CN103325070A - Assessment method of electric power system state estimation result accuracy based on cross entropy - Google Patents

Abstract

The invention relates to an assessment method of electric power system state estimation result accuracy based on cross entropy and belongs to the technical field of electric power system dispatching automation and power grid emulation. All measured residual error numeral values are calculated firstly according to an electric power system state estimation result and a cross entropy evaluation function, corresponding to each measured residual error numeral value, in a negative index square mode is calculated; comprehensive average is conducted on all of the measured cross entropy evaluation functions and meanwhile, a zero injection evaluation criterion is introduced for examining whether zero injection constraint is satisfied or not, so that comprehensive evaluation of the accuracy of the electric power system state estimation is obtained. The theoretical foundation of the method is stricter, the zero injection constraint is considered and the zero injection constraint examining criterion is added. The compatibility of the method and a widely-used traditional acceptability criterion is good and the mode of percentage is adopted, so that the method is convenient to achieve.

Description

Based on the Power system state estimation of the cross entropy appraisal procedure of precision as a result

Technical field

The present invention relates to the as a result appraisal procedure of precision of a kind of Power system state estimation based on cross entropy, belong to dispatching automation of electric power systems and grid simulation technical field.

Background technology

Power system state estimation provides basic tide model for various electrical network analysis calculate, and therefore the precision of its result of calculation is carried out qualitative assessment very necessary.

Traditional Power system state estimation as a result accuracy evaluation criterion is the qualification rate criterion, in this criterion, if the residual error of certain measurement less than given threshold value, then claims this measurement to be " qualified measurement "; If the residual error of certain measurement greater than given threshold value, then claims this measurement to be " defective measurement "; Add up the ratio of qualified measurement, this ratio is higher, thinks that then state estimation result's precision is better.The qualification rate criterion has the following disadvantages:

At first, traditional qualification rate criterion adopts the mode of " non-good namely bad " to divide qualified measurement and defective measurement; In fact, the residual error of two qualified measurements may be different, and the residual error of two defective measurements also may be different, and can't be embodied in the qualification rate criterion that do not coexist of these residual errors.

Secondly, traditional qualification rate criterion is used for dividing measurement, and whether qualified threshold value there is no strict theoretical foundation, usually determines according to artificial experience.

In addition, traditional qualification rate criterion does not have the situation that satisfies of method considering zero injection constraint; The qualification rate that the state estimation result may occur is very high, but has obvious power mismatch amount, does not satisfy the situation of power flow equation.Power system state estimation is the important foundation that electrical network analysis calculates, and is extremely important to state estimation result's precision quantitative assessment.Therefore, need as a result accuracy evaluation criterion of Power system state estimation that research has stricter theoretical foundation.

Summary of the invention

The objective of the invention is to propose the as a result appraisal procedure of precision of a kind of Power system state estimation based on cross entropy, to overcome traditional state estimation as a result in the used qualification rate criterion of accuracy evaluation, the qualified measurement inside that exists does not distinguish, threshold value lacks theoretical foundation, do not investigate the deficiency such as zero injection-constraint, so that assessment level carries out qualitative assessment to the Power system state estimation precision.

The present invention propose based on the Power system state estimation of the cross entropy appraisal procedure of precision as a result, may further comprise the steps:

(1) obtains the Power system state estimation result from the state estimation module of electric system energy management system: comprise the state variable of electric system, i.e. the estimated value of the amplitude of node voltage and phase angle vector in the electric system

And the measurement estimated value of electric system vector

And obtain the used measuring value of Power system state estimation vector z and measuring standard difference vector σ;

(2) calculate the residual vector r that measures, computing formula is:

$r=z-h\left(\hat{x}\right)$

(3) calculate based on the state estimation of cross entropy accuracy evaluation functional value ξ as a result, computing formula is:

$\mathrm{\ξ}=\frac{1}{m}\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\exp [-\frac{{(z_i-h_i\left(\hat{x}\right))}^2}{2{\mathrm{\σ}}_i^2}]\×100\%$

Wherein, m is the measurement number in the electric system, z _iI element among the expression measuring value vector z,

Expression estimated value vector In i element, σ _iI the element of expression measuring standard difference vector σ;

(4) the zero injection-constraint valuation functions value Δ of calculating electric system, computing formula is:

$\mathrm{\Δ}=\max \left(\underset{i\∈Z}{\mathrm{\Σ}}\right|P_i|+\underset{i\∈Z}{\mathrm{\Σ}}|Q_i\left|\right)$

Wherein Z represents that zero in the electric system injects node set,

The meritorious amount of mismatch absolute value sum of all the zero injection nodes in the expression electric system,

The idle amount of mismatch absolute value sum of all the zero injection nodes in the expression electric system;

(5) according to cross entropy valuation functions value ξ and zero injection-constraint assessment level Δ, precision to Power system state estimation is assessed: if Δ 〉=0.1 megavolt-ampere, or Δ＜0.1 megavolt-ampere is while the numerical value of cross entropy valuation functions value ξ less than 90%, is then judged as a result low precision of Power system state estimation; If Δ＜0.1MVA, and the numerical value of cross entropy valuation functions value ξ is greater than 90%, and precision is good as a result then to judge Power system state estimation.

A kind of Power system state estimation based on cross entropy that the present invention proposes is the appraisal procedure of precision as a result, its advantage is, Power system state estimation of the present invention is precision assessment method as a result, has strict theoretical foundation, in fact, this assessment level is the information science tolerance of similarity degree between state estimation result and the measurement.In this method each measures according to different separately measurement residuals cross entropy valuation functions value ξ is created in contribution different between 0～1, thereby can differentiate meticulously the measurement with different residual errors.This method has been considered zero injection-constraint problem, has added zero injection-constraint examination criterion.This method and present widely used traditional qualification rate criterion compatibility are very good, all have the form of number percent, implement easily.

Description of drawings

Fig. 1 is the IEEE 9 node system schematic diagram that relate to when using the inventive method.

Among Fig. 1,1-9 is node ID, and the black square represents gauge point, and the arrow that points to node represents that generator power injects, and points to the outer arrow of node and represents load power.

Embodiment

The present invention propose based on the Power system state estimation of cross entropy precision assessment method as a result, may further comprise the steps:

(1) obtains the Power system state estimation result from the state estimation module of electric system energy management system: comprise the state variable of electric system, i.e. the estimated value of the amplitude of node voltage and phase angle vector in the electric system

And the measurement estimated value of electric system vector

And obtain the used measuring value of Power system state estimation vector z and measuring standard difference vector σ;

(2) calculate the residual vector r that measures, computing formula is:

$r=z-h\left(\hat{x}\right)$

(3) calculate based on the state estimation of cross entropy accuracy evaluation functional value ξ as a result, computing formula is:

$\mathrm{\ξ}=\frac{1}{m}\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\exp [-\frac{{(z_i-h_i\left(\hat{x}\right))}^2}{2{\mathrm{\σ}}_i^2}]\×100\%$

Wherein, m is the measurement number in the electric system, z _iI element among the expression measuring value vector z,

Expression estimated value vector In i element, σ _iI the element of expression measuring standard difference vector σ;

(4) the zero injection-constraint valuation functions value Δ of calculating electric system, computing formula is:

$\mathrm{\Δ}=\max \left(\underset{i\∈Z}{\mathrm{\Σ}}\right|P_i|+\underset{i\∈Z}{\mathrm{\Σ}}|Q_i\left|\right)$

Wherein Z represents that zero in the electric system injects node set,

The meritorious amount of mismatch absolute value sum of all the zero injection nodes in the expression electric system,

The idle amount of mismatch absolute value sum of all the zero injection nodes in the expression electric system;

(5) according to cross entropy valuation functions value ξ and zero injection-constraint assessment level Δ, precision to Power system state estimation is assessed: if Δ 〉=0.1 megavolt-ampere, or the numerical value of Δ＜0.1 megavolt-ampere and cross entropy valuation functions value ξ is then judged as a result low precision of Power system state estimation less than 90%; If Δ＜0.1MVA, and the numerical value of cross entropy valuation functions value ξ is greater than 90%, and precision is good as a result then to judge Power system state estimation.

Below introduce the embodiment of inventive method:

For 9 node systems as shown in Figure 1, to construct one group of measurement, and suppose to have calculated 3 groups of state estimation results, 3 groups of estimated results represent with estimated result A, estimated result B and estimated result C respectively.The present embodiment adopts the Linear Estimation model, namely state variable only for the phase angle of node voltage, and only use the active power measurement.The electric pressure of supposing 9 node systems is 220kV, and then according to the regulation of State Grid Corporation of China, whether qualified threshold value is 6.10MW to distinguish meritorious measurement in the qualification rate criterion.Then actual value, the measuring value that constructs and the estimated value in 3 groups of estimated results of each measuring point that represents with the black square, residual error, whether qualified as shown in table 1 with cross entropy valuation functions value ξ.In the present embodiment, the injecting power of node 6 measures and is set to bad data, and represents with runic.

The actual value of table 1 measuring point, measuring value, 3 groups of estimated results and valuation functions value

, cross entropy functional value information whether qualified based on each measurement in the table 1 and the zero Injection amplitude mismatched amount of adding up 3 groups of estimated results can obtain the statistics such as table 2:

Table 2 total system state estimation is the accuracy evaluation criterion as a result

The 1st row the 1st by table 2 is listed as and can sees, the qualification rate criterion of estimated result A has reached 100%, can see but observe its actual phase angle deviation average, and in fact the evaluated error of estimated result A is very large, is a relatively poor estimated result of precision.Observe the 5th row of table 1 again, can find out, in estimated result A, in fact many measurements all have larger residual error, but all do not surpass threshold value 6.1MW.Because the qualification rate criterion do not do further differentiation in qualified measurement inside, can't reflect has like this some residual errors close to the existence of the measurement of threshold value, so its numerical value reached 100%, and " precision of estimation result is very high " this wrong information is provided.

And for estimated result B, can be found out by the 2nd row of table 2, its qualification rate criterion has also reached 100%, but zero very large injection assessment level numerical value has reflected this group estimated result exists significantly zero injecting power amount of mismatch, so its precision is very poor.Do not inject because the qualification rate criterion does not investigate zero, therefore for estimated result B, it also can provide " precision of estimation result is very high " this wrong information.

For estimated result C, the 3rd row last column by table 2 can be found out, this group precision of estimation result is very high, but in the qualification rate criterion, because it has got rid of bad data " node 6 injecting powers " exactly, cause on the contrary less than 100% of its qualification rate, namely the qualification rate criterion can think mistakenly that the precision of estimated result C is not so good as estimated result A and estimated result B.

And the method for using this patent to propose at first observes zero injection assessment level Δ just can find out, estimated result A and estimated result B precision are relatively poor, and among the estimated result C, satisfy the condition of Δ＜0.1MVA.On the other hand, the cross entropy criterion numerical value ξ of estimated result C also will be higher than estimated result A, B, and this precision that estimated result C has been described equally is better, and the precision of estimated result A and estimated result B is relatively poor.

By the present embodiment, can find out that the present invention proposes based on the Power system state estimation of the cross entropy superiority of the more traditional qualification rate criterion of accuracy evaluation criterion as a result.

Claims (1)

1. one kind based on the Power system state estimation of the cross entropy appraisal procedure of precision as a result, it is characterized in that the method may further comprise the steps:

(1) obtains the Power system state estimation result from the state estimation module of electric system energy management system: comprise the state variable of electric system, i.e. the estimated value of the amplitude of node voltage and phase angle vector in the electric system

And the measurement estimated value of electric system vector

And obtain the used measuring value of Power system state estimation vector z and measuring standard difference vector σ;

(2) calculate the residual vector r that measures, computing formula is:

$r=z-h\left(\hat{x}\right)$

(3) calculate based on the state estimation of cross entropy accuracy evaluation functional value ξ as a result, computing formula is:

$\mathrm{\ξ}=\frac{1}{m}\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\exp [-\frac{{(z_i-h_i\left(\hat{x}\right))}^2}{2{\mathrm{\σ}}_i^2}]\×100\%$

Wherein, m is the measurement number in the electric system, z _iI element among the expression measuring value vector z,

Expression estimated value vector In i element, σ _iI the element of expression measuring standard difference vector σ;

(4) the zero injection-constraint valuation functions value Δ of calculating electric system, computing formula is:

$\mathrm{\Δ}=\max \left(\underset{i\∈Z}{\mathrm{\Σ}}\right|P_i|+\underset{i\∈Z}{\mathrm{\Σ}}|Q_i\left|\right)$

Wherein Z represents that zero in the electric system injects node set,

The meritorious amount of mismatch absolute value sum of all the zero injection nodes in the expression electric system, The idle amount of mismatch absolute value sum of all the zero injection nodes in the expression electric system;

(5) according to cross entropy valuation functions value ξ and zero injection-constraint assessment level Δ, precision to Power system state estimation is assessed: if Δ 〉=0.1 megavolt-ampere, or the numerical value of Δ＜0.1 megavolt-ampere and cross entropy valuation functions value ξ is then judged as a result low precision of Power system state estimation less than 90%; If Δ＜0.1MVA, and the numerical value of cross entropy valuation functions value ξ is greater than 90%, and precision is good as a result then to judge Power system state estimation.

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