Research On Control Strategy Of MPPT And Inverter Midpoint Voltage Balance Of Photovoltaic Grid-connected System

In the development of new energy technology,photovoltaic power generation has become the main form of new energy technology due to its abundant sources,clean and efficient.With the gradual maturity and popularization of photovoltaic power generation technology,how to maximize the efficiency of photovoltaic power generation has become the current Research hotspots.However,with the popularization and use of photovoltaic power generation technology,some problems have gradually emerged,such as the lack of convergence speed and tracking accuracy of the maximum power point tracking algorithm of traditional photovoltaic cells,which causes the inverter bus voltage to oscillate and increases the grid-connected inverter.The control difficulty of the inverter and the harmonic content of the output current reduce the grid-connected efficiency of photovoltaic power generation.In order to improve the tracking speed of the maximum power point,reduce the bus voltage oscillation,and improve the grid efficiency and power quality,this paper takes the bipolar photovoltaic power generation grid-connected system as the research object,and proposes a maximum power based on sliding mode variable structure control.Point tracking control algorithm.The algorithm uses conductance and conductance change as parameters to design a sliding mode surface.By introducing an adaptive threshold,the algorithm can quickly converge to the maximum power point,while reducing the chattering problem of sliding mode control.MATLAB/Simulink software compares the tracking effect of the maximum power point tracking algorithm of sliding mode variable structure control and the traditional maximum power point tracking algorithm,which verifies the effectiveness of the algorithm in this paper.The back-stage DC-AC circuit adopts an active midpoint clamp type three-level inverter structure.Because the clamp tube adopts a controllable IGBT,an additional current path is added when the output is zero-level,so that each bridge The conduction losses of the switches inside and outside the arms are almost equal,so as to solve the problem of poor heat dissipation of the upper and lower arms of the three-level inverter clamped by the diode.At the same time,a redundant vector control based on the neutral point voltage balance of the DC side is proposed.This control algorithm is based on SVPWM control.Since only the action time of the redundant small vector is changed,the action sequence and switching frequency of all vectors are not changed,and the midpoint voltage is quickly stabilized and tends to be balanced.Under the premise,the output power quality is improved,and the prototype experiment proves the effectiveness of the above control strategy.There are 48 figures,4 tables and 64 references in this paper.