CN107271772A - A kind of mains frequency quick determination method of high accuracy and anti-noise jamming - Google Patents
A kind of mains frequency quick determination method of high accuracy and anti-noise jamming Download PDFInfo
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
- G01R23/12—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage by converting frequency into phase shift
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Abstract
The invention discloses a kind of high accuracy and the mains frequency quick determination method of anti-noise jamming, link and frequency closed loop detection are calculated including synchronized phase open loop detection, beat frequency phase, the mains voltage signal detected can be obtained into the locking phase of power network in real time through synchronized phase open loop detection, link is calculated by beat frequency phase and extracts beat frequency phase in synchronized phase, and by beat frequency phase information incoming frequency closed loop detection to obtain the real-time frequency of power network.The present invention is effectively improved the detectability of power network real-time frequency, and measurement accuracy is high, fast response time, good in anti-interference performance, can solve closed loop and survey the stability problem of phase, frequency measuring method under weak power grid environment, with good application value.
Description
The technical field is as follows:
the invention belongs to the technical field of power grid frequency detection, and particularly relates to a high-precision anti-noise-interference power grid frequency rapid detection method.
Background art:
the frequency is a quality inspection index which is necessary for power production and consumption, and is also an important parameter for measuring the running state of the power system, and the large-scale access of renewable energy sources to the power grid puts higher requirements on the accuracy and the real-time performance of power grid frequency detection. Existing frequency detection methods must rely on phase-locked loops, also known as soft-phase-locked loops (SPLL). Typical SPLLs are mainly of 3 types: a single synchronous reference frame (SSRF-SPLL), a symmetric component method (SSRF-SPLL), and a dual synchronous frame (DDSRF-SPLL). The SSRF-SPLL can be effectively applied to amplitude, frequency and phase detection during power grid balance, and has good dynamic and steady-state response performance. However, when the grid is unbalanced, harmonics exist in the frequency of the SSRF-SPLL output, and thus the steady state performance is not good. The improved SSRF-SPLL utilizes a symmetric component method to separate a positive sequence voltage component, and the positive sequence voltage component is sent into a closed loop regulator to obtain the frequency of an unbalanced power grid. However, this method uses a fixed-parameter all-pass filter, and when the frequency of the power grid drifts, the accuracy of frequency detection is poor. The DDSRF-SPLL adopts a double synchronous coordinate system structure based on positive and negative sequences, so that the decoupling of the positive and negative sequences is realized, and the frequency detection problem when three phases are asymmetric is effectively solved. However, due to the use of a dual synchronous coordinate system structure and the coupling effect between the PI regulator and the 4 low-pass filters, the dynamic process of the method is very complicated, and the long response time cannot meet the requirement of the frequency detection on rapidity. In addition, the loop filter of the SPLL almost always uses a PI regulator, so its dynamic response time is mainly determined by the characteristics of the regulator. When the power grid environment is severe, the parameters of the regulator are difficult to optimize, the time consumption of the dynamic process of the regulator is long, the response time of the conventional SPLL is almost more than 1 power frequency period, and the requirement of quickly and accurately detecting the frequency cannot be met. Eliminating the closed loop regulation process can significantly improve the frequency detection speed, which is also the starting point of open loop detection, however, when the grid voltage has high-frequency noise signals, the differential operation of the phase detected by the open loop method can amplify the noise signals, resulting in larger errors in the frequency detection.
The above methods all have some obvious disadvantages, and an ideal grid frequency detection technology should simultaneously meet the requirements of accuracy, rapidity and noise interference resistance, and the detection method should be simple and easy to implement so as to be conveniently realized in an embedded controller.
The invention content is as follows:
the invention discloses a high-precision and anti-noise interference power grid frequency rapid detection method, which is based on accurate real-time phase information detected by open loop, extracts a difference frequency phase therein and can obtain accurate power grid frequency information through a difference frequency closed loop detection link.
The technical scheme adopted by the invention is as follows: a method for quickly detecting the frequency of power network with high accuracy and noise interference resistance includes such steps as quickly opening the synchronous phase of power network by open loop, calculating the difference phase, closing the frequency by closed loop, and applying the voltage signal of power networkU a、U b、U cThe synchronous phase of the power grid can be obtained after the power grid synchronous phase quick open-loop detection link, the difference frequency phase in the power grid synchronous phase signal can be extracted through the difference frequency signal calculation link, and the real-time frequency of the power grid can be obtained after the difference frequency phase signal is input to the frequency closed-loop detection linkf。
The following will explain the basic principle of the fast open-loop detection method for the power grid synchronous phase in detail:
the three-phase grid voltage can be described by the following expression:
(1)
the network voltage is obtained after the transformation of rotating coordinatesU d、U qThe following were used:
assuming an initial phaseθ∈ (0,2 π), according to the additional angleθ exThe selection rule can obtain the following synchronization phases of the power grid:
(3)
wherein, arctan (U q/U d)+θ ex I.e. the difference frequency phase.
The frequency acquisition method comprises the following steps:
(1) collecting network voltage signals by voltage sensorU a、U b、U c；
(2) Carrying out synchronous rotation coordinate transformation on the collected power grid voltage signal through a synchronous rotation coordinate transformation module to obtain a voltage signal under a two-phase rotation coordinate systemU d 、U q；
(3) If high-frequency noise or harmonic components exist in the acquired power grid voltage signal, a filter module needs to be added behind the synchronous rotation coordinate transformation module to filter the output signal in the step (2) so as to eliminate the influence of the noise and the harmonic;
(4) obtained according to step (3)U d、U qSelecting correct one from the judgment conditionsθ exThe judgment conditions are as follows: if it isU d>0 andU q>0, thenθ ex= 0; if it isU d<0, thenθ ex= pi; if it isU d>0 andU q<0, thenθ ex=2π；
(5) Obtaining parameters according to the steps (3) and (4)U d 、U q 、θ exCalculating the real-time amplitude and phase of the power grid voltage by combining the amplitude and phase formulas disclosed by the invention; wherein, the amplitude calculation formula is as follows:the phase calculation formula is:(ii) a Wherein,ω s tnamely the power frequency phase; arctan (U q/U d)+θ exI.e. the difference frequency phase.
(6) Extracting the difference frequency phase in the synchronous phase of the power gridxIts delay by one sampling period is noted asy，Will cycle counternIs set to be 0, the phase information of the part is output after being adjusted by the difference frequency phase calculation link and is marked as phase, wherein phase =x+2*π*n；
(7) Delaying the output of step (6) by one sampling period and recording asθAs input for the closed-loop regulation, the output of the closed-loop regulation being integrated as feedback signalθ feedbackThe difference value of the two is used as the output of closed loop regulation after PI regulation, and is divided by 2 PI to obtain the difference frequency deltaf。
(8) Will difference frequency deltafThe power grid can be obtained by superposing the power grid with the power frequency (50 Hz in China)True frequency off。
In addition, a simulation model of the high-precision anti-noise-interference power grid frequency rapid detection method is established, the frequency detection method is subjected to simulation verification, and the simulation result also proves the correctness and the effectiveness of the scheme.
Through the technical scheme, the invention has the beneficial effects that: compared with the existing frequency detection method, the power grid frequency detection method disclosed by the invention is based on accurate real-time phase information, the real-time phase information can be accurately obtained, and the inherent stability problem of a closed-loop phase measurement system does not exist; the closed-loop frequency measurement method based on real-time accurate phase information avoids differential operation on the phase information, so that the noise interference resistance is high, and high-precision power grid frequency information can be obtained.
Description of the drawings:
FIG. 1 is a schematic diagram of a power grid synchronous phase quick open loop detection link according to the present invention;
FIG. 2 is a schematic diagram of a difference frequency phase calculation unit according to the present invention;
FIG. 3 is a schematic diagram of a frequency closed loop detection link according to the present invention;
FIG. 4 is a three-phase grid voltage waveform containing noise;
fig. 5 is a comparison graph of simulation waveforms before and after sudden change of the grid frequency when high-frequency noise exists.
The specific implementation mode is as follows:
the present invention is described in further detail below with reference to the attached drawings.
Fig. 1-3 are schematic diagrams of frequency acquisition according to the present invention, comprising: three-phase network voltage signalU a、U b、U cFast open loop detection of synchronous phase of power gridA measuring link, a difference frequency phase calculating link and a frequency closed loop detecting link.
Fig. 4 shows a three-phase grid voltage waveform with noise, the initial amplitude of the voltage is 1p.u, and the voltage becomes 1.5p.u. when the voltage is 2.5 s.
FIG. 5 is a comparison graph of simulation waveforms before and after sudden change of the grid frequency in the presence of high-frequency noise, wherein the initial frequency of the grid voltage is 60Hz, and the frequency is suddenly changed to 50Hz at 2.5 s.
As shown in figures 1-3, a high-precision and anti-noise-interference power grid frequency rapid detection method comprises a power grid synchronous phase rapid open-loop detection link, a difference frequency phase calculation link and a frequency closed-loop detection link, wherein a power grid voltage signal is detected as shown in figure 1U a、U b、U cThe synchronous phase of the power grid can be obtained after the power grid synchronous phase quick open-loop detection link, the difference frequency phase in the power grid synchronous phase signal can be extracted through the difference frequency signal calculation link, and the real-time frequency of the power grid can be obtained after the difference frequency phase signal is input to the frequency closed-loop detection linkf。
The following will explain the basic principle of the fast open-loop detection method for the power grid synchronous phase in detail:
the three-phase grid voltage can be described by the following expression:
(1)
the network voltage is obtained after the transformation of rotating coordinatesU d、U qThe following were used:
assuming an initial phaseθ∈ (0,2 π), according to the additional angleθ exThe selection rule can obtain the following synchronization phases of the power grid:
(3)
wherein, arctan (U q/U d)+θ ex I.e. the difference frequency phase.
The frequency acquisition method comprises the following steps:
(1) collecting network voltage signals by voltage sensorU a、U b、U c；
(2) Carrying out synchronous rotation coordinate transformation on the collected power grid voltage signal through a synchronous rotation coordinate transformation module to obtain a voltage signal under a two-phase rotation coordinate systemU d 、U q；
(3) If high-frequency noise or harmonic components exist in the acquired power grid voltage signal, a filter module needs to be added behind the synchronous rotation coordinate transformation module to filter the output signal in the step (2) so as to eliminate the influence of the noise and the harmonic;
(4) obtained according to step (3)U d、U qSelecting correct one from the judgment conditionsθ exThe judgment conditions are as follows: if it isU d>0 andU q>0, thenθ ex= 0; if it isU d<0, thenθ ex= pi; if it isU d>0 andU q<0, thenθ ex=2π；
(5) Obtaining parameters according to the steps (3) and (4)U d 、U q 、θ exCalculating the real-time amplitude and phase of the power grid voltage by combining the amplitude and phase formulas disclosed by the invention; wherein, the amplitude calculation formula is as follows:the phase calculation formula is:(ii) a Wherein,ω s tnamely the power frequency phase; arctan (U q/U d)+θ exNamely the difference frequency phase;
(6) extracting the difference frequency phase in the synchronous phase of the power gridxIts delay by one sampling period is noted asy，Will cycle counternIs set to 0, and comparedxAndythe size of (A), ify-x) Is greater than the threshold value M (the theoretical value of M is 2 pi, considering the error caused by the discrete sampling process, the value of M is slightly less than 2 pi, the larger the sampling period is, the smaller the threshold value is), then the period counternIncrease by 1, otherwise notnAccumulating, adjusting the phase information of the part by a difference frequency phase calculation link, and outputting the adjusted phase information, and recording as phase, wherein phase =x+2*π*n；
(7) Delaying the output of step (6) by one sampling period and recording asθAs input for the closed-loop regulation, the output of the closed-loop regulation being integrated as feedback signalθ feedbackThe difference value of the two is used as the output of closed loop regulation after PI regulation, and is divided by 2 PI to obtain the difference frequency deltaf。
(8) Will difference frequency deltafThe real frequency of the power grid can be obtained by superposing the power frequency (50 Hz in China)f。
In addition, a simulation model of the high-precision anti-noise-interference power grid frequency rapid detection method is established, the frequency detection method is subjected to simulation verification, and the simulation result also proves the correctness and the effectiveness of the scheme.
The above detailed description of the present invention is provided for the purpose of describing particular embodiments thereof, and it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the present invention as defined in the appended claims.
Claims (4)
1. A high-precision anti-noise-interference power grid frequency rapid detection method is characterized by comprising the following steps: the method comprises a power grid synchronous phase quick open-loop detection link, a difference frequency phase calculation link and a frequency closed-loop detection link, wherein the detected power grid voltage signal can obtain the synchronous phase of the power grid in real time through the power grid synchronous phase quick open-loop detection link, the difference frequency phase in the power grid synchronous phase is extracted through the difference frequency phase calculation link, and the difference frequency phase information is input into the frequency closed-loop detection link to obtain the real-time frequency of the power grid.
2. The method as claimed in claim 1, wherein the power grid synchronous phase fast open loop detection link comprises the following steps:
(1) detection of network voltage signals by means of voltage sensorsU a、U b、U c；
(2) The detected grid voltage signalU a、U b、U cSynchronous rotating coordinate transformation is carried out through a synchronous rotating coordinate transformation module to obtain a voltage signal under a two-phase rotating coordinate systemU d 、U q ；
(3) If high-frequency noise or harmonic components exist in the acquired power grid voltage signal, a filter module needs to be added behind the synchronous rotation coordinate transformation module to filter the output signal in the step (2) so as to eliminate the influence of the noise and the harmonic;
(4) obtained according to step (3)U d、U qSelecting correct one from the judgment conditionsθ exThe judgment conditions are as follows: if it isU d>0 andU q>0, thenθ ex= 0; if it isU d<0, thenθ ex= pi; if it isU d>0 andU q<0, thenθ ex=2π；
(5) Obtaining parameters according to the steps (3) and (4)U d 、U q 、θ ex Calculating the real-time amplitude and phase of the power grid voltage by combining an amplitude formula and a phase formula; wherein, the amplitude calculation formula is as follows:the phase calculation formula is:(ii) a Wherein,ω s tnamely the power frequency phase; arctan (U q/U d)+θ exI.e. the difference frequency phase.
3. The method as claimed in claim 1, wherein the difference frequency phase calculation unit comprises the following steps:
(1) the extracted difference frequency phase is recorded asxIts delay by one sampling period is noted asyCounting the periodnIs set to 0;
(2) comparisonxAndythe size of (A), ify-x) Is greater than the threshold value M (the theoretical value of M is 2 pi, considering the error caused by the discrete sampling process, the value of M is slightly less than 2 pi, the larger the sampling period is, the smaller the threshold value is), then the period counternIncrease by 1, otherwise notnAccumulating to output continuous phase information as phase, wherein phase =x+2*π*n。
4. A method for fast detecting the frequency of a power grid with high accuracy and anti-noise interference according to claim 1, wherein the frequency closed loop detection process comprises the following steps:
(1) the delay of the output phase of the difference frequency phase calculation link by one sampling period is recorded asθ；
(2) Outputting the step (1)θAs input signal for closed-loop regulation, the output of which is integrated as feedback signalθ feedbackThe difference value of the two signals is used as an output signal of closed loop regulation after PI regulation, and the output signal is divided by 2 PI to obtain a difference frequency deltaf；
(3) Will difference frequency deltafThe real frequency of the power grid can be obtained by superposing the power frequency (50 Hz in China)f。
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Cited By (3)
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| CN112151065A (en) * | 2019-06-28 | 2020-12-29 | 力同科技股份有限公司 | Method, device and equipment for detecting single tone signal frequency and computer storage medium |
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| CN112151065A (en) * | 2019-06-28 | 2020-12-29 | 力同科技股份有限公司 | Method, device and equipment for detecting single tone signal frequency and computer storage medium |
| CN112151065B (en) * | 2019-06-28 | 2024-03-15 | 力同科技股份有限公司 | Method, device, equipment and computer storage medium for detecting single-tone signal frequency |
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