Energy storage device controlling method and power management system

1. A method for controlling a charging amount of an energy storage device connected to a system according to a change in an operating frequency of the system by the energy storage device, the method comprising:

determining whether the operating frequency of the system falls within a dead band range corresponding to a preset frequency range;

determining whether an SOC level indicating the charging amount of the energy storage device falls within a preset maintaining range, in a case where the operating frequency falls within the dead band range; and

adjusting the SOC level so that the SOC level falls within the maintaining range in a case where the operating frequency of the system falls within the dead band range and the SOC level is outside the preset maintaining range,

wherein the maintaining range represents a range between a preset lower limit and a preset upper limit,

wherein the adjusting the SOC level comprises performing different adjusting operations respectively for a case where the SOC level is smaller than the lower limit and a case where the SOC level is larger than the upper limit.

2. The method according to claim 1 , wherein energy transfer is performed according to a hysteresis curve for gradual change of the energy transfer between the system and the energy storage device, with respect to a frequency falling within the dead band range.

3. The method according to claim 2 ,

wherein the dead band is set as a range between a preset maximum reference frequency and a preset minimum reference frequency,

wherein an upper limit inflection point having a lower value than that of the maximum reference frequency and a lower limit inflection point having a larger value than that of the minimum reference frequency are set within the dead band.

4. The method according to claim 3 , wherein, in a case where the system frequency has a value between the maximum reference frequency and the upper limit inflection point, an amount of energy transferred from the system to the energy storage device follows the hysteresis curve.

5. The method according to claim 4 , wherein, in a case where the system frequency has a value between the upper limit inflection point and the lower limit inflection point, an amount of energy transferred between the system and the energy storage device is constantly maintained regardless of a change in the system frequency.

6. The method according to claim 5 , wherein, the amount of energy constantly transferred between the system and the energy storage device for the case where the SOC level is smaller than the lower limit differs from the amount of energy constantly transferred between the system and the energy storage device for the case where the SOC level is larger than the upper limit.

7. The method according to claim 3 , wherein, in a case where the system frequency has a value between the minimum reference frequency and the lower limit inflection point, an amount of energy transferred from the energy storage device to the system follows the hysteresis curve.

8. The method according to claim 7 , wherein, in a case where the system frequency has a value between the upper limit inflection point and the lower limit inflection point, the amount of energy transferred between the system and the energy storage device is constantly maintained regardless of a change in the system frequency.

9. A power management system comprising:

a power conversion system configured to associate a generator, a battery, and a system with each other to supply power to a load, or receive DC power from the generator or the battery to convert the DC power; and

a charging control unit configured to read SOC level information of the battery and monitor an SOC change amount according to charging or discharging of the battery,

wherein the charging control unit reads a frequency of the system through the power conversion unit, determines whether the frequency of the system falls within a dead band range that is a preset frequency range, and adjusts the SOC level so that the SOC level falls within a preset maintaining range in a case where the frequency falls within the dead band range and the SOC level is outside the maintaining range.

10. The power management system according to claim 9 , wherein the charging control unit performs energy transfer according to a hysteresis curve for gradual change of the energy transfer between the system and the energy storage device, with respect to a frequency falling within the dead band range.

11. The power management system according to claim 10 ,

wherein the dead band is set as a range between a preset maximum reference frequency and a preset minimum reference frequency, and

wherein the charging control unit sets an upper limit inflection point having a lower value than that of the maximum reference frequency and a lower limit inflection point having a larger value than that of the minimum reference frequency within the dead band, and performs control differently for a case where the frequency of the system is between the upper limit inflection point and the maximum reference frequency and a case where the frequency of the system is between the lower limit inflection point and the minimum reference frequency.

12. The power management system according to claim 11 , wherein, in a case where the system frequency has a value between the maximum reference frequency and the upper limit inflection point, the charging control unit performs control so that an amount of energy transferred from the system to the energy storage device follows the hysteresis curve.

13. The power management system according to claim 12 , wherein, in a case where the system frequency has a value between the upper limit inflection point and the lower limit inflection point, the charging control unit constantly maintains an amount of energy transferred between the system and the energy storage device regardless of a change in the system frequency.