A Simple Digital Detection Method for Abnormal Sine Alternating Voltage Waveforms

Abstract

The present invention discloses a simple digital detection method for abnormal sine AC voltage waveforms. First, sample the sine wave voltage signal to be detected, calculate the difference between adjacent sampling values, and take the absolute value. Then, calculate the average value of the sum of these absolute values. Compare the average value of the sine wave voltage signal to be detected with the average value of the standard sine wave voltage signal to determine whether there is an abnormality in the sine AC voltage waveform to be detected. If the sine wave voltage signal to be detected is distorted, in the calculated average value, the sudden change value of the change value will be doubled, making the average value of the sine wave voltage signal to be detected significantly greater than the average value of the standard sine wave voltage signal. Therefore, it is determined that there is an abnormality in the waveform of the sine wave voltage signal to be detected. The calculation method of the present invention is simple, only involving simple calculations such as subtraction, addition, taking the absolute value, and division, and the result can be obtained within one sine period, with a fast detection speed and a simple algorithm.

Description

Technical Field

[0001] The present invention relates to the technical fields of sinusoidal AC power supplies and power data systems, and particularly to a digital simple detection method for abnormal sinusoidal AC voltage waveforms. Background Art

[0002] In the state detection, control, and protection of AC power supply devices, as well as in power system data acquisition and electrical quantity measurement operations, affected by problems such as electromagnetic disturbances and transmission distortions, the waveforms of sinusoidal AC voltages or currents will be distorted, which will affect the normal operation of AC power supply devices and power systems. Voltage or current waveform distortion will increase the harmonic content in the power grid, and these harmonic contents will resonate with components such as inductors and capacitors in the power grid, thus affecting the stability of the power grid. Voltage or current waveform distortion will affect the stable operation of electrical equipment, resulting in an increase in the failure rate of electrical equipment.

[0003] Since current signals can be converted into voltage signals, there is an urgent need for a detection method for sinusoidal AC voltage signal waveforms to increase the stability of the operation of electrical equipment. Summary of the Invention

[0004] In view of this, it is necessary to provide a digital simple detection method for abnormal sinusoidal AC voltage waveforms that can perform rapid detection.

[0005] A digital simple detection method for abnormal sinusoidal AC voltage waveforms, used for rapid detection of abnormal sinusoidal AC voltage signals, the specific steps include:

[0006] Step 1, sampling a standard sinusoidal AC voltage signal and converting it into a digital signal;

[0007] Step 2, calculating the absolute value of the difference between the current sampling value and the previous sampling value of the standard sinusoidal AC voltage signal, and finding the average value of the cumulative sum of the absolute values;

[0008] Step 3, sampling the analog AC voltage signal to be detected and converting the analog signal into a digital signal; calculating the difference between the current sampling value and the previous sampling value of the AC voltage signal to be detected, taking the absolute value and then accumulating, and calculating the average value of the accumulated value;

[0009] Step 4, comparing the average value of the accumulated value of the sinusoidal AC voltage signal to be detected with the sampling cumulative average value of the standard sinusoidal AC voltage signal to determine whether there is an abnormality in the sinusoidal AC voltage waveform to be detected.

[0010] Preferably, the specific steps of sampling the standard sinusoidal AC voltage signal in Step 1 include:

[0011] Step 1.1, determine the sampling period Ts or sampling frequency fs of the sampling signal, as shown in equations (1) and (2):

[0012] (1);

[0013] (2);

[0014] Step 1.2, divide a complete sine wave into four intervals, namely 0° - 90°, 90° - 180°, 180° - 270°, 270° - 360°. The sampling values at 0°, 90°, 180°, 270°, and 360° are respectively , , , , , where the n th sampling value is , then the value range of n is as shown in equation (3):

[0015] (3).

[0016] Preferably, for step two, the specific steps of calculating the absolute value of the difference between the current sampling value and the previous sampling value of the standard sine wave AC voltage signal and then finding the average of the sum of absolute values include:

[0017] Step 2.1, calculate the difference between the current sampling signal and the previous sampling signal and take the absolute value;

[0018] Step 2.2, after the sampling of a sine period is completed, accumulate and find the average of the absolute values of the differences between adjacent sampling values within a complete sine period , as shown in equation (4):

[0019] (4),

[0020] where is the n th sampling value, and is the (n - 1)th sampling value.

[0021] Preferably, for step 2.1, the specific steps of calculating the difference between the current sampling signal and the previous sampling signal and taking the absolute value include:

[0022] Step 2.1.1, interval Ⅰ, , the voltage sampling value gradually increases, that is , the accumulated value V I is as shown in equation (5):

[0023] (5);

[0025] Step 2.1.2, Interval II, , the voltage sampling value gradually decreases, that is , the cumulative value V II as shown in Equation (6):

[0026] (6);

[0028] Step 2.1.3, Interval III, , the voltage sampling value gradually decreases, that is , the cumulative value V III as shown in Equation (7):

[0029] (7);

[0031] Step 2.1.4, Interval IV, the voltage sampling value gradually increases, that is , the cumulative value V IV as shown in Equation (8):

[0032] (8);

[0034] Preferably, in Step 2.2, after the sampling in one sine period is completed, the absolute values of the differences between adjacent sampling values in a complete sine period are accumulated and averaged , and the specific steps include:

[0035] Step 2.2.1, substituting Equation (5), Equation (6), Equation (7), and Equation (8) into Equation (4), the sum of the absolute values of the differences between adjacent sampling values in a complete sine period can be obtained and averaged , as shown in Equation (9):

[0036] (9);

[0038] Since , , , therefore, the average value as shown in Equation (10):

[0039] (10);

[0040] wherein, is the fundamental peak value of the standard sine wave AC voltage signal.

[0041] Preferably, the specific steps of calculating the difference between the current sampling value and the previous sampling value of the AC voltage signal to be detected in step three include:

[0042] When calculating the difference between the current sampling signal and the previous sampling signal, if a non-standard sine wave voltage signal appears and there is a positive distortion, then the m + n th sampling value is larger than the standard sine wave voltage value large , that is, the m + n th sampling value As shown in equation (11):

[0043] (11);

[0044] Then the cumulative value is as shown in equation (12):

[0045] (12);

[0047] If a non-standard sine wave voltage signal appears and there is a negative distortion, then the m + N + n th sampling value is smaller than the standard sine wave voltage value small , that is, the m + N + n th sampling value As shown in equation (13):

[0048] (13);

[0049] Then the cumulative value is as shown in equation (14):

[0050]

[0051] (14).

[0052] Preferably, in step four, the specific steps of comparing the average value of the cumulative value with the sampling cumulative average value of the standard sine AC voltage signal to determine whether there is an abnormality in the sine AC voltage waveform to be detected include:

[0053] Compare the average value of the calculated cumulative value with the sampled cumulative average value of the standard sinusoidal AC voltage signal. If the average value of the calculated cumulative value is greater than the sampled cumulative average value of the standard sinusoidal AC voltage signal, it is determined that the analog AC voltage signal to be detected is distorted; otherwise, it is determined that the analog AC voltage signal to be detected is a normal signal.

[0054] In the above-mentioned digital simple detection method for abnormal sinusoidal AC voltage waveforms, first, sample the sinusoidal voltage signal to be detected, calculate the difference between adjacent sampled values, and take the absolute value. Then calculate the average value of the sum of the absolute values. Compare the average value of the sinusoidal voltage signal to be detected with the average value of the standard sinusoidal voltage signal. If the sinusoidal voltage signal to be detected is distorted, in the calculated average value, the sudden change value of the change value will be doubled, making the average value of the sinusoidal voltage signal to be detected significantly greater than the average value of the standard sinusoidal voltage signal. Therefore, it is determined that the waveform of the sinusoidal voltage signal to be detected is abnormal. The calculation method of the present invention is simple, only involving simple calculations such as subtraction, addition, taking the absolute value, and division, and the result can be obtained within one sinusoidal cycle. The detection speed is fast and the algorithm is simple. For an AC sinusoidal voltage signal with a stable effective value, it can also quickly detect whether its effective value exceeds the specified range. The algorithm of the present invention is simple, easy to implement, low in cost, and convenient for popularization. Brief Description of the Drawings

[0055] Figure 1 is a flowchart of the digital simple detection method for abnormal sinusoidal AC voltage waveforms in an embodiment of the present invention.

[0056] Figure 2 is a schematic diagram of the sampled signal of the standard sinusoidal AC voltage signal in the digital simple detection method for abnormal sinusoidal AC voltage waveforms in an embodiment of the present invention.

[0057] Figure 3 is a schematic diagram of the sampled signal of the abnormal sinusoidal AC voltage signal in the digital simple detection method for abnormal sinusoidal AC voltage waveforms in an embodiment of the present invention. Detailed Embodiments

[0058] Taking the digital simple detection method for abnormal sinusoidal AC voltage waveforms as an example, the present invention will be described in detail below with reference to specific embodiments and drawings.

[0059] Please refer to Figure 1 , which shows a digital simple detection method for abnormal sinusoidal AC voltage waveforms provided by an embodiment of the present invention, used for the rapid detection of abnormal sinusoidal AC voltage signals. The specific steps are as follows:

[0060] Step 1: Sample the standard sinusoidal AC voltage signal and convert it into a digital signal.

[0061] Specifically, in this embodiment, the high-voltage AC voltage is converted into a low-voltage signal by a hardware detection circuit, and then the ADC function of a high-speed MCU chip is used to convert the analog signal into a digital quantity and perform relevant calculations, improving the flexibility of signal processing.

[0062] Step 1.1, determine the sampling period Ts or sampling frequency fs of the sampling signal, as shown in equations (1) and (2):

[0063] (1);

[0064] (2);

[0065] Among them, the value of N depends on the frequency of the sine-wave voltage signal, and it is necessary to make the sampling frequency of the sampling signal meet the requirements of the Shannon sampling theorem.

[0066] According to the Shannon sampling theorem, the higher the frequency of the sine-wave voltage signal, the larger the value of N, and it is necessary to ensure that there are enough sampling values within a quarter of a sine period.

[0067] Step 1.2, divide a complete sine wave into four intervals, namely 0° - 90°, 90° - 180°, 180° - 270°, 270° - 360°. The sampling values at 0°, 90°, 180°, 270°, and 360° are respectively , , , , , where the n th sampling value is , then n The value range of

[0068] (3).

[0069] Step two, calculate the absolute value of the difference between the current sampling value and the previous sampling value of the standard sine-wave AC voltage signal, and find the average value of the accumulated sum of the absolute values.

[0070] Please refer to Figure 2 , and the specific steps include:

[0071] Step 2.1, calculate the difference between the current sampling signal and the previous sampling signal, and take the absolute value.

[0072] Step 2.1.1, interval I, , the voltage sampling value gradually increases, that is , the accumulated value V IAs shown in Equation (5):

[0073] (5);

[0075] Step 2.1.2, Interval II , the voltage sampling value gradually decreases, that is , the accumulated value V II As shown in Equation (6):

[0076] (6);

[0078] Step 2.1.3, Interval III , the voltage sampling value gradually decreases, that is , the accumulated value V III As shown in Equation (7):

[0079] (7);

[0081] Step 2.1.4, Interval IV The voltage sampling value gradually increases, that is , the accumulated value V IV As shown in Equation (8):

[0082]

[0083] (8).

[0084] Step 2.2, After the sampling in a sine period is completed, the absolute values of the differences between adjacent sampling values in a complete sine period are accumulated and averaged , as shown in Equation (4):

[0085] (4),

[0086] where is the n th sampling value, is the n -1th sampling value.

[0087] Step 2.2.1, Substitute Equation (5), Equation (6), Equation (7), and Equation (8) into Equation (4), and the accumulated sum and average value of the absolute values of the differences between adjacent sampling values in a complete sine period can be obtained , as shown in Equation (9):

[0088] (9);

[0090] Since 、 、 , therefore, the average value is as shown in Equation (10):

[0091] (10);

[0092] wherein, is the fundamental peak value of the standard sinusoidal AC voltage signal.

[0093] When performing sampling calculations on the standard sinusoidal wave, in the calculation result is the fundamental peak value of the standard sinusoidal AC voltage signal, that is, times the effective voltage value.

[0094] Specifically, in this embodiment, the average value after accumulating the absolute values of the differences between adjacent sampling values of the standard sinusoidal AC voltage signal is used as the standard value, that is, the calculation result in Step 2 is used as the standard value. Among them, the frequency and amplitude of the standard sinusoidal AC voltage signal are the same as those of the analog AC voltage signal to be detected.

[0095] Step 3: Sample the analog AC voltage signal to be detected and convert the analog signal into a digital signal; calculate the difference between the current sampling value and the previous sampling value of the AC voltage signal to be detected, take the absolute value and accumulate it, and calculate the average value of the accumulated value.

[0096] Specifically, the calculation process of sampling the analog AC voltage signal to be detected, calculating the difference between adjacent sampling values, taking the absolute value and accumulating it, and calculating the average value of the accumulated value is the same as the calculation process of calculating the standard value of the standard sinusoidal AC voltage signal in Steps 1 and 2, and the calculation steps will not be elaborated.

[0097] For non-standard sinusoidal AC voltage signals, if the AC voltage waveform is distorted, the calculation result will change. The following takes the voltage mutation at a single sampling point as an example for calculation. As Figure 3 shown, at the m + n th sampling point, the waveform has a positive distortion (the voltage increases), and at the m + N + n th sampling point, the waveform has a negative distortion (the voltage decreases).

[0098] (1) Positive mutation

[0099] Assume that the m + n th sampling value is higher than the standard sinusoidal voltage value Large , that is:

[0100]

[0101] Then,

[0102]

[0103] The mutation variable increases by approximately twice compared with the calculated value of the pure sine wave .

[0104] (2) Negative mutation

[0105] Assume the m + N + n th sampling value is smaller than the standard sine wave voltage value Small , that is:

[0106]

[0107] Then,

[0108]

[0109] The mutation variable increases by approximately twice compared with the calculated value of the pure sine wave

[0110] Therefore, regardless of whether the waveform distortion causes the voltage value to increase or decrease, the final calculated result is an increase, and the change value is doubled. If there are multiple distortions in the waveform, the value calculated by formula (4) will be significantly larger than the standard sine wave.

[0111] Specifically, in this embodiment, the average value of the accumulated absolute values of the differences between adjacent sampling values of the analog AC voltage signal to be detected is used as the calculated value, that is, the calculation result in step three is used as the calculated value.

[0112] Step four, compare the average value of the accumulated values of the sine AC voltage signal to be detected with the average value of the sampled accumulations of the standard sine AC voltage signal to determine whether there is an abnormality in the sine AC voltage waveform to be detected.

[0113] Specifically, compare the calculated value with the standard value. If the calculated value is greater than the standard value, it is determined that the analog AC voltage signal to be detected is distorted; otherwise, it is determined that the detected analog AC voltage signal is a normal signal.

[0114] The setting of the threshold is determined according to actual needs. The smaller the threshold, the more sensitive the detection result; the larger the threshold, the more accurate the detection result. In this embodiment, 20% exceeding the standard value is used as the threshold. When the calculated value is greater than the threshold, it is determined that the analog AC voltage signal to be detected is distorted.

[0115] In the above-mentioned digital simple detection method for abnormal sine AC voltage waveforms, first, sample the sine wave voltage signal to be detected, calculate the difference between adjacent sampling values, and take the absolute value. Then calculate the average value of the sum of these absolute values, and compare the average value of the sine wave voltage signal to be detected with the average value of the standard sine wave voltage signal. If the sine wave voltage signal to be detected is distorted, in the calculated average value, the sudden change of the change value will be doubled, making the average value of the sine wave voltage signal to be detected significantly greater than the average value of the standard sine wave voltage signal. Therefore, it is determined that the waveform of the sine wave voltage signal to be detected is abnormal. The calculation method of the present invention is simple, only involving simple calculations such as subtraction, addition, taking the absolute value, and division, and the result can be obtained within one sine period, with a fast detection speed and a simple algorithm. For an AC sine voltage signal with a stable effective value, it can also quickly detect whether its effective value exceeds the specified range. The algorithm of the present invention is simple, easy to implement, low in cost, and convenient for popularization.

[0116] It should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A digital simple detection method for abnormal sinusoidal AC voltage waveform, used for rapid detection of abnormal sinusoidal AC voltage signal, characterized in that: The specific steps include: Step 1: sampling the standard sinusoidal AC voltage signal and converting it into a digital signal; Step 2, calculating the absolute value of the difference between the current sampling value and the previous sampling value of the standard sinusoidal AC voltage signal, and averaging the accumulated sum of the absolute values; Step 3: Sample the analog AC voltage signal to be detected and convert the analog signal into a digital signal; calculate the difference between the current sampling value and the previous sampling value of the AC voltage signal to be detected, take the absolute value and add them up, and calculate the average value of the accumulated value; Step 4: compare the average value of the accumulated value of the sinusoidal AC voltage signal to be detected with the sampled accumulated average value of the standard sinusoidal AC voltage signal to determine whether the sinusoidal AC voltage waveform to be detected is abnormal.

2. The digital simple detection method for abnormal sinusoidal AC voltage waveform according to claim 1 is characterized in that: The specific steps of sampling the standard sinusoidal AC voltage signal in step 1 include: Step 1.1, determine the sampling period Ts or sampling frequency fs of the sampling signal, as shown in equations (1) and (2): （1）； （2）； Step 1.2: Divide a complete sine wave into four intervals: 0°~90°, 90°~180°, 180°~270°, and 270°~360°. The sampling values ​​at 0°, 90°, 180°, 270°, and 360° are , , , , , among which, n The sampling value is ,but n The value range of is shown in formula (3): （3）。 3. The digital simple detection method for abnormal sinusoidal AC voltage waveform according to claim 2 is characterized in that: The step 2, calculating the absolute value of the difference between the current sampling value and the previous sampling value of the standard sinusoidal AC voltage signal, and accumulating and averaging the absolute values, comprises: Step 2.1, calculate the difference between the current sampling signal and the previous sampling signal, and take the absolute value; Step 2.2: After sampling a sine cycle, add up the absolute values ​​of the differences between adjacent sampling values ​​within a complete sine cycle and calculate the average value. , as shown in formula (4): （4）， in, For the n Sample values, is the n-1th sampling value.

4. The digital simple detection method for abnormal sinusoidal AC voltage waveform as claimed in claim 3, characterized in that: The specific steps of calculating the difference between the current sampling signal and the previous sampling signal and taking the absolute value in step 2.1 include: Step 2.1.1, Interval I, , voltage sampling value Gradually increase, that is , accumulated value V I As shown in formula (5): （5）； Step 2.1.2, Interval II, , voltage sampling value Gradually decrease, that is , accumulated value V II As shown in formula (6): （6）； Step 2.1.3, Interval III, , voltage sampling value Gradually decrease, that is , accumulated value V III As shown in formula (7): （7）； Step 2.1.4, Interval IV, Voltage sampling value Gradually increase, that is , accumulated value V IV As shown in formula (8): （8）。 5. The digital simple detection method for abnormal sinusoidal AC voltage waveform according to claim 4, characterized in that: In step 2.2, after sampling of a sinusoidal cycle is completed, the absolute values ​​of the differences between adjacent sampling values ​​within a complete sinusoidal cycle are accumulated and the average value is calculated. The specific steps include: Step 2.2.1, substitute equations (5), (6), (7), and (8) into equation (4) to obtain the sum of the absolute values ​​of the differences between adjacent sampling values ​​within a complete sinusoidal period and calculate the average value. , as shown in formula (9): （9）； because , , , so the average As shown in formula (10): （10）； in, It is the fundamental peak value of the standard sinusoidal AC voltage signal.

6. The digital simple detection method for abnormal sinusoidal AC voltage waveform according to claim 2, characterized in that: The specific steps of calculating the difference between the current sampling value and the previous sampling value of the AC voltage signal to be detected in step 3 include: When calculating the difference between the current sampling signal and the previous sampling signal, if a non-standard sinusoidal voltage signal appears and there is positive distortion, then m + n Sample value Compared with standard sine wave voltage value big , that is, m + n Sample value As shown in formula (11): （11）； Then the accumulated value is as shown in formula (12): （12）； If a non-standard sinusoidal voltage signal appears and there is negative distortion, the m + N + n Sample value Compared with standard sine wave voltage value Small , that is, m + N + n Sample value As shown in formula (13): （13）； Then the accumulated value is as shown in formula (14): （14）。 7. The digital simple detection method for abnormal sinusoidal AC voltage waveform according to claim 1, characterized in that: The specific steps of comparing the average value of the accumulated value with the sampled accumulated average value of the standard sinusoidal AC voltage signal to determine whether the sinusoidal AC voltage waveform to be detected is abnormal include: The calculated average value of the accumulated value is compared with the sampled accumulated average value of the standard sinusoidal AC voltage signal. If the calculated average value of the accumulated value is greater than the sampled accumulated average value of the standard sinusoidal AC voltage signal, it is determined that the analog AC voltage signal to be detected is distorted; otherwise, the analog AC voltage signal to be detected is determined to be a normal signal.

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