CN112613734B - Electric energy state evaluation index selection method - Google Patents
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Abstract
The invention belongs to an index selection and determination method, and particularly relates to an electric energy state evaluation index selection method. It comprises the following steps: step one: sampling; sampling basic parameters; step two: normalizing the data; carrying out data normalization on the sampling parameters; step three: calculating a compensation value; calculating three compensation values; step four: calculating weights; calculating weights of different parameters; step five: revising the weight; revising the weight; step six: selecting parameters; according to the corrected weight W j And (5) performing parameter selection. The invention has the remarkable effects that: (1) According to the invention, a plurality of specific indexes with larger influence on the operation of the power grid are selected as evaluation basic indexes; (2) Calculating the basic weight of each index through the mutual relation of the parameters; (3) And the index can best represent the running state of the existing power grid by correcting the basic weight.
Description
Technical Field
The invention belongs to an index selection and determination method, and particularly relates to an electric energy state evaluation index selection method.
Background
The power grid is one of the essential infrastructures for production and life in the modern society, and the quality of the power grid operation directly influences the quality of production and life. In the prior art, the dimension of the power grid evaluation is large, such as an economic evaluation mode of power grid establishment, a quality evaluation mode of power grid operation, a power grid operation efficiency evaluation mode and the like.
Common to these evaluation modes is that: and evaluating the power grid by using the determined index dimension and the determined weight. However, the power grid is not constant during operation. With season replacement, resident electricity and industrial electricity are quite different; the industrial electricity also presents periodic regular changes under the influence of economic cycle; when an emergency is encountered, an index with a low original weight value suddenly becomes important, and the like.
Because the dead-plate and fixed evaluation indexes in the prior art cannot evaluate the power grid in real time, a power state evaluation index selection method needs to be established.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for selecting an electric energy state evaluation index.
The invention is realized in the following way: the electric energy state evaluation index selection method comprises the following steps:
step one: sampling
Sampling basic parameters;
step two: data normalization
Carrying out data normalization on the sampling parameters;
step three: calculating compensation value
Calculating three compensation values;
step four: calculating weights
Calculating weights of different parameters;
step five: weight revision
Revising the weight;
step six: parameter selection
According to the corrected weight W j And (5) performing parameter selection.
The method for selecting an electrical energy state evaluation index as described above, wherein the sampling parameters in the first step include: voltage deviation, frequency deviation, three-phase unbalance degree, harmonic duty ratio, voltage sag and line loss rate,
wherein,
voltage deviation: the difference between the actual voltage at each point and the nominal voltage of the system, expressed as a percentage, i.e
Wherein U is the actual voltage, U N For the nominal voltage of the system, deltaU is the voltage deviation, the formula is only a calculation formula of the voltage deviation, when a plurality of groups of sampling are needed, each voltage deviation is calculated by adopting the formula, for the three-phase voltage, the average value of the three-phase voltage is taken as the actual voltage,
frequency deviation: the difference between the actual frequency and the nominal frequency, i.e.
Δf＝|f-f N |
Where f is the actual frequency, f N For nominal frequency, Δf is the voltage deviation, the above formula is only a calculation formula for the frequency deviation, when multiple sets of samples are required, each frequency deviation is calculated using the above formula,
three-phase imbalance degree: refers to the degree of non-uniform amplitude of three-phase voltage in an electric power system, namely
Wherein max represents taking the maximum value, min represents taking the minimum value,
U A ，U B ，U C is an effective value of the three-phase voltage,
harmonic duty ratio: the ratio of the harmonic to the total amount is the ratio of the sum of the harmonic within 10 times to the fundamental wave, namely
Wherein R represents the harmonic duty cycle，U i harmonic The ith harmonic wave of U is represented, for the case of multiple sampling, the U obtained by each sampling is subjected to harmonic wave calculation within 10 times, the calculation result is used for calculating the harmonic wave duty ratio by the formula, for three-phase electricity, the respective harmonic wave duty ratio is calculated, then the harmonic wave duty ratio of the three-phase electricity is averaged to be used as the total harmonic wave duty ratio value, for the case of multiple sampling of the three-phase electricity, when sampling is carried out at a certain time point, the three-phase electricity is sampled, the harmonic wave duty ratio is calculated, then the harmonic wave duty ratio of the three-phase electricity is averaged to be used as the total harmonic wave duty ratio value sampled at the time point, the sampling at all time points is completed in sequence, the harmonic wave duty ratio sample data of all time points is obtained,
voltage dip: the effective value of the power supply voltage is rapidly reduced to 90% -10% of the rated value, the sampling content of the application comprises the voltage value and the duration of the voltage sag, and the sampling comprises the amplitude reduction U Lowering blood pressure And duration t Lowering blood pressure Taking the product of the two as a final sampling value of the item, for three-phase electricity, if no voltage sag condition occurs in the three phases at the same sampling time point, recording the parameter as 0, if voltage sag occurs, firstly taking the product of the amplitude reduction and the time of each voltage sag, then taking the parameter with the maximum product value as the parameter of the current sampling,
line loss rate: the line loss is the energy loss generated by the transmission of electric energy through the transmission line, and the ratio of the line loss is the line loss ratio, namely
Line loss ratio= (power supply amount-sold amount)/purchased amount x 100%
The electric energy state evaluation index selecting method as described above, wherein the sampling time of the sampling in the first step is 20 seconds to 40 seconds; the sampling frequency is 10-1000 times of the power grid frequency; the interval time ranges from 30 seconds to 10 minutes; the total sampling time is 1-24 hours.
The method for selecting the electric energy state evaluation index according to the above, wherein the sampling time in the first step is preferably 30 seconds; the sampling frequency is preferably 300 times; the interval is preferably 1 minute; the total sampling time ensures a minimum of 10 samples.
The electric energy state evaluation index selecting method comprises the following steps of normalizing by the following formula,
the normalized data only retains three bits of data after the decimal point,
after normalization is completed, a normalized data matrix is formed
The rows represent different sampling time points, and the columns represent different data, specifically, the first column is voltage deviation, the second column is frequency deviation, the third column is three-phase imbalance, the fourth column is harmonic duty ratio, the fifth column is voltage sag, and the sixth column is line loss rate, so n=6 in the application.
The electric energy state evaluation index selecting method comprises the following steps,
step 3.1: mean value of
Averaging each column of data, i.e. calculating each column of data by using the following formula
Wherein m is the number of rows of matrix B in step two, j represents the number of columns, i.e. the calculation is performed for the j-th column, the value range of j is 1-n, where n=6,
obtaining b through the calculation 1 are all 1 、b 2 are all 2 、b 3 all are 3 、b 4 all are provided with 、b 5 are all 5 、b 6 are all 6 Setting 6 weight correction values k 1 are all 1 、k 2 are all 2 、k 3 all are 3 、k 4 all are provided with 、k 5 are all 5 、k 6 are all 6 The 6 weight correction values correspond to 6 parameters, the specific values of the 6 weight correction values are determined according to the following principle,
anchor point taking
If it isThen let k j are all ＝0；
If it isThen let k j are all ＝0.5；
If it isThen let k j are all ＝1，
Step 3.2: median of
Taking the median of each row of data, if the row of data is odd, directly taking the median, if the row of data is even, taking the average value of the two middle numbers as the median,
obtaining b through the calculation 1 in 、b 2 in 、b In 3 、b In 4 、b In 5 、b 6 in 6 Setting 6 weight correction values k 1 in 、k 2 in 、k In 3 、k In 4 、k In 5 、k 6 in 6 The 6 weight correction values correspond to 6 parameters, the specific values of the 6 weight correction values are determined according to the following principle,
anchor point taking
If it isThen let k j is shown in ＝0；
If it isThen let k j is shown in ＝0.5；
If it isThen let k j is shown in ＝1，
Step 3.3: variance of
Taking the variance for each column of data, i.e. calculating the following formula for each column of data
Where m is the number of rows of matrix B in step two, j represents the number of columns, i.e. the calculation is performed for the j-th column, the value range of j is 1-n, where n=6,
obtaining b through the calculation 1 square 、b 2 square 、b 3 square 、b 4 square 、b 5 square 、b 6 square Setting 6 weight correction values k 1 square 、k 2 square 、k 3 square 、k 4 square 、k 5 square 、k 6 square The 6 weight correction values correspond to 6 parameters, the specific values of the 6 weight correction values are determined according to the following principle,
anchor point taking
If it isThen let k Square j ＝0；
If it isThen let k Square j ＝0.5；
If it isThen let k Square j ＝1。
The method for selecting the electric energy state evaluation index according to the above, wherein the fourth step comprises,
order the
When all p ij After calculation, E is calculated using the following formula j
Where ln () represents the logarithm of the base constant e, m is the number of rows of matrix B in step two,
if p is ij =0, then let E j ＝0，
Weight W j Calculated by the following formula
The electric energy state evaluation index selecting method comprises the following steps,
take weight W j Average value of (2)
If k j are all =0, then W j Is unchanged;
if k j are all Let correction =0.5The latter weight is
If k j are all Let the corrected weight be =1
If k j is shown in =0, then W j Is unchanged;
if k j is shown in Let the corrected weight be =0.5
If k j is shown in Let the corrected weight be =1
If k Square j =0, then W j Is unchanged;
if k Square j Let the corrected weight be =0.5
If k Square j Let the corrected weight be =1
The electric energy state evaluation index selecting method comprises the following two optional schemes,
scheme one: for corrected W j Sorting, discarding parameters corresponding to the minimum 2 weights, taking the rest parameters as evaluation indexes of the power grid,
scheme II: for corrected W j Sorting, taking the weight with the largest value as a reference, discarding the weight if one or a plurality of weights with the value smaller than 5% of the maximum weight exist, retaining all the weights which are not discarded,as an evaluation index of the power grid.
The invention has the remarkable effects that: (1) According to the invention, a plurality of specific indexes with larger influence on the operation of the power grid are selected as evaluation basic indexes; (2) Calculating the basic weight of each index through the mutual relation of the parameters; (3) And the index can best represent the running state of the existing power grid by correcting the basic weight.
Detailed Description
A method for selecting an electric energy state evaluation index comprises the following steps:
step one: sampling
The sampling parameters include: voltage deviation, frequency deviation, three-phase unbalance degree, harmonic duty ratio, voltage sag and line loss rate.
Wherein,
voltage deviation: the difference between the actual voltage at each point and the nominal voltage of the system, expressed as a percentage, i.e
Wherein U is the actual voltage, U N For the system nominal voltage, ΔU is the voltage deviation. The above formula is only a calculation formula of voltage deviation, and when a plurality of groups of samples are required, each voltage deviation is calculated by adopting the above formula. For the three-phase voltage, the average value of the three-phase voltage is taken as the actual voltage.
Frequency deviation: the difference between the actual frequency and the nominal frequency, i.e.
Δf＝|f-f N |
Where f is the actual frequency, f N For nominal frequency, Δf is the voltage deviation. The above formula is only a calculation formula of frequency deviation, and when a plurality of groups of samples are required to be performed, each frequency deviation is calculated by adopting the above formula.
Three-phase imbalance degree: refers to the degree of non-uniform amplitude of three-phase voltage in an electric power system, namely
Wherein max represents taking the maximum value, min represents taking the minimum value,
U A ，U B ，U C is an effective value of the three-phase voltage.
Harmonic duty ratio: the ratio of harmonics to the total. The application takes the ratio of the sum of the harmonics within 10 times to the fundamental wave. I.e.
Wherein R represents the harmonic duty ratio, U i harmonic Representing the ith harmonic of U. For the case of multiple sampling, the U obtained by each sampling carries out harmonic calculation for less than 10 times, and the harmonic duty ratio is calculated by the calculation result through the formula. For three-phase electricity, the respective harmonic duty ratio is calculated, and then the harmonic duty ratio of the three-phase electricity is averaged to be used as the total harmonic duty ratio value. And when sampling three-phase electricity for multiple times, sampling the three-phase electricity at a certain time point, respectively calculating harmonic duty ratios, and then averaging the harmonic duty ratios of the three-phase electricity to obtain the total harmonic duty ratio value sampled at the time point, and sequentially completing the sampling at all time points to obtain harmonic duty ratio sample data at all time points.
Voltage dip: the effective value of the power supply voltage is rapidly reduced to 90% -10% of the rated value. The sampling content of the application comprises a voltage value and a duration of a voltage sag. The term sampling includes a step down U Lowering blood pressure And duration t Lowering blood pressure The product of the two is taken as the final sampling value of the item. For three-phase electricity, if no voltage sag condition occurs in the three phases at the same sampling time point, recording the parameter as 0, and if voltage sag occurs, firstly, multiplying the decreasing amplitude and time of each voltage sag, and then taking the parameter with the maximum product value as the parameter of the current sampling.
Line loss rate: line loss is the energy loss generated by the transmission of electrical energy through a transmission line. The ratio of line losses is the line loss ratio, i.e
Line loss ratio= (power supply amount-sold amount)/purchased amount x 100%
The sampling time of the above sampling is 20 seconds to 40 seconds, preferably 30 seconds; the sampling frequency is 10-1000 times, preferably 300 times, of the power grid frequency; the interval time ranges from 30 seconds to 10 minutes, preferably 1 minute; the total sampling time is 1-24 hours, and the sampling is more than 10 times at least.
Step two: data normalization
All the data adopt a unified normalization formula, and particularly any existing normalization formula can be selected for use, and the application provides a simplest normalization formula, which is as follows:
the normalized data only retains three bits of data after the decimal point.
After normalization is completed, a normalized data matrix is formed
The rows represent different sampling time points, and the columns represent different data, specifically, the first column is voltage deviation, the second column is frequency deviation, the third column is three-phase imbalance, the fourth column is harmonic duty ratio, the fifth column is voltage sag, and the sixth column is line loss rate. Thus n=6 in the present application.
Step three: calculating compensation value
Step 3.1: mean value of
Averaging each column of data, i.e. calculating each column of data by using the following formula
Wherein m is the number of rows of the matrix B in the second step, j represents the number of columns, i.e. the calculation is performed for the j-th column, and the value range of j is 1-n, where n=6.
Obtaining b through the calculation 1 are all 1 、b 2 are all 2 、b 3 all are 3 、b 4 all are provided with 、b 5 are all 5 、b 6 are all 6 Setting 6 weight correction values k 1 are all 1 、k 2 are all 2 、k 3 all are 3 、k 4 all are provided with 、k 5 are all 5 、k 6 are all 6 The 6 weight correction values correspond to 6 parameters, and specific values of the 6 weight correction values are determined according to the following principle.
Anchor point taking
If it isThen let k j are all ＝0；
If it isThen let k j are all ＝0.5；
If it isThen let k j are all ＝1。
Step 3.2: median of
And taking the median of each row of data, if the number of the row of data is odd, directly taking the median, and if the number of the row of data is even, taking the average value of the two middle numbers as the median.
Obtaining b through the calculation 1 in 、b 2 in 、b In 3 、b In 4 、b In 5 、b 6 in 6 Setting 6 weight correction values k 1 in 、k 2 in 、k In 3 、k In 4 、k In 5 、k 6 in 6 The 6 weight correction values correspond to 6 parameters, and 6 weight correction valuesThe specific values of positive values are determined according to the following principles.
Anchor point taking
If it isThen let k j is shown in ＝0；
If it isThen let k j is shown in ＝0.5；
If it isThen let k j is shown in ＝1。
Step 3.3: variance of
Taking the variance for each column of data, i.e. calculating the following formula for each column of data
Wherein m is the number of rows of the matrix B in step two, j represents the number of columns, i.e. the calculation is performed for the j-th column, and the value range of j is 1-n, where n=6.
Obtaining b through the calculation 1 square 、b 2 square 、b 3 square 、b 4 square 、b 5 square 、b 6 square Setting 6 weight correction values k 1 square 、k 2 square 、k 3 square 、k 4 square 、k 5 square 、k 6 square The 6 weight correction values correspond to 6 parameters, and specific values of the 6 weight correction values are determined according to the following principle.
Anchor point taking
If it isThen let k Square j ＝0；
If it isThen let k Square j ＝0.5；
If it isThen let k Square j ＝1。
Step four: calculating weights
Order the
When all p ij After calculation, E is calculated using the following formula j
Where ln () represents the logarithm of the base constant e and m is the number of rows of matrix B in step two.
If p is ij =0, then let E j ＝0。
Weight W j Calculated by the following formula
Step five: weight revision
Take weight W j Average value of (2)
If k j are all =0, then W j Is unchanged;
if k j are all Let the corrected weight be =0.5
If k j are all Let the corrected weight be =1
If k j is shown in =0, then W j Is unchanged;
if k j is shown in Let the corrected weight be =0.5
If k j is shown in Let the corrected weight be =1
If k Square j =0, then W j Is unchanged;
if k Square j Let the corrected weight be =0.5
If k Square j Let the corrected weight be =1
For example, if k is a certain column of parameters j are all ＝k j is shown in ＝k Square j =1, then the column parameterThe weight is corrected to be
Step six: parameter selection
According to the corrected weight W j And (5) performing parameter selection.
The selection of the parameters can be performed according to the actual situation, and two specific selection schemes are provided, so that one of the schemes can be selected arbitrarily by a person skilled in the art, and other strategies can be adopted for selection according to the actual situation.
Scheme one: for corrected W j And (5) sorting, namely discarding parameters corresponding to the minimum 2 weights, and taking the rest parameters as evaluation indexes of the power grid.
Scheme II: for corrected W j And (3) sorting, namely taking the weight with the largest value as a reference, discarding the weight if the value of one or more weights is less than 5% of the maximum weight, and keeping all weights which are not discarded as evaluation indexes of the power grid.
When the method is used, the method is carried out once at intervals according to the need, and the weight value of each index in the power grid is redetermined so as to adjust the evaluation mode of the power grid at any time. Because the power utilization characteristics of the power grid in different time periods change rapidly, the adjustment of the index weight is recommended to be carried out once a week, and the sampling interval period can be adjusted according to actual conditions by a person skilled in the art, and the sampling interval period can be selected in one month, one quarter and half year.
Claims (1)
1. The electric energy state evaluation index selecting method is characterized by comprising the following steps of:
step one: sampling
Sampling basic parameters;
step two: data normalization
Carrying out data normalization on the sampling parameters;
step three: calculating compensation value
Calculating three compensation values;
step four: calculating weights
Calculating weights of different parameters;
step five: weight revision
Revising the weight;
step six: parameter selection
Parameter selection is carried out according to the corrected weight;
the sampling parameters in the first step include: voltage deviation, frequency deviation, three-phase unbalance degree, harmonic duty ratio, voltage sag and line loss rate,
wherein,
voltage deviation: the difference between the actual voltage at each point and the nominal voltage of the system, expressed as a percentage, i.e
Wherein U is the actual voltage, U N For the nominal voltage of the system, deltaU is the voltage deviation, the formula is only a calculation formula of the voltage deviation, when a plurality of groups of sampling are needed, each voltage deviation is calculated by adopting the formula, for the three-phase voltage, the average value of the three-phase voltage is taken as the actual voltage,
frequency deviation: the difference between the actual frequency and the nominal frequency, i.e.
Δf＝|f-f N |
Where f is the actual frequency, f N For nominal frequency, Δf is the voltage deviation, the above formula is only a calculation formula for the frequency deviation, when multiple sets of samples are required, each frequency deviation is calculated using the above formula,
three-phase imbalance degree: refers to the degree of non-uniform amplitude of three-phase voltage in an electric power system, namely
Wherein max represents taking the maximum value, min represents taking the minimum value,
U A ，U B ，U C is an effective value of the three-phase voltage,
harmonic duty ratio: the ratio of the harmonic to the total amount is the ratio of the sum of 10 th harmonic to the fundamental wave, namely
Wherein R represents the harmonic duty ratio, U i harmonic The ith harmonic of U is represented, for the case of multiple sampling, the voltage obtained by each sampling is subjected to 10 times of harmonic calculation, the calculation result is used for calculating the harmonic duty ratio by the formula, for three-phase electricity, the respective harmonic duty ratio is calculated, then the harmonic duty ratio of the three-phase electricity is averaged to be used as the total harmonic duty ratio value, for the case of multiple sampling of the three-phase electricity, when sampling is carried out at a certain time point, the three-phase electricity is sampled, the respective harmonic duty ratio is calculated, then the harmonic duty ratio of the three-phase electricity is averaged to be used as the total harmonic duty ratio value sampled at the time point, sampling at all time points is completed in sequence to obtain the harmonic duty ratio sample data of all time points,
voltage dip: the effective value of the power supply voltage is rapidly reduced to 10% -90% of the rated value, the sampling content comprises the voltage value and the duration of the voltage sag, and the sampling comprises the amplitude reduction U Lowering blood pressure And duration t Lowering blood pressure Taking the product of the two as a final sampling value of the item, for three-phase electricity, if no voltage sag condition occurs in three phases at the same sampling time point, recording the parameter as 0, if voltage sag occurs, firstly calculating the product of the amplitude reduction and the time of each phase of voltage sag, then taking the parameter with the maximum product value as the parameter of the current sampling,
line loss rate: the line loss is the energy loss generated by the transmission of electric energy through the transmission line, and the ratio of the line loss is the line loss ratio, namely
Line loss ratio= (power supply amount-sales amount)/purchase amount x 100%;
the sampling time of the sampling in the first step is 20 seconds to 40 seconds; the sampling frequency is 10-1000 times of the power grid frequency; the interval time ranges from 30 seconds to 10 minutes; sampling the total time of 1-24 hours;
the sampling time in the first step is preferably 30 seconds; the sampling frequency is preferably 300 times; the interval is preferably 1 minute; the total sampling time ensures that the sampling is performed for 10 times at least;
the second step comprises normalizing by the following formula,
the normalized data only retains three bits of data after the decimal point,
after normalization is completed, a normalized data matrix is formed
Wherein the rows represent different sampling time points, and the columns represent different data, specifically, a first column is voltage deviation, a second column is frequency deviation, a third column is three-phase imbalance, a fourth column is harmonic duty ratio, a fifth column is voltage sag, and a sixth column is line loss rate, wherein n=6;
the third step comprises the steps of,
step 3.1: mean value of
Averaging each column of data, i.e. calculating each column of data by using the following formula
Wherein m is the number of rows of matrix B in step two, j represents the number of columns, i.e. the calculation is performed for the j-th column, the value range of j is 1-n, where n=6,
through the calculationObtaining b 1 are all 1 、b 2 are all 2 、b 3 all are 3 、b 4 all are provided with 、b 5 are all 5 、b 6 are all 6 Setting 6 compensation values k 1 are all 1 、k 2 are all 2 、k 3 all are 3 、k 4 all are provided with 、k 5 are all 5 、k 6 are all 6 The 6 compensation values correspond to 6 parameters, the specific values of the 6 compensation values are determined according to the following principles,
anchor point taking
If it isThen let k j are all ＝0；
If it isThen let k j are all ＝0.5；
If it isThen let k j are all ＝1，
Step 3.2: median of
Taking the median of each row of data, if the row of data is odd, directly taking the median, if the row of data is even, taking the average value of the two middle numbers as the median,
obtaining b through the calculation 1 in 、b 2 in 、b In 3 、b In 4 、b In 5 、b 6 in 6 Setting 6 compensation values k 1 in 、k 2 in 、k In 3 、k In 4 、k In 5 、k 6 in 6 The 6 compensation values correspond to 6 parameters, the specific values of the 6 compensation values are determined according to the following principles,
anchor point taking
If it isThen let k j is shown in ＝0；
If it isThen let k j is shown in ＝0.5；
If it isThen let k j is shown in ＝1，
Step 3.3: variance of
Taking the variance for each column of data, i.e. calculating the following formula for each column of data
Where m is the number of rows of matrix B in step two, j represents the number of columns, i.e. the calculation is performed for the j-th column, the value range of j is 1-n, where n=6,
obtaining b through the calculation 1 square 、b 2 square 、b 3 square 、b 4 square 、b 5 square 、b 6 square Setting 6 compensation values k 1 square 、k 2 square 、k 3 square 、k 4 square 、k 5 square 、k 6 square The 6 compensation values correspond to 6 parameters, the specific values of the 6 compensation values are determined according to the following principles,
anchor point taking
If it isThen let k Square j ＝0；
If it isThen let k Square j ＝0.5；
If it isThen let k Square j ＝1；
The fourth step comprises the steps of,
order the
When all p ij After calculation, E is calculated using the following formula j
Where ln () represents the logarithm of the base constant e, m is the number of rows of matrix B in step two,
if p is ij =0, then let E j ＝0，
Weight W j Calculated by the following formula
The fifth step comprises the steps of,
weight W is taken j Average value of (2)
If k j are all =0, then W j Is unchanged;
if k j are all Let the corrected weight be =0.5
If k j are all Let the corrected weight be =1
If k j is shown in =0, then W j Is unchanged;
if k j is shown in Let the corrected weight be =0.5
If k j is shown in Let the corrected weight be =1
If k Square j =0, then W j Is unchanged;
if k Square j Let the corrected weight be =0.5
If k Square j Let the corrected weight be =1
Step six includes optionally one of two schemes,
scheme one: sorting the corrected weights, discarding the parameters corresponding to the smallest 2 weights, taking the rest parameters as evaluation indexes of the power grid,
scheme II: and sorting the corrected weights, taking the weight with the largest value as a reference, and if one or a plurality of weights with the value smaller than 5% of the maximum weight exist, discarding the parameters corresponding to the weights with the value smaller than 5% of the maximum weight, and keeping the parameters corresponding to the weights which are not discarded as evaluation indexes of the power grid.
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