Table of Content

25 June 2015, Volume 48 Issue 6

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Security Column

Optimal Configuration for Distributed Wind Generation Based on Cat and Mouse Swarm Algorithm

YANG Jun, ZHANG Chuang, HUANG Xu, SUN Qiuye

2015, 48(6):  1-7.  DOI: 10.11930.2015.6.1

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Smart grid is an important basis for energy sustainable development. One of important characteristic of smart grid is distributed renewable power generation. With consideration of economy, technology and environment factors, a new optimal algorithm, cat and mouse swarm algorithm, is presented based on flocking algorithm and cat swarm algorithm. Optimal configuration of distributed wind power generation is studied by using proposed algorithm, including wind turbine location and capacity selection. The proposed algorithm is insensitive to parameters, which is robust during optimization. Simulation results based on IEEE14 node system show the validity and superiority of the proposed algorithm.

Reliability Analysis on Wind and Solar Hybrid System

ZHANG Shixiang, DING Qian

2015, 48(6):  8-13.  DOI: 10.11930.2015.6.8

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Compared to wind and solar power generation system with conventional power generation systems , its strength is reflected in all aspects of rationality, and it improves the reliability of the system.In this paper, wind and solar power generation system is made as research subjects. Depth analysis on the building of model of wind farm output, model of solar power output and wind and solar system model. It is pointed out that the scenery complementary system with battery energy storage system can improve the reliability of wind power generation system.

Robust Adaptive Tracking Control of Individual Pitch for Wind Turbines

CUI Shuangxi, WANG Weiqing

2015, 48(6):  14-19.  DOI: 10.11930.2015.6.14

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The torques acting on the blades and the aerodynamic-caused unbalanced loads are analyzed for nonlinear motor-driven blade system. Based on the angular momentum theorem, a dynamic model is established for the uncertain time-variable system. A robust adaptive tracking controller of individual pitch is designed for wind turbine, and the adaptive algorithm of undated parameters is introduced. The stability of the blade control system is proved by using Lyapunov stability theory. In order to verify the effectiveness of the control strategy, a wind turbine blade dynamics simulation model is built by using Matlab/Simulink software. The simulation results show that the designed controller can quickly and accurately achieve the individual pitch angle tracking control task under the condition of uncertain time-variable system parameters and the impact of unbalanced loads. The controller is proved to have good and robust control effect for complex nonlinear blade model.

Optimization Model of Wind Power Accommodation for Interest-Balancing with Large Consumer

ZHANG Chen, CHEN Kun, TAN Zhongfu, DONG Anyou

2015, 48(6):  20-25.  DOI: 10.11930.2015.6.20

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China’s wind power is mainly distributed in West China which is far away from the load center. Large scale wind power accommodation would be confronted with problems related to power supply connection and electric power consumption. Large power consumers occupy a large proportion in power load. Wind power can be accommodated by adjusting production plan of large consumers. An optimization model is first established with the goal of maximizing wind power accommodation. With the joint dispatching of wind power and large consumer, profitability analysis of both sides is performed under two different scenarios: with and without cooperation. Large consumer’s productivity is reduced during night hence cost is increased. In order to encourage large consumer participates in wind power accommodation, a dispatching model is built with the goal of maximizing the benefits of both sides. The production loss of large consumer can be compensated from wind power generation in the model.

Configuration of Energy Storage in Power System with Wind Power Integration

HAN Yong, ZHENG Xiangyu, PENG Shengjiang, LI Zhen, SHEN Weicheng, LIANG Cai

2015, 48(6):  26-31.  DOI: 10.11930.2015.6.26

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The wind power may cause ever-growing and serious stability hazard for power system, and energy storage plays a very important role in improving the static and dynamic stability of power system. The role of energy storage is introduced in solving wind power integration problem and an electromechanical static model of flow-based energy storage is set up. The capacity requirement of energy storage for system stability with wind integration is calculated by simulation, and relevant configuration method is proposed. In view of a typical power system with wind power integration, the required energy storage capacity is calculated with the proposed method for achieving the static and dynamic stability. Finally, simulation has proved the effectiveness of the proposed configuration strategy.

Research on the Cascaded Energy Storage System Based on Common DC Bus

JIN Yiding

2015, 48(6):  32-38.  DOI: 10.11930.2015.6.32

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Along with the fast growth of distributed energy storage in urban grid, the voltage level climbs. The maturity of the multilevel topology has provided an effective solution to the power quality problem of large-scaled power conversion systems, while their development is restrained by the design, volume and noise of their power frequency transformers. This paper provides a multilevel power storage system based on a common dc bus, which combines the cascaded multilevel topology and the high frequency transformer techniques. The effectiveness of this structure is verified through the simulation and experimental tests. This kind of energy storage system is expected to be one of the optional ways to integrate large-scaled power storage into the urban grid in the future.

Research on MPPT Control of Partially Shaded Photovoltaic Array Based on Differential Evolution Algorithm

LIN Qirong, WANG Qiaoqiao, LIN Qiwei, LIN Lin, Dong Chenhui, LIU Hongxia

2015, 48(6):  39-44.  DOI: 10.11930.2015.6.39

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When PV module is partially shaded, there will be multi peeks in the power-voltage(P-V) characteristic curve. And conventional maximum power point tracking (MPPT) algorithm, such as perturbation and observation(P&O), cannot accurately track global maximum power point(GMPP) due to its local searching area. This paper proposes a differential evolution(DE) based GMPP tracking algorithm which makes all particles converging to the best solution by modifying the direction of mutation. This helps the algorithm to converge rapidly. Simulation of the proposed algorithm is carried out in Matlab/Simulink and is compared to P&O algorithm.

Estimation Method for Total Reserve and Technical Exploitation Amount of Wind Farm

LIU Zhiyuan, PENG Xiufang, FENG Lili

2015, 48(6):  45-50.  DOI: 10.11930.2015.6.45

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During the early stage of wind farm planning, wind resources assessment is needed to obtain the total reserve and technical exploitation amount of the wind farm. An estimation method for calculating the total reserve and technical exploitation amount of the wind farm is proposed. The method is applied to wind farm in Jiangsu Province at 90m height. The comparison with annual theoretical generated energy verifies practicability and accuracy of proposed method.

Power System

Voltage Control to Wind Power System with On-Load Tap Changer Based on Improved Genetic Algorithm

LI Shenghu, WANG Yanyan, LEI Qingkun, QIAN Zhuang

2015, 48(6):  51-57.  DOI: 10.11930.2015.6.51

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In order to overcome voltage control difficulty caused by wind power fluctuation, a multiple OLTC coordinated optimization model is proposed. The model targets on voltage security, power loss optimization and tap changer margin improvement, which aims to flexible tap changers switching under load and effective voltage regulation. The active output of wind turbine generators(WTGs) is divided into several sections according to the Weibull distribution of wind speed and WTG output characteristic. The sectional mean is applied to OLTC coordinated optimization for tap changer regulation scheme and estimation of voltage security probability. The global convergence of genetic algorithm is improved by integer coding and combination of probabilistic survival and optimal reservation strategy in offspring population selection. The crossover and mutation for individuals are based on random coordination array and random array within variation limits. The results show that improved genetic algorithm can effectively reduce round off error of original genetic algorithm. Reasonable selection of weight coefficient of objective function and dividing sections of wind power fluctuation can improve voltage security probability for optimization regulation scheme of tap changers. The smaller weight coefficient of voltage security and smaller number of divided sections yield lower probability of voltage security. The less active output of the WTGs for section combination yields smaller objective function value and better voltage security.

Design of Wide Area Damping Controller Based on Fuzzy Control

SUN Lin, LI Tianran, QIAN Junjie, CAI Wei, WU Huaren

2015, 48(6):  58-62.  DOI: 10.11930.2015.6.58

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In view of the low frequency oscillations of the interconnected power systems, a method is proposed for designing the excitation controller by using the wide-area feedback signals as additional stability signals. Fuzzy control is applied to compensate the communication time delay during transmission of the wide-area signals. A new method is introduced for determining the fuzzy rules. Firstly, the inputs and expected outputs of fuzzy logic controller are analyzed. Then, the universe of fuzzy sets, membership functions and fuzzy rules are determined based on the relationship between the relevant inputs and outputs, and the fuzzy logic controller is constituted consequently. A four-machine two-area power system is simulated by using Matlab/Simulink software in order to test the performance of the fuzzy control-based wide-area damping controller. Simulation results show that the designed controller can effectively compensate the large time delay and improve the damping of interconnected power system, which verifies the good robustness and adaptability of fuzzy control.

Research on Graph Theory-Based Service Restoration Algorithm of Distribution Network Containing Distributed Generation

FENG Jie, CHEN Junyu, CHEN Mingjun, WANG Jin

2015, 48(6):  63-71.  DOI: 10.11930.2015.6.63

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Service restoration strategy of the distribution network containing distributed generation is very important for the security of distribution networks. A graph theory-based service restoration algorithm is introduced in this paper for the distribution networks containing distributed generation and tie switches. Firstly, a service restoration model for distribution network containing distributed generation as well as an objective functions under service restoration are developed after consideration of the total quantities of restored load, the switching times of circuit breakers and the load losses. Secondly, a revision and adjustment mechanism of infeasible solutions is designed based on graph theory, which includes four steps, i.e., network state genera-tion, network region division, network structure revision and load checking. Then, the Quantum Discrete Particle Swarm Optimization(QPSO) algorithm is applied to achieve the optimization of the objective function. Finally, a case study has proved the superiority of the graph theory-based algorithm in revision of the infeasible solution and the effectiveness of the proposed graph theory-based algorithm in service restoration of distribution networks.

Research on Influencing Factors of Lightning Back-Strike Intruding Overvoltage of 500 kV Substation

WANG Jiannan, JIANG Kun, LUO Renyi

2015, 48(6):  72-79.  DOI: 10.11930.2015.6.72

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In order to reasonably choose lightning intruding overvoltage protection measures, the influencing strength(expressed by the significance level F) and sensitivity range of the main factors of lightning back-strike intruding overvoltage are studied with orthogonal experimental design (OED) method and ATP-EMTP simulation by taking a 500 kV substation as an example. The calculated results show that the ratio of F values between system operation and system parameters, including the distance between No 1 and No 0 tower, the installation location of CVT, the distance between arrester and equipment, the lightning point and tower impulse grounding resistance, are 5.56, 2.13, 1.00, 4.64, 24.58, 7.58 respectively. Meanwhile, several measures, including lowering the impulse grounding resistance of tower from 10 Ω to 5 Ω, setting the distance between No 1 and No 0 tower as around 200 m, and improving the lightning protection of the incoming line segment of 0~900 m, can significantly reduce the level of lightning back-Strike intruding overvoltage.

Research on Thermal Deicing Method for Live Substation Equipment

HUJi, SHAO Guiwei, CAI Huanqing, FU Jing, WEN Zhike, WAN Lifen

2015, 48(6):  80-85.  DOI: 10.11930.2015.6.80

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Based on a comparative analysis of various conventional deicing methods, a new method, i.e., the thermal live deicing method, that is suitable for substation equipment, is developed. An engineering calculation model is established respectively for three thermal deicing methods, including the hot wind-based deicing method, the hot water-based deicing method and the radiation heat-based deicing method. The deicing efficiency and power consumption of the above-mentioned three methods are analyzed both in theory and test, and the security of living working in the field is verified through theoretical analysis and test validation. The obtained results can provide technical support for practical implementation of the proposed deicing method for living equipment.

Evaluation System for Structural Stability of Expanded Diameter Conductor

WAN Jiancheng, SI Jiajun, LIU Long, LIU Zhen

2015, 48(6):  86-93.  DOI: 10.11930.2015.6.86

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Given the certain transmission capacity and engineering requirements, application of expanded diameter conductor can save conductor material and reduce the tower load and structure weight. Design schemes have been proposed and systematic studies have been carried out for four types of JL(X)K/G1A-530(630)/45 expanded diameter conductors, including simulation analysis and conductor-laying verification of structural stability, study of the suitability between the expanded diameter conductor and the conductor-laying equipment and study of the conductor crimping. Based on the studies, the expanded diameter round wires conductor with less strand of inner layer has been recommended for application in the Zhejiang~Fujian 1 000 kV ultra-high voltage transmission line, and guidance is provided on such construction equipment as tension equipment, tackle for paying-off, wire line cards and rotary joint. Finally, a stability evaluation system is established for the expanded-diameter conductor.

The Optimal Strategy of Level 2 Sharing Residential EVSE for Electric Vehicles

LI Min, SU Xiaolin, YAN Xiaoxia, ZHANG Yanjuan

2015, 48(6):  94-101.  DOI: 10.11930.2015.6.94

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It is of vital significance to choose an effective and efficient EVSE (Electric Vehicle Supply Equipment) for the development of plug-in electric vehicles (PEVs). A level 2 sharing residential EVSE is selected as best residential PEVs energy supply method based on present developing situation in China. Furthermore, the techno-economic Analysis of level 2 sharing residential EVSE, level 2 residential EVSE, DC fast charging and battery swapping is presented by improved analytic hierarchy process (AHP). The result shows that level 2 sharing residential EVSE is the most efficient and effective. The optimal strategy for level 2 residential EVSE is also presented though the key parameters analysis.

Analysis on Thermal Stability Parameters of OPGW Cable in Enterprise Standard

CHI Xinghe, SUN Peng, WEI Lieqiang, ZHAI Bin, SHI Nengsen, CHEN Bin

2015, 48(6):  102-106.  DOI: 10.11930.2015.6.102

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Short-circuit current thermal capacity is a critical parameter in the design of OPGW cable. For the OPGW cables with the same structure, a big difference exists in the recommended values between the enterprise standard and the state grid material database. In accordance with the code provisions, a comprehensive comparison and analysis is made on the calculation methods and parameter values of short-circuit current thermal capacity. For the OPGW cables with the aluminum-coated steel structure, the calculation parameters of steel and aluminum conductivity are reasonably selected. The calculation method of short-circuit current thermal capacity is simplified by adopting the comprehensive specific heat method. The results show that the short-circuit thermal capacity values recommended by the enterprise standard are significantly smaller than the normal, and recommended values in the enterprise standard and the state grid material database can be checked and corrected by the simplified calculation method.

Optimal Design of Seawater Desalination System based on Stand-alone Wind Power

LI Chao, ZHOU Zhe, LI Liping

2015, 48(6):  107-112.  DOI: 10.11930.2015.6.107

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Reverse osmosis desalination system driven by off-grid wind power is an essential solution for water shortage problem in coastal areas in China by using renewable energy. An optimal design approach of reverse osmosis desalination system is proposed based on wind power generation. The system design use goal of maximizing overall economic benefit of wind power driven reverse osmosis desalination system as objective function. The optimal seawater desalination system size and battery capacity can be obtained with the proposed method. Case analysis shows that the proposed design method has better economics benefit than empirical designs.

Development of Electrical Life Test Circuit of 145 kV Capacitors Switch for UHV Projects

CHENG Junqi, WANG Haoqing, LI Yuchun, LI Xiangyang, LI Qingyu

2015, 48(6):  113-117.  DOI: 10.11930.2015.6.113

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In order to meet the request of the key technology research of the capacitor switch with high electrical life that is used in UHV projects, the newly developed switches have to pass the type test. The test method, parameter calculation, test equipment and test result analysis of the electrical life test of 145 kV reactive power compensation capacitor switch are introduced in detail. The results show that the test circuit can meet the requirements of relevant standards.

Research of Associated Zone Protection for Microgrid Based on IED Technology

TANG Bo, LI Yu, PENG Youxian, CAO Hongying, CHEN Bin

2015, 48(6):  118-123.  DOI: 10.11930.2015.6.118

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The method of associated zone protection for Microgrid based on Intelligent Electric Device(IED) is proposed to solve the problems of relay protection setting and insufficient selectivity in microgrid protection. According to the division theory of 5 zones of microgrid, the concept of regional attribute is defined, and then 5 zones partition of microgrid could be defined clearly based on IED. The corresponding fault judgment theories and methods of each protection zone are formulated. Therefore, the associated zone protection program and IED protection process for microgrid are determined by protection strategy of distributed decision type. At last, the validity of proposed protection method is verified through PSCAD/EMTDC simulation.

The Analysis of Multi-Infeed HVDC’s Interactive Effect in Guangxi Power Grid Long-Term Plan

WANG Wei, KANG Yi, LI Kui, CHEN Qian

2015, 48(6):  124-127.  DOI: 10.11930.2015.6.124

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In the long term, the energy shortage of Guangxi Autonomous Region will be compensated by outside hydropower energy from DC transmission. However, multi-infeed HVDC has impact on power system operation security and stability. Several problems related to multi-infeed HVDC system in Guangxi grid are analyzed based on power construction planning, power acceptance planning and current operation conditions. The problems include infeed system location, scale, mutual impact and possible risk on gird security and stability. Preliminary judgment indicated that Guangxi power grid has ability to accept Multi-infeed HVDC. However, further research is needed for the detailed connection scheme.

Generation Technology

Wind Tunnel Simulation Experiment on Cooling Tower Emissions

MA Jin, JIANG Yishan, SHEN Fanhui, TIAN Wenxin, XU Yi,

2015, 48(6):  128-132.  DOI: 10.11930.2015.6.128

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Since more and more power plants have moved their chimneys into cooling towers(i.e., gas emission from cooling towers), it is necessary to use wind tunnel to simulate the flow fields inside the cooling tower. In this paper, based on the similarity theory, the main gas diffusion equations are presented; by virtue of wind tunnel experiment, the flow field and gas density in the integrated cooling tower and chimney are simulated; to study how the flow fields are affected inside the tower regarding the cases with full shades open, only upstream shades closed and only downstream shades closed at different environmental wind velocities. The flow field style and the moving direction and volume of the flue gas are then obtained, and it is figured out that the flue gas density on the tower wall is much lower than that on the chimney wall. In addition, the emerging conditions and ranges of going-through wind are studied with some preventive actions being simulated. Finally, the measured results of a power plant are compared with the simulation results, which exhibits very close similarity. This simulation proves that the gas diffusion equations describing the flue gas in the cooling tower are tenable.

Analysis and Treatment on Structural Vibrations in Large Turbo-Generators

HE Guoan, SHI Jun

2015, 48(6):  133-128.  DOI: 10.11930.2015.6.133

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In this paper, the analysis on the characteristics of large turbo-generator structural vibrations is conducted. Taking account of the structural and installation characteristics, it is concluded that the deterioration of the generator supporting stiffness is the major cause contributing to the structural vibration. Therefore, preventive measures are proposed to eliminate or alleviate the vibrations, such as adjusting the foundation bolts, increasing the weights on the generator stator, optimizing the installation of the generator stator and tuning dynamic balancing on the spot. Meanwhile, corresponding case studies are presented to demonstrate the troubleshooting technique.

Operational and Monitoring Analysis of Oxy-Fuel Combustion Power Plants

HUANG Yongli, LIU Jie, LIU Zhaohui, ZHENG Chuguang

2015, 48(6):  139-143.  DOI: 10.11930.2015.6.139

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In order to verify the technical feasibility, operational safety, equipment usability and system reliability of oxy-fuel combustion technology, the system configuration, structural features and practical operation process of traditional air combustion system and domestic existing oxy-fuel combustion demonstration project are analyzed by adopting the approach of characteristics contrast and qualitative analysis. Then the major technical characteristics and operational monitoring requirements of oxygen-fired system distinct from the traditional air combustion systems are put forward.

Experimental Study on Distribution Characteristics of Desalination Nozzles

LIU Qiusheng, YANG Qingwei, LI Huixiong, HAO Chenyu, FENG Yongchang

2015, 48(6):  144-150.  DOI: 10.11930.2015.6.144

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To verify the characteristics of a domestically-made nozzle, the experimental study on the flow distribution characteristics of an imported M5 engineering nozzle and a domestically-developed blue nozzle both used in low temperature multi-effect desalination (LT-MED) is conducted. In this study the influence of the volumetric flow rate and the brine concentration on the liquid distribution are analyzed. The experimental results show that the flow distribution characters of these two types of nozzles are basically the same, and the increasing in the volumetric flow rate makes little influence on the flow distribution; in addition, the change in the brine concentration does not cause obvious fluctuation of the flow distribution. The experiments indicate the domestically-made nozzle performs well enough for engineering application.

Design and Implementation of FCB Function for Domestically-made 1 000-MW Units

HUANG Weijian, ZHAN Zhigang, WAN Wenjun, YIN Wuchang, YANG Tieqiang

2015, 48(6):  151-155.  DOI: 10.11930.2015.6.151

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In this paper, the necessity of the fast cut back(FCB) function in thermal generation units is discussed according to the requirements of the power system operation, meanwhile, the key technologies and fundamentals to realize the FCB function are also put forward. Taking a 1 000-MW unit with no FCB function designed in the construction period for example, the system modification and control logical design schemes as well as the testing procedures of the FCB function are proposed based on the analysis of the unit configuration. Then, the FCB test results under 100% load condition are obtained, which proves that the modification and implementation schemes are correct and effective with the advantages of short modification cycle and low cost and can bring security and economic benefits to the power grid and the unit itself.

Application of Steam Combination and Decomposition on S209FA Gas Turbine “2 on 1” Combined Cycle

ZHAO Junfeng, HE Gaiping

2015, 48(6):  156-160.  DOI: 10.11930.2015.6.156

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In this paper, the thermal system features and startup mode of S209FA series“2 on 1” gas-steam combined cycle in Pakistan Guddu Power Plant are introduced. The bypass control strategy is optimized and tested in different steam combination and de-combination modes. The synchronous HP(high pressure) and IP(intermediate pressure) steam combination and decomposition are beneficial to axial thrust balance and stable operation, but are hard to realize automatically due to the large number of control devices and parameters. However, the automatic steam combination and decomposition can be realized by using the method of IP steam first, HP steam after, and LP(low pressure) steam the last. By adopting this method, the unit loads are stable and satisfy the requirements of quick startup and shutdown and stable operation, which indicates that the automation level of the unit is improved.