Table of Content

18 February 2016, Volume 49 Issue 2

Previous Issue    Next Issue

Generation Technology

Effects of Preheating and Post-Weld Heat Treatment on the Mechanical Properties of T23 Steel Weldment

LI Xiqiang, WANG Xue, YANG Chao, GE Zhaoxiang, YANG Xianbiao, REN Yaoyao

2016, 49(2):  1-5.  DOI: 10.11930/j.issn.1004-9649.2016.02.001.05

Asbtract ( )   PDF (7468KB) ( )  

References | Related Articles | Metrics

In order to optimize the welding techniques of T23 steel and avoid the cracking in its welded joints in the water-wall of ultra supercritical(USC) boilers, the hardness and toughness are tested for the joints welded with four different welding techniques, which are the ones of without preheating and post-weld heat treatment(PWHT), PWHT without preheating, preheating without PWHT, preheating and PWHT. The preheating is set at 150 ℃ and PWHT being at 740 ℃ for 0.5 h. The changes of their microstructures are also observed. The results show that preheating has little effect on the hardness of the weldments, but it makes the grain size and width of the over-heated zone enlarge, which lowers the toughness of the weld metal and the heat-affected zone (HAZ). PWHT significantly reduces the hardness of the weld metal and HAZ, and improves the toughness of the weld metal even though it has little effect on that of HAZ. In order to avoid the occuring of cold cracking, preheating with the temperatures below 150 ℃ or no prheating is recommended for the welding of T23 steel. For the sake of long-term operating properities of the T23 steel joints, PWHT is still necessary for the improvement.

Diagnosis and Analysis of Application Faults of Profibus Fieldbus Technology in Thermal Power Plants

HAN Chao, JIA Jing

2016, 49(2):  6-9.  DOI: 10.11930/j.issn.1004-9649.2016.02.006.04

Asbtract ( )   PDF (1437KB) ( )  

References | Related Articles | Metrics

The process control system based on Profibus fieldbus technology is applied in a new 1 000-MW thermal power plant. During the stages of installation and debugging, some faults appear in the individual fieldbus devices, such as unavailable communication with the master station, unstable fieldbus communication and unavailable remote control when the communication is established. In this paper, the classification and cause analysis on these faults are conducted. Based on the diagnosis results, the treatments are carried out in the aspects of network segment design, physical connection and parameter settings. In addition, the preventative self diagnostic measures are put forward for the application of the fieldbus devices. After the optimization, the voltage of the fieldbus communication network signals has become stable without any illegal messages, which safeguards the stable operation of the fieldbus control system.

The Innovation and Implementation of CFTRVO Test for CPR1000 Units

ZHAI Bajing, YAN Mingjing, BAI Xuan

2016, 49(2):  10-13.  DOI: 10.11930/j.issn.1004-9649.2016.02.010.04

Asbtract ( )   PDF (702KB) ( )  

References | Related Articles | Metrics

The Yangjiang Nuclear Power Project undertakes the mission of equipment localization and has the highest equipment localization rate. The debugging of RIS/EAS pumps and motors is a most tough issue. The EAS/RIS system is important not only for the project proceeding nodes, such as nuclear circuit cleaning (NCC) and cold functional test with reactor vessel open (CFTRVO), but also for the cold functional test(CFT), hot functional test(HFT) and pre-criticality test(PCT). The key of the nuclear safety is that the EAS/RIS pumps and motors should meet the related nuclear safety standards. However, as the first such project that adopts China-made pumps and motors, some problems exist in the Yangjiang project, such as insufficient water head, bad airproof, burrs in hydraulic parts and high vibrations. Along with the debugging progressing, the completion of the dome and pits of the reactor room has been making it difficult to solve these problems. Therefore, the open vessel CFT is optimized so that the performance of EAS/RIS pumps is verified successfully before the completion. The optimization, which can ensure the nuclear safety, has saved the costs substantially and can provide reference for the debugging of other systems.

Combustion Adjustment of Boiler with Medium-Speed Mill Firing High-Moisture Lignite

FU Lin, LIU Haishan, YI Xilai

2016, 49(2):  14-17.  DOI: 10.11930/j.issn.1004-9649.2016.02.014.04

Asbtract ( )   PDF (860KB) ( )  

References | Related Articles | Metrics

This paper focuses on the issues of the difficult dust control, spontaneous combustion of accumulated powder, explosions of coal pulverizing system and steam dryer, and coal bunker blockage caused by the steam drying processing of high-moisture(60%~63%), high- volatile and low calorific value lignite in Shenhua Guohua(Indonesia) Sue Power Generation. Through the test on increasing the raw coal moisture contents at the steam dryer outlet, the issues are thoroughly solved when the moisture contents are raised from about 40% to 52%~55%. However, the increase of raw coal moisture contents causes the insufficient pulverizer output, coal powder conveying pipeline blockage and boiler instable combustion problems. Through the pulverizer and combustion optimization tests, the boiler can fire the high- moisture(52%~55%) lignite successfully. Moreover, the optimization tests also exhibit that there will be no blockage when the pulverizer outlet temperature is over 57 ℃, and other problems, such as low primary air temperature and insufficient combustion, will also get controlled as the primary air ratio is under 45%. Consequently, the boiler combustion efficiency reaches as high as 90%, which realizes the goal of safe, stable and economic operation when the boiler with medium-speed pulverizer fires high-moisture lignite.

Research and Application of Counterflow Offline Cleaning Technology for EDI Modules

JIANG Xiaoyan, XU Zhen, ZHAI Shaojing, YU Yaohong, YANG Yonggang, LI Yajuan

2016, 49(2):  18-20.  DOI: 10.11930/j.issn.1004-9649.2016.02.018.03

Asbtract ( )   PDF (624KB) ( )  

References | Related Articles | Metrics

Recently, the electric demineralizer (EDI) technology has been gradually applied in the water treatment systems of power plants. It is becoming urgent to solve the issue of blockage and cleaning of EDI modules. This paper introduces the operation mechanism and infrastructure of EDI, analyzes the major cause contributing to deposit block, then puts forward corresponding design for cleaning and presents the development of an offline cleaning device for EDI modules. From the on-site application it is observed that by taking advantage of this device backwash cleaning can be conducted with better performance over the traditional cleaning. The offline chemical cleaning in combination with backwash cleaning achieves good effects. Specifically, the output of membrane modules is improved by over 60% after cleaning.

An Identification Method of Moment of Inertia Based on Generator Load Voltage Step Test

WU Kuayu, LU Cencen, GU Yilei, XIONG Hongtao, ZHAO Yiyan

2016, 49(2):  21-25.  DOI: 10.11930/j.issn.1004-9649.2016.02.021.05

Asbtract ( )   PDF (1924KB) ( )  

References | Related Articles | Metrics

This paper introduces definition and relationship of moment of inertia, inertia time constant and flywheel moment, and their effect on the analysis of power system stability. The conversion among these parameters is analyzed and summarized for different simulation software including PSASP, PSD-BPA and PSS/E. Mathematical relationship between generator mechanical inertia parameters and local oscillation frequency is derived from small signal stability model. An identification method of moment of inertia combining with generator load voltage step test and simulation is proposed. Finally, effectiveness and applicability of proposed method is verified by comparing parameter calculation and load rejection test data on an actual 600 MW steam turbine-generator.

Testing Study on the Low Voltage Ride-Through Capability of Thermal Power Unit Auxiliary Machinery Variable Frequency Speed-Regulating System

TANG Wei, LIU Ludeng, YIN Jun, LI Gang

2016, 49(2):  26-30.  DOI: 10.11930/j.issn.1004-9649.2016.02.026.05

Asbtract ( )   PDF (2278KB) ( )  

References | Related Articles | Metrics

In order to accurately analyze the low voltage ride-through capability of the thermal power unit variable frequency speed- regulating system for avoiding the equipment damage, unit stop or the sharp drop of unit output power caused by voltage sag in a short time (less than 5 s) or power supply interruption of the variable frequency speed regulation system of important auxiliary machinery of thermal power unit(such as the coal feeder, pulverized coal feeder, air preheater etc.), two methods are proposed for testing the low voltage ride-through capability of the thermal power unit variable frequency speed-regulating system by using the voltage sag generator. A comparative study of the two methods can provide a theoretical reference for testing the low voltage ride-through capability of the variable frequency speed regulation system. The practical application has proved the feasibility and validity of the proposed methods.

Power System

Derivation of Equivalent Slenderness Ratio of Cruciform Angle Section Members in Transmission Towers

HAN Junke, LI Zheng, ZHANG Chunlei, LIU Haifeng

2016, 49(2):  31-35.  DOI: 10.11930/j.issn.1004-9649.2016.02.031.05

Asbtract ( )   PDF (1737KB) ( )  

References | Related Articles | Metrics

Based on elastic bending buckling theory of axial compression components, the equivalent slenderness ratio of compression components in transmission tower cruciform angle section with considering of shearwas effects is calculated. Cruciform anglebolted by filler plate is simplified as fixed and pinned connection model. According to limb deformation, the equivalent slenderness ratio of virtual axis are deduced. In accordance with actual layout and connections of cruciform angles in transmission towers, formulas of equivalent slenderness ratio related to virtual axis of cruciform angle are derived. Finite element method is used to analyze effect of cruciform angle limb clearance on buckling bearing capacity.

Design and Research on Hybrid Steel Tube and Angle Steel Tower for 1 000 kV UHV Transmission Line

ZHANG Zifu, ZHU Binrong, YANG Jingbo, GAO Yuan, WANG Xibo

2016, 49(2):  36-40.  DOI: 10.11930/j.issn.1004-9649.2016.02.036.05

Asbtract ( )   PDF (2301KB) ( )  

References | Related Articles | Metrics

Almost all the towers of 1 000 kV UHV double-circuit transmission line in China used steel tube towers because of steel tube tower's obvious advantages against an angle steel tower. However, a steel tube tower requires complex manufacturing process and high quality control, and is difficult to construct. Even after a standardized design being adopted, the output of steel tube towers remains being challenged in meeting the increasing demand for large transmission towers. The paper presents a new plan and design of a hybrid tower with both steel tube and angle steel that meets the design conditions of the UHV steel tube tower for Anhui Electricity to East transmission project. The angle steel is used for all members above the lower cross arm with the rest of the hybrid tower using steel tube. The paper optimizes the transition node between the angle steel and the steel tube of the tower body, compares the dynamic characteristics between the hybrid tower and the steel tube tower, and conducts economic analysis on key economic parameters. The paper demonstrates the feasibility of using the new type hybrid tower to meet safe and stable operation of the transmission line, which significantly increases the proportion of angle steel used in the tower with corresponding reduction in the use of the steel tube, therefore effectively addresses the issue of insufficient output.

Study on the Influence of Typhoon Wind Parameters on Mechanical Characteristics of Transmission Tower

ZHANG Hongjie, YANG Jingbo, YANG Fengli, ZHANG Zhijun, ZHU Ledong

2016, 49(2):  41-47.  DOI: 10.11930/j.issn.1004-9649.2016.02.041.07

Asbtract ( )   PDF (2734KB) ( )  

References | Related Articles | Metrics

According to the wind load equation of transmission tower, the parameters of the mean wind speed, wind profile coefficient and turbulence intensity are believed to be the main influencing factors of wind load. Moreover, all above-said parameters, as well as the wind load and the static response, vary during the traveling of typhoon. Therefore, in order to identify the most influential factors of these three wind parameters, the wind fields at five different time interval of the typhoon Khanun are picked out firstly. Through the mechanical analysis, it can be found that the mean wind speed has significant influence on the mechanical characteristics of transmission tower. Then, under the condition of the same wind speed, a large-span transmission tower is chosen for case study. Through comparison of the wind load and mechanical characteristics, it is demonstrated that the wind profile coefficient may have greater influence and may induce tower collapse. Finally, by analyzing the member bar stress ratio distribution along the tower height, the weak point of transmission tower under typhoon is identified. Some reinforcing measures are proposed in this paper, which are proved to be effective by another widely used tower type.

Steady-State Temperature Field of HVDC Cable Joint and Its Influencing Factors

LI Zhaohong, YANG Lin, TIAN Ye, LI Licheng, FU Mingli, ZHUO Ran

2016, 49(2):  48-53.  DOI: 10.11930/j.issn.1004-9649.2016.02.048.06

Asbtract ( )   PDF (3800KB) ( )  

References | Related Articles | Metrics

Temperature is an important parameter to reflect the operating state of a cable joint. Different from AC, the change of temperature in the insulation layer of HVDC cable joint impacts the distribution of electric field and the accumulation of space charge. As such research attention is required not only on the temperature of cable joint conductor but also the temperature of the insulation layer and the change in temperature difference between interior and exterior surfaces of the insulation layer. A simplified model of the HVDC XLPE cable joint is created and the finite element software is used to analyze the distribution of steady state temperature in the insulation layer and the respective impacts of the conductor current and the surface temperature of the joint on the temperature of the joint conductor, the temperature distribution of XLPE insulation and SIR reinforced insulation, and the temperature difference between interior and exterior surfaces of the insulation layer. The results showes that in the case of HVDC, the conduct current has considerable impacts on all three parameters. Moreover, the exterior surface temperature of the cable joint affects the maximum temperature of the conductor, the maximum temperature of the insulation layer, and the temperature distribution in the insulation layer, but has minimal effect on the temperature difference between interior and exterior surfaces of the insulation layer.

Measurement of Transmission Line Galloping Based on Monocular Visual Analysis Method

SHAO Yingbiao, YANG Wei, LV Zhongbin, SONG Gaoli, XIE Kai, ZHENG Hanbo

2016, 49(2):  54-60.  DOI: 10.11930/j.issn.1004-9649.2016.02.054.07

Asbtract ( )   PDF (3406KB) ( )  

References | Related Articles | Metrics

Monocular visual analysis method is applied in measuring parameters of transmission line galloping in this paper. The comparison experiments on gallop test machine and small test line demonstrate high measurement accuracy of proposed method. The mismatch of frequency and amplitude measurement is less than 1% and 3%, respectively. The experiment data shows applicability and effectiveness of proposed method. Detailed analysis of two 500 kV galloping events of real size test transmission line are performed. Some parameters are obtained including amplitude, frequency, order, dynamic trajectories and two-dimensional section of feature points. Those results provide reference for design of 500 kV transmission line structure and anti-galloping device. The method and conclusion in this paper provide basic method and data support for galloping prevention and galloping mechanism study.

Research and Application of Massive Picture Data Refresh Method in Power Dispatch SCADA System

YE Fei, LI Changjun, LI Qipeng, WANG Heng, MEI Zheng, LI Junliang, PIAO Lin, MA Zhibin

2016, 49(2):  61-66.  DOI: 10.11930/j.issn.1004-9649.2016.02.061.06

Asbtract ( )   PDF (2025KB) ( )  

References | Related Articles | Metrics

The traditional method of picture data refresh typically use request / response mode. In large amount of picture refresh case, this method has some problem including data inefficiency and heavy SCADA server load. Method of Massive Picture Data Refresh(MPDR) is proposed in order to overcome those problems. The working principle and architecture of the MPDR method are described first. Key technologies of proposed method, including picture message model, picture data cache and picture subscription management are explained. The MPDR method has been successfully applied in the D5000 system and deployed in the dispatching and communication center of State Grid. The field application proves the efficiency of MPDR method under large amount of picture data refresh requirement. It can be used to ensure safe and stable operation of power SCADA system.

Forecasting and Studies on Load Characteristics of Nanjing Center Area Power Network

ZHU Bin, JIANG Ning, HUO Xuesong, WANG Yong, WU Haiwei, SUN Kaiqi, HU Shuang

2016, 49(2):  67-72.  DOI: 10.11930/j.issn.1004-9649.2016.02.067.06

Asbtract ( )   PDF (4523KB) ( )  

References | Related Articles | Metrics

Load characteristics and various contribution factors in city distribution network are analyzed. In order to overcome edge effect problems in Elman neural network of load forecasting method, a new short-term forecasting model is proposed by training strategy improvement. This model adopts multiple-hidden-layer networks and dynamic neural networks element as forecasting method, generating results by comparing different forecasting results of neural networks element. The testing results prove the adaptability and accuracy of proposed method under different conditions. It provides a feasible alternative for short-term forecasting of city central area power network.

Performance Assessment of Used Grain-Oriented Silicon Steel Sheet in Distribution Transformer and Its Inspection Technique

CHENG Ling, WEI Jianxiao, MA Guang, YANG Fuyao, CHEN Xin, ZHU Chengzhi

2016, 49(2):  73-77.  DOI: 10.11930/j.issn.1004-9649.2016.02.073.05

Asbtract ( )   PDF (2935KB) ( )  

References | Related Articles | Metrics

The grain-oriented silicon steel, once being processed into transformer core, has a direct impact on power network’s energy use and safety. This paper provides a thorough evaluation of the properties of used silicon steel. Our results show that serious product quality issues exist with used silicon steel sheet. For sample sheets from three regions of A, B and C, the highest core loss (P1.7) was 1.91 W/kg (high no load losses), the highest magnetostrictive coefficient (λ1.7T) was 3.9×10-6 (high noise), the lowest surface insulation resistance was only 1~2 Ω·cm2 per sheet(low insulation between sheets is a direct threat on the safety of the steel core), and the coating adhesive property was at D level or worse. The sustained use of used silicon steel in grid connected transformers presents a serious quality and safety concern. Whether or not the transformer core was made from used silicon steel can be determined through a comprehensive inspection of the surface quality, magnetic performance, coating property and microstructure of the silicon steel sheet.

Research on Adaptive Grounding Distance Protection in Grid with Photovoltaic Power Plant

ZHAI Xue, , LIN Tao, , WU Junpeng, , GUO Ziyu, , XU Xialing

2016, 49(2):  78-83.  DOI: 10.11930/j.issn.1004-9649.2016.02.078.06

Asbtract ( )   PDF (1884KB) ( )  

References | Related Articles | Metrics

With the development of smart grid, photovoltaic power is gaining wide applications. Integration of a photovoltaic power plant (PV plant) into the distribution network will change the topological structure of the 110 kV system. Meanwhile, the equivalent impedance of PV plant varies with the changes of operation modes, which may affect the original distance protection scheme. The relationship between the measured impedance of distance protection and the equivalent impedance of PV plant is derived based on the operation characteristics of PV plant. The impact mechanism of PV plant on the measured impedance of distance protection is reviewed. A method of adaptive grounding distance protection based on the measured impedance correction is put forward according to the real-time equivalent impedances of PV plant which is calculated in different operation modes. As a result, the proposed protection is supposed to be suitable for changes of operation condition of PV plant. Furthermore, the protection setting values are universally suitable in different operation modes. A typical distribution network with PV plant was simulated and analyzed in PSCAD/EMTDC, and the results have demonstrated the effectiveness and superiority of the proposed protection method.

Ground Temperature and Deformation Monitoring and Analysis of Tower Foundation for Qinghai-Tibet DC Transmission Engineering in Permafrost Regions

HUANG Yuansheng, LI Peng, YAN Fuzhang, WANG Yanbing

2016, 49(2):  84-89.  DOI: 10.11930/j.issn.1004-9649.2016.02.084.06

Asbtract ( )   PDF (5376KB) ( )  

References | Related Articles | Metrics

Due to the bad engineering geological condition of permafrost regions in the Qinghai-Tibet Plateau, immeasurable economic and technical problems are brought for Qinghai-Tibet DC transmission engineering. Ground temperature and deformation of eight sites and ten tower foundations with different soil types and foundation forms and thermal probes treatment were monitored and measured, the change laws and influential factor of ground temperature and deformation for tower foundation is analyzed, and also long-term stability is predicted in this paper based on the monitoring results, which provides data for design and stability analysis of tower foundation in permafrost regions.

DC Bias Active Defense System for AC Power Grid

XU Bichuan, WEN Xishan, ZHANG Lu, PAN Zhuohong, CHEN Wenguang, WEI Jian

2016, 49(2):  90-95.  DOI: 10.11930/j.issn.1004-9649.2016.02.090.06

Asbtract ( )   PDF (4659KB) ( )  

References | Related Articles | Metrics

In order to effectively prevent damage caused by DC bias, an active defense system for AC power grid is proposed. The system includes not only DC bias current risk evaluation and improvement for current network, but also evaluation and optimization for future grid expansion. A transformer DC bias evaluation method is proposed based on equivalent winding DC current. Taking Hubei power grid for example, winding DC currents of all transformers in Hubei power grid are reduced to below 10 A by adjusting operation method. Equivalent winding DC current of Yangjiawan Station drops by 62.4%, and that of Anfusi Station drops by 53.2%. Crossover and mutation of genetic algorithm module is used for optimizing stationing of DC bias suppression measures in Hubei power grid, after which the equivalent winding DC current of the whole system decreases by 50.95%. Artificial colony algorithm is used for optimization of substation site selection to minimize the DC bias risk of the new-built substation. Equivalent winding DC current of Chaoyang substation decreased by 71.3% after site optimization.

Research of Main Connection of 500 kV High Temperature Superconducting Fault Current Limiter

WANG Chuncheng, DING Wei, GUO Fang, CHEN Huixiang, ZHU Haojun, WEI Bin

2016, 49(2):  96-101.  DOI: 10.11930/j.issn.1004-9649.2016.02.096.06

Asbtract ( )   PDF (2008KB) ( )  

References | Related Articles | Metrics

The state of art 500 kV high temperature superconducting fault current limiter operates at the highest voltage level. The use of 500 kV high temperature superconducting fault current limiter can reduce short-circuit current in the system without reduction of reliability and flexibility. However, there is no well accepted main electrical connection for the limiter. Four different kinds of main connection schemes are discussed. Recommendation is made after comprehensive comparison on reliability, protection configuration and equipment cost. The recommended scheme is suitable for low reliability 500 kV high temperature superconducting fault current limiter which must be removed immediately after failure occurrence.

A LabVIEW Based Portable Power Quality Monitoring Device for Smart Substation

LIU Jianhua, LIU Pengfei, JIANG Yingxian, LI Tianyu, ZHOU Mingping, TANG Quan

2016, 49(2):  102-108.  DOI: 10.11930/j.issn.1004-9649.2016.02.102.07

Asbtract ( )   PDF (6975KB) ( )  

References | Related Articles | Metrics

At present, most of the power quality monitoring devices for IEC 61850 standard are on-line based and without portable monitoring functions, therefore unable to support third-party power quality monitoring. They are high in cost and lack of functional expandability. A portable power quality monitoring device for intelligent substation based on virtual instrument-LabVIEW is designed. Based on LabVIEW design, the power quality monitoring device connects to the process layer of the switches to capture SV messages, and uses high-performance PC hardware platform for data processing. The SV message collecting and parsing module conducts SV packet capture and analysis. The data calculation and display module calculates and displays power quality indicators. The data analysis module performs the waveform and trend analysis for various steady-state indicators, and wavelet analysis for transient power quality problems. The PQDIF file can be generated in accordance with IEEE standard format. A comparison of data from the devise and the data from the power quality monitoring system in the field operation demonstrates that the device has high monitoring precision and can be applied to intelligent substation for power quality monitoring.

Probabilistic Load Flow Based on Mixed Copula and Uniform Design Sampling

ZHOU Yiguang, LIU Tianqi

2016, 49(2):  109-113.  DOI: 10.11930/j.issn.1004-9649.2016.02.109.05

Asbtract ( )   PDF (2391KB) ( )  

References | Related Articles | Metrics

In order to describe the dependency structure of the random input variables comprehensively and improve the sampling efficiency of Monte Carlo, a probabilistic load flow method based on mixed Copula and uniform design sampling is proposed in this paper. Firstly, Mixed Copula is constructed to analyze the correlation of the random input variables and describe the non-linear, asymmetric and tail characteristics. In traditional Monte Carlo simulation, the sampling scale is too large and the computation time is too long. To overcome the shortcomings, the uniform design sampling is used. The case study applies IEEE30-bus system with wind forms. The analyzing results show that the proposed method is fast in speed and high in precision. Furthermore, it can reflect the dependency structure of the random input variables comprehensively compared with the simulation results with the measured discrete data.

A Network Parameter Errors Identification Method Considering Large Error Point Based on Robust State Estimation and Its Real Application

JIN Xuecheng, ZOU Genhua, ZHANG Hao, SUN Yue, CUI Bo

2016, 49(2):  114-117.  DOI: 10.11930/j.issn.1004-9649.2016.02.114.04

Asbtract ( )   PDF (2826KB) ( )  

References | Related Articles | Metrics

Network parameter errors can significantly deteriorate state estimation results in power system. Firstly, a robust state estimation model with ability to avoid bad data influence automatically is investigated. Then, a practical suspicious parameters identification method is developed. The method is based on measurement residuals and mismatch between states on two branch terminals. Finally, a variable step integration algorithm is used to estimate identified suspicious parameters. The proposed method has been deployed in several provincial power control centers. Numerical results of a real provincial power system are given to demonstrate its correctness and effectiveness.

A High Voltage Level MMC Submodule Equalization Algorithm

ZU Lifeng, HU Siquan, JI Panpan, LI Kun, FENG Min, MA Junjie

2016, 49(2):  118-121.  DOI: 10.11930/j.issn.1004-9649.2016.02.118.04

Asbtract ( )   PDF (3255KB) ( )  

References | Related Articles | Metrics

Capacitance voltage stabilizer module is essential for MMC operation stability. With large number of sub-modules caused by voltage rating increase, traditional sorting algorithms cannot meet control requirements. A capacitor voltage sub-module packet equalizing control algorithm suitable for high voltage level is proposed. The algorithm can greatly reduce resource consumption and calculation time with the same result as traditional method. It also simplifies the valve system design complexity and improve system reliability.

Study on the Theory of Partition Power Supply of 500 kV Received Power Grids Based on Partition Equivalent Models

LAN Haibo, FAN Xinqiao, ZHANG Jun, ZHANG Wenchao, DU Yanling, ZHAO Feng, WANG Sai, WU Xun

2016, 49(2):  122-127.  DOI: 10.11930/j.issn.1004-9649.2016.02.122.06

Asbtract ( )   PDF (1953KB) ( )  

References | Related Articles | Metrics

The short circuit problem caused by electromagnetic loop network emerges with the development of power grid. A reasonable grid structure is important to limit short circuit current of a power grid. Through analysis on several partition structure of received power grids of different areas, typical received power grid partition model of single 500 kV station, two 500 kV stations and three chain-link or circular 500 kV stations are built based on equivalent circuit theory. To verify basic accuracy of proposed model and method, the short-circuit current of typical power grid partition models at different positions are calculated. Comparison is made between calculation results and actual measurement. Considering power plant access, theoretical principles of received power grid partition is proposed. It is advised that 500 kV power grid can be partitioned by 2~3 stations and 4~6 transformers of 500 kV. Additional serial reactance can be used if the short-circuit current does not meet operation requirements under advised partition principles.

Study on the Optimization Model and Algorithm for the Transmission Curve of Seasonal Hydropower

BING Huanshuai, KANG Yi, YU Yafeng

2016, 49(2):  128-132.  DOI: 10.11930/j.issn.1004-9649.2016.02.128.04

Asbtract ( )   PDF (2801KB) ( )  

References | Related Articles | Metrics

Recently, seasonal hydropower has perplexed the provinces with large scale of hydropower generation. Seasonal hydropower has to be discarded if there is no consumption market, which will cause enormous economic losses and waste the clean resources. This paper investigates the characteristics and genesis of seasonal hydropower and discusses several possible consumption ways. An optimal model is established by using the heuristic algorithm with aims to maximize the utilization of seasonal hydroelectric power and minimize the thermal power generation. A case study is made to demonstrate the effectiveness of the proposed model and algorithm.

Research and Development of Standard Oil Dispensing System for Dissolved Gases in Transformer Oil

ZHU Hongbin, YU Xiang, ZHANG Xiaoqin

2016, 49(2):  132-135.  DOI: 10.11930/j.issn.1004-9649.2016.02.132.04

Asbtract ( )   PDF (2708KB) ( )  

References | Related Articles | Metrics

To ensure the accuracy of the field test results, the standard oil dispensing system of dissolved gases in transformer oil is developed. In this paper, the working principle of the system is introduced and the structures of the atmospheric pressure as well as the standard oil dispensing system are presented. In this system the absolute pressure is applied to quantitatively dispense the mixed gas such that the difficulties of large deviation between the target concentration and the practical concentration of the prepared mixed gas is overcome. Hence the accuracy of the prepared standard oil can be guaranteed. For the first time the negative pressure method is used to compound gases. By changing the pressures, the mixed gas consisting of any combinations and concentrations of components can be prepared. This method is also characterized by high stability, easy storage and straightforward preparation procedures. The oil data quantity value can remain stable for more than 180 days with the uncertainty degree less than 10% if it is preserved in the special storage device. The standard oil prepared by this system meets the requirements of the national standard for secondary substance, and is suitable for transportation in the whole country.

New Energy

Research on Monthly Power Generation Forecast of Wind Power Farm Based on Seasonal Auto-Regressive Integrated Moving Average Model

GUO Dan, HU Bo, LIU Junde, ZHAO Jingxiang, PIAO Zailin

2016, 49(2):  136-141.  DOI: 10.11930/j.issn.1004-9649.2016.02.136.05

Asbtract ( )   PDF (3191KB) ( )  

References | Related Articles | Metrics

Due to the characteristics of volatility and randomness, wind power brings a certain impact on reliable operation of power grid. Therefore, the accuracy of wind power generation forecast plays a critical role in scientific and reasonable dispatching, and will also influence the safe and stable operation of power grid. Under the background of big data analysis and multidisciplinary integration, the econometric method has been applied in this paper to analyze the monthly power generation data of wind power farms and models are constructed for power generation forecast based on the basic theory of load forecasting. The monthly power generation data of a 49.5 MW wind power farm in Liaoning area are collected and analyzed by using the econometric software EVIEWS, and the SARIMA model is used to forecast the monthly power generation of the wind power farm with a satisfactory results.

Analysis on Charging Behavior of Electric Taxis and Comparative Research of the Comprehensive Benefits in Multi-Region

ZHANG Xingping, RAO Rao, FENG Yifan

2016, 49(2):  141-147.  DOI: 10.11930/j.issn.1004-9649.2016.02.140.07

Asbtract ( )  

References | Related Articles | Metrics

China has introduced a number of policies to promote the development of electric vehicles. As one of the important fields for development, electric taxis have consistency across regions in operating characteristics. However, the impacts of electric taxis on grid operation and the benefits in carbon emission reduction are different in different regions due to their differences in power structure, taxi ownership and others. Focusing on this issue, this paper firstly simulates the actual operation data of electric taxis based on Gaussian mixture model and obtains the general running characteristics of electric taxis. By taking five southern China provinces as examples, models are built respectively to analyze the impacts of electric taxis on the power load and carbon reductions with consideration of the power structure, power load and taxi fleet scale. The results show that large scale electric taxis can assist reducing the load fluctuations during the valley load time, but increase the load fluctuations during the peak load periods. At the same time, the rate of grid load is varied geographically due to the impacts of electric taxis. Moreover, the amounts of carbon emission reduction are significantly different among regions. This study is based on the empirical analysis and can provide a reference for the relevant researches.

Energy Conservation and Environmentsl Protection

Experimental Study on the Reduction Treatment of Desulfurization Wastewater in Power Plants by Membrane

LIAN Kunzhou, CHEN Jingshuo, LIU Zhaoxia, MAO Jin, WANG Jing, ZHANG Jiangtao

2016, 49(2):  148-152.  DOI: 10.11930/j.issn.1004-9649.2016.02.148.05

Asbtract ( )   PDF (1899KB) ( )  

References | Related Articles | Metrics

To recycle the desulfurization wastewater and achieve the goal of zero wastewater discharge in power plants, the desulfurization wastewater after pretreatment is treated by adopting microfiltration(MF) and reverse osmosis(RO). The stability of MF system and the chemical cleaning method of MF membrane under different solid content conditions are explored as well as the stability and desalination rate of RO system under different recovery rate conditions. The study results show that the MF system can operate stably and the turbidity of its water production is less than 0.2NTU with the silt density index(SDI) less than 4.0. The RO system also operates stably without obvious scaling observed under various recovery rate conditions. Its desalination rate is more than 98%, and the desalination rate of single RO membrane is more than 99%. The salinity of its water production is less than 510 mg/L, which means that the water production can be used as the make-up water for the recycled water as well as the replenishment for other systems in the power plant such as the desulfurization processing water.

Optimization of FGD Wastewater Pretreatment Technique for Thermal Power Plant and Test Studies on Tubular Crossflow Microfiltration Process

LIU Yapeng, WANG Jinlei, CHEN Jingshuo, MAO Jin, WANG Jing

2016, 49(2):  153-158.  DOI: 10.11930/j.issn.1004-9649.2016.02.153.06

Asbtract ( )   PDF (2198KB) ( )  

References | Related Articles | Metrics

Considering the quality characteristics of FGD wastewater, the variations in particle size distribution of the pretreated-FGD wastewater and their effects on effluent quality during the tubular crossflow microfiltration process are studied based on the systematic analysis on four different pretreatment methods (i.e. calcium sulfate seeding technique, FS-66treatment, combination of calcium hydroxide and sodium carbonate, combination of sodium hydroxide and sodium carbonate). The results indicate that the combination of sodium hydroxide and sodium carbonate is the best pretreatment method compared with three other methods, which excels in the removal of Ca2+, Mg2+ and total silica. Under the designed testing conditions, the average particle size decreases rapidly from 14.5 μm to 5.1 μm. Meanwhile, both the flux and quality of water produced from microfiltration are quite stable during the entire experimental process. After further desalination the water can be even recycled and reused. This result has established the foundation for advanced FGD wastewater treatment of thermal power plants.

The Practice of General NOx Control of a 600-MW Boiler

ZHANG Boxing, LV Huabing

2016, 49(2):  159-163.  DOI: 10.11930/j.issn.1004-9649.2016.02.159.05

Asbtract ( )   PDF (2860KB) ( )  

References | Related Articles | Metrics

Coal-fired power plants are the major source of NOx generation and emission. The analysis on the operating status of a 600-MW coal-fired boiler reveals three problems, high NOx emission concentration, low denitrification equipment utilization factor and uneven SCR concentration distribution. To address the high NOx emission concentration problem,, the low NOx burner is adopted; to increase the utilization factor of the denitrification equipment, boiler combustion is adjusted and controlled low temperature denitrification operation is carried out; to improve the distribution uniformity of SCR concentration, the denitrification AIG ammonia injection system is adjusted and optimized. As the result, the concentration of NOx emission is reduced from 450~650 mg/m3 to 280 mg/m3; the utilization factor of denitrification equipment is increased from 55% to 99.5%; the concentration distribution uniformity is improved and the denitrification efficiency is increased by 3%. Therefore, with other NOx emission control measures applied simultaneously, the general NOx control level is enhanced significantly, which proves the feasibility of controlled low-temperature denitrification.

The Application of SNCR+SCR United Flue Gas Denitration Technique in Power Generation Boilers

ZHU Chenxi, ZHENG Yingjiu, ZHOU Hao

2016, 49(2):  164-169.  DOI: 10.11930/j.issn.1004-9649.2016.02.164.06

Asbtract ( )   PDF (3524KB) ( )  

References | Related Articles | Metrics

Regarding the NOx emission over national standard in Unit 5 of(130 MW) a power plant, this article briefly introduces the fundamentals of SNCR+SCR united flue gas denitration technique and establishes the corresponding implementation procedures through CFD numerical simulation. Firstly, the low-nitrogen combustion technique is utilized to control the boiler NOx emissions under 350 mg/m3 and guarantee low CO concentration in the SNCR zone. Secondly, the SNCR technique is adopted to control the NOx concentration before SCR under 200 mg/m3. At last the SCR technique is adopted to control the NOx emission concentration under 90 mg/m3. In this way, the NOx emissions can meet the related standards in major regions.

Overview of Mercury Removal from Coal-Fired Flue Gas

HE Shiyu, ZHAO Huimin, LIU Changdong, HU Chenhui

2016, 49(2):  170-175.  DOI: 10.11930/j.issn.1004-9649.2016.02.170.06

Asbtract ( )   PDF (1262KB) ( )  

References | Related Articles | Metrics

Mercury pollution from coal-fire flue gas is considered another severe environmental pollution after the dust, sulphur and nitrogen pollutions, and it has been getting more attention in recent years. This article discusses the policies and codes on mercury control, the mercury existence forms and affecting factors, the mercury emission detection methods, and the current mercury removal technologies. It also puts forward the prospect of the research on mercury pollution control for coal combustion in the future.

Smart Grid

A New Type Intelligent Phase Selection Controller Design and Anti-Interference Measures

XU Liqing, LI Shuai, CHEN Qingxu, CHEN Xinzhi, YU Huawu

2016, 49(2):  176-189.  DOI: 10.11930/j.issn.1004-9649.2016.02.176.04

Asbtract ( )   PDF (825KB) ( )  

References | Related Articles | Metrics

Some key technologies on phase-controller are analyzed. A controlled IGBT (Insulated Gate Bipolar Transistor) scheme of smart phase-controller with FPGA(Field Programmable Gate Array) is proposed to realize zero-crossing circuit breaker operation. In order to improve equipment anti-interference ability, differential control is used in each IGBT control circuit, and independent power source is adopted in drive circuit. The proposed scheme can be used in merging unit, intelligent terminal and phase-controller in smart station. Test results show that proposed intelligent phase selection controller has high reliability and broad application prospects.

Analysis and Proposition for Malfunction of Electronic Transformer in Intelligent Substation

DENG Wei, MAO Juan

2016, 49(2):  180-184.  DOI: 10.11930/j.issn.1004-9649.2016.02.180.05

Asbtract ( )   PDF (1500KB) ( )  

References | Related Articles | Metrics

Electronic transformer is very important in smart grid and digital substation. However, experience of manufacturing, operation and corrective maintenance of electronic transformer is still insufficient. After 3 years operation in one intelligent substation, secondary voltages of partial electronic voltage transformers are unstable and secondary currents of partial electronic current transformers has obvious deviation. The structures and principles for electronic transformers system are introduced; the malfunction reasons of equipment are analyzed and studied. It is found that equipment parameters may influence infrared temperature measurement results, shorted energy coil of voltage transformer leads to voltage drop and opening circuit of parallel resistance of current transformer results in current increase. Several suggestions are proposed for design, manufacture, quality control and maintenance of electronic transformers.