Research On Protection Scheme For Micro-grid With The Mobile Power Storage Units

This paper study on CERTS micro-grid model and analysis electric vehicle charging station development situation. The concept of micro-grid is given, the micro-grid include electric vehicles as mobile power storage units, photovoltaic power generation unit, wind power generation unit and battery.Through the analysis of the basic network structure and characteristics about charging station micro-grid, according to the distribution network voltage grade ideas put forward the concept of multi-level micro-grid and put forward the idea what is used protection scheme for minimum charging station micro-grid to make the protection scheme.Use PSCAD/EMTDC power system simulation software built a charging station micro-grid simulation model, then we given the protection scheme for micro-grid with mobile storage units according to the actual operation parameters.Micro-grid has two operation statuses, one is parallel operation model, the other one is islanding operation model. We make the protection scheme for both according to their operation characteristics.Firstly, the protection scheme for parallel operation is:direction over current protection as main protection for low voltage lines protection regions; bus completely current differential protection for bus protection region; internal protection circuit to protect micro-generator. Secondly, the protection scheme for islanding operation is: direction over current protection as main protection for low voltage lines protection regions, but the setting value must be set by actual operation parameters for islanding operation; bus completely current differential protection for bus protection region; internal protection circuit to protect micro-generator.