Secondary battery system and secondary battery control method

Abstract

To provide a secondary battery system capable of appropriately making a configuration in a case where batteries different in performances, e.g., an extension battery and an existing battery are mixed.SOLUTION: A secondary battery system 100 comprises a battery bank 3 including: a battery rack B including a plurality of battery cells connected in series; and a power converter 2 for a single or a plurality of battery racks B connected in parallel to charge / discharge a power system. The secondary battery system comprises: a switcher 4 capable of switching a battery rack B of the battery bank 3 with respect to a power converter of the other battery bank; and a controller 5 which monitors deterioration rates or years used of the battery racks B and controls the power converter 2 and the switcher 4. The controller 5 commands the switcher 4 to connect the power converter 2 to be connected based on the deterioration rates or the years used of the battery racks B.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a secondary battery system and a secondary battery control method. [Background technology]

[0002] In recent years, the implementation of large-scale stationary battery systems has progressed to resolve grid instability caused by the increase in renewable energy. However, the investment costs for large-scale stationary battery systems are high, and equipment performance changes due to degradation, making it difficult to introduce them all at once. Therefore, methods for leveling out investment costs by gradually adding battery systems are being considered.

[0003] When adding batteries, it is necessary to use both existing, deteriorated batteries and new batteries. However, the installation of the equipment did not anticipate the addition of batteries with different performance, and adding new batteries would require changes to the power wiring and layout, raising concerns that this would result in additional costs.

[0004] The energy storage system in Patent Document 1 is configured to connect multiple battery units that can be charged and discharged, and to have multiple power converters that charge and discharge the battery units. The energy storage system includes switches that are connected to each of the multiple battery units and enable the battery units to be switched to the multiple power converters, and a controller that controls the multiple power converters and the switches. The controller includes a combination determination unit that determines the battery units and power converters to be used for charging and discharging, a switch control unit that controls the open / closed state of the switches so that the battery units determined by the combination determination unit are connected to the power converters, and a power converter control unit that outputs charge / discharge commands to the power converters determined by the combination determination unit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-159631 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 1 shows an example in which the connection state and the number of parallel connections between multiple battery units and multiple power converters can be changed. However, Patent Document 1 does not change the connection state or the number of parallel connections based on the deterioration rate, and there is no description of control when batteries with different performance, such as expansion batteries and existing batteries, are mixed, making it impossible to control batteries with different levels of deterioration, which creates the problem of cross currents occurring and resulting in over-discharge or over-charge.

[0007] The present invention has been made to solve the above-mentioned problems, and aims to provide a secondary battery system and a secondary battery control method that can appropriately configure a system when batteries with different performance, such as expansion batteries and existing batteries, are mixed. [Means for solving the problem]

[0008] To achieve the above object, the secondary battery system of the present invention is a secondary battery system including a battery bank having a battery rack with a plurality of battery cells connected in series and a power converter for charging and discharging one or more parallel-connected battery racks to and from a power grid, the system further comprising: a switch that enables the battery rack of the battery bank to be switched to a power converter of another battery bank; and a controller that monitors the deterioration rate or age of the battery rack and controls the power converter and the switch, the controller instructing the switch to connect a power converter based on the deterioration rate or age of the battery rack. Other aspects of the present invention will be described in the embodiments below. [Effects of the Invention]

[0009] According to the present invention, it is possible to appropriately configure a battery when batteries with different performances, for example, expansion batteries and existing batteries, are mixed. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing a secondary battery system according to a first embodiment. [Figure 2] FIG. 10 is a flowchart showing a connection change process at the time of addition according to the first embodiment. [Figure 3] FIG. 4 is a flowchart showing an example of the addition timing according to the first embodiment. [Figure 4] FIG. 10 is a diagram showing a secondary battery system having a manual switch according to a second embodiment. [Figure 5] FIG. 10 is a diagram showing a secondary battery system according to a third embodiment in which multiple connection destinations can be selected. [Figure 6] FIG. 11 is a flowchart showing a connection change process taking into account an SOH difference at the time of addition according to the third embodiment. [Figure 7] FIG. 11 is a diagram illustrating a connection example in which an SOH difference at the time of expansion according to the third embodiment is taken into consideration. [Figure 8] FIG. 11 is a flowchart showing a connection change process taking into account the SOH difference before expansion according to the third embodiment. [Figure 9] FIG. 11 is a diagram illustrating a connection example in which the SOH difference before expansion is taken into consideration according to the third embodiment. [Figure 10] FIG. 11 is a flowchart showing a connection change process according to the third embodiment, taking into consideration the average SOC before expansion. [Figure 11] FIG. 11 is a diagram illustrating a connection example in which the average SOC before expansion is taken into consideration according to the third embodiment. [Figure 12] FIG. 10 is a diagram showing a secondary battery system according to a fourth embodiment in which there are multiple expansion timings. [Figure 13] FIG. 13 is a flowchart showing a connection change process in the case where there are multiple addition timings according to the fourth embodiment. [Figure 14] FIG. 13 is a diagram illustrating a connection change process when a power converter according to the fifth embodiment fails. [Figure 15] FIG. 13 is a diagram showing a secondary battery system in which a second-hand battery is added according to a sixth embodiment. [Figure 16]FIG. 13 is a flowchart showing a connection change process when adding a second-hand battery according to the sixth embodiment. [Figure 17] FIG. 13 is a diagram showing a connection example when adding a second-hand battery according to the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, etc. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various changes and modifications can be made by those skilled in the art within the scope of the technical ideas disclosed in this specification. Furthermore, in all drawings used to explain the present invention, parts having the same functions are designated by the same reference numerals, and repeated explanations thereof may be omitted.

[0012] <<First Embodiment>> FIG. 1 is a diagram showing a secondary battery system 100 according to a first embodiment. In this embodiment, a system configuration that can accommodate the expansion of secondary battery systems will be described. FIG. 1 shows the configuration of a large-scale secondary battery system, in which two battery racks B, each with batteries connected in series, are connected in parallel to a load via a power converter (Power Conditioning System: PCS) 2 that converts direct current to alternating current. The power converters 2 and the battery racks B are collectively referred to as a battery bank 3, and three battery banks 3 (battery banks 31, 32, and 33) are connected in parallel to a load (not shown). The number of series-connected batteries in battery rack B, the number of parallel-connected battery racks below the power converter, and the number of banks relative to the load may be any number. Hereinafter, the power converter will be referred to as a PCS where appropriate.

[0013] The secondary battery system 100 has a switch 4 (switches 41, 42) that enables the battery rack B of a battery bank 3 to be switched to a power converter of another battery bank, and a controller 5 that monitors the deterioration rate or age of the battery rack B and controls the power converter 2 and switch 4. The controller 5 has a power route determination unit 6 and instructs the switch 4 to connect the power converter 2 based on the deterioration rate or age of the battery rack B. In addition, additional battery rack installation positions 7 and additional battery rack wiring 8 required when adding a battery rack B are provided in advance from the time the secondary battery system 100 is operational. The additional battery rack installation positions 7 include additional battery rack installation position 71, which is the installation position for additional battery rack BE1, and additional battery rack installation position 72, which is the installation position for additional battery rack BE2.

[0014] Battery rack B21 is connected via a switch 41 that can connect to either PCS21 (PCS#1) or PCS22 (PCS#2), and battery rack B22 is connected to PCS22 (PCS#2) and PCS23 (PCS#3) via a similar switch 42. That is, battery rack B21 is connected to one side of switch 41, and PCS21 and PCS22 are switchably connected to the other side. Battery rack B22 is connected to one side of switch 42, and PCS22 and PCS23 are switchably connected to the other side.

[0015] Battery rack B21 is basically connected to PCS22 (PCS#2) except when expansion is required, and is connected to PCS21 (PCS#1) when expansion is required. Similarly, battery rack B22 is basically connected to PCS22 (PCS#2) except when expansion is required, and is connected to PCS23 (PCS#3) when expansion is required. The determination of this timing will be described later.

[0016] In addition, the controller 5 has the function of receiving from each battery rack B, operating information such as the battery voltage and temperature in each battery rack B, as well as the deterioration rate, and commanding the amount of power to the power converter 2. In addition to this function, the controller 5 also has a power route determination unit 6 that selects the power route for each relay, and the power route is selected mainly based on these voltage, temperature, and deterioration rate.

[0017] Fig. 2 is a flow diagram showing a connection change process S0 at the timing of addition according to the first embodiment. Fig. 3 is a flow diagram showing an example of the timing of addition according to the first embodiment. Figs. 2 and 3 show flow diagrams in which the controller 5 switches the power route using the switch 4.

[0018] First, the flow diagram (process S0) in Figure 2 will be explained. The controller 5 determines whether the timing for expansion has passed (process S1). A prerequisite for process S1 is that the previous power route was not a power route that assumed expansion. If the power route has already been switched to a route that assumes expansion, this calculation does not start. Process S0 starts, for example, when the battery system is connected to the grid and put into operation, but this is not limited to this. Process S1 determines whether it is the timing for expansion. This corresponds to the case where the administrator of the battery system specifies the timing for expansion. If it is the timing for expansion (process S1, Yes), proceed to S2; if it is not the timing for expansion (process S1, No), proceed to S5.

[0019] In step S2, the controller 5 determines whether the difference in degradation rate (SOH: State of Health) between the battery racks to be newly connected in parallel is equal to or less than a tolerance. For example, battery rack B21 will be connected to the PCS#1 side, so this is done for battery racks B11, B12, and battery rack B21. The controller 5 calculates whether there is a difference in these SOHs and determines whether the difference is equal to or less than the tolerance and the parallel connection can be safely changed. If it is equal to or less than the tolerance (step S2, Yes), the controller 5 proceeds to step S3. If it is not equal to or less than the tolerance (step S2, No), the controller 5 proceeds to step S5. In this embodiment, the SOH is the ratio of the current charge / discharge capacity to the charge / discharge capacity when new (capacity degradation rate: SOHQ). Another known SOH is SOHR, which represents the degradation rate of resistors.

[0020] In step S3, the controller 5 determines whether the difference in state of charge (SOC) between the battery racks to be newly connected in parallel is below a tolerance. For example, battery rack B21 will be connected to the PCS#1 side, so this is done for battery racks B11, B12, and battery rack B21. The controller 5 calculates whether there is a difference in SOC between these battery racks, and determines whether the difference is below the tolerance and the parallel connection can be safely changed. If it is below the tolerance (step S3, Yes), the controller 5 proceeds to step S4. If it is not below the tolerance (step S3, No), the controller 5 proceeds to step S5.

[0021] In process S4, since it is confirmed that it is the timing for addition and that it is safe, the controller 5 changes the power route and commands the switch 41 to switch so that battery rack B21 is connected to the PCS21 (PCS#1) side, and commands the switch 42 to switch so that battery rack B22 is connected to the PCS23 (PCS#3) side. Upon receiving the commands, the switches 41 and 42 each switch the connection.

[0022] In step S5, if the answer is No in any of steps S1 to S3, it is not the right time to add an additional battery or the safety of the connection cannot be ensured, so the status quo is maintained without switching. That is, the power route is not changed, and the switch 41 of battery rack B21 is kept on the PCS22 (PCS#2) side, and the switch 42 of battery rack B22 is kept on the PCS22 (PCS#2) side.

[0023] 3 shows a specific example of the timing of addition. In step S10, the controller 5 determines whether the average SOH of the battery system is equal to or less than a certain value (for example, A% or less). If the average SOH is equal to or less than A% (step S10, Yes), the process proceeds to step S11. If the average SOH is not equal to or less than A% (step S10, No), the process proceeds to step S15.

[0024] In step S11, the controller 5 determines whether the period of use is equal to or longer than a certain period (for example, B years or longer). If the period of use is equal to or longer than B years (step S11, Yes), the process proceeds to step S12, and if the period of use is less than B years (step S11, No), the process proceeds to step S15. Generally, adding a battery is performed when the battery has deteriorated and is no longer capable of providing satisfactory performance, or when the period during which adding a battery is possible has expired. Therefore, the controller 5 is configured to determine whether or not the battery has been added and switch the process accordingly. The following steps S12 to S15 correspond to steps S2 to S5 in FIG. 2.

[0025] In parallel with or after these power route changes in Figures 2 and 3, an additional battery rack is connected to the additional battery rack installation position 7. By doing so, three existing, somewhat degraded batteries are connected in parallel to PCS21 (PCS#1) and PCS23 (PCS#3), and a new additional battery rack is connected to PCS22 (PCS#2). If the capacity of the new battery rack is the same as the capacity of the existing new batteries, if A in process S10 is 67%, there will be no difference in the battery capacity under each PCS, and the expansion will ensure the same performance as at the time of initial delivery. Note that A is 67% because, if the capacity of the existing new batteries is 200% in a two-parallel configuration, and this is configured as a three-parallel configuration, the capacity becomes 67% (≒ 200 / 3).

[0026] Furthermore, by providing the main components of this embodiment, such as the power route switch 4, power route determination unit 6, wiring 8 for additional battery racks in anticipation of expansion, and securing additional battery rack installation positions 7, only the installation work for the additional battery racks is required at the time of expansion, making it possible to reduce construction work at the time of expansion.

[0027] <<Second embodiment>> In the second embodiment, an example will be described in which manual switches 41A, 42A (manual switches) are used to switch power routes, rather than the switch 4 that is driven by a communication command from the controller 5. Switches that are primarily used for switching at the timing of expansion and are not driven at other times must take into consideration the cost and reliability of the control portion. Therefore, similar processing is possible even with a manual switch that is driven manually. This example will be described with reference to FIG. 4.

[0028] 4 does not have a communication control line between the controller 5 and the manual switches 41A and 42A. Instead, the controller 5 has a communication function with an information terminal 90 of a maintenance worker.

[0029] The secondary battery system 100 has manual switches 41A, 42A that enable the battery rack B of a battery bank 3 to be switched to a power converter of another battery bank, and a controller 5 that monitors the deterioration or age of the battery rack B and controls the power converter 2.When the controller 5 determines that it is time to connect a power converter based on the deterioration rate or age of the battery rack B, it notifies the maintenance staff's information terminal 90 of the power converter to be connected.

[0030] The manual switches 41A and 42A can manually switch the power route in the same direction as in the first embodiment. Specifically, the battery rack B21 can select the power route between PCS #1 and #2, and the battery rack B22 can select the power route between PCS #2 and #3. When adding new equipment, manually performing the flow in Figure 3 allows the power route to be changed with a simple configuration that does not require any new control or controller functions.

[0031] <<Third Embodiment>> FIG. 5 is a diagram showing a secondary battery system 100A according to a third embodiment, which allows multiple connection destinations to be selected. In the third embodiment, a configuration in which a battery rack B can be connected to any PCS (power converter) is described. Similar to the first embodiment, a battery rack B, a PCS 2, and an additional battery rack installation position 7 are provided, and additional battery rack wiring 8 is prepared in advance for installation. However, each battery rack B has a power route switch 110 that can be connected to any PCS 2, and the controller 5A has a power route determination unit 6A that determines this power route. One end of the power route switch 110 is connected to each battery rack B, and is connected to PCSs #1 to #3 in response to a command from the controller 5A. Furthermore, providing a selector switch at the additional battery rack installation position 7 in advance can simplify installation work. This selector switch may be included in the battery rack B, or it may be attached to the additional battery rack B.

[0032] Next, the control flow of this power route switch 110 will be described with reference to FIGS. <Connection change processing taking into account SOH differences when adding new units> Fig. 6 is a flow diagram showing a connection change process S20 that takes into account the SOH difference at the time of expansion according to the third embodiment. Fig. 7 is a diagram showing a connection example that takes into account the SOH difference at the time of expansion according to the third embodiment.

[0033] Fig. 6 shows a control flow when the expansion timing is specified, similar to Fig. 2. First, after starting calculation, in step S21, the controller 5A determines whether it is the expansion timing (whether it has passed), and if it has passed the expansion timing (Yes in step S21), the process proceeds to step S22, and if it has not passed the expansion timing (No in step S21), the process proceeds to step S26.

[0034] In step S22, the controller 5A selects three battery racks B with similar SOHs and proceeds to step S22. The number three is the number of battery racks B assuming that the configuration of two battery racks B in parallel under the PCS is changed to three in parallel, as in the first embodiment, and the power route before expansion is changed, and may be any number depending on the expansion method. Note that the number of battery racks B is a unit of measurement.

[0035] Next, in step S23, controller 5A determines whether the SOH difference between the selected battery racks is equal to or less than the allowable value. If the SOH difference is equal to or less than the allowable value (step S23, Yes), the process proceeds to step S24. If the SOH difference is not equal to or less than the allowable value (step S23, No), the process proceeds to step S26.

[0036] In process S24, the controller 5A determines whether the SOC difference between the selected battery racks is equal to or less than the allowable value. If the SOC difference is equal to or less than the allowable value (process S24, Yes), the process proceeds to process S25. If the SOC difference is not equal to or less than the allowable value (process S24, No), the process proceeds to process S26.

[0037] In process S25, the controller 5A selects a combination to be connected in parallel, and determines that the SOH and SOC are within a safe range, so it issues a command to the power route switch 110 to switch so that the selected battery racks are connected in parallel. On the other hand, in process S26, it maintains the current state without switching.

[0038] Table T7 in Figure 7 shows the SOH of each battery rack and the PCS to which it is connected before and after the control shown in Figure 6 is implemented. Before the control, battery racks B11 and B12 are connected to PCS#1, battery racks B21 and B22 are connected to PCS#2, and battery racks B31 and B32 are connected to PCS#3. As shown in the figure, there is a difference in SOH between 80 and 85. When selecting three battery racks for expansion, it is preferable to select three battery racks with an SOH of 80 and three battery racks with an SOH of 85 and operate them under the same PCS to minimize cross current. Therefore, after the control, battery racks B11, B21, and B22, which have an SOH of 80, are connected to PCS#1, and battery racks B12, B31, and B32, which have an SOH of 85, are connected to PCS#2. After the control, PCS#3 is no longer connected to any battery racks, so two additional battery racks are connected. On the other hand, if the process proceeds to step S26, the connection is not changed and the PCSs connected to before the control are respectively connected.

[0039] <Connection change processing taking into account the SOH difference before expansion> Fig. 8 is a flow diagram showing a connection change process S30 taking into account the SOH difference before expansion according to the third embodiment. Fig. 9 is a diagram showing a connection example taking into account the SOH difference before expansion according to the third embodiment.

[0040] FIG. 8 shows an example of selecting battery racks with similar SOHs to operate them as much as possible, even when not adding batteries. First, in step S31, the controller 5A selects two battery racks with similar SOHs. The reason for selecting two battery racks in step S31, compared to three in the control flow of FIG. 6, is that when adding batteries, the number of parallel connections needs to be changed from two to three, leaving one PCS free. However, the control flow of FIG. 6 does not change the total number of parallel connections because it is based on deterioration other than during addition (e.g., before addition). Next, in step S32, the controller 5A determines whether the SOC difference between the selected battery racks is equal to or less than the allowable value. If the SOC difference is equal to or less than the allowable value (step S32, Yes), the process proceeds to step S33. If the SOC difference is not equal to or less than the allowable value (step S32, No), the process proceeds to step S34.

[0041] In process S33, the controller 5A commands the power route switch 110 to switch so that the selected battery racks are connected in parallel. On the other hand, in process S34, no switching is performed and the current state is maintained. This control flow will be explained with reference to FIG. 9.

[0042] Table T9 in Figure 9, like Table T7 in Figure 7, shows each battery rack and its respective SOH. The PCSs to which they were connected before control are also listed, and it can be seen that the SOH of the battery racks connected to each PCS was different before control. When the connections are determined using the control flow in Figure 8, battery rack B11 and battery rack B22, which have the same SOH of 80, are connected to PCS#1, battery rack B12 and battery rack B32, which have the same SOH of 85, are connected to PCS#2, and battery rack B21 and battery rack B31, which have the same SOH of 90, are connected to PCS#3. By rearranging battery racks with similar degradation rates in this way in a parallel configuration, unsafe events such as cross currents caused by differences in degradation rates can be suppressed.

[0043] <Connection change processing taking into account the average SOC before expansion> Fig. 10 is a flow diagram showing a connection change process S40 taking into account the average SOC before expansion according to the third embodiment. Fig. 11 is a diagram showing an example of a connection taking into account the average SOC before expansion according to the third embodiment.

[0044] The control flow in Figure 10 is effective in maintaining a uniform total capacity for the battery rack groups under each PCS. First, in step S41, the controller 5A selects a combination of battery rack groups that results in approximately the same average SOH. Next, in step S42, it is determined whether the SOC difference between the selected battery racks is equal to or less than the allowable value. If the SOC difference is equal to or less than the allowable value (step S42, Yes), the process proceeds to step S43. If the SOC difference is not equal to or less than the allowable value (step S42, No), the process proceeds to step S44. In step S43, the controller 5A commands the power route switch 110 to switch so that the selected battery racks are connected in parallel. On the other hand, in step S44, the current state is maintained without switching. This control will be described with reference to Figure 11.

[0045] Table T11 in Figure 11, like Table T9 in Figure 9, shows the SOH of each battery rack. For example, the SOH of the battery racks connected to PCS #1 is 80 and 85, resulting in an average of 82.5. The battery racks connected to PCS #2 are 85, and the battery racks connected to PCS #3 are 87.5. Because the average SOH differs before control, the usable capacity of each battery rack group differs. By implementing the control shown in Figure 10, the average SOH can be increased to 85 by connecting battery racks B11 and B21 in parallel, the average SOH can be increased to 85 by connecting battery racks B12 and B32 in parallel, and the average SOH can be increased to 85 by connecting battery racks B22 and B32 in parallel. This allows the degradation rate and capacity of each PCS to be kept uniform. Maintaining uniform capacity in this way prevents overcharging and overdischarging even when each PCS operates at the same output, simplifying control and maintaining safety.

[0046] As described above, by using the configuration shown in Figure 5, it is possible to flexibly respond to expansion and variations in deterioration rates.

[0047] <<Fourth Embodiment>> FIG. 12 is a diagram showing a secondary battery system 100B according to the fourth embodiment when there are multiple expansion timings. FIG. 12 shows a system in which the configuration of the first embodiment is doubled, with the difference being that the controller 5B determines all power routes even in a system configuration that is doubled. There are also differences in terms of control and operation, with the expansion timing of expansion battery racks BE1 and BE2 being different from the expansion timing of expansion battery racks BE3 and BE4. This is intended to spread out and flatten the investment timing by expanding batteries in multiple stages. The method for determining the power routes in this case is explained with reference to FIG. 13.

[0048] 13 is a flow diagram showing a connection change process S50 in the case where there are multiple expansion timings according to the fourth embodiment. First, the controller 5B (see FIG. 12) determines in process S51 whether the first expansion timing has been exceeded. If the first expansion timing has been exceeded (process S51, Yes), the process proceeds to process S52. If the first expansion timing has not been exceeded (process S51, No), the process proceeds to process S55, where the current state is maintained without switching.

[0049] In process S52, if the second expansion timing has passed (process S52, Yes), the controller 5B proceeds to process S53, and if the second expansion timing has not passed (process S52, No), the controller 5B proceeds to process S54.

[0050] In step S55, the initial power route has not been changed and the battery racks are connected to the respective PCSs.

[0051] In process S54, the controller 5B commands the battery rack B21 to switch to the PCS21 (PCS#1) side, commands the battery rack B22 to switch to the PCS23 (PCS#3) side, and maintains the current status of the battery racks B51 and B52 without switching.

[0052] In process S54, battery racks B21 and B22 that were connected to PCS#2 are connected to other PCSs, and PCS#2 is not in use, so the first expansion can be performed safely by installing additional battery racks BE1 and BE2 at additional battery rack installation positions 71 and 72 and connecting them to PCS#2.

[0053] In process S53, the controller 5B commands the battery rack B21 to switch to the PCS21 (PCS#1) side, commands the battery rack B22 to switch to the PCS23 (PCS#3) side, commands the battery rack B51 to switch to the PCS24 (PCS#4) side, and commands the battery rack B52 to switch to the PCS26 (PCS#6) side.

[0054] In process S53, battery racks B51 and B52 that were connected to PCS #5 are now connected to other PCSs, and PCS #5 is no longer in use, so a second expansion can be safely performed by installing expansion battery racks BE3 and BE4 in installation locations 73 and 74 and connecting them to PCS 5. In this way, by sequentially changing multiple power routes depending on the timing of the expansion, expansion can be performed safely and with reduced construction costs.

[0055] The partial expansion as in this embodiment can be implemented with the same concept even in the configurations as in the second and third embodiments.

[0056] <<Fifth Embodiment>> Fig. 14 is a diagram showing a connection change process S60 when a power converter according to the fifth embodiment fails. In the fifth embodiment, the details of ensuring redundancy using the switch 4 used in this embodiment will be described. The configuration is the same as that of Fig. 1 of the first embodiment.

[0057] In the configuration shown in Figure 1, it is possible that PCS#2 may stop functioning due to a malfunction or inspection. If the initial power route is left unchanged at this time, battery racks B21 and B22 below PCS#2 will not be used, resulting in a drop in equipment availability. In such a case, it is desirable to change the power route and use batteries. The control that occurs in this case is explained in Figure 14. The controller 5 has a function for detecting malfunctions in PCS2.

[0058] In process S61, the controller 5 determines whether PCS#2 is functioning. If PCS#2 is functioning (process S61, Yes), the process proceeds to process S62, where the power routes of battery racks B21 and B22 are not changed and the connection to PCS#2 is maintained. On the other hand, if PCS#2 is not functioning (process S61, No), the process proceeds to process S63, where the power routes of battery racks B21 and B22 are changed to connect them to PCS#1 and PCS#3, respectively. In this way, by controlling the power routes so that they can be changed even in the event of a failure, etc., it is possible to improve the equipment operating rate.

[0059] <<Sixth Embodiment>> FIG. 15 is a diagram showing a secondary battery system 100C according to a sixth embodiment when used batteries are added. In this embodiment, the processing when the added batteries are used batteries will be described. The system configuration is similar to that of FIG. 5, but the difference is that the added used battery racks are installed at positions 71S, 72S, and 73S. If the added used battery racks BS1, BS2, and BS3 are also used products of the same type and with the same capacity as the existing battery racks when new, it is likely that their capacity will be lower than when new, so it is assumed that three battery racks will be added in parallel. The control flow will be described with reference to FIGS. 16 and 17.

[0060] 16 is a flow diagram showing the connection change process S70 when adding a used battery according to the sixth embodiment. Process S70 in FIG. 16 starts after a used battery rack is added. First, in process S71, the controller 5C (see FIG. 15) selects a combination of battery racks that will have approximately the same average SOH, including the used battery rack after the addition, and then proceeds to process S72.

[0061] In step S72, the controller 5C determines whether the SOC difference between the selected battery racks is equal to or less than the allowable value. If the SOC difference between the selected battery racks is equal to or less than the allowable value (step S72, Yes), the controller 5C proceeds to step S73 and issues a command to switch the selected battery racks to a parallel connection.

[0062] If the SOC difference between the selected battery racks is not below the allowable value (No in step S72), the process proceeds to step S74, where the switches are not changed until the SOC difference is resolved, operation is performed without the additional battery rack, and the process returns to step S71. This is explained in FIG. 17.

[0063] FIG. 17 is a diagram showing a connection example when adding used batteries according to the sixth embodiment. Table T17 shows each battery rack and its SOH, the PCS to which it is connected before control, and the PCS to which it is connected after control. In this case, the added used battery racks BS1, BS2, and BS3 also contain used batteries, so the SOH is reduced and varies. Before control, no batteries were added, so the batteries were not used to operate the system, but after control, the added battery racks BS1, BS2, and BS3 will also be used to operate the system.

[0064] In step S71 of Figure 16, when selecting combinations of similar SOH, the battery racks with an SOH of 80 are battery racks B11 and B22 and additional battery rack BS1, the battery racks with an SOH of 85 are battery racks B12 and B32 and additional battery rack BS2, and the battery racks with an SOH of 90 are battery racks B21 and B31 and additional battery rack BS3, so these are the three combinations. After control, placing these under the same PCS can suppress cross currents, etc.

[0065] In this way, if the additional battery rack is of a different type from the existing batteries (for example, if the additional battery rack is new), the expansion methods of the first to fifth embodiments, which perform control under a different PCS, are preferable; however, when adding second-hand batteries with the same capacity and similar SOH, it is possible to achieve redundancy by considering all battery racks together.

[0066] In this embodiment, the same type of batteries are used, so the deterioration rate is used as the indicator, but if a battery rack with a different new capacity is added, it is possible to achieve the same effect by performing step S71 using the indicator of capacity x current capacity (SOH).

[0067] The secondary battery system and the secondary battery control method of this embodiment have the following features. (1) A secondary battery system including a battery bank 3 having a battery rack B with multiple battery cells connected in series and a power converter 2 for charging and discharging one or more parallel-connected battery racks B to and from a power grid, the system further comprising a switch 4 that enables switching of the battery rack B of one battery bank 3 to a power converter of another battery bank, and a controller 5 that monitors the deterioration rate or age of the battery rack B and controls the power converter 2 and switch 4, the controller 5 instructing the switch 4 to connect a power converter based on the deterioration rate or age of the battery rack B (see Figures 1 to 3). This allows for an appropriate configuration when batteries with different performance, such as expansion batteries and existing batteries, are mixed.

[0068] (2) A secondary battery system comprising a battery bank 3 having a battery rack B with a plurality of battery cells connected in series and a power converter 2 for charging and discharging one or more parallel-connected battery racks B to and from a power system, the system further comprising a manual switch 4 that enables the battery rack B of the battery bank 3 to be switched to a power converter of another battery bank, and a controller 5 that monitors the deterioration rate or years of use of the battery rack B and controls the power converter 2; when the controller 5 determines that it is time to change the connected power converter based on the deterioration rate or years of use of the battery rack B, it notifies the maintenance worker's information terminal 90 of the power converter to be connected (see Figure 4).

[0069] (3) In (1), the switch 4 is a switch capable of switching to a plurality of power converters, and the controller 5 can instruct the switch 4 as to which power converter to switch to (see Figures 1 and 5).

[0070] (4)(1) In the case of a power converter that is no longer connected after the connected power converter is changed, a mechanism (for example, an additional battery rack installation position 7 and wiring 8 for the additional battery rack) is installed in advance that allows power input from a newly installed battery rack based on a predetermined deterioration rate or number of years of use.

[0071] (5)(2) In the case of a power converter that is no longer connected after the connected power converter is changed, a mechanism (for example, an additional battery rack installation position 7 and wiring 8 for the additional battery rack) is installed in advance that allows power input from a newly installed battery rack based on a predetermined deterioration rate or number of years of use.

[0072] (6)(1) When changing the connection destination, if the charging rate or deterioration rate between the battery racks after the connection change is below a predetermined value, the controller 5 commands the switch 4 to change the connection destination (see Figure 2).

[0073] In (7)(2), when changing the connection destination, if the charging rate or deterioration rate between the battery racks after the connection change is equal to or lower than a predetermined value, the controller 5 notifies the information terminal 90 of the connection destination. This allows the maintenance personnel to accurately know when to switch the manual switch 4.

[0074] (8)(3) The controller 5 instructs the switch 4 to change the connection so that the difference in the deterioration rates of the battery racks connected in parallel becomes equal to or less than a predetermined value (see Figures 8 and 9).

[0075] (9)(3), the controller 5 instructs the switch 4 to select the connection destination so that the total capacity of the battery racks connected to the power converter and the total capacity of the battery racks connected to other power converters is less than a predetermined value (see Figures 10 and 11).

[0076] (10)(1) In the case where a newly installed battery rack is installed multiple times, the controller 5 instructs the switch 4 to select the connection destination based on the deterioration rate or years of use of the battery rack B for each installation (see Figures 12 and 13).

[0077] (11)(2) In the case where the newly installed battery rack is installed multiple times, The controller 5 notifies the information terminal 90 of the connection destination based on the deterioration rate or years of use of the battery rack B for each installation period (see FIG. 4). This allows the maintenance personnel to accurately know when to switch the manual switch 4.

[0078] (12) In (1), when the controller 5 detects that the connected power converter is not functioning, it commands the switch 4 to change the connection destination so that the power converter is connected to a power converter other than the detected power converter (see FIG. 14).

[0079] In (13)(2), when the controller 5 detects that the connected power converter is not functioning, it notifies the information terminal 90 of the connection destination so that the power converter is connected to a power converter other than the detected power converter (see FIGS. 4 and 14). This allows the maintenance personnel to accurately know when to switch the manual switch 4.

[0080] (14) In the cases of (1), (3), (4), (6), (8), (9), (10), and (12), when the newly installed battery rack is not new but deteriorated and can be treated the same as the existing battery rack, the controller 5 commands the switch 4 to change the connection destination so that the SOH difference between the battery racks connected to the power converter, including the new batteries and the existing batteries, is equal to or less than a predetermined value (see Figures 15 to 17).

[0081] (15) In (2), (5), (7), (11), and (13), when a newly installed battery rack is not new but deteriorated and can be treated the same as an existing battery rack, the controller 5 notifies the information terminal 90 of the connection destination so that the SOH difference between the battery racks connected to the power converter 2, combining the new batteries and the existing batteries, is equal to or less than a predetermined value. This allows the maintenance personnel to accurately know when to switch the manual switch 4.

[0082] (16) A secondary battery control method for a secondary battery system 100 including a battery bank 3 having a battery rack B with multiple battery cells connected in series and a power converter 2 for charging and discharging one or more parallel-connected battery racks to and from a power grid, the method including a switch 4 that enables switching of the battery rack B of the battery bank 3 to a power converter of another battery bank, and a controller 5 that monitors the deterioration rate or age of the battery rack B and controls the power converter 2 and the switch 4, and the controller 5 instructs the switch 4 to connect a power converter based on the deterioration rate or age of the battery rack B (see FIGS. 1 to 3). This allows for an appropriate configuration when batteries with different performance, such as expansion batteries and existing batteries, are mixed.

[0083] This embodiment makes it possible to reduce costs when rearranging or expanding batteries and ensure redundancy in the event of a converter failure or the like. [Explanation of symbols]

[0084] 2, 21, 22, 23 PCS (power converter) 3,31,32,33 Battery Bank 4,41,42 Switch 41A, 41A manual switch (manual switch) 5, 5A, 5B, 5C Controller 6 Power routing determination unit 7,71,72 Additional battery rack installation location 71S, 72S, 73S Additional used battery rack installation location 8. Wiring for additional battery rack 90 Information terminal 100, 100A, 100B, 100C secondary battery system 110 Power Route Switch (Switch) 71,72 Additional battery rack installation location B Battery rack B11, B12, B22, B31, B32 Battery Rack BE1, BE2, BE3, BE4 Additional battery racks BS1, BS2, BS3 Additional used battery rack

Claims

1. A secondary battery system including a battery bank having a battery rack with a plurality of battery cells connected in series and a power converter for charging or discharging one or more parallel-connected battery racks to or from a power grid, a switch that enables a battery rack of the battery bank to be switched to a power converter of another battery bank; a controller that monitors the deterioration rate or age of the battery rack and controls the power converter and the switch; The controller instructs the switch to connect a power converter based on the deterioration rate or age of the battery rack. A secondary battery system characterized by:

2. A secondary battery system including a battery bank having a battery rack with a plurality of battery cells connected in series and a power converter for charging or discharging one or more parallel-connected battery racks to or from a power grid, a manual switch that allows the battery rack of the battery bank to be switched to a power converter of another battery bank; a controller that monitors the deterioration rate or age of the battery rack and controls the power converter; When the controller determines that it is time to change the connected power converter based on the deterioration rate or the number of years of use of the battery rack, it notifies the information terminal of the maintenance worker of the power converter to be connected. A secondary battery system characterized by:

3. The secondary battery system according to claim 1, the switch is a switch capable of switching to a plurality of power converters, The controller instructs the switcher which power converter to switch to. A secondary battery system characterized by:

4. The secondary battery system according to claim 1, For power converters that are no longer connected after the connected power converter is changed, a mechanism is installed in advance that allows power input from a newly installed battery rack based on a specified deterioration rate or number of years of use. A secondary battery system characterized by:

5. The secondary battery system according to claim 2, For power converters that are no longer connected after the connected power converter is changed, a mechanism is installed in advance that allows power input from a newly installed battery rack based on a specified deterioration rate or number of years of use. A secondary battery system characterized by:

6. The secondary battery system according to claim 1, When changing the connection destination, if the charging rate or deterioration rate between the battery racks after the connection change is equal to or lower than a predetermined value, the controller commands the switch to change the connection destination. A secondary battery system characterized by:

7. The secondary battery system according to claim 2, When changing the connection destination, if the charging rate or deterioration rate between the battery racks after the connection change is equal to or lower than a predetermined value, the controller notifies the information terminal of the connection destination. A secondary battery system characterized by:

8. The secondary battery system according to claim 3, The controller instructs the switch to change the connection so that the difference in deterioration rates of the battery racks connected in parallel is equal to or less than a predetermined value. A secondary battery system characterized by:

9. The secondary battery system according to claim 3, The controller instructs the switch to select a connection destination so that the total capacity of the battery racks connected to the power converter and the total capacity of the battery racks connected to other power converters is equal to or less than a predetermined value. A secondary battery system characterized by:

10. The secondary battery system according to claim 1, When new battery racks are installed multiple times, The controller instructs the switch to select a connection destination based on the deterioration rate or the number of years of use of the battery rack for each installation period. A secondary battery system characterized by:

11. The secondary battery system according to claim 2, When new battery racks are installed multiple times, The controller notifies the information terminal of a connection destination based on a deterioration rate or years of use of the battery rack for each installation time. A secondary battery system characterized by:

12. The secondary battery system according to claim 1, When the controller detects that the connected power converter is not functioning, it commands the switch to change the connection destination so that the power converter is connected to a power converter other than the detected power converter. A secondary battery system characterized by:

13. The secondary battery system according to claim 2, When the controller detects that the power converter of the connection destination is not functioning, the controller notifies the information terminal of the connection destination so that the information terminal is connected to a power converter other than the power converter. A secondary battery system characterized by:

14. 13. The secondary battery system according to claim 1, wherein: When a newly installed battery rack is not new but deteriorated and can be treated the same as an existing battery rack, the controller commands the switch to change the connection destination so that the SOH difference between the battery racks connected to the power converter, combining the new batteries and the existing batteries, is equal to or less than a predetermined value. A secondary battery system characterized by:

15. 14. The secondary battery system according to claim 2, 5, 7, 11, or 13, When a newly installed battery rack is not new but deteriorated and can be treated the same as an existing battery rack, the controller notifies the information terminal of a connection destination so that the SOH difference between the battery racks connected to the power converter is equal to or less than a predetermined value by combining the new batteries and the existing batteries. A secondary battery system characterized by:

16. A secondary battery control method for a secondary battery system including a battery bank having a battery rack with a plurality of battery cells connected in series and a power converter for charging or discharging one or more parallel-connected battery racks to or from a power grid, the method comprising: a switch that enables a battery rack of the battery bank to be switched to a power converter of another battery bank; a controller that monitors the deterioration rate or age of the battery rack and controls the power converter and the switch; The controller instructs the switch to connect a power converter based on the deterioration rate or age of the battery rack. A secondary battery control method comprising:

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