Power storage device and method for controlling power storage device

Abstract

A power storage device according to the present invention comprises: a secondary battery that is chargeable and dischargeable; a control unit that controls charging and discharging of the secondary battery; a voltage detection unit that detects a voltage of the secondary battery; a current detection unit that detects a current flowing through the secondary battery; and a battery temperature detection unit that detects a temperature of the secondary battery. During charging of the secondary battery, the control unit performs a mid-charge capacity management process of obtaining a state of charge of the secondary battery on the basis of an integrated value of the current detected by the current detection unit and determining, on the basis of the state of charge, whether or not to continue charging of the secondary battery. While charging of the secondary battery is stopped, the control unit performs a during-stop-of-charge capacity management process of obtaining a state of charge of the secondary battery on the basis of the voltage detected by the voltage detection unit and the temperature detected by the battery temperature detection unit and determining, on the basis of the state of charge, whether or not to resume charging of the secondary battery. The control unit controls charging of the secondary battery on the basis of results of the mid-charge capacity management process and the during-stop-of-charge capacity management process.

Description

Power storage device and control method for power storage device

[0001] The present invention relates to an electricity storage device and a control method thereof.

[0002]

[0003] Conventionally, there has been known a backup power storage device that is connected to a power supply device that supplies power to various electrical devices such as communication devices used in communication base stations, stores the power supplied from the power supply device, and, if the power supply from the power supply device is interrupted, supplies power to the various electrical devices using the stored power instead of the power supply device. For example, Patent Document 1 describes a power supply system that uses a trickle charging method to charge a storage battery with a minute current, in which the storage battery is normally not connected to a load, and the storage battery is trickle charged with DC power generated by a charging power source based on AC power from a commercial power system, and in the event of a power outage in which the AC power from the commercial power system is interrupted, the storage battery is connected to the load, and DC power discharged from the storage battery is supplied to the load.

[0003] Japanese Patent No. 6690414

[0004] In the power supply system described in Patent Document 1, trickle charging of the storage battery is performed by controlling the voltage during trickle charging to a constant voltage in the range of 1.82 V to 1.86 V, and the current to 0.2 C. Therefore, these controls require additional equipment such as a DC / DC converter, which increases the cost of introducing the system.

[0005] In view of the above-mentioned problems, an object of the present invention is to provide a power storage device that can be used for backup purposes of a power supply device, and that can be introduced at low cost, and a control method for the same.

[0006] The power storage device according to the present invention is connected to a power supply facility, stores power supplied from the power supply facility, and supplies power to other electrical devices connected to the power supply facility when the power supply facility is stopped. The power storage device comprises a chargeable and dischargeable secondary battery, a control unit that controls the charging and discharging of the secondary battery, a voltage detection unit that detects the voltage of the secondary battery, a current detection unit that detects the current flowing through the secondary battery, and a battery temperature detection unit that detects the temperature of the secondary battery. While the secondary battery is being charged, the control unit determines the state of charge of the secondary battery based on an integrated value of the current detected by the current detection unit, and performs a capacity management process during charging to determine whether or not to continue charging of the secondary battery based on the state of charge. When charging of the secondary battery is stopped, the control unit determines the state of charge of the secondary battery based on the voltage detected by the voltage detection unit and the temperature detected by the battery temperature detection unit, and performs a capacity management process when charging is stopped to determine whether or not to resume charging of the secondary battery based on the state of charge. The control unit controls the charging of the secondary battery based on the results of the capacity management process during charging and the capacity management process when charging is stopped. A control method for a power storage device according to the present invention is a control method for a power storage device that is connected to a power supply equipment, stores power supplied from the power supply equipment in a secondary battery, and, when the power supply equipment is stopped, supplies the power stored in the secondary battery to other electrical devices connected to the power supply equipment. While the secondary battery is being charged, a capacity management process is performed in which the state of charge of the secondary battery is determined based on an integrated value of the current flowing through the secondary battery, and whether or not to continue charging the secondary battery is determined based on the state of charge. While charging of the secondary battery is stopped, a capacity management process is performed in which the state of charge of the secondary battery is determined based on the voltage and temperature of the secondary battery, and whether or not to resume charging of the secondary battery is determined based on the state of charge. The charging of the secondary battery is controlled based on the results of the capacity management process in charge and the capacity management process when charging is stopped.

[0007] According to the present invention, it is possible to provide a power storage device that can be introduced at low cost and a control method thereof.

[0008] 1 is a schematic diagram of a communication base station including a power storage device according to an embodiment of the present invention; 2 is a schematic diagram of a power storage device according to an embodiment of the present invention; 3 is a graph showing a specific example of charge / discharge control of a secondary battery; 4 is a flowchart showing a processing flow of a power storage device according to an embodiment of the present invention; 5 is a flowchart showing details of a capacity management process during charging; 6 is a flowchart showing details of a capacity management process when charging is stopped;

[0009] 1 is a schematic diagram of a communication base station including a power storage device according to an embodiment of the present invention. The communication base station 1 shown in Fig. 1 is a base station for wireless communication used in, for example, a mobile phone network, and includes a power supply facility 10, communication equipment 11, and one or more power storage devices 12.

[0010] The power supply facility 10 is connected to the power grid 2 via a circuit breaker 3, and converts AC power input from the power grid 2 into DC power, which is supplied to the communication equipment 11 and each power storage device 12. The power supply facility 10 is configured by combining, for example, a rectifier and a lead battery.

[0011] The communication device 11 operates using DC power supplied from the power supply facility 10, and performs processes such as transmitting and receiving, generating, and decoding wireless signals. The communication device 11 is configured by combining, for example, a modulator, a demodulator, an antenna, and the like.

[0012] The power storage device 12 is provided in the communication base station 1 as a backup for the power supply equipment 10 in the event of a power outage in the power grid 2. The power storage device 12 is connected to the power supply equipment 10, and stores the power supplied from the power supply equipment 10 when the power supply equipment 10 is operating. On the other hand, when the operation of the power supply equipment 10 stops due to a power outage in the power grid 2 or the like, the power storage device 12 supplies the power stored up to that point to the communication equipment 11. This allows the communication equipment 11 to continue operating even during a power outage.

[0013] The number of storage devices 12 installed in the communication base station 1 can be set arbitrarily depending on the power consumption of the communication equipment 11, the amount of electricity that can be stored per storage device 12, the maximum expected power outage duration during a power outage, etc.

[0014] Next, each of the power storage devices 12 will be described in detail below with reference to FIGS.

[0015] 2 is a schematic diagram of a power storage device according to one embodiment of the present invention. As shown in FIG. 2, the power storage device 12 according to this embodiment includes a secondary battery 20, a control unit 21, switches 22a and 22b, diodes 23a and 23b, a voltage detection unit 24, a current detection unit 25, a battery temperature detection unit 26, and a memory unit 27.

[0016] 1 via switches 22a and 22b. When power is supplied from power supply equipment 10, secondary battery 20 is charged under the control of control unit 21, thereby storing power in secondary battery 20. On the other hand, when the operation of power supply equipment 10 stops due to a power outage in power grid 2 or the like, secondary battery 20 is discharged under the control of control unit 21, and power is supplied from secondary battery 20 to communication equipment 11.

[0017] The switches 22a and 22b are provided between the secondary battery 20 and the power supply equipment 10 and the communication device 11, and are each switched between a conductive state and a cut-off state under the control of the control unit 21. The switches 22a and 22b are each configured using, for example, a relay, an insulated gate bipolar transistor (IGBT), a field effect transistor (FET), or the like. As shown in FIG. 2 , the switches 22a and 22b are connected in series. The series connection of the switches 22a and 22b constitutes a switching circuit in the power storage device 12 that can switch the electrical connection between the secondary battery 20 and the power supply equipment 10 and the communication device 11 between a conductive state and a cut-off state.

[0018] A diode 23a is connected in parallel to the switch 22a. As shown in Figure 2, the orientation of the diode 23a is set so that it conducts current in the direction (charging direction) flowing from the power supply equipment 10 to the secondary battery 20 and blocks current in the opposite direction.

[0019] A diode 23b is connected in parallel to the switch 22b. As shown in Figure 2, the direction of the diode 23b is opposite to that of the diode 23a, i.e., the direction of the diode 23b is set so that the current flows from the secondary battery 20 to the communication device 11 (discharge direction) and the current in the opposite direction is blocked.

[0020] When FETs are used for the switches 22 a and 22 b, the body diodes of the FETs may be used as the diodes 23 a and 23 b, respectively, which can reduce the number of components in the power storage device 12 and further reduce costs.

[0021] The voltage detection unit 24 detects the voltage between the positive and negative electrodes of the secondary battery 20 as the battery voltage and outputs the detection result to the control unit 21. The current detection unit 25 detects the charge / discharge current flowing through the secondary battery 20 and outputs the detection result to the control unit 21. The battery temperature detection unit 26 detects the surface temperature of the secondary battery 20 or the temperature of the members or space near the secondary battery 20 as the battery temperature and outputs the detection result to the control unit 21.

[0022] The control unit 21 controls charging and discharging of the secondary battery 20. The control unit 21 has the following functional blocks: a charging capacity management unit 211, a charging stop capacity management unit 212, a power outage capacity management unit 213, and a switching control unit 214. The control unit 21 is configured using, for example, a microcomputer, and can realize these functional blocks by executing a predetermined program. Note that the control unit 21 may also be configured using a logic circuit such as an FPGA (Field Programmable Gate Array) instead of a microcomputer.

[0023] The charging capacity management unit 211 calculates an SOC value representing the state of charge (SOC) of the secondary battery 20 while the secondary battery 20 is being charged, and manages the capacity of the secondary battery 20 based on this SOC value. The charging stop capacity management unit 212 calculates an SOC value when charging of the secondary battery 20 is stopped, and manages the capacity of the secondary battery 20 based on this SOC value. The power outage capacity management unit 213 calculates an SOC value of the secondary battery 20 when the operation of the power supply equipment 10 is stopped due to a power outage or the like, and power is not supplied from the power supply equipment 10, and manages the capacity of the secondary battery 20 based on this SOC value. The switching control unit 214 controls the switching states of the switches 22a and 22b in response to commands from the charging capacity management unit 211, the charging stop capacity management unit 212, and the power outage capacity management unit 213. Specific details of these processes will be described later.

[0024] The storage unit 27 is configured using a storage medium such as a RAM or a flash memory, and stores various information used in the processing of the control unit 21. For example, the storage unit 27 stores a program executed by the control unit 21, the latest SOC value of the secondary battery 20 calculated by the charging capacity management unit 211, the charging stop capacity management unit 212, or the power outage capacity management unit 213, and the like.

[0025] For example, a nickel-based battery (nickel-cadmium battery, nickel-metal hydride battery, nickel-zinc battery, etc.) or a lithium-ion battery can be used as the secondary battery 20. Any type of battery can be used as the secondary battery 20 as long as it is chargeable and dischargeable and its voltage decreases when the SOC value decreases due to self-discharge. In particular, a nickel-based battery with charge / discharge hysteresis characteristics is preferably used as the secondary battery 20, because the higher the rate of change in voltage relative to changes in the SOC value, the more accurate the capacity management becomes.

[0026] Next, a method for controlling charging and discharging of the secondary battery 20 by the control unit 21 will be described with reference to Fig. 3. Fig. 3 is a graph showing a specific example of charging and discharging control of the secondary battery 20. In the graph of Fig. 3, the horizontal axis represents time, and the vertical axis represents the SOC value of the secondary battery 20.

[0027] First, when the operation of the power storage device 12 is started in the communication base station 1, the control unit 21 starts charging the secondary battery 20 using power supplied from the power supply equipment 10. As a result, the charge / discharge state of the secondary battery 20 becomes "charging", and power is stored in the secondary battery 20. As a result, as shown by arrow 31, the SOC value of the secondary battery 20 gradually increases over time. At this time, the control unit 21 successively obtains the SOC value of the secondary battery 20 using the charging capacity management unit 211, and manages the capacity of the secondary battery 20 using this SOC value.

[0028] After that, at time t1, the SOC value of the secondary battery 20 reaches a predetermined upper limit S Ｈ (For example, S Ｈ = 95%), the control unit 21 stops charging the secondary battery 20. As a result, the charge / discharge state of the secondary battery 20 changes from "charging" to "stopped," and the power supply from the power supply equipment 10 to the secondary battery 20 stops. As a result, as shown by arrow 32, the SOC value of the secondary battery 20 gradually decreases due to self-discharge. At this time, the control unit 21 successively obtains the SOC value of the secondary battery 20 using the charge stop capacity management unit 212, and manages the capacity of the secondary battery 20 using this SOC value.

[0029] After that, at time t2, the SOC value of the secondary battery 20 reaches a predetermined lower limit S Ｌ (For example, S Ｌ = 90%), the control unit 21 resumes charging of the secondary battery 20. As a result, the charge / discharge state of the secondary battery 20 changes from "stopped" to "charging", and power is stored in the secondary battery 20. As a result, as shown by arrow 33, the SOC value of the secondary battery 20 gradually increases over time. At this time, the control unit 21, as in the period up to time t1, successively obtains the SOC value of the secondary battery 20 by the charging capacity management unit 211, and uses this SOC value to manage the capacity of the secondary battery 20.

[0030] After that, at time t3, the SOC value of the secondary battery 20 again reaches the upper limit value S ＨWhen the time t1 reaches time t2, the control unit 21 stops charging the secondary battery 20. As a result, the charge / discharge state of the secondary battery 20 changes from "charging" to "stopped," and the power supply from the power supply equipment 10 to the secondary battery 20 stops. As a result, as shown by arrow 34, the SOC value of the secondary battery 20 gradually decreases due to self-discharge. At this time, the control unit 21, as in the period from time t1 to time t2, successively obtains the SOC value of the secondary battery 20 using the charge stop capacity management unit 212, and manages the capacity of the secondary battery 20 using this SOC value.

[0031] After that, at time t4, the SOC value of the secondary battery 20 again reaches the lower limit value S Ｌ When the battery voltage reaches 10V, the control unit 21 resumes charging the secondary battery 20.

[0032] If the power supply equipment 10 is in operation, the same control is repeated thereafter. Ｌ to the upper limit S Ｈ The charging of the secondary battery 20 is controlled so as to maintain the charge within the range.

[0033] At time t5, a power outage occurs in the power grid 2, and the power supply from the power grid 2 to the power supply equipment 10 is interrupted, causing the power supply equipment 10 to stop operating. The power storage device 12 immediately starts supplying power to the communication device 11 in place of the power supply equipment 10. At this time, the control unit 21 discharges the power stored in the secondary battery 20, so that the power storage device 12 can cover the power supplied to the communication device 11. As a result, the charge / discharge state of the secondary battery 20 becomes "discharging," and the SOC value of the secondary battery 20 gradually decreases over time, as shown by arrow 36.

[0034] Thereafter, when the SOC value of the secondary battery 20 drops to 0% (discharge end SOC) at time t6, the control unit 21 stops discharging the secondary battery 20. As a result, the charge / discharge state of the secondary battery 20 changes from "discharging" to "stopped," and the supply of power from the power storage device 12 to the communication device 11 stops. Thereafter, as indicated by arrow 37, the SOC value of the secondary battery 20 is maintained at 0% until the power outage is resolved.

[0035] At time t7, the power outage is resolved, the power grid 2 is restored, and power supply from the power supply equipment 10 is resumed. The control unit 21 then resumes charging the secondary battery 20. As a result, the charge / discharge state of the secondary battery 20 changes from "stopped" to "charging," and power is stored in the secondary battery 20. As a result, as indicated by arrow 38, the SOC value of the secondary battery 20 gradually increases over time. At this time, the control unit 21, as in the period up to time t1 and the period from time t2 to time t3, successively obtains the SOC value of the secondary battery 20 using the charging capacity management unit 211, and uses this SOC value to manage the capacity of the secondary battery 20.

[0036] During the power outage period from time t5 to time t7, the control unit 21 successively obtains the SOC value of the secondary battery 20 using the power outage capacity management unit 213, and manages the capacity of the secondary battery 20 using this SOC value.

[0037] After that, at time t8, the SOC value of the secondary battery 20 reaches the upper limit value S Ｈ When the charging time reaches time t1, the control unit 21 stops charging the secondary battery 20. As a result, the charge / discharge state of the secondary battery 20 changes from "charging" to "stopped," and the power supply from the power supply equipment 10 to the secondary battery 20 stops. As a result, as shown by arrow 39, the SOC value of the secondary battery 20 gradually decreases due to self-discharge. At this time, the control unit 21 sequentially obtains the SOC value of the secondary battery 20 by the charging stop capacity management unit 212, as in the period from time t1 to time t2 and the period from time t3 to time t4, and performs capacity management of the secondary battery 20 using this SOC value.

[0038] After that, at time t9, the SOC value of the secondary battery 20 reaches the lower limit S Ｌ When the time t1 reaches the predetermined time, the control unit 21 resumes charging the secondary battery 20. The same applies to the control after time t9.

[0039] Note that, while FIG. 3 shows an example in which the secondary battery 20 is discharged during a power outage and its SOC value drops to 0%, there are cases in which the power outage is resolved and the power grid 2 is restored before the SOC value of the secondary battery 20 drops to 0%. In this case, it is preferable to resume charging of the secondary battery 20 regardless of the SOC value of the secondary battery 20. Alternatively, a predetermined SOC value greater than 0% may be set as the discharge end SOC, and if the SOC value of the secondary battery 20 reaches this discharge end SOC during discharging, discharging of the secondary battery 20 may be stopped even if the power outage is not resolved. In either case, when charging of the secondary battery 20 is resumed after power is restored to the power grid 2, the SOC value of the secondary battery 20 will reach the upper limit value S Ｈ Charging continues until the upper limit S Ｈ It is preferable to stop charging when the

[0040] 4 is a flowchart showing the flow of processing in the power storage device according to one embodiment of the present invention. The power storage device 12 controls charging and discharging of the secondary battery 20 by causing the control unit 21 to execute the processing shown in the flowchart in FIG. 3 at predetermined processing intervals.

[0041] In step S10, the control unit 21 determines whether the power grid 2 is in a power outage state. This determination can be made, for example, based on information about the power supply state from the power grid 2 to the power supply equipment 10, which information is acquired from the power supply equipment 10. If the result of the determination in step S10 is that the power grid 2 is in a power outage state, the process proceeds to step S50, and if not, the process proceeds to step S20.

[0042] In step S20, the control unit 21 determines whether the secondary battery 20 is being charged. This determination can be made based on the current value of the secondary battery 20, obtained from the current detection unit 25, for example. If the result of the determination in step S20 indicates that the secondary battery 20 is being charged, the process proceeds to step S30; otherwise, the process proceeds to step S40.

[0043] In step S30, the control unit 21 executes an in-charging capacity management process for managing the capacity of the secondary battery 20 during charging using the in-charging capacity management unit 211. Details of this process will be described later with reference to FIG.

[0044] In step S40, the control unit 21 executes a charge-stop capacity management process for managing the capacity of the secondary battery 20 when charging is stopped, using the charge-stop capacity management unit 212. Details of this process will be described later with reference to FIG.

[0045] In step S50, the control unit 21 executes a power outage capacity management process for managing the capacity of the secondary battery 20 during a power outage using the power outage capacity management unit 213. Details of this process will be described later with reference to FIG.

[0046] After executing the process of any one of steps S30, S40, and S50, the control unit 21 ends the process shown in the flowchart of FIG.

[0047] FIG. 5 is a flowchart showing the details of the charging capacity management process executed in step S30 of FIG.

[0048] In step S310, the charging capacity management unit 211 acquires the voltage value, current value, and temperature of the secondary battery 20 from the voltage detection unit 24, current detection unit 25, and battery temperature detection unit 26. Here, the charging voltage and charging current of the secondary battery 20, and the temperature of the secondary battery 20 during charging are acquired.

[0049] In step S320, the charging capacity management unit 211 determines whether the current value acquired in step S310 is equal to or greater than a predetermined upper limit current. If the current value is equal to or greater than the upper limit current, the process proceeds to step S390. If the current value is less than the upper limit current, the process proceeds to step S330.

[0050] In step S330, the charging capacity management unit 211 calculates an integrated current value for the period from the previous processing to the current processing. Here, for example, the integrated current value can be calculated by multiplying the current value acquired in step S310 by a predetermined processing period. Alternatively, the integrated current value may be calculated by acquiring a current value multiple times at predetermined sampling periods during one processing period, multiplying each current value by the sampling period, and adding up the results.

[0051] In step S340, the charging capacity management unit 211 updates the SOC value of the secondary battery 20 based on the current integration value calculated in step S330. Here, for example, the increase in the SOC value due to charging between the previous processing and the current processing is calculated from the ratio between the current integration value calculated in step S330 and the maximum capacity of the secondary battery 20, and this increase is added to the SOC value at the previous processing. This updates the SOC value of the secondary battery 20 to the latest value, reflecting the current integration value during the period from the previous processing to the current processing. The SOC value updated in step S340 is stored in the storage unit 27. The SOC value at the previous processing refers to the SOC value calculated in the charging capacity management process of step S30, the charging stop capacity management process of step S40, or the power outage capacity management process of step S50 when the processing of the flowchart of FIG. 3 was last executed, and is stored in the storage unit 27.

[0052] In step S350, the charging capacity management unit 211 checks whether the latest SOC value calculated in step S340 is equal to or lower than the predetermined upper limit S Ｈ It is determined whether the latest SOC value reaches the upper limit value S Ｈ When the upper limit S Ｈ If it is equal to or greater than the upper limit value S Ｈ If the upper limit S Ｈ If it is less than this, the process proceeds to step S360.

[0053] In step S360, the charging capacity management unit 211 calculates the end-of-charge voltage of the secondary battery 20. Here, the end-of-charge voltage V is calculated using the following equations (1) and (2) based on the current value and temperature respectively acquired in step S310. Ｈ In the formulas (1) and (2), A and T respectively represent the current value and temperature of the secondary battery 20. Furthermore, a, b, c, d, and e respectively represent constants, which can be set in advance through experiments, simulations, etc. When T>c, V Ｈ = (a·A+b) / (T-c)+d (1) When T≦c, V Ｈ = e ... (2)

[0054] In step S370, the charging capacity management unit 211 compares the voltage value of the secondary battery 20 acquired in step S310 with the charge end voltage V Ｈ As a result, it is determined whether the voltage value is equal to or greater than the end-of-charge voltage V Ｈ If the voltage is equal to or greater than the end-of-charge voltage V Ｈ If it is less than this, the process shown in the flowchart of FIG. 5 is terminated, and charging of the secondary battery 20 continues.

[0055] In step S380, the charging capacity management unit 211 stops charging the secondary battery 20. At this time, the charging capacity management unit 211 issues a switching command to the switching control unit 214 to switch the switches 22a and 22b, so as to switch the switch 22b from the conductive state to the cut-off state while maintaining the switch 22a in the conductive state. In response to this switching command, the switching control unit 214 switches the switch 22b, which is in the conductive state while the secondary battery 20 is being charged, to the cut-off state. As a result, the charging current to the secondary battery 20 is cut off by the switch 22b, while in the event of a power outage, the discharge current from the secondary battery 20 is immediately output to the communication device 11 via the diode 23b and the switch 22a without switching the switches 22a and 22b.

[0056] In step S390, the charging capacity management unit 211 determines that some abnormality has occurred in the secondary battery 20 and performs a major fault shutdown process for the secondary battery 20. In this major fault shutdown process, for example, the charging capacity management unit 211 issues a switching command to the switching control unit 214 to switch the switches 22a and 22b so that both switches 22a and 22b are switched from a conductive state to a cut-off state. In response to this switching command, the switching control unit 214 switches both switches 22a and 22b, which are in a conductive state while the secondary battery 20 is being charged, to a cut-off state. This stops charging and discharging of the secondary battery 20 and removes the power storage device 12 from the operational scope. Furthermore, a predetermined alarm signal or the like may be output to notify the administrator of the communication base station 1 of the occurrence of the abnormality.

[0057] When the charging of the secondary battery 20 is stopped by executing the process of step S380 or S390, the process shown in the flowchart of FIG. 5 ends.

[0058] In the above, in step S360, the charge end voltage V Ｈ Calculate the end-of-charge voltage V Ｈ In this case, regardless of the current value or temperature of the secondary battery 20, the predetermined end-of-charge voltage V Ｈ By using the above, the determination process of step S370 can be performed.

[0059] In the above example, when it is determined in step S320 that the current value of the secondary battery 20 is equal to or greater than a predetermined upper limit current, the major fault shutdown process of step S390 is immediately performed. However, this is not necessarily required when multiple power storage devices 12 are connected to the power supply equipment 10. For example, when it is determined that the current value of the secondary battery 20 in a certain power storage device 12 is equal to or greater than the upper limit current, charging of the secondary battery 20 in that power storage device 12 is temporarily stopped, and then charging of the secondary battery 20 is simultaneously started in all power storage devices 12, including that power storage device 12. This reduces the charging current flowing through each power storage device 12 so that it does not exceed the upper limit current. However, if the current value of the secondary battery 20 in that power storage device 12 still exceeds the upper limit current despite this, it is preferable to perform the major fault shutdown process of step S390 and stop charging and discharging of the secondary battery 20.

[0060] FIG. 6 is a flowchart showing the details of the capacity management process when charging is stopped, which is executed in step S40 of FIG.

[0061] In step S410, the charge-stop capacity management unit 212 acquires the voltage value and temperature of the secondary battery 20 from the voltage detection unit 24 and the battery temperature detection unit 26. Here, the open-circuit voltage (OCV) of the secondary battery 20 and the temperature of the secondary battery 20 when charging is stopped are acquired.

[0062] In step S420, the charging stop capacity management unit 212 calculates the SOC value of the secondary battery 20 based on the voltage value and temperature acquired in step S410. Here, for example, a preset relational expression between the OCV and the SOC value can be used to determine the SOC value corresponding to the current voltage value of the secondary battery 20 when charging is stopped. Note that the relational expression between the OCV and the SOC value generally changes depending on the temperature of the secondary battery 20. Therefore, it is preferable to use different relational expressions between the OCV and the SOC value used in the processing of step S420 based on the temperature acquired in step S410.

[0063] The SOC value calculated in step S420 is stored as the latest SOC value in storage unit 27. As a result, if charging of secondary battery 20 has just been stopped, the SOC value from the previous process based on current integration calculated in step S340 of Fig. 5 in the immediately preceding in-charging capacity management process is replaced with the SOC value calculated from the OCV in step S420 in the current process.

[0064] In step S430, the charge stop time capacity management unit 212 determines whether the latest SOC value calculated in step S420 is equal to or lower than the predetermined lower limit S Ｌ It is determined whether the latest SOC value reaches the lower limit value S Ｌ When the lower limit S Ｌ If the latest SOC value is equal to or less than the lower limit S Ｌ If the lower limit S Ｌ If the value is greater than 0.001, the process shown in the flowchart of FIG. 6 is terminated, and the suspension of charging of the secondary battery 20 continues.

[0065] In step S440, the charging stop capacity management unit 212 resumes charging of the secondary battery 20. At this time, the charging stop capacity management unit 212 issues a switching command to the switching control unit 214 to switch the switches 22a and 22b, so as to switch the switch 22b from the cut-off state to the conduction state while maintaining the switch 22a in the conduction state. In response to this switching command, the switching control unit 214 switches the switch 22b, which was in the cut-off state while charging of the secondary battery 20 was stopped, to the conduction state. This allows the charging current output from the power supply equipment 10 to flow into the secondary battery 20 via the switches 22a and 22b, and also allows the discharging current from the secondary battery 20 to be immediately output to the communication device 11 via the switches 22a and 22b in the event of a power outage, without the need to switch the switches 22a and 22b.

[0066] Once charging of the secondary battery 20 is resumed by executing the process of step S440, the process shown in the flowchart of FIG. 6 ends.

[0067] FIG. 7 is a flowchart showing the details of the power outage capacity management process executed in step S50 of FIG.

[0068] In step S510, the power outage capacity management unit 213 starts discharging the secondary battery 20. At this time, the power outage capacity management unit 213 issues a switching command to the switching control unit 214 to switch the switches 22a and 22b so that the switches 22a and 22b are each in a conductive state. In response to this switching command, if a power outage occurs while charging of the secondary battery 20 is stopped, the switching control unit 214 switches the switch 22b, which is in a cut-off state, to a conductive state. This causes the discharge current output from the secondary battery 20 to the communication device 11 via the diode 23b and the switch 22a to be output via the switches 22a and 22b. Note that if discharging of the secondary battery 20 has already started or if a power outage occurs while charging of the secondary battery 20 is in progress, the switches 22a and 22b are both in a conductive state, and therefore the switching states of the switches 22a and 22b do not change in step S510.

[0069] In step S520, the power failure capacity management unit 213 acquires the current value of the secondary battery 20 from the current detection unit 25. Here, the discharge current of the secondary battery 20 is acquired.

[0070] In step S530, the power outage capacity management unit 213 calculates an integrated current value for the period from the previous processing to the current processing. Here, similar to step S330 in FIG. 5, for example, the integrated current value can be calculated by multiplying the current value acquired in step S520 by a predetermined processing period. Alternatively, the integrated current value may be calculated by acquiring a current value multiple times at predetermined sampling periods during one processing period, multiplying each current value by the sampling period, and adding up the results.

[0071] In step S540, the power outage capacity management unit 213 updates the SOC value of the secondary battery 20 based on the current integrated value calculated in step S530. Here, for example, the amount of decrease in the SOC value due to discharge between the previous processing and the current processing is calculated from the ratio between the current integrated value calculated in step S530 and the maximum capacity of the secondary battery 20, and this decrease is subtracted from the SOC value at the time of the previous processing. In this way, the SOC value of the secondary battery 20 is updated to the latest value, reflecting the current integrated value during the period from the previous processing to the current processing. The SOC value updated in step S540 is stored in the storage unit 27.

[0072] In step S550, the power failure capacity management unit 213 determines whether the latest SOC value calculated in step S540 has reached the discharge end SOC (e.g., 0%). If the latest SOC value matches the discharge end SOC, the process proceeds to step S560. If the latest SOC value has not reached the discharge end SOC, i.e., if the SOC value is 1% or more, the process proceeds to step S570 without executing step S560.

[0073] In step S560, the power outage capacity management unit 213 stops discharging the secondary battery 20. At this time, the power outage capacity management unit 213 issues a switching command to the switching control unit 214 to switch the switch 22a from the conductive state to the cut-off state while maintaining the switch 22b in the conductive state. In response to this switching command, the switching control unit 214 switches the switch 22a, which is in the conductive state during the discharge of the secondary battery 20, to the cut-off state. As a result, the discharge current from the secondary battery 20 is cut off by the switch 22a, while at the time of power recovery, the charging current from the power supply equipment 10 is immediately input to the secondary battery 20 via the diode 23a and the switch 22b without switching the switches 22a and 22b.

[0074] In step S570, the power outage capacity management unit 213 determines whether power has been restored to the power system 2 from the power outage state. This determination can be made, for example, based on information about the state of power supply from the power system 2 to the power supply equipment 10, as in step S10 of Fig. 4 . If the determination in step S570 shows that power has been restored to the power system 2, the process proceeds to step S580. On the other hand, if power has not been restored to the power system 2 and the power outage state continues, the process shown in the flowchart of Fig. 7 is terminated, and power outage processing continues.

[0075] In step S580, the power outage capacity management unit 213 resumes charging of the secondary battery 20. At this time, similar to step S510, the power outage capacity management unit 213 issues a switching command to the switching control unit 214 to switch the switches 22a and 22b so that the switches 22a and 22b are each in a conductive state. In response to this switching command, when power is restored after the discharge of the secondary battery 20 has stopped, the switching control unit 214 switches the switch 22a, which is in a cut-off state, to a conductive state. This causes the charging current input from the power supply equipment 10 to the secondary battery 20 via the diode 23a and the switch 22b to be input via the switches 22a and 22b. Note that when power is restored while the secondary battery 20 is being discharged, both the switches 22a and 22b are in a conductive state, and therefore the switching states of the switches 22a and 22b do not change in step S580.

[0076] When charging of the secondary battery 20 is resumed by executing the process of step S580, the process shown in the flowchart of FIG. 7 ends.

[0077] According to the embodiment of the present invention described above, the following advantageous effects are achieved.

[0078] (1) The power storage device 12 is connected to the power supply equipment 10, stores power supplied from the power supply equipment 10, and supplies power to a communication device 11, which is another electrical device connected to the power supply equipment 10, when the power supply equipment 10 is not operating. The power storage device 12 includes a chargeable and dischargeable secondary battery 20, a control unit 21 that controls charging and discharging of the secondary battery 20, a voltage detection unit 24 that detects the voltage of the secondary battery 20, a current detection unit 25 that detects the current flowing through the secondary battery 20, and a battery temperature detection unit 26 that detects the temperature of the secondary battery 20. While the secondary battery 20 is being charged, the control unit 21 calculates an SOC value that represents the state of charge of the secondary battery 20 based on an integrated value of the current detected by the current detection unit 25, and performs a charging capacity management process (step S30) to determine whether to continue charging the secondary battery 20 based on the SOC value. Furthermore, when charging of the secondary battery 20 is stopped, a capacity management process during charging stop is performed in which the SOC value of the secondary battery 20 is calculated based on the voltage detected by the voltage detection unit 24 and the temperature detected by the battery temperature detection unit 26, and whether or not to resume charging of the secondary battery 20 is determined based on the SOC value (step S40). Then, charging of the secondary battery 20 is controlled based on the results of the capacity management process during charging and the capacity management process during charging stop. In this way, charging control of the secondary battery 20 can be achieved without detailed control of the voltage and current during charging, so that a low-cost power storage device 12 and a control method thereof can be provided.

[0079] (2) In the charging capacity management process, the control unit 21 determines whether the SOC value of the secondary battery 20 is greater than or equal to a predetermined upper limit value S Ｈ If the SOC value has not reached the upper limit value S (step S350: No), the charging of the secondary battery 20 is continued and the SOC value reaches the upper limit value S Ｈ , (step S350: Yes), it is determined that charging of the secondary battery 20 is not continued but is stopped (step S380). Ｈ a predetermined lower limit S Ｌ If the SOC value has reached the lower limit value S (step S430: Yes), charging of the secondary battery 20 is resumed (step S440). ＬIf the amount of charge in the secondary battery 20 does not reach the lower limit S (step S430: No), it is determined that the charging of the secondary battery 20 is to be continued without being restarted. Ｌ to the upper limit S Ｈ The charging of the secondary battery 20 can be controlled so that the charge is maintained within the range.

[0080] (3) If the magnitude of the current during charging of the secondary battery 20 becomes equal to or greater than a predetermined upper limit current (step S320: Yes), the control unit 21 stops charging of the secondary battery 20 regardless of the SOC value (step S390). This prevents an overcurrent from flowing through the secondary battery 20 during charging, suppresses deterioration of the secondary battery 20, and improves safety.

[0081] (4) The control unit 21 determines whether the voltage of the secondary battery 20 reaches a predetermined end-of-charge voltage V Ｈ If the SOC value is equal to or greater than this (step S370; Yes), charging of the secondary battery 20 is stopped regardless of the SOC value (step S380). This prevents overcharging of the secondary battery 20, suppresses deterioration of the secondary battery 20, and improves safety.

[0082] (5) The control unit 21 calculates the end-of-charge voltage V using the above-mentioned formulas (1) and (2) based on the magnitude of the current detected by the current detection unit 25 during charging of the secondary battery 20 and the temperature detected by the battery temperature detection unit 26. Ｈ In this way, the charge end voltage V for preventing overcharging can be calculated in various charging environments (step S360). Ｈ can be set to an appropriate value.

[0083] (6) The secondary battery 20 is connected to the power supply equipment 10 via a switching circuit consisting of switches 22a and 22b connected in series. The control unit 21 controls the charging of the secondary battery 20 by switching the switches 22a and 22b between a conductive state and a cut-off state. Specifically, a diode 23a is connected in parallel to the switch 22a. The diode 23a conducts the charging current flowing into the secondary battery 20 and cuts off the discharging current flowing out of the secondary battery 20. The diode 23b is connected in parallel to the switch 22b. The diode 23b conducts the discharging current and cuts off the charging current. When charging the secondary battery 20, the control unit 21 switches the switches 22a and 22b to the conductive state (steps S440 and S580). When stopping charging of the secondary battery 20, the control unit 21 switches the switches 22a and 22b to the conductive state (step S380). This ensures reliable charging control of the secondary battery 20, and in the event of a power outage, the discharge current from the secondary battery 20 can be immediately output to the communication device 11 without switching the switches 22a and 22b.

[0084] (7) When discharging the secondary battery 20, the control unit 21 switches the switches 22a and 22b to the conductive state (step S510), and when stopping the discharge of the secondary battery 20, the control unit 21 switches the switches 22a to the cutoff state and the switches 22b to the conductive state (step S560). This ensures that discharge control of the secondary battery 20 is performed reliably during a power outage, and when power is restored, charging current from the power supply equipment 10 can be immediately input to the secondary battery 20 without switching the switches 22a and 22b.

[0085] The present invention is not limited to the above-described embodiment, and can be implemented using any components without departing from the spirit of the present invention.

[0086] The above-described embodiments and modifications are merely examples, and the present invention is not limited to these details as long as the features of the invention are not impaired. Furthermore, although various embodiments and modifications have been described above, the present invention is not limited to these details. Other aspects that can be considered within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention.

[0087] 1: Communication base station 2: Power system 3: Circuit breaker 10: Power supply equipment 11: Communication equipment 12: Power storage device 20: Secondary battery 21: Control unit 22a, 22b: Switches 23a, 23b: Diodes 24: Voltage detection unit 25: Current detection unit 26: Battery temperature detection unit 27: Memory unit 211: Capacity management unit during charging 212: Capacity management unit when charging is stopped 213: Capacity management unit during power outage 214: Switching control unit

Claims

1. An energy storage device connected to a power supply equipment, storing power supplied from the power supply equipment, and supplying power to other electrical devices connected to the power supply equipment when the operation of the power supply equipment is stopped, the energy storage device comprising: a chargeable and dischargeable secondary battery; a control unit which controls the charging and discharging of the secondary battery; a voltage detection unit which detects the voltage of the secondary battery; a current detection unit which detects the current flowing through the secondary battery; and a battery temperature detection unit which detects the temperature of the secondary battery, wherein the control unit performs an in-charging capacity management process which obtains a state of charge of the secondary battery based on an integrated value of the current detected by the current detection unit while the secondary battery is being charged, and decides whether or not to continue charging of the secondary battery based on the state of charge, and performs a capacity management process when charging is stopped, which obtains the state of charge of the secondary battery based on the voltage detected by the voltage detection unit and the temperature detected by the battery temperature detection unit, and decides whether or not to resume charging of the secondary battery based on the state of charge, and controls the charging of the secondary battery based on results of the in-charging capacity management process and the capacity management process when charging is stopped.

2. An energy storage device as described in claim 1, wherein the control unit, in the capacity management process during charging, determines to continue charging of the secondary battery if the charging state has not reached a predetermined upper limit value, and determines to stop charging of the secondary battery without continuing it if the charging state has reached the upper limit value, and, in the capacity management process when charging is stopped, determines to resume charging of the secondary battery if the charging state has reached a predetermined lower limit value lower than the upper limit value, and determines to continue to stop charging of the secondary battery without resuming it if the charging state has not reached the lower limit value.

3. A power storage device according to claim 1, wherein the control unit stops charging of the secondary battery regardless of the charging state when the magnitude of the current during charging of the secondary battery becomes equal to or exceeds a predetermined upper limit current.

4. A power storage device according to claim 1, wherein the control unit stops charging of the secondary battery regardless of the charging state when the voltage of the secondary battery reaches or exceeds a predetermined end-of-charge voltage during charging of the secondary battery.

5. A power storage device according to claim 4, wherein the control unit calculates the end-of-charge voltage based on the magnitude of the current detected by the current detection unit during charging of the secondary battery and the temperature detected by the battery temperature detection unit.

6. A power storage device as claimed in claim 1, wherein the secondary battery is connected to the power supply equipment via a switching circuit, and the control unit controls charging of the secondary battery by switching the switching circuit to either a conductive state or a cut-off state.

7. A power storage device as claimed in claim 6, wherein the switching circuit has a first switch and a second switch connected in series, a first diode is connected in parallel to the first switch for conducting a charging current flowing into the secondary battery and cutting off a discharging current flowing out of the secondary battery, and a second diode is connected in parallel to the second switch for conducting the discharging current and cutting off the charging current, and the control unit switches the first switch and the second switch to a conductive state when charging the secondary battery, and switches the first switch to a conductive state and the second switch to a cut-off state when stopping charging of the secondary battery.

8. An energy storage device as claimed in claim 7, wherein the control unit switches the first switch and the second switch to a conductive state when discharging the secondary battery, and switches the first switch to a cut-off state and the second switch to a conductive state when stopping discharging of the secondary battery.

9. A control method for a power storage device that is connected to a power supply equipment, stores power supplied from the power supply equipment in a secondary battery, and when the operation of the power supply equipment is stopped, supplies the power stored in the secondary battery to other electrical equipment connected to the power supply equipment, wherein, while the secondary battery is being charged, a capacity management process is performed to determine a state of charge of the secondary battery based on an integrated value of a current flowing through the secondary battery, and to determine whether or not to continue charging of the secondary battery based on the state of charge; while charging of the secondary battery is stopped, a capacity management process is performed when charging is stopped, to determine a state of charge of the secondary battery based on the voltage and temperature of the secondary battery, and to determine whether or not to resume charging of the secondary battery based on the state of charge; and the control method for a power storage device that controls the charging of the secondary battery based on results of the capacity management process during charging and the capacity management process when charging is stopped.

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