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: In this article, it is shown how MPDTC can be adapted to the five-level active neutral-point-clamped converter topology, which offers low harmonic distortion and a high output voltage.
Abstract: The five-level active neutral-point-clamped converter is a recently introduced topology that offers low harmonic distortion and a high output voltage. In addition to a neutral point potential in the dc link, this topology features, in each phase, a flying phase capacitor. Balancing these four internal converter voltages around their references while providing fast torque and/or current control for the machine is an intrinsically challenging control problem. Model predictive direct torque control (DTC) (MPDTC) is an ideal control methodology to address this problem. It is shown, in this paper, how MPDTC, originally developed for three-level inverters, can be adapted to this new five-level topology. Compared to DTC, the performance results of MPDTC are very promising-for the same switching frequency, the harmonic distortions of the stator currents and the torque can be more than halved. At the same time, the very fast torque response of DTC is maintained.
90 citations
TL;DR: An analytical algebraic method based on formulating the line-voltage THD of multilevel inverters with unequal dc sources is presented, which is general and applicable to each number of switching angles, and implemented to a five-level inverter with staircase waveform as a case study.
Abstract: Multilevel inverters introduce harmonics to the network besides their remarkable advantages. Total harmonic distortion (THD) is one of the most important indexes to evaluate the harmonic contents of waveforms. The conventional method of line-voltage THD calculation gives approximate answers, because high-order harmonics are ignored. In this paper, an analytical algebraic method based on formulating the line-voltage THD of multilevel inverters with unequal dc sources is presented. This method, which is general and applicable to each number of switching angles, is implemented to a five-level inverter with staircase waveform as a case study. The implementing process of this method can be easily repeated for each number of levels. The accuracy of the proposed method is illustrated in comparison with the approximate method. Some advantages of the extracted formulas of line-voltage THD are simplicity and rapidity in calculations, considering all harmonics and the possibility of finding optimal switching angles analytically. Experimental results are presented to validate the theory.
90 citations
TL;DR: In this article, a pair of wedge transducers are used to generate and detect the fundamental (s1) and second harmonic (s2) Lamb waves, and the weak amplitude of the second harmonic wave is extracted from the spectrogram of a received signal.
Abstract: This research develops an experimental method for evaluating material damage due to plastic deformation in a metal plate using nonlinear-guided waves. An improved version of a previously proposed measurement technique is used. The material nonlinearities of aluminum specimens loaded to produce different levels of plastic strain are measured with Lamb waves. A pair of wedge transducers is used to generate and detect the fundamental (s1) and second harmonic (s2) Lamb waves. The weak amplitude of the second harmonic wave is extracted from the spectrogram of a received signal. The measured acoustic nonlinearity increases monotonically with the level of plasticity (plastic strain), which is similar to the behavior of longitudinal and Rayleigh waves. This result indicates that Lamb waves can be used to assess plasticity-driven material damage in the established framework of the second harmonic generation technique. The effects and the importance of signal processing in determining the nonlinearity parameter are also discussed.
90 citations
TL;DR: In this paper, the cylindrical capacitor is examined with emphasis on the configuration which applies to the variable-capacitor diode, which is used primarily for harmonic power generation.
Abstract: The equivalent circuit applicable to most semiconductor diodes contains a term R/sub s/ called the spreading resistance which is a very critical parameter of any diode. In a mixer diode, R/sub s/ limits the conversion efficiency and increases the noise temperature. In parametric amplifiers, R/sub s/ affects the overall impedance levels and determines the minimum noise figure of which the amplifier is capable. In harmonic generators it drastically affects the conversion efficiency, as it dissipates power not only at the input and output harmonic frequencies but also at every idler frequency for which current may flow through the diode. This paper details more specifically the problems encountered when high frequency operation must be evaluated. The cylindrical capacitor is examined with emphasis on the configuration which applies to the variable-capacitor diode, which is used primarily for harmonic power generation. The point-contact diode configuration is examined and the field equations are derived in terms of the oblate spheroidal coordinates. It is shown that this is the natural coordinate system for such an analysis and that the spreading resistance is quite easily derived in this system.
90 citations
TL;DR: In this paper, genetic algorithms and particle swarm optimization are applied to compute the switching angles in a three-phase seven-level inverter to produce the required fundamental voltage while, at the same time, specified harmonics are eliminated.
90 citations