Research On Protection Scheme For Electric Vehicle Charging Station

With the progress of the Battery Technology and the Whole Vehicle Technology,a rapid increasing in the popularity of EVs(Electric Vehicles,EVs)is coming.EVs will be the main means of transportation in the future.The planning and construction of Charging Infrastructures have become an urgent task.Combined of DC and AC system,Charging Station is different from normal low-voltage system in fault characteristic.The traditional protection scheme cannot meet the requirements of the sensitivity of protection.More seriously,breaker failure or misoperations maybe occur.It is necessary to make a specialized study of Charging Station Protection.Several results were gotten from the research to the protection of Charging Station.(1)At first,a summary for the operation mode of existing charging stations was made.The whole electrical structure of large charging station was designed.At the same time,the working principles of main equipment in the station are analyzed.(2)On the basis of analyzing the working principle of the charger,the mathematics model and the control strategy of the charger were made.Then based on Matlab/Simulink,the charging station simulation model was built.Charging station simulation model was composed of three single chargers in parallel.Set different rated output,through the analysis of DC output,the rationality of the simulation model was verified.(3)Divided Charging Station Protection into Charger-Protection,AC-Side-Protection and DC-Side-Protection.Theory analysis for the fault condition of each module was made.Then the protection scheme of each module was designed.The protection scheme was verified by simulations at last."Direction allowing Hybrid Variable Protection" was brought out in the DC-Side-Protection scheme.The change of the power direction was used to provide allowing single to each protection.Compared with ordinary protections,"Direction allowing Hybrid Variable Protection" has advantages in sensibility and feasibility.In the future,the charging station will run on V2G(Vehicle-to-grid,V2G)mode,and the power direction of charging stations will be more complex.The power direction was used in "Direction allowing Hybrid Variable Protection" as the criterion.It could also apply to the operation and fault protection of the V2 G charging stations.Its action logic will become more complex,the protection algorithm,communication and cooperation between requirements will also be increased.