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Due to active power demand in the distributed power system, the large voltage deviation appears in the grid network. The battery energy storage system is optimal solution to support the active power when it is needed, which improves the voltage stability. To maintain the accuracy in the active power injection, the modified hysteresis current control of multilevel converter for grid connected battery storage system is proposed in this paper. It supplies accurate active power by estimating the exact reference current from the grid voltage at every sampling period. This novel control mechanism ensures that there will not be any mismatch in the active power requirement and supply; thereby it enhances the quality of grid under nay situation. The detailed control block diagram is addressed to generate the required PWM signals. And also, the detailed operating waveforms are discussed in this paper. The equivalent circuit of power transfer to grid is also reported in this paper. Mathematically it gives that the proposed approach can inject the actual active power needed by the system. To validate the proposed modified hysteresis current control scheme of multi-level converter, the entire simulation study has been developed and carried out in PSCAD/EMDTC software. The measured results observed and presented in this paper and also it confirms that the proposed has practical feasibilities to implement in the real system.

We have developed a comprehensive 3D heating test simulation model of a Li-ion battery cylindrical cell and module, taking gas flow and combustion into account. The model is based on the equivalent circuit model and includes not only the heating of a cell (joule heating and thermal decomposition) but also gas ejection flow from the cell and combustion. First, the validation of the cell model for surface temperature and voltage profiles was conducted for a commercial 18650-type cell with an actual heating experiment. Subsequently, a simulation model of the battery module, composed of total 98 cells heated by a burner, was developed, and the behavior of thermal runaway was evaluated. This model makes it possible to evaluate the events that occur from the start of heating the battery module to gas ejection, including housing melting, separator shutdown, and the propagation of thermal decomposition reactions between the cells, and might be a helpful tool for designing battery cells and modules.

Despite great progress in lithium-sulfur (Li-S) batteries, the electrochemical reactions in the cell are not yet fully understood. Electrode processes, complex interfaces and internal resistance may be characterized by electrochemical impedance spectroscopy (EIS). EIS is a non-destructive technique and easy to apply, though there are challenges in ensuring the reproducibility of measurements and the interpretation of impedance data. Here, we present the impedance behavior of a 3.4 Ah Li-S pouch cell characterized by EIS. The impedance changes were analyzed over the entire depth-of-discharge, depth-of-charge, and at various temperatures. Based on the formation of intermediates during (dis)charging, the changes of resistances are observed. Overall, the increase in temperature causes a decrease in electrolyte viscosity, lowering the surface energy which can improve the penetration of the electrolyte into the electrode pores. Moreover, the effect of superimposed AC current during EIS measurement was analyzed, and the results show the dependence of the charge transfer resistance on superimposed AC current which was lower compared to steady-state conditions and consents with theory.

This experimental study aimed to obtain the actuation properties of Shape Memory Alloy (SMA) spring actuators available under the commercial names of Biometal® NiTiCu and KRL® NiTi NiTiCu, NiTiFe. An objective is to characterize the electro-thermo-mechano-electro behavior of shape memory spring through experimentation via simultaneous measurement techniques. These measurements are synchronized by embedding an impedance analyzer and data acquisition module through a unique program. Moreover, to obtain the mathematical model by parts of the SMA spring and equivalent circuit analysis of active spring through their electro-thermo-mechano-electro characteristics exhibited during shape memory effect. Based on the experimental results, the SMA spring's equivalent circuit is considered a series resistance - inductance​ circuit. It was found from the experimental results that the Biometal® actuator produced more resistance, inductance variation and offered more displacement as compared to KRL® actuators.

Compensated pulsed alternator (CPA) can exchange its kinetic energy into high current pulses. The pulse current waveform can be provided more flexibility by means of the trigger angle control of each phase from the multiphase CPA pulse driving system, which allows a flatter current pulse and higher piezometric efficiency. Because of multiphase CPA pulse driving system is complex, optimization variables are large quantities, the analytical method to optimize the current waveform by means of trigger angle control get more difficult. In this paper, an orthogonal two-phase CPA analytical model is established based on circuit theory. Focus on the multiphase CPA designed based on an orthogonal two-phase CPA, an approach to decrease trigger angle optimization variables is proposed. Finally, an eight-phase CPA pulse driving system adopted half wave rectification in practical application is established. The trigger angle optimization variables are decreased, and optimized in an equivalent circuit simulation model by genetic algorithm (GA). The discharge current after optimization is closed to a trapezoidal waveform, the approach is verified efficiency.

Focused on the hydraulic factor-induced ultra-low frequency oscillation phenomenon happened in a large hydropower plant, this paper investigates the precise modelling of hydraulic transient characteristics in its complex tailrace system and reveals the feasible oscillation suppression schemes from the source side. Combining telegraphist's equations with Saint-Venant equations, the mathematical expression of equivalent circuit model (ECM) for open channels is deduced, thus to expand the utilization of ECM to hydraulic transients description in pressurized pipe and open channel combination systems and to establish the high-order equivalent circuit topology of the overall tailrace system in a real hydropower plant. Based on the mathematical model, the feasibility and effectiveness of two different oscillation suppression approaches via respectively increasing the hydraulic losses on the branch tailrace channels or the main tailrace channel are discussed in detail via numerical simulation. Furthermore, the superiority of the oscillation suppression scheme via increasing hydraulic losses on branch channels in reducing the extra power generation loss is demonstrated. The application of equivalent circuit theory in complex hydraulic systems can contribute to the mechanism-related research on ultra-low frequency oscillations in hydro-dominant power systems.

Compared with a copper wire electrode, molybdenum wire with a poor conductor is usually used as the electrode in high speed wire-cut electrical discharge machining (HSWEDM), so the resistance of an ultra-fine wire cannot be ignored. To study the differences of discharge characteristics between the ultra-fine wire and the conventional diameter wire, the continuous discharge waveform of two kinds of wire electrodes was compared. It was found that there was a multi-channel discharge phenomenon in the discharge waveform cutting by ultra-fine wire. Through the establishment of a discharge equivalent circuit model and the simulation analysis of the electrostatic field, it was found that the reason why ultra-fine wire is easy to form multi-channel discharge phenomenon is that the potential difference between the wire and the workpiece increased linearly along the axis of the wire. Besides, etching products like metal particles will distort the electric field between the electrodes. Both of them make it easy to form a multi-channel discharge in machining. The results show that the distributions of the equivalent resistance and the peak current are affected by the multi-channel discharge position. Multi-channel discharge can disperse energy and increase effective discharge frequency. Compared with the 0 mm spacing, at a spacing of 100 mm, the machining efficiency increases by 8.7%, the surface roughness decreases by 37.7%, and the average recast layer thickness decreases by 46.6% under the condition of ultra-fine wire-EDM.

Modeling photovoltaic (PV) modules is fundamental for analyzing their efficiency and performance under different operating conditions. Generally, photovoltaic module modeling is based on a suitable equivalent circuit and a set of parameters representing the PV module's properties. Defining these parameters is not a trivial task, as they are usually not included in the technical documentation of the module. Therefore, the need to find suitable values for the model parameters becomes imperative. In this paper, we will test and compare two methods of extracting single-diode model (SDM) parameters: analytical and numerical, under standard test conditions (STC conditions). We examined the performance of six techniques: three analytical and three numerical. Except for Saleem technique, which tends to underestimate the I-V and P-V curves in the MPP zone, the results demonstrated that both approaches (analytical and iterative/numerical) are valid and accurate for predicting the I-V and P-V curves under STC conditions.

In order to describe the behavior and the performance of the photovoltaic modules we can found in the literature different equivalent circuit models such us: single diode model (SDM), double diode model (DDM), three diode model (TDM). Almost of the authors obtained that the SDM is the best solution to describe the electrical characterization of the PV modules. The PV parameters can be extracted by three common approaches: Analytical based on the derivation of mathematical equations, Numeric or iterative usually use non-linear optimization techniques, among all the technique the Newton Raphson is widely used. The last one is meta-heuristic approach characterized by their global search point and their soft computing algorithms. The aim of this study is to explore and discuss the behavior of the single-diode model, which require five parameters are estimated using Particle Swarm Optimization approach. The performance of this method is evaluated using the experimental values of R.T.C France PV cell at irradiation G = 1000 W/m2 and at temperature T = 33 °C. The obtained results are also compared with results of the others computing approach. After this study, we can conclude that the proposed PSO method has the best performance because the RMSE obtained using this approach is around the 1.73.10−4 A and low than those obtained through all compared algorithms.

In the process of membrane absorption, spontaneous wetting of hydrophobic microporous membrane causes membrane modification and increases membrane phase mass transfer resistance, which have attracted wide interest. However, due to the limitations of previous testing methods, the study of the spontaneous membrane wetting process is limited. Herein, we present a method for monitoring spontaneous membrane wetting by measuring its AC impedance. The impedance tests of the PVDF flat membranes and hollow fiber membranes were conducted in a two-electrode system. The results of equivalent circuit fitting indicate that the impedance value of the unwetted membrane is about 1.02 × 1010Ω, which is close to the theoretical value of 1.4 × 1010Ω, and this method can quantify the electrochemical impedance value of membranes with different degrees of spontaneous wetting. In addition, a method of impedance test for real-time monitoring of spontaneous wetting was designed. During the experiment, the timeliness and continuity of this method are confirmed with exact judgment under different conditions. In future work, the impedance data will be used to build model to predict the percentage of membrane wetting degree.

An effective online fault diagnosis system is of great significance to improve the reliability of fuel cell vehicles. In this paper, a fault diagnosis model for proton exchange membrane fuel cells is proposed. Firstly, the tests of electrochemical impedance spectroscopy under different fault types (flooding, drying, air starvation) and fault degrees (minor, moderate, severe) are carried out, and each polarization loss of the fuel cell is denoted by an equivalent circuit model (ECM). Then, the parameters of the ECM are identified by the proposed random mutation differential evolution algorithm. Furthermore, the parameters identified under different fault conditions are used to train and test a probabilistic neural network-based fault diagnosis model. The fault diagnosis model achieves diagnosis accuracies of 100% for the fault type and 96.67% for the fault degree. By setting operating conditions with different fault degrees, the fault diagnosis model proposed in this paper can realize the fault type and fault degree diagnosis, effectively avoiding the misjudgment of fault types, and is effective for improving the reliability of the fuel cell system.

This study proposes a reduced model based on the state space representation for identifying an accurate electric equivalent circuit of Lithium-Polymer Battery Cells. The parameter extraction process is formulated as non-linear optimization problem via three-stage procedure. The first stage estimates the state of charge (SoC) based on the non-linear characteristics associated with the battery current and the initial SoC condition. In the second stage, the open circuit voltage is estimated in terms of the resulted SoC that is employed in the first stage with varied linear and non-linear models. In the third stage, an Equilibrium Algorithm (EA), a recent optimizer, is developed for optimally identifying the battery parameters. The EA’s parameters are adjusted based on Taguchi’s design of experiment approach to reduce the computational time as well as the number of experiments that are required to get the optimum possible parameter arrangement Numerical simulations associated with experimental implementation are emulated on Li-Ion Battery to prove the high capability of the proposed EA an as efficient identification procedure. In Addition, the proposed EA is characterized with high accuracy compared with several recent optimization algorithms for ARTEMIS driving cycle profile. The solution quality improvement of the proposed reduced model is achieved with high closeness to the experimental measurements for battery voltage and SoC. Furthermore, 16 % less computational times 12 % more accuracy are obtained by the proposed reduced model compared with linear and non-linear models.

In this paper, a graphene-based metamaterial absorber is proposed and investigated numerically, in which the interaction between a split ring resonator (SRR) and graphene results in a high-Q absorption. To make a better understanding of the resonance mechanism, the electric and the magnetic fields, and the surface currents at the resonance frequency are investigated. In order to ease the analysis of the structure, an equivalent circuit model is introduced using the transmission line theory, and the accuracy of the proposed model is verified by the full-wave simulation. Finally, different aspects of the designed metamaterial are discussed as a potential label-free sensor for chemical and biomedical sensing. It is shown that by using this structure, a sensor with a sensitivity of 597 GHz/RIU can be achieved.

The hybrid HVDC system based on line commutated converter and modular multilevel converter is a feasible method to address the common commutation failure at the receiving end of conventional HVDC systems. At present, project Gezhouba–Shanghai in China is under the demonstration scheme of the conventional receiving end upgrading, which introduces the difficulty in sending-end AC system failure riding through. For this purpose, an electromagnetic simulation model is established in the PSCAD/EMTDC simulation platform firstly, and then a transient analytical expression of DC current is deduced through the system equivalent circuit and verified through the simulation model. The expression deeply reveals the variation pattern of DC current and lays the theoretical foundation for fault ride-through control. Base on this expression, the decreasing level of MMC DC voltage after fault is deduced, however, it is difficult to realize the decreasing of MMC voltage due to the modulation index limitation of DC voltage. In order to solve this problem, this paper uses MMC to absorb reactive power from AC power grid to broaden the range of DC voltage drop. To solve this problem, the reactive power MMC absorbing from the AC power grid is used in this paper to broaden the decreasing range of DC voltage. On this basis, due to the conflict between the rapidity and stability of fault ride-through control, a current ride-through control based on reactive power auxiliary is proposed. This control strategy can dynamically regulate the reactive power transmission between MMC and AC grid according to fault states, assist to reduce the MMC DC voltage, and enable the constant current control so as to realize the sending-end AC system fault ride-through. Finally, the effectiveness of this control is verified with various simulation results. The sending-end AC system fault ride-through control method proposed in this paper has profound project application significance on upgrade transformation for the conventional receiving end.

Background Supported liquid membrane (SLM) is a very promising method for the recovery and separation of valuable or toxic species from aqueous streams; however, stability is always a critical issue in practice. It is highly desired to develop a non-destructive technique to real-time monitor or detect the stability of an SLM process. Methods The stability of an SLM processes was real-time analyzed by electrical impedance spectroscopy (EIS). The separation of equimolar Zn(II) and Cu(II) from sulfate solution through an SLM containing di(2-ethylhexyl) phosphoric acid (D2EHPA) in kerosene was selected as the model system owing to the established knowledge of extraction chemistry. Experiments were performed with two types of membrane supports (polycarbonate and poly(vinylidene) fluoride), different D2EHPA concentrations in the organic phase (0.001–0.1 mol/L), pH values of the feed (3.0–5.0) and strip (1.0–3.0) phases, and stirring speeds (0–200 rpm). Correlations between the membrane impedances analyzed according to a proposed equivalent circuit diagram and the separation factors of Zn2+ over Cu2+ measured by SLMs were done to verify the progress of the loss of membrane liquid. Significant findings Under the conditions studied, the variations of membrane impedances and separation factors with time using both types of membrane support followed similar trends in most cases. A stability factor of a SLM process based on membrane impedance data was defined, which enables us to predict its relative stability. The present results also demonstrated that all parameters including membrane type, carrier concentration, aqueous pH values, and stirring speed influenced the transport and separation of Zn2+ over Cu2+ and SLM stability.

We have fabricated CZTSSe solar cells with H2S sulfo-selenization processes and investigated the electronic structure at the PN hetero- and back contact junctions by impedance spectroscopy. By decoupling each junction’s impedance spectroscopic responses, we systematically characterized the built-in potential of two local junction interfaces. A developed equivalent circuit model has been optimized for decoupling each junction’s property at different frequency bands. Modeling and numerical simulations were conducted with the in-house MATLAB modeling suites connected to external simulators of Sentaurus TCAD and LEVM/LEVMW software to estimate the impact of each junction component to impedance spectra. The optimized model is comprised of a parallel circuit combination with resistance and capacitor-like elements (constant phase elements), connected to one inductive element. The conversion efficiency of CZTSSe devices is 6.2% with bandgap energy 1.13 eV based on external quantum efficiency measurements. From the equivalent circuit model, the built-in potential of the hetero-junction is characterized as 956 meV, which is ~ 3% smaller than an ideal case from TCAD, 987 meV. Conversely, the built-in potential of the back contact junction is 476 meV. The apparent built-in potential is estimated as 480 meV from the Mott-Schottky equation.

The conventional approach to modeling a typical photovoltaic (PV) module under partial shading conditions is based on the equivalent circuit model, which provides the current–voltage (I–V) relationship in an implicit form. In this study, a novel method based on an explicit analytical model is proposed for estimating the performance of a PV module under partial shading conditions. An explicit expression of voltage in terms of current is derived from the implicit I–V expression of the single-diode model for a single PV cell under different environmental conditions. The model is then extrapolated to a submodule under partial shading conditions, and finally, to a PV module. Using the proposed method, the I–V curve and maximum power of a PV module are calculated analytically and accurately under different partial shading conditions. Owing to the explicitness of the proposed method, the computational complexity and time required are significantly less than Newton’s method and Lambert W function method with similar accuracy. The proposed method is verified via outdoor experiments under different partial shading conditions. The results show satisfactory agreement between the estimated and measured I–V curves and between the P–V curves and the maximum power. The proposed method is accurate and particularly effective for determining the actual performance of PV modules under partial shading conditions, and is thus scalable for direct online applications.

The effect of bias voltages (40 V, 80 V, and 40/60/80 V) on microstructure and electrochemical properties of arc-PVD CrN coatings were evaluated. Increasing the bias voltage produced microstructural changes, from well-defined columns to columnar grains, and increased defect size. The electrochemical response proved susceptible to the defect type. Nano-droplets promoted the formation of oxides, while large pores allowed the migration of the electrolyte to the substrate/CrN interface. An impedance equivalent circuit based on the Bisquert transmission line was proposed to fit the experimentally obtained impedance spectra. The equivalent circuit allowed correlating the coating electrochemical response to the defect densities and sizes. Samples deposited with 40 V showed the lowest corrosion current (0.05 μA/cm2 ± 0.01), which was supported by the highest resistances to the transport of ions through the pores (Rp = 1047 ± 88 kΩꞏcm2). Films obtained with 80 V reduced Rp values by two magnitude orders compared to CrN 40 V. The increase of pore resistance in CrN 40 V was associated with the oxidation of nano-droplets (proposed auto-protection phenomenon), which blocks open pinholes due to the smallest average size of defects. Tailoring a gradual increase of the bias voltage (40/60/80 V) preserves the auto-protection mechanism of droplets and improves the surface finish of the coating.

Optimized integration of fuel cells into grids or on-board power supplies is necessary to facilitate replacement of conventional energy producers by a reliable and plannable power generation technology. Due to the interdependency between fuel cell current and voltage, integration of fuel cells requires a power conditioning system, which increases integration weight and cost. For this reason, integration of electric field modifier electrodes into the setup of proton exchange membrane fuel cells is a new approach to control the output voltage in order to minimize the subsequent power conditioning system. This approach considers the physics of proton transport through the electrolyte membrane and could offer a lever to control the ohmic resistance. In this paper, a fuel cell model is implemented in MATLAB and extended by electric field modifier electrodes, allowing control of the ohmic resistance through an externally applied voltage. The concept of boosting and attenuating fuel cell voltage is presented along with different setups to enable this behavior. Furthermore, an electrical equivalent circuit for electrically controllable fuel cells is developed and implemented in MATLAB/Simulink. A method to parameterize the developed MATLAB and Simulink models by first experimental results is presented.

Dielectric capacitors with large energy storage density, low hysteresis loss, low temperature dependence and high temperature adaptability show great advantages in high temperature applications of electronic devices. In this work, a large energy storage density (W ~ 28.776 J/cm3) and ultra-high efficiency (η ~ 87.36%) have been simultaneously achieved in the CuX(Ba0.88Ca0.12)1-X(Zr0.12Ti0.88)O3 (X = 0.1) lead-free relaxor ferroelectric thin film capacitors deposited on Pt(111)/TiOX/SiO2/Si(100) substrates by using a sol-gel method. The results show that the dielectric permittivity and dielectric loss change a little in the temperature range of 30–400 °C. The reason of low dielectric loss and temperature insensitivity is revealed by means of Raman spectrum fitting and equivalent circuit model (the I-E curve of ferroelectric materials is regarded as an equivalent circuit of equivalent capacitance (C), equivalent resistance (R) and polarization charge (Ip(t)) in parallel, given by the equation I ( t ) = V ( t ) / R + K C + I p ( t ) ). The results prove that the stability of slope (K) is positively correlated with the stability of energy storage performance of ferroelectric materials, which provides the basis for the evaluation of energy storage performance of ferroelectric materials.

In this article, a broadband metamaterial (MTM) absorber is proposed that exhibits near-unity absorption in the terahertz regime. The proposed metamaterial absorber was initiated on a quartz (fused) substrate, whereas the resonator and backplane are constructed with tungsten. The resonator is designed with a square ring loaded with a face-to-face E structure at the center. It also consists of diagonally extended arrow-like shapes loaded from the corners and a concave-shaped structure extended from the middle of the square ring. Near-perfect absorption is observed at the frequencies of 465.2 THz, 585.2 THz, 648.8 THz, and 762.8 THz with absorption peaks of 99.8%, 99.9%, 99.92%, and 99.92%, respectively. Moreover, it exhibits broadband absorption properties above 90% absorption with bandwidths 20.4 THz, 80.8 THz, 41.6 THz, and 90 THz, respectively, at these resonance frequencies. Due to its symmetrical structure, it shows polarization-insensitivity behavior up to 90° with maximum absorption greater than 90% both in transverse (TE) and transverse magnetic (TM) modes. It also exhibits insensitivity to changes of incident angle from 0°–45°. Metamaterial properties of the proposed absorber are also analyzed, showing single negative behavior. Absorber property has been examined through surface current and equivalent circuit electric and magnetic field analysis. The effect of the cross-polarization is negligible and is verified through simulation. Due to its large bandwidth, polarization-insensitive behavior, and low PCR, the proposed MTM absorber can be incorporated into photovoltaic devices as a solar-energy harvester.

This work proposes a numerical methodology for the calculation of currents and voltages induced on underground pipelines by nearby overhead power lines. A previously developed quasi-3D methodology is extended, allowing the investigation of nonparallel routings of the pipelines with respect to the power lines. The proposed technique is based on a discretization of the pipeline path into several segments parallel to the power line. The section of the corridor corresponding to each pipeline segment is regarded as an electrical multi-port component, whose electrical parameters are extracted via finite element 2D analysis. Then, the obtained components are integrated into a network embodying the physical characteristics of the whole corridor. In this way, the circuital analysis is used to extend the capabilities of a standard two-dimensional field analysis. The proposed methodology is employed to simulate a pipeline running parallel to a power line for a distance of 12km. Afterwards, several nonparallel configurations – consisting of crossings between a pipeline and a power line – are assessed. The physical consequences of the crossing are discussed and a convergence study is performed to investigate the optimal pipeline subdivision procedure to be adopted for a set of different crossing angles.

Electrochemical impedance spectra is a useful tool for fuel cell water content analysis. However, the data processing efficiency is greatly reduced with the increment in the number and complexity of the experimental parameters. Thus, in this work, an impedance prediction model is developed to assess the impacts of operating conditions and cell position on fuel cell impedance. The model is based on the Randles equivalent circuit and convolutional neural networks. And after verification, this model shows satisfactory performance in impedance prediction. Based on the model, impedance parameters and impedance spectra can be obtained rapidly for any operating condition and cell position. By directly predicting the impedance parameters, a more detailed description about the impact of different operating conditions on internal state of fuel cell can be given. The model can be integrated into the fuel cell control system and determine the optimal operating parameters.

A narrow metal strip inspired by the left-handed metamaterial and sensitive LC resonator structure has been released in this work where the narrow metal strip is presented as a tunnel structure which can enhance electric and magnetic properties. A commercially available electromagnetic simulator CST Microwave Studio is utilized to design and investigate the eSRR (electric split-ring resonator) and tunnelled LC resonator structures. Furthermore, ADS (Advance Design software) is used to determine the scattering parameters of the equivalent circuit. The proposed metamaterial structure is employed as a sensor operating in the C-band (6.88 GHz) of the microwave region, and its sensing properties are tested using glossy paper as an obstacle. The designed metamaterial tunnelling structure exhibits very high sensitivity toward dielectric obstacles at different rotational angles and thus can be potentially used in various sensing applications. The field enhancement effects on sensing application are verified by measured obtained results for eSRR and tunnelled LC resonator structures.

Summary The development of efficient and stable lead-free perovskite solar cells (PSCs) is crucial for addressing the concern of environmental pollution from the toxic element lead. In recent years, tin PSCs have emerged as a promising candidate for high-performance, eco-friendly photovoltaic technology with a high certified power conversion efficiency (PCE) of more than 11%, indicating a great potential for future applications. Here, we review the recent efficiency progress of tin PSCs based on the equivalent circuit model of solar cells. We then discuss approaches toward efficiency improvement from the device viewpoint, such as optimizing the band gap, increasing the light-harvesting efficiency and carrier diffusion length, surface passivation, and regulating the interface energy-level alignment. Finally, we point out the possibility of reaching 20% PCE for tin PSCs and issues regarding enlarging the cell size and realizing scalable production in the future. We expect that these perspectives will be helpful for accelerating the commercialization of tin PSCs.

An approximated expression for the calculated solar cell current is usually used in parameters estimation of the 7-parameter double diode model (DDM) and the 9-parameter triple diode model (TDM) of solar photovoltaic (PV) equivalent circuits. Then the root mean square error (RMSE) is calculated between the measured and estimated values of the output current. In the mathematical sense, the RMSE calculation procedure is not correct. In this work, a novel iterative approach based on the Lambert W function is proposed to calculate the solar cell current in both DDM and TDM. Then, the RMSE values computed using the parameters found by many optimization algorithms presented in the literature are presented and discussed for the RTC France PV cell and Solarex MSX–60 PV module. The results obtained show that RMSE values were not accurately calculated in most of these methods. Further, an improved LSHADE optimization algorithm called Chaotic LSHADE algorithm is proposed to solve the 7-parameter and 9-parameter estimation problem of the PV equivalent circuits. The proposed methodology is also applied to current–voltage characteristics measured in the laboratory for solar modules of Clean Energy Trainer Setup. The 7 and 9 unknown parameters are estimated using the CLSHADE algorithm based on the minimization of the RMSE values calculated. The results obtained show that the proposed algorithm achieves better solutions than the solutions obtained by many optimization algorithms presented in the literature.

Hot-spot generation is critical to the reliability and performance of copper indium gallium selenide (CIGS) solar cells; however, its occurrence mechanism has not been fully elucidated. We conducted a partial shade stress test on three large-area CIGS modules (156 cm × 62.6 cm in size, with 102 cells) connected in series. Partial shade stress can cause irreversible and unpredictable damage to the modules, and we confirmed the generation of hot spots on the shaded cells via infrared imaging. To emulate numerically the internal electrical and thermal changes in the shaded cells, we present electrical and thermal equivalent circuits based on the material properties and layered structure of the CIGS cells and modules. Furthermore, we propose a hot-spot generation model describing the irreversible damage to CIGS cells via shunt resistance degradation because the dissipated electrical power exceeds the threshold power ( P t h ). The current–voltage characteristics simulated by the presented method are congruent with those measured under partial shade conditions. Partial shade induces high electrical power consumption in the shaded cells, up to ~34 mW/cm2 at a 5% shade ratio, ~1,500 times higher than that in the unshaded cells. The shunt resistance is degraded to ~18.5 Ω/mm2 (only ~0.1% of the initial normal value), and the P t h -value is estimated to be ~2.4 mW/cm2 at the center of the hot-spot cells. The presented method and P t h -parameter can be used to evaluate durability with respect to the effects of partial shade stress for CIGS and various other thin-film photovoltaic cells and modules.

The single–diode model is widely used for the analysis of photovoltaic systems and reproducing accurately the I–V curve. Numerical or analytical methods can be employed to estimate the model parameters; among them explicit methods are well assessed providing precise results and low computational complexity, thus suitable to be developed on embedded systems. Due to their approximated nature, the accuracy of such methods may be affected by the operating conditions and by the state of health of the photovoltaic modules that have been characterised. The main contribution of this paper is to analyse a selection of explicit methods with the aim of testing their capability to detect degradation in photovoltaic modules. Since different degradation phenomena are reflected in a variation of the series resistance of the single diode equivalent circuit, the study is mainly focused on the estimation of this parameter. The comparison of different explicit methods has been done by using outdoor experimental I–V curves of a photovoltaic module operating in normal as well as degraded conditions. The analysis shows that only few methods exhibit enough reliability to estimate correctly the model parameters in presence of degradation and are less sensible to the environmental operating conditions.

In this work, delay-lines loaded broadband reflectarray antenna is proposed for X-band applications. The array cells contain slotted square patch and quad meander delay-lines. The slotted square patch elements are combined with delay-lines to increase the reflection phase range. A smooth linear phase variation of 650° is realized through varying the length of delay-lines. The reflectarray unit element resonant behavior is observed through an equivalent circuit model approach. The reflectarray antenna is simulated and measured on a low-cost FR-4 substrate. A 23 × 23 elements reflectarray antenna is designed and simulated using a hybrid finite element boundary integral (FEBI) method. The proposed reflectarray antenna offers a measured gain of 25 dBi and 52.8% aperture efficiency for 10 GHz frequency band. The cross-polarization levels and side-lobe-levels and in E and H-plane are less than −35 dB and −22 dB respectively. Moreover, a measured 3-dB gain bandwidth of 29% and 1-dB gain of 19.5% is realized for the proposed reflectarray antenna.

To improve the efficiency of switchgear maintenance, a double-action switchgear is presented to realize the purpose of on-line maintenance in this paper. And to check the reliability and safety of the novel design, a research about the insulation performance of the new design switchgear under two different impulse action is carried out. The two different impulse phenomena refer the switching process of the double-action switchgear and the lighting impulse respectively. The switchgear conversion equivalent circuit is established to analyze the transient process of the switching and the mechanism of lightning surge strike on the switchgear is analyzed as well. Based on these, an 3D electric field model is established to calculate the distribution of electric field under switchgear transient condition and the lightning impulse condition respectively. The results show that when the new switchgear operates under the condition of the maximum overvoltage during the switching progress, the maximum field strength is 4.35×105V/m, which is less than the air breakdown field strength. Under the extreme conditions of lightning surge strike, the maximum field strength in the main switchgear and stand-by switchgear is 1.415×107V/m and 5.093×106V/m respectively, where the breakdown may occur. Lightning arresters is quite necessary to be adopted to protect the new switchgear.

In combination with an analogous circuit pattern, the electrochemical impedance (EIS) spectra aids in examining the physical origin of the different electrical components involved in the device. In this research, to illustrate the various physical processes taking place in energy-storing electrodes, the EIS spectra in the entire frequency area is divided into specific electrical elements such as resistors and capacitors with the help of Z view software and determined origin of their charge storage properties. The EIS spectra of activated carbon (AC) – TiO2 or MnO2 composites containing TiO2 in the range 5 – 20 wt% and nominal composition of MnO2 (5 wt% MnO2) are analyzed using the equivalent circuit fitting technique and the corresponding electrode parameters and performances are correlated.

The mismatch is a phenomenon intrinsically related to photovoltaic (PV) arrays, either because they are eventually subject to non-uniform irradiance and temperature conditions, or because of inner variations on the components, ageing or occurrence of failures. Despite mismatch losses being so present in the life of a PV system, the available tools for the study of PV arrays response through simulation today present limitations for the handling of mismatch conditions. Most of them do not support non-uniform conditions, and the ones that do, solely explore irradiance and temperature variations, ignoring other causes for mismatches, such as defects on PV cells. This paper proposes a simulation framework that allows manipulation of each parameter in each cell individually to reproduce mismatch conditions, including failures. Each PV cell is represented by the one diode equivalent circuit model, for which two different parameterisation methods were tested: California Energy Commission (CEC) and PVSyst. The proposed simulation framework was validated with laboratory measurements of a PV module under 15 different mismatch conditions of partial shading and failure (short circuit). The results showed a consistent similarity between calculated and measured I–V curves, and errors at the curves’ maximum power points stayed within the instruments’ accuracy range, roughly 1.0 V and 0.2 A. The proposed simulation framework brings great flexibility to the studies of mismatch through simulation, allowing the calculation of the I–V curve of PV strings and small arrays subjected to mismatch conditions due to non-uniform irradiance and temperature profiles, but most significantly failures in the cells.

In this study, LSM-YSZ composite cathodes were analyzed by changing the firing temperature, composition, and operating temperature to determine the contribution of each step of the oxygen reduction reaction (ORR). The overall resistance of the cathode reaction was characterized by fitting the AC impedance spectra with an equivalent circuit model. It was found that initial reactions of ORR (dissociative adsorption) are the main rate-determining step (RDS) regardless of operating or sintering temperature, while reactions on LSM surface become the main RDS when the ratio of LSM catalysts has a relatively small proportion. The [LSM-YSZ]5:5 cathode fired at 1100 °C showed the best microstructure and lowest resistance in the ORR at an operating temperature of 700 °C (RHF: 0.18 Ωcm2, RMF: 0.20 Ω cm2, RLF: 0.25 Ωcm2, Rcathode: 1.14 Ωcm2). This demonstrates the potential use of LSM-YSZ cathodes for IT/LT-SOFC without the use of expensive materials, such as LSCF and BSCF.

This paper investigates the parameter identification of a state-of-charge dependent equivalent circuit model (ECM) for Lithium-ion batteries. Different from most existing ECM identification methods, we focus on identifying the functional relations between ECM parameters and state-of-charge (SOC). By transforming the ECM into an ARX model, a Gaussian process regression (GPR) approach is proposed, without using parametric functions to describe the SOC dependence of ARX coefficients. The proposed approach derives the posterior distributions of ECM parameters, thus is capable to quantify the estimation uncertainties. Another advantage lies in the flexibility of incorporating the knowledge of batteries into the prior distributions used in GPR, which enhances the estimation performance in the presence of noises. The effectiveness of the proposed GPR approach is illustrated by simulation examples under both low and high noise levels.

In this article, a meander line with parasitic resonator based on ENG metamaterial is introduced, with nonlinear regression of sensitivity for sensing applications. The unit cell is manufactured on a dielectric substrate of FR-4 with a thickness of 1.5 mm. The electrical dimension of the optimized cell is 0.098λ×0.094λ, where λ is the calculated wavelength at 7.2 GHz resonance frequency. A sensor has been designed by the unit cell to measure the thickness of the polypropylene. The offered metamaterial architecture exhibits resonance frequency 7.2 GHz at C-band with the amplitude of −21.72 dB. The NRW approach based MATLAB software shows properties with an ENG behavior and permeability close to zero. For the analysis procedure, a frequency domain solver with the frequency range of 2–12 GHz was used. ADS software verified the scattering parameters (coefficient of transmission) of the equivalent circuit for the corresponding unit cell with the CST result. The result indicates that this design has SNG features at C-band. The EMR (effective medium ratio) of this suggested unit cell is 10.60 at 7.2 GHz resonance frequency. The bandwidth of the optimized cell is 6.75–7.36 GHz, and the negative permittivity region is 7.2–7.8 GHz 1 × 2, 2 × 2, 4 × 4, and 16 × 16 array of unit cell results have been examined. All the array results show the same with the unit cell. Substrate material has also been changed to see the effect of resonance frequency in the parametric study. Finally, the proposed meander line structure performance was further simulated numerically and experimentally investigated for sandwich combination thickness sensing. It shows a narrow bandwidth sensing range between 6.25 and 6.47 GHz with significant sensitivity (S) and accuracy. The design complies with superior effective medium parameters and affords miniaturization factor for the size. Due to its low profile and high EMR, the planned ENG metamaterial can be a suitable C-band aspirant for sensing applications.

Battery management systems (BMSs) are responsible for controlling and monitoring battery operations. In order to be effective, BMSs rely on mathematical models. The parameters of these latter are usually obtained through an identification procedure which provides limited accuracy. In addition, only cell current and voltage are usually measurable. For this reason, the model states need to be estimated. In the following, we propose an interval state estimation of a lithium-ion cell when using an equivalent circuit model, taking into account bounded parametric uncertainty and measurement noise. Simulation results show the suitability of the proposed interval estimator to provide a tight enclosure of the states, which is essential for fault detection and model-based control of a lithium-ion cell.

It is well known that, doping of semiconductor anticipate a huge impact on the AC-DC electric conductivity and its dielectric properties. In our current study, Ni-doped Zn2SnO4 NPs were successfully synthesized via hydrothermal method and then sintered at 500 °C. The XRD pattern exhibits a shift to higher angles which indicating the incorporation of Ni into the ZTO lattice. Moreover, we provide a more general study of electric and dielectric behaviours of Ni-doped Zn2SnO4 as a function of temperature and frequency. The impedance data were fitted using an equivalent circuit which mainly composed of resistors and constant phase elements (CPE). Complex impedance study highlighted the presence of a non-Debye type relaxation. At higher temperature, impedance measurements showed an improvement in the conductivity of ZTO -NPs. While the ZTO-NPs were less resistive before doping, they become more resistant with increasing Ni concentration and frequency. Also, we noted that for low frequencies, Ni doping reduces largely the values of both the imaginary dielectric constant (e”) and dielectric loss, suggesting that Ni-doped ZTO is an adequate material for low frequency device applications. Further, the imaginary part M″ of the complex electric modulus exhibited a shift toward high frequency upon the increase of temperature in the relaxor peak. Taken together the results obtained, indicating that the modified ZTO, could be a promising candidate for high-frequency device application.

This paper explores the state estimation method of lithium-ion battery pack through theoretical analysis and experimental research. Combining the advantages of the empirical models of various electrochemical models, a new type of composite electrochemistry-dual circuit polarization (E-DCP) model is proposed to better reflect the dynamic performance of the power lithium-ion battery under the conditions of meeting its safe and reliable energy supply requirements. Using the multi-innovation least squares (MILS) algorithm to identify the parameters in the E-DCP model online, so that it has the characteristics of high data utilization efficiency and high parameter identification accuracy. The battery charge and discharge efficiency function is introduced to dynamically modify the battery capacity, and the dynamic function is used to improve the Kalman gain in the extended Kalman filter (EKF), a new type of based on dynamic function improvement and combined with actual capacity correction (FC-DEKF) algorithm is applied to the estimation of battery pack operating characteristics, which solves the problem that the traditional EKF algorithm is difficult to estimate errors when the system input change rate is large. The experimental results of urban dynamometer driving schedule (UDDS) and complex charge-discharge cycle test show that the maximum error of terminal voltage does not exceed 0.04V, the accuracy is 99.05%, and the errors of MILS algorithm combined with FC-DEKF algorithm for SOC estimation are all within 1%. The proposed equivalent circuit modeling method and state estimation correction strategy provide a theoretical basis for the reliable application of high-power lithium-ion battery packs.

The synergy of electric vehicles (EVs) and renewable energy (RE) can improve the energy consumption, and participate in grid regulation by vehicle-to-grid (V2G) technology. In this paper, a hybrid charging strategy with adaptive current control for EVs is proposed in this synergistic process. First, the battery parameters are tested by the hybrid pulse power characteristic. Then, the equivalent circuit model is established and the charging characteristics are obtained. Second, inspired by the multi-stage constant current (MS-CC) method, a constant current-constant current-constant voltage (CC-CC-CV) charging strategy is proposed to moderate the temperature of the battery by suddenly dropping the charging rate in the second constant current stage. Third, for the first constant current stage, the adaptive current profile is utilized based on the variable internal resistance of the battery, which can effectively reduce the ohmic losses during the charging process. The comparative experiments show that the CC-CC-CV strategy can alleviate the maximum temperature of the battery. Without harming the charging time and capacity, the hybrid charging strategy can effectively reduce the ohmic losses by 1.2%. Moreover, these advantages are more significant as the charging current increases. Finally, the application of the proposed charging strategy in the smart building with RE is discussed.

As a cathode material, neodymium oxychloride (NdOCl) was used for neodymium extraction by through the solid-oxide oxygen-ion-conducting membrane (SOM) process. In this study, the preparation and sintering conditions of the neodymium oxychloride were discussed. The purity of materials phase compositions was confirmed by the X-ray diffraction method. Moreover, the electrical properties of NdOCl were investigated by Electrochemical Impedance Spectroscopy (EIS) in molten CaCl2 at temperature range 800–900 °C and voltage range of 1.4–1.6 V. The spectra were analyzed by the equivalent circuit fitting. Based on the values of equivalent circuits parameters, the specific conductivities were calculated and presented in the Arrhenius coordinates, and energy of activation of the charge transfer reaction (Nd2+→Nd) was also calculated.

This paper proposes a simple and efficient method to estimate the parameters of the photovoltaic (PV) cells at standard test conditions (STC). The proposed method is based on developing a mathematical model for each parameter of the single-diode equivalent circuit of the PV cell. The models are formulated using Eureqa software based on thousands of training data collected from simulating the equations that represent the equivalent circuit behavior of the PV cell. Only the data provided by the manufacturer’s datasheet are needed to execute the models and evaluate the parameters. The performance of the developed models is then assessed by comparison with simulation data, Simulink library modules, experimental data, and various recent reported algorithms. The assessments have shown an overall efficient performance of the models to evaluate the equivalent circuit parameters for any poly and monocrystalline PV cell/module at STC. In addition, the models are in good agreement and, in some cases, have outperformed various algorithms presented in the literature in terms of the accuracy of predicting the I-V curve characteristics.

Supercapacitor (SC) is completely valuable as an energy storage device for different applications such as electric vehicles and hybrid renewable systems. A simple SC model that composed of series RC circuit is insufficient to precisely characterize its dynamic performance. Consequently, an accurate mathematical model must be created for reliable and safe operation of SC. The equivalent circuit model that contains three RC branches, immediate, delayed and long is considered, the first branch includes voltage-dependent capacitance. The second one determines the terminal behavior in minute-time range while the last branch determines the behavior for time longer than 10 min. Such model has eight unknown parameters to be determined. A new formula to estimate the SC voltage is derived. For first time Interior Search Algorithm (ISA) is employed to identify these parameters. The obtained results are compared with those obtained by other different optimization algorithms like Genetic Algorithm (GA), Moth Flam Optimization (MFO), Antlion Optimizer (ALO), Gray Wolf Optimizer (GWO), Whale Optimization Algorithm (WOA), and Artificial ecosystem-based optimization (AEO). Two different capacitors with values of 470-F and 1500-F are considered during the validation process. Extensive statistical analysis is carried out to prove the reliability of the proposed methodology. The results confirmed high level of agreement between experimental data and optimized model circuit.

The origins of the relaxor behavior and low-temperature dielectric relaxation processes in AgNb7O18 ceramic were studied and a new relaxation mechanism was proposed through combined bond valence energy landscape (BVEL) calculation and equivalent circuit modeling (ECM). The BVEL calculation suggests that the Ag1 displacement subjects to a double-well potential that originates from the anisotropic coordination symmetry and low coordination number at Ag1 site. The relaxor ferroelectric behavior, observed at 200 K ≤ T ≤ 270 K, is sensitive to thermal history and is ascribed to the Ag1 hopping in double-well potential. The temperature dependence of the matrix capacitance (obtained by ECM) is very similar with that of b axis (obtained by in situ XRD) at 123 K

Graphical abstract The fractional-order modeling with structure identification, parameter estimation and the ability of revealing natures of battery are considered. The correlative information criterion is proposed based on the 1/f noise assisted I/O data, which is adept in evaluating the reliability of model structure and adaptiveness of model parameters. Experimental results validate the above conclusions., Highlights • Present an integrative modeling method regarding structure, parameters and states. • Parameterization by using online/offline EIS and iterative learning optimization. • Introduce 1/f noise to reveal correlations among parameters and eigen-voltages. • Provide the correlative information criterion to evaluate various battery models. • Present the strong negative correlation of ohmic resistance and state of health., In this paper, the fractional-order modeling of multiple groups of lithium-ion batteries with different states is discussed referring to electrochemical impedance spectroscopy (EIS) analysis and iterative learning identification method. The structure and parameters of the presented fractional-order equivalent circuit model (FO-ECM) are determined by EIS from electrochemical test. Based on the working condition test, a P-type iterative learning algorithm is applied to optimize certain selected model parameters in FO-ECM affected by polarization effect. What’s more, considering the reliability of structure and adaptiveness of parameters in FO-ECM, a pre-tested nondestructive 1/f noise is superimposed to the input current, and the correlative information criterion (CIC) is proposed by means of multiple correlations of each parameter and confidence eigen-voltages from weighted co-expression network analysis method. The tested batteries with different state of health (SOH) can be successfully simulated by FO-ECM with rarely need of calibration when excluding polarization effect. Particularly, the small value of CICα indicates that the fractional-order α is constant over time for the purpose of SOH estimation. Meanwhile, the time-varying ohmic resistance R0 in FO-ECM can be regarded as a wind vane of SOH due to the large value of CICR0. The above analytically found parameter-state relations are highly consistent with the existing literature and empirical conclusions, which indicates the broad application prospects of this paper.

With the development of new energy sources becoming the mainstream of energy development strategies, the role of electric vehicle-powered lithium-ion batteries in the field of automobile transportation is becoming more and more obvious. An efficient the Battery Management System is necessary for the real-time usage monitor of each battery cell, which analyzes the battery status to ensure its safe operation. A complex equivalent circuit model is proposed and established. The Improved Equivalent Circuit Model is used to realize the precise mathematical expression of the power lithiumion battery packs under special conditions. The State of Charge estimation method which is based on Unscented Kalman Filter has a good filtering effect on the nonlinear systems. Based on the State of Charge estimation of Support Vector Machine, the samples in the nonlinear space of lithium-ion battery are mapped to the linear space. It can be seen from the experimental analysis that a joint Unscented Kalman Filter and Support Vector Machine algorithms for State of Charge estimation has higher accuracy. The experimental results show that the tracking error is less than 1.00%.

This paper proposes a generalized methodology to calculate the parameters of the single-diode or double-diode models of a photovoltaic module. The presented method relies in the solution by a simple iterative process of the set of equations obtained from the photovoltaic-module’s equivalent circuit. The use of the generalized form of Tellegen’s theorem allows the solving of the equivalent circuit’s equations in an exact way, without making considerations or approximations commonly used in previous works. The parameters of the equivalent circuit are obtained from the standard conditions of: open-circuit, short-circuit and maximum power, provided by the manufacturer in the data sheet of the photovoltaic module. The presented method is applied to obtain the models of several commercial modules. The accuracy of the obtained parameters is greater than that of the results previously determined by other authors. The curves calculated with the obtained models matches the experimental curves supplied in the manufacturer’s data.

In this paper, an analytical solution to three-diode lumped-parameter equivalent circuit model is proposed to simulate and present S-shaped I-V characteristics of next generation solar cells, which are observed frequently in perovskite and organic solar cells, and occasionally in other kinds of solar cells. In general, because complicated transcendental equation includes three exponent items resulting from three diodes, the absence of an analytical solution has become a bottleneck that limits the adoptions of solar cells’ three-diode lumped-parameter model into practical applications and device simulations. To break through the above bottleneck, the analytical solution is derived in the regional approach, completed in Matlab platform, and verified by reconstructed experimental data measured from real solar cells. Such an analytical solution processes the key feature with high precise and efficiency. High precise results from the mathematical operations of the analytical solution to lumped-parameter model and high efficiency results from the avoidance of numerical iteration methods. In addition, this analytical solution facilitates researchers to accurately determine short circuit current and open circuit voltage, quickly extract model parameters in lumped-parameter circuit, and in detail assess effects from model parameters on DC characteristics of solar cells. Finally, the proposed analytical solution is able to be used to reproduce S-shaped I-V characteristics of solar cells, assist in extracting fitting parameters in three-diode lumped-parameter equivalent circuit model, and complete implementation of model into semiconductor device and circuit simulators.

Shingled solar modules are one of several technologies currently being considered to obtain higher solar module efficiencies. Using equivalent circuit modelling this paper investigates the robustness of shingled modules to partial shading with respect to the power produced and the power dissipated in shaded shingles. The modeling results are experimentally verified. We find that power losses in shingled modules can be larger than in conventional modules for similar shading conditions. The risk of significant local heating resulting from partial shading, potentially leading to catastrophic module failure can also be higher in shingled modules due to the substantially higher reverse biases experienced by shaded shingles. Both risks can effectively be mitigated by operating each shingled module at its own maximum power point, for instance by using module level power electronics on each module or by incorporating a sufficient number of bypass diodes into the module design.

In this paper, an impedance-transduced sensor is developed based on a nanostructured graphene (GN) and poly (methyl methacrylate) (PMMA) sensing film for the detection of individual volatile organic compounds (VOCs) in aqueous media. Benefiting from a porous and high surface area, the nanostructured nanofiber is characterized by scanning electron microscopy (SEM) and optimized by the electrochemical impedance spectroscopy (EIS) technique. The recorded EIS data indicate the selective recognition of four VOCs of interest at a constant pH while there is no redox probe. The non-faradaic responses to each analyte at different concentrations are correlated with a three-element equivalent circuit (resistances of the solution and the film, and a pseudo-capacitance). To analyze the ability of the sensing film in distinguishing between VOCs with similar average boiling points, the values of the individual equivalent circuit elements are used as features and clustered in three-dimensional (3D) plots. Among the features, the two representing the maximum differences between the VOCs are represented in a two-dimensional (2D) plot to show the selectivity of the sensor. The feature extraction analysis demonstrates that the constant phase element (CPE) of the equivalent circuit is a more accurate predictor of VOCs than the interfacial capacitance. These results show high selectivity of the sensorial platform due to the synergistic pairing of nanostructured GN and PMMA.