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Electrical contacts are important circuit components with diverse industrial applications, and their failure can lead to multiple unwanted effects. Hence, the behavior of electrical contacts is a widely studied topic in the scientific literature based on various approaches, tools, and techniques. The present study proposes a new approach to numerical modeling and simulation based on the Holm contact theory, aiming to study the dependence between the electric potential and the temperature within an electrical contact. Structured in five sections, the research was conducted using COMSOL Multiphysics software (version 5.3) and its solid-state mechanics, electric current, and heat transfer modules in order to highlight contact behavior from mechanical, electrical and thermal points of view: the von Mises stress, contact force, electric field amplitude, variation of the electrical potential along the current path, temperature gradient, and dependence of temperature along the contact elements edges were obtained by simulation, and are graphically represented. The results show that the temperature increase follows a parabolic curve, and that for values higher than 4 mV of voltage drop, the temperature of the contact increases to 79.25 degrees (and up to 123.81 degrees for 5 mV) over the ambient temperature, thus the integrity of insulation can be compromised. These values are close (10–12%) to the analytically calculated ones, and also in line with research assessed in the literature review. [ABSTRACT FROM AUTHOR]

In offshore oil platform power grid, high impedance arc fault occurs frequently. The fault characteristics of high- impedance arc information are weak and difficult to detect, which may not cause the protection method to activate. Therefore, it is important to detect and clear the high impedance fault. In the high impedance case, usually, the arc fault occurs. In the research, the arc model was established using the typical Cassie model and the high impedance arc fault characteristics in offshore oil platform power grids were analysed. An improved arc fault detection method using the phase angle difference between zero sequence voltage and zero sequence current was proposed to extract fault characteristics. This method requires limited detection information and high accuracy to solve the problem of small current and voltage changes in high-resistance arc faults. The offshore oil platform power grid and the arc were modelled using electromagnetic transients software PSCAD/EMTDC. The simulation results show that the arc model and fault detection method work well. [ABSTRACT FROM AUTHOR]

Epoxy asphalt has emerged as a high-performance pavement material. However, research on its curing mechanism and kinetics remains limited. This study aimed to investigate the kinetic equation of the epoxy asphalt curing system using non-isothermal differential scanning calorimetry for better understanding and prediction of the curing reaction. The results revealed that the epoxy asphalt system in this study is autocatalytic, with the conversion rate increasing as the heating rate rises. Additionally, this research employed Density Function Theory to simulate the surface electrostatic potential distribution of the curing agent and epoxy resin in epoxy asphalt. This approach identified potential active sites for chemical reactions, confirming the likelihood of a cross-linking reaction between carbon–carbon double bonds in the oleylamine curing agent. This cross-linking reaction contributes to the formation of a network structure in the cured epoxy resin system, resulting in superior mechanical properties for the cured epoxy asphalt. The study utilized transition state theory to simulate the ring-opening reaction between the primary amine group in oleylamine and epoxy resin. Finally, the above conclusions were verified using in situ infrared spectroscopy, and the microstructure of the epoxy asphalt at different curing times was observed using in situ fluorescence microscopy. In conclusion, this research provides valuable insights into the curing mechanism and kinetics of epoxy asphalt, offering guidance for future applications and development in the field of pavement materials. [ABSTRACT FROM AUTHOR]

In this work, we develop and analyze a third order and a fourth order perturbation theory for nonpolarizable dipolar hard spheres. The electrostatic potential is split into a short-ranged and a longranged part. A perturbation expansion is applied for the short-ranged potential where the contribution of higher order terms is approximated through a [2,1]-Padé approximation for the third order theory and by a [2,2]-Padé approximation for the fourth order theory. Rodgers andWeeks [J. Chem. Phys. 131, 244108 (2010)] developed the Local Molecular Field (LMF) theory for the long-ranged contribution of the electrostatic energy. The LMF theory requires the relative permittivity of the considered fluid. We apply a perturbation theory for the relative permittivity and show that the LMF is then in very good agreement with the results for the long-ranged energy from molecular simulations. The short-ranged contribution to the Helmholtz energy from the third order and from the fourth order perturbation theory is, for densities ρ* ≤ 1 and for dipole moments of μ*2 ≤ 1, in very good agreement with the data from molecular simulations. For larger dipole densities (up to μ*2 ≤ 4 for ρ* . 1), we observe significantly improved results for the fourth order perturbation theory compared to the third order perturbation theory. [ABSTRACT FROM AUTHOR]

This work describes a 4-bit Flash ADC with low power consumption. The performance metrics of a Flash ADC depend on the kind of comparator and encoder used. Hence openloop comparator and mux-based encoder are used to obtain improved performance. Simulation results show that the simulated design consumes 0.265mW of power in 90nm CMOS technology using cadence-virtuoso software. The circuit operates with an operating frequency of 100MHz and a supply voltage of 1V. [ABSTRACT FROM AUTHOR]

A thermoelectric unicouple is constructed with half-Heusler materials for characterizing power generation. The electric power and heat flow are measured simultaneously under various temperature differences, and the efficiencies are calculated. Phase structures and thermoelectric properties are characterized for the p- and n-type legs; the latter are used for finite-element simulations to calculate numerically the ideal electric power, heat flow and efficiency under the same temperature conditions. Seebeck voltage, internal resistance, electric power, heat flow, and efficiency are compared between the measurement and simulation. Thereby, the contact electrical resistance is estimated, and the extra thermal resistance is analyzed in terms of the compared open-circuit voltage and heat flow. The maximum efficiency of 4.0% is attained from the measurement with the hot side at 470 °C, in contrast to 5.7% from the simulation. The simulation permits an investigation on the one-dimensional heat flow through the p- and n-type legs that is coupled with Peltier, Thomson, and Joule heat. [ABSTRACT FROM AUTHOR]

In this paper, we study a weak Galerkin (WG) finite element method for semiconductor device simulations. We consider the one-dimensional drift–diffusion (DD) and high-field (HF) models, which involves not only first derivative convection terms but also second derivative diffusion terms, as well as a coupled Poisson potential equation. The main difficulties in the analysis include the treatment of the nonlinearity and coupling of the models. The weak Galerkin finite element method adopts piecewise polynomials of degree k for the approximations of electron concentration and electric potential in the interior of elements, and piecewise polynomials of degree k + 1 for the discrete weak derivative space. The optimal order error estimates in a discrete H 1 norm and the standard L 2 norm are derived. Numerical experiments are presented to illustrate our theoretical analysis. Moreover, numerical schemes also work out for the discontinuous diffusion coefficient problems. [ABSTRACT FROM AUTHOR]

It is very important that the quality of the energy obtained is at a high level while alternating energy is obtained from the direct current energy source. In order to improve the energy quality by reducing the harmonics in the generation of the alternating current, numerous studies have been done on multi-level inverter hardware structures and switching techniques. However, the effect of the slope formed by the difference between the levels in the generated multi-level alternating voltage structure on the resulting harmonic distortions has not been studied so far. So, the paper researches the effects of the inclination between the levels of the alternating voltage generated on load by the inverter. Firstly, after the multi-level inverter structure which can produce four levels of voltage is determined, the operation of this inverter is given in the tabular form. The value of voltage formation gradients (VFG) is calculated according to a generation of multi-level voltages with different amplitude sizes between the levels of the voltage on the R L load after simulation of the system is performed at the Matlab Simulink. After that, obtained load voltages at the simulation are validated in the experiment. The effects of these gradients on the quality of the voltages are determined by measuring harmonic distortions. When the distortion values obtained according to the slope of the alternating voltage structures are analysed, it is seen that the distortion values change significantly as the slope changes. Harmonic distortion caused by VFGs gives the appropriate source values that form voltage levels for the system. Therefore, if the harmonic distortion of the current produced in the load is to be reduced or eliminated, voltage levels of alternating must be generated according to the proposed VFG method. [ABSTRACT FROM AUTHOR]

On account of complementary control, reduced size, and energy saving, the switched-capacitor (SC) based equalizer becomes promising for the energy management of energy storage system. Traditionally, the number of the bypass capacitor in the SC based equalizer equals to the number of the battery module in series or parallel connections. The amount of bypass capacitors is enormous, thus costly and bulky for electric vehicles (EVs). In this paper, the integrated energy storage is proposed to reduce cost and save space, meanwhile, the equalizations between the batteries and the ultracapacitors (UCs) are achieved by the reutilization of SC network. UCs not only perform as energy storage units, but also work as energy exchange units. Thus, the number of balanced elements can be reduced significantly. The operational principles of the storage system and the analyses of the balancing process are examined in detail. The system simulation is performed for functionality evaluations. Meanwhile, an experimental prototype is also implemented for six cells to demonstrate the balancing process. The accordance of experiment and simulation can further testify the feasibility and effectiveness. [ABSTRACT FROM AUTHOR]

For the characteristics of a random distribution and a large number of buses in the power system, the authors introduce distributed compressed sensing to compress and reconstruct the power quality data. They built a distributed IEEE14 bus system in PSCAD. This model was used to analyse the correlation and sparsity of power quality data and to obtain the four types of data that should be used in the latter simulation, the power quality data used in this study are the voltage amplitude of each bus in a power system. To make the signal sparser, they constructed a distributed compressed sensing learning dictionary for power quality data. The simulation results show that the performance of the distributed compressed sensing learning dictionary constructed in this study is more suitable for power quality data. The application of distributed compressed sensing in a power system can ensure the accuracy of reconstructed data when the quantity of data is reduced by 1/3, which greatly reduces the system storage space. Additionally, the speed of reconstruction also increases by 3/5. [ABSTRACT FROM AUTHOR]

In this paper, a simple device under electrostatic discharge (ESD)event is considered. This work presents a simple experimental and simulated setup to measure ESD‐induced voltage to trace on a printed circuit board (PCB) when ESD current is injected directly onto the lumped element. Based on an ESD immunity test platform and ESD full‐wave model, the waveform of coupling voltage, which induced on a PCB, are measured at different discharging position. The voltage waveform of resistor on PCB with chip and without chip are compared to analyze the difference in two cases. The paper proposes a method that compares the measured results of experiment with simulation of full‐wave model. It is found that the results of simulation and experiment is in good match on the whole. [ABSTRACT FROM AUTHOR]

This article examines the performance of N+ pocket-doped vertical tunnel field-effect transistor (VTFET)-based label-free biosensors with the help of an analytical model developed for electrostatic potential, electric field, and drain current along with an extensive verification of the simulated device data. The model incorporates the effects of dielectric constant as well as charge and renders a generalized solution applicable for both neutral and charged biomolecules. Besides, the sensitivity has been analyzed by measuring the shift in drain current due to a change in the dielectric constant. It has been observed that the proposed sensor shows a large deviation in drain current, and hence, ON can be used as an appropriate sensing parameter. The variations in the drain current and threshold voltage (Vth) due to the impact of positive/negative charged biomolecules have also been studied. Extensive TCAD simulations have been performed to investigate the device performance when the nanogaps are fully filled, three-quarterly filled, half-filled, quarterly filled, and unequally filled. Furthermore, a comparison has been made with MOSFET-based biosensors. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Normally unbalanced grid voltage dips may lead to unbalanced non-sinusoidal current injections, DC-link voltage oscillations, and active and/or reactive power oscillations with twice the grid fundamental frequency in three-phase grid-connected Photovoltaic (PV) systems. Double grid frequency oscillations at the DC-link of the conventional two-stage PV inverters can further deteriorate the DC-link capacitor, which is one of the most important limiting components in the system. Proper control of these converters may efficiently address this problem. In such solutions, Current Reference Calculation (CRC) is one of the most important issues that should be coped with the reliable operation of grid-connected converters under unbalanced grid faults. Therefore, this paper proposes and simulates CRC methods and presents the results in order to improve the quality of the grid-connected PV system under unbalanced grid voltage fault. [ABSTRACT FROM AUTHOR]

This paper presents a modification of the Vienna rectifier (VR) to obtain more than three voltage levels at the DC line connection, while preserving the unity power factor at the AC grid side. The proposed unidirectional multilevel there-phase rectifier, called the “Negev rectifier”, has a reduced device count and utilizes a unique novel Time Division Multiplexed based control scheme, which makes the challenging N-level VR expansion possible. The Negev rectifier can serve as a grid interface for supplying dc voltage to multilevel inverters with 4 up to 7 voltage levels, eliminating the burden of inverter-side voltage balancing control. The Negev hardware can be constructed by two complementary topologies, making it suitable for either high current or high voltage applications. [ABSTRACT FROM AUTHOR]

Copyright of Scientific Bulletin of National Mining University is the property of National Mining University, State Higher Educational Institution and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Studia Poliana is the property of Studia Poliana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, a new idea is suggested for designing an appropriate bio-impedance probe in the form of a biopsy forceps to measure the electrical properties of the tissues inside the body. First, by analytically solving the Laplace equation for wedge-shaped tissue in the mouth of the probe, the relationship between electric potential (results from excitation current) in a different point on the tissue and the electrical properties of the tissue is obtained. Then, to evaluate the designed bio-impedance probe using the finite element method and the experimental data obtained for different tissues by Gabriel et al., modelling and simulation at different frequencies from 50 Hz to 5 MHz were done. Finally, to evaluate the performance of the designed probe in comparison to other methods, measurements were carried out using three methods for the same tissue. Nyquist curves were drawn and electrical properties extracted for all the three methods. It was found that the designed probe results are close to the actual values with an error of <2%. The main features of the designed probe are small size and non-invasive measurement. [ABSTRACT FROM AUTHOR]

A new attack against the Kirchhoff-Law-Johnson-Noise (KLJN) secure key distribution system is studied with unknown parasitic DC-voltage sources at both Alice's and Bob's ends. This paper is the generalization of our earlier investigation with a single-end parasitic source. Under the assumption that Eve does not know the values of the parasitic sources, a new attack, utilizing the current generated by the parasitic dc-voltage sources, is introduced. The attack is mathematically analyzed and demonstrated by computer simulations. Simple defense methods against the attack are shown. The earlier defense method based solely on the comparison of current/voltage data at Alice's and Bob's terminals is useless here since the wire currents and voltages are equal at both ends. However, the more expensive version of the earlier defense method, which is based on in-situ system simulation and comparison with measurements, works efficiently. [ABSTRACT FROM AUTHOR]

We have developed an analytical multi-frequency model, which results in accurate multi-peaks of the ion energy distributions (IEDs) for the given control parameters. The model can analytically calculate and predict the IEDs multiple peaks and energy width with necessary plasma parameters. This model can also predict the IEDs from multiple frequencies' drives at any voltage, the associated results are compared with particle-in-cell (PIC) simulations. The IED at a surface is an important parameter for processing in multiple radio frequencies driven capacitive discharges. The analytical model is developed for the IED in a low pressure discharge based on a linear transfer function that relates the time-varying sheath voltage to the time-varying ion energy response at the surface. This model is in good agreement with PIC simulations over a wide range of multiple frequencies driven capacitive discharge excitations. [ABSTRACT FROM AUTHOR]

How many steps are required to model permeation through ion channels? This question is investigated by comparing one- and two-step models of permeation with experiment and MD simulation for the first time. In recent MD simulations, the observed permeation mechanism was identified as resembling a Hodgkin and Keynes knock-on mechanism with one voltage-dependent rate-determining step [Jensen et al., PNAS 107, 5833 (2010)]. These previously published simulation data are fitted to a one-step knock-on model that successfully explains the highly non-Ohmic current-voltage curve observed in the simulation. However, these predictions (and the simulations upon which they are based) are not representative of real channel behavior, which is typically Ohmic at low voltages. A two-step association/dissociation (A/D) model is then compared with experiment for the first time. This two-parameter model is shown to be remarkably consistent with previously published permeation experiments through the MaxiK potassium channel over a wide range of concentrations and positive voltages. The A/D model also provides a first-order explanation of permeation through the Shaker potassium channel, but it does not explain the asymmetry observed experimentally. To address this, a new asymmetric variant of the A/D model is developed using the present theoretical framework. It includes a third parameter that represents the value of the 'permeation coordinate' (fractional electric potential energy) corresponding to the triply occupied state n of the channel. This asymmetric A/D model is fitted to published permeation data through the Shaker potassium channel at physiological concentrations, and it successfully predicts qualitative changes in the negative current-voltage data (including a transition to super-Ohmic behavior) based solely on a fit to positive-voltage data (that appear linear). The A/D model appears to be qualitatively consistent with a large group of published MD simulations, but no quantitative comparison has yet been made. The A/D model makes a network of predictions for how the elementary steps and the channel occupancy vary with both concentration and voltage. In addition, the proposed theoretical framework suggests a new way of plotting the energetics of the simulated system using a one-dimensional permeation coordinate that uses electric potential energy as a metric for the net fractional progress through the permeation mechanism. This approach has the potential to provide a quantitative connection between atomistic simulations and permeation experiments for the first time. [ABSTRACT FROM AUTHOR]

The differences in drain current and drain voltage (Id-Vd) characteristics of top and bottom contact organic thin film transistors (OTFTs) are analyzed by an OTFT devices simulator, which makes it possible to derive Id-Vd characteristics, potential distribution, and hole concentration distribution by solving Poisson’s equation and current continuity equation. It is found that the intrinsic characteristics of top contact devices are superior to those of the bottom contact ones, which is usually believed to be due to poor contact characteristics and poor semiconductor quality of bottom contact OTFTs. The mechanism behind the intrinsic characteristics differences is the deficiency of carriers at the source-channel interface, resulting to a very high potential drop, which the bottom contact devices suffer more. Remarkable improvements in drain current are expected by only inserting high carrier concentration region around the source/drain contact area, which totally eliminates the potential drop. [ABSTRACT FROM AUTHOR]

We have implemented a coarse-grained model to study voltage-driven as-DNA translocation through nanopores located in synthetic membranes. The simulated trajectory of the DNA through the nanopores was calculated using Langevin dynamics. We present the results based on more than 120 000 individual translocations. We are particularly interested in this work in probing the physical basis of various experimentally observed—yet poorly understood—phenomena. Notably, we observe in our simulations the formation of ds-DNA hairpins, widely suspected to be the basis for quantized blockage. We study the translocation time, a measurable quantity crucially important in polyelectrolyte characterization, as a function of hairpin vertex location along the polymer backbone, finding that this behavior can be tuned to some degree by simulation parameters. We also study the voltage dependence of the tendency of hairpins to serve as the initiators of translocation events. Surprisingly, we find that the resulting probability depends vitally upon whether the events counted are ultimately successful or not. Further details lead us to propose that failed attempts in experimental translocation studies may be more common—and deceptive—than is generally recognized. We find the time taken by successful single file translocations to be directly proportional to the ratio of chain length to the applied voltage. Finally, we address a common yet puzzling phenomenon in translocation experiments: translocation events in which the current through the pore is highly, yet incompletely, blocked. We present the findings that offer a new explanation for such events. [ABSTRACT FROM AUTHOR]

We report on the properties of 10 nm thick Co50Fe50 interdigitated electrodes deposited on lead zirconate titanate (PZT) substrates to achieve low power dynamic tuning of magnetic properties. The actuation of this combination relies on magnetoelectric coupling through the shear mode deformation of the PZT: numerical simulations confirmed that both uniaxial tensile and compressive strain can be achieved either by applying a bias voltage on the appropriate set of electrodes or by reversing the polarity of the bias voltage. Reversible electric field induced changes in the coercive field of more than 10% and a 0.08% change in the resistance were obtained for an applied electrical field of 5 kV/cm. [ABSTRACT FROM AUTHOR]

Different from the conventional current-voltage and capacitance-voltage methods, Schottky contact barrier height extraction by admittance measurement is proposed and discussed in this paper. In this method, the barrier height can be simply extracted from the difference between the measured admittance at zero bias and a reasonably high forward bias. Both simulation results and experimental data demonstrate that the proposed method is effective not only for extraction of Schottky contacts with higher barrier heights (>0.4 eV) but also for extraction of those with moderately lower barrier heights (0.2–0.4 eV). [ABSTRACT FROM AUTHOR]

This paper reports methods for measuring the spring constant and modeling the deflection of piezoelectric devices. Because this method uses the equivalent electric circuit of the piezoelectric device and deflection with respect to input voltage, it is a noncontact measurement method. Measurements of the spring constant from the equivalent circuit method and force versus deflection measurements are within 3.3% of each other. An equivalent electrical circuit of the piezoelectric device is also used to provide a model of the relationship between frequency and deflection according to input voltage. Input voltage and power with respect to driving frequency are modeled for a constant mechanical deformation. This model gives an estimation of the required input electrical power to piezoelectric devices for many applications. In order to verify the models, experiments are conducted and the models and experimental results show very good agreement. [ABSTRACT FROM AUTHOR]

The lack of dc fault clearance capability is a major obstacle that restricts the development of high-voltage direct current (HVdc) systems. Employing an active mechanical dc circuit breaker (M-DCCB) is an effective method to handle the dc fault. However, the existing active M-DCCBs can interrupt the fault current once but have problems in making the second interruption instantly in case of reclosing a permanent dc fault. In this paper, a novel topology of the active M-DCCB is proposed by inserting a precharged capacitor into a bridge formed by four spark gap switches. The operating strategy for the proposed M-DCCB is discussed to handle the dc faults. Its parameters, including the oscillation inductor and the oscillation capacitor, are determined by inequations derived from the requirements of dc fault interruption. The selection standard for the spark gap switch is set based on its breakdown characteristics. Finally, simulations are conducted to investigate the performance of the proposed M-DCCB. Results show that the capacitor can accumulate a sufficiently large reverse charge voltage automatically charged by the fault current. The proposed active M-DCCB topology and the dc fault handling strategy can interrupt the dc fault in HVdc power systems consecutively. [ABSTRACT FROM AUTHOR]

The modular multilevel converter (MMC) has attracted extensive research in recent years. An appropriate model is necessary to analyze stability or to design MMC controllers. Several published MMC models have been derived in single-phase form to simplify the modeling mathematics. However, little attention is given to the zero-sequence voltage, which introduces coupling in the single-phase model and leads to significant error. In this paper, after revealing the mechanism behind the zero-sequence voltage, a more accurate generalized single-phase MMC model is proposed, which eliminates the zero-sequence voltage coupling effect and is linearized based on harmonic state space (HSS) theory to precisely characterize the internal harmonic features of MMC. A systematic HSS modeling process is presented for both open-loop and closed-loop conditions. And the proposed model is generalized as it can incorporate different control strategy by controller transfer function substitution. Hence it is valuable to analyze MMC stability and dynamics. Model effectiveness is verified by simulation results. [ABSTRACT FROM AUTHOR]

A novel method for controlling direct voltage regulated active dc-link capacitance reduction circuits (ACRC) is proposed in this paper. Instead of forcing the dc-link voltage of the power conversion system to follow a constant reference, the ACRC imposes dc-bus voltage in proportion to the integral of its input current. Consequently, it resembles an adjustable value capacitor from the dc-link side. Therefore, as opposed to existing control strategies, the proposed method simultaneously allows the dc-link voltage to reflect the power balance of the system and the pulsating power component to be diverted into significantly reduced auxiliary capacitance via a bidirectional dc–dc converter. As a result, replacing bulk dc-link capacitance by the proposed circuitry does not require any modification of existing grid-connected power conversion system controllers, thus allowing plug-and-play operation. The proposed approach is validated by application to a commercial power factor correction front end by both simulations and experiments. [ABSTRACT FROM AUTHOR]

This paper describes a new phase difference measurement system based on the three-voltmeter method (3VM) by introducing differential ac/single-ended dc switching for a thermal voltage converter (TVC). The 3VM-based phase difference measurement system has been developed in consideration of the simulation results and the loading effects derived from the TVC. The expanded uncertainties of differential voltage and phase difference measurements have been estimated (e.g., $80~\mu \text{V}$ and 0.0073° at 10 V/1 V, 1 kHz, and 60°). The phase difference measurement uncertainties of two voltage conditions ($V_{1} > V_{2}$ and $V_{1} = V_{2}$) have been focused and theoretically formulated. The phase difference measurements by the system have been made in the voltage range of 1 to 10 V at 1 kHz and 60°. The measurement results agree well with those obtained by a phase standard. [ABSTRACT FROM AUTHOR]

In this paper, we formulate and solve the ac optimal power flow (AC-OPF) as an equivalent circuit problem in terms of current, voltage, and admittance state variables. The generator models are represented using conductance and susceptance state variables, and the operational and network constraints are translated to corresponding current/voltage constraints without loss of accuracy or generality. To understand the physics behind the optimality conditions of the optimization problem, we extend the linear adjoint circuit theory to translate them to equivalent circuit domain. It is shown that the operating point that defines the equivalent circuit solution precisely represents an AC-OPF solution. We then further exploit the equivalent circuit representation to use power flow simulation techniques to robustly solve the optimization problem. The efficiency of our approach is demonstrated for several AC-OPF benchmark test cases (up to 70 k buses) under nominal and congested operating conditions, and the runtime and scalability properties are presented. [ABSTRACT FROM AUTHOR]

Considering the difficulty in setting and observing the flux linkage in the existing direct torque control for the brushless direct current motor, which is the cumbersome torque calculation method in direct torque control systems without flux linkage observation, the torque observation, voltage vector selection, and speed loop were studied further in such systems. The fuzzy proportional–integral–derivative direct torque control strategy is presented without flux linkage observation. In terms of torque observation, the cumbersome counter electromotive force calculation method was abandoned, and observation was made combining the three-phase current and Hall signal. In terms of optimal choice of voltage vector, the voltage vector selection table was built using the voltage hysteresis output and Hall signal. In terms of rotation speed control, the adaptive fuzzy proportional–integral–derivative was used to replace the traditional proportional–integral–derivative for the proportional–integral–derivative parameter self-adjustment. A control system simulation model was set up in MATLAB/Simulink for simulation verification. A hardware experimental platform was set up using DSP2812 as the main control board for experimental verification. The research results show that the fuzzy proportional– integral–derivative direct torque control without flux linkage observation further increased the dynamic response rate of the motor speed and reduced the electromagnetic torque ripple amplitude; thus, it is more suitable for application in high-precision and high-stability systems. [ABSTRACT FROM AUTHOR]

The paper deals with a proposal for circuit configuration of series-series (SS) compensated wireless power transfer (WPT) system with reduced voltage stresses on compensation capacitors. Nowadays, a huge effort is given for the development of reliable, efficient and robust wireless charging systems and therefore the circuit configuration and component selection are crucial to meet suitable operational characteristics. For this purpose, the current trends in WPT systems are outlined in the first section. Next, the analysis of frequently utilized WPT system configuration is provided and the most critical issues related to practical utilization are discussed. Consequently, the proposal of how to eliminate negative aspects is given. All theoretical statements are supported by mathematical apparatus of the proposed system and consequently by the simulation analysis. [ABSTRACT FROM AUTHOR]

The measurement of the distorted power-frequency electric field needs to meet some special requirements such as appropriate insulation, quick response, passive measurement, and small size. In this paper, based on the Pockels effect, an integrated optical sensor is designed and used for measuring distorted power-frequency electric field for the first time. The input–output characteristic, frequency response, and temperature characteristic of the sensor are studied. The data show that the sensor has a linear measurable range from 100 V/m to 27 kV/m, a 3-dB bandwidth from 20 Hz to 10 MHz, with good temperature stability. The developed sensor is used to measure the distorted electric field and is compared with the Narda-NBM-550 sensor. The relative errors between the measured values of these two sensors and the simulation values obtained by the finite-element method are calculated. It is noted that the relative errors of the integrated optical sensor in different positions are within 12%. However, the Narda-NBM-550 sensor performs poorly at the edges of the barrier with an error of 22%. In conclusion, the findings demonstrate that the integrated optical sensor developed in this paper is more suitable for measuring distorted power-frequency electric field than the Narda-NBM-550 sensor. Further research needs to focus on the measurement of the 3-D distorted power-frequency electric field. [ABSTRACT FROM AUTHOR]

The performance of an oscillator-based read-out circuit for the linear variable differential transformer used as a displacement sensor is studied and various aspects of improving it are presented in this paper. The proposed read-out electronics treats the sensor’s secondary inductance as an unknown reactance, thereby incorporating an active oscillator circuit as a resonator to derive the position information. This method avoids the excitation of the primary coil using low-distortion sine-wave oscillators and the associated phase compensation circuitry as used in traditional signal conditioning circuits. The tradeoffs involved in choosing the frequency counter master clock frequency, the measurement update rate, and the achievable resolution are presented. Various factors that contribute to the nonlinearity have been studied from the standpoint of direct difference versus ratiometric formulas for deriving position information. It is shown that for the oscillator-based read-out procedure, resolutions in the range of 8–16 bits with update rates per channel ranging from 10 Hz to 7.86 kHz, and depending on the procedure used, a worst case full-scale nonlinearity error of ±0.14% are feasible. [ABSTRACT FROM AUTHOR]

Highlights • A health monitoring method was suggested for a solar power system. • It can detect the most degraded module without separating it from the system. • We simulated the method and demonstrated it on an outdoor photovoltaic string. Abstract Solar cell modules are connected in series and parallel in a photovoltaic system. All the solar cell modules degrade over time and the most degraded module in a string decides the output level of the string. In this study, we suggest a health monitoring method which enables to detect the most degraded module in a string without separating the module from the string. The method places a non-transparent film on a module in a string to make an artificial shading effect and monitors the current-voltage curve of the string while placing the film to the next one. We show analytically that the most degraded module can be detected by comparing all the string current-voltage curves. We demonstrate the method on an outdoor photovoltaic string. [ABSTRACT FROM AUTHOR]

Gas insulated transmission line (GIL) is an advanced power transmission mode. Since the extension of this kind of equipment is relatively long, the grounding design and layout of the GIL will have a direct impact on personal safety and the stability operation of equipment, which should be given full attention. In order to ensure the safe and stable operation of GIL, it needs reasonably design and arrangement of the integrated grounding system in the GIL pipelines. This study designed corresponding grounding scheme for the integrated grounding system of underground GIL pipelines combined with a 550 kV/4000 A GIL. The corresponding simulation model of the integrated grounding system was established with specific parameters of the GIL. The calculation results show that the grounding resistance of the integrated grounding system is 0.217 Ω, which is less than the grounding requirement value of 1 Ω, and it reduces 28.9% compared with the simulation model without considering the natural grounding body. In addition, the step voltage and touch voltage are reduced by 79.91 and 48.97%, respectively. The research results can give some references for the integrated grounding system design of GIL engineering. [ABSTRACT FROM AUTHOR]

This study proposes a hybrid DC/AC radial distribution feeder architecture for the future microgrids. The architecture includes multiple distributed energy resource (DER) integrated household premises with AC and DC ports. Voltage unbalance (VU) and voltage drop (VD) in AC or DC distribution feeders are a research area that needs to be revisited in the light of the DERs integration. This study analyses the voltage variations occurring as a result of household DERs integration in the proposed low-voltage hybrid DC/AC distribution feeders. The impact of DERs rating and its location on DC or AC distribution feeder voltage is analysed by varying these parameters stochastically, via Monte Carlo algorithm. Sweep backward-forward load flow analysis technique is implemented to gain knowledge of distribution node voltage profiles for different source and load scenarios. The impact of cross-feeder VU, sag, and swell conditions is also evaluated here. The test case studies are primarily conducted for static conditions which are further extended to dynamic test profiles. This study would help in predicting a failure index of voltage fluctuations in the proposed hybrid DC/AC radial feeders in the presence of the DERs. The results are obtained through the MATLAB and PSCAD/EMTDC-based simulation studies. [ABSTRACT FROM AUTHOR]

High-voltage and high-power voltage source converters (VSCs) are usually operated at low switching frequencies to minimise the switching losses. This study presents a new control method suitable for low switching frequencies. It consists of two stages. In the first stage, a simple proportional controller is used to suppress any overvoltage or overcurrent during the transients. Then, after the control variables have settled to steady-state values, the iterative controller is activated to finely adjust the modulation index and firing angle of the converter to fulfil the control objectives. To justify the proposed control method, various control objectives are realised in a 10 MVA VSC system, and the results are validated by PSCAD/EMTDC and hardware-in-the-loop simulation. The results show that state variables converge within a few iterative steps, and the transient response is sufficiently fast. The proposed method is shown to perform better than the conventional PI control for eliminating the power imbalance and DC second harmonics due to the imbalance at the grid voltage. [ABSTRACT FROM AUTHOR]

Highlights • Development of DP based higher index model of DAB. • Designing a robust control scheme based on the DP model of DAB using loop shaping technique. • Evaluation of system stability for the performance objectives of voltage regulation, robustness, attenuation of measurement noise and rejection of sinusoidal disturbances. • Demonstration of the effect of appropriate selection of model on stability. • Comparison of the open and closed loop responses of the existing DP model of DAB with DC and index 1 terms with the higher index model. • Experimental validation of the proposed scheme through HIL simulation using Opal-RT and dSPACE simulators. Abstract Renewable energy integration and control in microgrid demands computationaly efficient model along with effective control methodology for switched converters. The dual active bridge (DAB) being an integral part of the microgrid suffers from the stability issues. This research proposes dynamic phasor (DP) based higher index model of DAB and demonstrates the effect of appropriate selection of model on performance. To evaluate the system stability for performance objectives of voltage regulation, suppression of measurement noise, sinusoidal disturbances and robustness, a robust control strategy based on loop shaping technique for DP model of DAB is proposed. Comparison of the responses of the higher index model with existing DP model with dc and index 1 terms makes apparent the benefits of the proposed model. The Hardware-in-Loop (HIL) simulation using Opal-RT and dSPACE simulators is carried out for validation of the proposed control scheme. [ABSTRACT FROM AUTHOR]

In this paper, a complete flux scheme (CFS) has been implemented in 1-D fluid model for simulating the pulsed dielectric barrier discharge (DBD) in pure argon at atmospheric pressure. The characteristic quantities of the pulsed DBD have been systematically calculated by using the CFS and presented in comparison with those by using the exponential difference scheme (EDS). This paper shows the following results. There is the two-pulse discharge mode in the present simulation. The two discharge currents obtained using the CFS and EDS converge to the same result in good agreement with the experiment as spatial step length decreases, but the CFS has a fast convergence performance compared to the EDS. With a small grid number, the numerical scheme has an evident effect on the characteristic quantities in the time region corresponding to the first discharge pulse. This paper suggests that in the pulsed DBD, the usage of the CFS with a properly small grid number can give more accurate result and also presents a high calculation efficiency. [ABSTRACT FROM AUTHOR]

A capacitor-based pulsed power system of 4 MJ was designed and developed to propel projectiles of mass above 100 g to hypervelocites. The system used the modular approach, by integrating ten 400-kJ capacitor bank modules. A number of simulation studies were carried out viz., performance analysis of the system using Microcap simulation package, design of various pulsed power subsystems using ANSYS Maxwell simulation tool, and finite element transient analysis for current diffusion through the in-house developed software. Power transfer lines, coaxial cables, and pulse-shaping inductor were designed and fabricated. Various electromagnetic (EM) launchers were designed, developed, and fabricated. Modules are arranged on various racks and are integrated with the EM launcher. Launchers are initially test fired with four modules and then with ten modules. The data acquisition system was developed to measure module currents, in-bore position, velocity, and acceleration of armature. The pulsed power system was experimented up to 1.1-MA current pulse and was successfully test fired to accelerated 120-g mass projectile at a muzzle velocity of 2024 m/s. [ABSTRACT FROM AUTHOR]

Traditional current control methods for a single-phase rectifier in an electric traction drive system suffer from either long response time or nonzero steady-state error. A novel current vector control strategy in stationary-frame is therefore proposed, in this paper, to improve the control performance of a rectifier. The mathematic model of the single-phase two-level pulse rectifier was first analyzed by complex space vector. Then, the principle of the proposed current control method was described. Based on this, the implementation and parameter tuning method of the current control algorithm based on a space complex vector in a two-phase stationary coordinate system are presented. Moreover, two kinds of general current control algorithms are analyzed and compared with the proposed algorithm to demonstrate the advantages of the proposed algorithm. The proposed control scheme absorbs advantages of the conventional control schemes, including fast response, zero steady-state error, and active and reactive power independent control, but overcomes their shortcomings. Finally, the theoretical analysis is verified by means of simulation as well as a hardware-in-loop experimental test on an experimental laboratory setup and some comparisons with conventional current control algorithms prove the advantages of the utilized method. [ABSTRACT FROM AUTHOR]

This paper presents a practical strategy for utilizing the submodule (SM) redundancy of a modular multilevel converter (MMC) for its fault tolerance. This strategy provides a systematic framework for balancing the tradeoff between two conventional methods for using the active redundancy and, thus, achieves operational flexibility. One of the existing methods improves SM reliability owing to less voltage stress on the SM components by employing all of the SMs to form the ac or dc voltages (voltage-sharing mode). The other avoids transients by keeping the average SM voltage constant at the cost of slightly increased stress on the SM components (fixed-level mode), which, however, can be controlled to provide the grid-adaptive operation by reserving the energy of the SMs not in service. We, thus, develop a new redundancy management scheme by integrating these two methods and exploiting their technical benefits to meet the PQ requirements and MMC control performance. This research provides a theoretical basis and a technical guide to determining the number of SMs, which can further increase the voltage steps as per the MMC and grid conditions. This paper also connects the remaining PQ capability of the MMC at a particular operating point with the SM redundancy concept by defining a potential redundancy, especially useful when the physical redundancy is exhausted. The theoretical findings and efficacy of the proposed strategy are validated through PSCAD/EMTDC time-domain simulations followed by experiments using a nine-level single-phase MMC system. [ABSTRACT FROM AUTHOR]

A general radio frequency (RF)-photonic circuit design for implementing frequency multiplication is proposed. The circuit consists of cascaded differentially driven Mach-Zehnder modulators (MZMs) biased at the minimum transmission point with a progressive RF phase shift of applied to each stage. The frequency multiplication factor obtained is . The novelty of the design is the reduced input RF energy required in comparison to the functionally equivalent parallel MZM configuration. Using the transfer matrix method, an architecture is modelled to obtain frequency sextupling. An industry standard simulation tool is used to verify the architectural concepts and analysis. The proposed design requires neither optical or electrical filtering nor careful adjustment of the modulation index for correct operation. In addition, the overall intrinsic conversion efficiency of the cascade circuit is improved by  dB over a parallel MZM circuit. Finite MZM extinction and/or phase errors and power imbalances in the electric drive signals are also taken into consideration and their impact on the overall performance has been investigated. The circuit can be integrated in any material platform that offers electro-optic modulators. [ABSTRACT FROM AUTHOR]

This paper presents a quasi-static surface-based partial element equivalent circuit (PEEC) model for electromagnetic problems consisting of coupled conductors and heterogeneous dielectrics of finite size. The PEEC model is based on the surface equivalent principle. Unlike the traditional surface-based PEEC models, in which the integral equations are set up by enforcing the field continuity in the true field region, the homogeneous integral equations in this model are obtained by enforcing the tangential null field condition in the null field regions. Simplified integral equations are obtained under the quasi-static assumption, in which the circuit elements carrying electric currents and magnetic charges on the dielectric surfaces are vanished. Consequently, the size of the subcircuit describing dielectrics is reduced significantly compared to the full-wave surface-PEEC (S-PEEC) model. Since the quasi-static S-PEEC model only contains frequency-independent circuit elements, it can be conveniently used for time-domain simulation. Three numerical examples are presented to validate the new PEEC model for typical embedded RF passive components, packaging and interconnection problems in both the frequency domain and the time domain. Excellent agreement is observed between the results of the proposed PEEC model, S-PEEC model, and those of commercial software within the quasi-static frequency range. [ABSTRACT FROM AUTHOR]

Harmonic distortions at a point of common coupling (PCC) are caused by the harmonic sources in both supply system and customer facilities. In order to verify compliance with harmonic limits for an operating facility, it is essential to determine the contribution of a facility to the harmonic distortions measured at the PCC. Over the past many years, a significant amount of research work has been conducted in developing different harmonic analysis methods and especially harmonic contribution assessment methods. A common need of this line of research is consistent test systems that can be used to verify/validate a proposed method or to compare different approaches. To address this gap, a benchmark test system representing a typical medium-voltage/low-voltage network supplying industrial loads is proposed in this paper. This paper also includes examples on how to use the system to assess the performance of harmonic contribution determination methods. [ABSTRACT FROM AUTHOR]

Transient overvoltage represents a high magnitude voltage surge of a short duration which has to be considered when performing proper insulation coordination. Overhead line energisation is found to be a fundamental cause of transients. Both normal and faulty conditions are possible during line energisation. The latter implies the existence of an asymmetrical phase-to-ground fault and facing with two asymmetrical processes which take place concurrently. This type of energisation results in severe overvoltage, as well as in a voltage rise at the line receiving end. However, in practice, measuring devices are usually placed at the line sending end, which points to difficulties in determination of phase-voltages at the opposite end of the line. This study offers a solution for the aforementioned issue by proposing the frequency-dependent voltage transfer functions (TFs). By using the functions any voltage value at the sending line end will obtain the corresponding value at the receiving end. The functions are derived through complex mathematical modelling and by signal processing based on the empirical mode decomposition method. The TFs validity is confirmed through performed simulation in MATLAB Simulink and real-site measurements. [ABSTRACT FROM AUTHOR]

Time-domain reflectometry (TDR) is an important technique for verifying the impedance and quality of signal paths in components, interconnects, and transmission lines. However, the success of channel condition assessment through on-site interpretation of TDR echoes hinges on the skill and experience of the operator. This study presents a TDR simulator to assist loop diagnostics on copper twisted pairs widely used in current digital subscriber line (DSL) access networks. The simulator is developed based on established frequency-dependent cable models to synthesise realistic TDR echoes arising from various cable discontinuities. Modelling of arbitrary loop configurations and faults is accomplished by cascading multiple sub-lines with different characteristics through ABCD parameters modelling. The usability of the simulator is enhanced using a graphical user interface and its accuracy has been verified experimentally using TDR echoes obtained from commercial TDR testers. Since lengthy twisted pairs are deployed in real DSL access networks, the TDR simulator can be used to perform on-site simulation and verification during DSL network maintenance and troubleshooting, as well as to gain mastery of TDR handling while circumventing the need for bulky and costly cabling test beds. The simulator can also be useful to supplement the teaching of electromagnetics and high-frequency measurement. [ABSTRACT FROM AUTHOR]