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Localization method of subsynchronous oscillation source based on high-resolution time-frequency distribution image and CNN

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Global Energy Interconnection 2024年第1期7卷 1-13页

作者： Hui Liu Yundan Cheng yanhui xu Guanqun Sun Rusi Chen Xiaodong Yu Institute of Electric Power Systems School of Electrical and Electronic EngineeringNorth China Electric Power UniversityBeijing 102206P.R.China Electric Power Research Institute of State Grid Hubei Electric Power Co. Ltd.Wuhan 430077P.R.China Central China Branch of State Grid Corporation of China Wuhan 430077P.R.China

The penetration of new energy sources such as wind power is increasing,which consequently increases the occurrence rate of subsynchronous oscillation events.However,existing subsynchronous oscillation source-identification methods primarily analyze fixed-mode oscillations and rarely consider time-varying features,such as frequency drift,caused by the random volatility of wind farms when oscillations occur.This paper proposes a subsynchronous oscillation sourcelocalization method that involves an enhanced short-time Fourier transform and a convolutional neural network(CNN).First,an enhanced STFT is performed to secure high-resolution time-frequency distribution(TFD)images from the measured data of the generation unit ports.Next,these TFD images are amalgamated to form a subsynchronous oscillation feature map that serves as input to the CNN to train the localization model.Ultimately,the trained CNN model realizes the online localization of subsynchronous oscillation sources.The effectiveness and accuracy of the proposed method are validated via multimachine system models simulating forced and natural oscillation events using the Power Systems Computer Aided Design platform.Test results show that the proposed method can localize subsynchronous oscillation sources online while considering unpredictable fluctuations in wind farms,thus providing a foundation for oscillation suppression in practical engineering scenarios.

关键词： Subsynchronous oscillation source localization Synchronous squeezing transform Enhanced short-time Fourier transform Convolutional neural networks

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Sub-synchronous frequency domain-equivalent modeling for wind farms based on rotor equivalent resistance characteristics

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Global Energy Interconnection 2022年第3期5卷 293-300页

作者： yanhui xu Tianchu Gao North China Electric Power University BeijingP.R.China

The equivalent simplification of large wind farms is essential for evaluating the safety of power systems.However,sub-synchronous oscillations can significantly affect the stability of power systems.Although detailed mathematical models of wind farms can help accurately analyze the oscillation mechanism,the solution process is complicated and may lead to problems such as the“dimensional disaster.”Therefore,this paper proposes a sub-synchronous frequency domain-equivalent modeling method for wind farms based on the nature of the equivalent resistance of the rotor,in order to analyze sub-synchronous oscillations accurately.To this end,Matlab/Simulink is used to simulate a detailed model,a single-unit model,and an equivalent model,considering a wind farm as an example.A simulation analysis is then performed under the sub-synchronous frequency to prove that the model is effective and that the wind farm equivalence model method is valid.

关键词： Wind farm Sub-synchronous frequency domain Dynamic equivalence Rotor equivalent resistance characteristics

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Generation of typical operation curves for hydrogen storage applied to the wind power fluctuation smoothing mode

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Global Energy Interconnection 2022年第4期5卷 353-361页

作者： yanhui xu Yijia xu Yan Huang North China Electric Power University Beijing 102206P.R.China Energy Development Research Institute China Southern Power GridGuangzhou 510623P.R.China

In this paper,a typical-operation-curve generation method of a hydrogen energy storage system operating under the mode of stabilizing wind power fluctuations is proposed.This method is used to optimize the power and capacity configuration of the energy storage system.The time series curves of the charging and discharging powers of the hydrogen energy storage are obtained by EMD decomposition,and the curves are classified according to the similarities and differences of the characteristic parameters in different time periods.After the classification,typical charging and discharging power values of each type of curve at each moment are obtained by a cloud model,and then,typical operation curves of each type are obtained by integration.On this basis,the power and capacity of the energy storage system are optimized with the objective of economic optimization through the MATLAB CPLEX toolbox.Combined with the measured data of a wind farm with an installed capacity of 400 MW in Northeast China,the validity and rationality of the typical operation curve generation method proposed in this paper are verified.

关键词： Wind farm Hydrogen energy storage system Cluster analysis Typical operation curves Capacity configuration

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Layered power scheduling optimization of PV hydrogen production system considering performance attenuation of PEMEL

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Global Energy Interconnection 2023年第6期6卷 714-725页

作者： yanhui xu Haowei Chen Department of Electrical and Electronic Engineering North China Electric Power UniversityBeijing 102206P.R.China

To analyze the additional cost caused by the performance attenuation of a proton exchange membrane electrolyzer(PEMEL)under the fluctuating input of renewable energy,this study proposes an optimization method for power scheduling in hydrogen production systems under the scenario of photovoltaic(PV)electrolysis of water.First,voltage and performance attenuation models of the PEMEL are proposed,and the degradation cost of the electrolyzer under a fluctuating input is considered.Then,the calculation of the investment and operating costs of the hydrogen production system for a typical day is based on the life cycle cost.Finally,a layered power scheduling optimization method is proposed to reasonably distribute the power of the electrolyzer and energy storage system in a hydrogen production system.In the up-layer optimization,the PV power absorbed by the hydrogen production system was optimized using MALTAB+Gurobi.In low-layer optimization,the power allocation between the PEMEL and battery energy storage system(BESS)is optimized using a non-dominated sorting genetic algorithm(NSGA-Ⅱ)combined with the firefly algorithm(FA).A better optimization result,characterized by lower degradation and total costs,was obtained using the method proposed in this study.The improved algorithm can search for a better population and obtain optimization results in fewer iterations.As a calculation example,data from a PV power station in northwest China were used for optimization,and the effectiveness and rationality of the proposed optimization method were verified.

关键词： PV electrolysis of water Proton exchange membrane electrolyzer Performance attenuation Degradation cost Power scheduling optimization

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Lotus root-like RuIr alloys with close-packed(0001)branches:Strain-driven performance for acidic water oxidation

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Journal of Energy Chemistry 2024年第5期92卷 579-590页

作者： Mingyue Xiao Wanli xu Rongchao Li yanhui Sun Jingjun Liu Feng Liu Jun Gan Shixin Gao Beijing Key Laboratory of Electrochemical Process and Technology for Materials Beijing University of Chemical TechnologyBeijing 100029China Yunnan Precious Metals Lab Kunming 650100YunnanChina

Achieving composition tunability and structure editability of nanoalloys with high level strain may be an efficient strategy to remarkably boost catalytic performance toward oxygen evolution reaction(OER)in acidic water oxidation.Herein,lotus root-like RuIr alloys with native micro-strain were constructed by an epitaxial growth of Ru-richened hcp-(0001)branches on Ir-richened fcc-(111)seeds using a polyol thermal synthesis strategy.The resultant Ru_(60)Ir_(40) alloy shows an OER overpotential of 197 mV at 10 mA cm^(-2) and a Tafel slope of 46.59 mV dec^(-1),showing no obvious activity decay for 80 h continuous chronopotentiometry test in 0.5 M H_(2)SO_(4).The related characterizations including X-ray absorption fine structure(XAFS)spectroscopy and density functional theory(DFT)calculations show that that the remarkably improved activity of the lotus root-like alloy can be attributed to the(0001)facet-triggered strain,which can efficiently optimize the electronic band structure of the active metal and the weakening of the chemisorption of oxygen-containing substances to boost OER electrocatalysis.Therefore,this work provides a new strategy to designing a class of advanced electrocatalysts with high strain using diverse nanostructures as building materials for carbon-free clean energy conversion systems.

关键词： Rulr alloy Lotusroot-like structure Strain Oxygene volution reaction Activity

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Core-shell heterostructure by coupling layered ReS_(2) with Co_(9)S_(8) nanocubes for boosted oxygen evolution reaction

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Chinese Chemical Letters 2024年第3期35卷 518-522页

作者： xu Yu Zhiqiang Pan Chengang Pei Longjie Lin yanhui Lu Ho Seok Park Huan Pang School of Chemistry and Chemical Engineering Yangzhou UniversityYangzhou 225009China School of Chemical Engineering Sungkyunkwan University2066Seobu-roJangan-guSuwon-siGyeonggi-do 440-746Republic of Korea

The controllable morphology and composition of catalysts are crucial to improving the electrocatalytic activity of oxygen evolution reaction(OER).Herein,we construct a bimetallic heterostructure by sulfidation and hydrothermal methods,and the layered ReS_(2)is vertically aligned on Prussian blue-derived hollow Co_(9)S_(8)nanocubes(Co_(9)S_(8)@ReS_(2)).The core-shell structure of Co_(9)S_(8)@ReS_(2)can effectively prevent the restacking of layered ReS_(2),expose the abundant surface area and improve the utilization of electrocatalytic sites,resulting in fast electrolyte diffusion and charge transfer during OER.Due to the synergistic effect of the core-shell morphology and the formed bimetallic heterostructure,Co_(9)S_(8)@ReS_(2)exhibits excellent catalytic OER performance.At 10 mA/cm^(2),only 288 mV of overpotential is required with the Tafel slope of 73.3 mV/dec for Co_(9)S_(8)@ReS_(2),which are both lower than that of Co_(9)S_(8)and ReS_(2).Meanwhile,Co_(9)S_(8)@ReS_(2)exhibits high catalytic stability and low charge transfer resistance and the boosted active sites are confirmed by density functional theory.This work provides a rational design of the OER catalysts by constructing the bimetallic heterostructure.

关键词： Oxygen evolution reaction Rhenium disulfide Metal-organic framework Heterostructure Core-shell

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Data-driven Estimation for a Region of Attraction for Transient Stability Using the Koopman Operator

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CSEE Journal of Power and Energy Systems 2023年第4期9卷 1405-1413页

作者： Le Zheng Xin Liu yanhui xu Wei Hu Chongru Liu the School of Electrical and Electronic Engineering North China Electric Power UniversityBeijing 102206China Department of Electrical Engineering Tsinghua UniversityBeijing 100084China

This paper presents a novel Koopman Operator based framework to estimate the region of attraction for power system transient stability analysis.The Koopman eigenfunctions are used to numerically construct a Lyapunov function.Then the level set of the function is utilized to estimate the boundary of the region of attraction.The method provides a systematic method to construct the Lyapunov function with data sampled from the state space,which suits any power system models and is easy to use compared to traditional Lyapunov direct methods.In addition,the constructed Lyapunov function can capture the geometric properties of the region of attraction,thus providing useful information about the instability modes.The method has been verified by a simple illustrative example and three power system models,including a voltage source converter interfaced system to analyze the large signal synchronizing instability induced by the phase lock loop dynamics.The proposed method provides an alternative approach to understanding the geometric properties and estimating the boundary of the region of attraction of power systems in a data driven manner.Index Terms-Koopman operator,lyapunov function,power system transient stability,region of attraction.

关键词： Koopman operator lyapunov function power system transient stability region of attraction.

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Tuning interaction strength between CeO_(2) and iridium to promote CO oxidation over Ir/TiO_(2)

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Journal of Rare Earths 2024年第4期42卷 651-659页

作者： Lu Dai Binghua Li Yuhan Peng Xianwei Hao Runquan xuan Hua Huang Yiming Bi Liping xu yanhui Zhang Yun Guo Fangqi Du Li Wang Hui Wang Technology Center China Tobacco Zhejiang Industrial Co.Ltd.Hangzhou310024China Research Institute of Industrial Catalysis East China University of Science and TechnologyShanghai200237China

The interaction between support and noble metal plays a crucial role in heterogeneous catalysis design.However,how to tune metal support interactions to optimize the activity still needs further exploration.CeO_(2) was introduced to promote CO oxidation ove r Ir/TiO_(2) by adjusting the interaction strength between iridium(Ir)and CeO_(2).The strong interaction between Ir and CeO_(2) blocks CO adsorption and causes low CO oxidation activity.However,introducing CeO_(2) on Ir/TiO_(2) produces localized interaction between Ir and CeO_(2),which can tune the surface electronic state of Ir,so a"volcano curve"relationship between CO oxidation activity and electronic state is built.Limited amount of CeO_(2) on Ir/TiO_(2)(Ir/Ce_(0.2)Ti)leads to CO complete oxidization at 22℃,and a new pathway for CO oxidation was explored.The study demonstrates that the utilization of tuning interaction strength between active metal and support is a potential method to increase the catalytic activity.

关键词： CO oxidation CeO_(2) Localized interaction Interaction strength Supported Ir catalysts Rareearths

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Riverine sulfate sources and behaviors in arid environment,Northwest China:Constraints from sulfur and oxygen isotopes

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Journal of Environmental Sciences 2024年第3期137卷 716-731页

作者： Yifu xu Wenjing Liu Bing xu Zhifang xu Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Innovation Academy for Earth Science Chinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100049China

The fate of riverine sulfate ion (SO_(4)^(2-)) and its environmental effects in arid environment are difficult to evaluate due to its complicated sources and strongly coupled behaviors with water cycle which is significantly modified by humans.To understand the sulfur cycle in aquatic systems in arid environment,the chemical and sulfur and oxygen isotopic compositions (δ^(34)S_(SO4)and δ^(18)O_(SO4)) of major rivers around the Badain Jaran Desert,northwestern China,were investigated.These rivers had averaged SO_(4)^(2-)content at 1336μmol/L,over 10times higher than the global average.The δ^(34)S_(SO4)and δ^(18)O_(SO4)values ranged from-5.3‰to+11.8‰and+1.6‰to+12.8‰,respectively.The end-member analysis and the inverse model showed that riverine sulfate was mainly derived from evaporites dissolution (0-87%),sulfide oxidation (13%-100%) and precipitation (0-33%),indicating heterogeneity in sulfur sources and behaviors along the river drainage with the lithology variations and climate gradients.Multiple isotopic tools combining with hydro-chemistry compositions could be applied to reveal sulfur cycle in arid environment.Based on the calculation,sulfide oxidation plays the primary role in the headwater and upstream in the Qilian-Mountains area,where sulfide is widely exposed.While the proportion of evaporites dissolution contributing to riverine sulfate is much higher in downstream in a drier environment.Besides,less precipitation and higher temperature can lead to more intensive evaporation,affecting the process of sulfide oxidation and enhancing the rates of evaporites dissolution and sulfate precipitation in the basin.

关键词： Sulfur and oxygen isotopes Source apportionment Inverse model Arid environment Inland rivers Northwestern China

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Substation clustering based on improved KFCM algorithm with adaptive optimal clustering number selection

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Global Energy Interconnection 2023年第4期6卷 505-516页

作者： yanhui xu Yihao Gao Yundan Cheng Yuhang Sun xuesong Li Xianxian Pan Hao Yu School of Electrical and Electronic Engineering North China Electric Power UniversityBeijing 102206P.R.China Grid Planning&Research Center Guangdong Power Grid Co.Ltd.Guangzhou 510030P.R.China

The premise and basis of load modeling are substation load composition inquiries and cluster analyses.However,the traditional kernel fuzzy C-means(KFCM)algorithm is limited by artificial clustering number selection and its convergence to local optimal solutions.To overcome these limitations,an improved KFCM algorithm with adaptive optimal clustering number selection is proposed in this paper.This algorithm optimizes the KFCM algorithm by combining the powerful global search ability of genetic algorithm and the robust local search ability of simulated annealing algorithm.The improved KFCM algorithm adaptively determines the ideal number of clusters using the clustering evaluation index ratio.Compared with the traditional KFCM algorithm,the enhanced KFCM algorithm has robust clustering and comprehensive abilities,enabling the efficient convergence to the global optimal solution.

关键词： Load substation clustering Simulated annealing genetic algorithm Kernel fuzzy C-means algorithm Clustering evaluation

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