Current measurement system and current measurement method

Abstract

To provide a current measurement system and a current measurement method, which can acquire an offset error value of a current sensor without cutting off current to the current sensor.SOLUTION: A current measurement system 1 includes: a current sensor 4 with a core; first electric wire 41 and second electric wire 42 which are arranged in parallel with each other inside the core; and a third electric wire 40 arranged inside the core. A direction of current in the first electric wire 41 and a direction of current in the second electric wire 42 inside the core are opposite to each other. The current sensor 4 measures current inside the core when current flows in both of the first electric wire 41 and the second electric wire 42, and an offset error value of the current sensor 4 is acquired.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a current measurement system and a current measurement method for measuring a current. [Background technology]

[0002] Conventionally, various techniques have been proposed for acquiring an offset value, which is a value of an offset error of a current sensor that measures a current. As an example of such a technique, Patent Document 1 discloses an auxiliary battery control device that includes an auxiliary battery that supplies power to an auxiliary device, a current sensor that measures a current flowing through the auxiliary battery, a switch connected in series to the auxiliary battery, and a control unit that cuts off the switch and acquires the offset value of the current sensor when a DC / DC (Direct Current / Direct Current) converter that converts the power of a vehicle drive battery into power to be supplied to the auxiliary device is operating. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-33656 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the auxiliary battery control device disclosed in Patent Document 1 has a problem in that the current to the current sensor must be cut off in order to obtain the offset error value of the current sensor.

[0005] The present disclosure has been made to solve such problems, and aims to provide a current measurement system and a current measurement method that are capable of obtaining the value of the offset error of a current sensor without interrupting the current to the current sensor. [Means for solving the problem]

[0006] The current measurement system according to the present disclosure comprises: a current sensor having a core; a first electric wire and a second electric wire arranged parallel to each other inside the core; and a third electric wire disposed inside the core, The directions of the current in the first electric wire and the current in the second electric wire inside the core are opposite to each other, The current sensor obtains a value of the offset error of the current sensor by measuring the current inside the core when current is flowing through both the first wire and the second wire.

[0007] Moreover, the current measurement system may further include a current correction section that corrects the value of the current flowing through the current sensor using the acquired offset error value.

[0008] Furthermore, the first wire and the second wire can be arranged inside the core such that the waveform of the first current flowing in the first wire and the waveform of the second current flowing in the second wire are in phase with each other.

[0009] Further, the current sensor measures a measurement value of a current in the third electric wire when no current flows in the first electric wire and the second electric wire, and a measurement value in the first electric wire when no current flows in the second electric wire and the third electric wire; The current measurement system is The device may further include an average value calculation unit that calculates average values ​​of the current in the first electric wire and the current in the third electric wire based on the measured values ​​in the first electric wire and the third electric wire.

[0010] The current measurement system further includes an inductor for storing electrical energy provided by the power source; A current supplied from the inductor can flow through the first electric wire and the second electric wire.

[0011] A current measurement method performed by a current sensor having a core according to the present disclosure, A first electric wire, a second electric wire, and a third electric wire are arranged inside the core, the first electric wire and the second electric wire being parallel to each other. The directions of the current in the first electric wire and the current in the second electric wire inside the core are opposite to each other, The current measurement method obtains a value of the offset error of the current sensor by using the current sensor to measure a current inside the core when current flows through both the first electric wire and the second electric wire.

[0012] A current measurement method performed in a current measurement system according to the present disclosure, The current measurement system is a current sensor having a core; a first electric wire and a second electric wire arranged parallel to each other inside the core; and a third electric wire disposed inside the core, The directions of the current in the first electric wire and the current in the second electric wire inside the core are opposite to each other, The current measurement method is as follows: a current sensor measures a measurement of a current in the third wire when no current is flowing in the first wire and the second wire, and a measurement of a current in the first wire when no current is flowing in the second wire and the third wire; The computer Based on the measured values ​​in the first electric wire and the third electric wire, average values ​​of the current in the first electric wire and the current in the third electric wire are calculated. Effect of the Invention

[0013] The present disclosure makes it possible to provide a current measurement system and a current measurement method that are capable of acquiring the value of the offset error of a current sensor without interrupting the current to the current sensor. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 illustrates an example of a current measurement system according to the present disclosure. [Diagram 2] FIG. 2 is a diagram illustrating an example of a configuration of a control device according to the present disclosure. [Diagram 3] 5 is a flowchart illustrating an example of a process executed by a control device according to the present disclosure. [Figure 4] 1 is a diagram showing changes over time in a power switch, a diode changeover switch, a current supplied by a power supply, a current supplied by an inductor, and a measured current according to the present disclosure. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 1 is a diagram showing an example of a current measurement system 1 according to the present disclosure. The current measurement system 1 is a system for measuring a current. The current measurement system 1 can measure the current of a secondary battery installed in a stationary energy storage system, for example. A specific example of an apparatus in which the current measurement system 1 is implemented is a DC / DC converter. An embodiment in which the current measurement system is implemented in a DC / DC converter will be described below.

[0016] The current measurement system 1 includes a power supply 2, a power supply switch 3, a current sensor 4, diodes 5 and 6, a diode changeover switch 7, a capacitor 8, an inductor 9, and a load 10. These components are electrically connected via electric wires. In the embodiment shown in FIG. 1, the power supply 2, the capacitor 8, the diodes 5 and 6, and the load 10 are connected in parallel.

[0017] The power supply 2 is a power supply whose current is to be measured by the current measurement system 1. In this embodiment, the power supply 2 is a DC power supply.

[0018] The power switch 3 is a switch that controls the supply of current from the power supply 2 under the control of a control device described later. The power switch 3 is connected in series with the power supply 2.

[0019] The current sensor 4 is a sensor that measures a current measurement value. The current sensor 4 is connected in series with the power source 2 and the capacitor 8. The current sensor 4 has a core made of a magnetic material, and measures the magnitude of the current based on the strength of the magnetic field generated by the current flowing through an electric wire placed inside the core.

[0020] Three electric wires 40, 41, and 42 are arranged inside the core. The electric wires 41 and 42 correspond to the first and second electric wires. The electric wire 40 corresponds to the third electric wire. The first electric wire 41 and the second electric wire 42 are arranged parallel to each other inside the core. The first electric wire 41 and the second electric wire 42 are arranged such that the direction of the current in the first electric wire 41 and the direction of the current in the second electric wire 42 inside the core are opposite to each other. The third electric wire 40 may be arranged parallel to the first electric wire 41 and the second electric wire 42, or may not be arranged parallel to the first electric wire 41 and the second electric wire 42.

[0021] The diodes 5 and 6 are elements for controlling the current flowing through the first electric wire 41 and the second electric wire 42. The diodes 5 and 6 are connected in series with the current sensor 4 on the negative electrode side of the power source 2. The diode 5 allows the current to flow from the inductor 9 to both the first electric wire 41 and the second electric wire 42. On the other hand, the diode 6 allows the current to flow from the inductor 9 to the first electric wire 41 but does not allow the current to flow to the second electric wire 42.

[0022] The diode changeover switch 7 is connected in series with the diodes 5 and 6 on the negative electrode side of the power supply 2. The diode changeover switch 7 controls the current flowing through the first electric wire 41 and the second electric wire 42 under the control of a control device described later.

[0023] The capacitor 8 is an element that stores electricity supplied from the power source 2. The capacitor 8 stores the current supplied from the power source 2 and the inductor 9, and smoothes the voltage supplied to the load 10.

[0024] The inductor 9 is an element that stores electric energy supplied from the power supply 2, and is connected in series to the current sensor 4. The inductor 9 supplies power when the power supply 2 is off. Specifically, the inductor 9 passes a current to the current sensor 4 via the diodes 5 and 6.

[0025] The load 10 is any of various elements that consume the power supplied from the power source 2. Note that in other embodiments, the power source 2 and the load 10 do not have to be configured as components of the current measurement system 1.

[0026] The current measurement system 1 further includes a control device. Fig. 2 is a block diagram showing an example of the configuration of the control device 20. The control device 20 calculates an offset error of the current sensor 4 based on a current measurement value obtained from the current sensor 4, and calculates an average value of a current supplied by the power supply 2. The control device 20 includes a sensor communication interface (I / F) 21, a switch communication interface 22, a storage device 23, and a calculation device 24.

[0027] The sensor communication interface 21 is an interface for transmitting and receiving signals between the control device 20 and the current sensor 4 .

[0028] The switch communication interface 22 is an interface for transmitting and receiving signals between the control device 20 and the power switch 3 and the diode changeover switch 7 .

[0029] The storage device 23 is a storage device in which the control program executed by the arithmetic device 24 and various information processed by the arithmetic device 24 are stored.

[0030] The arithmetic device 24 is an arithmetic device such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The arithmetic device 24 executes a current measurement method by expanding a control program stored in the storage device 23 into a storage device in the arithmetic device 24 and executing the control program. The control program includes a measurement value acquisition unit 25, a switch control unit 27, an offset value acquisition unit 26, a current correction unit 28, and an average value calculation unit 29. The functions of these program modules may be realized by an integrated circuit such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The arithmetic device, FPGA, ASIC, or other integrated circuit corresponds to a computer.

[0031] The measurement value acquiring unit 25 is a program module that acquires a current measurement value (hereinafter referred to as a "current measurement value") from the current sensor 4 via the sensor communication interface 21. Specifically, the measurement value acquiring unit 25 acquires a current measurement value of the current sensor 4 when the power supply 2 is on and a current (current I_ON) from the power supply 2 flows to the third electric wire 40 arranged inside the core of the current sensor 4. In addition, the measurement value acquiring unit 25 acquires a current measurement value of the current sensor 4 when the power supply 2 is off and a current (current I_OFF) from the inductor 9 flows to the first electric wire 41 arranged inside the core of the current sensor 4.

[0032] The offset value acquiring unit 26 is a program module that acquires the value of the offset error of the current sensor 4. Specifically, when the power supply 2 is off, the offset value acquiring unit 26 acquires, as the value of the offset error, the current measurement value of the current sensor 4 when the current (current I_OFF) from the inductor 9 flows through the second electric wire 42 and the first electric wire 41 arranged inside the core of the current sensor 4.

[0033] The switch control unit 27 is a program module that controls the opening and closing of the power switch 3 and the diode changeover switch 7. The switch control unit 27 transmits a control signal to the power switch 3 via the switch communication interface 22 to control the on and off of the power switch 3. The switch control unit 27 also transmits a control signal to the diode changeover switch 7 via the switch communication interface 22 to connect the diode changeover switch 7 to the side of diode 5 or the side of diode 6.

[0034] The current correction unit 28 is a program module that corrects the value of the current flowing through the current sensor 4 by using the acquired offset error value.

[0035] The average value calculation unit 29 is a program module that calculates the average value of the current supplied from the power source 2 based on the current measurement value acquired by the measurement value acquisition unit 25.

[0036] Fig. 3 is a flowchart showing an example of a process executed by the control device 20. The process shown in Fig. 3 is executed in a power-on state. Moreover, the process shown in Fig. 3 can be periodically executed by the control device 20.

[0037] In step S1, the switch control section 27 of the control device 20 connects the diode changeover switch 7 to the side (D1) of the diode 5. This state corresponds to state 1 in FIG. 4. At this time, the current (current I_ON) from the power supply 2 becomes as in state 1.

[0038] In step S2, the switch control unit 27 turns the power switch 3 from on to off. As a result, the current from the power supply 2 (current I_ON) stops, and the current from the inductor 9 (current I_OFF) flows through the second electric wire 42 and the first electric wire 41 arranged inside the core of the current sensor 4. This state corresponds to state 2 in Fig. 4. At this time, the current from the power supply 2 (current I_ON) and the current from the inductor 9 (current I_OFF) become as shown in state 2.

[0039] In step S3, offset value acquisition unit 26 acquires a current measurement value from current sensor 4. As shown in Fig. 4, this measurement value corresponds to the value of the offset error of current sensor 4. Note that although the measurement value is a positive value in Fig. 4, the measurement value may also be a negative value.

[0040] In step S4, the switch control unit 27 turns the power switch 3 from off to on. In step S5, the switch control unit 27 connects the diode changeover switch 7 to the side (D2) of the diode 6. This causes a current (current I_ON) from the power supply 2 to flow to the third electric wire 40 arranged inside the core of the current sensor 4. This state corresponds to state 3 in FIG. 4. In state 3, no current flows through the first electric wire 41 and the second electric wire 42.

[0041] In step S6, the measurement value acquiring unit 25 acquires current measurement values ​​from the current sensor 4. At this time, the measurement value acquiring unit 25 can acquire multiple current measurement values ​​in state 3, i.e., multiple current measurement values ​​that change over time, in time series.

[0042] In step S7, the switch control unit 27 turns the power switch 3 from on to off. As a result, a current (current I_OFF) from the inductor 9 flows to the first electric wire 41 arranged inside the core of the current sensor 4. This state corresponds to state 4 in FIG. 4. In state 4, no current flows through the second electric wire 42 and the third electric wire 40.

[0043] In step S8, the measurement value acquiring unit 25 acquires current measurement values ​​from the current sensor 4. At this time, the measurement value acquiring unit 25 can acquire multiple current measurement values ​​in state 4, i.e., multiple current measurement values ​​that change over time, in time series.

[0044] In step S9, the current correction unit 28 corrects the multiple current measurement values ​​acquired in step S6 and the multiple current measurement values ​​acquired in step S8, using the value of the offset error of the current sensor 4 acquired in step S3. In other words, the current correction unit 28 corrects the multiple measurement values ​​in state 3 and the multiple measurement values ​​in state 4.

[0045] In step S10, average value calculation section 29 calculates the average value of the current flowing through current sensor 4 using the multiple measurement values ​​in state 3 and the multiple measurement values ​​in state 4 corrected by current correction section .

[0046] In step S11, the switch control unit 27 turns the power switch 3 from off to on, and ends the process in Fig. 3. The above-mentioned process in Fig. 3 is periodically repeated.

[0047] In the above-described embodiment, the current measurement system 1 includes a current sensor 4 having a core, a first electric wire 41 and a second electric wire 42 arranged parallel to each other inside the core, and a third electric wire arranged inside the core. The direction of the current in the first electric wire 41 and the direction of the current in the second electric wire 42 inside the core are opposite to each other. The current sensor 4 measures the current inside the core when a current flows through both the first electric wire 41 and the second electric wire 42, when a current flows through the third electric wire 40 in a state where no current flows through the first electric wire 41 and the second electric wire 42, and when a current flows through the first electric wire 41 in a state where no current flows through the second electric wire 42 and the third electric wire 40.

[0048] In this way, inside the core, currents flow in opposite directions in the first electric wire 41 and the second electric wire 42, so that the magnetic fields generated by the currents in the first electric wire 41 and the second electric wire 42 are offset. Therefore, it is possible to virtually create a state in which no current flows inside the core. By having the current sensor 4 measure the current in this state, it is possible to obtain the value of the offset error of the current sensor 4 without interrupting the current to the current sensor 4.

[0049] Moreover, the current measurement system 1 further includes a current correction unit 28 that uses the value of the offset error acquired in this manner to correct the value of the current flowing through the current sensor 4. This makes it possible to correct the current in the current sensor 4.

[0050] Moreover, the first electric wire 41 and the second electric wire 42 are arranged inside the core such that the waveform of the first current flowing in the first electric wire 41 and the waveform of the second current flowing in the second electric wire 42 are in phase with each other. By adopting such an arrangement, the magnetic fields generated by the first current and the second current can be effectively cancelled out. Therefore, the measurement accuracy of the offset value of the current sensor 4 can be improved.

[0051] Furthermore, the current sensor 4 measures a measurement value of the current in the third electric wire in a state where no current flows in the first electric wire 41 and the second electric wire 42, and a measurement value in the first electric wire 41 in a state where no current flows in the second electric wire 42 and the third electric wire 40. The average value calculation unit 29 calculates the average value of the current in the first electric wire 41 and the third electric wire 40 based on the measured measurement values ​​in the first electric wire 41 and the third electric wire 40. In this way, the average value of the current flowing in the current sensor 4 can be calculated.

[0052] In the above example, the program can be stored and provided to the computer using various types of non-transitory computer readable media. The non-transitory computer readable medium includes various types of tangible storage media. Examples of the non-transitory computer readable medium include magnetic recording media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROMs, CD-Rs, CD-R / Ws, and semiconductor memories (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, and RAMs). The program may also be provided to the computer by various types of transitory computer readable media. Examples of the transitory computer readable medium include electrical signals, optical signals, and electromagnetic waves. The transitory computer readable medium can provide the program to the computer via a wired communication path such as an electric wire and an optical fiber, or via a wireless communication path.

[0053] The present disclosure is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present disclosure. For example, in another embodiment, when a power supply that performs current control based only on the peak value of the output current is used, the diode 6 and the diode changeover switch 7 may be deleted. In another embodiment, the measurement value acquisition unit 25 and the offset value acquisition unit 26 may be configured as one functional means. [Explanation of symbols]

[0054] 1 Current measurement system 2 Power supply 3 Power Switch 4 Current Sensor 5. Diodes 6. Diodes 7 Diode Changeover Switch 8 Capacitors 9. Inductors 10 Load 20 Control device 21 Sensor communication interface 22 Communication interface for switch 23 Storage device 24 Arithmetic unit 25 Measurement value acquisition section 26 Offset value acquisition section 27 Switch control section 28 Current correction section 29 Average value calculation section 40 Electric Wire, Third Wire 41 Electric Wire, First Electric Wire 42 Electric Wire, Second Electric Wire

Claims

1. a current sensor having a core; a first electric wire and a second electric wire arranged parallel to each other inside the core; a third wire disposed inside the core; a direction of a current in the first electric wire and a direction of a current in the second electric wire inside the core are opposite to each other; the current sensor measures a current inside the core when a current flows through both the first electric wire and the second electric wire, thereby acquiring a value of an offset error of the current sensor; Current measurement system.

2. The current measurement system according to claim 1 , further comprising a current correction unit that corrects a value of a current flowing through the current sensor by using the acquired value of the offset error.

3. 3. The current measurement system according to claim 1, wherein the first electric wire and the second electric wire are arranged inside the core such that a waveform of a first current flowing in the first electric wire and a waveform of a second current flowing in the second electric wire are in phase with each other.

4. the current sensor measures a measurement value of a current in the third electric wire when no current flows in the first electric wire and the second electric wire, and a measurement value of the current in the first electric wire when no current flows in the second electric wire and the third electric wire, The current measurement system includes:

3. The current measurement system according to claim 1, further comprising an average value calculation unit that calculates an average value of the current in the first electric wire and the current in the third electric wire based on the measured values ​​in the first electric wire and the measured values ​​in the third electric wire.

5. The current measurement system includes an inductor that stores electrical energy supplied from a power source; 3. The current measuring system according to claim 1, wherein a current supplied from the inductor flows through the first electric wire and the second electric wire.

6. A current measurement method performed by a current sensor having a core, comprising: A first electric wire, a second electric wire, and a third electric wire are arranged inside the core, the first electric wire and the second electric wire being parallel to each other, a direction of a current in the first electric wire and a direction of a current in the second electric wire inside the core are opposite to each other; The current measurement method includes obtaining a value of an offset error of the current sensor by measuring a current inside the core when a current flows through both the first electric wire and the second electric wire. Current measurement method.

7. The current measuring method according to claim 6 , further comprising a current correction unit that corrects a value of a current flowing through the current sensor by using the acquired value of the offset error.

8. 8. The current measuring method according to claim 6, wherein the first electric wire and the second electric wire are arranged inside the core such that a waveform of a first current flowing in the first electric wire and a waveform of a second current flowing in the second electric wire are in phase with each other.

9. 8. The current measuring method according to claim 6, wherein a current supplied from an inductor storing electric energy supplied from a power source flows through the first electric wire and the second electric wire.

10. 1. A current measurement method performed in a current measurement system, comprising: The current measurement system includes: a current sensor having a core; a first electric wire and a second electric wire arranged parallel to each other inside the core; a third wire disposed inside the core; a direction of a current in the first electric wire and a direction of a current in the second electric wire inside the core are opposite to each other; The current measuring method includes: the current sensor measures a measurement value of a current in the third electric wire when no current flows in the first electric wire and the second electric wire, and a measurement value of the current in the first electric wire when no current flows in the second electric wire and the third electric wire; The computer A current measuring method comprising: calculating average values ​​of a current in the first electric wire and a current in the third electric wire based on measured values ​​in the first electric wire and a measured value in the third electric wire.

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