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A Hybrid Signal Processing Method Combining Mathematical Morphology and Walsh Theory for Power quality Disturbance Detection and Classification

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 584-592页

作者： Zhi Ding Tianyao Ji Mengshi li q.H.Wu School of Electric Power Engineering South China University of Technology(SCUT)Guangzhou 510641China

In this paper, a novel signal processing method combining mathematical morphology (MM) and Walsh theory is proposed, which uses Walsh functions to control the structuring element (SE) and MM operators. Based on the Walsh-MM method, a scheme for power quality disturbances detection and classification is developed, which involves three steps: denoising, feature extraction and morphological clustering. First, various evolution rules of Walsh function are used to generate groups of SEs for the multiscale Walsh-ordered morphological operation, so the original signal can be denoised. Next, the fundamental wave of the denoised signal is suppressed by Hadamard matrix;thus, disturbances can be extracted. Finally, the Walsh power spectrum of the waveform extracted in the previous step is calculated, and the parameters of which are taken by morphological clustering to classify the disturbances. Simulation results reveal the proposed scheme can effectively detect and classify disturbances, and the Walsh-MM method is less affected by noise and only involves simple calculation, which has a potential to be implemented in hardware and more suitable for real-time application.

关键词： Hadamard matrix mathematical morphology morphological clustering power quality disturbance Walsh theory

Location of Asymmetric Ground Fault Using Virtual Injected Current Ratio and Two-stage Recovery Strategy in Distribution Networks

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 151-161页

作者： Haiting Shan Luliang Zhang q.H.Wu Mengshi li School of Electric Power Engineering South China University of Technology(SCUT)Guangzhou 510641China

Sparse measurements challenge fault location in distribution networks.This paper proposes a method for asymmetric ground fault location in distribution networks with limited measurements.A virtual injected current vector is formulated to estimate the fault line,which can be reconstructed from voltage sags measured at a few buses using compressive sensing(CS).The relationship between the virtual injected current ratio(VICR)and fault position is deduced from circuit analysis to pinpoint the fault.Furthermore,a two-stage recovery strategy is proposed for improving reconstruction accuracy of the current vector,where two different sensing matrixes are utilized to improve the incoherence.The proposed method is validated in IEEE 34 node test feeder.Simulation results show asymmetric ground fault type,resistance,fault position and access of distributed generators(DGs)do not significantly influence performance of our method.In addition,it works effectively under various scenarios of noisy measurement and line parameter error.Validations on 134 node test feeders prove the proposed method is also suitable for systems with more complex structure.

关键词： Distribution networks fault location reconstruction accuracy two-stage recovery virtual injected current ratio

Convexification of Hybrid AC-DC Optimal Power Flow with line-Commutated Converters

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 617-628页

作者： Hongyuan liang Zhigang li J.H.Zheng q.H.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510641China

line-commutated converter (LCC)-based high-voltage DC (HVDC) systems have been integrated with bulk AC power grids for interregional transmission of renewable power. The nonlinear LCC model brings additional nonconvexity to optimal power flow (OPF) of hybrid AC-DC power grids. A convexification method for the LCC station model could address such nonconvexity but has rarely been discussed. We devise an equivalent reformulation for classical LCC station models that facilitates second-order cone convex relaxation for the OPF of LCC-based AC-DC power grids. We also propose sufficient conditions for exactness of convex relaxation with its proof. Equivalence of the proposed LCC station models and properties, exactness, and effectiveness of convex relaxation are verified using four numerical simulations. Simulation results demonstrate a globally optimal solution of the original OPF can be efficiently obtained from relaxed model.

关键词： AC-DC power system convex relaxation linecommutated converter optimal power flow second-order cone programming

Genome-wide distribution and functions of the AAE complex in epigenetic regulation in Arabidopsis

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Journal of Integrative Plant Biology 2021年第4期63卷 707-722页

作者： Yi-Zhe Zhang Juncheng lin Zhizhong Ren Chun-Xiang Chen Daisuke Miki Si-Si Xie Jian Zhang Ya-Nan Chang Jing Jiang Jun Yan qingshun q.li Jian-Kang Zhu Cheng-Guo Duan Shanghai Center for Plant Stress Biology and CAS Center of Excellence for Molecular Plant Sciences Chinese Academy of SciencesShanghai 201602China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems College of the Environment and EcologyXiamen UniversityXiamen 361102China State Key Laboratory of Crop Stress Adaptation and Improvement School of Life SciencesHenan UniversityKaifeng 475004China School of life Sciences East China Normal UniversityShanghai 200241China Graduate College of Biomedical Sciences Western University of Health SciencesPomona 91766USA Department of Horticulture and Landscape Architecture Purdue UniversityWest Lafayette 47907USA

Heterochromatin is widespread in eukaryotic genomes and has diverse impacts depending on its genomic context.Previous studies have shown that a protein complex,the ASI1-AIPP1-EDM2(AAE)complex,participates in polyadenylation regulation of several intronic heterochromatin-containing genes.However,the genome-wide functions of AAE are still unknown.Here,we show that the ASI1 and EDM2 mostly target the common genomic regions on a genome-wide level and preferentially interacts with genetic heterochromatin.Polyadenylation(poly(A)sequencing reveals that AAE complex has a substantial influence on poly(A)site usage of heterochromatin-containing genes,includingnotonlyintronicheterochromatincontaining genes but also the genes showing overlap with heterochromatin.Intriguingly,AAE is also involved in the alternative splicing regulation of a number of heterochromatin-overlapping genes,such as the disease resistance gene RPP4.We provided evidence that genic heterochromatin is indispensable for the recruitment of AAE in polyadenylation and splicing regulation.In addition to conferring RNA processing regulation at genic heterochromatin-containing genes,AAE also targets some transposable elements(TEs)outside of genes(including TEs sandwiched by genes and island TEs)for epigenetic silencing.Our results reveal new functions of AAE in RNA processing and epigenetic silencing,and thus representimportantadvancesinepigenetic regulation.

关键词： alternative polyadenylation alternative splicing epigenetic regulation heterochromatin transcription

Network Embedding Algorithm for Vulnerability Assessment of Power Transmission lines Using Integrated Structure and Attribute Information

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CSEE Journal of Power and Energy Systems 2024年第1期10卷 351-360页

作者： Xianglong lian Tong qian Zepeng li Xingyu Chen Wenhu Tang q.H.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China

In power systems,failures of vulnerable lines can trigger large-scale cascading failures,and vulnerability assessment is dedicated to locating these lines and reducing the risks of such failures.Based on a structure and attribute network embedding(SANE)algorithm,a novel quantitative vulnerability analysis method is proposed to identify vulnerable lines in this research.First,a two-layered random walk network with topological and electrical properties of transmission lines is established.Subsequently,based on the weighted degree of nodes in the two-layered network,the inter-layer and intra-layer walking transition probabilities are developed to obtain walk sequences.Then,a Word2Vec algorithm is applied to obtain lowdimension vectors representing transmission lines,according to obtained walk sequences for calculating the vulnerability index of transmissions lines.Finally,the proposed method is compared with three widely used methods in two test systems.Results show the network embedding based method is superior to those comparison methods and can provide guidance for identifying vulnerable lines.

关键词： Network embedding random walk transmission lines vulnerability assessment

Simulation Analysis of Deformation Control for Magnetic Soft Medical Robots

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IEEE/CAA Journal of Automatica Sinica 2024年第3期11卷 794-796页

作者： Jingxi Wang Baoyu liu Edmond q.Wu Jin Ma Ping li Key Laboratory of Biomechanics and Mechanobiology(Beihang University) Ministry of Education Beijing Advanced Innovation Center for Biomedical Engineeringthe School of Biological Science and Medical EngineeringBeihang UniversityBeijing100083China IEEE the Department of Automation Shanghai Jiao Tong UniversityShanghai 200240China the Department of Aerospace Medicine Air Force Medical UniversityXi’an 710032China

Dear Editor,This letter presents a biocompatible cross-shaped magnetic soft robot and investigates its deformation mode control strategy through COMSOL modeling and simulation.Magnetic soft robots offer novel avenues ... 详细信息

关键词： robot simulation COMSOL

Observability Analysis of Integrated Electricity and Heating Systems with Thermal quasi-dynamics in Pipelines

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CSEE Journal of Power and Energy Systems 2024年第3期10卷 1145-1158页

作者： Zhigang li Wenjian Zheng Junbo Zhao J.H.Zheng q.H.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510641China Fuzhou Changle District Power Supply Company of State Grid Fujian Electric Power Co. Ltd.Fuzhou 350000China Department of Electrical and Computer Engineering University of ConnecticutStorrsCT 06269USA CSEE IEEE

Observability analysis(OA)is vital to obtaining the available input measurements of state estimation(SE)in an integrated electricity and heating system(IEHS).Considering the thermal quasi-dynamics in pipelines,the measurement equations in heating systems are dependent on the estimated results,leading to an interdependency between OA and SE.Conventional OA methods require measurement equations be known exactly before SE is performed,and they are not applicable to IEHSs.To bridge this gap,a scenario-based OA scheme for IEHSs is devised that yields reliable analysis results for a predefined set of time-delay scenarios to cope with this interdependency.As its core procedure,the observable state identification and observability restoration are formulated in terms of integer linear programming.Numerical tests are conducted to demonstrate the validity and superiority of the proposed formulation.

关键词： Integrated electricity and heating system measurement observability analysis state estimation thermal quasi-dynamics

Microstructure evolution and shape memory behaviors of Ni_(47)Ti_(44)Nb_(9)alloy subjected to multistep thermomechanical loading with different prestrain levels

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Journal of Materials Science & Technology 2024年第4期171卷 80-93页

作者： Y.H.Zhang H.li Z.W.Yang X.liu q.F.Gu State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China Shaanxi Key Laboratory of High-Performance Precision Forming Technology and Equipment Northwestern Polytechnical UniversityXi’an 710072China

Ni_(47)Ti_(44)Nb_(9)shape memory alloy(SMA)is a promising material in the aerospace field due to its wide transformation hysteresis.The application of shape memory effect depends on multistep thermomechan-ical loading,viz.,low-temperature deformation and subsequent heating to recovery.Low-temperature deformation prestrain plays a pivotal role in shape memory properties tailoring of SMA components.However,microstructure evolution and deformation mechanisms of Ni_(47)Ti_(44)Nb_(9)SMA subjected to vari-ous prestrain levels are still unclear.To this end,microstructure evolution and shape memory behaviors of Ni_(47)Ti_(44)Nb_(9)alloy subjected to multistep thermomechanical loading with prestrain levels of 8%-16%at-28℃(M_(s)+30℃)were investigated.The results demonstrate that the stress-strain curve of the specimen exhibits four distinct stages at a maximal prestrain of 16%.Whereas stageⅡand stageⅢend at prestrains of∼8%and∼12%,respectively.In stageⅡ,the stress-induced martensitic transformation is accompanied by the dislocation slip of the NiTi matrix andβ-Nb inclusions.In stageⅢ,in addition to the higher density of dislocations and further growth of stress-induced martensite variants(SIMVs),(001)compound twins are introduced as a result of the(001)deformation twinning in stress-induced martensite.More{20-1}martensite twins are gradually introduced in stageⅣ.Correspondingly,after subsequent unloading and heating,a higher density of{114}austenite twins form in the specimen with a larger prestrain of 16%.With increasing prestrain from 8%to 16%,the recoverable strainε_(re)^(T)upon heating increases first and then decreases.Theε_(re)^(T)obtains a maximum of 7.03%at 10%prestrain and de-creases to 6.17%at 16%prestrain.The increase ofε_(re)^(T)can be attributed to the formation of new SIMVs,the further growth of existing SIMVs,and the recoverable(001)compound twins.While the decrease ofε_(re)^(T)is mainly associated with the irrecoverable strain by{20−1}martensite twins.The effect ofβ-Nb inclusions on the evolution of SIMVs i

关键词： Ni_(47)Ti_(44)Nb_(9)shape memory alloy Wide transformation hysteresis Thermomechanical loading Microstructure evolution Shape memory behaviors Stress-induced martensitic transformation Deformation twinning

Electromagnetic Performance Analysis of Variable Flux Memory Machines with Series-magnetic-circuit and Different Rotor Topologies

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CES Transactions on Electrical Machines and Systems 2024年第1期8卷 3-11页

作者： qiang Wei Z.q.Zhu Yan Jia Jianghua Feng Shuying Guo Yifeng li Shouzhi Feng Department of Electronic and Electrical Engineering The University of SheffieldSheffield S13JDU.K. IEEE the CRRC Zhuzhou Institute Company Ltd. Zhuzhou 412001China

In this paper,the electromagnetic performance of variable flux memory(VFM)machines with series-magnetic-circuit is investigated and compared for different rotor topologies.Based on a V-type VFM machine,five topologies with different interior permanent magnet(IPM)arrangements are evolved and optimized under same constrains.Based on two-dimensional(2-D)finite element(FE)method,their electromagnetic performance at magnetization and demagnetization states is evaluated.It reveals that the iron bridge and rotor lamination region between constant PM(CPM)and variable PM(VPM)play an important role in torque density and flux regulation(FR)capabilities.Besides,the global efficiency can be improved in VFM machines by adjusting magnetization state(MS)under different operating conditions.

关键词： Memory machine Permanent magnet Rotor topologies Series magnetic circuit Variable flux