Simplified Electrical Circuit Research Articles

Modeling of Gapless MOSA at Low Current Region Considering Harmonic Content of Operating Voltage

A surge arrester is modeled as a simplified electrical circuit in power frequency applied voltage that consists of a capacitance branch in parallel with a nonlinear resistor. Under applied harmonic voltage, the obtained resistive current of the simplified model exhibits some deficiency, especially in its harmonic contents. This paper presents a harmonic model for metal-oxide surge arresters that can be utilized to simulate their performances under applied harmonic voltage. It has three parallel RC branches to simulate fundamental, third and fifth harmonics contents of total leakage current. Proposed and conventional models have been simulated under different applied harmonic voltages to show the capability of the proposed model. Also, real voltage and leakage current signals, which have been measured experimentally from a 20 kV metal-oxide surge arrester, have been compared with simulation results. Results show that the proposed model can simulate the performance of metal-oxide surge arresters more accurately than the conventional ones under applied harmonic voltages.

Modelling of Supercapacitors Based on Simplified Equivalent Circuit

The need for energy storage devices especially in renewable energy applications has increased the use of supercapacitors. Accordingly, several supercapacitor models have been proposed in previous researches. Nevertheless, most of them require an intensive test to obtain the model parameters. These may not be suitable for an initial simulation study, where a simple model based on the datasheet is required to evaluate the system performance before building the hardware prototype. A simplified electrical circuit model for a supercapacitor (SC) based on the voltage-current equation is proposed in this paper to address this issue. This model doesn’t need an intensive test for accuracy. The structural simplicity and decent modelling accuracy make the equivalent electrical circuit model very suitable for power electronic applications and real-time energy management simulations. The parameters of the proposed model can be obtained from the datasheets value with a minimum test requirement. The experimental method to provide the parameters of the supercapacitor equivalent circuit is described. Based on the proposed method, the supercapacitor model is built in Matlab/Simulink, and the characteristics of equivalent series resistance (ESR) measurement and cycle life are compared with datasheets. The simulation results have verified that the proposed model can be applied to simulate the behaviour of the supercapacitor in most energy and power applications for a short time of energy storage. A supercapacitor test circuit is given to test the charge and discharge of supercapacitor modules. The experimental results are suitable for simulation results.

Switch Elements with S-Shaped Current-Voltage Characteristic in Models of Neural Oscillators

In this paper, we present circuit solutions based on a switch element with the S-type I–V characteristic implemented using the classic FitzHugh–Nagumo and FitzHugh–Rinzel models. Using the proposed simplified electrical circuits allows the modeling of the integrate-and-fire neuron and burst oscillation modes with the emulation of the mammalian cold receptor patterns. The circuits were studied using the experimental I–V characteristic of an NbO2 switch with a stable section of negative differential resistance (NDR) and a VO2 switch with an unstable NDR, considering the temperature dependences of the threshold characteristics. The results are relevant for modern neuroelectronics and have practical significance for the introduction of the neurodynamic models in circuit design and the brain–machine interface. The proposed systems of differential equations with the piecewise linear approximation of the S-type I–V characteristic may be of scientific interest for further analytical and numerical research and development of neural networks with artificial intelligence.

Comprehensive model of upper human body clothing ventilation in standing and walking conditions

The ventilation of the microclimate air of the clothed human body segment is a result of (1) the air flow from the environment through the clothing open apertures, (2) the penetration of the porous clothing, or (3) air flow originating in the microclimate of the other clothed body parts. The microclimate air flow at the connections of clothed segments is named the inter-segmental ventilation and constitutes a real physical boundary condition that leads to ventilation of connected segments. In this study, a simplified electric circuit model is developed to estimate clothing ventilation based on the analogy between the air flow in the microclimate air layer and an electric circuit composed of resistance and inductance elements. The model takes into account the inter-connection between the segments for the clothed human upper part driven by difference of pressure in the microclimate air of the trunk and the upper arms. The developed model is validated using the tracer gas method applied on a walking manikin placed in a climatic chamber under windy conditions. Good agreement was found between predicted segmental ventilation and the experimental values with a maximum error of 16%. It was found that the inter-segmental ventilation is significant at high relative velocity for permeable clothing and increased with the increase in the relative velocity constituting about 30% of the arm ventilation and 14% of the trunk ventilation.

(Invited) Experimental and Physically Based Modelling Analysis of Electrochemical Impedance in PEMFC to Interpret Performance Degradation Causes

The required target for mass deployment of PEMFC in different applications is still not fully achieved, because of a severe performance decay, determined by the interaction of several degradation mechanisms [1]. The comprehension of such mechanisms and the influence of operating condition stressors is still not satisfactory to accurately predict fuel cell lifetime during real operation. Especially the components structural and functional alteration in time, observed by ex-situ techniques, can be hardly associated to a distinct contribution to performance loss. Electrochemical impedance spectroscopy is a promising in-situ technique to distinguish the contributions of different degradation phenomena, but nowadays data analysis is widely performed modelling the fuel cell through simplified electrical circuits that do not permit to achieve a solid physical interpretation of performance degradation causes. A physically based modelling approach, recently explored in the literature [2,3], can cover this gap, however it is not fully consolidated yet and the required effort to develop appropriate tools limits today its utilization to modelling experts. The present work aims at presenting the effectiveness of an approach that combines experimental and physically based modelling analysis of electrochemical impedance in investigating performance degradation occurring in different technologies [4-7]: HT-PEMFC, Low-Pt PEMFC, DMFC, PGM-free PEMFC. The general methodology is presented, highlighting the possible onset of different regimes, where distinct phenomena prevail. The continuum model based on macro-homogenous assumption, solves mass and ionic conservation coupled with Stefan-Maxwell diffusion and Ohm’s law; electrochemical reactions are described with Butler-Volmer kinetics. EIS is solved according to the approach reported in [5]. Subsequently some relevant cases are discussed in details, emphasizing the influence of heterogeneous degradation [5] and local mass transport [7]. One analysis reported in this work is the effect of heterogeneity of ageing on EIS, which determine an increase of the cathodic charge transfer resistance that is not ascribed to a loss of electrochemical active surface, but to the uneven distribution of the reaction rate. Another analysis reported in this work consists in the simulation of EIS with commercial CFD codes: the effect of 3D geometrical features was analyzed, e.g bends in the flow field, flow bypass between channels, interdigitated flow pattern. [1] Boroup, R., & al. (2007). Scientific aspects of Polymer Electrolyte Fuel Cell durability and degradation. Chemical Reviews, 107, 3904-3951. [2] Baricci, A., Zago, M., & Casalegno, A. (2014). A quasi 2D model of a High Temperature Polymer Fuel Cell for the interpretation of impedance spectra. Fuel Cells, 14, 926-937. [3] Kulikovsky, A.A., (2012). A physical model for catalyst layer impedance. Journal of Electroanalytical Chemistry, 669, 28-34 [4] Bresciani, F., Casalegno, a., Zago, M., & Marchesi, R. (2013). A parametric analysis on DMFC anode degradation. Fuel Cells, 14, 386–394. [5] Baricci, A., Zago, M., & Casalegno, A. (2016). Modelling analysis of heterogeneity of ageing in high temperature polymer electrolyte fuel cells: insight into the evolution of electrochemical impedance spectra. Electrochimica Acta, 222, 596–607. [6] Casalegno, A., Baricci, A., Bisello, A., Odgaard, M., Serov, A., & Atanassov, P. (2017). Insight into degradation mechanism in non-precious metal composite catalysts for PEMFC. 7th FDFC, Stuttgart. [7] Baricci, A., Mereu, R., Messaggi, M., Zago, M., Inzoli, F., & Casalegno, A. (2017). Modeling analysis of flow field geometrical features in Polymer Electrolyte Fuel Cells porous media. 7th FDFC, Stuttgart.

Multi-chamber actuated micro-dispensing with a single nozzle for sub-nanoliter droplet formation

A novel concept of single-nozzle micro-dispensing device with multiple pressurizing chambers is proposed for high-throughput drug screening applications such as arraying new drug candidates with sub-nanoliter volume. The theoretical study with a simplified electrical circuit model of the fluidic system shows that the proposed model is effective to sustain jetting stability at high frequency due to an increase in the natural frequency of the fluidic system and high attenuation of the negative pressure wave in the fluidic system. The fabricated device was able to form uniform droplets at up to 7 kHz having 115 pL (1.15 × 10−10 L) in volume and 1.8 m s−1 ∼ 2.5 m s−1 in velocity.

Using Evolutionary Algorithms to Determine Frequency-Dependent Network Equivalents

The present paper presents an alternative methodology to determine frequency-dependent network equivalents from the frequency response of electric power networks. According to this methodology, one can substitute part of the power network through a simplified electric circuit, reducing the number of elements to be modeled without introducing any inaccuracy to the precise evaluation of large power networks. The main challenge relays on determining a rational function capable of producing the same frequency response characteristic of the original circuit that would be replaced by the equivalent. The rational function determines the impedance to be used in the network equivalent. The methodology is based on Evolutionary Algorithms (EAs). Basically, different set of values for the rational function parameters are evaluated. During the convergence process, the EAs modify the values for the function’s parameters suitably, reducing the RMS error between the original frequency response and the one produced by the equivalent circuit. The results obtained through this methodology were compared with those obtained through the “Vector Fitting” methodology, which is the methodology commonly used to solve similar problems.

静電容量式ボイド率計の高温高圧条件への適用研究(流体工学,流体機械)

The electro-void fraction meter (Capacitance type meter) was applied to higher pressure conditions of 18MPa than BWR operating conditions of 7MPa. The void fraction measurement system has been developed including the electrodes of void fraction measurement, instrumentation cables with mineral insulation and simplified electric circuit to provide good signal-to-noise ratio. It satisfied the performance of thermal and pressure resistance and electric insulating capacity. Calibration function for high temperature and high pressure conditions was confirmed through calibration test with 37-rod bundle against datum 19-rod bundle by the quick-shut valve method respectively under 2MPa conditions. It was confirmed that the measured data were consistent with those measured by the quick-shut valve method.

Synchrotron magnet power supply network with normal and common modes including noise filtering

We study theoretical aspects of power supply network for synchrotron magnets, particularly the Heavy Ion Medical Accelerator Complex (HIMAC) system that operates with good stability. We introduce a simplified electric circuit model, which uses a thyristor rectifier power supply, a noise filter, and synchrotron magnets, to introduce the concept of the normal and the common modes. The normal and common modes become decoupled when all the electric loads are placed symmetrically around the ground line for a three line circuit system. This construction makes the normal mode the dominant control of the magnetic fields of the accelerator magnets. It is then found that the connection of the ground (common) line to the middle point of the thyristor power supply is essential to make the common mode stable. These two arrangements can remove the noise at high frequency in the normal mode by the noise filter and hence the noise in the magnetic fields, resulting in stable performance of the synchrotron network.

Development of a Compact Video-Rate Range Finder Using RGB Signals from Binocular CCD Color Cameras.

This paper describes a compact video-rate range finder to be used in autonomous vehicles and intelligent robots, and as a vision substitutes for visually impaired people. The device, being composed of binocular CCD color cameras and a simplified electric circuit, can efficiently extract only the colors of red and blue from a scene, and can provide 3-D distance information continuously within object contours. This device was applied to the measurement of motion of a human body and the estimation of rotation diameter, rotation plane, trajectory, and fluctuation of a rotating body. It was confirmed that this device can be applied to real-time measurements of 3-D spatial positions and motion of objects.

電流再配分を伴うＣＩＣ型超電導撚線導体の安定性評価法

Cable-in-conduit conductors (CICCs), composed of multi-strand superconducting cables cooled with supercritical helium, are essential to superconducting magnets that require large current capacities, low AC losses and high rigidity for fusion machines. A conductor cabled by several hundreds of superconducting strands with superficial chrome plating, oxide or CuNi result in the problem of unbalanced current distribution among the strands. This is caused by small differences in the self-inductance of each strand as well as an electrical resistance difference several times larger at the portion of electrical contacts between each strand and the current leads. This unbalanced current decreases the minimum quench energy (MQE) under the case of uniform current distribution. The MQE of CIC multi-strand cables under unbalanced current distribution is greatly affected by the electrical resistance among the strands. This means that the stability is influenced by the current-sharing process among strands. A higher margin of stability is induced by increasing current sharing and more rapid current transfer to the neighboring strands rather than thermal diffusion to helium. The most suitable parameter to govern this process is the impedance between strands. A simplified electrical circuit model simulating the current-sharing process among strands was proposed to estimate stability. The circuit parameters, that is the impedance, governing the sharing process were measured easily using short samples of CIC cables at 4.2K. The experimental results of stability tests show that the CIC has an extensive stability margin according to lower impedance between strands. We also confirm that the proposed method is applicable to estimate the stability of CIC.

Stability of the multistrand superconducting cables under partial current distribution

AbstractThe stability of the multistrand cables under partial current distribution among strands is discussed. The stability is influenced by a current sharing process among the strands. Stability tests under controlled current distribution are carried out for some test samples that had various electric resistance among strands. Then numerical analysis of the stability is carried out with a simplified electric circuit model that simulates current sharing process among strands. The results of the numerical calculations had good agreement with the experimental data. For stability of the multistrand cables, the electrical resistance among strands, which is the key parameter, is required to be lower than the normal resistance. This corresponds to the length of the heated region.

Estimation method of stability for multi-strand superconducting cables under partial current distribution

The stability margin of CIC multi-strand superconducting cables under partial current distribution is affected by electrical resistance among the strands. This means that the stability is governed by the current sharing process among the strands. The achievement of high stability against partial current distribution will be realized by rapid current transfer to the other strands rather than by thermal diffusion of Joule heating to helium. A simplified electrical circuit model, that is a distributed constant circuit for two strands, simulating the current sharing process between strands, is proposed to estimate the stability. The results of the stability analysis, clarify the limiting condition to maintain stability. The circuit constants governing the sharing process can be investigated from the frequency properties of a characteristic impedance measured with CICC short samples. These results are confirmed with experimental results of stability tests under partial current distribution. The proposed estimation method is viable.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>