JP5916429B2 - Battery pack control system and battery pack control method - Google Patents

Description

  The present invention relates to an assembled battery control system and an assembled battery control method for controlling charging / discharging of an assembled battery in which a plurality of secondary batteries are connected in series.

  For example, lithium ion secondary batteries have advantages such as high energy density and low self-discharge, and have been used as power sources for small electronic devices such as mobile phones and laptop computers. Furthermore, in recent years, it has been regarded as a promising battery for electric vehicles, and its use as an industrial backup battery is expanding. In use, in order to obtain a voltage and capacity according to the purpose of use, a plurality of lithium ion cells, which are single cells, are connected in series to form an assembled battery, and further, these assembled batteries are connected in parallel. It may be used.

  When charging such an assembled battery, the voltage of each lithium ion cell may vary. That is, the charge voltage of some lithium ion cells is high and the battery is overcharged, and in some other lithium ion cells, the charge voltage is low and the battery is undercharged (not fully charged). For this reason, a technique of providing a bypass circuit (resistance) in order to properly charge each lithium ion cell without variation is known (see, for example, Patent Document 1). In this technology, each lithium ion cell connected in series is provided with a bypass circuit, and when the voltage of a certain lithium ion cell exceeds the upper limit of an appropriate charging voltage range (allowable charging voltage range) during charging, By the bypass circuit corresponding to the cell, the charging current to the cell is bypassed, and the cell is discharged (bypass discharge). Thereby, the voltage of the lithium ion cell having a high charging voltage is lowered, and the charging of the lithium ion cell having a low voltage is promoted.

Japanese Patent Application Laid-Open No. 2002-064947

  By the way, even if the bypass discharge as described above is performed, there may be a cell having an abnormal event such as a short circuit or an abnormal low voltage in the assembled battery. If such an abnormal cell exists, the entire assembled battery The discharge capacity may be reduced. That is, when the voltage of any cell reaches the end-of-discharge voltage (voltage at which discharge is to be terminated) during discharge, if the discharge is continued thereafter, an overdischarge state may occur and abnormal heating or the like may occur. For this reason, if the voltage of an abnormal cell reaches the discharge end voltage early during discharge, the discharge of the entire assembled battery must be terminated even though the voltage of other healthy cells has not reached the discharge end voltage. In other words, the discharge capacity may be reduced.

  For example, in the case of an assembled battery for backup, the assembled battery must be disconnected from the system when the voltage of the abnormal cell reaches the end-of-discharge voltage, and the backup time is significantly shortened. In particular, when only one set of assembled batteries is installed, the backup function is lost due to a mere failure of one cell, which greatly impedes the operation of the facility.

  Therefore, the present invention provides an assembled battery control system and an assembled battery control method capable of suppressing a reduction in the discharge capacity of the entire assembled battery even when an abnormal secondary battery is present. Objective.

In order to achieve the above object, the invention according to claim 1 is an assembled battery control system for controlling an assembled battery in which a plurality of secondary batteries are connected in series, and charging means for charging the assembled battery, Separating means for separating the secondary battery from the assembled battery, and a bypass that is provided in each secondary battery and bypasses the secondary battery when the charging voltage of the corresponding secondary battery reaches a predetermined voltage. a circuit, and a control means for monitoring the battery state including at least one of the voltage or temperature of each secondary battery, controls the charging means and the respective separating means based on the battery state of each secondary battery, The control means disconnects the secondary battery by the disconnecting means when the battery state of the secondary battery reaches a predetermined abnormal state, and disconnects the secondary battery when charging. Before according to the number of batteries Adjusting the output voltage of the charging means, characterized in that.

  According to the present invention, when the battery state of the secondary battery becomes a predetermined abnormal state, the secondary battery is disconnected from the assembled battery by the disconnecting means, and when being charged, the secondary battery is disconnected. The output voltage of the charging means is adjusted according to the number.

  According to a second aspect of the present invention, in the assembled battery control system according to the first aspect, when a plurality of the assembled batteries are connected in parallel, the control means is a battery of a secondary battery of a part of the assembled batteries. When the state reaches a predetermined abnormal state, the secondary battery is disconnected by the disconnecting means, and the same number of secondary batteries as the disconnected secondary batteries are disconnected from other assembled batteries by the disconnecting means. It is characterized by separating.

  According to this invention, when the battery state of a secondary battery of a certain assembled battery becomes a predetermined abnormal state, the secondary battery is disconnected from the assembled battery, and the same number of secondary batteries as the number of disconnected secondary batteries are obtained. The secondary battery is disconnected from the other assembled batteries. That is, in all the assembled batteries connected in parallel, the number of connected secondary batteries is the same.

  According to a third aspect of the present invention, in the assembled battery control system according to the first or second aspect, the disconnecting means is provided for each of the plurality of secondary batteries.

The invention according to claim 4 is an assembled battery control method for controlling an assembled battery in which a plurality of secondary batteries are connected in series, wherein the secondary battery is detachably connected to the assembled battery, and each of the two A battery state including at least one of a voltage or a temperature of the secondary battery is monitored, and when the charging voltage of the secondary battery reaches a predetermined voltage, the secondary battery is bypass-discharged, and the battery state of the secondary battery is When the battery reaches a predetermined abnormal state, the secondary battery is disconnected from the assembled battery, and when being charged, charging means for charging the assembled battery according to the number of the disconnected secondary batteries. The output voltage is adjusted.

  According to a fifth aspect of the present invention, in the assembled battery control method according to the fourth aspect, when a plurality of the assembled batteries are connected in parallel, the battery state of the secondary batteries of some assembled batteries is a predetermined abnormality. When the state is reached, the secondary battery is separated from the assembled battery, and the same number of secondary batteries as the number of separated secondary batteries are separated from other assembled batteries.

  According to the first and fourth aspects of the invention, when the battery state of the secondary battery becomes a predetermined abnormal state, the secondary battery is disconnected from the assembled battery. Therefore, it is possible to avoid a situation in which the discharge of the entire assembled battery must be terminated to reach That is, even when an abnormal secondary battery is present, it is possible to suppress an extreme decrease in the discharge capacity of the entire assembled battery. In addition, when charging is in progress, the output voltage of the charging means is adjusted according to the number of disconnected secondary batteries, and therefore the assembled battery with an appropriate charging voltage according to the number of connected secondary batteries. The whole can be used continuously.

  According to the second and fifth aspects of the present invention, when a plurality of assembled batteries are connected in parallel, the number of secondary batteries connected in all the assembled batteries is the same. Since the battery is disconnected, the voltage balance between the assembled batteries is maintained. As a result, no current flows between the assembled batteries, and a plurality of assembled batteries can be charged and discharged appropriately.

  According to the third aspect of the present invention, since the separation means is provided for each of the plurality of secondary batteries, the number of separation means provided is smaller than when each secondary battery is provided with a separation means. The reliability is improved, and the system can be simplified and simplified and the cost can be reduced.

It is a schematic block diagram which shows the state which applied the assembled battery control system which concerns on Embodiment 1 of this invention to the DC power supply system provided with 1 set of assembled batteries. It is a figure which shows the change of the output voltage and charging current of a rectifier by the system of FIG. It is a figure which shows the discharge characteristic etc. of the assembled battery by the system of FIG. It is a figure which shows the example of a discharge characteristic of the lithium ion cell in the system of FIG. It is a schematic block diagram which shows the state which applied the assembled battery control system which concerns on Embodiment 2 of this invention to the direct-current power supply system provided with 3 sets of assembled batteries. It is a schematic block diagram which shows the state which applied the system of FIG. 1 to the uninterruptible power supply. In FIG. 6, it is a schematic block diagram which shows the state which provided the isolation | separation switch for every some cell.

  The present invention will be described below based on the illustrated embodiments.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram showing a state in which the assembled battery control system 1 according to this embodiment is applied to a DC power supply system including a set of lithium ion assembled batteries 20. The assembled battery control system 1 is a system for controlling a lithium ion assembled battery 20 in which a plurality of lithium ion cells (lithium ion secondary batteries) 2 which are single cells are connected in series. Mainly, a rectifier (charging means) 3 And a bypass circuit 4 and a disconnect switch (disconnect means) 5, a cell controller (control means) 6, and a system controller (control means) 7 provided in each lithium ion cell 2. The bypass circuit 4 and the disconnect switch 5 are connected to the cell controller 6, the cell controller 6 and the system controller 7, and the system controller 7 and the rectifier 3 are communicably connected (signal transmission).

  The rectifier 3 is a device that charges the assembled battery 20 by converting the electric power from the commercial power supply 100 into a direct current and supplies it to the assembled battery 20, so that the output voltage / charging voltage is adjusted by the system controller 7. It has become. Further, the DC load device 101 is connected to the rectifier 3, and the electric power from the commercial power supply 100 is converted into DC by the rectifier 3 and supplied to the DC load device 101. Furthermore, the assembled battery 20 is connected via a backflow prevention device (not shown) having a function of allowing only the current flow from the assembled battery 20, thereby enabling discharge from the assembled battery 20 at all times. Electric power is supplied from the assembled battery 20 to the DC load device 101 via the backflow prevention device.

  The bypass circuit 4 is a cell voltage regulator provided with a resistor (load) and a switch. When the charging voltage of the corresponding lithium ion cell 2 reaches a predetermined voltage, the switch is turned on by the cell controller 6. The charging current to the cell 2 is bypassed, and the cell 2 is discharged by a resistor (bypass discharge). As a result, the charging voltage of the cell 2 is lowered, and the charging of the cell 2 having a low voltage is promoted.

  The disconnect switch 5 is a switch that disconnects the corresponding lithium ion cell 2 from the assembled battery 20, and includes a first terminal 51 and a second terminal 52. When the first terminal 51 is turned on, the cell 2 is connected to the assembled battery 20, and when the second terminal 52 is turned on, the cell 2 is disconnected from the assembled battery 20 ( Bypassed.) Such a disconnect switch 5 is normally controlled by the cell controller 6 as described later with the first terminal 51 turned on.

  The cell controller 6 controls the bypass circuit 4 based on the charging voltage of each cell 2 as described above, and constantly measures and monitors the battery state including the voltage and temperature of each lithium ion cell 2. This is a device that controls each disconnect switch 5 based on the battery state and transmits information necessary for controlling the rectifier 3 to the system controller 7. That is, a measuring instrument for measuring voltage, temperature, and the like is provided, and when the battery state of any cell 2 reaches a predetermined abnormal state during charging, the second terminal of the disconnect switch 5 of this cell 2 52 is turned on (the first terminal 51 is turned off), and the cell 2 is disconnected from the assembled battery 20. At the same time, the fact that the cell 2 has been disconnected from the assembled battery 20 and the separation information including the number of cells are transmitted to the system controller 7. In response to this, the output voltage of the rectifier 3 is adjusted by the system controller 7 as will be described later.

  In this manner, the abnormal cells 2 are disconnected from the assembled battery 20 and the output voltage of the rectifier 3 is adjusted to adjust the output voltage suitable for the number of cells connected to the assembled battery 20 so that the remaining cells 2 can be connected. It is something to charge. Here, the predetermined abnormal state includes short circuit, open circuit, abnormal voltage increase / decrease, abnormal temperature increase, abnormal pressure (internal pressure) increase, and the like.

  Similarly, when the battery state of any cell 2 reaches a predetermined abnormal state during discharging, the cell 2 is disconnected from the assembled battery 20. Here, in addition to the short circuit and the open circuit as described above, the predetermined abnormal state includes a state in which the voltage during the discharge is extremely (abnormally) low (suddenly drops), the voltage of the cell 2 is the discharge end voltage, A state where an abnormal voltage (overdischarge voltage) is reached is also included. The reason why the output voltage of the rectifier 3 is not adjusted is that there is no power supply from the rectifier 3 during discharge, so that it is not necessary to adjust the output voltage.

The system controller 7 is a device that adjusts the output voltage of the rectifier 3 based on the separation information from the cell controller 6 and the like. For example, when the optimum positive value (full charge voltage) of the charging voltage per cell is 4.1 V and the assembled battery 20 is composed of 12 cells, when one cell is disconnected from the assembled battery 20, The rectifier 3 is commanded to lower the output voltage of the rectifier 3 as described above.
Output voltage before separation V _T0 = 4.1 × 12 = 49.2V
Output voltage after separation V _T1 = 4.1 × 11 = 45.1V
In this way, the output voltage of the rectifier 3 is lowered according to the number of separated cells 2. Therefore, even after the output voltage of the rectifier 3 is lowered, the charging with the optimum positive value of the charging voltage is continued in each cell 2.

  Next, an operation of the assembled battery control system 1 having such a configuration, an assembled battery control method by the assembled battery control system 1, and the like will be described.

First, at the time of charging, with the first terminals 51 of all the disconnect switches 5 turned on and all the cells 2 are connected to the assembled battery 20, the initial total voltage V _T0 and the initial voltage as shown in FIG. It is charged by the rectifier 3 with the charging current I ₀ . Here, the initial total voltage V _T0 is a value (12 × 4.1 = 49.2 V) corresponding to the optimal positive value of the charging voltage of the 12 cells 2. In such a charged state, the battery state of each cell 2 is monitored in real time by the cell controller 6, and when the battery state of any cell 2 reaches the abnormal state as described above, 2 is disconnected from the assembled battery 20 and the output voltage of the rectifier 3 is adjusted. Thereby, as shown in FIG. 2, the output voltage of the rectifier 3 is adjusted to the total voltage V _T1 after disconnection, and the charging current becomes the post-disconnection charging current I ₁ . Here, the total voltage V _T1 after separation is a value (11 × 4.1 = 45.1 V) corresponding to the optimal positive value of the charging voltage of the 11 cells 2. Therefore, since the output voltage of the rectifier 3 and the total voltage of the assembled battery 20 are the same voltage V _T1 , the post-separation charging current I ₁ is converged to substantially the same value as the initial charging current I _0, and is the same as before the separation The remaining cell 2 is continuously charged with the charging current.

  Thus, when the cell 2 is disconnected from the assembled battery 20 during charging, the output voltage of the rectifier 3 is adjusted according to the number of the disconnected cells 2, so the number of connected cells 2 Accordingly, the entire assembled battery 20 can be appropriately charged.

  On the other hand, at the time of discharging, all the cells 2 are discharged in a state in which the first terminals 51 of all the disconnect switches 5 are turned on and all the cells 2 are connected to the assembled battery 20. In such a discharge state, the battery state of each cell 2 is monitored in real time by the cell controller 6. When the battery state of any cell 2 reaches the abnormal state as described above, 2 is disconnected from the assembled battery 20. For example, when the voltage of one of the cells 2 reaches the discharge end voltage in an extremely short time compared to the other cells 2, the cell 2 is disconnected from the assembled battery 20 and discharge by the remaining cells 2 continues. It is what is done.

  As described above, according to the assembled battery control system 1 and the assembled battery control method, when the battery state of any one of the cells 2 becomes a predetermined abnormal state, the cell 2 is disconnected from the assembled battery 20, and thus abnormal. It is possible to avoid a situation in which the discharge of the entire assembled battery 20 must be terminated in order for the cell 2 to reach the discharge end voltage early. That is, even when an abnormal cell 2 is present, it is possible to prevent the discharge capacity / discharge time of the assembled battery 20 from being extremely reduced.

  Specifically, when an abnormal cell 2 is discovered at the time of discharge, by disconnecting the cell 2 from the assembled battery 20 in advance, the abnormal cell 2 at the time of discharge reaches an end-of-discharge voltage early. The end of discharge of the entire assembled battery 20 can be avoided. Such an effect is shown in FIG. When all the cells 2 are healthy and normal, the total voltage of the assembled battery 20 at the time of discharge changes like an appropriate total discharge curve TD1, and the voltage of each cell 2 changes like the appropriate cell discharge curves CD1 to CD3. The discharge time until the total voltage reaches the final discharge voltage 43V is t3. Here, the appropriate cell discharge curves CD1 to CD3 indicate the maximum value, the average value, and the minimum value, respectively.

On the other hand, there is an abnormal cell 2, the total voltage of the assembled battery 20 changes as an abnormal total discharge curve TD2, and the voltage of the abnormal cell 2 changes as an abnormal cell discharge curve CD4. When the abnormal voltage _VE is reached, the discharge of the entire assembled battery 20 has been terminated at this point in the past. On the other hand, in the assembled battery control system 1 and the assembled battery control method, the cell 2 is disconnected from the assembled battery 20 at time t1, and discharge by the remaining cells 20 is continued. That is, the total voltage of the assembled battery 20 changes like the total discharge curve TD3 after disconnection, and the discharge is continued until the discharge end voltage 43V is reached at time t2. Thus, even when there is an abnormal cell 2, the discharge time can be extended to time t2, compared to the conventional discharge time t1.

Here, for example, when the discharge end voltage of the entire assembled battery 20 (voltage defined by the DC load device 101) is 43 V and one abnormal cell 2 is disconnected, the discharge end voltage per cell of the remaining 11 cells Is as follows.
End-of-discharge voltage = 43V ÷ 11 cells = 3.9V
On the other hand, the discharge end voltage per cell in the state of 12 cells before separating the cell 2 is as follows.
End-of-discharge voltage = 43V ÷ 12 cells = 3.6V

  Then, by disconnecting one abnormal cell 2 and changing the discharge end voltage from 3.6 V to 3.9 V, the discharge capacity of the cell 2 and the assembled battery 20 is, for example, 100 as shown in FIG. % To 60%. When the abnormal cell 2 is disconnected from the assembled battery 20 in this manner, the capacity of the remaining assembled battery 20 is reduced. However, when the abnormal cell 2 exists, the discharge of the entire assembled battery 20 is terminated early. In comparison, the discharge capacity and discharge time of the entire assembled battery 20 can be maintained large.

(Embodiment 2)
FIG. 5 is a schematic configuration diagram showing a state in which the assembled battery control system 1 according to this embodiment is applied to a DC power supply system including three sets of lithium ion assembled batteries 20. Here, about the structure equivalent to Embodiment 1, the description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  In this embodiment, three sets of assembled batteries 20 are connected in parallel, and for each assembled battery 20, a bypass circuit 4, a disconnect switch 5 and a cell controller 6 are provided. 6 is communicably connected. In the system controller 7, in addition to the control of the first embodiment (the output adjustment control of the rectifier 3), when the disconnection information is received from any of the cell controllers 6, the number is the same as the number of the disconnected cells 2. A command is transmitted to the other cell controllers 6 so as to separate the number of cells 2 from the other assembled batteries 20.

  For example, when receiving disconnection information indicating that one cell 2 (reference numeral C1 in the figure) has been disconnected from the C-th assembled battery 20, the cell controllers 6 of the A-th and B-th assembled batteries 20 A command is transmitted to disconnect one cell 2. Here, in the A and B assembled batteries 20, which cell 2 is to be separated is determined based on the battery state of each cell 2. For example, the cell 2 having the lowest voltage or the highest voltage is selected. In response to this command, the other cell controller 6 separates the cells 2 (reference numerals C2 and C3 in the figure) from the other assembled batteries 20 and maintains the same number of cells in all the assembled batteries 20.

  Thus, according to this embodiment, for example, when the battery state of a cell 2 with the C-th assembled battery 20 becomes abnormal, the cell 2 is disconnected from the C-th assembled battery 20 and The cell 2 is disconnected from the A-th and B-th assembled batteries 20, and the number of cells in all the assembled batteries 20 is maintained at the same number. For this reason, the voltage balance between the assembled batteries 20 is maintained, current does not flow between the assembled batteries 20, and a plurality of assembled batteries 20 can be charged and discharged appropriately.

  Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above embodiment, and even if there is a design change or the like without departing from the gist of the present invention, Included in the invention. For example, in the above embodiment, the case where the assembled battery charging system 1 is applied to a DC power supply system has been described. However, the present invention can also be applied to an uninterruptible power supply (UPS) or an electric vehicle. When applied to an uninterruptible power supply, as shown in FIG. 6, the electric power converted into direct current by the rectifier 3 is converted into alternating current by the AC / DC converter 103 and supplied to the AC load device 102. On the other hand, an assembled battery 20 is connected via a discharge switch 9. In addition, a charger 8 as a charging means is connected to the assembled battery 20, and the output voltage of the charger 8 is adjusted by the system controller 7 in accordance with the separation of the cell 2.

  Here, in FIG. 6, only five cells are shown for simplification, but in reality, several cells are separated from the assembled battery 20 because several tens to hundreds of cells 2 are connected. However, the capacity reduction of the assembled battery 20 as a whole is small. For example, when the assembled battery 20 is configured with 100 cells and the discharge end voltage of the entire assembled battery 20 is 350 V (discharge end voltage per cell is 3.5 V), even if one cell is disconnected from the assembled battery 20, The discharge end voltage per cell of the remaining 99 cells is about 3.53 V, and the discharge capacity is maintained near 100% (see FIG. 4). Similarly, even if 5 cells are separated from the assembled battery 20, the discharge end voltage per cell of the remaining 95 cells is about 3.68V, the discharge capacity is maintained at about 95%, and further, 10 cells are connected to the assembled battery 20 Even if it is disconnected from the battery, the discharge capacity of the remaining 90 cells is maintained at about 60% (the discharge end voltage per cell is about 3.9 V).

  In the above embodiment, the separation switch 5 is provided for each lithium ion cell 2, but the separation switch 5 may be provided for each of the plurality of cells 2. For example, as shown in FIG. 7, when applied to an uninterruptible power supply as described above, a separation switch 5 is provided for every three cells to be grouped. Then, when the battery state of any cell 2 in the same group reaches an abnormal state, the second terminal 52 of the disconnect switch 5 is turned on, and all three cells in this group are removed from the assembled battery 20. It may be separated.

  Thus, by providing the separation switch 5 for each of the plurality of cells 2, the number of the separation switches 5 can be reduced, the reliability of the system 1 can be improved, and the system 1 can be simplified. Simplification and cost reduction are possible. In particular, in an uninterruptible power supply device including a large number of cells 2, the effect is great.

  Furthermore, in the above embodiment, the cell controller 6 and the system controller 7 are separated, but the above-described control may be performed by one controller. Moreover, not only the lithium ion cell 2 but widely applicable to secondary batteries such as lead storage batteries.

1 Battery control system 2 Lithium ion cell (lithium ion secondary battery)
20 Lithium ion battery 3 Rectifier (charging means)
4 Bypass circuit 5 Disconnect switch (disconnect means)
6 Cell controller (control means)
7 System controller (control means)

Claims (5)

An assembled battery control system for controlling an assembled battery in which a plurality of secondary batteries are connected in series,
Charging means for charging the assembled battery;
Separating means for separating the secondary battery from the assembled battery;
A bypass circuit that is provided in each of the secondary batteries, and bypasses the secondary battery when the charging voltage of the corresponding secondary battery reaches a predetermined voltage;
Control means for monitoring a battery state including at least one of a voltage or a temperature of each secondary battery, and controlling the charging means and each disconnecting means based on the battery state of each secondary battery;
With
The control means disconnects the secondary battery by the disconnecting means when the battery state of the secondary battery reaches a predetermined abnormal state, and counts the number of the secondary batteries disconnected when charging. Adjusting the output voltage of the charging means according to
A battery pack control system. When the assembled battery is connected in parallel,
When the battery state of the secondary batteries of some of the assembled batteries has reached a predetermined abnormal state, the control means disconnects the secondary batteries by the disconnecting means and has the same number as the detached secondary batteries. A number of secondary batteries are separated from other assembled batteries by the separating means,
The assembled battery control system according to claim 1. The separation means is provided for each of the plurality of secondary batteries.
The assembled battery control system according to any one of claims 1 and 2. An assembled battery control method for controlling an assembled battery in which a plurality of secondary batteries are connected in series,
The secondary battery is detachably connected from the assembled battery,
Monitoring battery status including at least one of voltage or temperature of each secondary battery;
When the charging voltage of the secondary battery reaches a predetermined voltage, the secondary battery is bypass-discharged,
When the battery state of the secondary battery reaches a predetermined abnormal state, the secondary battery is disconnected from the assembled battery, and when being charged, depending on the number of the separated secondary batteries, Adjust the output voltage of the charging means to charge the battery,
And a battery pack control method. When the assembled battery is connected in parallel,
When the battery state of the secondary battery of some of the assembled batteries reaches a predetermined abnormal state, the secondary battery is disconnected from the assembled battery, and the same number of secondary batteries as the disconnected secondary batteries are removed. Disconnect from other batteries
The assembled battery control method according to claim 4.

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