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

The measured parameters change with the machine degradation, where the trends of the parameters can be applied in condition prediction. The deterioration of the parameters usually present characteristics in a monotonic or low-frequency way. As the measure signal are merged with instant signals, noise and measurement error in different frequency bands, model decomposition approaches are widely applied to separate the different bands for feature extraction. Among the model decomposition methods, Variational model decomposition is recently proposed by K. Dragomiretskiy and D. Zosso as a non-recursive model which can extract modes concurrently. This work will analyze its effectiveness in degradation feature extraction and application in condition prediction in prognosis. Firstly, variational model decomposition is analyzed, where the characteristics of variational model decomposition are compared with another mode decomposition method ensemble empirical mode decomposition. simulation data is applied to test the effectiveness of the mode decomposition methods. Secondly, field data with component degradation is collected, and the degradation feature extraction is applied with the three methods mentioned above.

关键词： Empirical mode decomposition

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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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A fast transient simulation model of DFIG based on the piecewise averaging method

A fast transient simulation model of DFIG based on the piece...

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2nd IET Renewable power generation Conference, RPG 2013

作者： Feng, G. Xu, Y. Chen, Y. Gao, H. Chen, L. State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781849197588

Due to the power electronic devices in doubly fed induction generators (DFIG), it is very time consuming to simulate the electromagnetic transients of DFIG using its detailed model. Thus it is necessary to have appropriately simplified model of DFIG that maintains desirable accuracy. In this paper, the piecewise averaged model of PWM converters is introduced and applied to the modelling of DFIG. The proposed model divides the simulation time interval into switching periods and recalculates the averaged state equations of PWM converters in each switching cycle. In addition, a predictorcorrector based EMTP algorithm is designed to iteratively solve the model. Instead of treating switching events at the time points when they happen, the new algorithm solves all the switching instants in a switching cycle at the same time, which avoids frequency modification of the system conductance matrix and speeds up EMT simulations of DFIG. simulation results of a single-machine infinity bus system with a DFIG show that the proposed model and algorithm can achieve satisfactory accuracy and efficiency.

关键词： Equations of state

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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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DC/DC Converter Applied in the Photovoltaic- Inclined Thermal Collector Hybrid systems for Brackish Water Desalination

DC/DC Converter Applied in the Photovoltaic- Inclined Therma...

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11th International Conference on Electrical Machines and systems(第11届国际电机与系统会议)

作者： Liqiang Yuan Mohamed Eltawil Zhengming Zhao Yaodong Lu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department o State Key Laboratory of Control and Simulation of Power System and Generation EquipmentDepartment of

A chronic drinking water shortage is one of the most important issues in the developing countries, and drinking water from dirty water sources causes serious damage to inhabitants health in some remote areas. The solar distillation remains the most favorable process for the supplying of water to small communities. Base on the traditional solar still, an improved hybrid photovoltaic/thermal (PVT) desalination system is presented. The PV modules that are combined with thermal units, constitute the PVT systems which has longer operating time and higher average fresh water production. This paper introduces the DC/DC converter applied in this type of systems, including its structure and control strategy which is suitable for PV array and driving supportive heater. The experimental results for the converter and the whole system are showed and analyzed.

关键词： DC-DC power converters Photovoltaic systems Solar power generation Desalination Temperature Water resources Hybrid power systems Solar energy Water heating power system simulation

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A Novel Direct power control Strategy for Three-Level PWM Rectifier Based on Fized Synthesizing Vectors

A Novel Direct Power Control Strategy for Three-Level PWM Re...

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11th International Conference on Electrical Machines and systems(第11届国际电机与系统会议)

作者： Ting Lu Yongchang Zhang Yingchao Zhang Zhengming Zhao Liqiang Yuan State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department o State Key Laboratory of Control and Simulation of Power System and Generation EquipmentDepartment of

A novel direct power control (DPC) strategy for three-level neutral-point-clamped (NPC) pulse-width-modulation (PWM) rectifier, based on fixed synthesizing vectors, is proposed in this paper. The strategy breaks through the restrictions of vector switching with a simple switching table, improves the excellent dynamic performance of DPC, avoids the neutral-point voltage unbalance and the excessive voltage jumps in phase and line-to-line voltages of the rectifier, and guarantees the proper minimum pulse width and switching intervals between switches in different phases simultaneously. Experimental results verify the validity and feasibility of the proposed scheme.

关键词： Pulse width modulation power control Rectifiers Space vector pulse width modulation Switches Thyristors Topology Voltage control Snubbers control system synthesis

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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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Initial-stage performance evolution of solid oxide fuel cells based on polarization analysis 17

Initial-stage performance evolution of solid oxide fuel cell...

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

作者： Wang, Yige Lyu, Zewei Han, Minfang Sun, Zaihong Sun, Kaihua Department of Energy and Power Engineering State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing100084 China Xuzhou Huatsing Jingkun Energy Co. Ltd. Jiangsu Province Xuzhou221005 China

ISBN: (纸本)9781607685395

The performance evolution of solid oxide fuel cells (SOFCs) is more pronounced and non-linear in the initial stage, determining the output level during subsequent long-term operation. In this study, an industrial-size (10×10 cm2) cell was tested under 0.1 A cm-2 for 96 hours. I-V-P curves and EIS data under different DC bias (0, 0.05, 0.10, 0.30, 0.50, 0.70 A cm-2) were periodically recorded every 24 hours to investigate the mechanism of initialstage performance evolution. The ohmic loss was identified as the main contributor to the total overpotential, especially under large current density. The cell performance increased during 4-24 h due to the enhancement of anode gas-phase diffusion/conversion processes, while the performance degraded significantly during 48- 96 h caused by the deterioration of anode charge transfer reaction. The EIS evolution trend under different DC bias was consistent, while the evolution degree was larger under smaller current density. © 2021 Electrochemical Society Inc.. All rights reserved.

关键词： Deterioration

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Space Charge Transport of Al2O3/Silicone Rubber Composites under Thermal Aging

Space Charge Transport of Al2O3/Silicone Rubber Composites u...

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2022 IEEE International Conference on High Voltage Engineering and Applications, ICHVE 2022

作者： Zhang, Yunxiao Yan, Chenning Wu, Kai Zhou, Yuanxiang Zhang, Tianfeng College of Electrical Engineering and Automation Fuzhou University Fujian Fuzhou China Tsinghua University State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Beijing China School of Electrical Engineering Xinjiang University The Wind Solar Storage Division State Key Laboratory of Power System and Generation Equipment Urumqi China Electric Power Research Institute Anhui Electric Power Company of State Grid Hefei China

ISBN: (纸本)9781665407502

Silicone rubber (SIR) has been widely used in the insulation of cable accessories due to its excellent performance. In this paper, pure SIR and nano Al2O3/SIR composites are thermally aged for 0-80 days at 200°C. The effects of long-term thermal aging on the space charge transport are analyzed. The results show that with the increase of thermal aging time, the accumulation of heteropolar charge of pure SIR and nano Al2O3/SIR composites gradually decreases and changes to the accumulation of homopolar charge. Compared with pure SIR, the space charge accumulation of Al2O3/SIR composites decreases significantly and changes little with the increase of thermal aging time. It is believed that when doped nano Al2O3 in SIR, the increase of carrier mobility and the introduction of metal oxides reacting with fallen free radicals to form stable compounds both lead to less space charge accumulation of Al2O3/SIR composites. © 2022 IEEE.

关键词： Aluminum oxide

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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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