JP6874652B2 - Battery system - Google Patents

Description

The present invention relates to battery systems, in particular limiting regenerative charging.

An electric vehicle (EV) is equipped with a large-capacity battery and runs by driving a motor with electric power from the battery. Then, when the capacity of the battery decreases, the battery is charged by the electric power supplied from the outside. As this charging method, there are AC charging in which a charger including a rectifier is mounted on the vehicle and connected to a household AC (alternating current) power source, and DC charging in which the vehicle is connected to an external direct current power source. DC charging often has a large capacity and can be quickly charged. Further, during traveling, charging is performed by the regenerative power of the motor.

Here, it is known that the battery deteriorates due to use, and particularly when the battery is continuously charged and discharged with a large current, high-rate deterioration occurs and the battery deteriorates significantly. Therefore, it has been proposed to calculate a deterioration index from the charge / discharge state of the battery, and when the deterioration index exceeds a predetermined value, limit the charge / discharge of the battery to suppress an increase in the amount of deterioration due to high-rate deterioration. There is. For example, in Patent Document 1, in a hybrid vehicle (HV), the load on the battery is reduced by starting the engine to prevent an increase in the deterioration index.

The calculation of the deterioration index is also described in Patent Documents 2 and 3.

Japanese Unexamined Patent Publication No. 2013-125607 Japanese Unexamined Patent Publication No. 2017-91602 Japanese Unexamined Patent Publication No. 2017-123245

Here, the electric vehicle is not equipped with an engine. Further, even in a plug-in hybrid vehicle, the driving of the engine may be prohibited and the vehicle may run as an electric vehicle. In such an electric vehicle, since a large current is discharged and a large current is charged while the vehicle is running, the high rate deterioration becomes larger than that of the hybrid vehicle, and the high rate deterioration suppression as in Patent Document 1 cannot be performed. Then, when the deterioration index becomes more than a predetermined value, charging is prohibited, but if the battery capacity is low at this time, the vehicle may not be able to run.

The present invention is a battery system that calculates a battery deterioration index and limits input when the calculated deterioration index exceeds the limit limit line for charging, and is a deterioration index ΣD when a predetermined amount of charging is performed. The amount of increase is calculated, and the value obtained by subtracting the amount of increase from the limit limit line is set as the regeneration limit line that limits charging by regeneration during running.

In addition, the second increase in the deterioration index that increases due to regeneration from the current SOC to the power shortage should be calculated, and the value obtained by subtracting the calculated second increase from the regeneration limit line should be further set as the partial regeneration limit line. Therefore, it is advisable to limit the charging by regeneration during running in two stages.

Further, when the deterioration index exceeds the regeneration restriction line, charging by regeneration may be prohibited.

Further, when the deterioration index exceeds the partial regeneration limit line, charging by regeneration in cooperation with the brake may be prohibited, and charging by regeneration equivalent to the engine brake may be permitted.

According to the present invention, in order to suppress an increase in the deterioration index during traveling, it is possible to perform a predetermined charging after the traveling is stopped, and it is possible to prevent the vehicle from being unable to travel due to being unable to charge.

It is a block diagram which shows the structure of the vehicle which mounted the battery system which concerns on embodiment. It is a flowchart which shows the process of charge control in a battery system. It is a timing chart which shows the state of SOC, deterioration index, input power limitation, and brake cooperative regeneration limitation in a battery system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described herein.

"overall structure"
FIG. 1 shows a vehicle 10 equipped with a battery system according to an embodiment of the present invention. The vehicle 10 is equipped with a battery 12. The battery 12 is a rechargeable secondary battery such as a nickel hydrogen secondary battery or a lithium ion secondary battery. An inverter 16 is connected to the battery 12 via a converter 14. The converter 14 includes, for example, two switching elements and a reactor, and by switching the switching elements, the output voltage of the battery 12 is boosted to a predetermined voltage and supplied to the inverter 16. The converter 14 can also be stepped down. A motor generator (MG) 18 is connected to the inverter 16, and the motor generator 18 is driven by an alternating current from the inverter 16. The inverter 16 has, for example, three arms in which two switching elements are connected in series between the positive and negative bus, and the midpoint of each arm is connected to the coil of each phase of the motor generator 18. Therefore, by controlling the switching of the switching element, a desired three-phase alternating current is supplied to the stator coil of the motor generator 18 to drive the motor generator 18. By controlling the switching element, the motor generator 18 can be put into a regenerative state, and the battery 12 can be charged with the obtained regenerative power.

The output shaft of the motor generator 18 is connected to the wheels 22 via a power transmission mechanism 20 including a differential gear or the like, and the wheels 22 are rotated by the output of the motor generator 18 to run the vehicle 10.

Further, an AC charging device 30 is connected to the battery 12. The AC charging device 30 includes a rectifier circuit, and an AC connector 32 is connected to the AC charging device 30. Therefore, the battery 12 can be charged by connecting a commercial AC power source (100V, 200V) to the AC connector 32 via a charging cable. A DC connector 36 is connected to the battery 12 via a DC charging device 34. Therefore, the battery 12 can be charged by connecting the DC quick charger to the DC connector 36 via the charging cable.

Further, the vehicle 10 has a control device 40, which has a vehicle ECU (Electronic Control Unit) 42, a motor ECU 44, and a battery ECU 46, and controls various operations of the vehicle.

A signal indicating a driver's request is input to the vehicle ECU 42 from an accelerator pedal, a brake pedal, a shift lever, or the like. Further, a signal indicating the state of the vehicle, such as a signal indicating the traveling speed from the vehicle speed sensor, is also input to the vehicle ECU 42. Further, the motor ECU 44 and the battery ECU 46 are connected to the vehicle ECU 42, and signals indicating the states of the motor generator 18, the battery 12, and the like are also supplied from these. Then, the vehicle ECU 42 supplies a control signal such as an output torque command to the motor ECU 44 and a charge control command to the battery ECU 46 so as to perform driving suitable for the driver's request and the state of the vehicle 10 from these signals. And so on.

The motor ECU 44 controls the operation of the motor generator 18 via the converter 14 and the inverter 16. For example, the converter 14 is controlled based on the output torque command to control the input voltage of the inverter 16 to the target voltage. Further, the inverter 16 is controlled based on the output torque command to control the output torque of the motor generator 18. The motor ECU 44 is supplied with the detection values of the sensor indicating the operating state of the motor generator 18 and the rotation angle sensor of the rotor.

The battery 12 is provided with a current sensor for detecting the battery current, a voltage sensor for detecting the battery voltage, and a temperature sensor for detecting the battery temperature. The signal detected by each sensor is supplied to the battery ECU 46. The battery ECU 46 calculates the remaining capacity (SOC) of the battery 12 based on the supplied signal, supplies the signal indicating the SOC to the vehicle ECU 42, and controls the charging of the battery 12 with reference to the battery temperature.

"Charge control"
The vehicle ECU 42 controls the charging of the battery 12 via the battery ECU 46 and the motor ECU 44. In particular, the battery ECU 46 receives the supply of the SOC, temperature, and charge / discharge current of the battery 12, and constantly calculates the deterioration index ΣD due to the high rate deterioration of the battery 12. The deterioration index ΣD is the accumulation of the deterioration (damage) D detected for each control loop Δt, and can be calculated by adopting a known method described in the prior art document or the like.

Then, the vehicle ECU 42 controls charging by the battery 12 by regeneration according to the deterioration index (current deterioration index) ΣD calculated by the battery ECU 46 and the SOC of the battery 12. This will be described with reference to FIG.

First, it is determined whether the SOC is currently equal to or lower than a predetermined value, or the deterioration index (cumulative value of damage due to high rate deterioration) ΣD is equal to or higher than a predetermined value (S11). If the determination in S11 is YES, the limit limit line ΣD1 is currently calculated from the SOC (S12). This limit limit line ΣD1 is a limit line that prohibits charging of the battery 12 due to the progress of high rate deterioration. ΣD1 is determined by the current battery temperature, SOC. If the determination in S11 is NO, it is not necessary to limit the charge, and the process for that time is terminated.

Next, it is determined whether to perform DC charging (S13). In this S13, if the DC charging device 34 for DC charging is not mounted, the result is NO. Further, if the DC charging device 34 is installed, it may be determined as YES, and if both the AC charging device 30 and the DC charging device 34 are installed, it depends on whether the previously performed charging is DC charging. You may judge. Further, the user setting may select whether the next charging is AC charging or DC charging. The DC charging is a rapid charging of a large DC current by a charging stand or the like.

If the determination in S13 is NO, the growth amount (increase amount) ΔΣD1 when a predetermined amount of AC is charged from the predetermined SOC (electricity shortage) at the temperature at the start of the previous charging is calculated (S14). In S13, if NO, it is determined that the next charging is AC charging, and this AC charging is usually charging from a commercial AC power source at home. Since ΔΣD1 can be determined based on the battery temperature and the amount of charging power, it is preferable to obtain it using a map prepared in advance. Further, it is preferable that the amount of increase ΔΣD1 of the deterioration index at the time of AC charging is determined with reference to the previous conditions. Regarding the battery temperature, it is considered that the temperature at the time of the previous charge is closer to the temperature at the time of the next charge than the current temperature during running. Therefore, in S14, the battery temperature at the time of the previous charging is adopted. Further, the history of the battery temperature at the time of charging in the past may be stored and estimated based on the history. However, if the past history is too old, it is not credible and should not be adopted. In such a case, it is also preferable to adopt a temperature in a state considered to be the same as that at the time of charging, for example, a battery temperature at the start of operation, rather than immediately after stopping.

Further, in S11, the condition of YES is a condition that the SOC is close to power shortage or the deterioration index ΣD is close to the limit and high, and in that case, the SOC is also considered to be low. Therefore, it is considered that charging after running is performed from a state of almost no electricity, and the SOC at the start of charging is regarded as no electricity. It is preferable that the AC charge is fully charged, but it is considered that an SOC that enables traveling to the facility for receiving maintenance on the battery 12 should be secured, and the SOC is set for that purpose. The difference between the SOC and the estimated SOC (for example, power shortage) when the vehicle is stopped may be set for charging, and the growth amount of the deterioration index when this charging is performed may be ΔΣD1. In particular, if a route to the home is set, the amount of SOC change due to the running can be estimated, and the changed SOC may be set as the base SOC for calculation. The power shortage is a low SOC that prohibits running (limited to an output of about 1 kW).

Next, the amount of increase ΔΣD2 in motor regeneration that may be recovered from the SOC to the time of power shortage is calculated (S15). For this, the amount of regenerative power in one normal trip may be set in advance. Further, it may be estimated from the past running history. Furthermore, if the trip has a route, the regenerative power on the route to the destination can be calculated.

Then, it is determined whether the current deterioration index ΣD is larger than the brake cooperative regeneration limiting line ΣD3 (S16). Here, the brake cooperative regeneration limit line ΣD3 is the first-stage regeneration limit line (partial regeneration limit) in the present embodiment, and the increase amount ΔΣD1 calculated in S14 from the limit limit line ΣD1 calculated in S12 and S15. It is a value obtained by subtracting the calculated increase amount ΔΣD2 (ΣD3 = ΣD1-ΔΣD1-ΔΣD2). That is, ΣD1 is a value at which charging is prohibited, but ΔΣD1 and ΔΣD2 are subtracted from this value, which is a value smaller than ΣD1. ΔΣD1 is the amount of increase in the deterioration index during charging, and ΔΣD2 is the amount of increase in future driving. When ΣD exceeds ΣD3 at present, charging is still possible when traveling to power shortage. It is in a state.

If the determination in S16 is YES, brake coordinated regeneration is prohibited (S17). Brake coordinated regeneration uses both mechanical (hydraulic) braking and regenerative braking as appropriate in order to obtain a corresponding deceleration when the brake of the vehicle 10 is depressed. Normally, regenerative braking is insufficient for deceleration. Is supplemented with a mechanical brake. If the determination in S16 is NO, there is no need to limit the regeneration, and the process ends.

Next, it is determined whether the current deterioration index ΣD is larger than the motor regeneration limiting line ΣD2 (S18). Here, the motor regeneration limit line ΣD2 is a second-stage regeneration limit line in the present embodiment, and is a value obtained by subtracting the increase amount ΔΣD1 calculated in S14 from the limit limit line ΣD1 calculated in S12 (ΣD2 = ΣD1-). ΔΣD1). That is, only ΔΣD1 is subtracted from ΣD1, which is smaller than ΣD1 but larger than ΣD3. ΔΣD1 is an increase amount of the deterioration index at the time of charging, and when ΣD exceeds ΣD2 at present, it is in a state where it can be charged on the premise that it will not be charged in running from now on.

If the determination in S18 is YES, motor regeneration is prohibited (S19). That is, by prohibiting the regeneration including the regeneration equivalent to the engine brake when the accelerator is released from the depressed state, the regeneration by the motor generator 18 is completely prohibited. If motor regeneration is prohibited, deceleration equivalent to engine braking will not be performed, so the user is notified of this by screen display, voice output, or the like.

If the determination in S18 is NO, it is determined that it is not necessary to prohibit all regeneration, and the process ends. Further, the prohibition of motor regeneration in S19 is a regeneration prohibition including the prohibition of brake coordinated regeneration. In the flowchart, the determination of S18 is performed before S16, and the determination of S16 is performed when the determination of S18 is NO. You may do so.

In the determination of S13, if YES, instead of the deterioration index increase amount ΔΣD1 when the predetermined amount of AC charging is performed, the deterioration index increase amount ΔΣD4 which increases when the predetermined amount of DC charging is performed is calculated (S20). ΔΣD4 is calculated from the current battery temperature and DC charging power, and is an increase amount of the deterioration index ΣD when DC charging is performed from a predetermined SOC (for example, power shortage).

DC charging is charging performed by a large quick charger, and is charging at a charging stand or the like. Therefore, it is difficult to estimate the state of the next charge from the state of the previous charge, and the battery temperature is set to the current temperature. The most popular type of charging power should be the default, and the user should be allowed to select the type.

The processes S21 to S25 differ only in that ΔΣD4 is used instead of ΔΣD1, and the processes S15 to S19 correspond to each process.

As described above, according to the present embodiment, the deterioration index ΣD controls the regenerative charging before reaching the limit limit line ΣD1 in which charging is prohibited. In particular, the deterioration index of the battery 12 is maintained in a rechargeable state in consideration of deterioration in the case of charging. Therefore, the battery 12 can be charged after the running is completed, and the running after that can be ensured. Further, by limiting the regeneration in two stages, it is possible to delay the prohibition period of the regenerative braking equivalent to the engine brake, and more efficient driving becomes possible.

FIG. 3 shows the states of SOC, deterioration index ΣD, input power limit Win, and brake coordinated regeneration limit during running. The thick line shows the embodiment, and the dotted line shows the comparative example. This battery system is installed in an electric vehicle, and is not charged except for regeneration while driving, and the SOC gradually decreases. On the other hand, the deterioration index ΣD of high rate deterioration due to charging gradually increases due to charging due to regeneration during traveling.

According to the present embodiment, when the deterioration index ΣD becomes ΣD3, the brake cooperative regeneration restriction is started. Therefore, the amount of charge due to regeneration is limited. Therefore, the decrease in SOC is larger than that in the comparative example. On the other hand, the amount of increase in the deterioration index ΣD is smaller than that in the comparative example.

Then, when the deterioration index ΣD becomes ΣD2, the input power limit Win shifts toward 0 and becomes 0, which prohibits charging by regeneration. Therefore, the increase of the deterioration index ΣD is suppressed.

In the comparative example, the input power limit Win is reduced when the deterioration index ΣD reaches ΣD2. As a result, regeneration is limited, but the deterioration index continues to increase, and when the limit limit line ΣD1 is reached, charging is prohibited.

10 Vehicles, 12 Batteries, 14 Converters, 16 Inverters, 18 Motor Generators, 22 Wheels, 30 AC Charging Device, 32 AC Connector, 34 DC Charging Device, 36 DC Connector, 40 Control Device, 42 Vehicle ECU, 44 Motor ECU, 46 Battery ECU.

Claims (1)

It is a battery system that calculates the deterioration index of the battery and limits the input when the calculated deterioration index exceeds the limit limit line for charging.
Calculate the amount of increase in the deterioration index ΣD when a predetermined amount of charge is performed,
Set the value obtained by subtracting the amount of increase from the limit limit line as the regeneration limit line that limits charging by regeneration during running.
Battery system.

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