Non-intrusive ac voltage measurement system based on capacitive coupling and reference signal injection

Abstract

The application discloses a non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection, belongs to the field of electric power measurement, and comprises a detection end, a measurement unit and a shielded cable. The detection end comprises two half-circular conductive electrodes which can be opened and closed and can be clamped on an insulated wire. The measurement unit comprises an instrument amplifier, a reference signal source, an analog-to-digital converter, a processor and an isolation power supply. The shielded cable is used for connecting the detection end and the measurement unit, and the shielding layer of the shielded cable is connected with the injected reference signal. The application adopts double-frequency injection and separation calculation, utilizes frequency separation of the reference signal and the power frequency signal, avoids similar numerical interference, reduces error propagation, and the frequency of the reference signal avoids multiples of the power frequency signal, so that fast Fourier transform extraction is facilitated.

Description

Technical Field

[0001] This invention belongs to the field of power measurement, specifically a non-intrusive AC voltage measurement system based on capacitive coupling and reference signal injection. Background Technology

[0002] Currently, non-contact AC voltage measurement mainly includes human body capacitive coupling type (such as...). Figure 3 As shown in the figure, this method relies on the operator's body as a grounding path, requiring the operator to touch specific conductive parts of the probe. Disadvantages include low reliability, significant susceptibility to human impedance and posture, and unsuitability for unattended or fixed installation scenarios. Furthermore, existing methods generally suffer from the following problems: sensitivity to changes in the coupling capacitance between the probe and the wire, requiring on-site calibration; susceptibility to parasitic capacitance, cable capacitance, and environmental noise interference; and error accumulation due to component tolerances in the measurement circuit. Summary of the Invention

[0003] This invention provides a non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection to address the shortcomings of existing technologies.

[0004] This invention is achieved through the following technical solution: A non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection, including a detection terminal, a measurement unit, and a shielded cable; The detection end includes two semi-circular conductive electrodes, which can be opened and closed and can be clamped onto the insulated wire. The measurement unit includes an instrumentation amplifier, a reference signal source, an analog-to-digital converter, a processor, and an isolated power supply; The shielded cable is used to connect the detection end and the measurement unit, and the shielding layer of the shielded cable is connected to the injected reference signal.

[0005] As described above, in the non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection, the instrumentation amplifier has: an inverting input terminal connected to the reference signal, a non-inverting input terminal connected to the shielded cable insulation layer, and a current sensing resistor. Connect the non-inverting and inverting terminals, and the current sensing resistor. The resistance is .

[0006] As described above, in the non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection, the reference signal source generates a frequency of 910Hz-3.3kHz, an amplitude of 1V-5V, and generates a sinusoidal signal.

[0007] In the non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection as described above, the processor performs a fast Fourier transform on the output signal of the instrumentation amplifier to extract the amplitude of the 50Hz power frequency component, as well as the amplitude and phase of the reference signal.

[0008] In the non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection as described above, the isolated power supply is a battery or an isolated DC-DC module.

[0009] In the non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection described above, the formula for calculating the voltage of the coupling wire at the detection end is: V x (t)= , where V x (t) represents the instantaneous value of the AC voltage; V x The effective value of the voltage on the detection terminal wire; The phase of the alternating current voltage; It is called the angular frequency of alternating current, ω=2πf; f is the frequency of the alternating current signal.

[0010] In the non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection described above, the formula for calculating the voltage of the reference signal injected by the reference signal source is as follows: ,in, The instantaneous value of the injected signal; The effective value of the injected signal voltage; This refers to the phase of the signal; The angular frequency of the signal. ; The frequency of the injected signal.

[0011] In the non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection described above, the processor performs a fast Fourier transform calculation to obtain the amplitude V at ω. xo , Amplitude as well as relative to phase difference .

[0012] In the non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection described above, the processor is capable of calculating the equivalent time constant of the grounding path. Equivalent time constant of grounding path It is the equivalent time constant used to characterize the impedance characteristics of the entire current return path between the measurement system ground and the power system ground. Its calculation formula is: ,in, ω is the angular frequency of the reference signal component extracted from the FFT.

[0013] In the non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection described above, the processor is capable of calculating the effective value V of the measured voltage. x The calculation formula is as follows: ,in, The effective value of the injected signal voltage; The amplitude of the power frequency component extracted from the FFT; The amplitude of the reference signal component extracted from the FFT; The angular frequency of the reference signal component extracted from the FFT depends on the angular frequency of the injected reference signal. Equal to the angular frequency of the injected reference signal: ; This is the equivalent time constant of the grounding path.

[0014] The advantages of this invention are: This invention employs dual-frequency injection and separation calculation, utilizing the frequency separation of the reference signal and the power frequency signal to avoid interference from similar values, reduce error propagation, and the frequency of the reference signal avoids multiples of the power frequency signal, facilitating fast Fourier transform extraction. This invention provides real-time phase difference extraction: through... Real-time estimation of grounding impedance characteristics enables adaptive compensation; This invention employs a full shielding and equipotential bonding design: the insulation layer of the shielded cable is connected... This reduces or even eliminates the impact of parasitic capacitance on measurements. This invention employs fully digital signal processing and amplitude and phase extraction based on Fast Fourier Transform, exhibiting strong anti-interference capabilities and ease of integration. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a functional structure diagram of the present invention; Figure 2 This is a schematic diagram of the equivalent circuit of the measuring unit of the present invention; Figure 3 This is a schematic diagram of existing human body capacitive coupling probe detection technology. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] like Figure 1-2 As shown, a non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection includes a detection terminal, a measurement unit, and a shielded cable. The detection end includes two semi-circular conductive electrodes, which can be opened and closed and can be clamped onto an insulated wire. The measurement unit includes an instrumentation amplifier, a reference signal source, an analog-to-digital converter, a processor, and an isolated power supply; The shielded cable is used to connect the detection end and the measurement unit, and the insulation layer of the shielded cable is connected to the injected reference signal.

[0019] Preferably, in this embodiment, the instrumentation amplifier (INA) has the following characteristics: the inverting input is connected to the reference signal, the non-inverting input is connected to the shielded cable insulation layer, and a current sensing resistor is used. Connect the non-inverting and inverting terminals, and the current sensing resistor. The resistance is .

[0020] Preferably, the reference signal source described in this embodiment generates a frequency of 910Hz-3.3kHz, an amplitude of 1V5V, and generates a sinusoidal signal.

[0021] Preferably, the processor (DSP or MCU) described in this embodiment performs a fast Fourier transform on the output signal of the instrumentation amplifier to extract the amplitude of the component with a power frequency of 50Hz, as well as the amplitude and phase of the reference signal.

[0022] Preferably, the isolated power supply described in this embodiment is a battery or an isolated DC-DC module to ensure electrical isolation between the system and the power grid.

[0023] Preferably, the formula for calculating the voltage of the coupling wire at the detection end in this embodiment is: V x (t)= , where V x (t) represents the instantaneous value of the AC voltage; V x The effective value of the voltage on the detection terminal wire; The phase of the alternating current voltage; It is called the angular frequency of alternating current, ω=2πf; f is the frequency of the alternating current signal.

[0024] Preferably, the formula for calculating the voltage of the reference signal injected by the reference signal source in this embodiment is as follows: ,in, The instantaneous value of the injected signal; This represents the effective voltage value of the injected signal. This refers to the phase of the signal; The angular frequency of the signal. ; The frequency of the injected signal.

[0025] Preferably, the processor described in this embodiment performs a fast Fourier transform calculation to obtain the amplitude V at ω. xo , Amplitude as well as relative to phase difference .

[0026] Preferably, the processor described in this embodiment is capable of calculating the equivalent time constant of the grounding path. Equivalent time constant of grounding path It is the equivalent time constant used to characterize the impedance characteristics of the entire current return path between the measurement system ground and the power system ground. Its calculation formula is: ,in, ω is the angular frequency of the reference signal component extracted from the FFT.

[0027] Preferably, the processor described in this embodiment is capable of calculating the effective value V of the measured voltage. x The calculation formula is as follows: ,in, This represents the effective voltage value of the injected signal. The amplitude of the power frequency component extracted from the FFT; The amplitude of the reference signal component extracted from the FFT; The angular frequency of the reference signal component extracted from the FFT depends on the angular frequency of the injected reference signal. Equal to the angular frequency of the injected reference signal: ; This is the equivalent time constant of the grounding path.

[0028] This invention requires no human contact and can automatically compensate for changes in coupling capacitance, suppress the influence of parasitic parameters, and achieve high linearity and low error (<3%) measurement over a wide voltage range (10400V). At the same time, this invention has a simple structure, low cost, and is easy to mass-produce and deploy in the field.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection, characterized in that: Includes the detection end, measurement unit, and shielded cable; The detection end includes two semi-circular conductive electrodes, which can be opened and closed and can be clamped onto the insulated wire. The measurement unit includes an instrumentation amplifier, a reference signal source, an analog-to-digital converter, a processor, and an isolated power supply; The shielded cable is used to connect the detection end and the measurement unit, and the shielding layer of the shielded cable is connected to the injected reference signal.

2. The non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection according to claim 1, characterized in that: The instrumentation amplifier has an inverting input connected to a reference signal and a non-inverting input connected to the shielded cable insulation layer, with a current sensing resistor passing through it. Connect the non-inverting and inverting terminals, and the current sensing resistor. The resistance is .

3. The non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection according to claim 1, characterized in that: The reference signal source has a generation frequency of 910Hz-3.3kHz, an amplitude of 1V5V, and generates a sinusoidal signal.

4. The non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection according to claim 1, characterized in that: The processor performs a fast Fourier transform on the output signal of the instrumentation amplifier to extract the amplitude of the 50Hz power frequency component, as well as the amplitude and phase of the reference signal.

5. The non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection according to claim 1, characterized in that: The isolated power supply is a battery or an isolated DC-DC module.

6. The non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection according to claim 1, characterized in that: The formula for calculating the voltage of the coupling wire at the detection end is: V x (t)= , where V x (t) represents the instantaneous value of the AC voltage; V x The effective value of the voltage on the detection terminal wire; The phase of the alternating current voltage; It is called the angular frequency of alternating current, ω=2πf; f is the frequency of the alternating current signal.

7. The non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection according to claim 1, characterized in that: The formula for calculating the voltage of the reference signal injected by the reference signal source is as follows: ,in, The instantaneous value of the injected signal; This represents the effective voltage value of the injected signal. This refers to the phase of the signal; The angular frequency of the signal. ; The frequency of the injected signal.

8. The non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection according to claim 4, characterized in that: The processor performs a fast Fourier transform calculation to obtain the result. The output amplitude V of the instrumentation amplifier xo , The amplitude of the reference signal component extracted from the FFT as well as relative to phase difference .

9. The non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection according to claim 8, characterized in that: The processor is capable of calculating the equivalent time constant of the grounding path. Equivalent time constant of grounding path It is the equivalent time constant used to characterize the impedance characteristics of the entire current return path between the measurement system ground and the power system ground. Its calculation formula is: ,in, ω is the angular frequency of the reference signal component extracted from the FFT.

10. The non-invasive AC voltage measurement system based on capacitive coupling and reference signal injection according to claim 9, characterized in that: The processor is capable of calculating the effective value V of the measured voltage. x The calculation formula is as follows: ,in, The effective value of the injected signal voltage; The amplitude of the power frequency component extracted from the FFT; The amplitude of the reference signal component extracted from the FFT; The angular frequency of the reference signal component extracted from the FFT depends on the angular frequency of the injected reference signal. Equal to the angular frequency of the injected reference signal: ; This is the equivalent time constant of the grounding path.

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