The Study Of Resonant Current Suppression Method Of LCL Grid-connected Inverter

Due to the traditional fossil energy depletion,environmental pollution and green house,distributed generation technology based on clean renewable energy has been widely concerned.Grid-connected inverter is one of the core parts of distributed generation,LCL grid-connected inverter is a research hotspot at present due to high frequency harmonic suppression.LCL filter itself is a three order system with resonance.In this paper,the method of resonant current suppression of LCL grid-connected inverter is studied.This paper firstly designed the parameters of LCL filter,analyzed the different LCL parameters influence on grid current harmonic and resonance frequency,and deduced the relationship between grid current harmonic and resonant frequency,reasonable LCL parameters can reduce the grid current harmonic.Then this paper analyzed resonance mechanism of LCL filter,A detailed explanation of the active damping of capacitor current feedback and passive damping of and capacitor series resistance are widely used.Currently most of the active damping need additional feedback channel,and some of the single grid current feedback need differentia that is difficult to implement in the project.In response to these questions,this paper proposed an improved method of active damping and only need sample the grid current,it was easier to implement due to not involve the grid current differential.According to amplitude margin and phase margin of system to design controller parameters finally,to make the system have strong robustness.A simulation model is built in MATLAB/Simulink to verify effectiveness of the proposed control strategy.Besides,experimental platform of LCL grid-connected inverter is built,the relevant control algorithm is verified on the experimental platform.The results show that the improved active damping of LCL grid-connected inverter can effectively suppress resonance.