JP7399695B2 - Charge/discharge control method for power storage system and charge/discharge control device - Google Patents

Description

The present invention relates to a technique for controlling charging and discharging of a power storage system including a plurality of battery units.

As solar power generation becomes more popular, solar power generation systems equipped with storage batteries are becoming more and more popular as a means of stabilizing power grids, adjusting supply and demand, and in preparation for long-term power outages caused by disasters. As the price of storage batteries declines, there is an increasing demand for adding additional storage batteries and using them as solar power generation systems that include multiple storage batteries.

In Patent Document 1, in a battery control system for controlling a SOC (State of Charge) indicating the remaining charge of a battery cell in a vehicle battery module including a plurality of battery cells connected in series, the lower limit of the SOC of the battery cell is disclosed. Techniques for preventing cracking have been disclosed.

Japanese Patent Application Publication No. 2017-112734

When a power storage system includes multiple battery units, for example, when the SOC of one battery unit reaches the lower limit, that battery unit cannot discharge any more, so the power capacity of the entire power storage system decreases. It will decrease. Therefore, in order to properly control charging and discharging of multiple battery units, each battery unit must be It is preferable to maintain the charged state.

An object of the present invention is to realize appropriate charge/discharge control in a power storage system including a plurality of battery units.

A first aspect of the present invention is a method for controlling charging and discharging of the first and second battery units in a power storage system including the first and second battery units, the SOC of the first and second battery units being (State of Charge, the ratio of the amount of remaining electricity to the electric capacity value) and uses the obtained SOC value to determine the amount of charge and discharge of the first and second battery units according to a predetermined calculation. and the predetermined calculation allocates a larger discharge amount to a battery unit with a higher SOC among the first and second battery units in the discharge mode, and the SOC of the first and second battery units is A discharge amount is assigned to the first and second battery units so that the discharge target value is reached at the same timing, and in the charging mode, a battery unit with a lower SOC is assigned a higher SOC. The charging amount is allocated to the first and second battery units so that the SOCs of the first and second battery units reach the charging target value at the same timing .

According to this configuration, in the power storage system, the amount of charge and discharge of the first and second battery units is determined by a predetermined calculation using the SOC. This predetermined calculation allocates a larger discharge amount to the battery unit with the higher SOC among the first and second battery units in the discharge mode, and assigns a larger discharge amount to the battery unit with the higher SOC among the first and second battery units in the charge mode. Allocate more charge to lower battery units. This makes it possible to keep the SOC of the first and second battery units as close as possible, and prevents the SOC of one battery unit from reaching the lower limit or upper limit before the other battery unit. It can be avoided. Therefore, more appropriate charge/discharge control can be achieved. For example, even when a battery unit with a different SOC from an existing battery unit is added to the power storage system, appropriate charge/discharge control can be achieved.

Furthermore, the predetermined calculation allocates the discharge amount so that the SOC of the first and second battery units reach the discharge target value at the same timing in the discharge mode, and in the charge mode, the SOC of the first and second battery units The amount of charge is allocated so that the SOC reaches the target charge value at the same timing. As a result, it is possible to reliably prevent the SOC of one battery unit from reaching the lower limit value or upper limit value before the other battery unit, so that it is possible to fully utilize the energy of the power storage system.

In this aspect, the predetermined calculation allocates discharge amounts to the first and second battery units so that the SOCs of the first and second battery units gradually approach each other while decreasing in the discharge mode; In the charging mode, charge amounts may be allocated to the first and second battery units so that the SOCs of the first and second battery units increase and gradually approach each other.

As a result, in the discharging mode, the SOCs of the first and second battery units gradually approach each other while decreasing, and in the charging mode, the SOCs of the first and second battery units gradually approach each other while increasing. This makes it possible to keep the SOC of the first and second battery units as close as possible, and prevents the SOC of one battery unit from reaching the lower limit or upper limit before the other battery unit. It can be avoided. Therefore, more appropriate charge/discharge control can be achieved.

Furthermore, in this aspect, the obtained SOC values of the first and second battery units are converted into new SOC values using the electric capacity values of the first and second battery units, respectively, and A predetermined calculation may be performed using the new SOC value instead of the acquired SOC value.

Thereby, even if the electric capacity values of the first and second battery units are different, charging and discharging control can be performed with high accuracy. For example, even if a battery unit with a different electric capacity value from an existing battery unit is added to the power storage system, appropriate charge/discharge control can be achieved.

Further, in the discharge mode, the obtained SOC value of the first and second battery units is multiplied by a conversion coefficient using the electric capacity values of the first and second battery units to obtain the new SOC value. The conversion coefficient by which the SOC of the first and second battery units with a larger electric capacity value is multiplied may be larger than the conversion coefficient by which the SOC of the other battery unit is multiplied. .

Thereby, even if the electric capacity values of the first and second battery units are different, discharge control can be performed with high accuracy.

A second aspect of the present invention is a method for controlling charging and discharging of a plurality of battery units in a power storage system including a plurality of battery units, the method comprising: (a) dividing the plurality of battery units into two groups; , (b) For each of the two groups, calculate the equivalent SOC using the SOC (State of Charge, ratio of remaining electricity amount to electric capacity value) of the battery unit belonging to the group, and (c) Using the calculated equivalent SOC, calculate the charge/discharge amounts of the two groups according to a predetermined calculation, and (d) further divide the plurality of battery units included in the group into two groups, and step (b) and (c) are executed, and (e) step (d) is repeatedly performed until each group includes only one battery unit, and the predetermined calculation is performed in the discharge mode. , a larger discharge amount is assigned to the group with a higher equivalent SOC among the two groups, and the two groups are arranged so that the equivalent SOC of the two groups reaches the discharge target value at the same timing. Allocate a discharge amount to the groups, and in charge mode, assign a larger charge amount to the group with a lower equivalent SOC among the two groups , and charge at the same timing when the equivalent SOC of the two groups is the same. The amount of charge is allocated to the two groups so as to reach the target value .

Accordingly, in a power storage system including three or more battery units, the amount of charge and discharge can be assigned to each battery unit, similar to the first aspect, so that more appropriate charge and discharge control can be achieved.

In a third aspect of the present invention, there is provided a control device for controlling charging and discharging of the first and second battery units in a power storage system including first and second battery units, the control device controlling charging and discharging of the first and second battery units. an arithmetic device that calculates the charging and discharging amount of the first and second battery units using a value of SOC (State of Charge, ratio of the amount of remaining electricity to the electric capacity value); the arithmetic device, in the discharging mode, The battery unit having a higher SOC among the first and second battery units is assigned a larger discharge amount, and the SOC of the first and second battery units reaches the discharge target value at the same timing. a discharge amount is allocated to a first and a second battery unit; in a charging mode, a larger charge amount is allocated to a battery unit with a lower SOC among the first and second battery units; Charge amounts are allocated to the first and second battery units so that the SOCs of the battery units reach the charge target value at the same timing .

Thereby, in the electricity storage system, the amount of charge and discharge of the first and second battery units is determined by the arithmetic device using the SOC value. In the discharging mode, the computing device allocates a larger discharge amount to the battery unit with a higher SOC among the first and second battery units, and in the charging mode, assigns a larger discharge amount to the battery unit with a lower SOC among the first and second battery units. Allocate a larger charge to the unit. This makes it possible to keep the SOC of the first and second battery units as close as possible, and prevents the SOC of one battery unit from reaching the lower limit or upper limit before the other battery unit. It can be avoided. Therefore, more appropriate charge/discharge control can be achieved.

Further, in the discharging mode, the arithmetic device allocates the discharge amount so that the SOC of the first and second battery units reach the discharge target value at the same timing, and in the charging mode, the computing device allocates the discharge amount so that the SOC of the first and second battery units Allocate the amount of charge so that the two reach the target charge value at the same time. As a result, it is possible to reliably prevent the SOC of one battery unit from reaching the lower limit value or upper limit value before the other battery unit, so that it is possible to fully utilize the energy of the power storage system.

According to the present invention, appropriate charge/discharge control can be achieved in a power storage system including a plurality of battery units.

Configuration example of energy storage system Example of power allocation algorithm according to embodiment 1 Example of power allocation algorithm according to embodiment 2 Configuration example of energy storage system Graph showing examples of changes in SOC and discharge power in discharge mode Graph showing examples of changes in SOC and charging power in charging mode Graph showing an example of change in discharge power in discharge mode

Hereinafter, embodiments of the present invention will be described in detail based on the drawings. The following description of preferred embodiments is merely illustrative in nature and is not intended to limit the invention, its scope of application, or its uses.

(Embodiment 1)
FIG. 1 shows an example of the configuration of a power storage system. The power storage system in FIG. 1 includes two chargeable and dischargeable battery units 1 and 2 and a power conditioner 3. Each battery unit 1, 2 includes a storage battery 11, 12 and a unit controller 12, 22, respectively. The power conditioner 3, which is an example of a charging/discharging control device, controls charging and discharging of the battery units 1 and 2. Unit controllers 12 and 22 include bidirectional DC/DC converters 13 and 23, and charge and discharge storage batteries 11 and 12 according to instructions from power conditioner 3. The power conditioner 3 includes a calculation device 31 that calculates the amount of charge and discharge of the battery units 1 and 2. This arithmetic device 31 is realized, for example, by a microcomputer equipped with a processor and a memory.

In the first embodiment, the calculation device 31 calculates the charge/discharge amount of the battery units 1 and 2 using the SOC (State Of Charge) values of the battery units 1 and 2. Here, in the present disclosure, the SOC is assumed to be the ratio of the amount of remaining electricity to the electric capacity value in the battery unit. The power conditioner 3 uses this calculation result to allocate the charge/discharge amount of the battery units 1 and 2.

Here, in a power storage system including a plurality of battery units, it is preferable to maintain the SOC of each battery unit as close as possible while all the battery units are operating. Therefore, in the present embodiment, in the discharge mode, a larger discharge amount is allocated to the battery unit with a higher SOC among the battery units 1 and 2, and in the charge mode, a larger discharge amount is allocated to the battery unit with a lower SOC among the battery units 1 and 2. Allocate a larger amount of charge to.

・Calculation example in discharge mode The total discharge power of the power storage system is P _Dschrg-Total , the SOC of battery units 1 and 2 are SOC ₁ and SOC ₂ , respectively, and the discharge power allocated to battery units 1 and 2, respectively, is P _Dschrg1 and P _Dschrg2. shall be. The calculation device 31 calculates P _Dschrg1 and P _Dschrg2 according to the following equations (1) and (2).

Equations (1) and (2) above are used to allocate a larger amount of discharge to the battery unit with a higher SOC among battery units 1 and 2 in order to balance the SOC of battery units 1 and 2 during discharging. This is an example of an arithmetic expression.

- Example of calculation in charging mode Let P _{Chrg-Total be} the total charging power of the power storage system, and let P _Chrg1 and P _Chrg2 be the charging powers allocated to battery units 1 and 2, respectively. The calculation device 31 calculates P _Chrg1 and P _Chrg2 according to the following equations (3) and (4).

Equations (3) and (4) above are used to allocate larger charging power to the battery unit with the lower SOC among battery units 1 and 2 in order to balance the SOC of battery units 1 and 2 during charging. This is an example of an arithmetic expression.

As described above, according to the present embodiment, in the power storage system, the amount of charge and discharge of the battery units 1 and 2 is determined by a predetermined calculation using the SOC. This predetermined calculation allocates a larger discharge amount to the battery unit with the higher SOC among the battery units 1 and 2 in the discharge mode, and assigns a larger discharge amount to the battery unit with the lower SOC among the battery units 1 and 2 in the charge mode. , allocate a larger charge amount. This makes it possible to keep the SOC of battery units 1 and 2 as close as possible, and prevents the SOC of one battery unit from reaching the lower limit or upper limit before the other battery unit. . Therefore, more appropriate charge/discharge control can be achieved. For example, even when a battery unit with a different SOC from an existing battery unit is added to the power storage system, appropriate charge/discharge control can be achieved.

Note that the derivation of equations (1) to (4) will be described later. Furthermore, the calculations in this embodiment are not limited to equations (1) to (4).

Furthermore, as a result of the calculation, there is a possibility that the charge/discharge amount of one of the battery units becomes a negative value. For example, in discharge mode, if P _Dschrg1 becomes a negative value, this means that battery unit 2 will discharge more than the total discharge power P _{Dischrg-Total} , and battery unit 1 will charge the excess power. represent. However, if power transmission between the battery units 1 and 2 is not permitted, the amount of charge and discharge of the battery units 1 and 2 cannot be set to a negative value, so a countermeasure is required. This is because transmitting power between battery units causes energy loss, which is not rational. Further, countermeasures are also required when a minimum charge amount or minimum discharge amount is set for the battery units 1 and 2.

FIG. 2 is an example of an algorithm according to this embodiment in a case where power transmission between battery units 1 and 2 is not permitted. The algorithm in FIG. 2 allocates power in discharge mode.

First, the discharge powers P _Dschrg1 and P _Dschrg2 to be allocated to the battery units 1 and 2 are calculated according to, for example, equations (1) and (2) (S101). Then, it is determined whether P _Dschrg1 is less than a lower limit value (here, 0.0) (S102). When P _Dschrg1 is below the lower limit value, P _Dschrg1 is set to the lower limit value, and (P _Dschrg1 - lower limit value) is added to P _Dschrg2 (S103). When P _Dschrg1 is not below the lower limit, it is determined whether P _Dschrg2 is below the lower limit (S104). When P _Dschrg2 is below the lower limit value, P _Dschrg2 is set to the lower limit value, and (P _Dschrg2 - lower limit value) is added to P _Dschrg1 (S105).

For example, assume that P _Dschrg-Total is 5.0 kW, SOC ₁ is 80%, and SOC ₂ is 20%. When calculated according to formulas (1) and (2),
P _Dschrg1 = ((3×0.8-0.2)/(2(0.8+0.2)))×5.0=5.5kw
P _Dschrg2 = ((3×0.2-0.8)/(2(0.2+0.8)))×5.0=-0.5kw
becomes. In this case, since P _Dschrg2 is less than 0.0, P _Dschrg2 is set to 0.0 and (P _Dschrg2 -0.0) is added to P _Dschrg1 . i.e.
P _Dschrg1 =5.5-0.5=5.0
P _Dschrg2 =0.0
shall be.

With such an algorithm, it is possible to avoid setting the charging and discharging amounts of the battery units 1 and 2 to negative values. Note that even in the charging mode, power allocation may be performed in the same manner as the algorithm in FIG. 2 .

Note that in the above explanation, the lower limit value was set to 0.0, but if, for example, a minimum discharge amount is set for battery units 1 and 2, the same action can be taken by giving the minimum discharge amount as the lower limit value. I can do it.

(Embodiment 2)
In a power storage system, each battery unit may have a mutually different maximum chargeable power/maximum dischargeable power. In such a case, if the charging/discharging power of each battery unit is allocated according to the SOC as shown in Embodiment 1, there is a possibility that a part of the charging/discharging capacity of the battery unit will remain unused. There is. This hinders effective utilization of the power of the entire power storage system.

Therefore, in the second embodiment, in addition to the SOC, charging/discharging power is allocated in consideration of the maximum chargeable power/maximum dischargeable power of each battery unit.

FIG. 3 is an example of an algorithm according to this embodiment. The algorithm in FIG. 3 allocates power in the discharge mode, and assumes a case where power transmission between battery units is not permitted.

First, the SOC of the battery units 1 and 2, the maximum dischargeable power P _Dislmt1 , P _Dislmt2 , and the total discharge power P _Dschrg-Total of the power storage system are updated (S201). Then, the flag indicating that the discharge power of the battery units 1 and 2 has reached the maximum dischargeable power is turned off (S202).

Next, discharge powers P _Dschrg1 and P _Dschrg2 to be allocated to battery units 1 and 2 are set (S10). This step S10 may be performed, for example, according to the algorithm shown in FIG. 2 in the first embodiment.

Thereafter, it is determined whether P _Dschrg1 exceeds P _Dislmt1 (S203). When P _Dschrg1 exceeds P _Dislmt1 , turn on the flag. Then, P _Dschrg1 is set to P _Dislmt1 , and P _Dschrg2 is set to (P _Dschrg-Total - P _Dschrg1 ) (S204). When P _Dschrg1 does not exceed P _Dislmt1 , P _Dschrg1 and P _Dschrg2 are not changed.

Thereafter, it is determined whether P _Dschrg2 exceeds P _Dislmt2 (S205). If P _Dschrg2 does not exceed P _Dislmt2 , the algorithm ends. When P _Dschrg2 exceeds P _Dislmt2 , P _Dschrg2 is set to P _Dislmt2 (S206). Then, it is determined whether the flag is ON (S207). When the flag is ON, the algorithm ends. When the flag is OFF, P _Dschrg1 is set to (P _Dschrg-Total - P _Dschrg2 ) (S208), and the algorithm ends.

For example, assume that P _Dschrg-Total is 7.0 kW, SOC ₁ is 30%, and SOC ₂ is 80%. In step S10, for example, when calculating according to equations (1) and (2),
P _Dschrg1 = ((3×0.3-0.8)/(2(0.3+0.8)))×7.0=0.32kw
P _Dschrg2 = ((3×0.8-0.3)/(2(0.3+0.8)))×7.0=6.68kw
becomes. Here, if P _Dislmt1 is 2.0kw and P _Dislmt2 is 5.0kw, P _Dschrg2 exceeds P _Dislmt2 , so
P _Dschrg2 = P _Dislmt2 = 5.0kw
P _Dschrg1 = (P _{Dischrg-Total} - P _Dschrg2 ) = (7.0-5.0) = 2.0kw
shall be.

In other words, according to this algorithm, if the charging/discharging power set using the SOC exceeds the maximum charging/discharging power of battery units 1 and 2, that setting is invalidated in order to utilize the maximum power capacity of the power storage system. Ru. Note that even in the charging mode, power allocation may be performed in the same way as the algorithm in FIG. 3 .

According to this embodiment, it is possible to avoid the possibility that part of the charging/discharging capacity of the battery unit remains unused, and it is possible to effectively utilize the power of the entire power storage system.

(Embodiment 3)
In a power storage system in which a plurality of battery units are installed, the electric capacity value of the entire system is equal to the sum of the electric capacity values of each battery unit. If the electric capacity values of the battery units are equal to each other, power may be allocated according to the algorithm shown in the first and second embodiments described above.

However, for example, when a new battery unit is added to an existing power storage system, the electric capacity values of each battery unit may differ from each other. If the battery units have different capacitance values, it is preferable to consider the difference in capacitance values when allocating power. This is because the SOC is a value representing the ratio of the amount of remaining electricity to the electric capacity value of the battery unit, and therefore the SOC has different meanings for battery units with different electric capacity values.

Therefore, in the third embodiment, when the electric capacity values of the battery units 1 and 2 are different, the SOC is converted into a new SOC in consideration of the difference, and then charging/discharging power is allocated. That is, the acquired SOC values of battery units 1 and 2 are converted into new SOC values using the electric capacity values of battery units 1 and 2, respectively.

- Example of calculation in discharge mode Let the electric capacity values of battery units 1 and 2 be WH ₁ and WH ₂ , respectively. According to the following equations (5) and (6), the SOCs of battery units ₁ and 2, SOC 1 and SOC ₂ , are converted into new SOCs, SOC _1-new-dschrg and SOC _2-new-dschrg .

After conversion, discharge power may be allocated using SOC _{1 -new-dschrg} and SOC _2-new-dschrg instead of SOC ₁ and SOC 2 in the same manner as in the first and second embodiments described above. As shown in equations (5) and (6) above, in the discharge mode, the SOC values of battery units 1 and 2 are multiplied by a conversion coefficient using the electric capacity values of battery units 1 and 2 to obtain a new value. Obtain the SOC value. Regarding the conversion coefficient, the conversion coefficient by which the SOC of the battery unit 1 and 2 with a larger electric capacity value is multiplied may be made larger than the conversion coefficient by which the SOC of the other battery unit is multiplied.

- Example of calculation in charging mode SOC ₁ and SOC ₂ are converted into new SOCs SOC _1-new-chrg and SOC _2-new-chrg according to the following equations (7) and (8).

After conversion, the new SOCs SOC _{1 -new-chrg} and SOC _2-new-chrg are used instead of SOC _{1 and} SOC 2, and the charging power is allocated in the same way as in the first and second embodiments described above. All you have to do is

For example, let SOC ₁ be 30%, SOC ₂ be 80%, WH ₁ be 3 kwh, and WH ₂ be 7 kwh. In this case, according to equations (5)-(8),
SOC _1-new-dschrg =0.3×3/(3+7)=0.09=9%
SOC _2-new-dschrg =0.8×7/(3+7)=0.56=56%
SOC _1-new-chrg = (0.3 x 3 + 7) / (3 + 7) = 0.79 = 79%
SOC _2-new-chrg = (0.8 x 7 + 3) / (3 + 7) = 0.86 = 86%
becomes. Using these values, calculations may be performed in the same manner as in the first and second embodiments described above to allocate charging and discharging power.

Further, the electric capacity value of the battery unit gradually decreases depending on the operating state. It is preferable to reflect this change in the above calculation using SOH (State of Health). SOH is a parameter indicating the state of deterioration of the battery unit, and is expressed, for example, as the ratio of the remaining capacity to the initial electric capacity. In this case, WH ₁ and WH ₂ are converted into corrected capacitance values WH ₁ ′ and WH ₂ ′ using equations (9) and (10).

Instead of WH ₁ and WH2, the corrected capacitance values WH ₁ ' and WH ₂ ' are used to calculate equations (5) to (8), and the new SOC is SOC _1-new- All you have to do is find _dschrg , SOC _2-new-dschrg , SOC _1-new-chrg , and SOC _2-new-chrg .

According to this embodiment, even if the battery units 1 and 2 have different capacitance values, charging and discharging control can be performed with high accuracy. For example, even if a battery unit with a different electric capacity value from an existing battery unit is added to the power storage system, appropriate charge/discharge control can be achieved.

(Embodiment 4)
Embodiments 1 to 3 above have been described using the case where there are two battery units as an example. Embodiment 4 will describe allocation of charging and discharging power in a case where the power storage system includes n battery units (n is an integer of 3 or more).

FIG. 4 shows an example of the configuration of the power storage system. The power storage system in FIG. 4 includes n battery units 1, 2, ..., m, ..., n (n is an integer of 3 or more). For such a power storage system, power can be allocated by hierarchically applying the algorithms shown in Embodiments 1 to 3 above.

That is, as shown in FIG. 4, the n battery units are divided into a first group consisting of m battery units and a second group consisting of (n−m) battery units. Then, the m battery units belonging to the first group are regarded as a single battery unit, and the (n−m) battery units belonging to the second group are regarded as a single battery unit. Charging and discharging assignments are performed by applying methods 1 to 3.

In this case, the equivalent capacitance value, SOC, maximum charging power, and maximum discharging power are calculated for the group considered as a single battery unit. Specifically, for example, for the first group consisting of m battery units, equivalent electric capacity values WH _eq-m , SOCSOC _eq-m , maximum charging power P _{DschrgMax-eq-m} , and maximum discharging power P _ChrgMax-eq-m is calculated using the following equations (11) to (14).

Similarly, for the second group consisting of (n−m) battery units, the equivalent electric capacity value, SOC, maximum charging power, and maximum discharging power are calculated. Then, using the equivalent capacitance value, SOC, maximum charging power, and maximum discharging power, charge/discharge allocation is performed by applying the methods of the first to third embodiments described above.

Next, the m battery units belonging to the first group are further divided into two groups. Then, each of the plurality of battery units belonging to each divided group is regarded as a single battery unit, and the equivalent capacitance value, SOC, maximum charging power, and maximum discharging power are calculated. Charge/discharge allocation is performed by applying method 3. Similarly, the (n−m) battery units belonging to the second group are further divided into two groups. Then, each of the plurality of battery units belonging to each divided group is regarded as a single battery unit, and the equivalent capacitance value, SOC, maximum charging power, and maximum discharging power are calculated. Charge/discharge allocation is performed by applying method 3.

The above process is repeated until each group includes only one battery unit.

As described above, according to the present embodiment, in a power storage system including three or more battery units, as in the first to third embodiments, it is possible to allocate the charge/discharge amount to each battery unit, so that more appropriate Charge/discharge control can be realized.

<About the derivation of formulas (1) to (4)>
The derivation of equations (1) to (4) used in the first embodiment will be explained below. As explained below, equations (1) and (2) allocate the discharge amount so that the SOC of battery units 1 and 2 reach 0.0 at the same timing in the discharge mode, and the equation ( 3) to (4) are for allocating the amount of charge so that the SOC of battery units 1 and 2 reach 1.0 at the same timing in the charging mode. By using equations (1) to (4), it is possible to make maximum use of the energy of the power storage system. Note that SOC=0.0 is an example of a discharge target value, and SOC=1.0 is an example of a charge target value.

-Discharge mode FIG. 5 is a graph showing an example of changes in SOC and discharge power in discharge mode. In FIG. 5, the discharge powers P ₁ and P ₂ of the two battery units 1 and 2 change as the SOCs of the battery units 1 and 2, SOC ₁ and SOC _2, change. Then, SOC ₁ and SOC ₂ reach 0.0 at the same timing, and at that time, discharge powers P ₁ and P ₂ become equal to each other (0.5P _t ). Equations (1) and (2) are derived based on the variation example shown in FIG. 5.

From the graph of FIG. 5, the discharge powers P ₁ and P ₂ of the battery units 1 and 2 are respectively expressed by the following equations.

K ₁ and K ₂ are the allocation ratios of the discharge amount to battery units 1 and 2 to the total discharge power,
K ₁ +K ₂ =1
It is.

The energy discharged by battery unit 1 until SOC ₁ reaches 0.0 is:

becomes. This energy is equal to SOC ₁ × WH ₁ . Therefore, the following formula holds.

Similarly, regarding the battery unit 2, the following equation holds true.

If Δt is eliminated and WH ₁ =WH ₂ is assumed, the following equation holds true.

Therefore, K ₁ and K ₂ are as follows.

From the above, equations (1) and (2) are derived.

-Charging mode FIG. 6 is a graph showing an example of changes in SOC and charging power in charging mode. In FIG. 6, the charging powers P ₁ and P _{2 of the two battery units 1 and 2} change as the SOCs of the battery units 1 and 2, SOC ₁ and SOC ₂ , change. Then, SOC ₁ and SOC ₂ reach 1.0 at the same timing, and at that time, charging powers P ₁ and P ₂ become equal to each other (0.5P _t ). Equations (3) to (4) are derived based on the variation example shown in FIG. 6.

Here, in the charging mode, the energy charged into battery units 1 and 2 until SOC ₁ and SOC ₂ reach 1.0 is (1-SOC ₁ )×WH ₁ , (1-SOC ₂ )×WH equals ₂ . Therefore, the following formula holds.

As in the discharge mode, if Δt is eliminated and WH ₁ =WH ₂ is assumed, K ₁ and K ₂ are as follows.

From the above, equations (3) and (4) are derived.

(Modification 1)
In the graph of FIG. 5, the SOC discharge target value in the discharge mode is set to 0.0, and in the graph of FIG. 6, the SOC charge target value in the charge mode is set to 1.0. However, the present invention is not limited to this, and the target SOC discharge value may be set to a value other than 0.0, and the SOC charge target value may be set to a value other than 1.0.

For example, the target value of SOC in the discharge mode is set to 0.05, and the target value in the charge mode is set to 0.95. In this case, in the discharge mode, the energy discharged by battery units 1 and 2 until the SOC reaches 0.05 is (SOC ₁ -0.05) x WH ₁ , (SOC ₂ -0.05) x WH Assuming that K 1 and K 2 are equal to ₂ , K ₁ and K ₂ can be found in the same manner as in the above explanation. Also, in the charging mode, the energy charged by battery units 1 and 2 until the SOC reaches 0.95 is equal to (0.95-SOC ₁ ) x WH1, (0.95-SOC ₂ ) x WH2. If so, K ₁ and K ₂ can be found in the same manner as described above.

The formula derived above allocates the discharge amount so that the SOC of battery units 1 and 2 reaches 0.05 at the same timing in the discharge mode, and in the charge mode, the SOC of the battery units 1 and 2 reaches 0.05. The amount of charge is allocated so that it reaches 0.95 at the same timing.

Alternatively, the amount of charge or discharge may be allocated so that the SOC of the battery units 1 and 2 approaches sufficiently after a predetermined period of time and falls within a predetermined target range. For example, the target range of SOC in discharge mode is set to 0.0 to 0.1, and the target range of SOC in charge mode is set to 0.9 to 1.0. Then, in the discharge mode, the amount of discharge is assigned so that the SOC of the battery units 1 and 2 falls within the range of 0.0 to 0.1 after a predetermined period of time has elapsed. Further, in the charging mode, the amount of charge is allocated so that the SOC of the battery units 1 and 2 falls within the range of 0.9 to 1.0 after a predetermined period of time has elapsed.

That is, the predetermined calculation for determining the amount of charge and discharge of the battery units 1 and 2 allocates the amount of discharge to the battery units 1 and 2 so that the SOC of the battery units 1 and 2 gradually approaches each other while decreasing in the discharge mode. In the charging mode, the amount of charge may be allocated to the battery units 1 and 2 so that the SOC of the battery units 1 and 2 gradually approaches each other while increasing.

(Modification 2)
In deriving the above-mentioned equations (1) to (4), it is assumed that the discharging power and charging power of the battery units 1 and 2 change as the SOC changes. Alternatively, as shown in FIG. 7, the charging and discharging powers P ₁ and P ₂ of the battery unit may be constant until the SOC becomes zero.

In this case, the following formula holds.

Therefore, K ₁ and K ₂ are as follows.

Even when using the calculation formula obtained by this modification, as in the first embodiment, a larger discharge amount is allocated to a battery unit with a higher SOC in the discharge mode, and a larger discharge amount is allocated to a battery unit with a lower SOC in the charge mode. A larger amount of charge can be allocated to the

INDUSTRIAL APPLICABILITY The present invention is extremely useful for performing appropriate charge/discharge control in a power storage system including a plurality of battery units.

1, 2 Battery unit 3 Power conditioner (charge/discharge control device)
31 Arithmetic device

Claims (6)

A method for controlling charging and discharging of the first and second battery units in a power storage system including first and second battery units, the method comprising:
Obtaining the SOC (State of Charge, ratio of the amount of remaining electricity to the electric capacity value) of the first and second battery units,
Using the obtained SOC value, the amount of charge and discharge of the first and second battery units is determined according to a predetermined calculation,
The predetermined operation is
In the discharge mode, a larger discharge amount is assigned to the battery unit with a higher SOC among the first and second battery units , and the SOCs of the first and second battery units reach the discharge target value at the same timing. allocating a discharge amount to the first and second battery units,
In the charging mode, a larger amount of charge is allocated to the battery unit with a lower SOC among the first and second battery units , and the SOCs of the first and second battery units reach the charging target value at the same timing. A charging/discharging control method , characterized in that the charge amount is allocated to the first and second battery units . The charge/discharge control method according to claim 1,
The predetermined operation is
In the discharge mode, a discharge amount is assigned to the first and second battery units so that the SOC of the first and second battery units decreases and gradually approaches each other;
A charging/discharging control method characterized in that, in a charging mode, charge amounts are allocated to the first and second battery units so that the SOCs of the first and second battery units increase and gradually approach each other. The charge/discharge control method according to claim 1 or 2 ,
Converting the acquired SOC values of the first and second battery units into new SOC values using the electric capacity values of the first and second battery units, respectively,
A charging/discharging control method characterized in that the predetermined calculation is executed using the new SOC value instead of the acquired SOC value. In the charge/discharge control method according to claim 3 ,
In the discharge mode, the obtained SOC value of the first and second battery units is multiplied by a conversion coefficient using the electric capacity values of the first and second battery units to obtain the new SOC value. and
The charge/discharge control method characterized in that the conversion coefficient by which the SOC of the first and second battery units with a larger electric capacity value is multiplied is larger than the conversion coefficient by which the SOC of the other battery unit is multiplied. . A method for controlling charging and discharging of the plurality of battery units in a power storage system including a plurality of battery units, the method comprising:
(a) dividing the plurality of battery units into two groups,
(b) For each of the two groups, calculate an equivalent SOC using the SOC (State of Charge, ratio of remaining electricity amount to electric capacity value) of the battery unit belonging to the group,
(c) Using the calculated equivalent SOC, calculate the charge and discharge amounts of the two groups according to a predetermined calculation, and
(d) further dividing the plurality of battery units included in the group into two groups and performing steps (b) and (c);
(e) repeating step (d) until each group includes only one battery unit;
The predetermined operation is
In the discharge mode, a larger discharge amount is assigned to the group with a higher equivalent SOC among the two groups, and the equivalent SOC of the two groups reaches the discharge target value at the same timing, Assigning discharge amounts to the two groups,
In the charging mode, a larger amount of charging is allocated to the group with a lower equivalent SOC among the two groups, and the equivalent SOC of the two groups reaches the charging target value at the same timing, A charging/discharging control method, characterized in that a charging amount is allocated to the two groups . In a power storage system including first and second battery units, a control device that controls charging and discharging of the first and second battery units,
comprising an arithmetic device that calculates the amount of charge and discharge of the first and second battery units using the SOC (State of Charge, ratio of the amount of remaining electricity to the electric capacity value) of the first and second battery units;
The arithmetic device is
In the discharge mode, a larger discharge amount is assigned to the battery unit with a higher SOC among the first and second battery units , and the SOCs of the first and second battery units reach the discharge target value at the same timing. allocating a discharge amount to the first and second battery units,
In the charging mode, a larger amount of charge is allocated to the battery unit with a lower SOC among the first and second battery units , and the SOCs of the first and second battery units reach the charging target value at the same timing. The charge/discharge control device is characterized in that the charging/discharging control device allocates a charge amount to the first and second battery units .

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