Research On Improved Measurement Method Of Power Harmonics Based On Fourier Transform

With the development of renewable energy and smart grids,A large number of non-linear loads are integrated,Power system suffers from increasingly serious harmonic pollution.Accurate estimation of harmonic electrical parameters is a prerequisite for safe and normal operation of electrical equipment.It is helpful to reduce the possibility of adverse effects,How to ensure the measurement accuracy of power harmonic electrical parameters has received wide attention.Among many measurement methods,the DFT-based methods have received widespread attention and use because of their efficiency,high estimation accuracy,and ease of application.However,due to problems such as windowing and non-synchronous sampling,if calculated directly,errors will occur due to the fence effect and spectrum leakage,measurement accuracy is therefore reduced.At present,the DFT-based correction measurement algorithm mainly has interpolation correction and phase difference correction methods.For the Hanning window single-peak spectral interpolation method,in this paper,the interpolation correction formula is improved,and the frequency compensation is performed after the first correction to obtain a new discrete sequence similar to the synchronous sampling,based on the Hanning window interpolation correction again to improve the accuracy of the frequency estimation.At the same time,the new discrete sequence directly solves the amplitude and phase based on the flat-top window function,and improves the accuracy of the electrical parameter estimation.For spectral leakage interference between different harmonic components,the traditional interpolation correction and phase difference correction methods are ignored in the derivation process.In response to this problem,this paper proposes another improved interpolation method.Through the interpolation correction based on the sine window function,the long-range spectral leakage interference of other harmonics is subtracted from a certain component by the current estimation result,the long-range spectral leakage interference of other harmonics is subtracted from the attention component by the current estimation result,the interpolation correction is performed again,and the loop iteration is performed several times to sequentially improve the estimation accuracy of the electrical parameter.In the case of shortening the sampling time window,it still has high measurement accuracy.For the phase difference algorithm,this paper also considers the improvement of spectral leakage interference between different components,he loop iterative correction is used to estimate the electrical parameters,so that the accuracy of the electrical parameter estimation is successively improved.The improved phase difference correction algorithm steps are arranged,and the improved correction formula is derived to achieve higher measurement accuracy.Finally,the above improved methods are simulated and compared in different environments to verify the estimation accuracy.The experimental results show that the improved algorithm improves the accuracy of harmonic parameters estimation of traditional algorithms and has some value.