Table of Content

05 January 2013, Volume 46 Issue 1

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Power Planning

Study on Issues Concerning Solar Power Development and Accommodation in China

HU Bo, XIN Song-xu, BAI Jian-hua, ZHANG Yun-zhou

2013, 46(1):  1-6.  DOI: 10.11930/j.issn.1004-9649.2013.1.1.5

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The planning, layout characteristics and existing problems of solar power development in China are introduced. Based on the output characteristic index of PV generations, the new requirements of large-scale PV power integration is analyzed on the power system planning, and the analytical method of solar power accommodation is proposed. According to the planning targets of solar power generation of the “12th Five-Year Plan” period in the northwestern region, the solar power accommodation capacity of the northwest grid is studied. It is predicted that by the year of 2015, the installed solar power capacity in the northwestern region will reach 13.2 GW, and the balancing capability of the local power grid can’t meet the accommodation requirement of such new energies as PV and wind power. Trans-region balance is therefore needed for accommodation of new energy.

Outlook 2013 of Power Supply and Demand in China and Related Suggestions

GU Yu-gui, LUO Zhi, SHAN Bao-guo

2013, 46(1):  7-10.  DOI: 10.11930/j.issn.1004-9649.2013.1.7.3

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The electric power consumption characteristics of the year 2012 was reviewed and the power demand, supply and balance of the year 2013 was forecasted, which indicates that as a result of macro economic controls, the growth rate of national power demand will pick up, and the national power demand and supply will be balanced as a whole if no extreme weather occurs. Based on the analysis of power supply and demand in 2012, it is predicted that the installed capacity of the whole country will increase by 75 000 MW and the utilization hours of generators will reach to 4 716 h. It is pointed out that the attention should be paid on power source area distribution, renewable energy power generation, power grid construction and thermal power price system.

New Energy

Operation Control and Economic Dispatch of Energy Storage System for Micro-Grid

GAO Wen-jie, JING Tian-jun, YANG Ming-hao, SHEN Dong

2013, 46(1):  11-15.  DOI: 10.11930/j.issn.1004-9649.2013.1.11.4

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Energy Storage Systems(ESSs) have critical impacts on the reliability and economy of micro-grid operation. In this paper, the control strategies of ESSs for a micro-grid in both grid-connected and islanded modes are analyzed. In order to solve the severe stability issues caused by high R/X ratio of line impedance in traditional voltage and frequency droop controls, an improved droop control strategy is designed that can enhance micro-grid transient performance by mitigating power fluctuation. A mathematical model of economic dispatch of ESSs is established under the time-of-use pricing, with which peak load shaving can be achieved. The proposed strategies in control and dispatch are verified through a study case.

Optimal Allocation of Distributed Generation Based onGenetic Algorithms and Differential Evolution Algorithm

YUAN Mian-qi, ZOU Zhen-yu, SUN Kai-qi, LIU He-jin, LI Ke-jun

2013, 46(1):  16-20.  DOI: 10.11930/j.issn.1004-9649.2013.1.16.4

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Selection of the position and rated capacity of the distributed generation (DG) is crucial for power system in planning, design and investment. Genetic algorithm and differential evolution algorithm are adopted for the optimal allocation of DG based on a 10-node distribution network and an uncertainty DG model is built and added into the optimization analysis with an optimization algorithm program. The load flow is calculated for a distribution network with DG and the relation between installed DG capacity and the system’s total transmission loss is analyzed. The computational example shows that the proposed method of optimal allocation is reasonable and effective in improving the voltage distribution of distribution network, reducing transmission loss and improving the system’s output factor.

Smoothing Control of Directly-Driven Wind Power System with Superconducting Magnetic Energy Storage

DANG Cun-lu, LIN Guo-fu

2013, 46(1):  21-25.  DOI: 10.11930/j.issn.1004-9649.2013.1.21.4

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In order to solve the problem of output fluctuations of active power occurring in directly-driven wind power generators integrated with power grid, based on the method of paralleling a superconducting magnetic energy storage system(SMESS) to the converter and the wind speed model analysis, a control strategy for the chopper of the SMESS was proposed with pulse judgment plus dual closed-loops, which can make the SMESS have energy throughput quickly and accurately, obtaining the results of maximum wind energy capture and smoother active power to the grid. Simulation of a directly-driven wind power generator with a superconducting magnetic energy storage system proves the correctness and effectiveness of the controlling strategies.

Comparison of Static Equivalent Models of Wind Farm with P-V Analysis

DING Ming, MA Biao, HAN Ping-ping

2013, 46(1):  26-29.  DOI: 10.11930/j.issn.1004-9649.2013.1.26.3

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Focusing on wind farms consisting of squirrel-cage induction wind turbines, equivalent models of wind farm performances were established by capacity-weighted, improved capacity-weighted and parameters transformation stand-alone turbine equivalent methods and multi-machine equivalent methods with variable-scale and reduced-order, in which parameters of electrical collection systems and transformers in wind farms were considered. Through the P-V analysis, the above equivalent models were compared to the real and comprehensive models in terms of approximations of static voltage stability margins. It was concluded that multi-machine equivalent method performs better when wind turbine parameters in a wind farm are the same; while parameter transformation method is suitable to the situation of different parameters.

Smart Grid

Orderly Charge and Discharge Measures for the Battery Charging and Swapping Demonstration Stations

LI Hong-mei

2013, 46(1):  30-35.  DOI: 10.11930/j.issn.1004-9649.2013.1.30.5

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With the substantial increase in ownership of electric vehicles in the future, uncontrolled charge for the electric vehicles will have a significant impact on the power grid. The measures of orderly charge and discharge for the battery charging and swapping demonstration stations are introduced in Shandong province from such two aspects as vehicle to grid(V2G) system and the operations management system. In the V2G system, an intelligent bi-directional charge and discharge equipment is designed and the peak-valley price based control systems of charge and discharge and the station monitoring systems are developed. In the operations management system, the methods of battery echelon utilization and the life cycle management are proposed and the structures, working principles and technological means of both the metering and billing system and the fast battery switching system are introduced.

Forecast of Electric Vehicles in China Based on Bass Model

ZENG Ming, ZENG Fan-xiao, ZHU Xiao-li, XUE Song

2013, 46(1):  36-39.  DOI: 10.11930/j.issn.1004-9649.2013.1.36.3

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Predicting the inventory of electric vehicles accurately for future 10 years in China is significant for adjusting relevant established industrial policies, achieving the orderly development of electric vehicles, and guiding the layout of the upstream and downstream industries reasonably. After a comprehensive analysis of the plan for electric vehicles in future 10 years, the Bass model, which has an advantage in taking full account of the internal and external factors in predicting the spread of new products, is used to predict the inventory of electric vehicles in China under the condition of the baseline oil price and high oil price in 2020. The results indicate that the electric vehicles will witness a rapid development in the next 10 years and the high oil price can promote the spread of electric vehicles to some extent.

Generation Technology

Turbo-Generator Rotor Crack Identification by Abnormal Vibration Analysis

ZHANG Xue-yan, LI De-yong, MU Fang-xin, WANG Guang-hui, LU Yi-bing

2013, 46(1):  40-45.  DOI: 10.11930/j.issn.1004-9649.2013.1.40.5

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Rotor cracks may lead to turbine-generator shaft broken accident, causing the unit to be destroyed and producing great losses. Therefore, how to timely detect rotor cracks to ensure the safe and stable operation of the unit is significantly and practically important. Based on the summarization of the research results of the vibration characteristics of cracked rotors and combined with the experience of field vibration fault diagnoses, a practical method of identifying cracked rotors with abnormal vibration analysis is proposed. Through analyzing the abnormal vibration of two 600-MW units, the process of detecting the rotor crack is introduced. Because the diagnosis is accurate, the unit is timely stopped for check, and the defect is identified, thus avoiding catastrophic accidents if the unit continues running.

Research and Application of Chemical Cleaning Technology for Ultra-Supercritical Boilers

WU Lai-gui, SHEN Jun-feng, FAN Hong-zhao, HE Zhen-kun, LI Yu-jie, CAO Yun, LI Yuan-yuan

2013, 46(1):  46-49.  DOI: 10.11930/j.issn.1004-9649.2013.1.46.3

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Water molecules under ultra-supercritical conditions have strong oxidizing nature, which makes boiler water wall tubes form dense scale. Based on the analysis of the scale composition for the two 600-MW ultra-supercritical units at one power plant, the static and dynamic simulation tests are conducted with three sorts of organic acids. And the corrosion rate and corrosion quantity of the metal piece are determined respectively. Following the dynamic simulation test result, 2% glycolic acid and 0.5% sodium fluoride with a certain amount of inhibitor is chosen as the cleaning agent for the two units. After cleaning, both the corrosion rate and corrosion quantity meet the related standard, which indicates that the cleaning effect is satisfactory.

Analysis and Solutions of High Governing Stage Pressure Problem for 600-MW Steam Turbines

CHEN Bin, TANG Hai-ning, XU Chen-guang

2013, 46(1):  50-53.  DOI: 10.11930/j.issn.1004-9649.2013.1.50.3

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The governing stage pressure of a supercritical steam turbine has been increasing since the unit commitment. During the overhaul, scaling is discovered on the turbine blades, which seriously influences the turbine operated at rated load. The analysis on the deposits finally discloses the reasons for scaling. Some measures such as shotpeening for the HP and IP flow paths, acid washing for the boiler and defect elimination for the water precision treatment equipment, are taken, which enables the turbine governing stage pressure to drop to the designed value and the turbine to carry the rated load. Therefore, the problem of high governing stage pressure is solved thoroughly.

Study on Steam-Side Oxidation Mechanism and Characterization of Oxide Scales Grown on T91 Tubes

XIE Guo-sheng, LONG Hui-guo, LONG Yi

2013, 46(1):  54-58.  DOI: 10.11930/j.issn.1004-9649.2013.1.54.4

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The oxidation mechanism and characterization of steam-side oxidation scale formed on the internal surface of the super-heater tubes made of T91 steel removed from the boiler of a power plant are studied by using the testing and analyzing methods of metallurgic inspection, scanning electron microscope-energy dispersive X-ray (SEM-EDX) and X-ray diffraction analysis. The results show that based on the section oxygen elemental distribution and the Fe-Cr elemental diffraction rule, the original steam-side oxidation scale normally consists of three layers. The inner layer is heterosphere oxides, which consists of Cr-enriched and Cr-depleted zones appearing alternatively; the middle layer is the loose and porous Fe3O4 with the columnar crystal microstructure; the outer layer is the thin Fe2O3. In the outer layer, there are small gaps among the oxides and the adhesion is weak, which makes it easy for the oxides to flake off during great temperature variation. The middle layer works better than the outer one.

Power System

A Novel Method of Fault Line Selection Based on Voting Mechanism of Prony Relative Entropy Theory

WANG Xiao-wei, WU Ji-wei, LI Ran-yue, TIAN Shu, CHU Zheng-chao

2013, 46(1):  59-64.  DOI: 10.11930/j.issn.1004-9649.2013.1.59.5

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A fault line selection method of small current to ground system was proposed in the essay. Firstly, Prony algorithm was used to fit the transient zero-sequence current signal in the first T/4 cycle after fault occurs; secondly, transient dominant components with fault features were selected based on the principle of maximum energy; lastly, the voting mechanism which combines the preliminary vote with the k value checking was used to vote the Prony relative entropy value. It is proved that this method can not only accurately detect the fault line but also improve the reliability of the results in fault line selection.

Evaluation Method for Concrete Pole Safety of Overhead Transmission Line

LIU Si-yuan, XIA Kai-quan

2013, 46(1):  65-68.  DOI: 10.11930/j.issn.1004-9649.2013.1.65.3

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It is common for the concrete poles of overhead transmission lines to crack in protection layer and rust in reinforcement due to the long-term load action and poor environment, which has significant adverse impacts on the function of overhead transmission lines. Based on the characteristics and relevant research results of concrete poles, a three-phase assessment system, an AHP(analytic hierarchy process)-based assessment method and a structural reliability theory-based gradation method are proposed respectively for the safety, safety state and safety performance of the concrete poles of overhead transmission lines. With these research results a complete safety assessment system is established for the concrete poles of overhead transmission lines, which is significant for accurately understanding the health state of the concrete poles, perfecting the service work of equipment and ensuring the steady function of overhead transmission lines.

The Influence of Transmission Line Arrangements on the Swing Angle of Suspension Insulator Sring

MIN Xuan, SHAO Gui-wei, LIU Yun-zheng, WEN Zhi-ke, CHEN Yi, HU Ji

2013, 46(1):  69-74.  DOI: 10.11930/j.issn.1004-9649.2013.1.69.5

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In calculation of transmission line windage yaw, the swing angle of suspension insulator strings is influenced by the gravity load and wind load of conductors and its magnitude is related to the arrangements of transmission lines,such as the constraints of neighboring conductor’s hanging points, the span and elevation difference. Based on three different arrangements of transmission lines, including the strain tower-tangent tower-strain tower, tangent tower-tangent tower-tangent tower and strain tower-tangent tower-tangent tower,the insulator string-conductor numerical models of two spans, four spans and six spans were established respectively and the swing angle and horizontal displacement of suspension insulator strings were obtained with simulation by changing the span, elevation difference and wind speed. By comparing the results with the swing angle and horizontal displacement calculated by static mechanical model, the influence of different arrangements of transmission lines on the swing angle of suspension insulator strings are analyzed and respective calculation methods of swing angles are proposed for different transmission line arrangements.

Design of Quantitative Risk Assessment System for Secondary Equipment of Power System

WU Jiang, WANG Yi, WANG Ren-min

2013, 46(1):  75-80.  DOI: 10.11930/j.issn.1004-9649.2013.1.75.5

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A system of risk assessment for secondary equipments of power system was proposed in this paper. Based on the characteristics of secondary equipment, a failure model was established by using the theory of risk assessment, reliability and full life cycle and a quantitative risk assessment model was established by combining status evaluation with risk assessment. A working mechanism was designed for quantitative risk assessment according to the data structure of the quantitative models. The proposed assessment system has been applied to the secondary equipment risk assessment of Guangdong power grid, which makes the power grid operation risk management change from superficial and qualitative assessment to elaborate and quantitative assessment. The assessment results provided a scientific basis for risk control management of secondary equipment.

Study on the Scheme of Pumped-Storage Power Station Connecting to Power System

CAI Li, CHEN Ling-yun

2013, 46(1):  81-85.  DOI: 10.11930/j.issn.1004-9649.2013.1.81.4

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A recommended scheme of the QZ pumped-storage power station connecting to power system was introduced. The reasonable operating mode was chosen for the QZ pumped-storage power station based on the real condition of the power grid. Power flow and stability calculation was conducted for its connecting scheme and it was found that in the typical low load operating mode in winter when the interconnection lines between HN power grid and the NF power grid were disconnected, the QZ pumped-storage power station had some stability problems in the pumping mode. The instability mechanism was analyzed according to the stability curves in the situation when HN power grid and the NF power grid were interconnected or disconnected and the problem was identified as transient stability problem. Several measures were proposed for solving the stability problems according to the factors that affect the transient stability of the power system and the actual situation of the HN power system and the QZ pumped-storage units. Quantitative analysis was conducted for the measures implemented, which can provide a reference for the emergency plan and the dispatching operation of the QZ pumped-storage power plant.

Energy Conservation and Environmental Protection

Study on Control of Economic NO_x Concentration at SCR Equipment Inlet

WANG Chun-chang

2013, 46(1):  86-89.  DOI: 10.11930/j.issn.1004-9649.2013.1.86.3

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The methods of computing the indirect running costs of the low NO_x staged combustion technology and the direct running costs of the reducing agent of SCR equipment are introduced. An equation for calculating the total costs of NO_x reduction with the two methods of NO_x control used in boilers is established. According to the principle of minimizing the total costs of NO_x reduction, the NO_x concentration at the inlet of SCR equipment is taken as the variable and, a viewpoint on the existence of the economic inlet NO_x concentration is put forward. The main conclusion is that the economic concentration is a critical value for equitably assigning the indirect costs of low NO_x staged combustion technology and the direct costs of SCR equipment. Only when the NO_x concentration is the economic value, are the total costs of NO_x reduction the least.

Analysis of Factors Affecting Photocatalytic Reduction of CO₂

ZHAO Yi, LIU Wei, ZHANG Zi-li, ZHU Xiao-yu

2013, 46(1):  90-95.  DOI: 10.11930/j.issn.1004-9649.2013.1.90.5

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Photocatalytic reduction of CO₂ is not only an effective method for solar energy utilization, but also a fairly good way to convert CO₂ emitted by combustion of fossil fuels such as coal, oil and natural gas to useful carbon sources. Based on relevant researches both in China and abroad, the effects of light sources, photocatalytic reactors, additives, irradiation time and photocatalysts on photocatalytic reduction of CO₂ are discussed from the mechanism of photocatalytic reduction of CO₂. It is discovered that the development of efficient catalysts, manufacturing of fine photocatalytic reactors and more thorough exploration of photocatalytic mechanism are of vital importance for the research in this field.

Innovations on 300-MW CFB Boilers for Energy Conservation

YUAN Deng-you

2013, 46(1):  96-98.  DOI: 10.11930/j.issn.1004-9649.2013.1.96.2

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According to the problem of high gas temperature of 300-MW CFB boilers, several innovations are made during overhauling. First, extended walls are added to the water-cooled walls. Second, the length of soot-blowers for high-temperature superheaters entering the furnace is shortened, and another group of soot-blowers is installed on the opposite side of the existing soot-blowers. Third, low-pressure economizer is installed, and finally, additional regenerative components are installed in the air preheater. After such modifications, the gas temperature is reduced by 16℃ with the heat consumption rate reduced by 42.31 kJ/(kW·h) and the gross coal consumption rate reduced by 1.6 g/(kW·h). The innovations yield excellent results in energy conservation.

Case Analysis and Solutions of Gypsum Dewatering for FGD Systems of Power Plants

LIANG Lei

2013, 46(1):  99-102.  DOI: 10.11930/j.issn.1004-9649.2013.1.99.3

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Based on the case of the lime/gypsum wet flue gas desulfurization(WFGD) system for the 3×75 t/h circulating fluidized bed boiler in the cogeneration power plant of Shanxi Datuhe Coking and Chemical Co., Ltd., the main causes for abnormal gypsum dewatering which leads to abnormal operation of the system are determined quickly and accurately by using the qualitative analysis method according to the color, setting and separation of the slurry and the appearance of the dewatered slurry filter cake, including the high fly ash content, high CaSO₃·1/2H₂O content and high dissolved calcium hydroxide content in the slurry. By lowering the fly ash content, dredging the oxidation air pipeline, adding gypsum seed and timely adjusting the operation condition, the problem is solved, which indicates that the qualitative analysis method is suitable for emergency treatment of WFGD systems.