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Harmonic

About: Harmonic is a research topic. Over the lifetime, 44833 publications have been published within this topic receiving 495922 citations. The topic is also known as: overtone & partial.


Papers
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Journal ArticleDOI
TL;DR: A reflectionless metal tube which can act as a pseudoinfinite termination of the vocal tract was used to collect glottal volume-velocity waveforms produced by 10 male and female adult subjects, indicating a wide variation of theglottal waveform shape, its rms intensity and fundamental frequency, phase spectrum, and intensity spectrum.
Abstract: A reflectionless metal tube which can act as a pseudoinfinite termination of the vocal tract was used to collect glottal volume‐velocity waveforms produced by 10 male and female adult subjects From each subject, glottal volume‐velocity samples were collected of normal, loud, and soft voice; falsetto and creaky voice; monosyllables with rising and falling intonation; and three‐syllable utterances containing primary lexical stress on one of the three syllables Analysis of the data indicates a wide variation of the glottal waveform shape, its rms intensity and fundamental frequency, phase spectrum, and intensity spectrum It is observed that as the fundamental frequency changes over time, the glottal source varies in one of two different ways In one type of change, the harmonic relations in the glottal spectrum become steeper as fundamental frequency rises In a different type of glottal‐wave change, relations between harmonics tend to remain the same despite a change in the fundamental frequency; the source spectrum in this case is simply shifted along the frequency and amplitude axes as a function of fundamental frequency To account for these variations in the glottal source, at least three factors must be known: the sex of the speaker, the voice register in which he phonates, and the linguistic context in which the phonation occurs

152 citations

Journal ArticleDOI
TL;DR: The proposed hybrid voltage and current control method allows the coordinated closed-loop control of the DG unit fundamental voltage and line harmonic currents and guarantees smooth transition during the grid-connected/islanding operation mode transfer.
Abstract: This paper presents a hybrid voltage and current control method to improve the performance of interfacing converters in distributed generation (DG) units. In general, current-controlled methods have been widely adopted in grid-connected converters nowadays. Nevertheless, in an islanded system, the voltage control of DG units is desired to provide direct voltage support to the loads. Due to the absence of closed-loop line current controller, the voltage control scheme can hardly regulate the DG unit's line current harmonics. Furthermore, if not addressed properly, the transfer between the grid-connected operation and autonomous islanding operation will introduce nontrivial transient currents. To overcome the drawbacks of voltage- and current-controlled DG units, this paper develops a hybrid voltage and current control method (HCM). The proposed method allows the coordinated closed-loop control of the DG unit fundamental voltage and line harmonic currents. With the HCM, local harmonic loads of the DG unit can even be compensated without using harmonic current extraction. In addition, the HCM guarantees smooth transition during the grid-connected/islanding operation mode transfer. Simulated and experimental results are provided to verify the feasibility of the proposed approach.

152 citations

Journal ArticleDOI
TL;DR: In this article, a method for calculating the harmonic currents and losses of induction motors excited with static frequency converters is presented, and experimental data are included to substantiate it. But, the authors do not consider the effect of motor load on the performance of inductive motors.
Abstract: Induction motors excited with static frequency converters almost invariably are subjected to nonsinusoidal voltage waveforms, and the presence of time harmonics in the applied voltage results in currents at the harmonic frequencies. These currents result in additional and sometimes rather large losses. A method for calculating these harmonic currents and losses is presented, and experimental data are included to substantiate it. The losses are separated into various components and it is shown that the largest loss is usually in the rotor bars as a result of deep bar effect. Harmonic losses are shown to be nearly independent of motor load and the fundamental magnetizing current is found to increase over that which would be present for the same rms fundamental voltage. These observations are explained on a theoretical basis. The encouraging correlation between test and calculated data confirms that the important elements which differ between motor performance on sinusoidal and nonsinusoidal waveforms have been identified and accounted for.

152 citations

Journal ArticleDOI
TL;DR: It is shown that randomCFM (RCFM) gives a more effective way to disperse the harmonics around the switching frequency than the periodic CFM (PCFM) with the same frequency deviation, however, RCFM introduces higher low-frequency harmonics than the PCFM at the converter output.
Abstract: A rigorous mathematical analysis and a comparative study of carrier-frequency modulation (CFM) techniques for the conducted electromagnetic interference (EMI) suppression in pulsewidth-modulated converters is presented. CFM techniques dither the switching period with a small amplitude variation around the nominal value, so that the harmonic power is redistributed over the spectrum of concern. Two types of dithering signals, including the periodic and random signals, are investigated in this paper. The operational characteristics as well as the input and output power spectra of the converters with the two modulating signals are compared. In particular, their characteristics in the low- and high-frequency harmonic power redistribution will be depicted. It is shown that random CFM (RCFM) gives a more effective way to disperse the harmonics around the switching frequency than the periodic CFM (PCFM) with the same frequency deviation. However, RCFM introduces higher low-frequency harmonics than the PCFM at the converter output. Furthermore, effects of the resolution filter bandwidth in the electromagnetic compatibility analyzer on conducted EMI measurement is discussed. The validity of the analyses is confirmed experimentally by using a dc/dc buck converter operating in continuous conduction mode.

151 citations

Journal ArticleDOI
TL;DR: In this article, a thorough analysis of the generalized delayed-signal cancellation (DSC) operator in both synchronous and stationary reference frames is first conducted, and the discretization error during digital implementation due to nonideal system sampling frequency and/or grid-frequency variation is quantified with the proposed concept of relative harmonic gain error.
Abstract: Phase-locked loop (PLL) is usually required to detect grid phase angle in grid-tied converters. Conventional PLL schemes have to compromise between steady-state accuracy and transient dynamics when grid voltage is polluted by unbalance and harmonics. To overcome this challenge, a generalized delayed-signal-cancellation (DSC) operator is proposed recently to form cascaded DSC (CDSC) operator to eliminate arbitrary harmonics. With the CDSC operator, the conditioned voltage can be used in PLL loop with very high bandwidth for fast tracking. However, for digital implementation, the CDSC operator may subject to delay-time error, which subsequently leads to residual distortions in the conditioned voltage. In this paper, a thorough analysis of the CDSC operator in both synchronous and stationary reference frames is first conducted. The discretization error during digital implementation due to nonideal system sampling frequency and/or grid-frequency variation is quantified with the proposed concept of relative harmonic gain error. An effective improvement method is then developed that is based on linear interpolation and is effective for all delay-based PLL schemes. Finally, experimental results are obtained to verify the harmonic elimination ability of CDSC in various scenarios and the effectiveness of the interpolation-based digital implementation scheme.

151 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,223
20222,724
20211,878
20202,330
20192,612
20182,495