Study On Islanding Detection For Grid-connect Inverter

Nowadays, with the rapid development of distributed power generation, such as photovoltaic and fuel cell, grid-connected run mode has more and more showed it's virtue. But the islanding phenomenon grid-connected run mode brings has hazards to load, inverter and life safety. So, all grid-connected inverters should have the ability of detecting islanding status and stopping the run mode of grid-connect. As the variety of islanding detection methods and rapid development of digital signal process (DSP), digital mode is the mainstream in islanding detection.Firstly, this thesis introduces the background of islanding detection of grid-connect inverter and the system equivalent mode. And deeply discuss the OVP/UVP, OFP/UFP and SFS's detection theory, none-detection zone, measure precision's affection of voltage and frequency to NDZ and communication between islanding detection system and inverter. Where, the main functions of inverter and islanding detection are realized through DSP TMS320LF2407. Also, this thesis has analyzed the reference waveform's aberration ration of AFD how much affect the quality of inverter's output current (THD). And then, the main circuit of islanding detection system and DSP control software's flow charts are introduced. Lastly, the experimental results are provided.