Current control of LCL grid-connected inverter with improved repeated control-fractional order linear active disturbance rejection
HE Biao
LIN Shan
WANG Xiao-hong
PAN Zhi-feng
Abstract：A three-phase LCL inverter has the advantages of significant high-frequency suppression and compact size.However,the inherent resonance of the LCL filter can easily lead to system instability.In this paper,a fractional order linear active disturbance rejection control(FOLADRC)based on fractional order linear expansion state observer(FOLESO)is designed.The disturbance compensation characteristics of FOLESO are used to suppress system resonance.On this basis,an improved repetitive control(RC)with a phase-shift-free low-pass filter and a reduced-order frequency-adaptive phase lag link is introduced to further enhance the system's capability to suppress periodic current harmonics.The detailed design process,parameter tuning,and related performance analysis of the improved repeated control-fractional order linear active disturbance rejection control(RC-FOLADRC)strategy are provided.Simulation and experimental results demonstrate that the proposed RC-FOLADRC exhibits strong robustness to disturbances in grid impedance,LCL filter parameters,and grid frequency,while ensuring accurate current tracking performance.Therefore,the RC-FOLADRC can be effectively applied to LCL inverters,resulting in optimal grid-connected current.
Keywords：LCL inverterimproved repetitive controlfractional order active disturbance rejection controlcurrent harmonic suppression
Publication Date：2025-06-30
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：13( 1101-1113 )