Power control device, power control method, and power control program

Abstract

To suppress deterioration of charging and discharging performance while suppressing a salt concentration unevenness.SOLUTION: A power control device contains: an acquisition part that acquires each current value of a current flowing in a plurality of secondary batteries connected in parallel; a calculation part that calculates each evaluation value regarding to salt concentration unevenness of the plurality of secondary batteries on the basis of each current value to be acquired; and a control part that control so as to apply a correction current of a direction for suppressing the salt concentration unevenness against the plurality of secondary batteries of an outside of a permission range previously determined by each evaluation value of the plurality of secondary batteries, and to apply a cancelling current in a direction for cancelling the correction current against each secondary battery of which the evaluation value is in the permission range from the plurality of secondary batteries.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a power control device, a power control method, and a power control program.

Background Art

[0002] Patent Document 1 discloses a vehicle equipped with a secondary battery that can be charged by an external power source installed outside the vehicle itself and driven by the secondary battery. The secondary battery is a lithium-ion secondary battery, and includes charge / discharge control means for controlling the charge and discharge of the lithium-ion secondary battery, and deterioration detection means for detecting output deterioration of the lithium-ion secondary battery. The charge / discharge control means includes external power source charging means for charging the lithium-ion secondary battery by the external power source, deterioration evaluation means for evaluating the degree of the output deterioration of the lithium-ion secondary battery detected by the deterioration detection means, and recovery means for performing recovery charge and discharge to recover the output deterioration of the lithium-ion secondary battery when the output deterioration is evaluated to be in a predetermined deterioration state by the deterioration evaluation means.

[0003] Patent Document 2 discloses a power control device characterized by including: a plurality of secondary batteries connected to an electrical device and independently controlled in charge / discharge states; a fuel cell connected to the plurality of secondary batteries and charging each of the secondary batteries; control means for setting a discharge target and a charge target from the plurality of secondary batteries and controlling a discharge state from the discharge target to the electrical device and a charge state from the fuel cell to the charge target; and pause control means for pausing charging of the charge target based on a charge rate of the discharge target and a battery temperature of the charge target.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] For example, in order to suppress the degradation of the charging performance of a secondary battery that is made up of multiple battery packs consisting of lithium-ion secondary batteries, it is necessary to suppress variations in the salt concentration of each battery pack.

[0006] However, the technology described in Patent Document 1 above has the problem that, in order to eliminate uneven salt concentration, recovery charging and discharging using an external power source is required, and therefore the charge and discharge performance of the secondary battery cannot be fully demonstrated during recovery charging and discharging.

[0007] Furthermore, the technology described in Patent Document 2 has the problem that, because it connects multiple battery packs in a way that allows for independent control of charging and discharging, and switches between battery packs for charging and discharging according to the battery degradation state and charge / discharge efficiency, it is difficult to fully utilize the charging and discharging performance of the secondary battery during battery pack switching or when the battery packs are idle.

[0008] This disclosure is made in consideration of the above facts and aims to provide a power control device, a power control method, and a power control program that can suppress deterioration of charge and discharge performance while suppressing uneven salt concentration. [Means for solving the problem]

[0009] To achieve the above objective, the power control device according to the first embodiment includes: an acquisition unit that acquires the current value of the current flowing through a plurality of secondary batteries connected in parallel; a calculation unit that calculates an evaluation value for the salt concentration unevenness of the plurality of secondary batteries based on the acquired current value; and a control unit that controls the plurality of secondary batteries to apply a correction current in a direction that suppresses the salt concentration unevenness to the secondary batteries whose evaluation value is outside a predetermined allowable range, and to apply a cancellation current in a direction that cancels out the correction current to the secondary batteries whose evaluation value is within the allowable range.

[0010] In the power control device according to the second embodiment, the calculation unit calculates the evaluation value by accumulating the integral value of the current value exceeding a predetermined appropriate range during the time period in which the current value of the current flowing through the secondary battery exceeds the predetermined appropriate range.

[0011] The power control device according to the third embodiment is a power control device according to the first or second embodiment, wherein the control unit controls the secondary battery whose evaluation value is outside the allowable range to apply a correction current in a direction that suppresses the salt concentration unevenness to the secondary battery with the largest absolute value of the evaluation value.

[0012] The power control device according to the fourth embodiment, in the power control device according to the third embodiment, controls the control unit to apply a correction current in a direction that suppresses the salt concentration unevenness to secondary batteries other than the secondary battery with the largest absolute value of the evaluation value among the secondary batteries whose evaluation value is outside the allowable range.

[0013] The power control device according to the fifth embodiment is a power control device according to the fourth embodiment, wherein the control unit controls the secondary battery whose evaluation value is within the allowable range to apply a cancellation current in a direction that cancels out the correction current.

[0014] To achieve the above objective, the power control method according to the sixth embodiment includes a process in which a computer acquires the current value of the current flowing through a plurality of secondary batteries connected in parallel, calculates an evaluation value for the salt concentration unevenness of the plurality of secondary batteries based on the acquired current value, applies a correction current in a direction that suppresses the salt concentration unevenness to the secondary batteries among the plurality of secondary batteries whose evaluation value is outside a predetermined allowable range, and applies a counteracting current in a direction that cancels out the correction current to the secondary batteries among the plurality of secondary batteries whose evaluation value is within the allowable range.

[0015] To achieve the above objective, the power control program according to the seventh embodiment causes the computer to perform a process that includes obtaining the current value of the current flowing through a plurality of secondary batteries connected in parallel, calculating an evaluation value for the salt concentration unevenness of the plurality of secondary batteries based on the obtained current value, applying a correction current in a direction that suppresses the salt concentration unevenness to the secondary batteries whose evaluation value is outside a predetermined allowable range, and applying a counteracting current in a direction that cancels out the correction current to the secondary batteries whose evaluation value is within the allowable range. [Effects of the Invention]

[0016] According to this disclosure, the effect is obtained that the degradation of charge and discharge performance can be suppressed while suppressing unevenness in salt concentration. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic diagram of the power control system. [Figure 2] This is a block diagram showing the hardware configuration of a power control device. [Figure 3] This is a functional configuration diagram of the CPU in a power control device. [Figure 4] This is a diagram to explain how evaluation values ​​are calculated. [Figure 5] This is a diagram showing the correspondence between the evaluation value and the amount of variation in salt concentration. [Figure 6] This is a flowchart showing the power control process flow. [Modes for carrying out the invention]

[0018] Hereinafter, an example of an embodiment for implementing the technology of the present disclosure will be described in detail with reference to the drawings. Note that components and processes with the same functions may be assigned the same reference numerals throughout the drawings, and redundant explanations may be omitted as appropriate. Each drawing only schematically shows the technology of the present disclosure to an extent that enables sufficient understanding. Therefore, the technology of the present disclosure is not limited to only the illustrated examples. Also, in this embodiment, descriptions of configurations that are not directly related to the present disclosure and well-known configurations may be omitted.

[0019] In this specification, the term "secondary battery" generally refers to rechargeable energy storage devices. Also, in this specification, the term "lithium-ion secondary battery" refers to a secondary battery that uses lithium ions as electrolyte ions and realizes charge and discharge through the movement of electrons associated with lithium ions between the positive and negative electrodes.

[0020] FIG. 1 is a diagram showing an example of the configuration of a power control system 10.

[0021] As shown in FIG. 1, the power control system 10 includes a secondary battery 20, a current distribution unit 30, and a power control device 40.

[0022] The secondary battery 20 includes n (n>2) battery packs 22-1 to 22-n and n current sensors 24-1 to 24-n provided corresponding to each of the battery packs 22-1 to 22-n. When not distinguishing each battery pack, it may be referred to as the battery pack 22.

[0023] The battery packs 22-1 to 22-n are connected in parallel to the load 50 via the current distribution unit 30. The battery packs 22 each have the same configuration and performance. Each battery pack 22 is composed of a plurality of single cells of the same type of secondary battery, in this embodiment, a lithium-ion secondary battery as an example.

[0024] The load 50 receives the total current Ia, which is the sum of the currents I-1 to In flowing through the battery packs 22-1 to 22-n. In this embodiment, the current value when currents I-1 to In flow in the direction of the arrows in Figure 1 is considered a positive current value, and the current value when they flow in the opposite direction is considered a negative current value.

[0025] The current distribution unit 30, in accordance with instructions from the power control device 40, distributes the current to be supplied to each battery pack 22 according to the required current Ia for the load 50. That is, it distributes the required current Ia to the currents I-1 to In that should be supplied to the battery packs 22-1 to 22-n.

[0026] Figure 2 is a block diagram showing the hardware configuration of the power control device 40. As shown in Figure 2, the power control device 40 includes a controller 42.

[0027] The controller 42 comprises a CPU (Central Processing Unit) 42A, a ROM (Read Only Memory) 42B, a RAM (Random Access Memory) 42C, and an input / output interface (I / O) 42D. The CPU 42A, ROM 42B, RAM 42C, and I / O 42D are connected to each other via a bus 42E. The bus 42E includes a control bus, an address bus, and a data bus. A communication unit 44 and a storage unit 46 are connected to the I / O 42D.

[0028] The communication unit 44 is an interface for data communication with external devices.

[0029] The storage unit 46 is composed of, for example, non-volatile memory. As shown in Figure 2, the storage unit 46 stores power control programs 46A, etc.

[0030] CPU42A is an example of a processor. The term "processor" here refers to a processor in a broad sense, including general-purpose processors (e.g., CPUs) or specialized processors (e.g., GPUs: Graphics Processing Units, ASICs: Application Specific Integrated Circuits, FPGAs: Field Programmable Gate Arrays, programmable logic devices, etc.).

[0031] The power control program 46A may be stored on a non-volatile, non-transitory recording medium or distributed via a network and installed in the power control device 40 as appropriate.

[0032] Examples of non-volatile, non-transitional recording media include CD-ROMs (Compact Disc Read Only Memory), magneto-optical disks, HDDs (Hard Disk Drives), DVD-ROMs (Digital Versatile Disc Read Only Memory), flash memory, and memory cards.

[0033] Figure 3 is a block diagram showing the functional configuration of the CPU 42A of the power control device 40. As shown in Figure 3, the CPU 42A functionally comprises an acquisition unit 60, a calculation unit 62, and a control unit 64. The CPU 42A functions as each of these functional units by reading and executing the power control program 46A stored in the storage unit 46.

[0034] The acquisition unit 60 acquires the current values ​​of the currents I-1 to In flowing through the parallel-connected battery packs 22-1 to 22-n from the current sensors 24-1 to 24-n.

[0035] The calculation unit 62 calculates evaluation values ​​for the salt concentration unevenness of the battery packs 22-1 to 22-n based on the current values ​​I-1 to In acquired by the acquisition unit 60.

[0036] The evaluation value is calculated, for example, as shown in Figure 4, by accumulating the excess current value when the current value (A) flowing through the battery pack 22 exceeds a predetermined lower threshold TL and a predetermined upper threshold TH. Specifically, the evaluation value is the cumulative value obtained by accumulating the integral values ​​of the excess current value during the time periods when the current value flowing through the battery pack 22 exceeds the appropriate range. In the example in Figure 4, the cumulative value of the integral values ​​for each time period indicated by hatching is the evaluation value. As the number of times the current value flowing through the battery pack 22 exceeds the appropriate range increases, the salt concentration unevenness progresses, and the evaluation value increases. In other words, the evaluation value is a value that indicates the degree of progression of salt concentration unevenness.

[0037] Furthermore, the lower threshold TL and upper threshold TH are set to values ​​with the same absolute value but different signs. That is, the lower threshold TL is set to a negative current value, and the upper threshold TH is set to a positive current value.

[0038] In the example in Figure 4, the current value flowing through the battery pack 22 exceeded the upper threshold TH three times. The integral values ​​of the excess current value during each time period in which the current value flowing through the battery pack 22 exceeded the upper threshold TH are +1(A), 0.5(A), and +1(A), respectively. Also, the current value flowing through the battery pack 22 exceeded the lower threshold TL two times. The integral values ​​of the excess current value during each time period in which the current value flowing through the battery pack 22 exceeded the lower threshold TL are -1(A) and -2(A), respectively. Therefore, in the example in Figure 4, the evaluation value, which is the sum of the integral values ​​during each time period in which the current value flowing through the battery pack 22 exceeded the appropriate range of being above the lower threshold TL and below the upper threshold TH, is -0.5(A).

[0039] Figure 5 shows a graph illustrating the relationship between the evaluation value and the amount of salt concentration variation. As shown in Figure 5, as the evaluation value increases in the positive direction, overcharging occurs, and the amount of salt concentration variation in the battery pack 22 increases. Conversely, as the evaluation value increases in the negative direction, overdischarging occurs, and the amount of salt concentration variation in the battery pack 22 increases. In other words, as the absolute value of the evaluation value increases, either overcharging or overdischarging occurs, and the amount of salt concentration variation in the battery pack 22 increases.

[0040] Therefore, the control unit 64 controls the current distribution unit 30 to apply a correction current in a direction that suppresses salt concentration unevenness to battery packs 22 among battery packs 22-1 to 22-n whose evaluation values ​​are outside a predetermined allowable range, and to apply a cancellation current in a direction that cancels out the correction current to battery packs 22 among battery packs 22-1 to 22-n whose evaluation values ​​are within the allowable range.

[0041] For example, as shown in Figure 5, the range of evaluation values ​​in which the amount of salt concentration unevenness is less than or equal to a predetermined threshold Tx is defined as the acceptable range. That is, the range in which the evaluation value is greater than or equal to the lower threshold Ta corresponding to the threshold Tx of salt concentration unevenness and less than or equal to the upper threshold Tb corresponding to the threshold Tx of salt concentration unevenness is set as the acceptable range of evaluation values. Accordingly, the control unit 64 controls the current distribution unit 30 to apply a correction current in the direction of suppressing salt concentration unevenness to battery packs 22 of the battery packs 22-1 to 22-n whose evaluation value is greater than the upper threshold Tb or less than the lower threshold Ta, because they are overcharged or overdischarged and the amount of salt concentration unevenness is greater than the threshold Tx. The threshold Tx is set to a value in which the application of a correction current to the battery pack 22 becomes necessary when the amount of salt concentration unevenness exceeds the threshold Tx.

[0042] The current value of the correction current is set according to, for example, the degree of overcharging or overdischarging. For example, the current value of the correction current is set using table data or a calculation formula such that the current value of the correction current increases as the difference between the evaluation value and the upper threshold Tb increases, and the current value of the correction current increases as the difference between the evaluation value and the lower threshold Ta increases.

[0043] Furthermore, the current value of the cancellation current is set to a value with the opposite sign to the current value of the correction current. That is, if the current value of the correction current is +50(A), the cancellation current is -50(A).

[0044] To simplify the explanation, let's assume that the secondary battery 20 is composed of two battery packs 22-1 and 22-2. If the required current Ia to flow through the load 50 is 100(A), and the evaluation values ​​of both battery packs 22-1 and 22-2 are within the acceptable range, the power control device 40 instructs the current distribution unit 30 to distribute 50(A) equally to both battery packs 22-1 and 22-2.

[0045] For example, if the evaluation value of battery pack 22-1 is greater than the upper threshold Tb, resulting in overcharging, and the correction current value is -150(A), then the cancellation current value is +150A. Therefore, a correction current of -150(A) is applied to battery pack 22-1, resulting in a current of -100(A) flowing through it. Additionally, a cancellation current of +150(A) is applied to battery pack 22-2, resulting in a current of 200(A) flowing through it. As a result, a total current of 100(A) flows through the load 50 from battery packs 22-1 and 22-2, satisfying the required current Ia.

[0046] Conversely, if the evaluation value of battery pack 22-1 is smaller than the lower threshold Ta, resulting in excessive discharge, and the correction current is +150(A), then the cancellation current is -150A. Therefore, a correction current of +150(A) is applied to battery pack 22-1, resulting in a current of +200(A) flowing through it. Additionally, a cancellation current of -150(A) is applied to battery pack 22-2, resulting in a current of -100(A) flowing through it. As a result, a total current of 100(A) flows through the load 50 from battery packs 22-1 and 22-2, satisfying the required current Ia.

[0047] Thus, if battery pack 22-1 becomes overcharged or overdischarged, a correction current is applied to battery pack 22-1 and a counteracting current is applied to battery pack 22-2. Therefore, it is possible to suppress the degradation of charge and discharge performance while suppressing uneven salt concentration in battery pack 22.

[0048] Furthermore, the control unit 64 may control the current distribution unit 30 to apply a correction current in a direction that suppresses salt concentration unevenness to the battery pack 22 with the largest absolute value of the evaluation value among the battery packs 22 whose evaluation value is outside the acceptable range. In this case, the control unit 64 may also control the current distribution unit 30 to apply a correction current in a direction that suppresses salt concentration unevenness to battery packs 22 other than the battery pack 22 with the largest absolute value of the evaluation value among the battery packs 22 whose evaluation value is outside the acceptable range. In addition, the control unit 64 may control the current distribution unit 30 to apply a counteracting current in a direction that cancels out the correction current to battery packs 22 whose evaluation value is within the acceptable range.

[0049] Next, the operation of the power control device 40 will be explained with reference to Figure 6.

[0050] Figure 6 is a flowchart showing an example of the processing flow by the power control program 46A. Note that the processing shown in Figure 6 is executed repeatedly.

[0051] In step S100 of Figure 6, the CPU 42A acquires the current value of the current flowing through each battery pack 22. That is, it acquires the current value detected by current sensors 24-1 to 24-n.

[0052] In step S101, the CPU 42A calculates an evaluation value for each battery pack 22 based on the current value of each battery pack 22 obtained in step S101. That is, as described above, if the current value of the current flowing through the battery pack 22 exceeds the lower threshold TL or the upper threshold TH, the evaluation value is updated by integrating the integral of the current value exceeding the threshold during the time period in which the threshold was exceeded into the evaluation value.

[0053] In step S102, the CPU 42A determines whether there are any battery packs 22 whose evaluation values ​​are outside the acceptable range, as calculated in step S101. If there are any battery packs 22 whose evaluation values ​​are outside the acceptable range, the process proceeds to step S103; otherwise, the process proceeds to step S104.

[0054] In step S103, the CPU 42A instructs the current distribution unit 30 to apply a correction current to the battery pack 22 with the highest evaluation value among the battery packs 22 whose evaluation value was determined to be outside the acceptable range in step S102. As described above, the current value of the correction current is determined according to the difference between the lower threshold Ta or upper threshold Tb and the evaluation value.

[0055] Meanwhile, in step S104, the CPU 42A instructs the current distribution unit 30 to distribute the required current Ia to the load 50 evenly among the battery packs 22. For example, if n=10 and the required current is 100(A), then 10(A) is distributed to each of the battery packs 22.

[0056] In step S105, the CPU 42A determines whether there are any other battery packs 22 with evaluation values ​​outside the acceptable range besides the battery pack 22 with the highest evaluation value. If there are other battery packs 22 with evaluation values ​​outside the acceptable range besides the battery pack 22 with the highest evaluation value, the process proceeds to step S106. If there are no other battery packs 22 with evaluation values ​​outside the acceptable range besides the battery pack 22 with the highest evaluation value, the process proceeds to step S108.

[0057] In step S106, the CPU 42A instructs the current distribution unit 30 to apply a correction current to the battery pack 22 whose evaluation value is outside the acceptable range.

[0058] In step S107, the CPU 42A instructs the current distribution unit 30 to apply a cancellation current to the battery pack 22 whose evaluation value is within the acceptable range.

[0059] For example, suppose n=10, the required current is 100(A), the correction current applied to the battery pack 22 with the highest evaluation value in step S103 is +30(A), and in step S105 there are 2 battery packs 22 whose evaluation values ​​are outside the acceptable range, with correction currents of +10A and -5A respectively. In this case, the total value of the correction currents is 35(A), so the current value of the cancellation current in step S107 is -35(A). Therefore, the cancellation current will be distributed to the 7 battery packs 22 whose evaluation values ​​are within the acceptable range, and a cancellation current of -5(A) will be applied to each battery pack 22.

[0060] Meanwhile, in step S108, the CPU 42A instructs the current distribution unit 30 to apply a canceling current to all battery packs 22 except for the one with the highest evaluation value.

[0061] For example, suppose n=10, the required current is 100(A), and the correction current applied to the battery pack 22 with the highest evaluation value in step S103 is +45(A). In this case, the current value of the cancellation current in step S108 will be -45(A). Therefore, the cancellation current will be distributed to the nine battery packs 22 whose evaluation values ​​are within the acceptable range, and a cancellation current of -5(A) will be applied to each battery pack 22.

[0062] As described above, according to this embodiment, a correction current is applied to the battery pack 22 whose salt concentration unevenness is outside the allowable range, and a cancellation current is applied to the battery pack 22 whose salt concentration unevenness is within the allowable range. This makes it possible to suppress salt concentration unevenness in the battery pack 22 while suppressing deterioration of charge and discharge performance.

[0063] The power control device 40 according to the embodiment has been described as an example. The embodiment may take the form of a program that causes a computer to execute the functions of the power control device 40. The embodiment may also take the form of a non-temporary storage medium that is readable by a computer and stores these programs.

[0064] Furthermore, the configuration of the power control device 40 described in the above embodiment is merely an example, and may be modified as needed without departing from the main purpose.

[0065] Furthermore, the processing flow of the power control program 46A described in the above embodiment is just one example, and unnecessary steps may be deleted, new steps added, or the processing order rearranged, as long as it does not deviate from the main purpose.

[0066] Furthermore, although the above embodiment describes a case in which the processing according to the embodiment is realized by a software configuration using a computer by executing the power control program 46A, the embodiment is not limited to this. The embodiment may also be realized by a hardware configuration or a combination of a hardware configuration and a software configuration. [Explanation of Symbols]

[0067] 10 Power control system 20 Secondary battery 22 battery packs 24 Current Sensor 30 Current distribution section 40 Power control device 42 controllers 44 Communications Department 46 Memory section 46A Power Control Program 50 load 60 Acquisition Department 62 Calculation Section 64 Control Unit

Claims

1. An acquisition unit that acquires the current value of the current flowing through multiple secondary batteries connected in parallel, A calculation unit calculates an evaluation value for the salt concentration unevenness of each of the multiple secondary batteries based on the current values ​​obtained for each of the above, A control unit controls the application of a correction current in a direction that suppresses the unevenness of the salt concentration to secondary batteries whose evaluation value is outside a predetermined allowable range, and to apply a counteracting current in a direction that cancels out the correction current to secondary batteries whose evaluation value is within the allowable range. Power control device including

2. The calculation unit calculates the evaluation value as the integrated value obtained by accumulating the integral values ​​of the current values ​​exceeding a predetermined appropriate range during the time period when the current value flowing through the secondary battery exceeds that range. The power control device according to claim 1.

3. The control unit controls the secondary battery whose evaluation value is outside the acceptable range to apply a correction current in a direction that suppresses the unevenness of the salt concentration to the secondary battery with the largest absolute value of the evaluation value. The power control device according to claim 1 or claim 2.

4. The control unit controls the secondary batteries, excluding the secondary battery with the largest absolute value of the evaluation value, to apply a correction current in a direction that suppresses the unevenness of the salt concentration, among the secondary batteries whose evaluation value is outside the allowable range. The power control device according to claim 3.

5. The control unit controls the secondary battery whose evaluation value falls within the allowable range to apply a cancellation current in a direction that cancels out the correction current. A power control device according to claim 4, comprising:

6. Computers Obtain the current value of each of the multiple secondary batteries connected in parallel, Based on the current values ​​obtained for each of the aforementioned secondary batteries, an evaluation value regarding the salt concentration unevenness is calculated for each of the aforementioned secondary batteries. For secondary batteries whose evaluation value falls outside a predetermined allowable range, a correction current is applied in a direction that suppresses the unevenness of the salt concentration. For secondary batteries whose evaluation value falls within the allowable range, a counteracting current is applied in a direction that cancels out the correction current. A power control method that performs a process including the following.

7. On the computer, Obtain the current value of each of the multiple secondary batteries connected in parallel, Based on the current values ​​obtained for each of the aforementioned secondary batteries, an evaluation value regarding the salt concentration unevenness is calculated for each of the aforementioned secondary batteries. For secondary batteries whose evaluation value falls outside a predetermined allowable range, a correction current is applied in a direction that suppresses the unevenness of the salt concentration. For secondary batteries whose evaluation value falls within the allowable range, a counteracting current is applied in a direction that cancels out the correction current. A power control program that performs a process that includes the following.

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