Table of Content

05 January 2018, Volume 51 Issue 1

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Research on Situation and Countermeasures of New Energy Integration in the 13th Five-Year Plan Period and Its Multi-Scenario Simulation

ZHANG Zhengling

2018, 51(1):  2-9.  DOI: 10.11930/j.issn.1004-9649.201711237

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With the rapid development of new energy generation, the consumption of new energy has been faced with severe situation in partial areas in China recently. In this study, key initiatives have been put forward to promote large-scale new energy domestic consumption in the 13th Five-Year Plan period through the design of power supply side, grid side, load side and market mechanism based on in-depth analysis of present status and principal problem of new energy consumption in China. Through multi-scenario analysis and time-sequential power system production simulation of new energy consumptive ability, contributions of different measures to possible consumption improvement are analyzed. Existing uncertainty in new energy consumption is also analyzed. Key initiatives for promoting joint efforts of all parties are proposed to stimulate consumption, aiming at keeping wind and photovoltaic power curtailment within 5% boundary.

Cost Analysis and Policy Suggestions of China's New Energy Development

ZHANG Yunzhou, HUANG Bibin

2018, 51(1):  10-15.  DOI: 10.11930/j.issn.1004-9649.201711268

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Sustainable development of new energy relies on technical advancement and cost reduction to reduce subsidy dependence. Government also set target that wind power reaches grid parity on distribution side and solar power reaches grid parity on customer side in 2020. Based on analysis of China's new energy power generation cost, including historical changes and future trends, new energy power generation cost in 2020 and 2030, as well as situation of future grid parity, are predicted. The result shows wind power in “Three North” will reach grid parity on distribution side and solar power in east central China will reach grid parity on customer side in 2020. LCOE for solar PV is expected to be lower than wind generation in 2030. With consideration of existing critical problems, several policy suggestions to promote sustainable development of new energy in China are also proposed.

Exploration and Practice of Transregional Electricity Spot Trading of Surplus Renewable Energy

PEI Zheyi, GUO Guoliang, HU Chaofan

2018, 51(1):  16-21.  DOI: 10.11930/j.issn.1004-9649.201711110

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As continuous growth of the installed capacities of renewable energy in China, the curtailments of wind, solar and water energy has become increasingly serious, especially in the "Three North"(i.e., north China, northwest China and northeast China) and southwest areas of China, due to the high concentration of installed generators, insufficient local consumption of electricity, imperfect transregional transmission mechanism and interprovincial protectionism, which has attracted high attentions from various sectors and government departments. This paper analyses the severe situation of renewable energy accommodation in the "Three North" and southwest areas of China and the necessity of promoting the use of renewable energy in the way of marketing, studies the transregional spot trading mechanism and method of surplus renewable energy, introduces the market operation performance and effectiveness, discusses the existing problems, and proposes relevant suggestions, which is of great significance in promoting the extensive accommodation of renewable energy in a large area and the construction of pilot electricity spot market in China.

The Practice and Perspective of Promoting Renewable Energy Integration in China Southern Power Grid

HU Feixiong, ZHOU Baorong, LU Siyu

2018, 51(1):  22-28.  DOI: 10.11930/j.issn.1004-9649.201711234

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In recent years, renewable energy absorption is promoted in China Southern Power Grid through measures of west-to-east power transmission strategy, renewable energy long-distance transmission and “Market+Plan” west-to-east power transmission market mechanism. In 2016, renewable energy generation reached 50.7% of total amount, which is 22.3 percentage higher than average level in China. Clean energy, distributed energy and energy mix is a development trend in China Southern Power Grid. During the 13th five-year plan period, China Southern Power Grid will continue to support renewable energy development and improve energy resources development and utilization efficiency. By 2020, renewable energy power generation capacity in China Southern Power Grid is expected to reach 174 million kW, with 129 million kW of hydro power, 28 million kW of wind power, 13 million kW of solar power and 4 million kW of biomass power.

High-Penetration New Energy Power System Development: Challenges, Opportunities and Countermeasures

WANG Ningbo, MA Ming, QIANG Tongbo, LV Qingquan, TAN Hongbin

2018, 51(1):  29-35,50.  DOI: 10.11930/j.issn.1004-9649.201711248

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Such problems as environmental pollution, climate change, energy security and sustainable development have become increasingly prominent. The world's major countries have included new energy sources in the priority development strategy of national energy. Major development opportunities and challenges are faced in high penetration renewable energy. On the basis of an analysis of the background and status quo of the renewable energy development both at home and abroad, this paper introduces the main features of large-scale development of renewable energy in China. By taking Gansu as an example to study the opportunities of high penetration development of renewable energy, the paper analyzes a series of challenges in terms of outward transmission, power accommodation, system stability, operation control, economy and efficiency, makes a prospect of development trend of high penetration renewable energy and proposes relevant countermeasures.

Research on DC Collection and Transmission for Large Scale Renewable Energy Generation Clusters

YAO Liangzhong, LIU Yanzhang, YANG Bo, CHEN Ning

2018, 51(1):  36-43.  DOI: 10.11930/j.issn.1004-9649.201711115

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With rapid development of advanced transmission technologies such as MTDC and DC grids, it may become one of main features for China's future grids that collect and transmit large renewable energy generation using DC technologies, and eventually form AC-DC hybrid power grids with high proportion of renewable energy generation connected. In this respect, a few studies have been conducted currently. This paper at first analyzes network topology characteristics of both renewable energy generation station and clusters are analyzed first. Based on the “lay and zone” criterion, a typical DC grid with multiple voltage levels for collection and transmission of large-scale renewable energy generation cluster is designed. The proposed design is presented based on scenario of Jiuquan renewable energy generation cluster. The requirements for transmission capacity, voltage levels and key equipment of such DC grid are also discussed. The results provide reference for future research of using DC technologies for collection and transmission of large-scale renewable energy generation cluster.

Serving Power System Stability by Motor-Generator Pair in Renewable Energy Power Plant

XU GuoRui, YIN Zhongdong, LIU Peng, ZHOU Yingkun, WEI Siming, HUANG Yongzhang

2018, 51(1):  44-50.  DOI: 10.11930/j.issn.1004-9649.201711124

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Environmental problem is a global problem. Developing clean energy and energy transformation is the best way to solve environmental problems. Building the global energy Internet is conducive in stabilizing renewable energy fluctuations and promoting clean energy development. However, there are still stability problems in high permeability power grid. Motor-Generator Pair (MGP) is proposed and its small signal stability and transient stability are analyzed to solve stability problems. Comparing with thermal power units, the stability of MGP is similar and frequency response characteristic is better. Experiment results also show the stable operation of MGP system. Accroding to results, MGP system can filter harmonics generated by power electronic inverter. Finally, advantages and possible application scenarios of MGP are summarized.

The Impact of Power Electronics Interfaces on Power System Frequency Control: A Review

LU Zongxiang, TANG Haiyan, QIAO Ying, TIAN Xinshou, CHI Yongning

2018, 51(1):  51-58.  DOI: 10.11930/j.issn.1004-9649.201711236

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Devices such as wind turbines, solar power, and flexible high voltage direct current (HVDC) transmission are connected into power system via voltage or current source converters, which bring changes to system frequency dynamics, power balance principle and control methods. Recent frequency events are reviewed first. Then impacts on system frequency control of large-scale power electronic interface are analyzed in aspect of system inertia. Interface control technology that is engaged in improving frequency support capability are summarized, and degree of equivalence of external characteristics between electronic interface and synchronous generators are analyzed based on inertia response and primary frequency control. Power frequency balance based on law of conservation and conversion of energy in power system with large-scale electronic interfaces are discussed. Finally, some questions worthy of exploration in terms of principles, models and methods are proposed.

Analysis and Prevention of the Lightning Fault of UHV DC Transmission Lines

LI Yanglin, XU Ning, LI Fan, ZOU Jianzhang, ZHOU Longwu, ZHANG Yu, RAO Binbin, KUANG Yanjun

2018, 51(1):  59-63.  DOI: 10.11930/j.issn.1004-9649.201611091

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According to the fault statistics of ultra-high voltage (UHV) DC transmission lines in China in recent years, lightning fault is in the first place among all kinds of faults. Lightning damage has become an important factor affecting the safe operation of UHV DC transmission equipment. The ±800 kV UHV DC transmission line from Yibin to Jinhua is an important channel of clean energy transmission in our country, so its safe and stable operation is particularly important. Based on two cases of lightning fault occurring on the Yibin to Jinhua UHV DC transmission line, a comprehensive analysis is made by using lightning location system, fault recording and ranging, field fault inspection and simulation, which indicates that the two lightning faults are both caused by lightning shielding failures. A risk assessment is made on the lightning fault of the Yibin to Jinhua UHV DC transmission line based on the measured data of lightning location system, and some preventive measures are proposed.

Lightning Current Distribution of Insulated Ground Wire in 500 kV Transmission Line

TANG Tao, XIANG Chengming

2018, 51(1):  64-70.  DOI: 10.11930/j.issn.1004-9649.201606210

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Ground wire icing severely affects the safeoperation of overhead transmission line in medium and heavyicing area. Direct Current (DC) melting ice is one of the effectivemeasures to solve overhead transmission line icing. When lightning stroke failure of the transmission line occurs, the lightning current distribution between insulated ground wire and towers decide the top potential of tower, which has impacts on lightning protection level and the grounding of transmission line. This paper uses the electromagnetic transient analysis program EMTP to calculate and analyze the lightning current distribution. The results show that the majority of lightning current pass through the towers in 500 kV transmission line, and lightning current amplitude, horizontal span of tower and grounding resistance have a greater impact on shunt coefficient of insulated ground wire and tower. This research has a significant theoretically value to tower shunt coefficient, potential's increase tower and economical design of power system.

Mechanical De-icing Sequence Optimization Considering Transmission Line Security

CHENG Song, YU Chen, WU Chen, HUANG Linyan, CHU Yunlong, CUI Wei

2018, 51(1):  71-77.  DOI: 10.11930/j.issn.1004-9649.201610143

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The mechanical de-icing technique is an important method for coping with icing disasters of transmission lines. Current research mainly focuses on the improvement of the deicing method while few researches are conducted on the effect of mechanical de-icing process. It is found that the unbalance force in transmission tower may exceed the design criteria in the process of deicing conducted according to the sequence from one end to the other, which affects the security of transmission lines. At the same time, the maximum unbalance force in transmission tower varies with different mechanical de-icing sequences. Therefore, it's necessary to optimize the mechanical de-icing sequence to increase the security of mechanical de-icing. Firstly, the impact of de-icing sequence on the unbalance force in transmission tower is analyzed. And then, a sequence optimization model of mechanical de-icing is constructed in this paper. Given the nonlinearity and multiple constraints of the model, the genetic algorithm is used to optimize the de-icing sequence of conductors with different spans. Simulation results show that the optimized mechanical de-icing sequence can effectively lower the unbalance force and improve the security of power lines in the process of mechanical de-icing.

The Research of Decoupling Technology Used to Smart Substation Model Configuration

ZOU Zhenyu, SUN Zhongwei, XIU Liming, HAN Benshuai, NIU Decun

2018, 51(1):  78-82.  DOI: 10.11930/j.issn.1004-9649.201606045

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Smart substation construction is a complex project involves multiple party participation and multiple professional collaboration. As the unity intelligent substation data source, Substation Configuration Description (SCD) file plays a very important role in station construction and operation process. SCD file integration process is optimized and redundancy link is removed. The interface file is clarified and dependency among modules are reduced. One exemplary station renovation project shows that proposed method redefines working modes and interfaces among design institute, equipment providers and integrators. Both cooperation efficiency among various units and construction quality are improved with shortened construction period.

Electric CPS Information Network Vulnerability and Assessment Method

YANG Guotai, WANG Yufei, LUO Jianbo, CHEN Xiong, LI Jun'e, LIU Jian, RU Yeqi, WU Yibei

2018, 51(1):  83-89.  DOI: 10.11930/j.issn.1004-9649.201609022

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Electric power information network is an integral part of electric CPS, and its threat assessment of vulnerability is one of the important basis for the risk assessment of the electric CPS. In view of the limitations of the existing vulnerability threat assessment technology of general information network, a new vulnerability threat assessment method is proposed for electric power information network based on the common vulnerability scoring system (CVSS). Three assessing elements are selected including vulnerability distribution threat, access vector and utilization complexity. The analytic hierarchy process (AHP) is adopted to build a vulnerability threat assessment model, and the way of forming parameters is given. The assessment results are defined into vulnerability threat levels on the basis of quantitative assessment. A case study of the assessment is made and the results are compared with the CVSS system. The assessment results show that the AHP-based vulnerability assessment of information network reflects the coupling relationship between information and physics.

Key Technical Design of Intelligent Analysis Expert System on Transmission Line Video Monitoring

HUANG Xinbo, XING Xiaoqiang, LI Juqing, ZHANG Huiying, LIU Xinhui, JI Chao, ZHANG Ye, WANG Xiaojing

2018, 51(1):  90-96.  DOI: 10.11930/j.issn.1004-9649.201612010

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With emergence of global energy Internet theory, it is very important to realize real-time remote monitoring, fault diagnosis and early warning of transmission lines and unattended substation. Based on MFC application framework, a video monitoring streaming system with intelligent analysis and identification of background fault is designed. The technologies used in the system include intelligent image recognition processing, multi-thread, ADO object database access, network communication, video transmission, video codec technology, National Grid Interface B standard protocol and XML parsing. The test results show that the system has high efficiency, good portability, strong stability and fast processing speed, which can be applied to real-time video monitoring of transmission line, providing reliable data sources and early warning information for intelligent online monitoring of transmission line.

Research of Unmanned Aerial Vehicle Comprehensive Inspection for Distribution Network Overhead Transmission Lines

WU Liyuan, BI Jiangang, CHANG Wenzhi, YANG Yuan, GONG Yanpeng

2018, 51(1):  97-101,138.  DOI: 10.11930/j.issn.1004-9649.201704085

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To satisfy need of distribution network overhead transmission lines inspection, an Unmanned Aerial Vehicle (‘UAV') comprehensive inspection method is proposed. The construction of UAV inspection platform is analyzed. Configuration requirements of visible light sensor, infrared sensor, ultraviolet and ultrasonic sensor and UHF sensor are researched and confirmed. Test result suggest that UAV inspection system has ability to operate normally in environment temperature from -20 ℃ to 45 ℃. The height limit is 2 000 m with 7 m/s wind loading rating. The hover accuracy is 0.5 m on vertical direction and 1.0 m on horizontal direction which can pinpoint electric tower inspection. The visible light sensor, with 12 million effective pixels, is equipped with variable focal length and variable focal length and auto-focusing function. The infrared sensor, with 300 thousand effective pixels, is equipped with auto-focusing function. The proposed UAV inspection platform can be applied in distribution network overhead transmission lines inspection to improve automation and intelligent level.

Power Inspection System Based on 3D Terminal Path Self-learning Navigation

ZHUANG Yuan, LI Conglin, LI Ping, XIAO Song

2018, 51(1):  102-109.  DOI: 10.11930/j.issn.1004-9649.201610150

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Combined with current situation of power system inspection system and existing problems in practical work, a three-dimensional path model is constructed and end-path self-learning navigation algorithm is designed. An intelligent power equipment inspection system is proposed. The embedded mobile patrol terminal and server-side supporting software are developed. Based on simulation results of multiple topography and landform samples, the high accuracy and good performance of proposed algorithm is proved. The proposed method can realize self-learning, recording and navigation of terminal path in different geographical environment. Finally, the system experiment is carried out to verify feasibility, validity and rationality of proposed algorithm.

Experimental Research on Unblended Coal Combustion in IGCC Power Station

LI Haiming, WU Ping, FU Bin, BU Xinzhan, WEN Ziqiang, ZHAO Lijia, HUANG Anpei

2018, 51(1):  110-116.  DOI: 10.11930/j.issn.1004-9649.201706118

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IGCC (Integrated Gasification Combined Cycle) is a clean and high-efficiency coal power generation technology. The stability and economy of the operation using different types of coal can be determined via the operation parameters of gasifier. Between 2014 and 2016, the comparative combustion tests of unblended coal and blended coal were carried out by stages in the gasifier of Tianjin IGCC power station. Since the kickoff of unblended coal combustion testing, the gasifier has been operated in stable condition, and the slag blocking has been significantly reduced. The operation costs of almost 14 million RMB have been saved, compared with the blended coals combustion. Therefore the feasibility of unblended coal combustion in gasifier is verified, which will provide references for future design and operation of gasifier, especially those in the IGCC stations.

Research on the Testing of Combustion Optimization and Adjustment of a W-Flame Boiler

HUANG Jianjun, ZHANG Xin, ZHANG Wenlong, YUAN Haifeng, LIU Yanpeng, DANG Yue

2018, 51(1):  117-125.  DOI: 10.11930/j.issn.1004-9649.201605106

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Through the optimization and adjustment testing on multiple coal type blending, air distribution mode, racemic rod position, operating oxygen, outlet temperature of the grinding coal mill, furnace flame temperature, and temperature distribution measurement, the W-flame boiler combustion status is studied under different working conditions. The study results show that the R₉₀ of the anthracite-combustion units is substantially high, which is the major cause of the high carbon contents of the fly ash. After the air distribution is optimized and adjusted, the local CO contents at multiple points have been reduced from (3 000~5 000)×10^-6 to less than 350×10^-6 with the carbon contents of the fly ash lowered down and the boiler efficiency improved. The NO_x emission is also controlled within the specified range. When the anthracite coal is burned, the grinding mill can be operated safely and stably at the outlet temperature of 118℃. Moreover, after the racemic rod is optimized and adjusted, the boiler efficiency can be distinctly improved while the superheater desuperheating water is reduced by more than 10 t/h. Meanwhile, the carbon contents of the fly ash are also reduced to some extents.

The Calculation of Turbine Exhaust Enthalpy Based on the Hybrid Model of the Principal Component Analysis and the BP Neural Network

YANG Bin, YANG Yongjun, ZHANG Ya, HUANG Meng, LI Kunlun, DENG Xinliang, BAI Huanqing

2018, 51(1):  126-132.  DOI: 10.11930/j.issn.1004-9649.201702049

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Taking a 300 MW turbine as an example, in this paperthe calculation of turbine exhaust enthalpy based on the hybrid model of the principal component analysis and the BP neural network is established. The principal component analysis and the BP neural network are introduced at first. Then,the historical data are collected as the main parameters that affect the steam turbine exhaust enthalpy.The data pre-processing is applied to exclude the bad points. The four major components, with the cumulative contribution value greater than 99.95%, are identified. The calculation model of turbine exhaust enthalpy is established with the four identified components as the BP neural network input parameters and the steam turbine exhaust enthalpy as the output parameter. After being trained and tested, the calculation model of turbine exhaust enthalpy is obtained to facilitate the real-time online monitoring. The results show that the principal component analysis can help to determine the reasonable BP neural network input parameters and improve the accuracy and the speed of the training. The precision of the hybrid model meets the requirements of the project. The fluctuation of the exhaust steam enthalpy is not big in all working conditions.

The Automatic Startup and Shutdown Technology for Double Inlet and Outlet Coal-pulverizing System Based on Expert Knowledge Base

WANG Zhijie, PENG Liang, ZHU Xiaoxing, CHEN Houtao

2018, 51(1):  133-138.  DOI: 10.11930/j.issn.1004-9649.201703007

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The automatic startup and shutdown technology for coal-pulverizing system is the prerequisite for fully automated combustion control . In this paper, the startup and shutdown timing and sequence of coal-pulverizing system was studied, and then the corresponding expert knowledge base for coal-pulverizing system was established to automatically optimize its timing and sequence. and hence the intelligent full-process control was set up for the coal-pulverizing system during unit startup and shutdown operations. The sequential procedures of startup and shutdown process for double inlet and outlet tube mills was also designed. In this way the complete automatic process control for the coal-pulverizing system was realized. The application practice shows that the expert knowledge based automatic startup and shutdown technology for the double inlet and outlet tube mills can meet the needs of the fully intelligent control for combustion , which has greatly improved the automation level and operation stability of the plant.

China Scattered Coal Consumption Map and Influence Factors

HUO Molin, ZHAO Jia, XU Zhao, SHAN Baoguo, JIA Dexiang

2018, 51(1):  139-146.  DOI: 10.11930/j.issn.1004-9649.201701147

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According to the government regulatory ability and replacement policies, the scattered coal definition is put forward in this paper, China's civil scattered coal consumption map is constructed, the data of scattered coal is provided in each sector at provincial level, and then the fact is identified that industrial small boilers and rural living are the most important areas of scattered coal, which concentrate in a few provinces on the line from the Northeast to the Southwest. The PM_2.5, SO₂ and NO_x emissions from concentrated coal and scattered coal are compared in the study. It can be seen that the PM_2.5 emission of scattered coal is more than that of coal-fired power plant. The influence of coal production supply, heating demand and infrastructure on the consumption and distribution of scattered coal is also analyzed, and the suggestions of policy and measures are put forward at last.

The Environmental Protection Status Quo of China's Gas Power Plants and the Trending in Policies

LIU Zhitan, LI Yugang, WANG Kai

2018, 51(1):  147-153.  DOI: 10.11930/j.issn.1004-9649.201708309

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In order to understand the current situation of environmental protection and the environmental protection facilities in China's gas power plants and grasp the trend in future environmental protection policies, research and study have been conducted on multiple gas-fired power plants in typical regions of China . The status of the emission reduction technology on NO_x, which is the main pollutant from gas power plants, and its existing problems of are analyzed from three aspects of the control of gas turbine combustion, the control of waste heat boiler SCR and the control of external factors. It is concluded from the comparison that the waste heat boiler SCR control technology is more mature and cost-effective and could be one of the the effective nitrogen reduction means for gas power plants in the future. Considering the domestic and foreign emission level and technical status, it is clear that the environmental protection standards on gas power plants in China is tending to be more stringent. Finally, Opinions and suggestions on reducing nitrogen emission are put forward from the aspects of power plant operation, scientific research and policy formulation.

Research on the Online Processing Method of Turbine Oil Emulsification

SUN Xiaodong, WANG Juan, ZHAO Xianhua, WU Xiaorong

2018, 51(1):  154-157.  DOI: 10.11930/j.issn.1004-9649.201701116

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The steam seal leakage occurs in the heating unit of a power plant in Shaanxi during the heating period, causing serious emulsification of the lubricating oil in the turbine and endangering the safety of the generator set operation. In order to avoid affecting the normal city heating, the effects of various online processing methods are studied and tested. The results show that the using of a polar selective adsorbent on the online regeneration of the oil is able to maximum the the demulsification reduction, making it demulsified in a very short time, and giving sufficient time for the separation of the oil and the water, This method completely solves the problem of the oil emulsification, which ensures the safe operation of the unit.

Diagnosis and Countermeasures of SCR Denitration Catalyst Abrasion in Coal-fired Power Plants

LEI Siyuan, KONG Fanhai, WANG Lele, YANG Xiaoning, DU Changfei

2018, 51(1):  158-163.  DOI: 10.11930/j.issn.1004-9649.201610116

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In order to solve the increasingly prominent issue of gas denitration catalyst system abrasion in coal-fired power plants, the mechanism as well as the causes and the damages of the catalyst abrasion are analyzed. The diagnostic idea and strategies are also summarized. Then detailed solution procedures are introduced by taking the example of the catalyst abrasion treatment for a 300 MW unit. Firstly, the distribution statistics of the abrasion was compiled. While sufficient mechanical resistances of the catalyst elements was confirmed, the steam sootblower was verified to cause no blowing loss of catalyst. Secondly, CFD numerical simulation was employed to investigate the flow fields inside both the honeycomb pores and the reactor. The root cause of abrasion was revealed as the extraordinarily high velocity and deviation of injection angle of gas flow at some parts of the upper layer. Afterwards the flow field design was optimized. Since the implementation of optimized plan, the catalyst abrasion has been effectively improved by eliminating the parts with high velocity and adjusting the injection angle of gas flow. The diagnosis strategy to the catalyst abrasion in this investigation is of great significance to solve the practical problem of the power plants.

Thermal Economic Analyses of a Power Unit Using Indirect Dry Cooling System With an Evaporative Cooler

ZOU Qingjiang, ZHANG Yijiang, GUO Minchen, CHU Dequan

2018, 51(1):  164-170.  DOI: 10.11930/j.issn.1004-9649.201706084

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Indirect dry cooling systems are widely used in coal-fired power plants. However, high environmental temperatures affect the heat dissipation performance of the dry cooling tower, causing the increase of the back pressure of the steam turbine. In this work, the evaporative cooler operating with the dry cooling tower is adopted to reduce the circulating water temperature and the exhaust steam pressure, and improve the thermal efficiency of the power unit. Taking a 600-MW steam turbine unit as the study object, an indirect dry-cooled system with evaporative cooler is designed and a mathematical model is established. The matching characteristics of the heat load distribution between the evaporative cooler and the dry cooling tower are analyzed. The back pressure, the water consumption and the pump power consumption are analyzed for various heat loads. The results show that at the rated load, when the ratio of the water flow rate for the evaporative cooler to the total circulating water flow rate is between 0.21 and 0.31, and the generation standard coal consumption rate decreases by about 7.4 g/(kW·h).

The Optimal Charging Strategy of EV Rational User Based on TOU Power Price

HOU Hui, FAN Hao, XIE Jun, LUO Junyang, KE Xianbin, WANG Chengzhi

2018, 51(1):  171-178.  DOI: 10.11930/j.issn.1004-9649.201610105

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As a mobile load, the charging and discharging behaviors of electric vehicles will have a huge impact on the power grid. This paper makes a study of the electric charging and discharging strategy under time-of-use (TOU) power prices. Four types of EV response models are established, and the optimal charging strategy of rational user is given based on five periods of charging prices and three periods of discharging prices. Under this price strategy, the paper calculates the charging fees of EV users, the gird load and network loss. The simulation results show that the optimal charging strategy proposed not only reduces the cost of EV users but also significantly reduces the power network loss rate.

An Electricity Peak and Valley Time Period Division Model Based on High Dimensional Normed Space and SGHSA Algorithm

LIU Shuyong, LI Na, FU Jingshuai

2018, 51(1):  179-184.  DOI: 10.11930/j.issn.1004-9649.201605027

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Scientific division of peak, flat and valley time period is fundamental for rational development of time-of-use tariff. Time division results should meet long-term applicability, and maximally reflect load differences in different time periods. Modeling problem of peak and valley time division is discussed. Firstly, data sample set of division model is founded by defining high dimensional load vectors which embody information of a long period and its norm at each time point. Secondly, by introduction of semi gradient membership function, membership degree of each time point to peak, flat and valley period are defined based on norm of load vectors. Thirdly, threshold optimization model is established to optimize threshold by using SGHSA searching algorithm. This completes the construction of period division model. Finally, exemplary application on a certain area proves reasonability of proposed model.