Method and system for reducing sampling frequency and preventing EMC electromagnetic interference

Abstract

The invention discloses a method for reducing sampling frequency to prevent EMC electromagnetic interference. The method comprises the following steps: acquiring sampling waveforms of a mutual inductor in a plurality of complete cycles at a first sampling frequency; judging whether each sampling point in the sampling waveform is distorted or not, and if so, filtering distorted points; and splitting cycle sampling points in the sampling waveform into odd and even waveforms, performing effective value calculation on the odd and even waveforms, and judging the effectiveness of the sampling waveform cycle according to the effective value of the odd and even waveforms. The invention further discloses a system for reducing the sampling frequency and preventing EMC electromagnetic interference. According to the invention, the technical problem of how to accurately and quickly filter out EMC electromagnetic interference distortion signals and output effective waveforms is solved.

Description

Technical Field

[0001] The present invention relates to the field of embedded technology, and in particular to a method and system for reducing sampling frequency to prevent EMC electromagnetic interference. Background Art

[0002] EMC electromagnetic interference exists in all aspects of embedded products. Whether sampling interference can be removed correctly is an important indicator for product promotion and application. Especially in low-voltage distribution network circuit breaker products, the circuit breaker detection fault protection action time is required to be less than 100ms, and this time includes power-on initialization and trip action time. How to design a system that can filter interference without affecting the judgment of CT sampling value and fault response time is the premise to ensure that the product fault protection can respond in real time. Considering that there are differences in the consistency of the trip unit of the circuit breaker, it is necessary to judge the fault in a relatively short time, leaving enough time for the trip to cut off the circuit fault. The patent document with application number CN202311017233.8 discloses an anti-interference servo drive and its wiring method. The traditional circuit breaker is an electrical protection device used in household and industrial power systems. It mainly provides current characteristics of circuits and equipment for disconnection protection. When the electrical line is overloaded or short-circuited, the circuit breaker will immediately cut off the circuit, thereby protecting the electrical equipment from damage. The fast disconnection supported by traditional circuit breakers relies on the backup protection of the circuit breaker body itself, which is mainly triggered by the armature release after the body overheats, and can only cut off the short-circuit current of more than 14 times the rated current of the body. The role of backup protection is to quickly start to cut off the fault when the main protection cannot quickly cut off the fault due to reasons such as the failure of the protection device to operate, damage to other links in the protection circuit, and failure of the circuit breaker to operate. It can solve the problem that all faulty components within the remote backup protection range cannot be cut off due to any reason; since the backup protection is not controlled by the controller, its disadvantages are: when multiple power supplies supply power to the power element, it is necessary to configure remote backup protection at the upper components on all power supply sides; the action will cut off all circuit breakers measured by the upper power supply, causing the accident to expand; it is difficult to meet the sensitivity requirements in high-voltage power grids. The traditional method of dealing with unstable waveforms is to use a delayed anti-shake method, that is, the sampling value meets a certain threshold judgment condition for multiple consecutive times, which can be considered as effective protection. This method can basically filter out the judgment of effective values ​​affected by individual signal distortion. The existing problems are that on the one hand, the distortion point still calculates a large effective value, and on the other hand, the delay affects the authenticity and real-time nature of the protection, especially for the scene of real instantaneous effective mutation values, which will cause missed judgments, thereby missing potential safety hazards. Therefore, it is urgent to propose a method and system for reducing the sampling frequency to prevent EMC electromagnetic interference, and solve the technical problem of how to accurately and quickly filter out EMC electromagnetic interference distortion signals and output effective waveforms. Summary of the invention

[0003] The main purpose of the present invention is to propose a method and system for reducing sampling frequency to prevent EMC electromagnetic interference, aiming to solve the technical problem of how to accurately and quickly filter out EMC electromagnetic interference distortion signals and output effective waveforms.

[0004] To achieve the above object, the present invention provides a method for reducing sampling frequency to prevent EMC electromagnetic interference, wherein the method for reducing sampling frequency to prevent EMC electromagnetic interference comprises the following steps:

[0005] S1, obtaining sampling waveforms of several complete cycles of the mutual inductor at a first sampling frequency;

[0006] S2, determining whether each sampling point in the sampled waveform is distorted, and if so, filtering the distorted points;

[0007] S3, splitting the cycle sampling points in the sampling waveform into odd and even waveforms, performing effective value calculation on the odd and even waveforms, and judging the validity of the cycle of the sampling waveform according to the effective values ​​of the odd and even waveforms.

[0008] In one of the preferred solutions, in step S1, the first sampling frequency is 50 Hz.

[0009] In one of the preferred solutions, the step S2 determines whether each sampling point in the sampled waveform is distorted, specifically:

[0010] The saturation value of the mutual inductor is obtained, and the value of each sampling point in the sampling waveform is compared with the saturation value of the mutual inductor. If the sampling point value is greater than the saturation value, the sampling point is determined to be a distortion point and filtered.

[0011] One of the preferred solutions, before step S3, further includes:

[0012] When the sampling cache points complete a cycle, the validity of the cycle is judged.

[0013] In one of the preferred solutions, step S3 is specifically:

[0014] S31, splitting each sampling point in a cycle of a sampling waveform that completes the sampling cache point into odd and even waveforms, and storing the odd and even waveforms in an array arry1[N] and an array arry2[N] respectively;

[0015] S32, respectively calculating the effective values ​​of the odd and even waveforms; the effective values ​​are respectively marked as: U 1 and U 2 ;

[0016] S33, calculating the relative error of the odd and even waveforms according to the effective value of the odd and even waveforms, and judging the validity of the sampling waveform according to the relative error.

[0017] In one preferred solution, step S33 is specifically:

[0018] Set relative error threshold;

[0019] The relative error of the odd and even waveforms is calculated based on the effective values ​​of the odd and even waveforms, specifically:

[0020]

[0021] Among them, X is the relative error of the odd and even waveforms, fabs() is the absolute value function, and U 1 , U 2 are the effective values ​​of odd and even waveforms respectively;

[0022] If the relative error of the odd and even waveforms is less than the relative error threshold, the cycle is determined to be a valid waveform; otherwise, it is an abnormal interference waveform, and the number of abnormalities is recorded.

[0023] In one of the preferred solutions, the relative error threshold is 25%.

[0024] A system for reducing sampling frequency to prevent EMC electromagnetic interference, the system for reducing sampling frequency to prevent EMC electromagnetic interference comprising the method for reducing sampling frequency to prevent EMC electromagnetic interference.

[0025] In the above technical solution of the present invention, the method of reducing the sampling frequency to prevent EMC electromagnetic interference includes the following steps: obtaining the sampling waveforms of several complete cycles of the mutual inductor at a first sampling frequency; judging whether each sampling point in the sampling waveform is distorted, and if so, filtering the distorted points; splitting the cycle sampling points in the sampling waveform into odd and even waveforms, and calculating the effective value of the odd and even waveforms, and judging the validity of the sampling waveform cycle according to the effective value of the odd and even waveforms. The present invention directly filters the distorted points at the source, and calculates the relative error based on the effective value of the odd and even waveforms of the reduced frequency, and judges the validity of the sampling waveform, thereby ensuring the sampling accuracy of the mutual inductor, ensuring the validity of the sampling, and providing a guarantee for the real-time completion of the mutual inductor protection judgment and action, and solving the technical problem of how to accurately and quickly filter out the EMC electromagnetic interference distortion signal and output a valid waveform. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0027] Figure 1A schematic diagram of a method for reducing sampling frequency to prevent EMC electromagnetic interference according to an embodiment of the present invention;

[0028] Figure 2 Schematic diagram of sampling waveforms according to an embodiment of the present invention.

[0029] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In addition, in the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0032] Furthermore, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in the field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0033] See also Figure 1-Figure 2 According to one aspect of the present invention, the present invention provides a method for reducing sampling frequency to prevent EMC electromagnetic interference, wherein the method for reducing sampling frequency to prevent EMC electromagnetic interference comprises the following steps:

[0034] S1, obtaining sampling waveforms of several complete cycles of the mutual inductor at a first sampling frequency;

[0035] S2, determining whether each sampling point in the sampled waveform is distorted, and if so, filtering the distorted points;

[0036] S3, splitting the cycle sampling points in the sampling waveform into odd and even waveforms, performing effective value calculation on the odd and even waveforms, and judging the validity of the cycle of the sampling waveform according to the effective values ​​of the odd and even waveforms.

[0037] Specifically, in the present embodiment, in the step S1, the first sampling frequency is 50 Hz, which is not specifically limited in the present invention and can be set as required.

[0038] Specifically, in this embodiment, the step S2 determines whether each sampling point in the sampling waveform is distorted, specifically: obtaining the saturation value of the mutual inductor, comparing the value of each sampling point in the sampling waveform with the saturation value of the mutual inductor, if the sampling point value is greater than the saturation value, the sampling point is determined to be a distorted point and filtered, and by filtering out the maximum mutation point in the sampling interruption, that is, taking out the distorted point that exceeds the sampling saturation value, the subsequent analysis steps of the sampling cache filtering abnormality can be simplified.

[0039] Specifically, in this embodiment, see the attached Figure 2 This is a typical sampling waveform of a transformer. Under the working condition of 50Hz, one cycle is 20ms. When the circuit is subject to EMC electromagnetic interference, a distortion point A will be generated. If the distortion point is not filtered, the effective value of each sampling point of the transformer waveform will be too large during the calculation process, thereby affecting the judgment of the protection logic and causing false operation. The generation of distortion points poses a great safety hazard to the protection equipment. When subject to magnetic and electric interference, an interference point C will be generated, but this interference point is generally near the theoretical value. Therefore, this point does not affect the accuracy of the transformer sampling protection.

[0040] Specifically, in this embodiment, before step S3, the following steps are further included:

[0041] When the sampling cache points complete a cycle, the validity of the cycle is judged.

[0042] Specifically, in this embodiment, step S3 is as follows:

[0043] S31, splitting each sampling point in a cycle of the sampling waveform that completes the sampling cache point into odd and even waveforms, and storing the odd and even waveforms in array arry1[N] and array arry2[N] respectively; wherein N is the number of cached sampling points;

[0044] S32, respectively calculating the effective values ​​of the odd and even waveforms; the effective values ​​are respectively marked as: U 1 and U 2 ;

[0045] S33. Calculate the relative error of the odd and even waveforms according to the effective value of the odd and even waveforms, and judge the validity of the sampling waveform according to the relative error; split the sampling frequency into odd and even waveforms and store them separately, calculate the effective value of the odd and even waveforms according to the integration, and judge the validity of the sampling waveform according to the comparison of the effective value of the odd and even waveforms with the relative error, filter out the distortion points according to the characteristics of the electromagnetic interference, and judge the validity of the sampling waveform, so as to ensure the real-time completion of the protection judgment and action of the mutual inductor.

[0046] Specifically, in this embodiment, the step S33 is specifically:

[0047] Set relative error threshold;

[0048] The relative error of the odd and even waveforms is calculated based on the effective values ​​of the odd and even waveforms, specifically:

[0049]

[0050] Among them, X is the relative error of the odd and even waveforms, fabs() is the absolute value function, and U 1 , U 2 are the effective values ​​of the odd and even waveforms, respectively, and the effective values ​​of the odd and even waveforms U 1 , U 2 In theory, they are equal. Therefore, in the relative error calculation process of the odd and even waveforms, the effective value U 1 Treated as true value;

[0051] If the relative error of the odd and even waveforms is less than the relative error threshold, the cycle is determined to be a valid waveform; otherwise, it is an abnormal interference waveform, and the number of abnormalities is recorded.

[0052] Specifically, in this embodiment, the relative error threshold is 25%, which is not specifically limited in the present invention and can be set according to needs.

[0053] Specifically, in this embodiment, after step S33, the process further includes: directly entering into protection logic judgment for a valid waveform, wherein an invalid waveform that appears multiple times in succession is regarded as a fault waveform.

[0054] Specifically, in the present embodiment, EMC interference is pervasive in the application environment of the power system. Designing a method that can filter interference without affecting the judgment of the sampling value of the transformer and the fault response time is an important prerequisite for ensuring whether the product can be safe and reliable. The present invention filters the distorted signal with different characteristics of the interference without increasing the hardware intervention, directly filters the distortion point at the source, and judges the validity of the waveform by the relative error of the odd and even waveforms generated by the frequency reduction of the sampling waveform, thereby improving the instantaneous protection function of the transformer and avoiding the missed judgment of abnormal conditions and potential safety hazards.

[0055] According to another aspect of the present invention, the present invention provides a system for reducing sampling frequency to prevent EMC electromagnetic interference, and the system for reducing sampling frequency to prevent EMC electromagnetic interference includes the method for reducing sampling frequency to prevent EMC electromagnetic interference.

[0056] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for reducing sampling frequency to prevent EMC electromagnetic interference, characterized in that: The following steps are involved: S1, obtaining sampling waveforms of several complete cycles of the mutual inductor at a first sampling frequency; S2, determining whether each sampling point in the sampled waveform is distorted, and if so, filtering the distorted points; S3, splitting the cycle sampling points in the sampling waveform into odd and even waveforms, performing effective value calculation on the odd and even waveforms, and judging the validity of the cycle of the sampling waveform according to the effective values ​​of the odd and even waveforms.

2. The method for reducing sampling frequency to prevent EMC electromagnetic interference according to claim 1, characterized in that: In the step S1, the first sampling frequency is 50 Hz.

3. The method for reducing sampling frequency to prevent EMC electromagnetic interference according to any one of claims 1-2, characterized in that: The step S2 determines whether each sampling point in the sampled waveform is distorted, specifically: The saturation value of the mutual inductor is obtained, and the value of each sampling point in the sampling waveform is compared with the saturation value of the mutual inductor. If the sampling point value is greater than the saturation value, the sampling point is determined to be a distortion point and filtered.

4. The method for reducing sampling frequency to prevent EMC electromagnetic interference according to any one of claims 1-2, characterized in that: Before step S3, the method further includes: When the sampling cache points complete a cycle, the validity of the cycle is judged.

5. The method for reducing sampling frequency to prevent EMC electromagnetic interference according to claim 4, characterized in that: The step S3 is specifically: S31, splitting each sampling point in a cycle of a sampling waveform that completes the sampling cache point into odd and even waveforms, and storing the odd and even waveforms in an array arry1[N] and an array arry2[N] respectively; S32, respectively calculating the effective values ​​of the odd and even waveforms; the effective values ​​are marked as: U1 and U2; S33, calculating the relative error of the odd and even waveforms according to the effective value of the odd and even waveforms, and judging the validity of the sampling waveform according to the relative error.

6. The method for reducing sampling frequency to prevent EMC electromagnetic interference according to claim 5, characterized in that: The step S33 is specifically as follows: Set relative error threshold; The relative error of the odd and even waveforms is calculated based on the effective values ​​of the odd and even waveforms, specifically: Among them, X is the relative error of the odd and even waveforms, fabs() is the absolute value function, and U1 and U2 are the effective values ​​of the odd and even waveforms respectively; If the relative error of the odd and even waveforms is less than the relative error threshold, the cycle is determined to be a valid waveform; otherwise, it is an abnormal interference waveform, and the number of abnormalities is recorded.

7. The method for reducing sampling frequency to prevent EMC electromagnetic interference according to claim 6, characterized in that: The relative error threshold is 25%.

8. A system for reducing sampling frequency to prevent EMC electromagnetic interference, characterized in that: The system for reducing sampling frequency to prevent EMC electromagnetic interference includes a method for reducing sampling frequency to prevent EMC electromagnetic interference as described in any one of claims 1-7.

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