Battery administrative system

Abstract

To suppress an overdischarge of a single battery (a battery cell) while suppressing a deviation between an actual SOC and an estimation SOC.SOLUTION: At a time t1, when the maximum voltage difference MAX [ΔVB] of a voltage difference ΔVB of a single battery becomes a predetermined value or larger, a pull-up quantity k is calculated on the basis of a SOC different of a battery at that time, a SOC control center of the battery is increased by the pull-up quantity k, and the SOC control center is pulled-up (is increased). At a time t4, when a timer T exceeds a resolution time H, the pulling-up of the SOC control center is stopped.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a battery management system. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2000-14029 (Patent Document 1) discloses a battery control device having a battery pack in which multiple battery blocks are connected in series. This battery control device issues a request to charge the battery when the voltage difference between the battery blocks reaches or exceeds a predetermined value. By issuing a charge request, subsequent discharge is prohibited, the charged state of the battery pack can be restored, and in particular, over-discharge of one battery cell in the battery pack can be prevented. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-14029 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the battery control device of Patent Document 1, when the voltage difference between each battery block becomes equal to or greater than a predetermined value, the SOC (State Of Charge) of the assembled battery is reset to a control lower limit value, and a charging request is issued. Then, based on the SOC reset to the control lower limit value, the subsequent SOC is calculated by current measurement. For this reason, there is a possibility that a discrepancy will occur between the actual SOC of the assembled battery and the calculated SOC (estimated SOC).

[0005] An object of the present disclosure is to suppress over-discharge of a single battery (battery cell) while suppressing the deviation between the actual SOC and the estimated SOC. [Means for solving the problem]

[0006] A battery management system according to the present disclosure includes a battery pack having multiple cells connected in series, and a control device that controls charging and discharging of the battery pack so that the SOC of the battery pack is within a first predetermined range centered on an SOC control center. The control device acquires an SOC difference, which is the SOC when a voltage difference between the multiple cells becomes equal to or greater than a predetermined value, calculates an SOC increase amount based on the SOC difference, and controls charging and discharging so that the SOC of the battery pack is within a second predetermined range centered on a value obtained by adding the SOC increase amount to the SOC control center for a predetermined period of time from when the voltage difference becomes equal to or greater than the predetermined value.

[0007] According to this configuration, the control device controls the charging and discharging of the battery pack so that the SOC of the battery pack is within a first predetermined range centered on the SOC control center. When the voltage difference between the cells is equal to or greater than a predetermined value, the cell with the lower voltage may be over-discharged, and therefore it is preferable to charge the cell. The control device obtains an "SOC difference," which is the SOC when the voltage difference between the cells is equal to or greater than the predetermined value, and calculates an amount of SOC increase based on the "SOC difference." Then, the control device controls the charging and discharging of the battery pack so that the SOC of the battery pack is within a second predetermined range centered on a value obtained by adding the amount of SOC increase to the SOC control center, for a predetermined period of time from when the voltage difference is equal to or greater than the predetermined value.

[0008] When the battery pack is charged and discharged so that the SOC of the battery pack is within the second predetermined range, charging of the cells is promoted, over-discharging of the cells can be suppressed, and the battery pack is used in a region (high SOC region) where the SOC is higher than the first predetermined range. The higher the SOC, the greater the self-discharge amount of the cells. By using the battery pack in the high SOC region for a predetermined period of time, the self-discharge amount of the high-voltage (high SOC) cells increases, and the voltage difference between the cells can be eliminated (reduced). Since the SOC increase amount is calculated based on the "SOC difference", the battery pack can be used in a high SOC region according to the voltage difference between the cells, and the voltage difference between the cells can be eliminated (reduced). In addition, since the SOC of the battery pack is not reset, the deviation between the actual SOC and the estimated SOC can be suppressed. Effect of the Invention

[0009] According to the present disclosure, it is possible to suppress the deviation between the actual SOC and the estimated SOC while suppressing over-discharge of a single battery (battery cell). [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a configuration of a hybrid vehicle equipped with a battery system according to an embodiment of the present invention. [Diagram 2] 4 is a flowchart showing an example of a SOC control center raising process executed by an HV-ECU. [Diagram 3] 4 is a time chart according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and the description thereof will not be repeated.

[0012] FIG. 1 is a diagram showing the configuration of a hybrid vehicle equipped with a battery system. The hybrid vehicle V includes an internal combustion engine 10, a first motor generator (hereinafter referred to as "first MG") 20, a second motor generator (hereinafter referred to as "second MG") 30, a power split device 40, a PCU (Power Control Unit) 50, and a battery 60. The power split device 40 is formed of a planetary gear mechanism. An output shaft 11 of the internal combustion engine 10 is connected to an input shaft 41 that rotates integrally with a carrier of the power split device 40. A rotor of the first MG 20 is connected to a sun gear of the power split device 40. A rotor of the second MG 30 is connected to an output shaft 42 that rotates integrally with a ring gear of the power split device 40. The power split device 40 splits the power output from the internal combustion engine 10 into power for driving the first MG 20 and power for driving drive wheels 80.

[0013] The first MG 20 and the second MG 30 are AC rotating electric machines, for example, interior permanent magnet synchronous motors (IPM motors), and have a function as an electric motor (motor) and a function as a generator (generator). The first MG 20 is mainly used as a generator driven by the internal combustion engine 10 via the power split device 40. Electric power generated by the first MG 20 is supplied to the second MG 30 or the battery 60 via the PCU 50. The second MG 30 mainly operates as an electric motor and drives the drive wheels 80 via the differential gear 70. The second MG 30 is driven by receiving at least one of electric power from the battery 60 and electric power generated by the first MG 20. On the other hand, when the hybrid vehicle V is braking or going downhill, the second MG 30 operates as a generator to perform regenerative power generation. The electric power generated by the second MG 30 is collected by the battery 60 via the PCU 50.

[0014] The PCU 50 converts the DC power received from the battery 60 into AC power for driving the first MG 20 and the second MG 30. The PCU 50 converts the AC power generated by the first MG 20 and the second MG 30 into DC power for charging the battery 60.

[0015] The battery 60 is an assembled battery in which a plurality of electric cells (battery cells) 5 are connected in series. In this embodiment, the battery 60 (assembled battery) is a bipolar nickel-metal hydride battery. The battery 60 includes an electric cell 5 in which an electrode plate (metal foil, current collector) 1, a negative electrode (negative electrode active material) 2, a separator 4, a positive electrode (positive electrode active material) 3, and an electrode plate 1 are stacked in this order. The plurality of electric cells 5 are stacked (connected in series) while sharing the electrode plate 1 to form the battery 60 (assembled battery). The positive electrode active material may be nickel hydride, and the negative electrode active material may be a hydrogen storage alloy.

[0016] The battery 60 is provided with a monitoring module 61. The monitoring module 61 includes a voltage sensor that detects the voltage VB of the single cell 5, and a current sensor and a temperature sensor that detect the input / output current IB and temperature TB of the battery 60. The monitoring module 61 outputs the detection values ​​of each sensor to an HV-ECU (Electronic Control Unit) 100. The monitoring module 61 also calculates the SOC of the battery 60 and outputs it to the HV-ECU 100.

[0017] The hybrid vehicle V includes an HV-ECU 100, an MG-ECU 200, an EG-ECU 300, and various sensors 400. The ECUs are configured to be able to communicate with each other via a CAN (Controller Area Network).

[0018] The HV-ECU 100 executes a predetermined calculation process based on information from the various sensors 400 and information from the monitoring module 61. The HV-ECU 100 outputs various commands to the MG-ECU 200 and the EG-ECU 300 based on the results of the calculation process. The MG-ECU 200 controls the PCU 50, and controls the first MG 20 and the second MG 30. The EG-ECU 300 controls the internal combustion engine 10.

[0019] When a start switch (power switch or ignition switch) (not shown) is turned ON to start the hybrid vehicle V, the HV-ECU 100 is started and goes into a Ready-ON state. In the Ready-ON state, the HV-ECU 100 closes (ON) a system main relay (SMR) 62 provided in a power line connecting the battery 60 and the PCU 50, enabling power to be exchanged between the battery 60 and the PCU 50. When the start switch is turned OFF, the HV-ECU 100 opens (OFF) the SMR 62, cutting off the electrical connection between the battery 60 and the PCU 50, and goes into a Ready-OFF state.

[0020] For driving control of the hybrid vehicle V, the HV-ECU 100 calculates a required drive torque Tr based on, for example, the accelerator opening AP, the vehicle speed SPD, etc., and multiplies the required drive torque Tr by the rotation speed of the drive wheels 80 to obtain a required power Pd. The HV-ECU 100 subtracts a charge / discharge power Pb (a positive value when discharging from the battery 60) based on the SOC of the battery 60 from the required power Pd to set a required power Pe required of the internal combustion engine 10. Then, the target engine rotation speed Ne*, the target engine torque Te*, the command torque Tm1 of the first MG 20, and the command torque Tm2 of the second MG 30 are set so that the required power Pe is output from the internal combustion engine 10 and the required drive torque Tr is output to the drive wheels 80. The HV-ECU 100 outputs a command to the EG-ECU 300 to operate the internal combustion engine 10 at the target engine speed Ne* and target engine torque Te*, and outputs a command to the MG-ECU 200 to drive the first MG 20 and the second MG 30 at command torques Tm1 and Tm2.

[0021] The HV-ECU 100 uses the control SOCi to control charging and discharging the battery 60. The control SOCi is a value obtained by correcting the SOC calculated by the monitoring module 61. In the charging and discharging control, the control SOCi is controlled to be within a range between an upper limit value Xi and a lower limit value Yi. For example, during driving, the charging and discharging power Pb is calculated so that the battery 60 is charged when the control SOCi falls below the lower limit value Yi, and the battery 60 is discharged when the control SOCi exceeds the upper limit value X1.

[0022] During the manufacture of the battery 60, minute foreign objects may be mixed in. In this case, a minute short circuit may occur in the cell 5, causing a drop in the voltage of the cell (battery cell) 5, resulting in over-discharge. In this embodiment, when over-discharge of the cell 5 is predicted, the SOC of the battery 60 is increased to suppress the over-discharge.

[0023] 2 is a flowchart showing an example of a SOC control center raising process executed by the HV-ECU 100. This flowchart is repeatedly processed at predetermined intervals during the Ready-ON state. In step (hereinafter, step is abbreviated as "S") 10, it is determined whether or not flag F1 is 1. Flag F1 is set to 1 in S15, which will be described later. If flag F1 is 1, the process proceeds to S16, and if flag F1 is 0, the process proceeds to S11.

[0024] In S11, the voltage difference ΔVB between adjacent cells 5 is calculated based on the voltage VB of each cell 5. In the following S12, it is determined whether the maximum voltage difference MAX[ΔVB], which is the maximum value of the voltage difference ΔVB, is greater than a predetermined value α. The predetermined value α may be, for example, 1 [V]. If the maximum voltage difference MAX[ΔVB] is greater than the predetermined value α (MAX[ΔVB]>α), the process proceeds to S13, and if the maximum voltage difference MAX[ΔVB] is equal to or less than the predetermined value α (MAX[ΔVB]≦α), the current routine is terminated.

[0025] In S13, the SOC difference ΔSOC is calculated based on the current SOC. In this embodiment, when a positive determination is made in S12, the SOC value calculated by the monitoring module 61 is calculated as the SOC difference ΔSOC.

[0026] In the next S14, the amount of increase k is calculated based on the SOC difference ΔSOC. The amount of increase k increases as the SOC difference ΔSOC increases, and is fixed to an upper limit value kmax when the SOC difference ΔSOC is s1 or more. For example, s1 may be 40[%] and kmax may be 5[%].

[0027] In S15, the SOC control center of the battery 60 is raised, the flag F1 is set to 1, and the timer T is started. The SOC control center is raised by subtracting the amount of increase k from the SOC calculated by the monitoring module 61, and calculating the result as the control SOCi (control SOCi=SOC-k). In this embodiment, as shown in the SOCi calculation map in FIG. 2, when the SOC is between A and B, the value obtained by subtracting the amount of increase k from the SOC is calculated as the control SOCi. When the SOC is equal to or lower than A0, and when the SOC is equal to or higher than B0, the value of the SOC is calculated as the control SOCi (control SOCi=SOC). When the SOC is between A0 and A, and when the SOC is between B and B0, the amount of increase k is gradually decreased to calculate the control SOCi. In the SOCi calculation map in FIG. 2, the two-dot chain line indicates that the control SOCi=SOC.

[0028] In the next step S16, the dissolution time H is acquired. The dissolution time H is the time required to dissolve the voltage difference ΔVB (maximum voltage difference MAX [ΔVB]) by utilizing the fact that the self-discharge amount of the cell 5 increases as the SOC increases. The dissolution time H is calculated in a subroutine (not shown). The self-discharge current of the cell 5 changes according to the SOC and temperature TB, and indicates different values ​​in the Ready-ON state (during driving) and the Ready-OFF state (during soaking). In the subroutine (not shown), the process of S15 is used as a trigger to obtain the self-discharge current that changes from moment to moment from the Ready-ON / OFF state (during driving), the SOC, and the temperature TB, and the dissolution time H is calculated based on the self-discharge current. The relationship between the self-discharge current and the dissolution time H is obtained in advance by experiment or the like.

[0029] In S17, it is determined whether or not the timer T is equal to or greater than the resolution time H. If the timer T is less than the resolution time H, the current routine is terminated. If the timer T is equal to or greater than the resolution time H, the routine proceeds to S18. In S18, the raising of the SOC control center is stopped (cancelled), and the flag F1 is set to 0, after which the current routine is terminated. The raising of the SOC control center is stopped by using the value of SOC as the control SOCi (control SOCi=SOC). Note that the raising amount k may be set to 0 at the same time as the raising of the SOC control is stopped.

[0030] 3 is a time chart of this embodiment (SOC control center raising process). At time t0, the battery 60 goes into the Ready-ON state and one trip (first trip) starts, and then the battery 60 is controlled for charging and discharging. The battery 60 is controlled for charging and discharging so that the control SOCi is within the range between the upper limit Xi and the lower limit Yi. If the SOC control center is not raised, the control SOCi is the value of the SOC (control SOCi=SOC), so that the SOC of the battery 60 is controlled to be within the range between the SOC upper limit X corresponding to the upper limit Xi and the SOC lower limit Y corresponding to the lower limit Yi. Therefore, the SOC control center is (X+Y) / 2 (for example, when X=40[%] and Y=60[%], the SOC control center is 50[%]).

[0031] When the voltage VB of a specific battery 5 drops and the maximum voltage difference MAX [ΔVB] becomes greater than a predetermined value α at time t1, the amount of boost k is calculated based on the SOC difference ΔSOC (S14), the SOC control center is boosted, a timer T starts, and a flag F1 is set to 1 (S15). The SOC control center is boosted by calculating the value obtained by subtracting the amount of boost k from the SOC as the control SOCi (control SOCi=SOC-k). The control SOCi is the value obtained by subtracting the amount of boost k from the SOC. Therefore, the SOC of the battery 60 is controlled to be within the range between the "SOC upper limit value X+k" and the "SOC lower limit value+k", the SOC control center becomes "((X+Y) / 2)+k", and the SOC control increases.

[0032] At time t3, the Ready-OFF state is entered, and even after one trip ends, the timer T continues counting (timekeeping). At time t3, the Ready-ON state is entered, and the second trip (next trip) starts, and the charging and discharging control of the battery 60 is performed by "control SOCi=SOC-k" until the timer T reaches the resolution time H. At time t4, when the timer T reaches the resolution time H, the raising of the SOC control center is stopped, and the flag F1 is set to 0. When the raising of the SOC control center is stopped, the charging and discharging control of the battery 60 is performed by "control SOCi=SOC". As a result, the SOC control center of the battery 60 becomes (X+Y) / 2. At this time, the raising amount k may be set to 0. The timer T is then set to 0.

[0033] According to this embodiment, charging and discharging of the battery 60, which is made up of cells 5 connected in series, is controlled so that the SOC of the battery 60 falls within a first predetermined range centered on the SOC control center ((X+Y) / 2). The SOC increase amount (increase amount k) is calculated based on the SOC difference ΔSOC, which is the SOC when the maximum voltage difference MAX [ΔVB], which is the maximum value of the voltage difference between the cells 5, becomes equal to or greater than a predetermined value α. Then, charging and discharging are controlled so that the SOC of the battery 60 falls within a second predetermined range centered on the value (((X+Y) / 2)+k) obtained by adding the SOC increase amount (increase amount k) to the SOC control center ((X+Y) / 2) for a period of resolution time H from when the maximum voltage difference MAX [ΔVB] becomes equal to or greater than the predetermined value α.

[0034] When the battery 60 is charged and discharged so that the SOC of the battery 60 falls within the second predetermined range, charging of the cells 5 is promoted, over-discharging of the cells 5 can be suppressed, and the battery 60 is used in a region (high SOC region) where the SOC is higher than the first predetermined range. The self-discharge amount of the cells 5 increases as the SOC becomes higher. By using the battery 60 in the high SOC region during the resolution time H, the self-discharge amount of the cells 5 with high voltage (high SOC) increases, and the voltage difference ΔVB between the cells 5 can be resolved (reduced). The boost amount k (SOC increase amount) is calculated based on the SOC difference ΔSOC, so the battery 60 can be used in the high SOC region according to the voltage difference ΔVB between the cells 5, and the voltage difference ΔVB between the cells 5 can be resolved (reduced). In addition, since the SOC calculated (estimated) by the monitoring module 61 is not reset, it is also possible to suppress the deviation between the actual SOC and the estimated SOC.

[0035] In the above embodiment, the voltage difference ΔVB between the cells 5 is the difference in voltage VB between adjacent cells 5, but it may be the difference between the average voltage of the cells 5 included in the battery 60 and the voltage VB of that cell 5. Also, the monitoring module 61 detects the voltage VB of the cell (battery cell) 5, but it may also be possible to detect the voltages of multiple (e.g., 3 to 6) cells 5 connected in series and use the detected voltage as the voltage VB to execute the above SOC control center raising process.

[0036] In the above embodiment, in S15, the SOC control center is raised by setting "control SOCi=SOC-k". However, the upper limit value may be set to "Xi+k" and the lower limit value to "Yi+k", and charging and discharging control may be performed using the control SOCi where "control SOCi=SOC" so that the control SOCi is within the range between the upper limit value (Xi+k) and the lower limit value (Yi+k). This also makes the SOC control center of the battery 60 "((X+Y) / 2)+k", and the SOC control center becomes larger.

[0037] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0038] 5 battery cell, 10 internal combustion engine, 20 first MG, 30 second MG, 40 power split device, 50 PCU, 60 battery, 61 monitoring module, 62 SMR, 100 HV-ECU, 200 MG-ECU, 300 EG-ECU, 400 various sensors, V hybrid vehicle.

Claims

[Claim 1] A battery pack in which a plurality of single cells are connected in series; a control device that controls charging and discharging of the battery pack so that the SOC of the battery pack is within a first predetermined range centered on an SOC control center; The control device includes: An SOC difference is obtained, which is the SOC when a voltage difference between the plurality of single cells becomes equal to or greater than a predetermined value; Calculating an SOC increase amount based on the SOC difference; a battery management system that controls the charging and discharging so that the SOC is within a second predetermined range centered on a value obtained by adding the SOC increase amount to the SOC control center for a predetermined period of time from when the voltage difference becomes equal to or greater than the predetermined value.

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