Study Of Nonlinear Phenomena For Inverters Based On Quasi PR Controller

With the rapid development of science and the development of power electronics technology,power electronic devices have been applied to various industries,including national defense,civilian production,agricultural production and so on.Because of the switching devices and feedback controlled system,the power electronic converter becomes a kind of strongly nonlinear system.The nonlinear phenomena such as bifurcation and chaos appear while the converter is working under certain conditions,which will seriously affect the service life and working state of power electronic converters.Inverter is an important part of the power electronic converter.There will be great practical significance and academic value owing to the research on nonlinear phenomena in it.Based on the analysis of predecessors’ research,the single-phase inverter and the three-phase grid-connected inverter with quasi-proportional resonance are taken as the research object in this thesis,and the nonlinear phenomena are analyzed.(1)First of all,the single-phase first-order full-bridge inverter based on quasi PR regulator is taken as the research object,and the mathematical model of its main circuit and control loop is established by stroboscopic mapping method.The proportional coefficient is used as the bifurcation parameter.The nonlinear phenomena are analyzed by the bifurcation diagram of the system,the eigenvalue trace of the Jacobian matrix,the folding graph and the simulation waveform of Simulink.The proportional coefficient and the integral coefficient are taken as bifurcation parameters,and the stability of the system under two bifurcation parameters is obtained by MATLAB.Then the analysis of the single-phase second-order double-loop H-bridge inverter with quasi-PR regulator is based on the first-order inverter,and the discrete mathematical model of the system is deduced.By analyzing the bifurcation diagram of the system,the eigenvalue trace of the Jacobian matrix,the folding graph and the simulation waveform of Simulink,the conclusion can be drawn and the stability of the system under three bifurcation control parameters is established.(2)Based on the above research,the research on the nonlinear phenomena of the inverter is extended from single-phase passive inverter to three-phase grid-connected inverter.The discrete mathematical model of three-phase LCL grid-connected inverter based on quasi-PR regulator is established in the α-β coordinate system.The stability of the system regulator have been obtained by the numerical analysis and stability analysis of the inverter.The bifurcation type and oscillation frequency of the system are determined by the bifurcation diagrams and the eigenvalue trace of the Jacobian matrix,then the correctness of the nonlinear analysis of three-phase grid connected inverter is verified by Simulink.(3)The time-delayed feedback control method and the second-order band-elimination filter are used to control the nonlinear behavior in inverters.The Jacobian matrix of discrete mathematical model is established.According to the characteristics of Jacobian matrix,the appropriate parameters of the two control methods are determined by MATLAB,and the validity of the two methods is verified by Simulink.