Статті в журналах: "Harmonic analysis"

1

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.

2

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.

3

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.

4

Bonilla, Axel Rivas, and Ha Thu Le. "Analysis and Mitigation of Harmonics for a Wastewater Treatment Plant Electrical System." WSEAS TRANSACTIONS ON CIRCUITS AND SYSTEMS 23 (February 9, 2024): 1–13. http://dx.doi.org/10.37394/23201.2024.23.1.

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Power quality has become a pressing issue that demands solutions as power electronic equipment has been increasingly used in industrial sectors. One critical problem is how to mitigate harmful harmonics generated by the power electronic equipment. This study investigates harmonic distortion issues in a wastewater treatment plant to verify compliance with IEEE standard 519 using simulation software ETAP and realistic data from the plant. Harmonic quantification shows that the plant harmonic situation violates IEEE Standard 519 where harmonic levels exceed its voltage and current limits. Different methods were used to mitigate the harmonic situation where the core is using passive harmonic filters. It is found that the biggest contributor to the harmonic distortion is the system variable frequency drives. Using high-pulse variable frequency drives, such as 18-pulse, is proven to be beneficial for harmonic reduction. Further, installing passive harmonic filters in appropriate locations helps lower voltage and current harmonics to meet IEEE Std. 519 limits. However, adding a passive harmonic filter higher up the power distribution or adding passive filters to the feeder buses is not effective in lowering the Total Harmonic Distortion (THD) of the system. This would have the drawback of increasing the rating of the system bus voltages. Other findings include a lack of medium voltage passive filters on the market and high costs. The study contributes some insight understanding, experience, and methods for engineers when developing solutions for controlling harmonics in similar plants or industrial applications.

5

Karomah, Akhlaqul. "Induction Motor Harmonics Voltage Waveform Analysis based on Machine Constriction." Jurnal EECCIS (Electrics, Electronics, Communications, Controls, Informatics, Systems) 14, no. 2 (August 28, 2020): 63–67. http://dx.doi.org/10.21776/jeeccis.v14i2.639.

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Abstractâ€” This paper discussed about harmonic analysis in an induction motor. Harmonics on induction motor appear due to the machine construction specially to its slots. The analysis of those harmonic will be one of the problems in the machine observation and design. In this paper a simulated computation of the flux magnet and emf induction voltage containing harmonic is proposed and discussed. FEMM simulation software is used and the result is compared to the mathematical analysis. The result shows that the emf induction harmonics wave derived from mathematic modelling and FEMM conform each other. Each of proposed methods can be used in the machine design or the evaluation analysis.Index Termsâ€”harmonic, induction motorÂ

6

Jiang, Peiyu, Zhanlong Zhang, Zijian Dong, and Yu Yang. "Vibration Measurement and Numerical Modeling Analysis of Transformer Windings and Iron Cores Based on Voltage and Current Harmonics." Machines 10, no. 9 (September 8, 2022): 786. http://dx.doi.org/10.3390/machines10090786.

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The operating condition and structural state of the converter transformer are closely related to vibration. Abundant harmonics aggravate the vibration of windings and iron cores, resulting in frequent mechanical structural failures, which seriously affect the stable operation of the power system. Traditional research mainly focuses on the vibration of AC transformers without harmonics and there is no in-depth discussion of the vibration mechanism and the numerical calculation model of windings and iron cores under harmonics. In addition, the influence of harmonics, winding connection method and other factors on the vibration characteristics are not clear. Therefore, this paper analyzes the voltage and current harmonic components and contents, establishes a harmonic-vibration numerical model and compares the vibration time-frequency characteristics with or without harmonics and different valve side winding connections through vibration measurement experiments. Finally, a combined simulation analysis reveals the contribution of the windings and core to the tank. The results show that the tank vibration amplitude and dominant frequency will increase under harmonica and the valve side current will affect the dominant frequency. Among these results, when there are harmonics, the amplitude increases by three times, the vibration dominant frequency changes from 100 Hz to 400 Hz and the frequency spectrum widens to 2000 Hz. In particular, the contribution of the winding vibration under the harmonic current will exceed the iron core. The research results reveal the influence of converter transformer harmonics on vibration, which can provide a theoretical basis for numerical calculation of vibration and monitoring of operating conditions and guide the design of structural vibration reduction to reduce mechanical failures caused by vibration.

7

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.

8

Wang, Xiangrong, and Guangtian Shi. "Analysis of harmonic influence of improved PFC circuit on SS4G electric locomotive." Journal of Physics: Conference Series 2260, no. 1 (April 1, 2022): 012032. http://dx.doi.org/10.1088/1742-6596/2260/1/012032.

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Abstract Compared with active filter, PFC circuit has simple structure and convenient operation. Introducing it into SS4G electric locomotive can greatly reduce system harmonics. Therefore, firstly, the corresponding PFC circuit is built, and the suppression measures of peak section and discontinuous section are proposed. By improving the discontinuous section, the waveform conduction angle is expanded from 129.564° to 162.882°. Accordingly, the current harmonic at the input side is reduced from 27.38% to 16.19%. After the voltage multiplier is further introduced, the harmonic is reduced to 15.77%. Then, the circuit is designed to absorb the high-order harmonic power in the peak section, and the harmonic is further reduced by about 0.33% to 15.44%. Two small order smoothing capacitors are connected in parallel in the load section to further absorb higher harmonics, which can reduce harmonics to 9.95%. Because the discontinuous section will also produce some spikes in the improvement process, improving the spikes can reduce the harmonics by 4.42% to 5.53%. Then the final improved circuit is introduced into SS4G circuit, and the current harmonic content of the circuit is reduced from 30.02% to 15.59%. The improved PFC circuit has achieved good results in SS4G.

9

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.

10

Damjanović, Ivana, Frano Tomašević, Ivica Pavić, Božidar Filipović-Grčić, and Alan Župan. "Harmonic Performance Analysis of Static Var Compensator Connected to the Power Transmission Network." Journal of Energy - Energija 67, no. 2 (June 2, 2022): 13–22. http://dx.doi.org/10.37798/201867276.

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The static var compensator (SVC) is a device which is designed to compensate reactive power, increase voltage stability and to reduce voltage fluctuations. Thyristor controlled reactors (TCRs) are composed of reactors in series with bidirectional pair of thyristors. Current through reactors can be continuously controlled by changing the firing angle of thyristor valves, thus the inductive power can be easily controlled. Typical applications of TCRs in AC systems are voltage stabilization and temporary overvoltage reduction, stability improvement, damping of power oscillations and load balancing. In this paper, harmonic performance analysis of SVC equipped with TCRs is presented. SVCs utilizing TCRs generate harmonic currents and therefore it is necessary to determine the effect of harmonics generated by the SVC on the power system and its elements. This includes interaction of the SVC with the system, the SVC performance under balanced and unbalanced operating conditions and finally, evaluation of countermeasures such as installation of harmonic filters. In order to carry out these analysis, it is necessary to determine harmonic characteristics of the network at the point of SVC connection, existing levels of harmonics, and to know appropriate standards regarding acceptable harmonic levels in the power system. Since harmonic distortions in the system are caused by the interaction between SVC and the system, all system contingencies which may affect system’s frequency response should be evaluated. Detailed power system model should be considered to make sure that parallel resonance points of system do not directly coincide with characteristic harmonics from the SVC. Harmonics generated by SVCs are largely dependent on the operating point within the SVC characteristic. A conservative approach is to use the maximum values of harmonics generated within the spectrum irrespective of the operating point. The results of harmonic performance analysis are important for appropriate design of SVC. Harmonic performance analysis related to SVC application which are presented in this paper include the determination of: frequency response of the transmission network impedance required for the specification and design of filters; the effects of SVC generated harmonics on the power system; the overall filter requirements and countermeasures to reduce harmonics to acceptable levels.

11

Wang, Xin Tong, Xiao Bo Wang, and Hui Zhong Zhang. "Waveform Measurement and Analysis of Common Household Appliances." Applied Mechanics and Materials 599-601 (August 2014): 767–75. http://dx.doi.org/10.4028/www.scientific.net/amm.599-601.767.

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Electricity power companies have the obligation to provide qualified electrical energy to the power user, the same as electricity customers, the power company claims to provide qualified energy, electricity customers are obliged to choose the right appliances to minimize the impact on the power quality of the power system . Higher harmonics is an important indicator of the impact of power quality, household appliances majority of non-linear loads, the use of the process will produce high harmonics, although the power is not, but a huge number, pooled together, will still PQ great impact. Therefore, the measurement of electrical waveforms common household appliances, will harmonic analysis, harmonic control, or other harmonic study is instructive.

12

Hasabelrasul, Hashim, Zhenjiang Cai, Mohaned Kamal, Lei Sun, and Xuesong Suo. "Practical Application for Reactor Installation to Reduce Harmonics Resonance of Steel Factory." Journal of Physics: Conference Series 2218, no. 1 (March 1, 2022): 012051. http://dx.doi.org/10.1088/1742-6596/2218/1/012051.

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Abstract Harmonicis one of the problems in the power system. It needs more focus due to the number of electrical devices that generate a considerable amount of harmonics. In this paper, a reactor was designed, installation and implementation for a steel factory. The installation objective is to solve harmonic resonance and reduce billing penalties for reactive power KVA by the electric power utility—technical analysis applied to the factory main panel. The ETAP software is used to discover the problem and evaluate the solution results. The power flow and harmonics analysis of an 11 kV system is modeled and implemented. Finally, the proper reactor was calculated and installation as practical to solve the harmonic and economic issues.

13

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.

14

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.

15

KULSHRESTHA, MANJUSHA, and A. M. SHEKH. "Estimation of soil temperature by Harmonic analysis." MAUSAM 52, no. 2 (December 29, 2021): 379–84. http://dx.doi.org/10.54302/mausam.v52i2.1705.

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Soil temperatures recorded at 5.10 and 20 cm depth at Anand station of Gujarat state for the period of 1982-93 were analyzed by harmonic analysis and tested it for the year 1998. The amplitude of the soil temperature wave for the various depths decreases from a maximum of 5.76° C in the first harmonic to 0.96°C in the third harmonic. First, second and third harmonic explained 55 to 76 percent, 18 to 37 percent and 2 to 4 percent of the total variance, respectively. Total percentage of total variance covered by the three harmonics at different depths are in the range of 95 to 97 percentage for the period of 1982-93 normalized data series which shows the applicability of harmonic analysis in describing soil temperatures. The weekly observed and computed soil temperatures by harmonic analysis were in agreement and their differences were non significant by Chi-Square test.

16

Mekhamer, S. F., A. Y. Abdelaziz, and S. M. Ismael. "Design Practices in Harmonic Analysis Studies Applied to Industrial Electrical Power Systems." Engineering, Technology & Applied Science Research 3, no. 4 (August 11, 2013): 467–72. http://dx.doi.org/10.48084/etasr.309.

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Power system harmonics may cause several problems, such as malfunctions of electrical equipment, premature equipment failures and plant shutdowns. Accordingly, mitigation of these harmonics is considered an important target especially for industrial applications where any short downtime period may lead to great economic losses. Harmonic analysis studies are necessary to analyze the current and voltage harmonic levels and check if these levels comply with the contractual or international standard limits. If the studies reveal that the preset limits are exceeded, then a suitable harmonic mitigation technique should be installed. Harmonic analysis studies in the industrial electrical systems are discussed in many references. However, a comprehensive procedure for the steps required to perform a harmonic study is rarely found in the literature even though it is strongly needed for design engineers. This paper provides a comprehensive procedure for the steps required to perform a harmonic study in the form of a flowchart, based on industrial research and experience. Hence, this paper may be considered as a helpful guide for design engineers and consultants of the industrial sector.

17

Adjie, Alfin Prima, and Muhammad Imran Hamid. "Harmonics Analysis of Input Current of 3-Phase PWM Rectifier." Andalas Journal of Electrical and Electronic Engineering Technology 1, no. 1 (May 7, 2021): 31–40. http://dx.doi.org/10.25077/ajeeet.v1i1.6.

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Rectifier is a non-linier load that causes harmonic distortion in the power system. Pulse-width modulation (PWM) method is an effective method in pressing the magnitude of harmonics in a rectifier application, it provides an almost sinusoidal input current. However, the variation of loads that supplied by a rectifier cause the harmonics that arise can still beyond the applicable standard. The amount of harmonics in the operating range of a rectifier need to be identified to determine the filter on the input side. In this research article, 3-phase PWM rectifier was designed with hysteresis current control technique using PSCAD software simulation. Harmonic compensation was carried out by applying an active filter based on P-Q theory to reduce the harmonic distortion that occurs in the input current, thus giving a low total harmonic distortion (THD) value. Based on the simulation, 3-phase PWM rectifier operation starting at a power level of 150 kW, giving a THD value above 5-10% by the increasing the amount of load supplied by the rectifier. The application of active filter based on the P-Q theory is able to compensate harmonics in the input current wave with a THD value below 5% in the rectifier operating range.

18

Li, Xiang Zhen, Guang Ming Hu, Peng Xin Hou, Yu Bo Fan, and Chun Lin Guo. "Analysis on Harmonics Caused by Connecting Electric Vehicle Chargers with Power Network." Advanced Materials Research 724-725 (August 2013): 1393–97. http://dx.doi.org/10.4028/www.scientific.net/amr.724-725.1393.

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As a class of nonlinear loads in the power system, electric vehicle chargers will produce a certain harmonic pollution for the grid. Before the construction of charging stations, it is necessary for electric vehicle charger (station) connected to the grid to simulate and predict harmonics. The models of single charger and charge station are built separately in order to simulate and analysis the impact of a single and multiple chargers on power quality. The factors of the harmonic current ratio (HRI) and the current total harmonic distortion (THDI) varied with the charging power and the number of the chargers are discussed and analyzed. The generation mechanism of harmonic counteraction and interaction between the chargers are analyzed. The simulation results show that: because of the impedance of the system and the transformer, the harmonic current ratio (HRI) and the current total harmonic distortion (THDI) both increase firstly to some extent and subsequently decrease gently with the increase of the number of the chargers in the same power charging. This phenomenon has nothing to do with the harmonic counteraction and how that happen is discussed and analysis in this paper. And the phenomenon of harmonics interaction and counteraction occurs with the increase of the number of the chargers in different power charging, and the current total harmonic distortion (THDI) declines and tends to maintain a relatively stable value.

19

Luo, Dan, Yi Xiao, and Jie Na Zhou. "Harmonic Analysis of Non-Sinusoidal Harmonic Signals in Electric Power System." Advanced Materials Research 1070-1072 (December 2014): 779–84. http://dx.doi.org/10.4028/www.scientific.net/amr.1070-1072.779.

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Harmonic Analysis and control is very important for the power system because harmonics have serious harm to its normal operation. Harmonic Analysis uses fast Fourier transform (FFT) to solve this problem though it causes the spectrum leakage which Increases the calculation error. To solve this problem, the interpolation algorithm combine with tapered time windows are used. The tapered time windows solve the long-range leakage and the interpolation algorithm solves the problem of short-range leakage.

20

Lee, Taeyoung. "Real Harmonic Analysis on the Special Orthogonal Group." International Journal of Analysis and Applications 20 (April 4, 2022): 21. http://dx.doi.org/10.28924/2291-8639-20-2022-21.

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This paper presents theoretical analysis and software implementation for real harmonics analysis on the special orthogonal group. Noncommutative harmonic analysis for complex-valued functions on the special orthogonal group has been studied extensively. However, it is customary to treat real harmonic analysis as a special case of complex harmonic analysis, and there have been limited results developed specifically for real-valued functions. Here, we develop a set of explicit formulas for real-valued irreducible unitary representations on the special orthogonal group, and provide several operational properties, such as derivatives, sampling, and Clebsch-Gordon coefficients. Furthermore, we implement both of complex and real harmonics analysis on the special orthogonal group into an open source software package that utilizes parallel processing through the OpenMP library. The efficacy of the presented results are illustrated by benchmark studies and an application to spherical shape matching.

21

Belchior, Fernando Nunes, Paulo Fernando Ribeiro, and Frederico Marques Carvalho. "Comparative Analysis of Instruments Measuring Time Varying Harmonics." International Journal of Emerging Electric Power Systems 17, no. 4 (August 1, 2016): 463–69. http://dx.doi.org/10.1515/ijeeps-2015-0175.

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Abstract This paper aims to evaluate the performance of commercial class A and class S power quality (PQ) instruments when measuring time-varying harmonics. By using a high precision programmable voltage and current source, two meters from different manufacturers are analyzed and compared. Three-phase voltage signals are applied to PQ instruments, considering 3 situations of time-varying harmonic distortions, whose harmonic distortion values are in accordance with typical values found in power systems. This work is relevant considering that international standardization documents do not pay much attention to this aspect of harmonic distortion.

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VIMALADEVI, S., A. S. DONA MOL, V. DURGALAKSHMI, and K. SUBHASHINI. "A REVIEW OF HARMONIC ANALYSIS AND MITIGATION TECHNIQUES USING FILTERS." YMER Digital 21, no. 05 (May 16, 2022): 742–52. http://dx.doi.org/10.37896/ymer21.05/85.

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Nonlinear loads draw non sinusoidal current and voltage from the utility.These nonsinusoidal current and voltages created due to nonlinear loads are called harmonics.The harmonic voltages and current disturbs the system back and creates big power quality problem.Therefore in order to mitigate harmonic problems different mechanisms are used.Here as introduction different power quality problems, harmonics and their mitigation techniques/filters are presented and discussed.Between the different ways to minimize/eliminate harmonics active power filters are most prominent one.

23

Gardiner, Stephen J. "Coincidence of Harmonic and Finely Harmonic Functions." Potential Analysis 34, no. 1 (April 27, 2010): 81–88. http://dx.doi.org/10.1007/s11118-010-9182-0.

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Liang, Chen, Mei Yang, Wei Zheng, and Yong Zhi. "Simulation Analysis on Harmonics Pollution of Large-Scale Wind System Accessed to Grid." Advanced Materials Research 997 (August 2014): 795–99. http://dx.doi.org/10.4028/www.scientific.net/amr.997.795.

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The harmonic sources model of wind grid accessed to power system is established by measurement and statistical methods based on the large scale wind system planning of Gansu jiuquan area. The harmonic power flow is analysed under different operation modes in power system. The harmonic pollution trend of the million kilowatt wind accessed to power system at present stage and 2015 are analysed and compared, the calculation results show that the harmonics pollution is most serious at the point which wind power accessed to the network, the harmonic pollution degree is damping along the line. The farther electrical distance from harmonic sources, the fewer harmonic, and the harmonic pollution is decreasing with the grid structure constantly reinforced. This research will provide reference data for power grid planning and wind power quality management.

25

Zhang, Min, Jinhao Wang, Shifeng Zhang, Le Gao, Xiangyu Guo, Lin Chen, and Yonghai Xu. "Harmonic Resonance Analysis and Impedance Remodeling Method of Multi-Inverter Grid-Connected System." Electronics 12, no. 17 (August 31, 2023): 3684. http://dx.doi.org/10.3390/electronics12173684.

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The harmonic and resonant characteristics of a multi-inverter grid-connected system can negatively affect power quality when weak grid conditions are present. In this paper, firstly, harmonic currents are modeled for the inverter, the correctness of low-frequency harmonics and high-frequency harmonics are verified in closed loop, and the characteristics of harmonic currents are analyzed when the parameters are varied. Secondly, the resonant characteristics of the inverter with feed-forward link are analyzed, and a multi-inverter grid-connected equivalent model based on the triple-decomposition conductance is developed and analyzed in conjunction with the resonant modal analysis method. Then, a harmonic resonance impedance reshaping method is proposed to suppress the background harmonics using improved weighted average current control (WACC), suppress the system resonance based on the point of common coupling (PCC) paralleling virtual conductance method, and improve the stability margin of the system combined with impedance reshaping resonance suppression method. Finally, simulations and comparison of results with different suppression methods verify the superiority and effectiveness of the proposed method.

26

Krantz, Steven G. "Harmonic analysis." Wiley Interdisciplinary Reviews: Computational Statistics 3, no. 2 (January 4, 2011): 163–67. http://dx.doi.org/10.1002/wics.143.

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27

Ma, Chenghu, Hui Han, and Xing Yan. "Error Analysis of Electric Energy Metering System Considering Harmonics." Journal of Physics: Conference Series 2310, no. 1 (October 1, 2022): 012086. http://dx.doi.org/10.1088/1742-6596/2310/1/012086.

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Abstract The watt hour metering system includes watt hour meter, voltage and current transformer, errors of them will affect the overall error of metering system. Considering harmonic, this paper studies the measurement accuracy of metering system, the harmonic equivalent circuits of energy meter, voltage and current transformer are established, their harmonic measurement errors and influencing factors are analyzed, the model of whole metering system is bulit and its measurement errors are anylyzed. Through the simulation of a specific watt hour metering system, the influence of harmonics on it is studied.

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Fetene, Zewdu Alamineh, Tesfay Mekonnen Weldegerima, Tadesse Terefe Zeleke, and Melessew Nigussie. "Harmonic Analysis of Precipitation Time Series in Lake Tana Basin, Ethiopia." Advances in Meteorology 2018 (June 7, 2018): 1–9. http://dx.doi.org/10.1155/2018/1598195.

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This study presents harmonic analysis of precipitation observations within the Lake Tana Basin for the periods of 1985–2015. The livelihood of several millions of people within the basin and outside the basin is governed by the precipitation conditions within this basin. Large spatial and temporal variabilities of precipitation can increase the incidence of extreme events such as floods and droughts. It is important to identify the characteristics of these variations, and this study aims at investigating the characteristics of the seasonal and annual cycles of precipitation within the Lake Tana Basin using harmonic analysis. Precipitation data of 31 years from four weather stations were used in the analysis. We then applied harmonic analysis to calculate the amplitude, phase shift, and variance of observation. Detailed characteristics of the first five harmonics are presented and discussed. We found the amplitude of the first harmonic to be 173.42, 177.93, 127.77, and 188.78 mm for Debre Tabor, Bahir Dar, Gondar, and Dangila, respectively. This shows that Dangila areas got more rainfall during this fundamental period than others increasing from Gondar to Dangila direction. Also, the variance in the first harmonic is smaller than the variances of other harmonics, and this means that the large variations of the precipitation originate from higher harmonics (short time periods). This shows that precipitation variations are governed mainly by monthly, seasonal, and semiannual variations. The analysis has shown that maximum precipitation for all stations occurred in July and August.

29

Hu, HeJun, JunJia Wang, YiYun Huang, XiaoFeng Li, and Hui Chen. "Analysis and Suppression of Harmonic Characteristic for Multi-pulse Rectifier Based on Phase-shifting Transformer." Journal of Physics: Conference Series 2237, no. 1 (March 1, 2022): 012003. http://dx.doi.org/10.1088/1742-6596/2237/1/012003.

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Abstract With the wide application of rectifiers, the harmonic content of power grid is increasing. In fact, the multi-pulse rectifier produces lower harmonic content than the lower pulse rectifier. In order to reduce harmonic content from harmonic source in power grid, the multi-pulse rectifier is designed based on the phase-shifting transformer in this paper. First of all, the design method of multi-pulse rectifier is introduced by theoretical analysis. Then, the harmonic mechanism is deduced by the mathematical formula, which explains the harmonic generation process. After that, the correctness and reliability of theory analysis are proved by simulation. Finally, the harmonics of the multi-pulse rectifier are suppressed by filtering branches.

30

Liu, Rong Hui, Ai Qang Pan, and Xiu Yang. "Analysis for Power System Transient Harmonics Based on Wavelet Packet Transform." Applied Mechanics and Materials 415 (September 2013): 241–44. http://dx.doi.org/10.4028/www.scientific.net/amm.415.241.

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In this paper, the principles of wavelet transform and wavelet packet transform were presented. The wavelet packet transform had good characteristics of uniform frequency decomposition, and thus transient harmonic analysis method was proposed based on wavelet packet transform. Finally, transient interharmonic, time varying harmonic and transient oscillation signals in power systems were simulated with Matlab emulator. The perfect results of simulation show that the presented method can accurately detect the transient harmonics, which provides support for harmonic analysis in power systems.

31

Ning, D., X. Zhuo, L. Chen, and B. Teng. "Nonlinear Numerical Investigation on Higher Harmonics at Lee Side of a Submerged Bar." Abstract and Applied Analysis 2012 (2012): 1–12. http://dx.doi.org/10.1155/2012/214897.

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The decomposition of a monochromatic wave over a submerged object is investigated numerically in a flume, based on a fully nonlinear HOBEM (higher-order boundary element method) model. Bound and free higher-harmonic waves propagating downstream the structure are discriminated by means of a two-point method. The developed numerical model is verified very well by comparison with the available data. Further numerical experiments are carried out to study the relations between free higher harmonics and wave nonlinearity. It is found that thenth-harmonic wave amplitude is growing proportional to thenth power of the incoming wave amplitude for weakly nonlinear wave condition, but higher-harmonic free wave amplitudes tend to a constant value for strong nonlinear wave condition.

32

Zheng, Wei Jie. "Admittance Elements Comparatively Amplitude Trend Analysis of Thyristor Controlled Reactor." Advanced Materials Research 918 (April 2014): 160–64. http://dx.doi.org/10.4028/www.scientific.net/amr.918.160.

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Thyristor controlled reactor was important reactive compensator which is widely used in power system, while it also a harmonic source which is necessary to be researched, especially the harmonic characteristics and harmonic amplitude changing trend, which is important to model, simulate and improve the equipment design. The paper analysed the admittance elements comparatively amplitude trend of thyristor controlled reactor.The research result will help to compensate or reduce the harmonics generated by thyristor controlled reactor, which also will be helpful to model and simulate other thyristor controlled reactive power equipments.

33

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.

34

Badugu, Jayababu, Y. P.Obulesu, and Ch Saibabu. "Harmonic Analysis of Three-phase Fixed Capacitor–thyristor Controlled Reactor under Balanced and Unbalanced Conditions." IAES International Journal of Robotics and Automation (IJRA) 7, no. 1 (March 1, 2018): 67. http://dx.doi.org/10.11591/ijra.v7i1.pp67-76.

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Three-phase Fixed Capacitor Thyristor Controlled Reactor is widely used for reactive power compensation in power systems because of reduced cost and high reliability. The problem with FC-TCR is that to generate current harmonics when it is partially conducting. When this harmonic current is interacted with system impedance, voltage waveform will distorted. This harmonic pollution is undesirable in power systems. Therefore, it is important to know the harmonic behaviour of three-phase FC-TCR before they can be used in a power system network. This paper presents the harmonic analysis of three-phase FC-TCR operating under balanced and unbalanced conditions. This analysis is useful to design the harmonic filter to reduce the harmonic pollution in power systems.The proposed work is implemented in MATLAB environment.

35

Zhukovsky, K. "Theoretical spectral analysis of FEL radiation from multi-harmonic undulators." Journal of Synchrotron Radiation 27, no. 6 (October 22, 2020): 1648–61. http://dx.doi.org/10.1107/s1600577520012230.

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A theoretical study of the spontaneous and stimulated undulator radiation (UR) from electrons in undulators with multiple periods in both transversal directions is presented. Exact expressions are derived for the UR intensities in terms of the generalized Bessel and Airy functions, accounting for undulator field harmonics of arbitrary strength and for real parameters of the beams and installations. Theoretical results are verified with numerical and experimental data for SWISS-XFEL, PAL-XFEL, LEUTL, LCLS etc. The spectrum, UR line shape and width, and the harmonic evolution along the undulators are analyzed and compared with the available data for these experiments. Moreover, the effect of the field harmonics is elucidated. It is demonstrated that the third field harmonic can cause distinct odd UR harmonics. The asymmetric undulator field configuration is identified, which allows intense radiation of these harmonics. The power evolution in a free-electron laser (FEL) with such an undulator is studied by means of an analytical FEL model. The latter is enhanced by a true description of the gradual power saturation of harmonics. A FEL with elliptic undulator and electron–photon phase-shifting is proposed and modeled. It is shown that the resulting harmonic power from the phase-shifted elliptic undulator can be significantly higher than from a planar undulator with the same phase-shifting.

36

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.

37

Nömm, Jakob, Sarah Rönnberg, and Math Bollen. "An Analysis of Voltage Quality in a Nanogrid during Islanded Operation." Energies 12, no. 4 (February 15, 2019): 614. http://dx.doi.org/10.3390/en12040614.

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Voltage quality data has been collected in a single house nanogrid during 48 weeks of islanded operation and 54 weeks of grid-connected operation. The voltage quality data contains the voltage total harmonic distortion (THD), odd harmonics 3 to 11 and 15, even harmonics 4 to 8, voltage unbalance, short-term flicker severity (Pst) and long-term flicker severity (Plt) values, and voltage variations at timescales below 10 min. A comparison between islanded and grid-connected operation values was made, were some of the parameters were compared to relevant grid standard limits. It is shown that some parameters exceed the defined limits in the grid-standards during islanded operation. It was also found that the islanded operation has two modes of operation, one in which higher values of the short circuit impedance, individual harmonic impedance, harmonic voltage distortion and voltage unbalance were reached.

38

Fox, William T. "Harmonic analysis of periodic extinctions." Paleobiology 13, no. 3 (1987): 257–71. http://dx.doi.org/10.1017/s009483730000885x.

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Fourier analysis of percent extinction data for genera of fossil marine animals during the past 260 million years indicates the existence of a 26 m.y. extinction cycle. The first three harmonics, which account for 51.7 percent of the sum of squares, show the major extinction trends in the late Paleozoic, Mesozoic and Cenozoic. The first ten harmonics, which account for 89.5 percent of the sum of squares, are aligned with eight extinction peaks. The tenth harmonic, with a period of 26 million years, has an amplitude of 6.5 percent and accounts for 12.7 percent of the sum of squares.Several different methods are used to test the validity of the apparent 26 m.y. extinction cycle. Analysis of variance indicated that the 26 m.y. extinction cycle is statistically significant at the 95 percent level. When the 260 m.y. sample interval is divided into equal 130 m.y. segments, the phases and amplitudes for the 26 m.y. cycle were almost equal within the two independent segments. When the 260 m.y. interval is divided into 10 shorter time segments of different lengths, the 26 m.y. cycle is represented in each time segment.A series of experiments is run to test the influence of the Late Permian and Cretaceous peaks on the observed 26 m.y. cycle. When all peaks are smoothed out except for the two major peaks, a pseudo-cycle with a period of 26 m.y. is generated that accounts for 3.0 percent of the sum of squares. When the Permian and Cretaceous peaks are reduced to about half their observed height, the sum of squares accounted for by the 26 m.y. cycle is reduced from 12.7 to 11.0 percent. When the number of extinctions within each stage is used in the harmonic analysis in place of extinction percent, the 26 m.y. cycle accounts for 19.3 percent of the sum of squares.Therefore, the evidence from harmonic analysis of fossil marine animals points toward a distinct and persistent 26 m.y. cycle in mass extinctions in the late Paleozoic, Mesozoic and Cenozoic.

39

Wu, Xiao Yu, Zhe Ming Chen, and Ze Hao Huang. "Analysis and Calculation of Electromagnetic Torque for the Voltage Source Traction Motors." Applied Mechanics and Materials 446-447 (November 2013): 672–77. http://dx.doi.org/10.4028/www.scientific.net/amm.446-447.672.

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The traction motor installed on the high-speed train is powered by inverter. A large number of harmonics may appear when motor is operating. Then the motor speed generate oscillation and finally the dynamic characteristic is affected in vehicle system. In this paper, relied on the electromagnetism of traction motor, the mechanism about emerging harmonic torque is analyzed. In addition, based on the equivalent circuit, the method of calculating the parameters in harmonic circuit is proposed. Two mathematical formulas are also proposed to obtain the fundamental electromagnetic torque and the harmonic electromagnetic torque on traction motor. The time domain and frequency domain distributions of the torques are gained and analyzed. Finally a calculation example of traction motor harmonic torque was analyzed and calculated, and prepared for further study of harmonic torque impacting on vehicle system dynamic performance.

40

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.

41

Jiang, Qinghua, Fanning Meng, and Guoqiang Dang. "Normality of the p-Harmonic and Log-p-Harmonic Mappings." Journal of Function Spaces 2020 (November 5, 2020): 1–7. http://dx.doi.org/10.1155/2020/1249617.

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In this paper, the concepts of p-harmonic mappings and log-p-harmonic mappings in the unit disk have been introduced and studied by many researchers. We proved the normality of the p-harmonic mappings and log-p-harmonic mappings, which extend the related results of harmonic mappings of earlier authors.

42

Xu, Shao, and Chen. "Data-Driven Compartmental Modeling Method for Harmonic Analysis—A Study of the Electric Arc Furnace." Energies 12, no. 22 (November 17, 2019): 4378. http://dx.doi.org/10.3390/en12224378.

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The electric arc furnace (EAF) contributes to almost one-third of the global iron and steel industry, and its harmonic pollution has drawn attention. An accurate EAF harmonic model is essential to evaluate the harmonic pollution of EAF. In this paper, a data-driven compartmental modeling method (DCMM) is proposed for the multi-mode EAF harmonic model. The proposed DCMM considers the coupling relationship among different frequencies of harmonics to enhance the modeling accuracy, meanwhile, the dimensions of the harmonic dataset are reduced to improve computational efficiency. Furthermore, the proposed DCMM is applicable to establish a multi-mode EAF harmonic model by dividing the multi-mode EAF harmonic dataset into several clusters corresponding to the different modes of the EAF smelting process. The performance evaluation results show that the proposed DCMM is adaptive in terms of establishing the multi-mode model, even if the data volumes, number of clusters, and sample distribution change significantly. Finally, a case study of EAF harmonic data is conducted to establish a multi-mode EAF harmonic model, showing that the proposed DCMM is effective and accurate in EAF modeling.

43

Li, Shupeng, Bin Wu, Qirui Li, Zhenbin Li, Zhaoyu Chen, and Chao Song. "Simulation and Analysis of Harmonic High Voltage Filters for Wind Farm." Journal of Physics: Conference Series 2503, no. 1 (May 1, 2023): 012076. http://dx.doi.org/10.1088/1742-6596/2503/1/012076.

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Abstract With the rapid development of the wind power industry, the total installed capacity of wind power has increased dramatically worldwide, and a large number of wind power installations need to be connected to the grid. In wind turbines, voltage flicker due to output power fluctuations caused by wind speed changes, and the application of a Voltage Source Converter (VSC) cause harmonic richness and other power quality problems to become more and more prominent. In this regard, the research is focused on the harmonic and reactive current distribution, impedance frequency characteristics, and voltage distortion rate of several offshore wind farm access systems, including the establishment of a harmonic current simulation model of the offshore wind farm delivery system, simulation analysis of network impedance frequency characteristics, simulation analysis of harmonic currents, and proposed a preferred filtering scheme. Taking into full consideration the characteristic harmonics of the wind farm, the system resonance generated by the submarine cable and the background harmonic level of the power grid, combined with the simulation results of the harmonic voltage, harmonic current, and network impedance frequency characteristics of each node, the technical solution of adding a direct-mounted high-voltage filtering device to the 220 kV bus at the metering station is proposed, which can destroy the system resonance conditions of the 3rd to 6th times of the submarine cable. Various wind farms and system operating conditions are able to form a stable harmonic absorption point to avoid the problem of harmonic amplification.

44

Jin, Tao, Yiyang Chen, and Rodolfo C. C. Flesch. "A novel power harmonic analysis method based on Nuttall-Kaiser combination window double spectrum interpolated FFT algorithm." Journal of Electrical Engineering 68, no. 6 (November 1, 2017): 435–43. http://dx.doi.org/10.1515/jee-2017-0078.

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AbstractHarmonics pose a great threat to safe and economical operation of power grids. Therefore, it is critical to detect harmonic parameters accurately to design harmonic compensation equipment. The fast Fourier transform (FFT) is widely used for electrical popular power harmonics analysis. However, the barrier effect produced by the algorithm itself and spectrum leakage caused by asynchronous sampling often affects the harmonic analysis accuracy. This paper examines a new approach for harmonic analysis based on deducing the modifier formulas of frequency, phase angle, and amplitude, utilizing the Nuttall-Kaiser window double spectrum line interpolation method, which overcomes the shortcomings in traditional FFT harmonic calculations. The proposed approach is verified numerically and experimentally to be accurate and reliable.

45

Skamyin, Aleksandr, Yaroslav Shklyarskiy, Kirill Lobko, Vasiliy Dobush, Tole Sutikno, and Mohd Hatta Jopri. "Impedance analysis of squirrel-cage induction motor at high harmonics condition." Indonesian Journal of Electrical Engineering and Computer Science 33, no. 1 (January 1, 2024): 31. http://dx.doi.org/10.11591/ijeecs.v33.i1.pp31-41.

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This study examines different methodologies for representing an asynchronous motor at higher harmonics by utilizing its equivalent circuit. Several approaches were compared based on simulation modeling. An experimental investigation was conducted in a laboratory setting using asynchronous electric motors with power ratings of 1.5 kW and 5.5 kW. The purpose of this investigation was to examine the characteristics of impedance in the presence of high-harmonic conditions. The generation of higher harmonics was achieved through the utilization of a precisely regulated thyristor rectifier in conjunction with a thyristor power controller. The findings indicate that the load on the shaft solely impacts the resistance at the fundamental harmonic, while the resistance at higher harmonics remains unaffected by the operating mode of the asynchronous motor (AM).

46

Chua, Kein Huat, Dick Sang Hoo, Yun Seng Lim, Mohammad BabrdelBonab, Li Wang, and Pei Yin Wong. "Harmonic Analysis of a Third Rail Systems: A Case Study in Malaysia." Journal of Electronics and Advanced Electrical Engineering 1, no. 2 (May 3, 2021): 26–33. http://dx.doi.org/10.47890/jeaee/2020/keinhuatchua/11120010.

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Harmonic distortion is one of the most important power quality issues in third rail electrification systems. The use of rectifiers and inverters in the third rail system can inject a significant amount of harmonic distortion to the electrical network. This paper aims to investigate the harmonic distortions for a DC urban third rail system at various operating conditions. The electrical network of Mass Rapid Transit Line 2 (MRT 2) Malaysia is modelled using ETAP software. The model had considered the effect of the inter-phase transformer in the 12-pulse rectifier. The current injection method is used to measure harmonic distortion at Point of Common Coupling (PCC) at the 132 kV and 33 kV buses. A normal and degraded operating conditions of power supply are investigated. From the simulation results, it is found that the 11th and 13th order harmonics have exceeded the statutory limit at 33 kV network for the normal operating condition. For the degraded operating condition, only the 11th harmonic order has exceeded the statutory limit. Keywords: Harmonic Distortion; DC Urban Rail; Various Operating Conditions

47

He, Qiang, Chao Fan, Guang Yang, Huiqi Li, Jiadong Li, and Xiaogang Chen. "Experimental Analysis of Transformer Core Vibration and Noise under Inter-Harmonic Excitation." Applied Sciences 12, no. 3 (February 8, 2022): 1758. http://dx.doi.org/10.3390/app12031758.

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With the wide application of power electronic devices and nonlinear loads, the resulting inter-harmonic pollution is becoming more and more serious in the power system. As important equipment in power systems, transformers have always been the focus of research. However, there are few studies on the abnormal increase in vibration and noise caused by inter-harmonic excitation. In this work, a transformer core vibration and noise measurement platform that can generate arbitrary inter-harmonic excitations was built. The real-time vibration displacement waveforms of the core model under normal and inter-harmonic conditions were experimentally measured as well as the surrounding noise level amplitude and spectrum analysis result. The influence law of excitation of intermediate harmonic content and frequency on core vibration displacement and surrounding sound pressure level was summarized. The work of this paper lays a theoretical foundation for studying the vibration and noise of power transformers and other equipment under inter-harmonics.

48

Kruchinina, Irina Yu, Yuvenaliy Khozikov, Alexandr Liubimtsev, and Valentina Paltceva. "Harmonic losses in high-speed PM synchronous machines." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 36, no. 3 (May 2, 2017): 683–91. http://dx.doi.org/10.1108/compel-09-2016-0401.

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Purpose The purpose of this paper is the development of a new numerical method for the calculation of the air-gap magnetic flux harmonics in synchronous machines with permanent magnet (PM) excitation. The harmonic analysis results are used as input data for the eddy-current loss calculation and for the rotor heating evaluation. Design/methodology/approach The method is based on the finite element analysis (FEA). The model takes into account toothed stator design, rotor asymmetrical magnetic reluctance and saturation. At first, a series of static DC magnetic (magnetostatic) simulations is run. Each problem corresponds to specific rotor position and the momentary stator winding currents. The Fourier analysis performed for each problem yields the harmonic spectrum variation in time. Then, a series of AC magnetic (time-harmonic) simulations is run. Each problem corresponds to a specific harmonic. The result is the eddy-current losses distribution. After total loss is calculated, the heat transfer analysis is conducted. Findings The analysis reveals that 90 per cent of losses are located in the sleeve that holds PMs together. Rotor eccentricity brings even harmonics of low magnitude that have little impact on heating. Originality/value In general, the study requires transient electromagnetic analysis with motion. The purposed method allows to simplify the problem. The method is based on static and quasi-static (time-harmonic) problems simulation. It is fast and highly automated. The method allows simultaneous taking into account of tooth-order harmonics, stator winding harmonics and eccentricity for heating calculation.

49

Zhukovsky, K. V. "Comparative theoretical analysis of harmonic generation in free electron lasers with various beam parameters." Izvestiya vysshikh uchebnykh zavedenii. Fizika, no. 9 (2022): 34–41. http://dx.doi.org/10.17223/00213411/65/9/34.

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We theoretically study the generation of odd and even harmonics in particular in free electron lasers (FELs). The comparative analysis is held for the spectral properties of SPARC and LEUTL FEL radiation. We analyze several different theoretical approaches to the harmonic power computation, in particular with regard to even harmonics. We compare the results with available data for SPARC and LEUTL FELs. The influence of such FEL parameters as the finite beam section, emittance and originating from it betatron oscillations on the harmonic generation and radiation is analyzed.

50

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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