Research On The Control Strategy Of The Three-phase Photovoltaic Grid-connected Inverter With LCL Filter

The main way for the large-scale development and utilization of renewable energy is based on distributed generation of renewable energy.Due to the distributed power generation system with high energy utilization rate,the development process of small pollution,high reliability,is a power generation mode of rapid development.Among them,the photovoltaic grid connected inverter composed of power electronic devices is used as the energy exchange interface between the photovoltaic power generation unit and the power grid.Grid connected inverter is very important for the whole power system,which determines the quality of grid connected current.In this paper,the main research object of the LCL three-phase grid connected inverter is the control strategy.The topology of LCL three-phase grid connected inverter is studied,and the mathematical model is established in the static coordinate system and the rotating coordinate system.This paper analyzes the filtering characteristics of the output filter LCL of the three-phase grid connected inverter,and the characteristics of the LCL filter are easy to resonate.The active damping method is used to suppress the resonance of the LCL filter without changing the filtering characteristics of the LCL structure.The filter parameters of LCL filter are designed.The current control strategy of LCL type three-phase inverter with double loop,comparing the inverter side current and grid current as feedback quantity when the effect of the stability of the system,using the grid current as outer loop control,the capacitor current feedback as an inner control volume ratio.By comparing the common current controller,the quasi proportional controller is used as the controller of grid connected current outer loop.The current double closed loop control strategy is proved to have good stability by MATLAB/Simulink.The influence of the grid voltage on the grid connected current is analyzed,and the structure and function of the full feed-forward function are analyzed.Build a LCL type three-phase grid connected inverter in MATLAB/Simulink model,the voltage of ideal and non ideal state,control strategy and grid voltage feedforward full current double loop,current quality meets the requirements of the grid current.