Research on fault current control method of DC microgrid battery energy storage system

Abstract Battery energy storage system has become an important link to maintain the stable operation of DC microgrid because of its flexible control and fast response speed. As the battery storage system generally does not have fault current control capability, when a fault occurs between the poles of the system, the battery storage system will provide a great short-circuit current to the fault point, which will cause a great danger to the system operation and equipment safety. At this stage, current-limiting reactors or fault current limiters are generally added to the ports of the energy storage system to reduce the fault current, which has the disadvantage of limited current-limiting effect or high cost and large area, so it is not suitable for wide application in DC microgrid. This paper proposes a fault current control method for DC microgrid battery storage system, which enables the battery storage system to be connected to DC microgrid through Buck DC/DC by increasing the rated voltage of the battery stack.The control mode of the battery storage system is power control mode when the DC microgrid is running on grid, and it will be changed to voltage control mode when the DC microgrid is running off-grid. In case of inter-pole fault, the Buck DC/DC of the battery storage system is controlled to operate with reduced voltage to achieve fault current limit. This scheme does not affect the normal operation of the system, and can quickly limit the peak short-circuit current without adding additional equipment, making the short-circuit current flexible and controllable. Therefore, this scheme has good fault current limiting capability and greatly reduces the technical requirements of DC microgrid for protection. Finally, this paper verifies the feasibility of the proposed scheme and its control strategy through PSCAD/EMTDC modeling simulation.