Journal articles: 'Harmonická'

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Wu, Shan-He, Imran Abbas Baloch, and İmdat İşcan. "On Harmonically(p,h,m)-Preinvex Functions." Journal of Function Spaces 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/2148529.

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We define a new generalized class of harmonically preinvex functions named harmonically(p,h,m)-preinvex functions, which includes harmonic(p,h)-preinvex functions, harmonicp-preinvex functions, harmonich-preinvex functions, andm-convex functions as special cases. We also investigate the properties and characterizations of harmonically(p,h,m)-preinvex functions. Finally, we establish some integral inequalities to show the applications of harmonically(p,h,m)-preinvex functions.

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Zhou, Xue Song, Guang Zhu Chen, and You Jie Ma. "A Survey on Detecting Methods for Harmonic of Power System." Advanced Materials Research 614-615 (December 2012): 907–10. http://dx.doi.org/10.4028/www.scientific.net/amr.614-615.907.

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This paper describes Detecting Methods for Harmonics of power system has been considered one of the serious harms for power system. The research of harmonics has obtained high attention among people. The researches of harmonics detection have many methods, such as Based on Fryze theory of harmonic power detection, Instantaneous reactive power theory detection method, Fourier Transformation harmonic detection method, wavelet transform detection method, neural networks harmonic detection method etc. Aiming at harmonic detection, the different detection methods of power system harmonics are summarized and compared. This paper reviews the existing harmonic detection methods, and discuss their advantages and disadvantages in terms of detection accuracy and response speed, and finally summarizes the development trend of the harmonic detection method.

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Markulin Konfic, Lucija. "Sedmi harmonik u glazbeno-teorijskom sustavu Giuseppea Michelea Stratica." Bosnian / Croatian / Serbian, no. 10 (October 22, 2018): 317–27. http://dx.doi.org/10.51515/issn.2744-1261.2018.10.1.317.

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Problem sedmog harmonika je tema kojoj su u glazbenoj teoriji 18. stoljeća pristupali s posebnim interesom. Dok su ga jedni potpuno ignorirali, drugi odbacivali, neki su autori izrazili stav prema kojem se septima bazirana na tom harmoniku smatra prijelaznim oblikom između konsonanci i disonanci, ili čak konsonancom. Giuseppe Michele Stratico u svom je glazbenom sustavu, razrađenom u više verzija njegovih rukopisnih traktata (sačuvanih u Biblioteci Marciana, Venezia I-Vnm), prihvatio sedmi harmonik kao dio konsonantnog sustava što je dalo osnovu za daljnju razradu sustava temeljenog na odnosima i proporcijama. U ovom radu dati će se pregled Straticovog rada na području glazbene teorije s posebnim osvrtom na problem sedmog harmonika, uspoređujući njegov stav o tom problemu s drugim značajnim teoretičarima 18. stoljeća. U prvom redu s teoretičarima padovanske škole, Giuseppeom Tartinijem, Straticovim učiteljem, te Francescantonijem Vallottijem, zatim matematičarem grofom Giordanom Riccatijem, te jednim od najvećih znanstvenika 18. stoljeća Leonhardom Eulerom.

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Alhaj, Hussam M. M., Nursyarizal Mohd Nor, Vijanth S. Asirvadam, M. F. Abdullah, and T. Ibrahim. "Time Delay Measurement Compensation in Harmonic State Estimation." Applied Mechanics and Materials 699 (November 2014): 745–50. http://dx.doi.org/10.4028/www.scientific.net/amm.699.745.

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The proliferation of power electronics equipments generates harmonics distortion problem. Harmonics have many effects to the power system grid and the main limitation of harmonics is heating of power system devices. To monitor and mitigate the harmonics, the source location and the level of harmonics should be known. However, harmonic measurements are costly and is not practical to put harmonic measurement in each location in the grid. Hence, harmonic state estimation is needed. The most common method in harmonic state estimation is singular value decomposition (SVD). A time delay of the measurements can affect the SVD performance, therfore,this paper presents a prediction method based on ARX model and modified normalized least mean square to compensate the time delay measurements. The result shows better performance of the proposed method as compared to least mean square.

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Zhang, Feng, Jue Long Li, Chong Feng Tian, Zong Jie Liu, Hai Feng Ye, and Xiu Chen Jiang. "Binary Scale Time Windows FFT for Harmonic Analysis." Applied Mechanics and Materials 448-453 (October 2013): 2003–10. http://dx.doi.org/10.4028/www.scientific.net/amm.448-453.2003.

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Various harmonics exist in the electrical power system, and the harmonics include both integer harmonics and non-integer harmonics. It is hard to analyze all the harmonics accurately. In order to improve the precision of harmonic analysis and the minimum resolution, this paper presents a new algorithm named binary scale time windows FFT based on traditional algorithm.This algorithm considers the calculative time and precision well. The results of the test indicate that this algorithm can both guarantee the accuracy and raise the resolving power in the harmonic analysis without increasing the hardware level and the time of calculation obviously. It can restrain the increasingly serious harmonic pollution in power system effectively.

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Wang, Guishuo, Xiaoli Wang, and Chen Zhao. "An Iterative Hybrid Harmonics Detection Method Based on Discrete Wavelet Transform and Bartlett–Hann Window." Applied Sciences 10, no. 11 (June 5, 2020): 3922. http://dx.doi.org/10.3390/app10113922.

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The current signal harmonic detection method(s) cannot reduce the errors in the analysis and extraction of mixed harmonics in the power grid. This paper designs a harmonic detection method based on discrete Fourier transform (DFT) and discrete wavelet transform (DWT) using Bartlett–Hann window function. It improves the detection accuracy of the existing methods in the low frequency steady-state part. In addition, it also separates the steady harmonics from the attenuation harmonics of the high frequency part. Simulation results show that the proposed harmonic detection method improves the detection accuracy of the steady-state part by 1.5175% compared to the existing method. The average value of low frequency steady-state amplitude detection of the proposed method is about 95.3375%. At the same time, the individual harmonic components of the signal are accurately detected and recovered in the high frequency part, and separation of the steady-state harmonics and the attenuated harmonics is achieved. This method is beneficial to improve the ability of harmonic analysis in the power grid.

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Gong, Chen Bin, Qing Hao Wang, Gang Chen, En Lu Wang, Tian Shu Hai, Xin Yu Li, Bo Li, Xue Wang, Chen Yang Liu, and Qi Dong Zhao. "Research on Harm of Harmonics on Electrical Equipment." Advanced Materials Research 986-987 (July 2014): 1846–49. http://dx.doi.org/10.4028/www.scientific.net/amr.986-987.1846.

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Through the analysis of harmonics caused by transformer, capacitor, electromagnetic voltage transformer and other accident, harmonics is an important indicator of power quality, which has been included in the “pollution" of power grid is found. In order to understand the harmonic, this paper from the concept of quality of electric energy, and then gradually extended to the field of harmonics. This paper firstly introduces the various reasons and equipment may produce harmonic, Secondly, illustrate harm of harmonic to operation of transformers, capacitors, electromagnetic voltage transformers and other electrical equipment, let more people know and understand the relevant knowledge of the harmonic, In order to save technical force and provide scientific basis for future effective harmonic.

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Zhao, Yong, Zi Long Yang, Du Feng Cao, Yi Bo Wang, and Hong Hua Xu. "Analysis of PCC Point Harmonics Caused by Nonlinearities of Grid-Tied PV Inverters." Advanced Materials Research 1070-1072 (December 2014): 1246–52. http://dx.doi.org/10.4028/www.scientific.net/amr.1070-1072.1246.

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Renewable energy are usually connected to the power grid through an inverter. As the penetration level of such inverter-based distribution generation resources increases, PCC point harmonics become an important concern for grid stability and power quality. In this paper, the PCC-point harmonics in a parallel-inverter-based photovoltaic station were measured and some significant characteristics of such harmonics were presented. These harmonics are stationary; the voltage and current waveforms are lower frequency, power correlation and inter-harmonic. And these harmonics are 3-phase symmetric and contain 3rd and 6th harmonic components. The transitions of the PCC harmonic occurrence and vanishing are instantaneous. The analysis indicates that the PCC harmonics are not produced by the resonances related to the linearities of PV inverters but the inverter nonlinearities are the primary reasons. The strategy to eliminate the PCC point harmonics are proposed in this study.

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Vijayalakshmi, V. J., C. S. Ravichandran, and A. Amudha. "Predetermination of Higher Order Harmonics by Dual Phase Analysis." Applied Mechanics and Materials 573 (June 2014): 13–18. http://dx.doi.org/10.4028/www.scientific.net/amm.573.13.

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Previous research was mainly concentrated on eliminating the selected lower order harmonics depending on the level of inverter which was assumed to be high. The harmonics may be present even in the higher order also. The analysis of harmonic spectrum by Finite Fourier Transform yields a very accurate result for lower order harmonics. For obtaining accurate Total Harmonic Distortion (THD) value and the harmonic spectrum, inclusion of higher order harmonics is essential. The method for accurate estimation is proposed in this paper. In normal practice, the higher order harmonics present in the output of the inverter are suppressed by using filters. In order to obtain more optimized higher order harmonics, it is necessary to obtain an accurate assessment of the higher order spectrum. The higher order spectrum is predetermined by proposed technique termed as Dual Phase Analysis (DPA) so as to obtain more optimized switching angles with the application of any Optimization Technique. This is an effective tool to analyze the various higher order components of the harmonic spectrum.

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Qin, Xuelong, Guoqiang He, Xuexia Yang, and Steven Gao. "A Compact Rectifier Design Method Utilizing Harmonics." Applied Sciences 11, no. 5 (March 5, 2021): 2295. http://dx.doi.org/10.3390/app11052295.

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This paper proposes a compact rectifier design method for utilizing harmonics. Based on total reflection generated by pure reactance loads at the second harmonic (2nd) and open circuit at the third harmonic (3rd), a compact DC-pass filter is designed to effectively utilize the 2nd and 3rd harmonics excited by the rectifying diode. The amplitudes of the harmonics can be controlled by adjusting the input impedances of the DC-pass filter at harmonics. A prototype operating at 5.8 GHz fundamental frequency is implemented and measured to validate the scenario. When the input power is 18.3 dBm, the measured rectifying efficiency is 71.3%, while the 2nd and the 3rd harmonic amplitudes are −2.4 dBm and 0.1 dBm respectively. This method could also be extended to design a rectifier only utilizing the 2nd or the 3rd harmonic.

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Kuchuk, Kfir, and Uri Sivan. "Accurate, explicit formulae for higher harmonic force spectroscopy by frequency modulation-AFM." Beilstein Journal of Nanotechnology 6 (January 13, 2015): 149–56. http://dx.doi.org/10.3762/bjnano.6.14.

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The nonlinear interaction between an AFM tip and a sample gives rise to oscillations of the cantilever at integral multiples (harmonics) of the fundamental resonance frequency. The higher order harmonics have long been recognized to hold invaluable information on short range interactions but their utilization has thus far been relatively limited due to theoretical and experimental complexities. In particular, existing approximations of the interaction force in terms of higher harmonic amplitudes generally require simultaneous measurements of multiple harmonics to achieve satisfactory accuracy. In the present letter we address the mathematical challenge and derive accurate, explicit formulae for both conservative and dissipative forces in terms of an arbitrary single harmonic. Additionally, we show that in frequency modulation-AFM (FM-AFM) each harmonic carries complete information on the force, obviating the need for multi-harmonic analysis. Finally, we show that higher harmonics may indeed be used to reconstruct short range forces more accurately than the fundamental harmonic when the oscillation amplitude is small compared with the interaction range.

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Vatansever, Fahri, and Nedim Aktan Yalcin. "The Design of Harmonic Simulator based on Hartley Transform." Academic Perspective Procedia 1, no. 1 (November 9, 2018): 21–24. http://dx.doi.org/10.33793/acperpro.01.01.7.

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Increase in the number of nonlinear loads and devices in energy and power systems have raised harmonic distortion on voltage and current signals. Harmonics are one of the primary factors in determining power quality. Therefore, measurement and control of harmonics are crucial. Many methods have developed for harmonic analysis. In this study, a simulator which uses Hartley transform for determining harmonics is designed. Harmonic distributions and parameters of loaded/defined signals can be calculated accurately and effectively and obtained results can be displayed numerically and graphically with developed systems which have user friendly interface.

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Abdullah, Muhammad, Tahir N. Malik, Ali Ahmed, Muhammad F. Nadeem, Irfan A. Khan, and Rui Bo. "A Novel Hybrid GWO-LS Estimator for Harmonic Estimation Problem in Time Varying Noisy Environment." Energies 14, no. 9 (May 1, 2021): 2587. http://dx.doi.org/10.3390/en14092587.

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The power quality of the Electrical Power System (EPS) is greatly affected by electrical harmonics. Hence, accurate and proper estimation of electrical harmonics is essential to design appropriate filters for mitigation of harmonics and their associated effects on the power quality of EPS. This paper presents a novel statistical (Least Square) and meta-heuristic (Grey wolf optimizer) based hybrid technique for accurate detection and estimation of electrical harmonics with minimum computational time. The non-linear part (phase and frequency) of harmonics is estimated using GWO, while the linear part (amplitude) is estimated using the LS method. Furthermore, harmonics having transients are also estimated using proposed harmonic estimators. The effectiveness of the proposed harmonic estimator is evaluated using various case studies. Comparing the proposed approach with other harmonic estimation techniques demonstrates that it has a minimum mean square error with less complexity and better computational efficiency.

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Qiu, Hongbo, Wenfei Yu, Yonghui Li, and Cunxiang Yang. "Research on the influence of driving harmonic on electromagnetic field and temperature field of permanent magnet synchronous motor." Archives of Electrical Engineering 66, no. 2 (June 27, 2017): 295–312. http://dx.doi.org/10.1515/aee-2017-0022.

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AbstractAt present, the drivers with different control methods are used in most of permanent magnet synchronous motors (PMSM). A current outputted by a driver contains a large number of harmonics that will cause the PMSM torque ripple, winding heating and rotor temperature rise too large and so on. In this paper, in order to determine the influence of the current harmonics on the motor performance, different harmonic currents were injected into the motor armature. Firstly, in order to study the influence of the current harmonic on the motor magnetic field, a novel decoupling method of the motor magnetic field was proposed. On this basis, the difference of harmonic content in an air gap magnetic field was studied, and the influence of a harmonic current on the air gap flux density was obtained. Secondly, by comparing the fluctuation of the motor torque in the fundamental and different harmonic currents, the influence of harmonic on a motor torque ripple was determined. Then, the influence of different current harmonics on the eddy current loss of the motor was compared and analyzed, and the influence of the drive harmonic on the eddy current loss was obtained. Finally, by using a finite element method (FEM), the motor temperature distribution with different harmonics was obtained.

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Ji, Yanpeng, Bin Li, and Jingcheng Sun. "Harmonic Analysis on Torque Ripple of Brushless DC Motor Based on Advanced Commutation Control." Journal of Control Science and Engineering 2018 (2018): 1–9. http://dx.doi.org/10.1155/2018/3530127.

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This paper investigates the relationship between current, back electromotive force (back-EMF), and torque for permanent-magnet brushless DC (PM BLDC) motors under advanced commutation control from the perspective of harmonics. Considering that the phase current is the influencing factor of both torque and torque ripple, this paper firstly analyzes the effects of advanced commutation on phase current and current harmonics. And then, based on the harmonics of the phase current and back-EMF, the torque harmonic expressions are deduced. The expressions reveal the relationship of harmonic order between the torque, phase current, and back-EMF and highlight the different contribution of individual torque harmonic to the total torque ripple. Finally, the proposed harmonic analysis method is verified by the experiments with different speed and load conditions.

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Santos, Sergio, Victor Barcons, Josep Font, and Albert Verdaguer. "Unlocking higher harmonics in atomic force microscopy with gentle interactions." Beilstein Journal of Nanotechnology 5 (March 11, 2014): 268–77. http://dx.doi.org/10.3762/bjnano.5.29.

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In dynamic atomic force microscopy, nanoscale properties are encoded in the higher harmonics. Nevertheless, when gentle interactions and minimal invasiveness are required, these harmonics are typically undetectable. Here, we propose to externally drive an arbitrary number of exact higher harmonics above the noise level. In this way, multiple contrast channels that are sensitive to compositional variations are made accessible. Numerical integration of the equation of motion shows that the external introduction of exact harmonic frequencies does not compromise the fundamental frequency. Thermal fluctuations are also considered within the detection bandwidth of interest and discussed in terms of higher-harmonic phase contrast in the presence and absence of an external excitation of higher harmonics. Higher harmonic phase shifts further provide the means to directly decouple the true topography from that induced by compositional heterogeneity.

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Rao, K. Venkateswara, and G. Joga Rao. "THD Minimization in Cascaded H-Bridge Inverter using Optimal Selective Harmonic Elimination." International Journal of Recent Technology and Engineering (IJRTE) 10, no. 2 (July 30, 2021): 170–74. http://dx.doi.org/10.35940/ijrte.b5984.0710221.

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Cascaded structured multilevel inverters are gaining lot of importance due to their simple structure and easiness in implementation. In this paper, the optimum selective harmonic elimination method is employed for a nine level inverter to suppress the selected lower order harmonic, which reduces the total harmonic distortion of the inverter considerably. The Newton rapson algorithm is employed in finding the switching angles that minimizes certain lower order harmonics. The order of the harmonics that are eliminated are third, fifth, and seventh harmonics. All the simulation results included for a nine level inverter using SIMULINK. Index Terms: Nine level MLI, Control of inverter, Modular Inverter.

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Zhao, Jinshuai, Honggeng Yang, Xiaoyang Ma, and Fangwei Xu. "Evaluation of Harmonic Contributions for Multi Harmonic Sources System Based on Mixed Entropy Screening and an Improved Independent Component Analysis Method." Entropy 22, no. 3 (March 12, 2020): 323. http://dx.doi.org/10.3390/e22030323.

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Evaluating the harmonic contributions of each nonlinear customer is important for harmonic mitigation in a power system with diverse and complex harmonic sources. The existing evaluation methods have two shortcomings: (1) the calculation accuracy is easily affected by background harmonics fluctuation; and (2) they rely on Global Positioning System (GPS) measurements, which is not economic when widely applied. In this paper, based on the properties of asynchronous measurements, we propose a model for evaluating harmonic contributions without GPS technology. In addition, based on the Gaussianity of the measured harmonic data, a mixed entropy screening mechanism is proposed to assess the fluctuation degree of the background harmonics for each data segment. Only the segments with relatively stable background harmonics are chosen for calculation, which reduces the impacts of the background harmonics in a certain degree. Additionally, complex independent component analysis, as a potential method to this field, is improved in this paper. During the calculation process, the sparseness of the mixed matrix in this method is used to reduce the optimization dimension and enhance the evaluation accuracy. The validity and the effectiveness of the proposed methods are verified through simulations and field case studies.

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Emagbetere, J. O., and P. A. Kuale. "Investigation of Harmonics in Power Generating Systems." Advanced Materials Research 18-19 (June 2007): 99–106. http://dx.doi.org/10.4028/www.scientific.net/amr.18-19.99.

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This paper investigates harmonics in power systems especially harmonics produced by synchronous generators as well as those by distributed generation systems, particularly these days when private generating systems are on the increase in Nigeria. For the work done so far, we found that some generators have near square waves, and these are characterized by their odd harmonics. An investigation of the harmonic emf waves conducted shows that these generators produces harmonic alternating mmf’s and fluxes. All harmonic fluxes produce emfs which are undesirable. The effect of these harmonics results in additional losses, vibration and noise, interferences, and very often stall motors. However the useful torque of a machine is usually produced by the fundamental flux wave which is a pure sine wave. The work is on-going. The waveforms are being analyzed so as to determine the full spectrum of the harmonics present in each case and subsequently investigate their effects in telecommunication systems including the present day GSM.

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Oğuz, Yüksel, Mustafa Şahin, Yılmaz Güven, and Hatice Zeliha Tuğcu. "Analysing of Harmonics Affecting the Energy Quality in Opium Alkaloids Plant's Power System." International Journal of Energy Optimization and Engineering 5, no. 4 (October 2016): 26–47. http://dx.doi.org/10.4018/ijeoe.2016100102.

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The quality of energy has been defined to control harmonics caused by non-linear loads and international standards were brought to overcome the harmonic related problems. In determining the power quality, parameters like current-voltage harmonic, transient, flicker, current and voltage imbalance between phases, K factor are examined according to these international standards. The biggest disadvantage of harmonics is that they do not affect the power quality over an individual network but also affect the entire energy system primarily neighbouring facilities. Therefore, the energy system of Opium Alkaloids Plant was examined by using measurements information of current and voltage harmonics affecting the energy quality. And, it has been determined that the harmonics have a negative impact on energy quality. According to these findings, it has been proposed to install a well-designed filter for elimination of harmonics. Besides, it has been emphasised that new hardwares and devices should be chosen to support this harmonic filtering system in the future.

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Li, Weibin, Mingxi Deng, and Younho Cho. "Cumulative Second Harmonic Generation of Ultrasonic Guided Waves Propagation in Tube-Like Structure." Journal of Computational Acoustics 24, no. 03 (August 30, 2016): 1650011. http://dx.doi.org/10.1142/s0218396x16500119.

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Second harmonic generation of ultrasonic waves propagating in unbounded media and plate-like structure has been vigorously studied for tracking material nonlinearity, however, second harmonic guided wave propagation in tube-like structures is rarely studied. Considering that second harmonics can provide sensitive information for structural health condition, this paper aims to study the second harmonic generation of guided waves in metallic tube-like structures with weakly nonlinearity. Perturbation method and modal analysis approach are used to analyze the acoustic field of second harmonic solutions. The conditions for generating second harmonics with cumulative effect are provided in present investigation. Flexible polyvinylidene fluoride comb transducers are used to measure fundamental wave modes and second harmonic ones. The work experimentally verifies that the second harmonics of guided waves in pipe have a cumulative effect with propagation distance. The proposed procedure of this work can be applied to detect material nonlinearity due to damage mechanism in tube-like structure.

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Xu, Yuan. "Harmonic Polynomials Associated With Reflection Groups." Canadian Mathematical Bulletin 43, no. 4 (December 1, 2000): 496–507. http://dx.doi.org/10.4153/cmb-2000-057-2.

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AbstractWe extend Maxwell’s representation of harmonic polynomials to h-harmonics associated to a reflection invariant weight function hk. Let 𝑫i, 1 ≤ i ≤ d, be Dunkl’s operators associated with a reflection group. For any homogeneous polynomial P of degree n,we prove the polynomial is a h-harmonic polynomial of degree n, where γ = ∑ki and 𝑫 = (𝑫1, … ,𝑫d). The construction yields a basis for h-harmonics. We also discuss self-adjoint operators acting on the space of h-harmonics.

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Gouda, O. E., G. M. Amer, and W. A. A. Salem. "A Study of K- Factor Power Transformer Characteristics by Modeling Simulation." Engineering, Technology & Applied Science Research 1, no. 5 (October 17, 2011): 114–20. http://dx.doi.org/10.48084/etasr.59.

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Harmonic currents generated by nonlinear loads can cause overheating and premature failure in power transformers. K-factor transformers are specially designed to accommodate harmonic currents and offer protection against overheating caused by harmonics. They minimize harmonic current loss and have an additional thermal capacity of known limits. According to IEEE C57-110, the winding eddy current losses are considered proportional to the harmonic current squared times its harmonic number. K-factor is only an indicative value and the authors' main objective in this paper is to study the effect of harmonics on oil filled transformer and to simulate harmonic behavior using Matlab Simulink. A case study is simulated in order to investigate K-factor values with pumping loads, with and without the use of harmonic filters. Results are compared with measured values.

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Snape-Jenkinson, C. J., S. Crozier, and L. K. Forbes. "NMR shim coil design utilising a rapid spherical harmonic calculation method." ANZIAM Journal 43, no. 3 (January 2002): 375–86. http://dx.doi.org/10.1017/s1446181100012578.

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AbstractA rapid spherical harmonic calculation method is used for the design of Nuclear Magnetic Resonance shim coils. The aim is to design each shim such that it generates a field described purely by a single spherical harmonic. By applying simulated annealing techniques, coil arrangements are produced through the optimal positioning of current-carrying circular arc conductors of rectangular cross-section. This involves minimizing the undesirable harmonics in relation to a target harmonic. The design method is flexible enough to be applied for the production of coil arrangements that generate fields consisting significantly of either zonal or tesseral harmonics. Results are presented for several coil designs which generate tesseral harmonics of degree one.

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Nisja, Indra, A. Z. Abdullah, S. Masri, and S. Hardi. "Laboratory Test of Current Transformer Operates under Harmonic Conditions." Applied Mechanics and Materials 793 (September 2015): 222–25. http://dx.doi.org/10.4028/www.scientific.net/amm.793.222.

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This research focused on the effect of harmonic to the performance of current transformer (CT) operates under harmonic conditions. Due to the increasing of harmonic in power system, the CT did not perform well. The CT may saturates due to the presence of voltage and current harmonics. In this project, a laboratory test was conducted to investigate and analyze the influence of harmonics to the CT performance. This CT has been test with different Total Harmonic Distortion Current (THDi) at primary side and constant primary current. The experiment result shows the secondary current CT errors will increases when THDi increases.

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Zhang, Hong Juan, and Yong Xing Hou. "The Study on Harmonic Characteristics of Three-Phase SPWM Inverter." Applied Mechanics and Materials 117-119 (October 2011): 1779–83. http://dx.doi.org/10.4028/www.scientific.net/amm.117-119.1779.

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Through using dual Fourier transform quantitative analysis and harmonic loss calculation on the output voltage of three phase voltage-Sinusoidal Pulse Width Modulation (SPWM) inverter, a valid harmonic inhibition scheme is presented. Carrier frequency is reasonably selected to eliminate low times harmonics, harmonics of carrier frequency times and triple frequency sideband. Analysis of fast Fourier transform is achieved in MATLAB. Simulation results show that harmonics are effectively inhibited, output voltage waveform is improved and voltage distortion factor is decreased from1.16% to 0.71%.

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Sayrac, Muhammed. "Generation of Coherent Extreme Ultraviolet Radiation in an Air Gas Cell with a High Power Femtosecond Laser System-=SUP=-*-=/SUP=-." Оптика и спектроскопия 129, no. 6 (2021): 764. http://dx.doi.org/10.21883/os.2021.06.50989.1041-20.

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High harmonic generation (HHG) in air medium is experimentally produced by using a state-of-the-art high power laser system. The harmonic orders up to 35th harmonics are well observed. Optical power dependence of harmonic spectrum is obtained. The dynamics of a free electron in an intense laser field presents good agreement with the experimental results. The air medium is used as an interaction medium since air is a ready source in abundance. The harmonic spectral distribution is similar to that obtained in noble gases. Experimental results of harmonics produced in air medium follow the same trends in terms of plateau region and cutoff harmonic order, which extends and enhances with increasing laser field.

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Ozaki, T., L. Elouga Bom, and R. A. Ganeev. "Extending the capabilities of ablation harmonics to shorter wavelengths and higher intensity." Laser and Particle Beams 26, no. 2 (June 2008): 235–40. http://dx.doi.org/10.1017/s026303460800027x.

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AbstractWe study the generation of high-order harmonics from plasma plume, by using the 20 TW, 10 Hz laser of the Advanced Laser Light Source (ALLS). We perform detailed studies on enhancement of single high-order harmonics generated in laser plasma using the fundamental and second harmonic of the ALLS beam line. Quasi-monochromatic harmonics are observed for Mn, Cr, Sb, Sn, and In plasmas. We identify most of the ionic/neutral transitions responsible for the enhancement, which all have strong oscillator strengths. Intensity enhancements of the 13th, 17th, 21st, 29th, and 33rd harmonics from these targets are demonstrated using the 800 nm pump laser and varying its chirp. We also observed harmonic enhancement from some targets for 400 nm pump laser. Using Mn plume, we demonstrated the highest harmonic photon energy (52.9 eV) at which enhancement has been observed (17th order, λ = 23.5 nm).

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Liu, Hang, and Liqiang Feng. "Electron-Nuclear Dynamics on Amplitude and Frequency Modulation of Molecular High-Order Harmonic Generation from H2+ and its Isotopes." Zeitschrift für Naturforschung A 72, no. 10 (September 26, 2017): 941–53. http://dx.doi.org/10.1515/zna-2017-0237.

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AbstractElectron-nuclear dynamics of molecular high-order harmonic generation from H2+ and its isotopes has been theoretically investigated beyond the Born-Oppenheimer approximations. The results show that (i) due to the different ionisation probabilities and the harmonic emission times, the intensities of the harmonics from H2+ and its isotopes are very sensitive to the initial vibrational state, the pulse duration, and the pulse intensity. (ii) Due to the nonadiabatic effects in molecular high-order harmonic generation, the red-shifts of the harmonics can be found in the lower pulse intensity. With the increase of the pulse intensity, the harmonics are from the red-shifts to the blue-shifts. Moreover, as the pulse duration increases, the blue-shifts of the harmonics can be enhanced. As the initial vibrational state increases, the red-shifts of the harmonics can be decreased, whereas the blue-shifts of the harmonics can be enhanced. However, the shifts of the harmonics are decreased as the nuclear mass increases. (iii) Due to the coupled electron-nuclear dynamics in molecules, the spatial symmetry of the system is broken. As a result, non-odd harmonics can be generated at the larger internuclear distance. With the increase of the initial vibrational state or the nuclear mass, the generation of the non-odd harmonics can be enhanced and reduced, respectively. As the pulse duration or the pulse intensity increase, the generation of the non-odd harmonics can be enhanced. However, the intensities of the non-odd harmonics are decreased when using the longer pulse duration with the much higher laser intensity.

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Mu, Siyuan, Jinsong Kang, Shuo Wang, Yusong Liu, and Cuiwei He. "A method of thrust ripple suppression for long stator linear synchronous motor." Transportation Systems and Technology 4, no. 2 (September 13, 2018): 30–44. http://dx.doi.org/10.17816/transsyst20184230-44.

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With the advantages of high speed, low noise and high efficiency, the electromagnetic suspension (EMS) type maglev train has a good prospect in railway transportation. It is based on the long stator linear synchronous motor (LSLSM). However, due to cogging effect, end effect and the harmonics in the stator current and flux density distribution around the air-gap, the thrust generated by the LSLSM fluctuates. The thrust ripple brings noise, drop of control accuracy, even causes the resonance of train. In this paper, the thrust ripple produced by the cogging effect and flux linkage harmonics is analyzed. Then a method of harmonic current injection is proposed to compensate cogging force and reduce the thrust ripple, without influence the decoupling control of traction and suspension system. The injected current harmonics are controlled under multiple rotating reference frames independently. Finally, based on voltage equations of harmonics, the decoupled harmonic current controllers with harmonic voltage feedforward are designed, which improve the performance of current harmonics response and thrust ripple suppression. Simulation results on Simulink verify the effectiveness of proposed thrust ripple suppression method for LSLSM.

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Kandil, Shaimaa A., A. A. Ali, Adel El Samahy, Sherif M. Wasfi, and O. P. Malik. "Harmonic Optimization in Voltage Source Inverter for PV Application using Heuristic Algorithms." International Journal of Emerging Electric Power Systems 17, no. 6 (December 1, 2016): 671–82. http://dx.doi.org/10.1515/ijeeps-2016-0052.

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Abstract Selective Harmonic Elimination (SHE) technique is the fundamental switching frequency scheme that is used to eliminate specific order harmonics. Its application to minimize low order harmonics in a three level inverter is proposed in this paper. The modulation strategy used here is SHEPWM and the nonlinear equations, that characterize the low order harmonics, are solved using Harmony Search Algorithm (HSA) to obtain the optimal switching angles that minimize the required harmonics and maintain the fundamental at the desired value. Total Harmonic Distortion (THD) of the output voltage is minimized maintaining selected harmonics within allowable limits. A comparison has been drawn between HSA, Genetic Algorithm (GA) and Newton Raphson (NR) technique using MATLAB software to determine the effectiveness of getting optimized switching angles.

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Junesco, Devan, Shahad Al-Youif, Mohannad Jabbar Mnati, and Mohammad Ali Tofigh. "Various Passive Filter Designs Proposed for Harmonic Extenuation in Industrial Distribution Systems." International Journal of Engineering & Technology 7, no. 4.11 (October 2, 2018): 75. http://dx.doi.org/10.14419/ijet.v7i4.11.20691.

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This paper discusses various passive filter designs to reduce the harmonic in the industrial distributions system. The passive filter used is a single and double tuned harmonic filter. In the designing of this filter, analyzing filter properties of passive component of the filter. The study was conducted to examine the efficacy of using single and double tuned filters in reducing harmonic as well as determining the best location to install the filters. Different system effects and load limits on harmonic distortion and performance of filters are also being examined. The output of the simulation indicated that a superior performance in extenuating harmonics by the double tuned filter is more effective in reducing harmonics when it is placed near the harmonic generating loads.

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Mohan, V., N. Stalin, and S. Jeevananthan. "A Tactical Chaos based PWM Technique for Distortion Restraint and Power Spectrum Shaping in Induction Motor Drives." International Journal of Power Electronics and Drive Systems (IJPEDS) 5, no. 3 (February 1, 2015): 383. http://dx.doi.org/10.11591/ijpeds.v5.i3.pp383-392.

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The pulse width modulated voltage source inverters (PWM-VSI) dominate in the modern industrial environment. The conventional PWM methods are designed to have higher fundamental voltage, easy filtering and reduced total harmonic distortion (THD). There are number of clustered harmonics around the multiples of switching frequency in the output of conventional sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM) inverters. This is due to their fixed switching frequency while the variable switching frequency makes the filtering very complex. Random carrier PWM (RCPWM) methods are the host of PWM methods, which use randomized carrier frequency and result in a harmonic profile with well distributed harmonic power (no harmonic possesses significant magnitude and hence no filtering is required). This paper proposes a chaos-based PWM (CPWM) strategy, which utilizes a chaotically changing switching frequency to spread the harmonics continuously to a wideband and to reduce the peak harmonics to a great extent. This can be an effective way to suppress the current harmonics and torque ripple in induction motor drives. The proposed CPWM scheme is simulated using MATLAB / SIMULINK software and implemented in three phase voltage source inverter (VSI) using field programmable gate array (FPGA).

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Liu, Yun Yun, Jiang Zeng, and Kai Liang Wang. "A Harmonic Detecting Scheme Based on BP Neural Network." Applied Mechanics and Materials 392 (September 2013): 759–64. http://dx.doi.org/10.4028/www.scientific.net/amm.392.759.

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General harmonic detecting scheme is using the Fast Fourier Transform (FFT) for detection of all the harmonics (such as 1 to 50 times). While power units often do not care about the specific values of all the harmonics, but is only concerned with some key harmonics or several overall indicators. For the above reason, a new harmonic detecting scheme based on the algorithm of BP neural network is presented in this paper. It does not need to calculate all the harmonics, when the detection of individual indicators or overall indicators which are concerned by users can be achieved,and to achieve the above-mentioned detection target, by the analysis of computation of BP, DFT and FFT algorithm, the superiority of the scheme in terms of computation is proved. After the simulation of the scheme using a set of measured harmonic data, the results validate that the above scheme is simple and feasible, and its detecting accuracy is close to which of FFT.

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Huang, Tian Hao, and Kuo Lung Lian. "Harmonic Modeling of a Diode-Clamped Multilevel Voltage Source Converter for Predicting Uncharacteristic Harmonics." Mathematical Problems in Engineering 2018 (December 5, 2018): 1–16. http://dx.doi.org/10.1155/2018/3250761.

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In response to the growing demand for medium- and high-power trends, multilevel voltage source converters (VSCs) have been attracting growing considerations. One of the widely used VSCs are the diode-clamped multilevel VSC (DCM-VSC). As these converters proliferate, their harmonic impact may become significant. Nevertheless, a harmonic model for the DCM-VSC is currently lacking in the literature. In this paper, the ABCD matrix, mapping the input harmonics to the output harmonics of DCM-VSC, is derived. As the matrix is formulated in the time-domain, the output harmonics are exact and do not suffer from harmonic truncation errors. As the paper will demonstrate, the derived ABCD matrix can be easily applied to a microgrid system and users can easily predict all the uncharacteristic harmonics when a microgrid is subjected to various conditions of imbalance. In addition to all the results being validated with those of PSCAD/EMTDC, the computation time of the proposed method is in contrast much shorter.

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Cheng, Gui Lin, and Jian Lin. "An Approach for Electrical Inter-Harmonic Analysis Based on W-H Transform." Advanced Materials Research 383-390 (November 2011): 2649–53. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.2649.

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With the non-linear load being used in great quantities, a large number of harmonics and inter-harmonics exist in electrical system. However, lacking of local information, traditional Fourier transform is not suitable for inter-harmonic analysis. In the method of time-frequency analysis, WVD is a joint distribution of energy time-frequency which provides a method for inter-harmonic analysis, but the influence of the cross terms limits application. W-H transform can effectively reduce the impact of cross terms and then extract effective information of inter-harmonic.

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Su, Yu Xiang, Guo Ping Liu, Lin Li, and Xiao Qun Shen. "Improved Hilbert-Huang Transform Applied in Power Quality Detection in Ship Power System." Applied Mechanics and Materials 88-89 (August 2011): 365–72. http://dx.doi.org/10.4028/www.scientific.net/amm.88-89.365.

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In this paper, Hilbert-Huang Transform (HHT) and its improved method is introduced for detection and analysis of power quality in ship power system for the first time. This method is applied in detecting surge current and voltage interruption etc. of the ship power grid. Beginning-ending time, time-frequency, time-amplitude of the disturbance signal can be obtained accurately with HHT method. Mode mixing occurs when using empirical mode decomposition (EMD) to analyze harmonics, and consequently, all single harmonic components cannot be effectively decomposed. The improved HHT method based on Fourier transform is used to solve the problem in this paper. Complicated Harmonic can be decomposed into single harmonic component, and time-amplitude and time -frequency of harmonics can be obtained accurately by the improved method. In MATLAB/Simulink platform, harmonic source model of ship power system is established. Simulation results show that the improved method has better performance in Harmonics analysis than wavelet packet analysis.

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Liu, Liyan, Carlos Lozano, and Dan Iredell. "Time–Space SST Variability in the Atlantic during 2013: Seasonal Cycle." Journal of Atmospheric and Oceanic Technology 32, no. 9 (September 2015): 1689–705. http://dx.doi.org/10.1175/jtech-d-15-0028.1.

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AbstractA 2-yr-long daily gridded field of sea surface temperature (SST) in the Atlantic centered for the year 2013 is projected onto orthogonal components: its mean, six harmonics of the year cycle, the slow-varying contribution, and the fast-varying contribution. The periodic function defined by the year harmonics, referred to here as the seasonal harmonic, contains most of the year variability in 2013. The seasonal harmonic is examined in its spatial and temporal distribution by describing the amplitude and phase of its maxima and minima, and other associated parameters. In the seasonal harmonic, the ratio of the duration of warming period to cooling period ranges from 0.2 to 2.0. There are also differences in the spatial patterns and dominance of the year harmonics—in general associated with regions with different insolation, oceanic, and atmospheric regimes. Empirical orthogonal functions (EOFs) of the seasonal harmonic allow for a succinct description of the seasonal evolution for the Atlantic and its subdomains. The decomposition can be applied to model output, allowing for a more incisive model validation and data assimilation. The decorrelation time scale of the rapidly varying signal is found to be nearly independent of the time of the year once four or more harmonics are used. The decomposition algorithm, here implemented for a single year cycle, can be applied to obtain a multiyear average of the seasonal harmonic.

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Wang, Yifan, and Guozhu Chen. "A multi-valve controlled saturable reactor and its harmonic optimization." COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 33, no. 4 (July 1, 2014): 1346–65. http://dx.doi.org/10.1108/compel-04-2013-0136.

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Purpose – As arc suppression coils (ASCs), magnetically controlled reactors (MCRs) are usually operated in the single-phase mode. Due to the lack of a third order harmonic compensation circuit, the current harmonics are high. The purpose of this paper is to propose a novel structure of MCR and a genetic algorithm (GA) to determine the parameters which will result in minimum total harmonics. Design/methodology/approach – This paper proposes the structure and the working principle of the multi-valve controlled saturable reactor (MCSR). There are several sorts of magnetic valves in the iron cores of the MCSR. The saturation degree of each magnetic valve is different when the same direct component of the magnetic flux is generated in the iron core, therefore current harmonics of different phases emerging, i.e. the total harmonics can be reduced. The magnetization characteristics and the mathematical model of the current harmonics of the MCSR are presented by introducing three parameters. The optimal values of the parameters that result in the smallest total harmonic distortion in the output current are calculated by a GA. Findings – The simulation and experimental results are coincident with the theoretical analyses, which prove the effectiveness of the proposed method on harmonic suppression. Practical implications – The method proposed in this paper can successfully reduce the current harmonics of the conventional MCR, including but not limited to the ASC. A prototype MCSR (540 kVA/10 kV) has been designed and constructed. Originality/value – In this paper, a MCSR is proposed. The mathematical model of the MCSR for harmonic analysis is developed. The optimal parameters that result in the smallest THD in the output current are calculated. The mathematical model can be also used for the harmonic analysis of conventional MCRs.

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Ozaki, T., L. B. Elouga Bom, J. Abdul-Hadi, and R. A. Ganeev. "Evidence of strong contribution from neutral atoms in intense harmonic generation from nanoparticles." Laser and Particle Beams 28, no. 1 (March 2010): 69–74. http://dx.doi.org/10.1017/s0263034609990589.

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AbstractWe show experimental evidence that, for the intense high-order harmonics from nanoparticles, there is a strong contribution from neutral atoms. We present the results of studies on the harmonics generated in laser-produced plasmas containing various nanoparticles, including Cr2O3, In2O3, Ag, MnTiO3, Sn, Cu, and Au. These results are compared with the harmonics generated from plasma produced on the surface of bulk targets. The harmonic spectrum from nanoparticle and bulk In2O3 show that there is a lack in the resonant enhancement of the 13th harmonic for the former. Along with the relatively low cut-off for nanoparticle harmonics, these results show that it is the neutral atom in the nanoparticle that emits the intense harmonics. Structural studies of plasma debris confirm the presence and integrity of nanoparticles in the plasma plumes.

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Yun, Yu Xin, Min Liu, and Hai Yan Yuan. "Harmonic Analysis of Yindong ±660kV HVDC Transmission System." Applied Mechanics and Materials 448-453 (October 2013): 2049–53. http://dx.doi.org/10.4028/www.scientific.net/amm.448-453.2049.

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Based on PSCAD/EMTDC simulation platform, this paper analyses the harmonics caused by the process of rectifier and inverter and DC bias of transformer in Yindong ±660kV HVDC transmission system. The results indicate that, characteristic harmonics of 660kV HVDC system AC bus give priority to 12k±1 time harmonics and bring serious influence to the AC system of the rectifier and converter station; the characteristic harmonics of DC lines are mainly about 12k time and the voltage ripple factor is in the specified scope; both the odd and even harmonic components are increasing significantly under DC bias than that without DC bias,which thereby makes the power transformers become the severe harmonic sources.

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Ting, Chao-Lung, and Ming-Chung Lin. "Generation of Harmonics by Non-Breaking Water Waves Over Permeable Submerged Breakwaters." Journal of Mechanics 20, no. 1 (March 2004): 57–67. http://dx.doi.org/10.1017/s1727719100004044.

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ABSTRACTThis work examines the interesting phenomenon of the generation of harmonics by non-breaking waves over permeable submerged obstacles. Nine model geometries, each with six different porosities, from 0.421 to 0.912, were considered to examine the effects of model width, porosity, and submergence depth on harmonic generation. The results revealed coupled effects on harmonic generation. A modified Ursell number was proposed to analyze experimental data. Almost no harmonic generation occurs at a modified Ursell number of less than five and/or a model width to wavelength ratio of over 1.6. After harmonics have been generated, wave profiles become dimpled, and the energy of the fundamental mode is transferred to higher-frequency components. Furthermore, the higher harmonics become more pronounced as the models widen, the depth of submergence becomes shallower, and model porosity declines.

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de Oliveira, Janaína Goncalves, Juan de Santiago, and Pedro Machado de Almeida. "Harmonic Mitigation in a Coreless Double-Wound Flywheel Machine: Experimental Verification." International Journal of Emerging Electric Power Systems 16, no. 3 (June 1, 2015): 243–51. http://dx.doi.org/10.1515/ijeeps-2014-0141.

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Abstract This paper aims at analyzing harmonics and interharmonics present in a flywheel-based driveline developed at Uppsala University. The flywheel machine is a permanent magnet synchronous machine with two sets of windings in the stator, with a Wye–Wye connection as standard. Different sources of harmonic distortion have been evaluated. Flywheel machine simulations are performed in finite element method (FEM) (Comsol) and experimental verifications are presented. Several methods for harmonic mitigation have been evaluated. The driveline suffers almost exclusively from second-order harmonics but the THD (total harmonic distortion) seldom exceeds 5%. Very little interharmonics are present. A Delta–Wye connection of the flywheel eliminates most of the harmonics but at the expense of a high-phase current through the Delta connection. Grounding the neutral conductor in Wye connections increases the distortion.

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Zhong, Qing, Junjie Feng, Gang Wang, and Haifeng Li. "Feedforward Harmonic Mitigation Strategy for Single-Phase Voltage Source Converter." Journal of Electrical and Computer Engineering 2018 (2018): 1–10. http://dx.doi.org/10.1155/2018/5909346.

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With the development of distributed generations (DGs), single-phase voltage source converter (SPVSC) has been widely used, but it brings about the problem of harmonic pollution to power grid. Hence, it is significant to explore the mechanism of harmonic injection from SPVSC and propose effective control strategies to mitigate the harmonic pollution. In this paper, a harmonic analysis model of SPVSC based on dynamic phasor (DP) has been established. With the model, the harmonics interaction between the ac side and the dc side can be analyzed with the consideration of the control strategies, which reveals the generation mechanism of the harmonics in SPVSC. Based on the mechanism, a feedforward harmonic mitigation strategy has been presented. The principle of the strategy is to add low-order harmonic signal to the PWM modulation signals to reduce the harmonic current on the ac side. The harmonic mitigation strategy not only has clear physical meaning and fast calculation, but also is robust for the uncertainty of parameters. Finally, the simulation and experiment results demonstrate the correctness of the model and the effectiveness of the harmonic mitigation strategy.

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Chen, K. C., S. Salimin, S. A. Zulkifli, and R. Aziz. "Single Phase Inverter System using Proportional Resonant Current Control." International Journal of Power Electronics and Drive Systems (IJPEDS) 8, no. 4 (December 1, 2017): 1913. http://dx.doi.org/10.11591/ijpeds.v8.i4.pp1913-1918.

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<span>This paper presents the harmonic reduction performance of proportional resonant (PR) current controller in single phase inverter system connected to nonlinear load. In the study, proportional resonant current controller and low pass filter is discussed to eliminate low order harmonics injection in single phase inverter system. The potential of nonlinear load in producing harmonics is showed and identified by developing a nonlinear load model using a full bridge rectifier circuit. The modelling and simulation is done in MATLAB Simulink while harmonic spectrum results are obtained using Fast Fourier Transfor. End result show PR current controller capability to overcome the injection of current harmonic problems thus improved the overall total harmonic distortion (THD).</span>

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Giesecke, A. L., C. Peth, T. Toncian, O. Willi, and M. Cerchez. "UV harmonics generated on modulated targets irradiated by high-intensity laser pulses." Laser and Particle Beams 37, no. 01 (February 18, 2019): 12–17. http://dx.doi.org/10.1017/s0263034619000090.

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AbstractThe generation of high-order harmonics in ultraviolet spectral range by targets of periodic modulation interacting with relativistic, high contrast laser pulse (Iλ2= 1020W/cm2· μm2) was investigated experimentally and numerically. The spectral intensity of the 2nd- and 3rd-order harmonic emission from grating of different periodicities (250, 410, and 480 nm) is presented. The enhancement of the 3rd harmonic order compared with 2nd was observed for a grating of 480 nm periodicity. The experimental results indicate the role of the grating periodicity on the emission efficiency of different higher order harmonics in the UV spectral range. The higher order harmonics are emitted at the grating surface separated from the specular reflection of the laser pulse, due of the interference effects. In addition, 2D numerical PIC simulations demonstrate a complex angular distribution of the higher harmonics (HH) spectral intensity and confirm the strong dependence of the HH efficiency of a specific order on the grating periodicity, as observed experimentally. These special features of the high harmonic emission by periodically modulated targets open the route toward the control of HH spectral composition and of the emission efficiency of the lower order harmonics.

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Zhukovsky, K. V. "Effect of the third undulator field harmonic on spontaneous and stimulated undulator radiation." Journal of Synchrotron Radiation 26, no. 5 (August 15, 2019): 1481–88. http://dx.doi.org/10.1107/s1600577519008415.

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The effect of undulator field harmonics on spontaneous and stimulated undulator radiation, both on and off the undulator axis, is studied. Bessel factors for the undulators with field harmonics have been analytically calculated and numerically verified. The influence of the third undulator field harmonic on single-pass free-electron laser radiation is explored. Harmonic generation at the LCLS and SPring-8 free-electron lasers is modeled and analyzed.

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Natarajan, Suresh, and R. Samuel Rajesh. "Comparison Of Cascaded H-bridge Inverters for Harmonic Mitigation Considering Various Loads." International Journal of Power Electronics and Drive Systems (IJPEDS) 8, no. 1 (March 1, 2017): 10. http://dx.doi.org/10.11591/ijpeds.v8.i1.pp10-19.

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This paper compares the reduction of harmonics in various level cascaded H-bridge inverters. The switching angles for the cascaded H-bridge inverter were calculated by evolutionary optimization technique. Fourier analysis is used to determine the switching angles for the desired electrical parameters. Lower order harmonics such as third, fifth, seventh, ninth and eleventh order harmonics were taken into consideration to reduce the total harmonic distortion. Simulation was done for thirteen, fifteen and seventeen level cascaded H-bridge inverters using Matlab. Total harmonic distortion of voltage and current for R, RL and Motor load were analyzed.

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Matsuoka, Osamu. "Molecular integrals over Laguerre Gaussian-type functions of real spherical harmonics." Canadian Journal of Chemistry 70, no. 2 (February 1, 1992): 388–92. http://dx.doi.org/10.1139/v92-055.

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Molecular integrals are formulated over the Laguerre Gaussian-type functions (LGTF) of real spherical harmonics. They include the overlap integrals and the energy integrals of kinetic, nuclear attraction, and electron repulsion. For the nuclear-attraction integrals the formulations based on the point as well as the Gaussian nuclear charge distribution models are presented. Integral formulas over the LGTFs of real spherical harmonics are found a little more complicated than those of the LGTFs of complex spherical harmonics due to the summations over magnetic quantum numbers. Keywords: molecular integral, Gaussian-type function, spherical harmonic, solid harmonic, Sonine polynomial.

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NIKOLAEV, NIKOLAY Y., and HITOSHI IBA. "GENETIC PROGRAMMING OF POLYNOMIAL HARMONIC NETWORKS USING THE DISCRETE FOURIER TRANSFORM." International Journal of Neural Systems 12, no. 05 (October 2002): 399–410. http://dx.doi.org/10.1142/s0129065702001242.

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This paper presents a genetic programming system that evolves polynomial harmonic networks. These are multilayer feed-forward neural networks with polynomial activation functions. The novel hybrids assume that harmonics with non-multiple frequencies may enter as inputs the activation polynomials. The harmonics with non-multiple, irregular frequencies are derived analytically using the discrete Fourier transform. The polynomial harmonic networks have tree-structured topology which makes them especially suitable for evolutionary structural search. Empirical results show that this hybrid genetic programming system outperforms an evolutionary system manipulating polynomials, the traditional Koza-style genetic programming, and the harmonic GMDH network algorithm on processing time series.

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Journal articles on the topic 'Harmonická'

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