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Micro-mechanism Study on the Different Antioxidants Protective Effect of Vegetable Oil by ReaxFF Molecular Dynamics

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CSEE Journal of power and energy systems 2024年第3期10卷 1269-1279页

作者： Haoxi Cong Xuefeng Hu Hao Pan Qingmin Li state key laboratory of alternate electrical power system With renewable energy sources North China Electric Power UniversityBeijing 102206China

The aging problem of vegetable oil has severely restricted the popularization and application of vegetable oil *** antioxidants is the most recommended *** present,there is insufficient research on the micromechanism application of the protective effect of antioxidants on vegetable *** this paper,multiple vegetable oil models with different types and concentrations of antioxidants are *** the molecular dynamics simulation based on ReaxFF is carried out at different temperatures and oxygen *** show that the protective mechanism of antioxidants is to release H and combine this with free radicals generated by the decomposition of unsaturated fatty acids(UFA)in the *** addition,the protective effects of four antioxidants show different *** stronger ones are tert-butyl hydroquinone(TBHQ)and butylated hydroxytoluene(BHT),while the weaker ones are butylated hydroxyanisole(BHA)and propyl gallate(PG).TBHQ has a better protective effect at lower concentrations,but the decomposition of UFA is promoted at higher *** the temperature rises,the decomposition of UFA is *** the addition of oxygen,smaller molecular compounds are easily oxidized,and the decomposition of UFA is *** above research could reveal the microscopic mechanism of antioxidant protection on vegetable oil,providing theoretical references for further exploration of effective vegetable oil aging protection technology.

关键词： Antioxidant molecular dynamics transformer vegetable oil

Framework for Preventive Control of power systems to Defend Against Extreme Events

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CSEE Journal of power and energy systems 2024年第2期10卷 856-870页

作者： Yuwei Xiang Tong Wang Zengping Wang state key laboratory of alternate electrical power system with renewable energy sources North China Electric Power UniversityBeijing 102206China

Enhancing power system resilience against extreme events is becoming increasingly critical. This paper discusses a unified framework for preventive control of power systems to enhance system resilience, which includes three parts: resilience assessment, resilience grading, and resilience enhancement. First, the resilience assessment contains facility-level and system-level resilience assessment. The concept of fragility curve is used in the facility-level resilience assessment. Various resilience indices are developed in system-level resilience assessment to roundly depict the impacts of extreme events on power systems and determine the system resilience. On this basis, the resilience is divided into different levels by resilience grading strategy, which can efficiently quantify the severity of the impact of extreme events and provide decision-making for the resilience enhancement strategies. Then, control strategies for enhancing power system resilience are also divided according to different resilience levels. A controlled islanding based preventive control is proposed to enhance system resilience, which aims to strengthen the first defensive line of power systems to deal with extreme events. Finally, taking the typhoon disaster in extreme events as an example, two tests carried out with two typhoons demonstrate the efficiency of the proposed method.

关键词： Controlled islanding extreme events power system resilience preventive control

Metal-free Optical Pressure Sensor with high Sensitivity and Extensive Range

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CSEE Journal of power and energy systems 2024年第3期10卷 1291-1300页

作者： Mao Ji Meng Huang Haomin Lyu Sheng Shi Bo Qi Chengrong Li state key laboratory of alternate electrical power system with renewable energy sources North China Electric Power UniversityBeijing 102206China IEEE CSEE

Pressure monitoring of a transformer oil tank can grasp the pressure change process caused by gas production when severe internal defects occur and take timely measures to ensure the safe operation of the *** pressure sensors generally use metal encapsulation or have an air cavity structure,threatening the transformer’s insulation if it is directly used inside the *** this end,this paper proposes a method for developing a high-sensitivity,large-range,and metallizationfree optical pressure sensing device with temperature *** grating is encapsulated by fluorosilicone rubber and supplemented by an epoxy resin shielding shell on the *** the same time,a double-grating vertical arrangement is adopted to improve pressure measurement sensitivity,further avoiding the influence of temperature rise caused by a defect of the transformer on the measurement result of the *** addition,by optimizing the geometric structure of the internal sensitizing element,pre-stretching length of the fiber grating,gap distance,and other parameters,probe size can be reduced while ensuring the sensor’s *** show the proposed method can meet the requirements of sensor fabrication with different sensitivities and ranges,and to a certain extent,both high sensitivity and extensive ranges can be taken into *** sensitivity of the fabricated prototype is 15 pm/kPa,and the range is about 0.2 *** the same time,the metal-free feature of the sensor makes it suitable for use in various oil-immersed power *** records oil pressure changes caused by oil discharge breakdown,making it sensitive to small pressure changes in early failures.

关键词： highly sensitive extensive range optical sensing no metallization pressure perception temperature compensation transformer

A spatiotemporal evolution model of a short-circuit arc to a secondary arc based on the improved charge simulation method

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Plasma Science and Technology 2024年第1期26卷 62-73页

作者：丛浩熹王宇轩乔力盼苏文晶李庆民 state key laboratory of alternate electrical power system with renewable energy sources North China Electric Power UniversityBeijing 102206People’s Republic of China

The initial shape of the secondary arc considerably influences its subsequent *** establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is *** this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit *** intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this ***,the accuracy of the model was evaluated by comparison with physical experimental *** the secondary arc current increased,the arcing time and dispersion *** is an overall trend of increasing arc length with increasing arcing ***,there is a reduction in arc length during arc ignition due to short circuits between the arc ***,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis *** work investigated the method by which short-circuit arcs evolve into secondary *** results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.

关键词： short-circuit arc secondary arc stochasticity improved charge simulation method arc time

Finite Element Method for Transient Electric Field by Using Indirect Laplace Transform with high Accuracy

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CSEE Journal of power and energy systems 2024年第1期10卷 401-411页

作者： Teng Wen Xiang Cui Xuebao Li Sijia Liu Zhibin Zhao state key laboratory of alternate electrical power system with renewable energy sources North China Electric Power UniversityBeijing 102206China China Electric power Planning&Engineering Institute Beijing 100120China

This paper focuses on the finite element method in the complex frequency domain(CFD-FEM)for the transient electric ***,the initial value and boundary value problem of the transient electric field under the electroquasistatic field in the complex frequency domain is *** addition,the finite element equation and the constrained electric field equation on the boundary are ***,the indirect algorithm of the numerical inverse Laplace transform is *** on it,the calculation procedures of the CFD-FEM are illustrated in ***,the step response,zero-state response under the positive periodic square waveform(PPSW)voltage,and the zero-input response by the CFD-FEM with direct algorithm and indirect algorithm are ***,the reason for the numerical oscillations of the zero-state response under the PPSW voltage is analyzed,and the method to reduce oscillations is *** results show that the numerical accuracy of the indirect algorithm of the CFD-FEM is more than an order of magnitude higher than that of the direct algorithm when calculating the step response of the transient electric *** proposed method can significantly reduce the numerical oscillations of the zero-state response under the PPSW *** proposed method is helpful for the calculation of the transient electric field,especially in the case of frequency-dependent parameters.

关键词： Electroquasistatic field transient electric field finite element method complex frequency domain numerical Laplace transform

Nanostructured AlFeO_(3) thin films as a novel photoanode for photoelectrochemical water splitting

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Nano Research 2024年第3期17卷 1075-1085页

作者： Xin Sun Min Wang Qi Geng Shuailin Chen Xiaojun Lv Xunlei Ding Meicheng Li state key laboratory of alternate electrical power system with renewable energy sources School of New EnergyNorth China Electric Power UniversityBeijing 102206China School of Mathematics and Physics North China Electric Power UniversityBeijing 102206China

The earth-abundant and robust aluminum ferrite,AlFeO_(3)(AFO),is mainly studied in the context of ***,we demonstrate that AFO can be used as a stable solar absorber in photoelectrochemical cells for solar water splitting,exhibiting attractive *** is the first report on the photoelectrochemical activity of *** thin-film photoelectrodes prepared by solution-processing methods are composed of vertically oriented thin nanosheets,featuring the rhombohedral symmetry(R3c)and n-type *** as-prepared AFO photoanodes generate a photocurrent density of+0.78 mA·cm^(-2) at 1.23 V *** hydrogen electrode(RHE)with the photocurrent _(onset) potential(U_(onset))close to the flat band potential of 0.5 V *** in the presence of hole ***,the U_(onset) of AFO for solar water splitting coincides with the flat band potential as well,which is rare in n-type inorganic *** also report other properties of AFO associated with photoelectrochemical *** films exhibit a band gap energy of 2.31 eV and positive band edges with low ***,the carrier lifetimes in AFO films are up to millisecond timescales under the mediation of defect *** on the photoelectrochemical behavior and optoelectronic properties,we believe that AFO has great potential for application in photoelectrochemical cells.

关键词： AlFeO_(3) photoanode nanosheets photoelectrochemistry onset potential

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

Vinyltrimethylsilane as a novel electrolyte additive for improving interfacial stability of Li-rich cathode working in high voltage

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Chinese Chemical Letters 2024年第2期35卷 534-538页

作者： Bing Jiang Hao Li Bi Luo Lehao Liu Lihua Chu Qiaobao Zhang Meicheng Li state key laboratory of alternate electrical power system with renewable energy sources School of New EnergyNorth China Electric Power UniversityBeijing 102206China state key laboratory of Physical Chemistry of Solid Surfaces College of MaterialsXiamen UniversityXiamen 361005China

Boosting the interfacial stability between electrolyte and Li-rich cathode material at high operating voltage is vital important to enhance the cycling stability of Li-rich cathode materials for high-performance Li-ion *** this work,vinyltrimethylsilane as a new type of organic silicon electrolyte additive is studied to address the interfacial instability of Li-rich cathode material at high operating *** cells using vinyltrimethylsilane additive shows the high capacity retention of 73.9%after 300 cycles at 1 C,whereas the cells without this kind of additive only have the capacity retention of 58.9%.The improvement of stability is mainly attributed to the additive helping to form a more stable surface film for Li-rich cathode material,thus avoiding direct contact between the electrolyte and the cathode material,slowing down the dissolution of metal ions and the decomposition of the electrolyte under high operating *** findings in this work shed some light on the design of stable cycling performance of Li-rich cathode toward advanced Li-ion batteries.

关键词： Vinyltrimethylsilane Electrolyte additive Li-rich cathode Interfacial stability Capacity retention

Cyber-physical Collaborative Restoration Strategy for power Transmission system Considering Maintenance Scheduling

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CSEE Journal of power and energy systems 2024年第3期10卷 1331-1341页

作者： Baozhong Ti Chuanyun Zhang Jingfei Liu Zhaoyuan Wu Ziyang Huang North China Branch of state Grid Corporation of China Beijing 100053China state Grid beijing Electric power Company Beijing 100031China state key laboratory of alternate electrical power system with renewable energy sources School of Electrical and Electronic EngineeringNorth China Electric Power UniversityBeijing 102206China IEEE CSEE

In order to improve the ability of power transmission system to cope with compound faults on the communication side and power side,a cyber-physical collaborative restoration strategy is ***,according to the information system’s role in fault diagnosis,remote control of equipment maintenance and automatic output adjustment of generator restoration,a cyber-physical coupling model is *** this basis,a collaborative restoration model of power transmission system is established by studying interactions among maintenance schedule paths,information system operation,and power system *** on power flow linearization and the large M-ε method,the above model is transformed into a mixed integer linear programming model,whose computational burden is reduced further by the clustering *** to the parameters of IEEE39 New England system,the geographic wiring diagram of the cyber-physical system is *** results show the proposed restoration strategy can consider the support function of the information system and space-time coordination of equipment maintenance at both sides comprehensively to speed up load recovery progress.

关键词： Clustering method collaborative restoration cyber-physical power system maintenance scheduling power transmission system restoration