Battery pack, method of controlling the same, and energy storage system including the battery pack

1. A method of controlling a battery pack comprising a plurality of battery cells, the method comprising:

calculating charge capacities of the battery cells;

obtaining a first average value, wherein the first average value is an average value of the calculated charge capacities;

establishing a first standard value for selecting an abnormal battery cell based on the first average value;

determining a first battery cell having the lowest charge capacity from among battery cells having charge capacities greater than the first standard value;

establishing a second standard value for selecting at least one battery cell that is to be discharged during a cell balancing operation; and

performing a cell balancing operation with respect to the at least one battery cell having charge capacities greater than the second standard value.

2. The method of claim 1 , further comprising determining a battery cell having a charge capacity less than the first standard value as an abnormal battery cell.

3. The method of claim 1 , further comprising removing a battery cell having a charge capacity less than the first standard value from the battery pack.

4. The method of claim 1 , wherein the cell balancing operation is performed to adjust the charge capacity of a battery cell that is to be discharged to a charge capacity of the first battery cell.

5. The method of claim 1 , wherein the cell balancing operation is performed to adjust the charge capacity of a battery cell that is to be discharged to the first average value.

6. The method of claim 1 , further comprising establishing the first standard value to be 90% of the first average value.

7. The method of claim 1 , further comprising establishing the second standard value to be 110% of the charge capacity of the first battery cell.

8. The method of claim 1 , further comprising establishing the second standard value to be 110% of the first average value.

9. The method of claim 1 , further comprising calculating a second average value, which is an average value of the charge capacities of the battery cells having charge capacities greater than the first standard value.

10. The method of claim 9 , further comprising establishing the first standard value based on the second average value.

11. The method of claim 10 , further comprising establishing the first standard value to be 90% of the second average value.

12. The method of claim 9 , further comprising establishing the second standard value to be 110% of the second average value.

13. A battery pack comprising:

a plurality of battery cells;

a capacity measuring unit configured to measure charge capacities of the battery cells;

an average value calculator configured to calculate an average value of the measured charge capacities;

a balancing controller configured to: establish a first standard value for selecting an abnormal battery cell based on the average value;

detect a first battery cell having the lowest charge capacity from among battery cells having charge capacities greater than the first standard value;

establish a second standard value for selecting a battery cell that is to be discharged during the cell balancing operation; and

establish that battery cells having charge capacities greater than the second standard value are to be discharged during the cell balancing operation; and

a balancing circuit unit configured to perform the cell balancing operation according to a control signal applied from the balancing controller.

14. The battery pack of claim 13 , wherein the balancing controller is configured to control the balancing circuit unit so as to adjust the charge capacity of a battery cell that is to be discharged to the charge capacity of the first battery cell.

15. The battery pack of claim 13 , wherein the balancing controller controls the balancing circuit unit so as to adjust the charge capacity of a battery cell that is to be discharged to the first average value.

16. The battery pack of claim 13 , wherein the second standard value is established based on the charge capacity of the first battery cell.

17. The battery pack of claim 13 , wherein the second standard value is established based on the first average value.

18. The battery pack of claim 13 , wherein the balancing controller is configured to send information of the battery cells having charge capacities greater than the first standard value to the average value calculator, and the average value calculator is configured to calculate a second average value, which is an average value of the charge capacities of the battery cells having charge capacities greater than the first standard value.

19. An energy storage system that is connected to a battery comprising a plurality of battery cells, a power generation system, and a grid so as to supply power to a load, the energy storage system comprising:

a capacity measuring unit configured to measure charge capacities of the battery cells;

an average value calculator configured to calculate an average value of the measured charge capacities; and

a balancing controller configured to:

establish a first standard value for selecting an abnormal battery cell based on the average value;

detect a first battery cell having the lowest charge capacity from among battery cells having charge capacities greater than the first standard value;

establish a second standard value for selecting a battery cell that is to be discharged during the cell balancing operation; and

establish that battery cells having charge capacities greater than the second standard value are to be discharged during the cell balancing operation, and wherein the balancing controller is further configured to perform a cell balancing operation with respect to the selected battery cell.