Research On The Islanding Detection Method For Micro-grid

With the rapid development of society and economy,and with the increasing serious energy shortage and environment pollution,more and more emphases have paid on the new energy technology while its wider applications have been found.In recent years,the photovoltaic(PV)power generation technology has been developed rapidly because of its non-pollution and unlimitedness.People have focused on developing the micro grid in many countries and regions.The micro grid(or micro-grid)is a power supply network consisting of a number of distributed power sources and loads in accordance with a certain topology.It is an important part of the current smart grid.The islanding effect of the micro grid is a severe practical problem that might occur in grid connection process.In this paper we analyzed the existing islanding detection methods.The methods of the active frequency drift method(AFD)and of the active frequency drift with positive feedback method(AFDPF)were mainly studied,with their advantages and disadvantages being investigated.It is revealed that in some cases,especially when the loads change,the speed of detection may be significantly affected,moreover failing to detect may occur.For these problems we proposed an improved detection method.By quickly determining the nature of the load and applying the proper disturbance,it can be achieved to detect the occurrence of the isolated island.As compared with the AFD or AFDPF methods,the proposed method possesses the characteristics of smaller blind area and higher efficiency.We used the Matlab/Simulink simulation environment to model and simulate the micro grid system,and carried out performance simulation for islanding detection with various methods.The results showed that the proposed method could detect the isolated island more rapidly with the advantages of less total harmonic distortion and less impact on the power quality.