Research On The Application Of The Spectrum Correction Theory In The Detection Of The Electric Parameters

Discrete fourier transform (DFT) is one of the most popular methods applied in computer-based measurement of electric parameters. However, the non-synchronous sampling, finiteization, and discretization of time-domain and frequency-domain during the spectrum analysis of electric signals cause measuring errors, which makes it difficult to satisfy the request of high detection precision. Spectrum correction theory is applied extensively in the field of machinery vibration signal analyzing and faults diagnose in recent years, but its application is seldom reported in power system, especially in the field of electric parameters measurement. Therefore, it has important theoretical significance and practical value to engage the research and supplement the detection method of electric parameters.From the viewpoint of improving the detection precision of electric parameters, this paper first reviews the development process of detection mode, and introduces the character of the usual electric parameters detection method and different kinds of improving method based on DFT algorithm to enhance the analysis precision, and elucidates the research background. Secondly this paper details the basic theory, form of fourier transform, and the problems which must be paid attention to in the practical application. The reasons of the error caused by the traditional electric parameter detection methods base on the windowed DFT are thoroughly analyzed. The analytic representation of the error caused by spectrum leakage and the numerical model of the correcting method are proposed. Mathematical derivation of the basic principle of many kinds of discrete spectrum correction method has been carried on. The detailed steps to realize the concrete algorithm are given in this paper. The characters of various methods and its applying condition in the electric parameters detection are discussed and compared. With the help of MATLAB language, simulation on detecting typical power system signals has been done by applying both the traditional DFT algorithm and the methods proposed in this paper. The analysis and comparison of the simulating results verifies the validity and advantage of the spectrum correction methods. The characters, advantages, and shortcomings of each algorithm are elaborated. At the same time, the problem about how to further expand the application occasion of the spectrum correction methods is discussed preliminarily. Based on the new detection principle, this paper designs a new measuring algorithm to measure the voltage parameters of a microcomputer based automatic quasi-synchronizationparalleling device, and introduces the realization steps and schemes of this algorithm. Finally the paper summarizes the research work of the whole paper and points out the flaws. The prospects about how to further improve the precision of correcting method and the developmental trend in the future are discussed.