Testing the Performance of the Digital Modular Protection for Grid-Connected Battery Storage Systems

This paper presents the performance evaluation of the digital modular protection for grid-connected battery storage systems (BSSs). The tested digital protection is designed using multiple digital relays that are located at different parts of the protected BSS. Each digital relay is featured with a phaselet-based fault detection to ensure accuracy and response speed. The outputs of the digital modular protection are control signals that operate circuit breakers in the charging and discharging circuits, battery units, and the point of common coupling. The tested digital modular protection is implemented for performance evaluation using a 250-kW grid-connected BSS that is charged through a <inline-formula><tex-math notation="LaTeX">$3\phi$</tex-math></inline-formula> ac–dc power electronic converter (PEC) and discharged through a <inline-formula><tex-math notation="LaTeX">$3\phi$</tex-math></inline-formula> dc–ac PEC. Performance results show that the digital modular protection can initiate fast, accurate, and reliable responses to faults occurring in different parts of the protected BSS. These response features have a negligible sensitivity to the type and/or location of faults, the charge/discharge mode of operation, and/or levels of power exchange with the host grid.