Measurement device

Abstract

A measurement device (20) is included in a power storage system (1) which is provided with a power storage unit (11) and a charging and discharging unit (12) that performs charging / discharging which is at least one of charging and discharging of the power storage unit (11). The measurement device (20) comprises: an intermediate circuit (30) that includes a condenser (31); and a differential amplifier circuit (40). One end of the condenser (31) is electrically connected to a high-potential-side terminal (11A) of the power storage unit (11). The other end of the condenser (31) is electrically connect to a first terminal (40A) on the input side of the differential amplifier circuit (40). The intermediate circuit (30) reflects, at the other end of the condenser (31), a voltage change at said one end of the condenser (31) when the charging / discharging is performed. The differential amplifier circuit (40) amplifies the voltage that is input from the other end of the condenser (31) via the first terminal (40A), and outputs the amplified voltage.

Description

Measuring equipment

[0001] The present disclosure relates to a measuring device.

[0002] Patent Document 1 discloses a method for measuring the resistance of a storage element. In this method, the storage element under test is charged or discharged. When the voltage of the storage element under test reaches a predetermined voltage, the charging or discharging of the storage element under test is stopped. This method detects a difference voltage between the voltage of the storage element under test at the time when charging or discharging is stopped and the voltage of the storage element under test a predetermined time after charging or discharging is stopped, and amplifies this difference voltage. This measurement method calculates the resistance of the storage element under test using the amplified voltage difference.

[0003] Japanese Patent Application Laid-Open No. 2017-116455

[0004] The configuration of Patent Document 1 requires a voltage holding element to hold the voltage of the storage element under test at the time when charging or discharging is stopped. It is desirable to amplify the voltage corresponding to the voltage of the storage unit without using such a voltage holding element.

[0005] An object of the present disclosure is to provide a technique that can amplify a voltage corresponding to a voltage change in a power storage unit without using a voltage holding element.

[0006] The measuring device of the present disclosure is a measuring device included in a power storage system that includes a power storage unit and a charging / discharging unit that performs charging and discharging, which is at least one of charging and discharging, of the power storage unit, and has an intermediate circuit including a capacitor and a differential amplifier circuit, one end of the capacitor is electrically connected to a high potential terminal of the power storage unit, and the other end of the capacitor is electrically connected to a first terminal on the input side of the differential amplifier circuit, the intermediate circuit reflects the voltage change at one end of the capacitor when the charging and discharging are performed to the other end of the capacitor, and the differential amplifier circuit amplifies and outputs the voltage input from the other end of the capacitor via the first terminal.

[0007] The technology according to the present disclosure can amplify the voltage according to the voltage change of the power storage unit without using a voltage holding element.

[0008] Fig. 1 is a schematic diagram of a power storage system including a measuring device according to a first embodiment. Fig. 2 is a flowchart of processing performed by a control unit according to the first embodiment. Fig. 3 is a schematic diagram of a power storage system including a measuring device according to a second embodiment. Fig. 4 is a flowchart of processing performed by a control unit according to the second embodiment.

[0009] [Description of Embodiments of the Present Disclosure] In the following, embodiments according to the present disclosure are listed and exemplified.

[0010] [1] A measuring device included in a power storage system that includes a power storage unit and a charge / discharge unit that performs at least one of charging and discharging of the power storage unit, the measuring device having an intermediate circuit including a capacitor and a differential amplifier circuit, one end of the capacitor being electrically connected to a high potential terminal of the power storage unit, and the other end of the capacitor being electrically connected to a first terminal on the input side of the differential amplifier circuit, the intermediate circuit reflecting a voltage change at one end of the capacitor when the charging / discharging is performed to the other end of the capacitor, and the differential amplifier circuit amplifying and outputting a voltage input from the other end of the capacitor via the first terminal.

[0011] In the measuring device, when charging and discharging are performed by the charging / discharging unit, a voltage change at one end of the capacitor is reflected at the other end of the capacitor. Because one end of the capacitor is electrically connected to the high-potential terminal of the storage unit, a voltage change at the high-potential terminal of the storage unit is reflected at the other end of the capacitor. The voltage reflected at the other end of the capacitor, i.e., the voltage corresponding to the voltage change of the storage unit, is amplified by the differential amplifier circuit. Therefore, the measuring device can amplify the voltage corresponding to the voltage change of the storage unit without using a voltage holding element.

[0012] [2] The intermediate circuit includes a resistor portion, one end of which is electrically connected to a conductive path between the other end of the capacitor and the first terminal, the other end of which is electrically connected to a reference conductive path, the reference conductive path being electrically connected to a second terminal on the input side of the differential amplifier circuit, and the differential amplifier circuit amplifies and outputs the voltage input from the other end of the capacitor using the potential of the reference conductive path as a reference. [1] The measuring device described in [1].

[0013] The measuring device can realize a configuration in which the voltage change at one end of the capacitor when charging or discharging is reflected at the other end of the capacitor by simply providing a resistor between the conductive path and the reference conductive path.

[0014] [3] The measuring device according to [1] or [2], further comprising a control unit for controlling the charge / discharge unit, wherein the control unit measures the internal resistance of the storage unit based on a change in the output voltage of the differential amplifier circuit when the charge / discharge unit is caused to perform the charge / discharge.

[0015] The measuring device can measure the internal resistance of the electricity storage unit by causing the charge / discharge unit to charge and discharge.

[0016] [4] The measuring device according to [3], wherein the control unit causes the charge / discharge unit to charge and discharge so that a constant current flows through the storage unit, and measures the internal resistance of the storage unit based on the difference between the voltage output from the differential amplifier circuit at the start of the charging / discharging and the voltage output from the differential amplifier circuit after a predetermined time has elapsed.

[0017] The measuring device can measure the internal resistance of the storage unit based on the voltage change from the start of charging and discharging until a predetermined time has elapsed by causing the charging and discharging unit to charge and discharge so that a constant current flows through the storage unit.

[0018] [5] The measuring device according to [3] or [4], wherein the power storage unit is mounted on a vehicle, and the control unit measures the internal resistance of the power storage unit mounted on the vehicle.

[0019] The measuring device can measure the internal resistance of a power storage unit mounted on a vehicle.

[0020] [Details of the embodiment of the present disclosure] 1. First embodiment 1-1. Configuration of power storage system 1 The power storage system 1 of the first embodiment is an in-vehicle system mounted on a vehicle. As shown in FIG. 1 , the power storage system 1 includes a power supply unit 10, a power storage unit 11, and a charge / discharge unit 12.

[0021] The power supply unit 10 is configured by, for example, a battery.

[0022] The power storage unit 11 includes, for example, a plurality of capacitors. The plurality of capacitors may be connected in series, in parallel, or in a combination of series and parallel connections.

[0023] The charging / discharging unit 12 charges and discharges the power storage unit 11. A first conductive path 91 is provided between the charging / discharging unit 12 and the power storage unit 11. The charging / discharging unit 12 charges and discharges the power storage unit 11 via the first conductive path 91. The charging / discharging unit 12 can charge the power storage unit 11 so that the charging current of the power storage unit 11 is a constant current. The charging / discharging unit 12 can discharge the power storage unit 11 so that the discharging current of the power storage unit 11 is a constant current. The charging / discharging unit 12 is, for example, a voltage conversion unit, more specifically, a DC / DC converter. The charging / discharging unit 12 is provided between the power supply unit 10 and the power storage unit 11. The charging / discharging unit 12 performs a first conversion operation to boost or lower a voltage input from the power supply unit 10 and output the voltage to the power storage unit 11. The charging / discharging unit 12 charges the power storage unit 11 by performing the first conversion operation. Furthermore, charging / discharging unit 12 performs a second conversion operation of stepping up or stepping down the voltage input from power storage unit 11 and outputting the voltage to power supply unit 10 (i.e., the side opposite to power storage unit 11). Charging / discharging unit 12 discharges power storage unit 11 by performing the second conversion operation.

[0024] The power storage system 1 includes a measuring device 20. The measuring device 20 includes the charge / discharge unit 12 described above.

[0025] The measuring device 20 is a device used to measure the resistance of the power storage unit 11. The measuring device 20 has an intermediate circuit 30, a differential amplifier circuit 40, a filter circuit 50, a current detection unit 60, and a control unit 70.

[0026] The intermediate circuit 30 includes a capacitor 31 and a first resistor section 32 .

[0027] The capacitor 31 is disposed between the first conductive path 91 and the differential amplifier circuit 40. One end of the capacitor 31 is electrically connected to the first conductive path 91, and is electrically connected to the high-potential terminal 11A of the power storage unit 11 via the first conductive path 91. The other end of the capacitor 31 is electrically connected to a first terminal 40A on the input side of the differential amplifier circuit 40. A ground 90 is electrically connected to a second terminal 40B on the input side of the differential amplifier circuit 40. In this embodiment, the ground 90 corresponds to the reference conductive path.

[0028] The first resistance portion 32 corresponds to an example of a resistance portion. The first resistance portion 32 is configured to include, for example, one or more resistors. One end of the first resistance portion 32 is electrically connected to a second conductive path 92 between the other end of the capacitor 31 and the first terminal 40A on the input side of the differential amplifier circuit 40. The second conductive path 92 corresponds to an example of a conductive path. The other end of the first resistance portion 32 is electrically connected to ground 90.

[0029] When the voltage at one end of capacitor 31 changes, the voltage at the other end of capacitor 31 also changes in the same way. In other words, intermediate circuit 30 reflects the change in voltage at one end of capacitor 31 when charging or discharging power storage unit 11 is performed to the other end of capacitor 31.

[0030] The differential amplifier circuit 40 is, for example, a non-inverting amplifier circuit and includes an operational amplifier 41, a second resistor unit 42, a third resistor unit 43, and a fourth resistor unit 44. The second resistor unit 42, the third resistor unit 43, and the fourth resistor unit 44 each include one or more resistors.

[0031] One end of the second resistor section 42 is electrically connected to the first terminal 40A. The other end of the second resistor section 42 is electrically connected to the non-inverting input terminal 41A of the operational amplifier 41. In other words, the other end of the capacitor 31 is electrically connected to the non-inverting input terminal 41A of the operational amplifier 41 via the second resistor section 42.

[0032] The third resistor unit 43 and the fourth resistor unit 44 are connected in series between the second terminal 40B and the output terminal 41C of the operational amplifier 41. The third resistor unit 43 is arranged closer to the second terminal 40B than the fourth resistor unit 44. A third conductive path 93 is provided between the third resistor unit 43 and the fourth resistor unit 44. The third conductive path 93 is electrically connected to the inverting input terminal 41B of the operational amplifier 41. The ground 90 is electrically connected to the inverting input terminal 41B of the operational amplifier 41 via the third resistor unit 43.

[0033] The operational amplifier 41 amplifies the voltage input to the non-inverting input terminal 41A according to a gain that corresponds to the ratio of the resistances of the third resistor section 43 and the fourth resistor section 44. The operational amplifier 41 outputs the amplified voltage from the output terminal 41C.

[0034] The differential amplifier circuit 40 amplifies the voltage input from the other end of the capacitor 31 and outputs the amplified voltage from the output terminal 40C. The differential amplifier circuit 40 amplifies the voltage input from the other end of the capacitor 31 with respect to the potential of the ground 90 and outputs the amplified voltage.

[0035] The filter circuit 50 is provided between the output terminal 40C of the differential amplifier circuit 40 and the control unit 70. The filter circuit 50 includes a filter capacitor 51 and a fifth resistor unit 52. The filter circuit 50 is configured as an RC low-pass filter. The signal output from the differential amplifier circuit 40 passes through the filter circuit 50 and is input to the control unit 70.

[0036] The current detection unit 60 detects the charging current and discharging current of the power storage unit 11. Specifically, the current detection unit 60 detects the current flowing through the first conductive path 91. The current detection unit 60 is configured by, for example, a known current sensor. A signal indicating the detection value of the current detection unit 60 is input to the control unit 70.

[0037] The control unit 70 includes, for example, a microcomputer. The control unit 70 controls the charge / discharge unit 12. The control unit 70 measures the internal resistance of the power storage unit 11 based on a change in the output voltage of the differential amplifier circuit 40 when the charge / discharge unit 12 is caused to charge / discharge. The control unit 70 causes the charge / discharge unit 12 to charge / discharge the power storage unit 11 so that a constant current flows through the power storage unit 11, and measures the internal resistance of the power storage unit 11 based on a difference ΔV between the voltage output from the differential amplifier circuit 40 at the start of charging / discharging and the voltage output from the differential amplifier circuit 40 after a predetermined time (e.g., the time required for the power storage unit 11 to reach a state where a constant current flows) has elapsed. For example, when the control unit 70 charges / discharges the power storage unit 11 so that a constant current I flows through the power storage unit 11, the control unit 70 calculates the internal resistance R of the power storage unit 11 using the following equation (1): R=ΔV / I (1)

[0038] When a predetermined measurement start condition is met, the control unit 70 performs, for example, the process shown in FIG. 2 . The measurement start condition may be a condition for charging the power storage unit 11, or may be a condition for not charging the power storage unit 11. It is assumed that the charging / discharging unit 12 is stopped and no current flows through the power storage unit 11 when the measurement start condition is met. Before causing the charging / discharging unit 12 to start charging the power storage unit 11, the control unit 70 acquires the output value VC1 of the differential amplifier circuit 40 in step S11 of FIG. 2 . After acquiring the output value VC1, the control unit 70 causes the charging / discharging unit 12 to start charging the power storage unit 11 in step S12. The control unit 70 controls the charging / discharging unit 12 so that a constant current flows through the power storage unit 11. When a predetermined time has elapsed since the start of charging, the control unit 70 acquires the output value VC2 of the differential amplifier circuit 40 in step S13. The control unit 70 measures the internal resistance of the power storage unit 11 based on the difference between the acquired VC1 and VC2. Specifically, when the power storage unit 11 is charged so that a constant current I flows through the power storage unit 11, the control unit 70 calculates the internal resistance R of the power storage unit 11 by the following formula (2): R=(VC2-VC1) / I Formula (2)

[0039] 1-2. Functions and Effects of Energy Storage System 1 In the measuring device 20, when charging / discharging is performed by the charge / discharge unit 12, a voltage change at one end of the capacitor 31 is reflected at the other end of the capacitor 31. Because one end of the capacitor 31 is electrically connected to the high-potential terminal 11A of the energy storage unit 11, a voltage change at the high-potential terminal 11A of the energy storage unit 11 is reflected at the other end of the capacitor 31. The voltage reflected at the other end of the capacitor 31, i.e., the voltage corresponding to the voltage change of the energy storage unit 11, is amplified by the differential amplifier circuit 40. Therefore, the measuring device 20 can amplify the voltage corresponding to the voltage change of the energy storage unit 11 without using a voltage holding element.

[0040] The measuring device 20 has a simple configuration in which a first resistance part 32 is provided between the second conductive path 92 and the ground 90, thereby realizing a configuration in which the voltage change at one end of the capacitor 31 when charging or discharging is performed is reflected at the other end of the capacitor 31.

[0041] Measuring device 20 can measure the internal resistance of power storage unit 11 by causing charge / discharge unit 12 to charge and discharge.

[0042] The measuring device 20 causes the charging / discharging unit 12 to charge and discharge so that a constant current flows through the storage unit 11, and can measure the internal resistance of the storage unit 11 based on the voltage change from the start of charging and discharging until a predetermined time has elapsed.

[0043] The measuring device 20 can measure the internal resistance of the power storage unit 11 mounted on the vehicle.

[0044] 2. Second Embodiment In the first embodiment, an example in which the reference conduction path is grounded and the power storage unit is charged is described. In the second embodiment, an example in which the reference conduction path is an electrical path to which the power supply voltage of the differential amplifier circuit is applied and the power storage unit is discharged is described. In the second embodiment, the same components as in the first embodiment are denoted by the same reference symbols, and detailed description thereof will be omitted.

[0045] The power storage system 201 of the second embodiment is an in-vehicle system mounted on a vehicle. As shown in Fig. 3 , the power storage system 201 includes a power supply unit 10, a power storage unit 11, and a charge / discharge unit 12. The power storage system 201 includes a measuring device 220. The measuring device 220 includes the charge / discharge unit 12.

[0046] The measuring device 220 is a device used to measure the resistance of the power storage unit 11. The measuring device 220 has an intermediate circuit 230, a differential amplifier circuit 40, a filter circuit 50, a current detection unit 60, and a control unit 70.

[0047] The intermediate circuit 230 includes a capacitor 31 and a first resistor section 232 .

[0048] The first resistance portion 232 corresponds to an example of a resistance portion. The first resistance portion 232 is configured to include, for example, one or more resistors. One end of the first resistance portion 232 is electrically connected to the second conductive path 92. The other end of the first resistance portion 232 is electrically connected to the reference conductive path 290. In this embodiment, the reference conductive path 290 is an electrical path to which the power supply voltage of the differential amplifier circuit 40 is applied. The reference conductive path 290 is electrically connected to the second terminal 40B on the input side of the differential amplifier circuit 40.

[0049] When a predetermined measurement start condition is met, the control unit 70 performs, for example, the process shown in FIG. 4 . The measurement start condition may be a condition for discharging the power storage unit 11, or may be a condition for not discharging the power storage unit 11. It is assumed that the charging / discharging unit 12 is stopped and no current flows through the power storage unit 11 when the measurement start condition is met. Before causing the charging / discharging unit 12 to start discharging the power storage unit 11, the control unit 70 acquires the output value VC1 of the differential amplifier circuit 40 in step S21 of FIG. 4 . After acquiring the output value VC1, the control unit 70 causes the charging / discharging unit 12 to start discharging the power storage unit 11 in step S22. The control unit 70 controls the charging / discharging unit 12 so that a constant current flows through the power storage unit 11. When a predetermined time has elapsed since the start of discharging, the control unit 70 acquires the output value VC2 of the differential amplifier circuit 40 in step S23. Based on the difference between the acquired VC1 and VC2, the control unit 70 measures the internal resistance of the power storage unit 11. Specifically, when the power storage unit 11 is discharged so that a constant current I flows through the power storage unit 11, the control unit 70 calculates the internal resistance R of the power storage unit 11 by the above-described formula (2).

[0050] The measuring device 220 of the second embodiment also has the same effects as the measuring device 20 of the first embodiment.

[0051] <Other Embodiments> The present disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of features of the above-described or below-described embodiments is possible within a range that does not contradict. Furthermore, any feature of the above-described or below-described embodiments may be omitted unless explicitly stated as essential. Furthermore, the above-described embodiments may be modified as follows.

[0052] The measuring device of the first embodiment may discharge the power storage unit when measuring the internal resistance of the power storage unit. In this case, the difference ΔV may be set to VC1-VC2, for example.

[0053] The measuring device of the second embodiment may charge the power storage unit when measuring the internal resistance of the power storage unit. In this case, the difference ΔV may be set to VC1-VC2, for example.

[0054] In the second embodiment, the power storage unit is discharged to a power supply unit, but the power storage unit may be discharged to a power consumption unit such as a load.

[0055] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, and is intended to include all modifications within the scope indicated by the claims or within the scope equivalent to the claims.

[0056] REFERENCE SIGNS LIST 1... Energy storage system 10... Power supply unit 11... Energy storage unit 11A... High potential side terminal of energy storage unit 12... Charging / discharging unit 20... Measuring device 30... Intermediate circuit 31... Capacitor 32... First resistor unit (resistor unit) 40... Differential amplifier circuit 40A... First terminal 40B... Second terminal 40C... Output terminal 41... Operational amplifier 41A... Non-inverting input terminal 41B... Inverting input terminal 41C... Output terminal 42... Second resistor unit 43... Third resistor unit 44... Fourth resistor unit 50... Filter circuit 51... Filter capacitor 52... Fifth resistor unit 60... Current detection unit 70... Control unit 90... Ground (reference conductive path) 91... First conductive path 92... Second conductive path (conductive path) 93... Third conductive path 201... Energy storage system 220... Measuring device 230... Intermediate circuit 232... First resistor section (resistance section) 290... Reference conductive path I... Constant current R... Internal resistance VC1... Output value VC2... Output value

Claims

1. A measuring device included in a power storage system comprising a power storage unit and a charge / discharge unit that performs charge / discharge, which is at least one of charging and discharging of the power storage unit, the measuring device having an intermediate circuit including a capacitor and a differential amplifier circuit, one end of the capacitor being electrically connected to a terminal on the high potential side of the power storage unit, the other end of the capacitor being electrically connected to a first terminal on the input side of the differential amplifier circuit, the intermediate circuit reflecting a voltage change at one end of the capacitor when the charge / discharge is performed at the other end of the capacitor, and the differential amplifier circuit amplifying and outputting a voltage input from the other end of the capacitor via the first terminal.

2. The measuring device according to claim 1, wherein the intermediate circuit includes a resistance unit, one end of the resistance unit being electrically connected to a conductive path between the other end of the capacitor and the first terminal, the other end of the resistance unit being electrically connected to a reference conductive path, the reference conductive path being electrically connected to a second terminal on the input side of the differential amplifier circuit, and the differential amplifier circuit amplifying and outputting a voltage input from the other end of the capacitor with reference to the potential of the reference conductive path.

3. The measuring device according to claim 1 or 2, further comprising a control unit that controls the charge / discharge unit, the control unit measuring an internal resistance of the power storage unit based on a change in an output voltage of the differential amplifier circuit when the charge / discharge unit is caused to perform the charge / discharge.

4. The measuring device according to claim 3, wherein the control unit causes the charge / discharge unit to perform the charge / discharge so that a constant current flows, and measures the internal resistance of the power storage unit based on a difference between a voltage output from the differential amplifier circuit at the start of the charge / discharge and a voltage output from the differential amplifier circuit after a predetermined time has elapsed.

5. The measuring device according to claim 3, wherein the power storage unit is mounted on a vehicle, and the control unit measures an internal resistance of the power storage unit mounted on the vehicle.

Images