JP6184815B2 - Secondary battery system, control method thereof, and program - Google Patents

Description

  The present invention relates to a secondary battery system, and more specifically to a secondary battery system that performs charge / discharge control by a battery management device.

  Some secondary batteries have high energy density and can be operated at room temperature, and are used for applications such as electric buses. As a bus, a bus using an internal combustion engine is generally used and has a life of about 10 years. Similarly, the electric bus is expected to be used for the same number of years, but the lifetime of the secondary battery has not reached that level. Therefore, in view of the characteristics of the secondary battery, various methods for an operation method for extending the life of the secondary battery have been studied.

For example, it is known that secondary batteries gradually deteriorate with use.
Thus, for example, in a hybrid vehicle using an internal combustion engine and a secondary battery, there is a method of charging / discharging with a target value of SOC (State Of Charge / relative ratio of charge to total power capacity) set to a constant value, for example, 50%. Are known.
On the other hand, the total power capacity gradually decreases as the secondary battery deteriorates. As described above, if the SOC target value is always 50%, a deteriorated secondary battery has a lower total power capacity than a new secondary battery. Will not be able to demonstrate the same ability.
Thus, for example, Patent Document 1 discloses that in a vehicle battery for a hybrid vehicle, the target value of the SOC of the battery is increased in accordance with the progress of battery deterioration.

Japanese Patent No. 3915258

  However, in the invention disclosed in Patent Document 1, since the purpose is to compensate for a decrease in output due to battery deterioration, the SOC target value is set to an appropriate value from the battery deterioration state and temperature. However, there is a problem that it is unclear whether or not it can provide the necessary amount of charge.

  The present invention has been made in view of such circumstances, and provides an appropriate SOC target value according to the operation when the SOC target value is changed in accordance with the deterioration of the battery. Objective.

In order to solve the above problems, the secondary battery system, the control method thereof, and the program of the present invention employ the following means.
A battery pack including a plurality of battery cells connected in series and a battery management device that performs charge / discharge control of the battery cell, the battery management device including a total charge when the battery pack is fully charged at the time of measurement. Total power capacity calculating means for calculating power capacity, target charge amount calculating means for calculating the target charge amount of the assembled battery, total power capacity when the assembled battery is fully charged at the time of measurement, and the target of the assembled battery SOC target value setting means for setting the SOC target value of the battery pack based on the charge amount, the target charge amount is the sum of the minimum charge amount and the demand predicted charge amount, and the SOC of the minimum charge amount is , The sum of the SOC of the charge amount of limp home necessary to reach a place that can be maintained in the event of an emergency, and the SOC of charge amount considering the variation considering the difference in SOC between the battery cells, S of the battery pack C to adopt secondary battery system characterized by performing the charge and discharge control to reach the SOC target value.

According to the present invention, since the SOC target value is calculated on the basis of the total power capacity and the target charge amount at the time of full charge at the time of measurement, the battery pack can not directly measure the charge amount charged. Even if it exists, SOC with respect to this charge amount is detected, and charging / discharging is attained to a SOC target value. Further, the amount of charge can be managed indirectly using this SOC.
Furthermore, since the SOC target value is set based on the total power capacity at the time of full charge that changes according to the deterioration of the assembled battery, the assembled battery can be used in a low SOC range when the assembled battery is not deteriorated. When the assembled battery is deteriorated, a necessary charge amount can be secured. As a result, when the assembled battery is not deteriorated, the SOC can be kept low, so that the life of the secondary battery system can be extended.
Further, according to the present invention, since the SOC of the minimum charge amount is the sum of the SOC of the charge amount for the limp home and the SOC of the charge amount for consideration of variation, the charge amount immediately before charging is as small as possible. However, it is possible to take into account the amount of charge for limp home required to return to the starting point in the event of a failure, etc., and the amount of charge for each battery cell, that is, the variation in SOC. Therefore, it is possible to operate safely by taking into account the characteristics of the assembled battery.

  In the above invention, the target charge amount may be a sum of a minimum charge amount and a demand predicted charge amount.

  According to the present invention, since the target charge amount is calculated from the minimum charge amount and the demand predicted charge amount, the minimum charge amount necessary for the operation of the secondary battery system can be set as a target.

  In the above invention, the predicted demand charge amount may be a predicted charge amount when the charge amount is consumed and the next charge is necessary after the charge / discharge of the assembled battery to the SOC target value is completed.

  According to the present invention, since the demand predicted charge amount is a predicted value of the charge amount required from the start of charging and discharging to the next charge, the battery demand such as weather, temperature, day of the week, etc. Considering various conditions, it is possible to set the amount of charge for which the demand is predicted according to the conditions, and it can be applied to various operating conditions.

The present invention includes an assembled battery including a plurality of battery cells connected in series and a battery management device that performs charge / discharge control of the battery cell, and the battery management device satisfies the condition of the assembled battery at the time of measurement. A total power capacity calculating step for calculating a total power capacity at the time of charging; a target charging amount calculating step for calculating a target charging amount of the assembled battery; a total power capacity at the time of full charging of the assembled battery at the time of measurement; and An SOC target value setting step for setting an SOC target value of the assembled battery based on a target charge amount of the assembled battery, wherein the target charge amount is a sum of a minimum charge amount and a demand predicted charge amount; SOC of the amount of charge for limp home necessary to reach a place where maintenance is possible in the event of an emergency, and SOC of amount of charge for variation considering the difference in SOC between the battery cells total There is provided a control method for a secondary battery system that SOC of the battery pack, characterized in that the charging and discharging control to reach the SOC target value.

The present invention includes an assembled battery including a plurality of battery cells connected in series and a battery management device that performs charge / discharge control of the battery cell, and the battery management device satisfies the condition of the assembled battery at the time of measurement. A total power capacity calculation program for calculating a total power capacity at the time of charging, a target charge amount calculation program for calculating a target charge amount of the battery pack, a total power capacity at the time of full charge of the battery pack at the time of measurement, and the An SOC target value setting program for setting an SOC target value of the assembled battery based on a target charge amount of the assembled battery, the target charge amount being a sum of a minimum charge amount and a demand predicted charge amount, and the minimum charge The SOC of the amount of limp home required to reach a place where maintenance is possible in the event of an emergency, and the SOC of the amount of charge charged considering variation taking into account the difference in SOC between the battery cells The sum, provides a program for executing a process of SOC of the battery pack is charging and discharging control to reach the SOC target value in the computer.

  According to the present invention, since the SOC target value is set based on the target charge amount and the total power capacity at the time of full charge according to deterioration by the battery management device, an appropriate SOC target value corresponding to the operation is determined. There is an effect that can.

1 is a schematic configuration diagram illustrating a secondary battery system according to an embodiment of the present invention. It is the graph which showed the full charge amount of each new battery and a deterioration battery, and each SOC in the secondary battery system concerning one Embodiment of this invention. It is a schematic block diagram at the time of using the program of the secondary battery system concerning one Embodiment of this invention.

Hereinafter, an embodiment of a secondary battery system according to the present invention will be described with reference to the drawings.
Hereinafter, an embodiment of the present invention will be described with reference to FIG.
FIG. 1 shows a schematic configuration of the secondary battery system according to the present embodiment.
As shown in FIG. 1, the secondary battery system 1 includes an assembled battery 10, a load 20 such as a motor and an inverter, a charging outlet 30 that is a member connected to an external charger 50, an assembled battery 10 and a circuit. The circuit breaker 40 which connects with is provided as a main structure.
The assembled battery 10 includes a battery management device 11, a current sensor 13, a voltage detector 15, and a battery cell 17 inside. A voltage detector 15 is arranged for each battery cell 17 connected in series. A current sensor 13 is connected to one end of each battery cell 17 connected in series, and the current sensor 13 is connected to a circuit breaker 40.
The secondary battery system 1 is charged by connecting the charging outlet 30 to the charging plug 60 provided in the external charger 50.
The secondary battery system 1 is discharged by the load 20.
Each battery cell 17 constituting the assembled battery 10 is a secondary battery, such as a lithium ion battery, a lead battery, or a nickel metal hydride battery. Although not particularly limited, the lithium ion battery has a high output density and energy density. Is preferably used.

The battery management device 11 is connected to the current sensor 13, each voltage detector 15, the circuit breaker 40, and the charging outlet 30. When the charging outlet 30 is connected to the charging plug 60, the battery management device 11 is connected to the charger 50 through the charging outlet 30 and the charging plug 60.
When the battery management device 11 is connected to the charger 50, the battery management device 11 controls charging.
Further, the battery management device 11 performs ON / OFF control of the circuit breaker 40.
Further, the battery management device 11 acquires a current value from the current sensor 13 and a voltage value from the voltage detector 15. Accordingly, the battery management device 11 performs various controls related to the assembled battery 10 such as acquisition and calculation of various information related to the assembled battery 10 such as the SOC of the assembled battery 10, current protection, overcharge protection, and overdischarge protection. Is.
In addition, the battery management device 11 includes a total power capacity calculation unit 111, a target charge amount calculation unit 112, and an SOC target value setting unit 113.

In the battery pack 10 as shown in FIG. 1, the charge amount cannot be directly measured. In this application, it is assumed that the SOC, which is a relative ratio of the charge amount to the total power capacity, is detected with respect to the charge amount that constantly varies with time.
Moreover, while detecting SOC, the deterioration degree of the assembled battery 10 is detected. About the deterioration degree of the assembled battery 10, it can calculate from the change of the total electric power capacity at the time of a full charge. The total power capacity at the time of full charge is calculated by the total power capacity calculation means 111 from the SOC and the discharge amount corresponding to the SOC.

The voltage when the battery pack 10 is left unloaded is called OCV (Open Circuit Voltage), which is detected by the voltage detector 15. Since this OCV is proportional to the SOC of the assembled battery 10, the SOC of the assembled battery 10 can be determined by detecting the OCV. In the electric bus, when the assembled battery 10 is not used, that is, when it is stopped, the battery management device 11 can determine the SOC at the time of measurement by detecting the OCV when not in use. .
Further, when the assembled battery 10 is used, that is, while traveling on an electric bus, the total power capacity calculating means 111 calculates the total power capacity of the assembled battery 10 when fully charged from the SOC used during traveling and the amount of discharge during that time. can do. Further, since the total power capacity of the assembled battery 10 becomes smaller due to deterioration due to use, the battery management device 11 can estimate the degree of deterioration of the assembled battery 10 from the rate of decrease of the total power capacity.
In this way, by correcting each value when the assembled battery 10 is used / not used, the battery management device 11 determines the total power capacity of the assembled battery 10, the SOC at the time of measurement, and the degree of deterioration of the assembled battery 10. More accurate detection is possible.

As described above, the assembled battery 10 gradually deteriorates with use. Due to various factors, the degree of progress of the deterioration varies depending on the battery. In addition, charging and using the SOC to a high value each time, or a usage method in which the SOC greatly fluctuates can greatly affect the deterioration of the assembled battery 10 and cause the deterioration to proceed.
Therefore, in the present invention, it is considered to operate the SOC within a low value range by setting the SOC target value as the SOC for the minimum charge amount necessary for operation.

A method for calculating the SOC target value will be described below.
Assuming that the target charge amount is Wtarget [Wh], Wtarget is the minimum charge amount necessary for operation, so the demand predicted charge calculated based on the minimum charge amount (Wlowest [Wh]) and the predicted power consumption It is assumed that the target charge amount calculation unit 112 calculates the amount from the amount (Woperation [Wh]).
Therefore, assuming that the SOC target value is SOCtarget, SOCtarget is expressed by the following equation (1).
SOCtarget = (Wtarget / Wfull) × 100
= {(Wlowest + Woperation) / Wfull} × 100
= SOClowest + SOCoperation (1)
In equation (1), Wfull [Wh] is the total power capacity at full charge at the time of measurement, SOClowest is the SOC of the minimum charge amount, and SOCoperation is the SOC of the demand predicted charge amount. Details of each SOC will be described later.

First, the SOC with the minimum charge amount will be described.
In the secondary battery system 1, when the SOC is lowest, that is, the charge amount immediately before charging is set as the minimum charge amount, and the value of this SOC is set as the SOC of the minimum charge amount. This minimum charge amount is between the limp home charge amount, which is the amount of power necessary to reach a serviceable location such as the starting point, in the event of an emergency such as a failure, and between each battery cell 17 in the assembled battery 10. It can be the sum of the amount of charge for variation considering the difference in SOC.

If a failure occurs, the amount of charge required to return to the starting point, for example, an electric bus, to the garage that is the starting point is constant regardless of the SOC if the usage conditions of the assembled battery 10 are the same. .
When the limp home charge amount is Wlimp [Wh], the corresponding SOC and limp home charge amount SOC are expressed by the following equation (2).
SOClimp = (Wlimp / Wfull) × 100 (2)
As expressed by the equation (2), SOClimp can be said to have a larger proportion of the charge amount of the limp home in the total power capacity, that is, SOClimp, because Wfull as the denominator decreases as the deterioration of the assembled battery 10 progresses.

Moreover, even if the battery cell 17 is a new article, it turns out that the voltage has dispersion | variation. For example, when there is a variation in the voltage of each battery cell 17 in series, the battery cell 17 having a higher voltage than the average is overcharged during charging, or the battery cell 17 having a lower voltage than the average is overdischarged during discharging. there is a possibility. In the battery management device 11, in order to prevent the variation in SOC in the battery cells 17 connected in series from expanding, the battery cell 17 having a high voltage is discharged, and control is performed to keep the variation in SOC below a certain level. Yes. The SOC variation limit of each battery cell 17 is defined as SOC dispersion. If the charge amount in this case is Wdispersion [Wh], the SOCdispersion is expressed by the following equation (3).
SOCdispersion = (Wdispersion / Wfull) × 100 (3)

From the SOClimp and SOCdispersion obtained as described above, SOClowest which is the lowest SOC is calculated. This calculation formula is expressed by the following formula (4).
SOClowest = SOClimp + SOCdispersion (4)

Next, the demand prediction SOC will be described.
In the case of the assembled battery 10 mounted on the electric bus, the SOC required for operation varies depending on various conditions.
For example, the difference between the highest SOC value and the lowest SOC value in the daily operation is represented as SOCday, assuming that it is the fluctuation amount of the daily SOC. Further, the fluctuation amount of the charge amount at this time is Wday [Wh].
The amount of fluctuation Wday required for daily operation varies from day to day due to fluctuations in the amount of power used by auxiliary equipment such as air conditioners due to seasonal changes, and fluctuations in demand due to the day of the week, so set a constant value. There is a problem. Therefore, a predicted value of the fluctuation amount of the charging amount necessary for the operation is set as Woperation [Wh], and a method for estimating this will be described below.

As mentioned above, Wday fluctuates from day to day. Therefore, Waverage [Wh] is obtained by taking an average value with the time constant Tf [day] in days. The average power Waverage is expressed by the following equation (5).
Waverage = {(Waverage ⁻¹ −Wday) / Tf} + Waverage ⁻¹ (5)
It can be considered that this Waverage is Woperation.

  When the average power Waverage is used as the predicted value Woperation, it is considered that the actually measured value is not greatly deviated from the predicted value Woperation. However, on the day when the temperature exceeds the average value or the day when the number of passengers exceeds the average value, the demand prediction SOC is not sufficient, and the SOC of the assembled battery 10 is below the set minimum SOC. That is, if an emergency occurs in this case, limp home may not be performed. Moreover, since the average is taken, theoretically, the predicted value will be off with about half the probability.

As described above, as a method for estimating the predicted value of the fluctuation amount of the charging amount necessary for the operation that does not fall below the minimum SOC, a method using the peak value of the fluctuation amount of the charging amount necessary for the daily operation as the predicted value is available. Conceivable.
In this method, the Wday peak value Wdaymax [Wh] is updated with the largest Wday in the operation results. Since this Wdaymax is the largest Wday in the past achievements, by setting this as Woperation, even if it is a day when the load on the assembled battery 10 is large, the demand is kept so as not to fall below the preset minimum SOC. It is considered possible to set the predicted SOC.
However, since the maximum power consumption through the operation results is the standard, for example, this demand prediction SOC is predicted to be excessive in the season when the power consumption of auxiliary machinery power is small or when there are few passengers. The

As described above, Waverage cannot cope with the case where the load on the secondary battery is larger than the average, that is, the demand prediction SOC is insufficient. On the other hand, surplus is likely to occur in demand forecast SOC in Wdaymax.
Accordingly, the amount of deviation from the average of the fluctuation amount of the charge amount necessary for the daily operation is defined as Westrangement [Wh]. Westrangement is expressed by the following equation (6).
Westrangement = | Wday-Waverage | (6)
Using this, Woperation is expressed by the following equation (7).
Woperation = Waverage + Westrangement (7)
Thereby, it is considered that a predicted value with further allowance can be set on the basis of the average power.

From the predicted value Woperation of the fluctuation amount of the charge required for the operation calculated by the equation (7), the predicted value SOCoperation of the SOC amplitude necessary for the operation is expressed by the following equation (8).
SOCoperation = (Woperation / Wfull) × 100 (8)

The SOC target that is the SOC target value of the assembled battery 10 is obtained from the sum of the SOClowest calculated by the equation (4) and the SOCoperation calculated by the equation (8) as in the equation (1). Then, by charging / discharging the SOC target set by the SOC target value setting means 113 as the SOC target value of the assembled battery 10, only the minimum SOC range necessary for operation is used according to the deterioration of the assembled battery 10 Operation is possible.
As shown in FIG. 2, in the case of a new battery and a deteriorated deteriorated battery, for example, when the target charge amount does not change, the SOC target value in the deteriorated battery is higher than the SOC target value in the new battery. . This is because the full charge amount decreases due to deterioration, that is, the SOC denominator decreases.
Therefore, in the case of a new battery or a battery in a state close thereto, operation in a low SOC range is possible. In addition, even if it is deteriorated, the necessary minimum target charge amount is secured, so that it can exhibit the same performance as a new battery until a certain degree of deterioration, and the same operation as when new is continued Is possible.

As described above, according to the secondary battery system, the control method, and the program according to the present embodiment, the battery management device 11 detects the OCV to determine the SOC, and the total power capacity calculation unit 111 The total power capacity at the time of full charge at the time of measurement of the assembled battery 10 is calculated from the SOC at the time of use and the amount of discharge between them. The SOC target value is calculated by the battery management device 11 based on the total power capacity and the target charge amount. As a result, even in the battery pack 10 in which the charged amount that is charged cannot be directly measured, the SOC with respect to this charged amount can be detected, and charging and discharging can be performed up to the SOC target value. Further, the amount of charge can be managed indirectly using this SOC.
Furthermore, since the SOC target value is set based on the total power capacity at the time of full charge that changes in accordance with the deterioration of the assembled battery 10, when the assembled battery 10 is not deteriorated, the assembled battery 10 is kept in a low SOC range. Available. Therefore, the progress of deterioration can be minimized. At the same time, when the assembled battery 10 is deteriorated, a necessary amount of charge can be secured, and the same operation as when new can be continued. Thereby, when the assembled battery 10 is not deteriorated, the SOC can be kept low, so that the life of the secondary battery system 1 can be extended.

  The target charge amount is the minimum charge amount required for operation. Therefore, the battery management device 11 calculates the target charge amount from the minimum charge amount that is the charge amount immediately before the charge with the lowest SOC and the demand predicted charge amount that is calculated based on the predicted power consumption. It was. Thereby, the minimum charge amount necessary for the operation of the secondary battery system 1 can be set as a target.

  Considering variation in consideration of variation in limp home charge, which is the amount of power required to reach a location where maintenance is possible in the event of an emergency, and SOC of each battery cell in battery pack 10 The total charge amount is assumed to be the total charge amount. Therefore, even when the amount of charge immediately before charging is as small as possible, the amount of charge required to reach a serviceable place such as the starting point and the charge for each battery cell 17 when a failure or the like occurs The amount, that is, the variation of the SOC can be taken into consideration, and a safe operation is possible by giving a minimum margin in preparation for an emergency and considering the characteristics of the assembled battery 10.

  In addition, the predicted value of the fluctuation amount of the charging amount necessary for the operation is set as the demand predicted charging amount, and the charging amount with further allowance is set based on the average power. That is, the estimated value of the amount of charge required from the start of charge / discharge to the next charge is set. Accordingly, it is possible to set a charge amount for which the demand is predicted according to the conditions such as the weather, temperature, day of the week, and the like, and it is applicable to various operating conditions.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

For example, in the secondary battery system 1 according to the above-described embodiment, as illustrated in FIG. 3, all or part of the above-described processing may be separately processed using software. In this case, since the secondary battery system 1 performs processing using a program, the CPU 81, a main storage device 82 such as a RAM, an auxiliary storage device 83, an input device 84 such as a keyboard and a mouse, and an output device 85 such as a display and a printer. And a communication device 86 for exchanging information by communicating with external devices.
The auxiliary storage device 83 stores a CPU 81, a main storage device 82 such as a RAM, and a computer-readable recording medium on which a program for realizing all or part of the above processing is recorded. Various processes are realized by reading and executing a program from the storage device 83 to the main storage device 82.
Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

DESCRIPTION OF SYMBOLS 1 Secondary battery system 10 Assembly battery 11 Battery management apparatus 13 Current sensor 15 Voltage detector 17 Battery cell 20 Load 30 Charging outlet 40 Breaker 50 Charger 60 Charge plug 81 CPU
82 Main storage device 83 Auxiliary storage device 84 Input device 85 Output device 86 Communication device 111 Total power capacity calculation means 112 Target charge amount calculation means 113 SOC target value setting means

Claims (5)

A plurality of battery cells connected in series;
A battery management device that performs charge / discharge control of the battery cell,
The battery management device includes: a total power capacity calculating unit that calculates a total power capacity when fully charged at the measurement time of the assembled battery; a target charge amount calculating unit that calculates a target charge amount of the assembled battery; and the measurement time point SOC target value setting means for setting the SOC target value of the assembled battery based on the total power capacity at the time of full charge of the assembled battery and the target charge amount of the assembled battery,
The target charge amount is the sum of the minimum charge amount and the demand prediction charge amount,
The SOC of the minimum charge amount is the charge amount for variation considering the difference between the SOC of the limp home charge amount required to reach a location where maintenance is possible in the event of an emergency and the SOC between the battery cells. Total with SOC,
Charge / discharge control is performed until the SOC of the assembled battery reaches the SOC target value.   The secondary battery system according to claim 1, wherein the target charge amount is a sum of a minimum charge amount and a demand predicted charge amount. The forecast amount of charge, after the charge-discharge completion to the SOC target value of the battery pack, according to claim 1 or 2 is the predicted amount of charge is when consumed charge amount required next charge Secondary battery system. A plurality of battery cells connected in series;
A battery management device that performs charge / discharge control of the battery cell,
The battery management device includes: a total power capacity calculating step for calculating a total power capacity when the assembled battery is fully charged at a measurement time; a target charge amount calculating step for calculating a target charge amount for the assembled battery; and the measurement time point A SOC target value setting step of setting an SOC target value of the assembled battery based on a total power capacity when the assembled battery is fully charged and a target charge amount of the assembled battery,
The target charge amount is the sum of the minimum charge amount and the demand prediction charge amount,
The SOC of the minimum charge amount is the charge amount for variation considering the difference between the SOC of the limp home charge amount required to reach a location where maintenance is possible in the event of an emergency and the SOC between the battery cells. Total with SOC,
A control method for a secondary battery system, wherein charge / discharge control is performed until the SOC of the assembled battery reaches the SOC target value. A plurality of battery cells connected in series;
A battery management device that performs charge / discharge control of the battery cell,
The battery management device includes a total power capacity calculation program for calculating a total power capacity when the assembled battery is fully charged at a measurement time, a target charge amount calculation program for calculating a target charge amount of the assembled battery, and the measurement time point. An SOC target value setting program for setting an SOC target value of the assembled battery based on a total power capacity when the assembled battery is fully charged and a target charge amount of the assembled battery,
The target charge amount is the sum of the minimum charge amount and the demand prediction charge amount,
The SOC of the minimum charge amount is the charge amount for variation considering the difference between the SOC of the limp home charge amount required to reach a location where maintenance is possible in the event of an emergency and the SOC between the battery cells. Total with SOC,
The program for making a computer perform the process which performs charging / discharging control until SOC of the said assembled battery reaches the said SOC target value.

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