谐波对电表计量的影响分析

基于感应式电表与全电子式电表的工作原理,推导出各自在谐波下的数学表达式,并分析出电表计量误差的影响因素,结合理论计算与仿真分析,得到谐波对电表计量影响的结论。     

并联有源电力滤波器的仿真研究

由于非线性负荷造成电网电能质量下降,各种调节控制补偿装置大量涌现,其中新型动态实时补偿装置并联有源电力滤波器(SAPF),具有优越的补偿性能.利用MATLAB的动态仿真软件SIMULINK模拟SAPF补偿负载产生谐波及无功电流.建立SAPF的仿真模型采用了传递函数法、IGBT三相桥式逆变器法,两种方法都能产生跟踪指令电流信号的补偿电流.分别阐述组建两种仿真模型的方法,并进行比较,指出传递函数法建立的SAPF仿真模型产生的补偿电流为计算量,而IGBT三相桥式逆变器法建立的模型能产生注入模拟电网的补偿电流,因此它更具适用性和研究价值.     

Effect of particle size of magnesium silicate filler on physical properties of paper

Fillers are essential component of printing papers to increase the opacity, brightness, and to improve formation and printing properties. As a very little work has been reported so far on magnesium silicate (talc), the study was conducted with the filler of different particle size for papermaking. The sheets were made in the laboratory with refined mixed hardwood chemical pulp with five grades of talc, ground calcium carbonate (GCC) and precipitated calcium carbonate (PCC) fillers with 15–24% ash level. Apparent density along with tensile, burst, tear index, Z‐direction tensile strength (ZDTS) and bending stiffness index were evaluated for talc filled sheets, and compared with GCC and PCC. Physical strength properties of talc filled sheets were decreased at a faster rate on increasing filler loading in paper and decreasing the particle size of the filler. With same type of filler its particle size determines the physical properties of paper. The postulate was not found to be valid for all the three varieties of fillers viz., talc, PCC and GCC. Shape and geometry of the PCC and GCC fillers determine the individual property. © 2012 Canadian Society for Chemical Engineering     

电力系统谐波统计分析与测量

介绍了一种新近研制的电力系统三相同时测量谐波分析仪,它是由MCS-98单片计算机构成的智能式数字谐波测量仪器。所设计的多通道采样保持和时分模数转换电路,在最小造价下实现了三相电压和电流的同步数据采集,由此给出了谐波幅值、初相位、含有率和总畸变度以及功率和阻抗等.其最显著的特点是向用户提供谐波统计分析估计值和最大筛选值以及日变化曲线.     

基于加窗插值FFT的电力谐波测量理论（Ⅱ）双插值FFT理论

本文用四项Ｂｌａｃｋｍａｎ－Ｈａｒｒｉｓ窗对采样数据加权，再用两次插值快速精密地计算出信号的谐波参数。与国外有关算法相比，达到相同的计算精度，本文提出的算法所需的采样频率约为国外通常使用的１／３左右。在信噪比大于４０ｄＢ时，一般信号谐波幅值、频率和相位精度分别可达０．５级、０．１级和１级。     

提高开关电源功率因数的方法

开关电源是电源的发展方向，但开关电源功率因数很低。它的输入电流波形严重畸变，所含谐波对电网有干扰，故如何提高开关电源的功率因数，抑制谐波，减小对电网的干扰是一个重要课题。本文对抑制谐波、改善功率因数的三种常用方法──串联谐振滤波器、并联谐振滤波器和升压式变换器进行了试验研究。表明有源升压式变换器是提高开关电源功率因数的最好方法。     

异步电机基于谐波磁场影响的槽配合综述

异步电机的槽配合与电机中谐波磁场有密切的关系。本文在谐波磁场分析的基础上,从研究异步电机定、转子槽配合对最小转矩、电磁振动和噪声及杂散损耗的影响出发,得出一系列合理选择槽配合规则,这些规则对异步电机优化设计具有指导意义。     

内循环好氧三相流化床处理造纸中段废水

本实验采用内循环好氧三相流化床处造纸中段废水，经过一段时间的驯化，获得了稳定的出水。CDO去除经保持在65％以上，系统对进水污染负荷的变化具有较大的承受能力。出水Cl^-的浓度有所增加，说明驯化后的微生物可能对有抽氯化物具有一定的降解作用。水气比在1／120至1／140之间可获得最好的COD去除效果。后进行絮凝处理后，出水COD降为60－80mg/L,BODo 50-60/L，色度为100－150CU，挥发性酚的质量浓度小于0．0265mg／L。     

Homogeneous complex solution formed through interactions of poly(acrylamide‐co‐acrylic acid)/poly(acrylamide‐co‐dimethyldiallylammonium chloride) complex with M n+ hydration metal ions in aqueous media

A homogeneous complex solution, formed through inter‐polyelectrolyte complexation of poly(acrylamide‐co‐acrylic acid) (P(AM‐AA)) with poly(acrylamide‐co‐dimethyldiallylammonium chloride) (P(AM‐DMDAAC)) and interaction of the P(AM‐AA)/P(AM‐DMDAAC) complex with M ⁿ⁺ hydrated metal ion, was prepared and the structure and properties of the P(AM‐AA)/P(AM‐DMDAAC)/M ⁿ⁺ homogeneous complex solution were studied by UV spectrometry, dynamic light scattering and viscometry. The experimental results show that the homogeneous complex solution can be obtained by controlling the composition of the P(AM‐AA)/P(AM‐DMDAAC) complex and the M ⁿ⁺ metal ion content. Compared to the constituents, ie the P(AM‐AA) solution, the P(AM‐DMDAAC) solution and the P(AM‐AA)/P(AM‐DMDAAC) complex solution, the P(AM‐AA)/P(AM‐DMDAAC)/M ⁿ⁺ complex solution has a new peak at 270 nm in its UV spectrum, a larger hydrodynamic radius, and hence a higher solution viscosity, all of which indicate that there exist specific interactions between polymers and M ⁿ⁺ metal ions. These interactions lead to the formation of a network structure and hence an obvious increase not only in solution viscosity but also in resistance of the polymer solution to simple salts, to temperature changes and to shearing. © 2001 Society of Chemical Industry