The Research Of Phovotoltaic Grid-connected System Based On Z-source Inverter

With the rapid development of the world economy, the demand for energy isincreasing. However, due to the fossil fuels are non-renewable and the problem ofenvironmental pollution, so the development and utilization of new energy is imminent.As an important aspect of the new energy development, photovoltaic grid powergeneration gets the wide attention of domestic scholars. Inverter is the core part of powergeneration system and it plays an important role in energy conversion and transfer process.In this paper, Z-source inverter replaces the traditional inverter, because it is able toovercome the deficiencies and limitations of traditional inverters and make thegrid-connected system has more excellent performance.First, analyzes the theoretical limitations of the traditional voltage-mode inverter andcurrent-mode inverter. On this basis, introduces the Z-source inverter topology, operationprinciple and modulation method. By comparing Z-source inverter with conventionalinverter, the advantages of Z-source inverter are summarized.Secondly, the entire circuit is divided into Z-source network and inverter bridge, thenuses the state space averaging method to model the two parts respectively and obtain thewhole model of the system. Based on the modeling, designs the control system whichconsists of grid current loop, Z-source capacitor voltage loop and PV output voltage loop.Grid current loop make sure the output current and grid voltage running with the unitypower factor, voltage loop indirectly regulate the bus voltage by adjusting Z-sourcecapacitor voltage; photovoltaic voltage loop regulating the output voltage of thephotovoltaic array to ensure it works on the maximum power point.On the basis of above theoretical analysis, the hardware parts of system such as maincircuit, drive circuit, sampling circuit are designed. At the same time, introduces theprinciple of maximum power tracking, pulse width modulation generator and single-phasephase locked loop. Construct the two-phase quadrate voltage through differential methodto achieve single-phase software phase lock based on synchronously rotating reference. Atlast, uses the digital signal processors TMS320LF2407A to complete the experimental prototype of a single-phase Z-source inverter. The experiment results verify the theoreticalanalyze is rational.