Analysis And Control Of Dynamic Characteristics Of DC Converters And Inverters In Photovoltaic Power Generation Systems

With the consumption of traditional energy and the increasingly serious environmental pollution,solar energy has developed rapidly by virtue of its clean,non-polluting,renewable advantages.However,with the increase of the scale and the grid capacity of photovoltaic power system,the stability control of the system has been put forward a severe test.Due to the power electronic devices such as DC/DC converter and inverter,the nonlinear characteristics of the photovoltaic power system are more obvious and prominent than the conventional power system.To ensure the security and stability operation of the power grid,the useful controllers must be built on the basis of detailed dynamic characteristics of the photovoltaic power system.In this thesis,the fundamental dynamic characteristics of DC/DC converter and inverter in photovoltaic power system are deeply analyzed,and the appropriate control method is selected to suppress the chaotic oscillation generated by the system.The main research contents of this paper are given as follows:Firstly,the switched inductance structure is added to the traditional converter,and the discrete model of the system is established with the strobe mapping method.The bifurcation and chaos dynamic behavior are analyzed through the bifurcation diagram,Poincare section and Lyapunov exponent spectrum.The range of chaotic motion in the photovoltaic power system is determined,and the sensitivity of the system to the reference current is intensively studied.The dynamic behavior of the system is more abundant compared to the traditional converter,and the Simulink simulation circuit is built to verify the accuracy of the discrete model.Secondly,the discrete mathematical model of inverter circuit for single phase H bridge is established.With the proportional regulation coefficient varying,the dynamic properties of the system are investigated through bifurcation diagram,Lyapunov exponent spectrum and Root locus diagram.The stability domain parameter range is divided through double parameter stable domain diagram.The study of nonlinear dynamics is extended to the grid connected inverter,which lays a foundation for the promotion and deepening of the follow-up research.Finally,the slope current compensation method is applied to control the chaos of switched inductor Boost converter,which makes the converter working in the unstable chaotic state enter to a stable periodic state.For the inverter circuit for single phase H bridge,the control effect of delayed feedback control is compared with the Washout filter control,which shows that the delayed feedback control has more advantages.