Electricity storage device, and power conversion device comprising electricity storage device

Abstract

An electricity storage device (10) comprises a plurality of units (12) connected in series to each other and a control part (11). Each of the plurality of units (12) is provided with a plurality of electricity storage elements (43) and a unit control part (31) to which power is supplied from the plurality of electricity storage elements. When an index value indicating the degree of variation in voltage or state of charge among the plurality of units (12) exceeds an upper limit value, the control part (11) causes the unit control part (31) of a unit having a relatively high voltage or state of charge to operate in a first operation mode and causes the unit control part (31) of a unit having a relatively low voltage or state of charge to operate in a second operation mode in which power consumption is lower than in the first operation mode.

Description

Power storage device and power conversion device including the same

[0001] The present disclosure relates to a power storage device and a power conversion device including the power storage device.

[0002] The power storage device includes a large number of power storage elements connected in series and in parallel. In order to maintain the performance of the power storage device, it is required to keep the voltages of the large number of power storage elements connected in series uniform. For this reason, the power storage device has a circuit for balancing the voltages of the power storage elements.

[0003] The power storage device disclosed in International Publication No. 2017 / 073018 (Patent Document 1) includes a plurality of power storage units connected in series, and each power storage unit includes a battery pack in which a plurality of power storage elements are connected in series. Further, in the power storage device of this document, each power storage unit includes a cell balance circuit and a unit balance circuit for equalizing the voltages or remaining capacities of the respective power storage elements in the power storage device. The cell balance circuit reduces the voltage and remaining capacity of a high-voltage power storage element by passing a current from the high-voltage power storage element to a corresponding discharge resistor for each power storage element in order to equalize the voltages and remaining capacities of the power storage elements constituting the battery pack in the power storage unit. The unit balance circuit reduces the voltage and remaining capacity of a high-voltage battery pack by passing a current from the high-voltage battery pack to a corresponding discharge resistor for each unit in order to equalize the voltages between the power storage units connected in series.

[0004] International Publication No. 2017 / 073018

[0005] As described above, in the power storage device disclosed in International Publication No. 2017 / 073018 (Patent Document 1), it is necessary to discharge energy from the high-voltage battery pack to such an extent that the voltages between the battery units can be equalized, and a large discharge resistor having a rated power and a rated voltage capable of such discharge is required. Even if it is connected to the discharge resistor via a DC / DC converter that converts the voltage of the battery pack to a low voltage, it is necessary to increase the rated power and the rated voltage of the components constituting the DC / DC converter. For this reason, there is a problem that the entire power storage device becomes large.

[0006] This disclosure has been made in consideration of the above-mentioned problems, and its purpose is to provide an energy storage device that includes a plurality of energy storage units connected in series, which can equalize the voltage or charge state between energy storage units even without providing a dedicated discharge resistor for discharging the energy storage units.

[0007] One embodiment of the energy storage device comprises a positive electrode and a negative electrode, a plurality of units connected in series between the positive electrode and the negative electrode, and one or more control units. Each of the plurality of units comprises a positive node and a negative node, a plurality of energy storage elements connected in series between the positive node and the negative node, an energy storage element balancing circuit, and a unit control unit. The energy storage element balancing circuit balances the voltage or charge state of the plurality of energy storage elements. The unit control unit is powered by the plurality of energy storage elements and has a first operating mode and a second operating mode which consumes less power than the first operating mode. When an index value representing the degree of variation in voltage or charge state among the plurality of units exceeds an upper limit during a stop in charging and discharging of the energy storage device, one or more control units operate the unit control unit of the unit with a relatively high voltage or charge state in the first operating mode and the unit control unit of the unit with a relatively low voltage or charge state in the second operating mode.

[0008] According to the above embodiment, the voltage or charge state can be equalized among multiple units by operating the unit control unit of a unit with a relatively high voltage or charge state in the first operating mode, and operating the unit control unit of a unit with a relatively low voltage or charge state in the second operating mode.

[0009] This figure shows an example of the configuration of a power converter according to this disclosure. This figure shows an example of the relationship between the SOC and OCV of a LIB. This figure shows an example of the relationship between the SOC and OCV of an EDLC. This figure shows an example of the configuration of the energy storage module in Figure 1. This figure shows an example of the power supply configuration of the unit control unit in Figure 1. This is a flowchart explaining the process of unit voltage balance control. This is a flowchart explaining the process of operation mode control in step S115 of Figure 6. This figure shows an example of the power supply configuration of the unit control unit in the energy storage device of Embodiment 2. This is a flowchart explaining the process of unit voltage balance control using the power supply mode. This is a flowchart explaining the process of power supply mode control in step S135 of Figure 9. This is a flowchart explaining the process of SOC balance control between units using the operation mode in the energy storage device of Embodiment 3. This is a flowchart explaining the process of operation mode control in step S155 of Figure 11. This is a flowchart explaining the process of SOC balance control between units using the power supply mode in the energy storage device of Embodiment 3. This is a flowchart explaining the process of power supply mode control in step S175 of Figure 13. This figure shows an example of the configuration of a unit in the energy storage device of Embodiment 4. This figure shows an example of the power supply configuration between the bank control unit and the unit control unit in the energy storage device of Embodiment 4. This figure shows an example of the internal configuration of the unit power supply unit in Figure 16. This figure shows an example of the configuration of the energy storage device of Embodiment 5.

[0010] Each embodiment will be described in detail below with reference to the drawings. Note that the same or corresponding parts will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0011] Embodiment 1. [Configuration of Power Conversion Device 100] Figure 1 is a diagram showing an example of the configuration of a power conversion device 100 according to the present disclosure. The power conversion device 100 comprises a power storage device 10, a power converter 20, and a control device 21 that controls the power converter 20. The power conversion device 100 is connected to a power system 1 and operates to exchange active power between the power system 1 and the power storage device 10. The power conversion device 100 may also have a function to supply reactive power to the power system.

[0012] The power converter 20 has its DC terminal 22 connected to the energy storage device 10 and its AC terminal 23 connected to the power system 1. The power converter 20 may be, for example, a modular multilevel converter in which multiple unit converters are cascaded together.

[0013] The circuit configuration of the power converter 20 is not limited to the form shown in Figure 1. For example, in Figure 1, two DC terminals are connected to the positive terminal P1 and negative terminal N1 of the energy storage device 10, but three or more terminals of the DC terminals may be connected to three or more terminals of the energy storage device 10. Also, the power converter 20 may be divided into a DC-DC converter and a DC-AC converter. Furthermore, a transformer may be provided between the AC terminal 22 and the power system 1, and the voltage level of the AC terminal 23 may be boosted to the voltage level of the power system 1 by the transformer.

[0014] The control device 21 generates command values ​​for controlling the power converter 20 and the energy storage device 10 based on information about the energy storage device 10 received from the energy storage device control unit 11 located in the energy storage device 10, and information about the power system 1, etc.

[0015] [Configuration of the Energy Storage Device 10] As shown in Figure 1, the energy storage device 10 comprises a plurality of units 12a to 12c (three in Figure 1) connected in series between the positive electrode P1 and the negative electrode N1, an energy storage device control unit 11 that manages and controls the energy storage device 10, and a switch 13 that disconnects the energy storage device 10 from the power converter 20. The switch 13 and the units 12a to 12c are connected in series.

[0016] Unit 12a comprises a unit control unit 31a that manages and controls Unit 12a, a plurality of (three in Figure 1) energy storage modules 41a to 41c connected in series with each other, a series switch 32a connected in series with the energy storage modules 41a to 41c, and a parallel switch 33a connected in parallel with the entirety of the energy storage modules 41a to 41c and switch 32a. The positive node of the series-connected energy storage modules 41a to 41c is denoted as P2, and the negative node as N2.

[0017] For simplicity, the units 12b and 12c are not shown in Figure 1, but they have the same configuration as unit 12a. Specifically, unit 12b comprises a unit control unit 31b, energy storage modules 41a to 41c, a series switch 32b, and a parallel switch 33b. Unit 12c comprises a unit control unit 31c, energy storage modules 41a to 41c, a series switch 32c, and a parallel switch 33c.

[0018] In Figure 1, for simplicity, the number of units connected in series and the number of energy storage modules connected in series are both set to 3. However, the number of units connected in series and the number of energy storage modules connected in series within each unit can be any number of 2 or more.

[0019] Furthermore, in the following, units 12a to 12c, energy storage modules 41a to 41c, unit control units 31a to 31c, series switches 32a to 32c, and parallel switches 33a to 33c will be referred to collectively as unit 12, energy storage module 41, unit control unit 31, series switch 32, and parallel switch 33, respectively, when referring to them or any one of them. Series switch 32 and parallel switch 33 will also be simply referred to as switches 32 and 33. Parallel switch 33 will also be called a bypass switch.

[0020] The energy storage module 41a comprises a module control unit 42a for monitoring and controlling the energy storage module 41a, and a plurality of identical energy storage elements 43a. In Figure 1, the plurality of energy storage elements 43a are connected in series, but this is not limited to this arrangement. For example, a collection of multiple energy storage elements connected in parallel may be further connected in series. Alternatively, a collection of multiple energy storage elements connected in series may be further connected in parallel.

[0021] Although not shown in Figure 1 for simplicity, the energy storage modules 41b and 41c have the same configuration as energy storage module 41a. Specifically, energy storage module 41b comprises a module control unit 42b and a plurality of energy storage elements 43b. Energy storage module 41c comprises a module control unit 42c and a plurality of energy storage elements 43c. Hereafter, the module control units 42a to 42c and the energy storage elements 43a to 43c will be referred to as module control unit 42 and energy storage element 43, respectively, when referring to them collectively or when referring to any one of them.

[0022] In each energy storage module 41, the module control unit 42 has various functions related to the energy storage elements 43 and the energy storage module 41. Specifically, the module control unit 42 functions as a voltage detector, a temperature measuring instrument, a current detector, and a State of Charge (SOC) calculator. Furthermore, the module control unit 42 has a function to detect abnormalities in the energy storage elements 43 from these measured values ​​and calculation results, an energy storage element balance control function to suppress voltage variations or SOC variations of the energy storage elements 43, and a communication function with the unit control unit 31.

[0023] In this disclosure, the energy storage device 10 is provided with an energy storage device control unit 11, each unit 12 constituting the energy storage device 10 is provided with a unit control unit 31, and each energy storage module 41 constituting the unit 12 is provided with a module control unit 42. That is, the energy storage device control unit 11, the unit control unit 31, and the module control unit 42 are arranged hierarchically. However, the configuration of the control units does not necessarily have to be in this way. Also, since each of the above control units may primarily perform monitoring or management, it is of course appropriate to call them monitoring devices or management devices. Furthermore, the division of functions is not fixed, and the above multiple control units may appropriately divide the functions.

[0024] The energy storage element 43 may be a battery cell, an electric double layer capacitor (EDLC), or a lithium-ion capacitor (LIC). The energy storage element 43 is not particularly limited as long as it can store energy and electrically input / output the stored energy. The energy storage elements 43 in unit 12 are composed of identical types and are controlled so that their voltage or state of charge (SOC) is equal, although there may be variations in their characteristics. If the energy storage element 43 is a lithium-ion battery (LIB) cell, an EDLC, or an LIC, it is common for the open-circuit voltage (OCV) to increase as the SOC increases.

[0025] Regarding the series switch 32 and the parallel switch 33, under normal conditions, the series switch 32 is closed and the parallel switch 33 is open. When the series switch 32 is closed, current can flow to each energy storage module 41 of unit 12. When both the series switch 32 and the parallel switch 33 of any unit 12 are open, no current flows to the energy storage device 10. In a certain unit 12, by opening the series switch 32 and closing the parallel switch 33, the switch 32 of that unit 12 and the multiple energy storage modules 41 within that unit 12 can be bypassed, and current can flow to other units 12. As a result, charging and discharging of the energy storage device 10 becomes possible. Hereinafter, a unit 12 in which the series switch 32 is open and the parallel switch 33 is closed will be referred to as the bypassed unit 12.

[0026] The series switch 32 may be any of the following: an electromagnetic contactor that can be opened and closed by an external signal, a no-fuse circuit breaker that can be opened and closed by manual operation or whose opening operation can only be controlled by an external signal, a semiconductor switch, a semiconductor current limiter, a disconnector, etc., and is selected according to the required functions of the system. Furthermore, the series switch 32 may be configured by a combination of two or more of the above types. The parallel switch 33 is a switch that can be fast-closed and has the capability to interrupt current. The high-speed switch may be combined with an electromagnetic contactor that can be opened and closed by an external signal. In addition, a fuse may be provided in series with the energy storage module 41 and the series switch 32 to interrupt the short-circuit current.

[0027] Each unit control unit 31 has a communication function with each module control unit 42 within its own unit 12, and collects the status of each energy storage element 43 from each module control unit 42 via a wired or wireless communication line 38. Furthermore, if each unit control unit 31 itself detects the voltage, current, temperature, etc. of its own unit 12, it monitors these detected values ​​and operates the series switch 32 and parallel switch 33 based on these detection results. In addition, each unit control unit 31 has a communication function with the energy storage device control unit 11, and receives operation commands for switches 32 and 33 from the energy storage device control unit 11 via a wired or wireless communication line 14, alerts the energy storage device control unit 11 to abnormalities in its own unit 12, and transmits the voltage, temperature, SOC, etc. of its own unit 12.

[0028] A switch 13 connected in series with multiple units 12 is normally closed. The switch 13 may be a contactor that can be opened and closed by an external signal, a circuit breaker that can be opened and closed by manual operation or whose opening operation can only be controlled by an external signal, a semiconductor switch, a semiconductor current limiter, a disconnector, etc., and is selected according to the required functions of the system. Alternatively, the switch 13 may be configured by a combination of two or more of the above types. Furthermore, the switch 13 may be provided not only on the positive P1 side but also on the negative N1 side for multiple units 12 of the energy storage device 10. Or, the switch 13 may be provided only on the negative N1 side for multiple units 12.

[0029] Although not shown in Figure 1, the energy storage device 10 may also be equipped with a fuse in series with the switch 13 and the multiple units 12.

[0030] The energy storage device control unit 11 has a communication function with each unit control unit 31. As described above, the energy storage device control unit 11 collects the status of each unit 12 from each unit control unit 31 via the communication line 14 and transmits operation commands for switches 32 and 33 of each unit 12. Furthermore, if the energy storage device control unit 11 itself detects the voltage, current, temperature, etc. of the energy storage device 10, it monitors these detected values ​​and operates switches 13 based on these detection results. In addition, the energy storage device control unit 11 has a communication function for communicating with the control device 21 that controls the power converter 20. The energy storage device control unit 11 receives operation commands for the energy storage device 10 from the control device 21 and transmits the status of the energy storage device 10 and the occurrence of abnormalities to the control device 21.

[0031] [Regarding SOC variations of energy storage elements 43] When the energy storage device 10 is composed of the same type of energy storage elements 43, if the initial SOCs match, ideally the variation in SOC will not increase even when charging and discharging is performed. However, if there are variations in the capacity, internal resistance, temperature, etc. of the energy storage elements 43, or if the initial SOCs are different, the variation in SOC may increase even if the energy storage elements 43 are connected in series. If use continues with large variations, when the energy storage device 10 is charged to nearly 100% SOC, some energy storage elements 43 may exceed the upper limit voltage, or when the energy storage device 10 is discharged to nearly 0% SOC, some energy storage elements 43 may fall below the lower limit voltage. As a result, there is a concern that some energy storage elements 43 may deteriorate or fail. On the other hand, if the energy storage device 10 is charged and discharged so that all energy storage elements 43 maintain a voltage between the upper and lower limits, the usable SOC range will decrease. To solve this problem, the module control unit 42 is equipped with a storage element balancing circuit (50 in Figure 4) that suppresses variations in SOC.

[0032] Figure 2 shows an example of the relationship between SOC and OCV in a LIB. Figure 3 shows an example of the relationship between SOC and OCV in an EDLC.

[0033] As shown in Figures 2 and 3, in LIBs and EDLCs, the OCV increases as the SOC increases from 0% (completely discharged) to 100% (fully charged). Generally, when charging and discharging pauses in an energy storage element, the terminal voltage changes for a while. The voltage at the point when the pause continues and the change in terminal voltage ends corresponds to the OCV. There are multiple time constants for terminal voltage change, ranging from long to short. The time constant varies depending on the type of energy storage element, temperature, and SOC, but for example, in the case of LIBs, the magnitude of the time constant is about 100 seconds. Therefore, it takes more than 1000 seconds for the terminal voltage of the energy storage element to stabilize. Also, because energy storage elements have a DC resistance component, the terminal voltage is higher than the OCV during charging and lower than the OCV during discharging.

[0034] However, for energy storage elements such as LIBs, EDLCs, and LICs, where the SOC-OCV curve increases monotonically, the difference between the terminal voltage and OCV of each energy storage element is not considered to differ significantly. Since energy storage element operation is also managed by terminal voltage, the energy storage element balancing circuit may suppress SOC variation by balancing the terminal voltage.

[0035] The energy storage element balancing circuit (50 in Figure 4) of the module control unit 42 discharges an energy storage element 43 whose terminal voltage is higher than the reference voltage by connecting a resistor (RA in Figure 4). The energy storage element 43 to which the resistor (RA in Figure 4) is connected is determined by the unit control unit 31 and commanded to the module control unit 42. This suppresses SOC variations in each energy storage element 43 within the unit 12.

[0036] By the way, if the energy storage device 10 is at a low voltage of 1500V or less, it is possible for the energy storage device control unit 11, rather than the unit control unit 31, to determine which energy storage element 43 to which resistor is connected and to command the module control unit 42. However, this is not easy in the case of high voltages such as 3kV to 30kV. The reason for this is as follows: When low-voltage units 12 are connected in series to form a high-voltage energy storage device 10, the devices within the units 12 are manufactured as low-voltage devices, so the unit control unit 31 and the module control unit 42 are constructed as a low-voltage system. However, since the energy storage device 10 is a high-voltage system, the unit control unit 31 and the energy storage device control unit 11 need to be isolated from each other, for example, using optical communication. In this case, only a limited number of signals can be exchanged between the unit control unit 31 and the energy storage device control unit 11.

[0037] [Example of the configuration of the energy storage module 41] Figure 4 is a diagram showing an example of the configuration of the energy storage module 41 shown in Figure 1. Referring to Figure 4, the energy storage module 41 comprises n energy storage elements 43_1 to 43_n connected in series, and a module control unit 42. The module control unit 42 includes an energy storage element balancing circuit 50, a voltage detection circuit 51, a current detection circuit 53, a temperature detector 54, a processing circuit 55, and a communication circuit 56.

[0038] The energy storage element balancing circuit 50 includes n resistors RA_1 to RA_n and n switches SW_1 to SW_n, each corresponding to n energy storage elements 43_1 to 43_n. The i-th (1 ≤ i ≤ n) resistor RA_i and switch SW_i are connected in series with each other and in parallel with the corresponding i-th energy storage element 43_i. Each of the n energy storage elements 43_1 to 43_n is normally controlled to be in an open state, and is controlled to be in a closed state when the voltage of the corresponding energy storage element 43 becomes excessively high compared to the average value, thereby discharging the corresponding energy storage element 43.

[0039] The voltage detection circuit 51 is connected to both ends of each of the n energy storage elements 43_1 to 43_n, detects the voltage of each energy storage element 43, and outputs the detection result to the processing circuit 55.

[0040] The current detection circuit 53 uses a current detector 52 to detect the currents output from the n power storage elements 43_1 to 43_n, and outputs the detection results to the processing circuit 55.

[0041] The temperature detector 54 detects the temperature inside the power storage module 41, and outputs the detection results to the processing circuit 55.

[0042] The processing circuit 55 is configured as a microprocessor including a CPU (Central Processing Unit) and a memory. At least a part of the processing circuit 55 may be configured by an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit) or a combination thereof.

[0043] The processing circuit 55 has (i) a SOC calculation function for calculating the SOC of the power storage module 41 based on the detection results of the voltage detection circuit 51, (ii) an abnormality detection function for detecting an abnormality of the power storage module 41 based on the respective detection results of the voltage detection circuit 51, the current detection circuit 53, and the temperature detector 54, (iii) a balance control function for balancing the voltages of the n power storage elements 43_1 to 43_n based on the detection results of the voltage detection circuit 51, and the like. Further, the processing circuit 55 communicates with the unit control unit 31 via the communication circuit 56.

[0044] [Configuration of the power supply relationship of the unit control unit 31] FIG. 5 is a diagram showing a configuration example of the power supply relationship of the unit control unit 31 in FIG. 1. In FIG. 5, together with the unit control unit 31, the power storage modules 41a, 41b, 41c, the series switch 32, and the parallel switch 33 constituting the unit 12 are also shown. As shown in FIG. 5, as a configuration of the power supply relationship, the unit control unit 31 has a unit power supply unit 61 connected between the positive node P2 and the negative node N2 of the unit 12 via a diode 63, and a unit control power supply unit 62.

[0045] The unit power supply unit 61 includes switches 64 and 67, a DC-DC converter 65, and a control storage device 66. Specifically, in the case of FIG. 5, the positive node P2 is connected to the positive input terminal of the DC-DC converter 65 via the forward diode 63 and the switch 64. The negative node N2 is connected to the negative input terminal of the DC-DC converter 65. The positive electrode of the control storage device 66 is connected to the positive output terminal of the DC-DC converter 65 via the switch 67. The negative electrode of the control storage device 66 is connected to the negative output terminal of the DC-DC converter 65.

[0046] When the switch 64 is closed, power is supplied from the storage modules 41a to 41c to the DC-DC converter 65, and the voltages of the storage modules 41a to 41c are converted by the DC-DC converter 65 into voltages suitable for the input of the unit control power supply unit 62. When the switch 67 is closed, the control storage device 66 is connected to the output of the DC-DC converter 65. Thereby, even if the switch 64 is opened or output power cannot be obtained from the DC-DC converter 65, the operation of the unit control unit 31 can be continued for a certain period.

[0047] The diode 63 is provided to prevent reverse current from the unit power supply unit 61 to the storage module 41. In the case of FIG. 5, the diode 63 is inserted on the positive node P2 side, but it may also be inserted on the negative node N2 side.

[0048] The switches 64 and 67 are composed of a contact, a relay, etc. In FIG. 5, single-pole switches 64 and 67 are used and inserted on the positive side, but they may also be inserted on the negative side. Or, by using two-pole switches 64 and 67, both the positive and negative sides may be opened and closed.

[0049] The specifications of the DC-DC converter 65 are not particularly limited, and either an insulated / non-insulated type is possible.

[0050] The control energy storage device 66 is a storage battery or an EDLC, etc. An initial charging circuit may be provided for initial charging of the control energy storage device 66. A DC-DC converter may be provided to convert the output voltage of the control energy storage device 66, so that the output voltage of the DC-DC converter 65 and the voltage from the control energy storage device 66 can be controlled independently.

[0051] The unit control power supply unit 62 generates and supplies control power of appropriate values ​​to the controller processing circuit 68, communication circuit 69, and detectors (not shown) within the unit control unit 31.

[0052] [Operating Mode of Unit Control Unit 31] When power is supplied from the energy storage module 41 to the unit control unit 31 and the module control unit 42, if the charging and discharging of the energy storage device 10 via the positive electrode P1 and the negative electrode N1 is paused for a long period of time, the supply of power to the unit control unit 31 and the module control unit 42 will cause the State of Control (SOC) of the energy storage module 41 to decrease. While the energy storage module 41 is charging and discharging, the unit control unit 31 and the module control unit 42 cannot be stopped. However, during periods when charging and discharging are paused, power consumption can be reduced by limiting their functions or by operating the unit control unit 31 and the module control unit 42 to intermittently monitor the state of the battery.

[0053] Therefore, the unit control unit 31 is provided with an operating mode that can reduce power consumption when the energy storage module 41 is paused during charging and discharging. The operating mode of the unit control unit 31 (hereinafter sometimes referred to as the "unit control unit operating mode") is commanded by the energy storage device control unit 11 based on the operating state of the power converter 100, which operates according to commands from the control device 21 or a higher-level computer. The unit control unit 31 controls the unit control power supply unit 62, the detector, and the controller according to the operating mode of the unit control unit.

[0054] The unit control unit 31 has at least two operating modes: a normal mode and a power-saving mode. In this disclosure, the normal mode is also referred to as the first operating mode, and the power-saving mode is also referred to as the second operating mode. During the charging and discharging pause of the energy storage module 41, the state of the energy storage element 43 rarely changes abruptly, and the state of switches 32 and 33 does not change, so the operating mode can be switched from the normal mode to the power-saving mode.

[0055] In power-saving mode, power consumption can be reduced by disabling the functions of the energy storage module control unit 42 or limiting the functions of the unit control unit 31. Specifically, in power-saving mode, the unit control unit 31 reduces power consumption by maintaining the open / closed state of switches 32 and 33, reducing the number of communication signals with the energy storage device control unit 11, or switching communication with the energy storage device control unit 11 to intermittent communication. Of course, by having three or more operating modes with different power consumption, it is possible to use different operating modes depending on the expected downtime, the degree to which monitoring of the energy storage elements is necessary, and the management level of the energy storage elements.

[0056] [Suppression of SOC Variation Between Units] The energy storage device control unit 11 receives the detected voltage V12 (also referred to as unit voltage V12) between the positive node P2 and the negative node N2 of each unit 12 from each unit control unit 31, and monitors the voltage variation between units based on the received voltage V12. In this embodiment, the range of the distribution of the unit voltage V12 (the difference between the maximum and minimum values) is used as an index value indicating the degree of voltage variation, but is not limited to this. For example, the variance of the unit voltage V12 may be used as an index value for voltage variation.

[0057] The energy storage device control unit 11 performs unit voltage balance control during power saving mode if the voltage variation reaches an upper limit value (ΔV1) of the voltage variation, which is a level at which there is concern about a decrease in the usable range of SOC as an energy storage device 10 or deviation from the upper and lower limit voltages of the energy storage elements 43. In unit voltage balance control, the energy storage device control unit 11 commands the unit control unit 31 of units 12 with relatively low voltage V12 to enter power saving mode until the voltage variation falls below an allowable value (ΔV2), and continues to command the unit control unit 31 of units 12 with relatively high voltage V12 to enter normal mode.

[0058] Figure 6 is a flowchart illustrating the unit voltage balance control process. The unit voltage balance control process will be explained below with reference to Figures 6 and 7.

[0059] In step S111 of Figure 6, the energy storage device control unit 11 determines whether the unit control unit operating mode is in power saving mode. If the unit control unit operating mode is in power saving mode (YES in step S111), the energy storage device control unit 11 proceeds to step S112.

[0060] In step S112, the energy storage device control unit 11 calculates the maximum value Vmax, the minimum value Vmin, and the distribution range Vdif by comparing the unit voltages V12 received from each unit 12. The distribution range Vdif is calculated as Vdif = Vmax - Vmin ... (1).

[0061] In the next step S113, the energy storage device control unit 11 compares the distribution range Vdif with the upper limit value ΔV1. If Vdif > ΔV1 (YES in step S113), it determines that there is a large voltage variation between units and unit voltage balance control is necessary, and proceeds to step S114.

[0062] In step S114, the energy storage device control unit 11 calculates the average value Vave of the unit voltage V12 of each unit, and then in the next step S115, it performs operation mode control processing.

[0063] Figure 7 is a flowchart illustrating the operation mode control process in step S115 of Figure 6. First, in step S121, the energy storage device control unit 11 sequentially selects the units to be processed from all units 12, and then performs the processing from step S122 onwards for the selected units.

[0064] In step S122, the energy storage device control unit 11 compares the unit voltage V12 of the selected unit 12 with the average value Vave. If V12 > Vave (YES in step S112), the process proceeds to step S123. In step S123, the energy storage device control unit 11 changes the unit control unit operation mode of the selected unit from power saving mode to normal mode.

[0065] On the other hand, if V12 > Vave (NO in step S122), the energy storage device control unit 11 proceeds to step S124. In step S124, the energy storage device control unit 11 maintains the unit control unit operation mode of the selected unit in power-saving mode.

[0066] After steps S123 and S124 are completed, the energy storage device control unit 11 proceeds to step S125. In step S125, the energy storage device control unit 11 determines whether there are any unprocessed units. If there are no unprocessed units (YES in step S125), the operation mode control process is completed. If there are unprocessed units (NO in step S125), the energy storage device control unit 11 returns to step S121 and selects a unit to be processed from among the unprocessed units. The above processing is then performed on the selected unit.

[0067] Thus, in the operation mode control process of step S115 in Figure 6, the energy storage unit control unit 11 changes the unit control unit operation mode from power saving mode to normal mode for units where the unit voltage V12 is greater than the average value Vave, and maintains the power saving mode for units where the unit voltage V12 is less than or equal to the average value Vave. After the completion of step S115 in Figure 6, the process proceeds to step S116.

[0068] Returning to Figure 6, in step S113, if Vdif > ΔV1 is not true, i.e., if Vdif ≤ ΔV1 (NO in step S113), the energy storage device control unit 11 proceeds to step S117.

[0069] In step S117, the energy storage device control unit 11 compares the distribution range Vdif with the allowable value ΔV2. If Vdif < ΔV2 (YES in step S117), it determines that the voltage variation between units is small and voltage balance control is unnecessary, and proceeds to step S119. Step S119 is the process of not performing operation mode control. If operation mode control was performed in the previous process, the energy storage device control unit 11 resets it before proceeding to step S116.

[0070] On the other hand, if Vdif < ΔV2, i.e., Vdif ≥ ΔV2 (NO in step S117), the energy storage device control unit 11 proceeds to step S118. In step S118, the energy storage device control unit 11 determines whether or not it performed operation mode control during the previous processing. If it is performing operation mode control (YES in step S118), the energy storage device control unit 11 proceeds to step S114 and continues operation mode control. On the other hand, if it is not performing operation mode control (NO in step S118), the energy storage device control unit 11 proceeds to step S119 and continues not performing operation mode control.

[0071] Note that if the system was in normal mode in the first step S111 (NO in step S111), it cannot switch to power-saving mode. Therefore, in this case, the energy storage device control unit 11 proceeds to step S119 and continues not to perform the operation mode control.

[0072] Since the operating mode of each unit (normal mode or power-saving mode) has been determined in steps S115 and S119 above, in the next step S116, the energy storage device control unit 11 commands the operating mode to each unit control unit 31 and terminates the process.

[0073] The following describes a specific example of the process when charging and discharging is paused and the system switches to power-saving mode. In the following description, the energy storage device 10 includes three units 12a, 12b, and 12c, and the unit voltages V12 of units 12a, 12b, and 12c are denoted as V12a, V12b, and V12c, respectively.

[0074] Assume that in step S112 of Figure 6, the energy storage device control unit 11 calculates Vmax = V12a, Vmin = V12b, and Vdif = V12a - V12b. Furthermore, assume that in step S113, the energy storage device control unit 11 determines that Vdif > ΔV1 (YES in step S113). In this case, the energy storage device control unit 11 calculates the average value Vave of the unit voltage V12 in step S114, and then proceeds to the operation mode control in step S115.

[0075] In step S122 of Figure 7, the energy storage device control unit 11 compares the unit voltages V12a, V12b, and V12c of units 12a, 12b, and 12c with the average value Vave. As a result, the unit voltages V12a and V12c are greater than the average value Vave, and the unit voltage V12b is less than the average value Vave. In this case, the energy storage device control unit 11 switches unit 12b from normal mode to power-saving mode as planned. As a result, the power supplied by unit 12b to the unit power supply unit 61 decreases, and the decrease in the SOC of unit 12b is suppressed. On the other hand, since operation mode control is performed on units 12a and 12c, they continue in normal mode without switching to power-saving mode. As a result, the decrease in the SOC of units 12a and 12c is not suppressed. Consequently, the range Vdif of the distribution of the unit voltage V12 decreases, and the variation in SOC between units also decreases.

[0076] Subsequently, when the unit voltage V12c of unit 12c falls below the average value Vave, the energy storage control unit 11 also switches unit 12c from normal mode to power-saving mode. Furthermore, when the distribution range Vdif of the unit voltage V12 decreases to less than the allowable value ΔV2, the energy storage control unit 11 terminates the operation mode control and also switches unit 12a from normal mode to power-saving mode. As for the energy storage elements 43 within each unit, the variation in SOC is suppressed by the function of the energy storage element balancing circuit 50, so the variation in SOC between energy storage elements 43 of different units 12 does not increase.

[0077] If any unit 12 is bypassed, that unit 12 is excluded from the operation mode control and is also excluded from the calculation of the maximum value Vmax, minimum value Vmin, and average value Vave. Normally, bypassed units are fixed in power-saving mode.

[0078] Figures 6 and 7 illustrate the case where there are two operating modes: normal mode and power-saving mode. However, even if there are three or more operating modes, the same approach can be used to set the operating mode that consumes more power to the unit with the highest unit voltage V12. Furthermore, in Figures 6 and 7, operating mode control is performed on units 12 that satisfy V12 > Vave based on a comparison between the unit voltage V12 and the average value Vave. However, the criteria for deciding whether or not to perform operating mode control are not limited to this. For example, operating mode control may be performed on units where the difference between the unit voltage V12 and the minimum value Vmin is greater than the reference value. Any other criteria can be used as long as the variation in the unit voltage V12 can be reduced by performing operating mode control on units with a relatively higher unit voltage V12 than other units.

[0079] [Effects of Embodiment 1] As described above, the energy storage device 10 of Embodiment 1 is equipped with an energy storage element balancing circuit 50 to suppress variations in the SOC of the energy storage elements 43 within each unit 12, and implements unit voltage balancing control (i.e., operation mode control) to suppress variations in the unit voltage V12 between units. As a result, even when there are many units 12 in series and the energy storage device 10 is a high-voltage system, variations in the SOC of the energy storage elements 43 can be suppressed. Here, the energy storage element balancing circuit 50 within the unit 12 and its control can be those conventionally used for low-voltage systems. Furthermore, since the unit voltage balancing control balances the voltage of the unit 12 using the power consumed by the unit control unit 31 and the energy storage module control unit 42, there is no need to provide an additional discharge resistor for discharging the energy storage elements 43 for each unit.

[0080] Embodiment 2. The energy storage device 10 of Embodiment 2 differs from the energy storage device 10 of Embodiment 1 in terms of the configuration of the power supply section of the unit control unit 31. Specifically, the energy storage device 10 of Embodiment 2 can also supply power to the unit control unit 31 from an external power source. Hereinafter, the same parts as in Embodiment 1 are denoted by the same reference numerals and their descriptions are omitted, and only the different parts will be described.

[0081] [Power supply configuration of the unit control unit 31 in Embodiment 2] Figure 8 shows an example of the power supply configuration of the unit control unit 31 in the energy storage device 10 of Embodiment 2. The unit control unit 31 in Figure 8 includes a unit power supply unit 61, a unit control power supply unit 62, a diode 63, a processing circuit 68, and a communication circuit 69, similar to the case of Embodiment 1. However, the input side of the unit power supply unit 61 of the unit control unit 31 is connected to the positive node P2 and the negative node N2 of the energy storage modules 41a to 41c via a diode 63 for preventing reverse current, and is also connected to an external AC control power supply 2.

[0082] More specifically, the unit power supply unit 61 of the unit control unit 31 further includes a switch 72 and an AC-DC converter 73, in addition to the switch 64, DC-DC converter 65, control energy storage device 66, and switch 67 shown in Figure 5 in the first embodiment.

[0083] In Figure 8, the first AC input terminal of the AC-DC converter 73 is connected to the first output terminal of the AC control power supply 2 via the switch 72, and the second AC input terminal of the AC-DC converter 73 is connected to the second output terminal of the AC control power supply 2. The positive DC output terminal of the AC-DC converter 73 is connected to the positive output terminal of the DC-DC converter 65, and the negative DC output terminal of the AC-DC converter 73 is connected to the negative output terminal of the DC-DC converter 65.

[0084] According to the configuration of the unit power supply unit 61 described above, when switch 64 is opened and switch 72 is closed, power is supplied from the AC control power supply 2 to the AC-DC converter 73, and the AC voltage of the AC control power supply 2 is converted by the AC-DC converter 73 to a DC voltage suitable for the input of the unit power supply unit 62. As a result, the unit power supply unit 62 can be powered from the external AC control power supply 2 instead of from the energy storage module 41, thus not consuming power from the energy storage module 41.

[0085] The switch 72 is composed of a contactor and a relay, etc. In Figure 8, a single-pole switch 72 is provided and inserted between one AC input terminal of the AC-DC converter 73 and one output terminal of the AC control power supply 2. Alternatively, a two-pole switch 72 may be inserted between both AC input terminals of the AC-DC converter 73 and both output terminals of the AC control power supply 2.

[0086] The specifications of the AC-DC converter 73 are not particularly limited. For example, the AC-DC converter 73 may be divided into an AC-DC conversion section and a DC-DC conversion section. Furthermore, it is desirable that the AC-DC converter 73 be isolated so that the potential of the output terminal of the AC-DC converter 73 can be matched to the potential level of the unit control unit 31. In particular, the potential of the unit 12 moves farther from the ground potential as the position of the unit 12 approaches the positive electrode P1 of the energy storage device 10, so it is preferable to isolate the AC control power supply 2 beforehand before supplying power from the AC control power supply 2 to the unit control unit 31.

[0087] As another variation, DC power may be supplied from a DC control power supply via a DC-DC converter instead of the AC control power supply 2 and the AC-DC converter 73. Alternatively, two or more control power supplies for inputs may be provided.

[0088] Either the energy storage module 41 or the AC control power supply 2 may be selected as the power source for the unit power supply section. If a mechanism is in place to prevent reverse current, both switches 64 and 72 may be closed so that the unit power supply section 61 can receive power from both the energy storage module 41 and the AC control power supply 2.

[0089] [Suppression of SOC Variation Between Units Using Power Supply Modes] The energy storage device control unit 11 of Embodiment 2 determines the power supply mode to the unit control unit 31. The power supply mode includes at least two modes: an energy storage module mode in which power is supplied from the energy storage module 41, and an external power supply mode in which power is supplied from the AC control power supply 2. In addition, a dual power source mode may be provided in which power can be supplied from both the energy storage module 41 and the AC control power supply 2. In this disclosure, the energy storage module mode is also referred to as the first power supply mode, and the external power supply mode is also referred to as the second power supply mode.

[0090] The energy storage device 10 of Embodiment 2 performs unit voltage balance control using a power supply mode, in addition to unit voltage balance control using operating modes with different power consumption (normal mode, power saving mode).

[0091] In balance control using the power supply mode, the energy storage device control unit 11 receives the detected value of the unit voltage V12 between the positive node P2 and the negative node N2 of each unit from each unit control unit 31, and monitors the voltage variation between units based on the received voltage V12. If the voltage variation reaches the upper limit of the voltage variation (ΔV3), which is a level at which there is concern about a decrease in the usable range of the SOC as an energy storage device 10 or deviation from the upper and lower limit voltages of the energy storage elements 43, the energy storage device control unit 11 performs unit voltage balance control using the power supply mode. Until the voltage variation falls below the allowable value (ΔV4), the energy storage device control unit 11 commands the unit control unit 31 of the unit 12 with a relatively low voltage V12 to use the external power supply mode, and commands the unit control unit 31 of the unit 12 with a relatively high voltage V12 to use the energy storage module mode.

[0092] Figure 9 is a flowchart illustrating the process of unit voltage balance control using the power supply mode. The process of unit voltage balance control using the power supply mode will be explained below with reference to Figures 9 and 10.

[0093] In step S132, the energy storage device control unit 11 calculates the maximum value Vmax, the minimum value Vmin, and the distribution range Vdif by comparing the unit voltages V12 received from each unit 12.

[0094] In the next step S133, the energy storage device control unit 11 compares the distribution range Vdif with the upper limit value ΔV3. If Vdif > ΔV3 (YES in step S133), it determines that there is a large voltage variation between units and unit voltage balance control is necessary, and proceeds to step S134.

[0095] In step S134, the energy storage device control unit 11 calculates the average value Vave of the unit voltage V12 of each unit, and then in the next step S135, it performs power supply mode control processing.

[0096] Figure 10 is a flowchart illustrating the power supply mode control process in step S135 of Figure 9. Power supply mode control refers to setting the power supply mode to either external power supply mode or energy storage module mode according to the unit voltage V12. For example, controlling the power supply mode to external power supply mode means changing the power supply mode to external power supply mode if energy storage module mode or dual power supply mode was selected as the power supply mode, or maintaining the power supply mode as external power supply mode if external power supply mode was selected as the power supply mode.

[0097] First, in step S141, the energy storage device control unit 11 sequentially selects the units to be processed from all the units 12, and then performs the processing from step S142 onwards on the selected units.

[0098] In step S142, the energy storage device control unit 11 compares the unit voltage V12 of the selected unit 12 with the average value Vave. If V12 > Vave (YES in step S142), the process proceeds to step S143. In step S143, the energy storage device control unit 11 controls the power supply mode of the selected unit to the energy storage module mode.

[0099] On the other hand, if V12 > Vave is not true (NO in step S142), the energy storage device control unit 11 proceeds to step S144. In step S144, the energy storage device control unit 11 controls the power supply mode of the selected unit to the external power supply mode.

[0100] After steps S143 and S144 are completed, the energy storage device control unit 11 proceeds to step S145. In step S145, the energy storage device control unit 11 determines whether there are any unprocessed units. If there are no unprocessed units (YES in step S145), the operation mode control process is completed. If there are unprocessed units (NO in step S145), the energy storage device control unit 11 returns to step S141 and selects a unit to be processed from among the unprocessed units. The above processing is then performed on the selected unit.

[0101] Thus, in the power supply mode control process of step S135 in Figure 9, the energy storage device control unit 11 controls the power supply mode to the energy storage module mode for units 12 whose unit voltage V12 is greater than the average value Vave, and controls the power supply mode to the external power supply mode for units whose unit voltage V12 is less than or equal to the average value Vave. After the completion of step S135 in Figure 9, the process proceeds to step S136.

[0102] Returning to Figure 9, in step S133, if Vdif > ΔV3 is not true, i.e., if Vdif ≤ ΔV3 (NO in step S133), the energy storage device control unit 11 proceeds to step S137.

[0103] In step S137, the energy storage device control unit 11 compares the distribution range Vdif with the allowable value ΔV4. If Vdif < ΔV4 (YES in step S137), it determines that the voltage variation between units is small and voltage balance control is unnecessary, and proceeds to step S139. Step S139 is the process of not performing power supply mode control. If power supply mode control was performed in the previous process, the energy storage device control unit 11 resets it before proceeding to step S136.

[0104] On the other hand, if Vdif < ΔV4 is not true, i.e., if Vdif ≥ ΔV4 (NO in step S137), the energy storage device control unit 11 proceeds to step S138. In step S138, the energy storage device control unit 11 determines whether power supply mode control was performed during the previous processing. If power supply mode control is being performed (YES), the energy storage device control unit 11 proceeds to step S134 and continues power supply mode control. On the other hand, if power supply mode control was not performed (NO in step S138), the energy storage device control unit 11 proceeds to step S139 and continues not performing power supply mode control.

[0105] Since the power supply mode for each unit (energy storage module mode or external power supply mode) has been determined in steps S135 and S139 above, in the next step S136, the energy storage device control unit 11 commands each unit control unit 31 to specify the power supply mode, and the process ends.

[0106] Power supply mode control can also be performed when the operating mode is normal mode. Below, a specific example of the processing when the power supply mode pre-set in the energy storage device control unit 11 is energy storage module mode will be described. In the following description, the energy storage device 10 includes three units 12a, 12b, and 12c, and the unit voltages V12 of units 12a, 12b, and 12c will be described as V12a, V12b, and V12c, respectively.

[0107] Assume that in step S132 of Figure 9, the energy storage device control unit 11 calculates Vmax = V12a, Vmin = V12b, and Vdif = V12a - V12b. Furthermore, assume that in step S133, the energy storage device control unit 11 determines that Vdif > ΔV3 (YES in step S133). In this case, in step S134, the energy storage device control unit 11 calculates the average value Vave of the unit voltage V12, and then proceeds to the power supply mode control in step S135.

[0108] In step S142 of Figure 10, the energy storage device control unit 11 compares the unit voltages V12a, V12b, and V12c of units 12a, 12b, and 12c with the average value Vave. As a result, it is assumed that the unit voltages V12a and V12c are greater than the average value Vave, and the unit voltage V12b is less than the average value Vave. In this case, the energy storage device control unit 11 commands the unit control units 31a and 31c of units 12a and 12c to enter energy storage module mode, and controls the unit control units 31a and 31c to receive power from the energy storage module 41. As a result, the SOC of units 12a and 12c decreases by the amount of power supplied to the unit control units 31a and 31c.

[0109] Meanwhile, the energy storage device control unit 11 commands the unit control unit 31b of unit 12b to enter external power mode, and controls the unit control unit 31b to be powered from the AC control power supply 2. As a result, power is not supplied from the energy storage module 41 to the unit control unit 31b, so the decrease in the SOC of unit 12b is suppressed. Consequently, the range Vdif of the distribution of the unit voltage V12 decreases, and the variation in SOC between units also decreases.

[0110] Subsequently, when the unit voltage V12c of unit 12c falls below the average value Vave, the energy storage device control unit 11 switches unit 12c from energy storage module mode to external power supply mode. Furthermore, when the distribution range Vdif of the unit voltage V12 decreases to less than the allowable value ΔV4, the energy storage device control unit 11 terminates the power supply mode control and commands the unit control units 31a to 31c of all units 12a to 12c to return to energy storage module mode.

[0111] Here, when the operating mode is normal mode, charging and discharging are performed as the energy storage device 10, so the current flowing through each energy storage element 43 is larger than the current supplied to the unit control unit 31, and furthermore, the magnitude of the current flowing through each energy storage element 43 changes transiently. Consequently, the fluctuation of the unit voltage V12 tends to be large, and the range Vdif of the distribution of the unit voltage V12 also tends to fluctuate. Therefore, it is desirable to set the upper limit value ΔV3 and the allowable value ΔV4 in the case of power supply mode control to be larger than the upper limit value ΔV1 and the allowable value ΔV2 in the case of operating mode control, with ΔV3 > ΔV1 and ΔV4 > ΔV2. Of course, it goes without saying that the upper limit value ΔV3 may be set to the same value as the upper limit value ΔV1, and the allowable value ΔV4 may be set to the same value as the allowable value ΔV2.

[0112] Furthermore, if any unit 12 is bypassed, that unit 12 is excluded from the power supply mode control and is also excluded from the calculation of the maximum value Vmax, minimum value Vmin, and average value Vave.

[0113] The following describes the relationship between the unit voltage balance control process using the operating mode and the power supply mode. When Vdif > ΔV1 during power saving mode, the operating mode control is performed. In this case, for unit 12 where V12 > Vave, the operating mode is changed from power saving mode to normal mode, and it is expected that more power will be discharged from the energy storage module 41. Therefore, for unit 12 that is set to normal mode in the operating mode control, the power supply mode must be set to energy storage module mode. For unit 12 that is set to power saving mode in the operating mode control, setting the power supply mode to external power supply mode will further enhance the power saving effect, but other modes (energy storage module mode or dual power supply mode) are also acceptable.

[0114] [Effects of Embodiment 2] As described above, the energy storage device 10 of Embodiment 2 is configured such that, in addition to the configuration of the energy storage device 10 of Embodiment 1, power is supplied to the unit control unit 31 from two or more power sources, including the energy storage module 41 and an external power supply. Furthermore, by implementing unit voltage balance control that utilizes power supply modes (energy storage module mode and external power supply mode), in addition to the effects of Embodiment 1, SOC variations between units can be suppressed even in normal mode. Therefore, even with a power converter 100 that pauses charging and discharging of the energy storage device 10 for a short period, the expansion of SOC variations between units can be suppressed.

[0115] Furthermore, a combination of unit voltage balance control and power supply mode control utilizing the operating mode may be used. In this case, by supplying power from the AC control power supply 2 to the unit control unit 31 of the unit 12 with a low SOC during the operating mode control, the effect of suppressing SOC variation between units can be enhanced.

[0116] Embodiment 3. In Embodiment 3, the energy storage device 10 uses SOC instead of the unit voltage V12 of unit 12 to suppress variations in SOC between units. That is, in Embodiments 1 and 2, unit voltage balance control was implemented to suppress variations in SOC of unit 12, whereas in Embodiment 3, SOC variations are suppressed by implementing unit SOC balance control.

[0117] The following description will primarily focus on the differences between this embodiment and embodiments 1 and 2. Parts common to embodiments 1 and 2 will be given the same reference numerals and will not be described again.

[0118] [Suppression of SOC Variation Between Units Using Operating Modes] The energy storage device control unit 11 acquires information on the charge state (SOC) of each unit 12 and monitors the variation in SOC based on the acquired SOC information. The SOC is calculated by the unit control unit 31 or the energy storage device control unit 11. The calculation method is not limited. In this embodiment, the range of the distribution of the SOC of unit 12 (the difference between the maximum and minimum values) is used as an index value indicating the degree of SOC variation, but is not limited to this. For example, the variance of the SOC of unit 12 may be used as an index value for SOC variation.

[0119] Figure 11 is a flowchart illustrating the process of controlling the SOC balance between units using the operating mode in the energy storage device of Embodiment 3. In the case of Figure 6 of Embodiment 1, the SOC variation is managed based on the unit voltage V12, whereas in the case of Figure 11 of Embodiment 3, it is managed based on the SOC of each unit 12. Embodiment 3 differs from Embodiment 1 in this respect. Hereinafter, referring to the flowcharts in Figures 11 and 12, we will mainly explain the steps that differ from the steps in the flowcharts in Figures 6 and 7, and similar steps will be given the same reference numerals and will not be explained in detail again.

[0120] Referring to Figure 11, the energy storage device control unit 11 proceeds to step S152 if the unit control unit operating mode is in power saving mode (YES in step S111). In step S152, the energy storage device control unit 11 calculates the maximum value SOCmax, the minimum value SOCmin, and the distribution range SOCdif by comparing the SOC of each unit. The distribution range SOCdif is calculated as SOCdif = SOCmax - SOCmin ... (2).

[0121] In the next step S153, the energy storage device control unit 11 compares the distribution range SOCdif with the upper limit value ΔSOC1 and determines whether SOCdif > ΔSOC1. The upper limit value ΔSOC1 is a value at which the SOC variation is judged to be large enough that there is concern about a reduction in the usable SOC range of the energy storage device 10. Here, the voltage of the energy storage element 43 must be managed so as not to deviate from the upper and lower voltage limits. Therefore, when judging by the SOC variation based on the SOC of each unit 12, it is necessary to estimate the terminal voltage from the SOC value of each unit 12, the characteristics of the energy storage element, the current flowing, etc., and set the upper limit value ΔSOC1 so that the estimated terminal voltage value does not deviate from the upper and lower voltage limits.

[0122] The energy storage device control unit 11 proceeds to step S154 if SOCdif > ΔSOC1 (YES in step S153). In step S154, the energy storage device control unit 11 calculates the average value SOCave of each unit 12, and then performs the operation mode control process in the next step S155. Details of the operation mode control process in step S155 will be described later with reference to Figure 12.

[0123] On the other hand, if SOCdiff > ΔSOC1 is not true, i.e., SOCdiff ≤ ΔSOC1 (NO in step S153), the energy storage device control unit 11 proceeds to step S157.

[0124] In step S157, the energy storage device control unit 11 compares the distribution range SOCdif with the allowable value ΔSOC2 and determines whether SOCdif < ΔSOC2. The allowable value ΔSOC2 is a value at which the variation in SOC is judged to be at an acceptable level.

[0125] If SOCdif < ΔSOC2 (YES in step S157), the energy storage device control unit 11 proceeds to step S119. Step S119 is a process that does not perform operation mode control, and if operation mode control is being performed, the operation mode control is reset. On the other hand, if SOCdif < ΔSOC2, i.e., SOCdif ≥ ΔSOC2 (NO in step S157), the energy storage device control unit 11 proceeds to step S154 to continue performing operation mode control if operation mode control is being performed (YES in step S118), and proceeds to step S119 to continue not performing operation mode control if operation mode control is not being performed (NO in step S118).

[0126] Figure 12 is a flowchart illustrating the operation mode control process in step S155 of Figure 11. The flowchart in Figure 12 differs from the flowchart in Figure 7 in that step S162 is provided to compare the SOC of the processing unit 12 with the average value of the SOC, SOCave, instead of step S122 to compare the unit voltage V12 with its average value Vave. Other aspects of Figure 12 are the same as in Figure 7, so the same or corresponding steps are denoted by the same reference numerals and their descriptions are not repeated.

[0127] Returning to Figure 11, since the operating mode of each unit (normal mode or power-saving mode) has been determined in steps S155 and S119 above, in the next step S116, the energy storage device control unit 11 commands the operating mode to each unit control unit 31 and terminates the process.

[0128] As described above, by performing SOC balance control processing for each unit shown in Figures 11 and 12, variations in SOC between units can be suppressed by utilizing operating modes (normal mode and power-saving mode), similar to the unit voltage balance control processing shown in Figures 6 and 7.

[0129] [Suppression of SOC Variation Between Units Using Power Supply Modes] In the flowcharts for unit voltage balance control using power supply modes shown in Figures 9 and 10, the processing related to the unit voltage V12 can be changed to processing related to the SOC of each unit 12, thereby changing it to a flowchart for unit SOC balance control using power supply modes. This makes it possible to suppress SOC variations between units using power supply modes, similar to the case of Embodiment 2. Hereinafter, the differences from Figures 9 and 10 will be mainly explained with reference to Figures 13 and 14, and the same reference numerals will be used for equivalent steps, and detailed explanations will not be repeated.

[0130] Figure 13 is a flowchart illustrating the process of SOC balance control between units using the power supply mode in the energy storage device of Embodiment 3. Referring to Figure 13, in step S172, the energy storage device control unit 11 calculates the maximum value SOCmax, the minimum value SOCmin, and the distribution range SOCdif by comparing the SOC of each unit 12.

[0131] In the next step S173, the energy storage device control unit 11 compares the distribution range SOCdif with the upper limit value ΔSOC3 and determines whether SOCdif > ΔSOC3. The upper limit value ΔSOC3 is a value at which the SOC variation is judged to be large enough that there is concern about a decrease in the usable SOC range for the energy storage device 10.

[0132] The energy storage device control unit 11 proceeds to step S174 if SOCdif > ΔSOC3 (YES in step S173). In step S174, the energy storage device control unit 11 calculates the average value SOCave of each unit 12, and then performs power supply mode control processing in the next step S175. Details of the power supply mode control processing in step S175 will be described later with reference to Figure 14.

[0133] On the other hand, if SOCdiff > ΔSOC3 is not true, i.e., SOCdiff ≤ ΔSOC3 (NO in step S173), the energy storage device control unit 11 proceeds to step S177.

[0134] In step S177, the energy storage device control unit 11 compares the distribution range SOCdif with the allowable value ΔSOC4 and determines whether SOCdif < ΔSOC4. The allowable value ΔSOC4 is a value at which the variation in SOC is judged to be at an acceptable level.

[0135] If SOCdif < ΔSOC4 (YES in step S177), the energy storage device control unit 11 proceeds to step S139. Step S139 is a process to not perform power supply mode control, and if power supply mode control is being performed, the power supply mode control is reset. On the other hand, if SOCdif < ΔSOC4 is not true, i.e., SOCdif ≥ ΔSOC4 (NO in step S177), if power supply mode control is being performed (YES in step S138), the energy storage device control unit 11 proceeds to step S174 to continue performing power supply mode control, and if power supply mode control is not being performed (NO in step S138), the process proceeds to step S139 to continue not performing power supply mode control.

[0136] Figure 14 is a flowchart illustrating the power supply mode control process in step S175 of Figure 13. The flowchart in Figure 14 differs from the flowchart in Figure 10 in that step S182 is provided to compare the SOC of the processing unit 12 with the average value of the SOC, SOCave, instead of step S142, which compares the unit voltage V12 with its average value Vave. Other aspects of Figure 14 are the same as in Figure 10, so the same or corresponding steps are denoted by the same reference numerals and their explanations are not repeated.

[0137] Returning to Figure 13, since the power supply mode (energy storage module mode or external power supply mode) for each unit has been determined in steps S175 and S139 above, in the next step S136, the energy storage device control unit 11 commands each unit control unit 31 to specify the power supply mode and terminates the process.

[0138] As described above, by performing the SOC balance control process for each unit shown in Figures 13 and 14, variations in SOC between units can be suppressed by utilizing the power supply mode (energy storage module mode and external power supply mode), similar to the unit voltage balance control process shown in Figures 11 and 12.

[0139] [Effects of Embodiment 3] As described above, the energy storage device 10 of Embodiment 3 provides the same effects as Embodiments 1 and 2 because, in addition to unit voltage balance control, unit SOC balance control based on monitoring of the variation in the SOC of the units is implemented. In addition, since the variation is suppressed by directly monitoring the SOC of the units, the effect of suppressing the variation in the SOC is enhanced when the estimation accuracy of the SOC is high.

[0140] Furthermore, in the case of a battery with a small slope in the SOC-OCV curve, and in the case of a battery where SOC cannot be estimated by OCV measurement alone and SOC is determined by other methods, such as current integration alone, the variation in SOC can be suppressed even when the degree of variation in SOC does not match the degree of variation in the unit voltage V12 between the positive node P2 and the negative node N2 of the unit.

[0141] Embodiment 4. The energy storage device 10 of Embodiment 4 differs from the energy storage devices 10 of Embodiments 1 to 3 in that the configuration of the unit 12 is large in scale. Specifically, the energy storage device 10 of Embodiment 4 is equipped with a plurality of banks 34 connected in parallel. The following description will mainly focus on the differences from the energy storage devices 10 of Embodiments 1 to 3, and the same reference numerals will be used for parts that are the same as or corresponding to the energy storage devices 10 of Embodiments 1 to 3, and their descriptions will not be repeated.

[0142] [Configuration of Unit 12 in Embodiment 4] Figure 15 shows an example of the configuration of Unit 12 in the energy storage device of Embodiment 4. As shown in Figure 15, Unit 12 comprises a plurality of banks 34a to 34c (three in Figure 15) connected in parallel to each other between the positive node P2 and the negative node N2. In Figure 1, the ends of the series-connected energy storage modules 41 were the positive node P2 and the negative node N2, but in Figure 15, the ends of the plurality of banks 34a to 34c are the positive node P2 and the negative node N2. When referring to the plurality of banks 34a to 34c collectively or to any one of them, it is written as Bank 34.

[0143] Furthermore, as in the case of Figure 1, unit 12 includes a series switch 32 connected in series with the multiple banks 34, a parallel switch 33 connected in parallel with the series switch 32 and the multiple banks 34 as a whole, and a unit control unit 31.

[0144] Each bank 34 comprises a plurality (three in the case of Figure 15) of energy storage modules 41a to 41c connected in series. The positive node of the series-connected energy storage modules 41 is designated as P3, and the negative node as N3. Each bank 34 further comprises a bank control unit 35 (35a, 35b, 35c) for managing and controlling the bank 34, a switch 36, and a fuse 37. The plurality of energy storage modules 41, the switch 36, and the fuse 37 are connected in series with each other.

[0145] In Figure 15, for simplicity, the number of parallel-connected banks 34 is set to three, and the number of energy storage modules 41 connected in series in each bank 34 is set to three. However, these numbers can be any value greater than or equal to two. Also, in Figure 15, for banks 34b and 34c, only the bank control units 35b and 35c are shown, respectively, and the illustration of the energy storage modules 41, switches 36, and fuses 37 is omitted.

[0146] The bank control unit 35 has a communication function with each module control unit 42 and unit control unit 31. When the bank 34 itself detects voltage, current, temperature, etc., the bank control unit 35 monitors these detected values, issues an alarm for abnormalities based on the detected values, and transmits the voltage, temperature, SOC, etc. of the bank 34 to the unit control unit 31. Furthermore, the bank control unit 35 receives operation commands for the switch 36 from the unit control unit 31 and operates the switch 36 according to the operation commands.

[0147] Switch 36 is normally closed. Switch 36 can be any of the following: one that can be opened and closed by an external signal, like an electromagnetic contactor; one that can be opened and closed by manual operation, like a no-fuse circuit breaker; or one that can only be opened by an external signal. The type of switch 36 is selected according to the required functions of the system. In addition, depending on the specifications of switch 36, the fuse 37 may be omitted, or a fuse may be added between the negative node N2 and the negative node N3 in addition to the fuse 37 provided between the positive node P2 and the positive node P3.

[0148] If an overcurrent is detected or a short-circuit current flows within bank 34, switch 36 will open or fuse 37 will blow. In this case, that bank will be disconnected, and the number of parallel banks in unit 12 will decrease, but the operation of the energy storage device 10 can continue.

[0149] In the fourth embodiment, the module control unit 42 communicates with the bank control unit 35, rather than with the unit control unit 31. The unit control unit 31 collects the state of each energy storage element 43 via the bank control unit 35.

[0150] [Example of Power Supply Configuration for Bank Control Unit 35 and Unit Control Unit 31] Figure 16 shows an example of the power supply configuration for the bank control unit 35 and unit control unit 31 in the energy storage device of Embodiment 4. In Figure 16, the power supply configurations for the bank control units 35a to 35c of banks 34a to 34c and the power supply configuration for the unit control unit 31 are shown inside the unit 12 of Figure 15. Since each bank control unit 35 has a similar power supply configuration, the power supply configuration of bank control unit 35a is shown as a representative example in Figure 16.

[0151] As shown in Figure 16, the bank control unit 35a has a power supply configuration that includes a bank power supply unit 81 connected to the positive node P3 and negative node N3 of bank 34a via diodes 83, and a bank control power supply unit 82. The bank power supply unit 81 of the bank control unit 35a is powered by a plurality of energy storage modules 41 connected in series between the positive node P3 and the negative node N3 in the bank.

[0152] The bank power supply unit 81 includes switches 84 and 87, a DC-DC converter 85, and a control energy storage device 86. The configuration of the bank power supply unit 81 is the same as that of the unit power supply unit 61 in Figure 5, with switches 84 and 87 corresponding to switches 64 and 67 in Figure 5, the DC-DC converter 85 corresponding to the DC-DC converter 65 in Figure 5, and the control energy storage device 86 corresponding to the control energy storage device 66 in Figure 5. Therefore, a detailed explanation of the configuration of the bank power supply unit 81 is omitted. The DC-DC converter 65 of the bank power supply unit 81 supplies power to the bank control power supply unit 82 and the unit power supply unit 61 of the unit control unit 31.

[0153] The bank control power supply unit 82 corresponds to the unit control power supply unit 62 in Figure 5. The bank control power supply unit 82 generates and supplies control power of appropriate values ​​to the controller processing circuit 88, communication circuit 89, and detectors (not shown) within the bank control unit 35a.

[0154] The unit control unit 31 in Figure 16 has a power supply configuration similar to the unit control unit 31 in Figure 5, including a unit power supply unit 61 and a unit control power supply unit 62. However, the method of supplying power to the unit power supply unit 61 differs from that in Figure 5. Specifically, the unit power supply unit 61 in Figure 16 does not receive power directly from the energy storage module 41, but rather receives power from the bank power supply units 81 of each of the banks 34a to 34c. Since banks 34a to 34c are connected in parallel, they have approximately the same potential while not disconnected.

[0155] The reference potential of the output of the bank power supply unit 81 of bank 34 is typically taken from the negative node N3 of bank 34. On the other hand, the reference potential of the input of the unit power supply unit 61 of unit 12 is taken from the negative node N2 of unit 12. The output voltage of each DC-DC converter 85 is input to the unit power supply unit 61 from the high-potential output terminal of the DC-DC converter 85 of each bank power supply unit 81 via the corresponding diode 63 (63a to 63c). The unit power supply unit 61 is equipped with switches 64a to 64c between itself and the output terminals of the bank control units 35a to 35c, respectively. These switches 64a to 64c are normally all closed, but if, for example, bank 34a is disconnected, the corresponding switch 64a is opened.

[0156] Figure 17 shows an example of the internal configuration of the unit power supply section 61 shown in Figure 16. Figure 17(A) shows an example of the configuration when a DC-DC converter 65 is provided, and Figure 17(B) shows an example of the configuration when a DC-DC converter 65 is not provided.

[0157] The unit power supply unit 61 in Figure 17(A) differs from the unit power supply unit 61 in Figure 5 in that it is equipped with a plurality of switches 64a to 64c (three in the figure) corresponding to the bank control units 35a to 35c, respectively. The high-potential input node ND1 of the DC-DC converter 65 is connected via switch 64a and diode 63a to the high-potential output terminal of the DC-DC converter 85 provided in the bank power supply unit 81 of the bank control unit 35a. The input node ND1 is further connected via switch 64b and diode 63b to the high-potential output terminal of the DC-DC converter 85 provided in the bank power supply unit 81 of the bank control unit 35b. The input node ND1 is further connected via switch 64c and diode 63c to the high-potential output terminal of the DC-DC converter 85 provided in the bank power supply unit 81 of the bank control unit 35c. Since the other components of the unit power supply unit 61 in Figure 16 are the same as those of the unit power supply unit 61 in Figure 5, the same reference numerals are used for the same or corresponding parts, and the explanation will not be repeated.

[0158] Alternatively, a DC-DC converter may be provided for each output voltage of the bank control units 35a to 35c, and the output voltages of these DC-DC converters may be combined.

[0159] The unit power supply unit 61 in Figure 17(B) has a configuration in which the DC-DC converter 65 is removed from the unit power supply unit 61 in Figure 17(A). Therefore, the combined voltage of the input node ND1 in Figure 17(B) is output as the output voltage on the high-potential side of the unit power supply unit 61. The voltage of the negative node N2 of the unit 12 is output as the output voltage on the low-potential side of the unit power supply unit 61.

[0160] Thus, in the energy storage device 10 of Embodiment 4, the unit control unit 31 receives power from the bank power supply unit 81 of each bank control unit 35, but the specific internal configuration of the power supply of the unit control unit 31 is not particularly limited.

[0161] [Suppression of SOC variation between units] In the energy storage device 10 of Embodiment 4, the multiple banks 34 are connected in parallel with each other and work to automatically balance the voltage. Therefore, if the SOC can be managed by managing the OCV of each energy storage element 43, the variation in SOC is less likely to become large.

[0162] In the energy storage device 10 of Embodiment 4, as in the energy storage devices 10 of Embodiments 1 and 2, if the energy storage device control unit 11 receives the unit voltage V12 between the positive node P2 and the negative node N2 for each unit from each unit control unit 31 and monitors the variation in the unit voltage V12, then unit voltage balance control using the operating mode and unit voltage balance control using the power supply mode can be implemented.

[0163] In unit voltage balance control using operating modes, the energy storage unit control 11 commands the unit control 31 to specify the operating mode according to the process described with reference to Figures 6 and 7. Furthermore, when the bank control 35 is receiving power from the AC control power supply 2, the energy storage unit control 11 commands the unit control 31 to specify the power supply mode according to the process described with reference to Figures 9 and 10. The unit control 31 commands the bank control 35 to specify the operating mode and / or power supply mode received from the energy storage unit control 11. The bank control 35 operates in the operating mode and / or power supply mode commanded by the energy storage unit control 11 via the unit control 31. This suppresses voltage and SOC variations between units.

[0164] Furthermore, in the energy storage device 10 of Embodiment 4, similar to the energy storage device 10 of Embodiment 3, if the energy storage device control unit 11 monitors the variation in SOC between units, unit SOC balance control using the operating mode and unit SOC balance control using the power supply mode can be implemented. In this case as well, the bank control unit 35 operates in the operating mode and / or power supply mode commanded from the energy storage device control unit 11 via the unit control unit 31. As a result, the variation in SOC of the unit 12 is suppressed.

[0165] Furthermore, if the SOC cannot be estimated solely by measuring the OCV of the energy storage element 43, there is a possibility that the SOC of the parallel-connected banks 34 may vary even if the voltages of the parallel-connected banks 34 are the same. In this case, the unit control unit 31 may change the operating mode and power supply mode received from the energy storage device control unit 11 and issue a command to the bank control unit 35. For example, if the SOC of bank 34a is lower than the SOC of banks 34b and 34c among the parallel-connected banks 34a, 34b, and 34c, the unit control unit 31 will switch bank 34a to power-saving mode and allow banks 34b and 34c to continue in normal mode. This can suppress SOC variations between banks.

[0166] [Effects of Embodiment 4] As described above, the energy storage device 10 of Embodiment 4 is equipped with a plurality of banks 34 connected in parallel within each unit 12, and a plurality of energy storage modules 41 connected in series within each bank 34. Therefore, the energy storage device 10 has a configuration suitable for increasing capacity. Even with this configuration in which each unit 12 is equipped with a plurality of banks 34 connected in parallel, unit voltage balance control similar to that of Embodiments 1 and 2 can be implemented, and unit SOC balance control similar to that of Embodiment 3 can be implemented, so the same effect of suppressing SOC variation between units as in Embodiments 1 to 3 can be obtained.

[0167] Embodiment 5. [Configuration of the Energy Storage Device 10 of Embodiment 5] Figure 18 is a diagram showing an example of the configuration of the energy storage device 10 of Embodiment 5. The energy storage device 10 of Embodiment 5 is equipped with a plurality of strings connected in parallel, and each string is equipped with a plurality of units 12 connected in series, thereby achieving even greater capacity.

[0168] Specifically, the energy storage device 10 in Figure 18 comprises a plurality of strings 91 (three in Figure 18) connected in parallel between the positive electrode P1 and the intermediate electrode C1, and a plurality of strings 94 (three in Figure 18) connected in parallel between the intermediate electrode C1 and the negative electrode N1. Therefore, each string 91 and each string 94 are connected in series between the positive electrode P1 and the negative electrode N1. The intermediate electrode C1 may or may not be grounded.

[0169] Each positive-side string 91 comprises a plurality of units 12 connected in series (three in the case of Figure 18), a string control unit 92, and a switch 93. The positive node of the string 91 is denoted as P4, and the negative node as N4. The positive node P4 is connected to the positive electrode P1 via switch 13p. The negative node N4 is connected to the intermediate electrode C1. The switch 93 is connected in series with the plurality of units 12 between the positive node P4 and the negative node N4, and is connected to the high-potential side relative to the plurality of units 12.

[0170] Each negative-side string 94 comprises a plurality of units 12 connected in series (three in the case of Figure 18), a string control unit 95, and a switch 96. The positive node of the string 94 is denoted as P5, and the negative node as N5. The positive node P5 is connected to the intermediate electrode C1. The negative node N5 is connected to the negative electrode N1 via a switch 13n. The switch 96 is connected in series with the plurality of units 12 between the positive node P5 and the negative node N5, and is connected to the lower potential side relative to the plurality of units 12.

[0171] As described above, string 91 and string 94 differ in that string 91 has switch 93 connected to the high-potential side, while string 94 has switch 96 connected to the low-potential side. However, the functions of string 91 and string 94 are almost the same.

[0172] It is preferable to set the reference potential of the string control unit 92 to a potential near the switch 93, and the reference potential of the string control unit 95 to a potential near the switch 96. However, this is not limited to these methods, and it is also possible to determine the potentials of the string control units 92 and 95 in other ways.

[0173] The string control units 92 and 95 share some of the functions of the energy storage device control unit 11 in embodiments 1 to 4. The functions remaining in the energy storage device control unit 11 in embodiment 5 are the function of communicating with the control device 21 that controls the power converter 20, the function of receiving operation commands for the energy storage device 10 from the control device 21, and the function of transmitting the status of the energy storage device 10 and the occurrence of abnormalities to the control device 21. In this disclosure, the energy storage device control unit 11 and the string control units 92 and 95 are collectively referred to as "one or more control units."

[0174] The switches 93 on each string 91 and 96 on each string 94 are normally closed. Opening the switch 93 on a string 91 allows that string 91 to be disconnected, and opening the switch 94 on a string 94 allows that string 94 to be disconnected.

[0175] In the example shown in Figure 18, three strings 91 are connected in parallel, and three units 12 are connected in series to each string 91. Similarly, three strings 94 are connected in parallel, and three units 12 are connected in series. The number of parallel strings 91 and 94 and the number of units 12 in series are just examples; the number of parallel and series strings is not limited as long as it is two or more. Furthermore, the system may consist only of strings 91 and not of strings 94, or conversely, only of strings 94 and not of strings 91.

[0176] [Suppression of SOC Variation Between Units] The string control units 92 and 95 perform control similar to the unit voltage balance control and / or unit SOC balance control performed by the energy storage device control unit 11 in Embodiments 1 to 4 for SOC variation between units within their respective strings 91 and 94. This suppresses SOC variation between units within strings 91 and 94.

[0177] SOC variation between the series-connected strings 91 and 94 can be suppressed in the following manner. When unit voltage balance control is used, the energy storage control unit 11 collects the string voltage or the average voltage of the units 12 within its own string from each of the strings 91 and 94. If the difference between the voltage of string 91 (or the average voltage of the units) and the voltage of string 94 (or the average voltage of the units) and the unit 12 exceeds a threshold, the voltage of string 91 (or the average voltage of the units) and the voltage of string 94 (or the average voltage of the units) are changed by utilizing the operating mode and power supply mode. This is done so that the difference between the two voltages becomes smaller than the threshold. SOC variation can be suppressed in the same manner when unit SOC balance control is used.

[0178] Furthermore, the voltages of strings 91 connected in parallel are equal, and the voltages of strings 94 connected in parallel are equal. Therefore, the voltages of the parallel-connected strings are automatically balanced, and no active control is necessary. If the SOC cannot be estimated by measuring the OCV of the energy storage element 43 alone, the voltages between the parallel-connected strings may vary, but even in this case, the variation in SOC can be suppressed by using the operating mode and / or power supply mode.

[0179] [Effects of Embodiment 5] As described above, the energy storage device 10 of Embodiment 5 has a configuration in which multiple strings 91 and 94, each containing multiple units 12 connected in series, are connected in parallel. This makes the energy storage device 10 more suitable for higher voltage and larger capacity. Even with an energy storage device 10 with such a configuration, the unit voltage balance control and / or unit SOC balance control described in Embodiments 1 to 4 can be implemented, so the same SOC variation suppression effect as in Embodiments 1 to 4 can be obtained. Furthermore, the difference in average voltage or SOC of the units 12 between the series-connected strings 91 and string 94 can also be suppressed, so SOC variation of the energy storage elements 43 in the energy storage device 10 can be suppressed.

[0180] Embodiment 6. Embodiment 6 describes an example of a method for supplying power to the energy storage device control unit 11 and the string control units 92 and 95. Embodiment 6 can be combined with Embodiments 1 to 5.

[0181] The method of supplying power to the unit power supply unit 61 provided in the unit control unit 31 is as described in Figures 8 and 16. Power can be further supplied from the output of the unit power supply unit 61 to the energy storage device control unit 11 and the string control units 92 and 95.

[0182] Let's take the power supply to the string control unit 92 as an example. Assume that units 12a, 12b, and 12c are connected in this order from the high potential side to the low potential side within the string 91. If the reference potential of the string control unit 92 is taken to be the potential near the switch 93, the potential of unit 12a will be closest to the potential of the string control unit 92. Therefore, supplying power to the string control unit 92 from the unit power supply unit 61 of unit 12a is advantageous in terms of insulation. In this case, the power consumption of unit 12a is expected to be greater than the power consumption of units 12b and 12c, but SOC variation can be suppressed by using unit voltage balance control and / or unit SOC balance control. Alternatively, if the string control unit 92 is configured to be powered from the unit power supply unit 61 of unit 12b or the AC control power supply 2, the power source may be switched according to the SOC variation. Furthermore, if each of the units 12a to 12c is configured to supply power to the string control unit 92 from its respective unit power supply section 61, then the power supply to the string control unit 92 can be actively utilized to suppress SOC variations between units.

[0183] Embodiment 7. Embodiment 7 describes an example of the use of a control energy storage device 66 provided in the unit power supply unit 61 and a control energy storage device 86 provided in the bank power supply unit 81 (generally, control energy storage devices provided in one or more control units). Embodiment 7 can be combined with Embodiments 1 to 6.

[0184] Referring to Figure 5, the case of the unit power supply unit 61 will be explained as an example. When switch 67 is closed, even if switch 64 is opened to stop the power supply from the energy storage module 41, power can still be supplied from the control energy storage device 66 to the unit control power supply unit 62. Therefore, when the unit control unit operating mode is normal mode and the variation in the voltage or SOC of unit 12 becomes large, power can be supplied from the control energy storage device 66 by opening switch 64 of unit 12 with a relatively low voltage or SOC and closing switch 67. This prevents the expansion of the variation in voltage or SOC between units.

[0185] As described above, if the energy of the control energy storage device 66 is used to suppress SOC variations, supplemental charging of the control energy storage device 66 becomes necessary. As a method to do this, for example, during a long period of pause in charging and discharging from the positive electrode P1 and negative electrode N1, unit voltage balance control and / or unit SOC balance control can be performed with switches 64 and 67 closed.

[0186] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. For example, it is possible to combine the energy storage devices and power converters equipped with energy storage devices shown in Embodiments 1 to 7 with other known technologies, and to make modifications, such as omitting parts, without departing from the spirit of this disclosure. The scope of this application is indicated by the claims rather than the above description, and all modifications within the meaning and scope equivalent to the claims are intended to be included.

[0187] 1 Power system, 2 Control power supply, 10 Energy storage device, 11 Energy storage device control unit, 12 Unit, 13, 32, 33, 36, 64, 67, 72, 84, 87, 93, 96, SW Switch, 14, 38 Communication line, 20 Power converter, 21 Control device, 22 DC terminal, 23 AC terminal, 31 Unit control unit, 34 Bank, 35 Bank control unit, 37 Fuse, 41 Energy storage module, 42 Module control unit, 43 Energy storage element, 50 Energy storage element balance circuit, 51 Voltage detection circuit, 52 Current detector, 53 Current detection circuit, 54 Temperature detector, 55, 68, 88 Processing circuit, 56, 69, 89 Communication circuit, 61 Unit power supply unit, 62 Unit control power supply unit, 63, 83 Diode, 65, 85 DC-DC converter, 66, 86 Control energy storage device, 73 AC-DC converter, 81 Bank power supply unit, 82 Bank control power supply unit, 91, 94 String, 92, 95 String control unit, 100 Power converter, C1 Intermediate electrode, N1 Negative electrode, N2, N3, N4, N5 Negative side node, ND1 Input node, P1 Positive electrode, P2, P3, P4, P5 Positive side node, RA Resistor element, SOCave, Vave Average value, SOCdif, Vdif Distribution range, SOCmax, Vmax Maximum value, SOCmin, Vmin Minimum value, V12 Unit voltage.

Claims

1. An energy storage device comprising: a positive electrode and a negative electrode; a plurality of units connected in series between the positive electrode and the negative electrode; and one or more control units, each of the plurality of units comprising: a positive node and a negative node; a plurality of energy storage elements connected in series between the positive node and the negative node; an energy storage element balancing circuit for balancing the voltage or charge state of the plurality of energy storage elements; and a unit control unit supplied with power from the plurality of energy storage elements, having a first operating mode and a second operating mode having lower power consumption than the first operating mode, wherein the one or more control units, when an index value representing the degree of variation in voltage or charge state among the plurality of units exceeds an upper limit during a halt in charging or discharging of the energy storage device, operate the unit control unit of a unit with a relatively high voltage or charge state in the first operating mode and operate the unit control unit of a unit with a relatively low voltage or charge state in the second operating mode.

2. The energy storage device according to claim 1, wherein the unit control unit has a first power supply mode in which power is supplied from the plurality of energy storage elements and a second power supply mode in which power is supplied from an external power source, and when an index value representing the degree of variation in voltage or charge state among the plurality of units exceeds an upper limit, one or more control units operate the unit control unit of a unit with a relatively high voltage or charge state in the first power supply mode and operate the unit control unit of a unit with a relatively low voltage or charge state in the second power supply mode.

3. The energy storage device according to claim 1, wherein each of the plurality of units comprises a plurality of banks connected in parallel between the positive node and the negative node, each of the plurality of banks comprises a plurality of energy storage elements connected in series, and a bank control unit powered by the plurality of energy storage elements in its own bank and having a first operating mode and a second operating mode as operating modes, the unit control unit is powered by the bank control unit of each of the plurality of banks, and when an index value representing the degree of variation in voltage or charge state among the plurality of units exceeds an upper limit during a stop in charging and discharging of the energy storage device, one or more control units operate the bank control unit in the unit with a relatively high voltage or charge state in the first operating mode and the bank control unit in the unit with a relatively low voltage or charge state in the second operating mode.

4. The energy storage device according to claim 3, wherein the bank control unit has a first power supply mode in which it is powered by the plurality of energy storage elements in its own bank and a second power supply mode in which it is powered by an external power source, and when an index value representing the degree of variation in voltage or charge state among the plurality of units exceeds an upper limit, one or more control units operate the bank control unit in the unit with a relatively high voltage or charge state in the first power supply mode and the bank control unit in the unit with a relatively low voltage or charge state in the second power supply mode.

5. The energy storage device according to claim 1 or 2, wherein one or more control units are powered by a unit control unit provided in at least one of the plurality of units.

6. The energy storage device according to claim 3 or 4, wherein the one or more control units are powered by each of the bank control units of the plurality of banks provided in at least one of the plurality of units.

7. The energy storage device according to claim 1 or 2, wherein the unit control unit is configured to be able to receive power from an energy storage device provided in its unit, and the unit control unit receives power from the energy storage device when an index value representing the degree of variation in voltage or charge state among the plurality of units exceeds an upper limit during operation in the first operating mode.

8. The energy storage device according to claim 3 or 4, wherein the bank control unit is configured to be able to receive power from an energy storage device provided in its own bank, and the bank control unit receives power from the energy storage device when an index value representing the degree of variation in voltage or charge state among the plurality of units exceeds an upper limit during operation in the first operating mode.

9. The energy storage device according to any one of claims 1 to 8, wherein the energy storage device comprises a plurality of strings connected in parallel between the positive electrode and the negative electrode, and each of the plurality of strings comprises the plurality of units connected in series.

10. A power converter comprising: an energy storage device according to any one of claims 1 to 9; and a power converter connected between the energy storage device and a power grid, configured to discharge energy stored in the energy storage device to the power grid and to charge the energy storage device from the power grid.

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