Power device and control method thereof

Abstract

An electrical power device (10) and a control method for the electrical power device (10) wherein an ECU (14) acquires voltage values of at least three electrical storage units (12 (12a–12d)) and, on the basis of the acquired voltage values, mutually connects two electrical storage units (12), among the electrical storage units (12), that have adjacent voltage values.

Description

[Technical field]

[0001] The present invention relates to a power device having at least three power storage units and a control method thereof. [Background technology]

[0002] A power device in which a plurality of batteries (power storage units) are connected in parallel to one another via voltage converters is disclosed in, for example, Japanese Patent Application Laid-Open No. 2016-25791. Summary of the Invention

[0003] Incidentally, when multiple power storage units with different voltages or SOCs (charging rates) are connected in parallel, charging and discharging are performed in which a current flows in proportion to the voltage difference between the power storage units so that the voltages or SOCs of the multiple power storage units are equalized. In this case, if the voltage difference is negligibly small when the multiple power storage units are simply connected, there is no problem in directly connecting the power storage units in parallel.

[0004] However, in the case of removable batteries (energy storage units) that are not fixed batteries, if the battery conditions, such as voltage, temperature, internal resistance, SOC, degree of deterioration, and chargeable capacity, differ from one another, if a large voltage difference occurs between multiple energy storage units connected in parallel after battery replacement, a large current (overcurrent) that exceeds the allowable current due to the voltage difference will flow.

[0005] In order to suppress the occurrence of such an overcurrent, it is conceivable to connect multiple power storage units in parallel via an equalization circuit and electrically control the equalization circuit to reduce the voltage difference between the multiple power storage units, but adding such an equalization circuit is costly.

[0006] The present invention has been made in consideration of such problems, and aims to provide a power device and a control method thereof that can minimize the impact of costs by connecting a storage unit through electrical control alone, without adding any circuits, and thereby suppressing the occurrence of overcurrent.

[0007] A first aspect of the present invention is a power device having at least three storage units, the power device having a voltage acquisition unit that acquires voltage values ​​of each of the storage units, and a connection unit that connects two of the storage units whose voltage values ​​are adjacent to each other based on the voltage values ​​of the storage units acquired by the voltage acquisition unit.

[0008] A second aspect of the present invention is a control method for a power device having at least three storage units, comprising the steps of acquiring voltage values ​​of each of the storage units by a voltage acquisition unit, and connecting two of the storage units whose voltage values ​​are adjacent to each other based on the voltage values ​​of the storage units acquired by the voltage acquisition unit.

[0009] According to the present invention, two storage units having adjacent voltage values ​​are selected from among at least three storage units and connected to each other. This makes it possible to connect the storage units only through electrical control without adding any circuitry, and to suppress the occurrence of an overcurrent. As a result, the impact of costs can be minimized. Therefore, compared to a case where all storage units are connected simultaneously, or a case where two or more storage units having voltage values ​​that are distant from each other (not adjacent) are connected, it is possible to suppress the flow of an overcurrent in the storage units while reducing the voltage difference. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a configuration diagram of a power device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a configuration diagram of the power storage unit in FIG. [Diagram 3] 2 is a flow chart illustrating the operation of the power device of FIG. [Figure 4] FIG. 1 is an explanatory diagram of a first embodiment. [Diagram 5] FIG. 1 is an explanatory diagram of a first embodiment. [Figure 6] FIG. 1 is an explanatory diagram of a first embodiment. [Figure 7] FIG. 1 is an explanatory diagram of a first embodiment. [Figure 8] FIG. 4 is an explanatory diagram of another connection example in the first embodiment. [Figure 9] FIG. 11 is an explanatory diagram of a second embodiment. [Figure 10] FIG. 11 is an explanatory diagram of a second embodiment. [Figure 11] FIG. 11 is an explanatory diagram of a second embodiment. [Figure 12] FIG. 11 is an explanatory diagram of a second embodiment. [Figure 13] FIG. 11 is an explanatory diagram of another connection example according to the second embodiment. [Figure 14] FIG. 13 is a configuration diagram of a power device according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a power device and a control method thereof according to the present invention will be described with reference to the accompanying drawings.

[0012] [1. Schematic configuration of this embodiment] As shown in Fig. 1, the power device 10 according to this embodiment has at least three power storage units 12, an ECU 14 (voltage acquisition unit, connection unit), a notification unit 16, an internal battery 18 (another power storage unit), and multiple switches 20 and 22. Note that Fig. 1 illustrates a case in which four power storage units 12 (hereinafter sometimes referred to as first to fourth power storage units 12a to 12d) are arranged.

[0013] The power device 10 is also applied to the power supply system of various electric vehicles such as unicycles, two-wheelers, three-wheelers, and four-wheelers. The power device 10 is not limited to application to electric vehicles. The power device 10 can also be applied to (1) moving bodies other than vehicles such as airplanes and ships, (2) various charging equipment such as home chargers, (3) various dischargers that output power from the power storage unit 12, (4) various working machines such as general-purpose working machines, lawnmowers, and tillers, and (5) power supply systems (Energy Storage Systems) that supply power to various electrical devices installed or disposed inside or outside buildings such as houses. The following description will mainly focus on the case where the power device 10 is applied to an electric vehicle.

[0014] Each power storage unit 12 is a power storage device that is detachable from the power device 10 and can be charged and discharged. For example, a battery pack of a detachable lithium ion battery is suitable as the power storage unit 12. Each power storage unit 12 is connected in parallel to a load 24 such as a motor of an electric vehicle and a PDU. That is, a positive terminal on the output side of each power storage unit 12 is connected to a positive terminal of the load 24. A negative terminal on the output side of each power storage unit 12 is connected to a negative terminal of the load 24.

[0015] The built-in battery 18 is a fixed type power storage device provided in the power device 10. The built-in battery 18 is connected in parallel to the load 24 via the switch 20. That is, the positive terminal of the built-in battery 18 is connected to the positive terminal of the load 24 via the switch 20. The negative terminal of the built-in battery 18 is connected to the negative terminal of the load 24. A voltage conversion circuit (not shown), such as a DC / DC converter, may be interposed between the built-in battery 18 and the load 24. In this way, when power is supplied to the load 24 from both the power storage units 12 and the built-in battery 18, the voltage of the built-in battery 18 can be adjusted by the voltage conversion circuit, and the adjusted voltage can be output to the load 24. In addition, when the built-in battery 18 alone supplies power to the load 24, or when power is supplied to the load 24 from the power storage units 12, the voltage conversion circuit may not be required.

[0016] Built-in battery 18 is the main power source for power device 10, and also a startup power source for starting up each power storage unit 12. Therefore, built-in battery 18 is also connected to each power storage unit 12 via each switch 22. That is, the positive terminal of built-in battery 18 is connected to the positive power supply terminal of each power storage unit 12 via each switch 22. The negative terminal of built-in battery 18 is connected to the negative power supply terminal of each power storage unit 12.

[0017] The ECU 14 is an electronic control device for the electric vehicle, and realizes various functions such as connection control for each switch 26 (see FIG. 2), which will be described later, by reading and executing a program stored in a non-transitory storage medium (not shown). The notification unit 16 is an output device such as a display device or a speaker provided in the electric vehicle, and notifies the processing result of the ECU 14 to the outside.

[0018] The ECU 14 can transmit and receive signals or information to and from each power storage unit 12, each switch 20, 22, and the load 24 via a communication line 28 of a Controller Area Network (CAN). Therefore, the ECU 14 controls and turns on each switch 20, 22 to electrically connect the built-in battery 18 and the load 24, or electrically connects the built-in battery 18 and each power storage unit 12.

[0019] Fig. 2 is a diagram showing the internal configuration of each power storage unit 12. Each power storage unit 12 has the same configuration, and Fig. 2 shows only one power storage unit 12. As shown in Fig. 2, each power storage unit 12 is a battery pack that houses a switch 26 (two-way connection circuit), a battery 30, a battery management system (BMU) 32, a resistor 34, a temperature sensor 36, and a communication unit 38.

[0020] The positive electrode of the battery 30 is connected to the positive terminal of the load 24 via the switch 26 and the positive terminal of the power storage unit 12. The negative electrode of the battery 30 is connected to the negative terminal of the load 24 via a resistor 34 and the negative terminal of the power storage unit 12. In addition, the communication unit 38 transmits and receives signals or information to and from the ECU 14 via the communication line 28.

[0021] The BMU 32 is started when the switch 22 is turned on under the control of the ECU 14 and power is supplied from the built-in battery 18. The BMU 32 monitors the battery 30. Specifically, the BMU 32 electrically connects the battery 30 and the load 24 by turning on the switch 26 based on a control signal received by the communication unit 38 from the ECU 14 via the communication line 28. The BMU 32 also sequentially detects the voltage values ​​across the resistor 34, and sequentially calculates the current value of the current (discharging current or charging current) flowing through the battery 30 based on the detected voltage value and the resistance value of the resistor 34. The BMU 32 also sequentially detects the voltage value of the battery 30, and sequentially calculates the SOC of the battery 30 based on the detected voltage value and the calculated current value. The BMU 32 also sequentially acquires the temperature of the battery 30 detected by a temperature sensor 36 such as a thermistor. The BMU 32 sequentially transmits information including the voltage value, the current value, the SOC, and the temperature from the communication unit 38 to the ECU 14 via the communication line 28 .

[0022] Therefore, the ECU 14 sequentially acquires the above information, and determines (judges) whether each switch 26 needs to be turned on (connected) or off (disconnected) based on each acquired information. The ECU 14 also transmits a control signal based on this determination result to each communication unit 38 via the communication line 28, thereby turning on or off the switch 26 of each power storage unit 12. Furthermore, the ECU 14 transmits a control signal to each switch 20, 22 via the communication line 28, thereby turning on or off each switch 20, 22.

[0023] 2. Operation of this embodiment The operation of the power device 10 according to the present embodiment configured as above (a control method for the power device 10) will be described with reference to Fig. 3. This operation involves connecting each of the power storage units 12 (see Figs. 1 and 2) in parallel with each other or with the load 24 in stages, and electrically controlling the voltage difference between each of the power storage units 12, thereby preventing a large current (overcurrent) exceeding the allowable current from flowing within the power device 10 including between each of the power storage units 12.

[0024] In this operational explanation, a case will be described in which power is supplied from each power storage unit 12 to load 24 when the connection between built-in battery 18 and load 24 is interrupted by turning switch 20 off. Note that when built-in battery 18 and load 24 are connected by turning switch 20 on, built-in battery 18 supplies power to load 24 via a voltage conversion circuit (not shown).

[0025] In step S1, ECU 14 supplies a control signal to each switch 22, thereby switching each switch 22 from off to on. This electrically connects built-in battery 18 and BMU 32 of each power storage unit 12, and power supply from built-in battery 18 to each power storage unit 12 (BMU 32) begins. This starts up each BMU 32. Also, each communication unit 38 reaches a state in which it can communicate with ECU 14 via communication line 28 (step S1: YES). Note that in step S1, ECU 14 and each power storage unit 12 may perform a numbering process to assign an ID number or the like to each power storage unit 12 via communication line 28.

[0026] In step S2, the BMU 32 of each power storage unit 12 detects the voltage value of the battery 30. In this case, each BMU 32 simultaneously acquires the temperature of the battery 30, calculates the current value of the current flowing through the battery 30, and calculates the SOC of the battery 30. Therefore, each BMU 32 transmits these pieces of information from the communication unit 38 via the communication line 28 to the ECU 14. Therefore, the ECU 14 can acquire information such as the voltage value of the battery 30 from each power storage unit 12.

[0027] In step S3, ECU 14 compares the voltage values ​​of batteries 30 of each power storage unit 12, and determines whether the voltage difference between the highest voltage value (maximum voltage value) and the lowest voltage value (minimum voltage value) is within a voltage threshold. Here, the voltage threshold is a threshold for determining whether a large current (overcurrent) will flow between each power storage unit 12 due to the voltage difference, and refers to a voltage difference value according to an allowable current. Therefore, if the voltage difference is within the voltage threshold, the occurrence of an overcurrent is suppressed. On the other hand, if the voltage difference exceeds the voltage threshold, there is a possibility that an overcurrent will occur.

[0028] If the voltage difference between the maximum voltage value and the minimum voltage value falls within the voltage threshold value (step S3: YES), then in step S4, ECU 14 determines that no overcurrent will occur even if all power storage units 12 are connected in parallel to load 24. Next, based on the result of this determination, ECU 14 transmits a control signal to communication units 38 of each power storage unit 12 via communication line 28 to instruct them to turn on switch 26.

[0029] The BMU 32 of each power storage unit 12 switches the switch 26 from off to on based on the control signal received by the communication unit 38. This connects each power storage unit 12 (battery 30) in parallel to the load 24. As a result, power can be supplied to the load 24 and charging / discharging can be performed between each power storage unit 12 while suppressing the voltage difference between each power storage unit 12 within the voltage threshold. This allows the voltage values ​​of the batteries 30 of each power storage unit 12 to be averaged.

[0030] On the other hand, in step S3, if the voltage difference between the maximum voltage value and the minimum voltage value exceeds the voltage threshold value (step S3: NO), ECU 14 determines that there is a possibility of an overcurrent occurring when all power storage units 12 are connected, and proceeds to step S5. In step S5, ECU 14 compares the voltage values ​​of batteries 30 of each power storage unit 12, and selects a connection combination of at least two power storage units 12 that results in a voltage difference within the voltage threshold value. That is, in the case of the selected connection combination, the voltage values ​​are close to each other (adjacent), so it is considered that an overcurrent will not occur if at least two power storage units 12 are connected in parallel.

[0031] Next, the ECU 14 transmits a control signal instructing to turn on the switch 26 to the communication unit 38 of the at least two power storage units 12 via the communication line 28. As a result, the BMUs 32 of the at least two power storage units 12 switch the switch 26 from off to on based on the control signal received by the communication unit 38. As a result, the at least two power storage units 12 (batteries 30) are connected in parallel to the load 24. This makes it possible to supply power to the load 24 and to charge and discharge the two power storage units 12 while keeping the voltage difference between the two power storage units 12 within the voltage threshold.

[0032] The BMU 32 sequentially acquires the voltage value, etc., of each battery 30. In the next step S6, the ECU 14 acquires information such as the voltage value of the battery 30 from at least two power storage units 12, and determines, from the voltage value included in the acquired information, whether or not the voltage value of the battery 30 has been averaged between the at least two power storage units 12 by charging and discharging.

[0033] When the voltage values ​​of the battery 30 are averaged (step S6: YES), the ECU 14 returns to step S2 and repeatedly executes the processes of steps S2, S3, S5, and S6. Therefore, in the power device 10 according to this embodiment, the ECU 14 repeatedly acquires the voltage value of the battery 30 of each power storage unit 12, determines the connection of each power storage unit 12, and connects each power storage unit 12 by each switch 26 until the voltage difference between the maximum voltage value and the minimum voltage value falls within the voltage threshold value (step S3: YES). That is, in this embodiment, the power storage units 12 are connected in parallel in stages, and charging and discharging are performed between the power storage units 12, thereby averaging the voltage differences of the power storage units 12.

[0034] 3. Specific Example of Operation of This Embodiment Next, specific examples (first embodiment and second embodiment) of the above-mentioned operation will be described with reference to FIGS.

[0035] The first embodiment, as shown in Figs. 4 to 8, illustrates a case in which, when the voltage values ​​of the first to fourth power storage units 12a to 12d (see Figs. 1 and 2) decrease in this order, parallel connection to load 24 is repeated in stages with first power storage unit 12a having the maximum voltage value as a reference, so that all power storage units 12a to 12d are finally connected in parallel. On the other hand, the second embodiment, as shown in Figs. 9 to 13, illustrates a case in which parallel connection to load 24 is repeated in stages with fourth power storage unit 12d having the minimum voltage value as a reference, so that all power storage units 12a to 12d are finally connected in parallel.

[0036] In the first and second examples, as shown in Fig. 4 and Fig. 9, the voltage values ​​before connection of the first to fourth power storage units 12a to 12d are V1 to V4, and the voltage threshold is Vthr. In Fig. 4 to Fig. 13, the first to fourth power storage units 12a to 12d are denoted as No. 1 to No. 4.

[0037] <3.1 First Example> The first embodiment will be described with reference to FIGS. 4 to 7. As shown in FIG. 4, |V1-V4|>Vthr (step S3: NO in FIG. 3). Therefore, when the first to fourth power storage units 12a to 12d are connected in parallel to the load 24 (see FIGS. 1 and 2), an overcurrent may flow (connection indicated by "NG" in FIG. 4). On the other hand, in the connection of the first to third power storage units 12a to 12c, the connection of the second to fourth power storage units 12b to 12d, the connection of the first power storage unit 12a and the second power storage unit 12b, the connection of the second power storage unit 12b and the third power storage unit 12c, and the connection of the third power storage unit 12c and the fourth power storage unit 12d, the voltage values ​​of the power storage units 12 to be connected are close to each other (adjacent to each other), so that the voltage difference is within the voltage threshold Vthr and no overcurrent occurs (connection indicated by "OK" in FIG. 4).

[0038] Therefore, in the case of FIG. 4, ECU 14 alternatively selects the connection between first power storage unit 12a and second power storage unit 12b (connection A) or the connection between first to third power storage units 12a to 12c (connection B) based on first power storage unit 12a having the maximum voltage value (voltage value V1).

[0039] Here, when ECU 14 selects connection A, ECU 14 transmits a control signal for turning on switch 26 to communication unit 38 of first power storage unit 12a and second power storage unit 12b via communication line 28. As a result, BMU 32 of first power storage unit 12a and second power storage unit 12b switches switch 26 from OFF to ON based on the control signal received by communication unit 38. As a result, first power storage unit 12a and second power storage unit 12b are connected in parallel to load 24, and charging and discharging are performed between first power storage unit 12a and second power storage unit 12b (step S5 in FIG. 3).

[0040] As a result of charging and discharging, the voltage value of first power storage unit 12a decreases from V1 to V12, while the voltage value of second power storage unit 12b increases from V2 to V12, as shown in Fig. 5. That is, the voltage values ​​of first power storage unit 12a and second power storage unit 12b are averaged to V12 (step S6 in Fig. 3: YES). As a result, the maximum voltage value decreases from V1 to V12.

[0041] However, as shown in Fig. 5, |V12-V4|>Vthr (step S3 in Fig. 3: NO), there is a possibility that an overcurrent will flow if first to fourth power storage units 12a-12d are connected in parallel to load 24 (connection "NG" in Fig. 5). On the other hand, in the connection of first to third power storage units 12a-12c and the connection of third power storage unit 12c and fourth power storage unit 12d, the voltage values ​​of the power storage units 12 to be connected are close to each other (adjacent), so the voltage difference is within the voltage threshold Vthr and no overcurrent will occur (connection "OK" in Fig. 5).

[0042] 5, ECU 14 selectively selects the connection of first to third power storage units 12a to 12c based on first and second power storage units 12a to 12b having the maximum voltage value (voltage value V12). Next, ECU 14 transmits a control signal for turning on switch 26 to communication unit 38 of first to third power storage units 12a to 12c via communication line 28. As a result, BMU 32 of first to third power storage units 12a to 12c turns on switch 26 based on the control signal received by communication unit 38. As a result, first to third power storage units 12a to 12c are connected in parallel to load 24, and charging and discharging are performed between first to third power storage units 12a to 12c (step S5 in FIG. 3).

[0043] 6, the voltage values ​​of first and second power storage units 12a and 12b decrease from V12 to V123, while the voltage value of third power storage unit 12c increases from V3 to V123. That is, the voltage values ​​of first to third power storage units 12a to 12c are averaged to V123 (step S6 in FIG. 3: YES). As a result, the maximum voltage value decreases from V12 to V123.

[0044] In this case, |V123-V4|≦Vthr (step S3 in FIG. 3: YES), and therefore no overcurrent occurs even if the first to fourth power storage units 12a-12d are connected in parallel to the load 24 (connection indicated by "OK" in FIG. 6). Therefore, the ECU 14 selectively selects the connection of the first to fourth power storage units 12a-12d based on the first to third power storage units 12a-12c having the maximum voltage value (voltage value V123). Next, the ECU 14 transmits a control signal for turning on the switch 26 to the communication unit 38 of the first to fourth power storage units 12a-12d via the communication line 28. As a result, the BMU 32 of the first to fourth power storage units 12a-12d turns on the switch 26 based on the control signal received by the communication unit 38. As a result, first to fourth power storage units 12a to 12d are connected in parallel to load 24, and charging and discharging are performed among first to fourth power storage units 12a to 12d (step S4 in FIG. 3).

[0045] 7, the voltage values ​​of first to third power storage units 12a to 12c decrease from V123 to V1234, while the voltage value of fourth power storage unit 12d increases from V4 to V1234. That is, the voltage values ​​of first to fourth power storage units 12a to 12d are averaged to V1234.

[0046] Incidentally, in the above description, a case has been described in which connection A in Fig. 4 is alternatively selected. When ECU 14 alternatively selects connection B, ECU 14 transmits a control signal for turning on switch 26 to communication unit 38 of first to third power storage units 12a to 12c via communication line 28. As a result, BMU 32 of first to third power storage units 12a to 12c switches switch 26 from off to on based on the control signal received by communication unit 38. As a result, first to third power storage units 12a to 12c are connected in parallel to load 24, and charging and discharging are performed between first to third power storage units 12a to 12c (step S5 in Fig. 3).

[0047] 8, the voltage value of first power storage unit 12a decreases from V1 to V123, the voltage value of second power storage unit 12b remains at V2 (=V123), and the voltage value of third power storage unit 12c increases from V3 to V123. That is, the voltage values ​​of first to third power storage units 12a to 12c are averaged to V123 (step S6 in FIG. 3: YES). As a result, the maximum voltage value decreases from V1 to V123.

[0048] In this case, |V123-V4|≦Vthr (step S3 in FIG. 3: YES), and therefore no overcurrent occurs even if the first to fourth power storage units 12a-12d are connected in parallel to the load 24, as in the case of FIG. 6 (connection indicated by "OK" in FIG. 8). Therefore, the ECU 14 selectively selects the connection of the first to fourth power storage units 12a-12d based on the first to third power storage units 12a-12c having the maximum voltage value (voltage value V123). Next, the ECU 14 transmits a control signal for turning on the switch 26 to the communication unit 38 of the first to fourth power storage units 12a-12d via the communication line 28. As a result, the BMU 32 of the first to fourth power storage units 12a-12d turns on the switch 26 based on the control signal received by the communication unit 38. As a result, first to fourth power storage units 12a to 12d are connected in parallel to load 24, and charging and discharging are performed among first to fourth power storage units 12a to 12d (step S4 in FIG. 3).

[0049] In this case as well, as a result of charging and discharging, the voltage values ​​of first to third power storage units 12a to 12c decrease from V123 to V1234, while the voltage value of fourth power storage unit 12d increases from V4 to V1234, as shown in Fig. 7. When connection B is selected, the voltage values ​​of first to fourth power storage units 12a to 12d can be averaged to V1234 more quickly than in the case of connection A.

[0050] <3.2 Second Example> The second embodiment will be described with reference to FIGS. 9 to 12. As shown in FIG. 9, |V1-V4|>Vthr (step S3 in FIG. 3: NO). Therefore, when the first to fourth power storage units 12a to 12d are connected in parallel to the load 24, an overcurrent may flow (connection indicated by "NG" in FIG. 9). On the other hand, in the connection of the first to third power storage units 12a to 12c, the connection of the second to fourth power storage units 12b to 12d, the connection of the first power storage unit 12a and the second power storage unit 12b, the connection of the second power storage unit 12b and the third power storage unit 12c, and the connection of the third power storage unit 12c and the fourth power storage unit 12d, the voltage values ​​of the power storage units 12 to be connected are close to each other (adjacent to each other) and the voltage difference is within the voltage threshold Vthr, so no overcurrent occurs (connection indicated by "OK" in FIG. 9).

[0051] Therefore, in the case of FIG. 9, ECU 14 alternatively selects the connection between third power storage unit 12c and fourth power storage unit 12d (connection C) or the connection between second to fourth power storage units 12b to 12d (connection D) based on fourth power storage unit 12d having the minimum voltage value (voltage value V4).

[0052] Here, when the ECU 14 selects the connection C, the ECU 14 transmits a control signal for turning on the switch 26 to the communication unit 38 of the third power storage unit 12c and the fourth power storage unit 12d via the communication line 28. As a result, the BMUs 32 of the third power storage unit 12c and the fourth power storage unit 12d switch the switch 26 from OFF to ON based on the control signal received by the communication unit 38. As a result, the third power storage unit 12c and the fourth power storage unit 12d are connected in parallel to the load 24, and charging and discharging are performed between the third power storage unit 12c and the fourth power storage unit 12d (step S5 in FIG. 3).

[0053] As a result of the charging and discharging, the voltage value of third power storage unit 12c decreases from V3 to V34, while the voltage value of fourth power storage unit 12d increases from V4 to V34, as shown in Fig. 10. That is, the voltage values ​​of third power storage unit 12c and fourth power storage unit 12d are averaged to V34 (step S6 in Fig. 3: YES). As a result, the minimum voltage value increases from V4 to V34.

[0054] However, since |V1-V34|>Vthr (step S3 in FIG. 3: NO), there is a possibility that an overcurrent will flow when first to fourth power storage units 12a to 12d are connected in parallel to load 24 (connection indicated as "NG" in FIG. 10). On the other hand, in the connection of second to fourth power storage units 12b to 12d and the connection of first power storage unit 12a and second power storage unit 12b, the voltage values ​​of the power storage units 12 to be connected are close to each other (adjacent to each other) and the voltage difference is within the voltage threshold Vthr, so no overcurrent will occur (connection indicated as "OK" in FIG. 10).

[0055] Therefore, ECU 14 selectively selects the connection of second to fourth power storage units 12b to 12d based on third power storage unit 12c and fourth power storage unit 12d having the minimum voltage value (voltage value V34). Next, ECU 14 transmits a control signal for turning on switch 26 to communication unit 38 of second to fourth power storage units 12b to 12d via communication line 28. As a result, BMU 32 of second to fourth power storage units 12b to 12d turns on switch 26 based on the control signal received by communication unit 38. As a result, second to fourth power storage units 12b to 12d are connected in parallel to load 24, and charging and discharging are performed between second to fourth power storage units 12b to 12d (step S5 in FIG. 3).

[0056] 11, the voltage value of second power storage unit 12b decreases from V2 to V234, while the voltage values ​​of third power storage unit 12c and fourth power storage unit 12d increase from V34 to V234. That is, the voltage values ​​of second to fourth power storage units 12b to 12d are averaged to V234 (step S6 in FIG. 3: YES). As a result, the minimum voltage value increases from V34 to V234.

[0057] In this case, |V1-V234|≦Vthr (step S3 in FIG. 3: YES), and therefore no overcurrent occurs even if the first to fourth power storage units 12a-12d are connected in parallel to the load 24 (connection indicated by "OK" in FIG. 11). Therefore, the ECU 14 selectively selects the connection of the first to fourth power storage units 12a-12d based on the second to fourth power storage units 12b-12d having the minimum voltage value (voltage value V234). Next, the ECU 14 transmits a control signal for turning on the switch 26 to the communication unit 38 of the first to fourth power storage units 12a-12d via the communication line 28. As a result, the BMU 32 of the first to fourth power storage units 12a-12d turns on the switch 26 based on the control signal received by the communication unit 38. As a result, first to fourth power storage units 12a to 12d are connected in parallel to load 24, and charging and discharging are performed among first to fourth power storage units 12a to 12d (step S4 in FIG. 3).

[0058] 12, the voltage value of first power storage unit 12a decreases from V1 to V1234, while the voltage values ​​of second to fourth power storage units 12b to 12d increase from V234 to V1234. That is, the voltage values ​​of first to fourth power storage units 12a to 12d are averaged to V1234.

[0059] Incidentally, in the above description, a case has been described in which connection C in Fig. 9 is alternatively selected. When ECU 14 alternatively selects connection D, ECU 14 transmits a control signal for turning on switch 26 to communication unit 38 of second to fourth power storage units 12b to 12d via communication line 28. As a result, BMU 32 of second to fourth power storage units 12b to 12d switches switch 26 from off to on based on the control signal received by communication unit 38. As a result, second to fourth power storage units 12b to 12d are connected in parallel to load 24, and charging and discharging are performed between second to fourth power storage units 12b to 12d (step S5 in Fig. 3).

[0060] 13, the voltage value of second power storage unit 12b decreases from V2 to V234, the voltage value of third power storage unit 12c remains at V3 (=V234), and the voltage value of fourth power storage unit 12d increases from V4 to V234. That is, the voltage values ​​of second to fourth power storage units 12b to 12d are averaged to V234 (step S6 in FIG. 3: YES). As a result, the minimum voltage value increases from V4 to V234.

[0061] In this case, since |V1-V234|≦Vthr (step S3 in FIG. 3: YES), no overcurrent occurs even if the first to fourth power storage units 12a-12d are connected in parallel to the load 24, as in the case of FIG. 11 (connection indicated by "OK" in FIG. 13). Therefore, the ECU 14 selectively selects the connection of the first to fourth power storage units 12a-12d based on the second to fourth power storage units 12b-12d having the minimum voltage value (voltage value V234). Next, the ECU 14 transmits a control signal for turning on the switch 26 to the communication unit 38 of the first to fourth power storage units 12a-12d via the communication line 28. As a result, the BMU 32 of the first to fourth power storage units 12a-12d turns on the switch 26 based on the control signal received by the communication unit 38. As a result, first to fourth power storage units 12a to 12d are connected in parallel to load 24, and charging and discharging are performed among first to fourth power storage units 12a to 12d (step S4 in FIG. 3).

[0062] In this case as well, as a result of charging and discharging, the voltage value of first power storage unit 12a decreases from V1 to V1234, while the voltage values ​​of second to fourth power storage units 12b to 12d increase from V234 to V1234, as shown in Fig. 12. When connection D is selected, the voltage values ​​of first to fourth power storage units 12a to 12d can be averaged to V1234 more quickly than in the case of connection C.

[0063] [4. Modifications] The power device 10 according to the present embodiment may have a configuration of a modified example shown in FIG. 14. In this modified example, each power storage unit 12 (12a to 12d) has only a battery 30 and a temperature sensor 36. A voltage sensor 40 that sequentially detects the voltage value of the battery 30 is connected in parallel to each battery 30. Furthermore, the positive terminal of each battery 30 is connected to the positive terminal of the load 24 via a current sensor 42 and a switch 26. Furthermore, the negative terminal of each battery 30 is connected to the negative terminal of the load 24. The current sensor 42 sequentially detects the current value of the current flowing through the battery 30.

[0064] The ECU 14 is connected to each of the temperature sensors 36, each of the voltage sensors 40, and each of the current sensors 42 via analog signal lines 44. The ECU 14 sequentially acquires the temperature of the battery 30 detected by each of the temperature sensors 36, the voltage values ​​of the battery 30 detected by each of the voltage sensors 40, and the current values ​​detected by each of the current sensors 42. Therefore, even in this modification, the ECU 14 can execute the above-mentioned process of connecting the switch 26, etc.

[0065] 1 and 2, the ECU 14 acquires a voltage value and the like from each power storage unit 12. In addition, in the configuration of FIG. 14, a voltage value detected by the voltage sensor 40 is input to the ECU 14. The present embodiment is not limited to these configurations, and the ECU 14 may estimate a voltage value based on information from each power storage unit 12.

[0066] [5. Effects of this embodiment] As described above, the present embodiment relates to the power device 10 having at least three power storage units 12 (12a to 12d) and the control method thereof.

[0067] In this case, the power device 10 has a voltage acquisition unit that acquires the voltage values ​​of each of the power storage units 12, and an ECU 14 that functions as a connection unit that connects two of the power storage units 12 that have adjacent voltage values ​​to each other based on the acquired voltage values ​​of the power storage units 12.

[0068] In addition, the control method of the power device 10 includes a step (step S2) in which the ECU 14 acquires the voltage values ​​of the power storage units 12, and a step (steps S4, S5) in which two of the power storage units 12 having adjacent voltage values ​​are connected to each other based on the acquired voltage values ​​of the power storage units 12.

[0069] In this manner, in this embodiment, two power storage units 12 having adjacent voltage values ​​are selected from among at least three power storage units 12 and connected to each other. This makes it possible to connect the power storage units 12 only through electrical control without adding any circuitry, and to suppress the occurrence of an overcurrent. As a result, it is possible to minimize the impact of costs. Therefore, compared to a case where all the power storage units 12 are connected simultaneously, or a case where two or more power storage units 12 having voltage values ​​that are distant from each other (not adjacent) are connected, it is possible to suppress the flow of an overcurrent through the power storage units 12 while reducing the voltage difference.

[0070] In this case, ECU 14 connects power storage unit 12 having a maximum voltage value (e.g., V1) or a minimum voltage value (e.g., V4) to a power storage unit 12 having an adjacent voltage value to said power storage unit 12. In this way, two power storage units 12 are connected with respect to power storage unit 12 having the maximum or minimum voltage value as a reference. As a result, the maximum voltage value is reduced or the minimum voltage value is increased. Therefore, the overall voltage difference of each power storage unit 12 is reliably reduced, and the occurrence of an overcurrent can be efficiently suppressed.

[0071] Moreover, it is preferable that ECU 14 mutually connects power storage unit 12 having the maximum voltage value with power storage unit 12 having a voltage value adjacent to that of power storage unit 12. The higher the voltage value of power storage unit 12, the lower the internal resistance value becomes, and the larger the current value of the current flowing during charging and discharging becomes. Therefore, by connecting two power storage units 12 with reference to power storage unit 12 having the maximum voltage value, it becomes possible to quickly average the voltage values ​​of the connected power storage units 12. Furthermore, since the higher the voltage value of power storage unit 12, power storage unit 12 tends to deteriorate more easily, by connecting power storage units 12 while keeping the voltage difference within a voltage threshold, it is possible to average the voltage values ​​of power storage units 12 while suppressing the occurrence of overcurrent and deterioration of power storage unit 12.

[0072] In this case, until the voltage difference between the maximum voltage value and the minimum voltage value falls within a predetermined voltage threshold, ECU 14 repeatedly obtains the voltage value of power storage unit 12 and connects power storage unit 12. This makes it possible to reliably average the voltage values ​​by connecting all power storage units 12 while suppressing the occurrence of overcurrent.

[0073] Furthermore, when the ECU 14 includes two power storage units 12 having substantially the same voltage values, the ECU 14 interconnects the three power storage units 12, i.e., the two power storage units 12 and a power storage unit 12 whose voltage values ​​are adjacent to the two power storage units 12. This allows the voltage values ​​of the power storage units 12 to be averaged quickly and efficiently.

[0074] In this case, the three power storage units 12 are connected in parallel to the load 24, so that each of the power storage units 12 can supply power to the load 24.

[0075] Furthermore, an internal battery 18 (another power storage unit) different from the three power storage units 12 is connected in parallel to the load 24 together with the power storage units 12. This makes it possible to supply power from the internal battery 18 to the load 24 and to supply power from the internal battery 18 to each power storage unit 12 to start up each of the power storage units 12.

[0076] Furthermore, when the voltage difference between two adjacent power storage units 12 exceeds a voltage threshold, ECU 14 prohibits the mutual connection of two power storage units 12. This can reliably suppress the occurrence of an overcurrent.

[0077] Moreover, the power device 10 includes three switches 26 (two-way connection circuits) that connect any two of the three power storage units 12 to each other. This allows the ECU 14 to electrically control each of the switches 26.

[0078] In this case, ECU 14 can connect power storage units 12 to each other by selecting one of switches 26.

[0079] It should be noted that the present invention is not limited to the above-described embodiment, and various configurations can be adopted based on the contents of this specification.

Claims

1. In a power device (10) having at least three power storage units (12, 12a to 12d), a voltage acquisition unit (14) that acquires a voltage value of each of the at least three power storage units; a connection unit (14) that connects two of the at least three power storage units, the two power storage units having adjacent voltage values, to each other based on the voltage values ​​of the at least three power storage units acquired by the voltage acquisition unit; Another power storage unit (18) different from at least three of the power storage units; having the other power storage unit is a startup power source for starting up the at least three power storage units, The power device includes two-way connection circuits (26) that connect any two of the at least three power storage units to each other, the number of which is the same as the number of the power storage units; Each of the at least three power storage units includes the two-way connection circuit, a battery (30), and a control unit (32) that controls the two-way connection circuit, the two-way connection circuit is a switch capable of connecting the battery to an outside of the power storage unit, Each of the at least three power storage units is started up by starting up the control unit in response to power being supplied from the other power storage units; When the control unit receives an instruction from the connection unit to select the two-way connection circuit while the power storage unit is activated, the control unit switches the switch from off to on, thereby causing charging and discharging to occur between the battery and the outside of the power storage unit.

2. 2. The power device according to claim 1, The connection portion connects the power storage unit having a maximum voltage value where the voltage value is maximum, or a minimum voltage value where the voltage value is minimum, to the power storage unit having an adjacent voltage value.

3. 3. The power device according to claim 2, The connection unit connects the power storage unit having the maximum voltage value to the power storage unit having an adjacent voltage value.

4. 4. The power device according to claim 2, The power device repeatedly acquires the voltage value of the power storage unit by the voltage acquisition unit and connects the power storage unit by the connection unit until a voltage difference between the maximum voltage value and the minimum voltage value becomes within a predetermined threshold value.

5. In the power device according to any one of claims 1 to 4, The connection unit of the power device is configured to, when there are two or more storage units having approximately the same voltage value, interconnect the two or more storage units and the storage units whose voltage values ​​are adjacent to the two or more storage units.

6. In the power device according to any one of claims 1 to 5, The at least three power storage units and the other power storage unit are connected in parallel to a load (24).

7. In the power device according to any one of claims 1 to 6, The connection unit prohibits mutual connection of the two power storage units when a voltage difference between the two power storage units whose voltage values ​​are adjacent to each other exceeds a predetermined threshold value.

8. In the power device according to any one of claims 1 to 7, A power device, wherein the connection unit connects the power storage units to each other by selecting one of the two-way connection circuits.

9. A method for controlling a power device (10) having at least three power storage units (12, 12a to 12d), comprising: supplying power from another power storage unit (18) to the at least three power storage units, thereby starting up the at least three power storage units; acquiring a voltage value of each of the at least three power storage units by a voltage acquisition unit (14); a step of connecting two of the at least three power storage units, the two power storage units having adjacent voltage values, to each other by a connection unit (14) based on the voltage values ​​of the at least three power storage units acquired by the voltage acquisition unit; having The power device includes two-way connection circuits (26) that connect any two of the at least three power storage units to each other, the number of which is the same as the number of the power storage units; Each of the at least three power storage units includes the two-way connection circuit, a battery (30), and a control unit (32) that controls the two-way connection circuit, the two-way connection circuit is a switch capable of connecting the battery to an outside of the power storage unit, Each of the at least three power storage units is started up by starting up the control unit in response to power being supplied from the other power storage units; A method for controlling a power device, in which, when the control unit receives an instruction from the connection unit to select the two-way connection circuit while the storage unit is activated, the control unit switches the switch from off to on, thereby causing charging and discharging to occur between the battery and the outside of the storage unit.

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