Topic
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.
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TL;DR: The change in ultrasonic nonlinear property of a titanium alloy subjected to cyclic loading has been studied, with an objective to develop a new characterization methodology for quantifying the level of damage in the material undergoing fatigue as mentioned in this paper.
Abstract: The change in ultrasonic nonlinear property of a titanium alloy subjected to cyclic loading has been studied, with an objective to develop a new characterization methodology for quantifying the level of damage in the material undergoing fatigue. In order to determine the degree of nonlinearity, the ultrasonic second harmonic generation technique has been used. The second harmonic signal was monitored during the fatigue process, and a substantial increase in the second harmonic amplitude (180% increase in nonlinear factor) was observed. This indicates that the second harmonic signal is very sensitive to the microstructural changes in the material caused by fatigue.
98 citations
TL;DR: Simulation and experimental results for the steady-state operating condition and transient operating conditions for the system subjected to a reactive current reference step change, a three-phase line to neutral fault, and a step load change are presented to demonstrate the effectiveness of the proposed controller.
Abstract: In this paper, a novel controller with fixed modulation index (MI) and variable dc capacitor voltage reference to minimize voltage and current harmonics is presented for a distribution static synchronous compensator (STATCOM). The STATCOM with the proposed controller consists of a three-phase voltage-sourced inverter and a dc capacitor and is used to provide reactive power compensation and regulate ac system bus voltage with minimum harmonics. A systematic design procedure based on pole-zero cancellation, root locus method, and pole assignment method has been developed to determine proper parameters for the current regulator, the dc voltage controller, and the ac voltage controller of the STATCOM. With the proposed STATCOM controller, harmonic distortions in the inverter output current and voltage can be reduced since the MI is held constant at unity in steady state. In addition, a fast adjustment in the STATCOM output reactive power is achieved to regulate the ac bus voltage through the adjustment of the dc voltage reference during the transient period. Simulation and experimental results for the steady-state operating condition and transient operating conditions for the system subjected to a reactive current reference step change, a three-phase line to neutral fault, and a step load change are presented to demonstrate the effectiveness of the proposed controller.
98 citations
TL;DR: In this paper, an analytical expresion for the efficiency of the gyrotron traveling wave amplifier is derived for the case of non-fundamental cyclotron harmonic interaction, which scales the efficiency with respect to the modes and parameters of operation.
Abstract: An analytical expresion for the efficiency of the gyrotron traveling wave amplifier is derived for the case of nonfundamental cyclotron harmonic interaction. It scales the efficiency with respect to the modes and parameters of operation. This relation, together with a general linear dispersion relation, also derived in the present paper, gives the characteristics and optimum operation conditions of the gyrotron traveling wave amplifier.
98 citations
Patent•
23 Mar 1998
TL;DR: In this article, a three-dimensional multi-level, multi-phase and multi-circuit array of H-bridges is proposed for high power applications, while providing a high degree of power quality.
Abstract: In the particular embodiments described, an unlimited voltage static power converter includes an array of multi-level phase drivers consisting of a plurality of H-bridge power modules connected in series. The midpoint node of the series-connected power semiconductors is connected to corresponding midpoint nodes in adjacent H-bridges to achieve a desired high output voltage using available power switch ratings. A three-dimensional multi-level, multi-phase, multi-circuit array of H-bridges permits the use of the static power converter for high power applications, while providing a high degree of power quality. The power semiconductor switches are operated in accordance with a two-dimensional interleaved pulse width modulation algorithm which produces a waveform with a switching frequency that can be more than an order of magnitude higher than the switching frequency of a single power switch. PWM complementary triangle carrier waves are used for individual PWM control of each H-bridge in each multi-level phase driver, resulting in a two-dimensional interleaved control algorithm. Injection of harmonic or non-harmonic content into the PWM reference waveform further reduces harmonic and non-harmonic content of the output voltage waveforms. Part-load efficiency is increased using unique load partitioning methods, five of which are described herein.
98 citations
TL;DR: In this paper, the second harmonic pulse shape generated from ultrashort pulses is calculated in long dispersive crystals, where the pulse width may be much broader than the incident pulse and the power conversion ratio may saturate at a low value.
Abstract: The second harmonic pulse shape generated from ultrashort pulses is calculated In long dispersive crystals the pulse width may be much broader than the incident pulse and the power conversion ratio may saturate at a low value These effects should be prominent in LiNbO3 with 4 × 10−13 sec pulses
98 citations