Method and system for judging working state of alternating current analog quantity plug-in

Abstract

The invention relates to a method and a system for judging the working state of an alternating current analog quantity plug-in, and belongs to the field of relay protection detection of power equipment. The method comprises the following steps: processing an analog quantity signal passing through a sampling channel of an alternating-current analog quantity plug-in to obtain a digital quantity signal; and then pre-determined signal characteristics in the digital quantity signals are extracted, and the extracted signal characteristics are compared with the same type of signal characteristics which are processed by a sampling channel when the alternating current analog quantity plug-in normally works, so that whether the alternating current analog quantity plug-in is in a normal working state or not can be effectively determined. According to the method, the hardware structure of the existing alternating current analog quantity plug-in is prevented from being changed, and the working state of the alternating current analog quantity plug-in is judged on the basis of stability and reliability.

Description

Technical Field

[0001] The invention relates to a working state determination method and system of an AC analog quantity plug-in, belonging to the field of relay protection detection of electric power equipment. Background Art

[0002] There are a large number of relay protection devices and process-level devices in the power system. These devices generally adopt a modular structural design composed of several different types of plug-ins. This type of design provides flexible matching capabilities for the power industry in the face of complex and changeable application environments. Only by replacing the plug-in on the basis of the device body can the device model with different functional configurations be switched. This is a very convenient design and reduces the redundant cost and waste of equipment production. However, at the same time, the use of such a structural design also contains many hidden dangers.

[0003] On the one hand, there is a risk of operational errors due to human factors during the commissioning of the plug-in. On the other hand, for specific equipment types with complex structures and a variety of plug-in types and quantities, any loose or damaged plug-in may cause problems with the normal use of the abnormal part of the function or even involve other modules, causing the entire device to fail. Therefore, the industry has always attached great importance to the research on various solutions for how to detect the working status of the plug-in, and has proposed and widely applied a variety of different solutions.

[0004] In the prior art, the working status is judged by using the specific power supply structure required for the power supply of the plug-in. When the plug-in is normally put into use, the internal power module works normally, and when it is offline, the power module is interrupted. Therefore, whether the power signal is normal can be used as the basis for judging the working status of the plug-in; the other is to monitor the real-time status of all plug-ins in the entire system based on the communication function of the CAN bus. The core of this solution is that as long as a single plug-in supports the CAN network function, it can send its own data to the bus by periodically sending heartbeat messages. The bus can directly and real-time determine the working status of the corresponding plug-in by monitoring the message. If the plug-in is offline and the heartbeat message is interrupted, the bus determines that the corresponding plug-in is in an offline state and can send an alarm message containing specific plug-in information to the device CPU.

[0005] However, for the AC analog quantity plug-in, no additional power supply is required when sampling the analog quantity signal, and the structure of the AC analog quantity sampling plug-in does not meet the requirements of bus communication. Summary of the invention

[0006] The purpose of the present invention is to provide a method and system for determining the working state of an AC analog quantity plug-in, so as to solve the problem that the working state of the AC analog quantity plug-in cannot be determined without relying on the hardware structure.

[0007] To achieve the above object, the solution of the present invention includes:

[0008] A method for determining the working state of an AC analog quantity plug-in of the present invention comprises the following steps:

[0009] 1) Processing the analog signal of the sampling channel of the AC analog plug-in to obtain a digital signal;

[0010] 2) extracting predetermined signal features from the digital signal, wherein the predetermined signal features are determined based on the feature differences of the digital signal obtained by processing the AC analog plug-in in a normal working state and in an offline state;

[0011] 3) Compare the extracted signal features with the signal features of the same type obtained through the sampling channel processing when the AC analog plug-in is working normally. If the digital signal features when the AC analog plug-in is working normally are met, the AC analog plug-in is in normal operating state, otherwise, the AC analog plug-in is in offline state.

[0012] Furthermore, the predetermined signal characteristics include amplitude and phase information of a DC component and an AC component.

[0013] Furthermore, a full-cycle Fourier algorithm is used to extract predetermined signal features.

[0014] Furthermore, as long as the digital signal characteristics obtained by processing one sampling channel meet the signal characteristics of the AC analog plug-in in the offline state, the AC analog plug-in is in the offline state.

[0015] Furthermore, the analog signal is converted into a small analog signal through the conversion of the sampling channel of the AC analog plug-in including the mutual inductor; the small analog signal is transmitted to the A / D conversion chip through the pre-low-pass filter circuit to obtain a digital signal.

[0016] A system for determining the working state of an AC analog plug-in of the present invention comprises a processor, and the processor is used to execute a computer program to implement the following method steps:

[0017] 1) Processing the analog signal of the sampling channel of the AC analog plug-in to obtain a digital signal;

[0018] 2) extracting predetermined signal features from the digital signal, wherein the predetermined signal features are determined based on the feature differences of the digital signal obtained by processing the AC analog plug-in in a normal working state and in an offline state;

[0019] 3) Compare the extracted signal features with the signal features of the same type obtained through the sampling channel processing when the AC analog plug-in is working normally. If the digital signal features when the AC analog plug-in is working normally are met, the AC analog plug-in is in normal operating state, otherwise, the AC analog plug-in is in offline state.

[0020] Furthermore, the predetermined signal characteristics include amplitude and phase information of a DC component and an AC component.

[0021] Furthermore, a full-cycle Fourier algorithm is used to extract predetermined signal features.

[0022] Furthermore, as long as the digital signal characteristics obtained by processing one sampling channel meet the signal characteristics of the AC analog plug-in in the offline state, the AC analog plug-in is in the offline state.

[0023] Furthermore, the analog signal is converted into a small analog signal through the conversion of the sampling channel of the AC analog plug-in including the mutual inductor; the small analog signal is transmitted to the A / D conversion chip through the pre-low-pass filter circuit to obtain a digital signal.

[0024] The beneficial effects of the present invention are as follows: the present invention is a pioneering invention, which processes the analog signal of the sampling channel of the AC analog plug-in to obtain a digital signal; then extracts the predetermined signal features in the digital signal, and compares the extracted signal features with the signal features of the same type of signal processed through the sampling channel when the AC analog plug-in is working normally, so as to effectively determine whether the AC analog plug-in is in a normal working state. The present invention avoids changing the hardware structure of the existing AC analog plug-in, and realizes the determination of the working state of the AC analog plug-in on a stable and reliable basis. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of a working state determination and monitoring process of an AC analog quantity plug-in of the present invention;

[0026] Figure 2 The present invention is a schematic diagram of the working state determination principle of an AC analog quantity plug-in. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0028] The idea of ​​the present invention is to extract features of a digital signal obtained through a sampling channel of an AC analog plug-in. Taking into account the differences in features of a digital signal obtained when the AC analog plug-in is in normal working condition and when it is in offline condition, the signal features to be extracted are determined based on the differences. The extracted signal features are then compared with the same type of signal features obtained through a sampling channel when the AC analog plug-in is in normal working condition. This allows determining whether the AC analog plug-in is in normal working condition.

[0029] Method Example:

[0030] This embodiment provides a method for determining the working state of an AC analog quantity plug-in. Figure 1 As shown, the following steps are included:

[0031] S1, the analog signal is processed by the AC analog plug-in sampling channel to obtain a digital signal;

[0032] S2, extracting predetermined signal features of the digital signal;

[0033] S3. Compare the extracted signal features with the digital signal features obtained after the AC analog plug-in channel works normally, to determine whether the AC analog sampling plug-in works normally.

[0034] Specifically, step S1 includes: the analog signal is converted into a small analog signal through a sampling channel including a mutual inductor, and the small analog signal is transmitted to an A / D (Analog to Digital) conversion chip through a low-pass filter circuit. The filtering processing of the low-pass filter circuit can effectively filter out noise interference, which is conducive to the subsequent algorithm to extract signal features close to the real one; under the control of an FPGA (Field-Programmable Gate Array), the A / D conversion chip converts the small analog signal into a digital signal.

[0035] Specifically, in step S2, the AC analog plug-in has different digital signal characteristics obtained by sampling channel processing in normal working state and offline state, and then the signal characteristics are determined. According to the difference, a suitable algorithm is selected to extract the corresponding signal characteristics.

[0036] Furthermore, after being processed by the sampling channels of different types of mutual inductors, the characteristics of the obtained digital quantity signals are also different, so it is necessary to select a corresponding algorithm to extract the corresponding signal characteristics.

[0037] In summary, the working status judgment principle of the AC analog plug-in is as follows: Figure 2 As shown, the following steps are included:

[0038] S4, determine the working state judgment basis of the AC analog plug-in and the corresponding signal feature extraction algorithm;

[0039] S5, extracting the characteristics of digital quantity signals passing through different types of sampling channels;

[0040] S6. Each channel is judged. If any channel characteristic is abnormal, it is determined that the AC analog plug-in is in an offline state.

[0041] Specifically, there are obvious differences in the digital signals obtained by processing different types of sampling channels. For example, due to the difference in the principle of the mutual inductor, when the AC analog plug-in is in normal working condition, the sampling channel has a clear AC component in the digital signal due to the existence of zero drift, while in the offline state, the DC component is dominant and the AC component almost disappears. Therefore, the relevant algorithm can be selected to extract the DC component of the digital signal and the amplitude and phase of the AC component of a specific frequency, and use it as a basis for judgment. As other implementation methods, the differences in the characteristics of the digital signals obtained by sampling channels of different types of mutual inductors in the normal working state and offline state of the AC analog plug-in can also be summarized to determine the corresponding basis for judgment.

[0042] Fourier transform and its different variants and various derived transformation algorithms are widely used in different research fields. In the power field, Fourier transform and other algorithms are mainly used in filtering out high-order harmonics, calculating DC components and AC components of different frequencies, and judging faults. There are many mature application scenarios, so we consider using specific Fourier transform algorithms to realize the extraction of digital signal features.

[0043] The standard Fourier transform can show the characteristic information of continuous periodic signals in the entire frequency domain. The full-cycle Fourier transform algorithm used in the power-related field usually takes the 50Hz power frequency as the fundamental frequency. Therefore, the full-cycle Fourier transform algorithm is used to extract the DC component of the digital signal processed by the sampling channel and the amplitude and phase of the 50Hz AC component. According to the number of sampling points N per power frequency cycle of the actual hardware used, the DC component and each harmonic are calculated as follows:

[0044] I is the digital signal, t represents the sampling time, I0 represents the DC component, I nr represents the real part of the nth harmonic, I ni represents the imaginary part of the nth harmonic, ω represents the fundamental frequency, and the Fourier series of the digital signal is expressed as:

[0045]

[0046] In one power frequency cycle T, the digital signal is integrated to obtain the representation results of the imaginary part and real part of the nth harmonic respectively:

[0047] Real part:

[0048]

[0049] Imaginary part:

[0050]

[0051] The digital signal is processed by using the trapezoidal method of numerical integration to obtain the representation results of the DC component, the real part and the imaginary part of each harmonic. k is the sampling point number, I k That is the digital value I(t) corresponding to the sampling time;

[0052] DC component:

[0053]

[0054] Real part of the nth harmonic:

[0055]

[0056] Imaginary part of the nth harmonic:

[0057] (6)

[0059] The AC component is composed of various harmonic components. i is an imaginary unit, so the AC component is expressed in complex form as:

[0060]

[0061] Then the amplitude and phase of the AC component of a specific frequency are calculated:

[0062] The amplitude of the nth harmonic:

[0063]

[0064] nth harmonic phase:

[0065]

[0066] The digital signals obtained from different sampling channels are processed using a Fourier transform algorithm with appropriate parameters. When the parameters are appropriate, rich frequency domain related information can be obtained. According to the predetermined conditions, when the extracted digital signal characteristics meet the corresponding signal characteristics obtained after processing through the sampling channel, it is considered that the AC analog sampling plug-in is in normal working state, otherwise, it is considered that the AC analog sampling plug-in is in an offline state, and then the alarm function is triggered.

[0067] System Example:

[0068] This embodiment provides a system for determining the working status of an AC analog plug-in. When determining the working status of the AC analog plug-in, the system adopts the method introduced in the method embodiment. Since the introduction of this method is clear enough, it will not be repeated here.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for determining the working state of an AC analog plug-in, characterized in that: The steps include: 1) Processing the analog signal of the sampling channel of the AC analog plug-in to obtain a digital signal; 2) extracting predetermined signal features from the digital signal, wherein the predetermined signal features are determined based on feature differences between the digital signal processed by the AC analog plug-in in a normal working state and in an offline state; 3) Compare the extracted signal features with the signal features of the same type obtained by processing the sampling channel when the AC analog plug-in is working normally. If the digital signal features when the AC analog plug-in is working normally are met, the AC analog plug-in is in normal operating state, otherwise, the AC analog plug-in is in offline state.

2. The working state determination method of the AC analog quantity plug-in according to claim 1 is characterized in that: The predetermined signal characteristics include amplitude and phase information of a DC component and an AC component.

3. The working state determination method of the AC analog quantity plug-in according to claim 2 is characterized in that: Predetermined signal features are extracted using a full-cycle Fourier algorithm.

4. The working state determination method of the AC analog quantity plug-in according to claim 3 is characterized in that: As long as the digital signal characteristics obtained by processing one sampling channel meet the signal characteristics of the AC analog plug-in in the offline state, the AC analog plug-in is in the offline state.

5. The working state determination method of the AC analog quantity plug-in according to claim 1 is characterized in that: The analog signal is converted into a small analog signal through the conversion of the sampling channel of the AC analog plug-in including the mutual inductor; the small analog signal is transmitted to the A / D conversion chip through the pre-low-pass filter circuit to obtain the digital signal.

6. A system for determining the working state of an AC analog quantity plug-in, comprising a processor, characterized in that: The processor is used to execute a computer program to implement the following method steps: 1) Processing the analog signal of the sampling channel of the AC analog plug-in to obtain a digital signal; 2) extracting predetermined signal features from the digital signal, wherein the predetermined signal features are determined based on feature differences between the digital signal processed by the AC analog plug-in in a normal working state and in an offline state; 3) Compare the extracted signal features with the signal features of the same type obtained by processing the sampling channel when the AC analog plug-in is working normally. If the digital signal features when the AC analog plug-in is working normally are met, the AC analog plug-in is in normal operating state, otherwise, the AC analog plug-in is in offline state.

7. The working state determination system of the AC analog quantity plug-in according to claim 6 is characterized in that: The predetermined signal characteristics include amplitude and phase information of a DC component and an AC component.

8. The working state determination system of the AC analog quantity plug-in according to claim 7 is characterized in that: Predetermined signal features are extracted using a full-cycle Fourier algorithm.

9. The working state determination system of the AC analog quantity plug-in according to claim 8 is characterized in that: As long as the digital signal characteristics obtained by processing one sampling channel meet the signal characteristics of the AC analog plug-in in the offline state, the AC analog plug-in is in the offline state.

10. The working state determination system of the AC analog quantity plug-in according to claim 6, characterized in that: The analog signal is converted into a small analog signal through the conversion of the sampling channel of the AC analog plug-in including the mutual inductor; the small analog signal is transmitted to the A / D conversion chip through the pre-low-pass filter circuit to obtain the digital signal.

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