Design Of Flyback Micro Photovoltaic Inverter

In today’s society where economic growth is accelerating,environmental pollution is the most important issue.Thermoelectricity power generation needs to consume more resources that are non-renewable and facing depletion.Oil resources will be depleted in 45 years.The combustion of coal causes great pollution to the environment,and new energy is attracting increasing attention.In this case,solar photovoltaic technologies came into being.In the background of photovoltaic power generation,this thesis explores photovoltaic inverter design.To begin with,this thesis introduces the research and development conditions of solar power generation,and compares existing popular schemes for solar photovoltaic power generation.Then,in close contact with actual demand,it puts forward a design scheme for distributed generation micro-inverter systems,which install solar photovoltaic modules to the roof of households and are easy to realize.Afterwards,it investigates the technical problems of micro-inverters,such as occlusion and photovoltaic efficiency.In this thesis,a single solar panel is used to design a grid-connected PV micro-inverter based on the flyback topology.First,it analyzes the flyback topology structure,compares Continuous Conduction Mode(CCM)with Discontinuous Conduction Mode(DCM)flyback converters,and applies CCM flyback converters to the boost mode.Moreover,it explores the working principle and driving mode of the H-Bridge circuit and designs the DC voltage sampling circuit,the primary current isolation sampling circuit in flyback converters,the grid voltage acquisition circuit and the zero crossing acquisition circuit.In terms of software,this thesis analyzes the common MPPT(maximum power point tracking)algorithm and presents a variable step perturbation and observation method.Through establishing a state space equation of the inverter system,this thesis obtains the transfer function and judges the stability of the system by running a BODE plot analysis,as well as the stability and response speed of adding the PI link and the feed-forward link correction system.Finally,the system is designed by MATLAB modeling.This design simplifies the micro-inverter topology by using the flyback topology,so that the structure of the micro-inverter system becomes practical and simple.Further,the MPPT algorithm enables maximum power points to be quickly tracked.The method is fast and highly accurate,and PI link and feed-forward control have effectively improved the tracking speed of current.The validity and feasibility of the proposed method are proved by simulation experiments.