The Development Of Interleaved Flyback Photovoltaic Grid-connected Micro-inverter

With the rapid development of the economy,energy resources in the world are becoming increasingly tense.Countries are seeking renewable and clean energy to replace traditional non-renewable energy sources.In recent years,solar energy has received increasing attention because of its own renewable advantages.The distributed power generation system built by the micro-inverter can overcome the problem of maximum power tracking in the local shadow of the traditional centralized photovoltaic power generation system,and has excellent performance such as high safety,high efficiency,and high scalability,thus the micro-inverter Research is of great significance.The research object of this thesis is a photovoltaic grid-connected micro-inverter.It grasps three key technical issues,analyzes the hardware principle,maximum power point tracking and control strategy,and designs a staggered flyback photovoltaic grid-connected microinverter.First,the advantages and disadvantages of common DC-DC circuit topologies are compared.The characteristics of flyback micro-inverters operating under different modes are analyzed.By analyzing the working principle of the micro-inverter main circuit in the intermittent conduction mode in detail,an active clamp circuit is added to increase the boosting capacity and conversion efficiency of the micro-inverter.Second,a sliding mode variable structure control strategy based on the perturbation observation method is proposed for the slow and unstable tracking requirements of the micro-inverter.The simulation proves the rapidity of tracking and stability.for the grid-connected control strategy,by modeling and analyzing the flyback inverter under non-ideal conditions,the current PI loop compensation and voltage feedforward compensation control methods based on fuzzy inference are determined,which simplifies the control loop.The simulation results show that the control method can reduce the harmonic distortion of the output current of the micro-inverter,improve the quality of the grid connection,and has the advantages of good stability and small control deviation.Thirdly,it was designed on hardware and software.detailed calculations and derivation are made for each parameter in the design,and the design of the flyback transformer and other circuits,and the selection of the main control chip and various components are introduced.On the software,the control flow of the main program and each subprogram is introduced.Finally,an experimental platform was set up to debug the 220 W flyback micro-inverter prototype.The simulation and experimental results proved the feasibility of the theoretical analysis.