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Multiple Random Forests Based Intelligent Location of Single-phase Grounding Fault in Power Lines of DFIG-based Wind Farm

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Journal of Modern Power Systems and Clean Energy 2022年第5期10卷 1152-1163页

作者： yongli zhu Hua Peng School of Electrical and Electronic Engineering North China Electric Power UniversityBaoding 071003China

To address the problems of wind power abandonment and the stoppage of electricity transmission caused by a short circuit in a power line of a doubly-fed induction generator(DFIG) based wind farm, this paper proposes an intelligent location method for a single-phase grounding fault based on a multiple random forests(multi-RF) algorithm. First, the simulation model is built, and the fundamental amplitudes of the zerosequence currents are extracted by a fast Fourier transform(FFT) to construct the feature set. Then, the random forest classification algorithm is applied to establish the fault section locator. The model is resampled on the basis of the bootstrap method to generate multiple sample subsets, which are used to establish multiple classification and regression tree(CART) classifiers. The CART classifiers use the mean decrease in the node impurity as the feature importance,which is used to mine the relationship between features and fault sections. Subsequently, a fault section is identified by voting on the test results for each classifier. Finally, a multi-RF regression fault locator is built to output the predicted fault distance. Experimental results with PSCAD/EMTDC software show that the proposed method can overcome the shortcomings of a single RF and has the advantage of locating a short hybrid overhead/cable line with multiple branches. Compared with support vector machines(SVMs)and previously reported methods, the proposed method can meet the location accuracy and efficiency requirements of a DFIG-based wind farm better.

关键词： Doubly-fed induction generator(DFIG)based wind farm power line multiple random forests(multi-RF) single-phase grounding fault fault location

A study of the upper limit of solid scatters density for gray Lattice Boltzmann Method

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Acta Mechanica Sinica 2008年第5期24卷 515-522页

作者： yongli Chen Keqin zhu Department of Engineering Mechanics Tsinghua University Beijing 100084 China

The upper limit of the solid scatters density ns （x）, a key parameter for the simulation of flows in porous media with a gray Lattice Boltzmann Method, is studied by an analytical way for the infiltration Poiseuille flow between two infinite parallel plates. Analyses of three different gray Lattice Boltzmann schemes, separately proposed by Gao and Sharma et al., Dardis and McCloskey, and Thorne and Sukop, indicate that the effective domain of Gao and Sharma＇s scheme is restricted to ns 〈 1/2√3≈0.289, Dardis and McCloskey＇s scheme is restricted to ns 〈（√57-1）/28≈0.234, and that there is no extra restriction on ns（x） with Thorne and Sukop＇s scheme. These results are obtained for the dimensionless relaxation time τ= 1. The above analytical results are verified by our numerical simulations. The use of a gray LBM is further illustrated by simulating the flow at the interface of a porous medium. Simulation results yield velocity profiles which agree very well with Brinkman＇s prediction.

关键词： Gray Lattice Boltzmann Method Infiltration flow Scattering density Porous media

A fault locating method for multi-branch hybrid transmission lines in wind farm based on redundancy parameter estimation

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Journal of Modern Power Systems and Clean Energy 2019年第5期7卷 1033-1043页

作者： Ke ZHANG yongli zhu Xuechun LIU State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources(North China Electric Power University) Baoding 071003China State Grid Wuxi Power Supply Company Wuxi 214000China

In order to solve the problem of‘‘abandoned’’wind caused by short circuit faults in a wind farm,a wind farm fault locating method based on redundancy parameter estimation is *** the characteristics of the traveling wave,transmission equations containing the position of the fault point are *** estimation from statistical theory is used to solve the redundant transmission equations formed by multiple measuring points to locate the *** addition,the bad data error detection capability of the parameter estimation is used to determine bad data and remove *** improves locating accuracy.A length coefficient is introduced to solve the error enlargement problem caused by a transmission line *** proposed fault locating method can solve the fault branch misjudgment problem caused by the short-circuit faults near the data measuring nodes of thewind farm based on the proposed fault interval *** also avoids the requirements to the traveling wave speed of traditional methods,thus its fault location is more *** effectiveness is verified through simulations in PSCAD/EMTDC,and the results show that it can be used in thefault locating of hybrid transmission lines.

关键词： Transmission line Fault location method Parameter estimation Wind power Least squares

Damping control for a target oscillation mode using battery energy storage

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Journal of Modern Power Systems and Clean Energy 2018年第4期6卷 833-845页

作者： yongli zhu Chengxi LIU Bin WANG Kai SUN Department of Electrical Engineering and Computer Science University of Tennessee

In this paper, a battery energy storage system(BESS) based control method is proposed to improve the damping ratio of a target oscillation mode to a desired level by charging or discharging the installed BESS using local measurements. The expected damping improvement by BESS is derived analytically for both a single-machineinfinite-bus system and a multi-machine system. This BESS-based approach is tested on a four-generator, twoarea power system. Effects of the power converter limit,response time delay, power system stabilizers and battery state-of-charge on the control performance are also investigated. Simulation results validate the effectiveness of the proposed approach.

关键词： Battery energy storage system(BESS) Battery Damping ratio Energy storage Power system oscillation State of charge(SOC)

Current Status, Influence and Countermeasure of Biological Invasion on Ecological Security in China

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Plant Diseases and Pests 2012年第2期3卷 64-67页

作者： yongli zhu College of Ecology & Tourism Shanghai Business School College of Landscape Architecture Nanjing Forestry University

The concept, pathways and the present status of biological invasion in China are reviewed in the paper, and the effect of biological invasion on ecological security is also introduced. On this basis, the measures such as establishing early-warning mechanism, strengthening the management of invasive species and quarantine of alien species, establishing scientific system of introduction and improving people awareness are proposed to control the invasion of alien species, so as to ensure the ecological security in china.

关键词： Biological invasion Current status Ecological security Control countermeasure China

Estimation of soil respiration in a paddy ecosystem in the subtropical region of China

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Chinese Science Bulletin 2007年第19期52卷 2722-2730页

作者： REN XiuE WANG QinXue TONG ChengLi WU JinShui WANG KeLin zhu yongli LIN ZeJian WATANABE Masataka TANG GuoYong Institute of Subtropical Agriculture Chinese Academy of Sciences Changsha 410125 China National Institute for Environmental Studies Tsukuba 305-8506 Japan Institute of Agricultural Engineering Jiangsu University Zhenjiang 212013 China Keio University Kanagawa 252-8520 Japan Graduate University of Chinese Academy of Sciences Beijing 100049 China

Water vapor, energy exchange, and CO2 flux were measured continuously from 2003 to 2005 using the eddy covariance technique in a paddy ecosystem in the subtropical region of China. The CO2 fluxes at nighttime during fallow periods (from middle October to late April) were used to analyze the dynamics of soil respiration and its relationship with soil temperature, and to simulate the annual dynamics of soil respiration in paddy ecosystems. The variation of soil respiration showed a clear seasonal pattern. The soil respiration rates at night during the fallow periods were 52―398 mg·m-2·h-1, and exponen- tially correlated (P<0.001) with soil temperatures at different depths of soil (5, 10, and 20 cm), particularly the temperature measured at a depth of 5 cm. Based on the simulated exponential equations developed, annual average soil respiration rates and total soil respiration of paddy soil in the subtropical region of China were estimated to be 178.5―259.9 mg·m-2·h-1 and 1.56―2.28 kg·m-2·a-1, respectively. The simulation equations can be applied to evaluating soil respiration in paddy ecosystems during the rice-growing season.

关键词：稻谷生态系休耕周期土地呼吸温度

Mechanics Analysis of Overhead Transmission Lines Based On-line Monitoring

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Open Journal of Applied Sciences 2013年第2期3卷 1-4页

作者： Lili Dai yongli zhu Zehui Liang School of Electrical and Electronic Engineering North China Electric Power University BaodingChina

At present, the on-line monitoring is widely applied to the power line monitoring. In this paper, a new mechanical calculation model is established according to the on-line monitoring. And this model is based on the parameters that tension sensors and angle sensors on suspended points detect, and combines with the parameters of the wire itself, and also considers the deflection angel of wires due to wind. In this model, mechanics parameters of wires are turned into the new coordinate plane after deflection angel of wires due to wind, or windage yaw plane. A statics tension balance equation is built in the vertical direction of the new windage yaw plane. According to the theoretical analysis and algorithm, we verify the accuracy of this newly developed mechanical calculation model.

关键词： Overhead Transmission Line On-line Monitoring Mechanical Analysis Tension Angle Icing Windage Yaw

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上海市栽培乐昌含笑开花及传粉生物学

林业科学 2024年第6期60卷 86-93页

作者：朱永莉张杰上海商学院上海201400 上海植物园上海200231

【目的】研究我国南方珍稀观赏树种乐昌含笑的开花及传粉生物学研究,以阐明迁地保护下乐昌含笑的开花特性及繁育特性,为有效地保护和杂交育种提供技术指导。【方法】对乐昌含笑花的形态和开花动态进行了观察,通过TTC法进行花粉活力的测... 详细信息

【目的】研究我国南方珍稀观赏树种乐昌含笑的开花及传粉生物学研究,以阐明迁地保护下乐昌含笑的开花特性及繁育特性,为有效地保护和杂交育种提供技术指导。【方法】对乐昌含笑花的形态和开花动态进行了观察,通过TTC法进行花粉活力的测定,采用联苯胺-过氧化氢法测定柱头的可授性,估算花粉胚株比(P/O)和杂交指数(OCI),并通过人工控制授粉试验和传粉媒介观察,分析乐昌含笑繁育系统的类型。【结果】乐昌含笑花期从3月中下旬到4月上中旬,单花的开放时间为7~12天,单花具有二次开合现象;单株开放时间6~20天。乐昌含笑为雌雄异熟且雌蕊先熟,开花当天柱头可授性最强,开花第2天花粉的生活力最强;乐昌含笑的杂交指数(OCI)等于4,花粉胚株比(P/O)为557.18±46.23。套袋试验表明:乐昌含笑不能进行自发传粉和无融合生殖,人工异花授粉的结实率显著高于自然授粉。繁育系统为兼性异交、自交亲和、传粉过程需要传粉媒介。【结论】乐昌含笑花的形态、开花动态等表明其具有虫媒传粉的特征,二次开合现象把雌雄蕊的成熟从时间上分隔开来,保证其异花传粉,传粉过程需要传粉者。

关键词：乐昌含笑开花生物学雌雄异熟繁育系统

图信号与图卷积网络相结合的局部放电模式识别方法

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中国电机工程学报 2021年第18期41卷 6472-6480页

作者：张翼朱永利华北电力大学电气与电子工程学院河北省保定市071003

为充分利用局部放电(partial discharge,PD)信号的特征信息和特征与特征之间的关联性,来提高局部放电诊断准确性,该文提出一种基于图信号和图卷积网络(graph convolutional network,GCN)的局部放电诊断方法。首先,选取局部放电脉冲的时... 详细信息

为充分利用局部放电(partial discharge,PD)信号的特征信息和特征与特征之间的关联性,来提高局部放电诊断准确性,该文提出一种基于图信号和图卷积网络(graph convolutional network,GCN)的局部放电诊断方法。首先,选取局部放电脉冲的时频谱构建图信号,将时频谱灰度矩阵的子矩阵(即局部特征)作为图节点,并考虑节点的空间相邻和特征相似性为每个节点匹配邻居,以形成局部特征区域间的拓扑关联,丰富局部放电时频谱的数据信息。然后,采用GCN融合图信号的节点特征和拓扑结构以自主学习局部放电特征、识别放电类型。结果表明,所提方法可以有效地诊断局部放电类型,相较于传统的深度学习方法,对于局部放电时频谱的信息利用更为全面,识别准确率更高,且随着样本规模减小,识别优势更加明显。

关键词：局部放电时频谱图信号图卷积网络深度学习