Harmonic Analysis In Power Quality Monitoring Its Implementation

Power quality included a lot of indexes,electric harmonic is one of important indexes in PQ event. The analysis objects in power system are very complicated, there are a lot of noise and breaks which indicate system's operation status in voltage and current signal. A rational analysis is needed. There are many methods in harmonic analysis, such as traditional Fast Fourier Transform, Short Time Fourier Transform and Wavelet Transform. They have different analytical emphasis and also apply to different kinds of harmonic.This paper analyze all kinds of curent hamonic analysis methods and compare those methods.FFT and wavelet method are mainly discussed,all types of harmonic singal models are created and apply two different methods to the same singal model.A conclusion about how to use different methods can be get by contrast. Based of all,a method which named Fourier and Wavelet comprehensive detecting algorithm using Fast Fourier Transform combining with Wavelet Transform is discussed.Using the special effect on detecting singularity point and high resolving degree in time domain of wavelet, combined with the exact frequency resolving ability of Fast Fourier Transform ,we can analyze all kinds of harmonic.In the paper the principle of the above method are given,put forward an analyse scheme and got the FFT and wavelet comprehensive method.In the same time methods used above are validated by algorithm emulating and it is compared with rational method by emulate as well.The emulating results are beter than traditional harmonic analysis method's.In the last part,an draft of designing an harmonic monitoring instrument is presented.