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.

Parallel-connections of pulsewidth modulated inverters using current sharing reactors

Abstract: A technique of parallel connection of power devices by using current sharing reactors for pulsewidth modulated (PWM) inverters is reported in this paper. The proposed technique not only increases the current capacity but also decreases the output harmonic contents. The output voltage waveforms of the proposed inverter have certain voltage levels during their half cycles, thus it is anticipated that it will be difficult to analyze the output waveforms. For such waveforms, a frequency analysis approach is described, whose results are verified by experiments. >

An instantaneous reactive volt-ampere compensator and harmonic suppressor system

Abstract: A novel control method for a reactive volt-ampere compensator and harmonic suppressor system is proposed. It operates without sensing the reactive volt-ampere demand and nonlinearities present in the load. The compensation process is instantaneous, which is achieved without employing any complicated and involved control logic. The compensator is operated in cycle-by-cycle reference-current-controlled mode to achieve the instantaneous compensating feature. A mathematical model of the scheme is developed. Detailed analysis and simulation results are presented. A laboratory prototype of the compensator is developed to validate the results.

Role of the Transition Dipole Amplitude and Phase on the Generation of Odd and Even High-Order Harmonics in Crystals.

Abstract: Since the first observation of odd and even high-order harmonics generated from ZnO crystals in 2011, the dependence of the harmonic yields on the orientation of the laser polarization with respect to the crystal axis has never been properly interpreted. This failure has been traced to the lack of a correct account of the phase of the transition dipole moment between the valence band and the conduction band. Using a simple one-dimensional two-band model, here we demonstrate that the observed odd harmonics is directly related to the orientation dependence of the magnitude of the transition dipole, while even harmonics is directly related to the phase of the transition dipole. Our result points out the essential role of the complex transition dipole moment in understanding harmonic generation from solids that has long been overlooked so far.

Planetary waves in the atmosphere

Abstract: A numerical method is presented for solving the non-linear barotropic vorticity equation in spherical coordinates. It is shown that, when the stream function is expressed as a sum of surface spherical harmonics, the barotropic vorticity equation gives rise to harmonic tendency equations which express the time rate of change of the harmonic coefficients as functions of all the harmonic coefficients. The harmonic tendency equations may be used in an iterative process to find the flow pattern at a future time from a knowledge of the harmonic coefficients at an initial time. The amount of computation is reduced greatly if the planetary waves are regarded as composed of perturbations superimposed on a steady zonal flow in which the angular velocity varies with colatitude. An example based on an actual synoptic situation is given. The effect of large scale lateral mixing is to curb the development of harmonics of large degree.