Research On Islanding Detection Of Grid-connected Photovoltaic System

The non-renewable energy crisis and environment pollution all around the world result in immense desire for renewable energy today, thus solar energy is wildly accepted for its particular advantages. Grid-connected photovoltaic (PV) system, as one way in solar energy utilization, is being developed rapidly because it is environment friendly, efficient to lighten the peak pressure of power system and valid to improve the living standards. Islanding phenomenon, which is inherent in grid-connected PVsystem and other distribute generators, is investigated deeply and some effective detecting methods are proposed.First, the mechanism of islanding with its hazard is described in details. The standards accepted both international and at home are introduced. Classifying the popular anti-islanding techniques into two major categories: the passive and the active methods, advantage and restriction are presented respectively.Then, for active frequency drift and auto phase shift being the most promising methods in future, their principles, guidelines and improvement are presented, which are evaluated by non detection zone (NDZ), and verified by Matlab based simulating and experiment. An efficient way to implement auto phase shift is proposed.Finally, with the scale expanding of grid connected PV systems, that inverters'operating in shunt indicates the trend in future. So how active frequency drift and auto phase shift work in multi inverters and how they influence each other are analyzed with experiment to verify.