Research On Algorithm Of Inter-harmonic Detection And Denoising

In recent years,with the increase in the level of industrial electrification and people’s dependence on electrical energy,the proportion of non-linear loads in the power grid is increasing.Especially the rapid development of various new energy sources(wind power and photovoltaic power generation,etc.),impact loads(high-speed rails,etc.)and electric vehicles,makes the harmonic and inter-harmonic components increase dramatically.As a result,there are many power quality problems.China is now at an important stage in the development of smart grid technology,therefore,it is necessary to urgently handle inter-harmonic problems.Studying interharmonics detection algorithms to improve data accuracy is an important foundation to solving such problems.Considering that signals in the actual environment are often disturbed by external noise,causes effective signals to be difficult to identify in the detection process,resulting in destruction of power quality data.This paper applies the wavelet threshold denoising algorithm in the field of image denoising before the detection algorithm,by analyzing the principles of wavelet decomposition,denoising and reconstruction,focus on improving the threshold and threshold functions.Based on the theory and simulation,it is proved that the improved wavelet threshold denoising algorithm can adapt to the denoising requirement of the grid signal.Due to the random time-varying characteristics of the inter-harmonics,it may not always be synchronized with the grid fundamental frequency.Spectral leakage and barrier effects tend to occur when using traditional FFT.This article aims at this kind of phenomenon,uses the window interpolation to improve the algorithm.It can accurately correct errors and improve detection accuracy without noise interference.By comparing several window functions and interpolation formulas,and using MATLAB to compare test data.Final selection of four-term three-tap Nuttall window algorithm with high precision and low computational complexity.It can accurately and quickly detect the steady-stateinter-harmonic based on the denoising algorithm.In the application of inter-harmonics detection and suppression,there is less research on the use of APF to eliminate the inter-harmonics of the power grid.This article proposes to add an improved inter-harmonics detection algorithm based on the Shunt APF to make it equally applicable to the inter-harmonic gird environment.The specific experiment is designed to build a DSP hardware experiment platform,introduces the principle of each circuit module,and realizes the detection and calculation of inter-harmonics.It has become an effective solution to the problem of inter-harmonics in the power grid.