Research On Islanding Detection Technology For Grid-connected Distributed Generation

In recent years,with the decrease of the utilization rate of fossil energy,the increasing development and utilization of new energy sources,distributed grid-connected generation has also emerged,and there are more and more technical problems encountered at the same time as the rapid development.The island effect problem is one of them.When the island occurs but it is not detected,it will not only affect the stable operation of the system,but also threaten the safety of users and maintenance personnel.At present,the problem of high harmonic distortion exists in the active island detection algorithm in single micro-source,and not only does the dilution effect exist in the detection of multiple micro-sources,resulting in the failure of the detection,but also has insufficient time limit for detection,and the detection speed is lower than the national standard.In this paper,we first study the high harmonic distortion rate of traditional active frequency shift island detection method,design a scheme combining phase sudden change and improved AFD method(combination method),and compare the traditional active frequency shift island detection method with the simulation method.The results show that the new scheme has higher detection speed and lower detection speed.Secondly,the traditional active frequency shift island detection method will produce dilution effect under the multiple micro-source connection condition,and the improved AFD method in this paper does not have this problem.The improved island detection method is proved to have good performance and the multiple micro-source island detection model is built for simulation.The experimental results show that the improved AFD method does not have dilution effect in the multiple grid-connected system,and the detection performance is better.Thirdly,in view of the shortcomings of the slow detection time of the traditional phase shift island detection method in multiple micro-source,thetraditional phase shift algorithm is optimized,and an improved active phase shift island detection algorithm is designed.The island detection simulation model is built in Matlab/Simulink.The simulation results of the two methods are compared and analyzed.Experimental results show that the new phase shift algorithm has better performance and improves the detection speed.