Equivalent Circuit Parameters Research Articles

HPPC Test Methodology Using LFP Battery Cell Identification Tests as an Example

The aim of this research was to create an accurate simulation model of a lithium-ion battery cell, which will be used in the design process of the traction battery of a fully electric load-hull-dump vehicle. Discharge characteristics tests were used to estimate the actual cell capacity, and hybrid pulse power characterization (HPPC) tests were used to identify the Thevenin equivalent circuit parameters. A detailed description is provided of the methods used to develop the HPPC test results. Particular emphasis was placed on the applied filtration and optimization techniques as well as the assessment of the quality and the applicability of the acquired measurement data. As a result, a simulation model of the battery cell was created. The article gives the full set of parameter values needed to build a fully functional simulation model. Finally, a charge-depleting cycle test was performed to verify the created simulation model.

Accelerating Bayesian Estimation of Solar Cell Equivalent Circuit Parameters Using JAX-Based Sampling

Equivalent circuit models that reproduce the current–voltage characteristics of solar cells are useful not only to gain physical insight into the power loss mechanisms that take place in solar cells but also for designing systems that use renewable solar energy as a power source. As mentioned in a previous paper, Bayesian estimation of equivalent circuit parameters avoids the drawbacks of nonlinear least-squares methods, such as the possibility of evaluating estimation errors. However, it requires a long computation time because the estimated values are obtained by sampling using a Markov chain Monte Carlo method. In this paper, a trial to accelerate the calculation by upgrading the Bayesian statistical package PyMC is presented. PyMC ver. 4, the next version of PyMC3 used in the previous paper, started to support the latest sampling libraries using a machine learning framework JAX, in addition to PyMC-specific methods. The acceleration effect of JAX is remarkable, achieving a calculation time of less than 1/20 times that of the case without JAX. Recommended calculation conditions were disclosed based on the results of a number of trials, and a demonstration with testable Python code on Google Colaboratory using the recommended conditions is published on GitHub.

Equivalent Circuits of Dipole Antennas for Broadband Applications

In this paper distributed parameter equivalent circuits are developed for linear dipoles, dielectric coated dipoles and lumped loaded dipoles. Theoretical solutions for each distributed parameter and the reasonable non-uniform segmentation of antennas serve as the foundation for the derivation. The accomplished validations of the modeling procedures indicate that the given equivalent circuits are capable of correctly describing dipole antennas in frequency and time domains, with the advantages of wideband, frequency independence and unambiguous physical meaning. Relying on the presented equivalent circuits, broadband issues such as simulating input impedance, predicting equivalent lengths and computing transient responses of dipole antennas can be readily addressed. In addition, the circuit model provides helpful insights into the analysis and design for the loaded dipole antennas.

An Efficient White Shark Optimizer for Enhancing the Performance of Proton Exchange Membrane Fuel Cells

This study investigates the substantial contribution of the recent numerical optimization technique known as the White Shark Optimizer (WSO) to evaluate the performance of proton exchange membrane fuel cell (PEMFC) design parameters that play a considerable role in boosting its effectiveness. A numerical code was developed and implemented via MATLAB software to achieve the research goal. The proposed WSO was employed to identify the unknown parameters of the PEMFC equivalent circuit, considering experimental data. The analyzed objective function was the root mean squared error (RMSE) between the measured and estimated fuel cell terminal voltages. Additionally, the proposed WSO was compared with other intelligent approaches such as the salp swarm algorithm (SSA), Harris hawks optimization (HHO), atom search optimization (ASO), dung beetle optimization algorithm (DBOA), stochastic paint optimizer (SPO), and comprehensive learning Archimedes optimization algorithm (HCLAOA). The numerical simulations revealed that the RMSE values varied between lower and higher values of 0.009095329 and 0.028663611, respectively. Additionally, the results indicated that the mean fitness value recorded in the considered PEMFC 250 W stack was 0.020057775. Moreover, the minimum fitness value was obtained using the proposed WSO, with an operating temperature of 353.15 K and working anode and cathode pressures are 3 bar and 5 bar, respectively. The proposed WSO offered the best results in terms of absolute errors compared to the other optimizers, confirming the robustness of the results in all considered cases.

Characterization of a small amorphous photovoltaic panel and derivation of its SPICE model

This paper presents a simple method to resolve the parameters of the single-diode equivalent circuit for small amorphous photovoltaic (PV) panels. It is based on a precise measurement using a test bench that allows the characterization of PV panels at different illumination levels from 10 lx to 3000 lx. The measurement under different illumination conditions allows the calculation of the model parameters using only a standard polynomial, logarithmic and exponential functions - no numerical approach or Lambert W function is required. The solved parameters are later used in LTspice simulations, which are compared with the real measurements. The Spice model presented in this paper is based on the single diode model, but is modified to be more reliable at low illumination levels. The Spice model can be used for the design of MPPT systems or for various indoor IoT applications, where it allows to predict the available energy under different conditions.

Charger Integrated Coestimation of Parameters and States of Battery

Accurate parameter and state estimations of batteries are crucial for increasing safety and reliability. The ageing of batteries leads to electrochemical changes, changing the impedance and the charge-discharge characteristics. The impedance and derived equivalent circuit model parameters values support state estimation algorithms. Hence, if the parameters of the battery are not updated at regular intervals of time or usage, the state estimation will be erroneous. The battery management system, which performs the state estimation, is limited in functionality and accuracy due to dependency on predefined parameter values fed during the initial set-up. Hence, this work proposes charger-side online parameters and state estimation algorithms based on the impedance and the equivalent circuit parameters determined during the start of charging. The accuracies of the proposed algorithms are verified experimentally for two batteries: a new and an old lithium iron phosphate battery. Further, the algorithms are tested for four types of charging: constant current, constant current-constant voltage, pulse charging without discharge, and pulse charging with discharge. The experimental results show the suitability of the proposed algorithms for estimating battery parameters and states for both batteries. Moreover, the proposed algorithms are suitable for other Li-ion battery chemistry also.

IMPLEMENTATION PECULIARITIES OF METHOD FOR LITHIUM BATTERIES TECHNICAL STATE MONITORING BASED ON ANALYSIS OF RELAXATION PROCESSES CAUSED BY LOAD VARIATIONS

The paper describes a technique for estimating the parameters of the second-order electrical model of lithium battery (LB), based on the analysis of its response to a step-like load change. The advantage of this approach is the implementation with simple and compact measuring equipment. Taking into account the limitations for the maximum LB load, the solution of a system of nonlinear equations when estimating the model parameters can be reduced to solving a system of linear algebraic equations. This finding makes it possible to implement the approach with inexpensive general-purpose microcontrollers. Thus, the paper proposes a method for reducing computational costs, which consists in sequential fitting of experimental relaxation curves with two single-exponential models instead of using a complex two-exponential model. It provides more than twofold reduction in the time for identifying the parameters of the LB’s electrical model. The experimental studies show that the obtained dependences of the equivalent circuit parameters can be explained by the general properties of physicochemical reactions occurring in LB. From a practical point of view, the proposed method has great advantages. First, it has better time localization compared to electrochemical impedance spectrometry. This advantage is especially important for LB due to the effect of the discharge processes on the results. In addition, the response time of diagnostic systems is significantly reduced. Secondly, the proposed method requires simpler and more inexpensive test equipment, which potentially makes it possible to integrate controls into the LB at the manufacturing and exploitation stages.

Determination of individual values of four-element equivalent circuits elements parameters at technical diagnostics of insulation by absorption methods

The aim of this article is to present a methodology of determining of the individual values of the parameters of four-element equivalent circuits for insulation with through conductivity. Methodology. The proposed method consists in the fact that at a time interval of more than 10 s, when the charge indicator no longer contributes to the leakage current, three points t1, t2 and t3 are selected, such that t2 – t1 = t3 – t2. To be able to determine the absorption coefficient R60/R15, it is recommended to take t1 = 15 s, t2 = 37.5 s and t3 = 60 s. At the same time, by subtracting I(t2) – I(t1) and I(t3) – I(t2), the constant component of the absorption curve is excluded and it becomes possible to determine the individual values of the parameters of the generalized equivalent circuit of insulation, additionally using its conductivity in operator form. Results. As calculations show, the correct determination of the parameters of insulation equivalent circuit according to the proposed method is possible only with a certain ratio of these parameters. The charge time of the geometric capacitance Cg(R0+Rd), where R0 and Rd are the resistance that forms the charging exponent, and the resistance of the sensor, should be within 0.2 s <Cg(R0+Rd)<1 s, the time constant CaRa, where Ca and Ra are the capacitance and resistance of the absorption chain, should be more than 3 s, the product of CgRl, where Rl is the leakage resistance, more 0.5 s, the leakage resistance Rl is less than the absorption resistance Ra. Checking the methodology on a model example gives the values of the parameters of the insulation equivalent circuit that match the specified ones with high accuracy. Practical value. The use of individual values of the parameters of insulation equivalent circuits when applying absorption diagnostic methods with considering the time values and dimensional factors, allow to calculate all currently used diagnostic parameters, to determine the conditions of certain insulation types, as well as in more detail, in comparison with the existing approach, to assess the technical condition of the insulation and the reasons of its changes.

Design of dual-band planar thin absorber for vehicular radar test scenario

ABSTRACT Aiming at the requirement of radar wave absorption in automotive radar tests for both the 24 GHz and 77 GHz vehicle radar bands, two ultra-thin dual-band circuit analog absorber designs based on frequency-selective conductive film have been proposed. They are obtained by first optimising the equivalent circuit parameters to achieve the desired reflection response, then determining the physical parameters (geometrical size and square resistance) of unit cells from the equivalent circuit parameters, and finally fine-tuning these physical parameters. Both designs employ unit cell based on the nested structure of conductive square ring and a conductive square patch, which has the advantages of simple structure, ease of processing, high design freedom, and good polarisation and angular stability. The 1st design employs different square resistance values for the conductive ring and patch, while the 2nd design employs a single square resistance value for both conductive shapes. Simulation results show that, for each of the two designs, the lower and upper 70% absorption or −10 dB reflection bands simultaneously cover the 24 GHz and 77 GHz vehicle radar bands, respectively, with good angular stability. The dual-band coverage keeps stable until the elevation incident angle reaches 20° and 50° for the 1st and 2nd designs, respectively. A realistic sample is processed regarding the 2nd design and its dual-band absorption performance has been verified by experimental results, which have good agreement with the simulated counterparts.

Predicting temperature distribution of passively balanced battery module under realistic driving conditions through coupled equivalent circuit method and lumped heat dissipation method

The current study intends to model a passively balanced battery module. The model provides scenario specific thermal predictions which can be used as input for designing and optimising Battery Thermal Management System (BTMS). The study includes the effects of module level passive balancing on thermal prediction and vice versa. The constituent cells used in the battery module are modelled by integrating Equivalent Circuit Model (ECM) in MATLAB Simulink and Computational Fluid Dynamics (CFD) simulations in COMSOL Multiphysics. The heat generation rate calculated in the MATLAB Simulink environment is used as input to COMSOL Multiphysics for temperature calculations. Successively, the average temperature of the cell is re-entered into ECM for calculation of the Equivalent Electric Circuit (EEC) parameters. The EEC parameters are SoC and temperature dependent. Therefore, the effect of temperature variation on Li-ion cell performance and heat generation is also considered. The Li-ion cell model is validated against experimental drive cycle data. The validated Li-ion cell model is used to create a passively balanced battery module with a 3S4P arrangement. The switching shunt resistor method is used for balancing circuit design. The modelled battery module is simulated with an actual drive cycle for the voltage, SoC, and thermal predictions.

Improved equivalent circuit characterization of an ultracapacitor for power electronic applications

Ultracapacitor-based energy storage systems are becoming increasingly popular as a secondary power source in Renewable energy and Electric Vehicle applications. The design of a well-tuned ultracapacitor-based energy storage system requires accurate characterization of its simplified electrical equivalent circuit. The existing approaches for estimating parameters of the simplified equivalent circuit rely on the initial slope of the ultracapacitor response, which can lead to inaccurate estimation. This work focuses on developing a simple and accurate linear regression-based approach for estimation of equivalent circuit parameters. We highlight some critical observations related to the equivalent circuit parameters of a simplified equivalent circuit of an ultracapacitor. In particular, this work indicates the non-uniqueness of capacitance during the charging and discharging modes. The characterization and analysis reported in this study are based on a 24 V laboratory prototype comprising 10 series-connected ultracapacitors.

Humidity-dependent electrical performance of CuO nanowire networks studied by electrochemical impedance spectroscopy.

Electrochemical impedance spectroscopy was applied for studying copper oxide (CuO) nanowire networks assembled between metallic microelectrodes by dielectrophoresis. The influence of relative humidity (RH) on electrical characteristics of the CuO nanowire-based system was assessed by measurements of the impedance Z. A slight increase of Z with increasing RH at low humidity was followed by a three orders of magnitude decrease of Z at RH above 50-60%. The two opposite trends observed across the range of the examined RH of 5-97% can be caused by water chemisorption and physisorption at the nanowire interface, which suppress electronic transport inside the p-type semiconductor nanowire but enhance ionic transport in the water layers adsorbed on the nanowire surface. Possible physicochemical processes at the nanowire surface are discussed in line with equivalent circuit parameters obtained by fitting impedance spectra. The new investigation data can be useful to predict the behavior of nanostructured CuO in humid environments, which is favorable for advancing technology of nanowire-based systems suitable for sensor applications.

Design and Analysis of a Miniaturized Broadband Resistive Film Absorber to Reduce Chip System Radiation

This study designed a resistive film absorber (RFA) with > 90% absorptivity in the 16–27 GHz broadband to reduce electromagnetic radiation in on-board chip architectures. The size of the RFA unit is miniature, which is only 0.1λ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_L</i> × 0.1λ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_L</i> × 0.06λ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_L</i> (where λ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_L</i> is the lowest operating frequency cutoff wavelength). First, the impedance matching and loss principle of the RFA are analyzed based on the intrinsic parametric method and equivalent circuit theory. This explains the influences of each parameter on absorption performance and verifies that the designed RFA has good polarization insensitivity and angle stability. In addition, the measurements of a prototype RFA were obtained and found to be consistent with simulation results, which proves the feasibility of the RFA. Finally, the RFA was added to a chip architecture to verify its electromagnetic suppression effect with consideration of the influence of temperature on absorption performance. The combined simulation results indicate a significant reduction in the far-field radiation values of the chip architecture, with the maximum electromagnetic radiation suppression effect being 12 dB. These results demonstrate the reliability of the proposed electromagnetic suppression scheme and indicate that the RFA has wide application prospects for radiation suppression in chip systems and electronic packaging.

Parameter Extraction of Solar Photovoltaic Modules Using a Novel Bio-Inspired Swarm Intelligence Optimisation Algorithm

For extracting the equivalent circuit parameters of solar photovoltaic (PV) panels, a unique bio-inspired swarm intelligence optimisation algorithm (OA) called the dandelion optimisation algorithm (DOA) is proposed in this study. The suggested approach has been used to analyse well-known single-diode (SD) and double-diode (DD) PV models for several PV module types, including monocrystalline SF430M, polycrystalline SG350P, and thin-film Shell ST40. The DOA is adopted by minimizing the sum of the squares of the errors at three locations (short-circuit, open-circuit, and maximum power points). Different runs are conducted to analyse the nature of the extracted parameters and the V–I characteristics of the PV panels under consideration. Obtained results show that for Mono SF430M, the error in the SD model is 2.5118e-19, and the error in the DD model is 2.0463e-22; for Poly SG350P, the error in the SD model is 9.4824e-21, and the error in the DD model is 2.1134e-20; for thin-film Shell ST40, the error in the SD model is 1.7621e-20, and the error in DD model is 7.9361e-22. The parameters produced from the suggested method yield the least amount of error across several executions, which suggests its better implementation in the current situation. Furthermore, statistical analysis of the SD and DD models using DOA is also carried out and compared with two hybrid OAs in the literature. Statistical results show that the standard deviation, sum, mean, and variance of various PV panels using DOA are lower compared to those of the other two hybrid OAs.

Enlightening Load Modeling by Means of Power Factor Decompositions

Considering the proliferation of power electronics applications and distributed energy resources, modern power grids are facing a significant increase in harmonic currents circulation and supply voltage deterioration, occasionally associated with small frequency variations. In such a context, the understanding of power phenomena in circuits with linear and non-linear loads under non-sinusoidal voltage conditions is nontrivial and still does not allow for an easy interpretation of harmonic sources, harmonic power flow or the identification of the parameters of a proper equivalent circuit. The main challenge is to develop modern theoretical approaches for load characterization, modeling, and parameter estimation so that new techniques can be formulated to provide adequate guiding for the analysis, compensation, revenue metering, accountability and other applications of power systems. Thus, based on the Conservative Power Theory (CPT) and further decomposition of its apparent power and power factor definitions, this paper proposes a novel methodology for estimating equivalent parameters and for proposing proper equivalent circuits capable of representing/modeling the main characteristics of single-phase generic loads (black boxes) and the related power phenomena in terms of passive dipoles (linear loads) or of harmonic voltage/current sources and their intrinsic transimpedances/transadmittances (non-linear loads). Simulation and experimental results were depicted to support and validate the proposed approach, showing that it might be a powerful modeling technique to represent generic loads in a modern power grid scenario, while being used for complex applications such as reactive power compensation or accountability in circuits with nonlinear loads and distorted voltages.

Electrochemical characterization of chloride ion transport in rubber concrete

Chloride-induced corrosion of steel in concrete structures is a significant issue. As an environmentally-friendly building material, rubber concrete has been proven to have the potential to resist chloride-induced permeation. In this paper, the transport behavior of chloride ion in rubber concrete was investigated by electrochemical impedance spectroscopy (EIS) approach. A novel electrochemical equivalent circuit Rs(Q1(Rct1W1)) (Q2(Rct2W2)) was used to study the electrochemical properties of rubber concrete systems and compare with other equivalent circuits by evaluation indicator. The results demonstrate that Rs(Q1(Rct1W1)) (Q2(Rct2W2)) is more suitable for the study of rubber concrete system and the increase of rubber will enhance the resistance to chloride ion transmission. The equation was established by the relation between the equivalent circuit parameter (Rct1) and the migration depth of chloride ion. On this basis, the EIS method can be utilized to predict the depth of chloride ion penetration in rubber concrete.

Research on Online Detection Method of Transformer Winding Deformation Based on VFTO Characteristics

At present, most of the winding fault detections of transformers use offline methods, which require the entire line to be powered off or after the transformer has been shut down due to a serious fault, and they cannot detect the running status of the windings in real time and online. Since the transformer will be impacted by VFTO during operation, the VFTO is used as the excitation, and the basic principle of the frequency response method is used to propose an online detection method of transformer winding deformation based on VFTO characteristics. The finite element software is used to calculate the equivalent circuit parameters of normal and deformed windings, and the equivalent circuit model of the transformer windings before and after deformation is established. Due to the uncertainty of the VFTO waveform, combined with the frequency response method, the VFTO waveform is injected into the transformer winding health, and the frequency response curve is obtained from the deformed equivalent circuit, which is used to analyze the change of the resonance point in the case of radial deformation, axial deformation, and axial displacement of the winding. The simulation results show that with VFTO as the excitation, the obtained resonance point change can comprehensively reflect the deformation information of the winding. At the same time, the feasibility of the method is verified by experiments.

Fractional equivalent circuit model and parameter identification of reactance components in high-frequency operation

PurposeThe purpose of this paper is to find a simpler model for the reactance components in the high-frequency range on the premise of ensuring the accuracy.Design/methodology/approachIn this paper, based on the fractional calculus theory and the traditional integer-order model, a reactance model suitable for high frequency is constructed, and the mutation cross differential evolution algorithm is used to identify the parameters in the model.FindingsBy comparing the integer-order model, high-frequency fractional-order model and the actual impedance characteristic curve of inductance and capacitance, it is verified that the proposed model can more accurately reflect the high-frequency characteristics of inductance and capacitance. The simulation and experimental results show that the oscillator constructed based on the proposed model can analyze the frequency and output waveform of the oscillator more accurately.Originality/valueThe model proposed in this paper has a simple structure and contains only two parameters to be identified. At the same time, the model has high precision. The fitting errors of impedance curve and phase-frequency characteristic curve are less than 5%. Therefore, the proposed model is helpful to improve the simplicity and accuracy of circuit system analysis and design.

A New Hybrid White Shark and Whale Optimization Approach for Estimating the Li-Ion Battery Model Parameters

Constructing a reliable equivalent circuit of Li-Ion batteries using real operating conditions by estimating optimal parameters is mandatory for many engineering applications, as it controls the energy management of the battery in a hybrid system. However, model parameters can vary according to the electrochemical nature of the battery, so improving the accuracy of the battery model parameters is essential to obtain reliable and accurate equivalent circuits. Therefore, this paper proposes a new efficient hybrid optimization approach for determining the proper parameters of Li-ion battery Shepherd model equivalent circuits. The proposed algorithm comprises a white shark optimizer (WSO) and the whale optimization approach (WOA) for modifying the stochastic behavior of the WSO while searching for food sources. Minimizing the root mean square error between the estimated and measured battery voltages is the objective function considered in this work. The hybrid variant of the WSO (HWSO) was examined with two different types of batteries. Moreover, the proposed HWSO was validated versus a set of recent meta-heuristic approaches including the sea horse optimizer (SHO), artificial gorilla troops optimizer (GTO), coyote optimization algorithm (COA), and the basic version of the WSO. Furthermore, statistical analyses, mean convergence, and fitting curves were conducted for the comparisons. The proposed HWSO succeeded in achieving the least fitness values of 2.6172 × 10−4 and 5.6118 × 10−5 with standard deviations of 9.3861 × 10−5 and 3.2854 × 10−4 for battery 1 and battery 2, respectively. On the other hand, the worst fitness values were 6.5230 × 10−2 and 6.6197 × 10−5 via SHO and WSO for both considered batteries. The proposed HWSO results prove the efficiency of the proposed approach in providing highly accurate battery model parameters with high consistency and a unique convergence curve compared to the other methods.

Toward a Diagnostic Method for Efficient Perovskite Solar Cells Based on Equivalent Circuit Parameters

The equivalent circuit model is one of the essential tools for revealing information about the material characteristics, working mechanisms, and operation state of perovskite solar cells. However, it is still challenging to accurately obtain the equivalent circuit parameters of the highly efficient solar cells with a power conversion efficiency more than 22%. In this work, we proposed a new scheme to estimate all the parameters of the high-performance solar cells only from their current–voltage curves by reasonably combining the traditional analytical method and the parameter optimization method. Then, we applied the proposed method to analyze the equivalent circuit parameters of a typical efficient perovskite solar cell under different light intensities and aging times. Through the parameters, we succeeded in bridging photovoltaic parameters and the structural, morphological, and optoelectronic changes of the solar cells. In particular, the proposed method is compatible with the notorious current–voltage hysteresis. To test the method further, it is compared with two typical approximate methods commonly used recently. By comparison, the proposed approach is simple, reliable, and insensitive to the initial values. Moreover, limitations and precautions for the traditional methods are given to ensure their effectiveness. Finally, we note that the proposed approach of this work provides a feasible solution to conduct real-time monitoring and analysis of the high-performance solar cells.