Battery control apparatus and energy storage system including same

A battery control apparatus connectable to a power conversion system through a first terminal and a second terminal of the power conversion system, the battery control apparatus comprising:

• a first battery pack;
• a second battery pack;
• a first switch connected in series to the first battery pack between the first terminal and the second terminal;
• a second switch connected in series to the second battery pack between the first terminal and the second terminal;
• and
• a control unit operably coupled to the first switch and the second switch, the control unit being configured to:
• turn on both the first switch and the second switch to connect the first battery pack and the second battery pack in parallel between the first terminal and the second terminal, if a voltage difference between the first battery pack and the second battery pack is less than a first threshold voltage at a first time point in a first charging cycle at which both the first switch and the second switch are turned off, and
• turn on the first switch and maintain the second switch off, if a voltage of the second battery pack is higher than a voltage of the first battery pack by the first threshold voltage or more at the first time point,
• wherein the control unit is further configured to transmit a first command to the power conversion system to induce the power conversion system to supply a first constant power between the first terminal and the second terminal, if a state of charge (SOC) difference between the first battery pack and the second battery pack is equal to or higher than a threshold SOC at a second time point after the first time point in the first charging cycle with the first switch turned on and the second switch off, and
• wherein each of a SOC of the first battery pack and a SOC of the second battery pack is determined based on a voltage and a current of a corresponding one of the first and second battery packs using ampere counting, an equivalent circuit model, or a Kalman filter.

A battery control method for connecting in parallel a first battery pack connected in series to a first switch between a first terminal and a second terminal of a power conversion system, and a second battery pack connected in series to a second switch between the first terminal and the second terminal, the battery control method comprising:

• determining whether a voltage difference between the first battery pack and the second battery pack is less than a first threshold voltage at a first time point in a first charging cycle at which both the first switch and the second switch are turned off;
• turning on both the first switch and the second switch to connect the first battery pack and the second battery pack in parallel, if the voltage difference between the first battery pack and the second battery pack is less than the first threshold voltage at the first time point;
• turning on the first switch, if a voltage of the second battery pack is higher than a voltage of the first battery pack by the first threshold voltage or more at the first time point;
• and
• transmitting a first command to the power conversion system to induce the power conversion system to supply a first constant power between the first terminal and the second terminal, if a state of charge (SOC) difference between the first battery pack and the second battery pack at a second time point after the first time point in the first charging cycle with the first switch turned on and the second switch off,
• wherein each of a SOC of the first battery pack and a SOC of the second battery pack is determined based on a voltage and a current of a corresponding one of the first and second battery packs using ampere counting, an equivalent circuit model, or a Kalman filter.