Equivalent Circuit Model Approach Research Articles

On the physical system modelling of energy storages as equivalent circuits with parameter description for variable load demand (Part I)

Energy storages take a key role in electrical energy balancing in our power grid in respect to the increasing utilization of renewable energies. Assessing the effectiveness of energy storages and finding the optimal use under varying load conditions is essential which requires accurate modelling. This study highlights the equivalent circuit modelling approach for different energy storages. The model parameters R, L, C and Ub define the storage system in question allowing us to analyse storage devices under varying load conditions. Technical assessment criteria (efficiency, response time etc.) of energy storages can also be deducted from these models. Energy storages feature non-linear characteristics which are reflected in variable model parameters.

A unified modeling framework for lithium-ion batteries: An artificial neural network based thermal coupled equivalent circuit model approach

The thermal coupled equivalent circuit model provides a vital role not only in accurate and reliable state monitoring, but also in effective thermal management of lithium-ion batteries. However, it lacks appropriate modeling strategies for including both the temperature and state of charge effects into the thermal coupled equivalent circuit model. In this study, a unified artificial neural network based thermal coupled equivalent circuit model approach is proposed to accurately and reliably capture the electrical and thermal dynamics of lithium-ion batteries. Both reversible and irreversible heat generation mechanisms are introduced in the thermal model. The quantitative relationship between circuit parameters and temperature/state of charge in equivalent circuit model is modeled by artificial neural network. Both electrical and thermal related parameters are simultaneously identified by means of least square strategy with l1-norm penalty on output weights in artificial neural network and positive constraints on circuit parameters. The effectiveness of the proposed artificial neural network based thermal coupled equivalent circuit model approach is validated by the experimental constant current discharge, pulse current discharge test and hybrid pulse power characterization test of a commercial large-format pouch-type lithium-ion battery. It implies that the proposed hybrid modeling strategy can provide a general framework for the inclusion of other effects such as health state and current into battery models and can be easily extended to more complicated models such as first-principle electrochemical-thermal model.

Interfacial Impedance Characterization and Equivalent Circuit Modeling Analysis of a Li-O2 Battery

Lithium-oxygen (Li-O2) battery electrodes are known to form a film of alkyl carbonates and lithium products over cycling between the electrode/electrolyte interface, known as the solid electrolyte interface (SEI). That dielectric mostly comprise of products such as HCO2Li, CH3CO2Li, or Li2CO3 [1-3] if there are carbonate solvents, LiO2 from O2 - superoxide formation [2], stable Li2O, or unstable Li2O2 [1,2,4]. SEI film is a significant influence to cell performance, cycle life, self-discharge, safety, faradaic efficiency and physical electrode quality [5,6]. That build-up of lithium product on the cathode attributes to impedance growth with both reversible and irreversible product formation on the electrode surface. Furthermore, charge migration and dipole relaxation processes that dominate at high frequencies are greatly influenced by the type and severity of product deposition [7]. Past studies involving EIS measurements of Li-O2 batteries are accompanied by an equivalent circuit model (ECM), similar to the simplified model in figure (a). Furthermore, ECMs of surface films may utilize constant phase elements (CPE) when impedance measurements exhibit non-deal, CPE-like behavior. This may be physically due to surface heterogeneities, porosity, non-uniform coating, or slow adsorption. In any or all cases, this CPE behavior reflects a resistive and capacitive dispersion that results in a distribution of time constants, τ. Hence, the ECM that is proposed to describe the electrolyte-electrode surface film interface comprise of a solution resistance, Rs , in series with serial Voigt type parallel RC elements, as shown in figure (b), distributed normal to the bare electrode surface. Each Voigt element is a portion of the layer, each with its resistance, capacitance, and a corresponding τ for the process that produces that portion of the microfilm, such as from oxygen reduction, aging, or other side reactions from electrolyte, adding additional product. However, there may be some ambiguity since fitted models are determined by mathematical optimization and not electrochemical phenomena [8]. This work introduces a method for extracting resistive and capacitive values directly from high frequency EIS measurements after both charge and discharge. The results are compared to the parameters of an ECM interpretation of the same EIS data. The objective of this work is to take a non-ECM approach to high frequency impedance characterization of a binder-free Li-O2 battery, which would then be compared to the more common ECM approach to modeling interfacial impedance. Furthermore, a statistical analysis of the impedance distribution throughout the RC network will be discussed, where impedance from dispersive soruces may indicate distributed impedance like that of a normal or chi-squared distribution, rather than uniform.

Analysis and Design of Compact High Gain Microstrip Patch Antenna with Defected Ground Structure for Wireless Applications

Dual band Microstrip-Line-Fed low profile Microstrip Patch Antenna is proposed for wireless applications. A rotated rectangular shaped defect is embedded in the ground plane and fed with a 50-ź open ended Microstrip-Line. Dual band is achieved at 2.55 and 7.55 GHz. Antenna shows good radiation characteristics with peak gain of 8.1 dBi. Proposed antenna may be used for WiMAX applications with omnidirectional radiation pattern. Theoretical analysis is done for the proposed antenna by equivalent circuit model approach. Further, corners of the rectangular defect are truncated and a defected square ring is inserted inside the truncated-corners-rectangular-defect on the ground plane. 40 % of miniaturization is achieved and antenna starts to respond at 1.55 GHz with better radiation characteristics in both planes. Measured results of fabricated antennas are in good match with theoretical and simulated results.

VeloCité – Development of an Energy Storage System for an E-bike

Within the framework of the development of an energy storage system for a lightweight electric bicycle the electric behavior of LiFePO4 cells was investigated. We propose a systematic and efficient procedure for identification and parameterization of a cell model based on measurements in the time domain. An equivalent circuit model approach was adopted using parameters dependent on temperature and state of charge. The model was parameterized for a wide range of operational conditions concerning temperature, state of charge and cell current. Finally, the accuracy of the proposed model is shown by the comparison of simulation results with real measurements of the given cell using a highly dynamic driving cycle.

An ultra-wideband absorber based on graphene

Stealth technology is of great importance and significance in reducing the radar cross section and improving the survivability of the target aircraft. Absorber is one of the most important structures in stealth technology. However, the present investigations of absorbers mainly focus on the narrow band or multi-band. To extend the operation bandwidth, a graphene-based absorber structure is proposed in this paper. The proposed absorber has a periodic structure whose unit cell consists of a square and a circular graphene-based ring. The surface impedance of the periodic structure can be optimized to match the impedance of the free space in a very wide band by adjusting the electrostatic bias voltage. Then the operation band is significantly extended. By using the commercial software, CST Microwave Studio 2014, the performance of the proposed absorber is studied. The simulated results show that the proposed absorber can absorb electromagnetic (EM) waves in an ultra-wideband from 2.1 to 9.0 GHz, with an absorbing rate of up to 90%. Moreover, the proposed absorber is insensitive to the polarization of the incident wave due to the symmetry of the structure. We also find that the absorber can be tuned to work at any frequency in a range from 2.0 to 9.0 GHz for a fixed geometrical parameter. The equivalent circuit model (ECM) approach and interference theory (INF) are employed to investigate the physical mechanism of the proposed absorber. According to the ECM, we analyze the resonant characteristics of the square and circular graphene rings. Owing to the existence of two different graphene rings, two resonant frequencies are detected. By optimizing the structure parameters of the graphene rings, the two resonant frequencies are brought closer, resulting in the increase of the operation band. On the other hand, the real part of the input impedance of the equivalent circuit reaches up to about 300 Ω and the imaginary part is close to 0 Ω, which provides good matching to the free space, leading to high absorption rate. According to the interference theory, the amplitudes and phases of the direct reflection and the multiple reflections of EM waves are studied. It is found that the destructive interference between the direct reflection and multiple reflection makes the absorber have high performance in an ultra-wideband. The results obtained from ECM and INF are in good agreement with the simulation ones.

A Novel Microstrip-to-Microstrip Vertical Via Transition in X-Band Multilayer Packages

This paper investigates a novel X-band microstrip-to-microstrip vertical via transition with matching pads loaded signal via. This design has been proposed for a multilayer substrate package. The matching pads, which are located in the center of the signal via on each ground layer, are adopted to further improve the impedance matching level and thus attain better signal transition performance. A physics-based equivalent circuit modeling approach has been employed for this research. The right angle MS-to-MS via transition was also designed using this technique. The simulatedS-parameters indicate that the match-pad design made a breakthrough in achieving an approximate −15 dB wide-band return loss reduction. The measuredS-parameter of MS-to-MS transition showed that return loss with the matching pads is better than that without the matching pads.

Modelling of insulation characteristics of Solar Photovoltaic (SPV) modules

Dry and wet insulation characteristics of a Solar Photovoltaic (SPV) module have been studied through theoretical modelling supported by experimental results. A new equivalent circuit model approach has been used to understand the effect of resistances of the individual material used in the SPV module and the overall impact on the insulation characteristics. The electrical resistances of all the individual material have also been measured separately prior to lamination. It has been seen that, post lamination, the characteristics change significantly. EVA (Ethyl Vinyl Acetate) and Back-sheet (Tedlar) looses their separate identity and exhibit properties of a different new combined material. The resistance of this material has been determined using the equivalent circuit modelling approach. It has been shown that the insulation behaviour is primarily governed by this material. The temperature characteristics of the insulation leakage currents follow Arrhenius behaviour with well defined activation energies. It has been determined from the activation energies that the primary leakage path is from cell to EVA–Tedlar to frame of the module.

Design of broadband and tunable terahertz absorbers based on graphene metasurface: equivalent circuit model approach

This study presents an effective method to model, analyse and design graphene metasurface-based terahertz (THz) absorbers using equivalent circuit model approach. Broadband and tunable absorbers consisting of graphene metasurface and metal-backed dielectric layer have been designed based on the formulas derived from this approach and verified by full-wave electromagnetic simulation. By properly constructing the graphene metasurface, broadband absorption over 70% fraction bandwidth has been achieved, showing that graphene can provide a wideband absorption in the low THz spectrum. Furthermore, tunability of the graphene metasurface has also been investigated. It is demonstrated that the absorption peak frequencies can be tuned while maintaining the peak absorption unchanged, which is highly desirable for THz sensing applications.

Characterization and Modeling of Hysteresis for Magnetic Materials Used in EMI Filters of Power Converters

The magnetic material when designing EMI filter determines the inductance value and the parasitic elements that influence the insertion loss effectiveness of the filter. Moreover, the EMI filter characterization is usually realized at low power levels (low current and low voltage). When the EMI filter is subjected to higher currents through its coils, the principal characteristics of the filter (inductance variation with current and frequency) are modified. To account for these variations in the design step, it is useful to take into account the hysteresis model that represents the inductive and dissipative effects. Therefore, in this paper, an approach combining a magnetic hysteresis model together with a concept of material capacitance is proposed. The model is identified from a single turn of flat copper ribbon (STFC) experimental setup. Then, the experimental data are modeled with the proposed hysteretic and capacitive material behavior model (HCM) that is implemented in an equivalent circuit modeling approach, accounting for both the magnetic behavior law together with the “material capacitance.” The robustness of the proposed approach is evaluated by comparison and validation with the experiment results, showing good representation of the inductive and partially the dissipative effects.

Effects of porous materials in an insert earphone on its frequency response -experiments and simulations

This article presents a promising approach to customize the sound-pressure response of an insert earphone by delicately tuning the acoustic impedance of porous materials in it. The effects of applying porous materials on and in various parts in the insert earphone were tested experimentally to determine the resulting sound pressure responses. An equivalent circuit model (ECM) is also presented to simulate the sound-pressure-level (SPL) response of the insert earphone. For each part of the earphone, the effect of applying porous materials was simulated using the ECM approach. For porous elements, modified formulae with correction factors are proposed to determine the acoustic impedance. Comparisons of the simulated responses with experimental data have verified the veracity of the ECM simulations. The present work has verified the feasibility of adjusting the aeration of the porous materials to customize the resulting SPL response of an earphone.

Analysis of Common-Mode Noise for Weakly Coupled Differential Serpentine Delay Microstrip Line in High-Speed Digital Circuits

This study investigates the mechanisms of generation of the transient transmission common-mode noise in a differential serpentine delay line under weak coupling condition. The generation mechanism and the frequency of common-mode noise are investigated with reference to the time-domain transmission waveform and the differential-to-common mode conversion mixed-mode S-parameters using the circuit solver HSPICE and 3-D full-wave simulator HFSS, respectively. The generation mechanisms of common-mode noise include length mismatch between vertical-turn-coupled traces, the length effect of parallel-coupled traces, and the crosstalk noise effect. Moreover, a graphical method based on wave tracing is presented to illustrate the cancellation mechanism of near-end common-mode noise for the symmetrical differential serpentine delay line. Some practical, commonly used layout routings of the differential serpentine delay line are investigated. Some important design guidelines are provided to help design differential serpentine delay line with low common-mode noise. A comparison between simulated and measured results validates the equivalent circuit model and analytical approach.

An investigation on dielectric properties of major constituents of grape must using electrochemical impedance spectroscopy

The Australian wine industry has been undergoing an unprecedented growth during the last decade in both winery establishments and export volumes. Though automated controlling processes are useful for maintaining high quality products and reducing costs, the techniques are not widely adopted by small to medium sized wineries due to their relative high initial costs. In this paper, we investigate the dielectric properties of ethanol and organic acids, two major chemical ingredients that need to be monitored during wine fermentation using electrochemical impedance spectroscopy. The relationships between solution concentrations and parameters derived from the measured impedance spectra were investigated by two methods, the Nyquist plot approach and the equivalent circuit modeling approach. The investigation was carried out for both pure solutions including ethanol, malic acid and tartaric acid, the major constituents of grape must, and their various mixed compound solutions to simulate the grape must under fermentation. Strong linear as well as inverse-squared relations were found between the concentrations of the pure solutions and the derived dielectric parameters, e.g., the diameter of the Nyquist plot for ethanol has a correlation with concentrations with a coefficient of determination of 0.9796 and the R s value obtained from electric circuit modeling also shows a strong inverse-squared relationship with the concentration of both malic and tartaric acids. A further investigation suggests that the individual concentration of mixed acid solutions can be handily determined by measuring the impedance of the mixed acid solutions and using the initial concentration value of one of the mixed acids. Furthermore, the dielectric properties of mixed ethanol, malic acid and tartaric acid show a combined effort from mixed acid solutions and pure ethanol. These findings suggest that the electrochemical impedance, which can be easily measured with satisfactory accuracy, is a good indicator of the concentration change of the essential ingredients of grape must and thus can be further utilized to develop a feedback loop for wine fermentation automatic control.

Reduction in Reflections and Ground Bounce for Signal Line Over Slotted Power Plane Using Differential Coupled Microstrip Lines

This paper investigates the noise reduction in the slot-induced ground bounce noise by using differential signaling. An efficient 2-D finite-difference time-domain method together with equivalent circuits for both the differential line and the slot is established and simulations are performed for a three-layer structure to characterize the ground bounce coupling. A simple model is then proposed to understand how the differential coupled microstrip lines can help reduce ground bounce. Different factors which affect noise reduction are investigated, such as the coupling coefficient, rising time, skew of differential signaling, and structure asymmetry in slotline. An experimental setup is devised to demonstrate the noise coupling between signal lines due to the slot-induced ground bounce and significant noise reduction by employing differential signaling. A favorable comparison between the simulation and measured results validates the proposed equivalent circuit model and analysis approach.

A Hybrid Evolutionary Modeling/Optimization Technique for Collector-Up/Down HBTs in RFIC and OEIC Modules

A hybrid computer-aided design (CAD) tool for automatic simulation and characterization of advanced collector-up/down heterojunction bipolar transistors (HBTs), which are expected to be used as the high-power-amplifier (HPA) module in radio-frequency integrated circuit (RFIC) and the blue laser diode (LD)/heterojunction phototransistor (HPT) module in optoelectronic integrated circuit (OEIC), has been successfully established. By expanding the essence of reported techniques, the newly-developed equivalent-circuit modeling approach focuses on combining the genetic algorithm (GA) with refined analytical-modeling equations yielding reliable initial values of model parameters. This SPICE-like simulator reliably and efficiently relates device/circuit performances directly to the direct current/radio frequency (dc/RF) measurements since it implicitly accounts for physical correlations among model parameters and does not require ad hoc de-embedding test structures as well as special simplifying assumptions in the optimization period. Evolutionary programming is performed to achieve tedious circuit-level simulations in shortest turnaround times and the computational efficiency permits execution of an optimization involving random generation of circuit parameters. In this study, a detailed comparison of direct-measured, analytical-derived, and numerical-simulated results, for the pnp InGaAs as well as npn InGaP collector-up HBTs as the HPA module in RFIC and the npn ZnSe-Ge collector-down HBT as the blue LD/HPT module in OEIC, is presented. To further demonstrate the accuracy and robustness of this approach, the npn AlGaAs-InGaAs collector-down HBT, which can be incorporated in a preamplifier for optical communication, is investigated.

Modeling of Lossy MOS Capacitors on Ge-Rich Si0.15Ge0.85 Substrates

A reconstruction technique of the gate capacitance from anomalous capacitance-voltage (C-V) characteristics in lossy gate dielectrics formed by rapid thermal oxidation of Ge-rich Si0.15Ge0.85 in dry O2 ambient is presented. An equivalent circuit model approach to MOS capacitance modeling is proposed.

Cavity Resonance Suppression in Power Delivery Systems Using Electromagnetic Band Gap Structures

The utilization of electromagnetic band gap (EBG) structures is a new and promising approach in plane pair noise cavity resonance suppression. In this paper, EBG/plane pair structures are studied with full-wave methods and results are experimentally verified. A new equivalent circuit modeling approach of characterizing the frequency behavior of the entire EBG/plane pair structure is presented. The equivalent circuit of the unit cell is proposed and the procedure to extract circuit parameters is described. The influence of EBG patch parameters on the band gap characteristics is quantified and the results provide some design rules to circuit designers. Examples of applications of EBG structures to power/ground plane noise suppression are given.

Study of the traps at a mercury cadmium telluride–anodic oxide interface using a transient photoconductive decay technique

An equivalent circuit model approach has been used to understand the influence of the DC bias on the physical behaviour of the peaks recently reported in the transient photoconductive (PC) decay curves of mercury cadmium telluride (HgCdTe) samples. This has resulted in an improved model, which provides more insight into the physical process responsible for the appearance of these peaks in the decay curves. Interpretation of the results and the effects of annealing on HgCdTe samples covered with anodic oxide are presented.

Composite effects of reflections and ground bounce for signal line through a split power plane

The signal propagating along a microstrip line over a slot on the power plane will suffer from composite effects of reflected noise by a discontinuity in signal return path and ground bounce between power and ground planes. A new equivalent circuit model is proposed and simulations are performed for multilayer structures to characterize these composite effects. An experimental setup is devised to demonstrate significant coupling between signal lines due to the slot-induced ground bounce. Favorable comparison between the simulation and measured results validates the proposed equivalent circuit model and analysis approach.

Frequency‐dependent expressions for inductance and resistance of microstrip line on silicon substrate

AbstractA new closed‐form expression to calculate frequency‐dependent distributed inductance and the associated distributed series resistance of microstrip lines on a lossy silicon substrate (CMOS technology) are presented. The proposed analytic model for series impedance is based on a self‐consistent field method and the vector magnetic potential equation. It is shown that the calculated frequency‐dependent distributed inductance and the associated resistance are in good agreement with the results obtained from rigorous full wave solutions and CAD‐oriented equivalent‐circuit modeling approach. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 349–352, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10318