Design Of Quasi-Z-Source Photovoltaic Grid-Connected Inverter

At present,one of the important bottleneck restricting energy development is the shortage of fossil energy and environmental pollution,and the effective solution is to vigorously develop renewable energy.Among them,photovoltaic power generation occupies a considerable proportion and is currently an important direction for the development of new energy power generation.The direct current output by the photovoltaic cell is converted into alternating current through an inverter circuit,and then connected to the grid after filtering.Therefore,a single-phase Quasi-Z-source inverter improved based on the topology of a typical Z-source inverter is studied in this paper.Firstly,the switching conditions of the Quasi-Z-source inverter network in different states and the working process of the inverter bridge are analyzed.When the Quasi-Z-source inverter works in the active state and the through state,it can output a stable sinusoidal alternating current.Then,based on the state averaging method,the state average model of the Quasi-Z source inverter system is established,and the transfer functions between different inputs and outputs are derived.The different parameters,including component parameters of the system,the capacitor voltage,inductor current,and load current in the Quasi-Z source topology circuit,would affect the roots distribution of the corresponding characteristic equation.By deriving the control models of different types of grid-connected controllers,its different amplitude frequency and phase-frequency characteristics are compared.A composite grid-connected controller based on proportional-integral controller and Quasi-proportional-resonant controller for Quasi-Z source inverter system is selected in this paper,which is suitable for Quasi-Z source inverter systems controller.Finally,according to the overall design index of the Quasi-Z source inverter system,reasonable design and device selection are performed for different circuit components,including the network elements of the Quasi-Z source topology,the switching tubes of the inverter bridge,and the output low-pass filter.Besides the main structure of the system control circuit and grid-connected control program and the interrupt control part is designed.Experimental results show the correctness of the control scheme and theoretical analysis in this paper.