Equivalent Circuit Simulation Research Articles

Equivalent circuit modeling and simulation of the zinc nickel single flow battery

This paper builds the equivalent circuit model for a single cell of zinc nickel single flow battery (ZNB) with 300 Ah. According to the experimental data of the single cell under 100 A pulse discharge conditions, the model parameters can be obtained by parameter identification, and the analytical expressions for each model parameter can be obtained by using the method of high degree polynomial fitting and exponential function fitting, then the mathematical model of the stack voltage can be built. The relative error of the simulation results for stack voltage is controlled within 3.2% by experimental comparison, which verifies the accuracy of the model and model parameters. The parameter formulas obtained by fitting method can effectively solve calculation problem of the battery parameters. And under 100 A constant-current discharge condition, the stack voltage of the battery is dropping relatively flat over about 110 minutes after loading current, and dropping dramatically within about 50 minutes at the end of discharge due to the increasing polarization.

Supercapacitive vertical graphene nanosheets in aqueous electrolytes

Vertical graphene nanosheets (VGN) is a potential material for high-performance supercapacitors due to its high surface area, open interconnected network and excellent electrical conductivity. Selection of proper aqueous electrolyte is crucial for its utilization as supercapacitor electrode. The present study reports supercapacitive performance of vertical graphene nanosheets in neutral (Na2SO4), alkaline (KOH), and acidic (H2SO4) aqueous electrolytes. Factors like ionic mobility and electrolyte wettability are found to influence supercapacitor performance. The highest capacitance observed for VGN in KOH (197 μF/cm2) is attributed to the higher wettability, whereas VGN /H2SO4 system with specific areal capacitance of 188 μF/cm2 is found to have highest capacitance retention (96.8%), shortest relaxation time (50 ms), low charge transfer resistance (72 Ω cm2) and minimal change in graphitic structure. The later observation is correlated to cationic mobility. Detailed supercapacitive investigation is presented including equivalent circuit simulation for deduction of electrode/electrolyte interface behavior.

Experimental verification of a thermal equivalent circuit dynamic model on an extended range electric vehicle battery pack

Abstract The development of a dynamic thermal battery model for hybrid and electric vehicles is realized. A thermal equivalent circuit model is created which aims to capture and understand the heat propagation from the cells through the entire pack and to the environment using a production vehicle battery pack for model validation. The inclusion of production hardware and the liquid battery thermal management system components into the model considers physical and geometric properties to calculate thermal resistances of components (conduction, convection and radiation) along with their associated heat capacity. Various heat sources/sinks comprise the remaining model elements. Analog equivalent circuit simulations using PSpice are compared to experimental results to validate internal temperature nodes and heat rates measured through various elements, which are then employed to refine the model further. Agreement with experimental results indicates the proposed method allows for a comprehensive real-time battery pack analysis at little computational expense when compared to other types of computer based simulations. Elevated road and ambient conditions in Mesa, Arizona are simulated on a parked vehicle with varying quiescent cooling rates to examine the effect on the diurnal battery temperature for longer term static exposure. A typical daily driving schedule is also simulated and examined.

Dual‐band, dual‐polarised metallic slot transmitarray antenna

A metallic, dual-band, dual polarised slot-based transmitarray antenna is presented. The antenna consists of three thin metallic layers do not use any dielectric substrates, with air gaps in between the layers. The unit cell uses interleaved orthogonal slots, as well as crossed-dipole slot and uniplanar compact photonic bandgap slot elements to provide the lower and upper frequency band resonators, respectively. The frequency separation between the two resonances can be adjusted from closely spaced to far from each other. The antenna provides dual linear polarisation and circular polarisation with the use of the appropriate feed. The fabricated transmitarray antenna provides two independent frequency bands with a band ratio of 1.13 and low mutual coupling. The measurement of a 14 × 14 element transmitarray antenna at 11 GHz shows a maximum gain of 23.74 dB with -1 dB gain bandwidth of 6.8% and aperture efficiency of 38%; at 12.5 GHz, a maximum gain of 24.45 dB is obtained with -1 dB gain bandwidth of 5.4% and aperture efficiency of 34.6%. The antenna is simulated by using the CST software; the ADS package is used for equivalent circuit simulation.

A Rotary-Type Contactless Power Transfer System Using HTS Primary

This paper investigates a new rotary-type contactless power transfer (CPT) system integrated with a high temperature superconducting (HTS) primary and a conventional copper secondary. The structural design, magnetic modeling, and equivalent circuit simulation of a pot-core rotating transformer using an HTS primary are presented to analyze the transfer power and efficiency characteristics of a 9-kW class CPT device. The corresponding superconducting ac loss properties of the HTS primary are also discussed to construct a circuit-field-superconductor-coupled analysis model and thus to clarify the functional relationships among the transfer power, the ac loss, and its equivalent resistance in the rotary-type CPT system.

Frequency control of self‐sustained push‐pull resonant converter using effective parasitic capacitances

A method to control the frequency of a self-sustained push-pull converter at megahertz (MHz) level is proposed by utilising the parasitic capacitances of the circuit. As the equivalent parasitic capacitance and the frequency of the converter can be controlled by a DC voltage, the converter works as a voltage-controlled oscillator and a phase locked loop (PLL) controller is developed to lock in the zero-voltage switching frequency under circuit parameter variations such as the load, the coupling coefficient etc. The effect of the parasitic capacitances on the operating frequency and why the DC voltage can control it are analysed in details with equivalent circuit analysis and simulation study. Practical experiments demonstrate that the PLL controller can lock the operating frequency within 20–30 MHz with relatively good waveforms.

Electrochemical Corrosion Behaviors of 304 Stainless Steel with the Bimodal Grain Size Distribution

Electrochemical corrosion behaviors of the bimodal microstructured (BMS) stainless steel (SS) were investigated by comparing with the coarse crystalline (CC) SS and the nanocrystalline (NC) SS. The BMS SS, consisting of the ultrafine grained matrix with an average gain size 350 nm (62 % (v/v)) and the micrometer embedded body with an average grain size 1.4 µm (38 % (v/v)), was obtained by post-ECAP heat treatment. Electrochemical corrosion properties of the BMS SS is found to be medium between the CC SS and NC SS from the results of the electrochemical tests, which is attributed to the “compound” microstructure including the relatively compact inner layer and the relatively porous outer layer in the passive film on the BMS SS according to the results of the equivalent electrical circuit (EEC) simulation and atomic force spectroscopy (AFM) analysis. Figure 1

Millisecond photo-thermal process on significant improvement of supercapacitor’s performance

Supercapacitors fabricated with nanomaterials usually have high specific capacitance and excellent performance. However, the small size of nanomaterials renders a considerable limitation of the contact area among nanomaterials, which is harmful to charge carrier transfer. This fact may hinder the development and application of nanomaterials in electrochemical storage systems. Here, a millisecond photo-thermal process was introduced to create a charge carries transfer path to decrease the contact resistance among nanomaterials, and enhance the electrochemical performance of supercapacitors. Polyaniline (PANI) nanowire, as a model nanomaterial, was used to modify electrodes under different photo-thermal process conditions. The modified electrodes were characterized by scanning electronic microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and the results were analysed by equivalent circuit simulation. These results demonstrate that the photo-thermal process can alter the morphology of PANI nanowires, lower the charge transfer resistances and thus improve the performance of electrodes. The specific capacitance increase of the modified electrodes is about 25%. The improvement of the circle stability and rate capability are above 10%. To the best of our knowledge, this is the first attempt on research the effect of photo-thermal process on the conductivity among nanomaterials and their electrochemical performances, which gives some new insights on modifying nanomaterials with a physical process.

Surface Modulation of Graphene Field Effect Transistors on Periodic Trench Structure.

In this work, graphene field effect transistors (FETs) were fabricated on a trench structure made by carbonized poly(methylmethacrylate) to modify the graphene surface. The trench-structured devices showed different characteristics depending on the channel orientation and the pitch size of the trenches as well as channel area in the FETs. Periodic corrugations and barriers of suspended graphene on the trench structure were measured by atomic force microscopy and electrostatic force microscopy. Regular barriers of 160 mV were observed for the trench structure with graphene. To confirm the transfer mechanism in the FETs depending on the channel orientation, the ratio of experimental mobility (3.6-3.74) was extracted from the current-voltage characteristics using equivalent circuit simulation. It is shown that the number of barriers increases as the pitch size decreases because the number of corrugations increases from different trench pitches. The noise for the 140 nm pitch trench is 1 order of magnitude higher than that for the 200 nm pitch trench.

Simulation Research on a New Spot-First-Aid of Foreign Body Asphyxia in the Hypopharynx

Airway suffocation is a kind of unexpected emergency. The author's research group proposed a new spot-first-aid method of foreign body asphyxia in the hypopharynx, and compares it with traditional “Heimlich Maneuver” first aid method by simulation comparative study. This article mainly introduced the main contents and methods of the research, primarily on: the processing of CT Imaging data, including: Visual C++ program is used to realize the contour extraction algorithm processing based on CT images pre-processing, and restore the respiratory organs in asphyxia status in the processing of image morphology. Compare the two spot first aid methods by simulation. The Main research steps including: establishing simulated equivalent circuit simulation to compare two different spot first aid methods influence on the change of respiratory airway pressure and the animals steps of the experiments.

Internal resonance with commensurability induced by an auxiliary oscillator for broadband energy harvesting

An internal resonance based broadband vibration energy harvester is proposed by introducing an auxiliary oscillator to the main nonlinear harvesting oscillator. Compared to conventional nonlinear energy harvesters, the natural frequencies of this two-degree-of-freedom nonlinear system can be easily adjusted to be commensurable which will result in more resonant peaks and better wideband performance. Experimental measurements and equivalent circuit simulations demonstrate that this design outperforms its linear counterpart. In addition to the open-circuit voltage, the optimal resistance to obtain the maximum power is determined. Nearly 130% increase in the bandwidth is achieved compared to the linear counterpart at an excitation level of 2 m/s2. The findings provide insight for the design of a broadband energy harvester when there is nonlinearity and internal resonance.

Monolithic Si nanocrystal/crystalline Si tandem cells involving Si nanocrystals in SiC

AbstractMonolithic tandem cells involving a top cell with Si nanocrystals embedded in SiC (Si NC/SiC) and a c‐Si bottom cell have been prepared. Scanning electron microscopy shows that the intended cell architecture is achieved and that it survives the 1100 °C anneal required to form Si NCs. The cells exhibit mean open‐circuit voltages Voc of 900–950 mV, demonstrating tandem cell functionality, with ≤580 mV arising from the c‐Si bottom cell and ≥320 mV arising from the Si NC/SiC top cell. The cells are successfully connected using a SiC/Si tunnelling recombination junction that results in very little voltage loss. The short‐circuit current densities jsc are, at 0.8–0.9 mAcm−2, rather low and found to be limited by current collection in the top cell. However, equivalent circuit simulations demonstrate that in current‐mismatched tandem cells such as the ones studied here, higher jsc, when accompanied by decreased Voc, can arise from shunts or breakdown in the limiting cell rather than improved current collection from the limiting cell. This indicates that Voc is a better optimisation parameter than jsc for tandem cells where the limiting cell exhibits poor junction characteristics. The high‐temperature‐stable cell architecture developed in this work, coupled with simulations highlighting potential pitfalls in tandem cell analysis, provides a suitable route for optimisation of Si NC layers for photovoltaics on a tandem cell device level. Copyright © 2016 John Wiley & Sons, Ltd.

An electrically resistive sheet of glial cells for amplifying signals of neuronal extracellular recordings.

Electrical signals of neuronal cells can be recorded non-invasively and with a high degree of temporal resolution using multielectrode arrays (MEAs). However, signals that are recorded with these devices are small, usually 0.01%-0.1% of intracellular recordings. Here, we show that the amplitude of neuronal signals recorded with MEA devices can be amplified by covering neuronal networks with an electrically resistive sheet. The resistive sheet used in this study is a monolayer of glial cells, supportive cells in the brain. The glial cells were grown on a collagen-gel film that is permeable to oxygen and other nutrients. The impedance of the glial sheet was measured by electrochemical impedance spectroscopy, and equivalent circuit simulations were performed to theoretically investigate the effect of covering the neurons with such a resistive sheet. Finally, the effect of the resistive glial sheet was confirmed experimentally, showing a 6-fold increase in neuronal signals. This technique feasibly amplifies signals of MEA recordings.

Modeling and detection of the short-circuit fault in PMSM using Finite Element Analysis

The paper presents a Finite Element Analysis (FEA) based efficient analysis procedure for permanent magnet synchronous motor (PMSM). The study based on finite element models (FEM) offers much more information on the phenomena characterizing the operation of electrical machines than the classical analytical models. This paper attempts to present a dynamic model involving FEA and equivalent circuit simulation together for PWM inverter fed PMSM assisted based on Maxwell 2D and Simplorer. The nonlinear magnetization characteristics have been considered and calculated by FE software Maxwell. The scheme of the inverter are built using the circuit components in Simplorer environment. Based on FEM, the influence of the inter turn fault on the PMSM behavior under various conditions and severity is studied. The comparison of the results obtained by simulation tests allowed verifying the precision of the proposed FEM model. Using the simulated model, this work presents a technical method based on Fast Fourier Transform (FFT) analysis of stator current and electromagnetic torque to detect the faults of inter turn using Simulink/Matlab. The technique used and the obtained results show clearly the possibility of extracting signatures to detect and locate faults.

Equivalent circuit for VO2 phase change material film in reconfigurable frequency selective surfaces

We developed equivalent circuits of phase change materials based on vanadium dioxide (VO2) thin films. These circuits are used to model VO2 thin films for reconfigurable frequency selective surfaces (FSSs). This is important as it provides a way for designing complex structures. A reconfigurable FSS filter using VO2 ON/OFF switches is designed demonstrating −60 dB isolation between the states. This filter is used to provide the transmission and reflection responses of the FSS in the frequency range of 0.1–0.6 THz. The comparison between equivalent circuit and full-wave simulation shows excellent agreement.

High-Efficient Wideband Slot Transmitarray Antenna

A novel high-efficient, wideband, and single-linear-polarized slot-based transmitarray antenna is presented. The unit cell comprises three thin metallic layers with air gap in between, without use of any dielectric substrate. Each metallic layer has a square wide slot within which there are a number of parallel stubs. The wide slot has a high-pass response with notch at zero frequency. Addition of the stubs creates an extra controllable notch within the wide slot high-pass response. Due to the large spacing between the two notches, a passband with low-slope phase shift response is created which leads to a wideband transmitarray. The linear polarization behavior of the antenna along with a suitable feed horn and with no dielectric loss present has resulted in higher antenna efficiency. The design of a three metallic layer unit cell is also carried out through a simple circuit-based analysis approach. The transmitarray is fabricated and results are compared with those of simulation. The proposed transmitarray has a measured $- 1\;\text{dB}$ -gain bandwidth of 15.5%, peak efficiency of 55%, and a cross-polarization level of better than $-29\;\text{dB}$ . The structure is simulated via HFSS software and ADS package is used for equivalent circuit (EC) simulation.

Intensity-Modulated Spectroscopy on Loaded Organic Photovoltaic Cells

We configured a generic digital lock-in amplifier as a light intensity-modulated spectrometer for photovoltaic (PV) cells for intensity-modulated spectroscopy (IMS) up to 250 kHz. We performed IMS on a state-of-the-art bulk heterojunction (BHJ) organic PV (OPV) cell and introduced a new mode of IMS, wherein PV cells work under finite load, including maximum power point (MPP). Quantitative analysis supported by equivalent circuit simulations establishes MPP-IMS as favorable alternative to the commonly used intensity-modulated photovoltage/photocurrent spectroscopy (IMVS/IMPS) modes. Using IMS under finite load, we identify a high-frequency feature that is invisible in both IMPS and IMVS. The feature is ageing-related and becomes more prominent after long-term storage. We propose an extended equivalent circuit model that locates the origin of this feature at the BHJ itself and link it to diffusion of indium ions etched from the transparent electrode by the hole extracting PEDOT:PSS. Finally, we introduce a method to determine BHJ capacitance by IMS without absolute calibration of light intensity.

Effect of gas bubble on cell voltage oscillations based on equivalent circuit simulation in aluminum electrolysis cell

A method to investigate the effect of gas bubble on cell voltage oscillations was established. The whole aluminum electrolysis cell was treated as a resistance circuit, and the dynamic simulation of the cell equivalent circuit was modeled with Matlab/Simulink simulation software. The time-series signals of cell voltage and anode current were obtained under different bubble conditions, and analyzed by spectral and statistical analysis methods. The simulation results show that higher bubble release frequency has a significant effect on the cell voltage oscillations. When the bubble coverage of one anode block exceeds 80%, the cell voltage may exceed its normal fluctuation amplitude. The simulation also proves that the anode effect detected by computer in actual production is mainly the whole cell anode effect.

가변 주파수 특성을 갖는 평면형 모노폴 안테나 설계

본 논문에서는 가변 커패시터를 이용한 주파수 재구성형 평면 안테나를 제안하였다. 제안된 안테나는 미앤더 타입의 평면 모노폴로 설계되었으며, 버랙터 다이오드를 사용하여 가변 커패시티브 로딩(capacitive loading)에 의해 공진 주파수를 변화하였다. 등가회로 분석과 EM 시뮬레이션 분석에 의해 안테나의 가변 특성 변화를 설계하였으며, 동일한 방사 패턴의 특성도 확인하였다. 제작된 주파수 가변 모노폴 안테나는 설계시 사용된 캐패시터를 실장한 안테나와 버랙터 다이오드의 인가 전압에 따른 공진 주파수 변화를 비교함으로써 설계 결과를 검증하였다. 제안된 안테나는 인가 전압에 따라 2.25 GHz에서 2.42 GHz까지 공진 주파수 가변 성능을 나타내었다. In this paper, a planar frequency reconfigurable antenna is proposed with variable capacitors. The proposed one is designed with a planar monopole, and varies resonant frequencies by variable capacitive loading of a varactor diode. The equivalent circuit and electromagnetic(EM) simulation are utilized for the analysis at the variable characteristic design of the antenna, and the same radiation performance. The implemented frequency variable monopole antenna has been verified by comparing prototypes with designed capacitors and ones with biased varactor diodes. The proposed antenna has presented the resonant frequency variations from 2.25 GHz to 2.42 GHz.

Estimation of operating temperature and energy output of concentrator photovoltaic module under concentration conditions

The operating temperature of a concentrator photovoltaic (CPV) module is a dominant factor in its conversion efficiency. It is necessary to reduce the operating temperature to generate a high output of a CPV module under field operation. Therefore, we estimated the operating temperature and conversion efficiency of a cell or module under real concentrating operations. First, we developed a heat transfer model for the CPV module. The operating temperature in the CPV module was calculated as functions of the thermal resistance and the heat transfer coefficient. A low thermal resistance between the solar cell and the back-surface and a high heat transfer coefficient of the back-surface were effective for reducing operating temperature. Next, the conversion efficiency of a triple-junction solar cell was calculated using an equivalent circuit simulation. We can evaluate the cell performance under actual operating conditions using the calculated operating temperatures of the cell.