Research On Single-Phase High Power Factor Grid-Connected Inverter System

As the energy conversion interface between renewable energy generation unit and power grid,the control performance of grid-connected inverters directly affects the stability and power quality of the system.The research on grid-connected inverters control strategy has important scientific significance and practical value.In this paper,the single-phase grid-connected inverter system is taken as the research background.Through the research of the inverter topology structure design,grid-connected current control strategy,grid information synchronization detection technology and filter parameter design,the power factor of grid-connected inverter system is improved,the system harmonics are reduced,and the system robustness is improved.Firstly,two current control methods of grid-connected inverters,based on the rotating coordinate system and based on the quasi PR control scheme,are analyzed and compared.The quasi PR control scheme with fast response and simple control structure is selected,and the parameters design basis of the quasi PR controller is given.Secondly,the synchronous detection methods of grid-connected inverters are analyzed,the common orthogonal signal generators are compared,and a phase-locked loop scheme with multi-SOGI coupling control is proposed,which can effectively eliminate the influence of the third and fifth harmonics.The repetitive control is introduced to effectively eliminate the static error of the system and improve the detection accuracy and stability under the harmonic grid.Thirdly,the circuit structure,filter element volume,dynamic response speed,anti-jamming ability of common L,LC and LCL filters are analyzed and compared,and the function of each element in LCL filter and the general criterion of parameter design are expounded.Finally,the mathematical model of grid-connected inverters is established,the stability of the system is analyzed.The full-voltage feed-forward control module is designed to restrain the harmonic of grid voltage.The source of harmonic of grid-connected inverters is analyzed,and the restraint scheme is given.The influence of grid impedance on the stability of grid-connected inverters and the improvement scheme are analyzed,which are verified by Simulink simulation.