JP2014085118A - Electricity storage system and abnormality discrimination method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate the resistance value of an electricity storage unit when charging or discharging the unit under a constant current.SOLUTION: An electricity storage system includes: an electricity storage unit (1, 100) for charging and discharging; a voltage sensor (201) for detecting a voltage value of the electricity storage unit; and a controller (300) for discriminating an event of the electricity storage unit being abnormal when a resistance value of the electricity storage unit is higher than the threshold. When charging or discharging the electricity storage unit under a constant current, the controller first uses a correlation between an electrification period and a polarization voltage to identify a polarization voltage value corresponding to the electrification period, and then uses the voltage value detected by the voltage sensor, the identified polarization voltage value, an open voltage value of the electricity storage unit after electrification and a current value at the electrification, to calculate a resistance value of the post-electrification electricity storage unit.

Description

  The present invention relates to a technique for determining an abnormal state of a power storage unit based on a resistance value of the power storage unit.

  Patent Document 1 describes a method for detecting an abnormality in the internal resistance of a battery. Specifically, the relationship between the current value and the voltage value when the battery is charged and discharged is plotted in a coordinate system having the current value and the voltage value as coordinate axes. Then, an approximate line (IV line) for a plurality of plots is calculated, and an abnormality in the internal resistance of the battery is detected based on the slope of the approximate line. Here, as the internal resistance value of the battery increases, the slope of the approximate straight line becomes steeper.

JP 2012-021931 A JP 2005-010032 A

  With the technique described in Patent Document 1, if the current value does not change, an approximate line cannot be obtained, and an abnormality in internal resistance cannot be detected based on the slope of the approximate line. That is, when charging or discharging a battery with a constant current, an approximate straight line cannot be obtained.

  Further, in a situation where noise is easily included in the current value, it is difficult to grasp the internal resistance of the battery. As a case where noise is included in the current value, for example, there is a case where a ripple current is generated or a noise accompanying switching operation is included in the current value. When noise is included in the current value, the current value changes according to the timing at which the current value is acquired, and it is difficult to accurately estimate the internal resistance when calculating the internal resistance based on the current value.

  The power storage system according to the first invention of the present application includes a power storage unit that performs charging / discharging, a voltage sensor that detects a voltage value of the power storage unit, and a power storage unit in an abnormal state when the resistance value of the power storage unit is higher than a threshold value. And a controller for determining that there is. When charging or discharging the power storage unit with a constant current, the controller first specifies the polarization voltage value corresponding to the energization time using the correspondence relationship between the energization time and the polarization voltage value. Then, the controller uses the detected voltage value of the voltage sensor, the specified polarization voltage value, the open-circuit voltage value of the energized unit after energization, and the current value during energization to determine the resistance value of the energized unit after energization. calculate.

  By specifying the detection voltage value of the voltage sensor, the polarization voltage value, the open-circuit voltage value of the electricity storage unit after energization, and the current value at the time of energization, even when charging or discharging the electricity storage unit under a constant current, The resistance value of the power storage unit after energization can be calculated. Specifically, the resistance value of the power storage unit after energization can be calculated by using the following formula (I).

  In the above formula (I), Rc is the resistance value of the electricity storage unit after energization, CCV is the voltage value of the electricity storage unit detected by the voltage sensor after energization, and OCV is the opening of the electricity storage unit after energization It is a voltage value. Vdyn is a polarization voltage value accompanying energization, and Ich is a current value (a constant value) during energization.

  The polarization voltage value changes according to the current value at the time of energization, but when charging or discharging the power storage unit under a constant current, it is not necessary to consider the fluctuation of the current value. It becomes easier to specify the value. That is, if the correspondence relationship between the energization time and the polarization voltage value is obtained in advance, the polarization voltage value corresponding to the energization time can be specified.

  As described above, since it is not necessary to consider the fluctuation of the current value, it becomes easier to estimate the polarization voltage value than when estimating the polarization voltage value when the current value fluctuates, and the estimation accuracy of the polarization voltage value is improved. Can be improved. As shown in the above formula (I), the resistance value of the electricity storage unit after energization is calculated from the polarization voltage value. Therefore, by improving the estimation accuracy of the polarization voltage value, the resistance value of the electricity storage unit after energization is increased. The estimation accuracy can also be improved.

  The open-circuit voltage value of the power storage unit after energization can be calculated from the open-circuit voltage value of the power storage unit when energization is started and the value obtained by integrating the detected current value of the current sensor during energization. Here, since the open-circuit voltage value and the state of charge (SOC) of the power storage unit are in a correspondence relationship, if the open-circuit voltage value at the start of energization is obtained, the charge state corresponding to this open-circuit voltage value Can be specified.

  If the detected current value of the current sensor is integrated while the power storage unit is energized, the state of charge of the power storage unit after energization can be calculated from the state of charge when the energization is started and the current integrated value. If the state of charge after energization is calculated, the open circuit voltage value corresponding to the state of charge after energization can be specified using the correspondence relationship between the open circuit voltage value and the state of charge.

  The power storage unit can be charged by supplying power from the external power source to the power storage unit. At this time, since the power storage unit can be charged with a constant current, the resistance value of the power storage unit can be calculated as described above. Here, the external power source is a power source provided separately from the power storage system.

  Further, when the electric power from the external power source is supplied to the power storage unit, the current value flowing through the power storage unit is less likely to include noise. That is, when the load is driven using the power output from the power storage unit, noise may easily be included in the current value of the power storage unit according to the driving of the load. Since the load is not driven when the power of the external power source is supplied to the power storage unit, it is possible to prevent noise from being included in the current value of the power storage unit.

  If noise is included in the current value of the power storage unit, an error is included in the resistance value calculated from the current value or the like, and the estimation accuracy of the resistance value may be reduced. As described above, if the current value of the power storage unit can be suppressed from including noise, the resistance value can be suppressed from including an error, and the resistance value estimation accuracy can be improved.

  For example, a motor can be used as the load. Specifically, the inverter can convert DC power output from the power storage unit into AC power and supply the AC power to the motor. The kinetic energy generated by the motor can be used as energy for running the vehicle.

  When the motor is driven using the electric power of the power storage unit, the current value of the power storage unit is likely to change according to the driving state of the motor. Therefore, the resistance value of the power storage unit can be calculated from the behavior of the current value and voltage value of the power storage unit. Specifically, in the coordinate system with the current value and the voltage value as coordinate axes, if the relationship between the current value and the voltage value is plotted and a straight line that approximates a plurality of plots is specified, the slope of the approximate straight line is Resistance value.

  When the resistance value of the power storage unit calculated when the power storage unit is charged or discharged with a constant current is higher than the first threshold, it can be determined that the power storage unit is in an abnormal state. Further, when the resistance value of the power storage unit calculated when power is supplied from the power storage unit to the motor is higher than the second threshold, it can be determined that the power storage unit is in an abnormal state.

  When the motor is driven using the power of the power storage unit, noise is likely to be included in the current value of the power storage unit according to the driving state of the motor. For this reason, the estimation accuracy of the resistance value calculated at this time tends to be lower than the estimation accuracy of the resistance value calculated when charging or discharging with a constant current.

  When the threshold value for specifying the abnormal state of the power storage unit is theoretically set, the first threshold value and the second threshold value are set in consideration of the estimation error. That is, the first threshold value and the second threshold value can be set by adding the estimated error amount to the theoretical threshold value. As described above, since the estimation errors of the resistance values are different from each other, the estimation error corresponding to the first threshold can be made smaller than the estimation error corresponding to the second threshold. As a result, the first threshold value can be smaller than the second threshold value.

  A second invention of the present application is an abnormality determination method for determining an abnormal state of a power storage unit. First, when charging or discharging the power storage unit with a constant current, the polarization voltage value corresponding to the energization time is specified using the correspondence relationship between the energization time and the polarization voltage value. Next, using the voltage value of the power storage unit detected by the voltage sensor, the specified polarization voltage value, the open-circuit voltage value of the power storage unit after power supply, and the current value at the time of power supply, Calculate the resistance value. When the calculated resistance value is higher than the threshold value, it is determined that the power storage unit is in an abnormal state. Also in the second invention of the present application, the same effect as that of the first invention of the present application can be obtained.

It is a figure which shows the structure of a battery system. It is a figure which shows the structure of a part of battery system. It is a flowchart explaining the process which discriminate | determines the abnormal state of a cell. It is a figure which shows the relationship between a polarization voltage value and the duration of external charging. It is a figure explaining the voltage component contained in the detection voltage of a monitoring unit. It is a figure which shows the correspondence of SOC and OCV. It is a figure which shows the relationship between a 1st threshold value and a 2nd threshold value.

  Examples of the present invention will be described below.

  FIG. 1 is a diagram illustrating a configuration of a battery system (corresponding to a power storage system) of the present embodiment. The battery system shown in FIG. 1 can be mounted on a vehicle, for example. Vehicles include PHV (Plug-in Hybrid Vehicle) and EV (Electric Vehicle). Note that the present invention can be applied to other than vehicles.

  In the PHV, as a power source for running the vehicle, in addition to the assembled battery described later, another power source such as an internal combustion engine or a fuel cell is provided. Moreover, in PHV, an assembled battery can be charged using the electric power from an external power supply. The EV includes only the assembled battery as a power source of the vehicle, and can receive the power supply from the external power source to charge the assembled battery. The external power source is a power source (for example, commercial power source) provided separately from the vehicle outside the vehicle.

  The assembled battery 100 includes a plurality of single cells (corresponding to power storage units) 1 connected in series. As the unit cell 1, a secondary battery such as a nickel metal hydride battery or a lithium ion battery can be used. An electric double layer capacitor can be used instead of the secondary battery.

  The number of unit cells 1 can be set as appropriate based on the required output of the assembled battery 100 and the like. The assembled battery 100 can also include a plurality of single cells 1 connected in parallel. The monitoring unit 201 detects a voltage (CCV: Closed Circuit Voltage) between the terminals of the assembled battery 100 or detects a voltage (CCV) of each unit cell 1 and outputs the detection result to the controller 300.

  As shown in FIG. 2, the monitoring unit 201 includes voltage monitoring ICs (Integrated Circuits) 201a as many as the number of unit cells 1 constituting the assembled battery 100, and each voltage monitoring IC (corresponding to a voltage sensor). 201a is connected to each unit cell 1 in parallel. Each voltage monitoring IC 201 a detects the voltage of the corresponding unit cell 1 and outputs the detection result to the controller 300.

  In the present embodiment, the voltage monitoring IC 201a is provided for each unit cell 1, but the present invention is not limited to this. For example, when the plurality of single cells 1 constituting the assembled battery 100 are divided into a plurality of battery blocks (corresponding to power storage units), a voltage monitoring IC 201a can be provided for each battery block. That is, the voltage monitoring IC 201a can be connected in parallel to each battery block.

  In this case, the voltage monitoring IC 201a detects the voltage of the corresponding battery block and outputs the detection result to the controller 300. Here, each battery block is configured by a plurality of single cells 1 connected in series, and the assembled battery 100 is configured by connecting the plurality of battery blocks in series. Each battery block can also include a plurality of single cells 1 connected in parallel.

  The current sensor 202 detects the current flowing through the assembled battery 100 and outputs the detection result to the controller 300. Here, when the assembled battery 100 is discharged, a positive value can be used as the current value detected by the current sensor 202. Further, when the assembled battery 100 is being charged, a negative value can be used as the current value detected by the current sensor 202.

  In this embodiment, the current sensor 202 is provided on the positive electrode line PL connected to the positive terminal of the assembled battery 100. However, the current sensor 202 only needs to be able to detect the current flowing through the assembled battery 100, and the position where the current sensor 202 is provided. Can be set as appropriate. A plurality of current sensors 202 can also be used.

  The controller 300 includes a memory 301, and the memory 301 stores various information for the controller 300 to perform predetermined processing (for example, processing described in the present embodiment). The controller 300 has a timer 302, and the timer 302 is used for time measurement. In this embodiment, the memory 301 and the timer 302 are built in the controller 300, but at least one of the memory 301 and the timer 302 can be provided outside the controller 300.

  A system main relay SMR-B is provided on the positive electrode line PL connected to the positive electrode terminal of the assembled battery 100. System main relay SMR-B is switched between ON and OFF by receiving a control signal from controller 300. A system main relay SMR-G is provided on the negative electrode line NL connected to the negative electrode terminal of the assembled battery 100. System main relay SMR-G is switched between on and off by receiving a control signal from controller 300.

  A system main relay SMR-P and a current limiting resistor 203 are connected in parallel to the system main relay SMR-G. System main relay SMR-P and current limiting resistor 203 are connected in series. System main relay SMR-P is switched between ON and OFF by receiving a control signal from controller 300. The current limiting resistor 203 is used to suppress an inrush current from flowing when the assembled battery 100 is connected to a load (specifically, an inverter 204 described later).

  The assembled battery 100 is connected to the inverter 204 via the positive electrode line PL and the negative electrode line NL. When connecting the assembled battery 100 to the inverter 204, the controller 300 first switches the system main relay SMR-B from off to on and switches the system main relay SMR-P from off to on. As a result, a current flows through the current limiting resistor 203.

  Next, after switching the system main relay SMR-G from off to on, the controller 300 switches the system main relay SMR-P from on to off. Thereby, the connection between the assembled battery 100 and the inverter 204 is completed, and the battery system shown in FIG. 1 is in a start-up state (Ready-On). Information about on / off of the ignition switch of the vehicle is input to the controller 300, and the controller 300 activates the battery system when the ignition switch is switched from off to on.

  On the other hand, when the ignition switch is switched from on to off, the controller 300 switches the system main relays SMR-B and SMR-G from on to off. As a result, the connection between the assembled battery 100 and the inverter 204 is cut off, and the battery system enters a stopped state (Ready-Off).

  The inverter 204 converts the DC power output from the assembled battery 100 into AC power, and outputs the AC power to the motor / generator 205. As the motor generator 205, for example, a three-phase AC motor can be used. Motor generator 205 receives AC power output from inverter 204 and generates kinetic energy for running the vehicle. The kinetic energy generated by the motor / generator 205 is transmitted to the wheels so that the vehicle can run.

  When the vehicle is decelerated or stopped, the motor generator 205 converts kinetic energy generated during braking of the vehicle into electric energy (AC power). The inverter 204 converts the AC power generated by the motor / generator 205 into DC power and outputs the DC power to the assembled battery 100. Thereby, the assembled battery 100 can store regenerative electric power.

  In this embodiment, the assembled battery 100 is connected to the inverter 204, but the present invention is not limited to this. Specifically, the battery pack 100 can be connected to the booster circuit, and the booster circuit can be connected to the inverter 204. By using the booster circuit, the output voltage of the assembled battery 100 can be boosted. The booster circuit can step down the output voltage from the inverter 204 to the assembled battery 100.

  A charger 206 is connected to the positive electrode line PL and the negative electrode line NL. Specifically, charger 206 is connected to positive line PL that connects system main relay SMR-B and inverter 204, and negative line NL that connects system main relay SMR-G and inverter 204. An inlet (connector) 207 is connected to the charger 206.

  Charging relays Rch1 and Rch2 are provided on the line connecting charger 206 and lines PL and NL. Charging relays Rch1 and Rch2 are switched between on and off by receiving a control signal from controller 300.

  A plug (connector) connected to an external power source (not shown) is connected to the inlet 207. By connecting the plug to the inlet 207, power from an external power source can be supplied to the assembled battery 100 via the charger 206. Thereby, the assembled battery 100 can be charged using an external power supply. Charging the assembled battery 100 using an external power supply is referred to as external charging.

  When the external power source supplies AC power, the charger 206 converts AC power from the external power source into DC power and supplies the DC power to the assembled battery 100. The controller 300 can control the operation of the charger 206. When performing external charging, the charger 206 can also convert the voltage.

  In the battery system of this embodiment, when the charging relays Rch1 and Rch2 and the system main relays SMR-B and SMR-G are on, power from an external power source is supplied to the assembled battery 100. When external charging is performed, a constant charging current can be passed through the assembled battery 100, and the assembled battery 100 can be charged under a constant current.

  The system for supplying power from the external power source to the assembled battery 100 is not limited to the system shown in FIG. For example, the charger 206 can be connected to the assembled battery 100 without passing through the system main relays SMR-B, SMR-P, and SMR-G. Specifically, the charger 206 charges the positive line PL connecting the assembled battery 100 and the system main relay SMR-B and the negative line NL connecting the assembled battery 100 and the system main relay SMR-G. It can be connected via relays Rch1 and Rch2. In this case, external charging can be performed by switching the charging relays Rch1 and Rch2 from off to on.

  In this embodiment, external charging is performed by connecting a plug to the inlet 207, but the present invention is not limited to this. Specifically, the power of the external power source can be supplied to the assembled battery 100 by using a so-called contactless charging system. In a non-contact charging system, electric power can be supplied without using a cable by using electromagnetic induction or a resonance phenomenon. As the non-contact charging system, a known configuration can be adopted as appropriate.

  In the present embodiment, the charger 206 is mounted on the vehicle, but is not limited thereto. That is, the charger 206 may be provided separately from the vehicle outside the vehicle. In this case, DC power is supplied from the outside of the vehicle to the battery system shown in FIG. In addition, the communication between the controller 300 and the charger 206 allows the controller 300 to control the operation of the charger 206.

  When the deterioration of the unit cell 1 progresses, the resistance value of the unit cell 1 increases, so that the deterioration state of the unit cell 1 can be grasped by calculating (estimating) the resistance value of the unit cell 1. And depending on the deterioration state of the unit cell 1, it can be determined that the unit cell 1 is in an abnormal state.

  Processing for determining an abnormal state of the unit cell 1 will be described with reference to the flowchart shown in FIG. The process shown in FIG. 3 is executed by the controller 300.

  In the processing described below, the resistance value of the unit cell 1 is calculated, and the abnormal state of the unit cell 1 (the assembled battery 100) is determined based on the calculated resistance value. However, the present invention is not limited to this. Specifically, the resistance value of the assembled battery 100 or the battery block described above can be calculated, and the abnormal state of the assembled battery 100 or the battery block can be determined based on the calculated resistance value. In this case, the assembled battery 100 and the battery block correspond to the power storage unit in the present invention.

  In step S101, the controller 300 determines whether or not to perform external charging. In the battery system of the present embodiment, since external charging can be started by connecting the plug to the inlet 207, the controller 300 determines whether or not the plug is connected to the inlet 207, thereby It can be determined whether or not charging is performed. Note that in the above-described contactless charging system, the controller 300 can determine whether or not external charging is performed by communicating with a system that supplies power.

  By performing external charging, for example, the assembled battery 100 can be fully charged. When external charging is performed, the voltage value of the assembled battery 100 (unit cell 1) is increased by continuously supplying a constant charging current to the assembled battery 100. If the voltage value of the assembled battery 100 (single cell 1) reaches the upper limit voltage value, the assembled battery 100 (single cell 1) can be fully charged.

  When performing external charging, the controller 300 performs the process of step S102, and when not performing external charging, the controller 300 performs the process of step S106. In step S102, the controller 300 estimates the polarization voltage value of the cell 1 when the external charging is completed. The polarization voltage value is a voltage fluctuation amount accompanying polarization when the single battery 1 is charged.

  When external charging is performed, a constant current continuously flows through the assembled battery 100. Therefore, the polarization voltage value can be estimated by preparing a map (example) shown in FIG. In FIG. 4, the vertical axis represents the polarization voltage value, and the horizontal axis represents the duration (energization time) of external charging. When the external charging is started, the single cell 1 is polarized and the polarization voltage value is increased.

  When the map shown in FIG. 4 is created, the relationship between the polarization voltage value and the duration of external charging may be obtained on the basis of the current value (constant value) when external charging is performed. The polarization voltage value also changes depending on the current value flowing through the assembled battery 100. However, when external charging is performed, only a specific current value continues to flow. Therefore, the map shown in FIG. 4 is based on the current value at this time. Should be created.

  When estimating the polarization voltage value after external charging, it is not necessary to consider the fluctuation of the current value. Therefore, the polarization voltage value can be accurately estimated only by considering the duration of external charging. Here, when the current value fluctuates, the polarization voltage value must be estimated in consideration of the fluctuation of the current value, and it becomes difficult to estimate the polarization voltage value. When external charging is performed, it is not necessary to consider the fluctuation of the current value, so that the polarization voltage value can be easily estimated. And when estimating the polarization voltage value after external charging, the estimation accuracy of the polarization voltage value can be improved compared to the case where the polarization voltage value is estimated in consideration of the fluctuation of the current value.

  The map shown in FIG. 4 can be stored in the memory 301. The controller 300 can specify the polarization voltage value corresponding to the measurement time from the map shown in FIG. 4 by measuring the time (duration) from the start of external charging. Here, the time from the start of external charging can be measured using the timer 302.

  In step S103, the controller 300 estimates the resistance value Rc of the unit cell 1. Specifically, the controller 300 can calculate the resistance value Rc of the unit cell 1 based on the following formula (1). In the present embodiment, the resistance value Rc of the unit cell 1 is calculated, but the resistance value of the assembled battery 100 can be calculated, or the resistance value of the battery block described above can be calculated. Even in this case, the resistance values of the assembled battery 100 and the battery block can be calculated by the same method as the method of calculating the resistance value Rc of the single cell 1.

  In the above formula (1), CCV (Closed Circuit Voltage) is a voltage value of the unit cell 1 detected by the monitoring unit 201, and OCV (Open Circuit Voltage) is an open voltage value of the unit cell 1. CCV and OCV are CCV and OCV of the unit cell 1 after completing external charging. Vdyn is the polarization voltage value estimated in the process of step S102. Ich is a current value when charging the assembled battery 100 (unit cell 1). When external charging is performed, the current value Ich is substantially constant.

  As shown in FIG. 5, the voltage value (CCV) of the single cell 1 detected by the monitoring unit 201 includes the OCV of the single cell 1 and the voltage increase amount associated with the internal resistance (resistance value Rc) of the single cell 1. Polarization voltage value. From the relationship shown in FIG. 5, the above equation (1) can be derived.

  The OCV of the cell 1 after completing the external charging is calculated based on the voltage (OCV) of the cell 1 when the external charging is started and the current integrated value during the external charging. Can do. Below, the method to calculate OCV of the cell 1 after completing external charging is demonstrated.

  First, before starting external charging, the OCV of the unit cell 1 can be measured using the monitoring unit 201. For example, in a state where the assembled battery 100 is not connected to a load (inverter 204), the OCV of the single battery 1 can be measured by passing a weak current through the single battery 1. Here, by passing a weak current through the cell 1, the amount of voltage change due to the internal resistance of the cell 1 can be ignored, and the voltage of the cell 1 detected by the monitoring unit 201 is changed to the cell 1. It can be regarded as an OCV.

  If the OCV of the unit cell 1 can be measured, the SOC (State of Charge) corresponding to this OCV can be specified. The SOC is the ratio of the current charge capacity to the full charge capacity. As shown in FIG. 6, since the OCV and the SOC are in a correspondence relationship, the SOC corresponding to the OCV can be specified if the correspondence relationship is obtained in advance by experiments or the like.

  Next, during external charging, the SOC after completion of external charging can be calculated by integrating the current values detected by the current sensor 202. That is, it is possible to calculate the SOC when the external charging is completed based on the SOC when starting the external charging and the current integrated value during the external charging. If the SOC is calculated, the OCV corresponding to the calculated SOC can be specified based on the correspondence relationship between the SOC and the OCV shown in FIG. Thereby, the OCV of the unit cell 1 when the external charging is completed can be calculated.

  In the present embodiment, the resistance value Rc of the unit cell 1 after completing the external charging is calculated, but the present invention is not limited to this. That is, if the above formula (1) is used, the resistance value Rc of the unit cell 1 can be calculated even during external charging. Here, CCV and OCV at a specific timing during external charging can be used as CCV and OCV shown in the above formula (1). Further, as Vdyn, a polarization voltage value corresponding to the duration until a specific timing can be used.

  In step S104, the controller 300 determines whether or not the resistance value Rc calculated in the process of step S103 is higher than the first threshold value Rth1. The first threshold value Rth1 is a threshold value for determining whether or not the unit cell 1 is in an abnormal state, and can be set as appropriate. Information relating to the first threshold value Rth1 can be stored in the memory 301.

  When the resistance values Rc of the plurality of unit cells 1 constituting the assembled battery 100 are different from each other, the highest resistance value Rc can be compared with the first threshold value Rth1. Thereby, it is possible to determine whether or not the resistance value Rc is lower than the first threshold value Rth1 in all the single cells 1 constituting the assembled battery 100.

  When calculating the resistance value of the assembled battery 100 or the battery block, the first threshold value Rth1 corresponding to this resistance value may be set. Further, when the resistance values are different from each other in the plurality of battery blocks, the highest resistance value can be compared with the first threshold value Rth1. Thereby, it is possible to determine whether or not the resistance value is lower than the first threshold value Rth1 in all the battery blocks.

  When the resistance value Rc is higher than the first threshold value Rth1, the controller 300 performs the process of step S105. When the resistance value Rc is lower than the first threshold value Rth1, the controller 300 ends the process shown in FIG. In step S105, the controller 300 determines that the unit cell 1 is in an abnormal state.

  When it is determined that the unit cell 1 is in an abnormal state, the assembled battery 100 includes the unit cell 1 in an abnormal state, so the controller 300 determines that the assembled battery 100 is in an abnormal state. You can also. Even when it is determined that the battery block is in an abnormal state based on the resistance value of the battery block, the battery pack 100 includes the battery block in the abnormal state. Can be determined to be in an abnormal state.

  When it is determined that the unit cell 1 (the assembled battery 100) is in an abnormal state, the controller 300 can notify the user or the like of information regarding the abnormal state. Sound and display can be used as the notification means. For example, the controller 300 can output information indicating that the assembled battery 100 is in an abnormal state by driving a speaker. Further, the controller 300 can display information indicating that the assembled battery 100 is in an abnormal state by driving the display.

  On the other hand, when the unit cell 1 (the assembled battery 100) is in an abnormal state, the controller 300 can limit input / output (charging / discharging) of the assembled battery 100. When the input / output of the assembled battery 100 is restricted, the upper limit value that allows the input / output of the assembled battery 100 can be reduced. The upper limit value is set for each of input (charge) and output (discharge) of the battery pack 100. Here, since charging / discharging of the assembled battery 100 is controlled so that the electric power when charging / discharging the assembled battery 100 does not exceed the upper limit value, the charging / discharging of the assembled battery 100 is limited by lowering the upper limit value. can do.

  If charging / discharging of the assembled battery 100 is restricted, it becomes difficult for current to flow through the unit cell 1 in an abnormal state, and the unit cell 1 can be protected. Here, lowering the upper limit value includes setting the upper limit value to 0 [kW]. If the upper limit value corresponding to the input is set to 0 [kW], the assembled battery 100 can be prevented from being charged. Further, if the upper limit value corresponding to the output is set to 0 [kW], the assembled battery 100 can be prevented from being discharged.

  When external charging is not performed, in other words, when the vehicle is running, the controller 300 performs the process of step S106. In step S106, the controller 300 determines whether or not the SN ratio is smaller than a threshold value. The threshold value is a threshold value for determining whether or not the current value flowing through the battery pack 100 is acceptable when noise is included. Information about this threshold value can be stored in the memory 301.

  When the vehicle is traveling, the controller 300 can calculate the resistance value of the unit cell 1 based on the current value and voltage value of the unit cell 1. Specifically, the relationship between the detected current value and voltage value is plotted in a coordinate system having the current value and the voltage value as coordinate axes. And if the straight line approximated to a some plot is calculated, the inclination of an approximate straight line will become the resistance value of the cell 1. FIG. Since the current value is likely to change when the vehicle is traveling, an approximate straight line can be obtained.

  Here, when the current value of the unit cell 1 includes noise, the current value varies depending on the magnitude of the noise. As the noise increases, the detected current value tends to deviate from the true current value. In such a state, even if the resistance value of the single cell 1 is calculated, the calculated resistance value deviates from the true resistance value, making it difficult to grasp the deterioration state of the single cell 1. Therefore, in this embodiment, a threshold value is set, and the resistance value of the unit cell 1 is calculated only when the SN ratio is smaller than the threshold value.

  When the S / N ratio is larger than the threshold value, the controller 300 ends the process shown in FIG. That is, when the SN ratio is larger than the threshold value, the controller 300 does not calculate the resistance value Rc of the unit cell 1. On the other hand, when the SN ratio is smaller than the threshold value, the controller 300 performs the process of step S107.

  In step S107, the controller 300 estimates the resistance value Rc of the unit cell 1. Specifically, as described above, the controller 300 can specify the resistance value Rc of the unit cell 1 by plotting the relationship between the detected current value and voltage value and calculating the slope of the approximate line. . The current value of the cell 1 can be detected using the current sensor 202, and the voltage value of the cell 1 can be detected using the monitoring unit 201.

  In step S108, the controller 300 determines whether or not the resistance value Rc calculated in the process of step S107 is higher than the second threshold value Rth2. The second threshold value Rth2 is a value corresponding to the above-described first threshold value Rth1, and is a threshold value for determining whether or not the cell 1 is in an abnormal state. Information regarding the second threshold value Rth2 can be stored in the memory 301.

  As shown in FIG. 7, the first threshold value Rth1 is lower than the second threshold value Rth2. When the abnormal state of the unit cell 1 is determined, a threshold value Rlim for distinguishing whether or not it is in an abnormal state is set. The threshold value Rlim is a theoretical value. The first threshold value Rth1 and the second threshold value Rth2 are set based on the threshold value Rlim.

  The second threshold value Rth2 is set in consideration of the resistance value estimation error ΔR2. That is, a value obtained by adding the estimation error ΔR2 to the threshold value Rlim becomes the second threshold value Rth2. The first threshold value Rth1 is set in consideration of the resistance value estimation error ΔR1. That is, a value obtained by adding the estimation error ΔR1 to the threshold value Rlim becomes the first threshold value Rth1.

  Here, when external charging is performed, a constant current continues to flow through the assembled battery 100, and the current value is unlikely to fluctuate. Therefore, an error does not easily occur in the resistance value Rc calculated from the above equation (1). Further, when external charging is performed, as described above, the polarization voltage value can be easily grasped, so that the estimation accuracy of the resistance value Rc can be improved.

  On the other hand, when external charging is not performed, in other words, when the vehicle is running, the current value detected by the current sensor 202 is likely to include noise. For example, noise due to switching of the inverter 204 may be included in the current value, or a ripple current may be generated when the motor / generator 205 is driven. In particular, when the motor / generator 205 is driven, the influence of noise on the current value is likely to occur.

  For this reason, the estimated accuracy of the resistance value Rc calculated when external charging is performed is based on the estimated accuracy of the resistance value Rc calculated when external charging is not performed, in other words, when the vehicle is running. Also gets higher. Therefore, as shown in FIG. 7, the estimation error ΔR1 can be made smaller than the estimation error ΔR2.

  If the estimation error ΔR2 is reduced in a situation in which noise is likely to be included in the current value, it becomes easy to erroneously determine the abnormal state of the unit cell 1. Therefore, when the vehicle is traveling, it is necessary to increase the estimation error ΔR2 by the amount that noise is likely to be included in the current value.

  On the other hand, when external charging is performed, the estimation accuracy of the resistance value Rc can be improved, so that the estimation error ΔR1 can be made smaller than the estimation error ΔR2. Here, by making the estimation error ΔR1 smaller than the estimation error ΔR2, the abnormal state of the unit cell 1 can be determined early.

  When the vehicle is traveling, it is determined that the unit cell 1 is in an abnormal state when the resistance value Rc becomes higher than the second threshold value Rth2. On the other hand, even if the resistance value Rc estimated at the time of external charging does not reach the second threshold value Rth2, it can be determined that the unit cell 1 is in an abnormal state when it becomes higher than the first threshold value Rth1. . Thereby, when external charging is performed, it is possible to determine the abnormal state of the unit cell 1 earlier than when the vehicle is traveling.

  According to the present embodiment, it is possible to estimate the resistance value Rc of the unit cell 1 not only when the vehicle is running but also when external charging is performed. Thereby, the chance of estimating the resistance value Rc of the cell 1 can be increased, and the current resistance value Rc of the cell 1 can be easily grasped. Here, when the vehicle is running, if the noise included in the current value is too large, the resistance value Rc is not estimated, so the opportunity to calculate the resistance value Rc is lost. By calculating the resistance value Rc even during external charging, the frequency of calculating the resistance value Rc can be increased.

  In this embodiment, the resistance value Rc is calculated when external charging is performed, in other words, when the assembled battery 100 is charged under a constant current. However, the present invention is not limited to this. Specifically, the resistance value Rc can be calculated also when the battery pack 100 is discharged under a constant current.

  For example, the assembled battery 100 can be connected to a device (external device) provided outside the vehicle, and the power of the assembled battery 100 can be supplied to the external device under a constant current. Further, when the battery system shown in FIG. 1 is in the activated state (Ready-On) and the shift position is in the P (Parking) range or the N (Neutral) range, the power of the assembled battery 100 is It may be supplied to auxiliary equipment mounted on the vehicle. In such a case, the assembled battery 100 is discharged under a constant current.

  As described above, when the battery pack 100 is discharged under a constant current, the resistance value Rc of the unit cell 1 can be calculated using the above formula (1). Here, since the assembled battery 100 is discharged under a constant current, the relationship between the polarization voltage value and the discharge duration (energization time) (corresponding to FIG. 4) can be obtained in advance by experiments or the like. For example, the polarization voltage value corresponding to the duration of discharge can be specified.

  Even when the assembled battery 100 is discharged under a constant current, it can be suppressed that noise is included in the current value, and the estimation accuracy of the resistance value Rc can be improved as in the present embodiment. The opportunity for calculating the resistance value Rc can be increased by calculating the resistance value Rc at the time of discharging at a constant current in addition to when the vehicle is running and external charging. Thereby, it becomes easy to grasp the current resistance value Rc of the unit cell 1.

1: single cell, 100: assembled battery, 201: monitoring unit, 201a: voltage monitoring IC,
202: current sensor, 203: current limiting resistor, 204: inverter,
205: Motor generator, 206: Charger, 207: Inlet,
300: Controller, 301: Memory, 302: Timer

Claims (7)

A power storage unit for charging and discharging;
A voltage sensor for detecting a voltage value of the power storage unit;
A controller that determines that the power storage unit is in an abnormal state when a resistance value of the power storage unit is higher than a threshold;
The controller is
When charging or discharging the power storage unit with a constant current,
Using the correspondence between the energization time and the polarization voltage value, identify the polarization voltage value corresponding to the energization time,
Using the detected voltage value of the voltage sensor, the specified polarization voltage value, the open-circuit voltage value of the electricity storage unit after energization, and the current value during energization, the resistance value of the electricity storage unit after energization is calculated. ,
A power storage system characterized by that. A current sensor for detecting a current flowing through the power storage unit;
The controller calculates the open-circuit voltage value of the power storage unit after energization using the open-circuit voltage value of the power storage unit when starting energization and the value obtained by integrating the detected current value of the current sensor during energization The power storage system according to claim 1, wherein:   3. The controller according to claim 1, wherein the controller calculates a resistance value of the power storage unit after charging when the power storage unit is charged with a constant current using electric power supplied from an external power source. The electricity storage system described. An inverter that converts DC power output from the power storage unit into AC power;
A motor that converts AC power output from the inverter into kinetic energy used for running the vehicle;
The power storage system according to any one of claims 1 to 3, wherein   The said controller calculates the resistance value of the said electrical storage unit from the behavior of the electric current value and voltage value of the said electrical storage unit, when supplying electric power from the said electrical storage unit to the said motor. The electricity storage system described. The controller is
When the resistance value of the power storage unit calculated when charging or discharging the power storage unit with a constant current is higher than a first threshold, it is determined that the power storage unit is in an abnormal state;
When the resistance value of the power storage unit calculated when power is supplied from the power storage unit to the motor is higher than a second threshold, it is determined that the power storage unit is in an abnormal state;
The first threshold is lower than the second threshold;
The power storage system according to claim 5. When charging or discharging the power storage unit with a constant current, using the correspondence relationship between the energization time and the polarization voltage value, the polarization voltage value corresponding to the energization time is specified,
Using the voltage value of the electricity storage unit detected by the voltage sensor, the specified polarization voltage value, the open-circuit voltage value of the electricity storage unit after energization, and the current value at the time of electricity energization, Calculate the resistance value,
When the calculated resistance value is higher than a threshold value, it is determined that the power storage unit is in an abnormal state.
An abnormality determination method characterized by the above.