Journal articles: 'Combined harmonics'

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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.

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Xu, Yamei, Qiang Miao, Pin Zeng, Zhichen Lin, Yiyang Li, and Xinmin Li. "Multiple Synchronous Rotating Frame Transformation-Based 12th Current Harmonic Suppression Method for an IPMSM." World Electric Vehicle Journal 13, no. 10 (October 20, 2022): 194. http://dx.doi.org/10.3390/wevj13100194.

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In order to solve the problem that the three-phase current of the interior permanent magnet synchronous motor (IPMSM) contains the 11th and 13th current harmonics, a multiple synchronous rotating frame transformation (MSRFT)-based current harmonic suppression method is established. Firstly, the influencing factors of current harmonics in IPMSM vector control are analyzed, and the influence mechanism of the inverter’s dead-time effect and the permanent magnet flux linkage harmonics on the current harmonics is described. Secondly, a simple current harmonic extraction method is proposed by optimizing the traditional current harmonic extraction method based on MSRFTs. The proposed method achieves the accurate extraction of the current harmonic components. Thirdly, a harmonic voltage generation method is established and is combined with the proposed current harmonic extraction method to form a current harmonic suppression strategy. Finally, the feasibility and effectiveness of the proposed method are verified via MATLAB/Simulink simulations and experiments. The simulation and experimental results show that the proposed current harmonic extraction method can extract the current harmonic components accurately, and the proposed current harmonic suppression strategy can suppress the 11th and 13th current harmonics effectively.

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Ge, Q. J., and J. Rastegar. "Bernstein-Be´zier Harmonics and Their Application to Robot Trajectory Synthesis With Minimal Vibrational Excitation." Journal of Mechanical Design 118, no. 4 (December 1, 1996): 509–14. http://dx.doi.org/10.1115/1.2826920.

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For a given high-speed machinery, a significant source of the internally induced vibrational excitation is the presence of high frequency harmonics in the trajectories that the system is forced to follow. This paper presents a Bernstein-Be´zier form of harmonic trajectory patterns for synthesizing low-harmonic trajectories. Similar to Bernstein-Be´zier polynomial curves, Bernstein-Be´zier harmonic trajectories can be defined either explicitly using Bernstein-Be´zier basis harmonics or recursively using the harmonic deCasteljau algorithm. The second part of the paper demonstrates how a Bernstein-Be´zier trajectory can be combined with the inverse dynamics of a robot manipulator for synthesizing a joint trajectory that demands “minimal” dynamic response from its actuators. An example involving a planar 2R robot is also presented.

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Cao, Yun Dong, and Xing Gang Chen. "Harmonics Analysis Based on FFT of Special Hanning Interpolation Combined with Wavelet Transform." Applied Mechanics and Materials 195-196 (August 2012): 777–82. http://dx.doi.org/10.4028/www.scientific.net/amm.195-196.777.

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In view of the problem that harmonics analysis by fast Fourier Transform can appear a higher error and the serious phenomenon of harmonics leakage and fence, it is put forward that a improved arithmetic that FFT of special Hanning interpolation combined with wavelet transform. It is proved by theory analysis and simulation calculation that: FFT arithmetic of special Hanning interpolation can raise the precision of steady-state harmonics analysis validly. And wavelet transform arithmetic can analyze time-varying harmonics and sudden-changing harmonics precisely. The arithmetic of wavelet transform combined with FFT can remedy the defects of harmonics analysis by FFT and analyze harmonics precisely, timely and validly.

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LAMBA, B. S., and SUNITA BHANDARI. "Some aspects of thermal diffusivity for various soil layers in different harmonics." MAUSAM 49, no. 2 (December 16, 2021): 255–58. http://dx.doi.org/10.54302/mausam.v49i2.3626.

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Values of thermal diffusivity (K) in different soil layers for the first three harmonics have been computed for six stations in the dry farming tract of India by using amplitude ratio and phase lag. In general, the combined effect of all these harmonics gives the values of K close to the order of the experimental values. It is found that the theory of simple heat conduction is not applicable to soil medium. While the lowest values of K in all the harmonics are found at Rajahmundry, the highest values are observed at either Hissar or Bhubaneshwar for the first two harmonics and at Pantnagar for the third harmonic. Strong annual and bi-annual cycles dominate at Hissar. Pantnagar and Bhubaneshwar while quarterly cycle is significant only at Pantnagar.

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Feng, Liqiang, and Hang Liu. "Attosecond source generation using polarized gating two-color field combined with unipolar pulse." Canadian Journal of Physics 94, no. 7 (July 2016): 651–58. http://dx.doi.org/10.1139/cjp-2015-0711.

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High-order harmonic generation and attosecond extreme-ultraviolet source generation have been theoretically investigated by controlling the two-color polarized gating field combined with the unipolar pulse. The results show that by properly optimizing the polarized two-color field as well as the unipolar pulse, not only is the harmonic cutoff remarkably extended, but the single short quantum path has also been selected to contribute to the harmonic spectrum, resulting in a 313 eV less modulated supercontinuum. Classical and quantum analyses are shown to explain the harmonic emission process. Finally, the proper superposition of harmonics, a series of isolated sub-50 as pulses, can be obtained.

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Fitzgerald, C. J., P. H. Taylor, R. Eatock Taylor, J. Grice, and J. Zang. "Phase manipulation and the harmonic components of ringing forces on a surface-piercing column." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 470, no. 2168 (August 8, 2014): 20130847. http://dx.doi.org/10.1098/rspa.2013.0847.

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A general phase-based harmonic separation method for the hydrodynamic loading on a fixed structure in water waves of moderate steepness is proposed. An existing method demonstrated in the experimental study described by Zang et al. (Zang et al. 2010 In Proc. Third Int. Conf. on Appl. of Phys. Modelling to Port and Coastal Protection. pp. 1–7.) achieves the separation of a total diffraction force into odd and even harmonics by controlling the phase of incident focused waves. Underlying this method is the assumption that the hydrodynamic force in focused waves possesses a Stokes-like structure. Under the same assumption, it is shown here how the harmonic separation method can be generalized, so that the first four sum harmonics can be separated by phase control and linear combinations of the resultant time-histories. The effectiveness of the method is demonstrated by comparisons of the Fourier transforms of the combined time-histories containing the harmonics of interest. The local wave elevations around the focus time are also visualized for the first three harmonics in order to reveal the local dynamics driving components within the wave force time-history.

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Suresh, D., G. Sravanthi, and R. Chander. "DSTATCOM with Improved LMS based IRP theory." E3S Web of Conferences 87 (2019): 01013. http://dx.doi.org/10.1051/e3sconf/20198701013.

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In this paper, grid connected DSTATCOM with three phase three wire has been proposed for harmonics elimination, reactive power compensation and active power injection into the grid. An improved instantaneous reactive power theory based on the least mean square is computed. The least mean square (LMS) algorithm is combined with instantaneous reactive power theory (IRPT) to improve its dynamics performance and eliminates the use of low pass filter requirement for computation of reference current. The harmonics component of the active power is estimated from LMS algorithm generated load harmonics currents. The performance characteristic of DSTATCOM is estimated with control scheme using computer simulation. The technique is based on the instantaneous transformation of instantaneous signals and taking advantage of the subsequent calculation of power from supply side to the loads. The neural network based method to estimate the harmonic online, DSTATCOM can compensate the harmonics. The computer simulation is carried out with MATLAB Simulink power system block sets.

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Blanco, Ana Maria, Sergey Yanchenko, Jan Meyer, and Peter Schegner. "Impact of supply voltage distortion on the current harmonic emission of non-linear loads." DYNA 82, no. 192 (August 25, 2015): 150–59. http://dx.doi.org/10.15446/dyna.v82n192.48591.

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Electronic devices have a non-linear characteristic and emit harmonics into the low voltage grid. Different harmonic studies analyze their impact on the grids based on different types of harmonic models. The most used model is the constant current source. Measurements have shown that the harmonic currents emitted by electronic devices depend on the circuit topology and the existing supply voltage distortion. This paper quantifies the impact of supply voltage distortion on the harmonic current emission of individual devices and the summation of multiple devices. After a classification of the commonly used circuit topologies a time-domain model is developed for each of them. Then the individual and combined impact of voltage harmonics on the harmonic current emission of the modeled devices is analyzed based on simulations. Finally the impact of voltage distortion on the summation of multiple devices is analyzed and the accuracy of constant current source models is evaluated.

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Feng, Liqiang, R. S. Castle, and Yi Li. "XUV pulse effect on harmonic emission spectra and attosecond pulse generation." Modern Physics Letters B 31, no. 34 (December 6, 2017): 1750282. http://dx.doi.org/10.1142/s0217984917502827.

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The generation of the high-order harmonic and the attosecond pulse from He atom driven by the near-infrared (NIR) field combined with the XUV pulse has been theoretically investigated by solving the three-dimensional time-dependent Schrödinger equation. The results show that by properly adding the XUV pulse into the NIR field, (i) not only the harmonic yield is enhanced, caused by the laser-induced excited state effect; but also the multi-cutoff extension of the harmonics can be found, caused by the absorption of the extra XUV photons during its recombination process. (ii) With the introduction of the XUV pulse, the frequency modulation of the high-order harmonic generation (HHG) can be found and controlled. (iii) By directly superposing the harmonics in the cutoff region, two isolated XUV pulses with the durations of 150 as can be obtained.

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Liu, Hang, and Liqiang Feng. "Theoretical exploration of harmonic emission and attosecond pulse generation from H2+ in the presence of terahertz pulse." Modern Physics Letters B 30, no. 17 (June 30, 2016): 1650226. http://dx.doi.org/10.1142/s0217984916502262.

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Harmonic generation spectra from H[Formula: see text] molecule ion driven by the chirped pulse combined with a terahertz (THz) pulse have been theoretically investigated by numerically solving the non-Born–Oppenheimer time-dependent Schrödinger equation (NBO-TDSE). The results show that with the introduction of the chirp, the harmonic cutoff is extended, resulting in a smooth supercontinuum. Further, when the initial vibrational state is prepared as [Formula: see text], and by properly adding a THz controlling pulse, the harmonic yield is enhanced by almost six orders of magnitude compared with the single chirped pulse case. Quantum analyses are shown to explain the harmonic extension and enhancement. Furthermore, through the investigation of the isotopic effect, we find that more intense harmonics are generated in the lighter nucleus. Finally, by properly superposing the harmonics, a series of intense 35 as XUV pulses can be obtained, which are almost six orders of magnitude improvement in comparison with the single chirped pulse case.

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Mager, P. N., and D. Yu Klimushkin. "On impulse excitation of the global poloidal modes in the magnetosphere." Annales Geophysicae 24, no. 10 (October 20, 2006): 2429–33. http://dx.doi.org/10.5194/angeo-24-2429-2006.

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Abstract. Through the combined action of the field line curvature and finite plasma pressure in some regions of the magnetosphere (plasmapause, ring current) there can exist global poloidal Alfvén modes standing both along field lines and across magnetic shells and propagating along azimuth. In this paper we investigate the spatio-temporal structure of such waves generated by an impulsive source. In general, the mode is the sum of radial harmonics whose structure is described by Hermitian polynomials. For the usually observed second harmonic structure along the background field, frequencies of these radial harmonics are very close to each other; therefore, the generated wave is almost a monochromatic oscillation. But mixing of the harmonics with different radial structure causes the evolution of the initially poloidal wave into the toroidal one. This casts some doubts upon the interpretation of observed high-m poloidal waves as global poloidal modes.

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Wang, Lu, Yiming Zhang, and Xuhong Wang. "Combined feed-forward control strategy for LCL-type grid-connected inverters." Journal of Physics: Conference Series 2354, no. 1 (October 1, 2022): 012002. http://dx.doi.org/10.1088/1742-6596/2354/1/012002.

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Abstract LCL-type grid-connected filter circuits are widely used for line network transmission because of their high ability to suppress current harmonics. However, due to the presence of resonance points in this third-order circuit, the system can generate severe oscillations. In order to improve power quality, a combined feed-forward factor control strategy is proposed in this paper. The control system introduces a combined feed-forward factor and incorporates the idea of dual PI control to ensure that the order of the system is reduced while improving its stability, followed by a detailed derivation of the constraint equations for each link parameter. The simulation verifies that the control scheme can regulate the output voltage of the line network and effectively reduce the harmonic content of the line network, providing a reference for reducing the harmonic content of grid-connected currents in engineering.

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Li, Yi, R. Liqiang Feng, and Yan Qiao. "Improvement of harmonic spectra from superposition of initial state driven by homogeneous and inhomogeneous combined field." Canadian Journal of Physics 98, no. 2 (February 2020): 198–209. http://dx.doi.org/10.1139/cjp-2019-0002.

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A larger harmonic cutoff with a higher harmonic yield is a necessary requirement for producing intense ultrashort extreme ultraviolet (XUV) and X-ray sources. In this paper, we present a potential method to improve the harmonic cutoff and harmonic yield from the superposition of initial states in the He atom driven by the low-intensity homogeneous and inhomogeneous combined field. The results can be separated into two parts, that is, (i) the extension of harmonic cutoff via the optimization of three-color homogeneous and inhomogeneous field (covering the carrier envelope phase, delay time, intensity ratio, and inhomogeneous effect); and (ii) the enhancement of harmonic yield via the superposition of ground state and excited state as the initial state. Consequently, a water window harmonic plateau with an intensity enhancement of six orders of magnitude can be obtained. Moreover, the harmonic plateau is contributed by a single harmonic emission peak. Finally, through the Fourier transformation of some selected harmonics on the spectral continuum, a number of sub-50 as water window attosecond pulses with the intensity enhancement of six orders of magnitude can be obtained.

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DAHDOUH, ADEL, SAID BARKAT, and AISSA CHOUDER. "A Combined Sliding Mode Space vector Modulation Control of the Shunt Active Power Filter Using Robust Harmonic Extraction Method." Algerian Journal of Signals and Systems 1, no. 1 (February 1, 2021): 37–46. http://dx.doi.org/10.51485/ajss.v1i1.17.

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This paper presents a combined sliding mode space vector modulation control of the shunt active power filter using robust harmonic extraction method to improve the power quality such as current harmonics and reactive power compensation due to the non-linear loads and unbalanced voltage source. To verify the validity of the analysis and the feasibility of the proposed control method a set of simulation tests have been conducted using Matlab/Simulink. A comparison between the conventional instantaneous powers method (PQ) used for harmonic extracting and the new PQ based on a multivariable extraction filter demonstrates the superiority of the proposed control scheme.

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Gramazio, Federico, Matteo Lorenzoni, Francesc Pérez-Murano, Enrique Rull Trinidad, Urs Staufer, and Jordi Fraxedas. "Functional dependence of resonant harmonics on nanomechanical parameters in dynamic mode atomic force microscopy." Beilstein Journal of Nanotechnology 8 (April 19, 2017): 883–91. http://dx.doi.org/10.3762/bjnano.8.90.

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We present a combined theoretical and experimental study of the dependence of resonant higher harmonics of rectangular cantilevers of an atomic force microscope (AFM) as a function of relevant parameters such as the cantilever force constant, tip radius and free oscillation amplitude as well as the stiffness of the sample’s surface. The simulations reveal a universal functional dependence of the amplitude of the 6th harmonic (in resonance with the 2nd flexural mode) on these parameters, which can be expressed in terms of a gun-shaped function. This analytical expression can be regarded as a practical tool for extracting qualitative information from AFM measurements and it can be extended to any resonant harmonics. The experiments confirm the predicted dependence in the explored 3–45 N/m force constant range and 2–345 GPa sample’s stiffness range. For force constants around 25 N/m, the amplitude of the 6th harmonic exhibits the largest sensitivity for ultrasharp tips (tip radius below 10 nm) and polymers (Young’s modulus below 20 GPa).

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Quy, Do Ngoc, Do Ba Phu, and Nguyen Kien Trung. "The new approach minimizes harmonics in a single-phase three-level NPC 400 Hz converter for airplanes." International Journal of Power Electronics and Drive Systems (IJPEDS) 12, no. 3 (September 1, 2021): 1738. http://dx.doi.org/10.11591/ijpeds.v12.i3.pp1738-1750.

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This paper provides a new approach to reducing high-order harmonics in 400 Hz inverter using a three-level neutral-point clamped (NPC) converter. A voltage control loop using the harmonic compensation combined with NPC clamping diode control technology. The capacitor voltage imbalance also causes harmonics in the output voltage. For 400 Hz inverter, maintain a balanced voltage between the two input (direct current) (DC) capacitors is difficult because the pulse width modulation (PWM) modulation frequency ratio is low compared to the frequency of the output voltage. A method of determining the current flowing into the capacitor to control the voltage on the two balanced capacitors to ensure fast response reversal is also given in this paper. The combination of a high-harmonic resonator controller and a neutral-point voltage controller working together on the 400 Hz NPC inverter structure is given in this paper.

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Feng, Liqiang, and Wenliang Li. "Carrier envelope phase measurement of multi-cycle mid-infrared field and its application on attosecond pulse generation." Canadian Journal of Physics 96, no. 5 (May 2018): 501–12. http://dx.doi.org/10.1139/cjp-2017-0069.

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A method for the carrier envelope phase (CEP) measurement of the multi-cycle mid-infrared field has been theoretically presented by using the CEP dependence of the harmonic cutoffs. It shows that by properly adding a CEP-known few-cycle near-infrared pulse to the multi-cycle mid-infrared field, the CEP dependence of the harmonic cutoffs from the combined field become much more distinct in comparison with those from the single mid-infrared field, which provides a route to a new CEP measurement technique. Further, by properly controlling the combined field, three supercontinua of 230, 242, and 266 eV with less modulation can be obtained. Finally, by selecting the generated harmonics, a series of sub-35 as pulses in the X-rays region can be produced.

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Pineda Allen, Juan Carlos Pineda, and Ching Tai Ng. "Mixing of Non-Collinear Lamb Wave Pulses in Plates with Material Nonlinearity." Sensors 23, no. 2 (January 8, 2023): 716. http://dx.doi.org/10.3390/s23020716.

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Guided waves have been extensively studied in the past few years, and more recently nonlinear guided waves have attracted significant research interest for their potential for early damage detection and material state characterization. Combined harmonic generation due to wave mixing can offer some advantages over second harmonic generation. However, studies focused on Lamb wave mixing are still very limited, and have mainly focused on collinear wave mixing and used plane wave assumption. In this paper, numerical simulations and experiments are conducted to understand the interaction of mixing non-collinear Lamb wave pulses with non-planar wavefronts. The results demonstrate that the generated secondary wave is cumulative under internal resonance conditions and the sum-frequency component of the combined harmonics is useful for characterizing material nonlinearities.

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Liu, Hang, and Li-Qiang Feng. "Selection of Single Harmonic Emission Peak for Producing Isolated Attosecond Pulse via Chirped-UV Combined Field." Zeitschrift für Naturforschung A 75, no. 1 (December 18, 2019): 1–10. http://dx.doi.org/10.1515/zna-2019-0220.

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AbstractA potential method to produce isolated attosecond pulses (IAPs) by using low-intensity chirped-UV combined field has been investigated. The results can be separated into three parts. First, by properly introducing the mid-chirp or down-chirp of the low-intensity laser field, the harmonic cutoff can be extended and achieve the referenced value, which is produced from the high-intensity referenced field. Moreover, the spectral continuum is contributed by a single harmonic emission peak, which is beneficial to produce IAPs. However, the harmonic yield is very low due to the lower driven laser intensity. Second, by properly adding a UV pulse, the harmonic yield can be enhanced and achieve the referenced value due to the UV resonance ionisation. The intensity of the combined field is lower than that of the referenced field, which reduces the experimental requirements for producing high-intensity spectral continuum. Third, with the introduction of the positive or negative inhomogeneous effect of the mid-chirped combined field or down-chirped combined field, respectively, the similar harmonic cutoff and harmonic yield can also be obtained but with a much lower driven laser intensity. Finally, by superposing the harmonics on the spectral continuum, the IAPs with the durations of sub-38 as can be obtained.

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Benedetto, Marco di, Mi Tang, Alessandro Lidozzi, Luca Solero, Andrea Formentini, and Pericle Zanchetta. "Resonant and a new disturbance-observer combined control for off-grid voltage source inverter." International Journal of Power Electronics and Drive Systems (IJPEDS) 13, no. 1 (March 1, 2022): 223. http://dx.doi.org/10.11591/ijpeds.v13.i1.pp223-236.

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This paper presents a new control strategy based on the combination between the resonant controller and the disturbance-observer (RSCDO) for stand-alone four-leg Voltage Source Inverter (VSI). The aim of the new controller is to regulate the inverter output voltage, reducing as much as possible the voltage Total Harmonic Distortion (THDv) in every load condition. The resonant controller allows to adjust the output voltage fundamental harmonic, whereas the disturbance observer is designed for compensating output voltage harmonics when non-linear loads have to be fed. The proposed control strategy has been tested using a 40 kVA three-phase 4-leg VSI and a dedicated control board, which uses the National Instruments System-on-Module sbRIO-9651. Experimental results demonstrate good behavior of the RSCDO controller to reject the disturbance in the output voltage, as well as a good dynamic response.

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Ray, R. N., D. Chatterjee, and S. K. Goswami. "Reduction of voltage harmonics using optimisation-based combined approach." IET Power Electronics 3, no. 3 (2010): 334. http://dx.doi.org/10.1049/iet-pel.2008.0299.

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Vlasov, R. A., and E. V. Doktorov. "Harmonics generated by solitons in a combined nonlinear medium." Journal of Applied Spectroscopy 58, no. 3-4 (March 1993): 229–33. http://dx.doi.org/10.1007/bf00662685.

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Chioreanu, Calin. "Upon Power Loses due to Current Harmonics in a Fotovoltaic System, Opperating at Maximum Power Point." Advanced Materials Research 853 (December 2013): 352–57. http://dx.doi.org/10.4028/www.scientific.net/amr.853.352.

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Photovoltaic panels (PF), combined with lead-acid battery (AE), are increasingly used, to produce electricity. To work in maximum power points, between (PF) and (AE) is interposed a static converter (DC-DC), which is a harmonic pollution source. Within the paper there are calculated the power losses, due to current harmonics, of a photovoltaic system working at its maximum power. Photovoltaic system works at its maximum power, if in the electronic system there is permanently voltage control among solar battery terminals.

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Liu, Meng Qi, Li Zhang, Jie Lou, Liang Zou, and Tong Zhao. "A Novel Method of Core Saturation Suppression for the AC+DC Distribution Network Transformer." Advanced Materials Research 960-961 (June 2014): 680–83. http://dx.doi.org/10.4028/www.scientific.net/amr.960-961.680.

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With the rapid development of smart grids, the interconnection between the grid and distributed renewable energy is the inevitable trend of future study. Because of the existence of the DC source in the combined AC-DC distribution network, the transformer iron core is easily saturated generating lots of harmonics and increasing the loss of the transformer. This paper presents a novel method based on inductive filtering technology of core saturation suppression of the transformer in the combined AC-DC distribution network, this novel method can suppress the harmonics caused by the flux saturation and forbid the harmonics intruding into the ac grid. In the end we build the simulation model to prove the correctness and practicability of this novel method.

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Munir, Hafiz, Jianxiao Zou, Chuan Xie, and Josep Guerrero. "Cooperation of Voltage Controlled Active Power Filter with Grid-Connected DGs in Microgrid." Sustainability 11, no. 1 (December 29, 2018): 154. http://dx.doi.org/10.3390/su11010154.

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Due to the excessive use of nonlinear loads and inverter interfaced distributed generators, harmonic issues have been regarded as a major concern in power distribution systems. Therefore, harmonic compensation in microgrids is a subject of current interest. Consequently, a novel direct harmonic voltage-controlled mode (VCM) active power filter (APF) is proposed to mitigate the harmonics in a cooperative manner and provide a better harmonic compensation performance of less than 5%. Due to the dispersive characteristics of renewable energy resources, voltage feedback based on a harmonic compensation control loop is implemented for the first time. This system can be smoothly combined with the current control loop. Our method proposes a better performance while mitigating the harmonics in comparison with conventional resistive active power filters (R-APF). Based on direct voltage detection at the point of common coupling (PCC), the proposed VCM-APF can therefore be seamlessly incorporated with multiple grid-connected generators (DGs) to enhance their harmonic compensation capabilities. The advantage of this scheme is that it avoids the need for designing and tuning the resistance, which was required in earlier conventional control schemes of R-APF for voltage unbalance compensation. Additionally, our scheme does not require the grid and load current measurements since these can be carried out at the PCC voltage, which further reduces the implementation cost of the system. Furthermore, the simulation results show the significance of proposed method.

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Zhang, Kai Tuo, and Ming Li. "EMD Analysis of Power Harmonics." Advanced Materials Research 706-708 (June 2013): 1331–34. http://dx.doi.org/10.4028/www.scientific.net/amr.706-708.1331.

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It can obtain intrinsic mode function (IMF) of signal wave with empirical mode decomposition (EMD) in harmonic analysis of power system. Harmonic frequency, amplitude and duration can be obtained through analysis of IMFs. Through EMD analysis on distortion waveform of single-phase AC inverter output as an example, combined with applied scene of distorted voltage, cause of distortion waveform can be deduced. The result shows that EMD analysis on non-stationary signals is of good performance, and a new substitute method of FFT transform in harmonic analysis.

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Barmpatza, Alexandra C., and Joya C. Kappatou. "Study of a Combined Demagnetization and Eccentricity Fault in an AFPM Synchronous Generator." Energies 13, no. 21 (October 27, 2020): 5609. http://dx.doi.org/10.3390/en13215609.

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This article investigates the combined partial demagnetization and static eccentricity fault in an Axial Flux Permanent Magnet (AFPM) Synchronous Generator. The machine is simulated using 3D FEM, while the EMF spectrum is analyzed in order to export the fault related harmonics using the FFT analysis. Firstly, the partial demagnetization fault, without the coexistence of eccentricity, and both the static angular and axis eccentricity faults, without the coexistence of partial demagnetization, are studied. In the case of eccentricity fault, the phase EMF sum spectrum has also been used as a diagnostic mean, because, when only eccentricity fault exists in the generator (either angular or axis) new harmonics do not appear in the EMF spectrum. Secondly the combination of partial demagnetization fault with static axis and static angular eccentricity is investigated and different comparisons are made when the demagnetization and the eccentricity level changes. The investigation revealed that the combination of eccentricity and demagnetization creates new harmonics in the EMF spectrum. The novelty of the article is that these combined faults are studied for the first time in the international literature, and the phase EMF sum spectrum has not been previously used for eccentricity diagnosis in this machine type.

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Kumar, Deepak, and Kalpana Chaudhary. "High Efficiency Harmonic Harvester Rectenna for Energy Storage Application." International Journal of Power Electronics and Drive Systems (IJPEDS) 9, no. 1 (March 1, 2018): 252. http://dx.doi.org/10.11591/ijpeds.v9.i1.pp252-259.

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This work presents harmonic harvester Rectenna integrated power management circuitry for improving RF-DC power conversion efficiency. The circuitry is developed for battery charging or energy storage application; resistance emulation method is used to realize a matching load resistance at output terminals. The proposed technique is useful for harvesting near maximum output power from the dual rectifiers (fundamental and harmonics) independently. Also, it delivers the combined maximal power to the energy storage cell. The power management module based on dual input buck-boost converter with simple open loop control is utilized.

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Gupta, Naveen. "Second harmonic generation of q-Gaussian laser beam in plasma channel created by ignitor heater technique." Laser and Particle Beams 37, no. 2 (April 26, 2019): 184–96. http://dx.doi.org/10.1017/s0263034619000193.

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AbstractThis paper presents a scheme for second harmonic generation (SHG) of q-Gaussian laser beam in plasma channel created by ignitor heater technique. The ignitor beam creates plasma by tunnel ionization of air. The heater beam heats the plasma electrons and establishes a parabolic density profile. The third beam (q-Gaussian beam) is guided in this plasma channel under the combined effects of density nonuniformity of the plasma channel and relativistic mass nonlinearity of the plasma electrons. The propagation of q-Gaussian laser beam through the plasma channel excites an electron plasma wave at pump frequency that interacts with the incident laser beam to produce its second harmonics. The formulation is based on finding the numerical solution of the nonlinear Schrodinger wave equation for the fields of the incident laser beams with the help of moment theory approach. Particular emphasis is put on dynamical variations of the spot size of the laser beams and conversion efficiency of the second harmonics with distance of propagation.

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Alghamdi, Sultan, Hatem F. Sindi, Ahmed Al-Durra, Abdullah Ali Alhussainy, Muhyaddin Rawa, Hossam Kotb, and Kareem M. AboRas. "Reduction in Voltage Harmonics of Parallel Inverters Based on Robust Droop Controller in Islanded Microgrid." Mathematics 11, no. 1 (December 29, 2022): 172. http://dx.doi.org/10.3390/math11010172.

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In this article, a distributed control scheme to compensate for voltage harmonics in islanded microgrids is presented, where each distributed generation (DG) source has a primary control level and a secondary control level. In addition to the voltage and current control loops, the primary control level of DGs includes virtual impedance control loops in the main and harmonic components, which are responsible for dividing the power of the main component and the non-main component (harmonic) between the DGs of the microgrid, respectively. For coordinated operation between the inverters when facing the islanding phenomenon, it is very beneficial to use a droop controller structure. Here, the traditional droop controller is modified in such a way that the power is proportionally divided between the DGs, which causes accurate voltage regulation at the output of the DGs. By presenting a model for the inverter connected to the nonlinear load, a harmonic droop controller is designed. Through the droop controller related to each harmonic, the harmonic voltages are calculated and added to the reference voltage, which improves the quality of the output voltage. Then, the inverter voltage control loop is modified with resistive impedance in the presence of nonlinear loads in such a way that, when combined with the harmonic droop controller, the total harmonic distortion (THD) of the output voltage is significantly reduced. Lastly, the proposed method is implemented on the microgrid through MATLAB software, and the results show the ability of the proposed method to reduce voltage harmonics in the parallel operation of inverters.

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Kildishev, A. V., S. A. Volokhov, and P. N. Dobrodejev. "The Transformation of Spatial Harmonics in a Combined Electromagnetic Shield." IEEE Transactions on Magnetics 40, no. 4 (July 2004): 3072–74. http://dx.doi.org/10.1109/tmag.2004.832362.

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Infield, D. G. "Combined switching harmonics from multiple grid-connected single-phase inverters." IEE Proceedings - Generation, Transmission and Distribution 148, no. 5 (2001): 427. http://dx.doi.org/10.1049/ip-gtd:20010434.

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Liu, H., L. Q. Feng, and R. M. Sani. "Effects of inhomogeneous laser field in time and space on the generation of broad spectral continuum and ultrashort attosecond pulse." Modern Physics Letters B 34, no. 13 (February 28, 2020): 2050131. http://dx.doi.org/10.1142/s0217984920501316.

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The inhomogeneous effects of laser field in time and space on the generations of high-order harmonic spectra and attosecond pulses from He atom have been investigated with the assistance of the frequency-chirping technique and the metallic nanostructure. We find that in different combinations of chirps and spatial inhomogeneous effects, not only can the harmonic cutoff be extended, but the single harmonic emission peak (HEP) can also be selected to contribute to the spectral continuum. In detail, with the combinations of (i) symmetric chirp in frequency and positive inhomogeneous effect in space or (ii) asymmetric down chirp in frequency and negative inhomogeneous effect in space, two broad spectral continua with bandwidths of 496 eV and 480 eV can be obtained. Further, by properly adding IR or UV controlling pulse, the harmonic emission efficiency can be enhanced by several orders of magnitude. The enhancement of harmonic yield from adding UV pulse is higher than that from adding IR pulse. Moreover, the difference of harmonic enhancement between UV combined field and IR combined field is much more obvious at lower controlling laser intensity. Through analyzing the ionization probability, we find that the higher enhancement of harmonic yield from UV combined field is because of UV-resonance-enhancement-ionization between the ground state and the excited state of He atom. Finally, by properly superposing some harmonics, a number of attosecond pulses with pulse durations of 45 as can be obtained.

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Dahdouh, Adel, Lakhdar Mazouz, and Brahim Elkhalil Youcefa. "PIL Implementation of Feedback Linearisation-SVM Control of 3-Phase Multifunctional Grid-Tied Solar PV Integrated UPQC." Journal Européen des Systèmes Automatisés 55, no. 3 (June 30, 2022): 307–22. http://dx.doi.org/10.18280/jesa.550303.

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In this paper, an implementation of a feedback linearisation-based on SVM control of a multifunctional unified power quality conditioner (UPQC) combined with a photovoltaic generator (PVG) using STM32F429I-DISC DSP board has been presented. Further, The PVG-UPQC is acting as a universal conditioner for power quality enhancement and renewable energy integration simultaneously with harmonics reduction in both grid voltage and current. Furthermore, the system can also compensate reactive power in presence of nonlinear loads. The presented system is made up of a shunt active power filter which acts as a current harmonics compensator in addition to a series filter that compensates voltage harmonics and fluctuations such as voltage sag/swell. In order to enhancing the PVG-UPQC performances, a nonlinear feedback linearisation control technique combined with SVM controller is applied. The performance of the suggested control scheme is validated by extensive PIL co-simulation technique. The obtained results prove the high performances and reliability of the presented system in the case of nonlinear load variations as well as eliminating voltage and current harmonics. These results accomplish the superiority and effectiveness of those obtained by a compared to a conventional PI controller.

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Song, Peng Fei, Jian Sheng Zhang, and Yong Hua Zhang. "Harmonic Detection Based on Genetic BP Neural Network." Applied Mechanics and Materials 427-429 (September 2013): 1892–95. http://dx.doi.org/10.4028/www.scientific.net/amm.427-429.1892.

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In view of the grid has a large number of harmonics, serious interference power quality, but the existing harmonic detection has many disadvantages, this paper uses genetic algorithm to optimize the BP neural network (GA-BP),Combined with fanaticism, independent component technique in the separation technology, achieve rapid separation and accurate fitting for harmonic reduction. The method to solve the problem of slow convergence speed of BP neural network and easier to fall into local optimal solution; Separation, independent component analysis in the signal could not accurate reduction the source signal. In this paper a signal containing harmonic component are simulated. Results show that GA-BP neural network optimization independent component analysis has convergence speed, high precision, compared with the single BP neural network and the independent component analysis of the superiority.

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CHENNAI, Salim. "Shunt Active Power Filter Performances based on Seven-level NPC Inverter using Fuzzy and LS-PWM Control Scheme." Electrotehnica, Electronica, Automatica 70, no. 1 (March 15, 2022): 23–30. http://dx.doi.org/10.46904/eea.22.70.1.1108003.

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This paper presents novel seven-level neutral point clamped (npc) shunt active power filter system based on LS-PWM and fuzzy control approaches which can eliminate current harmonics generated by nonlinear loads. Today, multi-level inverters are strongly used in the medium and high voltage applications; their advantages are low harmonic distortions, low switching losses, low electromagnetic interference, and low acoustic noise. Second, fuzzy logic techniques have been successfully employed in several power electronic applications. Fuzzy controller does not need an accurate mathematical model, can work with imprecise inputs, can handle non-linearity, and are more robust than conventional controllers. To benefit from these advantages a novel control scheme for seven-level (npc) inverter based on Fuzzy and LS-PWM technique is proposed. The reference current signals required to compensate harmonic currents use the synchronous current detection method, this technique is easy to implement and achieves good performances for harmonic compensation. The proposed shunt APF is evaluated using Matlab-Simulink software and SimPowerSystem Toolbox under transient and steady state for various operation conditions. The simulation results show the effectiveness of the proposed shunt active filter based on seven-level (NPC) inverter for improving the power quality and the superiority of combined fuzzy and LS-PWM control scheme to conventional controller in term of harmonics compensation and dynamic performances.

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Peng, Jin Jie, and Xiao Ping Fan. "Simulating Research on a New Current Controlling Method." Advanced Materials Research 354-355 (October 2011): 1016–21. http://dx.doi.org/10.4028/www.scientific.net/amr.354-355.1016.

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A new current detecting algorithm is proposed in the paper, which is applied in an improved hybrid active power filter. The filter equipment can be applied in high voltage system to suppress harmonics and compensate reactive power. The topology and filtering principle of the filter equipment is given. The harmonic suppressing function is adopted to analyze the influence by the grid impedance, quality factor and losing resonance of the resonance circuit. The feasibility of the proposed system is validated in theory. A single-phase current detecting method is also proposed. The corresponding current control is formed combined the DC-link current detecting method. The simulating results prove that the system is feasibility and the current control is validity. Harmonic and reactive power are suppressed well.

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Kim, Sungtae, Yangjin Kim, Naohiko Sugita, and Mamoru Mitsuishi. "Surface Assessment of Transparent Glass Plate with Wavelength-Modulated Interferometry and Harmonic Phase-Iterative Method." International Journal of Precision Engineering and Manufacturing-Smart Technology 1, no. 1 (January 1, 2023): 71–81. http://dx.doi.org/10.57062/ijpem-st.2022.0059.

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Multiple reflections and nonlinearity of phase modulating need to be compensated to accurately profile the surface of the glass plate using wavelength-modulated interferometry. In this study, to assess the glass plate surface using wavelength-modulated interferometry, a new phase-iterative method insensitive to the harmonic signals and nonlinear errors was developed. We developed the harmonic phase-iterative method by combining the phase-iterative method with irradiance signal considering the harmonic components. Moreover, for suppression of the harmonic-related errors in the iterative calculation, the noble pixel-selection technique and convergence formula were combined with the phase-iterative method. For estimation of the developed iterative method, we conducted the numerical simulation and assessed the glass plate surface with the Fizeau interferometer. The simulation and assessment results demonstrated that the proposed method could perform phase extraction with improved iterative calculation and suppression of the effects of the harmonics and nonlinearity.

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Zubiaga, Markel, Alain Sanchez-Ruiz, Eneko Olea, Eneko Unamuno, Aitor Bilbao, and Joseba Arza. "Power Capability Boundaries for an Inverter Providing Multiple Grid Support Services." Energies 13, no. 17 (August 20, 2020): 4314. http://dx.doi.org/10.3390/en13174314.

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It is getting more common every day to install inverters that offer several grid support services in parallel. As these services are provided, a simultaneous need arises to know the combined limit of the inverter for those services. In the present paper, operational limits are addressed based on a utility scale for a real inverter scenario with an energy storage system (ESS) (1.5 MW). The paper begins by explaining how active and reactive power limits are calculated, illustrating the PQ maps depending on the converter rated current and voltage. Then, the effect of the negative sequence injection, the phase shift of compensated harmonics and the transformer de-rating are introduced step-by-step. Finally, inverter limits for active filter applications are summarized, to finally estimate active and reactive power limits along with the harmonic current injection for some example cases. The results show that while the phase shift of the injected negative sequence has a significant effect in the available inverter current, this is not the case for the phase shift of injected harmonics. However, the amplitude of the injected negative sequence and harmonics will directly impact the power capabilities of the inverter and therefore, depending on the grid-side voltage, it might be interesting to design an output transformer with a different de-rating factor to increase the power capabilities.

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Sreedhar, T., and K. Udhayakumar. "Negative Harmonics Injection Cuddled Equal Area Criteria Based Selective Harmonic Elimination Pulse Width Modulation Techniques for Multilevel Cascaded Inverters." Journal of Computational and Theoretical Nanoscience 13, no. 10 (October 1, 2016): 7564–73. http://dx.doi.org/10.1166/jctn.2016.5754.

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Selective Harmonics Elimination (SHE) technique of power electronic converters can be generally defined as calculation of the optimized switching angles at any desired output (fundamental) voltage component to eliminate a set of preferred lower order harmonic components. This low switching frequency method adds values to Multilevel Inverter (MLI) based systems for the reason that MLI’s have the ability to synthesize waveforms closer to sinusoidal with a better harmonics spectrum. The traditional method for finding the optimized switching angles is by solving the Fourier non-linear transcendental equations of the MLI output voltage and various algorithms like Newton-Raphson (NR) algorithm, Genetic algorithm (GA), Resultant theory, Walsh function etc. are available. This paper proposes a novel approach for performing SHE in MLI working with both equal and unequal dc voltages. The basic principle in which the proposed technique works is a combined effect of equal area criteria and negative harmonics injection techniques. The major advantage is that the proposed methodology comprises of four simple equations for performing SHE instead of solving the complex non-linear transcendental equation. The computational efficiency of this algorithm is evaluated through comparison with traditional NR and GA. In addition, a prototype of three-phase seven-level cascaded MLI is designed through which several informative results are investigated and the effectiveness of the proposed algorithm is proved.

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Zhong, Lihua, Xiaolan Qiu, Bing Han, and Yuxin Hu. "An Improved Descalloping Method Combined With Imaging Parameters for GaoFen-3 ScanSAR." Remote Sensing 12, no. 5 (March 3, 2020): 822. http://dx.doi.org/10.3390/rs12050822.

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Due to the specific working mechanism of alternately transmitting and receiving signals between multiple adjacent swaths, scanning synthetic aperture radar (ScanSAR) will cause periodical wavelike modulation of the intensity image along azimuth direction, which is known as scalloping. Conventional descalloping methods are achieved by proper azimuth antenna pattern (AAP) correction and multi-looking techniques but are limited by the accuracy of Doppler centroid estimating and the thermal noise. Another type of method extracts and suppresses the scalloping texture on the image, but the scanning parameters of ScanSAR are insufficiently considered. The period of scalloping on the image is related to the period of switching between subswathes. While the harmonics can be calculated by the period of a periodic signal, an improved frequency filtering method combined with imaging parameters is proposed. The scalloping modulation model of ScanSAR combined with imaging parameters is constructed, and the harmonics of scalloping texture are accurately calculated and filtered. For the low signal to noise ratio (SNR) image, the antenna pattern is modified according to SNR to avoid scalloping caused by noise. For non-uniform scenes, scalloping suppression is achieved by using the scalloping features acquired by uniform scenes. To separate the non-uniform scenes from uniform scenes, we still use the characteristics of harmonics caused by scalloping. Our descalloping method achieves accurate suppression of scalloping without sea-land segmentation and ship mask and the residual scalloping is reduced from 1.0 to 0.3–0.5 dB. The residual scalloping and statistical characteristics of the image are analyzed to demonstrate the effectiveness of the proposed method.

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Feng, Liqiang, and Hang Liu. "High-intensity attosecond X-ray source generation by using low-intensity spatial inhomogeneous mid-infrared pulse combined with an ultraviolet pulse." International Journal of Modern Physics B 31, no. 01 (January 10, 2017): 1650239. http://dx.doi.org/10.1142/s0217979216502398.

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We theoretically investigate the high-order harmonic spectra and the attosecond pulse generation from He[Formula: see text] ion driven by the spatial inhomogeneous combined field, consisting of a two-color low-intensity mid-infrared pulse ([Formula: see text] W/cm2) and an ultraviolet (UV) pulse ([Formula: see text] W/cm2). The numerical results show that due to the spatial inhomogeneous effect, the harmonic cutoffs are remarkably extended, and a 986 eV super-continuum can be obtained. Further with the proper introduction of an UV pulse (from 60 nm to 20 nm) to the two-color field, the harmonic yields are enhanced, especially for adding the 30 nm pulse case, a 1113 eV super-continuum (corresponding to a 34.1 dB enhanced field) with less harmonic modulation and six orders of magnitude enhancement can be obtained. Similar calculations have been performed for He atom and an 896 eV super-continuum with four orders of magnitude enhancement can be produced. Time–frequency harmonic distribution and time-dependent electron populations show that the single short quantum path contribution is responsible for the less harmonic modulation and the laser-induced electron excitation is responsible for the harmonic enhancement. Finally, by properly superposing the harmonics, a series of sub-50-as pulses including the whole X-ray region with 3–6 orders of magnitude enhancement can be obtained.

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Afrasiabi, Morteza, and Esmaeel Rokrok. "An Improved Centralized Control Structure for Compensation of Voltage Distortions in Inverter-Based Microgrids." Energies 11, no. 7 (July 17, 2018): 1862. http://dx.doi.org/10.3390/en11071862.

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Recently, increased use of non-linear loads has intensified the harmonic distortion and voltage unbalance in distribution systems. Inverter Based Distributed Generators (IBDGs) can be employed as distributed compensators to improve the power quality, as well as to supply distribution systems. In this paper, an enhanced hierarchical control scheme for the compensation of voltage disturbance in an AC Micro Grid (MG) that includes of two control levels is proposed. The secondary control level is performed by a centralized controller. Data of voltage harmonics and voltage unbalance at the MG Sensitive Load Bus (SLB) is sent to the centralized controller by a measurement unit. A general case with a combined voltage harmonic and unbalance distortion is considered. The compensation coefficients for IBDG units are computed by the centralized controller, and reference commands are sent to the local controllers of the IBDG units that act as a primary level of control. In the secondary control level, harmonic analysis is performed for the MG in order to provide a guide for properly assigning the harmonics and unbalance compensation priorities to IBDGs at different locations in the distribution system. Some buses have more participation in exciting the MG resonance modes; therefore, larger harmonic compensation factors are considered for the IBDGs that are near to these buses. For other IBDGs, the voltage unbalance compensation factor is selected bigger. The control system of the IBDGs mainly includes a current controller, a virtual damping resistor loop, and a load compensation block. Effectiveness of the proposed control scheme is demonstrated through simulation studies.

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Zhang, Hua, Sheng Li, Xi Jing Jing, Yang Zhang, Teng Jiao, Peng Fei Zhang, Hao Lv, et al. "A Separation Technology for Biological Radar Signals of Respiration and Heartbeat." Applied Mechanics and Materials 411-414 (September 2013): 1564–68. http://dx.doi.org/10.4028/www.scientific.net/amm.411-414.1564.

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This research aimed to separate the signals of respiration and heartbeat effectively from the biological radar echo signals of vital signs detecting platform. Therefore the characteristics parameters of the respiration and heartbeat could be extracted to provide the basis for clinical diagnosis and disease prevention. This paper put forward a separation algorithm of heartbeat and respiration based on LMS adaptive harmonic cancellation, the combined harmonics of the breathing signal was regarded as a reference input signal of the adaptive filter to improve the algorithm. Related experiments were designed to conduct filter processing. Results show that the algorithm proposed proved to be more effective in the signals separation of respiration and heartbeat.

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Bolaño Martínez, Adrián, Isaac Jimenez Navarro, Vladimir Sousa Santos, Enrique Ciro Quispe, and Pablo Daniel Donolo. "MATLAB/Simulink modeling of electric motors operating with harmonics and unbalance." International Journal of Electrical and Computer Engineering (IJECE) 12, no. 5 (October 1, 2022): 4640. http://dx.doi.org/10.11591/ijece.v12i5.pp4640-4648.

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This paper aims to present a simulation model for the analysis of the operational characteristics of electric motors (EMs). The model was developed on the Simulink platform of the MATLAB program and allows analysis in supply conditions with harmonics and voltage unbalance. The contribution of the model is that it considers the mechanical losses and provides for the study of the effect of each component of the electrical sequence of the harmonics and the voltage unbalance on the electromechanical characteristics of the EM. The model developed was tested in a 37.3 kW EM, operating under four power supply conditions: balanced sinusoidal voltages, balanced non-sinusoidal voltages (i.e., harmonics), unbalanced sinusoidal voltages, and non-sinusoidal unbalanced voltages. The results showed that under the conditions of harmonics and unbalance, the efficiency was reduced by 2%, respectively and that with the combined effects, the efficiency decreased by 4%. The results made it possible to quantify, from the current, voltage, and electrical power values of each sequence, the adverse effects caused by voltage unbalance and harmonics.

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Dahdouh, Adel, Lakhdar Mazouz, and Brahim Elkhalil Youcefa. "Nonlinear Predictive Direct Power Control Based on Space Vector Modulation of 3-Phase 3-Level Solar PV Integrated Unified Power Quality Conditioner." European Journal of Electrical Engineering 24, no. 2 (April 30, 2022): 77–88. http://dx.doi.org/10.18280/ejee.240202.

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This paper presents a hybrid feedback linearisation-based predictive direct power control strategies of the unified power quality conditioner (UPQC) combined with a photovoltaic generator (PVG) using space vector modulation technique for power quality enhancement. The PVG-UPQC is acting as a universal conditioner for power quality enhancement and renewable energy integration simultaneously, and it mitigates harmonics in both voltage and current caused by nonlinear loads in addition to reactive power compensation. The PVG-UPQC is made up of a dc bus powered by the photovoltaic generator that connects shunt and series active power filters. The shunt filter functions as a current source and compensates for current harmonics. The series filter compensates for voltage harmonics and fluctuations such voltage sag/swell by acting as a voltage source. In order to enhance the performances of PVG-UPQC, a hybrid control method based on FL -PDPC combined with a three-level SVM controller is proposed. The aims are to deliver compensation signals faster and more accurately under a variety of load conditions, as well as eliminate voltage and current harmonics while maintaining good dynamic response. The performance of the suggested control scheme is validated by extensive simulation results obtained by Matlab/Simulink for a sensitive nonlinear load. These results are compared with those obtained with a linear PI controller proves the superiority and effectiveness of FL-PDPC controller.

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Mogal, S. P., and D. I. Lalwani. "Experimental Investigations of Single and Multi-Fault in Rotor System." Applied Mechanics and Materials 541-542 (March 2014): 628–34. http://dx.doi.org/10.4028/www.scientific.net/amm.541-542.628.

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Many researchers dealt with single fault but in real life situations, combined action of two or more single faults are usually present. Multi-faults (two and three combinations) were studied by few researchers. Researchers have mostly studied the vibration behavior of a rotor with misalignment, unbalance and rub separately. This paper presents one such case, where multiple faults are considered together in a rotor system, i.e. misalignment, unbalance and rub. The objective of this paper is to experimentally investigate the vibration response of combined of three faults misalignment, unbalance and rub using Fast Fourier Transform (FFT). FFT spectrum of combination of three faults misalignment, unbalance and rub show 1 X and 2 X are predominant and many sub harmonics are generated.1X peak represent unbalance, 2X peak represents misalignment and sub harmonics shows rub fault.

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Yu, G. L., Y. L. Wang, and W. K. Wang. "Resonance in the kidney system of rats." American Journal of Physiology-Heart and Circulatory Physiology 267, no. 4 (October 1, 1994): H1544—H1548. http://dx.doi.org/10.1152/ajpheart.1994.267.4.h1544.

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The pressure wave of the abdominal aorta and the flow wave of the renal artery were recorded simultaneously from a rat. The impedance of a kidney system that is derived by dividing the pressure of the corresponding frequency by that of the flow was studied in six rats. The data show that the system has two resonant frequencies, at the second and third harmonics. At the second harmonic, the pressure wave and fluid flow in a round trip through the branch of the kidney. Whereas it is difficult for the third harmonic flow to enter the kidney, it flows directly through the aorta. To obtain further proof, we compared the frequency components of the two flows measured simultaneously on the abdominal aorta and the renal artery and found the same result. The kidney, renal artery, and aorta combined show a coupled oscillation that is analogous to that of resonance circuits. The kidney vascular system exhibits a resonant frequency at the second harmonic of the heartbeat.

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Yu, Yang, Zengqiang Mi, Yiming Che, Tong Zhao, and Yikun Xu. "Global Harmonic Current Rejection of Nonlinear Backstepping Control with Multivariable Adaptive Internal Model Principle for Grid-Connected Inverter under Distorted Grid Voltage." Mathematical Problems in Engineering 2013 (2013): 1–15. http://dx.doi.org/10.1155/2013/749798.

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Based on a brief review on current harmonics generation mechanism for grid-connected inverter under distorted grid voltage, the harmonic disturbances and uncertain items are immersed into the original state-space differential equation of grid-connected inverter. A new algorithm of global current harmonic rejection based on nonlinear backstepping control with multivariable internal model principle is proposed for grid-connected inverter with exogenous disturbances and uncertainties. A type of multivariable internal model for a class of nonlinear harmonic disturbances is constructed. Based on application of backstepping control law of the nominal system, a multivariable adaptive state feedback controller combined with multivariable internal model and adaptive control law is designed to guarantee the closed-loop system globally uniformly bounded, which is proved by a constructed Lyapunov function. The presented algorithm extends rejection of nonlinear single-input systems to multivariable globally defined normal form, the correctness and effectiveness of which are verified by the simulation results.

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Journal articles on the topic 'Combined harmonics'

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