Research And Application Of Repetitive Control For Three-phase Grid-connected Inverter With LCL Filters

With the rapid development of the global economy,the demand for energy continues to increase rapidly.Relying on the pollution caused by traditional energy-oil and coal,global climate change is receiving more and more attention from all countries.Vigorously developing new energy industry has become the first choice of countries,and the new energy power generation industry has made considerable progress.As a core component of new energy power generation system,grid-connected inverter has become a research hotspot in this field.Power supply quality is the most important indicator for grid-connected inverters.This paper aims to improve grid-connected current quality and carry out research on grid-connected inverter’s repetitive control technology.The main contents are as follows:The overall design of the three-phase grid-connected inverter has been designed.Based on the analysis of common topologies and the characteristics of the fan system and the design requirements of the grid-connected inverter,the topology of the threephase grid-connected inverter with electrical isolation is designed.According to the working principle of the topology and the requirements of grid-connected parameters,the parameter design and selection method of the circuit components are given.A repetitive controller with fast dynamic response and its parameter design method are designed.Aiming at the slow dynamic response characteristics of the repetitive controller,a cascaded compound repetitive controller with fast response speed is proposed combined with the fast-dynamic response capability of the PI controller and the ability of the repetitive controller to suppress the steady-state error.Combined with the stability conditions of the control loop and the system response performance requirements,the design method of the controller parameters is given and simulated.A frequency adaptive repetitive controller and its parameter’s tuning method are designed.Considering the time-varying characteristics of the grid voltage frequency,it is difficult for the repetitive controller to accurately track the harmonic components and periodic disturbances,and the internal model of the repetitive controller needs to be optimized.The Lagrange interpolation method is used to fit the fractional internal model,and a third-order FIR filter is designed to optimize the internal model of the repetitive controller.Based on this scheme,a reasonable parameter design method for the third-order FIR filter is given and verified by simulation.The prototype of grid-connected inverter was designed and implemented,and the repetitive control method proposed in this paper is verified by experiments.Firstly,the overall scheme of the inverter is designed.Secondly,the DSP-based controller and inverter are designed and implemented.Finally,the superiority of the repetitive controller for reducing the steady-state error of the periodic signal and the effectiveness of the improved algorithm are verified by experiments.