Design And Experimental Study Of Single-phase Non-isolated Photovoltaic Grid-connected Inverter System

With the gradual depletion of fossil energy,the development of renewable energy has become the only way for the world’s energy problems.Considering the environmental factors and development potential of energy utilization,solar power generation has received more attention and because of its advantages,wide distribution and no noise.Due to the dispersive,diverse and random nature of solar energy,distributed generation systems have become the inevitable network structure for new energy generation.In this paper,the distributed photovoltaic power generation system is taken as the background,and the 5kW photovoltaic grid-connected inverter is considered as the research object.The key technologies are as follows:Firstly,the background and research significance of photovoltaic power generation are introduced.The common topological structures of photovoltaic grid-connected power generation system structure,isolated and non-isolated inverter topology,and common mode current are analyzed,and their advantages and disadvantages are described.The structure,working principle and technical advantages of the distributed generation system adopted in this paper are analyzed.The key problems of the power generation system are presented,such as the output voltage control of the power optimizer,the fault protection of the inverter,and the DC bus voltage control.The personal work content and inverter design indicators are explained.Secondly,the topology and working principle of single-phase non-isolated photovoltaic grid-connected inverter are discussed,and the topology of the common-mode current suppression is theoretically analyzed.Then,the hardware part and the software part are designed separately.The hardware part is designed with the auxiliary power supply,drive circuit and detection circuit for the high voltage input of the system.The software part is controlled by TI’s TMS320F28335 chip,including DC bus detection,DC side current detection and inverter pulse width control.The system’s double closed-loop regulator is designed,and the double closed-loop Bode diagram before and after correction using PI control strategy is drawn,and the program flow of the system software is designed.Finally,the single-phase photovoltaic grid-connected inverter system was simulated and verified based on the Psim simulation platform.At the same time,the experimental prototype was built according to the system index.The research focused on the design of auxiliary power supply,double closed loop of system,system SPWM drive waveform and output current.The simulation and experimental results prove the feasibility and theoretical analysis of the parameter design of single-phase non-isolated photovoltaic grid-connected inverter system.There are 58 figures,9 tables and 62 references in this paper.