Design Of Photovoltaic Grid-Connected Micro-Inverter

New types of photovoltaic (PV) micro-inverter increasingly draw people’s attention for their advantages, such as simple topologies, small volumes, high efficiency, etc.Main power circuit which is composed of interleaving paralleled flyback circuit and full-bridge inverter circuit., soft switching technology, grid-connected control strategies are researched. In this dissertation, following contents are included:1) The typical structures of grid-connected PV System and grid-connected inverter are analyzed. The development and application of micro-inverter are introduced and its key technologies are also explained here. And, the main circuit design framework and working principle of PV grid-connected micro-inverter are summarized and analyzed.2) The working principle and the main devices design methods of flyback circuit are discussed in detail. In this work, the paralleled interleaving flyback circuit is designed.Therefore the working principle and control methods are studied. And then, the working principle, control methods and the main devices design philosophy of full-bridge phase-shifted inverter circuit are also studied in this dissertation. At last, the control modules of micro-inverter are designed, and grid-connected control strategies is studied.3) The application and development of soft switching technology in inverter are studied. The soft switching elements which are designed in flyback circuit can reduce the volume of this system, minimize the switch loss, raise the working frequency, and improve the anti interference capability. In order to avoid the power turn-on in a same bridge arm, the dead zone issues of power transistor are analyzed, and the DSP dead zone control module is utilized for dead time setting.4) A floating point DSP chip of TMS320F28335 is utilized as the core controller, and main power circuit is designed, and the micro-inverter system diagram designing and PCB plate making are achieved. The emphatically research is performed on modules of TMS320F28335, such as ePWM, eCAP, A/D, etc. At last, the controlling programming and debugging are performed within the CCS integrated development environment.Grid-connected PV micro-inverter is designed, the system functions are tesed. The results show the design of micro-inverter systems in rural areas is feasible, and the function is achieved which DC inverte to AC.