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

Abstract

To provide a technique for preventing an increase in size and cost of products and requiring no complicated control in a power storage device in which a plurality of accumulator batteries are connected in parallel.SOLUTION: A power storage device in which a plurality of accumulator batteries are respectively detachably connected in parallel, has control means for controlling the accumulator batteries, discharge circuits through which discharge current from the accumulator batteries flows corresponding to the accumulator batteries respectively, and charge circuits through which charging current to the accumulator batteries flows. Each of the discharge circuits is configured so as to prevent reverse flow of power to the corresponding accumulator battery.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an energy storage device in which a plurality of storage batteries are connected in parallel, an energy storage system, and a control method and program for the energy storage device. [Background technology]

[0002] Recently, energy storage systems that use storage batteries to store electricity supplied from commercial power grids, solar power, etc., and use the stored electricity as an emergency power source or as a so-called peak shifting measure have become widespread. In addition, in such energy storage systems, it is possible to increase the storage capacity by connecting multiple storage batteries in parallel and increasing the number of batteries.

[0003] However, when simply connecting batteries in parallel, it is necessary to precisely match the open circuit voltage (OCV) of each battery to prevent uncontrollable abnormal current from occurring. In addition, to prevent overcharging and over-discharging of the batteries, there is an additional constraint that the state of health (SOH) of each battery must be consistent.

[0004] Various technologies have been proposed to address such problems.Specific examples include a technique in which a battery to be discharged is switched among a plurality of storage batteries (e.g., Patent Documents 1 and 2, etc.), a technique in which a power conversion unit (inverter and converter) corresponding to each of the plurality of storage batteries is provided in a power conversion device (PCS: Power Conditioning System) (e.g., Patent Document 3, etc.), and a technique in which a DC / DC converter corresponding to each of the plurality of storage batteries is provided (e.g., Patent Documents 4 to 6, etc.). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-211551 A [Patent Document 2] JP 2016-19350 A [Patent Document 3] JP 2018-196185 A [Patent Document 4] JP 2020-156200 A [Patent Document 5] Patent Publication No. 2021-19400 [Patent Document 6] Patent Publication No. 2021-103909 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the techniques described in Patent Documents 1 and 2 have the problem that, when switching between storage batteries, there are time periods when the PCS is not connected to any storage battery, and there are times when the power supply from the storage batteries is cut off (discontinuous discharging). In addition, when charging, it is necessary to create a state in which none of the storage batteries are connected to the PCS, and then switch to the storage battery to be charged. For this reason, if a power outage or the like occurs when switching between storage batteries for charging, the PCS cannot immediately switch from charging to discharging, and if a power outage or the like occurs during charging, only the storage battery remaining in the storage battery being charged can be used (or discharging must be stopped temporarily and switched to another storage battery).

[0007] In addition, the technology described in Patent Document 3 requires a power conversion unit to be provided for each storage battery (i.e., according to the number of storage batteries), which increases the size and cost of the PCS. In addition, the technologies described in Patent Documents 4 to 6 also require a DC / DC converter to be provided for each storage battery, which increases the size and cost of the power storage device, and multiple DC / DC converters are used simultaneously. Furthermore, there is a problem that they need to be appropriately controlled with each other, making the control extremely complicated.

[0008] The present invention has been made in consideration of the above-mentioned situation, and its purpose is to provide a technology for an energy storage device in which multiple storage batteries are connected in parallel, which prevents an increase in product size and cost and eliminates the need for complex control. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention adopts the following configuration. A power storage device in which a plurality of storage batteries are detachably connected in parallel, A control means for controlling the storage battery; a discharge circuit through which a discharge current flows from the storage battery and a charge circuit through which a charge current flows to the storage battery, Each of the discharge circuits is an electrical storage device configured to prevent reverse flow of electrical power to the corresponding battery.

[0010] According to this configuration, in an energy storage device in which multiple storage batteries are connected in parallel, the size and cost of the product can be reduced, and complex control for properly operating the DC / DC circuit (and inverter) for each storage battery is not required.

[0011] The power storage device may be configured such that a diode is provided in each of the discharge circuits to prevent a backflow of power to the corresponding storage battery.

[0012] In addition, the discharge circuit and the charge circuit are each provided with a switching element, The control means When discharging from the storage battery, control is performed so that the switching elements of all the discharging circuits are in a short-circuit state and the switching elements of all the charging circuits are in an open state; When charging the storage batteries, control may be performed so that the switching element of the charging circuit corresponding to any one of the storage batteries is short-circuited, and the switching element of the charging circuit corresponding to the other storage batteries is open.

[0013] With this configuration, when the discharge voltage of the discharging battery drops and becomes the same as that of the other batteries with lower OCVs, it becomes possible to automatically start discharging the other batteries as well. In other words, without switching the battery to be discharged or providing a converter or inverter for each battery, it is possible to continuously discharge the multiple batteries connected in parallel, and to use the charging power (SOC: State Of Charge) of each battery until it reaches the discharge cutoff voltage.

[0014] In addition, with this configuration, there is no need to consider the OCV or SOH of each battery when adding batteries, so there is no need to replace all the batteries or make prior preparations to increase the battery capacity, and the battery capacity can be increased at low cost. In addition, it is possible to eliminate waste materials that are generated when increasing the battery capacity, and it is possible to reuse used batteries, which contributes to resource conservation.

[0015] The switching element provided in the discharge circuit may be of a normally closed type, and the switching element provided in the charge circuit may be of a normally open type. With this configuration, when the power storage system is installed, the circuit breaker in the power storage device is manually turned on, thereby enabling power supply to the control means, and power supply to the PCS while the control means is monitoring each storage battery. Therefore, even if the power storage system cannot be connected to the grid, the power storage system can be started up, and the operation of the power storage system can be checked.

[0016] The power storage device further includes an ammeter for each of the storage batteries that measures a charge / discharge current of the storage batteries, The control means When charging of the storage batteries is started, the presence or absence of an abnormality in the normally closed switching element corresponding to the storage batteries other than the one being charged may be determined based on the current values ​​output by each of the ammeters.

[0017] The storage device further includes a voltmeter that measures a voltage of a circuit to which the plurality of storage batteries are connected, The control means When charging of the storage battery is completed, the presence or absence of an abnormality in the normally open switching element corresponding to the storage battery to be charged may be determined based on the voltage value output by the voltmeter.

[0018] With this configuration, it is possible to check whether there is an abnormality in each switching element (for example, welding of the relay contacts) during charging operation. Therefore, inspection is performed during each charging operation, rather than periodically in a special diagnostic mode, and it is possible to prevent uncontrollable circulating current (abnormal current) caused by welding, and the resulting fire or smoke.

[0019] The switching element provided in the discharge circuit may be a semiconductor switching element. When discharging from the storage battery starts, a soft start may be performed by PWM-controlling the semiconductor switching element.

[0020] As the semiconductor switching element, for example, a high-speed switching element such as an IGBT (Insulated Gate Bipolar Transistor) can be used. This can reduce the rush current to the PCS internal capacitor caused by the voltage difference between the batteries when the switching element of the discharge circuit is short-circuited after or during charging.

[0021] The power storage device may be configured to include a main body having the control means, and a plurality of storage battery modules having the storage batteries and the corresponding discharge circuits and charge circuits, and configured to be detachable from the main body. With such a configuration, the power storage capacity can be increased as much as desired simply by adding more storage modules, and the power storage capacity can be flexibly and easily changed according to the usage conditions of the power storage system.

[0022] In addition, in the main body, a reactance may be provided on a main circuit to which the plurality of storage batteries are connected, thereby reducing a rush current to a capacitor inside the PCS that occurs when a discharge circuit switching element is short-circuited.

[0023] The present invention can also be understood as a power storage system having the power storage device and a power conversion device.

[0024] The present invention also provides a method for controlling an electricity storage device in which a plurality of storage batteries are connected in parallel, a discharge circuit and a charge circuit corresponding to each of the storage batteries are provided, and the discharge circuit and the charge circuit are each provided with an opening / closing element, and the discharge circuit is provided with a diode for preventing a reverse flow of power to the storage batteries, a first step of opening the switching elements of all the charging circuits and shorting the switching elements of all the discharging circuits; A second step of selecting one storage battery to be charged from the plurality of storage batteries; The discharge corresponding to the storage battery other than at least one storage battery selected in the second step a third step of opening the switching element of the electrical circuit; a fourth step of shorting the switching element of the charging circuit corresponding to one of the storage batteries selected in the second step; A fifth step of supplying power to one of the storage batteries selected in the second step; a sixth step of opening the switching element of the charging circuit corresponding to one of the storage batteries selected in the second step after the fifth step; A seventh step of shorting the switching elements of all the discharge circuits after the sixth step; The control method can also be regarded as having the above-mentioned feature.

[0025] According to this method, even when the storage batteries are being charged, one of the storage batteries is always connected to the DC / DC circuit of the PCS via a diode. Therefore, even when the charging is suddenly stopped and the operation is switched to discharging, for example, during a power outage, the operation can be switched to discharging immediately without loss of switching time. In addition, when discharging is continued after switching to discharging operation in this way, the other storage batteries are connected to the DC / DC circuit of the PCS via diodes. Therefore, when the discharge voltage of the storage battery being discharged becomes the same as the OCV of the other storage batteries, discharging will also start from the other storage batteries, so that the total storage capacity available as a storage system can be used for discharging operation without interruption without relying on only one of the storage batteries.

[0026] Further, the power storage device according to the control method includes an ammeter for each of the storage batteries that measures a value of a charge / discharge current of the storage battery, The switching element provided in the discharge circuit is a normally closed type, and the switching element provided in the charging circuit is a normally open type, Between the third step and the fourth step, a process may be performed to determine whether or not there is an abnormality in the normally closed type switching element corresponding to the storage battery other than the storage battery to be charged, based on the current value output by each of the ammeters.

[0027] Moreover, the storage device according to the control method includes a voltmeter that measures a voltage of a main circuit to which the plurality of storage batteries are connected, The switching element provided in the discharge circuit is a normally closed type, and the switching element provided in the charging circuit is a normally open type, Between the fifth step and the seventh step, a process may be performed to determine whether or not there is an abnormality in the normally open switching element corresponding to the storage battery to be charged, based on the voltage value output by the voltmeter.

[0028] Furthermore, the present invention can also be understood as a program for causing a computer to execute each of the above methods, or a computer-readable recording medium on which such a program is non-transiently recorded.

[0029] The present invention can be achieved by combining the above-described configurations and processes as long as no technical contradiction occurs. Effect of the Invention

[0030] According to the present invention, it is possible to provide a technology that prevents an increase in product size and cost and eliminates the need for complex control in an electricity storage device in which a plurality of storage batteries are connected in parallel. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a power storage system according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing a transition of an output voltage from each storage battery during discharging of the power storage system according to the embodiment. [Diagram 3] FIG. 3 is a first flowchart showing an example of a flow of processing performed by the BMS during a charging operation according to the embodiment. [Figure 4] FIG. 4 is a second flowchart showing an example of the flow of processing performed by the BMS during a charging operation according to the embodiment. [Diagram 5] FIG. 5 is a schematic diagram showing a first modified example of the embodiment. [Figure 6] FIG. 6 is a schematic diagram showing a second modified example of the embodiment. [Figure 7] FIG. 7 is a schematic diagram showing a third modified example of the embodiment. [Figure 8] FIG. 8 is a schematic diagram showing a fourth modified example of the embodiment. [Figure 9] FIG. 9 is a schematic diagram showing a fifth modified example of the embodiment. [Figure 10] FIG. 10 is a flowchart showing a part of a flow of processing performed by the BMS when diagnosing a discharge circuit relay according to the sixth modified example of the embodiment. [Figure 11]FIG. 11 is a flowchart showing a part of a flow of processing performed by the BMS when diagnosing a charging circuit relay according to the seventh modification of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, and the like of the components described in each of the following examples are not intended to limit the scope of the present invention.

[0033] <Application Examples> The present invention can be applied, for example, as a storage battery unit 101 as shown in Fig. 1. Fig. 1 is a schematic diagram showing a power storage system 100 that has a storage battery unit 101, a PCS 90, and a solar power generation panel 3, and is interconnected with a commercial power system (hereinafter simply referred to as a system) 2.

[0034] The storage battery unit 101 according to this application example is an electricity storage device including a main body 10 and storage battery modules 20a, 20b, and 20c each configured to be detachable from the main body 10. Note that, although the present specification describes the case where the main body 10 is connected to three storage battery modules 20a, 20b, and 20c, the number of storage battery modules actually connected to the main body 10 may be two or less, or may be four or more.

[0035] The main body 10 is composed of a BMS (Battery Management System) 11 as a control means for controlling each of the connected storage battery modules 20a, 20b, 20c, a power supply circuit 12 that supplies power to the BMS 11, a main body circuit relay 13, a reactance 14 that reduces rush current to a capacitor (not shown) inside the PCS 90, a circuit breaker 15, and a connection terminal with the PCS 90.

[0036] The battery module 20a is configured to include a battery 1a, such as a lithium ion battery, a discharge circuit 21a through which a discharge current from the battery 1a flows, a charge circuit 22a through which a charge current flows to the battery 1a, a voltmeter V1 that measures the output voltage of the battery 1a, an ammeter A1 that measures the current flowing through the battery module 20, and a fuse, all housed in a housing (not shown). The discharge circuit 21a is further provided with a diode 23a that prevents reverse flow of power to the battery 1a, and a normally closed discharge circuit relay 24a. The charge circuit 22a is further provided with a normally open charge circuit relay 25a. Although the discharge circuit 21a and the charge circuit 22a share a part of the circuit, the diode 23a and the discharge circuit relay 24a of the discharge circuit 21a are configured to be in parallel with the part where the charge circuit relay 25a of the charge circuit 22a is provided.

[0037] The storage battery modules 20b and 20c have the same configuration as the storage battery module 20a, and each of them includes a storage battery (1b, 1c), a discharge circuit (21b, 21c), and a charge circuit (22b , 22c), diodes (23b, 23c), discharge circuit relays (24b, 24c), and charge circuit relays (25b, 25c). In the following, when there is no need to distinguish between elements having the same configuration, they will be described without making any particular distinctions between them, such as storage battery module 20, storage battery 1, discharge circuit 21, charge circuit 22, diode 23, discharge circuit relay 24, charge circuit relay 25, etc.

[0038] The BMS 11 acquires information on the voltage value and current value of each storage battery 1, and outputs control signals to open and close the discharge circuit relays 24 and the charge circuit relays 25 of each storage battery module 20. Then, the control circuit 91 of the PCS 90 to which the storage battery unit 101 is connected controls the DC / DC converter 93 based on commands from the BMS 11, and appropriate charging and discharging operations of the storage battery unit 101 are performed.

[0039] According to the configuration of the storage battery unit 11 as described above, it becomes possible to use a plurality of storage batteries 1 (storage battery modules 20) connected in parallel without providing a DC / DC circuit for each storage battery 1.

[0040] <Embodiment 1> (System Configuration) The following describes the embodiment of the present invention in more detail. Fig. 1 is a schematic diagram showing a schematic configuration of a power storage system 100 according to this embodiment. The power storage system 100 is a grid-connected system that has a storage battery unit 101, a PCS 90, and a photovoltaic power generation panel 3 similar to those described in the application example, and is connected to a system 2 and a load (not shown). Note that the configuration of the storage battery unit 101 has already been described in the application example, so a repeated description will be omitted.

[0041] The power storage system 100 receives (purchases) power from the grid 2 during times when electricity rates are low, such as at night, converts the power from AC to DC in the PCS 90, outputs the power to the storage battery unit 101, and charges the storage battery 1. Since the power storage system 100 also includes a solar power generation panel 3, solar-generated power is also transmitted to the PCS 90 via a DC / DC converter 4, and the power can also be used to charge the storage battery 1. On the other hand, when the remaining power capacity of the storage battery 1 is equal to or greater than a predetermined value, the storage battery 1 is discharged, and the power can be supplied to a load (not shown) connected to the grid via the PCS 90.

[0042] The PCS 90 is a so-called hybrid power conditioner, and is connected to the storage battery unit 101 and the photovoltaic power generation panel 3 (through the DC / DC converter 4). The PCS 90 has a control circuit 91 that controls the entire PCS 90, a power supply circuit 92 that supplies power to the control circuit 91, a DC / DC converter 93, and an inverter 94. The charge / discharge operation (current value and charge / discharge time) of the storage battery unit 101 is determined by the control circuit 91 controlling the DC / DC converter 93. The PCS 90 in this embodiment corresponds to the power conversion device according to the present invention.

[0043] (Discharge control) The operation of the power storage system 100 when discharging from the storage battery unit 101 will be described below with reference to Fig. 2. Fig. 2 is a graph showing the transition of the output voltage of each storage battery 1 connected to the storage battery unit 101 when discharging from the storage battery unit 101.

[0044] First, under the control of the BMS 11 of the storage battery unit 101, all the charge circuit relays 25 of all the connected storage battery modules 20 are opened, and the discharge circuit relays 24 are shorted.

[0045] Here, since the storage battery modules 20 are connected in parallel, when a discharge operation is started under the control of the PCS 90, even if the OCVs of the storage batteries 1 are different, only the storage battery 1 with the highest OCV will first supply power to the PCS 90. Note that in this embodiment, as shown in Fig. 2, a case will be described as an example in which, at the start of discharge, the OCV of storage battery 1a is the highest, the OCV of storage battery 1b is the next highest, and the OCV of storage battery 1c is the lowest.

[0046] As shown in Fig. 2, at the start of discharge, only the storage battery 1a with the highest OCV is discharged. After that, as the voltage of the storage battery 1a decreases due to discharge, when it matches the OCV of the other storage batteries, power is supplied from the multiple storage batteries 1 to the PCS 90 without control from the BMS 11. First, when the OCV and output voltage of the storage battery 1b match, the storage batteries 1a and 1b are discharged, and when these output voltages further decrease and match the OCV of the storage battery 1c, all the storage batteries 1a, 1b, and 1c are discharged.

[0047] Then, when the output voltages of all the storage batteries 1a, 1b, 1c finally match and reach the discharge end voltage managed by the BMS 11, the control circuit 91 of the PCS 90 stops the DC / DC converter 93 in the PCS 90 and stops the discharge operation based on a command from the BMS 11. That is, it becomes possible to perform continuous discharge operation of the remaining capacity of all the connected storage batteries 1 without control from the BMS 11.

[0048] (Charging control) Next, an operation of the power storage system 100 of this embodiment when charging the storage battery 1 connected to the storage battery unit 101 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 and Fig. 4 are flowcharts showing a process flow when charging the storage battery 1 connected to the storage battery unit 101 according to this embodiment.

[0049] First, the BMS 11 determines whether the open / closed state of each discharge circuit relay 24 and each charge circuit relay 25 of each storage battery module 20 is in a discharge standby state, i.e., whether all discharge circuit relays 24 are in a short-circuited state and all charge circuit relays 25 are in an open state (S101). If it is determined that they are not in a standby state, the BMS 11 opens all discharge circuit relays 24 and charge circuit relays 25 to enter a discharge standby state (S102), and proceeds to step S103. On the other hand, if it is determined in step S101 that they are in a discharge standby state, the process proceeds directly to step S103.

[0050] In step S103, the BMS 11 selects the storage battery 1 with the lowest SOC from among the connected storage batteries 1 (S103). In the following description, it is assumed that the storage battery 1a in the storage battery module 20a is the storage battery with the lowest SOC. Then, the BMS 11 opens the discharge circuit relays 24b, 24c corresponding to all the storage batteries 1b, 1c other than the selected storage battery 1a (S104).

[0051] Next, the PCS 90 controls the DC / DC converter 93 to perform processing to match the supply voltage to the OCV (output value of V1) of the storage battery 1a to be charged (S105). After that, the BMS 11 shorts the charging circuit relay 25a corresponding to the selected storage battery 1a (S106).

[0052] Then, the BMS11 monitors the voltage value (output value of V1) and current value (output value of A1) of the storage battery 1a to be charged, and based on instructions from the BMS11, the control circuit 91 of the PCS90 controls the DC / DC converter 93 to control the charging current, thereby charging the storage battery 1a (S107).

[0053] The PCS 90 monitors whether a reason for interrupting charging (such as a power outage) occurs during charging of the storage battery 1a (S108), and when it is determined that a reason for interrupting charging has occurred, the PCS 90 controls the storage battery 1a to start discharging from the storage battery 1a that had been charging (i.e., the charging circuit relay 25a is short-circuited) (s109). The BMS 11 then opens the charging circuit relay 25a (S110), and discharging from the storage battery 1a is switched to discharging via the discharge circuit relay 24a that has been maintained in a short-circuited state. That is, at the timing of step S109, discharging via the charging circuit relay 25a may be performed instantaneously, but since the charging circuit relay 25a is immediately opened, discharging from the storage battery 1a is performed seamlessly.

[0054] Thereafter, the BMS 11 shorts the discharge circuit relays 24b, 24c corresponding to the storage batteries 1b, 1c that were not being charged (S111), and transitions to normal discharging operation in which all discharge circuit relays 24 are shorted and all charge circuit relays 25 are open.

[0055] On the other hand, if no reason for interrupting charging occurs in step S108, the storage battery 1a is charged to SOC 100%, and then the BMS 11 opens the charging circuit relay 25a (S112). Next, the BMS 11 determines whether to charge the other storage battery (1b or 1c) based on the SOC of each storage battery 1 and a predetermined rule (S113). If it is determined that the other storage battery (1b or 1c) is to be charged, the storage battery 1 with the lowest SOC is selected, and the discharge circuit relay 24 corresponding to that storage battery 1 is short-circuited (S114), and the process returns to step S104 and repeats the subsequent processes.

[0056] On the other hand, if it is determined in step S113 that no other rechargeable batteries are to be charged, the discharge circuit relays 24 corresponding to all of the storage batteries 1 are short-circuited to transition to a discharge standby state (S115), and the series of routines is terminated.

[0057] According to the storage battery unit 101 configured as described above and the control method for the storage battery unit 101, it is possible to perform continuous discharge operation for the remaining capacity of all the connected storage batteries 1 based on the OCV of each storage battery 1 connected in parallel without requiring complicated control. Also, even during charging, one of the storage batteries 1 is always connected to the PCS 90 via the diode 23, so that even when charging is suddenly stopped and a discharge operation is started due to a power outage, for example, a discharge operation can be started immediately without loss of switching time.

[0058] In addition, according to the above configuration, the storage capacity can theoretically be increased as much as desired by adding more storage battery modules 20. Moreover, since the SOH and OCV of the storage batteries 1 used in the storage battery modules 20 do not need to be the same, it is possible to add new storage batteries 1 or, conversely, to utilize second-hand storage batteries 1, which contributes to resource conservation.

[0059] The storage battery unit 101 and the power storage system 100 according to the above-described first embodiment are merely examples of the embodiments of the present invention, and various modified examples can be adopted as described below. In the following, the same configurations and processes as those of the power storage system 100 according to the first embodiment are denoted by the same reference numerals, and repeated explanations will be omitted.

[0060] <Variation 1> 5 is a schematic diagram showing a power storage system 200 according to a first modified example. In this modified example, the internal configuration of the storage battery modules 30a, 30b, and 30c in a storage battery unit 201 is different from that of the first embodiment. The other configurations are the same as those of the power storage system of the first embodiment.

[0061] As shown in FIG. 5, a storage battery module 30a according to this modification includes a discharge circuit 31a and a charge circuit 31b. Although the charging circuit 32a partially shares the circuit, the charging circuit relay 25a of the charging circuit 32a is configured to be in parallel with the portion of the discharge circuit 31a where the diode 23a is provided. That is, in this modification, a current flows through the discharge circuit relay 24a not only during discharging but also during charging. The same applies to the discharge circuits (31b, 31c) and charging circuits (32b, 32c) of the other storage battery modules (30b, 30c).

[0062] Even with such a configuration according to this modification, the same effects as those of the first embodiment can be obtained by performing the same discharge control and charge control as those of the first embodiment.

[0063] <Variation 2> In addition, in the storage battery unit 101 of embodiment 1, the diode 23 and the discharge circuit relay 24 of the discharge circuit 21 and the charge circuit relay 25 of the charge circuit 22 are configured to be provided in the storage battery module 20, but this is not necessarily required.

[0064] FIG. 6 is a schematic diagram showing a schematic configuration of a power storage system 300 according to this modification. As shown in FIG. 6, in this modification, the configuration of a storage battery unit 301 is different from that of the first embodiment. Specifically, the diodes (23a, 23b, 23c) and the discharge circuit relays (24a, 24b, 24c) of the discharge circuits (41a, 41b, 41c), the charging circuit relays (25a, 25b, 25c) of the charging circuits (42a, 42b, 42c), and the ammeters (A1, A2, A3) are provided in the main body 302, not in the storage battery modules (40a, 40b, 40c). In addition, the storage battery modules (40a, 40b, 40c) that are detachable from the main body 302 are provided with storage batteries (1a, 1b, 1c), voltmeters (V1, V2, V3), and fuses.

[0065] Even with this configuration, the same effects as those of the first embodiment can be obtained by performing the same discharge control and charge control as those of the first embodiment. Furthermore, since each storage battery module 40 has a simple configuration, the versatility of the storage battery module 40 can be improved.

[0066] <Variation 3> It is also possible to adopt a modified example that combines the configurations of the above modified example 1 and modified example 2. Fig. 7 is a schematic diagram showing a schematic configuration of a power storage system 400 according to such a modified example. As shown in Fig. 7, in a storage battery unit 401 according to this modified example, the power storage modules (40a, 40b, 40c) have the same configuration as in modified example 2. Also, like modified example 2, a main body 402 is provided with diodes (23a, 23b, 23c) and discharge circuit relays (24a, 24b, 24c) of discharge circuits (51a, 51b, 51c), charging circuit relays (25a, 25b, 25c) of charging circuits (52a, 52b, 52c), and ammeters (A1, A2, A3). However, this modification differs from the modification 2 in that the charging circuit relays (25a, 25b, 25c) of each charging circuit (52a, 52b, 52c) are connected in parallel only to the diodes (23a, 23b, 23c) of each discharge circuit (51a, 51b, 51c), and has the same configuration as the modification 1. That is, in this modification, a current flows through the discharge circuit relay 24a not only during discharging but also during charging.

[0067] <Modification 4> Although the above-mentioned examples employ a normally closed relay as the discharge circuit relay, this is not necessarily required, and the discharge circuit relay may be a normally open relay. Fig. 8 shows a schematic diagram of a power storage system 500 that is a modified example of such a case.

[0068] As shown in FIG. 8, a storage battery unit 501 according to this modification includes discharge circuit relays (61a, 61b, 61c) in the discharge circuits (61a, 61b, 61c) of the storage battery units (60a, 60b, 60c). 4a, 64b, and 64c) are configured as normally open relays, and a main body relay is not provided in a main body 502.

[0069] By making both the discharge circuit relay 64 and the charge circuit relay 25 normally open relays, even if the power supply in the storage system 500 is suddenly lost for some reason (if an abnormal condition occurs), it is possible to cut off the circuit between the PCS 90 and each storage battery 1 even if there is no normally open relay in the main body 502.

[0070] <Variation 5> It is also possible to adopt a semiconductor switching element as the discharge circuit relay (and the charge circuit relay). Fig. 9 shows a schematic diagram of a storage battery system 600 which is a modified example of such a case. As shown in Fig. 9, a storage battery unit 601 according to this modified example differs from the first embodiment in that a semiconductor switching element (e.g., one having a high-speed switching element such as an IGBT) is used as the discharge circuit relay (74a, 74b, 74c) of the discharge circuit (71a, 71b, 71c).

[0071] By configuring the discharge circuit relay 74 in this manner, when the discharge circuit relay 74 is short-circuited after charging (or during charging), PWM control is performed to perform a soft start, making it possible to reduce the rush current to the capacitor in the PCS 90 even without the reactance 14.

[0072] <Variation 6> In addition to the circuit configuration of the storage battery unit, the process for controlling charging and discharging can also be changed in order or additional processes can be performed as appropriate, instead of following the procedure in embodiment 1. Here, a modified example in which additional processes are performed between steps S104 and S105 of the charging control described in embodiment 1 will be described with reference to the flowchart shown in FIG.

[0073] 10, in this modification, after the process of step S104 is completed, the PCS 90 operates the DC / DC converter 93 to perform light discharge with a current of about several amperes (S201). Then, the BMS 11 acquires current values ​​from ammeters A2 and A3 corresponding to the storage batteries 1b and 1c other than the storage battery 1a selected in step S103, and calculates the sum (CToff) (S202). The BMS 11 further acquires a current value (CTon) from ammeter A1 corresponding to the selected storage battery 1a (S203).

[0074] Then, the BMS 11 uses the total value calculated in step S202 and the value acquired in step S203 to determine whether or not contact welding has occurred in the discharge circuit relays 24b, 24c corresponding to the storage batteries 1b, 1c other than the selected one (S204). More specifically, in step S204, it determines whether or not the condition that CToff is less than a first threshold value and CTon exceeds a second threshold value is satisfied. If it is determined that the condition is not satisfied, it is determined that contact welding has occurred in either of the discharge circuit relays 24b, 24c, and a predetermined abnormality occurrence process is executed (S205). The abnormality occurrence process may, for example, stop charging and discharging (circuit interruption), issue an error alarm, or the like.

[0075] On the other hand, if the BMS 11 determines in step S204 that the condition is satisfied, the process proceeds to step S105, and thereafter executes the same charge control as described in the first embodiment.

[0076] <Variation 7> Next, based on the flowchart shown in FIG. 11, the charging control described in the first embodiment will be described. A modified example in which additional processing is executed after the determination in step S108 is NO and before proceeding to step S113 will be described.

[0077] 11, in this modification, if no reason for stopping charging occurs in step S108, the BMS 11 acquires the value of the voltmeter V4 (V4on) when the charging circuit relay 25a corresponding to the storage battery 1a to be charged is in a short-circuited state (step S301). After that, the BMS 11 opens the charging circuit relay 25a of the storage battery 1a that has been charged (S112), and in this state, further acquires the value of the voltmeter V4 (V4off).

[0078] After that, BMS11 performs a process to determine whether or not the condition that V4on is equal to or greater than V4off plus a predetermined value is satisfied (S303). If the condition is not satisfied (i.e., there is no difference of the predetermined value between the voltage during short-circuit control and during release control of charging circuit relay 25a), it determines that charging circuit relay 25a has a welded contact and performs a predetermined abnormality occurrence process (S304). On the other hand, if BMS11 determines in step S303 that the condition is satisfied, it proceeds to step S113, and thereafter performs charging control similar to that described in the first embodiment.

[0079] In a storage battery unit in which multiple storage batteries can be connected in parallel as shown in each of the above examples, if a relay placed between each storage battery and the main circuit to which it is connected experiences a short circuit failure due to contact welding or other reasons, and the storage batteries cannot be disconnected, a dangerous circulating current (abnormal current) that cannot be controlled by the BMS will occur between the multiple connected storage batteries and into a storage battery with a low SOC, which could lead to the storage battery catching fire or emitting smoke, or the complete shutdown of the energy storage system. For this reason, it is necessary to regularly check whether there are any abnormalities such as contact welding in each relay.

[0080] In this regard, by incorporating a process for checking whether or not each relay is welded during normal charging operation as in Modifications 6 and 7, it becomes possible to perform a welding inspection during each charging operation without operating the energy storage unit in a specific mode for the purpose of inspection. This makes it possible to detect relay abnormalities early and eliminates the need to operate the device for inspection, thereby improving the operating efficiency of the device.

[0081] <Other> The above-mentioned embodiment and modified examples are merely illustrative of the present invention, and the present invention is not limited to the above-mentioned specific embodiments. Various modifications and combinations of the present invention are possible within the scope of the technical concept. For example, in the above-mentioned embodiment, the discharge circuit relay corresponding to the storage battery to be charged is short-circuited during charging control, but it may be opened. In addition, it is also possible to execute both of the processes described in the above modified examples 6 and 7 during charging control.

[0082] Also, a configuration in which a normally open relay is used as the discharge circuit relay of the storage battery unit of Modifications 2 and 3, such as the discharge circuit relay 64 according to Modification 4 above, may be adopted. Also, for example, in the case of performing PWM control by using a semiconductor switching element as the discharge circuit relay 75 as in Modification 5 above, a configuration in which the reactance 14 is not provided in the main body 10 may be adopted.

[0083] In the above example, the criterion for selecting the storage battery to be charged was the storage battery with the lowest SOC, but the storage battery to be charged may be selected based on a different criterion. For example, the selection criterion for charging may be "the storage battery with an SOC less than 100% and the highest SOC." This can prevent the occurrence of a rush current when discharging begins.

[0084] In addition, in the above embodiment, a grid-connected system that combines a storage battery unit and a PCS (and a solar power generation system) has been described as an example, but the present invention is not limited to such systems and can be widely applied to devices that use multiple storage batteries connected in parallel, such as a dedicated energy storage system to which no PV is connected, or an uninterruptible power supply (UPS).

[0085] (Appendix 1) A power storage device (101) in which a plurality of storage batteries (1a, 1b, 1c) are detachably connected in parallel, A control means (11) for controlling the storage batteries (1a, 1b, 1c); a discharge circuit (21a, 21b, 21c) corresponding to each of the storage batteries (1a, 1b, 1c) through which a discharge current flows from the storage batteries (1a, 1b, 1c), and a charge circuit (22a, 22b, 22c) through which a charge current flows to the storage batteries (1a, 1b, 1c), Each of the discharge circuits (21a, 21b, 21c) is configured to prevent a backflow of power to the corresponding storage battery (1a, 1b, 1c). An electricity storage device (101).

[0086] (Appendix 2) a diode (23a, 23b, 23c) is provided in each of the discharge circuits (21a, 21b, 21c) to prevent a reverse flow of power to the corresponding storage battery (1a, 1b, 1c); The electricity storage device (101) according to claim 1.

[0087] (Appendix 3) the discharge circuits (21a, 21b, 21c) and the charge circuits (22a, 22b, 22c) are provided with switching elements (24a, 24b, 24c, 25a, 25b, 25c), respectively; The control means (11) When discharging the storage batteries (1a, 1b, 1c), control is performed so that the switching elements (24a, 24b, 24c) of all the discharge circuits (21a, 21b, 21c) are short-circuited and the switching elements (25a, 25b, 25c) of all the charging circuits (22a, 22b, 22c) are open; When the storage batteries (1a, 1b, 1c) are charged, the switching element (25a) of the charging circuit (22a) corresponding to any one of the storage batteries (1a) is short-circuited, and the switching elements (25b, 25c) of the charging circuits (22b, 22c) corresponding to the other storage batteries (1b, 1c) are controlled to be in an open state. 3. The power storage device (101) according to claim 1 or 2.

[0088] (Appendix 4) the switching elements (24a, 24b, 24c) provided in the discharge circuits (21a, 21b, 21c) are of normally closed type, and the switching elements (25a, 25b, 25c) provided in the charging circuits (22a, 22b, 22c) are of normally open type; The electricity storage device (101) according to appendix 3.

[0089] (Appendix 5) an ammeter (A1, A2, A3) for measuring a value of a charge / discharge current of the storage batteries (1a, 1b, 1c) is provided for each of the storage batteries (1a, 1b, 1c); The control means (11) When starting charging the storage batteries (1a, 1b, 1c), the presence or absence of an abnormality in the normally-closed switching elements (24a, 24b, 24c) corresponding to the storage batteries other than the one being charged is determined based on the current values ​​output by the ammeters (A1, A2, A3). The electricity storage device (101) according to claim 4.

[0090] (Appendix 6) a voltmeter (V4) for measuring a voltage of a main circuit to which the plurality of storage batteries (1a, 1b, 1c) are connected; The control means (11) When charging of the storage batteries (1a, 1b, 1c) is completed, the presence or absence of an abnormality in the normally open switching element (25a, 25b, 25c) corresponding to the storage battery (1a, 1b, 1c) to be charged is determined based on the voltage value output by the voltmeter (V4). The electricity storage device (101) according to claim 4.

[0091] (Appendix 7) The switching elements (74a, 74b, 74c) provided in the discharge circuits (71a, 71b, 71c) are composed of semiconductor elements. The power storage device (601) according to claim 3.

[0092] (Appendix 8) When discharging from the storage batteries (1a, 1b, 1c) starts, a soft start is performed by PWM controlling the semiconductor elements (74a, 74b, 74c). The power storage device (601) according to claim 7.

[0093] (Appendix 9) a main body portion (10) including the control means (11); a plurality of storage battery modules (20a, 20b, 20c) including the storage batteries (1a, 1b, 1c), the discharge circuits (21a, 21b, 21c) corresponding thereto, and the charge circuits (22a, 22b, 22c), and configured to be detachable from the main body portion (10). 9. The electricity storage device (101) according to any one of appendix 1 to 8.

[0094] (Appendix 10) In the main body (10), a reactance (14) is provided on a main circuit to which the plurality of storage batteries (1a, 1b, 1c) are connected. The electricity storage device (101) according to claim 9.

[0095] (Appendix 11) and a power conversion device (90); and the power storage device (101) according to any one of appendices 1 to 10.

[0096] (Appendix 12) A method for controlling an electricity storage device (101) in which a plurality of storage batteries (1a, 1b, 1c) are connected in parallel, the device includes discharge circuits (21a, 21b, 21c) and charge circuits (22a, 22b, 22c) corresponding to the storage batteries (1a, 1b, 1c), the discharge circuits (21a, 21b, 21c) and the charge circuits (22a, 22b, 22c) are provided with switching elements (24a, 24b, 24c, 25a, 25b, 25c), respectively, and the discharge circuits (21a, 21b, 21c) are provided with diodes (23a, 23b, 23c) for preventing a reverse flow of power to the storage batteries (1a, 1b, 1c), comprising: The switching elements (25a, 25b, a first step (S102) of opening the switching elements (24a, 24b, 24c) of all the discharge circuits (21a, 21b, 21c) and shorting the switching elements (24a, 24b, 24c) of all the discharge circuits (21a, 21b, 21c); a second step (S103) of selecting one storage battery (1a) to be charged from the plurality of storage batteries (1a, 1b, 1c); a third step (S104) of opening the switching elements of the discharge circuits (21b, 21c) corresponding to the storage batteries (1b, 1c) other than at least one storage battery selected in the second step (S103); a fourth step (S106) of short-circuiting the switching element (25a) of the charging circuit (22a) corresponding to one storage battery (1a) selected in the second step (S103); a fifth step (S107) of supplying power to one of the storage batteries (1a) selected in the second step (S103); a sixth step (S112) of opening the switching element (25a) of the charging circuit (22a) corresponding to one of the storage batteries (1a) selected in the second step after the fifth step (S107); a seventh step (S115) of shorting the switching elements (24a, 24b, 24c) of all the discharge circuits (21a, 21b, 21c) after the sixth step (S112); The control method includes:

[0097] (Appendix 13) The electricity storage device (101) includes ammeters (A1, A2, A3) for measuring the charge / discharge currents of the storage batteries (1a, 1b, 1c), respectively; the switching elements (24a, 24b, 24c) provided in the discharge circuits (21a, 21b, 21c) are of normally closed type, and the switching elements (25a, 25b, 25c) provided in the charging circuits (22a, 22b, 22c) are of normally open type, Between the third step (S104) and the fourth step (S106), a process is performed to determine the presence or absence of an abnormality in the normally-closed switching elements (24b, 24c) corresponding to the storage batteries (1b, 1c) other than the storage batteries to be charged, based on the current values ​​output by the ammeters (A1, A2, A3). 13. The control method according to claim 12,

[0098] (Appendix 14) The electricity storage device (101) includes a voltmeter (V4) that measures a voltage of a main circuit to which the plurality of storage batteries (1a, 1b, 1c) are connected, the switching elements (24a, 24b, 24c) provided in the discharge circuits (21a, 21b, 21c) are of normally closed type, and the switching elements (25a, 25b, 25c) provided in the charging circuits (22a, 22b, 22c) are of normally open type, Between the fifth step (S107) and the seventh step (S115), a process is performed to determine whether or not there is an abnormality in the normally-open switching element (25a) corresponding to the storage battery (1a) to be charged, based on the voltage value output by the voltmeter (V4). 13. The control method according to claim 12,

[0099] (Appendix 15) A program for causing a computer to execute each step of the control method according to any one of appendixes 12 to 14. [Explanation of symbols]

[0100] 1a, 1b, 1c...storage battery 2...Commercial power system 3. Solar power panels 4, 93...DC / DC converter 10, 302, 402, 502... Main body 11. BMS 12, 92...Power circuit 13 Main body relay 14. Reactance 15 Circuit Breaker 20a, 20b, 20c, 30a, 30b, 30c, 40a, 40b, 40c, 60a, 60b, 60c, 70a, 70b, 70c... Battery module 21a, 21b, 21c, 31a, 31b, 31c, 41a, 41b, 41c, 51a, 51b, 51c, 61a, 61b, 61c, 71a, 71b, 71c...discharge circuit 22a, 22b, 22c, 32a, 32b, 32c, 42a, 42b, 42c, 52a, 52b, 52c,...charging circuit 23a, 23b, 23c...Diodes 24a, 24b, 24c, 64a, 64b, 64c, 74a, 74b, 74c... Discharge circuit relay 25a, 25b, 25c... Charging circuit relay 90···PCS 91 Control circuit 94...Inverter 100, 200, 300, 400, 500, 600... Energy storage system 101, 201, 301, 401, 501, 601... Battery unit A1, A2, A3... Ammeter V1, V2, V3, V4,... Voltage gauge

Claims

1. A power storage device in which a plurality of storage batteries are detachably connected in parallel, A control means for controlling the storage battery; a discharge circuit through which a discharge current flows from the storage battery and a charge circuit through which a charge current flows to the storage battery, Each of the discharge circuits is configured to prevent reverse flow of power to the corresponding storage battery. Energy storage device.

2. A diode is provided in each of the discharge circuits to prevent reverse flow of power to the corresponding storage battery. The power storage device according to claim 1 .

3. The discharge circuit and the charge circuit are each provided with a switching element, The control means When discharging from the storage battery, control is performed so that the switching elements of all the discharging circuits are short-circuited and the switching elements of all the charging circuits are open; When charging the storage batteries, the switching element of the charging circuit corresponding to any one of the storage batteries is controlled to be in a short-circuit state, and the switching element of the charging circuit corresponding to the other storage batteries is controlled to be in an open state. The power storage device according to claim 1 .

4. The switching element provided in the discharge circuit is a normally closed type, and the switching element provided in the charging circuit is a normally open type. The power storage device according to claim 3 .

5. an ammeter for measuring a charge / discharge current of each of the storage batteries; The control means When starting charging the storage batteries, the presence or absence of an abnormality in the normally-closed switching element corresponding to the storage batteries other than the one being charged is determined based on the current values ​​output by each of the ammeters. The power storage device according to claim 4 .

6. A voltmeter is provided to measure a voltage of a main circuit to which the plurality of storage batteries are connected, The control means When charging of the storage battery is completed, the presence or absence of an abnormality in the normally open switching element corresponding to the storage battery to be charged is determined based on the voltage value output by the voltmeter. The power storage device according to claim 4 .

7. The switching element provided in the discharge circuit is composed of a semiconductor element. The power storage device according to claim 3 .

8. When discharging from the storage battery is started, a soft start is performed by PWM control of the semiconductor element. The power storage device according to claim 7 .

9. A main body including the control means; The storage battery and the corresponding discharge circuit and charge circuit are provided, A plurality of storage battery modules configured to be detachable from the main body portion. The power storage device according to claim 1 .

10. In the main body, a reactance is provided on a main circuit to which the plurality of storage batteries are connected. The power storage device according to claim 9 .

11. A power storage system comprising: a power conversion device; and the power storage device according to any one of claims 1 to 10.

12. A control method for a power storage device in which a plurality of storage batteries are connected in parallel, a discharge circuit and a charge circuit corresponding to each of the storage batteries are provided, and the discharge circuit and the charge circuit are each provided with an opening / closing element, and the discharge circuit is provided with a diode for preventing a reverse flow of power to the storage batteries, comprising: a first step of opening the switching elements of all the charging circuits and shorting the switching elements of all the discharging circuits; A second step of selecting one storage battery to be charged from the plurality of storage batteries; a third step of opening the switching element of the discharge circuit corresponding to at least one storage battery other than the one storage battery selected in the second step; a fourth step of shorting the switching element of the charging circuit corresponding to one of the storage batteries selected in the second step; A fifth step of supplying power to one of the storage batteries selected in the second step; a sixth step of opening the switching element of the charging circuit corresponding to one of the storage batteries selected in the second step after the fifth step; a seventh step of shorting the switching elements of all the discharge circuits after the sixth step; The control method includes:

13. the power storage device includes an ammeter for each of the storage batteries that measures a value of a charge / discharge current of the storage battery; The switching element provided in the discharge circuit is a normally closed type, and the switching element provided in the charging circuit is a normally open type, Between the third step and the fourth step, a process is performed to determine whether or not there is an abnormality in the normally-closed switching element corresponding to the storage battery other than the storage battery to be charged, based on the current value output by each of the ammeters.

13. The control method according to claim 12.

14. the power storage device includes a voltmeter that measures a voltage of a main circuit to which the plurality of storage batteries are connected; The switching element provided in the discharge circuit is a normally closed type, and the switching element provided in the charging circuit is a normally open type, Between the fifth step and the seventh step, a process is performed to determine whether or not there is an abnormality in the normally-open type switching element corresponding to the storage battery to be charged, based on the voltage value output by the voltmeter.

13. The control method according to claim 12.

15. A program for causing a computer to execute each step of the control method according to any one of claims 12 to 14.

Images