Battery storage system

Abstract

A storage battery system (100) comprises a storage battery pack (20) that includes: a power terminal (25) to / from which power is input / output; a capacitive storage battery (11); and a main power storage battery and an auxiliary power storage battery (12a, 12b) that have lower internal resistance than that of the capacitive storage battery. The main power storage battery is connected in parallel with the capacitive storage battery via the switches (13a, 13b), and the auxiliary power storage battery is connected in parallel with the capacitive storage battery via the switches (13a, 13b). The storage battery system further comprises a switch control unit (14) that controls the ON and OFF of the switches (13a, 13b). The switch control unit sets the switch of the auxiliary power storage battery to the OFF state before starting discharging of the storage battery pack, and if the difference between the voltage of the storage battery pack and the voltage of the auxiliary power storage battery reaches a predetermined setting range during the discharging of the storage battery pack, then sets the switch of the auxiliary power storage battery to the ON state.

Description

[Technical Field]

[0001] The present application relates to a battery storage system. [Background technology]

[0002] When a capacity-type storage battery, which has a large charge / discharge capacity, is repeatedly required to output a large amount of power temporarily, the deterioration of the capacity-type storage battery accelerates. In order to solve this problem, Patent Document 1 proposes a storage battery system configuration in which a power-type storage battery, which has the characteristic of being able to output a large current in a short time, has a lower internal resistance than a capacity-type storage battery, and has a high output density, is connected in parallel to the capacity-type storage battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-182856 A (Figs. 1, 6, and 7) Summary of the Invention [Problem to be solved by the invention]

[0004] In the combined energy storage system described in Patent Document 1, the wiring resistance from the power-type storage battery to the inverter is made smaller than the wiring resistance from the capacity-type storage battery to the inverter, thereby increasing the load due to charging and discharging of the power-type storage battery and suppressing deterioration of the capacity-type storage battery. However, in the combined energy storage system of Patent Document 1, if the capacity of the power-type storage battery becomes insufficient first in the low charging rate region, the load on the capacity-type storage battery increases in the later stage of discharge. As a result, the combined energy storage system of Patent Document 1 has problems such as deterioration of the capacity-type storage battery and an increase in temperature of the capacity-type storage battery.

[0005] The technology disclosed in the present specification aims to prevent a shortage of capacity in a power-type storage battery during discharge and to prevent an increase in load on a capacity-type storage battery. [Means for solving the problem]

[0006] An example battery system disclosed herein includes a battery pack having power terminals for inputting and outputting power, a capacity-type battery, and main and auxiliary power-type batteries having lower internal resistance than the capacity-type batteries. The main power-type battery is connected in parallel to the capacity-type battery via a switch or at all times, and the auxiliary power-type battery is connected in parallel to the capacity-type battery via a switch. The battery system also includes a switch control unit that controls the on and off of the switches. The switch control unit turns off the switch of the auxiliary power-type battery before starting to discharge the battery pack, and turns on the switch of the auxiliary power-type battery when a secondary power-type battery connection condition is met, which is when the difference between the voltage of the battery pack and the voltage of the auxiliary power-type battery reaches a predetermined range while the battery pack is being discharged. [Effects of the Invention]

[0007] In one example of a storage battery system disclosed in the present specification, when the switch control unit is discharging the storage battery and the difference in voltage between the storage battery pack and the secondary power-type storage battery reaches a predetermined set range, the switch of the secondary power-type storage battery is turned on, thereby preventing a capacity shortage in the power-type storage battery during discharging and preventing an increase in the load on the capacity-type storage battery. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a configuration of a battery system according to a first embodiment and a first application example. [Figure 2] 3A and 3B are diagrams illustrating a configuration of a storage battery system according to a first embodiment and a second application example. [Figure 3] 4 is a flowchart showing control of the storage battery system according to the first embodiment. [Figure 4] 4 is a flowchart showing the charging process of FIG. 3. [Figure 5] 4 is a flowchart showing the discharge process of FIG. 3. [Figure 6] FIG. 10 is a diagram showing current characteristics of a comparative example. [Figure 7] FIG. 4 is a diagram showing current characteristics of the battery system according to the first embodiment. [Figure 8] 5A and 5B are diagrams illustrating the operation of the storage battery system according to the first embodiment. [Figure 9] 2 is a diagram illustrating an example of a hardware configuration that realizes the functions of a switch control unit according to the first embodiment. FIG. [Figure 10] FIG. 10 is a diagram showing a configuration of a storage battery system according to a second embodiment. [Figure 11] 10 is a flowchart showing a charging process according to the second embodiment. [Figure 12] 10 is a flowchart showing a discharging process according to the second embodiment. [Figure 13] FIG. 10 is a diagram showing an example of characteristics of a power storage battery according to the second embodiment. [Figure 14] FIG. 10 is a diagram showing the configuration of a storage battery system according to a third embodiment. [Figure 15] 10 is a flowchart showing a charging process according to the third embodiment. [Figure 16] 10 is a flowchart showing a discharge process according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Embodiment 1 FIG. 1 is a diagram showing the configuration of a storage battery system according to a first embodiment and a first application example, and FIG. 2 is a diagram showing the configuration of a storage battery system according to the first embodiment and a second application example. FIG. 3 is a flowchart showing control of the storage battery system according to the first embodiment. FIG. 4 is a flowchart showing the charging process of FIG. 3, and FIG. 5 is a flowchart showing the discharging process of FIG. 3. FIG. 6 is a diagram showing current characteristics of a comparative example, and FIG. 7 is a diagram showing current characteristics of the storage battery system according to the first embodiment. FIG. 8 is a diagram explaining the operation of the storage battery system according to the first embodiment. FIG. 9 is a diagram showing an example of a hardware configuration that realizes the function of a switch control unit according to the first embodiment. A storage battery system 100 according to the first embodiment includes a storage battery pack 20 having a capacity-type storage battery 11 and power-type storage batteries 12a and 12b having an internal resistance lower than that of the capacity-type storage battery 11, and a switch control unit 14 that controls the on and off of switches 13a and 13b of the power-type storage batteries 12a and 12b. The power battery 12a is connected in parallel to the capacity battery 11 via a switch 13a, and the power battery 12b is connected in parallel to the capacity battery 11 via a switch 13b.

[0010] The battery pack 20 will now be described. The battery pack 20 includes a power terminal 25 for inputting and outputting power, a capacity-type battery 11, power-type batteries 12a and 12b, switches 13a and 13b, a voltmeter 21a for detecting the voltage of the power-type battery 12a (i.e., detected voltage V1), a voltmeter 21b for detecting the voltage of the power-type battery 12b (i.e., detected voltage V2), a positive wiring 41, and a negative wiring 45. The negative sides of the capacity-type battery 11 and the power-type batteries 12a and 12b are connected to the negative wiring 45, which is a reference wiring. The battery positive terminal 26, which is the positive side of the capacity-type battery 11, is connected to the power terminal 25 by the positive wiring 41. The battery positive terminal 27a, which is the positive side of the power-type battery 12a, is connected to the positive wiring 41 via the switch 13a, and the battery positive terminal 27b, which is the positive side of the power-type battery 12b, is connected to the positive wiring 41 via the switch 13b. The voltmeter 21a measures the detected voltage V1 between the positive and negative sides of the power battery 12a and outputs a voltage signal sig3a. The voltmeter 21b measures the detected voltage V2 between the positive and negative sides of the power battery 12b and outputs a voltage signal sig3b.

[0011] Power terminal 25 is connected to power converter 10 via power line 3. Power converter 10 is connected to power system 2. A first example of power system 2 has a generator 8 and a load 9 as shown in FIG. 1. A second example of power system 2 is a system 7 such as a commercial power system as shown in FIG. 2. When power system 2 is the first example, power converter 10 is connected to generator 8 via power line 4a during charging, and is connected to load 9 via power line 4b during discharging. When power system 2 is the second example, power converter 10 receives power from system 7 via power line 4a during charging, and outputs power to system 7 via power line 4a during discharging.

[0012] The switch control unit 14 includes a processing unit 31, a communication unit 32, and a memory 33. The switch control unit 14 determines charging and discharging of the battery pack 20 based on power conversion information sig1, which is output from a higher-level control system 50 that controls the power converter 10 and indicates the operating state of the power converter 10. The higher-level control system 50 is, for example, an energy management system (EMS) or a battery management system (BMS). The switch control unit 14 outputs a switch control signal sig2a that controls the on / off of the switch 13a and a switch control signal sig2b that controls the on / off of the switch 13b based on the power conversion information sig1 and voltage signals sig3a and sig3b. The communication unit 32 receives the power conversion information sig1 and the voltage signals sig3a and sig3b and outputs the switch control signals sig2a and sig2b. The processing unit 31 generates the switch control signals sig2a and sig2b based on the power conversion information sig1 and the voltage signals sig3a and sig3b. The memory 33 stores a charging voltage Vso, which will be described later.

[0013] The power converter 10 is, for example, an inverter that converts AC power to DC power, a DC-DC converter that converts DC power to DC power, or a unit that combines these, etc. The storage battery system 100 is used as a DC power source that outputs DC power by connecting to, for example, a DC motor, a DC-DC converter, etc., or outputs DC power to an inverter that outputs AC power to a power grid.

[0014] The capacity-type battery 11 is an electricity storage device characterized by a higher energy density than the power-type batteries 12a and 12b. The capacity-type battery 11 is, for example, a lithium-ion battery, a nickel-metal hydride battery, a lead-acid battery, etc. The power-type batteries 12a and 12b are electricity storage devices characterized by a higher output density and the ability to withstand sudden input / output fluctuations due to, for example, a lower internal resistance than the capacity-type battery 11. The power-type batteries 12a and 12b are, for example, lithium-ion batteries, electric double-layer capacitors, lithium-ion capacitors, etc. The lithium-ion battery used in the capacity-type battery 11 and the lithium-ion batteries used in the power-type batteries 12a and 12b have different characteristics due to differences in the configuration of electrode materials, etc. The capacity-type battery 11 and the power-type batteries 12a and 12b are each composed of a single or multiple electricity storage devices as described above. The number of power storage devices constituting the capacity type storage battery 11 and the power type storage batteries 12a and 12b is set to an optimum number of series and / or parallel connections depending on the purpose for which the storage battery system 100 is used.

[0015] The battery system 100 of the first embodiment is configured so that the power-type batteries 12a and 12b are used alternately without being fixed as the main power-type battery connected in parallel to the capacity-type battery 11 from the beginning of discharge and the auxiliary power-type battery that is not connected in the beginning of discharge but is connected in parallel later. The main power-type battery and the auxiliary power-type battery are referred to as the main battery Bm and the auxiliary battery Bs as appropriate. Therefore, one of the power-type batteries 12a and 12b is the main power-type battery (main battery Bm) and the other is the auxiliary power-type battery (auxiliary battery Bs). When the power-type battery 12a is the main power-type battery (main battery Bm), the power-type battery 12b is the auxiliary battery Bs, the switch 13a connected to the power-type battery 12a is the main switch Swm, and the switch 13b connected to the power-type battery 12b is the auxiliary switch Sws. When the power battery 12b is the main power battery (main battery Bm), the power battery 12a becomes the sub-battery Bs, the switch 13b connected to the power battery 12b becomes the main switch Swm, and the switch 13a connected to the power battery 12a becomes the sub-switch Sws.

[0016] A method for controlling charging and discharging of the storage battery system 100 of the first embodiment will be described. In step ST01, the switch control unit 14 checks the power conversion information sig1 and determines whether to execute or terminate the charging process or the discharging process (charge / discharge determination process). If the power conversion information sig1 indicates charging, the switch control unit 14 proceeds to the charging process of step ST02, if the power conversion information sig1 indicates discharging, proceeds to the discharging process of step ST03, and terminates if the power conversion information sig1 indicates stopping. The flow of the charging process of step ST02 and the flow of the discharging process of step ST03 are shown in Figures 4 and 5, respectively.

[0017] The charging process will be described. In the battery system 100 of the first embodiment, the roles of the power type battery 12a and the power type battery 12b are interchangeable, and so the main battery Bm, main switch Swm, sub battery Bs, and sub switch Sws are initially set. For example, the initial settings are such that the main battery Bm and main switch Swm are the power type battery 12a and switch 13a, respectively, and the sub battery Bs and sub switch Sws are the power type battery 12b and switch 13b, respectively. The role interchange between the power type battery 12a and the power type battery 12b, i.e., the power type battery setting interchange, is performed based on the number of charge reaches Nm at which the main battery Bm reaches a predetermined set voltage Vmu.

[0018] In step ST11, the switch control unit 14 determines whether the charge arrival count Nm of the main battery Bm is equal to the set arrival count Nms (charge arrival count determination step). If the determination condition is met in step ST11, the process proceeds to step ST12, and if the determination condition is not met, the process proceeds to step ST13. In step ST12, the switch control unit 14 switches the settings of the main battery Bm and main switch Swm with the settings of the sub battery Bs and sub switch Sws, and resets the charge arrival count Nm (setting switching step). If the process proceeds from step ST11 to step ST13 without passing through step ST12, the current settings of the main battery Bm and main switch Swm, and the current settings of the sub battery Bs and sub switch Sws are maintained.

[0019] In step ST13, the switch control unit 14 turns on the main switch Swm and the secondary switch Sws (charging start step). Specifically, the switch control unit 14 outputs switch control signals sig2a and sig2b indicating on to the assembled storage battery 20. The switches 13a and 13b receive the switch control signals sig2a and sig2b indicating on, respectively, and enter the on state. When the switches 13a and 13b, i.e., the main switch Swm and the secondary switch Sws, are turned on and enter the on state, the capacity-type storage battery 11 and the power-type storage batteries 12a and 12b are connected in parallel. When the main storage battery Bm and the secondary storage battery Bs are the power-type storage battery 12a and the power-type storage battery 12b, respectively, the switch control signals sig2a and sig2b become the main switch control signal and the secondary switch control signal, respectively. In the charging start step, power is supplied from the power converter 10 to the capacity-type storage battery 11 and the power-type storage batteries 12a and 12b, and charging of the battery pack 20 starts.

[0020] In step ST14, the switch control unit 14 determines whether the detected voltage Vs of the sub battery Bs has reached a predetermined set voltage Vss based on the sub voltage signal (sub battery voltage determination step). If the detected voltage Vs of the sub battery Bs has reached the predetermined set voltage Vss in step ST14, the process proceeds to step ST16. If the detected voltage Vs of the sub battery Bs has not reached the predetermined set voltage Vss, the process proceeds to step ST15. If the sub battery Bs is the power battery 12b, the detected voltage Vs is the detected voltage V2, and the sub voltage signal is the voltage signal sig3b. The set voltage Vss is a voltage that sets the upper limit voltage of the main battery Bm.

[0021] In step ST15, the switch control unit 14 checks whether the power conversion information sig1 indicates charging. If the power conversion information sig1 indicates charging, the process returns to step ST14; if the power conversion information sig1 does not indicate charging, the process ends. If the charging process has ended, the process proceeds to step ST01. In step ST16, the switch control unit 14 turns off the secondary switch Sws and stores the charging voltage Vso of the secondary storage battery Bs (secondary switch off process). Specifically, the switch control unit 14 outputs a secondary switch control signal indicating off, for example, a switch control signal sig2b indicating off, to the battery pack 20. By turning off the secondary switch Sws, the secondary storage battery Bs is disconnected from the capacity-type storage battery 11 and the main storage battery Bm. The switch control unit 14 stores the open circuit voltage (OCV) of the secondary storage battery Bs with the secondary switch Sws turned off in the memory 33 as the charging voltage Vso.

[0022] Step ST17 is executed after step ST16. In step ST17, the switch control unit 14 determines whether the detected voltage Vm of the main battery Bm has reached a predetermined set voltage Vmu based on the main voltage signal (main battery voltage determination step). In step ST17, if the detected voltage Vm of the main battery Bm has reached the predetermined set voltage Vmu, the process proceeds to step ST19, and if the detected voltage Vm of the main battery Bm has not reached the predetermined set voltage Vmu, the process proceeds to step ST18. The set voltage Vmu is greater than the set voltage Vss. When the main battery Bm is the power battery 12a, the detected voltage Vm is the detected voltage V1, and the main voltage signal is the voltage signal sig3a.

[0023] In step ST18, the switch control unit 14 checks whether the power conversion information sig1 indicates charging. If the power conversion information sig1 indicates charging, the process returns to step ST17; if the power conversion information sig1 does not indicate charging, the process ends. If the charging process ends, the process proceeds to step ST01. In step ST19, the switch control unit 14 stores the charge arrival count Nm, which is the number of times the main storage battery Bm has reached the predetermined set voltage Vmu, in the memory 33 (arrival count storage step). After executing step ST19, the charging process ends, and the process proceeds to step ST01.

[0024] Next, the discharging process will be described. In step ST21, the switch control unit 14 turns on the main switch Swm and turns off the secondary switch Sws (discharge start process). Specifically, the switch control unit 14 outputs a main switch control signal indicating ON and a secondary switch control signal indicating OFF to the battery pack 20. As the first battery pack setting, a case will be described in which the main battery Bm and the secondary battery Bs are the power type battery 12a and the power type battery 12b, respectively. Note that if the main battery Bm and the secondary battery Bs are the power type battery 12b and the power type battery 12a, respectively, the second battery pack setting will be used. When the switch 13a, which is the main switch Swm, receives the switch control signal sig2a, which is the main switch control signal indicating ON, it turns on and enters the ON state. When the switch 13b, which is the secondary switch Sws, receives the switch control signal sig2b, which is the secondary switch control signal indicating OFF, it turns off and enters the OFF state. If step ST16 has been executed in the charging step before the current discharging step, the states of the main switch Swm and the sub switch Sws remain unchanged and the on / off states continue. By the discharge start step, power is discharged from the capacity-type battery 11 and the power-type battery 12a, which is the main battery Bm, and the power is output to the power converter 10 via the power terminal 25.

[0025] In step ST22, the switch control unit 14 determines, based on the main voltage signal, whether the difference voltage Vm-Vso between the detected voltage Vm of the main battery Bm and the charging voltage Vso stored in the memory 33 has reached a predetermined set range Rv (differential voltage determination step). If the difference voltage Vm-Vso has reached the predetermined set range Rv in step ST22, the process proceeds to step ST24. If the voltage difference Vm-Vso has not reached the predetermined set range Rv, the process proceeds to step ST23. In the charging step, the charging of the sub-battery Bs usually finishes before the charging of the main battery Bm. Even if the charging is completed in step ST15, the charging of the sub-battery Bs finishes at the same time as the main battery Bm. Therefore, if measurement error is not taken into consideration, the detected voltage Vm of the main battery Bm in the discharging step is equal to or higher than the charging voltage Vso of the sub-battery Bs. However, when measurement errors are taken into consideration, the detected voltage Vm of the main battery Bm during the discharging process may be lower than the charging voltage Vso of the sub-battery Bs. The set range Rv is set taking into consideration measurement errors and cross currents that occur between the batteries, which will be described later.

[0026] In step ST23, the switch control unit 14 checks whether the power conversion information sig1 indicates discharging. If the power conversion information sig1 indicates discharging, the process returns to step ST22; if the power conversion information sig1 does not indicate discharging, the process ends. If the discharging step has ended, the process proceeds to step ST01. In step ST24, the switch control unit 14 turns on the secondary switch Sws (secondary switch on step). Specifically, the switch control unit 14 outputs a secondary switch control signal indicating on, for example, a switch control signal sig2b indicating on, to the battery pack 20. By turning on the secondary switch Sws, the secondary battery Bs is connected in parallel to the capacity type battery 11 and the main battery Bm.

[0027] Step ST25 is executed after step ST24. In step ST25, the switch control unit 14 determines whether the detected voltage Vm of the main storage battery Bm has become equal to or lower than a predetermined lower limit voltage Vbl based on the main voltage signal (lower limit voltage determination step). In step ST25, if the detected voltage Vm of the main storage battery Bm has become equal to or lower than the predetermined lower limit voltage Vbl, the process proceeds to step ST27, and if the detected voltage Vm of the main storage battery Bm has not become equal to or lower than the predetermined lower limit voltage Vbl, the process proceeds to step ST26.

[0028] In step ST26, the switch control unit 14 checks whether the power conversion information sig1 indicates discharging. If the power conversion information sig1 indicates discharging, the process returns to step ST25; if the power conversion information sig1 does not indicate discharging, the process ends. If the discharging process has ended, the process proceeds to step ST01. In step ST27, the switch control unit 14 turns off the main switch Swm and the secondary switch Sws (power type storage battery disconnecting process). Specifically, the switch control unit 14 outputs a main switch control signal and a secondary switch control signal indicating OFF, for example, switch control signal sig2a and switch control signal sig2b indicating OFF, to the assembled storage battery 20. By turning off the main switch Swm and the secondary switch Sws, the main storage battery Bm and the secondary storage battery Bs are disconnected and opened from the capacity type storage battery 11. After executing step ST27, the discharging process ends, and the process proceeds to step ST01.

[0029] As described above, the set range Rv is set taking into account the cross current that occurs between the batteries. Specifically, the set range Rv is set to minimize the influence of the cross current that occurs between the batteries when the sub-battery Bs is connected to the capacity-type battery 11 and the main battery Bm via the sub switch Sws. It is generally known that when batteries with different voltages are directly connected in parallel, current flows from the higher-voltage battery to the lower-voltage battery so that the voltage difference between the batteries converges to zero. The current that occurs in this case is called a cross current. Because the cross current is a transfer of power only between the batteries, it prevents the battery system 100 from achieving highly efficient output to a load, etc. Therefore, in the battery system 100 of the first embodiment, it is desirable to minimize the voltage difference between the batteries when the sub-battery Bs is connected to the capacity-type battery 11 and the main battery Bm.

[0030] A specific example of the setting range Rv is shown below. Consider an example in which power batteries 12a and 12b are single cells with a capacity of 10 Ah, an internal resistance of 10 mΩ, and a maximum input current of 36 A. The setting is 3.0 V. If the measurement error of detection voltages V1 and V2 is ±2% of the setting, even if power batteries 12a and 12b are connected in parallel when the voltage reaches 3.0 V, a maximum voltage difference of 3.0 V × 0.02 × 2 = 0.12 V will actually occur between the batteries. Here, the setting is also the median of the setting range Rv. In this case, a maximum cross current of 0.12 V / 10 mΩ = 12 A will flow between power batteries 12a and 12b to eliminate the voltage difference. Considering that the magnitude of the cross current must be kept below the maximum input current, the maximum allowable voltage difference between the batteries when connected in parallel is 0.36 V, or three times 0.12 V. This 0.36 V is ±6% when the set value is 3.0 V. However, because measurement error must still be taken into consideration here, the set range Rv of the voltage difference Vm-Vso can be set to, for example, within ±4% of the set value.

[0031] The following summarizes the general operation of the switch control unit 14 of the first embodiment when charging and discharging the assembled battery 20. When charging the assembled battery 20, if the voltage of the secondary power-type battery, i.e., the detected voltage Vs of the secondary battery Bs, reaches a predetermined set voltage Vss while the assembled battery 20 is being charged, the switch control unit 14 of the first embodiment turns off the switch of the secondary power-type battery, i.e., the secondary switch Sws of the secondary battery Bs, and stores the charging voltage Vso, which is the voltage of the secondary power-type battery in the OFF state. Furthermore, the switch control unit 14 of the first embodiment controls the charging of the assembled battery 20 to end when the voltage of the main power-type battery, i.e., the detected voltage Vm of the main battery Bm, reaches a predetermined set voltage Vmu while the assembled battery 20 is being charged. The set voltage Vmu is greater than the set voltage Vss.

[0032] Furthermore, when operating the assembled battery 20, the switch control unit 14 of the first embodiment initially sets either the first power-type battery (i.e., power battery 12a) or the second power-type battery (i.e., power battery 12b) as the main power-type battery (i.e., main battery Bm), and sets the first power-type battery or the second power-type battery that was not set as the main power-type battery as the auxiliary power-type battery (i.e., auxiliary battery Bs). When charging the assembled battery 20, the switch control unit 14 of the first embodiment stores a charge reach count Nm, which is the number of times that the voltage of the main power-type battery (i.e., the detected voltage Vm of the main battery Bm) reaches a predetermined set voltage Vmu while the assembled battery 20 is being charged. Furthermore, when the charge reach count Nm reaches a predetermined set reach count Nms, the switch control unit 14 of the first embodiment alternates between the main power-type battery setting and the auxiliary power-type battery setting (i.e., the main battery Bm setting and the auxiliary battery Bs setting), and resets the charge reach count Nm.

[0033] When discharging the assembled battery 20, the switch control unit 14 of the first embodiment turns off the switch of the secondary power battery, i.e., the secondary switch Sws of the secondary battery Bs, before starting to discharge the assembled battery 20. Furthermore, while the assembled battery 20 is being discharged, the switch control unit 14 of the first embodiment turns on the switch of the secondary power battery, i.e., the secondary switch Sws of the secondary battery Bs, when the difference between the voltage of the assembled battery 20 and the voltage of the secondary power battery, i.e., the difference between the detected voltage Vm of the main battery Bm and the charging voltage Vso of the sub battery Bs, reaches a predetermined set range Rv. The voltage of the assembled battery 20 is the same as the detected voltage Vm of the main battery Bm, which is connected in parallel with the capacity battery 11.

[0034] The operation and effect of the storage battery system of the first embodiment will be described with reference to Figs. 6 to 8. Fig. 6 shows the current characteristics of a comparative example, and Fig. 7 shows the current characteristics of the storage battery system 100 of the first embodiment. Fig. 8 is an enlarged view of the current characteristics from time t1 to time t3 in Fig. 7. In Figs. 6 to 8, the vertical axis represents current (A) and the horizontal axis represents time. Current characteristic 61 is an example of the current change of the power-type storage batteries 12a and 12b of the comparative example, and current characteristic 62 is an example of the current change of the capacity-type storage battery 11 of the comparative example. Current characteristic 63 is an example of the current change of the power-type storage batteries 12a and 12b of the first embodiment, and current characteristic 64 is an example of the current change of the capacity-type storage battery 11 of the first embodiment. A case where the main storage battery Bm and the sub storage battery Bs are set as the first battery pack will be described. The comparative example differs from the storage battery system 100 of the first embodiment in that the capacity-type storage battery 11 and the power-type storage batteries 12a and 12b are connected in series in parallel, and the power-type storage batteries 12a and 12b are not controlled. The total capacity of the two power-type storage batteries 12a and 12b in the comparative example is the same as the capacity of the power-type storage battery 12a, which is the main storage battery Bm of the first embodiment. The capacity of the power-type storage battery 12a, which is the main storage battery Bm of the first embodiment, is also assumed to be equal to the capacity of the power-type storage battery 12b, which is the sub-storage battery Bs of the first embodiment.

[0035] Charging occurs from time t0 to time t1, and discharging occurs from time t1 to time t3. The right side of the figure shows a portion of the current characteristics during charging, starting from time t3. First, we will explain the approximate current characteristics of a battery pack in which a capacity-type battery and a power-type battery are connected in parallel. It is generally known that the approximate current characteristics of such a battery pack approach the inverse ratio of the internal resistances of the batteries in the early stages of charging and discharging, and then approach the capacity ratio between the batteries in the later stages of charging and discharging. Therefore, in the early stages of charging and discharging, the current input and output to the power-type batteries 12a and 12b, which have low internal resistance, is large, and then the relationship is reversed, with the current input and output to the capacity-type battery 11 becoming larger.

[0036] In the comparative example shown in Figure 6, charging begins at time t0, and because the internal resistance of power-type batteries 12a, 12b is smaller than that of capacity-type battery 11, the input current to power-type batteries 12a, 12b is large. Later in charging, the capacity of power-type batteries 12a, 12b is smaller than that of capacity-type battery 11, so the magnitude relationship of the current characteristics reverses from the initial charging start and approaches the capacity ratio. When the voltage of the battery pack reaches the upper limit voltage, charging is terminated.

[0037] In the comparative example shown in FIG. 6 , discharge begins at time t1. Similar to the initial charging period, the internal resistances of the power-type batteries 12a and 12b are smaller than that of the capacity-type battery 11, resulting in a larger output current for the power-type batteries 12a and 12b. Later in the discharge period, the capacity of the power-type batteries 12a and 12b is smaller than that of the capacity-type battery 11, resulting in a reversed relationship between the current characteristics and the capacity ratio. However, if the capacity of the power-type batteries 12a and 12b is insufficient relative to the power supply in the later discharging period, the current characteristics approaching the capacity ratio cannot be maintained. To compensate for this, the current characteristics of the capacity-type battery 11 rapidly increase, as seen after time t2. If the demand for high power supply from the capacity-type battery 11 continues, the capacity-type battery 11 will rapidly deteriorate. Furthermore, if the demand for power supply from the capacity-type battery 11 exceeds the output fluctuations that the capacity-type battery 11 can withstand, the temperature of the capacity-type battery 11 will rapidly increase, resulting in an abnormality.

[0038] In the current characteristics of the battery system 100 of the first embodiment shown in FIG. 7, charging begins at time t0. Because the internal resistance of the power-type batteries 12a, 12b is smaller than that of the capacity-type battery 11, the input current to the power-type batteries 12a, 12b is large. Later in the charging period, the capacity of the power-type batteries 12a, 12b is smaller than that of the capacity-type battery 11, so the magnitude relationship of the current characteristics reverses from the initial charging period and approaches the capacity ratio. When the voltage of the battery pack reaches the upper limit voltage, charging is terminated. The current characteristics during charging in the first embodiment change in the same way as the current characteristics in the comparative example.

[0039] In the battery system 100 of the first embodiment shown in FIG. 7, discharge of the capacity-type battery 11 and the power-type battery 12a (main battery Bm) begins at time t1. As in the comparative example, the internal resistance of the power-type battery 12a is lower than that of the capacity-type battery 11 at the beginning of discharge, resulting in a large output current from the power-type battery 12a. Thereafter, at time ta, the difference between the voltages of the capacity-type battery 11 and the power-type battery 12a (main battery Bm) and the OCV (i.e., charging voltage Vso) of the power-type battery 12b (sub-battery Bs) reaches a predetermined range Rv, causing discharge from the power-type battery 12b (sub-battery Bs). At this time, the parallel connection of the power-type battery 12a and the power-type battery 12b reduces the overall internal resistance. Therefore, when the power-type battery 12b begins discharging, the output current from the power-type batteries 12a and 12b is greater than the output current from the capacity-type battery 11. In Fig. 8, the current characteristic 63 of the power-type batteries 12a and 12b after time ta is shown by a thick solid line, and the current characteristic 64 of the capacity-type battery 11 after time ta is shown by a thick dashed line. Note that the current characteristic 63 from time t1 to time ta is the current of the power-type battery 12a, and the current characteristic 63 from time ta to time t3 is the total current of the power-type batteries 12a and 12b. Fig. 8 also shows, after time ta, current characteristic 61 (solid line) of the power-type batteries 12a and 12b of the comparative example and current characteristic 62 (dashed line) of the capacity-type battery 11 of the comparative example.

[0040] In the storage battery system 100 of the first embodiment, the remaining capacity of the power-type storage battery is increased in the later stage of discharge compared to the comparative example. This suppresses a capacity shortage of the power-type storage battery that occurs before the storage battery system 100 reaches the lower limit voltage and terminates discharging, thereby eliminating a sudden increase in load on the capacity-type storage battery 11. As indicated by the direction of arrow 65 in FIG. 8, after time ta, the current characteristic 61 of the comparative example of the power-type storage batteries 12a and 12b becomes the current characteristic 63 of the first embodiment, indicating an increase in the discharge current of the power-type storage batteries 12a and 12b. As indicated by the direction of arrow 66 in FIG. 8, after time ta, the current characteristic 62 of the comparative example of the capacity-type storage battery 11 becomes the current characteristic 64 of the first embodiment, indicating a decrease in the discharge current of the capacity-type storage battery 11. Note that, after time ta, the area enclosed by the current characteristic 61 of the comparative example and the current characteristic 63 of the first embodiment indicates an increase in the discharge current output of the power-type storage batteries 12a and 12b compared to the comparative example. After time ta, the area surrounded by the current characteristic 62 of the comparative example and the current characteristic 64 of the first embodiment indicates the decrease in the discharge current output of the capacitance type storage battery 11 compared to the comparative example.

[0041] In the storage battery system 100 of the first embodiment, the switch control unit 14 executes a charge reach count determination step in step ST11 at the beginning of the charging step of the assembled storage battery 20. That is, the switch control unit 14 determines whether the charge reach count Nm of the main storage battery Bm is equal to the set reach count Nms. If the determination condition of step ST11 is not met, the switch control unit 14 executes a charge start step in step ST13. If the determination condition of step ST11 is met, the switch control unit 14 executes a setting replacement step in step ST12. In the setting replacement step, the switch control unit 14 replaces the settings of the main storage battery Bm and main switch Swm with the settings of the sub storage battery Bs and sub switch Sws, and resets the charge reach count Nm. That is, in the setting replacement step, the switch control unit 14 replaces the power storage batteries 12a, 12b that are set as the main storage battery Bm and sub storage battery Bs of the storage battery system 100. When the main battery Bm and the sub battery Bs are set as the power type battery 12a and the power type battery 12b, respectively, that is, when they are set as the first set of batteries, the setting replacement process is executed to set the main battery Bm and the sub battery Bs as the power type battery 12b and the power type battery 12a, respectively, that is, when they are set as the second set of batteries.

[0042] If the setting replacement step of the first embodiment is not performed, the sub battery Bs will only be charged and discharged in a lower SOC range (state of charge range) than the main battery Bm. In this case, a decrease in the capacity utilization rate of the power type battery fixed as the sub battery Bs may occur, and the deterioration level may vary between the power type battery fixed as the main battery Bm and the power type battery fixed as the sub battery Bs. Therefore, by performing the setting replacement step, the storage battery system 100 of the first embodiment switches the roles of the power type battery 12a and the power type battery 12b at regular intervals. This improves the utilization rate of the power type battery fixed as the sub battery Bs in the storage battery system 100 compared to when the setting replacement step is not performed, while preventing the power type battery fixed as the main battery Bm from deteriorating more rapidly than the power type battery fixed as the sub battery Bs.

[0043] 9. In this case, the processing unit 31 and the communication unit 32 are realized by the processor 98 executing a program stored in the memory 99. Furthermore, a plurality of processors 98 and a plurality of memories 99 may cooperate to execute each function.

[0044] As described above, the battery system 100 of the first embodiment includes a power terminal 25 for inputting and outputting power, a capacity-type battery 11, and a battery pack 20 including a main power-type battery (main battery Bm) and a sub-power-type battery (sub-battery Bs) that have lower internal resistance than the capacity-type battery 11. The main power-type battery (main battery Bm) is connected in parallel to the capacity-type battery 11 via a switch (main switch Swm), and the sub-power-type battery (sub-battery Bs) is connected in parallel to the capacity-type battery 11 via a switch (sub-switch Sws). The battery system 100 of the first embodiment further includes a switch control unit 14 that controls the on and off of the switches (main switch Swm, sub-switch Sws). The switch control unit 14 turns off the switch (sub switch Sws) of the secondary power type battery (sub battery Bs) before starting to discharge the assembled storage battery 20, and turns on the switch (sub switch Sws) of the secondary power type battery (sub battery Bs) when the secondary power type battery connection condition is met, that is, when the difference between the voltage (detection voltage Vm) of the assembled storage battery 20 and the voltage (charging voltage Vso) of the secondary power type battery (sub battery Bs) reaches a predetermined set range Rv while the assembled storage battery 20 is being discharged. With this configuration, the storage battery system 100 of embodiment 1 turns on the switch (sub-switch Sws) of the secondary power-type battery (sub-battery Bs) when the switch control unit 14 is discharging the assembled storage battery 20 and the difference between the voltage (detection voltage Vm) of the assembled storage battery 20 and the voltage (charging voltage Vso) of the secondary power-type battery (sub-battery Bs) reaches a predetermined set range Rv. This prevents a capacity shortage of the power-type batteries (main storage battery Bm, sub-battery Bs) during discharging and prevents an increase in the load on the capacity-type battery 11.

[0045] Embodiment 2 FIG. 10 is a diagram showing the configuration of a storage battery system according to embodiment 2. FIG. 11 is a flowchart showing a charging process according to embodiment 2, and FIG. 12 is a flowchart showing a discharging process according to embodiment 2. FIG. 13 is a diagram showing an example of the characteristics of a power-type storage battery according to embodiment 2. Storage battery system 100 according to embodiment 2 differs from storage battery system 100 according to embodiment 1 in that the main power-type storage battery, i.e., main storage battery Bm, is always connected in parallel to capacity-type storage battery 11. The following mainly describes the differences from storage battery system 100 according to embodiment 1.

[0046] The storage battery system 100 of the second embodiment is an example that can improve the capacity utilization efficiency of the sub storage battery Bs compared to the storage battery system 100 of the first embodiment. In the first embodiment, the power type batteries 12a, 12b that were set as the main storage battery Bm and the sub storage battery Bs were replaced, but in the second embodiment, the main storage battery Bm is fixed to be the power type battery 12a, and the sub storage battery Bs is fixed to be the power type battery 12b. To improve the capacity utilization efficiency of the sub storage battery Bs, i.e., the power type battery 12b, there are, for example, two possible methods for selecting the power type batteries 12a, 12b.

[0047] In a first selection method for the power batteries 12a, 12b, the capacity of the power battery 12b, which is the sub-battery Bs, is selected so that it is smaller than the capacity of the power battery 12a, which is the main battery Bm. In a second selection method for the power batteries 12a, 12b, a battery with little change in the OCV (open circuit voltage) versus SOC (state of charge) characteristic (hereinafter referred to as the open circuit voltage characteristic) is selected as the sub-battery Bs, which is the power battery 12b, and a battery with a large change in the open circuit voltage characteristic is selected as the main battery Bm, which is the power battery 12a. Figure 13 shows the open circuit voltage characteristics. In Figure 13, the horizontal axis represents the state of charge, i.e., SOC (%), and the vertical axis represents the open circuit voltage, i.e., OCV (V). The characteristic 68 shows less change than the characteristic 67, and the battery having the open circuit voltage characteristic shown in the characteristic 68 is selected as the sub-battery Bs, or power battery 12b, and the battery having the open circuit voltage characteristic shown in the characteristic 67 is selected as the main battery Bm, or power battery 12a. The battery having less change in the open circuit voltage characteristic is a lithium ion battery or the like.

[0048] A method for controlling charging and discharging of the storage battery system 100 of the second embodiment will be described. The method for controlling charging and discharging of the storage battery system 100 of the second embodiment, like the storage battery system 100 of the first embodiment, executes a charging / discharging determination step of step ST01, a charging step of step ST02, and a discharging step of step ST03, all shown in FIG. 3. In the charging step of the second embodiment shown in FIG. 11, steps ST11, ST12, and ST13 of the charging step of the first embodiment are replaced by step ST20, and step ST19 is omitted. In the storage battery system 100 of the second embodiment, the main storage battery Bm is always connected in parallel with the capacitance-type storage battery 11, and there is no main switch Swm. Therefore, step ST20 is executed, and step ST19 is unnecessary. In step ST20, the switch control unit 14 turns on the secondary switch Sws (charging start step). Specifically, the switch control unit 14 outputs a switch control signal sig2b indicating ON to the assembled storage battery 20. The switch 13b, which is the secondary switch Sws, receives a switch control signal sig2b indicating ON and enters an ON state. When the switch 13b, which is the secondary switch Sws, enters an ON state, the capacity-type battery 11 and the power-type batteries 12a, 12b are connected in parallel. In the charging start step, power is supplied from the power converter 10 to the capacity-type battery 11 and the power-type batteries 12a, 12b, and charging of the assembled battery 20 begins. After step ST20, step ST14 is executed. Steps ST14 to ST16 and ST18 are the same as the charging step in the first embodiment, and therefore their description will not be repeated. In step ST17, if the detected voltage Vm of the main battery Bm has reached the predetermined set voltage Vmu, the charging step ends and the process proceeds to step ST01. If the detected voltage Vm of the main battery Bm has not reached the predetermined set voltage Vmu, the process proceeds to step ST18.

[0049] In the discharging process of the second embodiment shown in FIG. 12, steps ST21 and ST27 in the discharging process of the first embodiment are replaced by steps ST30 and ST31, respectively. In the storage battery system 100 of the second embodiment, the main storage battery Bm is always connected in parallel with the capacity-type storage battery 11, and there is no main switch Swm, so steps ST30 and ST31 are executed. In step ST30, the switch control unit 14 turns off the secondary switch Sws (discharge start process). Specifically, the switch control unit 14 outputs a secondary switch control signal indicating off to the assembled storage battery 20. When the switch 13b, which is the secondary switch Sws, receives a switch control signal sig2b, which is a secondary switch control signal indicating off, it turns off and enters the off state. Note that if step ST16 was executed in the charging process before this discharging process, there is no change in the state of the secondary switch Sws, and it remains in the off state. In the discharge start process, power is discharged from the capacity-type storage battery 11 and the power-type storage battery 12a, and the power is output to the power converter 10 via the power terminal 25. Steps ST22 to ST24 and ST26 are the same as the charging process in embodiment 1, and therefore description thereof will not be repeated. In step ST25, if the detected voltage Vm of the power type battery 12a, which is the main storage battery Bm, is equal to or lower than the predetermined lower limit voltage Vbl, the process proceeds to step ST31, and if the detected voltage Vm of the main storage battery Bm is not equal to or lower than the predetermined lower limit voltage Vbl, the process proceeds to step ST26.

[0050] In step ST31, the switch control unit 14 turns off the secondary switch Sws (power battery disconnection step). Specifically, the switch control unit 14 outputs a secondary switch control signal indicating OFF, i.e., a switch control signal sig2b indicating OFF, to the battery pack 20. By turning off the secondary switch Sws, the secondary battery Bs is disconnected and disconnected from the capacity battery 11 and the main battery Bm. After step ST31 is executed, the discharging step ends and the process proceeds to step ST01.

[0051] Like the storage battery system 100 of embodiment 1, the storage battery system 100 of embodiment 2 can suppress the capacity shortage of the power-type batteries (main battery Bm, sub-battery Bs) that occurs in the storage battery system 100 of the comparative example in the later stage of discharge until the discharge current of the power-type battery and the capacity-type battery reaches the capacity ratio and the discharge is terminated, thereby eliminating the sudden increase in load on the capacity-type battery 11.

[0052] A first example of a storage battery system 100 according to the second embodiment will be described, which includes power-type batteries 12a and 12b selected by the first selection method. The power-type battery 12b, which is the sub-storage battery Bs, finishes charging before the power-type battery 12a, which is the main storage battery Bm. In the first example of the storage battery system 100 according to the second embodiment, the capacity of the sub-storage battery Bs is small, so even if the charging voltage Vso of the sub-storage battery Bs is the same, the charging rate is higher compared to the storage battery system 100 according to the first embodiment, in which the main storage battery Bm and the sub-storage battery Bs have the same or similar capacities. This improves the capacity utilization efficiency of the sub-storage battery Bs. In other words, when discharging the battery pack 20, the power-type battery 12b, which is the auxiliary battery Bs that is used only in the later stage of discharging the capacity-type battery 11 and the power-type battery 12a, which is the main battery Bm, narrows the unused capacity area compared to when the power-type batteries 12a and 12b have approximately the same capacity, thereby improving the capacity utilization rate of the power-type battery 12b, which is the auxiliary battery Bs.

[0053] A second example of storage battery system 100 of Embodiment 2 including power-type batteries 12a, 12b selected by the second selection method will be described. In this second example of storage battery system 100 of Embodiment 2, the battery having the open-circuit voltage characteristic shown in characteristic 68 is selected as power-type battery 12b, which is the sub-battery Bs, and the battery having the open-circuit voltage characteristic shown in characteristic 67 is selected as power-type battery 12a, which is the main battery Bm. Therefore, power-type battery 12b, which is the sub-battery Bs (sub-power-type battery), has a region with less change in the open-circuit voltage characteristic, i.e., the charge rate vs. switch-off voltage characteristic, than power-type battery 12a, which is the main battery Bm (main power-type battery).

[0054] In the second example of the battery system 100 of the second embodiment, when the capacity-type battery 11 and the power-type battery 12a (main battery Bm) are connected to the power-type battery 12b (sub-battery Bs) via the sub-switch Sws (switch 13b) during the latter stage of discharge, even if the SOC of the power-type battery 12b is higher than that of the power-type battery 12a, the difference between the voltage of the power-type battery 12a and the OCV of the power-type battery 12b is small, and connection is possible as long as the difference is within the predetermined range Rv. As shown in Figure 13, when the SOC is higher than the intersection P between the characteristic curves 67 and 68, the voltage, i.e., the OCV, of the power-type battery 12b (sub-battery Bs) is lower than that of the power-type battery 12a (main battery Bm) even if the state of charge is higher.

[0055] Therefore, the power-type battery 12b, which is the auxiliary battery Bs in the second example of the battery system 100 of embodiment 2, can have a higher capacity utilization rate than when this second example is not implemented, thereby improving the capacity utilization rate.

[0056] In the battery storage system 100 of the second embodiment, the power-type battery 12a serving as the main battery Bm and the capacity-type battery 11 are always connected in series in parallel, and therefore the battery storage system 100 does not need to include the switch 13a serving as the main switch Swm, unlike the battery storage system 100 of the first embodiment. If the switch 13a serving as the main switch Swm is not provided, the structures of the assembled battery 20 and the switch control unit 14 can be simplified. Therefore, the battery storage system 100 of the second embodiment can have a simpler structure and lower costs than the battery storage system 100 of the first embodiment.

[0057] Although FIG. 10 shows an example in which the power system 2 has the generator 8 and the load 9, the power system 2 may be a system 7 such as a commercial power system.

[0058] As described above, the battery system 100 of the second embodiment includes a power terminal 25 for inputting and outputting power, a capacity-type battery 11, and a battery pack 20 including a main power-type battery (main battery Bm, power battery 12a) and a sub-power-type battery (sub-battery Bs, power battery 12b) that have lower internal resistance than the capacity-type battery 11. The main power-type battery (main battery Bm, power battery 12a) is always connected in parallel to the capacity-type battery 11, and the sub-power-type battery (sub-battery Bs, power battery 12b) is connected in parallel to the capacity-type battery 11 via switches (sub-switch Sws, switch 13b). The battery system 100 of the second embodiment further includes a switch control unit 14 that controls the on and off of the switches (sub-switch Sws, switch 13b). Before starting to discharge the assembled battery 20, the switch control unit 14 turns off the switches (sub-switch Sws, switch 13b) of the secondary power-type batteries (sub-battery Bs, power-type battery 12b), and while the assembled battery 20 is being discharged, when the difference between the voltage (detection voltage Vm) of the assembled battery 20 and the voltage (charging voltage Vso) of the secondary power-type batteries (sub-battery Bs, power-type battery 12b) reaches within a predetermined setting range Rv, which is the secondary power-type battery connection condition, the switch control unit 14 turns on the switches (sub-switch Sws, switch 13b) of the secondary power-type batteries (sub-battery Bs, power-type battery 12b). With this configuration, the storage battery system 100 of embodiment 2 turns on the switches (sub-switch Sws, switch 13b) of the sub-power-type batteries (sub-battery Bs, power-type battery 12b) when the difference between the voltage (detection voltage Vm) of the assembled storage battery 20 and the voltage (charging voltage Vso) of the sub-power-type batteries (sub-battery Bs, power-type battery 12b) reaches a predetermined set range Rv while the assembled storage battery 20 is being discharged. This prevents a capacity shortage of the power-type batteries (main storage battery Bm, power-type battery 12a, sub-battery Bs, power-type battery 12b) during discharge, and prevents an increase in the load on the capacity-type battery 11.

[0059] Embodiment 3 Fig. 14 is a diagram showing the configuration of a storage battery system according to embodiment 3. Fig. 15 is a flowchart showing a charging process according to embodiment 3, and Fig. 16 is a flowchart showing a discharging process according to embodiment 3. Storage battery system 100 according to embodiment 3 differs from storage battery system 100 according to embodiment 2 in that assembled storage battery 20 includes another power terminal 28 that is different from, i.e., separate from, power terminal 25 and to which another-terminal load 15 is connected, and another-terminal switch 16 that switches between the other power terminal 28 and the secondary power-type storage battery (sub-storage battery Bs) and the ON / OFF state. The following mainly describes the differences from storage battery system 100 according to embodiment 2.

[0060] The battery positive terminal 27b of the power battery 12b, which is the sub-storage battery Bs, is connected to the positive wiring 41 via the switch 13b and to the power terminal 28 via the separate-terminal switch 16. The switch control unit 14 outputs a switch control signal sig2b that controls the on / off of the switch 13b and a separate-terminal switch control signal sig4 that controls the on / off of the separate-terminal switch 16 based on power conversion information sig1 and voltage signals sig3a and sig3b. The communication unit 32 receives the power conversion information sig1 and the voltage signals sig3a and sig3b and outputs the switch control signal sig2a and the separate-terminal switch control signal sig4. The processing unit 31 generates the switch control signal sig2a and the separate-terminal switch control signal sig4 based on the power conversion information sig1 and the voltage signals sig3a and sig3b.

[0061] The separate terminal load 15 is, for example, another storage battery, auxiliary equipment, an inverter, a DC-DC converter, or a unit combining these. The separate terminal load 15 is constantly operating, and part of the power supplied to the separate terminal load 15 is borne by the power type storage battery 12b. The other storage battery is, for example, a storage battery for an uninterruptible power supply (UPS), and in this case, power is supplied to the separate terminal load 15 by float charging. The auxiliary equipment is, for example, a stationary storage battery system, an air conditioner used to adjust the temperature inside a container, etc.

[0062] In the battery system 100 of the third embodiment, when discharging, the power type battery 12b, which is the sub-battery Bs, is connected to the separate terminal load 15 to supply power while it is not connected to the capacity type battery 11 or the power type battery 12a, which is the main battery Bm. By supplying power to the separate terminal load 15, the switch control unit 14 does not need to control the charge amount of the power type battery 12b, which is the sub-battery Bs, and the capacity utilization rate of the power type battery 12b, which is the sub-battery Bs, can be increased. This is explained below.

[0063] First, a description will be given of a method for controlling charging and discharging of the storage battery system 100 according to the third embodiment. The method for controlling charging and discharging of the storage battery system 100 according to the third embodiment, like the storage battery system 100 according to the first embodiment, executes a charging / discharging determination step in step ST01, a charging step in step ST02, and a discharging step in step ST03 shown in FIG.

[0064] 15 omits steps ST14, ST16, and ST15 from the charging process of embodiment 2, and instead performs steps ST17 and ST18 after step ST20. In storage battery system 100 of embodiment 3, power type battery 12b, which is sub-storage battery Bs, is connected to separate terminal load 15 to supply power during discharge while not connected to capacity type battery 11 or power type battery 12a, which is main battery Bm. Therefore, unlike the charging processes of embodiments 1 and 2, switch control unit 14 performs step ST20 of turning on switch 13b, which is sub-switch Sws, during the charging process, and performs step ST17 without performing the charge adjustment process of steps ST14 and ST16 for power type battery 12b, which is sub-storage battery Bs.

[0065] In step ST17, the switch control unit 14 determines whether the detected voltage Vm of the main battery Bm has reached a predetermined set voltage Vmu based on the main voltage signal (main battery voltage determination step). If the detected voltage Vm of the main battery Bm has reached the predetermined set voltage Vmu in step ST17, the charging step is terminated and the process proceeds to step ST01. If the detected voltage Vm of the main battery Bm has not reached the predetermined set voltage Vmu, the process proceeds to step ST18. In step ST18, the switch control unit 14 checks whether the power conversion information sig1 indicates charging. If the power conversion information sig1 indicates charging, the process returns to step ST17, and if the power conversion information sig1 does not indicate charging, the process ends. If the charging step is terminated, the process proceeds to step ST01.

[0066] Next, the discharging step will be described. In step ST32, the switch control unit 14 turns off the secondary switch Sws and turns on the separate-terminal switch Swa (discharge start step). The separate-terminal switch Swa is the separate-terminal switch 16 shown in FIG. 14. The reference symbol for the separate-terminal switch will also be Swa where appropriate. In step ST33, the switch control unit 14 determines whether the detected voltage Vs of the secondary battery Bs has fallen below a predetermined lower limit voltage Vsl based on the secondary voltage signal, i.e., the voltage signal sig3b (lower limit voltage determination step). If the detected voltage Vs of the secondary battery Bs has fallen below the predetermined lower limit voltage Vsl in step ST33, the process proceeds to step ST34; if the detected voltage Vs of the secondary battery Bs has not fallen below the predetermined lower limit voltage Vsl, the process proceeds to step ST35. The detected voltage Vs is the detected voltage V2.

[0067] In step ST34, the separate-terminal switch Swa is turned off (separate-terminal switch off step). Specifically, the switch control unit 14 outputs a separate-terminal switch control signal sig4 indicating off to the battery pack 20. By turning off the separate-terminal switch Swa, the separate-terminal load 15 is disconnected and released from the sub-battery Bs. If step ST34 determines that the sub-battery Bs is not sufficiently charged, discharging to the separate-terminal load 15 is not performed. Step ST35 is executed after step ST34. In step ST35, the switch control unit 14 determines whether the difference voltage Vm-Vs between the detected voltage Vm of the main battery Bm and the detected voltage Vs of the sub-battery Bs has reached a predetermined set range Rv based on the main voltage signal and the sub-voltage signal (difference voltage determination step). The main voltage signal is voltage signal sig3a, and the sub-voltage signal is voltage signal sig3b. In step ST35, if the voltage difference Vm-Vs reaches within the predetermined setting range Rv, proceed to step ST37, and if the voltage difference Vm-Vs does not reach within the predetermined setting range Rv, proceed to step ST36.

[0068] In step ST36, the switch control unit 14 checks whether the power conversion information sig1 indicates discharging. If the power conversion information sig1 indicates discharging, the process returns to step ST33; if the power conversion information sig1 does not indicate discharging, the process ends. If the discharging step has ended, the process proceeds to step ST01. In step ST37, the switch control unit 14 turns off the separate-terminal switch Swa and turns on the secondary switch Sws (secondary switch-on step). Specifically, the switch control unit 14 outputs a separate-terminal switch control signal sig4 indicating OFF and a secondary switch control signal indicating ON, i.e., a switch control signal sig2b indicating ON, to the assembled storage battery 20. By turning off the separate-terminal switch Swa, the separate-terminal load 15 is disconnected and released from the secondary storage battery Bs. Furthermore, by turning on the secondary switch Sws, the secondary storage battery Bs is connected in parallel to the capacity-type storage battery 11 and the main storage battery Bm.

[0069] Step ST25 is executed after step ST37. In step ST25, the switch control unit 14 determines whether the detected voltage Vm of the main storage battery Bm has become equal to or lower than a predetermined lower limit voltage Vbl based on the main voltage signal (lower limit voltage determination step). In step ST25, if the detected voltage Vm of the main storage battery Bm has become equal to or lower than the predetermined lower limit voltage Vbl, the process proceeds to step ST31, and if the detected voltage Vm of the main storage battery Bm has not become equal to or lower than the predetermined lower limit voltage Vbl, the process proceeds to step ST26.

[0070] In step ST26, the switch control unit 14 checks whether the power conversion information sig1 indicates discharging. If the power conversion information sig1 indicates discharging, the process returns to step ST25; if the power conversion information sig1 does not indicate discharging, the process ends. If the discharging process has ended, the process proceeds to step ST01. In step ST31, the switch control unit 14 turns off the secondary switch Sws (power type battery disconnecting process). Specifically, the switch control unit 14 outputs a secondary switch control signal indicating OFF, i.e., a switch control signal sig2b indicating OFF, to the assembled battery 20. By turning off the secondary switch Sws, the secondary battery Bs is disconnected and opened from the capacity type battery 11 and the main battery Bm. After step ST31 is executed, the discharging process ends, and the process proceeds to step ST01.

[0071] The reason for executing steps ST32 to ST37 is to suppress cross current that occurs in response to a voltage difference between the capacity-type battery 11 and the power-type battery 12a (main battery Bm) and the power-type battery 12b (sub-battery Bs) when switch 13b (sub-switch Sws) is turned on to connect power-type battery 12b (sub-battery Bs) to capacity-type battery 11 and power-type battery 12a (main battery Bm) during the latter part of discharge. For example, if the power-type battery 12b (sub-battery Bs) does not supply power to separate-terminal load 15 for a long period during discharge, the voltages of capacity-type battery 11 and the power-type battery 12a (main battery Bm) become lower than the OCV of power-type battery 12b (sub-battery Bs) as the discharge progresses. This is because, at this time, it is conceivable that the cross current generated when the switch 13b (sub-switch Sws) is turned on and the power-type storage battery 12b (sub-storage battery Bs) is connected to the capacity-type storage battery 11 and the power-type storage battery 12a (main storage battery Bm) may become large.

[0072] The following is a summary of the general operation of the switch control unit 14 of the third embodiment when discharging the assembled battery 20. When discharging the assembled battery 20, if the switches (sub switch Sws, switch 13b) of the secondary power type batteries (sub battery Bs, power type battery 12b) are in the OFF state, the switch control unit 14 of the third embodiment turns on the separate terminal switch Swa (separate terminal switch 16) to connect the other power terminal 28 and the secondary power type batteries (sub battery Bs, power type battery 12b). When the secondary power-type battery (sub-battery Bs, power-type battery 12b) is discharging to the separate-terminal load 15 and the voltage (detected voltage Vs) of the secondary power-type battery (sub-battery Bs, power-type battery 12b) becomes equal to or lower than a predetermined set voltage (lower limit voltage Vsl), the switch control unit 14 turns off the separate-terminal switch Swa (separate-terminal switch 16). ... If the first condition is not met and the secondary power-type battery connection condition is met, that is, if the difference between the voltage (detected voltage Vm) of the battery pack 20 and the voltage (detected voltage Vs) of the secondary power-type battery (sub-battery Bs, power-type battery 12b) falls within a predetermined setting range Rv, the separate-terminal switch Swa (separate-terminal switch 16) is turned off before the switch (sub-switch Sws, switch 13b) of the secondary power-type battery (sub-battery Bs, power-type battery 12b) is turned on.

[0073] The battery system 100 of the third embodiment, like the battery systems 100 of the first and second embodiments, can suppress the capacity shortage of the power-type batteries (main battery Bm, sub-battery Bs) that occurs in the battery system 100 of the comparative example in the later stage of discharge until the discharge current of the power-type battery and the capacity-type battery reaches the capacity ratio and the discharge is terminated, and can eliminate the sudden increase in load on the capacity-type battery 11.

[0074] In the battery storage system 100 of the third embodiment, similarly to the battery storage system 100 of the second embodiment, the power type battery 12a serving as the main battery Bm and the capacity type battery 11 are always connected in series in parallel, and therefore, unlike the battery storage system 100 of the first embodiment, the switch 13a serving as the main switch Swm does not have to be provided. If the switch 13a serving as the main switch Swm is not provided, the structures of the assembled battery 20 and the switch control unit 14 can be simplified, and therefore the battery storage system 100 of the third embodiment can have a simpler structure and lower costs than the battery storage system 100 of the first embodiment.

[0075] Although FIG. 14 shows an example in which the power system 2 has the generator 8 and the load 9, the power system 2 may be a system 7 such as a commercial power system.

[0076] As described above, the battery system 100 of the third embodiment includes a power terminal 25 for inputting and outputting power, a capacity-type battery 11, and a battery pack 20 including a main power-type battery (main battery Bm, power battery 12a) and a sub-power-type battery (sub-battery Bs, power battery 12b) that have lower internal resistance than the capacity-type battery 11. The main power-type battery (main battery Bm, power battery 12a) is always connected in parallel to the capacity-type battery 11, and the sub-power-type battery (sub-battery Bs, power battery 12b) is connected in parallel to the capacity-type battery 11 via switches (sub-switch Sws, switch 13b). The battery system 100 of the third embodiment further includes a switch control unit 14 that controls the on and off of the switches (sub-switch Sws, switch 13b, separate-terminal switch Swa, separate-terminal switch 16). The battery pack 20 includes another power terminal 28 different from the power terminal 25, and an additional terminal switch 16 that switches between the other power terminal 28 and the secondary power type battery (secondary battery Bs, power type battery 12b) on and off, and an additional terminal load 15 is connected to the other power terminal 28. Before starting to discharge the assembled battery 20, the switch control unit 14 turns off the switches (sub-switch Sws, switch 13b) of the secondary power-type batteries (sub-battery Bs, power-type battery 12b), and while the assembled battery 20 is being discharged, when the difference between the voltage (detected voltage Vm) of the assembled battery 20 and the voltage (detected voltage Vs) of the secondary power-type batteries (sub-battery Bs, power-type battery 12b) reaches within a predetermined set range Rv, which is the secondary power-type battery connection condition, the switch control unit 14 turns on the switches (sub-switch Sws, switch 13b) of the secondary power-type batteries (sub-battery Bs, power-type battery 12b). In addition, when the switch (sub switch Sws, switch 13b) of the secondary power type storage battery (sub storage battery Bs, power type storage battery 12b) is in the OFF state, the switch control unit 14 turns on the separate terminal switch Swa (separate terminal switch 16) to connect the other power terminal 28 and the secondary power type storage battery (sub storage battery Bs, power type storage battery 12b).The switch control unit 14 turns off the separate-terminal switch Swa (separate-terminal switch 16) when the secondary power-type battery (sub-battery Bs, power-type battery 12b) is discharging to the separate-terminal load 15 and the voltage (detected voltage Vs) of the secondary power-type battery (sub-battery Bs, power-type battery 12b) is equal to or lower than a predetermined set voltage (lower limit voltage Vsl), which is a first condition.When the secondary power-type battery (sub-battery Bs, power-type battery 12b) is discharging to the separate-terminal load 15 and the first condition is not met and the secondary power-type battery connection condition is met, the switch control unit 14 turns off the separate-terminal switch Swa (separate-terminal switch 16) before turning on the switch (sub-switch Sws, switch 13b) of the secondary power-type battery (sub-battery Bs, power-type battery 12b). With this configuration, the storage battery system 100 of embodiment 3 turns on the switches (sub-switch Sws, switch 13b) of the sub-power-type batteries (sub-battery Bs, power-type battery 12b) when the switch control unit 14 is discharging the storage battery 20 and the difference between the voltage (detected voltage Vm) of the storage battery 20 and the voltage (detected voltage Vs) of the sub-power-type batteries (sub-battery Bs, power-type battery 12b) reaches a predetermined set range Rv. This prevents a capacity shortage of the power-type batteries (main battery Bm, power-type battery 12a, sub-battery Bs, power-type battery 12b) during discharge, and prevents an increase in the load on the capacity-type battery 11.

[0077] In the storage battery systems 100 of the first to third embodiments, the power conversion information sig1 is checked in the charge / discharge determination process of step ST01, and the charging process, the discharging process, and the control is stopped by terminating the control. This allows various charge / discharge controls to be performed, not only when charging / discharging is repeated, but also when there is an operation pause period after charging / discharging, etc. Furthermore, the storage battery systems 100 of the first to third embodiments are systems that may become fully charged if the set voltage Vmu is set to the full charge voltage.

[0078] Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment. [Explanation of symbols]

[0079] 10...power converter, 11...capacitive storage battery, 12a, 12b...power storage battery, 13a, 13b...switch, 14...switch control unit, 15...separate terminal load, 16...separate terminal switch, 20...assembled storage battery, 25...power terminal, 28...power terminal (other power terminal), 100...storage battery system, Bm...main storage battery, Bs...sub storage battery, Nm...charge arrival count, Nms...set arrival count, sig1...power conversion information, Swm...main switch, Sws...sub switch, Swa...separate terminal switch, Vss...set voltage, Vmu...set voltage, Vso...charge voltage, Vm...detection voltage, Vs...detection voltage, Rv...setting range, Vbl...lower limit voltage, Vsl...lower limit voltage

Claims

1. A storage battery system including a battery pack including a power terminal for inputting and outputting power, a capacity-type storage battery, and a main power-type storage battery and a sub-power-type storage battery having an internal resistance lower than that of the capacity-type storage battery, The main power battery is connected in parallel with the capacity battery via a switch or at all times; the auxiliary power battery is connected in parallel to the capacity battery via a switch; A switch control unit is provided to control the on and off of the switch, The switch control unit before starting to discharge the assembled storage battery, turning off the switch of the auxiliary power storage battery; when a secondary power-type battery connection condition is met, which is when a difference between a voltage of the assembled battery and a voltage of the secondary power-type battery reaches a predetermined set range while the assembled battery is being discharged, a switch of the secondary power-type battery is turned on; Battery storage system.

2. The main power battery is connected in parallel to the capacity battery via a switch. The battery system according to claim 1 .

3. the main power battery is always connected in parallel with the capacity battery; The battery system according to claim 1 .

4. The switch control unit When the voltage of the secondary power type battery reaches a predetermined set voltage while the battery pack is being charged, Turning the switch of the secondary power type storage battery to an OFF state, and storing a charging voltage that is the voltage of the secondary power type storage battery in the OFF state; When the voltage of the main power type battery reaches a predetermined set voltage while the assembled battery is being charged, the charging of the assembled battery is terminated; The voltage of the secondary power-type storage battery when the switch of the secondary power-type storage battery is turned on is the charging voltage. The battery system according to claim 1 or 2.

5. The switch control unit When the voltage of the secondary power type battery reaches a predetermined set voltage while the battery pack is being charged, Turning the switch of the secondary power type storage battery to an OFF state, and storing a charging voltage that is the voltage of the secondary power type storage battery in the OFF state; When the voltage of the main power type battery reaches a predetermined set voltage while the assembled battery is being charged, the charging of the assembled battery is terminated; The voltage of the secondary power-type storage battery when the switch of the secondary power-type storage battery is turned on is the charging voltage. The battery system according to claim 3 .

6. a first power-type battery and a second power-type battery having an internal resistance smaller than that of the capacity-type battery; the main power-type battery is either the first power-type battery or the second power-type battery, and the auxiliary power-type battery is either the first power-type battery or the second power-type battery different from the main power-type battery; the first power battery is connected in parallel to the capacity battery via a first switch; the second power battery is connected in parallel to the capacity battery via a second switch; The switch control unit When operating the battery pack, one of the first power-type battery and the second power-type battery is set as the main power-type battery, and the other of the first power-type battery and the second power-type battery that is not set as the main power-type battery is set as the auxiliary power-type battery; storing a charge reaching count, which is the number of times that the voltage of the main power type storage battery reaches a predetermined set voltage while the battery pack is being charged; When the charge count reaches a predetermined set count, the setting of the main power type storage battery and the setting of the sub power type storage battery are switched, and the charge count is reset. The battery system according to claim 1 or 2.

7. A first power-type storage battery and a second power-type storage battery having an internal resistance smaller than that of the capacity-type storage battery, the main power-type battery is either the first power-type battery or the second power-type battery, and the auxiliary power-type battery is either the first power-type battery or the second power-type battery different from the main power-type battery; the first power battery is connected in parallel to the capacity battery via a first switch; the second power battery is connected in parallel to the capacity battery via a second switch; The switch control unit When operating the battery pack, one of the first power-type battery and the second power-type battery is set as the main power-type battery, and the other of the first power-type battery and the second power-type battery that is not set as the main power-type battery is set as the auxiliary power-type battery; storing a charge reaching count, which is the number of times that the voltage of the main power type storage battery reaches a predetermined set voltage while the battery pack is being charged; When the charge count reaches a predetermined set count, the setting of the main power type storage battery and the setting of the sub power type storage battery are switched, and the charge count is reset. The battery system according to claim 4.

8. The secondary power battery has a smaller capacity than the primary power battery. The battery system according to any one of claims 1, 3 and 5.

9. The secondary power battery has a region in which the characteristics of the voltage in the switch-off state with respect to the charging rate change less than that of the primary power battery. The battery system according to any one of claims 1, 3 and 5.

10. the assembled storage battery includes another power terminal different from the power terminal, and a separate terminal switch that switches between an on state and an off state between the other power terminal and the secondary power type storage battery, a separate terminal load is connected to the other power terminal; The switch control unit When the switch of the secondary power type storage battery is in an OFF state and the battery pack is being discharged, the separate terminal switch is turned ON to connect the other power terminal and the secondary power type storage battery, turning off the separate-terminal switch when a first condition is met in which the voltage of the secondary power-type battery becomes equal to or lower than a predetermined set voltage while the secondary power-type battery is discharging to the separate-terminal load; when the secondary power type battery is discharging to the separate-terminal load and the first condition is not met and the secondary power type battery connection condition is met, turning the separate-terminal switch to an OFF state before turning on the switch of the secondary power type battery; The battery system according to claim 3 .

11. the power terminals of the battery pack are connected to a power converter that converts power; the switch control unit determines charging or discharging of the assembled storage battery based on power conversion information indicating an operating state of the power converter. The battery system according to any one of claims 1 to 3, 5 and 10.

12. The power terminals of the battery pack are connected to a power converter that converts power, the switch control unit determines charging or discharging of the assembled storage battery based on power conversion information indicating an operating state of the power converter. The battery system according to claim 4.

13. The power terminals of the battery pack are connected to a power converter that converts power, the switch control unit determines charging or discharging of the assembled storage battery based on power conversion information indicating an operating state of the power converter. The battery system according to claim 6.

14. The power terminals of the battery pack are connected to a power converter that converts power, the switch control unit determines charging or discharging of the assembled storage battery based on power conversion information indicating an operating state of the power converter. The battery system according to claim 7.

15. The power terminals of the battery pack are connected to a power converter that converts power, the switch control unit determines charging or discharging of the assembled storage battery based on power conversion information indicating an operating state of the power converter. The battery system according to claim 8.

16. The power terminals of the battery pack are connected to a power converter that converts power, the switch control unit determines charging or discharging of the assembled storage battery based on power conversion information indicating an operating state of the power converter. The battery system according to claim 9.

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