Abnormally degraded cell detection device and abnormally degraded cell detection method

Abstract

To provide an abnormally degraded cell detection device and an abnormally degraded cell detection method that are capable detecting a cell which is abnormally degraded in an early stage.SOLUTION: The present invention relates to an abnormally degraded cell detection device and a method for the same. An abnormally degraded cell detection method for a battery module containing a plurality of cells according to an embodiment of the present invention includes: a step of acquiring a first statistic value indicating a capacity deviation at a first point of time for the plurality of cells; a step of acquiring a second statistic value indicting the capacity deviation at a second point of time for the plurality of cells; and a step of comparing the first and second statistic values to each other to detect an abnormally degraded cell.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to an abnormal degradation cell detection device and an abnormal degradation cell detection method.

Background Art

[0002] A secondary battery is a battery that can be charged and discharged, unlike a primary battery that cannot be charged. Low-capacity secondary batteries are used in portable small electronic devices such as smartphones, feature phones, notebook computers, digital cameras, and camcorders, and high-capacity secondary batteries are widely used as power sources for motor drives such as hybrid vehicles and electric vehicles, and as power storage batteries. Such a secondary battery includes an electrode assembly composed of a positive electrode and a negative electrode, a case that houses the electrode assembly, electrode terminals connected to the electrode assembly, and the like.

[0003] In a secondary battery, a cell in which events such as internal foreign matter, internal short circuit, and degradation occur may cause safety problems such as thermal runaway and ignition, and such an abnormal cell may act as a cause of a fire in the secondary battery. Therefore, early detection of abnormal cells in a secondary battery is an extremely important issue.

[0004] The above-described information disclosed in the technology that becomes the background of such an invention is only for improving the understanding of the background of the present invention, and therefore may include information that does not constitute the prior art.

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide an abnormal degradation cell detection device and an abnormal degradation cell detection method capable of early detecting an abnormally degraded cell.

[0006] However, the technical problems to be solved by the present invention are not limited to the above-described problems, and other problems not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

Means for Solving the Problem

[0007] A method for detecting an abnormally deteriorated cell of a battery module including a plurality of cells according to an embodiment of the present invention for solving the above technical problem includes: obtaining a first statistical value indicating a capacity deviation at a first time point for the plurality of cells; obtaining a second statistical value indicating a capacity deviation at a second time point for the plurality of cells; and comparing the first statistical value and the second statistical value with each other to detect an abnormally deteriorated cell.

[0008] The step of obtaining the first statistical value includes obtaining the first statistical value using the initial capacity value of each of the plurality of cells, and the initial capacity value can correspond to the formation capacity of each cell.

[0009] The step of obtaining the first statistical value using the initial capacity value may include: obtaining an average value and a standard deviation of the initial capacity value for the plurality of cells; calculating a first sigma for each of the plurality of cells using the initial capacity value, the average value, and the standard deviation; and obtaining the calculated first sigma for each of the plurality of cells as the first statistical value.

[0010] The step of obtaining the first statistical value may include: detecting a first SOC (State Of Charge) change amount during a first period for each of the plurality of cells; obtaining an average value and a standard deviation of the first SOC change amount for the plurality of cells; calculating a second sigma for each of the plurality of cells using the first SOC change amount, the average value, and the standard deviation; and determining the calculated second sigma for each of the plurality of cells as the first statistical value.

[0011] The step of detecting the first SOC change amount includes, in a first rest period of the battery module, detecting a first SOC value of each of the plurality of cells, in a second rest period after the first rest period of the battery module, detecting a second SOC value of each of the plurality of cells, and for each of the plurality of cells, calculating the first SOC change amount from a difference value between the first SOC value and the second SOC value.

[0012] The step of detecting the first SOC value includes, for each of the plurality of cells, obtaining a first cell voltage value detected at a time point when a predetermined time has elapsed since the start of the first rest period, and for each of the plurality of cells, determining the first SOC value using the first cell voltage value.

[0013] The step of detecting the second SOC value includes, for each of the plurality of cells, obtaining a second cell voltage value detected at a time point when a predetermined time has elapsed since the start of the second rest period, and for each of the plurality of cells, determining the second SOC value using the second cell voltage value.

[0014] The step of obtaining the second statistical value includes, for each of the plurality of cells, detecting a second SOC change amount during a second period, obtaining an average value and a standard deviation of the second SOC change amount for the plurality of cells, for each of the plurality of cells, calculating a third sigma using the second SOC change amount, the average value and the standard deviation, and determining the third sigma calculated for each of the plurality of cells as the second statistical value.

[0015] The step of detecting the second SOC change amount includes, in the third rest period of the battery module, detecting the third SOC value of each of the plurality of cells, in the fourth rest period after the third rest period of the battery module, detecting the fourth SOC value of each of the plurality of cells, and for each of the plurality of cells, calculating the second SOC change amount from the difference value between the third SOC value and the fourth SOC value.

[0016] The step of detecting the third SOC value includes, for each of the plurality of cells, obtaining a third cell voltage value detected at a time point when a predetermined time has elapsed since the start of the third rest period, and for each of the plurality of cells, determining the third SOC value using the third cell voltage value.

[0017] The step of detecting the fourth SOC value includes, for each of the plurality of cells, obtaining a fourth cell voltage value detected at a time point when a predetermined time has elapsed since the start of the fourth rest period, and for each of the plurality of cells, determining the fourth SOC value using the fourth cell voltage value.

[0018] The step of detecting the second SOC change amount includes, for each of the plurality of cells, detecting the fourth SOC change amount between the charge post-rest period and the discharge post-rest period for each charge-discharge cycle, and determining the second SOC change amount from the average value of the fourth SOC change amounts detected during the second period. The second period can include at least one charge-discharge cycle.

[0019] The step of detecting the abnormally deteriorated cell includes comparing the difference value between the first statistical value and the second statistical value with a threshold value, and determining a cell for which the difference value is equal to or greater than the threshold value as an abnormally deteriorated cell.

[0020] The step of detecting the abnormally deteriorated cell may include, for each of the plurality of cells, calculating a difference value between the first statistical value and the second statistical value, using the Grubbs’ test method to detect an outlier from among the difference values of the plurality of cells, and determining, as an abnormally deteriorated cell, a cell whose difference value is an outlier among the plurality of cells.

[0021] An abnormally deteriorated cell detection device for a battery module including a plurality of cells according to an embodiment includes a control device that obtains a first statistical value indicating a capacity deviation at a first time point for the plurality of cells, obtains a second statistical value indicating a capacity deviation at a second time point for the plurality of cells, and compares the first statistical value and the second statistical value with each other to detect an abnormally deteriorated cell.

[0022] The abnormally deteriorated cell detection device may further include a storage device that stores initial capacity values of the plurality of cells. The control device can calculate a first sigma for each of the plurality of cells using the initial capacity value of each of the plurality of cells, the average value and the standard deviation of the initial capacity values of the plurality of cells, and use the calculated first sigma for each of the plurality of cells as the first statistical value. The initial capacity value may correspond to the formation capacity of each cell.

[0023] The control device can detect a first SOC change amount during a first period for the plurality of cells, and calculate an average value and a standard deviation of the first SOC change amount for the plurality of cells. The control device can calculate a second sigma for each of the plurality of cells using the first SOC change amount, the average value, and the standard deviation, and use the calculated second sigma for each of the plurality of cells as the first statistical value.

[0024] The control device can determine the first SOC value in the first post-charge rest period by using the first cell voltage value detected at the time when a predetermined time has elapsed since the start of the first post-charge rest period for each of the plurality of cells. The control device can determine the second SOC value in the first post-discharge rest period by using the second cell voltage value detected at the time when a predetermined time has elapsed since the start of the first post-discharge rest period for each of the plurality of cells. The control device can determine the first SOC change amount from the difference value between the first SOC value and the second SOC value.

[0025] The control device can detect the second SOC change amount for the plurality of cells during the second period, and calculate the average value and the standard deviation of the second SOC change amount for the plurality of cells. The control device can calculate the third sigma for each of the plurality of cells by using the second SOC change amount, the average value, and the standard deviation, and use the calculated third sigma for each of the plurality of cells as the second statistical value.

[0026] The control device can determine the third SOC value in the second post-charge rest period by using the third cell voltage value detected at the time when a predetermined time has elapsed since the start of the second post-charge rest period for each of the plurality of cells. The control device can determine the fourth SOC value in the second post-discharge rest period by using the fourth cell voltage value detected at the time when a predetermined time has elapsed since the start of the second post-discharge rest period for each of the plurality of cells. The second SOC change amount can be determined from the difference value between the third SOC value and the fourth SOC value.

[0027] The control device can detect, for each of the plurality of cells, the fourth SOC change amount between the post-charge rest period and the post-discharge rest period for each charge cycle during the second period, and determine the second SOC change amount from the average value of the fourth SOC change amount detected during the second period. The second period can include at least one charge-discharge cycle.

[0028] The control device can compare the difference value between the first statistical value and the second statistical value with a threshold value, and determine a cell in which the difference value is equal to or greater than the threshold value as an abnormally deteriorated cell.

Advantages of the Invention

[0029] According to the present invention, by detecting an abnormally deteriorated cell at an early stage, it is possible to prevent a safety problem from occurring due to the abnormal cell.

[0030] However, the effects that can be obtained by the present invention are not limited to the effects described above, and other technical effects not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

Brief Description of the Drawings

[0031] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and are for further understanding the technical idea of the present invention together with the detailed description of the invention to be described later. Therefore, the present invention should not be construed as being limited only to the matters described in the drawings.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0032] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings. Based on the principle that the inventor can appropriately define the concept of the terms in order to explain his invention in the best way, they should be construed in a meaning and concept that conforms to the technical idea of the present invention. Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are only some of the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. Thus, there may be various equivalents and modifications that can replace them at the time of this application. Also, as used in this specification, "comprise", "include" and / or "comprising", "including" are used to specify the presence of the recited shape, number, step, operation, member, element and / or group thereof, and do not exclude the presence or addition of one or more other shapes, numbers, operations, members, elements and / or groups. Also, when describing embodiments of the present invention, "can be" and "can be" can include "one or more embodiments of the present invention".

[0033] Also, for the purpose of assisting in the understanding of the invention, the attached drawings are not shown at actual scale, and the dimensions of some components may be exaggerated. Also, the same reference numerals may be given to the same components in different embodiments.

[0034] A reference that two comparison targets are "identical" means "substantially identical". Therefore, substantial identity can include cases having a deviation considered to be a low level in the art, for example, a deviation within 5%. Also, the fact that a parameter in a given region is uniform may mean that it is uniform from an average perspective.

[0035] Although the first, second, etc. are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are merely used to distinguish one component from another, and of course, unless otherwise stated to the contrary, the first component can be the second component.

[0036] Throughout the specification, unless otherwise stated to the contrary, each component may be singular or plural.

[0037] The statement that any configuration is arranged "above (or below)" a component or "on (or under)" a component means not only that any configuration is arranged in contact with the upper (or lower) surface of the component, but also that other configurations may be interposed between the component and any configuration arranged "above (or below)" the component.

[0038] Also, when a component is described as "connected", "coupled" or "joined" to another component, it should be understood that the components may be directly connected or joined to each other, but other components may be "interposed" between the components, or the components may be "connected", "coupled" or "joined" through other components. Also, when a part is said to be electrically coupled to another part, this includes not only the case where they are directly connected, but also the case where other elements are interposed therebetween.

[0039] Throughout the specification, when "A and / or B" is mentioned, unless otherwise stated to the contrary, it means A, B, or A and B. That is, "and / or" includes all combinations or any combination of the listed multiple items. When "C to D" is mentioned, unless otherwise stated to the contrary, it means greater than or equal to C and less than or equal to D.

[0040] Hereinafter, an abnormal degradation cell detection device and method according to an embodiment will be described in detail with reference to the necessary drawings.

[0041] FIG. 1 schematically shows an abnormal degradation cell detection device for a battery pack according to an embodiment.

[0042] Referring to FIG. 1, the battery pack 10 can include a battery module 11 including a plurality of cells 111 and a battery management system (BMS) 12 for managing the same. At least one charge-discharge cycle can be performed on the battery pack 10 every day. In this document, one charge-discharge cycle can include one charging period and one discharging period. Also, one charge-discharge cycle can additionally include an idle period after the charging period and an idle period after the discharging period. For example, one charge-discharge cycle can be configured to sequentially include a charging period, an idle period, a discharging period, and an idle period. Also, for example, one charge-discharge cycle can be configured to sequentially include a discharging period, an idle period, a charging period, and an idle period. Charging and discharging of the battery pack 10 can be completely stopped during the idle period.

[0043] The BMS 12 can detect the cell voltage of each cell 111 every idle period of the battery pack 10. That is, the BMS 12 can detect the cell voltage of each cell 111 during the idle period following the charging period and also detect the cell voltage of each cell 111 during the idle period following the discharging period. The BMS 12 can obtain the cell voltage value measured after a predetermined time has elapsed from the start of the idle period (that is, after the polarization voltage has been removed from the cell voltage of each cell 111) as the cell voltage value of the idle period in order to obtain voltage data close to the open circuit voltage (OCV) of each cell 111. For example, the BMS 12 can obtain the cell voltage value measured when 20 minutes or more have elapsed from the start of the idle period as the cell voltage value of the idle period.

[0044] BMS12 can also obtain the state of charge (SOC) value of each cell 111 by using the cell voltage values detected for each rest period. In this case, BMS12 can calculate the SOC value of each cell by various known methods. For example, BMS12 can obtain the SOC value of each cell 111 by using OCV-SOC data in which the SOC corresponding to each OCV is mapped.

[0045] BMS12 can transmit state data including at least one of the cell voltage value and the SOC value of each cell 111 for each rest period to the abnormal degradation cell detection device 20. When transmitting the state data, BMS12 can also transmit the identification information of the battery module 11 and the cell 111 so that it can be identified which cell 111 the state data belongs to in which battery module 11.

[0046] The abnormal degradation cell detection device 20 can detect abnormal degradation cells by monitoring the capacity deviation between the cells 111 included in the same battery module 11. In the following description, the "capacity" of the cell 111 can indicate the "usable capacity" of the cell 111. Also, the "abnormal degradation cell" can indicate a cell that has been abnormally degraded due to abnormalities such as internal short circuits and poor electrode plate coating.

[0047] The abnormal degradation cell detection device 20 can include a communication device 21, a storage device 22, and a control device 23.

[0048] The communication device 21 can perform a wired / wireless communication function between the abnormal degradation cell detection device 20 and an external device of the abnormal degradation cell detection device 20. For example, the communication device 21 can perform a wired / wireless communication function between the BMS 12 of the battery pack 10 and the abnormal degradation cell detection device 20. Also, for example, the communication device 21 can also perform a wired / wireless communication function between the upper controller 30 and the abnormal degradation cell detection device 20. The upper controller 30 is a controller that can manage the operation of the abnormal cell detection device 20 outside the abnormal cell detection device 20, and can include a manager terminal, a main controller of a system equipped with the battery pack 10, and the like.

[0049] The storage device 22 can store the state data (for example, cell voltage value, SOC value, etc.) of each cell 111 received from the battery pack 10. The control device 23 can monitor the state data of each cell 111 over a long period for detecting an abnormal degradation cell. Therefore, when the state data of each cell 111 is received, the control device 23 can map and store it in time series (that is, in date order) to the corresponding battery module 11 and the corresponding cell 111.

[0050] The storage device 22 can also store OCV-SOC data in which the SOC corresponding to each OCV of the cell 111 is mapped. The OCV-SOC data can be obtained in advance using a reference cell having the same characteristics as the cell 111. For example, the OCV-SOC data can be obtained using various methods such as experiments on the reference cell, charge / discharge simulations, and deep learning. The storage device 22 can store the OCV-SOC data in a table form.

[0051] The storage device 22 can also store the initial capacity value of each cell 111 constituting the battery pack 10. The initial capacity value of each cell 111 can be a value obtained at the manufacturing stage of each cell 111. For example, the initial capacity value of each cell 111 can be the formation capacity value obtained in the formation process of each cell.

[0052] The storage device 22 can store data (sigma) indicating the statistical distribution of the initial capacity values of the plurality of cells 111 (that is, the initial capacity deviation).

[0053] The following Equation 1 shows a method for calculating a statistical value indicating the initial capacity deviation from the initial capacity values of each cell 111 (hereinafter referred to as "initial capacity sigma"). [Equation 1] Initial capacity sigma(i) = -(Initial capacity value(i) - AVG(Initial capacity value(1), Initial capacity value(2), …, Initial capacity value(N))) / STDEV(Initial capacity value(1), Initial capacity value(2), …, Initial capacity value(N)) In the above formula, AVG is the average value and STDEV is the standard deviation.

[0054] The above Equation 1 is for calculating the initial capacity sigma(i) for the i-th cell 111 among the N cells 111 constituting the battery module 11. The initial capacity sigma(i) is a value indicating the degree to which the initial capacity value of the i-th cell 111 deviates from the average of the initial capacity values of the N cells 111 constituting the battery module 11. By using this value, the statistical distribution of the initial capacity values of the cells 111 can be confirmed. In Equation 1, as described above, the initial capacity values of each cell 111 obtained at the manufacturing stage can be used. Also, AVG(Initial capacity value(1), Initial capacity value(2), …, Initial capacity value(N)) and STDEV(Initial capacity value(1), Initial capacity value(2), …, Initial capacity value(N)) respectively indicate the average value and the standard deviation of the initial capacity values for all the cells 111 constituting the battery module 11.

[0055] The following Table 1 shows an example of the initial capacity values of each cell 111 and the initial capacity sigma derived therefrom for each cell 111.

[0056]

Table 1

[0057] Referring to Table 1, the smaller the initial capacity of the cell, the larger the value of the initial capacity sigma can be. In Table 1, the initial capacity of Cell#10 is the smallest, and therefore the initial capacity sigma of Cell#10 has the largest value of 1.301. On the contrary, Cell#8 has the largest initial capacity, and therefore the initial capacity sigma of Cell#8 has the smallest value of -2.394. The initial capacity sigma stored in the storage device 22 can be calculated by the control device 23 described later. The initial capacity sigma can also be calculated by an external device (for example, the upper controller 30) of the abnormal degradation cell detection device 20 and transmitted to the abnormal degradation cell detection device 20.

[0058] The control device 23 can control the overall operation of the abnormal degradation cell detection device 20.

[0059] The control device 23 can communicate with the BMS12 or the upper controller 30 through the communication device 21. For example, the control device 23 can receive the state data of each cell 111 from the BMS12 through the communication device 21. Also, for example, the control device 23 can receive at least one of the OCV-SOC data, the initial capacity value of each cell 111, and the statistical value (initial capacity sigma) indicating the initial capacity deviation between the cells 111 from the upper controller 30 through the communication device 21.

[0060] The control device 23 can also manage the data stored in the storage device 22. For example, the control device 23 can store and manage the state data of each cell 111 received from the BMS12 in the storage device 22. Also, for example, the control device 23 can store and manage the OCV-SOC data, the initial capacity value of each cell 111, the initial capacity sigma of each cell 111, etc. in the storage device 22.

[0061] When the initial capacity value of each cell 111 is received from the upper controller 30, the control device 23 can also calculate the initial capacity sigma of the cells 111 included in the battery module 11 using the initial capacity value of each cell 111 and the formula 1.

[0062] When the control device 23 receives the cell voltage values detected from each cell 111 in the rest period from the BMS 12, it can calculate the SOC value of each cell 111 in the rest period using the received cell voltage values and the OCV-SOC data. For example, when the control device 23 receives the cell voltage values (hereinafter referred to as "post-charge cell voltage values") detected from each cell 111 in the rest period after the charge period from the BMS 12, it can obtain the SOC value (hereinafter referred to as "post-charge SOC value") corresponding to the post-charge cell voltage value using the OCV-SOC data. Also, for example, when the control device 23 receives the cell voltage values (hereinafter referred to as "post-discharge cell voltage values") detected from each cell 111 in the rest period after the discharge period from the BMS 12, it can obtain the SOC value (hereinafter referred to as "post-discharge SOC value") corresponding to the post-discharge cell voltage value using the OCV-SOC data. The control device 23 can obtain the SOC change amount (post-charge SOC value - post-discharge SOC value) in the charge-discharge cycle using the post-charge SOC value and the post-discharge SOC value calculated in this way.

[0063] Table 2 below shows an example of the post-charge SOC value and the post-discharge SOC value of each cell 111 derived from the post-charge cell voltage value and the post-discharge cell voltage value of each cell 111 using the OCV-SOC table. Also, Table 2 shows an example of the SOC change amount of each cell 111 derived from the post-charge SOC value and the post-discharge SOC value of each cell 111.

[0064]

Table 2

[0065] The control device 23 can also receive the SOC values (post-charge SOC value, post-discharge SOC value) detected from each cell 111 in the rest period from the BMS 12, and obtain the SOC change amount (post-charge SOC value - post-discharge SOC value) in the charge-discharge cycle using the received SOC values. The control device 23 can also continuously perform statistical analysis on the capacity deviation of each cell 111 and detect abnormal degradation cells based on the analysis results.

[0066] Cell 111 may have its capacity decreased as it deteriorates. Charging and discharging are performed under the same conditions for all cells 111 that make up the same battery module 11. Therefore, cells 111 included in the same battery module 11 should theoretically have similar degrees of deterioration and similar capacity reduction patterns. However, a cell 111 in which an abnormality such as an internal short circuit has occurred may have its deterioration accelerated compared to other cells, and as a result, the capacity reduction rate over time may increase compared to other cells. That is, the abnormally deteriorated cell may have an increasing capacity deviation from other cells as time passes. Therefore, by monitoring the change in the capacity deviation of cell 111 over time, it is possible to detect a cell with a greater degree of deterioration compared to other cells, and thus a cell in which an abnormality has occurred.

[0067] The amount of change in the SOC of cell 111 during charging and discharging under the same conditions depends on the capacity of each cell 111, and the smaller the capacity of cell 111, the greater the amount of change in SOC per unit time can be shown. That is, a cell 111 in which deterioration has been abnormally accelerated and its capacity has relatively decreased more than other cells may have a greater amount of change in SOC per unit time compared to other cells. Therefore, the deviation in the amount of change in SOC of cell 111 can show a statistical distribution similar to the capacity deviation of cell 111.

[0068] Therefore, even if the control device 23 does not know the current capacity value of each cell 111, it can calculate a statistical value indicating the current capacity deviation of cell 111 using the amount of change in the SOC of cell 111. The following mathematical formula 2 shows a method for calculating a statistical value (hereinafter referred to as "current capacity sigma") indicating the current capacity deviation of cell 111 from the amount of change in the SOC of each cell 111. [Mathematical formula 2] Current capacity sigma(i) = (△SOC(i) - AVG(△SOC(1), △SOC(2), …, △SOC(N))) / STDEV(△SOC(1), △SOC(2), …, △SOC(N))

[0069] The above formula 2 is for calculating the current capacity sigma(i) for the i-th cell 111 among the N cells 111 that make up the battery module 11. Referring to the formula 2, the control device 23 can calculate the degree to which the SOC change amount (△SOC(i)) of the i-th cell 111 deviates from the average SOC change amount of the cells 111 that make up the battery module 11, and calculate the current capacity sigma(i) of the i-th cell 111. The current capacity sigma(i) calculated in this way can also be used as a value indicating the degree to which the current capacity value of the i-th cell 111 deviates from the average capacity value of the battery module 11. However, considering that the SOC change amount becomes larger as the capacity of the cell is smaller, in formula 2, unlike formula 1, the minus sign ("-") in the numerator can be deleted.

[0070] In formula 2, the SOC change amount (△SOC) of each cell 111 can be obtained from the difference value between the post-charge SOC value and the post-discharge SOC value of each cell 111 as described above. Also, AVG(△SOC(1), △SOC(2), …, △SOC(N)) and STDEV(△SOC(1), △SOC(2), …, △SOC(N)) respectively indicate the average value and standard deviation of the SOC change amount (△SOC) for all the cells 111 that make up the battery module 11.

[0071] The following Table 3 shows an example of the current capacity sigma of each cell 111 derived from the SOC change amount of each cell 111.

[0072]

Table 3

[0073] Referring to Table 3, the larger the change in SOC of a cell, the larger the value of the current capacity sigma can be. In Table 3, the change in SOC of Cell#8 is the largest, and therefore the current capacity sigma of Cell#8 has the largest value of 2.957. It is sometimes difficult to directly compare the deviation of the change in SOC of Cell 111 with the capacity deviation of Cell 111. However, when the deviation of the change in SOC of Cell 111 is converted to the current capacity sigma using the above formula (2), a direct comparison with the initial capacity sigma becomes possible as shown in Table 4 below.

[0074] Table 4 below shows an example of the initial capacity sigma and the current capacity sigma of each Cell 111. Also, FIG. 2 is a graph showing the distribution of the initial capacity sigma and the current capacity sigma in Table 4.

[0075]

Table 4

[0076] Referring to FIG. 2 and Table 4, the smaller the capacity of a cell, the larger the value of the capacity sigma can be. Therefore, a cell in which the current capacity sigma has increased compared to the initial capacity sigma can be regarded as having a relatively higher degradation rate compared to other cells. On the contrary, a cell in which the current capacity sigma has decreased compared to the initial capacity sigma can be regarded as having a lower degradation rate compared to other cells. According to this, in Table 4 above, Cell#10 had the smallest initial capacity, but the degradation rate was rather lower compared to other cells. On the contrary, Cell#8 had the largest initial capacity, but the degradation rate was rather higher compared to other cells. In particular, it can be seen that the capacity sigma of Cell#8 has increased abnormally compared to other cells. Table 5 below shows another example of the initial capacity sigma and the current capacity sigma of each Cell 111. Also, FIG. 3 is a graph showing the distribution of the initial capacity sigma and the current capacity sigma in Table 5.

[0077]

Table 5

[0078] Referring to FIG. 3 and Table 5, Cell #8 is the cell with the smallest initial capacity and current capacity. That is, Cell #8 is the cell with the most deteriorated state among all the initial and current states. All the cells in Table 5 were charged and discharged under the same conditions. Therefore, a cell with a significantly smaller initial capacity compared to other cells, like Cell #8, can maintain a smaller capacity compared to other cells even over time. On the other hand, in FIG. 3 and Table 5, Cell #2 has values of both initial capacity and current capacity larger than those of Cell #8, but it is the cell with the largest increase in capacity sigma. That is, Cell #2 is the cell with the fastest deterioration progress rate among the cells, that is, the cell with the most deterioration. Referring to the above, the control device 23 can detect the cell 111 with the smallest capacity in the current battery module 11, that is, the most deteriorated cell 111, based on the current capacity sigma. That is, the control device 23 can determine the cell 111 with the largest current capacity sigma in the battery module 11 as the most deteriorated cell.

[0079] The control device 23 can also detect the cell 111 with the fastest deterioration rate in the battery module 11 based on the change amount of capacity sigma (current capacity sigma - initial capacity sigma). The control device 23 can determine the cell 111 with the largest increase in capacity sigma in the battery module 11 as the cell with the fastest deterioration rate, that is, the cell with the most deterioration compared to the initial state.

[0080] The control device 23 can also determine an abnormally deteriorated cell based on the change amount of capacity sigma (current capacity sigma - initial capacity sigma) of each cell 111. For example, the control device 23 can determine the cell 111 with a change amount of capacity sigma equal to or greater than the threshold value as an abnormally deteriorated cell. Here, a fixed value can be used as the threshold value, or it can be variable according to the change amount of capacity sigma of the cell 111. In the latter case, for example, the control device 23 can determine the threshold value based on the average value, minimum value, median value, etc. of the change amounts of capacity sigma of the cells 111 included in the battery module 11.

[0081] The control device 23 can also determine an abnormally degraded cell by using the Grubbs’ test method, which is used to detect outliers from a data set. The control device 23 can use the Grubbs’ test method to determine an outlier from the amount of change in the capacity sigma (current capacity sigma - initial capacity sigma) of the cells 111 included in the battery module 11. When an outlier is determined, the control device 23 can determine the corresponding cell 111 as an abnormally degraded cell.

[0082] When the most degraded cell 111 in the battery module 11 is determined, the control device 23 can transmit information about this (such as cell identification information, current capacity sigma, etc.) to the upper controller 30. When the cell 111 with the fastest degradation rate in the battery module 11 is determined, the control device 23 can also transmit information about this (such as cell identification information, amount of change in capacity sigma, etc.) to the upper controller 30. When an abnormally degraded cell 111 in the battery module 11 is determined, the control device 23 can also transmit information about this (such as cell identification information, etc.) to the upper controller 30.

[0083] The SOC value determined using the OCV-SOC data and the amount of change in SOC calculated using this may include error components due to voltage measurement errors, environmental factors, etc. Such error components can vary depending on the state of the battery pack 10 at the time of cell voltage measurement. The control device 23 can flatten such error components in order to improve the accuracy of the amount of change in SOC and the current capacity sigma. That is, the control device 23 can calculate the average value of the amount of change in SOC of each cell 111 over several days or during multiple charge-discharge cycles, and use this to calculate the current capacity sigma of each cell 111. In this case, the amount of change in SOC (△SOC) of each cell 111 in the formula 2 may be the average value of the amount of change in SOC of each cell 111 detected over several days or during multiple charge-discharge cycles.

[0084] In order to improve the accuracy of the SOC change amount and the accuracy of the current capacity sigma, the control device 23 can also perform filtering on the SOC change amount. For example, for a charge-discharge cycle in which the SOC change amounts of all the cells 111 are equal to or greater than the threshold value, the control device 23 can detect the current capacity sigma of each cell 111 using the SOC change amount. On the contrary, for a charge-discharge cycle in which the SOC change amount of at least one cell 111 is less than the threshold value, the control device 23 can also not calculate the current capacity sigma. Also, for example, for a charge-discharge cycle in which the average value of the SOC change amounts of the cells 111 is equal to or greater than the threshold value, the control device 23 can detect the current capacity sigma of each cell 111 using the SOC change amount. On the contrary, for a charge-discharge cycle in which the average value of the SOC change amounts of the cells 111 is less than the threshold value, the control device 23 can also not calculate the current capacity sigma.

[0085] When the control device 23 does not know the initial capacity values of the respective cells 111, at the initial use of the battery pack 10, the control device 23 can also determine the initial capacity sigma of each cell 111 using the above formula (2). That is, when the control device 23 does not know the initial capacity values of the respective cells 111, the control device 23 can determine the initial capacity sigma using the SOC change amounts of the respective cells 111 in the same manner as the method for determining the current capacity sigma.

[0086] On the other hand, in FIG. 1, the case where the abnormal degradation cell detection device 20 is separately present outside the battery pack 10 is shown as an example, but the abnormal degradation cell detection device 20 can also be integrated into the battery pack 10. In this case, the above-described functions of the abnormal degradation cell detection device 20 can be performed by the BMS 12.

[0087] Hereinafter, with reference to FIG. 4, an abnormal degradation cell detection method of the abnormal degradation cell detection device 20 according to an embodiment will be described in detail. The abnormal degradation cell detection method of FIG. 4 described below can be performed by the control device 23 of the abnormal degradation cell detection device 20 described with reference to FIG. 1.

[0088] FIG. 4 schematically shows an abnormal degradation cell detection method according to an embodiment.

[0089] Referring to FIG. 4, in an abnormal degradation cell detection device 20 according to an embodiment, an initial capacity sigma can be determined for each cell 111 included in the battery module 11 during the initial use of the battery pack 10 (S10). In step S10, the abnormal degradation cell detection device 20 can calculate the initial capacity sigma of each cell 111 using the initial capacity value of each cell 111 and the formula 1. The initial capacity sigma calculated in this way can be used as a statistical value indicating the initial capacity deviation among the cells 111 included in the battery module 11.

[0090] Thereafter, the abnormal degradation cell detection device 20 can obtain the cell voltage value of each cell 111 included in the battery module 11 during the rest period (S11). The battery pack 10 can measure the cell voltage value of each cell 111 included in the battery module 11 during the rest period after charging and the rest period after discharging for each charge-discharge cycle. Thereafter, the battery pack 10 can transmit the state data of each cell 111 including the cell voltage value measured during each rest period to the abnormal degradation cell detection device 20.

[0091] The abnormal degradation cell detection device 20 can use the cell voltage value obtained through step S11 to determine the SOC value of each cell 111 included in the battery module 11 during the rest period respectively (S12). In step S12, the abnormal degradation cell detection device 20 can determine the SOC value of each cell 111 using the cell voltage value of each cell 111 detected during each rest period and the preset OCV-SOC data.

[0092] The abnormal degradation cell detection device 20 can determine the amount of change in the state of charge (SOC) for each cell 111 included in the battery module 11 using the SOC value determined through step S12 (S13). In step S13, the amount of change in the SOC indicates the amount by which the SOC of each cell 111 has changed due to charging and discharging during the corresponding charge-discharge cycle. The abnormal degradation cell detection device 20 can determine the amount of change in the SOC of each cell 111 by comparing the SOC values in two rest periods (the post-charge rest period and the post-discharge rest period) belonging to the same charge-discharge cycle with each other. For example, the abnormal degradation cell detection device 20 can determine the amount of change in the SOC of each cell 111 by subtracting the SOC value in the post-discharge rest period from the SOC value in the post-charge rest period.

[0093] The abnormal degradation cell detection device 20 can determine the current capacity sigma for each cell 111 included in the battery module 11 using the amount of change in the SOC of each cell 111 determined through step S13 (S14). In step S14, the abnormal degradation cell detection device 20 can determine the current capacity sigma of each cell 111 using the amount of change in the SOC of each cell 111 and the above formula 2.

[0094] When the current capacity sigma of each cell 111 is determined, the abnormal degradation cell detection device 20 can compare this with the initial capacity sigma to determine the amount of change in the capacity sigma of each cell 111 included in the battery module 11 (S15). In step S15, the abnormal degradation cell detection device 20 can determine the difference value (current capacity sigma - initial capacity sigma) between the current capacity sigma and the initial capacity sigma as the amount of change in the capacity sigma.

[0095] Based on the amount of change in the capacity sigma of each cell 111 determined through step S15, the abnormal degradation cell detection device 20 can detect an abnormally degraded cell from the battery module 11 (S16).

[0096] In step S16, the abnormal degradation cell detection device 20 can compare the capacity sigma change amount of each cell 111 with a threshold value. The abnormal degradation cell detection device 20 can determine a cell 111 whose capacity sigma change amount is equal to or greater than the threshold value as an abnormal degradation cell.

[0097] In step S16, the abnormal degradation cell detection device 20 can detect an outlier from the capacity sigma change amounts of the cells 111 using the Grubbs verification method. When an outlier is detected, the abnormal degradation cell detection device 20 can determine the corresponding cell 111 as an abnormal degradation cell.

[0098] When it is determined that there is an abnormal degradation cell in the battery module 11 through step S16 (S17), the abnormal degradation cell detection device 20 can transmit information about the abnormal degradation cell to the upper controller 30 (S18).

[0099] The abnormal degradation cell detection device 20 continuously performs steps S11 to S18 to continuously monitor the degradation deviation of the cells 111 during the use of the battery pack 10 and can detect abnormal degradation cells.

[0100] In the above, in step S10, it was explained that the abnormal degradation cell detection device 20 determines the initial capacity sigma using the initial capacity values of the cells 111. However, when the abnormal degradation cell detection device 20 does not know the initial capacity values of the cells 111, it can also determine the initial capacity sigma of each cell 111 by performing the same steps as steps S11 to S14 during the initial use of the battery pack 10.

[0101] The above-described abnormal degradation cell detection device 20 can also be used to detect abnormal degradation cells in an energy storage system (ESS: Energy Storage System).

[0102] FIG. 5 shows an example of an energy storage system including an abnormal degradation cell detection device according to an embodiment. The abnormal degradation cell detection device 20 in the ESS of FIG. 5 corresponds to the abnormal degradation cell detection device 20 described with reference to FIGS. 1 to 4.

[0103] Referring to FIG. 5, the ESS can include a battery bank 1, a system BMS 2, an energy management system (EMS), and a power conversion system (PSC) 5.

[0104] The battery bank 1 can include a plurality of cells (not shown) connected in series or parallel to each other. For example, the battery bank 1 can include a plurality of battery racks (or battery systems) electrically connected in series or parallel to each other. Further, each battery rack can include a plurality of battery modules 11 electrically connected in series or parallel to each other. Also, each battery module 11 can include a plurality of cells (not shown) electrically connected in series or parallel to each other.

[0105] Such a battery bank 1 can be charged using electrical energy supplied from a power grid (not shown) through the PSC 5. Also, the PSC 5 can supply the electrical energy stored in the battery bank 1 to the power grid through the PSC 5.

[0106] The PSC 5 can operate as a power conversion device that converts electrical characteristics (such as direct current (DC), alternating current (AC), voltage, frequency, etc.) to transfer electrical energy between the battery bank 1 and the power grid. Usually, in the battery bank 1, electrical energy in the form of direct current (DC) is used, and in the power grid, electrical energy in the form of alternating current (AC) is used. Therefore, the PSC 5 can transfer the electrical energy stored in the battery bank 1 to the power grid through DC-AC conversion, or transfer the electrical energy supplied from the power grid to the battery bank 1 through AC-DC conversion.

[0107] In addition to the power conversion and distribution functions described above, PSC5 can also perform control functions for power quality such as the active power and reactive power of the ESS. PSC5 can also perform a monitoring / control function for monitoring the voltage and operating state of the ESS. PSC5 can also perform a system interconnection protection function for protecting the power system during a power outage. PSC5 can also perform an independent operation function such as operating the ESS by utilizing Battery Bank 1 even when there is no power supply.

[0108] Battery Bank 1 can be managed by System BMS2. System BMS2 can monitor the state of Battery Bank 1 and control it so that Battery Bank 1 operates in an optimal state. For this purpose, System BMS2 can perform functions such as state (cell voltage, current, temperature, SOC, life (SOH: State Of Health), etc.) monitoring function, control function (for example, temperature control, cell balancing control), and protection function (for example, prevention of over-discharge, over-charging, over-current, etc.) for the battery cells that make up Battery Bank 1.

[0109] For monitoring the state of Battery Bank 1, System BMS2 can collect state data (such as cell voltage value, SOC value, current value, temperature value, etc.) from Battery Bank 1. The battery rack that makes up Battery Bank 1 can collect state data from the battery module 11 belonging to it and transmit this to System BMS2. The battery rack that makes up Battery Bank 1 can communicate with other battery racks or System BMS2 through CAN (Controller Area Network) communication and transmit and receive data in a Daisy Chain manner.

[0110] EMS4 is an integrated control device that monitors and controls the power usage of the power system and the power supply of the ESS in real time for efficient energy operation of the ESS. EMS4 can monitor the state of the entire system (Battery Bank 1, System BMS2, and PSC5) that makes up the ESS and control the operation of the ESS.

[0111] The ESS can be operated to perform at least one charge-discharge cycle per day. One charge-discharge cycle can include a charging period, a rest period after charging, a discharging period, and a rest period after discharging.

[0112] The system BMS2 can collect the state data (such as cell voltage value, SOC value, etc.) of each battery module 11 that constitutes the battery bank 1 for each rest period. The system BMS2 can transmit the state data collected in this way to the abnormal degradation cell detection device 20.

[0113] Upon receiving this, the abnormal degradation cell detection device 20 can classify the state data for each battery module 11 and perform a process for detecting abnormal degradation cells for each battery module 11 using the state data classified in this way. Since the method by which the abnormal degradation cell detection device 20 detects abnormal degradation cells for each battery module 11 has been described in detail with reference to FIGS. 1 to 4 described above, duplicate explanations are omitted.

[0114] On the other hand, in FIG. 5, the case where the abnormal degradation cell detection device 20 exists separately from the system BMS2 is shown as an example, but the abnormal degradation cell detection device 20 can also be integrated into the system BMS2. In this case, the above-described functions of the abnormal degradation cell detection device 20 can be performed by the system BMS2.

[0115] According to the above, the abnormal degradation cell detection device 20 according to the embodiment can detect abnormally degraded cells at an early stage. Therefore, it is possible to prevent safety problems such as ignition caused by abnormally degraded cells in advance.

[0116] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it goes without saying that various modifications and variations are possible within the equivalent scope of the technical idea of the present invention and the scope of the claims described below by those having ordinary knowledge in the technical field to which the present invention belongs.

Description of Symbols

[0117] 1: Battery bank 2: System BMS 3: EMS 4: PSC 10: Battery pack 11: Battery module 111: Cell 12: BMS 20: Abnormal degradation cell detection device 21: Communication device 22: Storage device 23: Control device 30: Higher-level controller

Claims

1. A method for detecting an abnormally deteriorated cell in a battery module including a plurality of cells, comprising: obtaining a first statistical value indicative of a capacity deviation at a first time point for the plurality of cells; obtaining second statistics indicative of a capacity deviation at a second time for the plurality of cells; comparing the first statistical value and the second statistical value to detect an abnormally degraded cell.

2. The step of acquiring the first statistical value comprises: obtaining the first statistical value using an initial capacity value of each of the plurality of cells; The initial capacitance value corresponds to the formation capacitance of each cell. The method for detecting an abnormally deteriorated cell according to claim 1 .

3. The step of obtaining the first statistical value using the initial capacity value comprises: obtaining a mean and a standard deviation of the initial capacitance values ​​for the plurality of cells; calculating a first sigma for each of the plurality of cells using the initial capacity value, the mean and the standard deviation; obtaining the first sigma calculated for each of the plurality of cells as the first statistical value; The method for detecting an abnormally deteriorated cell according to claim 2 .

4. The step of acquiring the first statistical value comprises: Detecting a first state of charge (SOC) change amount during a first period for each of the plurality of cells; obtaining an average value and a standard deviation of the first SOC change amount for the plurality of cells; calculating a second sigma for each of the plurality of cells using the first SOC change, the average, and the standard deviation; determining the second sigma calculated for each of the plurality of cells as the first statistical value; The method for detecting an abnormally deteriorated cell according to claim 1 .

5. The step of detecting the first SOC change amount includes: detecting a first SOC value of each of the plurality of cells during a first rest period of the battery module; detecting a second SOC value of each of the plurality of cells in a second rest period of the battery module after the first rest period; Calculating the first SOC change amount from a difference between the first SOC value and the second SOC value for each of the plurality of cells; The method for detecting an abnormally deteriorated cell according to claim 4.

6. The step of detecting the first SOC value includes: acquiring a first cell voltage value detected at a time when a predetermined time has elapsed since the start of the first pause period for each of the plurality of cells; and determining, for each of the plurality of cells, the first SOC value using the first cell voltage value; The step of detecting the second SOC value includes: acquiring a second cell voltage value detected at a time when a predetermined time has elapsed since a time when the second pause period is started for each of the plurality of cells; and determining, for each of the plurality of cells, the second SOC value using the second cell voltage value. The method for detecting an abnormally deteriorated cell according to claim 5 .

7. The step of acquiring the second statistical value comprises: Detecting a second SOC change amount during a second time period for each of the plurality of cells; obtaining an average value and a standard deviation of the second SOC change amount for the plurality of cells; calculating a third sigma for each of the plurality of cells using the second SOC change, the average, and the standard deviation; determining the third sigma calculated for each of the plurality of cells as the second statistical value; The method for detecting an abnormally deteriorated cell according to claim 1 .

8. The step of detecting the second SOC change amount includes: detecting a third SOC value of each of the plurality of cells during a third rest period of the battery module; detecting a fourth SOC value of each of the plurality of cells in a fourth rest period after the third rest period of the battery module; Calculating the second SOC change amount from a difference between the third SOC value and the fourth SOC value for each of the plurality of cells. The method for detecting an abnormally deteriorated cell according to claim 7.

9. The step of detecting the third SOC value includes: acquiring a third cell voltage value detected at a time when a predetermined time has elapsed since a time when the third pause period is started for each of the plurality of cells; and determining, for each of the plurality of cells, the third SOC value using the third cell voltage value; The step of detecting the fourth SOC value includes: acquiring a fourth cell voltage value detected at a time when a predetermined time has elapsed since a time when the fourth pause period is started for each of the plurality of cells; and determining, for each of the plurality of cells, the fourth SOC value using the fourth cell voltage value. The method for detecting an abnormally deteriorated cell according to claim 8.

10. The step of detecting the second SOC change amount includes: Detecting a fourth SOC change amount between a post-charge pause section and a post-discharge pause section for each of the plurality of cells in each charge / discharge cycle; determining the second SOC change amount from an average value of the fourth SOC change amount detected during the second period; The second period includes at least one charge / discharge cycle. The method for detecting an abnormally deteriorated cell according to claim 7.

11. The step of detecting the abnormally degraded cell comprises: comparing a difference between the first statistical value and the second statistical value with a threshold; determining a cell for which the difference value is equal to or greater than the threshold as an abnormal degraded cell; The method for detecting an abnormally deteriorated cell according to claim 1 .

12. The step of detecting the abnormally degraded cell comprises: calculating a difference between the first statistical value and the second statistical value for each of the plurality of cells; detecting an outlier from among the difference values ​​of each of the plurality of cells using a Grubbs' test method; determining a cell, the difference value of which is an outlier, from among the plurality of cells as an abnormally degraded cell; The method for detecting an abnormally deteriorated cell according to claim 1 .

13. An abnormally deteriorated cell detection device for a battery module including a plurality of cells, An abnormally degraded cell detection device including a control device that acquires a first statistical value indicating a capacity deviation at a first point in time for the plurality of cells, acquires a second statistical value indicating a capacity deviation at a second point in time for the plurality of cells, and compares the first statistical value and the second statistical value with each other to detect an abnormally degraded cell.

14. a storage device for storing initial capacity values ​​of the plurality of cells; the control device calculates a first sigma for each of the plurality of cells using the initial capacity value for each of the plurality of cells, an average value and a standard deviation of the initial capacity values ​​for the plurality of cells, and uses the first sigma calculated for each of the plurality of cells as the first statistical value; The initial capacitance value corresponds to the formation capacitance of each cell. The abnormally deteriorated cell detection device according to claim 13.

15. The control device includes: Detecting a first SOC change amount during a first period for the plurality of cells; Calculating an average value and a standard deviation of the first SOC change amount for the plurality of cells; calculating a second sigma for each of the plurality of cells using the first SOC change, the average, and the standard deviation; using the second sigma calculated for each of the plurality of cells as the first statistical value; The abnormally deteriorated cell detection device according to claim 13.

16. The control device includes: determining a first SOC value in the first post-charge pause period using a first cell voltage value detected at a time point when a predetermined time has elapsed since a time point when a first post-charge pause period is started for each of the plurality of cells; determining a second SOC value in the first post-discharge pause interval using a second cell voltage value detected at a time point when a predetermined time has elapsed since a time point when a first post-discharge pause interval is started for each of the plurality of cells; determining the first SOC change amount from a difference value between the first SOC value and the second SOC value; The abnormally deteriorated cell detection device according to claim 15.

17. The control device includes: Detecting a second SOC change amount during a second period for the plurality of cells; Calculating an average value and a standard deviation of the second SOC change amount for the plurality of cells; calculating a third sigma for each of the plurality of cells using the second SOC change, the average, and the standard deviation; using the third sigma calculated for each of the plurality of cells as the second statistical value; The abnormally deteriorated cell detection device according to claim 13.

18. The control device includes: determining a third SOC value in the second post-charge pause period using a third cell voltage value detected at a time point when a predetermined time has elapsed since a time point when a second post-charge pause period is started for each of the plurality of cells; determining a fourth SOC value in the second post-discharge pause interval using a fourth cell voltage value detected at a time point when a predetermined time has elapsed since a time point when a second post-discharge pause interval is started for each of the plurality of cells; determining the second SOC change amount from a difference value between the third SOC value and the fourth SOC value; The abnormally deteriorated cell detection device according to claim 17.

19. The control device includes: Detecting a fourth SOC change amount between a post-charge pause section and a post-discharge pause section for each of the plurality of cells in each charge cycle during the second period, and determining the second SOC change amount from an average value of the fourth SOC change amounts detected during the second period; the second period of time includes at least one charge / discharge cycle; The abnormally deteriorated cell detection device according to claim 17.

20. The control device includes: comparing a difference between the first statistical value and the second statistical value with a threshold; determining a cell whose difference value is equal to or greater than the threshold value as an abnormally degraded cell; The abnormally deteriorated cell detection device according to claim 13.

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