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A novel algorithm for frequency dependent modeling of ferrite ring and its optimum design to study VFTO behaviors within GIS

Mehrdad MAJIDI, Hamid JAVADI, Moein MANBACHI

《能源前沿（英文）》 2014年 第8卷 第1期   页码 90-100 doi: 10.1007/s11708-013-0286-2

摘要： One of the fundamental issues in gas insulated substations (GIS) which has destructive effects on GIS equipment is the very fast transient over-voltages (VFTOs). This paper models a 400/230 kV substation in order to study the effects of VFTO extensively implemented on EMTP-RV. In addition, the application of ferrite rings for suppressing VFTOs is assessed thoroughly. The main advantage of this paper is its new proposed algorithm according to the ferrite ring frequency dependent modeling that is validated with experimental results. This paper examines the effects of three compositions of the ferrite ring on VFTO suppression. Moreover, it estimates the dimension of the ferrite ring based on the SF6 gas insulation withstand and the maximum effect of ferrite rings on VFTO suppression constraint with the COMSOL multiphysics software. Furthermore, it gains VFTO attenuated percentages due to the installation of the ferrite ring in different GIS nodes. Finally, it analyzes the offered VFTO amendment technique in various GIS switching scenarios.

关键词： comsol multiphysics     EMTP-RV     ferrite ring     gas insulated substations (GIS)     transient over-voltage     insulation coordination    

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大规模新能源发电经直流送出的技术挑战与思考 Review

王伟胜, 李光辉, 郭剑波

《工程（英文）》 2022年 第19卷 第12期   页码 252-267 doi: 10.1016/j.eng.2022.04.017

摘要：

新能源发电经直流送出成为碳达峰、碳中和战略背景下新能源大基地、规模化开发利用的主导形式之一。在高压直流输电送端已初步形成高比例新能源、高比例电力电子的局部双高电力系统。与以同步发电机为主导的传统电力系统相比，系统运行特性发生了深刻变化，逐渐出现宽频振荡和暂态过电压等新型稳定问题，导致大规模新能源脱网事故频发，传统电力系统的分析方法和设计原则面临挑战。本文针对双高电力系统的特性认知、作用机理、分析方法、研究手段、工程应用开展研究，明确宽频振荡和暂态过电压产生机理，提出小信号阻抗分析方法和电磁暂态仿真研究手段相结合的技术路线，研究成果已在我国华北、西北和东北地区新能源基地经直流送出重大工程中得到验证。最后，针对未来建设以新能源为主体的新型电力系统给出思考与建议。

关键词： 宽频振荡     双高电力系统     高压直流输电     新能源发电     暂态过电压    

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Transient performance comparison of grid-forming converters with different FRT control strategies

《能源前沿（英文）》 2023年 第17卷 第2期   页码 239-250 doi: 10.1007/s11708-022-0856-2

摘要： Grid-forming converters (GFMs) are faced with the threat of transient inrush current and synchronization instability issues when subjected to grid faults. Instead of disconnecting from the grid unintentionally, GFMs are required to have fault ride through (FRT) capability to maintain safe and stable operation in grid-connected mode during grid fault periods. In recent studies, different FRT control strategies with distinguishing features and that are feasible for different operation conditions have been proposed for GFMs. To determine their application scope, an intuitive comparison of the transient performance of different FRT control strategies is presented in this paper. First, three typical FRT control strategies (virtual impedance, current limiters, and mode-switching control) are introduced and transient mathematical models are established. A detailed comparison analysis on transient inrush current and transient synchronization stability is then presented. The results will be useful for guiding the selection and design of FRT control strategies. Finally, simulation results based on PSCAD/EMTDC are considered to verify the correctness of the theoretical analysis.

关键词： grid-forming converters (GFMs)     fault ride through (FRT)     transient stability     transient inrush current     transient modeling    

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Topology optimization of transient problem with maximum dynamic response constraint using SOAR scheme

《机械工程前沿（英文）》 2021年 第16卷 第3期   页码 593-606 doi: 10.1007/s11465-021-0636-4

摘要： This paper proposes a novel method for the continuum topology optimization of transient vibration problem with maximum dynamic response constraint. An aggregated index in the form of an integral function is presented to cope with the maximum response constraint in the time domain. The density filter solid isotropic material with penalization method combined with threshold projection is developed. The sensitivities of the proposed index with respect to design variables are conducted. To reduce computational cost, the second-order Arnoldi reduction (SOAR) scheme is employed in transient analysis. Influences of aggregate parameter, duration of loading period, interval time, and number of basis vectors in the SOAR scheme on the final designs are discussed through typical examples while unambiguous configuration can be achieved. Through comparison with the corresponding static response from the final designs, the optimized results clearly demonstrate that the transient effects cannot be ignored in structural topology optimization.

关键词： topology optimization     solid isotropic material with penalization     transient response     aggregation function     second-order Arnoldi reduction    

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Development of new transient liquid phase system Au-Sn-Au for microsystem technology

Kirsten BOBZIN, Nazlim BAGCIVAN, Lidong ZHAO, Stefania FERRARA, Jan PERNE

《机械工程前沿（英文）》 2010年 第5卷 第4期   页码 370-375 doi: 10.1007/s11465-010-0107-9

摘要： In the last decade, microsystems evolved to decisive technology in many technical applications. With increasing requirements on the performance of microsystems, more and more dissimilar materials are used in the same assembly. Correspondingly, suitable joining methods are required to fulfil the requirements on good properties of joints. In this study, a new transient liquid phase (TLP) system Au-Sn-Au was developed for potential medical applications in hybrid microsystems. The high and low melting phases Au and Sn were deposited onto diverse substrates by magnetron-sputter-ion plating. The coated substrates were soldered in a microsoldering station under different conditions. The influence of soldering conditions on the microstructure and properties of the joints was investigated. Results show that the developed solder led to high-quality joints that can be used in microsystems for medical applications.

关键词： transient liquid phase     microtechnology     soldering     diffusion     physical vapor deposition (PVD)    

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Sensitivity analysis and numerical experiments on transient test of compact heat exchanger surfaces

REN Hesheng, LAI Lingjun, CUI Yongzheng

《能源前沿（英文）》 2008年 第2卷 第4期   页码 374-380 doi: 10.1007/s11708-008-0079-1

摘要： A single-blow transient testing technique considering the effect of longitudinal heat conduction is suggested for determining the average convection heat transfer coefficient of compact heat exchanger surface. By matching the measured outlet fluid temperature variation with similar theoretical curves, the dimensionless longitudinal conduction parameter , the time constant of the inlet fluid temperature , and the number of heat transfer units can be determined simultaneously using the Levenberg-Marquardt nonlinear parameter estimation method. Both sensitivity analysis and numerical experiments with simulated measurements containing random errors show that the method in the present investigation provides satisfactory accuracy of the estimated parameter , which characterizes the heat transfer performance of compact heat exchanger surfaces.

关键词： coefficient     dimensionless longitudinal     longitudinal     temperature     conduction    

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State identification of home appliance with transient features in residential buildings

《能源前沿（英文）》 2022年 第16卷 第1期   页码 130-143 doi: 10.1007/s11708-022-0822-z

摘要： Nonintrusive load monitoring (NILM) is crucial for extracting patterns of electricity consumption of household appliance that can guide users’ behavior in using electricity while their privacy is respected. This study proposes an online method based on the transient behavior of individual appliances as well as system steady-state characteristics to estimate the operating states of the appliances. It determines the number of states for each appliance using the density-based spatial clustering of applications with noise (DBSCAN) method and models the transition relationship among different states. The states of the working appliances are identified from aggregated power signals using the Kalman filtering method in the factorial hidden Markov model (FHMM). Thereafter, the identified states are confirmed by the verification of system states, which are the combination of the working states of individual appliances. The verification step involves comparing the total measured power consumption with the total estimated power consumption. The use of transient features can achieve fast state inference and it is suitable for online load disaggregation. The proposed method was tested on a high-resolution data set such as Labeled hIgh-Frequency daTaset for Electricity Disaggregation (LIFTED) and it outperformed other related methods in the literature.

关键词： nonintrusive load monitoring (NILM)     load disaggregation     online load disaggregation     Kalman filtering     factorial hidden Markov model (FHMM)     Labeled hIgh-Frequency daTaset for Electricity Disaggregation (LIFTED)    

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Parameter identification of interconnected power system frequency after trip-out of high voltage transmission

Xuzhan ZHOU,Shanshan LIU,Mingkun WANG,Yiping DAI,Yaohua TANG

《能源前沿（英文）》 2014年 第8卷 第3期   页码 386-393 doi: 10.1007/s11708-014-0323-9

摘要： Accurate modeling and parameters of high voltage (HV) grid are critical for stability research of system frequency. In this paper, simulation modeling of the system frequency was conducted of an interconnected power system with HV transmission lines in China. Based on recorded tripping data of the HV transmission lines, system parameters were identified by using genetic algorithm (GA). The favorable agreement between simulation results and recorded data verifies the validity of gird models and the accuracy of system parameters. The results of this paper can provide reference for the stability research of HV power grid.

关键词： high voltage (HV) grid     frequency stability parameter identification     primary frequency regulation (PFR)    

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Recent advances toward high voltage, EC-free electrolytes for graphite-based Li-ion battery

Tong Zhang, Elie Paillard

《化学科学与工程前沿（英文）》 2018年 第12卷 第3期   页码 577-591 doi: 10.1007/s11705-018-1758-z

摘要：

Lithium-ion batteries are a key technology in today’s world and improving their performances requires, in many cases, the use of cathodes operating above the anodic stability of state-of-the-art electrolytes based on ethylene carbonate (EC) mixtures. EC, however, is a crucial component of electrolytes, due to its excellent ability to allow graphite anode operation–also required for high energy density batteries–by stabilizing the electrode/electrolyte interface. In the last years, many alternative electrolytes, aiming at allowing high voltage battery operation, have been proposed. However, often, graphite electrode operation is not well demonstrated in these electrolytes. Thus, we review here the high voltage, EC-free alternative electrolytes, focusing on those allowing the steady operation of graphite anodes. This review covers electrolyte compositions, with the widespread use of additives, the change in main lithium salt, the effect of anion (or Li salt) concentration, but also reports on graphite protection strategies, by coatings or artificial solid electrolyte interphase (SEI) or by use of water-soluble binder for electrode processing as these can also enable the use of graphite in electrolytes with suboptimal intrinsic SEI formation ability.

关键词： lithium-ion     electrolyte     solid electrolyte interphase     additives     high voltage     graphite    

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Analysis and stabilization control of a voltage source controlled wind farm under weak grid conditions

《能源前沿（英文）》 2022年 第16卷 第6期   页码 943-955 doi: 10.1007/s11708-021-0793-5

摘要： This paper investigates and discusses the interaction stability issues of a wind farm with weak grid connections, where the wind turbines (WTs) are controlled by a new type of converter control strategy referred to as the voltage source (VS) control. The primary intention of the VS control method is to achieve the high-quality inertial response capability of a single WT. However, when it is applied to multiple WTs within a wind farm, its weak-grid performance regarding the stability remains concealed and needs to be clarified. To this end, a frequency domain model of the wind farm under the VS control is first developed. Based on this model and the application of a stability margin quantification index, not only the interactions between the wind farm and the weak grid but also those among WTs will be systematically assessed in this paper. A crucial finding is that the inertial response of VS control has negative impacts on the stability margin of the system, and the dominant instability mode is more related to the interactions among the WTs rather than the typical grid-wind farm interaction. Based on this knowledge, a stabilization control strategy is then proposed, aiming for stability improvements of VS control while fulfilling the demand of inertial responses. Finally, all the results are verified by time-domain simulations in power systems computer aided design/electromagnetic transients including DC(PSCAD/EMTDC).

关键词： weak grids     voltage source (VS) control     wind turbine (WT)     stabilization control     wind farm     inertial response    

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Development and advances in modular multilevel converter based HVDC projects in China

《工程管理前沿（英文）》   页码 183-189 doi: 10.1007/s42524-022-0248-7

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关键词： high voltage direct current     power converter     power systems     renewable energy     ultra-high voltage    

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Collapse fragility assessment of steel roof framings with force limiting devices under transient wind

Linjia BAI, Yunfeng ZHANG

《结构与土木工程前沿（英文）》 2012年 第6卷 第3期   页码 199-209 doi: 10.1007/s11709-012-0168-4

摘要： Steel structural frame is a popular structural form to cover large-span roof space and under high winds. Either part of the roof enclosure or the entire roof structure can be lifted off a building, particularly for low sloped roofs subject to wind-induced suction force. Collapse of roof could cause severe economic loss and poses safety risk to residents in the building. The buckling of members in a steel roof frame structure, which may lead to progressive collapse, may be dynamic in nature. This paper presents a fragility analysis of the collapse of steel roof frame structures under combined static and transient wind loading. Uncertainties associated with wind load change rate and member imperfections are taken into account in this study. A numerical example based on a Steel Joist Institute (SJI) K series joist was used to demonstrate the use of force limiting devices for collapse risk mitigation. For the presented fragility assessment of steel roof collapse, a Monte Carlo method combined with response surface approach was adopted, which greatly reduces the computation time and makes the Monte Carlo simulation feasible for probabilistic collapse analysis of steel roof frame structures.

关键词： collapse     dynamic response     fragility analysis     Monte Carlo simulation     wind load    

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Photodynamic therapy combined with intravitreal injection of triamcinolone acetonide for choroidal neovascularization

YU Xiaobing, DAI Hong, LU Yingyi, LONG Li

《医学前沿（英文）》 2007年 第1卷 第4期   页码 405-409 doi: 10.1007/s11684-007-0079-2

摘要： The aim of this research was to evaluate the efficacy and safety of photodynamic therapy (PDT) combined with intravitreal injection of triamcinolone acetonide (TA) in the treatment of choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD) and pathological myopia. PDT combined with intravitreal injection of TA was performed on 16 eyes of 16 patients with CNV diagnosed by visual acuity, fluorescein fundus angiography (FFA) and optical coherent tomography (OCT), including 14 eyes secondary to age-related macular degeneration and two eyes secondary to pathological myopia. TA was injected intravitreally 72 h post PDT on 12 eyes and from three months to one year (mean nine months) post PDT on four eyes respectively. All the patients were followed up for 3 to 18 months (mean 18.6 months). Best-corrected visual acuity, intraocular pressure, retinal thickness and FFA were observed. The visual acuity was improved in seven eyes (43.8%) of all the 16 eyes and stable in nine eyes (56.2%), respectively. FFA revealed complete or partial closure of CNV in all patients. OCT showed that the macular edema disappeared or was alleviated. Transient intraocular pressure elevation occurred in one patient (6.25%) of all the 16 eyes and intraocular pressure returned to the normal after a transient treatment with anti-glaucoma medication. The mean number of PDTs during the first year was 1.1. PDT combined with intravitreal injection of TA for CNV is safe and effective. It can reduce the risk of visual loss and the treatment frequency.

关键词： intraocular pressure     fluorescein fundus     transient treatment     Transient intraocular     number    

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Predictor-corrector algorithm for solving quasi-separated-flow and transient distributed-parameter model

Ping ZHANG, Guoliang DING

《能源前沿（英文）》 2010年 第4卷 第4期   页码 535-541 doi: 10.1007/s11708-010-0113-y

摘要： The successive sub?stitution (SS) method is a suitable approach to solving the transient distributed-parameter model for heat exchangers. However, this method must be enhanced because its convergence heavily depends on the iterative initial pressure. When the iterative initial pressure is improperly assigned, the calculated flow rates become negative values, causing the state parameters to exhibit negative values as well. Therefore, a predictor-corrector algorithm (PCA) is proposed to improve the convergence of the SS method. A predictor is developed to determine an appropriate iterative initial pressure. Total fluid mass is adopted as the convergence criterion of pressure iteration instead of outlet flow rate as is done in the SS method. Convergence analysis and case study of the PCA and SS method are conducted, which show that the PCA has better convergence than the SS method under the same working conditions.

关键词： algorithm     convergence     heat exchanger     modeling     transient    

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A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication

null

《机械工程前沿（英文）》 2014年 第9卷 第2期   页码 156-167 doi: 10.1007/s11465-014-0297-7

摘要：

A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication (EHL) problems is presented. First, by introducing a special matrix splitting iteration method into the traditional compound direct iterative method, the full matrices for the linear systems of equations are transformed into sparse banded ones with any half-bandwidth; then, an extended Thomas method which can solve banded linear systems with any half-bandwidth is derived to accelerate the computing speed. Through the above two steps, the computational complexity of each iteration is reduced approximately from O(N3/3) to O(β2N), where N is the total number of nodes, and β is the half-bandwidth. Two kinds of numerical results of transient EHL line contact problems under sinusoidal excitation or pure normal approach process are obtained. The results demonstrate that the new algorithm increases computing speed several times more than the traditional compound direct iterative method with the same numerical precision. Also the results show that the new algorithm can get the best computing speed and robustness when the ratio, half-bandwidth to total number of nodes, is about 7.5%–10.0% in moderate load cases.

关键词： elastohydrodynamic lubrication     transient     line contact     matrix splitting iteration method     the Thomas method    

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标题 作者 时间 类型 操作

A novel algorithm for frequency dependent modeling of ferrite ring and its optimum design to study VFTO behaviors within GIS

Mehrdad MAJIDI, Hamid JAVADI, Moein MANBACHI

期刊论文

大规模新能源发电经直流送出的技术挑战与思考

王伟胜, 李光辉, 郭剑波

期刊论文

Transient performance comparison of grid-forming converters with different FRT control strategies

期刊论文

Topology optimization of transient problem with maximum dynamic response constraint using SOAR scheme

期刊论文

Development of new transient liquid phase system Au-Sn-Au for microsystem technology

Kirsten BOBZIN, Nazlim BAGCIVAN, Lidong ZHAO, Stefania FERRARA, Jan PERNE

期刊论文

Sensitivity analysis and numerical experiments on transient test of compact heat exchanger surfaces

REN Hesheng, LAI Lingjun, CUI Yongzheng

期刊论文

State identification of home appliance with transient features in residential buildings

期刊论文

Parameter identification of interconnected power system frequency after trip-out of high voltage transmission

Xuzhan ZHOU,Shanshan LIU,Mingkun WANG,Yiping DAI,Yaohua TANG

期刊论文

Recent advances toward high voltage, EC-free electrolytes for graphite-based Li-ion battery

Tong Zhang, Elie Paillard

期刊论文

Analysis and stabilization control of a voltage source controlled wind farm under weak grid conditions

期刊论文

Development and advances in modular multilevel converter based HVDC projects in China

期刊论文

Collapse fragility assessment of steel roof framings with force limiting devices under transient wind

Linjia BAI, Yunfeng ZHANG

期刊论文

Photodynamic therapy combined with intravitreal injection of triamcinolone acetonide for choroidal neovascularization

YU Xiaobing, DAI Hong, LU Yingyi, LONG Li

期刊论文

Predictor-corrector algorithm for solving quasi-separated-flow and transient distributed-parameter model

Ping ZHANG, Guoliang DING

期刊论文

A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication

null

期刊论文