An absolute time delay calibration method for a pulse-triggered sampling channel

Abstract

The present invention provides a method for calibrating the absolute time delay of a pulse-triggered sampling channel. A high-precision dual-channel signal source is used to generate a sine wave and a square wave signal. The sampling board is triggered by the square wave signal to synchronously sample the sine wave signal, and the initial phase of the sine wave and its corresponding time are calculated. Further, the square wave signal output by the signal source is converted into a sine wave, and through dual-channel synchronous sampling, the initial phases and corresponding times of the two channels are calculated to obtain the total time difference between the output times of the two channels of the signal source and the time difference of dual-channel synchronous sampling of the sampling board. Subsequently, the sampling board synchronously samples the same high-frequency sine wave signal through two channels to obtain the time difference of dual-channel synchronous sampling. Finally, by changing the frequency of the signal source, the relationship between the time series of the square wave-triggered sampling of the sine wave signal and the time difference series of the two-channel output of the signal source is analyzed, and inverse fitting is performed with the signal frequency as the independent variable to finally obtain the trigger delay of the sampling board.

Description

Technical Field

[0001] The present invention belongs to the field of precise measurement of alternating current signals, and particularly relates to an absolute time delay calibration method for a pulse-triggered sampling channel. Background Art

[0002] In recent years, the new energy power generation in China has achieved rapid development. With the in-depth promotion of the construction of the new power system, a large number of new energy and power electronic devices have been connected to the power grid. Due to the randomness and volatility of new energy power generation, and the weak inertia characteristics commonly existing in power electronic devices, the dynamic change behaviors of the power system are becoming more and more frequent. Under this background, the Phasor Measurement Unit (PMU) has become one of the core tools for monitoring the dynamic behaviors of the power system by virtue of its data synchronization and fast response capabilities. The PMU can not only provide the time-domain waveforms of voltage and current, but also calculate key parameters such as frequency and phase angle, and generate vector measurement data of voltage and current, providing important support for constructing a more accurate and complex power grid model and carrying out stability analysis.

[0003] To ensure the high reliability and high precision of the PMU measurement data, it is particularly important to develop a synchronous phasor metering standard device. The synchronous phasor metering standard device can calibrate the PMU in a laboratory environment, so as to ensure that it accurately reflects the dynamic changes of the power system during the actual power grid operation. Therefore, accelerating the research, development and popularization application of the synchronous phasor metering standard device has become a key task that needs to be solved urgently at present.

[0004] In the synchronous phasor metering standard device, ensuring the accurate measurement of the orthogonal components of the synchronous phasor is one of the core technologies, and the sampling trigger delay is an important factor affecting the measurement accuracy of the orthogonal components of the synchronous phasor. The error of the trigger delay will directly lead to the phasor measurement deviation, thereby reducing the measurement accuracy and reliability of the system. Therefore, the precise calibration of the trigger delay is crucial. Summary of the Invention

[0005] The content of the present invention lies in providing an absolute time delay calibration method for a pulse-triggered sampling channel to solve the problem of precise calibration of the trigger delay.

[0006] The present invention provides an absolute time delay calibration method for a pulse-triggered sampling channel, including the following steps:

[0007] S10: Use a high-precision dual-channel signal source to generate a sine wave and a square wave, use a sampling board card to trigger the sampling of the sine wave through the edge of the square wave, and calculate the initial phase and corresponding time of the sine wave through Fourier transform.

[0008] S20: Convert the square wave output by the S10 signal source into a sine wave, synchronously sample through a dual-channel sampling board, calculate the initial phase and corresponding time of the sine signals of the two channels, and obtain the total time difference synthesized by the time difference between the two-channel output of the signal source and the time difference of the synchronous sampling of the two channels of the sampling board.

[0009] S30: The signal source outputs a high-frequency sine wave, and synchronously samples through a dual-channel sampling board, calculates the time corresponding to the initial phase difference of the sampling of the two channels, and obtains the time difference of the synchronous sampling of the two channels of the sampling board.

[0010] S40: Adjust the frequency of the signal source, repeat S10 and S20, and obtain the time series corresponding to the initial phase of the square wave-triggered sampling sine signal and the time difference series of the two-channel output of the signal source at different frequencies. Calculate the difference between the two and fit with the signal frequency as the independent variable to obtain the inverse formula of the trigger delay. The constant in the inverse formula is the trigger delay of the sampling board.

[0011] Further, the specific steps of the step S10 are as follows:

[0012] S101: Use a high-precision dual-channel signal source, set one channel to output a sine signal, and the other channel to output a square wave signal. The output frequencies of the two channels are both f1, and the two channels output synchronously.

[0013] S102: Set the sampling rate of the sampling board to f s , sample N data points, and set the edge trigger mode. Use the square wave signal as the trigger signal to sample the sine signal, and obtain the sampling sequence x1(n).

[0014] S103: Perform Fourier transform on the sampling sequence x1(n), calculate its initial phase and calculate the corresponding time based on the signal frequency f1

[0015] Further, in steps S101 - S103, when performing Fourier transform on the sampling sequence x1(n), its frequency resolution is The signal frequency f1 is an integer multiple of the resolution, ensuring whole-cycle sampling, avoiding frequency leakage and ensuring the accuracy of the initial phase calculation.

[0016] Further, the specific steps of the step S20 are as follows:

[0017] S201: Change the square wave signal output by the high-precision dual-channel signal source in S101 to sine signal output. The output frequencies of the two channels are both f1, and the two channels output synchronously.

[0018] S202: Use a dual-channel sampling board to synchronously sample the two sine signals output by the high-precision dual-channel signal source, and set the sampling rate to fs , sample N data points to obtain a sampling sequence x 21 (n), x 22 (n).

[0019] S203: Perform Fourier transform on the sampling sequences x 21 (n), x 22 (n), calculate its initial phase and calculate the corresponding time based on the signal frequency f1 Let t 21 and t 22 Take the difference to obtain the total time difference Δt2 = t 21 - t 22 .

[0020] Furthermore, in step S202, during the synchronous sampling process, the sampling time difference between the two channels of the selected dual-channel sampling board is fixed.

[0021] Furthermore, the specific steps of step S30 are as follows:

[0022] S301: One channel of a high-precision dual-channel signal source outputs a high-frequency sine signal with a signal frequency of f0, and this signal is simultaneously input to the two channels of the sampling board.

[0023] S302: Set the sampling rate of the dual-channel sampling board to f s , sample L data points, perform synchronous sampling to obtain sampling sequences x 31 (l), x 32 (l).

[0024] S303: Perform Fourier transform on the sampling sequences x 31 (l), x 32 (l), calculate its initial phase Take the difference between the calculated initial phases of the two channels to obtain and calculate the corresponding time based on the signal frequency f0 which is the synchronous sampling time difference Δt0 of the dual channels of the sampling board.

[0025] Furthermore, in steps S301 - S303, when performing Fourier transform on the sampling sequences x 31 (l), x 32 (l), its frequency resolution is The signal frequency f0 is an integer multiple of the resolution, ensuring sampling over a full period, avoiding frequency leakage and ensuring the accuracy of initial phase calculation.

[0026] Further, in steps S301 - S303, a high - frequency sine signal output by a high - precision dual - channel signal source is input into the two channels of the sampling board card through two identical coaxial cables, and the transmission delays of the two paths are the same.

[0027] Further, the specific steps of step S40 are as follows:

[0028] S401: Change the output frequency of the high - precision dual - channel signal source, repeat steps S10 and S20 for m measurements, and respectively obtain the time - series t1(m) corresponding to the initial phase of the square - wave - triggered sampled sine signal and the time - difference series Δt2(m) - Δt0 of the dual - channel output of the signal source at different frequencies.

[0029] S402: At the same frequency, subtract the time - difference of the dual - channel output of the signal source from the time corresponding to the initial phase of the square - wave - triggered sampled sine signal to obtain the time - series t4(m) = t1(m) - [Δt2(m) - Δt0].

[0030] S403: Curve - fit the time - series t4(m) with the frequency as the independent variable. The fitting result conforms to an inverse relationship, and the expression is where y is the time - series t4(m), a is a constant representing the phase, and b is the trigger delay of the sampling board card. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flowchart of a method for calibrating the absolute time delay of a pulse - triggered sampling channel provided by the present invention DETAILED IMPLEMENTATION MANNER

[0032] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0034] The present invention provides a method for calibrating the absolute time delay of a pulse - triggered sampling channel to solve the problem of accurate calibration of the trigger delay, including the following steps:

[0035] S10: Generate a sine wave and a square wave using a high-precision dual-channel signal source. Use a sampling board to trigger the sampling of the sine wave through the edge of the square wave, and calculate the initial phase and corresponding time of the sine wave through Fourier transform.

[0036] S20: Convert the square wave output by the S10 signal source into a sine wave, synchronously sample through a dual-channel sampling board, calculate the initial phase and corresponding time of the dual-channel sine signals, and obtain the total time difference synthesized by the time difference between the dual-channel outputs of the signal source and the time difference between the dual-channel synchronous samplings of the sampling board.

[0037] S30: The signal source outputs a high-frequency sine wave, and synchronously samples through a dual-channel sampling board. Calculate the time corresponding to the initial phase difference between the two-channel samplings to obtain the time difference between the dual-channel synchronous samplings of the sampling board.

[0038] S40: Adjust the frequency of the signal source, repeat S10 and S20, and obtain the time series corresponding to the initial phase of the square wave-triggered sampled sine signal and the time difference series of the dual-channel outputs of the signal source at different frequencies. Calculate the difference between the two and fit with the signal frequency as the independent variable to obtain the inverse formula of the trigger delay. The constant in the inverse formula obtained by fitting is the trigger delay of the sampling board.

[0039] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0040] The present invention provides a method for calibrating the absolute time delay of a pulse-triggered sampling channel to solve the problem of precise calibration of the trigger delay. As Figure 1 shown, in this embodiment, the method for calibrating the absolute time delay of the pulse-triggered sampling channel includes the following steps:

[0041] S10: Generate a sine wave and a square wave using a high-precision dual-channel signal source. Use a sampling board to trigger the sampling of the sine wave through the edge of the square wave, and calculate the initial phase and corresponding time of the sine wave through Fourier transform.

[0042] Specifically, in this embodiment, the specific steps of step S10 are as follows:

[0043] S101: Use a high-precision dual-channel signal source, set one channel to output a sine signal, and the other channel to output a square wave signal. The dual-channel output frequencies are both f1, and the dual-channel outputs synchronously.

[0044] S102: Set the sampling rate of the sampling board to f s , sample N data points, and set the edge trigger mode. Use the square wave signal as the trigger signal to sample the sine signal to obtain the sampling sequence x1(n).

[0045] S103: Perform a Fourier transform on the sampling sequence x1(n) and calculate its initial phase. And calculate the corresponding time based on the signal frequency f1.

[0046] Furthermore, in steps S101 - S103, when performing a Fourier transform on the sampling sequence x1(n), its frequency resolution is The signal frequency f1 is an integer multiple of the resolution to ensure full - period sampling, avoid frequency leakage, and ensure the accuracy of the initial phase calculation.

[0047] S20: Convert the square wave output by the signal source into a sine wave, synchronously sample through a dual - channel sampling board, calculate the initial phases and corresponding times of the two - channel sine signals, and obtain the total time difference composed of the time difference between the two - channel outputs of the signal source and the time difference between the two - channel synchronous samplings of the sampling board.

[0048] Specifically, in this embodiment, the specific steps of step S20 are as follows:

[0049] S201: Change the square - wave signal output by the high - precision dual - channel signal source in S101 to a sine - wave output, with both dual - channel output frequencies being f1 and dual - channel synchronous output.

[0050] S202: Use a dual - channel sampling board to synchronously sample the two sine signals output by the high - precision dual - channel signal source, set the sampling rate to fs, sample N data points, and obtain the sampling sequences x 21 (n), x 22 (n).

[0051] S203: Perform a Fourier transform on the sampling sequences x 21 (n), x 22 (n) to calculate their initial phases And calculate the corresponding time based on the signal frequency f1 Subtract t 21 from t 22 to obtain the total time difference Δt2 = t 21 - t 22 .

[0052] Furthermore, in step S202, during the synchronous sampling process, the sampling time difference between the two channels of the selected dual - channel sampling board is fixed.

[0053] S30: The signal source outputs a high - frequency sine wave, and synchronously samples through a dual - channel sampling board, calculates the time corresponding to the initial phase difference between the two - channel samplings, and obtains the time difference between the two - channel synchronous samplings of the sampling board.

[0054] Specifically, in this embodiment, the specific steps of step S30 are as follows:

[0055] S301: One channel of a high-precision dual-channel signal source outputs a high-frequency sine signal with a signal frequency of f0, and this signal is simultaneously input to both channels of the sampling board.

[0056] S302: Set the sampling rate of the dual-channel sampling board to f s , sample L data points, perform synchronous sampling, and obtain the sampling sequences x 31 (l), x 32 (l).

[0057] S303: Perform Fourier transform on the sampling sequences x 31 (l), x 32 (l), calculate their initial phases Subtract the calculated initial phases of the two channels to obtain and calculate the corresponding time based on the signal frequency f0 which is the synchronous sampling time difference Δt0 between the two channels of the sampling board.

[0058] Furthermore, in steps S301 - S303, when performing Fourier transform on the sampling sequences x 31 (l), x 32 (l), the frequency resolution is The signal frequency f0 is an integer multiple of the resolution to ensure integer-period sampling, avoid frequency leakage, and ensure the accuracy of initial phase calculation.

[0059] Furthermore, in steps S301 - S303, a high-frequency sine signal output by the high-precision dual-channel signal source is input to the two channels of the sampling board through two identical coaxial cables, and the two transmission delays are the same.

[0060] S40: Adjust the signal source frequency, repeat S10 and S20, and obtain the time series corresponding to the initial phases of the square-wave-triggered sampled sine signals and the time difference series of the dual-channel output of the signal source at different frequencies. Calculate the difference between the two and fit with the signal frequency as the independent variable to obtain the inverse formula of the trigger delay, and the constant in the inverse formula is the trigger delay of the sampling board.

[0061] Specifically, in this embodiment, the specific steps of step S40 are as follows:

[0062] S401: Change the output frequency of the high-precision dual-channel signal source, repeat steps S10 and S20 for m measurements, and respectively obtain the time series t1(m) corresponding to the initial phases of the square-wave-triggered sampled sine signals and the time difference series Δt2(m) - Δt0 of the dual-channel output of the signal source at different frequencies.

[0063] S402: At the same frequency, subtract the time difference of the dual-channel output of the signal source from the time corresponding to the initial phase of the sine signal triggered by the square wave sampling, to obtain the time series t4(m) = t1(m) - [Δt2(m) - Δt0].

[0064] S403: Use the frequency as the independent variable for curve fitting of the time series t4(m). The fitting result conforms to an inverse relationship, and the expression is where y is the time series t4(m), a is a constant characterizing the phase, and b is the trigger delay of the sampling board.

[0065] To facilitate understanding of the solution and its effects of the embodiments of the present invention, the following gives a specific application example. Those skilled in the art should understand that this example is only for facilitating the understanding of the present invention, and any specific details are not intended to limit the present invention in any way.

[0066] Application Example 1

[0067] PXI-5922 Channel Trigger Delay Calibration:

[0068] 1. Select Keysight 33522B as the signal source. Channel 1 outputs a sine signal with a frequency of 1 kHz and an amplitude of 1.5 V, and channel 2 outputs a square wave signal with a frequency of 1 kHz and an amplitude of 1.5 V. The outputs of the two channels are phase-locked to the external PPS signal at the same time to make them synchronously output. Select PXI-5922 as the sampling board. The sine signal is input as the measured signal into channel 1 of PXI-5922, and the square wave signal is input as the trigger signal into channel 2 of PXI-5922. Set the rising edge trigger mode, the sampling rate is 1 MHz, and trigger PXI-5922 channel 1 to sample 100k data points. Perform Fourier transform on the sampling values to calculate the time corresponding to the initial phase as t′1.

[0069] 2. Change the square wave output by channel 2 of Keysight 33522B to a sine wave output with a frequency of 1 kHz and an amplitude of 1.5 V. PXI-5922 uses the dual-channel sampling mode to sample the sine signals output by channels 1 and 2 of 33522B, and calculate the total time difference synthesized by the time difference of the dual-channel output of 33522B and the time difference of the dual-channel synchronous sampling of PXI-5922 as Δt′2 through Fourier transform.

[0070] 3. Use channel 1 of the Keysight 33522B signal generator to output a sine signal with a frequency of 100 kHz and an amplitude of 1.5 V. Through two coaxial cables of the same specification with a length of 1 m, input this sine signal into the two channels of PXI-5922 at the same time. Calculate the time corresponding to the initial phase difference of the two channels through Fourier transform to obtain the time difference Δt′0 of the dual-channel synchronous sampling of the sampling board.

[0071] 4. Change the output frequencies of Keysight 33522B to 1 kHz, 2 kHz, 3 kHz, 5 kHz, 7 kHz, 10 kHz, 13 kHz, 15 kHz, 17 kHz, and 20 kHz. Repeat steps 1 and 2, subtract the Keysight 33522B dual-channel output time difference from the time corresponding to the initial phase of the square-wave triggered sampled sine signal, and fit with the signal frequency as the independent variable to obtain the inverse formula where b is the pulse trigger delay of PXI-5922 in the above experiment process.

[0072] The above embodiments further elaborate on the features and advantages of the technical solution of the present invention. Those skilled in the art can design more specific implementation manners without departing from the scope of the technical solution of the present invention. However, these embodiments designed based on the present invention should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for calibrating the absolute time delay of a pulse-triggered sampling channel, characterized in that, It includes the following steps: S10: Use a high-precision dual-channel signal source to generate a sine wave and a square wave. Use a sampling board to trigger the sampling of the sine wave through the edge of the square wave, and calculate the initial phase and corresponding time of the sine wave through Fourier transform; S20: Convert the square wave output by the S10 signal source into a sine wave, synchronously sample through a dual-channel sampling board, calculate the initial phase and corresponding time of the dual-channel sine signals, and obtain the total time difference synthesized by the time difference between the dual-channel outputs of the signal source and the time difference between the dual-channel synchronous samplings of the sampling board; The specific steps of the step S20 are as follows: S201: Change the square wave signal output by the high-precision dual-channel signal source in S101 to a sine signal output, with the dual-channel output frequency both being f1, and the dual-channel outputs synchronously; S202: Synchronously sample two sinusoidal signals output by a high-precision dual-channel signal source using a dual-channel sampling board, and set the sampling rate to f s , sample N data points to obtain a sampling sequence x 21 (n), x 22 (n); S203: Fourier transform the sampling sequences x 21 (n) and x 22 (n), calculate their initial phases and calculate the corresponding time based on the signal frequency f1 Subtract t 21 from t 22 to obtain the total time difference Δt2 = t 21 - t 22 which is the combined time difference of the dual-channel output time of the signal source and the dual-channel sampling time of the sampling board; S30: The signal source outputs a high-frequency sine wave, and synchronously samples through a dual-channel sampling board, calculates the time corresponding to the initial phase difference of the two-channel sampling, and obtains the dual-channel synchronous sampling time difference of the sampling board; The specific steps of the step S30 are as follows: S301: One channel of the high-precision dual-channel signal source outputs a high-frequency sine signal with a signal frequency of f0, and input this signal to both channels of the sampling board simultaneously; S302: Set the sampling rate of the dual-channel sampling board to f s , sample L data points, perform synchronous sampling, and obtain the sampling sequence x 31 (l), x 32 (l); S303: Perform Fourier transform on the sampling sequence x 31 (l), x 32 (l) and calculate its initial phase Subtract the calculated initial phases of the two channels to obtain and calculate the corresponding time based on the signal frequency f0 which is the synchronous sampling time difference Δt0 of the two channels of the sampling board; S40: Adjust the signal source frequency, repeat S10 and S20, and obtain the time series corresponding to the initial phase of the square wave-triggered sampled sine signal and the time difference series of the dual-channel outputs of the signal source at different frequencies; Calculate the difference between the two and fit with the signal frequency as the independent variable to obtain the trigger delay of the sampling board; The specific steps of the step S40 are as follows: S401: Change the output frequency of the high-precision dual-channel signal source, repeat steps S10 and S20 for m measurements, and respectively obtain the time series t1(m) corresponding to the initial phase of the square wave-triggered sampled sine signal and the time difference series Δt2(m) - Δt0 of the dual-channel outputs of the signal source at different frequencies; S402: At the same frequency, subtract the time difference between the dual-channel outputs of the signal source from the time corresponding to the initial phase of the square wave-triggered sampled sine signal to obtain the time series t4(m) = t1(m) - [Δt2(m) - Δt0]; S403: Curve fitting is performed on the time series t4(m) with the frequency as the independent variable, and the fitting result conforms to an inverse relationship, and the expression is y is the time series t4(m), a is a constant representing the phase, and b is the trigger delay of the sampling board.

2. The absolute time delay calibration method for a pulse-triggered sampling channel according to claim 1, wherein The specific steps of the step S10 are as follows: S101: Use a high-precision dual-channel signal source, set one channel to output a sine signal and the other channel to output a square wave signal, with the dual-channel output frequency both being f1, and the dual-channel outputs synchronously; S102: The sampling board sets the sampling rate to f s , samples N data points, and sets the edge trigger mode. Using the square wave signal as the trigger signal, samples the sine signal to obtain the sampling sequence x1(n); S103: Perform a Fourier transform on the sampling sequence x1(n) and calculate its initial phase. And calculate the corresponding time based on the signal frequency f1.

3. A method for calibrating the absolute time delay of a pulse-triggered sampling channel according to claim 2, characterized in that, When performing Fourier transform on the sampled sequence x1(n), its frequency resolution is The signal frequency f1 is an integer multiple of the resolution, ensuring whole-period sampling, avoiding frequency leakage and ensuring the accuracy of initial phase calculation.

4. A method for calibrating the absolute time delay of a pulse-triggered sampling channel according to claim 2, characterized in that In the step S10, for the selected dual-channel signal source, when the dual-channel outputs synchronously, the time difference between the two-channel outputs is fixed.

5. A method for calibrating the absolute time delay of a pulse-triggered sampling channel according to claim 1, characterized in that, In the step S20, for the selected dual-channel sampling board, when the dual-channel synchronously samples, the time difference between the two-channel samplings is fixed.

6. A method for calibrating the absolute time delay of a pulse-triggered sampling channel according to claim 1, characterized in that For the sampled sequence x 31 (l), x 32 (l), when performing Fourier transform, its frequency resolution is The signal frequency f0 is an integer multiple of the resolution, ensuring sampling over a complete period, avoiding frequency leakage and ensuring the accuracy of the initial phase calculation.

7. A method for calibrating the absolute time delay of a pulse-triggered sampling channel according to claim 1, characterized in that, A high-frequency sine signal output by the high-precision dual-channel signal source is input to the two channels of the sampling board through two identical coaxial cables, and the two-channel transmission delays are the same.

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