Key Technologies Of Islanding Detection Applied To Distributed Generation And Microgrid

The problem of energy shortage is becoming more and more prominent.In order to solve the energy problem,the new energy generation is constantly developing,and the new micro grid is also being built.But the operation of the micro grid will bring a series of influence to the power grid system.In order to ensure the safe operation of the entire power system,we must coordinate the cooperation and cooperation between the microgrid and the large power grid.The islanding effect is a potential risk factor for the operation of large power grid.In order to ensure the safety of the entire power system operation and maintenance,it is of great practical significance to research good island detection.At present,there are two kinds of anti islanding detection methods,one is islanding detection scheme based on communication,the other is the local islanding detection scheme.The local islanding detection scheme also includes passive islanding detection and active islanding detection.The passive anti isolation island detection method is simple and does not affect the power quality,but the blind area is large and the threshold is difficult to set.The detection method of active anti isolation island detection is small and sensitive,but it will affect the power quality.In order to study the isolated island detection method of distributed power supply,the theory and the basis of isolated island detection are studied first,and then a new method of anti isolated island detection is proposed based on the different characteristics of active and passive island detection and passive anti isolation island detection.In order to study the better anti isolated island detection scheme,three most commonly used schemes are selected for active isolated island detection,namely,active frequency shift(AFD)detection method,active frequency shift method based on positive feedback(AFDPF)method of isolated island detection,and synovial frequency shift(SMS)imitating island detection method.Passive islanding detection adopts over / Underfrequency and over / under voltage anti islanding detection method.After that,through the blind area analysis and simulation,the three active and passive anti isolated island detection methods are studied and compared in depth.Finally,it is found that the SMS anti isolated island detection scheme has better performance.Although the components of microgrid contain distributed generation,the islanding detection of microgrid is not equivalent to the islanding detection of distributed generation.Microgrid contains multiple distributed power sources,and the islanding detection schemes adopted by each distributed generation may be different.In order to study the anti isolated island detection of multiple distributed power sources in the micro grid,this paper first based on the antiisolated island detection scheme adopted by the distributed power supply,through the blind area analysis and Simulation simulation,using the scheme of active and passive combination,the different schemes are analyzed,studied and compared.The main research programs include the anti isolated island detection scheme used by AFD and AFDPF,the anti isolated island detection scheme used by AFD and SMS,all the SMS anti isolated island detection schemes and all the AFDPF anti isolated island detection schemes.It is concluded that in the case of multi machine parallel,any scheme has more or less dilution effect,but all of the schemes using SMS anti isolation island detection have the best comprehensive efficiency in the area of blind area,dilution effect and detection speed.In order to get better microgrid anti islanding detection scheme,the traditional SMS scheme is improved at last.Through simulation and blind area analysis,it is concluded that the improved scheme has smaller blind area and faster detection speed.