WO2013187316A1

WO2013187316A1 - Voltage equalization device and method

Info

Publication number: WO2013187316A1
Application number: PCT/JP2013/065779
Authority: WO
Inventors: 正彰鈴木; 慎司広瀬
Original assignee: 株式会社豊田自動織機
Priority date: 2012-06-13
Filing date: 2013-06-07
Publication date: 2013-12-19

Abstract

In the present invention, a controller (105), while detecting a voltage for each block (102(#1-#N)) from voltage sensors (104(#1-#N)), for a block (102) for which such voltage is separated from a target voltage by a first threshold or more, turns on a switch element (114) connected to said block and operates a switch element (109). Due to this, individual equalization control is implemented only for said block (102). After that, by turning on all of the switch elements (114 (#1-#N)) and operating the switch element (109), the controller (105) implements equalization control en masse on all blocks (102(#1-#N)). Effective and high precision equalization control is implemented, while shortening the time therefor, in respect to each block (102).

Description

Voltage equalization apparatus and method

The present invention relates to a voltage equalization apparatus and method for controlling voltage equalization of a battery pack configured by connecting a plurality of battery cells.

A so-called hybrid car, plug-in hybrid car, hybrid vehicle, hybrid electric vehicle, or other vehicle or transport machine (hereinafter referred to as “vehicle”) equipped with a motor (electric motor) as a power source in addition to the engine is put into practical use. Has been. Furthermore, an electric vehicle that does not include an engine and drives the vehicle only by a motor is being put into practical use. As a power source for driving these motors, lithium ion batteries having small and large capacity features have been used. In such an application, for example, a plurality of battery cells are connected in series to form a battery block (hereinafter simply referred to as “block”), and further configured as an assembled battery connected by combining these blocks. There is a case. The high voltage required to drive the motor of the vehicle is obtained by the series connection of the battery cells, and the necessary current capacity and the further high voltage can be obtained by connecting the blocks in combination in series and parallel.

In this case, the characteristics of the lithium ion battery change greatly depending on the temperature, and the remaining capacity and charging efficiency of the battery change greatly depending on the temperature of the environment in which the battery is used. This is especially true in environments where automobiles are used.

As a result, in the battery cells constituting the block, the remaining capacity and output voltage of each battery cell vary. When variations occur in the voltage generated by each battery cell, it becomes necessary to stop or suppress the entire power supply when the voltage of one cell falls below the driveable threshold, resulting in reduced power efficiency. Resulting in. For this reason, the voltage equalization control which equalizes the voltage of each battery cell is required. Furthermore, it is necessary to equalize the voltage between the blocks.

As a conventional technique for voltage equalization control, the so-called active voltage equalization is performed by charging the battery cells that need to be charged with a balance circuit that is configured by combining an inductor and a transformer. A control technology is known (for example, the technology described in Patent Document 1).

In this prior art, between battery cells in a block, power is transferred between battery cells using a switching element and an inductor that are repeatedly turned on and off from a battery cell that needs to be discharged to a battery cell that needs to be charged. Perform cell balance. In addition, by using switch elements and transformers that repeatedly turn on and off between the blocks, the power discharged from the entire assembled battery is moved from the primary winding of the transformer to each block via the secondary winding, Perform cell balance between blocks.

This prior art reduces the power loss by using the discharge power from one battery cell as the charge power to the other battery cell, and the voltage balance of all battery cells in a multi-series storage cell with many series connections. The purpose is to make corrections quickly and smoothly.

However, in this conventional technique, power is evenly supplied to each block via the secondary winding of the transformer, so that it is difficult to efficiently perform cell balance, for example, for a block having a particularly low voltage. Has a problem.

JP 2008-35680 A

An object of the present invention is to perform cell balance efficiently and accurately for each block.

An example of an aspect is a voltage equalization apparatus that equalizes voltages of a plurality of battery cells in an assembled battery including a configuration in which a plurality of blocks configured by connecting a plurality of battery cells in series are connected in series. A balance circuit that has a transformer including a winding connected to each block and equalizes the voltage of each block individually or collectively by transferring energy between each block via each winding; A control unit that controls the operation of the balance circuit so that the voltages of all the blocks are equalized at once after the voltages of the blocks that are separated from the target voltage by a predetermined threshold or more are individually equalized. Prepare.

According to the present invention, equalization for each block from each secondary winding of the transformer is performed individually by individual switching of each block, and equalization driving (final adjustment of equalization) is collectively performed for all blocks. Since switching can be performed, cell balancing can be executed efficiently and with high accuracy while reducing the time for each block.

It is a figure which shows a voltage equalization apparatus. It is a figure for demonstrating voltage equalization control. It is a flowchart (the 1) for demonstrating operation | movement of a control part. It is a flowchart (the 2) for demonstrating operation | movement of a control part. It is a flowchart (the 3) for demonstrating operation | movement of a control part. It is a flowchart (the 4) for demonstrating operation | movement of a control part. It is a figure which shows the voltage equalization apparatus of other embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a voltage equalizing apparatus according to an embodiment of the present invention. In addition, the voltage equalization apparatus of this embodiment is mounted in vehicles, such as a hybrid car, a plug-in hybrid car, or an electric vehicle, for example, Comprising: The assembled battery (battery) mounted in the vehicle is comprised. It is assumed that the voltages of the plurality of battery cells are equalized.

A plurality of battery cells are connected in series to form a block 102, and a plurality of the blocks 102 are connected in series to form an assembled battery 101. In FIG. 1, an assembled battery 101 is configured by connecting N blocks 102 of # 1 to #N (N is a natural number of 1 or more) in series.

The cell balance between the battery cells in each block 102 is performed by a balance circuit (not shown). For example, the balance circuit is a circuit that charges the electric power discharged from each battery cell in the block 102 to the adjacent battery cell in the block 102 via a circuit including a switch element and an inductor.

The transformer balance circuit 103 (balance circuit) includes a switch element 109, a transformer 108, diodes # 1 to #N, and switch elements 114 # 1 to #N. These switch elements 114 together with the switch element 109 constitute a switching unit. The transformer 108 includes # 1 to #N secondary windings 111, a primary winding 110, an iron core 112, an auxiliary winding 118, and a voltage sensor 115. The primary winding 110 is connected to both

output terminals

106 and 107 of the assembled battery 101. Each of the secondary windings 111 of # 1 to #N is reversely wound with respect to the primary winding 110 and has a predetermined turn ratio, and each of the switching elements of # 1 to #N diodes 113 and # 1 to #N It is connected to both poles of the respective blocks 102 of # 1 to #N via 114.

The switch element 109 is, for example, an FET (field effect transistor), and performs a switching operation that repeatedly turns on and off by a pulse signal from the control unit 105. The switch element 114 is also an FET (field effect transistor), for example, but performs an on or off switch operation according to an instruction from the control unit 105 via the control line 116.

The auxiliary winding 118 of the transformer 108 has the same turn ratio as each secondary winding 111, and detects a voltage equivalent to the voltage generated in each secondary winding 111 via the voltage sensor 115.

The voltage sensors 104 of # 1 to #N monitor the output voltages of the blocks 102 of # 1 to #N and notify the control unit 105 via the control line 117.

The control unit 105 is constituted by, for example, a digital signal processor (DSP: Digital Signal Processor).

At the time of individual balance control (equalization control), the control unit 105 detects the block voltage of the blocks 102 of # 1 to #N via the voltage sensors 104 of # 1 to #N, and sets the block voltage to the target. A block that is separated from the voltage by a predetermined threshold or more is detected as a control target block. Then, the control unit 105 turns on the switch element 114 corresponding to the block 102 to be controlled and a pulse signal that operates the switch element 109 according to the difference between the block voltage of the block 102 to be controlled and the target voltage. The frequency and the duty ratio are determined, and the pulse signal is supplied to the switch element 109. As a result, the switching element 109 based on the pulse signal is connected to the secondary winding 111 based on the voltage generated on the secondary winding 111 side connected to the control target block 102 by the switching operation. Through the diode 113 and the switch element 114, individual balance control charging is performed on the block 102 to be controlled. The individual balance control is equalizing only the voltage of the block to be controlled among the voltages of all the blocks 102.

The control unit 105 turns on all the switch elements 114 of # 1 to #N corresponding to all the blocks 102 of # 1 to #N at the time of collective balance control after individual balance control for each block 102. Then, the control unit 105 detects the voltage equivalent to the voltage on the secondary winding 111 side via the auxiliary winding 118 and the voltage sensor 115 of the transformer 108, and compares the voltage with the target voltage, Perform balance control. At this time, the control unit 105 determines the frequency and duty ratio of the pulse signal for operating the switch element 109 according to the difference between the voltage of the voltage sensor 115 and the target voltage, and sends the pulse signal to the switch element 109. Supply. As a result, the diode 113 connected to each secondary winding 111 based on the voltage generated on the side of all the secondary windings 111 of # 1 to #N by the switching operation of the switch element 109 based on the pulse signal. In addition, all the blocks 102 of # 1 to #N are charged in a collective balance control via the switch element 114. The collective balance control is equalizing the voltages of all the blocks 102.

For example, the voltage equalization control as shown in FIG. 2 is performed in the elapse of time after the start of the cell balance executed when the ignition of the vehicle is turned off. First, in a range 204 in which the voltage difference between the voltage 202 of the block 102 that is the target of cell balance control and the average value (target voltage) of all the blocks 102 is large among the plurality of blocks 102, the control target When only the switch element 114 connected to the block 102 is turned on, individual balance control is performed only for the block 102. As a result, the voltage of each block 102 can be equalized in a shorter time than before. At the same time, when the difference between the voltage of each block 102 and the average value (target voltage) of all the blocks 102 is within a period 205 that falls within a certain threshold value 1, # 1 to #N When all the switch elements 114 of # 1 to #N connected to all the blocks 102 are turned on, collective balance control is performed on all the blocks 102.

With the balance control that combines the individual control and the collective control described above, the voltage equalization control is performed with the average voltage of each block 102 detected through the auxiliary winding 118 and the voltage sensor 115 in the addition to the target voltage. With the voltage accuracy between the windings of the secondary winding 111 of the transformer 108, it is possible to perform control such that all the blocks 102 reach the target voltage at once. As a result, it is possible to efficiently and accurately perform cell balance control while reducing the time for each block 102.

3 to 5 are flowcharts showing the operation of the control unit shown in FIG. This operation example is realized as an operation in which a processor (not shown) in the control unit 105 in FIG. 1 executes a control program stored in a memory (not shown). In the following description, reference is made to each part of FIG.

First, the control unit 105 calculates an average value of the voltages (block voltages) # 1 to #N of the blocks 102 detected by the voltage sensors 104 of # 1 to #N, and uses the average value for individual balance control. A target value (target voltage) is set (step S301 in FIG. 3).

Next, the control unit 105 sets # i = 1 as the number #i of the block 102 to determine whether or not to perform individual balance control (step S302 in FIG. 3), and then increments #i by +1. While (step S306 in FIG. 3), until it is determined that the block voltage #i of the # i-th block 102 is not higher than the voltage value obtained by subtracting the threshold value 1 from the target value calculated in step S301 (FIG. 3). Step S303: No), or until it is determined that # i = N (Step S305: YES in FIG. 3), the processes of Steps S303, S305, and S306 are repeated.

The control unit 105 determines whether or not the block voltage #i of the # i-th block 102 is higher than a voltage value obtained by subtracting the threshold value 1 from the target value calculated in step S301 (step S303).

If the block voltage #i is higher than (target value−threshold value 1) and the determination in step S303 is YES, the control unit 105 does not need to perform individual cell balance control for the block 102 of #i, so step S305 Advances to step S306, and #i is incremented by one.

If block voltage #i is not higher than (target value−threshold 1) and the determination in step S303 is NO, control unit 105 determines that individual cell balance control needs to be performed for block 102 of #i. .

In this case, the control unit 105 sets the block voltage of the block #i to be controlled as the control target and turns on only the #i switch element 114 (step S304 in FIG. 3). Thereafter, the control unit 105 proceeds to step S401 in FIG. 4 and performs individual balance control for the block 102 of #i. The block voltage to be controlled is fed back to the control unit 105 via the control line 117.

First, the control unit 105 calculates an average value of the voltages (block voltages) # 1 to #N of the respective blocks 102 detected by the # 1 to #N voltage sensors 104, and calculates the average value as the #i block 102. Is set as a target value for the individual balance control (step S401 in FIG. 4).

Next, the control unit 105 calculates and sets the frequency and duty ratio of the pulse signal for switching control of the switch element 109 from the value (or temperature) of the internal resistance of the block #i (step S402 in FIG. 4). .

Specifically, the control unit 105 separately calculates a block voltage #i detected from the # 1 voltage sensor 104 when it is determined that a current is flowing through the assembled battery 101, for example, when the vehicle is idling. The internal resistance of the block 102 of #i is calculated by dividing by the value of the current flowing through the assembled battery 101. In addition, for example, when it is determined that no current is flowing through the assembled battery 101, for example, when the vehicle is turned off, the control unit 105 acquires the temperature value of the assembled battery 101 from a temperature sensor (not shown). Then, the control unit 105 estimates the internal resistance by referring to the voltage / temperature vs. internal resistance map for each temperature held inside the block voltage #i and the temperature value.

Next, the control unit 105 calculates the frequency and duty ratio of the pulse signal from the value of the internal resistance calculated as described above, for example, based on the following calculation.

First, the number of turns of the primary winding 110 of the transformer 108 is N1, and the number of turns of the secondary winding 111 is N2. If the frequency of the pulse signal is freq, the period is T, the pulse on time is t _on , the duty ratio is D, the voltage on the primary winding 110 side is Vin, and the voltage on the secondary winding 111 side is Vo, then Holds.

By controlling the frequency freq and the duty ratio D of the pulse signal based on this equation, the charge / discharge output voltage Vo for the battery cell can be changed.

Also, since the output power is output based on the following equation, the output power can be changed by controlling the duty ratio. Where Lp is the inductance of the primary winding 110 and P is the output power.

The duty ratio D of the pulse signal applied to the switch element 109 based on the current allowable value set in accordance with the calculated value of the internal resistance, the power to be output, and the pulse frequency freq based on the equation 1 and the equation 2 Can be calculated. Alternatively, on the contrary, the duty ratio D may be determined arbitrarily, and the pulse frequency freq may be determined.

Note that the frequency freq and the duty ratio D of the pulse signal may be simply set to arbitrary values.

The control unit 105 executes switching control by supplying a pulse signal having the pulse frequency freq and the duty ratio D determined as described above to the switch element 109 (performing PWM output) (step S403 in FIG. 4). ).

Next, after the switching control for a predetermined time, the control unit 105 sets the target value calculated in step S401 and the block voltage #i notified from the #i block 102 to be controlled through the control line 117 (FIG. 3 is calculated as an error (see step S404 in FIG. 4). The control target is a target that feeds back a voltage to the control unit 105.

And the control part 105 determines whether the said error became smaller than the predetermined threshold value 2 smaller than the threshold value 1 (step S405). In the individual balance control, the threshold value 2 may be equal to or less than the threshold value 1, and is preferably smaller than the threshold value 1.

If the error is not smaller than the threshold value 2 and the determination in step S405 is NO, the control unit 105 returns to the process of step S401, recalculates the target value, and performs individual balance control for the block 102 of #i. Run repeatedly.

When the error is smaller than the threshold value 2 and the determination in step S405 is YES by the series of iterative processes from step S401 to step S405 in FIG. 4 described above, the control unit 105 performs switching control (PWM output) for the switch element 109. Is stopped (step S406 in FIG. 4). As a result, the individual balance control for the block 102 of #i ends.

Next, the control unit 105 returns to the process in step S301 in FIG. 3 and performs a series of processes in steps S301 to S306 in FIG. 3 to determine again whether or not there is a block 102 to be subjected to individual balance control. Return.

When any block voltage of # 1 to #N becomes higher than (target value−threshold 1) and there is no block 102 to be subjected to individual balance control, and the determination in step S305 in FIG. In step 105, the process proceeds to step S501 in FIG. Thereafter, collective balance control is performed.

First, the control unit 105 determines that any one of the block voltages # 1 to #N detected from the # 1 to #N voltage sensors 104 is based on the current target value (the value set in step S301 in FIG. 3). It is determined whether or not the threshold is 2 or more (step S501 in FIG. 5).

If any one of the block voltages # 1 to #N is more than the threshold value 2 from the target value and the determination in step S501 is YES, the control unit 105 is output via the auxiliary winding 118 of the transformer 108 and the voltage sensor 115. The target voltage is controlled. Further, the control unit 105 turns on all the switch elements 114 of # 1 to #N (step S502 in FIG. 5). As a result, thereafter, the control unit 105 executes batch balance control.

First, the control unit 105 calculates an average value of the voltages (block voltages) # 1 to #N of the respective blocks 102 detected by the voltage sensors 104 of # 1 to #N, and uses the average value for batch balance control. The target value is set (step S503 in FIG. 5).

Next, the control unit 105 calculates and sets the frequency and duty ratio of the pulse signal for switching control of the switch element 109 from the value (or temperature) of the internal resistance of the assembled battery 101 as a whole (step S504 in FIG. 5).

Next, based on the internal resistance value calculated as described above, the control unit 105 is based on the calculation of Equation 1 and Equation 2 described above in the description of Step S404 in FIG. Calculate the frequency and duty ratio of the pulse signal.

The control unit 105 performs switching control by supplying a pulse signal having the pulse frequency freq and the duty ratio D determined as described above to the switch element 109 (performing PWM output) (step S505 in FIG. 5). ).

Next, the control unit 105 calculates a difference between the target value calculated in step S403 and the lowest block voltage (see step S502 in FIG. 5) as an error after switching control for a certain time (step in FIG. 5). S506).

And the control part 105 determines whether the said error became smaller than the predetermined threshold value 2 smaller than the threshold value 1 (step S507 of FIG. 5).

If the error is not smaller than the threshold value 2 and the determination in step S507 is NO, the control unit 105 returns to the process in step S503 to recalculate the target value, and for all the blocks 102 of # 1 to #N. Repeat batch balance control.

When the error is smaller than the threshold value 2 and the determination in step S507 is YES by the series of iterative processes from step S503 to step S507 in FIG. 5 described above, the control unit 105 performs switching control (PWM output) for the switch element 109. Is stopped (step S508 in FIG. 5). Thus, the collective balance control for all the blocks 102 of # 1 to #N is completed.

Before performing the above-described collective balance control, all of the block voltages # 1 to #N detected from the voltage sensors 104 of # 1 to #N are within a range smaller than the threshold value 2 from the target value. If the determination in step S501 of FIG. 5 is NO, the control unit 105 does not need to perform batch balance control and ends the cell balance control operation.

FIG. 6 is a diagram showing a flowchart of another example of the control operation in place of the example of the control operation in FIG.

In the control operation example of FIG. 6, the processing from step S302 to S306 in FIG. 3 is replaced with the processing of steps S501 and S502 in FIG. The processing in step S301 is the same as that in FIG.

After the process of step S301, the control unit 105 detects that any one of the block voltages # 1 to #N detected from the voltage sensors 104 of # 1 to #N is separated from the target value calculated in step S301 by a threshold value 1 or more. It is determined whether or not (step S601).

If any of the block voltages # 1 to #N is more than the threshold value 1 from the target value and the determination in step S601 is YES, the control unit 105 performs individual cell balance control for the block 102 having the lowest block voltage. Judge that it is necessary.

In this case, the control unit 105 uses the lowest block voltage as the control voltage and turns on the switch element 114 connected to the block 102 (step S602 in FIG. 6). Thereafter, the control unit 105 proceeds to step S401 in FIG. 4 and performs individual balance control on the block 102. The processing in FIG. 4 is the same as that described above.

If any of the block voltages # 1 to #N is not more than the threshold value 1 or more from the target value and the determination in step S601 is NO, the control unit 105 proceeds to the process of step S501 in FIG. Thereafter, the above-described collective balance control is performed.

With the above control operation example of the first embodiment, balance control combining individual control and collective control becomes possible.

In the embodiment described above with reference to FIG. 1, the circuit configuration example using the transformer 108 as the transformer balance circuit 103 has been described. However, this circuit portion is not limited to the above circuit configuration example.

As the transformer balance circuit, for example, as shown in FIG. 7A, two transformers T1 and T2, two switch elements SW1 and SW2 for driving them, and a rectifying diode D connected to each block 102 are provided. It can be realized by a flyback circuit provided. The part of the block 102 is the same as in FIG. In this case, either switch element SW1 or SW2 operates individually during individual balance control, and both operate synchronously during collective balance control.

Alternatively, as a transformer balance circuit, for example, as shown in FIG. 7B, a transformer T similar to the transformer 108 in FIG. 1, switch elements SW1 and SW2 similar to the switch element 114 in FIG. 1, and a switch in FIG. This can also be realized by a forward circuit including two diodes D and one inductor L for each block 102 in the configuration including the switch element SW3 similar to the element 109. In this case, at the time of individual balance control, as in the embodiment of FIG. 1, the switch element SW3 is switched on after either of the switch elements SW1 or SW2 is individually turned on. Further, at the time of collective balance control, both the switch elements SW1 and SW2 are turned on, and the switch element SW3 is switched.

Claims

A voltage equalizing device for equalizing the voltages of the plurality of battery cells in an assembled battery including a configuration in which a plurality of blocks configured by connecting a plurality of battery cells in series are connected in series,
A balance circuit having a transformer including windings connected to each block, and equalizing the voltages of the blocks individually or collectively by transferring energy between the blocks via the windings When,
A control unit that controls the operation of the balance circuit so that the voltages of all the blocks are equalized at once after the voltages of the blocks that are separated from the target voltage by a first threshold or more are individually equalized. When,
A voltage equalizing apparatus comprising:
When performing the individual equalization, the control unit compares the voltage with the target voltage while detecting the voltage for each block via a voltage sensor provided for each block. When performing equalization and performing the collective equalization, the collective equalization while comparing the voltage with the target voltage while detecting the voltage on the winding side via the auxiliary winding provided in the transformer I do,
The voltage equalizing apparatus according to claim 1.
A voltage equalization method for equalizing voltages of the plurality of battery cells in a battery pack including a configuration in which a plurality of blocks configured by connecting a plurality of battery cells in series is connected in series,
By transferring energy in each block through each winding constituting the transformer, the voltage of each block is equalized individually or collectively,
After individually equalizing the voltages of the blocks that are separated from the target voltage by a predetermined threshold or more, the voltages of all the blocks are equalized at once.
A voltage equalization method comprising:
When performing the individual equalization, performing the individual equalization while comparing the voltage and the target voltage while detecting the voltage of each block through a voltage sensor provided for each block,
When performing the batch equalization, the batch equalization is performed while comparing the voltage and the target voltage while detecting the voltage on the winding side via the auxiliary winding provided in the transformer.
The voltage equalization method according to claim 3, wherein: