JP2004271410A - Battery control device for electric car - Google Patents

Abstract

In a conventional battery internal resistance detection method, a battery current and a battery voltage are sampled at a predetermined cycle, and a slope of a solid line approximated by a least square method is used as an internal resistance. In a small-capacity battery such as that mounted in a hybrid electric vehicle or the like, the open-circuit voltage of the battery changes during data sampling, and the error in the estimated value of the internal resistance increases.
A battery remaining capacity is calculated based on at least one of information of a battery current, a voltage, and a temperature, a battery open-circuit voltage is calculated based on a battery remaining capacity, and a battery initial resistance is calculated based on a battery temperature. It has a calculation means for calculating the internal resistance of the battery from the voltage information obtained by subtracting the open-circuit voltage from the battery voltage and the current of the battery, and processing means for these.
[Selection] Fig. 2

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a battery control device, and more particularly, to a device or a method for estimating a battery deterioration state.
[0002]
[Prior art]
As a method for detecting the internal resistance of a battery in a method for estimating the remaining capacity of a battery of an electric car, as described in Japanese Patent Application Laid-Open No. 10-271695, a battery current and a battery voltage are sampled at a predetermined sampling cycle, and the horizontal axis represents the current, After plotting data representing the relationship between the battery current and the battery voltage on coordinates with the vertical axis as voltage, these plot data are approximated by the least squares method, and the slope of the approximated solid line is defined as the internal resistance. Methods have been reported.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 10-271695
[Problems to be solved by the invention]
However, such a conventional battery internal resistance detection method requires sampling data of a battery current and a battery voltage for a certain period of time in order to draw an approximate straight line by the least squares method. In the case of a small-capacity battery as mounted, there is a problem that the open-circuit voltage of the battery changes while data is being sampled.
[0005]
The approximation straight line by the least squares method is a method of estimating the internal resistance from the slope of a straight line in which the intercept of the voltage axis becomes an open voltage. The error in the estimated value of the resistance increases.
[0006]
For example, if a current is applied only to the discharge side while data is being sampled, the open-circuit voltage decreases, and the plotted voltage data is affected by the decrease in open-circuit voltage. That is, an error occurs on the side where the internal resistance is large.
[0007]
If current is applied only to the charging side while data is being sampled, the open circuit voltage increases and the plotted voltage data is affected by the increase in open circuit voltage. Is sudden, that is, an error occurs on the side where the internal resistance is large.
[0008]
As described above, if a current of only charge or discharge is applied while data is being sampled, the estimated internal resistance has a problem that an error increases to a larger value than an actual value. .
[0009]
An object of the present invention is to provide an apparatus and a method for detecting the internal resistance of a battery having a small capacity, such as a battery for a hybrid electric vehicle, with high accuracy. Further, there is provided an apparatus or a method for estimating a state of deterioration of a battery from a value of a detected internal resistance and determining a life of the battery.
[0010]
[Means for Solving the Problems]
In order to detect the internal resistance of a battery having a small capacity with high accuracy, the battery control device of the present invention calculates the remaining battery capacity based on at least one of the information of the battery current, voltage and temperature. Calculates the battery open-circuit voltage based on the remaining battery capacity, calculates the battery initial resistance based on the battery temperature, and calculates the battery internal resistance from the battery current by subtracting the open-circuit voltage from the battery voltage and the battery current. And having these processing means.
[0011]
Further, in order to determine the life of the battery, a method of determining the state of deterioration of the battery based on the initial resistance of the battery and the internal resistance of the battery or a processing means for these is provided.
[0012]
Further, the battery control device of the present invention is characterized in that the use range of the remaining capacity of the battery is determined based on the deterioration information of the battery, and the use range of the battery according to the deterioration state of the battery is limited or controlled.
[0013]
Further, the present invention is characterized in that a driver is notified of a battery replacement time when the battery is in a degraded state or in a predetermined value range.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0015]
FIG. 1 is a hardware configuration diagram of a vehicle system 20 according to an embodiment of the present invention. Engine 1 that generates torque by combustion of fuel, engine 1 coupled to engine 1 and belt 2, power generation motor 4 for generating power for charging battery 3 and generating torque for starting engine 1, crankshaft of engine 1 The clutch 7, which is an interrupter for mechanically connecting or disconnecting the torque generated from the drive shaft 5 to the drive shaft 6, the vehicle drive motor 8, which is connected to the drive shaft 6 to generate the vehicle drive torque, and converts the drive shaft torque. Transmission 10 for transmitting to driving wheels 9, power converter 11 for supplying power from battery 3 to vehicle driving motor 8 and power generation motor 4, engine control device 80 for controlling engine 1, vehicle driving motor 8 and a motor control device 81 for controlling the power generation motor 4, a clutch control device 82 for controlling the clutch 7, a remaining amount of the battery 3 and the like are detected. Vehicle control device 21 for generating a like command signal for controlling the engine and the motor based on the vehicle system and the signal from the sensor consists of a battery control device 83 is mounted.
[0016]
The vehicle control device 21, the engine control device 80, the motor control device 81, the clutch control device 82, and / or the battery control device 83 exchange data and control signals with the communication means 40 capable of bidirectional communication. The vehicle control device 21 is provided with an engine speed and an engine torque, which is an operation state of the engine 1, from the engine control device 80, and a vehicle which is an operation state of the vehicle drive motor 8 and the power generation motor 4 from the motor control device 81. The rotation speed and torque of the driving motor 8 and the rotation speed and torque of the power generation motor 4 are given, and information such as the remaining capacity of the battery and the limit value of the charge / discharge power is given or received from the battery control device 83.
[0017]
From the vehicle control device 21, an engine torque command is sent to the engine control device 80, a vehicle drive motor torque command and a power generation motor torque command and rotation speed command are sent to the motor control device 81, and the clutch 7 is connected to the clutch control device 82. Alternatively, a disconnection command or the like is given or transmitted. In this manner, various information for driving the vehicle is exchanged between the vehicle control device and the engine control device, the motor control device or the clutch control device.
[0018]
The vehicle control device 21 includes a shift position sensor 23 provided on a shift lever 22, which is a driver operation signal, an accelerator position sensor 25 provided on an accelerator pedal 24, a brake position sensor 27 provided on a brake pedal 26, and a vehicle. A vehicle speed sensor 28 and the like provided on the wheel axle side of the transmission 10 as a state signal are connected, and the engine 1, the vehicle driving motor 8 , And a means for calculating the above-mentioned command value to the power generation motor 4 and the clutch 7.
[0019]
Various sensors such as a rotation sensor 30 for detecting the number of rotations and the rotation angle of the crankshaft 5 of the engine 1 for detecting the operating state of the engine 1 for controlling the engine 1 are input to the engine control device 80. A means for detecting the number of revolutions and output torque of the engine 1 is provided, and the throttle valve opening, fuel injection amount, ignition timing, and the like are controlled based on the information and the command value from the vehicle control device 21 described above. Thus, the output of the engine 1 is controlled according to the operating state.
[0020]
The motor control device 81 detects the number of rotations and the rotation angle of each motor to control the vehicle driving motor 8 and the power generation motor 4 and to detect the state of the power generation motor 4. Various sensors such as rotation sensors 31 and 32 are input, and are provided with means for detecting the number of rotations and output torque of each motor, and a current or the like is determined based on the information and the command value from the vehicle control device 21 described above. , The output is controlled in accordance with the operating state.
[0021]
Various sensors indicating the clutch state for controlling the clutch 7 are input to the clutch control unit 82. Based on the information and the command value from the vehicle control unit 21 described above, the clutch control unit 82 7 is connected or disconnected.
[0022]
A voltage sensor 33 for detecting the voltage of the battery 3, a current sensor 34 for detecting the charge / discharge current of the battery 3, and a temperature sensor 35 for detecting the temperature of the battery 3 are input to the battery control device 83. A means for calculating the remaining capacity of the battery 3 and the limit value of the charge / discharge power is provided.
[0023]
The engine control device 80, the motor control device 81, the clutch control device 82, and the battery control device 83 include a microcomputer having a CPU, a RAM, a ROM, and the like, and perform signal processing according to a predetermined program. The engine control device 80, the motor control device 81, the clutch control device 82, and the battery control device 83 can be mounted inside the vehicle control device 21.
[0024]
The vehicle running operation state of this embodiment will be described below.
[0025]
When the vehicle is started, the clutch 7 is disengaged, the engine 1 is stopped, and the vehicle runs using only the torque generated by the vehicle drive motor 8 as a power source. When the vehicle speed becomes equal to or higher than a certain value, the power generation motor 4 is started to start the engine 1 to start the engine 1 with the clutch 7 disconnected, and the clutch 7 is connected when the start of the engine 1 is completed. After the clutch 7 is connected, the vehicle can be driven by the torque generated by the engine 1 alone by setting the generated torque of the vehicle drive motor 8 to zero. In this state, when acceleration is required, the vehicle driving motor 8 generates torque, and when deceleration is required, the vehicle driving motor 8 generates regenerative torque. When the remaining capacity of the battery 3 is reduced, the power is generated by regenerating the power generation motor 4.
[0026]
When the vehicle is decelerated, the fuel to the engine 1 is cut off while the clutch 7 is connected, and the vehicle driving motor 8 generates regenerative torque to decelerate the vehicle. When the vehicle speed falls below a certain value, the clutch 7 is disengaged.
[0027]
Further, when the remaining capacity of the battery 3 is reduced, the engine 1 is started by the power generation motor 4 when the engine 1 is stopped with the clutch 7 disconnected while the vehicle is stopped, and the like. Thereafter, the battery 3 is charged by the power generation motor 4 using the torque generated by the engine 1.
[0028]
Next, a method for estimating the internal resistance, a method for diagnosing deterioration, and a method for determining the life of the battery control device 83 and a device for realizing these methods will be described.
[0029]
FIG. 2 shows a functional block diagram of the battery control device.
[0030]
2, the battery control device 83 calculates the battery current Ib from the signal of the current sensor 34 by the current detecting means 200, calculates the battery temperature Tb from the signal of the temperature sensor 35 by the temperature detecting means 201, The battery voltage Vb is calculated from the signal by the voltage detecting means 202.
[0031]
The charge state calculation means 203 calculates the charge state SOC of the battery from the integrated value of the battery current Ib. Here, the state of charge SOC of the battery refers to a state in which the full charge capacity (Ah: ampere hour) of the battery is 100%, and when the discharge current amount of the battery matches the full charge capacity of the battery, the state of charge of the battery is 0. %.
[0032]
More specifically, in the case of a battery having a capacity of 10 Ah when fully charged, a state where the integrated value of the battery discharge current and the discharge time becomes 10 Ah is defined as a remaining capacity of 0%. That is, when the battery is discharged at 10 A for 1 hour from a fully charged state, the remaining battery capacity is set to 0%. Since the capacity of the battery is the integrated value of the current over time, in the case of the above-described battery, when the discharge current is 20 A, the battery has a remaining battery capacity of 0% when discharged for 30 minutes and discharged for 1 hour at 10 A, as in the case of discharging for 1 hour. Become.
[0033]
The open circuit voltage calculating means 204 calculates the open circuit voltage OCV of the battery from the state of charge SOC of the battery. FIG. 3 shows the relationship between the state of charge SOC of the battery and the open circuit voltage OCV of the battery. In FIG. 3, the horizontal axis indicates the state of charge SOC of the battery, and the vertical axis indicates the open circuit voltage OCV of the battery. When the state of charge SOC of the battery is 100%, the open-circuit voltage OCV of the battery becomes the highest value, and the open-circuit voltage OCV decreases as the state of charge SOC of the battery decreases. Here, the relationship between the state of charge SOC of the battery and the open-circuit voltage OCV of the battery shown in FIG. 3 is based on the battery temperature Tb, as shown in FIG. 4, as the battery temperature Tb decreases as the battery temperature Tb decreases. There is a characteristic that the amount of change in voltage OCV is reduced. For this reason, the open-circuit voltage calculating means 204 previously converts the relationship between the state of charge SOC of the battery and the battery open-circuit voltage OCV with respect to the battery temperature Tb into table data, and calculates the open-circuit voltage OCV of the battery by searching the table.
[0034]
In this embodiment, as described above, the state of charge SOC of the battery is obtained from the integrated value of the battery current Ib to derive the open voltage OCV of the battery. However, the open voltage OCV may be calculated using other methods.
[0035]
The initial resistance estimating means 205 converts the resistance value Rbini of the initial performance of the battery with respect to the battery temperature Tb into, for example, table data in advance, and obtains the resistance value Rbini by searching a table.
[0036]
The internal resistance estimating means 206 estimates the internal resistance Rb of the battery based on data obtained by subtracting the open-circuit voltage OCV of the battery from the battery current Ib and the battery voltage Vb.
[0037]
First, voltage data obtained by subtracting the open-circuit voltage OCV of the battery from the battery current Ib and the battery voltage Vb at a predetermined sampling cycle is sampled, and the data is plotted on the coordinate with the current on the horizontal axis and the voltage on the vertical axis as shown in FIG. Plot. When an approximate straight line is drawn from the plotted data by the least squares method, this straight line passes through the origin and has a slope equal to the internal resistance Rb of the battery as shown by the equation (1).
[0038]
(Equation 1)
Vdata = Rb × Idata (1)
For this reason, the internal resistance Rb of the battery is obtained from the slope of the approximate straight line.
[0039]
Since the internal resistance of the battery increases with deterioration as shown in FIG. 6, the deterioration determining means 207 estimates the deterioration state Rblife of the battery from the amount of increase of the internal resistance Rb of the battery with respect to the initial resistance value Rini of the battery. The deterioration state Rblife of the battery is obtained from the equation (2), where Rbend is a resistance value that indicates the life of the battery.
[0040]
(Equation 2)
Rblife = (Rb−Rini) ÷ (Rbend−Rbini) × 100 (2)
Here, since the increase amount (Rb-Rini) of the internal resistance of the battery changes depending on the battery temperature Tb, the resistance value Rbend which is the life of the battery with respect to the battery temperature Tb is made into table data in advance, and the resistance value Rbend is obtained by searching the table. Ask for. Also, from the equation (2), when the battery is in a new state, the internal resistance Rb of the battery matches the initial resistance value Rini of the battery, so that the battery deterioration state Rblife becomes 0%, and the battery life has expired. If it is in the state, the battery deterioration state Rblife becomes 100%. The battery deterioration state Rblife is transmitted by the communication means 40 to the vehicle control device 21 which is the host controller. When the battery deterioration state Rblife reaches a state of 100%, the use limit of the battery is reached, so the vehicle control device 21 notifies the driver of the battery replacement time using the battery replacement notification unit 50. In this embodiment, since the vehicle control device 21 manages the entire vehicle, the battery replacement notifying means 50 is operated. Means for notifying the driver may be provided.
[0041]
As shown in FIG. 7, the SOC use range calculating means 208 calculates the use upper limit SOCupper and the use lower limit SOCLower of the state of charge SOC of the battery from the battery deterioration state Rblife. The range of use of the state of charge SOC of the battery is, for example, as in a lithium ion battery, further discharged from a fully discharged state where the state of charge SOC is 0%, or further charged from a fully charged state where the state of charge SOC is 100%. If the continuation is continued, the performance of the battery may be degraded. Therefore, it is necessary to control the charge / discharge power so that the state of charge SOC of the battery falls within the range of 0% to 100%. For this reason, the calculated state of charge SOC of the battery and the upper limit SOCupper and lower limit of use SOClower of the state of charge SOC of the battery are transmitted by the communication means 40 to the vehicle controller 21 and the motor controller 81 which are upper-level controllers. The upper controller controls the charge / discharge power of the battery so that the state of charge SOC of the battery falls within the range of the upper limit SOCupper and the lower limit SOCLower of the state of charge SOC of the battery.
[0042]
Note that the above processing is not only used in the form of table data, but also in advance, the arrangement of data in the memory, the arrangement of data groups corresponding to the addresses of the memory, and the approximation taking into account the characteristics of each vehicle and battery. It is possible to substitute by an expression or the like.
[0043]
As described above, the internal resistance estimating means of the battery uses the voltage data obtained by subtracting the estimated open circuit voltage from the battery voltage detected by the sensor, so that the battery having a small capacity such as a battery for a hybrid electric vehicle is used. The internal resistance can also be estimated with high accuracy.
[0044]
In addition, since the internal resistance of the battery can be estimated with high accuracy, the life of the battery can also be estimated with high accuracy, and the driver can be properly notified of the battery replacement time.
[0045]
Furthermore, since the range of use of the battery can be appropriately limited according to the life of the battery, power control that suppresses deterioration of the battery can be performed without overcharging or overdischarging the battery.
[0046]
【The invention's effect】
According to the present invention, it is possible to provide a device and a method for detecting the internal resistance of a battery having a small capacity, such as a battery for a hybrid electric vehicle, with high accuracy. Further, it is possible to provide a device or a method for estimating the state of deterioration of the battery from the detected value of the internal resistance and determining the life of the battery.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a vehicle system according to an embodiment of the present invention.
FIG. 2 is a block diagram of a battery control device according to an embodiment of the present invention.
FIG. 3 shows an open-circuit voltage characteristic with respect to a charged state of a battery, which constitutes an embodiment of the present invention.
FIG. 4 shows the temperature dependence of the open-circuit voltage characteristics of a battery according to an embodiment of the present invention.
FIG. 5 is a diagram showing estimated internal resistance coordinates of a battery according to an embodiment of the present invention.
FIG. 6 shows an internal resistance characteristic with respect to battery deterioration, which constitutes an embodiment of the present invention.
FIG. 7 shows a use range of a state of charge with respect to battery deterioration, which constitutes an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Belt, 3 ... Battery, 4 ... Power generation motor, 5 ... Crankshaft, 6 ... Drive shaft, 7 ... Clutch, 8 ... Vehicle drive motor, 9 ... Drive wheel,
DESCRIPTION OF SYMBOLS 10 ... Transmission, 11 ... Power converter, 20 ... Vehicle system, 21 ... Vehicle control device, 22 ... Shift lever, 23 ... Shift position sensor, 24 ... Accelerator pedal, 25 ... Accelerator position sensor, 26 ... Brake pedal, 27 ... Brake position sensor, 28 ... Vehicle speed sensor, 30, 31, 32 ... Rotation sensor, 33 ... Voltage sensor, 34 ... Current sensor, 35 ... Temperature sensor, 40 ... Communication means, 50 ... Battery replacement notification means, 80 ... Engine control Device, 81: motor control device, 82: clutch control device, 83: battery control device.

Claims (4)

Current detection means for detecting battery current;
Voltage detection means for detecting a battery voltage;
Temperature detecting means for detecting a battery temperature;
Remaining capacity calculating means for calculating a remaining capacity of the battery based on at least one of information of current, voltage and temperature of the battery;
Open-circuit voltage calculating means for calculating a battery open-circuit voltage based on the remaining capacity of the battery;
Initial resistance calculating means for calculating a battery initial resistance based on the temperature of the battery,
A battery control device comprising: voltage information obtained by subtracting the open-circuit voltage obtained by the calculation from the battery voltage; and internal resistance calculating means for calculating the internal resistance of the battery from the current of the battery. The battery control device according to claim 1,
A battery control device comprising: a deterioration determining unit that compares an initial resistance of the battery with an internal resistance of the battery and determines a state of deterioration of the battery. The battery control device according to claim 2,
A battery control apparatus comprising: a remaining capacity use range determining unit that determines a use range of a remaining capacity of a battery based on deterioration information indicating a deterioration state of the battery obtained by the deterioration determination unit. The battery control device according to claim 2 or 3,
A battery control device comprising: a battery replacement time notification unit that notifies a driver of a battery replacement time when the battery deterioration state becomes equal to or more than a predetermined value.

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