Equivalent Current Source Research Articles

Large-Signal Stable Nonlinear Control of DC/DC Power Converter With Online Estimation of Uncertainties

The passivity-based control (PBC) is recognized as an effective energy shaping approach to guarantee the asymptotic stability of the whole system by using the passivity property. However, the model- and sensor-based characteristics limit its development and application. The combination of the PBC and online estimation technique can solve these problems. The purpose of this article is to propose a controller and an observer, which are designed simultaneously based on Hamiltonian framework and Lyapunov criterion. It leads to the system design without separation of the dynamics of the controller and the observer. The uncertainties in the model and parameters are considered as equivalent voltage and current sources. To reduce the number of sensors, input voltage, output current, and equivalent sources are estimated together. The steady-state error is eliminated by using this estimation technique. The exponential stability of the whole system (converter, controller, and observer) is proved by using a proper Lyapunov function. Simulation and experimental results from a 3-kW 270–350-V dc/dc boost converter with a constant power load (CPL) are performed to confirm the proposed control algorithm. Since the system parameter values may vary with temperature and the equilibrium point, the robustness of the proposed method is verified without and with parameters uncertainties.

Analytical Correlation Between Time and Frequency Domain Shielding Effectiveness of Metallic Enclosures With Apertures

Time domain shielding effectiveness (SE) of metallic enclosures with apertures against electromagnetic pulse excitation has been analytically estimated and correlated to the frequency domain characteristics. The method is based on the analysis of the transient process at the aperture and an equivalent magnetic current source, to derive the initial peak amplitude appearing at the very beginning of the coupled field waveforms. The equivalent circuit model is utilized to analytically describe the frequency domain SE data. Then, a simple correlation formula has been derived, which relates the peak value reduction of the E-field and H-field to the specified spectral data minus a specially defined factor. Especially, the correlation for the E-field is shown to link the spectral SE data near the fundamental resonant frequency of TE101 mode with the peak amplitudes in time domain. A series of numerical and experimental cases have been checked to confirm the applicability of the analytical formulas. Comparisons between the data and the analysis exhibit reasonable agreements.

“Voltage-Current Ratio Difference” Concept for identifying the dominant harmonic source

This paper proposes a new concept for identifying the harmonic dominant side. The proposed concept is named as “voltage-current ratio difference” for determining the dominant equivalent harmonic voltage source and “current-voltage ratio difference” for determining the dominant equivalent harmonic current source. In contrast to most previous methods, the proposed concept does not require the equivalent harmonic impedance (or admittance) of the utility and customer sides as input data. Indeed, this concept requires the measured harmonic voltage as well as current at the point of common coupling in two states: in normal operation and in operation with the installation of a known serial impedance (or parallel admittance) between the utility and customer. The methodology and application of this concept are thoroughly presented in this paper. In addition, some practical issues about the implementation of the concept are discussed. In this regard, requirements for the serial impedance (or parallel admittance) at the fundamental frequency and at each harmonic order are defined to yield reliable results.

A Perturbative Stochastic Galerkin Method for the Uncertainty Quantification of Linear Circuits

This paper presents an iterative and decoupled perturbative stochastic Galerkin (SG) method for the variability analysis of stochastic linear circuits with a large number of uncertain parameters. State-of-the-art implementations of polynomial chaos expansion and SG projection produce a large deterministic circuit that is fully coupled, thus becoming cumbersome to implement and inefficient to solve when the number of random parameters is large. In a perturbative approach, component variability is interpreted as a perturbation of its nominal value. The relaxation of the resulting equations and the application of a SG method lead to a decoupled system of equations, corresponding to a modified equivalent circuit in which each stochastic component is replaced by the nominal element equipped with a parallel current source accounting for the effect of variability. The solution of the perturbation problem is carried out in an iterative manner by suitably updating the equivalent current sources by means of Jacobi- or Gauss-Seidel strategies, until convergence is reached. A sparse implementation allows avoiding the refinement of negligible coefficients, yielding further efficiency improvement. Moreover, for time-invariant circuits, the iterations are effectively performed in post-processing after characterizing the circuit in time or frequency domain by means of a limited number of simulations. Several application examples are used to illustrate the proposed technique and highlight its performance and computational advantages.

A new analytical conducted EMI prediction method for SiC motor drive systems

Abstract Although silicon carbide (SiC) devices can greatly improve the energy efficiency of electric motor drive systems and increase the power density of inverters as well in electric vehicle applications, fast switching and high-frequency operations of the devices bring more serious electromagnetic compatibility (EMC) problems. It is very important to predict the electromagnetic interference (EMI) level of SiC motor drive systems at design phase. However, since the megahertz resonances caused by the system parasitic parameters can’t be ignored, conventional EMI prediction methods need to be improved. In this paper, the fast switching transient of SiC devices, the power module parasitic parameters, and other detailed circuit parameters are modeled into the EMI sources and propagation paths. In the differential mode (DM) and common mode (CM) EMI sources modeling, both the equivalent switching current sources and the equivalent switching voltage sources of SiC devices are simultaneously taken into account. The proposed analytical method can accurately predict conducted EMI in the SiC motor drive system in frequency range from 150 kHz to 30 MHz. Compared with the previous conventional methods, the proposed method improves DM EMI prediction accuracy of the SiC motor drive system in high frequency range.

Coupling analysis of multiple linear antennas fed by coaxial lines on electronic system with a time domain hybrid method

AbstractDue to the shielding structures of electronic system and coaxial lines feeding the antennas are complex, full‐wave algorithms applied for the coupling analysis of multiple linear antennas on electronic system excited by ambient wave should occupy amount of memories by meshing the structures of coaxial lines and electronic system in fine grid, which may affect the computation efficiency. This paper presents a time domain hybrid method, which consisting of thin wire finite‐difference time domain (FDTD) method, transmission line (TL) equations, higher order FDTD scheme, and an auto mesh generator technique. In this method, the thin wire FDTD combined with the auto mesh generator technique is utilized to mesh the shielding structure of electronic system rapidly and obtain the current responses on the conductor columns of linear antennas, which are extracted equivalent current sources for the further coupling analysis of coaxial lines. And then the TL equations are adopted to build the coupling models of coaxial lines, and solved by the higher order FDTD scheme to compute the transient responses on the coaxial lines and terminal loads of the lines. This method has one significant feature is that it can avoid modeling the structures of linear antennas and coaxial lines directly. The accuracy of this method has been verified by comparing with the simulation software Computer Simulation Technology (CST) via the coupling simulations of one and three linear antennas on electronic system excited by ambient plane wave.

A volume structure based ECS-PER algorithm for the hybrid electromagnetic field-circuit simulation

A new algorithm for the hybrid electromagnetic (EM) field-circuit simulation is proposed. It employs the equivalent current source with parallel equivalent resistance (ECS-PER) to simulate the effect of an EM subsystem on a circuit subsystem and adopts the volume structure to map the lumped circuit into the finite-difference time-domain cells. By including an additional current term in Maxwell-Ampere’s Law to represent the current density of the lumped circuit and using the finite difference scheme, the formulas of the proposed volume structure based ECS-PER algorithm is deduced for the first time. Two numerical examples of microwave circuits radiated under external EM incidence are simulated, and the results verify the accuracy and versatility of the proposed algorithm.

A Quasi-Magnetic-Electric Circularly Polarized Antenna With Wide Bandwidth

A new quasi-magnetic-electric circularly polarized (CP) patch antenna with a wide bandwidth is proposed. The proposed antenna has a low-profile structure with a single feed and provides CP radiation with a stable gain. It consists of a shorted bowtie patch antenna that works as an equivalent magnetic current source and a bowtie dipole that acts as an electric current source. With a single feed, the two orthogonal current sources are combined to generate a circular polarization. For the proposed antenna, measurement results show that an impedance bandwidth of 31.7% and a 3 dB axial-ratio bandwidth of 15.3% are achieved. The antenna has a gain of about 7 dBic in the band of interest and a cross-polarization level of about -19 dB at the central frequency.

General Diffraction Mechanism Interpretation of Electromagnetic Transient Scattering From Large Scatterers by Time-Domain Aperture Integration Technique

The diffraction mechanisms of electromagnetic (EM) transient scattering from large scatterers are examined by applying a general time-domain aperture integration (TD-AI) technique when the scatterer is illuminated by an incident EM field. This incident field exhibits a transient-step field response and can be the radiation from a relatively arbitrary EM source located at any place. The mechanism is interpreted by considering an equal time-delay curved aperture (ETDCA) where a set of EM equivalent current sources are defined to radiate the scattering field. The transient responses at any instant time are then found by considering the effects of equal net time-delay in propagation when the incident wave propagates to the field point via EM scattering from the scatterer. A contributing contour in the radiation integral of the equivalent currents define on the ETDCA by its intersection with a time-varying equal path-length sphere defined by the field point is therefore extracted to reduce the surface integral into a line one. The characteristics of this contributing contour are employed to interpret the EM scattering mechanisms. Practical numerical examples are presented to demonstrate the validity and feasibility of this general TD-AI technique.

A time-domain method for the electromagnetic transient response of multiconductor transmission lines excited by the electromagnetic pulse

An efficient field-to-line coupling method in the time-domain is developed based on the waveform relaxation (WR) techniques for evaluating the electromagnetic(EM) transient response of multiconductor transmission lines (MTLs) excited by an electromagnetic pulse(EMP). Firstly, the incident EMP electric fields on the lines are calculated as equivalent distributed sources introduced into the MTLs equations. Then, the telegraphs equations of lossless transmission lines are decoupled by applying the WR techniques and different types of equivalent current sources at the terminal of MTLs are calculated using the iterative convolution and analytical method separately. Finally, the equivalent circuit is established and the transient currents/voltages induced on the lines are obtained by using the circuit simulation software PSCAD. The proposed time-domain method has the advantages of accuracy and high efficiency compared with the method based on finite-difference time-domain (FDTD) via two numerical examples.

Common mode electronic noise in differential circuits

Differential circuits are assumed to reject common-mode noise yet no parameter is available to describe that rejection as the Common Mode Rejection Ratio (CMRR) applies only to deterministic signals, not to random noise. We propose a model and a method to analyze the contribution of the input common-mode electronic noise to the output voltage noise of differential circuits. The analysis shows that the same parameter-matching conditions that improve the CMRR determine common-mode noise rejection but CMRR is more sensitive to mismatching. For example, a low-frequency CMRR as low as 8 dB implies that more than 82% of common-mode noise is rejected. Thus, often only differential-mode noise is relevant. However, if the equivalent input current noise sources predominate over equivalent input voltage noise sources, cross-correlation between them partially yields common-mode noise that will also be rejected. We also propose a simple test that yields an estimate of that correlation.

Equivalent current dipole source localization of deceptive response during crime-relevant sentence processing

Equivalent current dipole source localization of deceptive response during crime-relevant sentence processing

Thunderstorm generators operating as voltage sources in global electric circuit models

The description of global electric circuit (GEC) generators in continuous numerical models is analysed and discussed. It is shown that voltage-source generators, sometimes employed in simple lumped-element GEC models, have a consistent generalisation in continuous GEC models: just as current-source generators generalise to source current density distributions, voltage-source generators generalise to distributions of the relative potential on cloud boundaries. The difference between non-ideal and ideal current or voltage sources is investigated for both lumped-element and continuous GEC models. As in modern three-dimensional GEC models the formal generalisation of voltage-source thunderstorms turns out to be difficult to implement, two alternative approaches involving the replacement of voltage-source generators with equivalent current-source generators are developed. One approach is based upon a rough estimation of the source current producing the same contribution to the GEC as the original voltage source; the other approach uses the fact that each voltage-source generator can be shown to be a limiting case of a certain current-source generator with increased conductivity. For the first time voltage-source generators are implemented in a numerical GEC model (using both the direct generalisation and the suggested alternative approaches).

2-D Equivalent Source Method for a Finite Periodically Loaded Multiconductor Transmission Line Analysis With an Application to EBG Power Distribution Networks

A novel theoretical model based on an equivalent source method and a modal superposition technique is proposed to derive a dyadic Green's function for two-dimensional (2-D) finite periodically loaded multiconductor transmission lines (MTLs) to efficiently analyze electromagnetic band gap (EBG) structures embedded in power distribution networks (PDNs) for noise suppression. Many of such structures can be easily modeled using an MTL model with periodically loaded series and shunt components. By treating each periodic load as an equivalent local current source at the center of each unit cell, based on equivalent source theory, a finite uniform 2-D MTL excited by a group of equally spaced equivalent current sources is obtained. The amplitude of these local exciting sources may be analytically evaluated for the modes in the structure. Upon identifying these local equivalent current sources, a simple analytical expression for the 2-D dyadic Green's function is derived based on the modal superposition technique. For validation, a mushroom-type EBG structure embedded in a typical PDN is examined using the proposed approach and comparison with full-wave simulations and measurements are presented.

Improving of operation stability of frequency converters with active rectifiers in electric steel-making complex electrical equipment switching

Frequency converters with active rectifiers (FC-AR) are now used in rolling mill electric drives. Modern control systems of ARs are not adapted to voltage sags in power supply systems, which leads to converter tripping. The known methods of ensuring AR operation stability, such as kinetic buffering, correction signals based on negative sequence voltage and others, do not eliminate these emergency trips. As an additional measure the paper proposes the method of voltage sag compensation by using static var compensators (SVC) of electric arc furnaces (EAF) for parallel operation of frequency converters with active rectifiers and electric arc furnaces. However, it remains unknown how disturbances (such as overvoltages of switching of SVC harmonic filters (HF) and voltage sags during furnace transformer switching) affect operation stability of frequency converters with active rectifiers. All this makes it necessary to study the effect of these processes on the operation conditions of FC-AR and to improve the active rectifier control system. The authors used experimental arrays of instantaneous values of voltages and currents of the real-life complex «EAF-SVC» («Electric Arc Furnace – Statistic VAR Compensator») in this study. They also applied mathematical models of FC-AR with different PWM algorithms realized in Matlab-Simulink software. The main assumption of the model consists in using equivalent current sources modelling the operation of autonomous voltage invertors. An improved control system of AR has been developed. The main feature that distinguishes it from the known systems is the fact that it ensures operation stability during SVC harmonic filter and EAF transformer switching by using a signal conditioning unit for setting the active rectifier reactive current component as a function of power supply and AR input voltage difference. Implementation of the improved AR control system improves FC-AR stability during parallel operation with EAFs through reactive power consumption of the supply system. As a result, it reduces the amplitude of inrush current and voltage deviations in the DC-link of the FC-AR to the values lower than the setpoints of the AR protection system.

Experimental and numerical analysis of the magnetophoresis of magnetic nanoparticles under the influence of cylindrical permanent magnet

Abstract Dye-tracing and concentration-measuring experiments are carried out to investigate the magnetophoresis of magnetic nanoparticles (MNP) in the presence of an external cylindrical permanent magnet. The magnetophoresis of MNP, inducing an obvious forced-convective flowing of the carrier fluid, which can be observed by visualizing flowing of carrier fluid, results in a temporal and spatial variation of particle concentration. Moreover, in order to get insight into the physical mechanisms of magnetophoresis of MNP, a coupled particle-fluid analysis, in which the non-linear drift-diffusion differential equation is incorporated into the Navier-Stokes equation, is adopted to discuss the influence of particle-fluid interaction on the variation of particle concentration and the kinetics of carrier fluid. It is worth noting that the equivalent current source (ECS) method is adopted to obtain a closed-form field analysis, which provides exactly prediction of the Kelvin force and enables magnetophoretic analysis more efficient. In dye-tracing experiments, an obvious vortex can be observed as the methylene blue moves with the convection of carrier fluid. Furthermore, this phenomenon is also predicted by using the coupled particle-fluid model. A comparison between the experimental and numerical results shows that the hydrodynamic interactions between MNP and carrier fluid plays an important role in inducing forced-convective flowing of carrier fluid and enhancing the magnetophoresis of MNP. Furthermore, these results also denote that the coupled particle-fluid model provides a more efficient and accurate method in investigating the magnetophoresis of MNP.

Electromagnetic Transient-Transient Stability Analysis Hybrid Real-Time Simulation Method of Variable Area of Interest

To make the object of electromagnetic transient (EMT) simulation flexible to change, the authors propose using the method of electromagnetic transient-transient stability analysis (TSA) hybrid real-time simulation of the variable area of interest. The area where the fault is to be set, or where the operation takes place, is defined as the area of interest. The simulation object is divided into multiple sub-networks. The EMT simulation range is determined according to the voltage drop depth at the boundary of the adjacent sub-network caused by the three-phase short-circuit fault at the boundary of an area of interest. The Norton equivalent is obtained by using the sub-network as a basic unit. The electromagnetic sub-network forms its own Norton equivalent on the TSA side by means of the Norton equivalent admittance of its TSA model. Based on this, the overall framework of hybrid real-time simulation of the variable area of interest is constructed. The fundamental phasor prediction and Norton equivalent current source prediction are adopted to reduce the interface error. The performance of the proposed method in terms of feasibility, flexibility, and effectiveness have been verified by the simulation studies on the IEEE 118-bus system.

On the Dominant Harmonic Source Identification— Part I: Review of Methods

Analyzing the harmonic distortions at the point of common coupling is thoroughly addressed in this two-part paper. The main aim of such an analysis is to identify which of the utility and customer sides is significantly responsible for the harmonic distortions at the point of common coupling. In Part I, the meaning of the dominant side is challenged fundamentally. Here, two different definitions for the dominant side are discussed: The side with the larger equivalent harmonic “voltage” or “current” source. It is shown that these definitions are not identical. Subsequently, common methods are categorized in three general concepts based on: the direction of active power flow, the reactive power, and the voltage-current ratio. These three categories as well as their validity are analytically reviewed for both the definitions. The concept based on the voltage–current ratio has been explicitly presented in the original work for identifying the dominant equivalent harmonic voltage source. This concept is developed in this paper for identifying the dominant equivalent harmonic current source as well. In Part II, the application of the methods is illustrated using some common calculation examples. In addition, these methods are described verbally to provide a physical interpretation. Some practical aspects regarding the implementation of the methods are discussed as well.

Electric power transfer in spin-pumping experiments

Spin pumping has become an established method for generating voltages using magnetic dynamics. The standard detection method of spin pumping is based on open-circuit voltage measurement. In this study, we demonstrate that it is also possible to measure the associated electric current by using macroscopic closed circuitry. Using variable load resistors connected in series to the sample, we quantified the charge currents and associated electric power dissipation with respect to the load resistance. Through basic circuit analysis, we can describe spin-pumping cells as a non-ideal voltage source or an equivalent current source with an internal resistor.

Application of Shifted Frequency Internal Equivalence to Multifrequency Scattering Problems

In this paper, a simple solution is presented for multifrequency electromagnetic scattering from inhomogeneous bodies. Shifted frequency internal equivalence is used to replace the electromagnetic problem at operating frequency $\omega $ by equivalent volume and current sources at internal frequency $\omega _{0}$ , and hence repeated calculation of system matrix as in the solution of volume integral equation at multiple frequencies is avoided. The volume field equation and surface tangent field equations obtained from the internal and external problems, the substitutes of the original scattering problem internally and externally, are solved by method of moments with pulse function expansion and point matching. Numerical results demonstrate that the proposed method is accurate and efficient within a wideband, fractional bandwidth being typically 100%.