AC voltage phase jitter error compensation system and method based on differential sampling

Abstract

The invention provides an AC voltage phase jitter error compensation system and method based on differential sampling, and the system is characterized in that a to-be-detected AC source is connected with one side of a self-made double-pole double-throw switch; the common end of the double-pole-double-throw switch is connected with the low end of the digital-to-analog conversion board card serving as the voltage standard and the low end of the transformed sampling voltmeter. Two groups of reference signals sent by the rubidium clock are respectively connected to external reference clocks of the two groups of arbitrary waveform generators and external reference signals of the digital-to-analog conversion board card through the self-made optical isolator; the group of arbitrary waveform generators are respectively connected with an external phase-locked end of the AC signal calibration source to be tested, the transformed sampling voltmeter and a trigger signal end of the standard digital-to-analog conversion board card through three optical isolators; and the other group of arbitrary waveform generator is connected with an external reference signal end of the sampling voltmeter through a self-made optical isolator. According to the invention, measurement errors caused by phase jitter can be effectively compensated, so that the accuracy of high-frequency AC voltage magnitude transmission is improved.

Description

Technical Field

[0001] This invention belongs to the field of electrical measurement technology and relates to an AC voltage phase jitter error compensation system and method based on differential sampling, especially a system and method for compensating phase jitter error in the AC voltage value transmission process based on differential sampling under high frequency conditions. Background Technology

[0002] In recent years, precision differential sampling measurement of AC signals based on differential sampling has been widely used in metrology institutions in various countries. This method involves acquiring the difference between a standard voltage and the voltage to be measured using a sampler, and then reconstructing the measured signal using methods such as Fourier transform to achieve voltage value transfer. When the measured frequency increases, phase jitter becomes the main influencing factor affecting the precision measurement of AC signals based on differential sampling. However, existing studies have focused on phase jitter at low frequencies, lacking analysis, error models, and compensation methods for phase jitter at high frequencies. Therefore, the problem of increased measurement error due to phase jitter at higher frequencies in current differential sampling methods for measuring AC voltage signals urgently needs to be addressed. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0004] Therefore, the present invention provides an AC voltage phase jitter error compensation system and method based on differential sampling.

[0005] The technical solution of the present invention is as follows:

[0006] According to one aspect, an AC voltage phase jitter error compensation system based on differential sampling is provided. This compensation system includes: a calibration source for the AC signal under test, a sampling voltmeter, a digital-to-analog converter board as a voltage standard, a rubidium clock, two sets of arbitrary waveform signal generators, a double-pole double-throw switch, and six optical isolators. The calibration source for the AC signal under test is connected to one side of the self-made double-pole double-throw switch; the common terminal of the self-made double-pole double-throw switch is connected to the low end of the digital-to-analog converter board and the low end of the sampling voltmeter, respectively; the high end of the digital-to-analog converter board and the high end of the sampling voltmeter are connected in phase... The connection is made so that the rubidium clock emits two sets of reference signals. One set is output to the digital-to-analog converter board through an optical isolator as an external reference signal for the digital-to-analog converter board. The other set of reference signals is connected to the external reference clocks of two arbitrary waveform signal generators through optical isolators. The arbitrary waveform signal generators are connected to the external phase-locked terminal of the AC signal calibration source under test, the sampling voltmeter, and the trigger signal terminal of the digital-to-analog converter board through three optical isolators. The arbitrary waveform signal generators are connected to the external reference signal terminal of the sampling voltmeter through an optical isolator.

[0007] Furthermore, the AC signal calibration source under test can generate an AC voltage with a clean signal spectrum, and the phase of the generated waveform can be adjusted through its external phase-locked loop function.

[0008] Furthermore, the sampling voltmeter is designed as follows: a self-made external clock signal board replaces the crystal oscillator on its main board to provide the instrument's time base signal from the outside.

[0009] Furthermore, the time base signal of the digital-to-analog converter board that provides the reference signal is connected to the rubidium clock via a coaxial cable, and the time base signal of the digital-to-analog converter board is routed to the chassis via software settings.

[0010] Furthermore, the digital-to-analog converter board measures the DC voltage corresponding to each step voltage value as the standard voltage, while in differential measurement it measures a step-type sinusoidal signal.

[0011] Furthermore, the two sets of arbitrary waveform signal generators are dual-channel, synchronous, and externally triggerable arbitrary waveform signal generators.

[0012] According to another aspect, an AC voltage phase jitter error compensation method based on differential sampling is provided. The compensation method is implemented based on the aforementioned system and includes:

[0013] Step 1: Use a digital-to-analog converter board to generate a sinusoidal stepped wave voltage signal with the same frequency and amplitude as the calibration source of the AC signal under test;

[0014] Step 2: Connect the common terminal S of the self-made double-pole double-throw switch to terminals C and D. Use the modified sampling voltmeter to sample and measure the difference signal generated by the AC signal calibration source and the digital-to-analog converter in DCV mode.

[0015] Step 3: Configure the digital-to-analog converter board to maintain a constant reference voltage for each step, which is the DC signal for each step;

[0016] Step 4: Connect the common terminal S of the self-made double-pole double-throw switch to terminals A and B, and use the modified sampling voltmeter to measure the voltage in step 3 in DCV mode.

[0017] Step 5: Add the difference signal obtained in Step 2 to the corresponding step voltage measured in Step 4 to obtain the reconstructed signal. Then, perform Discrete Fourier Transform (DFT) on the reconstructed signal to obtain the amplitude and phase information of each harmonic of the signal under test.

[0018] Step 6: Divide the amplitude values ​​of each harmonic obtained in Step 5 by the phase jitter error compensation coefficient C. k The amplitude values ​​of each harmonic after compensation are obtained.

[0019] Furthermore, the phase jitter error compensation coefficient and the measured phase jitter distribution u(t) satisfy: C k =DFT k [u(t)].

[0020] By applying the above technical solution, a method and system are provided to effectively compensate for measurement errors caused by phase jitter, thereby improving the accuracy of high-frequency AC voltage value transmission. The system's components are designed to work together to obtain the compensated harmonic amplitudes. This invention establishes a mathematical relationship between phase jitter error and the voltage under test; the error caused by phase jitter is the result of convolving the probability density function of phase jitter with the waveform without phase jitter. Software algorithms compensate for hardware defects, effectively reducing the error component introduced by phase jitter into the final measurement uncertainty as the calibration frequency increases, thus improving the measurement uncertainty of AC voltage measurement based on differential sampling at high frequencies. This compensation model is applicable to signals of different frequencies and amplitudes, exhibiting good versatility, and the algorithm has low computational complexity, making it suitable for online real-time compensation. Attached Figure Description

[0021] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0022] Figure 1 This is a schematic diagram of the AC voltage phase jitter error compensation system based on differential sampling according to the present invention. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. 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 a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0026] like Figure 1 As shown, in one embodiment of the present invention, an AC voltage phase jitter error compensation system based on differential sampling is provided. The compensation system includes: a calibration source 1 for the AC signal under test, a sampling voltmeter 2, a digital-to-analog converter board 3 as a voltage standard, a rubidium clock 4, two sets of arbitrary waveform signal generators 5 and 6, a double-pole double-throw switch 7, and six optical isolators 8, 9, 10, 11, 12, and 13. The calibration source 1 for the AC signal under test is connected to one side of the self-made double-pole double-throw switch 7; the common terminal of the self-made double-pole double-throw switch 7 is connected to the low end of the digital-to-analog converter board 3 and the low end of the sampling voltmeter 2, respectively; the high end of the digital-to-analog converter board 3 and the sampling voltmeter 2 are connected to the low end of the sampling voltmeter 2, respectively. The high end of voltmeter 2 is connected to the circuit. Rubidium clock 4 emits two sets of reference signals. One set is output to digital-to-analog converter board 3 through optical isolator 8 as an external reference signal for digital-to-analog converter board 3. The other set of reference signals is connected to the external reference clocks of two arbitrary waveform signal generators 5 and 6 through optical isolator 9. The arbitrary waveform signal generator 5 is connected to the external phase-locked terminal of the AC signal calibration source 1 under test, the sampling voltmeter 2, and the trigger signal terminal of the digital-to-analog converter board 3 through three optical isolators 10, 11, and 12, respectively. The arbitrary waveform signal generator 6 is connected to the external reference signal terminal of the sampling voltmeter 2 through optical isolator 13.

[0027] That is, all trigger signals in the system, namely the trigger signals of the digital-to-analog converter board 3 generated by the two sets of arbitrary waveform signal generators 5 and 6, the sampling trigger signal of the sampling voltmeter 2, the phase-locking signal of the AC signal calibration source 1 under test, and the time base signal, namely the two 10MHz signals generated by the rubidium clock 4, are connected through optical isolators 8, 9, 10, 11, 12, and 13.

[0028] In this embodiment of the invention, the AC signal calibration source 1 under test can generate an AC voltage with a pure signal spectrum, and the phase of the generated waveform can be adjusted through its external phase-locked loop function.

[0029] In this embodiment of the invention, the sampling voltmeter 2 is designed as follows: a self-made external clock signal board replaces the crystal oscillator on its main board to provide the instrument's time base signal from the outside.

[0030] In this embodiment of the invention, the time base signal of the digital-to-analog converter board 3 that provides the reference signal is connected to the back of the chassis and the rubidium clock 4 via a coaxial cable, and the time base signal of the digital-to-analog converter board 3 is routed to the chassis via software settings.

[0031] In other words, the AC voltage phase jitter error compensation system based on differential sampling must first ensure the uniformity of the time base signals of all instruments in the system. Therefore, this embodiment of the invention modifies the sampling voltmeter 2 by replacing the crystal oscillator on its mainboard with a self-made external clock signal board to provide the instrument's time base signal from an external source. Furthermore, the time base signal of the digital-to-analog converter board 3, which provides the reference signal, is connected to the rubidium clock 4 via a coaxial cable on the back of the chassis, and the routing of the time base signal of the digital-to-analog converter board 3 to the chassis is configured via software. Thus, the uniformity of all time base signals in the measurement system is ultimately achieved.

[0032] In this embodiment of the invention, the digital-to-analog converter board 3 is used as a standard voltage measurement for the DC voltage corresponding to each step voltage value, while in differential measurement it is a step-type sinusoidal signal.

[0033] In this embodiment of the invention, the two sets of arbitrary waveform signal generators 5 and 6 are dual-channel, synchronous, and externally triggerable arbitrary waveform signal generators.

[0034] Preferably, in this embodiment, an AC calibration source with adjustable phase and high signal spectral purity is selected to generate a sinusoidal signal to be measured, specifically the Fluke 5720A; a low-noise, low-drift 16-bit digital-to-analog converter board is selected as the reference voltage generation module, specifically the PXI 6733 digital-to-analog converter board; and an 8.5-bit precision sampling voltmeter with extremely high linearity and measurement accuracy in DC measurement mode is selected, specifically the Agilent 3458A for measurement.

[0035] The AC voltage phase jitter error compensation method based on the above system specifically includes:

[0036] Step 1: Use the digital-to-analog converter board 3 to generate a sinusoidal stepped wave voltage signal with the same frequency and amplitude as the calibration source 1 of the AC signal to be measured.

[0037] Step 2: Connect the common terminal S of the self-made double-pole double-throw switch 7 to terminals C and D. Use the modified sampling voltmeter 2 to sample and measure the difference signal generated by the AC signal calibration source 1 and the digital-to-analog converter board 3 in DCV mode.

[0038] Step 3: Set up the digital-to-analog converter board 3 to keep the reference voltage of each step constant, which is the DC signal of each step;

[0039] Step 4: Connect the common terminal S of the self-made double-pole double-throw switch 7 to terminals A and B, and use the modified sampling voltmeter 2 to measure the voltage in step 3 in DCV mode.

[0040] Step 5: Add the difference signal obtained in Step 2 to the corresponding step voltage measured in Step 4 to obtain the reconstructed signal. Then, perform Discrete Fourier Transform (DFT) on the reconstructed signal to obtain the amplitude and phase information of each harmonic of the signal under test.

[0041] Step 6: Divide the amplitude values ​​of each harmonic obtained in Step 5 by the phase jitter error compensation coefficient C. k The amplitude values ​​of each harmonic after compensation are obtained.

[0042] Among them, the phase jitter error compensation coefficient and the measured phase jitter distribution u(t) satisfy: C k =DFT k [u(t)].

[0043] That is, this compensation method is related to the probability density function of phase jitter. If the distribution of phase jitter is measured as u(t), then the compensation coefficient C for the kth harmonic of the AC voltage under test is... k The Discrete Fourier Transform (DFT) of u(t) specifically satisfies the following functional relationship: C k =DFT k [u(t)].

[0044] As can be seen, the embodiments of the present invention provide a method and system that can effectively compensate for measurement errors caused by phase jitter, thereby improving the accuracy of high-frequency AC voltage value transmission. The system's components are designed to work together to obtain the compensated harmonic amplitudes. The present invention obtains the mathematical relationship between phase jitter error and the voltage under test; that is, the error caused by phase jitter is the result of convolving the probability density function of phase jitter with the waveform without phase jitter. By compensating for hardware defects through software algorithms, the error component introduced by phase jitter to the final measurement uncertainty is effectively reduced as the calibration frequency increases, thus improving the measurement uncertainty of AC voltage measurement based on differential sampling at high frequencies. This compensation model is applicable to signals of different frequencies and amplitudes, has good versatility, and the algorithm has low computational complexity, making it suitable for online real-time compensation.

[0045] The features described and / or illustrated above with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, and / or in combination with or in lieu of features in other embodiments.

[0046] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, components, or combinations thereof.

[0047] Many features and advantages of these embodiments are apparent from this detailed description, and therefore the appended claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. Furthermore, since many modifications and alterations will readily occur to those skilled in the art, the embodiments of the invention are not intended to be limited to the precise structures and operations illustrated and described, but rather can be covered to those falling within their scope.

[0048] There are suitable modifications and equivalents.

[0049] The parts of this invention not described in detail are techniques known to those skilled in the art.

Claims

1. An AC voltage phase jitter error compensation system based on differential sampling, characterized in that, The compensation system includes: a calibration source (1) for the AC signal under test, a sampling voltmeter (2), a digital-to-analog converter board (3) as a voltage standard, a rubidium clock (4), two sets of arbitrary waveform signal generators (5) and (6), a double-pole double-throw switch (7), and six optical isolators (8), (9), (10), (11), (12), and (13), wherein: the calibration source (1) for the AC signal under test is connected to one side of the self-made double-pole double-throw switch (7); the common terminal of the self-made double-pole double-throw switch (7) is connected to the low end of the digital-to-analog converter board (3) and the low end of the sampling voltmeter (2) respectively; the high end of the digital-to-analog converter board (3) is connected to the high end of the sampling voltmeter (2), and the rubidium clock (4) generates... Two sets of reference signals are output. One set is output to the digital-to-analog converter board (3) through an optical isolator (8) as an external reference signal of the digital-to-analog converter board (3). The other set of reference signals is connected to the external reference clocks of two arbitrary waveform signal generators (5) and (6) through an optical isolator (9). The arbitrary waveform signal generator (5) is connected to the external phase-locked terminal of the AC signal calibration source (1) under test, the sampling voltmeter (2), and the trigger signal terminal of the digital-to-analog converter board (3) through three optical isolators (10), (11), and (12), respectively. The arbitrary waveform signal generator (6) is connected to the external reference signal terminal of the sampling voltmeter (2) through an optical isolator (13).

2. The AC voltage phase jitter error compensation system based on differential sampling according to claim 1, characterized in that, The AC signal calibration source (1) under test can generate AC voltage with a pure signal spectrum, and the phase of the generated waveform can be adjusted through its external phase-locked loop function.

3. The AC voltage phase jitter error compensation system based on differential sampling according to claim 1 or 2, characterized in that, The sampling voltmeter (2) is designed as follows: a self-made external clock signal board is used to replace the crystal oscillator on its main board in order to provide the instrument with a time base signal from the outside.

4. The AC voltage phase jitter error compensation system based on differential sampling according to claim 3, characterized in that, The time base signal of the digital-to-analog converter board (3) that provides the reference signal is connected to the back of the chassis and the rubidium clock (4) via a coaxial cable, and the time base signal of the digital-to-analog converter board (3) is routed to the chassis via software settings.

5. The AC voltage phase jitter error compensation system based on differential sampling according to claim 4, characterized in that, The digital-to-analog converter board (3) is used as a standard voltage measurement for the DC voltage corresponding to each step voltage value, while in differential measurement it is a step-type sinusoidal signal.

6. The AC voltage phase jitter error compensation system based on differential sampling according to claim 1, characterized in that, The two sets of arbitrary waveform signal generators (5) and (6) are dual-channel, synchronous, and externally triggerable arbitrary waveform signal generators.

7. A method for compensating AC voltage phase jitter error based on differential sampling, characterized in that, The compensation method is implemented based on the system described in claims 1-6, and the compensation method includes: Step 1: Use the digital-to-analog converter board (3) to generate a sinusoidal stepped wave voltage signal with the same frequency and amplitude as the AC signal calibration source (1) under test; Step 2: Connect the common terminal S of the self-made double-pole double-throw switch (7) to the C and D terminals, and use the modified sampling voltmeter (2) to sample and measure the difference signal generated by the AC signal calibration source (1) and the digital-to-analog converter board (3) in DCV mode; Step 3: Set up the digital-to-analog converter board (3) to keep the reference voltage of each step constant, which is the DC signal of each step; Step 4: Connect the common terminal S of the self-made double-pole double-throw switch (7) to terminals A and B, and use the modified sampling voltmeter (2) to measure the voltage in step 3 in DCV mode; Step 5: Add the difference signal obtained in Step 2 to the corresponding step voltage measured in Step 4 to obtain the reconstructed signal. Then, perform Discrete Fourier Transform (DFT) on the reconstructed signal to obtain the amplitude and phase information of each harmonic of the signal under test. Step 6: Divide the amplitude values ​​of each harmonic obtained in Step 5 by the phase jitter error compensation coefficient C. k The amplitude values ​​of each harmonic after compensation are obtained.

8. The AC voltage phase jitter error compensation method based on differential sampling according to claim 7, characterized in that, The phase jitter error compensation coefficient and the measured phase jitter distribution u(t) satisfy: C k =DFT k [u(t)].

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