Research On Islanding Detection Of Distributed Generation System

With the rapid development of science culture and human economy, the contradictionsbetween economic development and environmental issues are irreconcilable increasingly.With the expanding scale of economies, the environment is polluted more severely. In recentyears, In order to manage environmental issues effectively, new energy has gained strongsupport from various industries of each country, and the new variety of distributed energygeneration systems are widely used in life. Islanding detection technology is the keytechnology in the research of distributed generation and grid system. Island effect refers to thecase of electrical failure or other reasons, the grid power interruption occurs, distributedpower generation system failed to detect the power status and continuing to supply power tothe grid, and make the system and load up a self-powered island state. Island effect wouldcause great harm on equipment and personnel. Islanding detection technique is to detect anddetermine the island effect, and make the appropriate action quickly.Islanding detection methods are mainly divided into active islanding detection andpassive islanding detection. Passive islanding detection technology is mainly by detecting thechanges of voltage or parameters at the common point to determine the island; Activeislanding detection technology is by adding different disturbance to determine the island. Inthis paper, the active frequency offset method and sliding frequency shift method of activeislanding detection technology are researched deeply. The main contents are:1. Analyze the research status and development trend of islanding detection technology.Describe the occurrence mechanism of island effect. Evaluate the advantages anddisadvantages of active and passive islanding detection methods according to internationalstandards of islanding detection.2. For all the islanding detection methods, the no detectable region (NDZ) is existed. Inorder to estimate the effectiveness of islanding detection, four different coordinate systems arepresented in this paper. Moreover, the advantages and disadvantages of the four differentcoordinate systems are analyzed and compared.3. The principle of the active frequency offset method and positive feedback activefrequency offset method are analyzed in detail. The Qf0×Cnormcoordinate system is adoptedto deduce the NDZ boundary of these two methods. Furthermore, a model is built in Matlab/Simulink system.4. The principle of sliding mode frequency shift method is elaborated, and the causes ofexisting blind are analyzed, and the Qf0×Cnormcoordinate system is adopted to deduce theNDZ boundary of islanding detection method. An improved method based on sliding modefrequency shift method is proposed, and this method can detect the island quickly and accurately. Simultaneously, the blind of sliding mode frequency shift method is reduced. Toverify the feasibility and correctness of the improved method, the simulation experiment ofthe sliding mode frequency shift method and its improved method are carried out onMatlab/Simulink.