JP2002330552A - Battery capacity control device and battery capacity control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately maintain a battery capacity at the level of a desired target capacity relating to a battery capacity control device and a battery capacity control method. SOLUTION: A battery 10 for charging and discharging between M/G 14 and the battery via an inverter 12 is mounted. When the target capacity SOC0 of the battery 10 is set, a target battery voltage V0 corresponding to the target capacity SOC0 is calculated by referring a prescribed map. Then, the target battery voltage V0 is compared with a battery voltage V detected by a voltage sensor 20; a duty is calculated so that the battery voltage V approximates to the target battery voltage V0; and the inverter 12 is driven by the calculated duty. In this case, the battery 10 charges and discharges according to the duty of the inverter 12, and the battery voltage V is made to change to the target battery voltage V0 corresponding the target capacity SOC0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery capacity control device and a battery capacity control method, and more particularly, to a battery capacity control device and a battery for controlling the capacity of a battery for charging and discharging with an electric load to a target capacity. It relates to a capacity control method.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-2000-217
As disclosed in Japanese Patent Publication No. 206, an apparatus for controlling charging and discharging of a vehicle-mounted battery is known. This device normally charges the battery to a full charge state, and controls the battery to a target capacity of about 90% that does not reach the full charge when relatively large power regeneration is expected to be performed by the vehicle. For this reason, according to the above-described conventional device, when relatively large power is regenerated, the remaining power for storing the regenerative power remains in the battery, so that the regenerative power generated by the vehicle can be effectively collected in the battery. Becomes

[0003]

In the above-described conventional apparatus, as a method of controlling the capacity of the battery to the target capacity, the current capacity of the battery and the target capacity are compared in magnitude and based on the comparison result. The battery is charged or discharged such that the battery capacity matches the target capacity. However, in such a method, it is necessary to always accurately detect the capacity of the battery in order to control the capacity of the battery to the target capacity, but it is difficult to accurately detect the capacity in the process of repeating charging and discharging of the battery. is there. For this reason, in the above-mentioned conventional device, there is a possibility that the capacity of the battery cannot be accurately maintained at a desired target capacity.

[0004] The present invention has been made in view of the above points, and an object of the present invention is to provide a battery capacity control device and a battery capacity control method capable of accurately maintaining a battery capacity at a desired target capacity. Aim.

[0005]

The above object is achieved by the present invention.
A battery capacity control device that controls a capacity of a battery that performs charging and discharging with a predetermined electric load to a target capacity, wherein the battery is charged and discharged at a battery open voltage corresponding to the target capacity. Is achieved by a battery capacity control device comprising a capacity control means for controlling the capacity of the battery to the target capacity.

Further, the above object is to provide a battery capacity control method for controlling a capacity of a battery for charging / discharging with a predetermined electric load to a target capacity. The battery capacity is controlled at the target capacity by charging / discharging the battery at a battery open voltage corresponding to the above.

According to the first and fifth aspects of the present invention, the battery is controlled to the target capacity by charging and discharging at a battery open voltage corresponding to the target capacity. Generally, in a battery, there is a correlation between the battery open-circuit voltage and the capacity. Therefore, the capacity of the battery approaches the target capacity by repeating charging and discharging at the battery open voltage. For this reason, according to the present invention, the capacity of the battery can be accurately maintained at the desired target capacity.

In this case, as described in claim 2, in the battery capacity control device according to claim 1, the battery corresponding to the target capacity of the battery is determined by using a map indicating a relationship between the target capacity and the battery open-circuit voltage. Target open-circuit voltage calculating means for calculating an open-circuit voltage, wherein the capacity control means performs charging and discharging of the battery with the battery open-circuit voltage calculated by the target open-circuit voltage calculating means, thereby reducing the capacity of the battery. The target capacity may be controlled.

[0009] The relationship between the battery capacity and the battery open-circuit voltage changes according to the temperature of the battery.

Therefore, as set forth in claim 3, in the battery capacity control device according to claim 2, the battery open-circuit voltage calculating means changes the relationship between the target capacity and the battery open-circuit voltage according to the battery temperature. If the battery open-circuit voltage corresponding to the target capacity of the battery is calculated using the map, the capacity of the battery can be more accurately controlled to the target capacity.

In a situation where the actual capacity of the battery and the target capacity are largely separated from each other, it is assumed that the battery is charged / discharged at a voltage corresponding to the battery open voltage corresponding to the target capacity. Controlling the capacity of the battery to its target capacity can take a lot of time.

Accordingly, in the battery capacity control device according to any one of claims 1 to 3, the capacity control means may control the capacity of the battery to a target capacity. If the difference between the battery capacity and the target capacity is equal to or greater than a predetermined value, if the battery is charged or discharged at a voltage higher or lower than the battery open voltage corresponding to the target capacity, The capacity of the battery can reach the target capacity in a relatively short time.

[0013]

FIG. 1 is a block diagram showing a vehicle system provided with a battery capacity control device according to an embodiment of the present invention. The system of this embodiment includes a battery 10 functioning as a vehicle power supply. The battery 10 includes a plurality of battery cells connected in series, and is, for example, a nickel-metal hydride battery having an output voltage of about 36V.

A motor generator (hereinafter, referred to as M / G) 14 is connected to the battery 10 via an inverter 12. The inverter 14 has a built-in motor power transistor, and converts the DC power of the battery 10 into the AC power of the M / G 14 according to the switching operation of the motor power transistor. M / G14
When the power transistor for the motor is in the ON state, the power is supplied from the battery 10 to drive the battery with the battery 10 as a power source and generate a predetermined torque. That is, when the motor power transistor of the inverter 12 is in the ON state, the battery 10
Power is supplied to G14.

Further, the M / G 14 functions as a generator by rotating the engine similarly to a normal alternator, and also functions as a generator for converting kinetic energy of the vehicle into electric energy during regenerative braking of the vehicle. The inverter 12 also has a built-in power transistor for a generator, and converts the AC power generated by the M / G 14 into the DC power of the battery 10 according to the switching operation of the power transistor for the generator. That is, the battery 10 is in a state where the generator power transistor of the inverter 12 is in the ON state.
M / M by rotation drive of the engine or regenerative braking of the vehicle
The power is supplied and charged by the power generation by the G14.

The inverter 12 is connected to an electronic control unit (hereinafter referred to as an ECU) 16 constituted by a microcomputer. When the ECU 16 determines that power supply from the battery 10 to the M / G 14 is necessary, the ECU 16 controls the inverter 12 so that the battery 10 is discharged.
A command signal is supplied to the motor power transistor. When it is determined that power supply from the M / G 14 to the battery 10 is necessary, a command signal is supplied to the power transistor for generator so that the battery 10 is charged.

A voltage sensor 20 disposed between the positive and negative terminals of the battery 10 is connected to the ECU 16. Voltage sensor 20 outputs a signal corresponding to a voltage between terminals of battery 10 (hereinafter, referred to as battery voltage V). The output signal of the voltage sensor 20 is supplied to the ECU 16. EC
U16 detects the battery voltage V of the battery 10 based on the output signal of the voltage sensor 20.

A current sensor 22 disposed between the battery 10 and the inverter 12 is connected to the ECU 16. The current sensor 22 detects a current flowing between the battery 10 and the inverter 12 (hereinafter referred to as a battery current I
) Is output. The output signal of the current sensor 22 is supplied to the ECU 16. The ECU 16
The battery current I flowing through the battery 10 is detected based on the output signal of the current sensor 22.

The ECU 16 is further connected to a temperature sensor 24 built in the battery 10. Temperature sensor 24 outputs a signal corresponding to the internal temperature of battery 10 (hereinafter, referred to as battery temperature T). The output signal of the temperature sensor 24 is supplied to the ECU 16. ECU16
Is based on the output signal of the temperature sensor 24.
Is detected.

In the present embodiment, the ECU 16 first
When the M / G 14 is not loaded, the state of charge (hereinafter referred to as battery capacity SOC) is detected from the open voltage V of the battery 10. And M / G1
After the start of the driving of the battery 4, the battery capacity SOC is calculated from the integrated amount of the battery current I with reference to the battery capacity SOC based on the open voltage V.

By the way, if the capacity SOC of the battery 10 is controlled to be 100%, which is a fully charged state, as the target capacity, there is a possibility that when the vehicle is braked, the braking energy cannot be recovered to the battery 10 as regenerative energy. Will be higher. If the battery 10 cannot recover the braking energy as regenerative energy, the braking energy has to be mechanically consumed as heat energy, so that the energy efficiency deteriorates. Therefore, it is not appropriate that the target capacity of the battery 10 is always 100%, and the target capacity of the battery 10 is considered in consideration of the charge / discharge balance so that most of the braking energy of the vehicle can be recovered as regenerative energy during braking. It is appropriate to set Less than,
The set target capacity is referred to as “SOC0”.

Here, as a method of controlling the capacity SOC of the battery 10 to the set target capacity SOC0, EC
Battery capacity SOC and target capacity SOC detected by U16
It is conceivable to charge / discharge the battery 10 by controlling the inverter 12 on / off so that the battery capacity SOC matches the target capacity SOC0 based on the comparison result. However, with such an approach,
The ECU 16 must always accurately detect the battery capacity SOC. However, since it is difficult to accurately detect the battery capacity SOC in the course of repeated charging and discharging of the battery 10, the actual capacity SOC of the battery 10 is determined as desired. There is a possibility that the target capacity SOC0 may be maintained while being deviated.
That is, there is a possibility that the actual capacity SOC of the battery 10 cannot be accurately maintained at the desired target capacity SOC0. Therefore, in controlling the actual capacity SOC of the battery 10 to the target capacity SOC0, the method of comparing the battery capacity SOC detected by the ECU 16 with the target capacity SOC0 is not appropriate.

FIG. 2 shows the EC in the system of the present embodiment.
4 shows a map used by U16 to control the capacity of battery 10 to target capacity SOC0. In FIG. 2, the case where the battery temperature T is low (for example, −25 ° C.) is indicated by a dashed line, and the case where the battery temperature T is high (for example, + 60 ° C.).
° C) is indicated by a broken line, and the case where the battery temperature T is medium (for example, + 20 ° C) is indicated by a solid line.

Generally, the actual capacity of the battery 10 is correlated with the battery open circuit voltage. Therefore, the system according to the present embodiment sets the capacity SOC of the battery 10 to the target capacity SO
When controlling to C0, the battery 10 is charged and discharged at a battery open-circuit voltage (hereinafter, referred to as target battery voltage V0) corresponding to the target capacity SOC0, instead of using the battery capacity SOC detected by the ECU 16. That is, in the present embodiment, the ECU 16
A map indicating the relationship between the target capacity SOC0 and the target battery voltage V0 is stored in advance, and the target battery voltage V0 corresponding to the set target capacity SOC0 is calculated. Then, the calculated target battery voltage V0
Is driven at a duty ratio that realizes the following.

Note that the target battery voltage V0 and the target capacity SO
The correlation with C0 differs depending on the battery temperature T. Therefore, as shown in FIG. 2, the ECU 16 sets a map in which the relationship between the target battery voltage V0 and the target capacity SOC0 changes according to the battery temperature T, that is, the target battery voltage V0 and the target capacity set for each battery temperature T. A map indicating a relationship with SOC0 is stored, and a corresponding target battery voltage V0 is calculated by referring to a map as shown in FIG. 2 based on the target capacity SOC0 and the battery temperature T. At this time, if the target capacity SOC0 or the battery temperature T has a value between the values shown in FIG. 2, the corresponding target battery voltage V0 is calculated by linear interpolation. Then, ECU 16 drives inverter 12 at a duty ratio at which the calculated target battery voltage V0 is realized.

FIG. 3 shows an inverter 12 in this embodiment.
Shows the time change of the actual capacity SOC of the battery 10 when driven at the duty ratio at which the target battery voltage V0 is realized. In FIG. 3, the target capacity SOC0 is shown by a broken line, for example, as 75%, and the duty of the inverter 12 is set under a situation where the actual capacity SOC of the battery 10 is larger than the target capacity SOC0 (SOC = 80%). The case where the driving is performed is indicated by a solid line, under a situation where the actual capacity SOC of the battery 10 is smaller than the target capacity SOC0 (S
The case where the inverter 12 is duty-driven at (OC = 70%) is indicated by alternate long and short dash lines.

When the actual capacity SOC of the battery 10 deviates from the target capacity SOC0, the inverter 12 is driven at a duty ratio at which the target battery voltage V0 corresponding to the target capacity SOC0 is realized as described above. ,
The battery 10 repeats the charge state and the charge stop state at a duty ratio corresponding to the target battery voltage V0, or repeats the discharge state and the discharge stop state.
In this case, after the duty driving of the inverter 12 is started, the voltage V of the battery 10 changes toward the target battery voltage V0 corresponding to the target capacity SOC0, that is, the actual capacity SOC of the battery 10 decreases as shown in FIG. As shown in the figure, the value changes toward the target capacity SOC0. Therefore, according to the method of the present embodiment, the capacity SO of the battery 10 is
C can be accurately maintained at the desired target capacity SOC0.

FIG. 4 is a flowchart showing an example of a control routine executed by the ECU 16 in this embodiment to realize the above-described functions. The routine shown in FIG. 4 is a routine started every predetermined time. When the routine shown in FIG. 4 is started, first, the process of step 100 is executed.

In step 100, a process for setting the target capacity SOC0 based on various states of the vehicle is executed.
In the present embodiment, the target capacity SOC0 is set to, for example, basically 75%, and M / G1
4 is changed according to the load state and the like. Step 1
In 02, a process of reading the battery temperature T based on the output signal of the temperature sensor 24 is executed.

In step 104, it is determined whether or not the difference between the battery capacity SOC detected in the processing in step 104 and the target capacity SOC0 set in step 100 is equal to or greater than a predetermined value α. Note that the predetermined value α
Is the target battery voltage V0 corresponding to the target capacity SOC0.
When the battery 10 is charged and discharged at
This is the minimum capacitance value difference at which it can be determined that it takes a long time for the OC to reach its target capacitance SOC0.

As a result, if | SOC−SOC | ≧ α is not established, the battery capacity SOC becomes equal to the target capacity SOC.
It can be determined that it does not take much time to reach zero. Therefore, in step 104, | SOC-S
If it is determined that OC0 | ≧ α is not satisfied, the process of step 106 is executed next. On the other hand, | SOC-S
If OC0 | ≧ α holds, it can be determined that it takes a long time for the battery capacity SOC to reach the target capacity SOC0. In this case, it is appropriate to shorten the time. Therefore, when it is determined that | SOC-SOC | ≧ α is satisfied, the process of step 108 is executed next.

In step 106, the above step 100
The process of calculating the target battery voltage V0 of the battery 10 is executed by referring to the map shown in FIG. 2 based on the target capacity SOC0 and the battery temperature T read in Steps 102 and 102.

In Step 108, the above Step 100
2, the target battery voltage V0 of the battery 10 is calculated by referring to the map shown in FIG. 2 based on the target capacity SOC0 and the battery temperature T read in 102. A process of setting a value obtained by adding or subtracting the predetermined value β to a new target battery voltage V0 is executed. Whether the predetermined value β is added or subtracted depends on the battery capacity SOC and the target capacity SOC0.
Is determined by which is greater, and specifically,
The predetermined value β is subtracted when the battery capacity SOC is larger than the target capacity SOC0, and is added when the battery capacity SOC is smaller than the target capacity SOC0. When the processing of step 106 or 108 is completed, next step 1
Ten processes are executed.

In step 110, the above-mentioned step 106
Alternatively, a process of comparing the target battery voltage V0 calculated in 108 with the actual battery voltage V detected using the voltage sensor 20 and calculating the duty ratio so that the battery voltage V approaches the target battery voltage V0 is executed. Is done.

The duty ratio is set to an arbitrary initial value (for example, a value corresponding to the maximum power generation state) at the start of control, and the duty ratio between the target battery voltage V0 and the actual battery voltage V detected by the voltage sensor 20 is set. The duty ratio may be increased or decreased by an amount corresponding to the deviation according to the deviation. At this time, when it is determined that the fluctuation amount of the battery voltage V increases with the increase / decrease amount of the duty ratio, regardless of the deviation between the target battery voltage V0 and the actual battery voltage V detected by the voltage sensor 20, It is preferable that the duty ratio is gradually changed by setting a constant duty ratio increase / decrease amount.

In step 112, the above-mentioned step 110
A process for driving the inverter 12 with the duty ratio calculated in the step is performed. After the process of step 112 is performed, the battery 10 performs charge / discharge with the M / G 14 according to the duty drive of the inverter 12, and the charge / discharge control of the battery 10 is performed. This step 112
Is completed, the current routine ends.

According to the routine shown in FIG. 4, the target battery voltage V0 corresponding to the target capacity SOC0 is calculated,
Inverter 12 can be driven at a duty ratio at which target battery voltage V0 is realized. Inverter 1
2 is driven at such a duty ratio, the battery 10
Of the actual capacity SOC changes toward the target capacity SOC0. Therefore, according to the battery capacity control device of the present embodiment, the capacity of the battery 10 is reduced to the desired target capacity SO.
C0 can be accurately maintained. For this reason, in the present embodiment, the capacity of the battery 10 is equal to the target capacity SOC.
Since the deviation from zero is avoided, the charging and discharging of the battery 10 can be performed effectively, and the energy efficiency can be improved.

In this embodiment, the ECU 16 stores a map in which the relationship between the target capacity SOC0 and the target battery voltage V0 is changed according to the battery temperature T.
The target battery voltage V0 is set based on the target capacity SOC0 and the battery temperature T. Therefore, according to the present embodiment,
Even when the battery temperature T fluctuates, the target capacity S
The target battery voltage V0 corresponding to OC0 can be calculated, and thereby, the capacity of the battery 10 can be accurately maintained at the desired target capacity SOC0.

In the routine shown in FIG. 4, when the battery capacity SOC is larger than the target capacity SOC0 by a predetermined value α or more, a value obtained by subtracting a predetermined value β from the target battery voltage V0 corresponding to the target capacity SOC0. Is the new target battery voltage V0, and the battery capacity S
When OC is smaller than target capacity SOC0 by a predetermined value α or more, a value obtained by adding predetermined value β from target battery voltage V0 can be set as new target battery voltage V0.

In such a configuration, the duty ratio of the inverter 12 is reduced or increased by the amount of the added or subtracted voltage as compared with the normal operation. Therefore, the battery 10 is easily charged and discharged, and the capacity of the battery 10 quickly approaches the target capacity SOC0. In the present embodiment, the battery 1
After the capacity of 0 approaches the target capacity SOC0, the duty ratio of the inverter 12 is changed to the duty ratio corresponding to the target battery voltage V0 as usual. Therefore, according to the battery capacity control device of the present embodiment, it is possible to cause the capacity of the battery 10 to reach the target capacity SOC0 in a relatively short time even in a situation where the battery capacity SOC is greatly separated from the target capacity SOC0. Becomes

In the present embodiment, when the target capacity SOC0 is changed in the course of changing the capacity of the battery 10 toward the target capacity SOC0, the ECU 16 changes the target battery voltage V0 to the target capacity SOC after the change. The value is changed to a value corresponding to SOC0, and the duty ratio of inverter 12 is changed to a value at which target battery voltage V0 after the change is realized. Therefore, according to the battery capacity control device of the present embodiment, even when the target capacity SOC0 is changed, the capacity of the battery 10 can be relatively easily changed to the target capacity SO after the change.
It is possible to control to C0.

In the above embodiment, M / G14
In the "predetermined electrical load" described in the claims,
The battery 10 corresponds to a “battery” described in the claims, and the ECU 16
By executing the processing of steps 106 to 112 in the routine shown in FIG. 4, the “capacity control unit” described in the claims can use the map shown in FIG.
Target battery voltage V0 corresponding to target capacity SOC0 of 0
Thus, the “target open-circuit voltage calculating means” described in the claims is realized.

In the above embodiment, the battery temperature T is measured by the temperature sensor 24 built in the battery 10.
However, a temperature sensor disposed around the battery 10 may be used.
In the above embodiment, the battery 10 is applied to a system using a nickel-metal hydride battery. However, the present invention can be applied to a system using another storage battery such as a lead battery instead of the nickel hydride battery. is there.

In the above embodiment, the target battery voltage V0 is calculated based on the target capacity SOC0 and the battery temperature T. At this time, these parameters are set to values between the values shown in FIG. In such a case, the linear interpolation is performed. However, the interpolation is not limited to the linear interpolation, and may be performed using another method. Further, in the above-described embodiment, the corresponding battery voltage V is calculated based on the battery temperature T together with the target capacity SOC0. , The corresponding battery voltage V may be calculated.

As described above, according to the first, second and fifth aspects of the present invention, the capacity of the battery can be accurately maintained at a desired target capacity.

According to the third aspect of the present invention, even when the battery temperature fluctuates, the battery capacity can be accurately maintained at a desired target capacity.

According to the present invention, when the battery capacity and the target capacity are largely separated from each other,
The battery capacity can reach the desired target capacity in a relatively short time.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a system including a battery capacity control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a map used when controlling the capacity of a battery to a target capacity in the system of the present embodiment.

FIG. 3 is a diagram showing a change over time of a battery capacity in the present embodiment.

FIG. 4 is a flowchart illustrating an example of a control routine executed to control a battery capacity to a target capacity in the present embodiment.

[Explanation of symbols]

 Reference Signs List 10 battery 12 inverter 14 motor generator (M / G) 16 electronic control unit (ECU) 20 voltage sensor 22 current sensor 24 temperature sensor SOC battery capacity

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5G003 AA07 BA01 CA01 CA12 CB01 CB10 GB06 5H030 AA01 AS08 BB01 FF22 FF43 5H115 PC06 PG04 PI16 PO02 PO06 PO10 PO17 PU23 PU25 PV09 TO05 TO13 TU04 TU11

Claims (5)

[Claims] 1. A battery capacity control device for controlling a capacity of a battery that charges and discharges with a predetermined electric load to a target capacity, wherein the battery is charged and discharged at a battery open voltage corresponding to the target capacity. And a capacity control unit for controlling the capacity of the battery to the target capacity. 2. The battery capacity control device according to claim 1, wherein a battery open-circuit voltage corresponding to the target capacity of the battery is calculated using a map indicating a relationship between the target capacity and the battery open-circuit voltage. Means, wherein the capacity control means controls the capacity of the battery to the target capacity by charging and discharging the battery at the battery open voltage calculated by the target open voltage calculation means. Battery capacity control device. 3. The battery capacity control device according to claim 2, wherein the battery open-circuit voltage calculating means uses the map in which the relationship between the target capacity and the battery open-circuit voltage changes according to the battery temperature. A battery capacity control device for calculating a battery open voltage corresponding to a target capacity. 4. The battery capacity control device according to claim 1, wherein the capacity control unit controls the capacity of the battery and the target capacity when controlling the capacity of the battery to the target capacity. The battery capacity control device is characterized in that when the difference is equal to or more than a predetermined value, the battery is charged / discharged at a voltage higher or lower than a battery open voltage corresponding to the target capacity. 5. A battery capacity control method for controlling a capacity of a battery that charges and discharges with a predetermined electric load to a target capacity, wherein the battery is charged and discharged at a battery open voltage corresponding to the target capacity. And thereby controlling the capacity of the battery to the target capacity.