CN113848383A - Method and system for rapidly calculating fundamental frequency signals of disturbed three-phase unbalanced system - Google Patents

Method and system for rapidly calculating fundamental frequency signals of disturbed three-phase unbalanced system Download PDF

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CN113848383A
CN113848383A CN202111075846.8A CN202111075846A CN113848383A CN 113848383 A CN113848383 A CN 113848383A CN 202111075846 A CN202111075846 A CN 202111075846A CN 113848383 A CN113848383 A CN 113848383A
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phase
signal
fundamental frequency
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CN113848383B (en
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刘书铭
叶华
郑晨
韩一江
王毅
唐钰政
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State Grid Corp of China SGCC
Institute of Electrical Engineering of CAS
Electric Power Research Institute of State Grid Henan Electric Power Co Ltd
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State Grid Corp of China SGCC
Institute of Electrical Engineering of CAS
Electric Power Research Institute of State Grid Henan Electric Power Co Ltd
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    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
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    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract

The application discloses a method and a system for rapidly calculating a fundamental frequency signal of a disturbed three-phase unbalanced system, wherein the method comprises the following steps of 1: acquiring three-phase signals of a power distribution network of the disturbed three-phase unbalanced system; step 2: analyzing the three-phase signals to obtain corresponding three-phase complex signals under a static coordinate system; and step 3: constructing a synthetic value of the three-phase complex signal by adopting a sequence component method; and 4, step 4: separating out fundamental frequency components in the three-phase signals by adopting discrete Fourier transform based on the synthesized value; and 5: and on the basis of the step 4, calculating fundamental frequency components in the three-phase signals by adopting recursive discrete Fourier transform. The invention adopts the recursive discrete Fourier transform to calculate the fundamental frequency component in the three-phase signals of the power distribution network, accelerates the separation and calculation speed of the fundamental frequency signals of the disturbed three-phase unbalanced system, and provides an algorithm basis for the voltage sag analysis of the main fundamental frequency signals of the power distribution network.

Description

Method and system for rapidly calculating fundamental frequency signals of disturbed three-phase unbalanced system
Technical Field
The invention belongs to the technical field of power systems and automation thereof, and relates to a method and a system for quickly calculating a fundamental frequency signal of a disturbed three-phase unbalanced system.
Background
Large-scale distributed new energy sources such as wind power and photovoltaic power generation are generally connected to a power distribution system in a single-phase or three-phase mode through a power electronic converter. Similarly, charging and discharging of an electric vehicle also requires the inverter device to interact with the active power distribution system. Based on the high frequency switching characteristics of power electronic devices, the transient dynamic characteristics of modern power distribution systems are broadband characteristics, covering fundamental frequencies and multiple harmonics. Considering the broadband dynamic characteristics of a three-phase alternating current system, the detection and analysis of fundamental frequency and multiple harmonics of three-phase voltage and current of the three-phase alternating current system are very important. Whether the detection is accurate or not affects the feedback control, the power quality analysis and the like of the power electronic device, and further affects the safety and the stability of distributed wind power generation, photovoltaic power generation and charging and discharging of the electric automobile.
The power electronic device acquires three-Phase alternating-current voltage, tracks a system fundamental frequency component in a synchronous coordinate system, and further realizes synchronous operation with a power distribution system through a Phase Locked Loop (PLL). In view of the instantaneous tracking of the phase-locked loop on the frequency of the ac system, it is difficult to obtain the fundamental frequency component, and the phase-locked loop is sensitive to unbalanced signals and irregular waveforms. The existing detection method can be used for detecting the fundamental frequency component of the unbalanced system, but is easily influenced by higher harmonics and cross harmonics.
Fourier Transform (DFT) is widely used for detection of fundamental frequency and harmonic components of a single-phase signal. Usually, PLL and DFT are combined to extract the fundamental frequency components of the three-phase system, however, the fundamental frequency components extracted by this method need to be further separated into positive sequence and negative sequence components, which seriously affects the detection and analysis speed.
Disclosure of Invention
In order to solve the defects in the prior art, the application provides a method and a system for rapidly calculating a fundamental frequency signal of a disturbed three-phase unbalanced system, a Recursive Discrete Fourier Transform (RDFT) algorithm is adopted to analyze the three-phase signal, the fundamental frequency signal can be detected on line, the detection speed is increased, the method and the system can be better suitable for the operation conditions of a power distribution system comprising a high-proportion distributed power supply and a high-proportion power electronic device, the fundamental frequency and harmonic frequency components of a three-phase input signal can be rapidly and accurately detected, the difficult problems of detection and analysis of the fundamental frequency and multiple harmonics of the three-phase system are solved, and the power grid friendly access of distributed wind power, photovoltaic power generation and electric vehicle charging and discharging facilities is realized.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a method for quickly calculating a fundamental frequency signal of a disturbed three-phase unbalanced system comprises the following steps:
step 1: acquiring three-phase signals of a power distribution network of the disturbed three-phase unbalanced system;
step 2: analyzing the three-phase signals to obtain corresponding three-phase complex signals under a static alpha-beta coordinate system;
and step 3: constructing a synthetic value of the three-phase complex signal by adopting a sequence component method;
and 4, step 4: separating out fundamental frequency components in the three-phase signals by adopting discrete Fourier transform based on the synthesized value;
and 5: and on the basis of the step 4, calculating fundamental frequency components in the three-phase signals by adopting recursive discrete Fourier transform.
The invention further comprises the following preferred embodiments:
preferably, in step 1, a low-pass infinite impulse response filter based on an ellipse approximation algorithm is adopted to collect the analog signal, and a three-phase signal of the power distribution network of the disturbed three-phase unbalanced system is obtained.
Preferably, in step 2, the three-phase signal is analyzed by using a second-order generalized integrator or hilbert transform, so as to obtain a corresponding three-phase complex signal in a stationary α - β coordinate system.
Preferably, in step 2, the disturbed three-phase unbalanced signal of the power distribution network is used as an input quantity of a second-order generalized integrator, and the resonant frequency ω is set0And outputting real parts and imaginary parts of the three-phase unbalanced signals under a static alpha-beta coordinate system, and forming three-phase complex signals by adopting the real parts and the imaginary parts.
Preferably, in the second-order generalized integrator, the real and imaginary transfer functions of the α - β axes for three-phase signals of the power distribution network a, b and c are as follows:
Figure BDA0003262148140000021
Figure BDA0003262148140000022
Figure BDA0003262148140000023
in the formula, ω0The second-order generalized integrator is the resonance frequency, s is an integral operator, and K is the transfer function gain, namely the damping ratio;
xain、xbin、xcinrespectively are a phase signal, b phase signal and c phase signal of the power distribution network;
xaα、xbα、xcαthe alpha-axis real parts of the a-phase signal, the b-phase signal and the c-phase signal generated by the second-order generalized integrator are respectively;
xaβ、xbβ、xcβrespectively generating beta-axis imaginary parts of a phase signal, a phase signal and a phase signal which are generated by a second-order generalized integrator;
and the real part and the imaginary part are adopted to form the following three-phase complex signals: .
x a＝xaα+jxaβ，x b＝xbα+jxbβ，x c＝xcα+jxcβ (12)
In the formula (I), the compound is shown in the specification,x a、x b、x crespectively a, b and c phase complex signals under a static alpha-beta coordinate system.
Preferably, in step 3, the vectors are sorted by using a sequence component method
Figure BDA0003262148140000031
And vectorx a,x b，x c]TMultiplying to obtain a composite value of the three-phase complex signals:
Figure BDA0003262148140000032
in the formula (I), the compound is shown in the specification,x αβthe composite value of the three-phase complex signals of the power distribution network under the static alpha-beta coordinate system.
Preferably, in step 4, the product obtained in step 3 is subjected tox αβSampling a signal, extracting N sampling values under one power frequency period, wherein N is an even number, and assuming that the N sampling values are respectively at N moments, namely T is (k-N) Ts，...，t＝(k-1)TsAnd T issFor the sampling interval time, kTsK is a sampling count value at the current sampling moment;
taking the sampling value as the input of Discrete Fourier Transform (DFT), wherein the DFT expression is as follows:
Figure BDA0003262148140000033
c is the harmonic frequency of discrete Fourier transform, and n is the counting value of the adopted numerical value;
when c is 1, equation (4) is a fundamental frequency component in the three-phase signal.
Preferably, in step 4, the product obtained in step 3 is subjected tox αβAnd sampling the signal, and extracting N sampling values in one power frequency period, wherein N is more than or equal to 2 and less than or equal to 50, and N is an even number.
Preferably, in step 5, the formula (4) is improved by using a recursive discrete fourier transform to calculate fundamental frequency components in the three-phase signal, specifically:
based on equation (4) in step 4, the fourier spectrum calculation formula for the current sampling instant is written in columns:
Figure BDA0003262148140000041
according to the formula (8), obtaining a Fourier spectrum calculation formula at any time, and further obtaining the following recursion formula:
Figure BDA0003262148140000042
and when c is 1, extracting the latest value and the stored value in the sampling period, and calculating the fundamental frequency component in the three-phase signal of the power distribution network by a recursive formula (9).
The invention also discloses a system for rapidly calculating the base frequency signals of the disturbed three-phase unbalanced system, which comprises a signal acquisition module, a signal analysis module, a signal synthesis module, a DFT module and an RDFT module;
the signal acquisition module is used for acquiring three-phase signals of a power distribution network of the disturbed three-phase unbalanced system;
the signal analysis module is used for analyzing the three-phase signals to obtain corresponding three-phase complex signals under a static alpha-beta coordinate system;
the signal synthesis module is used for constructing a synthetic value of the three-phase complex signal by adopting a sequence component method;
the DFT module is used for separating fundamental frequency components in the three-phase signals by adopting discrete Fourier transform based on the synthesized value;
and the RDFT module is used for calculating the fundamental frequency component in the three-phase signal by adopting recursive discrete Fourier transform on the basis of the DFT module.
The beneficial effect that this application reached:
the invention adopts the low-pass infinite impulse response filter based on the ellipse approximation algorithm to collect the analog signal, the filter can filter the high-frequency noise in the signal, has good frequency selectivity and real-time performance, and can meet the subsequent rapid calculation requirement;
according to the invention, a second-order generalized integrator or Hilbert transform is selected to analyze the three-phase signals according to actual conditions to obtain corresponding three-phase complex signals under a static alpha-beta coordinate system, and further, a sequence component method is applied to complex analysis signal calculation, so that the asymmetry problem can be better solved;
in order to accelerate the separation and calculation speed of the disturbed three-phase unbalanced system fundamental frequency signal, the invention adopts recursive discrete Fourier transform to calculate the fundamental frequency component in the three-phase signal of the power distribution network, thereby realizing the rapid calculation of the disturbed three-phase unbalanced system fundamental frequency signal and providing an algorithm basis for the voltage sag analysis of the main fundamental frequency signal of the power distribution network.
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FIG. 1 is a flow chart of a method for rapidly calculating fundamental frequency signals of a disturbed three-phase unbalanced system according to the present invention;
FIG. 2 is a block diagram illustrating a Second Order Generalized Integrator (SOGI) topology according to an embodiment of the present invention.
Detailed Description
The present application is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present application is not limited thereby.
As shown in fig. 1, the method for rapidly calculating the fundamental frequency signal of the disturbed three-phase unbalanced system of the present invention includes the following steps:
step 1: acquiring three-phase signals of a power distribution network of the disturbed three-phase unbalanced system;
in specific implementation, a low-pass infinite impulse response filter based on an ellipse approximation algorithm is adopted to collect analog signals, and three-phase signals of the power distribution network of the disturbed three-phase unbalanced system are obtained.
The filter can filter high-frequency noise in signals, has good frequency selectivity and real-time performance, and can meet subsequent rapid calculation requirements.
Step 2: analyzing the three-phase signals by adopting a second-order generalized integrator to obtain corresponding three-phase complex signals under a static alpha-beta coordinate system;
the three-phase signals can also be analyzed by using Hilbert transform to obtain corresponding three-phase complex signals under a static alpha-beta coordinate system. The second-order generalized integrator is easier to implement than using the hilbert transform.
Aiming at three-phase unbalanced signals after disturbance of the power distribution network, a Second-Order Generalized Integrator (SOGI) is adopted to process each phase signal of the power distribution network respectively in the step, so that three-phase real and imaginary parts are obtained, and three-phase complex signals are constructed.
The SOGI algorithm has a simple structure, can well inhibit higher harmonics in a power distribution network, and provides an algorithm basis for analyzing the frequency spectrum and frequency fast detection of a three-phase unbalanced system.
In specific implementation, a second-order generalized integrator as shown in fig. 2 is used to generate an α - β axis complex analysis signal, specifically:
three-phase measurement signals (such as voltage or current, represented by x) of an alternating current port of the power electronic converter are used as input quantities of a second-order generalized integrator, and a resonant frequency omega is set0The real and imaginary variables of the alpha-beta axis, i.e. x, are outputαAnd xβ。
For the phase signals of a, b and c of the power distribution network respectively, the transfer functions of the column writing alpha-beta axis real and imaginary part signals are as follows:
Figure BDA0003262148140000061
Figure BDA0003262148140000062
Figure BDA0003262148140000063
in the formula, ω0Is the resonant frequency of the second-order generalized integrator, s is the integral operator, K is the gain of the transfer function, i.e. the damping ratio, xain、xbinAnd xcinThree-phase physical continuous signals, x, of the distribution networkaα、xbαAnd xcαAlpha-axis real part signal, x, generated for a second-order generalized integratoraβ、xbβAnd xcβRespectively, the beta-axis imaginary part signals generated by the second-order generalized integrator.
On the basis, a, b and c phase complex signals under a static alpha-beta coordinate system are constructed, namely
x a＝xaα+jxaβ，x b＝xbα+jxbβ，x c＝xcα+jxcβ (12)
In the formula (I), the compound is shown in the specification,x a、x bandx crespectively a, b and c complex signals under a static alpha-beta coordinate system.
And step 3: constructing a synthetic value of the three-phase complex signal of the power distribution network by adopting a sequence component method;
in order to process the three-phase complex signal obtained in step 2, a sequence component method is generally adopted. Compared with the traditional sequence component usage, the sequence component method is applied to the computation of complex analytic signals, can better handle the asymmetry problem, and specifically comprises the following steps:
will vector
Figure BDA0003262148140000064
And vectorx a,x b，x c]TMultiplying to obtain a composite value of the three-phase complex signals as follows:
Figure BDA0003262148140000065
in the formula (I), the compound is shown in the specification,x αβthe composite value of the three-phase complex signals of the power distribution network under the static alpha-beta coordinate system.
Will be provided withx αβExpressed as complex envelope values in a rotated alpha-beta coordinate system, as follows:
Figure BDA0003262148140000066
in the formula (I), the compound is shown in the specification,
Figure BDA0003262148140000067
the complex envelope value of the three-phase signal of the power distribution network under the alpha-beta coordinate system is rotated, h is the harmonic frequency in the three-phase signal of the power distribution network, and omega0The power frequency of the power distribution network is the same as the resonant frequency of the second-order generalized integrator.
Accordingly, the number of the first and second electrodes,
Figure BDA0003262148140000071
can be derived from the formula (2) as follows
Figure BDA0003262148140000072
In the formula (I), the compound is shown in the specification,
Figure BDA0003262148140000073
and
Figure BDA0003262148140000074
respectively are complex envelope values of three-phase signals of a distribution network a, b and c,
Figure BDA0003262148140000075
Figure BDA0003262148140000076
and
Figure BDA0003262148140000077
the phase angles of the three-phase signals of the power distribution network a, b and c at the initial sampling time are respectively, and h is the harmonic frequency in the three-phase signals of the power distribution network.
And 4, step 4: based on the composite value, discrete Fourier transform is adopted to separate fundamental frequency components in three-phase signals of the power distribution network
Steps 2 and 3 are analog signal acquisition and processing, while this step performs digital signal processing, i.e., the output of step 3x αβSampling a signal:
extracting N sampling values under one power frequency period, wherein N is an even number, and assuming that the N sampling values stored in the sampling are respectively at N moments, namely T ═ k-N Ts，...，t＝(k-1)TsAnd T issFor the sampling interval time, kTsIs the current sampling instant.
According to the Nyquist sampling theorem, the discrete Fourier transform can only separate Nf for N sampling values0Sub-harmonic, f0The power frequency of the power distribution system is 50 Hz.
Because the invention only focuses on low frequency, especially fundamental frequency components, N is more than or equal to 2 under one power frequency period, namely N is not necessarily too large, and N is recommended to be set between 2 and 50 considering that the PWM frequency of a port of the converter is generally less than 2500 HZ. Based on step 3, formula (2) can be rewritten as
Figure BDA0003262148140000078
Taking the discrete sample value of equation (8) as the input of the discrete fourier transform DFT, the DFT expression can be written as:
Figure BDA0003262148140000079
further, formula (14) may be substituted for formula (4):
Figure BDA00032621481400000710
formula (15) may be further organized as:
Figure BDA00032621481400000711
in the formula, k is a sampling count value, namely the kth sampling, c is the harmonic frequency of discrete Fourier transform, N is the number of sampling values in one power frequency period, and T is the number of sampling values in the power frequency periodsIs a sampling time interval, h is a harmonic count value, n is a count value using numerical values,
Figure BDA0003262148140000081
the complex envelope value of the three-phase signal of the power distribution network under the alpha-beta coordinate system is rotated.
In this step, the following mathematical relationship is considered for equation (5):
Figure BDA0003262148140000082
the compound represented by formula (6) may be substituted for formula (5):
Figure BDA0003262148140000083
however, the h-th harmonic contained in the complex envelope value of the three-phase signal of the power distribution network on the right side of the equation (7) is unknown at present.
And 5: calculating fundamental frequency components in three-phase signals of the power distribution network by adopting recursive discrete Fourier transform;
in order to increase the calculation speed of solving the Fourier series by the discrete Fourier transform in the step 4, the formula (4) is improved by a recursive discrete Fourier transform method in the step 5, and the specific method is as follows.
Based on equation (4) in step 4, the fourier spectrum calculation formula for the current sampling instant is written in columns:
Figure BDA0003262148140000084
like equation (8), the following fourier spectrum calculation formula for the next sampling instant is written:
Figure BDA0003262148140000085
further combining equation (8) with equation (16), the recursive equation can be obtained as follows:
Figure BDA0003262148140000086
when c is 1, the latest value and the stored value in the sampling period are extracted, and the fundamental frequency component in the three-phase signal of the power distribution network can be quickly and conveniently calculated by the recursive formula (9).
The invention discloses a system for quickly calculating a base frequency signal of a disturbed three-phase unbalanced system, which comprises a signal acquisition module, a signal analysis module, a signal synthesis module, a DFT module and an RDFT module;
the signal acquisition module is used for acquiring three-phase signals of a power distribution network of the disturbed three-phase unbalanced system;
the signal analysis module is used for analyzing the three-phase signals to obtain corresponding three-phase complex signals under a static alpha-beta coordinate system;
the signal synthesis module is used for constructing a synthetic value of the three-phase complex signal by adopting a sequence component method;
the DFT module is used for separating fundamental frequency components in the three-phase signals by adopting discrete Fourier transform based on the synthesized value;
and the RDFT module is used for calculating the fundamental frequency component in the three-phase signal by adopting recursive discrete Fourier transform on the basis of the DFT module.
In conclusion, in order to accelerate the separation calculation speed of the disturbed three-phase unbalanced system fundamental frequency signal, the invention adopts the recursive discrete Fourier transform to calculate the fundamental frequency component in the three-phase signal of the power distribution network, thereby realizing the rapid calculation of the disturbed three-phase unbalanced system fundamental frequency signal and providing an algorithm basis for the voltage sag analysis of the main fundamental frequency signal of the power distribution network.
The present applicant has described and illustrated embodiments of the present invention in detail with reference to the accompanying drawings, but it should be understood by those skilled in the art that the above embodiments are merely preferred embodiments of the present invention, and the detailed description is only for the purpose of helping the reader to better understand the spirit of the present invention, and not for limiting the scope of the present invention, and on the contrary, any improvement or modification made based on the spirit of the present invention should fall within the scope of the present invention.

Claims (10)

1. A method for quickly calculating a fundamental frequency signal of a disturbed three-phase unbalanced system is characterized by comprising the following steps:
the method comprises the following steps:
step 1: acquiring three-phase signals of a power distribution network of the disturbed three-phase unbalanced system;
step 2: analyzing the three-phase signals to obtain corresponding three-phase complex signals under a static alpha-beta coordinate system;
and step 3: constructing a synthetic value of the three-phase complex signal by adopting a sequence component method;
and 4, step 4: separating out fundamental frequency components in the three-phase signals by adopting discrete Fourier transform based on the synthesized value;
and 5: and on the basis of the step 4, calculating fundamental frequency components in the three-phase signals by adopting recursive discrete Fourier transform.
2. The method for rapidly calculating the fundamental frequency signal of the disturbed three-phase unbalanced system according to claim 1, wherein the method comprises the following steps:
in the step 1, a low-pass infinite impulse response filter based on an ellipse approximation algorithm is adopted to collect analog signals, and three-phase signals of a power distribution network of the disturbed three-phase unbalanced system are obtained.
3. The method for rapidly calculating the fundamental frequency signal of the disturbed three-phase unbalanced system according to claim 1, wherein the method comprises the following steps:
in step 2, the three-phase signals are analyzed by using a second-order generalized integrator or Hilbert transform to obtain corresponding three-phase complex signals under a static alpha-beta coordinate system.
4. The method for rapidly calculating the fundamental frequency signal of the disturbed three-phase unbalanced system according to claim 1, wherein the method comprises the following steps:
in the step 2, the three-phase unbalanced signal after the disturbance of the power distribution network is used as the input quantity of a second-order generalized integrator, and then the resonant frequency omega is set0To output real and imaginary parts of the three-phase unbalanced signal under a static alpha-beta coordinate system, and the real and imaginary parts are adopted to form a three-phase complex signal.
5. The method for rapidly calculating the fundamental frequency signal of the disturbed three-phase unbalanced system according to claim 4, wherein the method comprises the following steps:
in the second-order generalized integrator, the real and imaginary part transfer functions of the alpha-beta axis for three-phase signals of a, b and c of the power distribution network are as follows:
Figure FDA0003262148130000011
Figure FDA0003262148130000021
Figure FDA0003262148130000022
in the formula, ω0The second-order generalized integrator is the resonance frequency, s is an integral operator, and K is the transfer function gain, namely the damping ratio;
xain、xbin、xcinrespectively are a phase signal, b phase signal and c phase signal of the power distribution network;
xaα、xbα、xcαthe alpha-axis real parts of the a-phase signal, the b-phase signal and the c-phase signal generated by the second-order generalized integrator are respectively;
xaβ、xbβ、xcβrespectively generating beta-axis imaginary parts of a phase signal, a phase signal and a phase signal which are generated by a second-order generalized integrator;
and the real part and the imaginary part are adopted to form the following three-phase complex signals: .
xa＝xaα+jxaβ，x b＝xbα+jxbβ，xc＝xcα+jxcβ (12)
In the formula (I), the compound is shown in the specification,x a、x b、x crespectively a, b and c phase complex signals under a static alpha-beta coordinate system.
6. The method for rapidly calculating the fundamental frequency signal of the disturbed three-phase unbalanced system according to claim 5, wherein the method comprises the following steps:
in step 3, a sequence component method is adopted to combine the vectors [1,
Figure FDA0003262148130000023
and vectorx a，x b，x c]TMultiplying to obtain a composite value of the three-phase complex signals:
Figure FDA0003262148130000024
in the formula (I), the compound is shown in the specification,x αβthe composite value of the three-phase complex signals of the power distribution network under the static alpha-beta coordinate system.
7. The method for rapidly calculating the fundamental frequency signal of the disturbed three-phase unbalanced system according to claim 6, wherein the method comprises the following steps:
in step 4, the product obtained in step 3 is subjected tox αβSampling a signal, extracting N sampling values under one power frequency period, wherein N is an even number, and assuming that the N sampling values are respectively at N moments, namely T is (k-N) Ts，...，t＝(k-1)TsAnd T issFor the sampling interval time, kTsK is a sampling count value at the current sampling moment;
taking the sampling value as the input of Discrete Fourier Transform (DFT), wherein the DFT expression is as follows:
Figure FDA0003262148130000031
c is the harmonic frequency of discrete Fourier transform, and n is the counting value of the adopted numerical value;
when c is 1, equation (4) is a fundamental frequency component in the three-phase signal.
8. The method for rapidly calculating the fundamental frequency signal of the disturbed three-phase unbalanced system according to claim 7, wherein the method comprises the following steps:
in step 4, the product obtained in step 3 is subjected tox αβAnd sampling the signal, and extracting N sampling values in one power frequency period, wherein N is more than or equal to 2 and less than or equal to 50, and N is an even number.
9. The method for rapidly calculating the fundamental frequency signal of the disturbed three-phase unbalanced system according to claim 7, wherein the method comprises the following steps:
in step 5, a recursive discrete fourier transform is adopted to improve the formula (4), and a fundamental frequency component in the three-phase signal is calculated, specifically:
based on equation (4), the column writes the fourier spectrum calculation equation for the current sampling instant:
Figure FDA0003262148130000032
according to the formula (8), obtaining a Fourier spectrum calculation formula at any time, and further obtaining the following recursion formula:
Figure FDA0003262148130000033
and when c is 1, extracting the latest value and the stored value in the sampling period, and calculating the fundamental frequency component in the three-phase signal of the power distribution network by a recursive formula (9).
10. The disturbed three-phase unbalanced system fundamental frequency signal fast calculation system of the disturbed three-phase unbalanced system fundamental frequency signal fast calculation method according to any one of claims 1 to 9, characterized in that:
the system comprises a signal acquisition module, a signal analysis module, a signal synthesis module, a DFT module and an RDFT module;
the signal acquisition module is used for acquiring three-phase signals of a power distribution network of the disturbed three-phase unbalanced system;
the signal analysis module is used for analyzing the three-phase signals to obtain corresponding three-phase complex signals under a static alpha-beta coordinate system;
the signal synthesis module is used for constructing a synthetic value of the three-phase complex signal by adopting a sequence component method;
the DFT module is used for separating fundamental frequency components in the three-phase signals by adopting discrete Fourier transform based on the synthesized value;
and the RDFT module is used for calculating the fundamental frequency component in the three-phase signal by adopting recursive discrete Fourier transform on the basis of the DFT module.
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