Table of Content

25 July 2017, Volume 45 Issue 7

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Power & Electrical Engineering

Equivalent Modeling of External Network in New Energy Power Grid Taking Voltage Support into Consideration

ZHU Ge-lan SHENG Jian-lan

2017, 45(7):  1-7.  doi:10.3969/j.issn.1000-565X.2017.07.001

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Proposed in this paper is a new equivalent modeling method of external network considering voltage sup- port.Firstly,on the basis of short circuit information of all external network boundary nodes obtained by multiple fault simulation with Power System Analysis Software Package,an equivalent model of external network in the form of current source branch is established.Secondly,in order to overcome the errors of boundary node voltages due to the ignorance of internal network,the model is converted into a model in the form of Thevenin impendence branch.Then,a potential correction method,which takes actual steady-state voltages as the expectations in equivalent power injection branch,is proposed.The modified equivalent model on the basis of boundary node information can ac- curately reflect the voltage support of external network.Finally,by taking Ningxia regional new energy power grid for example,two external networks respectively with long chain-type and ring-type internal networks are modeled.Simulated results verify the validity and accuracy of the proposed modeling method.

Dynamic Active Power Optimization Control of Microgrid on the Basis of Credibility Theory

DONG Ping QIN Chuan FENG Yong-qing

2017, 45(7):  8-15.  doi:10.3969/j.issn.1000-565X.2017.07.002

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Aiming at the microgrid parallel operation system containing various distributed generations,a credibility theoretical analysis is made to establish a dynamic active power optimization model.Then,by taking the minimum microgrid operation cost as the objective function,the model is solved and the results are compared with those ob- tained by the optimization via scenario analysis.Calculation example verifies the correctness of the proposed model,as well as the effectiveness and practicability of above-mentioned method in dealing with the active power optimiza- tion of microgrid containing various small-scale distributed generations.

Power & Electrical Engineering

Optimal Distribution of Active Power for Tie-Lines in Long-Distance AC/DC Parallel Transmission Channel

LU Wen-tian LIN Shun-jiang LIU Ming-bo

2017, 45(7):  16-24.  doi:10.3969/j.issn.1000-565X.2017.07.003

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According to the hierarchical and zoned dispatching characteristics of multi-area interconnected AC/DC power systems,an optimal distribution method of active power for tie-lines in long-distance AC/DC parallel trans- mission channel is proposed on the basis of a given total power exchange schedule among regions.In the optimiza- tion model,the minimum active power loss of AC/DC tie-lines is used as the objective function,and,security con- straints of the inter-province AC tie-line sections,as well as the constraints of power regulation range and regulation frequency limit of DC tie-lines,are taken into consideration,Then,a power transmission schedule of AC/DC chan- nels is obtained.Instead of DC power flow model,a practical model called simplified AC power flow model is pro- posed,which is used to calculate the transmission power of inter-province AC tie-lines with hundreds of kilometers in length more accurately.Moreover,for the purpose of satisfying the constraints of DC tie-line power regulation frequency limit and the minimum duration limit of each power state of DC tie-lines,an improved three-stage method is applied to the optimization model.Thus,the optimization model can be decoupled in each dispatch period,and each sub-model can be parallelly computed in each dispatch period.Finally,by taking a practical large-scale AC/ DC interconnected multi-area power system for example,the correctness and effectiveness of the proposed optimiza- tion model and the corresponding solving algorithm are both verified.

Cooling Channel Design of Permanent Magnetic Synchronous Motor Considering Heat Exchange and Pressure Loss

WAN Zhen-ping WEN Wan-yu WU Bo-xi FU Yong-qing

2017, 45(7):  25-32,40.  doi:10.3969/j.issn.1000-565X.2017.07.004

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As the existing researches on the water cooling system of motors applied to electric vehicles mainly focus on the heat exchange performance without taking full consideration into pressure loss,the influences of cooling channel parameters on heat exchange performance and pressure loss are analyzed theoretically for the frequently- used driving motor-permanent magnetic synchronous motor ( PMSM),finding that the twist number of cooling chan- nels influences heat exchange and pressure loss greatly,and that the transverse dimensions of cooling channel have little influence on heat transfer but have great influence on pressure loss.Thus,an optimal range of cooling channel parameters is obtained,with its validity being verified by simulating PMSM temperature field and pressure loss of cooling channels with optimized parameters through a finite element analysis.Finally,a new design method of cool- ing channels considering both heat exchange and pressure loss is presented.The research provides a reference for the design of water cooling system of PMSM with high power density.

A Method to Assess Commutation Failure of HVDC Systems Taking Space-Time Discreteness into Consideration

CAI Ze-xiang YANG Huan-huan YU Chao-yun LI Xiao-hua

2017, 45(7):  33-40.  doi:10.3969/j.issn.1000-565X.2017.07.005

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As the characteristics of commutation failure of high-voltage direct current ( HVDC) systems vary with not only fault close angle but also fault positions,the existing assessment methods that only consider the influence of voltage dip of converter bus are not accurate enough.In order to solve this problem,firstly,the space-time dis- creteness of commutation failure is investigated.Secondly,the influence of fault close angle on the process of com- mutation failure is analyzed,and the most unfavorable angle is pointed out.Then,two main causes for the impact of fault position on commutation failure,namely the electrical distance and the phase difference between fault bus and DC inverter bus,are discovered.Moreover,in light of the analytical results of space-time discreteness under the condition of commutation failure,a criterion of extinction angle,which takes both voltage amplitude and phase distortion into consideration,is proposed.Thus,a method to assess commutation failure is presented.Finally,a comparison of the proposed method is made with PSCAD/EMTDC and BPA on a three-node AC/DC system in Chi- na Southern Power Grid.The results show that the proposed method is effective and practicable.

Effect of Radial Temperature Difference on Sag Calculation for Overhead Conductors

LIU Gang LI Yang CHEN Yuan YANG Yu-hang

2017, 45(7):  41-47,54.  doi:10.3969/j.issn.1000-565X.2017.07.006

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In this paper,firstly,a thermal circuit model of ACSR( Aluminium Cable with Steel Reinforcement) was established to analyze the radial temperature field distribution.Secondly,the temperature field of conductor section in different loading conditions was calculated via a finite element analysis.Then,the causes for radial temperature gra- dient were analyzed through the simulation and were verified by the experiments of temperature distribution on the steel-reinforced layer and the surface.Finally,on the basis of experimental results,the calculation errors of different sags caused respectively by temperature difference and span difference were discussed.It is found that,with the im- provement of current carrying capacity,the radial temperature difference increases,leading to the gradual expansion of sag’s calculation error.For example,when the outer temperature achieves 70℃,the steel core temperature under natural convection is 73. 5℃.Moreover,it is found that,at a certain radial temperature difference between the steel- reinforced layer and the surface,greater span may result in larger calculation error and smaller relative error.

Gray Correlation Analysis of Atmospheric Conditions and Prediction of Air Gap Discharge Voltage

NIU Hai-qing XU Jia WU Ju-zhuo YU Jia

2017, 45(7):  48-54.  doi:10.3969/j.issn.1000-565X.2017.07.007

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In order to discover the impact of atmospheric condition parameters on air gap discharge voltage,a auto- matic discharge monitoring device with ball-ball electrode was used to monitor and record the discharge voltage and atmospheric condition parameters in natural environment,and a calculation model of gray correlation was estab- lished,by which the gray correlations between atmospheric condition parameters and discharge voltage were ob- tained,finding that the gray correlations of atmospheric condition parameters are indicative of the following order: pressure ＞ temperature ＞ wind speed ＞ relative humidity ＞ illumination.Then,by taking the atmospheric condition parameters as inputs,Chebyshev neural network was used to predict the discharge voltage,with better prediction results being obtained in comparison with BP neural network.Finally,according to the sort of atmospheric condi- tion parameters,the first two ( pressure and temperature) ,the first three ( pressure,temperature and wind speed) and the first four ( pressure,temperature,wind speed and relative humidity) parameters were respectively taken as the inputs of Chebyshev neural network to predict the discharge voltage.The results show that,with the reduction of the number of inputs,the average relative error and maximum relative error of the predicted values both have little change.

Computer Science & Technology

Pedestrian Re-Identification on the Basis of Dictionary Learning and Fisher Discrimination Sparse Representation

ZHANG Jian-wei LIN Wen-zhao QIU Long-qing

2017, 45(7):  55-62.  doi:10.3969/j.issn.1000-565X.2017.07.008

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In order to overcome the inadequate consideration of the existing dictionary learning taken into the con- nection of pedestrian features of different camera views,a new pedestrian re-identification method is proposed on the basis of dictionary learning and Fisher discrimination sparse representation.By considering the similar sparse representation of features of the same pedestrian in different scenes,the concept of pedestrian re-identification scat- ter function is put forward through adding a regularization term that constrains the sparse representation.The regu- larization term aims at maximizing the between-class scatter of the sparse representation of different pedestrians,and minimizing the within-class scatter of the sparse representation of the same pedestrian.Thus,sparse representation with strong discrimination ability can be obtained via dictionary learning.Experimental results on VIPeR,PRID 450s and CAVIAR4REID datasets indicate that the recognition rate of the proposed method is higher than that of other dictionary learning-based pedestrian re-identification methods.

A Novel Structured Data Center Network with Constant Degree and Small-World Characteristics

LI Mei-sheng XIAO Wen-jun LAI Zheng-wen ZHANG Zhan-ying HAN Dong

2017, 45(7):  63-68.  doi:10.3969/j.issn.1000-565X.2017.07.009

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Firstly,Gcoset,an algebraic graph with constant degree,is defined.Secondly,on the basis of Gcoset,a virtualized topology structure named GDCN,which is of eight-degree regularity and symmetry for data center net- work,is proposed.Then,the static model of GDCN and the routing algorithm of GCoset are both described in de- tail,and a concrete implementation of GDCN is presented.Finally,a comparison between GDCN and other data center network models is made.The results show that GDCD is of a network diameter of only O ( logN) and needs relatively simple routing algorithm,and that it possesses simple structure,high communication performance,good scalability and excellent fault tolerance.

A Secure Multi-Party Computation Protocol on the Basis of Multi-Key Homomorphism

WANG Hui-yong FENG Yong ZHAO Ling-zhong TANG Shi-jie

2017, 45(7):  69-76.  doi:10.3969/j.issn.1000-565X.2017.07.010

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In order to build a multi-key secure multi-party computation ( SMC) protocol with high performance,the key homomorphic properties of Gentry-Sahai-Waters ( GSW13) fully-homomorphic encryption ( FHE) scheme is in- vestigated.Afterwards,a general multi-key SMC protocol with simple structure,which needs only 3 rounds of inter- actions,is proposed on the basis of leveled GSW13.In the semi-honesty and semi-malicious setting as well as in the common random string model,the security of the protocol relies on the learning with errors ( LWE) problem and a variant of LWE.Then,the difficulty in solving the variant is analyzed,and a formalized security proof in semi- malicious setting is given.The proposed SMC protocol naturally constitutes a leveled multi-key FHE scheme in the same setting.Comparative analysis results show that the proposed protocol is superior to the existing schemes in terms of overall performance.

A Method to Analyze Amplitude-Time Inflection Point of Mutation Signals

DAI Yi-mei ZHANG He-sheng LI Dong QI Hong-mei FANG Ke

2017, 45(7):  77-83.  doi:10.3969/j.issn.1000-565X.2017.07.011

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As the mutation signals hidden in the vibration data of engine's high-speed bearing are difficult to pin- point in time domain,a new algorithm to obtain the amplitude-time inflection point of mutation signals is proposed.Firstly,the characteristic frequency of the signal is extracted via discrete Fourier transform.Secondly,a time-lapse Fourier analysis of the frequency is executed,which helps obtain amplitude-time inflection points.Then,the ap- pearing and disappearing moments of the mutation signal are discovered according to the inflection points.Finally,the amplitude of the mutation signal is obtained via the quadratic Fourier analysis of the signal in a certain period.The results of theoretical analysis,theoretical simulation and engineering simulation all indicate that the proposed algorithm can capture the amplitude of mutation signals accurately,and obtain the appearing and disappearing mo- ments of mutation signals in vibration data.

A Fast Run-Based Two-Pass Algorithm for Connected Components Labeling

LYU Chang-kui XU Yan LUO Bing-xin

2017, 45(7):  84-89.  doi:10.3969/j.issn.1000-565X.2017.07.012

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In order to improve the calculation efficiency of connected component labeling ( CCL) algorithms of bi- nary images,firstly,an algorithm named FRL,which optimizes the conventional overlapping runs detection algo- rithm for run-based two-pass labeling algorithms,is proposed.Secondly,a general algorithm on the basis of FRL and union find is introduced.Then,some experiments are carried out to verify the computational efficiency of FRL.Finally,a comparative analysis is made between the general algorithm and other two typical two-pass CCL algo- rithms ( namely RTS and SAUF) . The results demonstrate that,as FRL saves unnecessary subsequent connectivity checks on runs between adjacent rows,the connectivity detection process is optimized into a chain-like mode,the calculation efficiency of run length labeling process improves greatly,the time complexity reduces from conventional O ( mn) to O ( m + n －1) ,and the execution time decreases to the same level as the union find algorithm mod- ule.Moreover,it is found that the proposed general algorithm greatly outperforms RTS but is slightly better than SAUF in general.

CPBF: an IP Package Identification Algorithm Using Bloom Filter

LI Long-fei HE Zhan-zhuang SHI Yang-chun

2017, 45(7):  90-97,106.  doi:10.3969/j.issn.1000-565X.2017.07.013

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As the traditional Bloom filters adopt the same process for different IP packages and ignore not only IP package identification invalidation cost but also hardware resource in the process of flow identification,an algorithm called CPBF ( Classified and Pipelined Bloom Filter) for IP package identification is presented.CPBF differentiates IP packages depending on ToS ( Type of Service),which can reflect their identification invalidation cost in some ways.In order to minimize the identification invalidation rate,different numbers of Hash functions are applied to different types of IP packages.Specifically,pipelined Hash functions are adopted to accelerate the identification speed.Moreover,on the basis of the theories of probability and differential equation,the description and analytical expression of CPBF are deduced.Finally,an implementation of CPBF is conducted on FPGA.The results indicate that CPBF is superior to standard Bloom filter and multi-dimensional Bloom filter because it helps achieve lower i- dentification invalidation rate and hardware resource cost without sacrificing identification speed.

Multi-Modal Image Registration on the Basis of Local Structure Tensor-Mutual Information

ZHANG Li LI Bin TIAN Lian-fang LI Xiang-Xia

2017, 45(7):  98-106.  doi:10.3969/j.issn.1000-565X.2017.07.014

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Mutual information ( MI) measure considers the global characteristics of image gray statistics only,and ignores spatial structure information and local characteristics of image gray statistics.In order to overcome these drawbacks,a registration method on the basis of the new measure of local structure tensor-mutual information ( LST- MI) is proposed.The proposed LST-MI measure considers the structure information of image neighborhood fully,gives the pixel position with greater importance larger weighting factor.Thus,the distinguishing of global extremum strengthens,the risk of trapping at local extremum reduces,the success rate improves,and the robustness of regis- tration enhances.Moreover,some registration experiments are conducted on simulated brain images and clinical im- ages.The results show that,in comparison with the registration method on the basis of mutual information and local mutual information,the proposed method improves the success rate of registration by more than 50%,and enhances the registration robustness significantly.

Electronics, Communication & Automation Technology

Fast Searching-Based Iterative Multi-Hypothesis Algorithm Applied to Compressed Video Sensing

YANG Chun-ling XIONG Guang-yin DAI Chao

2017, 45(7):  107-112,125.  doi:10.3969/j.issn.1000-565X.2017.07.015

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As the two-stage multi-hypothesis reconstruction ( 2sMHR) for the prediction in both measurement and pixel domains is of low reconstruction quality at low subrate as well as low prediction accuracy and high computa- tional complexity for fast movement sequences,on the basis of 2sMHR scheme,a novel iterative multi-hypothesis ( IMH) prediction reconstruction algorithm utilizing fast searching technology is proposed.This algorithm utilizes the flexibility of block partition in pixel domain to conduct overlapping block-based iterative multi-hypothesis pre- diction,and adopts the scheme of jointing cross-shaped and regional searching to lessen matching complexity in large-range searching for fast sequences.In addition,by utilizing the space correlation in images,an adaptive in- terframe/intraframe hypothesis-block selecting scheme is presented.In comparison with the existing algorithms,the proposed IMH prediction reconstruction algorithm suppresses the prediction block effect,reduces the computational complexity for large-range searching and improves the video reconstruction quality.

Power Efficiency Optimization-Based D2D Power Control Method

LI Yong-zhao DU Si-qi ZHANG Rui LIANG Hai-tao LIU Xiao-man

2017, 45(7):  113-119.  doi:10.3969/j.issn.1000-565X.2017.07.016

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Device-to-device ( D2D) communication underlaying LTE-A cellular networks can increase the utiliza- tion efficiency of cellular resources effectively.However,the co-channel interference caused by cellular resources reuse may degrade the system throughput.An effective power control scheme can effectively suppress the interfer- ence and improve the overall performance.In order to further improve the power efficiency of cellular users,a pow- er control scheme on the basis of power efficiency optimization is presented.Firstly,according to the characteristics of network resources reuse,power efficiency is redefined from the viewpoint of resource usage.Then,power alloca- tion is formulated with the objective of maximizing power efficiency,and a step length-variable incremental iteration algorithm is proposed to derive the optimal power for both cellular and D2D users.Simulation results indicate that the proposed power control scheme helps obtain higher throughput with lower power consumption,outperforms the existing scheme by approximately 15% increment in power efficiency,decreases the computational complexity,and reduces the impact of mutual interference effectively.

Effects of Biaxially-Tensile Strain on Working Performances of Germanium Laser

LI Xi-yue LI Bin XIA Guangrui

2017, 45(7):  120-125.  doi:10.3969/j.issn.1000-565X.2017.07.017

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In order to explore a performance optimization scheme for germanium laser,firstly,a model of double- heterojunction Fabry-Perot electrically-pumped edge emitting germanium laser is established on the basis of biaxial- ly-tensile strain.Then,the relationship between the biaxially tensile strain and the optimal doping density is dis- cussed with the help of the proposed model.Finally,the variations of such laser parameters as threshold current density and electro-optical conversion efficiency with both biaxially-tensile strain and doping density are analyzed.The results show that ( 1) the optimal doping density decreases as biaxially-tensile strain increases,and,excessive doping may lead to laser performance degradation; ( 2) at the same doping density,both optical gain and peak gain wavelength increase as biaxially-tensile strain increases; and ( 3) in comparison with the literature data,germanium laser with 0. 8% biaxially-tensile strain and with the corresponding optimal doping density ( 8 ×10¹⁹cm^-3 ) posses- ses a threshold current density as low as 1/10 of that of the literature value,while the electro－optical conversion efficiency nearly increases by 10 folds.

Feedback Control of Car Following Model on the Basis of Time-Varying Safety Distance

ZHAI Cong WU Wei-tiao HUANG Ling LIU Wei-ming ZHENG Li-yuan

2017, 45(7):  126-134,152.  doi:10.3969/j.issn.1000-565X.2017.07.018

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In order to reflect the traffic flow's characteristics more realistically,on the basis of CM ( Coupled-Map) car following model proposed by Konishi,a new expression of safely distance is established,with the consideration of the safe distance of vehicles at different speeds.Then,a CM car following model on the basis of time-varying safety distance is proposed subsequently,of which the stability is studied.Moreover,on the basis of stability theo- ry,the sufficient conditions that the traffic congestion phenomenon will never occur are presented,and,in order to suppress the traffic congestion,a delay-feedback controller is designed.Finally,a comparison between the pro- posed model and Konishi model is made in terms of inhibiting traffic congestion and carbon dioxide emission,Simu- lated results show that the convergence rate of the proposed model is faster than that of Konishi model,and that the designed controller is effective in suppressing the traffic congestion and reducing the carbon dioxide emission via ad- justing motorcade speed.

An ICDF-Based Fast Parameter Optimization Approach for Support Vector Machines

WANG Jia-peng HU Yue-ming LUO Jia-xiang

2017, 45(7):  135-142.  doi:10.3969/j.issn.1000-565X.2017.07.019

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In the process of parameter optimization for support vector machines ( SVMs) with Gaussian kernel,in- ter-cluster distance in feature spaces ( ICDF) is an effective measure.However,ICDF may result in heavy compu- tational load and large time consumption.In order to solve this problem,firstly,the theorem that ICDF is a positive strictly-unimodal function about Gaussian kernel parameter is proved.Then,according to this theorem,a modified golden section algorithm ( MGSA) is proposed to search a shrunk value fast for kernel parameter in the candidate set.Thus,a fast parameter optimization approach on the basis of both MGSA and differential evolutionary algorithm is presented.Finally,some experiments are carried out to verify the effectiveness and rapidity of the proposed ap- proach.

Improved Graph MST-Based Image Segmentation with Non-Subsampled Contourlet Transform

LIAO Yi-peng WANG Wei-xing

2017, 45(7):  143-152.  doi:10.3969/j.issn.1000-565X.2017.07.020

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In order to improve the segmentation accuracy of graph's minimum spanning tree and reserve more edge details,a new image segmentation method,which is on the basis of non-subsampled Contourlet transform ( NSCT) and improved graph's minimum spanning tree ( MST) is proposed.Firstly,an image is decomposed into a low-fre- quency sub-band and several high-frequency direction sub-bands through NSCT decomposition.Secondly,the high- frequency direction sub-bands are denoised according to the improved Bayes shrink threshold,and edge points are detected according to the module maxima.Then,a multi-scale multi-direction MST edge weight is constructed ac- cording to the grey value of low-frequency sub-band and the coefficients of high-frequency sub-bands,and the edge weight of edge points is increased.Moreover,MST algorithm is improved in two main aspects,one is the function of intra-regional and inter-regional differences,and the other is the re-merge mechanism after segmentation.Thus,the impact of noises or isolated points can be reduced.Finally,the optimal position adjustment strategy of harmony search is improved and adopted to find the optimal parameters of global optimal MST segmentation results adaptive- ly.Experimental results show that,in comparison with other improved MST algorithms,the proposed method im- proves both anti-noise performance and segmentation accuracy,and helps obtain images with higher segmentation accuracy and better edge details.