JP2015089156A - Voltage equalization device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of voltage equalization when equalizing voltages of a plurality of batteries connected in series in consideration of polarization of the batteries.SOLUTION: A voltage equalization device is configured to include a storage unit 6 in which information showing correspondence relations between charge/discharge times T of batteries B1 to B3 and offset voltages Vofs indicative of voltage variations of the batteries B1 to B3 after charge/discharge due to an influence of polarization of the batteries B1 to B3 is stored, and a control unit 5 which acquires offset voltages Vofs corresponding to current charge/discharge times T of the batteries B1 to B3 from the information stored in the storage unit 6 and controls voltages V1 to V3 so that voltages detected by voltage detection units VS1 to VS3 are equalized to voltages obtained by adding the offset voltages Vofs to an average voltage Vave or by subtracting the offset voltages Vofs from the average voltage Vave. The control unit 6 corrects the offset voltage Vofs in accordance with currents I1 and I2.

Description

  The present invention relates to a technique for equalizing voltages of a plurality of batteries connected in series.

  In order to extend the life of a plurality of batteries connected in series, the voltage of each battery is equalized. As a voltage equalizing device for equalizing the voltage of each battery, for example, a resistor is connected in parallel to each battery, and a battery having a higher voltage than other batteries is used using a resistor connected to the battery. There is what discharges (for example, refer to Patent Document 1).

However, since such a voltage equalizing apparatus is configured to consume battery energy by resistance, energy loss is large.
Therefore, as a voltage equalizing apparatus that suppresses energy loss, there is an apparatus that uses a switch and an inductor to transfer energy between batteries so that the voltage of each battery is equal to the average value of the voltages.

  However, when charging / discharging of each battery is completed, the polarization of each battery (due to the electrical resistance component depending on the electrode or the like and the chemical resistance component depending on the electrolyte when the battery is charging / discharging) The voltage of each battery fluctuates due to the influence of the phenomenon that the electrode potential fluctuates). Therefore, even when the voltage equalization processing using a switch and an inductor is performed, the voltage of each battery is changed. There is a possibility that it cannot be made equal to the average value of the voltage.

  Therefore, it is conceivable to perform the voltage equalization process in consideration of the voltage fluctuation amount of the battery due to the influence of the polarization of the battery.

JP 2009-159794 A

  However, if the charge / discharge current flowing through each battery changes during the voltage equalization process, the voltage fluctuation amount of each battery changes due to the polarization of each battery, so that the voltage of each battery is equalized. There is a risk that it will not be possible.

  In view of this, an object of the present invention is to improve the accuracy of voltage equalization when equalizing the voltages of a plurality of batteries connected in series in consideration of the polarization of the batteries.

The voltage equalization apparatus according to the embodiment is a voltage equalization apparatus that equalizes voltages of a plurality of batteries connected in series, and includes a voltage detection unit, a current detection unit, a storage unit, and a control unit.
A voltage detection part detects the voltage of a some battery.

The current detection unit detects a current flowing through the plurality of batteries.
The storage unit stores information indicating a correspondence relationship between the charge / discharge time of the battery and the offset voltage indicating the voltage fluctuation amount of the battery after charge / discharge due to the influence of the polarization of the battery.

  The control unit acquires an offset voltage corresponding to the current battery charge / discharge time from the information stored in the storage unit, and the voltage detected by the voltage detection unit is a voltage obtained by adding the offset voltage to the target voltage, Alternatively, the voltages of a plurality of batteries are controlled so that the offset voltage is subtracted from the target voltage.

Further, the control unit corrects the offset voltage in accordance with a change in current detected by the current detection unit.
As described above, since the offset voltage is corrected according to the change in the charge / discharge current of the battery during the voltage equalization process, the offset voltage can be obtained more accurately and the accuracy of voltage equalization can be improved. it can.

  ADVANTAGE OF THE INVENTION According to this invention, when equalizing the voltage of the some battery connected in series considering the polarization of a battery, the precision of the voltage equalization can be improved.

It is a figure which shows an example of the voltage equalization apparatus of embodiment. It is a figure which shows an example of the voltage fluctuation of each battery at the time of a voltage equalization process. It is a figure which shows an example of the information of the correspondence of charging / discharging time and an offset voltage. It is a figure which shows an example of the information of the correspondence of charging / discharging time and an offset voltage. It is a flowchart which shows the operation example of a control part. It is a flowchart which shows the other operation example of a control part.

FIG. 1 is a diagram illustrating an example of a voltage equalization apparatus according to an embodiment.
A voltage equalizing apparatus 1 shown in FIG. 1 equalizes voltages of batteries B1 to B3 connected in series, and includes switches Sw1 to Sw4, inductors L1 and L2, voltage detection units VS1 to VS3, Current detection units IS1 and IS2, a control unit 5 and a storage unit 6 are provided.

  The switch Sw1 is connected in parallel to the battery B1, the switch Sw2 is connected in parallel to the battery B2, the switch Sw3 is connected in parallel to the battery B2, and the switch Sw4 is connected in parallel to the battery B3. Note that the switches Sw1 to Sw4 are, for example, MOSFETs or IGBTs.

  The inductor L1 is provided between the connection point of the batteries B1 and B2 connected in series and the connection point of the switches Sw1 and Sw2. The inductor L2 is provided between the connection point of the batteries B2 and B3 connected in series and the connection point of the switches Sw3 and Sw4.

  The voltage detector VS1 detects the voltage V1 of the battery B1, the voltage detector VS2 detects the voltage V2 of the battery B2, and the voltage detector VS3 detects the voltage V3 of the battery B3. The voltage detection units VS1 to VS3 are, for example, voltmeters.

  The current detection unit IS1 detects a current I1 flowing through the battery B1 or the battery B2 (a current flowing from the battery B1 during discharging to the battery B2 during charging or a current flowing from the battery B2 during discharging to the battery B1 during charging). To do. The current detection unit IS2 detects a current I2 flowing through the battery B2 or the battery B3 (a current flowing from the battery B2 during discharging to the battery B3 during charging, or a current flowing from the battery B3 during discharging to the battery B2 during charging). To do. The current detection units IS1 and IS2 are, for example, ammeters.

  The control unit 5 includes a control signal S1 for controlling on / off of the switch Sw1, a control signal S2 for controlling on / off of the switch Sw2, a control signal S3 for controlling on / off of the switch Sw3, and on of the switch Sw4, The voltage V1 to V3 is controlled by generating the control signal S4 for controlling the off and controlling the operation of the switches Sw1 to Sw4.

  For example, as shown in FIG. 2, in the active type equalization in which the electric power discharged from one or more batteries among the plurality of batteries B1 to B3 is charged to one or more other batteries, the voltage V2 is Consider a case where the voltage is higher than the average voltage Vave, the voltage V1 is lower than the average voltage Vave, and the voltage V3 is lower than the voltage V1. The average voltage Vave (target voltage) is an average voltage of the voltages V1 to V3. The offset voltage Vofs is a voltage fluctuation amount of the batteries B1 to B3 after charging and discharging due to the influence of the polarization of the batteries B1 to B3.

  First, the control part 5 controls operation | movement of switch Sw1-Sw4, and makes battery B1, B3 charge with the discharge energy of battery B2. At this time, the voltage V2 decreases and the voltages V1 and V3 increase.

  Next, when the voltage V1 rises to (average voltage Vave + offset voltage Vofs), the control unit 5 stops the switches Sw1 and Sw2. Thereafter, the voltage V1 decreases to the average voltage Vave due to the influence of polarization.

  Next, the control unit 5 continuously controls the operations of the switches Sw3 and Sw4, and charges the battery B3 with the discharge energy of the battery B2. At this time, the voltage V2 decreases and the voltage V3 increases.

  Then, when the voltage V3 increases to (average voltage Vave + offset voltage Vofs) and the voltage V2 decreases to (average voltage Vave−offset voltage Vofs), the control unit 5 stops the switches Sw2 and Sw3. Thereafter, the voltage V2 increases to the average voltage Vave due to the influence of polarization, and the voltage V3 decreases to the average voltage Vave due to the influence of polarization.

Thereby, since the voltages V1 to V3 coincide with the average voltage Vave, the voltages V1 to V3 can be equalized.
Further, the offset voltage Vofs changes according to the charge / discharge time T of the batteries B1 to B3.

  Therefore, in this embodiment, for example, as shown in FIG. 3, information indicating a correspondence relationship between the charge / discharge time T and the offset voltage Vofs is obtained by experiments and the information is stored as a charge / discharge time-offset voltage correspondence map. Stored in the unit 6. The control unit 5 refers to the charge / discharge time-offset voltage correspondence map stored in the storage unit 6, acquires the offset voltage corresponding to the current charge / discharge time T, and uses the acquired offset voltage to As described above, the end timing of the voltage equalization process is determined.

  Further, when the charge / discharge current flowing through the batteries B1 to B3 changes during the voltage equalization process, the correspondence between the charge / discharge time T and the offset voltage Vofs changes according to the change in the charge / discharge current.

  For example, as shown in FIG. 4, the currents I1 and I2 are 1C (a constant current when the fully discharged batteries B1 to B3 are fully charged in one hour, or the fully charged batteries B1 to B3 are completely charged in one hour. Charge / discharge time-offset voltage correspondence map obtained by multiplying the charge / discharge time T of the offset voltage Vofs by 1/2 and the current I1 and I2 are 2C. This is almost the same as the charge / discharge time-offset voltage correspondence map required sometimes. Further, when the charge / discharge time T in the charge / discharge time-offset voltage correspondence map obtained when the currents I1 and I2 are 1C is doubled and the offset voltage Vofs is halved, the currents I1 and I2 are 0. This is almost the same as the charge / discharge time-offset voltage correspondence map obtained at 5C.

  Therefore, in the present embodiment, by using this fact, it is used when determining the end timing of the voltage equalization process according to the change in the charge / discharge current flowing through the batteries B1 to B3 during the voltage equalization process. The offset voltage Vofs is corrected.

  First, the control unit 5 calculates the corrected charge / discharge time T = the charge / discharge time T before correction × (1 / (current I1, I2 after change / current I1, I2 before change)). Thereby, the charging / discharging time T (corrected charging / discharging time T) of the charge / discharge time-offset voltage correspondence map corresponding to the currents I1, I2 after the change can be obtained.

  Next, the control unit 5 calculates the corrected offset voltage Vofs = the offset voltage Vofs before correction × (currents I1 and I2 / changed / currents I1 and I2 before change). Thereby, the offset voltage Vofs (corrected offset voltage Vofs) of the charge / discharge time-offset voltage correspondence map corresponding to the currents I1 and I2 after the change can be obtained.

And the control part 5 calculates | requires the offset voltage Vofs corresponding to the present charging / discharging time T with reference to the charging / discharging time-offset voltage correspondence map after this change.
Thereby, the offset voltage Vofs used when determining the end timing of the voltage equalization process can be corrected according to the change in the charge / discharge current flowing through the batteries B1 to B3 during the voltage equalization process.

  For example, consider a case where the current charge / discharge time T is 10 [s] and the currents I1 and I2 change from 1C to 2C. The charge / discharge time-offset voltage correspondence map shown in FIG. 3 is a charge / discharge time-offset voltage correspondence map obtained when the currents I1 and I2 are 1C.

  First, the control unit 5 changes 10 [s] of the charge / discharge time T in the charge / discharge time-offset voltage correspondence map shown in FIG. 3 to 5 [s], and changes 20 [s] to 10 [s]. , ..., 60 [s] is changed to 30 [s], ..., 3600 [s] is changed to 1800 [s].

  Next, the control unit 5 changes 20 [mV] of the offset voltage Vofs in the charge / discharge time-offset voltage correspondence map shown in FIG. 3 to 40 [mV], and changes 40 [mV] to 80 [mV]. ..., 50 [mV] is changed to 100 [mV].

  And the control part 5 calculates | requires 80 [mV] as offset voltage Vofs corresponding to 10 [s] which is the present charging / discharging time T with reference to the charging / discharging time-offset voltage correspondence map after the change.

  As described above, when the currents I1 and I2 change from 1C to 2C at the current charge / discharge time T of 10 [s], the offset voltage Vofs can be corrected from 20 [mV] to 80 [mV].

  In the above description, the charge / discharge time-offset voltage correspondence map itself is changed according to the change in the charge / discharge current flowing through the batteries B1 to B3 during the voltage equalization process. The reference destination (current charge / discharge time T) of the charge / discharge time T in the charge / discharge time-offset voltage correspondence map may be changed according to the change in the charge / discharge current flowing in B3.

First, the control unit 5 calculates the current charge / discharge time T after correction = current charge / discharge time T * before correction (currents I1 and I2 after change / currents I1 and I2 before change).
Next, the control unit 5 obtains the offset voltage Vofs corresponding to the current charge / discharge time T after correction with reference to the charge / discharge time-offset voltage correspondence map shown in FIG.

  Then, the control unit 5 calculates the corrected offset voltage Vofs = the offset voltage Vofs × (current after change I1, I2 / current I1, I2 before change) corresponding to the current charge / discharge time T after correction. .

  Thereby, the offset voltage Vofs used when determining the end timing of the voltage equalization process can be corrected according to the change in the charge / discharge current flowing through the batteries B1 to B3 during the voltage equalization process.

For example, consider a case where the current charge / discharge time T is 10 [s] and the currents I1 and I2 change from 1C to 2C.
First, the control unit 5 calculates 20 [s] = 10 [s] × (2C / 1C) as the current charge / discharge time T after correction.

Next, the control part 5 calculates | requires 40 [mV] as offset voltage Vofs corresponding to 20 [s] with reference to the charging / discharging time-offset voltage correspondence map shown in FIG.
Then, the control unit 5 calculates 80 [mV] = 40 [mV] × (2C / 1C) as the corrected offset voltage Vofs.

  As described above, when the currents I1 and I2 change from 1C to 2C at the current charge / discharge time T of 10 [s], the offset voltage Vofs can be corrected from 20 [mV] to 80 [mV].

FIG. 5 is a flowchart illustrating an operation example of the control unit 5 during the voltage equalization process.
First, the control unit 5 starts measuring the charge / discharge time T of the batteries B1 to B3 (S41), and determines whether or not the currents I1 and I2 detected by the current detection units IS1 and IS2 have changed (S42). ).

  Next, when the control unit 5 determines that the currents I1 and I2 have changed (S42: Yes), the currents I1 and I2 before the change, the currents I1 and I2 after the change, and the charge / discharge time-offset voltage correspondence map Are used to obtain the offset voltage Vofs corresponding to the current charge / discharge time T (S43). At this time, as described above, the control unit 5 changes the charge / discharge time-offset voltage correspondence map itself or changes the reference destination of the charge / discharge time T of the charge / discharge time-offset voltage correspondence map. Thus, the offset voltage Vofs is corrected.

  On the other hand, when determining that the currents I1 and I2 have not changed (S42: No), the control unit 5 uses only the charge / discharge time-offset voltage correspondence map and uses the offset voltage Vofs corresponding to the current charge / discharge time T. Is acquired (S44).

  Next, when the control unit 5 determines that the voltages V1 to V3 do not match (average voltage Vave ± offset voltage Vofs) (S45: No), the control unit 5 returns to S42, and the voltages V1 to V3 become (average voltage Vave ±). If it is determined that it matches the offset voltage Vofs) (S45: Yes), the voltage equalization process is terminated (S46).

  According to the voltage equalization apparatus 1 of the present embodiment, the offset voltage Vofs is corrected according to the change in the charge / discharge current of the batteries B1 to B3 during the voltage equalization process, and therefore the offset voltage Vofs is obtained more accurately. And the accuracy of voltage equalization of the batteries B1 to B3 can be improved.

  As shown in FIG. 6, when the control unit 5 determines that the voltages V1 to V3 have not reached the average voltage Vave (S421: No), the control unit 5 returns to S421, and the voltages V1 to V3 reach the average voltage Vave. When it is determined that the operation has been performed (S421: Yes), the operation after S42 may be executed. By configuring in this way, it is not necessary to perform the operation after S42 until the voltage V1 to V3 reaches the average voltage Vave after the voltage equalization process is started, and thus the voltage equalization process is simplified accordingly. can do.

  Moreover, in the said embodiment, although it is the structure which equalizes the voltage of each battery by exchanging energy between two batteries via an inductor, each battery is discharged by the load connected to each battery. Thus, the voltage of each battery may be equalized. That is, the control unit 5 sets the lowest voltage among the voltages V1 to V3 as the target voltage, and sets the voltage other than the lowest voltage to (target voltage-offset voltage Vofs) other than the battery having the lowest voltage. Discharge the battery. At this time, as described above, the control unit 5 obtains the offset voltage Vofs according to the charge / discharge time T, and corrects the offset voltage Vofs according to changes in the currents I1 and I2.

  Moreover, in the said embodiment, although it is the structure which correct | amends offset voltage Vofs according to the change of the charging / discharging current of battery B1-B3 in voltage equalization processing, it is the time of voltage equalization processing with respect to the reference | standard electric current. When the charging / discharging currents of the batteries B1 to B3 are different, the offset voltage Vofs may be corrected based on the reference current and the charging / discharging currents of the batteries B1 to B3 during the voltage equalization process.

  For example, one charge / discharge time-offset voltage correspondence map corresponding to the reference current (1C) is prepared. When the controller 5 determines that the charge / discharge current (2C) of the batteries B1 to B3 during the voltage equalization process is different from the reference current (1C), as described above, the charge / discharge time-offset voltage correspondence map itself The offset voltage Vofs is corrected by changing the reference destination of the charge / discharge time T in the map of charge / discharge time-offset voltage correspondence.

  That is, when the offset voltage Vofs is corrected by changing the charge / discharge time-offset voltage correspondence map itself, first, the control unit 5 first corrects the charge / discharge time T after correction = charge / discharge time T × (before correction). 1 / (Charge / discharge current of the batteries B1 to B3 at the time of voltage equalization processing / current as a reference)) is calculated. Thereby, the charge / discharge time T (corrected charge / discharge time T) of the charge / discharge time-offset voltage correspondence map corresponding to the charge / discharge currents of the batteries B1 to B3 during the voltage equalization process can be obtained. Next, the control unit 5 calculates the corrected offset voltage Vofs = the offset voltage Vofs before correction × (the charge / discharge current of the batteries B1 to B3 during the voltage equalization process / the reference current). Thereby, the offset voltage Vofs (corrected offset voltage Vofs) of the charge / discharge time-offset voltage correspondence map corresponding to the charge / discharge currents of the batteries B1 to B3 during the voltage equalization process can be obtained. And the control part 5 calculates | requires the offset voltage Vofs corresponding to the present charging / discharging time T with reference to the charging / discharging time-offset voltage correspondence map after this change.

  When the offset voltage Vofs is corrected by changing the reference destination of the charge / discharge time T in the charge / discharge time-offset voltage correspondence map, first, the control unit 5 first corrects the current charge / discharge time T = after correction. Current charge / discharge time T × before correction (charge / discharge current of batteries B1 to B3 at the time of voltage equalization processing / current as a reference) is calculated. Next, the control unit 5 refers to the charge / discharge time-offset voltage correspondence map to obtain the offset voltage Vofs corresponding to the current charge / discharge time T after correction. Then, the control unit 5 corrects the offset voltage Vofs after correction = the offset voltage Vofs corresponding to the current charge / discharge time T after correction × (charge / discharge current of the batteries B1 to B3 at the time of voltage equalization processing / current as a reference) ).

DESCRIPTION OF SYMBOLS 1 Voltage equalization apparatus Sw1-Sw4 Switch L1, L2 Inductor VS1-VS3 Voltage detection part IS1, IS2 Current detection part 5 Control part 6 Memory | storage part

Claims (6)

A voltage equalizing device for equalizing voltages of a plurality of batteries connected in series,
A voltage detector for detecting voltages of the plurality of batteries;
A current detection unit for detecting current flowing in the plurality of batteries;
A storage unit for storing information indicating a correspondence relationship between a charge / discharge time of the battery and an offset voltage indicating a voltage fluctuation amount of the battery after charge / discharge due to an influence of polarization of the battery;
The offset voltage corresponding to the current charge / discharge time of the battery is acquired from information stored in the storage unit, and the voltage detected by the voltage detection unit adds the acquired offset voltage to a target voltage. A control unit that controls the voltages of the plurality of batteries so as to be a voltage obtained by subtracting the acquired offset voltage from the target voltage, or
With
The control unit corrects the offset voltage according to a current detected by the current detection unit. The voltage equalization apparatus according to claim 1,
The control unit calculates the charge / discharge time of the battery after correction = charge / discharge time of the battery before correction × (1 / (current flowing through the battery / current as a reference)), and the corrected charge / discharge time. The offset voltage is corrected by calculating the offset voltage before correction × (current flowing in the battery / current as a reference) and changing information stored in the storage unit. Voltage equalizing device. The voltage equalization apparatus according to claim 1,
The control unit calculates the current charge / discharge time of the battery after correction = the current charge / discharge time of the battery before correction × (current flowing through the battery / reference current), and the corrected current The offset voltage corresponding to the charging / discharging time of the battery is acquired from the information stored in the storage unit, and the offset voltage after correction = the offset corresponding to the current charging / discharging time of the battery The voltage equalizing apparatus, wherein the offset voltage is corrected by calculating voltage x (current flowing through the battery / reference current). The voltage equalization apparatus according to claim 1,
The voltage equalizing apparatus, wherein the control unit corrects the offset voltage in accordance with a change in current detected by the current detection unit. The voltage equalization apparatus according to claim 4, wherein
The controller calculates the charge / discharge time of the battery after correction = charge / discharge time of the battery before correction × (1 / (current flowing through the battery after change / current flowing through the battery before change)). And calculating the offset voltage after correction = the offset voltage before correction × (current flowing through the battery after change / current flowing through the battery before change) to store information stored in the storage unit. The voltage equalizing apparatus, wherein the offset voltage is corrected by changing. The voltage equalization apparatus according to claim 4, wherein
The controller calculates the current charge / discharge time of the battery after correction = the current charge / discharge time of the battery before correction × (current flowing through the battery after change / current flowing through the battery before change). Then, an offset voltage corresponding to the current charge / discharge time of the battery after the correction is acquired from the information stored in the storage unit, and the offset voltage after correction = the current battery after the correction The voltage equalizing apparatus, wherein the offset voltage is corrected by calculating an offset voltage corresponding to a charge / discharge time × (current flowing through the battery after change / current flowing through the battery before change).

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