Research On The Control Strategy Of Photovoltaic Grid-connected Inverter Based On Three-phase Double Buck Topology

Along with the shortage of fossil fuels and the increase of serious environmental pollution,the distributed generation of new energy such as solar energy and wind energy has received more and more attention.Grid-connected inverters play an important role as a link connecting distributed generation to the grid.The three-phase dual-buck inverter solves the bridge arm straight-through problem of the traditional bridge inverter and avoids the low-frequency harmonics resulted from adding the dead zone,which can effectively improve the current quality of the incoming network current.The structure of the three-phase dual-buck photovoltaic grid-connected inverter is relatively simple.The fast recovery diodes can be individually optimized.This thesis proposes a dynamic parameter tuning mechanism for fuzzy decision making in the grid-connected control of three-phase dual buck inverters to further improve the quality and efficiency of electrical energy.This thesis mainly studies from the following aspects:1.The introduction and analysis of grid-connected inverters,which is based on three-phase dual-buck topology,is presented in detail.Next,based on the analysis of the advantages over traditional bridge inverters,the discussion of its working principle under two different working modes,and the comparison of difference between the two different operating modes,the mathematical model of the three-phase dual-buck grid-connected inverter is proposed,and the principle of space vector pulse width modulation(SVPWM)is also analyzed.2.The characteristics and the damping control strategy of LCL filter are analyzed in this thesis,which also studies several methods of passive damping and the parameter limiting conditions as well.3.The thesis studies the control strategy adopted for photovoltaic inverter based on three-phase dual-buck topology,including maximum power point tracking(MPPT)control and grid-connected control.A fuzzy PI regulator dynamic parameter tuning mechanism is proposed in grid-connected control.And the parameter tuning mechanism is also simulated on the Matlab/simulink to evaluate its performance.