Energy Storage System

Abstract

To provide a power storage system with improved reliability by using multiple power storage devices equally.SOLUTION: The power storage system used in a flight vehicle includes a plurality of power storage devices and a power transfer circuit that is connected to the plurality of power storage devices and transfers power between the plurality of power storage devices.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an electricity storage system including a plurality of electricity storage devices. [Background technology]

[0002] Conventionally, electric aircraft have been developed. For example, it is envisioned to realize a high-altitude platform station (HAPS) by mounting a radio relay station on an electric aircraft. An aircraft used as a HAPS is equipped with solar cells and a power storage device, and is required to continue flying non-stop for a long period of time, such as six months. An aircraft used as a HAPS flies during the day using power generated by the solar cells and charges the power storage device, and flies at night using the power stored in the power storage device. Patent Document 1 discloses a technology for configuring a communication network using a HAPS. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-54490 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an aircraft, if a malfunction such as a breakdown, deterioration, or power shortage occurs in the power storage device due to a normally unforeseen reason, it becomes difficult to supply power from the power storage device, causing a malfunction. The power storage device is required to have high reliability so as not to cause a malfunction in the aircraft. It is possible to provide a spare power storage device in the aircraft in preparation for a malfunction of the power storage device. However, if no malfunction occurs, the spare power storage device becomes a useless facility. Furthermore, continuing to use the power storage device in a charged state leads to deterioration of the power storage device.

[0005] An object of the present invention is to provide a power storage system with improved reliability by evenly utilizing a plurality of power storage devices. [Means for solving the problem]

[0006] One aspect of the present invention is a power storage system for use in an aircraft, the power storage system including: a plurality of power storage devices; and a power transfer circuit connected to the plurality of power storage devices and configured to transfer power between the plurality of power storage devices. The plurality of power storage devices include power storage devices each of which supplies power to a different load. Effect of the Invention

[0007] With the above configuration, in the power storage system, even if a malfunction occurs in one of the power storage devices, power is transferred from the other power storage devices, thereby improving the reliability of the power supply. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic diagram showing an example of the arrangement of a power storage system. [Diagram 2] FIG. 1 is a block diagram showing a configuration example of a power storage system. [Diagram 3] 2 is a block diagram showing an example of the internal functional configuration of a control device and a BMU. [Figure 4] 10 is a flowchart showing a first example of a processing procedure for transferring power between a plurality of power storage devices. [Diagram 5] FIG. 4 is a block diagram showing a state in which power is transferred from a spare power storage device to another power storage device. [Figure 6] 10 is a flowchart showing a second example of a processing procedure for transferring power between a plurality of power storage devices. [Figure 7] 13 is a flowchart showing a third example of a processing procedure for transferring power among a plurality of power storage devices. [Figure 8] 13 is a flowchart showing a fourth example of a processing procedure for transferring power among a plurality of power storage devices. [Figure 9] FIG. 2 is a block diagram showing a state in which power is transferred between a plurality of power storage devices connected to a load. [Figure 10] FIG. 2 is a block diagram showing a state in which power is transferred from a plurality of power storage devices to another power storage device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The power storage system used in an aircraft includes a plurality of power storage devices and a power transfer circuit connected to the plurality of power storage devices and transferring power between the plurality of power storage devices.

[0010] The power storage system includes a plurality of power storage devices, and transfers power between the plurality of power storage devices. Even if some of the power storage devices run short of power to be supplied to a load, power is transferred from the other power storage devices. Even if a malfunction occurs in one of the power storage devices, power is transferred from the other power storage devices, and power supply to the load is continued. This improves the efficiency of power utilization in the entire power storage system, and improves the reliability of power supply.

[0011] The plurality of power storage devices may include a first power storage device that does not supply power to a load, and a second power storage device that supplies power to the load. The power storage system can transfer power from the first power storage device that does not supply power to the load to the second power storage device that supplies power to the load. The plurality of power storage devices, including the first power storage device that serves as a reserve, may be used evenly. The reserve power storage device is used effectively, and the reserve power storage device is not continuously unused.

[0012] The plurality of power storage devices may further include a third power storage device that supplies power to a load different from the load to which the second power storage device supplies power. By having the plurality of power storage devices supply power to different loads, the performance of each power storage device can be appropriately designed according to each load, such as by setting the full charge capacity to a value according to the load.

[0013] The power storage system may further include a control device that controls the power transfer circuit based on the states of the plurality of power storage devices. By controlling the power transfer circuit based on the states of the power storage devices, such as differences in battery temperature or the presence or absence of malfunctions, the control device transfers power from other devices to a power storage device requiring power, thereby evenly utilizing the plurality of power storage devices.

[0014] The control device may cause the power transfer circuit to transfer power from a low-temperature storage device to a high-temperature storage device, thereby reducing the power supply from the high-temperature storage device to the load and increasing the power supply from the low-temperature storage device to the load. When the temperature of a certain storage device is relatively high due to heat buildup or the like, the control device may perform control to reduce the burden rate of the storage device on the load. In other words, the control device may control the power transfer circuit to reduce the power supply from a high-temperature storage device to the load and increase the power supply from a low-temperature storage device to the load. This makes it possible to reduce the temperature of the high-temperature storage device and prevent the storage device from deteriorating relatively quickly.

[0015] The control device may cause the power transfer circuit to transfer power from a power storage device having a high discharge voltage to a power storage device having a low discharge voltage. Even if the discharge voltage of one power storage device drops due to a malfunction or the like, the power storage system can continue to supply power to the load by transferring power from the other power storage device.

[0016] The control device may cause the power transfer circuit to transfer power from a power storage device with a high charging rate to a power storage device with a low charging rate. Even if the charging rate of one power storage device decreases and the power to be supplied from that power storage device to the load is insufficient, the power storage system can continue to supply power to the load by transferring power from another power storage device.

[0017] The control device may cause the power transfer circuit to transfer power from a power storage device with a high health level to a power storage device with a low health level. When a power storage device deteriorates, the health level decreases. Even if one power storage device deteriorates and there is a shortage of power to be supplied to a load, the power storage system can continue to supply power to the load by transferring power from another power storage device.

[0018] The power transfer circuit may use a bidirectional DC-DC converter. The bidirectional DC-DC converter can transfer power from one side to the other or from the other side to the one side. By using the bidirectional DC-DC converter, the power storage system can appropriately transfer power from one power storage device to another power storage device as needed.

[0019] The present invention will now be described in detail with reference to the drawings showing embodiments thereof. <Embodiment> FIG. 1 is a schematic diagram showing an example of the arrangement of the power storage system 1. The power storage system 1 is provided in an aircraft 2. For example, the aircraft 2 is a HAPS. The aircraft 2 includes a load 21 such as a motor and a communication device, a solar cell 22, and the power storage system 1. The load 21 and the solar cell 22 are each connected to the power storage system 1. The power storage system 1 includes a plurality of power storage devices. The power storage device included in the power storage system 1 is supplied with power generated by the solar cell 22 and charged. The power storage device discharges and supplies power to the load 21. The load 21 includes a motor that generates power for flying the aircraft 2, and the power generated by the solar cell 22 and the power discharged by the power storage system 1 are supplied to the motor. The solar cell 22 and the power storage system 1 may be connected in parallel to the load 21. For example, during the daytime, power generated by the solar cell 22 is supplied to the power storage system 1 and the load 21. At night, the power of the power storage device is supplied to the load 21.

[0020] FIG. 2 is a block diagram showing a configuration example of the power storage system 1. The power storage system 1 includes a plurality of power storage devices 11, 12, and 13. Each of the power storage devices 11, 12, and 13 includes a plurality of power storage modules 32, and configures a bank in which the plurality of power storage modules 32 are connected in series. The plurality of power storage modules 32 may include the power storage modules 32 connected in parallel. Each of the power storage modules 32 is configured by connecting a plurality of power storage cells 33 in series. Although a single power storage cell 33 is illustrated in FIG. 2 in the power storage module 32, in reality, the power storage module 32 includes a plurality of power storage cells 33. The power storage module 32 may include the power storage cells 33 connected in parallel. The power storage cells 33 or the power storage modules 32 are power storage elements that perform charging and discharging, respectively. For example, the power storage cells 33 are lithium ion batteries.

[0021] Each of the power storage devices 11, 12, and 13 includes a BMU (Battery Management Unit) 31. The BMU 31 measures the states of a plurality of power storage modules 32 included in the power storage device, and controls the operation of the plurality of power storage modules 32. The power storage system 1 includes a control device 5 that controls the power storage devices 11, 12, and 13. The BMU 31 included in each of the power storage devices 11, 12, and 13 is connected to the control device 5.

[0022] The power storage devices 11, 12, and 13 are all connected to a solar cell 22, and are supplied with power from the solar cell 22 to perform charging. Of the power storage devices 11, 12, and 13, the power storage device 11 is not connected to a load 21 via a power line, and does not supply power to the load 21. The power storage device 11 functions as a spare power storage device that assists the other power storage devices. The power storage device 11 corresponds to the first power storage device.

[0023] The power storage devices 12 and 13 are connected to a load 21 via a power line, discharge, and supply power to the load 21. Among the multiple loads included in the load 21, the power storage device 12 supplies power to some of the loads, and the power storage device 13 supplies power to a load different from the load to which the power storage device 12 supplies power. For example, the power storage device 12 supplies power to a motor, and the power storage device 13 supplies power to a communication device. The power storage device 12 corresponds to a second power storage device, and the power storage device 13 corresponds to a third power storage device. By having the multiple power storage devices supply power to different loads, the performance of each power storage device can be appropriately designed according to each load, such as setting the full charge capacity to a value according to the load.

[0024] The energy storage system 1 includes a power transfer circuit 4 that transfers power between a plurality of energy storage devices 11, 12, and 13. FIG. 2 includes an example of a circuit diagram of the power transfer circuit 4. The energy storage devices 11, 12, and 13 are connected to each other via the power transfer circuit 4. The power transfer circuit 4 includes a pair of relay bus lines 43, and includes a plurality of bidirectional DCDC converters 41 connected to the energy storage devices 11, 12, and 13. The bidirectional DCDC converter 41 has two pairs of power lines, one pair of power lines is connected to any one of the energy storage devices 11, 12, and 13, and the other pair of power lines is connected to a pair of relay bus lines 43. A smoothing capacitor 42 is connected between the other pair of power lines. Each of the energy storage devices 11, 12, and 13 is connected to a pair of relay bus lines 43 via the bidirectional DCDC converter 41 and the smoothing capacitor 42. A buffer capacitor 44 is connected between the pair of relay bus lines 43.

[0025] The bidirectional DC-DC converter 41 has a transformer 411 and switching elements 412 and 413. The switching elements 412 and 413 are configured using, for example, FETs (field effect transistors). The transformer 411 and the switching element 412 are connected between one pair of power lines connected to any one of the power storage devices 11, 12, and 13. The transformer 411 and the switching element 413 are connected between the other pair of power lines connected to the pair of relay bus lines 43. A current flows between each of the power storage devices 11, 12, and 13 and the pair of relay bus lines 43 via the transformer 411, and power is transferred. Depending on the operation of the switching elements 412 and 413, the bidirectional DC-DC converter 41 can transfer power from one side to the other, and can also transfer power from the other side to one side.

[0026] The smoothing capacitor 42 smoothes high-frequency components contained in the current. The buffer capacitor 44 temporarily stores power. The control device 5 controls the power transfer circuit 4. The control device 5 controls the switching elements 412 and 413 to be on or off. The control device 5 controls the switching elements 412 and 413 to cause the bidirectional DC-DC converter 41 to transfer power from one side to the other and from the other side to one side. The circuit configuration of the bidirectional DC-DC converter 41 shown in FIG. 2 is an example. The bidirectional DC-DC converter 41 may have other circuit configurations.

[0027] 3 is a block diagram showing an example of the internal functional configuration of the control device 5 and the BMU 31. The BMU 31 measures the state of a plurality of power storage modules 32 and controls the power storage device 11, 12, or 13. The BMU 31 includes a calculation unit 311, a memory 312, a storage unit 313, a voltage acquisition unit 314, a current acquisition unit 315, a temperature acquisition unit 316, and a communication unit 317. The calculation unit 311 is, for example, a CPU (Central Processing Unit). The memory 312 stores information required for calculation in the calculation unit 311. The storage unit 313 is non-volatile and stores programs and data. For example, the storage unit 313 is a non-volatile semiconductor memory. The calculation unit 311 executes processing according to the program stored in the storage unit 313.

[0028] The voltage acquisition unit 314 acquires the voltage of each of the plurality of power storage modules 32, the voltage of each of the plurality of power storage cells 33, or the discharge voltage of the power storage device 11, 12, or 13. The current acquisition unit 315 acquires the current flowing through the plurality of power storage modules 32. For example, the current acquisition unit 315 acquires the current flowing through the plurality of power storage modules 32 connected in series, or acquires the current flowing through each power storage module 32 individually. The temperature acquisition unit 316 acquires the temperature inside the power storage device 11, 12, or 13. For example, the power storage devices 11, 12, and 13 are provided with a temperature measuring element for measuring temperature, such as a thermocouple, and the temperature acquisition unit 316 acquires the temperature using the temperature measuring element. The temperature acquisition unit 316 may acquire the temperature of each of the plurality of power storage modules 32 or the temperature of each of the plurality of power storage cells 33. The communication unit 317 is connected to the control device 5. The communication unit 317 communicates with the control device 5. The calculation unit 311 causes the communication unit 317 to transmit information indicating the acquired voltage and current to the control device 5.

[0029] The control device 5 includes a calculation unit 51, a memory 52, a storage unit 53, a communication unit 54, and a power adjustment unit 55. The calculation unit 51 is, for example, a CPU. The memory 52 stores information necessary for calculations in the calculation unit 51. The storage unit 53 is non-volatile and stores programs and data. For example, the storage unit 53 is a hard disk. The calculation unit 51 executes processing according to the programs stored in the storage unit 53. The communication unit 54 is connected to multiple BMUs 31. The communication unit 54 communicates with each of the BMUs 31. The power adjustment unit 55 is connected to multiple bidirectional DC-DC converters 41. The power adjustment unit 55 controls the operation of the multiple bidirectional DC-DC converters 41.

[0030] 4 is a flowchart showing a first example of a process procedure for transferring power between a plurality of power storage devices. In each BMU 31, the voltage acquisition unit 314 acquires the voltage of each power storage module 32, the voltage of each power storage cell 33, or the discharge voltage of the power storage device 11, 12, or 13. The communication unit 317 transmits information indicating the acquired voltage to the control device 5. The control device 5 receives information indicating the voltage transmitted from the plurality of BMUs 31 at the communication unit 54, thereby acquiring the voltage related to each of the power storage devices 11, 12, and 13 (S11).

[0031] The calculation unit 51 determines whether or not there is a power storage device with a low discharge voltage based on the acquired voltage (S12). When acquiring the discharge voltage of the power storage device, the calculation unit 51 determines that there is a power storage device with a low discharge voltage when the discharge voltage is equal to or lower than a predetermined voltage. When acquiring the voltage of the power storage module 32 or the voltage of the power storage cell 33, the calculation unit 51 specifies the discharge voltage of the power storage device based on the acquired voltage, and determines that there is a power storage device with a low discharge voltage when the specified discharge voltage is equal to or lower than a predetermined voltage. The predetermined voltage is stored in the storage unit 53 in advance. Alternatively, the calculation unit 51 may determine that there is a power storage device with a low discharge voltage when the discharge voltage is lower than the predetermined voltage. Alternatively, the calculation unit 51 may determine that there is a power storage device with a low discharge voltage when the difference between the discharge voltages of the multiple power storage devices is equal to or higher than a predetermined threshold value or exceeds the threshold value.

[0032] If there is no power storage device with a low discharge voltage (S12: NO), the calculation unit 51 ends the process. If there is a power storage device with a low discharge voltage (S12: YES), the calculation unit 51 performs a process for transferring power from the power storage device with a high discharge voltage to the power storage device with a low discharge voltage (S13). In S13, the calculation unit 51 causes the power adjustment unit 55 to operate the power transfer circuit 4 to transfer the power.

[0033] FIG. 5 is a block diagram showing a state in which power is transferred from a spare storage device 11 to another storage device 12. When the power demand in the load connected to the storage device 12 is large, or when the storage device 12 breaks down, the discharge voltage of the storage device 12 may drop. Since the storage device 11 is not connected to a load, the discharge voltage tends to be stable. When the discharge voltage of the storage device 11 is high and the discharge voltage of the storage device 12 drops, the calculation unit 51 causes the power adjustment unit 55 to operate the power transfer circuit 4 so as to transfer power from the storage device 11 to the storage device 12. The power adjustment unit 55 operates the bidirectional DC-DC converter 41 connected to the storage device 11 to flow a current from the storage device 11 to the relay bus line 43 by controlling the switching elements 412 and 413. In addition, the power adjustment unit 55 operates the bidirectional DC-DC converter 41 connected to the storage device 12 to flow a current from the relay bus line 43 to the storage device 12.

[0034] As shown by the solid arrow in Fig. 5, a current flows from the power storage device 11 to the power storage device 12 via the power transfer circuit 4, and power is transferred. High-frequency components contained in the current are smoothed by the smoothing capacitor 42, and noise is suppressed. The transferred power charges the power storage device 12. Alternatively, the transferred power is supplied to a load connected to the power storage device 12. When the discharge voltage of the power storage device 13 is low, power is similarly transferred from the power storage device 11 to the power storage device 13.

[0035] After S13 ends, the control device 5 ends the process. Even if the discharge voltage of one power storage device drops, the power storage system 1 can continue to supply power to the load by transferring power from another power storage device. For example, even if the power demand of the load temporarily increases or one storage battery breaks down, power is continuously supplied to the load.

[0036] 6 is a flowchart showing a second example of the procedure of the process of transferring power between a plurality of power storage devices. In each BMU 31, the current acquisition unit 315 acquires the current flowing through the power storage module 32, and the communication unit 317 transmits information indicating the acquired current to the control device 5. The control device 5 receives the information indicating the current transmitted from the plurality of BMUs 31 at the communication unit 54, thereby acquiring the current related to each of the power storage devices 11, 12, and 13 (S21).

[0037] The calculation unit 51 calculates the state of charge (SOC) of the power storage devices 11, 12, and 13 based on the acquired current (S22). In S22, for example, the calculation unit 51 calculates the state of charge by integrating the current values ​​acquired so far. The calculation unit 51 may calculate the state of charge by a method other than integrating the current values. Alternatively, the power storage system 1 may not perform the processes of S21 and S22, and the BMU 31 may calculate the state of charge of the power storage devices based on the current acquired by the current acquisition unit 315, transmit the calculated state of charge to the control device 5, and the control device 5 may acquire the state of charge.

[0038] The calculation unit 51 then determines whether or not there is a power storage device with a low charging rate (S23). In S23, the calculation unit 51 determines that there is a power storage device with a low charging rate when the calculated charging rate is equal to or lower than a predetermined threshold. The threshold is stored in advance in the storage unit 53. Alternatively, the calculation unit 51 may determine that there is a power storage device with a low charging rate when the charging rate is less than the threshold. Alternatively, the calculation unit 51 may determine that there is a power storage device with a low charging rate when the difference in charging rate of the multiple power storage devices is equal to or higher than a predetermined threshold or exceeds the threshold.

[0039] If there is no power storage device with a low charging rate (S23: NO), the calculation unit 51 ends the process. If there is a power storage device with a low charging rate (S23: YES), the calculation unit 51 performs a process for transferring power from the power storage device with a high charging rate to the power storage device with a low charging rate (S24). In S24, the calculation unit 51 causes the power adjustment unit 55 to operate the power transfer circuit 4 to transfer power.

[0040] As a result of the storage device 12 continuing to supply power to the load, the charging rate of the storage device 12 may drop significantly. Since the storage device 11 is not connected to a load, the charging rate is unlikely to drop. When the charging rate of the storage device 11 is high and the charging rate of the storage device 12 drops, the calculation unit 51 causes the power adjustment unit 55 to operate the power transfer circuit 4 so as to transfer power from the storage device 11 to the storage device 12. As shown by the solid arrow in FIG. 5, power is transferred from the storage device 11 to the storage device 12 via the power transfer circuit 4. The storage device 12 is charged by the transferred power. Alternatively, the transferred power is supplied to a load connected to the storage device 12. When the charging rate of the storage device 13 is low, power is similarly transferred from the storage device 11 to the storage device 13.

[0041] After S24 ends, the control device 5 ends the process. Even if the charging rate of one power storage device decreases, the power storage system 1 can continue to supply power to the load by transferring power from another power storage device. For example, even if the power to be supplied from one power storage device to the load is insufficient, power can be continuously supplied to the load by using the other power storage device.

[0042] 7 is a flowchart showing a third example of the procedure of the process of transferring power between a plurality of power storage devices. In each BMU 31, the voltage acquisition unit 314 acquires the voltage related to the power storage device 11, 12, or 13, and the communication unit 317 transmits information indicating the acquired voltage to the control device 5. The control device 5 acquires the voltage related to each of the power storage devices 11, 12, and 13 by receiving the information indicating the voltage transmitted from the plurality of BMUs 31 at the communication unit 54 (S31).

[0043] The calculation unit 51 calculates a state of health (SOH) indicating a ratio of the actual full charge capacity of the power storage devices 11, 12, and 13 to the initial full charge capacity based on the acquired voltage (S32). In S32, for example, the calculation unit 51 identifies a change in the voltage acquired so far over time, and calculates the state of health based on the change in voltage according to a relationship between the change in voltage and the state of health stored in advance in the storage unit 53. The calculation unit 51 may calculate the charging rate by other methods. Alternatively, the power storage system 1 may not perform the processes of S31 and S32, and the BMU 31 may calculate the state of health of the power storage device based on the voltage acquired by the voltage acquisition unit 314, transmit the calculated state of health to the control device 5, and the control device 5 may acquire the state of health.

[0044] The calculation unit 51 then determines whether or not there is a power storage device with a low level of health (S33). The calculation unit 51 determines that there is a power storage device with a low level of health when the calculated health level is equal to or lower than a predetermined threshold. The threshold is stored in advance in the storage unit 53. Alternatively, the calculation unit 51 may determine that there is a power storage device with a low level of health when the health level is less than the threshold. Alternatively, the calculation unit 51 may determine that there is a power storage device with a low level of health when the difference in health levels of a plurality of power storage devices is equal to or higher than a predetermined threshold or exceeds the threshold.

[0045] If there is no power storage device with a low health level (S33: NO), the calculation unit 51 ends the process. If there is a power storage device with a low health level (S33: YES), the calculation unit 51 performs a process for transferring power from the power storage device with a high health level to the power storage device with a low health level (S34). In S34, the calculation unit 51 causes the power adjustment unit 55 to operate the power transfer circuit 4 to transfer the power.

[0046] A storage device with a low health level is a storage device with advanced deterioration. As a result of repeated charging and discharging of the storage device 12, the storage device 12 may deteriorate and the health level may decrease. Since the storage device 11 is not connected to a load, deterioration is relatively unlikely to progress. When the health level of the storage device 11 is high and the health level of the storage device 12 decreases, the calculation unit 51 causes the power adjustment unit 55 to operate the power transfer circuit 4 so as to transfer power from the storage device 11 to the storage device 12. As shown by the solid arrow in FIG. 5, power is transferred from the storage device 11 to the storage device 12 via the power transfer circuit 4. The transferred power is supplied to a load connected to the storage device 12. The storage device 12 may be charged with the transferred power. When the health level of the storage device 13 is low, power is similarly transferred from the storage device 11 to the storage device 13.

[0047] After S34 ends, the control device 5 ends the process. Even if the health of one power storage device is degraded, the power storage system 1 can continue to supply power to the load by transferring power from another power storage device. For example, even if one power storage device is degraded and the power to be supplied to the load is insufficient, power can be continuously supplied to the load by using the other power storage device.

[0048] 8 is a flowchart showing a fourth example of the procedure of the process of transferring power between a plurality of power storage devices. In each BMU 31, the temperature acquisition unit 316 acquires the internal temperature of the power storage device 11, 12, or 13, and the communication unit 317 transmits information indicating the acquired temperature to the control device 5. The control device 5 acquires the internal temperature of each of the power storage devices 11, 12, and 13 by receiving the information indicating the temperature transmitted from the plurality of BMUs 31 at the communication unit 54 (S41).

[0049] The calculation unit 51 determines whether or not there is a high-temperature power storage device based on the acquired temperature (S42). The calculation unit 51 determines that there is a high-temperature power storage device when the acquired temperature is equal to or higher than a predetermined temperature. The predetermined temperature is stored in advance in the storage unit 53. Alternatively, the calculation unit 51 may determine that there is a high-temperature power storage device when the acquired temperature exceeds a predetermined temperature. Alternatively, the calculation unit 51 may determine that there is a high-temperature power storage device when the difference in temperature between the multiple power storage devices is equal to or higher than a predetermined threshold value or exceeds the threshold value.

[0050] If there is no high temperature storage device (S42: NO), the calculation unit 51 ends the process. If there is a high temperature storage device (S42: YES), the calculation unit 51 performs a process for transferring power from the low temperature storage device to the high temperature storage device (S43). In S43, the calculation unit 51 causes the power adjustment unit 55 to operate the power transfer circuit 4 to transfer power.

[0051] The higher the internal temperature of the power storage device, the more likely it is to deteriorate. When there is a temperature difference between the multiple power storage devices, the power storage device with a relatively high temperature deteriorates relatively quickly. When heat buildup occurs in the power storage device 12, or when the load of power supply is high in the power storage device 12, the temperature inside the power storage device 12 may become high. Since the power storage device 11 is not connected to a load, the internal temperature is likely to become relatively low. When the power storage device 12 is at a high temperature and the power storage device 11 is at a low temperature, the calculation unit 51 causes the power adjustment unit 55 to operate the power transfer circuit 4 so as to transfer power from the power storage device 11 to the power storage device 12. As shown by the solid arrow in FIG. 5, power is transferred from the power storage device 11 to the power storage device 12 via the power transfer circuit 4. When the power storage device 13 is at a high temperature, power is similarly transferred from the power storage device 11 to the power storage device 13.

[0052] The calculation unit 51 reduces the power supplied from the high temperature storage device to the load (S44). In S44, the calculation unit 51 transmits a control signal for reducing the power from the communication unit 54 to the BMU 31 of the high temperature storage device. In the BMU 31, the communication unit 317 receives the control signal, and the calculation unit 311 performs control to reduce the power supplied from the storage device in accordance with the control signal. For example, power equivalent to the power transferred from the low temperature storage device is reduced from the supplied power. The power transferred from the low temperature storage device is supplied to the load connected to the high temperature storage device.

[0053] After S44 ends, the control device 5 ends the process. When one of the power storage devices has a high temperature, the power storage system 1 transfers power from the low temperature power storage device to the high temperature power storage device and reduces the power supplied from the high temperature power storage device to the load. The power transferred from the low temperature power storage device is supplied to the load, and the power supply to the load is continued. As a result, the power supply from the high temperature power storage device to the load decreases, and the power supply from the low temperature power storage device to the load increases. The reduction in the power supply to the load reduces the burden on the high temperature power storage device, and the temperature inside the power storage device decreases. The temperature difference between the multiple power storage devices becomes small, and the state in which any of the power storage devices is at a high temperature does not continue. This prevents any of the multiple power storage devices from deteriorating relatively quickly.

[0054] The power storage system 1 can also transfer power between a plurality of power storage devices connected to a load. FIG. 9 is a block diagram showing a state in which power is transferred between a plurality of power storage devices 12 and 13 connected to a load. When the discharge voltage of the power storage device 12 is high and the discharge voltage of the power storage device 13 is low, when the charging rate of the power storage device 12 is high and the charging rate of the power storage device 13 is low, when the health of the power storage device 12 is high and the health of the power storage device 13 is low, or when the temperature of the power storage device 12 is low and the temperature of the power storage device 13 is high, the control device 5 operates the power transfer circuit 4 to transfer power from the power storage device 12 to the power storage device 13. The power adjustment unit 55 operates the bidirectional DC-DC converter 41 connected to the power storage device 12 to pass a current from the power storage device 12 to the relay bus line 43. The power adjustment unit 55 also operates the bidirectional DC-DC converter 41 connected to the power storage device 13 to pass a current from the relay bus line 43 to the power storage device 13.

[0055] 9, a current flows from the power storage device 12 to the power storage device 13 via the power transfer circuit 4, and power is transferred. The power storage device 13 is charged by the transferred power. Alternatively, the transferred power is supplied to a load connected to the power storage device 13. Depending on the states of the power storage devices 12 and 13, the power storage system 1 is also capable of transferring power from the power storage device 13 to the power storage device 12.

[0056] The power storage system 1 can also transfer power from a plurality of power storage devices to another power storage device. FIG. 10 is a block diagram showing a state in which power is transferred from a plurality of power storage devices 11 and 12 to another power storage device 13. When the discharge voltages of the power storage devices 11 and 12 are high and the discharge voltage of the power storage device 13 is low, when the charging rates of the power storage devices 11 and 12 are high and the charging rate of the power storage device 13 is low, when the health levels of the power storage devices 11 and 12 are high and the health level of the power storage device 13 is low, or when the temperatures of the power storage devices 11 and 12 are low and the temperature of the power storage device 13 is high, power can be transferred from the power storage devices 11 and 12 to the power storage device 13. The control device 5 operates the power transfer circuit 4 to transfer power from the power storage devices 11 and 12 to the power storage device 13.

[0057] The power adjustment unit 55 operates the bidirectional DCDC converter 41 connected to the power storage device 11 to allow a current to flow from the power storage device 11 to the relay bus line 43. The power adjustment unit 55 operates the bidirectional DCDC converter 41 connected to the power storage device 12 to allow a current to flow from the power storage device 12 to the relay bus line 43. In addition, the power adjustment unit 55 operates the bidirectional DCDC converter 41 connected to the power storage device 13 to allow a current to flow from the relay bus line 43 to the power storage device 13.

[0058] 10, current flows from the power storage devices 11 and 12 to the power storage device 13 via the power transfer circuit 4, and power is transferred. The power storage device 13 is charged by the transferred power. Alternatively, the transferred power is supplied to a load connected to the power storage device 13. Depending on the states of the power storage devices 11, 12, and 13, the power storage system 1 is also capable of transferring power from the power storage devices 11 and 13 to the power storage device 12.

[0059] The process of S11 to S13, the process of S21 to S24, the process of S31 to S34, or the process of S41 to S44 is repeatedly executed. In this way, the control device 5 controls the power transfer circuit 4 based on the states of the power storage devices 11, 12, and 13, and transfers power from the other power storage devices to the power storage device that is insufficient in power. When the states of the power storage devices 11, 12, and 13 change, the control device 5 changes the power transfer state. For example, when the state changes from a state in which the discharge voltage of the power storage device 12 is low to a state in which the discharge voltage of the power storage device 13 is low, the control device 5 causes the power transfer circuit 4 to stop the transfer of power from the power storage device 11 to the power storage device 12, and start the transfer of power from the power storage device 11 to the power storage device 13. After the transfer of power is stopped and before the next transfer of power is started, the power stored in the buffer capacitor 44 is discharged, and a current flows through the power transfer circuit 4. The current flowing through the power transfer circuit 4 is not interrupted, and the power transfer state is changed smoothly.

[0060] As described above in detail, the power storage system 1 includes a plurality of power storage devices, and transfers power between the plurality of power storage devices. In particular, power is transferred from the spare power storage device 11 that does not supply power to the load to a power storage device connected to a load. Even if some of the power storage devices are short of power to be supplied to the load, power is transferred from the other power storage devices, so that the efficiency of power use in the entire power storage system 1 is improved. Even if some of the power storage devices are malfunctioning, power is transferred from the other power storage devices, and power supply to the load is continued, so that the reliability of power supply is improved. By transferring power between the plurality of power storage devices, the plurality of power storage devices including the spare power storage device 11 are used evenly, and all of the power storage devices including the spare power storage device 11 are used effectively. The power storage device is not continuously unused in a charged state, so that the reliability of the power storage system 1 is improved. Furthermore, since any one of the multiple power storage devices does not continue to be in a relatively high temperature state, any one of the power storage devices is prevented from deteriorating relatively quickly, improving the reliability of the entire power storage system 1. The highly reliable power storage system 1 is useful as a power storage system to be provided in an aircraft 2 used as a HAPS.

[0061] In the present embodiment, the power storage system 1 executes the processes of S11 to S13, S21 to S24, S31 to S34, and S41 to S44. Alternatively, the power storage system 1 may execute at least one of the processes of S11 to S13, S21 to S24, S31 to S34, and S41 to S44. For example, in a case where the power storage system 1 executes the processes of S11 to S13, S21 to S24, or S31 to S34, but does not execute the processes of S41 to S44, the BMU 31 may not include the temperature acquisition unit 316.

[0062] In the present embodiment, the power storage system 1 includes the power storage devices 11, 12, and 13. Alternatively, the power storage system 1 may include two power storage devices. The power storage system 1 may include four or more power storage devices. In the present embodiment, the power storage cell 33 is a lithium ion battery. Alternatively, the power storage cell 33 may be a secondary battery other than a lithium ion battery. In the present embodiment, the power storage devices 11, 12, and 13 are a bank including a plurality of power storage modules 32. Alternatively, the power storage devices 11, 12, and 13 may be configured from a single power storage module 32.

[0063] The present invention is not limited to the contents of the above-described embodiment, and various modifications are possible within the scope of the claims. In other words, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention. [Explanation of symbols]

[0064] 1. Energy storage system 11, 12, 13 Energy storage device 2. Flying Objects 21 Load 22 Solar Cells 31 BMU 32 Energy storage module 33 Energy storage cell 4 Power Transfer Circuit 41 Bidirectional DC-DC converter 411 Trans 412, 413 Switching element 42 Smoothing capacitor 43 Intermediate bus line 44 Buffer capacitor 5. Control device

Claims

1. A power storage system for use in an aircraft, comprising: A plurality of power storage devices; a power transfer circuit connected to the plurality of power storage devices and configured to transfer power between the plurality of power storage devices; The plurality of power storage devices are A power storage device that supplies power to each of the different loads; and a power storage device that is not connected to a load and does not supply power to the load. Energy storage system.

2. The plurality of power storage devices are all connected to a solar cell. The power storage system according to claim 1 .

3. The power storage device further includes a control device that controls the power transfer circuit based on states of the plurality of power storage devices. The power storage system according to claim 1 or 2.

4. The control device causes the power transfer circuit to transfer power from the low-temperature power storage device to the high-temperature power storage device, thereby reducing the power supply from the high-temperature power storage device to a load and increasing the power supply from the low-temperature power storage device to the load. The power storage system according to claim 3 .

5. The control device causes the power transfer circuit to transfer power from a power storage device having a high discharge voltage to a power storage device having a low discharge voltage. The power storage system according to claim 3 or 4.

6. The control device causes the power transfer circuit to transfer power from a power storage device with a high charging rate to a power storage device with a low charging rate. The power storage system according to claim 3 .

7. The control device causes the power transfer circuit to transfer power from a power storage device with a high health level to a power storage device with a low health level. The power storage system according to claim 3 .

8. The power transfer circuit uses a bidirectional DC-DC converter. The power storage system according to claim 1 .

Images