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Context: Why are the halonium cations so effective in forming strongly-bound complexes? We directed our research to address this question and we present electrostatic potential data for the valence-state halogen atoms X and halonium cations X+, where X = Cl, Br, I. The electron densities and electrostatic potentials of the halonium cations show considerably greater anisotropy than do the valence state halogens. The distances from the electrostatic potential surface maxima to the halogen nuclei are about 0.5 Å smaller than the distances from the electrostatic potential surface minima to the nuclei, giving the halonium cations each a more disk-like shape than the corresponding neutral valence state halogens. Their surface electrostatic potentials are totally consistent with the directionalities of halonium cations in complexes and the strengths of their interactions. To add perspective to this brief report, we have included calculations of the isotropic cation K+ and noble gas Kr. Methods: The calculations of the electrostatic potentials of the valence states of the halogen atoms Cl, Br and I and the halonium cations Cl+, Br+ and I+, as well as K+ and Kr, on 0.001 au contours of their electronic densities were carried out with Gaussian O9 and the Wave Function Analysis – Surface Analysis Suite (WFA-SAS) at the M06-2X/6–31 + G(d,p) and M06-2X/3-21G* levels. [ABSTRACT FROM AUTHOR]

Purpose: The objective of present work is to investigate seismic wave reflection/transmission in an orthotropic layer bonded between two piezoelectric half-spaces in presence of an imperfect corrugated superstratum and sliding lower interface. Methods: Closed form analytical expressions for displacement field, electric potential, and velocity profile of quasi seismic waves are deduced for respective geomedia using time harmonic plane wave solution approach with appropriate boundary conditions. Rayleigh's first-order approximation, generalized Snell's law and spectrum theorem are used to determine the analytical solution for reflection, transmission (RT) coefficients for regularly and irregularly scattered waves. Results: Numerical simulations for specific geophysical model have been carried out and results are presented through multiple plots to analyze the impact of incident angle, dimensionless layer width, sliding parameter, and corrugated boundary on resultant velocity profile and RT coefficients. The energy flux ratios of all regularly and irregularly propagating waves are also analyzed and portrayed against angle of incidence (AOI). Conclusions: Reflection and transmission angle for all the quasi-waves are found monotonically increasing with rise in incident angle. Waves and material parameters are found to have different impact on resultant velocity and RT coefficients. Simulation also reveals the effect of two extrema of sliding parameter corresponding to welded and free contact on RT coefficients. The coefficients obtained by first-order approximation to corrugation are found to have proportional impact of corrugation amplitude. [ABSTRACT FROM AUTHOR]

In order to improve the electrical performance of the inverter system and make its output waveform close to a sinusoidal waveform, an inverter based on a linear phase‐shifting transformer is proposed, which can eliminate the low harmonics with opposite phase by the effect of phase shift and superposition. Firstly, the components and working process of the multiple superposition inverter system are introduced, and the working principle and winding structure of the linear phase‐shifting transformer are analyzed; Secondly, the Fourier decomposition of the inverter output voltage is carried out to obtain the harmonic currents at the same frequency as it, and it is demonstrated that the inverter is capable of eliminating most of the harmonics below the 23rd order by calculating the magneto‐dynamic potential synthesized in the air gap; Again, in order to overcome the harmonic electric potential caused by the edge‐end effect and the tooth slot structure of the linear phase‐shifting transformer, the secondary side winding of the linear phase‐shifting transformer adopts a short pitch structure, and it is proved that this structure has a significant suppression effect on the 5th and 7th harmonics without reducing the fundamental wave amplitude; Then, the model of multiple superposition inverter system is built based on Maxwell simulation software, and the effectiveness of the inverter device and winding structure on harmonic suppression is proved through spectral analysis of voltage waveforms with different load types and power factors; Finally, its reasonableness and accuracy are verified by experiments. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Capacitively coupled radio frequency plasmas driven by customized voltage waveforms provide enhanced opportunities to control process-relevant energy distributions of different particle species. Here, we present an experimental investigation of the spatio-temporal electron heating dynamics probed by Phase-Resolved Optical Emission Spectroscopy (PROES) in an argon discharge driven by up to three consecutive harmonics of 13.56 MHz with individually adjustable harmonics' amplitudes and phases. PROES and voltage measurements are performed at fixed total voltage amplitudes as a function of the number of driving harmonics, their relative phases, and pressure to study the effects of changing the applied voltage waveform on the heating dynamics in collisionless and collisional regimes. Additionally, the ion energy distribution function (IEDF) is measured at low pressure. In this collisionless regime, the discharge is operated in the α-mode. The velocity of energetic electron beams generated by the expanding sheaths is found to be affected by the number of driving harmonics and their relative phases. This is understood based on the sheath dynamics obtained from a model that determines sheath voltage waveforms. The formation of the measured IEDFs is understood and found to be directly affected by the observed changes in the electron heating dynamics. It is demonstrated that the mean ion energy can be controlled by adjusting the harmonics' phases. In the collisional regime at higher pressures changing the number of harmonics and their phases at fixed voltage is found to induce heating mode transitions from the α- to the c-mode. Finally, a method to use PROES as a non-invasive diagnostic to monitor and detect changes of the ion flux to the electrodes is developed. [ABSTRACT FROM AUTHOR]

Subdural ECoG data recorded from the matrix of electrodes during syllable pronunciation are analyzed by the method of circular-linear regression. Phase waves in 1D electrode arrays and in the whole 2D set of electrodes are detected, and their spatial organization and temporal evolution are studied. Phase portraits of wave vectors indicate the presence of sources, sinks, and saddle points. The analysis of temporal evolution of phase portraits shows that they changed more at the beginning of syllable pronunciation. Furthermore, wave sources were more stable in their localization during the pronunciation. Overall, in spite of large variability of phase portraits, they represent some characterization of the dynamics of electric potential in the cerebral cortex. [ABSTRACT FROM AUTHOR]

In the present study, 3-Ethoxy Salicilaldehyde (3ES) was investigated in terms of structural, vibrational spectroscopic and theoretical analyses. All the theoretical calculations were done with the density functional theory method. The natural bond orbital analysis had been done to understand the probable charge transfer interaction in the molecule. The Frontier molecular orbitlas' molecular electrostatic potential surface has been plotted and the reactive sites of electrophilic and nucleophilic attacks of the molecule have been estimated. The possible vibrations were identified and analysed using the Vibrational Energy Distribution Analysis 4 (VEDA 4) program and Vibrational spectrum. The Fukui function analysis was also used to predict the reactive sites of electrophilic and nucleophilic attacks for the 3ES molecule. Based on electron density, weak interactions of the studied molecules were identified with the aid of RDG analysis. The dipole moment, polarisaility, first-order hyperpolarisability (α0) and related properties (β, α0 and Δα) and second-order hyperpolarisabilties were calculated for the identification of non-linear optical activity of the molecule. The second harmonic generation study also has been done for understanding the non-linear optical activity of the molecule. [ABSTRACT FROM AUTHOR]

We present here an analysis of the discharge characteristics of a He plasma jet operating under three different types of applied voltage waveform: (a) a μs-pulse voltage waveform with a slow voltage rise time, (b) ns-pulse, and (c) rectangular voltage waveforms with fast voltage rise time. Optical emission measurements show that the application of a voltage with a fast voltage rise time induces rapid discharge growth and, consequently, produces an abundance of energetic electrons, which in turn leads to high optical emission from the O atoms. We also estimate the optical emission efficiency of the O atom (ηo), which corresponds roughly to the production efficiency of the reactive O species. ηo increases with increasing applied voltage, and the highest value of ηo is obtained in the shortest pulse discharge, which was ignited by a ns-pulse voltage waveform with a fast voltage rise time and short pulse width. [ABSTRACT FROM AUTHOR]

In this work, we present a detailed analysis on the observed streamer characteristics of PEEK (polyetheretherketone) surface in nitrogen at atmospheric pressure driven by positive repetitive pulse voltage, including the forward discharge streamer and the back discharge streamer. Fast oscilloscopic technique and digital photographic technique were employed to observe the streamers of surface discharges, and current pulse waveform analysis technique and image analysis technique were used to analyze the characteristics of the observed streamers. The experimental results show that the current pulse of forward discharge streamer has a shorter rise time, a higher current amplitude, a faster current rising rate, a shorter fall time, a faster current falling rate and a smaller charge quantity than those of back discharge streamer at the same voltage amplitude. Besides, the forward discharge streamer has a longer stopping length, a faster propagation velocity and a stronger maximum light intensity than back discharge streamer at the same voltage amplitude. Furthermore, the correlation between the electrical characteristics and optical characteristics of the streamer was analytically derivated, and the current rising rate of the streamer is proportionally correlated to the product of the streamer stopping length and the streamer velocity square. [ABSTRACT FROM AUTHOR]

Although the dielectric barrier discharge (DBD) has been widely considered and studied for ozone generation, only a few studies have examined the influence of the alternating voltage waveform on the ozone rate production. This paper analyses the influence of the voltage shape on the ozone concentration and the energy efficiency of a DBD cylindrical ozone generator. Three voltage signals were studied using a high-voltage amplifier: sinusoidal, triangular and rectangular signals with voltage values up to 8 kV and frequencies up to 1.1 kHz. The obtained results showed that the efficiency of the ozone generator depends strongly on the type of the voltage waveform. The maximum values of the energy efficiency and the ozone concentration were obtained with the triangular voltage signal. This wave shape configuration has been successfully used for discolouration of water contaminated by textile dye. [ABSTRACT FROM AUTHOR]

Broadband power amplifier (PA) designs are usually based on optimized-load-impedance ($Z_{\text{opt}}$) searching, which can be guided by PA theories or a load–pull method. After practical devices’ internal dc I–V curves and package parasitics are known, a direct impedance calculation method is realized in this paper to offer an alternate option. This method can offer relatively accurate $Z_{\text{opt}}$ solutions, which can satisfy both operation-mode and performance requirements for a practical device. Following this large-signal impedance calculation method, waveform regulations can be added to the design steps to realize a specific PA operation-mode through a robust and fast small-signal S-parameter simulator. A waveform-guided perturbation and selection process is introduced to expand the impedance space further. A broadband quasi-class-E PA example, across 1.4 to 2.4 GHz, is given to demonstrate this method. Its output matching network is designed accordingly to fit into the expanded impedance space, and its theoretical performances are verified by harmonic balance simulations and measurements. Finally, this PA is fabricated and measured to offer 39.0 to 40.9 dBm power, 11.6 to 14.0 dB gain, and 73% to 83% drain efficiency in its frequency band. [ABSTRACT FROM AUTHOR]

Highlights • Single end cable and overhead line protection in MTDC grids using morphological gradient of voltage (MGV); • Discrimination between internal and external faults; • Protection stability against breaker opening and opposite pole faults; • Threshold setting based on line series inductor and maximum fault resistance; • Fast, reliable and low sampling frequency protection up to a significant high fault resistance. Abstract This paper presents a new method for the protection of transmission lines in voltage source converter based multi-terminal HVDC grids. The fault generated travelling waves at the faulted line ends are filtered by series inductors. The filtered voltage waveform processed by morphological gradient accompanied by fault voltage drop is employed for fast single-end protection of HVDC lines. The proposed method is stable against external DC and AC faults, as well as faults at opposite pole and the breaker opening transients from the adjacent lines. Moreover, it does not require communications between the line ends, it is capable to detect and discriminate relatively high resistance faults, and uses relatively low sampling rate. The effectiveness of the proposed protection method is validated by simulation study on a four-terminal HVDC grid including modular multilevel voltage source converters. [ABSTRACT FROM AUTHOR]

Determining the Marx generator configuration, including the values of series and parallel resistors as well as the number of series and parallel stages to obtain standard lightning impulse (LI) waveforms, is usually done in a trial and error process in the high voltage test fields of power transformer manufacturers. This practical process may take excessive time and is boring for test engineers. In this paper, a simple simulation method is proposed to model the LI test circuit of the transformer by computer, which is helpful in identifying the Marx generator set up. This method is based on modeling the LI test circuit as well as the transformer's high frequency impedance in discrete frequency domain. The measured frequency response of the transformer is used to model its high frequency characteristics. Digital signal processing methods are used to simulate the circuit and obtain waveforms. The accuracy of the proposed method is validated using experimental tests performed on three transformers with different ratings. [ABSTRACT FROM AUTHOR]

In this study, the strain gradient theory is employed to derive governing equations of motion of a functionally graded Timoshenko's sandwich microbeam resting on Pasternak's foundation. The microbeam is including a micro-core and two piezoelectric face-sheets on top and bottom. The plate is actuated with applied electric potential at top of piezoelectric face-sheets. The governing equations of motion are derived using Hamilton's principle and strain gradient theory. After derivation of governing equations of motion, the problem is solved for three classes of analysis including wave propagation, free vibration and bending analysis. The numerical results are presented to reflect the effect of important parameters such as wave number, applied voltage, inhomogeneous index, parameters of foundation and material length-scale parameters on the different responses. The obtained results indicated that changing material length-scale parameters leads to a stiffer structure that increase natural frequencies and decreases transverse deflection and maximum electric potential. [ABSTRACT FROM AUTHOR]

In this paper, an asymmetrical cascaded H-bridge 81 level inverter powered by a single photo voltaic (PV) unit is presented. The PV unit drives an interleaved soft switched boost converter that drives a simple three level inverter, which in turn drives a multiple secondary winding transformer. The AC output of the four isolated secondary windings of the transformer is rectified and filtered to deliver four isolated DC voltages in the ratio 1:3:9:27. The system incorporates maximum power point tracking at the front end boost DC-DC converter level. Overall reduced THD is achieved by strategically spacing on the time axis, for each AC cycle, the discrete voltage levels of the 81 level inverter. The mathematical formulation, the results of simulation in the MATLAB/SIMULINK environment and the results of experimental verifications are provided. [ABSTRACT FROM AUTHOR]

A drop of liquid will levitate on its own vapor on a sufficiently hot surface (the Leidenfrost effect). Application of an electric field across the vapor gap suppresses the Leidenfrost state by electrostatically attracting liquid towards the surface. This study highlights and quantifies the statistical nature of wetting during electrostatic suppression via electrical impedance characterization of Leidenfrost pools under electrostatic suppression. The influence of the electric field, surface superheat, and size of the Leidenfrost pool on the wetted area is studied. High-speed measurements (0.01 s resolution) indicate that the wetted area is not constant during electrostatic suppression, but instead fluctuates. This technique can also be used to study the onset of suppression. Interestingly, we identify two distinct threshold voltages required to initiate periodic and continuous electrostatic suppression, respectively. The dependence of these voltages on surface superheat and the frequency of the applied AC waveform is studied. Together, these results enable an in-depth understanding of electrostatic suppression and highlight the benefits of impedance-based characterization towards understanding the Leidenfrost effect. [ABSTRACT FROM AUTHOR]

This paper presents a new method for automatic monitoring of noisy power quality, which is based on the Hilbert transform (HT) and the proposed slip-singular value decomposition (SVD)-based noise-suppression algorithm. The proposed method first employs the fast Fourier transform (FFT)-based low-pass filter and HT to obtain the instantaneous fundamental amplitude and the FFT sequence of the signal. Second, the slip-SVD-based noise-suppression algorithm and threshold filtering are used to extract cleaned singular value characteristic waveform of the high-frequency signal. Through judging the instantaneous fundamental amplitude, cleaned singular value characteristic waveform, and the FFT sequence, the presence of disturbances including single and combined disturbances can be easily detected by the proposed method. To demonstrate the effectiveness of the proposed method, extensive tests are conducted on the diverse simulation disturbances and the actual data obtained from the practical power systems of China. The test results show that the proposed method has the advantages such as low false detection rate, good noise tolerance capability, short computational time, fewer parameters, practicability, and compatibility in comparison with the traditional disturbance detection methods. Besides, the proposed method can provide some important features such as amplitude, duration, and frequency for classification. Such advantages make the proposed method to be a good choice for real-time applications. [ABSTRACT FROM AUTHOR]

Under the influence of series compensation (SC) capacitance and rated voltage rise, when ultra high voltage (UHV) high SC line occurs inner fault, the short-circuit current through the SC line is greater and the residual voltage across the SC is higher, which cause the electromagnetic transient process excited by high amplitude current and voltage to be more serious in the event of fault occurrence and removal. The security of circuit breaker (CB) equipment is threatened, which make it need further research on the characteristics and put forward some effective solutions. In this study, the characteristics of macroscopic statistical distribution of peak value via short-circuit current of transient recovery voltage (TRV) across CB fracture during switching after short-circuit current zero crossing for UHV high SC line are put forward, and also of the microscopic characterization parameter of waveform rise rate and peak value time. It shows that the TRV switching capability of existing UHV CBs can not cover all the fault scenarios of high SC line. Solutions including comprehensive comparison of TRV optimal suppression measures and increase of the UHV CB switching expected TRV test requirements are put forward, which provide feasible technical scheme for CBs reliable switching of UHV high SC line. [ABSTRACT FROM AUTHOR]

With the rapid development of flexible DC transmission and multi-terminal high voltage direct current transmission (HVDC) (MTDC) grid, the protection schemes of flexible DC transmission lines are still the traditional methods, which do not achieve the properties of fast and selective operation in the DC grid. In this study, using Zhangbei MTDC grid as the research object, the fast protection of DC transmission lines of MTDC grid has been studied. First, the voltage response characteristics of fault line and non-fault line at the boundary of DC lines are analysed. On the basis of this, using wavelet transform to extract the characteristic value of voltage pole-wave, this study put forward a high-speed non-unit protection criterion to identify the internal and external faults. In addition, two auxiliary criteria are constructed to identify lightning disturbance and faulted pole, respectively. Finally, a simulation model of Zhangbei MTDC grid is constructed, and the effectiveness of the proposed protection scheme is verified by extensive simulation results. [ABSTRACT FROM AUTHOR]

The characteristics of the pole-to-pole fault in the tree-structured DC system are complicated, and the transient analytic expressions of high-order current and voltage can make the calculation difficulty increase significantly. In response to this phenomenon, on the one hand, when the parameters are the same, the impact of the changes of the number about the terminals on the waveform is considered. On the other hand, when the number of terminals is fixed, the influence of the change of the parameter on the waveform is studied. Taking the interaction between different ports into account, correct the short-circuit current and voltage expression of single-ended DC system and the calculation method of short-circuit current and voltage expression for multi-ended DC system is proposed. This method can reduce the computational complexity of transient expression for multi-ended DC system. The calculation results are verified by MATLAB/Simulink simulation tool. The calculated transient expressions of voltage and current are in good agreement with the results of simulation, which provide the theoretical basis for the fault location and calculation of setting value. [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]

The impulse voltage wave invading a transformer is not the double exponential impulse wave (DEIW) specified by the IEC but a non-standard waveform with oscillation attenuation characteristics, and this fact leads to doubts about the scientificity and optimality of insulation coordination. A key solution for this issue is the establishment of an equivalent relationship between the measured non-standard impulse voltage wave and the DEIW. In this study, a test platform of multiparameter impulse voltage was set up. Then, the authors obtained the 50% breakdown voltage (U50%) of the oil-impregnated paper (OIP) for transformer under the bipolar oscillatory attenuated impulse wave (BOAIW) and the DEIW with different waveform parameters. The effects of waveform parameters on the breakdown characteristics of the OIP were finally revealed. On the basis of experimental data and several mathematical methods, the authors established the U50% prediction mathematical models for the OIP under the BOAIW and DEIW. Based on the prediction models and the microfluctuation characteristics of measured overvoltage's waveform parameters, the authors proposed a method for evaluating the waveform equivalence. The characteristics of voltage amplitude and change rate were regarded as the two key factors for the waveform equivalence of this method. [ABSTRACT FROM AUTHOR]

Selective-harmonic-eliminated pulsewidth modulation (SHE-PWM) can be utilized to improve the efficiency of multilevel voltage-source converters due to its ability to provide low switching frequency and tight control of low-order harmonics. In addition, SHE-PWM with half-wave (HW) symmetry provides a higher number of solutions than quarter-wave (QW) symmetry, and therefore, the waveform design can be improved. This work proposes a universal formulation, which can be utilized with HW symmetry, that provides a unique system of equations valid for any possible multilevel waveform. Thereby, without using predefined waveforms, this formulation provides the ability to search simultaneously both the firing angles and the switching patterns, simplifying significantly the search process and providing a high number of solutions. With the aim of selecting the optimum sets of firing angles, the solutions provided by HW and QW symmetries are compared, based on several metrics of harmonic performance, for particular test cases. Experimental results also validate the universal formulation with HW symmetry. [ABSTRACT FROM AUTHOR]

In this paper, a modified selective harmonic mitigation pulse amplitude modulation (SHM-PAM) is presented to be capable of canceling all triplen harmonic orders and suitable for single-phase application of five-level type of voltage source inverters. To this end, a new constraint is established for the two switching angles (α1, α2) to derive the new formula for the harmonics’ amplitude, which results in self-elimination of all triplen harmonics (e.g., 3rd, 9th, 15th, …). The fifth and seventh harmonic orders are mitigated through normal operation of the proposed SHM-PAM technique. It is also shown that the proposed technique is extendable to other multilevel voltage waveforms and a flowchart of self-elimination of all triplen harmonics has been presented. Mathematical analysis supported by experimental investigations show the desired performance of the proposed SHM-PAM algorithm on a two-cell single-phase cascaded H-bridge inverter as a typical five-level configuration in dealing with linear and nonlinear loads. Then, it is demonstrated that the maximum number of harmonic orders would be controlled with the minimum number of available angles in a low switching frequency voltage waveform. [ABSTRACT FROM AUTHOR]

This paper presents an open-source package developed in Python that controls and drives a programmable Josephson array to synthesize dc and ac quantum-accurate voltages. Programmable arrays are devices subdivided into independent subsections, each counting a number of series connected Josephson junctions that follows a binary sequence (1, 2, 4, 8, …) to control the output voltage. Our software allows to independently measure the current-voltage characteristics of each subsection by means of a set of arbitrary waveform generators and a nanovoltmeter that measures the voltage across the whole array with high sensitivity. A quantization test tool is also provided to check with sub-microvolt resolution whether the array is operating on its quantum margins. The code is modular and easily expandable with the support of many libraries, allowing prompt reconfiguration for different calibration and testing purposes. It is aimed at being a starting point for cooperation between National Metrology Institutes towards the realization of a shared quantum voltage calibration infrastructure. [ABSTRACT FROM AUTHOR]

In this paper, we thoroughly review all analytical solutions (both exact and approximate) presented to date in the literature for evaluation of voltages induced on a lossless horizontal conductor, placed over an infinite-conductivity ground, and excited by an external field produced by either a step function or a linearly rising current, moving unattenuated and undistorted along a vertical lightning channel. We also obtain the exact analytical solution for the step-function current case in the time domain via development in the s-domain. To date, there had been three attempts to obtain such solution, all of which yielding incorrect results. [ABSTRACT FROM AUTHOR]

This paper applies the electromagnetic time reversal method to the identification of the location and to the quantification of the impedance Zd of longitudinal defects along transmission lines. A closed-form expression for the time-reversal current transfer function is derived. This new transfer function benefits from the same properties of that for solid or soft transversal faults, and hence, can be used for locating the defects along the line. Different scenarios are considered ranging from power lines to signals channels for high-speed digital systems at printed circuit board and package level. The results are discussed and used to assess the accuracy and scalability of the proposed method. [ABSTRACT FROM AUTHOR]

Islanded grids operate isolated from the main grid and they allow the use of ac with a different frequency from the main grid. In this paper, it is proposed to use more than one frequency at the same time in such autonomous systems. The grid voltage amplitude at the fundamental frequency can be increased while the voltage peak is constant by adding odd harmonics to the voltage waveform. The grid currents and the power converter currents are decreased for the same power level, which leads to reduced losses in the system. The currents can be minimized if waveform shaping is additionally applied to the current waveforms. The approach also offers the possibility of mitigating the influence of low power factor in single-phase systems. This paper presents the impact of multifrequency power transfer on single-phase converters and grid components such as power cables and protection, and verifies the results with analysis, simulations, and experiments. [ABSTRACT FROM AUTHOR]

Linear permanent magnet Vernier machines (LPMVM) have received more and more attention in recent years due to the advantages of high thrust density and low thrust ripple, which are both required in many direct-drive applications. In this paper, a double-sided toroidal-winding LPMVM (DSTWLPMVM) is proposed, and the thrust ripple sources for this type of machine are analyzed. To emphasize the specificity of LPMVM in aspect of thrust ripple optimization, a traditional fractional-slot linear permanent magnet synchronous machine is selected as a reference. Two indexes [amplitude difference (AD) and phase shifting (PS)] are defined to quantify the thrust ripple caused by the AD and the PS among three-phase electromotive force (EMF), respectively. Additionally, detent force is also considered when optimizing the three-phase EMF. Finally, a prototype of DSTWLPMVM is manufactured and tested. The measured EMF is basically symmetrical sinusoidal waveforms and the peak-to-peak value of the detent force is lower than 10 N. [ABSTRACT FROM AUTHOR]

There are two hypotheses in the leader progression model to illustrate the insulator breakdown process. One is the streamer onset time is relatively small that can be ignored. The other is the leader velocity at both sides of the composite insulator strings are equal. These assumptions are mostly based on the experimental results in rod-rod air gaps. In this paper, experiments were performed to study the breakdown process of a 220-kV composite insulator string with grading rings under positive short tail lightning impulses. The discharge current at the high-voltage side and the high-speed photographs were recorded synchronously. The method of identifying four typical stages of the breakdown process from the current waveform was proposed. The experimental results show that the streamer onset time should not be ignored when calculating the breakdown time, especially for the composite insulator string with grading rings. By fitting the experimental results, the relationship between the streamer onset time andUP/U ${}_{\text{50}}$ has been given. The results also indicate that the velocity of the positive leader is nearly 1.3 times than that of the negative leader during the breakdown process when the positive impulse is applied to the composite insulator string. [ABSTRACT FROM AUTHOR]

On transmission lines where switching surges are not mitigated with closing resistors and/or surge arresters, high-speed reclosing on a line with trapped charge will produce high overvoltages that have been measured above 3 p.u. Careful simulations of these switching events using available electromagnetic transient (EMT) programs consistently produce significantly higher voltages than the measurements. This indicates a phenomenon present on the line that acts to reduce the switching surge magnitudes but is not typically modeled. This paper aims to identify the required simulation practices in reproducing the field measured overvoltages in EMT simulations and investigates the sensitivity of results to modeling approaches and electrical parameters. Field measurements from a switching surge test of a 230-kV line without surge mitigation have been used for model comparisons. Variations in frequency-dependent line modeling, ground resistivity, skin effect, shunt conductance, parallel lines, and source-side detail have been tested in an unsuccessful attempt to decrease the difference between the field measurements and the higher simulation overvoltages. It is demonstrated that even though the pattern of the transient voltage waveforms can be reproduced very well using frequency-dependent line models, the magnitude of the maximum overvoltage is significantly overestimated unless the effect of corona is considered. Two types of corona models are tested, and both demonstrate that corona is the primary factor that allows the simulations to correctly reproduce high peak overvoltage measurements. [ABSTRACT FROM AUTHOR]

Objective of this paper is to investigate the transient response of a PV module irradiated by an impulse light flash. The impulse flash with a waveform of 8/20 μs was considered. LTSpice was employed for the numerical simulation. Based on the numerical results, the short-circuit current and the electrical properties of some cell components (such as the diode, capacitance and inductance) are demonstrated and discussed. It is found that the irradiation by the pulsed flash causes not only the oscillation of the short-circuit current, but also the oscillation of voltage and current of cell components, depending both on the capacitance C of the PV cell and on the inductance L of wiring and cables. It is also found that, under a certain condition of L and C, the diode voltage becomes negative; namely, application of the large reverse voltage to the cell is pointed out. It is concluded that the response of the PV module against the pulsed photo-current is composed of two sequential stages; the first stage is a charging stage of C by the pulsed photo-current, and the next stage is a discharging stage of C. The latter stage causes a damping oscillation of short-circuit current. [ABSTRACT FROM AUTHOR]

[Display omitted] • The vibrational assignments of observed and stimulated FT-IR (Fourier Transform Infrared spectroscopy) spectra were compared with theoretically obtained values. • Density functional computations were used to identify the energy gap between HOMO and LUMO at the B3LYP/6-311++G(d,p) level. • The density of electrons and the interactions among molecules may be explained using multiwave functions such as RDG, ELF, LOL, and TDOS. • Electrostatic potential (ESP) was used to map the surface's electron density, revealing information on the molecule's size, shape, charge distribution, and chemical reactivity. The present study focuses on structural and chemical analyses of N-phenylmorpholine-4-carboxamide benzene-1,2-diamine (PMCBD) using quantum computational methods. The calculated bond angle, length, and dihedral angle between atoms were compared with measured values. The observed and stimulated FT-IR (Fourier Transform Infrared Spectroscopy) spectra parameters for vibrational wavenumbers and their associated PED (Potential Energy Distribution) values in percentage have been obtained from VEDA4 software. The electronic transitions of PMCBD were discussed by TD-SCF/DFT/B3LYP based on the 6-311++G(d,p) basis set with solvents such as chloroform, ethanol, and dimethyl sulfoxide (DMSO) and gas. Density functional computations were used to study the band energy between HOMO and LUMO using the B3LYP/6-311++G(d,p) level. Mulliken analysis and natural population analysis were used for a better understanding of charge levels on different atoms such as N, H and O. The natural bonding orbital (NBO) analysis proved helpful in studying molecular and bond strengths. (NBO). The ESP acquired data on the molecule's size, shape, charge density distribution, and chemical reactivity site. This was done by mapping electron density on the surface with electrostatic potential. Non-linear optical detection of PMCBD was also discussed. Aside from the electron localization function map, state densities are also mapped using Multiwfn software, a wave function analyzer. [ABSTRACT FROM AUTHOR]

Abstract Capacitive deionization (CDI) performance metrics can vary widely with operating methods. Conventional CDI operating methods such as constant current and constant voltage show advantages in either energy or salt removal performance, but not both. We here develop a theory around and experimentally demonstrate a new operation for CDI that uses sinusoidal forcing voltage (or sinusoidal current). We use a dynamic system modeling approach, and quantify the frequency response (amplitude and phase) of CDI effluent concentration. Using a wide range of operating conditions, we demonstrate that CDI can be modeled as a linear time invariant system. We validate this model with experiments, and show that a sinusoid voltage operation can simultaneously achieve high salt removal and strong energy performance, thus very likely making it superior to other conventional operating methods. Based on the underlying coupled phenomena of electrical charge (and ionic) transfer with bulk advection in CDI, we derive and validate experimentally the concept of using sinusoidal voltage forcing functions to achieve resonance-type operation for CDI. Despite the complexities of the system, we find a simple relation for the resonant time scale: the resonant time period (frequency) is proportional (inversely proportional) to the geometric mean of the flow residence time and the electrical (RC) charging time. Operation at resonance implies the optimal balance between absolute amount of salt removed (in moles) and dilution (depending on the feed volume processed), thus resulting in the maximum average concentration reduction for the desalinated water. We further develop our model to generalize the resonant time-scale operation, and provide responses for square and triangular voltage waveforms as two examples. To this end, we develop a general tool that uses Fourier analysis to construct CDI effluent dynamics for arbitrary input waveforms. Using this tool, we show that most of the salt removal (∼95%) for square and triangular voltage forcing waveforms is achieved by the fundamental Fourier (sinusoidal) mode. The frequency of higher Fourier modes precludes high flow efficiency for these modes, so these modes consume additional energy for minimal additional salt removed. This deficiency of higher frequency modes further highlights the advantage of DC-offset sinusoidal forcing for CDI operation. Graphical abstract Image 1 Highlights • Developed a dynamic system modeling approach for capacitive deionization (CDI). • CDI behaves as a first order linear time invariant system for practical conditions. • Demonstrated sinusoidal voltage/current operation for CDI as an efficient operation. • Identified a system "resonant" frequency that maximizes concentration reduction. • Developed a tool for CDI to predict effluent dynamics for arbitrary forcing input. [ABSTRACT FROM AUTHOR]

This paper introduces a novel hybrid-excited stator slot opening permanent magnet (PM) machine (HSSPMM). The operation principle of the machine is described and the effects of rotor eccentricity and magnetic saturation due to PMs on electromagnetic performance, with particular emphasis on back electromotive force (EMF), are analyzed by finite element method (FEM). It shows that different from the conventional PM machines, the open-circuit back EMF in this novel HSSPMM should be zero but may become non-zero if significant magnetic saturation exists, and furthermore, the rotor eccentricity has a detrimental effect on the waveforms, amplitudes, and symmetries of three-phase back EMFs, as confirmed by FEM and tests. [ABSTRACT FROM AUTHOR]

In this paper, a frequency-based analytical approach for dynamic analyzing of unbalanced three-phase systems in the presence of harmonic distortion using sequence domain is put forward. As will be shown, classical symmetrical components proposed by Fortescue is not applicable under nonsinusoidal periodic condition. In such cases, generalized symmetrical components proposed by Tenti et al. can be used to calculate sequences from phase domain values. However, it introduces a new sequence component called residual component, which has a different value for each phase and cannot be directly obtained based on sequence networks. To such aim, using dynamic harmonic domain, an approach that makes it possible to use features of classical symmetrical components and modify the outputs to compute sequences based on the concept of generalized symmetrical components is proposed. Moreover, it is shown that using equivalent circuit for triplen harmonics is essential to find a relation between residual components since if sequences are connected in parallel, it is not possible to modify results of classical symmetrical components and this equivalent circuit should be directly analyzed. Time domain software is used to perform conventional lumped circuit simulation and validate the time domain responses resulted from DHD. [ABSTRACT FROM AUTHOR]

For the purpose of reducing cost and volume, as well as to increase reliability in hostile environments, techniques of reconstructing three-phase current through a single current sensor have been reported for a three-phase alternating current motor vector control system. Based on the phase current reconstruction method, this paper proposes a novel open-circuit fault diagnosis method for the low-power voltage source inverter in the three-phase permanent-magnet synchronous motor drive. Other than sampling the single dc-link current sensor, the zero voltage vector sampling method (ZVVSM) is adopted to implement the fault diagnosis. By placing the single current sensor at a special position, ZVVSM is able to sample current during the two zero voltage vectors and reconstruct the three-phase currents. The reconstructed three-phase currents are used to generate the diagnostic variables that can detect and locate the faulty power switches. The PWM modulation strategy remains unchanged in this method and the reconstructed phase currents are with less waveform distortion and less harmonic contents, which are suitable for the fault diagnosis. The effectiveness of the proposed method is verified by experiments. [ABSTRACT FROM AUTHOR]

When an electrostatic discharge (ESD) event reaches a nongrounded metallic part within a product, the voltage of this metal with respect to ground will increase. If the isolation to the ground is insufficient, a secondary ESD event can occur. As secondary ESD often leads to system upset or damage, and to poorly reproducible results, it is important to detect the occurrence of secondary ESD. If the discharge current is monitored using an oscilloscope, the test equipment may miss the secondary discharge waveform. This is because the time delay between the primary and secondary discharge events can vary between nanoseconds to milliseconds. Present oscilloscopes do not offer functionality to autodetect a secondary discharge event. The goal of this study is to analyze different types of secondary discharge events acquired with various measurement setups and identify waveform parameters for software-assisted detection methods. A learning sequence is proposed for identifying secondary ESD events starting fromlow ESD gun test voltages. The data are analyzed with respect to the waveform parameters such as the vertical threshold of the rising edge, the dI/dt of the current waveform, and total charge delivered, which enable automatic detection of secondary ESD while monitoring the discharge waveform at the ESD gun tip. [ABSTRACT FROM AUTHOR]

For electrohydrodynamic jetting-on-demand, the conventional positive voltage pulse superposed by a dc bias voltage have been widely used. Once this voltage pulse was induced, the meniscus at the nozzle tip oscillated and its volume changed owing to the fluid supplied through the nozzle as well. To increase the maximum frequency for consistent jetting, it is desirable to minimize these phenomena. When the oscillation amplitude was sufficiently small to assume the occurrence of linear behavior and no jetting, the above phenomena could be well explained by using a harmonic oscillator model and a one-dimensional flow model. Based on this physical understanding, the root-polar voltage waveform was proposed and could significantly decrease the change in meniscus height; thus it was possible to increase the maximum frequency for consistent jetting. In addition, the residual oscillation could be also suppressed using an extra voltage pulse waveform. Furthermore, the root-polar voltage waveforms with a minus voltage pulse as well as a positive one could be demonstrated; thus it was shown that the root-polar voltage waveform could be implemented into ac-pulse modulated EHD jetting as well. [ABSTRACT FROM AUTHOR]

This paper presents a high-levels multilevel inverter (MLI) with a reduced number of the required switches. Forty-nine levels can be obtained in the output voltage from this circuit by using only 12 semiconductor switches, while in conventional topologies of MLI, a higher number of switches is required producing a lower number of levels in the output voltage. Reduction in the number of semiconductor switches, gate drivers, DC voltage sources and increasing the number of voltage levels are advantages of the proposed MLI compared with other topologies. These advantages result in smaller size, lower loss and low installation cost. Total harmonic distortion (THD) in the output waveform of the inverter is very low, thus, using a filter to improve the output waveform is not needed. A switching pulse system has been presented to produce nearly sinusoidal waveforms. Mathematical relations and switching states of the proposed topology have been discussed. Simulation results have been obtained and studied. The prototype of the modified MLI has been built and tested in the laboratory using a dSPACE (DS1104) evaluation board in order to verify the simulation results. Several of the experimental results of the proposed topology have been included and discussed. [ABSTRACT FROM AUTHOR]

In this paper, we present a new black-box arc model that was validated using tests with short-line fault interruption of high-voltage circuit breakers. This new arc model shows superior performance compared with four types of existing black-box arc models. Black-box arc models are widely used to simulate current and voltage waveforms during the interruption process. Applied together with arc parameters, they determine arc conductance and interruption behavior. In this study, the arc parameters of each arc model are derived from an optimization approach in a defined time interval to minimize the difference between the measured and simulated arc voltages. The black-box arc models with optimized arc parameters are applied to a simplified circuit for short-line fault simulation, and the model accuracy of the interruption prediction and waveform fitting is quantitatively scored. [ABSTRACT FROM PUBLISHER]

An electric arc furnace exhibits highly nonlinear characteristics and can cause power quality issues. Its performance is a vital issue for electric utilities. In this paper, a novel multiobjective optimization technique has been proposed for the estimation of the electric arc furnace parameters to predict the voltage and current waveforms and evaluate the performance of the furnace under various conditions. The multiobjective optimization technique minimizes the extinction voltage error and arc resistance error simultaneously to enhance the performance of the electric arc furnace model. The proposed optimization model employs a genetic algorithm and the stochastic variation of the arc length to estimate the parameters of a nonlinear time-variant resistance model of the electric arc furnace by using actual current and voltage data. These data have been obtained from a steel plant in Saudi Arabia. Optimization has been carried out in MATLAB/SIMULINK environment and the model of the electric arc furnace with the estimated parameters has been developed in PSCAD/EMTDC. The results obtained from the PSCAD model have been validated with actual data from the steel industry. The validation shows that the proposed method is efficient and accurate in the estimation of the electric arc furnace parameters. [ABSTRACT FROM PUBLISHER]

The continuing development of HVDC power transmission systems presents many problems related to evaluation of the reliability of power system assets [1]-[5]. In this context the identification of insulation defects plays a key role in preventing unexpected failures of electrical components. Partial discharge (PD) measurement is a useful approach to assessing the condition of HV power apparatus and cables. Such measurements are also widely employed for HVAC systems. The inception mechanisms of PD in AC systems are well-known, and measurements are usually performed following the IEC 60270 standard [6]. PD measurements under DC voltage present complexities related to the nature of the phenomenon and the supply conditions [7]. In AC systems phase-resolved-partial-discharge (PRPD) patterns allow assessment of the insulation condition, and provide information on the types of defect present [8]. Such analysis cannot be performed under DC voltage, since each discharge event cannot be related to a phase value. The interpretation of the acquired data therefore requires a different approach. [ABSTRACT FROM AUTHOR]

This paper presents experimental results obtained from the Guangdong comprehensive observation experiment on lightning discharge during summer 2014. Residual voltages and current flows in a surge protective device (SPD) connected to an overhead distribution line were observed due to nearby M-components of a triggered lightning flash. Residual voltages with varying characteristics caused by different M-components are analyzed at two terminals of the SPD, and corresponding formation mechanisms for the different characteristics are also discussed. Our results show that the residual voltages at two terminals of the SPD caused by three types of M-component are determined from both the line induction and the ground potential rise (GPR) in a nearby triggered lightning at 40 m distance. The M-component with a large peak current would produce large surge energies in the power line. Under a given peak current, the M-component has greater surge energy than the return stroke. The ground terminal of the SPD is still affected by the GPR, and our results also show that the continuing current superimposed with M-components is an important factor in determining the magnitude of line coupling in power distribution lines when a lightning flash occurs nearby. [ABSTRACT FROM PUBLISHER]

A new method to numerically estimate the primary voltage waveform of coupling capacitor voltage transformers is presented. The outcome is a simple digital filter suitable for the frequency range from 10 to 60 Hz, enabling us to recover the transformer primary voltage waveform from its secondary voltage waveform. Unlike the techniques reported in the literature, the method does not depend directly on the transformer topology nor on the operational characteristics of the protected system, once only the coupling capacitor voltage transformer frequency response is required as input. The evaluation of the technique is performed through digital simulations using the Alternative Transients Program and transmission-line data from the Brazilian National Power System Grid. Frequency- and time-domain analysis of two coupling capacitor voltage transformers with different topologies and voltage levels are presented. It is shown that the proposed method is effective for the dynamic correction of low-frequency disturbances that may improve the speed, reliability, and security of the numerical distance relay. [ABSTRACT FROM AUTHOR]

This paper extends our previous bubble actuation study using a simple constant voltage by including the oscillating effect created by voltage modulation. Rather than normal contact angle change due to the constant voltage, voltage modulation exhibits preferable characteristics of periodical contact angle variation which is proved to be helpful for bubble detachment within a thin liquid film. Different waveform and frequency modulations were evaluated to acquire an optimal signal input for the purpose of inducing the maximum oscillation effects with which bubble detachment in a thin liquid film can be enhanced. The thick liquid film results show that the square waveform coupled with a frequency of 1 Hz allows for maximum contact angle change scope and induces the largest vertical bubble velocity. With the optimal signal, the tests of bubble detachment within a thin liquid film were conducted and characterized. Three different bubble detachment modes were observed and classified as follows: direct detachment, delayed detachment, and non-detachment. The actuation mechanism of the electrowetting effect on the bubble behavior within a thin liquid film was analyzed. The dimensionless parameter, Weber number, was used to characterize the bubble deformation. A high-speed frame analysis shows that a Weber number greater than 0.5 × 10−3 is necessary to break the energy barrier of the ultra-thin film and achieve the direct detachment mode. It is expected that a proper electrowetting actuation mechanism causing a relatively large Weber number can effectively enhance the bubble detachment within a thin liquid film which will provide promising applications to improve two-phase heat transfer. [ABSTRACT FROM AUTHOR]

This paper describes a compact model for a silicon-carbide (SiC) MOSFET, which features both characterization and modeling of a new drain-gate capacitor. In addition, the internal gate resistance and the internal stray inductances of the discrete package are experimentally evaluated and modeled by a newly-proposed method. The gate drive circuit is also modeled and involved in this simulation. The comprehensive modeling procedure is also considered, which offers an efficient modeling process. The model shows excellent agreements in transient behavior of both gate drive circuit and main power circuit between experimental and simulated waveforms. The comparison shows accurate reproducibility of a rate of drain-source voltage change and a rate of drain-current change within an error of 15%, which could not be realized with the conventional stray capacitance models. This successful validation indicates that the developed model would offer a new modeling concept and be expected to open up the possibilities of the simulation study for evaluating and designing detailed performance of SiC-MOSFETs. [ABSTRACT FROM PUBLISHER]

The article reports that integrated circuits (ICs) have incredibly dense transistor packing that can fail due to miniscule defects, which require electrical fault isolation (EFI). Of several available EFI techniques, laser voltage probing (LVP) and derivatives using continuous-wave near-infrared laser are very popular.

The present paper covers a review of documents that specify measurement methods of voltage waveform distortion. It also presents measurement stages of waveform components that are uncommon in the classic fundamentals of electrotechnics and signal theory, including the creation process of groups and subgroups of harmonics and interharmonics. Moreover, the paper discusses selected distortion factors of periodic waveforms and presents analyses that compare the values of these distortion indices. The measurements were carried out in the cycle per cycle mode and the measurement methodology that was used complies with the IEC 61000-4-7 norm. The studies showed significant discrepancies between the values of analyzed parameters. [ABSTRACT FROM AUTHOR]