Research On Three PV Grid-connected Inverters Based On PI Control And Repeated Control

With the advancement of science and technology and the development of the times,energy has occupied a dominant position on the world stage.In the case of increasing global warming and other problems,green and environmentally friendly new energy sources have become the objects of development in various countries around the world.The inexhaustible features have attracted the attention of various countries.Among them,photovoltaic power generation is one of the most common and efficient ways to use solar energy.As an important component of the entire photovoltaic power generation system,photovoltaic grid-connected inverters have always been a research hotspot.This article takes three-phase LCL photovoltaic grid-connected inverter as the main research object,analyzes the advantages of LCL filter compared to L filter and the mathematical model of LCL grid-connected inverter in different coordinate systems,and in order to suppress resonance spikes,The active damping control and passive damping control methods are analyzed,on this basis,the PI control and repetitive control of grid-connected inverters are studied.The specific research contents are as follows:(1)To construct a photovoltaic grid-connected system,firstly,by comparing the LCL filter and the L filter,it is found that the LCL filter is more suitable for the research in this paper,and then mathematical modeling of the LCL grid-connected inverter system is established to establish the LCL grid-connected inverse The equation of state of the transformer in three-phase stationary abc and two-phase stationary ?? coordinate system.(2)In view of the existence of resonance spikes in the filtering process that affect the stability of the inverter,a comparative analysis is conducted from two perspectives of passive damping control and active damping control,and it is decided to use a passive damping control method based on capacitor series resistance to suppress resonance Peak,and set the parameter value of LCL photovoltaic grid-connected inverter according to the passive damping control scheme.(3)Based on PI control,repetitive control and improved repetitive control,the grid-connected photovoltaic inverters are studied respectively.On the basis of sufficient research on single PI control and repetitive control,a compound control strategy of PI control+repetitive control is proposed.And research and design it,verify the stability of the controller,and theoretically get the PI control+repetitive control compound control scheme is feasible.(4)Modeling simulation and analysis,using Matlab/Simulink software to build a single PI control inverter and PI+repetitive control composite inverter model.Under ideal conditions,the grid-connnected quality of the composite inverter compares with other The control method is higher,and the simulation results obtained are analyzed and compared to verify that the composite control method based on PI control+repetitive control is superior to the single PI control method.Compared with the existing PIR control under the same damping conditions,PI+repetitive control THD The value of 0.78%is much smaller than 1.73%of PIR control,confirming that PI+repetitive control is superior in suppressing harmonics.