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2012 IEEE 7th International power Electronics and Motion control Conference - ECCE Asia, IPEMC 2012

作者： Wang, Kui Li, Yongdong Zheng, Zedong Xu, Lie Ma, Hongwei State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9781457720864

Five-level active neutral-point-clamped (ANPC) converter is a newly emerging topology which can overcome the drawbacks of traditional neutral-point-clamped and flying-capacitor multilevel converters. During the start-up of the converter, it must be ensured that the switches and capacitors cannot be overvoltage and overcurrent due to the uncharged floating capacitors. In this paper, a floating capacitor self-precharge method is proposed which, by transferring the circuit into a booster, charges the floating capacitors to the reference voltage with a very small average load current. simulation and experimental results are presented to verify the validity of this method. © 2012 IEEE.

关键词： power converters

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generation of Atmospheric Pressure Plasma by Repetitive Nanosecond Pulses in Air Using Water Electrodes

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Plasma Science and Technology 2011年第6期13卷 735-739页

作者：邵涛于洋章程姜慧严萍周远翔 Institute of Electrical Engineering Chinese Academy of Sciences Key Laboratory of Power Electronics and Electric Drive Chinese Academy of Sciences State Key Laboratory of Control and Simulation of Power Systems and Generating Equipment Electrical Engineering DepartmentTsinghua University

Dielectric barrier discharge （DBD） excitated by pulsed power is a promising method for producing nonthermal plasma at atmospheric pressure. Discharge characteristic in a DBD with salt water as electrodes by a home-made unipolar nanosecond-pulse power source is presented in this paper. The generator is capable of providing repetitive pulses with the voltage up to 30 kV and duration of 70 ns at a 300 Ω resistive load. Applied voltage and discharge current are measured under various experimental conditions. The DBD created between two liquid electrodes shows that the discharge is homogeneous and diffuse in the whole discharge regime, Spectra diagnosis is conducted by an optical emission spectroscopy. The air plasma has strong emission from nitrogen species below 400 nm, notably the nitrogen second positive system.

关键词： non-thermal plasma dielectric barrier discharge pulsed power nanosecondpulse pulse repetition frequency atmospheric pressure air emission spectra.

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Performance evolution of NI-YSZ anode-supported Sofcs during initial-stage operation 17

Performance evolution of NI-YSZ anode-supported Sofcs during...

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17th International Symposium on Solid Oxide Fuel Cells, SOFC 2021

作者： Lyu, Zewei Han, Minfang Department of Energy and Power Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing100084 China

ISBN: (纸本)9781607685395

Performance evolution of typical Ni-YSZ anode-supported SOFCs during the initial-stage operation ( 20 h), regardless of the operating current. In the activation stage, the cell performance maintains stable or slightly increases due to the enhanced anode gas-phase diffusion. While in the subsequent aging stage, the cell performance decreases significantly and gradually approaches a plateau in about 100 hours, mainly due to the weakened anode charge transfer reaction and ionic transport processes. Therefore, it is suggested that more efforts should be focused on improving the stability of anode microstructure, especially the stability of anode functional layer. © 2021 Electrochemical Society Inc.. All rights reserved.

关键词： Chemical activation

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Optimization of methane reforming for high efficiency and stable operation of SOFC stacks 17

Optimization of methane reforming for high efficiency and st...

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17th International Symposium on Solid Oxide Fuel Cells, SOFC 2021

作者： Liu, Yaodong Lyu, Zewei Han, Minfang Department of Energy and Power Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing100084 China

ISBN: (纸本)9781607685395

Solid Oxide Fuel Cells (SOFCs) provides an efficient and clean pathway to generate electricity. In addition to hydrogen, SOFCs also hold the possibility for the utilization of a variety of carbon containing fuels. A practical kilowatt-class SOFC system fueled by methane has been preliminarily integrated previously. This study intended to obtain the optimized working conditions for the prereformer, with which the SOFC module can exhibit higher electrical performance. Detailed thermodynamic analysis and experimental measurements of steam methane reforming (SMR) were carried out under different steam to carbon ratios (S/C) and temperatures, where the experimental results matched well with the thermodynamic calculation. Based on the optimized working condition of SMR, the electrical performance and stability of a planar single-layer stack (10×10 cm2) fueled by the reformate syngas was evaluated. The maximum electrical efficiency reached 65.39% (LHV) at 750 C, and 50-hour stable operation under 50% (LHV) electrical efficiency was achieved. © 2021 Electrochemical Society Inc.. All rights reserved.

关键词： Electrical efficiency

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simulation of Arc Erosion on the Main Contact of On-Load Tap Changer 4th

Simulation of Arc Erosion on the Main Contact of On-Load Tap...

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4th International Symposium on Insulation and Discharge Computation for power equipment, IDCOMPU 2023

作者： Zhou, Yuanxiang Dai, Yasong Chen, Jianning Li, Yuhang Hou, Xuzhao Zhang, Zhen State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing100084 China The Wind Solar Storage Division of State Key Laboratory of Power System and Generation Equipment School of Electrical Engineering Xinjiang University Urumqi830047 China

ISBN: (纸本)9789819974047

Long-term operation and switching of transformer on-load tap-changers can cause degradation and deterioration of the main contact material, even leading to contact arcing damage in severe cases. However, the arcing mechanism of the main contact during the switching has not been clarified yet. A magneto-hydrodynamic simulation method of main contact arcing has been proposed. The geometry of the main contact in transformer oil is simplified, and the simulation model of the arc temperature field of the main contact in transformer oil coupled with electric, magnetic, thermal and fluid fields is proposed. The dynamic evolution of the arc temperature has been investigated at peak currents of 2100 A, 1500 A, 600 A and 300 A, respectively. The results show that with the increase of the spacing between contacts, the temperature at arc core rises rapidly and then decreases slowly, and the temperature can reach 50177 K at 2100A. Due to the electron bombardment at the anode surface, the temperature at anode surface is higher than that at cathode surface under different chopped currents. The highest temperatures at anode and cathode surface can reach 4142.5 K and 4081.7 K respectively. © Beijing Paike Culture Commu. Co., Ltd 2024.

关键词： Deterioration

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Calculation on the thermal field of the water cooling stator of three-gorge hydro-generator

Calculation on the thermal field of the water cooling stator...

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ICEMS 2005: 8th International Conference on Electrical Machines nd systems

作者： Wang, H.Y. Su, P.S. Wang, X.H. Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing 10084 China

ISBN: (纸本)7506274078

To simplify the calculation of winding bar temperature for the condition monitoring of the water cooling stator of Three-Gorge Hydro-Generator, this paper calculates three of two-dimension thermal fields. Using the three fields simulates the different section along the axial direction of the generator. The total amount of heat taken away by water can be calculated by weighting the result of three fields on the total axial length of them. Four groups of thermal-fields with different outlet-water temperature are calculated by using ANSYS multi-physical software. The calculation results of temperature of measurement-point between up-layer and down-layer bars in stator are partly supported by the measurement data. And the relatively error between the heat taken by cooling-water and the heat generated by the stator bar is always less than 5%.

关键词： Stators

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Influences of temperature on Space Charge in Gas-to-Liquid Oil-Impregnated Paper 7

Influences of temperature on Space Charge in Gas-to-Liquid O...

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7th IEEE International Conference on High Voltage Engineering and Application, ICHVE 2020

作者： Zhou, Yuanxiang Huang, Xin Zhang, Ling Zhang, Yunxiao Zhou, Zhongliu Teng, Chenyuan China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Department of Electrical Engineering Beijing China

ISBN: (纸本)9781728155111

Gas-to-liquid (GTL) transformer oil has been on trial in converter transformers. However, its influence on the space charge characteristic is not clear. This work aims at exploring space charge characteristics of GTL oil at different temperatures as well as comparing with commercial naphthenic oil (KI50X). Space charge distribution during the polarization and the dissipation process in the GTL oil-impregnated paper at different temperature was measured by the pulse electroacoustic method (PEA), which were contrasted with those of the KI50X oil-impregnated paper. Results illustrated that high temperature accelerated the injection and migration of charge carriers in the oil-impregnated paper. And the polarity of the accumulated charge in the vicinity of anode changed from positive to negative with the increase of temperature. It was perceived that oil-paper conductivity and carrier mobility grew with the increase of temperature, resulting in the easier migration of injected charge to another electrode. Furthermore, the space charge dissipation rate in the GTL oil-impregnated paper is lower than that in the naphthenic oil-impregnated paper at the same temperature. Thus, a longer time interval of tests or switch operation in the factory test and operation process may need if GTL oil is used rather than naphthenic oil. © 2020 IEEE.

关键词： Electric space charge

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A Joint Prediction Method of Multi-state Variables for High-Voltage Cables Based on GRU 10th

A Joint Prediction Method of Multi-State Variables for High-...

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10th Frontier Academic Forum of Electrical Engineering, FAFEE 2022

作者： Chen, Jianning Zhou, Yuanxiang Lin, Menglong Pan, Zehua Ge, Jiamin State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing100084 China

ISBN: (纸本)9789819934034

In order to carry out risk warning for high-voltage cable transmission system and realize differentiated operation and maintenance decision-making, it is necessary to carry out time series prediction for online monitoring state quantities of high-voltage cables such as load current, partial discharge, and grounding circulating current. Therefore, a joint prediction method for multi-state variables of high-voltage cables based on Gate Recurrent Unit (GRU) is proposed. Taking the online monitoring state quantities of a certain area in central China in May as the analysis data set, a GRU network is built to predict the sequence of multi-state quantities, compared with different models. Taking the phase A load current of a node of the cable as an example to carry out state prediction, the results show that compared with the Long Short Term Memory (LSTM) neural network, back-propagation neural network (BPNN), and Auto Regressive Integrated Moving Average (ARIMA) model, the accuracy of the sequence prediction model based on GRU is Higher. When predicting for 5 min, the MAE and RMSE are 1.94 and 2.65 A, respectively, with the MAPE of 0.54%. When predicting for 30 min, the MAE and RMSE are 9.81 and 15.36 A, respectively, with the MAPE of 2.89%. When predicting for 1 h, the MAE and RMSE are 17.05 and 27.47 A, respectively, with the MAPE of 4.91%. The GRU model performs better due to the suppression on over-fitting of training data with simpler model structure. © Beijing Paike Culture Commu. Co., Ltd. 2023.

关键词： Forecasting

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Research on the prediction-model of the surface-temperature of large oil-immersed power transformer

Research on the prediction-model of the surface-temperature ...

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ICEMS 2005: 8th International Conference on Electrical Machines nd systems

ISBN: (纸本)7506274078

In order to detect the abnormal temperature of large oil-Immersed power transformer earlier, this paper presents a new prediction-model of surface-temperature for the transformer to predict the normal surf ace-temperature. And to compare the difference between the predicted value and the measured value can judge If the condition of the transformer Is fit to operate. The model parameters are estimated from the field data by using the Partial-Least-Square method, which overcomes the instability of results estimated by using the traditional Least-Square method. Furthermore, the appropriate amount of data for the parameter estimation was decided according to the principle of Heat Transfer and the characteristics of the predicted deviation, such as mean, variance and normal distribution. The prediction model is verified from the accuracy of results predicted with one year of field data.

关键词： Electric transformers

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A combined time-and-frequency-domain model for integration of wind power generation

A combined time-and-frequency-domain model for integration o...

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2016 IEEE Innovative Smart Grid Technologies - Asia, ISGT-Asia 2016

作者： Chen, Xiaoshuang Lin, Jin Wan, Can Song, Yonghua Guo, Wanfang State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing100084 China

ISBN: (纸本)9781509043033

Wind power generations (WPGs) are different from traditional generations for their considerable fluctuations. It is challenging to describe the status of a system with power fluctuation injections, especially when considering complicated network constraints. This paper proposes a combined time-and-frequency-domain (CTFD) model to evaluate whether the constraints will be violated under fluctuating wind power injection. The constraints of energy units and branch power flow are described in a generalized form, and are related to the power spectral density of power fluctuations. The distributions of the constraint variables are then discussed based on the CTFD model, and a chance criterion is conducted to describe the probability of the constraints being violated. Case studies show the effectiveness of the proposed model. © 2016 IEEE.

关键词： Probability distributions

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