Table of Content

05 February 2013, Volume 46 Issue 2

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Power Planning

Mid-Long Term Development Prospects of Coal-Fired Power in China

ZHANG Dong, BAI Jian-hua

2013, 46(2):  1-4.  DOI: 10.11930/j.issn.1004-9649.2013.2.1.3

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Coal-fired power will still be the main power sources at present and in the mid-long term in China. The sustainable development of coal-fired power is crucial to guarantee reliable power supplies. From the aspects of installed capacity, management and investments, the development status quo of coal-fired power was analyzed briefly. Based on the power demand forecast, and the renewable energy and nuclear power development plan, the future installed capacity requirement of coal-fired power in mid-long term period was predicted. In addition, the related factors, such as power coal demand and supply situation, operation prospects, development layouts, clean and efficient development, etc., were analysized to gave a comprehensive future situation of coal-fired power development in China. In the end, some vital problems were summaried that need to be solved to achieve sustainable development of coal-fired power.

Review on Energy Decision-making Supporting Technology

LIU Jun, JIA De-xiang

2013, 46(2):  5-6.  DOI: 10.11930/j.issn.1004-9649.2013.2.5.1

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In order to meet the requirements of energy saving and emission reduction, and diversification and intelligentization of energy supply, promote healthy and sustainable development of energy demand and supply, it is urgent to study the energy decision-making supporting technology in accordance with the trend of energy demand and supply. In this paper, the development process of energy decision-making technology is reviewed. The characteristics of classic energy decision-making technology based on conventional energy and the modern energy decision-making technology considering the new energy and power transmission are summarized. Moreover, the key factors and the module-model-application architecture of future energy decision-making technology are proposed, which can provide a reference for study of energy decision-making technology in China.

Generation Technology

System Optimization of Wind Turbine Independent Pitch Control Technology

LI Gui-bin, ZHANG Hong-li

2013, 46(2):  11-16.  DOI: 10.11930/j.issn.1004-9649.2013.2.11.5

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According to the problems of over large pitch load and instable output power and voltage of the independent variable pitch wind turbines, the model reference adaptive control(MRAC) method was used to study the optimal control of independent variable pitch of wind turbines. The selection process of reference model was discussed. The controller was designed based on Lyapunov stability theory and applied to the independent pitch. The simulation results show that the control method not only improved the response speed of the pitch controller but also improved the tracking accuracy, and stabilized the output power and voltage. Meanwhile it reduced the blade flapping vibration. The model reference adaptive controller can be used for wind turbine control.

Research on the Application of Advanced Construction Techniques for Nuclear Power Plants

LIU Zhi-tao, FAN Ji-hong

2013, 46(2):  17-23.  DOI: 10.11930/j.issn.1004-9649.2013.2.17.6

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In this paper, the research is carried out on the advanced techniques for the construction of nuclear power plants. In combination of the actual engineering situation, the main characteristics and impacts of the techniques are analyzed such as the foundation pit excavation by blasting, the once-off complete concrete placement of raft foundation, the steel plate reinforced concrete structure, the open top construction, the advanced welding process, the modern engineering materials, as well as the prefabrication preassembly and modularization. The trends of the advanced construction techniques are also predicted.

Calculation and Analysis of Hydrodynamic Characteristics for First 600-MWSupercritical Down-Fired Boiler

WU Yan-hua, YANG Dong, CHENG Gong-ming, CHEN Yi-ping

2013, 46(2):  24-30.  DOI: 10.11930/j.issn.1004-9649.2013.2.24.6

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In order to check the security and reliability of the water-wall, the hydrodynamic characteristic computation program is adopted with the operating parameters taken as initial values to calculate the flow rate and outlet temperature of the working substance in a 600-MW boiler of one thermal power plant which is the first supercritical down-fired boiler designed and put into operation in the world. The hydrodynamic characteristics in normal and coking conditions are compared. The overall calculation values of the outlet working substance temperature match well with the operation data, which illustrates that the program is suitable for practical application. The results show that the lower-furnace water-walls with low mass-flux optimized rifled tubes exhibit a strong positive flow response while the upper-furnace water-walls with vertical smooth tubes exhibit an evident negative mass flux response. Compared to the normal condition, in the coking conditions the mass velocities of the coking circuits in the lower furnace decrease with the outlet fluid temperatures of all circuits being decreased.

Design and Application of Single PA/SA Fan for 330-MW CFB Boilers

JIN Sheng-xiang, LI Qian-yu, HE Qi-shan, ZHENG Ya-gang, HUANG Bin

2013, 46(2):  31-35.  DOI: 10.11930/j.issn.1004-9649.2013.2.31.4

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In order to reduce the comprehensive costs of capital construction and improve the economic level of unit operation, a technical innovation is carried out in the air-gas system for one 330-MW CFB unit in a certain power plant. The scheme of single primary air (PA) fan and single secondary air(SA) fan is adopted for the first time in China, which significantly reduces the construction costs and land occupation. However, some new requirements are put forward for the air-gas system design accordingly. The half-a-year operation shows that single PA fan and single SA fan can operate stably and reliably with high efficiency and low maintenance costs.

Research on 3 033-t/h Ultra-Supercritical Boiler Startup with no Circulating Pump

YANG Bao-e, LIN Hong, FENG Ting-you, SUN Wei-peng

2013, 46(2):  36-39.  DOI: 10.11930/j.issn.1004-9649.2013.2.36.3

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With the analysis of the pros and cons between the boiler startup with and without boiler water circulating pump for the 1 036-MW ultra-supercritical unit, and with the coordinated control of the boiler feed water flow, the temperature, the air flow, fuel and the starting speed during the startup process, the pump free startup is completed. The operating mode, procedures and critical control points for the boilerand the related considerations are proposed, which are practically valuable for the operators in the industry.

Discussion of Alumina Acid Production from Fly Ash of Power Plants

LI Rui-bing, ZHANG Ting-an, LI Jing-jiang, LI Xin, WU Nan

2013, 46(2):  40-45.  DOI: 10.11930/j.issn.1004-9649.2013.2.40.5

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Coal fly ash from power plants contains large amounts of alumina. When it is used to produce alumina, it can not only overcome the shortage of alumina resources, but also avoid environmental contamination. The methods and the status quo of the research on alumna production from fly ash are reviewed and the characteristics, trends and feasibility of these methods are analyzed. Some recommendations are given for improving the product quality, reducing the investment and lowering the cost of the alumina production. One method of acid extracting alumina from fly ash(GP method) is introduced, which consists of three steps of leaching with sulfuric acid, removing impurities with hydrochloric acid and ammonia conversion. With this method, the reaction temperature, the energy consumption and the production cost are low and there are not new solid emissions generated from the closed cycle process. The issues on the alumina crystal size, acid-resistant materials as well as iron and other impurities removal need to be further studied.

Power System

Coherency Analysis of Disturbed Generator Groups Based on TwoStep Cluster

CAI Guo-wei, SUN Zheng-long, KONG Ling-guo, YANG De-you, WANG Yu-wei

2013, 46(2):  46-49.  DOI: 10.11930/j.issn.1004-9649.2013.2.46.3

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Based on TwoStep Cluster, a new method to analyze the coherency of disturbed generator groups is proposed. Firstly, the generator rotor speed gathered from the Wide Area Measurement System (WAMS) is disposed to build CF tree and produce sub-clusters by dint of BIRCH algorithm method; then through hierarchical clustering, the sub-clusters are clustered into the specified number of clusters that is automatically determined; finally the clustering result is used to analyze the coherency of the disturbed generator groups. The effectiveness of applying the proposed method to identify the coherent generators, as well as the feature to determine the clustering numbers automatically, is verified by simulation of New England 10-machine 39-bus system and by comparing the results of different methods of identification of coherent generators.

Assessment of Black Start Plans Based on Improved Data Envelopment Analysis Model

SHA Feng, YANG Jian-biao, AI Xin, LAN Hua, LAN Zi-hao

2013, 46(2):  50-54.  DOI: 10.11930/j.issn.1004-9649.2013.2.50.4

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A scientific and reasonable black start plan is of great importance for quick and stable system restoration after blackouts. Due to the ineffectiveness of the traditional data envelopment analysis (DEA) model in ranking the plans, a novel method is proposed for black start plan assessment using improved DEA model. On the basis of the traditional DEA model, two virtual plans of which one is the best and the other one is the worst are introduced into the black plan set. By establishing the improved DEA model, a set of common weights is acquired and used to calculate the efficiency index of the plans to rank the black start plans. The method is applied to the black start case of two actual grids and the result is compared with those from other methods, which shows that this method can rank the black start plans correctly and improve the distinguishability of the evaluation results.

Analysis of a Mal-operation of Differential Protection After the DC Resistance Testing

LI Yan-jun, LI Xiao-mei, ZHAO Han

2013, 46(2):  55-59.  DOI: 10.11930/j.issn.1004-9649.2013.2.55.4

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After the DC resistance testing of a transformer, the residual magnetism will affect the judgement of transformer’s differential protection. Upon charging the transformer with no-load, large inrush current will be created with big magnitude and low harmonics, which may lead to the secondary harmonic blocking failure of differential protection. The combined judgement method of secondary harmonics and waveform symmetry will improve the reliability of the differential protection action. An analysis is conducted of the mal-operation of differential protection after the DC resistance testing, and the difference in identifying the inrush current is compared between the blocking criteria of secondary harmonics and waveform symmetry. Based on the analysis, some feasible measures are proposed to avoid the mal- operation of differential protection. At last, with different residual magnetism modeling, the different blocking methods are tested again.

Site Selection of Electricity Office Based on Set Covering Model

JIANG Yuan, WANG Bing, ZHANG Ting, XIONG Wei, HE Yong-xiu

2013, 46(2):  60-64.  DOI: 10.11930/j.issn.1004-9649.2013.2.60.4

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In the context of extensive marketing system, the provincial and municipal power companies are making efforts to implement the idea of“Electricity payment within ten-minute walk” in order to provide fast, convenient, and diversified bill payment methods. Based on the analysis of the existing domestic and foreign electricity payment methods, a set covering model of site selection for electricity payment office based on the idea is established. In addition, a weighted set covering model that takes the electricity payment rates as weight is built at the same time. By analyzing the locations of electricity payment offices and the neighbourhoods in Anning District of Lanzhou, Gansu Province, the optimization and solution of the set covering model is carried out with the LINDO software, which proves the feasibility of the model. The result indicates that the model can help all regions to select the appropriate electricity payment partners to maximize the user satisfaction with minimal investment cost.

Analysis of Single-phase Grounding Fault with Line-Broken on Overhead Transmission Lines

ZHANG Hui-fen, SANG Zai-zhong

2013, 46(2):  65-71.  DOI: 10.11930/j.issn.1004-9649.2013.2.65.6

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Single-phase grounding faults with line-broken occur frequently in overhead distribution systems of 6~66 kV, which may endanger personal safety and interrupt power supply. Considering the grounding points on load side and the types of loads, the currents and voltages at grounding and broken points and protection installation positions and on the load sides were analyzed respectively, and the formulas and phasor diagrams of voltages and currents at each point were deduced. The study results show that voltages of grounding points and protection installation positions have a relationship with load characteristics and fault resistance. However, the broken point voltage has a relationship with load characteristics only. PSCAD simulation proves correctness of the conclusions. Thus a theoretical foundation is established to identify the single-phase grounding faults, line-broken faults and grounding faults with line-broken.

A Study of Intelligent Monitoring and Protection System for Substation Operating Worker

YU Zhen, ZHU Chao-yang, FANG Dian-ge

2013, 46(2):  72-75.  DOI: 10.11930/j.issn.1004-9649.2013.2.72.3

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The status of power production safety is analyzed. Based on the realization principle of intelligent monitoring and protection system, the positioning technology and intelligent video analysis technology are researched. According to the functional classification, the technical architecture is proposed. The system is divided into four layers including the device layer, supporting layer, business layer and presentation layer. And a functional architecture of the substation intelligent monitoring and protection system is designed, which consists of such functions as work task management, real-time monitoring, alarm warning, region division, trajectory replay.

Determination of Ultimate Uplift Capacity of Plate Anchors in Homogeneous Saturated Clay by Variational Solution

HAO Dong-xue, ZHANG Yong-jian, CHEN Rong

2013, 46(2):  76-81.  DOI: 10.11930/j.issn.1004-9649.2013.2.76.5

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Limited equilibrium theory and variational method are used together to analyze the ultimate uplift capacity of strip anchor embedded in homogeneous saturated clay, where soil stresses satisfy the yielding criteria of Mohr-Coulomb in limited conditions. The function of sliding surface, the normal stress distribution along it, and ultimate uplift capacity can be obtained by this method. And the effects of soil strength, loading eccentricity, and horizontal loading on failure surface and ultimate uplift capacity are investigated by a series of calculations. It is concluded that the method can be applied to predict the ultimate uplift capacity of plate anchors of saturated clay under rapid uplift and loading eccentricity presents more significant influences on uplift capacity and sliding surface. When loading eccentricity is less than 0.5, the breakaway between plate and its underneath soil will not take place. Also, the formulas of factors of ultimate uplift capacity are suggested under central, eccentric uplift loadings and horizontal loading.

Reactive Power Optimization Based on IGSO and Harmonic Voltage Distortion

HONG Xiao, DING Xiao-qun, YANG Hai-dong, HUANG Heng-shuo

2013, 46(2):  82-86.  DOI: 10.11930/j.issn.1004-9649.2013.2.82.4

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In recent years, power electronic devices have been widely used and caused harmonic pollution. If the power system is optimized directly under the harmonic frequency, the harmonic resonance or harmonic amplification between the system and the capacitor is apt to occur, which will lead to increase of harmonic distortion and damage the safety operation of the power system. A mathematical model of reactive power optimization is proposed with consideration of harmonic voltage distortion. Based on the minimum network loss, the fundamental voltage and the total harmonic distortion over the limit of each node were added to the target function by the form of penalty terms and the improved glowworm swarm optimization(IGSO) was applied to reactive power optimization. The specific procedures for reactive power optimization based on IGSO and harmonic voltage distortion are given in this paper. A simulation of the IEEE 30-bus case was conducted to test the feasibility and the superiority of this method. The results of this optimization show that this method reduces the network loss and total harmonic distortions, and has a better convergence efficiency and a higher computational precision.

New Energy

Control Strategies of a Wind / Photovoltaic / Storage Micro-Grid for Load Shifting Schedule of the Main Grid

HUANG Xiu-qiong, LU Ji-yuan, NIU Huan-na, FEI Biao-qing

2013, 46(2):  87-92.  DOI: 10.11930/j.issn.1004-9649.2013.2.87.5

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Scheduling and control strategies of a wind / photovoltaic / storage micro-grid are studied to achieve the goals of the maximum use of renewable energy sources and load shifting of the main grid. The state space of the wind / photovoltaic / storage micro-grid is divided into 6 sub-state-spaces, according to its operation modes of connection with the main grid in conditions of peak/flat/valley periods and islanding with the balance between generation and load. Furthermore, the transfer premises between each state are analyzed. Based on the scheduling and control strategies for each state made through the studies above, the ultimate control program of charge / discharge power of the energy storage unit is obtained. Taking the demonstration project of wind / photovoltaic / storage micro-grid of an island in Guangxi as an example, simulation of operational control in representative days is conducted to verify the correctness and effectiveness of the proposed control strategies of load shifting schedule.

Variable Pitch Tracking Control for a Wind Power System Based on Feedback Linearization Theory

CUI Shuang-xi, WANG Wei-qing, ZHANG Xin-yan

2013, 46(2):  93-97.  DOI: 10.11930/j.issn.1004-9649.2013.2.93.4

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A mathematical model of second-order for a doubly-fed induction wind generator was established to deal with the problem of inconstant output of the wind generator when wind speed is higher than the rated wind speed. According to the feedback linearization and the optimal control theory, the presentation of the state feedback linearization control law was given. In addition, the optimal tracking controller was designed on the basis of the definition of tracking errors. By using Matlab/Simulink software as a simulation platform, the correctness and efficiency of the designed controller was verified. Comparing with traditional PI control, no matter what changes the wind speed has, the proposed optimal controller is able to better keep the output basically constant and behave robustly.

Short-Term Wind Speed and Wind Power Prediction Based on the Grey-Markov Chain

ZHANG Wei, DENG Yuan-chang

2013, 46(2):  98-102.  DOI: 10.11930/j.issn.1004-9649.2013.2.98.4

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Wind speed has the characteristics of large stochastic volatility, which affects the wind power and the stability of the grid connected with it. Good predictions of wind speed and wind power are the key to solve the integration problem of wind power with grid. A comparison between grey models and Markov chain models for predicting wind speed is made. The gray-Markov chain prediction model and the wind speed prediction error are obtained by analyzing the error transfer series of the fitted values with grey models and establishing Markov state transition probability matrices. The expected values of the transfer matrices are used to correct the traditional Markov chain, and the improved gray-Markov chain model can thus be obtained to predict the wind power directly. Comparing with the real power curve, the improved grey-Markov model is better in prediction accuracy.