SOC estimation device

Abstract

To provide an SOC estimation device that can improve the estimation accuracy of an SOC.SOLUTION: In an SOC estimation device, a first estimation unit 36 estimates a reference value of an SOC of a battery on the basis of a voltage of a chargeable / dischargeable battery (a sub-battery 14). A second estimation unit 38 estimates an estimation value of the SOC of the battery on the basis of the estimated reference value and an integrated value of an electrical current of the battery. When the first estimation unit 36 does not engage in executing estimation processing of the reference value, the voltage of the battery is controlled within a first range. When the first estimation unit 36 engages in executing the estimation processing of the reference value, the voltage of the battery is controlled within a second range. The second range includes a specific range outside of the first range. The first estimation unit 36 estimates the reference value on the basis of the voltage of the battery at a time when the voltage becomes a value within the specific range.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a SOC estimation device. [Background technology]

[0002] Lithium ion batteries are mounted on vehicles etc. Patent Document 1 discloses an energy storage device that measures a stage capacity corresponding to a stage until or after the stage is switched to another adjacent stage, and estimates the full charge capacity of the lithium ion battery based on the reference capacity and the stage capacity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-139652 A Summary of the Invention [Problem to be solved by the invention]

[0004] The SOC (State of Charge) of a battery can be estimated based on the measured battery voltage and the SOC-voltage characteristics of the battery acquired in advance. However, in a lithium-ion battery or the like, the SOC-voltage characteristics have a generally flat region. The battery may be controlled to charge and discharge within this flat region. In this region, the SOC fluctuates relatively greatly with a slight fluctuation in voltage, which may reduce the accuracy of the SOC estimation.

[0005] An object of the present invention is to provide a SOC estimation device capable of improving the accuracy of SOC estimation. [Means for solving the problem]

[0006] In order to solve the above problem, an SOC estimation device according to an embodiment of the present invention includes a first estimation unit that estimates a reference value of an SOC of a chargeable / dischargeable battery based on the voltage of the battery, and a second estimation unit that estimates an estimated value of the SOC of the battery based on the estimated reference value and an integrated value of a current of the battery. When the first estimation unit is not executing a process to estimate the reference value, the voltage of the battery is controlled within a first range, and when the first estimation unit is executing a process to estimate the reference value, the voltage of the battery is controlled within a second range, the second range including a specific range outside the first range. The first estimation unit estimates the reference value based on the voltage of the battery when the voltage becomes a value within the specific range. Effect of the Invention

[0007] According to the present invention, it is possible to provide a SOC estimating device that can improve the accuracy of estimating SOC. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a solar charging system according to an embodiment. [Diagram 2] 2 is a diagram illustrating an example of SOC-voltage characteristics of the auxiliary battery of FIG. 1. [Diagram 3] 3(a) to 3(c) are diagrams for explaining the charging operation of the auxiliary battery in the second control mode. [Figure 4] 4(a) and (b) are diagrams for explaining the pumping operation in the second control mode. [Diagram 5] 5(a) and (b) are diagrams for explaining the operation in the first control mode. [Figure 6] 5 is a flowchart showing a process for estimating a reference value of the SOC of the auxiliary battery. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Fig. 1 shows a schematic configuration of a solar charging system 1 according to an embodiment. The solar charging system 1 is mounted on an electric vehicle (not shown). The electric vehicle may be, for example, a battery electric vehicle (BEV) that uses an electric motor as a power source, a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a fuel cell electric vehicle (FCEV). The electric vehicle may be a vehicle driven by a driver or an autonomous vehicle.

[0010] The solar charging system 1 includes a solar panel 10, a DC / DC converter 12, an auxiliary battery 14, an auxiliary device 16, a bidirectional DC / DC converter 18, a drive battery 20, and a control device 30.

[0011] The solar panel 10 is a solar cell module that is an assembly of solar cell cells that generate power from irradiated sunlight. The power generated by the solar panel 10 depends on the solar radiation intensity. The solar panel 10 is connected to an input terminal of a DC / DC converter 12. The power generated by the solar panel 10 is output to the DC / DC converter 12. The solar panel 10 is installed, for example, on the roof of a vehicle.

[0012] An output terminal of the DC / DC converter 12 is connected to the auxiliary battery 14, the auxiliary device 16, and the bidirectional DC / DC converter 18. The DC / DC converter 12 is capable of converting the power generated by the solar panel 10 and supplying the power to the auxiliary battery 14, the auxiliary device 16, and the bidirectional DC / DC converter 18. The DC / DC converter 12 steps down or steps up the output voltage of the solar panel 10 to a predetermined voltage under the control of the control device 30, and outputs the stepped-down or stepped-up voltage to the auxiliary battery 14, etc. The DC / DC converter 12 performs MPPT (Maximum Power Point Tracking) control so that the output power of the solar panel 10 is maximized.

[0013] The auxiliary battery 14 is a chargeable and dischargeable secondary battery, such as a lithium ion battery. The auxiliary battery 14 is a low-voltage battery with a lower voltage than the drive battery 20. The auxiliary battery 14 can be charged with power generated by the solar panel 10. The auxiliary battery 14 may also be charged with power from the drive battery 20. The auxiliary battery 14 can supply power to the accessories 16. The auxiliary battery 14 may also charge the drive battery 20.

[0014] The auxiliary devices 16 are loads such as electronic devices provided in the vehicle. The auxiliary devices 16 may include, for example, headlamps, a navigation device, an audio device, an air conditioner, an automatic driving system, an advanced driving assistance system, etc. The auxiliary devices 16 operate using power supplied from the auxiliary battery 14.

[0015] Bidirectional DC / DC converter 18 has a first terminal and a second terminal. The first terminal is connected to the output terminal of DC / DC converter 12 and auxiliary battery 14. The second terminal is connected to driving battery 20. Bidirectional DC / DC converter 18 operates under the control of control device 30 in a first state in which it boosts the voltage at the first terminal and outputs the boosted voltage from the second terminal, or in a second state in which it lowers the voltage at the second terminal and outputs the lowered voltage from the first terminal.

[0016] The driving battery 20 is a chargeable and dischargeable secondary battery such as a lithium ion battery. The driving battery 20 can also be called a high voltage battery. The driving battery 20 can supply power to an electric motor that generates driving force for the vehicle via an inverter (not shown) or the like. The driving battery 20 can be charged with power supplied from a charging station or the like outside the vehicle via an on-board charging device (not shown).

[0017] The control device 30 controls the DC / DC converter 12 and the bidirectional DC / DC converter 18 based on the output voltage of the solar panel 10 detected by a voltage sensor and a current sensor (not shown), the voltage and current of the auxiliary battery 14, and the voltage of the drive battery 20. The control device 30 has a SOC estimator 32 and a controller 34.

[0018] The configuration of the control device 30 can be realized in hardware terms by the CPU, memory, and other LSI of any computer, and in software terms by programs loaded into memory, but here the functional blocks realized by the cooperation of these are depicted. Therefore, it will be understood by those skilled in the art that these functional blocks can be realized in various forms by hardware alone, software alone, or a combination of both.

[0019] The SOC estimating unit 32 sequentially estimates an estimated value of the SOC of the auxiliary battery 14 based on the voltage and current of the auxiliary battery 14, and sequentially supplies the estimated SOC value to the control unit .

[0020] The control unit 34 controls the charging and discharging of the auxiliary battery 14 by controlling the bidirectional DC / DC converter 18 based on the received SOC estimate, the output voltage of the solar panel 10, the voltage and current of the auxiliary battery 14, and the voltage of the drive battery 20.

[0021] The control unit 34 outputs a request for estimating the reference value of SOC to the SOC estimating unit 32, for example, at regular time intervals. The regular time interval can be appropriately determined by experiment or simulation so that the error in the estimated value of SOC falls within an allowable range. The control unit 34 may output the request for estimating the reference value of SOC when a predetermined reference value estimation condition is satisfied, such as when the power switch or ignition switch of the vehicle is turned on.

[0022] The SOC estimation unit 32 includes a first estimation unit 36 ​​and a second estimation unit 38. When the first estimation unit 36 ​​receives a request to estimate the reference value of the SOC from the control unit 34, the first estimation unit 36 ​​starts a process to estimate the reference value. The first estimation unit 36 ​​estimates the reference value of the SOC of the auxiliary battery 14 based on the voltage of the auxiliary battery 14 and the SOC-voltage characteristic of the auxiliary battery 14. The SOC-voltage characteristic is stored in advance in a storage unit (not shown) of the control device 30. As will be described later, after receiving a request to estimate the reference value of the SOC, the first estimation unit 36 ​​waits until the voltage of the auxiliary battery 14 changes to a value within a specific range and then estimates the reference value. When the first estimation unit 36 ​​completes one estimation of the reference value, it notifies the control unit 34 of the end of the process to estimate the reference value. The period from receiving the request to estimate the reference value of the SOC to notifying the control unit 34 of the end of the process to estimate the reference value is defined as the period during which the first estimation unit 36 ​​is executing the process to estimate the reference value.

[0023] The length of the period during which the first estimation unit 36 ​​is executing the process of estimating the reference value varies depending on the SOC of the auxiliary battery 14 at the time when a request to estimate the SOC reference value is made, the operating state of the solar charging system 1, and the amount of power generation of the solar panel 10, etc.

[0024] Fig. 2 shows an example of the SOC-voltage characteristics of the auxiliary battery 14 in Fig. 1. The higher the SOC, the higher the voltage.

[0025] In the SOC-voltage characteristic, when the SOC is in the range of a first value SL or more and a second value SH or less, that is, when the voltage is in the range of a first value VL or more and a second value VH or less, the change in voltage per unit change in SOC is equal to or less than a predetermined value. This range is a region where the SOC-voltage characteristic is roughly flat, and can also be called a plateau region.

[0026] On the other hand, in the SOC-voltage characteristic, in the range where the SOC is equal to or greater than 0 and less than the first value SL, and in the range where the SOC is greater than the second value SH, i.e., in the range where the voltage is less than the first value VL and in the range where the voltage is greater than the second value VH, the amount of change in voltage per unit change in SOC is greater than a predetermined value. This range can also be called a non-plateau region. In this way, the auxiliary battery 14 is a secondary battery having a plateau region and a non-plateau region.

[0027] The first range Rs1 of SOC is in a plateau region and is a range from the lower limit S1L to the upper limit S1H. The first range Rv1 of voltage corresponds to the first range Rs1 of SOC and is a range from the lower limit V1L to the upper limit V1H. Within the first range Rs1, i.e., within the first range Rv1, the amount of change in voltage per unit amount of change in SOC of the auxiliary battery 14 is equal to or less than a predetermined value.

[0028] The second range Rs2 of SOC spans the plateau region and the non-plateau region, and is a range not less than the lower limit S2L ​​and not more than the upper limit S2H. The second range Rv2 of voltage corresponds to the second range Rs2 of voltage, and is a range not less than the lower limit V2L and not more than the upper limit V2H.

[0029] The lower limit value S2L of the SOC is smaller than the lower limit value S1L and smaller than the first value SL. The upper limit value S2H is larger than the upper limit value S1H and larger than the second value SH. In other words, the upper limit value S2H and the lower limit value S2L of the second range Rs2 of the SOC are outside the first range Rs1.

[0030] The lower limit value V2L of the voltage is smaller than the lower limit value V1L and smaller than the first value VL. The upper limit value V2H is larger than the upper limit value V1H and larger than the second value VH. In other words, the upper limit value V2H and the lower limit value V2L of the second voltage range Rv2 are outside the first range Rv1.

[0031] The first ranges Rs1, Rv1 are determined to be ranges that easily suppress deterioration of the auxiliary battery 14. The first ranges Rs1, Rv1 and the second ranges Rs2, Rv2 can be determined appropriately through experiments or simulations.

[0032] The second range Rv2 of voltage includes a specific range Rv3 and a specific range Rv4 outside the first range Rv1. Within the second range Rv2, a range less than the first value VL is set as the specific range Rv3, and a range greater than the second value VH is set as the specific range Rv4. That is, within the specific ranges Rv3 and Rv4, the amount of change in voltage per unit change in the SOC of the auxiliary battery 14 is greater than a predetermined value. Note that the upper limit of the specific range Rv3 may be less than the first value VL, and the lower limit of the specific range Rv4 may be greater than the second value VH.

[0033] In addition, the upper limit values ​​S2H, V2H of the second ranges Rs2, Rv2 may be larger than the second values ​​SH, VH, and the lower limit values ​​S2L, V2L may be within the first ranges Rs1, Rv1. In this case, the specific range Rv4 exists, but the specific range Rv3 does not exist. Alternatively, the lower limit values ​​S2L, V2L of the second ranges Rs2, Rv2 may be smaller than the first values ​​SL, VL, and the upper limit values ​​S2H, V2H may be within the first ranges Rs1, Rv1. In this case, the specific range Rv3 exists, but the specific range Rv4 does not exist. In these cases, the second ranges Rs2, Rv2 may be wider or narrower than the first ranges Rs1, Rv1, or may be the same width as the first ranges Rv1, Rs1.

[0034] The control unit 34 controls the charging and discharging of the auxiliary battery 14 so that the estimated value of the SOC of the auxiliary battery 14 falls within the first range Rs1 from when the first estimating unit 36 ​​notifies the control unit 34 of the end of the process of estimating the reference value until the control unit 34 outputs a request for estimating the next SOC reference value. In this case, the control unit 34 may control the charging and discharging of the auxiliary battery 14 so that the voltage of the auxiliary battery 14 falls within the first range Rv1. Alternatively, the control unit 34 may control the charging and discharging of the auxiliary battery 14 so that the voltage of the auxiliary battery 14 falls within the first range Rv1 and the estimated value of the SOC falls within the first range Rs1. The voltage of the auxiliary battery 14 falling within the first voltage range Rv1 is equivalent to the estimated value of the SOC falling within the first SOC range Rs1. In other words, when the first estimating unit 36 ​​is not executing the process of estimating the reference value, the voltage of the auxiliary battery 14 is controlled within the first range Rv1. Details of the charging and discharging control will be described later.

[0035] The control unit 34 controls the charging and discharging of the auxiliary battery 14 so that the estimated value of SOC falls within the second range Rs2 from when the control unit 34 outputs a request to estimate the reference value of SOC until the control unit 34 is notified by the first estimating unit 36 ​​of the end of the process of estimating the reference value. In this case, the control unit 34 may control the charging and discharging of the auxiliary battery 14 so that the voltage of the auxiliary battery 14 falls within the second range Rv2. Alternatively, the control unit 34 may control the charging and discharging of the auxiliary battery 14 so that the voltage of the auxiliary battery 14 falls within the second range Rv2 and the estimated value of SOC falls within the second range Rs2. The voltage of the auxiliary battery 14 falling within the second voltage range Rv2 is equivalent to the estimated value of SOC falling within the second SOC range Rs2. In other words, when the first estimating unit 36 ​​is executing the process of estimating the reference value, the voltage of the auxiliary battery 14 is controlled within the second range Rv2.

[0036] The first estimation unit 36 ​​estimates a reference value of the SOC based on the voltage of the auxiliary battery 14 when the voltage becomes within a specific range Rv3 or Rv4 of the second range Rv2 and the SOC-voltage characteristics of the auxiliary battery 14. As described later, the voltage of the auxiliary battery 14 changes between the lower limit and upper limit of the second range Rv2 depending on the operating state of the solar charging system 1 and the amount of power generated by the solar panel 10, and therefore may change to within the specific range Rv3 or Rv4. The first estimation unit 36 ​​supplies the estimated reference value to the second estimation unit 38.

[0037] The second estimation unit 38 sequentially estimates an estimated value of the SOC of the auxiliary battery 14 based on the reference value estimated by the first estimation unit 36 ​​and the integrated value of the charging current or discharging current of the auxiliary battery 14 from the time the reference value was estimated. A known technique can be used to estimate the estimated value of the SOC using the reference value and the integrated value of the current. When a new reference value is estimated by the first estimation unit 36, the second estimation unit 38 updates the reference value used to estimate the estimated value of the SOC to the new reference value and resets the integrated value of the current to zero.

[0038] Compared to the first range Rv1, the variation in SOC per unit variation in voltage is small within the specific range Rv3 or the specific range Rv4, so the accuracy of estimating the reference value of SOC can be improved. Therefore, the accuracy of the estimated value of SOC derived from the reference value can be improved. This makes it possible to suppress unintended overcharging and overdischarging of the auxiliary battery 14.

[0039] In contrast, in the comparative example in which the voltage of the auxiliary battery 14 is controlled within the first range Rv1 even during the process of estimating the reference value of SOC, the variation in SOC per unit variation in voltage is relatively large. Therefore, compared to the embodiment, the estimation accuracy of the reference value of SOC is likely to decrease depending on the error of the detected voltage value, and the reference value of SOC may deviate relatively greatly from the actual SOC. When the error of the reference value of SOC is relatively large, the error of the estimated value of SOC is also relatively large, and the charge / discharge control of the auxiliary battery 14 is performed based on the estimated value, so that unintended overcharging or overdischarging may occur.

[0040] In addition, in the embodiment, the reference value of SOC is estimated at regular intervals, and the estimated value of SOC is estimated based on the current accumulated value from the time when the reference value was estimated, so that the error in the current accumulated value caused by the error in the detected current value can be prevented from becoming larger than a certain value. Therefore, the error in the estimated value of SOC can be prevented from becoming larger than a certain value.

[0041] In addition, because both the upper limit value S2H and the lower limit value S2L of the second SOC range Rs2 are outside the first range Rs1, a higher specific range Rv4 and a lower specific range Rv3 exist. As a result, when a request to estimate the reference value of the SOC is made while the auxiliary battery 14 is being charged, the voltage of the auxiliary battery 14 is more likely to enter the higher specific range Rv4 in a shorter time than to enter the lower specific range Rv3.

[0042] If a request for estimating the reference value of SOC is made while the auxiliary battery 14 is discharging without being charged, the voltage of the auxiliary battery 14 is more likely to fall within the lower specific range Rv3 in a shorter time than within the higher specific range Rv4. Therefore, one of the upper limit value S2H and the lower limit value S2L of the second range Rs2 is outside the first range Rs1, and the reference value is more likely to be estimated in a shorter time regardless of the timing of the request for estimating the reference value of SOC, compared to the case where there is only one specific range.

[0043] (Charge / discharge restrictions) Incidentally, the control unit 34 may change the control range of charging and discharging the auxiliary battery 14 depending on whether or not there is a predetermined charging and discharging constraint. For example, the control unit 34 may determine that there is a charging and discharging constraint when the temperature of the auxiliary battery 14 or the like satisfies a predetermined condition, and may determine that there is no charging and discharging constraint when the predetermined condition is not satisfied.

[0044] When there is a charge / discharge constraint, the control unit 34 controls the charge / discharge of the auxiliary battery 14 so that at least one of the voltage of the auxiliary battery 14 and the estimated value of the SOC falls within a third range (not shown) different from the first range. In other words, when there is a charge / discharge constraint, the voltage of the auxiliary battery 14 is controlled within the third range.

[0045] The third range is in a plateau region. The third range is determined in advance according to the contents of the charge / discharge constraint. The third range may be wider or narrower than the first ranges Rv1 and Rs1, or may be the same width as the first ranges Rv1 and Rs1. The third range may be set to a range obtained by shifting the first ranges Rv1 and Rs1 in a lower direction so as to prevent overcharging. The third range may be set to a range obtained by shifting the first ranges Rv1 and Rs1 in a higher direction so as to prevent overdischarging. A known technique can be used to set the charge / discharge constraint and the third range.

[0046] When there is no charge / discharge constraint, the control unit 34 controls the charge / discharge of the auxiliary battery 14 so that at least one of the voltage of the auxiliary battery 14 and the estimated value of the SOC falls within the first range from when it is notified of the end of the process for estimating the reference value until it outputs a request to estimate the next SOC reference value. In other words, when there is no charge / discharge constraint and the first estimating unit 36 ​​is not executing the process for estimating the reference value, the voltage of the auxiliary battery 14 is controlled within the first range Rv1.

[0047] When there is no charge / discharge constraint, the control unit 34 controls the charge / discharge of the auxiliary battery 14 so that at least one of the voltage of the auxiliary battery 14 and the estimated value of the SOC falls within the second range from when it outputs a request to estimate the reference value of the SOC until it is notified of the end of the process of estimating the reference value by the first estimating unit 36. In other words, when there is no charge / discharge constraint and the first estimating unit 36 ​​is executing the process of estimating the reference value, the voltage of the auxiliary battery 14 is controlled within the second range Rv2.

[0048] When there is no charge / discharge constraint, the first estimation unit 36 ​​estimates the reference value based on the voltage of the auxiliary battery 14 when the voltage becomes within the specific range Rv3 or the specific range Rv4. When there is a charge / discharge constraint, the first estimation unit 36 ​​estimates the reference value based on the voltage of the auxiliary battery 14 within the third range.

[0049] In this way, when there is a charge / discharge constraint, the charge / discharge control within the third range can be prioritized even while the first estimator 36 is executing the process of estimating the reference value of SOC. When there is no charge / discharge constraint, the estimation accuracy of the reference value of SOC can be improved.

[0050] (Charge / discharge control) Next, the charging and discharging operations of the solar charging system 1 will be described with reference to Figures 3 to 5. In Figures 3 to 5, the control device 30 is omitted from the illustration.

[0051] The control unit 34 operates in a first control mode or a second control mode. The control unit 34 operates in the first control mode when the solar panel 10 is not performing solar charging and the bidirectional DC / DC converter 18 is not operating in the first state. The control unit 34 operates in the second control mode when the solar panel 10 is performing solar charging or the bidirectional DC / DC converter 18 is operating in the first state. Performing solar charging corresponds to the solar panel 10 generating power.

[0052] In the first control mode, the controller 34 controls the bidirectional DC / DC converter 18 to the second state or the stopped state so that the estimated value of the SOC of the auxiliary battery 14 is within the control range. The control range is the first range Rs1, the second range Rs2, or the third range, and is selected as described above. In the second control mode, the controller 34 controls the bidirectional DC / DC converter 18 to the first state, the second state, or the stopped state so that the estimated value of the SOC of the auxiliary battery 14 is within the control range.

[0053] (Second control mode) 3(a) to 3(c) are diagrams for explaining the charging operation of the auxiliary battery 14 in the second control mode.

[0054] FIG. 3(a) shows a state where the amount of solar radiation is relatively large and the power generated by the solar panel 10 is relatively large. The bidirectional DC / DC converter 18 is controlled to a stopped state. In the state of FIG. 3(a), the power generated by the solar panel 10 is greater than the power consumed by the auxiliary device 16. Therefore, the auxiliary battery 14 is charged with the generated power, and the SOC of the auxiliary battery 14 increases. This is highly convenient because the auxiliary battery 14 can be charged using solar energy. Note that in FIGS. 3 to 5, the arrows indicate the power supply paths, and the thickness of the arrows roughly indicates the magnitude of the power.

[0055] When the situation changes from one in which the amount of solar radiation is relatively high to one in which the amount of solar radiation is relatively low, the state transitions to that shown in Figure 3(b).

[0056] Fig. 3(b) shows a state where the solar radiation is relatively low and the power generated by the solar panel 10 is relatively small. The bidirectional DC / DC converter 18 is controlled to a stopped state. In the state of Fig. 3(b), the power generated by the solar panel 10 is assumed to be smaller than the power consumption of the auxiliary device 16. Therefore, the SOC of the auxiliary battery 14 decreases due to the power consumption of the auxiliary device 16. When the solar radiation recovers, the state returns to that of Fig. 3(a).

[0057] When the solar radiation does not recover and the estimated value of the SOC of the auxiliary battery 14 reaches the lower limit of the control range, the operation transitions to that shown in Fig. 3(c). That is, when the estimated value of the SOC of the auxiliary battery 14 reaches the lower limit of the control range during solar charging, the control unit 34 controls the bidirectional DC / DC converter 18 to the second state so as to charge the auxiliary battery 14. Specifically, when the bidirectional DC / DC converter 18 is stopped during solar charging, the control unit 34 controls the bidirectional DC / DC converter 18 to the second state when the estimated value of the SOC of the auxiliary battery 14 reaches the lower limit of the control range.

[0058] Fig. 3(c), which follows Fig. 3(b), shows a state in which the solar radiation is relatively low, the power generated by the solar panel 10 is relatively small, and the auxiliary battery 14 is charged using the power of the driving battery 20 as well. In the state of Fig. 3(c), the bidirectional DC / DC converter 18 operates in a second state in which the power of the driving battery 20 is supplied to the auxiliary battery 14. As a result, the auxiliary battery 14 is charged using the power of the driving battery 20 and the power generated by the solar panel 10, and the SOC of the auxiliary battery 14 increases. Therefore, the SOC of the auxiliary battery 14 can be increased even if the solar radiation is insufficient.

[0059] When the estimated value of the SOC of the auxiliary battery 14 reaches the upper limit of the control range due to charging, the operation shifts to the pumping operation shown in FIG. 4(a).

[0060] On the other hand, if the condition of relatively high solar radiation continues in the state of Figure 3(a) and the estimated value of the SOC of the auxiliary battery 14 reaches the upper limit of the control range due to charging using power generated by the solar panel 10, the pumping operation of Figure 4(a) will be initiated.

[0061] Specifically, during solar charging, when the estimated value of the SOC of the auxiliary battery 14 reaches the upper limit of the control range, the control unit 34 controls the bidirectional DC / DC converter 18 to the first state so that the driving battery 20 is charged with the power generated by the solar panel 10 and the power of the auxiliary battery 14.

[0062] 4(a) and (b) are diagrams for explaining the pumping operation in the second control mode. FIG. 4(a) shows a state where there is solar radiation and the solar panel 10 is generating power. In the state of FIG. 4(a), the bidirectional DC / DC converter 18 operates in a first state in which the power generated by the solar panel 10 and the power of the auxiliary battery 14 are supplied to the driving battery 20. As a result, the driving battery 20 is charged by the power of the auxiliary battery 14 and the power generated by the solar panel 10. This operation is called a pumping operation. The SOC of the driving battery 20 increases and the SOC of the auxiliary battery 14 decreases. Since the driving battery 20 can be charged by the power generated by the energy of sunlight and the power of the auxiliary battery 14 including the generated power, it is highly convenient and economical.

[0063] When the estimated value of the SOC of the auxiliary battery 14 reaches the lower limit of the control range in the state of Fig. 4(a), the operation transitions to the above-mentioned operation of Fig. 3(a) and (b). That is, when the estimated value of the SOC of the auxiliary battery 14 reaches the lower limit of the control range during solar charging, the control unit 34 controls the bidirectional DC / DC converter 18 to a stopped state so that the auxiliary battery 14 is charged with the power generated by the solar panel 10. Specifically, when the bidirectional DC / DC converter 18 is operating in the first state during solar charging, the control unit 34 controls the bidirectional DC / DC converter 18 to a stopped state when the estimated value of the SOC of the auxiliary battery 14 reaches the lower limit of the control range. This allows the auxiliary battery 14 to be charged again using the power generated by the solar panel 10. When the solar radiation is sufficient, the states of Fig. 3(a) and Fig. 4(a) are alternately repeated, so that the driving battery 20 can be repeatedly charged with the power generated by the energy of the sun.

[0064] FIG. 4(b) shows a state in which the solar panel 10 stops generating power due to the absence of solar radiation in the state shown in FIG. 4(a). When the bidirectional DC / DC converter 18 is operating in the first state in the second control mode, i.e., during pumping operation, the control unit 34 continues the second control mode even after solar charging ends. Therefore, the bidirectional DC / DC converter 18, which continues operating in the first state, continues to supply power from the auxiliary battery 14 to the driving battery 20. Therefore, the SOC of the auxiliary battery 14 decreases. When the control unit 34 continues the second control mode even after solar charging ends, if the estimated value of the SOC of the auxiliary battery 14 reaches the lower limit of the control range in a state where there is no power generated by the solar panel 10, the control unit 34 switches to the first control mode.

[0065] With this control, even if solar charging ends during pumping operation, the pumping operation can be continued, and the power of the auxiliary battery 14, including the power generated by the solar panel 10, can be supplied to the drive battery 20 until the lower limit of the control range is reached.

[0066] 3(a) to 3(c), if the generated power of the solar panel 10 runs out during the charging operation of the auxiliary battery 14, solar charging also ends at that point. If the bidirectional DC / DC converter 18 is not operating in the first state in the second control mode, that is, if the pumping operation is not in progress, the control unit 34 transitions to the first control mode when solar charging ends.

[0067] (First control mode) 5(a) and (b) are diagrams for explaining the operation of the first control mode. Fig. 5(a) shows a state in which the bidirectional DC / DC converter 18 is stopped. In the state of Fig. 5(a), the solar panel 10 is not generating power, and therefore the SOC of the auxiliary battery 14 decreases due to the power consumption of the auxiliary 16.

[0068] When the estimated value of the SOC of the auxiliary battery 14 reaches the lower limit of the control range, the operation transitions to that shown in Fig. 5(b). Specifically, when the estimated value of the SOC of the auxiliary battery 14 reaches the lower limit of the control range in the first control mode, the controller 34 controls the bidirectional DC / DC converter 18 to the second state.

[0069] Fig. 5(b) shows a state in which the auxiliary battery 14 is being charged. In the state of Fig. 5(b), the bidirectional DC / DC converter 18 operates in a second state in which the bidirectional DC / DC converter 18 supplies power from the driving battery 20 to the auxiliary battery 14. As a result, the auxiliary battery 14 is charged with power from the driving battery 20, and the SOC of the auxiliary battery 14 increases.

[0070] When the estimated value of the SOC of the auxiliary battery 14 reaches the upper limit of the control range due to charging, the operation returns to that shown in Fig. 5(a). Specifically, in the first control mode, when the estimated value of the SOC of the auxiliary battery 14 reaches the upper limit of the control range, the controller 34 controls the bidirectional DC / DC converter 18 to a stopped state.

[0071] In the first control mode, when the solar panel 10 starts generating power, solar charging starts. When solar charging starts in the first control mode, the control unit 34 transitions to the second control mode.

[0072] Next, a description will be given of the overall operation of the solar charging system 1 configured as above. Fig. 6 is a flow chart showing a process for estimating a reference value of the SOC of the auxiliary battery 14. The process in Fig. 6 is executed repeatedly.

[0073] If there is no request to estimate the reference value of SOC (N in S10), the control unit 34 maintains the current control. That is, the control unit 34 controls the SOC of the auxiliary battery 14 within the first range or the third range (S12), and ends the process.

[0074] If there is a request to estimate the reference value of SOC (Y in S10), and if there is no charge / discharge constraint (N in S14), the control unit 34 controls the SOC of the auxiliary battery 14 within the second range (S20). The first estimation unit 36 ​​determines whether the voltage of the auxiliary battery 14 is within the specific range (S22). If the voltage of the auxiliary battery 14 is not within the specific range (N in S22), the process returns to S22. If the voltage of the auxiliary battery 14 is within the specific range (Y in S22), the first estimation unit 36 ​​estimates the reference value of SOC based on the voltage of the auxiliary battery 14 (S24), and the control unit 34 controls the SOC of the auxiliary battery 14 within the first range (S26), and ends the process.

[0075] If there is a charge / discharge constraint in S14 (Y in S14), the control unit 34 controls the SOC of the auxiliary battery 14 within a third range (S16). The first estimation unit 36 ​​estimates a reference value of the SOC based on the voltage of the auxiliary battery 14 (S18), and ends the process.

[0076] 6, the second estimation unit 38 sequentially estimates an estimated SOC value based on the reference value and the integrated value of the current. When a new reference value of the SOC is estimated in S18 or S24, the second estimation unit 38 estimates an estimated SOC value based on the new reference value and the integrated value of the current from the point in time when the new reference value is estimated.

[0077] According to the embodiment, the reference value of the SOC of the auxiliary battery 14 is estimated based on the voltage of the auxiliary battery 14 when the voltage of the auxiliary battery 14 is within the specific range Rv3 or Rv4 of the second range Rv2, so that the reference value of the SOC can be estimated outside the region where the SOC-voltage characteristic is generally flat, thereby improving the accuracy of the SOC estimation.

[0078] Furthermore, since charging and discharging are controlled within the second ranges Rs2, Rv2 only while the process of estimating the reference value of the SOC is being executed, deterioration of the auxiliary battery 14 can be suppressed.

[0079] The present invention has been described above based on the embodiments. The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each processing step, and that such modifications are also within the scope of the present invention.

[0080] For example, in the embodiment, an example of estimating the SOC in the solar charging system 1 has been described, but the SOC of the auxiliary battery 14 may be estimated in a battery system in which the solar panel 10 and the DC / DC converter 12 are removed from the solar charging system 1. In this configuration, a step-down converter capable of supplying the power of the driving battery 20 to the auxiliary battery 14 may be used instead of the bidirectional DC / DC converter 18. When the voltage or SOC of the auxiliary battery 14 reaches the lower limit of the control range due to discharging to the auxiliary device 16, the control unit 34 operates the step-down converter to charge the auxiliary battery 14 with the power of the driving battery 20. When the voltage or SOC of the auxiliary battery 14 reaches the upper limit of the control range, the control unit 34 stops the step-down converter. In other words, the step-down converter is stopped except when the auxiliary battery 14 is being charged. As in the embodiment, when the first estimator 36 is not executing the process of estimating the reference value, the voltage of the auxiliary battery 14 is controlled within a first range, and when the first estimator 36 is executing the process of estimating the reference value, the voltage of the auxiliary battery 14 is controlled within a second range. In this modification, the same effect as in the embodiment can be obtained. Also in this modification, the control according to the presence or absence of the charge / discharge constraint of the embodiment may be executed. [Explanation of symbols]

[0081] 1...solar charging system, 10...solar panel, 12...DC / DC converter, 14...auxiliary battery, 16...auxiliary, 18...bidirectional DC / DC converter, 20...driving battery, 30...control device, 32...SOC estimation unit (SOC estimation device), 34...control unit, 36...first estimation unit, 38...second estimation unit.

Claims

1. a first estimation unit that estimates a reference value of an SOC of a chargeable / dischargeable battery based on a voltage of the battery; a second estimation unit that estimates an estimated value of an SOC of the battery based on the estimated reference value and an integrated value of a current of the battery; Equipped with When the first estimation unit is not executing a process of estimating the reference value, the voltage of the battery is controlled within a first range; When the first estimation unit is executing the process of estimating the reference value, the voltage of the battery is controlled within a second range, and the second range includes a specific range outside the first range; The first estimation unit estimates the reference value based on a voltage of the battery when the voltage of the battery becomes a value within the specific range.

1. An SOC estimation device comprising:

2. Within the first range, a change in voltage per unit change in SOC of the battery is equal to or less than a predetermined value, Within the specific range, the amount of change in voltage per unit change in SOC of the battery is greater than the predetermined value.

2. The SOC estimating device according to claim 1 .

3. When there is no predetermined charge / discharge constraint and the first estimation unit is not executing a process of estimating the reference value, the voltage of the battery is controlled within the first range; When there is no charge / discharge constraint and the first estimation unit is executing the process of estimating the reference value, the voltage of the battery is controlled within the second range; When the charging / discharging constraint exists, the voltage of the battery is controlled within a third range different from the first range; The first estimation unit is When there is no charge / discharge constraint, the reference value is estimated based on the voltage of the battery when the voltage falls within the specific range; When the charge / discharge constraint exists, the reference value is estimated based on a voltage of the battery within the third range.

3. The SOC estimating device according to claim 1 or 2.

4. the battery is a lithium ion battery, The battery is charged with power generated by a solar panel.

3. The SOC estimating device according to claim 1 or 2.

5. The first estimation unit is When receiving a request to estimate a reference value of SOC, a process of estimating the reference value is started; when the voltage of the battery falls within the specific range, the reference value is estimated, and the process of estimating the reference value is terminated.

3. The SOC estimating device according to claim 1 or 2.

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