JP2023161254A - battery system - Google Patents

Abstract

To reduce a processing load required for heat protection of a current-application component inside a battery system.SOLUTION: A battery system comprises a current-application passage where a current-application component including a battery is placed, a current sensor for detecting current flowing in the current-application passage, and a control circuit for controlling the current flowing in the current-application passage. The control circuit calculates a plurality of current filter values each corresponding to an average current obtained from a plurality of continuous current-application time durations, sets a plurality of current limit values corresponding to the respective continuous current-application time durations so as to be less than an allowable current of the current-application component and limits the current flowing in the current-application passage to the current limit value or less if at least one of the plurality of current filter values exceeds the current limit value corresponding to the current filter value, by subjecting a value detected by the current sensor to filter processing of infinite impulse response.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to techniques for preventing overheating of current-carrying components within a battery system.

Japanese Patent No. 5687340 (Patent Document 1) discloses a battery system that prevents components constituting a battery from overheating. In this battery system, a current limit value for preventing overheating is set for each current-carrying component in the battery system. The current limit value is set as a plurality of average current values that are respectively allowed during a plurality of preset time window widths (continuous energization time width) within a range that does not exceed the thermal allowable current of the energized component. This battery system calculates the average current for each of multiple time window widths, and limits the current flowing through the battery to a current limit value or less so that each average current does not exceed the thermal allowable current corresponding to each average current. .

Patent No. 5687340

In the battery system disclosed in Japanese Patent No. 5,687,340, in which the average current is calculated for each of a plurality of continuous energization time widths, the processing load required for thermal protection of energized components becomes enormous. For example, if one continuous energization time width is 20 seconds and current is detected at a 0.1 second cycle, data of 200 current detection values detected in the past 20 seconds is stored in memory, and these 200 It is necessary to calculate the moving average value of the current detection values at the points. Since such processing is performed for each of a plurality of continuous energization time widths, the processing load becomes enormous. Furthermore, if a plurality of continuous energization time widths are set for each of a plurality of energized components, the processing load will further increase.

The present 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.

(Section 1) A battery system according to the present disclosure includes a current-carrying path in which a current-carrying component including a battery is arranged, a current sensor that detects a current flowing through the current-carrying path, and a control circuit that controls the current flowing through the current-carrying path. . The control circuit calculates a plurality of current filter values each corresponding to the average current during a plurality of predetermined continuous energization times by performing infinite impulse response filter processing on the detected value of the current sensor. If multiple current limit values corresponding to continuous energization time are set to be less than the allowable current of the energized parts, and at least one of the multiple current filter values exceeds the current limit value corresponding to the current filter value. , limits the current flowing through the energization path to below the current limit value.

(Section 2) In the battery system described in Section 1, the control circuit performs filter processing of a plurality of infinite impulse responses having mutually different filter coefficients on the detected value of the current sensor. Calculate the filter value.

(Section 3) In the battery system according to item 1 or 2, the control circuit changes each of the plurality of current limit values according to a current filter value corresponding to the current limit value.

(Section 4) In the battery system described in Section 3, if the current filter value is less than a second value that is smaller than the first value, the control circuit sets the current limit value corresponding to the current filter value to the first value. If the current filter value is greater than or equal to the second value and less than the first value, the larger the current filter value is, the more the current limit value corresponding to the current filter value is directed toward the first value. If the current filter value is larger than the first value, the current limit value corresponding to the current filter value is set to the first value.

(Section 5) In the battery system according to any one of Items 1 to 4, the control circuit sets a current filter value and a plurality of current limits according to at least one of the environmental temperature of the current-carrying component and the period of use of the current-carrying component. Change at least one of the values.

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

(Section 7) In the battery system described in Section 5, the control circuit sets the plurality of current limit values to smaller values as the environmental temperature of the current-carrying parts is higher and/or the period of use of the current-carrying parts is longer. do.

(Section 8) In the battery system according to any one of Items 1 to 7, the control circuit stores the current filter value when the battery system is stopped, when the battery system changes from an operating state to a stopped state. The control circuit uses the current filter value stored when the system was stopped and the time period during which the battery system has been in a stopped state to start the system when it changes to an operating state after the battery system has been in a stopped state. Calculate the current filter value at startup.

According to the present disclosure, it is possible to reduce the processing load required for thermal protection of current-carrying components in a battery system.

1 is a diagram schematically showing the overall configuration of a battery system. FIG. 3 is a diagram schematically showing thermal limit characteristics of a current-carrying component. FIG. 3 is a functional block diagram of a control circuit. FIG. 7 is a diagram comparing the waveform characteristics of an average current calculated by conventional averaging processing and the waveform characteristics of a current filter value IF calculated by IIR filter processing. FIG. 2 is a diagram (part 1) showing the flow of processing of the control circuit. FIG. 2 is a diagram (part 2) showing the flow of processing of the control circuit.

Embodiments of the present disclosure will be described in detail below with reference to the drawings. In addition, the same reference numerals are attached to the same or corresponding parts in the drawings, and the description thereof will not be repeated.

<System configuration>
FIG. 1 is a diagram schematically showing the overall configuration of a battery system 1 according to the present embodiment. The battery system 1 is mounted, for example, on a vehicle that uses an inverter and a motor generator, which are examples of the load 20, as driving power sources.

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. Battery pack 10 includes a battery 11, a fuse 12, a monitoring unit 13, and a system main relay SMR.

The battery 11 is an assembled battery including a plurality of cells. Each cell is a secondary battery such as a lithium ion battery.

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

System main relay SMR is electrically connected between battery 11 and load 20. System main relay SMR is closed according to a command from control circuit 100. By closing system main relay SMR, a current-carrying path between battery 11 and load 20 is formed.

Fuse 12 is provided between battery 11 and system main relay SMR. When a large current flows through the fuse 12, the built-in alloy components melt and the current-carrying path between the battery 11 and the load 20 is electrically interrupted.

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

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 energization path). Note that the current I detected by the current sensor 14 assumes a positive value when the battery 11 is discharged and a negative value when the battery 11 is charged. Voltage sensor 15 detects the voltage of battery 11. Temperature sensor 16 detects the temperature of battery 11 . Each sensor within the monitoring unit 13 outputs a 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. (not shown). Control circuit 100 controls system main relay SMR and load 20 based on programs and maps stored in memory, signals received from each sensor, and the like.

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

The maximum input/output current of the battery 11 is determined based on the thermal limit of each current-carrying component in order to protect each component on the current-carrying path (hereinafter also referred to as "current-carrying component") from heat while satisfying the input/output requirements of the load 20 side. It is desirable that the current be within a range that does not exceed the rated current (hereinafter also referred to as "allowable current") determined in consideration of the characteristics. Note that the allowable current according to this embodiment includes a thermal allowable current.

Thermal limit characteristics (permissible current characteristics) of a current-carrying component are sometimes defined by the continuous current-carrying time of the current-carrying component and the average current during the continuous current-carrying time.

FIG. 2 is a diagram schematically showing the thermal limit characteristics of current-carrying components. In FIG. 2, the vertical axis shows the continuous energization time (unit: sec), and the horizontal axis shows the average current during the continuous energization time (unit: A (ampere)). Note that, in FIG. 2, the allowable currents of three components A to C are illustrated as thermal limit characteristics of current-carrying components. The allowable current of components A to C shown in FIG. 2 is a line that must not be exceeded in order to thermally protect components A to C.

As shown in FIG. 2, the allowable current of each component A to C is different from each other, but all have the characteristic that the longer the continuous energization time, the smaller the allowable current becomes. In order to appropriately thermally protect each component A to C, it is desirable to suppress the current I flowing through the current-carrying path so that the average current flowing through each component A to C does not exceed its respective allowable current.

As a method for this, conventionally, as in the battery system disclosed in the above-mentioned Japanese Patent No. 5,687,340, a plurality of continuous energization time widths are set in advance, and a moving average of the current is calculated for each of the plurality of continuous energization time widths. In some cases, averaging was performed. However, the conventional average processing has a problem in that the processing load required for thermal protection of current-carrying components becomes enormous.

For example, if the three continuous energization time widths T1=0.1s (seconds), T2=1s, and T3=20s shown in FIG. 2 are set in advance, the average of the three continuous energization time widths T1, T2, and T3 The method of calculating each current is the conventional averaging process. This conventional averaging process imposes an enormous processing load. For example, when acquiring the detected value of the current sensor 14 at a period of 0.1 s, in order to calculate the average current for the continuous energization time width T3 (=20 s), it is necessary to It is necessary to store the data in memory and calculate the moving average value of the current detection values at these 200 points. Since such averaging processing needs to be performed for each continuous energization time width T1, T2, and T3, the processing load becomes enormous.

Therefore, the control circuit 100 according to the present embodiment does not calculate the average current for each of a plurality of continuous energization times, but instead responds to the current I, which is the detected value of the current sensor 14, by responding to an infinite impulse response (IIR). ) By performing filter processing, a "current filter value IF" corresponding to the average current is calculated for each of a plurality of continuous energization times. Then, the control circuit 100 suppresses overheating of each current-carrying component by limiting the magnitude of the current I based on each current filter value IF.

The IIR filter is a digital filter that obtains desired filter characteristics with a smaller number of taps (number of coefficients used in calculations) by incorporating feedback rather than simply taking a moving average. Therefore, by performing IIR filter processing, the processing load can be significantly reduced compared to simply performing moving average processing. Therefore, compared to the conventional case of calculating the average current for each of a plurality of continuous energization time widths, the processing load required for thermal protection of energized components can be reduced. Hereinafter, thermal protection of current-carrying components according to this embodiment will be explained in detail.

<How to set continuous energization time>
Before explaining the IIR filter processing according to the present embodiment, a method for setting the continuous energization time according to the present embodiment will be explained with reference to FIG. 2.

As shown in FIG. 2, the allowable currents of each component A to C are different from each other. In order to protect each component A to C from heat while suppressing the processing load, it is desirable to appropriately set the number and value of continuous energization time. In this embodiment, the number and value of continuous energization time are set in the following procedure.

(Step 1) Set a current limit target line as shown in FIG. 2 in a region that does not exceed the allowable current of parts A to C.

(Step 2) Continuous energization time (20 s in the example shown in FIG. 2) at the intersection P3 of the smallest allowable current value I3 (200 A in the example shown in FIG. 2) and the current limit target line among the allowable currents of parts A to C ) is set to "continuous energization time width T3". Further, the allowable current value I3 is set to the "current limit value Ilim3".

(Step 3) The smallest allowable current value I2 among the intersections of the continuous energization time width T3 and the allowable current of parts A to C (in the example shown in FIG. 2, the continuous energization time width T3 = 20 s and the allowable current of component B) The continuous energization time (1 s in the example shown in FIG. 2) at the intersection P2 between the current limit target line and the current limit target line is set to the "continuous energization time width T2". Further, the allowable current value I2 is set to the "current limit value Ilim2".

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

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

By setting the number and value of continuous energization times using such a procedure, the number of continuous energization times can be suppressed to an appropriate number necessary and sufficient for thermal protection of components A to C. Therefore, the number of continuous energization times is suppressed from becoming excessively large. As a result, processing load can be reduced.

Furthermore, the current limit values Ilim set through such a procedure are all values less than the allowable currents of components A to C. Therefore, by limiting the current I to below the current limit value Ilim, the current I can be controlled so as not to exceed the allowable currents of the components A to C. Therefore, the parts A to C can be appropriately thermally protected.

<Thermal protection of current-carrying components using IIR filter processing>
The control circuit 100 according to the present embodiment performs IIR filter processing for each of the continuous energization time widths T1, T2, and T3 set as described above. ``filter value IF1'', ``current filter value IF2'' corresponding to the average current during continuous energization time width T2, and ``current filter value IF3'' corresponding to the average current during continuous energization time width T3 are calculated, respectively.

The control circuit 100 sets current limit values Ilim1, Ilim2, and Ilim3 corresponding to continuous energization time widths T1, T2, and T3, respectively. Note that in this embodiment, the current limit values Ilim1, Ilim2, and Ilim3 are set in advance to allowable current values I1 (=700A), I2 (=400A), and I3 (=200A), respectively, as described above. There is.

Then, 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 energization path to the current limit value Ilim1. This suppresses use in "region Z" where the average current is larger than the current limit value Ilim1 (=700 A) and the continuous energization time exceeds the continuous energization time width T1 (=0.1 s).

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 energization path to the current limit value Ilim2. This suppresses use in "region Y" where the average current is larger than the current limit value Ilim2 (=400 A) and the continuous energization time exceeds the continuous energization 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 energization path to the current limit value Ilim3. This suppresses use in "region X" where the average current is larger than the current limit value Ilim3 (=200 A) and the continuous energization time exceeds the continuous energization time width T3 (=20 s).

FIG. 3 is a functional block diagram of a portion of the control circuit 100 related to thermal protection of current-carrying components. The control circuit 100 includes a current acquisition section 110, IIR filters 121 to 123, determination sections 131 to 133, and a current limiting section 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 "absolute current value |I|") to the IIR filters 121 to 123.

As mentioned above, the current I takes a positive value when the battery 11 is discharged and takes a negative value when the battery 11 is charged. However, since the amount of heat generated by the current-carrying parts is proportional to the square of the current I, the temperature of the current-carrying parts is proportional to the current I. Regardless of whether the current I is positive or negative, the larger the absolute value of the current I, the higher the current I becomes. Considering this point, the current acquisition unit 110 transmits the current absolute value |I| to the IIR filters 121 to 123 instead of the current I itself. As a result, the current absolute value |I| becomes a target of IIR filter processing. Note that the object of the IIR filter processing may be the square value of the current I instead of the current absolute value |I|.

The IIR filter 121 performs IIR filter processing on the current absolute value |I| from the current acquisition unit 110 by setting the IIR filter coefficient α to "first coefficient α1", thereby reducing the average current during the continuous energization time width T1. A corresponding current filter value IF1 is calculated, and the calculation result is transmitted to the determination unit 131.

The IIR filter 122 performs IIR filter processing on the current absolute value |I| from the current acquisition unit 110 by setting the IIR filter coefficient α to "second coefficient α2", thereby reducing the average current during the continuous energization time width T2. A corresponding current filter value IF2 is calculated and the calculation result is sent to the determination unit 132.

The IIR filter 123 performs IIR filter processing on the current absolute value |I| from the current acquisition unit 110 by setting the IIR filter coefficient α to "third coefficient α3", thereby reducing the average current during the continuous energization time width T3. A corresponding current filter value IF3 is calculated, and the calculation result is sent to the determination unit 133.

The determination unit 131 sets a current limit value Ilim1 for the continuous energization time width T1, and determines the magnitude relationship between the current filter value IF1 from the IIR filter 121 and the current limit value Ilim1. In this embodiment, as described above, the current limit value Ilim1 is fixed in advance to the allowable current value I1 (=700A) shown in FIG. 2.

The determination unit 132 sets a current limit value Ilim2 for the continuous energization time width T2, and determines the magnitude relationship between the current filter value IF2 from the IIR filter 122 and the current limit value Ilim2. Note that in this embodiment, as described above, the current limit value Ilim2 is fixed in advance to the allowable current value I2 (=400A) shown in FIG. 2.

The determination unit 133 sets a current limit value Ilim3 for the continuous energization time width T3, and determines the magnitude relationship between the current filter value IF3 from the IIR filter 123 and the current limit value Ilim3. Note that in this embodiment, as described above, the current limit value Ilim3 is fixed in advance to the allowable current value I3 (=200A) shown in FIG. 2.

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

FIG. 4 is a diagram comparing the waveform characteristics of the average current calculated by the conventional averaging process and the waveform characteristics of the current filter value IF calculated by the IIR filter process according to the present embodiment.

Conventional averaging processing simply performs a moving average. Note that the conventional averaging process can be performed using, for example, a FIR (Finite Impulse Response) low-pass filter. The FIR low-pass filter has a configuration in which a weighting parameter is added for each of a plurality of elements to be subjected to a moving average. An example of the configuration of the FIR low-pass filter is shown in the lower part of FIG.

In contrast, the IIR filter (IIR low-pass filter) according to the present embodiment does not simply take a moving average, but incorporates feedback to achieve desired filter characteristics with a smaller number of taps (number of coefficients used for calculation). It has a configuration that obtains. Therefore, the processing load can be significantly reduced compared to a case where moving average is simply performed as in the case of an FIR filter. An example of the configuration of the IIR low-pass filter is shown in the lower part of FIG. Note that the configuration of the IIR low-pass filter shown in FIG. 4 is just an example, and is not limited thereto. For example, the configuration shown in FIG. 4 may be included as a basic configuration, and more complex configurations may be added.

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

In the example shown in FIG. 4, the IIR filter coefficient α (second coefficient α2) is adjusted to "0.1667". Similarly, the IIR filter coefficient α (third coefficient α3) for calculating the current filter value IF3 is set to “0. 0091". In this way, by adjusting the value of the IIR filter coefficient α, the current filter values IF1, IF2, and IF3 can be adapted to the values corresponding to the average currents during the continuous energization time widths T1, T2, and T3, respectively. .

FIG. 5 is a diagram showing the flow of processing when the control circuit 100 performs thermal protection of current-carrying components.

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

Next, the control circuit 100 calculates a current filter value IF1 corresponding to the average current of the continuous energization time width T1 by applying IIR filter processing of α=α1 to the current absolute value |I| (step S21). Then, the control circuit 100 sets the current limit value Ilim1 for the continuous energization 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 energization time width T1 is 0.1 s and the current I is acquired at a 0.1 s period, the current absolute value |I| may be set as the current filter value IF1. good.

The control circuit 100 calculates a current filter value IF2 corresponding to the average current of the continuous energization time width T2 by applying IIR filter processing of α=α2 to the current absolute value |I| (step S22). Then, the control circuit 100 sets the current limit value Ilim2 for the continuous energization time width T2, and determines the magnitude relationship between the current filter value IF2 and the current limit value Ilim2 (step S32).

The control circuit 100 calculates a current filter value IF3 corresponding to the average current of the continuous energization time width T3 by applying IIR filter processing of α=α3 to the current absolute value |I| (step S23). Then, the control circuit 100 sets a current limit value Ilim3 for the continuous energization time width T3, and determines the magnitude relationship between the current filter value IF3 and the current limit value Ilim3 (step S33).

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

As described above, the control circuit 100 according to the present embodiment performs IIR filter processing on the magnitude of the current I, which is the detected value of the current sensor 14, so that Current filter values IF1, IF2, and IF3 respectively corresponding to the average current are calculated. Therefore, it is possible to obtain an average current with the same accuracy as the conventional method with less processing load. As a result, the processing load required for thermal protection of current-carrying components can be reduced.

[Modification 1]
In the embodiment described above, 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, but in this case, the current before current limit If the difference between the magnitude of I and the magnitude of the current I after current limitation (=current limit value Ilim) is large, a sudden current limit will be applied.

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

FIG. 6 is a diagram showing the flow of processing when the control circuit 100A according to Modification 1 performs thermal protection of energized components. The process in FIG. 6 is obtained by changing steps S31 to S33 and S40 in FIG. 5 described above to steps S31A to S33A and S40A, respectively. The other processing in FIG. 6 is the same as the processing in FIG. 5 described above, so detailed description will not be repeated here.

Control circuit 100 sets current limit value Ilim2 according to current filter value IF2 (step S32A). Specifically, when the current filter value IF2 is less than 0.9 times the allowable current value I2 (=400A×0.9=360A), the control circuit 100 sets the current limit value Ilim2 to the allowable current value I2. Set to a value greater than (unlimited value). When the current filter value IF2 is at least 0.9 times the allowable current value I2 and less than the allowable current value I2, the control circuit 100 sets the current limit value Ilim2 to the allowable current value I2 as the current filter value IF2 becomes larger. Monotonically decreases towards. When the current filter value IF2 is larger 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 (=200A×0.9=180A), the control circuit 100 sets the current limit value Ilim3 to the allowable current value I3. Set to a value greater than (unlimited value). When the current filter value IF3 is at least 0.9 times the allowable current value I3 and less than the allowable current value I3, the control circuit 100 sets the current limit value Ilim3 to the allowable current value I3 as the current filter value IF3 becomes larger. Monotonically decreases towards. When the current filter value IF3 is larger 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, as each current filter value IF approaches each allowable current value, each current limit value Ilim is gradually decreased toward each allowable current value, thereby suppressing the sudden application of current limit. I can do it.

[Modification 2]
In the embodiment described above, as shown in FIG. 2 described above, it is assumed that the thermal limit characteristics of the current-carrying component are 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 a current-carrying component may also change depending on the environmental temperature (exposure temperature) of the current-carrying component and the period of use (deterioration state) of the current-carrying component. Specifically, even if the continuous current-carrying time and average current are the same, the allowable current value of current-carrying parts decreases as the environmental temperature increases and the period of use increases (the degree of deterioration over time increases). do. In particular, the fuse 12 tends to be easily affected by the period of use because its fusing temperature changes due to component deterioration.

In view of this point, at least one of the current filter value IF and the current limit value Ilim may be changed depending on at least one of the environmental temperature and the period of use of the current-carrying component. For example, the control circuit 100 sets the current filter value IF to a larger value as the environmental temperature of the current-carrying component is higher and/or the period of use of the current-carrying component is longer, thereby making it easier to apply current restriction. Good too. In addition, the control circuit 100 sets the current limit value Ilim to a smaller value, so that 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, the easier the current restriction is applied. Good too. Note that the control circuit 100 can change each current filter value IF by changing the IIR filter coefficient α according to the environmental temperature and period of use of the current-carrying component. Note that the environmental temperature of the current-carrying component may be ascertained from the detection result of the temperature sensor 16, for example.

[Modification 3]
When the battery system 1 changes from a stopped state to an operating state (for example, when the battery system 1 is installed in a vehicle and the vehicle user turns on the IG), the previous system stoppage is detected. The current filter value IF at the time of system startup is read from the memory 102, and the current filter value IF at the time of system startup is calculated based on the current filter value IF at the time of the previous system stop and the time from the previous system stop to the current system startup (system (stop time).

For example, assuming that the absolute current value |I| is 0 while the system is stopped, the current filter value IF at the time of the previous system stop divided by the system stop time is set as the current filter value IF at the time of system startup. Good too. Thereby, the current filter value IF at the time of system startup can be set to a value that takes into account the amount of heat dissipated from the energized components while the system is stopped.

[Modification 4]
In the embodiments described above, the current limit value is set for thermal protection of current-carrying components, but the purpose of limiting the current is not limited to thermal protection of current-carrying components, and various purposes may exist. Therefore, a plurality of current limit values may be calculated in accordance with a plurality of purposes, and the minimum value among the plurality of current limit values may be selected.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the claims rather than the above description, and it is intended that all changes within the meaning and range equivalent to the claims are included.

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 section, 140 current limiting section, NL negative electrode line, PL positive electrode line, SMR system main relay.

Claims (8)

a current-carrying path in which current-carrying parts including batteries are placed;
a current sensor that detects the current flowing through the current-carrying path;
and a control circuit that controls the current flowing through the energization path,
The control circuit includes:
calculating a plurality of current filter values each corresponding to an average current during a plurality of predetermined continuous energization times by performing infinite impulse response filter processing on the detected value of the current sensor;
setting a plurality of current limit values respectively corresponding to the plurality of continuous energization times to be less than the allowable current of the energized component;
A battery system in which, 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 energization path is limited to below the current limit value. The control circuit calculates the plurality of current filter values by subjecting the detection value of the current sensor to filter processing of a plurality of infinite impulse responses having mutually different filter coefficients. battery system. The battery system according to claim 1 or 2, wherein the control circuit changes each of the plurality of current limit values according to a current filter value corresponding to the current limit value. The control circuit includes:
If the current filter value is less than a second value smaller than the first value, setting a current limit value corresponding to the current filter value to a value larger than the first value,
If the current filter value is greater than or equal to the second value and less than the first value, the larger the current filter value is, the more the current limit value corresponding to the current filter value is monotonically decreased toward the first value;
The battery system according to claim 3, wherein when the current filter value is larger than the first value, a current limit value corresponding to the current filter value is set to the first value. The battery according to claim 1, wherein the control circuit changes at least one of the current filter value and the plurality of current limit values in accordance with at least one of an environmental temperature of the current-carrying component and a usage period of the current-carrying component. system. The battery system according to claim 5, wherein the control circuit increases the current filter value as the environmental temperature of the current-carrying component is higher and/or the period of use of the current-carrying component is longer. The battery system according to claim 5, wherein the control circuit sets the plurality of current limit values to smaller values as the environmental temperature of the current-carrying component is higher and/or the period of use of the current-carrying component is longer. The control circuit stores a current filter value when the battery system changes from an operating state to a stopped state when the system is stopped;
The control circuit stores the current filter value stored when the system was stopped and the time period during which the battery system remained in a stopped state when the system starts up and changes to an operating state after the battery system continues to be in a stopped state. The battery system according to claim 1, wherein the current filter value at the time of system startup is calculated using the battery system.

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