JP2019017215A - Power storage device and equalization method therefor - Google Patents

Abstract

To achieve efficient equalization of a power storage device.SOLUTION: A power storage device 1 controls additional discharge means 4 connected with each of a plurality of battery units to additionally discharge a battery unit E with a higher voltage than a reference voltage Vt1 when at least one battery unit E of the plurality of battery units E is discharged to a predetermined reference voltage Vt1 during discharging of a battery pack 2 connected between two terminals P. Additional discharge power subjected to additional discharge is supplied to a terminal P by regeneration means provided between the additional discharge means 4 and the terminal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power storage device having an assembled battery composed of a plurality of battery units and a method for equalizing the power storage devices.

  Conventionally, a technique for equalizing the voltage of a battery cell constituting a power storage device or the amount of stored electric power is known.

  For example, in the battery equalization apparatus of Patent Document 1, each battery cell in the assembled battery is discharged by discharging a high voltage in a stack unit or a battery unit in the stack and charging the discharged power with a low voltage. The same voltage is used.

  Moreover, in the battery equalization apparatus of patent document 2, the 1st equalization control which charges the electric power discharged from one or more battery cells to the other battery cell, and the 2nd which discharges and consumes the electric power of the selected battery cell. A technique for selectively operating equalization control is disclosed.

International publication WO2013 / 114757 pamphlet JP2013-116006A

  However, the conventional techniques such as Patent Documents 1 and 2 have a problem in that power loss occurs in the process of transferring charges between battery cells. Specifically, a power loss due to a discharging circuit or the like occurs in the discharging process of the battery cell, and a power loss due to the charging circuit or the like also occurs in the charging process of the battery cell. As a method for increasing the accuracy of equalization between battery cells, it is conceivable to increase the frequency of moving charges between the battery cells. However, there is a problem that the power loss increases accordingly.

  In addition, when transferring charges between battery cells as in the prior art, it is desirable to reduce the charge / discharge current related to charge transfer between the battery cells and the stack as much as possible based on the viewpoint of suppressing an increase in power loss. However, there is a problem that it takes time to equalize the batteries.

  In addition, as in Patent Document 2, it is conceivable to discharge and consume the power of a battery cell having a high voltage. However, power loss is caused by consumption, and heat generated with power consumption is cooled. There is a problem that it is serious.

  In view of the above problems, an object of the present invention is to efficiently realize equalization of power storage devices.

  The power storage device according to the first aspect of the present invention includes an assembled battery including a plurality of battery units connected in series between two terminals, voltage measuring means for measuring the voltage of each battery unit, and each battery unit. When the additional discharge means connected in parallel and at least one battery unit among the plurality of battery units is discharged to a predetermined reference voltage when discharging the assembled battery, the additional discharge means is controlled to control the reference Control means for additionally discharging a battery unit having a voltage higher than the voltage, and regenerative means provided between the additional discharge means and the terminal and supplying the additional discharged additional discharge power to the terminal. It is characterized by that.

  Here, the “battery unit” includes a single battery cell and a stack configured by connecting a plurality of battery cells in series, parallel, or series-parallel.

  According to this aspect, the battery unit having a voltage higher than the reference voltage is additionally discharged, and the additional discharge power is supplied to the outside through the terminal. That is, the additional discharge power is output so as to be added (supported) to the discharge power from the assembled battery. Thereby, an efficient equalization operation can be realized as compared with the case where the power storage devices are equalized by moving the charge between the battery units.

  Further, for example, when an external load is connected to the terminal of the power storage device, the additional discharge power is added to the supply current supplied to the external load. As a result, it is possible to cause a larger current to flow as compared with the case of moving the charge between the battery units. Therefore, the convergence speed of the equalization operation (equalization process) can be increased. Further, since the additional discharge power is output from the terminal to the outside, it is not necessary to take a heat dissipation measure as in the case of discharging the additional discharge power.

  Furthermore, in this aspect, since a circuit for charging the electric power discharged by the additional discharging means to other battery units is unnecessary, it is realized with a simple circuit configuration as compared with the techniques such as Patent Documents 1 and 2. There is a merit that can be.

  The control means may discharge a battery unit having a voltage higher than the reference voltage with an electric energy corresponding to a difference from the reference voltage. Specifically, for example, the discharge amount of the battery unit having a large difference from the reference voltage is set to be larger than that of the battery unit having a small difference from the reference voltage.

  Thereby, the speed of equalization of the power storage devices can be increased.

  The power storage device according to the present invention can realize an efficient equalization operation with a simple circuit, as compared with a power storage device equalization unit that moves charges between battery units.

It is a block diagram which shows schematic structure of the electrical storage apparatus which concerns on this embodiment. It is a block diagram which shows schematic structure of the electrical storage apparatus which concerns on this embodiment. It is a flowchart which shows charging / discharging operation | movement of an electrical storage apparatus. It is a flowchart which shows equalization operation | movement of an electrical storage apparatus. It is a figure for demonstrating equalization operation | movement of an electrical storage apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or its application.

<Configuration of power storage device>
The power storage device 1 according to this embodiment includes an assembled battery 2 connected between two terminals P. The assembled battery 2 includes a plurality of battery units E connected in series. The assembled battery 2 can be connected to various external loads 8 such as household, industrial, and various devices. The battery unit E may be a single battery cell or a stack composed of a plurality of battery cells. The stack is composed of, for example, a plurality of battery cells connected in series. The battery cell is, for example, a lithium ion battery, and the battery voltage in a fully charged state is set to a predetermined value. The type of battery cell and the battery voltage are not limited to the above example, and can be arbitrarily selected and set according to the specifications required for the power storage device 1.

  The power storage device 1 is added by a voltage measuring unit 3 that measures the voltage of each battery unit E, an additional discharging unit 4 that additionally discharges the battery unit E that satisfies a predetermined condition when the assembled battery 2 is discharged, and an additional discharging unit 4 Regeneration means 6 for regenerating discharged additional discharge power and a controller 5 as control means are further provided.

  The voltage measuring means 3 measures the voltage of the battery unit E and outputs it to the controller 5 as a voltage measurement signal MV. The voltage measuring means 3 is, for example, a voltmeter 31 connected between both terminals of the battery unit E, and a pulsed voltage measurement signal MV is output from the voltmeter 31. The phase of this pulse signal does not need to be set to be the same in the circuit example of FIG. 1, but is set to be the same in the circuit example of FIG.

  The additional discharge means 4 is provided in parallel with the battery unit E, and has a function of additionally discharging the battery unit E based on the additional discharge control signal CS from the controller 5. More specifically, when electric power is supplied from the assembled battery 2 to the external load 8, each battery unit E is discharged, but the additional discharging means 4 is connected to the battery unit E in addition to discharging as the assembled battery 2. Has a function to cause the additional discharge.

  The regenerative unit 6 has a function of receiving the additional discharge power output from the additional discharge unit 4 and additionally supplying the additional discharge power to the terminal P arranged in the discharge path of the assembled battery 2. For example, the regeneration means 6 is connected in parallel with the assembled battery 2 between the two terminals P of the assembled battery 2. Further, a boosting function may be added to the regeneration means 6. This is useful when the voltage of the additional discharge power is lower than the voltage of the assembled battery.

  The controller 5 has a function of controlling the operation of the power storage device 1 and is configured to use the method for equalizing the power storage device 1 according to the present embodiment. The controller 5 is composed of, for example, a microcomputer. Specifically, the controller 5 grasps the voltage state of each battery unit E based on the voltage measurement signal MV output from the voltage measurement means 3. When the assembled battery 2 is discharged, the additional discharge means 4 is controlled via the additional discharge control signal CS, and the battery unit E that satisfies the predetermined condition is additionally discharged.

  1 and 2 illustrate block diagrams illustrating a schematic configuration of the power storage device 1 according to the present embodiment. FIG. 1 shows an example in which a circuit using a transformer T is employed as the additional discharge means 4. FIG. 2 shows an example in which the additional discharge means 4 is realized by a transformerless circuit. 1 and 2 are illustrated for easy understanding of the invention, and are not limited to the configurations of FIGS.

  Moreover, in the following description, the battery unit E is demonstrated as what consists of a stack in which the some battery cell was connected in series. That is, an example in which the assembled battery 2 is configured by connecting N stacks in series will be described. For convenience of explanation, in FIGS. 1 and 2 and FIG. 5 to be described later, the battery unit E is described as E1, E2,..., EN sequentially from the upper side to the lower side of the drawing, and is described using the symbols. It shall be. However, when it does not indicate a specific battery unit, it may be simply referred to as battery unit E.

  In FIG. 1 and FIG. 2, the same number of voltage measuring means 3 and additional discharging means 4 as the battery units E are provided, and each battery unit E is connected in parallel. This configuration is based on the viewpoint of simplifying the processing by the controller 5. Note that, from the viewpoint of circuit area and cost reduction, the number of voltage measuring means 3 and additional discharging means 4 may be reduced as compared with FIGS. 1 and 2, and these may be shared by a plurality of battery units E. Specifically, for example, a selector (not shown) that groups a plurality of battery units E and outputs the voltage of the battery unit E selected from the plurality of battery units E for each group is provided. Then, the voltage output from the selector may be measured by the voltage measuring means 3. The same applies to the additional discharge means 4, and a selector (not shown) for connecting the battery unit E selected from the above group and the additional discharge means 4 is provided, and the additional discharge means 4 is selected by the selector. The unit E may be additionally discharged.

In FIG. 1, the additional discharge means 4 has a primary winding of a transformer T and a switching element Tr connected in series between both terminals of the battery unit E. The switching element Tr is, for example, a MOSFET (Metal-oxide-semiconductor field-effect transistor), and an additional discharge control signal CS output from the controller 5 is applied to the gate thereof. In this configuration, the additional discharge control signal CS is a three-state control signal of, for example, “High”, “Low”, and “Floating”. The controller 5 puts the additional discharge control signal CS supplied to the additional discharge means 4 not to be additionally discharged into a floating state, and gives a pulsed additional discharge control signal CS to the additional discharge means 4 to be additionally discharged. The secondary winding of the transformer T is connected to the regenerative means 6. In the configuration of FIG. 1, as the boosting unit that boosts the voltage of the battery unit E to the voltage of the assembled battery 2 with respect to the additional discharging unit 4 by changing the winding ratio of the transformer T of the additional discharging unit 4. Features can be included. Further, FIG. 1 shows an example in which the regenerative unit 6 is realized by a combination circuit of a plurality of diodes D ₁₁ and D ₁₂ and a plurality of capacitors C ₁₁ and C ₁₂ .

In FIG. 2, in the additional discharge means 4, an NPN transistor Tr ₂₁ and a PNP transistor Tr ₂₂ are connected in series between both terminals of the battery unit E. Further, an additional discharge control signal CS is supplied to the bases of the transistors Tr ₂₁ and Tr ₂₂ via the input capacitor C ₂₁ . Also in this configuration, the additional discharge control signal CS is a three-state control signal of, for example, “High”, “Low”, and “Floating”. The controller 5 puts the additional discharge control signal CS supplied to the additional discharge means 4 not to be additionally discharged into a floating state, and gives a pulsed additional discharge control signal CS to the additional discharge means 4 to be additionally discharged. Further, the bases of the transistors Tr ₂₁ and Tr ₂₂ are connected to each other, and the connection node is connected to a node connecting the emitters of the transistors Tr ₂₁ and Tr ₂₂ via the resistor R ₂₁ . Further, an intermediate node connecting the emitters of the transistors Tr ₂₁ and Tr ₂₂ is connected to the regenerative means 6 via the output transistor C ₂₂ .

  In FIG. 2, the regeneration means 6 may be constituted by a Cockcroft-Walton circuit or a multistage rectifier circuit similar thereto. FIG. 2 shows an example in which the regeneration means 6 is realized by a Cockcroft-Walton circuit, and the number of stages is determined based on the difference between the voltage of the additional discharge power and the voltage between both ends of the assembled battery 2. Good. That is, the regeneration means 6 of FIG. 2 includes a function as a boosting means for boosting the voltage of the additional discharge power output from the additional discharge means 4 to the voltage of the assembled battery 2.

<Equalization control of power storage device>
Hereinafter, the equalization control of the power storage device 1 using the equalization method according to the present embodiment will be described in detail. In the following, it is assumed that the controller is the controller 5 unless otherwise specified. For convenience of explanation, as shown in FIG. 5A, the N battery units E1, E2,..., EN constituting the assembled battery 2 are substantially equalized (for example, about 60%). It is assumed that the operation starts from the beginning. Here, in FIG. 5 and the following description etc., in order to facilitate the understanding of the invention, the difference in the charging state between the battery units E, the change in the charging state, etc. are described exaggerated from the actual one. There may be.

  First, in step S1, the presence or absence of a fully charged battery unit is determined based on the voltage measurement signal MV. If there is no fully charged battery unit (NO in S1), an external power source (not shown) (for example, solar Charging the assembled battery 2 is started from a distributed power source such as a battery or a commercial power source system (S2). If it does so, all the battery units E will be charged simultaneously, and it will be in a full charge state from the battery unit E with a small absolute accumulative amount. In the example of FIG. 5B, the battery unit E1 is first fully charged. At this time, both the battery unit E (for example, E1 in FIG. 5 (b)) having a small absolute chargeable amount and the battery unit E (for example, E2 in FIG. 5 (b)) having a large absolute chargeable amount have the absolute charged amount. It can be regarded as almost the same. Here, the absolute power storage amount indicates the maximum amount of electric charge or the maximum amount of electric energy that can be taken out from the battery unit at each time point. The absolute chargeable amount refers to the maximum amount of charge that can be stored in the battery unit.

  When the fully charged battery unit E1 is detected (YES in S3), charging of the assembled battery 2, that is, charging of all the battery units E1 is stopped based on the detection result, and a standby state is entered. (S4). 5B shows an example in which only the battery unit E1 is fully charged, but a plurality of battery units E out of the N battery units E are fully charged almost simultaneously. Even in such a case, charging of the assembled battery 2 is stopped based on the detection of the fully charged state, and the standby state is entered. The fully charged state is determined by the controller 5 based on the voltage measurement signal MV from the voltage measuring means 3, for example.

  In step S <b> 5, normal discharge is performed from the assembled battery 2 to the external load 8. Normal discharge refers to a state in which only the discharge power of the assembled battery 2 is supplied to the external load 8. In other words, in the normal discharge, the additional discharge by the additional discharge means 4 is not performed, and the additional discharge power from the regenerative means 6 is not supplied to the external load 8. That is, during the period from step S1 to step S5, the additional discharge control signal CS is set in a floating state.

  In step S6, when battery unit E that has decreased to a predetermined reference voltage Vt1 is detected (YES in S6), the flow proceeds to equalization processing in S7 (step S71 in FIG. 4). In the example of FIG. 5C, the battery unit E2 is lowered to a predetermined reference voltage Vt1.

-Equalization processing-
In the equalization process (equalization step), the controller 5 causes the battery unit E having a large absolute power storage amount to perform additional discharge and causes the external load 8 to regenerate the additional discharge power. Thereby, in addition to the discharge power from the assembled battery 2, the regenerative power from the battery unit E having a large absolute power storage amount is supplied to the external load 8. Here, the predetermined reference voltage Vt1 can be arbitrarily set based on the characteristics of the battery unit E and the assembled battery 2, and is stored in advance in a storage unit (not shown) attached to or built in the controller 5, for example. Has been. Further, the predetermined reference voltage Vt1 stored in the storage unit may be able to be recorded and rewritten from the outside. More specifically, the predetermined reference voltage Vt1 is, for example, a voltage obtained by adding a voltage margin Vm (hereinafter simply referred to as voltage margin Vm) necessary for the equalization operation to the discharge end voltage Vf of the battery unit E. is there. The voltage margin Vm is preferably set based on, for example, the additional discharge rate of each battery unit E with respect to the discharge rate of the assembled battery 2. For example, the voltage margin Vm is set to a voltage at which the equalization process between the battery units E ends until the battery unit E that first reaches the predetermined reference voltage Vt1 reaches the end-of-discharge voltage Vf. Is desirable.

  Hereinafter, the equalization process will be described more specifically with reference to FIGS. 4 and 5.

  In step S71 of FIG. 4, the controller 5 specifies a battery unit E (hereinafter referred to as a discharge target unit E) having a large absolute charged amount based on the voltage measurement signal VM. For example, FIG. 5C shows a state in which the voltage of the battery unit E2 is lowered to a predetermined reference voltage Vt1, and in this case, the battery units E1, E3,. Identify.

  And the controller 5 outputs the additional discharge control signal CS (for example, pulse signal) which instruct | indicates additional discharge to the additional discharge means 4 arranged in parallel with the discharge target unit E, and discharges the discharge target unit E further. The additional discharge power of the discharge target unit E is additionally supplied to the external load 8 via the regeneration means 6 and the terminal P. At this time, the normal discharge power from the assembled battery 2 decreases by the amount of additional discharge power additionally supplied from the regeneration means 6.

  In addition, the additional discharge method of each discharge target unit E when there are a plurality of discharge target units E is not particularly limited. For example, from the viewpoint of simplifying the processing, all the discharge target units E are subjected to additional discharge of the same discharge amount at the same time, and the battery unit E having a predetermined reference voltage Vt1 (FIG. 5C) In this example, the additional discharge may be stopped sequentially from the discharge target unit E having the same voltage as E2). Further, for example, paying attention to the difference in the absolute power storage amount between the discharge target units E, and from the viewpoint of reducing this as early as possible, each discharge amount and timing according to the magnitude of the absolute power storage amount of the discharge target unit E The discharge target unit E may be discharged. For example, as shown in FIG. 5 (c), another reference voltage Vt2 (Vt2> Vt1) different from the predetermined voltage is set, and the discharge target unit E (FIG. In the example of c), E1) is discharged first, and after the discharge of the discharge target unit E exceeding the reference voltage Vt2 has progressed to some extent, the other discharge target units E (E3, EN in the example of FIG. 5C) ) May be discharged in a multistage manner.

  Thereafter, when the battery capacities between the battery units E1, E2,..., EN are equalized (YES in S72) and no battery unit E has reached the discharge end voltage (NO in S74), the discharge target unit E The additional discharge is stopped, and normal discharge is performed until any one of the battery units E reaches the discharge end voltage Vf (S73). In the normal discharge in step S73, when any one of the battery units E reaches the discharge end voltage Vf, the controller 5 stops the discharge of the assembled battery 2 and the process ends.

  After returning to step S71 and starting additional discharge, if any battery unit E reaches the discharge end voltage Vf (YES in S76), the controller 5 performs additional discharge of the discharge target unit E and the assembled battery 2. The discharge is stopped, and the process ends.

  As described above, according to this embodiment, when the assembled battery 2 is normally discharged, the controller 5 is added when at least one of the battery units E in the assembled battery 2 is discharged to the predetermined reference voltage Vt1. The discharging unit 4 is controlled so that the battery unit E having a large absolute charged amount of the battery is additionally discharged. Further, the regeneration means 6 supplies the additional discharge power discharged from the additional discharge means 4 to the terminal P. That is, the discharge power from the assembled battery 2 and the additional discharge power from the regeneration means 6 are output from the terminal P of the power storage device 1. As a result, power loss can be reduced and efficient equalization operation can be realized as compared with the case where charges are transferred between battery units or the case where battery units having a large absolute storage amount are discharged and consumed. be able to. In addition, the circuit configuration can be simplified and simplified as compared with the case where charges are transferred between the battery units E. Furthermore, since the additional discharge power is output from the terminal P and supplied to the external load 8, the heat dissipation required for discharging and consuming a battery unit having a large absolute storage amount of the battery as in the prior art. There is no need to provide a structure.

<Comparative example>
As in the present embodiment, for equalization control with a focus on discharge, a technology that focuses on the state of charge of each battery unit at a position where the absolute power storage amount of the battery is relatively high is known. . In such technologies, the main focus is to devise battery unit charging methods, such as transferring charge between batteries or selecting a cell to be charged when charging an assembled battery. Etc. are combined. As a background of adopting such a method, for example, when the battery cell is a lithium ion battery, even if the voltage of one battery cell is discharged to the discharge end voltage or the vicinity thereof, the entire power supply is stopped or suppressed. There is a need to reduce the power efficiency. However, if it is attempted to align the charging state of each battery cell (battery unit) at a position where the absolute charged amount of the battery is relatively high, it takes longer to charge and the electric power than when the absolute charged amount of the battery is low. There is a problem that the loss also increases. Furthermore, when the battery is additionally charged from a state where the absolute charged amount of the battery is high (for example, a state close to full charge), the battery cell may be deteriorated.

  On the other hand, the power storage device 1 according to the present embodiment performs equalization control at a position where the absolute power storage amount of the battery is relatively low, that is, at a voltage near the discharge end voltage Vf. Therefore, the problem of deterioration of the battery unit E as in the comparative example does not occur. In addition, since the additional discharge power is supplied from the regenerative unit 6 to the external load 8, a relatively large current can flow. Thereby, the convergence time of equalization operation (equalization control) can be greatly shortened. Further, as described above, the predetermined reference voltage Vt1 is set to, for example, a voltage obtained by adding the voltage margin Vm to the discharge end voltage Vf, so that the voltage of all the battery cells is equalized before reaching the discharge end voltage. Can be completed. Therefore, it is not necessary to stop or suppress the entire power supply, and the power efficiency does not decrease.

  The predetermined reference voltage Vt1 may be set to a voltage higher than the voltage obtained by adding the voltage margin Vm to the discharge end voltage Vf. However, when the predetermined reference voltage Vt1 is closer to the discharge end voltage Vf, there is an advantage that the remaining capacity of the battery capacity can be grasped more accurately.

  In the above embodiment, an example in which a battery unit in which the absolute power storage amount of the battery is larger than the predetermined absolute power storage amount is specified as the discharge target unit has been described. A battery unit whose possible capacity is larger than a predetermined power storage rate may be specified as a unit to be discharged. Specifically, since the controller 5 can estimate the magnitude of the absolute charged amount based on the voltage measurement signal VM, the battery unit E specifying the “battery charge rate” is large based on the information. Can do. Other operations are the same as those in the above embodiment, and a detailed description thereof is omitted here. Thereby, also in the control based on the “battery storage rate”, the same effect as in the above embodiment can be obtained.

  The present invention is extremely useful because equalization of power storage devices can be efficiently realized.

DESCRIPTION OF SYMBOLS 1 Power storage device 2 Battery assembly 3 Voltage measurement means 4 Additional discharge means 5 Controller (control means)
6 Regenerative means E Battery unit P terminal

Claims (5)

An assembled battery comprising a plurality of battery units connected in series between two terminals;
Voltage measuring means for measuring the voltage of each battery unit;
Additional discharge means connected in parallel to each of the battery units;
When at least one battery unit of the plurality of battery units is discharged to a predetermined reference voltage when the assembled battery is discharged, a battery unit having a voltage higher than the reference voltage is controlled by controlling the additional discharge means. Control means for additional discharge;
A power storage device comprising: regenerative means that is provided between the additional discharge means and the terminal and supplies the additional discharge power that has been additionally discharged to the terminal. The power storage device according to claim 1,
At least one of the additional discharge unit and the regeneration unit includes a booster circuit that boosts the discharge voltage of the battery unit to the output voltage of the assembled battery. The power storage device according to claim 1,
The control unit discharges a battery unit having a voltage higher than the reference voltage with an electric energy corresponding to a difference from the reference voltage. The power storage device according to claim 1,
The power storage device, wherein the control unit stops additional discharge when a voltage difference between the battery units becomes less than a predetermined threshold. A method for equalizing a power storage device having an assembled battery in which a plurality of battery units are connected in series,
A normal discharging step of discharging the assembled battery and supplying the discharged power to an output line;
A voltage measuring step for measuring a voltage of each battery unit;
In the normal discharge step, when the voltage of at least one battery unit is lowered to a predetermined reference voltage, an additional discharge step of additionally discharging a battery unit having a voltage higher than the reference voltage in addition to the discharge of the assembled battery; ,
And a regeneration step for equalizing the state of charge of the plurality of battery units by supplying the additional discharged power to the output line.

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