JP2017060313A - Vehicle electric power system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power system capable of surely securing an opportunity to perform equalization processing with respect to an in-vehicle power storage device.SOLUTION: An electric power system 10 to be mounted on a vehicle comprises: a main battery 12 constituted by connecting a plurality of chargeable and dischargeable battery cells; a solar panel 18 for generating power by photovoltaic power; a solar charging device for charging the main battery 12 by power generated by the solar panel 18; an equalization circuit for performing equalization processing to discharge partial battery cells in order to eliminate a voltage dispersion among the plurality of battery cells; and a control section 30 being the control section 30 for controlling at least the drive of the equalization circuit and prohibiting the performance of equalization processing during charging/discharging of the main battery 12. When the non-performance time of equalization processing becomes equal to or more than a previously regulated reference time, the control section 30 exceptionally permits the performance of equalization processing during the execution of solar charging.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply system mounted on a vehicle.

  2. Description of the Related Art Conventionally, electric vehicles that travel using electric power, such as hybrid vehicles and electric vehicles, are widely known. Such an electric vehicle is equipped with a power storage device for charging and discharging electric power. Such an in-vehicle power storage device is usually configured by electrically connecting a plurality of chargeable / dischargeable battery elements.

JP 2009-159794 A Japanese Patent Laid-Open No. 2015-115978

  Here, it is known that the voltage values gradually vary as the plurality of battery elements are used. When such variations in voltage value occur, there is a risk that some battery elements are overcharged or overdischarged. Therefore, conventionally, the voltage values of each of the plurality of battery elements are monitored, and when there are variations in the voltage values of the plurality of battery elements, some of the battery elements are set so that the variations in the voltage values are within an allowable range. There is known a technique for performing an equalization process for discharging the gas. (For example, patent document 1 etc.).

  By performing the equalization process, it is possible to effectively eliminate variations in the voltage values of the battery elements. However, such equalization processing cannot be performed in principle while the battery element is charging and discharging. Therefore, depending on the vehicle, there is a possibility that sufficient equalization processing opportunities cannot be secured.

  In particular, recently, an electric vehicle having a solar charging function for charging a power storage device using electric power generated by sunlight has been proposed (for example, Patent Document 2). Such solar charging is performed over a relatively long time during the day. Therefore, in an electric vehicle having such a solar charging function, there is little time during which the power storage device is neither charged nor discharged, and it is difficult to ensure an equalization processing opportunity.

  Therefore, an object of the present invention is to provide a power supply system that can more reliably ensure an opportunity to perform equalization processing on an in-vehicle power storage device.

  The power supply system of the present invention is a power supply system mounted on a vehicle, and is a power storage device configured by connecting a plurality of chargeable / dischargeable battery elements, a solar power generation device that generates power by sunlight, and the solar power generation device. A solar charging device that charges the power storage device with the electric power generated by the battery, and an equalization circuit that performs an equalization process for discharging some of the battery elements in order to eliminate voltage variations between the battery elements. A control unit that controls at least the drive of the equalization circuit, the control unit prohibiting execution of the equalization process during charging and discharging of the power storage device, and the control unit includes the equalization circuit When the non-execution time of the process is equal to or more than a predetermined reference time, the equalization process is permitted during the solar charging.

  According to the present invention, when the non-equalization time of the equalization process is equal to or more than a predetermined reference time, the equalization process is performed on the power storage device in order to allow the equalization process to be performed during the solar charge execution. It is possible to secure the opportunity to implement

It is a figure which shows the structure of the power supply system which is embodiment of this invention. It is a figure which shows the structure of a battery stack. It is a figure which shows an example of the variation in the voltage of a battery cell. It is a flowchart which shows the flow which determines the implementation decision of an equalization process. It is a flowchart which shows the flow of a normal equalization process. It is a flowchart which shows the flow of the equalization process in a solar.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a power supply system 10 according to an embodiment of the present invention. The power supply system 10 is mounted on an electric vehicle, for example, a hybrid vehicle or an electric vehicle. The main battery 12 provided in the power supply system 10 is charged with power supplied from an external power source (hereinafter referred to as “external charging”), charged with regenerative power of the motor generator 100 (hereinafter referred to as “regenerative charging”), and The battery can be charged with electric power obtained by solar power generation. Hereinafter, the power supply system 10 will be described in detail.

  The power supply system 10 includes three batteries, that is, a main battery 12, an auxiliary battery 14, and an additional battery 16. The main battery 12 is a battery that accumulates energy for driving the vehicle and is a chargeable / dischargeable power storage device. The main battery 12 has one or more battery stacks, and each battery stack is configured by connecting a plurality of battery cells 32 (see FIG. 2) in series. The battery cell 32 is a chargeable / dischargeable secondary battery, for example, a nickel hydride battery, a lithium ion battery, or the like.

  The main battery 12 incorporates an equalization circuit 34 for eliminating variations in voltage values between battery cells 32 as battery elements. The equalization circuit 34 is provided for each battery cell 32 as will be described in detail later. And the dispersion | variation in the voltage value between battery elements is eliminated by discharging the battery cell 32 with a high voltage value.

  The main battery 12 is connected to the power conversion device 102 via the relay 104 and supplies power to the power conversion device 102 and the motor generator 100 for running the vehicle. The power conversion device 102 and the motor generator 100 are mounted on the vehicle, and generate driving force for running the vehicle with electric power supplied from the main battery 12. The motor generator 100 can also generate electric power, and the main battery 12 is regeneratively charged by supplying the generated electric power to the main battery 12 via the power converter 102.

  The main battery 12 is further connected to a charger 24 and connectors 26 and 28 for enabling external charging. The connector has an AC connector 26 connected to an AC power source and a DC connector 28 connected to a DC power source. The DC connector 28 is connected to the main battery 12 via the charging relay 29. The AC connector 26 is connected to the main battery 12 via a charger 24 that performs AC / DC conversion and a charging relay 29. As is well known, the auxiliary battery 14 supplies driving power to auxiliary equipment mounted on the vehicle, for example, an air conditioner, the control unit 30 and the like.

  The solar panel 18 is a solar power generation device that is mounted on a vehicle and generates power using sunlight. The electric power generated by the solar panel 18 is supplied to and stored in the additional battery 16. A part of the electric power generated by the solar panel 18 is stepped down by the step-down converter 22 and supplied to the auxiliary battery 14. In addition, the white arrow in FIG. 1 has shown the flow of the electric power obtained by the solar power generation. Naturally, power generation by the solar panel 18, that is, solar power generation, is performed only during the day when the sun is out.

  The additional battery 16 is a secondary battery that temporarily stores electric power obtained by solar power generation. The electric power stored in the additional battery 16 is boosted by the boost converter 20 and supplied to the main battery 12, or is stepped down by the step-down converter 22 and supplied to the auxiliary battery 14. The dashed arrows in FIG. 1 indicate the flow of power from the additional battery 16. Among these, the process of supplying the power of the additional battery 16 to the main battery 12 and charging the main battery 12 is referred to as “solar charging”. The additional battery 16 and a circuit that connects the additional battery 16 to the solar panel 18 and the main battery 12 correspond to a solar charger that charges the main battery 12 with the electric power generated by the solar panel 18.

  In principle, solar charging is performed when the vehicle is not running and no external charging is performed. Here, this solar charging can be executed even at night. However, since the capacity of the additional battery 16 is much smaller than that of the main battery 12, normally, in order to fully charge the main battery 12 with the power generated by solar power, solar power generation and solar charging are repeatedly performed. There is a need. As a result, in practice, the solar charging execution time zone is limited to the daytime, similar to solar power generation.

  The control unit 30 controls the driving of each unit constituting the power supply system 10 and includes, for example, a CPU and a memory. As will be described later, the control unit 30 of the present embodiment controls driving of the equalization circuit. For this control, the voltage value of the battery cell detected by various sensors, the current value flowing through the circuit, and the like are input to the control unit 30. In addition, the control unit 30 stores a travel history of the vehicle, particularly a night travel time, etc. in order to control the driving of the equalization circuit.

  Next, the equalization process of the main battery 12 will be described with reference to FIG. FIG. 2 is a diagram illustrating a circuit configuration of the battery stack. As described above, the main battery 12 has one or more battery stacks, and each battery stack has a plurality of battery cells 32 connected in series. The number of battery cells 32 constituting the battery stack can be appropriately set based on the required output of the battery stack and the like.

  In each battery cell 32, an equalization circuit 34 and a voltage monitoring IC 36 are connected in parallel to the battery cell 32. The voltage monitoring IC 36 detects the voltage value of the corresponding battery cell 32 and outputs it to the control unit 30. The equalization circuit 34 is a circuit in which a resistor 38 and a switch 40 are connected in series. When the switch 40 of the equalization circuit 34 is turned on, the corresponding battery cell 32 is discharged. The equalization circuit 34 is used to align the voltage values between the battery cells 32. For example, when the voltage value of a specific battery cell 32 is higher than the voltage values of other battery cells 32, the switch 40 of the equalization circuit 34 corresponding to the specific battery cell 32 is turned on, and the specific battery cell 32 is turned on. Discharge.

  The reason why the variation in the voltage value between the battery cells 32 is eliminated by using the equalizing circuit 34 is to secure a charge / discharge operation region. This will be described with reference to FIG. FIG. 3 is a diagram illustrating an example of variations in voltage values of a plurality (five in the illustrated example) of battery cells 32. In general, the voltage of the battery cell 32 is controlled to be not less than a predetermined lower limit voltage value and not more than an upper limit voltage value in order to avoid overcharge and overdischarge. As shown in FIG. 3, in the state in which the voltage value varies in the plurality of battery cells 32, in order to avoid overdischarge, the battery cell 32 having a low voltage value (cell 3 in the example of FIG. 3) If the lower limit voltage value is reached, the discharge from the main battery 12 must be stopped even if the other battery cells 32 have not reached the lower limit voltage value. Further, in order to avoid overcharging, if a battery cell 32 having a high voltage value (cell 2 in the example of FIG. 3) reaches the upper limit voltage value, the main battery main cell 32 may not reach the upper limit voltage value. Charging to the battery 12 must be stopped. In other words, when there is a variation in voltage value, charging or discharging must be stopped earlier than when there is no variation, and the charge / discharge operating region (allowable voltage fluctuation range) is narrow. Become.

  Therefore, conventionally, the voltage of each battery cell 32 is monitored, and when the voltage value varies, the battery cell 32 having a high voltage value is discharged, and an equalization process is performed to equalize the voltage value. Has been proposed. By performing the equalization process, it is possible to prevent the charge / discharge operation region from being narrowed. In the present embodiment, the voltage monitoring IC 36 and the equalization circuit 34 are provided for each battery cell 32. However, in addition to or instead of such a configuration, the voltage monitoring IC 36 for detecting the voltage for each battery stack or the like. An equalization circuit 34 that performs discharge for each voltage stack may be provided.

  By the way, such equalization processing is desirably performed in a state where the voltage of the battery cell 32 is stable, that is, in a state where there is no voltage fluctuation amount associated with polarization. Usually, the polarization of the secondary battery is caused by charging / discharging. However, if the secondary battery is left without being charged / discharged, the polarization is eliminated. Therefore, the equalization process is performed when the main battery 12 is not charged / discharged in principle.

  However, if this principle is strictly followed, a vehicle having a solar charging function may not have an equalization process. That is, as described above, solar charging is usually performed during the day. Therefore, in a vehicle having a solar charging function, the equalization process can be performed at night when the vehicle is neither running nor being externally charged. In the case of a vehicle that frequently travels at night, for example, in the case of a taxi or the like that continues to operate at night, there is a possibility that the equalization processing opportunity may be reduced.

  Therefore, in this embodiment, when it is estimated that there are many night runs and the non-equalization time is equal to or longer than a predetermined reference time, solar charging and equalization processing are performed in parallel, as an exception. I am doing so. That is, normally, when discharging the battery cell 32 for equalization processing, feedback control is performed to switch the switch 40 of the equalization circuit 34 on and off according to the voltage value of the battery cell 32 detected by the voltage monitoring IC 36. ing. Thereby, the voltage of each battery cell 32 can be adjusted correctly, and a highly accurate equalization process is attained.

  When solar charging is being performed, the voltage value of each battery cell 32 is not stable, so feedback control as described above cannot be performed, and equalization processing with high accuracy is difficult. However, during solar charging, the value of the current flowing through the main battery 12 is very small compared to other charging / discharging processes, for example, external charging processes or discharging processes for running a vehicle, resulting from polarization. Voltage fluctuation is small. Therefore, although the accuracy is lower than when the polarization is completely eliminated (when the charge / discharge is not complete), the equalization process can be performed even during the solar charging. Therefore, in the present embodiment, when specific conditions are satisfied, such as a high frequency of night driving, solar charging and equalization processing are allowed to be performed in parallel.

  In addition, since the voltage value of the battery cell 32 is not stable during solar charging, feedback control for controlling discharge according to the detected voltage value becomes difficult. Therefore, when performing the equalization process in parallel with solar charging, for each battery cell 32, calculate the required discharge capacity by calculation, and further calculate the discharge time required for discharging the discharge capacity, Feed forward control is performed to continue the discharge for the calculated discharge time. In the following, the equalization process by feed-forward control that allows parallel execution with solar charging is `` equalization process during solar '', and the equalization process by feedback control that is performed when charging / discharging is completely stopped is `` normal equalization process '' "To distinguish. A specific control flow of the equalization process in the solar and the normal equalization process will be described in detail later.

  Next, a flow for determining whether or not to perform equalization processing will be described with reference to FIG. In order to determine whether or not the equalization process can be performed, the control unit 30 first checks whether or not the main battery 12 is being discharged or being externally charged (S10). When the main battery 12 is being discharged or being externally charged, the voltage of each battery cell 32 is not stable. In this case, the control unit 30 does not perform either normal equalization processing or solar equalization processing.

  On the other hand, when the main battery 12 is not being discharged or being externally charged, the control unit 30 determines whether or not the present time is night (S12). This determination may be performed based on, for example, a time obtained with a clock mounted on the vehicle. Moreover, when solar power generation is not performed more than a predetermined amount, it may be determined that it is nighttime. As a result of the determination, when the present is night, it can be determined that the main battery 12 is not discharged, externally charged, or solar charged. Therefore, in this case, since normal equalization processing can be performed, the process proceeds to step S28.

  In step S28, the control unit 30 determines whether or not the polarization of the battery cell 32 has been eliminated. The polarization state is determined based on the elapsed time after the no-load condition is established. Specifically, the control unit 30 counts an elapsed time after the current consumption becomes 0 A or the power consumption becomes 0 W. Then, the control unit 30 determines that the polarization is eliminated if the elapsed time exceeds a predetermined polarization elimination time. Since the polarization elimination time varies depending on the temperature, it is desirable to previously store the polarization elimination time with respect to the temperature in the form of a map or the like.

  When the polarization has not been eliminated, the control unit 30 stands by until the polarization is eliminated. If it can be determined that the polarization has been eliminated, the control unit 30 acquires the voltage value (open voltage value: OCV) of each battery cell 32 and performs normal equalization processing based on the obtained voltage value ( S30, 32).

  On the other hand, when it is determined in step S12 that it is not nighttime, the control unit 30 subsequently checks whether or not solar charging is in progress (S14). When solar charging is not in progress, that is, when power is not supplied from the additional battery 16 to the main battery 12, normal equalization processing can still be performed, so the control unit 30 proceeds to step S28 and performs normal equalization. Processing (S30, 32) is performed.

  If it is determined in step S14 that the solar battery is being charged, that is, if power is supplied from the additional battery 16 to the main battery 12, the control unit 30 subsequently determines whether the frequency of night driving is high. (S16). The frequency of night driving is evaluated by, for example, the accumulated time of night driving during a predetermined time (for example, one month) or the cumulative number of days in which night driving has been performed for a predetermined time or more during a predetermined time (for example, one month). That's fine. In addition, these accumulated times and accumulated days are not simply added, but may be weighted and added so that the evaluation becomes higher as the most recent running time and running days. In any case, the control unit 30 determines that the frequency of night driving is high when the numerical value indicating the frequency of night driving exceeds a predetermined threshold.

  Here, as described above, when the frequency of night driving is high, there is a high possibility that the time during which the equalization processing is not performed is long. On the other hand, when the frequency of night driving is not high, the equalization process can be performed during the past night, and it can be estimated that the time during which the equalization process is not performed is short. Therefore, when it can be estimated that the frequency of night travel is not high and the non-equalization processing non-execution time is shorter than the predetermined reference time, the equalization processing is not performed at the present time and the processing ends.

  On the other hand, when the frequency of night driving is high and it can be estimated that the non-equalization time is longer than the predetermined reference time, it is desirable to perform the equalization process even during solar charging. Therefore, in this case, the control unit 30 performs the equalizing process in the solar (S24). When performing the solar equalization process, first, solar charging currently being executed is temporarily prohibited (S18), and the system waits until the polarization of each battery cell 32 is eliminated (S20). When the polarization is eliminated, the voltage value (open voltage value: OCV) of each battery cell 32 is acquired (S22). If the open-circuit voltage value OCV is obtained, the equalizing process in the solar is performed based on the value (S24). In addition, the solar charging is permitted in parallel with the in-solar equalization process (S26).

  In this way, when it is estimated that the frequency of night driving is high and the non-equalization process is long, the solar charging and the equalization process are performed in parallel, so that the equalization process can be performed more reliably. Can be secured.

  Next, the normal equalization process and the solar equalization process will be described with reference to FIGS. When performing normal equalization processing, the control unit 30 first defines a difference value ΔV = | Vmax−Vmin | between the maximum voltage value Vmax and the minimum voltage value Vmin among the plurality of battery cells 32. Is compared with the reference value ΔVdef (S40). If the difference value ΔV is smaller than the reference value ΔVdef as a result of the comparison, it is determined that the plurality of battery cells 32 have already been equalized, and the equalization process ends. On the other hand, when the difference value ΔV is greater than or equal to the reference value ΔVdef, some of the battery cells 32 are discharged for equalization.

  Specifically, the control unit 30 calculates a difference value ΔVci between the voltage value Vci and the minimum voltage value Vmin of the i-th battery cell 32, and compares the difference value ΔVci with the reference value ΔVdef (S42). As a result of the comparison, if the difference value ΔVci is less than the reference value ΔVdef, it is determined that discharging of the i-th battery cell 32 is unnecessary, and the process proceeds to the next battery cell 32 (S48, S49). On the other hand, if the difference value ΔVci is greater than or equal to the reference value ΔVdef, the switch 40 of the equalization circuit 34 corresponding to the i-th battery cell 32 is turned on to start discharging the i-th battery cell 32 (S44). Then, the discharge is continued until the voltage value Vci detected by the voltage monitoring IC 36 reaches the minimum voltage value Vmin (S46). If the voltage value Vci of the i-th battery cell 32 reaches the minimum voltage value Vmin as a result of the discharge, the discharge is terminated (S47). Thereafter, the same process is performed on all the battery cells 32.

  As described above, in the normalization process, the voltage value Vci detected by the voltage monitoring IC 36 is monitored during the discharge, and the discharge is continued and switched according to the voltage value Vci. Therefore, the battery cells 32 can be set to the target voltage value (Vmin) with high accuracy, and as a result, equalization can be performed with high accuracy.

  Next, the in-solar equalization process will be described with reference to FIG. Also in the solar equalization process, the control unit 30 first sets a difference value ΔV = | Vmax−Vmin | between the maximum voltage value Vmax and the minimum voltage value Vmin among the plurality of battery cells 32 as a prescribed reference. It is compared with the value ΔVdef (S50). If ΔV <ΔVdef, the equalization process is terminated. On the other hand, when ΔV ≧ ΔVdef or more, some of the battery cells 32 are discharged for equalization.

  Specifically, the control unit 30 calculates a difference value ΔVci between the voltage value Vci and the minimum voltage value Vmin of the i-th battery cell 32, and compares the difference value ΔVci with the reference value ΔVdef (S52). As a result of the comparison, if the difference value ΔVci is less than the reference value ΔVdef, it is determined that discharging of the i-th battery cell 32 is unnecessary, and the process proceeds to the next battery cell 32 (S58, S59). On the other hand, if the difference value ΔVci is greater than or equal to the reference value ΔVdef, the required discharge time Tci is calculated from the difference value ΔVci (= | Vci−Vm |) (S53). That is, if the voltage difference value ΔVci is known, the discharge capacity necessary to reduce the voltage of the i-th battery cell 32 to Vmin can be calculated. If the required discharge capacity is known, the necessary discharge time Tci required to discharge the required amount of discharge can be calculated.

  If the required discharge time Tci can be calculated, the control unit 30 starts discharging the i-th battery cell 32 (S54). This discharge continues until the calculated required discharge time Tci elapses (S56). If the discharge time of the i-th battery cell 32 reaches the required discharge time Tci, the discharge is terminated (S57). Thereafter, the same process is performed on all the battery cells 32.

  As apparent from the above description, in the solar equalization process, the required discharge time is calculated based on the difference between the voltage value of each battery cell and the target voltage value (minimum voltage value), and feedforward is performed according to this required discharge time. Control is in progress. Further, the cell voltage value and the target voltage value used for calculating the necessary discharge time are both open circuit voltage values OCV obtained during the time in which solar charging is temporarily prohibited, and are highly reliable values. It is. Therefore, although the accuracy is inferior to that of the normal equalization process in which feedback control is performed, equalization can be performed with a certain degree of accuracy.

  The configuration described so far is an example, and when the non-equalization time of the equalization process is equal to or more than a predetermined reference time, if the equalization process is allowed to be performed during solar charging, Other configurations may be changed as appropriate. For example, in the present embodiment, the configuration is such that the non-equalization process execution time is estimated from the frequency of night driving, but the equalization process execution history is recorded and the equalization process is not performed with reference to the record. You may make it acquire implementation time. Further, in the present embodiment, the processing content is different between the equalization processing during solar charging and the equalization processing performed when charging / discharging is not performed at all, but both may have the same content. . In the flowcharts shown in FIGS. 5 and 6, the battery cells 32 are discharged one by one in order, but a plurality of battery cells 32 may be discharged simultaneously. In any case, by allowing parallel execution of solar charging and equalization processing when a specific condition is satisfied, the equalization processing opportunity can be more reliably secured.

10 power supply system, 12 main battery, 14 auxiliary battery, 16 additional battery, 18 solar panel, 20 step-up converter, 22 step-down converter, 24 charger, 26, 28 connector, 29 charge relay, 30 control unit, 32 battery cell, 34 equalization circuit, 36 voltage monitoring IC, 38 resistance, 40 switch, 100 motor generator, 102 power converter, 104 relay.

Claims (1)

A power supply system mounted on a vehicle,
A power storage device configured by connecting a plurality of chargeable / dischargeable battery elements;
A solar power generation device that generates power by sunlight;
A solar charging device that charges the power storage device with the power generated by the solar power generation device; and
An equalization circuit for performing an equalization process for discharging some of the battery elements in order to eliminate voltage variation between the plurality of battery elements;
A control unit that controls at least the driving of the equalization circuit, and during the charge and discharge of the power storage device, a control unit that prohibits the execution of the equalization process;
With
When the non-execution time of the equalization process is equal to or more than a predetermined reference time, the control unit permits the execution of the equalization process during execution of the solar charging.
A power supply system for a vehicle.

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