Load Harmonic Emission Characteristic Extraction Method, Device and Computer Equipment

Abstract

The present application relates to a method, device and computer equipment for extracting load harmonic emission characteristics. The method includes: obtaining a voltage waveform signal and a current waveform signal of a bus; obtaining a first preset number of current harmonic phasors according to the fast Fourier transform; screening and obtaining a second preset number of qualified harmonic current data according to an effective value screening coefficient; obtaining an expected value and a standard deviation of the harmonic current phase, and obtaining a corresponding preset confidence interval; if the standard deviation is greater than or equal to a preset threshold, changing the effective value screening coefficient and repeating the above screening and standard deviation calculation process until the standard deviation is less than the preset threshold; outputting the load harmonic emission characteristics according to the expected value and the preset confidence interval. By using this method, the interference of most background voltages can be excluded, and more accurate load harmonic characteristics can be obtained, so as to more accurately detect the power quality of the power system.

Description

Technical Field

[0001] The present application relates to the technical field of power grid harmonic governance, and particularly to a method, device and computer equipment for extracting load harmonic emission characteristics. Background Art

[0002] With the rapid development of power electronics technology, it has been widely applied in industrial and transportation sectors as well as electrical equipment. These nonlinear loads inject a large amount of harmonics into the public power grid, causing voltage and current distortion and seriously polluting the public power grid. Moreover, as the proportion of important precision loads in the power load increases day by day, users' requirements for power quality are becoming more and more stringent. Therefore, the harmonic problem of the power system, as an important aspect of power quality, has become an urgent problem to be solved.

[0003] In traditional technologies, load harmonic emission characteristics are extracted based on actual monitored and collected data; or load harmonic emission characteristics are extracted after screening using the smaller value of background interference voltage.

[0004] However, in current traditional methods, the concerned interference current not only depends on the user-side interference current but is also affected by the background interference voltage, which will cause a large deviation in the results; when using the second method, the concerned interference voltage is positively correlated with the load-side interference current, that is, as the load-side interference current increases, the occurrence amount of the concerned interference voltage also increases synchronously. When the background interference voltage is small, the load-side interference current is often small, and the harmonic current data selected by screening the smaller value of the interference voltage is also small. Therefore, it cannot accurately reflect the interference current emission characteristics of the concerned point. Summary of the Invention

[0005] Based on this, in view of the above technical problems, it is necessary to provide a method, device and computer equipment for extracting load harmonic emission characteristics to accurately detect the power quality of the power system.

[0006] In a first aspect, the present application provides a method for extracting load harmonic emission characteristics. The method includes:

[0007] Obtain the voltage waveform signal and current waveform signal of the busbar;

[0008] Obtain the first preset number of current harmonic phasors according to the fast Fourier transform;

[0009] Screen and obtain the second preset number of harmonic current data that meet the conditions according to the effective value screening coefficient;

[0010] Obtain the expected value and standard deviation of the harmonic current phase, and obtain the corresponding preset confidence interval;

[0011] If the standard deviation is greater than or equal to a preset threshold, change the effective value screening coefficient and repeat the above screening and standard deviation calculation process until the standard deviation is less than the preset threshold;

[0012] Output the load harmonic emission characteristics according to the expected value and the preset confidence interval.

[0013] In the above load harmonic emission characteristic extraction method, in order to reduce the data processing difficulty of the fast Fourier transform, the voltage waveform signal and the current waveform signal are obtained and the cycle is intercepted by a time interval. The signal is preprocessed, and then screened by the effective value screening coefficient until the standard deviation is less than the preset threshold, so that it is in a higher confidence interval, thereby obtaining more obvious load harmonic phase characteristics.

[0014] In one embodiment, the obtaining the first preset number n of current harmonic phasors according to the fast Fourier transform includes:

[0015] Obtain the voltage waveform signal u of each phase k (t) and the current waveform signal i of each phase k (t) at intervals of a second preset time within a first preset time;

[0016] Perform a transform on the voltage waveform signal of each phase and the current waveform signal of each phase by means of the fast Fourier transform;

[0017] Obtain the nth current harmonic phasor with the zero-crossing point of the rising edge of the fundamental voltage of phase A as the reference benchmark:

[0018]

[0019] where n is a positive integer greater than or equal to 1 and less than or equal to N, is the hth harmonic phasor of the kth phase current signal, is the corresponding effective value, is the current phase with the zero-crossing point of the rising edge of the fundamental voltage of phase A as the reference benchmark, and N is the number of harmonic current phasors.

[0020] In one embodiment, the second preset time is 4 s - 6 s.

[0021] In one embodiment, the method further includes:

[0022] Initialize the harmonic current effective value screening coefficient, and the screening criterion is the maximum value of the hth harmonic current of each phase.

[0023] In one embodiment, the obtaining the expected value and standard deviation of the harmonic current phase, and obtaining the corresponding preset confidence interval includes:

[0024] Obtain the expected value of the k-th phase and h-th harmonic current phase:

[0025]

[0026] Obtain the standard deviation according to the expected value:

[0027]

[0028] In one embodiment, the step of changing the effective value screening coefficient and repeating the above screening and standard deviation calculation process until the standard deviation is less than the preset threshold when the standard deviation is greater than or equal to the preset threshold includes:

[0029] If the standard deviation is greater than or equal to the preset threshold, re-obtain the effective value screening coefficient s1:

[0030] s1 = s0 + l;

[0031] Wherein, s1 is the changed effective value screening coefficient, s0 is the initial effective value screening coefficient, and l is the preset step size.

[0032] In one embodiment, the preset step size is 0.05 - 0.15;

[0033] The preset threshold is 0.5 - 0.7.

[0034] In a second aspect, the present application further provides a load harmonic emission characteristic extraction device for detecting the power quality of a power system. The device includes:

[0035] A harmonic current data module for obtaining the voltage waveform signal and current waveform signal of the bus, obtaining the first preset number of current harmonic phasors according to the fast Fourier transform, and screening and obtaining the second preset number of qualified harmonic current data according to the effective value screening coefficient;

[0036] A characteristic parameter acquisition module for obtaining the expected value and standard deviation of the harmonic current phase, and obtaining the corresponding preset confidence interval; if the standard deviation is greater than or equal to the preset threshold, changing the effective value screening coefficient and repeating the above screening and standard deviation calculation process until the standard deviation is less than the preset threshold;

[0037] A characteristic extraction module for outputting the load harmonic emission characteristic according to the expected value and the preset confidence interval.

[0038] In a third aspect, the present application further provides a computer device. The computer device includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of any method in the embodiments of the present application are implemented.

[0039] Fourthly, the present application also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of any of the methods described in the embodiments of the present application are implemented. Description of the Drawings

[0040] Figure 1 It is an application environment diagram of the load harmonic emission characteristic extraction method provided in an embodiment of the present application;

[0041] Figure 2 It is a schematic flowchart of the load harmonic emission characteristic extraction method provided in an embodiment of the present application;

[0042] Figure 3 It is a schematic flowchart of the load harmonic emission characteristic extraction method provided in another embodiment of the present application;

[0043] Figure 4 It is a schematic flowchart of the load harmonic emission characteristic extraction method provided in yet another embodiment of the present application;

[0044] Figure 5 It is a schematic diagram of the phase distribution trend of the 7th harmonic of phase A corresponding to different screening coefficients provided in an embodiment of the present application;

[0045] Figure 6 It is a schematic diagram of the phase distribution trend of the 7th harmonic of phase B corresponding to different screening coefficients provided in an embodiment of the present application;

[0046] Figure 7 It is a schematic diagram of the phase distribution trend of the 7th harmonic of phase C corresponding to different screening coefficients provided in an embodiment of the present application;

[0047] Figure 8 It is a schematic diagram of the phase distribution characteristics of the 7th harmonic current under different screening coefficients provided in an embodiment of the present application;

[0048] Figure 9 It is a probability distribution diagram of the 7th harmonic current under different screening coefficients provided in an embodiment of the present application;

[0049] Figure 10 It is a schematic flowchart of the load harmonic emission characteristic extraction method provided in yet another embodiment of the present application;

[0050] Figure 11 It is a schematic structural diagram of the load harmonic emission characteristic extraction device provided in an embodiment of the present application;

[0051] Figure 12 It is an internal structure diagram of a computer device provided in an embodiment of the present application. Detailed Embodiments

[0052] To facilitate the understanding of this application, the following will provide a more comprehensive description of this application with reference to the relevant drawings. Embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of this application more thorough and comprehensive.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0054] The method for extracting load harmonic emission characteristics provided by the embodiments of this application can be applied to an application environment as Figure 1 shown. Among them, the terminal 102 communicates with the server 104 through the network. The data storage system can store the data that the server 104 needs to process. The data storage system can be integrated on the server 104, or can be placed in the cloud or on other network servers. Among them, the terminal 102 can be, but is not limited to, various personal computers, laptop computers, smart phones, and tablet computers. The server 104 can be implemented by an independent server or a server cluster composed of multiple servers.

[0055] In one embodiment, as Figure 2 shown, a method for extracting load harmonic emission characteristics is provided, including the following steps:

[0056] Step S10: Obtain the voltage waveform signal and current waveform signal of the bus.

[0057] Specifically, according to the voltage transformer and current transformer, cooperate with the data acquisition and monitoring control system to obtain the voltage waveform signal u k (t) and the current waveform signal i k (t) of the bus. Where k represents the three phases A, B, and C in the power grid, and the sampling frequency of each channel waveform signal is not less than 12.8 kHz.

[0058] Step S20: Obtain the first preset number of current harmonic phasors according to the fast Fourier transform.

[0059] Specifically, as Figure 3 shown, step S20 further includes steps S21 to S23:

[0060] Step S21: Obtain the voltage waveform signal u k (t) of each phase and the current waveform signal i k (t) of each phase at intervals of the second preset time within the first preset time.

[0061] Specifically, the second preset time is 4s - 6s. For example, in some embodiments, the second preset time can be 4s, 5s, or 6s. Assuming that the first preset time is 12 hours and the second preset time is 5s, it means that within 12 hours, the per-phase voltage waveform signal u k (t) and the per-phase current waveform signal i k (t) are acquired at intervals of 5s, and at this time, the number of harmonic phasors N = 12 hours * 60 minutes * 60 seconds / 5 seconds = 8640.

[0062] Step S22: Perform a transformation on the basis of the per-phase voltage waveform signal and the per-phase current waveform signal by using the fast Fourier transform.

[0063] Specifically, for the per-phase voltage waveform signal u k (t) and the per-phase current waveform signal i k (t) collected in the previous step S21 at intervals of 5s, 10 cycles (200 milliseconds) are respectively intercepted and transformed by using the fast Fourier transform.

[0064] Step S23: Obtain the nth current harmonic phasor by using the zero-crossing point of the rising edge of the fundamental voltage of phase A as a reference benchmark:

[0065]

[0066] where n is a positive integer greater than or equal to 1 and less than or equal to N, is the hth harmonic phasor of the kth-phase current signal, is the corresponding effective value, is the current phase with the zero-crossing point of the rising edge of the fundamental voltage of phase A as a reference benchmark, and N is the number of harmonic current phasors.

[0067] Specifically, using the zero-crossing point of the rising edge of the fundamental voltage as a reference benchmark can more accurately reflect the harmonic current phase distribution and also has the ability to tolerate phase sequence errors.

[0068] Please continue to refer to Figure 2 , Step S30: Screen and obtain the second preset number of qualified harmonic current data according to the effective value screening coefficient;

[0069] Step S40: Obtain the expected value and standard deviation of the harmonic current phase, and obtain the corresponding preset confidence interval.

[0070] Specifically, please refer to Figure 4 , Step S40 further includes steps S41 to S42:

[0071] Step S41: Obtain the expected value of the hth harmonic current phase of the kth phase:

[0072]

[0073] Step S42: Obtain the standard deviation according to the expected value:

[0074] The preset confidence interval can be a 95% confidence interval.

[0075] Please continue to refer to Figure 2 , Step S50: If the standard deviation is greater than or equal to the preset threshold, change the effective value screening coefficient and repeat the above screening and standard deviation calculation process until the standard deviation is less than the preset threshold;

[0076] Specifically, Step S50 further includes Step S51:

[0077] Step S51: If the standard deviation is greater than or equal to the preset threshold, re-obtain the effective value screening coefficient s1:

[0078] s1 = s0 + l;

[0079] where s1 is the changed effective value screening coefficient, s0 is the initial effective value screening coefficient, and l is the preset step size.

[0080] Specifically, in some embodiments, the preset step size can be 0.05, 0.1, 0.15; the preset threshold can be 0.5, 0.6, 0.7. For example, in some embodiments, if it is assumed that the load harmonic order h is 7, the preset step size can be 0.1 and the preset threshold can be 0.6.

[0081] Please continue to refer to Figure 2 , Step S60: Output the load harmonic emission characteristics according to the expected value and the preset confidence interval.

[0082] Specifically, when it is assumed that the load harmonic order h is 7, the harmonic current phase distribution characteristic parameters are shown in Table 1:

[0083] Table 1

[0084]

[0085] As can be seen from Table 1, starting from the initial value of the screening coefficient, when s = 0, the standard deviation is greater than the preset threshold of 0.6, so the effective value screening coefficient needs to be re-obtained; when s1 = s + l = 0 + 0.1 = 0.1, the standard deviation is greater than 0.6, so continue to re-obtain the effective value screening coefficient; until when the screening coefficient s = 0.8, the standard deviation meets the requirements. For the trend chart of the phase distribution expectation and standard deviation, please refer to Figures 5 to 7 , as the screening coefficient increases. The standard deviation of the 7th harmonic distribution decreases significantly, indicating that the phase distribution of the three-phase 7th harmonic current tends to be stable. The 95% confidence interval narrows, and the phase characteristics of the 7th harmonic tend to be obvious.

[0086] Specifically, the 7th harmonic current phase distribution characteristics under different screening coefficients are obtained, as Figure 8 shown. It can be seen that as the screening coefficient increases, the 7th harmonic current phase distribution of residential electricity loads gradually becomes more consistent. The probability density distributions under different screening coefficients are as Figure 9 shown. When the screening coefficient is 0.8, the phase normal distribution characteristics appear. In addition Figures 5 - 7 in, when the screening coefficient changes from 0.8 to 0.9, the standard deviation hardly changes, which also indicates that when the screening coefficient is 0.8, most of the interference of the background voltage has been excluded, so that the load harmonic emission characteristics are more representative.

[0087] In one embodiment, as Figure 10 shown, the method includes:

[0088] Step S10: Obtain the voltage waveform signal and current waveform signal of the bus;

[0089] Step S20: Obtain the first preset number of current harmonic phasors according to the fast Fourier transform;

[0090] Step S70: Initialize the effective value screening coefficient of the harmonic current, and the screening criterion is the maximum value of the hth harmonic current of each phase;

[0091] Step S30: Screen and obtain the second preset number of qualified harmonic current data according to the effective value screening coefficient;

[0092] Step S40: Obtain the expected value and standard deviation of the harmonic current phase, and obtain the corresponding preset confidence interval;

[0093] Step S50: If the standard deviation is greater than or equal to the preset threshold, change the effective value screening coefficient and repeat the above screening and standard deviation calculation process until the standard deviation is less than the preset threshold;

[0094] Step S60: Output the load harmonic emission characteristics according to the expected value and the preset confidence interval.

[0095] It should be understood that although the steps in the flowcharts involved in the above-described embodiments are shown in sequence according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear description in this article, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-described embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily executed at the same moment, but can be executed at different moments. The execution order of these steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or steps or stages in other steps.

[0096] In one embodiment, as Figure 11 shown, a device for extracting load harmonic emission characteristics is provided, including a harmonic current data module 10, a characteristic parameter acquisition module 20, and a characteristic extraction module 30. The harmonic current data module 10 is configured to acquire the voltage waveform signal and current waveform signal of the bus, obtain the first preset number of current harmonic phasors according to the fast Fourier transform, and screen and obtain the second preset number of qualified harmonic current data according to the effective value screening coefficient; the characteristic parameter acquisition module 20 is configured to obtain the expected value and standard deviation of the harmonic current phase, and obtain the corresponding preset confidence interval; if the standard deviation is greater than or equal to the preset threshold, change the effective value screening coefficient and repeat the above screening and standard deviation calculation process until the standard deviation is less than the preset threshold; the characteristic extraction module 30 is configured to output the load harmonic emission characteristics according to the expected value and the preset confidence interval.

[0097] Each module in the above load harmonic characteristic extraction device can be implemented in whole or in part by software, hardware, and their combination. The above modules can be embedded in the processor of the computer device in hardware form or be independent of it, or can be stored in the memory of the computer device in software form, so as to facilitate the processor to call and execute the operations corresponding to the above modules.

[0098] In one embodiment, a computer device is provided. The computer device can be a terminal, and its internal structure diagram can be as Figure 12As shown in the figure. The computer device includes a processor, a memory, a communication interface, a display screen, and an input device connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be implemented through WIFI, a mobile cellular network, NFC (Near Field Communication), or other technologies. When the computer program is executed by the processor, it realizes a method for extracting load harmonic emission characteristics. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covering the display screen, or a button, a trackball, or a touchpad provided on the casing of the computer device, or an external keyboard, touchpad, or mouse, etc.

[0099] Those skilled in the art can understand that Figure 12 the structure shown in the figure is only a block diagram of some structures related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

[0100] In one embodiment, a computer device is provided, including a memory and a processor. A computer program is stored in the memory. When the processor executes the computer program, the following steps are realized:

[0101] Step S10: Obtain the voltage waveform signal and current waveform signal of the busbar;

[0102] Step S20: Obtain the first preset number of current harmonic phasors according to the fast Fourier transform;

[0103] Step S30: Screen and obtain the second preset number of qualified harmonic current data according to the effective value screening coefficient;

[0104] Step S40: Obtain the expected value and standard deviation of the harmonic current phase, and obtain the corresponding preset confidence interval;

[0105] Step S50: If the standard deviation is greater than or equal to the preset threshold, change the effective value screening coefficient and repeat the above screening and calculation of the standard deviation process until the standard deviation is less than the preset threshold;

[0106] Step S60: Output the load harmonic emission characteristics according to the expected value and the preset confidence interval.

[0107] In one embodiment, when the processor executes the computer program, the following steps are also implemented:

[0108] Step S21: Obtain the per-phase voltage waveform signal u k (t) and the per-phase current waveform signal i k (t) at intervals of a second preset time within a first preset time;

[0109] Step S22: Perform a transformation on the basis of the per-phase voltage waveform signal and the per-phase current waveform signal by using a fast Fourier transform;

[0110] Step S23: Obtain the nth current harmonic phasor by taking the zero-crossing point of the rising edge of the fundamental voltage of phase A as a reference:

[0111]

[0112] where n is a positive integer greater than or equal to 1 and less than or equal to N, is the hth harmonic phasor of the kth-phase current signal, is the corresponding effective value, is the current phase with the zero-crossing point of the rising edge of the fundamental voltage of phase A as a reference, and N is the number of harmonic current phasors.

[0113] In one embodiment, when the processor executes the computer program, the following steps are also implemented:

[0114] Step S40: Obtain the expected value and standard deviation of the harmonic current phase, and obtain the corresponding preset confidence interval;

[0115] Specifically, referring to Figure 4 , step S40 further includes steps S41 to S42:

[0116] Step S41: Obtain the expected value of the hth harmonic current phase of the kth phase:

[0117]

[0118] Step S42: Obtain the standard deviation according to the expected value:

[0119]

[0120] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, database, or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memories. Non-volatile memory can include Read-Only Memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The databases involved in the embodiments provided in the present application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., without limitation. The processors involved in the embodiments provided in the present application can be general-purpose processors, central processors, graphics processors, digital signal processors, programmable logic devices, data processing logics based on quantum computing, etc., without limitation.

[0121] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0122] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.

Claims

1. A method for extracting load harmonic emission characteristics, characterized in that, For detecting the power quality of a power system, the method includes: Obtain the voltage waveform signal and current waveform signal of the busbar; Obtaining the first preset number of current harmonic phasors according to the fast Fourier transform, including: obtaining the voltage waveform signal of each phase at intervals of a second preset time within a first preset time and the current waveform signal of each phase ; performing a transform on the basis of the voltage waveform signal of each phase and the current waveform signal of each phase by using the fast Fourier transform; obtaining the nth current harmonic phasor by using the zero-crossing point of the rising edge of the fundamental voltage of phase A as a reference benchmark: ； where n is a positive integer greater than or equal to 1 and less than or equal to N, is the h - th harmonic phasor of the k - th phase current signal, is the corresponding effective value, is the current phase with the zero - crossing point of the rising edge of the fundamental voltage of phase A as the reference benchmark, and N is the number of harmonic current phasors; Screen and obtain the second preset number of harmonic current data that meet the conditions according to the effective value screening coefficient; Obtain the expected value and standard deviation of the harmonic current phase, and obtain the corresponding preset confidence interval, including: obtaining the expected value of the h-th harmonic current phase of the k-th phase: ； Where M represents the second preset number, and m represents the index variable in the process of summing the expected values, which is used to traverse M harmonic current data; Obtain the standard deviation according to the expected value; ； If the standard deviation is greater than or equal to the preset threshold, change the effective value screening coefficient and repeat the above screening and standard deviation calculation process until the standard deviation is less than the preset threshold, including: if the standard deviation is greater than or equal to the preset threshold, re-obtain the effective value screening coefficient s1: ； Where s1 is the changed effective value screening coefficient, s0 is the initial effective value screening coefficient, and l is the preset step size; Output the load harmonic emission characteristics according to the expected value and the preset confidence interval.

2. The method according to claim 1, characterized in that, The second preset time is 4s - 6s.

3. The method according to claim 1 or 2, characterized in that, The method further includes: Initialize the harmonic current effective value screening coefficient, and the screening criterion is the maximum value of the h-th harmonic current of each phase.

4. The method according to claim 1, wherein The preset step size is 0.05 - 0.15; The preset threshold is 0.5 - 0.

7.

5. A device for extracting load harmonic emission characteristics, characterized in that, For detecting the power quality of a power system, the device includes: Harmonic current data module, which is used to obtain the voltage waveform signal and current waveform signal of the busbar, obtain the first preset number of current harmonic phasors according to the fast Fourier transform, and screen and obtain the second preset number of qualified harmonic current data according to the effective value screening coefficient; wherein, obtaining the first preset number of current harmonic phasors according to the fast Fourier transform includes: obtaining the voltage waveform signal of each phase at intervals of the second preset time within the first preset time and the current waveform signal of each phase ; performing transformation on the voltage waveform signal of each phase and the current waveform signal of each phase by using the fast Fourier transform; obtaining the nth current harmonic phasor with the zero-crossing point of the rising edge of the fundamental voltage of phase A as the reference benchmark: ; wherein, n is a positive integer greater than or equal to 1 and less than or equal to N, is the hth harmonic phasor of the kth phase current signal, is the corresponding effective value, is the current phase with the zero-crossing point of the rising edge of the fundamental voltage of phase A as the reference benchmark, and N is the number of harmonic current phasors; A characteristic parameter acquisition module is used to obtain the expected value and standard deviation of the harmonic current phase, and obtain a corresponding preset confidence interval; if the standard deviation is greater than or equal to a preset threshold, the effective value screening coefficient is changed and the above screening and standard deviation calculation process is repeated until the standard deviation is less than the preset threshold; wherein, obtaining the expected value and standard deviation of the harmonic current phase, and obtaining a corresponding preset confidence interval includes: obtaining the expected value of the h-th harmonic current phase of the k-th phase: ; wherein, M represents a second preset quantity, and m represents an index variable in the expected value summation process, which is used to traverse M harmonic current data; obtaining the standard deviation according to the expected value: ; if the standard deviation is greater than or equal to a preset threshold, change the effective value screening coefficient and repeat the above screening and standard deviation calculation process until the standard deviation is less than the preset threshold, including: if the standard deviation is greater than or equal to the preset threshold, re-obtain the effective value screening coefficient s1: ; where s1 is the changed effective value screening coefficient, s0 is the initial effective value screening coefficient, and l is the preset step size; A characteristic extraction module for outputting the load harmonic emission characteristics according to the expected value and the preset confidence interval.

6. A computer device, comprising a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 4.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method according to any one of claims 1 to 4.

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