Optimization And Design On LCL Filter In Photovoltaic Grid-connected Inverter

Photovoltaic(PV)power generation plays an important role in the global energy consumption,so solar PV power generation is no doubt an important source of energy supply in the future.PV grid-connected inverter,as a key part of PV power generation system,which plays an important role in energy conversion and control,so the research of grid-connected inverter has become the focus of the content of the power electronics industry.Inverter switching device is an important source of harmonic pollution in power system.The gridconnected inverter with LCL filter has high filtering performance so that it is widely used in high voltage and high power applications.However,the problem of self-resonance will lead to the unstable state of the system,it is required to add the relevant control methods and improve the structure to meet the requirements of the grid.This paper mainly studies the following points.Firstly,this paper introduces the research status of grid-connected inverter by focusing on analysis of the inverter,which is the key link of the system.Harmonic elimination scheme is proposed according to the requirement of grid-connected current harmonic.It introduces the basic topology of PV grid-connected inverter,establishes the mathematical model.From the point of grid filter,it studies the control method of grid-connected inverter adopting different filter structure with the research status of its control scheme,The LCL type structure is the key of the study.Secondly,it analyzes the selection requirements in LCL filter parameters at home and abroad in detail,the system parameter optimization scheme with low inductance and well filtering effect is put forward,And It gives the corresponding design examples.For LCL filter resonance problem,compared to the domestic and foreign key resonance suppression method,the LCL filter resonance suppression scheme optimization,split capacitor damping scheme and split capacitor improved scheme is put forward,and their resonance suppression effect and damping loss were studied.In view of the high frequency harmonic,especially harmonic in the switch frequency and 2 times the switching frequency,two kinds of LCL topology structure improvement is put forward to optimize the LCL filter,and it analyzes and compares their filter performance.Thirdly,a grid-connected inverter model is established on the Simulink platform of MATLAB for simulation and theoretical verification.simulation experiment shows that,splitcapacitor damping scheme and split capacitor improved scheme can further reduce the distortion rate of the grid-connected current and the loss of the system,and LLCL and LCLLC type topology,which are LCL filter topology optimization schemes,have better harmonic suppression ability.At the same time,the two damping schemes in LLCL and LCLLC are compared and analyzed,and the simulation results are obtained,LLCL and LCLLC filters can effectively filter the harmonic wave at the switching frequency,and the LCLLC has stronger high frequency harmonic attenuation characteristics than LLCL.Finally,the key modules of PV grid-connected inverter hardware testing platform are designed,which includes the design of main circuit and control circuit with the TMS320F2812 as the main control chip,to provide a certain basis for further hardware testing...