Study On Micro Grid-Connected Photovoltaic Inverter And Its Key Technologies

The main task of distributed photovoltaic technology is the research of small-scale photovoltaic power generation components and the networking between these components. Micro grid-connected photovoltaic inverter is the core part of distributed Photovoltaic systems.Basing on the analysis of the micro grid-connected photovoltaic inverter topology, the photovoltaic grid-connected control strategy and the island detection technology, micro grid-connected photovoltaic inverter and its key technologies are deeply studied in this thesis.The thesis designs a high frequency link isolated type micro inverter. The topology structure and characteristic of DC/DC converter and DC/AC converter are compared and analyzed. Then the topology of the flyback converter and full-bridge converter is chosen as the main circuit structure of micro grid-connected inverter. At last the Matlab/Simulink tool has been used to verify the correctness of the design.The simulation control model of maximum power point tracing is established by Matlab/Simulink based on the analysis of characteristics of photovoltaic cells. Several current maximum power point tracing control strategies are compared and analyzed and then the optimal gradient strategy is chosen as maximum power point tracing control strategy in this thesis.The damage and mechanism of the island effect are analyzed. And the active frequency drift method is improved based on the comparative analysis of passive and active islanding detection methods.At last the active frequency drift method strategy is also simulated and verified.Finally, a micro grid-connected photovoltaic inverter experimental platform is designed and some main hardware circuits are studied.