Storage battery control apparatus, storage battery control method, and storage battery system

1. A storage battery control apparatus which controls charge and discharge of the storage battery to adjust power supply and demand of a grid in a supply and demand control period, the storage battery control apparatus comprising:

a first obtainer that obtains a remaining state of charge (SOC) which is an SOC of the storage battery at a start of the supply and demand control period;

an offset power value determiner that determines an offset power value which is a power value indicating charge or discharge and is a reference of the charge and discharge of the storage battery in the supply and demand control period, the offset power value being determined using a difference between the remaining SOC and a target SOC, and the target SOC being (i) a target value of the SOC of the storage battery at an end of the supply and demand control period and (ii) a fixed value less than 100% of a capacity of the storage battery;

a second obtainer that obtains an adjustment instruction value which is an instruction value of the charge and discharge of the storage battery and indicates a change amount of a power value from a predetermined reference power value; and

a charge and discharge controller that performs control of discharging power from the storage battery to the grid or charging power from the grid to the storage battery, the power having a magnitude of a first power value that is a power value obtained by adding the offset power value to an adjustment instruction power value that is a power value indicated by the adjustment instruction value.

2. The storage battery control apparatus according to claim 1 ,

wherein in a case where the adjustment instruction power value is a positive value when the adjustment instruction value indicates a power supply instruction to the grid, and the adjustment instruction power value is a negative value when the adjustment instruction value indicates a power consumption instruction in the grid:

the offset power value determiner determines, as the offset power value, a power value having a polarity identical to the polarity of a power amount obtained by subtracting the target SOC from the remaining SOC; and

the charge and discharge controller performs control of discharging power having a magnitude of the first power value from the storage battery to the grid when the first power value is a positive value, and performs control of charging power having a magnitude of the first power value from the grid to the storage battery when the first power value is a negative value.

3. The storage battery control apparatus according to claim 1 ,

wherein the offset power value determiner determines the offset power value, using a power value obtained by dividing a power amount obtained by subtracting the target SOC from the remaining SOC, by a duration of the supply and demand control period.

4. The storage battery control apparatus according to claim 1 , further comprising

a memory that stores power loss information which is information related to a power loss generated when, in the supply and demand control period, the storage battery is discharged to the grid or the storage battery is charged from the grid,

wherein the offset power value determiner further determines the offset power value using a power amount corresponding to the power loss indicated by the power loss information.

5. The storage battery control apparatus according to claim 1 ,

wherein the second obtainer obtains the adjustment instruction value at every predetermined period in the supply and demand control period.

6. The storage battery control apparatus according to claim 5 ,

wherein the first obtainer further obtains the SOC of the storage battery at the every predetermined period:

the storage battery control apparatus further includes a corrected power value determiner that compares the SOC of the storage battery obtained at the every predetermined period with the target SOC, and then determines a corrected power value which is a power value of acceptable error range in the adjustment instruction power value and a power value for reducing a difference of a power amount between the SOC obtained at the every predetermined period and the target SOC; and

the charge and discharge controller performs, at the every predetermined period, control of discharging power from the storage battery to the grid or charging power from the grid to the storage battery, the power having a magnitude of the first power value obtained by adding the offset power value to the adjustment instruction power value and by further adding the corrected power value.

7. The storage battery control apparatus according to claim 6 ,

wherein in a case where the adjustment instruction power value is a positive value when the adjustment instruction value indicates a power supply instruction to the grid, and the adjustment instruction power value is a negative value when the adjustment instruction value indicates a power consumption instruction in the grid:

the corrected power value determiner determines, as the corrected power value, a power value having a polarity identical to the polarity of a power amount obtained by subtracting the target SOC from the SOC of the storage battery obtained at the every predetermined period; and

the charge and discharge controller performs control of discharging power having a magnitude of the first power value from the storage battery to the grid when the first power value is a positive value, and performs control of charging power having a magnitude of the first power value from the grid to the storage battery when the first power value is a negative value.

8. The storage battery control apparatus according to claim 1 , further comprising

a control capability determiner that determines a control capability which is largest power of the storage battery and is used in the charge and discharge of the storage battery in the supply and demand control period,

wherein the control capability determiner:

determines the control capability by setting, as an upper limit, power obtained by subtracting the magnitude of the offset power value from largest power that is dischargeable from the storage battery to the grid, when the offset power value indicates discharge from the storage battery; and

determines the control capability by setting, as an upper limit, power obtained by subtracting the magnitude of the offset power value from largest power that is chargeable from the grid to the storage battery, when the offset power value indicates charge to the storage battery.

9. The storage battery control apparatus according to claim 1 , further comprising

an SOC predictor that predicts a difference of the SOC of the storage battery at the end of the supply and demand control period, from the SOC of the storage battery at the start of the supply and demand control period, using a previous adjustment instruction value obtained in a previous supply and demand control period,

wherein the offset power value determiner further determines the offset power value using the difference of the SOC predicted by the SOC predictor.

10. The storage battery control apparatus according to claim 1 , further comprising

a price information obtainer that obtains price information that is information related to benefit by performing the charge and discharge of the storage battery in the supply and demand control period,

wherein the offset power value determiner determines, as the offset power value, a power value that is smaller as the value of the price indicated by the price information is larger.

11. The storage battery control apparatus according to claim 1 ,

wherein the first obtainer obtains the adjustment instruction value transmitted from a power system operation apparatus which operates the grid.

12. The storage battery control apparatus according to claim 1 , further comprising

an instruction value determiner that measures a frequency of an AC current of the grid and then determines the adjustment instruction value according to the frequency,

wherein the first obtainer obtains the adjustment instruction value from the instruction value determiner.

13. The storage battery control apparatus according to claim 1 ,

wherein the remaining SOC is an actually measured value or an estimated value of the SOC of the storage battery at the start of the supply and demand control period.

14. A storage battery control method for controlling charge and discharge of the storage battery to adjust power supply and demand of a grid in a supply and demand control period, the storage battery control method comprising:

obtaining a remaining state of charge (SOC) which is an SOC of the storage battery at a start of the supply and demand control period;

determining an offset power value which is a power value indicating charge or discharge and is a reference of the charge and discharge of the storage battery in the supply and demand control period, the offset power value being determined using a difference between the remaining SOC and a target SOC, and the target SOC being (i) a target value of the SOC of the storage battery at an end of the supply and demand control period and (ii) a fixed value less than 100% of a capacity of the storage battery;

obtaining an adjustment instruction value which is an instruction value of the charge and discharge of the storage battery and indicates a change amount of a power value from a predetermined reference power value; and

performing control of discharging power from the storage battery to the grid or charging power from the grid to the storage battery, the power having a magnitude of a first power value that is a power value obtained by adding the offset power value to an adjustment instruction power value that is a power value indicated by the adjustment instruction value.

15. A storage battery system comprising:

the storage battery control apparatus according to claim 1 ; and

the storage battery.

16. The storage battery control apparatus according to claim 1 ,

wherein the target SOC is at or around 50% of the capacity of the storage battery, and the target SOC is a fixed value determined according to a ratio of average charge and discharge loss of the storage battery.