Harmonic detection method and system based on combination of half-wave DFT and full-wave DFT

Abstract

The application discloses a kind of harmonic detection method and system based on half-wave DFT and full-wave DFT combination, method includes: obtaining the sampling data of the electrical signal of power system to be detected;Based on one power frequency period, construct full-wave DFT sliding window, and it is equally divided into the front half-wave DFT sliding window and the rear half-wave DFT sliding window sequentially arranged along time axis;Respectively using full-wave DFT sliding window, front half-wave DFT sliding window and rear half-wave DFT sliding window, the sampling data in respective window is carried out discrete fourier transform calculation, and the full-wave window harmonic content rate hr, front half-wave window harmonic content rate hr1 And rear half-wave window harmonic content rate hr2;hr, hr1, hr2 are compared with preset threshold value, and harmonic detection result is obtained according to comparison result.The application has the advantages, such as accurately distinguishing real harmonic and step pseudo-harmonic.

Description

Technical Field

[0001] This invention mainly relates to the field of power system technology, specifically to a harmonic detection method and system based on the combination of half-wave DFT and full-wave DFT. Background Technology

[0002] In power system relay protection, the content of second and third harmonics is often used as a criterion for blocking functions such as inrush current and external current transformer (CT) saturation. Currently, the Discrete Fourier Transform (DFT) algorithm is commonly used to calculate the fundamental and harmonic components of current and voltage signals. A sliding window of one power frequency cycle (20ms) is typically used for full-wave DFT calculation. However, under certain operating conditions, such as during detection, when the input signal undergoes a step change (e.g., a fault occurs, a sudden signal is applied by the testing instrument, or a switching operation), spectral leakage occurs because the signal does not meet the periodic extension condition of the DFT, leading to a false third harmonic component in the full-wave DFT calculation.

[0003] During relay protection device testing, the testing instrument outputs a step-changing power frequency signal to simulate a fault. The protection device detects these spurious harmonics, affecting its accurate judgment of abnormal operating conditions and potentially leading to maloperation or failure to operate. In actual operation, sudden signal changes (such as the occurrence of a fault) can also cause similar problems, affecting the protection's performance.

[0004] In existing technologies, methods such as windowed interpolation DFT and recursive DFT are commonly used to reduce spectral leakage. In order to ensure the real-time performance and accuracy of the measurement, half-wave window DFT or single-cycle (full-wave) window DFT are generally used. This makes it difficult to fundamentally distinguish between real harmonics and pseudo-harmonics caused by step.

[0005] As mentioned above, existing full-wave or half-wave DFT algorithms generate spurious harmonic components when power frequency signals undergo a step change, which may lead to maloperation or failure of relay protection. While spurious harmonic components caused by power frequency step signals can be reduced by using Hamming windows and increasing the window function length, the computational complexity slows down the response speed when real harmonics appear. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention provides a harmonic detection method and system based on the combination of half-wave DFT and full-wave DFT that accurately distinguishes between real harmonics and step pseudo-harmonics.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A harmonic detection method based on a combination of half-wave DFT and full-wave DFT includes the following steps: S1. Acquire sampling data of the electrical signals of the power system to be detected; S2. Construct a full-wave DFT sliding window based on one power frequency cycle, and divide it into a first half-wave DFT sliding window and a second half-wave DFT sliding window arranged sequentially along the time axis; the three windows slide synchronously, and the sampled data first enters the first half-wave window and then enters the second half-wave window; S3. Perform Discrete Fourier Transform calculations on the sampled data in each window using the full-wave DFT sliding window, the first half-wave DFT sliding window, and the second half-wave DFT sliding window respectively, and output the harmonic content rate hr of the full-wave window, the harmonic content rate hr1 of the first half-wave window, and the harmonic content rate hr2 of the second half-wave window. The system includes preset harmonic content rate thresholds HR for the full-wave window, upper thresholds HR1t and HR1b for the first half-wave window, and upper thresholds HR2t and HR2b for the second half-wave window. HR1b is a preset threshold for the full-wave window harmonic content rate. <HR1t,HR2b<HR2t; S4. Compare hr, hr1, and hr2 with each preset threshold, and obtain the harmonic detection result based on the comparison result.

[0008] Preferably, in step S4, when the full-wave threshold condition, the first half-wave threshold condition, and the second half-wave threshold condition are all satisfied, it is determined that a real harmonic is detected; when the full-wave threshold condition is satisfied but at least one of the first half-wave threshold condition and the second half-wave threshold condition is not satisfied, it is determined to be a pseudo-harmonic caused by a signal step, and the harmonic detection result is output.

[0009] Preferably, in step S4, the full-wave threshold condition is: The threshold condition for the first half of the wave is The threshold condition for the second half of the wave is The simultaneous satisfaction of the full-wave threshold condition, the first-half-wave threshold condition, and the second-half-wave threshold condition includes the following situations: Scenario 1: , ,and ; Scenario 2: , ,and ; Scenario 3: , ,and .

[0010] Preferably, in step S4, when ,but and / or When the signal is stepped, it is determined to be a pseudo-harmonic caused by a signal step.

[0011] Preferably, in step S4, when and At that time, it was determined that no real harmonics were detected.

[0012] Preferably, in step S3, the full-wave window harmonic content rate hr, the first half-wave window harmonic content rate hr1, and the second half-wave window harmonic content rate hr2 are the ratios of the target harmonic amplitude to the fundamental amplitude obtained by discrete Fourier transform of the sampled data within their respective windows.

[0013] Preferably, in step S4, HR1t and HR2t are both equal to HR, and HR1b and HR2b are obtained by multiplying HR by a preset proportionality coefficient k, where 0 <k<1。

[0014] The present invention also discloses a computer program product, comprising a computer program that, when executed by a processor, performs the steps of the method described above.

[0015] The present invention further discloses a computer-readable storage medium having a computer program stored thereon, the computer program executing the steps of the method described above when run by a processor.

[0016] The present invention also discloses a harmonic detection system based on a combination of half-wave DFT and full-wave DFT, comprising a memory and a processor connected to each other, wherein the memory stores a computer program, and the computer program executes the steps of the method described above when run by the processor.

[0017] Compared with the prior art, the advantages of the present invention are as follows: Accurately distinguish between real harmonics and step pseudo-harmonics: By comparing and analyzing half-wave and full-wave windows, combined with upper and lower threshold logic, it is possible to effectively distinguish between pseudo-harmonics caused by signal step jumps and real harmonics, fundamentally solving the problem of protection misjudgment caused by signal abrupt changes during testing and faults.

[0018] Improved protection reliability: During relay protection device testing, it can avoid protection maloperation caused by signal steps in the testing instrument, thus improving testing accuracy and efficiency. During field operation, it can accurately identify true harmonics, ensuring correct protection operation.

[0019] Fast response: Utilizing the shorter data window length of the half-wave window, harmonic changes can be detected more quickly. With appropriate threshold settings, it is possible to quickly determine when actual harmonics occur, meeting the protection's speed requirements.

[0020] Low computational complexity: It only requires adding two half-wave DFT calculations to the original full-wave DFT, with a limited increase in computational load, and is easy to implement on existing relay protection hardware platforms.

[0021] High adaptability: By adjusting the upper and lower thresholds, it can adapt to the needs of different application scenarios. The algorithm has a certain degree of robustness to noise interference and can adapt to the actual operating environment of power systems.

[0022] Good compatibility: The method of this invention can be seamlessly integrated with existing protection logic without changing the original protection principle. Only the harmonic authenticity discrimination needs to be added in the measurement stage.

[0023] Dual application value: It can be used in test mode to eliminate the influence of test signals; it can also be used in operation mode to improve the reliability of protection under fault conditions. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the analysis of each window in an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram illustrating the change in harmonic content rate of each window over time when the actual third harmonic occurs in an embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram illustrating the change of harmonic content in each window over time when a single power frequency signal undergoes a step change, according to an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram illustrating the change of harmonic content in each window over time during two power frequency signal steps in an embodiment of the present invention.

[0028] Figure 5 This is a flowchart of a harmonic detection method based on the combination of half-wave DFT and full-wave DFT in an embodiment of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0030] This invention targets a full-wave DFT window and divides it into two half-wave DFT windows. By comparing the harmonic content of the full-wave window and the two half-wave windows, and combining the set threshold logic, it accurately distinguishes between real harmonics and pseudo-harmonics caused by step transitions.

[0031] Specifically, when dealing with a step-transition power frequency signal, if the step transition occurs within the full-wave DFT window, the full-wave DFT will calculate harmonics, affecting subsequent identification and judgment. If this full-wave DFT window is divided into two half-wave DFT windows, namely the first half-wave window and the second half-wave window, new sampled data first enters the first half-wave window and then the second half-wave window. When the power frequency signal step transition occurs within the first half-wave window, the first half-wave window DFT calculation will show a relatively high content of the 3rd harmonic, while the second half-wave window will still calculate the fundamental frequency; when the power frequency signal step transition occurs within the second half-wave window, the second half-wave window DFT calculation will show a relatively high content of the 3rd harmonic, while the first half-wave window will calculate the fundamental frequency after the step transition.

[0032] Although the full-wave window DFT has a large number of third harmonics, the two half-wave DFT windows will not have a high content of third harmonics at the same time. In this case, it can be considered that the harmonics are caused by the power frequency step transition, which provides a reference for subsequent judgment.

[0033] In addition, to enable the fastest possible detection and measurement of the true third harmonic, the harmonic content threshold for the full-wave window is set to HR. The upper threshold for the harmonic content in the first half-wave window is HR1t, and the lower threshold is HR1b. The upper threshold for the harmonic content in the second half-wave window is HR2t, and the lower threshold is HR2b. The lower threshold of the half-wave window is lower than the upper threshold.

[0034] When the waveform contains the third harmonic, by combining a threshold and judging the harmonic content of each half-wave, the third harmonic can be detected as quickly as possible. When the waveform only contains a power frequency step, by combining a threshold and judging the harmonic content of each half-wave, the third harmonic will not be detected.

[0035] like Figure 5 As shown, based on the above principles, the harmonic detection method based on the combination of half-wave DFT and full-wave DFT provided in this embodiment of the invention is used to detect third harmonics or odd harmonics, and specifically includes the following steps: S1. Acquire sampling data of the electrical signals of the power system to be detected. The analog signal acquisition unit of the relay protection device is used to sample at a preset frequency. ( The electrical signal is sampled at equal intervals (where the integer is positive) to obtain time-series sampled data. One power frequency cycle The number of sampling points within (corresponding to the rated frequency of the 50Hz power system) is , It is a positive integer.

[0036] S2. Constructing a DFT sliding window like Figure 1As shown, a full-wave DFT sliding window is constructed based on one power frequency period (T=20ms), which includes consecutive sampling points. The full-wave window is equally divided into a first half-wave DFT sliding window arranged in sequence along the time axis (the first sampling points) and a second half-wave DFT sliding window (the last sampling points). The three windows slide synchronously with a step length of 1 sampling point. The newly acquired sampling data first enters the first half-wave window, then enters the second half-wave window. As the windows slide point by point, the sampling data flows through the three windows in sequence, forming a continuous DFT calculation data stream.

[0037] S3. Perform DFT calculation on each window to obtain the harmonic content ratios (all are odd harmonic content ratios) Taking the sampling data in the three windows constructed in step S2 as input, real-time calculation is performed using the DFT algorithm respectively, and the full-wave window harmonic content ratio hr, the first half-wave window harmonic content ratio hr1, and the second half-wave window harmonic content ratio hr2 are output. The harmonic content ratio of each window is defined as the ratio of the target-order harmonic amplitude to the fundamental wave amplitude: hr is the ratio of the target-order harmonic amplitude calculated in the full-wave window to the fundamental wave amplitude, hr1 is the ratio of the target-order harmonic amplitude calculated in the first half-wave window to the fundamental wave amplitude, and hr2 is the ratio of the target-order harmonic amplitude calculated in the second half-wave window to the fundamental wave amplitude.

[0038] As described above, the threshold of the full-wave window harmonic content ratio is set to HR, the upper threshold of the first half-wave window harmonic content ratio is HR1t and the lower threshold is HR1b, and the upper threshold of the second half-wave window harmonic content ratio is HR2t and the lower threshold is HR2b. For each half-wave window, the lower threshold is strictly less than the upper threshold, that is, HR1b<HR1t and HR2b<HR2t.

[0039] Preferably, HR1t=HR2t=HR, HR1b=HR2b=k×HR, where 0<k<1 is a preset proportional coefficient. In this embodiment, k is 30%, that is, HR1b=HR2b=30%HR. The upper and lower two-level thresholds provide a flexible interval for the judgment of the harmonic content ratio of the half-wave window, which not only ensures the sensitivity of real harmonic detection, but also enhances the ability to identify step pseudo-harmonics.

[0040] S4. Execute the judgment logic and output the harmonic detection result.

[0041] Taking hr, hr1, hr2 output in step S3 and each set threshold as input, the preset judgment logic is executed to judge whether the harmonic detected in the full-wave DFT window is a real harmonic or a pseudo-harmonic caused by signal step, and output the harmonic detection result.

[0042] The preset judgment logic is based on the following core principle: a signal step only affects a portion of the sampled data within the full-wave window. The half-wave window within the step's influence range will calculate a higher harmonic content, while the other half-wave window only reflects the fundamental component or the stable signal after the step. The two half-wave windows will not simultaneously detect high harmonic content. When true harmonics persist, both half-wave windows can simultaneously detect a certain amount of harmonics. Based on this principle, by comparing the harmonic content of each window with preset multi-level thresholds, true harmonics and pseudo-harmonics can be accurately distinguished.

[0043] The judgment rules of the preset judgment logic are as follows: Judgment Rule 1: At any given time, if the harmonic content rate of at least one half-wave window fails to reach the upper threshold, while the harmonic content rate of another half-wave window reaches the lower threshold, and the harmonic content rate of the entire wave window also meets the threshold, then the third harmonic content rate can be considered to have reached the threshold. This specifically covers the following three scenarios: 1. The harmonic content hr1 of the first half-wave window reaches the upper threshold HR1t, the harmonic content hr2 of the second half-wave window does not reach the upper threshold HR2t, but reaches the lower threshold HR2b, and the harmonic content hr of the whole wave window reaches the threshold HR. As shown in equation (1): (1) 2. The harmonic content hr2 of the second half-wave window reaches the upper threshold HR2t, the harmonic content hr1 of the first half-wave window does not reach the upper threshold HR1t, but reaches the lower threshold HR1b, and the harmonic content hr of the whole wave window reaches the threshold HR. As shown in equation (2).

[0044] (2) 3. The harmonic content hr1 of the first half-wave window reaches the upper threshold HR1t, the harmonic content hr2 of the second half-wave window reaches the upper threshold HR2t, and the total content reaches the lower threshold HR. As shown in equation (3): (3) Judgment Rule 2: If at least one half-wave window harmonic content rate does not reach the lower threshold at the same time, even if the harmonic content rate of the full-wave window reaches the threshold, it cannot be judged that the third harmonic content rate has reached the threshold. As shown in Equation (4).

[0045] or or (4) Rule 3: If the harmonic content of both half-wave windows does not reach the upper threshold at the same time, it cannot be determined that the third harmonic content has reached the threshold. As shown in equation (5).

[0046] (5) Compared with the prior art, the present invention has the following advantages: Accurately distinguish between real harmonics and step pseudo-harmonics: By comparing and analyzing half-wave and full-wave windows, combined with upper and lower threshold logic, it is possible to effectively distinguish between pseudo-harmonics caused by signal step jumps and real harmonics, fundamentally solving the problem of protection misjudgment caused by signal abrupt changes during testing and faults.

[0047] Improved protection reliability: During relay protection device testing, it can avoid protection maloperation caused by signal steps in the testing instrument, thus improving testing accuracy and efficiency. During field operation, it can accurately identify true harmonics, ensuring correct protection operation.

[0048] Fast response: Utilizing the shorter data window length of the half-wave window, harmonic changes can be detected more quickly. With appropriate threshold settings, it is possible to quickly determine when actual harmonics occur, meeting the protection's speed requirements.

[0049] Low computational complexity: It only requires adding two half-wave DFT calculations to the original full-wave DFT, with a limited increase in computational load, and is easy to implement on existing relay protection hardware platforms.

[0050] High adaptability: By adjusting the upper and lower thresholds, it can adapt to the needs of different application scenarios. The algorithm has a certain degree of robustness to noise interference and can adapt to the actual operating environment of power systems.

[0051] Good compatibility: The method of this invention can be seamlessly integrated with existing protection logic without changing the original protection principle. Only the harmonic authenticity discrimination needs to be added in the measurement stage.

[0052] Dual application value: It can be used in test mode to eliminate the influence of test signals; it can also be used in operation mode to improve the reliability of protection under fault conditions.

[0053] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0054] Example 1 (Real 3rd Harmonic Detection Scenario): like Figure 2 As shown, HR1t = HR2t = HR, HR1b = HR2b = 30%HR. When the third harmonic begins to appear in the waveform, the full-wave window, the first half-wave window, and the second half-wave window will calculate the third harmonic. According to the DFT calculation principle, with the fundamental frequency and the third harmonic remaining unchanged: The third harmonic content calculated in the first half-wave window increases rapidly. At time t1, the harmonic content hr1 calculated in the first half-wave window reaches HR1t(HR) first. However, at this time, the harmonic content calculated by hr in the full-wave window is lower than HR, and the harmonic content calculated in the second half-wave window... If the probability of occurrence of harmonic 2 is still 0, it cannot be determined that the probability of occurrence of harmonic 3 has reached the threshold.

[0055] As the window continues to slide, at time t2, the harmonic content hr2 calculated by the second half-wave window reaches HR2b (30%HR), while the harmonic content hr calculated by the full-wave window is still lower than HR.

[0056] At time t3, the harmonic content hr calculated by the full-wave window reaches HR. At this time, the harmonic content hr1 calculated by the first half-wave window is greater than HR1t, and the harmonic content hr2 calculated by the second half-wave window is greater than HR2b, and hr is greater than HR. Therefore, it can be determined that the third harmonic content in the waveform has reached HR.

[0057] Example 2 (Single power frequency signal step scenario): like Figure 3 As shown, HR1t = HR2t = HR, HR1b = HR2b = 30%HR. A step power frequency signal appears in the waveform, and the signal amplitude changes by more than 100% in the new cycle. The full-wave window, the first half-wave window, and the second half-wave window will calculate the 3rd harmonic, according to the DFT calculation principle: The harmonic content rate hr1 in the first half-wave window reaches the upper threshold HR1t at time t1, and the harmonic content rate calculated for the whole wave window reaches the threshold HR at time t2. However, the harmonic content rate hr2 in the second half-wave window cannot reach the lower threshold HR2b at this time, so it cannot be determined that the third harmonic exceeds the threshold.

[0058] As the window continues to slide, the harmonic content hr2 of the second half-wave window reaches the upper threshold HR2t at time t3, and the harmonic content calculated by the full-wave window reaches the threshold HR again at time t4. However, the harmonic content hr1 calculated by the first half-wave window cannot reach the lower threshold HR1b at this time, so it cannot be determined that the third harmonic exceeds the threshold.

[0059] Example 3 (Scenario of connecting two power frequency signal step transitions): like Figure 4 As shown, HR1t = HR2t = HR, HR1b = HR2b = 30%HR. The waveform shows two step-frequency power frequency signals, with the signal amplitude changing by more than 100% in each step cycle. According to the DFT calculation principle, the full-wave window, the first half-wave window, and the second half-wave window will calculate the three harmonics: The harmonic content rate hr1 in the first half-wave window reaches the upper threshold HR1t at time t1, and the harmonic content rate calculated for the whole wave window reaches the threshold HR at time t2. However, the harmonic content rate hr2 in the second half-wave window cannot reach the lower threshold HR2b at this time, so it cannot be determined that the third harmonic exceeds the threshold.

[0060] As the window continues to slide, the harmonic content hr2 of the second half-wave window reaches the upper threshold HR2t at time t3, and the harmonic content calculated by the full-wave window reaches the threshold HR again at time t4. However, the harmonic content hr1 calculated by the first half-wave window cannot reach the lower threshold HR1b at this time, so it cannot be determined that the third harmonic exceeds the threshold.

[0061] At time t5, the signal steps again at the zero crossing. The harmonic content rate hr1 of the first half-wave window reaches the upper threshold HR1t at time t6, and the harmonic content rate calculated for the whole wave window reaches the threshold HR at time t7. However, the harmonic content rate hr2 of the second half-wave window cannot reach the lower threshold HR2b at this time. Therefore, it cannot be determined that the third harmonic exceeds the threshold at this time.

[0062] As the window continues to slide, the harmonic content hr2 of the second half-wave window reaches the upper threshold HR2t at time t8, and the harmonic content calculated by the full-wave window reaches the threshold HR again at time t9. However, the harmonic content hr1 calculated by the first half-wave window cannot reach the lower threshold HR1b at this time, so it cannot be determined that the third harmonic exceeds the threshold.

[0063] This invention employs a combination of half-wave and full-wave window calculations, enabling rapid and accurate differentiation between real harmonics and step pseudo-harmonics. It avoids misjudging harmonics during power frequency signal step changes and can quickly and accurately detect real harmonics, thereby improving the reliability of relay protection without affecting its normal operation.

[0064] The present invention also discloses a computer program product, comprising a computer program that, when executed by a processor, performs the steps of the method described above.

[0065] The present invention further discloses a computer-readable storage medium having a computer program stored thereon, the computer program executing the steps of the method described above when run by a processor.

[0066] The present invention also discloses a harmonic detection system based on a combination of half-wave DFT and full-wave DFT, comprising a memory and a processor connected to each other, wherein the memory stores a computer program, and the computer program executes the steps of the method described above when run by the processor.

[0067] The products, media, and systems of the present invention, corresponding to the methods described above, also possess the advantages described above.

[0068] The present invention can implement all or part of the processes in the methods of the above embodiments, or it can be implemented by hardware related to computer program instructions. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, it can implement the steps of the above method embodiments. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable storage medium includes: any entity or device capable of carrying computer program code, recording media, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. The memory is used to store computer programs and / or modules. The processor implements various functions by running or executing the computer programs and / or modules stored in the memory, and by calling data stored in the memory. The memory may include high-speed random access memory, as well as non-volatile memory, such as hard disks, RAM, plug-in hard disks, smart media cards (SMC), secure digital (SD) cards, flash cards, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.

[0069] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A harmonic detection method based on a combination of half-wave DFT and full-wave DFT, characterized in that, Includes the following steps: S1. Acquire sampling data of the electrical signals of the power system to be detected; S2. Construct a full-wave DFT sliding window based on one power frequency cycle, and divide it into a first half-wave DFT sliding window and a second half-wave DFT sliding window arranged sequentially along the time axis; the three windows slide synchronously, and the sampled data first enters the first half-wave window and then enters the second half-wave window; S3. Perform Discrete Fourier Transform calculations on the sampled data in each window using the full-wave DFT sliding window, the first half-wave DFT sliding window, and the second half-wave DFT sliding window respectively, and output the harmonic content rate hr of the full-wave window, the harmonic content rate hr1 of the first half-wave window, and the harmonic content rate hr2 of the second half-wave window. The system includes preset harmonic content rate thresholds HR for the full-wave window, upper thresholds HR1t and HR1b for the first half-wave window, and upper thresholds HR2t and HR2b for the second half-wave window. HR1b is a preset threshold for the full-wave window harmonic content rate. <HR1t,HR2b<HR2t; S4. Compare hr, hr1, and hr2 with each preset threshold, and obtain the harmonic detection result based on the comparison result.

2. The harmonic detection method based on the combination of half-wave DFT and full-wave DFT according to claim 1, characterized in that, In step S4, when the full-wave threshold condition, the first half-wave threshold condition, and the second half-wave threshold condition are all satisfied simultaneously, it is determined that a real harmonic is detected. When the full-wave threshold condition is met, but at least one of the first-half-wave threshold condition and the second-half-wave threshold condition is not met, it is determined to be a pseudo-harmonic caused by a signal step, and the harmonic detection result is output.

3. The harmonic detection method based on the combination of half-wave DFT and full-wave DFT according to claim 2, characterized in that, In step S4, the full-wave threshold condition is: The threshold condition for the first half of the wave is The threshold condition for the second half of the wave is The simultaneous satisfaction of the full-wave threshold condition, the first-half-wave threshold condition, and the second-half-wave threshold condition includes the following situations: Scenario 1: , ,and ; Scenario 2: , ,and ; Scenario 3: , ,and .

4. The harmonic detection method based on the combination of half-wave DFT and full-wave DFT according to claim 2, characterized in that, In step S4, when ,but and / or When the signal is stepped, it is determined to be a pseudo-harmonic caused by a signal step.

5. The harmonic detection method based on the combination of half-wave DFT and full-wave DFT according to claim 2, characterized in that, In step S4, when and At that time, it was determined that no real harmonics were detected.

6. The harmonic detection method based on the combination of half-wave DFT and full-wave DFT according to any one of claims 1-5, characterized in that, In step S3, the full-wave window harmonic content rate hr, the first half-wave window harmonic content rate hr1, and the second half-wave window harmonic content rate hr2 are the ratios of the target harmonic amplitude to the fundamental amplitude obtained by discrete Fourier transform of the sampled data within their respective windows.

7. The harmonic detection method based on the combination of half-wave DFT and full-wave DFT according to any one of claims 1-5, characterized in that, In step S4, HR1t and HR2t are both equal to HR, and HR1b and HR2b are obtained by multiplying HR by a preset proportional coefficient k, where 0 <k<1。 8. A computer program product, comprising a computer program, characterized in that, The computer program is executed by the processor to perform the steps of the method as described in any one of claims 1-7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, The computer program, when run by a processor, performs the steps of the method as described in any one of claims 1-7.

10. A harmonic detection system based on a combination of half-wave DFT and full-wave DFT, comprising an interconnected memory and a processor, wherein the memory stores a computer program, characterized in that, The computer program, when run by a processor, performs the steps of the method as described in any one of claims 1-7.

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