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High Voltage 2024年第1期9卷 217-229页

作者： Lijing Zhang Yingting Luo Gehao Sheng Zizhan Ni Xiuchen Jiang Department of electrical Engineering Shanghai Jiao Tong UniversityShanghaiChina electric power research institute of guangdong power Grid Corporation GuangzhouChina

Accurate assessment of hot-spot temperature is essential for the safe operation of power *** dynamic thermal models cannot estimate hot-spot temperature accurately since some input parameters are roughly determined by transformer capacity and cooling mode while ignoring the effect of winding structure,tank dimensions,and material physical *** improve the accuracy of temperature assessment,empirical parameters of the IEC thermal model including thermal constants,winding and oil exponents are optimised with the help of numerical simulation in this *** on energy conservation and heat transfer theory,a computational fluid dynamic(CFD)model of a transformer in oil natural air natural(ONAN)cooling mode is *** CFD model simulates the entity's structure,sizes,and multi-stage heat dissipation processes realistically,so it can more precisely calculate the dynamic hot-spot *** to the simulated temperature curves at different operating conditions,the thermal constants and oil exponent are estimated using non-linear regression,and the winding exponent is optimised using linear regression.A case study is conducted on an ONAN *** shows the improved IEC model with optimised parameters can more accurately evaluate hot-spot temperature,and the absolute error is decreased by 2.4 K(38.7%)compared with traditional thermal models.

关键词： temperature properties. thermal

High-frequency Resonance Analysis and Impedance Reshaping Control of MMC-HVDC System Based on Frequency Coupling Impedance Model

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Journal of Modern power Systems and Clean Energy 2024年第2期12卷 646-657页

作者： Juanjuan Wang Wei Chen Yuekun Liu Chuang Fu Yunming Ye Junjie Feng School of electric power South China University of TechnologyGuangzhouChina guangdong power Grid Co. Ltd.GuangzhouChina electric power research institute China Southern Power GridGuangzhouChina

In recent years, high-frequency resonance (HFR) events occurred in several modular multilevel converter based high-voltage direct current (MMC-HVDC) projects. The time delay of an MMC-HVDC system is the critical factor that induces HFR. The frequency coupling affects the impedance characteristics of an MMC and further deteriorates system stability. Therefore, in this paper, a multi-input multi-output admittance model of an MMC-HVDC system is developed to analyze its frequency characteristics. The effects of current loop, power loop, phase-locked loop, and operating point on the MMC frequency coupling degree are analyzed in detail. Meanwhile, to further suppress HFR in the MMC-HVDC system, an enhanced impedance reshaping control strategy based on the equivalent single-input single-output impedance model is proposed. Finally, the accuracy of the enhanced impedance model and the effectiveness of the impedance reshaping control are verified by electromagnetic transient simulations in PSCAD.

关键词： Modular multilevel converter based high-voltage direct current(MMC-HVDC) high-frequency resonance frequency coupling impedance model impedance reshaping control

Optimal Bidding Strategy for PV and BESSs in Joint Energy and Frequency Regulation Markets Considering Carbon Reduction Benefits

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Journal of Modern power Systems and Clean Energy 2024年第2期12卷 427-439页

作者： Jing Bian Yuheng Song Chen Ding Jianing Cheng Shiqiang Li Guoqing Li Key Laboratory of Modern power System Simulation and Control&Renewable Energy Technology Ministry of Education Northeast Electric Power UniversityJilin 132000China Datang Northeast electric power test&research institute Co. Ltd.Changchun 130102China

Photovoltaic(PV)and battery energy storage systems(BESSs)are key components in the energy market and crucial contributors to carbon emission reduction *** systems can not only provide energy but can also generate considerable revenue by providing frequency regulation services and participating in carbon *** study proposes a bidding strategy for PV and BESSs operating in joint energy and frequency regulation markets,with a specific focus on carbon reduction benefits.A two-stage bidding framework that optimizes the profit of PV and BESSs is *** the first stage,the day-ahead energy market takes into account potential real-time forecast *** the second stage,the real-time balancing market uses a rolling optimization method to account for multiple ***,a real-time frequency regulation control method is proposed for the participation of PV and BESSs in automatic generation control(AGC).This is particularly relevant given the uncertainty of grid frequency fluctuations in the optimization model of the real-time balancing *** control method dynamically assigns the frequency regulation amount undertaken by the PV and BESSs according to the control interval in which the area control error(ACE)*** case study results demonstrate that the proposed bidding strategy not only enables the PV and BESSs to effectively participate in the grid frequency regulation response but also yields considerable carbon emission reduction benefits and effectively improves the system operation economy.

关键词： Photovoltaic(PV) battery energy storage system(BESS) energy market carbon market frequency regulation service bidding strategy

Modification of streamer-to-leader transition model based on radial thermal expansion in the sphere-plane gap discharge at high altitude

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Plasma Science and Technology 2024年第1期26卷 42-49页

作者：耿江海林果王平丁玉剑丁杨俞华 Department of electric power Engineering North China Electric Power UniversityBaoding 071003People’s Republic of China China electric power research institute Beijing 100192People’s Republic of China Xinjiang electric power Company research institute Urumchi 830000People’s Republic of China Shanxi electric power Company research institute Taiyuan 030001People’s Republic of China

Historically,streamer-to-leader transition studies mainly focused on the rod-plane gap and low altitude analysis,with limited attention paid to the sphere-plane gap at high altitude *** this work,sphere-plane gap discharge tests were carried out under the gap distance of 5 m at the Qinghai Ultra High Voltage(UHV)test base at an altitude of 2200 *** experiments measured the physical parameters such as the discharge current,electric field intensity and instantaneous optical *** duration of the dark period and the critical charge of streamer-toleader transition were obtained at high *** on radial thermal expansion of the streamer stem,we established a modified streamer-to-leader transition model of the sphere-plane gap discharge at high altitude,and calculated the stem temperature,stem radii and the duration of streamer-to-leader *** with the measured duration of sphere-plane electrode discharge at an altitude of 2200 m,the error rate of the modified model was 0.94%,while the classical model was 6.97%,demonstrating the effectiveness of the modified *** the comparisons and analysis,several suggestions are proposed to improve the numerical model for further quantitative investigations of the leader inception.

关键词： streamer-to-leader transition model high altitude streamer stem convective diffusion radial thermal expansion

Effect of Low-Temperature Thermal Oxidation on the Capillary Performance of Sintered Copper Powder Wicks

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Journal of Thermal Science 2024年第1期33卷 29-40页

作者： ZHU Minghan FANG Runquan HU Yanxin ZHANG Jiangyun SHAO Dan HUANG Jin School of Material and Energy Guangdong University of TechnologyGuangzhou 510006China School of electric power Engineering Guangdong Polytechnic of Water Resources and Electric EngineeringGuangzhou 510006China research into Artifacts Guangdong Key Laboratory of Battery SafetyGuangzhou Institute of Energy testingGuangzhou 511447China

In this study,a composite powder capillary wick is prepared,manufactured by sintering copper powder and surface treated by low-temperature thermal *** is used to improve the performance of the capillary *** forced flow method and infrared imaging method are used to test the permeability and capillary performance of the *** effects of different oxidation temperatures on the performance of capillary wick are *** experimental results show that the wetting performance of the oxidized samples is significantly *** the increase of oxidation temperature,the permeability *** capillary height and velocity of the thermally oxidized samples are significantly higher than those of the untreated capillary ***,the oxidation temperature needs to be adjusted to obtain the best capillary *** highest capillary performance is found at oxidation temperature of 300℃,with an increase of 46% compared to the untreated *** with other composite wicks show that the sample with an oxidation temperature of 300℃ has competitive capillary performance,making it a favorable alternative to two-phase heat transfer *** study shows that combining low-temperature thermal oxidation technology with powder sintering is a convenient and effective method to improve the capillary performance of powder wicks.

关键词： low-temperature thermal oxidation capillary performance copper powder permeability

Coordinated Voltage Control of Distribution Network ConsideringMultiple Types of electric Vehicles

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Energy Engineering 2024年第2期121卷 377-404页

作者： Liang Liu Guangda Xu Yuan Zhao Yi Lu Yu Li Jing Gao State Grid Jibei electric power research institute(North China electric power research institute Co. Ltd.)Beijing100045China

The couple between the power network and the transportation network(TN)is deepening gradually with the increasing penetration rate of electric vehicles(EV),which also poses a great challenge to the traditional voltage control *** this paper,we propose a coordinated voltage control strategy for the active distribution networks considering multiple types of *** the first stage,the action of on-load tap changer and capacitor banks,etc.,are determined by optimal power flow calculation,and the node electricity price is also determined based on dynamic time-of-use tariff *** the second stage,multiple operating scenarios of multiple types of EVs such as cabs,private cars and buses are considered,and the scheduling results of each EV are solved by building an optimization model based on constraints such as queuing theory,Floyd-Warshall algorithm and traffic flow *** the third stage,the output power of photovoltaic and energy storage systems is fine-tuned in the normal control *** charging power of EVs is also regulated in the emergency control mode to reduce the voltage deviation,and the amount of regulation is calculated based on the fair voltage control mode of ***,we test the modified IEEE 33-bus distribution system coupled with the 24-bus Beijing *** simulation results show that the proposed scheme can mitigate voltage violations well.

关键词： electric vehicle transportation network voltage control queuing theory

Study on the dynamic mechanical properties of winding-block axial structure considering short circuit strain rate effect

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High Voltage 2024年第2期9卷 380-390页

作者： Xinyu Wang Ping Wang Jianghai Geng Zikang Zhang Fangcheng Lü Shuguo Gao Hebei Provincial Key Laboratory of power Transmission Equipment Security Defense North China Electric Power UniversityBaodingChina State Grid Hebei electric power research institute ShijiazhuangChina

Transformers may suffer multiple short-circuit impacts during long-term operation,and axial instability is one of the typical types of serious accidents caused by short-circuit *** axial instability form of the winding-block structure is analysed,and the dynamic solution of the winding short-circuit electromagnetic force is obtained by estab-lishing the three-dimensional magnetic-circuit-force multi-physical field coupling simulation *** influence of strain rate on the cushion block constitutive equation is corrected,and the modified model is verified by short-circuit impact test and quasi-static *** research results show that for 110 kV 31.5 MVA transformers,the maximum electromagnetic axial resultant force of winding is 363.16 kN,and the ultimate tilt force is 1214.2 *** pre-tightening force configuration is accordingly recom-mended to range from 363.16 to 608.28 kN,which is narrowed by 18.49%compared with the static calculation method;Meanwhile,adding a logarithmic strain rate correction term to the classical constitutive equation of the cushion block can achieve a good correction of the stress-strain relationship with the coefficient of determination above 0.99,and the cushion block has a larger elastic modulus under high strain rate *** research results provide an important theoretical reference for the axial stability structure of transformers.

关键词： axial correction structure

Exploring the Mechanism,Advancements,and Application of Thermogalvanic Effect in Hydrogels

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Chinese Journal of Chemistry 2024年第5期42卷 543-556页

作者： Xiaoyu Yang Peng Wang Xiaolong Wu Yongli Liao Senyun Liu Wei Duan Ying Yue School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBaodingHebei071000 China Hebei Key Laboratory of electric Machinery Health Maintenance & Failure Prevention North China Electric Power UniversityBaodingHebei071003 China electric power research institute China South Power GridGuangzhouGuangdong510000 China Key Laboratory of Icing and Anti/De-icing China Aerodynamics Research and Development CenterMianyangSichuan621000 China

The issue of energy consumption has garnered significant interest due to its excessive ***,thermoelectric devices have been getting increased attention,as they can harness waste heat from various sources,such as solar radiation,human body,and industrial ***,the recovery of low-grade heat has been a challenge,resulting in unsustainable energy use and significant *** considerable advances have been made in thermoelectric materials in recent decades,the majority of these devices still primarily employ ***,the emergence of quasi-solid-state thermoelectric materials represents a novel development with profound promise for the environment and *** materials offer several advantages,such as improved energy conversion capacities,cost-effectiveness,versatility,and scalability,to support increased ***,this review explores the application of thermoelectric materials in self-powered sensors,integrated modules,and heat harvesting ***,the potential of high-performance thermocouples based on thermogalvanic effects is assessed,along with the challenges that must be overcome to realize this goal.

关键词： Hydrogel Thermogalvanic effect Thermochemistry Electrolytes Flexible electronics

Influence of Repetitive Impulse Waveforms on Surface Discharge Characteristics and Insulation Life for Polyimide Film

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CSEE Journal of power and Energy Systems 2024年第2期10卷 746-755页

作者： Zhiyun Han Qingmin Li Yujin Guo Tao Liu Guojing Dong Hanwen Ren State Key Laboratory of Alternate electrical power System with Renewable Energy Sources North China Electric Power UniversityBeijing 102206China electric power research institute Beijing 100085China Inner Mongolia electric Economy and Technology Academy Hohhot 010020China

Accelerated insulation aging problems under high frequency repetitive impulses in power electronic transformers are drawing more and more attention in modern power systems. Partial discharge (PD) characteristics including discharge inception voltage, phase distribution and statistical characteristics on polyimide (PI) surface under different impulse waveforms and the insulation life of PI films are studied in this paper. We carry out experiments based on PD and insulation lifetime test systems, using five different types of repetitive impulses, including three bipolar waves and two unipolar waves. The experimental results show that there is little variation in discharge inception voltage under different waveforms, but great variation in phase distribution and statistical characteristics of PD. In addition, insulation life is approximately the same under different waveforms with the same polarity, and the aging rate under bipolar waveforms is larger than that under unipolar waveforms. We explain the differences between the bipolar and unipolar waveforms on insulation life, which can be concluded that the surface charge under unipolar waveform accumulates more significnatly compared with bipolar waveform and decreases the electric filed strength in discharging the air gap and inhibits surface discharge from occurring.

关键词： Insulation life polyimide film power electronic transformer repetitive impulse surface discharge characteristics

Root cause of corrosion failure of tin coating on wire clamp in marine atmosphere

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Journal of Iron and Steel research International 2024年第4期31卷 998-1014页

作者： Zhen Zhong Wang-yan Ly Teng-yuan Liu Yi Xie Yang Yang Zhen-zhu Wang Deng-ke Li Xiao-bo Li Tang-qing Wu School of Materials Science and Engineering Xiangtan UniversityXiangtan 411105HunanChina electric power research institute of guangdong power Grid Co. Ltd.Guangzhou 510080GuangdongChina Shenyang National L aboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016LiaoningChina School of Materials Science and Engineering.University of Science and Technology of China Shenyang 110016LiaoningChina electric power research institute State Grid Hunan Electric Power CompanyChangsha 410007HunanChina School of Mechanical Engineering and Mechanics Xiangtan UniversityXiangtan 411105HunanChina School of Information Science and Engineering Changsha Normal UniversityChangsha 410199HunanChina

The failure cause of a tinned copper wire clamp in marine atmosphere was studied systematically by X-ray photoelectron spectroscopy,scanning electron microscopy with energy dispersive spectroscopy and electrochemical *** main components of the green rust on the surface of the damaged wire clamp are SnO_(2),CuO,Cu_(2)Cl(OH)_(3) and CuCO(OH)_(2).Much of green rust distributes at the platform edge along the axial direction on the crimp connection,and severe corrosion and corrosion pits occur at the platform edge zone along the axial *** enriching Cl-at the marine atmosphere and the existing O_(2) in air collectively enhance the corrosion process of the tin coating and the copper *** element model results show that the residual stress and strain of the tin coating are the largest at the platform edge along the axial direction on the crimp connection,and the corresponding electrode potential of the tin coating at this zone drops *** above results indicate that the residual strain increases the driving force of the corrosion electrochemical reactions and accelerates the corrosion rate and the pit corrosion of the tin coating at this zone.

关键词： Tin coating Marine atmosphere Residual strain-Chloride ion Corrosion failure