JP2014186007A - Power storage system, control apparatus and malfunction detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect malfunction of a battery with high accuracy.SOLUTION: A power storage system includes a power storage device composed of a plurality of power storage elements and is installed in a vehicle. The power storage system comprises; a voltage sensor detecting a voltage of the power storage element; a current sensor detecting current flowing through the power storage element; a temperature sensor detecting a temperature of the power storage device; and a controller detecting malfunction of the power storage element. The controller calculates the internal resistance of the power storage element based on a voltage value and a current value which are detected, with a predetermined interval. When a reduction amount between the calculated internal resistances exceeds a predetermined value, the controller determines malfunction of the power storage element, and further variably controls the predetermined value to be smaller as the temperature of the power storage device is higher relative to a heating value of the power storage element based on the value of current flowing for a change between the calculated internal resistances.

Description

  The present invention relates to an abnormality detection technique for a power storage device mounted on a vehicle.

  In Patent Document 1, the internal resistance is calculated from the voltage value and current value of the battery, and the abnormality of the battery is detected by monitoring the fluctuation of the internal resistance. For example, when the internal resistance value is larger than the threshold value or the difference between the internal resistance values between the batteries is larger than the threshold value, it is determined that the battery is abnormal.

JP 2000-260481 A

  However, the internal resistance value of the battery varies depending on the battery temperature. For example, when the battery temperature increases, the internal resistance value may decrease. In such a case, the battery abnormality may not be detected with high accuracy simply by comparing the internal resistance value with the threshold value or comparing the internal resistance values between the batteries.

  In view of the above, an object of the present invention is to provide a power storage system and an abnormality detection method capable of accurately detecting an abnormality of a power storage device in consideration of a change in internal resistance value due to a temperature rise.

  1st invention of this application is an electrical storage system provided with the electrical storage apparatus comprised from several electrical storage elements, and mounted in a vehicle, The electric current which detects the voltage sensor which detects the voltage of an electrical storage element, and the electric current which flows through an electrical storage element A sensor; a temperature sensor that detects a temperature of the power storage device; and a controller that detects an abnormality of the power storage element. The controller calculates the internal resistance of the power storage element at a predetermined interval based on the detected voltage value and current value, and if the amount of decrease between the calculated internal resistances is larger than the predetermined value, the power storage element is abnormal. It is determined that there is, and variably controlled so that the predetermined value decreases as the temperature of the power storage device increases with respect to the heat generation amount of the power storage element based on the calculated current value between the internal resistances. .

  According to the first invention of the present application, even if the internal resistance is decreased due to a temperature rise due to the internal resistance of the storage element in which an abnormality has occurred is larger than that of a normal storage element, the internal resistance calculated at a predetermined interval Since the abnormality of the storage element is determined based on the amount of decrease during the period, for example, compared to the case where the abnormality is determined by comparing the internal resistance of the storage element in which the abnormality has occurred or the internal resistance of a normal storage element. Even in a state where the discharge load is high and the temperature rise is high due to heat generation, the abnormality determination can be performed with high accuracy.

  The predetermined value, which is a reference value for determining abnormality of the power storage element, is variably controlled so as to decrease as the temperature of the power storage device increases with respect to the heat generation amount of the power storage element. The internal resistance of the electricity storage element depends on the temperature, and the resistance value decreases as the temperature goes from low to high. At this time, the degree of decrease in the resistance value with respect to the temperature increase (the amount of decrease) is smaller at the high temperature than at the low temperature (the degree at which the resistance value decreases with increasing temperature is lower). Therefore, the degree of decrease in the resistance value according to the temperature that rises due to the heat generation of the power storage element is smaller at the high temperature than at the low temperature, and therefore is a reference value for determining abnormality of the power storage element as the temperature of the power storage device increases. By reducing a certain predetermined value, it is possible to easily determine a decrease in internal resistance due to a temperature rise due to an internal resistance of a storage element in which an abnormality has occurred as compared to a normal storage element as an abnormality of the storage element, Element abnormality determination can be performed with high accuracy.

  The controller can variably control the predetermined value so that the temperature becomes smaller as the temperature of the power storage device is higher and the calorific value is smaller, and becomes larger as the temperature of the power storage device is lower and the calorific value is larger. As described above, since the internal resistance of the power storage element depends on the temperature, if the temperature rise according to the heat generation amount of the power storage element is large, the change in the resistance value becomes large. Therefore. The degree to which the resistance value decreases with respect to temperature rise (the amount to decrease) is lower than the low temperature. If the heat generation amount of the power storage element at high temperature is small, the predetermined value is decreased, and the resistance value decreases with temperature rise. If the amount of heat generated by the electricity storage element at a low temperature is greater than the high temperature (the amount to be reduced), by increasing the predetermined value, the storage element in which an abnormality has occurred has a higher internal resistance than the normal electricity storage element. Therefore, it is possible to accurately determine the abnormality of the storage element based on the decrease in internal resistance due to the increased temperature.

  The controller uses a correspondence map in which a predetermined value is previously associated with the square value of the current value related to the temperature of the power storage device and the amount of heat generation, and based on the detected temperature and the square value of the detected current value by the current sensor, A predetermined value can be calculated.

  When the square value of the current value detected by the current sensor is larger than a predetermined threshold value, the controller performs a process of determining an abnormality of the power storage element based on a decrease amount between the internal resistances calculated at a predetermined interval. Can be controlled. By configuring in this way, for example, between the internal resistances calculated at a predetermined interval in a state larger than a predetermined charging / discharging load that can ensure a change in resistance value due to a temperature rise according to the amount of heat generated by the storage element. By performing the process of determining the abnormality of the power storage element based on the amount of decrease, according to the decrease in the internal resistance due to the temperature rise caused by the internal resistance of the power storage element in which the abnormality has occurred is larger than the normal power storage element It is possible to accurately determine abnormality of the storage element.

  A plurality of temperature sensors can be provided at different locations of the power storage device. At this time, the controller can perform the above processing using the minimum value among the detected temperatures of the plurality of temperature sensors. The degree of decrease in the resistance value according to the temperature rising due to the heat generation of the storage element is smaller at the high temperature than at the low temperature, so that the predetermined value is not reduced more than necessary by using the minimum detection temperature (abnormal This makes it possible to determine the abnormality of the electricity storage element and improve the accuracy of the abnormality determination (without excessively reducing the decrease in internal resistance due to temperature rise due to the internal resistance of the electricity storage element having a larger internal resistance than the normal electricity storage element). To do.

  The controller can determine the slope of the approximate line with respect to the correspondence relationship between the current value and the voltage value detected in a predetermined time, and can calculate the slope as the internal resistance of the storage element.

  As the amount of decrease, the difference between the internal resistances calculated at a predetermined interval or the rate of change per unit time can be used.

  A second invention of the present application is a control device for a power storage device mounted on a vehicle, and the power storage device includes a plurality of power storage elements. The control device calculates the internal resistance of the power storage element at a predetermined interval based on the voltage value detected by the voltage sensor and the current value detected by the current sensor, and the amount of decrease between the calculated internal resistances is less than the predetermined value. Is larger, the power storage element is determined to be abnormal, and the higher the temperature of the power storage device, the higher the temperature of the power storage device relative to the calorific value of the power storage element based on the calculated current value between the internal resistances. Variable control is performed so that the value becomes smaller. According to the second invention of the present application, the same effect as that of the first invention of the present application can be obtained.

  A third invention of the present application is a method for detecting an abnormality of a power storage device mounted on a vehicle, and the power storage device includes a plurality of power storage elements. Calculating the internal resistance of the power storage element at a predetermined interval based on the voltage value detected by the voltage sensor and the current value detected by the current sensor; calculating the amount of decrease between the calculated internal resistances; A step of determining that the power storage element is abnormal when the amount of decrease is greater than a predetermined value, and a calorific value of the power storage element based on a current value that flows with respect to a change between the calculated internal resistances On the other hand, as the temperature of the power storage device is higher, the predetermined value is variably controlled so that the predetermined value becomes smaller based on the square value of the current value detected by the current sensor related to the heat generation amount and the detected temperature of the power storage device. Further calculating. According to the third 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 each behavior (IV plot) of the electric current and voltage of a cell, and is a figure which shows the example which calculates internal resistance from each behavior of an electric current and a voltage. It is a figure which shows the example of a battery abnormality detection based on the internal resistance of the conventional cell. It is a figure which shows the relationship between the internal resistance of a cell, and temperature. It is a figure which shows the example of a battery abnormality detection based on the fall amount of internal resistance. It is a figure which shows the example of calculation of the threshold value (predetermined value) with respect to the fall amount of internal resistance for determining battery abnormality. It is a flowchart which shows the abnormality detection operation | movement of a battery system. It is a flowchart which shows the modification of the abnormality detection operation | movement of a battery system.

  Examples of the present invention will be described below.

  FIG. 1 is a diagram showing the configuration of the battery system of this example. The battery system shown in FIG. 1 can be mounted on a vehicle, for example. Examples of vehicles include HV (Hybrid Vehicle) and EV (Electric Vehicle).

  In the HV, as a power source for running the vehicle, in addition to the assembled battery described later, another power source such as an engine or a fuel cell is provided. Further, in a plug-in hybrid vehicle (PHV), the assembled battery can be charged using electric power from an external power source. Further, in the HV and PHV equipped with the engine, the kinetic energy generated by the engine is converted into electric energy, whereby the assembled battery can be charged using the electric energy.

  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. An external power source is a power source (for example, a commercial power source) installed separately from the vehicle outside the vehicle.

  The assembled battery (corresponding to a power storage device) 100 has a plurality of unit cells (corresponding to power storage elements) 10 connected in series. As the unit cell 10, 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 10 can be appropriately set based on the required output of the assembled battery 100 and the like. In the assembled battery 100 of the present embodiment, all the unit cells 10 are connected in series, but the assembled battery 100 may include a plurality of unit cells 10 connected in parallel.

  The monitoring unit 200 detects the inter-terminal voltage of the battery pack 100 or detects the inter-terminal voltage of each unit cell 10 and outputs the detection result to an ECU (Electric Control Unit) 300.

  The temperature sensor 201 detects the temperature of the assembled battery 100 (unit cell 10) and outputs the detection result to the ECU 300. Here, the temperature sensor 201 can be provided at one place of the assembled battery 100, or can be provided at a plurality of different places in the assembled battery 100. When using the detection temperatures of the plurality of temperature sensors 201, the temperature of the assembled battery 100 can be appropriately used as a minimum value, a maximum value, a median value or an average value of the plurality of detection temperatures, among the plurality of detection temperatures.

  Current sensor 202 detects a current flowing through battery pack 100 and outputs the detection result to ECU 300. In this embodiment, the current value detected by the current sensor 202 when the assembled battery 100 is discharged is a positive value. Further, the current value detected by the current sensor 202 when charging the assembled battery 100 is a negative value.

  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. For example, the current sensor 202 can be provided on the negative electrode line NL connected to the negative electrode terminal of the assembled battery 100. A plurality of current sensors 202 can also be used.

  The ECU (corresponding to a controller) 300 has a memory 301, and the memory 301 stores various information for the ECU 300 to perform predetermined processing (for example, processing described in the present embodiment). . In the present embodiment, the memory 301 is built in the ECU 300, but the memory 301 may be provided outside the ECU 300.

  A system main relay SMR-B is provided in the positive electrode line PL. System main relay SMR-B is switched between ON and OFF by receiving a control signal from ECU 300. A system main relay SMR-G is provided in the negative electrode line NL. System main relay SMR-G is switched between on and off by receiving a control signal from ECU 300.

  A system main relay SMR-P and a current limiting resistor 203 are connected in parallel to the system main relay SMR-G. Here, the system main relay SMR-P and the 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 ECU 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).

  When connecting the assembled battery 100 to the inverter 204, the ECU 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, ECU 300 switches system main relay SMR-P from on to off after switching system main relay SMR-G from off to on. Thereby, the connection between the assembled battery 100 and the inverter 204 is completed, and the battery system shown in FIG. 1 is in the activated state (Ready-On). Information regarding on / off (IG-ON / IG-OFF) of the ignition switch of the vehicle is input to ECU 300, and ECU 300 activates the battery system in response to the ignition switch switching from OFF to ON.

  On the other hand, when the ignition switch is switched from on to off, ECU 300 switches 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. By transmitting the kinetic energy generated by the motor / generator 205 to the wheels, the vehicle can be driven.

  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.

  The battery system shown in FIG. 1 can include a charger (not shown) that charges the assembled battery 100 with power supplied from an external power source. By connecting a charging plug extended from an external power source to the vehicle (inlet), external charging can be performed via a charger.

  ECU 300 calculates (estimates) or calculates the SOC of battery pack 100 based on the voltage value detected by monitoring unit 200, the battery temperature detected by temperature sensor 201, and the current value detected by current sensor 202. The charge / discharge control of the assembled battery 100 can be performed based on the SOC and the full charge capacity.

  The SOC of the assembled battery 100 indicates the ratio (charged state) of the current charging capacity with respect to the full charging capacity of the assembled battery 10, and the full charge capacity is the upper limit value of the SOC. The SOC can be specified from an open circuit voltage (OCV) of the assembled battery 100. For example, the correspondence relationship between the OCV and the SOC of the assembled battery 100 is stored in advance in the memory 301 as an OCV-SOC map. The ECU 300 can calculate the OCV of the assembled battery 100 from the voltage (CCV: Closed Circuit Voltage) detected by the monitoring unit 200, and can calculate the SOC from the OCV-SOC map.

  Since the correspondence relationship between the OCV and the SOC of the assembled battery 100 changes according to the battery temperature, the OCV-SOC map is stored in the memory 301 for each battery temperature, and the SOC is estimated from the OCV of the assembled battery 100. The SOC of the battery pack 100 may be estimated by switching (selecting) the SOC-OCV map according to the battery temperature at that time. In addition to the SOC of the battery pack 100, the SOC of each of the battery cells 10 connected in series constituting the battery pack 100 can be calculated, and the SOC of the battery pack 10 as a whole and the SOC of each battery cell 11 are managed. You can also.

  Therefore, the ECU 300 can grasp the overcharged state and the overdischarged state of the assembled battery 100 by monitoring the voltage value (CCV) detected by the monitoring unit 200 during charging and discharging. For example, charging / discharging control may be performed to limit charging of the battery pack 100 so that the calculated SOC does not become higher than a predetermined upper limit SOC with respect to the full charge capacity, or to limit discharging so as not to become lower than the lower limit SOC. it can.

  The ECU 300 detects an abnormality of the assembled battery 100 (unit cell 10) using each detection value detected by the monitoring unit 200, the temperature sensor 201, and the current sensor 202. The ECU 300 of the present embodiment can function as a control device that controls charging / discharging of the assembled battery 100 and detects an abnormality of the assembled battery 100. It should be noted that a control device for detecting an abnormality of the assembled battery 100 may be provided in the battery system separately from the ECU 300, and the abnormality detection device may be provided externally or internally with respect to the ECU 300. Can be configured.

  ECU 300 detects the current value of unit cell 10 using current sensor 202 and detects the voltage value of each unit cell 10 using monitoring unit 200 in charge / discharge control during traveling of the vehicle. When the battery system is activated, the current value and the voltage value vary according to charging / discharging of the assembled battery 100. Here, the IV plot (the relationship between the current value and the voltage value) shown in FIG. 2 is obtained by acquiring the relationship between the current value and the voltage value at a plurality of timings within a certain period.

  In FIG. 2, the vertical axis represents the voltage value, and the horizontal axis represents the current value. In the coordinate system shown in FIG. 2, the internal resistance of the unit cell 10 can be calculated by plotting a plurality of relationships between the current value and the voltage value. As shown in FIG. 2, ECU 300 plots the relationship between the acquired current value and voltage value in a coordinate system (IV coordinate system) in which the horizontal axis is the current value and the vertical axis is the voltage value. Based on this point, the approximate line L is calculated, and the slope of the approximate line L is calculated as the internal resistance R of the cell 10. The approximate straight line L can be obtained by, for example, the least square method.

  The ECU 300 performs the IV plot processing as in the example of FIG. 2 using the current value and the voltage value acquired at predetermined time intervals during the charge / discharge control, and is acquired within a certain period of time. Based on the plots of a plurality of current values and voltage values, the approximate line L is redrawn to calculate the internal resistance R of each unit cell 10 each time, or the acquired current value and voltage value are plotted each time. By redrawing the approximate straight line L, the internal resistance R of each unit cell 10 can be calculated. The internal resistance R of the present embodiment is a learning value calculated while learning a past IV plot (internal resistance value) from the calculation timing.

  Here, the abnormality detection of the conventional assembled battery 100 is demonstrated. FIG. 3 is a diagram for explaining an example of battery abnormality detection based on the internal resistance R of the conventional assembled battery 100. In FIG. 3, the solid line indicates the internal resistance of the normal unit cell 10, and the alternate long and short dash line indicates the internal resistance of the unit cell 10 in the abnormal state.

  As shown in FIG. 3, conventionally, when the internal resistance R of the unit cell 10 constituting the assembled battery 100 exceeds a preset threshold value, it is determined that the assembled battery 100 has a battery abnormality, When the internal resistance difference between the batteries 10 is larger than a predetermined value, it is determined that the battery pack 100 is abnormal.

  However, it is known that the internal resistance R of the unit cell 10 depends on the battery temperature. FIG. 4 is a diagram showing the relationship between the internal resistance of the unit cell 10 and the temperature. As shown in FIG. 4, when the battery temperature increases, the internal resistance R decreases, and when the battery temperature decreases, the internal resistance increases. For this reason, as shown in FIG. 3, depending on the battery temperature at the time of calculation of the internal resistance R, the internal resistance R is lower than the threshold value because the internal resistance value is lower than the threshold value to be determined as battery abnormality. Or the difference of the internal resistance value from the normal unit cell 10 is small.

More specifically, when a current flows through the unit cell 10, Joule heat corresponding to the internal resistance R is generated. Joule heat can be calculated from the current value I flowing per unit time and the internal resistance R, and can be calculated as I ² R. The I ² value represents the amount of heat generated with respect to the charge / discharge load of the assembled battery 100 (unit cell 10), and the temperature rise increases as the I ² value increases.

  Since the unit cell 10 in the abnormal state has a higher internal resistance R than the normal unit cell 10, when the current value flowing in charge / discharge is large (the charge / discharge load is large), the normal unit cell 10. The speed at which the internal resistance R decreases as the temperature rises (the speed at which the internal resistance R decreases) is faster than that of the normal unit cell 10. For this reason, in a state where the charge / discharge load is high and the temperature rise is high due to heat generation, the internal resistance of the unit cell 10 in which the abnormality has occurred is lower than that of the normal unit cell 10, resulting in a decrease in the internal resistance. In some cases, the unit cell 10 to be determined to be abnormal in battery cannot be detected with high accuracy at the time of calculation of the internal resistance R.

  In particular, as described above, the calculation process of the internal resistance R performs the IV plot process using the current value and the voltage value acquired at predetermined time intervals during the charge / discharge control. From the viewpoint of the calculation accuracy of the internal resistance, a certain amount of time is required because the current and voltage sampling numbers are required to some extent. However, when the calculation interval of the internal resistance R becomes long, the internal resistance R of the unit cell 10 that should be determined as a battery abnormality has become lower than the threshold due to a decrease in internal resistance accompanying a temperature rise, The difference in internal resistance value with the unit cell 10 becomes small, and battery abnormality cannot be detected with high accuracy.

  Therefore, in this embodiment, the abnormal state of the unit cell 10 rises faster than the normal unit cell 10 and the internal resistance R is more likely to decrease than the normal unit cell 10 as the temperature rises. In consideration of the above, the abnormality determination of the unit cell 10 is performed based on the amount of change in the internal resistance R.

  FIG. 5 is a diagram illustrating an example of battery abnormality detection based on the amount of change in internal resistance. In FIG. 5, t1 and t2 are timings for calculating the internal resistance R. A change amount ΔR (= R2−R1) is calculated as an internal resistance R1 calculated at the detection timing t1 and an internal resistance R2 calculated at the detection timing t2, and a decrease amount of the internal resistance R2 with respect to the internal resistance R1.

  As described above, the internal resistance R1 calculated at the detection timing t1 is calculated from IV plots of current values and voltage values acquired in a certain period before the detection timing t1. The internal resistance R2 calculated at the detection timing t2 is calculated from IV plots of a plurality of acquired current values and voltage values within a certain period from the detection timing t1 to the detection timing t2.

  As shown in FIG. 5, since the normal unit cell 10 has a smaller internal resistance R than the abnormal unit cell 10, the temperature does not easily increase with respect to the flowing current, and the amount of decrease in the internal resistance R accompanying the temperature increase is small. . On the other hand, since the abnormal unit cell 10 has a large internal resistance R, the calorific value is larger than that of the normal unit cell 10 and the amount of decrease (change amount) of the internal resistance R due to the temperature rise is large.

  Therefore, if the decrease amount of the internal resistance R2 calculated at the current detection timing is larger than a predetermined value with respect to the internal resistance R1 calculated at the previous detection timing, the unit cell 10 is determined to be abnormal. Can do. By using the fact that the amount of change (decrease amount) in the internal resistance R of the cell 10 is larger than the amount of change in the internal resistance R of the normal cell 10, the battery abnormality of the cell 10 is determined. As shown in FIG. 5, battery abnormality can be accurately detected even when the internal resistance is lower than the threshold as the temperature rises or when the difference in internal resistance value from the normal unit cell 10 is small. Can do.

  In the abnormality detection method of the present embodiment, even if the internal resistance R is reduced due to a temperature rise due to the internal resistance R being greater than that of the normal single battery 10 in the abnormal cell 10, the calculation is performed at a predetermined interval. Since the abnormality of the single cell 10 is determined (detected) based on the amount of reduction between the internal resistances, the abnormality determination can be performed with high accuracy even when the charge / discharge load is high and the temperature is high due to heat generation. However, the predetermined value, which is a reference value for determining the abnormality of the unit cell 10, is variably controlled so as to decrease as the temperature of the assembled battery 100 increases with respect to the amount of heat generated by the unit cell 10. .

  Returning to FIG. 4 again, the temperature dependence of the internal resistance R of the unit cell 10 will be described in detail. As shown in FIG. 4, the internal resistance R of the unit cell 10 has a resistance value that decreases as the temperature increases from a low temperature to a high temperature. High temperature is smaller than low temperature. That is, when the temperature rises from a low temperature state, the change amount (decrease amount) of the internal resistance R is large. In the region where the temperature is low, the rate of change (slope) of the internal resistance R with respect to the temperature is large, so that the internal resistance R changes (decreases) greatly with respect to the temperature increase of ΔT. On the other hand, when the temperature rises from a high temperature state, the amount of change (decrease amount) in the internal resistance R is small. Since the change rate (slope) of the internal resistance R with respect to the temperature is small in the region where the temperature is high, the change of the internal resistance R is small even if the temperature rises by the same ΔT.

  Therefore, even when the temperature rising due to the heat generation of the unit cell 10 is the same, the degree of decrease in the internal resistance value is higher than the low temperature when the temperature rises from a low temperature state and when the temperature rises from a high temperature state. Is smaller. For this reason, in this embodiment, as the temperature of the assembled battery 100 increases, the predetermined value, which is a reference value for determining the abnormality of the single battery 10, is reduced, so that the single battery 10 in which the abnormality has occurred is normal. A decrease in internal resistance due to a temperature rise due to the internal resistance R being larger than that of the battery 10 is easily determined as an abnormality of the unit cell 10, and the abnormality determination is performed with high accuracy.

  FIG. 6 is a diagram illustrating a calculation example of the threshold value ΔRth with respect to the amount of decrease in internal resistance according to the present embodiment. As shown in FIG. 6, the threshold value ΔRth is set to be smaller as the temperature of the assembled battery 100 is higher and the heat generation amount (the square value of the current value related to the heat generation amount) is smaller. It is set so as to increase as the amount increases.

  In this way, if the amount of heat generated by the unit cell 10 at a high temperature, which is lower than the low temperature when the internal resistance value decreases with increasing temperature, the threshold ΔRth is decreased, and the internal resistance value decreases with increasing temperature. If the calorific value of the unit cell 10 at a low temperature, which is greater than the high temperature, is large, the threshold value ΔRth is increased so that the unit cell 10 in which the abnormality has occurred has a larger internal resistance R than the normal unit cell 10. The abnormality determination of the unit cell 10 based on the decrease in the internal resistance R due to the temperature rise caused can be accurately performed.

  Note that the amount of decrease due to the temperature increase of the internal resistance R of the normal unit cell 10 can be calculated in advance for each battery temperature as in the example of FIG. 4, so the lower limit value of the threshold ΔRth is calculated in advance. It can be set to a value larger than the maximum value of the amount of decrease accompanying the temperature rise of the normal cell 10.

Further, the threshold value ΔRth shown in FIG. 6 can be stored in the memory 301 as a correspondence map previously associated with the square value of the current value related to the temperature of the assembled battery 100 and the amount of heat generated by the unit cell 10. The ECU 300 can calculate the threshold value ΔRth by referring to the correspondence map and using the detected temperature by the temperature sensor 201 and the square value of the detected current value by the current sensor 202 (average value of I ² values).

  Further, in this embodiment, the temperature detected by the assembled battery 100 by the temperature sensor 201 is used to calculate the threshold value ΔRth. However, when a plurality of temperature sensors 201 are provided at different locations of the assembled battery 100, a plurality of temperature sensors 201 are used. The minimum value among the detected temperatures of the temperature sensor 201 is used. As described above, the degree of decrease in the internal resistance value according to the temperature that rises due to the heat generation of the battery cell 10 is smaller at the high temperature than at the low temperature. It is possible to prevent a decrease in the internal resistance R due to a temperature rise due to the internal resistance R being larger than that of the normal unit cell 10 from being too small, and an abnormality with a threshold ΔRh smaller than necessary. The determination can be suppressed and the accuracy of the abnormality determination of the unit cell 10 can be improved.

  The temperature sensor 201 can be provided at an arbitrary position such as a central part, an end part in the arrangement direction of the unit cells 10, an upstream side or a downstream side of the cooling path with respect to the assembled battery 100. When providing the several temperature sensor 201, it can provide arbitrarily in each of these positions.

Further, as the I ² value used for calculating the threshold value ΔRth, an average value of square values of a plurality of current values acquired during a certain period until the time when the internal resistance R is calculated and the battery temperature is detected is used. Can do. For example, the I ² value of each of the plurality of acquired current values is calculated, and the average value of the plurality of I ² values is calculated.

The plurality of detection period of the current value used for calculating an I ² value may be used each current value in the IV plot used to calculate the current internal resistance R, in this case, I ² value And the detected current value used for each calculation of the internal resistance R are the same. On the other hand, the detection current value used for each calculation of the I ² value and the internal resistance R can be made different. For example, the I ² value and the detection current value used for the calculation are calculated at the current internal resistance R calculation timing (or The temperature detection timing of the latest assembled battery 100 may be configured to use a plurality of detected current values acquired within a predetermined period from the latest detected current value.

  Furthermore, in the above description, the difference between the internal resistances R calculated at a predetermined interval is described as an example as the amount of decrease in the internal resistance R of the unit cell 10, but for example, the internal resistance R calculated at a predetermined interval is used. The rate of change in resistance per unit time (dR / dt) between them can be the amount of decrease in the internal resistance R of the unit cell 10. In this case, the threshold ΔRth is also a resistance change rate per unit time.

  FIG. 7 is a flowchart showing an abnormality detection operation of the battery system of the present embodiment. The process shown in FIG. 7 is executed by ECU 300. For example, the ECU 300 performs an abnormality detection process for the assembled battery 100 when the ignition switch of the vehicle is switched from OFF to ON, and the system main relays SMR-B and SMR-G are turned ON to start charge / discharge control. It can be started (S101).

  Further, the abnormality detection process can be performed periodically at a predetermined time interval after the ignition switch is turned on, or at a predetermined timing during charge / discharge. Further, the voltage value, current value, and battery temperature acquired during charging / discharging can be stored in the memory 301 and can be configured to be performed at a predetermined timing after the ignition switch is turned off.

  In step S102, the ECU 300 calculates the internal resistance R of each of the unit cells 10 connected in series with the assembled battery 100. The ECU 300 acquires the detected voltage value and the detected current value from the monitoring unit 200 and the current sensor 202, and uses the plurality of detected voltage values and detected current values acquired in a certain period, the horizontal axis represents the current value, and the vertical axis The relationship between the current value and the voltage value is plotted in the IV coordinate system where is a voltage value. An approximate straight line L is calculated based on the plotted points, the inclination of the approximate straight line L is obtained, and the internal resistance R of the unit cell 10 is calculated.

  In step S <b> 103, the ECU 300 acquires the battery temperature of the assembled battery 100 via the temperature sensor 201. As described above, when a plurality of temperature sensors 201 are provided, the minimum detected temperature among the plurality of acquired detected temperatures is grasped as the battery temperature of the assembled battery 100. Note that the battery temperature acquisition timing of the assembled battery 100 may be a timing related to the calculation timing of the internal resistance R in step S102. For example, the detected temperature can be acquired from the temperature sensor 201 at the end of a certain period in which a plurality of detected voltage values and detected current values are acquired, or at a predetermined timing after the certain period.

In step S104, ECU 300 calculates an average value of the I ² values. For example, the ECU 300 calculates an I ² value of each of a plurality of detected current values for the internal resistance R calculated this time from the time when the internal resistance R was calculated last time, and calculates an average value of the calculated I ² values. Can do.

  In step S105, the ECU 300 calculates a difference ΔR (R2-R1) between the internal resistance R (R2) calculated this time and the previously calculated internal resistance R (R1). At this time, the ECU 300 ends the abnormality detection process when the previously calculated internal resistance R does not exist.

Next, ECU 300 calculates threshold value ΔRth in step S106. The ECU 300 uses the detected temperature of the assembled battery 100 acquired in step S103 and the average value of the I ² values calculated in step S104, and the temperature of the assembled battery 100 and the amount of heat generated by the single battery 10 stored in the memory 301. The threshold value ΔRth is calculated from the correspondence map of the threshold value ΔRth previously associated with the square value of the current value related to.

  In step S107, the ECU 300 compares ΔR calculated in step S105 with the threshold value ΔRh calculated in step S106. If ΔR is larger than ΔRth, the ECU 300 proceeds to step S108 and counts up the abnormality determination counter Cr.

  When ΔR is larger than ΔRth, the assembled battery 100 (unit cell 10) may be immediately determined to be abnormal. However, in this embodiment, the number of times that ΔR is determined to be larger than ΔRth is predetermined. When the number of times is continuous, in other words, when a continuous abnormality determination is made, it is determined that the assembled battery 100 (single cell 10) is in an abnormal state, and the determination error due to the usage environment is suppressed because of the battery temperature and charge / discharge load. In addition, the abnormality determination accuracy of the assembled battery 100 (unit cell 10) is further improved.

  Therefore, after the abnormality determination counter Cr is counted up in step S108, the ECU 300 determines whether or not the abnormality determination counter Cr exceeds the counter threshold value Cth in step S109. The cell 10) is determined as abnormal (S110). On the other hand, when it is determined in step S109 that the abnormality determination counter Cr does not exceed the counter threshold Cth, the process proceeds to step S112, and the assembled battery 100 (single cell 10) is determined to be normal (S112).

  In step S107, if it is determined that ΔR is smaller than ΔRth, the ECU 300 proceeds to step S111 to initialize (for example, set to 0) an abnormality determination counter, and proceeds to step S112 to perform the assembled battery 100. The (single cell 10) is determined as normal.

  FIG. 8 is a flowchart showing a modification of the abnormality detection operation of the battery system of the present embodiment. The example of FIG. 8 is an example of an abnormality detection process that combines the abnormality detection process of this embodiment and the conventional abnormality detection process.

  As described above, the abnormality detection method shown in FIG. 7 is based on a single unit based on a decrease in the internal resistance R due to a temperature rise due to the fact that the unit cell 10 in which an abnormality has occurred has a larger internal resistance R than the normal unit cell 10. If it is an abnormality determination of the battery 10 and the temperature rise according to the calorific value of the single battery 10 is large, the change in the internal resistance R becomes large. For this reason, if the calorific value accompanying the temperature rise is large, the change in the internal resistance R can be captured more greatly, and the accuracy of abnormality determination can be improved.

Therefore, as shown in the example of FIG. 8, when the current value flowing in charging / discharging is large, the temperature of the abnormal unit cell 10 rises faster than that of the normal unit cell 10, and the internal resistance R increases as the temperature rises. When the I ² value representing the heat generation amount with respect to the charge / discharge load of the assembled battery 100 (single cell 10) is larger than a predetermined value because the phenomenon in which the rate of decrease of the battery is faster than the normal unit cell 10 can be grasped more accurately. In addition, when the abnormality detection process (first abnormality detection process) shown in FIG. 7 is performed and the I ² value is smaller than a predetermined value, the conventional abnormality detection process (second abnormality detection process) shown in FIG. I do.

  In the example of FIG. 8, steps 301 to S304 are the same as steps S101 to S104 of FIG.

In step S305, ECU 300 determines whether or not the average value of I ² values calculated in step S304 is greater than threshold value I ² th. When the average value of the I ² values is larger than the threshold value I ² th, the process proceeds to the first abnormality detection process (S306), and the abnormality detection process (process after step S105) shown in FIG. 7 is performed.

On the other hand, when it is determined in step S305 that the average value of the I ² values calculated in step S304 is smaller than the threshold value I ² th, the ECU 300 proceeds to the second abnormality detection process (S307).

  In step S308, the ECU 300 compares the internal resistance R calculated in step S302 with a preset threshold value Rth (for example, an upper limit value of a constant internal resistance). If R is larger than Rth, the ECU 300 proceeds to step S309. Then, the abnormality determination counter C is counted up. Each process of steps S309 to S313 is the same as steps S108 to S112 shown in FIG. Note that step S308 may be a conventional abnormality determination process based on the comparison of the internal resistance R between the single cells 10 as described above.

  As described above, in the modification of FIG. 8, the internal resistance calculated at a predetermined interval in a state larger than the predetermined charge / discharge load that can ensure the change in the internal resistance value due to the temperature rise according to the heat generation amount of the unit cell 10. By performing the process of determining the abnormality of the unit cell 10 based on the amount of decrease in the interval, the internal unit due to the temperature rise caused by the unit cell 10 in which the abnormality has occurred has a larger internal resistance than the normal unit cell 10 It is possible to accurately determine abnormality according to the decrease in resistance.

In addition, in the modification of FIG. 8, you may further consider the detected temperature of the assembled battery 100. FIG. For example, from the relationship between the internal resistance R and the temperature of the unit cell 10 shown in FIG. 4, a region where the amount of change in internal resistance with respect to temperature rise is smaller than a certain value is a high temperature region, and a region where the variation is larger than a certain value is a low temperature. The area is partitioned in advance. Even when the average value of the calculated I ² values is smaller than the threshold value I ² th, when the detected temperature is in the high temperature region (when the change amount of the internal resistance is small with respect to the temperature rise), the first By configuring so that one abnormality detection process is performed, the assembled battery 100 is adapted according to a decrease in internal resistance due to a temperature increase caused by the internal resistance of the unit cell 10 in which an abnormality has occurred is larger than that of a normal unit cell 10. The abnormality determination of (single cell 10) can be performed with high accuracy.

10: single cell, 100: assembled battery, 200: monitoring unit, 201: temperature sensor,
202: current sensor, 203: current limiting resistor,
204: Inverter, 205: Motor generator
300: ECU, 301: Memory,
SMR-B, SMR-P, SMR-G: System main relay,
PL: positive line, NL: negative line

Claims (9)

A power storage system including a power storage device including a plurality of power storage elements and mounted on a vehicle,
A voltage sensor for detecting a voltage of the storage element;
A current sensor for detecting a current flowing through the power storage element;
A temperature sensor for detecting a temperature of the power storage device;
The internal resistance of the power storage element is calculated at a predetermined interval based on the detected voltage value and current value, and the power storage element is abnormal when the amount of decrease between the calculated internal resistances is greater than a predetermined value. A controller for determining
The controller is variably set so that the predetermined value decreases as the temperature of the power storage device increases with respect to the heat generation amount of the power storage element based on the current value flowing with respect to the calculated change between the internal resistances. A power storage system that is controlled.   The controller variably controls the predetermined value so that the temperature is smaller as the temperature of the power storage device is higher and the heat generation amount is smaller, and is smaller as the temperature of the power storage device is lower and the heat generation amount is larger. The power storage system according to claim 1.   The controller uses a correspondence map in which the predetermined value is associated in advance with the square value of the current value related to the temperature of the power storage device and the amount of generated heat, and the square of the detected temperature and the current value detected by the current sensor. The power storage system according to claim 1, wherein the predetermined value is calculated based on a value.   The said controller performs the process which determines the abnormality of the said electrical storage element based on the said fall amount, when the square value of the detected current value by the said current sensor is larger than a predetermined threshold value. 4. The power storage system according to any one of items 1 to 3. A plurality of the temperature sensors are provided at different locations of the power storage device,
The power storage system according to any one of claims 1 to 4, wherein the controller uses a minimum value among the detected temperatures of a plurality of temperature sensors.   6. The controller according to claim 1, wherein the controller calculates an inclination of an approximate line with respect to a correspondence relationship between a plurality of current values and voltage values detected within a predetermined time, and calculates the inclination as an internal resistance of the power storage element. The electrical storage system as described in any one of these.   The power storage system according to any one of claims 1 to 6, wherein the amount of decrease is a difference between internal resistances calculated at the predetermined interval or a rate of change per unit time. A control device for a power storage device mounted on a vehicle and configured by a plurality of power storage elements,
When the internal resistance of the power storage element is calculated at a predetermined interval based on the voltage value detected by the voltage sensor and the current value detected by the current sensor, and the amount of decrease between the calculated internal resistances is greater than the predetermined value And determining that the power storage element is abnormal,
Variably controlling the predetermined value to be smaller as the temperature of the power storage device is higher than the calorific value of the power storage element based on the current value that flows with respect to the calculated change between the internal resistances. A control device for a power storage device. A method for detecting an abnormality of a power storage device that is mounted on a vehicle and includes a plurality of power storage elements, wherein an internal resistance of the power storage element is determined based on a voltage value detected by a voltage sensor and a current value detected by a current sensor. A step of calculating at intervals of
Calculating a reduction amount between the calculated internal resistances;
Determining that the power storage element is abnormal when the amount of decrease is greater than a predetermined value,
With respect to the calorific value of the electricity storage element based on the current value that flows with respect to the calculated change between the internal resistances, the higher the temperature of the electricity storage device, the higher the temperature of the electricity storage device, so that the predetermined value is variably controlled, An abnormality detection method for a power storage device, further comprising: calculating the predetermined value based on a square value of a current value detected by the current sensor related to a heat generation amount and a temperature detected by the power storage device.

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