Digital simple detection method for sine alternating-current voltage waveform abnormity

Abstract

The invention discloses a simple digital detection method for sine alternating-current voltage waveform abnormity, which comprises the following steps of: firstly, sampling a sine-wave voltage signal to be detected, calculating a difference value between adjacent sampling values, taking an absolute value, and then calculating an average value of the sum of the absolute values; and comparing the average value of the sine-wave voltage signal to be detected with the average value of the standard sine-wave voltage signal, and judging whether the sine alternating-current voltage waveform to be detected is abnormal or not. If the to-be-detected sine-wave voltage signal has distortion, increasing the break variable of the change value by two times in the calculated average value, so that the average value of the to-be-detected sine-wave voltage signal is obviously greater than the average value of the standard sine-wave voltage signal, and the waveform of the to-be-detected sine-wave voltage signal is judged to be abnormal. The calculation method is simple, only subtraction, addition, absolute value taking, division and other simple calculation are involved, the result can be obtained in one sine period, the detection speed is high, and the algorithm is simple.

Description

Technical Field

[0001] The invention relates to the technical field of sinusoidal alternating current power supply and electric power data system, and in particular to a digital simple detection method for abnormal sinusoidal alternating current voltage waveform. Background Art

[0002] In the process of AC power supply status detection, control, protection, power system data collection, and electrical measurement, the sinusoidal AC voltage or current waveform will be distorted due to electromagnetic disturbances, transmission distortion, and other problems, affecting the normal operation of the AC power supply device and the power system. The voltage or current waveform distortion will increase the harmonic content in the power grid, which will resonate with components such as inductors and capacitors in the power grid, thereby affecting the stability of the power grid. The voltage or current waveform distortion will affect the stable operation of electrical equipment and increase the failure rate of electrical equipment.

[0003] Since current signals can be converted into voltage signals, a method for detecting the waveform of a sinusoidal AC voltage signal is urgently needed 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 and simple detection method for abnormal sinusoidal AC voltage waveform that can quickly detect abnormalities.

[0005] A digital simple detection method for abnormal sinusoidal AC voltage waveform is used for rapid detection of abnormal sinusoidal AC voltage signals. 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.

[0006] Preferably, 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).

[0007] Preferably, 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.

[0008] Preferably, 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); Preferably, 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 averaged. 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.

[0013] Preferably, the specific step 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 includes: 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):

[0015] (14).

[0016] Preferably, 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 and determining 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.

[0017] In the above-mentioned digital simple detection method for abnormal sinusoidal AC voltage waveform, first, the sinusoidal voltage signal to be detected is sampled, the difference between adjacent sampling values ​​is calculated, and the absolute value is taken, and then the average value of the sum of the absolute values ​​is calculated, and the average value of the sinusoidal voltage signal to be detected is compared with the average value of the standard sinusoidal voltage signal. If the sinusoidal voltage signal to be detected is distorted, the calculated average value will increase the mutation amount of the change value by two times, so that the average value of the sinusoidal voltage signal to be detected is significantly greater than the average value of the standard sinusoidal voltage signal, so 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, involving only simple calculations such as subtraction, addition, taking 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 cost, and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1The figure is a flow chart of a digital simple detection method for abnormal sinusoidal AC voltage waveform according to an embodiment of the present invention.

[0019] Figure 2 It is a schematic diagram of sampling signals of a standard sinusoidal alternating voltage signal of a digital simple detection method for abnormal sinusoidal alternating voltage waveform according to an embodiment of the present invention.

[0020] Figure 3 It is a schematic diagram of sampling signals of abnormal sinusoidal alternating voltage signals in a digital simple detection method for abnormal sinusoidal alternating voltage waveform according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] This embodiment takes the digital simple detection method of abnormal sinusoidal AC voltage waveform as an example, and the present invention will be described in detail below in conjunction with specific embodiments and drawings.

[0022] See also Figure 1 , showing a digital simple detection method for abnormal sinusoidal AC voltage waveform provided by an embodiment of the present invention, which is used for rapid detection of abnormal sinusoidal AC voltage signals, and the specific steps are as follows: Step 1: Sample the standard sinusoidal AC voltage signal and convert it into a digital signal.

[0023] Specifically, in this embodiment, the high voltage AC voltage is converted into a low voltage signal through a hardware detection circuit, and then the ADC function of the high-speed MCU chip is used to convert the analog signal into a digital quantity, and related calculations are performed, thereby improving the flexibility of signal processing.

[0024] 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); The value of N depends on the frequency of the sinusoidal voltage signal, and the sampling frequency of the sampling signal needs to meet the requirements of Shannon's sampling theorem.

[0025] According to Shannon's sampling theorem, the higher the frequency of the sinusoidal voltage signal, the larger the value of N is, and it is necessary to ensure that there are enough sampling values ​​within a quarter of the sinusoidal period.

[0026] 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).

[0027] Step 2: Calculate the absolute value of the difference between the current sampling value and the previous sampling value of the standard sinusoidal AC voltage signal, and calculate the average value of the accumulated sum of the absolute values.

[0028] See also Figure 2 , the specific steps include: Step 2.1, calculate the difference between the current sampling signal and the previous sampling signal, and take the absolute value.

[0029] 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):

[0032] (8).

[0033] 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, For the n -1 sample value.

[0034] 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.

[0036] When a standard sine wave is sampled and calculated, the calculation result is the fundamental peak value of the standard sinusoidal AC voltage signal, that is, the effective value of the voltage .

[0037] Specifically, in this embodiment, the average value of the absolute values ​​of the differences between adjacent sampling values ​​of the standard sinusoidal AC voltage signal is accumulated as the standard value, that is, the calculation result in step 2 is taken as the standard value. The frequency and amplitude of the standard sinusoidal AC voltage signal are the same as the frequency and amplitude of the analog AC voltage signal to be detected.

[0038] Step three, 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 it, and calculating the average value of the accumulated value.

[0039] 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 then accumulating, 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 one and two, and the calculation steps are not repeated here.

[0040] For non-standard sinusoidal AC voltage signals, if the AC voltage waveform is distorted, the calculation results will change. The following calculation takes a single sampling point voltage mutation as an example. Figure 3 As shown,m + n The waveform of the first sampling point has positive distortion (voltage increases), m + N + n There is negative distortion in the waveform of each sampling point (the voltage decreases).

[0041] (1) Positive mutation Assume m + n Sample value Compared with standard sine wave voltage value big ,Right now:

[0042] but,

[0043] Therefore, the mutation amount is increased by about two times compared with the pure sine wave calculation value. .

[0044] (2) Negative mutation Assume m + N + n Sample value Compared with standard sine wave voltage value Small ,Right now:

[0045] but,

[0046] Compared with the pure sine wave calculation value, the mutation amount is increased by about two times

[0047] 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 is distortion in multiple places on the waveform, the value calculated by formula (4) will be significantly larger than the standard sine wave.

[0048] Specifically, in this embodiment, the average value of the absolute values ​​of the differences between adjacent sampling values ​​of the analog AC voltage signal to be detected is accumulated as the calculated value, that is, the calculation result in step three is used as the calculated value.

[0049] 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.

[0050] Specifically, the calculated value is compared 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.

[0051] The setting of the threshold is determined according to actual needs. The smaller the threshold, the more sensitive the detection result, and the larger the threshold, the more accurate the detection result. In this embodiment, the threshold is 20% higher than the standard value. When the calculated value is greater than the threshold, it is determined that the analog AC voltage signal to be detected is distorted.

[0052] In the above-mentioned digital simple detection method for abnormal sinusoidal AC voltage waveform, first, the sinusoidal voltage signal to be detected is sampled, the difference between adjacent sampling values ​​is calculated, and the absolute value is taken, and then the average value of the sum of the absolute values ​​is calculated, and the average value of the sinusoidal voltage signal to be detected is compared with the average value of the standard sinusoidal voltage signal. If the sinusoidal voltage signal to be detected is distorted, the calculated average value will increase the mutation amount of the change value by two times, so that the average value of the sinusoidal voltage signal to be detected is significantly greater than the average value of the standard sinusoidal voltage signal, so 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, involving only simple calculations such as subtraction, addition, taking 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 cost, and easy to promote.

[0053] It should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in 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 1 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 1, 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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