JP6115484B2 - Battery charge rate estimation device - Google Patents

Description

  The present invention relates to a battery charge rate estimation device that estimates a battery charge rate when a power supply system is activated.

  In order to use the battery in a range of an appropriate charging rate, the current charging rate must be estimated with high accuracy. As a method for estimating the charging rate, there is a method of estimating an initial value of the charging rate at the time of starting a power supply system including a battery, and then accumulating charging / discharging currents to sequentially estimate the charging rate. In this method, if there is a large error in the initial value of the charging rate, the charging rate estimated thereafter will also include a large error, so it is necessary to estimate the initial value of the charging rate with high accuracy. Therefore, an estimation device that estimates the initial value of the charging rate with high accuracy at the time of starting the power supply system has been proposed.

  For example, in Patent Document 1, any one of the first charge rate initial value, the second charge rate initial value, and the third charge rate initial value is selected based on the stop time of the power supply system. The first charge rate initial value is a value calculated from the correlation between the stable open circuit voltage and the charge rate by regarding the voltage measurement value at the time of starting the power supply system as the stable open circuit voltage. The second charging rate initial value is a final value of the charging rate at the time of stopping the power supply system. The initial value of the third charging rate was calculated from the correlation between the stable open circuit voltage and the charging rate by measuring the battery voltage for a predetermined period after the power supply system stopped, predicting and calculating the stable open circuit voltage from the measured battery voltage. Value.

JP 2008-145349 A

  In Patent Document 1, in order to measure the voltage of the battery for a predetermined period while the power supply system is stopped, it is necessary to supply power to the microcomputer of the power supply system from another to start the microcomputer for a predetermined period. However, in the case of a moving power supply system mounted on a vehicle or the like, since the power supply is limited, it is heavy to start the microcomputer for a predetermined period while the power supply system is stopped.

  In view of the above circumstances, the present invention provides a battery charge rate estimation device capable of accurately estimating the initial value of the charge rate at the time of starting the power supply system without measuring the battery voltage while the power supply system is stopped. The main purpose is to do.

  In order to solve the above-described problem, the present invention provides a battery charge rate estimation device that estimates an initial value of the battery charge rate at the time of startup of a power supply system including a battery, and is measured at the time of startup of the current system. A first estimation means for estimating the initial value from the correlation between the stable open circuit voltage and the charging rate, and the charging rate of the battery at the end of the previous system Based on the second estimation means for estimating the initial value, and means for estimating the initial value based on a comparison between a stop time from the end time point to the start time point and a determination time. And a selection means for selecting one of the second estimation means, and the determination time flows through the battery at a predetermined time immediately before the end point In accordance with the accumulated value of the discharge current is varied.

  According to the present invention, the battery voltage measured at the time of starting the power supply system this time by the first estimation unit is regarded as a stable open circuit voltage, and the charging rate is calculated from the correlation between the stable open circuit voltage and the charging rate. The initial value of is estimated. Moreover, the initial value of the charging rate is estimated by the second estimating means based on the charging rate at the end of the previous power supply system.

  Then, based on the comparison between the stop time from the end time of the previous power supply system to the start time of the current power supply system and the determination time, the initial value of the charging rate estimated by the first estimation means, and the second estimate One of the initial values of the charging rate estimated by the means is selected.

  Here, when the polarization of the battery has not been eliminated while the power supply system is stopped, the battery voltage measured at the time of starting is regarded as a stable open circuit voltage, and the initial value of the charging rate is estimated, the error is large. Become. The time required for eliminating the polarization of the battery changes according to the integrated value of the charge / discharge current in a predetermined time immediately before the end of the power supply system.

  Therefore, the determination time used when selecting one of the first estimation unit and the second estimation unit is changed according to the integrated value of the charge / discharge current in a predetermined time immediately before the end point of the power supply system. As a result, when the battery polarization is eliminated while the power supply system is stopped, the initial value of the charging rate is estimated by the first estimating means, and when the battery polarization is not eliminated, the second estimation is performed. The initial value of the charging rate is estimated by the estimating means. Therefore, the initial value of the charging rate at the time of starting the power supply system can be estimated with high accuracy without measuring the battery voltage while the power supply system is stopped.

The figure which shows the structure of the power supply system which concerns on this embodiment. The figure which shows the method of estimating the initial value of SOC, when system stop time is below determination time. The figure which shows the method of estimating the initial value of SOC, when system stop time is longer than determination time. The figure which shows the relationship between an electric current integrated value and determination time. The figure which shows the process sequence which estimates SOC. The figure which shows the relationship between an electric current integrated value and determination time.

  Hereinafter, an embodiment in which a battery charge rate estimation apparatus is embodied will be described with reference to the drawings. The battery charging rate estimation device according to the present embodiment is assumed to estimate the charging rate of a battery included in a power supply system mounted on a hybrid vehicle or an EV vehicle.

  First, the configuration of the power supply system 80 according to the present embodiment will be described with reference to FIG. The power supply system 80 includes a battery 50, a charging circuit 40, and an SOC estimation device 70 (battery charge rate estimation device), and is mounted on a vehicle using a motor as a travel drive source.

  The battery 50 is a secondary battery that is charged by being supplied with electric power from the charging circuit 40 and is discharged by supplying electric power to the load 60. In the present embodiment, a lithium ion secondary battery is assumed as the battery 50. The charging circuit 40 is an alternator connected to the battery 50, and the load 60 is a traveling motor connected to the battery 50. The charging circuit 40 and the load 60 may operate as a generator and may be a single motor generator that operates as an electric motor. When the motor generator operates as a generator, the charging circuit 40 is used. When the motor generator operates as an electric motor, the load 60 is used.

  The SOC estimation device 70 includes a microcomputer 10, a storage device 20, a current sensor 31, and a voltage sensor 32, and estimates an initial value of a state of charge (SOC) when the power supply system 80 is activated. Further, SOC estimation device 70 calculates a current integrated value obtained by integrating charging / discharging currents at predetermined intervals after activation of power supply system 80, and sequentially estimates SOC from the estimated initial SOC value and current integrated value. .

  The current sensor 31 measures the charge / discharge current flowing through the battery 50 and transmits the measured current value to the microcomputer 10. In the present embodiment, the current value during discharging is positive, and the current value during charging is negative. The voltage sensor 32 measures the voltage between the terminals of the battery 50 and transmits the measured voltage value to the microcomputer 10.

  The microcomputer 10 is a microcomputer including a CPU, a RAM, a ROM, an I / O, and the like, and operates by receiving power supply from the battery 50. The microcomputer 10 implements the functions of the first estimation unit, the second estimation unit, and the selection unit by executing various programs stored in the ROM.

  As shown in FIG. 3, the first estimating means regards the voltage of the battery 50 measured at the time of starting the power supply system 80 as a stable open circuit voltage, and correlates the stable OCV (Open Circuit Voltage) with the SOC. From this, the initial value of the SOC at the time of startup is estimated. That is, the SOC estimated sequentially during the previous activation of the power supply system 80 is reset, and the initial value of the SOC is calculated from the voltage measurement value at the time of activation and the OCV-SOC characteristic.

  Here, when a charging / discharging current flows through the battery 50, polarization accompanying Li diffusion in the positive and negative active materials and Li diffusion in the electrolytic solution is generated inside the battery 50. The polarization generated in the battery 50 is alleviated and eliminated with the passage of time while no charge / discharge current flows through the battery 50. When the polarization of the battery 50 is eliminated at the time of starting the power supply system 80, the voltage of the battery 50 measured at the time of starting matches the stable OCV. On the other hand, if the polarization of the battery 50 is not eliminated at the time of starting the power supply system 80, the voltage of the battery 50 measured at the time of starting becomes a value in which the polarization voltage is superimposed on the stable OCV. Cannot be considered.

  As shown in FIG. 2, the second estimation means estimates the initial value of the SOC at the start-up time based on the SOC of the battery 50 at the end time of the previous power supply system 80. In the present embodiment, the second estimating means sets the SOC of the battery 50 at the end of the previous power supply system 80 as the initial value of the SOC at the start of the current power supply system 80.

  The selection means is a first estimation means and a first estimation means as means for estimating the initial value of the SOC based on the comparison between the stop time Ts from the previous end time of the power supply system 80 to the current start time and the determination time Tj. 2. Select one of the estimation means. The determination time Tj is a time during which it is possible to determine whether or not the polarization of the battery 50 has been eliminated. When the stop time Ts is longer than the determination time Tj, that is, when the polarization of the battery 50 has been eliminated, selection means. Selects the first estimation means. On the other hand, when the stop time Ts is equal to or shorter than the determination time Tj, that is, when the polarization of the battery 50 is not eliminated, the selection unit selects the second estimation unit. Note that when the polarization of the battery 50 is not eliminated, the stop time Ts is short, so it is not necessary to consider the decrease in SOC due to natural discharge during the stop time Ts.

  If the polarization of the battery 50 is eliminated during the stop time Ts, the voltage measured at the time of starting can be regarded as a stable OCV. The SOC at the end of the previous power supply system 80 is a value sequentially estimated from the initial SOC value and the current integrated value at the time of starting the previous power supply system 80, and errors included in the current integrated value are accumulated. Yes. Therefore, when the measured voltage at the time of start-up can be regarded as a stable OCV, it is easier to use the measured voltage at the time of start-up and the OCV-SOC characteristic than to use the SOC at the end of the previous power supply system 80. Can be estimated with high accuracy. Therefore, when the polarization of the battery 50 is eliminated during the stop time Ts, the initial value of the SOC at the time of starting is calculated by the first estimating means.

  On the other hand, when the polarization of the battery 50 is not eliminated during the stop time Ts, the voltage measured at the time of starting cannot be regarded as a stable OCV. In this case, when the initial value of the SOC is calculated from the measured voltage and the OCV-SOC characteristic at the time of starting, the error included in the initial value of the SOC becomes large, and the SOC at the end of the previous power supply system 80 is the initial value. As a result, the estimation accuracy of the initial value of the SOC may be deteriorated. Therefore, when the polarization of the battery 50 is not eliminated during the stop time Ts, the initial value of the SOC is estimated by the second estimating means.

  That is, the selection means is a means for estimating the initial value of the SOC at the start-up time depending on whether or not the polarization of the battery 50 is eliminated during the stop time Ts. Switch with.

  Here, the time required for eliminating the polarization of the battery 50 varies depending on the integrated value of the charge / discharge current at the predetermined time T. The predetermined time T is a predetermined time immediately before the end point of the previous power supply system 80 (see FIG. 2C). Therefore, the microcomputer 10 changes the determination time Tj according to the integrated value of the charge / discharge current at the predetermined time T.

  Specifically, as the absolute value of the integrated value of the charging / discharging current at the predetermined time T is larger, the polarization of the battery 50 is larger, so that the time required for eliminating the polarization is longer. Therefore, as shown in FIG. 4, the microcomputer 10 increases the determination time Tj as the absolute value of the integrated value of the charge / discharge current at the predetermined time T increases. Note that the slope of the determination time Tj with respect to the magnitude of the integrated value is determined by the design of the battery 50, and the charge / discharge current integrated value is positive (in the case of excessive discharge) and the integrated value is negative (in the excessive charge). In case) does not necessarily match.

  Furthermore, the lithium concentration in the active material of the battery 50 differs depending on the SOC at the end of the previous power supply system 80, and the electrical conductivity in the active material differs. Therefore, the time required to eliminate the polarization of battery 50 varies depending on the SOC at the end of the previous power supply system 80. Therefore, the microcomputer 10 changes the determination time Tj according to the SOC at the end of the previous power supply system 80. Specifically, in FIG. 4, an SOC axis is added, and the determination time Tj may be calculated from a three-dimensional map of the integrated value of charge / discharge current and the SOC at the end time and the determination time Tj.

  Further, the time required for eliminating the polarization of the battery 50 is excessive discharge or excessive charge during the start-up time from the start time to the end time of the previous power supply system 80 even if the integrated value at the predetermined time T is the same. It depends on whether the charge / discharge balance is balanced to some extent. Therefore, the microcomputer 10 changes the determination time Tj according to the total integrated value of the charge / discharge current at the previous startup time of the power supply system 80.

  Specifically, in the previous start-up time of the power supply system 80, the more the battery is over-discharged or over-charged, the longer the polarization of the battery 50 becomes, so the time required to eliminate the polarization becomes longer. Therefore, the microcomputer 10 increases the determination time Tj as the absolute value of the total integrated value in the previous activation time of the power supply system 80 increases.

  In the present embodiment, when the total integrated value is smaller than the predetermined value, the microcomputer 10 determines the determination time from the relationship (correlation 2) between the integrated value and the determination time Tj at the predetermined time T shown by the solid line in FIG. Tj is calculated. On the other hand, when the total integrated value is equal to or greater than the predetermined value, the determination time Tj is calculated from the relationship (correlation 1) between the integrated value and the determination time Tj at the predetermined time T shown by the broken line in FIG. The curve indicated by the broken line in FIG. 4 is obtained by offsetting the curve indicated by the solid line in FIG. 4 so that the determination time Tj is increased by a predetermined value. Actually, whether the relationship between the integrated value at the predetermined time T indicated by the solid line and the determination time Tj is used or when the above relationship indicated by the broken line is used, a three-dimensional map to which the SOC axis is added is used. The determination time Tj is calculated.

  The storage device 20 is connected to the microcomputer 10 and stores detection values detected by the current sensor 31 and the voltage sensor 32, a current integrated value, an SOC value, and the like.

  Next, a processing procedure for estimating the SOC of the battery 50 will be described with reference to the flowchart of FIG. This processing procedure is executed by the microcomputer 10 every time the power supply system 80 is activated.

  First, the total integrated value of the charge / discharge current at the start-up time of the previous power supply system 80 is read from the storage device 20, and it is determined whether or not the absolute value of the total integrated value is greater than or equal to a predetermined value (S10). That is, it is determined whether or not there was excessive discharge or excessive charge during the previous startup time of the power supply system 80.

  When the absolute value of the total integrated value at the start-up time of the previous power supply system 80 is equal to or greater than a predetermined value (S10: YES), it takes more time to eliminate the polarization of the battery 50 than when the charge / discharge balance is balanced to some extent. . Therefore, in this case, the determination time Tj is calculated from the three-dimensional map (correlation 1) offset so that the determination time Tj becomes longer than when the charge / discharge balance is balanced to some extent (S11).

  Specifically, the integrated value of the charge / discharge current at a predetermined time T immediately before the end of the previous power supply system 80 and the SOC at the end of the previous power supply system 80 are read from the storage device 20. Then, the determination time Tj is calculated from the three-dimensional map showing the correspondence between the integrated value of the charge / discharge current at the predetermined time T, the SOC at the end of the previous power supply system 80, and the determination time Tj.

  In the case of excessive discharge or excessive charge in the previous start-up time of the power supply system 80, when the EV travel is performed in the previous start-up time of the power supply system 80, or the battery 50 is used by using a plug. The case where it charges is mentioned.

  On the other hand, when the absolute value of the total integrated value at the start-up time of the previous power supply system 80 is smaller than the predetermined value (S10: NO), the polarization of the battery 50 is eliminated more than when it is excessively discharged or excessively charged. It does not take time. Therefore, in this case, the determination time Tj is calculated from the three-dimensional map (correlation 2) offset so that the determination time Tj is shorter than that in the case of excessive discharge or excessive charge, similarly to S11 ( S12).

  An example of a case where the charge / discharge balance is balanced to some extent during the previous startup time of the power supply system 80 includes a case where HV traveling is performed during the previous startup time of the power supply system 80.

  Subsequently, it is determined whether or not the stop time Ts from the previous end time of the power supply system 80 to the current start time is longer than the determination time Tj calculated in S11 or S12 (S13). That is, it is determined whether or not the polarization of the battery 50 is eliminated during the stop time Ts of the power supply system 80.

  When the stop time Ts is longer than the determination time Tj (S13: YES), the polarization of the battery 50 is eliminated. Therefore, the voltage of the battery 50 measured at the time of starting the power supply system 80 is regarded as a stable OCV, and the initial value of the SOC at the time of starting is calculated from the voltage measurement value at the time of starting and the OCV-SOC characteristic (S14). ).

  On the other hand, when the stop time Ts is equal to or shorter than the determination time Tj (S13: NO), since the polarization of the battery 50 is not eliminated, the voltage of the battery 50 measured at the time of starting the power supply system 80 is regarded as a stable OCV. I can't. In this case, the SOC at the end of the previous power supply system 80 is set as the initial value of the SOC at the start of the current power supply system 80 (S15).

  Subsequently, an integrated value of the charge / discharge current flowing through the battery 50 is calculated at predetermined time intervals (S16). Then, the SOC is calculated at predetermined time intervals from the initial value of SOC calculated at S14 or S15 and the integrated value calculated at predetermined time intervals.

  Subsequently, it is determined whether or not the process is shifted to the stop process of the power supply system 80 (S17). When the process is not shifted to the stop process of the power supply system 80 (S17: NO), the process returns to the process of S16, the integrated value of the charge / discharge current is calculated at a predetermined time interval, and the SOC is calculated at the predetermined time interval.

  On the other hand, when the process is proceeding to the stop process of the power supply system 80 (S17: YES), the total accumulated value of the charge / discharge current from the start of the current power supply system 80 to the present time, the charge / discharge current at the latest predetermined time T The integrated value and the current SOC are stored in the storage device 20 (S18). This process is complete | finished above.

  According to this embodiment described above, the following effects are obtained.

  The time required for eliminating the polarization of the battery 50 varies depending on the integrated value of the charge / discharge current at the predetermined time T. Therefore, the determination time Tj used when selecting one of the first estimation unit and the second estimation unit is set according to the integrated value of the charge / discharge current at the predetermined time T immediately before the end point of the previous power supply system 80. Change. Thereby, when the polarization of the battery 50 is eliminated while the power supply system 80 is stopped, the SOC of the power supply at the time of start-up is calculated from the voltage measurement value at the time of power-up of the power supply system 80 and the OCV-SOC characteristic. An initial value is calculated. If the polarization of the battery 50 has not been eliminated, the SOC at the end of the previous power supply system 80 is set as the initial value of the SOC at the start of the current power supply system 80. Therefore, the initial value of the SOC at the time of starting up the power supply system 80 can be estimated with high accuracy without measuring the voltage of the battery 50 while the power supply system 80 is stopped.

  Even if the integrated value at the predetermined time T is the same, the lithium concentration and conductivity in the active material of the battery 50 differ depending on the SOC at the end of the power supply system 80, so the time required to eliminate the polarization of the battery 50 differs . Thus, the determination time Tj is further changed according to the SOC of the battery 50 at the end of the previous power supply system 80, so that the initial value of the SOC at the start-up time of the power supply system 80 is estimated with higher accuracy. be able to.

  Even if the integrated value at the predetermined time T is the same, the polarization of the battery 50 is eliminated depending on whether the total integrated value at the previous start-up time of the power supply system 80 was excessive discharge or excessive charge, or whether the charge / discharge balance was balanced to some extent. The time required for is different. Therefore, by changing the determination time Tj according to the total integrated value of the charge / discharge current at the previous start-up time of the power supply system 80, the initial value of the charge rate at the start-up time of the power supply system 80 is further increased. The accuracy can be estimated.

  -As the absolute value of the integrated value of the charging / discharging current at the predetermined time T is larger, the polarization of the battery 50 is larger, so the time required for eliminating the polarization is longer. Therefore, the initial value of the SOC can be estimated with high accuracy by increasing the determination time as the absolute value of the integrated value of the charge / discharge current at the predetermined time T is larger.

  In the previous start-up time of the power supply system 80, the more the battery is over-discharged or over-charged, the greater the polarization of the battery 50, and the longer it takes to eliminate the polarization. Therefore, when the absolute value of the total integrated value at the previous activation time of the power supply system 80 is greater than or equal to the predetermined value, the determination time Tj is made longer than when the absolute value of the total integrated value is smaller than the predetermined value. The initial value of SOC can be estimated with high accuracy.

(Other embodiments)
The second estimating means may correct the self-discharge during the stop of the power supply system 80 with respect to the SOC at the end of the previous power supply system 80, and use the initial value of the SOC at the start of the current power supply system 80. .

  The absolute value of the integrated value at the predetermined time T may be divided into a plurality of sets in order of magnitude, and the determination time Tj may be calculated using a map in which the determination time Tj is associated with each set.

  The SOC value at the end of the previous power supply system 80 may be divided into a plurality of groups in order of magnitude, and the determination time Tj may be calculated using a map in which the determination time Tj is associated with each group. .

  The determination time Tj is calculated using only the integrated value at the predetermined time T without using the total integrated value at the start-up time of the previous power supply system 80 and the SOC at the end of the previous power supply system 80. Also good. Alternatively, the determination time Tj may be calculated by using two values of the integrated value at the predetermined time T and the total integrated value at the previous activation time of the power supply system 80. Alternatively, the determination time Tj may be calculated using the integrated value at the predetermined time T and the two SOC values at the end of the previous power supply system 80.

  The temperature of the battery 50 may be measured, and the determination time Tj may be corrected using the measured temperature of the battery 50. Specifically, the higher the temperature of the battery 50, the faster the diffusion rate of lithium in the active material and the shorter the time required to eliminate the polarization. Therefore, the higher the temperature of the battery 50, the shorter the determination time Tj. Correct as follows.

  -As the upper limit current value determined by the system design of the power supply system 80 is larger, the discharge tends to be excessive. Therefore, as the upper limit current value is larger, the slope of the determination time Tj with respect to the integrated value at the predetermined time T may be increased on the excessive discharge side as shown by the broken line in FIG.

  -The larger the lower limit current value determined by the system design of the power supply system 80, the more likely it is to charge excessively. Therefore, as the lower limit current value is larger, the slope of the determination time Tj with respect to the integrated value at the predetermined time T may be increased on the overcharge side as shown by the one-dot chain line in FIG.

  DESCRIPTION OF SYMBOLS 10 ... Microcomputer, 31 ... Current sensor, 32 ... Voltage sensor, 50 ... Battery, 70 ... SOC estimation apparatus, 80 ... Power supply system.

Claims (5)

A battery charge rate estimation device (70) for estimating an initial value of the battery charge rate at the time of activation of a power supply system (80) including the battery (50),
A first estimating means that regards the voltage of the battery measured at the time of starting the system as a stable open circuit voltage, and estimates the initial value from a correlation between the stable open circuit voltage and a charging rate;
Second estimation means for estimating the initial value based on the charge rate of the battery at the end of the previous system;
Selection means for selecting one of the first estimation means and the second estimation means as means for estimating the initial value based on a comparison between a stop time from the end time to the start time and a determination time; With
The battery charge rate estimation apparatus according to claim 1, wherein the determination time is changed in accordance with an integrated value of a charge / discharge current flowing through the battery in a predetermined time immediately before the end point.   The battery charge rate estimation apparatus according to claim 1, wherein the determination time is further changed according to a charge rate of the battery at the end point.   3. The battery charge rate estimation device according to claim 1, wherein the determination time is further changed according to a total integrated value of the charge / discharge current during a start-up time from a previous start-up time of the system to the end time. .   The battery determination rate estimation apparatus according to claim 1, wherein the determination time is increased as the absolute value of the integrated value increases.   The determination time is further changed according to the total integrated value of the charge / discharge current during the start-up time from the previous start-up time of the system to the end time, and is increased as the absolute value of the total integrated value increases. The charge rate estimation apparatus of the battery in any one of Claims 1-4.

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