Equivalent Circuit Research Articles

A Fractional Order-Kepler Optimization Algorithm (FO-KOA) for single and double-diode parameters PV cell extraction

The primary objective of this study is to investigate the effects of the Fractional Order Kepler Optimization Algorithm (FO-KOA) on photovoltaic (PV) module feature identification in solar systems. Leveraging the strengths of the original KOA, FO-KOA introduces fractional order elements and a Local Escaping Approach (LEA) to enhance search efficiency and prevent premature convergence. The FO element provides effective information and past expertise sharing amongst the participants to avoid premature converging. Additionally, LEA is incorporated to boost the search procedure by evading local optimization. The single-diode-model (SDM) and Double-diode-model (DDM) are two different equivalent circuits that are used for obtaining the unidentified parameters of the PV. Applied to KC-200, Ultra-Power-85, and SP-70 PV modules, FO-KOA is compared to the original KOA technique and contemporary algorithms. Simulation results demonstrate FO-KOA's remarkable average improvement rates, showcasing its significant advantages and robustness over earlier reported methods. The proposed FO-KOA demonstrates exceptional performance, outperforming existing algorithms by 94.42 %–99.73 % in optimizing PV cell parameter extraction, particularly for the KC200GT module, showcasing consistent superiority and robustness. Also, the proposed FO-KOA is validated of on SDM and DDM for the well-known RTC France PV cell.

Constructing carbon nanotube (CNTs)/silica superhydrophobic coating with multi-stage rough structure for long-term anti-corrosion and low-temperature anti-icing in the marine environment

The rough superhydrophobic surface is beneficial for capturing more gases underwater, which enhances corrosion and ice resistance for marine equipment. In this work, a PVAc-PVDF-FMCS (PPFMCS) multi-stage rough superhydrophobic coating was manufactured by a cold spraying method, significantly improving the anti-corrosion and anti-icing of aluminium alloy. The point-line structure was designed by cross-linking between multi-walled carbon nanotubes (MWCNTs) and silicon dioxide (SiO2), which facilitated the formation of multi-stage rough surface. The porous skeleton and interfacial adhesion of the PPFMCS coating were attributed to the introduction of polyvinylidenefluoride (PVDF) and polyvinylacetate (PVAc), respectively. The PPFMCS coating had good superhydrophobicity with a water contact angle of 163.5°, while exhibiting the outstanding performance of long-term anti-corrosion and anti-icing. The |Z|0.01 Hz value of the PPFMCS coating was still 9.62 × 109 Ω cm2 in 3.5 wt% NaCl solution for 35 days, only two orders of magnitude lower than that of the original coating, the equivalent circuits were further investigated and the metal protection is evaluated on the shore or in the deep ocean of the South China Sea. The PPFMCS coating was able to obviously delay icing for 5 min at −20 °C, the ice adhesion of its surface was as low as 85.5 kPa. The icing phase transition was analysed by a thermodynamic method. The coating also had good stability and drag reduction performance. This high-performance coating based on point-line structural design is expected to have practical applications in marine transportation, oil exploration and polar exploration.

A Time-varying Equivalent Circuit Modeling and Measuring Approach for Intracardiac Communication in Leadless Pacemakers.

Intracardiac wireless communication is crucial for the development of multi-chamber leadless cardiac pacemakers (LCP). However, the time-varying characteristics of intracardiac channel pose major challenges. As such, mastering the dynamic conduction properties of the intracardiac channel and modeling the equivalent time-varying channel are imperative for realizing LCP multi-chamber pacing. In this paper, we present a limiting volume variational approach based on the electrical properties of cardiac tissues and trends in chamber volume variation. This approach was used to establish a quasi-static and a continuous time-varying equivalent circuit model of an intracardiac channel. An equivalence analysis was conducted on the model, and a discrete time-varying equivalent circuit phantom grounded on the cardiac cycle was subsequently established. Moreover, an ex vivo cardiac experimental platform was developed for verification. Results indicate that in the frequency domain, the congruence between phantom and ex vivo experimental outcomes is as high as 94.3%, affirming the reliability of the equivalent circuit model. In the time domain, the correlation is up to 75.3%, corroborating its effectiveness. The proposed time-varying equivalent circuit model exhibits stable and standardized dynamic attributes, serving as a powerful tool for addressing time-varying challenges and simplifying in vivo or ex vivo experiments.

Effect of high resistivity soil under high impulse currents

In this paper, experimental test results of several ground electrodes surrounded with gravelly soil medium subjected to high impulse currents were studied, to investigate the effect of confined soil surround electrodes. Ground resistance measurements were performed at low magnitude of voltage and current, where the results are compared to the impulse characteristics of ground electrodes. This paper shows a significant difference in the RDC values and impulse characteristics of ground electrodes when gravelly soil medium surrounded the ground electrode in comparison to the electrodes installed in natural soil. This indicates that the confined soil around the electrode has a major effect on the performance of ground electrodes, whether at steady state or under high impulse conditions. Equivalent circuit for each tested electrode was developed with personal simulation program with integrated circuit emphasis (PSPICE), where the effect of inductance was seen in the electrodes surrounded with gravelly soil.

SOC and SOH state estimation of lithium battery based on ffrls and kalman filter

Abstract In the energy storage System, the Battery Management System (BMS) is responsible for the charge and discharge control and energy balance control of the lithium battery, and the accuracy of lithium battery state estimation is directly affected by the control effect of BMS. In order to ensure the normal operation of lithium batteries, this paper selects the State of Charge (SOC) and State of Health (SOH) of lithium batteries as the research object and accurately estimates the SOC and SOH of lithium batteries as the research goal. The equivalent circuit model based on lithium battery is established, and the identification model parameters are based on the recursive least squares method with forgetting factor. Based on the Thevenin equivalent circuit model, the Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF) are used to estimate the SOC of the battery, respectively. FFRLS and Double Extended Kalman Filter (DEKF) are used to estimate the ohm internal resistance in the equivalent model based on lithium battery, and then the SOH is estimated.

Seepage modelling and seepage-stress coupling properties of fractured rock mass based on equivalent circuit principle

Seepage modelling and seepage-stress coupling properties of fractured rock mass based on equivalent circuit principle

Design and validation of a novel 2.5‐D miniaturized FSS with angular and superior polarization stability for mobile technology

AbstractThis paper presents a novel 2.5D miniaturized frequency‐selective surface (FSS) measuring 6.1 mm × 6.1 mm, designed to effectively shield smartphones and tablets from unwanted electromagnetic radiation. The FSS is notable for its stable attenuation peaks in the high‐frequency stopband under transverse magnetic (TM) polarization, offering dual‐frequency response and exceptional angular stability in both transverse electric and TM modes. An equivalent circuit analysis, prototype fabrication, and empirical evaluation confirmed its effectiveness. The prototype exhibits superior polarization stability and minimal peak attenuation reduction of just 1.9 dB (10%) across a 0°–60° incidence angle, outperforming similar studies.

Capacity and Resistance Diagnosis of Batteries with Voltage-Controlled Models

Capacity and internal resistance are key properties of batteries determining energy content and power capability. We present a novel algorithm for estimating the absolute values of capacity and internal resistance from voltage and current data. The algorithm is based on voltage-controlled models. Experimentally-measured voltage is used as an input variable to an equivalent circuit model. The simulation gives current as output, which is compared to the experimentally-measured current. We show that capacity loss and resistance increase lead to characteristic fingerprints in the current output of the simulation. In order to exploit these fingerprints, a theory is developed for calculating capacity and resistance from the difference between simulated and measured current. The findings are cast into an algorithm for operando diagnosis of batteries operated with arbitrary load profiles. The algorithm is demonstrated using cycling data from lithium-ion pouch cells operated on full cycles, shallow cycles, and dynamic cycles typical for electric vehicles. Capacity and internal resistance of a “fresh” cell was estimated with high accuracy (mean absolute errors of 0.9% and 1.8%, respectively). For an “aged” cell, the algorithm required adaptation of the model’s open-circuit voltage curve to obtain high accuracies.

A method for measuring capacitive current in distribution networks based on injection signal method

Abstract In view of the problems that exist in the current distribution network, such as the narrow range of measurement capacitance to the ground and the difficulty of selecting the appropriate signal frequency. Based on the phasor method, this paper proposes a method for measuring capacitance current in a distribution network based on injected signal and analyzes and calculates the error of the method. The measurement technique involves inputting two constant-amplitude signals—one high-frequency and one low-frequency—into a zero-sequence PT (Potential Transformer) configured with an open delta connection. Based on the equivalent circuit models for both high and low-frequency signals, the high-frequency signal’s increased frequency allows the magnitude to be disregarded, simplifying the calculations. Using a simplified equation for the low-frequency signal component, this method enables rapid calculation of the capacitor current in the distribution network. Based on MATLAB software, the simulation calculation model is established, and the simulation results show that the measurement method is simple to calculate and has high accuracy, which can be used to measure the large-capacity grounding capacitance current test, so as to improve the measurement accuracy of the capacitance current of medium and low voltage distribution network.

Research on the photoelectricity mismatch loss of photovoltaic and thermal (PV/T) units connected in series at different temperatures

Abstract A simulation study was conducted on the mismatch loss caused by temperature differences between photovoltaic and thermal (PV/T) modules connected in series. A calculation method for the IV curve of PV/T modules connected in series was proposed, and an equivalent circuit model of PV/T units was established using Multisim software. Two different temperature zones, three different temperature zones, and four different temperature zones of PV/T units connected in series were separately established. A numerical calculation model based on the Lambert W function was used to study the series mismatch characteristics of PV/T cells at different temperature ranges. The series connection method of PV/T modules obtained through experimental comparison research: (1) The maximum temperature difference of PV/T modules in the series should be controlled within the range of 10-20°C as much as possible; (2) The temperature of adjacent PV/T modules in the string should achieve continuous distribution; (3) Considering that the maximum operating current of a concentrated PV/T system is greater than that of a regular photovoltaic system, it is necessary to reduce the system output current and increase the system output voltage as much as possible in engineering. A series connection should be the main connection method for a string connection.

Modeling and analysis of crosstalk induced effects in graphene-carbon nanotube composite interconnects

This paper proposes an equivalent circuit model for two-line coupled multilayer graphene nanoribbon - single-wall carbon nanotube (MLGNR-SWCNT) composite interconnects (MSCs), incorporating the effects of coupling capacitance and mutual inductance. We also examine the temperature-dependent crosstalk effect on the victim line of MSCs in the time domain using decoupling techniques and the ABCD parameter matrix approach. This analysis is conducted at the global level of 7 nm, 14 nm, and 22 nm technology nodes, comparing the performance of MSCs with MLGNR, SWCNT, and copper (Cu) interconnects, validated through HSPICE simulations. Our results reveal that the crosstalk delay of all interconnects induced by dynamic crosstalk exhibits superior performance in the in-phase crosstalk mode compared to the out-of-phase mode at room temperature. In particular, MSCs demonstrate less crosstalk delay in both crosstalk modes compared to SWCNT and Cu interconnects. In addition, we analyze the crosstalk delay of the victim line for two-line coupled MSCs at varying temperatures in out-of-phase crosstalk mode, comparing them with MLGNR, SWCNT, and Cu interconnects. Simulation results indicate that the crosstalk delay is temperature-dependent, increasing with rising temperatures, and the crosstalk delay of MSCs is the least of all interconnects. Furthermore, we investigate the crosstalk noise of MSCs induced by functional crosstalk at different temperatures, comparing it with MLGNR, SWCNT, and Cu interconnects. It is observed that the crosstalk noise peak remains constant with temperature changes across all interconnects; however, the holding time and width of crosstalk noise increases with rising temperatures and MSCs have the least crosstalk noise peak and crosstalk noise width of all interconnects. Also, numerical results exhibit that reducing interconnect temperature, SWCNT diameter, and edge roughness of MLGNR are effective strategies to diminish the crosstalk delay of MSCs. In addition, increasing line spacing is identified as an effective method to reduce crosstalk noise peak of MSCs of different lengths. The proposed model results show excellent agreement with HSPICE simulation data. Therefore, our analysis of crosstalk effect manifests that MLGNR-SWCNT composite can be a promising material to replace SWCNT and copper as an ideal material for global interconnect applications in thermally variable environments.

Total harmonic distortion estimation in piezoelectric micro-electro-mechanical-system loudspeakers via a FEM-assisted reduced-order-model

Piezoelectric micro-electro-mechanical-system (MEMS) loudspeakers are attracting growing research interest in the last years due to the increasing interest towards miniaturization required by new wireless audio devices. Finite Element Models (FEM) and Lumped Element Models (LEM) able to accurately simulate their linear response have been recently proposed in the literature. However, a nonlinear model suitable to predict the Total Harmonic Distortion (THD) of these devices is to date still missing. In this work, we present a FEM-assisted lumped-parameters equivalent circuit for THD estimation which accounts for geometric nonlinearities and piezoelectric hysteresis. The loudspeaker nonlinear electro-mechanical domain is simulated through a Reduced Order Model (ROM) which considers as basis function the pre-stressed undamped actuated mode of the device computed via FEM, to account for loudspeaker diaphragms of arbitrarily complex geometry. Parameters of the acoustical circuit are computed through analytical formulas. The good matching between numerical predictions and experimental results, carried out on a piezoelectric MEMS loudspeaker prototype for in-ear condition, demonstrates the accuracy of the proposed tool.

Analytical modeling of cylindrical eddy current brakes and multi-objective optimization based on game theory

With the research and development of eddy current brake (ECB), today ECBs have been applied in a variety of fields including vibration control and braking of strong impact loads.The application of a new cylindrical structure eddy current brake (ECB) for strong impact braking of large machinery has been discussed recently. Its high-speed and high-kinetic-energy braking conditions require different analytical and optimization design models and methods from what has been addressed in previous studies. For subsequent more engineering-oriented research and optimization, modeling methods are needed, as well as analysis and optimization studies for braking forces and critical speeds of interest. In this work, a magnetic equivalent circuit model is established, and the influence of eddy current induced during application is taken into account by considering it as a magnetomotive force in the model. The braking force is calculated with the MEC model and an approximate electric field cross-section method. A small prototype experiment is carried out and proves the correctness of the proposed model. Using the proposed and FEM model, parameters of the ECB are analyzed. Then, aiming at design objectives of the ECB that are somewhat competitive under this special braking condition, a multi-objective optimization model is established using the Stackelberg game strategy. An FEM model is built and assessed based on optimization results. The results indicate that the multi-objective optimization model based on the Stackelberg game is effective for the design of this ECB structure.

A Physics-Based Equivalent Circuit Model and State of Charge Estimation for Lithium-Ion Batteries

A Physics-Based Equivalent Circuit Model and State of Charge Estimation for Lithium-Ion Batteries

Design of a microstrip Wilkinson power divider using a low pass filter with the particle swarm optimization algorithm

In this paper, a microstrip Wilkinson power divider (MWPD) based on particle swarm optimization (PSO) algorithm is designed, simulated, and fabricated using novel resonators. In addition, attenuators and open-ended stubs are incorporated to generate a broad cut-off band and reduce unwanted harmonics. The proposed power divider has a central frequency of 1 GHz. The performance of each used resonator is analyzed based on lumped-element circuit models.The L and C parameters of the equivalent circuit of the used resonators are predicted and optimized with the assistance of the PSO method. The subsequent phase was the fabrication of the proposed MWPD, after which its performance was evaluated in the light of the results obtained from the simulation. It was discovered that there was a high degree of concordance between the two. On the other hand, the fabricated circuit has several benefits, including a suitable S12 of − 3.15 dB, a high return loss of less than − 24 dB at the operating frequency, a compact size of 0.058 λg\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\varvec{\\lambda}}_{{\\varvec{g}}}$$\\end{document} × 0.064 λg\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\varvec{\\lambda}}_{{\\varvec{g}}}$$\\end{document}, and the ability to remove undesired harmonics. The results show a high level of suppression of the unwanted harmonics (up to the 16th harmonic) and a great responsiveness in the passband, while having very low ripple. As a result, the proposed circuit may be used in a wide variety of electronic devices, such as radar transmitter and receiver circuits, and many other high-frequency systems.

A kirigami-based reconfigurable metasurface for selective electromagnetic transmission modulation

Tunable three-dimensional (3D) electromagnetic metasurfaces are essential for achieving selective modulation of polarized waves, but they usually require complex designs and the use of smart materials, posing great implementation challenges. Here, we propose a novel kirigami-based reconfigurable electromagnetic metasurface, which consists of a kirigami-based deformable thin polyimide substrate and periodically arranged copper split-ring resonators. By simple stretch, the two-dimensional (2D) planar metasurface can be uniformly transformed into a 3D state, enabling it to effectively and selectively modulate linearly and circularly polarized waves. Experimental and numerical results reveal the mechanical deformation and transmission characteristics of the metasurface under applied strains. It is shown that the metasurface exhibits good selective transmission tunability while the resonant frequency remains basically unchanged for both transverse electric and transverse magnetic polarized waves. Furthermore, the selective tuning mechanism and the influence of geometrical parameters are also illustrated by the equivalent circuit analysis.

Resistive ink based polarization and incident angle independent wideband absorber for RCS reduction at KU and K band

In this paper, a thin, single layered, wideband, polarization-insensitive, frequency selective surface absorber for radar cross section reduction (RCS) at KU and K bands has been studied analytically and experimentally. The lossy resistive patterns on unit cell is printed using resistive ink and arranged periodically over a low-cost metal-backed FR-4 dielectric substrate. Through appropriate design and optimization, the proposed absorber demonstrates above 90 % absorption for broadband ranging from 15 GHz to 26.6 GHz, with multi-absorption peaks at 15.7, 18.5, and 22.9 GHz. The structure shows a high absorptivity of 96.8 % in the KU band and 95.7 %, and 99.3 % in the K band at the above mentioned frequencies. A fractional bandwidth of 55.8 % has been obtained at the expense of a thickness of 0.0835 λ1 (λ1 being the wavelength associated with the lower absorbing frequency). The absorption mechanism has been described with the help of surface current distribution, induced electric field, and equivalent circuit. Further, for both TE and TM waves, analysis of various polarization angles and oblique incidence angles have been investigated. It shows polarization insensitivity to normal incidence and a stable response up to 60° for oblique incidence to TM wave. The proposed absorber’s novelty comes through its thin, single-layered structure with wide band response at the KU and K frequency bands via a unique resistive ink pattern on a low cost FR-4. A prototype of the absorber has been fabricated and measured results have been validated with simulated results. A proposed single layered, wideband, thin, polarization, and angular stable absorber using resistive ink is commercially viable for RCS reduction applications at the KU and K band.

Applicability of linear models in modeling dynamic behavior of alkaline water electrolyzer stack

Linear equivalent circuit models are commonly used to estimate the effect of current ripple on the performance of water electrolyzers, thus it is important that the validity of this approach is examined. The effect of the amplitude and frequency of the sinusoidal current ripple on the performance of the alkaline water electrolyzer stack is studied experimentally. The increased current ripple amplitude produces additional losses in the electrolyzer stack, while the effect of ripple frequency appears to be insignificant. Linear models based on an equivalent circuit and polarization curve tangent are compared with waveform measurements with differing ripple amplitudes and frequencies to study their dynamic modeling capabilities. Under dynamic operation the experimental results show that operating voltage differs considerably from the static polarization curve, especially at low operating currents, due to nonlinear behavior. It is also shown that the dynamic equivalent circuit model using only linear components is not enough to accurately model electrolyzer behavior under dynamic operation.

Insights from dispersion in carbon nanotubes‐based poly(vinylidene fluoride‐co‐hexafluoropropylene) wearable sensors via solvent casting

AbstractFlexible sensors, made of PVDF‐HFP reinforced with carbon nanotubes (CNTs), are manufactured by solvent casting. More specifically, the effect of evaporation temperature and sonication time is explored. It is seen that two effects govern the dispersion of CNT: the sedimentation half‐time, and the breakage induced by the ultrasonication process. In this regard, it is found that 60°C is an optimum evaporation temperature to reach the highest value of electrical conductivity, since it offers a good balance between these effects, leading to the creation of a more efficient electrical network. This is also confirmed by the AC analysis, where these samples show the highest characteristic frequencies. The electromechanical results show a greater dependency on evaporation temperature for low sonication times, as the breakage induced by an ultrasonic process is not so pronounced and, therefore, the sedimentation effect plays a more dominant role. In addition, cycling tests show robust electromechanical response with cycling, and creep tests prove good electrical response of the sensors, less than 200 ms in some cases. Finally, proof of concept testing of wrist, shoulder, and neck monitoring highlights the potential of the proposed materials for sensing applications.Highlights PVDF‐HFP/CNT nanocomposite strain sensors via solvent casting are proposed. The effect of evaporation temperature and sonication time is studied. DC and AC conductivities were analyzed and modeled via an equivalent circuit. An outstanding Gauge Factor of 86.30 × 104 is achieved at 95% of strain level. Two proof‐of‐concepts of medium and large movements are successfully achieved.

Equivalent circuit fitting method for microwave characterisation of low-k dielectric thin films

Abstract A new equivalent circuit fitting analysis scheme is proposed to analyse the measured data of test structures originally developed to characterise high-κ dielectrics at frequencies up to 5 GHz (Zhengxiang et al 1998 IEEE Trans. Electron Devices 45 1811–6). It is compared to an extension of the analysis which can be used for high-κ dielectrics at up to 50 GHz (Rundqvist et al 2004 Integr. Ferroelectr. 60 1–19). The proposed scheme focuses on the accurate characterisation of low-κ dielectrics, which exhibit greater sensitivity to various parasitics. The scheme utilises the same concentric capacitor devices and measurement setup as the original method, maintaining the advantage of ease in fabrication of the original approach. The physical model employed in the analysis step of the original method, which tended to overestimate the dielectric permittivity, has been enhanced by incorporating fringing fields and a parasitic gap capacitance as circuit elements. The accuracy of the new approach is validated using experimental data, demonstrating its ability to more accurately determine the dielectric permittivity compared to the original method.