A new digital protection for grid-connected battery storage systems

In this paper, a new digital protection is developed and tested for grid-connected battery storage systems (BSSs). The proposed protection is designed using multiple digital relays that are located in different parts of the protected BSS. Each digital relay is featured with a phaselet-based fault detection. The outputs of the developed protection are trip signals to operate circuit breakers in the charging and discharging circuits, battery units, and point-of-common-coupling. The developed modular digital protection is implemented for simulation testing on a 250 kW grid-connected BSS that is charged through a 3φ ac-dc power electronic converter (PEC), and discharged through a 3φ dc-ac PEC. Simulation results show that the developed protection can initiate fast, accurate, and reliable responses to faults occurring in different parts of the protected BSS. These response features have negligible sensitivity to the type and/or location of faults, charge/discharge cycles of the BSS, and/or levels of power exchange with the host power system.