| Now to improve increasingly severe climate change,reducing dependence on fossil fuels is a global trend.With the development and application of the new energy power generation technology,many countries pay more and more attention to grid-connected generation system.In China combustible gas generation technology is started lately,but in recent years,China made large steps forward.Grid-connected inverter is used as the interface of new energy generation to power grid,it takes very important part in grid connection and directly affects the quality of grid-connected current.The problems such as current distortion,power losses,stability of power network and power control are the key points of this research.This paper can be divided into the following sections:The topological structure of several grid-connected inverters is analyzed.LCL filter has good high frequency filtering properties.It also has the characteristics of low cost and small total inductance.So,it has been widely studied and applied in recent years.This paper takes the single-phase LCL grid-connected inverter as an example.The mathematical model is established and the theoretical analysis and research of the control algorithm are carried out.A new method for design and optimization of controller parameters is presented.Finally,computer simulation experiment proofs that this method is availability.This paper analyzes capacitive current proportional control of inner ring,and the outer ring adopts the proportional integral(PI)or proportional resonant(PR)control algorithm for the single-phase LCL grid-connected inverter.The traditional PI parameter tuning is used to be the empirical method,trial method,frequency domain analysis.The traditional method always took a long time,and eventually couldn’t get a good outcome.Parameters optimization method of genetic algorithm is applied in this article,combined with frequency domain method and the open loop system root locus based on satisfy the system stability and robustness,then the overall optimization of the parameters is given in the convergence domain of the system.PI parameters optimization based on the genetic algorithm have no relation to gradient information.Global optimization is performed within the range of system stability.And in ITAE(index error absolute value of a moment),the introduction of rise time and overshoot as fitness function,the introduction of the rise time and overshoot effectively coordinate system stability and dynamic characteristics.In this paper,MATLAB/Simulink simulation is used to obtain the waveform of grid-connected current in the power grid.The three-phase parallel network model of PI control is constructed under the abc-αβ coordinate.It is verified that the whole set of PI parameters of the inverter has a good effect on suppressing the harmonic of the power grid,and the system obtains better dynamic and static characteristics. |
