Research On Supraharmonic Detection And Filtering In Low Voltage Distribution Network

With the development and progress of electronic technology and material technology,the propagation characteristics of supraharmonics in the frequency range of 2k Hz-150 k Hz have become more complicated,causing more serious power quality problems,which has attracted the attention of many scholars.This article focuses on the generation mechanism and distribution characteristics of supraharmonics,supraharmonic detection methods,the improvement of resampling methods,the improvement of filtering methods,and the verification of the feasibility of the method by hardware-in-the-loop simulation.This article first classifies the common supraharmonic harmonic sources in low-voltage distribution networks,simulates SPWM circuits and Boost circuits and derives mathematical models,analyzes the generation mechanism of supraharmonics,and introduces the supraharmonic sources in low-voltage distribution networks.The characteristics of sub-harmonics,high-frequency power electronic converters and new-type lighting equipment are simulated and analyzed to verify the characteristics of supraharmonics in low-voltage distribution networks.The standard harmonic grouping method and frequency band aggregation method are used to analyze the supraharmonics.The distribution characteristics of harmonics are studied.After that,this paper introduces the hybrid segmented detection method of characteristic frequency acquisition,and designs the corresponding simulation,and obtains the advantages and disadvantages of this method through simulation.In order to improve the shortcomings of this method,this paper proposes a simultaneous sampling method of the merging unit at equal intervals,and simulates the method.The simulation finds that this method can improve the synchronization of sampling,but there may be a time difference in the sampling process.Cubic spline interpolation resampling can eliminate this time difference,but the calculation of cubic spline interpolation resampling is complicated and not very practical.This article improves the cubic spline interpolation resampling based on the relevant characteristics of the merging unit and the calculation of the matrix at equal intervals.The feature reduces the complexity of the algorithm,and on this basis,the feasibility of the method is proved by simulation.Subsequently,this article discusses the shortcomings of the traditional active power filter through simulation,and proposes an improved method to increase the corresponding speed by changing the phase-locked loop in the AHF from an integer order to a fractional order,and to lock the fractional-order SRF-PLL.The principle and control model of phase loop and 0.7-order Butterworth filter are described accordingly,and the rationality and feasibility of the improved AHF are verified through simulation.Finally,this article combines hardware and software to realize an improved three-bending moment method cubic spline interpolation resampling method through hardware-in-the-loop simulation and demonstrates the superiority of the method.