Research On The Micro Grid-connected Photovoltaic Inverter System Based On STM32F407

In recent years,the solar power industry developing rapidly and grid power gradually have become the main trend of solar photovoltaic utilization.In the grid-connected(PV)system,inverter plays an important role in connecting the device to the side and the grid side.The topology and control strategy of grid connected inverter can improve the efficiency of the system and reduce the leakage current and improve the quality of grid connected current.The quasi Z source inverter has the characteristics that they can boost and buck at the same time,which is suitable for the wide range of voltage output of photovoltaic power generation system.In this paper,the research is based on the grid-connected PV system of quasi Z source.Its topology structure,the maximum power point tracking technology,control strategy and so on has carried on the thorough research.Firstly,of quasi Z source H4 topology photovoltaic(pv)grid inverter working in the state of zero and through,the alternating current through the switch tube internal diode stream cause greater loss problem,this paper proposes a quasi Z source inverter H6 topology and its working status and booster principle is discussed in detail,and corresponding to pulse width modulation strategy.Finally,the main waveforms are analyzed in theory.Then introduce single-phase quasi Z source grid inverter control technology,including the maximum power point tracking technology,grid current control technology and quasi Z source capacitance voltage control technology.The improved variable step perturbation method is proposed for the maximum power point tracking,and the amplitude of the disturbance near the maximum power point is reduced on the basis of ensuring fast tracking.In view of the traditional PI controller sinusoidal current command generates a steady-state tracking error and cause the more current ripple problems,the control strategy of quasi proportional resonant controller applied to the quasi Z source inverter is selected.Secondly,set up the single-phase quasi Z source H6 topology PV grid inverter experimental based on STM32F407,which used to verify the grid current tracking effect and the overall system efficiency and the size of current harmonic.The main circuit and filter circuit are introduced in this paper.The design of signal acquisition circuit and control circuit is introduced.A new type of digital PWM is designed.Finally,design software of the control system.Finally,the system is simulated and tested by MATLAB software and the experimental platform.The topology and control strategy are verified,and the simulation and test results are analyzed and explained.