Islanding Detection Based On Phtovolotaic Grid-connected System

With the development of photovoltaic (PV) technologies, applications of it in grid-connected situations have more and more showed their virtues,which indicating that they will become an important energy source in the future for diverse purposes instead of a complmentarity for nowadays.But the islanding phenomenon which brought by the grid-connected run modes has hazards to the loads, inverters and life safety. So, all grid-connected inverters should have the ability of detecting islanding status.The grid-connected PV systems which have the ability of reactive power compensation show their importance on supplying power and improving its quality. So they have attracted more and more attention in recent years. Based on the single-stage three-phase grid-connected inverter, this paper presents an islanding detection scheme, which controls the active and reactive power independently and combines active-power perturbance in MPPT control. It makes the best of the advantages of the pessive and active methods of islanding detection. With this method, PV grid-connected system can detects the islanding in time, as well as reducing the impacts of the perturbance on the powr quality when there is no fault in powr supply from power grid.