Patent Publication Number: US-2015077125-A1

Title: Setting device, battery assembly device and setting method

Description:
TECHNICAL FIELD 
     The present invention relates to a setting device, a battery assembly device and a setting method, in particular relates to a setting device, a battery assembly device and a setting method for setting the SOC of a storage battery unit to be set among a plurality of storage battery units. 
     BACKGROUND ART 
     There has been known a battery assembly formed of a plurality of connected storage batteries (e.g., a plurality of lithium-ion secondary battery cells). 
     Patent Document 1 discloses a battery assembly system in which a plurality of series battery units, each having multiple storage batteries connected in series, are connected in parallel. Hereinbelow, the series battery unit may also be called storage battery unit. 
     The remaining storage capacity of a storage battery unit is generally represented by SOC (State of Charge). 
     SOC may be calculated from the voltage of the storage battery unit, or may be calculated by addition and subtraction of the charged capacity and discharged capacity of the storage battery unit. 
     Related Art Documents 
     Patent Documents 
     Patent Document 1: JP2010-29015A 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     When SOC is calculated from the voltage of the storage battery unit, if a change in the voltage of the storage battery unit is small during discharge, it is difficult to accurately relate the change in voltage to the change in SOC, and thus it becomes difficult to determine the exact SOC. 
     For this reason, it is preferable to determine SOC by performing addition and subtraction of the charged capacity and discharged capacity of the storage battery unit, instead of calculating SOC from the voltage of the storage battery unit. 
     When SOC is determined by performing addition and subtraction of the charged capacity and discharged capacity of the storage battery unit, as the initial setting, the SOC needs to be set at 100% when the storage battery unit is fully charged and the SOC needs to be set at 0% when the storage battery unit is completely discharged, then the SOC is calculated by performing addition and subtraction of the charged capacity and discharged capacity of the storage battery unit. 
     However, errors often arise when SOC is estimated from the charged capacity and discharged capacity. As a result, when storage battery units are used in a power system in which the storage battery units are repeatedly charged and discharged without having been fully charged or fully discharged, a problem will occur in which SOC errors accumulate. 
     The object of the present invention is to provide a setting device, a battery assembly device and a setting method that can resolve the above problem. 
     Means for Solving the Problems 
     The setting device of the present invention is a setting device for determining the SOC of a target storage battery unit for setting among a plurality of storage battery units for which charging and discharging is performed using a power line, and comprises: a state setting means that sets the storage battery unit into one of two predetermined states, a the fully charged state or a fully discharged state; 
     a plurality of first switches, corresponding to the plural storage battery units respectively, and each interposed between the corresponding storage battery unit and the state setting means; 
     a plurality of second switches, corresponding to the plural storage battery units respectively, and each interposed between the corresponding storage battery unit and the power line; and, 
     a control means that turns on the first switch, among the plural first switches, corresponding to the target storage battery unit to be set into a predetermined state, turns on the second switches among the plural second switches, other than the second switch, corresponding to the target storage battery unit to be set into a predetermined state, and determines the SOC of the target storage battery unit that is to be set to the value corresponding to the predetermined state when the state setting means sets the target storage battery unit that is to be set into the predetermined state. 
     The battery assembly device of the present invention includes a plurality of storage battery units and the above setting device. 
     The setting method of the present invention is a setting method for use in a setting device for determining the SOC of a target storage battery unit for setting among a plurality of storage battery units for which charging and discharging is performed using a power line, the setting device including a state setting means for setting the storage battery unit to one of predetermined states, either the fully charged state or the fully discharged state, and comprises the steps of: 
     turning on the first switch corresponding to the target storage battery unit for setting among the plural first switches that respectively correspond to the plural storage battery units and that are each interposed between the corresponding storage battery unit and the state setting means; 
     turning on the second switches other than the second switch corresponding to the target storage battery unit for setting among the plural second switches that respectively correspond to the plural storage battery units and that are each interposed between the corresponding storage battery unit and the power line; and, 
     determining the SOC of the target storage battery unit for setting to be the value corresponding to the predetermined state when the state setting means sets the target storage battery unit for setting the storage battery unit into the predetermined state. 
     Effect of the Invention 
     According to the present invention, it is possible to prevent SOC errors of storage battery units from accumulating, in a power system in which the storage battery unit is repeatedly charged and discharged without being fully charged or fully discharged. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS [FIG.  1 ] 
       A block diagram showing battery assembly device  100  of one exemplary embodiment of the present invention. 
       [ FIG. 2 ] 
       A flow chart for illustrating the operation of setting device  20 . [ FIG. 3 ] 
       A diagram for illustrating one example of on/off states of switches. [ FIG. 4 ] 
       A diagram showing setting device  20  formed of bi-directional DCDC converter  2   a , switches  2   b   1  to  2   b   3  and switches  2   c   1  to  2   c   3 , and controller  2   e.    
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinbelow, one exemplary embodiment of the present invention will be described with reference to the drawings. 
       FIG. 1  is a block diagram showing battery assembly device  100  of one exemplary embodiment of the present invention. 
     In  FIG. 1 , battery assembly device  100  includes series battery units  11  to  13  and setting device  20 . 
     Series battery units  11  to  13  are one example of the plural storage battery units. Series battery units  11  to  13  are connected in parallel to each other. Series battery units  11  to  13  each have a plurality of storage batteries (e.g., plural lithium-ion secondary battery cells) connected in series. 
     Here, the storage battery is not limited to a lithium-ion secondary battery cell, but may be changed as appropriate. As the storage battery unit, a single secondary battery cell may be used instead of the series battery unit. Further, in  FIG. 1 , the number of series battery units is 3, but the number of series battery units may be 2 or more. 
     Setting device  20  includes bi-directional DCDC converter  2   a,  switches  2   b   1  to  2   b   3 , switches  2   c   1  to  2   c   3 , detector  2   d,  and controller  2   e.  Detector  2   d  includes voltage detectors  2   d   1  to  2   d   3 . 
     Bi-directional DCDC converter  2   a  is one example of the state setting means. 
     Bi-directional DCDC converter  2   a  selectively performs charging and discharging of a series battery unit for which SOC is set or calibrated (which will be referred to hereinbelow as “target battery unit for setting”), among series battery units  11  to  13 . Bi-directional DCDC converter  2   a  is used to set the target battery unit for setting, into one of the predetermined states, either the fully charged state or fully discharged state (which will be simply referred to hereinbelow as “the predetermined state”). 
     Here, the target battery unit for setting is one example of the target storage battery unit for setting. 
     Switches  2   b   1  to  2   b   3  are one example of the plural first switches. 
     Switches  2   b   1  to  2   b   3  correspond to series battery units  11  to  13 , respectively. For example, switch  2   b   1  corresponds to series battery unit  11 , and switch  2   b   3  corresponds to series battery unit  13 . 
     Switches  2   b   1  to  2   b   3  each are interposed between the corresponding series battery unit and bi-directional DCDC converter  2   a.    
     Here, the number of the first switches (switches  2   b   1  to  2   b   3 ) is equal to the number of the series battery units. 
     Switches  2   c   1  to  2   c   3  are one example of the plural second switches. 
     Switches  2   c   1  to  2   c   3  correspond to series battery units  11  to  13 , respectively. For example, switch  2   c   1  corresponds to series battery unit  11 , and switch  2   c   3  corresponds to series battery unit  13 . 
     Switches  2   c   1  to  2   c   3  each are interposed between the corresponding series battery unit and power line  2   f.    
     Here, the number of the second switches (switches  2   c   1  to  2   c   3 ) is equal to the number of the series battery units. 
     Detector  2   d  detects each voltage of series battery units  11  to  13 . 
     Voltage detectors  2   d   1  to  2   d   3  correspond to series battery units  11  to  13 , respectively. For example, voltage detector  2   d   1  corresponds to series battery unit  11  and voltage detector  2   d   3  corresponds to series battery unit  13 . 
     Voltage detectors  2   d   1  to  2   d   3  detect the voltage of the corresponding series battery units, respectively. 
     Controller  2   e  is one example of the control means. 
     Controller  2   e  holds each SOC of series battery units  11  to  13  in the internal database (not shown). 
     Controller  2   e  selects a target battery unit for setting, from series battery units  11  to  13 . 
     Controller  2   e,  for example, periodically selects one target battery unit for setting, in turn, from series battery units  11  to  13 . 
     Controller  2   e  turns on the switch corresponding to the target battery unit for setting (which will be referred to hereinbelow as “the control switch”) among switches  2   b   1  to  2   b   3 , and turns off the switches other than the control switch, among switches  2   b   1  to  2   b   3 . 
     Controller  2   e  turns off the switch corresponding to the target battery unit for setting (which will be referred to hereinbelow as “the corresponding switch”) among switches  2   c   1  to  2   c   3 , and turns on the switches other than the corresponding switch, among switches  2   c   1  to  2   c   3 . 
     Controller  2   e  turns on the control switch among switches  2   b   1  to  2   b   3  and turns off the switches other than the control switch, and turns off the corresponding switch and turns on the switches other than the corresponding switch among switches  2   c   1  to  2   c   3 , then causes bi-directional DCDC converter  2   a  to set the target battery unit for setting into the predetermined state (fully charged state or fully discharged state). 
     When bi-directional DCDC converter  2   a  has set the target battery unit for setting into the predetermined state, controller  2   e  determines the SOC of the target battery unit for setting to be the value corresponding to the predetermined state. 
     For example, when the predetermined state is the fully charged state, controller  2   e  determines the SOC of the target battery unit for setting to be 100% at the time of the fully charged state. When the predetermined state is the fully discharged state, the controller  2   e  determines the SOC of the target battery unit for setting to be 0% at the time of the fully discharged state. Controller  2   e  modifies the SOC of the target battery unit for setting, held in the internal database, to the determined result of the SOC of the target battery unit for setting. 
     Power line  2   f  is connected to, for example a power system (not shown) that uses battery assembly device  100 . The power system (not shown) using battery assembly device  100  controls charging and discharging of series battery units  11  to  13  using power line  2   f.    
     Next, the operation will be described. 
       FIG. 2  is a flow chart for illustrating the operation of setting device  20 . 
     Here, it is assumed that at the start of operation switches  2   b   1  to  2   b   3  are turned off and switches  2   c   1  to  2   c   3  are turned on. It is also assumed that the predetermined state is the fully charged state. 
     Controller  2   e  selects one target battery unit for setting from series battery units  11  to  13  at predetermined timing (e.g., at 2 a.m. on every Monday, or at 3 a.m. on the first of every month) (Step S 201 ). The predetermined timing should not be limited to the above, but can be changed as appropriate. 
     Subsequently, controller  2   e  turns off the switch (the corresponding switch) corresponding to the target battery unit for setting, among switches  2   c   1  to  2   c   3 , and turns on the switches other than the corresponding switch among switches  2   c   1  to  2   c   3  (Step S 202 ). 
     When, of switches  2   c   1  to  2   c   3 , the corresponding switch is turned off while the switches other than the corresponding switch are turned on, the target battery unit for setting among series battery units  11  to  13  is separated from power line  2   f.    
     Since switches  2   c   1  to  2   c   3  have been turned on before Step S 202 , the switches other than the corresponding switch among switches  2   c   1  to  2   c   3  continue to be in the turned on state. 
     Then, controller  2   e  turns on the switch (control switch) corresponding to the target battery unit for setting, among switches  2   b   1  to  2   b   3 , and turns off the switches other than the control switch among switches  2   b   1  to  2   b   3  (Step S 203 ). 
     When, of switches  2   b   1  to  2   b   3 , the control switch is turned on while the switches other than the control switch are turned off, the target battery unit for setting among series battery units  11  to  13  is connected to bi-directional DCDC converter  2   a.    
     Since switches  2   b   1  to  2   b   3  have been turned off before Step S 203 , the switches other than the control switch among switches  2   b   1  to  2   b   3  continue to be in the off state. 
     Next, controller  2   e  causes bi-directional DCDC converter  2   a  to operate so as to charge the target battery unit for setting (Step S 204 ). 
       FIG. 3  is a diagram for illustrating the on/off states of switches  2   b   1  to  2   b   3  and switches  2   c   1  to  2   c   3  when series battery unit  11  is the target battery unit for setting. 
     In  FIG. 3 , switch  2   b   1  corresponding to series battery unit  11  is turned on, switches  2   b   2  and  2   b   3  are turned off, switch  2   c   1  corresponding to series battery unit  11  is turned off, and switches  2   c   2  and  2   c   3  are turned on. As a result, bi-directional DCDC converter  2   a  performs charging of series battery unit  11 . 
     Then, controller  2   e,  referring to the result of detection from the voltage detector corresponding to the target battery unit for setting (which will be referred to hereinbelow as “the corresponding voltage detector”) among voltage detectors  2   d   1  to  2   d   3 , determines whether the voltage of the target battery unit for setting has reached the upper limit that corresponds to the fully charged state, that is, whether the target battery unit for setting has been fully charged (Step S 205 ). Here, the upper limit has been previously stored in controller  2   e.    
     When the voltage of the target battery unit for setting has not reached the upper limit, that is, when the target battery unit for setting has not been fully charged (Step S 205 ), controller  2   e  returns the operation to Step S 204 . 
     On the other hand, when the voltage of the target battery unit for setting has reached the upper limit, that is, when the target battery unit for setting has been fully charged (Step S 205 ), controller  2   e  determines the SOC of the target battery unit for setting to be 100%, and holds the determined result in the internal database (Step S 206 ). 
     Subsequently, controller  2   e,  while maintaining the off/off state of each switch, causes bi-directional DCDC converter  2   a  to discharge the target battery unit for setting (Step S 207 ). 
     Then, controller  2   e,  referring to the result of detection from voltage detectors  2   d   1  to  2   d   3 , determines whether the voltage of the target battery unit for setting has become equal to the voltage of the other series battery units (Step S 208 ). 
     If the voltage of the target battery unit for setting has not yet become equal to the voltage of the other series battery units (Step S 208 ), controller  2   e  returns the operation to Step S 207 . 
     On the other hand, when the voltage of the target battery unit for setting has become equal to the voltage of the other series battery units (Step S 208 ), controller  2   e  determines whether controller  2   e  has selected all of series battery units  11  to  13  as the target battery units for setting after the predetermined timing (Step S 209 ). 
     If controller  2   e  has not yet selected all of series battery units  11  to  13  as the target battery unit for setting (Step S 209 ), controller  2   e  selects another target battery unit for setting, from the series battery units that have not bee selected as the target battery unit (Step S 210 ) and returns the operation to Step S 202 . 
     On the other hand, only when controller  2   e  has selected all of series battery units  11  to  13  as the target battery unit for setting (Step S 209 ), controller  2   e  ends the SOC setting process of the target battery unit for setting. 
     Here, when the fully discharged state is used as the predetermined state, controller  2   e  causes bi-directional DCDC converter  2   a  to operate so that the target battery unit for setting is discharged at Step S 204 , determines whether the voltage of the target battery unit for setting has reached the lower limit that corresponds to the fully discharged state at Step S 205 , and sets the SOC of the target battery unit to be 0% when the voltage of the target battery unit for setting has reached the lower limit at Step S 206 . Here, the lower limit has been previously stored in controller  2   e.    
     Next, the effect of the present exemplary embodiment will be described. 
     According to the present exemplary embodiment, bi-directional DCDC converter  2   a  sets the series battery unit at one of the predetermined states, either the fully charged state or the fully discharged state. Switches  2   b   1  to  2   b   3  are made to correspond to series battery units  11  to  13 , respectively, and each is interposed between the corresponding series battery unit and bi-directional DCDC converter  2   a.    
     Switches  2   c   1  to  2   c   3  are made to correspond to series battery units  11  to  13 , respectively, and each is interposed between the corresponding series battery unit and power line  2   f.    
     Controller  2   e  turns on the control switch corresponding to the target battery unit for setting among switches  2   b   1  to  2   b   3 , turns on the switches other than the corresponding switch corresponding to the target battery unit for setting among switches  2   c   1  to  2   c   3 , so as to cause bi-directional DCDC converter  2   a  to set the target battery unit for setting into the predetermined state, then determines the SOC of the target battery unit for setting to be the value corresponding into the predetermined state. 
     It is therefore possible to set the SOC of the target battery unit for setting to be the value corresponding to the predetermined state while connecting the series battery units other than the target battery unit for setting among series battery units  11  to  13  to power line  2   f  and while keeping the target battery unit for setting, at the predetermined state (fully charged state or fully discharged state). 
     As a result, even if power line  2   f  is connected to a power system in which the series battery units  11  to  13  are repeatedly charged and discharged without being fully charged or fully discharged, it is possible to correct the error of the SOC of the target battery unit for setting. 
     The above effect can also be obtained in setting device  20  formed of bi-directional DCDC converter  2   a,  switches  2   b   1  to  2   b   3 , switches  2   c   1  to  2   c   3  and controller  2   e.    
       FIG. 4  is a diagram showing setting device  20  formed of bi-directional DCDC converter  2   a,  switches  2   b   1  to  2   b   3  and switches  2   c   1  to  2   c   3 , and controller  2   e.    
     Also in this exemplary embodiment, controller  2   e  determines the SOC of the target battery unit for setting to be 100% at the time of the fully charged state when the predetermined state is the fully charged state and determines the SOC of the target battery unit for setting to be 0% at the time of the fully discharged state when the predetermined state is the fully discharged state. 
     Accordingly, it is possible to correctly calibrate the SOC of the target battery unit for setting. 
     In the exemplary embodiments described heretofore, the illustrated configurations are mere examples, so that the present invention should not be limited to the configurations. 
     Although the present invention has been explained with reference to the exemplary embodiments, the present invention should not be limited to the above exemplary embodiments. Various modifications that can be understood by those skilled in the art may be made to the structures and details of the present invention within the scope of the present invention. This application claims priority based on Japanese Patent Application No. 2012-65445, filed on Mar. 22, 2012, and should incorporate all the disclosures thereof herein. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
       100  battery assembly device 
       11 - 13  series battery unit 
       20  setting device 
       2   a  bi-directional DCDC converter 
       2   b   1  to  2   b   3 ,  2   c   1  to  2   c   3 , switch 
       2   d  detector  2   d   1  to  2   d   3  voltage detector 
       2   e  controller