WO2013114696A1

WO2013114696A1 - Balancing device

Info

Publication number: WO2013114696A1
Application number: PCT/JP2012/078921
Authority: WO
Inventors: 正彰鈴木; 守倉石; 宗隆山本
Original assignee: 株式会社豊田自動織機
Priority date: 2012-01-31
Filing date: 2012-11-08
Publication date: 2013-08-08
Also published as: JP5482809B2; JP2013158190A

Abstract

A battery (1) is configured by connecting a plurality of battery cells (11) in series. When performing balancing for reducing the differences among the inter-terminal voltage values between the battery cells (11) of the battery (1), the battery cells (11) are divided into a plurality of groups (62) in consideration of an average value (61) calculated from the inter-terminal voltage values of the respective battery cells (11). The balancing is performed for each of the groups (62) so as to make the inter-terminal voltage values of the respective battery cells (11) belonging to the each of the groups (62) closer to the average value (61).

Description

Equalization equipment

The present invention relates to a technique for performing equalization for reducing a difference in charge state between battery cells for a battery including a plurality of battery cells connected in series.

Rechargeable batteries (secondary batteries) are now widely used. Actually, the voltage obtained between the terminals of one battery is relatively small. For this reason, the battery which needs to generate a higher voltage employs a configuration in which a plurality of battery cells as constituent elements are connected in series.

In a battery having a configuration in which a plurality of battery cells are connected in series, the charging state of each battery cell varies as charging and discharging are repeated. The charged state means a remaining charge capacity, a battery cell voltage, and the like. Hereinafter, for convenience, the charged state is assumed to be a remaining charge capacity (SOC: StateＳＯof Charge).

This SOC is a state quantity defined as the ratio of the remaining charge to the charge capacity of the battery cell. The variation is not only caused to cause overcharge and overdischarge of the battery cell, but also stored in the entire battery. It becomes a cause to enlarge the part that cannot be used in the electric power. Overcharge and overdischarge accelerate the deterioration of battery cell performance. The deterioration of the performance of the battery cell causes a decrease in the charge capacity of the entire battery. For this reason, in a battery including a plurality of battery cells, the SOC of each battery cell, that is, the remaining amount is managed. One of the management methods is an active cell balance method that dynamically controls and equalizes SOC between battery cells (Patent Document 1).

The conventional equalization apparatus that equalizes the SOC of each battery cell by the active cell balance method identifies the battery cells having a difference in SOC between two adjacent battery cells, and determines the battery cell having a high SOC. Equalization was performed by moving energy (electric power) to battery cells with low SOC (Patent Document 1). However, in such energy transfer between two battery cells, equalization in the whole battery cell cannot always be performed appropriately.

It is desirable that the equalization is performed so that the SOC of all battery cells is the same. However, the average SOC of two battery cells having different SOCs is not necessarily the same as the average SOC of all battery cells. For this reason, even if energy is transferred only between two battery cells having different SOCs, even if the degree of variation in SOC can be further reduced, equalization across the battery cells cannot be performed with high accuracy. Hereinafter, for convenience, the average SOC of all the battery cells is referred to as “overall average SOC”, and the average SOC of the two battery cells is referred to as “local average SOC”.

When the specification between two battery cells having different SOCs and the transfer of energy between the two specified battery cells are repeatedly performed, the accuracy of equalization in the whole battery cell can be further improved. However, the energy transfer between the two battery cells brings the SOC of the two battery cells closer to the local average SOC. Therefore, if the local average SOC and the overall average SOC do not match, the variation remains even if energy is transferred between the two battery cells. In such a case, it is not expected that the equalization can be efficiently performed by the method in which the specification between the two battery cells and the energy transfer between the two specified battery cells are repeatedly performed. This means that the method must take a very long time for high-precision equalization.

In order to reduce the amount of energy stored in the battery that cannot be used effectively, the variation in SOC of each battery cell needs to be reduced. The variation occurs even during discharge. As a result, the equalization apparatus adopting the active cell balance method is required to perform equalization as necessary. This means that, for example, in a vehicle equipped with a motor as a power source, equalization must be performed while it is necessary to assume a short time such as when the vehicle is stopped or idling. Such a vehicle is equipped with a battery having a very large number of battery cells. In consideration of this, it can be said that it is necessary to perform highly accurate equalization in a shorter time.

JP 2010-220373 A JP 2005-341645 A Japanese Patent Application Laid-Open No. 11-234917 JP 2004-080909 A

An object of the present invention is to provide a technique for performing equalization for reducing a difference in charge state between battery cells of a battery with high accuracy and in a short time.

1 aspect of this invention is the equalization apparatus which performs equalization which reduces the difference of the charge condition between each battery cell for the battery provided with the several battery cell connected in series, and is a plurality of switching And a switching means provided on the moving means, each of which is capable of transferring energy between the two adjacent battery cells by turning on / off the switching element. Based on the drive means that can be turned off, the information acquisition means for acquiring the state information indicating the charge state of each battery cell, and the state information acquired for each battery cell by the information acquisition means, the energy transfer using the moving means is performed. When the determination means that determines whether or not to move and the determination means determines that energy transfer should be performed, the plurality of battery cells are divided into two or more groups, and the drive means is controlled for each group. And comprises a control means for equalization using a mobile unit.

Another aspect of the present invention is an equalization device that performs equalization for reducing a difference in charge state between each battery cell for a battery including a plurality of battery cells connected in series. Each of the switching elements provided in the moving means can be moved separately between two adjacent battery cells by switching on / off the switching elements, and the switching elements provided in the moving means are individually provided. Energy transfer using moving means based on driving means that can be turned on / off, information acquisition means for acquiring state information indicating the state of charge of each battery cell, and state information acquired by the information acquisition means for each battery cell A plurality of battery cells from the state information acquired by the information acquisition unit for each battery cell when the determination unit determines whether the energy transfer should be performed. It obtains the state of charge of the average, based on the charge state of the average, by controlling the drive means comprises a control means for performing equalization using a mobile device.

The state of charge targeted for equalization of the present invention is specifically a state in which the SOC (remaining charge capacity), battery cell voltage, discharge capacity, charge amount, etc. can be quantified.

In the present invention, equalization for reducing the difference in charge state between the battery cells of the battery can be performed with high accuracy and in a short time.

It is a figure explaining the structure of the equalization apparatus by this embodiment. It is a figure showing the example of the voltage between terminals of each battery cell of a battery. It is a flowchart of a battery cell monitoring process. It is a flowchart of the balance control process at the time of applying the method of patent document 1. FIG. It is a figure explaining the grouping method of the power cell by this embodiment. It is a figure explaining the equalization performed in a group. It is a flowchart of the balance control process by this embodiment. It is a figure explaining the equalization performed by the modification of a grouping method, and a group. It is a flowchart of the balance control process by the modification of this embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram illustrating the configuration of an equalization apparatus according to the present embodiment.

The equalizing device 2 is mounted on a vehicle that can charge the battery 1 with a charging function (not shown), for example, an automobile, and employs an active cell balance method. The battery 1 is used to supply electric power to a motor that is a power source of the vehicle. For that purpose, the battery 1 includes a plurality of battery cells 11 connected in series. Therefore, the equalizing device 2 is mounted on the vehicle in order to dynamically control and equalize (smooth) the SOC between the battery cells 11 provided in the battery 1. The target for mounting the equalizing device 2 is not limited to a vehicle, as long as the battery 1 having a configuration in which a plurality of battery cells are connected in series is used as a power supply source. In addition, although four battery cells 11a to 11d are illustrated in FIG. 1 as the battery cells 11 included in the battery 1, the number of the battery cells 11 is not limited to four. Actually, the battery 1 includes a large number of battery cells 11. The subject of equalization of the present invention is not limited to SOC (remaining charge capacity), but may be other charge states such as battery cell voltage or discharge capacity.

As shown in FIG. 1, the equalizing apparatus 2 includes a moving circuit 21 that is a moving unit that can realize energy transfer between two adjacent battery cells 11, that is, between two battery cells 11 that are directly connected. I have. The moving circuit 21 includes a total of six switching elements 25 (25a to 25f) and a total of three inductors 26 (26a to 26c) when the battery 1 including the four battery cells 11 is targeted. Thereby, the equalization apparatus 2 controls the switch control unit 22 as a driving unit for individually turning on / off the six switching elements 25 of the moving circuit 21 and the switch control unit 22 in addition to the moving circuit 21. A CPU (Central Processing Unit) 23 is provided.

Each switching element 25 of the moving circuit 21 realizes a closed loop circuit that connects terminals of one battery cell 11. Each closed loop circuit includes one inductor 26 in addition to one switching element 25. The inductor 26 of each closed loop circuit is used for accumulation (storage) of energy to be moved between the two battery cells 11.

The movement of energy between the two battery cells 11 by the moving circuit 21 is performed as follows.

For example, when energy is transferred from the battery cell 11a to the battery cell 11b, first, the switching element 25a is turned on. When the switching element 25a is turned on, a closed loop circuit is formed between the terminals of the battery cell 11a, and a current flows from the positive side terminal to the negative side terminal of the battery cell 11a via the switching element 25a and the inductor 26a. As the current flows in such a manner, energy (electric power) is stored in the inductor 26a.

Next, the switching element 25a is turned off and the switching element 25b is turned on. For this reason, the closed loop circuit formed between the terminals of the battery cell 11a is released, and a closed loop circuit is newly formed between the terminals of the battery cell 11b. As a result, the energy of the inductor 26a is stored in the battery cell 11b by a closed loop circuit formed between the terminals of the battery cell 11b. Thereby, the movement of energy from the battery cell 11a to the battery cell 11b is realized. The closed loop circuit formed between the terminals of the battery cell 11b is released after the energy is transferred.

On the other hand, when energy is transferred from the battery cell 11b to the battery cell 11a, the switching elements 25a and 25b are turned on / off in the reverse order. That is, first, the switching element 25b is turned on, a closed loop circuit is formed between the terminals of the battery cell 11b, and the energy of the battery cell 11b is stored in the inductor 26a. Next, the switching element 25b is turned off and the switching element 25a is turned on. Thereby, the closed loop circuit formed between the terminals of the battery cell 11b is released, and a closed loop circuit is newly formed between the terminals of the battery cell 11a. Therefore, the energy of the inductor 26a is stored in the battery cell 11a by the closed loop circuit formed between the terminals of the battery cell 11a. As a result, energy transfer from the battery cell 11b to the battery cell 11a is realized.

Thus, the energy transfer between the battery cell 11a and the battery cell 11b is performed by turning on / off the switching elements 25a and 25b. Energy transfer between the battery cell 11b and the battery cell 11c is performed by turning on / off the

switching elements

25e and 25f. Energy transfer between the battery cell 11c and the battery cell 11d is performed by turning on / off the

switching elements

25c and 25d. The battery cell moving circuit 21 that realizes the energy transfer between the two battery cells 11 is used for equalization to reduce the variation in SOC between the battery cells 11.

The switch control unit 22 is realized as a driving unit that individually turns on / off each switching element 25 in order to transfer energy between the two battery cells as described above. Each switching element 25 is turned on / off according to the control of the CPU 23. Thereby, the CPU 23 functions as a control unit that controls the switch control unit 22.

The CPU 23 is equipped with a non-volatile memory 23a and controls the switch control unit 22 by executing a program stored in the memory 23a. The voltage of each battery cell 11 of the battery 1 is monitored by the voltage monitoring unit 3, and the monitoring result, that is, the voltage value between terminals of each battery cell 11 is output to the CPU 23. The CPU 23 refers to the voltage value between the terminals of each battery cell 11 input from the voltage monitoring unit 3 and determines whether or not equalization should be performed. Thereby, equalization is performed when the CPU 23 determines that equalization should be performed. The equalization is hereinafter referred to as “battery cell balance”.

The voltage value between terminals of each battery cell 11 varies depending on the SOC. From this, the voltage value between terminals of each battery cell 11 input from the voltage monitoring unit 3 corresponds to state information representing SOC. The CPU 23 inputs the voltage value between the terminals of each battery cell 11 and determines whether or not the energy transfer between the two battery cells 11 should be performed, so that the information acquisition means for acquiring the state information, and the battery It also functions as a determination means for determining whether or not to perform cell balance.

The voltage monitoring unit 3 is used to monitor the SOC of each battery cell 11 even when the battery 1 is charged. For this reason, in the present embodiment, the voltage monitoring unit 3 is not a component of the equalization apparatus 2. However, means for generating and outputting state information such as the voltage monitoring unit 3 may be a component of the equalization apparatus 2.

FIG. 2 is a diagram illustrating an example of a voltage between terminals of each battery cell of the battery. Here, the horizontal axis represents the battery cell, and the vertical axis represents the terminal voltage. The number of battery cells 11 is 16, each battery cell 11 connected in series is represented by a position on the horizontal axis, and the voltage between terminals of each battery cell 11 is individually represented by a bar graph.

The SOC of each battery cell 11 of the battery 1 varies while charging and discharging are repeated, and the variation appears as a difference in the voltage value between the terminals of each battery cell 11 as shown in FIG. Therefore, the CPU 23 refers to the voltage value between the terminals of each battery cell 11 input from the voltage monitoring unit 3, extracts the maximum value and the minimum value of the voltage value between the terminals, and extracts the extracted maximum value and minimum value. It is determined whether or not equalization is performed depending on whether or not the difference between the two is equal to or greater than a threshold value. The voltage monitoring unit 3 outputs the voltage value between the terminals of each battery cell 11 every time a predetermined time elapses, or outputs it according to a request from the CPU 23. Here, for convenience, it is assumed that the CPU 23 acquires the voltage value between the terminals of each battery cell 11 from the voltage monitoring unit 3 as necessary.

FIG. 3 is a flowchart of the battery cell monitoring process. This battery cell monitoring process acquires the voltage value between terminals of each battery cell 11 from the voltage monitoring unit 3, determines whether equalization should be performed from the acquired voltage value between terminals of each battery cell 11, and the determination This is a process for performing equalization according to the result. This monitoring process is realized by the CPU 23 executing a program stored in the memory 23a. In a vehicle such as an automobile, this monitoring process is executed when a predetermined condition is satisfied on the assumption that the vehicle is idling or stopped. Here, the battery cell monitoring process will be described in detail with reference to FIG. Note that the predetermined condition is satisfied, for example, that at least one of the elapsed time, the moving distance, and the power consumption amount since the battery cell monitoring process was executed last time is equal to or more than a set threshold value. It is.

First, the CPU 23 inputs a voltage value between terminals of each battery cell 11 obtained by the voltage monitoring unit 3 measuring a voltage between terminals of each battery cell 11 (S1). Next, the CPU 23 extracts the maximum value and the minimum value from the input inter-terminal voltage value of each battery cell 11, and calculates the difference (S2).

After calculating the difference between the maximum value and the minimum value, the CPU 23 determines whether or not the difference is greater than or equal to a threshold value (S3). If the difference is less than the threshold, the determination in S3 is NO, and the battery cell monitoring process ends here. On the other hand, if the difference is greater than or equal to the threshold, the determination in S3 is YES and the process proceeds to S4.

In S4, the CPU 23 executes a balance control process for equalization (battery cell balance). After the execution, the process returns to S1.

The following processing is executed as the balance control processing in S4. Here, in order to better understand the difference from the present embodiment, the processing in the case of applying the method described in Patent Document 1 will also be described.

FIG. 4 is a flowchart of balance control processing when the method described in Patent Document 1 is applied. First, the balance control process in that case will be described in detail with reference to FIGS.

First, the CPU 23 selects between the two battery cells 11 to which energy is transferred from the voltage value between the terminals of each battery cell 11, and for each of the two selected battery cells 11, the difference between the voltage values between the terminals ( From the potential difference, a pulse frequency for performing switching control of the corresponding switching element 25 and a duty ratio, which is a ratio for turning on the switching element 25 in one cycle, are calculated and set (S11).

In addition, when transferring the energy of the amount assumed beforehand between the two battery cells 11, one of the pulse frequency and the duty ratio is fixed, and the other is determined from the value of the internal resistance of the battery cell 11 or the temperature. May be set. The battery 1 has characteristics that the higher the temperature, the lower the viscosity of the electrolyte, the higher the charge transfer rate, and the lower the internal resistance. For this reason, the value of internal resistance and temperature can be used as an index for setting the pulse frequency or duty ratio.

Next, the CPU 23 performs switching control with the set pulse frequency and duty ratio between the two selected battery cells 11, and moves energy by turning on / off the two switching elements 25. Thereafter, the balance control process ends.

In FIG. 2, an arrow between two adjacent battery cells 11 indicates the direction of energy transfer performed between the two battery cells 11 actually selected. As shown in FIG. 2, the selection between the two battery cells 11 as a whole is such that the variation in the voltage value between the terminals of each battery cell 11 becomes smaller, that is, the terminals of each battery cell 11 within a narrower range. It is performed so that the inter-voltage value falls.

Even if such a selection is made between the two battery cells 11 and the energy transfer between them is appropriately performed, the voltage value between the terminals of each battery cell 11 does not always match with high accuracy. This is because the energy transfer between the two battery cells 11 makes the voltage value between the terminals of the two battery cells 11 equal to the voltage value between the terminals of the other battery cells 11 even if the voltage values between the terminals of the two battery cells 11 match. This is because it is not guaranteed to match. The voltage value between the terminals after energy transfer depends on the two battery cells 11 to be selected, and the voltage value between the terminals of the two battery cells 11 to be selected varies.

In the battery cell monitoring process shown in FIG. 3, after the balance control process is executed, the process returns to S <b> 1, so that the difference between the maximum value and the minimum value extracted from the inter-terminal voltage value of each battery cell 11 is less than the threshold value. The balance control process is repeatedly executed. Thereby, the voltage value between terminals of each battery cell 11 can be stored in a range where the difference between the maximum value and the minimum value is less than the threshold value. However, the number of repetitions until the difference between the maximum value and the minimum value converges below the threshold greatly depends on the size of the threshold and the variation state of the voltage value between terminals of each battery cell 11.

For example, the smaller the threshold value, the greater the number of repetitions. Further, for example, when the battery cells 11 having a high inter-terminal voltage value are concentrated around the battery cell 11 having the maximum inter-terminal voltage value, the maximum value is reduced by executing the balance control process once. Since the number is small, the number of repetitions tends to increase. For this reason, the technique described in Patent Document 1 cannot be expected to perform equalization efficiently. Thereby, in this embodiment, in order to efficiently perform high-precision equalization, the battery cells 11 are divided into a plurality of groups and equalization is performed in units of groups.

分け Dividing the battery cells 11 into a plurality of groups and performing equalization in units of groups means equalizing a smaller number of battery cells 11 in parallel. By such grouping, the time required for equalization of the whole battery 1 becomes the same as or close to the time required for equalization most in the group. Therefore, the time required for equalization can be greatly shortened as compared with the case where energy is simply transferred between the two battery cells 11 individually.

It is desired that the equalization is performed so that the variation in the inter-terminal voltage value between the battery cells 11 becomes smaller. From this, equalization in units of groups is performed by calculating the average value of the inter-terminal voltage values of all the battery cells 11 and making the calculated inter-terminal voltage value of each battery cell 11 coincide with the calculated average value. ing.

In the equalization paying attention to the voltage value between the terminals of the two battery cells 11, the variation state of the voltage value between the terminals of the battery cells 11 is not taken into consideration. There is a very high possibility that multiple energy transfers will be performed. However, in the equalization performed by setting the target value (average value) of the voltage value between the terminals of each battery cell 11 and making the voltage value between the terminals of each battery cell 11 coincide with the target value, the same two battery cells It is possible to avoid performing a plurality of energy transfers targeting 11. For this reason, equalization can be performed with high accuracy, and equalization can be efficiently advanced. Since the equalization can be performed efficiently, the time required for the equalization is greatly reduced. As described above, the grouping further reduces the time required for equalization. For these reasons, in the present embodiment, high accuracy is realized while equalization can be performed in an extremely short time.

FIG. 5 is a diagram for explaining a method of grouping power cells. In FIG. 5, as in FIG. 2, the horizontal axis represents the battery cell and the vertical axis represents the voltage across the terminals. A group 62 that divides the power cells 11 is represented by a frame surrounded by a broken line. Accordingly, the grouping example shown in FIG. 5 is a case where the 16 power cells 11 constituting the battery 1 are divided into four groups 61a to 62d.

The grouping as shown in FIG. 5 is performed by paying attention to the average value of the inter-terminal voltage values calculated from the inter-terminal voltage values of each power cell 11. A straight line 61 in FIG. 5 represents the average value of the voltage values between the terminals. Accordingly, the straight line 61 is hereinafter referred to as “average value 61”.

In the grouping focusing on the average value 61, the average value of the inter-terminal voltage values of the power cells 11 belonging to the group 62 (hereinafter referred to as “group average value” in order to clarify the difference from the average value 61) is an average. The value 61 is matched with the allowable range. This is because the equalization of the entire battery 1 is completed by the end of the equalization in units of 62 groups. Thereby, the time required for equalization is the time of the group 62 that takes the longest time for equalization among the groups 62.

Since energy transfer is locally performed between two adjacent battery cells 11, grouping is performed between battery cells 11 belonging to the same group 62 and battery cells 11 belonging to other groups 62. This is done so that they are not connected in series. Thereby, as shown in FIG. 5, the battery cells 11 belonging to the same group 62 are continuously connected in series.

FIG. 6 is a diagram for explaining equalization performed in a group. FIG. 6 shows an equalization procedure for each group 62, taking as an example two groups 62 with different variations in the inter-terminal voltage value of each power cell 11.

In the group 62 shown in FIG. 6A, among the four power supply cells 11a to 11d, the voltage values between the terminals of the two

power supply cells

11a and 11b adjacent to the end thereof coincide with the average value 61 within an allowable range. ing. Therefore, as represented by the arrow in FIG. 6A, in the equalization of the group 62, only energy transfer from the power cell 11d to the power cell 11c is performed. Due to the movement of the energy, the inter-terminal voltage values of all the power cells 11a to 11d belonging to the group 62 are equalized with high accuracy so as to coincide with the average value 61 within an allowable range.

In the group 62 shown in FIG. 6B, among the four power cells 11a to 11d, the voltage values between the terminals of the two

power cells

11b and 11c adjacent to the center in the center coincide with the average value 61 within an allowable range. ing. However, on both sides of the two

power cells

11b and 11c, there are power cells a and 11d whose inter-terminal voltage values do not coincide with the average value 61 within an allowable range. Therefore, as shown by the arrow in FIG. 6B, in the equalization of the group 62, for example, the energy transfer from the power cell 11d to the power cell 11c → the energy transfer from the power cell 11c to the power cell 11b → the power source Energy transfer is performed in the order of energy transfer from the cell 11b to the power source cell 11a. By the energy transfer performed in this order, the voltage values between terminals of all the power cells 11a to 11d belonging to the group 62 are equalized with high accuracy so as to coincide with the average value 61 within an allowable range.

FIG. 7 is a flowchart of the balance control process according to this embodiment. Next, the balance control processing according to the present embodiment will be described in detail with reference to FIG.

First, the CPU 23 calculates an average value 61 of the inter-terminal voltage value using the inter-terminal voltage value of each battery cell 11 input from the voltage monitoring unit 3 in S1 of FIG. 3 (S21). Next, the CPU 23 compares the calculated average value 61 with the inter-terminal voltage value of each battery cell 11, so that the battery cell 11 whose terminal voltage value does not coincide with the average value 61 within the allowable range (“average” in FIG. 7). Extract the above and below cells). At the time of the comparison, the difference (potential difference) between the inter-terminal voltage value and the average value 61 is calculated for each battery cell 11 to be extracted (S22).

After extracting the battery cells 11, the CPU 23 uses several battery cells 11 (indicated as “adjacent several cells” in FIG. 7) that are continuously connected in series for all the battery cells 11 of the battery 1. Grouping is performed by dividing the cumulative value of the calculated potential difference so that it becomes 0 (S23). After grouping, CPU23 determines the range of the battery cell 11 which should perform energy transfer for every group by making each group into a control unit of equalization (S24).

The cumulative value of the potential difference of several battery cells 11 connected in series continuously is not necessarily 0 or a value close to 0. If the upper limit number of the battery cells 11 belonging to the group 62 is increased, the cumulative value of the potential difference is likely to be close to zero. However, the time required for equalization tends to become longer as the number of battery cells 11 belonging to the group 62 increases. Therefore, in the present embodiment, the upper limit number is set to a relatively small number so that the value obtained by dividing the cumulative value by the number of battery cells 11 belonging to the group 62 becomes smaller. Grouping is performed so as to be closer to the average value 61. Thereby, the standard for equalization in the group 62 is actually the group average value. The average value 61 is actually used as a reference when the grouping can be performed ideally so that the average value 61 and the group average value match within an allowable range.

When the inter-terminal voltage value of the battery cell 11 located at either end among the battery cells 11 belonging to the group 62 matches the group average value within an allowable range, the battery cell 11 located at that end moves the energy. Are excluded from the target. When the voltage value between the terminals of the battery cell 11 located at the end and the adjacent battery cell 11 matches the group average value within the allowable range, the adjacent battery cell 11 is also excluded from the energy transfer target. (FIG. 6A). The range of the battery cell 11 that should perform the energy transfer is set in such a manner that the battery cell 11 that should be excluded from the target for the energy transfer is excluded.

When the range of the battery cells 11 to which the energy transfer is to be performed is determined for each group 62, the CPU 23 then describes two battery cells 11 to which the energy is transferred for each group 62 (in FIG. 7, "adjacent cell pair"). ) Is used to calculate and set the pulse frequency and the duty ratio in one cycle for switching control of the corresponding switching element 25 (S25). Thereafter, the CPU 23 performs switching control for the range of the battery cell 11 to which energy transfer is to be performed for each group 62, and moves energy by sequentially turning on / off the plurality of switching elements 25 ( S26). After the switching control of all the groups 62 is finished, this balance control process is finished.

Since the energy transfer between two different battery cells 11 is performed sequentially by equalization of 62 group units, the potential difference between the two battery cells 11 is the result of the energy transfer performed so far, and thereafter It takes into account the energy transfer to be performed. For example, in the group 62 shown in FIG. 6B, the voltage values between the terminals of the

battery cells

11c and 11b are substantially equal, but the energy of the battery cell 11d is moved to the battery cell 11a via the

battery cells

11c and 11b. I have to let it. From this, when the energy transfer between the

battery cells

11d and 11c is performed first, the potential difference between the

battery cells

11d and 11c takes into account the amount of energy to be transferred from the battery cell 11d in addition to the potential difference between them. Will be. The potential difference between the

battery cells

11c and 11b is not limited to the difference between the voltage value between the terminals of the battery cell 11c after the energy transfer and the voltage value between the terminals of the battery cell 11b before the energy transfer. It takes into account the amount of energy to be transferred from. Assuming such a potential difference, by performing energy transfer between the two battery cells 11, the battery cells 11 belonging to each group 62 have an inter-terminal voltage value that matches the average value 61 or the group average value. So that it is equalized.

In this embodiment, since the equalization is performed so that the inter-terminal voltage value of each battery cell 11 approaches the average value 61, the inter-terminal voltage of the battery cell 11 is adopted as an index for equalization. Yes. However, the index may be a state quantity other than voltage. That is, the index may be SOC, remaining charge capacity, discharge capacity, or charge amount. Since the remaining charge capacity, the discharge capacity, and the charge amount of the battery cell 11 can be specified by monitoring the flow of charge from the battery cell 11 and the flow of charge to the battery cell 11, the charge flow monitoring results Alternatively, an integration result obtained using the monitoring result may be adopted as the status information.

In this embodiment, grouping is performed so that the group average value matches the average value 61, but the grouping may be performed according to a predetermined rule. That is, the grouping may be performed without placing importance on bringing the group average value close to the average value 61.

Here, with reference to FIG. 8 and FIG. 9, a modification of grouping according to a predetermined rule will be described in detail. FIG. 8 is a diagram for explaining a modification of the grouping method and equalization performed in the group. FIG. 9 is a flowchart of balance control processing when a modification of the grouping method is applied.

8 is a case where the battery cells 11 of the entire battery 1 are divided into two groups 62. The modification of the grouping method shown in FIG. In order to explain the equalization procedure performed in the group 62, in FIG. 8, the state of the battery 1 at times t0 to t3 is represented by the inter-terminal voltage value of each battery cell 11. The state at time t0 is the state before starting equalization (initial state), the state at time t1 is the state after starting equalization, the state at time t2 is the state after time t1, and the state at time t3 is equal. Represents the state at the end of conversion. As shown in FIG. 8, in the modification, it is assumed that the energy transfer is sequentially performed inward from the battery cells 11 located at both ends of the battery 1.

The battery cells 11 of the entire battery 1 are divided into two groups 62 with the same number or almost the same number according to the number. The broken line drawn in the state at time t0 represents the boundary between the two groups 62.

In such a case of dividing into two groups, the actual number of battery cells 11 belonging to each group 62 becomes relatively large. Therefore, it can be considered that the group average value of each group 62 matches the average value 61 with high accuracy. Thereby, the voltage values between the terminals of the battery cells 11 of the battery 1 are equalized so as to coincide with the average value 61 sequentially from both ends of the battery 1 as represented by the states at the times t1 and t2. At the end of equalization, the voltage values between the terminals of all the battery cells 11 are in a state where the average value 61 coincides with high accuracy. The state at time t <b> 2 is a state before the last energy transfer between the two battery cells 11 in each group 62.

When grouping is performed as shown in FIG. 8 and energy is transferred, for example, the following balance control process may be executed as S4 of FIG. The balance control process will be described in detail with reference to FIG.

First, the CPU 23 calculates an average value 61 of the inter-terminal voltage values using the inter-terminal voltage value of each battery cell 11 input from the voltage monitoring unit 3 in S1 of FIG. 3 (S31). Next, the CPU 23 determines the distance between the two battery cells 11 to which the energy is transferred, the pulse frequency for performing the switching control of the corresponding switching element 25 from the potential difference between the two battery cells 11, and one cycle thereof. The duty ratio is calculated and set (S32). Then, CPU23 performs switching control for moving energy between the determined two battery cells 11 using the set pulse frequency and duty ratio (S33). As described above, the potential difference between the two battery cells 11 considers the result of energy transfer performed so far and the energy transfer to be performed thereafter.

CPU23 which performed switching control next determines whether between all the two battery cells 11 (it describes with "all the cell pairs" in FIG. 9) was balanced (S34). The movement of energy starts from the battery cells 11 positioned at both ends of the battery 1 and ends at each battery cell 11 in contact with the boundary of the group 62. Thereby, equalization of each group 62 is complete | finished by performing the movement of the energy between the two battery cells 11 including the battery cell 11 used as an end point. From this, the determination in S34 is NO when the transfer of energy between the two battery cells 11 including the battery cells 11 that are the end points in the two groups 62 is not completed by the switching control executed in S33 immediately before. Become. In that case, it returns to said S32 and the determination between the two battery cells 11 which transfers energy is performed.

On the other hand, when the transfer of energy between the two battery cells 11 including the battery cells 11 that are the end points in the two groups 62 is completed by the switching control executed immediately before in S33, the determination in S34 is YES. In that case, the balance control process ends here, assuming that equalization for all the battery cells 11 of the battery 1 is completed.

As described above, in the battery cell monitoring process shown in FIG. 3, after the balance control process is executed, the process returns to S <b> 1, so that the confirmation of the equalization result using the measurement result of the voltage value between the terminals of each battery cell 11 is confirmed. Will be done. Thereby, when equalization cannot be appropriately performed by executing the balance control process once, the balance control process is executed again. However, since equalization can be performed with high accuracy as shown in FIG. 8, execution of the balance control process again is avoided with a very high probability.

In the above modification, energy is transferred with the battery cell 11 in contact with the boundary of the group 62 as the end point, but the battery cell 11 in contact with the boundary may not be set as the end point. When the inter-terminal voltage value of the battery cell 11 in contact with the boundary coincides with the average value 61 within an allowable range, the battery cell 11 directly connected to the battery cell 11 may be the end point (FIG. 6A )). When the voltage value between terminals of the battery cell 11 in contact with the boundary and the one or more battery cells 11 connected to the battery cell coincides with the average value 61 within an allowable range, all of the battery cells 11 are subjected to energy transfer. May be excluded.

In this embodiment including the above-described modification, energy is transferred within each group 62, but energy may be transferred between groups 62 as necessary. When such energy transfer between the groups 62 is performed as necessary, it is possible to cope with variations in group average values between the groups 62. For this reason, the equalization of each group 62 can be performed with high accuracy regardless of whether or not the grouping considering the average value 61 is performed.

Claims

In an equalization apparatus that performs equalization to reduce the difference in the state of charge between each battery cell, targeting a battery including a plurality of battery cells connected in series,
A moving means having a plurality of switching elements and capable of transferring energy between the two battery cells separately between two adjacent battery cells by turning on / off the switching elements;
Driving means capable of individually turning on / off switching elements provided in the moving means;
Information acquisition means for acquiring state information representing the state of charge of each battery cell;
A determination unit that determines whether or not to move the energy using the moving unit, based on the state information acquired for each battery cell by the information acquiring unit;
When the determination unit determines that the energy transfer should be performed, the plurality of battery cells are divided into two or more groups, and the driving unit is controlled for each group to use the movement unit. Control means for performing the equalization;
An equalizing device comprising:
The control means obtains an average state of charge of the entire plurality of battery cells from the state information acquired for each battery cell by the information acquisition means, and based on the average state of charge, the averaging for each group I do,
The equalizing apparatus according to claim 1, wherein:
The control means obtains an average charge state of the plurality of battery cells from the state information acquired for each battery cell by the information acquisition means, and determines the plurality of battery cells based on the average charge state. Divided into two or more groups,
The equalizing apparatus according to claim 1 or 2, characterized in that
In an equalization apparatus that performs equalization to reduce the difference in the state of charge between each battery cell, targeting a battery including a plurality of battery cells connected in series,
A moving means having a plurality of switching elements and capable of transferring energy between the two battery cells separately between two adjacent battery cells by turning on / off the switching elements;
Driving means capable of individually turning on / off switching elements provided in the moving means;
Information acquisition means for acquiring state information representing the state of charge of each battery cell;
A determination unit that determines whether or not to move the energy using the moving unit, based on the state information acquired for each battery cell by the information acquiring unit;
When the determination unit determines that the energy transfer should be performed, an average charging state of the plurality of battery cells is obtained from the state information acquired for each battery cell by the information acquisition unit, and the average charging is performed. Control means for controlling the driving means based on the state and performing the equalization using the moving means;
An equalizing device comprising: