Study On Repetitive Control Strategy For Harmonic Suppression Of Lcl Grid-connected Inverter

In this paper,Three-phase two-level LCL filter inverter is used as the controlled plant,and the mechanism of the work of the repetitive control on the system is studied.Based on this,the optimization method of the controller is studied in order to achieve good dynamic and static operating characteristics under the premise,and improve the parameter adaptability of the controller.First,the working principle of the LCL grid-connected inverter is studied,mathematical models of continuous domain and discrete domain in the three-phase stationary coordinate system(a,b,c)and two-phase stationary coordinate system(?,?)of the LCL grid-connected inverter under grid-side current control and inverter-side current control are established respectively.The influence of the resonant frequency of the LCL filter and the digital control delay on the stability of the system are analyzed.The basis for selecting the parameters of the LCL filter is discussed.Secondly,under the conditions of grid-side current control and inverter-side current control,the effect of different controllers on the system is studied respectively.The gain range of the system controller under single closed-loop control is clarified,and respectively combine embedded repetitive control and repetitive compensation control as outer loop;the repetitive controller parameters and filter parameters,digital control frequency,digital delay,and current loop and the limiting relationship between control gain are studied.On this basis,the general design method of the embedded repetitive control and repetitive compensation control as outer loop are given.And through the improvement of the current inner loop under the premise of ensuring the advantages of waveform control of the repetitive control,the parameter adaptability of the repetitive compensation control as outer loop is optimized,thereby improve the stability of the system.Finally,the feasibility and effectiveness of the research content and the control method studied are verified through experiments.Through simulation and experiment comparison,the correctness and effectiveness of the design method of the repeated controller parameter design are verified.what's more,the parameter adaptability and system operation stability margin of the repetitive compensation control as outer loop control method can be improved on the basis of effectively suppress the content of harmonic of the grid-connected current...