JP6794947B2 - Rechargeable battery system - Google Patents

Description

The present disclosure relates to a secondary battery system, and more specifically, to charge / discharge control of a secondary battery in the secondary battery system.

In recent years, hybrid vehicles, electric vehicles, and the like, which are vehicles equipped with a secondary battery system, have become widespread. In the secondary battery system mounted on these vehicles, generally, the upper limit (SOC upper limit) and the lower limit (SOC lower limit) of the use area of the SOC (State Of Charge) of the secondary battery are predetermined. When the SOC of the secondary battery exceeds the SOC upper limit, overcharging of the secondary battery is prevented by suppressing further charging of the secondary battery. Further, when the SOC of the secondary battery falls below the SOC lower limit, over-discharging of the secondary battery is prevented by suppressing further discharge of the secondary battery.

In a secondary battery system in which such charge / discharge control is executed, the performance of the secondary battery is fully utilized, thereby improving the fuel efficiency of a hybrid vehicle or the mileage of an electric vehicle (EV mileage). It is required to estimate the SOC of the secondary battery with high accuracy in order to extend the battery. Since a certain amount of error is inevitably generated in the SOC estimation, it is conceivable to charge and discharge the secondary battery in consideration of the SOC estimation error. For example, according to Japanese Patent Application Laid-Open No. 2013-182779 (Patent Document 1), a secondary battery should be used in an SOC region of 0% to 100% in consideration of a margin corresponding to an estimation error of SOC. Examples of using a secondary battery in a SOC region of 20% to 80% have been described (see, for example, paragraph [0005] of Patent Document 1).

Japanese Unexamined Patent Publication No. 2013-182779

As an SOC estimation method, there is a method of estimating SOC from OCV based on information indicating the correspondence between OCV (Open Circuit Voltage) of a secondary battery and SOC (hereinafter, also referred to as “OCV-SOC curve”). It is known. On the other hand, Patent Document 1 discloses a method of estimating "pseudo SOC" by using CCV (Closed Circuit Voltage) of a secondary battery instead of OCV of the secondary battery.

According to Patent Document 1, the pseudo SOC of the secondary battery is the amount of the SOC corresponding to the voltage difference ΔV between the CCV and the OCV as compared with the SOC estimated from the OCV of the secondary battery. The value becomes low when the battery is discharged, and becomes high when the secondary battery is charged. That is, the pseudo SOC is a value on the safe side (a value closer to the SOC upper limit or the SOC lower limit) than the SOC estimated from the OCV. Therefore, when controlling the charging / discharging of the secondary battery based on the pseudo SOC, the SOC region to be used is set to the SOC region originally desired to be used (0% to 100% region in the above example). Will be possible. Therefore, it is not necessary to set an excessive margin (20% margin each in the above example), so that the secondary battery can be used more effectively (for example, paragraphs [0017] to [0019] of Patent Document 1). reference).

However, the voltage difference ΔV between CCV and OCV corresponds to the product of the charge / discharge current of the secondary battery and the internal resistance. Therefore, when the voltage difference ΔV is relatively large (more specifically, in the case of charging / discharging at a large current, or in the case of charging / discharging in a secondary battery whose internal resistance has increased due to deterioration), a pseudo SOC Is likely to reach the SOC upper limit or SOC lower limit. Then, charging / discharging of the secondary battery is suppressed, and there is a possibility that the secondary battery cannot be effectively used.

The present disclosure has been made to solve the above problems, and an object of the present invention is to provide a technique capable of effectively utilizing a secondary battery while appropriately protecting the secondary battery in a secondary battery system. That is.

A secondary battery system according to an aspect of the present disclosure comprises a secondary battery, a power converter that converts the power of the secondary battery, and power so that the secondary battery is charged and discharged between the upper limit SOC and the lower limit SOC. It includes a control device that controls the conversion device. The control device acquires the OCV of the secondary battery, calculates the "reference SOC" corresponding to the OCV by referring to the predetermined correspondence between the OCV and the SOC (OCV-SOC curve), and calculates the "reference SOC" corresponding to the OCV from the reference SOC. When the "first charge amount", which is the amount of charge input to the secondary battery when the secondary battery is charged to the upper limit SOC, is calculated, and when the secondary battery is discharged from the reference SOC to the lower limit SOC. The "second charge amount", which is the charge amount output from the secondary battery, is calculated. The control device integrated the amount of electric charge input to and from the secondary battery as the secondary battery was charged and discharged from the time when the OCV of the secondary battery was acquired, and the integrated amount of charge exceeded the amount of the first charge. In this case, the charging of the secondary battery is suppressed, and when the accumulated charge amount is less than the second charge amount, the discharge of the secondary battery is suppressed.

According to the above configuration, the OCV of the secondary battery is first acquired. Then, the first and second charge amounts are calculated based on the reference SOC corresponding to the acquired OCV. By suppressing the charging and discharging of the secondary battery based on the first and second charge amounts, the secondary battery can be appropriately protected.

Further, when the secondary battery is charged and discharged after the OCV of the secondary battery is acquired, the amount of charge input / output to the secondary battery is calculated by current integration, and the integrated charge amount is the first charge amount or the second charge amount. It is determined whether or not the amount of electric charge has been reached. An error can occur in the current integration. However, since the error of the current integration can be reset at the timing of acquiring the OCV of the secondary battery, it is possible to perform the current integration with high accuracy. Therefore, it is not necessary to set an excessive margin for the upper limit SOC and the lower limit SOC in consideration of the SOC estimation error. Further, even when charging / discharging is performed with a large current or when the internal resistance is increased, an error based on the voltage difference between CCV and OCV does not occur. Therefore, a sufficient usable SOC area can be secured, and the secondary battery can be effectively used.

According to the present disclosure, in a secondary battery system, the secondary battery can be effectively utilized while appropriately protecting the secondary battery.

It is a figure which shows schematic the whole structure of the vehicle which mounted the secondary battery system which concerns on this Embodiment. It is a figure which shows an example of the relationship between the temperature of a secondary battery and the deterioration rate. It is a figure which shows an example of the relationship between the deterioration amount of a secondary battery, and the OCV-SOC curve. It is a figure for demonstrating charge / discharge suppression control of a secondary battery. It is a figure which shows the flowchart which shows the charge amount calculation process in this embodiment. It is a figure for demonstrating the calculation method of the input charge amount and output charge amount. It is a figure which shows the flowchart for demonstrating charge / discharge suppression control in this embodiment.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals, and the description thereof will not be repeated.

In the present embodiment, a configuration in which the "secondary battery system" according to the present disclosure is mounted on a vehicle will be described as an example. However, the application of the secondary battery system according to the present disclosure is not limited to the vehicle, and may be, for example, stationary.

[Embodiment]
<Vehicle configuration>
FIG. 1 is a diagram schematically showing an overall configuration of a vehicle equipped with a secondary battery system according to the present embodiment. Hereinafter, the case where the vehicle 1 is a hybrid vehicle will be typically described, but the secondary battery system according to the present disclosure can be mounted not only on the hybrid vehicle but also on all vehicles in which the secondary battery is used for traveling. is there.

With reference to FIG. 1, the vehicle 1 includes a secondary battery system 2, motor generators 210 and 220, an engine 230, a power splitting device 240, a drive shaft 250, and drive wheels 260. The secondary battery system 2 includes a secondary battery 10, a monitoring unit 20, a power control unit (PCU: Power Control Unit) 30, and an electronic control unit (ECU: Electronic Control Unit) 100.

The secondary battery 10 is an assembled battery including a plurality of cells. Each cell is a secondary battery such as a lithium ion secondary battery or a nickel hydrogen battery, but the type of the secondary battery is not particularly limited. The secondary battery 10 stores electric power for driving the motor generators 210 and 220, and supplies electric power to the motor generators 210 and 220 through the PCU 30. Further, the secondary battery 10 is charged by receiving the generated power through the PCU 30 when the motor generators 210 and 220 generate power.

The monitoring unit 20 includes a voltage sensor 21, a current sensor 22, and a temperature sensor 23. The voltage sensor 21 detects the voltage VB of each cell contained in the secondary battery 10. The current sensor 22 detects the current IB input / output to / from the secondary battery 10. The temperature sensor 23 detects the temperature TB for each cell. The detection unit by the voltage sensor 21 and the temperature sensor 23 is not limited to the cell, and may be a block (module) composed of a plurality of cells. In the present disclosure, the number of cells contained in the secondary battery 10 is not particularly limited. Therefore, the cells or blocks are not particularly distinguished below, and the term “secondary battery 10” is comprehensively described below.

The PCU 30 executes bidirectional power conversion between the secondary battery 10 and the motor generators 210 and 220 according to the control signal from the ECU 100. The PCU 30 is configured so that the states of the motor generators 210 and 220 can be controlled separately. For example, the motor generator 220 can be put into a power running state while the motor generator 210 is in a regenerative state (power generation state). The PCU 30 includes, for example, two inverters provided corresponding to the motor generators 210 and 220, and a converter (neither shown) that boosts the DC voltage supplied to each inverter to a voltage higher than the output voltage of the secondary battery 10. Consists of including. The PCU 30 corresponds to the "power conversion device" according to the present disclosure.

Each of the motor generators 210 and 220 is an AC rotating electric machine, for example, a three-phase AC synchronous motor in which a permanent magnet is embedded in a rotor. The motor generator 210 is mainly used as a generator driven by the engine 230 via the power splitting device 240. The electric power generated by the motor generator 210 is supplied to the motor generator 220 or the secondary battery 10 via the PCU 30. The motor generator 220 mainly operates as an electric motor and drives the drive wheels 260. The motor generator 220 is driven by receiving at least one of the electric power from the secondary battery 10 and the electric power generated by the motor generator 210, and the driving force of the motor generator 220 is transmitted to the drive shaft 250. On the other hand, when the vehicle is braking or the acceleration is reduced on a downward slope, the motor generator 220 operates as a generator to generate regenerative power generation. The electric power generated by the motor generator 220 is supplied to the secondary battery 10 via the PCU 30.

The engine 230 is an internal combustion engine that outputs power by converting the combustion energy generated when the air-fuel mixture is burned into the kinetic energy of movers such as pistons and rotors.

The power splitting device 240 includes, for example, a planetary gear mechanism (not shown) having three rotating shafts of a sun gear, a carrier, and a ring gear. The power dividing device 240 divides the power output from the engine 230 into a power for driving the motor generator 210 and a power for driving the drive wheels 260.

The ECU 100 includes a CPU (Central Processing Unit) 101, a memory 102, and input / output ports (none of which are shown) for inputting / outputting various signals. The ECU 100 controls the engine 230 and the PCU 30 so that desired charging and discharging are performed based on the signal received from each sensor and the program and the map stored in the memory 102. Further, as a main control of the ECU 100 in the present embodiment, there is a "charge / discharge suppression control" that suppresses the charge / discharge of the secondary battery 10 according to the SOC of the secondary battery 10. The charge / discharge suppression control will be described in detail later.

<Amount of deterioration of secondary battery>
The secondary battery 10 may deteriorate with the repetition of charging and discharging or the passage of time, and the internal resistance of the secondary battery 10 may increase. Therefore, in the present embodiment, the deterioration amount D for quantitatively evaluating the progress of deterioration of the secondary battery 10 is calculated. The deterioration rate β, which is the rate of increase in the internal resistance of the secondary battery 10, is used to calculate the deterioration amount D.

FIG. 2 is a diagram showing an example of the relationship between the temperature TB of the secondary battery 10 and the deterioration rate β of the secondary battery 10. In FIG. 2, the horizontal axis represents the reciprocal of the temperature TB of the secondary battery 10. The vertical axis shows the natural logarithmic value of the deterioration rate β of the secondary battery 10.

As shown in FIG. 2, the temperature dependence of the deterioration rate β according to the Arrhenius side is understood. The relationship between the temperature TB of the secondary battery 10 and the deterioration rate β is obtained in advance by an experiment or the like, and is stored in the memory 102 of the ECU 100 as, for example, a map (not shown). Then, the deterioration rate β of the secondary battery 10 is calculated based on the temperature TB of the secondary battery 10 detected by the temperature sensor 23. By integrating the deterioration rate β (that is, the amount of increase in internal resistance per unit time), the amount of deterioration D (amount of increase in internal resistance) of the secondary battery 10 is calculated.

<OCV-SOC curve>
In the SOC estimation of the secondary battery, a method of estimating the SOC from the OCV by referring to the OCV-SOC curve acquired in advance by an experiment or the like is known. The OCV-SOC curve of the secondary battery 10 can change according to the deterioration amount D of the secondary battery 10. Therefore, in the present embodiment, the OCV-SOC curve to be referred to is selected based on the deterioration amount D of the secondary battery 10.

FIG. 3 is a diagram showing an example of the relationship between the deterioration amount D of the secondary battery 10 and the OCV-SOC curve. In FIG. 3 and FIGS. 4 and 6 described later, the horizontal axis represents the SOC of the secondary battery 10 and the vertical axis represents the OCV of the secondary battery 10.

As shown in FIG. 3, the OCV-SOC curve can change as the deterioration amount D of the secondary battery 10 increases. Therefore, for example, in an experiment in advance, a plurality of secondary batteries having different deterioration amounts D are prepared, and an OCV-SOC curve is acquired for each secondary battery. Then, the acquired plurality of OCV-SOC curves are stored in the memory 102 of the ECU 100 (two curves are shown in FIG. 3). By doing so, in the present embodiment, the OCV-SOC curve to be referred to when estimating the SOC of the secondary battery 10 can be selected according to the deterioration amount D.

<Charging / discharging suppression control>
FIG. 4 is a diagram for explaining charge / discharge suppression control of the secondary battery 10. In FIG. 4, for example, one of the two OCV-SOC curves shown in FIG. 3 is exemplified.

With reference to FIG. 4, the SOC of the secondary battery 10 is defined as an SOC upper limit UL indicating an upper limit value of the SOC used area and an SOC lower limit LL indicating the lower limit value of the SOC used area. When the SOC of the secondary battery 10 is higher than the SOC upper limit UL, charging of the secondary battery 10 is suppressed (for example, prohibited) as compared with the case where the SOC of the secondary battery 10 is equal to or lower than the SOC upper limit UL. On the other hand, when the SOC of the secondary battery 10 is less than the SOC lower limit LL, the discharge of the secondary battery 10 is suppressed (for example, prohibited) as compared with the case where the SOC of the secondary battery 10 is the SOC lower limit LL or more.

It is also conceivable to execute such charge / discharge suppression control based on the estimation result of SOC. However, in the method of estimating SOC from OCV based on the OCV-SOC curve, a certain amount of SOC estimation error inevitably occurs. Therefore, in order to properly protect the secondary battery, it is required to set a margin in consideration of the SOC estimation error when determining the SOC upper limit UL and the SOC lower limit LL. That is, it is required to set the SOC upper limit UL lower than the originally desired value by a margin, while setting the SOC lower limit LL higher than the originally desired value. The usable SOC area is narrowed by the amount of this margin.

On the other hand, as an SOC estimation method, a method based on current integration (current integration method) is also known. However, in the current integration method, the detection error of the current sensor is accumulated as time elapses, and as a result, the SOC estimation error may increase.

It is also conceivable to use a pseudo SOC based on CCV as in Patent Document 1. However, in this method, a voltage difference ΔV (= CCV-OCV) between CCV and OCV occurs. Since this voltage difference ΔV depends on the current IB of the secondary battery 10, for example, in the case of charging / discharging with a large current (or when the internal resistance increases due to deterioration of the secondary battery 10), a pseudo SOC Is likely to reach the SOC upper limit or SOC lower limit. Then, the charging / discharging of the secondary battery 10 may be excessively suppressed.

Therefore, in the present embodiment, the SOC estimation accuracy is improved by combining the SOC estimation using the OCV-SOC curve and the current integration (charge amount integration) using the current sensor, thereby satisfying the cost estimation accuracy. Adopt a configuration that appropriately executes discharge suppression control. Hereinafter, the "charge amount calculation process" for calculating the amount of charge that can be input to and received from the secondary battery 10 by combining the SOC estimation using the OCV-SOC curve and the integration of the charge amount will be described in detail.

<Processing flow of charge amount calculation processing>
FIG. 5 is a diagram showing a flowchart showing a charge amount calculation process according to the present embodiment. This flowchart shows the main routine (not shown) every time a predetermined condition is satisfied (for example, when the vehicle 1 is ignited on (IG-ON) or when the vehicle 1 is parked / stopped at a traffic light or the like). Called from, and executed by the ECU 100. Further, each step (hereinafter abbreviated as "S") included in the flowcharts shown in FIGS. 5 and 7 described later is basically realized by software processing by the ECU 100, but the dedicated hardware manufactured in the ECU 100 is used. It may be realized by hardware (electric circuit).

With reference to FIGS. 1 and 5, in S110, the ECU 100 acquires the temperature TB of the secondary battery 10 from the temperature sensor 23. Further, the ECU 100 calculates the deterioration rate β of the secondary battery 10 based on the temperature TB acquired in S110 (S120). Since the method of calculating the deterioration rate β based on the temperature TB has been described in FIG. 2, the detailed description will not be repeated.

In S130, the ECU 100 calculates the deterioration amount D of the secondary battery 10 based on the temperature TB of the secondary battery 10 and the deterioration rate β. More specifically, the deterioration rate β is integrated, and the deterioration amount ΔD of the secondary battery 10 is calculated from the integrated value. Since the deterioration rate β is the internal resistance increase rate as described above, the integrated value of the deterioration rate β indicates the amount of increase in the internal resistance of the secondary battery 10. Therefore, the current deterioration amount D can be calculated by sequentially adding the deterioration amount ΔD from the internal resistance value of the secondary battery 10 in the initial state.

In S140, the ECU 100 selects the OCV-SOC curve corresponding to the deterioration amount D calculated in S130 from the plurality of OCV-SOC curves stored in the memory 102 in advance (see FIG. 4).

In S150, the ECU 100 receives the voltage VB of the secondary battery 10 from the voltage sensor 21 during the period when the secondary battery 10 is not charged / discharged (in other words, during the period when the secondary battery 10 is in the no-load state). By acquiring, the OCV of the secondary battery 10 is acquired. In the following, this OCV will be referred to as a reference OCVref. The period during which the secondary battery 10 is in the no-load state may be, for example, the period immediately after the vehicle 1 is IG-ONed (the period until the vehicle 1 starts traveling), or the vehicle 1 signals. It may be a period when the vehicle is parked or stopped due to waiting or the like.

In S160, the ECU 100 calculates the reference SOCref, which is the SOC corresponding to the reference OCVref acquired in S150, by referring to the OCV-SOC curve selected in S140.

In S170, the ECU 100 is "inputtable" which is the amount of charge to be input to the secondary battery 10 when the secondary battery 10 is charged from the reference SOCref to the SOC upper limit UL based on the reference SOCref calculated in S160. "Amount of charge" Qin is calculated. Further, the ECU 100 calculates the “outputtable charge amount” Qout, which is the amount of charge output from the secondary battery 10 when the secondary battery 10 is discharged from the reference SOCRef to the SOC lower limit LL (S180). The inputtable charge amount Qin corresponds to the "first charge amount" according to the present disclosure, and the output chargeable charge amount Qout corresponds to the "second charge amount".

FIG. 6 is a diagram for explaining a method for calculating the input charge amount Qin and the output charge amount Qout. With reference to FIG. 6, the full charge capacity FCC of the secondary battery 10 is known from, for example, the specification value (catalog value) of the secondary battery 10. Therefore, the amount of electric charge stored in the secondary battery 10 at the time of processing S160 and S170 (that is, the amount of electric charge corresponding to the reference SOCref) can be calculated by Qref = FCC × SOCRef.

The full charge capacity FCC may decrease as the deterioration amount D of the secondary battery 10 increases. Therefore, by obtaining the correspondence relationship between the full charge capacity FCC and the deterioration amount D in advance, the full charge capacity FCC corresponding to the deterioration amount D calculated in S130 may be used for calculating the charge amount Qref.

Further, the charge amount QL corresponding to the SOC upper limit UL can be calculated from the relational expression of QUAL = FCC × UL. Therefore, the inputtable charge amount Qin (first charge amount) is calculated by the difference between the charge amount QL corresponding to the SOC upper limit UL and the charge amount Qref corresponding to the reference SOCRef, as shown in the following formula (1). can do.
Qin = QL-Qref ... (1)

Similarly, the charge amount QLL corresponding to the SOC lower limit LL can be calculated from the relational expression of QLL = FCC × LL. Therefore, the outputable charge amount Qout can be calculated by the difference between the charge amount Qref corresponding to the reference SOCRef and the charge amount QLL corresponding to the SOC lower limit LL, as shown in the following equation (2).
Qout = Qref-QLL ... (2)

The correspondence between the charge amount Qref, the inputtable charge amount Qin, and the output charge amount Qout may be obtained in advance and stored in the memory 102 of the ECU 100 as a map (not shown), for example. By referring to this map, the input charge amount Qin and the output charge amount Qout can be directly calculated from the charge amount Qref.

<Control flow of charge / discharge suppression control>
FIG. 7 is a diagram showing a flowchart for explaining charge / discharge suppression control in the present embodiment. This flowchart shows the main routine every time a predetermined calculation cycle elapses after the reference SOCref is calculated by the charge amount calculation process (see FIG. 5) and the inputtable charge amount Qin and the output chargeable charge amount Qout are calculated. Called from, and executed by the ECU 100.

With reference to FIGS. 1 and 7, in S210, the ECU 100 is an integrated value of the amount of charge ΔAhc input to the secondary battery 10 based on the detected value of the current IB acquired by the current sensor 22. = ΣΔAhc) is calculated. That is, the ECU 100 calculates the total amount of input charges to the secondary battery 10. Similarly, in S220, the ECU 100 calculates Ahd (= ΣΔAhd), which is an integrated value of the charge amount ΔAhd output from the secondary battery 10, based on the detected value of the current IB acquired by the current sensor 22. That is, the ECU 100 calculates the total amount of output charges from the secondary battery 10.

The charge amounts ΔAhc and ΔAhd can be integrated from, for example, the calculation of the reference SOCref (the processing of S160). The order of the processes of S210 and S220 may be changed, or these processes may be executed in parallel.

In S230, the ECU 100 calculates the charge amount difference (Ahc-Ahd), which is the difference between the integrated value Ahc of the input charge amount to the secondary battery 10 and the integrated value Ahd of the output charge amount from the secondary battery 10. (See FIG. 6). This difference in the amount of charge is the difference between the total amount of charge charged to the secondary battery 10 and the total amount of discharge charge from the secondary battery 10, and is the amount of charge substantially charged and discharged in the secondary battery 10. Equivalent to.

In S240, the ECU 100 determines whether or not the charge amount difference (Ahc-Ahd) is larger than the inputtable charge amount Qin (see S170 in FIG. 5) calculated by the charge amount calculation process. When the charge amount difference (Ahc-Ahd) is larger than the inputtable charge amount Qin (YES in S240), the ECU 100 is secondary as compared with the case where the charge amount difference (Ahc-Ahd) is less than or equal to the inputtable charge amount Qin. Suppresses the charge of the battery 10 (S250).

On the other hand, when the charge amount difference (Ahc-Ahd) is less than or equal to the input charge amount Qin (NO in S240), the ECU 100 advances the process to S260, and the charge amount difference (Ahc-Ahd) is the output charge amount Qout. It is further determined whether or not it is less than (see S180 in FIG. 5). When the charge amount difference (Ahc-Ahd) is less than the outputable charge amount Qout (YES in S260), the ECU 100 compares with the case where the charge amount difference (Ahc-Ahd) is equal to or more than the outputable charge amount Qout. The discharge of the next battery 10 is suppressed (S270).

When the charge amount difference (Ahc-Ahd) is equal to or greater than the outputable charge amount Qout in S260 (NO in S260), that is, the charge amount difference (Ahc-Ahd) is the outputable charge amount Qout and the inputtable charge amount. In the case of Qin, the ECU 100 returns the process to the main routine without particularly suppressing the charge / discharge of the secondary battery 10. After that, a series of controls (charge / discharge suppression control) shown in FIG. 7 are repeatedly executed every time a predetermined calculation cycle elapses.

As described above, according to the present embodiment, first, the timing when the secondary battery 10 is in the no-load state (for example, the state when the vehicle 1 is in the IG-ON state or the state in which the vehicle 1 is parked / stopped). The reference OCVref of the secondary battery 10 is acquired at. Then, the input charge amount Qin and the output charge amount Qout are calculated based on the reference SOCref corresponding to the reference OCVref. The secondary battery 10 can be appropriately protected by suppressing the charging / discharging of the secondary battery 10 based on the inputtable charge amount Qin and the output chargeable charge amount Qout.

Further, at the time of charging / discharging the secondary battery 10 after calculating the inputtable charge amount Qin and the output chargeable charge amount Qout, the charge amount input / output to the secondary battery 10 is calculated by current integration, and the calculated charge amount ( It is determined whether or not the charge amount difference) reaches the input charge amount Qin or the output charge amount Qout. An error can occur in the current integration. However, since the current integration error can be reset by reacquiring the OCV (reference OCVref) at the timing when the secondary battery 10 is in the no-load state, the current integration can be performed with high accuracy. Therefore, it is not necessary to set an excessive margin for the SOC upper limit UL and the SOC lower limit LL in consideration of the SOC estimation error. Further, unlike the method started in Patent Document 1, even when the secondary battery 10 is charged and discharged with a large current or the internal resistance of the secondary battery 10 is increased. , There is no error based on the voltage difference between CCV and OCV. Therefore, it is possible to secure a usable SOC region and effectively utilize the secondary battery 10.

The embodiments disclosed this time should be considered as exemplary in all respects and not restrictive. The scope of the present disclosure is indicated by the scope of claims rather than the description of the embodiment described above, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 vehicle, 2 secondary battery system, 10 secondary battery, 20 monitoring unit, 21 voltage sensor, 22 current sensor, 23 temperature sensor, 30 PCU, 100 ECU, 101 CPU, 102 memory, 210, 220 motor generator, 230 engine , 240 power dividers, 250 drive shafts, 260 drive wheels.

Claims (1)

With a secondary battery
A power conversion device that converts the power of the secondary battery and
A control device for controlling the power conversion device so that the secondary battery is charged and discharged between the upper limit SOC and the lower limit SOC is provided.
The control device is
The OCV of the secondary battery is acquired, and the reference SOC corresponding to the OCV is calculated by referring to the predetermined correspondence between the OCV and the SOC, and the secondary battery moves from the reference SOC to the upper limit SOC. The first charge amount, which is the amount of charge input to the secondary battery when charged, is calculated, and when the secondary battery is discharged from the reference SOC to the lower limit SOC, the secondary battery is used. Calculate the second charge amount, which is the output charge amount,
The amount of charge input to and from the secondary battery was integrated with the charging and discharging of the secondary battery from the time of acquiring the OCV of the secondary battery, and the integrated amount of charge exceeded the amount of the first charge. A secondary battery system that suppresses the charging of the secondary battery in the case of the case, and suppresses the discharge of the secondary battery when the accumulated charge amount is less than the second charge amount.

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