Patent ID: 8716892

Claim:
An energy storage system for supplying power to a load, in conjunction with a power generating system, a battery, and a grid, the energy storage system comprising: a power converting unit for converting a voltage output from the power generating system into a direct current (DC) link voltage; a bidirectional converter configured to perform mutual conversion between an output voltage of the battery and the DC link voltage; a DC link unit for constantly maintaining a level of the DC link voltage; a bidirectional inverter for converting the DC link voltage into an alternating current (AC) voltage appropriate for the grid and for converting an AC voltage of the grid into the DC link voltage; a detector for detecting the DC link voltage; and an integrated controller for controlling the power converting unit, the bidirectional converter, and the bidirectional inverter, and for controlling operation modes of the energy storage system in accordance with the DC link voltage, wherein the integrated controller selects an operation mode by comparing the detected DC link voltage to a first voltage and to a second voltage, different from the first voltage, the first to second voltages defining a predetermined range.