Study On Spectrum Analysis Method Of Multi-frequency Synchronous Signal Of Current Transformer

The electrical harmonic pollution is getting more and more serious with the far-ranging use of nonlinear components in the complex environment of electric and electronic devices. It requires that the current transformer has a better performance in frequency characteristics, which is the key device of the power protection and energy metering systems. However, the traditional methods of the frequency detection with the current transformer have the inherent drawback of the heavy workload, long detection cycle and so on. Therefore, it is necessary to make a research on the method that can measure accurately and quickly the frequency of the current transformer.In order to solve the problem of traditional method in estimating the frequency characteristic of current transformer mentioned above, this paper proposes a synchronized signal's spectrum analysis method of a multi-frequency as a excitation for current transformer. Specifically, it analyzes the power signal of input and output signal of the current transformer, using the H_n-ave method estimate the frequency response function?FRF? of current transformer which can assessment the frequency characteristic of measured system. There had four main aspects was included in this thesis. Firstly, introducing the principle of generating multi-frequency synchronous signal based on Walsh function, simultaneously, analyzing the time domain and frequency domain characteristic of the multi-frequency synchronous signal. Based on the principle, design a power amplification module, which can output high power current suitable for measurement experiment.Illustrating the theory of the windowed interpolated fast Fourier transform ?WIFFT?, and the application in spectrum analysis in the second part. It had introduced the performance, as well as the selection principle of the window functions in this part. It has shown that the interpolated fast Fourier transform with the second-order Hanning self-convolution window, performing high accuracy for multi-frequency signal spectrum calculation.Describing the method of calculating current transformer spectral, and analyze the principle of frequency response function and the theory of H_n-ave estimation method in the third part. It is of high accuracy from the result of the simulation that the multi-frequency is calculated from the correlation function and the interpolating windowed FFT.Finally, the experimental platform was set up to acquire the input and output current signal from the two miniature current transformer. By contrast with the traditional method, the results calculated from Matlab show more accurate and practical significance.