High Frequency SAPF Optimization Method Based On Vector DFT Selective Harmonic Extraction And Wide-frequency Grid Adaptive Technology

In the development process of "full electrification",aircraft has gradually entered the stage of multi-electric aircraft,and the number of electrical equipment used in aviation has gradually increased.Therefore,the harmonic pollution faced by the aviation power grid has become more and more serious.The operating frequency of the aviation power grid varies in a wide range of 360-800 Hz,which is at least 7 times higher than the frequency of the traditional power grid.Therefore,the harmonic problem of the aviation power grid has high harmonic frequencies,easy changes,and wide harmonic frequency bands.The traditional active power filter(APF)based on Si devices is faced with the challenges of insufficient current control bandwidth and wide grid frequency adaptability.In recent years,the new device technology has gradually matured.In this paper,a high-frequency parallel active power filter(SAPF)based on Si C devices is used to control the harmonic problems in the aviation power grid.The SAPF operating frequency is increased to 100.8k Hz and the current control is increased.This article proposes three optimization methods to improve the ability of harmonic control in response to the difficulty of harmonic control of aviation power grid.Aiming at the slow dynamic response speed of harmonic extraction and the highfrequency SAPF calculation load,this paper proposes a fast designated sub-harmonic extraction optimization method based on Vector Discrete Fourier Transform(VDFT).This method reduces the computational burden of DSP and overcomes the shortcomings of slow dynamic response based on the iterative discrete Fourier transform(RDFT)harmonic extraction method and the inability to decouple the positive and negative sequence components of the harmonic.The ability to extract the specified sub-harmonics from the nonlinear load harmonics within the wave period was verified by simulation.Aiming at the problem of wide-range changes in aviation power grid frequency,this paper proposes a frequency adaptive method based on fractional-order delay approximation to extract specified sub-harmonics.It realizes the automatic tracking of the harmonic extraction link to the grid frequency,reduces the error of the harmonic extraction link caused by the frequency change,and carries out simulation verification on this.Aiming at the problem of insufficient control bandwidth of the PI current controller for the harmonics in the aviation power grid,this paper adopts a quickspecified sub-harmonic compensation method with phase compensation function.This method can maximize the effect of the steady state compensation.PI regulator has the advantage of fast response speed.Combined with the VDFT-based fast designated subharmonic extraction optimization method,the harmonics can be tracked and compensated for 1/6 cycles after the load sudden change,and this has been verified by simulation.Therefore,the high dynamic response speed of high-frequency SAPF will be suitable for aviation power grids with frequent frequency changes and frequent load switching.This paper proposes three optimization methods that are also used in traditional50 Hz power grids.Finally,this paper verifies the performance of high-frequency SAPF in a 50 Hz power grid.