The Design Of Digital Mutual Inductor Calibration Software System

With the continuous development of power system in our country.especially in the digital substation technology unceasing popularization,the traditional electronic instrument transformer calibration system is more and more difficult to meet the actual needs.Traditional equipment in addition to the low working efficiency,great error.The output signal cannot be directly with the microcomputer and protection equipment for data exchange.which greatly affect the normal work of the smart grid and the quick response of failure occurs.So there needs to be a new generation transformer calibration which based on digital signal processing to meet the require of practical engineeringThe article mainly is divided into three parts:The first part of the article mainly introduced the principle of current transformer and voltage transformer.Analyze the causes of error which mutual inductor work occurred.as well as the special error of electronic transform er.then calculate the principle for the transformer error,clear the definition of ratio error and angular difference.Meanwhile provide the workflow and basic composition digital transformer.The second part introduces the core algorithm,which is used in correcting signal--FFT transform.then analyzes the causes of error may occur in FFT transform.Processing the practical problems.we encountered in discrete time signals are cut out from infinite long signal,the truncation of discrete data is through a sequence and the window function multiplication,there will have two kinds of problems to influence the results:1.Discretization error,2.Truncation error.Increasing the sampling point could reduce the discretization error.In order to achieve the purpose of reduce the truncation error,window function is introduced,then detail introduced window function’s parameters and characteristics which is commonly used in digital signal processing.At lastin order to eliminate window function can not inhibit the leakage,eliminate the error of intercept data when the spectral line is not on the peak.further for amplitude and phase accurately.By cosine window together with the discrete spectrum calibration which proposed in this paper.it processing the FFT signal and reduce the transformation error, then calculate the peak of frequency after FFT by the discrete spectrum calibration method.according to the frequency to calibration amplitude and phase.through such methods to reduce error.and then get precise amplitude.frequency and phase.First out the theory of the scheme,then using Matlab as a working platform realizes the scheme in the application of the simulation experiment.And be able to use the scheme amounted to0.148%of the theoretical value of the ratio error.and the Angle difference error amounted to1.119%of the theoretical value.