Table of Content

25 April 2015, Volume 48 Issue 4

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Special Conlribulion

China’s Power Supply and Demand Review in 2014 and Prediction in 2015

TAN Xiandong, HAN Xinyang, FENG Yi, GUO Lijie, SHAN Baoguo

2015, 48(4):  1-5.  DOI: 10.11930.2015.4.1

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The features of China’s electricity demand and supply in 2014 are analyzed and the power supply and demand situation in the year of 2015 are forecasted in the paper, based on which some suggestions are proposed to guarantee the electric power supply. The analyis shows that the power consumption growth and the using hours of thermal power generation units in 2014 were the lowest in 16 years and 37 years respectively in China, which was mainly affected by the economic slowdown in growth and the uncommon weather of cool summer and warm winter. It is predicted that China’s national electricity demand will reach 5 769~5 879 TW?h in 2015, growing by 4.0%~6.0%, the net installed generation capacity will increase by 91.4 million kilowatts with the total installed generation capacity reaching 1.45 billion kilowatts by the end of 2015 and the using hours of the thermal power generation units will drop futher to about 4 638 hours; and the electric power demand and supply will be in balance in China as a whole, sub-regionally, the North China is deficient slightly in power supply, the East China, Central China and the South China are basically in balance between power demand and supply, while the Northeast and Northwest have some surplus in power supply.

Column of Flue Gas Denilralion

Chemical Cleaning Regeneration Technology for Deactivated SCR Catalysts

BAI Wei, ZHAO Dongmei，, XIAO Yuting

2015, 48(4):  6-10.  DOI: 10.11930.2015.4.6

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The regeneration of the deactivated SCR catalysts abandoned by a coal-fired power plant is conducted with the chemical cleaning technology to explore the effects of the effective components concentration of the cleaning solution, and the ratio of liquid to solid on the removal of Fe2O3, K2O and Na2O. Meanwhile, the specific surface area, pore volume and de-NOx activity of the deactivated and regenerated catalysts are also measured, and the surface morphologies of these SCR catalysts are compared. The results show that the sulfuric acid or nitric acid is very effective in removing the poisoning elements, in which the optimum mass concentration of the nitric acid solution is 2%. Increasing the liquid-to-solid ratio adequately is beneficial for completely removing the poisoning elements on the catalyst surface. After the regeneration, the catalyst surface becomes rougher, and the BET result is increased to 93.88% of the new catalyst, which proves that the de-NOx activity of the regenerated catalyst is improved substantially and can be recovered to as much as 89% of the fresh one.

System for Performance Evaluation and Lifetime Management of SCR DeNOx Catalysts in Coal-Fired Power Plants

ZHOU Jianxin, YU Cong, JIANG Xiaoming, FANG Xuwen, HAN Chaobing, SI Fengqi, XU Zhigao

2015, 48(4):  11-15.  DOI: 10.11930.2015.4.11

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In the absence of enough experience in flue gas denitration catalyst management in thermal power plants, a SCR catalyst performance evaluation and lifetime prediction system is developed, in which a catalyst information database is designed and established to store the catalyst performance test data from multiple units since commissioning, keep track of the changes of the catalyst activity, and timely acquire and update the catalyst lifetime curve. In this system, a catalyst lifetime prediction model is also built to conduct the performance evaluation and lifetime prediction according to the real-time information such as the SCR denitration efficiency, the SCR system commissioning time and the inlet and outlet NOx concentrations, which can provide technical guidance for the catalyst replacement and optimization. It can not only enhance the data sharing and technical exchanges between SCR system operators and catalysts providers, but also ensure the safe, economic and reliable operation of the denitration system. The successful practice demonstrates its broad application prospects.辉

Evaluation on Effects of SCR Ammonia Injection System Modification for Flue Gas Denitrification

WANG Lele, ZHOU Jian, YAO Yougong, YAO Yan, SONG Yubao, FANG Chaojun, CHEN Weiwu

2015, 48(4):  16-22.  DOI: 10.11930.2015.4.16

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Taking the modification of ammonia injection grid(AIG) in a coal-fired power plant for instance, the effects of the modification are evaluated through numerical simulation and calculation. The results demonstrate that the two-way regulating function is beneficial to the even distribution of ammonia and it improves the adaptability to the uneven flue gas velocities. Moreover, the relative standard deviation of the outlet NOx distribution declines from 40% to lower than 15%. The modification improves SCR ammonia spraying effectiveness, increases the catalyst life span, eliminates the local high concentration of ammonia slip at the reactor outlet, reduces the risk of downstream ABS corrosion in the air pre-heater, and it therefore helps the coal-fired power plant achieve super-low NOx emissions.

Influence of SNCR System on CFB Boiler Operation

YANG Yonglong, ZHAO Kai, SU Qiufeng, ZHANG Yang, WANG Fengji, ZHU Yue

2015, 48(4):  23-26.  DOI: 10.11930.2015.4.23

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In this paper, the performance testing of a CFB boiler is introduced. And then through the testing, the impact of SNCR system on CFB boiler operation is analyzed. The results show that the deNOx efficiency of SNCR system can reach over 60%. High ammonia slip will accelerate the block of air preheater by fly ash. The interaction between the slipped ammonia and SO3 can cause fouling at the low-temperature end of the air preheater, which makes the resistance of the air preheater increase, but on the other hand it may lower the emission concentrations of ammonia slip and SO3.

Principles and Key Techniques for SCR De-NOx Engineering Design

YANG Zelun

2015, 48(4):  27-31.  DOI: 10.11930.2015.4.27

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Aiming at the existing problems in SCR system due to the lack of SCR engineering design experience in the country, such as short lifecycle of SCR catalyst, high equipment erosion, high ammonia slip and SO2/SO3 transforming ratios, the principles and key techniques for SCR engineering design are introduced based on the foreign and domestic experiences as well as the summaries of continuous research and development practices. In particular, the effects and applications of the techniques are presented in details. Meanwhile, the analysis on the problems arising from the current SCR design and operation is conducted, and the technical precautions for the design are proposed to improve the application level of the SCR technology so that SCR can reach higher efficiency, better economic performance and higher reliability.

Key Technical Issues of SCR Denitrification from Coal-fired Boiler Flue Gas

ZHANG Yang, YANG Yonglong, FENG Qianwei, WANG Jianfeng, HE Sheng, ZHU Yue

2015, 48(4):  32-35.  DOI: 10.11930.2015.4.32

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Presently, the SCR flue gas denitrification projects in thermal power plants are entering into the stage of substantial commissioning services. Unfortunately since then many hidden problems from the process of project implementation have emerged gradually. Regarding the present situation of the flue gas denitrification in thermal power plants, several key technical issues are analyzed and explored based on the summary of present SCR denitrification projects, such as the selection of design parameters, the determination of performance guarantee values, the type selection of catalyst and sootblower, the fluid field design, the ash bucket setup and other related modifications. Finally, corresponding suggestions are provided and solutions to these problems are put forward.

Technical Measures to Raise the Inlet Flue Gas Temperature of SCR Reactor

XIE Weiyang

2015, 48(4):  36-39.  DOI: 10.11930.2015.4.36

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The flue gas temperature may have significant impact on the activity of SCR catalyst. The denitrification system will have to be turned off from service when the flue gas temperature falls down below the allowed minimum commissioning temperature of the catalyst. As it is designed in the conventional denitrification systems, it is not uncommon that the SCR inlet flue gas temperature is lower than the minimum catalyst commissioning temperature at low loads, which will cause the NOx emissions higher than the standard limit. In this paper, in order to make the inlet flue gas temperature of SCR reactor meet the catalyst commissioning conditions in boiler routine operation, the technical measures to raise the inlet flue gas temperature are proposed such as heating by high temperature flue gas, economizer partition arrangement, bypassing the economizer on the waterside and raising the feedwater temperature. In addition, the comparative analysis on the characteristics of these measures is also conducted.

Application of SCR Catalyst Regeneration Technology in Coal-Fired Power Plants

WANG Ping, LIN Haibo, YAO Yougong, ZENG Biqun

2015, 48(4):  40-43.  DOI: 10.11930.2015.4.40

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In this paper, the selective catalytic reduction(SCR) catalysts regeneration technology is introduced with the basic technical process and its procedure controls being summarized which provide reference for the standardization of the regeneration process and quality control. In combination with the application experience of SCR catalyst regeneration technology in Beijing and Shantou, problems in the regeneration process onsite are thoroughly analyzed and the solutions are proposed accordingly.

Influence of Ammonia Concentration in Fly Ash on Ammonia Slip Detection of Denitration Equipments

WANG Jianfeng, LIU Peiqi, YOU Liangzhou, YAN Min, ZHU Yue

2015, 48(4):  44-46.  DOI: 10.11930.2015.4.44

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In order to control the corrosion on the cold section of the air preheater caused by NH4HSO4 in the flue gas, reduce the risk of ash accretion in the air preheater and lower the consumption of denitration catalyst, the specifications on ammonia slip are quite strict for the denitration equipments. The tests on ammonia slip indicate that the ammonia contents in fly ash have great impacts on ammonia slip; the NH3 and NH4+ absorption by fly ash is the main reason for the low ammonia slip but the large pressure drop of the denitration equipments. Therefore, it is suggested that power plants detect ammonia slip and the ammonia contents in fly ash at the same time to determine whether the air preheater is blocked up.

Evaluation of SCR System Performance for the 600-MW Generation Unit of a Power Plant

CHEN Chongming, ZHANG Lijun, SONG Guosheng, ZHANG Zhiqiang

2015, 48(4):  47-49.  DOI: 10.11930.2015.4.47

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The evaluation on the denitration system performance is helpful for the system lifetime management and secure operation. Taking the SCR flue gas denitration system of the 600-MW generation unit in a thermal power plant for example, the evaluation procedures and methodologies are described. By testing the basic parameters of the SCR system, such as the denitration efficiency, the reaction temperature, the conversion from SO2 to SO3, the NH3 leakage, the pressure drop, the flue gas velocity in the catalyst and the fly ash concentration, the performance of the SCR system of the generation unit is obtained, which demonstrates excellent performance of the system. At last, suggestions on operation tune-ups are put forward to prevent the rising SO2 to SO3 conversion rate under high temperatures and high flue gas flow rate in the catalyst at heavy loads.

omparative Analysis on the Performance of High-Content Aluminium De-NOx Catalysts before and after Operation

YAN Min, CHEN Jinsheng, SONG Xiaoning, DU Zhen

2015, 48(4):  50-53.  DOI: 10.11930.2015.4.50

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In order to study the impact of excessive Al2O3 added to the catalyst carrier on the catalyst and its performance the appearance, technological characteristics, main chemical components, micro mechanisms, crystal structures and SEM between the fresh and 8 000-h-used high-content aluminum catalyst are compared and analyzed. The results show that after 8 000 hours of operation, the Al2O3 in the catalysts interacts with the SO2 and SO3 in the flue gas and turns to Al2(SO4)3 , which causes not only the catalysts to deform and break down, but also the micro specific surface area to fall off rapidly and the particles of the catalysts to sintering. Consequently, the denitration efficiency drops down sharply. Therefore, high-content aluminium de-NOx catalysts should be avoided being applied in the de-NOx reactors.

Generalion Technology

Study on Mercury Removal Technique using Modified Fly Ash Based Sorbents in Guohua Sanhe Power Plant

JIANG Congjin, LIU Qiushen, CHEN Chuangshe

2015, 48(4):  54-56.  DOI: 10.11930.2015.4.54

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In order to achieve high efficient green power generation and reduce mercury emissions from coal-fired power plants, according to the requirements of “Pilot Experiment of Mercury Control in Coal-Fired Power Plant” issued by the Ministry of Environmental Protection of China, testings on mercury control technique with fly ash based sorbent spray are carried out in Guohua Sanhe Power Plant on the basis of mercury emission concentration measurement. Through the testing, the feasibility of fly ash based sorbent spray method is verified. As a technology of high mercury removal efficiency, it can lower the mercury emission concentration further by 30%~50% with the mercury removal efficiency reaching as much as 75%~90% by taking advantage of the existing pollutant control equipments such as desulfurization, denitrification, dust removal and mercury removal. In this way, the mercury emission concentration in the flue gas can be lowered down far less than the national standard. Hence, the application of fly ash based sorbent spray method shows a prospect of popularization.

Study on Mercury Emission Characteristics during Coal Slime Isothermal Heating Experiments

GAO Zhengyang, FAN Yuanzhou, CHEN Songtao, YIN Libao, CHEN Chuanmin

2015, 48(4):  57-60.  DOI: 10.11930.2015.4.57

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In order to utilize coal slimes substantially and comprehensively, studies on mercury releasing characteristics in coal slime combustion should be conducted. In this paper, the isothermal heating experiments on two kinds of selected coal slimes are carried out to investigate the impact of heating time and temperature on mercury releasing characteristics in the normal air. The experiment results indicate that the mercury in coal slimes begins to release at about 200 ℃ and is released substantially between 200 ℃ and 400 ℃. When the temperature gets higher than 400 ℃, it is released almost completely. The higher the temperature, the faster mercury is released and the shorter time period is needed to achieve the maximum mercury emissions. In addition, the isothermal experiment shows some differences between the mercury release courses of the two slimes, which means that different raw coal sorting process may result in different mercury distribution in slimes.

Application of New Type of Low NOx M-PM Burner in 700 MW Unit

YUAN Li, ZHANG Dianping, YU Weiquan, GONG Jixing, YASUHIRO Ukeguch, KAZUHIRO Takeuchi,KAZUHIRO Domoto, KEIGO Matsumoto

2015, 48(4):  61-65.  DOI: 10.11930.2015.4.61

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The applications of Mitsubishi ultra-low NOx burner (the M-PM burner) in two 700-MW subcritical boilers in Zhuhai Power Plant are introduced in this paper. The M-PM burner is newly developed based on the A-PM low NOx burner by Mitsubishi, which is characterized as better ignitability, flame holding performance and impressive effect on NOx emission reduction. After boiler burner retrofitting, while the Shenhua coal is burned in the boiler, the concentration of NOx emission is reduced from 360 mg/m3 to 136 mg/m3, about 62% less than before. In addition, the problems of low boiler steam temperature, large heat deviation of flue gas and high operating angle of burner are solved, and the boiler efficiency is also improved slightly.

Transient Calculation of Deaerator and Control Scheme of Cavitation Prevention for AP1000 Nuclear Power Plants

GU Xianqing, GAO Zhiqing, TU Pan, CHENG Xueqing

2015, 48(4):  66-70.  DOI: 10.11930.2015.4.66

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In order to formulate a reasonable NPSH(net positive suction head) control scheme under load rejection conditions of AP1000 nuclear power plants and effectively prevent cavitation in the main feed water pumps during the operation, the cavitation mechanism and the control logics of deaerator water level and pressure are analyzed and the model for deaerator transient calculation is established based on the collected data. The calculation results show that with the setting value of the condensate flow limit at 30% and the deaerator transient pressure decreasing rate at 0.001 77 MPa/s, the NPSH requirements for the main feed water pumps can be met. Therefore, the cavitation prevention schemes and optimization methods for typical load rejection conditions are proposed as the guidance for commissioning and operation to improve the safety of nuclear power plants.

Modification of Single Tube Chimney Desulfurization Antisepsis in Thermal Power Plants

XIE Bao’an

2015, 48(4):  71-75.  DOI: 10.11930.2015.4.71

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The structure of the old-type single tube chinmney is unfit for the wet FGD flue emission in the coal-fired power plants with no GGH equipped and it needs modification. Based on the practice and study of the chimney leakage and corrosion prevention modification in over 40 thermal power plants using the wet desulphurization technology, and in consideration of the safety and reliability, convenience and adaptability of inspection and maintenance, the modification plan on leakage and corrosion prevention of the single tube chimneies in service is proposed This proposal is suitable for the wet FGD without GGH in China, in which the plan of a new exhaust inner cylinder with the titanium clad steel lining installed inside the concrete chimney is recommended rather than that of adding brick masonry lining or anti seepage and antisepsis layer on the inner surface of the original chimney.

Power Syslem

Development and Application of Measurement Device for DC Partial Discharge

SHA Yanchao, ZHOU Yuanxiang, NIE Dexin, DENG Jiangang, LIU Zehong, LU Licheng

2015, 48(4):  76-82.  DOI: 10.11930.2015.4.76

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With the development of UHVDC transmission engineering in China, the safety and reliability of such electrical equipment as converter transformer is particularly important. DC partial discharge is a prominent indicator of insulation defects, and its test can help prevent dielectric breakdown of DC power transmission equipment. Based on the DC partial discharge principle, a DC partial discharge test system was established to monitor the insulation status of converter transformers. Characterized by strong anti-interference ability, and high-speed, persistent and real-time capability in data acquisition, the proposed system can record the DC partial discharge signal efficiently and entirely. The system’s performance was verified through a typical oil-paper compound insulation model. The practical results show that the proposed system can effectively and conveniently measure the DC partial discharge time-domain signal of oil-paper insulation. Time-frequency analysis and statistical analysis of DC partial discharge signal indicates that the statistical characteristic parameters in the model of same electrodes varies significantly with time and can be used to forecast the severity caused by partial discharge, and the the statistical characteristic parameters in the model of different electrodes have the similar distribution tendency and can be used to estimate the defect types. The measuring systemt is expected to be implemented widely in testing DC power transmission devices in China.

AGC Power Control Strategy Model of UHVAC Tie-Line

HU Hao, ZHONG Wuzhi, SONG Xinli, ZHUO Junfeng, CHEN Yanbo, LIU Tao, YE Xiaohui, MA Jin

2015, 48(4):  83-89.  DOI: 10.11930.2015.4.83

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In recent years, the operation ultra-high voltage(UHV) AC projects in China has brought about new challenges to the effective control of automatic generation control system. Digital simulation is an effective means for system analysis. But in the full dynamic simulation program, no control strategy model is suitable for UHV tie-line. In order to dynamically simulate the active power control of the 1 000 kV UHV AC tie-line between the north China power grid and the central China power grid, a new T standard-based automatic generation control(AGC) strategy model is proposed based on the T standard - the AGC performance assessment standard, the controlling requirements of the UHVAC tie-line and field operational experience, the CPS control strategy model, the product of the UHV AC tie-line bias and the area control error(ACE), and the characteristics of the product in the receiving-end system and the sending-end system. The new model is achieved in the full dynamic simulation program (PSD-FDS) and is proved to be effective through simulation case study based on field data. The result of the case study confirms that the T standard strategy has better effectiveness than the CPS standard strategy.

Design of Adaptive Coordination Control of Multiple TCSC

XIAO Liwu, QI Guigang, LI Canbing, CAO Yijia, KUANG Yonghong

2015, 48(4):  90-94.  DOI: 10.11930.2015.4.90

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The coordinated operation of multiple thyristor controlled series compensator(TCSC) can improve the capability of the power transmission. However, the mutual effects of TCSCs may decrease the transient stability. In this paper, a new adaptive control scheme is designed through dynamic adaptive adjustment of the parameters of multiple TCSCs to avoid the negative interactions of TCSCs. By using energy function to evaluate the stability of the TCSC, a differential observer adaptive TCSC controller is then designed, which uses expert controller and neural network to adaptively adjust the proportion integral differential(PID) parameters. The effectiveness of the proposed control scheme was demonstrated through simulating a two-area and four-machine power system. A comparison of the proposed controller, the adaptive FACTS controller and the BP-PI controller (back propagation-proportional integral controller) was conducted, which shows that the adaptive FACTS controller can improve the transient stability of power system.

Research on Three-Phase Shunt Reactor Compensation of UHV Transmission Lines

SHANG Liqun, CHEN Qi,

2015, 48(4):  95-100.  DOI: 10.11930.2015.4.95

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The shunt reactor has the function of limiting the power frequency overvoltage, inhibiting secondary arc current, avoiding the resonance overvoltage and keeping reactive power balance in the ultra high voltage(UHV) transmission line. The characteristics of the shunt reactor for limiting power frequency overvoltage are studied firstly, which shows that the shunt reactors can only effectively suppressed the load shedding power frequency overvoltage where the shunt reactors are located. In order to ensure the voltage along the line controlled in the allowable range, sectional compensation should be used for the line of more than 550 km in length. Then an analysis is made on the principle of the secondary arc current and the non full phase resonance and their relationship with the shunt compensation degree. Finally, the configurations principles and calculation methods of shunt reactor are proposed.

Multiple WAMS-Based Coordinated Analysis and Monitoring of Low Frequency Oscillations

DUAN Gang, ZHAN Qingcai, YANG Dong, XIE Xiaodong, WU Jingtao, XIAO Xiaogang,WANG Jian, LIU Tao

2015, 48(4):  101-106.  DOI: 10.11930.2015.4.101

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For low frequency oscillation spanning several control areas, local WAMS cannot identify the oscillation mode if only according to the information obtained in its own control area. A coordinated analysis and monitoring method for low frequency oscillations is proposed based on the information from several wide Area Measurement Systems (WAMS). For the power system with several WAMS control centers, one of the control centers is selected as the master WAMS, the others are treated as slave WAMS. In case that one of the WAMS detects a dangerous low frequency oscillation occurring in its control area, it will trig the coordinated analysis of low frequency oscillation based on the data from all WAMS. The slave WAMSs make frequency analysis of their own measurements respectively, and send the results to the master station. The master station synchronizes the analysis results from different WAMS and different frequency analysis methods, and then makes coherent group of the buses and calculate the relative contributions of key buses to the power oscillation. The analysis result is then returned to the slave WAMS. By this method, each control center can clearly understand its role in a wide area when low frequency oscillation involves several control centers, which will help to control the low frequency oscillation.

Study on Strength-Difference Forged Hubbed Flange Test

HE Changhua, XING Haijun, LI Qinghua, WU Jing

2015, 48(4):  107-112.  DOI: 10.11930.2015.4.107

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In recent years, the forged hubbed flange has been widely used on steel tube tower of power transmission line. However, the hubbed flange is of single specification and mismatch with steel tube in stress(i.e., the steel tube with relatively low bearing capacity is connected to the forged flange with relatively high bearing capacity), which makes the steel tube tower uneconomical. Based on the existing design method and practical use of hubbed flange, a strength difference arrangement scheme is determined for forged flange according to the stress characteristics of the members of steel tube tower and the specification bank for steel tube. The stress characteristics of flange and bolt are tested and the rationality of strength-difference-based arrangement of forged hubbed flange and the stress correction coefficient of bolts are verified through the axial tensile test in which the specimen of strength-difference-arranged Q420 high-strength buttwelded forged hubbed flange is used. The test can provide the fundamental data for the design of steel structure in future.

Insight into Demand Response in PJM Interconnection and its Enlightenment to China

CHEN Xinyi, YAN Zheng, WEI Xuehao, SONG Yiqun, HAN Dong

2015, 48(4):  113-120.  DOI: 10.11930.2015.4.113

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As an essential tool to enhance efficiency and reliability of global power grids, demand response can be an ideal breakthrough point in the construction of modern strong smart grid in China. This paper explores the implementation of demand response in PJM Interconnection and analyzes related benefits. A broader approach to demand response in PJM, price responsive demand(PRD), is investigated from the aspects of system operation and market mechanism. Based on the operational experiences of PJM and the current status of Chinese power grids, several measures are suggested in order to implement demand response in China.

Improvement and Application on the Meteorological Geographical Method in the Drawing of Galloping Region Distribution Map

LI Junhui, CHENG Yongfeng, GONG Jiangang, ZHU Kuanjun, ZHANG Lichun, LIU Bin

2015, 48(4):  121-126.  DOI: 10.11930.2015.4.121

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Power grid galloping region distribution map is basis of prevention and treatment of transmission lines galloping during construction and operation phases. It plays an important role in power grid operation safety and stability. In addition to frequency method, the meteorological geographical method is used widely in SGCC as a drawing method for galloping region distribution map without consideration of influence from actual lines. In order to reduce galloping meteorological calculation error resulted from daily meteorological data, a new drawing method based on hourly meteorological data is proposed. The application results in Zhejiang province shows the feasibility of proposed method.

Development of Capacitive Current Measuring Instrument Based on PLC for Power Distribution System

YANG Yunyang, XIA Bin, ZHANG Yu, ZHOU Da, ZHANG Chunhui

2015, 48(4):  127-130.  DOI: 10.11930.2015.4.127

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Accurate measurement of capacitive current of resonant grounding system determines the compensation effect of Petersen coil. However, key to distribution system capacitive current measurement by maximum displacement voltage method is to find the neutral point maximum displacement voltage accurately. A capacitive current measuring device is designed based on Programmable Logic Controller (PLC). The ideas of automatic system operation tracking, capacitance current measuring by close-loop control are explained. The experimental results show that proposed measurement device is able to measure system capacitive current accurately. The device is also able to monitor system neutral point displacement voltage, arc suppression coil loop current and number of energized feeders in real time. Based on current system operation condition, the device can track system operation closely and improve compensation effect of Petersen coil in system.

Adaptive Harmony Search Algorithm for Optimal Network Reconfiguration

RONG Desheng, HAH Shumin

2015, 48(4):  131-136.  DOI: 10.11930.2015.4.131

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The harmony search algorithm(HSA) is affected by initial parameter values when it is used to search the optimal scheme for distribution network reconfiguration. Therefore, an adaptive harmony search algorithm(AHSA) is proposed and improved by adding local search, thus enhancing the optimization performance of the algorithm. A mathematical model of distribution network reconfiguration is built for the purpose to reduce the active and reactive power loss, and a load flow calculation is made for the network with the forward and back/forward substitution method based on node-layer. The IEEE 69-bus radial distribution system is simulated and the simulation result is compared with that calculated with the harmony search algorithm and genetic algorithm (GA), which shows that the proposed algorithm has less iterative times and better convergence effect. The adaptive harmony search algorithm is proved feasible through its application in distribution network reconfiguration.

Assessing Harmonic Impedance and the Harmonic Emission Level Based on Partial Ridge Estimate

CUI Yangliu, MA Hongzhong, TANG Yiming, GONG Jiewei, WANG Taoyun

2015, 48(4):  137-140.  DOI: 10.11930.2015.4.137

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A new method for assessing harmonic impedance is presented based on partial ridge regression. This method improves estimation accuracy of harmonic impedance. Using equivalent circuit consisted of both system side and customer side, harmonic voltage and current can be measured synchronously at public connection(PCC). Regression coefficients is deduced through regression equation and ridge parameter is calculated by ridge trail method. The proposed method generates smaller estimation error and overcomes estimation problem resulted from generalized ridge estimation method. Simulation results proved that proposed method is useful to analyze harmonic impedance.

Application of Static Synchronous Compensator Device in Hainan Power Grid

GUI Yongguang, LIU Guiying, SU Shiping, JIA Xuerui, LIU Qingfeng, ZHENG Gang

2015, 48(4):  141-146.  DOI: 10.11930.2015.4.141

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With the load growth and network topology change, transient voltage stability is becoming increasingly serious in Hainan power grid. In order to compensate reactive power shortage in Haikou area during full blackout, the application prospect of STATCOM in Hainan power grid is studied. Based on network frame structure in year 2014, different STATCOM configurations are simulated and compared. The dynamic support function of STATCOM to transient voltage is demonstrated. The study result provides preliminary guidance for practical application of STATCOM in Hainan power system.

Digital & Analog Electro-Hydraulic Control System in Isolated Grid

TIAN Jun, WU Tianming, XIE Guoqiang, WANG Junxiang, LI Mingjun, LI Bo

2015, 48(4):  147-150.  DOI: 10.11930.2015.4.147

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The paper analyzes the characteristics and relations of primary frequency modulation and secondary frequency modulation of steam turbines in isolated grid. A digital & analog electro-hydraulic control system is researched, which, through the primary frequency modulation module and valve curve module, can realize the quick hardware frequency modulation, improve the response speed and stability of the primary frequency modulation and reduce the frequency adjustment period. The hardware and software features of the system is described and the dead band of primary frequency modulation is canceled. It is proved in practice that the united control system of hardware primary frequency modulation and software secondary frequency modulation is feasible.

New Energy

A Distributed Wind Farms Siting Method based on Fuzzy Analytic Hierarchy Process

YANG Jun, ZENG Zhaoqiang, SUN Qiuye, HUANG Xu

2015, 48(4):  151-155.  DOI: 10.11930.2015.4.151

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Wind farms siting is foundation and critical point of wind farm construction and operation. In order to improve the consistency checking and adjusting problem in analytic hierarchy process(AHP), a distributed wind farms siting method based on fuzzy AHP is proposed. Firstly, the fuzzy AHP is explained briefly. Next, the siting analysis method based on fuzzy AHP is introduced with consideration of different evaluation indexes such as scintillation, lighting and noise effect. Wind farm candidates can be sorted by proposed method. The application result in engineering project proves effectiveness and validity of the proposed siting method.

Table 2 Estimation accuracy of three forecasting methods Method for Selecting Similar Days in Short-term Load Forecasting of Microgrid

ZHANG Lingling, YANG Mingyu, LIANG Wu

2015, 48(4):  156-160.  DOI: 10.11930.2015.4.156

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The small base load, high fluctuation and randomness of the microgrid increase the difficulty of short-term load forecasting. Scientific and proper selection of similar days can improve to some extent the effectiveness of the short-term load forecasting. Firstly, the factors which may affect selecting similar days are analyzed in this paper. Then, in view of the characteristics of microgrid load, a novel method for selecting similar days is proposed in microgrid short-time load forecasting based on load point scale. The proposed method considers the cumulative effects of the weather factors, the continuity and periodicity of short-term load and the effects of time distance, and its evaluation function of day character similarity takes into account of day similarity and partial similarity and introduces the time factor. Thus, the proposed method overcomes the subjectivity of the traditional method which is based on personal experience. Case study demonstrates that the proposed method can improve the accuracy of short-term forecasting and can be applied in practice.