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International Conference on power Electronics (ICPE)

作者： Wenhao Xie Shiqi Ji Zhengming Zhao Xin Mo Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University China Tsinghua Sichuan Energy Internet Research Institute China

Compared to Si IGBTs, SiC MOSFETs can reduce switching losses, achieve higher switching frequencies and enable smaller converter size. However, due to the high dv/dt of SiC MOSFETs, certain topologies, such as two SiC MOSFETs in a phase-leg configuration, are highly sensitive to crosstalk, which can slow down switching speed and even reduce gate oxide’s lifetime. In this paper, an accurate model of crosstalk is established by considering the impacts of both dv/dt and di/dt in the power loop. The proposed model can simulate the gate-source voltage on bare die of SiC MOSFETs, allowing for a more accurate evaluation of the impact of crosstalk. Model verification is implemented using a double pulse test (DPT) platform and a gate driver with active miller clamp technology. key parameters of the model are extracted from both 3D simulation models and measurement experiments. The DPT waveform of power loop is used as the excitation source in the simulation, and the simulated gate-source waveform shows good agreement with the experimental waveform. Based on the model, parameter sensitivity analysis is performed, and suggestions for improving crosstalk suppression are proposed.

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A Pi-based control scheme for primary cascaded H-bridge rectifier in transformerless traction converters

A Pi-based control scheme for primary cascaded H-bridge rect...

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International Conference on Electrical Machines and systems (ICEMS)

作者： Tao Xinghua Li Yongdong Sun Min Department of Electrical Engineering Naval University of Engineering China State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University China

Cascaded H-Bridge rectifier (CHBR) is a more attractive solution in traction application for its transformerless structure. Because of the currents of different cells are exactly the same one, it is a challenge job to regulate the voltages of cells with only one current controller. In this paper, a PI-based control scheme is presented to deal with the voltages balance issue in CHBR. To satisfy the demand of rectifier such as unity power factor and regulated output DC voltages, the proposed control scheme consists of two parts. One is for shaping the grid current waveform and regulating the sum of DC-link voltages of all the cells; the other one is for balancing DC-link voltages. The latter is more concerned in this paper and is discussed in detail especially. simulations and experiments are carried on. The results verified the feasibility and effectiveness of the proposed scheme.

关键词： Rectifiers Voltage control Voltage measurement Converters Pulse width modulation Mathematical model

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Space Charge Behavior in AC Electrically Aged Low-Density Polyethylene Films

Space Charge Behavior in AC Electrically Aged Low-Density Po...

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China International Electrical and Energy Conference (CIEEC)

作者： Zixia Cheng Jinxing Shi Ling Zhang Yuanxiang Zhou Zekai Lu Shaowei Guo School of Electrical Engineering Zhengzhou University Zhengzhou China State Key Lab of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China Electric Power Research Institute State Grid Jibei Electric Power Company Beijing China

ISBN: (纸本)9781538653937

In order to study the effect of AC aging on space charge characteristics of low-density polyethylene (LDPE) films, an AC electric field of 50 kV/mm (peak value) was adopted for the accelerated aging test and space charge measurements of AC aged LDPE films were carried out subsequently. The results show that no significant space charge accumulation in the LDPE samples aged under a 50 kV/mm AC electric field. It can be seen that a significant positive space charge accumulation occurs inside the sample, when DC electric fields were applied to the AC aged LDPE samples. The long-term AC aging also causes more and deeper cracks on the surface of LDPE samples. Moreover, AC aging promotes the oxidation reaction of LDPE. The longer the aging time, the higher the degree of oxidation. On this basis, the probable relationship between space charge characteristics and material physicochemical properties of LDPE during AC electrical aging is clarified.

关键词： Aging Space charge Electric fields Anodes Insulation Polyethylene

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The Actual Operation of Transmission Line and Evaluation of the Reclosing Time of Reclosure

The Actual Operation of Transmission Line and Evaluation of ...

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2017 International Conference on Mechanical and Mechatronics Engineering(ICMME2017)

作者： Rui-ming OU Gun YANG Zhan-qing YU Jin-bo WU Shui-ming CHEN Hong-jun ZHEN Qingyuan Power Supply Bureau of Guangdong Grid Company State Key Lab.of Control and Simulation of Power Systems and Generation Equipment Department of Electrical EngineeringTsinghua University

In this paper,the actual trip of typical transmission line is *** includes the trip frequency of transmission lines and the tripping frequency caused by lightning,seasonal distribution characteristics of transmission line trip,and the success rate of reclosing on the transmission *** this paper,the probability of the occurrence of the trip again is evaluated based on the duration of ground lightning *** the increase of the time of reclosure,the probability of the occurrence of the trip will *** this calculating method,the average probability of tripping of reclosure decreased significantly during a ground lightning stroke process,when the reclosing time t0 is 1 s.

关键词： Trip of transmission line Trip caused by lightning Reclosing time of reclosure Probability of tripping of reclosure

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Electrical tree initiation and propagation in silicone rubber under long-term AC aging

Electrical tree initiation and propagation in silicone rubbe...

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Conference on Electrical Insulation and Dielectric Phenomena, (CEIDP)

作者： Yunxiao Zhang Yuanxiang Zhou Ling Zhang Ming Chen Xu Zhang Yanchao Sha State Key Lab of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing Beijing CN State Key Lab of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing China North China Electric Power Research Institute Co Ltd Beijing Beijing CN North China Electric Power Research Institute Co Ltd. Beijing China

Electrical tree break-down is the major failure problem in cable accessories, however, mechanisms of the electrical tree initiation and propagation are still lack of deeply research, especially in silicone rubber (SIR) which is widely used as insulation material for cable accessories. Long-term aging (0- 1000 h) experiments under the different voltages were conducted to observe electrical tree initiation and propagation processes. In trees initiation stage, with increasing of applied voltage, electrical tree initiation probability becomes larger, while tree initiation time dramatically decreases. The experiment observations demonstrated four shapes of trees which are dominated. As applied voltage increasing, the numbers of electrical trees life-cycles increased and exponential relationship was found between tree length and magnitude of applied voltage. It is noted that charges, whose energy exceeding a certain critical value, destroy microstructure of dielectric accumulatively via injection and extraction, and cause electrical trees initiate when it accumulates to a visible extent.

关键词： Electrodes Aging power cables Electric fields Needles power cable insulation

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Nonlinear E-field simulation of HVDC Converter Transformer Busing and Its Structure Optimization With RBF Neural Network and NSGA-II Algorithm

Nonlinear E-field Simulation of HVDC Converter Transformer B...

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IEEE International Conference on power and Energy systems (ICPES)

作者： Yongsheng He Shiling Zhang Zongxiang Lu Pengbo Wang State Grid Chongqing Electric Power Company Chongqing Electric Power Research Institute Chongqing China State Key Lab of Control and Simulation of Power Systems and Generation Equipment Haidian China Dept name of State Key Laboratory of Power Transmission Equipment and System Security and New Technology Chongqing China

Static DC and PR are typical operation conditions of HVDC converter transformer bushing outlet device, moreover, the electrical parameters of RIP, transformer oil and OIP have the nonlinear relationship with E-field stress and temperature. Under the temperature gradient, the electrical parameters will modify the static DC and PR E-field distribution of the composite insulation. In order to simulate static DC and PR electric field of the composite insulation structure, this paper established the full model of the converter transformer outlet. Then, the structure parameters of converter transformer outlet have been optimized using combined RBF neural network and NSGA-II algorithm. Moreover, electric field verification calculation has been carried out under AC and PR conditions. The results show that under uniform temperature condition, E-field strength is larger than that under iso-thermal condition. The overshoot coefficient of the bushing end and barrier reach 65% and 45%, respectively. The study can provide reference for the design of outlet structure of the converter transformer.

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Summary of Health Index Theory and Application of state Maintenance Equipment

Summary of Health Index Theory and Application of State Main...

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The 5th International Conference on Reliability of Electrical Products and Electrical Contacts

作者： Lin CHENG Manjun LIU Feijin PENG Dept.of Elec.Eng. Tsinghua UniversityState Key Lab of Control and Simulation of Power Systems and Generation Equipments Guangdong Power Grid Company Foshan Power Supply Bureau

This paper describes several methods for condition-based maintenance,introduced CBM,RCM development process,the main theoretical logic,techniques and *** on the health index based on equipment maintenance strategies,namely *** on the development of narrative context,theoretical foundation,model healthy *** for its application in power transformers were introduced.

关键词： Health Index(HI) Condition-Based Maintenance(CBM) Reliability Centered Maintenance(RCM) Condition Based Risk Maintenance(CBRM)

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Study of a new grid-connected LCL filter for shunt active power filter

Study of a new grid-connected LCL filter for shunt active po...

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IEEE Conference and Expo Transportation Electrification Asia-Pacific (ITEC Asia-Pacific)

作者： Yi Wang Jian-zheng Liu Xing-Tao Xu State Key Lab of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing Beijing CN Jiangsu Electric Power Company Research Institute Nanjing China

LCL filter can improve the output current of the shunt active power filter. The paper proposes a resonant LCL filter structure with a LC high-frequency filter branches adding to LCL filter with damping resistor. By LC resonance effect, the switching frequency harmonics are filtered more efficiently and the loss of the system is reduced. The paper also builds the system modeling and analyzes the stability of the grid filter with the deadbeat control, then gives parameter selection methods and simulates with PSCAD/EMTDC. All these are verified through the experiments on a 70-KW shunt APF prototype using deadbeat controller.

关键词： power harmonic filters Damping Active filters Harmonic analysis power filters Switching frequency Resonant frequency

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The Method for Evaluating the Reclosing Time of Reclosure Based on Lightning Parameters

The Method for Evaluating the Reclosing Time of Reclosure Ba...

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2017 International Conference on Mechanical and Mechatronics Engineering(ICMME2017)

作者： Gun YANG Zhan-qing YU Hong-jun ZHEN Chao SU Shui-ming CHEN Rong ZENG Jin-liang HE State Key Lab.of Control and Simulation of Power Systems and Generation Equipment Department of Electrical EngineeringTsinghua University Qingyuan Power Supply Bureau of Guangdong Grid Company

The fault of transmission line is mostly caused by lightning,and a ground lightning stroke process is often accompanied by multiple *** duration of ground lightning stroke are also *** this paper,a method for evaluating the reclosing time of reclosure based on lightning parameters is *** addition,this paper also gives an expression for the cumulative rate of the duration of ground lightning stroke,and an expression for probability distribution of the amplitude of lightning current in Guangdong *** also proposed a method for calculating the probability of tripping of *** this calculating method,the average probability of tripping of reclosure is less than 1/10000 during a ground lightning stroke process,when the reclosing time t0 is greater than 1.012 s.

关键词： Ground lightning stroke Lightning parameters Reclosing time of reclosure Probability of tripping of reclosure

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Analysis and simulation research on cascading trips of multiple wind farms

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Dianwang Jishu/power system Technology 2014年第6期38卷 1425-1431页

作者： Xu, Fengda Guo, Qinglai Sun, Hongbin Zhang, Boming Wang, Bin Li, Zhengshuo Ding, Tao Jia, Lin Xu, Xiaofei State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China North China Grid Company Limited Xuanwu District Beijing 100053 China

A simulation based analysis is proposed to find out the most relative factors during the cascading process, which is significant to support the future voltage control schemes for wind integration region. A hierarchical distributed simulation platform is built, which contains both the transmission and wind farms' distribution grid. In this way both the coupling among wind farms and the detailed characteristics of device level can be considered. By simulating shunt capacitors, wind turbine generators and static var compensators (SVCs) under different control mode, the different impact to cascading trips process are analyzed. With the simulation, it is found that centralized integrated wind farms are so closed-coupled that variations of active or reactive power in one wind farm would cause great changes of voltages in wind farms nearby. Researching results also indicate that coordination of various reactive power implements is essential to system voltage safety.

关键词： Wind farm

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