Research Of Quantifying The Harmonic Contribution Of Multiple Harmonic Sources In Power System

With the increasing of nonlinear load in the power grid,the harmonic problem of power system is attracting more and more attention.Amount of harmonics is injected into the power system by various nonlinear loads,which affects the electrical environment of the power grid and cause many hazards.With the rapid development of the electricity market,it is not an effective method to restrict the access and operation of nonlinear loads only with the limit value of harmonic injection.In order to more effectively manage harmonics in power grid,"A harmonic rewards and punishment method" is proposed,internationally.This method is aimed at limitating and controlling the harmonic pollution through the establishment of a fair and effective harmonic rewards and punishment mechanism.Therefore,the research of quantifying the harmonic contibutin of multiple harmonic sources could not only provide the basis for the implementation of the "harmonic rewards and punishments"and improve the user’s credibility,but also provide reference for improving the harmonic management measures.Firstly,considering the influence of outlier data on the results of multiple harmonic sources’ contribution in this thesis,a method of quantitative calculation of multiple harmonic sources contribution is proposed which is based on weighted complex least square method.Reference to the concept of bad value distance from statistics,a judgment method is proposed to determine whether including outlier data in the sample data.In this thesis,a new thought for determining the weight coefficient by Andrew wave function is presented,and the method of determining the weight coefficient matrix is given.Compared with the complex least square method,this method could reduce the influence of outlier data on the regression results,and have a good robustness.Secondly,the multi-harmonic contribution quantization method based on partial variable-coefficient model is proposed in this thesis,considering the fluctuation of background harmonics.The method to determine the optimal smooth parameter is improved,which reduces the calculation error of the harmonic contribution with the flutuation of background harmonics.The method could improve the accuracy of the harmonic coontribution calculation results in the context,where the amplitude of bachground harmonics fluctuation and the amplitude of the harmonic current source are similar.In the end,the weighted subdivision iterative method which combines weighted least square method and subdivision iterative method is proposed for the special case where the background harmonics fluctuates and outlier data exists.By weighting the sample data,the algorithm gives a small weight coefficient to the outlier data points,and finds the calculation window width with the least error accuracy through the subdivision iteration method.Through the analysis of simulation case,it is verified that the weighted iteration method could improve the accuracy of the system side impedance calculation,in the special condition where the background harmonics flutuation and outlier data exist at the same time.The method improves the feasibility of quanlityfing multi-harmonic contribution in this condition.