阅读说明：本技术 一种输电线路参数修正方法 (Power transmission line parameter correction method ) 是由 赵化时 赵旋宇 周华锋 胡亚平 何宇斌 于 2021-05-10 设计创作，主要内容包括：本发明提出一种输电线路参数修正方法,克服了当前将参数作为状态变量增广到状态估计中进行的计算方法导致增广参数后的状态估计数值稳定性变差、计算时间增加的缺陷,首先确定每个状态估计周期及待修正的输电线路参数,包括输电线路电抗参数与输电线路对地电纳参数,根据有功量测质量和电抗参数可辨识性分析,利用线路两端中有功量测质量得分高的一端的有功量测值以及线路两端电压幅值和相角的状态估计值,计算线路电抗参数的修正值；根据无功量测质量,利用线路两端无功量测值以及电压幅值和相角的状态估计值,计算线路对地电纳参数的修正值,无需修改现有状态估计程序,且数值稳定性强、计算速度快,具有较高的工程实用价值。(The invention provides a power transmission line parameter correction method, which overcomes the defects that the stability of a state estimation numerical value is poor and the calculation time is increased after the parameter is expanded into a state estimation by using a calculation method which is currently carried out by expanding the parameter as a state variable, firstly, each state estimation period and power transmission line parameters to be corrected are determined, wherein the power transmission line parameters comprise power transmission line reactance parameters and power transmission line ground-to-ground sodium parameters, and according to the identifiability analysis of active measurement quality and reactance parameters, the correction value of the line reactance parameters is calculated by using the active measurement value of one end with high active measurement quality score in two ends of a line and the state estimation values of voltage amplitude values and phase angles of the two ends of the line; according to the reactive power measurement quality, the correction value of the ground-to-earth electric parameter of the line is calculated by utilizing the reactive power measurement values at two ends of the line and the state estimation values of the voltage amplitude and the phase angle, the existing state estimation program is not required to be modified, the numerical stability is high, the calculation speed is high, and the engineering practical value is high.)

1. A method for correcting parameters of a power transmission line is characterized by at least comprising the following steps:

s1, determining each state estimation period and power transmission line parameters to be corrected, wherein the power transmission line parameters to be corrected comprise power transmission line reactance parameters and power transmission line ground-to-ground sodium permeability parameters, and setting a power transmission line parameter correction frequency threshold to be corrected;

s2, setting an active measurement quality score threshold and a reactive measurement quality score threshold, and scoring the measurement quality of the active measurement quality and the reactive measurement quality of the power transmission line in each state estimation period;

s3, according to the active measurement quality score condition, calculating a correction value of the reactance parameter of the power transmission line by using the active measurement value of one end of the two ends of the line, which has the higher active measurement quality score, and the state estimation values of the voltage amplitude value and the phase angle of the two ends of the line, and correcting the reactance parameter of the power transmission line;

and S4, according to the reactive power measurement quality score condition, calculating a correction value of the power transmission line to the earth-electricity-capacity parameter by using the reactive power measurement values at the two ends of the line and the state estimation values of the voltage amplitude and the phase angle of the two ends of the line, and correcting the earth-electricity-capacity parameter by the power transmission line.

2. The method according to claim 1, wherein the state estimation period in step S1 is 1 minute, and the threshold of the number of times of correction of the reactance parameter of the power transmission line to be corrected is 30, the time window for correction of the reactance parameter of the power transmission line is half an hour; and if the threshold of the correction times of the ground-to-ground sodium-reception parameters of the power transmission line to be corrected is 30, the time window for correcting the ground-to-ground sodium-reception parameters of the power transmission line is half an hour.

3. The method according to claim 2, wherein the rules for scoring the active and reactive power quality measurements of the power transmission line in each state estimation period are as follows:

the rule for scoring the measurement quality of the active measurement quality of the power transmission line in each state estimation period is as follows:

A) the active power of a bus connected with the power transmission line is balanced, 1 minute is added, and otherwise, 1 minute is subtracted; the bus active power imbalance criterion is as follows:

wherein, P_jThe active injection power of the transmission line j connected with the bus i; epsilon_PbusThreshold with unbalanced power for bus iA value; epsilon_PbusSetting according to the voltage level;

B) the active power at the two ends of the power transmission line is balanced, 1 point is added, and otherwise, 1 point is subtracted; the criterion of the active power imbalance at the two ends of the power transmission line is as follows:

|P_ij+P_ji-P_loss|>ε_Pline

wherein, P_ij、P_jiRespectively the active power of the I end and the j end of the transmission line flowing into the line; p_lossActive power loss for the transmission line; epsilon_PlineA threshold for power unbalance of the power transmission line; the active imbalance threshold of the power transmission line is set according to the voltage level;

C) if the PQIs at the end where the power transmission line is successfully measured are matched, adding 1 point, and otherwise, subtracting 1 point; wherein the PQI mismatch criterion is:

|I_cal-I_scada|>ε_I

wherein, I_calThe current value is calculated according to the active power and the reactive power of the transmission line and the voltage of the connected bus; i is_scadaIs the measured current value; epsilon_IA PQI mismatch threshold; the PQI mismatch threshold is set according to the voltage level;

the rule for scoring the reactive power measurement quality of the power transmission line in each state estimation period is as follows:

a) adding 1 minute for reactive power balance of a bus connected with the power transmission line, or not adding the minute; the bus reactive unbalance criterion is as follows:

wherein Q is_jThe reactive injection power of the transmission line j connected with the bus i is obtained; epsilon_QbusA reactive unbalance threshold value is a bus i; epsilon_QbusSetting according to the voltage level;

b) and adding 1 point when the PQI at the reactive power measurement end of the power transmission line is matched, or not adding points.

4. The method for correcting the parameters of the power transmission line according to claim 3, wherein the specific process of the step S3 includes:

s31, judging whether at least one end of active power measurement at two ends of the power transmission line is effective, if so, executing step S32; otherwise, the power transmission line does not carry out power transmission line reactance parameter correction, and the parameter correction process is finished;

s32, determining the active power measurement quality score conditions of two ends of the power transmission line;

s33, taking the higher active power measurement quality score at the two ends of the power transmission line, judging whether the active power measurement quality score is larger than a set active power measurement quality score threshold, and if so, executing a step S34; otherwise, the power transmission line does not carry out power transmission line reactance parameter correction, and the parameter correction process is finished;

s34, setting an active deviation threshold, and determining the deviation between an active measurement value and a state estimation value at one end of the two ends of the power transmission line, wherein the active measurement value has high active measurement quality score;

s35, judging whether the deviation between the active measurement value and the state estimation value at the end with high active measurement quality score in the two ends of the line is greater than an active deviation threshold, if so, executing a step S36; otherwise, the reactance parameter of the power transmission line does not need to be corrected, the correction frequency is set to be 0, and the step S4 is executed;

s36, setting a minimum threshold value of the number of branches of the ring, judging whether the power transmission line is in the ring network or not, and judging whether the minimum value of the number of branches of the ring containing the power transmission line is smaller than the set minimum threshold value of the number of branches of the ring or not, and if so, correcting the anti-parameter of the power transmission line; otherwise, the power transmission line does not carry out power transmission line reactance parameter correction, and the parameter correction process is finished.

5. The method for correcting parameters of an electric transmission line according to claim 4, wherein the specific process of correcting the parameters of the electric transmission line in step S36 is as follows:

s361, obtaining a unitary quadratic equation of the reactance of the power transmission line according to the active power flow equation of the power transmission line:

the end with high active power measurement quality score in the two ends of the power transmission line is set as an i end; the other end of the transmission line is set as a j end; r is the resistance of the transmission line; x is the reactance of the transmission line and is an unknown number to be solved;an active measurement value of the i end of the power transmission line is obtained; v_iAn i-terminal voltage amplitude state estimation value of the power transmission line is obtained; v_jThe estimated value of the j-end voltage amplitude value state of the power transmission line is obtained;

θ_ij＝θ_i-θ_j

wherein, theta_iEstimating the phase angle state of the i-terminal voltage of the power transmission line; theta_jThe phase angle state estimation value of j terminal voltage of the power transmission line is obtained;

and S362, solving a unitary quadratic equation of the reactance of the power transmission line, and judging whether the reactance correction failure condition is met, wherein if yes, the power transmission line reactance parameter correction calculation fails, otherwise, the power transmission line reactance parameter correction calculation succeeds, and the power transmission line reactance parameter correction value is obtained.

6. The method according to claim 5, wherein the failure condition of step S362 is:

1) a quadratic equation of a single element of the reactance of the transmission line is not solved;

2) the absolute value of the i-end active state estimated value is greater than the absolute value of the i-end active measurement value, and the greater of two solutions of the unary quadratic equation of the reactance of the power transmission line is less than or equal to 0;

3) the absolute value of the i-end active state estimated value is greater than the absolute value of the i-end active measurement value, and the greater of two solutions of the unary quadratic equation of the reactance of the power transmission line is less than or equal to the value before the parameter correction of the reactance of the power transmission line;

4) the absolute value of the i-end active state estimated value is smaller than the absolute value of the i-end active measurement value, and the small one of two solutions of a unary quadratic equation of the reactance of the power transmission line is smaller than or equal to 0;

5) the absolute value of the i-end active state estimated value is smaller than the absolute value of the i-end active measurement value, and the smaller of two solutions of a unary quadratic equation of the reactance of the power transmission line is larger than or equal to the value of the reactance parameter of the power transmission line before correction;

and if any item in 1) to 5) is satisfied, the power transmission line reactance parameter correction calculation fails.

7. The transmission line parameter correction method of claim 6, wherein the transmission line reactance parameter correction calculation is successful, and the obtained transmission line reactance parameter correction value is:

if the absolute value of the active state estimated value of the i end is larger than the absolute value of the active measured value of the i end, dividing (the reactance parameter correction value of the transmission line in the last state estimation period multiplied by the reactance parameter correction times of the transmission line multiplied by the larger one of the two solutions of the unary quadratic equation of the reactance of the transmission line) by (the reactance parameter correction times of the transmission line multiplied by 1);

if the absolute value of the i-end active state estimated value is smaller than the absolute value of the i-end active measurement value, dividing (the transmission line reactance parameter corrected value in the last state estimated period multiplied by the transmission line reactance parameter corrected times plus the small of the two solutions of the unary quadratic equation of the transmission line reactance) by (the transmission line reactance parameter corrected times plus 1);

in addition, the correction times of the reactance parameters of the transmission line are increased by 1, if the correction times of the reactance parameters of the transmission line are more than or equal to the correction time threshold of the reactance parameters of the transmission line, the reactance parameters of the transmission line are replaced by correction values, and the correction times of the reactance parameters of the transmission line are set to be 0; the reactance parameters of the power transmission line are subjected to rolling correction by adopting a first-order low-pass filtering algorithm, and the filtering coefficient is inversely proportional to the correction times.

8. The method for correcting the parameters of the power transmission line according to claim 3, wherein the specific process in step S4 is as follows:

s41, judging whether the reactive power measurements at the two ends of the power transmission line are effective or not, and if yes, executing a step S42; otherwise, the power transmission line does not carry out the correction of the ground susceptance parameter of the power transmission line, and the parameter correction process is finished;

s42, determining reactive power measurement quality score conditions of two ends of the power transmission line;

s43, judging whether the reactive power measurement quality scores at the two ends of the power transmission line are both larger than a set reactive power measurement quality score threshold, if so, executing a step S44; otherwise, the power transmission line does not carry out the correction of the ground susceptance parameter of the power transmission line, and the parameter correction process is finished;

s44, setting a reactive deviation threshold, and determining the deviation between the sum of reactive measurement values at two ends of the power transmission line and the sum of state estimation values;

s45, judging whether the deviation of the sum of the reactive measurement values at the two ends of the power transmission line and the sum of the state estimation values is larger than a reactive deviation threshold, if so, executing a step S46; otherwise, the electric transmission line does not need to correct the earth-electricity parameter, the correction frequency is set to be 0, and the parameter correction process is ended;

s46, correcting the earth-electric-capacity parameter of the power transmission line by using the reactive measurement values at the two ends of the power transmission line and the state estimation values of the amplitude value and the phase angle of the voltage at the two ends of the power transmission line to obtain a corrected value of the earth-electric-capacity parameter of the power transmission line, and ending the parameter correction process.

9. The method for correcting the parameters of the power transmission line according to claim 8, wherein the specific process of step S46 is as follows:

s461, obtaining a one-dimensional linear equation of the power transmission line to ground susceptance according to the reactive power flow equation of the power transmission line:

wherein, y_cThe power line ground susceptance is an unknown number to be solved;the i end reactive power measurement value of the power transmission line is obtained;a j-end reactive power measurement value of the power transmission line is obtained; b is the transmission line susceptance; satisfies the following conditions:

wherein r represents a line resistance; x represents the line reactance;

s462, solving a one-dimensional linear equation of the power transmission line to the earth susceptance, and judging whether the condition of the failure of the correction of the earth susceptance is met or not, if so, failing to correct and calculate earth susceptance parameters by the power transmission line, otherwise, successfully correcting and calculating the earth susceptance parameters by the power transmission line, and obtaining a corrected value of the earth susceptance parameters by the power transmission line;

the ground susceptance correction failure conditions are:

d. the solution of the unary linear equation of the power transmission line to the ground susceptance is more than 0;

e. the sum of the estimated reactive state values at two ends of the line is larger than the sum of the measured reactive state values, and the solution of the unary linear equation of the power transmission line to the earth susceptance is smaller than or equal to the value of the power transmission line to the earth susceptance before parameter correction;

f. the sum of the estimated reactive state values at the two ends of the line is less than the sum of the reactive measurement values, and the solution of the unary linear equation of the power transmission line to the earth susceptance is more than or equal to the value of the line to the earth susceptance before parameter correction;

and if one of the conditions is met, the correction and calculation of the earth-electricity parameter of the power transmission line fails.

10. The method for correcting parameters of an electric transmission line according to claim 9, wherein the successful calculation of the correction of the ground-to-ground susceptance parameters of the electric transmission line in step S462 results in a specific correction result of the correction value of the ground-to-ground susceptance parameters of the electric transmission line as follows:

the correction value of the ground susceptance parameter of the transmission line pair (the correction value of the ground susceptance parameter of the transmission line pair x the correction times of the ground susceptance parameter of the transmission line pair + the solution of the unary linear equation of the ground susceptance of the transmission line) divided by (the correction times of the ground susceptance parameter of the transmission line pair + 1);

the correction times of the electric transmission line to the earth-ground sodium parameter are increased by 1, at the moment, if the correction times of the electric transmission line to the earth-ground sodium parameter are more than or equal to the correction time threshold of the electric transmission line to the earth-ground sodium parameter, the electric transmission line to the earth-ground sodium parameter is replaced by the correction value, and the correction times of the electric transmission line to the earth-ground sodium parameter is set to be 0; the power transmission line performs rolling correction on the earth-sodium parameter by adopting a first-order low-pass filtering algorithm, and the filtering coefficient is inversely proportional to the correction times.

Technical Field

The invention relates to the technical field of power transmission line parameter correction, in particular to a power transmission line parameter correction method.

Background

Modern Energy Management Systems (EMS) are application software systems that analyze, evaluate and make decisions using grid models (including parameters) and real-time acquisition, and parameter errors are a difficult problem that plagues EMS practicality for a long time. With the expansion of the power grid scale and the rapid development of the power market, the requirements on the reliability and precision of EMS software analysis and decision are higher and higher, and the research on a practical error parameter identification and correction method has important practical significance.

Because the actual operating condition of the power transmission line is very complex, the terrain environment, meteorological conditions and the like of the overhead power transmission line can cause large difference between the design value and the actual parameter, and therefore the relevant regulations stipulate that the power transmission line parameters should adopt measured values. However, the actual measurement of the transmission line parameters is generally performed before commissioning, and the transmission line parameters may change due to changes in the operating conditions of the transmission line or due to aging of the transmission line, that is, the actual parameters of the transmission line may differ from the actual measurement values before commissioning. Therefore, it is necessary to identify and roll-correct the error parameters of the transmission line, so as to improve the accuracy of the basic data of the power grid.

On 8 th 10 th 2014, the invention discloses an online identification method for power grid transmission line parameters considering a large error point of state estimation in Chinese invention patent, which firstly calculates a state estimation value of a transmission line measurement point by using state estimation and obtains a deviation between the measurement value and the state estimation value of the transmission line measurement point; defining the measuring point with the deviation larger than the set threshold value as a measuring large error point, and setting the power transmission line corresponding to the measuring point as a suspicious power transmission line; and identifying whether the suspicious power transmission line has measurement data errors or not by taking whether the measurement data at two ends of the power transmission line and the accumulated values of the data measured by all the devices of the bus connected with the power transmission line are balanced as a criterion. For the power transmission line with normal measurement data, gradually changing parameters of the power transmission line by adopting a variable step length integration method according to the deviation between the measurement value and the state estimation value, and obtaining the estimation value after changing the parameters; and setting the parameter with the minimum deviation between the measured value and the estimated value as the estimated parameter of the power transmission line.

In addition, the existing power transmission line parameter correction technology research mainly focuses on how to obtain the estimated value of the parameter, and the most common method is to add the parameter as a state variable to the state estimation for calculation. However, since the parameters and the state variables (voltage amplitude and phase angle) have different physical meanings, the derivative component of the parameters measured in the jacobian matrix easily causes the jump of the matrix condition number, and the condition number of the information matrix and the condition number of the jacobian matrix are in a square relation, so that the stability of the state estimation value after the parameters are expanded becomes poor. Moreover, the state estimation after parameter augmentation can only be calculated by a Newton method, a fast decomposition method is not applicable any more, and the calculation time is greatly increased.

Disclosure of Invention

In order to overcome the defects that the stability of the state estimation value after the parameters are expanded is poor and the calculation time is increased due to the fact that the current method for expanding the parameters into the state estimation as the state variables to carry out calculation is adopted, the invention provides a power transmission line parameter correction method. The method has the advantages of strong numerical stability, high calculation speed and higher engineering practical value.

In order to achieve the technical effects, the technical scheme of the invention is as follows:

a method for correcting parameters of a power transmission line at least comprises the following steps:

s1, determining each state estimation period and power transmission line parameters to be corrected, wherein the power transmission line parameters to be corrected comprise power transmission line reactance parameters and power transmission line ground-to-ground sodium permeability parameters, and setting a power transmission line parameter correction frequency threshold to be corrected;

s2, setting an active measurement quality score threshold and a reactive measurement quality score threshold, and scoring the measurement quality of the active measurement quality and the reactive measurement quality of the power transmission line in each state estimation period;

s3, according to the active measurement quality score condition, calculating a correction value of the reactance parameter of the power transmission line by using the active measurement value of one end of the two ends of the line, which has the higher active measurement quality score, and the state estimation values of the voltage amplitude value and the phase angle of the two ends of the line, and correcting the reactance parameter of the power transmission line;

and S4, according to the reactive power measurement quality score condition, calculating a correction value of the power transmission line to the earth-electricity-capacity parameter by using the reactive power measurement values at the two ends of the line and the state estimation values of the voltage amplitude and the phase angle of the two ends of the line, and correcting the earth-electricity-capacity parameter by the power transmission line.

Preferably, the state estimation period in step S1 is 1 minute, and the correction time threshold of the reactance parameter of the power transmission line to be corrected is 30, and the time window for correcting the reactance parameter of the power transmission line is half an hour; and if the threshold of the correction times of the ground-to-ground sodium-reception parameters of the power transmission line to be corrected is 30, the time window for correcting the ground-to-ground sodium-reception parameters of the power transmission line is half an hour.

In this case, the transmission line parameters are replaced with the correction values and then directly used for state estimation in the next state estimation period, which is beneficial to improving the estimation quality of state estimation, especially the estimation quality of active power and reactive power.

Preferably, the rules for scoring the measurement quality of the active measurement quality and the reactive measurement quality of the power transmission line in each state estimation period are respectively as follows:

the rule for scoring the measurement quality of the active measurement quality of the power transmission line in each state estimation period is as follows:

A) the active power of a bus connected with the power transmission line is balanced, 1 minute is added, and otherwise, 1 minute is subtracted; the bus active power imbalance criterion is as follows:

wherein, P_jThe active injection power of the transmission line j connected with the bus i; epsilon_PbusA value of a power unbalance threshold is set for the bus i; epsilon_PbusSetting according to the voltage level;

B) the active power at the two ends of the power transmission line is balanced, 1 point is added, and otherwise, 1 point is subtracted; the criterion of the active power imbalance at the two ends of the power transmission line is as follows:

|P_ij+P_ji-P_loss|>ε_Pline

wherein, P_ij、P_jiRespectively the active power of the I end and the j end of the transmission line flowing into the line; p_lossActive power loss for the transmission line; epsilon_PlineA threshold for power unbalance of the power transmission line; the active imbalance threshold of the power transmission line is set according to the voltage level;

C) if the PQIs at the end where the power transmission line is successfully measured are matched, adding 1 point, and otherwise, subtracting 1 point; wherein the PQI mismatch criterion is:

|I_cal-I_scada|>ε_I

wherein, I_calThe current value is calculated according to the active power and the reactive power of the transmission line and the voltage of the connected bus; i is_scadaIs the measured current value; epsilon_IA PQI mismatch threshold; the PQI mismatch threshold is set according to the voltage level;

the rule for scoring the reactive power measurement quality of the power transmission line in each state estimation period is as follows:

a) adding 1 minute for reactive power balance of a bus connected with the power transmission line, or not adding the minute; the bus reactive unbalance criterion is as follows:

wherein Q is_jThe reactive injection power of the transmission line j connected with the bus i is obtained; epsilon_QbusA reactive unbalance threshold value is a bus i; epsilon_QbusSetting according to the voltage level;

b) and adding 1 point when the PQI at the reactive power measurement end of the power transmission line is matched, or not adding points.

Preferably, the specific process of step S3 includes:

s31, judging whether at least one end of active power measurement at two ends of the power transmission line is effective, if so, executing step S32; otherwise, the power transmission line does not carry out power transmission line reactance parameter correction, and the parameter correction process is finished;

s32, determining the active power measurement quality score conditions of the two ends of the power transmission line;

s33, taking the higher active power measurement quality score at the two ends of the power transmission line, judging whether the active power measurement quality score is larger than a set active power measurement quality score threshold, and if so, executing a step S34; otherwise, the power transmission line does not carry out power transmission line reactance parameter correction, and the parameter correction process is finished;

s34, setting an active deviation threshold, and determining the deviation between an active measurement value and a state estimation value at one end of the two ends of the power transmission line, wherein the active measurement value has high active measurement quality score;

s35, judging whether the deviation between the active measurement value and the state estimation value at the end with high active measurement quality score in the two ends of the line is greater than an active deviation threshold, if so, executing a step S36; otherwise, the reactance parameter of the power transmission line does not need to be corrected, the correction frequency is set to be 0, and the step S4 is executed;

s36, setting a minimum threshold value of the number of branches of the ring, judging whether the power transmission line is in the ring network or not, and judging whether the minimum value of the number of branches of the ring containing the power transmission line is smaller than the set minimum threshold value of the number of branches of the ring or not, and if so, correcting the anti-parameter of the power transmission line; otherwise, the power transmission line does not carry out power transmission line reactance parameter correction, and the parameter correction process is finished.

Preferably, the specific process of correcting the transmission line reactance parameter in step S36 is as follows:

s361, obtaining a unitary quadratic equation of the reactance of the power transmission line according to the active power flow equation of the power transmission line:

the end with high active power measurement quality score in the two ends of the power transmission line is set as an i end; the other end of the transmission line is set as a j end; r is the resistance of the transmission line; x is the reactance of the transmission line and is an unknown number to be solved;an active measurement value of the i end of the power transmission line is obtained; v_iEstimation of i-terminal voltage amplitude state for transmission lineEvaluating; v_jThe estimated value of the j-end voltage amplitude value state of the power transmission line is obtained;

θ_ij＝θ_i-θ_j

wherein, theta_iEstimating the phase angle state of the i-terminal voltage of the power transmission line; theta_jThe phase angle state estimation value of j terminal voltage of the power transmission line is obtained;

and S362, solving a unitary quadratic equation of the reactance of the power transmission line, and judging whether the reactance correction failure condition is met, wherein if yes, the power transmission line reactance parameter correction calculation fails, otherwise, the power transmission line reactance parameter correction calculation succeeds, and the power transmission line reactance parameter correction value is obtained.

Preferably, the correction failure condition in step S362 is:

1) a quadratic equation of a single element of the reactance of the transmission line is not solved;

2) the absolute value of the i-end active state estimated value is greater than the absolute value of the i-end active measurement value, and the greater of two solutions of the unary quadratic equation of the reactance of the power transmission line is less than or equal to 0;

3) the absolute value of the i-end active state estimated value is greater than the absolute value of the i-end active measurement value, and the greater of two solutions of the unary quadratic equation of the reactance of the power transmission line is less than or equal to the value before the parameter correction of the reactance of the power transmission line;

4) the absolute value of the i-end active state estimated value is smaller than the absolute value of the i-end active measurement value, and the small one of two solutions of a unary quadratic equation of the reactance of the power transmission line is smaller than or equal to 0;

5) the absolute value of the i-end active state estimated value is smaller than the absolute value of the i-end active measurement value, and the smaller of two solutions of a unary quadratic equation of the reactance of the power transmission line is larger than or equal to the value of the reactance parameter of the power transmission line before correction;

and if any item in 1) to 5) is satisfied, the power transmission line reactance parameter correction calculation fails.

Preferably, the power transmission line reactance parameter correction calculation is successful, and the obtained power transmission line reactance parameter correction value is as follows:

if the absolute value of the active state estimated value of the i end is larger than the absolute value of the active measured value of the i end, dividing (the reactance parameter correction value of the transmission line in the last state estimation period multiplied by the reactance parameter correction times of the transmission line multiplied by the larger one of the two solutions of the unary quadratic equation of the reactance of the transmission line) by (the reactance parameter correction times of the transmission line multiplied by 1);

if the absolute value of the i-end active state estimated value is smaller than the absolute value of the i-end active measurement value, dividing (the transmission line reactance parameter corrected value in the last state estimated period multiplied by the transmission line reactance parameter corrected times plus the small of the two solutions of the unary quadratic equation of the transmission line reactance) by (the transmission line reactance parameter corrected times plus 1);

in addition, the correction times of the reactance parameters of the transmission line are increased by 1, if the correction times of the reactance parameters of the transmission line are more than or equal to the correction time threshold of the reactance parameters of the transmission line, the reactance parameters of the transmission line are replaced by correction values, and the correction times of the reactance parameters of the transmission line are set to be 0; the reactance parameters of the power transmission line are subjected to rolling correction by adopting a first-order low-pass filtering algorithm, and the filtering coefficient is in inverse proportion to the correction times, so that oscillation in the correction process can be effectively avoided, and reliable convergence of the reactance parameter correction of the power transmission line is ensured.

Preferably, the specific process in step S4 is:

s41, judging whether the reactive power measurements at the two ends of the power transmission line are effective or not, and if yes, executing a step S42; otherwise, the power transmission line does not carry out the correction of the ground susceptance parameter of the power transmission line, and the parameter correction process is finished;

s42, determining reactive power measurement quality score conditions of two ends of the power transmission line;

s43, judging whether the reactive power measurement quality scores at the two ends of the power transmission line are both larger than a set reactive power measurement quality score threshold, if so, executing a step S44; otherwise, the power transmission line does not carry out the correction of the ground susceptance parameter of the power transmission line, and the parameter correction process is finished;

s44, setting a reactive deviation threshold, and determining the deviation between the sum of reactive measurement values at two ends of the power transmission line and the sum of state estimation values;

s45, judging whether the deviation of the sum of the reactive measurement values at the two ends of the power transmission line and the sum of the state estimation values is larger than a reactive deviation threshold, if so, executing a step S46; otherwise, the electric transmission line does not need to correct the earth-electricity parameter, the correction frequency is set to be 0, and the parameter correction process is ended;

s46, correcting the earth-electric-capacity parameter of the power transmission line by using the reactive measurement values at the two ends of the power transmission line and the state estimation values of the amplitude value and the phase angle of the voltage at the two ends of the power transmission line to obtain a corrected value of the earth-electric-capacity parameter of the power transmission line, and ending the parameter correction process.

Preferably, the specific process of step S46 is:

s461, obtaining a one-dimensional linear equation of the power transmission line to ground susceptance according to the reactive power flow equation of the power transmission line:

wherein, y_cThe power line ground susceptance is an unknown number to be solved;the i end reactive power measurement value of the power transmission line is obtained;a j-end reactive power measurement value of the power transmission line is obtained; b is the transmission line susceptance; satisfies the following conditions:

wherein r represents a line resistance; x represents the line reactance.

S462, solving a one-dimensional linear equation of the power transmission line to the earth susceptance, and judging whether the condition of the failure of the correction of the earth susceptance is met or not, if so, failing to correct and calculate earth susceptance parameters by the power transmission line, otherwise, successfully correcting and calculating the earth susceptance parameters by the power transmission line, and obtaining a corrected value of the earth susceptance parameters by the power transmission line;

the ground susceptance correction failure conditions are:

d. the solution of the unary linear equation of the power transmission line to the ground susceptance is more than 0;

e. the sum of the estimated reactive state values at two ends of the line is larger than the sum of the measured reactive state values, and the solution of the unary linear equation of the power transmission line to the earth susceptance is smaller than or equal to the value of the power transmission line to the earth susceptance before parameter correction;

f. the sum of the estimated reactive state values at the two ends of the line is less than the sum of the reactive measurement values, and the solution of the unary linear equation of the power transmission line to the earth susceptance is more than or equal to the value of the line to the earth susceptance before parameter correction;

and if one of the conditions is met, the correction and calculation of the earth-electricity parameter of the power transmission line fails.

Preferably, in step S462, the power transmission line to ground sodium chloride parameter correction calculation is successful, and a specific correction result of the power transmission line to ground sodium chloride parameter correction value is obtained as follows:

the correction value of the ground susceptance parameter of the transmission line pair (the correction value of the ground susceptance parameter of the transmission line pair x the correction times of the ground susceptance parameter of the transmission line pair + the solution of the unary linear equation of the ground susceptance of the transmission line) divided by (the correction times of the ground susceptance parameter of the transmission line pair + 1);

the correction times of the electric transmission line to the earth-ground sodium parameter are increased by 1, at the moment, if the correction times of the electric transmission line to the earth-ground sodium parameter are larger than or equal to the correction time threshold of the electric transmission line to the earth-ground sodium parameter, the electric transmission line to the earth-ground sodium parameter is replaced by the correction values, the correction times of the electric transmission line to the earth-ground sodium parameter are set to be 0, the electric transmission line to the earth-ground sodium parameter adopts a first-order low-pass filtering algorithm to carry out rolling correction, and the filtering coefficient is inversely proportional to the correction times, so that oscillation in the correction process can be effectively avoided, and reliable convergence of the line to the earth-ground sodium parameter correction is ensured.

Compared with the prior art, the technical scheme of the invention has the beneficial effects that:

the invention provides a power transmission line parameter correction method, which comprises the steps of firstly determining each state estimation period and power transmission line parameters to be corrected, wherein the power transmission line parameters comprise power transmission line reactance parameters and power transmission line ground-to-earth sodium parameters, and calculating the correction value of the line reactance parameters by utilizing the active measurement value of one end with high active measurement quality score in two ends of a line and the state estimation values of the voltage amplitude and the phase angle of the two ends of the line according to the active measurement quality and the identifiability analysis of the reactance parameters; and calculating the correction value of the line to the earth-ground sodium parameter by using the reactive power measurement values at the two ends of the line and the state estimation values of the voltage amplitude and the phase angle according to the reactive power measurement quality. The method does not need to modify the existing state estimation program, and has strong numerical stability, high calculation speed and higher engineering practical value.

Drawings

Fig. 1 shows a flowchart of a method for correcting parameters of a power transmission line according to an embodiment of the present invention.

Detailed Description

The drawings are for illustrative purposes only and are not to be construed as limiting the patent;

for better illustration of the present embodiment, certain parts of the drawings may be omitted, enlarged or reduced, and do not represent actual dimensions;

it will be understood by those skilled in the art that certain well-known descriptions of the figures may be omitted.

The positional relationships depicted in the drawings are for illustrative purposes only and are not to be construed as limiting the present patent;

the technical solution of the present invention is further described below with reference to the accompanying drawings and examples.

Examples

As shown in fig. 1, a flowchart of a method for correcting parameters of a power transmission line, referring to fig. 1, includes:

a method for correcting parameters of a power transmission line at least comprises the following steps:

s1, determining each state estimation period and power transmission line parameters to be corrected, wherein the power transmission line parameters to be corrected comprise power transmission line reactance parameters and power transmission line ground-to-ground sodium permeability parameters, and setting a power transmission line parameter correction frequency threshold to be corrected;

in this embodiment, the state estimation period is 1 minute, the correction time threshold of the reactance parameter of the power transmission line to be corrected is 30, and the time window for correcting the reactance parameter of the power transmission line is half an hour; the threshold of the correction times of the ground-to-ground sodium-reception parameters of the power transmission line to be corrected is 30, and the time window of the correction of the ground-to-ground sodium-reception parameters of the power transmission line is half an hour

S2, setting an active measurement quality score threshold and a reactive measurement quality score threshold, and scoring the measurement quality of the active measurement quality and the reactive measurement quality of the power transmission line in each state estimation period;

the rule for scoring the measurement quality of the active measurement quality of the power transmission line in each state estimation period is as follows:

A) the active power of a bus connected with the power transmission line is balanced, 1 minute is added, and otherwise, 1 minute is subtracted; the bus active power imbalance criterion is as follows:

wherein, P_jThe active injection power of the transmission line j connected with the bus i; epsilon_PbusA value of a power unbalance threshold is set for the bus i; epsilon_PbusAccording to a voltage class setting, for example, a 525kV voltage class setting of 12 MW; the 230kV voltage level was set to 9W.

B) The active power at the two ends of the power transmission line is balanced, 1 point is added, and otherwise, 1 point is subtracted; the criterion of the active power imbalance at the two ends of the power transmission line is as follows:

|P_ij+P_ji-P_loss|>ε_Pline

wherein, P_ij、P_jiRespectively the active power of the I end and the j end of the transmission line flowing into the line; p_lossActive power loss for the transmission line; epsilon_PlineA threshold for power unbalance of the power transmission line; the active imbalance threshold of the power transmission line is set according to the voltage level; for example, the 525kV voltage level is set to 12 MW; the 230kV voltage level was set to 9W.

C) If the PQIs at the end where the power transmission line is successfully measured are matched, adding 1 point, and otherwise, subtracting 1 point; wherein the PQI mismatch criterion is:

|I_cal-I_scada|>ε_I

wherein, I_calFor calculating according to the active and reactive power of the transmission line and the voltage of the connected busThe current value of (a); i is_scadaIs the measured current value; epsilon_IA PQI mismatch threshold; the PQI mismatch threshold is set according to the voltage level; for example, the 525kV voltage level is set to 10A; the 230kV voltage level was set to 8A.

The rule for scoring the reactive power measurement quality of the power transmission line in each state estimation period is as follows:

a) adding 1 minute for reactive power balance of a bus connected with the power transmission line, or not adding the minute; the bus reactive unbalance criterion is as follows:

wherein Q is_jThe reactive injection power of the transmission line j connected with the bus i is obtained; epsilon_QbusA reactive unbalance threshold value is a bus i; epsilon_QbusSetting according to the voltage level; for example, the 525kV voltage level is set at 12 MVar; the 230kV voltage level was set to 9 MVar.

b) And adding 1 point when the PQI at the reactive power measurement end of the power transmission line is matched, or not adding points.

The higher the voltage level is, the higher the power transmitted by the power grid is, and the unbalance amount caused by the measurement error is relatively large, so that a large unbalance threshold needs to be set.

In this embodiment, the active quality score threshold is set to 0. In some embodiments, if the bus connected to the line is in active balance, the two ends of the line are in active balance, and the PQI at the end where the line is in active measurement is matched, at this time, the active measurement quality score is 3 and is greater than 0, it can be determined that the active measurement data of the line is good data and can be used for parameter modification; in other embodiments, it is assumed that the line active measurement is still good data, but the active measurement of another device on the bus connected to the line is bad data, at this time, the bus connected to the line is unbalanced in active power, but the active measurements at the two ends of the line are balanced and the PQI at the end where the line active measurement is located is matched, so that the active measurement quality score 1 is still greater than 0, and it can be still identified that the line active measurement data is good data; in other embodiments, assuming that the line active measurement is bad data, at this time, the bus connected to the line has unbalanced active power, the two ends of the line have unbalanced active power, and the PQI at the end of the line active measurement does not match, so that the active measurement quality score is-3 and not greater than 0, and the line active measurement data is identified as bad data.

S3, according to the active measurement quality score condition, calculating a correction value of the reactance parameter of the power transmission line by using the active measurement value of one end of the two ends of the line, which has the higher active measurement quality score, and the state estimation values of the voltage amplitude value and the phase angle of the two ends of the line, and correcting the reactance parameter of the power transmission line;

the specific process comprises the following steps:

s31, judging whether at least one end of active power measurement at two ends of the power transmission line is effective, if so, executing step S32; otherwise, the power transmission line does not carry out power transmission line reactance parameter correction, and the parameter correction process is finished;

s32, determining the active power measurement quality score conditions of the two ends of the power transmission line;

s33, taking the higher active power measurement quality score at the two ends of the power transmission line, judging whether the active power measurement quality score is larger than a set active power measurement quality score threshold, and if so, executing a step S34; otherwise, the power transmission line does not carry out power transmission line reactance parameter correction, and the parameter correction process is finished;

s34, setting an active deviation threshold, and determining the deviation between an active measurement value and a state estimation value at one end of the two ends of the power transmission line, wherein the active measurement value has high active measurement quality score;

s35, judging whether the deviation between the active measurement value and the state estimation value at the end with high active measurement quality score in the two ends of the line is greater than an active deviation threshold, if so, executing a step S36; otherwise, the reactance parameter of the power transmission line does not need to be corrected, the correction frequency is set to be 0, and the step S4 is executed;

s36, setting a minimum threshold value of the number of branches of the ring, judging whether the power transmission line is in the ring network or not, and judging whether the minimum value of the number of branches of the ring containing the power transmission line is smaller than the set minimum threshold value of the number of branches of the ring or not, and if so, correcting reactance parameters of the power transmission line; otherwise, the power transmission line does not carry out power transmission line reactance parameter correction, and the parameter correction process is finished.

Here, the deviation between the active measurement value and the state estimation value is large, and the reactive parameter of the power transmission line is suspicious under the condition that the active measurement value is credible. The active deviation threshold is set to be 2% of the power measurement reference value of the power transmission line of each voltage class, for example, the power measurement reference value of the power transmission line of 500kV voltage class is 1082MW, and the deviation threshold is 21.64 MW; the power measurement reference value of the 220kV voltage class power transmission line is 305MW, and the deviation threshold is 6.1 MW. Only when the transmission line is in the ring and the number of branches of the ring is small, the reactance parameter of the transmission line can obviously influence the active power flow distribution on the ring, namely, the transmission line has identifiability. The minimum threshold of the number of branches of the loop can be adjusted appropriately according to the actual grid conditions, and is set to 8 in the exemplary embodiment of the present application.

In addition, the effective or ineffective active power measurement at two ends of the power transmission line is comprehensively interpreted by the SCADA according to the information sent by the substation, and is a flag bit, and the ineffective active power measurement indicates that the measurement data is unavailable.

The specific process of correcting the reactance parameter of the power transmission line in the step S36 is as follows:

s361, obtaining a unitary quadratic equation of the reactance of the power transmission line according to the active power flow equation of the power transmission line:

the end with high active power measurement quality score in the two ends of the power transmission line is set as an i end; the other end of the transmission line is set as a j end; r is the resistance of the transmission line; x is the reactance of the transmission line and is an unknown number to be solved;an active measurement value of the i end of the power transmission line is obtained; v_iAn i-terminal voltage amplitude state estimation value of the power transmission line is obtained; v_jThe estimated value of the j-end voltage amplitude value state of the power transmission line is obtained;

θ_ij＝θ_i-θ_j

wherein, theta_iEstimating the phase angle state of the i-terminal voltage of the power transmission line; theta_jTo be transportedEstimating a phase angle state of j terminal voltage of the electric line;

and S362, solving a unitary quadratic equation of the reactance of the power transmission line, and judging whether the reactance correction failure condition is met, wherein if yes, the power transmission line reactance parameter correction calculation fails, otherwise, the power transmission line reactance parameter correction calculation succeeds, and the power transmission line reactance parameter correction value is obtained.

The correction failure condition in step S362 is:

1) a quadratic equation of a single element of the reactance of the transmission line is not solved;

2) the absolute value of the i-end active state estimated value is greater than the absolute value of the i-end active measurement value, and the greater of two solutions of the unary quadratic equation of the reactance of the power transmission line is less than or equal to 0;

3) the absolute value of the i-end active state estimated value is greater than the absolute value of the i-end active measurement value, and the greater of two solutions of the unary quadratic equation of the reactance of the power transmission line is less than or equal to the value before the reactance parameter of the power transmission line is corrected;

4) the absolute value of the i-end active state estimated value is smaller than the absolute value of the i-end active measurement value, and the small one of two solutions of a unary quadratic equation of the reactance of the power transmission line is smaller than or equal to 0;

5) the absolute value of the i-end active state estimated value is smaller than the absolute value of the i-end active measurement value, and the smaller of the two solutions of the unary quadratic equation of the reactance of the power transmission line is larger than or equal to the value of the reactance parameter of the power transmission line before correction;

and if any item in 1) to 5) is satisfied, the power transmission line reactance parameter correction calculation fails.

Successfully correcting and calculating the reactance parameters of the power transmission line to obtain the corrected values of the reactance parameters of the power transmission line as follows:

if the absolute value of the active state estimated value of the i end is larger than the absolute value of the active measured value of the i end, dividing (the reactance parameter correction value of the transmission line in the last state estimation period multiplied by the reactance parameter correction times of the transmission line multiplied by the larger one of the two solutions of the unary quadratic equation of the reactance of the transmission line) by (the reactance parameter correction times of the transmission line multiplied by 1);

if the absolute value of the i-end active state estimated value is smaller than the absolute value of the i-end active measurement value, dividing (the transmission line reactance parameter corrected value in the last state estimated period multiplied by the transmission line reactance parameter corrected times plus the small of the two solutions of the unary quadratic equation of the transmission line reactance) by (the transmission line reactance parameter corrected times plus 1);

in addition, the correction times of the reactance parameters of the transmission line are increased by 1, if the correction times of the reactance parameters of the transmission line are more than or equal to the correction time threshold of the reactance parameters of the transmission line, the reactance parameters of the transmission line are replaced by correction values, and the correction times of the reactance parameters of the transmission line are set to be 0; the reactance parameter of the power transmission line is subjected to rolling correction by adopting a first-order low-pass filtering algorithm, and the filtering coefficient is in inverse proportion to the correction times, so that oscillation in the correction process can be effectively avoided, and reliable convergence of the reactance parameter correction of the power transmission line is ensured.

And S4, according to the reactive power measurement quality score condition, calculating a correction value of the power transmission line to the earth-electricity-capacity parameter by using the reactive power measurement values at the two ends of the power transmission line and the state estimation values of the voltage amplitude values and the phase angles at the two ends of the power transmission line, and correcting the earth-electricity-capacity parameter by the power transmission line.

The specific process of step S4 is:

s41, judging whether the reactive power measurements at the two ends of the power transmission line are effective or not, and if yes, executing a step S42; otherwise, the power transmission line does not carry out the correction of the ground susceptance parameter of the power transmission line, and the parameter correction process is finished;

s42, determining reactive power measurement quality score conditions of two ends of the power transmission line;

s43, judging whether the reactive power measurement quality scores at the two ends of the power transmission line are both larger than a set reactive power measurement quality score threshold, if so, executing a step S44; otherwise, the power transmission line does not carry out the correction of the ground susceptance parameter of the power transmission line, and the parameter correction process is finished;

wherein, the reactive power measurement quality score threshold is set to be 0; in some embodiments, if the bus connected to the transmission line is in reactive power balance and the reactive power measurement end of the transmission line is PQI matched, and the reactive power measurement quality score is 2 and is greater than 0, the reactive power measurement data of the transmission line can be determined to be good data and can be used for parameter correction; in other embodiments, if the reactive power measurement of the power transmission line is still good data, but the reactive power measurement of another device on the bus connected with the power transmission line is bad data, at this time, the bus connected with the power transmission line is unbalanced in reactive power, but the end PQI where the reactive power measurement of the power transmission line is located is matched, so that the reactive power measurement quality score is 1 which is still larger than 0, or the reactive power measurement data of the power transmission line can be identified as good data; in other embodiments, assuming that the reactive power measurement of the power transmission line is bad data, at this time, the reactive power of the bus connected to the power transmission line is unbalanced and the PQI at the reactive power measurement end of the power transmission line is also not matched, so that the reactive power measurement quality score is 0 and is not greater than 0, and the reactive power measurement data of the power transmission line is identified as bad data.

S44, setting a reactive deviation threshold, and determining the deviation between the sum of reactive measurement values at two ends of the power transmission line and the sum of state estimation values;

s45, judging whether the deviation of the sum of the reactive measurement values at the two ends of the power transmission line and the sum of the state estimation values is larger than a reactive deviation threshold, if so, executing a step S46; otherwise, the electric transmission line does not need to correct the earth-electricity parameter, the correction frequency is set to be 0, and the parameter correction process is ended;

s46, correcting the earth-electric-capacity parameter of the power transmission line by using the reactive measurement values at the two ends of the power transmission line and the state estimation values of the amplitude value and the phase angle of the voltage at the two ends of the power transmission line to obtain a corrected value of the earth-electric-capacity parameter of the power transmission line, and ending the parameter correction process.

Here, the deviation between the reactive power measurement value and the state estimation value is large, and when the reactive power measurement value is credible, it is described that the line is suspicious of the ground-to-ground susceptance parameter. In an embodiment, the reactive deviation threshold is set to be 3% of the line power measurement reference value of each voltage class, for example, the line power measurement reference value of 500kV voltage class is 1082MW, and the deviation threshold is 32.46 MVar; the power measurement reference value of the 220kV voltage level line is 305MW, and the deviation threshold is 9.15 MVar.

The specific process of step S46 is:

s461, obtaining a one-dimensional linear equation of the power transmission line to ground susceptance according to the reactive power flow equation of the power transmission line:

wherein, y_cThe power transmission line is the unknown number to be solved;the i end reactive power measurement value of the power transmission line is obtained;a j-end reactive power measurement value of the power transmission line is obtained; b is the transmission line susceptance; satisfies the following conditions:

wherein r represents a line resistance; x represents the line reactance.

S462, solving a one-dimensional linear equation of the power transmission line to the earth susceptance, and judging whether the condition of the failure of the correction of the earth susceptance is met or not, if so, failing to correct and calculate earth susceptance parameters by the power transmission line, otherwise, successfully correcting and calculating the earth susceptance parameters by the power transmission line, and obtaining a corrected value of the earth susceptance parameters by the power transmission line;

the ground susceptance correction failure conditions are:

d. the solution of the unary linear equation of the power transmission line to the ground susceptance is more than 0;

e. the sum of the estimated values of the reactive states at the two ends of the power transmission line is larger than the sum of the measured values of the reactive states, and the solution of the unary linear equation of the power transmission line to the earth susceptance is smaller than or equal to the value of the power transmission line to the earth susceptance before parameter correction;

f. the sum of the estimated values of the reactive states at the two ends of the power transmission line is less than the sum of the reactive measurement values, and the solution of the unary linear equation of the power transmission line to the earth susceptance is more than or equal to the value of the power transmission line to the earth susceptance before parameter correction;

and if one of the conditions is met, the correction and calculation of the earth-electricity parameter of the power transmission line fails.

In step S462, the power transmission line to earth susceptance parameter correction calculation is successful, and a specific correction result of the power transmission line to earth susceptance parameter correction value is obtained as follows:

the correction value of the power transmission line to earth susceptance parameter is (the correction value of the power transmission line to earth susceptance parameter in the last state estimation period is multiplied by the correction times of the power transmission line to earth susceptance parameter + the solution of the unary linear equation of the power transmission line to earth susceptance) ÷ (the correction times of the power transmission line to earth susceptance parameter + 1);

and (3) increasing the correction times of the ground susceptance parameter of the power transmission line by 1, and replacing the ground susceptance parameter of the power transmission line by a correction value if the correction times of the ground susceptance parameter of the power transmission line is more than or equal to the correction times threshold of the ground susceptance parameter of the power transmission line, wherein the correction times of the ground susceptance parameter of the power transmission line are set. The power transmission line performs rolling correction on the earth-electric-sodium parameter by adopting a first-order low-pass filtering algorithm, and the filtering coefficient is inversely proportional to the correction times, so that oscillation in the correction process can be effectively avoided, and reliable convergence of the power transmission line on the earth-electric-sodium parameter correction is ensured.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.