JP2017112736A - Power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply system where further deterioration is suppressed even when some of a plurality of battery cells are overcharged.SOLUTION: A power supply system 10 includes: a plurality of power converters 32 provided for each of a plurality of battery cells 20 that are aligned in a row in a thickness direction; and a control device 60 for individually controlling operation of the plurality of power converters 32 and changing an SOC for each of the cells 20. The control device 60 estimates the SOC for each of the battery cells 20. When the plurality of battery cells 20 include an overcharged cell that is a battery cell 20 having an estimated SOC equal to or higher than a predetermined overcharge value and a normal cell that is a battery cell 20 having an estimated SOC less than the predetermined value, and a number of the overcharged cells is equal to or less than half a number of the plurality of battery cells, the control device controls operation of the power converter 32 corresponding to the overcharged cell to reduce the SOC of the overcharged cell, and controls operation of the power converter 32 corresponding to the normal cell to increase the SOC of the normal cell.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply system including a battery block having a plurality of battery cells.

  A battery block capable of outputting a high voltage and a large current required for an electric device mounted on a vehicle is configured by connecting a plurality of unit cells called battery cells in series and in parallel. Since the battery block deteriorates when it is overcharged or overdischarged, measures such as prevention of deterioration and recovery from deterioration are required.

  In Patent Document 1, in a battery block having a plurality of battery cells, the charging voltage and charging current of the battery block are set in three stages according to the number of overcharged battery cells and the number of overcharges, and further deterioration is suppressed. Is disclosed. It also states that if even one of the plurality of battery cells is overdischarged, the threshold value for overdischarge of the battery block is raised to make it an unreasonable discharge and further deterioration is suppressed.

  In Patent Document 2, for battery blocks having a plurality of battery cells, each battery cell is expanded by increasing the allowable range of SOC (State Of Charge) indicating the state of charge of the battery cell with little deterioration and internal resistance being less than the average value. It is disclosed that the deterioration of the resin is uniformly promoted. In addition, for the battery block, a bypass circuit is provided for each battery cell, and the overcharged battery cell is bypassed to charge another battery cell, or the overcharged battery cell is bypassed and another battery is bypassed. It is also mentioned that the cell is discharged.

JP 2015-29388 A JP 2013-85315 A

  When the battery block is overcharged, further deterioration can be suppressed by changing the setting of the charging current and discharging current thereafter. Since this method controls charging / discharging in units of the entire battery block, it is effective when all of a plurality of battery cells constituting the battery block are overcharged. However, for example, when only one battery cell becomes an overcharged overcharged cell, it is difficult to suppress further deterioration of the one overcharged cell. Therefore, there is a demand for a power supply system that can suppress further deterioration even when some of the plurality of battery cells become overcharged cells.

  In a power supply system according to one aspect of the present invention, a plurality of battery cells having the characteristic that the dimension in the thickness direction increases as the SOC indicating the state of charge increases, are arranged in a row in the thickness direction. A battery block in which the distance between both ends aligned in a row is restrained by a restraining member, and a plurality of power converters connected to both terminals of the battery cell for each battery cell are electrically connected in series with each other, Power converter blocks having terminals connected to an external charging / discharging device at both ends where the power converters are connected in series, and the operations of the plurality of power converters are individually controlled, and each SOC of the battery cell And a control device that estimates each SOC for each battery cell, and in the plurality of battery cells, the estimated SOC is a battery having a predetermined overcharge predetermined value or more. Cell is over The battery block is a single-cell overcharge type when the number of overcharged cells is less than half of a plurality of normal cells that are battery cells whose estimated SOC is less than a predetermined value. When the single cell overcharge type is selected, the operation of the power converter corresponding to the overcharge cell is controlled to reduce the SOC of the overcharge cell, and the power converter corresponding to the normal cell is controlled. The SOC of the normal cell is increased.

  It is known that deterioration of an overcharged cell progresses as the expansion increases. According to the above configuration, as the characteristic of the battery cell, the dimension in the thickness direction increases as the SOC increases. Therefore, when the SOC of the overcharged cell is decreased to increase the SOC of the normal cell, the thickness direction of the normal cell is increased. The dimension of the overcharged cell is increased and the overcharged cell is pressed. Thus, since the expansion of the overcharged cell is suppressed by the pressing force from the normal cell, further deterioration of the overcharged cell can be suppressed.

  According to the power supply system of the present invention, even when some of the plurality of battery cells become overcharged cells, further deterioration can be suppressed.

It is a block diagram of the power supply system of embodiment which concerns on this invention. It is a figure which shows the relationship between the dimension of the thickness direction in a battery cell used for the power supply system of embodiment which concerns on this invention, and SOC. It is an internal block diagram of the power converter used for the power supply system of embodiment which concerns on this invention. It is a figure which shows the state of the dimension of the thickness direction when a battery cell is overcharged in a battery block. FIG. 4A is a diagram illustrating a state in which all battery cells are overcharged cells, and FIG. 4B is a diagram illustrating a state of single cell overcharge in which only one battery cell is an overcharged cell. is there. It is a flowchart which shows the procedure which suppresses overcharge degradation when the battery block is a single cell overcharge type in the power supply system of embodiment which concerns on this invention. It is a figure which shows an example of the content of the procedure of FIG. It is a flowchart which shows the procedure regarding the reduction process of SOC in FIG. 5, and the increase process of SOC. It is a figure which shows the effect of the suppression method of the overcharge degradation at the time of the single cell overcharge type shown in FIG. FIG. 8A is a diagram showing dimensions in the thickness direction of the overcharged cell before performing the processing for the single cell overcharge type, and FIG. 8B shows the processing for the single cell overcharge type. It is a figure which shows the dimension of the thickness direction of the overcharged cell after.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. Below, the power supply system mounted in a vehicle is described, but this is an example for explanation. If it is a power supply system including a battery block having a plurality of battery cells, it may be used for purposes other than being mounted on a vehicle. For example, a stationary power supply system may be used.

  The shape, dimensions, number, arrangement relationship, and the like described below are examples for explanation, and can be appropriately changed according to the specifications of the power supply system. Below, the same code | symbol is attached | subjected to the same element in all the drawings, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a configuration diagram of a power supply system 10 mounted on a vehicle. The power supply system 10 includes a battery block 12, a power converter block 14, and a control device 60. FIG. 1 shows a charge / discharge device 16 that is not a component of the power supply system 10 but is connected to the power converter block 14.

  The battery block 12 is an assembled battery in which a plurality of battery cells 20 are arranged in a line and are electrically connected in series via the power converter block 14. The battery block 12 is a high-voltage battery that can output a high voltage and a large current necessary for an electric device mounted on the vehicle by connecting a plurality of battery cells 20 in series. In the example of FIG. 1, only eight battery cells 20 are illustrated, but as a whole, for example, ten or more battery cells 20 are arranged in a line to constitute the battery block 12. Hereinafter, it is assumed that the battery block 12 includes 40 battery cells 20. The number of the battery cells 20 is an example, and may be other than 40. As a special example, two battery cells 20 may be used.

  The battery cell 20 is a thin plate unit cell having a substantially rectangular side wall. The plurality of battery cells 20 are arranged in a line along the thickness direction of the thin plate to form the battery block 12. FIG. 1 shows the thickness direction of the battery block 12. The thickness direction is the direction of the thin plate-like thickness of the battery cell 20, but is also the alignment direction of the plurality of battery cells 20 in the battery block 12.

  Each battery cell 20 has a positive electrode terminal 22 and a negative electrode terminal 24. The voltage between both ends of the positive electrode terminal 22 and the negative electrode terminal 24 is about 1V to 4V, although it varies depending on the type of the unit cell. As the type of the single battery, a lithium ion battery, a nickel metal hydride battery, or the like can be used.

  Both-end voltage, charge / discharge current, temperature, and the like of the 40 battery cells 20 constituting the battery block 12 are transmitted to the control device 60 as SOC information 18 using an appropriate signal line.

  The thin plate-like battery cell 20 having a substantially rectangular side wall has a characteristic that the dimension in the thickness direction increases as the SOC increases due to an electrochemical reaction inside. In FIG. 2, the relationship between the dimension of the thickness direction of the battery cell 20 and SOC is shown. The horizontal axis of FIG. 2 is the SOC, and the vertical axis is the dimension of the battery cell 20 in the thickness direction. The dimension in the thickness direction of the battery cell 20 increases as the SOC increases, but has a non-linear characteristic in which the increase in the dimension in the thickness direction gradually decreases as the SOC increases.

  The restraint plates 26 and 27 are flat plates respectively disposed at both end portions in which 40 battery cells 20 are aligned in a row. The restraining members 28 and 29 are elongated members that join between the restraining plates 26 and 27 on the terminal side of the 40 battery cells 20. Similarly, the restraining members 30 and 31 are elongate members that join between the restraining plates 26 and 27 on the bottom surface side opposite to the terminal side of the 40 battery cells 20. Since the restraining plates 26 and 27 are coupled by the restraining members 28, 29, 30, and 31, the distance between both ends of the plurality of battery cells 20 aligned in one row is restrained to a predetermined value L0 (see FIG. 4). .

  Due to this restraining action, even if the SOC of each of the plurality of battery cells 20 varies due to charging and discharging, the overall dimension along the thickness direction of the battery block 12 is maintained at a constant value. In other words, the plurality of battery cells 20 change in the thickness direction according to the characteristics shown in FIG. 2 as the SOC changes due to charging / discharging, but the change in the thickness direction is suppressed by the constraint action. The For example, when the SOC of all the battery cells 20 increases, all the battery cells 20 receive a pressing force in the thickness direction due to the restraining action.

  The power converter block 14 includes the same number of power converters 32 as the number of battery cells 20. In the example of FIG. 1, since the number of battery cells 20 is 40, the power converter block 14 includes 40 power converters 32. The 40 power converters 32 have the same configuration.

  FIG. 3 shows the internal configuration of one power converter 32. The power converter 32 is a small DCDC converter. The power converter 32 has four terminals 34, 36, 38 and 40. One power converter 32 is arranged corresponding to one battery cell 20, the terminal 34 of the power converter 32 is connected to the positive terminal 22 of the battery cell 20, and the terminal 36 is the negative terminal of the battery cell 20. 24.

  The 40 power converters 32 are electrically connected in series with each other using the terminals 38 and 40 of each power converter 32. In the example of FIG. 1, of the 40 power converters 32 connected in series, the two adjacent power converters 32 of the power converter 32 on one side are excluded except for the power converters 32 a and 32 b at both ends. The terminal 40 and the terminal 38 of the power converter 32 on the other side are electrically connected to each other. The terminal 38 of the power converter 32a and the terminal 40 of the power converter 32b are drawn out to be the one side terminal 50 and the other side terminal 52 of the power converter block 14, respectively. The one side terminal 50 is connected to the positive electrode side terminal of the charging / discharging device 16, and the other side terminal 52 is connected to the negative electrode side terminal of the charging / discharging device 16.

  The power converter 32 includes a coil 42, two switching elements 44 and 46, and a capacitor 48 inside. The coil 42 and the switching element 44 are connected in series with each other and are disposed between the terminal 36 and the terminal 38. The switching element 46 is disposed between a connection point between the coil 42 and the switching element 44 and the terminal 36. The capacitor 48 is provided between the terminal 38 and the terminal 40.

  Switching elements 44 and 46 each include a semiconductor transistor that operates under the control of control device 60 and a diode that is reversely connected to the semiconductor transistor. The diode reversely connected to the semiconductor transistor indicates that the diode is connected so that current flows in a direction opposite to the direction of current that flows when the semiconductor transistor is on. In FIG. 3, since an N-channel MOS transistor is used as the semiconductor transistor, the cathode of the diode is connected to the drain of the N-channel MOS transistor, and the anode of the diode is connected to the source of the N-channel MOS transistor. Details of the operation and action of the power converter 32 will be described later.

  The charging / discharging device 16 is connected in parallel between the one side terminal 50 and the other side terminal 52 of the power converter block 14. The charging / discharging device 16 includes a charging power source that supplies a charging current to the battery block 12 via the power converter block 14 and a discharging load that receives the discharging current from the battery block 12 via the power converter block 14. It is. Charging / discharging device 16 includes a rotating electrical machine 54 and an inverter 56. The rotating electrical machine 54 is a motor / generator (MG) serving as a drive source for the vehicle. The motor / generator is a three-phase synchronous rotating electric machine that functions as a motor when electric power is supplied from the battery block 12 and functions as a generator during braking of the vehicle. The inverter 56 is a circuit that performs AC / DC conversion between the DC power of the battery block 12 and the three-phase AC power of the rotating electrical machine 54. The AC / DC conversion includes conversion of DC power of the battery block 12 into three-phase AC power of the rotating electric machine 54 or conversion of three-phase AC power of the rotating electric machine 54 into DC power of the battery block 12. Inverter 56 includes a plurality of switching elements and a plurality of diodes.

  As the charging / discharging device 16, a DC power source such as a power storage device, an AC power source such as a commercial power source, a load device such as an electric device, or the like can be used instead of or in addition to the combination of the rotating electrical machine 54 and the inverter 56. . For example, when the vehicle is a plug-in hybrid vehicle that receives power supply from a charging station or the like, a power supply device in the charging station or the like is used as the charging / discharging device 16. In addition, in a vehicle having a power output port that can supply power to an external load, the external load becomes a discharge load in the charge / discharge device 16.

  The control device 60 acquires the SOC information 18 from the battery block 12 and communicates with the power converter block 14 to control the operation of the power supply system 10 as a whole. As the control device 60, a computer suitable for mounting on a vehicle is used.

  The control device 60 includes a power converter control unit 62 that individually controls the 40 power converters 32 constituting the power converter block 14. Furthermore, in order to suppress further deterioration when the battery cell 20 is overcharged, the SOC estimation unit 64, the single cell overcharge type determination unit 66, and suppression of overcharge deterioration when the single cell overcharge type is used. And a processing unit 68. Hereinafter, suppression of further deterioration of the overcharge cell in the single cell overcharge type is referred to as suppression of overcharge deterioration unless otherwise specified. These functions are realized by causing the control device 60, which is a computer, to execute software. Specifically, it is realized by causing the control device 60 to execute an overcharge deterioration suppression program.

  The power converter control unit 62 controls on / off of the switching elements 44 and 46 in the power converter 32 and controls increase or decrease of the SOC of the battery cell 20 connected to the power converter 32. The operation and action of the power converter 32 under the control of the power converter control unit 62 will be described with reference to FIG.

As shown in FIG. 3, the voltage across the capacitor 48 is V _OUT , the charge / discharge current flowing through the capacitor 48 is I _OUT , the voltage across the battery cell 20 is V _B , and the charge / discharge current of the battery cell 20 is I _B. . In the two adjacent power converters 32, the terminal 40 of the power converter 32 on one side and the terminal 38 of the power converter 32 on the other side are electrically connected to each other. Capacitors 48 are connected in series. Thus, the 40 power converters 32 are connected in series in an alternating manner. In the 40 capacitors 48, I _OUT has the same value and the same value as the charging current from the charging / discharging device 16 or the discharging current to the charging / discharging device 16.

Assuming that there is no internal loss in the power converter 32, (V _OUT × I _OUT ) = (V _B × I _B ). When this is rewritten, I _B = {(V _OUT × I _OUT ) / V _B }, so that the charge / discharge current I _B of the battery cell 20 can be controlled by controlling V _OUT . About 40 of the power converter 32, the voltage across V _OUT of each of the capacitors 48 by controlling individually, can control the charge and discharge current I _B of 40 battery cells 20, thereby, 40 battery cells The 20 SOCs can be increased or decreased individually. The voltage V _OUT across the capacitor 48 in the power converter 32 can be controlled by the same control method as a general boost converter having the coil 42 and the two switching elements 44 and 46.

In the power converter 32 of FIG. 3, when the switching element 46 is turned on and the switching element 44 is turned off, the discharge current I _B from the battery cell 20 flows into the coil 42 and is stored in the coil 42 as electromagnetic energy. As a result, (potential at the connection point between the coil 42 and the switching element 44) gradually increases, {(potential at the connection point between the switching element 44 and the terminal 38) + (order of the diode reversely connected to the switching element 44). Direction rising voltage)}. When the switching element 46 is turned off in this state, the electromagnetic energy accumulated in the coil 42 flows to the capacitor 48. By repeating this, the voltage V _OUT across the capacitor 48 gradually increases. As described above, the battery cell 20 is discharged by the boost control for increasing V _OUT, and the SOC of the battery cell 20 decreases.

On the other hand, when the switching element 46 is turned off and the switching element 44 is turned on, a charging current flows from the capacitor 48 to the battery cell 20 via the coil 42. In this way, the battery cell 20 is charged by the step-down control that causes the current to flow out of the capacitor 48 and drop V _OUT, and the SOC of the battery cell 20 increases.

  In summary, the SOC of the battery cell 20 increases according to the charging time that is the time for which the switching element 44 is turned on, and the SOC of the battery cell 20 decreases according to the discharge time that is the time for which the switching element 46 is turned on. . Since charging and discharging of one battery cell 20 do not occur simultaneously, the switching element 46 is turned off when the switching element 44 is turned on, and the switching element 44 is turned off when the switching element 46 is turned on. Therefore, when the charge time ratio is increased and the discharge time ratio is decreased in the cycle time of charge / discharge control, the SOC of the battery cell 20 is increased. Conversely, when the charge time ratio is decreased and the discharge time ratio is increased, the battery The SOC of the cell 20 is reduced. If there is a period in which the switching elements 44 and 46 are simultaneously turned on, the terminals 38 and 40 are short-circuited and an excessive through current flows. Therefore, in switching the switching elements 44 and 46 on and off, the switching elements 44 and 46 are switched. Are provided with a dead time period during which both are turned off. In this case, (charge time ratio + discharge time ratio) <1.

  In this manner, by setting the charging time ratio and the discharging time ratio for the switching elements 44 and 46, the increase / decrease in the SOC of the battery cell 20 can be controlled. Since the power converter 32 is provided for each battery cell 20, by controlling the charging time ratio and the discharging time ratio for each of the 40 power converters 32, the SOC of each of the 40 battery cells 20 is controlled. Increase / decrease can be controlled. When both the switching element 44 and the switching element 46 are turned off, the battery cell 20 is disconnected from the capacitor 48, and the terminals 38, 40 and the battery cell 20 are also disconnected. Even at this time, since the terminal 38 and the terminal 40 are connected by the capacitor 48, an AC connection state is maintained between the adjacent power converters 32.

  Next, the SOC estimation unit 64, the single cell overcharge type determination unit 66, and the overcharge deterioration suppression processing unit 68 for suppressing further deterioration when the battery cell 20 becomes the single cell overcharge type will be described with reference to FIG. Will be described with reference to FIG.

  First, the meaning of the single cell overcharge type will be described. FIG. 4 is a schematic diagram showing the difference between a general overcharge and a single cell overcharge type. FIG. 4 is a diagram showing a state of the dimension in the thickness direction when the battery cell 20 is overcharged in the battery block 12. Hereinafter, the battery cell 20 that is overcharged is referred to as an overcharge cell 20A, and the battery cell 20 that is not overcharged is referred to as a normal cell 20S.

  FIG. 4A is a diagram illustrating a case where all the battery cells 20 are overcharged cells 20A, and this is called general overcharge. (B) is a diagram showing a case where only one battery cell 20 becomes the overcharge cell 20A, but each remaining battery cell 20 remains a normal cell 20S, which is called "single cell overcharge". . In these drawings, the interval between the constraining plates 26, 27 is fixed to a predetermined value L0 by the constraining members 28-31.

  In FIG. 4A, since all the battery cells 20 are overcharge cells 20A, as described in FIG. 2, all the overcharge cells 20A try to expand in the thickness direction. However, since the interval between the constraining plates 26 and 27 is a predetermined value L0, all the overcharged cells 20A are pressed against each other in the thickness direction. Thereby, the expansion in the thickness direction of each overcharge cell 20A is suppressed, and the dimension in the thickness direction of all the overcharge cells 20A is only slightly increased.

  On the other hand, in FIG. 4B, since only one battery cell 20 is the overcharge cell 20A, the one overcharge cell 20A tends to expand in the thickness direction. The other battery cell 20 is the normal cell 20S, and the dimension in the thickness direction remains the same. Also at this time, since the interval between the constraining plates 26 and 27 facing each other is a predetermined value L0, one overcharged cell 20A receives almost no pressing force from the other normal cells 20S. Thereby, only one overcharge cell 20A expands in the thickness direction, and the dimension in the thickness direction of one overcharge cell 20A increases considerably compared to the case of FIG.

  The battery cell 20 is in an overcharge deterioration state in which the battery characteristics deteriorate in the overcharge state. It is known that when the battery cell 20 expands in the overcharged state, the overcharge deterioration further progresses compared to when it does not expand, and it is preferable to apply a pressing force so as to suppress the expansion in the overcharged state. As shown in FIG. 4A, when all 40 battery cells 20 constituting the battery block 12 are overcharge cells 20A, the restraint action of the restraint plates 26 and 27 suppresses the expansion of each overcharge cell 20A. Further progress of deterioration is suppressed. On the other hand, as shown in FIG. 4B, when one of the 40 battery cells 20 constituting the battery block 12 becomes the overcharge cell 20A, there is a restraining action of the restraining plates 26 and 27. However, the expansion of the overcharged cell 20A is not suppressed, and further deterioration proceeds.

  In the above, the example in which only one of the 40 battery cells 20 constituting the battery block 12 is the overcharge cell 20A has been described. Even if the number of overcharge cells 20A is not one but several, compared with the case where only one is the overcharge cell 20A, the expansion of the overcharge cell 20A is suppressed by the restraining action. The overcharge cell 20A expands in the thickness direction, and further deterioration proceeds. Thus, in the battery block 12, regardless of the number of the overcharged cells 20A, a single cell overcharged type in which the overcharged cells expand and further deterioration proceeds. In general, the single cell overcharge type is a case where overcharged cells 20A and normal cells 20S are mixed in 40 battery cells 20. When the number of overcharge cells 20A is larger than the number of normal cells 20S, the effect of the overcharge cells 20A pressing against each other is great. Hereinafter, it is assumed that the battery block 12 is of a single cell overcharge type when half or less of the plurality of battery cells 20 of the battery block 12 are overcharge cells 20A. When the number is 40, the number of overcharge cells 20A is 20 or less and the number of normal cells 20S is 20 or more is defined as a single cell overcharge type. When the number is two, one is the overcharge cell 20A and one is the normal cell 20S.

  FIG. 5 is a flowchart showing a procedure for suppressing further deterioration in the single cell overcharge type. Each procedure corresponds to each processing procedure of the overcharge deterioration suppression program executed by the control device 60. When the overcharge deterioration suppression program is started in the control device 60, the state of each element of the power supply system 10 is initialized. Thereafter, the SOC of each battery cell 20 is estimated (S10). This processing procedure is executed by the function of the SOC estimation unit 64 of the control device 60.

The estimation of the SOC of each battery cell 20 is performed based on the SOC information 18 transmitted from the battery block 12. Since the SOC information 18 includes charging current or discharging current data of each battery cell 20 every moment, the integrated value of (discharge current × discharge time) is subtracted from the integrated value of (charge current × charge time). The SOC of each battery cell 20 is estimated. The estimated SOC and SOC _1. Instead of this method, when an open circuit voltage (OCV), which is a voltage when each battery cell 20 is unloaded, is included, the SOC of each battery cell 20 is estimated based on the OCV. Good. Other suitable SOC estimation methods can also be used.

Next, based on the estimated SOC ₁ data of each battery cell 20, it is determined whether or not the battery block 12 is a single cell overcharge type (S12). This processing procedure is executed by the function of the single cell overcharge type determination unit 66 of the control device 60. Specifically, when the overcharged cell 20A is less than half of the plurality of battery cells 20 constituting the battery block 12, it is determined as the single cell overcharge type. Battery cell 20 in the determination Kano overcharged cell 20A or normal cell 20S, using SOC _th is a predetermined value for overcharge determined in advance with respect to SOC ₁ of battery cells 20. When the SOC ₁ is _{equal to} or higher than the SOC _th , the overcharge cell 20A is set, and when the SOC ₁ is _lower than the SOC _th , the normal cell 20S is set. For example, the SOC ₁ of the first battery cell 20 is compared with the SOC _th in the order arranged in series, and if it is the normal cell 20S, the SOC of the second and subsequent battery cells 20 is output until the overcharge cell 20A comes out. ₁ is sequentially compared with SOC _th . If one overcharge cell 20A comes out, it is determined that the battery block 12 is a single cell overcharge type, and the process proceeds to the next procedure. When all of the 40 battery cells 20 are normal cells 20S, the procedure for suppressing overcharge deterioration is terminated.

If it is determined in S12 that it is a single cell overcharge type, then each battery cell 20 is classified into an overcharge cell 20A or a normal cell 20S (S14). This procedure is performed by determining whether or not each SOC ₁ is greater than or _equal to SOC _th for 40 battery cells 20 (S16). When the determination in S16 is affirmative, the battery cell 20 is set as an overcharged cell 20A (S18), and when the determination in S16 is negative, the battery cell 20 is set as a normal cell 20S (S22).

FIG. 6 shows an example of the processing of S12, S14, S16, S18, S20, and S22. In this example, about 40 battery cells 20, a battery cell number is attached | subjected with C1-C40 in the order arranged in series. Then, assuming that the predetermined value SOC _th for overcharging is 70%, the SOC ₁ of each battery cell 20 is compared with the SOC _{th in} order from C1 for 40 battery cells 20. From the battery cell number C1 to C6 is SOC ₁ is smaller than SOC _th, next SOC ₁ = 75% in cell number C7, SOC _th or more overcharge cell 20A is currently Waru. Thus, the determination in S12 is affirmed, and it is determined that the battery block 12 is a single cell overcharge type. Therefore, SOC ₁ is obtained for each of the battery cell numbers C1 to C40. FIG. 6 shows SOC ₁ for battery cell numbers C5 to C9 in the vicinity of the overcharge cell 20A. Based on this result, the battery cells 20 in S14 and S16 are classified. In FIG. 2, the battery cell numbers C5, C6, C8, and C9 are normal cells 20S, and the battery cell number C7 is an overcharged cell 20A.

  Returning to FIG. 5 again, the SOC reduction process is performed for the overcharged cell 20A in S18 (S22), and the SOC increase process is performed for the normal cell 20S in S20 (S24). This processing procedure is executed by the function of the overcharge deterioration suppression processing unit 68 of the control device 60. Here, a pressing force is applied in the thickness direction of the overcharged cell 20A by increasing the dimension in the thickness direction of the normal cell 20S caused by the increase in the SOC of the normal cell 20S, and the thickness direction due to the overcharge of the overcharged cell 20A is increased. The increase in size is suppressed, and further deterioration of battery characteristics is suppressed.

  FIG. 7 is a flowchart illustrating a procedure in which SOC reduction or increase processing is performed. In S30, it is determined whether it is necessary to cope with the single cell overcharge type. Here, when the determination of S12 in FIG. 5 is affirmed, the response to the single cell overcharge type is required, and when the determination of S12 is negative, the response to the single cell overcharge type is not required. . In the example of FIG. 6, since the determination of S12 is affirmed, the determination of S30 is also affirmed.

  Next, the overcharge cell 20A is subjected to a process of bringing the charge time ratio closer to 0 and simultaneously increasing the discharge time ratio (S32). This process corresponds to S22 in FIG. 5 and decreases the SOC of the overcharged cell 20A.

On the other hand, with respect to the normal cell 20S, whether or not SOC _{1 of the} normal cell 20S is less than SOC ₀ using SOC ₀ that is a predetermined value that is a target of the SOC increase processing in the processing corresponding to the single cell overcharge type. Is determined (S34). If the determination in S34 is negative, the procedure for performing the SOC increasing process is terminated. If the determination in S34 is affirmative, a process for increasing the charging time ratio and simultaneously decreasing the discharging time ratio for the normal cell 20S is performed (S36). This process corresponds to S24 in FIG. 5 and increases the SOC of the normal cell 20S. This process is performed in a range where the increased SOC does not become SOC ₀ or more.

When the charging time ratio and the discharging time ratio are set for each battery cell 20 in S32 and S34, the duty control of the switching elements 44 and 46 in the power converter 32 corresponding to each battery cell 20 is performed based on these. Is executed (S38). The duty is the ratio of the ON time of the switching elements 44 and 46 to the cycle time of charge / discharge control. The duty for the switching element 44 corresponds to the charge time ratio, and the duty for the switching element 46 corresponds to the discharge time ratio. By executing S38, the SOC of the overcharged cell 20A decreases from the initial SOC ₁ , and the SOC of the normal cell 20S increases from the initial SOC ₁ .

FIG. 6 shows the SOC after the processing corresponding to the single cell overcharge type. Here, the SOC of the battery cell 20 with the battery cell number C7, which is the overcharge cell 20A, decreases from the initial SOC ₁ = 75% to 45% after the processing corresponding to the single cell overcharge type. In addition, the SOC of the battery cells 20 with the battery cell numbers C5, C6, C8, and C9, which are the normal cells 20S, is changed from the initial SOC ₁ = 60% to 65% after the processing corresponding to the single cell overcharge type. Increase. This value is increased to the full limit with SOC ₀ being a predetermined value as a target of the SOC increase processing at the time of overcharge being 65%.

  FIG. 8 is a diagram showing the operational effect of the method for suppressing overcharge degradation in the single cell overcharge type shown in FIG. FIG. 8A is a diagram showing the dimension in the thickness direction of the overcharged cell 20A before performing the processing corresponding to the single cell overcharge type, and FIG. 8B shows the processing corresponding to the single cell overcharge type. It is a figure which shows the dimension of the thickness direction of 20 A of overcharge cells after performing. These figures correspond to FIG. 4 and show battery cell numbers C5 to C9 in the example of FIG. C7 is an overcharge cell 20A, and C5, C6, C8, and C9 are normal cells 20S. Before the processing for the single cell overcharge type is performed, the overcharged cell 20A is considerably expanded in the thickness direction. On the other hand, when the processing for the single cell overcharge type is performed, another normal cell 20S is processed. The expansion of the overcharge cell 20A is suppressed in response to the pressing force from. Thereby, further deterioration of the overcharge cell 20A is suppressed.

  DESCRIPTION OF SYMBOLS 10 Power supply system, 12 Battery block, 14 Power converter block, 16 Charging / discharging apparatus, 18 SOC information, 20 Battery cell, 20A Overcharge cell, 20S Normal cell, 22 Positive terminal, 24 Negative terminal, 26, 27 Restraint plate, 28, 29, 30, 31 Restraining member, 32, 32a, 32a, 32b Power converter, 34, 36, 38, 40 terminal, 42 Coil, 44, 46 Switching element, 48 Capacitor, 50 One side terminal, 52 The other side Terminal, 54 Rotating electric machine, 56 Inverter, 60 Control device, 62 Power converter control unit, 64 SOC estimation unit, 66 Single cell overcharge type determination unit, 68 Overcharge deterioration suppression processing unit.

Claims (1)

A plurality of battery cells having a characteristic that the dimension in the thickness direction increases as the SOC indicating the state of charge increases, and are arranged in a row in the thickness direction, and the interval between both ends aligned in the row is constrained. A battery block restrained by a member;
For each battery cell, a plurality of power converters connected to both terminals of the battery cell are electrically connected in series with each other, and a plurality of the power converters are connected to the external charging terminals at both ends connected in series. A power converter block having terminals connected to the discharge device;
A control device for individually controlling the operation of the plurality of power converters and individually changing the SOC of each of the battery cells;
With
The controller is
Estimating the respective SOC for each battery cell;
In the plurality of battery cells, the estimated SOC is an overcharged cell that is equal to or greater than a predetermined value for overcharging, and the estimated SOC is the battery cell that is less than the predetermined value. When the number of the overcharge cells is less than half of the plurality of cells, the battery block is a single cell overcharge type,
When the single cell overcharge type is selected, the operation of the power converter corresponding to the overcharge cell is controlled to reduce the SOC of the overcharge cell, and the power converter corresponding to the normal cell To increase the SOC of the normal cell.

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