Nonlinear modeling of magnetic saturation and hysteresis in an electromagnetic device

The cores of most electromagnetic devices, in their normal operating regions, enter saturation by design or otherwise. Some devices, such as ferroresonant transformers, utilize the saturating properties of their core materials to perform their intended tasks. In other devices, such as power transformers, saturation is an undesirable phenomenon imperative to their economically competitive designs.A second phenomenon, known as hysteresis, associated with the operation of electromagnetic devices is the non-uniqueness of the core magnetic flux for a given excitation. That is, core flux is a multivalued function depending on the excitation as well as its own previous states.Computer simulation of a saturable electromagnetic device requires mathematical models for the device saturation and hysteresis characteristics. A general approach to modeling saturation and hysteresis is proposed in this paper. A model which is nonlinear in a parameter is proposed; however, a linearizing transformation is used to allow the estimation of the model parameters by linear estimators.The results of modeling saturation and hysteresis for a two-winding ferroresonant transformer are given. The hysteresis loop obtained from simulation is compared with the actual loop for a given operating condition. These results indicate that accurate modeling of the hysteresis loop is possible with the proposed technique.     

变压器铁心磁滞模型参数辨识

针对描述铁心磁滞特性的Jiles-Atherton模型中参数确定较难问题,通过找出各参数对磁滞回线特征量的影响规律,确定各参数比较合理的拟合初始值。参数采用逐个优化算法,以实验获取的磁滞回线与计算得到的磁滞回线之间的均方误差最小值作为优化目标,并以2者之间的均方误差反馈控制每个参数的优化启动、优化停止及变化百分比,从而得到一组最佳逼近的Jiles-Atherton模型参数。研究结果表明该算法简单实用。通过拟合数据与理论数据、实际硅钢片数据及实验数据的对比,验证了该算法的正确性和有效性。     

并联有源电力滤波器滞环电流比较控制研究

在理论和仿真研究并联有源电力滤波器(PAPF)滞环电流比较控制方法中,首先介绍了PAPF的整体结构与工作原理,阐述了基于瞬时无功功率理论的指令电流信号检测方法和滞环电流比较控制方法的基本思想、实现原理和主要特点;然后,对三相四线制的不对称非线性系统和PAPF仿真实验以验证它的可行性。结果显示,该有源滤波器输出特性好,控制系统简单易行、可靠性高、适用性广。     

分布式电源并网系统控制策略的研究

滞环电流控制方法以其动态响应速度快,电路跟踪性能好的优点而获得了广泛的应用和发展。从降低开关频率和改善系统输入电流谐波总畸变率(Total Harmonic Distortion,简称THD)的角度出发,研究并设计了一种具有倍频效果的改进三态正弦电流滞环宽度的控制方法,有效地减少了开关管的功率损耗;降低了并网逆变器系统的THD。根据实验结果的分析,以及与传统固定滞环电流控制方法相比较,在相同电路参数和控制参数的条件下,应用改进三态正弦电流滞环宽度控制方法,可减小功率开关管的损耗,降低脉宽调制(PWM)逆变器系统中的THD,从而有利于提高并网系统的稳定性和运行效率。     

Systematic realization of a class of hysteresis chaotic oscillators

A systematic method for realizing a class of hysteresis RC chaotic oscillators is described. The method is based on direct coupling of a general second‐order sinusoidal oscillator structure to a passive non‐monotone current‐controlled non‐linear resistor. Owing to this passive non‐linearity, the power consumption, supply voltage and bandwidth limitations imposed upon the chaotic oscillator are mainly those due to the active sinusoidal oscillator alone. Tunability of the chaotic oscillator can be achieved via a single control parameter and the evolution of the two‐dimensional sinusoidal oscillator dynamics into a three‐dimensional state‐space is clearly recognized. The flexibility of this method is demonstrated by two examples using PSpice simulations and experimental results. Numerical simulations of derived mathematical models are also shown. Copyright © 2000 John Wiley & Sons, Ltd.     

电力系统电磁暂态计算中含铁芯元件磁滞特性的分析与仿真

在分析电力系统铁磁元件磁滞特性的基础上，将多值的励磁特性模拟为一个主磁滞回环和动 态磁滞回环族，建立了计及铁芯饱和、磁滞、动态磁滞回环等特性的铁磁元件的数学模型， 并给出算例。结果表明，该模型不仅能较好模拟铁磁元件的动态磁化特性，而且方法简单。     

基于非接触滞环调节器和动态基准调节的自激闭环控制策略

提出了一种基于非接触滞环调节器和动态基准调节的自激闭环控制策略,可自动快速响应感应式无线电能传输系统中耦合机构与负载参数的变化,并实现输出电压的精确控制.首先,针对串/串补偿感应式无线电能传输系统,提出基于动态基准调节的自激控制策略.然后,引入相移时间参数描述动态基准的变化,详细分析了动态基准对自激振荡频率与输出电压增益特性的影响,并给出输出电压调控的单调区间与可调输出电压限值.进一步,提出了基于过/欠压状态信息反馈的非接触滞环调节器实现方案,将其与基于动态基准调节的自激控制相结合,实现了输出电压的闭环调节.最后,搭建了一台80 W实验样机,验证了理论分析的正确性与所提控制策略的优越性.     

Transfer function‐matched capacitor‐current sensing and its circuit implementation for high‐frequency power converters

It would effectively achieve a fast load transient response in switching‐mode power converters when introducing capacitor current into the feedback control loop. In these schemes, an accurate and rapid sensing of capacitor current is crucial in the control circuit design. On this issue, a paralleled nonintrusive sensing scheme for capacitor current is proposed in this paper, which is implemented by matching the transfer functions of the sensing circuit and the sensed capacitor branch. With the proposed transfer function matching approach, 4 possible circuit topologies are derived in theory, and on this basis, a parameter design flow chart is given for 2 of candidate topologies. With the application of the proposed capacitor‐current sensing circuit to a constant‐frequency hysteresis controlled Buck converter, a fast and accurate sensing of capacitor current is achieved in experiment, as well as a fast load transient response.     

基于变结构的协同控制方法及其在DC/DC开关变换器中应用

为解决滑模控制因开关频率不固定而不能实用的问题,引入协同控制方法并将其应用于DC/DC开关变换器。简要介绍协同控制方法的解析生成过程。利用变结构理论分析协同控制方法的收敛速度以及对外部干扰和内部参数变化的鲁棒性。分析表明,协同控制方法开关频率恒定、容易数字实现和离开流形的动态特性较好;从任意初始状态都能按指数收敛到流形;对满足一定匹配条件的系统内部参数扰动和外部干扰具有不变性。以带恒功率负载的Boost变换器为例,讨论了协同控制器的设计问题,给出该闭环系统的稳定条件,基于稳定条件设置协同控制参数。Simulink仿真结果表明,协同控制器能渐近稳定在目标工作点上,对负载突变和负载功率突变具有较强的鲁棒性。     

基于状态优化的单相有源滤波器边带控制方案

分析了单相有源滤波器电流边带控制方案的特性，指出将单个桥臂人为控制对象而造成的在定边带条件下开关频率变化范围大、定频率条件下控制精度差的弱点。提出应将有源滤波器看成一个整体，利用桥臂间的关联关系，以所有桥臂的状态变化作为滤波器的控制手段，构造了基于状态优化的边带控制方案。理论分析和仿真结果表明，在相同的边带要求下，该方案可以大大降低器件的开关频率，这对于大功率有源滤波器的工程实现非常有利。     

PSPICE computer modeling of hysteresis effects

Recent versions of PSPICE, a personal computer implementation of the SPICE circuit simulation computer software program, have the capability of simulating the hysteresis loops of magnetic materials. In order to model the hysteresis loop of a particular manufacturer's magnetic core material, the values of five parameters that affect the shape of the hysteresis loop must be established. A method for illustrating the effect that each parameter has on the shape of the hysteresis loop is presented. The method speeds the process of establishing the parameter values for modeling a particular hysteresis loop     

基于主导和非主导参数的参数可估计性辨识

通过对参数估计应用难点的分析,介绍了参数的可估计性问题。借助电网线性模型的近似分析,提出了参数估计中的主导参数和非主导参数概念。据此解释了参数估计实践中遇到的一些现象,并得出了关于参数估计软件运行方式等的相关结论。根据非主导参数易受量测噪声影响的特点,提出了通过噪声敏感试验的方法辨识主导及非主导参数的方法。对IEEE算例进行了仿真实验,验证了文中提出的参数估计时应去除非主导参数的观点。     

矩阵变换器电流控制策略

分析了传统矩阵变换器空间矢量调制策略,提出一种新型的矩阵变换器电流控制策略.该控制策略在虚拟整流部分,通过适当选取输入电压可实现高输入功率因数控制;在虚拟逆变部分,在一个采样周期内通过对输出电流进行基于规则的滞环跟踪控制及对虚拟逆变器的合适矢量选择,确保输出电流的误差在一个小的滞环宽度内.新型电流控制策略相比传统的基本滞环控制,减少了输入电流的谐波,改善了矩阵变换器的输入、输出性能.通过Matlab软件仿真分析并搭建Dspace硬件实时仿真平台对所提控制策略进行了实验研究,仿真及实验结果验证了新型电流控制策略的正确性.     

Power losses in steel pipe delivering very large currents

This paper presents a finite difference time domain solution for the electromagnetic fields in ferromagnetic conducting steel pipes of the type used to deliver large currents for in situ heating of heavy oil reservoirs and for in situ environmental decontamination. A method is described whereby a single measured hysteresis loop can be used to deduce the family of hysteresis loops that governs the variable magnetic behavior throughout the pipe wall. Hysteresis and eddy current losses are calculated, and it is shown that hysteresis effects greatly alter the eddy current distribution and can more than triple the total power losses in the steel pipe when compared to the power losses that would be present if hysteresis effects are ignored and magnetic permeability is assumed constant     

An example of dB/dt characteristics of the dynamic magnetic loss parameter

Ferrite cores are used for power electronics circuits operating under excitation conditions of frequency ranging from hundreds of kilohertz to several tens of megahertz. Development of a mathematical model enabling the estimation of the power loss of ferrites in high‐frequency regions, contributes to the designing of power circuits. The power loss in high‐frequency regions consists of hysteresis and dynamic magnetic losses. Although hysteresis loss does not depend on the excitation frequency, the dynamic magnetic loss increases with increasing excitation frequency. The dynamic magnetic loss parameter, λ_f, has been introduced for identifying the power loss in high‐frequency regions. In this study, λ_f − dB/dt characteristics are experimentally obtained by a newly introduced hysteresis model that uses a normal distribution function. It is found that the λ_f − dB/dt characteristics do not depend on the size of B − H loops. The instantaneous power loss of a ferrite core in the high‐frequency region can be calculated using the λ_f − dB/dt characteristics. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

电力系统负载的数字模拟

由于传统电机模拟线性负载和电力系统负荷的诸多不便之处,故提出了利用SPWM功率变换技术替代电机模拟的方法,并对电路拓扑机构和控制方法做出介绍。主电路采用双SPWM变换器结构,其中一变换器采用电压反馈PI控制方法,而另一变换器采用滞环电流控制,同时给出了MATLAB的仿真结果。仿真结果表明,这种AC—DC—AC功率变换电路能很好地模拟RLC的静态和动态特性,以及电力系统综合负荷的稳态特性。利用这种原理和技术可进一步实现电动机和发电机的模拟。     

Robust analysis and design of load frequency controller for power systems

Robust load frequency control for power systems is discussed. A detailed robustness analysis of the existing control laws shows that parameter variation is not a critical issue but more attention should be paid to the unmodeled dynamics in robust load frequency controller design. A new robust load frequency control method is then proposed considering the unmodeled dynamics of power systems. Finally, a new configuration is proposed to overcome the effects of generation rate constraints (GRC). Simulation results show that the design method and the anti-GRC configuration are effective.     

一种用于电流互感器铁心J-A磁滞参数识别的改进方法

模拟电流互感器铁心的动态磁化过程,需要建立准确的磁滞模型.改进J-A磁滞模型能够更准确地模拟铁心的磁滞特性.针对改进J-A磁滞模型关键参数难以确定的问题,提出了一种基于烟花算法的电流互感器改进J-A磁滞模型参数识别方法.该方法首先建立改进J-A模型,然后建立参数识别模型,以求出的磁感应强度与已知的磁感应强度之间的绝对误...     

运行工况对电力系统稳定器PSS现场参数整定影响的研究

在简单介绍了电力系统稳定器PSS原理及其现场参数整定方法的基础上,提出了影响励磁系统无补偿频率响应特性测量的几个主要因素。通过仿真计算,全面地分析和总结了Eq′/Us和Ut/Us频率响应特性的区别,励磁系统调差设置、发电机有功功率、无功功率、机端电压等发电厂本机组工况和其它机组出力、PSS投退和出线数量等对滞后特性测量结果的影响,提出了PSS现场参数整定时正确考虑工况影响因素的对策。     

变环宽的APF滞环控制方法研究

针对有源电力滤波器(APF)滞环控制方法存在开关频率不固定的问题,提出了一种新的滞环控制方法。根据给定工作频率与实际工作频率的偏差,采用频率反馈,应用模糊递推积分控制器调整滞环宽度,实现开关频率的稳定方法,具有稳定性好、响应速度快、控制精度高等优点,有效提高了APF的工作性能。最后,在Matlab/Simulink中建立仿真模型,验证了所提方法的可行性。