Study On The Method Of Isolated Island Detection Of Photovoltaic Grid System

Solar photovoltaic power generation is one of the energy sources that scientists and engineers have been concerned about in recent years.Electricity generation,transmission and electricity use of conventional energy constitute a reliable and reliable power system The photovoltaic power generation system needs to be connected with the large power grid to function effectively.When the photovoltaic system normally generates electricity,it can efficiently supply power to the big power grid and transfer the power to the power grid,which provides effective active power and reactive power.When the power grid fails or overhaul,the photovoltaic system is isolated from the grid.If not timely quickly broken network,is bound to appear photovoltaic power generation systems and large load operation of the system,the stability of the system reliability is very poor so that it is difficult to control,and this phenomenon is called an island effect.Once this effect occurs,the system will bring great threat and personnel safety.In other words,it is necessary to avoid the island effect in a timely and accurate manner.Photovoltaic system,therefore,in addition to the stability of the power generation system,need to have the ability to detect islanding,and can effectively control electric current,voltage to maintain the same frequency and phase's ability to maintain the stability of the systemIn this paper,on the basis of consulting a large number of literature,firstly some detailed analysis have been done about island phenomenon of process,impact and detection standard in the process of the interconnection of photovoltaic network.Furthermore,the studies and analyzes are researched about the basic islanding detection method,and through software simulation and analysis,the accuracy of the result is analyzed and discussed.On this basis,the detection capability of isolated island effect blind area is evaluated,and the method to detect the photovoltaic island detection based on the change of active power is presented.In the improved algorithm,the variable of the system of active power is introduced into the offset of the positive feedback,improve the frequency offset,to improve public node voltage frequency offset,greatly reducing the island detection time.Finally based on the islanding which produces the phenomenon of the change of active power,proposed an improved active frequency shift island detection method,this method is based on the active power change which is derived from positive feedback active frequency shift photovoltaic island detection method.In the improved algorithm,the system of active power is introduced into the positive feedback of offset,increasing the frequency offset,increase the public node voltage frequency offset,reduced the time consumption of island dection.In this paper,the proposed method made the analysis of the detection blind area,at the same time,this method has carried on the detailed simulation analysis and simulation experiment,further verify the superiority of the proposed method and accuracy.