Electrical Power Signals Research Articles

Source Location Identification of Distribution-Level Electric Network Frequency Signals at Multiple Geographic Scales

The distribution-level electric network frequency (ENF) extracted from an electric power signal is a promising forensic tool for multimedia recording authentication. Local characteristics in ENF signals recorded in different locations act as environmental signatures, which can be potentially used as a fingerprint for location identification. In this paper, a reference database is established for distribution-level ENF using FNET/GridEye system. An ENF identification method that combines a wavelet-based signature extraction and feedforward artificial neural network-based machine learning is presented to identify the location of unsourced ENF signals without relying on the availability of concurrent signals. Experiments are performed to validate the effectiveness of the proposed method using ambient frequency measurements at multiple geographic scales. Identification accuracy is presented, and the factors that affect identification performance are discussed.

Analysis of Power Quality Signals Using an Adaptive Time-Frequency Distribution

Spikes frequently occur in power quality (PQ) disturbance signals due to various causes such as switching of the inductive loads and the energization of the capacitor bank. Such signals are difficult to analyze using existing time-frequency (TF) methods as these signals have two orthogonal directions in a TF plane. To address this issue, this paper proposes an adaptive TF distribution (TFD) for the analysis of PQ signals. In the proposed adaptive method, the smoothing kernel’s direction is locally adapted based on the direction of energy in the joint TF domain, and hence an improved TF resolution can be obtained. Furthermore, the performance of the proposed adaptive technique in analyzing electrical PQ is thoroughly studied for both synthetic and real world electrical power signals with the help of extensive simulations. The simulation results (specially for empirical data) indicate that the adaptive TFD method achieves high energy concentration in the TF domain for signals composed of tones and spikes. Moreover, the local adaptation of the smoothing kernel in the adaptive TFD enables the extraction of TF signature of spikes from TF images, which further helps in measuring the energy of spikes in a given signal. This new measure can be used to both detect the spikes as well as to quantify the extent of distortion caused by the spikes in a given signal.

Compression of electrical power signals from waveform records using genetic algorithm and artificial neural network

This paper proposes a methodology for compression of electrical power signals from waveform records in electric systems, using genetic algorithm (GA) and artificial neural network (ANN). The genetic algorithm is used to select and preserve the points that better characterize the waveform contours; and the artificial neural network is used in the compression of other points as well as on the signal reconstruction process. Thus, the data resulting from the proposed methodology are formed by a part of the original signal and by a compressed complementary part in the form of synaptic weights. The proposed methodology selects and preserves a percentage of the original signal samples, which are aspects not explored in the literature. The method was tested using field data obtained from an oscillographic recorder installed in a 230kV electrical power system. The results presented compression rates ranging from 8.59:1.00 to 24.16:1.00 for preservation rates ranging from 2.5% to 10%, respectively.

The monitoring of transient regimes on machine tools based on speed, acceleration and active electric power absorbed by motors

This paper intend to propose some new results related with computer aided monitoring of transient regimes on machine-tools based on the evolution of active electrical power absorbed by the electric motor used to drive the main kinematic chains and the evolution of rotational speed and acceleration of the main shaft. The active power is calculated in numerical format using the evolution of instantaneous voltage and current delivered by electrical power system to the electric motor. The rotational speed and acceleration of the main shaft are calculated based on the signal delivered by a sensor. Three real-time analogic signals are acquired with a very simple computer assisted setup which contains a voltage transformer, a current transformer, an AC generator as rotational speed sensor, a data acquisition system and a personal computer. The data processing and analysis was done using Matlab software. Some different transient regimes were investigated; several important conclusions related with the advantages of this monitoring technique were formulated. Many others features of the experimental setup are also available: to supervise the mechanical loading of machine-tools during cutting processes or for diagnosis of machine-tools condition by active electrical power signal analysis in frequency domain.

Indices to Study the Electrical Power Signals in Active and Passive Distribution Lines: A Combined Analysis with Empirical Mode Decomposition

The broad diffusion of renewable energy-based technologies has introduced several open issues in the design and operation of smart grids (SGs) when distributed generators (DGs) inject a large amount of power into the grid. In this paper, a theoretical investigation on active and reactive power data is performed for one active line characterized by several photovoltaic (PV) plants with a great amount of injectable power and two passive lines, one of them having a small peak power PV plant and the other one having no PV power. The frequencies calculated via the empirical mode decomposition (EMD) method based on the Hilbert-Huang transform (HHT) are compared to the ones obtained via the fast Fourier transform (FFT) and the wavelet transform (WT), showing a wider spectrum of significant modes mainly due to the non-periodical behavior of the power signals. The results obtained according to the HHT-EMD analysis are corroborated by the calculation of three new indices that are computed starting from the electrical signal itself and not from the Hilbert spectrum. These indices give the quantitative deviation from the periodicity and the coherence degree of the power signals, which typically deviate from the stationary regime and have a nonlinear behavior in terms of amplitude and phase. This information allows to extract intrinsic features of power lines belonging to SGs and this is useful for their optimal operation and planning.

Prony’s Method with Reduced Sampling - Numerical Aspects

Abstract This paper presents a new modification of the least-squares Prony’s method with reduced sampling, which allows for a significant reduction in the number of the analysed signal samples collected per unit time. The specific combination of non-uniform sampling with Prony’s method enables sampling of the analysed signals at virtually any average frequency, regardless of the Nyquist frequency, maintaining high accuracy in parameter estimation of sinusoidal signal components. This property allows using the method in measuring devices, such as for electric power quality testing equipped with low power signal processors, which in turn contributes to reducing complexity of these devices. This paper presents research on a method for selecting a sampling frequency and an analysis window length for the presented method, which provide maximum estimation accuracy for Prony’s model component parameters. This paper presents simulation tests performed in terms of the proposed method application for analysis of harmonics and interharmonics in electric power signals. Furthermore, the paper provides sensitivity analysis of the method, in terms of common interferences occurring in the actual measurement systems.

Group velocity dispersion monitoring for QPSK signals using direct detection

ABSTRACTIn this letter, we propose a technique to monitor the group velocity dispersion analyzing a quadrature phase‐shift keying modulated optical signal. The method is based on the analysis of the direct detection electrical signal power, measured at the clock frequency, being able to return the dispersion magnitude value and sign. The proposed method was tested for 20 Gb/s signal in a dispersion range of [−600,600] ps/nm. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2078–2080, 2014

Demonstration of the Merit and Limitation of Generalised Space Shift Keying for Indoor Visible Light Communications

This paper demonstrates the merit and de-merit of a low complexity, multiple transmitter generalised space shift keying (GSSK) signalling technique for short range indoor visible light communications. To illustrate the high spectral efficiency credential of GSSK, an array of Nt white light emitting diodes (LEDs) is used to demonstrate Nt bits/symbol transmission by exploiting the natural differences in the channel gains of the spatially separated LED array. With two low power white LEDs each having a 3 dB modulation bandwidth of 8 MHz, data transmission of up to 40 Mbits/s ( 20 Mbaud) is demonstrated. For an average received electrical signal power of -12.5 dBm and 2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> data symbols, the measured symbol error rate at 20 Mbaud is 7 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> and 5 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> at 10 Mbaud ( 20 Mbits/s) without any error control coding. The GSSK technique is experimentally shown to be most suitable for a fixed configuration as its performance is quite sensitive to receiver mobility.

Functional change of neurotransmitters in central nervous system for outpatients with methadone maintenance treatment

Objective To detect neurotransmitters function in the brain and the brain functional index of outpatients with methadone maintenance treatment, and understand the change features of brain function. Methods Collect brain electrical power signals were collected from 58 outpatients with methadone maintenance treatment(MMT) and 44 healthy adults, and the correlations between the power of the neurotransmitters and the brain functional status were analyzed. Results (1)In MMT group, all neurotransmitters were lower generally than those in the control group, and the differences of GABA((17.73±3.54)μV2 vs. (121.48±44.64)μV2, P<0.01), Glu((42.18±12.84)μV2 vs. (105.31±34.95)μV2, P<0.05)were significant.(2)The relative powers of GABA((17.10±51.72)μV2 vs. (78.67±10.93)μV2 , P<0.001) and Glu((30.48±21.61)μV2 vs. (69.23±42.26)μV2 , P<0.001) reduced significantly, while 5-HT((297.18±31.54)μV2 vs. (280.18±31.54)μV2 , P<0.01), ACh((235.08±37.72)μV2 vs. (217.23±40.60)μV2 , P<0.05), NE((164.11±33.05)μV2 vs (146.39±30.80)μV2 , P<0.01), DA((98.87±22.48)μV2 vs. (91.49±21.04)μV2 , P<0.05) rised significantly in MMT group.(3)The global power was lower((1012.01±195.09)μV2 vs. (1775.94±458.99)μV2 , P<0.01), and the excitement-inhibition index(2.19±1.46 vs. 0.99±0.47, P<0.001)and the relative entropy((89.45±9.71)% vs. (75.48±9.97)%, P<0.01)were higher than those in the controls.(4) In MMT group, there were positive correlation between all neurotransmitters and global power, as well as that between Glu and excitement-inhibition index(r=0.264, P<0.05), NE and Vasomotor index(r=0.269, P<0.05), but negative correlation between relative entropy and 5-HT(r=-0.276, P<0.05)as well as DA(r=-0.375, P<0.01)significantly. Conclusion The brain function of outpatients with MMT are lower than the normal significantly, and there are clearly imbalance between the excitement and inhibition among the brain neurotransmitters. Key words: Methadone maintenance treatment; Encephalofluctuograph(EFG); Neurotransmitters; Brain electrical power

The Compression of Electric Signal Waveforms for Smart Grids: State of the Art and Future Trends

In this paper, we discuss the compression of waveforms obtained from measurements of power system quantities and analyze the reasons why its importance is growing with the advent of smart grid systems. While generation and transmission networks already use a considerable number of automation and measurement devices, a large number of smart monitors and meters are to be deployed in the distribution network to allow broad observability and real-time monitoring. This situation creates new requirements concerning the communication interface, computational intelligence and the ability to process data or signals and also to share information. Therefore, a considerable increase in data exchange and in storage is likely to occur. In this context, one must achieve an efficient use of channel communication bandwidth and a reduced need of storage space for power system data. Here, we review the main compression techniques devised for electric signal waveforms providing an overview of the achievements obtained in the past decades. Additionally, we envision some smart grid scenarios emphasizing open research issues regarding compression of electric signal waveforms. We expect that this paper will contribute to motivate joint research efforts between electrical power system and signal processing communities in the area of signal waveform compression.

In line 40 Gb/s group‐velocity dispersion monitoring

ABSTRACTIn this article, we propose a technique to monitor the group‐velocity dispersion (GVD) of an optical signal modulated at 40 Gb/s. The described method is based on the measurement of the electrical signal power at the clock frequency and is able to return the magnitude value and sign of the GVD. We show that this technique is capable to return the GVD in the range [−60, 60] ps/nm, with an error of 3 ps/nm. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:206–208, 2014

Reverse polarity optical-OFDM (RPO-OFDM): dimming compatible OFDM for gigabit VLC links

Visible light communications (VLC) technology permits the exploitation of light-emitting diode (LED) luminaries for simultaneous illumination and broadband wireless communication. Optical orthogonal frequency-division multiplexing (O-OFDM) is a promising modulation technique for VLC systems, in which the real-valued O-OFDM baseband signal is used to modulate the instantaneous power of the optical carrier to achieve gigabit data rates. However, a major design challenge that limits the commercialization of VLC is how to incorporate the industry-preferred pulse-width modulation (PWM) light dimming technique while maintaining a broadband and reliable communication link. In this work, a novel signal format, reverse polarity O-OFDM (RPO-OFDM), is proposed to combine the fast O-OFDM communication signal with the relatively slow PWM dimming signal, where both signals contribute to the effective LED brightness. The advantages of using RPO-OFDM include, (1) the data rate is not limited by the frequency of the PWM signal, (2) the LED dynamic range is fully utilized to minimize the nonlinear distortion of the O-OFDM communication signal, and (3) the bit-error performance is sustained over a large fraction of the luminaire dimming range. In addition, RPO-OFDM offers a practical approach to utilize off-the-shelf LED drivers. We show results of numerical simulations to study the trade-offs between the PWM duty cycle, average electrical O-OFDM signal power, radiated optical flux as well as human perceived light.

Analysis of EEG via Multivariate Empirical Mode Decomposition for Depth of Anesthesia Based on Sample Entropy

In monitoring the depth of anesthesia (DOA), the electroencephalography (EEG) signals of patients have been utilized during surgeries to diagnose their level of consciousness. Different entropy methods were applied to analyze the EEG signal and measure its complexity, such as spectral entropy, approximate entropy (ApEn) and sample entropy (SampEn). However, as a weak physiological signal, EEG is easily subject to interference from external sources such as the electric power, electric knives and other electrophysiological signal sources, which lead to a reduction in the accuracy of DOA determination. In this study, we adopt the multivariate empirical mode decomposition (MEMD) to decompose and reconstruct the EEG recorded from clinical surgeries according to its best performance among the empirical mode decomposition (EMD), the ensemble EMD (EEMD), and the complementary EEMD (CEEMD) and the MEMD. Moreover, according to the comparison between SampEn and ApEn in measuring DOA, the SampEn is a practical and efficient method to monitor the DOA during surgeries at real time.

Online Group-Velocity Dispersion Monitor Based on Clock Frequency Power Analysis

In this letter, we demonstrate a cost-effective technique to monitor the group-velocity dispersion (GVD) of an optical fiber link. The described method is based on the measurement of the electrical signal power at clock frequency, and is able to return the magnitude value and sign of the GVD. We demonstrate, through simulation, that this technique enables the measurement of the group-velocity along a fiber link in the range [-625, 625] ps.nm-1 for a 10-Gb-s-1 optical signal.

Research of Harmonics Measurement Aalgorithim Based on HHT

The measurement of power parameters is one of the most basic calculation in power systems, it plays a key role on running power systems in security, economy and reliability. This thesis studys the application of the Hilbert-Huang transform in the field of nonstationary electric power signal in the aspects of amplitude nonstationary, on which the traditional methods work not very well. Much MATLAB simulation shows that HHT is more suitable than DFT to analyze the nonstationary electric power signal. HHT is excellent in the amplitude nonstationary signal analysis. In this thesis, the structure, the function, the communication mode, the application and the trend of development of Power Analyzer are analyzed. Finally, a self-developed chip named Power Analyzer used for measuring of power parameter based on TMS320F2812 processor is designed. The instrument can attain 0.2 grade of RMS, 0.2 grade of power and high-precision measurement of 2 to 31 harmonics. Its real-time performance is very good.

Tunable Er-doped fiber ring laser with single longitudinal mode operation based on Rayleigh backscattering in single mode fiber

A tunable and single longitudinal mode Er-doped fiber ring laser (SLM-EDFRL) is proposed and demonstrated based on Rayleigh backscattering (RBS) in single mode fiber-28e (SMF-28e). Theory and experimental study on formation of SLM from normal multi-mode ring laser is demonstrated. The RBS feedback in 660 m SMF-28e is the key to ensure SLM laser oscillation. This tunable SLM laser can be tuned over 1549.7-1550.18 nm with a linewidth of 2.5-3.0 kHz and a side mode suppression ratio (SMSR) of ~72 dB for electrical signal power. The tuning range is determined by the bandpass filter and gain medium used in the experiment. The laser is able to operate at S+C+L band.

On the Performance of Different OFDM Based Optical Wireless Communication Systems

This paper analyzes the performance of indoor orthogonal frequency division multiplexing (OFDM) optical wireless communication systems in the presence of light emitting diode (LED) nonlinear distortions. There are several forms of optical OFDM using intensity modulation [7th Int. Symp. on Communication Systems Networks and Digital Signal Processing (CSNDSP), 2010, pp. 566-570]. In this paper, DC-biased optical OFDM (DCO-OFDM) and asymmetrically clipped optical OFDM (ACO-OFDM) are considered. ACO-OFDM produces a half-wave symmetry time signal at the output of the OFDM modulator by special assignment of subcarriers, thus allowing signal clipping at the zero level and avoiding the need for DC bias at the expense of data rate reduction. DCO-OFDM assigns data to all possible subcarriers to increase the data rate. However, half-wave symmetry signals cannot be achieved and a high DC bias is needed to convert the bipolar signal to a unipolar signal before modulating the LED intensity. This paper considers a practical LED model and studies the performance of both systems in terms of average electrical OFDM signal power versus bit error ratio in the presence of an additive white Gaussian noise (AWGN) channel. In addition, DC power consumption and the transmitted optical power for the two systems are compared. The analytical results are validated through Monte Carlo simulations and the obtained results demonstrate close match. It is shown that LED clipping has significant impact on the performance of both systems and an optimum system design should take into account the OFDM signal power, DC-bias point, and LED dynamic range.

Micro-PIV (micro particle image velocimetry) visualization of red blood cells (RBCs) sucked by a female mosquito

A mosquito's pump is a highly effective system in the small suction domain. To understand a mosquito's blood suction mechanism, we analysed the characteristics of red blood cells (RBCs) in human blood during and after suction by a female mosquito. Focussing on the flow patterns of the RBCs in human blood being sucked by a mosquito, we visualized blood flow by using a micro-particle image velocimetry (μ-PIV) system, which combines an optical microscope and a PIV method. In an ex vivo experiment, a female mosquito was supplied diluted blood at the tip of the proboscis. We examined the blood flow around the tip of the proboscis and observed that RBCs were periodically sucked towards a hole around the tip. The sucked RBCs then homogeneously flowed parallel to the inner surface of the proboscis without adhering to the wall. Furthermore, using a bioelectric recording system, we directly measured electrical signals generated during suction by the pump muscles located in the mosquito's head. We found that the electrical signal power was synchronized with the acceleration of the RBCs in the sucking phase. A histological stain method was adapted for the observation of the form and internal structure of RBCs in the mosquito. Although the blood flow analysis revealed that the RBCs underwent shear stress during suction, RBCs in the mosquito's stomach maintained their original shape.

Tunable fiber fabry‐perot filter for PM‐IM conversion and efficiency improvement in radio‐over‐fiber links

AbstractA novel method is proposed and demonstrated to simultaneously realize phase‐to‐intensity modulation conversion (PM‐IM) and efficiency improvement using a fiber Fabry‐Perot (FFP) tunable filter. To achieve the conversion of phase modulation to intensity modulation, the phase‐modulated light is transmitted from one of the slopes of the FFP tunable filter to break the amplitude balance of the sidebands. Meanwhile, the modulation depth is increased due to the more suppression of the optical carrier than one of the first‐order sidebands. The results demonstrate that the PM‐IM conversion has been achieved and an about 10‐dB gain of electrical signal power could be obtained with suitable optical carrier suppression for both 10‐and 20‐GHz microwave input. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2090–2095, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25389

A Reduced Prony's Method in Power-Quality Analysis—Parameters Selection

This paper presents a new modification of the least-squares Prony's method for power-quality analysis in terms of estimation of harmonics and interharmonics in an electric power signal. The so-called reduced Prony's method can be competitive, in some specific case, to the Fourier transformation method and the classical LS Prony's method. The modification constitutes in a specific selection of a constant frequency vector in a Fourier-like manner leading to a remarkable reduction of the computational burden and enabling online real-time computations. In addition, a sampling frequency and an analysis window length can be selected to provide the numerical stability of the new algorithm.