JP7028068B2 - Battery system - Google Patents

Description

The present disclosure relates to charge / discharge control of a battery system composed of a plurality of battery elements.

For example, Japanese Patent Application Laid-Open No. 2010-124575 (Patent Document 1) describes the temperature of a plurality of power storage devices in a configuration in which a plurality of power storage devices and power conversion devices for converting input / output power of the power storage devices are connected in parallel. By charging and discharging the power storage device using the power conversion device according to the difference from the target temperature calculated by averaging the temperatures of multiple power storage devices, the temperature difference between each power storage device is eliminated and the difference in deterioration is eliminated. Technology to reduce is disclosed.

Japanese Unexamined Patent Publication No. 2010-124575

However, as disclosed in Patent Document 1 described above, when the charging / discharging of the power storage device using the power conversion device is continued in order to reduce the temperature difference, the SOC (State Of Charge) of each power storage device is continued. May make a difference. When there is a difference in SOC between each power storage device, when controlling the SOC of a plurality of power storage devices as a whole, charging is started according to the power storage device having the lowest SOC among the plurality of power storage devices, or the SOC is the highest. Charging is completed according to the expensive power storage device. As a result, the effective full charge capacity of the entire plurality of power storage devices is reduced. Therefore, it is required to suppress the increase in the temperature difference between the power storage devices and the increase in the SOC difference between the power storage devices.

The present disclosure has been made to solve the above-mentioned problems, and an object thereof is to provide a battery system that suppresses an increase in temperature difference and SOC difference between a plurality of battery elements.

The battery system according to a certain aspect of the present disclosure includes an assembled battery in which a plurality of battery elements are connected in series, an adjusting device connected to each of the battery elements and adjusting the current flowing through each of the battery elements. Each of the battery elements includes a control device that controls the adjusting device so that the current reaches a target value. When the current flowing through the assembled battery is in the first state, the control device sets the magnitude of the first target value of the first battery element among the plurality of battery elements to be lower than that of the first battery element. A thermalization control is performed to reduce the magnitude of the second target value of the second battery element. When the current flowing through the assembled battery is in the second state where the heat equalization of the battery element is not required more than in the first state, the control device is discharged from the size of the second target value at the time of discharging the assembled battery. The first equalization control that increases the size of the first target value and the second equalization control that reduces the size of the first target value at the time of charging rather than the size of the second target value at the time of charging the assembled battery. Do one of the two.

By doing so, when the current flowing through the assembled battery is in the first state, the temperature of the second battery element can be raised by increasing the calorific value of the second battery element on the low temperature side. As a result, it is possible to suppress the expansion of the temperature difference between the first battery element and the second battery element and to achieve thermalization. If such thermalization control is continuously performed, the difference between the SOC of the first battery element and the SOC of the second battery element may increase. Therefore, when the current flowing through the assembled battery is in the second state where thermalization is not required more than in the first state, either the first equalization control or the second equalization control is executed. Thereby, the expansion of the difference between the SOC of the first battery element and the SOC of the second battery element can be suppressed.

According to the present disclosure, it is possible to provide a battery system that suppresses an increase in temperature difference and SOC difference between a plurality of battery elements.

FIG. 3 is a block diagram schematically showing an overall configuration of a vehicle equipped with a battery system according to an embodiment of the present disclosure. It is a figure which showed an example of the detailed structure of a battery pack. It is a figure for demonstrating an example of the operation which transfers electric power from one cell to the other cell, and adjusts the current which flows in a cell. It is a flowchart (the 1) which shows an example of the control process executed by an ECU. It is a flowchart (the 2) which shows an example of the control process executed by an ECU. It is a flowchart (3) which shows an example of the control process executed by an ECU.

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.

Hereinafter, an example in which the battery system according to this embodiment is applied to an electric vehicle will be described. FIG. 1 is a block diagram schematically showing an overall configuration of a vehicle 1 equipped with a battery system 2 according to the present embodiment.

With reference to FIG. 1, the vehicle 1 includes a motor generator (hereinafter, referred to as “MG (Motor Generator)”) 10, a power transmission gear 20, a drive wheel 30, and a power control unit (hereinafter, “PCU (Power)”. It includes a 40 (referred to as "Control Unit)", a system main relay (hereinafter referred to as "SMR (System Main Relay)") 50, and a battery system 2. The battery system 2 includes a battery pack 100, a voltage sensor 210, a current sensor 220, a temperature sensor 230, and an electronic control unit (hereinafter referred to as "ECU (Electronic Control Unit)") 300. The battery pack 100 includes a battery 101 and an adjusting device 102.

MG10 is, for example, a three-phase AC rotary electric machine. The output torque of the MG 10 is transmitted to the drive wheels 30 via a power transmission gear 20 configured by a speed reducer or the like. The MG 10 can also generate electricity by the rotational force of the drive wheels 30 during the regenerative braking operation of the vehicle 1. Although FIG. 1 shows a configuration in which only one MG is provided, the number of MGs is not limited to this, and a configuration in which a plurality of MGs (for example, two) are provided may be used.

The PCU 40 includes an inverter and a converter (neither is shown). When the battery 101 is discharged, the converter boosts the voltage supplied from the battery 101 and supplies it to the inverter. The inverter converts the DC power supplied from the converter into AC power and drives the MG 10. On the other hand, when charging the battery 101, the inverter converts the AC power generated by the MG 10 into DC power and supplies it to the converter. The converter steps down the voltage supplied from the inverter and supplies it to the battery 101.

The SMR 50 is electrically connected to a current path connecting the battery 101 and the PCU 40. When the SMR 50 is closed in response to a control signal from the ECU 300, power can be exchanged between the battery 101 and the PCU 40.

The battery 101 is a DC power source configured to be rechargeable. The battery 101 is an assembled battery including a plurality of cells (for example, 7 in this embodiment) as storage elements of a secondary battery such as a nickel hydrogen battery or a lithium ion battery.

The current sensor 220 detects the current Ib input / output to / from the battery 101. Each of the voltage sensor 210 and the temperature sensor 230 is provided, for example, one for each cell constituting the battery 101. Therefore, the voltage sensor 210 detects the voltages Vb (1) to Vb (7) for each cell of the battery 101. The temperature sensor 230 detects the temperatures Tb (1) to Tb (7) for each cell of the battery 101. Each sensor outputs the detection result to the ECU 300.

The ECU 300 includes a CPU (Central Processing Unit) 301, a memory 302, and an input / output buffer (not shown). The memory 302 includes a ROM (Read Only Memory), a RAM (Random Access Memory), and a rewritable non-volatile memory. Various controls are executed by the CPU 301 executing the program stored in the memory 302 (for example, ROM). The ECU 300 controls each device so that the vehicle 1 and the battery system 2 are in a desired state based on, for example, a signal received from each sensor and a map and a program stored in the memory 302. The various controls performed by the ECU 300 are not limited to software processing, but can also be processed by dedicated hardware (electronic circuits).

The ECU 300 stores the acquired information (calculation result by the CPU 301, etc.) in the memory 302. The memory 302 may store information used for detecting the charge state (that is, SOC) of the battery 101 and controlling the vehicle 1 in advance. For example, the memory 302 may store the initial information of the battery 101 (cell type, capacity, internal resistance, electrode thickness, basis weight, etc.) in advance.

The ECU 300 controls the charge / discharge power of the battery 101 according to the used SOC range determined by the lower limit SOC and the upper limit SOC. For example, when the SOC of the battery 101 approaches the upper limit SOC, the ECU 300 limits the input power (charging power) of the battery 101 so that the SOC of the battery 101 does not exceed the upper limit SOC. Further, when the SOC of the battery 101 approaches the lower limit SOC, the ECU 300 limits the output power (discharge power) of the battery 101 so that the SOC of the battery 101 does not fall below the lower limit SOC. The lower limit SOC and the upper limit SOC are stored in the memory 302, for example. The numerical values of the lower limit SOC and the upper limit SOC can be changed by the ECU 300. As a method for measuring SOC, various known methods such as a method based on current value integration (coulomb count) or a method based on estimation of open circuit voltage (OCV) can be adopted.

The ECU 300 controls the charge / discharge power of the battery 101 based on the charge power limit value Win indicating the upper limit value of the charge power of the battery 101 and the discharge power limit value Wout indicating the upper limit value of the discharge power of the battery 101. It is composed of. The ECU 300 executes a process of limiting the charging power to the battery 101 so that the charging power to the battery 101 does not exceed the charging power limit value Win. Further, the ECU 300 executes the discharge power limiting process from the battery 101 so that the discharge power from the battery 101 does not exceed the discharge power limit value Wout. These restriction processes are performed, for example, by controlling the PCU40, SMR50, and the like. The charge power limit value Win and the discharge power limit value Wout are stored in, for example, the memory 302. The respective numerical values of the charge power limit value Win and the discharge power limit value Wout can be changed by the ECU 300.

FIG. 2 is a diagram showing an example of a detailed configuration of the battery pack 100. As described above, the battery pack 100 is connected to each of the battery 101 including the seven cells 101a, 101b, 101c, 101d, 101e, 101f, 101g and the cells 101a to 101g, and the cells 101a to 101g. Includes a regulator 102 capable of adjusting the current in each of the above.

The adjusting device 102 includes current adjusting circuits 150a, 150b, 150c, 150d, 150e, 150f, 150g provided in the cells 101a to 101g, respectively, and a DC / DC control IC (Integrated Circuit) 108. For example, the current adjusting circuit 150a includes a transformer 103a, a first switching element 104a, a first resistor 105a, a second switching element 106a, and a second resistor 107a.

The transformer 103a includes a primary coil 110a and a secondary coil 111a. One end of the primary coil 110a is connected to one end of the first resistor 105a via the first switching element 104a. The other end of the primary coil 110a is connected to the positive electrode of the battery 101. The other end of the first resistor 105a is connected to the negative electrode of the battery 101.

One end of the secondary coil 111a is connected to one end of the second resistor 107a via the second switching element 106a. One end of the secondary coil 111a is connected to the positive electrode of the cell 101a. The other end of the second resistor 107a is connected to the negative electrode of the cell 101a.

The current adjusting circuits 150b to 150g have the same configuration as the current adjusting circuits 150a. Therefore, those detailed explanations will not be repeated.

The first switching elements 104a to 104g and the second switching elements 106a to 106g both operate based on the control signal from the DC / DC control IC 108. The DC / DC control IC 108 operates, for example, at least one of the first switching elements 104a to 104g and the second switching elements 106a to 106g based on the control signal from the ECU 300.

Power flows into the cell by transferring power between at least one of the cells 101a to 101g and at least one of the other cells using the adjusting device 102 having such a configuration. The current can be adjusted.

FIG. 3 is a diagram for explaining an example of an operation of transferring electric power from any one cell to another cell to adjust the current flowing through the cell. For example, as shown in FIG. 3, it is assumed that electric power is transferred between the cells 101f and the cells 101a to 101e and 101g to adjust the current flowing through the cells 101a to 101g. Further, for example, it is assumed that the current I flows through the battery 101 and both the first switching elements 104a to 104g and the second switching elements 106a to 106g are in the off state.

For example, as the first operation, the ECU 300 turns on the second switching element 106f of the current adjusting circuit 150f provided in the cell 101f. As a result, in the secondary coil 111f of the current adjustment circuit 150f of the cell 101f, the current (hereinafter, the current flowing in the secondary coil) in the direction of the arrow shown in FIG. 3 (A) (that is, toward the negative electrode side of the cell 101f). Is referred to as a secondary side auxiliary current) flows. At this time, for example, if the secondary side auxiliary current ia flows in the secondary side coil 111f, the current I + ia will flow in the cell 101f.

After that, as the second operation, the ECU 300 turns off the second switching element 106f and turns on the first switching elements 104a to 104g. As a result, in the primary coil 110a to 110e and 110g, the current (hereinafter, the current flowing through the primary coil is referred to as the primary auxiliary current) ib (=) in the direction of the arrow shown in FIG. 3 (B). ia / 6 cell) flows, and in the primary side coil 110f, the primary side auxiliary current ia flows in the direction of the arrow shown in FIG. 3 (B).

Then, as the third operation, the ECU 300 turns each of the first switching elements 104a to 104g into an off state, and turns each of the second switching elements 106a to 106e and 106g into an on state. As a result, in the secondary coil 111a to 111e and 111g, the secondary auxiliary current ib flows in the direction of the arrow shown in FIG. 3C (that is, to the positive electrode side of the cells 101a to 101e and 101g, respectively). At this time, the current I-ib flows through each of the cells 101a to 101e and 101g.

In this case, the current ia is supplied from the cells 101a to 101e and 101g to the cell 101f. In the following description, the current supplied from one cell to the other cell may be referred to as a supply current.

Alternatively, the ECU 300, for example, turns on each of the second switching elements 106a to 106e and 106g as the first operation. As a result, in the current adjusting circuits 150a to 150e and 150g of the cells 101a to 101e and 101g, the secondary is directed to the negative electrode side of the cells 101a to 101e and 101g in the direction opposite to the direction of the arrow shown in FIG. 3 (C). At this time, for example, if the secondary side auxiliary current ib flows in each of the secondary side coils 111a to 111e and 111g, the current I + ib flows in each of the cells 101a to 101e and 101g. become.

After that, as the second operation, the ECU 300 turns off each of the second switching elements 106a to 106e and 106g, and turns on the first switching elements 104a to 104g. As a result, in the primary coil 110a to 110e and 110g, the primary auxiliary current ib flows in the direction opposite to the direction of the arrow shown in FIG. 3B, and in the primary coil 110f, FIG. 3 (B). ), The primary side auxiliary current ia (= ib × 6 cells) flows in the direction opposite to the direction of the arrow.

Then, as the third operation, the ECU 300 turns each of the first switching elements 104a to 104g into an off state and turns the second switching element 106f into an on state. As a result, in the secondary coil 111f, the secondary auxiliary current ia flows in the direction opposite to the direction of the arrow shown in FIG. 3A (that is, on the positive electrode side of the cell 101f). At this time, the current I-ia flows through the cell 101f.

In this case, the current ia is supplied from the cell 101f to the cells 101a to 101e and 101g.

In the battery pack 100 configured as described above, the ECU 300 adjusts the current amounts of the seven cells using the above-mentioned adjusting device 102 when the battery 101 is being charged or discharged, and the temperature difference between the cells is increased. Performs thermalization control to suppress expansion.

Specifically, the ECU 300 acquires the temperature distribution of the seven cells and identifies the hottest cell and the coldest cell. As described above, the ECU 300 supplies an auxiliary current from the high temperature cell to the low temperature cell to reduce the magnitude of the current flowing in the high temperature cell to be smaller than the magnitude of the current flowing in the low temperature cell, thereby reducing the heat generation amount of the high temperature cell. Make the cell lower than the calorific value. As a result, while suppressing the temperature rise of the high temperature cell, the temperature rise of the low temperature cell is promoted and the expansion of the temperature difference between the cells is suppressed.

In this case, the ECU 300 can adjust the calorific value in the high temperature cell and the low temperature cell according to the temperature of the high temperature cell or the temperature of the low temperature cell. Specifically, the ECU 300 generates heat by adjusting the current load (square value of auxiliary current x auxiliary time) while keeping the amount of electric charge (auxiliary current x auxiliary time (time for flowing auxiliary current)) constant, for example. The amount can be adjusted. Therefore, for example, the lower the cell temperature, the larger the auxiliary current and the shorter the auxiliary time, and the higher the cell temperature, the smaller the auxiliary current and the longer the auxiliary time. The amount of heat generated can be adjusted using the same amount of charge.

By adjusting the calorific value between the high temperature cell and the low temperature cell in this way, it is possible to appropriately suppress the expansion of the temperature difference between the cells and to achieve thermalization.

However, if the state in which the magnitude of the current flowing in the low temperature cell is increased more than the magnitude of the current flowing in the high temperature cell is continued by executing the thermalization control, the difference in SOC between the cells 101a to 101g is continued. May expand. When a difference in SOC occurs between the cells 101a to 101g, for example, when charging the battery 101, charging is started according to the cell having the lowest SOC among the cells 101a to 101g. At this time, in the cell having the highest SOC, charging is started even if the remaining battery level can be discharged. Then, when the charging of the battery 101 is completed, the charging is completed according to the cell having the highest SOC. At this time, in the cell having the lowest SOC, even if there is room for charging, the charging is terminated in accordance with the cell having the highest SOC. As a result, the effective full charge capacity of the battery 101 is reduced. Therefore, it is required to suppress the expansion of the temperature difference and the expansion of the SOC difference between the cells.

Therefore, in the present embodiment, the ECU 300 shall perform the following operations. That is, when the current flowing through the battery 101 is in the first state, the ECU 300 sets the magnitude of the first target value of the current flowing through the high temperature cell among the plurality of cells to the low temperature cell having a lower temperature than the high temperature cell. It is assumed that the thermalization control is performed so that the current flowing through the current is smaller than the magnitude of the second target value. Then, when the current flowing through the battery 101 is in the second state in which the heat equalization of the cell is not required more than in the first state, the ECU 300 causes the battery 101 to be larger than the size of the second target value at the time of discharging the battery 101. It is assumed that equalization control for increasing the magnitude of the first target value at the time of discharge is executed.

By doing so, when the current flowing through the battery 101 is in the first state, the temperature of the low temperature cell can be raised by increasing the calorific value of the low temperature cell. As a result, it is possible to suppress the expansion of the temperature difference between the high temperature cell and the low temperature cell and to achieve thermalization. If such thermalization control is continuously performed, the difference between the SOC of the high temperature cell and the SOC of the low temperature cell may increase. Therefore, when the current flowing through the battery 101 is in the second state where thermalization is not required more than in the first state, the equalization control is executed, so that the difference between the SOC of the high temperature cell and the SOC of the low temperature cell is reached. Expansion can be suppressed.

Hereinafter, an example of the control process executed by the ECU 300 will be described with reference to FIGS. 4, 5 and 6. 4, FIG. 5 and FIG. 6 are all flowcharts showing an example of the control process executed by the ECU 300.

With reference to FIG. 4, in step 100 (hereinafter, S is referred to as a step) 100, the ECU 300 estimates the temperature distribution of cells 101a to 101g in the battery pack 100. The ECU 300 estimates the temperature distribution of the cells 101a to 101g in the battery pack 100 by using, for example, the temperatures Tb (1) to Tb (7) of the cells 101a to 101g detected by the temperature sensor 230.

In S102, the ECU 300 calculates the difference in the amount of heat generated between the required cells. Specifically, the ECU 300 uses the acquired temperature distribution to identify the hottest cell and the coldest cell among the cells 101a to 101g. The ECU 300 calculates the temperature difference between the two specified cells, and uses the calculated temperature difference to calculate the difference in the amount of heat generated between the required cells. The ECU 300 may calculate the difference in calorific value from the temperature difference, for example, by using a map showing the relationship between the temperature difference and the calorific value difference. The map showing the relationship between the temperature difference and the calorific value difference is adapted by, for example, an experiment, and is stored in the memory of the ECU 300 in advance.

In S104, the ECU 300 determines whether or not the magnitude of the difference in the amount of heat generated between the required cells is equal to or greater than a predetermined value. The predetermined value is, for example, a predetermined value and is adapted by an experiment or the like. When it is determined that the magnitude of the difference in calorific value between the required cells is equal to or greater than a predetermined value (YES in S104), the process is transferred to S106. When it is determined that the magnitude of the difference in calorific value between the required cells is smaller than the predetermined value (NO in S104), the difference in temperature difference is small, and this process is terminated.

In S106, the ECU 300 estimates the full charge capacity and SOC in each of the cells 101a to 101g. Since the SOC estimation method is as described above, the detailed description thereof will not be repeated. The ECU 300 estimates the full charge capacity from, for example, the integrated value (electric energy) of the charge current or the discharge current with respect to a predetermined change amount of the SOC. As the method for estimating the full charge capacity, a known method may be used, and the method is not limited to the above method.

In S108, the ECU 300 calculates the required equalization amount in each of the cells 101a to 101g. Specifically, the ECU 300 calculates an average value using each SOC of the cells 101a to 101g. The ECU 300 calculates the required equalization amount from the excess amount and the shortage amount with respect to the average value in the cells 101a to 101g. For example, when a cell has an excess of ΔSOC (0) with respect to the average value, the ECU 300 calculates the amount of power corresponding to −ΔSOC (0) as the required equalization amount of the cell. Alternatively, for example, when a cell lacks ΔSOC (0) with respect to the average value, the ECU 300 calculates the amount of power corresponding to ΔSOC (0) as the required equalization amount of the cell.

In S110, the ECU 300 determines whether or not the required equalization amount is smaller than the predetermined value. The ECU 300 may determine, for example, whether or not the value having the largest size of the required equalization amounts in each of the cells 101a to 101g is smaller than the predetermined value. Alternatively, the ECU 300 may determine, for example, whether or not the value having the smallest required equalization amount in each of the cells 101a to 101g is smaller than the predetermined value. Alternatively, the ECU 300 may determine, for example, whether or not the average value of the required equalization amounts in each of the cells 101a to 101g is smaller than the predetermined value. The predetermined value is a predetermined value and is adapted by an experiment or the like. When it is determined that the required equalization amount is smaller than the predetermined value (YES in S110), the process is transferred to S112 in the flowchart shown in FIG.

With reference to FIG. 5, in S112, the ECU 300 acquires an energizing current (current flowing through the battery 101). That is, the ECU 300 acquires the current detected by the current sensor 220 as the energizing current.

In S114, the ECU 300 determines whether or not the energizing current is smaller than the predetermined value. The predetermined value is a predetermined value for determining whether or not to execute the thermalization control, and is adapted by an experiment or the like. In the present embodiment, the case where the energizing current is equal to or higher than the predetermined value corresponds to the "first state", and the case where the energizing current is smaller than the predetermined value corresponds to the "second state" in which thermalization is not required. do. When it is determined that the energizing current is smaller than the predetermined value (YES in S114), the process is transferred to S116.

In S116, the ECU 300 sets the supply current I1 from the low temperature cell to the high temperature cell, and controls the adjusting device 102 so that the set supply current I1 flows from the low temperature cell to the high temperature cell.

The ECU 300 identifies, for example, the cell having the highest temperature among the cells 101a to 101f as a high temperature cell. The other 6 cells are identified as cold cells. Therefore, for example, when it is assumed that the current I flows through the battery 101, the ECU 300 adjusts the device 102 so that the current I + I1 flows in the high temperature cell and the current I—I 1/6 flows in each of the other six low temperature cells. To control. The current I + I1 flowing through the high temperature cell corresponds to the target current of the high temperature cell, and the current I-I1 / 6 flowing through each of the low temperature cells corresponds to the target current of the low temperature cell.

For example, when the supply current I1 is set to 12A, the ECU 300 has elapsed a predetermined time after operating the second switching element of the high temperature cell so that an auxiliary current in which the current flowing in the high temperature cell increases by 12A flows. Later, the second switching element is turned off. Then, after a predetermined time has elapsed from turning on the first switching elements 104a to 104g, the first switching elements 104a to 104g are turned off. After that, the second switching element of the low temperature cell is operated so that an auxiliary current in which the current flowing in the low temperature cell of 6 cells decreases by 2 A flows.

In S118, the ECU 300 calculates the integrated value A1 of the supply current I1. The ECU 300 calculates the integrated value A1 (current value) by, for example, adding a value obtained by multiplying the elapsed time from the previous calculation time point and the supply current I1 to the previous value of the integrated value A1. The initial value of the integrated value A1 is zero.

If it is determined in S114 that the energizing current is equal to or higher than a predetermined value (NO in S114), the process is transferred to S120. In S120, the ECU 300 sets the supply current I2 from the high temperature cell to the low temperature cell, and controls the adjusting device 102 so that the set supply current I2 flows from the high temperature cell to the low temperature cell.

The ECU 300 controls the adjusting device 102 so that, for example, when it is assumed that the current I flows through the battery 101, the current I-I2 flows in the high temperature cell and the current I + I1 / 6 flows in each of the other six low temperature cells. do.

For example, when the supply current I2 is set to 12A, the ECU 300 sets the second switching element of the 6-cell low-temperature cell so that an auxiliary current in which the current flowing in each of the 6-cell low-temperature cells increases by 2A flows. After a predetermined time has elapsed from the operation, the second switching element is turned off. Then, after a predetermined time has elapsed from turning on the first switching elements 104a to 104g, the first switching elements 104a to 104g are turned off. After that, the second switching element of the high temperature cell is operated so that an auxiliary current in which the current flowing in the high temperature cell is reduced by 12 A flows.

In S122, the ECU 300 calculates the integrated value A2 of the supply current I2. The ECU 300 calculates the integrated value A2 (current value) by, for example, adding a value obtained by multiplying the elapsed time from the previous calculation time point and the supply current I2 to the previous value of the integrated value A2. The initial value of the integrated value A2 is zero.

In S124, the ECU 300 determines whether or not the value of the integrated value A1-integrated value A2 within the predetermined time is smaller than the predetermined value. For example, the ECU 300 sets the increase of the integrated value A1 and the increase of the integrated value A2 from the time point back by a predetermined time with respect to the present time as the integrated value A1 within the predetermined time and the integrated value A2 within the predetermined time, respectively. The difference is calculated to calculate the integrated value A1-integrated value A2 within a predetermined time. The predetermined value is a predetermined value and is adapted by an experiment or the like. When it is determined that the integrated value A1-integrated value A2 within the predetermined time is smaller than the predetermined value (YES in S124), the process is transferred to S128.

If it is determined that the integrated value A1-integrated value A2 within the predetermined time is equal to or greater than the predetermined value (NO in S124), the process is transferred to S126. In S126, the ECU 300 sets the supply current I1 to zero and controls the adjusting device 102 so that the supply current I1 becomes the set supply current I1.

In S128, the ECU 300 determines whether or not the value of the integrated value A2-integrated value A1 within the predetermined time is smaller than the predetermined value. The predetermined value is a predetermined value and is adapted by an experiment or the like. Therefore, it may be the same value as the predetermined value used in S124, or it may be a different value. When it is determined that the integrated value A2-integrated value A1 within the predetermined time is smaller than the predetermined value (YES in S128), the process is transferred to S132.

When it is determined that the integrated value A2-integrated value A1 in the predetermined time is equal to or greater than the predetermined value (NO in S128), the process is transferred to S130. In S130, the ECU 300 sets the supply current I2 to zero and controls the adjusting device 102 so that the supply current I2 becomes the set supply current I2.

In S132, the ECU 300 estimates the temperature distribution of the cells 101a to 101g in the battery pack 100. Since the method for estimating the temperature distribution is the same as the method for estimating the temperature distribution in the above-mentioned processing of S100, the detailed description thereof will not be repeated.

In S134, the ECU 300 determines whether or not the maximum temperature difference between cells is smaller than a predetermined value. The ECU 300 uses the estimated temperature distribution to identify the hottest cell and the coldest cell among the cells 101a to 101g. The ECU 300 calculates the temperature difference between the two specified cells as the maximum temperature difference between the cells. The predetermined value is a predetermined value and is adapted by an experiment or the like. When it is determined that the maximum temperature difference between cells is smaller than the predetermined value (YES in S132), this process is terminated. If it is determined that the maximum temperature difference between cells is equal to or greater than a predetermined value (NO in S132), the process is returned to S114.

If the required equalization amount is equal to or greater than a predetermined value in S110 of FIG. 4 (NO in S110), the process is transferred to S134 in the flowchart shown in FIG.

With reference to FIG. 6, in S136, the ECU 300 acquires the energizing current. In S138, the ECU 300 determines whether or not the energizing current is smaller than the predetermined value. The predetermined value is the same as the predetermined value in the process of S114. When it is determined that the current flowing through the battery 101 is smaller than the predetermined value (YES in S138), the process is transferred to S140.

In S140, the ECU 300 sets the supply current I1 from the low temperature cell to the high temperature cell, and controls the adjusting device 102 so that the set supply current I1 flows from the low temperature cell to the high temperature cell. Since an example of the specific operation of the adjusting device 102 at this time is as described in the above-mentioned processing of S116, the detailed description thereof will not be repeated.

In S142, the ECU 300 calculates the integrated value A1 of the supply current I1. Since the calculation method of the integrated value A1 is as described in the above-mentioned processing of S118, the detailed description thereof will not be repeated.

If it is determined in S138 that the energizing current is equal to or higher than a predetermined value (NO in S138), the process is transferred to S144. In S144, the ECU 300 sets the supply current I2 from the high temperature cell to the low temperature cell, and controls the adjusting device 102 so that the set supply current I2 flows from the high temperature cell to the low temperature cell. Since an example of the specific operation of the adjusting device 102 at this time is as described in the above-mentioned processing of S120, the detailed description thereof will not be repeated.

In S146, the ECU 300 calculates the integrated value A2 of the supply current I2. Since the calculation method of the integrated value A2 is as described in the above-mentioned processing of S122, the detailed description thereof will not be repeated.

In S148, the ECU 300 determines whether or not the value of the integrated value A1-integrated value A2 within the predetermined time is smaller than the value obtained by adding the required equalization amount to the predetermined value. The predetermined value is the same as the predetermined value in the process of S124. When it is determined that the value of the integrated value A2-integrated value A1 within the predetermined time is smaller than the value obtained by adding the required equalization amount to the predetermined value (YES in S148), the process is transferred to S152.

If it is determined that the integrated value A1-integrated value A2 within the predetermined time is equal to or greater than the value obtained by adding the required equalization amount to the predetermined value (NO in S148), the process is transferred to S150. In S150, the ECU 300 sets the supply current I1 to zero and controls the adjusting device 102 so that the supply current I1 becomes the set supply current I1.

In S152, the ECU 300 determines whether or not the value of the integrated value A2-integrated value A1 within the predetermined time is smaller than the value obtained by adding the required equalization amount to the predetermined value. The predetermined value is the same as the predetermined value for the processing of S128. When it is determined that the value of the integrated value A2-integrated value A1 within the predetermined time is smaller than the value obtained by adding the required equalization amount to the predetermined value (YES in S152), the process is transferred to S156.

If it is determined that the integrated value A2-integrated value A1 within the predetermined time is equal to or greater than the value obtained by adding the required equalization amount to the predetermined value (NO in S152), the process is transferred to S154. In S154, the ECU 300 sets the supply current I2 to zero and controls the adjusting device 102 so that the supply current I2 becomes the set supply current I2.

In S156, the ECU 300 estimates the temperature distribution of the cells 101a to 101g in the battery pack 100. Since the method for estimating the temperature distribution is the same as the method for estimating the temperature distribution in the above-mentioned processing of S100, the detailed description thereof will not be repeated.

In S158, the ECU 300 determines whether or not the maximum temperature difference between cells is smaller than a predetermined value. The predetermined value is the same as the predetermined value in the processing of S134. When it is determined that the maximum temperature difference between cells is smaller than a predetermined value (YES in S158), this process is terminated. If it is determined that the maximum temperature difference between cells is equal to or greater than a predetermined value (NO in S158), the process is returned to S138.

The operation of the battery system 2 according to the present embodiment based on the above structure and the flowchart will be described.

For example, when the vehicle 1 is powered by the MG 10, the battery 101 is in a discharged state. In such a case, the temperature distribution of the cells 101a to 101g in the battery pack 100 is estimated (S100), and the difference in the calorific value between the required cells is calculated (S102). When the difference in calorific value between the required cells is greater than or equal to a predetermined value due to the large temperature difference between the cells 101a to 101g (YES in S104), the full charge capacity of each of the cells 101a to 101g is reached. And SOC are estimated (S106), and the required equalization amount of each of the cells 101a to 101g is calculated (S108). When it is determined that the required equalization amount is smaller than the predetermined value due to the small SOC difference between the cells 101a to 101g (YES in S110), the energizing current is acquired (S112), and the acquired energizing current is predetermined. It is determined whether or not it is smaller than the value (S114).

<When the energizing current is above the specified value>
When it is determined that the energizing current is equal to or higher than a predetermined value (NO in S114), the supply current I2 from the high temperature cell to the low temperature cell is set, and the adjusting device 102 is controlled so that the set supply current I2 flows. (S120). Therefore, since the current of the high temperature cell becomes a value reduced by the supply current I2, the increase in the calorific value is suppressed. On the other hand, since the current of each of the low temperature cells becomes a value increased by the supply current I2 / 6, the increase in the calorific value is promoted. Therefore, thermalization is achieved in the cells 101a to 101g. At this time, the decrease in SOC of the high temperature cell is smaller than the decrease in SOC of each of the low temperature cells.

The integrated value A2 of the supply current I2 is calculated (S122), the integrated value A1-the integrated value A2 within the predetermined time is smaller than the predetermined value (YES in S124), and the integrated value A2- within the predetermined time. When it is determined that the value of the integrated value A1 is smaller than the predetermined value (YES in S128), the temperature distribution of the cells 101a to 101g in the battery pack 100 is estimated (S132). When the maximum temperature difference between cells is smaller than a predetermined value (YES in S134), the thermalization control by the adjusting device 102 is terminated.

When the integrated value A2-integrated value A1 within a predetermined time becomes equal to or more than a predetermined value (NO in S128) due to an increase in the power consumed by the thermalization control, the supply current I2 is zero. Is set to, and the thermalization control is stopped.

<When the energizing current is smaller than the specified value>
When it is determined that the energizing current is smaller than the predetermined value (YES in S114), the supply current I1 from the low temperature cell to the high temperature cell is set, and the adjusting device 102 is controlled so that the set supply current I1 flows. (S116). Therefore, since the current of the high temperature cell becomes a value increased by the supply current I1, the decrease of SOC is promoted. On the other hand, since the current of each of the low temperature cells is reduced by the current I1 / 6, the decrease in SOC is suppressed. Therefore, SOC can be equalized in the cells 101a to 101g.

The integrated value A1 of the supply current I1 is calculated (S118), the integrated value A1-the integrated value A2 within the predetermined time is smaller than the predetermined value (YES in S124), and the integrated value A2- within the predetermined time. When it is determined that the value of the integrated value A1 is also smaller than the predetermined value (YES in S128), the temperature distribution of the cells 101a to 101g in the battery pack 100 is estimated (S132). When the maximum temperature difference between cells is smaller than a predetermined value (YES in S134), the control of the adjusting device 102 is terminated.

<When the required equalization amount is equal to or greater than the specified value>
When it is determined that the required equalization amount is equal to or more than a predetermined value due to the large difference in SOC between the cells 101a to 101g (NO in S110), the energizing current is acquired (S136), and the acquired energization is acquired. It is determined whether or not the current is smaller than the predetermined value (S138).

Then, either the supply current I1 or the supply current I2 is set according to the magnitude of the energizing current, the adjusting device 102 is controlled (S140 or S142), and the integrated value A1 or the integrated value A2 is calculated (the integrated value A1 or the integrated value A2). S144 or S146).

When the supply current I1 and the supply current I2 are set, the control of the adjusting device 102 is performed as much as the required equalization amount (S148 or S152), so that the SOC varies between the cells 101a to 101g. Is suppressed.

As described above, according to the battery system 2 according to the present embodiment, when the energization current is equal to or higher than a predetermined value, the temperature of the low temperature cell can be raised by increasing the calorific value of the low temperature cell. .. Further, by reducing the calorific value of the high temperature cell, it is possible to suppress an increase in the temperature of the high temperature cell. As a result, it is possible to suppress the expansion of the temperature difference between the high temperature cell and the low temperature cell and to achieve thermalization. If such thermalization control is continuously performed, the difference between the SOC of the high temperature cell and the SOC of the low temperature cell may increase. Therefore, when the energizing current is smaller than the predetermined value, it is possible to suppress the expansion of the difference between the SOC of the high temperature cell and the SOC of the low temperature cell by reducing the current of the high temperature cell and increasing the current of the low temperature cell. can. In this way, while trying to homogenize the heat of the cells 101a to 101g in the battery pack 100, by suppressing the variation in the SOC of the cells 101a to 101g, the aged deterioration of the battery capacity can be suppressed and the electric vehicle can run. It is possible to suppress the shortening of the distance. Therefore, it is possible to provide a battery system that suppresses an increase in temperature difference and SOC difference between a plurality of battery elements.

Hereinafter, modification examples will be described.
In the above-described embodiment, an example in which the battery system 2 is applied to an electric vehicle has been described, but the application target of the battery system 2 is not limited to the electric vehicle, and may be, for example, a hybrid vehicle. Further, the use of the battery system 2 is not limited to that for vehicles, and may be, for example, for stationary use.

Further, in the above-described embodiment, the battery 101 has been described as an example of a configuration including seven cells as a power storage element, but the number of cells is not limited to seven.

Further, in the above-described embodiment, the case where the current adjusting circuit is provided for each cell of the battery 101 has been described as an example, but when the battery 101 is provided with a plurality of battery modules including two or more cells as a power storage element, the case is described. , A current adjustment circuit may be provided for each battery module.

Further, in the above-described embodiment, when the energization current is equal to or higher than a predetermined value, the heat equalization control is executed to reduce the calorific value of the high temperature cell and increase the calorific value of the low temperature cell, and the energization current is smaller than the predetermined value. Although it has been described that the equalization control that suppresses the variation in SOC between the high temperature cell and the low temperature cell is sometimes executed, for example, when the discharge current is equal to or higher than a predetermined value (corresponding to the first state), the equalization control is performed. It may be executed, and equalization control for suppressing the variation of SOC of cells 101a to 101g may be executed when the energizing current is the current at the time of charging (corresponding to the second state). In this case, the ECU 300 may reduce the size of the charge amount per unit time for the high temperature cell rather than the size of the charge amount per unit time for the low temperature cell during charging. In this way, the increase in SOC of the low temperature cell whose SOC has decreased by the thermalization control can be made larger than the increase in SOC of the high temperature cell whose SOC has increased by the thermalization control. Therefore, it is possible to suppress variations in SOC of each cell.

Further, in the above-described embodiment, the temperature distribution of the cell is estimated using the detection value of the temperature sensor provided in the cell. For example, the ambient temperature in the battery pack 100, the current load of each cell, and each of them. The temperature distribution of the cell may be estimated from the calorific value from the time of the previous calculation of each cell calculated from the internal resistance value of the cell and the temperature distribution in the previous calculation.

Further, in the above-described embodiment, it has been described as determining whether or not the energization current is equal to or higher than a predetermined value in order to determine whether the state is the first state or the second state. It may be determined whether the accelerator pedal is in the first state or the second state by determining whether or not the amount of depression of the accelerator pedal is larger than the threshold value.

Further, in the above-described embodiment, when the required equalization amount is equal to or more than a predetermined value, the case where the control of the adjusting device 102 is controlled for a long time by the amount of the required equalization amount uniquely set has been described as an example. The current adjusting circuits 150a to 150g may be controlled so as to meet the required equalization amounts of the cells 101a to 101g. By doing so, it is possible to suppress an increase in the difference in SOC between the cells 101a to 101g.

Further, in the above-described embodiment, the cell having the highest temperature among the cells 101a to 101g is regarded as a high temperature cell, the other 6 cells are referred to as a low temperature cell, and a current is exchanged between the high temperature cell and the low temperature cell. However, for example, current may be transferred between the hottest cell and the coldest cell.

In addition, the above-mentioned modification may be carried out by appropriately combining all or a part thereof.
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 vehicle, 2 battery system, 20 power transmission gear, 30 drive wheels, 40 PCI, 50 SMR, 100 battery pack, 101 battery, 101a, 101b, 101c, 101d, 101e, 101f, 101g cell, 102 adjuster, 150a, 150b, 150c, 150d, 150e, 150f, 150g Current adjustment circuit, 210 voltage sensor, 220 current sensor, 230 temperature sensor, 300 ECU, 301 CPU, 302 memory.

Claims (1)

An assembled battery consisting of multiple battery elements connected in series,
An adjusting device connected to each of the battery elements and adjusting the current flowing through each of the battery elements,
Each of the battery elements includes a control device that controls the adjusting device so that the current reaches a target value.
The control device is
When the current flowing through the assembled battery is in the first state, the magnitude of the first target value of the first battery element among the plurality of battery elements is set to a temperature lower than that of the first battery element. 2 Perform thermalization control to reduce the size of the second target value of the battery element.
When the current flowing through the assembled battery is in the second state where the soaking of the battery element is not required more than in the first state, the discharge is larger than the magnitude of the second target value at the time of discharging the assembled battery. The first equalization control that increases the magnitude of the first target value at the time, and the magnitude of the first target value at the time of charging is decreased from the magnitude of the second target value at the time of charging the assembled battery. A battery system that performs either one of the second equalization controls.

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