Fast Analysis of Power/Ground Networks via Circuit Reduction

This paper presents an efficient algorithm for reducing RLC power/ground network complexities by exploitation of the regularities in the power/ground networks. The new method first builds the equivalent models for many series RLC-current chains based on their Norton＇s form companion models in the original networks,and then the precondition conjugate gradient based iterative method is used to solve the reduced networks,which are symmetric positive definite. The solutions of the original networks are then back solved from those of the reduced networks.Experimental results show that the complexities of reduced networks are typically significantly smaller than those of the original circuits, which makes the new algorithm extremely fast. For instance, power/ground networks with more than one million branches can be solved in a few minutes on modern Sun workstations.

An Integrated Tool for Power/Ground Network Design, Optimization,and Verification for Cell Based VLSIs

A CAD tool based on a group of efficient algorithms to verify,design,and optimize power/ground networks for standard cell model is presented.Nonlinear programming techniques,branch and bound algorithms and incomplete Cholesky decomposition conjugate gradient method (ICCG) are the three main parts of our work.Users can choose nonlinear programming method or branch and bound algorithm to satisfy their different requirements of precision and speed.The experimental results prove that the algorithms can run very fast with lower wiring resources consumption.As a result,the CAD tool based on these algorithms is able to cope with large-scale circuits.

The changing process and trend of ground temperature around tower foundations of Qinghai-Tibet Power Transmission line

After the construction of Qinghai-Tibet Highway and Railway, the Qinghai-Tibet Power Transmission(QTPT) line is another major permafrost engineering project with new types of engineering structures. The changing process and trend of ground temperature around tower foundations are crucial for the stability of QTPT. We analyzed the change characteristics and tendencies of the ground temperature based on field monitoring data from 2010 to 2014. The results reveal that soil around the tower foundations froze and connected with the artificial permafrost induced during the construction of footings after the first freezing period, and the soil below the original permafrost table kept freezing in subsequent thawing periods. The ground temperature lowered to that of natural fields, fast or slowly for tower foundations with thermosyphons,while for tower foundations without thermosyphons, the increase in ground temperature resulted in higher temperature than that of natural fields. Also, the permafrost temperature and ice content are significant factors that influence the ground temperature around tower foundations. Specifically, the ground temperature around tower foundations in warm and ice-rich permafrost regions decreased slowly, while that in cold and ice poor permafrost regions cooled faster. Moreover, foundations types impacted the ground temperature, which consisted of different technical processes during construction and variant of tower footing structures. The revealed changing process and trend of the ground temperature is beneficial for evaluating the thermal regime evolution around tower foundations in the context of climate change.

Research on single hole heat transfer power of ground source heat pump system

In this paper,the single hole heat transfer power of the ground source heat pump system in Hengshui is compared with data gained from thermal response test.The results show that maximum monitoring data of heat transfer power per meter in summer is 97.1% of the test data,and the average value accounts for 81.8%.The per meter heat power data through on-site thermal response test can provide references for designing engineering project and optimizing ground source heat pump system as these data do not vary greatly from the actual monitoring data.

The Research of Voltage Sag and Power Frequency Overvoltage on 110kV Resistance Grounding System

This paper researches the voltage transfer characteristics when one-phase ground fault occurred in the resistance grounding system, by using the theory of the asymmetric variable characteristics and the sequence network analysis of the -11 transformer, and concludes the scope of voltage sag and swell and the degree of power frequency overvoltage and their influencing factors in the 110 kV resistance grounding system. Accordingly this paper puts forward the resistance choosing principle: the resistance grounding coefficient must be equal to or greater than 10. So it can not only wipe out the voltage sag and voltage swell but also make sure the overvoltage is limited to electrical equipment allowing range. The method mentioned above is verified by simulation results of a 110 kV power system in ATP.

Texture Feature Extraction Method for Ground Nephogram Based on Contourlet and the Power Spectrum Analysis Algorithm

It is important to extract texture feature from the ground-base cloud image for cloud type automatic detection.In this paper,a new method is presented to capture the contour edge,texture and geometric structure of cloud images by using Contourlet and the power spectrum analysis algorithm.More abundant texture information is extracted.Cloud images can be obtained a multiscale and multidirection decomposition.The coefficient matrix from Contourlet transform of ground nephogram is calculated.The energy,mean and variance characteristics calculated from coefficient matrix are composed of the feature information.The frequency information of the data series from the feature vector values is obtained by the power spectrum analysis.Then Support Vector Machines(SVM)classifier is used to classify according to the frequency information of the trend graph of data series.It is shown that altocumulus and stratus with different texture frequencies can be effectively recognized and further subdivided the types of clouds.

Application of Fault Location Mode Based on Travelling Waves for Neutral Non-effective Grounding Systems

Fault location for distribution feeders short circuit especially single-phase grounding fault is an important task in distribution system with non-effectively grounded neutral.Fault location mode for distribution feeders using fault generated current and voltage transient traveling waves was investigated.The characteristics of transient traveling waves resulted from each short circuit fault and their transmission disciplinarian in distribution feeders are analyzed.This paper proposed that double end travelling waves theory which measures arriving time of fault initiated surge at both ends of the monitored line is fit for distribution feeders but single end traveling waves theory not.According to different distribution feeders,on the basis of analyzing original traveling waves reflection rule in line terminal, Current-voltage mode,voltage-voltage mode and current-current mode for fault location based on traveling waves are proposed and aerial mode component of original traveling waves is used to realize fault location.Experimental test verify the feasibility and correctness of the proposed method.

Protection of Zero-Sequence Power Variation in Mountain Wind Farm Collector Lines Based on Multi-Mode Grounding

The arc-suppression coil(ASC)in parallel low resistance(LR)multi-mode grounding is adopted in the mountain wind farm to cope with the phenomenon that is misoperation or refusal of zero-sequence protection in LR grounding wind farm.If the fault disappears before LR is put into the system,it is judged as an instantaneous fault;while the fault does not disappear after LR is put into the system,it is judged as a permanent fault;the single-phase grounding fault(SLG)protection criterion based on zerosequence power variation is proposed to identify the instantaneous-permanent fault.Firstly,the distribution characteristic of zero-sequence voltage(ZSV)and zero-sequence current(ZSC)are analyzed after SLGfault occurs in multi-mode grounding.Then,according to the characteristics that zero-sequence power variation of non-fault collector line is small,while the zero-sequence power variation of fault collector line can reflect the active power component of fault resistance,the protection criterion based on zero-sequence power variation is constructed.The theoretical analysis and simulation results show that the protection criterion can distinguish the property of fault only by using the single terminal information,which has high reliability.

Analysis on the Irregular and Asymmetrical Power/Ground Structure by PEEC Modeling

In order to provide some reference for the design of the power/ground system, a complicated power/ground system in time and frequency domains was analyzed, which is based on PEEC (Partial Element Equivalent Circuit). According to the actual requirements, characteristics of some common power/ground structures in time and frequency domains, such as SSN (Simultaneous Switching Noise), are obtained for the future research. The results show the first resonance point is changed with the structure of the power/ground networks.

Study on Site Specific Design Earthquake Ground Motion of Nuclear Power Plants in China

The main technical backgrounds and requirements are introduced with regard to earthquake ground motion design parameters in several domestic and American standards,codes and guides involved in the seismic analysis and design activities of nuclear power plants in China.Based on the research results from site seismic safety evaluation of domestic nuclear power plant projects in the last years,characteristics and differences of site specific design spectra are analyzed in comparison with standard response spectra,and the suitability of standard response spectra for domestic nuclear power plant projects is discussed.

内蒙古地区强震动台站背景噪声与数据质量分析

计算了内蒙古地区193个强震动台站2022年连续观测数据的加速度功率谱密度,通过绘制不同时空、不同加速度计、不同频段的功率谱密度和功率谱概率密度函数图及背景噪声速度均方根值分布图,评估了该区强震动台站的背景噪声变化特征,对出现的功率谱密度异常进行了具体分析,并针对强震动台站数据异常检测及处理提出了相应的建议。研究结果显示:不同加速度计、不同时空强震动台站的背景噪声功率谱密度昼夜差异主要体现在1 Hz以上频段,且不同区域的昼夜差异变化较大;QA-2g型、JS-A2型和TDA-33M型三种加速度计在2 s频点的背景噪声功率谱密度随区域和三分向变化较小;从强震动台站2 s频点背景噪声的监控能得到可靠的观测数据异常,数据异常主要由加速度计零点漂移大、加速度计故障、脉冲干扰、系统参数有误造成,建议优化站点观测环境,进一步规范仪器安装、调试及JOPENS系统的参数配置和审核。

道路地下空洞探地雷达波场和时频特性

根据城市道路地下介质的分布特征和电性参数设计模型,采用时域有限差分法和广义S变换,对道路地下存在的充气空洞、充水空洞、回填不密实、埋藏金属物状态进行探地雷达正演模拟和时频特征提取。结果表明,地下空洞顶界面的反射波同相轴均呈弧形反射形态,但充气空洞的反射波能量强于充水空洞;地下空洞发育区域的中心频率集中在某个低频区间,其余频率成分分布较均匀;埋藏金属物区域出现两簇高幅值能量团,频率分布较分散;回填不密实区域频率未能显示出较明显的规律。最后,通过工程实测验证了数值模拟的可靠性。

自我决定理论视角下在线学习力模型构建——基于扎根理论的质性分析

在线学习已经成为重要的学习方式之一,与之相对应的在线学习力成为一个热点问题。通过收集S校7位大学生的在线讲座信息、对Y校8位优秀网络教育学生进行访谈获取的资料,以自我决定理论为指导,基于扎根理论的三级编码方法,利用NVivo12.0质性分析软件构建了动机—行为—绩效的在线学习力模型,具体包括学习动机、学习投入、学习技能、学习情绪和学习绩效5个维度。其中,学习动机由目标倾向和价值意义组成;学习投入由意识认知、行为努力和社交支撑构成;学习技能落实在学习策略、信息能力和综合能力3个方面;学习情绪具有积极心态和负面情绪2个类别;学习绩效则体现在学习业绩和学习满意度2个层面。从教育视角来看,提高在线学习力必须强化在线学习体验,加强教师的教学设计和教学干预,完善在线学习绩效评价等。

“光储直柔”建筑配电系统应用研究

以某项目为例分析“光储直柔”在建筑物中的应用,并对“光储直柔”系统的应用场景、建筑直流配电系统的关注点及“光储直柔”系统关键设备进行阐述。

浙江新材料科创高地支撑全球先进制造业基地建设的动力机制与实现路径

新材料是浙江省“315”科技创新体系三大科创高地之一,是支撑浙江建设全球先进制造业基地着重打造的4个世界级先进产业群之一。依据浙江省建设全球新材料先进制造业基地的目标与要求,构建由新材料科创高地为基本支撑,以“政、产、学、研、用”多元创新主体协同,以“制度、技术、人才、市场、资本”多要素协同为基本动力的新材料全球先进制造业基地建设动力机制模型,并据此提出加强新材料产业集群顶层设计、支持新材料产业研发创新、完善新材料产业集群价值网络、健全专精特新小巨人企业梯度培育机制的实现路径,为新形势下浙江新材料产业发展和新材料先进制造业基地建设提供借鉴。

励磁系统交流侧接地对转子接地保护的影响

励磁系统交流侧接地将引起注入式转子接地保护、乒乓切换式转子接地保护误动作。本文介绍了一起相关案例,并对引起误动的基本原理进行了深入分析和定量计算,总结了励磁系统交流侧接地引起采样数据变化的典型特征,提出了关于缩小转子接地保护定位范围的思考。当转子一点接地保护动作后,应首先根据采样数据的变化,对故障点位于励磁系统交流侧还是直流侧做出初步判断,缩小故障定位范围,为快速查找故障提供决策依据。

大型光伏电站全直流送出关键问题研究

研究浙江舟山地区小洋山薄刀咀118 MW光伏电站全直流送出方案。介绍全直流送出系统的构建原理,重点阐述拓扑结构选择、接地方式、直流电压控制等关键技术问题。明确多级直流升压系统的构建原理。在PSCAD/EMTDC平台上搭建相应仿真系统,通过时域仿真验证所提小洋山薄刀咀118 MW光伏电站全直流送出方案的可行性。

基于系统参数优化的对称双极海上风电送端联接变阀侧单相接地故障应力调控方法

为应对海上风电系统送端联接变阀侧单相接地故障引起的换流阀内过电压、过电流及风电场并网点电压跌落共存的问题,提出了一种基于系统参数优化的对称双极海上风电系统故障应力调控方法。首先,构建换流阀的数学模型与风电机组控制模型,通过电路分析揭示故障后换流阀过电压和过电流特性、风电场并网点电压跌落特性及其影响规律;其次,根据系统关键参数对故障后电压和电流的影响机制,提出一种基于系统参数优化的故障应力调控方案,即通过系统关键参数优化配置,实现过电压、过电流以及并网点电压跌落的综合调控,显著延长系统故障后换流阀的耐受时间和风电场不脱网运行时间;最后,通过对称双极海上风电经柔性直流系统仿真分析,验证了本文所提出方法对系统故障应力调控的有效性,为海上风电优化设计提供支撑。

站用10 kV系统中性点接地方式对避雷器地电位升安全限值的影响

随着电网容量变大和新型电力系统的发展,站用10 kV系统中性点接地方式发生改变,仍沿用系统中性点不接地方式下避雷器耐受接地网地电位(U_(GPR))升高的安全限值可能会导致避雷器在其他接地方式下出现安全事故。采用电磁暂态程序ATP-draw可以搭建不同中性点接地方式下U_(GPR)反击避雷器的模型,通过校核避雷器在U_(GPR)作用下动作过程中的吸收能量,得到了中性点接地方式对避雷器耐受U_(GPR)安全限值的影响规律:中性点不接地时,避雷器耐受U_(GPR)安全限值为10~23 kV,随线路对地电容变大而减小;中性点经消弧线圈接地时,U_(GPR)在消弧线圈和线路对地电容的串联回路中产生振荡,导致避雷器耐受U_(GPR)安全限值更低,安全限值主要由脱谐度与阻尼率决定,典型值为8~9.5 kV;中性点经电阻接地时,U_(GPR)大部分耦合至高压母线,使避雷器耐受U_(GPR)安全限值更高,并随线路对地电容和中性点电阻的增大而减小,大电阻接地工况下的典型值大于15 kV,小电阻接地工况下的典型值大于25 kV。

永磁直驱型风机海上风电送出系统不对称接地及甩负荷电磁暂态研究

为明确海上风电交流送出系统过电压的特征与水平,需考虑风电机组的故障穿越特性。该文结合永磁直驱风机变流器的控制原理,提出海上风电送出系统不对称接地过电压的解析计算方法。基于PSCAD对风电机组进行精确电磁暂态建模与故障电压穿越测试,以国内某500 kV大规模海上风电工程为背景,仿真计算送出系统不对称接地及甩负荷过电压。结果表明:系统不对称接地过电压大小与风机正负序控制策略有关;海缆电网侧甩负荷将产生持续百ms的1.3 pu以上的暂态过电压,风机过电压保护动作延时越长,暂态过电压越严重。实际海上风电工程计算需紧密联系风机控制保护策略及其参数,并综合关键设备耐压水平进行评估,通过风机控制策略优化可以降低系统过电压水平。