| With the rapid development of China’s economy, power quality requiremen-ts are increasing. Continuing technological revolution in power electronics industry has brought great convenience for people’s life, but the usage of power electronics and non-linear devices in the power grid and power users at all levels result in a lot of harmonics,which cause serious pollution to the power environment. More and more scientists of electricity devote to the power quality harmonic research work.Firstly, this paper begins with the generation roots of the harmonic which analyze the serious harm caused by harmonics, combining the harmonic study of the current situations at home and abroad, and introducing the commonly used harmonic detection theory. Fourier transform is proposed and combined with wavelet transform, to a certain extent, which improves the accuracy of detection, and then this paper designs a PCI data acquisition card using harmonic detection system.More representative signal models are constructed in Matlab, respectively using FFT and wavelet transform to analyze the signal models. Through simulation results, it can be visually found that the different characteristics of them: the Fourier transform is more suitable for stable signal processing, and the use of window mode can reduce spectral leakage in some degree. Wavelet transform is along with the time domain and frequency domain localization features, but FFT spectrum analyzing capability is more precise and intuitive.Based on the system of PCI8620 data acquisition card, signal conditioning circuit is designed, using CLF call dynamic link library, to achieve the connection of non-NI’s data acquisition card and Labview. Program design uses FFT algorithm to calculate the amplitude of the signal acquisition and other contents and describes how to call Matlab Labview program. Experimental measurements demonstrate that the system design is reasonable and effective, in line with the relevant national standards. |
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