In a large battery-storage system, the rated output voltage of a battery string is 650V (dc) and the rated current is 1200 A. The voltage can vary in a range from 500V to 800 V. This output voltage is boosted to 900V (dc), as an input to an inverter that interfaces with the three-phase utility grid. A DC-DC converter with a bi-directional power capability is used. The switching frequency is selected to be 50 kHz, and the inductor value is selected such that the peak-to-peak ripple in the inductor current is less than 10% of the rated battery current, with the battery