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Electrical tree degradation of MgO/epoxy resin composites at different voltage frequencies

High Voltage 2024年第3期9卷 581-590页

作者： Yunxiao Zhang Wenxin Lin Yuanxiang Zhou Weiwei Xing Jiayu Cheng Chenyuan Teng College of Electrical Engineering and Automation Fuzhou UniversityFujian Key Laboratory of New Energy Generation and Power ConversionFuzhouChina State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical EngineeringTsinghua UniversityBeijingChina

Electrical tree degradation is one of the main causes of insulation failure in high-frequency *** tree degradation is studied on pure epoxy resin(EP)and MgO/EP composites at frequencies ranging from 50 Hz to 130 *** results show that the tree initiation voltage of EP decreases,while the growth rate and the expansion coefficient increase with ***,the bubble phenomenon at high frequencies in EP composites is *** with trap distribution character-istics within the material,the intrinsic mechanism of epoxy composites to inhibit the growth of the electrical tree at different frequencies is *** can be concluded that more deep traps and blocking effect are introduced by doping nano-MgO into EP bulks,which can improve the electrical tree resistance performance of EP composites in a wide frequency range.

关键词： composites tree Electrical

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Commutation Failure Mitigation Method Based on Improved Commutation Area in HVDC system 8

Commutation Failure Mitigation Method Based on Improved Comm...

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8th IEEE International Conference on Advanced power System Automation and Protection, APAP 2019

作者： Wang, Haozong Dong, Xinzhou Tsinghua University State Key Lab of Control and Simulation of Power Systems and Generation Equipment Beijing China

ISBN: (纸本)9781728117225

Commutation failure (CF) is one of the major concerns in high-voltage direct current (HVDC) transmission system. Of many methods to mitigate CF, advancing firing angle is preferred one since it can be easily implemented in current HVDC controllers without extra hardware modification. However, methods in previous works either lack for quantitative analysis or based on much strong hypothesis. In this paper, we propose a novel CF mitigation method based on improved commutation area. The salient feature of proposed strategy is that DC current is not considered as a constant under fault conditions. simulations on PSCAD/EMTDC software demonstrate the good performance of proposed method. © 2019 IEEE.

关键词： Electric commutation

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Significant potential of Solid Oxide Fuel Cell systems for distributed power generation and carbon neutrality

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Frontiers in Energy 2022年第6期16卷 879-882页

作者： Ziyuan TENG Minfang HAN Fuel Cell and Energy Storage Center Department of Energy and Power EngineeringState Key Laboratory of Control and Simulation of Power Systems and Generation EquipmentTsinghua UniversityBeijing 100084China

Energy is important for human survival and *** September 2020,the Chinese government announced that“China aims to have their CO_(2) emissions peak before 2030 and achieve carbon neutrality before 2060.”As China’s reformation and opening-up proceeds into its fifth decade,this new vision for its future is in line with that of the world’s major economies in terms of the need to reach net zero emissions globally by the mid-21stcentury[1].However,coal-fueled thermal power generation is currently dominant and accounts for more than 70%of the total amount of power generated in China,making it the world’s largest energy consumer and carbon *** on the country’s domestic resources,namely the abundance of coal and scarcity of oil and gas,it would be difficult to fundamentally change this coal-based energy structure in the short *** 2021,the global total energy sector was responsible for 36.3 Gt of CO_(2) emissions,including approximately 12 Gt from China,which thus accounts for one-third of the total global emissions[2].The demand for efficiency,energy savings,and emissions reduction in the power generation industry has become increasingly *** need has arisen to enhance ways in which to use coal cleanly and efficiently,reduce the consumption thereof,and replace coal with other forms of *** addition,carbon emissions need to be lowered by promoting the adoption of alternative power generation technologies that are more energy *** would require transformation away from coal power and the exploration of clean,efficient,flexible,and safe forms of energy as the main future development directions[3].

关键词： neutral carbon replace

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Stochastic processes in renewable power systems: From frequency domain to time domain

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Science China(Technological Sciences) 2019年第12期62卷 2093-2103页

作者： SONG YongHua CHEN XiaoShuang LIN Jin LIU Feng QIU YiWei Department of Electrical and Computer Engineering University of MacaoMacaoChina State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical EngineeringTsinghua UniversityBeijing 100084China

With the increasing penetration of renewable energy resources(RESs), the uncertainties of volatile renewable generations significantly affect the power system operation. Such uncertainties are usually modeled as stochastic variables obeying specific distributions by neglecting the temporal correlations. Conventional approaches to hedge the negative effects caused by such uncertainties are thus hard to pursue a trade-off between computation efficiency and optimality. As an alternative, the theory of stochastic process can naturally model temporal correlation in closed forms. Attracted by this feature, our research group has been conducting thorough researches in the past decade to introduce stochastic processes within renewable power systems. This paper summarizes our works from the perspective of both the frequency domain and the time domain, provides the tools for the analysis and control of power systems under a unified framework of stochastic processes, and discusses the underlying reasons that stochastic process-based approaches can perform better than conventional approaches on both computational efficiency and optimality. These work may shed a new light on the research of analysis, control and operation of renewable power ***, this paper outlooks the theoretic developments of stochastic processes in future’s renewable power systems.

关键词： renewable energy resources renewable power systems stochastic processes frequency domain time domain

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On Dispatching power systems with Significant Wind generation Using Disturbance Feedbacks

On Dispatching Power Systems with Significant Wind Generatio...

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第三十二届中国控制会议

作者： WEI Wei MEI Shengwei LIU Feng State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical EngineeringTsinghua University

ISBN: (纸本)9781479900305

With the rapid development of renewable energies,especially wind power,how to manage unexpected generation variations economically and reliably in dispatch has become crucial for modern power *** address this issue,this paper presents an affine disturbance feedback robust dispatch(ADF-RD) methodology for power systems with large scale wind power integration in the framework of adjustable robust optimization(ARO).This methodology divides the dispatching process into pre-dispatch and ***-dispatch decision immunizes against all possible realizations of uncertainties in a set,while re-dispatch which can be regarded as a feedback will be adaptively adjusted using an affine function with respect to the realized uncertainty in real *** ADF-RD methodology is applied to an hourly ahead dispatch(HAD) *** effectiveness and efficiency of the proposed ADF-RD methodology are demonstrated by numerical experiments carried on a five-bus system.

关键词： Adjustable robust optimization affine disturbance feedback power system dispatch uncertainty wind power

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Study on the operating parameters of the 10 kW SOFC-CHP system with syngas

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International Journal of Coal Science & Technology 2021年第4期8卷 500-509页

作者： Biao Li Zewei Lyu Jianzhong Zhu Minfang Han Zaihong Sun State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China Suzhou Huatsing Power Co. LtdJiangsu 210094China

Solid oxide fuel cell combined with heat and power(SOFC-CHP)system is a distributed power generation system with low pollution and high *** this paper,a 10 kW SOFC-CHP system model using syngas was built in Aspen *** operating parameters,such as steam to fuel ratio,stack temperature,reformer temperature,air flow rate,and air preheating temperature,were *** was conducted based on the simulation *** suggest that higher steam to fuel ratio is beneficial to the electrical efficiency,but it might decrease the gross system *** stack and reformer temperatures contribute to the electrical efficiency,and the optimal operating temperatures of stack and reformer when considering the stack degradation are 750℃and 700℃,*** air preheating temperature barely affects the electrical efficiency but affects the thermal efficiency and the gross system efficiency,the recommended value is around 600℃under the reference condition.

关键词： SOFC-CHP system Operational parameters Optimization Efficiency

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Design and validation of real-time dynamic spectrum management in OFDM-based HNPLC systems

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High Technology Letters 2015年第4期21卷 379-387页

作者：刘雯静 Guo Jingbo Yan Yanxin Zhang Tongfei State Key Lab of Control and Simulation of Power Systems and Generation Equipment Department of Electrical EngineeringTsinghua University ROHM Semiconductor(Shanghai) Co. Ltd.Design Center

Time-varying frequency selective attenuation and colored noises are unfavorable characteristics of power line communication(PLC) channels of the low voltage *** overcome these disadvantages,a novel real-time dynamic spectrum management(DSM) algorithm in orthogonal frequency division multiplexing(OFDM)-based high-speed narrow-band power line communication(HNPLC) systems is proposed,and the corresponding FPGA circuit is designed and *** of the proposed DSM is validated with a large amount of network experiments under practical PLC *** the noise in each narrow subcarrier is approximately Gaussian,the proposed DSM adopts the BER/SER expression formulized via the AWGN channel to provide a handy and universal strategy for power *** real-time requirement is guaranteed by choosing subcarriers in group and employing the same modulation scheme within each *** measures are suitable for any modulation scheme no matter the system criterion is to maximize data rate or minimize power/*** design and hardware implementation of the proposed DSM are given with some flexible and efficient *** DSM circuit is carried out with Xilinx *** and practical experiments validate that the proposed real-time DSM significantly improves system performance.

关键词： real-time dynamic spectrum management high-speed narrowband power line com-munication (HNPLC) subcarrier grouping rate adaptive multi-carrier

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Effect of Multiple Models of Closed-loop Transfer Functions on Inter-harmonic Oscillation Characteristics of Grid-connected PMSG

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CSEE Journal of power and Energy systems 2024年第5期10卷 1955-1964页

作者： Jingyi Li Jianjun Yang Xiaorong Xie Haozhi Li Ke Wang Zhaohui Shi Key Laboratory of Far-shore Wind Power Technology of Zhejiang Province Huadong Engineering Corporation LimitedPower ChinaHangzhou 310014China. State Key Lab of Control and Simulation of Power Systems and Generation Equipment(Dept.of Electrical Engineering Tsinghua University)Beijing 100084China.

Establishing a suitable closed-loop transfer function model for the grid-connected PMSG system is the key basis in performing inter-harmonic characteristics *** closed-loop transfer functions can be constructed when different components of the converter controller are taken into ***,the effect of different components of the converter controller on inter-harmonic stability analysis is not *** this paper,the complete transfer function,considering different loops,is first *** on the complete closed-loop transfer function,the DC-link,PLL and voltage forward-feed are removed step by step to derive different closed-loop transfer *** inter-harmonic related poles of different closed-loop transfer functions are further calculated to analyze the effect of closedloop transfer functions on inter-harmonic characteristics ***,by performing time domain simulation,the correctness of the theoretical analysis results is *** results show that under the conditions of a weak AC system,each loop of the converter control system will reduce the stability of the interharmonic in the sub-synchronous frequency range and influence the inter-harmonic oscillation *** transfer function needs to consider the influence of each loop to accurately calculate the inter-harmonic stability of the system.

关键词： Closed-loop transfer function converter controller inter-harmonic characteristics PMSG

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Electron relaxation properties of Ar magnetron plasmas

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Plasma Science and Technology 2018年第3期20卷 87-94页

作者： Xinjing CAI Xinxin WANG Xiaobing ZOU Department of Electrical Engineering Northeast Electric Power UniversityJilin 132012People's Republic of China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua UniversityBeijing 100084People's Republic of China

An understanding of electron relaxation properties in plasmas is of importance in the application of *** improved multi-term approximation of the Boltzmann equation is employed to study electron transport and relaxation properties in ***,inelastic and nonconservative collisions between electrons and neutral particles are *** expressions for the transport coefficients are obtained using the expansion coefficients and the collision operator *** solutions of the matrix equations for the expansion coefficients are also *** calculations of the Reid model are presented to demonstrate the accuracy of the improved multi-term *** is shown that the twoterm approximation is generally not accurate enough and the magnetic fields can reduce the anisotropy of the velocity distribution *** electron relaxation properties of Ar plasmas in magnetrons for various magnetic fields are *** is demonstrated that the energy parameters change more slowly than the momentum parameters.

关键词： electron transport electron relaxation Boltzmann equation multi-term approximation

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Analysis of Application of Superconducting Fault Current Limiter to AC Line of HVDC 8

Analysis of Application of Superconducting Fault Current Lim...

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8th IEEE International Conference on Advanced power System Automation and Protection, APAP 2019

作者： Chen, Binshu Dong, Xinzhou Tsinghua University Key Lab of Control and Simulation of Power Systems and Generation Equipment Dept. of Electrical Engineering China

ISBN: (纸本)9781728117225

In LCC-HVDC hybrid grid, commutation failure is an important factor affecting system stability. When there is a fault or a large voltage fluctuation in AC line of LCC-HVDC, a commutation failure will occur. Fault current limiter (FCL) can limit the fault current and prevent commutation failure. Superconducting current limiters using superconducting materials as the core component, have no power loss and do not affect the dynamic performance of the system during normal operation. This article analyze how SFCL acts to suppress commutation failure in AC/DC hybrid systems, and describes the various types of SCFCLs and their limitations for this scene. By building simulation models of SCFCLs applied to AC line of LCC-HVDC invert, the author analyzes the effect of SCFCL on the hybrid grid. © 2019 IEEE.

关键词： Superconducting fault current limiters

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