Lagrangian‐based equivalent circuit of basic electric‐field coupling wireless power transfer system

Electric‐field coupling wireless power transfer has been commonly analyzed using the circuit model. However, the circuit behavior of this model is not necessarily apparent because their resonant modes can be far complicated than the basic LC oscillation. This issue is addressed in this paper by proposing a novel equivalent circuit for a basic wireless power transfer system. This equivalent circuit has a simpler topology than the conventional circuit model. Furthermore, the equivalent circuit allows intuitive understanding of three types of the resonant modes. Along with theoretical derivation of the proposed equivalent circuit, this paper also presents simulation results, which verified the appropriateness of the equivalent circuit. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Electrical analysis of step-up multi-layered piezoelectric transformer

In this paper, the equivalent circuit model of a multilayer piezoelectric transformer (MPT) has been proposed and MPT has also been fabricated using PMS-PZT to investigate the load and frequency characteristics. The model taking into account the loss and the shift of resonant frequency due to the change of a stiffness caused from the lamination is developed based on Mason’s equivalent circuit. The symbolic expressions were derived from the model. To verify the accuracy of the proposed equivalent circuit model, MPT have been simulated. The simulation results have been compared with the experimental data. They are shown to agree well over a wide range of various frequency and the load resistance.     

Fault calculations using three terminal Thevenin’s equivalent circuit

The aim of this paper is to present a systematic approach of calculating fault currents due to the switching of elements or fault impedances that involve two buses and ground. Traditionally, Thevenin’s equivalent circuits are made up of two terminals suitable for calculating the current into an element connected between both terminals of the equivalent circuit. In such cases, the current entering the element is equal to the current leaving the element. So many practical cases involve elements that have a third terminal connected to ground. Tee and pi models of transmission lines are examples of such cases. Traditionally, the two terminals Thevenin’s equivalent circuit is used to tackle such problems by decomposing the three terminal element into its basic elements. The problem is then transferred to a multi element application where each element is processed once a time. This approach is cumbersome and time consuming. In this paper, a systematic approach to applying the three terminal Thevenin’s equivalent circuit to three terminal elements is proposed.     

Circuit modeling and efficiency analysis for wireless power transfer system with shielding

It is an effective way to use magnetic shielding scheme in magnetic coupled wireless power transfer (WPT) system to reduce magnetic flux leakage. However, the additional shielding material would affect the equivalent circuit model and the power transmission efficiency of WPT system. Although the impact of some common shielding materials on the transmission efficiency has been studied using finite element simulation, there is still a lack of understanding about the impact to the equivalent model in theory. In this paper, the equivalent circuit and transmission efficiency of WPT system are analyzed theoretically under the influence of different shielding materials, and the relationship between material electrical characteristics and transmission efficiency is presented. In our WPT prototype with two 166-mm diameter coils under ferrite shielding and aluminum shielding, the achieved maximum transmission efficiencies are 95.7% for 100-kHz resonant frequency and 97.9% for 1-MHz resonant frequency under the ferrite shielding, and the efficiency errors between the analytical and experimental results are less than 5% for 100-kHz resonant frequency and 10% for 1-MHz resonant frequency.     

应用StatMod对开关电路传导共模电流的建模

开关电路的EMI噪声与电路的拓扑布线密切相关。由于对共模电流精确仿真的需要,采用基于局部元等效电路法（partial element equivalent circuit,PEEC)的软件StatMod分析开关电路的共模电流,对电路的寄生参数进行抽取和计算。建立这一模型的基础在于,共模电流主要和各个节点的分布电容有关,尤其是那些具有高di/dt和高dv/dt的电路节点。实验结果表明,所建立的共模电流模型10MHz范围内和仿真结果基本符合。     

Using a Debye polarization cell to predict double-layer capacitorperformance

Many different circuit models have been proposed for double-layer capacitors (DLCs). Presented in this paper is an evaluation of the Debye polarization cell as a model for a double-layer capacitor (DLC). In comparison to other circuit models, the primary advantage of this model is that the circuit elements can be related to chemical reactions which occur inside the DLC. The circuit element values are found from AC impedance measurements for a DLC and a computer program which utilizes a nonlinear least-squares fitting technique. Variations in circuit element values with DC bias level and manufacturing have been investigated. The performance of the Debye polarization cell in slow discharge and pulse load applications has been compared to actual circuit measurements and to simulated results using a classical equivalent circuit     

Electromechanical energy conversion in a system with a bulk high-temperature superconductor. Part 2. Device operation analysis

The operation of a linear electromechanical vibration device with a part made of a high-temperature superconducting (HTS) material is analyzed. Converter models considered in the first part of this paper [1] are used in the calculations. The parameters of the model of HTS material properties are determined by comparison of the data obtained by calculations and by experimental investigations of force interactions in the laboratory device model. Functions of flux linkage and current force in the coil and permanent magnet movements are calculated for a macroscopic model based on analysis of the electromagnetic field. The calculation results of the operation parameters of the electromechanical converter are shown in the form of amplitude-frequency characteristics of the current in the coil, the permanent magnet movement amplitude, and electrical and mechanical power. Dependences of powers, efficiency, and current phase on the active mechanical load on the resonant frequency are determined. The obtained characteristics are compared with simulation data of a similar converter without the HTS element. It is concluded that the HTS elements significantly change the parameters of the conversion of electrical energy into mechanical energy. It is shown that the electromechanical converters with bulk HTS elements can be more efficient than converters of traditional design.     

基于同轴谐振腔法的材料电参数测量

以岩石电参数测量为背景,根据岩石材料的电性特点,对谐振腔法测试电参数进行了比较详细的研究.利用仿真软件设计并改进了常规谐振腔的结构,设计了一种小型化和有效的测量仪器,以方便携带和使用.然后,利用微扰法和建立等效电路模型对谐振腔进行建模,推导出电参数和谐振腔参数直接的关系,再通过拟合的办法得到关系式的参数信息.对模型进行仿真测试,比较了等效电路模型和微扰法的精度,可以看出等效电路模型的测量误差小于5%.最后搭建了测试系统,对一些材料进行测试,得到了满足测试要求的结果,并分析了测量系统的不足以及改进方法.     

高压电容器充电电源谐振变换器的定频控制

为有效控制高压电容器高频恒流充电电源谐振变换电路的开关频率,研制了定频控制(占空比为50%,开关频率在整个充电过程中保持不变)的20 kW高压电容器充电装置逆变电路开关电路。通过提出的充电电源电路的并联负载谐振(PLR)DC-DC变换电路的等效电路模型,研究了充电电源装置的恒流充电原理,找出了电容充电初始阶段谐振电流和开关频率的数值关系。实验研究结果表明,当谐振变换电路开关频率接近于等效电路固有谐振频率的奇数分之一时,产生较大的谐振电流;为了实现谐振变换电路开关器件的零电流开通和关断,开关频率的大小始终可控制在小于等效电路固有谐振频率的1/2的范围之内。     

双斜槽转子感应电机的快速场路耦合分析

为克服双斜槽感应电机轴向拓扑仿真时需采用低效率高精度的三维有限元仿真的问题,针对错开双斜槽转子感应电机(DSRIM)提出一种等效电路,然后基于多层有限元模型建立DSRIM的轴向分层等效电路。在等效电路与磁场耦合分析的基础上,运用分布磁路法求出气隙磁场分布与稳态性能指标。与试验结果进行对比,对比结果显示该方法的计算结果具有指导意义。     

一种高频LCC谐振变换器的近似分析方法

为了研究具有电容型滤波器的LCC串并联谐振变换器的电路特性,在变换器工作原理分析的基础上,用一种近似分析方法对电路进行了数学分析,推导了该变换器的等效电路,并在等效电路的基础上讨论了该变换器的电路特性.研究负载电容的取值对变换器输出电压纹波的影响,并介绍LCC谐振变换器等效电路元件参数的计算表达式.仿真和实验提供的数据...     

基于等效电路模型映射的DGS低通滤波器设计

在分析缺陷地结构(DGS)单元及其等效电路模型的基础上,采用了一种新颖的椭圆DGS单元并建立了椭圆DGS单元与其等效电路之间的映射关系。根据该映射关系利用电磁仿真的S参数提取出等效电路模型的元件值,通过基于矩量法(MoM)的快速电路仿真优化得到目标频率响应对应的电路元件值,根据电路优化的结果调谐低通滤波器的电磁模型。最终获得所需低通滤波器结构。实验证明该滤波器的电磁仿真、等效电路仿真及实测结果吻合,验证了该设计方法的有效性和准确性。     

双定子超环面电机磁路模型与气隙磁场研究

双定子超环面电机是一种新型结构的空间电机,将动力和减速机构有机结合,在机器人和航空航天领域具有很好的应用前景。在对该电机的结构特点及运行原理进行分析的基础上,将其三维磁路分解为周向和环向磁路,并建立了简化的等效磁路模型。根据该电机的结构特点对磁路模型中各磁阻进行推导,并对其静态磁场的气隙磁密进行了解析求解。为了验证该磁路模型的准确性,运用有限元方法对其三维磁场进行仿真分析,并对研制实验样机的反电动势进行了测试实验。通过与仿真结果和实验结果进行对比分析表明,该等效磁路模型和参数计算方法是可行的,为进一步定量分析该电机的电磁性能提供了理论依据。     

Equivalent circuit for RF flexural free-free MEMS resonators

A method to extract a lumped-parameter equivalent circuit for a free-free flexural MEMS resonator, based on the Euler-Bernoulli beam equation and exploiting a modal analysis approach, is presented. The dynamic behaviour predicted by the equivalent circuit is compared with FEM simulations, and the effect of a geometrical mismatch is investigated as well. The resonance frequency and the quality factor are correctly predicted. The method could be used for more complex systems of interconnected beams. The circuit can be used as a quick and intuitive analysis tool for the system-level designer and to allow the simulation of the device in a system-level design environment.     

Modeling and analysis method of fractional-order buck–boost converter

In this paper, the equivalent small parameter method (ESPM) is used to establish the nonlinear mathematical model of the fractional-order buck–boost converter in continuous current mode (CCM), and the analytical expression of approximate steady-state period of converter state variable is obtained by using equivalent small parameter method and combining with harmonic balance principle. The Matlab/Simulink is used to construct the fractional-order capacitance and inductance and to build the circuit model as well as the simulation model of fractional-order buck–boost converter. Moreover, the simulation results of Oustaloup circuit model and numerical simulation model are compared with those of ESPM model to verify the validity and accuracy of the ESPM. The model is simulated by changing the orders of the capacitor and inductor to obtain the influence rule of the order of fractional element on harmonic characteristics of the state variables.     

27.5 kV永磁机构真空断路器动作特性仿真与试验研究

针对27.5kV永磁机构真空断路器并根据其动作特点,进行了基于Ansoft和Matlab软件的静态、动态特性仿真。首先,建立有限元模型,利用Ansoft软件包对永磁机构的静态特性进行仿真。其次,根据耦合电压平衡方程和达朗贝尔机械运动特征方程,在静态仿真基础上采用Matlab构建永磁机构断路器的运动模型,对永磁机构动铁心、断路器动触头运动特性进行了仿真分析。最后,对设计的样机进行了动态测试,测试结果表明仿真的正确性。     

基于自定义模型的变压器纵差动保护PSCAD仿真

为了减少变压器的继电保护设计、整定计算存在的误差,提出一种根据内部漏抗参数等值计算与短路阻抗实际参数测定相结合的方法,利用曲线拟合技术,得出变压器在不同故障条件下的精确等值短路阻抗参数。在此基础上,采用FORTRAN语言接口技术,在PSCAD/EMTDC中,结合实际数字式变压器保护装置建立了主保护及后备保护的精确短路阻抗自定义模型,并利用等值系统模型对变压器线圈内部不同位置的对地短路、匝间短路、相间短路分别进行了仿真计算。结果表明,采用新型的拟合方法及自定义元件能准确地模拟并分析变压器内部故障及继电保护装置的动作行为,为继电保护的原理设计及实际应用提供科学依据。     

RTWUSM30环型行波超声波电机谐振升压驱动器的研究

从超声波电机等效电路出发,研究了无变压器驱动的谐振升压超声波电机驱动原理,以RTWUSM30超声波电机为对象分析了输出电压与电感、输出电压与占空比的关系,以及输出信号各次谐波幅值和谐波所占的总功率比值同驱动信号占空比的关系。并设计了电路驱动RTWUSM30超声波电机,试验结果证明了该方案的有效性和可行性。