CN105372479B - A kind of voltage flicker measuring method of quality of power supply measuring instrument - Google Patents
A kind of voltage flicker measuring method of quality of power supply measuring instrument Download PDFInfo
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Abstract
The present invention relates to a kind of voltage flicker measuring method of quality of power supply measuring instrument, enters line slip convolutional calculation according to acquired voltage effective value envelop data and default identification function and obtains identifier.When positive and negative change occurs for identifier, search and obtain the time corresponding to the extreme value and extreme value in corresponding convolutional calculation section.The flickering value in the time of measuring cycle is calculated according to the time corresponding to the difference and extreme value of each two neighboring extreme value.It is the definition that is influenceed on power system voltage of the random switching of heavy load that this computational methods, which complies fully with national standard on flickering, and the flickering changed available for cyclically-varying or at random calculates, measurement accuracy height.
Description
Technical Field
The invention relates to the technical field of power grids, in particular to a voltage flicker measuring method of a power quality measuring instrument.
Background
The visual response of human eyes caused by the voltage fluctuation to cause unstable illumination (flicker) of the light is called flicker, in other words, the flicker reflects the influence of the flicker of the light caused by the voltage fluctuation to the visual response of the human eyes. Voltage flicker is a result of voltage fluctuations and is an important descriptive parameter of power quality standards.
The voltage flicker measurement method of the traditional power quality measurement instrument is calculated according to the calculation method recommended by the national standard before the version 2000, when a stable period signal is measured, due to the truncation of an incomplete period, the measurement calculation error is mostly over 10%, while the flicker is mostly in an unstable period, and the actual measurement calculation error is still large. Therefore, the voltage flicker measuring method of the traditional power quality measuring instrument has the defect of low measuring accuracy.
Disclosure of Invention
In view of the above, it is necessary to provide a voltage flicker measurement method for a power quality measurement apparatus with higher measurement accuracy.
A voltage flicker measuring method of a power quality measuring instrument comprises the following steps:
performing sliding convolution calculation according to the acquired envelope data of the effective voltage value and a preset identification function to obtain an identification value;
when the identification value is changed positively and negatively, searching and acquiring an extreme value in the corresponding convolution calculation section and time corresponding to the extreme value;
and calculating to obtain and output a flicker value in the measurement time period according to the difference value of each two adjacent extreme values and the time corresponding to the extreme values.
The voltage flicker measurement method of the electric energy quality measurement instrument is a fuzzy identification method for curves, and the identification value is obtained by performing sliding convolution calculation according to the acquired envelope data of the effective voltage value and a preset identification function. And when the identification value is changed positively and negatively, searching and acquiring the extreme value in the corresponding convolution calculation segment and the time corresponding to the extreme value. And calculating to obtain a flicker value in the measurement time period according to the difference value of each two adjacent extreme values and the time corresponding to the extreme values. The method not only eliminates the limited resolution fluctuation generated in the digital quantization process, but also meets the detection requirement of the curve variation trend, can be used for the flicker calculation of periodic variation or random variation, and has high measurement accuracy.
Drawings
FIG. 1 is a flow chart of a voltage flicker measurement method of an electric energy quality measuring instrument according to an embodiment;
FIG. 2 is a schematic diagram of a sliding convolution calculation of an identification function and a data curve according to an embodiment;
FIG. 3 is a flowchart illustrating finding and obtaining an extremum and a time corresponding to the extremum in a corresponding convolution calculation segment when the identification value varies between positive and negative values according to an embodiment;
fig. 4 is a flowchart of calculating a flicker value in a measurement time period according to a difference between two adjacent extreme values and a time corresponding to the extreme value in an embodiment.
Detailed Description
A voltage flicker measuring method of an electric energy quality measuring instrument can be used for flicker calculation of periodic variation and random flicker calculation. As shown in fig. 1, the above method comprises the following steps:
step S120: and performing sliding convolution calculation according to the acquired envelope data of the effective voltage value and a preset identification function to obtain an identification value. And setting an identification function according to the measurement data structure and the national standard requirement, and performing sliding convolution calculation on the identification function and the acquired envelope data of the effective voltage value to obtain an identification value. The recognition function may be linear and satisfy the recognition time difference greater than 30mS. The identification function in this embodiment is: fs (j) = { -2, -1,0,1,2}, the occupied time is 40mS, and the requirement of invalid change within 30mS in the national standard is met.
Further, in one embodiment, step S120 specifically includes:
wherein Ux [ i ] represents voltage effective value envelope data, m is the total number of voltage effective value envelope data acquired in a measurement time period, fs (j) represents an identification function, and Dn represents an identification value. Starting from the 1 st data of the voltage effective value envelope data Ux [ i ], when the gradient of the trend of the data is greater than zero, dn is greater than 0; when the slope is negative, dn is <0. FIG. 2 is a schematic diagram illustrating the calculation of the sliding convolution of the identification function and the data curve according to an embodiment.
In one embodiment, before step S120, the voltage flicker measuring method of the power quality measuring instrument may further include step 110.
Step 110: and processing the received measurement data to obtain the envelope data of the effective voltage value.
And acquiring measurement data measured by the power quality measuring instrument, and processing the measurement data into voltage effective value envelope data of one point per 10mS according to a preset standard. Data sequences of one point every 8.333mS should be processed in a 60 hz system. And the measured data is processed into the data of the envelope curve of the effective voltage value, so that the subsequent data processing is facilitated.
Step S130: and when the identification value is changed positively and negatively, searching and acquiring the extreme value in the corresponding convolution calculation section and the time corresponding to the extreme value. And searching effective extreme points according to the identification values to obtain extreme values in the corresponding convolution calculation sections and time corresponding to the extreme values, wherein the extreme values refer to the maximum value or the minimum value of the envelope data of the effective voltage value in the corresponding convolution calculation sections. In one embodiment, the extremum includes a maximum value and a minimum value. As shown in fig. 3, step S130 includes step S132 and step S134.
Step S132: and when the identification value is changed from positive to negative, acquiring the maximum value in the corresponding convolution calculation section and the time corresponding to the maximum value. When the identification value Dn is changed from positive to negative, finding out the maximum value Bn (k) in the convolution calculation section corresponding to the identification function fs (j) from the data corresponding to the point i, recording the value i corresponding to the maximum value point as a time value t (k), and calculating the time in seconds; at the same time i = i +5, i.e. the extreme point is no longer valid within the searched segment.
Step S134: and when the identification value is changed from negative to positive, acquiring the minimum value in the corresponding convolution calculation section and the time corresponding to the minimum value. Similarly, when the identification value Dn is changed from negative to positive, starting from the data corresponding to the point i, the minimum value in the convolution calculation segment corresponding to the identification function fs (j) is found, and the value i corresponding to the minimum value point is recorded as the time value, and the time is calculated in seconds.
Step S140: and calculating to obtain and output a flicker value in the measurement time period according to the difference value of each two adjacent extreme values and the time corresponding to the extreme values. After all data are scanned, the obtained extreme value and the corresponding time are used as data bases to calculate the flicker value, and the flicker value in the measuring time period can be obtained. The output flicker value can be directly displayed through a display, or the flicker value can be sent to the main controller for storage. In one embodiment, as shown in fig. 4, the step S140 calculates a flicker value in the measurement time period according to the difference between each two adjacent extreme values and the time corresponding to the extreme value, and specifically includes the steps S142 and S144.
Step S142: and calculating the flicker value generated by the change of each amplitude value according to the difference value of the two adjacent extreme values and the time corresponding to the extreme values. The method comprises the following specific steps:
wherein, the numerator term is the absolute value of the variation difference value, and the denominator term is the current envelope value. Pkk represents a flicker value generated by the kth amplitude change, and pk1 is a change 1 value corresponding to a flicker of 1 corresponding to a change frequency fk = 60/(t [ k +1] -t [ k ]), which can be obtained by looking up a table. In the embodiment, the change standard 1 value is obtained by inquiring GBT 12326-2008 power quality voltage fluctuation and flicker as shown in table 1. Bn [ k ] and Bn [ k +1] are extreme values of the identification value at kth time and kth +1 time respectively, and t [ k ] and t [ k +1] are time corresponding to Bn [ k ] and Bn [ k +1] respectively and are in second scale.
| Fki frequency (times/min) | Pk1 denotes the value 1 | Fki frequency (times/min) | Pk1 denotes the value 1 |
| 0.75 | 3 | 26.6 | 1 |
| 0.84 | 2.9 | 32 | 0.95 |
| 0.95 | 2.8 | 39 | 0.9 |
| 1.01 | 2.7 | 48.7 | 0.85 |
| 1.2 | 2.6 | 61.8 | 0.8 |
| 1.36 | 2.5 | 80.5 | 0.75 |
| 1.55 | 2.4 | 110 | 0.7 |
| 1.78 | 2.3 | 175 | 0.65 |
| 2.05 | 2.2 | 275 | 0.6 |
| 2.39 | 2.1 | 380 | 0.55 |
| 2.79 | 2 | 475 | 0.5 |
| 3.29 | 1.9 | 580 | 0.45 |
| 3.92 | 1.8 | 690 | 0.4 |
| 4.71 | 1.7 | 795 | 0.35 |
| 5.72 | 1.6 | 1052 | 0.29 |
| 7.04 | 1.5 | 1180 | 0.3 |
| 8.79 | 1.4 | 1400 | 0.35 |
| 11.16 | 1.3 | 1620 | 0.4 |
| 14.44 | 1.2 | 1800 | 0.45 |
| 19.1 | 1.1 |
TABLE 1
Further, if the calculated frequency fk is not at the corresponding point in Table 1, at fk i And fk i+1 Pk1 corresponding between i Is pk1 i+1 Then, the following formula is used to calculate pk1 value corresponding to fk for linear interpolation.
Wherein fk ∈ [ ] i+1 ，fk i ]. When the frequency fk is not at the corresponding point in table 1, the processing is performed by linear interpolation, so that data calculation is facilitated, and calculation accuracy is improved.
Step S144: and calculating the flicker value in the measuring time period according to the flicker values generated by the amplitude changes. The method comprises the following specific steps:
P＝∑pkk×[t(k+1)-t(k)]/T
after the amplitude difference of 2 adjacent extreme points, the corresponding time difference and the corresponding frequency are determined, the ratio of the time difference to the actual measurement period is defined as the time probability of the flicker existence of the point, and the unit flicker value corresponding to the frequency is divided by the percentage of the amplitude difference and then multiplied by the time existence probability, so that the flicker value can be accurately calculated by accumulating in the whole measurement time period.
The voltage flicker measurement method of the electric energy quality measurement instrument can be used for flicker calculation with periodic variation or random variation, is the same as flicker definition specified by the national standard, and has high accuracy.
All possible combinations of the technical features of the above embodiments may not be described for the sake of brevity, but should be considered as within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that, for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements can be made, such as changing the slope of fs () and making corresponding extreme value searching method modifications due to the slope change, which all belong to the protection scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (5)
1. A voltage flicker measuring method of an electric energy quality measuring instrument is characterized by comprising the following steps:
performing sliding convolution calculation according to the acquired envelope data of the effective voltage value and a preset identification function to obtain an identification value; the identification function is linear and meets the requirement that the identification time difference is more than 30mS;
when the identification value is changed positively and negatively, searching and acquiring an extreme value in the corresponding convolution calculation section and time corresponding to the extreme value; the extreme value refers to the maximum value or the minimum value of the envelope data of the effective voltage value in the corresponding convolution calculation section;
calculating to obtain a flicker value in a measuring time period according to the difference value of each two adjacent extreme values and the time corresponding to the extreme values, and outputting the flicker value;
the calculating according to the difference value of each two adjacent extreme values and the time corresponding to the extreme values to obtain the flicker value in the measurement time period comprises the following steps: calculating a flicker value generated by the change of each amplitude value according to the difference value of two adjacent extreme values and the time corresponding to the extreme values; and calculating the flicker value in the measuring time period according to the flicker value generated by the amplitude change.
2. The voltage flicker measuring method of claim 1, wherein the identification function is: fs (j) = { -2, -1,0,1,2}.
3. The voltage flicker measurement method of the electric energy quality measurement instrument according to claim 1, wherein the identification value is obtained by performing sliding convolution calculation according to the acquired envelope data of the effective voltage value and a preset identification function, and specifically comprises:
wherein Ux [ i ] represents voltage effective value envelope data, m is the total number of voltage effective value envelope data acquired in a measurement time period, fs (j) represents an identification function, and Dn represents an identification value.
4. The method of claim 1, wherein the extreme values include a maximum value and a minimum value; the step of searching and acquiring the extreme value in the corresponding convolution calculation segment and the time corresponding to the extreme value when the identification value is changed positively and negatively comprises the following steps:
when the identification value is changed from positive to negative, acquiring the maximum value in the corresponding convolution calculation section and the time corresponding to the maximum value;
and when the identification value is changed from negative to positive, acquiring the minimum value in the corresponding convolution calculation section and the time corresponding to the minimum value.
5. The voltage flicker measurement method of the electric energy quality measurement instrument according to claim 1, wherein the step of calculating the flicker value generated by each amplitude value change according to the difference between two adjacent extreme values and the time corresponding to the extreme values comprises:
wherein, pkk represents a flicker value generated by the kth amplitude change, pk1 is a change index 1 value corresponding to a flicker corresponding to a change frequency fk = 60/(t [ k +1] -t [ k ]), bn [ k ] and Bn [ k +1] are extreme values when the identification value changes for the kth time and the kth +1 time respectively, and t [ k ] and t [ k +1] are time corresponding to Bn [ k ] and Bn [ k +1] respectively, and are scaled by seconds;
the step of calculating the flicker value in the measurement time period according to the flicker values generated by the amplitude changes specifically comprises the following steps:
P＝∑pkk×[t(k+1)-t(k)]/T
wherein, P is a flicker value in a measuring time period, [ T (k +1] -T (k) ]/T is a probability value of the time occupied by the flicker value Pkk with the k-th amplitude change in the actual measuring period, and T is the actual measuring period and is calculated in seconds.
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