Current sampling device and method for eliminating zero drift

Abstract

This disclosure belongs to the field of nuclear power technology, specifically relating to a current sampling device and method for eliminating zero drift. This disclosure, by adding a small current input circuit, ensures that the sampling voltage of the current sensor remains at a certain magnitude when the sampling current of the current sensor is too small. This prevents the current sensor from being interfered with by external signals and also ensures that devices such as the analog-to-digital converter and operational amplifier do not operate in the offset region. Thus, by adding a small current input circuit, when the measured current is less than a set threshold value, a small current of the same frequency (or an integer multiple of the frequency) as the measured current is injected, maintaining the measured current at least above the dead zone current.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power technology, specifically relating to a current sampling device and method for eliminating zero drift. Background Technology

[0002] Currently, all AC current sampling methods can employ current transformers (CTs), Hall effect sensors, shunts, etc. These methods all face the problem of zero drift in practical applications: when the primary input value is too small, especially zero, the sampled current will fluctuate irregularly due to external interference, temperature changes, etc., resulting in creeping and other unfavorable measurement phenomena during metering. To address current zero drift, the main sampling methods currently available include: 1. Setting a dead-zone current. This is currently the mainstream method for handling zero drift. When the measured current value is less than the set value, the system automatically sets the current to 0. When the input is zero, this method can prevent the influence of zero drift on measurement / metering by setting a reasonable dead-zone threshold. Due to the increasing use of various low-power and micro-power electrical devices (such as LED lighting), this method cannot distinguish between zero drift and the operating status of low-power electrical devices, leading to inaccurate metering.

[0003] 2. Improve sampling accuracy. By upgrading hardware configurations, such as using higher-precision operational amplifiers and ADC devices, the zero-drift value can be limited to an extremely low level, reducing the impact of zero drift. However, this method may significantly increase product costs and does not offer good cost-effectiveness. Moreover, this method can only reduce the occurrence of zero drift, not completely prevent it.

[0004] 3. Software Compensation Method. This method uses software techniques such as appropriate filtering algorithms to suppress sampling value drift caused by external interference and temperature drift. However, this method is limited by the system hardware's computing power and cannot completely eliminate zero drift. Furthermore, some filtering algorithms may reduce data real-time performance, causing additional delays.

[0005] Given these circumstances, there is an urgent need for an effective solution to eliminate current drift. Summary of the Invention

[0006] To overcome the problems existing in related technologies, a current sampling device and method for eliminating zero drift are provided.

[0007] According to one aspect of the present disclosure, a current sampling device for eliminating zero drift is provided, the device comprising: a current sensor, an analog-to-digital converter, an injected current sampler, an injected current generator, and a controller; The current sensor is connected to the analog-to-digital converter and the power supply under test respectively, and is used to convert the current of the AC power supply under test into a secondary current with a smaller current value, and output it to the analog-to-digital converter for sampling. The analog-to-digital converter is connected to the controller and is used to sample the secondary current output by the current sensor to obtain a first current value, which is then output to the controller. The injected current generator is connected to the controller and the current sensor respectively. When the controller determines that the first current value is less than or equal to a preset threshold, it controls the injected current generator to inject current into the current sensor until it determines that the first current value is greater than the preset threshold, and controls the injected current generator to stop injecting current. The frequency and phase of the current injected by the injected current generator into the current sensor are matched with the frequency and phase of the secondary current. The injected current sampler is connected to the analog-to-digital converter and is used to convert the injected current output by the injected current generator into a voltage signal and output it to the analog-to-digital converter for sampling. The analog-to-digital converter is also used to sample the output voltage signal of the injected current sampler to obtain a second current value, which is then output to the controller. When the controller determines that the first current value is less than or equal to a preset threshold, it performs vector calculation on the first current value and the second current value to eliminate the injected current value from the real-time measured current value of the power supply under test, thereby obtaining the measured current value.

[0008] In one possible implementation, when the controller determines that the first current value is less than or equal to a preset threshold, it determines the frequency difference between the frequency of the secondary current and the preset frequency, and determines whether the frequency difference falls within the set difference range. When the controller determines that the frequency difference is not within the set difference range, it sets the injection current frequency of the injection current generator to a preset frequency, which is an integer multiple of the secondary current frequency. When the controller determines that the frequency difference is within the set difference range, it sets the injection current frequency and phase of the injection current generator to be the same as the frequency and phase of the secondary current.

[0009] In one possible implementation, the current sensor includes: an iron core, an output current coil, and an injection current coil, with the conductor of the power supply being measured passing through the iron core; The output current coil is wound on the iron core and connected to the analog-to-digital converter for outputting secondary current. The injection current coil is wound on the iron core, separated from the output current coil, and connected to the injection current generator to realize the function of the injection current generator injecting current into the current sensor.

[0010] In one possible implementation, the injected current generator is an analog-to-digital converter or a pulse width modulator.

[0011] According to another aspect of the present disclosure, a current sampling method for eliminating zero drift is provided, the method being applied in the above-described apparatus, the method comprising: Step 10: When the controller determines that the first current value is less than or equal to a preset threshold, it controls the injection current generator to inject current into the current sensor until it determines that the first current value is greater than the preset threshold, and then controls the injection current generator to stop injecting current. The frequency and phase of the current injected into the current sensor by the injection current generator are matched with the frequency and phase of the secondary current. Step 11: When the controller determines that the first current value is less than or equal to a preset threshold, it performs vector calculation on the acquired first current value and second current value to eliminate the injected current value from the real-time measured current value of the power supply under test, and obtains the measured current value.

[0012] In one possible implementation, the method further includes: Step 12: When the controller determines that the first current value is less than or equal to a preset threshold, it determines the frequency difference between the frequency of the secondary current and the preset frequency, and determines whether the frequency difference falls within the set difference range. Step 13: When the controller determines that the frequency difference is not within the set difference range, it sets the injection current frequency of the injection current generator to a preset frequency, which is an integer multiple of the secondary current frequency. Step 14: When the controller determines that the frequency difference is within the set difference range, it sets the injection current frequency and phase of the injection current generator to be the same as the frequency and phase of the secondary current.

[0013] According to another aspect of the embodiments of this disclosure, a current sampling device for eliminating zero drift is provided, the device comprising: The first control module is used to control the injection current generator to inject current into the current sensor when it is determined that the first current value is less than or equal to a preset threshold, until it is determined that the first current value is greater than the preset threshold, and then control the injection current generator to stop injecting current. The frequency and phase of the current injected by the injection current generator into the current sensor are matched with the frequency and phase of the secondary current. The first control module is used to perform vector calculations on the acquired first current value and second current value when the first current value is determined to be less than or equal to a preset threshold, so as to eliminate the injected current value from the real-time measured current value of the power supply under test and obtain the measured current value.

[0014] In one possible implementation, the device further includes: The third control module is used to determine the frequency difference between the frequency of the secondary current and the preset frequency when the first current value is less than or equal to the preset threshold, and to determine whether the frequency difference is within the set difference range. The fourth control module is used to set the injection current frequency of the injection current generator to a preset frequency when the frequency difference is determined to be within a set difference range. The fifth control module is used to set the injection current frequency of the injection current generator to the frequency of the secondary current when the frequency difference is determined to be outside the set difference range.

[0015] According to another aspect of the present disclosure, a non-volatile computer-readable storage medium is provided, on which computer program instructions are stored, which, when executed by a processor, implement the above-described method.

[0016] The beneficial effects of this disclosure are as follows: By adding a small current input circuit, when the sampling current of the current sensor is too small, the sampling voltage of the current sensor is maintained at a certain magnitude by injecting current. This prevents the current sensor from being interfered with by external signals and also ensures that devices such as the analog-to-digital converter and operational amplifier do not operate in the offset region. Furthermore, by adding a small current input circuit, when the measured current is less than a set threshold, a small current of the same frequency (or an integer multiple of the frequency) as the measured current is injected, maintaining the measured current at least above the dead zone current. Attached Figure Description

[0017] Figure 1 This is a block diagram illustrating a current sampling device for eliminating zero drift according to an exemplary embodiment.

[0018] Figure 2 This is a flowchart illustrating a current sampling method for eliminating zero drift according to an exemplary embodiment.

[0019] Figure 3 This is a schematic diagram of a current sensor according to an exemplary embodiment.

[0020] Figure 4 This is a schematic diagram of an injection current generator according to an exemplary embodiment. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Figure 1 This is a block diagram illustrating a current sampling device for eliminating zero drift, according to an exemplary embodiment. Figure 1 As shown, the device may include: a current sensor, an analog-to-digital converter, an injected current sampler, an injected current generator, and a controller.

[0023] In this disclosure, the current sensor may include a current transformer, a Hall current sensor, or a shunt, etc., and this disclosure does not limit the type of current sensor.

[0024] The current sensor is connected to the analog-to-digital converter and the power supply under test respectively, and is used to convert the current of the AC power supply under test into a secondary current with a smaller current value, and output it to the analog-to-digital converter for sampling. The analog-to-digital converter is connected to the controller and is used to sample the secondary current output by the current sensor to obtain a first current value, which is then output to the controller. The injected current generator is connected to both the controller and the current sensor, thereby forming a small current input loop.

[0025] Figure 2 This is a flowchart illustrating a current sampling method for eliminating zero drift according to an exemplary embodiment. Figure 2 As shown, the controller monitors the magnitude of the measured current in real time. When the controller determines that the first current value is less than or equal to a preset threshold, it controls the injection current generator to inject current into the current sensor. When the controller determines that the first current value is greater than the preset threshold, it controls the injection current generator to stop injecting current.

[0026] The injected current generator injects a current into the current sensor whose frequency and phase match the secondary current (this can be expressed as the injected current frequency being the same as the secondary current, or having a very small difference, or the injected current frequency being an integer multiple of the secondary current frequency; the multiple can be determined according to the actual measurement needs). For example... Figure 2 As shown, when the controller determines that the first current value is less than or equal to a preset threshold, it determines the frequency difference between the frequency of the secondary current and the preset frequency, and determines whether the frequency difference falls within the set difference range.

[0027] When the controller determines that the frequency difference is not within the set difference range, it sets the injection current frequency of the injection current generator to a preset frequency, which is an integer multiple of the secondary current frequency, and the phase of the injection current can be random.

[0028] When the controller determines that the frequency difference is within the set difference range, it sets the injection current frequency and phase of the injection current generator to be the same as the frequency and phase of the secondary current.

[0029] The injected current sampler is connected to the analog-to-digital converter and is used to convert the injected current output by the injected current generator into a voltage signal and output it to the analog-to-digital converter for sampling. The analog-to-digital converter is also used to sample the output voltage signal of the injected current sampler to obtain a second current value, which is then output to the controller. When the controller determines that the first current value is less than or equal to a preset threshold, it performs vector calculation on the first current value and the second current value to eliminate the injected current value from the real-time measured current value of the power supply under test, thereby obtaining the measured current value.

[0030] In related technologies, whether measuring DC or AC current, the final measurement involves circuit conversion and isolation to obtain a small current signal, which is then passed through a sampling resistor. For example, a current transformer converts the measured current into a small current signal according to the CT ratio, which is then passed through a sampling resistor to form a voltage signal. Finally, an ADC obtains a digital signal for calculation to obtain the current value. Compared to current signals, voltage signals are more susceptible to external interference, leading to errors; especially small voltage signals are prone to errors. Furthermore, ADCs, when sampling small signals, are also prone to significant errors due to the influence of operational amplifiers and the accuracy of AD devices. Therefore, this invention adds an isolated small current input loop to the current sensor. During current measurement, the magnitude of the measured current is monitored in real time. When the measured current is lower than a set lower limit, a small current is injected into the small current input loop to maintain the current in the sensor's detection loop. After the sampling resistor converts the current into voltage, it ensures that the sampling voltage remains at a certain magnitude to prevent interference from external signals and to ensure that the AD and operational amplifier devices do not operate in the offset region.

[0031] Figure 3 This is a schematic diagram of a current sensor according to an exemplary embodiment, such as... Figure 3 As shown, the current sensor includes an iron core 9, an output current coil 11, and an injection current coil 12. The conductor 10 of the power supply being measured passes through the iron core 9. The output current coil 11 is wound around the iron core 9 and connected to the analog-to-digital converter (ADC). Figure 3 (Not shown in the image) Connection used for outputting secondary current; The injection current coil 12 is wound on the iron core 9, separated from the output current coil 11, and connected to the injection current generator to realize the function of the injection current generator injecting current into the current sensor. In this way, this disclosure can add an auxiliary coil to the coil of a conventional Hall current sensor or current transformer, and the auxiliary coil is connected to the injection current generator to realize the current injection function.

[0032] In one possible implementation, the injected current generator is an analog-to-digital converter or a pulse width modulator. Figure 4 This is a schematic diagram of an injection current generator according to an exemplary embodiment, such as... Figure 4As shown, the DAC function inside the microcontroller 13 can be used to output the current with rated frequency, phase, and amplitude. After being amplified and isolated by the operational amplifier 14 and the amplification resistor 15, the current is injected into the current sensor via the output resistor 16. It can be directly used for sampling the injected current.

[0033] In one application example, the current sampling device implemented by the method provided in this disclosure can easily achieve a reference accuracy of 0.1% or a measurement accuracy of 0.2S, even when using an MCU's internal ADC to implement the sampling circuit at extremely low cost, thereby overcoming the impact of current sampling zero drift on the accuracy of the metering device.

[0034] In one possible implementation, a current sampling method for eliminating zero drift is provided, the method being applied in the aforementioned device, the method comprising: Step 10: When the controller determines that the first current value is less than or equal to a preset threshold, it controls the injection current generator to inject current into the current sensor until it determines that the first current value is greater than the preset threshold, and then controls the injection current generator to stop injecting current. The frequency and phase of the current injected into the current sensor by the injection current generator are matched with the frequency and phase of the secondary current. Step 11: When the controller determines that the first current value is less than or equal to a preset threshold, it performs vector calculation on the acquired first current value and second current value to eliminate the injected current value from the real-time measured current value of the power supply under test, and obtains the measured current value.

[0035] In one possible implementation, the method further includes: Step 12: When the controller determines that the first current value is less than or equal to a preset threshold, it determines the frequency difference between the frequency of the secondary current and the preset frequency, and determines whether the frequency difference falls within the set difference range. Step 13: When the controller determines that the frequency difference is not within the set difference range, it sets the injection current frequency of the injection current generator to a preset frequency, which is an integer multiple of the secondary current frequency. Step 14: When the controller determines that the frequency difference is within the set difference range, it sets the injection current frequency and phase of the injection current generator to be the same as the frequency and phase of the secondary current.

[0036] In one possible implementation, a current sampling device for eliminating zero drift is provided, the device being applied in the aforementioned device, the device comprising: The first control module is used to control the injection current generator to inject current into the current sensor when it is determined that the first current value is less than or equal to a preset threshold, until it is determined that the first current value is greater than the preset threshold, and then control the injection current generator to stop injecting current. The frequency and phase of the current injected by the injection current generator into the current sensor are matched with the frequency and phase of the secondary current. The first control module is used to perform vector calculations on the acquired first current value and second current value when the first current value is determined to be less than or equal to a preset threshold, so as to eliminate the injected current value from the real-time measured current value of the power supply under test and obtain the measured current value.

[0037] In one possible implementation, the device further includes: The third control module is used to determine the frequency difference between the frequency of the secondary current and the preset frequency when the first current value is less than or equal to the preset threshold, and to determine whether the frequency difference is within the set difference range. The fourth control module is used to set the injection current frequency of the injection current generator to a preset frequency when the frequency difference is determined to be within a set difference range. The fifth control module is used to set the injection current frequency of the injection current generator to the frequency of the secondary current when the frequency difference is determined to be outside the set difference range.

[0038] The descriptions of the above methods and virtual devices have already been elaborated in the descriptions of the above physical devices, and will not be repeated here.

[0039] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0040] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0041] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0042] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0043] Various aspects of this disclosure are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this disclosure. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0044] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that, when executed by the processor of the computer or other programmable data processing apparatus, they create means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium that causes a computer, programmable data processing apparatus, and / or other device to operate in a particular manner; thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing aspects of the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0045] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to perform the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0046] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those shown in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0047] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A current sampling device for eliminating zero drift, characterized in that, The device includes: a current sensor, an analog-to-digital converter, an injected current sampler, an injected current generator, and a controller; The current sensor is connected to the analog-to-digital converter and the power supply under test respectively, and is used to convert the current of the AC power supply under test into a secondary current with a smaller current value, and output it to the analog-to-digital converter for sampling. The analog-to-digital converter is connected to the controller and is used to sample the secondary current output by the current sensor to obtain a first current value, which is then output to the controller. The injected current generator is connected to the controller and the current sensor respectively. When the controller determines that the first current value is less than or equal to a preset threshold, it controls the injected current generator to inject current into the current sensor until it determines that the first current value is greater than the preset threshold, and controls the injected current generator to stop injecting current. The frequency and phase of the current injected by the injected current generator into the current sensor are matched with the frequency and phase of the secondary current. The injected current sampler is connected to the analog-to-digital converter and is used to convert the injected current output by the injected current generator into a voltage signal and output it to the analog-to-digital converter for sampling. The analog-to-digital converter is also used to sample the output voltage signal of the injected current sampler to obtain a second current value, which is then output to the controller. When the controller determines that the first current value is less than or equal to a preset threshold, it performs vector calculation on the first current value and the second current value to eliminate the injected current value from the real-time measured current value of the power supply under test, thereby obtaining the measured current value.

2. The apparatus according to claim 1, characterized in that, When the controller determines that the first current value is less than or equal to a preset threshold, it determines the frequency difference between the frequency of the secondary current and the preset frequency, and determines whether the frequency difference falls within the set difference range. When the controller determines that the frequency difference is not within the set difference range, it sets the injection current frequency of the injection current generator to a preset frequency, which is an integer multiple of the secondary current frequency. When the controller determines that the frequency difference is within the set difference range, it sets the injection current frequency and phase of the injection current generator to be the same as the frequency and phase of the secondary current.

3. The apparatus according to claim 1, characterized in that, The current sensor includes an iron core, an output current coil, and an injection current coil, with the wire of the power supply being measured passing through the iron core. The output current coil is wound on the iron core and connected to the analog-to-digital converter for outputting secondary current. The injection current coil is wound on the iron core, separated from the output current coil, and connected to the injection current generator to realize the function of the injection current generator injecting current into the current sensor.

4. The apparatus according to claim 1, characterized in that, The injected current generator is an analog-to-digital converter or a pulse width modulator.

5. A current sampling method for eliminating zero drift, characterized in that, The method is applied to the apparatus as described in any one of claims 1 to 4, the method comprising: Step 10: When the controller determines that the first current value is less than or equal to a preset threshold, it controls the injection current generator to inject current into the current sensor until it determines that the first current value is greater than the preset threshold, and then controls the injection current generator to stop injecting current. The frequency and phase of the current injected into the current sensor by the injection current generator are matched with the frequency and phase of the secondary current. Step 11: When the controller determines that the first current value is less than or equal to a preset threshold, it performs vector calculation on the acquired first current value and second current value to eliminate the injected current value from the real-time measured current value of the power supply under test, and obtains the measured current value.

6. The method according to claim 5, characterized in that, The method further includes: Step 12: When the controller determines that the first current value is less than or equal to a preset threshold, it determines the frequency difference between the frequency of the secondary current and the preset frequency, and determines whether the frequency difference falls within the set difference range. Step 13: When the controller determines that the frequency difference is not within the set difference range, it sets the injection current frequency of the injection current generator to a preset frequency, which is an integer multiple of the secondary current frequency. Step 14: When the controller determines that the frequency difference is within the set difference range, it sets the injection current frequency and phase of the injection current generator to be the same as the frequency and phase of the secondary current.

7. A current sampling device for eliminating zero drift, characterized in that, The device is used in the apparatus as described in any one of claims 1 to 4, the apparatus comprising: The first control module is used to control the injection current generator to inject current into the current sensor when it is determined that the first current value is less than or equal to a preset threshold, until it is determined that the first current value is greater than the preset threshold, and then control the injection current generator to stop injecting current. The frequency and phase of the current injected by the injection current generator into the current sensor are matched with the frequency and phase of the secondary current. The first control module is used to perform vector calculations on the acquired first current value and second current value when the first current value is determined to be less than or equal to a preset threshold, so as to eliminate the injected current value from the real-time measured current value of the power supply under test and obtain the measured current value.

8. The apparatus according to claim 7, characterized in that, The device further includes: The third control module is used to determine the frequency difference between the frequency of the secondary current and the preset frequency when the first current value is less than or equal to the preset threshold, and to determine whether the frequency difference is within the set difference range. The fourth control module is used to set the injection current frequency of the injection current generator to a preset frequency when the frequency difference is determined to be within a set difference range. The fifth control module is used to set the injection current frequency of the injection current generator to the frequency of the secondary current when the frequency difference is determined to be outside the set difference range.

9. A non-volatile computer-readable storage medium storing computer program instructions thereon, characterized in that, When the computer program instructions are executed by the processor, they implement the method of claim 5 or 6.

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