Research On Harmonic Source Detection And Location Method For Distribution Network

With the advancement of industrial technology,the power market demand for power quality is gradually increasing,and the power supply in the power system uses power electronic equipment to generate harmonics into the power grid during the transmission and distribution process,and the non-linear load is also used by the power supplier.Harmonics are generated to affect the power quality of the distribution network.The decline of power quality will adversely affect the safe operation of the distribution network,and effectively controlling the harmonic content of the distribution network is a necessary means to improve the quality of the power.Therefore,the harmonics of the distribution network are detected and the harmonic source is determined.The location to clarify the responsibility of harmonic pollution,and ultimately achieve the purpose of improving power quality.The actual harmonic signals in the distribution network include steady-state signals and unsteady signals.For steady-state harmonic signals,they can be detected by Fast Fourier Transform.Four 3rd-order Nutall windows are used for its spectral leakage and fence effect problems.Four-line interpolation detection method is used to obtain accurate amplitude,frequency and phase by simulating a given signal;for unsteady harmonic signals,it can be separated into high and low frequency bands by wavelet transform,and fast Fourier detection is used for low frequency bands.The method of high-frequency band wavelet reconstruction combines the two methods to improve the accuracy of detection.By giving a certain signal model,the simulation obtains the accurate harmonic amplitude and verifies the effectiveness of the method.In order to clarify the harmonic responsibility,it is necessary to carry out the research on the harmonic source location of the distribution network.and quantitatively estimate the harmonic emission level of the user side.The judgment protocol is proposed for different distribution network lines,combined with the quantitative estimation of the harmonic emission level to determine the position of the harmonic source.Quantitative estimation includes"interventional"estimation method and"non-interventional"estimation method,and the harmonic emission level of each harmonic source is estimated by calculating the harmonic impedance.The multi-collinearity problem exists in the non-interventional binary linear regression method.The ridge regression estimation method can effectively solve the collinearity problem,and the regression coefficient is obtained by using the ridge regression estimation,and then the specific harmonic emission level is estimated.For the simple distribution network,the MATLAB model is used to analyze the third,fifth and seventh harmonics.Compared with the binary linear regression estimation results,the superiority of the ridge regression estimation in solving the collinearity problem can be obtained.Harmonic emission level,clear harmonic responsibility,and achieve harmonic source positioning.In order to verify the effectiveness of the proposed method,the actual data is collected in the laboratory,and the data processing is carried out to finally realize the harmonic source localization.