Research On Control Technologies Of Single-phase Gird-connected Inverter

Nowadays,the consumption of traditional energy,such as oil,coil and natural gas,is gradually increasing,which makes the world face severe environmental challenges and pay more and more attention to the renewable energy including solar energy and wind power.The research on grid-connected inverter hold great significance,for the reseason that grid-connected inverter is a vital link in the energy exchang between the grid and distributed power generation based on renewable energy. Aimed at the control technologies of single-phase grid-connected inverter,every chapter in this thesis launched the research at following works.Chapter 2 introduces the structure of the single-phase grid-connected inverter, the continuous-domain model and discrete-domain model is ginven on the basic of charateristics of single-phase grid-connected inverter for the preparation of follow-up work.In Chapter 3,the linear model of second-order generalized integrator(SOGI) based phase lock loop(PLL) is implemented according to the characteristics of SOGI-PLL. Several key parameters is designed according to the performance analysis of SOGI-PLL.Simulation results prove the design method of parmaters in SOGI-PLL is reasonable.In chapter 4, based on the characteristics of sing-phase inverter,the influence of harmonic distribution of the inverter’s output voltage,performance of filter and control strategy on the design in LCL filter is analyzed, and restriction in design of LCL filter is given. The parameters of LCL filter can be obtained by adopting graphic method. Simulation result verify that design method of LCL filter is reasonable.In chapter 5, discrete root locus is used to analyse system’s stability.It’s found that single-loop control stractegy can’t damp the resonance of the LCL filter.There’re two poles outside the unit cycle in the root locus of double-loop control system whose occurrence condition is ginven.Based on the Nyquist stability criterion, the stability conditions of system is deduced by the analysis on bode diagram of system.In chapter 6,the controller in current loop is simplified through the investigation on the frequency response of proportional resonant(PR)controller and harmonic compensator(HC).Selection range of each controller parameters are obtained through the analysis on the requirements on steady state error of grid current and system’s stability,and the method is given to select the controller prameters. Simulation results prove that the adopted control strategy makes the system obtain great harmonics antijamming capacity and dynamic performance under the distortion of grid background harmonics.