JP5738784B2 - Power storage system - Google Patents

Description

  The present invention relates to a power storage system that estimates a positive electrode potential and a negative electrode potential of a power storage element.

  In charge / discharge control of the secondary battery, the voltage of the secondary battery is detected, and charge / discharge of the secondary battery is controlled so that the detected voltage changes between the upper limit voltage and the lower limit voltage.

Patent No. 0401288 JP 2011-003318 A JP 2009-302038 A JP 2006-345634 A JP 2006-340447 A

  The voltage of the secondary battery includes a positive electrode potential (electrical potential energy of the positive electrode active material with respect to a reference potential between the positive electrode potential and the negative electrode potential) and a negative electrode potential (electricity of the negative electrode active material with respect to the reference potential). (Potential energy) difference. However, since there are factors that affect the voltage in addition to the positive electrode potential and the negative electrode potential, the voltage of the secondary battery may not correspond to the positive electrode potential and the negative electrode potential.

  Specifically, even if the voltage of the secondary battery reaches the upper limit voltage or the lower limit voltage, the positive electrode potential or the negative electrode potential may not reach the threshold value. On the other hand, even if the voltage of the secondary battery does not reach the upper limit voltage or the lower limit voltage, the positive electrode potential or the negative electrode potential may reach the threshold value. The threshold value is a predetermined value from the viewpoint of protecting the secondary battery (positive electrode or negative electrode).

The power storage system according to the present invention includes a power storage element that charges and discharges, a memory, and a controller. The memory stores a ratio between a change amount of the positive electrode potential and a change amount of the negative electrode potential when the storage element is discharged or charged . The controller estimates at least one electrode potential of the positive electrode potential and the negative electrode potential of the power storage element. Here, the controller acquires the voltage of the power storage element, and calculates at least one electrode potential using the acquired voltage and the ratio .

One electrode potential can be calculated using the acquired voltage and the above ratio . Specifically, the electrode potential corresponding to the acquired voltage can be calculated by multiplying the acquired voltage by the ratio of one electrode potential in the above ratio . The other electrode potential can be calculated by subtracting the calculated one electrode potential from the acquired voltage.

If by measuring the amount of change in pre Me positive electrode potential and negative electrode potential, the ratio of these variation can be stored in the memory.

  A correction coefficient corresponding to a change in the element state can be stored in the memory with respect to at least one element state among the temperature state, the charging state, and the deterioration state of the power storage element. When the element state changes, a correction coefficient corresponding to the element state value can be set in advance. The temperature state can be acquired using a temperature sensor. The state of charge indicates the ratio of the current capacity to the full charge capacity. The deterioration state can be expressed by a resistance change rate or a capacity change rate.

  The controller can correct the electrode potential by multiplying the calculated electrode potential by a correction coefficient corresponding to the current element state. Thereby, the electrode potential corresponding to the element state can be estimated.

  If the electrode potential is estimated, charge / discharge of the power storage element can be controlled based on the electrode potential. Specifically, charge / discharge of the power storage element can be controlled such that the electrode potential changes within a predetermined range. Since the electrode potential is related to the performance (input / output characteristics) of the power storage element, the performance of the power storage element can be maximized by controlling charging / discharging of the power storage element while monitoring the electrode potential.

  Specifically, charging of the power storage element can be limited according to the electrode potential reaching the upper limit value or according to the prediction that the electrode potential reaches the upper limit value. Moreover, discharge of an electrical storage element can be restrict | limited according to predicting that electrode potential will reach | attain a lower limit value according to electrode potential reaching | attaining a lower limit value. When limiting charging / discharging, the case where charging / discharging is suppressed or the case where charging / discharging is prohibited are included.

  A power storage device can be configured by connecting a plurality of power storage elements in series. Then, the voltage of the power storage device can be detected using the voltage sensor. In this case, the voltage of each power storage element can be calculated by dividing the voltage detected by the voltage sensor by the number of power storage elements. The electrode potential can be estimated based on the calculated voltage of the storage element.

  By using the power storage element, energy for running the vehicle can be obtained. Here, the kinetic energy generated during braking of the vehicle can be stored in the power storage element as regenerative power.

  According to the present invention, the positive electrode potential and the negative electrode potential can be estimated from the voltage of the power storage element. Thereby, the state of an electrode (a positive electrode or a negative electrode) can be monitored, and charging / discharging according to the state of the electrode can be performed.

It is a figure which shows the structure of the battery system which is Example 1. FIG. In Example 1, it is a flowchart which shows the process which estimates a positive electrode potential and a negative electrode potential. It is a figure which shows the relationship between temperature and a correction coefficient. It is a figure which shows the relationship between SOC and a correction coefficient. It is a figure which shows the relationship between a deterioration degree and a correction coefficient. In Example 1, it is a flowchart which shows the process which controls charging / discharging of an assembled battery based on an electrode potential.

  Examples of the present invention will be described below.

  A battery system (corresponding to a power storage system) that is Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of a battery system. The battery system of the present embodiment can be mounted on a vehicle.

  The battery system of this embodiment includes an assembled battery (corresponding to a power storage device) 10. The assembled battery 10 includes a plurality of single cells (corresponding to power storage elements) 11 connected in series. As the cell 11, a secondary battery such as a nickel metal hydride battery or a lithium ion battery can be used. An electric double layer capacitor (capacitor) can be used instead of the secondary battery.

  The unit cell 11 has a power generation element housed in a battery case. The power generation element is an element that performs charging and discharging, and can be composed of a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate. The separator contains an electrolytic solution. Here, a solid electrolyte may be used instead of the separator.

  The number of the cells 11 can be set as appropriate based on the required output. In the present embodiment, the plurality of single cells 11 are connected in series, but the plurality of single cells 11 connected in parallel may be included in the assembled battery 10.

  The voltage sensor 21 detects the inter-terminal voltage (total voltage) of the assembled battery 10 and outputs the detection result to the controller 30. The current sensor 22 detects the charge / discharge current flowing through the assembled battery 10 and outputs the detection result to the controller 30. As a value detected by the current sensor 22, the charging current can be a positive value and the discharging current can be a negative value.

  The temperature sensor 23 detects the temperature of the assembled battery 10 and outputs the detection result to the controller 30. The number of temperature sensors 23 can be set as appropriate. When a plurality of temperature sensors 23 are used, the temperature sensors 23 can be arranged at different positions.

  The controller 30 has a memory 30a, and the memory 30a stores various information for the controller 30 to perform predetermined processing. In the present embodiment, the memory 30 a is built in the controller 30, but the memory 30 a may be provided outside the controller 30.

  A system main relay SMR-B is connected to the positive terminal of the assembled battery 10. System main relay SMR-B is switched between on and off by receiving a control signal from controller 30. A system main relay SMR-G is connected to the negative terminal of the assembled battery 10. System main relay SMR-G is switched between on and off by receiving a control signal from controller 30.

  A system main relay SMR-P and a limiting resistor 24 are connected in parallel to the system main relay SMR-G. System main relay SMR-P is switched between on and off by receiving a control signal from controller 30. The limiting resistor 24 is used to suppress the inrush current from flowing when the assembled battery 10 is connected to the inverter 31.

  When connecting the assembled battery 10 to the inverter 31, the system main relay SMR-B is switched from OFF to ON, and the system main relay SMR-P is switched from OFF to ON. As a result, a current flows through the limiting resistor 24.

  Next, after the system main relay SMR-G is switched from OFF to ON, the system main relay SMR-P is switched from ON to OFF. Thereby, the connection of the assembled battery 10 and the inverter 31 is completed. On the other hand, when the connection between the assembled battery 10 and the inverter 31 is cut off, the system main relays SMR-B and SMR-G may be switched from on to off.

  The inverter 31 converts the DC power from the assembled battery 10 into AC power, and outputs the AC power to the motor / generator 32. As the motor generator 32, for example, a three-phase AC motor can be used. The motor / generator 32 receives AC power from the inverter 31 and generates kinetic energy for driving the vehicle. The kinetic energy generated by the motor generator 32 is transmitted to the wheels.

  When the vehicle is decelerated or stopped, the motor / generator 32 converts kinetic energy generated during braking of the vehicle into electric energy (AC power). The inverter 31 converts the AC power generated by the motor / generator 32 into DC power and outputs the DC power to the assembled battery 10. Thereby, the assembled battery 10 can store regenerative electric power.

  In the present embodiment, the assembled battery 10 is connected to the inverter 31, but this is not a limitation. Specifically, the assembled battery 10 can be connected to the booster circuit, and the booster circuit can be connected to the inverter 31. By using the booster circuit, the output voltage of the assembled battery 10 can be boosted. Further, the booster circuit can step down the output voltage from the inverter 31 to the assembled battery 10.

  The battery system of the present embodiment can estimate the electrode potential (positive electrode potential or negative electrode potential) of the unit cell 11 and control the input / output of the assembled battery 10 based on the estimated electrode potential. First, the process for estimating the electrode potential of the unit cell 11 will be described with reference to the flowchart shown in FIG. The process shown in FIG. 2 is executed by the controller 30.

  In step S <b> 101, the controller 30 acquires the voltage of the assembled battery 10 from the output of the voltage sensor 21. In step S <b> 102, the controller 30 calculates the voltage of the single battery 11. The voltage of the cell 11 can be calculated based on the following formula (1).

Vcell = Vbat / N (1)
In the formula (1), Vcell is the voltage of the unit cell 11. Vbat is the voltage of the assembled battery 10 and is the voltage acquired in step S101. N is the number of unit cells 11 constituting the assembled battery 10, in other words, the number of unit cells 11 connected in series.

  In the assembled battery 10, since all the unit cells 11 are connected in series, the voltage Vcell of the unit cell 11 can be obtained by dividing the voltage Vbat of the assembled battery 10 by the number N of the unit cells 11. Even if the battery cells 11 connected in parallel are included in the assembled battery 10, the voltage Vcell of the battery cells 11 can be calculated based on the number of the battery cells 11 connected in series. In the present embodiment, the voltage Vcell of the unit cell 11 is calculated from the voltage Vbat of the assembled battery 10, but the present invention is not limited to this.

  Specifically, if a voltage sensor is provided for each unit cell 11, the voltage of each unit cell 11 can be detected. Moreover, all the single cells 11 constituting the assembled battery 10 can be divided into a plurality of blocks, and the voltage of each block (referred to as a block voltage) can be detected. Each block includes two or more single cells 11. When the block voltage is detected, the voltage Vcell of each unit cell 11 can be calculated by dividing the block voltage by the number of unit cells 11 constituting each block. Note that the number of voltage sensors 21 can be reduced by providing one voltage sensor 21 for the battery pack 10 as in the present embodiment.

  Alternatively, only the voltages of some unit cells 11 may be detected, and the voltages of other unit cells 11 may be estimated. For example, the voltage of one of the cells 11 connected in series may be detected, and the voltage of the other cells 11 may be estimated to be the same value as the detected voltage of the cells 11.

  The controller 30 calculates the negative electrode potential of the single battery 11 in step S103, and calculates the positive electrode potential of the single battery 11 in step S104. A method for calculating the negative electrode potential and the positive electrode potential will be described.

  The voltage of the unit cell 11 is constituted by a negative electrode potential and a positive electrode potential. If the ratio between the negative electrode potential and the positive electrode potential is specified in advance, the negative electrode potential and the positive electrode potential can be calculated from the voltage of the unit cell 11. The ratio here is the ratio of the negative electrode potential and the positive electrode potential in the voltage of the unit cell 11.

  The ratio between the negative electrode potential and the positive electrode potential can be determined by the method described below.

  The cell 11 is discharged from the start voltage to the end voltage. Specific values of the start voltage and the end voltage can be set as appropriate. While the unit cell 11 is being discharged, the negative electrode potential and the positive electrode potential of the unit cell 11 are measured. If a reference electrode serving as a reference is arranged inside the unit cell 11, the negative electrode potential and the positive electrode potential can be measured.

  Then, when the discharge of the unit cell 11 is completed, a negative electrode potential change amount ΔV (−) and a positive electrode potential change amount ΔV (+) are calculated. In this embodiment, the ratio between the negative electrode potential and the positive electrode potential is the ratio between the changes in electrode potential ΔV (−) and ΔV (+). Information regarding the ratio between the negative electrode potential and the positive electrode potential can be stored in the memory 30a in advance. In the above description, the negative electrode potential change ΔV (−) and the positive electrode potential change V (+) when the unit cell 11 is discharged are calculated. However, the negative electrode potential when the unit cell 11 is charged is calculated. It is also possible to calculate the change amount ΔV (−) and the change amount V (+) of the positive electrode potential.

  In the present embodiment, the voltage of the unit cell 11 is constituted by the negative electrode potential and the positive electrode potential, but is not limited thereto. Specifically, the voltage of the unit cell 11 can take into account not only the negative electrode potential and the positive electrode potential but also the resistance of the battery component and the resistance of the electrolyte.

  The battery component is a component that constitutes the unit cell 11, and specifically includes a component that constitutes the power generation element described above. Since the resistance component of the battery component can be measured in advance, the ratio of the resistance component of the battery component in the voltage of the unit cell 11 can be specified.

  Further, if the potential change amount ΔVe due to the resistance of the electrolytic solution is measured while the unit cell 11 is being discharged, the potential change amount ΔVe is defined as a ratio of the voltage of the unit cell 11 to the electrolytic solution resistance. be able to.

  The measurement of the positive electrode potential and the negative electrode potential is started when the unit cell 10 is in a predetermined environment. In the predetermined environment, each of the temperature, the state of charge (SOC), and the deterioration state of the unit cell 11 is in the predetermined state. The SOC indicates the ratio of the current capacity to the full charge capacity. Here, when the unit cell 11 is in the fully charged state, the SOC becomes 100%, and the SOC decreases as the unit cell 11 in the fully charged state is discharged.

  The deterioration state indicates deterioration of the unit cell 11 due to wear or the like. For example, a resistance change rate or a capacity change rate can be used as an index representing the deterioration state. The resistance change rate can be calculated based on, for example, the following formula (2).

ΔR = | Rini−Rn | / Rini (2)
In Expression (2), ΔR represents a resistance change rate. Rini indicates the internal resistance of the unit cell 11 in the initial state (immediately after manufacture), and Rn indicates the internal resistance of the unit cell 11 at the present time. The internal resistance of the unit cell 11 can be calculated by measuring the current and voltage of the unit cell 11. As the deterioration of the unit cell 11 proceeds, the internal resistance of the unit cell 11 increases, so the resistance change rate ΔR increases according to the deterioration of the unit cell 11.

  When the capacity change rate is used as an index representing the deterioration state, for example, the deterioration state can be specified based on the following equation (3).

ΔC = | Cini−Cn | / Cini (3)
In the formula (3), Cini indicates the capacity of the single battery 11 in the initial state (immediately after manufacture), and Cn indicates the current capacity of the single battery 11. When the unit cell 11 deteriorates, the capacity starts to decrease, so the capacity change rate ΔC increases according to the deterioration of the unit cell 11.

  The controller 30 calculates the negative electrode potential based on the following formula (4), and calculates the positive electrode potential based on the following formula (5).

V (−) ref = Vcell × r (−) / (r (+) + r (−)) (4)
V (+) ref = Vcell × r (+) / (r (+) + r (−)) (5)

  In the formula (4), V (−) ref indicates a negative electrode potential and is a negative value. In Formula (5), V (+) ref indicates a positive electrode potential and is a positive value. Further, in the expressions (4) and (5), Vcell represents the voltage of the unit cell 11 and is the value calculated in step S102. Further, r (−) and r (+) indicate respective values in the ratio between the positive electrode potential and the negative electrode potential, and are acquired from the memory 30a.

  r (−) and r (+) have a relationship represented by the following formula (6).

r (−): r (+) = ΔV (−): ΔV (+) (6)
In Expression (6), ΔV (−) and ΔV (+) are the amounts of change in the negative electrode potential and the positive electrode potential when the unit cell 11 is discharged (or charged).

  In the above formulas (4) and (5), the resistance component of the battery component and the resistance component of the electrolytic solution are not taken into consideration. However, when the resistance component of the battery component and the resistance component of the electrolytic solution are known, , (5) may be replaced with the following equations (7), (8).

V (−) ref = Vcell × r (−) / (r (+) + r (−) + rcell + re) (7)
V (+) ref = Vcell × r (+) / (r (+) + r (−) + rcell + re) (8)
In equations (7) and (8), rcell represents the ratio of the resistance of the battery component, and re represents the ratio of the resistance of the electrolytic solution.

  In step S103, the controller 30 calculates the negative electrode potential based on the equation (4). In step S104, the controller 30 calculates the positive electrode potential based on Expression (5).

  In step S105, the controller 30 corrects the negative electrode potential according to the temperature of the single battery 11. As the temperature of the cell 11, the detection result of the temperature sensor 23 can be used. The controller 30 corrects the negative electrode potential based on the following formula (9).

V (−) c1 = V (−) ref × K (T) (9)
In Expression (9), K (T) represents a correction coefficient corresponding to the temperature. V (−) c1 represents the negative electrode potential after correction, and V (−) ref represents the positive electrode potential calculated in step S103.

  A map shown in FIG. 3 is stored in the memory 30a. The map shown in FIG. 3 shows the correspondence between temperature and correction coefficient K (T). The map shown in FIG. 3 can be created by conducting an experiment in advance. The correction coefficient K (T) can be obtained by measuring the change in the negative electrode potential while keeping the SOC and the deterioration state constant, changing only the temperature.

  When the temperature of the unit cell 11 is the reference temperature Tref, the correction coefficient K (T) is 1. The reference temperature Tref is a temperature when the negative electrode potential is measured, and is a temperature in the predetermined environment described above. The controller 30 can specify the temperature of the unit cell 11 based on the output of the temperature sensor 23. If the temperature of the unit cell 11 can be specified, the correction coefficient K (T) can be specified based on the map shown in FIG.

  In this embodiment, the negative electrode potential V (−) ref is corrected using the map shown in FIG. 3, but the present invention is not limited to this. For example, if the negative electrode potential can be expressed by a function using the temperature of the unit cell 11 as a variable, the negative electrode potential can be calculated (corrected) using this function.

  In step S <b> 106, the controller 30 corrects the positive electrode potential according to the temperature of the unit cell 11. Specifically, the controller 30 calculates the positive electrode potential based on the following formula (10).

V (+) c1 = Vcell- | V (-) c1 | (10)
In Expression (10), Vcell is the voltage of the single battery 11 and is the value calculated in step S102. V (−) c1 is the value of the negative electrode potential calculated in step S105. V (+) c1 is the value of the positive electrode potential corrected based on the temperature of the unit cell 11.

  In step S107, the controller 30 corrects the negative electrode potential according to the SOC of the single battery 11. Specifically, the controller 30 calculates (corrects) the negative electrode potential based on the following formula (11).

V (−) c2 = V (−) c1 × K (SOC) (11)
In Equation (11), K (SOC) represents a correction coefficient corresponding to the SOC. V (−) c1 is the value of the negative electrode potential calculated in step S105. V (−) c2 is a value of the negative electrode potential corrected in consideration of the SOC of the unit cell 11.

  A map shown in FIG. 4 is stored in the memory 30a. The map shown in FIG. 4 shows the correspondence between the SOC and the correction coefficient K (SOC). The map shown in FIG. 4 can be created by conducting an experiment in advance. If the negative electrode potential is measured by changing only the SOC while keeping the temperature and the deterioration state constant, the correction coefficient K (SOC) can be obtained.

  When the SOC of the cell 11 is the reference value SOCref, the correction coefficient K (SOC) is 1. The reference value SOCref is the SOC when the negative electrode potential is measured, and is the SOC in the predetermined environment described above.

  The controller 30 can estimate the SOC of the unit cell 11 based on the output of the voltage sensor 21. Specifically, the controller 30 measures the OCV (Open Circuit Voltage) of the single cell 11 using the voltage sensor 21 and specifies the SOC of the single cell 11 based on the OCV of the single cell 11. Can do.

  Since the OCV and SOC of the unit cell 11 are in a correspondence relationship, the SOC of the unit cell 11 can be identified from the OCV of the unit cell 11 if this correspondence relationship is specified in advance. On the other hand, if the charging / discharging current of the single battery 11 is integrated based on the output of the current sensor 22, the SOC of the single battery 11 can be estimated based on this integrated value.

  If the SOC of the unit cell 11 can be specified, the correction coefficient K (SOC) can be specified based on the map shown in FIG.

  In the present embodiment, the negative electrode potential is corrected using the map shown in FIG. 4, but the present invention is not limited to this. For example, if the negative electrode potential can be expressed by a function using the SOC of the unit cell 11 as a variable, the negative electrode potential can be calculated using this function.

  In step S108, the controller 30 corrects the positive electrode potential according to the SOC of the single battery 11. Specifically, the controller 30 calculates the positive electrode potential based on the following formula (12).

V (+) c2 = Vcell- | V (-) c2 | (12)
In Expression (12), Vcell is the voltage of the single battery 11 and is the value calculated in step S102. V (−) c2 is the value of the negative electrode potential calculated in step S107. V (+) c2 is the value of the positive electrode potential corrected based on the SOC of the unit cell 11.

  In step S <b> 109, the controller 30 corrects the negative electrode potential according to the deterioration state of the unit cell 11. Specifically, the controller 30 calculates (corrects) the negative electrode potential based on the following formula (13).

V (−) c3 = V (−) c2 × K (R) (13)
In Equation (13), K (R) represents a correction coefficient corresponding to the deterioration state. V (-) c2 is the value of the negative electrode potential calculated in step S107. V (−) c3 is a value of the negative electrode potential corrected in consideration of the deterioration state of the unit cell 11.

  A map shown in FIG. 5 is stored in the memory 30a. The map shown in FIG. 5 shows the correspondence between the degree of deterioration and the correction coefficient K (R). The degree of deterioration is an index representing a deterioration state, and as described above, the resistance change rate and the capacity change rate can be used. The map shown in FIG. 5 can be created by conducting an experiment in advance. The correction coefficient K (R) can be obtained by measuring the negative electrode potential while keeping the temperature and SOC constant and changing only the deterioration state.

  When the degree of deterioration of the cell 11 is the reference value Rref, the correction coefficient K (R) is 1. The reference value Rref is the degree of deterioration when the negative electrode potential is measured, and is the degree of deterioration in the predetermined environment described above.

  The degree of deterioration of the unit cell 11 can be obtained by calculating the resistance change rate or the capacity change rate as described above. What is necessary is just to obtain | require the internal resistance of the cell 11 when calculating a resistance change rate. What is necessary is just to obtain | require the capacity | capacitance of the cell 11 when calculating a capacity | capacitance change rate. If the degree of deterioration of the cell 11 can be specified, the correction coefficient K (R) can be specified based on the map shown in FIG.

  In this embodiment, the negative electrode potential is corrected using the map shown in FIG. 5, but the present invention is not limited to this. For example, if the negative electrode potential can be expressed by a function with the degree of deterioration of the unit cell 11 as a variable, the negative electrode potential can be calculated using this function.

  In step S110, the controller 30 corrects the positive electrode potential according to the deterioration state of the unit cell 11. Specifically, the controller 30 calculates the positive electrode potential based on the following formula (14).

V (+) c3 = Vcell− | V (−) c3 | (14)
In the equation (14), Vcell is the voltage of the single battery 11 and is the value calculated in step S102. V (−) c3 is the value of the negative electrode potential calculated in step S109. V (+) c3 is the value of the positive electrode potential corrected based on the deterioration state of the unit cell 11.

  In the process shown in FIG. 2, the negative electrode potential is corrected by multiplying the value of the negative electrode potential by a correction coefficient. However, the present invention is not limited to this. Specifically, the positive electrode potential can be corrected by multiplying the value of the positive electrode potential by a correction coefficient. In this case, it is necessary to prepare a correction coefficient corresponding to the positive electrode potential in each of the temperature, the SOC, and the deterioration state. After correcting the positive electrode potential, the negative electrode potential can be obtained by subtracting the corrected positive electrode potential from the voltage Vcell of the cell 11.

  In addition, the order in which the electrode potential is corrected by temperature, the electrode potential is corrected by SOC, and the electrode potential is corrected by the deterioration state can be set as appropriate. That is, it is not necessary to correct the electrode potential in the order described in FIG.

  In the present embodiment, the positive electrode potential and the negative electrode potential are corrected according to the temperature, SOC, and deterioration state of the unit cell 11, but the present invention is not limited to this. Specifically, the positive electrode potential and the negative electrode potential can be corrected according to at least one of the temperature, SOC, and deterioration state of the unit cell 11.

  For example, when correcting the negative electrode potential, at least one of the processes of steps S105, S107, and S109 can be performed. When correcting the positive electrode potential, at least one of the processes of steps S106, S108, and S110 can be performed. In this embodiment, the positive electrode potential and the negative electrode potential are calculated by correcting each, but after calculating only one of the positive electrode potential and the negative electrode potential, the calculated value of one potential is calculated. May be subtracted from the voltage of the unit cell 11 to calculate the other potential.

  By performing the processing shown in FIG. 2, it is possible to estimate the positive electrode potential and the negative electrode potential of the current single battery 11. The process shown in FIG. 2 can be repeatedly performed at a predetermined timing. And charging / discharging of the assembled battery 10 can be controlled based on the estimated electrode potential.

  FIG. 6 shows a flowchart when charging / discharging of the assembled battery 10 is controlled. The process shown in FIG. 6 can be executed by the controller 30.

  In step S201, the controller 30 determines whether or not the positive electrode potential estimated in the process of FIG. 2 is higher than the upper limit value. The upper limit value is a preset value and can be stored in the memory 30a. Here, the charging / discharging of the unit cell 11 may be controlled so that the voltage of the unit cell 11 changes within the range of the upper limit voltage and the lower limit voltage. The upper limit value used in step S201 can be a value corresponding to the above-described upper limit voltage.

  In step S201, when the positive electrode potential is higher than the upper limit value, the process proceeds to step S202. When the positive electrode potential is lower than the upper limit value, the process proceeds to step S203.

  In step S <b> 202, the controller 30 restricts input (charging) of the assembled battery 10. Limiting the input of the assembled battery 10 includes a case where the preset limit value Win is lowered or a case where the input of the assembled battery 10 is prohibited. The limit value Win is a preset value and is an upper limit value (unit: W) that allows input of the assembled battery 10.

  In step S203, the controller 30 determines whether or not the positive electrode potential estimated in the process of FIG. 2 is lower than the lower limit value. The lower limit value is a preset value and can be stored in the memory 30a. As a lower limit, it can be set as the value corresponding to the lower limit voltage at the time of controlling charging / discharging of the single battery 11 based on the voltage of the single battery 11.

  In step S203, when the positive electrode potential is lower than the lower limit value, the process proceeds to step S204. Further, when the positive electrode potential is higher than the lower limit value, this process is terminated. In step S204, the controller 30 limits the output (discharge) of the assembled battery 10. Limiting the output of the assembled battery 10 includes a case where the preset limit value Wout is lowered or a case where the output of the assembled battery 10 is prohibited. The limit value Wout is a preset value and is an upper limit value (unit: W) that allows the output of the assembled battery 10.

  In the process illustrated in FIG. 6, charging / discharging of the assembled battery 10 is controlled based on the positive electrode potential, but is not limited thereto. Specifically, charging / discharging of the assembled battery 10 can be controlled based on the negative electrode potential estimated in the process of FIG. That is, charging / discharging of the assembled battery 10 can be controlled such that the negative electrode potential changes between a predetermined upper limit value and lower limit value. Here, the upper limit value and the lower limit value are values corresponding to the upper limit voltage and the lower limit voltage when charging / discharging of the cell 11 is controlled based on the voltage of the cell 11. On the other hand, charging / discharging of the assembled battery 10 can also be controlled based on both the positive electrode potential and the negative electrode potential.

  According to the present embodiment, since the electrode potential (positive electrode potential or negative electrode potential) of the single cell 11 is estimated instead of the voltage of the single cell 11, the internal state of the single cell 11 can be easily estimated. Since the voltage of the cell 11 is determined by the positive electrode potential and the negative electrode potential, it is preferable to monitor the positive electrode potential and the negative electrode potential when estimating the internal state of the cell 11.

  Moreover, charging / discharging according to the state of a positive electrode and a negative electrode can be performed by controlling charging / discharging of the cell 11 (assembled battery 10) based on the estimated electrode potential. Thereby, for example, the input / output range of the cell 11 can be expanded, and the cell 11 can be used efficiently. In other words, the performance of the input / output characteristics of the unit cell 11 can be maximized.

  Here, in the configuration in which only the voltage of the unit cell 11 is monitored, for example, when the voltage of the unit cell 11 reaches the upper limit voltage, the input of the unit cell 11 is limited. However, even if the voltage of the unit cell 11 reaches the upper limit voltage (or lower limit voltage), the positive electrode potential may not reach the upper limit value (or lower limit value). In this case, the cell 11 can be charged (or discharged) until the positive electrode potential reaches the upper limit (or lower limit).

  Moreover, even if the voltage of the unit cell 11 does not reach the upper limit voltage (or lower limit voltage), the positive electrode potential may have reached the upper limit value (or lower limit value). In this case, before the voltage of the unit cell 11 reaches the upper limit voltage (or lower limit voltage), the input (or output) of the unit cell 11 (the assembled battery 10) can be limited, and the unit cell 11 is protected. can do.

10: assembled battery (power storage device)
11: Single cell (electric storage element)
21: Voltage sensor 22: Current sensor 23: Temperature sensor 24: Limiting resistor 30: Controller 30a: Memory 31: Inverter 32: Motor generator

Claims (8)

A power storage element for charging and discharging; and
A memory for storing a ratio of a change amount of a positive electrode potential and a change amount of a negative electrode potential when the storage element is discharged or charged ;
A controller for estimating at least one of the positive electrode potential and the negative electrode potential of the electricity storage device,
The controller acquires a voltage of the power storage element, and calculates the at least one electrode potential using the acquired voltage and the ratio . The controller calculates one electrode potential of the positive electrode potential and the negative electrode potential using the acquired voltage and the ratio , and subtracts the calculated one electrode potential from the acquired voltage. The power storage system according to claim 1, wherein an electrode potential is calculated. The memory stores a correction coefficient corresponding to a change in the element state with respect to at least one element state among a temperature state, a charged state, and a deteriorated state of the power storage element,
The power storage system according to claim 1 or 2 , wherein the controller corrects the electrode potential by multiplying the calculated electrode potential by a correction coefficient corresponding to the current element state. The power storage system according to any one of claims 1 to 3 , wherein the controller controls charging / discharging of the power storage element so that the calculated electrode potential changes within a predetermined range. The controller limits the charging of the electric storage element in response to the calculated electrode potential reaching or reaching the upper limit value, and the calculated electrode potential reaches the lower limit value, or The power storage system according to claim 4 , wherein discharge of the power storage element is limited in accordance with prediction of reaching. A power storage device in which a plurality of the power storage elements are connected in series;
A voltage sensor for detecting a voltage of the power storage device,
The said controller calculates the voltage of each said electrical storage element by dividing the voltage detected by the said voltage sensor by the number of the said electrical storage elements, The one of Claim 1 to 5 characterized by the above-mentioned. Power storage system. The said electrical storage element outputs the energy used for driving | running | working of a vehicle, The electrical storage system as described in any one of Claim 1 to 6 characterized by the above-mentioned. A method for estimating an electrode potential of at least one of a positive electrode potential and a negative electrode potential of a storage element that performs charge and discharge,
Obtaining the voltage of the storage element,
Using the acquired voltage and the ratio of the change amount of the positive electrode potential and the change amount of the negative electrode potential when the storage element is discharged or charged , the at least one electrode potential is calculated.
An estimation method characterized by that.

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