JP7787751B2 - Power System - Google Patents

Description

The present invention relates to a power system.

In a power system that combines a rechargeable battery and solar cells, a configuration has been disclosed that enables compliance with output suppression commands from the power grid by adjusting the amount of active power output from a power conditioning system (PCS) connected to the solar cell panels and the amount of charge and discharge from a power control system connected to the battery (Non-Patent Document 1).

Also disclosed is a hybrid energy storage system that employs two types of batteries: a capacity-type battery with a large capacity and low output, and a power-type battery with a high output relative to its capacity (Patent Document 1). The capacity-type battery is a lithium-ion (Li-ion), nickel-metal hydride (Ni-MH), lead battery, etc., while the power-type battery is a capacitor, etc. By using two types of batteries in an energy storage system, it is possible to operate the battery in an SOC range of around 50%, avoiding high SOC ranges (e.g., 80% or higher) and low SOC ranges (e.g., 20-30% or lower) where capacity degradation accelerates during battery charging and discharging. Furthermore, different types of batteries can be used depending on the application; for example, when the power system requires high power instantaneously, output is primarily from the power-type battery, and when low-output, long-term power is required, output is primarily from the capacity-type battery.

Japanese Patent Application Laid-Open No. 2019-198149

Hikaru Akutsu, Kenji Hirata, Akihiro Ohori, Nobuyuki Hattori and Yoshito Ohta, “Decentralized Control Approach to Power Curtailment Instruction problem for PV Generation Plants with Storage”, 2017 11th Asian Control Conference (ASCC).

Incidentally, the power system in Non-Patent Document 1 is capable of tracking the system power required by the power company, but it is not able to control multiple different types of batteries in a way that takes advantage of the respective characteristics of high-capacity, low-output batteries and low-capacity, high-output batteries.

Furthermore, while the energy storage system in Patent Document 1 is capable of efficiently operating heterogeneous batteries with different characteristics, it employs a centralized control method in which a central server that primarily manages the system determines the output of all batteries based on battery information (such as SOC). Patent Document 1 states that "instead of a centralized control method, a method of decentralized control of individual battery output may be employed," but does not specifically state what type of decentralized control method should be used or whether target tracking is ensured. In other words, there is no suggestion whatsoever about decentralized control, and it is unclear how the system will be operated efficiently.

One aspect of the present invention is a power system that includes a first battery and a second battery that has a lower capacity and higher output than the first battery, and controls the input/output power of the first battery and the second battery so as to reduce the difference between a system required power value and the total input/output power value of the first battery and the second battery. The power system controls the input/output power of the first battery in accordance with the relationship between the SOC of the first battery and the long-cycle component of the system required power value and the long-cycle component of the difference value, and controls the input/output power of the second battery in accordance with the relationship between the SOC of the second battery and the system required power value and the difference value.

Here, when the long-cycle component in the system required power value and the long-cycle component in the difference value indicate a discharge request, it is preferable to perform control so that the output power from the first battery increases as the SOC of the first battery increases.

Furthermore, when the long-cycle component of the system required power value and the long-cycle component of the difference value indicate a time when charging is required, it is preferable to perform control so that the input power to the first battery decreases as the SOC of the first battery increases.

It is also preferable to limit the input/output power of the first battery depending on the SOC of the first battery.

Furthermore, when the system required power value and the difference value indicate a discharge request, it is preferable to perform control so that the output power from the second battery increases as the SOC of the second battery increases.

Furthermore, when the system required power value and the difference value indicate a charging request, it is preferable to perform control so that the input power to the second battery decreases as the SOC of the second battery increases.

It is also preferable to limit the input/output power of the second battery depending on the SOC of the second battery.

It is also preferable to limit the input and output of the second battery so that fluctuations in the SOC of the second battery fall within a predetermined fluctuation range.

It is also preferable to provide a low-pass filter that extracts long-period components in the system required power value and the difference value.

This invention makes it possible to make the total output match the system's required power while taking advantage of the characteristics of different types of batteries.

1 is a diagram illustrating a configuration of a power system according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a control logic of the power system according to the embodiment of the present invention. 3 is a flowchart showing a control method for a power system according to an embodiment of the present invention. 4 is a flowchart showing a method for controlling a first battery in the embodiment of the present invention. FIG. 2 is a diagram illustrating a battery model. FIG. 4 is a diagram illustrating a gain setting method according to an embodiment of the present invention. 5A and 5B are diagrams illustrating a method for setting an output command value according to an embodiment of the present invention. 5 is a flowchart illustrating a control method for a second battery according to the embodiment of the present invention. FIG. 4 is a diagram illustrating a method for setting a charge/discharge request amount in an embodiment of the present invention. FIG. 2 is a diagram illustrating a pattern of power required by a system in an embodiment of the present invention. FIG. 10 is a diagram showing a simulation result in an example of the present invention. FIG. 10 is a diagram showing a simulation result in an example of the present invention.

As shown in FIG. 1, the power system 100 according to an embodiment of the present invention includes a power grid 10, a power conditioner system (PCS) 12, a first battery 14, and a second battery 16. The power system 100 appropriately distributes and outputs output power to the two types of batteries, the first battery 14 and the second battery 16, under the control of the power conditioner system 12, according to the power required by the power grid 10 (system required power). In other words, power control is performed in a decentralized manner by the power conditioner system 12 provided in the power system 100, without centralized control from a central server or the like.

The power system 100 can be used not only as a stationary power storage system, but also as a power system for mobile vehicles such as electric vehicles, hybrid vehicles, and aircraft.

In this embodiment, the first battery 14 is a high-capacity, low-output battery. The second battery 16 is a lower-capacity, higher-output battery than the first battery 14. For example, the first battery 14 can be a lithium-ion (Li-ion) battery. The second battery 16 can be a nickel-metal hydride (Ni-MH) battery. This embodiment illustrates a configuration in which two second batteries, 16a and 16b, are provided.

However, the types and numbers of the first battery 14 and second battery 16 are not limited to these, and other types of batteries may be used or the numbers may be changed as needed.

Fig. 2 shows a control logic for making the total output of the first battery 14 and the second battery 16 follow the system required power P _r in the power system 100. The power conditioner system 12 controls the supply and charging of power in the power system 100 based on the control logic. Fig. 3 is a flowchart showing a control method for the power system 100 in this embodiment.

In step S10, the output target power _Pcr of the entire system is determined based on the system required power _Pr from the power grid and the time constant _Tp according to equation (1), where _Tp is a delay time constant that takes into account power transmission and measurement.

In step S12, the supply power _Pco supplied from the first battery 14 and the second battery 16 to the power grid 10 is measured. Here, the supply power Pco has a relationship with the total output power P of the first battery 14 and the second battery 16 and the time constant _Tp as expressed by Equation (2).

The total output power P of the first battery 14 and the second battery 16 can be calculated using equation (3), where P _Li is the output power of the first battery 14, P _Ni-1 is the output power of the second battery 16a, and P _Ni-2 is the output power of the second battery 16b.

In step S14, a power difference value e, which is the difference between the output target power P _cr and the supply power P _co , is calculated using equation (4). The control in the power system 100 is to make the supply power P _co follow the output target power P _cr , that is, to minimize the power difference value e.

In step S16, the long-cycle component e1 of the power difference value e and the long-cycle component _Prl of the system required power _Pr are extracted to correspond to the long-cycle component of the system required power _Pr so that the _SOC of the high-capacity first battery 14 changes gradually. The long-cycle component can be extracted using, for example, a low-pass filter, as shown in FIG. 2 . Here, the long cycle is preferably a cycle of 10 minutes or more. The processing of the long-cycle component of the high-capacity first battery 14 will be described later.

In step S18, in addition to the short-cycle component of the system required power _Pr , the low-capacity second battery 16 is controlled relative to the first battery 14 to compensate for the short-cycle component that could not be input or output due to the control of the high-capacity first battery 14 for the long-cycle component. Here, the short cycle preferably refers to a cycle shorter than the long cycle in step S16. The processing of the short-cycle component of the low-capacity second battery 16 will be described later.

If control of the power system 100 continues, steps S10 to S18 are repeated.

<Processing of long-period components>
4 shows a control method for performing long-cycle control on the first battery 14 in step S16 of the main routine. The first battery 14 is controlled as follows using the long-cycle component e _l of the power difference value e and the long-cycle component P _rl of the system required power P _r .

In step S20, the long-cycle component e _l of the power difference value e and the long-cycle component P _rl of the system required power P _r are obtained.

In step S22, the SOC of the first battery 14 is calculated. The SOC of the battery can be calculated based on the battery model shown in FIG. 5. That is, the output voltage V of the battery is calculated by equation (5) using the open circuit voltage Vo, internal resistance R, and output current I of the battery. Furthermore, the relationship between the battery power P and the output current V and output current I is expressed by equation (6).

The SOC of the battery is expressed by equation (7): where C is the capacity of the battery, Q(t) is the amount of electricity stored in the battery at time t, and SOC(0) is the initial SOC.

In step S24, a gain _KLi is determined based on the sign of the long-cycle component _Prl of the system required power _Pr , the long-cycle component _e1 of the power difference value e, and the SOC of the first battery 14. As shown in the setting method in Fig. 6 , the gain _KLi is determined depending on the sign of the long-cycle component _Prl of the system required power _Pr , i.e., whether discharge is required or charge is required.

When the long-period component P _rl of the system required power P _r is positive, i.e., when discharge is requested, the gain K _Li is set to 0 when the SOC of the first battery 14 is below a predetermined lower limit. This stops discharge from the first battery 14 in a low SOC state to prevent battery capacity degradation. When the SOC of the first battery 14 is greater than the lower limit and less than the upper limit, the gain K _Li is increased as the SOC increases. For example, the gain K _Li is increased in proportion to the SOC of the first battery 14. This increases the discharge output of the battery with a higher SOC so that the SOCs of the multiple batteries are uniform. When the SOC of the first battery 14 is equal to or greater than the upper limit, the gain K _Li is set to the upper limit. This limits the output from the first battery 14 in a high SOC state to the upper limit determined by the gain K _Li to prevent battery capacity degradation.

When the long-period component P _rl of the system required power P _r is negative, i.e., when charging is required, the gain K _Li is set to 0 if the SOC of the first battery 14 is equal to or higher than the upper limit. As a result, charging of the first battery 14 in a high SOC state is stopped to suppress battery capacity degradation. When the SOC of the first battery 14 is lower than the upper limit and higher than the lower limit, the gain K _Li is increased as the SOC decreases. For example, the gain K _Li is increased in proportion to the decrease in the SOC of the first battery 14. As a result, the charge input for the battery with a lower SOC is increased so that the SOCs of the multiple batteries are uniform. When the SOC of the first battery 14 is equal to or lower than the lower limit, the gain K _Li is set to the upper limit. As a result, the charge input for the first battery 14 in a low SOC state is limited to the upper limit determined by the gain K _Li to suppress battery capacity degradation.

The upper and lower limits of the SOC may be the same when a discharge request is made and when a charge request is made, or may be set to different values. The upper and lower limits of the SOC may also be set to different values for each battery.

In step S26, the switching variable ψ _Li is calculated. That is, the switching variable ψ _Li is calculated by time-integrating Equation (8). Note that, when the SOC of the first battery 14 reaches the upper limit or the lower limit as a result of the processing in step S24, the switching variable ψ _Li is limited.

In step S28, an output command value σ _Li (ψ _Li ) for the first battery 14 is determined. As shown in the determination method of Fig. 7 , the output command value σ _Li (ψ _Li ) is determined depending on the sign of the long-cycle component P _rl of the system required power _Pr , i.e., whether discharge is required or charge is required, in order to suppress excessive input/output of the battery and make the measured supply power P _co follow the output target power P _cr of the entire system.

When the long-period component P _rl of the system required power P _r is positive, i.e., when discharge is required, the output command value σ _Li (ψ _Li ) is set to 0 when the switching variable ψ _Li is 0 or less. In other words, when the battery is over-output and the switching variable ψ _Li becomes negative, the output command value σ _Li (ψ _Li ) is set to 0, thereby stopping discharge from the first battery 14. When the switching variable ψ _Li is greater than 0 and less than a predetermined upper limit, the output command value σ _Li (ψ Li ) is increased as the switching variable ψ _Li increases. For example, the output command value σ _Li (ψ _Li ) is increased in proportion to the switching variable ψ _Li . This allows the discharge output of the first battery 14 to be obtained according to the switching variable ψ _Li . When the switching variable ψ _Li is equal to or greater than the upper limit _, the output command value σ _Li (ψ _Li ) is set to the upper limit. This makes it possible to prevent the battery from experiencing a continuous shortage of output. It is preferable to set the upper limit of the output command value σ _Li (ψ _Li ) to a value that can prevent the deterioration of the battery capacity. It is also preferable to set the upper limit of the output command value σ _Li (ψ _Li ) to a value that can prevent circuit failure due to heat generation.

When the long-period component P _rl of the system required power P _r is negative, i.e., when charging is required, the output command value σ _Li (ψ _Li ) is set to 0 when the switching variable ψ _Li is 0 or greater. That is, when the battery is overcharged and the switching variable ψ _Li becomes positive, the output command value σ _Li (ψ _Li ) is set to 0, thereby stopping charging of the first battery 14. When the switching variable ψ _Li is less than 0 and greater than a predetermined lower limit, the output command value σ _Li (ψ _Li ) is decreased as the switching variable ψ _Li decreases. For example, the output command value σ _Li (ψ _Li ) is decreased in proportion to the decrease in the switching variable ψ _Li . This allows the charging input to the first battery 14 to be obtained according to the switching variable ψ _Li . When the switching variable ψ _Li is equal to or less than the lower limit, the output command value σ _Li (ψ _Li ) is set to the lower limit. This makes it possible to prevent the battery from being continuously overcharged. It is preferable to set the lower limit of the output command value σ _Li (ψ _Li ) to a value that can suppress deterioration of the battery capacity.

In step S30, the first battery 14 is controlled in accordance with the output command value σ _Li (ψ _Li ). That is, charging and discharging of the first battery 14 are controlled so as to correspond to the output command value σ _Li (ψ _Li ) set in step S28. When the long-cycle component P _rl of the system required power P _r is positive, i.e., when discharging is requested, discharging from the first battery 14 is controlled in a range from 0 to the output power P _Li-out corresponding to the upper limit value of the output command value σ _Li (ψ _Li ). When the long-cycle component P _rl of the system required power P _r is negative, i.e., when charging is requested, charging of the first battery 14 is controlled in a range from 0 to the charging power P _Li-in corresponding to the lower limit value. The current value of the first battery 14 for performing this charging and discharging control can be calculated using equations (5) and (6). Furthermore, the change in SOC due to charging and discharging of the first battery 14 is calculated using equation (7). The calculated value of the SOC is fed back to the process of step S24.

In this embodiment, one first battery 14 is provided, but if multiple first batteries 14 are provided, the above processing can be performed for each battery.

<Processing of short-period components>
8 shows a control method for short-cycle control of the second battery 16 in step S18 of the main routine. The second battery 16 is controlled as follows using the system required power P _r and the power difference value e.

In step S32, the system required power P _r and the power difference value e are acquired. In step S34, the SOC of the second battery 16 is calculated. The SOC of the battery can be calculated in the same manner as in the processing of the long-period component described above.

In step S36, a gain _KNi is determined based on the sign of the system required power _Pr , the power difference value e, and the SOC of the second battery 16. As shown in the setting method in FIG. 6 , the gain _KNi is determined depending on the sign of the system required power _Pr , i.e., whether discharging is required or charging is required.

When the system required power _Pr is positive, i.e., when discharge is requested, the gain K _Ni is set to 0 if the SOC of the second battery 16 is below a predetermined lower limit. This stops discharge from the second battery 16, which is in a low SOC state, to suppress battery capacity degradation. When the SOC of the second battery 16 is greater than the lower limit and less than the upper limit, the gain K _Ni is increased as the SOC increases. For example, the gain K _Ni is increased in proportion to the SOC of the second battery 16. This increases the discharge output of a battery with a higher SOC so that the SOCs of the multiple batteries are uniform. When the SOC of the second battery 16 is equal to or greater than the upper limit, the gain K _Ni is set to the upper limit. This limits the output from the second battery 16, which is in a high SOC state, to the upper limit determined by the gain K _Ni to suppress battery capacity degradation.

When the system required power _Pr is negative, i.e., when charging is requested, the gain K _Ni is set to 0 if the SOC of the second battery 16 is equal to or higher than the upper limit. As a result, charging of the second battery 16, which is in a high SOC state, is stopped to suppress battery capacity degradation. When the SOC of the second battery 16 is lower than the upper limit and higher than the lower limit, the gain K _Ni is increased as the SOC decreases. For example, the gain K _Ni is increased in proportion to the decrease in the SOC of the second battery 16. As a result, the charge input is increased for batteries with lower SOCs so that the SOCs of the multiple batteries are uniform. When the SOC of the second battery 16 is equal to or lower than the lower limit, the gain K _Ni is set to the upper limit. As a result, the charge input to the second battery 16, which is in a low SOC state, is limited to the upper limit determined by the gain K _Ni to suppress battery capacity degradation.

The upper and lower limits of the SOC may be the same when a discharge request is made and when a charge request is made, or may be set to different values. The upper and lower limits of the SOC may also be set to different values for each battery.

In step S38, the switching variable ψ _Ni is calculated. That is, the switching variable ψ _Ni is calculated by time-integrating Equation (9). Note that, when the SOC of the second battery 16 reaches the upper limit or the lower limit as a result of the processing in step S36, the switching variable ψ _Ni is limited.

In step S40, an output command value σ _Ni (ψ _Ni ) for the second battery 16 is determined. As shown in the determination method of Fig. 7, the output command value σ _Ni (ψ _Ni ) is determined depending on the sign of the system required power Pr, i.e., whether discharge is required or charge is required, in order to suppress excessive input/output of the battery and make the measured supply power P _co follow the output target power P _{cr of the} entire system.

When the system required power P _r is positive, i.e., when discharge is required, the output command value σ _Ni (ψ _Ni ) is set to 0 if the switching variable ψ _Ni is 0 or less. In other words, when the battery is over-output and the switching variable ψ _Ni becomes negative, the output command value σ _Ni (ψ _Ni ) is set to 0, thereby stopping discharge from the second battery 16. When the switching variable ψ _Ni is greater than 0 and less than a predetermined upper limit, the output command value σ _Ni (ψ _Ni ) is increased as the switching variable ψ _Ni increases. For example, the output command value σ _Ni (ψ _Ni ) is increased in proportion to the switching variable ψ _Ni . This makes it possible to obtain a discharge output of the second battery 16 that corresponds to the switching variable ψ _Ni . When the switching variable ψ _Ni is equal to or greater than the upper limit, the output command value σ _Ni (ψ _Ni ) is set to the upper limit. This makes it possible to avoid a continuation of insufficient battery output. The upper limit of the output command value σ _Ni (ψ _{Ni )} is preferably set to a value that can suppress deterioration of the _battery capacity, and is also preferably set to a value that can suppress circuit failure due to heat generation.

When the system required power P _r is negative, i.e., when charging is required, the output command value σ _Ni (ψ _Ni ) is set to 0 when the switching variable ψ _Ni is 0 or greater. That is, when the battery is overcharged and the switching variable ψ _Ni becomes positive, the output command value σ _Ni (ψ _Ni ) is set to 0, thereby stopping charging of the second battery 16. When the switching variable ψ _Ni is less than 0 and greater than a predetermined lower limit, the output command value σ _Ni (ψ _Ni ) is decreased as the switching variable ψ _Ni decreases. For example, the output command value σ _Ni (ψ _Ni ) is decreased in proportion to the decrease in the switching variable ψ _Ni . This allows the charging input to the second battery 16 to be obtained according to the switching variable ψ _Ni . When the switching variable ψ _Ni is equal to or less than the lower limit, the output command value σ _Ni (ψ _Ni ) is set to the lower limit. This makes it possible to prevent the battery from continuing to be overcharged. The lower limit of the output command value σ _Ni (ψ _Ni ) is preferably set to a value that can suppress deterioration of the battery capacity.

In step S42, the charge/discharge demand amount P _chrg is set. That is, as shown in FIG. 9 , the charge/discharge demand amount P _chrg is set so that the second battery 16, which has a low capacity, does not enter the high SOC region or the low SOC region where capacity degradation is likely to occur, but operates near the central SOC region. The central SOC region is preferably set to, for example, a range of 50% to 60% of the maximum SOC of the second battery 16. If the SOC of the second battery 16 is higher than the central region, the second battery 16 is forcibly discharged, and if the SOC is lower than the central region, the second battery 16 is forcibly charged.

In step S44, the second battery 16 is controlled in accordance with the output command value σ _Ni (ψ _Ni ) and the charge/discharge request amount P _chrg . That is, the output command value for the second battery 16 is obtained by adding the charge/discharge request amount P _chrg set in step S42 to the output command value σ _Ni (ψ _Ni ) set in step S40. When the system required power P _r is positive, that is, when discharge is requested, discharge from the second battery 16 is controlled in a range from 0 to an output power P _Ni-out obtained by adding the upper limit of the output command value σ _Ni (ψ _Ni ) and the charge/discharge request amount P _chrg . When the system required power P _r is negative, that is, when charge is requested, charge to the second battery 16 is controlled in a range from 0 to a charge power P _Ni-in obtained by adding the lower limit of the output command value σ _Ni (ψ _Ni ) and the charge/discharge request amount P _chrg . The current value of the second battery 16 for performing this charge/discharge control can be calculated using formulas (5) and (6). The change in SOC due to the charge/discharge of the second battery 16 is calculated using formula (7). The calculated SOC value is fed back to the processing of step S36.

In this embodiment, two second batteries 16 are provided, but the above processing can be performed for each of multiple second batteries 16.

<Example>
In this example, a simulation was performed on the control of the power system 100 when the system required power P r changes in a pattern in which a one-minute short-period component that changes in a power range of +30 kW to −30 kW is superimposed on a one-hour long-period component that changes in a power range of +17 _kW to −17 kW, as shown in FIG. 10 .

The power system 100 is configured with one lithium-ion (Li-ion) battery as the first battery 14 and two nickel-metal hydride (Ni-MH) batteries as the second batteries 16. The initial SOC of the lithium-ion (Li-ion) battery serving as the first battery 14 is set to 70%. The input limit of the nickel-metal hydride (Ni-MH) batteries serving as the second batteries 16 is set to -25 kW per battery, and the output limit is set to +25 kW per battery. The initial SOC of both batteries is set to 60%, and the center SOC of both batteries is set to 60%.

A Butterworth filter was used as a low-pass filter to extract the long-period components of the system required power P _r and the power differential value e. The filter characteristics of the Butterworth filter are expressed by Equation (10). The order n of the Butterworth filter was set to 5, and the cutoff frequency ω _c was set to 30ω ₀ (where ω ₀ is the fundamental frequency of the long-period component: ω ₀ = 2πf ₀ , f ₀ = 1/1 time = 1/3600 Hz).

11 and 12 show the results of a simulation in this example. As shown in region A in Fig. 11 , there are sections where the output target power P _cr and the supply power P _co differ, but control was performed so that the output target power P _cr and the supply power P _co matched over almost the entire range in which the simulation was performed. The reason for the difference between the output target power P _cr and the supply power P _co in region A is thought to be that, as shown in region B in Fig. 11 , a delay in control switching occurred in the time change of the long-period component P _rl of the system required power P _r after application of the low-pass filter, causing the lithium-ion (Li-ion) battery, which is the first battery 14, to be charged, to discharge.

Furthermore, as shown in Figure 12, the SOC of the lithium ion (Li-ion) battery, which is the first battery 14, changed in synchronization with the set long cycle of one hour, while the SOC of the nickel metal hydride (Ni-MH) battery, which is the second battery 16, changed in synchronization with the set short cycle of one minute. Furthermore, the range of change in the SOC of the nickel metal hydride (Ni-MH) battery, which is the second battery 16, was well within the range of 50% to 60%.

As described above, although a slight delay was observed in switching between discharging and charging of the long-period component, it is possible to make the supply power _Pco appropriately track the output target power _Pcr while taking advantage of the characteristics of the different types of batteries, the first battery 14 and the second battery 16.

In addition, it becomes possible to supply and charge power in a decentralized manner in each power system 100, taking advantage of the characteristics of different types of batteries, without relying on a centralized control system from a central server.

10 Power system, 12 Power conditioner system, 14 First battery, 16 (16a, 16b) Second battery, 100 Power system.

Claims (9)

1. A power system including a first battery and a second battery having a lower capacity and a higher output than the first battery, the power system controlling input/output power of the first battery and the second battery so as to reduce a difference between a system required power value and a total input/output power value of the first battery and the second battery,
controlling the input/output power of the first battery according to a relationship between an SOC of the first battery, a long-cycle component in the system required power value, and a long-cycle component in the difference value;
A power system comprising: a power system that controls input/output power of the second battery according to a relationship between an SOC of the second battery, the system required power value, and the difference value. 2. The power system of claim 1,
a power system configured to perform control such that, when the long-period component in the system required power value and the long-period component in the difference value indicate a discharge request time, the output power from the first battery increases as the SOC of the first battery increases. 3. The power system according to claim 1 or 2,
a power system, characterized in that, when the long-cycle component in the system required power value and the long-cycle component in the difference value indicate a time when charging is required, control is performed so that the input power to the first battery becomes smaller as the SOC of the first battery becomes larger. The power system according to any one of claims 1 to 3,
1. A power system comprising: a power supply system for supplying a power to and from the first battery in accordance with an SOC of the first battery; The power system according to any one of claims 1 to 4,
a power system configured to perform control such that, when the system required power value and the difference value indicate a discharge request time, the output power from the second battery increases as the SOC of the second battery increases. 3. The power system according to claim 1 or 2,
a power system, characterized in that, when the system required power value and the difference value indicate a time when charging is required, control is performed so that the input power to the second battery becomes smaller as the SOC of the second battery becomes higher. The power system according to any one of claims 1 to 6,
10. A power system comprising: a power supply system for supplying a power to and from the second battery in accordance with an SOC of the second battery; The power system according to any one of claims 1 to 7,
10. A power system comprising: a power supply that limits input and output of the second battery so that fluctuations in SOC of the second battery fall within a predetermined fluctuation range. The power system according to any one of claims 1 to 8,
A power system comprising a low-pass filter that extracts long-cycle components in the system required power value and long-cycle components in the difference value.