JP6163879B2 - Battery temperature estimation device and battery temperature estimation method - Google Patents

Description

  The present invention relates to an apparatus and method for estimating the temperature of a battery.

  For example, when a secondary battery such as a lithium ion battery is mounted on a vehicle, a battery control device that calculates many parameters such as the full charge capacity of the battery cell, the current remaining capacity, and the internal resistance value is required. Become. When calculating the above parameters, it is necessary to obtain the accurate temperature of the battery, particularly in the case of a lithium ion battery in which various properties are highly temperature dependent.

  That is, accurately calculating the battery temperature leads to accurate calculation of each parameter, which leads to an improvement in battery control accuracy.

  In this regard, Patent Document 1 calculates the amount of heat generated by the current flowing through the internal resistance using the estimated internal resistance value and the current value, and uses this and the initial value of the battery cell temperature to calculate the battery temperature. The estimation is described.

JP 2006-101694 A

  However, when the battery temperature is estimated as in the above document, if the estimated value of the internal resistance value includes an error, the calculation result of the calorific value also includes an error. The calculation for temperature estimation is repeated. That is, it is difficult to accurately estimate the battery temperature. In addition, in the above document, a temperature sensor for detecting the temperature of the battery is provided, and the internal resistance is corrected based on the detected value of the temperature sensor at a predetermined timing. However, a constant error occurs in the detected value of the temperature sensor. In this case, an error also occurs in the estimated value (correction value) of the internal resistance value. Therefore, even if the internal resistance value is corrected based on the detection value of the temperature sensor, an error occurs in the estimated value (correction value) of the internal resistance due to the detection error of the temperature sensor, and the battery temperature is accurately estimated. Is difficult. Therefore, an object is to accurately estimate the battery temperature.

According to an aspect of the present invention, there is provided a battery temperature estimation device that periodically repeats battery temperature estimation calculation. The battery temperature estimation device includes a current detection unit that detects a current value, an internal resistance value calculation unit that calculates an internal resistance value of the battery, and a heating value of the battery during the calculation cycle using the internal resistance value and the current value. A calorific value calculating means for calculating and a temperature change estimating means for estimating the temperature change of the battery based on the calorific value are provided. Furthermore, the battery temperature estimated value update means which makes this time the battery temperature estimated value what added the battery temperature variation | change_quantity to the last value of battery temperature estimated value is provided. Then, the internal resistance value calculating means corrects the internal resistance value based on the previous value of the battery temperature estimated value so as to decrease as the previous value of the battery temperature estimated value increases.

  According to the above aspect, the internal resistance value calculating means calculates the internal resistance value based on the previous value of the battery temperature estimated value, and estimates the current value of the battery temperature estimated value based on the internal resistance value. Negative feedback is applied to the calculation, and the battery temperature can be accurately estimated.

FIG. 1 is a configuration diagram of a cooling system to which the first embodiment is applied. FIG. 2 is a block diagram illustrating a schematic configuration of the temperature estimation unit of the first embodiment. FIG. 3 is an example of a table used to calculate the internal resistance correction estimated value. FIG. 4 is a block diagram illustrating a schematic configuration of the temperature estimation unit of the second embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a configuration diagram showing an example of a system to which the first embodiment of the present invention is applied. This system is a cooling system that cools a lithium ion battery (hereinafter simply referred to as “battery”) 1 mounted on an electric vehicle using a cooling fan 5. For example, when the temperature of the battery 1 rises to a preset temperature, the cooling fan 5 is turned on. The rotational speed in the ON state may be a fixed value, or the rotational speed may be increased as the temperature increases according to the temperature of the battery 1.

  The control of the cooling fan 5 as described above is executed by the fan control unit 10. Then, the fan control unit 10 sets the ON / OFF and the rotation speed of the cooling fan 5 based on the battery temperature estimated by the temperature estimation unit 20.

  The temperature estimation unit 20 detects the voltage sensor 2 that detects the voltage value V of the battery 1, the current sensor 3 that detects the current value I of the battery 1, and the temperature sensor 4 that detects the environmental temperature Ta at the installation location of the battery 1. The value is read and the temperature of the battery 1 is estimated by a calculation described later.

  In addition, when the fan control unit 10 sets the ON / OFF and the rotation speed of the cooling fan 5, the fan control unit 10 outputs the information to the temperature estimation unit 20.

  The fan control unit 10 is constituted by a microcomputer including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). It is also possible to configure the fan control unit 10 with a plurality of microcomputers.

  Next, battery temperature estimation calculation by the temperature estimation unit 20 will be described.

  FIG. 2 is a block diagram illustrating a schematic configuration of the temperature estimation unit 20. The battery temperature estimation calculation is repeatedly executed at a predetermined cycle during system operation. The predetermined period is arbitrarily set between several tens of milliseconds and several seconds, for example. In addition, each block shown in FIG. 2 shows the function of the temperature estimation part 20 as a virtual unit, and does not mean physical existence.

  The temperature estimation unit 20 corrects the internal resistance estimated value Re read from a calculation unit different from the temperature estimation unit 20 based on the battery temperature, and calculates an internal resistance correction estimated value R. A calorific value calculation unit B2 for calculating a calorific value Qrh due to internal resistance at the time is provided. In addition, a heat balance calculation unit B3 that calculates a balance between heat absorption amount and heat generation amount (hereinafter referred to as “heat balance”) Qcr due to a chemical reaction of the battery 1, and a cooling amount calculation unit that calculates a cooling amount Qc including cooling due to thermal diffusion. B4 is provided. Furthermore, a temperature change amount calculation unit B5 that calculates the temperature change amount ΔTe of the battery 1 from the heat generation amount Qrh, the heat balance Qcr, and the cooling amount Qc, and the temperature change amount ΔTe is added to the battery temperature estimated by the previous calculation. The battery temperature estimated value update part B6 which updates battery temperature estimated value Te obtained as a temperature estimated value of this calculation is provided. Hereafter, the calculation in each part is demonstrated in detail.

(Internal resistance calculation unit B1)
The internal resistance calculator B1 reads the internal resistance estimated value Re. The internal resistance estimated value Re is obtained by performing a moving average or the like on the basis of a temporal change in the current measurement value and the voltage measurement value in a long cycle such as several tens of minutes to several hours or several days in another control unit (not shown). Is used for update calculation. Therefore, in the battery temperature estimation calculation having a sufficiently short calculation cycle compared to the internal resistance estimation calculation, the internal resistance estimation value Re may be considered as a fixed value. The estimated internal resistance value Re is calculated based on the slope of the IV straight line obtained by linearly approximating the voltage change with respect to the current change, or is calculated by substituting it into the battery model equation using the voltage value and current value as parameters. It is calculated by the method of.

  The internal resistance calculation unit B1 also reads the previous value of the estimated battery temperature value Te. At the time of the first calculation after the system is operated, the previous value (that is, the initial value) of the estimated battery temperature value Te is set as follows. First, when a predetermined time or more has elapsed since the end of the previous run, the environmental temperature Ta is set as the previous value of the battery temperature estimated value Te. On the other hand, if it is shorter than the predetermined time, the battery temperature estimated value Te at the end of the previous run, the elapsed time from the end of the previous run, and the temperature estimated using the environmental temperature Ta are set as the previous estimated value. The predetermined time here is the time required for the battery temperature to drop to the environmental temperature after the end of traveling, and is set to 2-3 hours, for example. By setting the previous value of the battery temperature estimated value Te used in the first calculation in this manner, the temperature estimation calculation can be started using a temperature close to the actual battery temperature.

  Then, the internal resistance correction estimated value R is calculated based on the internal resistance estimated value Re, the previous value of the battery temperature estimated value Te, and the characteristics of the internal resistance with respect to the battery temperature.

  FIG. 3 is an example of a table used to calculate the internal resistance correction estimated value R. The vertical axis represents the internal resistance R, and the horizontal axis represents the battery temperature T.

  The internal resistance calculation unit B1 first determines a point A in FIG. 3 from the read internal resistance estimated value Re and the previous value of the battery temperature estimated value Te. Then, the characteristic R = f (T) of the change in the internal resistance with respect to the temperature change is examined in advance by experiments or the like, and a curve passing through the point A and having the change characteristic R = f (T) is created.

  The curve created in this way is the temperature-dependent characteristic line of the internal resistance of the battery 1, and in the next and subsequent calculations, this temperature-dependent characteristic line and the battery temperature estimated value Te updated by the battery temperature estimated value updating unit B6 described later. Is used to estimate the internal resistance. That is, it can be said that the internal resistance correction estimated value R is obtained by correcting the internal resistance estimated value Re using the battery temperature estimated value Te and the temperature dependence characteristic line. Here, as shown in FIG. 3, the internal resistance of the battery generally decreases as the temperature increases and increases as the temperature decreases. Therefore, when the estimated internal resistance value Re is corrected with reference to the temperature dependence characteristic line based on the estimated battery temperature value Te, the estimated internal resistance value Re is decreased as the temperature increases, and is increased as the temperature decreases, thereby correcting the internal resistance. An estimated value R is calculated.

(Heat generation amount calculation unit B2)
The calorific value calculation unit B2 calculates the calorific value Qrh due to the current flowing through the internal resistance based on the internal resistance correction estimated value R, the current value I detected by the current sensor 3, and the coefficient k1, as shown in Equation (1). Calculated by

Qrh = RI ² × k1 (1)

(Heat balance calculation unit B3)
The heat balance calculation unit B3 calculates a heat balance Qcr due to a chemical reaction inside the battery 1 based on the current value I that is a detection value of the current sensor 3 and the coefficient k2, using Equation (2). The coefficient k2 varies depending on whether it is charging or discharging, and also depending on the material used.

  Instead of the equation (2), the heat absorption amount and the heat generation amount with respect to the current value I may be mapped in advance, and a map search may be performed using the read current value I.

    Qcr = I × k2 (2)

(Cooling amount calculation unit B4)
The cooling amount calculation unit B4 reads the cooling control state Sc that indicates the operating state of the cooling fan 5 and the environmental temperature Ta that is a detection value of the environmental temperature sensor 4, and calculates a thermal diffusion coefficient according to the cooling control state Sc and the environmental temperature Ta. The cooling amount Qc is calculated by using this. The cooling amount Qc is larger when the cooling fan 5 is operating than when the cooling fan 5 is not operating. When the cooling fan 5 is operating, the cooling rate Qc is higher when the rotational speed is higher. Further, the cooling amount Qc increases as the environmental temperature decreases.

(Temperature change amount calculation unit B5)
The temperature change amount calculation unit B5 adds the heat balance Qcr to the heat generation amount Qrh, subtracts the cooling amount Qc therefrom, calculates the amount of heat changed from the previous calculation, and further uses the specific heat of the battery 1 or the like. Then, a temperature change amount ΔTe of the battery 1 due to a change in the amount of heat is calculated.

(Battery temperature estimated value update unit B6)
The battery temperature estimated value updating unit B6 updates the battery temperature estimated value Te obtained by adding the temperature change amount ΔTe calculated by the temperature change amount calculating unit B5 as a new battery temperature estimated value Te. Then, the updated battery temperature estimated value Te is output to the fan control unit 10 and the internal resistance calculation unit B1.

  Next, operations and effects of the battery temperature estimation calculation described above will be described.

(1) In the present embodiment, the internal resistance R is calculated based on the previous value of the estimated battery temperature, the heat generation amount Qrh is calculated using the internal resistance R and the current value I, and the battery is calculated based on the heat generation amount Qrh. A temperature change amount ΔTe of 1 is calculated, and this temperature change amount ΔTe is added to the previous value of the battery temperature estimated value Te to obtain the current value of the battery temperature estimated value. The effect of this is as follows.

  In general, the internal resistance of the battery 1 decreases as the temperature increases, and increases as the temperature decreases. Here, it is assumed that the battery temperature estimation value Te in a certain calculation cycle includes an error so as to be lower than the true value. In this case, in the next cycle, the internal resistance R is calculated using the estimated battery temperature Te that is lower than the true value, so that the internal resistance R greater than the true value is calculated. Since the heat generation amount Qrh is proportional to the internal resistance R, the heat generation amount Qrh is also larger than the true value, and in this cycle, a temperature change amount ΔTe larger than the true value is calculated. Then, a new battery temperature estimated value Te is obtained by adding the temperature change amount ΔTe larger than the true value to the battery temperature estimated value Te lower than the true value.

  On the other hand, if an error is included so that the battery temperature estimated value Te of a certain calculation cycle becomes higher than the true value, a calorific value Qrh smaller than the true value is calculated contrary to the above, and the temperature change amount ΔTe. Is also smaller than the true value. Then, a new battery temperature estimated value Te is obtained by adding the temperature change amount ΔTe smaller than the true value to the battery temperature estimated value Te higher than the true value.

  In any case, the estimated battery temperature value Te calculated in the current calculation cycle is closer to the true value than the previous value. In this way, negative feedback is applied to the calculation, so that stable and accurate battery temperature estimation can be performed.

  Further, even if an error is included in the battery temperature used for the initial calculation, it is possible to gradually approach the true value by repeating the calculation and cancel the error.

(2) Since the temperature change amount calculation unit B5 calculates the temperature change amount ΔTe using the cooling amount Qc of the battery 1 in addition to the heat generation amount Qrh due to the internal resistance, rather than estimating based on only the heat generation amount Qrh. The temperature of the battery 1 can be estimated with high accuracy.

(3) Since the temperature change amount calculation unit B5 calculates the temperature change amount ΔTe using the heat balance Qcr due to the chemical reaction in addition to the calorific value Qrh and the cooling amount Qc, the temperature change amount ΔTe is calculated with higher accuracy. Can be estimated.

(4) Since the previous value of the estimated temperature Te used for the first calculation after the system is operated is set according to the elapsed time from the end of the previous run, the calculation is started using a value close to the actual battery temperature. be able to. As a result, the estimation error can be further reduced from the initial stage of the temperature estimation calculation.

(Second Embodiment)
This embodiment relates to the temperature estimation of the battery 1 in the same cooling system as the first embodiment, and a part of the battery temperature estimation calculation is different from the first embodiment.

  FIG. 4 is a block diagram illustrating a schematic configuration of the temperature estimation unit 20. The heat generation amount calculation unit B2, the heat balance calculation unit B3, the cooling amount calculation unit B4, the temperature change amount calculation unit B5, and the battery temperature estimated value update unit B6 are the same as in FIG.

Internal resistance computing unit B1 ', in addition to the previous value and the internal resistance estimated value Re of the battery temperature estimation value Te, read deterioration degree D _R of the battery 1. Deterioration degree D _R are calculated by another control unit similar to the internal resistance estimated value Re. Deterioration degree D _R may be calculated by a known method, for example, determine the available capacity of the battery 1 from the previous value of the current accumulated value and the battery temperature estimation value Te during charging, deterioration of the internal resistance estimated value Re and space The degree can be calculated.

Then, using the read previous value of the estimated battery temperature value Te and the estimated internal resistance value Re, a temperature-dependent characteristic line of the internal resistance of the battery 1 is created as in the first embodiment. Here being created is a temperature-dependent characteristic line for the current deterioration degree D _R.

In the next operation, the deterioration degree D _R is unless changed from the current value to calculate the internal resistance correction estimate R as in the first embodiment using the temperature dependent characteristic curve prepared this time.

On the other hand, if the deterioration degree D _R is changed, based on the characteristic that the internal resistance increases as deterioration progresses, and create a new temperature-dependent characteristic lines corresponding to the deterioration degree D _R, the internal resistance correction estimate The value R is calculated. The new temperature-dependent characteristic line is, for example, the first temperature-dependent characteristic line created as shown in FIG. 4 moved in the direction in which the internal resistance at the same temperature increases. Movement amount are those determined according to the deterioration degree D _R, is set in advance based on the relationship between the deterioration degree D variation of _R and the internal resistance change amount.

As described above, by a variable for calculating the internal resistance correction estimate R including deterioration degree D _R to calculate the internal resistance correction estimate R, estimation accuracy of the battery temperature is further improved.

  In the first embodiment and the second embodiment, the application to the control of the cooling fan has been described. However, the temperature estimation of the battery 1 is necessary for many other control calculations. Therefore, if the accuracy of the temperature estimation of the battery 1 is improved, a lot of calculation accuracy is improved. Hereinafter, an example in which the calculation accuracy is improved by improving the accuracy of temperature estimation of the battery 1 will be described.

(Charge charge)
The amount of charge such as the remaining capacity of the battery 1 and SOC (state of charge) is normally calculated as an increase and a decrease using a current integrated value obtained by integrating current measurement values detected by the current sensor 3. However, error components such as offset error and gain error of the current measurement value are gradually accumulated. For this reason, it is necessary to periodically perform a reset process for removing the error component. Generally, the SOC is reset using a table indicating the relationship between the OCV (open circuit voltage) and the SOC, but the table needs to be corrected based on the battery temperature. For this reason, the accuracy of temperature estimation is required to be high.

(Internal resistance value)
As described in the above-described embodiment, the internal resistance is calculated from temporal changes in the current measurement value and the voltage measurement value. Further, the internal resistance value is highly dependent on the temperature of the battery 1. When determining deterioration or abnormality based on the internal resistance value, it can be accurately determined by converting the internal resistance value at the reference temperature (for example, 25 ° C.), but this conversion Therefore, high accuracy of temperature estimation is required.

(Output power value)
The output possible power value of the battery 1 is calculated based on the SOC and temperature of the battery 1 at that time. Further, the output limit value for limiting the output of the battery 1 greatly depends on the internal resistance value of the battery 1, and the internal resistance value greatly depends on the temperature of the battery 1, so that the output power value also greatly depends on the temperature of the battery 1. Will be. Since the output possible power value is a calculated value that greatly affects the vehicle performance, it is required that the error be small in order to sufficiently bring out the battery performance. For this reason, the accuracy of temperature estimation is required to be high.

(Input power)
The inputtable power value of the battery 1 is calculated based on the SOC and temperature of the battery 1 at that time. Further, the input possible limit value for limiting the input to the battery 1 greatly depends on the internal resistance of the battery 1, and the internal resistance value greatly depends on the temperature of the battery 1. Will be dependent. Therefore, the accuracy of temperature estimation is required to be high as with the outputable power value.

(Driving distance)
The travelable distance of the vehicle using battery 1 as a drive source is calculated based on the SOC, average current value, and internal resistance value of battery 1 at that time. Since the internal resistance value greatly depends on the temperature of the battery 1, the travelable distance also greatly depends on the temperature of the battery 1. Therefore, the accuracy of temperature estimation is required to be high as with the outputable power value.

(Remaining charge time)
The remaining charge time, which is the time required to reach a fully charged state, is calculated based on the SOC and internal resistance value of the battery 1 at that time. The internal resistance value greatly depends on the temperature of the battery 1. Therefore, high accuracy of temperature estimation is also required in calculating the remaining charge time.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

DESCRIPTION OF SYMBOLS 1 Lithium ion battery 2 Voltage sensor 3 Current sensor (current detection means)
4 Temperature sensor 5 Cooling fan 10 Fan control unit 20 Temperature estimation unit B1 Internal resistance calculation unit (internal resistance calculation means)
B2 Heat generation amount calculation unit (heat generation amount calculation means)
B3 Heat balance calculator (Chemical reaction heat calculation means)
B4 Cooling amount calculation unit (heat dissipation amount calculation means)
B5 Temperature change amount calculation unit (temperature change amount estimation unit)
B6 battery temperature estimated value update unit (battery temperature estimated value update means)

Claims (6)

In the battery temperature estimation device that periodically repeats the battery temperature estimation calculation,
Current detection means for detecting a current value flowing through the battery;
An internal resistance value calculating means for calculating an internal resistance value of the battery;
A calorific value calculating means for calculating a calorific value of the battery during a calculation cycle using the internal resistance value calculated by the internal resistance value calculating means and the current value detected by the current detecting means;
A temperature change amount estimation means for estimating a temperature change amount of the battery based on the heat generation amount calculated by the heat generation amount calculation means;
A battery temperature estimated value updating means for adding the battery temperature estimated value estimated by the temperature change amount estimating means to the previous value of the battery temperature estimated value as a current value of the battery temperature estimated value;
With
The internal resistance value calculation means, based on the previous value of the battery temperature estimation value, the battery temperature estimation unit for correcting the internal resistance value so as to decrease the higher the previous value of the battery temperature estimate. The battery temperature estimation device according to claim 1,
A heat dissipation amount calculating means for calculating a heat dissipation amount of the battery during the calculation cycle;
The temperature change amount estimation unit is a battery temperature estimation device that estimates the temperature change amount based on the heat dissipation amount calculated by the heat dissipation amount calculation unit and the heat generation amount calculated by the heat generation amount calculation unit. The battery temperature estimation device according to claim 2,
Chemical reaction heat calculation means for calculating the heat of chemical reaction of the battery during the calculation cycle,
The temperature change amount estimation means is based on the heat dissipation amount calculated by the heat dissipation amount calculation means, the heat generation amount calculated by the heat generation amount calculation means, and the chemical reaction heat calculated by the chemical reaction heat calculation means. A battery temperature estimation device for estimating a temperature change amount. In the battery temperature estimation device according to any one of claims 1 to 3,
The internal resistance value calculation means is a battery temperature estimation device that calculates an internal resistance value of the battery based on a degree of deterioration of the battery in addition to the estimated battery temperature value. In the battery temperature estimation device according to any one of claims 1 to 4,
The battery temperature estimated value updating means is a battery temperature estimating device that sets the battery temperature estimated value at the time of initial calculation according to the elapsed time from the previous stop to the start of the system including the battery. In the battery temperature estimation method that periodically repeats the battery temperature estimation calculation,
A current detection step for detecting a current value flowing through the battery;
An internal resistance value calculating step for calculating an internal resistance value of the battery;
Using the internal resistance value estimated in the internal resistance value calculating step and the current value detected in the current detecting step, a calorific value calculating step for calculating the calorific value of the battery during the calculation cycle;
A temperature change amount estimation step for estimating a temperature change amount of the battery during the calculation period based on the heat generation amount calculated in the heat generation amount calculation step;
A battery temperature update step of updating the battery temperature estimated value by adding the battery temperature estimated amount estimated in the temperature change amount estimating step to the previous value of the battery temperature estimated value;
Have
In the internal resistance value calculating step, a battery temperature estimating method for correcting the internal resistance value so that the higher the battery temperature estimated value is, the lower the internal resistance value is based on the battery temperature estimated value updated in the battery temperature updating step.

Images