Control Strategy Research And Implementaion Of Single Phase LCL Grid-connected Inverter

With the improvement of environmental protection awareness,new energy power generation has received more and more attention.As a key equipment of distributed power generation,grid-connected inverter plays an important role in the stable operation of distributed power generation system and even large power grid.The control performance of grid-connected inverter largely depends on its control algorithm,so it is necessary to study the control algorithm of grid-connected inverter.In this thesis,through the relevant simulation and design,the experimental prototype of the grid-connected inverter is built,and the feasibility of the control strategy is verified on the experimental prototype.Inverter in synchronous rotating coordinates all state variables are straight flow,d-q coordinate transformation can be ac signal with static coordinates transform into dc signal synchronous rotating coordinate system,this thesis discusses a kind of synchronous rotating coordinate system under the PI control strategy,the control strategy of the first to use second-order generalized integrator constructing orthogonal signal,then based on two orthogonal signal using Park transformation of coordinate transformation,d-q coordinates is established under the grid inverter control model,and based on this the right PI controller is designed,the high accuracy tracking grid current of inverter.Coordinate transformation can increase the design difficulty of system,and based on the control strategy of PR and PR of the control strategy of the inverter can be realized under natural coordinate current zero steady-state error tracking,but after analysis showed that the Quasi PR stronger anti-interference ability of the controller,so this article in the design of two kinds of control strategies of current use on outer ring must PR controller;To exist in practical engineering applications,the sensor noise pollution,the problem of low precision etc,this thesis proposes a state observer based active damping + control strategy of PR,Luenberger state observer is used to estimate the capacitive current,avoid the use of sensor noise pollution brought by the question,then using capacitive current observations feedback to realize active damping of LCL grid inverter,again through the Quasi PR control current loop to realize zero steady-state error control;System of pole distribution determines the main performance of the system,in order to improve the LCL performance,this thesis proposes a state feedback based on state observer must PR + control strategy,,based on state observer is designed state feedback,configuration LCL system pole fell in the desired location,improves the performance of the LCL system,realize the active damping at the same time,because the state feedback inhibition of steady-state error effect is poorer,then add a PR control of current loop,and then realize the grid current without error tracking control.At last,this thesis carries out the corresponding experimental verification on the experimental prototype.The simulation and experimental results show that the PI control strategy based on the synchronous rotating coordinate system can achieve better control accuracy.The control strategy of active damping + Quasi-PR based on state observer can realize zero steady-state error control of grid-connected inverter.The control strategy of state feedback + Quasi-PR based on state observer can obtain the performance of zero steady-state error tracking of grid-connected current without increasing the sensor.