JP2013162597A - Assembled battery discharge control system and assembled battery discharge control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize stored energy by extending an overall discharge time of an assembled battery even if there is an anomalous secondary battery.SOLUTION: An assembled battery discharge control system includes: diodes 3 connected in parallel with respective cells 2 to permit only a flow of current in a direction of discharge from an assembled battery 20; disconnection switches 4 disposed for the respective cells 2 to disconnect the cells 2 from the assembled battery 20; and a controller 5 for monitoring battery states of the respective cells 2 including voltage and temperature, and when the battery state of a certain cell 2 reaches a predetermined anomalous state during discharge, disconnecting the cell 2 from the assembled battery 20 by means of the disconnection switch 4.

Description

  The present invention relates to an assembled battery discharge control system and an assembled battery discharge control method for controlling discharge 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, when discharging the assembled battery, conventionally, when the voltage of any cell (specific cell) reaches the discharge end voltage (voltage at which discharge should be terminated) during the discharge, the discharge of the entire assembled battery is terminated. . This is because if the discharge is continued after that, the specific cell may be in an overdischarged state and abnormal heating or the like may occur. On the other hand, due to variations in the degree of deterioration, manufacturing variations, and the like, there may be lithium ion cells in which the state of charge (SOC) is low and the voltage drop during discharge is large (fast). If the voltage of such a cell reaches the discharge end voltage early during discharge, the discharge of the entire assembled battery is terminated even though the voltage of other healthy cells has not reached the discharge end voltage. As a result, the discharge capacity and discharge time are reduced, and energy that can be discharged is left in other healthy cells, resulting in a problem that the battery pack cannot be efficiently operated.

  For example, in the case of an assembled battery for backup, when the voltage of a specific cell reaches the discharge end voltage, the assembled battery must be disconnected from the system, and the backup time is significantly shortened. In particular, when only one set of assembled batteries is installed, the backup function is lost, which greatly impedes the operation of the facility. In addition, it becomes a big problem in an HVDC (High Voltage Direct Current) power supply system and an uninterruptible power supply (UPS) that are composed of more cells and require a high voltage assembled battery. Furthermore, such a problem occurs not only when the voltage of a specific cell reaches the end-of-discharge voltage at an early stage, but also when the discharge of the entire assembled battery has to be terminated due to an abnormality (such as a temperature rise) of some cells. It also occurred when it was not possible.

  Therefore, the present invention provides an assembled battery discharge control system and an assembled battery discharge control method capable of extending and extending the discharge time of the entire assembled battery and effectively utilizing the accumulated energy even when an abnormal secondary battery exists. The purpose is to provide.

  In order to achieve the above object, the invention described in claim 1 is an assembled battery discharge control system for controlling discharge of an assembled battery in which a plurality of secondary batteries are connected in series, and for each of the secondary batteries. A bypass path connected in parallel and allowing only a current flow in the discharge direction from the assembled battery; and a disconnecting means provided for each of the secondary batteries, and separating the secondary battery from the assembled battery; The battery state including the voltage and temperature of each secondary battery is monitored, and when the battery state of the secondary battery reaches a predetermined abnormal state during discharging, the secondary battery is assembled by the disconnecting means. And a control means for separating from the battery.

  According to this invention, when the battery state of the secondary battery becomes a predetermined abnormal state during discharge, for example, when the voltage reaches the discharge end voltage, the secondary battery is disconnected from the assembled battery by the disconnecting means, A discharge current from another secondary battery flows through the bypass path of the secondary battery.

  The invention according to claim 2 is an assembled battery discharge control method for controlling discharge of an assembled battery in which a plurality of secondary batteries are connected in series, wherein the discharge from the assembled battery is performed for each of the secondary batteries. A bypass path that allows only a current flow in the direction is connected in parallel, each secondary battery is detachably connected from the assembled battery, and the battery state including the voltage and temperature of each secondary battery is monitored. When the battery state of the secondary battery reaches a predetermined abnormal state during discharging, the secondary battery is disconnected from the assembled battery.

  According to the first and second aspects of the present invention, when the battery state of the secondary battery becomes a predetermined abnormal state during discharging, the secondary battery is disconnected from the assembled battery, so that the remaining secondary batteries are discharged. Can continue. In other words, it is possible to avoid the situation where the discharge of the entire assembled battery has to be terminated due to the abnormal secondary battery reaching the end-of-discharge voltage at an early stage, and when there is an abnormal secondary battery. Even in this case, the discharge time of the entire assembled battery can be extended, the stored energy can be used effectively, and the power supply reliability can be improved. Moreover, since the bypass path is connected in parallel to the secondary battery, when the secondary battery is disconnected from the assembled battery, the discharge can be continued without instantaneous interruption.

It is a schematic block diagram which shows the state which applied the assembled battery discharge control system which concerns on embodiment of this invention to the DC power supply system. In embodiment of this invention, it is the figure (a) which shows the initial state which discharged the assembled battery, and the figure (b) which shows the state which discharge advanced. FIG. 2A shows a state where the discharge has further progressed from the state of FIG. 2B and the voltage of the first cell has reached the discharge end voltage, and FIG. 2B shows a state where the disconnect switch of this cell is turned off. (B). FIG. 4 is a diagram showing a state in which all the disconnect switches are turned on after the rectifier has recovered from the state of FIG.

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

  FIG. 1 is a schematic configuration diagram showing a state in which an assembled battery discharge control system 1 according to an embodiment of the present invention is applied to a DC power supply system. This assembled battery discharge control system 1 is a system that controls the discharge of a lithium ion assembled battery 20 in which a plurality of lithium ion cells (lithium ion secondary batteries) 2 that are unit cells are connected in series. A diode (bypass path) 3 and a disconnect switch (disconnect means) 4 provided in the cell 2 and a controller (control means) 5 are provided. Each disconnect switch 4 and the cell controller 5 are connected so that communication (signal transmission) is possible.

  Here, the assembled battery 20 is connected to the rectifier 101, and the electric power from the commercial power supply 100 is converted into direct current by the rectifier 101 and supplied to the assembled battery 20. Further, a DC load device 102 is connected to the rectifier 101, and DC power is similarly supplied to the DC load device 102.

  The diode 3 is connected in parallel to the lithium ion cell 2 and the disconnect switch 4 connected in series as will be described later, and has a function of allowing only a current flow in the discharge direction from the assembled battery 20. ing. That is, only the flow of current (discharge current) to the DC load device 102 side is allowed, and the flow of current (charge current) from the rectifier 101 side is not allowed.

  The disconnect switch 4 is a switch that is connected in series to the lithium ion cell 2 and disconnects the corresponding cell 2 from the assembled battery 20. That is, in a state where the disconnect switch 4 is turned on, the cell 2 is connected to the assembled battery 20, and when the disconnect switch 4 is turned off, the cell 2 is disconnected from the assembled battery 20 (bypassed). .) In a normal state, all the disconnect switches 4 are turned on and are controlled by the controller 5 as described later.

  The controller 5 is a control device that constantly measures and monitors the battery state including the voltage and temperature of each lithium ion cell 2 and controls each disconnect switch 4 and the like based on the battery state of each cell 2. That is, a measuring instrument that measures the voltage, temperature, and the like of each cell 2 is provided, and when the battery state of the cell 2 reaches a predetermined abnormal state during discharge, the cell 2 is assembled by the corresponding disconnect switch 4. Separate from 20. Here, the predetermined abnormal state includes a state in which the voltage of the cell 2 has reached the end-of-discharge voltage, a state in which the voltage in the middle of the discharge is extremely low or extremely low (a sudden drop), an abnormal temperature rise, and an abnormal pressure. Includes (internal pressure) rise.

  Further, the controller 5 is communicably connected to the rectifier 101, and when the output voltage of the rectifier 101 becomes equal to or higher than the total voltage of the assembled battery 20 during discharging, that is, the commercial power supply 100 / rectifier 101 is recovered / recovered from a power failure. In this case, all the separation switches 4 (the separation switches 4 being turned off) are turned on to charge all the cells 2.

Next, an operation of the assembled battery discharge control system 1 having such a configuration, an assembled battery discharge control method by the assembled battery discharge control system 1, and the like will be described. Here, it is assumed that the fully charged voltage of the lithium ion cell 2 is 4.1 V, and the assembled battery 20 is composed of 12 cells. The DC load device 102 is a constant power load, and the load power value is Q. To do. Furthermore, the first cell 2 ₁ in the state of charge · SOC is low, the voltage drop during discharge and QUICKLY.

First, when the commercial power supply 100 and the rectifier 101 are powered down in a state where all the disconnect switches 4 are turned on and all the cells 2 are connected to the assembled battery 20, the discharge of the assembled battery 20 is started. At this time, as shown in FIG. 2A, when the voltage of each cell 2 is 4.0 V, for example, and the total voltage of the assembled battery 20 is 48 V, the discharge current value I ₀ is as follows.
Discharge current value I ₀ = Load power Q ÷ 48V

In this discharge state, the battery state of each cell 2 is monitored in real time by the controller 5, the discharge progresses, as shown in FIG. 2 (b), for example, the first cell 2 ₁ voltage is 3.2 V, the other The voltage of the cell 2 is 3.5V, and the total voltage of the assembled battery 20 reaches 41.7V. The discharge current value I ₁ at this time is as follows (I ₁ > I ₀ ).
Discharge current value I ₁ = Load power Q ÷ 41.7V

Further discharge progresses, as shown in FIG. 3 (a), in reaching 3.0V first cell 2 ₁ voltage is final discharge voltage, for example, a voltage of the other cell 2 3.3V, the set The total voltage of the battery 20 reaches 39.3V. The discharge current value I ₂ at this time is as follows (I ₂ > I ₁ > I ₀ ).
Discharge current value I ₂ = Load power Q ÷ 39.3V

With such first cell 2 ₁ voltage reaches the discharge cutoff voltage, the controller 5 as described above, as shown in FIG. 3 (b), disconnecting switches 4 of cells 2 are turned off. Thus, the first cell 2 ₁ is ended discharge is separated from the assembled battery 20, the discharge current from the other cells 2, flows to the DC load device 102 via a first cell 2 _first diode 3 . That is, the first cell 2 _1, a short-circuit state through the diode 3. At this time, when a voltage drop due to the diode 3 and 0.5V, the total voltage is 35.8V next battery pack 20, the discharge current value _{I 3} is as follows _{(I 3> I 2> I} 1> I 0 ).
Discharge current value I ₃ = Load power Q ÷ 35.8V

In a state where the first cell 2 ₁ is disconnected, then, is discharged by the remaining cells 2 is continued. Subsequently, when the voltage of any one of the cells 2 reaches the end-of-discharge voltage, the cell 2 is similarly disconnected from the assembled battery 20, and such control is performed until the rectifier 101 returns to power or the assembled battery 20. Until the total voltage reaches a predetermined voltage. Also, when the battery state of any of the cells 2 reaches the abnormal state as described above (for example, when the temperature rises abnormally), the cell 2 is similarly disconnected from the assembled battery 20 and the remaining Discharging by the cell 2 is continued.

  On the other hand, when the commercial power source 100 and the rectifier 101 are restored and restored during discharging, the controller 5 turns on all the disconnect switches 4 as shown in FIG. 4 to charge all the cells 2 as described above. It will be started.

  As described above, according to the assembled battery discharge control system 1 and the assembled battery discharge control method, when the voltage of any cell 2 reaches the discharge end voltage during discharging, the cell 2 is disconnected from the assembled battery 20. Therefore, the overdischarge of the cell 2 can be prevented and the discharge by the remaining cells 2 can be continued. That is, it is possible to avoid a situation in which the discharge of the entire assembled battery 20 has to be terminated in order for some of the cells 2 to reach the end-of-discharge voltage early, and there is an abnormal cell 2. In addition, the discharge time of the assembled battery 20 as a whole can be extended, the stored energy can be used effectively, and the power supply reliability can be improved.

  Similarly, when any one of the cells 2 is in an abnormal state as described above, the cell 2 is disconnected from the assembled battery 20 and the discharge by the remaining cells 2 is continued. As described above, even if some of the cells 2 are abnormal, discharge by the remaining cells 2 can be continued while preventing overdischarge of the abnormal cells 2 and the reliability of power supply can be improved. .

  Moreover, since the diodes 3 are connected in parallel to each cell 2, when the switch 2 is turned off and the cell 2 is disconnected from the assembled battery 20, the discharge by the remaining cells 2 continues without interruption. Can be made.

  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 discharge control system 1 is applied to a DC power supply system has been described, but the present invention can also be applied to an uninterruptible power supply device, an HVDC power supply system, an electric vehicle, and the like. For example, when applied to an uninterruptible power supply, the assembled battery 20 is composed of a large number of cells 2 from several tens to a hundred or more, so even if several cells are separated from the assembled battery 20, the capacity of the entire assembled battery 20 The decrease is small, the discharge time of the entire assembled battery 20 can be extended, the accumulated energy can be used more effectively, and the power supply reliability can be improved.

  Furthermore, it is not limited to the lithium ion cell 2 and can be widely applied to secondary batteries in general, such as a lead storage battery, and the DC load device 102 may not be a constant power load.

1 Battery pack discharge control system 2 Lithium ion cell (lithium ion secondary battery)
20 Lithium-ion battery pack 3 Diode (bypass path)
4 Disconnect switch (Disconnect means)
5 Controller (control means)

Claims (2)

An assembled battery discharge control system for controlling discharge of an assembled battery in which a plurality of secondary batteries are connected in series,
A bypass path connected in parallel to each of the secondary batteries and allowing only a current flow in the discharge direction from the assembled battery;
A separation means provided for each of the secondary batteries, for separating the secondary battery from the assembled battery;
The battery state including the voltage and temperature of each secondary battery is monitored, and when the battery state of the secondary battery reaches a predetermined abnormal state during discharging, the secondary battery is assembled by the disconnecting means. Control means for disconnecting from the battery;
An assembled battery discharge control system comprising: A battery pack discharge control method for controlling discharge of a battery pack in which a plurality of secondary batteries are connected in series,
For each secondary battery, a bypass path that allows only a current flow in the discharge direction from the assembled battery is connected in parallel,
Each of the secondary batteries is detachably connected from the assembled battery,
Monitor battery status including voltage and temperature of each secondary battery,
When the battery state of the secondary battery reaches a predetermined abnormal state during discharging, the secondary battery is disconnected from the assembled battery;
And a battery pack discharge control method.

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