JP5492055B2 - Battery protection device and battery protection method - Google Patents

Description

  The present invention relates to a battery protection technique for performing output control so that a battery mounted on an electric automobile does not reach an upper limit protection temperature.

  A battery (for example, a secondary battery or the like) mounted on an electric vehicle (EV (Electric Vehicle), PHEV (Plug-in Hybrid Electric Vehicle), etc.) is deteriorated by becoming high temperature. Therefore, in order to ensure the soundness of the battery, output suppression for suppressing the output of the battery is performed for the purpose of suppressing resistance heat generation of the battery when the battery is hot. In general, this output suppression is executed from a temperature (for example, 45 ° C.) lower than the upper limit protection temperature (for example, 50 ° C.) of the battery in consideration of a heat transfer delay in the measured battery temperature.

  In Patent Document 1, when the battery temperature is suddenly increased, the output is suppressed despite the remaining capacity of the battery, and it is expected that the vehicle is almost unable to travel. To output power and remaining time until output suppression is started. Then, based on the calculated output power and the remaining time until output suppression is started, the battery capacity meter display is corrected to be less than actual so that the remaining travelable distance matches the actual feeling of the driver. A technique for displaying is displayed. Further, in Patent Document 1, as an effect of the correction display of this capacity meter, it is mentioned that the merchantability of an electric vehicle is improved without causing dissatisfaction or discomfort to the driver.

Japanese Patent No. 3733663

  However, as described above, the technique described in Patent Document 1 is based on the premise that output suppression is performed from the remaining battery capacity. Therefore, output suppression is performed uniformly from a temperature at which the battery temperature is lower than the upper limit protection temperature, which may impair running performance. In addition, since the capacity meter displays a small value even though there is actually a remaining battery capacity, when the battery temperature drops after the battery has stopped discharging, the capacity meter The display value is increasing, and there is a risk of confusing the user.

In other words, in electric vehicles, battery output suppression directly affects driving performance, so if you do not fall into an event that impairs the soundness of the battery, you will need to suppress output unnecessarily from before the upper limit protection temperature. It is preferable not to do so.
Accordingly, an object of the present invention is to provide a control technique that can avoid unnecessary output suppression.

  In order to solve the above problems, the present invention provides a battery protection device that suppresses the output of the battery when the temperature of the battery is high, the battery reaching when the current remaining capacity of the battery is used up A final ultimate temperature estimating means for estimating the final ultimate temperature, an output suppression judgment means for comparing the final ultimate temperature with a temperature threshold and judging whether or not to suppress the output of the battery, and the output suppression judgment means If the final attainment temperature is determined to be lower than the temperature threshold, the output of the battery is prevented from being suppressed, and if the final attainment temperature is determined to be equal to or higher than the temperature threshold, the output of the battery is suppressed. And a control means.

  According to such a configuration, the output control unit avoids the suppression of the output of the battery (battery) when the final attainment temperature is determined to be lower than the temperature threshold (battery upper limit protection temperature) by the output suppression determination unit. Therefore, the battery protection device can avoid unnecessary output suppression. In addition, when the output suppression determination unit determines that the final temperature reaches or exceeds the temperature threshold, the output control unit suppresses the output of the battery, thereby protecting the battery.

  According to the present invention, it is possible to provide a control technique that can avoid unnecessary output suppression.

It is a figure which shows an example of a structure of a battery protection apparatus. It is a figure which shows an example of the processing flow of a battery protection apparatus.

  Next, modes for carrying out the invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate.

First, a configuration example of a battery protection device that can avoid unnecessary output suppression will be described with reference to FIG.
As shown in FIG. 1, the battery protection device 1 includes a battery final temperature estimation unit 10, an output suppression determination unit 20, and an output control unit 30.

  The battery final temperature estimation means 10 uses the battery at the maximum output assumed (for example, the state where the accelerator is depressed most; hereinafter, also referred to as the assumed maximum output) from the current state of the battery, and the remaining battery capacity is The temperature finally reached when 0 [Ah] is reached (battery estimated final temperature; the final temperature described in the claims) is estimated.

The output suppression determination means 20 protects the battery estimated final temperature calculated by the battery final temperature estimation means 10 (T _end in equation (1) described later) and the battery stored in a storage unit (not shown). Is compared with the battery upper limit protection temperature (temperature threshold described in claims), and a determination result as to whether or not to suppress output is transmitted to the output control means 30 as a high temperature output suppression unnecessary flag.

  The output control means 30 calculates a maximum permitted output value indicating the maximum output value allowed for the battery, and calculates a weight for multiplying the maximum permitted output value based on the difference between the battery upper limit protection temperature and the battery maximum temperature. The indicated output attenuation coefficient is calculated. Then, based on the determination result received from the output suppression determination unit 20, the output control unit 30 calculates either the maximum permitted output value or the value obtained by multiplying the maximum permitted output value by the output attenuation coefficient (high temperature output suppression value). Output as output value (limit value).

  Note that the output value output from the output control means 30 is a limit value for applying an output limit when the output value exceeds the output value if an attempt is made to satisfy the output request (for example, depression of the accelerator). Used as When the output request does not exceed the output value, the output is not restricted and the output is output as requested. That is, if the output request does not exceed the output value, the output restriction is not restricted even if it is determined by the output suppression determination means 20 that output suppression is to be performed.

Here, the battery maximum temperature (T _max in equation (1) described later) will be described. The battery is configured by further connecting a plurality of modules configured by connecting a plurality of unit cells in series. The battery temperature is generally measured for each module. That is, the battery maximum temperature means the maximum temperature among the plurality of modules. Note that the temperature of each unit cell may be estimated from the measured module temperature, and the highest temperature among the estimated temperatures may be used as the battery maximum temperature.

Next, an example of a method for calculating the estimated battery final temperature in the battery final achieved temperature estimation means 10 will be described (see FIG. 1 as appropriate).
The battery estimated final temperature can be estimated by the following equation (1). In addition, the heat_generation | fever raise temperature [degreeC] in Formula (1) is computable using Formula (2)-(6).

T _end [° C.] = T _max [° C.] + Exothermic temperature rise [° C.] Equation (1)
Heat generation rising temperature [° C.] = ((Resistance heating value [W] −cooling capacity [W]) × output time [s])
/ M _batt [J / K] ・ ・ Formula (2)
Resistance heating value [W] = (P _max [W] / V _ave [V]) ² × R _batt [Ω] Equation (3)
Cooling capacity [W] = K _box [W / K] × (T _max [° C.] − T _air [° C.]) Equation (4)
Output time [s] = battery remaining capacity [Wh] / P _max [W] (5)
Battery remaining capacity [Wh] = C _batt [Ah] × SOC [%] × V _ave [V]... (6)
However,
T _end : Estimated final battery temperature [° C]
T _max : Maximum battery temperature [° C]
M _batt : Battery heat capacity [J / K]
P _max : Load per unit battery at the assumed maximum output [W]
V _ave : Battery average voltage [V]
R _batt : Battery resistance [Ω]
K _box : Battery box cooling coefficient [W / K]
T _air : Intake air temperature [° C]
C _batt : Total battery capacity [Ah]
SOC (State of Charge): Battery charge depth [%]

The above formula (1) calculates the estimated battery final temperature T _end by adding the heat generation rising temperature when the remaining capacity of the battery is exhausted at the assumed maximum output to the current maximum battery temperature T _max .
In addition, equation (2) subtracts the cooling capacity calculated using equation (4) from the resistance heating value at the assumed maximum output calculated using equation (3) (the calorific value described in the claims). To calculate the difference, multiply the difference by the output time to calculate the heat generation capacity, and divide the heat generation capacity by the battery heat capacity M _batt (the heat capacity described in the claims) to calculate the heat generation rising temperature. Represents. That is, it is only necessary to estimate how much the temperature of the battery will be when the remaining capacity of the battery is used up at the assumed maximum output (for example, at the fastest speed).

It should be noted that the variables used for calculating the battery estimated final temperature _Tend shown in equation (1) are calculated using known battery resistance value estimation means, SOC estimation means, total capacity estimation means, and cooling capacity calculation means. Can do.
For example, as for the resistance value estimating means, there is a means for estimating based on the behavior of voltage and current using a sequential least square method.
As for the SOC estimating means, means for estimating based on current integration, or means for obtaining the OCV (Open Circuit Voltage) of the battery using the estimated resistance and obtaining the SOC based on the SOC-OCV correlation. Etc.
As for the total capacity estimating means, there are means for calculating the SOC change based on the OCV before and after charging and determining the amount of electricity required for charging by dividing the SOC change.
As for the cooling capacity calculation means, there is a method of measuring the relationship between the rotational speed of the fan and the cooling capacity and calculating the cooling capacity from the rotational speed of the fan.

  In addition, instead of using the equation (2), the battery final temperature estimation means 10 may obtain the heat generation rising temperature by searching a table associated with the remaining battery capacity and the internal resistance.

Next, an example of an output suppression determination method in the output suppression determination unit 20 will be described (see FIG. 1 as appropriate).
The output suppression determination unit 20 compares the estimated battery final temperature received from the final battery temperature estimation unit 10 with the battery upper limit protection temperature stored in a storage unit (not shown) by the comparator 21. The output suppression determination means 20 sets the high temperature output suppression unnecessary flag to “1”, which means that output suppression is avoided (not executed) when the estimated battery final temperature is lower than the battery upper limit protection temperature as a determination result. And transmitted to the output control means 30. Further, as a determination result, the output suppression determination unit 20 sets a high temperature output suppression unnecessary flag, which means that output suppression is executed, to “0” when the estimated battery final temperature is equal to or higher than the battery upper limit protection temperature, It transmits to the output control means 30.

Next, an example of a battery output value calculation method in the output control means 30 will be described (see FIG. 1 as appropriate).
In the output control means 30, a means for executing output suppression (hereinafter referred to as high temperature output suppression) is not particularly limited, but a subtractor 31 for subtracting the battery maximum temperature from the battery upper limit protection temperature. Is used to obtain an output attenuation coefficient corresponding to the difference. The output attenuation coefficient can be obtained from a graph (output attenuation coefficient calculation map) as shown in FIG. The graph shown in FIG. 1 has a characteristic that the output attenuation coefficient increases (decreases) as the difference increases (decreases). Further, the output attenuation coefficient may be calculated based on a function instead of being obtained from a graph.

  The output control means 30 includes a maximum allowable output value indicating the maximum output value when the output suppression calculated by the battery maximum allowable output calculator 34 is not executed, and an output attenuation coefficient via the multiplier 32 to the maximum allowable output value. The output suppression value at high temperature multiplied by is calculated. The output control means 30 outputs the maximum permitted output value as an output value via the selection means 33 when the high temperature output suppression unnecessary flag is “1” (when output suppression is not executed). Further, when the high temperature output suppression unnecessary flag is “0” (when executing output suppression), the output control means 30 outputs the high temperature output suppression value as an output value via the selection means 33. The high temperature output suppression value may be limited by subtracting the specified output for each calculation process from the maximum permitted output value when the high temperature output suppression unnecessary flag becomes “0”. The specified output used for subtraction at this time may be referred to the map from the difference calculated by subtracting the battery maximum temperature from the battery upper limit protection temperature, but may be a fixed value. That is, in the output control means 30, the high temperature output suppression unnecessary flag is set to “0”, and it is sufficient that the maximum permitted output value can be reduced to suppress the heat generation of the battery when executing the output suppression, and the means is not specified.

  The maximum allowable output value is not particularly limited in the battery maximum allowable output calculator 34, but can be calculated using the estimated internal resistance value and estimated OCV of the battery. For example, the maximum permitted output value can be calculated by Expression (7).

Maximum allowable output value [W] = V _min [V] × (eOCV [V] −V _min [V])
/ ER _batt [Ω] × n Equation (7)
However,
V _min : Battery lower limit voltage [V]
eOCV: Estimated OCV [V]
eR _batt : Estimated internal resistance [Ω]
n: Number of batteries

  The maximum permitted output value may be a fixed value.

  Next, an example of a processing flow in the battery protection device 1 will be described with reference to FIG. 2 (see FIG. 1 as appropriate).

  In step S201, the battery final reached temperature estimating means 10 calculates the battery estimated final reached temperature.

  In step S202, the battery maximum allowable output calculator 34 of the output control means 30 calculates the maximum allowable output value of the battery. The maximum permitted output value may be a fixed value.

  In step S203, the output suppression determination means 20 determines whether or not the estimated battery final temperature is lower than the battery upper limit protection temperature. Then, when the estimated battery final temperature is lower than the battery upper limit protection temperature (Yes in step S203), the output suppression determination unit 20 sets the high temperature output suppression unnecessary flag to “1” because output suppression is unnecessary. To the output control means 30. Further, when the estimated battery final temperature is equal to or higher than the battery upper limit protection temperature (No in step S203), the output suppression determination unit 20 sets the high temperature output suppression unnecessary flag to “0” because output suppression is necessary. To the output control means 30. The high temperature output suppression unnecessary flag is not limited to “1” or “0” as long as it can identify whether output suppression is necessary or not, and may be a character or a symbol.

  In step S203, when the estimated battery final temperature is lower than the battery upper limit protection temperature (Yes in step S203), in step S204, the output control means 30 outputs the maximum permitted output value. Then, the process returns to step S201.

  In step S203, when the estimated battery final temperature is equal to or higher than the battery upper limit protection temperature (No in step S203), in step S205, the output control means 30 subtracts the battery maximum temperature from the battery upper limit protection temperature and calculates the difference. To do.

  In step S206, the output control means 30 refers to the output attenuation coefficient calculation map (see FIG. 1) and acquires the output attenuation coefficient corresponding to the difference.

  In step S207, the output control means 30 outputs a value (high temperature output suppression value) obtained by multiplying the maximum allowable output value by the output attenuation coefficient. Then, the process returns to step S201.

  As described above, the battery protection device 1 according to this embodiment includes the battery final temperature estimation means 10, the output suppression determination means 20, and the output control means 30, as shown in FIG. The battery final reached temperature estimating means 10 calculates the estimated battery final reached temperature estimated from the remaining battery capacity and the internal resistance value at the time of maximum output traveling assumed in the electric vehicle. When the output suppression determination unit 20 determines that the estimated battery final temperature is lower than the battery upper limit protection temperature, the output control unit 30 does not perform output suppression. As a result, if the remaining battery capacity is low and the battery temperature may not exceed the battery upper limit protection temperature even if the battery is exhausted at the assumed maximum output, the battery upper limit protection temperature will not be exceeded. It is possible to avoid restricting the output as necessary, and it is possible to improve the traveling merchandise of the electric vehicle.

  Moreover, since unnecessary output suppression can be avoided, the battery can be used up to the maximum and the travel distance can be increased. Furthermore, in the present embodiment, the remaining travel distance only needs to display the actual battery remaining capacity as it is, so that the display value is reduced when the remaining battery capacity is displayed on the capacity meter as in the prior art. There is no fear of displaying and confusing the user. Moreover, in this embodiment, since it controls so that it does not exceed upper limit protection temperature based on the determination result of the output suppression determination means 20, protection of a battery is possible.

  Moreover, the output control means 30 calculates the output attenuation coefficient which suppresses the output of a battery based on the difference of battery upper limit protection temperature and battery maximum temperature. That is, the battery protection device 1 according to this embodiment does not suddenly suppress the output to zero when reaching a specific temperature, but changes the output attenuation coefficient depending on the temperature of the battery. Therefore, the user's uncomfortable feeling accompanying output suppression can be reduced.

  Further, in this embodiment, the output suppression determination means 20 outputs a high temperature output suppression unnecessary flag “1” when output suppression is not executed, and outputs a high temperature output suppression unnecessary flag “0” when output suppression is executed. It was transmitted to the control means 30. However, the output suppression determination unit 20 may transmit “1” to the output control unit 30 as a high temperature output suppression unnecessary flag only when output suppression is not executed. In this case, the selection means 33 of the output control means 30 selects the maximum allowable output value only when the high temperature output suppression unnecessary flag is received, and otherwise selects the high temperature output suppression value. You should do it.

  In addition, since a fuel cell vehicle (FC vehicle) can also be driven by a secondary battery (battery), this technique may be applied to the fuel cell vehicle.

DESCRIPTION OF SYMBOLS 10 Battery final reached temperature estimation means 20 Output suppression judgment means 30 Output control means 33 Selection means

Claims (7)

A battery protection device that suppresses the output of the battery when the temperature of the battery is high,
Final reached temperature estimating means for estimating the final reached temperature of the battery, which is reached when the current remaining capacity of the battery is used up,
Output suppression determination means for comparing the final temperature reached with a temperature threshold and determining whether to suppress the output of the battery;
When the final suppression temperature is determined by the output suppression determination means to be lower than the temperature threshold, suppression of the output of the battery is avoided, and when the final ultimate temperature is determined to be equal to or higher than the temperature threshold, A battery protection device comprising output control means for suppressing output. 2. The battery protection device according to claim 1, wherein the final ultimate temperature estimating unit calculates the final ultimate temperature based on at least a calorific value, a cooling capacity, and an output time of the battery. The battery protection device according to claim 2, wherein the final temperature estimation means calculates the final temperature further based on a heat capacity of the battery. 2. The battery protection device according to claim 1, wherein the final temperature estimation means calculates the final temperature based on a battery having the highest temperature among the plurality of batteries. The output control means, when suppressing the output of the battery, calculates a difference by subtracting the temperature of the battery from the temperature threshold, and decreases the output of the battery as the difference decreases. The battery protection device according to claim 1. A battery protection method used in a battery protection device that suppresses the output of the battery when the temperature of the battery is high,
The battery protection device is:
A final reached temperature estimating step for estimating a final reached temperature of the battery, which is reached when the current remaining capacity of the battery is used up,
An output suppression determination step of comparing the final temperature reached with a temperature threshold and determining whether to suppress the output of the battery;
When it is determined by the output suppression determination step that the final reached temperature is lower than the temperature threshold, suppression of the output of the battery is avoided, and when the final reached temperature is determined to be equal to or higher than the temperature threshold, An output control step for suppressing the output is performed. The battery protection method according to claim 6, wherein, in the final reached temperature estimation step, the final reached temperature is calculated based on at least a heat generation amount, a cooling capacity, and an output time of the battery.

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