Method for estimating state of storage battery, method for operation simulation of storage battery, and storage battery system

Abstract

This method for estimating the state of a storage battery constituted by a plurality of battery modules connected in series, and controlled by a predetermined control device, comprises: a comparison step for comparing, for each of a plurality of battery modules which include an cell assembly in which a plurality of unit cells are connected, and which are formed by accommodating the cell assembly in a housing having a vacuum heat insulating structure, actual measurement temperatures when a charging / discharging action is performed in the storage battery and actual temperatures when the charging / discharging action was performed under the same conditions as the charging / discharging action; and an estimation step for estimating the state of the storage battery on the basis of the comparison results in the comparison step. In the estimation step, it is possible to distinguish and estimate the occurrence of any of the abnormal states among a failure of a unit cell in any of the plurality of battery modules, the occurrence of deviation of a discharge depth management value held in the control device from the actual discharge depth in the storage battery, and a decrease in the degree of vacuum in the housing in any of the plurality of battery modules.

Description

Battery state estimation method, battery operation simulation method, and battery system

[0001] The present invention relates to estimating the state of a battery and utilizing the results of such estimation.

[0002] Sodium-sulfur batteries (NaS batteries), which are high-temperature operating storage batteries, are used as the main components of power storage compensation devices for leveling power demand (load), emergency power supply devices in the event of natural disasters, and for the purpose of monetizing by performing charge / discharge operations according to the electricity price in the electricity market. In operating such NaS batteries, two important points are to properly manage the depth of discharge (or remaining capacity) and to properly control the operating temperature. In light of this, a guidance device designed to enable even inexperienced operators to easily perform these operations is already known (see, for example, Patent Document 1).

[0003] Furthermore, such NaS batteries include modular batteries in which one or more blocks are housed in a housing, each block consisting of a plurality of strings connected in parallel, each of which is made up of a large number of unit cells (also called cells) connected in series. Techniques for detecting unit cell failures in such NaS batteries and for calculating the number of healthy strings (the number of healthy strings) without any unit cell failures are already known (see, for example, Patent Documents 2 and 3).

[0004] Furthermore, as NaS batteries are used over a long period of time, a discrepancy occurs between the actual depth of discharge of each cell and the control value for that depth of discharge (depth of discharge control value) managed by a control device, and the degree of this discrepancy varies from cell to cell. A method for correcting the depth of discharge control value that can solve this problem is already known (for example, Patent Document 4).

[0005] Also, a power storage device equipped with a Hall current detector that measures the charge / discharge current value of a NaS battery is already known (for example, Patent Document 5).

[0006] The guidance device disclosed in Patent Document 1 simulates the remaining capacity and battery temperature of the NaS battery at the end of an operation based on an operation plan (charge / discharge plan), and determines whether or not to execute the operation plan based on the results. Examples of parameters used in the simulation (simulation parameters) include the charge / discharge power, remaining capacity, battery current, battery internal resistance, module battery heat capacity, and time interval for the NaS battery.

[0007] In a simulator such as this guidance device, the initial values ​​of the simulation parameters are usually set so that the difference between the actual measurement values ​​and the simulated values ​​is small. Furthermore, if the simulation using the simulator is repeated while the object of the simulation is in operation, the simulation parameters that have been set may be corrected based on the latest actual measurement values ​​in order to maintain the accuracy of the simulation.

[0008] Therefore, in the NaS battery that is the subject of the simulation in the guidance device disclosed in Patent Document 1, if a deviation in the depth-of-discharge control value occurs due to a failure of a single cell or long-term continuous use, and techniques such as those disclosed in Patent Documents 2 to 4 are applied, the guidance device will also need to appropriately change the simulation parameters to maintain the accuracy of the simulation. For example, because the initial value of the remaining capacity is set according to the depth-of-discharge control value, if a deviation occurs in the depth-of-discharge control value, the initial value of the remaining capacity needs to be changed.

[0009] However, the detection of cell failures disclosed in Patent Document 2 is performed when the voltage of the NaS battery stabilizes during the rest period from the end of discharge to the start of charge. Furthermore, the calculation of the number of healthy strings disclosed in Patent Document 3 is performed when the NaS battery is in the single-phase region after charge and discharge are completed. Furthermore, the correction of the depth-of-discharge control value disclosed in Patent Document 4 is performed when the end of charge or discharge is detected.

[0010] In other words, the application aspects of the techniques disclosed in Patent Documents 2 to 4 depend on the operating state of the NaS battery and cannot be performed at any time. Therefore, depending on the operating state of the NaS battery, situations may arise where it is not possible to address a malfunction of a single cell or a deviation in the depth of discharge control value.

[0011] In such a case, it is naturally impossible to reset the simulation parameters in a simulator such as the guidance device disclosed in Patent Document 1, and therefore the actual state of the NaS battery is not reflected in the simulation, making it impossible to obtain accurate simulation results.For example, even if the NaS battery is operated according to an operation plan determined to be operable by the simulator, there may be cases where the charge / discharge amount is insufficient or the battery temperature rises beyond the control range, making it impossible to operate as planned.

[0012] Furthermore, since both a cell failure and a deviation in the depth-of-discharge control value are events that affect the battery temperature during discharge, simply monitoring the battery temperature makes it impossible to estimate which event is the cause of a rise in battery temperature. If the cause remains unknown, the simulation parameters cannot be reset, and in such cases, the actual state of the NaS battery is not reflected in the simulation, and accurate simulation results cannot be obtained.

[0013] JP 2008-210586 A JP 2004-247319 A WO 2010 / 134515 JP 2008-84677 A WO 2010 / 150667

[0014] The present invention has been made in view of the above-mentioned problems, and has an object to provide a method capable of distinguishing and estimating abnormal states that are causes of temperature changes occurring in a storage battery.

[0015] In order to solve the above-mentioned problems, a first aspect of the present invention is a method for estimating the state of a storage battery composed of a plurality of module batteries connected in series and controlled by a predetermined control device, each of the plurality of module batteries including an assembly battery to which a plurality of single cells are connected, the assembly battery being housed in a housing having a vacuum insulation structure, the method comprising: a comparison step of comparing, for each of the plurality of module batteries, an actual measurement value of the temperature when a charge / discharge operation is performed in the storage battery with an actual value of the temperature when a charge / discharge operation is performed under the same conditions as the charge / discharge operation; and an estimation step of estimating the state of the storage battery based on the comparison result in the comparison step, wherein the estimation step is capable of distinguishing and estimating the occurrence of an abnormal state of any of the following: a failure of a single cell in any of the plurality of module batteries; a deviation of a depth-of-discharge control value held in the control device from the actual depth of discharge of the storage battery; and a decrease in the degree of vacuum in the housing of any of the plurality of module batteries.

[0016] A second aspect of the present invention is a method for estimating the state of a storage battery according to the first aspect, characterized in that in the estimation step, if the difference between the actual measurement value and the performance value is positive and equal to or greater than a first threshold value in some of the plurality of module batteries, it is estimated that a failure has occurred in a single cell in that module battery, and if the difference between the actual measurement value and the performance value is positive and equal to or greater than the first threshold value in all of the plurality of module batteries, it is estimated that the depth-of-discharge control value held in the control device deviates from the actual depth of discharge of the storage battery.

[0017] A third aspect of the present invention is a method for estimating the state of a storage battery according to the second aspect, characterized in that in the estimation step, if the difference between the actual measurement value and the performance value is positive and is equal to or greater than a second threshold value that is smaller than the first threshold value, and this is repeated multiple times in all of the plurality of module batteries, it is estimated that the depth-of-discharge control value held in the control device deviates from the actual depth of discharge of the storage battery.

[0018] A fourth aspect of the present invention is a method for estimating the state of a storage battery according to the first aspect, characterized in that in the estimation step, if, in some of the plurality of module batteries, the difference between the actual measurement value and the performance value is negative and the absolute value of the difference is equal to or greater than a predetermined threshold, it is estimated that a decrease in the degree of vacuum has occurred in the casing of the module battery, and if, in all of the plurality of module batteries, the difference between the actual measurement value and the performance value is negative and the absolute value of the difference is equal to or greater than the predetermined threshold, it is estimated that the depth-of-discharge control value held in the control device deviates from the actual depth of discharge of the storage battery.

[0019] A fifth aspect of the present invention is a method for estimating the state of a storage battery composed of a plurality of serially connected module batteries and controlled by a predetermined control device, wherein each of the plurality of module batteries includes an assembled battery to which a plurality of single cells are connected, and the assembled battery is housed in a housing having a vacuum insulation structure, the method comprising: a comparison step of comparing, for each of the plurality of module batteries, an actual measured value of the temperature when a charge / discharge operation is performed in the storage battery with a previously estimated value of the temperature; and an estimation step of estimating the state of the storage battery based on the comparison result in the comparison step, wherein the estimated value is estimated based on charge / discharge power values ​​from previous charge / discharge operations performed in the storage battery and the temperatures of each of the plurality of module batteries, and the estimation step is capable of distinguishing and estimating the occurrence of any of the following abnormal states: a failure of a single cell in any of the plurality of module batteries; a deviation of a depth-of-discharge management value held in the control device from the actual depth of discharge of the storage battery; and a decrease in the degree of vacuum in the housing of any of the plurality of module batteries.

[0020] A sixth aspect of the present invention is a method for estimating the state of a storage battery according to the fifth aspect, characterized in that in the estimation step, if the difference between the actual measurement value and the estimated value in some of the plurality of module batteries is positive and equal to or greater than a first threshold, it is estimated that a failure has occurred in a single cell in that module battery, and if the difference between the actual measurement value and the estimated value in all of the plurality of module batteries is positive and equal to or greater than the first threshold, it is estimated that the depth-of-discharge control value held in the control device deviates from the actual depth of discharge of the storage battery.

[0021] A seventh aspect of the present invention is a method for estimating the state of a storage battery according to the sixth aspect, characterized in that in the estimation step, if the difference between the actual measured value and the estimated value is positive and is equal to or greater than a second threshold value that is smaller than the first threshold value and is repeated multiple times in all of the plurality of module batteries, it is estimated that the depth-of-discharge control value held in the control device deviates from the actual depth of discharge of the storage battery.

[0022] An eighth aspect of the present invention is a method for estimating the state of a storage battery according to the fifth aspect, characterized in that in the estimation step, if, in some of the plurality of module batteries, the difference between the actual measurement value and the estimated value is negative and the absolute value of the difference is equal to or greater than a predetermined threshold, it is estimated that a decrease in the degree of vacuum has occurred in the casing of the module battery, and if, in all of the plurality of module batteries, the difference between the actual measurement value and the estimated value is negative and the absolute value of the difference is equal to or greater than the predetermined threshold, it is estimated that the depth-of-discharge control value held in the control device deviates from the actual depth of discharge of the storage battery.

[0023] A ninth aspect of the present invention is the method for estimating a state of a storage battery according to any one of the first to eighth aspects, characterized in that the cell is a sodium-sulfur battery.

[0024] A tenth aspect of the present invention is a method for simulating the operation of a storage battery based on a pre-created operation plan, comprising: a result acquisition step for acquiring, for the storage battery, an estimation result in the estimation step of a state estimation method relating to any of the first to eighth aspects; and a correction step for correcting parameters used in the simulation according to the content of the abnormal state when the estimation result estimates that any of the abnormal states has occurred.

[0025] An eleventh aspect of the present invention is a storage battery system comprising: a storage battery composed of a plurality of module batteries connected in series; and a control system for the storage battery, wherein each of the plurality of module batteries includes an assembly battery to which a plurality of single cells are connected, and the assembly battery is housed in a housing having a vacuum insulation structure; the control system comprising: control means for controlling the storage battery based on a preset depth-of-discharge management value; comparison means for comparing, for each of the plurality of module batteries, an actual measurement value of the temperature when a charge / discharge operation is performed in the storage battery with an actual value of the temperature when a charge / discharge operation is performed under the same conditions as the charge / discharge operation; and estimation means for estimating a state of the storage battery based on a comparison result by the comparison means, wherein the estimation means is capable of distinguishing and estimating the occurrence of an abnormal state of any of the following: a failure of a single cell in any of the plurality of module batteries; a deviation of the depth-of-discharge management value from the actual depth of discharge of the storage battery; and a decrease in the degree of vacuum in the housing of any of the plurality of module batteries.

[0026] A twelfth aspect of the present invention is a storage battery system according to the eleventh aspect, characterized in that the estimation means estimates that a failure has occurred in a single cell in a module battery when, in some of the plurality of module batteries, the difference between the actual measurement value and the performance value is positive and equal to or greater than a first threshold value, and estimates that the depth-of-discharge control value deviates from the actual depth of discharge of the storage battery when, in all of the plurality of module batteries, the difference between the actual measurement value and the performance value is positive and equal to or greater than the first threshold value.

[0027] A thirteenth aspect of the present invention is the storage battery system according to the twelfth aspect, wherein the estimation means estimates that the depth-of-discharge control value deviates from the actual depth of discharge of the storage battery when, for all of the plurality of module batteries, the difference between the actual measurement value and the performance value is positive and is equal to or greater than a second threshold value that is smaller than the first threshold value, and this is repeated multiple times.

[0028] A fourteenth aspect of the present invention is the storage battery system according to the eleventh aspect, wherein the estimation means estimates that a decrease in the degree of vacuum has occurred in the casing of a module battery when, for some of the plurality of module batteries, the difference between the actual measurement value and the performance value is negative and the absolute value of the difference is equal to or greater than a predetermined threshold, and estimates that the depth-of-discharge control value deviates from the actual depth of discharge of the storage battery when, for all of the plurality of module batteries, the difference between the actual measurement value and the performance value is negative and the absolute value of the difference is equal to or greater than the predetermined threshold.

[0029] A fifteenth aspect of the present invention is a storage battery system comprising: a storage battery composed of a plurality of module batteries connected in series; and a control system for the storage battery, wherein each of the plurality of module batteries includes an assembled battery having a plurality of unit cells connected thereto, and the assembled battery is housed in a housing having a vacuum insulation structure; and the control system comprises: a control means for controlling the storage battery based on a preset depth-of-discharge management value; and a comparison means for comparing, for each of the plurality of module batteries, an actual measured value of the temperature when a charge / discharge operation is performed in the storage battery with a previously estimated value of the temperature. and an estimation means for estimating the state of the storage battery based on the comparison result by the comparison means, wherein the estimated value is estimated based on the charge / discharge power value during a previous charge / discharge operation performed in the storage battery and the temperature of each of the plurality of module batteries, and the estimation means is capable of distinguishing and estimating the occurrence of any of the following abnormal states: a failure of a single cell in any of the plurality of module batteries; a deviation of the depth-of-discharge management value from the actual depth of discharge of the storage battery; and a decrease in the degree of vacuum in the casing of any of the plurality of module batteries.

[0030] A sixteenth aspect of the present invention is a storage battery system according to the fifteenth aspect, characterized in that the estimation means estimates that a failure has occurred in a single battery in a part of the plurality of module batteries when the difference between the actual measurement value and the estimated value is positive and equal to or greater than a first threshold value, and estimates that the depth-of-discharge control value deviates from the actual depth of discharge of the storage battery when the difference between the actual measurement value and the estimated value is positive and equal to or greater than the first threshold value for all of the plurality of module batteries.

[0031] A seventeenth aspect of the present invention is the storage battery system according to the sixteenth aspect, wherein the estimation means estimates that the depth-of-discharge control value deviates from the actual depth of discharge of the storage battery when, for all of the plurality of module batteries, the difference between the actual measured value and the estimated value is positive and is equal to or greater than a second threshold value that is smaller than the first threshold value, and this is repeated multiple times.

[0032] An 18th aspect of the present invention is a storage battery system according to the 15th aspect, characterized in that the estimation means estimates that a decrease in the degree of vacuum has occurred in the casing of a module battery when, in some of the plurality of module batteries, the difference between the actual measurement value and the estimated value is negative and the absolute value of the difference is equal to or greater than a predetermined threshold, and estimates that, in all of the plurality of module batteries, the difference between the actual measurement value and the estimated value is negative and the absolute value of the difference is equal to or greater than the predetermined threshold, the depth-of-discharge control value deviates from the actual depth of discharge of the storage battery.

[0033] A nineteenth aspect of the present invention is the storage battery system according to any one of the eleventh to eighteenth aspects, characterized in that the cells are sodium-sulfur batteries.

[0034] A twentieth aspect of the present invention is a storage battery system according to any one of the eleventh to eighteenth aspects, further comprising a simulation means for simulating the operation of the storage battery based on a pre-created operation plan, wherein the simulation means acquires an estimation result from the estimation means, and if the estimation result estimates that any of the abnormal conditions has occurred, modifies parameters used in the simulation according to the content of the abnormal condition.

[0035] According to the first to ninth and eleventh to nineteenth aspects of the present invention, it is possible to distinguish and estimate the causes of temperature changes that may occur when charging and discharging operations are repeated in a storage battery, which changes are different from those expected from previous charging and discharging operations under the same conditions, and therefore it is possible to reliably take measures according to each cause.

[0036] Furthermore, according to the tenth and twentieth aspects, the parameter settings used in the operation simulation of the storage battery can be reliably optimized, so that even if the storage battery is used continuously for a long period of time, the accuracy of the simulation can be maintained by setting parameters that reflect the latest state of the storage battery.

[0037] 1 is a diagram showing a schematic configuration of a storage battery system 100 according to a first embodiment. It is a schematic control block diagram for one module battery 12. It is a schematic vertical cross-sectional view showing a specific embodiment of the module battery 12. It is a diagram schematically showing the electrical connection mode of a plurality of cells 14 in an assembled battery 16 housed in a box 42. It is a block diagram showing the functional components of a storage battery control device 10 and an operation guidance device 11. It is a diagram showing a certain charge / discharge pattern PT according to a charge / discharge schedule, and a measured temperature profile PF1 when charge / discharge is performed according to the charge / discharge pattern PT. It is a diagram showing the charge / discharge pattern PT and a measured temperature profile PF2 when charge / discharge is performed according to the charge / discharge pattern PT. It is a diagram showing the charge / discharge pattern PT and a measured temperature profile PF3 when charge / discharge is performed according to the charge / discharge pattern PT. It is a block diagram showing the functional components of a storage battery control device 10 and an operation guidance device 11 according to a second embodiment. 1 is a diagram showing a charge / discharge pattern PT, a temperature measurement profile PF4 when charge / discharge is performed according to the charge / discharge pattern PT, and a temperature estimation profile PF4α estimated based on the charge / discharge schedule and actual values ​​of charge / discharge power and battery temperature.

[0038] 1 is a diagram showing a schematic configuration of a storage battery system 100 according to a first embodiment of the present invention. The storage battery system 100 mainly includes a storage battery 100B and a storage battery control system 100C.

[0039] The storage battery 100B is configured as a module string 13 in which a large number of module batteries 12 are connected in series. Although simplified in FIG. 1 , in reality, the multiple module batteries 12 that make up the module string 13 are housed in a predetermined storage vessel, also called a container. The multiple module strings 13 may also be connected in series and / or in parallel.

[0040] The battery control system 100C has as its main components a battery control device 10 that controls the operation of the battery 100B, and an operation guidance device 11 that handles processing related to the operation of the battery 100B, such as simulating an operation plan for the battery 100B.

[0041] Fig. 2 is a schematic control block diagram for one battery module 12. Fig. 3 is a schematic vertical cross-sectional view showing one specific embodiment of the battery module 12.

[0042] Each module battery 12 that makes up the module string 13 generally has a configuration in which an assembled battery 16 made up of multiple cells 14 is housed in a housing 18. Although shown separately in Figure 2 for convenience, the housing 18 of each module battery 12 further comprises a heat sink 22 and a heater 24 as temperature maintaining means 20 for maintaining the temperature of the module battery 12 (more specifically, the temperature inside the housing 18) within a certain allowable range (operating temperature range) during operation. A temperature sensor 26 for measuring the temperature inside the housing 18 is also provided.

[0043] 3 does not necessarily reflect the actual location of the temperature sensor 26. The actual location of the temperature sensor 26 within the housing 18 may be determined as appropriate, and multiple temperature sensors 26 may be arranged in one housing 18.

[0044] In this embodiment, the battery control device 10 controls the charge / discharge operation and temperature (battery temperature) of each module battery 12. More specifically, the charge / discharge operation of the module battery 12 is controlled by a charge / discharge control unit 2 ( FIG. 5 ) described below that is provided in the battery control device 10. Meanwhile, the battery temperature is controlled by the battery control device 10 controlling the operation of the heat dissipation device 22 and heater 24 based on the measurement value of the temperature sensor 26.

[0045] As shown in Fig. 3, the housing 18 is made up of a box body 42 and a lid body 44 that closes the opening of the box body 42. Fig. 4 is a diagram schematically showing the electrical connection state of the plurality of cells 14 in the battery assembly 16 housed in the box body 42.

[0046] The box 42 has a generally rectangular parallelepiped shape and includes four side walls (first side wall 68a to fourth side wall 68d) and one bottom wall, with an opening on the side facing the bottom wall. The box 42 is placed and fixed on a horizontal base 40 made of, for example, steel, with the opening facing vertically upward.

[0047] Box 42 is made of, for example, a stainless steel plate and has a box-like shape with a hollow portion 48. Cover 44 includes a top wall 52 and a canopy 54. Like box 42, cover 44 is also made of, for example, a stainless steel plate and has a box-like shape with a hollow portion 56.

[0048] The hollow portion 48 of the box 42 and the hollow portion 56 of the lid 44 are both airtightly sealed spaces, and are structured to be able to communicate with the outside space by means of vacuum valves (not shown). These hollow portions 48 and 56 are each evacuated with the vacuum valves open (the air in the hollow portions is discharged to the outside space), and then the vacuum valves are closed to disable communication with the outside space. This allows the box 42 and the lid 44 to have a vacuum insulation structure.

[0049] The plurality of cells 14 that make up the battery pack 16 are housed in the box 42 with their axial direction aligned with the vertical direction (the direction from the bottom wall of the box 42 toward the opening).

[0050] In this embodiment, the unit cells 14 are assumed to be sodium-sulfur batteries (NaS batteries) that use sulfur as a positive electrode active material and metallic sodium as a negative electrode active material. In a NaS battery, for example, sulfur impregnated in graphite felt and metallic sodium are housed in a cylindrical aluminum container (cell) while being separated by a solid electrolyte tube made of β-alumina.

[0051] During discharge from the battery module 12, an exothermic reaction occurs in each cell 14, in which metallic sodium reacts with sulfur to produce sodium polysulfide, causing the temperature of the battery module 12 to rise. However, the heat resistance of the components of the NaS battery cell 14, particularly the solid electrolyte tube, aluminum container, and α-alumina insulating ring interposed between the two when they are joined, as well as the glass joints, TCB joints, and aluminum welds that seal between these components, is limited. Furthermore, if these components come into contact with highly chemically active sodium, sulfur, sodium polysulfide, etc. at high temperatures for a long period of time, corrosion and deterioration are likely to occur. Therefore, it is undesirable for the temperature of the battery module 14 to exceed a certain value due to continued discharge, i.e., the continued exothermic reaction.

[0052] On the other hand, the conductivity of sodium ions in the solid electrolyte β-alumina, and the conductivity of the positive electrode active material sulfur and sulfur-impregnated graphite felt, increase with increasing temperature. In other words, the higher the temperature due to heat generated by discharge, the lower the internal resistance of the battery module 12. Therefore, from the perspective of charge / discharge efficiency, it is preferable to operate the battery module 12 at high temperatures. Furthermore, considering the diffusibility of the active material in the positive electrode and the equilibrium of the exothermic reaction during discharge, operation at low temperatures is disadvantageous in terms of charge recovery.

[0053] As described above, in consideration of the utilization of heat generated by the exothermic reaction during discharge and the constraints imposed by the characteristics of the materials and components that make up the NaS battery, the module battery 12 is generally operated within a temperature range of 280° C. to 350° C. Therefore, in this embodiment, this temperature range is considered to be the operating temperature range of the module battery 12.

[0054] In some cases, the operating temperature range of the battery module 12 is set to 305°C to 360°C, prioritizing reducing the internal resistance of the battery and improving charge / discharge recovery.

[0055] The battery assembly 16 is composed of one or more blocks 64, each of which is composed of several cells 14. Although not shown in Fig. 3, a positive electrode external terminal 60 and a negative electrode external terminal 62 are provided on the outside of the box 42, and the one or more blocks 64 are connected in series from the positive electrode external terminal 60 to the negative electrode external terminal 62. Each block 64 is composed of two or more strings 66, each of which has two or more cells 14 connected in series, connected in parallel.

[0056] However, although FIG. 4 shows the battery assembly 16 connected to the positive electrode external terminal 60 and the negative electrode external terminal 62 that are respectively arranged on the outside of the opposing first side wall 68 a and second side wall 68 b of the box body 42 that is rectangular in plan view, and the battery assembly 16 connected along the opposing third side wall 68 c and fourth side wall 68 d, this is merely a schematic diagram, and the actual arrangement of the battery assembly 16 and the connection between the positive electrode external terminal 60 and the negative electrode external terminal 62 are not limited to this.

[0057] A module string 13, each of which has the above-described configuration of module batteries 12, is connected to the DC side of a known PCS (AC-DC converter: Power Conversion System) via a charge / discharge current detector (neither of which is shown). The AC side of the PCS is connected to a load, an external system, or the like via a transformer. The charge / discharge current detector measures the charge / discharge current flowing through the storage battery 100B, and a known device such as the Hall current detector disclosed in Patent Document 5 can be used.

[0058] <Temperature Maintenance Means> As shown in Figure 3, heaters 24 are installed on the inner bottom surface and inner wall surfaces of the box 42 as part of the temperature maintenance means 20. The heaters 24 are used to maintain the module batteries 12 at a predetermined temperature during standby when no discharge is occurring, or to raise the temperature of a module battery 12 (temperature inside the housing 18) in order to operate a module battery 12 that has been stopped. The heaters 24 are resistance heaters that are heated by external current, and their ON / OFF operation is performed by a mechanical relay. The ON / OFF operation of the heater 24 is controlled by a heater control unit 3 (Figure 5), described below, provided in the battery control device 10.

[0059] The gaps between the box 42 and the battery assembly 16 and the gaps between the cells 14 are filled with sand 46. The sand 46 also covers the openings of the box 42. The sand 46 not only transfers heat from the heater 24 to the cells 14 and absorbs heat generated by the cells 14, but also absorbs any contents that may leak out of the cells 14. Examples of the sand 46 include expanded vermiculite and silica sand.

[0060] As described above, the housing 18 is also provided with a heat dissipation device 22 as temperature maintenance means 20. Because the reaction between metallic sodium and sulfur that occurs in each cell 14 during discharge from the module battery 12 is an exothermic reaction, the temperature of the module battery 12 rises as discharge continues. The heat dissipation device 22 is used to dissipate heat from within the housing 18 in order to suppress this temperature rise and ensure the discharge time.

[0061] As shown in FIG. 3, the heat dissipation device 22 includes a metal duct 72 , an electrically insulating plate member 74 , and a fan 76 for circulating the fluid 70 through the duct 72 .

[0062] In the duct 72, a fluid introduction section 78, a heat transport section 80, and a heat release section 82 are arranged in this order from upstream to downstream, forming a flow path for the fluid 70. The fluid 70 flows through the duct 72 as shown by arrows AR. The plate member 74 is embedded in the sand material 46 between the battery assembly 16 and the duct 72.

[0063] The fluid introduction section 78 is a section provided along the first side wall 68a of the box body 42 and adjacent to the fan 76. However, the fluid introduction section 78 and the first side wall 68a of the box body 42 are spaced apart from each other by the interposition of a buffer material 84. The buffer material 84 preferably has a heat insulating function.

[0064] When the fan 76 is operated (turned on), the fluid 70 is introduced from the fluid inlet 78 into the duct 72. The operation of the fan 76 is controlled by a heat dissipation control unit 4 ( FIG. 5 ) described below that is provided in the battery control device 10. The fluid 70 may be a gas such as air, nitrogen gas, or helium gas.

[0065] More specifically, the fluid introduction unit 78 has a fluid supply unit 86 to which the fluid 70 is supplied from the fan 76, and a fluid guide unit 88 that communicates with the fluid supply unit 86 and guides the fluid 70 supplied to the fluid supply unit 86 to the heat transporting unit 80. The fluid supply unit 86 has an air chamber 90. Preferably, the duct of the air chamber 90 has a shape that gradually becomes larger toward the fluid guide unit 88.

[0066] The heat transporting part 80 is a part that is mainly installed between the top wall 52 of the lid 44 and the box 42. The heat generated in the box 42 is transported downstream by the fluid 70 that flows through the heat transporting part 80.

[0067] The lower surface 80a of the heat transporting part 80 faces the battery pack 16 (and the plate member 74), and the lower surface 80a is provided with a plurality of metal fins 92 extending toward the battery pack 16. The fins 92 are provided for the purpose of further improving the efficiency of heat transfer from the inside of the box body 42 to the heat transporting part 80.

[0068] Preferably, a plurality of support parts (not shown) for maintaining the shape of the pipe 94 are installed inside the pipe 94 of the heat transporting part 80. As such support parts, flat, corrugated or strip-shaped members can be used.

[0069] The heat release portion 82 is a portion that is open to the outside and is provided in contact with the second side wall 68b of the box body 42. When the fluid 70 is released from the heat release portion 82, heat generated within the housing 18 is released (dissipated) to the outside.

[0070] In the heat dissipation device 22 having the above configuration, as the fan 76 is driven, cooled (e.g., room temperature) fluid 70 is supplied from the fluid inlet 78 into the duct 72. Accordingly, heat generated within the housing 18 (particularly within the box 42) is transferred to the fluid 70 flowing through the heat transporting section 80, causing the fluid 70 to heat up. The heated fluid 70 is released to the outside through the heat releasing section 82, thereby dissipating heat from the housing 18. As described above, both the box 42 and the lid 44 have a thermally insulated structure, and this forced heat dissipation (cooling) efficiently cools the inside of the housing 18. This makes it possible to maintain the temperature of the module battery 12 within the operating temperature range, even when the discharge output is high or the discharge time is long, and to continue operating the module battery 12 in an appropriate operating environment.

[0071] <Storage Battery Control Device and Operation Guidance Device> Next, a description will be given of the storage battery control device 10 and the operation guidance device 11. Fig. 5 is a block diagram showing the functional components of the storage battery control device 10 and the operation guidance device 11.

[0072] The battery control device 10 can be realized by a general-purpose or dedicated computer (control computer) equipped with a CPU, memory, storage, etc. By loading and executing a predetermined program stored in the storage into the CPU, the battery control device 10 mainly includes, as functional components, a charge / discharge schedule acquisition unit 1, a charge / discharge control unit 2, a heater control unit 3, a heat dissipation control unit 4, an operation history accumulation unit 5, and a battery state estimation unit 6.

[0073] The charge / discharge schedule acquisition unit 1 acquires a schedule for charging and discharging (charge / discharge schedule) for the storage battery 100B, and provides the charge / discharge schedule to the charge / discharge control unit 2, the heater control unit 3, and the heat dissipation control unit 4.

[0074] In this embodiment, the charge / discharge schedule refers to an operation plan (operation plan) related to the charging and discharging schedule for the storage battery 100B, which is created in the storage battery control system 100C or externally, and which has been determined to be operable in advance as a result of a simulation in the operation guidance device 11.

[0075] If the charge / discharge schedule acquisition unit 1 has a function for creating an operation plan realized by the above program, the operator of the battery control device 10 may create the charge / discharge schedule using input means such as a mouse, keyboard, or touch panel (not shown) provided on the control computer.

[0076] The charge / discharge schedule includes, for example, the start and end times of charging and discharging, the output during discharging, the charge amount during charging, and the operating temperature range.

[0077] The charge / discharge control unit 2 controls the charging and discharging operations of the storage battery 100B in accordance with the contents of the charge / discharge schedule. In general, the charge / discharge control unit 2 connects the storage battery 100B to the outside when the discharge start time described in the charge / discharge schedule arrives, starts discharging from each module battery 12 to the outside, and then, when the discharge end time arrives, disconnects the storage battery 100B from the outside and ends the discharging. The charge / discharge control unit 2 also connects the storage battery 100B to the outside when the charge start time described in the charge / discharge schedule arrives, starts charging the storage battery 100B from the outside, and then, when the charge end time arrives, disconnects the storage battery 100B from the outside and ends charging each module battery 12 from the outside.

[0078] The charge and discharge control unit 2 controls the charging and discharging operations of the storage battery 100B by managing the depth of discharge of the entire storage battery 100B. The depth of discharge is an index that indicates the degree of discharge of the cells 14 that make up each module battery 12 in the storage battery 100B. When the depth of discharge is 0%, the module battery 12 is at the end of charge, and when the depth of discharge is 100%, the module battery 12 is at the end of discharge.

[0079] However, when multiple module batteries 12 are connected in series to form a module string 13 as shown in Fig. 1, the depth of discharge of the cells 14 that make up each module battery 12 is generally uniform. Therefore, in this embodiment, the depth of discharge of the entire storage battery 100B is expressed by a single common value, and this value is referred to as the depth of discharge control value.

[0080] In principle, the charge / discharge control unit 2 sets the depth of discharge of the storage battery 100B at 0% when it reaches the end of charge, and calculates a depth of discharge control value by successively increasing or decreasing the charge / discharge amount converted from the charge / discharge current value detected by the charge / discharge current detector from the initial value each time a charge / discharge operation is performed, and stores the latest value.The charge / discharge control unit 2 then controls the charge / discharge operation of the storage battery 100B so that the depth of discharge control value remains between 0%, which corresponds to the end of charge, and 100%, which corresponds to the end of discharge.A known control method can be appropriately applied to control the charge and discharge operations in the charge / discharge control unit 2, including the management of the depth of discharge.

[0081] The charge / discharge control unit 2 also monitors the measurement values ​​of the temperature sensors 26 provided in each module battery 12. If the measurement value obtained from any of the temperature sensors 26 is within the operating temperature range but approaches the upper or lower limit of that range, or if the operating temperature range is not met, the charge / discharge control unit 2 stops or postpones charging / discharging in accordance with the contents of the charge / discharge schedule.

[0082] The heater control unit 3 controls the operation (ON / OFF switching) of the heater 24 during a heating control period described in a heater schedule that is set based on the charge / discharge schedule.

[0083] The heat radiation control unit 4 controls the operation (ON / OFF switching) of the fan 76 during a heat radiation control period described in a heat radiation schedule that is set based on the charge / discharge schedule.

[0084] The operational performance accumulation unit 5 accumulates, as log data, the actual values ​​(actual charge / discharge values) of the charge / discharge time and charge / discharge output when charging / discharging is actually performed on the storage battery 100B based on the charge / discharge schedule (i.e., when the storage battery 100B is operated), together with the measured values ​​(actual temperature values) of the temperatures of the individual module batteries 12 measured by the temperature sensors 26 during such operation.

[0085] While the storage battery 100B continues to operate according to a certain charge / discharge schedule, the battery state estimation unit 6 monitors the temperatures of the individual module batteries 12 measured by the temperature sensors 26. The battery state estimation unit 6 then compares the monitored temperature values ​​(real-time measured values) with actual temperature values ​​from past charge / discharge results accumulated in the operation history accumulation unit 5, which were obtained when charging / discharging was performed under the same charge / discharge conditions (charge / discharge time and charge / discharge output) as those set in the ongoing charge / discharge schedule, and estimates the state of the storage battery 100B based on the results of the comparison.

[0086] Details will be described later, but the results of the estimation by the battery state estimation unit 6 are used to detect failures in the single cells 14 in the module batteries 12 that make up the storage battery 100B, and to correct the discharge depth control value held in the charge / discharge control unit 2.

[0087] Although it is desirable to compare the monitored value with the actual temperature value in real time, it is also possible to compare the recorded monitored value with the actual temperature value collectively after charge / discharge is performed, for example, once a day. Even in this case, it is possible to obtain the effects of detecting a malfunction and correcting the depth-of-discharge control value.

[0088] Preferably, when the storage battery 100B has been operated under a certain charge / discharge condition multiple times, the battery state estimation unit 6 compares the battery temperature during the most recent charge / discharge operation, thereby making it possible to estimate the latest state change that has occurred in the storage battery 100B.

[0089] Like the battery control device 10, the operational guidance device 11 can be realized by a general-purpose or dedicated computer (control computer) equipped with a CPU, memory, storage, etc. A predetermined program stored in the storage is read into the CPU and executed, and the operational guidance device 11 mainly includes, as functional components, an operation plan acquisition unit 7 and a simulation execution unit 8.

[0090] The operation plan acquisition unit 7 acquires an operation plan (charge / discharge plan) for the storage battery 100B. The operation plan is created by setting a charge / discharge period and a charge / discharge output for a predetermined plan period.

[0091] In this embodiment, a day (0:00 to 24:00) is divided into 30-minute unit time segments, also called "frames," and an operational plan is created by setting the charge / discharge output for each of the 48 frames each day for two weeks.

[0092] The operation plan acquisition unit 7 may acquire an operation plan created outside the operation guidance device 11, such as by the charge / discharge schedule acquisition unit 1 of the battery control device 10, or the operation guidance device 11 itself (for example, the operation plan acquisition unit 7) may have an operation plan creation function, and an operation plan created by an operator of the operation guidance device 11 using this creation function may be acquired.

[0093] The simulation execution unit 8 executes a simulation of the charge / discharge operation of the storage battery 100B in accordance with the operation plan, and determines whether or not the charge / discharge operation based on the operation plan can be executed (whether or not the operation plan can be operated). In this embodiment, only the operation plans determined to be "operable" by the simulation execution unit 8 are included in the charge / discharge schedule acquired by the charge / discharge schedule acquisition unit 1 of the storage battery control device 10. When setting the initial value of the remaining capacity used in the simulation, the depth-of-discharge management value held in the charge / discharge control unit 2 is referenced.

[0094] In addition, if the battery state estimation unit 6 of the battery control device 10 estimates that there is an abnormality in the state of the storage battery 100B based on the battery temperature as described above, the simulation execution unit 8 acquires that information (temperature abnormality estimation information) and uses it to correct the simulation parameters.

[0095] <Estimation of Battery State> Next, we will explain the estimation of the state of the storage battery 100B based on the battery temperature, which is performed by the battery state estimation unit 6 of the storage battery control device 10. The battery state estimation unit 6 estimates three types of abnormal states that can occur in the storage battery 100B: a failure of a cell 14 constituting the module battery 12 (single cell failure), a deviation between the depth-of-charge / discharge control value and the actual depth of discharge of the storage battery 100B (depth-of-discharge control value deviation), and a decrease in the degree of vacuum in the housing 18 of the module battery 12 (at least one of the box 42 and the lid 44) ​​(enclosure vacuum decrease).

[0096] 4, in a battery module 12, a string 66 is formed by connecting a plurality of battery cells 14 in series, and a block 64 is formed by connecting a plurality of strings 66 in parallel. In a battery module 12 configured in this way, a battery cell 14 may fail in open mode due to accidental factors such as manufacturing variations. When a failure occurs in a battery cell 14 of a battery module 12, current stops flowing in the string 66 to which that battery cell 14 belongs (the failed string).

[0097] In this case, if the charge and discharge conditions of the module battery 12 in which the faulty cell 14 is located are the same before and after the failure, the cells 14 belonging to strings 66 other than the faulty string (healthy strings) in the module battery 12 will be discharged to a deeper depth than before the failure. Since the internal resistance of a cell 14 increases as the depth of discharge increases, the battery temperature of the module battery 12 in which the faulty cell 14 is located will be higher than before the failure. Furthermore, if the charge and discharge conditions of all module batteries 12 constituting the module string 13 in the storage battery 100B are the same before and after the failure, the battery temperature of the module battery 12 in which the faulty cell 14 is located will be higher than that of the other module batteries 12 in which the cell 14 is not faulty.

[0098] However, it is extremely rare for multiple cells 14 to fail simultaneously when the storage battery 100B is operating normally, and it is unlikely that failures will occur simultaneously in the cells 14 of all the module batteries 12 that make up the module string 13 in the storage battery 100B.

[0099] [Depth of discharge control value deviation] The depth of discharge control value is a value calculated by the charge / discharge control unit 2 to manage the depth of discharge in the storage battery 100B. However, as the charge / discharge operations in the storage battery 100B are repeatedly performed, errors that occur in the charge / discharge current values ​​detected by the charge / discharge current detector are accumulated, which can cause the depth of discharge control value to deviate from the actual depth of discharge in the storage battery 100B.

[0100] For example, if the actual depth of discharge of the storage battery 100B at the start of discharge is higher than the depth of discharge control value at the start of discharge held by the charge / discharge control unit 2, the actual internal resistance of the module battery 12 will be higher than the value estimated from the depth of discharge control value, and the battery temperature after the start of discharge will also be higher than expected. Therefore, even if the battery temperature is determined to be within the allowable range in a charge / discharge operation in simulation, the battery temperature may actually exceed the upper limit of the allowable range.

[0101] Conversely, if the actual depth of discharge of the storage battery 100B at the start of discharge is lower than the depth of discharge control value at the start of discharge held by the charge / discharge control unit 2, the actual internal resistance of the module battery 12 will be lower than the value estimated from the depth of discharge control value, and the battery temperature after the start of discharge will also be lower than estimated. Therefore, even if the simulation indicates that the battery temperature will be within the allowable range even without heating by the heater 24, in reality, the battery temperature may exceed the lower limit of the allowable range if heating by the heater 24 is not performed.

[0102] These events occur when the actual depth of discharge at the start of discharge deviates from the depth of discharge control value.

[0103] Since NaS batteries hardly self-discharge, and the depth of discharge of each of the individual cells 14 in each of the multiple module batteries 12 that make up the storage battery 100B changes roughly uniformly, temperature changes due to deviations in the depth of discharge control values ​​can occur simultaneously in all of the module batteries 12 that make up the storage battery 100B.

[0104] [Case Vacuum Degree Decrease] In order to ensure thermal insulation, the box 42 and lid 44 constituting the case 18 of each module battery 12 constituting the storage battery 100B have a vacuum insulation structure as described above. However, as the storage battery 100B continues to be used, in extremely rare cases, a manufacturing defect in the box 42 or lid 44 or a defect in the vacuum valve may cause the degree of vacuum in the box 42 or lid 44 to abnormally decrease, resulting in a deterioration in thermal insulation (case vacuum degree decrease). In a module battery 12 in which such a decrease in case vacuum has occurred, a decrease in peak battery temperature occurs over time.

[0105] More specifically, even in a normal vacuum valve, a minute amount of air flows in. Therefore, even in a normal module battery 12, the degree of vacuum decreases slightly over time. The above-mentioned decrease in the degree of vacuum in the enclosure refers to an event in which a significant decrease in the degree of vacuum occurs, rather than such a slight decrease.

[0106] However, although a slight decrease in vacuum level can occur simultaneously in all of the module batteries 12 that make up the module string 13 in the storage battery 100B, a decrease in the housing vacuum level is merely an accidental event, and it is unlikely that such a decrease in the housing vacuum level will occur simultaneously in all of the module batteries 12 that make up the module string 13 in the storage battery 100B.

[0107] [Estimation Pattern] While the storage battery 100B is operating in accordance with the charge / discharge pattern PT, the operation history accumulation unit 5 sequentially accumulates the charge / discharge power and battery temperature as log data for each of the module batteries 12 that make up the storage battery 100B. The battery state estimation unit 6 then monitors the battery temperature (real-time measurement value) of each module battery 12 and compares the monitored battery temperature value with the actual battery temperature value (same condition temperature actual value) recorded in the log data for a past charge / discharge operation performed under the same charge / discharge conditions as the ongoing charge / discharge operation.

[0108] Based on the results of this comparison, the battery state estimation unit 6 makes the following estimations regarding a battery failure, a deviation in the depth of discharge control value, and a decrease in the degree of vacuum in the casing.

[0109] (Estimation 1) In only some of the module batteries 12, the difference between the real-time measurement value and the actual temperature value under the same conditions is positive and is equal to or greater than the first threshold value → a failure has occurred in a cell 14 in that module battery 12; (Estimation 2) In all of the module batteries 12, the difference between the real-time measurement value and the actual temperature value under the same conditions is positive and is equal to or greater than the first threshold value → a depth-of-discharge control value deviation has occurred, in which the depth-of-discharge control value is smaller than the actual discharge intensity; (Estimation 3) In all of the module batteries 12, the difference between the real-time measurement value and the actual temperature value under the same conditions is positive and is equal to or greater than the second threshold value, and this is repeated multiple times → a depth-of-discharge control value deviation has occurred, in which the depth-of-discharge control value is smaller than the actual discharge intensity; (Estimation 4) In only some of the module batteries 12, the difference between the real-time measurement value and the actual temperature value under the same conditions is negative and the absolute value is equal to or greater than the third threshold value → a decrease in the housing vacuum has occurred in that module battery 12; (Estimation 5) The difference between the real-time measurement values ​​for all module batteries 12 and the actual temperature values ​​under the same conditions is negative, and the absolute value is greater than the third threshold value → a deviation in the depth of discharge control value has occurred, where the depth of discharge control value is greater than the actual discharge intensity; (Estimation 6) None of (Estimation 1) to (Estimation 5) is true → neither a failure of a single battery 14, a deviation in the depth of discharge control value, nor a decrease in the vacuum level of the housing has occurred.

[0110] The first to third thresholds are set in advance and stored in a memory or storage (not shown) of the battery control device 10. The second threshold is assumed to be smaller than the first threshold. For example, the first threshold is 1°C, and the second and third thresholds are each 0.1°C.

[0111] First, (Estimation 1) and (Estimation 2) will be described with reference to Fig. 6. Fig. 6 is a diagram showing a certain charge / discharge pattern PT according to a charge / discharge schedule, and a profile (measured temperature profile) PF1 of actual battery temperature values ​​measured by the temperature sensor 26 in one module battery 12 of the storage battery 100B when charging and discharging are performed according to the charge / discharge pattern PT.

[0112] In the charge-discharge pattern PT shown in Fig. 6, three discharges, Discharge (1) to Discharge (3), are performed at time intervals Δt (for example, Δt = 24 hours) with the same discharge time and discharge power. For simplicity of explanation, it is also assumed that the depth of discharge (remaining capacity) immediately before Discharge (1) to Discharge (3) is the same.

[0113] In this case, for Discharge (2), Discharge (1) corresponds to the most recent charge / discharge operation under the same charge / discharge conditions. Therefore, as Discharge (2) progresses, the battery state estimation unit 6 compares the monitored battery temperatures for all module batteries 12 with the changes in battery temperature during Discharge (1), which was most recently performed under the same charge / discharge conditions. Similarly, for Discharge (3), Discharge (2) corresponds to the most recent charge / discharge operation under the same charge / discharge conditions. Therefore, as Discharge (3) progresses, the battery state estimation unit 6 compares the monitored battery temperatures for all module batteries 12 with the changes in battery temperature during Discharge (2), which was most recently performed under the same charge / discharge conditions.

[0114] In Figure 6, even though the charge and discharge conditions for discharges (1) to (3) are all the same, in the temperature measurement profile PF1, the peak battery temperature T1 during discharge (2) is higher by ΔTa than the peak battery temperature T0 during discharge (1).

[0115] 6, if it is determined that in only a certain portion of the battery modules 12, there is a temperature difference ΔTa between the peak battery temperature T1 (real-time measurement value) in the ongoing discharge (2) and the peak battery temperature T0 (actual battery temperature value) in the most recent discharge (1), and that this temperature difference ΔTa is higher than the first threshold, the battery state estimation unit 6 estimates that a failure occurred in a battery cell 14 at time t1 between discharge (1) and discharge (2) in the battery module 12 where this temperature difference ΔTa occurred. In other words, the battery state estimation unit 6 determines that (Inference 1) is true.

[0116] On the other hand, as described above, it is extremely rare for all of the cells 14 to fail at the same time, so if a temperature difference ΔTa that exceeds the first threshold occurs in all of the battery modules 12, it is reasonable to determine that this is an event unrelated to a failure of the battery cells 14. Therefore, if a temperature difference that exceeds the first threshold occurs between the peak battery temperature T1 and the peak battery temperature T0 in all of the battery modules 12, the battery state estimation unit 6 estimates that a deviation in the depth-of-discharge control value has occurred in the storage battery 100B. In other words, the battery state estimation unit 6 determines that (Estimation 2) is true.

[0117] Since the deviation in the depth of discharge control value in storage battery 100B occurs when the depth of discharge is maintained approximately uniform, the situation where (Estimation 1) holds and the situation where (Estimation 2) hold are clearly distinguished.

[0118] Next, (Estimation 3) will be described with reference to Fig. 7. Fig. 7 is a diagram showing the same charge / discharge pattern PT as Fig. 6, together with a temperature measurement profile PF2 of one module battery 12 of the storage battery 100B when charging and discharging are performed according to the charge / discharge pattern PT.

[0119] Discharges (1) to (3) in the charge / discharge pattern PT are performed under the same charge / discharge conditions, and in the temperature measurement profile PF2, peaks Pa, Pb, and Pc appear corresponding to each of these discharges, but the peak battery temperatures (T0, T2, T3) increase as time passes. However, the difference in peak battery temperatures between adjacent peaks is smaller than the temperature difference ΔTa in the temperature measurement profile PF1 shown in Figure 6 and is at least less than the first threshold value.

[0120] In the battery state estimation unit 6, as discharge (2) progresses, the peak battery temperature T2 (real-time measurement value) is compared with the peak battery temperature T0 (actual battery temperature value) in the most recent discharge (1), but because the difference between the two temperatures is smaller than the first threshold, it is not estimated that a failure has occurred in a cell 14 in the target module battery 12. Similarly, as discharge (3) progresses, the peak battery temperature T3 (real-time measurement value) is compared with the peak battery temperature T2 (actual battery temperature value) in the most recent discharge (2), but because the difference between the two temperatures is also smaller than the first threshold, it is not estimated at this point that a failure has occurred in a cell 14 in the target module battery 12.

[0121] However, while a discharge operation under the same discharge conditions should result in the same battery temperature, if such a temperature difference, even if small, occurs in all battery modules 12 each time a discharge is performed, it is possible that a deviation in the depth-of-discharge control value has occurred. Therefore, if the battery state estimation unit 6 determines that a temperature difference of at least the second threshold value has repeatedly occurred in all battery modules 12, it estimates that a deviation in the depth-of-discharge control value has occurred. In other words, the battery state estimation unit 6 determines that (Inference 3) is true.

[0122] Next, (Estimation 4) and (Estimation 5) will be explained with reference to Fig. 8. Fig. 8 shows the same charge / discharge pattern PT as Fig. 6, together with the temperature measurement profile PF3 of one module battery 12 of the storage battery 100B when charging and discharging are performed according to the charge / discharge pattern PT. In the case shown in Fig. 8, it is assumed that an abnormality in the vacuum valve, which is a cause of a decrease in the degree of vacuum, occurred in the housing 18 of the module battery 12 at time t2 between discharge (1) and discharge (2).

[0123] 8, discharges (1) to (3) in the charge / discharge pattern PT are performed under the same charge / discharge conditions, and peaks Pa, Pd, and Pe appear in the temperature measurement profile PF3. However, in the temperature measurement profile PF3, contrary to the temperature measurement profile PF2 shown in FIG. 7, the peak battery temperatures (T0, T4, T5) decrease as time passes.

[0124] Therefore, when it is determined that a decrease in peak battery temperature such that the absolute value of the temperature difference between adjacent peaks is higher than the third threshold value has occurred over time (repeatedly) only in some module batteries 12, the battery state estimation unit 6 estimates that a decrease in the housing vacuum has occurred in the module battery 12 where such a temperature decrease has occurred. In other words, the battery state estimation unit 6 determines that (Inference 4) is true.

[0125] In contrast, as described above, it is extremely rare for a decrease in the degree of vacuum in the housing to occur simultaneously in all battery modules 12. Therefore, if a decrease in peak battery temperature over time, such as that shown in Figure 8, occurs in all battery modules 12, it is reasonable to determine that this is an event unrelated to a decrease in the degree of vacuum in the housing. Therefore, if it is determined that a decrease in peak battery temperature over time (repeatedly) occurs in all battery modules 12 such that the absolute value of the temperature difference between adjacent peaks is higher than the third threshold, the battery state estimation unit 6 estimates that a deviation in the depth-of-discharge control value has occurred in the storage battery 100B. In other words, the battery state estimation unit 6 determines that (Estimation 5) is true.

[0126] On the other hand, if the comparison of the real-time measured battery temperature values ​​of each battery module 12 with the actual battery temperature values ​​recorded in the log data by the operation performance accumulation unit 5 results in none of (Inference 1) to (Inference 5) being true, it means that no single battery failure, deviation in the depth-of-discharge control value, or decrease in the degree of vacuum in the housing has occurred. In such cases, the battery state estimation unit 6 determines that (Inference 6) is true.

[0127] The results of the estimation by the battery state estimation unit 6 are displayed on a display unit (not shown) in a manner recognizable to the operator of the battery control device 10, and can also be output as data or a printout, and are used for correcting the depth-of-discharge control value in the charge / discharge control unit 2, and for repairing or maintaining the module batteries 12 in the storage battery 100B. This makes it possible to reliably perform repairs or maintenance of the module batteries 12 at appropriate times according to the estimation results. For example, the processing disclosed in Patent Documents 2 to 4 may be performed at appropriate times, or a display may be displayed to prompt the operator of the battery control device 10 to perform such processing.

[0128] In addition, the battery state estimation unit 6 passes information related to the estimation (temperature abnormality estimation information) to (the simulation execution unit 8 of) the operational guidance device 11. The simulation execution unit 8 of the operational guidance device 11, which has acquired the temperature abnormality estimation information, appropriately modifies the simulation parameters used when simulating the operation plan for the storage battery 100B based on the temperature abnormality estimation information. This makes it possible to execute a simulation that is in line with the latest state of the storage battery 100B, thereby suppressing a decrease in simulation accuracy. Alternatively, the depth-of-discharge management value corrected in the charge / discharge control unit 2 may be passed to the operational guidance device 11.

[0129] For example, the initial depth of discharge or remaining capacity value when performing a simulation is set based on the depth of discharge control value. Therefore, if a depth of discharge control value smaller than the actual depth of discharge is used as the initial depth of discharge value in the simulation, the actual internal resistance of the module battery 12 will be higher than assumed in the simulation, and the battery temperature will also be higher than assumed in the simulation. Therefore, even if the battery temperature during a charge / discharge operation is within the allowable range in the simulation, the battery temperature may actually exceed the upper limit of the allowable range.

[0130] When the simulation parameters are modified as in this embodiment, problems caused by discrepancies between the simulation in the operational guidance device 11 and the actual operation can be preferably avoided, and the storage battery 100B can be operated safely.

[0131] As described above, according to this embodiment, it is possible to distinguish and estimate abnormal conditions that may occur when charging and discharging operations are repeated in a storage battery, and that are causing temperature changes that differ from those expected from previous charging and discharging operations under the same conditions, and therefore it is possible to reliably take measures according to each cause.

[0132] In particular, since the parameter settings used in the battery operation simulation can be reliably optimized, even when the battery is used continuously for a long period of time, the accuracy of the simulation can be maintained by setting parameters that reflect the latest state of the battery.

[0133] <Second embodiment> In the above-described embodiment, the battery state estimation unit 6 provided in the storage battery control device 10 compares the real-time measurement value of the battery temperature with the past actual value, and makes an estimation regarding an abnormality based on the battery temperature based on the result. However, in the present embodiment, the battery state estimation unit 6 is provided in the operation guidance device 11, and the battery state estimation unit 6 compares the real-time measurement value of the battery temperature with an estimated temperature estimated from the past actual value, and makes an estimation regarding an abnormality based on the battery temperature (i.e., a failure of a single cell, a deviation in the depth of discharge control value, or a decrease in the vacuum degree of the housing) based on the result.

[0134] The configuration of the storage battery 100B in this embodiment is the same as that in the first embodiment. Meanwhile, Fig. 9 is a block diagram showing functional components of the storage battery control device 10 and the operation guidance device 11 in this embodiment.

[0135] The configuration of the battery control device 10 in this embodiment is the same as that in the first embodiment, except that the battery state estimation unit 6 is not included.

[0136] In contrast, the operational guidance device 11 of this embodiment is the same as the first embodiment in that it has an operational plan acquisition unit 7 and a simulation execution unit 8, but in addition to these, it also has a battery state estimation unit 6 and a battery temperature estimation unit 9.

[0137] In this embodiment, as in the first embodiment, while the storage battery 100B is operating according to the charge / discharge pattern PT, the operation history accumulation unit 5 of the storage battery control device 10 sequentially accumulates the charge / discharge power and battery temperature as log data for each module battery 12 that constitutes the storage battery 100B.

[0138] Meanwhile, the battery temperature estimation unit 9 of the operation guidance device 11 acquires actual values ​​of charge / discharge power and battery temperature from the operation record accumulation unit 5 of the storage battery control device 10, and also acquires the latest charge / discharge schedule executed by the storage battery 100B from the charge / discharge schedule acquisition unit 1 of the storage battery control device 10. Based on these, the battery temperature estimation unit 9 estimates a time change profile (temperature estimation profile) of the battery temperature of each module battery 12 when the storage battery 100B is operated in accordance with the charge / discharge schedule. Note that the temperature calculation process performed in the simulation execution unit 8 for the operation plan can be used to generate the temperature estimation profile.

[0139] In addition, the battery state estimation unit 6 acquires the battery temperature (real-time measurement value) of each module battery 12 measured by the temperature sensor 26 via the battery control device 10, and compares this value with the battery temperature (estimated battery temperature) estimated by the battery temperature estimation unit 9.

[0140] Then, based on the results of this comparison, the battery state estimation unit 6 makes the following estimations regarding a battery failure, a deviation in the depth of discharge control value, and a decrease in the degree of vacuum in the casing.

[0141] (Estimation 1') In only some of the module batteries 12, the difference between the real-time measurement value and the estimated battery temperature is positive and is equal to or greater than the fourth threshold → a failure of a cell 14 has occurred in that module battery 12; (Estimation 2') In all of the joule batteries 12, the difference between the real-time measurement value and the estimated battery temperature is positive and is equal to or greater than the fourth threshold → a depth-of-discharge control value deviation has occurred, in which the depth-of-discharge control value is smaller than the actual discharge intensity; (Estimation 3') In all of the module batteries 12, the difference between the real-time measurement value and the estimated battery temperature is positive and is equal to or greater than the fifth threshold, and this is repeated multiple times → a depth-of-discharge control value deviation has occurred, in which the depth-of-discharge control value is smaller than the actual discharge intensity; (Estimation 4') In only some of the module batteries 12, the difference between the real-time measurement value and the estimated battery temperature is negative and the absolute value is equal to or greater than the sixth threshold → a decrease in the housing vacuum has occurred in that module battery 12; (Estimation 5') The difference between the real-time measurement values ​​and the estimated battery temperature for all module batteries 12 is negative, and the absolute value is greater than the sixth threshold value → a deviation in the depth of discharge control value has occurred, where the depth of discharge control value is greater than the actual discharge intensity; (Estimation 6') None of (Estimation 1') to (Estimation 5') is true → No failure of the single battery 14, deviation in the depth of discharge control value, or decrease in the vacuum level of the housing has occurred.

[0142] The fourth to sixth thresholds are set in advance and stored in a memory or storage (not shown) of the battery control device 10. The fifth threshold is assumed to be smaller than the fourth threshold. For example, the fourth threshold is 1°C, and the fifth and sixth thresholds are each 0.1°C.

[0143] Of the above, (Estimation 1') and (Estimation 2') will be described with reference to Fig. 10. Fig. 10 is a diagram similar to Fig. 6 and the like, showing a charge / discharge pattern PT according to a certain charge / discharge schedule, a profile of actual battery temperature values ​​(actual temperature measurement profile) PF4 measured by temperature sensor 26 in one module battery 12 of storage battery 100B when charging / discharging is performed according to the charge / discharge pattern PT, and a profile of estimated battery temperature values ​​(temperature estimation profile) PF4α estimated based on the charge / discharge schedule and the actual values ​​of charge / discharge power and battery temperature stored in operation record storage unit 5.

[0144] 10, three discharges, Discharge (1) to Discharge (3), are performed at time intervals Δt (for example, Δt = 24 hours) with the same discharge time and discharge power. For simplicity of explanation, it is assumed that the depth of discharge (remaining capacity) immediately before Discharge (1) to Discharge (3) is the same.

[0145] 10, the charge and discharge conditions for discharges (1) to (3) are all the same, and the same peak battery temperature T6 appears in the temperature estimation profile PF4α for each discharge, and there is no difference between the measured temperature profile PF4 and the temperature estimation profile PF4α at least until the end of discharge (1). However, in the measured temperature profile PF4, the peak battery temperature T7 during discharges (2) and (3) is higher by ΔTb than the peak battery temperature T6 during discharge (1).

[0146] 10, when a certain discharge operation is performed in only some of the battery modules 12, there is a temperature difference ΔTb between the peak battery temperature T7 (real-time measured value) in the temperature measurement profile PF4 and the peak battery temperature T6 (estimated battery temperature) in the temperature estimation profile PF4α, and when it is determined that the temperature difference ΔTb is higher than the fourth threshold, the battery state estimation unit 6 estimates that a failure occurred in a battery cell 14 at a certain time t1 between discharge (1) and discharge (2) in the battery module 12 where the temperature difference ΔTb occurred. In other words, the battery state estimation unit 6 determines that (Inference 1') is true.

[0147] On the other hand, as described in the first embodiment, it is extremely rare for all of the cells 14 to fail simultaneously, so if a temperature difference ΔTb exceeding the fourth threshold occurs in all of the battery modules 12, it is reasonable to determine that this is an event unrelated to a failure of the battery cells 14. Therefore, if a temperature difference exceeding the fourth threshold occurs between the actually measured peak battery temperature T7 and the estimated peak battery temperature T6 in all of the battery modules 12, the battery state estimation unit 6 estimates that a deviation in the depth-of-discharge control value has occurred in the storage battery 100B. In other words, the battery state estimation unit 6 determines that (Estimation 2') is true.

[0148] That is, the contents of (Estimation 1') and (Estimation 2') are the same as (Estimation 1) and (Estimation 2) in the first embodiment, except that the real-time measured value of the battery temperature is compared with an estimated battery temperature instead of a past actual measured value. Furthermore, the contents of the estimations in (Estimation 3') to (Estimation 6') are the same as (Estimation 3) to (Estimation 6) in the first embodiment, except that the real-time measured value of the battery temperature is compared with an estimated battery temperature instead of a past actual measured value. Therefore, detailed explanations of these will be omitted.

[0149] The results of the estimation by the battery state estimation unit 6 are provided to the battery control device 10, and, similar to the first embodiment, are used to correct the depth-of-discharge control value in the discharge control unit 2 and for repair and maintenance of the module batteries 12 in the storage battery 100B. Also, similar to the first embodiment, temperature abnormality estimation information is passed to the simulation execution unit 8, and simulation parameters are appropriately corrected.

[0150] In this manner, in the present embodiment as well, as in the first embodiment, it is possible to reliably perform repairs and maintenance of the module battery 12 at appropriate times. Furthermore, it is possible to avoid problems arising from a discrepancy between the simulation in the operational guidance device 11 and the actual operation, and to operate the storage battery 100B safely.

[0151] That is, in this embodiment, the same effects as those in the first embodiment can be obtained.

[0152] <Example of Simulation Execution and Parameter Modification> Finally, an overview of the simulation of an operation plan performed by the simulation execution unit 8 of the operation guidance device 11 will be described. FIG. 11 is a diagram showing the flow of this simulation. Note that this simulation is based on the battery simulation disclosed in Patent Document 1. FIG. 11 illustrates an example of a simulation targeting a certain operation output time. When an operation plan is set by dividing it into a plurality of "frames" as in the above-described embodiment, the simulation shown in FIG. 11 is performed for each frame. In the following, an example will be described in which the operation plan is set on a frame-by-frame basis.

[0153] First, initial values ​​of the simulation parameters are set (step S1). The initial values ​​are set for the following: operational output time: T; time interval: Δt; operational output: Pn; remaining capacity: SOC; and battery temperature: Temp.

[0154] More specifically, the operational output time T is 30 minutes, which is the length of the frame. The time interval Δt is set to approximately 10 seconds to 10 minutes. The operational output Pn is set to the charge / discharge power value of the frame described in the operation plan.

[0155] The initial value of the remaining capacity SOC is set based on the depth-of-discharge control value at the start of the operation plan to be simulated. In this embodiment, the remaining capacity SOC = 100% - depth of discharge (control value).

[0156] The initial value of the battery temperature Temp is set in the range of 305° C. to 360° C. depending on the initial value of the remaining capacity SOC, that is, depending on the degree of charge and discharge of the storage battery 100B.

[0157] Furthermore, although the SOC and battery temperature of each of the module batteries 12 that make up the storage battery 100B may differ in nature, these module batteries 12 are connected in series to form the module string 13. Therefore, in the simulation, the individual module batteries 12 are not distinguished from one another, and the remaining capacity SOC and battery temperature Temp of each module battery 12 are assumed to be the same, and each is represented by a single simulation value.

[0158] Next, the number of loops N to be executed in the latter half of the simulation is calculated by the formula N=T / Δt (step S2).

[0159] Next, n is set to 1 (step S3), and the battery current In is calculated from the operational output Pn (step S4).

[0160] Furthermore, the remaining capacity SOC at the point when time has passed by Δt is calculated using the value of the battery current In calculated in step S4, the time interval Δt set as the initial value in step S1, and the most recent value of the remaining capacity SOC according to the formula SOC = SOC - In × Δt (step S5).

[0161] Furthermore, the battery temperature Temp at the time when time has elapsed by Δt is calculated using the formula Temp = Temp + (In x In x r) x Δt / C from the value of the battery current In calculated in step S4, the time interval Δt set as the initial value in step S1, the most recent battery Temp value, the internal resistance r of the module battery 12, the heat dissipation loss, and the heat capacity C (step S6). Here, the internal resistance r of the module battery 12, the heat dissipation loss, and the heat capacity C are constants that are specified in advance and stored in a memory unit (not shown) of the operational guidance device 11. The order of steps S5 and S6 may be reversed, or both may be performed in parallel.

[0162] Next, n=n+1 is set (step S7), and if n>N is not satisfied for the new n (NO in step S8), steps S5 to S7 are repeated at every time step Δt.

[0163] On the other hand, if n>N (YES in step S8), the latest calculated value of remaining capacity SOC and the latest calculated value of battery temperature Temp are output as the remaining capacity and battery temperature of storage battery 100B at the end of the frame (step S9).

[0164] If the remaining capacity and battery temperature output in step S9 are both values ​​within a predetermined allowable range, the simulation executing unit 8 determines that the operation plan that was the subject of the simulation is executable ("operable"). On the other hand, if at least one of the remaining capacity and battery temperature output in step S9 deviates from the predetermined allowable range, the simulation executing unit 8 determines that the operation plan that was the subject of the simulation is not executable ("not operable").

[0165] As described above, in the second embodiment, the temperature estimation profile is created using the simulation by the battery temperature estimation unit 9 of the operational guidance device 11. This is realized by setting the initial values ​​in step S1 based on the contents of the charge / discharge schedule and the actual values ​​of the charge / discharge power and the battery temperature stored in the operational performance storage unit 5, and then performing the processes of steps S2 to S8 to create a data set of the output values ​​of the battery temperature Temp for each time interval Δt obtained in step S6 and the times corresponding to the output values ​​specified based on the charge / discharge schedule.

[0166] In addition to the above, when the battery state estimation unit 6 estimates that an abnormal state has occurred in the storage battery 100B, such as a single cell failure, a deviation in the discharge depth control value, or a decrease in the vacuum level of the housing, as in the first and second embodiments described above, the simulation execution unit 8 modifies the simulation parameters according to the content of the estimation.

[0167] For example, if (Estimation 2) or (Estimation 2') is true and the temperature difference ΔTa or ΔTb is 1°C, it is estimated that the actual depth of discharge was smaller than the depth of discharge control value, and the simulation execution unit 8 reduces the initial value of the remaining capacity SOC. The reduction amount is, for example, 5%. That is, if the initial value of the remaining capacity SOC was set to 50%, the value is changed to 45%. Furthermore, if (Estimation 3) or (Estimation 3') is true and a battery temperature difference of about 0.1°C per cycle accumulates to 1°C, a similar change is made.

[0168] Furthermore, if (Estimation 1) or (Estimation 1') is established and it is estimated that a cell has failed, the method of calculating the battery temperature Temp in step S6 is changed. In general, for a module battery 12 that has a failed cell 14, a value In×In×r that gives the heat generation amount of that module battery 12 in a fault-free state is calculated as the sum of the heat generation amounts Inc×Inc×rc in healthy strings.

[0169] Here, Inc is the current (cell current) flowing through the cells 14 that make up each healthy string, and rc is the internal resistance of the cell 14. For example, in a module battery 12 in which a block 64 is made up of k strings 66 (k is a natural number of 2 or greater), if a cell 14 belonging to m strings 66 (m is an integer such that 0≦m<k) fails, the internal resistance rc of the healthy string in that block 64 is rc=r / (k−m).

[0170] Even if the battery current In during discharge is the same, if a cell failure occurs, the cell current Inc increases, the depth of discharge deepens, and the internal resistance rc increases, resulting in a larger amount of heat generated by the cells. Therefore, when a cell failure occurs, no current flows in the faulty string and no heat is generated, so the number of cells 14 that generate heat decreases, but the temperature of the module battery 12 rises because the impact of the increase in the amount of heat generated by the cells in the healthy string is greater.

[0171] <Modification> In the above-described embodiment, it is assumed that the storage battery control device 10 and the operation guidance device 11 constituting the storage battery control system 100C are devices configured as separate computers, but the storage battery control device 10 and the operation guidance device 11 may be realized on a single computer. In other words, the storage battery control system 100C may be realized on a single computer.

[0172] Also in the second embodiment, the storage battery control device 10 may include a battery state estimation unit 6 similar to that in the first embodiment, and may perform the same processing as in the first embodiment. Alternatively, the battery state estimation unit 6 included in the operational guidance device 11 according to the second embodiment may be capable of performing the same processing as in the first embodiment.

[0173] The above-described embodiment is directed to the case where the cells 14 are NaS batteries with almost no self-discharge, but the present invention can be applied to any storage battery in which secondary batteries with little self-discharge are used as the cells 14. For example, the present invention can also be applied to a storage battery in which lithium-ion batteries are used as the cells 14. However, application to a storage battery in which NaS batteries are used as the cells 14 is more suitable in terms of the accuracy of the estimation.

Claims

1. A method for estimating the state of a storage battery composed of a plurality of serially connected module batteries and controlled by a predetermined control device, wherein each of the plurality of module batteries includes an assembled battery to which a plurality of unit cells are connected, and the assembled battery is housed in a housing having a vacuum insulation structure, the method comprising: a comparison step of comparing, for each of the plurality of module batteries, an actual measurement value of the temperature when a charge / discharge operation is performed in the storage battery with an actual temperature value when a charge / discharge operation is performed under the same conditions as the charge / discharge operation; and an estimation step of estimating the state of the storage battery based on the comparison result in the comparison step, wherein the estimation step is capable of distinguishing and estimating the occurrence of any of the following abnormal states: a failure of a unit cell in any of the plurality of module batteries; a deviation of the depth-of-discharge control value held in the control device from the actual depth of discharge of the storage battery; and a decrease in the degree of vacuum in the housing of any of the plurality of module batteries.

2. A method for estimating the state of a storage battery as described in claim 1, characterized in that in the estimation step, if the difference between the actual measurement value and the performance value is positive and equal to or greater than a first threshold value in some of the plurality of module batteries, it is estimated that a failure has occurred in a single cell in that module battery, and if the difference between the actual measurement value and the performance value is positive and equal to or greater than the first threshold value in all of the plurality of module batteries, it is estimated that the depth-of-discharge control value held in the control device deviates from the actual depth of discharge of the storage battery.

3. A method for estimating the state of a storage battery as described in claim 2, characterized in that in the estimation step, if the difference between the actual measurement value and the performance value is positive and is equal to or greater than a second threshold value that is smaller than the first threshold value and is repeated multiple times in all of the plurality of module batteries, it is estimated that the depth-of-discharge control value held in the control device deviates from the actual depth of discharge of the storage battery.

4. A method for estimating the state of a storage battery as described in claim 1, characterized in that in the estimation step, if the difference between the actual measurement value and the actual performance value is negative and the absolute value of the difference is equal to or greater than a predetermined threshold value in some of the plurality of module batteries, it is estimated that a decrease in the degree of vacuum has occurred in the casing of the module battery, and if the difference between the actual measurement value and the actual performance value is negative and the absolute value of the difference is equal to or greater than the predetermined threshold value in all of the plurality of module batteries, it is estimated that the depth-of-discharge control value held in the control device deviates from the actual depth of discharge of the storage battery.

5. A method for estimating the state of a storage battery composed of a plurality of serially connected module batteries and controlled by a predetermined control device, wherein each of the plurality of module batteries includes an assembled battery to which a plurality of unit cells are connected, and the assembled battery is housed in a housing having a vacuum insulation structure, the method comprising: a comparison step of comparing, for each of the plurality of module batteries, an actual measured value of the temperature when a charge / discharge operation is performed in the storage battery with a previously estimated value of the temperature; and an estimation step of estimating the state of the storage battery based on the comparison result in the comparison step, wherein the estimated value is estimated based on charge / discharge power values ​​from previous charge / discharge operations performed in the storage battery and the temperatures of each of the plurality of module batteries, and the estimation step is capable of distinguishing and estimating the occurrence of any of the following abnormal states: a failure of a unit cell in any of the plurality of module batteries; a deviation of the depth-of-discharge management value held in the control device from the actual depth of discharge of the storage battery; and a decrease in the degree of vacuum in the housing of any of the plurality of module batteries.

6. A method for estimating the state of a storage battery as claimed in claim 5, characterized in that in the estimation step, if the difference between the actual measurement value and the estimated value is positive and equal to or greater than a first threshold value in some of the plurality of module batteries, it is estimated that a failure has occurred in a single cell in that module battery, and if the difference between the actual measurement value and the estimated value is positive and equal to or greater than the first threshold value in all of the plurality of module batteries, it is estimated that the depth-of-discharge control value held in the control device deviates from the actual depth of discharge of the storage battery.

7. A method for estimating the state of a storage battery as described in claim 6, characterized in that in the estimation step, if the difference between the actual measured value and the estimated value is positive and is equal to or greater than a second threshold value smaller than the first threshold value and is repeated multiple times in all of the plurality of module batteries, it is estimated that the depth-of-discharge control value held in the control device deviates from the actual depth of discharge of the storage battery.

8. A method for estimating the state of a storage battery as described in claim 5, characterized in that in the estimation step, if the difference between the actual measurement value and the estimated value is negative and the absolute value of the difference is equal to or greater than a predetermined threshold value in some of the plurality of module batteries, it is estimated that a decrease in the degree of vacuum has occurred in the casing of the module battery, and if the difference between the actual measurement value and the estimated value is negative and the absolute value of the difference is equal to or greater than the predetermined threshold value in all of the plurality of module batteries, it is estimated that the depth-of-discharge control value held in the control device deviates from the actual depth of discharge of the storage battery.

9. A method for estimating the state of a storage battery according to any one of claims 1 to 8, characterized in that the unit cells are sodium-sulfur batteries.

10. A method for simulating the operation of a storage battery based on an operation plan created in advance, comprising: a result acquisition step for acquiring, for the storage battery, an estimation result in the estimation step of a state estimation method according to any one of claims 1 to 8; and a correction step for correcting parameters used in the simulation in accordance with the content of the abnormal state when it is estimated in the estimation result that any one of the abnormal states has occurred.

11. A battery system comprising: a battery configured with a plurality of battery modules connected in series; and a control system for the battery, wherein each of the battery modules includes a battery assembly having a plurality of battery cells connected thereto, the battery assembly being housed in a housing having a vacuum insulation structure; and the control system comprising: control means for controlling the battery based on a preset depth-of-discharge control value; comparison means for comparing, for each of the battery modules, an actual temperature measurement value when a charge / discharge operation is performed in the battery with an actual temperature measurement value when a charge / discharge operation is performed under the same conditions as the charge / discharge operation; and estimation means for estimating the state of the battery based on the comparison result by the comparison means, wherein the estimation means is capable of distinguishing and estimating the occurrence of any of the following abnormal states: a failure of a battery in any of the battery modules; a deviation of the depth-of-discharge control value from the actual depth of discharge of the battery; and a decrease in the degree of vacuum in the housing of the battery modules.

12. A storage battery system as described in claim 11, wherein the estimation means estimates that a failure has occurred in a single cell in a module battery when the difference between the actual measurement value and the performance value is positive and equal to or greater than a first threshold value in some of the plurality of module batteries, and estimates that the depth-of-discharge control value deviates from the actual depth of discharge in the storage battery when the difference between the actual measurement value and the performance value is positive and equal to or greater than the first threshold value in all of the plurality of module batteries.

13. A storage battery system as described in claim 12, characterized in that the estimation means estimates that the depth-of-discharge control value deviates from the actual depth of discharge of the storage battery when, in all of the plurality of module batteries, the difference between the actual measured value and the performance value is positive and is equal to or greater than a second threshold value that is smaller than the first threshold value, and this difference is repeated multiple times.

14. A storage battery system as described in claim 11, wherein the estimation means estimates that a decrease in the degree of vacuum has occurred in the casing of a module battery when, in some of the plurality of module batteries, the difference between the actual measurement value and the actual performance value is negative and the absolute value of the difference is equal to or greater than a predetermined threshold, and estimates that, in all of the plurality of module batteries, the difference between the actual measurement value and the actual performance value is negative and the absolute value of the difference is equal to or greater than the predetermined threshold.

15. A storage battery system comprising: a storage battery composed of a plurality of module batteries connected in series; and a control system for the storage battery, wherein each of the plurality of module batteries includes an assembled battery to which a plurality of unit cells are connected, and the assembled battery is housed in a housing having a vacuum insulation structure, and the control system comprises: control means for controlling the storage battery based on a preset depth-of-discharge management value; comparison means for comparing, for each of the plurality of module batteries, an actual measured value of the temperature when a charge / discharge operation is performed in the storage battery with a previously estimated value of the temperature; and estimation means for estimating the state of the storage battery based on the comparison result by the comparison means, wherein the estimated value is estimated based on charge / discharge power values ​​from previous charge / discharge operations performed in the storage battery and the temperatures of each of the plurality of module batteries, and the estimation means is configured to estimate the state of the storage battery based on the following: a failure of a unit cell in any of the plurality of module batteries; a deviation of the depth-of-discharge management value from the actual depth of discharge of the storage battery; a decrease in the degree of vacuum in the housing of any of the plurality of module batteries; The battery system is characterized in that it is possible to distinguish and estimate whether any one of the above abnormal states has occurred.

16. A storage battery system as described in claim 15, wherein the estimation means estimates that a failure has occurred in a single cell in a module battery when the difference between the actual measurement value and the estimated value is positive and equal to or greater than a first threshold value in some of the plurality of module batteries, and estimates that the depth-of-discharge control value deviates from the actual depth of discharge in the storage battery when the difference between the actual measurement value and the estimated value is positive and equal to or greater than the first threshold value in all of the plurality of module batteries.

17. A storage battery system as described in claim 16, characterized in that the estimation means estimates that the depth-of-discharge control value deviates from the actual depth of discharge of the storage battery when, for all of the plurality of module batteries, the difference between the actual measured value and the estimated value is positive and is equal to or greater than a second threshold value that is smaller than the first threshold value, and this difference is repeated multiple times.

18. A storage battery system as described in claim 15, wherein the estimation means estimates that a decrease in the degree of vacuum has occurred in the casing of a module battery when, in some of the plurality of module batteries, the difference between the actual measurement value and the estimated value is negative and the absolute value of the difference is equal to or greater than a predetermined threshold value, and estimates that, in all of the plurality of module batteries, the difference between the actual measurement value and the estimated value is negative and the absolute value of the difference is equal to or greater than the predetermined threshold value, the depth-of-discharge control value deviates from the actual depth of discharge of the storage battery.

19. A storage battery system according to any one of claims 11 to 18, characterized in that the unit cells are sodium-sulfur batteries.

20. A storage battery system as claimed in any one of claims 11 to 18, further comprising a simulation means for simulating the operation of the storage battery based on a pre-created operation plan, wherein the simulation means acquires the estimation results of the estimation means, and if the estimation results indicate that any of the abnormal conditions has occurred, modifies the parameters used in the simulation according to the nature of the abnormal condition.

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