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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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Lightning overvoltage suppression to UHV power transformer by ferromagnetic ring

Lightning overvoltage suppression to UHV power transformer b...

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作者： Zhang, Xiao He, Jinliang State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China

Lightning overvoltage protection is of great importance to the safety of devices in UHV GIS. In practice, insulation failure of UHV transformer due to lightning strike is often reported. The widely used UHV metal-oxide arresters can suppress the magnitude of lightning overvoltage but lack effectiveness on alleviating the steepness. A new protection method is proposed in this paper using ferromagnetic ring as supplement to the arresters in suppressing lightning overvoltage within UHV GIS. Moreover, equivalent model based on the characteristic of ferromagnetic material and factual dimensions of the ring is established. simulation of an actual 1000 kV GIS is carried out to thoroughly evaluate the lightning overvoltage suppressing effect of ferromagnetic rings with different materials and structure parameters. © 2012 Elsevier B.V. All rights reserved.

关键词： power transformers

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Research of algorithm and analysis of performance for DC surge impedance relay

Research of algorithm and analysis of performance for DC sur...

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12th IET International Conference on Developments in power System Protection, DPSP 2014

作者： Lei, Aoyu Dong, Xinzhou State Key Lab of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 10084 China

Surge Impedance Relay(SIR) is applied to DC system. Characteristics of SIR in DC line are analysed. A DC SIR algorithm implementing wavelet transform applied to HVDC line protection is proposed. The feasibility of DC ... 详细信息

ISBN: (纸本)9781849198349

关键词： Wavelet transforms

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A cooperative game theory based multi-objective reactive voltage optimization model and its solution

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Dianli Xitong Zidonghua/Automation of Electric power systems 2012年第18期36卷 116-121+133页

作者： Zhang, Mingye Guo, Qinglai Sun, Hongbin Zhang, Boming Wu, Wenchuan Wang, Bin State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing 100084 China

To coordinately consider the economy and security of the system during reactive voltage control, a multi-objective reactive power optimization model is proposed. Apart from the conventional economic objective, the new model has the system static security added to the multi-objective to seek their optimization simultaneously. And the solution for the model is proposed based on the cooperative game theory. As two players of the game, the economy side and the security side decide on their game strategies alternately until equilibrium is attained. Tests on a 2-bus system and IEEE 9-bus system demonstrate the feasibility and advantages of the model along with the proposed method. © 2012 state Grid Electric power Research Institute Press.

关键词： Multiobjective optimization

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Experimental investigation and analysis of some common faults for wind turbine 68

Experimental investigation and analysis of some common fault...

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68th Society for Machinery Failure Prevention Technology Conference: Technology Solutions for Affordable Sustainment, MFPT 2014

作者： Yang, Wenguang Li, Shaohua Jiang, Dongxiang State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing100084 China

This paper focus on the fault characteristic by experimental research. A test rig is built for the direct driving stall fix-pitch horizontal axis wind turbine. 8 signals are collected by the experiment system, including wind speed, rotor rotational speed, shaft torque, the output electric power, vertical and horizontal vibration displacement of main shaft, vibration acceleration of the front bearing pedestal and the back bearing pedestal. 11 common wind turbine faults are researched by experiment. These faults are rotor mass imbalance, pneumatic asymmetry, airfoil changed, yaw fault, shaft horizontal misalignment, shaft vertical misalignment, front bearing pedestal looseness, rear bearing pedestal looseness, front bearing outer ring fault, front bearing inner ring fault, and front bearing roller fault. Several signal analysis methods, which are waveform analysis, orbit analysis, amplitude domain analysis, frequency domain analysis and envelope spectrum analysis, are adopted to extract characteristics from vibration signals. The influence on output power and vibration characteristics of these faults is presented by comparing with normal operation. The findings can be used to guide wind turbine fault diagnosis in engineering applications.

关键词： Wind

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Modal analysis of wind turbine tower

Modal analysis of wind turbine tower

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2010 2nd World Non-Grid-Connected Wind power and Energy Conference, WNWEC 2010

作者： Chen, Jie Jiang, Dongxiang State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781424489213

As the support structure of wind turbine, the tower bears alternating loads of wind when the wind turbine runs. To ensure the reliability of the wind turbine, it's necessary to carry out modal analysis on the tower, and this would prevent the natural frequency of the tower close to the rated speed of wind turbine. In this paper, finite element analysis of the tower is solved using ANSYS, and the natural frequencies and modes of the tower are presented. After comparing the results of three models, a simple model for modal analysis, which can be calculated in short time, is finally determined. © 2010 IEEE.

关键词： Modal analysis

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Finite element analysis on damping characteristics for vibro-impact of integral shroud blade

Finite element analysis on damping characteristics for vibro...

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Joint Conference on Society for Machinery Failure Prevention Technology Conference, MFPT 2015 and ISA's 61st International Instrumentation Symposium, IIS 2015 - Technology Evolution: Sensors to systems for Failure Prevention

作者： Wang, Nan-Fei Jiang, Dong-Xiang Chen, Jing-Ming State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing100084 China

By using theoretical and experimental methods, dynamic characteristics of turbine blades with integral shrouds are studied, and the mechanism of vibro-impact and the effective factors of integrally shrouded blades are mainly presented. By means of finite element calculation, the dynamic frequencies and vibration mode shapes of single shrouded blade are explored under different rotating speeds. The three-dimensional entity unit integral dynamics equation of blades with vibro-impact are established by using nonlinear damping model in this paper. With the help of 3D software Solidworks, the solid model of blade is built. With the aid of FEA software ANSYS, the dynamics and static characteristics of single blade are obtained. Meanwhile, by building the model to set different shroud clearance and exciting force amplitude, the relationships between displacement of blade tip and influence of such as blade shroud clearance and exciting force amplitude are demonstrated. The results of the analysis indicate that the collision structural is an ideal damping structure. As the clearance between blade shrouds is smaller, the damping effect is better. Moreover, results show that blades adopting collision damping mechanism can achieve good damping effect when the blades are subjected to greater exciting force.

关键词： Finite element method

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Vibration characteristics on a wind turbine rotor using modal and harmonic analysis of FEM

Vibration characteristics on a wind turbine rotor using moda...

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2010 2nd World Non-Grid-Connected Wind power and Energy Conference, WNWEC 2010

作者： Liu, Chao Jiang, Dongxiang Chen, Jie State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781424489213

A wind turbine rotor system containing blades has its own characteristics. The vibration characteristics of blades with special airfoil can influence the vibration characteristics of the rotor system. This paper analyzed the vibration characteristics of a wind turbine rotor including blades with two-dimensional airfoil. The Finite Element Method (FEM) is applied to establish the rotor model, with the purpose that the FEM can adjust complex blades airfoils and acquire the details of the blades vibration characteristics. The modal characteristics are extracted based on the wind turbine model established in the laboratory. Using harmonic analysis of FEM, the excitation forces on the blades caused by the stochastic wind load are imposed on the rotor model and the stable response of the rotor system is calculated using ANSYS. Then the vibration characteristics are analyzed and the characteristics of the harmonic response are studied under different phases of the circumferential and axial forces. © 2010 IEEE.

关键词： Harmonic analysis

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Diagnosis method for rub-impact fault of rotating machinery based on EMD and Hilbert envelop spectrum

Diagnosis method for rub-impact fault of rotating machinery ...

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Joint Conference on Machinery Failure Prevention Technology Conference, MFPT 2016 and ISA's 62nd International Instrumentation Symposium, IIS 2016

作者： Wang, Nan-Fei Jiang, Dong-Xiang Han, Te State Key Laboratory of Control and Simulation of Power System and Generation Equipments Departments of Thermal Engineering Tsinghua University Beijing100084 China

Aiming at the characteristics of the casing vibration acceleration signal of rotating machinery with rubbing fault, a diagnosis method based on EMD (empirical mode decomposition) and Hilbert envelop spectrum is put forward. When the rubbing fault occurs between the rotor and the stator, the vibration acceleration signals from the casing of the rooting machinery will present amplitude-modulated feature due to the periodical rub-impact between the rotor and the stator. However, it is relatively difficult to extract the rub-impact feature since the rub-impact signal in the process of transferring to the casing is always buried in the noise and background signals. In this paper, by means of the powerful capability of EMD and Hilbert envelop spectrum in processing nonlinear signal can accurately describe nonlinear behaviours, the fault signal is adaptively decomposed by EMD to acquire intrinsic mode functions (IMF) containing obvious feature of amplitude modulation. Then some of the sensitive IMF components are transformed by FFT and their Hilbert spectrum are analysed. The analysis results from the experimental signal show that the EMD provides an effective and adaptive method to obtain 'purified' casing vibration acceleration signal, which demonstrates the transient casing vibration more precisely and vividly, decreasing misinterpretation of the machine running condition. Therefore, the EMD approach can be applied to the single-point rubbing fault diagnosis of the rotor systems efficiently. © 2016, Society for Machinery Failure Prevention Technology. All rights reserved.

关键词： Empirical mode decomposition

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Cascaded battery energy storage system based on dual active bridges and a common dc bus

Cascaded battery energy storage system based on dual active ...

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2010 9th International power and Energy Conference, IPEC 2010

作者： Jin, Yiding Song, Qiang Liu, Wenhua Sun, Weixin State Key Lab. of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing China

ISBN: (纸本)9781424473991

Along with the increasing system capacity, large-scaled energy storage systems are supposed to be connected into 10kV or higher networks. Urban network has strict criterions on power quality of the power electronic devices connected. Moreover, the occupancy and noise of industrial frequency transformers also become restraints to the promotion of urban network energy storage. For that reason, this paper proposes a battery energy storage system based on cascaded dc-ac converter, dual active bridges, and a common dc bus. High frequency transformers are used to replace the industrial frequency transformer for insulation, and battery groups are connected to the common dc bus with respective dc-dc interfaces. This multilevel converter system is easy to modularize, easy to extend, and allows different kinds of batteries to work together. The main circuit and proper control system are designed, with the soft-switching condition and current control issues of the dual active bridge analyzed in detail. The simulation results from EMTDC model verify the operation principles and corresponding control strategies. ©2010 IEEE.

关键词： Electric inverters

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