CN103547328B

CN103547328B - Harmonic detecting method and relevant apparatus

Info

Publication number: CN103547328B
Application number: CN201280003068.4A
Authority: CN
Inventors: 刘海威
Original assignee: Shenzhen Invt Electric Co Ltd
Current assignee: Shenzhen Invt Electric Co Ltd
Priority date: 2012-05-22
Filing date: 2012-05-22
Publication date: 2015-12-23
Anticipated expiration: 2032-05-22
Also published as: CN103547328A; WO2013173975A1

Abstract

The invention discloses a kind of harmonic detecting method and relevant apparatus.Wherein, a kind of harmonic detecting method comprises: electric signal of sampling from power circuit is to obtain the electrical signal sequence of N point; The Real Fast Fourier Transform RFFT computing electrical signal sequence of N point being carried out N point obtains the first sequence of complex numbers; Harmonic wave extraction process is carried out to the first sequence of complex numbers and obtains the second sequence of complex numbers; Actual situation is carried out to the second sequence of complex numbers and combines process to obtain the 3rd sequence of complex numbers; RFFT computing is carried out to the 3rd sequence of complex numbers and obtains the 4th sequence of complex numbers; 4th sequence of complex numbers is carried out actual situation and combine process to obtain N point harmonic sequence.The advantageous of the embodiment of the present invention can take into account storage space and computing time when at harmonic detecting.

Description

Harmonic detection method and related device

Technical Field

The invention relates to the technical field of electronics, in particular to a harmonic detection method and a related device.

Background

At present, various power electronic devices and nonlinear loads are widely applied in power systems, so that a large amount of harmonics are generated. The harmonic waves threaten the safe operation of the power system, and may bring great influence and harm to the surrounding electrical environment.

An Active Power Filter (APF) is a power electronic device for dynamically suppressing harmonics and compensating reactive power. Static Var Generators (SVG) are one of the main devices in Flexible Alternating Current Transmission Systems (FACTS). The APF can compensate harmonic waves with variable sizes and frequencies and reactive power with variable frequencies, and the detection of harmonic signals by the APF is the key for ensuring the compensation performance of the APF. SVG can dynamic compensation reactive, also can compensate the harmonic, and SVG stands for the new development direction of power system reactive compensation technique, and the detection of same harmonic signal is the key of guaranteeing SVG harmonic compensation performance.

Harmonic signals in power systems are typically referred to as current harmonics and voltage harmonics. When APF/SVG is deployed in a parallel mode, current harmonic waves are usually detected and treated; when APF/SVG is deployed in a series mode, voltage harmonics are generally detected and treated. The existing harmonic detection technology is difficult to consider both storage space and calculation time.

Disclosure of Invention

The embodiment of the invention provides a harmonic detection method and a related device, aiming at realizing both storage space and calculation time for harmonic detection.

An embodiment of the present invention provides a harmonic detection method, including: sampling an electric signal from an electric power line to obtain an N-point electric signal sequence; carrying out real number fast Fourier transform (RFFT) operation on the electrical signal sequence of the N points to obtain a first complex sequence; carrying out harmonic extraction processing on the first complex sequence to obtain a second complex sequence; performing virtual-real combining processing on the second complex sequence to obtain a third complex sequence, wherein the performing virtual-real combining processing on the second complex sequence includes: in the second complex number sequence comprising a plurality of second complex numbers, generating a third complex number corresponding to each second complex number except for the data corresponding to the direct current component and the Nyquist frequency point by a virtual-real combination processing mode, wherein the real part of the third complex number is equal to the sum of the imaginary part coefficient and the real part of the corresponding second complex number, and the imaginary part coefficient of the third complex number is equal to the difference between the real part coefficient and the imaginary part coefficient of the corresponding second complex number; performing Real Fast Fourier Transform (RFFT) operation on the third complex sequence to obtain a fourth complex sequence; and performing virtual-real combination processing on the fourth complex sequence to obtain an N-point harmonic sequence, wherein the performing virtual-real combination processing on the fourth complex sequence includes: in the fourth complex number sequence comprising a plurality of fourth complex numbers, each fourth complex number except the data corresponding to the direct current component and the Nyquist frequency point generates a sixth complex number corresponding to each fourth complex number through a virtual-real combination processing mode, wherein the real part of the sixth complex number is equal to the sum of the imaginary part coefficient and the real part of the corresponding fourth complex number, and the imaginary part coefficient of the sixth complex number is equal to the difference between the real part coefficient and the imaginary part coefficient of the corresponding fourth complex number.

Optionally, the step of sampling the electrical signal from the power line to obtain an N-point electrical signal sequence includes: within one signal fundamental period, electrical signals are sampled at equal intervals from the power line to obtain an N-point electrical signal sequence.

Optionally, the step of performing harmonic extraction processing on the first complex sequence to obtain a second complex sequence includes: removing a fundamental component in the first complex sequence to obtain the second complex sequence;

or,

and enabling harmonic components in the first complex sequence to be zero to obtain a fifth complex sequence, and then subtracting the fifth complex sequence from the first complex sequence to obtain the second complex sequence.

Optionally, the step of performing N-point Real Fast Fourier Transform (RFFT) operation on the N-point electrical signal sequence to obtain a first complex sequence includes: dividing the electrical signal sequence of the N points by the N, and then performing RFFT operation of the N points to obtain a first complex sequence;

or,

the step of performing harmonic extraction processing on the first complex sequence to obtain a second complex sequence comprises: after the first complex sequence is divided by the N, harmonic extraction processing is carried out to obtain a second complex sequence;

or,

the step of performing virtual-real combination processing on the second complex sequence to obtain a third complex sequence includes: after dividing the second complex sequence by the N, performing virtual-real combination processing to obtain a third complex sequence;

or, the step of performing an RFFT operation on the third complex sequence to obtain a fourth complex sequence includes: dividing the third complex sequence by the N and then performing RFFT operation to obtain a fourth complex sequence;

or,

the step of performing virtual-real combination processing on the fourth complex sequence to obtain an N-point harmonic sequence includes: after dividing the fourth complex sequence by the N, carrying out virtual-real combination processing to obtain an N-point harmonic sequence;

or,

the harmonic detection method further includes: dividing the obtained N-point harmonic sequence by the N.

Another aspect of the embodiments of the present invention further provides a harmonic detection apparatus, which may include: the sampling unit is used for sampling the electric signals from the electric power circuit to obtain an N-point electric signal sequence; the first RFFT operation unit is used for carrying out real number fast Fourier transform (RFFT) operation on the N-point electric signal sequence obtained by the sampling unit to obtain a first complex sequence; a harmonic extraction unit, configured to perform harmonic extraction processing on the first complex sequence obtained by the first RFFT operation unit to obtain a second complex sequence; an imaginary-real combining processing unit, configured to perform imaginary-real combining processing on the second complex sequence obtained by the harmonic extraction unit to obtain a third complex sequence, specifically, the imaginary-real combining processing unit generates, in the second complex sequence obtained by the harmonic extraction unit and including a plurality of second complex numbers, a third complex number corresponding to each second complex number through an imaginary-real combining processing manner, where a real part of the third complex number is equal to a sum of an imaginary part coefficient and a real part of the corresponding second complex number, and an imaginary part coefficient of the third complex number is equal to a difference between the real part and the imaginary part of the corresponding second complex number, so as to obtain a third complex sequence including a plurality of third complex numbers; a second RFFT operation unit, configured to perform RFFT operation on the third complex sequence obtained by the virtual-real combination processing unit to obtain a fourth complex sequence; and the virtual-real combining processing unit is further configured to perform virtual-real combining processing on the fourth complex sequence obtained by the second RFFT operation unit to obtain an N-point harmonic sequence, and specifically, the virtual-real combining processing unit generates, in the fourth complex sequence obtained by the second RFFT operation unit and including a plurality of fourth complex numbers, a sixth complex number corresponding to each fourth complex number by a virtual-real combining processing manner, where a real part of the sixth complex number is equal to a sum of an imaginary part coefficient and a real part of the corresponding fourth complex number, and an imaginary part coefficient of the sixth complex number is equal to a difference between the real part and the imaginary part coefficient of the corresponding fourth complex number, so as to obtain the N-point harmonic sequence including the plurality of sixth complex numbers.

Optionally, the first RFFT operation unit is specifically configured to divide the electrical signal sequence of N points obtained by the sampling unit by the N, and then perform RFFT operation of N points to obtain a first complex sequence;

or,

the harmonic extraction unit is specifically configured to divide the first complex sequence obtained by performing RFFT operation on the first RFFT operation unit by the N, and then perform harmonic extraction processing to obtain a second complex sequence;

or,

the virtual-real combination processing unit is specifically configured to, after dividing the second complex sequence obtained by the harmonic extraction unit by the N, perform virtual-real combination processing to obtain a third complex sequence;

or,

the second RFFT operation unit is specifically configured to divide the third complex sequence obtained by the virtual-real combination processing unit by the N, and then perform RFFT operation to obtain a fourth complex sequence;

or,

the virtual-real combination processing unit is further configured to divide the fourth complex sequence obtained by the second RFFT operation unit by the N, and then perform virtual-real combination processing to obtain an N-point harmonic sequence;

or,

the virtual-real combination processing unit is further configured to perform virtual-real combination processing on the fourth complex sequence obtained by the second RFFT operation unit to obtain an N-point harmonic sequence, and divide the N-point harmonic sequence by the N to output the N-point harmonic sequence.

Still another aspect of the embodiments of the present invention provides a harmonic cancellation apparatus, including:

the harmonic detection device is used for sampling the electric signals from the electric power circuit to obtain an N-point electric signal sequence; carrying out real number fast Fourier transform (RFFT) operation on the electrical signal sequence of the N points to obtain a first complex sequence; carrying out harmonic extraction processing on the first complex sequence to obtain a second complex sequence; carrying out virtual-real combination processing on the second complex sequence to obtain a third complex sequence; performing RFFT operation on the third complex sequence to obtain a fourth complex sequence; carrying out virtual-real combination processing on the fourth complex sequence to obtain an N-point harmonic sequence and outputting the N-point harmonic sequence;

an electric signal feedback device, configured to generate a compensation electric signal based on the N-point harmonic sequence output by the harmonic detection device, and feed back the generated compensation electric signal to the electric power line to cancel harmonics generated in the electric power line;

wherein, the harmonic detection device performs virtual-real combination processing on the second complex sequence to obtain a third complex sequence, including: in the second complex number sequence comprising a plurality of second complex numbers, generating a third complex number corresponding to each second complex number except for the data corresponding to the direct current component and the Nyquist frequency point by a virtual-real combination processing mode, wherein the real part of the third complex number is equal to the sum of the imaginary part coefficient and the real part of the corresponding second complex number, and the imaginary part coefficient of the third complex number is equal to the difference between the real part coefficient and the imaginary part coefficient of the corresponding second complex number;

the harmonic detection device performs virtual-real combination processing on the fourth complex sequence to obtain an N-point harmonic sequence, including: in the fourth complex number sequence comprising a plurality of fourth complex numbers, each fourth complex number except the data corresponding to the direct current component and the Nyquist frequency point generates a sixth complex number corresponding to each fourth complex number through a virtual-real combination processing mode, wherein the real part of the sixth complex number is equal to the sum of the imaginary part coefficient and the real part of the corresponding fourth complex number, and the imaginary part coefficient of the sixth complex number is equal to the difference between the real part coefficient and the imaginary part coefficient of the corresponding fourth complex number.

As can be seen from the above, in the technical solution provided in the embodiment of the present invention, an electrical signal is sampled from an electrical power line to obtain an electrical signal sequence of N points, and an RFFT operation of N points is performed to obtain a first complex sequence; carrying out harmonic extraction processing on the first complex sequence to obtain a second complex sequence; carrying out virtual-real combination processing on the second complex sequence to obtain a third complex sequence; performing RFFT operation on the third complex sequence to obtain a fourth complex sequence; and carrying out virtual-real combination processing on the fourth complex sequence to obtain an N-point harmonic sequence. According to the technical scheme, conjugation operation and data extraction operation are not needed before and after the RFFT, and only two times of virtual and real combination processing operation, namely simple addition and subtraction operation, are needed, so that the calculation time is saved compared with the prior art, and the code space can be saved as the RFFT code can be fully utilized for operation.

Furthermore, the code space, the number of storage units and the calculation time can be comprehensively optimized without increasing additional storage space.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic flow chart of a harmonic detection method according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of storage of calculation data provided by an embodiment of the present invention;

FIG. 3 is a schematic diagram of a harmonic detection apparatus according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a harmonic cancellation apparatus provided by an embodiment of the present invention;

fig. 5a is a schematic diagram of an architecture for applying a harmonic cancellation device to a power grid according to an embodiment of the present invention;

fig. 5b is a schematic diagram of another architecture for applying a harmonic cancellation device to a power grid according to an embodiment of the present invention;

fig. 5c is a schematic diagram of another architecture for applying the harmonic cancellation device to the power grid according to the embodiment of the present invention.

Detailed Description

The following are detailed descriptions of the respective embodiments.

In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terms "first," "second," "third," "fourth," and the like in the description and in the claims, as well as in the drawings, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The harmonic signal detection range of the present invention includes detection of harmonic voltages and/or harmonic currents.

The harmonic signal detection method mainly comprises the following steps: analog band-pass filter detection, detection based on the instantaneous reactive power theory, Fast Fourier Transform (FFT) detection, and the like. The detection method based on the analog fusion filter can only detect the harmonic waves in a fixed frequency range, cannot compensate the changed harmonic waves in real time, and is easy to cause resonance; the fast Fourier transform method and the detection method based on the instantaneous reactive power theory can detect the harmonic waves in a wide frequency domain range, and therefore, the method is widely applied to an electric power system. The detection method based on instantaneous reactive power has unique advantages in the aspects of reactive power and harmonic integral compensation and quick response, while the FFT detection method cannot be replaced in the aspects of signal spectrum detailed analysis and data display, and has obvious advantages particularly in the aspects of harmonic content analysis and individual spectrum compensation. In consideration of duality of FFT and IFFT, for devices (such as part of APF and SVG) which use FFT detection method to analyze and display harmonic content, existing codes can be directly called to carry out inverse transformation to obtain harmonic instructions, so that the FFT has more advantages in application of the occasions. The FFT-based harmonic extraction method has the advantages of being complex in calculation, poor in instantaneity and large in memory occupation during calculation.

When one or more specific subharmonics need to be compensated simultaneously in the APF/SVG, FFT calculation is indispensable, and harmonic signal extraction based on the inverse FFT principle is blocked in large-scale real-time processing because of more occupied memory and longer program operation time.

Some FFT-based improved harmonic detection methods are analyzed as follows:

(1) the harmonic sequence is obtained by FFT calculation, although the forward and reverse transformation can share the same FFT program segment, the cost is that the forward transformation efficiency is reduced, 1 time of storage space is increased, and extra conjugation (or sequencing) operation and data extraction operation are needed for the reverse transformation method.

(2) The harmonic sequence is obtained by combining real number and complex number FFT calculation, the forward conversion operation time and the storage space can be optimized, and although the forward conversion efficiency is improved compared with the former method, the method sacrifices code sharing and increases the complexity of a program.

(3) The harmonic sequence is calculated by Real Fast Fourier Transform (RFFT), although the method can multiplex codes, 1 time of storage space is additionally increased, two real and virtual separation operations are required, the operation amount is greatly increased, and the operation speed of the processor is influenced. It can be seen that the above methods have advantages and disadvantages, and none of them can give consideration to the comprehensive performance of code reuse, storage space and computation time.

One embodiment of the harmonic detection method of the present invention may comprise: sampling an electric signal from an electric power line to obtain an N-point electric signal sequence; carrying out real number fast Fourier transform (RFFT) operation on the electrical signal sequence of the N points to obtain a first complex sequence; carrying out harmonic extraction processing on the first complex sequence to obtain a second complex sequence; carrying out virtual-real combination processing on the second complex sequence to obtain a third complex sequence; performing RFFT operation on the third complex sequence to obtain a fourth complex sequence; and carrying out virtual-real combination processing on the fourth complex sequence to obtain an N-point harmonic sequence.

Referring to fig. 1, fig. 1 shows a harmonic detection method according to an embodiment of the present invention, which includes the following steps:

step 101, sampling an electric signal from an electric power line to obtain an electric signal sequence of N points.

In some embodiments of the present invention, the electrical signal may be sampled at equal or unequal intervals from the power line during one fundamental period of the signal to obtain a sequence of N points of the electrical signal. For example, three-phase current signals (or three-phase voltage signals) at equal intervals or unequal intervals in one signal fundamental wave period can be extracted from a three-phase power line to obtain an N-point current signal sequence (or an N-point voltage signal sequence) corresponding to each phase current.

And 102, performing N-point RFFT operation on the N-point electric signal sequence to obtain a first complex sequence.

The first complex number sequence comprises a plurality of first complex numbers.

Referring to fig. 2, fig. 2 is a schematic diagram illustrating storage of calculation data according to an embodiment of the present invention. As shown in FIG. 2, the sequence of the electrical signals at N points is represented as R₀～R_N-1Suppose that N memory cells are used to store a sequence of N electrical signals (R)₀～R_N-1) The sequence of the electrical signals (R) of N points₀～R_N-1) Performing RFFT operation of N points to obtain a first complex sequence, and correlating the DC component in the first complex sequence with Nyquist frequency point (such as R)₀And R_N/2) Storing in 2 memory units, and storing (N-2)/2 complex numbers (R) of the remaining N-2 complex numbers in the first complex number sequence₁～R_N/2-1) Is stored in (N-2)/2 storage units, and the imaginary part coefficient of the (N-2)/2 complex numbers is stored in (N-2)/2 storage units, because the data corresponding to the direct current component and the Nyquist frequency point (such as R) is divided in the first complex number sequence₀And R_N/2) Other two-part complex (R)₁～R_N/2-1) And (R)_N/2+1～R_N-1) Has conjugate symmetry, thus using the stored complex number (R)₁～R_N/2-1) The complex numbers not stored in the first complex number sequence can be recovered, so that the storage space can be greatly saved, and of course, the (R) in the first complex number sequence can also be stored_N/2+1～R_N-1) Part, not storing (R) in the first complex sequence₁～R_N/2-1) According to (R)_N/2+1～R_N-1) Can also recover (R)₁～R_N/2-1) And (4) partial. It is understood that other complex numbers having conjugate symmetry in the complex sequence may be usedStorage is performed in this manner.

Please refer to fig. 1, step 103, the harmonic extraction processing is performed on the first complex sequence to obtain a second complex sequence.

In some embodiments of the present invention, the step of performing harmonic extraction processing on the first complex sequence to obtain the second complex sequence may include: removing the fundamental component in the first complex sequence to obtain a second complex sequence (of course, the harmonic component of the unnecessary order can also be removed, that is, only one or a few harmonic components of the set order can be extracted), for example, the fundamental component in the first complex sequence can be made to be zero to obtain the second complex sequence; alternatively, the harmonic component in the first complex sequence may be zeroed to obtain a fifth complex sequence, and then the fifth complex sequence is subtracted from the first complex sequence to obtain a second complex sequence.

Wherein the second complex sequence comprises a plurality of second complex numbers.

And 104, performing virtual-real combination processing on the second complex sequence to obtain a third complex sequence.

In some embodiments of the present invention, for example, in the second complex sequence including a plurality of second complex numbers, each second complex number except for the data corresponding to the dc component and the nyquist frequency point generates a third complex number corresponding to each second complex number by a virtual-real combining processing manner, and a real part of the third complex number is equal to a sum of an imaginary part coefficient and a real part of the corresponding second complex number, and an imaginary part coefficient of the third complex number is equal to a difference between the real part and the imaginary part coefficient of the corresponding second complex number, so that the virtual-real combining processing performed on each second complex number except for the data corresponding to the dc component and the nyquist frequency point in the second complex sequence can obtain a third complex sequence of N points, that is, the third complex sequence includes a plurality of third complex numbers, wherein the third complex sequence of N points includes the data corresponding to the dc component and the nyquist frequency point in the second complex sequence, and the third complex number corresponding to each second complex number is generated by a processing mode of combining virtual and real for each second complex number except the data corresponding to the direct current component and the Nyquist frequency point in the second complex number sequence.

And 105, performing RFFT operation on the third complex sequence to obtain a fourth complex sequence.

Wherein the fourth complex sequence comprises a plurality of fourth complex numbers.

And 106, carrying out virtual-real combination processing on the fourth complex sequence to obtain an N-point harmonic sequence.

In some embodiments of the present invention, for example, in a fourth complex sequence including a plurality of fourth complex numbers, each fourth complex number except for data corresponding to a dc component and a nyquist frequency point generates, by means of a virtual-real combining process, a sixth complex number corresponding to each fourth complex number, a real part of the sixth complex number is equal to a sum of an imaginary part coefficient and a real part of the corresponding fourth complex number, and an imaginary part coefficient of the sixth complex number is equal to a difference between the real part coefficient and the imaginary part coefficient of the corresponding fourth complex number, so that the virtual-real combining process performed on each complex number in the fourth complex sequence can obtain an N-point harmonic sequence including a plurality of sixth complex numbers, wherein the N-point harmonic sequence includes data corresponding to a dc component and a nyquist frequency point in the fourth complex sequence, and the N-point harmonic sequence is further included in the fourth complex sequence, and each fourth complex number except the data corresponding to the direct current component and the Nyquist frequency point is generated into a sixth complex number corresponding to each fourth complex number by a processing mode of combining virtual and real.

The mode of the two real and virtual combination processing is the same, code multiplexing can be realized, and further the code storage space can be saved. According to the scheme, conjugation operation is not needed, only simple addition and subtraction operation is needed to be carried out on data, the multiplexing of RFFT codes can be achieved to complete harmonic calculation on the premise of less calculation amount and no additional storage unit, the output result can be free of operations such as data extraction and sorting, the initial real number sequence can be completely corresponded, calculation time is saved, and additional code space and storage space are not increased. If the harmonic amplitude, phase and Total Harmonic Distortion (THD) need to be calculated, the code can be fully multiplexed to reduce the program storage space.

It should be noted that N in the embodiment of the present invention refers to the number of points of the inverse fourier transform, i.e., the length of the output harmonic sequence.

In addition, in order to obtain the true amplitude, the amplitude may be restored, that is, the amplitude is subjected to a "divide by N" operation (which may be referred to as a 1/N operation in the embodiment of the present invention).

For example, in an embodiment of the present invention, the step 102 of performing an N-point RFFT operation on the N-point electrical signal sequence to obtain the first complex sequence may include the following specific steps: after dividing the electrical signal sequence of N points by N, performing RFFT operation of N points to obtain a first complex sequence.

Alternatively, in another embodiment of the present invention, the harmonic extraction processing on the first complex sequence in step 103 to obtain the second complex sequence may include the following specific steps: and after the first complex sequence is divided by N, harmonic extraction processing is carried out to obtain a second complex sequence.

Alternatively, in another embodiment of the present invention, the performing the virtual-real combination process on the second complex sequence in step 104 to obtain the third complex sequence may include the following specific steps: after dividing the second complex sequence by N, performing a virtual-real combining process to obtain a third complex sequence.

Alternatively, in another embodiment of the present invention, the performing the RFFT operation on the third complex sequence in step 105 to obtain the fourth complex sequence may include the following specific steps: and performing RFFT operation after dividing the third complex sequence by N to obtain a fourth complex sequence.

Alternatively, in another embodiment of the present invention, the step 106 of performing virtual-real combination processing on the obtained fourth complex sequence to obtain an N-point harmonic sequence includes the following specific steps: after the fourth complex sequence is divided by N, the imaginary-real combination processing is carried out to obtain an N-point harmonic sequence.

Alternatively, in another embodiment of the present invention, the obtained N-point harmonic sequence may be divided by N and then output.

In order to facilitate a better understanding of the embodiments of the present invention, some analysis will be made below on the basis of the methods provided by the embodiments of the present invention.

For RFFT, the sequence of sampled electrical signals can be represented as:

x(n)＝x_R(n),0≤n≤N-1；

since the imaginary part of the sampled electrical signal sequence is 0, it can be derived from the DFT definition and properties:

that is, after RFFT, the real part is a cosine component and is a real even sequence, and the imaginary part is a sine component and is a real odd sequence.

For inverse fourier transform, the input sequence is:

X(k)＝X_R(k)+jX_I(k),0≤k≤N-1；

the inverse transformation result is x (n), and according to the property of inverse Fourier transformation, the method can obtain the following results:

x(n)＝IFFT(X(k))

＝IFFT(X_R(k)+jX_I(k))

＝IFFT(X_R(k))+j*IFFT(X_I(k))

＝conj(FFT(X_R(k)))+j*conj(FFT(X_I(k)))

＝FFT(X_R(k))+j*(-1)*(FFT(X_I(k))

thus obtaining the following components: x (n) ═ FFT (X)_R(k))-j*(FFT(X_I(k))，

Wherein k is more than or equal to 0 and less than or equal to N-1;

it should be noted that, 1/N operation is omitted from the above formula, and considering that 1/N only affects the final amplitude, no analysis is performed here, and it can be understood that, if a true amplitude needs to be obtained, 1/N operation may be performed on the result.

By X (n) ═ FFT (X)_R(k))-j*(FFT(X_I(k) It can be seen that the results still containTwo FFT transforms, each of which requires N data, therefore, the equation X (N) FFT (X) is also required_R(k))-j*(FFT(X_I(k) For further analysis) as follows:

let S (K) be X_R(k)+X_I(k) Then at S (K) ═ X_R(k)+X_I(k) The FFT is calculated on two sides to obtain:

S(K)＝X_R(k)+X_I(k)；

wherein, FFT (X)_R(k) Are purely real numbers, and FFT (X)_I(k) Is a pure imaginary number.

Thus, it is possible to obtain:

s＝FFT(X_R(k))+FFT(X_I(k))＝s_R+j*s_Iwherein k is more than or equal to 0 and less than or equal to N-1;

wherein s ═ FFT (X)_R(k))+FFT(X_I(k))＝s_R+j*s_I。

Therefore, the formula X (n) FFT (X)_R(k))-j*(FFT(X_I(k) Can be simplified to:

x(n)＝s_R+s_Iwherein k is more than or equal to 0 and less than or equal to N-1;

by the formula x (n) ═ s_R+s_IIt can be seen that s (k) is constructed and FFT is performed, so that s can be obtained by the formula x (n) ═ s_R+s_IThe original sequence of real numbers x (n) is reduced. In fact, when the number of memory cells is consistent, s (k) and the formula x (n) s need to be constructed_R+s_IAre identical expressions, so that one program segment can be shared.

As can be seen from fig. 2, after a typical N-point real number sequence is subjected to RFFT transform, only half of the data (i.e., spectral values) can be stored by using the conjugate symmetry of the N-point real number sequence, so that if N points are to be calculated, the other half of the data needs to be restored, and because the other half of the data is conjugate and symmetric to the stored data, the construction manner of s (k) can be decomposed as:

obviously, x (n) can be realized by the above method, and will not be described herein.

As can be seen from the above, in the present embodiment, the electrical signal sequence obtained by sampling the electrical signal from the power line to obtain N points is subjected to N-point RFFT operation to obtain a first complex sequence; carrying out harmonic extraction processing on the first complex sequence to obtain a second complex sequence; carrying out virtual-real combination processing on the second complex sequence to obtain a third complex sequence; performing RFFT operation on the third complex sequence to obtain a fourth complex sequence; the fourth complex sequence is subjected to virtual-real combination processing to obtain an N-point harmonic sequence, conjugate operation is not required before and after the RFFT, data extraction operation is not required, and simple addition and subtraction operation is only required to be performed by performing virtual-real combination operation twice, so that compared with the prior art, the calculation time is saved, and the code space can be saved because the RFFT code can be fully utilized for operation. Furthermore, the code space, the number of storage units and the calculation time can be comprehensively optimized without increasing additional storage space.

To facilitate a better understanding and practice of the above-described aspects of embodiments of the present invention, the following also provides related apparatus for practicing the above-described aspects.

Referring to fig. 3, an embodiment of the invention further provides a harmonic detection apparatus 300, which may include: a sampling unit 301, a first RFFT operation unit 302, a harmonic extraction unit 303, a virtual-real combination processing unit 304, and a second RFFT operation unit 305.

The sampling unit 301 is configured to sample an electrical signal from the power line to obtain an N-point electrical signal sequence.

In some embodiments of the present invention, the sampling unit 301 may sample the electrical signal at equal or unequal intervals in the power line to obtain an N-point electrical signal sequence in one signal fundamental period. For example, the sampling unit 301 may extract three-phase current signals (or three-phase voltage signals) at equal intervals or unequal intervals in one signal fundamental period from a three-phase power line to obtain an N-point current signal sequence (or N-point voltage signal sequence) of each phase current.

A first RFFT operation unit 302, configured to perform an RFFT operation on the N-point real fast fourier transform of the N-point electrical signal sequence obtained by the sampling unit 301 to obtain a first complex sequence. The first complex number sequence comprises a plurality of first complex numbers.

A harmonic extraction unit 303, configured to perform harmonic extraction processing on the first complex sequence obtained by the first RFFT operation unit 302 to obtain a second complex sequence. Wherein the second complex sequence comprises a plurality of second complex numbers.

And an imaginary-real combining processing unit 304, configured to perform imaginary-real combining processing on the second complex sequence obtained by the harmonic extraction unit 303 to obtain a third complex sequence. Wherein the third complex sequence comprises a plurality of third complex numbers.

A second RFFT operation unit 305, configured to perform an RFFT operation on the third complex sequence obtained by the virtual-real combination processing unit 304 to obtain a fourth complex sequence. Wherein the fourth complex sequence comprises a plurality of fourth complex numbers.

The virtual-real combining processing unit 303 is further configured to perform virtual-real combining processing on the fourth complex sequence obtained by the second RFFT operation unit 305 to obtain an N-point harmonic sequence.

In some embodiments of the present invention, the imaginary-real combining processing unit 304 may be specifically configured to, in the second complex sequence obtained by the harmonic extraction unit 303 and including a plurality of second complex numbers, generate, by means of an imaginary-real combining processing, a third complex number corresponding to each second complex number in addition to the data corresponding to the direct-current component and the nyquist frequency point, where a real part of the third complex number is equal to a sum of an imaginary part coefficient and a real part of the second complex number corresponding thereto, and an imaginary part coefficient of the third complex number is equal to a difference between the real part and the imaginary part of the second complex number corresponding thereto, and obtain the third complex sequence by performing the imaginary-real combining processing on each second complex number.

In some embodiments of the present invention, the imaginary-real combining processing unit 304 is further specifically configured to, for each fourth complex number except for the data corresponding to the dc component and the nyquist frequency point in the fourth complex number sequence including the plurality of fourth complex numbers obtained by the second RFFT operation unit 305, generate a sixth complex number corresponding to each fourth complex number through an imaginary-real combining processing manner, wherein a real part of the sixth complex number is equal to a sum of an imaginary part coefficient and a real part of the fourth complex number corresponding thereto, an imaginary part coefficient of the sixth complex number is equal to a difference between the real part and the imaginary part of the fourth complex number corresponding thereto, and obtain an N-point harmonic sequence including the plurality of sixth complex numbers by performing an imaginary-real combining processing on each fourth complex number.

It can be understood that the third complex sequence obtained by the virtual-real combination processing unit 304 includes data corresponding to the dc component and the nyquist frequency point in the second complex sequence, and further includes a third complex number corresponding to each second complex number generated by a virtual-real combination processing manner for each second complex number in the second complex sequence except for the data corresponding to the dc component and the nyquist frequency point. The N-point harmonic sequence obtained by the virtual-real combination processing unit 304 includes the dc component in the fourth complex sequence and the data corresponding to the nyquist frequency point, and further includes a sixth complex number corresponding to each fourth complex number generated by a virtual-real combination processing method for each fourth complex number in the fourth complex sequence except the data corresponding to the dc component and the nyquist frequency point.

In some embodiments of the present invention, the harmonic extraction unit 303 is specifically configured to remove a fundamental component in the first complex sequence to obtain the second complex sequence.

In some embodiments of the present invention, the first RFFT operation unit 302 may be specifically configured to divide the N-point electrical signal sequence obtained by the sampling unit 301 by N, and then perform an RFFT operation on the N points to obtain a first complex sequence.

Or,

the harmonic extraction unit 303 may be specifically configured to divide the first complex sequence obtained by performing the RFFT operation on the first RFFT operation unit 302 by N, and then perform harmonic extraction processing to obtain the second complex sequence.

Or,

the virtual-real combining processing unit 304 is specifically configured to divide the second complex sequence obtained by the harmonic extraction unit 303 by N, and then perform virtual-real combining processing to obtain a third complex sequence.

Or,

the second RFFT operation unit 305 is specifically configured to divide the third complex sequence obtained by the virtual-real combination processing unit 304 by N, and then perform RFFT operation to obtain a fourth complex sequence.

Or,

the virtual-real combining unit 304 is further configured to divide the fourth complex sequence obtained by the second RFFT operation unit 305 by N, and then perform virtual-real combining to obtain an N-point harmonic sequence.

Or,

the virtual-real combining processing unit 304 is further configured to perform virtual-real combining processing on the fourth complex sequence obtained by the second RFFT operation unit 305 to obtain an N-point harmonic sequence, and divide the N-point harmonic sequence by N to output the N-point harmonic sequence.

It can be understood that the functions of the functional modules of the harmonic detection apparatus 300 of this embodiment can be specifically implemented according to the method in the foregoing method embodiment, and the specific implementation process thereof can refer to the related description in the foregoing method embodiment, and is not described herein again. The harmonic detection device 300 of the present embodiment can be deployed in the APF/SVG to serve as a device for harmonic detection in the APF/SVG.

Referring to fig. 4, an embodiment of the invention further provides a harmonic cancellation apparatus 400, which may include: a harmonic detection device 410 and an electrical signal feedback device 420.

The harmonic detection device 410 is used for sampling an electric signal from the electric power line to obtain an N-point electric signal sequence; performing RFFT operation on the N-point electric signal sequence to obtain a first complex sequence; carrying out harmonic extraction processing on the first complex sequence to obtain a second complex sequence; carrying out virtual-real combination processing on the second complex sequence to obtain a third complex sequence; performing RFFT operation on the third complex sequence to obtain a fourth complex sequence; and carrying out virtual-real combination processing on the fourth complex sequence to obtain and output an N-point harmonic sequence.

An electrical signal feedback device 420 for generating a compensation electrical signal based on the N-point harmonic sequence output by the harmonic detection device 410, and feeding the generated compensation electrical signal back to the power line to eliminate the harmonics generated in the power line.

In some embodiments of the present invention, the harmonic detection device 410 may sample the electrical signal from the power line at equal or unequal intervals during one fundamental period of the signal to obtain a sequence of N points of the electrical signal. For example, the harmonic detection device 410 may extract three-phase current signals (or three-phase voltage signals) at equal or unequal intervals in one signal fundamental period from a three-phase power line, for example, to obtain an N-point current signal sequence (or N-point voltage signal sequence) of each phase current.

In some embodiments of the present invention, the harmonic detection device 410 may store data by using a data storage method as shown in fig. 2. The sequence of electrical signals, e.g. N points, is denoted R₀～R_N-1Suppose that N memory cells are used to store a sequence of N electrical signals (R)₀～R_N-1) The sequence of the electrical signals (R) of N points₀～R_N-1) Performing RFFT operation of N points to obtain a first complex sequence, and correlating the DC component in the first complex sequence with Nyquist frequency point (such as R)₀And R_N/2) Storing in 2 memory units, and storing (N-2)/2 complex numbers (R) of the remaining N-2 complex numbers in the first complex number sequence₁～R_N/2-1) Is stored in (N-2)/2 storage units, and the imaginary part coefficient of the (N-2)/2 complex numbers is stored in (N-2)/2 storage units, because the data corresponding to the direct current component and the Nyquist frequency point (such as R) is divided in the first complex number sequence₀And R_N/2) Other two-part complex (R)₁～R_N/2-1) And (R)_N/2+1～R_N-1) Has conjugate symmetry, thus using the stored complex number (R)₁～R_N/2-1) The complex numbers not stored in the first complex sequence can be recovered, so that the storage space can be greatly saved, and of course, the harmonic detection device 410 can also store (R) in the first complex sequence_N/2+1～R_N-1) Part, not storing (R) in the first complex sequence₁～R_N/2-1) According to (R)_N/2+1～R_N-1) Can also recover (R)₁～R_N/2-1) And (4) partial. It will be appreciated that complex numbers having conjugate symmetry in other complex sequences may also be stored in this manner.

In some embodiments of the present invention, the harmonic detection apparatus 410 performing the harmonic extraction processing on the first complex sequence to obtain the second complex sequence may include: removing the fundamental component in the first complex sequence to obtain a second complex sequence (of course, the harmonic component of the unnecessary order can also be removed, that is, only one or a few harmonic components of the set order can be extracted), for example, the fundamental component in the first complex sequence can be made to be zero to obtain the second complex sequence; alternatively, the harmonic component in the first complex sequence may be zeroed to obtain a fifth complex sequence, and then the fifth complex sequence is subtracted from the first complex sequence to obtain a second complex sequence. Wherein the second complex sequence comprises a plurality of second complex numbers.

In some embodiments of the present invention, the harmonic detection apparatus 410 performs a virtual-real combining process on the second complex sequence to obtain a third complex sequence, which may include: in a second complex sequence comprising a plurality of second complex numbers, each second complex number except for the data corresponding to the dc component and the nyquist frequency point generates a third complex number corresponding to each second complex number by a virtual-real combining processing method, wherein a real part of the third complex number is equal to a sum of an imaginary part coefficient and a real part of the corresponding second complex number, and an imaginary part coefficient of the third complex number is equal to a difference between the real part and the imaginary part coefficient of the corresponding second complex number, so that the virtual-real combining processing is performed on each second complex number except for the data corresponding to the dc component and the nyquist frequency point in the second complex sequence to obtain a third complex sequence of N points, that is, the third complex sequence comprises a plurality of third complex numbers, wherein the third complex sequence of N points comprises the data corresponding to the dc component and the nyquist frequency point in the second complex sequence, and the third complex number corresponding to each second complex number is generated by a processing mode of combining virtual and real for each second complex number except for the direct current component and the data corresponding to the Nyquist frequency point in the second complex number sequence.

In some embodiments of the present invention, the harmonic detection apparatus 410 performs virtual-real combination processing on the fourth complex sequence to obtain an N-point harmonic sequence, for example, may include generating, by means of virtual-real combination processing, a sixth complex number corresponding to each fourth complex number in the fourth complex sequence including a plurality of fourth complex numbers, where a real part of the sixth complex number is equal to a sum of an imaginary part coefficient and a real part of the corresponding fourth complex number, and an imaginary part coefficient of the sixth complex number is equal to a difference between the real part coefficient and the imaginary part coefficient of the corresponding fourth complex number, so that performing the virtual-real combination processing on each complex number in the fourth complex sequence as described above can obtain an N-point harmonic sequence including a plurality of sixth complex numbers, where the N-point harmonic sequence includes data corresponding to dc components and nyquist frequency points in the fourth complex sequence, the method also comprises a sixth complex number which is generated by a processing mode of combining virtual and real for each fourth complex number except the data corresponding to the direct current component and the Nyquist frequency point in the fourth complex number sequence and corresponds to each fourth complex number.

The mode of the two real and virtual combination processing is the same, code multiplexing can be realized, and further the code storage space can be saved. According to the scheme, conjugation operation is not needed, only simple addition and subtraction operation is needed to be carried out on data, the multiplexing of RFFT codes can be achieved to complete harmonic calculation on the premise of less calculation amount and no additional storage unit, the output result can be free of operations such as data extraction and sorting, the initial real number sequence can be completely corresponded, calculation time is saved, and additional code space and storage space are not increased. If the harmonic amplitude, phase and Total Harmonic Distortion (THD) need to be calculated, the codes can be fully multiplexed to reduce the program storage space.

In addition, in order to obtain the actual amplitude, in some embodiments of the present invention, the harmonic detection device 410 may further perform a reduction on the amplitude, i.e. a "divide by N" operation (which may be referred to as a 1/N operation in embodiments of the present invention).

For example, in an embodiment of the invention, the harmonic detection apparatus 410 may divide the electrical signal sequence of N points by N, and then perform the RFFT operation of N points to obtain the first complex sequence.

Alternatively, in another embodiment of the present invention, the harmonic detection apparatus 410 may perform harmonic extraction processing after dividing the first complex sequence by N to obtain the second complex sequence.

Alternatively, in another embodiment of the present invention, the harmonic detection apparatus 410 may perform a virtual-real combining process after dividing the second complex sequence by N to obtain a third complex sequence.

Alternatively, in another embodiment of the present invention, the harmonic detection device 410 may perform an RFFT operation after dividing the third complex sequence by N to obtain a fourth complex sequence.

Alternatively, in another embodiment of the present invention, the harmonic detection apparatus 410 may perform a virtual-real combining process after dividing the fourth complex sequence by N to obtain an N-point harmonic sequence.

Alternatively, in another embodiment of the present invention, the harmonic detection device 410 may also divide the obtained N-point harmonic sequence by N and output the result.

It is understood that the harmonic detection device 410 may be, for example, the harmonic detection device 300, and may have some or all of the functions of the harmonic detection device 300. The functions of the harmonic detection apparatus 410 can be specifically implemented according to the method in the above method embodiment, and the specific implementation process thereof can be referred to the related description in the above method embodiment, and will not be described herein again.

In some embodiments of the invention, the harmonic detection means 410 and the electrical signal feedback means 420 in the harmonic cancellation device 400 may be deployed, for example, in each of the power grid topologies as shown in fig. 5 a-5 c, to cancel harmonics in the power grid.

To further illustrate the topological location and function of the harmonic cancellation device 400 of the present invention, the harmonic cancellation device 400 is taken as APF/SVG for example, and is described with reference to the parallel compensation harmonic current APF/SVG. It is noted that those skilled in the art will appreciate that the principles of the present invention are equally applicable to series or series-parallel harmonic compensation and are within the scope of the present invention.

Referring to fig. 5b, fig. 5b is a schematic diagram of a parallel connection APF/SVG reactive power compensation and harmonic compensation architecture, a nonlinear load runs in a power grid, and the APF/SVG is connected in parallel to the power grid to compensate harmonic and reactive power of the nonlinear load. Wherein i_S(including i in the figure)_Sa、i_Sb、i_Sc) Is the supply current i_L(including i in the figure)_La、i_Lb、i_Lc) Is the load current i_M(including i in the figure)_Ma、i_Mb、i_Mc) For feedback of electric signalsThe compensation current generated by means 420.

Referring to fig. 5c, the APF/SVG may detect harmonic components in the load current through a harmonic detection device 410 therein. The harmonic detection device 410 outputs a harmonic current sequence, the reactive detection device 430 can calculate to obtain load current fundamental wave reactive power by adopting a classical instantaneous reactive theory, and outputs a reactive current sequence, and the reactive current sequence and the harmonic current sequence are added to obtain a reactive current sequence and a harmonic current sequence to be compensated. The electrical signal feedback device 420 in fig. 5c comprises: a current controller 421, a dc voltage controller 422, and a power device 423 (such as an Insulated Gate Bipolar Transistor (IGBT)), wherein the current controller 421 is connected to the harmonic detection device 410, the reactive detection device 430, the dc voltage controller 422 is connected to the power device 423, and the dc voltage controller 422 is also connected to the power device 423. The dc voltage controller 422 is mainly used for outputting a dc voltage adjusting signal. The current controller 421 is mainly configured to generate a Pulse Width Modulation (PWM) signal according to the reactive current sequence, the harmonic current sequence, and the dc voltage adjustment signal output by the dc voltage controller 422. The power device 423 is mainly used for generating a current signal output for compensating for harmonics and reactive power according to the PWM signal output from the current controller 421 to compensate for reactive and harmonic currents of the load. Compensation current i generated by power device 423_M(including i in the figure)_Ma、i_Mb、i_Mc) Can be equal in magnitude and opposite in direction to the harmonic component in the load current, so that the harmonic component and the harmonic component can cancel each other out, so that the power supply current only contains a basic active component.

An embodiment of the present invention further provides a computer storage medium, where the computer storage medium may store a program, and the program includes, when executed, some or all of the steps of the data processing method described in the foregoing method embodiment.

It should be noted that, for simplicity of description, the above-mentioned method embodiments are described as a series of acts or combinations, but those skilled in the art should understand that the present invention is not limited by the described acts or sequences, as some steps may be performed in other sequences or simultaneously according to the present invention. Further, those skilled in the art should also appreciate that the embodiments described in the specification are preferred embodiments and that the acts and modules referred to are not necessarily required by the invention.

In the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.

In summary, in the technical solution provided in the embodiment of the present invention, an electrical signal sequence obtained by sampling an electrical signal from an electrical power line to obtain N points is subjected to N-point RFFT operation to obtain a first complex sequence; carrying out harmonic extraction processing on the first complex sequence to obtain a second complex sequence; carrying out virtual-real combination processing on the second complex sequence to obtain a third complex sequence; performing RFFT operation on the third complex sequence to obtain a fourth complex sequence; the fourth complex sequence is subjected to virtual-real combination processing to obtain an N-point harmonic sequence, conjugate operation is not required before and after FFT, data extraction operation is not required, and simple addition and subtraction operation is only required to be performed twice, so that compared with the prior art, the calculation time is saved, and the code space can be saved as RFFT codes can be fully utilized for operation.

Those skilled in the art will appreciate that all or part of the steps in the methods of the above embodiments may be implemented by associated hardware instructed by a program, which may be stored in a computer-readable storage medium, and the storage medium may include: read-only memory, random access memory, magnetic or optical disk, and the like.

The harmonic detection method and the related device provided by the embodiment of the present invention are described in detail above, and the principle and the embodiment of the present invention are explained in detail herein by applying specific examples, and the description of the above embodiments is only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.

Claims

1. A method of harmonic detection, comprising:

sampling an electric signal from an electric power line to obtain an N-point electric signal sequence;

carrying out real number fast Fourier transform (RFFT) operation on the electrical signal sequence of the N points to obtain a first complex sequence;

carrying out harmonic extraction processing on the first complex sequence to obtain a second complex sequence;

performing virtual-real combining processing on the second complex sequence to obtain a third complex sequence, wherein the performing virtual-real combining processing on the second complex sequence includes: in the second complex number sequence comprising a plurality of second complex numbers, generating a third complex number corresponding to each second complex number except for the data corresponding to the direct current component and the Nyquist frequency point by a virtual-real combination processing mode, wherein the real part of the third complex number is equal to the sum of the imaginary part coefficient and the real part of the corresponding second complex number, and the imaginary part coefficient of the third complex number is equal to the difference between the real part coefficient and the imaginary part coefficient of the corresponding second complex number;

performing Real Fast Fourier Transform (RFFT) operation on the third complex sequence to obtain a fourth complex sequence; and

performing virtual-real combination processing on the fourth complex sequence to obtain an N-point harmonic sequence, wherein the performing virtual-real combination processing on the fourth complex sequence includes: in the fourth complex number sequence comprising a plurality of fourth complex numbers, each fourth complex number except the data corresponding to the direct current component and the Nyquist frequency point generates a sixth complex number corresponding to each fourth complex number through a virtual-real combination processing mode, wherein the real part of the sixth complex number is equal to the sum of the imaginary part coefficient and the real part of the corresponding fourth complex number, and the imaginary part coefficient of the sixth complex number is equal to the difference between the real part coefficient and the imaginary part coefficient of the corresponding fourth complex number.

2. The harmonic detection method of claim 1, wherein the step of sampling electrical signals from the power line to obtain an N-point electrical signal sequence comprises:

within one signal fundamental period, electrical signals are sampled at equal intervals from the power line to obtain an N-point electrical signal sequence.

3. The harmonic detection method according to claim 1, wherein the step of performing harmonic extraction processing on the first complex sequence to obtain a second complex sequence comprises:

removing a fundamental component in the first complex sequence to obtain the second complex sequence;

or,

4. The harmonic detection method according to any one of claims 1 to 3, wherein the step of subjecting the N-point sequence of electrical signals to an N-point Real Fast Fourier Transform (RFFT) operation to obtain a first sequence of complex numbers comprises: dividing the electrical signal sequence of the N points by the N, and then performing RFFT operation of the N points to obtain a first complex sequence;

or,

the harmonic detection method further includes:

dividing the obtained N-point harmonic sequence by the N.

5. A harmonic detection apparatus, comprising:

the sampling unit is used for sampling the electric signals from the electric power circuit to obtain an N-point electric signal sequence;

the first RFFT operation unit is used for carrying out real number fast Fourier transform (RFFT) operation on the N-point electric signal sequence obtained by the sampling unit to obtain a first complex sequence;

a harmonic extraction unit, configured to perform harmonic extraction processing on the first complex sequence obtained by the first RFFT operation unit to obtain a second complex sequence;

an imaginary-real combining processing unit, configured to perform imaginary-real combining processing on the second complex sequence obtained by the harmonic extraction unit to obtain a third complex sequence, specifically, the imaginary-real combining processing unit generates, in the second complex sequence obtained by the harmonic extraction unit and including a plurality of second complex numbers, a third complex number corresponding to each second complex number through an imaginary-real combining processing manner, where a real part of the third complex number is equal to a sum of an imaginary part coefficient and a real part of the corresponding second complex number, and an imaginary part coefficient of the third complex number is equal to a difference between the real part and the imaginary part of the corresponding second complex number, so as to obtain a third complex sequence including a plurality of third complex numbers;

a second RFFT operation unit, configured to perform RFFT operation on the third complex sequence obtained by the virtual-real combination processing unit to obtain a fourth complex sequence; and

the virtual-real combining processing unit is further configured to perform virtual-real combining processing on the fourth complex sequence obtained by the second RFFT operation unit to obtain an N-point harmonic sequence, and specifically, the virtual-real combining processing unit generates, in the fourth complex sequence obtained by the second RFFT operation unit and including a plurality of fourth complex numbers, a sixth complex number corresponding to each fourth complex number by a virtual-real combining processing manner, where a real part of the sixth complex number is equal to a sum of an imaginary part coefficient and a real part of the corresponding fourth complex number, and an imaginary part coefficient of the sixth complex number is equal to a difference between the real part and the imaginary part coefficient of the corresponding fourth complex number, so as to obtain the N-point harmonic sequence including the plurality of sixth complex numbers.

6. The harmonic detection device according to claim 5,

the first RFFT operation unit is specifically configured to divide the electrical signal sequence of N points obtained by the sampling unit by the N, and then perform RFFT operation of N points to obtain a first complex sequence;

or,

7. A harmonic cancellation apparatus, comprising:

the harmonic detection device is used for sampling the electric signals from the electric power circuit to obtain an N-point electric signal sequence; carrying out real number fast Fourier transform (RFFT) operation on the electrical signal sequence of the N points to obtain a first complex sequence; carrying out harmonic extraction processing on the first complex sequence to obtain a second complex sequence; carrying out virtual-real combination processing on the second complex sequence to obtain a third complex sequence; performing RFFT operation on the third complex sequence to obtain a fourth complex sequence; carrying out virtual-real combination processing on the fourth complex sequence to obtain and output an N-point harmonic sequence;