Abstract:
An apparatus for specifying an abnormality-occurrence area of a secondary battery system includes an information transmission unit for outputting block voltage values and an average block voltage value, an information acquisition unit for acquiring information about a module accommodating a block that has output a block voltage value when the difference between a reference block voltage value obtained from the correlation between the block voltage value and the average block voltage value and the block voltage value is equal to or greater than a preset voltage threshold, a notification reception unit for receiving a notification about the occurrence of an abnormality in a secondary battery, and a module specification unit for specifying at least the module corresponding to the latest module information as the module in which an abnormality occurred when the notification reception unit receives a notification.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Continuation of International Application No. PCT/JP2014/071601 filed on Aug. 19, 2014, which is based upon and claims the benefit of priority from Japanese Patent Application No 2013-180563 filed on Aug. 30, 2013, the contents all of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to an apparatus (device), a method, and a non-transitory recording medium storing a program for identifying (specifying) a position of an abnormality (abnormality-occurrence area) occurred in a secondary battery system including two or more modules each accommodating one or more blocks. Each of the blocks is formed by connecting battery cells of two or more secondary batteries. 
       BACKGROUND ART 
       [0003]    In general, frequency adjustment in an electric power system and adjustment of power demands and power supplies in the electric power system are carried out using a plurality of power generators, storage batteries, etc., equipped in the electric power system. Further, in most cases, adjustment in the difference between the generated electric power from natural energy based power generators and its planned output electric power, and reduction in the changes of electric power generated by the natural energy based power generators are also performed using the power generators, storage batteries, etc. In comparison with general electric power generators, the storage batteries can change the electric power output at high speed, and can be used effectively in frequency adjustment of the electric power system, adjustment of the difference between the generated electric power from natural energy based power generators and its planned output electric power, and adjustment of power demands and power supplies in the electric power system. 
         [0004]    In this regard, as a storage battery operated at high temperature connected to the electric power system, a sodium-sulfur battery (hereinafter referred to as the NaS battery) is used, for example. This NaS battery is a high temperature secondary battery containing metal sodium and sulfur as active materials in an isolated manner using a solid electrolyte tube. When the NaS battery is heated at about 300° C., a certain amount of energy is produced by an electrochemical reaction of both of the melted active materials. Normally, the NaS battery is formed by assembling a plurality of battery cells, and used in a form of a module including a plurality of battery cells connected together. That is, the module has structure where circuits (strings) each formed by connecting a plurality of battery cells in series are connected in parallel to form a block, and at least two blocks are connected in series, and placed in a heat insulating container. 
         [0005]    As a method of reporting occurrence of an abnormality of such a module, a method of detecting an abnormality of a battery by comparing electric discharge depth of each block, and notifying the abnormality is disclosed (e.g., see Japanese Laid-Open Patent Publication No. 03-158781). In this method, the presence of the abnormality is determined for each of the blocks of the module. Therefore, in comparison with the case of detecting the abnormality for each of the individual NaS battery cells of the block, the apparatus is not complicated, and the production cost can be reduced advantageously. 
       SUMMARY OF INVENTION 
       [0006]    It is considered that failures in the battery cells, and consequently, failures in the modules are caused by internal short circuiting or external short circuiting in the battery cells. 
         [0007]    For example, external short circuiting of the battery cells may be caused by formation of an external short circuiting loop due to leakage of active materials in the battery cells. For example, internal short circuiting of the battery cells may be caused by damages, etc. of a beta tube. 
         [0008]    External short circuiting and internal short circuiting of these battery cells can be detected by checking the electric discharge depth in each block as can be seen from Japanese Laid-Open Patent Publication No. 03-158781. However, the change in the electric discharge depth due to short circuiting does not occur rapidly, but occur gradually over a relatively long period of time. Therefore, it is difficult to determine which module (or which block) has the abnormality, and initial response to the occurrence of the abnormality may be delayed undesirably. 
         [0009]    The present invention has been made to take the problems of this type into account, and an object of the present invention is to provide an apparatus, a method, and a non-transitory recording medium storing a program for identifying a position of an abnormality occurred in a secondary battery system in which if an abnormality occurs, it is possible to identify a module as the abnormality source at an early stage, and it is possible to implement an initial response to the occurrence of the abnormality at an early stage. 
         [0000]    [1] An apparatus according to the first invention is an apparatus for identifying a position of an abnormality occurred in a secondary battery system. The secondary battery system includes a plurality of modules each accommodating one or more blocks. Each of the blocks is formed by connecting battery cells of two or more secondary batteries. The apparatus includes a voltage measurement unit configured to detect voltage of the secondary batteries on a block by block basis, and to output the detected voltage as a block voltage value every unit time, an average block voltage calculation unit configured to calculate an average block voltage value of each module, based on the block voltage value provided from the voltage measurement unit every unit time, an information acquisition unit configured to acquire information of a module (module information) accommodating a block as an output source of the block voltage value, when a reference block voltage value is obtained from correlation relationship between the block voltage value and an average block voltage value of the corresponding module, and a difference between the reference block voltage value and the block voltage value is a predetermined voltage threshold value or more, a report reception unit configured to receive a report of an abnormality occurred in the secondary batteries, and a module identification unit configured to identify, as a module having the abnormality, the module corresponding to the module information at time of receiving the report by the report reception unit. 
         [0010]    If external short circuiting or internal circuiting occurs in any one of the battery cells, the block voltage value of the block including the battery cell having the short circuiting is decreased steeply. Thereafter, in some cases, after the elapse of a certain time period, the voltage returns to the original voltage level before short circuiting. Further, if the scale of the system becomes large, the number of blocks to be monitored is increased correspondingly. Therefore, it becomes further difficult to recognize the decrease in the voltage due to short circuiting from the changes of the block voltage values of all of the blocks. However, in the present invention, the reference block voltage is obtained from correlation relationship between the block voltage value and the average block voltage value. When the difference between the reference block voltage and the block voltage value is the predetermined voltage threshold value or more, information of the module which accommodates the block as the output source of the block voltage value is acquired. In this manner, it is possible to accurately detect whether there is a decrease in the block voltage, and detect occurrence of an abnormality due to short circuiting. 
         [0011]    Therefore, in the present invention, by identifying the module which is the source of the abnormality, it becomes possible to send a report to a local user, a local administrator, etc. Thus, countermeasures focused on the identified abnormality source can be taken at an early stage. It becomes possible to suppress expansion of damage. 
         [0000]    [2] In the first invention, the information acquisition unit may include a voltage comparator unit configured to compare the difference between the block voltage value and the reference block voltage value with a predetermined voltage threshold value, and the voltage comparator unit may include a linear regression processing unit configured to perform linear regression processing of relationship between a plurality of block voltage values and a plurality of average block voltage values accumulated in a fixed period to obtain information of one regression line, and a reference voltage acquisition unit configured to acquire the reference block voltage value corresponding to the block voltage value every unit time, based on information of the regression line. In this manner, it is possible to obtain the reference block voltage value easily based on the correlation relationship between the block voltage value and the average block voltage value, and achieve acceleration of computation.
 
[3] In the case [2], the linear regression processing unit may accumulate the plurality of block voltage values and the plurality of average block values, and concurrently, perform linear regression processing of relationship between the plurality of block voltage values and the plurality of average block voltage values accumulated in the fixed period in last time to obtain information of one regression line.
 
[4] In this case, the regression line may be updated at every interval of the fixed period, and the reference voltage acquisition unit may acquire the reference block voltage value of the fixed period in present time, based on the information of the regression line acquired in the fixed period in the last time.
 
[5] In the case [2], the linear regression processing unit may accumulate the plurality of block voltage values and the plurality of average block values in the fixed period, and in a period corresponding to the unit time at an end of the fixed period, may perform linear regression processing of relationship between the plurality of block voltage values and the plurality of average block voltage values accumulated in the fixed period to acquire information of one regression line.
 
[6] In this case, the regression line may be updated at every interval of the fixed period, and the reference voltage acquisition unit may acquire the reference block voltage value in the fixed period in present time based on information of the regression line acquired in a period corresponding to the unit time at the end of the fixed period in last time.
 
[7] In any of the cases [2] to [6], in a period from time of starting operation of the secondary battery system to time at which information of the regression line is acquired for first time, since information of the regression line is not acquired, no operation may be performed at least in the reference voltage acquisition unit and the information acquisition unit.
 
[8] In any of cases [2] to [7], the block voltage value may be inputted to the linear regression processing unit and the reference voltage acquisition unit through a delay circuit for introducing a delay by the fixed period, and the average block voltage value may be inputted to the linear regression processing unit through a delay circuit configured to introduce a delay by the fixed period. In this manner, it becomes possible to determine the fixed period arbitrarily depending on the system scale, etc., to achieve excellent versatility.
 
[9] In this case, delay time in the delay circuits may be selected in accordance with behavior where the block voltage drops temporarily due to short circuiting of at least one of the battery cells. In this manner, it is possible to improve the detection accuracy of the block having a temporary drop in the block voltage due to short circuiting of at least one of the battery cells.
 
[10] In the first invention, as the voltage threshold value, a voltage value of a temporary drop in the block voltage due to short circuiting of at least one of the battery cells may be selected. In this manner, it is possible to improve the detection accuracy of the block having a temporary drop in the block voltage due to short circuiting of at least one of the battery cells.
 
[11] In the first invention, the apparatus may further include an error output unit configured to receive the module information from the information acquisition unit, and to output the module information together with an error message. By outputting the module information together with the error message to a monitor or a printer, the position of the identified module can be recognized at a glance advantageously.
 
[12] A method according to the second invention is a method of identifying a position of an abnormality occurred in a secondary battery system. The secondary battery system includes a plurality of modules each accommodating one or more blocks. Each of the blocks is formed by connecting battery cells of two or more secondary batteries. The method includes the steps of performing voltage measurement by detecting voltage of the secondary batteries on a block by block basis, and outputting the detected voltage as a block voltage value every unit time, performing average block voltage calculation by calculating an average block voltage value of each module, based on the block voltage value provided from the voltage measurement step every unit time, performing information acquisition by acquiring information of a module (module information) accommodating a block as an output source of the block voltage value, when a reference block voltage value is obtained from correlation relationship between the block voltage value and an average block voltage value of the corresponding module, and a difference between the reference block voltage value and the block voltage value is a predetermined voltage threshold value or more, performing report reception by receiving a report of an abnormality occurred in the secondary batteries, and performing module identification by identifying, as a module having the abnormality, the module corresponding to the module information at time of receiving the report by the report reception step.
 
[13] A non-transitory recording medium according to the third invention stores a program for a secondary battery system. The second battery system includes a plurality of modules each accommodating one or more blocks. Each of the blocks is formed by connecting battery cells of two or more secondary batteries. Further, the secondary battery system includes a voltage measurement unit configured to detect voltage of the secondary batteries on a block by block basis, and to output the detected voltage as a block voltage value every unit time, and an average block voltage calculation unit configured to calculate an average block voltage value of each module, based on the block voltage value provided from the voltage measurement unit every unit time. The program is configured to allow the secondary battery system to perform functions of acquiring information of a module (module information) accommodating a block as an output source of the block voltage value, when a reference block voltage value is obtained from correlation relationship between the block voltage value and an average block voltage value of the corresponding module, and a difference between the reference block voltage value and the block voltage value is a predetermined voltage threshold value or more, receiving a report of an abnormality occurred in the secondary batteries, and identifying, as a module having the abnormality, the module corresponding to the module information at time of receiving the report by the report reception function.
 
         [0012]    As described above, in the apparatus, the method, and the non-transitory recording medium storing the program for identifying a position where an abnormality occurs in a secondary battery system, it is possible to identify a module (or a block) as the abnormality source at an early stage, and it is possible to implement an initial response to the occurrence of the abnormality at an early stage. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  is a diagram showing structure of a secondary battery system and an apparatus for identifying a position of an abnormality occurred in the secondary battery system according to an embodiment of the present invention; 
           [0014]      FIG. 2  is an equivalent circuit diagram showing a battery structural body included in a module; 
           [0015]      FIG. 3  is a block diagram showing structure of a voltage value output unit; 
           [0016]      FIG. 4  is a diagram showing an example of a format of a transmission file; 
           [0017]      FIG. 5  is a block diagram showing structure of an information acquisition unit and an information transmission unit; 
           [0018]      FIG. 6  is a block diagram showing structure of a voltage comparator circuit; 
           [0019]      FIG. 7A  is a graph showing an example of changes in the block voltage value and the average block voltage value in a fixed period; 
           [0020]      FIG. 7B  is a graph showing a correlation diagram between the average block voltage value and the block voltage value, and a regression line matching the correlation diagram; 
           [0021]      FIG. 8A  is a timing chart showing a first processing sequence in a linear regression processing unit; 
           [0022]      FIG. 8B  is a timing chart showing a second processing sequence; 
           [0023]      FIG. 9  is a diagram showing an example of a format of alarm information data; and 
           [0024]      FIG. 10A  is a flow chart showing an example of processing operation of an information request unit; 
           [0025]      FIG. 10B  is a flow chart showing an example of processing operation of a voltage value accumulation unit of the linear regression processing unit; 
           [0026]      FIG. 10C  is a flow chart showing an example of processing operation of a regression line creation unit of the linear regression processing unit; and 
           [0027]      FIG. 11  is a flow chart showing an example of processing operation in a reference voltage acquisition unit, a subtracter, a voltage comparator circuit, alarm information creation unit, etc. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0028]    Hereinafter, an apparatus, a method, and a non-transitory recording medium storing a program for identifying a position of an abnormality occurred in a secondary battery system according to an embodiment of the present invention will be described with reference to  FIGS. 1 to 11 . 
         [0029]    Firstly, as shown in  FIG. 1 , a secondary battery system  10  to which the apparatus, the method, and the non-transitory recording medium storing the program according to the embodiment of the present invention is applied includes a secondary battery storage unit  12 , an abnormality detection unit  14 , and a reporting unit  16 . 
         [0030]    The secondary battery storage unit  12  has structure where a plurality of box shaped packages  18  are arranged in a lateral direction. In an example of  FIG. 1 , four packages  18  (first package  18 A to fourth package  18 D) are arranged in the lateral direction. Further, the secondary battery storage unit  12  has a battery control device  20  for controlling operation of the secondary batteries. 
         [0031]    Two or more modules  22  are stacked in a vertical direction inside each of the packages  18 . Further, each of the packages  18  accommodates a module string  24  formed by connecting these two or more modules  22  in series. In the structure of the example shown in  FIG. 1 , five modules  22  are stacked to form one module string  24 . 
         [0032]    As shown in  FIG. 2 , the module  22  is formed by connecting two or more blocks  26  in series. Each of the blocks  26  is formed by connecting two or more circuits (strings  30 ) in parallel, and each of the strings  30  is formed by connecting two or more battery cells  28  as the secondary batteries in series. For example, eight battery cells  28  are connected in series to form one string  30 ,  12  strings  30  are connected in parallel to form one block  26 , and four blocks  26  are connected in series to form one module  22 . As the secondary battery, a NaS battery, a lithium ion battery, a sodium ion battery, etc. may be used. 
         [0033]    The abnormality detection unit  14  detects abnormal conditions such as a fire based on signals from sensors  32  (heat sensor, smoke sensor, etc.) provided in each of the packages  18 . 
         [0034]    The reporting unit  16  issues a report (abnormality report) indicating occurrence of an abnormality, and transmits the report to a monitoring center, etc., based on an input of an abnormality detection signal Sa (signal indicating occurrence of an abnormality) from the abnormality detection unit  14 . In this case, the report may be transmitted through a public communications network such as the Internet or a mobile phone network. Further, the report may be transmitted to a local user, a local administrator, etc. instead of and/or in addition to the monitoring center. 
         [0035]    Further, the reporting unit  16  outputs an operation stop signal Sb to the battery control device  20  in addition to the above report, based on the input of the abnormality detection signal Sa from the abnormality detection unit  14 . The battery control device  20  stops operation of the secondary batteries in accordance with a predetermined sequence for stopping operation, based on the operation stop signal Sb. 
         [0036]    Further, as shown in  FIG. 1 , an apparatus for identifying a position of an abnormality according to an embodiment of the present invention (hereinafter referred to as an abnormality position identification apparatus  50 ) includes an information transmission unit  52 , an information acquisition unit  54 , a report reception unit  56 , and a module identification unit  58 . 
         [0037]    The information transmission unit  52  has a plurality of voltage value output units  60  provided for the respective module strings  24 . As shown in  FIG. 3 , each of the voltage value output units  60  includes a plurality of block voltage measurement units  62  provided for the respective blocks, a plurality of average block voltage calculation units  64  provided for the respective modules  22 , and one transmission file creation unit  66 . 
         [0038]    Each of the block voltage measurement units  62  measures the voltage across both ends of the corresponding block  26  in accordance with a predetermining monitoring cycle. For example, the block voltage measurement unit  62  measures the voltage across both ends of the corresponding block  26  at a time interval arbitrarily selected in a range from 0.5 to 2 seconds (e.g., one second interval: monitoring cycle). 
         [0039]    The average block voltage calculation unit  64  calculates the average block voltage value Va of the corresponding module  22  based on the block voltage value V from the block voltage measurement unit  62  at each monitoring cycle. 
         [0040]    Each of the transmission file creation units  66  creates a transmission file  68  including information of the corresponding module string  24  at each monitoring cycle. For example, the information of the module string  24  includes an identification number of the module string  24  (module string information), information of a plurality of modules  22  included in the module string  24 , etc. For example, the information of the module  22  includes an identification number of the module  22  (module information), the average block voltage value Va of the module  22 , identification numbers of a plurality of blocks  26  included in the module  22  (block information), and the present block voltage value V corresponding to the plurality of blocks  26 , respectively. 
         [0041]    As an example of a format of a transmission file  68 , a format of the transmission file  68  associated with the first module string  24  is shown in  FIG. 4 . Specifically, in the order from the beginning, the format of the transmission file  68  includes an identification number (MR 1 ) of the first module string  24 , and information of a plurality of modules  22  included in the first module string  24 . 
         [0042]    As an example of the information of the module  22 , the format of information of the first module  22  includes an identification number (M 1 ) of the first module  22 , an average block voltage value Va of this module  22 , and information of a plurality of blocks  26  included in this module  22 . 
         [0043]    For example, the information of the plurality of blocks  26  includes the following items of information: 
         [0044]    (1a) Identification number (B 1 ) of the first block  26   
         [0045]    (1b) Present block voltage value V of the first block  26   
         [0046]    (1c) Identification number (B 2 ) of the second block  26   
         [0047]    (1d) Present block voltage value V of the second block  26   
         [0048]    (1e) Identification number (B 3 ) of the third block  26   
         [0049]    (1f) Present block voltage value V of the third block  26   
         [0050]    (1g) Identification number (B 4 ) of the fourth block  26   
         [0051]    (1h) Present block voltage value V of the fourth block  26   
         [0052]    In the meanwhile, when the reference block voltage value Vb is obtained from the correlation relationship between the block voltage value V and the average block voltage value Va, and the difference between the reference block voltage value Vb and the block voltage value V exceeds a predetermined voltage threshold value Vth or more, the information acquisition unit  54  acquires information of a module  22  accommodating a block  26  as an output source of the block voltage value V. 
         [0053]    Specifically, as shown in  FIG. 5 , the information acquisition unit  54  includes an information request unit  70 , a voltage comparator unit  72 , an alarm information creation unit  74 , an alarm information storage unit  76 , and an alarm information output unit  78 . 
         [0054]    The information request unit  70  requests each of the voltage output units  60  of the information transmission unit  52  to transmit information at each monitoring cycle. Upon the transmission request of information from the information request unit  70 , each of the voltage output units  60  transmits the transmission file  68  including information of the corresponding module string  24 , to the information request unit  70 . 
         [0055]    The voltage comparator unit  72  will be described taking one block  26  as an example. As shown in  FIG. 6 , a linear regression processing unit  80 , a reference voltage acquisition unit  82 , a subtracter  84 , and a voltage comparator circuit  86 . 
         [0056]    The linear regression processing unit  80  performs linear regression processing of relationship between a plurality of block voltage values V accumulated in a fixed period and a plurality of average block voltage values Va to acquire information of one regression line. The reference voltage acquisition unit  82  acquires a reference block voltage value Vb corresponding to the block voltage value V based on the information of regression line every unit time. The subtracter  84  calculates the difference (differential voltage value ΔV) between the block voltage value V and the reference block voltage value Vb. The voltage comparator circuit  86  compares the differential voltage value ΔV from the subtracter  84  with a predetermined voltage threshold value Vth. 
         [0057]    The block voltage value V is inputted to each of the linear regression processing unit  80 , the reference voltage acquisition unit  82 , and the subtracter  84  through a first delay circuit  88   a , respectively. The average block voltage value Va is inputted to the linear regression processing unit  80  through a second delay circuit  88   b.    
         [0058]    The linear regression processing unit  80  includes a voltage value accumulation unit  90  and a regression line creation unit  92 . The voltage value accumulation unit  90  accumulates a plurality of block voltage values V and a plurality of average block voltage values Va inputted every unit time, over a fixed period, in a first memory  94   a . The regression line creation unit  92  creates a correlation diagram (dispersion diagram) of the plurality of block voltage values V and the plurality of average block voltage values Va accumulated in the first memory  94   a , performs least squares regression processing of a regression line (map information) matching this regression diagram, and stores the resulting data in a second memory  94   b.    
         [0059]    For example, as shown in  FIG. 7A , it is assumed that the monitoring cycle is one second and that the fixed period is 20 seconds. The voltage value accumulation unit  90  obtains the block voltage value V and the average lock voltage value Va every second, and accumulates  20  block voltage values V and  20  average block voltage values Va in the first memory  94   a  in the fixed period. Then, as shown in  FIG. 7B , the voltage value accumulation unit  90  creates a correlation diagram of the average block voltage values Va and the block voltage values V stored in the first memory  94   a , determines a regression line La (map information) matching this correlation diagram by performing at least square regression processing, and stores the regression line La in the second memory  94   b.    
         [0060]    In the case where almost no changes are present in the block voltage value V over a fixed period or more, in order to avoid instability in the estimation formula used in least squares regression processing, a regression line (map information) which forcibly use 1 as a correlation coefficient is created. 
         [0061]    The average block voltage value Va on the regression line La corresponding to the block voltage value V is the reference block voltage value Vb corresponding to this block voltage value V. Therefore, the reference voltage acquisition unit  82  acquires the reference block voltage value Vb corresponding to the block voltage value V, based on the map information of the regression line La at each monitoring cycle. 
         [0062]    If the output (differential voltage value ΔV) from the subtracter  84  is the predetermined voltage threshold value Vth or more, the voltage comparator circuit  86  outputs an event log signal Sel to the alarm information creation unit  74 . 
         [0063]    For example, the following two types of processing sequence may be used in the above described linear regression processing unit  80 . 
         [0064]    In the first processing sequence, as shown in  FIG. 8A , in a fixed period (cycle  1 ) from the time t 1  of starting operation of the secondary battery system  10 , the block voltage value V and the average block voltage value Va are not inputted to the linear regression processing unit  80  due to the delays in the first delay circuit  88   a  and the second delay circuit  88   b.    
         [0065]    The block voltage value V and the average block voltage value Va are inputted to the linear regression processing unit  80  from the start point t 2  of the next fixed period (cycle  2 ). The block voltage value V and the average block voltage value Va are inputted over this fixed period at each monitoring cycle, and accumulated in the first memory  94   a.    
         [0066]    In the next fixed period (cycle  3 ), the block voltage value V and the average block voltage value Va are inputted at each monitoring cycle, and while the block voltage value V and the average block voltage value Va are accumulated in the first memory  94   a , the following processes are performed concurrently. Specifically, in the regression line creation unit  92 , a regression line La (map information) is created based on the block voltage values V and the average block voltage values Va previously accumulated in the fixed period (cycle  2 ), and the regression line La is stored in a second memory  94   b.    
         [0067]    In the three fixed periods (cycle  1  to cycle  3 ) from the time t 1  of starting operation of the secondary battery system  10 , since the regression line La (map information) is not created, operations of the reference voltage acquisition unit  82  and the voltage comparator circuit  86  are stopped. That is, these periods define an operation stop period Ts of the reference voltage acquisition unit  82  and the voltage comparator circuit  86 . 
         [0068]    In the next fixed period (cycle  4 ), the block voltage value V and the average block voltage value Va are inputted at each monitoring cycle, and while the block voltage value V and the average block voltage value Va are accumulated in the first memory  94   a , the following processing is performed concurrently. Specifically, in the regression line creation unit  92 , a regression line La (map information) is created based on the block voltage value V and the average block voltage value Va accumulated in the first memory  94   a  in the previous fixed period (cycle  3 ), and the regression line La is stored in a second memory  94   b . Further, in this cycle  4 , a reference block voltage value Vb corresponding to the block voltage value V is acquired based on the regression line La (map information) created in the previous fixed period (cycle  3 ) at each monitoring cycle. Further, the difference between the block voltage value V and the reference block voltage value Vb (differential voltage value ΔV) is compared with a predetermined voltage threshold value Vth. From the next fixed period (cycle  5 ), the same processes as in the case of the cycle  4  are performed. 
         [0069]    In the second processing sequence, as shown in  FIG. 8B , in the fixed period (cycle  1 ) from the time t 1  of starting operation of the secondary battery system  10 , the block voltage value V and the average block voltage value Va are not inputted to the linear regression processing unit  80  due to the delay in the first delay circuit  88   a  and the second delay circuit  88   b.    
         [0070]    The block voltage value V and the average block voltage value Va are inputted to the linear regression processing unit  80  from the start point t 2  of the next fixed period (cycle  2 ). The block voltage value V and the average block voltage value Va are inputted at each monitoring cycle over this fixed period (cycle  2 ), and accumulated in the first memory  94   a . In a period corresponding to the last monitoring cycle of this cycle  2 , in the regression line creation unit  92 , a regression line La (map information) is created based on the block voltage value V and the average block voltage value Va accumulated in this cycle  2 , and the regression line La is stored in the second memory  94   b.    
         [0071]    In this case, in the two fixed periods (cycle  1  and cycle  2 ) from the time t 1  of starting operation of the secondary battery system  10 , since the regression line La (map information) is not created, operations of the reference voltage acquisition unit  82  and the voltage comparator circuit  86  are stopped (operation stop period Ts). 
         [0072]    In the next fixed period (cycle  3 ), the block voltage value V and the average block voltage value Va are inputted at each monitoring cycle, and accumulated in the first memory  94   a . In a period corresponding to the last monitoring cycle, in the regression line creation unit  92 , a regression line La (map information) is created based on the block voltage values V and the average block voltage values Va accumulated in this cycle  3 , and the regression line La is stored in the second memory  94   b . Further, in this cycle  3 , at each monitoring cycle, a reference block voltage value Vb corresponding to the block voltage value V is obtained based on the regression line La (map information) created in the previous fixed period (cycle  2 ). Moreover, the difference between the block voltage value V and the reference block voltage value Vb (differential voltage value ΔV) is compared with a predetermined voltage threshold value Vth. From the next fixed period (cycle  4 ), the same processes as in the case of the cycle  3  are performed. 
         [0073]    The above delay time in the first delay circuit  88   a  and the second delay circuit  88   b  corresponds to the fixed period. This time period can be adopted based on the behavior where the corresponding string  30  turns into an object having insulating property due to short circuiting of one battery cell  28 , and the block voltage value is dropped temporarily. For example, a period selected from 10 to 60 seconds can be adopted arbitrarily (e.g., 20 seconds) as this delay time. Further, as the voltage threshold value Vth, a voltage value of a temporary drop due to short circuiting of one battery cell  28 , e.g., 200 mV may be selected. 
         [0074]    The alarm information creation unit  74  creates alarm information data  96  (see  FIG. 9 ) based on the input of the event log signal Sel outputted from the voltage comparator circuit  86 , and transmits the alarm information data  96  to the alarm information storage unit  76  and the alarm information output unit  78 . For example, the following items of information are registered as the alarm information data  96 . 
         [0075]    (2a) Identification number of the module string  24  accommodating the block  26  corresponding to the voltage comparator circuit  86  as an output source of the event log signal Sel (module string information) 
         [0076]    (2b) Identification number of the module  22  (module information) 
         [0077]    (2c) Identification number of the block  26  (block information) 
         [0078]    For example, as shown in  FIG. 9 , as one piece of alarm information data  96 , from the beginning part, the present date (year, month, day), the present time (hour, minute), the module string information, the module information, the block information, and the present block voltage value V are stored. 
         [0079]    The alarm information storage unit  76  stores the alarm information data  96  created by the alarm information creation unit  74  in a memory  98  which adopts a stack method (last-in first-out method). Therefore, the alarm information data  96  retrieved from the memory  98  is the latest alarm information data  96 . 
         [0080]    The alarm information output unit  78  converts the alarm information data  96  transmitted successively from the alarm information creation unit  74  into display data and printing data, and outputs these items of data to a monitor  100  and a printer  102 , respectively, together with an error message (such as a message “SHORT-CIRCUITING ABNORMALITY”). Consequently, the alarm information (year, month, day, time, module string information, module information, block information, present block voltage value V) is displayed together with the error message on the monitor  100 , and printed by the printer  102  together with the error message. 
         [0081]    In the meanwhile, as shown in  FIG. 1 , the report reception unit  56  receives the report (abnormality report) indicating occurrence of an abnormality from the reporting unit  16 . Specifically, when the report reception unit  56  receives the abnormality report, the report reception unit  56  starts operation of the module identification unit  58 . 
         [0082]    The module identification unit  58  identifies, among the plurality of modules  22 , a module  22  corresponding to the module string information and the module information registered in the latest alarm information data  96  as a module  22  having the abnormality. 
         [0083]    Specifically, operation of the module identification unit  58  is started by the report reception unit  56 , and the module identification unit  58  identifies, as a module  22  having the abnormality, the module  22  corresponding to the module string information and the module information registered in the latest alarm information data  96  stored in the memory  98 . The identified module  22  is notified to, e.g., an operator by outputting the module information and the error message (for example, “ACCIDENT IN THE FIRST MODULE”) to the monitor  100  and/or the printer  102 . Further, preferably, an image with a symbol indicating occurrence of the accident may be displayed on the monitor  100 , or printed on a printing paper, together with a schematic image of the secondary battery storage unit  12 , at the position of the identified module  22 . In this manner, the position of the identified module  22  can be recognized at a glance. 
         [0084]    Next, processing operation of the abnormality identification apparatus according to the embodiment of the present invention will be described with reference to flow charts in  FIGS. 10A to 11 . Each of functional units of at least the information acquisition unit  54  operates under a multitask environment. 
         [0085]    At the outset, processing operation of the information request unit  70  will be described with reference to  FIG. 10A . Firstly, in step S 1 , the information request unit  70  requests each of the voltage value output units  60  of the information transmission unit  52  to transmit information. Upon the transmission request of information from the information request unit  70 , each of the voltage value output units  60  transmits a transmission file  68  including information of the corresponding module string  24  to the information acquisition unit  54 . 
         [0086]    In step S 2 , the information request unit  70  receives the transmission file  68  from each of the voltage value output units  60 . 
         [0087]    In step S 3 , it is determined whether or not there is a request for stopping operation of the information request unit  70  (e.g., end request due to interruption of the power supply, maintenance operation, etc.). If there is no request for stopping operation, the routine returns to step S 1  to repeat the processes of step S 1  and the subsequent steps. If there is an end request, operation of the information request unit  70  is finished. 
         [0088]    Next, processing operation of the voltage value accumulation unit  90  of the linear regression processing unit  80  will be described with reference to  FIG. 10B . Firstly, in step S 101 , the block voltage value V of each of all of the blocks  26  included in the acquired transmission file  68  and the average block voltage value Va of each module are obtained, and accumulated in the first memory  94   a.    
         [0089]    In step S 102 , it is determined whether there is an end request to the voltage value accumulation unit  90  of the linear regression processing unit  80 . If there is no request for stopping operation, the routine returns to step S 101  to repeat the processes of step S 101  and the subsequent steps. If there is an end request, operation of the voltage value accumulation unit  90  is finished. 
         [0090]    Next, processing operation of the regression line creation unit  92  of the linear regression processing unit  80  will be described with reference to  FIG. 10C . Firstly, in step S 201 , a regression line La (map information) is created based on the block voltage values V and the average block voltage values Va accumulated in the first memory  94   a , and the regression line La is stored in the second memory  94   b.    
         [0091]    In step S 202 , it is determined whether there is an end request to the regression line creation unit  92  of the linear regression processing unit  80 . If there is no request for stopping operation, the routine returns to step S 201  to repeat the processes of step S 201  and the subsequent steps. When an end request is made, operation of the regression line creation unit  92  is finished. 
         [0092]    Next, operation of the reference voltage acquisition unit  82 , the subtracter  84 , the voltage comparator circuit  86 , the alarm information creation unit  74 , etc. will be described with reference to  FIG. 11 . 
         [0093]    Firstly, in step S 301 , it is determined whether the present period is the operation stop period Ts. If the present period is the operation stop period Ts, the routine waits for the end of the operation stop period Ts. When operation of the operation stop period Ts is finished, the routine proceeds to the next step S 302 . The reference voltage acquisition unit  82  acquires the reference block voltage value Vb corresponding to the block voltage value V based on the latest regression line La (map information) created by the regression line creation unit  92 . 
         [0094]    In step S 303 , the subtracter  84  calculates the difference between the block voltage value V and the reference block voltage value Vb (differential voltage value ΔV). In step S 304 , the voltage comparator circuit  86  compares the difference voltage value ΔV with the voltage threshold value Vth. In step S 305 , if it is determined that the differential voltage value ΔV is the voltage threshold value Vth or more, the routine proceeds to step S 306  to output an event log signal Sel from the voltage comparator circuit  86  to the alarm information creation unit  74 . 
         [0095]    In step S 307 , the alarm information creation unit  74  creates the alarm information data  96 . Specifically, the alarm information creation unit  74  creates the alarm information data  96  having registrations of the following items of information, 
         [0096]    (3a) Present date and time 
         [0097]    (3b) Identification number of the module string  24  accommodating the block  26  corresponding to the voltage comparator circuit  86  as an output source of the event log signal Sel (module string information) 
         [0098]    (3c) Identification number of the module  22  (module information) 
         [0099]    (3d) Identification number of the block  26  (block information) 
         [0100]    In step S 308 , the alarm information output unit  78  converts the created alarm information data  96  into display data and printing data, and outputs these items of data to the monitor  100  and the printer  102 , respectively, together with an error message (such as a message “SHORT-CIRCUITING ABNORMALITY”). 
         [0101]    In step S 309 , the alarm information storage unit  76  stores the alarm information data  96  created by the alarm information creation unit  74  in the memory  98  which adopts a stack method (last-in first-out method). 
         [0102]    In step S 310 , the report reception unit  56  determines whether there is any report (abnormality report) indicating occurrence of an abnormality from the reporting unit  16 . If no abnormality report has been received, the routine returns to step S 302  to repeat the processes of step S 302  and the subsequent steps. 
         [0103]    If any abnormality report has been received, the routine proceeds to the next step S 311  to perform operation in the module identification unit  58 . Specifically, the module identification unit  58  identifies, as a module  22  having the abnormality, a module  22  corresponding to the module string information and the module information registered in the latest alarm information data  96  stored in the memory  98 . Then, the module identification unit  58  outputs the module information and the error message regarding the identified module  22  to the monitor  100  and/or the printer  102 . 
         [0104]    In step S 312 , it is determined whether or not there is a request for stopping operation of the information acquisition unit  54 . If there is no request for stopping operation, the routine returns to step S 302  to repeat the processes of step S 302  and the subsequent steps. When a request for stopping operation is made, operations of the reference voltage acquisition unit  82 , the subtracter  84 , the voltage comparator circuit  86 , the alarm information creation unit  74 , etc. are stopped. 
         [0105]    As described above, in the abnormality position identification apparatus  50  and the abnormality identification method according to the embodiment of the present invention, the following advantages are obtained. 
         [0106]    Specifically, normally, if external short circuiting or internal short circuiting occurs in any one of the battery cells  28 , the block voltage value V of the block  26  including the battery cell  28  having the short circuiting is decreased steeply. Thereafter, in some cases, after the elapse of 1.5 to 2 minutes, the voltage returns to the original voltage level before short circuiting. Further, if the scale of the system becomes large, the number of blocks to be monitored is increased correspondingly. Therefore, it becomes more difficult to recognize the decrease in the voltage due to short circuiting from the changes of the block voltage values V of all of the blocks  26 . 
         [0107]    Further, when the block voltage value V is decreased temporarily, e.g., by adjustment in the frequency of the electric power system, adjustment in the difference between the generated electric power from natural energy based power generators and its planned output electric power, and adjustment of power demands and power supplies in the electric power system, in some cases, this decrease in the block voltage value V may be detected erroneously as the temporary drop of the block voltage value V due to short circuiting of at least one of the battery cells  28 . 
         [0108]    However, in the embodiment of the present invention, among the plurality of module  22 , information of the following module  22  is acquired. Specifically, the reference block voltage value Vb is obtained from the correlation relationship between the block voltage value V and the average block voltage value Va. In the case where the difference ΔV between the reference block voltage value Vb and the block voltage value V is the predetermined voltage threshold value Vth or more, information of the module  22  accommodating the block  26  as the output source of the block voltage value V is acquired. Then, alarm information data  96  is created based on the acquired information of the module  22 . At the time of receiving the abnormality report in the report reception unit  56 , a module  22  corresponding to at least the latest alarm information data  96  is identified as a module  22  having the abnormality. In this manner, by identifying the module  22  which is the source of the abnormality, it becomes possible to transmit a report to a local user, a local administrator, etc. Therefore, countermeasures focused on the identified abnormality source can be taken at an early stage. It becomes possible to suppress expansion of the damage. 
         [0109]    Further, it is possible to accurately detect whether there is a decrease in the block voltage value V, and detect occurrence of an abnormality due to short circuiting. Further, it is possible to improve the detection accuracy of the block  26  having a temporary drop in the block voltage value V due to short circuiting of at least one of the battery cells  28 . Moreover, even if the block voltage value V is decreased temporarily, e.g., by adjustment in the frequency of the electric power system, adjustment in the difference between the generated electric power from natural energy based power generators and its planned output electric power, and adjustment of power demands and power supplies in the electric power system, this decrease in the block voltage value V is not detected erroneously as the temporary drop of the block voltage value V due to short circuiting of at least one of the battery cells  28 . 
         [0110]    In particular, in the embodiment of the present invention, in the linear regression processing unit  80 , the relationship between the plurality of block voltage values V and the plurality of average block voltage values Va accumulated in the fixed period is subjected to linear regression processing to acquire one regression line La (map information). Further, in the reference voltage acquisition unit  82 , the reference block voltage Vb corresponding to the block voltage value V is acquired based on the information of the regression line La every unit time. In this manner, it is possible to obtain the reference block voltage value Vb easily based on the correlation relationship between the block voltage value V and the average block voltage value Va, and achieve acceleration of computation. 
         [0111]    It is a matter of course that the apparatus, the method, and the non-transitory recording medium storing the program for identifying a position of an abnormality occurred in a secondary battery system according to the embodiment of the present invention are not limited to the embodiments described above, and various structures can be adopted without deviating the gist of the present invention.