Research On The Control System Of Grid-connected Single-phase Photovoltaic Inverter

With the continuous depletion of traditional fossil energy and the environmental problems it brings,solar energy has been widely used due to its clean,pollution-free and inexhaustible advantages.Among them,the most important is the application of photovoltaic grid-connected power generation.Grid-connected inverters,as the most important part of photovoltaic power generation,are a key part of converting solar energy into electricity and into the power grid.The article mainly related to the research of grid-connected single-phase PV inverter control technology,mainly including maximum power tracking,grid-connected control technology and islanding detection technology.In this paper,a grid-connected single-phase photovoltaic inverter is studied.First,the topology structure is analyzed,and a two-stage non-isolated system topology is selected.The Boost circuit is used in the front stage and the single-phase full-bridge inverter circuit is used in the rear stage.First of all,the principle of the photovoltaic cell and its output characteristics are related analyzed to establish a corresponding simulation model.The maximum power point tracking is studied and an improved conductance increment method is used.Compared with the traditional conductance increment method,it has a better tracking effect.Secondly,it is the study of grid-connected control technology.The control strategy of the voltage outer loop current inner loop based on the grid voltage feed forward is given.The pre-level and post-level systems are controlled separately.The pre-stage achieves maximum power tracking,the post-level realizes grid-connected control.In order to accelerate the response speed of the system when the external environment changes,the power feedforward control is added,and establishes the system's simulation model.Finally,the related researches on islanding detection in grid-connected systems are carried out.In view of the shortcomings of the active frequency offset method,the active frequency offset method based on positive feedback is used in this paper.Build a corresponding simulation model in Matlab/Simulink,indicating that the improved conductance increment method has higher tracking efficiency and smaller power fluctuations.Through the simulation analysis of the two-level grid-connected system,it shows that the control strategy is feasible,the grid can be successfully implemented,the power quality meets the grid connection requirements,and the response speed to the external environment changes quickly.Finally,for the islanding effect of the grid-connected system,the positive feedback-based active frequency offset method can quickly detect the generation of isolated islands,and the current distortion rate also meets the requirements of the grid connection.