CN102621388A - Electric transmission line lumped parameter on-line determination method based on synchronous time domain signals - Google Patents

Abstract

The invention relates to an electric transmission line lumped parameter on-line determination method based on synchronous time domain signals, which adopts current and voltage synchronous time domain signals on two sides of an electric transmission line to calculate lumped parameters of the electric transmission line. In an equivalent circuit diagram of the lumped parameters of the electric transmission line, differential equations are listed according to a Kirchhoff circuit law (KCL) and a Kirchhoff voltage law (KVL) to obtain expressions relevant to line parameters of resistance R, inductance L and capacitance C, the current and voltage synchronous time domain signals on two sides of the line are substituted in the expressions to obtain concrete parameters. The electric transmission line lumped parameter on-line determination method is free of influences on computational accuracy caused by attenuation direct current and attenuation high frequency signals, calculates short windows of needed data, has high accuracy and has fast response speed.

Description

Based on the online definite method of the transmission line of electricity lumped parameter of synchronous time domain signal

Technical field

The present invention relates to the online definite method of a kind of power system transmission line parameter, the online definite method of especially a kind of transmission line of electricity lumped parameter based on the synchronous time domain signal.

Background technology

Along with moving forward steadily fast of China's intelligent grid construction, also increasingly high to the requirement of power network safety operation, the rapid rising of electrical network physical complexity makes power network safety operation face a severe challenge.Along with scale of power is increasing, network structure becomes increasingly complex, and the management and running personnel also more and more depend on the accuracy of electric network model parameter to the assurance of electrical network characteristic.Line parameter circuit value is that the running technology personnel obtain electric network composition, generate the important evidence that trend is calculated required bus admittance matrix and impedance matrix, carried out calculation of short-circuit current, protective relaying device is adjusted.Improving accuracy, reliability and real-time that electrical network parameter calculates, is the primary demand of building intelligent grid, and the safe and stable operation of electrical network is significant.

Have operating experience to show at present: can there be certain error in the calculated value and the measured value of links such as in some electrical network, state estimation, trend are calculated, protection fixed value adjusting, and this error is bigger under some situation, even has influence on the normal and stable operation of system.Find that through big quantitative analysis the main cause that this error produces is that line parameter circuit value is not accurate enough, i.e. circuit theoretical parameter value and actual parameter value difference that analytical calculation is adopted are bigger.The line parameter circuit value value that adopts at the scene at present is the off-line measurement value that empirical value or producer provide mostly, rather than the parameter during the circuit actual motion, has error between the two unavoidably, thereby influence the accuracy and the precision of Power System Analysis calculating.Strictly speaking, the parameter of the different moment, different service condition line all can have difference, if calculate comparatively accurately, these difference can't be ignored.If can online calculate the parameter value of transmission line of electricity through the electric parameters of real-time power network operation, carry out Power System Analysis and calculating based on real-time transmission line parameter, certainly will can improve the analytical calculation precision, thereby improve the security and stability of electrical network.

Time-domain signal refers to time dependent signal, is reacted in the electric system, is exactly the analog quantity sampled value to electric current, voltage signal.These signals only are that electric current, voltage are carried out the signal after time discretization is handled; Need not to calculate link through digital filtering, Fourier transform etc.; Therefore can avoid the influence of the selection of DC component, harmonic wave and algorithm to result of calculation; And have computing velocity faster, application prospect is better.

One Chinese patent application 201110024996 discloses a kind of identification and method of estimation of the power circuit parameter based on the PMU metric data.This method is utilized computing machine, through program, at first imports by the master data of identification and estimation of line; Then according to the PMU metric data of a plurality of periods at these circuit two ends; The wrong parameter of elder generation's identification this circuit is estimated the correct parameter of this circuit again, draws the estimated value of the correct parameter of circuit.This invention is based on the PMU metric data, the wrong parameter of identification circuit at first, and the selection of discrimination method can influence the estimation to the correct parameter of circuit, and only to the moderate-length high pressure and the extra high voltage network that are equiped with the PMU device.

One Chinese patent application 200910107854 discloses a kind of power transmission line parameter online measurement method based on failure wave-recording.This method utilizes the gps clock of wave recording device to carry out the integral point startup; Draw positive sequence voltage, the electric current at circuit two ends; And be kept at respectively in the wave recording device at two ends with record ripple document form; Central dispatching computer reads two ends positive sequence voltage, current value and residual voltage, current value then, measures the positive order parameter and the Zero sequence parameter of circuit.This invention can make wave recording device be used for power transmission line parameter online measurement, and is asynchronous when remedying the positive order parameter of existing on-line measurement measurement device, do not have the defective of zero sequence power supply when measuring Zero sequence parameter, but but is too dependent on wave recording device, and certain limitation is arranged.

One Chinese patent application 200810079455 discloses a kind of measurement method for positive sequence parameter of high-voltage transmission line.This invention is used single-phase experiment power supply to treat the survey line road and is applied positive phase voltage, reverse voltage; The voltage, electric current, the magnitude of power that utilize the anti-phase fore-and-aft survey to obtain; Combined circuit applies the interference voltage that records before the voltage, through calculating the influence that excludes interference voltage, obtains alternate impedance; Again other two is measured its alternate impedance respectively mutually, after calculating, obtain the positive order parameter of ultra-high-tension power transmission line.This invention can particularly under the situation that the three-phase interference voltage has nothing in common with each other, accurately measure the positive order parameter of ultra-high-tension power transmission line under strong electromagnetic interference environment, but the normal operation that applies circuit of single-phase experiment power supply can exert an influence.

Summary of the invention

The objective of the invention is for overcoming the deficiency of above-mentioned prior art; Provide a kind of transmission line of electricity lumped parameter online definite method based on the synchronous time domain signal; The transmission line of electricity lumped parameter and the error between the actual parameter that calculate through this method are very little, have very high precision, and the computational accuracy of this method do not receive the influence of decaying dc, attenuates high frequency signals; It is very short to calculate the desired data window, has response speed faster.

For realizing above-mentioned purpose, the present invention adopts following technical proposals:

The online definite method of a kind of transmission line of electricity lumped parameter based on the synchronous time domain signal may further comprise the steps:

The first step: with the transmission line of electricity equivalence is π type lumped parameter model, lists the differential equation of pi-network according to Kirchhoff's first law KCL and Kirchhoff's second law KVL;

Second step: differential equation abbreviation is merged, obtain differential equation group about transmission line of electricity lumped parameter resistance R, inductance L, capacitor C;

The 3rd step: bring the voltage and current synchronous time domain signal of transmission line of electricity both sides into differential equation group, adopt least square method to find the solution the occurrence that draws line parameter circuit value resistance R, inductance L, capacitor C.

The row write method of the differential equation in the described first step is: be π type equivalent circuit with the transmission line of electricity equivalence at first, write out KCL, the KVL differential equation according to the structure of π type equivalent circuit.

$\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="i"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">i</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="i\; c"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">i</figure-callout>}}_c+{\mathrm{<figure-callout\; id="2"\; label="i\; c"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">i</figure-callout>}}_c+{\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">i</figure-callout>}}_2=\frac{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">C</figure-callout>}}{2}\frac{{\mathrm{du}}_1}{\mathrm{dt}}+\frac{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">C</figure-callout>}}{2}\frac{{\mathrm{du}}_2}{\mathrm{dt}}+i_2\\ u_1-[R(i_1-i_{c1})+L\frac{d(i_1-i_{c1})}{\mathrm{dt}}]={\mathrm{<figure-callout\; id="2"\; label="u"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">u</figure-callout>}}_2\end{array}\right.$

The differential equation group that abbreviation obtains after merging in described second step is:

$\left\{\begin{array}{c}C=2(i_1-i_2)/(\frac{{\mathrm{du}}_1}{\mathrm{dt}}+\frac{{\mathrm{du}}_2}{\mathrm{dt}})\\ u_1-{\mathrm{<figure-callout\; id="2"\; label="u"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">u</figure-callout>}}_2={\mathrm{Ri}}_1-\frac{\mathrm{RC}}{2}\frac{{\mathrm{du}}_1}{\mathrm{dt}}+L\frac{{\mathrm{di}}_1}{\mathrm{dt}}-\frac{\mathrm{LC}}{2}\frac{d^2{u}_1}{{\mathrm{<figure-callout\; id="2"\; label="dt"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">dt</figure-callout>}}^2}\end{array}\right.$

Wherein, u ₁, u ₂, i ₁, i ₂Be respectively voltage, the electric current synchronous time domain signal at transmission line of electricity two ends, i _C1, i _C2For flowing through the electric current time-domain signal of both sides distributed capacitance, resistance R, inductance L, capacitor C are that the transmission line of electricity equivalence is the line parameter circuit value behind the pi-network.

Method for solving in described the 3rd step is: synchronizing voltage and the electric current time-domain signal of gathering the circuit two ends; And time-domain signal asked for first order derivative and second derivative; In the differential equation group in second step of substitution; Adopt least square method solving equation group, obtain the occurrence of line parameter circuit value resistance R, inductance L, capacitor C.

The present invention adopts the synchronous time domain signal that the transmission line of electricity lumped parameter is carried out in line computation, has following advantage with existing similar compared with techniques:

1. time-domain signal refers to time dependent signal, is reacted in the electric system, is exactly the analog quantity sampled value to electric current, voltage signal.These signals only are that electric current, voltage are carried out the signal after time discretization is handled, and need not to calculate link through digital filtering, Fourier transform etc., can greatly simplify computation process, and have calculated response speed faster;

2. can avoid DC component, decay harmonic wave to the influence of computational solution precision based on synchronous time domain calculated signals transmission line of electricity lumped parameter;

3. the transmission line of electricity lumped parameter on-line calculation method that the present invention carried does not receive the influence of circuit running status, can both carry out calculation of parameter under no matter under normal operating condition, still nonserviceabling, and can provide in real time, electrical network parameter accurately.

Description of drawings

Fig. 1 is two ends power system model structural representations;

Fig. 2 is a π type lumped parameter equivalent circuit synoptic diagram;

Fig. 3 is the transmission line parameter figure that calculates under system's normal operating condition;

Fig. 4 is the transmission line parameter figure that calculates under the fault state;

Embodiment

Below in conjunction with accompanying drawing and instance the present invention is further specified.

In order to explain that institute of the present invention extracting method can both accurately carry out line parameter circuit value and confirm under the various running statuses of electric system, designed two kinds of different operation states, be respectively normal operating condition and malfunction.

1. the transmission line parameter under the normal operating condition calculates

In both-end power system model shown in Figure 1, its π type equivalent circuit is as shown in Figure 2.

Among the figure, u ₁, u ₂, i ₁, i ₂Be respectively the synchronous time domain signal of circuit voltage, electric current, i _C1, i _C2For flowing through the electric current time-domain signal of both sides distributed capacitance.It is following to write the differential equation according to Kirchhoff's first law KCL row:

$i_1=i_{\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">c</figure-callout>}1}+i_{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">c</figure-callout>}2}+i_2=\frac{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">C</figure-callout>}}{2}\frac{{\mathrm{du}}_1}{\mathrm{dt}}+\frac{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">C</figure-callout>}}{2}\frac{{\mathrm{du}}_2}{\mathrm{dt}}+i_2$

Abbreviation obtains the expression formula of capacitor C:

$C=\frac{2(i_1-i_2)}{\frac{{\mathrm{du}}_1}{\mathrm{dt}}+\frac{{\mathrm{du}}_2}{\mathrm{dt}}}$

As long as obtain the synchronous time domain signal u of circuit both sides voltage, electric current ₁, u ₂, i ₁, i ₂, and the voltage time-domain signal asked for after the first order derivative, the substitution following formula can obtain the parameter of line distribution capacitance C.

It is following to write the differential equation according to Kirchhoff's second law KVL row to Fig. 2:

$u_1-[R(i_1-i_{c1})+L\frac{d(i_1-i_{c1})}{\mathrm{dt}}]={\mathrm{<figure-callout\; id="2"\; label="u"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">u</figure-callout>}}_2$

Known

with its substitution following formula, finally obtains about the expression formula of line parameter circuit value resistance R, inductance L being:

$u_1-{\mathrm{<figure-callout\; id="2"\; label="u"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">u</figure-callout>}}_2={\mathrm{Ri}}_1-\frac{\mathrm{RC}}{2}\frac{{\mathrm{du}}_1}{\mathrm{dt}}+L\frac{{\mathrm{di}}_1}{\mathrm{dt}}-\frac{\mathrm{LC}}{2}\frac{d^2{u}_1}{{\mathrm{<figure-callout\; id="2"\; label="dt"\; filenames="HDA0000153067710000014.png"\; state="\{\{state\}\}">dt</figure-callout>}}^2}$

Following formula has comprised two unknown numbers; Be respectively resistance R and inductance L; Can adopt many group synchronous time domain signals to find the solution, obtain final resistance R and inductance L parameter value, the transmission line parameter curve of Fig. 3 for calculating under the normal operating condition based on least square method.

2. the transmission line parameter under the malfunction calculates

If fault occurs in F1 point place shown in Figure 1; Fault type is the short circuit of A phase metallic earthing; Calculate the voltage and current time-domain signal that adopts transmission line of electricity both sides under the malfunction, as shown in Figure 4 according to lumped parameter resistance, inductance and capacitance curve that the computing method that the present invention carried obtain.Can know that with Fig. 3 contrast the transmission line parameter value that calculates under two kinds of running statuses is almost equal, shows that computing method that the present invention carries have the advantage that not influenced by the circuit running status, and has higher computational accuracy.

Claims (3)

1. the online definite method of the transmission line of electricity lumped parameter based on the synchronous time domain signal is characterized in that, may further comprise the steps:

The first step: with the transmission line of electricity equivalence is π type lumped parameter model, lists the differential equation of pi-network according to Kirchhoff's first law KCL and Kirchhoff's second law KVL;

Second step: differential equation abbreviation is merged, obtain differential equation group about transmission line of electricity lumped parameter resistance R, inductance L, capacitor C;

The 3rd step: synchronizing voltage and the electric current time-domain signal of gathering the circuit two ends; And time-domain signal asked for first order derivative and second derivative; In the differential equation group in second step of substitution, adopt least square method solving equation group, obtain the occurrence of line parameter circuit value resistance R, inductance L, capacitor C.

2. the online definite method of the transmission line of electricity lumped parameter based on the synchronous time domain signal as claimed in claim 1; It is characterized in that; The row write method of the differential equation in the said first step is: be π type equivalent circuit with the transmission line of electricity equivalence at first, write out KCL, the KVL differential equation according to the structure of π type equivalent circuit;

$\left\{\begin{array}{c}{i}_1=i_{c1}+i_{c2}+i_2=\frac{C}{2}\frac{{\mathrm{du}}_1}{\mathrm{dt}}+\frac{C}{2}\frac{{\mathrm{du}}_2}{\mathrm{dt}}+i_2\\ u_1-[R(i_1-i_{c1})+L\frac{d(i_1-i_{c1})}{\mathrm{dt}}]=u_2\end{array}\right.$

Wherein, u ₁, u ₂, i ₁, i ₂Be respectively voltage, the electric current synchronous time domain signal at transmission line of electricity two ends, i _C1, i _C2For flowing through the electric current time-domain signal of both sides distributed capacitance, resistance R, inductance L, capacitor C are that the transmission line of electricity equivalence is the line parameter circuit value behind the pi-network.

3. the online definite method of the transmission line of electricity lumped parameter based on the synchronous time domain signal as claimed in claim 1 is characterized in that, the differential equation group that abbreviation obtains after merging in described second step is:

$\left\{\begin{array}{c}C=2(i_1-i_2)/(\frac{{\mathrm{du}}_1}{\mathrm{dt}}+\frac{{\mathrm{du}}_2}{\mathrm{dt}})\\ u_1-u_2={\mathrm{Ri}}_1-\frac{\mathrm{RC}}{2}\frac{{\mathrm{du}}_1}{\mathrm{dt}}+L\frac{{\mathrm{di}}_1}{\mathrm{dt}}-\frac{\mathrm{LC}}{2}\frac{d^2{u}_1}{{\mathrm{dt}}^2}\end{array}\right.$

Wherein, u ₁, u ₂, i ₁, i ₂Be respectively voltage, the electric current synchronous time domain signal at transmission line of electricity two ends, resistance R, inductance L, capacitor C are that transmission line of electricity equivalence is the line parameter circuit value behind the pi-network.

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