WO2013133265A1

WO2013133265A1 - Cell balancing device

Info

Publication number: WO2013133265A1
Application number: PCT/JP2013/055975
Authority: WO
Inventors: 慎司広瀬; 守倉石; 正彰鈴木
Original assignee: 株式会社豊田自動織機
Priority date: 2012-03-06
Filing date: 2013-03-05
Publication date: 2013-09-12
Also published as: JP2013187930A

Abstract

In an active-type cell balancing device, a plurality of primary coils which are mutually connected in series are connected in parallel to an assembled battery. Further, a secondary coil is connected in parallel to each battery cell forming the assembled battery. Also, a switching circuit is connected in series to the plurality of primary coils. Then, the plurality of primary coils are transformer-coupled with the plurality of secondary coils which are connected to at least two battery cells of the respective plurality of battery cells.

Description

Cell balance device

The present invention relates to a cell balance device that equalizes the voltages of a plurality of battery cells constituting an assembled battery, and more particularly to an active cell balance device that transfers power between battery cells via a transformer.

A battery block configured by connecting a plurality of battery cells such as lithium ion batteries mounted in a hybrid vehicle or an electric vehicle in series is an assembled battery in which a plurality of battery blocks are connected in series in order to obtain a high voltage. in use.

When the voltage of each battery block constituting such an assembled battery (hereinafter referred to as a block voltage) varies, the deterioration of each battery cell constituting the battery block progresses at an accelerated rate or can be obtained from the battery block. The amount of energy is reduced. Therefore, it is desirable that each block voltage is equal. However, variations in the block voltages may occur due to non-uniform capacity, internal resistance, self-discharge rate, etc. of each battery block. Therefore, conventionally, it has been proposed to eliminate variations in the block voltages by using a cell balance device which is a device for equalizing the block voltages.

And, as a configuration of the cell balance device, conventionally, a switch and a resistor are connected to each battery block constituting the assembled battery, and when there is a battery block with a high block voltage in each battery block, A passive system that equalizes the voltage of each battery block by discharging the battery block is used.

However, since the passive method in principle discharges the power of the battery block, it consumes power wastefully.

Therefore, attention has been paid to an active method for transferring power between each battery block via a transformer as a configuration of the cell balance device. Since this active method is a method of transferring power between the battery blocks, each block voltage can be equalized with less power consumption than the passive method.

However, since the conventional active type cell balance device has a configuration in which one battery block is connected to each tap of the transformer, the number of taps increases as the number of battery blocks in series increases. As a result, the active type cell balance device has a problem that the variation in characteristics between taps increases as the number of battery blocks increases.

Further, the technology relating to the cell balance device is disclosed in the following Patent Documents 1 to 4 and the like.

JP 2004-072975 A JP 2007-274837 A JP 2004-129455 A JP 2005-080469 A

In view of the above circumstances, an object of the present invention is to suppress variation in characteristics between taps due to an increase in the number of battery cells included in an assembled battery in an active cell balance device.

In order to solve the above-described problems, a cell balance device of the present invention is a cell balance device that equalizes each cell voltage of a battery pack in which a plurality of battery cells are connected in series, and is connected in series to each other and in parallel to the battery pack. A plurality of primary coils, a plurality of secondary coils connected in parallel to each battery cell, and a switching circuit connected in series with the plurality of primary coils, the plurality of primary coils comprising: Each of the plurality of battery cells is transformer-coupled to a plurality of secondary coils connected to at least two of the battery cells.

According to the present invention, in the active cell balance device, it is possible to suppress variations in characteristics between taps due to an increase in the number of battery cells included in the assembled battery.

It is a block diagram which shows the cell balance apparatus of Embodiment 1 of this invention. It is a flowchart of the cell balance control of Embodiment 1 of this invention. It is a block diagram which shows the cell balance apparatus of Embodiment 2 of this invention.

[Embodiment 1]
Hereinafter, an active cell balance device according to a first embodiment of the present invention will be described with reference to the drawings. In the following description, it is assumed that the cell balance device according to the first embodiment of the present invention is an active method.

FIG. 1 is a configuration diagram illustrating a cell balance device according to a first embodiment of the present invention.

With reference to FIG. 1, the cell balance apparatus of Embodiment 1 of this invention is demonstrated.

The cell balance device of Embodiment 1 of the present invention that equalizes each block voltage of a battery pack in which

2n battery blocks

11a, 11b to 1na, and 1nb are connected in series includes, for example, 2n

secondary coils

21a, 21b to 2na, 2nb,

2n rectifier circuits

31a, 31b to 3na, 3nb,

2n voltmeters

41a, 41b to 4na, 4nb, n primary coils 51 to 5n, and one switching The circuit 6 includes n cores 71 to 7n, a control unit 8, and a storage unit 9.

In addition, the cell balance device according to the first embodiment of the present invention includes two secondary coils, one primary coil, and one core that are transformer-coupled to each other from the above configurations. The transformer coupling circuits 101 to 10n are configured. A set of battery blocks connected to each transformer coupling circuit will be referred to as battery stacks 201 to 20n, respectively. In the above code, n is an integer of 2 or more. 2n is the number obtained by multiplying 2 by n.

Each of the

battery blocks

11a, 11b to 1na, and 1nb has a configuration in which a plurality of battery cells including storage batteries such as lithium ion batteries, lead batteries, nickel cadmium batteries, and nickel hydride batteries are connected in series. And each battery block comprises an assembled battery by mutually connecting in series. The power line PL1 and the ground line NL1 connected to the assembled battery are connected to a load such as an inverter circuit for driving a motor via a terminal A and a terminal A ′, respectively. And the assembled battery is used in the state electrically insulated from the vehicle body. Each battery block may be replaced with one battery cell.

The

secondary coils

21a, 21b to 2na, 2nb have a configuration in which an electric wire such as a copper wire is wound, for example. Each secondary coil is connected in parallel to one different battery block. Thus, each secondary coil supplies the battery block with an induced current generated by electromagnetic induction when the current flowing through the transformer-coupled primary coil changes.

Further, the number of turns of each secondary coil and the number of turns of the primary coil connected to each secondary coil are set so as to obtain an induced voltage suitable for charging the battery block to be connected. As an example, the winding ratio of one primary coil and one secondary coil may be set to primary coil: secondary coil = 2: 1, respectively. Accordingly, an induced voltage having an amplitude of the block voltage average value, which is an average value of the block voltage values (hereinafter referred to as block voltage values) calculated by the following formula (1), is supplied to each battery block. be able to.
Block voltage average value = total of each block voltage value constituting the assembled battery / 2n (1)
In the above description, the coupling coefficient between each primary coil and each secondary coil is 1, and there is no loss other than leakage flux. In the following description, the same conditions are assumed unless otherwise specified.

The

rectifier circuits

31a, 31b to 3na, 3nb are composed of semiconductor elements such as diodes, for example. The diodes of each rectifier circuit are connected in series between the positive side of each battery block and each secondary coil so that the direction of current flow from the secondary coil to the positive side of the battery block is the forward direction. It is connected. Thereby, each rectifier circuit rectifies the induced current generated in each secondary coil and supplies the current to each battery block. Although FIG. 1 shows an example in which each rectifier circuit is composed of one diode, a known rectifier circuit to which a smoothing capacitor or the like is added may be used. When a smoothing capacitor is added, each battery block and the smoothing capacitor are connected in parallel.

As the

voltmeters

41a, 41b to 4na, 4nb, known voltmeters can be adopted. Each voltmeter is connected in parallel to each battery block. Thereby, each voltmeter measures the block voltage of each battery block connected thereto, and outputs the obtained block voltage value to the control unit 8.

The primary coils 51 to 5n are configured by winding an electric wire such as a copper wire, for example. And each primary coil is mutually connected in series. The primary coils 51 to 5n connected in series with each other are connected in parallel with the assembled battery and connected in series with the switching circuit 6.

The switching circuit 6 can employ a switching element such as an electromagnetic relay, for example. The switching circuit 6 performs an on / off operation (hereinafter referred to as switching) as needed under the control of the control unit 8. As described above, when the switching circuit 6 is switched, intermittent current is supplied from the assembled battery to the primary coils 51 to 5n connected in series. Note that the switching cycle of the switching circuit 6 may be appropriately selected as a cycle in which the power transmission efficiency is increased according to the characteristics of each secondary coil, each primary coil, and each core.

For the cores 71 to 7n, for example, a ferromagnetic or ferrimagnetic material such as iron or ferrite can be used. In each core, two secondary coils in the

secondary coils

21a, 21b to 2na, and 2nb and one primary coil in the primary coils 51 to 5n are wound. . Thereby, each core is increasing the coupling coefficient of the wound secondary coil and the primary coil. In order to improve the power transmission efficiency between the secondary coil and the primary coil, it is desirable to increase the coupling coefficient by using the core in each transformer coupling circuit as described above. However, if the power transmission efficiency of the air-core coil is sufficient depending on the application, the cores 71 to 7n may be omitted.

As the control unit 8, for example, a computer equipped with a memory as a work space such as an ECU (Electronic Control Unit) can be employed. And the control part 8 performs control which switches the switching circuit 6, if each block voltage measured with each voltmeter varies. This control will be described in detail in the description of the operation using the flowchart of the cell balance control in FIG. In addition to the above control, the control unit 8 may perform overall control related to the assembled battery, such as charging control of the assembled battery, output control of the assembled battery, and abnormality detection of each battery block.

The storage unit 9 can employ, for example, an HDD (Hard Disk Drive), an SSD (Solid State Drive), or the like. The storage unit 9 stores an OS program, an application program, and various data necessary for controlling the assembled battery. The various data includes at least a specified value (hereinafter referred to as a variation specified value) for determining whether or not each block voltage varies.

Here, the variation regulation value is a value defined by the user so that the control unit 8 can determine whether or not each block voltage varies. An example is shown below, but the variation regulation value is not limited to the following regulation method.

As an example of the variation regulation value, the battery block having the maximum block voltage value (hereinafter referred to as the block voltage maximum value) among the

battery blocks

11a, 11b to 1na, 1nb constituting the assembled battery, and the minimum block voltage value There is a variation regulation value defined as a difference in the block voltage value (hereinafter referred to as a first block voltage difference) with the battery block (hereinafter referred to as a minimum block voltage value).

A method of determining the variation of each block voltage in the control unit 8 using the specified variation value will be described. First, the control unit 8 acquires each block voltage value from each voltmeter. Then, the control unit 8 extracts the block voltage maximum value and the block voltage minimum value from the acquired block voltage values. Further, the control unit 8 calculates the first block voltage difference by substituting the extracted block voltage maximum value and block voltage minimum value into the following equation (2).
Block voltage maximum value-block voltage minimum value = first block voltage difference (2)
Then, the control unit 8 compares the first block voltage difference obtained by Equation (2) with the variation prescribed value, and when the first block voltage difference is greater than the variation prescribed value. Then, it is determined that each block voltage varies. This determination is performed in the control unit 8 by using the following formula (3).
Specified variation value ≤ 1st block voltage difference (3)
As another example of the prescribed variation value, the absolute value of the difference between the block voltage average value, the block voltage maximum value, and the block voltage minimum value (hereinafter referred to as the second block voltage difference and the third block voltage difference, respectively). There is a prescribed variation value.

A method of determining the variation of each block voltage in the control unit 8 using the specified variation value will be described. First, the control unit 8 acquires each block voltage value from each voltmeter. And the control part 8 substitutes each acquired block voltage value for Formula (1), and calculates a block voltage average value. Further, the control unit 8 extracts a block voltage maximum value and a block voltage minimum value from the acquired block voltage values. Further, the control unit 8 calculates the second block voltage difference by substituting the calculated block voltage average value and the extracted block voltage maximum value into the following equation (4). Further, the control unit 8 calculates the third block voltage difference by substituting the calculated block voltage average value and the extracted block voltage minimum value into the following equation (5).
Block voltage maximum value-block voltage average value = second block voltage difference (4)
Block voltage average value-block voltage minimum value = third block voltage difference (5)
Then, the control unit 8 compares the second block voltage difference and the third block voltage difference obtained by the equations (4) and (5) with the variation specified values, respectively. Then, the control unit 8 determines that each block voltage varies when at least one of the second block voltage difference and the third block voltage difference is greater than or equal to the variation regulation value. This determination is performed by using the following equations (6) and (7) in the control unit 8.
Variation specified value ≦ second block voltage difference (6)
Specified variation value ≤ Third block voltage difference (7)
In the above, an example of two determination methods for determining the variation of each block voltage and two specified variation values used for each block voltage is shown. Further, the present invention is not limited to this, and when using another conceivable method for determining the variation of each block voltage, a prescribed variation value suitable for the determination method may be appropriately defined.

FIG. 2 is a flowchart of cell balance control according to the first embodiment of the present invention.

The cell balance control for equalizing each block voltage according to the first embodiment of the present invention will be described with reference to FIG.

First, the control unit 8 acquires the block voltage values of the

battery blocks

11a, 11b to 1na, 1nb constituting the assembled battery (S201). Specifically, a periodic timing is obtained by counting a signal input by pressing an input unit such as a button type (not shown), a signal input by turning on an ignition key, and an ECU clock. A control start signal for performing cell balance control is input to the control unit 8 using the signal repeatedly input in step 1 as a trigger. Then, the control unit 8 recognizes that cell balance control is started when a control start signal is input, and outputs a block voltage value request signal to each voltmeter. Each voltmeter outputs the measured block voltage value to the control unit 8 when the block voltage value request signal is input. Thereby, the control part 8 acquires a block voltage value from each voltmeter. In addition to the above, the trigger for performing cell balance control is preferably set so as to be generated at an appropriate timing.

Next, the control unit 8 determines whether or not the block voltage value varies by comparing each acquired block voltage with a variation regulation value (S202).

When determining that the block voltage does not vary (No in S202), the control unit 8 outputs a stop signal for stopping the switching circuit 6 to the switching circuit 6.

When this stop signal is input, the switching circuit 6 stops switching (S204) and ends the cell balance control. In S204, when the switching circuit 6 is stopped, the switching circuit 6 is kept stopped.

Further, when it is determined that the block voltages vary (Yes in S202), the control unit 8 outputs a switching signal for switching the switching circuit 6 to the switching circuit 6.

When this switching signal is input, the switching circuit 6 starts switching (S203). If the switching circuit 6 has already been switched, the switching is continued as it is. Then, the process returns to S201.

Then, by repeating the operations of S201 to S204, power is preferentially supplied to the battery cells having a low voltage, and the block voltages are equalized.

Here, the flow of power delivery by the cell balance device will be described. In the following, each secondary coil has the same number of turns, each primary coil has the same number of turns, and the turn ratio of each primary coil to each secondary coil is the primary coil: secondary coil = Take as an example the case of 2: 1. For simplicity, in the following description, the switching cycle of the switching circuit 6 is adjusted as appropriate, and the sum of the amplitudes of the induced voltages of the primary coils (hereinafter referred to as the first induced voltage value) It shall be equal to the voltage value (the sum of the block voltage values of 2n battery blocks).

First, when the switching circuit 6 is switched, a first induced voltage is generated in each primary coil. Since the number of windings of each primary coil is equal, the value of the first induced voltage is equal for each primary coil, and the voltage of the assembled battery is the number of primary coils as shown in the following equation (8). The voltage value divided by is the first induced voltage value.
First induced voltage value = battery voltage value / n (8)
Further, by supplying intermittent current to each primary coil, second induction voltage is generated in each secondary coil by electromagnetic induction from each primary coil. The amplitude of the second induced voltage (hereinafter referred to as the second induced voltage value) is that the number of turns of each secondary coil is ½ of the number of turns of the primary coil. Thus, the voltage value is obtained by dividing the first induced voltage by 2. That is, as is clear from the equations (8) and (9), the second induced voltage value is a block voltage average value.
2nd induced voltage value = 1st induced voltage value / 2 = block voltage average value (9)
Therefore, the battery block having a block voltage value equal to or higher than the block voltage average value has no inductive current flowing from the connected secondary coil, and no power is supplied. Conversely, an induced current generated in the connected secondary coil flows into a battery block having a block voltage value equal to or lower than the block voltage average value, and power is preferentially supplied.

Further, each battery block discharges power from the power line PL1 side while the switching circuit 6 is switching.

In view of the above-described flow of power transfer, only the discharge of power from the power line PL1 is performed in the battery block whose block voltage value is equal to or higher than the block voltage average value. Moreover, in the battery block whose block voltage value is less than the block voltage average value, the electric power is discharged from the power line PL1 and the electric power is charged by the induced current generated in the secondary coil at the same time. When the terminals A and A ′ are not connected to the load, in principle, the power supplied from the assembled battery to each primary coil is equal to the power supplied to the assembled battery via each secondary coil. Become. And since the battery block more than a block voltage average value is performing only discharge of electric power, the electric power discharged from an assembled battery is distributed with the battery block below a voltage average value. Therefore, the charge / discharge amount of the battery block less than the voltage average value is larger in the charge amount. Therefore, as a result, electric power is supplied to the battery block below the voltage average value, and the block voltage increases.

As described above, since the power is transferred by the cell balance device, each block voltage is automatically equalized.

As described above, in the cell balance device according to the first embodiment of the present invention, separate transformer coupling circuits are connected to the battery stacks 201 to 20n. This suppresses an increase in the number of coils wound around one transformer. Therefore, an increase in the number of taps included in one transformer can be suppressed, and variations in characteristics between taps can be suppressed. Furthermore, when increasing or decreasing the number of battery blocks in series, it is only necessary to increase or decrease the number of series of transformer coupling circuits without changing the transformer in the cell balance device.

In addition, the cell balance device according to the first embodiment of the present invention has a configuration in which each block voltage can be equalized only by switching the switching circuit 6. Thereby, each block voltage can be equalized only by controlling one switching circuit, so that the control of the switching circuit can be simplified. Moreover, since the number of switching circuits required for the cell balance device is only one regardless of the number of battery blocks, the cost can be suppressed.

In the first embodiment of the present invention, each transformer coupling circuit has been described as having two secondary coils, one primary coil, and one core. Not limited. The number of each may be changed as appropriate within the range in which the object of Embodiment 1 of the present invention can be achieved.

Moreover, in Embodiment 1 of this invention, when each battery block which comprises an assembled battery is replaced with one battery cell, the cell voltage which is the voltage of a battery cell can be equalized.
[Embodiment 2]
Hereinafter, an active cell balance apparatus according to a second embodiment of the present invention will be described with reference to the drawings. Unless otherwise specified, the cell balance device described in Embodiment 2 of the present invention is assumed to be an active method.

FIG. 3 is a configuration diagram showing a cell balance device according to the second embodiment of the present invention.

Hereinafter, the cell balance device according to the second embodiment of the present invention will be described with reference to FIG.

In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

As shown in FIG. 3, the cell balance device according to the second embodiment of the present invention includes a system power supply 30, a charging device 40, and

changeover switches

50a and 50b in addition to the configuration of the first embodiment of the present invention illustrated in FIG. It is a configuration. By adding these configurations, the second embodiment of the present invention can charge the assembled battery while controlling the cell balance of each battery block by the electric power supplied from the system power supply 30.

The charging device 40 includes an AC / DC converter and a DC / DC converter. Charging device 40 is connected to system power supply 30 via power line PL2 and ground line NL2. Charging device 40 is connected to changeover switch 50a via power line PL3. Furthermore, the charging device 40 is connected to the changeover switch 50b via the ground line NL3. As described above, when the changeover switch 50a is connected to the power line PL3 and the changeover switch 50b is connected to the ground line NL3, a direct current is supplied to the primary coils 51 to 5n connected in series.

Further, for example, a switch element such as an electromagnetic relay can be employed as the changeover switch 50a. The changeover switch 50a is connected to a terminal B which is a connection terminal to the outside of the primary coils 51 to 5n connected in series with each other, and the connection destination can be switched between the power line PL1 and the power line PL3. Has been. When a switching signal for switching the connection destinations of primary coils 51 to 5n connected in series with each other is input from control unit 8, the connection destination of terminal B is switched between power line PL1 and power line PL3.

Further, for example, a switch element such as an electromagnetic relay can be employed as the changeover switch 50b. The changeover switch 50b is connected to a terminal B ′ that is a connection terminal of the primary coils 51 to 5n connected in series with each other, and the connection destination is switched between the ground line NL1 and the ground line NL3. It is configured to be possible. When the switching signal for switching the connection destinations of the primary coils 51 to 5n connected in series with each other is input from the control unit 8, the connection destination of the terminal B ′ is set between the ground line NL1 and the installation line NL3. Switch with.

Further, when the changeover switch 50a is connected to the power line PL1 under the control of the control unit 8, the changeover switch 50b is connected to the ground line NL1. Further, when the changeover switch 50a is connected to the power line PL3 under the control of the control unit 8, the changeover switch 50b is connected to the ground line NL3. In this way, the changeover switch 50a and the changeover switch 50b are switched in synchronization under the control of the control unit 8.

In the cell balance device according to the second embodiment of the present invention configured as described above, the changeover switches 50a and 50b are connected to the control unit 8 in order to charge the assembled battery when the charging device 40 is connected to the system power supply 30. Through the control, the connection destination can be switched to the power line PL3 and the ground line NL3, respectively. The charging device 40 is controlled by the control unit 8 to convert the alternating current of the system power supply 30 into a direct current and supply it to the primary coils 51 to 5n. Thereafter, the control unit 8 switches the switching circuit 6. Thereby, in each transformer coupling circuit, an induced current is generated from each primary coil to each secondary coil by electromagnetic induction. And each battery block which comprises an assembled battery can be charged with the induced current. That is, the cell balance device according to the second embodiment of the present invention can equalize each block voltage while charging the assembled battery using the power from the system power supply 30.

Further, the voltage supplied from the system power supply 30 to the primary coils 51 to 5n connected in series via the charging device 40 and the switching cycle of the switching circuit may be appropriately adjusted by the control unit 8. . Specifically, when each of the induced voltages and induced currents generated in the

secondary coils

21a, 21b to 2na, 2nb is adjusted by the control unit 8 so as to have a magnitude suitable for charging each battery block. good.

Claims

In a cell balance device that equalizes each cell voltage of an assembled battery in which a plurality of battery cells are connected in series,
A plurality of primary coils connected in series to each other and in parallel to the assembled battery;
A plurality of secondary coils connected in parallel to each of the battery cells;
A switching circuit connected in series with the plurality of primary coils;
With
The plurality of primary coils are transformer-coupled to a plurality of secondary coils respectively connected to at least two or more battery cells of the plurality of battery cells.
When the voltage of each battery varies, a control unit that switches the switching circuit;
The cell balance device according to claim 1, further comprising:
A charging device that converts alternating current supplied from the system power source into direct current;
A changeover switch for switching a connection destination of the plurality of primary coils between the assembled battery and the charging device;
With
The controller is
3. The cell according to claim 2, wherein when the assembled battery is charged, the switching circuit is switched by switching the changeover switch so that a connection destination of the plurality of primary coils is the charging device. 4. Balance device.