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Harmonic Detection For Active Power Filter

Posted on:2008-04-15Degree:MasterType:Thesis
Country:ChinaCandidate:Z L LvFull Text:PDF
GTID:2178360212993255Subject:Signal and Information Processing
Abstract/Summary:PDF Full Text Request
With the modernization of production and living, people have continuous high quality demand for electricity supply. However, harmonics flow into the power system as the result of the massive use of power electronic devices. The negative impacts of harmonics on quality and safety of electricity supply are catching great attentions. Recently, harmonics problem has been spotted by several academic journals and conferences. The standards of harmonics control have been set by related international organization and several other countries. While the methodology for harmonics control is being renovating, it still needs some significant break-through. The unique predominance of active power filter has attracted lots of scholars' attention.The active power filter has several different types according to its various compensating currents, but the principles are all the same. Harmonic detector inspects harmonics in the system and produces opposed current in order to compensate. Almost all of the active power filters are composed by three main parts: harmonic detection circuit, control circuit, and main circuit. Among which, realtime harmonic detection is the first and foremost for the working procedure of active power filter. Analysis shows harmonic control could be done in the field of signal processing. In recent years, the theory behind signal processing, especially digital signal processing experienced rapid evolution. Kalman filter, adaptive filter, neural network, and wavelet are being widely used in every industry, including harmonic detection.Through detailed analysis on difference harmonic detection methodology, the paper reveals their various and unique characteristics. Meanwhile, a novel adaptive harmonics detecting algorithm for active power filter is presented. This new method can greatly shorten the transient period of weighting factors while keeping steady-state accuracy, which brings very little additional calculation. Because transient period are in direct ratio to the weighting factor, while the accuracy are in inverse ratio to the weighting factor, contradiction exists between accuracy and transient period. Starting with the adaptive filter theory, based on the analysis of transient behavior of adaptive weighting factors, a new intelligent harmonic detection method are proposed in the paper. According to this new method, harmonic detection could be done within half base wavelength, with little impact on accuracy. Matlab is used to test its effectiveness. Future applications are also overlooked in the paper.
Keywords/Search Tags:Harmonic Control, Active Power Filter, Harmonic Detection, Adaptive Filter
PDF Full Text Request
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