Power Harmonic Analysis Based On Fourier Transform And Wavelet Transform

Total Harmonic Distortion (THD) is a crucial index of power quality. Due to the negative impacts on electronic devices from harmonics, it is of engineering significance to do research on harmonic suppression. However, harmonic detection is the premise of harmonics suppression. Under the support from the projects, Research On Signal Processing Technology For Smart Sensor(No.08ZC010), Research On Highly Efficient Delivery Of Power With Strong Intermittency(No.Z2012015), Research On Highly Efficient Delivery Of Power With Randomness(No.13ZA0025) and another project(No.CHUANJIAOCAI[2013]203), this paper focuses on studying the methods of harmonic detection.Firstly, the current development and several main methods of harmonic analysis are introduced and described. Then the strengths and defects of Fast Fourier Transform (FFT) and Wavelet Transform (WT) that have been a research focus in recent years are deeply discussed. There are spectrum leakage and Barrier effect in asynchronous sampling by using FFT. Though this can be solved by utilizing Windowed Fourier Transform, it brings heavy computing burden and has limitations. However, WT solves the problem that FFT can’t be utilized to do time-frequency analysis.A hardware system based on DSP is designed to detect the harmonics in power system. Modulation of measured signals and relevant algorithm are implemented, including base-2FFT and base-4FFT, fast algorithm, the decomposing and reconstruction of wavelets.In the end, signal recovery parameters of the signal modulation circuit are obtained via LMS method. Due to the complicated condition and diversified interference signal in power system harmonic detection, both stationary signals and non-stationary signals are analyzed by using FFT and WT respectively.