wall temperature deviation control, upgrade of the water wall design and manufacturing techniques, and so on. The results show that the requirement of 630℃ parameter can be achieved effectively by adopting the technology of front and rear wall burning off combustion, π type layout and temperature control with three flue baffles.

Application of UCMS10 Online Fly Ash Carbon Content Measurement Technology on a 660-MW Unit

ZHANG Yixin, FU Hui, WEI Songwei, GAO Peng

2018, 51(9):  78-82.  DOI: 10.11930/j.issn.1004-9649.201802086

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In order to lower the carbon contents in boiler fly ash and improve the boiler combustion efficiency, based on the techniques such as spectrum scanning, equivalent mass sampling, in-situ measurement and synchronous sampling and taking the characteristics of fly ash collecting equipments into account, a new online fly ash monitoring device is developed for the electrostatic precipitator and has been applied on the 660-MW unit of a power plant. By sampling the fly ash in the electrostatic precipitator, the comparative test on the device is carried out under different loadings. The test results show that the measurement accuracy coefficient of the device is 0.95 and the sampling representative coefficient is 0.86, which means that the device is ready to be used for the verification of the boiler combustion efficiency.

Cause Analysis and Prevention of Drainage-Tank Leakage in Ultra-supercritical Power Plant

YU Baoqing, PENG Xingna, CONG Xiangzhou, PENG Xiankuan, DU Zhanjiang, GAO Zhi

2018, 51(9):  83-87,150.  DOI: 10.11930/j.issn.1004-9649.201707073

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The cause of drainage-tank leakage of the reheat steam pipe is analyzed in a 1000MW ultra-supercritical power plant which has been operated for less than two years. Firstly, the tank is examined using ultrasonic, then the crack is dissected, and finally the microstructure and fracture morphology of the crack are inspected carefully and analyzed. The results show that, the cracking of the pipeline hydrophobic tank in the reheating section can largely be attributed to the repeated reflux of the condensate water on the reheat pipe, which causes significant temperature difference between the upper and lower parts of the pipe, and hence the thermal fatigue cracks are generated. Eventually the thermal fatigue crack propagation leads to the leakage. Therefore, it is suggested that the structure of the drain tank should be improved and the superheat control mode should be adopted. Additionally the ultrasonic inspection for the tank should be carried out regularly.

Antenna Detection Method for Corona Discharge of Transmission Lines

XIA Yunfeng, SONG Xinming, QI Jinfeng, XU Zheng

2018, 51(9):  88-92,100.  DOI: 10.11930/j.issn.1004-9649.201712054

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Detection of corona discharge of the transmission line can reflect its health status and provide warning information for maintenance. Some existing detection methods are flawed and can't be used widely. This paper presents a new method by measuring the electromagnetic wave caused by corona discharge with RF antenna. Then a circularly polarized log-periodic antenna was designed by making two pairs of log-periodic antennas 90° orthogonal. Then this antenna was simulated, and its performance of direction, gain and frequency meets the design requirements. Finally it was manufactured to detect electromagnetic signals, the result shows that the time domain signal of corona discharge is a high frequency oscillation wave and its FFT main distributes between 200 MHz and 350 MHz.

Attenuation Model of Transformer Noise Based on All-Phase FFT

ZHOU Yaqi, YING Liming, HU Kefei, LIU Xianmin

2018, 51(9):  93-100.  DOI: 10.11930/j.issn.1004-9649.201801199

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It is conducive to the studies on control technologies of the soured noise in a substation that analyzing the frequency domain properties and the attenuation model of a transformer's noise signal. In this paper, the noises collected from the transformer were analyzed using the full-phase FFT spectrum, and of which the frequency domain curve was obtained. As shown in the spectrogram, the fundamental frequency of the noises was 100 Hz and at this frequency the sound pressure level corresponding to every frequency point reached its maximum. In this study the full-phase FFT spectrum was utilized to obtain the octave band sound pressure levels and to analyze the noise signal of the reference point. Then the acoustic attenuation of the set point could be calculated and the attenuation model could be built by combining the parameters of the substation. The A sound pressure level and 100 Hz sound pressure distribution could be draw. The utilization of the noise attenuation model is beneficial to calculate the substation noise distribution more accurately, what's more, to evaluate their impacts on the surroundings more directly.

Modelling and Simulation of No-load Transformer during Power Plant Charging and Mitigation Strategy of Power Fluctuation Based on RTDS

XIA Xiaojun, MA Hongxing, GU Qiubin, TANG Shuo, LIN Jikeng, JIANG Wei

2018, 51(9):  101-109.  DOI: 10.11930/j.issn.1004-9649.201707084

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Normally, putting on-load transformer of nearby generators into operation will lead to power fluctuations of on-line generators. To restage the accident, the paper proposes a simulation model, which includes the UMEC model of transformer in RTDS environment, the equivalent model of external network, and the model of power generation system (including generator, excitation control and speed control). These three parts constitute the no-load transformer energizing simulation system, which can be used to restage the accident where no-load energizing induces low voltage of bus and power fluctuation of nearby generators. Moreover, a method of phase-splitting is proposed to mitigate low voltage of bus and power fluctuation of nearby generators. The correctness and effectiveness of the proposed method is demonstrated and validated via case study.

A New Method for One-Stage Distribution System Reconfiguration Based on Optimal Flow Algorithm and Mayeda Spanning Tree Algorithm

ZHANG Zhongshi, WANG Gaomeng, ZHANG Tanyong, LIN Jikeng

2018, 51(9):  110-117.  DOI: 10.11930/j.issn.1004-9649.201805095

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For the problem that the stochastic optimization algorithms have long calculation time and the heuristic algorithm has low accuracy when used for distribution network reconfiguration, this paper presents a new method of one-stage distribution network reconfiguration based on the optimal flow method and Mayeda spanning tree algorithm. The optimal flow method is employed to quickly select the branches that are used for branch exchanging in the Mayeda spanning tree algorithm from the candidate sets of branch exchanging, which avoids the slow evolution problem of the stochastic evolutionary selection method as well as the problem of too many poor trees generated by the exhaustive method, and is equivalent to partially eliminating the trees that are worse than the current tree by using the optimization technique, consequently speeding up the searching process for the optimal tree. The proposed method enjoys the advantages of the efficiency of the optimal flow method and the completeness of the solution space of Mayeda spanning tree algorithm, which are well integrated to improve the computational efficiency. The proposed method has been proved effective by case study and is valuable for engineering application due to its efficiency and its ability to find at least a suboptimal solution.

Relationship Between Lightning Overvoltage and Impulse Grounding Resistance of 500 kV Transmission Line

GAN Yan, GU Dewen, ZHANG Chang, YAO Yong, HUANG Ruiying

2018, 51(9):  118-125.  DOI: 10.11930/j.issn.1004-9649.201707066

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In order to consider the dynamic dispersion process of lightning current in lightning protection line, tower, grounding grid and soil after lightning strike transmission line, the full-wave electromagnetic transient model of transmission line-pole-grounding grid is established to calculate the impact grounding resistance and counter overvoltage. Based on the full-wave electromagnetic transient model, from the concept of impact grounding, the influence of soil resistivity, lightning current wavefront time and amplitude on the transmission line is directly reflected on the lightning overvoltage, and the lightning overvoltage and the grounding resistance are calculated. The formula is fitted. Studies have shown that both the reduction of the wavefront time and the increase of the soil resistivity increase the impact grounding resistance value and the lightning overvoltage. The impact grounding resistance value regardless of the spark effect is independent of the lightning current amplitude, and the lightning overvoltage increases proportionally with the lightning current. When designing the grounding grid, consider the effective length of the grounding grid ray that can reduce the lightning overvoltage value.

Long-term Daily Load Forecast of Electric Vehicle Based on System Dynamics and Monte Carlo Simulation

CHEN Rongjun, HE Yongxiu, CHEN Fenkai, DONG Mingyu, LI Dezhi, GUANG Fengtao

2018, 51(9):  126-134.  DOI: 10.11930/j.issn.1004-9649.201711126

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A private electric vehicle quantity forecasting model is established from macro, medium and micro perspective based on system dynamics model. Then the charging and discharging characteristics of electric vehicles are analyzed. Besides, the Monte Carlo method is used to simulate the charging and discharging behavior of private electric cars. Finally, the actual data is used to predict the change of grid load curve considering large-scale electric vehicles accessing to the grid in the future. The results show that, in the case of unregulated charging mode, the larger the quantity of electric private cars is, the greater the difference between the peak and the valley load and the adverse impact are. Moreover, it is found by further calculation that private electric cars participating in the discharge can, to some extent, cut down the grid peak load increased by EV charging and has a certain peak-load shifting benefits.

Business Models for Promotion of Electric Power Substitution Technology

GUO Bingqing, SHEN Yu, ZHONG Ming, YUE Yuanyuan, HUANG Wei

2018, 51(9):  135-142.  DOI: 10.11930/j.issn.1004-9649.201801149

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Electric power substitution is one of the major routes to facilitate a clean, safe and intelligent energy consumption mode and has risen to the national strategic level. A comprehensive analysis of the business model of electric power substitution is conducted in this paper. Firstly, influencing factors, stakeholders, profit modes and income distribution of the business model are analyzed. Secondly, some typical business models including EMC, BT, BOT, PPP and so on are studied in detail, which can be applied to different types of electric power substitution projects. According to development stage and characteristics of electric power substitution application and projects, some appropriate types of business models are recommended. Finally, a business model for electric vehicles is provided as an example of electric power substitution application.

Participation Mechanism of Renewable Energy in the Electricity Market in Denmark and Its Implications for China

WANG Caixia, LI Ziqian, LI Qionghui, Kaare Sandholt, LEI Xuejiao, WANG Jiangbo

2018, 51(9):  143-150.  DOI: 10.11930/j.issn.1004-9649.201708219

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The integration of renewable energy is increasingly becoming a critical issue in China. With the new round of electricity market reform in China, it has attracted wide attention how to use the market to facilitate the renewable energy integration. The key issues are how renewable energy participates in the electricity market and how the market balances the fluctuations of renewable energy. Most of the foreign countries with high penetration of renewable energy have mature electricity markets and have accumulated rich experiences on integration of renewable energy in the market. An in-depth analysis of the foreign countries' experience on participation of renewable energy in the electricity market can provide valuable reference for China to integrate the renewable energy and build the electricity market. Denmark is selected as a representative of Europe to study the participation mechanism of renewable energy in the electricity market and its implications for China. The power system and renewable energy development in Denmark is firstly introduced, and then the market structure and rules are analyzed, based on which the participation mechanism of renewable energy in the electricity market are studied. Finally, the implications of Demark experience for China are proposed considering the renewable energy policy and electricity market reform in China.

Study on Evolutionary Game Model of Thermal Power Regulation in Large-scale Wind Power Grid Integration

DONG Fugui, WU Nannan, YAO Jun, LI Hujun, BAI Hongkun, JIN Chunxu

2018, 51(9):  151-157.  DOI: 10.11930/j.issn.1004-9649.201708144

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To solve the absorption problem caused by large-scale wind power grid connection, under condition of fairness, the criteria to determine paid and unpaid peak-shaving units is set up for different types of units based on the capacity of thermal power units and their maximum peak-rates. The peaking evolutionary behavior of thermal power units can be transformed into the evolutionary game between electricity bidding and peaking auxiliary service revenue. Under the context of two market scenarios, the bidding strategy and the corresponding revenue of all kinds of thermal power plants are discussed comprehensively, then corresponding stability strategy is solved respectively. The game problem of two kinds of power plants is analyzed empirically. It is shown that at the current stage there is a huge gap between the compensation amount of peak-shaving auxiliary service and the revenue of the on-grid electricity, which will exist for some time in the future. Therefore it is becoming urgent to establish reasonable auxiliary service market and promote the positiveness of peak regulations of thermal power units so as to improve the ability for absorbing large-scale wind power generation.

Research on the Development and Transmission of Clean Energy in Western China Considering Wide Range Coordination of Multi-Energy

PAN Ersheng, LI Hui, XIAO Jinyu, SHI Rui, WANG Shuai, YI Haiqiong, WANG Zhidong

2018, 51(9):  158-164.  DOI: 10.11930/j.issn.1004-9649.201706095

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The environmental problem caused by fossil energy consumption is increasingly prominent. To replace the fossil energy with clean energy is the inevitable requirement of ecological civilization construction. The clean energy in China is mainly concentrated in the north and western regions, where the clean energy is difficult to be consumed locally due to the low electricity demand, and it is necessary to optimize the energy allocation in the whole country. Based on an analysis of the supplementary characteristics of wind, photovoltaic and hydro power in China's western region in view of the renewable energy features, this paper studies the benefits of multi-energy coordination to reduce the intermittency, randomness and fluctuation of renewable energy. A sequential power system operation simulation technique is proposed considering the network constraints and the random characteristics of renewable energy sources. A simulation is made on the large scale development scenario of clean energy in northwest China, and the results show that construction of interconnection transmission channels between northwest and southwest regions can realize multi-energy coordination, improve clean energy power quality, and raise the utilization efficiency of clean energy transmission lines.

Coordinated Control of Hybrid Energy Storage System Based on Variational Mode Decomposition

ZHANG Xiaoyu, ZHANG Jiancheng, WANG Ning, WANG Guan

2018, 51(9):  165-173.  DOI: 10.11930/j.issn.1004-9649.201708091

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In view of the active power fluctuation and intermittence of photovoltaic (PV) power systems, based on a hybrid energy storage system consisting of super capacitors and lead-acid batteries, a layered active power allocation strategy is formulated to optimize the output power of PV source based on the method of variational mode decomposition (VMD). First, the net load which is supplied by the hybrid energy storage system is decomposed by VMD method. Then the low-frequency components and high-frequency components are allocated to the lead-acid batteries and super capacitors respectively to smooth out the fluctuations of output power of PV. At the same time, the orders of VMD filter are adjusted secondarily according to the state of charge (SOC) and the largest chargable/dischargable power in real time. The simulation tests demonstrate that using this method can effectively smooth out the fluctuation of net load, and the regulation performance and long-term and stable operation of the hybrid energy storage system are able to be optimized.

Economic Analysis of Pyrolysis and Hydrolysis for SCR Flue Gas Denitrification Urea

PEI Yukun, ZHANG Yang, XU Ketao, ZHU Yue

2018, 51(9):  174-178.  DOI: 10.11930/j.issn.1004-9649.201704026

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Because of its safety and convenience for transportation and storage in addition to its harmlessness to environment, urea has become a reliable substitute for liquid ammonia, a reducing agent for SCR flue gas denitrification in coal-fired power plants. The key part of the project to switch to urea from liquid ammonia is how to select suitable urea technology. In this paper, the investment cost and operation cost of urea pyrolysis process and urea hydrolysis process are analyzed through engineering modeling. The energy consumption level of urea ammonia production system is also studied by using thermodynamic method. The results show that the cost of urea hydrolysis is slightly higher than that of urea pyrolysis, but the operation cost is lower and the technical economy performance is better. The main reason for the high operation cost of urea pyrolysis is found out to be the low conversion rate of urea and the application of high quality electric energy as heat source.

Research on the Industrial Scale-Up of Regeneration Technology for the Deactivated SCR Flue-Gas De-NO_x Catalyst

ZHAO Huimin, YIN Shunli, LIU Changdong, ZHU Chaoyang, LU Zhifei, DAI Jian, HUO Wenqiang, ZHOU Wen

2018, 51(9):  179-184.  DOI: 10.11930/j.issn.1004-9649.201707040

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While the SCR flu-gas de-NO_x catalyst has been used widely, a large number of deactivated catalyst are produced. Thus it is of great importance to regenerate those deactivated catalysts for economic purpose and environmental protection. The deactivated SCR flue gas denitrification catalyst which has been put into operation for nearly 25 000 hours in a coal-fired power plant is taken as the research object. Based on the deactivation principle of the catalyst, the main influencing factors (compressed air soot blowing pressure, ultrasonic cleaning time, etc.) in the regeneration process of the catalyst are analyzed. Then the regeneration process of deactivated catalyst is introduced, including ash removal, pre-cleaning, deep cleaning, active component loading, heat treatment and so on. The various testing results show that the pollutants such as alkali metal, alkaline earth metal and sulfate in the deactivated catalyst are removed effectively after regeneration process with the developed technology. The through-cell ratio of the catalyst reaches up to 98.7%. The specific surface area is obviously recovered and the relative activity of the regenerated catalyst is remarkably improved to 99%. The compressive strength and the single layer SO₂/SO₃ conversion rate of the catalyst are able to satisfy the application requirements, which means the physicochemical properties, the process performance and the mechanical strength of regenerated catalyst are effectively recovered for the continuing usage in the denitrification reactor.