CN113848383B - 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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CN113848383B
CN113848383B CN202111075846.8A CN202111075846A CN113848383B CN 113848383 B CN113848383 B CN 113848383B CN 202111075846 A CN202111075846 A CN 202111075846A CN 113848383 B CN113848383 B CN 113848383B
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CN113848383A (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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Abstract

The application discloses a method and a system for rapidly calculating fundamental frequency signals of a disturbed three-phase unbalanced system, wherein the method comprises the following steps of: acquiring three-phase signals of a power distribution network of a disturbed three-phase unbalanced system; step 2: analyzing the three-phase signals to obtain corresponding three-phase complex signals under a static coordinate system; step 3: constructing a synthesized value of the three-phase complex signals by adopting a sequence component method; step 4: based on the synthesized value, separating out fundamental frequency components in the three-phase signals by adopting discrete Fourier transform; step 5: based on the step 4, a recursive discrete Fourier transform is adopted to calculate the fundamental frequency component in the three-phase signal. According to the invention, the fundamental frequency component in the three-phase signal of the power distribution network is calculated by adopting the recursive discrete Fourier transform, so that the separation and calculation speed of the fundamental frequency signal of the disturbed three-phase unbalanced system is increased, and an algorithm foundation is provided for the voltage sag analysis of the main fundamental frequency signal 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 rapidly calculating fundamental frequency signals of a disturbed three-phase unbalanced system.
Background
Large-scale distributed new energy sources such as wind power and photovoltaic power generation are commonly connected into a power distribution system in a single-phase or three-phase mode through a power electronic converter. Likewise, electric vehicle charging and discharging also requires the inverter device to interact with the active power distribution system. Based on the high frequency switching characteristics of the power electronics, the transient dynamics of modern power distribution systems exhibit broadband characteristics, covering fundamental frequencies and multiple harmonics. Considering the broadband dynamic characteristics of a three-phase alternating current system, it is important to detect and analyze fundamental frequency and multiple harmonics of three-phase voltage and current. Whether the detection is accurate or not influences feedback control, power quality analysis and the like of the power electronic device, and further influences safety and stability of distributed wind power, photovoltaic power generation and charging and discharging of the electric automobile.
The power electronics acquire three-phase ac voltages and track the fundamental frequency components of the system in a synchronous coordinate system, thereby achieving synchronous operation with the power distribution system through a phase locked loop (Phase Locked Loop, PLL). In view of the instantaneous tracking of the ac system frequency by the phase-locked loop, it is difficult to obtain the fundamental frequency component, and the phase-locked loop is sensitive to unbalanced signals and irregular waveforms. Existing detection methods, although capable of detecting the fundamental frequency component of an unbalanced system, are susceptible to higher harmonics and cross harmonics.
Fourier transforms (Discrete Fourier Transform, DFT) are widely used for fundamental and harmonic component detection of single phase signals. PLL and DFT are usually combined to perform extraction of fundamental frequency components of a three-phase system, however, the fundamental frequency components extracted by the method need to be further separated into positive sequence components 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 rapid calculation method and a rapid calculation system for a base frequency signal of a disturbed three-phase unbalanced system, which analyze the three-phase signal by adopting a recursive discrete Fourier transform (recursive discrete Fourier transform, RDFT) algorithm, can realize the on-line detection of the base frequency signal and improve the detection speed, can better adapt to the running condition of a power distribution system comprising a high-proportion distributed power supply and a high-proportion power electronic device, rapidly and accurately detect the base frequency and harmonic frequency components of the three-phase input signal, and solve the problems of detection and analysis of the base frequency and multiple harmonics of the three-phase system so as to realize the friendly access of a power grid of distributed wind power, photovoltaic power generation and electric automobile charging and discharging facilities.
In order to achieve the above object, the present invention adopts the following technical scheme:
a rapid calculation method for a base 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 a 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;
step 3: constructing a synthesized value of the three-phase complex signals by adopting a sequence component method;
step 4: based on the synthesized value, separating out fundamental frequency components in the three-phase signals by adopting discrete Fourier transform;
step 5: based on the step 4, a recursive discrete Fourier transform is adopted to calculate the fundamental frequency component in the three-phase signal.
The invention further comprises the following preferable schemes:
preferably, in step 1, an analog signal is acquired by using a low-pass infinite impulse response filter based on an elliptic approximation algorithm, so as to obtain a three-phase signal of a power distribution network of the disturbed three-phase unbalanced system.
Preferably, in step 2, the three-phase signal is resolved by using a second-order generalized integrator or hilbert transformation, so as to obtain a corresponding three-phase complex signal under a stationary α - β coordinate system.
Preferably, in step 2, the three-phase unbalanced signal after the power distribution network is disturbed is used as the input quantity of the second-order generalized integrator, and the resonant frequency omega is set 0 And outputting real and imaginary parts of the three-phase unbalanced signal under a static alpha-beta coordinate system, and adopting the real and imaginary parts to form a three-phase complex signal.
Preferably, in the second-order generalized integrator, the real and imaginary part transfer functions of the α - β axes for the three-phase signals of the power distribution network a, b, and c are:
Figure BDA0003262148140000021
Figure BDA0003262148140000022
Figure BDA0003262148140000023
wherein omega is 0 The resonance frequency of the second-order generalized integrator is s is an integration operator, and K is a transfer function gain, namely a damping ratio;
x ain 、x bin 、x cin the signals are respectively a phase signal, a b phase signal and a c phase signal of the power distribution network;
x aα 、x bα 、x cα alpha-axis real parts of a phase signal, b phase signal and c phase signal generated by a second-order generalized integrator respectively;
x aβ 、x bβ 、x cβ the imaginary parts of the beta axes of a phase signal, b phase signal and c phase signal generated by the second-order generalized integrator are respectively;
the real part and the imaginary part are adopted to form the following three-phase complex signals: .
x a ＝x aα +jx aβ ，x b ＝x bα +jx bβ ，x c ＝x cα +jx cβ (12)
In the method, in the process of the invention,x a 、x b 、x c the signals are a, b and c phases of complex signals under a static alpha-beta coordinate system.
Preferably, in step 3, the vector is applied by sequential component method
Figure BDA0003262148140000031
And vector [x a ,x b ，x c ] T Multiplying to obtain the composite value of the three-phase complex signal:
Figure BDA0003262148140000032
in the method, in the process of the invention,x αβ is the synthesized value of three-phase complex signals of the power distribution network under a static alpha-beta coordinate system.
Preferably, in step 4, the method obtained in step 3x αβ Sampling the signal, extracting N sampling values under a power frequency period, wherein N is an even number, and assuming that the N sampling values are respectively at N moments, namely t= (k-N) T s ，...，t＝(k-1)T s And T is s For sampling interval time, kT s K is the sampling count value for the current sampling time;
taking the sampling value as the input of a discrete Fourier transform DFT, the DFT expression is as follows:
Figure BDA0003262148140000033
c is the harmonic frequency of discrete Fourier transform, n is the count value of the adopted numerical value;
when c=1, equation (4) is a fundamental frequency component in the three-phase signal.
Preferably, in step 4, the method obtained in step 3x αβ Sampling signals to extract 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 recursive discrete fourier transform is used to modify equation (4) to calculate the fundamental frequency component in the three-phase signal, specifically:
based on equation (4) in step 4, the fourier spectrum calculation formula for the current sampling time is written in columns:
Figure BDA0003262148140000041
according to the formula (8), a Fourier spectrum calculation formula at any moment is obtained, and then the following recurrence formula is obtained:
Figure BDA0003262148140000042
when c=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 is calculated by a recursive formula (9).
The invention also discloses a system for rapidly calculating the fundamental 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 the 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 synthesis value of the three-phase complex signal by adopting a sequence component method;
the DFT module is used for separating out fundamental frequency components in the three-phase signals by adopting discrete Fourier transform based on the synthesized value;
the RDFT module is used for calculating fundamental frequency components in the three-phase signals 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 elliptic approximation algorithm to collect the analog signals, and the filter can filter out high-frequency noise in the signals, has good frequency selectivity and instantaneity, and can meet the subsequent rapid calculation requirement;
according to the invention, a second-order generalized integrator or Hilbert transformation is selected to analyze the three-phase signals according to actual conditions, so that corresponding three-phase complex signals under a static alpha-beta coordinate system are obtained;
the invention adopts recursive discrete Fourier transform to calculate the fundamental frequency components in the three-phase signals of the power distribution network so as to realize the rapid calculation of the fundamental frequency signals of the disturbed three-phase unbalanced system and provide an algorithm foundation for the voltage sag analysis of the main fundamental frequency signals of the power distribution network.
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FIG. 1 is a flow chart of a method for rapidly calculating a baseband signal of a disturbed three-phase unbalanced system according to the present invention;
fig. 2 is a schematic block diagram of a Second Order Generalized Integrator (SOGI) topology in 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 more clearly illustrating the technical solutions of the present invention and are not intended to limit the scope of protection of the present application.
As shown in FIG. 1, the method for rapidly calculating the fundamental frequency signal of the disturbed three-phase unbalanced system comprises the following steps:
step 1: acquiring three-phase signals of a power distribution network of a disturbed three-phase unbalanced system;
in the specific implementation, a low-pass infinite impulse response filter based on an elliptic approximation algorithm is adopted to collect analog signals, and three-phase signals of a power distribution network of a disturbed three-phase unbalanced system are obtained.
The filter can filter high-frequency noise in signals, has good frequency selectivity and instantaneity, 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 be analyzed by Hilbert transformation 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 the three-phase unbalanced signals of the power distribution network after being disturbed, a Second-order generalized integrator (Second-Order Generalized Integrator, SOGI) is adopted in the step to respectively process each phase of the power distribution network to obtain three-phase real and imaginary parts, and a three-phase complex signal is constructed.
The SOGI algorithm has a simple structure, can well inhibit higher harmonics in the power distribution network, and provides an algorithm foundation for analyzing the frequency spectrum and the frequency rapid detection of the three-phase unbalanced system.
In specific implementation, a second-order generalized integrator shown in fig. 2 is adopted to generate an alpha-beta axis complex analysis signal, and the specific steps are as follows:
three-phase measuring signals (such as voltage or current, represented by x) of an alternating-current side port of the power electronic converter are used as input quantity of a second-order generalized integrator, and the resonant frequency omega is set 0 Outputting real-imaginary variables of alpha-beta axis, i.e. x α And x β 。
The transfer functions of the alpha-beta axis real imaginary signals are written as follows for the power distribution networks a, b and c phase signals, respectively:
Figure BDA0003262148140000061
Figure BDA0003262148140000062
Figure BDA0003262148140000063
wherein omega is 0 Is the resonance frequency of the second-order generalized integrator, s is an integrating operator, K is the transfer function gain, i.e. the damping ratio, x ain 、x bin And x cin Three-phase physical continuous signals, x of the distribution network respectively aα 、x bα And x cα Alpha-axis real part signals, x respectively generated by second-order generalized integrator aβ 、x bβ And x cβ And respectively, the beta-axis imaginary signal generated by the second-order generalized integrator.
On the basis, a complex signal of a, b and c phases under a static alpha-beta coordinate system is constructed, namely
x a ＝x aα +jx aβ ，x b ＝x bα +jx bβ ，x c ＝x cα +jx cβ (12)
In the method, in the process of the invention,x a 、x b and (3) withx c The signals are complex signals of a, b and c phases under a static alpha-beta coordinate system respectively.
Step 3: constructing a synthesized value of three-phase complex signals 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 used. Compared with the traditional sequence component usage, the sequence component method is applied to complex analytic signal calculation, can better solve the problem of asymmetry, and specifically comprises the following steps:
vector is combined with
Figure BDA0003262148140000064
And vector [x a ,x b ，x c ] T Multiplying to obtain the synthesized value of the three-phase complex signal as follows:
Figure BDA0003262148140000065
in the method, in the process of the invention,x αβ is the synthesized value of three-phase complex signals of the power distribution network under a static alpha-beta coordinate system.
Will bex αβ Expressed as complex envelope values in the rotating α - β coordinate system, as follows:
Figure BDA0003262148140000066
in the method, in the process of the invention,
Figure BDA0003262148140000067
for the complex envelope value of the three-phase signal of the power distribution network under the rotation alpha-beta coordinate system, h is the harmonic frequency in the three-phase signal of the power distribution network, omega 0 For power frequency of distribution networkAnd is the same as the second-order generalized integrator resonant frequency described above.
In response to this, the control unit,
Figure BDA0003262148140000071
can be deduced from formula (2) as follows
Figure BDA0003262148140000072
In the method, in the process of the invention,
Figure BDA0003262148140000073
and->
Figure BDA0003262148140000074
Complex envelope values of three-phase signals of distribution networks a, b and c, respectively, < >>
Figure BDA0003262148140000075
Figure BDA0003262148140000076
And->
Figure BDA0003262148140000077
And 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 of the three-phase signals of the power distribution network.
Step 4: based on the synthesized 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, and the step performs digital signal processing, i.e. the output of step 3x αβ Sampling signals:
extracting N sampling values under a power frequency period, wherein N is an even number, and assuming that N numerical values stored by sampling are respectively at N moments, namely t= (k-N) T s ，...，t＝(k-1)T s And T is s For sampling interval time, kT s Is the current sampling instant.
According to the nyquist sampling theorem, for N samplesValue, discrete Fourier transform can only separate Nf 0 Subharmonic, f 0 The power frequency of the power distribution system is 50Hz.
Because the invention only focuses on low frequency, especially fundamental frequency components, N is more than or equal to 2 in one power frequency period, namely N is not needed to be too large, and N is recommended to be between 2 and 50 in consideration of that PWM modulation frequency of a converter port is generally less than 2500 HZ. Based on step 3, formula (2) is rewritable as
Figure BDA0003262148140000078
Taking the discrete sample value of equation (8) as an input to the discrete fourier transform DFT, the DFT expression can be written as:
Figure BDA0003262148140000079
further, substitution of formula (14) into formula (4) can be obtained:
Figure BDA00032621481400000710
formula (15) may be further finished as:
Figure BDA00032621481400000711
wherein k is the sampling count value, namely the kth sampling, c is the discrete Fourier transform harmonic frequency, N is the number of sampling values in one power frequency period, T s For the sampling time interval, h is the harmonic count value, n is the count value of the value,
Figure BDA0003262148140000081
is the complex envelope value of the three-phase signals of the power distribution network under the rotation alpha-beta coordinate system.
In this step, for equation (5), the following mathematical relationship is considered:
Figure BDA0003262148140000082
substitution of formula (6) into formula (5) yields:
Figure BDA0003262148140000083
however, the h-order harmonic contained in the complex envelope value of the three-phase signal of the power distribution network on the right side of the formula (7) is not known at present.
Step 5: calculating fundamental frequency components in three-phase signals of the power distribution network by adopting recursive discrete Fourier transform;
in order to accelerate the calculation speed of the discrete Fourier transform solution Fourier series in the step 4, the step 5 adopts a recursive discrete Fourier transform method to improve the formula (4), and the specific method is as follows.
Based on equation (4) in step 4, the fourier spectrum calculation formula for the current sampling time is written in columns:
Figure BDA0003262148140000084
in the same way as in the formula (8), the fourier spectrum calculation formula of the next sampling time is written in the column:
Figure BDA0003262148140000085
further combining equation (8) with equation (16), a recurrence equation is obtained as follows:
Figure BDA0003262148140000086
when c=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 rapidly and conveniently calculated by the recursion formula (9).
The invention relates to a rapid baseband signal computing system 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 the 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 synthesis value of the three-phase complex signal by adopting a sequence component method;
the DFT module is used for separating out fundamental frequency components in the three-phase signals by adopting discrete Fourier transform based on the synthesized value;
the RDFT module is used for calculating fundamental frequency components in the three-phase signals by adopting recursive discrete Fourier transform on the basis of the DFT module.
In summary, in order to accelerate the separation and calculation speed of the base frequency signals of the disturbed three-phase unbalanced system, the invention calculates the base frequency components in the three-phase signals of the power distribution network by adopting the recursive discrete Fourier transform, thereby realizing the rapid calculation of the base frequency signals of the disturbed three-phase unbalanced system and providing an algorithm foundation for the voltage sag analysis of the main base frequency signals of the power distribution network.
While the applicant has described and illustrated the embodiments of the present invention in detail with reference to the drawings, it should be understood by those skilled in the art that the above embodiments are only 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 to limit the scope of the present invention, but any improvements or modifications based on the spirit of the present invention should fall within the scope of the present invention.

Claims (7)

1. A rapid calculation method for a base frequency signal of a disturbed three-phase unbalanced system is characterized by comprising the following steps of:
the method comprises the following steps:
step 1: acquiring three-phase signals of a power distribution network of a 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;
in step 2, the disturbed three-phase unbalanced signal of the power distribution network is used as the input quantity of a second-order generalized integrator, and the resonant frequency omega is set 0 Outputting real and imaginary parts of the three-phase unbalanced signal under a static alpha-beta coordinate system, and adopting the real and imaginary parts to form a three-phase complex signal;
in the second-order generalized integrator, the real and imaginary transfer functions of the alpha-beta axes aiming at three-phase signals of the power distribution network a, b and c are as follows:
Figure FDA0004261073660000011
Figure FDA0004261073660000012
Figure FDA0004261073660000013
wherein omega is 0 The resonance frequency of the second-order generalized integrator is s is an integration operator, and K is a transfer function gain, namely a damping ratio;
x ain 、x bin 、x cin the signals are respectively a phase signal, a b phase signal and a c phase signal of the power distribution network;
x aα 、x bα 、x cα alpha-axis real parts of a phase signal, b phase signal and c phase signal generated by a second-order generalized integrator respectively;
x aβ 、x bβ 、x cβ the imaginary parts of the beta axes of a phase signal, b phase signal and c phase signal generated by the second-order generalized integrator are respectively;
the real part and the imaginary part are adopted to form the following three-phase complex signals:
x a ＝x aα +jx aβ ，x b ＝x bα +jx bβ ，x c ＝x cα +jx cβ (12)
in the method, in the process of the invention,x a 、x b 、x c a, b and c phase complex signals under a static alpha-beta coordinate system respectively;
step 3: constructing a synthesized value of the three-phase complex signals by adopting a sequence component method;
step 4: based on the synthesized value, separating out fundamental frequency components in the three-phase signals by adopting discrete Fourier transform;
step 5: based on the step 4, a recursive discrete Fourier transform is adopted to calculate the fundamental frequency component in the three-phase signal.
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 a 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 3, the vector is processed by adopting a sequence component method
Figure FDA0004261073660000021
And vector [x a ,x b ，x c ] T Multiplying to obtain the composite value of the three-phase complex signal:
Figure FDA0004261073660000022
in the method, in the process of the invention,x αβ is the synthesized value of three-phase complex signals of the power distribution network under a static alpha-beta coordinate system.
4. A method for rapidly calculating a baseband signal of a disturbed three-phase unbalanced system according to claim 3, wherein:
in step 4, the method obtained in step 3x αβ Sampling the signal, extracting N sampling values under a power frequency period, wherein N is an even number, and assuming that the N sampling values are respectively at N moments, namely t= (k-N) T s ，...，t＝(k-1)T s And T is s For sampling interval time, kT s K is the sampling count value for the current sampling time;
taking the sampling value as the input of a discrete Fourier transform DFT, the DFT expression is as follows:
Figure FDA0004261073660000023
c is the harmonic frequency of discrete Fourier transform, n is the count value of the adopted numerical value;
when c=1, equation (4) is a fundamental frequency component in the three-phase 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 step 4, the method obtained in step 3x αβ Sampling signals to extract 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.
6. 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 step 5, the recursive discrete fourier transform is adopted to improve the formula (4), and fundamental frequency components in the three-phase signals are calculated, specifically:
based on equation (4), the column writes the fourier spectrum calculation formula for the current sampling time:
Figure FDA0004261073660000031
according to the formula (8), a Fourier spectrum calculation formula at any moment is obtained, and then the following recurrence formula is obtained:
Figure FDA0004261073660000032
when c=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 is calculated by a recursive formula (9).
7. A disturbed three-phase unbalanced system fundamental frequency signal rapid calculation system according to any one of claims 1 to 6, 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 the 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 synthesis value of the three-phase complex signal by adopting a sequence component method;
the DFT module is used for separating out fundamental frequency components in the three-phase signals by adopting discrete Fourier transform based on the synthesized value;
the RDFT module is used for calculating fundamental frequency components in the three-phase signals by adopting recursive discrete Fourier transform on the basis of the DFT module.
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