Amplitudes Of Harmonic Components Research Articles

An efficient iterative optimization-based algorithm for the real-time estimation of harmonics under power system frequency deviations

In current electrical power industry, a great number of power electronic devices produce harmonics. Moreover, the fundamental system frequency of a power line can deviate in the cases of fluctuating and periodically varying loads and transients. This frequency deviation introduces further undesirable frequency components in the spectrum. Correct measurement of harmonics under such system frequency deviations has prominent importance for the protection of power electronics devices. For this goal, this paper proposes a new iterative optimization-based algorithm for the estimation of harmonics in these circumstances. The method is based on time-domain Gauss-Newton optimization of distorted power line signal which attains its parameters directly from the spectrum of the signal by employing local extrema of the corresponding spectrum. In the first phase of the algorithm, the deviated system frequency is estimated. In the second phase, the harmonic components are estimated and fine-tuned correspondingly. Case studies show that the proposed method is robust and precisely estimates deviations in the system’s fundamental frequency and measure the amplitudes of harmonic components very accurately. It requires just a stoppage criterion. The computational assessment of the method also shows its time efficiency in identifying harmonics. Thus, it is a very good candidate for real-time harmonic measurements.

Filtering properties of Hodgkin–Huxley neuron on different time-scale signals

Neurons can be excited and inhibited by filtered signals. The filtering properties of neural networks have a huge impact on memory, learning, and disease. In this paper, the frequency selection of Hodgkin–Huxley (HH) neuron in response to band-pass filtered signals is investigated. It is found that the neuronal filtering property depends on the locking relationship between the band-pass filtered signal’s center frequency and the neuronal natural frequency. The natural firing frequency is a combination of the fundamental component and the various level harmonic components. The response of the neuron to the band-pass filtered signal is related to the amplitude of the harmonic components. Neuron responds better to the low-frequency filtered signals than the high-frequency filtered signals because of the reduction in the harmonic component amplitude. The filtering ability of the neuron can be modulated by the excitation level, and is stronger around the excitation threshold. Our results might provide novel insights into the filtering properties of neural networks and guide the construction of artificial neural networks.

Using a Low-Cost Components e-Nose for Basic Detection of Different Foodstuffs

A low-cost handheld e-nose unit for assessing composition and quality of food in the field or for automatic discrimination of different foodstuffs would have significant commercial advantages and provide a positive impact on consumer safety and confidence. Whilst many studies have focused on the freshness of specific foodstuffs, the preliminary results presented in this report indicate that a low-cost (circa 30 euro) e-nose, based on MQ series gas sensors, using sinusoidally varying heater voltages, can successfully differentiate between samples of unspoiled lamb, hake, salmon, beef, pork and chicken, even using default, non-optimized control parameters, which could be applied in food adulteration and fraudulent labelling detection or in smart appliances to automatically select cooking parameters. Samples were exposed to the e-nose for five cycles of two minutes each and, by subjecting the response waveforms to Discrete Fourier Transform (DFT) analysis, harmonic component amplitudes were extracted. These data items were then fed into two different Machine Learning supervised classification methods (discriminant analysis and random forest) to determine which foodstuff was present. The relevance of the different DFT harmonic components and MQ sensors in the foodstuffs classification was quantified. Classification accuracies in excess of 95% were demonstrated.

Statistical Models of EAF Harmonics Developed for Harmonic Estimation Directly From Waveform Samples Using Deep Learning Framework

In this research work, a deep learning (DL)-based method for the fast and accurate analysis of current harmonics of electric arc furnaces (EAF) is proposed. For such a system, a large amount of EAF current data is required for the training phase of the DL-based structure, which is not only a thorny but also an expensive procedure. Hence, the second focus of this research work is to gain the ability to generate EAF currents with realistic harmonic contents based on a much smaller amount of field data of EAF currents. For this purpose, EAF current data, recorded at a transformer substation supplying an EAF plant during a tap-to-tap time of the EAF operation, are examined in terms of harmonic component amplitudes and phases. Then, a significantly larger amount of EAF current data is regenerated based on the statistics of current harmonics mimicking the real EAF behavior and this synthetic data are used to train the DL-based harmonic estimator. This estimator is able to estimate both amplitudes and phases of the harmonics without computing any time- or frequency-domain features during the estimation process. Hence, the outcomes of this research work are twofold: First, detailed analysis of the EAF current harmonic behavior is achieved, which reveals the operation principles of the EAF. Second, a DL-based harmonic estimator is trained, which is able to output the amplitude and phase estimations directly out of waveform samples without any feature extraction. The proposed system aims to serve the needs of active power filters of the EAF installations in the electricity system, since it has been shown that fast and accurate harmonic amplitude and phase estimations are obtained.

Detection of Lethal Bronzing Disease in Cabbage Palms (Sabal palmetto) Using a Low-Cost Electronic Nose.

Lethal Bronzing Disease (LB) is a disease of palms caused by the 16SrIV-D phytoplasma. A low-cost electronic nose (eNose) prototype was trialed for its detection. It includes an array of eight Taguchi-type (MQ) sensors (MQ135, MQ2, MQ3, MQ4, MQ5, MQ9, MQ7, and MQ8) controlled by an Arduino NANO® microcontroller, using heater voltages that vary sinusoidally over a 2.5 min cycle. Samples of uninfected, early symptomatic, moderate symptomatic, and late symptomatic infected palm leaves of the cabbage palm were processed and analyzed. MQ sensor responses were subjected to a 256 element discrete Fourier transform (DFT), and harmonic component amplitudes were reviewed by principal component analysis (PCA). The experiment was repeated three times, each showing clear evidence of differences in sensor responses between the samples of uninfected leaves and those in the early stages of infection. Within each experiment, four groups of responses were identified, demonstrating the ability of the unit to repeatedly distinguish healthy leaves from diseased ones; however, detection of the severity of infection has not been demonstrated. By selecting appropriate coefficients (here demonstrated with plots of MQ5 Cos1 vs. MQ8 Sin3), it should be possible to build a ruleset classifier to identify healthy and unhealthy samples.

Experimental Determination of Diagnostic Signs of Damage to the Rotor Windings of High-Voltage Power Plant Motors in Startup Mode

Induction electric motors are widely used as drives of various mechanisms in power engineering and industry. Their failure can lead to costly repairs, to a reduction in power, or, for example, to a complete shutdown of a power plant unit. One of the reasons for the failure of high-voltage induction motors operating under severe starting conditions is damage to the squirrel-cage rotor winding. Existing methods for monitoring the breakage of the winding bars of such electric motors are ineffective due to the peculiarities of their operating modes. Therefore, monitoring the condition of the bars of high-voltage motors at startup and searching for diagnostic signs is an urgent task. Initially, the studies were carried out with a model of a high-voltage induction motor, developed in the ANSYS software package. To confirm the results obtained for a real motor, research has also been conducted on the developed experimental bench. The recorded signals were processed based on the method of short-time Fourier transform in the MatLab environment. In the course of the study, it was shown that, in the presence of bar breaks, the spectrum of an induction motor exhibits sharply increased amplitudes of harmonic components of the dummy rotor winding at the lower side frequencies of the first orders; this confirms the possibility of using external magnetic field signal at startup to detect the presence of bar breaks in the squirrel-cage rotor winding of high-voltage induction motors with heavy prolonged starts.

Tidal current observations through Admiralty Inlet from ferry-mounted current profilers

Admiralty Inlet is a narrow sill located at the northern end of Puget Sound (WA, USA). Circulation through Admiralty Inlet is complex, with tidal currents exceeding 3 $$\hbox {ms}^{-1}$$ , large variations in fresh water input to the system, and seasonal ocean water intrusions. Long-term observations of the currents across the entire inlet are crucial for understanding circulation through Puget Sound. In this context, the Washington State Department of Transportation (WSDOT) Ferries, which run year round through Admiralty Inlet, provide a cost-effective platform to mount instruments and obtain long time series of currents distributed across the inlet. Through the Ferry-Base Monitoring of Puget Sound Currents project, two down-looking acoustic Doppler current profilers (ADCPs) are installed on board two WSDOT ferries, providing depth profiles of velocities across the inlet since May 2014. All data are quality controlled and organized in an horizontal and vertical grid across the inlet. Data within each grid cell are analyzed to capture tidal current harmonic components. Results agree well with data from fixed bottom-mounted ADCPs, and show large spatial variability in the amplitude of harmonic components, probably related to the bathymetric features of the inlet. Further analysis provides estimates of tidal asymmetry and residual currents through the inlet, which are relevant to water quality within the Puget Sound.

Minimum variance based fusion of fundamental and second harmonic ultrasound imaging: Simulation and experimental study

Harmonic imaging is widely used in clinical ultrasound due to its higher resolution in comparison with fundamental mode. However, the low amplitude of harmonic components in this imaging method is a crucial problem, resulting in a high sensitivity to noise, while the fundamental imaging is more robust against noise. To exploit the benefits of both the fundamental and harmonic imaging, we propose a minimum variance (MV)-based adaptive combination of fundamental and harmonic images. The performance of the proposed mixing-together MV (MTMV) beamformer is evaluated on simulated and experimental RF data. The results of the simulated point targets show that in the regions near of point targets, where the desire signals exist, the proposed MTMV beamformer mostly follows the MV-beamformed harmonic image to retain a better resolution. In the regions far from the point targets, where there is just noise, it follows the MV-beamformed fundamental image to benefit from more robustness. Also, the results of the simulated and experimental cyst phantoms indicate that MTMV reduces the background noise level and improves the contrast without compromising the high resolution of the MV-beamformed harmonic image. In the simulated cyst phantom, in comparison to DAS (fundamental), DAS (harmonic), MV (fundamental), MV (harmonic), and wavelet fusion, the image contrast ratio (CR) is increased, in average, about 5.2 dB, 3.5 dB, 1.5 dB, 3.6 dB, and 2.8 dB, respectively. The contrast-to-noise ratio (CNR) is significantly improved; about 59%, 53%, 41%, 37%, and 24%, respectively. In the experimental cyst phantom, these relative improvements are about 6.6 dB, 3.5 dB, 4.2 dB, 2.1 dB, and 3.8 dB for CR, and about 64%, 52%, 25%, 33%, and 33%, for CNR, respectively.

Experimental Simulation on Harmonic Component Analysis of Rectangular Pulse Signal

The pulse signal is not only expressed as superposition of harmonic component, but also can be decomposed to the corresponding harmonic component. In this study, we designed an experimental simulation for make students learn knowledge of the signal process, which as a continuous cycle rectangular pulse signal, the function of relationship on harmonic component amplitude and duty cycle was discussed. Meanwhile, based on the simulation analysis and Fourier analysis, the relationship curve of duty cycle and harmonic component amplitude of rectangular pulse signal was given, and a new technique about changing harmonic amplitude or eliminating some or other harmonic component based on pulse duty cycle was proposed. The parsing circuit model of second-order active band-pass filter, by setting the center frequency of narrow-band band-pass filter circuit, decomposed the harmonic component of rectangular pulse signal under the given duty cycle with the method of simulation experiment. The results also showed that harmonic component amplitude of rectangular pulse signal could be changed in the form of sinusoidal function, by adjusting the duty cycle. When the duty cycle and amplitude of rectangular pulse signal were at the same time, its higher harmonic order component and harmonic amplitude were the same.

Uncertainty analysis of phase and amplitude of harmonic components of bearing inner ring four-point roundness measurement

The four-point roundness measurement method enables the measurement of roundness without a requirement for a precise rotating motion of the workpiece or a measurement sensor. The four-point roundness measurement method can separate the roundness profile and the motion of the rotating axis of the workpiece. In the present study, the uncertainty of the four-point roundness measurement of a bearing inner ring was analysed. The bearing inner ring was installed in its operating position on the shaft of a large rotor during the measurement in order to investigate the bearing inner ring roundness profile in operating conditions. Since the measurement evaluation using the four-point method is complex, the uncertainty analysis was conducted through a Monte-Carlo simulation, using realistic error sources in typical measurement conditions. The uncertainty of both the amplitude and phase of the harmonic components of the roundness profile was analysed for the 2nd till the 30th harmonic component. Attention was directed especially towards the phase of the harmonic components, since the uncertainty of the phase is analysed very little in existing research studies. In addition, the phase of the harmonic components of the roundness profile is important when considering compensative precision grinding applications of round workpieces. The results show that below the 10th harmonic component, the maximum amplitude standard uncertainty was circa 0.5 μm, and the maximum phase standard uncertainty was circa 5°. The standard uncertainties of the amplitudes for the complete harmonic component range were below 1.3 μm for odd components and 0.2 μm for even components. The maximum standard uncertainties of the phases for the complete harmonic component range were circa 15° for odd components and circa 5° for even components. The measured roundness profile itself did not have an effect on the uncertainty of the method.

A Modified Algorithm based on the Equal-Areas PWM for the Extend of Linear Operation of a Microprocessor-Controlled PWM-VSI

A modified algorithm based on the Equal-Areas PWM (EAPWM) is being presented in order to extend the linear operation of the inverter in the overmodulation region, while improving the voltage output in terms of fundamental harmonic component amplitude and Total Harmonic Distortion (THD). EAPWM provides an alternative to Regular Sampling (RS) PWM and Space Vector PWM (SVPWM) strategies. EAPWM is a direct digital PWM method that uses the equal areas theorem to determine the pulse widths. This method maintains the commutations through a complete fundamental cycle, in contrast to naturally and regular sampling PWM techniques, where switched pulses progressively disappear for values of modulation index M greater than unity. In addition, this algorithm reveals several linear operating regions of controlling the output fundamental. Simulation and experimental work carried out using a single-phase voltage source inverter (VSI), showing less harmonic content is present for the first harmonic cluster at the switching frequency, compared to (RS) PWM and Space Vector PWM (SVPWM) strategies. This method is suitable for robotic applications where online control through a microcontroller is needed to drive rotating type loads such us ac motor drives and stepper motors.

Geomagnetic field variations observed by INTERMAGNET during 4 total solar eclipses

We investigate variations of the geomagnetic field observed by INTERMAGNET geomagnetic observatories over which the totality path passed during a total solar eclipse. As a result, we have presented results of examining the geomagnetic field data observed by 6 geomagnetic observatories during the 4 total solar eclipses (11 August 1999, 1 August 2008, 11 July 2010, and 20 March 2015). These total solar eclipses are the only total solar eclipse, since 1991 when the INTERMAGNET began to work, during which the umbra of the Moon swept an INTERMAGNET geomagnetic observatory and simultaneously variations of the geomagnetic field are recorded at the geomagnetic observatory. We have confirmed previous reports that, at least on average, during the solar eclipse characteristic increase of Y component of the geomagnetic field Y and decreases of X,Z and F are conspicuous. Interestingly, we have noted that variations of X,Y,Z and F observed during the total solar eclipse at Isla de Pascua Mataveri (Easter Island) in Chile (IPM) in the southern hemisphere show distinct decrease of Y and increases of X and Z on the contrary. We have found, however, that variations of X,Y,Z and F observed at Hornsund in Norway (HRN) at 77°N in latitude seem to be dominated by other geomagnetic occurrence since the solar activity is near maximum, and the geomagnetic field is disturbed on the day of eclipse. We further discuss a possibility of exploring an effect of the solar eclipse on the amplitude of harmonic components of the geomagnetic field using the wavelet analysis technique, which has revealed suppression in the amplitude during the middle of a solar eclipse. Finally, we conclude by discussing implications of what we have found.

Analysis and modeling of harmonic distortions in consumer’s distribution networks, containing a powerful non-linear load

The paper proposes to simulate a random variability of the nonlinear load in the form of probabilistic characteristics of the amplitudes of harmonic components of powers. The influence of the variability of distribution of amplitude values of the power harmonics on the load flow in the network, power losses and maximum power transmission in lines is studied. The results of design experiments for one of distribution networks of Azerbaijan power system, feeding the non-linear load, are given.

Nutation and geometrical parameters estimation of cone-shaped target based on micro-Doppler effect

The extraction of the nutation and geometrical parameters for cone-shaped target is the critical point for target identification. This paper presents a method to estimate the nutation and geometrical parameters of cone-shaped target based on micro-Doppler effect. The theoretical micro-Doppler effects for conic node and bottom scattering sources of nutation cone-shaped target is analyzed, which is decomposed into high order harmonic components by Bessel function. The angular frequency of coning and nutation is obtained by the spectrum characteristics of scattering sources’ micro-Doppler effects and the conic node and bottom scattering sources are distinguished by spectrum entropy. The harmonic components of conic node scattering source's micro-Doppler frequency are extracted by frequency-domain gate and the distance from cone barycenter to conic node and residual nutation parameters are gained by the harmonic component's amplitude items and initial phase items. The conic bottom radius and distance between the cone barycenter and the conic bottom center are also obtained by conic bottom scattering source's micro-Doppler. The feasibility of the method in this paper is validated by numerical simulation, which may offer some references for the recognition of spatial nutation cone-shaped target.

Комбинированная обмотка «славянка»

The magnetomotive force (MMF) of a usiual symmetrical three-phase winding contains higher harmonic components of the orders v= 6k ±1, k= 1,2,3,... The MMF of the combined winding does not contain harmonic components with the odd numbers k= 2n- 1, n= 1,2,3,..., which make half of the above-mentioned harmonic components. This MMF contains the remaining higher harmonics of the same orders v= 6k ±1, but only with the even numbers k= 2n, n= 1,2,3,.... The amplitudes of these harmonic components are almost identical with the amplitudes of similar harmonic components generated by a conventional winding that produces the combined one. Therefore, the MMF curve of the combined winding is closer to a sinusoidal waveform as compared with the MMF waveform generated by the classic winding. Electrical machines fitted with a combined winding will have a lower level of additional losses in the active materials of rotor and stator. Switched machines fitted with a combined stator winding will produce lower levels of vibration and noise due to more than half as high amplitude of electromagnetic torque pulsations, which also have twice as high frequency.

Application of Monte Carlo simulation for estimation of uncertainty of four-point roundness measurements of rolls

Large-scale rotors in the paper and steel industry are called rolls. Rolls are reground at regular intervals and roundness measurements are made throughout the machining process. Measurement systems for roundness and diameter variation of large rolls (diameter <2000mm) are available on the market, and generally use two to four sensors and a roundness measurement algorithm. These methods are intended to separate roundness of the rotor from its movement. The hybrid four-point method has improved accuracy, even for harmonic component amplitudes. For reliable measurement results, every measurement should be traceable with an estimation of measurement uncertainty. In this paper, the Monte-Carlo method is used for uncertainty evaluation of the harmonic components of the measured roundness profile under typical industrial conditions. According to the evaluation, the standard uncertainties for the harmonic amplitudes with the hybrid method are below 0.5μm for the even harmonics and from 1.5μm to 2.5μm for the odd harmonics, when the standard uncertainty for the four probes is 0.3μm each. The standard uncertainty for roundness deviation is 3.3μm.

Influence of domain structure on the nonlinear polarization properties of A 2 BX 4-group crystals

Harmonic analysis of repolarization in A 2 BX 4-group crystals in the ferroelectric phase near phase-transition temperature T c is used to separate the contributions to the harmonic-component amplitudes in the output signal of a Sawyer-Tower circuit from charging the reference capacitor with capacitive and conductive current through such a crystal. Harmonic analysis of dielectric hysteresis loops obtained by placing a specimen in an electric field with harmonically changing strength reveals general regularities in the evolution of the domain walls of A 2 BX 4-group crystals. It is established that the domain structure affects the nonlinear polarization properties of our specimens. The dependence of the potential relief of ferroelectric ion motion in a harmonically changing electric field is plotted on the basis of the experimental results.

Nonlinear harmonic identification of breathing cracks in beams

The dynamic behavior of structures with breathing cracks forced by harmonic excitation is characterized by the appearance of sub and super-harmonics in the response even in presence of cracks with small depth. Since the amplitude of these harmonics depends on the position and the depth of the crack, it is possible to develop an identification technique once such a dependency is assessed and used in an inverse formulation of the problem. Exploiting this basis idea, an identification method is developed by considering several modes with different modal curvature in view of improving its performance. The method is presented and detailed through the numerical example of a cantilever beam harmonically excited at the free edge; finite elements are used to model the damaged structure and to evaluate the relation between the harmonic component amplitude and damage characteristics. The amount of data to obtain a unique solution and the optimal choice of the observed quantities are discussed. Furthermore, the robustness of the identification, evaluated through a Monte Carlo simulation, is shown to be quite strong to both measuring and modeling errors envisioning the possibility for in-field applications of this method even in the case of very small cracks.

Accurate Single-Phase Fault-Location Method for Transmission Lines Based on K-Nearest Neighbor Algorithm Using One-End Voltage

In this paper, some useful features are extracted from voltage signals measured at one terminal of the transmission line, which are highly efficient for accurate fault locating. These features are the amplitude of harmonic components, which are extracted after fault inception through applying discrete Fourier transform on one cycle of three-phase voltage signals and then are normalized by a transformation. In this paper, the location of single-line-to-ground faults as the most probable type of fault in the transmission networks is considered. The SLG fault locator, which is designed based on the simple algorithm of k-nearest neighbor ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> -NN) in regression mode, estimates the location of fault related to the new input pattern based on existing available patterns. The proposed approach only needs the measured data from one terminal; hence, data communication between both ends of the line and synchronization are not required. In addition, current signals are not used; therefore, the proposed approach is immune against current-transformer saturation and its related errors. Tests conducted on an untransposed transmission line indicate that the proposed fault locator has accurate performance despite simultaneous changes in fault location, fault inception angle, fault resistance, and magnitude and direction of load current.

A Method for Improving Signal-to-Noise Ratio of Tissue Harmonic Imaging Based on Bayesian Inference Using Information of Fundamental Echoes

A medical ultrasound imaging technique with a high spatial resolution and a high signal-to-noise ratio (SNR) is strongly required for precise diagnosis. To obtain high-resolution images, tissue harmonic imaging (THI) can be effectively adopted because of its wide bandwidth characteristics compared with fundamental imaging. However, the amplitude of harmonic components is much smaller than that of a fundamental component. Additionally, frequency dependent attenuation is severe, especially for harmonic components. These phenomena mean that THI is susceptible to noise. From these considerations, in this study, we propose a method for improving the SNR of THI by reducing noise using a signal processing technique. The proposed method is constructed based on the Bayesian inference using fundamental components of echoes, and it can hold the high-resolution nature of THI. We show the effectiveness of the proposed method through simulations.