应用按层积分矢量单元法进行多层RAM电磁散射计算

对多层RAM结构进行电磁散射计算时,为了获得精确的计算结果,需要对每层RAM进行精细网格划分,这将大大增加网格数量和计算规模.为此,本文结合曲边四边形矢量单元,应用按层积分方法进行单元计算,以单层整体建模代替多层建模,大幅度减少了网格数量,降低了计算规模.通过算例证实了这种按层积分矢量单元方法计算精度高,具有较好的工程应用价值.     

基于MRAS无速度传感器矢量控制系统研究

根据异步电动机矢量控制基本原理,构建了基于转子磁链定向的模型参考自适应系统,并针对其基准模型易受积分初值和漂移问题的影响,提出了一种改进的速度辨识方法。该方法由改进的电压参考模型和电流可调模型构成。利用Matlab/Simulink对系统进行了仿真,仿真结果表明该系统能较好地估计电机的磁链及转速,收敛速度快,具有良好的...     

基于MRAS的异步电机无速度传感器的矢量控制

由于电机定转子参数的变化,利用一般的转子磁链对转速进行估算,将导致不能得到准确的结果。这里采用积分型转子磁链的参考和可调模型构建出一个基于MRAS的异步电机无速度传感器的矢量控制模型。该模型提高了矢量控制系统的动态性能并利用MATLAB,sIMULINK进行了异步电机无速度传感器矢量控制系统的仿真,验证了文中所采用的模型参考自适应的速度估算方法的可行性以及对参数误差的鲁棒性。     

采用检测信号并考虑主磁链饱和的异步电机无传感器矢量控制

异步电机无速度传感器矢量控制需要通过由定子电压和电流建立的模型来计算磁链矢量和转速。如果磁链矢量的估计中存在误差，例如由电机模型参数不准确造成的误差，那么系统的稳定性就会出现问题。本文提出了一种考虑了主磁链饱和效应的方法来辨识磁链矢量甚至是在定子频率为零时的磁链。因此保证了全速和全转矩范围内的系统的稳定运行。     

平面缝隙天线中磁流格林函数分析

介绍了等效磁流在平面缝隙结构中的应用,利用传输线理论推导了混合位积分方程中的谱域和空域磁流格林函数,得到了一种简洁的表达式,为缝隙结构电磁问题的分析仿真提供了便利,与文献的对比证明了结果的正确性.     

电磁轴承定子磁极不同拓扑结构的磁场分析

当电磁轴承设计有容错要求时,往往采用磁极独立驱动的方案,磁极的拓扑结构体现更加复杂多样化.本文以8极结构独立驱动的径向电磁轴承为研究对象,对电磁轴承定转子本体模型进行网格剖分,以变分原理和分片差值为基础的数值分析,来确定网格内各点的矢量磁位,得到了不同拓扑结构(全N(S)型、NSNS型和NNSS型)下,电磁轴承定转子磁...     

基于磁链预测的永磁直驱风力发电机SVM-DTC技术

永磁直驱风力发电机传统直接转矩控制（DTC）通过查表法选择固定电压矢量来控制定子磁链和电磁转矩,导致磁链和转矩的双重控制要求不能同时兼顾,造成磁链和转矩脉动过大。针对传统DTC的不足,研究了一种永磁直驱风力发电机基于定子磁链预测的空间矢量脉宽调制（SVPWM）DTC方法,通过对下一个控制周期磁链矢量的预测计算需要补偿的电压矢量,并引入SVPWM模块代替查表法来合成该电压矢量。仿真和实验结果表明,此方案能明显降低磁链和转矩脉动,改善永磁直驱风力发电系统的控制性能。     

基于阻抗边界条件建模的涂敷目标电磁散射分析

针对飞行器上常用的涂敷吸波材料结构开展电磁散射数值建模和散射特性分析。利用涂敷结构表面电磁场的阻抗边界条件,建立表面电流和表面磁流的新型积分方程形式,并利用快速算法进行求解。数值结果表明:该型积分方程在不增加额外计算量和存储量的条件下,显著改善了迭代求解收敛性,为复杂涂敷结构的电磁散射分析提供了快速、可靠的技术途径。     

带ABC底面的共形完全匹配层按层积分算法

本文构造了一种共形完全匹配层(Conformal Perfectly latched Layer,CPML)矢量单元按层积分算法,将多层单元积分运算叠加到一层单元中进行,即保留了多层单元的几何和材料信息,又减少了计算规模;为了进一步增强吸收,减少底面反射,应用矢量ABE(Absorbing Boundary Condition,ABC)吸收边界作为CPML底面.数值算例表明,这种按层积分CPML结合矢量ABC吸收边界的方法,吸收效果好,计算量小,效率高;具有良好的应用前景.     

一种改进磁链计算模型分析

准确获取异步电动机转子磁链信号在高性能电机控制系统中具有十分重要的意义。介绍了常用转子磁链计算的电压和电流模型,针对各自存在的部分问题,提出了一种基于磁链计算方程进行组合的改进计算模型。在此基础上,根据矢量控制理论,采用Matlab／Simulink软件设计了异步电机矢量控制系统。仿真结果表明了该理论的正确性和可行性。     

A PEEC with a new capacitance model for circuit simulation ofinterconnects and packaging structures

In this paper, a modified partial-element equivalent-circuit (PEEC) model, i.e., (L_p, A&oarr;, R, ϵf)PEEC, is introduced. In such a model, no equivalent circuit, but a set of state equations for the variables representing the function of circuit, are given to model a three-dimensional structure. Unlike the original (L_p, P, R, ϵf) PEEC model, the definition of vector potential A&oarr; with integral form and the Lorentz gauge are used in expanding the basic integral equation instead of the definition of the scalar potential φ with integral form. This can directly lead to the state equations, and the capacitance extraction can be replaced by the calculation of the divergence of A&oarr;, which is analytical. For analysis of most interconnect and packaging problems, generally containing complex dielectric structures, the new model can save a large part of computing time. The validity of the new model is verified by the analysis in time and frequency domain with several examples of typical interconnect and packaging structures, and the results with this new method agree well with those of other papers     

Generalized Partial-Element Equivalent-Circuit Analysis for Planar Circuits With Slotted Ground

A generalized partial-element equivalent-circuit (PEEC) method is proposed for modeling a planar circuit with a thin narrow slot on the ground. The approach is based on the coupled mixed potential integral equations for a problem with mixed electric and magnetic currents. The coupled integral equations are converted into a lumped-element circuit network using Kirchhoff's voltage law and Kirchhoff's current law of the circuit theory. The full-wave Green's functions for a grounded dielectric substrate problem are used. The interactions between electric current on a microstrip line and magnetic current on a slot are taken into account by introducing two kinds of controlled sources. This generalized PEEC model will be very useful in signal-integrity analysis for multilayered circuits. To validate the generalized model, three numerical examples consisting of microstrip lines and slots on the ground are presented. The results obtained by the proposed generalized PEEC model are compared with those obtained by commercial electromagnetic simulation software and published experimental results. Good agreement is obtained.      

Accuracy and stability improvements of integral equation modelsusing the partial element equivalent circuit (PEEC) approach

The partial element equivalent circuit (PEEC) technique is a formulation which transforms an electric field integral equation (EFIE) into a full-wave equivalent circuit solution. In this paper, improvements are made to the PEEC model through the development of a refined method of computing both the partial inductances as well as the coefficients of potential. The method does not increase the number of unknowns. In addition, damping is added to the PEEC model in order to further reduce nonphysical resonances which may occur above the useful frequency range, The observations and solutions presented in this paper are especially important for time domain solvers. The effectiveness of the method is illustrated with several examples     

Comprehensive Broad-Band Electromagnetic Modeling of On-Chip Interconnects With a Surface Discretization-Based Generalized PEEC Model

A surface integral equation formalism is proposed for broad-band electromagnetic modeling of on-chip signal and power distribution networks. The discrete model is developed in the spirit of the partial element equivalent circuit (PEEC) model, which is extended with several attributes that lead to enhanced modeling versatility, modeling accuracy, and numerical solution robustness from dc to multigigahertz frequencies. Instead of the volumetric discretization model, which has dominated the PEEC-based schemes for handling the tall and slim cross sections of the on-chip wiring, the proposed model relies on a computationally more efficient conductor surface discretization. Key to the effectiveness and accuracy of the proposed surface discretization is the definition of a frequency- and position-dependent impedance quantity on the conductor surface. Its numerical computation over the frequency bandwidth of interest is expedited through the implementation of a complex frequency-hopping algorithm. The resulting effective surface impedance is combined with a mixed triangular/rectangular meshing of the conducting surfaces for the approximation of the surface electric current and charge densities. A systematic strategy for the identification of loops in the resulting discrete model is used to ensure a numerically stable mesh analysis-based PEEC formulation for on-chip signal and power distribution modeling with electromagnetic accuracy from dc to multigigahertz frequencies.     

Stability of discretized partial element equivalent EFIE circuitmodels

The instabilities associated with integral equation techniques for-the solution of electromagnetic problems in the time domain are well known. Instabilities may be due to either the numerical technique used for the time integration, or problems created by the discrete representation for the numerical solution of the problem. In this paper, we concentrate on the discretization issue. The stability problem occurs for various discretizations and formulations. Here, we use the partial element equivalent circuit (PEEC) formulation of the electric field integral equation (EFIE) in the circuit domain. This leads to a better understanding of the issues at hand. We show why the discretized model can be unstable and we suggest a circuit motivated technique to stabilize the solution     

Solving Low-Frequency EM-CKT Problems Using the PEEC Method

The partial element equivalent circuit (PEEC) formulation is an integral equation based approach for the solution of combined electromagnetic and circuit (EM-CKT) problems. In this paper, the low-frequency behavior of the PEEC matrix is investigated. Traditional EM solution methods, like the method of moments, suffer from singularity of the system matrix due to the decoupling of the charge and currents at low frequencies. Remedial techniques for this problem, like loop-star decomposition, require detection of loops and therefore present a complicated problem with nonlinear time scaling for practical geometries with holes and handles. Furthermore, for an adaptive mesh of an electrically large structure, the low-frequency problem may still occur at certain finely meshed regions. A widespread application of loop-star basis functions for the entire mesh is counterproductive to the matrix conditioning. Therefore, it is necessary to preidentify regions of low-frequency ill conditioning, which in itself represents a complex problem. In contrast, the charge and current basis functions are separated in the PEEC formulation and the system matrix is formulated accordingly. The incorporation of the resistive loss (R) for conductors and dielectric loss (G) for the surrounding medium leads to better system matrix conditioning throughout the entire frequency spectrum, and it also leads to a clean dc solution. We demonstrate that the system matrix is well behaved from a full-wave solution at high frequencies to a pure resistive circuit solution at dc, thereby enabling dc-to-daylight simulations. Finally, these techniques are applied to remedy the low-frequency conditioning of the electric field integral equation matrix     

Analysis of 3-D interconnect structures with PEEC using SPICE

This paper discusses the possibilities of using the circuit simulation program, simulation program with integrated circuit emphasis (SPICE) for the simulation of partial element equivalent circuit (PEEC) models. After an introduction into the PEEC method, the simulation of quasi-stationary models is considered. An enhancement of SPICE is described, allowing the simulation of retarded PEEC models. This enables the computation of electric fields radiated from an interconnection structure. With the modified SPICE simulator it is possible to use existing SPICE models and combine them with full wave PEEC models     

Impact of partial element accuracy on PEEC model stability

This paper details the impact of partial element accuracy on quasi-static partial element equivalent circuit (PEEC) model stability in the time domain. The potential sources of inaccurate partial element values are found to be poor geometrical meshing and the use of unsuitable partial element calculation routines. The impact on PEEC model stability of erroneous partial element values, and the coefficients of potential and partial inductances, are shown as theoretical constraints and practical results. Projection meshing, which is a discretization strategy suitable for the PEEC method, is shown to improve calculated partial element values for the same number of unknowns, thus improving model stability.     

Broadband Macromodels for Retarded Partial Element Equivalent Circuit (rPEEC) Method

The partial element equivalent circuit (PEEC) method is, nowadays, widely used in electromagnetic compatibility and signal integrity problems in both the time and frequency domains. Similar to other integral-equation-based techniques, its time domain implementation may suffer from late time instabilities, especially when considering delays [(Lp,P,R,tau)PEEC] (rPEEC). The cause of the instabilities may be either the numerical technique used for the time integration or problems created by the discrete representation of the electromagnetic continuous problem. In this paper, we concentrate on the latter and show that frequency dispersion plays an important role and must be taken into account in order to preserve accuracy and mitigate instabilities issues. An enhanced formulation of the PEEC method is presented that is based on a more accurate computation of partial elements describing the electric and magnetic field couplings; broadband macromodels are generated incorporating the frequency dependence of such elements, thus, allowing us to obtain better stability properties of the resulting (Lp,P,R,tau)PEEC model. The proposed equivalent circuits resemble those of the standard PEEC formulation but are able to capture the dispersion that, when neglected, might contribute to inaccuracies and late time instabilities     

PEEC Formulation Based on Dyadic Green's Functions for Layered Media in the Time and Frequency Domains

This paper presents a novel time- and frequency-domain concept of modeling with the partial element equivalent circuit (PEEC) method, which applies the mixed potential integral equation (MPIE) with dyadic Green's functions for layered media (DGFLM-PEEC). On the one hand, it represents an exact full-wave semianalytical solution for an arbitrary configuration of traces and via holes in multilayered printed circuit boards. On the other hand, the DGFLM-PEEC model is represented in a circuit form, and thus, may be included in general-purpose circuit simulators. The paper derives a general DGFLM-PEEC formulation, which may be applied to all types of the MPIE with dyadic Green's functions. Using this concept, a particular type of layered media, namely a lossy dielectric between two grounds (stripline region), is thoroughly investigated and used to set up a particular DGFLM-PEEC model. The closed-form expressions for partial inductances and potential coefficients have been derived for this case. The time- and frequency-domain DGFLM-PEEC models for the stripline region have been validated using the measurements and the simulation by the method of moments.