新型电力电子技术实验方法的研究

传统电力电子技术实验主要基于实验台操作方式,实验效果不是很好,比如:学生对实验台、实验操作不熟悉.误操作、实验装置损坏较多;分析和解决问题的能力较难建立.为此,提出了一种新型的实验方法:以计算机仿真为前导,以实验验证及设计为目标的双环节实验方法.基于专业的PSPICE仿真环境,开发了电力电子技术高仿真平台,与实验台高度一致.学生在仿真平台上可进行与实验台操作一样的连线,且可突破实验台的局限,可对模块内部操作,研究其对电路特性的影响.该方法对全方位训练学生实验技能、培养学生科学研究方法和创新思维、提高实验教学水平具有重要作用.     

基于群灰色关联度分析方法的电力变压器绝缘故障诊断

基于变压器油中溶解气体分析,提出了一种基于群灰色关联度分析的变压器绝缘故障诊断新方法.首先根据故障类型与灰色参考序列构造,选择变压器典型故障样本构造多组参考序列,这些参考序列组构成一个灰色参考序列群.其次根据给出的新的关联系数计算方法,计算个体关联系数和关联度.然后根据给出的群灰色关联度计算方法,计算群灰色关联度和构造群灰色关联度矩阵.最后根据关联序识别变压器绝缘故障诊断.通过大量变压器绝缘故障诊断实例分析,所提方法诊断准确性与可靠性优于三比值法和传统的灰色关联分析方法,具有较好的分类诊断能力和可靠性.     

新能源发电技术在特色专业建设中的应用

提出了新能源发电技术在电气专业建设中的应用,采用了探索性实验项目来加强学生的实践能力培养。以浙江省财政厅专项电气工程专业能力实践基地建设项目为依托,建设了电力系统继电保护、电力系统自动化与新能源发电系统相结合的综合型实验平台。设计了一系列围绕新能源技术的探索性实验,建立了基于学校网络平台的实验仿真辅助系统。教学实践表明,实施教学改革后电气类课程教学质量得到了较大提高,这些改革方法具有较强的推广性和示范性。     

新能源分布式发电虚拟仿真实践教学平台建设

针对新能源发电课程实验教学设备不能满足教学需求的问题,构建了新能源分布式发电虚拟仿真实践教学平台。介绍了平台的建设目标、建设原则、建设内容及实施计划。该平台可提供验证性、创新性、综合性实验和企业实习内容,适用于风能与动力工程、能源科学与工程、新能源材料与器件、电力系统及其自动化等专业的本科生进行风力发电与太阳能发电的工作原理、故障检测与设备维护、系统性能测试实践教学。     

运用软开关及谐振技术的电流谐波补偿与建模采样分析研究及发展

论文分析和讨论了电力电子技术、非线性与智能控制和信号处理等基础理论的谐振软开关和网侧电流谐波补偿智能整流关键技术的研究与发展,抑制电子装置谐波污染的途径有对电网实施谐波补偿,以及对电力电子装置自身进行改进,也包括无功补偿和有功补偿等方面;讨论了一种DC/DC开关变流器仿真方法。其物理概念清楚、可用波德(Bode)图设计校正环节,因此该方法对变换器的优化分析和设计具有一定影响。     

A Generation Pricing Method with Capacity Bidding

Due to historic reasons China encounters some special difficulties in ESI(electricity system industry) restructureing,An easy and simple electricity value equivalent(es-EVE) method for day-ahead pool purchase pricing of China is therefore presented in this paper.The es-EVE method is different from two-part and one-part tariffs.It is more like the UK‘s method in form,but revised for China with some new concepts and procedure.The main contributions of it include:(1) Find two kinds of eigenvalue,namely EVEs,in an optimization model.(2) Define new concepts of virtual units units and feasible region,(3) Twice merit orderings are employed successively to find marginal price.They are simple maximum and minimum comparison procedures and so on.The special economic significance of the method for China is discussed.and some suggestion for ESI Restructuring based on es-EVE method are provided.A case study is offered at the end of the paper.     

太阳能-地源热泵系统的交替运行特性

为了探讨太阳能-地源热泵系统的交替运行特性,提出并定义了各交替运行模式,建立了交替运行时考虑冻融相变的U形埋管周围土壤传热模型.基于对该模型的数值求解,探讨了各交替运行模式下地下埋管周围土壤温度的变化趋势.结果表明：各交替运行模式均可有效改善埋管周围土壤温度的恢复效果,对于无太阳能补热的昼夜交替与短时间间隔交替运行模式,在以24h为交替运行周期时,其太阳能热源承担的时间比例可控制在50%～58%;同时,利用日间太阳能补热来强制土壤温度的恢复,可有效克服土壤温度的自然恢复缺陷,与其他交替模式综合使用可达最佳运行效果.此外,利用钻孔壁实测数据对所建模型的预测精度进行了验证.研究结论可为太阳能-地源热泵系统的优化运行提供参考.     

激光无线能量传输用低纹波半导体激光器驱动电源

提出1种并联型开关线性复合结构的半导体激光器(laser diode,LD)驱动电源及其相应的控制策略。由于激光能量传输系统中LD驱动电源一般采用线性电源来满足其对输入电流低纹波的要求,而在大功率能量传输的场合,线性电源效率较低,限制了激光传能系统的发展和应用,故用高效率的开关电源代替传统的线性电源作为驱动电源。为补偿开关电源的输出电流纹波,采用高线性度的线性放大器与开关电源并联来抑制电源的输出电流纹波。为保证电源效率,开关电源采样线性放大器的输出电流并将其限制在0附近波动,以此提供绝大部分的负载功率。为保证电源输出电流的低纹波,线性放大器直接采样电源的输出电流来抑制开关电流纹波。此外,为实现良好的补偿效果,还对其电流环路进行了理论分析和设计。最后搭建了1台原理样机,通过实验使得电源的输出电流纹波减少了95%,为输出电流的1.2%。     

Birkhoff系统积分的新方法

将Vujanovi(c)提出的用于积分完整非保守系统动力学方程的梯度法思想移植到Bitkho行系统,给出了Birkhoff系统积分的一种新方法.首先,列写出Birkhoff系统的运动微分方程;其次,将2n个Birkhoff变量分成2部分,并假设其中一部分变量是其余变量及时间的函数,由此建立拟线性的基本偏微分方程组;如果...     

Failure analysis of a kind of low power connector

A kind of low power connector used e.g. in household appliances was partly burned in routine experiment. The heat sources were four paralleled contacts constructed by springs (Sn/CuSn-alloy) in socket and a plug sheet (Ni/Steel) while mating. The contact interfaces were detected by scanning electronic microscope (SEM) and X-ray energy dispersive spectros- copy (XEDS), obvious wear tracks and various contaminants, including element Si, Al, Na, K, S, Cl, O, etc., were found. The contamination degrees on the four paralleled contacts were different, so that the ratio of average contact resistance on the four contacts was about 5:8:3:1. The maximum contact resistance on contacts of the plug sheet reached 28 ?. The main failure rea- sons were fretting and contamination between the contact interfaces. Fretting simulation showed that connection resistance of connectors was raised up, even to ohms level. When the current increased to 5 A, the socket housing was heated and decom- posed. By the thermal analysis, it was estimated that the connector would be burned under the lower current if the current was not evenly distributed on the four paralleled contacts caused by uneven contamination. Improvement methods for connector failure are also discussed.     

社会权力来源的法哲学研究路径

学术史上对社会权力来源的研究基本上通过两条路径展开:即价值判断的路径和事实判断的路径.每条路径都有其合理之处,因此在研究社会权力来源时,把价值判断与事实判断进行有机结合,才是符合马克思主义的做法.     

一种新的入侵检测方法

将一种基于聚类算法的RBF(径向基函数)神经网络方法运用于入侵检测中。在这种方法中采用两阶段学习方法,在利用非监督学习算法确定网络隐层中心时,提出一种基于高斯基的距离度量,并联合输入输出聚类的策略。基于F isher可分离率设计高斯基距离量度中的惩罚因子,可以提高聚类的性能。通过构建入侵检测模型,一方面可以加速网络训练速度,另一方面可以提高入侵检测在预测误报漏报中的性能。     

一种直流力矩电机精确控制的新方法

针对直流力矩的闭环调速控制,提出一种渐近调速算法,主要解决调速过程的快速、平稳、精确控制问题.介绍算法,并给出实现这一算法的技术方案.方案以数字信号处理器为核心,与集成马达控制器和锁相倍频测速单元共同组成闭环随动控制系统.给出驱动控制通道设计和速度反馈通道设计,并对测速单元的测量方法做出精度分析.     

诵读千古美文 滋养一代新人——浅谈小学阶段诵读古诗文

一、诵读经典诗文的重要性中国青基会于 1998年 6月正式启动中华古诗文经典诵读工程 ,如今已有 2 9个省、市、自治区的 80多万孩子直接参加了诵读工程。活动越到后来家长们越认为 ,孩子们在经典古诗文中吸取了做人的精神力量 ,气质也高了 ,就是苏轼说的“腹有诗书气自华”(“古文诵读”工程全国组委会主任陈越光与中科院院士杨叔子于 2 0 0 0年 11月 2 9日的谈话语 )。紧接着 ,小学语文教学大纲修订版第一次明确规定背诵古诗文的篇数 (小学阶段背诵优秀诗文不少于 15 0篇 ,含课文 ) ,并在大纲后面附有古诗背诵推荐篇目 80首。再紧接着 ,下发…     

From power‐machines to intelligent‐machines: A new education for a new technological era

The technological revolution of our epoch is based upon a new kind of tool, the development and use of which requires not physical strength but higher education. The computer and its many industrial applications have completely changed technology, opening up new vistas for the participation of women in the labour force. An important problem raised by these changes is the technical education of both sexes. This paper discusses the experience acquired in Romania in this respect and the results obtained in the last decades.     

A new structure of serial hybrid active power filter for high power application

This paper proposes a new structure of serial hybrid active power filter which can reduce the power rating of the active power filter dramatically, and has good performance for harmonic suppression. The principle and designing rules are analyzed. The proposed structure is rational and feasible for high kVA applications. Simulation results are presented too. Project supported by DELTA Science, Technology and Education Development Foundation for Power Electronics of China.     

Parameters optimization of a parallel-flow heat exchanger with a new type of anti-vibration baffle and coiled wire using Taguchi method

This study presents the thermal-hydraulic optimization of the design parameters of a parallel-flow shell-and-tube heat exchanger with a new type of anti-vibration hexagon clamping baffle and equilateral triangle cross-sectioned coiled wire. A periodic flow unit duct with non-staggered tube layout is adopted as the numerical analysis model by Fluent. The Taguchi method is used to explore the influence of five geometric parameters including baffle distance (A), baffle width (B), coil diameter (C), coil pitch (D), and the side length of the equilateral triangle (E). An L18 (3⁵) orthogonal array is chosen to carry out the numerical simulation. The comprehensive thermal-hydraulic performance evaluation criterion (PEC) is set as the optimization goal. The results show that the order of the factor effectiveness for the Nusselt number is E>C>A>D>B, for the flow friction is C>E>A>B>D and for the PEC is C>E>A>B>D. This means that the coil pitch has a great influence while the baffle width and the coil diameter have a trifling effect. Finally, the optimal factor combination for PEC is obtained. The PEC of the optimal combination is 0.19%–1.92% higher than the model with better comprehensive performance among 18 cases for Reynolds number in the range from 14 465 to 32 547.