Line parameter identification protection method and system based on two-port network model

Abstract

The invention discloses a line parameter identification protection method based on a two-port network model. The method comprises the steps that an impedance parameter port characteristic equation of the two-port network model is established, and measurement results of voltage and current phasors at protection installation positions on the two sides of the two-port network model are obtained; determining two-port network impedance parameters under the internal fault and the external fault according to the network line parameters; according to the two-port network impedance parameters, constructing a unified identification parameter matrix under an internal fault and an external fault; combining the unified identification parameter matrix with the measurement results of the voltage and current phasors, establishing an impedance network multi-dimensional equation of multiple phasor points, and solving parameters to be identified; and according to the solved to-be-identified parameters and fault identification criteria, internal and external faults are discriminated, and dual-terminal protection is realized. The method has high protection sensitivity in a new energy-containing access power grid, and is high in transition resistance resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power system relay protection, and relates to a line parameter identification protection method and system based on a two-port network model. BACKGROUND

[0002] With the landing of the clean energy strategy in China and the rapid promotion of new energy, direct current transmission and flexible alternating current transmission technologies, the proportion of power electronic devices in the power grid is becoming larger and larger. The fast regulation performance of power electronic devices makes the short-circuit current of alternating current present new fault characteristics such as amplitude limitation, phase angle control and harmonic increase, which brings great uncertainty to traditional power frequency quantity protection, and the sensitivity checking work is complex, which is a difficult problem to be solved in the field of relay protection at present.

[0003] The phase angle difference between the short-circuit current of the new energy power supply and the short-circuit current of the system side may be large, even opposite. For a double weakly fed power supply system, such as a weakly fed system connected to a new energy source and both sides supplied by a converter, it is easy to cause the traditional current differential protection to be insufficient in sensitivity and to refuse to act. SUMMARY

[0004] To solve the problems in the prior art, the application provides a line parameter identification protection method and system based on a two-port network model, which constructs a parameter identification protection scheme not affected by the type of power supply, has high protection sensitivity in a power grid containing new energy access, and has strong transition resistance capacity.

[0005] The application adopts the following technical scheme.

[0006] The application provides a line parameter identification protection method based on a two-port network model, which comprises the following steps: An impedance parameter port characteristic equation of a two-port network model is established, and the measurement results of voltage and current phasors at the protection installation positions on both sides of the two-port network model are obtained; Based on the impedance parameter port characteristic equation and line parameters, two-port network impedance parameters under an in-zone fault and an out-of-zone fault are determined; According to the two-port network impedance parameters, a unified identification parameter matrix under the in-zone fault and the out-of-zone fault is constructed; The unified identification parameter matrix is combined with the measurement results of the voltage and current phasors, an impedance network multi-dimensional equation of multiple phasor points is established, and the to-be-identified parameters are solved; According to the solved to-be-identified parameters and a fault identification criterion, the in-zone fault and the out-of-zone fault are distinguished, and a two-terminal quantity protection is realized.

[0007] Preferably, the impedance parameter port characteristic equation of the two-port network is:

[0008] wherein: V1 is the voltage at port 1; I1 is the current at port 1; Y1 is the input impedance at port 1; Z12 is the transfer impedance between port 1 and port 2; V2 is the voltage at port 2; I2 is the current at port 2; Y2 is the input impedance at port 2; Z21 is the transfer impedance between port 2 and port 1.

[0009] Preferably, the two-port network impedance parameters under the in-zone fault are determined based on the impedance parameter port characteristic equation and the line parameters, comprising: When the in-zone fault occurs, at the fault occurrence position increasing the transition resistance For the metallic or small transition resistance fault, the two-port network impedance parameters under the in-zone fault are:

[0010] For the high resistance fault, the two-port network impedance parameters under the in-zone fault are:

[0011] wherein: Z is the line impedance; C is the line-to-ground capacitance; R is the transition resistance.

[0012] Preferably, the two-port network impedance parameters under the out-zone fault are determined based on the impedance parameter port characteristic equation and the line parameters, comprising: When the out-zone fault occurs, the power transmission line is characterized by two π-type lumped parameter models, and the two-port network impedance parameters under the out-zone fault are:

[0013] wherein: the symbol " / / " represents parallel circuit calculation, Z is the line impedance, C is the line-to-ground capacitance.

[0014] Preferably, according to the two-port network impedance parameters, a unified identification parameter matrix under the in-zone fault and the out-zone fault is constructed:

[0015] wherein: , , and are all to-be-identified parameters.

[0016] Preferably, the unified identification parameter matrix is combined with the measurement results of the voltage and current phasors to establish a multi-dimensional equation of the impedance network of the multi-phasor point and to solve the to-be-identified parameters, wherein the multi-dimensional equation of the impedance network of the multi-phasor point is:

[0017] In the formula, V1x and V1y are the real part and the imaginary part of the voltage phasor of port 1, respectively;

[0018] Preferably, the fault identification criterion is:

[0019] In the formula, X is the reactance low limit value, Y is the reactance high limit value, R is the resistance limit value, N is the number of continuous points, and ε is the relative error threshold value.

[0020] Preferably, X is 3, and Y is 5%.

[0021] Preferably, if the to-be-identified parameters satisfy the fault identification criterion, the fault is an internal fault; otherwise, the fault is an external fault.

[0022] The second aspect of the present application provides a line parameter identification protection system based on a two-port network model, comprising: a data acquisition module configured to establish an impedance parameter port characteristic equation of the two-port network model and to acquire measurement results of voltage and current phasors at two sides of the two-port network model where protections are installed; a parameter determination module configured to determine two-port network impedance parameters under internal faults and external faults based on the impedance parameter port characteristic equation and network model line parameters; a matrix construction module configured to construct a unified identification parameter matrix under internal faults and external faults according to the two-port network impedance parameters; a parameter solving module configured to combine the unified identification parameter matrix with the measurement results of the voltage and current phasors to establish a multi-dimensional equation of the impedance network of the multi-phasor point and to solve the to-be-identified parameters. ​​​​​​​​​​​​​​​The identification protection module is used for identifying the in-zone fault and the out-of-zone fault according to the solved to-be-identified parameter and the fault identification criterion, and realizing the double-terminal quantity protection.

[0023] Compared with the prior art, the beneficial effects of the present application at least include: The present application uses the measurement values of the two-terminal voltage and current of the two-port network to completely describe the electrical parameter information in the two-port network, and is not affected by the power type, has higher protection sensitivity in the power grid with new energy access, and has stronger transition resistance resistance. The fault identification criterion constructed by the present application is not affected by the backside power, and therefore has natural advantages in the high proportion of new energy access scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a method flow diagram in the embodiment of the present application; Figure 2 is a two-port circuit schematic diagram of the out-of-zone fault in the embodiment of the present application; Figure 3 is a two-port circuit schematic diagram of the in-zone fault in the embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described clearly and completely below in combination with the drawings in the embodiment of the present application. The embodiments described in the present application are only a part of the embodiments of the present application, not all the embodiments. Based on the spirit of the present application, other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0026] As Figure 1 shown, the embodiment 1 of the present application provides a line parameter identification protection method based on a two-port network model, comprising the following steps: S1: establishing an impedance parameter port characteristic equation of the two-port network model and obtaining the measurement results of the voltage and current phase quantities at the two sides of the protection installation of the two-port network model; S2: determining the self-impedance and mutual-impedance information of the two-port network under different working conditions such as in-zone and out-of-zone based on the impedance parameter port characteristic equation and in combination with the known line parameters (such as , , ); Further preferably, the impedance parameter port characteristic equation of the passive linear two-port network is:

[0027] In the formula, is the voltage of port 1; is the current of port 1; is the input impedance of port 1; is the transfer impedance between port 1 and port 2; is the voltage of port 2; is the current of port 2; is the input impedance of port 2; is the transfer impedance between port 2 and port 1.

[0028] As shown in Figure 2 , when the external fault occurs, the transmission line is represented by two π-type lumped parameter models, and the impedance parameters of the external fault are:

[0029] In the formula, the symbol " / / " represents the parallel circuit calculation, is the line impedance, is the line-to-ground capacitance.

[0030] As shown in Figure 3 , when the internal fault occurs, the transition resistance is added at the fault occurrence position (the distance from the set port to the fault) , and the impedance parameters of the internal fault are:

[0031] In the formula, the coefficients , , , and the like are expressed as:

[0032] For the metallic or small transition resistance (<100Ω) fault, the impedance parameters of the internal fault can be simplified as:

[0033] For the high resistance (>100Ω) fault, the impedance parameters of the internal fault can be simplified as:

[0034] In the formula, is the input impedance of port 1; is the transfer impedance between port 1 and port 2; is the input impedance of port 2; is the transfer impedance between port 2 and port 1; is the line impedance; is the line-to-ground capacitance; is the transition resistance.

[0035] S3: According to the impedance parameters of the intra-zone and extra-zone faults calculated in S2, a unified identification parameter matrix under intra-zone and extra-zone faults can be constructed; Further preferably, through analyzing the impedance parameter equations of the extra-zone fault, the intra-zone metallic or small transition resistance fault, and the intra-zone high resistance fault, a unified identification parameter matrix under intra-zone and extra-zone faults can be constructed:

[0036] In the formula, , , and are parameters to be solved, representing the resistance and capacitive reactance of the fault impedance. In this embodiment, the parameter matrix accurately conforms to the self / mutual impedance characteristics of the extra-zone fault and the high resistance fault, and approximately conforms to the self / mutual impedance characteristics of the metallic or small transition resistance fault.

[0037] S4: The unified identification parameter matrix of the intra-zone and extra-zone fault impedance parameters constructed in S3 is combined with the impedance parameter port characteristic equation of the two-port network and the measurement results, and a multi-dimensional equation of the impedance network of multiple phasor points can be established for solving the identification parameters to be solved; Further preferably, in combination with the unified identification parameter matrix of the intra-zone and extra-zone fault impedance parameters and the impedance parameter port characteristic equation of the two-port network, the solving expression of the parameters to be solved , , and is:

[0038] In the formula, is the real part and the imaginary part of the voltage phasor of port 1; is the real part and the imaginary part of the current phasor of port 1; is the real part and the imaginary part of the voltage phasor of port 2; is the real part and the imaginary part of the current phasor of port 2; r and x represent the real part and the imaginary part of the phasor, respectively.

[0039] S5: According to the identification parameters to be solved and the fault identification criterion, the intra-zone and extra-zone faults are distinguished, and the two-terminal quantity protection is realized; Further preferably, the identification parameter characteristics under different fault conditions are summarized, and the fault identification criterion is constructed:

[0040] In the formula, is the low fixed value of the reactance, is the high fixed value of the reactance, is the fixed value of the resistance, is the number of continuous points, is a relative error threshold. Preferably, is 3, is 5%.

[0041] The low fixed value reactance criterion should deal with non-high resistance faults in the area, and is a fast acting section; the high fixed value impedance criterion solves high resistance faults in the area, and is a slow section; the relative error criterion mainly prevents transient overreach misoperation when the fault is metallic.

[0042] The to-be-identified parameter is solved by S4, and is substituted into the constructed fault identification criterion, so as to identify the faults in the area and outside the area, and realize the double-terminal quantity protection.

[0043] Embodiment 2 of the present application provides a line parameter identification protection system based on a two-port network model, comprising: A data acquisition module is configured to establish an impedance parameter port characteristic equation of the two-port network model, and acquire measurement results of voltage and current phasors at both sides of a protection installation of the two-port network model; A parameter determination module is configured to determine two-port network impedance parameters under faults in the area and outside the area based on the impedance parameter port characteristic equation and network model line parameters; A matrix construction module is configured to construct a unified identification parameter matrix under faults in the area and outside the area according to the two-port network impedance parameters; A parameter solving module is configured to combine the unified identification parameter matrix with the measurement results of the voltage and current phasors, establish a multi-dimensional equation of an impedance network of a multi-phase point, and solve a to-be-identified parameter; An identification protection module is configured to identify faults in the area and outside the area according to the solved to-be-identified parameter and a fault identification criterion, and realize double-terminal quantity protection.

[0044] Compared with the prior art, the present application has at least the following beneficial effects: The present application uses the measurement values of the two-terminal voltage and current of the two-port network to completely describe the electrical parameter information in the two-port network, and is not affected by the type of power supply, has high protection sensitivity in a power grid with new energy access, and has strong transition resistance resistance. The fault identification criterion constructed by the present application is not affected by the backside power supply, and therefore has natural advantages in the high proportion of new energy access scenarios.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit them, and although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced, without departing from the spirit and scope of the present application, any modification or equivalent replacement thereof should be covered within the protection scope of the claims of the present application.

Claims

1. A line parameter identification protection method based on a two-port network model, characterized in that, The method comprises the following steps: establishing an impedance parameter port characteristic equation of a two-port network model and obtaining measurement results of voltage and current phasors at both sides of the two-port network model where protections are installed; determining two-port network impedance parameters under an in-zone fault and an out-zone fault based on the impedance parameter port characteristic equation and line parameters; constructing a unified identification parameter matrix under the in-zone fault and the out-zone fault according to the two-port network impedance parameters; combining the unified identification parameter matrix with the measurement results of the voltage and current phasors, establishing an impedance network multi-dimensional equation of multi-phase points, and solving to-be-identified parameters; distinguishing between the in-zone fault and the out-zone fault according to the to-be-identified parameters and a fault identification criterion, and realizing two-terminal quantity protection.

2. The line parameter identification protection method based on the two-port network model according to claim 1, wherein the impedance parameter port characteristic equation of the two-port network is:

3. The line parameter identification protection method based on the two-port network model according to claim 2, wherein the two-port network impedance parameters under the in-zone fault are determined based on the impedance parameter port characteristic equation and line parameters, and the determination comprises the following steps: where: V1 is the voltage at port 1 ; I1 is the current at port 1 ; Z1 is the input impedance at port 1 ; Y1 is the transfer admittance between port 1 and port 2; V2 is the voltage at port 2; I2 is the current at port 2; Z2 is the input impedance at port 2; Y2 is the transfer admittance between port 2 and port 1. for a high-resistance fault, the two-port network impedance parameters under the in-zone fault are:

4. The line parameter identification protection method based on the two-port network model according to claim 2, wherein the two-port network impedance parameters under the out-zone fault are determined based on the impedance parameter port characteristic equation and line parameters, and the determination comprises the following steps: In case of a fault within the zone, at the fault occurrence Increasing the transition resistance For metallic or small transition resistance faults, the two-port network impedance parameters for the fault within the zone are: when the out-zone fault occurs, the power transmission line is represented by two π-type lumped parameter models, and the two-port network impedance parameters under the out-zone fault are: wherein: is the line impedance; is the line-to-ground capacitance; is the transition resistance.

5. The line parameter identification protection method based on the two-port network model according to any one of claims 2-4, wherein the unified identification parameter matrix under the in-zone fault and the out-zone fault is constructed according to the two-port network impedance parameters:

6. The line parameter identification protection method based on the two-port network model according to claim 5, wherein the impedance network multi-dimensional equation of multi-phase points is established by combining the unified identification parameter matrix with the measurement results of the voltage and current phasors, and the impedance network multi-dimensional equation of multi-phase points is:

7. The line parameter identification protection method based on the two-port network model according to claim 1, wherein the fault identification criterion is: wherein the symbol " / / " represents parallel circuit calculation, Zo is the line impedance, Co is the line-to-ground capacitance.

8. The line parameter identification protection method based on the two-port network model according to claim 7, wherein the fault identification criterion is:

9. The line parameter identification protection method based on the two-port network model according to claim 1, wherein the in-zone fault and the out-zone fault are distinguished according to the to-be-identified parameters and the fault identification criterion, and the distinguishing comprises the following steps: In the formulae: , , and are parameters to be identified. if the to-be-identified parameters satisfy the fault identification criterion, the fault is an in-zone fault, otherwise, the fault is an out-zone fault. The system comprises: wherein: V1R and V1I are the real and imaginary parts of the voltage phasor at port 1 ; I1R and I1I are the real and imaginary parts of the current phasor at port 1 ; V2R and V2I are the real and imaginary parts of the voltage phasor at port 2; I2R and I2I are the real and imaginary parts of the current phasor at port 2. a data acquisition module configured to establish an impedance parameter port characteristic equation of a two-port network model and obtain measurement results of voltage and current phasors at both sides of the two-port network model where protections are installed; ​ In the formula: is a low reactance fixed value, is a high reactance fixed value, is a resistance fixed value, , , and are to-be-identified parameters solved, is the number of continuous points, is a relative error threshold. ​ is 3, is 5%. ​ ​ ​ 10. A line parameter identification protection system based on a two-port network model for implementing the method of any one of claims 1 to 9, characterized by ​ ​ A parameter determination module is configured to determine two-port network impedance parameters under in-zone fault and out-zone fault based on the impedance parameter port characteristic equation and network model line parameters; A matrix construction module is configured to construct a unified identification parameter matrix under in-zone fault and out-zone fault based on the two-port network impedance parameters; A parameter solution module is configured to combine the unified identification parameter matrix with the measurement results of the voltage and current phasors, establish a multi-dimensional equation of the impedance network of multiple phasor points and solve the to-be-identified parameters; An identification protection module is configured to identify in-zone fault and out-zone fault based on the solved to-be-identified parameters and fault identification criteria, and realize double-terminal quantity protection.

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