Development and design of wave SC filters

A direct z-domain simulation of LC ladder and unit-element filters by means of wave SC circuits is presented. the development of a wave SC circuit is achieved by interconnecting a limited number of basic SC building blocks. the derived circuits are fully parasitic-free, symmetric and can be optimally designed for dynamic range maximization and capacitance area minimization. the number of operational amplifiers in the simulated unit-element filters is essentially low in comparison to earlier presented parasitic-insensitive wave SC filters and to leap-frog-type SC filters. Four- and two-phase multiplexed simulated LCR filters can be developed. Bilinear s-z transformation applies for all the circuits; thus the design is exact and there is no requirement for a high clock frequency. Filters with transmission zeros can be developed. the simulated responses of various types of filters are in good agreement with the theory. Detailed examples of different designs are given.     

双电容混合型直流断路器

在混合型直流断路器的基础上采用电流转移法,针对高压直流系统短路故障问题提出了一种双电容混合型高压直流断路器的拓扑模型.不仅能让高速机械开关在零压零流的条件下安全无弧分断,附带自充电功能,而且可以大幅度降低单电容直流断路器分断时的反向充电电压,从而缩短了拓扑运行时间.对拓扑运行中的各个临界阶段进行数学公式推导,通过仿真验...     

一般矩阵式电力变换器的等效电路及其应用

基于Ｐａｒｋ 变换原理, 提出了升压式和降压式矩阵变换器统一的等效电路模型, 应用线性电路理论对等效电路模型进行了分析, 得出了输入电流、功率因数、电压增益、输出阻抗等性能指标的解析表达式, 对矩阵变换器的分析与设计具有一定理论意义和实用价值     

同塔双回不换位线路电压不平衡度研究

在线路走廊特别紧张的地区,部分线路可能没有条件采用完全换位,而同塔多回输电线路中采用不换位架设将导致电力系统三相参数不对称。针对这个问题,以某地区一条750 kV同塔双回线路为例,对该线路不平衡度计算进行了理论推导,并应用PSCAD/EMTDC软件从杆塔类型、相序排列方式、回间距离、线路长度几个方面对线路不平衡度进行了仿真分析。仿真结果表明,输电线路较短时采用同塔同窗逆相序方式架设并适当调整回间距离,能将电压不平衡度控制在一定范围内。输电线路过长时则需采取换位措施,避免对系统造成不良影响。     

Equivalent Circuit of Distribution Line for Lightning‐Induced Voltage Analysis Using Analytical Formulas

This paper proposes an equivalent circuit at a transition point of distribution line for lightning‐induced voltage analysis. The lightning‐induced voltages caused by a piecewise linearly varying lightning current are expressed by analytical formulas. The equivalent circuit is represented by resistors and current sources, which are known from past history and given by the lightning‐induced voltage on an infinite‐length line. Transient voltages and currents at the transition point are accurately obtained in small computation time using the equivalent circuit. Thus, the proposed equivalent circuit is very convenient for analyzing the lightning‐induced effect in complicated electric power networks. This paper presents an example of EMTP data cards to use the proposed equivalent circuit in the EMTP.     

750 kV同塔双回不换位线路电流不平衡度研究

在线路走廊特别紧张的地区,部分线路可能没有条件采用完全换位的方式架设,而同塔多回线路采用不换位架设将导致电气三相参数不对称。针对这个问题,对同塔双回不换位线路不平衡度计算进行了推导,并应用PSCAD/EMTDC软件从杆塔类型、相序排列方式、回间距离、线路长度几个方面对750 kV同塔双回不换位线路进行了仿真分析。仿真结果表明,输电线路较短时采用同塔同窗逆相序方式架设并适当调整回间距离,电流不平衡度能控制在一定的范围之内。输电线路较长时则需进行换位,避免对系统造成不良影响。     

广义反馈理论

本文在导纳矩阵的基础上,从分析的高度披露了反馈理论的数学本质;揭示出反馈理论与一般线性电路分析方法之间的内在联系及其特殊性。文中,对反馈理论所用参数给出了严格的定义,并给出解析表达式。在此基础上,得到开、闭环性能指标之间的四个普通关系式。这些结论是严格的,形式是统一的,与反馈种类无关。对高频、低频、宽频、选频、运放电路都成立。     

Equivalent circuit characterization of resonant magnetic coupling for wireless transmission of electrical energy

This paper provides the accurate characterization of a wireless power transfer system consisting of two resonant air‐core coils mutually coupled in free space. The lumped‐circuit parameters of the equivalent circuit are determined with analytical formulas taken from the literature and validated by comparison with numerical simulations with a finite‐element computer code and with experiments. The parameters are determined taking as input only the geometry of the system (coil size and mutual distance, conductor radius, and turn distance) and the frequency. Once the lumped‐circuit parameters are known with good accuracy, the assessment of the power transfer system can be carried out by evaluating the current and voltage gains and efficiency for different system geometries, operating frequencies and load conditions. The Scilab programming environment was used to perform all the calculations. The characterization presented in this paper can then be considered as an effective tool in designing an efficient wireless power system. Copyright © 2012 John Wiley & Sons, Ltd.     

无槽环形绕组轴向磁通永磁电机空载反电动势解析

无槽环形绕组有两种类型,即扇形绕组和矩形绕组。针对这两种绕组空间分布对空载反电动势的影响,分别对两种绕组轴向磁通永磁电机的空载反电动势进行了解析推导。在气隙磁密解析计算时,提出通过建立虚拟等效直线电机模型用以计算气隙磁场端部效应函数。为了验证解析公式的正确性,以一台电机方案为例,利用推导的解析公式对空载反电动势进行了计算,与有限元计算结果进行了对比,结果表明解析计算结果和有限元计算结果相对误差小于2.1%,满足工程要求。因此,推导的空载反电动势解析公式可以作为电机设计人员参考使用。     

Damping circuit to suppress motor terminal overvoltage and ringingin PWM inverter-fed AC motor drive systems with long motor leads

This paper proposes an equivalent circuit analysis to suppress overvoltage and ringing in pulsewidth modulation inverter-fed ac motor drive systems where long motor leads are required. Conventional analysis of the phenomenon is based on voltage reflection theory for the terminal end of the long cable. The authors implemented another analytical method using equivalent lumped L and C of the cable, and a transfer function for the equivalent circuit with a simple damping circuit, C-R or L-R damping circuit constants are determined from the nonoscillatory condition of the transfer function. Digital simulations and experiments are used to verify that a simple damping circuit can satisfactorily suppress overvoltage and ringing in a drive system with a long cable, such as a 100-m cable     

大电力系统可靠性评估的解析计算模型

该文导出了失负荷概率LOLP、失负荷频率LOLF和电力不足期望EDNS对元件可靠性参数的解析表达式,详细阐述了解析表达式中的系数K1~K4和D1、D2的实际物理意义。基于这些解析表达式,论文建立了一套完整的大电力系统可靠性指标对元件可靠性参数的灵敏度计算公式。利用可靠性指标的解析表达式不但可以高效精确地求取元件可靠性参数改变后的系统可靠性指标,而且可以得到系统可靠性指标对元件可靠性参数的函数曲线,开拓了通过解析方式计算大电力系统可靠性指标的新思路,在缓解计算灾方面取得了较大进展。应用可靠性指标的灵敏度公式则能有效地找到钳制系统可靠性的薄弱环节,可为电力系统规划和运行提供重要的指导意见。     

分相无功补偿装置在城网中的应用

供电线路中的无功补偿装置，在杆上变压器上的应用是个新课题。根据民用电的用电特点，采用分相无功补偿装置就能够达到一定的效果，随着新技术、新材料的大量面世，已经能够解决分相无功补偿装置的技术难点。提出了零相接入线处理方法，推荐一种单片机自动复位电路。     

New formulas for predicting audible noise from overhead HVAC linesusing evolutionary computations

Audible noise (AN) produced by corona discharges from high voltage transmission lines is one of the more important considerations in line design. Therefore, line designers must predetermine the AN using prediction formulas. This paper presents the results of applying evolutionary computation techniques using AN data from lines throughout the world to develop new highly accurate formulas for predicting the A-weighted AN during heavy rain and stable rain from overhead AC lines. Calculated ANs using these new formulas and existing formulas are compared with measured data     

Revolving-field polygon technique for performance prediction of single-phase induction motors

This paper presents a new analytical technique for improving the performance prediction of single-phase induction motors, especially capacitor motors. The technique uses the split-phase motor electrical equivalent circuit analysis together with electrical and magnetic parameters whose variation is computed from the equivalent balanced polyphase motor, so that the same magnetic circuit analysis can be used for both. (The term split-phase is used to cover motors operating from a single-phase supply but with the phase windings split into two orthogonal windings, one of which may have a capacitor in series with it during running or starting.) The technique accounts for the elliptical envelope of the magnetizing field vector and results in improved precision, since the three-phase electromagnetic model is considered to be more precise than the normal split-phase motor analysis. An important result is the computation of vector polygons of flux density for each section of the magnetic circuit, providing a better basis for core loss prediction. The double-frequency torque ripple is also obtained from the stator magnetomotive force and flux-density polygons. Three different electrical equivalent circuit methods for the split-phase motor (based respectively on the cross-field theory, forward- and backward-revolving fields, and symmetrical components) are evaluated to determine the method best suited for incorporating the variation of the circuit parameters from the polyphase magnetic circuit analysis, and it is discussed how the core losses can be included in these circuits to obtain the best overall performance prediction.     

高稳定型倍压器中起因于电路非对称性的纹波

轻负载高稳定对称型Cockcroft-Walton倍压器中 ,电路非对称性引起的交流纹波已成为影响其输出直流高压稳定性的重要因素。采用传输线理论 ,在线性近似条件下推导出起因于输入电压的非对称和电路元器件非对称的纹波的解析表达式。 1 0段模型电路上的实验结果验证了理论的正确性。由得到的理论结果还分析了纹波与电路非对称性和电路参数间的关系。     

关于同杆双回线检修回路中接地开关开断工况的研究

本推导了同杆双回线路当一回线停电检修时，在检修线上产生的感应电压和电流的计算公式，并以此编制程序，计算了西南地区宝珠寺－龙王双回线路中检修线上电压和电流的数值，提出了国内各电压等级同杆双回线路感应电压和电流的参考数据，从而为制订国内接地开关开断感应电流的标准提供了依据。中还推导了接地开关开合感应电流的等价试验回路。     

时变幅频信号下的三相系统动态过程有功及无功功率物理概念理解与数学计算

电力系统动态过程中,其三相交流电压和电流电气量的幅值及频率实质上均为时变量,故该文称其为时变幅频信号。目前,在电压和电流的幅值、频率随时间任意变化的系统动态情况下,如何正确理解三相有功及无功功率的物理概念,相关的研究工作还尚未开展。为此,该文以瞬时幅值和瞬时频率描述动态过程中的电压、电流电气量,同时给出时变幅频信号下三相交流电压和电流的解析表达式,然后依据三相系统基本的有功及无功功率物理含义,通过对时变幅频信号下的电流空间旋转矢量进行正交分解,得到各相有功、无功电流和各相瞬时功率有功、无功分量的表达式,并推导出三相有功及无功功率的计算公式。该文在时变幅频信号下所阐释与计算的有功及无功功率具有明确的物理意义和简明的数学形式,适用于系统动态过程电压和电流的幅值、频率随时间任意变化的情况,从而克服了传统功率理论仅针对正弦稳态电路的局限性。最后通过Matlab/Simulink中的时域仿真说明该文对传统正弦稳态三相系统功率理论进行推广的有效性。     

平面变压器漏电感解析建模研究(一):综述

漏电感是平面变压器的重要寄生参数,其解析建模问题近些年得到广泛研究。已提出的方法主要可以分为两大类:基于磁动势的方法和基于部分元等效电路公式的方法。通过分析和总结两类方法的原理,比较了二者的优缺点,从应用出发为磁性器件设计人员提供一些参考和帮助。     

Memristor‐based voltage‐controlled relaxation oscillators

This paper introduces two voltage‐controlled memristor‐based reactance‐less oscillators with analytical and circuit simulations. Two different topologies which are R‐M and M‐R are discussed as a function of the reference voltage where the generalized formulas of the oscillation frequency and conditions for oscillation for each topology are derived. The effect of the reference voltage on the circuit performance is studied and validated through different examples using PSpice simulations. A memristor‐based voltage‐controlled oscillator (VCO) is introduced as an application for the proposed circuits which is nano‐size and more efficient compared to the conventional VCOs. Copyright © 2013 John Wiley & Sons, Ltd.