Current measurement system and current measurement method
The current measurement system, composed of current-voltage conversion, signal conditioning, digitization, and isolation devices, reduces the distributed capacitance value, solves the impact of high common-mode voltage on small current measurement, and achieves higher measurement accuracy.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SHENZHEN CLOU ELECTRONICS
- Filing Date
- 2025-12-30
- Publication Date
- 2026-07-30
AI Technical Summary
In the existing technology, the influence of high common-mode voltage on current measurement leads to insufficient accuracy of small current measurement and a large error, especially at a current of 10mA, the error can reach 0.069% to 0.692%.
The current measurement system, which consists of a current-to-voltage conversion device, a voltage signal conditioning device, a signal digitization device, a digital signal isolation device, and an isolation power supply device, reduces the influence of common-mode voltage by lowering the distributed capacitance value, thereby improving measurement accuracy.
It effectively reduces the impact of common-mode voltage on small current measurements, improves the accuracy of current measurements, reduces leakage current to 0.00692%, and significantly improves measurement precision.
Smart Images
Figure CN2025147271_30072026_PF_FP_ABST
Abstract
Description
Current measurement system and current measurement method
[0001] This application claims priority to Chinese Patent Application No. 202510099739.0, filed on January 21, 2025, entitled "Current Measurement System and Current Measurement Method", the entire contents of which are incorporated herein by reference. Technical Field
[0002] This application relates to the field of electrical measuring instrument technology, and more specifically, to a current measuring system and a current measuring method. Background Technology
[0003] As shown in Figures 1 and 2, Figure 1 is a simplified diagram of the current sampling circuit of a 0.02-class three-phase multi-function standard meter in related technologies, and Figure 2 is a simplified diagram of the current sampling circuit of a 0.01-class three-phase AC energy comparator in related technologies. In related technologies, high-class AC standard energy meters, such as standard energy meters with an error class of 0.05 or higher (including 0.02, 0.01, and 0.005 classes), often divide the wide dynamic range of current, such as from 1mA to 100A, into several intervals, using multiple ranges such as 0.1A, 1A, 10A, and 100A to achieve accurate measurement. For example, the CL3112, a 0.02-class three-phase multi-function standard meter, has a current transformer with multiple primary windings at its current input port (each primary winding corresponds to one range, and the ampere-turns product is consistent for each range at full-scale input), as shown in Figure 1. The primary winding has windings of 1T, 10T, 100T, and 1000T, while the secondary winding of 2000T is connected to a high-precision sampling resistor to achieve current-to-voltage conversion. Because the primary and secondary windings have a large number of turns and are wound on the same magnetic core, the distributed capacitance Cps between them is generally large, ranging from approximately 100pF to 300pF. The capacitive reactance Xc of this distributed capacitance at a frequency of 50Hz is calculated using the formula Xc = 1 ÷ (2 × π × f × Cps). The capacitive reactance of 100pF is 31.8MΩ, and that of 300pF is 10.6MΩ.
[0004] It should be noted that three-phase multi-function standard meters often need to measure the phase current in the power grid. Therefore, the primary of each phase current transformer will carry a common-mode voltage as high as the phase voltage. The phase voltage of the power grid is AC220V. In addition, the secondary of all phase current transformers has a common reference point, which is 0V by default, as shown in Figure 1. Therefore, the voltage between the primary and secondary of the current transformer is AC220V.
[0005] Under the aforementioned operating conditions, in addition to the actual phase current, the current flowing through the primary winding of the phase current transformer will be superimposed with a common-mode current formed by the distributed capacitance Cps between the primary and secondary windings of the current transformer. This common-mode current Ips = 220V / Xc, approximately 6.92μA to 20.8μA, which will severely affect the measurement of phase currents of 10mA and below. Given the significant impact of common-mode voltage in designs similar to the aforementioned standard meters, some industry professionals have adopted a solution where the secondary winding of each phase current transformer is independent, such as the approach used in 0.01-class three-phase AC energy comparators. This solution also provides a short-circuit option, allowing a single-point short circuit between the secondary and primary windings of the current transformer, completely eliminating the voltage difference between them, as shown in Figure 2.
[0006] This seemingly perfect solution to the common-mode voltage effect also has problems, for the following reasons: The secondary winding of the current transformer contains many processing circuits, all requiring a power supply. The aforementioned comparator uses a low-voltage winding of a power frequency transformer for power. The distributed capacitance Cps between this low-voltage winding and the shielding layer (generally connected to protective ground PE, defaulting to 0V) of the primary and secondary windings of the power frequency transformer is between 100pF and 1000pF. The common-mode voltage also creates a leakage current Ips within this distributed capacitance Cps, with an amplitude between 6.92μA and 69.2μA. No wonder the instruction manual for this model of comparator emphasizes that, to ensure the measurement accuracy of small currents, the voltage difference between the primary winding of the current transformer and protective ground cannot exceed AC2V.
[0007] It is evident that neither of the two commonly used technical solutions mentioned above can resolve the impact of high common-mode voltage. They exhibit significant errors in low-current measurements, ranging from 0.069% to 0.692% at 10mA, far below the required accuracy. Therefore, a technical solution is needed that can substantially reduce the impact of high common-mode voltage on current measurement and improve the accuracy of low-current measurements. Technical solutions
[0008] This application aims to address at least one of the technical problems existing in the prior art or related technologies.
[0009] Therefore, the first aspect of this application proposes a current measurement system.
[0010] The second aspect of this application proposes a current measurement method.
[0011] In view of the above, according to the first aspect of this application, a current measurement system is proposed, comprising: a current-to-voltage conversion device, one end of which is connected to the circuit under test for acquiring a current signal of the circuit under test and converting the current signal into a first voltage signal; a voltage signal conditioning device, one end of which is connected to the other end of the current-to-voltage conversion device for converting the first voltage signal into a second voltage signal; a signal digitization device, one end of which is connected to the other end of the voltage signal conditioning device for converting the second voltage signal into a digital signal; a digital signal isolation device, a first side of which is connected to the signal digitization device for isolating digital signals between different electrical systems; and a control device, wherein the control device is connected to... The second side of the digital signal isolation device is connected to determine the current value corresponding to the current signal based on the digital signal; it also includes: an isolation power supply device, the load side of which is connected to the current-to-voltage conversion device, the voltage signal conditioning device, the signal digitization device, and the digital signal isolation device respectively, and the power supply side of which is connected to the control device to obtain power from the control device and provide power to the current-to-voltage conversion device, the voltage signal conditioning device, the signal digitization device, and the digital signal isolation device; the capacitance value of the distributed capacitance between the first side and the second side of the digital signal isolation device is less than or equal to the capacitance threshold; the capacitance value of the distributed capacitance between the load side and the power supply side of the isolation power supply device is less than or equal to the capacitance threshold.
[0012] The current measurement system provided in this application mainly includes a current-to-voltage conversion device, a voltage signal conditioning device, a signal digitization device, a digital signal isolation device, and a control device connected in sequence.
[0013] In this technical solution, the current input terminal of the current-to-voltage converter is connected to the circuit under test, and the current input terminal can acquire the current signal of the circuit under test. The voltage output terminal of the current-to-voltage converter is connected to the voltage signal conditioning device. The current signal of the circuit under test can be converted into a first voltage signal in the current-to-voltage converter, and the first voltage signal is input to the voltage signal conditioning device.
[0014] It is understandable that the circuit under test can be a three-phase circuit. By setting up a digital signal isolation device, the currents of the three different phases can be prevented from interfering with each other, thereby ensuring the accuracy of the measurement.
[0015] In this technical solution, one end of the voltage signal conditioning device is connected to the voltage output terminal of the current-to-voltage conversion device, and the other end is connected to the signal digitization device. The other end of the signal digitization device is connected to the digital signal isolation device. When the signal digitization device receives the second voltage signal, it processes the signal, converts it into a digital signal, and transmits it to the digital signal isolation device. Upon receiving the digital signal, the digital signal isolation device isolates the potential and noise between different electrical systems. The control device is connected to the digital signal isolation device and can determine the current value of the current signal of the circuit under test based on the digital signal, thus completing the current measurement of the circuit under test.
[0016] In this technical solution, the current measurement system also includes an isolated power supply device. The power supply side of the isolated power supply device is connected to the control device, and the isolated power supply device can obtain electrical energy from the control device. That is, in the current measurement system provided in this application, in addition to determining the current value corresponding to the current signal based on the digital signal, the control device can also supply power to the entire machine, i.e., supply power to the isolated power supply device. The load side of the isolated power supply device is connected to the current-to-voltage conversion device, the voltage signal conditioning device, the signal digitization device, and the digital signal isolation device, respectively. When the isolated power supply device obtains electrical energy from the control module, it supplies electrical energy to the current-to-voltage conversion device, the voltage signal conditioning device, the signal digitization device, and the digital signal isolation device through the load side, thereby enabling the current-to-voltage conversion device, the voltage signal conditioning device, the signal digitization device, and the digital signal isolation device to operate normally.
[0017] It should be noted that the isolated power supply device can adopt the electrical energy-non-electromagnetic energy-electrical energy conversion mode. Non-electromagnetic energy can be ultrasonic energy, mechanical energy, light energy, wind energy, etc.
[0018] In the current measurement system provided in this application, the distributed capacitance between the two sides of the digital signal isolation device and the two sides of the isolated power supply device is relatively small. It is understood that distributed capacitance refers to a distributed parameter formed in a non-capacitive form. Distributed capacitance exists between any two conductors with a voltage difference and which are mutually insulated. Therefore, distributed capacitance exists on both sides of the digital signal isolation device and the isolated power supply device. However, when the distributed capacitance is too large, the amplitude of the leakage current generated by the common-mode voltage through the distributed capacitance will be too large during current measurement, thus affecting the accuracy of the current measurement. Therefore, to improve the accuracy of current measurement, the distributed capacitance between the two sides of the digital signal isolation device and the two sides of the isolated power supply device needs to be set as small as possible to ensure the accuracy of current measurement.
[0019] In this embodiment, the capacitance threshold ranges from greater than 5 pF to less than or equal to 15 pF. For example, the capacitance threshold can be 10 pF. When the distributed capacitance is 10 pF, the leakage current is 0.0692 μA when the common-mode voltage AC is 220 V. This is 0.00692% of 10 mA, which is much smaller than the 0.0692% to 0.692% of the related technologies. It can be seen that when the distributed capacitance is 10 pF, the influence of the common-mode voltage on the accurate measurement of small currents is greatly reduced.
[0020] The current measurement system according to the present application may also have the following technical features:
[0021] In some technical solutions, the isolated power supply device optionally includes: a high-frequency switching power supply.
[0022] In this technical solution, the isolation power supply device can be a high-frequency switching power supply. Because the primary and secondary windings of the isolation transformer in a high-frequency switching power supply have fewer turns, their distributed capacitance is relatively small.
[0023] In some technical solutions, the high-frequency switching power supply may optionally include: a square wave generator, one end of which is connected to a control device; an LC (inductor, capacitor) filter, one end of which is connected to the other end of the square wave generator; a high-frequency transformer, one end of which is connected to the other end of the LC filter; and a rectifier filter circuit, one end of which is connected to the other end of the high-frequency transformer, the other end of which is the load side of the isolated power supply device.
[0024] In this technical solution, a square wave generator, an LC filter, a high-frequency transformer, and a rectifier and filter circuit are installed in the high-frequency switching power supply, so that the high-frequency switching power supply can stably supply power to the current-to-voltage conversion device, the voltage signal conditioning device, the signal digitization device, and the digital signal isolation device.
[0025] In some technical solutions, the high-frequency transformer can optionally be an air-core transformer without a ferromagnetic core. Since there is no core as an intermediate medium, the distributed capacitance between the primary and secondary windings of the air-core transformer can be made smaller.
[0026] In this technical solution, the high-frequency transformer can also be a ceramic electronic transformer. A ceramic electronic transformer, also known as a ceramic piezoelectric transformer, is a special type of electronic transformer that converts electrical energy using the piezoelectric and inverse piezoelectric effects of piezoelectric ceramic materials. When an AC voltage is applied to the piezoelectric ceramic, mechanical vibration is generated, inducing a voltage in the secondary coil through this mechanical vibration, thus realizing the transmission and conversion of electrical energy. By using a ceramic electronic transformer in the high-frequency transformer, the distributed capacitance between the primary and secondary coils can be reduced.
[0027] In some technical solutions, the circuit structure of the isolated power supply device can optionally be a resonant soft-switching DC-DC converter topology.
[0028] In this technical solution, the circuit structure in the isolated power supply device can be a resonant soft-switching DC-DC converter topology. Specifically, the resonant soft-switching DC-DC converter topology can be an LLC (inductor-inductor-capacitor) topology or an LCC (inductor-capacitor-capacitor) topology.
[0029] In some technical solutions, the current measurement system may optionally include: an equipotential connection line, one end of which is connected to one end of the current-to-voltage conversion device, and the other end of which is connected to the other end of the current-to-voltage conversion device.
[0030] In this technical solution, the current measurement system also includes an equipotential bonding line. One end of the equipotential bonding line is connected to the current input side of the current-to-voltage converter, and the other end is connected to the voltage output side of the current-to-voltage converter. That is, there is an equipotential, low-impedance connection between the current input and voltage output sides of the current-to-voltage converter. Electrically, the current input and voltage output sides of the current-to-voltage converter can be considered to be at the same potential, with a voltage difference of 0 between them.
[0031] In some technical solutions, the isolated power supply device may optionally adopt a two-stage conversion architecture of electrical energy to non-electromagnetic energy conversion and non-electromagnetic energy to electrical energy conversion. The non-electromagnetic energy may include one or a combination of mechanical energy, wind energy, acoustic energy and light energy.
[0032] In this technical solution, the isolated power supply device can also adopt a two-stage conversion architecture of electrical energy to non-electromagnetic energy conversion and non-electromagnetic energy to electrical energy conversion. The non-electromagnetic energy can include one or a combination of mechanical energy, wind energy, infrasound energy, ultrasonic energy, and light energy. That is, in the isolated power supply device, the input electrical energy can first be converted into non-electromagnetic energy, namely one or a combination of mechanical energy, wind energy, infrasound energy, ultrasonic energy, and light energy, and then the non-electromagnetic energy, namely one or a combination of mechanical energy, wind energy, infrasound energy, ultrasonic energy, and light energy, can be converted back into electrical energy for output.
[0033] For example, when the isolated power supply device adopts a two-stage conversion architecture of electrical energy to mechanical energy conversion and mechanical energy to electrical energy conversion, the isolated power supply device may include: a motor, a transmission mechanism, and a generator. The working process is that the motor rotates after receiving electrical energy, thereby converting the electrical energy into rotational mechanical energy. The transmission mechanism drives the generator to generate electricity, thereby converting the rotational mechanical energy into electrical energy to obtain isolated electrical energy. This realizes the two-stage conversion of electrical energy to mechanical energy conversion and mechanical energy to electrical energy conversion. The transmission mechanism is made of a material with low distributed capacitance, such as nylon gears.
[0034] For example, when the isolated power supply device adopts a two-stage conversion architecture of power-to-wind power conversion and wind power-to-power conversion, the isolated power supply device may include an electric blower and a wind turbine. The working process is that the electric blower generates wind energy after obtaining electrical energy, which enables the wind turbine to generate electricity. This isolated power supply method uses air as a medium, and the distance can achieve low distributed capacitance.
[0035] For example, when the isolated power supply device adopts a two-stage conversion architecture of electrical energy to acoustic energy conversion and acoustic energy to electrical energy conversion, the isolated power supply device may include: a moving-coil loudspeaker at the excitation end, a sealed sound transmission duct, and a moving-coil loudspeaker at the generation end. The moving-coil loudspeaker at the excitation end is driven by an audio or ultrasonic signal to emit sound waves, thereby realizing the conversion of electrical energy to acoustic energy. These sound waves then act on the moving-coil loudspeaker at the generation end through the sealed sound transmission duct, causing the moving-coil loudspeaker at the generation end to work in reverse, generating electrical energy, thus realizing the conversion of acoustic energy to electrical energy. This isolated power supply method uses air as a medium, and the distance can achieve low distributed capacitance.
[0036] For example, when the isolated power supply device adopts a two-stage conversion architecture of electrical energy to light energy conversion and light energy to electrical energy conversion, the isolated power supply device may include: a light-emitting diode (LED) and a photovoltaic cell. The LED emits light when energized, thereby generating light energy. When the light emitted by the LED shines on the photovoltaic cell, it causes the photovoltaic cell to generate electrical energy, thus realizing the two-stage conversion of electrical energy to light energy conversion and light energy to electrical energy conversion. This isolated power supply method uses air as a medium, and the distance can achieve low distributed capacitance.
[0037] In some technical solutions, the digital signal isolation device may optionally be one or a combination of an optocoupler, a fiber optic transceiver, a magnetic digital isolator, and a capacitive digital isolator.
[0038] In this technical solution, since the digital signal isolation device can isolate high-voltage and low-voltage digital signals and prevent mutual interference between circuits, the digital signal isolation device can be an optocoupler, fiber optic transceiver, magnetic digital isolator, or capacitive digital isolator, etc. By using optocouplers, fiber optic transceivers, magnetic digital isolators, and capacitive digital isolators as digital signal isolators, high-resistance isolation characteristics are achieved during digital signal transmission, isolating the electronic system from the user, reducing grounding loop noise, and avoiding safety risks.
[0039] In some technical solutions, the current-to-voltage conversion device may optionally include one or a combination of multiple shunts or current transformers with multiple primary windings.
[0040] In this technical solution, the current-to-voltage conversion device can be constructed using multiple shunts, multiple current transformers with primary windings, or a combination of multiple shunts and multiple current transformers with primary windings. By utilizing multiple shunts or multiple current transformers with primary windings to construct the current-to-voltage conversion device, the received current signal is cleverly converted into a voltage signal.
[0041] According to a second aspect of this application, a current measurement method is proposed, comprising: acquiring a current signal of a circuit under test; converting the current signal into a corresponding first voltage signal; conditioning the first voltage signal to obtain a second voltage signal; converting the second voltage signal into a digital signal; and determining a current value corresponding to the current signal based on the digital signal.
[0042] The current measurement method provided in this application mainly includes: first, connecting a current measurement system to the circuit under test, enabling the current measurement system to acquire the current signal flowing in the circuit under test; then, using a current-to-voltage conversion device to convert the current signal into a corresponding first voltage signal. It is understood that the acquired current signal is obtained through devices such as sensors, therefore the obtained current signal is weak, and the first voltage signal is also weak. Therefore, a voltage signal conditioning device can process the first voltage signal to convert it into a more stable, reliable, and accurate second voltage signal. Subsequently, a signal digitization device converts the second voltage signal into a digital signal, then separates the digital signals to separate digital signals of different voltages. Finally, the current value corresponding to the current signal is determined based on the digital signal, thus completing the current measurement of the circuit under test. This application reduces the capacitance of the distributed capacitance of the signal processing section in the current measurement system, thereby reducing the amplitude of the leakage current generated by the common-mode voltage through the distributed capacitance. This significantly reduces the impact of the common-mode voltage on the accurate measurement of small currents, thus achieving the technical effect of reducing the impact of high common-mode voltage on current measurement and improving the accuracy of current measurement.
[0043] Additional aspects and advantages of this application will become apparent in the following description or may be learned by practice of this application. Attached Figure Description
[0044] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:
[0045] Figure 1 shows one of the structural schematic diagrams of a current measurement system in the related art;
[0046] Figure 2 shows a second schematic diagram of the structure of a current measurement system in the related technology;
[0047] Figure 3 shows a schematic diagram of the structure of a current measurement system according to an embodiment of this application;
[0048] Figure 4 shows a schematic diagram of the structure of a high-frequency switching power supply in a current measurement system according to an embodiment of this application;
[0049] Figure 5 shows a schematic flowchart of a current measurement method according to an embodiment of this application.
[0050] The correspondence between the reference numerals and component names in Figures 3 and 4 is as follows:
[0051] 100 Current measurement system, 102 Current-to-voltage conversion device, 104 Voltage signal conditioning device, 106 Signal digitization device, 108 Digital signal isolation device, 110 Control device, 112 Isolated power supply device, 114 Load side, 116 Power supply side, 118 High-frequency switching power supply, 1182 Square wave generator, 1184 LC filter, 1186 High-frequency transformer, 1188 Rectifier and filter circuit, 120 Equipotential connection line. Embodiments of the present invention
[0052] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.
[0053] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.
[0054] As shown in Figure 3, this application proposes a current measurement system 100, including: a current-to-voltage conversion device 102, one end of which is connected to the circuit under test for acquiring the current signal of the circuit under test and converting the current signal into a first voltage signal; a voltage signal conditioning device 104, one end of which is connected to the other end of the current-to-voltage conversion device 102 for converting the first voltage signal into a second voltage signal; a signal digitization device 106, one end of which is connected to the other end of the voltage signal conditioning device 104 for converting the second voltage signal into a digital signal; a digital signal isolation device 108, one side of which is connected to the signal digitization device 106 for isolating digital signals between different electrical systems; and a control device 110, the control device 110 being connected to the second side of the digital signal isolation device 108. The system includes a connection for determining the current value corresponding to the current signal based on the digital signal; it also includes an isolated power supply device 112, the load side 114 of which is connected to the current-to-voltage conversion device 102, the voltage signal conditioning device 104, the signal digitization device 106, and the digital signal isolation device 108, respectively; and the power supply side 116 of the isolated power supply device 112 is connected to the control device 110, for obtaining power from the control device 110 and providing power to the current-to-voltage conversion device 102, the voltage signal conditioning device 104, the signal digitization device 106, and the digital signal isolation device 108; the capacitance value of the distributed capacitance between the first side and the second side of the digital signal isolation device 108 is less than or equal to a capacitance threshold; and the capacitance value of the distributed capacitance between the load side 114 and the power supply side 116 of the isolated power supply device 112 is less than or equal to a capacitance threshold.
[0055] The current measurement system 100 provided in this application mainly includes a current-to-voltage conversion device 102, a voltage signal conditioning device 104, a signal digitization device 106, a digital signal isolation device 108, and a control device 110 connected in sequence.
[0056] In Figure 3, Iin represents the current input, and I+ and I- represent the positive and negative terminals, respectively.
[0057] In this embodiment, the current input terminal of one end of the current-to-voltage conversion device 102 is connected to the circuit under test, and the current input terminal can acquire the current signal of the circuit under test. The voltage output terminal of the current-to-voltage conversion device 102 is connected to the voltage signal conditioning device 104. The current signal of the circuit under test can be converted into a first voltage signal in the current-to-voltage conversion device 102, and the first voltage signal is input to the voltage signal conditioning device 104.
[0058] It is understandable that the circuit under test can be a three-phase circuit. By setting up a digital signal isolation device, the currents of the three different phases can be prevented from interfering with each other, thereby ensuring the accuracy of the measurement.
[0059] In this embodiment, one end of the voltage signal conditioning device 104 is connected to the voltage output terminal of the current-to-voltage conversion device 102, and the other end of the voltage signal conditioning device 104 is connected to the signal digitization device 106. One end of the signal digitization device 106 is connected to the voltage signal conditioning device 104, and the other end of the signal digitization device 106 is connected to the digital signal isolation device 108. When the signal digitization device 106 receives the second voltage signal, it processes the second voltage signal, converts it into a digital signal, and transmits it to the digital signal isolation device 108. When the digital signal isolation device 108 receives the digital signal, it isolates the potential and noise between different electrical systems. The control device 110 is connected to the digital signal isolation device 108. The control device 110 can determine the current value of the current signal of the circuit under test based on the digital signal, thereby completing the current measurement of the circuit under test.
[0060] In this embodiment, the current measurement system 100 further includes an isolated power supply device 112. The power supply side 116 of the isolated power supply device 112 is connected to the control device 110, and the isolated power supply device 112 can obtain electrical energy from the control device 110. That is, in the current measurement system 100 provided in this application, in addition to determining the current value corresponding to the current signal based on the digital signal, the control device 110 can also supply power to the entire device, i.e., supply power to the isolated power supply device 112. The load side 114 of the isolated power supply device 112 is connected to the current-to-voltage conversion device 102, the voltage signal conditioning device 104, the signal digitization device 106, and the digital signal isolation device 108, respectively. When the isolated power supply device 112 obtains power from the control module, it will supply power to the current-to-voltage conversion device 102, the voltage signal conditioning device 104, the signal digitization device 106, and the digital signal isolation device 108 through the load side 114, thereby enabling the current-to-voltage conversion device 102, the voltage signal conditioning device 104, the signal digitization device 106, and the digital signal isolation device 108 to work normally.
[0061] It should be noted that the isolated power supply device 112 can adopt an electrical energy-non-electromagnetic energy-electrical energy conversion mode. The non-electromagnetic energy can be ultrasonic energy, mechanical energy, light energy, wind energy, etc.
[0062] In the current measurement system 100 provided in this application, the distributed capacitance between the two sides of the digital signal isolation device 108 and the two sides of the isolation power supply device 112 is relatively small. It is understood that distributed capacitance refers to a distributed parameter formed in a non-capacitive form. Distributed capacitance exists between any two conductors with a voltage difference and which are mutually insulated. Therefore, distributed capacitance exists on both sides of the digital signal isolation device 108 and the isolation power supply device 112. However, when the distributed capacitance is too large, the amplitude of the leakage current generated by the common-mode voltage through the distributed capacitance will be too large during current measurement, thus affecting the accuracy of the current measurement. Therefore, in order to improve the accuracy of current measurement, the distributed capacitance between the two sides of the digital signal isolation device 108 and the two sides of the isolation power supply device 112 needs to be set as small as possible to ensure the accuracy of current measurement.
[0063] In this embodiment, the capacitance threshold ranges from greater than 5 pF to less than or equal to 15 pF. For example, the capacitance threshold can be 10 pF. When the distributed capacitance is 10 pF, the leakage current is 0.0692 μA when the common-mode voltage AC is 220 V. This is 0.00692% of 10 mA, which is much smaller than the 0.0692% to 0.692% of related technologies. It can be seen that when the distributed capacitance is 10 pF, the influence of the common-mode voltage on the accurate measurement of small currents is greatly reduced.
[0064] In some embodiments, the isolated power supply device 112 may optionally include a high-frequency switching power supply 118.
[0065] In this embodiment, the isolation power supply device 112 can be a high-frequency switching power supply 118. The primary and secondary windings of the isolation transformer in the high-frequency switching power supply 118 have relatively small distributed capacitance due to the small number of turns.
[0066] In some embodiments, optionally as shown in FIG4, the high-frequency switching power supply 118 includes: a square wave generator 1182, one end of which is connected to the control device 110; an LC (inductor, capacitor) filter 1184, one end of which is connected to the other end of the square wave generator 1182; a high-frequency transformer 1186, one end of which is connected to the other end of the LC filter 1184; and a rectifier filter circuit 1188, one end of which is connected to the other end of the high-frequency transformer 1186, the other end of which is the load side 114 of the isolated power supply device 112.
[0067] In this technical solution, a square wave generator 1182, an LC filter 1184, a high-frequency transformer 1186, and a rectifier and filter circuit 1188 are installed in the high-frequency switching power supply 118, so that the high-frequency switching power supply 118 can stably supply power to the current-to-voltage conversion device 102, the voltage signal conditioning device 104, the signal digitization device 106, and the digital signal isolation device 108.
[0068] In some embodiments, the high-frequency transformer 1186 is optionally an air-core transformer without a ferromagnetic core. Since there is no core as an intermediate medium, the distributed capacitance between the primary and secondary windings of the air-core transformer can be made smaller.
[0069] In this embodiment, the high-frequency transformer 1186 can also be a ceramic electronic transformer. A ceramic electronic transformer, also known as a ceramic piezoelectric transformer, is a special type of electronic transformer that converts electrical energy using the piezoelectric and inverse piezoelectric effects of piezoelectric ceramic materials. When an AC voltage is applied to the piezoelectric ceramic, mechanical vibration is generated, inducing a voltage in the secondary coil through this mechanical vibration, thus realizing the transmission and conversion of electrical energy. By using a ceramic electronic transformer in the high-frequency transformer 1186, the distributed capacitance between the primary and secondary windings of the transformer is reduced.
[0070] In some embodiments, the circuit structure of the isolated power supply device 112 is optionally a resonant soft-switching DC-DC converter topology.
[0071] In this embodiment, the circuit structure in the isolated power supply device 112 can be a resonant soft-switching DC-DC converter topology. The resonant soft-switching DC-DC converter topology can be an LLC (inductor-inductor-capacitor) topology or an LCC (inductor-capacitor-capacitor) topology.
[0072] In some embodiments, as shown in FIG3, the current measurement system 100 may optionally include: an equipotential connection line 120, one end of which is connected to one end of the current-to-voltage conversion device 102, and the other end of which is connected to the other end of the current-to-voltage conversion device 102.
[0073] In this embodiment, the current measurement system 100 further includes an equipotential connection line 120. One end of the equipotential connection line 120 is connected to the current input side of the current-to-voltage conversion device 102, and the other end of the equipotential connection line 120 is connected to the voltage output side of the current-to-voltage conversion device 102. That is, there is an equipotential, low-impedance connection between the current input side and the voltage output side of the current-to-voltage conversion device 102. Electrically, the current input side and the voltage output side of the current-to-voltage conversion device 102 can be considered to be at the same potential, and the voltage difference between the two sides is 0. In some embodiments, optionally, the isolated power supply device 112 adopts a two-stage conversion architecture of electrical energy to non-electromagnetic energy conversion and non-electromagnetic energy to electrical energy conversion, wherein the non-electromagnetic energy may include one or a combination of mechanical energy, wind energy, acoustic energy, and light energy.
[0074] In this embodiment, the isolated power supply device 112 may also employ a two-stage conversion architecture of electrical energy to non-electromagnetic energy conversion and non-electromagnetic energy to electrical energy conversion. The non-electromagnetic energy may include one or a combination of mechanical energy, wind energy, infrasound energy, ultrasonic energy, and light energy. That is, in the isolated power supply device 112, the input electrical energy can first be converted into non-electromagnetic energy, i.e., one or a combination of mechanical energy, wind energy, infrasound energy, ultrasonic energy, and light energy, and then converted back into electrical energy for output.
[0075] For example, when the isolated power supply device 112 adopts a two-stage conversion architecture of electrical energy to mechanical energy conversion and mechanical energy to electrical energy conversion, the isolated power supply device 112 may include: a motor, a transmission mechanism, and a generator. The working process is that the motor rotates after receiving electrical energy, thereby converting the electrical energy into rotational mechanical energy. The generator generates electricity through the transmission mechanism, thereby converting the rotational mechanical energy into electrical energy and obtaining isolated electrical energy. This realizes the two-stage conversion of electrical energy to mechanical energy conversion and mechanical energy to electrical energy conversion. The transmission mechanism is made of a material with low distributed capacitance, such as nylon gears.
[0076] For example, when the isolated power supply device 112 adopts a two-stage conversion architecture of power to wind power conversion and wind power to power conversion, the isolated power supply device 112 may include an electric blower and a wind turbine. The working process is that the electric blower generates wind power after obtaining power, so that the wind turbine generates electricity. This isolated power supply method uses air as a medium, and the distance can achieve low distributed capacitance.
[0077] For example, when the isolated power supply device 112 adopts a two-stage conversion architecture of electrical energy to sound energy conversion and sound energy to electrical energy conversion, the isolated power supply device 112 may include: a moving-coil loudspeaker at the excitation end, a sealed sound transmission duct, and a moving-coil loudspeaker at the generation end. The moving-coil loudspeaker at the excitation end is driven by an audio or ultrasonic signal to emit sound waves, thereby realizing the conversion of electrical energy to sound energy. These sound waves then act on the moving-coil loudspeaker at the generation end through the sealed sound transmission duct, causing the moving-coil loudspeaker at the generation end to work in reverse, emitting electrical energy, thus realizing the conversion of sound energy to electrical energy. This isolated power supply method uses air as a medium, and the increased distance can achieve low distributed capacitance.
[0078] For example, when the isolated power supply device 112 adopts a two-stage conversion architecture of power-to-light conversion and light-to-power conversion, the isolated power supply device 112 may include: a light-emitting diode (LED) and a photovoltaic cell. The LED emits light when energized, thereby generating light energy. When the light emitted by the LED shines on the photovoltaic cell, it causes the photovoltaic cell to generate electrical energy, thus realizing the two-stage conversion of power-to-light conversion and light-to-power conversion. This isolated power supply method uses air as a medium, and the distance can achieve low distributed capacitance. In some embodiments, the digital signal isolation device 108 may optionally be one or a combination of an optocoupler, a fiber optic transceiver, a magnetic digital isolator, and a capacitive digital isolator.
[0079] In this embodiment, since the digital signal isolation device 108 can isolate high-voltage and low-voltage digital signals and prevent mutual interference between circuits, the digital signal isolation device 108 can be an optocoupler, fiber optic transceiver, magnetic digital isolator, or capacitive digital isolator, etc. By using optocouplers, fiber optic transceivers, magnetic digital isolators, and capacitive digital isolators as digital signal isolators, high-resistance isolation characteristics are achieved during digital signal transmission, isolating the electronic system from the user, reducing ground loop noise, and avoiding safety risks.
[0080] In some embodiments, the current-to-voltage conversion device 102 may optionally include one or a combination of a plurality of shunts or a current transformer having a plurality of primary windings.
[0081] In this embodiment, the current-to-voltage conversion device 102 can be constructed using multiple shunts, multiple current transformers with primary windings, or a combination of multiple shunts and multiple current transformers with primary windings. By utilizing multiple shunts or multiple current transformers with primary windings to construct the current-to-voltage conversion device 102, the received current signal is cleverly converted into a voltage signal.
[0082] Figure 5 shows a flowchart of a current measurement method according to an embodiment of this application; wherein, the current measurement method includes:
[0083] Step 502: Acquire the current signal of the circuit under test;
[0084] Step 504: Convert the current signal into the corresponding first voltage signal;
[0085] Step 506: Condition the first voltage signal to obtain the second voltage signal;
[0086] Step 508: Convert the second voltage signal into a digital signal;
[0087] Step 510: Determine the current value corresponding to the current signal based on the digital signal.
[0088] The current measurement method provided in this application mainly includes: first, connecting a current measurement system to the circuit under test, enabling the current measurement system to acquire the current signal flowing in the circuit under test; then, using a current-to-voltage conversion device to convert the current signal into a corresponding first voltage signal. It is understood that the acquired current signal is obtained through devices such as sensors, therefore the obtained current signal is weak, and the first voltage signal is also weak. Therefore, a voltage signal conditioning device can process the first voltage signal to convert it into a more stable, reliable, and accurate second voltage signal. Subsequently, a signal digitization device converts the second voltage signal into a digital signal, then separates the digital signals to separate digital signals of different voltages. Finally, the current value corresponding to the current signal is determined based on the digital signal, thus completing the current measurement of the circuit under test. This application reduces the capacitance of the distributed capacitance of the signal processing section in the current measurement system, thereby reducing the amplitude of the leakage current generated by the common-mode voltage through the distributed capacitance. This significantly reduces the impact of the common-mode voltage on the accurate measurement of small currents, thus achieving the technical effect of reducing the impact of high common-mode voltage on current measurement and improving the accuracy of current measurement.
[0089] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance, unless otherwise expressly specified and limited. The terms "connection," "installation," and "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0090] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0091] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
[0092] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A current measurement system (100), wherein, include: A current-to-voltage conversion device (102) is provided, one end of which is connected to the circuit under test and is used to acquire the current signal of the circuit under test and convert the current signal into a first voltage signal. A voltage signal conditioning device (104) is provided, one end of which is connected to the other end of the current-voltage conversion device (102) for converting the first voltage signal into a second voltage signal. A signal digitization device (106) is provided, one end of which is connected to the other end of the voltage signal conditioning device (104), for converting the second voltage signal into a digital signal. A digital signal isolation device (108) is provided, the first side of which is connected to the signal digitization device (106) for isolating digital signals between different electrical systems. A control device (110) is connected to the second side of the digital signal isolation device (108) and is used to determine the current value corresponding to the current signal based on the digital signal. Also includes: An isolated power supply device (112) is provided, the load side (114) of which is connected to the current-to-voltage conversion device (102), the voltage signal conditioning device (104), the signal digitization device (106), and the digital signal isolation device (108), respectively. The power supply side (116) of the isolated power supply device (112) is connected to the control device (110) for obtaining power from the control device (110) and providing power to the current-to-voltage conversion device (102), the voltage signal conditioning device (104), the signal digitization device (106), and the digital signal isolation device (108). The capacitance value of the distributed capacitance between the first side and the second side of the digital signal isolation device (108) is less than or equal to the capacitance threshold. The capacitance value of the distributed capacitance between the load side (114) and the power supply side (116) of the isolated power supply device (112) is less than or equal to the capacitance threshold.
2. The current measurement system (100) according to claim 1, wherein, The isolated power supply device (112) includes: a high-frequency switching power supply (118).
3. The current measurement system (100) according to claim 2, wherein, The high-frequency switching power supply (118) includes: A square wave generator (1182), one end of which is connected to the control device (110); An LC filter (1184) is provided, one end of which is connected to the other end of the square wave generator (1182). A high-frequency transformer (1186) is provided, one end of which is connected to the other end of the LC filter (1184). A rectifier filter circuit (1188) is provided. One end of the rectifier filter circuit (1188) is connected to the other end of the high-frequency transformer (1186). The other end of the rectifier filter circuit (1188) is the load side (114) of the isolation power supply device (112).
4. The current measurement system (100) according to claim 3, wherein, The high-frequency transformer (1186) is a transformer without a ferromagnetic core.
5. The current measurement system (100) according to claim 1, wherein, The circuit structure of the isolated power supply device (112) is a resonant soft-switching DC-DC converter topology.
6. The current measurement system (100) according to claim 1, wherein, Also includes: An equipotential connection line (120) is provided, one end of which is connected to one end of the current-voltage conversion device (102), and the other end of which is connected to the other end of the current-voltage conversion device (102).
7. The current measurement system (100) according to claim 1, wherein, The isolated power supply device (112) adopts a two-stage conversion architecture of electrical energy to non-electromagnetic energy conversion and non-electromagnetic energy to electrical energy conversion, wherein non-electromagnetic energy may include one or a combination of mechanical energy, wind energy, acoustic energy and light energy.
8. The current measuring system (100) according to any one of claims 1 to 7, wherein, The digital signal isolation device (108) is one or a combination of an optocoupler, an optical fiber transceiver, a magnetic digital isolator, and a capacitive digital isolator.
9. The current measuring system (100) according to any one of claims 1 to 7, wherein, The current-voltage conversion device (102) includes one or a combination of multiple shunts or current transformers with multiple primary windings.
10. A current measurement method, wherein, include: Acquire the current signal of the circuit under test; The current signal is converted into a corresponding first voltage signal; The first voltage signal is conditioned to obtain the second voltage signal; Convert the second voltage signal into a digital signal; The current value corresponding to the current signal is determined based on the digital signal.