JP3750567B2 - Apparatus and method for calculating output deterioration of secondary battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an output deterioration calculation device and an output deterioration calculation method for a secondary battery that can be charged and discharged.
[0002]
[Prior art]
Conventionally, as an output deterioration calculation method for a secondary battery mounted on an electric vehicle including a hybrid electric vehicle, there is a method described in Japanese Patent Application Laid-Open No. 2000-261901. In this conventional method, when the motor is driven using the electric power stored in the secondary battery, that is, when the secondary battery is discharged, the current and voltage are detected, and the voltage value and the current value are sampled at a plurality of points. A regression line indicating the discharge characteristics of the battery is obtained. The degradation coefficient of the secondary battery is obtained by calculating the internal resistance of the secondary battery at the time of battery deterioration calculation from the obtained regression line and calculating the ratio with the internal resistance in the initial state.
[0003]
[Problems to be solved by the invention]
However, in the conventional secondary battery deterioration calculation method, it is possible to detect, as a sampling point, a superposition of an error caused by a current sensor when detecting a current and an error caused by a voltage sensor when detecting a voltage. There is sex. In this case, since the internal resistance calculated from the regression line has a value different from the actual internal resistance, there is a problem that an accurate deterioration coefficient cannot be obtained.
[0004]
An object of the present invention is to provide an output deterioration calculation device and an output deterioration calculation method for a secondary battery that can accurately calculate the deterioration of the secondary battery.
[0005]
[Means for Solving the Problems]
The present invention will be described with reference to FIG. 1 showing an embodiment.
(1) The present invention is, in the output deterioration calculation method of the secondary battery to calculate a battery output deterioration from the output ratio between the deterioration time of cell output and the initial cell output of the rechargeable battery 15, the open-circuit voltage and the secondary of the secondary battery 15 Only the voltage of the secondary battery 15 when the secondary battery 15 is charged with constant power is detected, and the detected open-circuit voltage of the secondary battery 15 and the voltage of the secondary battery 15 when charged with constant power Based on the constant power, the internal resistance Rc1 of the secondary battery is obtained, and the ratio between the obtained internal resistance Rc1 of the secondary battery 15 and the internal resistance Ri0 in the initial state of the secondary battery 15 is calculated, The output ratio is calculated.
(2) The invention of claim 2 is a secondary battery output deterioration calculation device for calculating battery output deterioration from an output ratio between the battery output at the time of deterioration of the secondary battery 15 and the initial battery output. The voltage detection means 19 for detecting the voltage, the control means 16 for controlling the secondary battery 15 to be charged with a constant power, the open voltage of the secondary battery 15 detected by the voltage detection means 19, and the control means 16 Based on the voltage of the secondary battery 15 when being charged with a constant power and the constant power controlled by the control means 16, the calculation means 16 for calculating the output ratio , Based on the open voltage of the secondary battery detected by the voltage detection means 19, the internal resistance Ri0 of the initial state of the secondary battery 15 is calculated, and the secondary battery is charged with the open voltage and constant power. 1 Voltage, and calculates the internal resistance Rc1 of the rechargeable battery 15 on the basis of the constant power, by calculating the calculated ratio of the two internal resistors, characterized by calculating an output ratio.
(3) The invention according to claim 3 is the secondary battery output deterioration calculating device according to claim 2, wherein the calculating means 16 includes the voltage V1 and the open circuit voltage V0 of the secondary battery 15 when being charged with a constant power. The internal resistance Rc1 of the secondary battery 15 is calculated by dividing a value obtained by multiplying the difference by the voltage V1 by a constant power P0 .
(4) In the secondary battery output deterioration calculating device according to claim 2 or 3, the secondary battery 15 is a secondary battery 15 for supplying electric power to an electric motor mounted on a hybrid electric vehicle. .
[0006]
In the section of means for solving the above problems, the present invention is associated with FIG. 1 of the embodiment for easy understanding. However, the present invention is not limited to the embodiment. .
[0007]
【The invention's effect】
The present invention has the following effects.
(1) According to the invention of claim 1, since only the voltage of the secondary battery is detected and the output deterioration calculation is performed, there is no need to provide a current sensor. Therefore, since it is not affected by the detection error when the current is detected by the current sensor, the accuracy of the deterioration calculation can be improved as compared with the method of detecting the current and performing the output deterioration calculation.
(2) According to the invention of claim 2, since the output deterioration calculation is performed based on the open voltage of the secondary battery, the voltage when charging the secondary battery with constant power, and the constant power, The calculation accuracy can be improved as compared with the method of sampling the voltage value and the current value and obtaining the regression line. Further, it is not necessary to consider the influence of calculation error at high load.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing a configuration of an embodiment in which a secondary battery output deterioration computing device according to the present invention is applied to a hybrid electric vehicle. In the figure, a thick solid line indicates a transmission path of mechanical force, and a thick broken line indicates a power line. A thin solid line indicates a control line, and a double line indicates a hydraulic system. The power train of this vehicle includes a motor 1, an engine 2, a clutch 3, a motor 4, a continuously variable transmission 5, a speed reducer 6, a differential device 7, and drive wheels 8. The output shaft of the motor 1, the output shaft of the engine 2, and the input shaft of the clutch 3 are connected to each other. The output shaft of the clutch 3, the output shaft of the motor 4, and the input shaft of the continuously variable transmission 5 are connected to each other.
[0009]
When the clutch 3 is engaged, both the engine 2 and the motor 4 or only the engine 2 serves as a vehicle propulsion source. When the clutch 3 is released, only the motor 4 serves as a vehicle propulsion source. The driving force of the engine 2 and / or the motor 4 is transmitted to the drive wheels 8 via the continuously variable transmission 5, the speed reducer 6, and the differential device 7. An oil pump (not shown) of the hydraulic device 9 is driven by the motor 10 and supplies pressure oil to the continuously variable transmission 5.
[0010]
The motors 1, 4 and 10 are AC machines such as a three-phase synchronous motor or a three-phase induction motor. The motor 1 is mainly used for engine starting and power generation, and the motor 4 is mainly used for vehicle propulsion and braking. The motor 10 is for driving the oil pump of the hydraulic device 9. The motors 1, 4, and 10 are not limited to AC machines, and DC motors can also be used. In addition, when the clutch 3 is engaged, the motor 1 can be used for vehicle propulsion and braking, and the motor 4 can be used for engine starting and power generation.
[0011]
The clutch 3 is a powder clutch and can adjust the transmission torque. The clutch 3 may be a dry single plate clutch or a wet multi-plate clutch. The continuously variable transmission 5 is a continuously variable transmission such as a belt type or a toroidal type, and the gear ratio can be adjusted steplessly.
[0012]
Inverters 11, 12, and 13 drive and control motors 1, 4, and 10, respectively. When a DC motor is used for the motors 1, 4 and 10, a DC / DC converter is used instead of the inverter. The inverters 11 to 13 are connected to the main battery 15 via a common DC link 14, convert the DC charging power of the main battery 15 into AC power, and supply the AC power to the motors 1, 4 and 10. Further, the AC power generated by the motors 1 and 4 is converted into DC power to charge the main battery 15. In addition, since the inverters 11 to 13 are connected to each other via the DC link 14, the electric power generated by the motor during the regenerative operation can be directly supplied to the motor during the power running operation without going through the main battery 15. it can. As the main battery 15, various batteries such as a lithium-ion battery, a nickel-hydrogen battery, and a lead battery, and so-called power capacitors such as an electric double layer capacitor can be used.
[0013]
The current sensor 18 detects a current during charging / discharging of the main battery 15, and the voltage sensor 19 detects a terminal voltage of the main battery 15. As will be described later, the current sensor 18 may not be provided. The vehicle speed sensor 20 detects the vehicle speed of the vehicle. The detection value of each sensor is input to the controller 16. The controller 16 includes a microcomputer and its peripheral components, various actuators, etc., and the rotational speed and output torque of the engine 2, the transmission torque of the clutch 3, the rotational speed and output torque of the motors 1, 4 and 10, and the continuously variable transmission 5. To control the gear ratio.
[0014]
2 and 3 are flowcharts showing a control procedure of an embodiment of the output deterioration calculating device for a secondary battery according to the present invention. The control starting from step S1 is performed by the controller 16 when the vehicle is started. Hereinafter, description will be made in order from step S1. In step S1, it is determined whether or not an ignition switch (IGN-SW) (not shown) is turned on. If it is determined that it is on, the process proceeds to step S2. If it is determined that it is not turned on, it waits in step S1 until it is turned on.
[0015]
In step S2, the vehicle speed is detected by the vehicle speed sensor 20. The detected vehicle speed is input to the controller 16. In the next step S3, it is determined whether or not the vehicle is stopped. This determination is made based on the vehicle speed detected in step S2. When the vehicle is not stopped, that is, while the vehicle is running, there is a high possibility that the battery 15 is being charged and discharged, and the open voltage of the battery 15 cannot be detected. Accordingly, when it is determined that the vehicle is not stopped (running), the present control is terminated, and when it is determined that the vehicle is stopped, the process proceeds to step S4.
[0016]
In step S4, it is determined whether or not the motor 1 that performs power generation (hereinafter referred to as the power generation motor 1) is operating. The controller 16 transmits a control command signal for the generator motor 1 to the inverter 11 to control the generator motor 1. That is, based on the control command signal of the generator motor 1 transmitted from the controller 16, it is determined whether or not the generator motor 1 is operating. If the power generation motor 1 is operating, the battery 15 is being charged. Therefore, it is not necessary to perform a battery deterioration calculation until the power generation operation of the power generation motor 1 is stopped. Even when the operation of the generator motor 1 is stopped and the battery deterioration calculation is performed, in order to detect the voltage of the battery 15, it is necessary to wait until the voltage is stabilized. If it is determined that the generator motor 1 is operating in consideration of these matters, the present control is terminated without performing a battery deterioration calculation. If it determines with the electric motor 1 not operating, it will progress to step S5.
[0017]
In step S5, the voltage sensor 19 detects the open voltage V0 of the battery 15. When the open circuit voltage V0 is detected, the process proceeds to step S6. In step S6, the internal resistance Ri of the battery 15 is detected based on the open circuit voltage V0 detected in step S5. This method will be described using the voltage-internal resistance characteristic curve of the secondary battery shown in FIG. In the voltage-internal resistance characteristic curve of the secondary battery shown in FIG. 4, the solid line is a graph showing a new battery, that is, the initial characteristics of the secondary battery, and the dotted line is a graph when the battery is deteriorated. Yes. The internal resistance Ri corresponding to the open circuit voltage V0 detected in step S5 is detected using the graph showing the initial characteristics represented by the solid line. When the internal resistance Ri is detected, the process proceeds to step S7.
[0018]
In step S7, temperature correction is performed on the internal resistance Ri detected in step S6. That is, the temperature-corrected internal resistance Ri0 is calculated and stored by the following equation (1) using the temperature coefficient α based on the battery temperature detected by a temperature sensor (not shown).
Ri0 = Ri × α / 100 (1)
When the internal resistance Ri0 after temperature correction is calculated, the process proceeds to step S8. In step S8, the engine is started and the process proceeds to step S9. In step S <b> 9, a drive command signal for the generator motor 1 is transmitted to the inverter 11 to drive the generator motor 1. Here, it drives so that the output value (electric power) by the generator motor 1 may be kept at P0. The constant power P0 generated by the generator motor 1 is stored in the battery 15.
[0019]
In step S10, the voltage sensor 19 detects the voltage value V1 of the battery 15 being charged. The detected voltage value V1 is input to the controller 16. In the next step S11, the internal resistance Rc1 is calculated and stored from the voltage value V1 of the battery 15 being charged detected in step S10.
[0020]
FIG. 5 is a graph showing the relationship between the current I flowing from the battery 15 and the voltage V when the output value from the generator motor 1 is P0. The internal resistance Rc1 when calculating the output deterioration of the secondary battery can be calculated by the following equation (2).
Rc1 = V1. (V1-V0) / P0 (2)
As can be seen from the above equation (2), the internal resistance Rc1 indicates the slope of a straight line connecting the point (I, V1) and the point (0, V0) in FIG. Assuming that the voltage value when the battery deterioration has progressed is V1 ′, the internal resistance Rc1 ′ when the output deterioration has progressed can be calculated by the following equation (3).
Rc1 ′ = V1 ′ · (V1′−V0) / P0 (3)
Also in this case, the internal resistance Rc1 ′ indicates the slope of a straight line connecting the point (I ′, V1 ′) and the point (0, V0). As can be seen from FIG. 5, the internal resistance increases as the battery deteriorates.
[0021]
When the internal resistance Rc1 is calculated, the process proceeds to step S12. In step S12, the output deterioration coefficient γ is calculated using the internal resistance Ri0 in the initial state of the battery and the internal resistance Rc1 in the output deterioration calculation. The output deterioration coefficient γ indicating the output deterioration state of the battery can be calculated by the following equation (4).
γ = Pc / Pint = Ri0 / Rc1 × 100 (4)
Here, Pint is a dischargeable output in the initial state of the battery, and Pc is a dischargeable output when the battery is deteriorated. As can be seen from the equation (4), when the output deterioration of the secondary battery proceeds, the internal resistance Rc1 increases, so the output deterioration coefficient γ decreases. When the output deterioration coefficient γ is calculated, the process proceeds to step S13. In step S13, the output deterioration coefficient γ calculated in step S12 is stored in the memory 21 in the controller 16. This output deterioration coefficient γ is used until the vehicle next stops. When the output deterioration coefficient γ is stored in the memory 21, the process proceeds to step S14. In step S <b> 14, a command signal for stopping the operation of the generator motor 1 is sent to the inverter 11. When the operation of the generator motor 11 is stopped, this control is terminated.
[0022]
According to the output deterioration calculation apparatus for a secondary battery according to the present invention, battery deterioration calculation control is started when the vehicle is started (step S1). The open circuit voltage V0 of the battery 15 in a state where the vehicle is stopped and the generator motor 1 is not operating is detected (steps S2 to S5). After calculating the internal resistance Ri of the battery 15 based on the open circuit voltage V0, the internal resistance Ri0 after temperature correction is calculated (steps S6 to S7). Then, the voltage value Vi when the engine is operated and the battery 15 is charged with the constant power P0 is detected (steps S8 to S10). After calculating the internal resistance Rc1 using the detected voltage value Vi, the output deterioration coefficient γ is calculated using the internal resistance Ri0 and the internal resistance Rc1 (steps S11 to S12). When the calculated output deterioration coefficient γ is stored in the memory 21 and the operation of the generator motor 1 is stopped, this control is terminated.
[0023]
In the conventional output deterioration calculation control of the secondary battery, a calculation error occurs when the vehicle is traveling at a high load such as when suddenly accelerating or when climbing a steep slope. This is because the discharge current from the battery 15 increases during high load traveling, and an error occurs in the regression line obtained using sampling points of a plurality of current values and voltage values. Therefore, when the battery output deterioration calculation is performed under a high load, a calculation result different from the actual battery deterioration state is calculated. However, in the output deterioration calculation control of the secondary battery according to the present invention, the battery deterioration calculation is performed by calculating the internal resistance from the current-voltage characteristic curve when the output from the generator motor 1 is a constant value (P0). Therefore, the vehicle is not affected by the high load traveling of the vehicle.
[0024]
Further, since the regression calculation is not performed as in the conventional deterioration calculation control, no calculation error is caused by performing the regression calculation. That is, when performing the regression calculation, if a plurality of points at which the voltage value and the current value are sampled vary, the regression line obtained by the regression calculation is different from the line indicating the actual current-voltage characteristics. In the output deterioration calculation control of the secondary battery according to the present invention, since the regression calculation is not performed, the calculation accuracy is higher than the conventional deterioration calculation control.
[0025]
Furthermore, since the internal resistance of the battery is calculated using the open voltage V0, the constant output value P0 from the generator motor 1, and the voltage value V1 at that time, there is no need to detect the current value when determining the internal resistance of the battery. . Therefore, it is not necessary to provide a current sensor, and even if a current sensor is provided, it is not necessary to increase current detection accuracy. Thereby, the cost of the current sensor can be reduced. In addition, in the method of performing the deterioration calculation by detecting the current, a detection error may occur at the time of current detection. However, in the output deterioration calculation control of the secondary battery according to the present invention, such a detection error does not occur. Therefore, the calculation accuracy can be improved.
[0026]
The present invention is not limited to the embodiment described above. In the above-described embodiment, the example in which the output deterioration calculating device for the secondary battery is applied to the hybrid electric vehicle has been described. However, the embodiment can also be applied to the electric vehicle. That is, when the battery 15 (secondary battery) is charged by a charger installed outside the vehicle, the battery deterioration calculation can be performed in the same manner. Moreover, if it mounts the battery which can be charged / discharged, it will not be limited to a vehicle.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an embodiment of a hybrid electric vehicle to which an output deterioration calculation device for a secondary battery according to the present invention is applied. FIG. 2 is an embodiment of an output deterioration calculation device for a secondary battery according to the present invention. FIG. 3 is a flowchart showing a control procedure following FIG. 2. FIG. 4 is a graph showing an initial state of the secondary battery and a voltage-internal resistance characteristic at the time of deterioration. Graph showing current-voltage characteristics 【Explanation of symbols】
DESCRIPTION OF SYMBOLS 1 ... Electric power generation motor, 2 ... Engine, 3 ... Clutch, 4 ... Motor, 5 ... Continuous transmission, 6 ... Reduction gear, 7 ... Differential gear, 8 ... Drive wheel, 9 ... Hydraulic device, 10 ... Motor, 11 ... Inverter, 12 ... Inverter, 13 ... Inverter, 14 ... DC link, 15 ... Battery, 16 ... Controller, 17 ... Compressor, 18 ... Current sensor, 19 ... Voltage sensor, 20 ... Vehicle speed sensor, 21 ... Memory

Claims (4)

In the secondary battery output deterioration calculation method for calculating the battery output deterioration from the output ratio between the battery output at the time of deterioration of the secondary battery and the initial battery output,
Only detecting the secondary battery open voltage and the secondary battery voltage when charging the secondary battery at a constant power,
Based on the detected open-circuit voltage of the secondary battery and the voltage of the secondary battery when charging with constant power, and the constant power, the internal resistance Rc1 of the secondary battery is obtained,
A method for calculating an output deterioration of a secondary battery , wherein the output ratio is calculated by calculating a ratio between the obtained internal resistance Rc1 of the secondary battery and the internal resistance Ri0 in the initial state of the secondary battery. In the secondary battery output deterioration calculation device that calculates the battery output deterioration from the output ratio between the battery output at the time of deterioration of the secondary battery and the initial battery output,
Voltage detection means for detecting the voltage of the secondary battery;
Control means for controlling the secondary battery to be charged with a constant power;
Based on the open-circuit voltage of the secondary battery detected by the voltage detection means, the voltage of the secondary battery when being charged with constant power by the control means, and the constant power controlled by the control means And calculating means for calculating the output ratio ,
The calculation means calculates an internal resistance Ri0 of the secondary battery in an initial state based on the open voltage of the secondary battery detected by the voltage detection means, and is charged with the open voltage and the constant power. The output ratio is calculated by calculating the internal resistance Rc1 of the secondary battery based on the voltage of the secondary battery and the constant power and calculating the ratio of the two calculated internal resistances. An output deterioration calculating device for a secondary battery, characterized in that: In the secondary battery output deterioration arithmetic unit according to claim 2,
The calculation means divides a value obtained by multiplying the difference between the voltage V1 of the secondary battery when the battery is charged with the constant power and the open voltage V0 by the voltage V1 by the constant power P0. A secondary battery output deterioration calculating device, characterized by calculating an internal resistance Rc1 of the secondary battery. In the secondary battery output deterioration arithmetic unit according to claim 2 or 3,
The secondary battery output deterioration computing device, wherein the secondary battery is a secondary battery that supplies electric power to an electric motor mounted on a hybrid electric vehicle.

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