CN111915222A - Spatial domain multi-voltage level power quality level ranking evaluation method - Google Patents

Abstract

The invention relates to a spatial domain multi-voltage level power quality level sequencing evaluation method, belonging to the field of power system analysis, and the method comprises the following steps: step 1) single-point single power quality index evaluation; step 2), simplifying three-phase indexes; step 3), normalization; step 4), unifying multiple indexes with the same attribute; step 5), unifying multiple indexes with different attributes; step 6), sorting the electric energy quality levels of the spatial domain multi-voltage levels according to the UPQI for the monitoring points of the spatial domain with different voltage levels; the smaller the UPQI, the higher its power quality level. The invention solves the problem of sorting and evaluating the power quality hazards of different voltage grades and different power quality monitoring points in a spatial domain.

Description

Evaluation method for power quality level ranking of multi-voltage levels in space domain

technical field

The invention relates to an evaluation method, in particular to a spatial domain multi-voltage level power quality level ranking evaluation method. It belongs to the field of power system analysis.

Background technique

At present, the evaluation of power quality indicators is mostly concentrated on a single indicator based on the national standard limit value of the corresponding voltage level. It is one of the urgent problems that quality monitoring points are ranked and evaluated according to their power quality hazards to carry out comprehensive power quality management.

One of the main methods used now is the evaluation method of the probability large value of a single power quality index of the same voltage level. The high probability value is the target value corresponding to a percentile: set the target value of the Xth percentile to Px, it divides all the observed values of the power quality index into two parts, of which x% of the observed values are less than Px , (100-x)% observations are greater than Px. It is mainly used to describe the level of a set of data at each percentile position, represented by a set of percentiles such as P5, P25, P50, P75, P95, P99, and P100. Generally, the probability value of 95% and above is used. The disadvantage of this method is that it cannot realize the ranking and evaluation of power quality monitoring points of different voltage levels according to their power quality hazards, and it is even more impossible to realize the ranking and evaluation of power quality monitoring points of different voltage levels.

Another method is to use the average value method to summarize multiple power quality comprehensive indicators at the same voltage level, which is to average the quantification levels of different power quality indicators at the same monitoring point with the same voltage level to obtain a comprehensive index. The potential risk of this method is that the harm of different power quality indicators can be offset, which is obviously wrong, and it cannot realize the sorting and evaluation of power quality monitoring points of different voltage levels.

Another method is to use the maximum value method to summarize multiple power quality comprehensive indicators at the same voltage level, that is, take the maximum value of the quantification levels of different power quality indicators at the same voltage level and the same monitoring point to obtain a comprehensive index. The main problem of this method is that it amplifies the harm of different power quality indicators, and cannot realize the sorting and evaluation of power quality monitoring points of different voltage levels.

SUMMARY OF THE INVENTION

In order to overcome the disadvantage that the traditional method cannot realize the ranking and evaluation of the power quality monitoring points of different voltage levels according to their power quality hazards. The purpose of the present invention is to provide a multi-voltage level power quality level ranking evaluation method in space domain, specifically a method for sorting and evaluating power quality monitoring points of different voltage levels according to their power quality hazard degrees. The invention solves the problem of sorting and evaluating power quality hazards at different power quality monitoring points with different voltage levels.

The technical scheme of the present invention is: a multi-voltage level power quality level ranking evaluation method in space domain, comprising the following steps:

Step 1) Evaluation of single point and single power quality index

The evaluation of single point and single power quality index is carried out by the method of high probability value, and the evaluation result of its high probability value is obtained;

Step 2) Reduction of the three-phase index

On the basis of single-point single power quality index evaluation, if the power quality index has three-phase attributes of A, B, and C, the maximum value of the three-phase evaluation results is selected as the representative; the three-phase attribute refers to each of A, B, and C. Phases have the same indicator;

Step 3) Normalization

Divide the maximum value of the three-phase evaluation result by the national standard limit of the index corresponding to the voltage level;

Step 4) Multi-index simplification of the same attribute

For the harmonics and flicker in the power quality index, which have multiple index phenomena with the same attribute, take the maximum value as the representative, and finally obtain a representative value of the same attribute index;

Step 5) Multi-index simplification of different attributes

The multiple different attribute indicators in the power quality indicators of the same monitoring point are represented by a certain rule, which is recorded as UPQI;

Step 6) Sorting the power quality levels of different voltage levels

For monitoring points with different voltage levels in the spatial domain, the power quality levels of different voltage levels in the spatial domain are sorted according to the size of the UPQI; the smaller the UPQI, the higher the power quality level.

Further, the power quality indicators include: voltage deviation, flicker, three-phase unbalance and harmonics; the maximum probability value is the target value corresponding to a certain percentile; the maximum probability value of the step 1) is taken The method for evaluating a single point and single power quality index is as follows: set the target value of the Xth percentile as Px, then x divides all the observed values of the power quality index into two parts, in which there are x% observed values Less than Px, (100-x)% observations are greater than Px.

Further, the multiple indicators of harmonics in the step 4) include the total harmonic distortion rate and the voltage content ratio of each harmonic; the multiple indicators of flicker include short-term flicker and long-term flicker.

Beneficial effects of the present invention: the present invention characterizes multiple power quality indexes of monitoring points of different voltage levels with one index through normalization, thereby realizing the sorting of power quality levels of multiple voltage levels in the space domain; applying the method of the present invention solves the problem of current The problem that the power quality monitoring points of different voltage levels cannot be sorted and evaluated according to their power quality hazards, provides technical support for the development of comprehensive power quality management.

Detailed ways

The embodiments of the present invention are described below by specific embodiments, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Terms (including scientific and technical terms) used herein have the commonly understood meanings to those skilled in the art.

Example 1

The evaluation method of power quality level ranking of multiple voltage levels in space domain includes the following steps:

Step 1) Evaluation of single point and single power quality index

The evaluation of single point and single power quality index is carried out by the method of high probability value, and the evaluation result of its high probability value is obtained;

Step 2) Reduction of the three-phase index

On the basis of single-point single power quality index evaluation, if the power quality index has three-phase attributes of A, B, and C, the maximum value of the three-phase evaluation result is selected as the representative; the three-phase attribute refers to each of A, B, and C. Phases have the same indicator;

Step 3) Normalization

Divide the maximum value of the three-phase evaluation result by the national standard limit of the index corresponding to the voltage level;

Step 4) Multi-index simplification of the same attribute

For the harmonics and flicker in the power quality index, which have multiple index phenomena with the same attribute, take the maximum value as the representative, and finally obtain a representative value of the same attribute index;

Step 5) Multi-index simplification of different attributes

The multiple different attribute indicators in the power quality indicators of the same monitoring point are represented by a certain rule, which is recorded as UPQI;

Step 6) Sorting the power quality levels of different voltage levels

For monitoring points with different voltage levels in the space domain, the power quality levels of multiple voltage levels in the space domain are sorted according to the size of the UPQI; the smaller the UPQI, the higher the power quality level.

Example 2

On the basis of Embodiment 1, the power quality indicators include: voltage deviation, flicker, three-phase unbalance and harmonics; the maximum probability value is a target value corresponding to a certain percentile;

Further, in the step 1), the evaluation of the single-point single power quality index by the method of taking a large probability value is specifically: set the target value of the Xth percentile as Px, then x is all the observed values of the power quality index. Divided into two parts, in which x% observations are less than Px, and (100-x)% observations are greater than Px.

Further, the multiple indices of harmonics in the step 4) include the total harmonic distortion rate and the voltage content ratio of each harmonic; the multiple indices of flicker include short-term flicker and long-term flicker.

Further, in the step 5), a plurality of indicators of different attributes in the power quality indicators of the same monitoring point are represented by a certain rule and one indicator is specifically:

If each index of different attributes of the monitoring point is less than 1, then UPQI = the maximum value of each attribute index;

If each index of the different attributes of the monitoring point has a value greater than 1, then UPQI = 1 + the sum of the parts of the different attribute indexes exceeding 1.

Example 3

This embodiment is an example of an application scenario

Set point 1 voltage to 380V: then:

1) For voltage deviation (380V voltage level corresponds to the national standard of ±7%)

The first step: find out the 95% probability of the three-phase voltage deviation of A, B, and C as ΔVa, ΔVb, ΔVc;

The second step: the simplicity of the three-phase index: ΔVa, ΔVb, ΔVc, the maximum value of the three is ΔVb, then keep ΔVb;

Step 3: Normalization: Divide ΔVb by 7%, set the result to 0.6

2) For three-phase unbalance (corresponding to the national standard of 2%)

The first step: find the 95% probability of the three-phase unbalance degree and the maximum value is ε;

Step 2: Since there is only one index for the three-phase, the simplicity of the three-phase index is not required;

Step 3: Normalization: Divide ε by 2%, let the result be 0.6

3) For flicker (the standard for long-term flicker is 1, and the standard for short-term flicker is 0.8)

Step 1: Find the 95% maximum probability of long-term flicker of A, B, and C three-phase voltages, which are PLA, PLB, PLC, respectively; The values are PSA, PSB, PSC,

The second step: the simplicity of the three-phase index: the maximum value of PLA, PLB, PLC is PLA, then PLA is retained; the maximum value of PSA, PSB, PSC is PSC, then PSC is retained

Step 3: Normalization: divide PLA by 1, set the result to 0.5; divide PLC by 0.8, set the result to be 0.8;

Step 4: Multi-index simplification of the same attribute: take the maximum value of long-term flicker and short-term flicker as the representative, PLC=0.8 is the largest, and finally obtain a representative value of the same attribute index of flicker, that is, 0.8;

4) For harmonics: since each phase of harmonics has 25 indicators (total distortion rate, 2-25th harmonic content rate), and three-phase total of 75 indicators, the process is omitted (belonging to the well-known technology and common sense in this field. , which will not be described in detail here), which is the same as the flickering steps, and the final result after the fourth step is set to 0.8.

Through the above process, the results of point 1 voltage deviation, unbalance, flicker, and harmonics are shown in the first column of Table 1. Similarly, the results of point 2 and point 3 in Table 1 are the same as the steps of point 1.

5) The multiple indicators of different attributes are simplified, that is, the four different attribute indicators of voltage deviation, harmonics, flicker and unbalance at each point are represented by one UPQI. The specific method is:

Point 1: The different attribute indicators of this point are all less than 1, then UPQI=the maximum value of each different attribute index=0.8;

Point 2: There is a value greater than 1 in each different attribute index at this point, then UPQI=1+the sum of the parts of each different attribute index exceeding 1=1+0.4+0.4=1.8.

Point 3: There is a value greater than 1 in each different attribute index at this point, then UPQI=1+the sum of the parts of each different attribute index exceeding 1=1+0.4=1.4.

After three monitoring points of different voltage levels pass through steps 1) to 4) of the present invention, the power quality indicators are shown in Table 1:

Table 1: Analysis results of three monitoring points at three different voltage levels

6) It can be seen from the comparison of the above UPQI results: UPQI1<UPQI3<UPQI2, indicating that the smaller the UPQI, the higher the power quality level. Here, point 1 has the best power quality, point 3 is the second, and point 2 is the worst. This conclusion is consistent with the actual situation (actually: point 1 does not exceed the standard, two indicators at point 2 exceed the standard, and only one indicator at point 3 exceeds the standard).

The process steps and components that are not described in detail in this embodiment are common means or well-known components in the industry, and will not be described one by one here.

Claims (3)

1. The spatial domain multi-voltage level power quality level ranking evaluation method is characterized by comprising the following steps: the method comprises the following steps:

step 1) evaluation of single-point single power quality index

Evaluating the single-point single power quality index by adopting a probability maximum value method to obtain a probability maximum value evaluation result;

step 2) reduction of three-phase indexes

On the basis of single-point single power quality index evaluation, if the power quality index has A, B, C three-phase attributes, selecting the maximum value of the three-phase evaluation result as a representative; wherein the three-phase attribute means A, B, C each phase has a same index;

step 3) normalization

Dividing the maximum value of the three-phase evaluation result by the national standard limit value of the index corresponding to the voltage grade;

step 4) same-attribute multi-index simplification

Taking the maximum value as a representative value for a plurality of index phenomena with the same attribute, such as harmonic waves and flicker in the electric energy quality index, and finally obtaining a representative value of the index with the same attribute;

step 5) multi-index unification of different attributes

Representing a plurality of different attribute indexes in the power quality index of the same monitoring point by using one index by adopting a certain rule, and recording the indexes as UPQI;

step 6) sorting the quality levels of the electric energy with different voltage grades

For monitoring points with different voltage levels of the spatial domain, sorting the power quality levels with different voltage levels of the spatial domain according to the size of UPQI; the smaller the UPQI, the higher its power quality level.

2. The spatial domain multi-voltage level power quality level ranking evaluation method of claim 1, characterized by: the electric energy quality indexes comprise: voltage deviation, flicker, three-phase imbalance and harmonics; the probability maximum value is a target value corresponding to a certain percentile; the evaluation of the single-point single power quality index by adopting a probability maximum value method in the step 1) is specifically as follows: let the target value of the xth percentile be Px, X divides all observations of the power quality indicator into two parts, where X% of the observations are smaller than Px and (100-X)% of the observations are larger than Px.

3. The spatial domain multi-voltage level power quality level ranking evaluation method of claim 1, characterized by: the multiple indexes of the harmonic waves in the step 4) comprise a total harmonic wave distortion rate and a voltage content rate of each harmonic wave; the multiple indicators of flicker include short-time flicker, long-time flicker.