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Numerical Analysis of Space Charge Characteristics in Low-density Polyethylene Nanocomposite Under External DC Electric Field

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高电压技术 2013年第8期39卷 1813-1820页

作者： ZHOU Yuanxiang ZHANG Ling SHA Yanchao TIAN Jihuan State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing 100084 China ABB Corporate Research Center Beijing 100015 China

The dynamic characteristics of space charge in nanocomposite of low-density polyethylene (LDPE) mixed with inorganic nano- fillers. Different from previous qualitatively theoretical works, we investigated the influence of trap depth, trap volume charge density and injection barrier height on the space charge and the electric field distribution in the nanocomposite under a DC external electric field (100 MV/m) systematically and quantificationally, through numerical simulations based on a bipolar charge transport model. The simulation re- sults showed that, the increase of trap depth would severely distort the balanced electric field distribution with the highest and the lowest electric field of 119 MV/m and 47 MV/m, respectively. It is concluded that the introduction of nanofillers creates more deep traps, which would block space charges by capturing most of them in the vicinity of electrode and hence reduce the local electric field largely. Further theoretical analysis of the simulation indicates that both the high permittivity and the low local electric field of the nanocomposite contri- buted to the increase of injection barrier height, and almost no charge could overcome an injection barrier higher than 1.25 eV. At last, a mechanism of space charge suppression in the LDPE nanocomposite was presented.

关键词：纳米复合材料低密度聚乙烯直流电场空间电荷电荷特性数值分析无机纳米填料陷阱深度

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Exergy Analysis of Electric Vehicle Heat Pump Air Conditioning System with Battery Thermal Management System

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Journal of Thermal Science 2020年第2期29卷 408-422页

作者： ZHANG Kexin LI Ming YANG Changhai SHAO Zhiyuan WANG Lihong State Key Laboratory of Automotive Simulation and Control Jilin UniversityChangchun 130025China College of Automotive Engineering Jilin UniversityChangchun 130025China School of Energy and Power Engineering Xi’an Jiaotong UniversityXi’an 710049China FAW-Valeo Climate Control Systems Co.Ltd. Changchun 130011China

The exergy analysis of an electric vehicle heat pump air conditioning system(HPACS) with battery thermal management system was carried out by studying the exergy loss of each component. The results indicate that the compressor is the main source of system exergy loss in all operation conditions. The exergy loss distribution of HPACS is almost the same when the battery thermal management system integrated into the HPACS in cabin and battery mixed cooling mode and the system exergy loss was linearly related to the compressor speed in cooling modes. The performance of the HPACS is better than that of the positive temperature coefficient(PTC) heater in cabin heating mode. The degree of exergy efficiency improvement of the alternative mode was discussed at all operation conditions in cabin heating mode. The results indicate that the optimization effect using the electric vehicle HPACS to replace the PTC heater is obvious at lower compressor speed, surrounding temperature and internal condenser air flow rate.

关键词： electric vehicle heat pump exergy efficiency battery thermal management

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The parameter design method of smoothing inductance based on MMC-MTDC with R-type superconducting fault current limiter 16

The parameter design method of smoothing inductance based on...

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16th IET International Conference on AC and DC power Transmission, ACDC 2020

作者： Guo, Peiqian Yuan, Zhichang Liu, Guowei Zhao, Yuming Shi, Zinan State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China Shenzhen Power Supply Corporation Shenzhen China Sichuan Energy Internet Research Institute Tsinghua University Chengdu China

ISBN: (纸本)9781839533914

The rapid increase of voltage sourced converter brings the great development of the multi-terminal DC technology, both in the DC transmission and DC distribution fields. However, because of the weak impedance characteristic of the VSC-HVDC system, how to suppress and clear DC fault currents becomes a challenge. Considering the stability, the response speed and the system structure, it is not possible to apply excessive inductance at the DC side, hence, the current limiting effectiveness is relatively restricted. On the one hand, with the effective properties, Resistive type Superconducting Fault Current Limiter (R-SFCL) becomes an effective device to solve the problem of VSC-HVDC system under DC faults. On the other hand, because of dynamic energy-impedance characteristics of R-SFCL, the fixed impedance selection method at a certain time to carry out dynamic current limiting analysis is no longer applicable. Therefore, the DC fault current research and R-SFCL characteristic are comprehensively analyzed firstly in this paper. Based on that, a smoothing inductance determination method is proposed to cut off the DC fault current by DC breaker and ensure the continuous operation of remaining parts. Finally, based on a multi-terminal DC system simulation, the improvement and effectiveness of the proposed method are validated. © 2020 Institution of Engineering and Technology. All rights reserved.

关键词： Inductance

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A schedule power flow auto generating technology in day-ahead security validation

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Dianli Xitong Zidonghua/Automation of Electric power systems 2012年第20期36卷 68-73页

作者： Lin, Yi Sun, Hongbin Wu, Wenchuan Yu, Jun Zhang, Boming State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing 100084 China National Electric Power Dispatching and Communication Center Beijing 100031 China

Formulation of day-ahead operation schedule for large-scale power grid requires security validation, including static security, dynamic and transient stability. It is an important and basic task for day-ahead security validation to generate an AC power flow that satisfies the demand of the schedule. A new method of generating the day-ahead schedule power flow is proposed, which consists in dividing the problem into two subproblems-the active subproblem and the reactive subproblem. The inconsistency of various kinds of schedule data is coordinated by solving the active subproblem, while a rational voltage distribution is achieved by solving the reactive subproblem. Both of the two problems are formulated as optimization models with constraints satisfied and are solved with an interior point algorithm. Numerical test results on the testing system and real power systems show that the method is capable of providing rational day-ahead schedule power flow. © 2012 state Grid Electric power Research Institute Press.

关键词： Numerical methods

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Modeling and simulation of air-gapped current transformer based on Preisach Theory

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Protection and control of Modern power systems 2017年第1期2卷 111-121页

作者： Ya Hui Wu Xin Zhou Dong Sohrab Mirsaeidi State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical EngineeringTsinghua UniversityBeijing 100084China

Current Transformer(CT)modeling,by which CT’s characteristics can be studied has a significant importance in CT selection and *** spite of numerous studies about closed-core CT model,only a few works have been conducted on air-gapped ones with the following problems:models of which required data is easily-accessible,have poor simulations of magnetization process;on the contrary,models which have satisfactory simulations,are hard to be established because of the hard-to-get required ***,based on Preisach Theory,a novel air-gapped CT model is deduced from the closed core CT *** proposed model is accurate and can be established *** saturation and remanence properties of closed-core CT and air-gapped CT are simulated and compared.

关键词： CT modeling Air gap Preisach Theory Saturation Remanence

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A time-of-use based electricity price package mechanism in retail market considering consumers' diversity 10

A time-of-use based electricity price package mechanism in r...

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2020 10th International Conference on power, Energy and Electrical Engineering, CPEEE 2020

作者： Luo, Gang He, Yujun Zhao, Chen Zhang, Xuan Lin, Shaohua Zhao, Yue Cai, Yuanji Power Dispatch and Control Centre Guangdong Power Grid Co. Ltd. Guangzhou510000 China State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing100084 China

In the deregulated retail market, consumers should have more right of choice for paying for their energy demand. This paper focuses on the design of electricity price package mechanism in retail market considering the demand elasticity of consumers. An optimal price package mechanism is proposed to incentivize consumers for peak-clipping/valley-filling. Consumers are able to choose the appropriate one from a set of price packages, each of which consists of specific time-of-use energy price and maximum-demand price. A numerical case study has shown the usefulness and effectiveness of the proposed mechanism. © 2020 The Authors, published by EDP Sciences.

关键词： Commerce

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Retraction notice to “Multi-objective planning of microgrid based on renewable energy sources and energy storage system” [J. Energy Storage 68 (2023) 107803]

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Journal of Energy Storage 2025年 117卷

作者： Hao Tian Keqing Wang Xiufeng Cui Zexi Chen Ergang Zhao Sara Saeedi School of Automation Wuxi University Wuxi 214105 China State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing 100086 China Beijing Sifang Engineering Co. Ltd Beijing 100085 China State Grid Beijing Urban Power Supply Company Beijing 100034 China Electrical Engineering Department Sun-Life Company Baku Azerbaijan

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Discussion on setting calculation of loss-of-excitation protection for large turbogenerator

Discussion on setting calculation of loss-of-excitation prot...

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2010 International Conference on Electrical Machines and systems, ICEMS2010

作者： Yao, Siwang Wang, Weijian Luo, Ling Gui, Lin Qiu, Arui State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing China

Loss of excitation (LOE) is a common fault found in the generators. The most widely applied method for detecting a generator loss of excitation is the use of impedance relays to sense the variation of impedance as viewed from the generator terminals [1]. However, compared with China's approachs, in the setting of impedance circle, the IEEE's allow the circle to extend along the negative X axis, meanwhile, in the latest edition of the "IEEE Guide for AC Generator Protection", the circle is further extended, reaching to -1.25X_d.We think this is adverse, to prove our point, the paper ,basing on the IEEE 9 bus model and using computer digital simulation, have studied various loss-of-excitation conditions and some system disturbances that may lead to the relay false tripping. simulation results indicate that the IEEE's method not only can't accelerate the operation effectively, but also will increase the chances of maloperation.

关键词： Impedance Generators Relays Analytical models power system stability Reactive power

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Surface Partial Discharge Characteristics of Oil-paper Insulation Under Combined AC-DC Voltage

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高电压技术 2013年第8期39卷 1902-1910页

作者： SHA Yanchao ZHOU Yuanxiang NIE Dexin WU Zhirong DENG Jiangang LU Licheng State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China State Key Laboratory of Electrical Insulation and Power Equipment Department of Electrical Engineering State Grid Electric Power Research Institute Wuhan 467001 China State Grid Corporation of China Beijing 100031 China

The valve side windings of converter transformers bear AC, DC, impulse, and reversal-polarity voltages during operation, which could result in serious insulation problems of the equipment. By performing experiments with surface discharge model of oil-paper insula- tion at 80 ℃ under combined AC-DC voltage for 200 h, we studied the spectrums and statistical parameters of partial discharges at different discharge stages. Furthermore, some fingerprint parameters were calculated in order to estimate the development situation of par- tial discharge, while the characteristic gases dissolved in the transformer oil were measured by gas chromatography. The surface discharges in the experiments were observed using a high speed camera, and a full discharge process could be marked off into four stages as follows. ①The elementary stage. When a partial discharge occurs near electrodes, electrical charges are injected into the region near electrodes and causing bubble generation. ②Due to their high resistivity and low dielectric constant, the bubbles would bare the major part of the voltage applied to samples. Therefore, discharge happens inside the small bubbles, and it emits a lot of light. ③Micromolecules of gas are produced in discharge, and further ionization in the transformer oil takes place simultaneously when high-energy electrons collide with oil molecules. ④The carrier charge moves forward to electrodes driven by the applied electric field, till they neutralize with the charge from electrodes, and hence discharge channels are formed subsequently.

关键词： AC-DC 放电特性绝缘表面电压油纸油中溶解气体换流变压器合作

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Wind power generation Capacity Evaluation Based on Correlation Analysis of Adjacent Wind Farms

Wind Power Generation Capacity Evaluation Based on Correlati...

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2021 IEEE Sustainable power and Energy Conference, iSPEC 2021

作者： Sun, Shuxin Qiao, Ying Lu, Zongxiang Ma, Yanhong Tsinghua University State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Beijing100084 China State Grid Gansu Electric Power Company Wind Power Technology Center Lanzhou730050 China

ISBN: (纸本)9781665414395

Accurate assessment of the power generation capacity of the wind farm is the key basis for incorporating it into power system scheduling and other optimizing operation activities. Traditional evaluation methods, such as benchmarking wind turbine method, have higher requirements for input data, but many wind farms in operation for many years are difficult to meet such data conditions. A new power generation capacity evaluation method based on correlation analysis of adjacent wind farms is proposed in this paper. Meteorological data and power of adjacent wind farms are used as replaced input data based on correlation analysis between the target farm with its adjacent farms. First, anticipate wind speed data and then construct the wind power curve with three different neural networks to evaluate power generation capacity. Afterwards, adjacent wind farms are used as data sources to fit the power data of the target wind farm with the application of influence radius method, inverse square distance method and bilinear interpolation method. Finally, combined with data in the actual case, investigate the advantages and disadvantages of different methods in the evaluation of power generation capacity. © 2021 IEEE.

关键词： Time delay

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