Research On Frequency Adaptive Repetitive Control And Inverter Control System

With the development of renewable energy and distributed power generation,grid-connected inverters and their control strategies have received more and more research and attention.The main research content in this paper is the method of harmonic suppression for the grid-connected current of single-phase grid-connected inverter.The principle,stability,parameter design and adaptability to the frequency variation of improved repetitive control are studied.This paper first establishes the mathematical model of the LCL grid-connected inverter.The influence of passive damping and active damping on the stability of the system is analyzed,and the inductance and capacitance parameters have been designed according to the technical index requirements.Then it introduces the principle,stability and harmonic suppression ability of traditional repetitive control.For the problem of periodic delay and poor dynamic performance of repetitive controllers,a Proportional Integral Multi-Resonant(PIMR)control scheme has been proposed by scholars to improve the dynamic response speed of the system.The design method of the parameters of PIMR controller has been given,and the stability of PIMR controller is analyzed in the discrete domain.Then,a frequency adaptive RC(FA-PIMR type)scheme based on IIR filters is proposed to improve the steady-state performance of grid-connected inverter.When the grid frequency varies,the coefficients of IIR filter can be adjusted online to make the resonance frequency of FA-PIMR controller close to the actual grid frequency,so that the system can maintain good harmonic suppression performance.Finally,the MATLAB/Simulink simulation model of the grid-connected inverter and DSP controlled experiment setup have been built.The parameter design of the grid-connected inverter and the adaptive repetitive controller strategy are simulated and experimentally verified.The results show that the adaptive repetitive control system based on IIR filter can maintain admirable harmonic suppression ability when the grid frequency varies.