Short-time flicker real-time calculation method and device

Abstract

The invention relates to a short-time flicker real-time calculation method and device, and belongs to the technical field of power system measurement. According to the method, only the cumulative probability required by short-time flicker calculation needs to be converted into the probability value matched with the self-adaptive method, the probability value serves as the quantile probability, and then the quantile value corresponding to each quantile probability is calculated through the obtained quantile probability, the range to which the instantaneous flicker degree value belongs and the instantaneous flicker degree value; and finally, performing short-time flicker real-time calculation based on the obtained quantile probability and the corresponding quantile value. According to the method, statistics of cumulative probability distribution of data in detection time is not needed, piecewise linear interpolation is not needed, only the range to which the instantaneous flicker degree value belongs and the instantaneous flicker degree value are needed to calculate the quantile value corresponding to each quantile probability, the calculation mode is simple, and a large amount of data does not need to be stored; meanwhile, the estimation value can be adaptively adjusted according to the dynamic change of the instantaneous flicker value, and the estimation precision is ensured.

Description

Technical Field

[0001] The invention relates to a short-time flicker real-time calculation method and device, belonging to the technical field of power system measurement. Background Art

[0002] The visual response of the human eye to unstable lighting illumination (light flickering) caused by voltage fluctuations is called flicker. In other words, flicker reflects the impact of light flickering caused by voltage fluctuations on human vision. Short-term flicker value (short termseverity, Pst) is a statistical value that measures the intensity of flicker in a short period of time (several minutes). Usually, Pst=1 is the limit value of visual stimulation caused by flicker. Flicker, as an important technical indicator in power quality monitoring, can reflect the real-time fluctuation of voltage. There are more and more studies on flicker, but basically, it is necessary to cache the instantaneous visual sensitivity data for a period of time and then perform statistical calculations. For example, the short-term flicker value needs to be calculated once every 10 minutes. According to the sampling rate of 400hz, 240,000 data need to be cached, which not only requires a large storage space, but also the large amount of calculation affects the calculation efficiency.

[0003] To this end, a short-time flicker calculation method that can reduce the amount of storage has been proposed. The Chinese patent application document with application publication number CN102928703A discloses a method and system for measuring short-time flicker. The method can store only the number of instantaneous flicker values ​​at each level in the data storage space by grading the instantaneous flicker value, and can reduce the amount of data that needs to be stored in the calculation process. This scheme reduces the number of data required to store for calculating short-time flicker from 240,000 to the number of grades (at least 64 grades according to the IEC standard). However, this method requires pre-setting the grading threshold, grading all instantaneous flicker values ​​within the preset time one by one according to the preset threshold, and storing the number of each grade of the grading, that is, calculating the instantaneous flicker value distribution histogram in real time, and the flicker value in the real environment is often unpredictable. Once the preset threshold value does not conform to the instantaneous flicker value distribution law, the calculated distribution histogram will also be distorted, and the accurate short-time flicker value cannot be obtained. Summary of the invention

[0004] The purpose of the present invention is to provide a method and device for real-time calculation of short-time flicker, so as to solve the problem of poor calculation accuracy caused by the need to pre-set classification thresholds in the current real-time calculation of short-time flicker.

[0005] In order to solve the above technical problems, the present invention provides a short-term flicker real-time calculation method, which comprises:

[0006] 1) Obtain the instantaneous flicker value within the detection time;

[0007] 2) Convert the cumulative probability required for short-term flicker calculation into a probability value that is compatible with the adaptive method, called the quantile probability. Each quantile probability is equal to 1 minus the corresponding cumulative probability.

[0008] 3) Calculate the quantile values ​​corresponding to each quantile probability using the obtained quantile probability, the range of the instantaneous flicker value and the instantaneous flicker value;

[0009] 4) Multiply each quantile probability by the corresponding quantile value and then sum them to obtain the short-term flicker value within the detection time.

[0010] Furthermore, the calculation formula used for the quantile values ​​corresponding to each quantile probability in step 3) is:

[0011]

[0012] Among them, P m (n) is the quantile value corresponding to the mth quantile probability, P' m is the mth quantile probability, R(n) is the range of the instantaneous flicker value corresponding to the nth sampling value, and S(n) is the instantaneous flicker value corresponding to the nth sampling value.

[0013] Furthermore, the range of the instantaneous flicker value is updated in real time, and the calculation formula used is:

[0014] R(n)=Rmax(n)-Rmin(n)

[0015]

[0016] Among them, Rmax(n) and Rmin(n) are the upper and lower limits of the range of instantaneous flicker values, respectively. R(n) is the range of instantaneous flicker values ​​corresponding to the nth sampling value. S(n) is the instantaneous flicker value corresponding to the nth sampling value. α and β are coefficients greater than 0 and less than 1.

[0017] Furthermore, the calculation formula used for the short-time flicker value within the detection time in step 4) is:

[0018]

[0019] Where P0 ′ .999 、P0 ′ .99 、P0 ′ .97 、P0 ′ .9 and P0 ′ .5are the quantile probabilities corresponding to the cumulative probabilities of 0.1%, 1%, 3%, 10% and 50% within the detection time, respectively, P 0.999 , P 0.99 , P 0.97 , P 0.9 and P 0.5 They are the quantile probability P0 within the detection time. ′ .999 、P0 ′ .99 、P0 ′ .97 、P0 ′ .9 and P0 ′ .5 The corresponding quantile value.

[0020] Furthermore, the instantaneous flicker value within the detection time is obtained by subjecting the voltage sampling signal within the detection time to square processing, bandpass filtering, visual sensitivity weighted filtering and smoothing weighted filtering.

[0021] Furthermore, the band-pass filter used in the band-pass filtering is composed of a high-pass filter with a cut-off frequency of 0.05 Hz and a low-pass filter with a cut-off frequency of 35 Hz.

[0022] Furthermore, the transfer function of the sensitivity weighted filter used in the sensitivity weighted filtering is:

[0023]

[0024] Among them, w1=2π*9.15494, w2=2π*2.27979, w3=2π*1.22535, w4=2π*21.9, k=1.74802, λ1=2π*4.05981.

[0025] Furthermore, the visual sensitivity weighted filter is implemented by converting the bilinear function of MATLAB into a digital filter.

[0026] Furthermore, the transfer function used in the smoothing weighted filtering is:

[0027]

[0028] Among them, τ is selected as 300ms.

[0029] The present invention also provides a short-time flicker real-time calculation device, comprising a processor, wherein the processor is used to execute computer program instructions to implement the short-time flicker real-time calculation method of the present invention.

[0030] The beneficial effects of the present invention are as follows: as an improved invention, the present invention only needs to convert the required cumulative probability of short-time flicker calculation into a probability value adapted to the adaptive method, and use the probability value as the quantile probability, and then use the obtained quantile probability, the range of the instantaneous flicker value and the instantaneous flicker value to calculate the quantile value corresponding to each quantile probability; finally, based on the obtained quantile probability and the corresponding quantile value, short-time flicker real-time calculation can be performed. The present invention does not need to perform statistics on the cumulative probability distribution of the data within the detection time, nor does it need piecewise linear interpolation. It only needs to use the range of the instantaneous flicker value and the instantaneous flicker value to calculate the quantile value corresponding to each quantile probability. The calculation method is simple and does not need to store a large amount of data. At the same time, the estimated value can be adaptively adjusted according to the dynamic changes of the instantaneous flicker value to ensure the estimation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart of the short-time flicker real-time calculation method of the present invention;

[0032] Figure 2 Schematic diagram of a quantile estimation curve obtained in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0034] The present invention only needs to convert the required cumulative probability of short-time flicker calculation into a probability value that is compatible with the adaptive method, and use the probability value as the quantile probability, and then use the obtained quantile probability, the range of the instantaneous flicker value and the instantaneous flicker value to calculate the quantile value corresponding to each quantile probability; finally, based on the obtained quantile probability and the corresponding quantile value, short-time flicker real-time calculation can be performed. The present invention does not need to perform statistics on the cumulative probability distribution of the data within the detection time, nor does it need piecewise linear interpolation. It only needs to estimate the 5 probability quantiles and flicker range required for short-time flicker calculation in real time based on the input instantaneous flicker value, dynamically update and store these 6 data, and take out the 5 quantile values ​​at this time to calculate the short-time flicker value at the preset time. The method further reduces the number of cache data from the level to 6, and takes into account the range change of the instantaneous flicker value when estimating, and can adaptively adjust the estimated value according to the dynamic change of the instantaneous flicker value to ensure the estimation accuracy.

[0035] Embodiment of a real-time calculation method for short-term flicker

[0036] The present invention first converts the required cumulative probability of short-time flicker calculation into a probability value that is compatible with the adaptive method, called quantile probability; then uses the obtained quantile probability, the range of the instantaneous flicker value and the instantaneous flicker value to calculate the quantile value corresponding to each quantile probability; finally, each quantile probability is multiplied by the corresponding quantile value and then summed to obtain the short-time flicker value within the detection time. The calculation process of this method is as follows: Figure 1 As shown, the detailed description is given below.

[0037] 1. Obtain the voltage sampling signal containing flicker and pre-process it.

[0038] The flicker signal of this embodiment adopts a square wave signal with a fluctuation of 0.722% and a frequency of 0.916, and a sampling rate of fs=400h. The preprocessing of the voltage sampling signal containing flicker by the present invention includes square calculation, bandpass filtering and weighted filtering, wherein the voltage sampling signal containing flicker obtained is:

[0039]

[0040] The voltage square signal obtained by square calculation of the above voltage sampling signal is: 2 (n) = f1(n) + f2(n) + f3(n),

[0041] in:

[0042]

[0043] Where m f is the flicker signal modulation index, w f is the flicker signal frequency, U is the fundamental wave rated voltage value, w is the fundamental wave frequency, and n is the sampling point.

[0044] The voltage square signal is subjected to 0.05 Hz-35 Hz bandpass filtering to remove out-of-band signals and obtain f(n). The bandpass filter used in this embodiment is composed of a high-pass filter with a cutoff frequency of 0.05 Hz and a low-pass filter with a cutoff frequency of 35 Hz. The obtained f(n) is:

[0045]

[0046] The obtained passband voltage square signal f(n) is subjected to visual sensitivity weighted filtering to convert all frequency fluctuations within the band into fluctuations at a frequency of 8.8 Hz to obtain a signal f4(n). The visual sensitivity weighted filter transfer function used in this embodiment is:

[0047]

[0048] Among them, w1=2π*9.15494, w2=2π*2.27979, w3=2π*1.22535, w4=2π*21.9, k=1.74802, λ1=2π*4.05981, and the bilinear function of MATLAB is used to convert it into a digital filter.

[0049] The signal f4(n) obtained by using the above-mentioned visual sensitivity weighted filter is:

[0050]

[0051] 2. Calculate the instantaneous flicker value f5(n) based on the signal after visual sensitivity weighted filtering and perform normalization.

[0052] The obtained signal f4(n) is squared and smoothed weighted filtered to obtain the instantaneous flicker value f5(n). The smoothing weighted filter used in this embodiment is:

[0053]

[0054] The instantaneous flicker value f5(n) obtained by using the above-mentioned smoothing weighted filter is:

[0055]

[0056] Normalize f5(n) to get S(n).

[0057] 3. Calculate the instantaneous flicker value P based on the normalized instantaneous flicker value obtained m , and then calculate the short-time flicker value according to the IEC standard formula.

[0058] The IEC marking formula is:

[0059]

[0060] Where P 0.1 , P1, P3, P 10 and P 50 The flicker visual sensitivity values ​​corresponding to the probability of exceeding 0.1%, 1%, 3%, 10%, and 50% within the detection time (10 minutes in this embodiment) are respectively. The present invention does not need to perform cumulative probability distribution statistics on the data within the detection time (such as 10 minutes), nor does it need piecewise linear interpolation. Instead, it uses quantile adaptive estimation to update in real time. The specific steps are:

[0061] 1) Convert the cumulative probability value required in the IEC standard calculation formula into a probability value P' that is compatible with the adaptive estimation method m , the cumulative probability value Pcdf given by the IEC standard m= [0.1% 1% 3% 10% 50%] converted into the probability value P' required for subsequent estimation m =(1-Pcdf m ), Pcdf m is the cumulative probability value in the calculation formula in the IEC recommended calculation scheme. Based on this, the present invention obtains 5 P' m The values ​​are 0.999, 0.99, 0.97, 0.9, and 0.5 respectively. The first 2400 data in the detection time are used to calculate the initial value of the estimate. The initial value of the estimate here is obtained by probability statistics of 2400 instantaneous flicker values ​​to obtain 5 quantile values, which can accelerate the estimation convergence speed.

[0062] 2) According to the input instantaneous flicker value S(n), the real-time estimated update range R(n) = Rmax(n)-Rmin(n), Rmax(n) and Rmin(n) are the upper and lower bounds of the estimated value, respectively, P' m is the quantile probability,

[0063]

[0064] Wherein 0<α<1, 0<β<1, in this embodiment, α=0.1, β=0.996.

[0065] 3) Real-time estimation probability P' m The corresponding quantile value P m , the specific calculation formula used is:

[0066]

[0067] The current input S(n) is greater than P m When (n-1) is large, let the increment Δ + =λ*P' m *R(n),P m (n-1) value plus the increment value; input S(n) is greater than P m (n-1) hours, let the increment Δ - =λ*(1-P' m )*R(n),P m (n-1) value minus the increment value, the range of λ is (0, 1), which is selected according to the debugging results. Other feasible values ​​can be selected. The value selection needs to comprehensively consider the estimated convergence speed and the estimated value fluctuation range. Here, λ=1 / 2048 is selected, and the estimated quantile curve is as follows Figure 2 shown.

[0068] 4) The 5 Ps estimated at 10 minutes m =[2.3704, 2.3529, 2.3194, 2.1047, 1.0900], substitute into P stCalculation formula to obtain short-time flicker P st =1.0133, the P used in the present invention st The calculation formula is:

[0069]

[0070] Where P0' .999 P0 is the quantile probability corresponding to the cumulative probability of 0.1% within the detection time. ′ .99 P0 is the quantile probability corresponding to the cumulative probability of 1% within the detection time. ′ .97 P0 is the quantile probability corresponding to the cumulative probability of 3% within the detection time. ′ .9 P0' is the quantile probability corresponding to a cumulative probability of 10% within the detection time. .5 P is the quantile probability corresponding to the cumulative probability of 50% within the detection time. 0.999 , P 0.99 , P 0.97 , P 0.9 and P 0.5 They are the quantile probability P0 within the detection time. ′ .999 、P0 ′ .99 、P0 ′ .97 、P0 ′ .9 and P0 ′ .5 The corresponding quantile value.

[0071] According to the test standard modulated square wave flicker signal in Table 1, the calculation results of the present invention are compared with the calculation results of the traditional method, and the results are shown in Table 1.

[0072] Table 1

[0073]

[0074] It can be seen from Table 1 that the calculation results of the two methods are basically the same, and the present invention only needs to use the range of the instantaneous flicker value and the instantaneous flicker value to calculate the quantile value corresponding to each quantile probability. During the calculation process, only 6 data need to be cached, and the instantaneous flicker probability distribution change can be tracked dynamically in real time, and the estimated value can be adaptively adjusted to meet different P st The flicker test scenario of the value has a simple calculation method, high calculation efficiency, and does not require the storage of a large amount of data.

[0075] Embodiment of a short-term flicker real-time calculation device

[0076] A short-time flicker real-time calculation device of the present invention can be used to execute computer program instructions to implement the short-time flicker real-time calculation method in the above method embodiment. The specific implementation process of the method has been detailed in the short-time flicker real-time calculation method embodiment, and will not be repeated here.

Claims

1. A short-term flicker real-time calculation method, characterized in that: The method includes: 1) Obtain the instantaneous flicker value within the detection time; 2) Convert the cumulative probability required for short-term flicker calculation into a probability value that is compatible with the adaptive method, called the quantile probability. Each quantile probability is equal to 1 minus the corresponding cumulative probability. 3) Calculate the quantile values ​​corresponding to each quantile probability using the obtained quantile probability, the range of the instantaneous flicker value and the instantaneous flicker value; 4) Multiply each quantile probability by the corresponding quantile value and then sum them to obtain the short-term flicker value within the detection time.

2. The short-term flicker real-time calculation method according to claim 1 is characterized in that: The calculation formula used for the quantile values ​​corresponding to each quantile probability in step 3) is: Among them, P m (n) is the quantile value corresponding to the mth quantile probability, P' m is the mth quantile probability, R(n) is the range of the instantaneous flicker value corresponding to the nth sampling value, and S(n) is the instantaneous flicker value corresponding to the nth sampling value.

3. The short-duration flicker real-time calculation method according to claim 1 or 2, characterized in that: The range of instantaneous flicker value is updated in real time, and the calculation formula used is: R(n)=Rmax(n)-Rmin(n) Among them, Rmax(n) and Rmin(n) are the upper and lower limits of the range of instantaneous flicker values, respectively. R(n) is the range of instantaneous flicker values ​​corresponding to the nth sampling value. S(n) is the instantaneous flicker value corresponding to the nth sampling value. α and β are coefficients greater than 0 and less than 1.

4. The short-duration flicker real-time calculation method according to claim 1 or 2, characterized in that: The calculation formula used for the short-time flicker value within the detection time in step 4) is: Where P0 ′ .999 、P0 ′ .99 、P0 ′ .97 、P0 ′ .9 and P0 ′ .5 are the quantile probabilities corresponding to the cumulative probabilities of 0.1%, 1%, 3%, 10% and 50% within the detection time, respectively. 0.999 , P 0.99 , P 0.97 , P 0.9 and P 0.5 They are the quantile probability P0 within the detection time. ′ .999 、P0 ′ .99 、P0 ′ .97 、P0 ′ .9 and P0 ′ .5 The corresponding quantile value.

5. The short-duration flicker real-time calculation method according to claim 1 or 2, characterized in that: The instantaneous flicker value within the detection time is obtained by processing the voltage sampling signal within the detection time through square processing, bandpass filtering, visual sensitivity weighted filtering and smoothing weighted filtering.

6. The short-duration flicker real-time calculation method according to claim 5 is characterized in that: The band-pass filter used in the band-pass filtering is composed of a high-pass filter with a cut-off frequency of 0.05 Hz and a low-pass filter with a cut-off frequency of 35 Hz.

7. The short-duration flicker real-time calculation method according to claim 5, characterized in that: The transfer function of the sensitivity weighted filter used in the sensitivity weighted filtering is: Among them, w1=2π*9.15494, w2=2π*2.27979, w3=2π*1.22535, w4=2π*21.9, k=1.74802, λ1=2π*4.05981.

8. The short-duration flicker real-time calculation method according to claim 7, characterized in that: The visual sensitivity weighted filter is implemented by converting the bilinear function of MATLAB into a digital filter.

9. The short-duration flicker real-time calculation method according to claim 5, characterized in that: The transfer function used in the smoothing weighted filtering is: Among them, τ is selected as 300ms.

10. A short-term flicker real-time calculation device, comprising a processor, characterized in that: The processor is used to execute computer program instructions to implement the short-time flicker real-time calculation method as described in any one of claims 1-9.

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