JP2021019457A - Monitoring device and monitoring method - Google Patents

Abstract

To reduce the effect of voltage error due to thermo-electromotive force.SOLUTION: A monitoring device includes a current sensor and a correction unit. The current sensor is a battery current sensor composed of a secondary battery. The correction unit corrects a current measurement value with an offset value according to a cell voltage immediately before an execution section based on a correlation table between the offset value of the current measurement value generated in advance and the cell voltage during a current measurement within a predetermined time range based on a cell balancing execution section of the battery.SELECTED DRAWING: Figure 5

Description

The disclosed embodiments relate to monitoring devices and monitoring methods.

Conventionally, a monitoring device for monitoring the state of a lithium ion secondary battery (LiB: Lithium-Ion rechargeable battery) mounted on an HEV (Hybrid Electric Vehicle), an EV (Electric Vehicle), etc. as an auxiliary battery, for example, has been known. (See, for example, Patent Document 1).

In such a monitoring device, measurement of cell voltage and current value in LiB, equalization of energy capacity between cells (so-called cell balancing), and the like are performed.

Japanese Unexamined Patent Publication No. 2016-025794

However, there is room for further improvement in the above-mentioned prior art in reducing the influence of the voltage error due to the thermoelectromotive force.

Specifically, in the monitoring device, the connectors of various sensors for acquiring the LiB state are solder-bonded and mounted on the board, but since they are dissimilar metal joints, the solder-bonded parts (hereinafter, "solder"). There is a small potential difference due to thermoelectromotive force in the part), which changes with temperature.

Then, during cell balancing, the discharge resistance of the cell balance IC (Integrated Circuit) generates heat, and heat conduction causes variations in the temperature of each part of the substrate. Here, if there is a temperature difference between the lands of the connector due to such a variation, a minute error is caused in the input voltage due to the difference in thermoelectromotive force.

When the current sensor for measuring the current value of LiB is, for example, a magnetic type, even if there is an input voltage error due to the above-mentioned thermoelectromotive force, the sensor's resolution with respect to the voltage error is low, so the current sensor current measurement The value is unlikely to be affected. However, when the current sensor is, for example, a shunt resistance type, the resolution of the sensor with respect to the voltage error is higher than that of the magnetic type, so that the above-mentioned input voltage error causes an offset error in the current measured value.

One aspect of the embodiment is made in view of the above, and an object of the present invention is to provide a monitoring device and a monitoring method capable of reducing the influence of a voltage error due to thermoelectromotive force.

The monitoring device according to one aspect of the embodiment includes a current sensor and a correction unit. The current sensor is a battery current sensor composed of a secondary battery. The correction unit is based on a correlation table between an offset value of a pre-generated current measurement value and a cell voltage at the time of current measurement within a predetermined time range based on an execution section of cell balancing of the battery. The current measurement value is corrected by the offset value corresponding to the cell voltage immediately before the execution section.

According to one aspect of the embodiment, the influence of the voltage error due to the thermoelectromotive force can be reduced.

FIG. 1 is an explanatory diagram of a mechanism in which a temperature difference occurs between lands. FIG. 2 is a correlation diagram between the input voltage and the detected value in the current sensor. FIG. 3 is a schematic explanatory view (No. 1) of the monitoring method according to the embodiment. FIG. 4 is a schematic explanatory view (No. 2) of the monitoring method according to the embodiment. FIG. 5 is a block diagram of the monitoring system according to the embodiment. FIG. 6 is an operation explanatory diagram when a plurality of cells are cell-balanced. FIG. 7 is a flowchart showing a processing procedure executed by the monitoring device according to the embodiment.

Hereinafter, embodiments of the monitoring device and the monitoring method disclosed in the present application will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments shown below.

Further, in the following, a case where the monitoring device 10 to which the monitoring method according to the embodiment is applied is a monitoring device for monitoring the state of LiB2 mounted on the vehicle will be described as an example.

First, prior to the description of the monitoring method according to the embodiment, the mechanism of the temperature difference between the lands and the correlation between the input voltage and the detected value in the current sensor will be described with reference to FIGS. 1 and 2. FIG. 1 is an explanatory diagram of a mechanism in which a temperature difference occurs between lands L1 and L2. Further, FIG. 2 is a correlation diagram between the input voltage and the detected value in the current sensor.

As shown in FIG. 1, it is assumed that there is a substrate S included in the monitoring device 10. Further, it is assumed that a connector C connected to the current sensor is mounted on the substrate S, and there are lands L1 and L2 which are copper foils for soldering the connector C. Further, although not shown, it is assumed that the cell balance IC is mounted on the substrate S.

Since the connectors C are solder-bonded to the lands L1 and L2, that is, dissimilar metals are bonded, a minute potential difference due to thermoelectromotive force exists in the solder portion and changes depending on the temperature.

Here, the heat generating portion shown in FIG. 1 is, for example, the discharge resistance of the cell balance IC. In such a case, the heat generating portion generates heat during cell balancing, but if the distance from the heat generating portion is different, the temperature varies due to heat conduction in each portion of the substrate S. As shown in FIG. 1, for example, if the distance d1 <distance d2, the temperature of the land L1 is higher than that of the land L2 at the time of cell balancing.

When a temperature difference occurs between the lands L1 and L2 in this way, as shown in FIG. 2, for example, the input voltage to the current sensor via the connector C becomes the input voltage between the cell balancing and the normal time other than that. A minute error pd will occur.

Here, if the current sensor is of the magnetic type, the width of the section dividing the input voltage is large, that is, the resolution of the sensor with respect to the voltage error is low. Therefore, as shown in FIG. 2, the current measurement value is based on the thermoelectromotive force. The effect of voltage error is unlikely to appear (see the detected value I1 in the figure).

On the other hand, if the current sensor is of the shunt resistance type, the width of the section dividing the input voltage is small, that is, the sensor's resolution with respect to the voltage error is high, so that the current measurement value is heated as shown in FIG. Due to the influence of the voltage error due to the electric force, an offset error occurs in the measured current value (see the detected values I2 and I3 in the figure).

Therefore, in the monitoring method according to the embodiment, when the current is measured within a predetermined time range based on the cell balancing execution section of LiB2, the current measurement value generated in advance based on the measured value for each different cell voltage is obtained. Based on the correlation table of the offset value and the cell voltage of, the current measurement value is corrected by the offset value according to the cell voltage immediately before the execution section.

3 and 4 are schematic explanatory views (No. 1) and (No. 2) of the monitoring method according to the embodiment. As described above, since the heat generating portion is, for example, the discharge resistance of the cell balance IC, the amount of heat generated is proportional to the discharge time and the cell voltage at the time of discharge. Further, the heat conduction depends on the arrangement relationship of each component on the substrate S including the lands L1 and L2.

Therefore, in the monitoring method according to the embodiment, first, the actual machine of the monitoring device 10 is used to actually measure the offset value of the current measured value at each of the different cell voltages within the voltage range that can be used in the normal operation, and based on the measured result, the offset value is measured. As shown in FIG. 3, a correlation table in which the correlation between the cell voltage and the offset value is linearly interpolated is generated in advance.

Such a correlation table is generated based on the offset value actually measured based on the cell voltage input through the solder portion.

This makes it possible to correct the current measurement value only when a voltage error due to thermoelectromotive force occurs.

Further, in the correlation table, the correlation between the offset value and the cell voltage is obtained by inputting the cell voltage according to the amount of heat generated from the power of the cell balance IC on the substrate S in which the solder portion is present. It is generated by considering it as a correlation with the temperature change of the above and the calorific value.

This makes it possible to correct the current measurement value based on the voltage error due to the thermoelectromotive force without using parameters related to temperature.

Then, in the monitoring method according to the embodiment, cell balancing is executed during the actual operation of the monitoring device 10, and when the current is measured at the timing when the voltage error due to the thermoelectromotive force affects, the cell is based on the above-mentioned correlation table. The current measurement value by the current sensor is corrected by the offset value according to the cell voltage immediately before the balancing is executed.

More specifically, as shown in FIG. 4, for example, cell balancing is executed at times t3 to t4, and immediately after such an execution section, that is, the M2 portion at times t5 to t6, which is the timing at which the voltage error due to thermoelectromotive force affects. Consider the case where the current is measured by the current sensor.

In such a case, in the monitoring method according to the embodiment, when the current is measured within a predetermined time range based on the M2 part, in other words, the cell balancing execution section, the cell in the M1 part at the time t1 to t2 immediately before the cell balancing The current measured value by the current sensor is corrected by the offset value of the correlation table according to the voltage (see "corrected current value = current measured value-offset value @ cell voltage" in the figure).

That is, in the monitoring method according to the embodiment, the above-mentioned voltage error occurs with respect to the current measurement value at the timing when it is assumed that the current measurement value by the current sensor includes an error due to the influence of the voltage error due to the thermoelectromotive force. The cell voltage measured in the M1 section immediately before the cell balancing is used, that is, the current measurement value by the current sensor is corrected by the offset value corresponding to the cell voltage.

As a result, according to the monitoring method according to the embodiment, the influence of the voltage error due to the thermoelectromotive force can be reduced.

Since the effect of the voltage error due to the thermoelectromotive force is so small that it can be ignored except when the cell is discharged in cell balancing, the above-mentioned correction of the current measurement value is performed only when necessary (for example, the timing of the above-mentioned M2 part). It doesn't have to be done all the time.

Further, in the monitoring method according to the embodiment, as shown in the correlation table described above, the offset value of the current measurement value is estimated from the correlation with the cell voltage, in other words, the thermoelectromotive force is estimated from the correlation with the calorific value of the cell discharge. I'm estimating. Therefore, according to the monitoring method according to the embodiment, it is possible to easily implement the correction means for the current measurement value, and it is not necessary to newly provide a circuit for correction, and it is possible to implement it by software, for example. ..

Hereinafter, a configuration example of the monitoring system 1 to which the monitoring method according to the above-described embodiment is applied will be described in more detail.

FIG. 5 is a block diagram of the monitoring system 1 according to the embodiment. In FIG. 5, only the components necessary for explaining the features of the present embodiment are represented by functional blocks, and the description of general components is omitted.

In other words, each component shown in FIG. 5 is a functional concept and does not necessarily have to be physically configured as shown. For example, the specific form of distribution / integration of each functional block is not limited to the one shown in the figure, and all or part of the functional blocks are functionally or physically distributed in arbitrary units according to various loads and usage conditions. -It is possible to integrate and configure.

As shown in FIG. 5, the monitoring system 1 includes a LiB2, a monitoring device 10, and a host ECU 20. LiB2 is a lithium ion secondary battery, which is mounted on a vehicle and is used, for example, as an auxiliary battery.

The higher-level ECU 20 is a higher-level ECU of the monitoring device 10, and obtains the vehicle state from various sensors mounted on the vehicle at any time, and at any time acquires the state of LiB2 from the monitoring device 10 according to each acquired state. Control the power system of the vehicle.

The monitoring device 10 includes a voltage sensor 11, a current sensor 12, a cell balance IC 13, a storage unit 14, and a control unit 15.

The voltage sensor 11 is connected between the LiB2 and the control unit 15, measures the cell voltage input from the LiB2, and outputs the cell voltage to the control unit 15. The current sensor 12 is connected in series with the LiB2 and outputs a voltage corresponding to the current value flowing through the LiB2 to the control unit 15.

The cell balance IC 13 executes cell balancing that equalizes the energy capacities of a plurality of cells connected in series in LiB2 based on an instruction from the control unit 15.

The storage unit 14 is realized by, for example, a semiconductor memory element such as a RAM (Random Access Memory) or a flash memory (Flash Memory), or a storage device such as a hard disk or an optical disk, and in the example of FIG. 5, the correlation table 14a is stored. To do. The correlation table 14a corresponds to the correlation table described with reference to FIG.

Further, as shown in FIG. 5, the control unit 15 is a controller, and various programs stored in the storage unit 14, for example, by a CPU (Central Processing Unit), an MPU (Micro Processing Unit), or the like. Is realized by executing RAM as a work area. Further, the control unit 15 can be realized by, for example, an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

The control unit 15 includes an acquisition unit 15a, a correction unit 15b, and an equalization control unit 15c, and realizes or executes a function or operation of information processing described below.

The acquisition unit 15a acquires the state of LiB2 and outputs it to the upper ECU 20. For example, the acquisition unit 15a acquires the cell voltage measured by the voltage sensor 11 and the current measurement value measured by the current sensor 12 and outputs them to the host ECU 20. Further, the acquisition unit 15a acquires the execution state of the cell balancing of LiB2 and notifies the correction unit 15b.

The correction unit 15b determines whether or not it is within a predetermined time range based on the cell balancing execution section (that is, whether or not it is the above-mentioned M2 unit) based on the notified execution state of cell balancing. To do.

Further, when the correction unit 15b is within the time range, the cell voltage acquired by the acquisition unit 15a in the above-mentioned M1 unit is obtained by the current measurement value from the current sensor 12 acquired by the acquisition unit 15a within the time range. The offset value of the correlation table 14a corresponding to is corrected.

The correction unit 15b does not correct the current measurement value acquired by the acquisition unit 15a from the current sensor 12 unless it is within the time range.

The equalization control unit 15c causes the cell balance IC 13 to execute the cell balancing of LiB2, for example, based on the instruction of the program executed by the control unit 15.

Next, the operation when a plurality of cells are cell-balanced will be specifically described with reference to FIG. FIG. 6 is an operation explanatory diagram when a plurality of cells are cell-balanced.

As shown in FIG. 6, the cell balance IC 13 executes cell balancing of each cell # 1, # 2, # 3 ... In LiB2 via each channel of CH # 1, # 2, # 3 .... Here, it is assumed that cell balancing is executed in cells # 1 and cells # 3 shown in bold frames in the figure.

At this time, the correction unit 15b acquires the cell voltages V _{CH # 1} , _{CH # 3,} and the current measurement value I via the voltage sensor 11, the current sensor 12, and the acquisition unit 15a (not shown).

Here, as shown in FIG. 6, the correlation table 14a is a CH # 1 table corresponding to each CH # 1, # 2, # 3 ... (that is, each cell # 1, # 2, # 3 ...). It has a CH # 2 table, a CH # 3 table, and so on. Each table corresponds to the correlation table described with reference to FIG.

Therefore, in the case of the example of FIG. 6, the correction unit 15b refers to the CH # 1 table and the CH # 3 table from these tables, and the offset value Off _{CH #} based on the cell voltages V _{CH # 1} and _{CH # 3. 1.} Acquire _{CH # 3} .

Then, the correction unit 15b corrects the current measurement value I with the total value of the acquired offset values Off _{CH # 1} and _{CH # 3} . In this way, the correction unit 15b actually performs cell balancing based on each table showing the correlation between the offset value Off of the current measurement value I and the cell voltage V generated in advance for each cell # 1, # 2, # 3 ... The current measurement value I can be corrected by the total value of the offset values Off of each cell # 1, # 2, # 3 ... As a result, it is possible to perform accurate correction according to the actual cell balancing situation.

Next, the processing procedure executed by the monitoring device 10 according to the embodiment will be described with reference to FIG. 7. FIG. 7 is a flowchart showing a processing procedure executed by the monitoring device 10 according to the embodiment.

As shown in FIG. 7, the acquisition unit 15a acquires the cell voltage V from the voltage sensor 11 (step S101). Further, the acquisition unit 15a acquires the current measurement value I from the current sensor 12 (step S102).

Then, the correction unit 15b determines whether or not it is immediately after cell balancing, that is, whether or not it is within a predetermined time range based on the cell balancing execution section (step S103).

Here, in the case immediately after cell balancing (step S103, Yes), the correction unit 15b corrects the current measurement value I with the offset value Off of the correlation table 14a corresponding to the cell voltage V immediately before cell balancing (step S104). .. Then, the process from step S101 is repeated.

Further, even if it is not immediately after cell balancing (steps S103 and No), the processing from step S101 is repeated.

As described above, the monitoring device 10 according to the embodiment includes the current sensor 12 and the correction unit 15b. The current sensor 12 is a current sensor of LiB2 (corresponding to an example of a “battery composed of a secondary battery”). The correction unit 15b sets the correlation table 14a between the offset value Off of the pre-generated current measurement value I and the cell voltage V at the time of current measurement within a predetermined time range based on the cell balancing execution section of LiB2. Based on this, the current measurement value I is corrected by the offset value Off corresponding to the cell voltage V immediately before the execution section.

Therefore, according to the monitoring device 10 according to the embodiment, the influence of the voltage error due to the thermoelectromotive force can be reduced.

Further, the correlation table 14a is information in which the correlation between the offset value Off and the cell voltage V is linearly interpolated based on the offset value Off actually measured for each of the different cell voltages V.

Therefore, according to the monitoring device 10 according to the embodiment, it is possible to correct the current measurement value I while maintaining monotony, with a small amount of calculation while the number of samplings is at least according to the variation for each actual machine. Become.

Further, the correlation table 14a is generated based on the offset value Off actually measured at the output voltage of the current sensor 12 input via the solder portion (corresponding to an example of the “dissimilar metal joint portion”).

Therefore, according to the monitoring device 10 according to the embodiment, it is possible to correct the current measurement value I only when a voltage error due to thermoelectromotive force occurs.

Further, the correlation table 14a is described by inputting the cell voltage V according to the amount of heat generated estimated from the electric power of the cell balance IC 13 (corresponding to an example of the “discharge circuit”) on the substrate S in which the solder portion is present. It is generated by regarding the correlation between the offset value Off and the cell voltage V as the correlation between the temperature change of the solder portion and the calorific value.

Therefore, according to the monitoring device 10 according to the embodiment, it is possible to correct the current measured value I based on the voltage error due to the thermoelectromotive force without using the parameter related to the temperature.

Further, the correlation table 14a is provided for each cell of LiB2, and the correction unit 15b acquires the offset value Off corresponding to each of the cells in which the cell balancing is executed from the correlation table 14a, and the offset value Off is set. The current measurement value I is corrected by the total value.

Therefore, according to the monitoring device 10 according to the embodiment, it is possible to perform accurate correction according to the actual cell balancing situation.

In the above-described embodiment, for example, as shown in FIG. 4, the time of current measurement within a predetermined time range based on the execution section of cell balancing of LiB2 is represented by one M2 part, but the offset value. The correction of the current measurement value I by Off is not limited to once immediately after cell balancing.

Therefore, the period during which the influence of heat conduction due to cell balancing remains and the temperatures of lands L1 and L2 are not expected to drop until the normal time is regarded as within a predetermined time range based on the cell balancing execution section of LiB2. Therefore, the correction may be performed each time the current is measured during this period.

Further, in the above-described embodiment, as shown in FIG. 5, an example in which the monitoring device 10 is configured separately from the LiB2 is given, but the present invention is not limited to this, and for example, the monitoring device 10 is used as one battery pack. LiB2 may be integrally configured.

Further, the monitoring device 10 may be integrally configured with the upper ECU 20 and may be configured as a part of the function of the control device that controls the electric power system of the vehicle, for example.

Further, in the above-described embodiment, the case where the monitoring device 10 is a monitoring device for monitoring the state of the LiB2 mounted on the vehicle is taken as an example, but the present invention is not limited to this, and the mounting destination of the LiB2 is not questioned. .. Therefore, it can be applied to the case where LiB2 is mounted in addition to the vehicle.

Further effects and variations can be easily derived by those skilled in the art. For this reason, the broader aspects of the invention are not limited to the particular details and representative embodiments expressed and described as described above. Therefore, various modifications can be made without departing from the spirit or scope of the general concept of the invention as defined by the appended claims and their equivalents.

1 Monitoring system 10 Monitoring device 11 Voltage sensor 12 Current sensor 13 Cell balance IC
14 Storage unit 14a Correlation table 15 Control unit 15a Acquisition unit 15b Correction unit 15c Equalization control unit 20 Upper ECU
C connector L1, L2 land S board

Claims (6)

A battery current sensor consisting of a secondary battery and
At the time of current measurement within a predetermined time range based on the cell balancing execution section of the battery, immediately before the execution section based on the correlation table between the offset value of the current measurement value generated in advance and the cell voltage. A monitoring device including a correction unit that corrects the current measurement value with the offset value according to the cell voltage. The correlation table is
The monitoring device according to claim 1, wherein the correlation between the offset value and the cell voltage is linearly interpolated information based on the offset value actually measured for each of the different cell voltages. The correlation table is
The monitoring device according to claim 1 or 2, wherein the monitoring device is generated based on the offset value actually measured at the output voltage of the current sensor input through the dissimilar metal joint. The correlation table is
By inputting the cell voltage according to the calorific value estimated from the electric power of the discharge circuit on the substrate on which the dissimilar metal joint exists, the correlation between the offset value and the cell voltage is changed by the temperature of the dissimilar metal joint. The monitoring device according to claim 3, wherein the monitoring device is generated in consideration of a correlation with the calorific value. The correlation table is
It is provided for each cell of the battery.
The correction unit
Any of claims 1 to 4, wherein the offset value corresponding to each of the cells for which cell balancing has been executed is acquired from the correlation table, and the current measurement value is corrected by the total value of the offset values. The monitoring device described in one. It is a monitoring method using a monitoring device equipped with a battery current sensor consisting of a secondary battery.
At the time of current measurement within a predetermined time range based on the cell balancing execution section of the battery, immediately before the execution section based on the correlation table between the offset value of the current measurement value generated in advance and the cell voltage. A monitoring method comprising a correction step of correcting the current measurement value with the offset value according to the cell voltage.

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