Research On Z-Source Grid-connected Photovoltaic Inverter

Nowadays, the energy shortage and environmental pollution problems in the worldare becoming increasingly serious, and so the energy and environmental issues become thefocus of the countries. Wind power, fuel cells, solar and other emerging renewable energyare being used in the power generation fields. And among them, the development of thesolar energy is developing most rapidly. The application of solar energy in powergeneration fields is mainly the photovoltaic power generation. A photovoltaic cellsproduce the direct current, but we should turn the direct current into alternating currentand then merge into the utility grid or used to provide a life electricity, so the inverterplays an important role. The traditional converter includes the voltage source converterand the current source convert, but both of them have its shortcomings in application.Z-source inverter, an inverter equipped with Z-source network which has just beenproposed in recent years, has aroused attention of domestic scholars because of its uniqueadvantages which can overcome the shortcomings of the traditional inverters.First, the propose background, the topology and the operation principle of Z-sourceinverter is introduced. Then the buck-boost characteristics of Z-Source inverter is analyzed.By comparing Z-Source inverter with the traditional voltage source converter and thetraditional current source convert inverter, the advantages and disadvantages of Z-Sourceinverter are summarized. The SPWM control method and the boost control method of theZ-Source inverter and the principle of modified SPWM control method is mainly analyzed.Subsequently, the MATLAB simulation model is founded to verify the theory. The DSPprogramming to control four switch devices is performed effectively, and theshoot-through zero vector state is inserted successfully. The small-signal model of thewhole photovoltaic system is studied to control the dynamic response of the system. Thena double-closed-loop system is designed: inner loop control of grid-connected current andouter loop control of Z-source network capacitance. Based on the theoretical analysis, theparameters of the capacitor and the inductance in Z-source impedance network and thegrid-connected inductance are calculated. At last, based on all the work above, simulationon the system is performed and a experimental prototype is founded to verity the simulation results and theoretic alanalysis.