Research On Microgrid Protection Based On Inverter-interfaced DG Fault Characteristics

In recent years,with the rapid development of microgrids with distributed generation(DG),they have made great contributions to protecting the environment and building a low-carbon world.The safe and stable operation is of great significance.Due to the changing operation mode of the microgrid and the influence of factors such as DG access location,capacity,control strategy,etc.,its fault characteristics are more intricate compared to traditional distribution networks,which is the rapidity of microgrid relay protection.And coordination pose new challenges.Aiming at the above problems,this paper proposes an improved microgrid overcurrent protection method to meet the requirements of fast-moving and coordination protection in the microgrid.First,this paper analyzes the fault output characteristics of inverter-type DG,microgrid fault characteristics,and the applicability of traditional distribution network protection methods in microgrids under different control strategies.According to the principle of inverter-type DG with constant power and constant voltage and constant frequency control strategies,the fault output characteristics under different fault severity conditions are analyzed;then,the faults of the microgrid in grid-connected operation mode and island operation mode are analyzed separately.Characteristics,and establish a microgrid simulation model in the DIg SILENT/Power Factory simulation software for simulation verification;then,theoretically analyze the applicability of the traditional distribution network relay protection method in the microgrid,and verify it with simulation software At the same time,the impact of DG access on the autoreclosing system was also analyzed.According to the above theory and simulation analysis,it can be concluded that the traditional relay protection method is no longer applicable in microgrids.Then,according to the fault characteristics of the microgrid and the defects of the traditional current protection method in the microgrid,this paper proposes a microgrid based on the coordinated optimization of the composite fault compensation factor and the beetle antenna search(BAS)algorithm.Current protection method.A composite fault compensation factor is constructed through the voltage drop of the bus and the relationship between the measured impedance and the fault distance,and the traditional inverse-time overcurrent protection method is improved to improve the rapidity of protection.Then,the DG access status in the microgrid is considered.Under the premise of the classification,the operating conditions of the microgrid are classified and the parameters of the protection method proposed in this paper are optimized and adjusted using the BAS algorithm to ensure the coordination of adjacent protections.Finally,the paper is verified in DIg SILENT/Power Factory simulation software.The correctness of the proposed protection method is compared with the action delay of the traditional inverse time overcurrent protection.Simulation results and comparative data show that the method is effective in different operating modes,different operating conditions,different fault locations and types of the microgrid.It can ensure the quickness and coordination of protection,and is better than traditional protection methods.This article studies the fault output characteristics of inverter-type DG under different control strategies,the fault characteristics of different operating modes of the microgrid,and the applicability analysis of traditional distribution network relay protection in the microgrid.It provides theoretical support,and this paper proposes an improved inverse time-delay microgrid overcurrent protection method,which provides new ideas for the research of microgrid protection.