CN110988469B - Rapid harmonic detection method - Google Patents

Rapid harmonic detection method Download PDF

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CN110988469B
CN110988469B CN201911111057.8A CN201911111057A CN110988469B CN 110988469 B CN110988469 B CN 110988469B CN 201911111057 A CN201911111057 A CN 201911111057A CN 110988469 B CN110988469 B CN 110988469B
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harmonic
phase
sampling
component amplitude
detection
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CN110988469A (en
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叶宗彬
张延澳
任思远
邓先明
谭国俊
于东升
梁睿
耿程飞
张经纬
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China University of Mining and Technology CUMT
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    • G01—MEASURING; TESTING
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Abstract

The invention discloses a rapid harmonic detection method, which comprises the following specific steps: a. sampling multiphase signals needing harmonic detection; b. calculating real and imaginary components of the spatial harmonics; c. and calculating the amplitude and phase angle of the spatial harmonic wave. The advantages are that: the time required by harmonic detection is shortened, and the storage space required by calculation is reduced.

Description

Rapid harmonic detection method
Technical Field
The invention relates to a rapid harmonic detection method.
Background
The harmonic analysis and detection technology is widely applied to the fields of power quality monitoring, electronic product production inspection, electrical equipment monitoring and the like, and is an important technical means for power grid monitoring, quality inspection and equipment monitoring.
In a power supply grid, harmonic waves are generated due to the input of a large number of nonlinear loads. With the rapid development of power electronic technology in recent years, many industrial enterprises introduce a large amount of impact loads, asymmetric loads and nonlinear loads, which inevitably generate harmonic pollution when being connected to a power grid. Therefore, harmonic analysis and detection are carried out on the voltage and current signals of the power supply grid, the power quality condition of the power grid can be better observed, and harmonic suppression and compensation are further carried out on the power grid.
Currently, the most widely used techniques for harmonic analysis are Discrete Fourier Transform (DFT), Fast Fourier Transform (FFT), and sliding window discrete fourier transform (SDFT). However, these algorithms require a long time to obtain effective information of the harmonics. This patent aims at providing a quick harmonic detection means, shortens the time that the harmonic detected greatly, provides technical support for places such as power grid electric energy quality treatment equipment carries out harmonic suppression and compensation.
Disclosure of Invention
In order to solve the problems, the invention provides a rapid harmonic detection method, which greatly shortens the time of harmonic detection and provides technical support for occasions such as harmonic suppression and compensation of power grid power quality management equipment.
The invention adopts the following technical scheme for solving the technical problems:
the invention provides a rapid harmonic detection method, which comprises the following specific steps:
step 1, performing equal-interval signal sampling on an m symmetric circuit with a period of T and needing harmonic detection;
step 2, respectively storing the signal data obtained by sampling in the step 1 into m storage depths of
Figure BDA0002272722370000011
N is the number of sampling points in T time;
step 3, when the sampling serial number
Figure BDA0002272722370000012
Then, the real component amplitude and the imaginary component amplitude of the nth harmonic of each phase are iterated by the formula:
Figure BDA0002272722370000013
wherein k is the serial number of the sampling point; a (k) is the real component amplitude of the nth harmonic of each phase of detection signal at k sampling points; b (k) is the imaginary component amplitude of the nth harmonic of each phase of detection signal at k sampling points; u shapej(k) Sampling value of j phase detected signal when k sampling point is;
when in use
Figure BDA0002272722370000021
And then FIFO updates data, and the real component amplitude and the imaginary component amplitude of the nth harmonic of each phase are iterated by the formula:
Figure BDA0002272722370000022
Figure BDA0002272722370000023
step 4, the amplitude U of the nth harmonic of the j phase signal needing harmonic detectionjnAngle of sum
Figure BDA0002272722370000024
Calculating the formula:
Figure BDA0002272722370000025
Figure BDA0002272722370000026
as a further technical scheme of the invention, the sampling frequency in the step 1 is fs＝N/T。
As a further technical scheme of the invention, in step 2, the latest FIFO is stored in each FIFO
Figure BDA0002272722370000027
The resulting signal data is sampled.
Compared with the prior art, the invention adopting the technical scheme has the following technical effects: the invention greatly shortens the harmonic detection time of the multiphase symmetrical circuit and provides technical conditions for quick response and quick treatment of the power quality treatment device.
Drawings
FIG. 1 is a diagram of phase a current on the AC side of a three-phase uncontrolled rectifier bridge and 5 th harmonic detection waveforms of the present invention.
FIG. 2 is a waveform diagram of phase a current on the AC side of a three-phase uncontrolled rectifier bridge, 5 th harmonic detection of the present invention and 5 th harmonic detection of full-period sliding window iterative DFT.
FIG. 3 is a waveform diagram of phase a current on the AC side of a three-phase uncontrolled rectifier bridge, 5 th harmonic detection of the present invention and 5 th harmonic detection of half-cycle sliding window iterative DFT.
FIG. 4 is a waveform diagram of phase a current on the AC side of a three-phase uncontrolled rectifier bridge and 7 th harmonic detection of the present invention.
FIG. 5 is a waveform diagram of the phase a current on the AC side of the three-phase uncontrolled rectifier bridge, the 7 th harmonic detection of the present invention and the 7 th harmonic detection of the full-period sliding window iterative DFT.
FIG. 6 is a waveform diagram of the phase a current on the AC side of the three-phase uncontrolled rectifier bridge, the 7 th harmonic detection of the present invention and the 7 th harmonic detection of the half-cycle sliding window iterative DFT.
FIG. 7 is a flow chart of the method of the present invention.
Detailed Description
The technical scheme of the invention is further explained in detail by combining the attached drawings:
this patent aims at providing a quick harmonic detection means, shortens the time that the harmonic detected greatly, provides technical support for places such as power grid electric energy quality treatment equipment carries out harmonic suppression and compensation.
In order to achieve the above purpose, as shown in fig. 7, the technical solution of the present invention includes the following steps:
a. for signal U with period T of m symmetrical circuits needing harmonic detection1,U2,…,UmSampling is carried out with a sampling frequency fsN is the number of sampling points in a period of T time. For m-phase signal U generated by symmetrical circuit1,U2,…,UmObtaining sampling data after sampling at equal intervals: u shape1(k),U2(k),…,Um(k) K is the sample point number, k is 1,2,3, …. And store it into m storage depths of
Figure BDA0002272722370000031
FIFO (first-in first-out memory)) Always keeping the latest in each FIFO
Figure BDA0002272722370000032
And (4) data.
b. When the sampling sequence number
Figure BDA0002272722370000033
Then, the real component amplitude and the imaginary component amplitude of the nth harmonic of each phase are iterated by the formula:
Figure BDA0002272722370000034
Figure BDA0002272722370000035
wherein k is the serial number of the sampling point; a (k) is the real component amplitude of the nth harmonic of each phase of detection signal at k sampling points; b (k) is the imaginary component amplitude of the nth harmonic of each phase of detection signal at k sampling points; u shapej(k) Sampling value of j phase detected signal when k sampling point is;
c. when the sampling sequence number
Figure BDA0002272722370000036
The FIFO updates the data. Move in the latest sampled data U1(k),U2(k),…,Uj(k),…,Um(k) Moving out the current oldest data
Figure BDA0002272722370000037
Figure BDA0002272722370000038
Where j is 1, 2.
At this time, the real component amplitude and the imaginary component amplitude of the nth harmonic of each phase are iteratively formulated as:
Figure BDA0002272722370000041
Figure BDA0002272722370000042
d. amplitude U of nth harmonic of j-th phase detection signal to be subjected to harmonic detectionjnAngle of sum
Figure BDA0002272722370000043
Calculated by the following formula;
Figure BDA0002272722370000044
Figure BDA0002272722370000045
the traditional harmonic detection algorithm needs at least half power grid power frequency period, and the effective information of the harmonic can be obtained only by one power grid power frequency period. Due to the adoption of the scheme, only m symmetrical circuits need to be subjected to
Figure BDA0002272722370000046
The effective information of the harmonic can be obtained in one power grid power frequency period.
The following two examples are used to verify the effect of the present invention in rapidly performing harmonic detection.
Example 1 three-phase symmetrical circuit a-phase current 5 th harmonic current detection
The system parameters are as follows: 380V/50Hz three-phase alternating current at the power grid side; the load side is bridged with a pure resistance load through three-phase uncontrolled rectification, and R is 30 omega; the sampling frequency is 15kHz, and 300 sampling points exist in one power grid power frequency period; the oscilloscope model is Agilent MSO-X3014A.
1. Starting a 380V three-phase power supply to supply power to a three-phase uncontrolled rectifying circuit;
2. carrying out equal interval data sampling on three-phase current signals of a, b and c at the alternating current side of the three-phase uncontrolled rectifier bridge: i isa(k)，Ib(k)，Ic(k)，k is the sample point number, k is 1,2,3, …. Storing the sampling data into 3 FIFOs (first-in first-out memories) with the storage depth of 50 respectively, and always storing the latest 50 data in each FIFO;
3. when the sampling sequence number k is less than or equal to 50, the real component amplitude and the imaginary component amplitude of each phase of the 5 th harmonic are subjected to an iterative formula:
Figure BDA0002272722370000051
Figure BDA0002272722370000052
wherein k is the serial number of the sampling point; a (k) is the real component amplitude of the 5 th harmonic of each phase of detection signal at k sampling points; b (k) the magnitude of the imaginary component of the 5 th harmonic of each phase of the detected signal; u shapej(k) Sampling value of j phase detected signal when k sampling point is;
4. when the sampling serial number k is larger than 50, FIFO updates data, and calculates the iterative formula of the real component amplitude and the imaginary component amplitude of the 5 th harmonic of the a-phase current:
Figure BDA0002272722370000053
Figure BDA0002272722370000054
amplitude I of the 5 th harmonic of phase current aa5Angle of sum
Figure BDA0002272722370000055
Obtained from the following equation:
Figure BDA0002272722370000056
Figure BDA0002272722370000057
6. the fast harmonic detection method of the invention detects the 5 th harmonic of the phase current (shown as the upper waveform diagram in fig. 1 to 3) of the three-phase uncontrolled rectifier circuit a, and the harmonic detection result is shown as the lower waveform diagram in fig. 1, the middle waveform diagram in fig. 2 and the middle waveform diagram in fig. 3.
As can be seen from the lower waveform diagram in fig. 1, under the fast harmonic detection method of the present invention, the 5 th harmonic can be stably output after 1/6 cycles of delay. Compared with the traditional full-period sliding window DFT algorithm (such as a waveform diagram at the lower part in fig. 2) and the half-period sliding window DFT algorithm (such as a waveform diagram at the lower part in fig. 3), the method greatly shortens the harmonic detection time and improves the real-time performance of the harmonic detection of the three-phase symmetrical circuit on the basis of further reducing the calculated amount.
Example 2 phase a current 7 th harmonic current detection for three-phase symmetrical circuit
The system parameters are as follows: 380V/50Hz three-phase alternating current at the power grid side; the load side is bridged with a pure resistance load through three-phase uncontrolled rectification, and R is 30 omega; the sampling frequency is 15kHz, and 300 sampling points exist in one power grid power frequency period; the oscilloscope model is Agilent MSO-X3014A.
1. Starting a 380V three-phase power supply to supply power to a three-phase uncontrolled rectifying circuit;
2. carrying out equal interval data sampling on three-phase current signals of a, b and c at the alternating current side of the three-phase uncontrolled rectifier bridge: i isa(k)，Ib(k)，Ic(k) K is the sample point number, k is 1,2,3, …. Respectively storing the data into 3 FIFOs (first-in first-out memories) with the storage depth of 50, and always storing the latest 50 data in each FIFO;
3. when the sampling sequence number k is less than or equal to 50, the real component amplitude and the imaginary component amplitude of each phase of the 7 th harmonic are subjected to an iterative formula:
Figure BDA0002272722370000061
Figure BDA0002272722370000062
wherein k is the serial number of the sampling point; a (k) is the real component amplitude of the 7 th harmonic of each phase of detection signal at k sampling points; b (k) the magnitude of the imaginary component of the 7 th harmonic of each phase of the detected signal; u shapej(k) Sampling value of j phase detected signal when k sampling point is;
4. when the sampling serial number k is larger than 50, FIFO updates data, and calculates the iterative formula of the real component amplitude and the imaginary component amplitude of the 7 th harmonic of the a-phase current:
Figure BDA0002272722370000071
Figure BDA0002272722370000072
5. detecting the amplitude I of the 7 th harmonic of the a-phase currenta7Angle of sum
Figure BDA0002272722370000073
Obtained from the following equation:
Figure BDA0002272722370000074
Figure BDA0002272722370000075
6. the fast harmonic detection method of the invention detects the 7 th harmonic of the phase current (shown as the upper waveform diagram in fig. 4 to 6) of the three-phase uncontrolled rectifier circuit a, and the harmonic detection results are shown as the lower waveform diagram in fig. 4, the middle waveform diagram in fig. 5 and the middle waveform diagram in fig. 6.
As can be seen from the lower waveform diagram in fig. 4, under the fast harmonic detection method of the present invention, the 7 th harmonic can be stably output after 1/6 cycles of delay. Compared with the traditional full-period sliding window DFT algorithm (such as the lower waveform diagram in FIG. 5) and the half-period sliding window DFT algorithm (such as the lower waveform diagram in FIG. 6), the method greatly shortens the harmonic detection time and improves the real-time performance of the harmonic detection of the three-phase symmetrical circuit on the basis of further reducing the calculated amount.
The method for rapidly detecting the harmonic waves is not only suitable for detecting the harmonic waves of the three-phase symmetrical circuit, but also suitable for detecting the harmonic waves of the multi-phase symmetrical circuit.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood that modifications and variations that can be achieved without inventive changes in the technical solutions of the present invention by those skilled in the art should fall within the scope of the claims of the present invention.

Claims (3)

1. A rapid harmonic detection method is characterized by comprising the following specific steps:
step 1, performing equal-interval signal sampling on an m symmetric circuit with a period of T and needing harmonic detection;
step 2, respectively storing the signal data obtained by sampling in the step 1 into m storage depths of
Figure FDA0002272722360000011
N is the number of sampling points in T time;
step 3, when the sampling serial number
Figure FDA0002272722360000012
Then, the real component amplitude and the imaginary component amplitude of the nth harmonic of each phase are iterated by the formula:
Figure FDA0002272722360000013
wherein k is the serial number of the sampling point; a (k) is k sample points each timeThe real component amplitude of the nth harmonic of the phase detection signal; b (k) is the imaginary component amplitude of the nth harmonic of each phase of detection signal at k sampling points; u shapej(k) Sampling value of j phase detected signal when k sampling point is;
when in use
Figure FDA0002272722360000014
And then FIFO updates data, and the real component amplitude and the imaginary component amplitude of the nth harmonic of each phase are iterated by the formula:
Figure FDA0002272722360000015
Figure FDA0002272722360000016
step 4, the amplitude U of the nth harmonic of the j phase signal needing harmonic detectionjnAngle of sum
Figure FDA0002272722360000017
Calculating the formula:
Figure FDA0002272722360000018
Figure FDA0002272722360000019
2. the fast harmonic detection method according to claim 1, wherein the sampling frequency in step 1 is fs＝N/T。
3. A fast harmonic detection method according to claim 1, characterized in that in step 2 the latest data is stored in each FIFO
Figure FDA00022727223600000110
The resulting signal data is sampled.
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