Single Phase Quasi-Z-Source Inverter In Grid-Connected Photovoltaic Systems

Energy is closely linked with the development of society.But with the shortage of traditional energy and its pollution to the environment,people pay more attention to renewable clean energy.Various new energy power generation systems,such as fuel cell,wind power,photovoltaic power generation,tidal power generation and so on,have been greatly developed.Among these,photovoltaic power generation is considered as the most clean,the safest and the most potential way to power generation,which becomes the industry's research hotspot.As the output of the photovoltaic battery is DC,the inverter circuit is needed to convert the DC to AC,and then be incorporated into the power grid after filtering.Because of the limitation of the traditional voltage fed(current fed)inverter,a new inverter topology,single-phase quasi Z source inverter,is discussed in this paper.In this paper,the steady operation principle of the quasi Z-source inverter is first to discuss in the theoretical analysis.All the boost control method is described,as well as the settings of impedance network parameters in the simple boost control.In order to analyze the dynamic performance of the system,the small signal model is established based on the state space average method.The transfer function between input variables and state variables and its root locus are obtained,and the influence of parameters on the dynamic response of the system is analyzed.Furthermore,the grid connected PV system is studied by using the method of constant capacitor voltage control.This method can keep the capacitor voltage constant,which decouples the input power and output power.In the grid connected current control,a quasi PR controller is designed,which can avoid the disturbance of the grid voltage and no static error.Then,the simulation on Matlab/Simulink is carried out to verify the validity of the method of constant capacitor voltage control,and the maximum power point tracking is achieved by using the variable step perturbation method.