CN116859115A - Current sampling device and method for eliminating zero drift - Google Patents
Current sampling device and method for eliminating zero drift Download PDFInfo
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Abstract
The disclosure belongs to the technical field of nuclear power, and particularly relates to a current sampling device and method for eliminating zero drift. The present disclosure. According to the current sensor, the small current input loop is added, under the condition that the sampling current of the current sensor is small, the sampling voltage of the current sensor is ensured to be kept at a certain level in a current injection mode, so that the current sensor is prevented from being interfered by external signals, devices such as an operational amplifier of an analog-to-digital converter are ensured to not work in an offset area. Therefore, by adding the small current input loop, when the measured current is smaller than the set critical value, the small current with the same frequency (or integral multiple frequency) as the measured current is injected, and the measured current is kept not to be lower than the dead zone current.
Description
Technical Field
The invention belongs to the technical field of nuclear power, and particularly relates to a current sampling device and method for eliminating zero drift.
Background
All current alternating current sampling can be performed by adopting a Current Transformer (CT), a Hall sensor, a current divider and the like. These approaches all face zero drift problems in practical applications: when the primary input value is too small, particularly zero, the sampling current can have irregular fluctuation due to external interference, temperature change and the like, and the phenomenon of measurement is unfavorable due to the fact that the sampling current is fluctuated during metering. For zero drift of current, the current sampling method mainly comprises the following steps:
1. the dead-zone current is set. This is the current mainstream method of handling zero drift, when the measured current value is less than the set point, the system automatically sets the current at this point to 0. When the input is zero, the method can prevent the influence of zero drift on measurement/metering by setting a reasonable dead zone threshold. Due to the continuous application of various low-power and micro-power electric equipment (such as an LED illuminating lamp), the method cannot distinguish the working conditions of the low-power electric equipment and zero drift, so that the metering inaccuracy condition is caused.
2. And the sampling precision is improved. By improving hardware configuration, such as using operational amplifier and ADC device with higher precision, the zero drift value is limited to an extremely low value, and the influence caused by zero drift is reduced. The method can greatly improve the product cost and has no good cost performance. In addition, the method can only reduce the occurrence of zero drift, and cannot completely prevent the zero drift phenomenon.
3. Software compensation mode. And the sampling value drift caused by factors such as external interference, temperature drift and the like is inhibited by reasonable software modes such as a filtering algorithm and the like. This approach is limited by the computational power of the system hardware and cannot completely eliminate zero drift. In addition, some filtering algorithms may reduce the real-time nature of the data, causing additional delays.
In view of the above, there is a need for an effective solution to eliminate the zero drift of current.
Disclosure of Invention
In order to overcome the problems in the related art, a current sampling device and a method for eliminating zero drift are provided.
According to an aspect of an embodiment of the present disclosure, there is provided a current sampling apparatus for eliminating zero drift, the apparatus including: the system comprises a current sensor, an analog-to-digital converter, an injection current sampler, an injection current generator and a controller;
the current sensor is respectively connected with the analog-to-digital converter and the tested power supply and is used for converting the current of the tested alternating current power supply into secondary current with smaller current value and outputting the secondary current to the analog-to-digital converter for sampling;
the analog-to-digital converter is connected with the controller and is used for sampling the secondary current output by the current sensor to obtain a first current value and outputting the first current value to the controller;
the injection current generator is respectively connected with the controller and the current sensor, and the controller controls the injection current generator to inject current into the current sensor when the obtained first current value is smaller than or equal to a preset threshold value, until the obtained first current value is larger than the preset threshold value, controls the injection current generator to stop injecting current, and the injection current generator injects current into the current sensor to be matched with the frequency and the phase of the secondary current;
the injection current sampler is connected with the analog-to-digital converter and is used for converting the injection current output by the injection current generator into a voltage signal and outputting the voltage signal to the analog-to-digital converter for sampling;
the analog-to-digital converter is further used for sampling the voltage signal output by the injection current sampler to obtain a second current value, and outputting the second current value to the controller, and the controller performs vector calculation on the first current value and the second current value under the condition that the first current value is smaller than or equal to a preset threshold value, so that the injection current value is eliminated from the real-time measurement current value of the measured power supply, and the measurement current value is obtained.
In one possible implementation manner, the controller determines a frequency difference value between the frequency of the secondary current and the preset frequency and determines whether the frequency difference value belongs to a set difference value range when the first current value is determined to be less than or equal to a preset threshold value;
the controller sets the injection current frequency of the injection current generator to be a preset frequency which is an integer multiple of the secondary current frequency under the condition that the frequency difference value is judged not to be in the set difference value range;
and the controller 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 under the condition that the frequency difference value is judged to be in the set difference value range.
In one possible implementation, the current sensor includes: the device comprises an iron core, an output current coil and an injection current coil, wherein a lead of a tested power supply passes through the iron core;
the output current coil is wound on the iron core and connected with 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 with the injection current generator, and is used for realizing the function of injecting current from the injection current generator to the current sensor.
In one possible implementation, the injection current generator is an analog-to-digital converter or a pulse width modulator.
According to another aspect of the embodiments of the present disclosure, there is provided a current sampling method for eliminating zero drift, where the method is applied to the apparatus described above, and the method includes:
step 10, the controller controls the injection current generator to inject current into the current sensor under the condition that the obtained first current value is less than or equal to a preset threshold value, until the controller controls the injection current generator to stop injecting current under the condition that the obtained first current value is greater than the preset threshold value, and the injection current generator injects current into the current sensor to be matched with the frequency and the phase of the secondary current;
and step 11, under the condition that the first current value is smaller than or equal to a preset threshold value, the controller carries out vector calculation on the obtained first current value and second current value so as to eliminate the injection current value from the real-time measurement current value of the measured power supply, and the measurement current value is obtained.
In one possible implementation, the method further includes:
step 12, the controller determines a frequency difference value between the frequency of the secondary current and a preset frequency under the condition that the first current value is smaller than or equal to a preset threshold value, and judges whether the frequency difference value belongs to a set difference value range;
step 13, setting the injection current frequency of the injection current generator as a preset frequency which is an integer multiple of the secondary current frequency under the condition that the frequency difference value is judged not to be in the set difference value range;
and 14, setting the injection current frequency and phase of the injection current generator to be the same as those of the secondary current when the controller judges that the frequency difference value is within the set difference value range.
According to another aspect of embodiments of the present disclosure, there is provided a zero-drift-removal current sampling apparatus, which is applied to the apparatus as set forth in any one of claims 1 to 4, the apparatus comprising:
the first control module is used for controlling the injection current generator to inject current into the current sensor under the condition that the acquired first current value is smaller than or equal to a preset threshold value, and controlling the injection current generator to stop injecting current under the condition that the acquired first current value is larger than the preset threshold value, wherein the injection current generator injects current into the current sensor and is matched with the frequency and the phase of the secondary current;
the first control module is used for carrying out vector calculation on the obtained first current value and the second current value under the condition that the first current value is smaller than or equal to a preset threshold value, so that the injection current value is eliminated from the real-time measurement current value of the measured power supply, and the measurement current value is obtained.
In one possible implementation, the apparatus further includes:
the third control module is used for determining a frequency difference value between the frequency of the secondary current and the preset frequency and judging whether the frequency difference value belongs to a set difference value range or not under the condition that the first current value is smaller than or equal to the preset threshold value;
the fourth control module is used for setting the injection current frequency of the injection current generator to be a preset frequency under the condition that the frequency difference value is judged to be in the set difference value range;
and the fifth control module is used for setting the injection current frequency of the injection current generator to be the frequency of the secondary current when the frequency difference value is judged not to be in the set difference value range.
According to another aspect of the disclosed embodiments, there is provided a non-transitory computer readable storage medium having stored thereon computer program instructions which, when executed by a processor, implement the above-described method.
The beneficial effects of the present disclosure are: according to the current sensor, the small current input loop is added, under the condition that the sampling current of the current sensor is small, the sampling voltage of the current sensor is ensured to be kept at a certain level in a current injection mode, so that the current sensor is prevented from being interfered by external signals, devices such as an operational amplifier of an analog-to-digital converter are ensured to not work in an offset area. Therefore, by adding the small current input loop, when the measured current is smaller than the set critical value, the small current with the same frequency (or integral multiple frequency) as the measured current is injected, and the measured current is kept not to be lower than the dead zone current.
Drawings
Fig. 1 is a block diagram illustrating a zero-drift canceling current sampling apparatus according to an exemplary embodiment.
Fig. 2 is a flow chart illustrating a method of current sampling to eliminate zero drift, according to an example embodiment.
Fig. 3 is a schematic diagram of a current sensor shown according to an exemplary embodiment.
Fig. 4 is a schematic diagram illustrating an injection current generator according to an exemplary embodiment.
Detailed Description
The invention will be described in further detail with reference to the accompanying drawings and specific examples.
Fig. 1 is a block diagram illustrating a zero-drift canceling current sampling apparatus according to an exemplary embodiment. As shown in fig. 1, the apparatus may include: the system comprises a current sensor, an analog-to-digital converter, an injection current sampler, an injection current generator and a controller.
In the present disclosure, the current sensor may include a current transformer, a hall current sensor, a shunt, or the like, and the present disclosure does not limit the type of the current sensor.
The current sensor is respectively connected with the analog-to-digital converter and the tested power supply and is used for converting the current of the tested alternating current power supply into secondary current with smaller current value and outputting the secondary current to the analog-to-digital converter for sampling;
the analog-to-digital converter is connected with the controller and is used for sampling the secondary current output by the current sensor to obtain a first current value and outputting the first current value to the controller; the injection current generator is connected to the controller and the current sensor, respectively, thereby forming a small current input loop.
Fig. 2 is a flow chart illustrating a method of current sampling to eliminate zero drift, according to an example embodiment. As shown in fig. 2, the controller monitors the magnitude of the measured current in real time, and when the controller determines that the obtained first current value is smaller than or equal to a preset threshold value, the controller controls the injection current generator to inject current into the current sensor until the controller determines that the obtained first current value is larger than the preset threshold value, the controller controls the injection current generator to stop injecting current.
The injection current generator injects current to the current sensor to match the frequency and phase of the secondary current (which may be expressed as the frequency of the injection current being the same as the secondary current or having little difference, or the frequency of the injection current being an integer multiple of the frequency of the secondary current, the magnitude of the multiple may be determined according to the actual measured need). As shown in fig. 2, the controller determines a frequency difference between the frequency of the secondary current and the preset frequency and determines whether the frequency difference belongs to a set difference range, if it is determined that the first current value is less than or equal to the preset threshold.
And under the condition that the frequency difference value is not in the set difference value range, the controller sets the injection current frequency of the injection current generator as a preset frequency, wherein the preset frequency is an integral multiple of the secondary current frequency, and the phase of the injection current can be random.
And the controller 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 under the condition that the frequency difference value is judged to be in the set difference value range.
The injection current sampler is connected with the analog-to-digital converter and is used for converting the injection current output by the injection current generator into a voltage signal and outputting the voltage signal to the analog-to-digital converter for sampling;
the analog-to-digital converter is further used for sampling the voltage signal output by the injection current sampler to obtain a second current value, and outputting the second current value to the controller, and the controller performs vector calculation on the first current value and the second current value under the condition that the first current value is smaller than or equal to a preset threshold value, so that the injection current value is eliminated from the real-time measurement current value of the measured power supply, and the measurement current value is obtained.
In the related art, whether direct current or alternating current is measured, the low current signal is obtained through circuit conversion isolation finally, and the low current signal is realized through a sampling resistor. For example, the current transformer converts the measured current into a small current signal according to the CT transformation ratio, forms a voltage signal through a sampling resistor, finally obtains a digital signal through an ADC, and calculates to obtain a current value. Compared with the current signal, the voltage signal is easier to be interfered by the outside, and errors are generated; particularly, a tiny voltage signal is extremely easy to generate errors; in addition, the ADC is prone to large errors due to the influence of the precision of the operational amplifier and the AD device for small signal sampling. In view of this, the present invention adds an isolated small current input loop to the current sensor. In the process of measuring the current, the measured current is monitored in real time, and when the measured current is smaller than the set lower limit value, the small current is injected into the small current input loop, so that the sensor is maintained to detect the loop current. After the sampling resistor converts the current into the voltage, the sampling voltage is ensured to be kept at a certain level, the interference of external signals is prevented, and devices such as AD, operational amplifier and the like are ensured not to work in an offset area.
FIG. 3 is a schematic diagram of a current sensor, as shown in FIG. 3, according to an exemplary embodiment, including: the device comprises an iron core 9, an output current coil 11 and an injection current coil 12, wherein a lead 10 of the tested power supply passes through the iron core 9. The output current coil 11 is wound on the iron core 9 and connected with the analog-to-digital converter (not shown in fig. 3) for outputting a secondary current;
the injection current coil 12 is wound on the iron core 9, separated from the output current coil 11, and connected with the injection current generator, so as to realize the function of injecting current from the injection current generator to the current sensor. Therefore, the auxiliary coil can be added in the traditional Hall current sensor or the current transformer coil, and the auxiliary coil is connected with the injection current generator to realize the current injection function.
In one possible implementation, the injection current generator is an analog-to-digital converter or a pulse width modulator. Fig. 4 is a schematic diagram of an injection current generator according to an exemplary embodiment, as shown in fig. 4, a DAC function inside the single-chip microcomputer 13 may be used to output current with rated frequency, phase and amplitude, and after the operational amplifier 14 is matched with the amplifying resistor 15 to perform amplification isolation, the current sensor is injected through the output resistor 16. Can be directly used for sampling injection current.
In an application example, even if the sampling circuit is realized by adopting the MCU internal ADC, the current sampling device realized by the method can easily reach the reference precision of 0.1% or the measurement precision of 0.2S, thereby overcoming the influence of zero drift of current sampling on the precision of the metering device.
In one possible implementation manner, a current sampling method for eliminating zero drift is provided, and the method is applied to the device, and includes:
step 10, the controller controls the injection current generator to inject current into the current sensor under the condition that the obtained first current value is less than or equal to a preset threshold value, until the controller controls the injection current generator to stop injecting current under the condition that the obtained first current value is greater than the preset threshold value, and the injection current generator injects current into the current sensor to be matched with the frequency and the phase of the secondary current;
and step 11, under the condition that the first current value is smaller than or equal to a preset threshold value, the controller carries out vector calculation on the obtained first current value and second current value so as to eliminate the injection current value from the real-time measurement current value of the measured power supply, and the measurement current value is obtained.
In one possible implementation, the method further includes:
step 12, the controller determines a frequency difference value between the frequency of the secondary current and a preset frequency under the condition that the first current value is smaller than or equal to a preset threshold value, and judges whether the frequency difference value belongs to a set difference value range;
step 13, setting the injection current frequency of the injection current generator as a preset frequency which is an integer multiple of the secondary current frequency under the condition that the frequency difference value is judged not to be in the set difference value range;
and 14, setting the injection current frequency and phase of the injection current generator to be the same as those of the secondary current when the controller judges that the frequency difference value is within the set difference value range.
In one possible implementation manner, a current sampling apparatus for eliminating zero drift is applied to the apparatus, and the apparatus includes:
the first control module is used for controlling the injection current generator to inject current into the current sensor under the condition that the acquired first current value is smaller than or equal to a preset threshold value, and controlling the injection current generator to stop injecting current under the condition that the acquired first current value is larger than the preset threshold value, wherein the injection current generator injects current into the current sensor and is matched with the frequency and the phase of the secondary current;
the first control module is used for carrying out vector calculation on the obtained first current value and the second current value under the condition that the first current value is smaller than or equal to a preset threshold value, so that the injection current value is eliminated from the real-time measurement current value of the measured power supply, and the measurement current value is obtained.
In one possible implementation, the apparatus further includes:
the third control module is used for determining a frequency difference value between the frequency of the secondary current and the preset frequency and judging whether the frequency difference value belongs to a set difference value range or not under the condition that the first current value is smaller than or equal to the preset threshold value;
the fourth control module is used for setting the injection current frequency of the injection current generator to be a preset frequency under the condition that the frequency difference value is judged to be in the set difference value range;
and the fifth control module is used for setting the injection current frequency of the injection current generator to be the frequency of the secondary current when the frequency difference value is judged not to be in the set difference value range.
The descriptions of the method and the virtual device are described in detail in the descriptions of the physical device, and are not repeated here.
The present disclosure may be a system, method, and/or computer program product. The computer program product may include a computer readable storage medium having computer readable program instructions embodied thereon for causing a processor to implement aspects of the present disclosure.
The computer readable storage medium may be a tangible device that can hold and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium would include the following: 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 disk read-only memory (CD-ROM), digital Versatile Disks (DVD), memory sticks, floppy disks, mechanical coding devices, punch cards or in-groove structures such as punch cards or grooves having instructions stored thereon, and any suitable combination of the foregoing. Computer-readable storage media, as used herein, are not to be construed as transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., optical pulses through fiber optic cables), or electrical signals transmitted through wires.
The computer readable program instructions described herein may be downloaded from a computer readable storage medium to a respective computing/processing device or to an external computer or external storage device over a network, such as the internet, a local area network, a wide area network, and/or a wireless network. The network may include copper transmission cables, fiber optic transmissions, wireless transmissions, routers, firewalls, switches, gateway computers and/or edge servers. The network interface card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium in the respective computing/processing device.
Computer program instructions for performing the operations of the present disclosure can be assembly instructions, instruction Set Architecture (ISA) instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, c++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer readable program instructions may be executed entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any kind of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or may be connected to an external computer (for example, through the Internet using an Internet service provider). In some embodiments, aspects of the present disclosure are implemented by personalizing electronic circuitry, such as programmable logic circuitry, field Programmable Gate Arrays (FPGAs), or Programmable Logic Arrays (PLAs), with state information of computer readable program instructions, which can execute the computer readable program instructions.
Various aspects of the present 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 the disclosure. It will 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.
These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable medium having the instructions stored therein includes an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.
The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer, other programmable apparatus or other devices implement the functions/acts specified in the flowchart and/or block diagram block or blocks.
The flowcharts and block diagrams in the figures 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 the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
The foregoing description of the embodiments of the present disclosure has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described. The terminology used herein was chosen in order to best explain the principles of the embodiments, the practical application, or the improvement of technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
Claims (9)
1. A zero-drift-removal current sampling apparatus, the apparatus comprising: the system comprises a current sensor, an analog-to-digital converter, an injection current sampler, an injection current generator and a controller;
the current sensor is respectively connected with the analog-to-digital converter and the tested power supply and is used for converting the current of the tested alternating current power supply into secondary current with smaller current value and outputting the secondary current to the analog-to-digital converter for sampling;
the analog-to-digital converter is connected with the controller and is used for sampling the secondary current output by the current sensor to obtain a first current value and outputting the first current value to the controller;
the injection current generator is respectively connected with the controller and the current sensor, and the controller controls the injection current generator to inject current into the current sensor when the obtained first current value is smaller than or equal to a preset threshold value, until the obtained first current value is larger than the preset threshold value, controls the injection current generator to stop injecting current, and the injection current generator injects current into the current sensor to be matched with the frequency and the phase of the secondary current;
the injection current sampler is connected with the analog-to-digital converter and is used for converting the injection current output by the injection current generator into a voltage signal and outputting the voltage signal to the analog-to-digital converter for sampling;
the analog-to-digital converter is further used for sampling the voltage signal output by the injection current sampler to obtain a second current value, and outputting the second current value to the controller, and the controller performs vector calculation on the first current value and the second current value under the condition that the first current value is smaller than or equal to a preset threshold value, so that the injection current value is eliminated from the real-time measurement current value of the measured power supply, and the measurement current value is obtained.
2. The apparatus according to claim 1, wherein the controller determines a frequency difference between the frequency of the secondary current and a preset frequency and judges whether the frequency difference belongs to a set difference range, in a case where it is judged that the first current value is less than or equal to a preset threshold;
the controller sets the injection current frequency of the injection current generator to be a preset frequency which is an integer multiple of the secondary current frequency under the condition that the frequency difference value is judged not to be in the set difference value range;
and the controller 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 under the condition that the frequency difference value is judged to be in the set difference value range.
3. The apparatus of claim 1, wherein the current sensor comprises: the device comprises an iron core, an output current coil and an injection current coil, wherein a lead of a tested power supply passes through the iron core;
the output current coil is wound on the iron core and connected with 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 with the injection current generator, and is used for realizing the function of injecting current from the injection current generator to the current sensor.
4. The apparatus of claim 1, wherein the injection current generator is an analog-to-digital converter or a pulse width modulator.
5. A method of current sampling to eliminate zero drift, the method being applied to the apparatus of any one of claims 1 to 4, the method comprising:
step 10, the controller controls the injection current generator to inject current into the current sensor under the condition that the obtained first current value is less than or equal to a preset threshold value, until the controller controls the injection current generator to stop injecting current under the condition that the obtained first current value is greater than the preset threshold value, and the injection current generator injects current into the current sensor to be matched with the frequency and the phase of the secondary current;
and step 11, under the condition that the first current value is smaller than or equal to a preset threshold value, the controller carries out vector calculation on the obtained first current value and second current value so as to eliminate the injection current value from the real-time measurement current value of the measured power supply, and the measurement current value is obtained.
6. The method of claim 5, wherein the method further comprises:
step 12, the controller determines a frequency difference value between the frequency of the secondary current and a preset frequency under the condition that the first current value is smaller than or equal to a preset threshold value, and judges whether the frequency difference value belongs to a set difference value range;
step 13, setting the injection current frequency of the injection current generator as a preset frequency which is an integer multiple of the secondary current frequency under the condition that the frequency difference value is judged not to be in the set difference value range;
and 14, setting the injection current frequency and phase of the injection current generator to be the same as those of the secondary current when the controller judges that the frequency difference value is within the set difference value range.
7. A zero drift cancellation current sampling apparatus, wherein the apparatus is applied to an apparatus as claimed in any one of claims 1 to 4, the apparatus comprising:
the first control module is used for controlling the injection current generator to inject current into the current sensor under the condition that the acquired first current value is smaller than or equal to a preset threshold value, and controlling the injection current generator to stop injecting current under the condition that the acquired first current value is larger than the preset threshold value, wherein the injection current generator injects current into the current sensor and is matched with the frequency and the phase of the secondary current;
the first control module is used for carrying out vector calculation on the obtained first current value and the second current value under the condition that the first current value is smaller than or equal to a preset threshold value, so that the injection current value is eliminated from the real-time measurement current value of the measured power supply, and the measurement current value is obtained.
8. The apparatus of claim 5, wherein the apparatus further comprises:
the third control module is used for determining a frequency difference value between the frequency of the secondary current and the preset frequency and judging whether the frequency difference value belongs to a set difference value range or not under the condition that the first current value is smaller than or equal to the preset threshold value;
the fourth control module is used for setting the injection current frequency of the injection current generator to be a preset frequency under the condition that the frequency difference value is judged to be in the set difference value range;
and the fifth control module is used for setting the injection current frequency of the injection current generator to be the frequency of the secondary current when the frequency difference value is judged not to be in the set difference value range.
9. A non-transitory computer readable storage medium having stored thereon computer program instructions, which when executed by a processor, implement the method of claim 5 or 6.
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