A Harmonic Detection Method Based On Convolution For Ground Current Of Converter Transformer Core

With the progress of electronic power technology in recent years,and the expanding of the scope,the nonlinear load is increasing,especially for uhv dc transmission system,the characteristics of high voltage,large capacity will inevitably cause the emergence of a large number of harmonic,not only affects on the main equipment operation,are more likely to endanger the safety of the power system.In order to reduce the influence and harm of harmonics on the main equipment such as transformer of converter station,improving the accuracy of parameters in harmonic detection has become an important research content.Timely discovery of converter transformer core multi-point grounding fault,real-time online monitoring,to ensure the normal operation of converter transformer,reduce equipment damage,reduce economic losses.At present,the traditional harmonic detection method has a high accuracy for monitoring the grounding current value of the transformer core in the conventional intelligent substation,but it has the problem of large error and low accuracy when ap plied in the converter station containing a large number of high frequency harmonic interference.Fast Fourier transform harmonic detection method has been widely used in harmonic analysis field,and has achieved remarkable results.Therefore,this paper mainly studies the use of convolution algorithm to build a new hybrid convolutional window trispectral interpolation method to improve FFT detection of harmonic parameter values,and the use of FIR low-pass filter signal processing methods for noise elimination applications.The whole research work of this paper revolves around the convolution algorithm.First,the design method is Kaiser window function method to eliminate the noise of high order harmonics by using FIR low-pass filter.Second,due to the harmonic detection method of fast Fourier transform of frequency spectrum leakage and fence effect problems,this article selects the main lobe width narrow Hanning window and can automatically adjust the sidelobe ratio of Kaiser build a window using convolution operation to a new type of hybrid convolution window function inhibition spectrum leakage problems and three line interpo latio method is used to suppress the fence effect as a harmonic detection method.This method can improve the precision of harmonic detection by using the excellent characteristics of the two window functions and selecting more information near the target frequency point spectrum line.Is studied through simulation experiment,the classic signals,comp lex and contains three kinds of situation of noise environment influence on harmonic detection accuracy,under the same conditions three line hybrid convolution window interpolation harmonic detection accuracy is superior to the single window function three line interp olation method and other window convolution spectrum interpolation method and verify the effectiveness of the method in this paper.The method presented in this paper is applied to the controller of the on-line monitoring device for the grounding current of converter transformer core,and its structure principle and algorithm flow design are studied.