Analysis And Research Of The Power System Harmonic Detection Method

In the actual operation of the power system,due to the attention and use of power electronics,distributed generation and new energy technologies.In recent years,a large number of non-linear devices such as rectifiers and variable-frequency drive have been used in various industrial processes and people's living departments.Inevitably,more and more complex non-sinusoidal harmonics will injected into the grid.This will cause great threaten to the operation of the power system.Therefore,the harmonic treatment of power system is also more and more difficult,as a prerequisite for harmonic management,harmonic detection must be accurate in order to carry out effective governance.This paper introduces the research significance of harmonics in power system and expounds the status of domestic and foreign research on harmonic detection.Analyzeds the harmonic detection method based on Fourier transform,wavelet transform and wavelet entropy.Through Matlab establishes power system signal models,and uses the above three methods to detect each other,draw a conclusion that the application range of different harmonic detectionz: The wavelet multi-resolution analysis method is localized in both time domain and frequency domain.The signal can be divided into high frequency and low frequency according to the frequency.The Fourier transform can accurately obtain the characteristics of the steady-state signal.The wavelet entropy can accurately detect the information of singular signal.According to the importance of harmonic detection in power system,the three methods are combined to achieve the purpose of simultaneous detection of steady-state signals and non-steady-state signals.And use the Blackman window and bimodal spectrum interpolation algorithm to modify the harmonic detection method based on FFT.In this paper,establish a complex signal containing the features of power system.Detectes the complex signal by the above combined algorithm.The simulation results show that the combined method is feasible and accurate,and it can improve the methods that can accuracy simultaneous detect both the steady-state harmonics and non-steady-state harmonics.Finally,establishs a Matlab/simulink model of typical power system harmonic sourcethe power source of intermediate frequency furnace,and uses the combined algorithm detect the grid side current signal generated by the model.The results show that the combined algorithm can accurately detect the steady-state harmonics and non-steady-state harmonics of the power system,is the existing harmonic detection method to further improve.