JP2017138127A - Soc management system of onboard battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a reduction in the accuracy of SOC correction due to memory effects when correcting an estimated SOC value based on current integration value with an estimated SOC value based on open end voltage value.SOLUTION: When SOC_I is included in a prescribed low-SOC region and a battery is in a discharge state, a first correction process to gradually bring SOC_I closer to SOC_V is executed by repeatedly carrying out a correction for adding a difference value ΔSOC between SOC_I and SOC_V that is multiplied by a correction coefficient α less than 1 to SOC_I. Further, when the battery is switched from the discharge state to a charge state, the first correction process is discontinued and a second correction process to add a maximum difference value ΔSOCmax between the estimated SOC value SOC_I and SOC_V from the start time Ready_On of a first correction period to a switched point of time t9 successively over time to SOC_I at a prescribed rate β is executed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a management system that manages SOC (State Of Charge) of a battery mounted on a vehicle.

  A battery made of a secondary battery is mounted on an electric vehicle, a hybrid vehicle, or the like that uses a rotating electrical machine as a drive source. In order to suppress overcharge and overdischarge of the battery, the state of charge of the battery, that is, SOC [%] is managed. For example, a current sensor is connected to the battery, the current flowing into and out of the battery is measured, and the SOC of the battery is estimated based on the integrated value (current integrated value).

  In some cases, the battery may undergo a self-discharge due to a chemical reaction or the like, and the SOC decreases due to this. However, since the self-discharge is an internal reaction of the battery and does not involve the flow of current to the outside, even if the self-discharge occurs, it is not reflected in the integrated current value. As a result, the difference between the current integrated value-based SOC estimated value and the actual SOC increases as self-discharge progresses. Therefore, in Patent Document 1, the SOC is estimated based on the open circuit voltage value (OCV) of the battery, and the current estimated value-based SOC estimated value is corrected based on the estimated SOC.

  It is known that when the battery has a low SOC (for example, 30% or less) or a high SOC (for example, 70% or more), there is a high accuracy correlation between the open-circuit voltage and the SOC. Therefore, the open-circuit voltage value when the battery is low SOC or high SOC is measured or estimated, and the SOC corresponding to this is obtained. Further, the difference between the obtained open-circuit voltage value based SOC and the integrated current value based SOC is obtained.

  If the obtained difference is directly added to the integrated current value-based SOC, the SOC rapidly increases or decreases, and battery control and vehicle control based on the SOC may change suddenly. In order to ensure the stability of the control, a value obtained by multiplying the difference value of the SOC by a correction coefficient of less than 1 (for example, 0.1) is added to the SOC based on the integrated current value. Thereafter, the difference between the open-circuit voltage value-based SOC and the accumulated current value-based SOC is obtained again, and this is multiplied by a correction coefficient and added to the accumulated current value-based SOC. In this way, the integrated current value based SOC is gradually brought closer to the open-circuit voltage value based SOC.

JP 2005-114646 A

  By the way, when a battery is comprised from a nickel metal hydride battery, what is called a memory effect that a shift | offset | difference arises in the correspondence of SOC and the open circuit voltage value (OCV) of a battery may arise. For example, when switching from discharging to charging when the battery has a low SOC, the open end voltage during charging appears higher than the open end voltage during discharging even with the same SOC. As described above, even when correction of the current integrated value-based SOC estimated value based on the open-circuit voltage value-based SOC estimated value is performed in a state in which the correspondence between the SOC and the open-ended voltage is deviated, high-accuracy can be achieved. It is difficult to correct. Accordingly, an object of the present invention is to provide an in-vehicle battery SOC management system capable of suppressing a decrease in accuracy of SOC correction due to a memory effect.

  An SOC management system for an in-vehicle battery according to the present invention includes a battery made of a nickel metal hydride battery, a current sensor that measures an inflow / outflow current of the battery, a voltage sensor that measures a terminal voltage of the battery, and a temperature of the battery. A temperature sensor to measure is provided. Further, the management system calculates an estimated value of the SOC of the battery from a current integrated value obtained by integrating the current values measured from the current sensor, and is measured from the current sensor, the voltage sensor, and the temperature sensor, respectively. A calculation unit is provided that calculates an estimated SOC value of the battery corresponding to the open-circuit voltage value of the battery obtained based on the current value, the terminal voltage value, and the temperature. The calculation unit includes the SOC estimation value based on the current integration value and the open-circuit voltage when the SOC estimation value based on the current integration value is included in a predetermined low SOC region and the battery is in a discharged state. By repeatedly performing a correction by adding a value obtained by multiplying the difference value from the value-based SOC estimated value by a correction coefficient of less than 1 to the current accumulated value-based SOC estimated value, the current accumulated value-based SOC estimated value A first correction process for gradually approaching the SOC estimation value based on the open-circuit voltage value is executed. Further, the arithmetic unit interrupts the first correction process when the battery is switched from the discharged state to the charged state, and from the start point of the first correction process, the discharge state to the charged state. The maximum difference value between the current integrated value-based SOC estimated value and the open-ended voltage value-based SOC estimated value up to the time of switching is sequentially added to the current integrated value-based SOC estimated value sequentially at a predetermined rate. A second correction process is executed.

  According to the present invention, when the battery is switched from the discharged state to the charged state and a memory effect occurs, the current estimated value-based SOC estimated value is corrected without using the subsequent open-ended voltage value-based SOC estimated value. It is carried out. By doing in this way, the fall of SOC correction precision by a memory effect can be suppressed.

1 is a system configuration diagram of a vehicle equipped with an SOC management system according to the present embodiment. It is a time chart explaining the correction process of the SOC estimated value based on the current integrated value according to the present embodiment. It is a flowchart explaining the correction process of SOC estimated value based on an electric current integrated value based on this embodiment. It is a time chart explaining the correction process of SOC estimated value based on an electric current integrated value based on another example of this embodiment. It is a flowchart explaining the correction process of SOC estimated value based on an electric current integrated value based on the other example of this embodiment.

  FIG. 1 illustrates the configuration of an in-vehicle battery SOC management system and its peripheral devices according to this embodiment. The SOC management system according to this embodiment is mounted on an electric vehicle, a hybrid vehicle, or the like that uses the rotating electrical machine 10 as a drive source. The SOC management system includes a battery 12, a calculation unit 14, a current sensor 16, a voltage sensor 18, and a temperature sensor 19. As will be described later, the SOC management system corrects the estimated current value SOC_I based on the current integrated value.

  The DC power output from the battery 12 is boosted by the DC / DC converter 20. Further, the boosted electric power is orthogonally converted by the inverter 22 and supplied to the rotating electrical machine 10 which is a driving source of the vehicle. In addition, when the rotating electrical machine 10 is regenerated, the regenerative power is AC / DC converted by the inverter 22. The converted DC power is stepped down by the DC / DC converter 20 and supplied to the battery 12.

  The battery 12 is composed of a nickel metal hydride battery. For example, the battery 12 includes a stacked body (stack) in which a plurality of nickel metal hydride cells (battery cells) are connected in series. Note that some battery cell groups may be connected in parallel, and the battery cell groups may be connected in series.

  As described above, in the nickel metal hydride battery, there may be a deviation in the correspondence between the SOC and the open-circuit voltage value, and this phenomenon is called a memory effect. Specifically, when charging is performed when the SOC of the battery 12 is included in a predetermined low SOC region (for example, 30% or less), the open-circuit voltage at the time of charging is the same at the time of discharging even if the SOC is the same. Appears higher than the open-circuit voltage. Further, if discharging is performed when the SOC of the battery 12 is included in a predetermined high SOC region (for example, 70% or more), the open-circuit voltage at the time of discharging is the open-circuit voltage at the time of charging even if the SOC is the same. Appears lower than the voltage. As will be described later, the SOC management system according to the present embodiment corrects the current integrated value-based SOC estimated value SOC_I without using the open-ended voltage value-based SOC estimated value SOC_V after the occurrence of the memory effect. .

  The vehicle shown in FIG. 1 is provided with a control unit 24 that performs drive control of the rotating electrical machine 10 and management of the battery 12. The control unit 24 may be configured by a computer, and the calculation unit 14, the storage unit 26, the clock 27, and a device / sensor interface (not shown) are connected to each other via an internal bus.

  The calculation unit 14 includes an arithmetic circuit such as a CPU. As will be described later, the calculation unit 14 performs calculation processing for each calculation cycle counted by the clock 27. The storage unit 26 includes a nonvolatile memory such as a ROM and a volatile memory such as a RAM. The storage unit 26 corrects a current integrated value-based SOC estimated value SOC_I, which will be described later, a maximum difference value ΔSOCmax between the current integrated value-based SOC estimated value SOC_I and the open-circuit voltage value-based SOC estimated value SOC_V, and the battery 12. An OCV-SOC map in which the correspondence relationship between the open circuit voltage value OCV and the SOC is stored is stored.

  The control unit 24 receives signals from various sensors via the device / sensor interface. Specifically, each of the voltage sensor 18 that detects the terminal voltage (both-end voltage) Vb of the battery 12, the current sensor 16 that detects the inflow / outflow current Ib of the battery 12, and the temperature sensor 19 that detects the temperature Tb of the battery 12 respectively. Receive measurements. The control unit 24 also receives a vehicle system start (Ready-On) and shutdown (Ready-Off) command from the vehicle start switch 28.

  Further, the control unit 24 obtains the output of the rotating electrical machine 10 based on the depression amount of an accelerator pedal sensor (not shown), and on / off controls the switching elements (not shown) of the DC / DC converter 20 and the inverter 22 based on this.

  Further, the control unit 24 controls the charge / discharge of the battery 12 and the behavior of the load based on the current integrated value-based SOC estimated value SOC_I obtained by the calculation unit 14. For example, when the estimated SOC value SOC_I is close to a predetermined limit lower limit value, the power supplied to the rotating electrical machine 10 is limited to limit the discharge of the battery 12. Further, when the SOC estimated value SOC_I is close to a predetermined limit upper limit value, the regenerative drive of the rotating electrical machine 10 is limited to limit the charging to the battery 12.

  The computing unit 14 receives the current value Ib measured from the current sensor 16. Further, calculation unit 14 integrates current value Ib, and obtains SOC estimated value SOC_I (hereinafter also simply referred to as SOC estimated value SOC_I) of battery 12 from current accumulated value ΣIb. The integrated current value ΣIb indicates the balance between the current flowing out of the battery 12 (discharge current) and the flowing-in current (charging current), and the change in the capacity of the battery 12, that is, the change in the SOC can be obtained according to the balance. it can.

  In addition, the calculation unit 14 determines whether the battery 12 is in a discharged state or in a charged state according to the sign of the current value Ib received from the current sensor 16. For example, when the current value Ib is positive, it is determined as a discharged state, and when it is negative, it is determined as a charged state.

  Further, the calculation unit 14 receives the terminal voltage value Vb measured from the voltage sensor 18 and the temperature Tb of the battery 12 measured from the temperature sensor 19. The calculation unit 14 calculates (estimates) the open-circuit voltage (OCV) of the battery 12 based on the terminal voltage value Vb, the battery temperature Tb, and the current value Ib measured from the current sensor 16. Specifically, the open-circuit voltage value (OCV) is calculated from the mathematical formula: open-circuit voltage value (OCV) = terminal voltage value Vb− (current value Ib × internal resistance). The internal resistance can be obtained based on the current value Ib and the battery temperature Tb. For example, the internal resistance may be stored in the storage unit 26 as a resistance map or a function. For example, the internal resistance of the battery 12 corresponding to the current value Ib acquired from the current sensor 16 and the battery temperature Tb acquired from the temperature sensor 19 can be obtained using a resistance map.

  As described above, there is a correlation between the SOC of the battery 12 and the open circuit voltage (OCV), and qualitatively, the open circuit voltage is low when the SOC is low. In particular, when the SOC of the battery 12 is included in a predetermined high SOC region (for example, 70% or more) and a low SOC region (for example, 30% or less), and the memory effect is not exhibited, the battery 12 is opened. It has been conventionally known that there is a highly accurate correspondence (for example, a one-to-one relationship) between the end voltage OCV and the SOC.

  The storage unit 26 stores, in advance, a combination of the open-circuit voltage value OCV of the battery 12 in the high SOC region and the low SOC region and the estimated SOC value SOC_V corresponding thereto as an OCV-SOC map. As an OCV-SOC map, for example, in the low SOC region, the correspondence between the open-circuit voltage value and the SOC when the battery 12 is discharged, and the correspondence between the open-circuit voltage value and the SOC when the battery 12 is charged in the high SOC region The relationship is stored in the storage unit 26. The computing unit 14 refers to the OCV-SOC map to obtain the estimated SOC value SOC_V corresponding to the open-circuit voltage value obtained by the computing unit 14.

<Correction Process for Current Estimated Value-Based SOC Estimated Value SOC_I (1)>
The correction process of the current integrated value-based SOC estimated value SOC_I according to the present embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 illustrates a correction process and time charts before and after the correction process. The horizontal axis represents time, and the vertical axis represents SOC. Further, the SOC estimated value SOC_I is indicated by a solid line, the SOC estimated value SOC_V is indicated by a two-dot chain line, and the actual SOC is indicated by a one-dot chain line. Only the actual SOC (one-dot chain line) is shown for a portion where the SOC estimated value SOC_V and the actual SOC overlap. FIG. 2 shows an example in which the estimated SOC value SOC_V and the actual SOC are equal from time t2 to time t10. Furthermore, the broken line parallel to the vertical axis represents the calculation cycle.

  As described above, the self-discharge of the battery 12 proceeds with time. Since self-discharge does not involve the flow of current to the outside of the battery 12, the current estimated value-based SOC estimated value SOC_I deviates from the actual SOC (actual SOC) as the self-discharge proceeds. Therefore, the calculation unit 14 corrects the current integrated value-based SOC estimated value SOC_I using the open-circuit voltage value-based SOC estimated value SOC_V.

  In order to facilitate understanding, the outline of the correction process illustrated in the time chart of FIG. 2 will be described in advance. The calculation unit 14 executes the first correction process from Ready_On to time t10, and from time t10. The second correction process is executed until time t11.

  As shown in FIG. 2, the actual SOC of the battery 12 decreases due to self-discharge occurring during the period from the latest vehicle system shutdown (Ready-Off) to the startup (Ready-On). On the other hand, the current estimated value SOC_I maintains the value at Ready-Off. This gradually opens the difference between the two.

  Arithmetic unit 14 performs the first correction process when the SOC of battery 12 is included in a predetermined low SOC region, that is, not more than upper limit SOC_ThL of the low SOC region and battery 12 is in a discharged state. . In the first correction process, a difference value ΔSOC (t) between the estimated value SOC_I (t) and the estimated value SOC_V (t) is calculated, and a value obtained by multiplying ΔSOC (t) by the coefficient α is estimated value SOC_I (t). Add to. Further, this process is repeated every calculation cycle. By executing such a first correction process, the estimated value SOC_I (t) is gradually brought closer to the estimated value SOC_V (t).

  On the other hand, when it is determined that the charging state is switched to the charging state at time t9, the calculation unit 14 interrupts the first correction process from time t10, which is the calculation period immediately thereafter, and enters the second correction process. Switch. In the second correction process, the maximum difference value ΔSOCmax in a period from the start point (Ready_On) of the first correction process to the switching point (time t9) when the battery 12 is switched from the discharged state to the charged state is set to a predetermined ratio. Are sequentially added to the estimated SOC value SOC_I (t) over time.

  Specifically, the maximum difference value ΔSOCmax is sequentially added from time t10 to time t11 at a rate of β per second. The coefficient β is a real number less than 1 (for example, 0.3). In this way, the maximum difference value ΔSOCmax obtained from the estimated value SOC_V (t) with high estimation accuracy can be gradually added to the estimated value SOC_I (t).

  FIG. 3 illustrates a flowchart for executing the first and second correction processes. First, when the start switch 28 is pressed and the control unit 24 receives a start command (Ready-On command) for the vehicle system, the control unit 24 switches the system main relay (not shown) from the shut-off state to the connected state, and the battery 12 and the rotating electrical machine. A load such as 10 is conducted.

  At this time, the calculation unit 14 obtains a difference ΔOCV between the open-ended voltage value of the battery 12 at the time of shutdown (Ready-Off) and the open-ended voltage value of the battery 12 at the time of system startup (Ready-On). Further, it is determined whether or not the value ΔOCV is equal to or greater than a predetermined threshold value ΔOCV_th (S10). As described above, there is a correlation between the open-circuit voltage and the SOC. In this step, the SOC (actual SOC) from Ready-Off to Ready-On is determined based on the difference in the open-circuit voltage. The magnitude of change is judged.

  When ΔOCV is greater than or equal to threshold value ΔOCV_th, operation unit 14 proceeds to the next step S12. When ΔOCV is less than the threshold value ΔOCV_th, it is considered that the difference between the current integrated value-based SOC estimated value SOC_I and the actual SOC is not so large, and thus the current integrated value-based SOC estimated value SOC_I is corrected. Without ending this flow.

  In step S12, operation unit 14 determines whether or not current estimated value-based SOC estimated value SOC_I (t) at time t is equal to or lower than upper limit value SOC_ThL of the low SOC region. In this step, it is determined whether or not the actual SOC of the battery 12 is included in a region where the estimation accuracy of the open-circuit voltage value-based SOC estimation value SOC_V is high. The upper limit SOC_ThL of the low SOC region is, for example, 30%.

  When the SOC estimated value SOC_I (t) exceeds the upper limit SOC_ThL, this flow is terminated without correcting the SOC estimated value SOC_I. When SOC estimated value SOC_I (t) is equal to or lower than upper limit SOC_ThL of the low SOC region, operation unit 14 refers to the measurement value of current sensor 16 to determine whether battery 12 is in a discharged state or not. (S14). When not in the discharging state (in the charging state), the estimation accuracy of the SOC estimated value SOC_V is low due to the memory effect. Therefore, the present flow is terminated without correcting the SOC estimated value SOC_I.

  When the battery 12 is being discharged, the calculation unit 14 calculates a difference value ΔSOC (t) between the current integrated value-based SOC estimated value SOC_I (t) and the open-ended voltage value-based estimated value SOC_V (t) at time t. Obtained (S16). For example, a value obtained by subtracting the SOC estimated value SOC_I (t1) from the SOC estimated value SOC_V (t1) at time t1 in FIG. ).

  Further, the calculation unit 14 adds a value obtained by multiplying the difference value ΔSOC (t) by the correction coefficient α to the SOC estimated value SOC_I (t) based on the current integrated value (S18). The correction coefficient α is a real number less than 1 (for example, 0.1), and the difference value ΔSOC (t) is prevented from being added to the SOC estimated value SOC_I (t) as it is. The SOC estimated value SOC_I (t) gradually approaches the SOC estimated value SOC_V (t) by the correction coefficient α. By performing such gentle correction, a sudden change in the SOC estimated value SOC_I (t) is avoided, and as a result, a sudden change in battery control and vehicle control based on the SOC estimated value SOC_I (t) is avoided.

  The calculation unit 14 determines whether or not the difference between the SOC estimated value SOC_I (t) and the difference value ΔSOC (t) × α and the SOC estimated value SOC_V (t) is sufficiently narrowed (S20). ). Since the correction coefficient α is a real number less than 1, the SOC estimated value SOC_I (t) does not completely match the SOC estimated value SOC_V (t) and gradually approaches gradually. Therefore, when the difference between the estimated value SOC_I (t) and the estimated value SOC_V (t) is reduced to such an extent that it can be evaluated that the estimated value has disappeared, the correction flow of the estimated value SOC_I is terminated. For example, when the value obtained by dividing the estimated value SOC_V (t) by the estimated value SOC_I (t) is included in the range of 0.9 to 1.1, the calculation unit 14 ends the correction flow illustrated in FIG.

  When the difference between the value obtained by adding the difference value ΔSOC (t) × α to the estimated value SOC_I (t) and the SOC estimated value SOC_V (t) is still open, the calculation unit 14 proceeds to step S22. In this step, it is determined whether or not the maximum value (maximum difference value) ΔSOCmax of the difference value ΔSOC from the start time of the first correction process to the current time (step S22 execution time) can be updated. The computing unit 14 determines whether or not the currently stored maximum difference value ΔSOCmax is less than the difference value ΔSOC (t) calculated in step S16.

  When ΔSOC (t)> ΔSOCmax, the calculation unit 14 updates the maximum difference value ΔSOCmax to the difference value ΔSOC (t) calculated in step S16 (S24). Specifically, the maximum difference value ΔSOCmax stored in the storage unit 26 is rewritten. On the other hand, if ΔSOC (t) ≦ ΔSOCmax in step S22, the process proceeds to the next step S26 while maintaining the current maximum difference value ΔSOCmax.

  For example, in the example illustrated in FIG. 2, first, the difference value ΔSOC (t1) at time t1 is stored in the storage unit 26 as the maximum difference value ΔSOCmax. Next, at time t2, since ΔSOCmax (= ΔSOC (t1)) <ΔSOC (t2), ΔSOC (t2) is updated as ΔSOCmax. Since ΔSOCmax (= ΔSOC (t2))> ΔSOC (t3) at time t3, ΔSOCmax is maintained without being updated. Further, at time t4, since ΔSOCmax (= ΔSOC (t2)) <ΔSOC (t4), ΔSOC (t4) is updated as ΔSOCmax.

  In step S26, the process waits until the next calculation cycle. At this time, the count of the calculation cycle is incremented (t → t + 1). After that, the calculation unit 14 determines whether or not the estimated value SOC_I (t) is equal to or lower than the upper limit value SOC_ThL of the low SOC region, similarly to step S12 (S28). When the estimated value SOC_I (t) exceeds the upper limit SOC_ThL, the accuracy of the SOC correction using the open-circuit voltage value-based SOC estimated value SOC_V is low, and the calculation unit 14 ends the correction flow shown in FIG.

  When the estimated value SOC_I (t) is equal to or lower than the upper limit value SOC_ThL, the calculation unit 14 refers to the measured value of the current sensor 16 and determines whether or not the battery 12 is switched from the discharged state to the charged state (S30). When the discharge state is continued, the calculation unit 14 returns to step S16, calculates again the difference value ΔSOC (t) between the estimated value SOC_I (t) and the estimated value SOC_V (t), and further calculates a coefficient to ΔSOC (t). A value multiplied by α is added to the estimated value SOC_I (t) (S18). As described above, the first correction process is executed to repeat the correction for adding the value obtained by multiplying the difference value ΔSOC (t) between the estimated value SOC_I (t) and the estimated value SOC_V (t) by the coefficient α to the estimated value SOC_I (t). Thus, the estimated value SOC_I (t) is gradually brought closer to the estimated value SOC_V (t).

  On the other hand, when it is determined in step S30 that the battery 12 has been switched from the discharged state to the charged state, the calculation unit 14 performs the first operation in the calculation cycle (time t10 in FIG. 2) immediately after switching from the discharged state to the charged state. The maximum difference value ΔSOCmax in the period from the start time (Ready_On) of the correction process to the time point (time t9) when switching from discharging to charging is sequentially added to the SOC estimated value SOC_I (t) sequentially at a predetermined rate. A second correction process is executed (S32).

  Specifically, the maximum difference value ΔSOCmax is sequentially added at a rate of β per second. The coefficient β is a real number less than 1 (for example, 0.3). In this way, the maximum difference value ΔSOCmax obtained from the estimated value SOC_V (t) with high estimation accuracy can be gradually added to the estimated value SOC_I (t).

  Further, in the flowchart shown in FIG. 3, not all the difference values ΔSOC (t) are stored from the start of the first correction process to the time when the battery 12 switches from discharging to charging, as in steps S22 and S24. In addition, only the maximum difference value ΔSOCmax is stored. In this way, the load on the storage unit 26 can be reduced.

<Correction Process (2) of Current Estimated Value-Based SOC Estimated Value SOC_I>
In the correction processes shown in FIGS. 2 and 3, the SOC estimation value SOC_I is corrected (first correction process) with the SOC of the battery 12 included in the low SOC region and the battery 12 in a discharged state. Although it went, it is not restricted to this form. As described above, even when the SOC of the battery 12 is included in the high SOC region and the battery 12 is in a charged state, the estimation accuracy of the open-circuit voltage value-based SOC estimated value SOC_V is high. Therefore, as shown in FIG. 4 and FIG. 5, correction of the SOC estimation value SOC_I based on the current integrated value is performed aiming at the time when the SOC of the battery 12 is included in the high SOC region and the battery 12 is in a charged state. You may go.

  FIG. 4 illustrates a correction process according to the present embodiment and a time chart before and after the correction process. The legend relating to the time chart is the same as in FIG. 5 is obtained by replacing steps S12, S14, S28, and S30 in the flowchart of FIG. 3 with steps S42, S44, S48, and S50, respectively. In addition, below, description is abbreviate | omitted suitably about what overlaps a step number.

  As shown in FIG. 4, the actual SOC of the battery 12 decreases due to self-discharge occurring during a period from when the vehicle system is shut down (Ready-Off) to when the vehicle system is started (Ready-On). On the other hand, the current estimated value-based SOC estimated value SOC_I maintains the value at the time of shutdown (Ready-Off). This gradually opens the difference between the two.

  When the start switch 28 is pressed and the control unit 24 receives the Ready-On command, the control unit 24 switches the system main relay (not shown) from the disconnected state to the connected state, thereby conducting the battery 12 and the load such as the rotating electrical machine 10.

  The calculation unit 14 determines whether or not the difference ΔOCV between the open-circuit voltage value of the battery 12 at Ready-Off and the open-circuit voltage value of the battery 12 at Ready-On is equal to or greater than a predetermined threshold value ΔOCV_th (FIG. 5 S10).

  When ΔOCV is greater than or equal to threshold ΔOCV_th, operation unit 14 determines whether or not current integrated value-based SOC estimated value SOC_I (t) is greater than or equal to lower limit SOC_ThH in the high SOC region (S42). When the SOC estimated value SOC_I (t) is less than the lower limit SOC_ThH, the present flow is terminated without correcting the SOC estimated value SOC_I (t). When the estimated SOC value SOC_I (t) is equal to or greater than the lower limit SOC_ThH, the calculation unit 14 refers to the measured value of the current sensor 16 and determines whether or not the battery 12 is in a charged state (S44).

  If the battery 12 is not in the charged state (in the discharged state) in step S44, the estimation accuracy of the SOC estimated value SOC_V (t) is reduced due to the memory effect, and thus the SOC estimated value SOC_I (t) is not corrected. This flow is terminated. When the battery 12 is being charged, the calculation unit 14 proceeds to the next step S16.

  As a case where step S44 is satisfied when the vehicle system is activated, that is, the battery 12 is in a charged state immediately after activation, for example, a case where the vehicle is stopped on a downhill can be cited. When the vehicle system is activated (Ready-On) in this stopped state, the vehicle travels downhill. At this time, a charging current is supplied from the rotating electrical machine 10 to the battery 12 by regenerative braking. At this time, if the battery 12 has a high SOC, the condition of step S42 is also satisfied.

  In step S16, a difference value ΔSOC (t) between the current integrated value-based SOC estimated value SOC_I (t) and the open-circuit voltage value-based estimated value SOC_V (t) is obtained. Further, the calculation unit 14 adds a value obtained by multiplying the difference value ΔSOC (t) by the correction coefficient α to the SOC estimated value SOC_I (t) based on the current integrated value (S18).

  The calculation unit 14 determines whether or not the difference between the SOC estimated value SOC_I (t) and the difference value ΔSOC (t) × α and the SOC estimated value SOC_V (t) is sufficiently narrowed (S20). ). If the difference between the two is still open, the calculation unit 14 proceeds to steps S22 and S24, and determines whether or not the maximum difference value ΔSOCmax can be updated. Then, it waits until the next calculation cycle (S26).

  When the calculation cycle is incremented in step S26, the calculation unit 14 determines whether or not the estimated value SOC_I (t) is equal to or higher than the lower limit value SOC_ThH in the high SOC region, similarly to step S42 (S48). When the estimated value SOC_I (t) is less than the lower limit SOC_ThH, the computing unit 14 ends the correction flow shown in FIG.

  When the estimated value SOC_I (t) is greater than or equal to the lower limit SOC_ThH, the calculation unit 14 refers to the measurement value of the current sensor 16 and determines whether or not the battery 12 has been switched from the charged state to the discharged state (S50). When the state of charge is continued, the calculation unit 14 returns to step S16, calculates again the difference value ΔSOC (t) between the estimated value SOC_I (t) and the estimated value SOC_V (t), and further calculates a coefficient in ΔSOC (t). A value multiplied by α is added to the estimated value SOC_I (t) (S18).

  When it is determined in step S50 that the battery 12 has been switched from the charged state to the discharged state, the calculation unit 14 calculates immediately after the charge state is switched to the discharged state (time t29), as shown at time t30 in FIG. In the cycle, the first correction process is interrupted and switched to the second correction process. That is, the maximum difference value ΔSOCmax in the period from the start time point (Ready_On) of the first correction process to the switching time point (time t29) is sequentially added to the estimated SOC value SOC_I (t) over time at a predetermined ratio (β). (S32). In the example shown in FIG. 4, this addition period (that is, the second correction processing period) is a period from time t30 to t31. The maximum difference value ΔSOCmax is the difference value ΔSOC (t24) at time t24.

<Current Correction Value-Based SOC Estimated Value SOC_I Correction Process Other Embodiments>
In the embodiment of FIGS. 2 to 5, the current estimated value-based SOC estimated value SOC_I is corrected when the vehicle system is activated, that is, when the vehicle system is activated (Ready-On). Not exclusively. The correction flow of FIGS. 2 to 5 may be executed for the purpose of correcting the error of the current sensor 16.

  The estimated SOC value SOC_I is obtained by integrating the measured value Ib of the current sensor 16. If the measured value of the current sensor 16 includes an error, the error is also accumulated in the process of integrating the measured value Ib. Due to the accumulation of this error, the estimated SOC value SOC_I may deviate from the actual SOC. Therefore, the calculation unit 14 may execute the correction flow of FIGS. 2 to 5 after a predetermined time has elapsed since the end of the correction flow of the previous SOC estimated value SOC_I.

  In the correction process flow shown in FIGS. 2 to 5, the correction process after the memory effect is generated is performed based on the maximum difference value ΔSOCmax. However, the present invention is not limited to this form. For example, the difference value ΔSOC (t9) when switching from discharging to charging if the SOC is low, and the difference value ΔSOC (t29) when switching from charging to discharging if the SOC is high are the predetermined ratio (β). You may make it add to SOC estimated value SOC_I (t) sequentially sequentially.

  When the difference between the maximum difference value ΔSOCmax and the difference value ΔSOC (t9) or ΔSOC (t29) exceeds the estimation error of the SOC estimation based on the open circuit voltage, the difference value ΔSOC ( By performing the correction process based on t9) or ΔSOC (t29), more accurate correction can be performed.

  DESCRIPTION OF SYMBOLS 10 Rotating electrical machine, 12 Battery, 14 Computation part, 16 Current sensor, 18 Voltage sensor, 19, Temperature sensor, 24 Control part, 26 Memory | storage part, SOC_I SOC estimated value based on current integration value, SOC_V Open end voltage value based SOC Estimated value.

Claims (1)

A battery comprising a nickel metal hydride battery;
A current sensor for measuring an inflow / outflow current of the battery;
A voltage sensor for measuring a terminal voltage of the battery;
A temperature sensor for measuring the temperature of the battery;
The SOC estimated value of the battery is calculated from the current integrated value obtained by integrating the current values measured from the current sensor, and the current value and the terminal voltage value respectively measured from the current sensor, the voltage sensor, and the temperature sensor. And a calculation unit for calculating an estimated value of the SOC of the battery corresponding to the open circuit voltage value of the battery obtained based on the temperature,
An in-vehicle battery SOC management system comprising:
The computing unit is
When the current integrated value-based SOC estimated value is included in a predetermined low SOC region and the battery is in a discharged state, the current integrated value-based SOC estimated value and the open-circuit voltage value-based SOC estimated By repeatedly performing correction by adding a value obtained by multiplying the difference value from the value by a correction coefficient of less than 1 to the current integrated value based SOC estimated value, the current integrated value based SOC estimated value is converted into the open-circuit voltage value base. A first correction process for gradually approaching the estimated SOC value of
When the battery is switched from the discharged state to the charged state, the first correction process is interrupted, and from the start time of the first correction process to the time point when the discharged state is switched to the charged state, A second correction process for sequentially adding a maximum difference value between the current estimated value-based SOC estimated value and the open-circuit voltage value-based SOC estimated value to the current accumulated value-based SOC estimated value sequentially at a predetermined rate; Run,
In-vehicle battery SOC management system characterized by the above.

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