JP7492549B2 - Battery System - Google Patents

Description

This disclosure relates to technology that prevents overheating of current-carrying components in a battery system.

Japanese Patent Publication No. 5687340 (Patent Document 1) discloses a battery system that prevents overheating of components that make up a battery. In this battery system, a current limit value to prevent overheating is set for each current-carrying component in the battery system. The current limit value is set as a number of current average values that are allowed during a number of pre-set time window widths (continuous current-carrying time widths) within a range that does not exceed the thermal allowable current of the current-carrying component. This battery system calculates the average current for each of the multiple time window widths, and limits the current flowing through the battery to less than the current limit value so that each average current does not exceed the thermal allowable current corresponding to each average current.

Patent No. 5687340

In a method of calculating the average current for multiple continuous current-flow time spans, such as the battery system disclosed in Patent Publication No. 5687340, the processing load required for thermal protection of current-carrying components becomes enormous. For example, if one continuous current-flow time span is 20 seconds and the current is detected at 0.1 second intervals, it is necessary to store in memory data on 200 current detection values detected in the past 20 seconds and calculate the moving average value of these 200 current detection values. Since this processing is performed for multiple continuous current-flow time spans, the processing load becomes enormous. Furthermore, if multiple continuous current-flow time spans are set for multiple current-carrying components, the processing load increases even further.

This disclosure has been made to solve the above-mentioned problems, and its purpose is to reduce the processing load required for thermal protection of current-carrying components in a battery system.

(1) A battery system according to the present disclosure includes a current path in which a current-carrying component including a battery is disposed, a current sensor that detects a current flowing through the current path, and a control circuit that controls the current flowing through the current path. The control circuit calculates a plurality of current filter values corresponding to average currents during a plurality of predetermined continuous current-carrying times by performing infinite impulse response filtering on the detection value of the current sensor, sets a plurality of current limit values corresponding to the plurality of continuous current-carrying times so as to be less than the allowable current of the current-carrying component, and limits the current flowing through the current path to less than the current limit value when at least one of the plurality of current filter values exceeds the current limit value corresponding to the current filter value.

(2) In the battery system described in 1, the control circuit calculates multiple current filter values by filtering the detection value of the current sensor with multiple infinite impulse responses having different filter coefficients.

(3) In the battery system described in 1 or 2, the control circuit changes each of the multiple current limit values according to the current filter value corresponding to the current limit value.

(4) In the battery system described in 3, the control circuit sets the current limit value corresponding to the current filter value to a value greater than the first value when the current filter value is less than a second value that is smaller than the first value, and when the current filter value is equal to or greater than the second value and less than the first value, monotonically decreases the current limit value corresponding to the current filter value toward the first value as the current filter value becomes larger, and when the current filter value is greater than the first value, sets the current limit value corresponding to the current filter value to the first value.

(5) In the battery system described in any one of paragraphs 1 to 4, the control circuit changes at least one of the current filter value and the multiple current limit values in response to at least one of the environmental temperature of the current-carrying component and the period of use of the current-carrying component.

(6) In the battery system described in 5, the control circuit increases the current filter value the higher the environmental temperature of the current-carrying component is and/or the longer the period of use of the current-carrying component is.

(7) In the battery system described in 5, the control circuit reduces the multiple current limit values the higher the environmental temperature of the current-carrying components and/or the longer the period of use of the current-carrying components.

(Item 8) In the battery system described in any one of items 1 to 7, the control circuit stores the current filter value when the system is stopped and the battery system changes from an operating state to a stopped state. When the system is started and the battery system changes to an operating state after the stopped state has continued, the control circuit calculates the current filter value at the time of system start-up using the current filter value stored when the system was stopped and the time during which the stopped state of the battery system continued.

This disclosure makes it possible to reduce the processing load required for thermal protection of current-carrying components in a battery system.

1 is a diagram illustrating an overall configuration of a battery system. FIG. 2 is a diagram showing a schematic diagram of a thermal limit characteristic of a current-carrying component. FIG. 2 is a functional block diagram of a control circuit. 11 is a diagram comparing the waveform characteristics of an average current calculated by conventional averaging processing with the waveform characteristics of a current filtered value IF calculated by IIR filtering processing. FIG. FIG. 1 is a diagram showing a process flow of a control circuit (part 1). FIG. 2 is a diagram showing the process flow of the control circuit (part 2).

The following describes in detail the embodiments of the present disclosure with reference to the drawings. Note that the same or corresponding parts in the drawings are given the same reference numerals and their description will not be repeated.

<System Configuration>
1 is a diagram showing a schematic overall configuration of a battery system 1 according to the present embodiment. The battery system 1 is mounted on, for example, a vehicle having an inverter and a motor generator, which are an example of a load 20, as a driving power source.

The battery system 1 includes a battery pack 10, a load 20, a positive electrode line PL, a negative electrode line NL, and a control circuit 100. The battery pack 10 includes a battery 11, a fuse 12, a monitoring unit 13, and a system main relay SMR.

Battery 11 is a battery pack including multiple cells. Each cell is a secondary battery, such as a lithium-ion battery.

The positive electrode line PL electrically connects the positive electrode of the battery 11 to the load 20. The negative electrode line NL electrically connects the negative electrode of the battery 11 to the load 20.

The system main relay SMR is electrically connected between the battery 11 and the load 20. The system main relay SMR is closed in accordance with a command from the control circuit 100. When the system main relay SMR is closed, a current path is formed between the battery 11 and the load 20.

The fuse 12 is provided between the battery 11 and the system main relay SMR. When a large current flows through the fuse 12, the built-in alloy component melts, electrically cutting off the current path between the battery 11 and the load 20.

The load 20 is an electrical component that operates using power supplied from the battery 11. For example, the load 20 includes a motor generator that generates driving force for the vehicle and an inverter for driving the motor generator.

The monitoring unit 13 includes a current sensor 14, a voltage sensor 15, and a temperature sensor 16. The current sensor 14 detects the current flowing through the battery 11 (current I flowing through the current path). The current I detected by the current sensor 14 is a positive value when the battery 11 is discharging, and a negative value when the battery 11 is charging. The voltage sensor 15 detects the voltage of the battery 11. The temperature sensor 16 detects the temperature of the battery 11. Each sensor in the monitoring unit 13 outputs the detection result to the control circuit 100.

The control circuit 100 includes a processor 101 such as a CPU (Central Processing Unit), a memory 102 such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and ports for inputting and outputting various signals (all not shown). The control circuit 100 controls the system main relay SMR and the load 20 based on the programs and maps stored in the memory, as well as the signals received from each sensor.

<Thermal protection of current-carrying components (suppression of overheating)>
As described above, a plurality of components such as the battery 11, the system main relay SMR, and the fuse 12 are arranged in the current path of the battery system 1.

It is desirable that the maximum input/output current of the battery 11 is within a range that satisfies the input/output requirements of the load 20 while not exceeding the rated current (hereinafter also referred to as the "allowable current") determined in consideration of the thermal limit characteristics of each current-carrying component in order to provide thermal protection for each component (hereinafter also referred to as the "current-carrying component") on the current-carrying path. Note that the allowable current in this embodiment includes the thermal allowable current.

The thermal limit characteristics (allowable current characteristics) of a live component are sometimes specified in terms of the duration for which the component is continuously energized and the average current during that duration.

Figure 2 is a diagram that shows a schematic of the thermal limit characteristics of a current-carrying component. In Figure 2, the vertical axis shows the continuous current-carrying time (unit: sec (seconds)), and the horizontal axis shows the average current during the continuous current-carrying time (unit: A (amperes)). Note that Figure 2 shows the allowable current of three components A to C as examples of the thermal limit characteristics of the current-carrying components. The allowable current of components A to C shown in Figure 2 is the line that must not be exceeded in order to provide thermal protection for components A to C.

As shown in Figure 2, the allowable current of each of the components A to C is different, but each has the characteristic that the longer the continuous current is passed through, the smaller the allowable current becomes. In order to provide proper thermal protection for each of the components A to C, it is desirable to suppress the current I flowing through the current path so that the average current flowing through each of the components A to C does not exceed the allowable current of each of them.

Conventionally, as in the battery system disclosed in the above-mentioned Patent Publication No. 5687340, one method for achieving this has been to set multiple continuous current-flow time spans in advance and perform averaging to calculate the moving average of the current for each of the multiple continuous current-flow time spans. However, the conventional averaging process has the problem that the processing load required for thermal protection of current-carrying components becomes enormous.

For example, when the three continuous current flow time spans T1 = 0.1 s (seconds), T2 = 1 s, and T3 = 20 s shown in FIG. 2 are preset, the conventional averaging process calculates the average current for each of the three continuous current flow time spans T1, T2, and T3. This conventional averaging process imposes a huge processing load. For example, when obtaining the detection value of the current sensor 14 at a 0.1 s cycle, in order to calculate the average current for the continuous current flow time span T3 (= 20 s), it is necessary to store data on 200 current detection values detected in the past 20 seconds in memory and calculate the moving average value of these 200 current detection values. This averaging process must be performed for each continuous current flow time span T1, T2, and T3, which imposes a huge processing load.

Therefore, the control circuit 100 according to the present embodiment does not calculate the average current for each of the multiple continuous current-flow periods, but instead calculates a "current filter value IF" equivalent to the average current for each of the multiple continuous current-flow periods by applying infinite impulse response (IIR) filtering to the current I, which is the detection value of the current sensor 14. The control circuit 100 then limits the magnitude of the current I based on each current filter value IF, thereby preventing overheating of each current-flow component.

The IIR filter is a digital filter that does not simply take a moving average, but rather incorporates feedback to obtain the desired filter characteristics with a smaller number of taps (the number of coefficients used in the calculation). Therefore, by performing IIR filter processing, the processing load can be significantly reduced compared to simple moving average processing. Therefore, the processing load required for thermal protection of current-carrying components can be reduced compared to the conventional method of calculating the average current for each of multiple consecutive current-carrying time spans. The thermal protection of current-carrying components according to this embodiment will be described in detail below.

<How to set the continuous current flow time>
Before describing the IIR filter processing according to this embodiment, a method for setting the continuous current application time according to this embodiment will be described with reference to FIG.

As shown in FIG. 2, the allowable current of each of the components A to C is different from one another. In order to provide thermal protection for each of the components A to C while suppressing the processing load, it is desirable to appropriately set the number and value of the continuous current-flow times. In this embodiment, the number and value of the continuous current-flow times are set in the following manner.

(Step 1) Set the current limit target line as shown in Figure 2 in the area that does not exceed the allowable current of components A to C.

(Step 2) The continuous current flow time (20 s in the example shown in FIG. 2) at the intersection P3 between the smallest allowable current value I3 (200 A in the example shown in FIG. 2) among the allowable currents of components A to C and the current limit target line is set as the "continuous current flow time width T3." In addition, the allowable current value I3 is set as the "current limit value Ilim3."

(Step 3) The smallest allowable current value I2 (400 A at the intersection of the continuous current duration T3 = 20 s and the allowable current of component B in the example shown in Figure 2) among the intersections of the continuous current duration T3 and the allowable current of components A to C is set as the "continuous current duration T2" (1 s in the example shown in Figure 2) at the intersection P2 of the current limit target line and the continuous current duration T2. Also, the allowable current value I2 is set as the "current limit value Ilim2".

(Step 4) Repeat the setting of the continuous current flow time according to step 3 until the current limit value exceeds the maximum value of the current limit target line. In the example shown in Figure 2, the smallest allowable current value I1 among the intersections of the continuous current flow time width T2 and the allowable currents of components A to C (700 A in the example shown in Figure 2 at the intersection of the continuous current flow time width T2 = 2 s and the allowable current of component C) already exceeds the maximum value of the current limit target line, so the continuous current flow time is set only once according to step 3.

(Step 5) Finally, the allowable current value I1 (=700A) at the intersection of the continuous current flow time width T2 = 1s and the allowable current of component C is set as the "current limit value Ilim1", and 0.1s is set as the "continuous current flow time width T1". Note that, considering that the allowable current value I1 (=700A) exceeds the maximum value (=400A) of the current limit target line, the current limit value Ilim1 may be set to the maximum value (=400A) of the current limit target line instead of the allowable current value I1 (=700A).

By setting the number and value of continuous current flow times in this manner, the number of continuous current flow times can be kept to an appropriate number that is necessary and sufficient to provide thermal protection for components A through C. This prevents the number of continuous current flow times from becoming excessively large. As a result, the processing load can be reduced.

The current limit value Ilim set in this manner is a value less than the allowable current of components A to C. Therefore, by limiting the current I to the current limit value Ilim or less, the current I can be controlled so that it does not exceed the allowable current of components A to C. This allows for appropriate thermal protection of components A to C.

Thermal Protection of Current-Carrying Components Using IIR Filtering
The control circuit 100 according to the present embodiment performs IIR filter processing for each of the continuous current-flow time widths T1, T2, and T3 set as described above, to calculate a "current filter value IF1" equivalent to the average current during the continuous current-flow time width T1, a "current filter value IF2" equivalent to the average current during the continuous current-flow time width T2, and a "current filter value IF3" equivalent to the average current during the continuous current-flow time width T3.

The control circuit 100 sets current limit values Ilim1, Ilim2, and Ilim3 corresponding to the continuous current flow durations T1, T2, and T3, respectively. In this embodiment, the current limit values Ilim1, Ilim2, and Ilim3 are preset to the allowable current values I1 (= 700 A), I2 (= 400 A), and I3 (= 200 A), respectively, as described above.

When the current filter value IF1 exceeds the current limit value Ilim1, the control circuit 100 limits the magnitude of the current I flowing through the current path to the current limit value Ilim1. This suppresses use in "area Z" where the average current is greater than the current limit value Ilim1 (=700A) and the continuous current flow time exceeds the continuous current flow time width T1 (=0.1s).

Similarly, when the current filter value IF2 exceeds the current limit value Ilim2, the control circuit 100 limits the magnitude of the current I flowing through the current path to the current limit value Ilim2. This suppresses use in "area Y" where the average current is greater than the current limit value Ilim2 (=400 A) and the continuous current flow time exceeds the continuous current flow time width T2 (=1 s).

Similarly, when the current filter value IF3 exceeds the current limit value Ilim3, the control circuit 100 limits the magnitude of the current I flowing through the current path to the current limit value Ilim3. This suppresses use in "area X" where the average current is greater than the current limit value Ilim3 (=200A) and the continuous current flow time exceeds the continuous current flow time width T3 (=20s).

Figure 3 is a functional block diagram of the portion of the control circuit 100 that is related to thermal protection of current-carrying components. The control circuit 100 has a current acquisition unit 110, IIR filters 121-123, determination units 131-133, and a current limiting unit 140.

The current acquisition unit 110 acquires the current I detected by the current sensor 14 and transmits the magnitude of the acquired current I (hereinafter also referred to as "current absolute value |I|") to the IIR filters 121 to 123.

As described above, the current I is positive when the battery 11 is discharged and negative when the battery 11 is charged, but since the amount of heat generated by a current-carrying component is proportional to the square of the current I, the temperature of the current-carrying component increases as the absolute value of the current I increases, regardless of whether the current I is positive or negative. Taking this into consideration, the current acquisition unit 110 transmits the current absolute value |I| to the IIR filters 121 to 123, rather than the current I itself. As a result, the current absolute value |I| becomes the target of IIR filter processing. Note that the target of IIR filter processing may be the squared value of the current I instead of the current absolute value |I|.

The IIR filter 121 performs IIR filtering on the absolute current value |I| from the current acquisition unit 110, with the IIR filter coefficient α set to the "first coefficient α1", to calculate a current filter value IF1 that corresponds to the average current during the continuous current flow time width T1, and transmits the calculation result to the determination unit 131.

The IIR filter 122 performs IIR filtering on the absolute current value |I| from the current acquisition unit 110, with the IIR filter coefficient α set to the "second coefficient α2", to calculate a current filter value IF2 equivalent to the average current during the continuous current flow time width T2, and transmits the calculation result to the determination unit 132.

The IIR filter 123 performs IIR filtering on the absolute current value |I| from the current acquisition unit 110, with the IIR filter coefficient α set to the "third coefficient α3", to calculate a current filter value IF3 equivalent to the average current during the continuous current flow time width T3, and transmits the calculation result to the determination unit 133.

The determination unit 131 sets a current limit value Ilim1 for the continuous current flow duration T1, and determines whether the current filter value IF1 from the IIR filter 121 is larger than the current limit value Ilim1. In this embodiment, as described above, the current limit value Ilim1 is pre-fixed to the allowable current value I1 (=700 A) shown in FIG. 2.

The determination unit 132 sets a current limit value Ilim2 for the continuous current flow duration T2, and determines which of the current filter value IF2 from the IIR filter 122 is larger than the current limit value Ilim2. In this embodiment, as described above, the current limit value Ilim2 is fixed in advance to the allowable current value I2 (= 400 A) shown in FIG. 2.

The determination unit 133 sets a current limit value Ilim3 for the continuous current flow duration T3, and determines whether the current filter value IF3 from the IIR filter 123 is larger than the current limit value Ilim3. In this embodiment, as described above, the current limit value Ilim3 is pre-fixed to the allowable current value I3 (=200 A) shown in FIG. 2.

The determination units 131 to 133 transmit the determination results to the current limiting unit 140. The current limiting unit 140 limits the magnitude of the current I based on the determination results from the determination units 131 to 133. Specifically, when the current filter value IF1 exceeds the current limiting value Ilim1, the magnitude of the current I is limited to the current limiting value Ilim1. When the current filter value IF2 exceeds the current limiting value Ilim2, the magnitude of the current I is limited to the current limiting value Ilim2. When the current filter value IF3 exceeds the current limiting value Ilim3, the magnitude of the current I is limited to the current limiting value Ilim3.

Figure 4 is a diagram comparing the waveform characteristics of the average current calculated by conventional averaging processing with the waveform characteristics of the current filter value IF calculated by the IIR filter processing according to this embodiment.

Conventional averaging involves simply performing a moving average. Conventional averaging can be performed, for example, using an FIR (Finite Impulse Response) low-pass filter. An FIR low-pass filter has a configuration in which a weighting parameter is added to each of the multiple elements that are the subject of the moving average. An example of the configuration of an FIR low-pass filter is shown in the lower part of Figure 4.

In contrast, the IIR filter (IIR low-pass filter) according to this embodiment does not simply take a moving average, but rather has a configuration that incorporates feedback to obtain the desired filter characteristics with a smaller number of taps (the number of coefficients used in the calculation). Therefore, compared to a simple moving average such as an FIR filter, the processing load can be significantly reduced. An example of the configuration of an IIR low-pass filter is shown in the lower part of Figure 4. Note that the configuration of the IIR low-pass filter shown in Figure 4 is merely an example and is not limited to this. For example, a more complex configuration may be added to include the configuration shown in Figure 4 as a basic configuration.

As can be seen from FIG. 4, the waveform characteristics of the current filter value IF calculated by the IIR filter processing are almost the same as the waveform characteristics of the average current calculated by the conventional averaging processing. In view of this, in this embodiment, an IIR filter is used as a substitute for the conventional averaging processing. This makes it possible to obtain an average current with the same accuracy as the conventional one with a small processing load.

In the example shown in FIG. 4, the IIR filter coefficient α (second coefficient α2) for calculating the current filter value IF2 is adjusted to 0.1667 so that the current filter value IF2 matches the value corresponding to the average current during the continuous current flow time width T2. Similarly, the IIR filter coefficient α (third coefficient α3) for calculating the current filter value IF3 is adjusted to 0.0091 so that the current filter value IF3 matches the value corresponding to the average current during the continuous current flow time width T3. In this way, by adjusting the value of the IIR filter coefficient α, the current filter values IF1, IF2, and IF3 can be matched to values corresponding to the average current during the continuous current flow time widths T1, T2, and T3, respectively.

Figure 5 shows the process flow when the control circuit 100 performs thermal protection for a current-carrying component.

First, the control circuit 100 acquires the current I detected by the current sensor 14 at a predetermined period (e.g., every 0.1 s) (step S10), and calculates the absolute current value |I|, which is the magnitude of the current I (step S12).

Next, the control circuit 100 calculates a current filter value IF1 equivalent to the average current of the continuous current flow time width T1 by performing an IIR filter process with α=α1 on the current absolute value |I| (step S21). Then, the control circuit 100 sets a current limit value Ilim1 for the continuous current flow time width T1, and determines the magnitude relationship between the current filter value IF1 and the current limit value Ilim1 (step S31). Note that if the continuous current flow time width T1 is 0.1 s and the current I is acquired at 0.1 s intervals, the current absolute value |I| may be set directly to the current filter value IF1.

The control circuit 100 calculates a current filter value IF2 equivalent to the average current of the continuous current flow time width T2 by performing an IIR filter process of α=α2 on the current absolute value |I| (step S22). The control circuit 100 then sets a current limit value Ilim2 for the continuous current flow time width T2 and determines whether the current filter value IF2 is larger than the current limit value Ilim2 (step S32).

The control circuit 100 calculates a current filter value IF3 equivalent to the average current of the continuous current flow time width T3 by performing an IIR filter process with α=α3 on the current absolute value |I| (step S23). The control circuit 100 then sets a current limit value Ilim3 for the continuous current flow time width T3 and determines whether the current filter value IF3 is larger than the current limit value Ilim3 (step S33).

The control circuit 100 limits the magnitude of the current I based on the determination results of steps S31 to S33 (step S40). Specifically, when the current filter value IF1 is greater than the current limit value Ilim1, the control circuit 100 limits the magnitude of the current I to the current limit value Ilim1. When the current filter value IF2 is greater than the current limit value Ilim2, the control circuit 100 limits the magnitude of the current I to the current limit value Ilim2. When the current filter value IF3 exceeds the current limit value Ilim3, the control circuit 100 limits the magnitude of the current I to the current limit value Ilim3.

As described above, the control circuit 100 according to this embodiment calculates current filter values IF1, IF2, and IF3 that correspond to the average current during the continuous current flow time widths T1, T2, and T3, respectively, by performing IIR filtering on the magnitude of the current I, which is the detection value of the current sensor 14. Therefore, it is possible to obtain an average current with the same accuracy as in the past, with a smaller processing load. As a result, it is possible to reduce the processing load required for thermal protection of current-carrying components.

[Modification 1]
In the above-described embodiment, when each current filter value IF exceeds each current limit value Ilim, the magnitude of the current I is limited to each current limit value Ilim. In this case, however, if there is a large difference between the magnitude of the current I before the current limit and the magnitude of the current I after the current limit (=current limit value Ilim), a sudden current limit will be applied.

In consideration of this, the control circuit 100 according to this modification 1 changes each current limit value Ilim1 according to the current filter value IF corresponding to each current limit value Ilim.

Figure 6 is a diagram showing the flow of processing when the control circuit 100A according to this modification 1 performs thermal protection of a current-carrying component. The processing in Figure 6 is obtained by replacing steps S31 to S33 and S40 in Figure 5 described above with steps S31A to S33A and S40A, respectively. The other processing in Figure 6 is the same as the processing in Figure 5 described above, and therefore detailed description will not be repeated here.

The control circuit 100 sets the current limit value Ilim2 according to the current filter value IF2 (step S32A). Specifically, when the current filter value IF2 is less than 0.9 times the allowable current value I2 (= 400 A × 0.9 = 360 A), the control circuit 100 sets the current limit value Ilim2 to a value (unlimited value) greater than the allowable current value I2. When the current filter value IF2 is equal to or greater than 0.9 times the allowable current value I2 and less than the allowable current value I2, the control circuit 100 monotonically decreases the current limit value Ilim2 toward the allowable current value I2 as the current filter value IF2 increases. When the current filter value IF2 is greater than the allowable value Ilim2, the control circuit 100 sets the current limit value Ilim2 to the allowable current value I2.

Similarly, the control circuit 100 sets the current limit value Ilim3 according to the current filter value IF3 (step S33A). Specifically, when the current filter value IF3 is less than 0.9 times the allowable current value I3 (= 200 A × 0.9 = 180 A), the control circuit 100 sets the current limit value Ilim3 to a value (unlimited value) greater than the allowable current value I3. When the current filter value IF3 is equal to or greater than 0.9 times the allowable current value I3 and less than the allowable current value I3, the control circuit 100 monotonically decreases the current limit value Ilim3 toward the allowable current value I3 as the current filter value IF3 increases. When the current filter value IF3 is greater than the allowable current value I3, the control circuit 100 sets the current limit value Ilim3 to the allowable current value I3.

In a similar manner, the control circuit 100 sets the current limit value Ilim1 according to the current filter value IF1 (step S31A).

Then, the control circuit 100 limits the magnitude of the current I to less than the current limit values Ilim1, Ilim2, and Ilim3 (step S40A).

In this way, by gradually decreasing each current limit value Ilim toward each allowable current value as each current filter value IF approaches each allowable current value, it is possible to prevent the current from being suddenly limited.

[Modification 2]
In the above embodiment, as shown in FIG. 2, it is assumed that the thermal limit characteristic of the current-carrying component is defined by the continuous current-carrying time of the current-carrying component and the average current during the continuous current-carrying time.

However, in reality, the thermal limit characteristics of an energized component can change depending on the environmental temperature (exposure temperature) of the energized component and the period of use (deterioration state) of the energized component. Specifically, the allowable current value of an energized component decreases the higher the environmental temperature and the longer the period of use (the greater the degree of deterioration over time), even if the continuous current-carrying time and average current are the same. In particular, the fuse 12 tends to be easily affected by the period of use, as its melting temperature changes due to component deterioration.

In view of this, at least one of the current filter value IF and the current limit value Ilim may be changed according to at least one of the environmental temperature and the period of use of the current-carrying component. For example, the control circuit 100 may set the current filter value IF to a larger value the higher the environmental temperature of the current-carrying component and/or the longer the period of use of the current-carrying component, so that the current limit is more likely to be applied. The control circuit 100 may set the current limit value Ilim to a smaller value the higher the environmental temperature of the current-carrying component and/or the longer the period of use of the current-carrying component, so that the current limit is more likely to be applied. The control circuit 100 can change each current filter value IF by changing the IIR filter coefficient α according to the environmental temperature and the period of use of the current-carrying component. The environmental temperature of the current-carrying component may be determined, for example, from the detection result of the temperature sensor 16.

[Modification 3]
At system startup when battery system 1 changes from a stopped state to an operating state (for example, when the vehicle user turns on the IG in a case where battery system 1 is installed in a vehicle), the current filter value IF at the time of the previous system shutdown may be read from memory 102, and the current filter value IF at system startup may be calculated from the current filter value IF at the time of the previous system shutdown and the time from the previous system shutdown to the current system startup (system shutdown time).

For example, assuming that the absolute current value |I| during system shutdown is 0, the current filter value IF during system startup may be the current filter value IF obtained by dividing the current filter value IF at the previous system shutdown by the system shutdown time. This allows the current filter value IF during system startup to be a value that takes into account the amount of heat dissipated by current-carrying components while the system is stopped.

[Modification 4]
In the above embodiment, the current limit value is set to protect the current-carrying components from heat, but the purpose of limiting the current is not limited to protecting the current-carrying components from heat and may be various purposes. Therefore, multiple current limit values may be calculated according to multiple purposes, and the minimum value of the multiple current limit values may be selected.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope of the claims.

1 Battery system, 10 Battery pack, 11 Battery, 12 Fuse, 13 Monitoring unit, 14 Current sensor, 15 Voltage sensor, 16 Temperature sensor, 20 Load, 100, 100A Control circuit, 101 Processor, 102 Memory, 110 Current acquisition unit, 121, 122, 123 IIR filter, 131, 132, 133 Judgment unit, 140 Current limiting unit, NL Negative pole line, PL Positive pole line, SMR System main relay.

Claims (6)

a current-carrying path in which a current-carrying component including a battery is disposed;
a current sensor for detecting a current flowing through the current path;
A control circuit for controlling a current flowing through the current path,
The control circuit includes:
calculating a plurality of current filter values corresponding to average currents during a plurality of predetermined continuous current application periods by performing infinite impulse response filtering on the detection value of the current sensor;
setting a plurality of current limit values corresponding to the plurality of continuous current application times, respectively, so that the current limit values are less than an allowable current of the current-carrying component;
When at least one of the plurality of current filter values exceeds a current limit value corresponding to the current filter value, the current flowing through the current path is limited to the current limit value or less ;
the control circuit changes each of the plurality of current limit values in accordance with a current filter value corresponding to the current limit value;
The control circuit includes:
When the current filter value is less than a second value that is smaller than the first value, the current limit value corresponding to the current filter value is set to a value greater than the first value;
When the current filter value is equal to or greater than the second value and less than the first value, the current limit value corresponding to the current filter value is monotonically decreased toward the first value as the current filter value increases;
When the current filter value is greater than the first value, the current limit value corresponding to the current filter value is set to the first value . The battery system of claim 1, wherein the control circuit calculates the multiple current filter values by filtering the detection value of the current sensor with multiple infinite impulse responses having different filter coefficients. a current-carrying path in which a current-carrying component including a battery is disposed;
a current sensor for detecting a current flowing through the current path;
A control circuit for controlling a current flowing through the current path,
The control circuit includes:
calculating a plurality of current filter values corresponding to average currents during a plurality of predetermined continuous current application periods by performing infinite impulse response filtering on the detection value of the current sensor;
setting a plurality of current limit values corresponding to the plurality of continuous current application times, respectively, so that the current limit values are less than an allowable current of the current-carrying component;
When at least one of the plurality of current filter values exceeds a current limit value corresponding to the current filter value, the current flowing through the current path is limited to the current limit value or less;
The control circuit changes at least one of the current filter value and the plurality of current limit values in response to at least one of an environmental temperature of the current-carrying component and a period of use of the current-carrying component. The battery system according to claim 3 , wherein the control circuit increases the current filter value as an environmental temperature of the current-carrying component increases and/or as a period of use of the current-carrying component increases. The battery system according to claim 3 , wherein the control circuit reduces the plurality of current limiting values as an environmental temperature of the current-carrying component increases and/or as a period of use of the current-carrying component increases. 1. A battery system comprising:
a current-carrying path in which a current-carrying component including a battery is disposed;
a current sensor for detecting a current flowing through the current path;
A control circuit for controlling a current flowing through the current path,
The control circuit includes:
calculating a plurality of current filter values corresponding to average currents during a plurality of predetermined continuous current application periods by performing infinite impulse response filtering on the detection value of the current sensor;
setting a plurality of current limit values corresponding to the plurality of continuous current application times, respectively, so that the current limit values are less than an allowable current of the current-carrying component;
When at least one of the plurality of current filter values exceeds a current limit value corresponding to the current filter value, the current flowing through the current path is limited to the current limit value or less;
The control circuit stores a current filter value when the battery system is stopped and changes from an operating state to a stopped state;
The control circuit calculates a current filter value at system startup, when the battery system changes to an operating state after having been in a stopped state for a long time, using the current filter value stored when the system was stopped and the time during which the stopped state of the battery system continued.

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