Design And Implementation Of Flyback Inverter With Harmonic Suppression Function

A large number of power and electronic devices in the power system have resulted in a decline in the quality of their power,while the uncontrollability and random fluctuation of the distributed power supply greatly increase the harmonic content in the load injected into the power grid.Grid connected inverter is an important energy interface between distributed generation system and large power grid and users,how to make the distributed generation system transmit active power to the grid and suppress the harmonic currents generated by nonlinear loads has become a research hotspot.Based on the research of grid connected technology of distributed generation,combined with the structure and principle of grid connected inverter and active power filter,a micro inverter with harmonic suppression function is designed.Firstly,the single-phase micro inverter as the research object,the topology classification and working principle of the micro inverter are introduced in detail.The mathematical model of the micro inverter is analyzed,the state equation of the micro inverter system is obtained,and the dynamic characteristics of the micro inverter system are analyzed.Secondly,the control strategy of grid connected inverter and the main method of harmonic detection are described in detail.The compound control strategy,which takes the PI closed loop as the core and the output voltage as feedforward,is determined.The principle of harmonic detection method based on FFT transform is emphatically analyzed.From the theoretical point of view,this paper presents a method to realize the harmonic compensation of the specified order by the FFT result.The simulation model of the flyback micro inverter system is established through Simulink,and the effectiveness of the control system is verified.Finally,a prototype is designed to verify the feasibility of harmonic compensation through a grid connected inverter.The design of the main circuit,driving circuit and sampling circuit of the prototype is described in detail.The design idea and process of the software system are introduced.The logic of fast FFT transform based on FPGA is designed.The experimental results show that the designed flyback inverter can achieve the function of active output and harmonic suppression.