Research On Islanding Effect In Distributed Generation System

Due to the environmental and sustainable development issues faced by mankind,distributed generation technologies using solar energy as the energy source have been rapidly developed in various countries in recent years,and small-scale household photovoltaic power generation has entered millions of households.This generation mode will become An important direction for future electric power business reform.The research of islanding detection method is the key to ensure the safe and reliable operation of distributed power generation system,so it has become an important research field of distributed generation technology.Firstly,this paper gives an overview of the significance of distributed generation and the mechanism of islanding effect.The necessary conditions for the islanding effect are obtained;the load quality factor is introduced,and the influence of different load quality factors on islanding detection is revealed through MATLAB programming.The four spatial coordinate systems describe the advantages and disadvantages of the detection blind zone,and determine the description methods used in this paper;and classify the islanding detection methods into two categories: local detection method and remote detection method based on inverters.And analysis of commonly used island detection methods yields advantages and disadvantages.Then,the principle of active frequency drift(AFD)islanding detection was studied.The main defects of the active frequency drift method and the reasons for the failure of the detection are analyzed.The blind area distribution of the method is described by the coordinate system.Because the perturbation amount of this method is fixed,the direction of the load frequency offset for different properties is the same,which easily causes islanding detection failure under capacitive load.At the same time,another drawback of this method is that the selection of the truncation factor is a contradictory problem.When the truncation coefficient is too small,the islanding detection time will become longer.When the truncation coefficient is too large,the detection time is shortened but a large amount of time is introduced.The harmonic components.The cut-off coefficient of the AFD islanding detection method with the nature of determining the load is defined as a variable,which reduces the detection time and also reduces the harmonic distortion rate.Finally,on the basis of theoretical analysis,a simulation model was built to verify the feasibility of the detection method.Finally,from the point of view of multi-inverter parallel operation,the blind zone distribution maps under load quality factor and standard capacitance coordinate system fortwo islands with different island detection methods are depicted,and the purely passive type is studied through simulation.Islanding detection methods,AFD detection methods,and AFD detection methods with determining the nature of the load,and the effectiveness of islanding detection.Through analysis and simulation,it can be seen that when the two inverters are operated in parallel,the AFD detection method with the nature of determining the load is more effective,and the detection methods are not affected by the dilution effect.