JP7097741B2 - Current detection system, power storage system - Google Patents

Description

The present invention relates to a current detection system and a power storage system that detect a current flowing through an object such as a battery.

In recent years, hybrid vehicles (HVs), plug-in hybrid vehicles (PHVs), and electric vehicles (EVs) have become widespread. Furthermore, in order to extend the cruising range by motor driving, the number of vehicles with increased battery capacity by connecting cells and modules in parallel is increasing. In order to extend the cruising range by motor running while ensuring safety, it is important to manage the SOC (State Of Charge) of the cell with high accuracy. In order to estimate the SOC of the cell during the period when the current is flowing through the cell, it is common to use the current integration method. The current integration method estimates the current SOC by adding the integrated value of charge / discharge current to the initial value of the SOC, with the SOC corresponding to the OCV (Open Circuit Voltage) of the cell at the start of charging / discharging as the initial value. How to do it.

In order to estimate SOC with high accuracy by the current integration method, it is important to improve the detection accuracy of the current sensor (see, for example, Patent Document 1). As described above, with the increase in the capacity of the in-vehicle battery, the value of the current flowing through the cell is increasing, and a current sensor having a wide current detection range is required.

Japanese Unexamined Patent Publication No. 2004-226154

However, a current sensor having a wide current detection range tends to have a large offset error. It is difficult to find a current sensor with a wide current detection range and high detection accuracy as a general-purpose product, and even if it exists, the unit price will be high.

The present invention has been made in view of these circumstances, and an object of the present invention is to provide a technique for detecting a wide range of currents with high accuracy.

In order to solve the above problems, the current detection system according to an embodiment of the present invention has a wider current detection range than the first current detection unit for detecting the current flowing through a predetermined detection target and the first current detection unit. A current detection unit having a lower current detection accuracy than the first current detection unit, a second current detection unit that detects the current flowing through the detection target in parallel with the first current detection unit, and the first current detection unit. Based on the difference between the first integrated value obtained by integrating the current values detected by the unit and the second integrated value obtained by integrating the current values detected by the second current detecting unit, the first current detecting unit A correction unit for correcting the output value of the first current detection unit in a period exceeding the current detection range is provided.

According to the present invention, a wide range of currents can be detected with high accuracy.

It is a figure which shows the structure of the current detection system which concerns on embodiment of this invention. 2 (a) and 2 (b) are diagrams showing a configuration example of the first current detection unit. 3 (a)-(c) are diagrams showing an example of a current waveform detected by the first current detection unit and the second current detection unit. It is a figure for demonstrating the example which applied the current detection system of FIG. 1 to the electric power storage system for vehicle.

FIG. 1 is a diagram showing a configuration of a current detection system 50 according to an embodiment of the present invention. The current detection system 50 is a system that detects the current flowing through the object 5, and includes a first current detection unit 11, a second current detection unit 12, and a correction unit 15. The object 5 is a battery or a load connected on the current path Pc. The first current detection unit 11 and the second current detection unit 12 simultaneously detect the current flowing in the current path Pc to which the object 5 is connected. The first current detection unit 11 has higher detection accuracy than the second current detection unit 12, but has a narrower current detection range (hereinafter referred to as a range) than the second current detection unit 12. When a current outside the range of the first current detection unit 11 flows, the value is out of the guarantee of the first current detection unit 11, so it is necessary to use the value detected by the second current detection unit 12.

2A and 2B are diagrams showing a configuration example of the first current detection unit 11. Configuration example 1 shown in FIG. 2A is an example in which the first current detection unit 11 is configured by the Hall element 11a, the differential amplifier 11b, and the A / D converter 11c. The Hall element 11a utilizes the Hall effect to convert the magnetic field generated by the current flowing in the current path Pc into a voltage and output it. The Hall element 11a is installed, for example, in the gap of the magnetic core installed in the vicinity of the current path Pc. The magnetic core may be installed so as to surround the current wiring. A constant current is supplied to the Hall element 11a, and the Hall element 11a outputs a voltage corresponding to the magnetic field generated in the magnetic core.

The differential amplifier 11b amplifies and outputs the voltage input from the Hall element 11a. The A / D converter 11c converts the analog voltage input from the differential amplifier 11b into a digital value and outputs it.

Configuration example 2 shown in FIG. 2B is an example in which the first current detection unit 11 is configured by the shunt resistor Rs, the differential amplifier 11b, and the A / D converter 11c. The shunt resistance Rs is inserted into the wiring constituting the current path Pc. The differential amplifier 11b amplifies and outputs the voltage across the shunt resistor Rs. The A / D converter 11c converts the analog voltage input from the differential amplifier 11b into a digital value and outputs it.

In any of the configuration example 1 shown in FIG. 2A and the configuration example 2 shown in FIG. 2B, an offset error may occur in the output value of the first current detection unit 11. In the differential amplifier 11b and the A / D converter 11c, the wider the range, the more likely the offset error is to occur, and the larger the offset error is. In particular, A / D converters have a wide range, and it is difficult to realize high resolution and high accuracy. A / D converters with a wide range tend to have low detection accuracy. Further, with respect to the Hall element 11a and the shunt resistor Rs, an offset error that cannot be ignored may occur depending on the process, environmental conditions, and the like.

As the first current detection unit 11 and the second current detection unit 12, the same configuration example may be used, or different configuration examples may be used. In any case, the second current detection unit 12 has a wider range and lower detection accuracy than the first current detection unit 11.

3 (a)-(c) is a diagram showing an example of a current waveform detected by the first current detection unit 11 and the second current detection unit 12. 3 (a)-(c) are simulation results when a sinusoidal current having an amplitude of ± 600 A is flowing in the current path Pc. The vertical axis shows the current and the horizontal axis shows the time. The first range indicates the current detection range of the first current detection unit 11, and the second range indicates the current detection range of the second current detection unit 12. In the example shown in FIGS. 3A to 3C, the first range is set to ± 400A, and the second range is set to ± 800A or more. The offset error of the first current detection unit 11 is 0A, and the offset error of the second current detection unit 12 is −40A.

FIG. 3B shows the current waveform detected by the first current detection unit 11. In FIG. 3B, the current waveform is correctly drawn even in the range exceeding ± 400 A, but the value is not guaranteed in the range exceeding ± 400 A in the actual measurement. FIG. 3C shows the current waveform detected by the second current detection unit 12. The second current detection unit 12 outputs a current value 40 A lower than the actual current value due to an offset error. FIG. 3A shows a waveform of a current value output from the selection unit 15b, which will be described later. The current value in the first range has no offset error, and the current value outside the first range and in the second range includes an offset error, but the value is guaranteed.

Return to FIG. The current values detected by the first current detection unit 11 and the second current detection unit 12 are output to the correction unit 15, respectively. The correction unit 15 also has a difference between the first integrated value obtained by integrating the current values detected by the first current detecting unit 11 and the second integrated value obtained by integrating the current values detected by the second current detecting unit 12. In addition, the output value of the first current detection unit 11 in the period exceeding the first range is corrected. Hereinafter, a specific configuration example of the correction unit 15 will be described.

The correction unit 15 includes a range determination unit 15a, a selection unit 15b, a compensation value addition unit 15c, a first integration unit 15d, a second integration unit 15e, a difference calculation unit 15f, and a compensation unit 15g. The correction unit 15 can be realized by, for example, digital signal processing using a microcomputer or the like. It should be noted that the functions of all or part of the correction unit 15 may be realized by a hardware element.

The range determination unit 15a determines whether or not the current flowing in the current path Pc is within the first range based on the current value detected by the first current detection unit 11 and / or the second current detection unit 12. judge. The range determination unit 15a outputs the determination result to the selection unit 15b.

The selection unit 15b outputs the output value of the first current detection unit 11 to the first integration unit 15d when the determination result indicates that it is within the first range, and adds the compensation value when the determination result indicates that it is outside the range. The output value of the unit 15c is output to the first integration unit 15d.

In principle, the first integrating unit 15d integrates the current value detected by the first current detecting unit 11. In principle, the second integrating unit 15e integrates the current value detected by the second current detecting unit 12. The difference calculation unit 15f calculates the difference between the first integrated value integrated in the first integrated unit 15d and the second integrated value integrated by the second integrated unit 15e. In the example shown in FIG. 1, the difference calculation unit 15f outputs the difference value generated by subtracting the second integrated value from the first integrated value to the compensation unit 15g.

The compensation unit 15g generates a compensation value by PI compensation based on the difference value calculated by the difference calculation unit 15f. In addition, P compensation or PID compensation may be used instead of PI compensation. The compensation value addition unit 15c adds the compensation value generated by the compensation unit 15g to the output value of the second current detection unit 12. The compensation value becomes 0 if the detection value of the first current detection unit 11 and the detection value of the second current detection unit 12 continue to be ideally the same value. The output value of the compensation value addition unit 15c is output to the selection unit 15b and the second integration unit 15e.

When the current flowing in the current path Pc is within the first range, the first integrating unit 15d continues to integrate the current value detected by the first current detecting unit 11. The second integration unit 15e continues to integrate the current value detected by the second current detection unit 12 corrected by the compensation value addition unit 15c. The offset error of the output value of the second current detection unit 12 is larger than the output value of the first current detection unit 11, but the offset error is corrected by the compensation value addition unit 15c and input to the second integration unit 15e. The accuracy of the current value is improved.

When the current flowing in the current path Pc is out of the first range, the first integrating unit 15d is not the current value detected by the first current detecting unit 11, but the second one corrected by the compensation value adding unit 15c. The current value detected by the current detection unit 12 is added to the first integrated value. Therefore, the accuracy of the first integrated value is improved when the current flowing in the current path Pc exceeds the first range.

The correction unit 15 has an output value (instantaneous value 1) of the first current detection unit 11, an output value of the first integration unit 15d (integrated value 1), an output value of the second current detection unit 12 (instantaneous value 2), and a second. 2 The output value (integrated value 2) of the integrating unit 15e is output to the processing unit (not shown) in the subsequent stage. In various application processing, the processing unit uses the instantaneous value 1 when the current flowing in the current path Pc is within the first range, and uses the instantaneous value 2 when the current is outside the first range. When the integrated value is used, the processing unit may use the integrated value 1, the integrated value 2, or the averaged value of the two.

FIG. 4 is a diagram for explaining an example in which the current detection system of FIG. 1 is applied to an in-vehicle power storage system 1. The power storage system 1 includes a power storage module 20 and a management device 10. In the example shown in FIG. 4, the object 5 for current detection shown in FIG. 1 is the power storage module 20. The power storage system 1 is connected to the motor 2 via the contactor relay 4 and the inverter 3. The inverter 3 converts the DC power supplied from the power storage system 1 into AC power and supplies it to the motor 2 during power running. At the time of regeneration, the AC power supplied from the motor 2 is converted into DC power and supplied to the power storage system 1. The motor 2 is a three-phase AC motor, and rotates according to the AC power supplied from the inverter 3 during power running. At the time of regeneration, the rotational energy due to deceleration is converted into AC power and supplied to the inverter 3.

The contactor relay 4 is inserted between the wiring connecting the power storage module 20 of the power storage system 1 and the inverter 3. The management device 10 controls the contactor relay 4 in an on state (closed state) during traveling, and electrically connects the power storage module 20 and the power system of the vehicle. In principle, the management device 10 controls the contactor relay 4 to an off state (open state) when the vehicle is not running, and electrically shuts off the power storage module 20 and the power system of the vehicle.

The power storage module 20 is formed by connecting a plurality of cells E1-Em in series. As the cell, a lithium ion battery cell, a nickel hydrogen battery cell, a lead battery cell, an electric double layer capacitor cell, a lithium ion capacitor cell and the like can be used. Hereinafter, in the present specification, it is assumed that a lithium ion battery cell (nominal voltage: 3.6-3.7V) is used. The number of cells E1-Em in series is determined according to the drive voltage of the motor 2.

In the case of a plug-in hybrid vehicle (PHV), the power storage module 20 can be charged from the outside by connecting an external charger and the power storage system 1 with a charging cable.

The management device 10 includes a first current detection unit 11, a second current detection unit 12, a voltage detection unit 13, a control unit 14, and a drive unit 17. The first current detection unit 11 and the second current detection unit 12 are the same as the first current detection unit 11 and the second current detection unit 12 shown in FIG. 1, and detect the current flowing through the power storage module 20 in parallel. ..

The voltage detection unit 13 is connected to each node of a plurality of cells E1-Em connected in series by a plurality of voltage lines, and by detecting the voltage between two adjacent voltage lines, each cell E1-Em. Detects the voltage of. The voltage detection unit 13 transmits the detected voltage of each cell E1-Em to the control unit 14.

The voltage detection unit 13 can be configured by an ASIC (Application Specific Integrated Circuit) or a general-purpose analog front-end IC. The voltage detection unit 13 includes a multiplexer and an A / D converter. The multiplexer outputs the voltage between two adjacent voltage lines to the A / D converter in order from the top. The A / D converter converts the analog voltage input from the multiplexer into a digital value.

The drive unit 17 generates a drive signal for opening / closing the contactor relay 4 based on the control signal from the control unit 14, and supplies the drive signal to the contactor relay 4.

The control unit 14 can be configured by a microcomputer and a non-volatile memory (for example, EEPROM, flash memory). The control unit 14 is based on the voltage, current, and temperature of each of the plurality of cells E1-Em detected by the voltage detection unit 13, the first current detection unit 11, the second current detection unit 12, and the temperature detection unit (not shown). Manages the power storage module 20. For example, when an overvoltage, undervoltage, overcurrent, or temperature abnormality occurs in at least one of the plurality of cells E1-Em, the control unit 14 controls the drive unit 17 to shut off the contactor relay 4, and the plurality of cells E1-Em. Protect Em.

The control unit 14 includes a correction unit 15 and an SOC estimation unit 16. The correction unit 15 is the same as the correction unit shown in FIG. The SOC estimation unit 16 estimates the SOC of each of the plurality of cells E1-Em. SOC can be estimated by the OCV method or the current integration method. When estimating by the OCV method, the SOC estimation unit 16 determines each cell E1 based on the OCV of each cell E1-Em detected by the voltage detection unit 13 and the characteristic data of the SOC-OCV curve held in the non-volatile memory. -Estimate the SOC of Em. When estimating by the current integration method, the SOC estimation unit 16 applies to the OCV at the start of charging / discharging of each cell E1-Em detected by the voltage detection unit 13 and the plurality of cells E1-Em input from the correction unit 15. The SOC is estimated based on the integrated value of the flowing current.

As described above, according to the present embodiment, the first current detection unit 11 having a narrow range and high accuracy and the second current detection unit 12 having a wide range and low accuracy are used in combination, and the first integrated value and the second integrated value are used. The offset error is corrected by feedback control based on the difference of the integrated values. This makes it possible to detect a wide range of current with high accuracy. Further, it is better to use the first current detection unit 11 having a narrow range and high accuracy and the second current detection unit 12 having a wide range and low accuracy in combination than when one current detection unit having a wide range and high accuracy is adopted. , Cost can be suppressed, and redundancy is high.

As described above, according to the present embodiment, it is possible to detect a wide range of currents at low cost and with high accuracy. When used in an in-vehicle power storage system, the SOC estimation accuracy is improved, so that the capacity in the power storage system can be used efficiently, and the cruising range due to motor running can be extended.

The present invention has been described above based on the embodiments. It is understood by those skilled in the art that the embodiments are exemplary and that various modifications are possible for each of these components and combinations of processing processes, and that such modifications are also within the scope of the present invention. ..

In the above-described embodiment, an example of applying the current detection system to the power storage system 1 for in-vehicle use has been described. In this respect, it can also be applied to a power storage system for stationary power storage applications. It can also be applied to power storage systems for electronic devices such as notebook PCs and smartphones.

Further, the current detection system according to the present embodiment is applicable not only to the application for detecting the current flowing through the battery but also to the general application for detecting the integrated current. For example, it can be applied to an application for measuring the amount of power generated by a photovoltaic power generation system, an application for measuring the power consumption of a load at a predetermined time, and the like. For example, it can also be applied to smart meters.

The embodiment may be specified by the following items.

[Item 1]
The first current detection unit (11) that detects the current flowing through the predetermined detection target (5), and
The current detection unit has a wider current detection range than the first current detection unit (11) and has a lower current detection accuracy than the first current detection unit (11), and the current flowing through the detection target (5) is measured. A second current detection unit (12) that detects in parallel with the first current detection unit (11),
The difference between the first integrated value obtained by integrating the current values detected by the first current detecting unit (11) and the second integrated value obtained by integrating the current values detected by the second current detecting unit (12). Based on the correction unit (15) that corrects the output value of the first current detection unit (11) during the period exceeding the current detection range of the first current detection unit (11).
A current detection system (50).
According to this, a wide range of current can be detected with high accuracy.
[Item 2]
The correction unit (15)
The first integrating unit (15d) for integrating the current value detected by the first current detecting unit (11), and the first integrating unit (15d).
A second integrating unit (15e) for integrating the current value detected by the second current detecting unit (12), and a second integrating unit (15e).
A difference calculation unit (15f) that calculates the difference between the first integrated value integrated in the first integrated unit (15d) and the second integrated value integrated by the second integrated unit (15e).
A compensation unit (15 g) that generates a compensation value according to the difference calculated by the difference calculation unit (15f), and a compensation unit (15 g).
A compensation value addition unit (15c) that adds the compensation value generated by the compensation unit (15g) to the current value detected by the second current detection unit (12).
A determination unit (15a) for determining whether or not the current value of the detection target (5) is within the current detection range of the first current detection unit (11).
As a result of the determination by the determination unit (15a), when the current value is within the current detection range of the first current detection unit (11), the output value of the first current detection unit (11) is sent to the first integration unit. A selection unit (15b) that outputs and outputs the output value of the compensation value addition unit to the first integration unit when the current value is outside the current detection range of the first current detection unit (11).
The current detection system (50) according to item 1, wherein the current detection system (50) comprises.
According to this, it is possible to improve the accuracy of the first integrated value when the current value exceeds the current detection range of the first current detection unit (11).
[Item 3]
The detection target (5) is a cell (E1-Em) capable of storing electricity.
50. The current detection system (50) according to item 1 or 2, wherein the SOC (State Of Charge) of the cell (E1-Em) is calculated based on the first integrated value or the second integrated value. ).
According to this, it is possible to estimate the SOC with high accuracy.
[Item 4]
Multiple cells (E1-Em) connected in series and
A voltage detection unit (13) that detects the voltage of each of the plurality of cells (E1-Em), and
The current detection system (50) according to item 1 or 2 for detecting the current flowing through the plurality of cells (E1-Em), and the current detection system (50).
Based on the voltage of each cell (E1-Em) detected by the voltage detection unit (13) and the current flowing through the plurality of cells (E1-Em) detected by the current detection system (50). The SOC estimation unit (16) that estimates the SOC (State Of Charge) of each cell,
A power storage system (1).
According to this, the current flowing through the power storage system (1) can be detected with high accuracy.

1 Power storage system, 11 1st current detection unit, 12 2nd current detection unit, 13 voltage detection unit, 15 correction unit, 15b selection unit, 15c compensation value addition unit, 15d 1st integration unit, 15e 2nd integration unit, 15f Difference calculation unit, 15g compensation unit, 16 SOC estimation unit, E1, E2, E3, Em cell, 50 current detection system.

Claims (3)

A first current detector that detects the current flowing through a predetermined detection target, and
It is a current detection unit that has a wider current detection range than the first current detection unit and has a lower current detection accuracy than the first current detection unit, and causes the current flowing through the detection target to flow in parallel with the first current detection unit. The second current detector to detect and
A first integrating unit for integrating the current value detected by the first current detecting unit, and a first integrating unit.
A second integrating unit for integrating the current value detected by the second current detecting unit, and a second integrating unit.
A difference calculation unit that calculates the difference between the first integrated value integrated in the first integrated unit and the second integrated value integrated by the second integrated unit.
A compensation unit that generates a compensation value by performing PI compensation, P compensation, or PID compensation for the difference calculated by the difference calculation unit.
A compensation value addition unit that adds the compensation value generated by the compensation unit to the current value detected by the second current detection unit, and a compensation value addition unit.
A determination unit for determining whether or not the current value of the detection target is within the current detection range of the first current detection unit, and a determination unit.
As a result of the determination by the determination unit, when the current value is within the current detection range of the first current detection unit, the output value of the first current detection unit is output to the first integration unit, and the current value is the first. 1 When the current detection range of the current detection unit is out of range, the selection unit that outputs the output value of the compensation value addition unit to the first integration unit, and
A current detection system characterized by being equipped with. The detection target is a cell that can store electricity.
The current detection system according to claim 1 , wherein the SOC (State Of Charge) of the cell is calculated based on the first integrated value or the second integrated value. With multiple cells connected in series,
A voltage detector that detects the voltage of each of the plurality of cells,
The current detection system according to claim 1, which detects currents flowing through the plurality of cells.
The SOC (State Of Charge) of each cell is estimated based on the voltage of each cell detected by the voltage detection unit and the first integrated value or the second integrated value generated by the current detection system. SOC estimation unit and
A power storage system characterized by being equipped with.

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