Power Line Frequency Research Articles

Gradiometer Using Separated Diamond Quantum Magnetometers

The negatively charged nitrogen-vacancy (NV) center in diamonds is known as the spin defect and using its electron spin, magnetometry can be realized even at room temperature with extremely high sensitivity as well as a high dynamic range. However, a magnetically shielded enclosure is usually required to sense weak magnetic fields because environmental magnetic field noises can disturb high sensitivity measurements. Here, we fabricated a gradiometer with variable sensor length that works at room temperature using a pair of diamond samples containing negatively charged NV centers. Each diamond is attached to an optical fiber to enable free sensor placement. Without any magnetically shielding, our gradiometer realizes a magnetic noise spectrum comparable to that of a three-layer magnetically shielded enclosure, reducing the noises at the low-frequency range below 1 Hz as well as at the frequency of 50 Hz (power line frequency) and its harmonics. These results indicate the potential of highly sensitive magnetic sensing by the gradiometer using the NV center for applications in noisy environments such as outdoor and in vehicles.

Estimating the energy in current signals during electrical sounding: a novel approach

Despite the rapidity in the use of electrical sounding/expanding probe technique in the study of hydrology, mineralogy, contamination, and other geophysically based studies over decades, it appears that our ability to identify the relationships between the energy loaded in direct currents injected into the ground between two electrodes at low polarizing frequency is not yet realized and hence the drive for this research. This study is insightfully undertaken to address this problem by establishing the novel links associated with the existing geo-resistivity theories and the two complementary energies, the voltage-driven energy called charging energy and the charge-driven energy called the discharging energy. This was achieved by sorting the resistivity values realized from electrical sounding technique into regimes (trends of resistivities representing certain geologic layers) and plotting each regime in a location against the signal current low polarizing frequency measured from the relationship between power line frequency and the ratio of potential to current separations. The two energies, which are determinable from the slopes of regressed resistivity-period plots and the novel relations established in this work, depend on the dynamic parameters βv and βq, which are respectively called the voltage geometric index of energy and charge geometric index of energy. These indices connect earth resistivity to energy and frequency/relaxation period. Calculating the energy for each sounding at its polarizing frequency, the complementary charging and discharging energies were traced to be dependent on conductivity/resistivity of the geological sequence/regimes. The established equations, graphs, and contour maps give insightful and expanded information on the dependence of energy loaded on injected currents into the ground. The charging energy, which is enhanced in arenaceous layers, has low conductivity and is believed to have high permittivity and low energy loss factor, which is not determined in this work while discharging energy in argillites is high as conductivity and energy loss factor increase at decreasing permittivity. In all cases, the currents and its loaded energy are in comparatively minute magnitudes.

Real-Time Fast Fourier Transform-Based Notch Filter for Single-Frequency Noise Cancellation: Application to Electrocardiogram Signal Denoising.

Despite the considerable improvement of the common-mode rejection ratio of digital filtering techniques, the electrocardiogram (ECG) traces recorded by commercialized devices are still contaminated by residual power line interference (PLI). In this study, we address this issue by proposing a novel real-time filter adapted to single-frequency noise cancellation and automatic power line frequency detection. The filtering process is principally based on a point-by-point fast Fourier transform and a judicious choice of the analysis window length. Intensive experiments conducted on real and synthetic signals have shown that our filtering method offers very clean ECGs, due to the suppression of spikes corresponding to the PLI and the preservation of spikes outside the filter band. In addition, this method is characterized by its low computational complexity which makes it suitable for real-time cleaning of ECG signals and thus can serve for more accurate diagnosis in computer-based automated cardiac system.

Dynamics of electric and magnetic fields in case of the urban environment

This paper studies the temporal dynamics of power-line frequency electric and magnetic fields in Saint-Petersburg and environs. It is found that electromagnetic fields generated by high-voltage transmission lines (HVTL) constantly change, depending on their loading and weather conditions. The dependence on weather conditions involves both the direct effect of air electrical conductivity as a function of its humidity, and indirect effects including the dependence of energy consumption on temperature and also the correlations between meteorological characteristics. An attempt has been made to evaluate the role of influencing factors.

Electrical and Optical Characterization of Gliding Arc Discharge (GAD) Operated at Line Frequency (50 Hz) Power Supply

In this study, an atmospheric alternating-current gliding arc device using line frequency (50 Hz) has been designed for the generation of various reactive species in different working gases. Electrical characteristics of the generated discharge are investigated by oscilloscope while the optical characteristics are analyzed using optical emission spectroscopy. The role of different working gases (oxygen, argon and air) on discharge voltages and power consumption per cycle in the discharge are calculated and compared. Electron density and electron temperature of the discharge are estimated by electrical and optical method respectively. The production of reactive species in the discharge is affirmed by optical emission spectroscopy. The outcomes of the results confirm that the GAD can generate non-equilibrium plasma having reactive nitrogen and oxygen species (RONS) which are essential for plasma chemistry applications.

Efficient Reduction of Powerline Signals in Magnetic Data Acquired From a Moving Platform

High-bandwidth magnetic data are normally distorted by ubiquitous 50- or 60-Hz noise from powerlines and similar sources. The powerline noise can be orders of magnitude larger than the magnetic signal from targets and must be culled from data sets prior to interpretation. Suppression of the powerline noise by simple filtering can result in artifacts and an unacceptable reduction in resolution of ground-based and unmanned aerial vehicle magnetic surveys. Removal approaches such as those based on Biot–Savart modeling are sensitive to the estimated position of the powerline systems, in addition to their limited applicability due to the requirement of a DC source. Moreover, the powerline noise in data acquired from a moving platform is inherently nonstationary and removal techniques must be specifically developed with this in mind. We propose a model-based method that does not rely on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a priori</i> knowledge of the powerline system by fitting and subtracting a set of sinusoids to the data. These sinusoids are computed on small windows of data, tied together with regularization terms within the fitting process to reduce discontinuities between segments. We further incorporate powerline frequency as a nonlinear parameter, allowing for fluctuations in the fundamental frequency as loads on the power grid change. Through synthetic and field examples, we show that periodic noise can be reliably removed automatically without the need for filtering or significant alterations of the frequency content. Powerline noise is reduced by over 98% in the field example.

1.25-inch 3-CMOS Multi-Functional High-Speed 8K Camera System

We develop UHD-2/8K cameras capable of high-speed recording at 120 frames/sec or more to support the highest video format of ultrahigh definition television and for shooting slow-motion video. Previously, we developed a 1.25-in. 3-CMOS UHD-2/8K 240-frames/sec high-speed camera system capable of capturing smooth slow-motion video at one-fourth speed. In this article, we describe a multi-functional high-speed 8K camera system with significantly upgraded functionality, compared with the conventional UHD-2/8K 240 frames/sec camera system. The upgraded high-speed camera has three new features. The first feature is a 480-frames/sec shooting mode. With this, we achieved twice the frame frequency of a previously developed camera system by operating the analog-to-digital converter (ADC) at twice the speed in the image sensor and subsampling the image. The video signal was processed in GBR 4:2:0 format on conventional hardware and was output in YCbCr 4:2:0 format. The second feature is a 120-frames/sec random-noise-reduction shooting mode. We applied the multisampling technique to reduce the random noise caused by the readout circuit in the image sensor. This technique can improve the signal-to-noise ratio of the camera by approximately 4 dB. The third feature is a 120-frames/sec flicker reduction mode. We generated an image with an exposure time of 1/100 sec by combining three successive frames of short- (1/600 sec), long- (1/150 sec), and short-exposure-time images to suppress the 20-Hz flicker caused by illumination with a power line frequency of 50 Hz. From the experimental results, it was found that the flicker could be reduced to 1/10 or less .

Sizing of dc-link capacitor for a grid connected solar photovoltaic inverter

Objective: To determine the optimum size of a dc-link capacitor for a grid connected photovoltaic inverter. Methods: Dc-link capacitors are considered as one of the sensitive parts of the grid connected photovoltaic systems and needs effort to design a reliable and optimal size capacitor as its reliability is concerned with the overall system reliability. The double line frequency power flows between the input and outside of a Φ grid connected PV system which produces voltage ripples at the capacitor and dc link. This voltage ripple increases temperature of passive components and dc source which affects the MPP operation of the photovoltaic modules and the system life. Therefore, it is essential to limit the voltage ripples at the input side of the system. The easiest way to limit the double frequency ripple voltage is to connect a capacitor in parallel to the PV module and the inverter which buffers the double line frequency power and supply a constant power to the inverter. This study proposed a general method for sizing a dc-link capacitor for a Φ grid connected voltage source inverter. It is seen that the capacitance is inversely proportional to the nominal dc and ripple voltage. Thus an increase in the nominal system voltage decreases the size of the capacitor and at the same time increases the voltage ripple. Therefore to limit voltage ripple within permissible limits and to ensure better system performance the dc-link capacitor must be appropriately sized. The simulations based on 3kW grid connected PV system are carried out in DIgSILENT Power Factory software. Findings: A capacitor of 410µF is needed to be connected in parallel with a 3kVA inverter having an nominal input voltage of 370V and maintaining a voltage ripple under 8.5%. Novelty: After determining optimized dc-link capacitor size we will limit the voltage ripple under permissible limits and hence improves the system efficiency and life of the grid connected PV system. Keywords: Voltage source inverter; voltage ripple; Dc-link capacitor sizing; distributed generation; grid connected PV system

Analysis and Suppression of Resonant Current Envelope Ripple of LLC Converter in Cascaded Modular PV Solid-State Transformer

Featured with the advantages of expandable modular structure, simple layout, and low dependence on copper and steel, three-phase solid-state transformer-based cascaded H-bridge (HB) topology has been replacing traditional inverters in high-voltage and high-power photovoltaic power generation applications. However, due to the double line-frequency power fluctuation on the dc side of HB converters, if the LLC topology is used as the front-stage isolated dc/dc converter, its resonant current will produce an envelope ripple with the same frequency. The envelope ripple will not only increase the current stress of switching devices and diodes in LLC converter but also increase the losses of switching devices and magnetic components. Aiming at this problem, this article analyzes the mechanism of enveloping ripple in detail by mean of the concept of calculus, expounds the influence of envelope ripple on the whole system, and then proposes a control method to suppress envelope ripple of resonant current. The validity of the proposed method is verified by simulation and experimental results.

A Single Stage Common Ground Three-Level PV Inverter With Integrated Power Decoupling

In this paper, a T-type common ground transformer-less single phase inverter with dynamic swing of the dc-link voltage is presented for photovoltaic (PV) application. The topology is a combination of a bi-directional, partial-power-processing boost stage and an asymmetric half-bridge inverter stage along with a T-branch. It takes advantage of the three-level switching states with reduced voltage stress on the main switches to achieve lower switching loss and almost one-half the inductor current ripple w.r.t. two level implementation. The double line frequency power decoupling is addressed by a dynamic dc-link approach, which allows a large swing of the dc-link to reduce the decoupling capacitor requirement, enabling an all-film capacitor implementation. This topology also significantly reduces the high-frequency capacitive coupled ground current by directly connecting the PV negative terminal to the grid neutral. Moreover, an adaptive dc-link voltage control scheme that optimally changes the average value of the dc-link voltage as the operating conditions (load and power factor) vary, has been proposed and thoroughly investigated from the perspective of better utilization of passive components and further reduction of switching losses. A SiC MOSFETs-based 1 kVA laboratory prototype has been built to validate the converter's operation at 200 V dc nominal input and 120 V/60 Hz ac nominal output with a wide range of power factor and load operations. Extensive experimental results validate the superior performance of the topology with the adaptive dc-link voltage control implementation showing a peak efficiency of 98.22% and a CEC efficiency of 98.03% at 50 kHz switching frequency.

Effect of Seawater Immersion on Power Frequency Over Voltage Calculation of AC Three-core Submarine Cable

AC three-core submarine cable is an important carrier to transmit offshore wind power. Limited by the laying conditions, the reactive power compensation is generally carried out at both ends of the submarine cable line. And the armour along the submarine cable is immersed by seawater until the metal sheath, which causes the sheath of the submarine cable line to be grounded everywhere. With the growth of submarine cable lines, power frequency overvoltage becomes more and more serious. In order to effectively limit power frequency overvoltage, it is necessary to study and compare the effect of different reactive power compensation schemes on overvoltage. This paper is based on the research of double loop AC three-core submarine cables. The submergence of seawater is simulated by dividing the submarine cable into sections and grounding the sheath and armour of each section of submarine cable through resistance. On the basis of this model, the changes of line power frequency overvoltage under the conditions of “55” compensation, “28” compensation and three terminal compensation are calculated and compared. Under the scheme of “28” compensation at both ends, the maximum power frequency overvoltage of the line is the lowest. The research results provide a theoretical reference for the reactive power compensation scheme of offshore wind power access system.

Proposal of Instantaneous Power-Line Frequency Synchronized Superimposed Chart for Communications Quality Evaluation of broadband PLC System

Proposal of Instantaneous Power-Line Frequency Synchronized Superimposed Chart for Communications Quality Evaluation of broadband PLC System

An adaptive denoising approach to powerline interference reduction in ECG recording

The objective of this paper is to develop an adaptive denoising algorithm for the reduction of powerline interference (PLI) in electrocardiogram (ECG) recording. The problem of mode mixing and inability to deal with non-stationary characteristics have the major drawbacks posed by existing PLI removal techniques. The technique used in the proposed work has been combined with the concept of synchrosqueezing transform with an adaptive filter to overcome such limitations. The synchrosqueezing transform has facilitated as a mode decomposition tool to disintegrate the signal into a set of intrinsic mode functions and then applying adaptive filter on decomposition results to estimate PLI so as to recover noise free ECG. The performance assessment of the proposed techniques have been carried out with several established ECG database available in physio net and its adaptability to powerline frequency drift has also been studied. A comparative analysis has been conducted to validate the proposed techniques. Experimental results have suggested that the proposed SST based PLI reduction approaches provide better denoising effect than state of the art methods.

ESPRIT associated with filter bank for power-line harmonics, sub-harmonics and inter-harmonics parameters estimation

Detection of power-line frequency components and estimating their parameters are crucial tasks for maintenance of applied power quality, especially due to uncertainties originated from growing utilization of renewable power sources, hybrid energy storages and increasing demand for electrical vehicles. This manuscript introduces the association of filter bank to ESPRIT (FB-ESPRIT) for higher efficiency in detection and estimation of the harmonics, inter-harmonics, and sub-harmonics parameters in power quality measurement. FB-ESPRIT initially applies an analysis filter bank of parameter L to the signal, then individually implements ESPRIT to each of L resultant signal sub-band while it is spread over the full bandwidth of the signal. Due to individual ESPRIT implementation on L times spectrum spread of subbands, FB-ESPRIT is expected to have L times higher accuracy and robustness in parameter estimation compared to ESPRIT. Its efficiency analysis has been carried out over three case studies composed of multiple harmonics, inter-harmonics, sub-harmonic and fundamental components; a synthesized signal with under 500 Hz bandwidth, a synthesized signal with a bandwidth up to 64th harmonic in 50,000 Monte Carlo simulations (MCS) at different noise levels, and a real power signal measured at the output of a photovoltaic solar power plant in a partly cloudy windy summer morning. The comparative evaluations approve the multiple times accuracy and robustness dominance of efficiency of ESPRIT with versus without filter bank association. It has been theoretically illustrated that a FB-ESPRIT calibrated to give the same efficiency as ESPRIT has the advantage of L2 times less complexity order, as well approved via the mean result of extensive simulations runs.

Effect of Multi-site Variabilities on Electrovestibulography: Environmental and Physical Factors

Background: There are physiological changes in pathologies such as Alzheimer’s Disease (AD) within the lower vestibuloacoustic system, which may be potentially useful when used as neurodegeneration features. We hypothesize two Electrovestibulography feature types (Field Potential (FP) shape and the Firing pattern of detected FP’s) may have utility as Neurodegeneration features. Our long term objective is to use a population of Parkinson’s Disease (PD), AD, Post-Concussion Syndrome (PCS), Bipolar Disorder (BD) and Major Depressive Disorder (MDD) patients together with individual pathology-wise age and gender matched control cohorts to determine the degree to which each of these pathologies varies from controls and in proportion to the level of Neurodegeneration often associated (either temporarily or permanently) with each pathology. However, before such a comparison can be made it is necessary to ensure the various populations recorded across different countries are comparable. This paper determines which populations are comparable.&#x0D; Methods: An initial comparison of AD (with N = 16) and a best matched healthy control population (with specific age/gender/recording site/electrode matched controls) from a pool of 112 controls produced two EVestG features (FP shape and FP firing pattern). These features were examined for their variability with respect to electrode type, age, gender, powerline frequency and environmental factors.&#x0D; Results: Age and gender did not have a significant impact on the features. Powerline and environmental artefacts could be accounted for by filtering; thus, they did not significantly affect the features measured. However, electrode type had a significant effect on the extracted features.&#x0D; Conclusions: For the two EVestG features tested only electrode type had a significant effect on the recordings, and hence the extracted features. Thus, only populations with the same electrode type can be compared.

Energy Efficient FIR Filter for Biomedical Application using FPGA

This research work proposes a low power Finite Impulse Response (FIR) digital filter system using Field Programmable Gate Array (FPGA) to filter biomedical signals. A major issue regarding such implementations is associated with computational complexity that may hinder its practical application. Several researches that aim to overcome this problem have been found by using various designs like booth multiplier, distributive arithmetic design, reduce adder graph (RAG), common sub-expression elimination method etc. This work has achieved the target of power line frequency of 50Hz noise cancellation. It is shown that the proposed design using RAG can give faster speed and require less hardware resources than that for the Direct Structure-I design. The performance of the proposed method is also compared with several existing research works to study its efficacy and it is shown that proposed design can achieve nearly 2% area delay product and 43% less power consumptions in implementation of an FIR low-pass filter. The designed filter is also tested on ECG waves as example of biomedical signal from samples of the MIT-BIH Arrhythmia database corrupted with power frequency noise. The entire system has been implemented on the ALTERA DE-II FPGA education board by synthesizing Verilog HDL using Quartus II tool.

A modified modulation for single-phase photovoltaic/battery inverter to improve AC power quality with low DC-link capacitance

The current modulation for single-phase inverter is typically implemented by the assumption of constant DC-link voltage. However, as the inherent double line frequency power pulsation exists in single-phase photovoltaic (PV)/battery inverter, the DC-link voltage often contains double line frequency voltage ripple, which results in distortion of the AC output voltage. In this letter, a modified modulation for full bridge single-phase inverter is proposed. With the new active modulation, harmonics (especially the third order harmonic) in the AC side, are reduced dramatically, and the utilization of low-capacitance DC-link capacitors becomes possible. The effectiveness of the proposed improved modulation is demonstrated by experimental results on a 3 kVA prototype of single-phase PV/battery inverter.

Effects of extremely low-frequency electromagnetic fields on B16F10 cancer cells

ABSTRACTThis paper presents a method to inhibit B16F10 cancer cells using extremely low-frequency electromagnetic fields (ELF-EMFs) and to evaluate cell viability using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. The study examined the effect of a natural EMF resonance frequency (7.83 Hz) and a power line frequency (60 Hz) on B16F10 cancer cells for 24 and 48 h. The B16F10 cancer cells were also exposed to sweep frequencies in several sweep intervals to quantitatively analyze the viability of cancer cells. The results yielded a 17% inhibition rate under 7.83 Hz compared with that of the control group. Moreover, sweep frequencies in narrow intervals (7.83 ± 0.1 Hz for the step 0.05 Hz) caused an inhibition rate of 26.4%, and inhibitory effects decreased as frequency sweep intervals increased. These results indicate that a Schumann resonance frequency of 7.83 Hz can inhibit the growth of cancer cells and that using a specific frequency type can lead to more effective growth inhibition.

Frequency-Dependent Effective Capacitance of Supercapacitors Using Electrospun Cobalt-Carbon Composite Nanofibers

Mixing carbon-based materials with pseudocapacitive material is a widely used strategy to prepare high-energy, high-power supercapacitors. However, phase separation is inevitable after extended charging/discharging which leads to the degradation of performance metrics of the device. Here, we prepare in a single step cobalt-incorporated carbon nanofibers (CNF) by electrospinning homogeneous solutions of polyacrylonitrile (PAN) with cobalt acetate at different nominal proportions (1:0 to 1:1), and investigate their stability and capacitive behavior in symmetric supercapacitors. The electrochemical analyzes demonstrated up to an order of magnitude increase in the effective capacitive with increasing the cobalt content at both close-to-dc frequencies and at around 50/60 Hz power line frequencies. The maximum capacitance is recorded for a nominal cobalt acetate-to-PAN ratio of 0.9 (e.g. 29, 27, 22 and 10 mF at 0.01. 0.1, 1 and 100 Hz respectively; both electrodes are loaded with 1 mg cm− 2 of active material each). All devices showed also an outstanding capacitance retention exceeding 99% for 10000 cycles at 1 mA and 5 mA charging/discharging rates each. The improved energy storage capabilities are attributed to both the increased electrical conductivity and high pyridinic nitrogen content which was revealed from the material characterization results using XRD, FE-SEM/TEM, and XPS.

The effect of 20-week continuous 60 Hz magnetic field exposure on testicular function in sprague-dawley rats.

Accumulating evidence does not yet confirm the effect of power line frequency magnetic field (MF) on human health and fertility. We recently reported that, at continuous 60 Hz MF exposure in mice, the dose given as magnetic flux density (tesla; T) and duration of exposure was related to induce testicular germ cell apoptosis. We aimed to characterize the effect of a 20-week continuous exposure to 60 Hz MF on the motility, morphology, and number of sperm as well as the apoptosis of testicular germ cell in rats. Sprague-Dawley rats were exposed for 20 weeks to 60 Hz MF of 2, 20, or 200 μT for 24 h/day with rats exposed to sham conditions, serving as the control. The exposure to 60 Hz MF of 2 and 20 μT had no effects on testicular in this study. The exposure to 60 Hz MF of 200 μT for 20 weeks induced increases of the apoptotic cells (P < 0.001) in germ cells and decreases of sperm numbers (P < 0.05). However, the MF did not significantly affect the body or testis mass, seminiferous tubule diameter, or the motility or morphology of sperm. This study concluded that exposure to 60 Hz MF of 200 μT can increase testicular germ cell apoptosis, especially spermatogonia, and reduce sperm count. Also compared to previous mice studies, rats are less sensitive than mice to exposure to 60 Hz MF. Bioelectromagnetics. 39:539-546, 2018. © 2018 Wiley Periodicals, Inc.