Harmonic extraction module and harmonic extraction method
By designing multiple single-harmonic gain modules and a closed-loop structure, high-precision, low-delay harmonic separation is achieved, solving the problems of poor dynamic tracking capability and insufficient real-time performance in existing technologies. It is particularly suitable for power converters and power quality detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DELTA ELECTRONICS (THAILAND) PUBLIC CO LTD
- Filing Date
- 2026-01-30
- Publication Date
- 2026-05-15
AI Technical Summary
Existing harmonic extraction techniques suffer from poor dynamic tracking capabilities, high algorithm complexity, and poor real-time performance.
Multiple single-harmonic gain modules are used, combined with rotating coordinate transformation, integral operation and inverse rotating coordinate transformation to construct a closed-loop structure, so as to realize the independent extraction of harmonic components of different frequencies, and to perform signal processing through adders and DC component extraction modules.
It achieves high-precision, low-latency harmonic separation, reduces computational load, improves real-time performance, and maintains high precision even when the input signal changes abruptly. It is suitable for power converters, grid-connected inverters, and power quality detection.
Smart Images
Figure CN122052479A_ABST
Abstract
Description
Technical Field
[0001] This case pertains to the technical field of power electronics and signal processing, and specifically relates to a harmonic extraction module and a harmonic extraction method. Background Technology
[0002] In switching power supplies and power systems, the input signal often contains multiple harmonics due to the influence of the power grid environment and nonlinear loads. If these harmonics are not suppressed or separated, they may cause electronic devices to overheat, have reduced lifespan, or generate electromagnetic interference (EMI).
[0003] To mitigate the impact of harmonics, it is often necessary to accurately extract each harmonic and control them accordingly. Existing harmonic extraction techniques mainly include Fourier transform (FFT), wavelet transform, and intelligent algorithm extraction, but these methods generally suffer from poor dynamic tracking capabilities, high algorithm complexity, and poor real-time performance.
[0004] In view of this, it is necessary to provide a harmonic extraction module and method with a simple computational structure, capable of multi-module parallel operation, and able to maintain high accuracy and low latency even when the input signal changes abruptly, in order to solve the problems faced by the existing technology. Summary of the Invention
[0005] The purpose of this case is to provide a harmonic extraction module and a harmonic extraction method to solve the problems of poor dynamic tracking capability, high algorithm complexity, and poor real-time performance of traditional harmonic extraction technology.
[0006] To achieve the above objectives, this invention provides a harmonic extraction module that receives a source signal and is configured to extract multiple harmonic components of different frequencies from the source signal. The harmonic extraction module includes: multiple single-harmonic gain modules, each with a default target frequency. Each single-harmonic gain module is configured to extract harmonic components of a specific frequency from the source signal and outputs a corresponding first output signal. The frequencies of the harmonic components extracted by each single-harmonic gain module are different. Each single-harmonic gain module includes: a rotation coordinate transformation module for performing a rotation coordinate transformation on the input signal according to the default target frequency to obtain a first signal and a second signal; and an integration module for... The first and second signals are integrated to obtain the third and fourth signals, respectively; the inverse rotation coordinate transformation module is used to perform inverse rotation coordinate transformation on the third and fourth signals according to the default target frequency to obtain the first separate output signal; the DC component extraction module is used to extract the DC component from the source signal and output the DC component signal; and the adder is connected to multiple single harmonic gain modules and the DC component extraction module to perform addition operations on the first separate output signal and the DC component signal output by the multiple single harmonic gain modules to generate a total output signal, wherein the total output signal is fed back to the input side of the harmonic extraction module to form a closed loop structure.
[0007] To achieve the above objectives, this application further provides a harmonic extraction method applied to a harmonic extraction module. The harmonic extraction module receives a source signal and includes multiple single-harmonic gain modules. Each single-harmonic gain module has a different default target frequency. Each single-harmonic gain module is configured to extract harmonic components of a specific frequency from the source signal and outputs a corresponding first output signal. The frequencies of the harmonic components extracted by each single-harmonic gain module are different. The harmonic extraction method includes: S1: Each single-harmonic gain module performs a rotational coordinate transformation on the input signal according to the default target frequency to obtain a first signal and... S2: Each single harmonic gain module integrates the first and second signals to obtain the third and fourth signals respectively; S3: Each single harmonic gain module performs inverse coordinate transformation on the third and fourth signals according to the default target frequency to obtain the first separate output signal; S4: Extract the DC component from the source signal and output the DC component signal; S5: Add the first separate output signal and the DC component signal output by the multiple single harmonic gain modules respectively to generate the total output signal, wherein the total output signal is fed back to the input side of the harmonic extraction module to form a closed loop structure. Attached Figure Description
[0008] Figure 1 This is a schematic diagram of the architecture of the harmonic extraction module in this embodiment.
[0009] Figure 2This is a flowchart illustrating the steps of the harmonic extraction method in this embodiment.
[0010] [List of Labels in the Attached Image]
[0011] 1: Harmonic Extraction Module
[0012] 2: Single Harmonic Gain Module
[0013] 3: DC component extraction module
[0014] 4: Adder
[0015] 5: Subtractor
[0016] 20: Rotation Coordinate Transformation Module
[0017] 21: Integral Module
[0018] 22: Inverse Rotation Coordinate Transformation Module
[0019] Vsource: Source signal
[0020] Vin: Input signal
[0021] X1: First signal
[0022] X2: Second signal
[0023] Xc: Third signal
[0024] Xs: Fourth signal
[0025] Ya: The first one should output a signal.
[0026] Yb: The second output signal
[0027] Vdc: DC component signal
[0028] Vfb: Total output signal Detailed Implementation
[0029] Some typical embodiments embodying the features and advantages of this invention will be described in detail in the following description. It should be understood that this invention can have various variations in different implementations, all of which do not depart from the scope of this invention, and the descriptions and illustrations herein are for illustrative purposes only and not intended to limit this invention.
[0030] For example, different embodiments in this disclosure may use repeated reference numerals and / or designations. These repetitions are for simplification and clarity and are not intended to limit the relationships between the various embodiments and / or the described appearance structures. Furthermore, when a component is referred to as "connected to" or "coupled to" another component, it may be directly connected to or coupled to the other component, or there may be intervening components. Additionally, it is understood that while terms such as "first," "second," and "third" may be used in the claims to describe different components, these components should not be limited by these terms, and the components described accordingly in the embodiments are represented by different component symbols. These terms are used to distinguish different components. For example, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component without departing from the scope of the embodiments. The term "and / or" as thus used includes any or all combinations of one or more of the associated listed embodiments.
[0031] Please see Figure 1 This is a schematic diagram of the harmonic extraction module architecture in this embodiment. The input side of the harmonic extraction module 1 in this embodiment can receive a source signal Vsource and extract multiple harmonic components corresponding to different frequencies from the source signal Vsource. The harmonic extraction module 1 includes multiple single-harmonic gain modules 2, a DC component extraction module 3, an adder 4, and a subtractor 5.
[0032] Each single-harmonic gain module 2 has a different default target frequency. Each single-harmonic gain module 2 is designed to extract harmonic components of a specific frequency from the source signal Vsource based on the default target frequency and output a corresponding first output signal Ya. The frequencies of the harmonic components extracted by each single-harmonic gain module 2 are different. Furthermore, each single-harmonic gain module 2 includes a rotation coordinate transformation module 20, an integration module 21, and an inverse rotation coordinate transformation module 22. The rotation coordinate transformation module 20 performs a rotation coordinate transformation on the input signal Vin according to the default target frequency of the single-harmonic gain module 2 to obtain a first signal X1 and a second signal X2. The integration module 21 performs integration operations on the first signal X1 and the second signal X2 respectively to obtain a third signal Xc and a fourth signal Xs. The inverse rotation coordinate transformation module 22 performs an inverse rotation coordinate transformation on the third signal Xc and the fourth signal Xs according to the default target frequency to obtain the first output signal Ya.
[0033] The DC component extraction module 3 is used to extract the DC component from the source signal Vsource to output the corresponding DC component signal Vdc.
[0034] Adder 4 is connected to multiple single harmonic gain modules 2 and DC component extraction module 3 to perform addition operations on the first individual output signal Ya and DC component signal Vdc output by the multiple single harmonic gain modules 2 respectively, so as to generate a total output signal Vfb, wherein the total output signal Vfb is fed back to the input side of harmonic extraction module 1 to form a closed loop structure.
[0035] Subtractor 5 is connected to multiple single harmonic gain modules 2 and DC component extraction module 3. Subtractor 5 receives source signal Vsource and performs subtraction operation on source signal Vsource and total output signal Vfb to generate input signal Vin, which is then further output to multiple single harmonic gain modules 2 and DC component extraction module 3.
[0036] In some embodiments, each single harmonic gain module 2 may also output a second separate output signal Yb. The inverse rotation coordinate transformation module 22 performs an inverse rotation coordinate transformation on the third signal Xc and the fourth signal Xs according to the default target frequency to obtain the second separate output signal Yb. The phase of the second separate output signal lags by 90 degrees relative to the phase of the first separate output signal, and is used for further calculations, such as dq transformation or phase-locked loop.
[0037] With the aforementioned structural configuration, the harmonic extraction module 1 of this invention can independently extract each harmonic component in the source signal Vsource, achieving the separation of multiple harmonics. Since each single-harmonic gain module 2 is based on rotating coordinate transformation and integral operation, harmonic component separation can be completed without complex spectrum analysis, thereby reducing computational load and improving real-time performance. Furthermore, the design of a second separate output signal can further provide phase information to facilitate subsequent dq transformation or phase-locked loop control applications, enabling the system to possess both high precision and low latency characteristics. Moreover, each single-harmonic gain module 2 operates at a fixed target frequency, continuously tracking and extracting harmonic components corresponding to the target frequency, avoiding interference between different frequency bands. Therefore, the harmonic extraction module of this invention has advantages such as simple structure, easy implementation, high real-time performance, and good scalability, making it particularly suitable for power converters, grid-connected inverters, and power quality detection fields. Furthermore, by using the DC component extraction module 3, the DC component in the source signal Vsource can be suppressed / compensated under closed-loop operation, thus avoiding interference from the DC component to the second output signal Yb.
[0038] In some embodiments, the rotating coordinate transformation module 20 performs rotating coordinate transformation by multiplying the input signal Vin with the sine and cosine functions of the target frequency, respectively. After transformation, the input signal Vin can be converted from the stationary coordinate system to the rotating coordinate system to obtain the first signal X1 and the second signal X2. The mathematical expressions for the first signal X1 and the second signal X2 are as follows: = ; in The input signal is Vin. For the first signal X1, For the second signal X2, The angular frequency corresponding to the target frequency of the single harmonic gain module 2 is the frequency component of the nth harmonic in the source signal Vsource.
[0039] In some embodiments, the inverse rotation coordinate transformation module 22 generates a first separate output signal Ya by performing operations on the third signal Xc and the fourth signal Xs with a first matrix, wherein the first matrix is as follows: ;
[0040] In addition, the inverse rotation coordinate transformation module 22 also generates a second output signal Yb by performing operations on the third signal Xc and the fourth signal Xs with the second matrix, wherein the second matrix is as follows: ;
[0041] In other embodiments, each single-harmonic gain module 2 has a first transfer function between its input signal Vin and its first output signal Ya, and is expressed as follows: ; in The Laplace transform of the input signal Vin. For the Laplace transform of the first output signal Ya, For the integral transfer function of integral module 21, This is the first equivalent transfer function of the single-harmonic gain module 2. Furthermore, a second transfer function exists between the input signal Vin and the second output signal Yb of each single-harmonic gain module 2, and is expressed as follows: ; in For the Laplace transform of the second output signal Yb, This is the second equivalent transfer function of the single harmonic gain module 2.
[0042] In some embodiments, the integration module 21 is a first-order integrator, and the integration transfer function of the integration module 21 is... It is expressed as follows: ; in The integral time constant is... For the Laplace transform variables. Each single-harmonic gain module 2 has a first equivalent transfer function. and the second equivalent transfer function Based on the first equivalent transfer function Based on the frequency domain characteristics, specific frequency harmonic components in the source signal Vsource are extracted in the closed-loop structure, using the second equivalent transfer function. The frequency domain characteristics are used to generate a second output signal Yb in the closed-loop structure, where the first equivalent transfer function... Represented as: ; Second equivalent transfer function Represented as: ;
[0043] The following will discuss the first equivalent transfer function. and the second equivalent transfer function Further analysis is needed to demonstrate the characteristics of the gain. and These can be used to construct resonant elements, and when performing frequency response analysis, let... = ,in In frequency response analysis, angular frequency is used to represent the response characteristics at different angular frequencies. = Substitute into the first equivalent transfer function and the second equivalent transfer function Then, its frequency response expressions can be obtained as follows: ; ; When the angular frequency of a certain harmonic component in the input signal Vin is close to the default target angular frequency At that time, the first equivalent transfer function and the second equivalent transfer function The denominator in As the frequency approaches 0, the amplitude gain approaches infinity, meaning that the frequency of this element approaches 0. The input component has infinite gain, and from the above expression, it can also be seen that the first output signal Ya leads the second output signal Yb by 90°.
[0044] In some embodiments, the DC component extraction module 3 is a first-order integrator with a transfer function of: As shown below: .
[0045] In some embodiments, the source signal Vsource may contain multiple AC signals of different frequencies.
[0046] As previously stated, after each single-harmonic gain module 2 in the system is tuned for a different target frequency, multiple single-harmonic gain modules 2 can be configured in parallel to form a multi-frequency harmonic extraction structure. Therefore, the equivalent closed-loop transfer function of the nth single-harmonic gain module 2 relative to the source signal Vsource is defined as follows: ; in This is the equivalent closed-loop transfer function. The equivalent transfer function of the nth single-harmonic gain module 2 is the angular frequency corresponding to its default target frequency. , H is the equivalent transfer function of the remaining single harmonic gain modules 2 except for the nth single harmonic gain module 2. Let be the equivalent transfer function of the DC component extraction module 3, and k represent the number of all single-harmonic gain modules 2 participating in the superposition. For angular frequency... = The closed-loop gain of the nth single-harmonic gain module 2 is expressed as follows: ; For angular frequency = The components ( ≠ ), No. The closed-loop gain of the single harmonic gain module 2 is: ; Due to the aforementioned equivalent closed-loop transfer function At angular frequency = The closed-loop gain approaches 1 at certain frequencies and approaches 0 at other frequencies. Therefore, the source signal Vsource(t) can be represented as follows: ; in Indicates the source signal DC component, Indicates the source signal The amplitude of the k-th harmonic component, Let be the fundamental angular frequency. Under this condition, the first output signal Ya from the nth single-harmonic gain module 2 can be expressed as: ; in, Let V be the amplitude of the nth harmonic component in the source signal Vsource.
[0047] Therefore, it can be seen that multiple single-harmonic gain modules 2 correspond to different target frequencies, so that each specific frequency component in the source signal Vsource is concentrated in the corresponding single-harmonic gain module 2 for extraction. Through the closed-loop structure composed of multiple single-harmonic gain modules 2, DC component extraction module 3, adder 4 and subtractor 5, the system can achieve independent extraction and reconstruction of multiple harmonics in the time domain, so that harmonic components of different frequencies are completely separated and do not interfere with each other between modules, thereby achieving high-precision and low-delay multiple harmonic extraction effect, which is particularly suitable for applications such as power converters, grid-connected inverters and power quality detection.
[0048] Please see Figure 2 This is a flowchart illustrating the steps of the harmonic extraction method in this embodiment. The harmonic extraction method of this embodiment can be applied to... Figure 1 The harmonic extraction module 1 shown below includes the following steps in its harmonic extraction method.
[0049] In step S1, each single harmonic gain module 2 performs a rotational coordinate transformation on the input signal Vin according to the default target frequency to obtain the first signal X1 and the second signal X2.
[0050] In step S2, each single harmonic gain module 2 performs integration operations on the first signal X1 and the second signal X2 respectively to obtain the third signal Xc and the fourth signal Xs.
[0051] In step S3, each single harmonic gain module 2 performs an inverse rotation coordinate transformation on the third signal Xc and the fourth signal Xs according to the default target frequency to obtain the first separate output signal Ya.
[0052] Step S4: Extract the DC component from the source signal Vsource and output the DC component signal Vdc.
[0053] Step S5: The first output signal Ya and the DC component signal Vdc output by the multiple single harmonic gain modules 2 are added to generate the total output signal Vfb, which is fed back to the input side of the harmonic extraction module 1 to form a closed loop structure.
[0054] In some embodiments, in step S1, a rotational coordinate transformation is performed by multiplying the input signal Vin with the sine and cosine functions of the target frequency, respectively.
[0055] In some embodiments, in step S3, the first individual output signal Ya is generated by performing operations on the third signal and the fourth signal with the aforementioned first matrix.
[0056] In some embodiments, in step S3, a second output signal Yb is generated by performing operations on the third signal and the fourth signal with the aforementioned second matrix.
[0057] In some embodiments, in step S4, the DC component extraction module 3 extracts the DC component from the source signal Vsource using a first-order integrator, wherein the transfer function of the first-order integrator is as described above and will not be repeated here.
[0058] In summary, this invention provides a harmonic extraction module and method. This module can independently extract each harmonic component from the source signal, achieving separation of multiple harmonics. Since each single-harmonic gain module is based on rotating coordinate transformation and integral operation, harmonic component separation can be completed without complex spectrum analysis, thereby reducing computational load and improving real-time performance. Furthermore, the design of a second separate output signal can provide phase information for subsequent dq transformation or phase-locked loop control applications, giving the system both high precision and low latency. Moreover, each single-harmonic gain module operates at a fixed target frequency, continuously tracking and extracting harmonic components at the corresponding target frequency, avoiding interference between different frequency bands. Therefore, the harmonic extraction module of this invention has advantages such as simple structure, easy implementation, high real-time performance, and good scalability, making it particularly suitable for power converters, grid-connected inverters, and power quality detection. Furthermore, by setting up a DC component extraction module, the DC component of the input signal can be removed before it enters each single harmonic gain module, thus avoiding interference from the DC component to the second output signal.
Claims
1. A harmonic extraction module for receiving a source signal, characterized in that, Include: Multiple single-harmonic gain modules are provided, each with a different default target frequency. Each single-harmonic gain module is configured to extract harmonic components of a specific frequency from the source signal and output a corresponding output signal. The frequencies of the harmonic components extracted by each single-harmonic gain module are different. Each single-harmonic gain module includes: A rotation coordinate transformation module is used to perform rotation coordinate transformation on an input signal according to the default target frequency to obtain a first signal and a second signal; An integration module is used to integrate the first signal and the second signal respectively to obtain a third signal and a fourth signal; and An inverse rotation coordinate transformation module is used to perform inverse rotation coordinate transformation on the third signal and the fourth signal according to the default target frequency to obtain the first individual output signal; A DC component extraction module is used to extract the DC component from the source signal and output a DC component signal; and An adder is connected to the plurality of single harmonic gain modules and the DC component extraction module to perform addition operations on the first individual output signals and the DC component signals output by the plurality of single harmonic gain modules respectively, so as to generate a total output signal, wherein the total output signal is fed back to the input side of the harmonic extraction module to form a closed loop structure.
2. The harmonic extraction module as described in claim 1, wherein the rotating coordinate transformation module performs rotating coordinate transformation by multiplying the input signal with a sine and a cosine function of the target frequency, respectively, wherein the first signal and the second signal are represented as: = ； in The input signal, For the first signal, The second signal, This is the angle frequency corresponding to the target frequency by default for the single harmonic gain module.
3. The harmonic extraction module as described in claim 1, wherein the inverse rotation coordinate transformation module generates the first individual output signal by performing operations on the third signal and the fourth signal with a first matrix, wherein the first matrix is: in This is the angle frequency corresponding to the target frequency by default for the single harmonic gain module.
4. The harmonic extraction module as described in claim 1, wherein the inverse rotation coordinate transformation module further performs inverse rotation coordinate transformation on the third signal and the fourth signal according to the default target frequency to obtain a second separate output signal, wherein the phase of the second separate output signal lags behind the phase of the first separate output signal by 90 degrees.
5. The harmonic extraction module as described in claim 4, wherein the inverse rotation coordinate transformation module generates the second individual output signal by performing operations on the third signal and the fourth signal with a second matrix, wherein the second matrix is: ； in This is the angle frequency corresponding to the target frequency by default for the single harmonic gain module.
6. The harmonic extraction module as described in claim 4, wherein a first transfer function between the input signal and the first individual output signal of each of the single harmonic gain modules is expressed as: ； in The Laplace transform of the input signal, The Laplace transform of the first individual output signal, This is a transfer function of the integral module. The default angular frequency corresponding to the target frequency of the single harmonic gain module; The second transfer function between the input signal and the second individual output signal of each of the single harmonic gain modules is expressed as follows: ； in This is the Laplace transform of the second individual output signal.
7. The harmonic extraction module as described in claim 6, wherein the integration module is a first-order integrator and its transfer function is... Each of the single-harmonic gain modules has a first equivalent transfer function and a second equivalent transfer function. Based on the frequency domain characteristics of the first equivalent transfer function, harmonic components of a specific frequency in the source signal are extracted in the closed-loop structure. Based on the frequency domain characteristics of the second equivalent transfer function, the second individual output signal is generated in the closed-loop structure. The first equivalent transfer function is expressed as: ； in, Let be the first equivalent transfer function. It is an integral time constant; The second equivalent transfer function is expressed as: ； in, This is the second equivalent transfer function.
8. The harmonic extraction module as described in claim 1, wherein the harmonic extraction module further includes a subtractor connected to the plurality of single harmonic gain modules and the DC component extraction module, the subtractor receiving the source signal and performing a subtraction operation on the source signal and the total output signal to generate the input signal.
9. The harmonic extraction module as described in claim 8, wherein the equivalent closed-loop transfer function of the nth single-harmonic gain module among the plurality of single-harmonic gain modules relative to the source signal is defined as: ； in Let be the equivalent closed-loop transfer function. Let n be an equivalent transfer function of the nth single-harmonic gain module. H is an equivalent transfer function for the remaining single-harmonic gain modules except for the nth single-harmonic gain module. Let be an equivalent transfer function of the DC component extraction module, and k represent the number of all the single harmonic gain modules participating in the superposition.
10. The harmonic extraction module as claimed in claim 1, wherein the source signal comprises multiple AC signals of different frequencies.
11. The harmonic extraction module as described in claim 1, wherein, The DC component extraction module is a first-order integrator with the following transfer function: ； in Let be the transfer function.
12. A harmonic extraction method, applied to a harmonic extraction module, characterized in that, The harmonic extraction module receives a source signal and includes multiple single-harmonic gain modules. Each single-harmonic gain module defaults to a different target frequency. Each single-harmonic gain module is configured to extract harmonic components of a specific frequency from the source signal and outputs a corresponding single-harmonic gain module output signal. The frequencies of the harmonic components extracted by each single-harmonic gain module are different. The harmonic extraction method includes: Step S1: Each of the single harmonic gain modules performs a rotational coordinate transformation on an input signal according to the default target frequency to obtain a first signal and a second signal; Step S2: Each of the single harmonic gain modules performs integration operations on the first signal and the second signal respectively to obtain a third signal and a fourth signal; Step S3: Each of the single harmonic gain modules performs an inverse rotation coordinate transformation on the third signal and the fourth signal according to the default target frequency to obtain the first individual output signal; Step S4: Extract the DC component from the source signal and output the DC component signal; Step S5: Add the first individual output signals and the DC component signals output by the multiple single harmonic gain modules respectively to generate a total output signal, wherein the total output signal is fed back to the input side of the harmonic extraction module to form a closed loop structure.
13. The harmonic extraction method as described in claim 12, wherein in step S1, the input signal is multiplied by a sine and a cosine function of the target frequency respectively to perform a rotating coordinate transformation, wherein the first signal and the second signal are represented as: = ； in The input signal, For the first signal, The second signal, This is the angle frequency corresponding to the target frequency by default for the single harmonic gain module.
14. The harmonic extraction method as described in claim 12, wherein in step S3, the first individual output signal is generated by performing an operation on the third signal and the fourth signal with a first matrix; wherein the first matrix is: in This is the angle frequency corresponding to the target frequency by default for the single harmonic gain module.
15. The harmonic extraction method of claim 12, wherein step S3 further comprises: performing an inverse rotation coordinate transformation on the third signal and the fourth signal according to the default target frequency to obtain a second separate output signal, wherein the phase of the second separate output signal lags behind the phase of the first separate output signal by 90 degrees.
16. The harmonic extraction method as described in claim 15, wherein in step S3, the third signal and the fourth signal are processed with a second matrix to generate the second individual output signal, wherein the second matrix is: ； in This is the angle frequency corresponding to the target frequency by default for the single harmonic gain module.
17. The harmonic extraction method of claim 15, wherein a first transfer function between the input signal and the first individual output signal of each of the single harmonic gain modules is expressed as: ； in The Laplace transform of the input signal, The Laplace transform of the first individual output signal, This is a transfer function of the integration module. The default angular frequency corresponding to the target frequency of the single harmonic gain module; The second transfer function between the input signal and the second individual output signal of each of the single harmonic gain modules is expressed as follows: ； in This is the Laplace transform of the second individual output signal.
18. The harmonic extraction method as described in claim 17, wherein the integration module is a first-order integrator and its transfer function is... Each of the single-harmonic gain modules has a first equivalent transfer function and a second equivalent transfer function. Based on the frequency domain characteristics of the first equivalent transfer function, harmonic components of a specific frequency in the source signal are extracted in the closed-loop structure. Based on the frequency domain characteristics of the second equivalent transfer function, the second individual output signal is generated in the closed-loop structure. The first equivalent transfer function is expressed as: ； in, Let be the first equivalent transfer function. It is an integral time constant; The second equivalent transfer function is expressed as: ； in, This is the second equivalent transfer function.
19. The harmonic extraction method as described in claim 12, further comprising: the harmonic extraction module receiving the source signal and performing a subtraction operation on the source signal and the total output signal to generate the input signal.
20. The harmonic extraction method of claim 19, wherein the equivalent closed-loop transfer function of the nth single harmonic gain module among the plurality of single harmonic gain modules relative to the source signal is defined as: ； in Let be the equivalent closed-loop transfer function. Let n be an equivalent transfer function of the nth single-harmonic gain module. H is an equivalent transfer function for the remaining single-harmonic gain modules except for the nth single-harmonic gain module. To extract an equivalent transfer function of the DC component, k represents the number of all the single-harmonic gain modules involved in the superposition.
21. The harmonic extraction method as described in claim 12, wherein the source signal comprises multiple AC signals of different frequencies.
22. The harmonic extraction method as described in claim 12, wherein in step S4, a first-order integrator is used to extract the DC component from the source signal, and the transfer function of the first-order integrator is: ； in Let be the transfer function.