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.
Papers published on a yearly basis
Papers
More filters
TL;DR: A novel PLL scheme based on a real-time implementation of the discrete Fourier transform (DFT) is presented in this paper and can be considered to be a PLL in which phase detection is performed via a DFT-based algorithm.
Abstract: Phase-locked loop (PLL) algorithms are commonly used to track sinusoidal components in currents and voltage signals in three-phase power systems. Despite the simplicity of those algorithms, problems arise when signals have variable frequency or amplitude, or are polluted with harmonic content and measurement noise, as can be found in aircraft ac power systems where the fundamental frequency can vary in the range 360-900 Hz. To improve the quality of phase and frequency estimates in such power systems, a novel PLL scheme based on a real-time implementation of the discrete Fourier transform (DFT) is presented in this paper. The DFT algorithm calculates the amplitudes of three consecutive components in the frequency domain. These components are used to determine an error signal which is minimized by a proportional-integral loop filter in order to estimate the fundamental frequency. The integral of the estimated frequency is the estimated phase of the fundamental component, and this is fed back to the DFT algorithm. The proposed algorithm can therefore be considered to be a PLL in which phase detection is performed via a DFT-based algorithm. A comparison has been made of the performances of a standard PLL and the proposed DFT-PLL using computer simulations and through experiments.
99 citations
TL;DR: In this article, a frequency-domain harmonic model for the CFL is presented, which is suitable for assessing the collective impact of a large number of CFLs since it includes the impact of supply-voltage harmonics on the harmonic currents produced by the CFLs.
Abstract: Compact fluorescent lamps (CFLs) are gaining widespread acceptance due to energy conservation concerns. The CFL is a significant harmonic source since its current total harmonic distortion can exceed 100%. Although each CFL consumes only a small amount of power, mass-deployed CFLs could become a significant harmonic source. This paper presents a frequency-domain harmonic model for the CFL. This model is suitable for assessing the collective impact of a large number of CFLs since it includes the impact of supply-voltage harmonics on the harmonic currents produced by the CFLs. The model is subsequently simplified and two variations are proposed. The model and its variations are verified by comparing their results with the measurements taken from various CFLs. Furthermore, the attenuation characteristics of CFLs are investigated. The results reveal the conditions in which the simplified models can be applied with acceptable errors.
99 citations
TL;DR: In this paper, the authors compared the voltage and current total harmonic distortion (THD) and total demand distortion (TDD) with the IEEE519, IEC 61000/EN50160 standards and concluded that the use of TDD was a better indicator than THD, since the former uses the maximum current (I L ) and the latter uses the fundamental current, sometimes misleading conclusions, hence it is suggested it should be included in IEC/EN standard updates.
99 citations
TL;DR: In this paper, the frequency response of the zeroth- and second-order filters is established and illustrated and it is demonstrated that, for orders greater than or equal to two, the filters are able to form zero flat phase response about the operation frequency and then able to provide instantaneous estimates.
Abstract: Recently, the TaylorK Kalman filter was proposed for estimating instantaneous oscillating phasors. Its performance was examined through time-domain simulations using the benchmark test signals specified in the IEEE Standard for Synchrophasors for Power Systems. It was discovered that the estimation error level was abruptly reduced by a factor of ten from the second order, mainly because those filters were able to provide instantaneous phasor estimates. In this paper, the frequency response of the zeroth- and second-order filters is established and illustrated. They demonstrate that, for orders greater than or equal to two, the filters are able to form zero flat phase response about the operation frequency and then able to provide instantaneous estimates. By assessing the behavior of the estimates before signals with harmonics, or noise, not contemplated in the signal model, the frequency response method leads us to design more robust filters, referred to as TaylorK Kalman-Fourier, because they incorporate the whole set of harmonics in their multiharmonic signal model. It turns out that the bank of comb filters achieved with K = 0 is equivalent to that of the discrete Fourier transform, with a computational cost of one and a half products per harmonic estimate, which is lower than the FFT cost for more than eight components, and the bank of fence filters obtained with K = 2 is similar to that of the Taylor2 Fourier transform but with the advantage of providing estimates devoid of delay and needing only four products per harmonic set of estimates. Due to their instantaneous character, and computational simplicity, those estimates are certainly very useful for real-time harmonic analysis and power system control applications.
99 citations
Patent•
14 Aug 1996
TL;DR: In this paper, a solid state laser system producing coherent radiations at deep ultraviolet wavelengths includes a solid-state laser producing a first beam having a wavelength near 1 micron, passed to both a harmonic generation stage and to a tunable optical parametric oscillator.
Abstract: A solid state laser system producing coherent radiations at deep ultraviolet wavelengths includes a solid state laser producing a first beam having a wavelength near 1 micron. The 1 micron beam is passed to both a harmonic generation stage and to a tunable optical parametric oscillator. The harmonic generation stage is configured to produce a fifth harmonic of the 1 micron beam, while the optical parametric oscillator produces a tunable beam in the near infrared spectrum (e.g., approximately 2.075 micron). The fifth harmonic and the near infrared beams are mixed in a sum frequency generator to produce a highly coherent beam in the deep ultraviolet (e.g., between approximately 180 nm to 213 nm).
99 citations