A broadband voltage phase difference measurement method and measurement device

Abstract

The present application provides a voltage phase difference measurement method, comprising: synchronously sampling measured signals from multiple channels at a fixed frequency, performing analog-to-digital conversion to obtain a digital sequence of fixed length; selecting one of the multiple channels as a reference channel, solving the spectrum of the measured signal of the reference channel through FFT, and calculating the fundamental frequency according to the three-spectral line method; synchronously truncating the digital sequence of each channel for a full cycle; synthesizing an orthogonal basis operator based on the fundamental frequency to coherently demodulate the truncated digital sequence of each channel with the orthogonal basis operator to obtain an in-phase component and an orthogonal component, and calculating the phase value of each channel; and calculating the phase difference between each channel and the reference channel.

Description

Technical Field

[0001] The present application generally relates to a voltage phase difference measurement method and a measurement device thereof, and in particular to a wide-band voltage phase difference precision measurement method and a measurement device thereof based on the frequency compensation correction principle. Background Art

[0002] In phase standard sources, broadband power meters, power analyzers, and related measurement and testing instruments, the accuracy of phase difference measurement determines the measurement accuracy of parameters such as phase angle, power factor, and active power. Conventional electric power measurement standards have a phase difference measurement uncertainty of 0.003° at power frequency. Under low power factor conditions, this introduces a measurement uncertainty of approximately 52 ppm for active power measurements.

[0003] The mainstream voltage precision phase difference measurement technology is based on the principle of digital sampling. Its basic processing process is as follows: Figure 1 shown.

[0004] The measured pair of AC voltages is sampled at the sampling clock f s After the digital sampling process is realized through the analog-to-digital converter, a series of discrete sampling points are cached in the memory, and the sampling data of L points are intercepted for digital signal processing. These discrete points are pre-processed by the window function to improve frequency leakage, and then the discrete Fourier transform (DFT) digital signal processing technology is used to solve the initial phase of the fundamental wave of the measured signal, and the phase difference between the measured AC voltage 1 and the AC current voltage 2 is obtained by subtraction calculation.

[0005] In actual sampling circuits, it is difficult for the sampling frequency to achieve a strict integer multiple relationship with the fundamental frequency of the measured signal, and the sampling points used for DFT digital signal processing are not infinitely long sequences. A finite-length digital sequence (L points) must be intercepted. Spectrum leakage is easily generated during the interception process, which is a major source of phase difference measurement error. The phase measurement accuracy can be improved by using a window function, but the optimal measurement accuracy is still on the order of 0.001°, and under conditions where the amplitude ratio of the measured signal is large, the measurement accuracy will further decrease. Although the use of a hardware phase-locked loop to implement a sampling frequency multiplication circuit can improve this problem to a certain extent, it increases the complexity of the hardware circuit. In addition, the sampling problem caused by the distortion of the measured signal and the phase jitter of the phase-locked loop of the sampling frequency multiplication circuit is still an important factor limiting the improvement of phase difference measurement accuracy. Summary of the Invention

[0006] In order to overcome the problem of low measurement accuracy due to spectrum leakage when measuring voltage phase difference using digital sampling technology, the present application proposes a wide-band voltage phase difference measurement method and a measurement device based on the frequency compensation correction principle. The method improves the frequency measurement accuracy and obtains the phase difference by synthesizing the fundamental frequency orthogonal operator, thereby improving the voltage phase measurement accuracy over a wide frequency range.

[0007] This application provides a voltage phase difference measurement method, including:

[0008] S1: synchronously samples the measured signals from multiple channels at a fixed frequency and performs analog-to-digital conversion to obtain a digital sequence of fixed length;

[0009] S2: selecting one of the multiple channels as a reference channel, solving the spectrum of the measured signal of the reference channel by FFT, and calculating the fundamental frequency according to the three-spectral method;

[0010] S3: Synchronize and truncate the digital sequence of each channel into a full cycle;

[0011] S4: synthesizing an orthogonal basis operator according to the fundamental frequency;

[0012] S5: coherently demodulate the truncated digital sequence of each channel with the orthogonal basis operator to obtain the in-phase component and the orthogonal component, and calculate the phase value of each channel;

[0013] S6: Calculate the phase difference between each channel and the reference channel.

[0014] According to an embodiment of the present application, a sampling frequency for synchronously sampling the measured signals from multiple channels is 10 times or more of a frequency of the measured signals.

[0015] According to one embodiment of the present application, the step of calculating the fundamental frequency f0 according to the three-spectral-line method includes:

[0016] Find the highest spectral line X k and the adjacent second highest spectral line X k-1 、X k+1 , enter the following calculation formula:

[0017] f0=(k+δ)f0 / L

[0018] δ=-Re[(X k+1 -X k-1 ) / (2X k -X k-1 -X k+1 )]

[0019] Where: k——highest spectral line X k The number of spectral lines;

[0020] f s - sampling frequency;

[0021] L——The number of sampling signal points.

[0022] According to one embodiment of the present application, step S3 includes:

[0023] According to the fundamental frequency f0, the sampling frequency f s , calculate the number sequence u0(n)~u with a finite length of L m (n) in the maximum number of integral period points L', for the digital sequence u0(n)~u m (n) Perform synchronous full cycle truncation, the calculation method includes:

[0024] First, the digital sequence u0(n)~u m The period number c of (n) is:

[0025] c=L / (f s / f0)

[0026] After rounding down, the integer cycle number C is: C = INT(c);

[0027] The number of points in the entire cycle l' is calculated as: l'=C·(f s / f0), round l' to the nearest integer to obtain the maximum integer cycle point number L',

[0028] For the digital sequence u0(n)~u m (n), after taking the maximum number of full-cycle points L' from the starting point, the remaining points are discarded.

[0029] According to one embodiment of the present application, step S4 includes: synthesizing an orthogonal basis operator sequence according to the fundamental frequency f0, which are respectively:

[0030] a[n]=sin[(n / L)(f s / f0)·2π](n=0,1,2,...,L');

[0031] b[n]=cos[(n / L)(f s / f0)·2π] (n=0, 1, 2,..., L').

[0032] According to one embodiment of the present application, step S5 includes:

[0033] Using orthogonal basis operators, for the digital sequence u0(n)~u m (n) and calculate the average value to obtain the digital sequence u0(n)~u m The in-phase component u of (n) 0a ~uma and the orthogonal component u 0b ~u mb ;

[0034] The phase of each signal is calculated using the inverse tangent formula. For example, the phase of u0(t) and u1(t) as follows.

[0035]

[0036] According to an embodiment of the present application, step S6 includes: calculating the voltage phase difference between each channel and the reference channel according to a subtraction calculation or a vector angle formula.

[0037] For example, the phase difference between u0(t) and u1(t) for

[0038]

[0039] According to one embodiment of the present application, step S1 further includes: storing the obtained fixed-length digital sequence.

[0040] The present application also provides a voltage phase difference measurement device for executing the above method, wherein the voltage phase difference measurement device includes: a range conversion device, an analog-to-digital converter, a voltage reference module, a frequency reference module, a programmable logic device, a memory, and a main controller, wherein:

[0041] The range converter is used to extend the voltage measurement range;

[0042] The voltage reference module and the frequency reference module are used to provide voltage reference and frequency reference to the analog-to-digital converter;

[0043] The analog-to-digital converter is used to sample at a fixed frequency and perform analog-to-digital conversion to obtain a digital sequence of fixed length, and provide the digital sequence to the memory;

[0044] The memory is used to store digital sequences;

[0045] The main controller is used to run the voltage measurement software, realize the data reception of the programmable logic device, and calculate the phase and phase difference of each measured signal based on the in-phase component and the orthogonal component;

[0046] Programmable logic devices include:

[0047] An FFT transform unit is used to read the digital sequence of the reference channel and calculate the spectrum;

[0048] A three-spectrum frequency measurement unit, used to solve the fundamental frequency of the reference channel according to the three-spectrum method;

[0049] The full-cycle sampling unit is used to synchronously truncate the digital sequence of each channel into a full cycle;

[0050] An orthogonal basis synthesis unit, used for synthesizing an orthogonal basis operator according to a fundamental wave frequency;

[0051] Phase-sensitive detection unit, used to coherently demodulate the digital sequence after truncating each channel with the orthogonal basis operator to obtain in-phase component and orthogonal component;

[0052] The serial bus interface control unit is used to upload the fundamental frequency, in-phase component and quadrature component to the main controller via the serial bus.

[0053] The present application also provides a computer-readable storage medium having software instructions stored thereon, wherein the software instructions implement the above method when executed.

[0054] The voltage phase difference measurement method provided in this application uses a three-line frequency calculation method with fixed-frequency sampling to achieve precise measurement of the fundamental frequency. The sampling points are synchronously truncated according to the frequency, minimizing spectrum leakage, avoiding complex synchronous frequency multiplication circuit design, and simplifying the circuit. Furthermore, an orthogonal basis is synthesized based on the measured fundamental frequency, and phase-sensitive detection technology is used to achieve precise measurement of the fundamental phase difference. This method has strong anti-interference capabilities and reduces the impact of measured signal distortion on the phase difference.

[0055] The voltage phase difference measurement method provided in this application can be used in measuring instruments such as wideband digital power meters, and can significantly improve the measurement accuracy of standard electric power meters and phase standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The following will further illustrate the above-mentioned characteristics, technical features, advantages and implementation methods of the present application in a clear and understandable manner through the description of preferred embodiments and in conjunction with the accompanying drawings. The following drawings are intended only to illustrate and explain the present application and do not limit the scope of the present application. Among them:

[0057] Figure 1 The principle of voltage phase difference measurement technology in the prior art is shown.

[0058] Figure 2 A flow chart of a voltage phase difference measurement method according to an embodiment of the present application is shown.

[0059] Figure 3 The figure shows a structural diagram of a voltage phase difference measuring device according to an embodiment of the present application. DETAILED DESCRIPTION

[0060] In order to have a clearer understanding of the technical features, purposes and effects of this application, the specific implementation methods of this application are now described with reference to the accompanying drawings.

[0061] In order to improve the impact of spectrum leakage on the accuracy of phase difference measurement, the technical solution of this application adopts frequency estimation and phase-sensitive detection technology. The measured signal is synchronously sampled at a fixed frequency. After obtaining a digital sequence of fixed length, the spectrum of the measured signal is solved by FFT (Fast Fourier Transform). The fundamental frequency of the measured signal is calculated by the three-spectral line method using the highest spectral line and the adjacent second-highest spectral line. Then, the digital sequence is approximately truncated to an integer cycle, and the measured signal is synthesized according to the calculated fundamental frequency. The digital orthogonal basis is multiplied and averaged to obtain the in-phase component and quadrature component of the measured signal. The phase difference is calculated by the vector angle formula to achieve precise measurement of the phase difference of the broadband voltage signal. This method can improve the phase measurement accuracy to 0.0001° near 50Hz.

[0062] The measurement process of the voltage phase difference measurement method provided in one embodiment of the present application is as follows: Figure 2 As shown, the following steps are included:

[0063] S1: Sampling at a fixed frequency and performing analog-to-digital conversion to store several cycles of waveforms.

[0064] Multiple measured signals u0(t)~u from multiple channels are measured at a fixed frequency m (t) Perform synchronous sampling and analog-to-digital conversion to convert analog quantities into digital quantities, thereby obtaining a fixed-length digital sequence u0(n)~u m (n), and then store several cycles of waveforms.

[0065] Note that the sampling frequency should be much greater than the frequency of the measured signal. Preferably, the sampling frequency is 10 times or more of the frequency of the measured signal.

[0066] S2: Use FFT to solve the spectrum of the measured signal of the reference channel and calculate the fundamental frequency according to the three-spectral method.

[0067] One of the multiple channels is selected as a reference channel. The spectrum of the digital sequence u0(n) of the reference channel is solved by FFT, and the fundamental frequency is calculated according to the three-spectral line method.

[0068] The specific method of using the three-spectral method to calculate the fundamental frequency f0 of the measured signal is as follows: find the highest spectral line X k and the adjacent second highest spectral line X k-1 、X k+1 , enter the following calculation formula:

[0069] f0=(k+δ)f0 / L

[0070] δ=-Re[(X k+1 -X k-1) / (2X k -X k-1 -X k+1 )]

[0071] Where: k——highest spectral line X k The number of spectral lines;

[0072] f s ——The frequency of the sampling signal, in Hz;

[0073] L——the number of sampling signal points;

[0074] S3: For the digital sequence u0(n)~u m (n) Perform synchronous full cycle truncation.

[0075] According to the measured signal fundamental frequency f0, the sampling frequency f s , calculate the number sequence u0(n)~u with a finite length of L m (n) in the maximum number of integral period points L', for the digital sequence u0(n)~u m (n) Perform synchronous full cycle truncation.

[0076] The calculation method is as follows: First, a finite length digital sequence u0(n)~u m The period number c of (n) is:

[0077] c=L / (f s / f0)

[0078] After rounding down, the integer cycle number C is: C = INT(c);

[0079] The number of points in the entire cycle l' is calculated as: l'=C·(f s / f0), round l' to the nearest integer to obtain the maximum integer cycle point number L'.

[0080] For the digital sequence u0(n)~u m (n), after taking the maximum number of full-cycle points L' from the starting point, the remaining points are discarded.

[0081] S4: Synthesize the orthogonal basis operator according to the fundamental frequency of the measured signal.

[0082] According to the calculated fundamental frequency f0, the orthogonal basis operator sequences are synthesized, which are:

[0083] a[n]=sin[(n / L)(f s / f0)·2π](n=0,1,2,...,L');

[0084] b[n]=cos[(n / L)(f s / f0)·2π] (n=0, 1, 2,..., L').

[0085] S5: coherently demodulate the truncated digital sequence of each channel with the orthogonal basis operator to obtain the in-phase component and the orthogonal component, and calculate each phase value.

[0086] Using orthogonal basis operators, for the digital sequence u0(n)~u m (n) and calculate the average value to obtain the digital sequence u0(n)~u m The in-phase component u of (n) 0a ~u ma and the orthogonal component u 0b ~u mb , calculate the phase according to the inverse tangent formula and calculate the phase between each signal. For example, the phase of u0(t) and u1(t) as follows.

[0087]

[0088] S6: Calculate the phase difference between each channel and the reference channel.

[0089] Calculate the voltage phase difference between each channel and the reference channel using subtraction or the vector angle formula.

[0090] For example, the phase difference between u0(t) and u1(t) for

[0091]

[0092] As described above, the voltage phase difference measurement method provided in this embodiment includes analog-to-digital conversion, frequency estimation, orthogonal basis synthesis, and phase-sensitive detection calculation steps. The measured signal is synchronously sampled at a fixed frequency. After obtaining a digital sequence of a fixed length, the spectrum of the measured signal is solved by FFT. The fundamental frequency of the measured signal is calculated by the three-spectral line method using the highest spectral line and the adjacent second-highest spectral line. The digital sequence is truncated to an approximate integer cycle, and the measured signal is multiplied and averaged according to the calculated fundamental frequency using a digital orthogonal basis to obtain the in-phase component and the orthogonal component of the measured signal. The phase difference is calculated using the vector angle formula to achieve precise measurement of the phase difference of the wide-band voltage signal.

[0093] According to one embodiment of the present application, a voltage phase difference measurement method is provided, using a three-line frequency calculation method based on fixed-frequency sampling to achieve precise measurement of the fundamental frequency. The sampling points are synchronously truncated according to the frequency, minimizing spectrum leakage, avoiding complex synchronous frequency multiplication circuit design, and simplifying the circuit. Furthermore, an orthogonal basis is synthesized based on the measured fundamental frequency, and phase-sensitive detection technology is employed to achieve precise measurement of the fundamental phase difference. This method has strong anti-interference capabilities and reduces the impact of measured signal distortion on the phase difference.

[0094] The voltage phase difference measurement method provided in this application can be used in measuring instruments such as wideband digital power meters, and can significantly improve the measurement accuracy of standard electric power meters and phase standards.

[0095] According to another embodiment of the present application, a broadband voltage phase difference measuring device is provided, the structure of which is as follows: Figure 3 As shown, it includes: a range converter, an analog-to-digital converter, a voltage reference module, a frequency reference module, a programmable logic device, a memory, and a main controller. The voltage phase difference measurement device realizes the wideband voltage phase difference measurement function based on frequency estimation and phase-sensitive detection technology.

[0096] Among them, the range conversion device is used to expand the voltage measurement range;

[0097] The voltage reference module and the frequency reference module are used to provide voltage reference and frequency reference to the analog-to-digital converter.

[0098] The analog-to-digital converter is used to: sample at a fixed frequency and perform analog-to-digital conversion to obtain a digital sequence of fixed length, and provide the digital sequence to the memory.

[0099] The memory is used to store the digital sequence.

[0100] The main controller is used to run the voltage measurement software, realize the data reception of the programmable logic device, and calculate the phase and phase difference of each measured signal based on the in-phase component and the orthogonal component.

[0101] Programmable logic devices include:

[0102] An FFT transform unit is used to read the digital sequence of the reference channel and calculate the spectrum;

[0103] A three-spectrum frequency measurement unit, used to solve the fundamental frequency of the reference channel according to the three-spectrum method;

[0104] The full-cycle sampling unit is used to synchronously truncate the digital sequence of each channel into a full cycle;

[0105] An orthogonal basis synthesis unit, used for synthesizing an orthogonal basis operator according to a fundamental wave frequency;

[0106] Phase-sensitive detection unit, used to multiply and average the truncated digital sequence of each channel with the in-phase operator and the quadrature operator to obtain the in-phase component and the quadrature component;

[0107] The serial bus interface control unit is used to upload parameters such as fundamental frequency, in-phase component of each channel, orthogonal component of each channel to the main controller through the serial bus.

[0108] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0109] The above description is only an illustrative embodiment of the present application and is not intended to limit the scope of the present application. Any equivalent changes, modifications and combinations made by any person skilled in the art without departing from the concept and principle of the present application shall fall within the scope of protection of the present application.

Claims

1. A method for measuring a voltage phase difference, comprising: S1: synchronously samples the measured signals from multiple channels at a fixed frequency and performs analog-to-digital conversion to obtain a digital sequence of fixed length; S2: selecting one of the multiple channels as a reference channel, solving the spectrum of the measured signal of the reference channel by FFT, and calculating the fundamental frequency according to the three-spectral method; S3: Synchronize and truncate the digital sequence of each channel into a full cycle; S4: synthesizing an orthogonal basis operator according to the fundamental frequency; S5: coherently demodulate the truncated digital sequence of each channel with the orthogonal basis operator to obtain the in-phase component and the orthogonal component, and calculate the phase value of each channel; S6: Calculate the phase difference between each channel and the reference channel.

2. The method according to claim 1, wherein The sampling frequency for synchronously sampling the measured signals from the plurality of channels is 10 times or more the frequency of the measured signals.

3. The method according to claim 1, wherein Step S3 includes: According to the fundamental frequency f0, the sampling frequency f s , calculate the number sequence u0(n)~u with a finite length of L m (n) in the maximum number of integral period points L', for the digital sequence u0(n)~u m (n) Perform synchronous full cycle truncation, the calculation method includes: First, the digital sequence u0(n)~u m The period number c of (n) is: c=L / (f s / f0) After rounding down, the integer cycle number C is: C = INT(c); The number of points in the entire cycle l' is calculated as: l'=C·(f s / f0), round l' to the nearest integer to obtain the maximum integer cycle point number L', For the digital sequence u0(n)~u m (n), after taking the maximum number of full-cycle points L' from the starting point, the remaining points are discarded.

4. The method according to claim 3, wherein: Step S5 includes: Using orthogonal basis operators, for the digital sequence u0(n)~u m (n) and calculate the average value to obtain the digital sequence u0(n)~u m The in-phase component u of (n) 0a ~u ma and the orthogonal component u 0b ~u mb ; The phase of each signal is calculated using the inverse tangent formula.

5. The method according to claim 1, wherein Step S6 includes calculating the voltage phase difference between each channel and the reference channel according to a subtraction calculation or a vector angle formula.

6. The method according to claim 1, step S1 further comprising: The obtained fixed-length digital sequence is stored.

7. A voltage phase difference measuring device, configured to perform the method according to any one of claims 1 to 6, the voltage phase difference measuring device comprising: Range conversion device, analog-to-digital converter, voltage reference module, frequency reference module, programmable logic device, memory, main controller, wherein, The range converter is used to extend the voltage measurement range; The voltage reference module and the frequency reference module are used to provide voltage reference and frequency reference to the analog-to-digital converter; The analog-to-digital converter is used to sample at a fixed frequency and perform analog-to-digital conversion to obtain a digital sequence of fixed length, and provide the digital sequence to the memory; The memory is used to store digital sequences; The main controller is used to run the phase measurement software to realize data reception of the programmable logic device and calculate the phase and phase difference of the measured voltage based on the in-phase component and the orthogonal component; Programmable logic devices include: An FFT transform unit is used to read the digital sequence of the reference channel and calculate the spectrum; A three-spectrum frequency measurement unit, used to solve the fundamental frequency of the reference channel according to the three-spectrum method; The full-cycle sampling unit is used to synchronously truncate the digital sequence of each channel into a full cycle; An orthogonal basis synthesis unit, used for synthesizing an orthogonal basis operator according to a fundamental wave frequency; Phase-sensitive detection unit, used to coherently demodulate the digital sequence after truncating each channel with the orthogonal basis operator to obtain in-phase component and orthogonal component; The serial bus interface control unit is used to upload the fundamental frequency, in-phase component and quadrature component to the main controller via the serial bus.

8. A computer-readable storage medium having stored thereon software instructions, which when executed implement the method according to any one of claims 1 to 6.

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