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.

Neural Network and Bandless Hysteresis Approach to Control Switched Capacitor Active Power Filter for Reduction of Harmonics

Abstract: This paper proposes a combination of neural network and a bandless hysteresis controller, for a switched capacitor active power filter (SCAPF), to improve line power factor and to reduce line current harmonics. The proposed active power filter controller forces the supply current to be sinusoidal, in phase with line voltage, and has low current harmonics. Two main controls are proposed for it: neural network detection of harmonics and bandless digital hysteresis switching algorithm. A mathematical algorithm and a suitable learning rate determine the filter's optimal operation. A digital signal controller (TMS320F2812) verifies the proposed SCAPF, implementing the neural network and bandless hysteresis algorithms. A laboratory SCAPF system is built to test its feasibility. Simulation and experimental results are provided to verify performance of the proposed SCAPF system.

Active power filter control circuit based on the instantaneous active and reactive current i/sub d/-i/sub q/ method

Abstract: This paper presents the control circuit of a shunt active power filter based on the instantaneous active and reactive current i/sub d/-i/sub q/ method The presented method is compared with the instantaneous active and reactive power p-q method under several mains voltage conditions and for different harmonic injection highpass filters The i/sub d/-i/sub q/ method as an excellent harmonic compensation performance and presents the advantage of being frequency-independent The DC voltage regulation system is analysed and its synthesis is performed Extensive simulation results are used to show the stability of the voltage regulation system and to establish the superior performance of i/sub d/-i/sub q/ method based compensator

Complete synthetic seismograms for a spherically symmetric earth by a numerical computation of the green's function in the frequency domain

Abstract: SUMMARY We present a new method to calculate complete synthetic seismograms for a spherically symmetric earth model which uses neither eigenfrequencies and eigenfunctions nor an earth-flattening transformation. The response of the earth to a moment tensor point source is evaluated in the frequency domain for both spheroidal and toroidal motion by numerical integration of the appropriate system of ordinary differential equations with source term and summation over vector spherical harmonics. Attenuation is included by using complex elastic moduli. Owing to the discrete sampling of the response in the frequency domain, the numerical effort is proportional to the length of the desired time series for a fixed maximum frequency. This makes the method much more efficient than normal-mode calculations for higher frequency applications, where often seismogram lengths of 20 to 40 min are sufficient. Since the angular degree of the spherical harmonics provide a natural discretization in the wavenumber domain, spatial aliasing is unimportant. Time aliasing is suppressed by evaluating the response at complex frequencies with constant imaginary part. We have compared synthetic seismograms obtained by the new method with normal-mode seismograms up to a frequency of 20 mHz and achieve excellent agreement for all three components. The accuracy of the method is further corroborated by comparisons with real data up to a frequency of 200 mHz. We tested the numerical scheme up to frequencies of 1 Hz and harmonic degrees of 12 000 and did not find any numerical instabilities. Incidentally, the approach sheds some light on how normal modes make up body waves.