Method, system and computer-readable storage medium for extracting DC component of AC signal
By eliminating low-frequency harmonics step by step and limiting high-frequency noise, the problem of insufficient speed and accuracy of DC component extraction in the existing technology is solved, and fast and accurate DC component extraction is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2026-04-14
- Publication Date
- 2026-06-02
AI Technical Summary
In existing technologies, low-pass filters have large response delays and poor dynamic performance, while fixed parameters of band-stop filters lead to decreased extraction accuracy when the AC signal frequency shifts, making it difficult to quickly and accurately extract the DC component.
A method for eliminating low-frequency harmonics in stages is adopted. By setting a limit value significantly higher than that of the DC component, high-frequency noise and high-order harmonics are amplified and limited to a high-amplitude range, and the DC component is extracted by combining filtering processing.
It achieves rapid and accurate extraction of DC components, improves the reliability and efficiency of extraction, and reduces response delay and noise interference.
Smart Images
Figure CN122137212A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power electronics technology, and in particular to a method, system, and computer-readable storage medium for extracting the DC component of an AC signal. Background Technology
[0002] In power electronic devices such as photovoltaic grid-connected inverters and electric vehicle traction inverters, the AC signal output by the inverter often contains a certain DC component. This DC component can adversely affect the power grid, motors, and other equipment, therefore it needs to be detected and suppressed. Furthermore, in harmonic control, specific harmonics are often converted into DC signals for processing through rotational transformation; therefore, the rapid extraction of the DC component is crucial for the real-time performance and accuracy of the control system.
[0003] Currently, common methods for extracting DC components mainly employ low-pass filters or band-stop filters. Low-pass filters suffer from large response delays and poor dynamic performance; band-stop filters typically have fixed parameters, and their extraction accuracy decreases when the AC signal frequency shifts. Summary of the Invention
[0004] This application provides a method, system, and computer-readable storage medium for extracting the DC component of an AC signal. The method can achieve fast and accurate extraction of the target DC component.
[0005] In a first aspect, this application provides a method for extracting the DC component of an AC signal, comprising: Acquire the AC signal to be processed and its fundamental angular frequency; Following the order of harmonics from high to low, the AC signal is sequentially processed for low-frequency harmonic cancellation based on the fundamental angular frequency. Each low-frequency harmonic cancellation process is configured as follows: Eliminate the low-frequency harmonics of the current target, while amplifying the high-frequency noise and high-order harmonics in the AC signal that have not been eliminated, so that the high-frequency noise and high-order harmonics trigger amplitude limiting. After completing the low-frequency harmonic elimination process for a preset number of times, the resulting signal is filtered to extract the target DC component from the AC signal. The amplitude limiting value is set to be significantly higher than the amplitude of the target DC component in the AC signal, so that the amplitude of high-frequency noise and high-order harmonics after limiting is far away from the amplitude of the target DC component.
[0006] In one embodiment, the low-frequency harmonic cancellation process includes: The signal to be processed is sampled three times at equal time intervals to obtain the first sampled signal, the second sampled signal, and the third sampled signal; The sum of the first sampled signal and the third sampled signal is multiplied by the first filter coefficient, and then the product of the second sampled signal and the second filter coefficient is subtracted to obtain the mixed signal that eliminates the target low-frequency harmonics. The mixed signal includes: a coarse feed current component modulated by a first filter coefficient, a second filter coefficient, and a fundamental angular frequency; The first and second filter coefficients are configured such that the coarse input current component containing the target low-frequency harmonic in the mixed signal is 0, thereby eliminating the current target low-frequency harmonic.
[0007] In one embodiment, the mixed signal further includes a coarse-lifted DC component modulated by a first filter coefficient and a second filter coefficient, wherein the first filter coefficient and the second filter coefficient are further configured such that the gain of the coarse-lifted DC component is 1.
[0008] In one embodiment, the mixed signal further includes: a coarsely extracted DC component modulated by a first filter coefficient and a second filter coefficient; The extraction method also includes: calculating the gain of the coarsely extracted DC component based on the first filter coefficient and the second filter coefficient; multiplying the mixed signal by an adjustment coefficient when the gain of the coarsely extracted DC component is not equal to 1, so that the gain of the coarsely extracted DC component is equal to 1; and then limiting the high-frequency noise and high-order harmonics contained in the mixed signal.
[0009] In one embodiment, after completing a preset number of low-frequency harmonic cancellation processes, the resulting signal is filtered to extract the target DC component from the AC signal, including: The amplitude of the mixed signal obtained from the last low-frequency harmonic elimination process is compared. If the absolute value of the amplitude of the mixed signal is less than the preset amplitude threshold, the mixed signal is determined to be a valid signal, and the output is updated to obtain the target DC component. Otherwise, the mixed signal is determined to be an invalid signal, the output is not updated, and the previous valid signal output is maintained.
[0010] In one embodiment, signal rate of change detection is performed when the absolute value of the amplitude of the mixed signal is less than a preset amplitude threshold. If the absolute value of the difference between the amplitude of the mixed signal and the previous valid signal is less than or equal to the preset rate of change threshold, the mixed signal is determined to be a valid signal, and the output is updated to obtain the target DC component; otherwise, the mixed signal is determined to be an invalid signal, the output is not updated, and the output of the previous valid signal is maintained.
[0011] In one embodiment, the order of the target low-frequency harmonic to be eliminated is less than or equal to the 9th harmonic order.
[0012] Secondly, this application also provides a system for extracting the DC component of an AC signal, comprising: The signal acquisition module is used to acquire the AC signal to be processed and its fundamental angular frequency; Multiple harmonic cancellation modules, cascaded together, are used to sequentially cancel low-frequency harmonics in AC signals according to the fundamental angular frequency, in descending order of harmonic order. Each low-frequency harmonic cancellation process is configured as follows: Eliminate the low-frequency harmonics of the current target, while amplifying the high-frequency noise and high-order harmonics in the AC signal that have not been eliminated, so that the high-frequency noise and high-order harmonics trigger amplitude limiting. The filtering module is used to filter the obtained signal after completing a preset number of low-frequency harmonic elimination processes in order to extract the target DC component in the AC signal. The amplitude limiting value is set to be significantly higher than the amplitude of the target DC component in the AC signal, so that the amplitude of high-frequency noise and high-order harmonics after limiting is far away from the amplitude of the target DC component.
[0013] In one embodiment, the low-frequency harmonic cancellation process includes: The signal to be processed is sampled three times at equal time intervals to obtain the first sampled signal, the second sampled signal, and the third sampled signal; The sum of the first sampled signal and the third sampled signal is multiplied by the first filter coefficient, and then the product of the second sampled signal and the second filter coefficient is subtracted to obtain the mixed signal that eliminates the target low-frequency harmonics. The mixed signal includes: a coarse feed current component modulated by a first filter coefficient, a second filter coefficient, and a fundamental angular frequency; The first and second filter coefficients are configured such that the coarse input current component containing the target low-frequency harmonic in the mixed signal is 0, thereby eliminating the current target low-frequency harmonic.
[0014] Thirdly, this application also provides a computer-readable storage medium including a processing program that, when executed, performs the DC component extraction method for AC signals of the first aspect.
[0015] The aforementioned method for extracting the DC component of an AC signal eliminates the target low-frequency harmonics stepwise from high to low, and amplifies and forcibly limits the amplitude of the uneliminated high-frequency noise and higher-order harmonics to a high amplitude range, thus significantly separating them from the DC component in the amplitude domain. This allows for more accurate and faster extraction of the target DC component during filtering, improving the reliability and efficiency of the extraction. Attached Figure Description
[0016] Figure 1 This is a flowchart of a method for extracting the DC component of an AC signal in one embodiment; Figure 2This is a flowchart illustrating the process of extracting the target DC component from an AC signal in one embodiment. Figure 3 This is a simulation diagram of a method for extracting the DC component of an AC signal in one embodiment; Figure 4 This is a schematic diagram of a DC component extraction system for an AC signal in one embodiment; Figure 5 This is a schematic diagram of a harmonic cancellation module in one embodiment. Detailed Implementation
[0017] The present application will be described in detail below with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present application. Any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the protection scope of the present application.
[0018] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.
[0019] In one embodiment, such as Figure 1 As shown, a method for extracting the DC component of an AC signal is provided, comprising: Step 101: Obtain the AC signal to be processed and its fundamental angular frequency.
[0020] Specifically, the AC signal to be processed can be a digital sequence of voltage or current obtained by sampling through a sensor and undergoing analog-to-digital conversion; the fundamental angular frequency corresponding to the AC signal to be processed needs to be determined according to the specific application scenario.
[0021] For example, in a photovoltaic grid-connected scenario, the AC signal to be processed can be taken from the inverter output current, and the fundamental angular frequency of the AC signal can be obtained in real time by the phase-locked loop tracking the grid voltage; in an electric vehicle drive scenario, the AC signal to be processed can be taken from the motor phase current, and the fundamental angular frequency of the AC signal can be dynamically given by the speed fed back by the motor encoder or the frequency estimated by the observer; in a frequency converter control scenario, the AC signal to be processed can be taken from the output voltage, and the fundamental angular frequency of the AC signal can be directly taken from the command frequency given by the controller or estimated in real time through signal analysis.
[0022] Step 102: According to the order of harmonics from high to low, perform low-frequency harmonic cancellation processing on the AC signal in sequence based on the fundamental angular frequency. Each low-frequency harmonic cancellation process is configured to: eliminate the current target low-frequency harmonics, and at the same time amplify the high-frequency noise and high-order harmonics in the AC signal that have not been eliminated, so that the high-frequency noise and high-order harmonics trigger amplitude limiting; wherein, the amplitude limiting value is set to be significantly higher than the amplitude of the target DC component in the AC signal, so that the amplitude of the high-frequency noise and high-order harmonics after amplitude limiting is far away from the amplitude of the target DC component. Specifically, based on the known fundamental angular frequency, a first low-frequency harmonic cancellation process is performed on the AC signal targeting the highest harmonic to be eliminated (e.g., the 9th harmonic). This low-frequency harmonic cancellation process can amplify the high-frequency noise and higher harmonics in the amplified AC signal that have not been eliminated while eliminating the current target low-frequency harmonic. Furthermore, a limiting operation is applied to the AC signal after the low-frequency harmonic cancellation process. The limiting value set in the limiting operation is significantly higher than the amplitude of the target DC component in the AC signal, thereby limiting the amplitude of the amplified high-frequency noise and higher harmonics to a level much higher than that of the target DC component, achieving effective separation of the target DC component from the amplified high-frequency noise and higher harmonics.
[0023] Using the output AC signal as input, the harmonic elimination and limiting operations are repeated for the next lower-order target harmonic (e.g., the 7th harmonic). This process proceeds sequentially from highest to lowest harmonic order until the lowest-order harmonic (e.g., the fundamental frequency) is eliminated.
[0024] It should be noted that, in order to balance extraction accuracy and real-time performance, the order of harmonics to be eliminated is usually limited to less than or equal to the 9th order, thereby avoiding unnecessary processing delays in the process of eliminating higher-order harmonics whose amplitudes have been significantly attenuated.
[0025] Step 103: After completing the low-frequency harmonic elimination process for a preset number of times, the obtained signal is filtered to extract the target DC component in the AC signal.
[0026] Specifically, after the low-frequency harmonic elimination process from high to low, the main low-frequency harmonic components in the AC signal have been effectively removed, and the high-frequency noise and higher-order harmonics have been significantly amplified and limited to a level much higher than the target DC component due to the amplitude limiting effect.
[0027] At this point, the AC signal mainly consists of a target DC component with stable amplitude and high-frequency noise whose amplitude is clamped to a value far from the target DC component. Further, the AC signal at this point is filtered to extract the target DC component.
[0028] For example, filtering AC signals can be performed by analyzing the dynamic characteristics of the AC signal (such as instantaneous rate of change and absolute amplitude), setting reasonable logical judgment thresholds, thereby continuously tracking and filtering the signal value of the target DC component, effectively distinguishing the stable target DC component from the violently fluctuating high-frequency noise, and achieving rapid and accurate extraction of the target DC component.
[0029] In this embodiment, the method eliminates the target low-frequency harmonics step by step from high to low, and amplifies the uneliminated high-frequency noise and high-order harmonics and forces them to be limited to a high amplitude range, so that they are significantly separated from the DC component in the amplitude domain. This allows for more accurate and faster extraction of the target DC component in the filtering process, improving the reliability and efficiency of extracting the target DC component.
[0030] In one embodiment, the low-frequency harmonic cancellation process includes: The signal to be processed is sampled three times at equal time intervals to obtain a first sampled signal, a second sampled signal, and a third sampled signal; the sum of the first sampled signal and the third sampled signal is multiplied by a first filter coefficient, and then the product of the second sampled signal and the second filter coefficient is subtracted to obtain a mixed signal that eliminates the target low-frequency harmonics. The mixed signal includes a coarse input current component modulated by a first filter coefficient, a second filter coefficient, and a fundamental angular frequency; wherein the first filter coefficient and the second filter coefficient are configured such that the coarse input current component containing the target low-frequency harmonic in the mixed signal is 0, thereby eliminating the current target low-frequency harmonic.
[0031] Specifically, let the sampling interval be... t s And the fundamental angular frequency is known to be Assume the input signal at time t is... Furthermore, in consecutive moments t , t + t s , t +2 t s For the input signal is Three samples are taken at equal time intervals to obtain the first sampled signal. Second sampling signal Third sampling signal .
[0032] The first sampled signal With the third sampled signal The sum multiplied by the first filter coefficient Subtract the second sampled signal With the second filter coefficient The product of these two signals yields a mixed signal that eliminates the target low-frequency harmonics. : .
[0033] Furthermore, the first sampling signal First sampling signal and the third sampling signal With the third sampled signal Substitute the expression It can be deduced that: .
[0034] in, It can represent the amplitude of the fundamental AC component in the processed signal. For the coarse current component of the target low-frequency harmonic, This represents the DC component to be extracted.
[0035] To make the coarse input current component containing the target low-frequency harmonics in the mixed signal zero, the coefficients of the coarse input current component need to be set to zero, i.e. .
[0036] In one embodiment, the mixed signal further includes a coarsely extracted DC component modulated by a first filter coefficient and a second filter coefficient, wherein the first filter coefficient and the second filter coefficient are further configured such that the gain of the coarsely extracted DC component is 1.
[0037] Specifically, mixed-signal The expression is: .
[0038] To make the coarse DC component If the gain is 1, then the coarse DC component needs to be extracted. The coefficient is 1, that is .
[0039] It should be noted that when and When the values shown in the following formula are taken, the coarse DC component gain is 0, and the coarse DC component gain remains unchanged at 1: .
[0040] In another embodiment, the gain of the coarse DC component is calculated based on the first filter coefficient and the second filter coefficient. If the gain of the coarse DC component is not equal to 1, the mixed signal is multiplied by an adjustment coefficient so that the gain of the coarse DC component is equal to 1, and then the high-frequency noise and high-order harmonics contained in the mixed signal are limited.
[0041] Specifically, the first filter coefficient Second filter coefficient The relationship between them only needs to satisfy the condition that , It doesn't have to be equal to 1.
[0042] Assume the gain of the coarse DC component is Then an adjustment coefficient will be calculated. The resulting mixed signal after harmonic elimination is processed before amplitude limiting. Multiply the whole by the adjustment factor This restores the corrected straight coarse lift component gain to * .
[0043] In one embodiment, after performing a preset number of low-frequency harmonic cancellation processes, filtering the resulting signal to extract the target DC component from the AC signal includes: The amplitude of the mixed signal obtained from the last low-frequency harmonic elimination process is compared. If the absolute value of the amplitude of the mixed signal is less than the preset amplitude threshold, the mixed signal is determined to be a valid signal, and the output is updated to obtain the target DC component. Otherwise, the mixed signal is determined to be an invalid signal, the output is not updated, and the previous valid signal output is maintained.
[0044] Specifically, the mixed signal obtained from the final stage of low-frequency harmonic cancellation processing is acquired. The low-frequency harmonic components in this mixed signal have been eliminated, and the main body of the mixed signal is the target DC component to be extracted. However, the mixed signal is also mixed with high-frequency noise that has been amplified and clipped by the previous stage processing. The amplitude of this high-frequency noise is limited to a level much higher than that of the DC component.
[0045] Further, the absolute value of the currently obtained mixed signal amplitude is calculated, and it is determined whether the absolute value of the mixed signal amplitude is less than a preset amplitude threshold. This preset amplitude threshold is usually set to be higher than the amplitude of the target DC component, but lower than or equal to the amplitude limit. If the absolute value of the current mixed signal amplitude is less than the preset amplitude threshold, the mixed signal is determined to be a valid signal, and the output is updated to obtain the target DC component. If the absolute value of the current mixed signal amplitude is not less than this preset amplitude threshold, it is determined that the sampling time corresponding to the last low-frequency harmonic cancellation process was severely interfered with by high-intensity high-frequency noise, and the mixed signal is an invalid signal. In this case, the output is not updated, but the previous valid signal value is retained as the output.
[0046] In one embodiment, when the absolute value of the amplitude of the mixed signal is less than a preset amplitude threshold, signal change rate detection is performed. If the absolute value of the difference between the amplitude of the mixed signal and the amplitude of the previous valid signal is less than or equal to the preset change rate threshold, the mixed signal is determined to be a valid signal, and the output is updated to obtain the target DC component. Otherwise, the mixed signal is determined to be an invalid signal, the output is not updated, and the output of the previous valid signal is maintained.
[0047] Specifically, if the absolute value of the current mixed signal amplitude is less than a preset amplitude threshold, it is further determined whether the absolute value of the difference between the current mixed signal amplitude and the amplitude of the previously determined valid signal is greater than a preset rate of change threshold. This preset rate of change threshold is set to be much greater than the rate of change that the target DC component can generate under normal fluctuations. If the absolute value of the difference between the mixed signal amplitude and the amplitude of the previous valid signal is less than or equal to the preset rate of change threshold, the mixed signal is determined to be a valid signal, and the output is updated to obtain the target DC component. If the absolute value of the difference between the mixed signal amplitude and the amplitude of the previous valid signal is greater than the preset rate of change threshold, it indicates that the mixed signal is in a state of violent fluctuation, and the current sampling point is also determined to be an invalid signal, maintaining the previous valid output.
[0048] A mixed signal is considered valid only if the absolute value of its amplitude is less than a preset amplitude threshold and the absolute value of the difference between the amplitude of the mixed signal and the amplitude of the previous valid signal is less than or equal to a preset rate of change threshold. In this case, the output is updated to the current mixed signal value to obtain the target DC component.
[0049] In one embodiment, such as Figure 2 As shown, filtering the obtained signal to extract the target DC component from the AC signal includes the following steps: Step 201: Obtain the mixed signal obtained after the final low-frequency harmonic cancellation process; Step 202: Determine whether the absolute value of the mixed signal amplitude obtained from the last low-frequency harmonic cancellation process is less than the preset amplitude threshold; If the absolute value of the mixed signal amplitude is less than the preset amplitude threshold, proceed to step 203; if the absolute value of the mixed signal amplitude is not less than the preset amplitude threshold, proceed to step 205.
[0050] Step 203: Determine whether the absolute value of the difference between the amplitude of the mixed signal and the previous effective signal is less than or equal to a preset rate of change threshold; If the absolute value of the difference between the amplitude of the mixed signal and the amplitude of the previous valid signal is less than or equal to the preset rate of change threshold, proceed to step 204; if the absolute value of the difference between the amplitude of the mixed signal and the amplitude of the previous valid signal is greater than the preset rate of change threshold, proceed to step 205.
[0051] Step 204: The mixed signal is a valid signal; update the output to obtain the target DC component. Step 205: The mixed signal is invalid, so the output is not updated, and the output of the previous valid signal is maintained.
[0052] In one embodiment, under the condition of no high-order harmonics, the fundamental frequency and low-order harmonics have been effectively removed after low-frequency harmonic elimination processing. The output mixed signal contains almost only the target DC component. At this time, the target DC component can be directly output without filtering logic to achieve the fastest response.
[0053] In the quasi-steady-state condition containing high-order harmonics but with a slow change in fundamental frequency, the filtering process mainly judges the magnitude between the absolute value of the mixed signal amplitude and the preset amplitude threshold. By utilizing the characteristic of high-frequency noise amplitude saturation after amplification, the target DC component and noise can be effectively separated by a single amplitude threshold.
[0054] In dynamic operating conditions where high-order harmonics and fundamental frequencies change rapidly, it is necessary to simultaneously activate a dual judgment mechanism of amplitude threshold and rate of change threshold. The amplitude threshold is used to suppress amplified high-frequency noise, while the rate of change threshold is used to capture and filter out drastic signal fluctuations caused by rapid frequency changes, so as to accurately track the target DC component even under complex operating conditions.
[0055] In one embodiment, Figure 3 This is a simulation diagram of the DC component extraction method for AC signals provided in this application. (Top curve) This is the AC input signal to be processed, exhibiting irregular fluctuations. (See the curve below.) The target DC component, extracted by the DC component extraction method for AC signals provided in this application, is a relatively stable, nearly horizontal straight line. The input signal contains a 50Hz fundamental frequency component and the 3rd, 5th, and 7th harmonic components commonly found in inverters. The input signal also contains a 1kHz high-frequency random noise signal. The overall signal DC bias is 20°. Based on the DC component extraction method for AC signals provided in this application, DC component information can be extracted quickly and accurately in less than half a fundamental frequency cycle. If a low-pass filter or band-stop filter is used to extract DC component information, at least several cycles are required to output the DC component information, thus verifying the advantages of the embodiments of this application in terms of extraction speed and real-time performance.
[0056] Based on the same concept, such as Figure 4 As shown, this application also provides a DC component extraction system for AC signals, the system comprising: Signal acquisition module 401 is used to acquire the AC signal to be processed and its fundamental angular frequency; Multiple harmonic cancellation modules 402 are cascaded and used to perform low-frequency harmonic cancellation processing on AC signals in descending order of harmonic order according to the fundamental angular frequency. Each low-frequency harmonic cancellation process is configured to: eliminate the current target low-frequency harmonic, and at the same time amplify the high-frequency noise and high-order harmonics in the AC signal that have not been eliminated, so that the high-frequency noise and high-order harmonics trigger amplitude limiting. The filtering module 403 is used to filter the obtained signal after completing a preset number of low-frequency harmonic elimination processes in order to extract the target DC component in the AC signal; wherein, the limiting value of the limiting is set to be significantly higher than the amplitude of the target DC component in the AC signal, so that the amplitude of high-frequency noise and high-order harmonics after limiting is far away from the amplitude of the target DC component.
[0057] Specifically, the signal acquisition module 401 can acquire the AC signal to be processed. And its fundamental angular frequency ω. Multiple harmonic cancellation modules 402 correspond to... Figure 4 The system consists of a harmonic cancellation module chain consisting of harmonic cancellation module n, harmonic cancellation module n-1, ..., harmonic cancellation module 1 cascaded together. These harmonic cancellation modules 402 are connected sequentially in descending order of harmonic order. The output of the previous harmonic cancellation module 402 serves as the input of the next harmonic cancellation module 402. For example, harmonic cancellation module n eliminates the highest nth harmonic, and its output signal is then fed into the next stage to eliminate lower harmonics, until harmonic cancellation module 1 eliminates the fundamental component.
[0058] It should be noted that, while eliminating the current target low-frequency harmonics, the harmonic cancellation module 402 amplifies the high-frequency noise and higher-order harmonics that were not eliminated in the amplified AC signal. Amplification can be achieved by limiting the amplitude of the amplified high-frequency noise and higher-order harmonics within a preset limit value. This limit value can be set to be significantly higher than the amplitude of the target DC component, thereby significantly separating the limited high-frequency noise and higher-order harmonics from the target DC component in the amplitude domain.
[0059] After multi-stage harmonic cancellation and amplitude limiting, the low-frequency AC components in the mixed signal have been eliminated. The remaining components of the AC signal at this point mainly include the target DC component with stable amplitude and high-frequency noise whose amplitude is clamped to a value far from the target DC component. The filter module 503 analyzes the rate of change and amplitude of the signal to finally filter out and output the target DC component from the mixed signal.
[0060] In one embodiment, the schematic diagram of the harmonic cancellation module is as follows: Figure 5 As shown. The AC signal to be processed. It is fed into two cascaded delay units, each introducing a fixed sampling time interval. t s By using two delay units, three values that lag behind each other in time can be obtained simultaneously. t s The sampled signal, i.e., the first sampled signal without delay. The second sampled signal after one delay And the third sampled signal after two delays To achieve the input signal Three samples were taken at equal intervals.
[0061] Simultaneously, the fundamental angular frequency ω is input as another parameter to the filter parameter calculation unit. Based on the specific harmonic order (e.g., the nth harmonic) to be eliminated and the fundamental angular frequency ω, the filter parameter calculation unit calculates the first filter coefficient λ and the second filter coefficient δ. This calculation must satisfy specific constraints to ensure that the harmonic cancellation module can accurately eliminate the target low-frequency harmonics and maintain the DC component gain at 1.
[0062] The signal processing unit receives the first sampled signal. First sampling signal and the third sampling signal With the third sampled signal The signal processing unit calculates the mixed signal, along with the first filter coefficient λ and the second filter coefficient δ. The relation is: .
[0063] Through specific linear combinations, the mixed signal is made The coefficients of low- and mid-frequency harmonics are zero, thus eliminating low-frequency harmonics, while DC components are retained without attenuation, and higher-frequency components are amplified.
[0064] Mixed signal The signal is then sent to a limiting unit for processing, where a preset limiting value is applied to the mixed signal. For mixed signals The portion of the amplitude exceeding the limit is limited. The limit is set to be significantly higher than the amplitude of the target DC component. After limiting, the amplitudes of the amplified high-frequency noise and harmonics are restricted to a high level far removed from the DC component, thus achieving separation from the DC component in the amplitude domain, ultimately outputting a mixed signal. .
[0065] Based on the same concept, this application also provides a computer-readable storage medium including a processing program that executes the above-described method for extracting the DC component of an AC signal when the processing program is run.
[0066] Computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means.
[0067] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device.
[0068] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The above are merely preferred embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.
Claims
1. A method for extracting the DC component of an AC signal, characterized in that, The extraction method includes: Acquire the AC signal to be processed and its fundamental angular frequency; The AC signal is subjected to low-frequency harmonic cancellation processing sequentially according to the fundamental angular frequency, in descending order of harmonic order. Each low-frequency harmonic cancellation process is configured as follows: Eliminate the low-frequency harmonics of the current target, while amplifying the high-frequency noise and high-order harmonics in the AC signal that have not been eliminated, so that the high-frequency noise and the high-order harmonics trigger amplitude limiting; After completing the low-frequency harmonic elimination process a preset number of times, the resulting signal is filtered to extract the target DC component from the AC signal. The amplitude limiting value is set to be significantly higher than the amplitude of the target DC component in the AC signal, so that the amplitudes of the high-frequency noise and the higher harmonics after amplitude limiting are far away from the amplitude of the target DC component.
2. The method for extracting the DC component of an AC signal according to claim 1, characterized in that, The low-frequency harmonic elimination process includes: The signal to be processed is sampled three times at equal time intervals to obtain the first sampled signal, the second sampled signal, and the third sampled signal; The sum of the first sampled signal and the third sampled signal is multiplied by the first filter coefficient, and then the product of the second sampled signal and the second filter coefficient is subtracted to obtain a mixed signal that eliminates the target low-frequency harmonics. The mixed signal includes: a coarse feedthrough component modulated by the first filter coefficient, the second filter coefficient, and the fundamental angular frequency; The first and second filter coefficients are configured such that the coarse feed current component containing the target low-frequency harmonic in the mixed signal is 0, thereby eliminating the current target low-frequency harmonic.
3. The method for extracting the DC component of an AC signal according to claim 2, characterized in that, The mixed signal further includes a coarsely extracted DC component modulated by the first filter coefficient and the second filter coefficient, wherein the first filter coefficient and the second filter coefficient are further configured such that the gain of the coarsely extracted DC component is 1.
4. The method for extracting the DC component of an AC signal according to claim 2, characterized in that, The mixed signal further includes: a coarsely extracted DC component modulated by the first filter coefficient and the second filter coefficient; The extraction method further includes: calculating the gain of the coarsely extracted DC component based on the first filter coefficient and the second filter coefficient; if the gain of the coarsely extracted DC component is not equal to 1, multiplying the mixed signal by an adjustment coefficient so that the gain of the coarsely extracted DC component is equal to 1; and then limiting the high-frequency noise and the higher harmonics contained in the mixed signal.
5. The method for extracting the DC component of an AC signal according to claim 3 or 4, characterized in that, After completing the low-frequency harmonic elimination process a preset number of times, the resulting signal is filtered to extract the target DC component from the AC signal, including: The amplitude of the mixed signal obtained from the last low-frequency harmonic elimination process is compared. If the absolute value of the amplitude of the mixed signal is less than a preset amplitude threshold, the mixed signal is determined to be a valid signal, and the output is updated to obtain the target DC component. Otherwise, the mixed signal is determined to be an invalid signal, the output is not updated, and the previous valid signal output is maintained.
6. The method for extracting the DC component of an AC signal according to claim 5, characterized in that, If the absolute value of the amplitude of the mixed signal is less than a preset amplitude threshold, the signal rate of change is detected. If the absolute value of the difference between the amplitude of the mixed signal and the amplitude of the previous valid signal is less than or equal to a preset rate of change threshold, the mixed signal is determined to be a valid signal, and the output is updated to obtain the target DC component; otherwise, the mixed signal is determined to be an invalid signal, the output is not updated, and the output of the previous valid signal is maintained.
7. The method for extracting the DC component of an AC signal according to claim 1, characterized in that, The target low-frequency harmonics to be eliminated are of order less than or equal to the 9th harmonic order.
8. A system for extracting the DC component of an AC signal, characterized in that, The extraction system includes: The signal acquisition module is used to acquire the AC signal to be processed and its fundamental angular frequency; Multiple harmonic cancellation modules, cascaded together, are used to sequentially cancel low-frequency harmonics in the AC signal according to the fundamental angular frequency, in descending order of harmonic order. Each low-frequency harmonic cancellation process is configured as follows: Eliminate the low-frequency harmonics of the current target, while amplifying the high-frequency noise and high-order harmonics in the AC signal that have not been eliminated, so that the high-frequency noise and the high-order harmonics trigger amplitude limiting; The filtering module is used to filter the obtained signal after completing the low-frequency harmonic elimination process a preset number of times in order to extract the target DC component in the AC signal. The amplitude limiting value is set to be significantly higher than the amplitude of the target DC component in the AC signal, so that the amplitudes of the high-frequency noise and the higher harmonics after amplitude limiting are far away from the amplitude of the target DC component.
9. The AC signal DC component extraction system according to claim 8, characterized in that, The low-frequency harmonic elimination process includes: The signal to be processed is sampled three times at equal time intervals to obtain the first sampled signal, the second sampled signal, and the third sampled signal; The sum of the first sampled signal and the third sampled signal is multiplied by the first filter coefficient, and then the product of the second sampled signal and the second filter coefficient is subtracted to obtain a mixed signal that eliminates the target low-frequency harmonics. The mixed signal includes: a coarse feedthrough component modulated by the first filter coefficient, the second filter coefficient, and the fundamental angular frequency; The first and second filter coefficients are configured such that the coarse feed current component containing the target low-frequency harmonic in the mixed signal is 0, thereby eliminating the current target low-frequency harmonic.
10. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a processing program that, when executed, performs the method for extracting the DC component of an AC signal as described in any one of claims 1 to 7.