Fault phase selection method and system for power system based on electrical quantity vector model

Abstract

The present invention discloses a method and system for fault phase selection of a power system based on an electrical quantity vector model, the method comprising: calculating the three-phase load current component on the power supply route according to the circuit matrix relationship of the three-phase electrical quantity of the power supply route; collecting the three-phase total current flowing through the relay protection device, subtracting the three-phase load current component from the three-phase total current, and obtaining the three-phase fault current component flowing into the fault point in the three-phase total current; converting the three-phase fault current component into a vector parameter, the vector parameter including a forward rotating vector, a reverse rotating vector and a pulsation vector; determining the fault phase under the current vector parameter according to the logical relationship between different fault phases and the vector parameter. The method does not make any simplification or assumption on the electrical quantity after the fault, and can be applied to the fault phase selection problem under the condition of time-varying amplitude and frequency, and the phase selection result is not affected by the short circuit / grounding resistance at the fault point.

Description

Technical Field

[0001] The present invention belongs to the technical field of relay protection of electric power systems, and more specifically, relates to a method and system for selecting fault phases in an electric power system based on an electrical quantity vector model. Background Art

[0002] As the proportion of electronic power sources such as wind power and photovoltaic power in the power system gradually increases, many large-scale electronic power source disconnection accidents caused by asymmetric grid faults have occurred at home and abroad, undermining the safe and stable operation of the power system. Relay protection is the first line of defense for the stable operation of the power system. When an asymmetric fault occurs in the power system, the relay protection device should be able to correctly identify the fault phase and promptly remove the fault phase after determining that a fault has occurred in the protection area to ensure the safe and stable operation of the power system.

[0003] The current typical fault phase selection method is based on sequence component phase selection. This method calculates the phase difference α between the zero-sequence current phasor and the negative-sequence current phasor at the installation location of the protection device, and the phase difference β between the positive-sequence current phasor change and the negative-sequence current phasor, and combines the phase selection results corresponding to the phase intervals of α and β to determine the fault phase. The theoretical basis of this method is the symmetrical component method, and its mathematical basis is that the amplitude and frequency of the electrical quantity in the system are constant. However, during an asymmetric fault in a power system dominated by power electronic power supplies, the amplitude and frequency of the potential in the power electronic power supply are no longer constant due to the transient characteristics of the power electronic power supply, and the amplitude and frequency of the electrical quantity in the system are no longer constant. Therefore, the phase selection method based on sequence components is no longer applicable to the phase selection problem after an asymmetric fault occurs in a power system dominated by power electronic power supplies. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a power system fault phase selection method and system based on an electrical quantity vector model, which aims to solve the technical problem that it is difficult to perform fault phase selection after an asymmetric fault occurs in a power system dominated by power electronic power sources.

[0005] To achieve the above object, according to one aspect of the present invention, a method for selecting a fault phase in a power system based on an electrical quantity vector model is provided, comprising:

[0006] Determine a power supply route for supplying power to the fault point, the power supply route being provided with a relay protection device, and calculate the three-phase load current components on the power supply route according to the circuit matrix relationship of the three-phase electrical quantities of the power supply route;

[0007] Collecting a three-phase total current flowing through the relay protection device, and subtracting the three-phase load current component from the three-phase total current to obtain a three-phase fault current component flowing into the fault point in the three-phase total current;

[0008] Converting the three-phase fault current components into vector parameters, wherein the vector parameters include a forward rotating vector, a reverse rotating vector and a pulsation vector, wherein the imaginary axis component of the pulsation vector is zero and the real axis component is equal to the zero axis component obtained by Clarke transformation of the three-phase fault current components;

[0009] According to the logical relationship between different fault phases and vector parameters, the fault phase under the current vector parameters is determined.

[0010] In one embodiment, the power supply route has a voltage source t1 and a voltage source t2 located on both sides of the fault point, and the relay protection device is located between the voltage source t1 and the fault point;

[0011] The circuit matrix relationship of the three-phase electrical quantities of the power supply route is:

[0012]

[0013] Among them, u t1a ,u t1b ,u t1c Respectively represent the instantaneous values ​​of the A-phase, B-phase, and C-phase voltages of the voltage source t1; u t2a ,u t2b ,u t2c Respectively represent the instantaneous values ​​of the A-phase, B-phase, and C-phase voltages of the voltage source t2; i t1La ,i t1Lb ,i t1Lc They represent the instantaneous values ​​of phase A, phase B, and phase C of the load current component flowing from the voltage source t1 to the voltage source t2, respectively. s , R m , L s , L m They represent the self-resistance, mutual resistance, self-inductance and mutual inductance of the power supply line between voltage source t1 and voltage source t2 respectively, and p is a differential operator, which represents

[0014] The three-phase fault current components are:

[0015]

[0016] Among them, i t1Fa ,i t1Fb ,i t1Fc They represent the instantaneous values ​​of phase A, phase B, and phase C of the three-phase fault current components flowing from voltage source t1 to the fault point, respectively. t1a ,i t1b ,i t1c They respectively represent the instantaneous values ​​of phase A, phase B and phase C in the three-phase total current flowing through the relay protection device.

[0017] In one embodiment, the three-phase fault current components are converted into vector parameters with any one of phase A, phase B, and phase C as the reference phase using the following transformation formula:

[0018] Among them, the positive rotation vector of phase A is taken as the reference phase. Reverse Rotation Vector and pulse vector The vector transformation formula is

[0019]

[0020] In the formula, i t1Fa ,i t1Fb ,i t1Fc Indicates the instantaneous values ​​of phase A, phase B, and phase C in the three-phase fault current components flowing to the fault point;

[0021] The positive rotation vector with phase B as the reference phase Reverse Rotation Vector and pulse vector The vector transformation formula is

[0022]

[0023] Positive rotation vector with C phase as the reference phase Reverse Rotation Vector and pulse vector The vector transformation formula is

[0024]

[0025] In one embodiment, the logical relationship between different fault phases and vector parameters includes one or more of the following:

[0026] Ground fault logic: When The corresponding fault type is non-ground fault; when The corresponding fault type is ground fault; among them, is the pulse vector;

[0027] Two-phase short circuit fault logic: When And I t1bc ,I t1ac ,I t1ab If any of the items is 0, the corresponding fault type is a two-phase short circuit fault; t1bc ,I t1ac ,I t1ab is the fault index of two-phase short circuit, and the calculation formula is:

[0028]

[0029]

[0030]

[0031] In the formula, are the positive rotation vectors with phase A, phase B and phase C as the reference phase, They are reverse rotating vectors with phase A, phase B and phase C as reference phases respectively;

[0032] Three-phase short circuit fault logic: And I t1bc ,I t1ac I t1ab When both are not 0, the corresponding fault type is a three-phase short circuit fault;

[0033] Single-phase ground fault logic: When And I t1ag ,I t1bg ,I t1cg If any of the items is 0, the corresponding fault type is a single-phase grounding fault. t1ag ,I t1bg ,I t1cg is the fault index of single-phase grounding, and the calculation formula is:

[0034]

[0035]

[0036]

[0037] In the formula, are the pulse vectors with phase A, phase B and phase C as reference phases respectively;

[0038] Two-phase short circuit ground fault logic: When I t1ag ,I t1bg ,I t1cg Both are not 0 and I t1bcg ,I t1acg ,I t1abg If any of the items is 0, the corresponding fault type is a two-phase short-circuit grounding fault;

[0039] Among them, I t1bcg ,I t1acg ,I t1abg It is the fault index of two-phase short circuit grounding; calculation formula

[0040]

[0041]

[0042]

[0043] In one embodiment,

[0044] In the two-phase short-circuit fault logic, I t1bc ,I t1ac ,I t1ab They are the fault indicators of BC short circuit, AC short circuit and AB short circuit respectively.

[0045] when When the I t1bc ,I t1ac ,I t1ab If any of the items is 0, the corresponding fault type is a two-phase short circuit fault, including:

[0046] When I t1bc =0, the corresponding fault type is BC short circuit fault;

[0047] When I t1ac =0, the corresponding fault type is AC short circuit fault;

[0048] When I t1ab =0, the corresponding fault type is AB short circuit fault.

[0049] In one embodiment,

[0050] In the single-phase ground fault logic, I t1ag ,I t1bg ,I t1cg They are the fault indicators of phase A grounding, phase B grounding and phase C grounding respectively;

[0051] when When the I t1ag ,I t1bg ,I t1cg If any of the items is 0, the corresponding fault type is a single-phase grounding fault, including:

[0052] When I t1ag =0, the corresponding fault type is phase A grounding fault;

[0053] When I t1bg =0, the corresponding fault type is phase B grounding fault;

[0054] When I t1cg =0, the corresponding fault type is phase C ground fault.

[0055] In one embodiment,

[0056] In the two-phase short-circuit ground fault logic, I t1bcg ,I t1acg ,I t1abg They are the fault indicators of BC short circuit to ground, AC short circuit to ground, and AB short circuit to ground;

[0057] when I t1ag ,I t1bg ,I t1cg When both are not 0, the I t1bcg ,I t1acg ,I t1abg If any of the items is 0, the corresponding fault type is a two-phase short-circuit grounding fault, including:

[0058] When I t1bcg =0, the corresponding fault type is BC short circuit grounding fault;

[0059] When I t1acg =0, the corresponding fault type is AC short circuit grounding fault;

[0060] When I t1abg =0, the corresponding fault type is AB short circuit grounding fault.

[0061] In one embodiment, determining the fault phase under the current vector parameters according to the logical relationship between different fault phases and vector parameters includes:

[0062] Step S41: Determination Is it 0? If yes, go to step S42; if no, go to step S44;

[0063] Step S42: Determination I t1bc ,I t1ac ,I t1ab Is there an indicator of 0 in the logic? If not, the fault type is determined to be a three-phase short circuit fault logic; if so, it is determined to be a two-phase short circuit fault and step S43 is executed;

[0064] Step S43: Identification I t1bc ,I t1ac ,I t1ab The indicator is 0, when I t1bc =0, the fault type is determined to be a BC short circuit fault; when I t1ac =0, it is determined to be an AC short circuit fault; when I t1ab =0, it is judged as AB short circuit fault;

[0065] Step S44: Determination I t1ag ,I t1bg ,I t1cg Whether there is an indicator of 0 in the logic, if not, the fault type is determined to be a two-phase short circuit grounding fault and the process jumps to step S45; if so, it is determined to be a single-phase grounding fault and the process jumps to step S46;

[0066] Step S45: Identification I t1bcg ,I t1acg,I t1abg The indicator is 0, when I t1bcg =0, the fault type is determined to be a BC short-circuit grounding fault; when I t1acg =0, it is determined to be an AC short circuit grounding fault; when I t1abg =0, it is determined to be an AB short-circuit grounding fault;

[0067] Step S46: Identification I t1ag ,I t1bg ,I t1cg The indicator is 0, when I t1ag =0, the corresponding fault type is phase A ground fault; when I t1bg =0, the corresponding fault type is phase B grounding fault; when I t1cg =0, the corresponding fault type is phase C ground fault.

[0068] In one embodiment, the voltage source t1 and the voltage source t2 are both equivalent voltage sources.

[0069] According to another aspect of the present invention, there is provided a power system fault phase selection system based on an electrical quantity vector model, characterized in that it comprises:

[0070] A three-phase load current component calculation unit, used to calculate the three-phase load current components on the power supply route according to the circuit matrix relationship of the three-phase electrical quantities of the power supply route supplying power to the fault point when a fault occurs;

[0071] A three-phase fault current component calculation unit is used to obtain the collected three-phase total current flowing through the relay protection device, and to subtract the three-phase load current component from the three-phase total current to obtain the three-phase fault current component flowing into the fault point in the three-phase total current;

[0072] A vector conversion unit, used for converting the three-phase fault current into vector parameters, wherein the vector parameters include a forward rotating vector, a reverse rotating vector and a pulsation vector, wherein the imaginary axis component of the pulsation vector is zero and the real axis component is equal to the zero axis component obtained by Clarke transformation of the three-phase fault current;

[0073] The phase selection unit is used to determine the fault phase under the current vector parameters according to the logical relationship between different fault phases and vector parameters.

[0074] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0075] After an asymmetric fault occurs in a power system dominated by power electronic power sources, the electrical quantities in the system show time-varying characteristics of amplitude and frequency, which makes the phase selection method based on sequence components impossible to perform. This is a technical problem that needs to be solved by the current power system relay protection. In the present invention, fault phase selection of the power system is realized through a vector model. The fault current component flowing through the relay protection device is first calculated and converted into a forward rotating vector, a reverse rotating vector and a pulsation vector. According to the logical relationship between the vector parameters and different fault types, the fault phase under the current vector parameters is quickly determined, wherein the logical relationship between the vector parameters and different fault types is obtained in advance through the analysis of multiple groups of measurement data. This method does not make any simplifications or assumptions on the electrical quantities after the fault, and can be applied to the fault phase selection problem under the condition of time-varying amplitude and frequency, and the phase selection result is not affected by the size of the short circuit / grounding resistance at the fault point. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 A flowchart of the steps of a method for selecting a fault phase in a power system based on an electrical quantity vector model according to an embodiment;

[0077] Figure 2 A schematic diagram of a power system network topology according to an embodiment;

[0078] Figure 3 A fault phase selection logic diagram of an embodiment;

[0079] Figure 4 The schematic diagram of the framework of a power system fault phase selection system based on an electrical quantity vector model according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0080] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0081] like Figure 1 The figure is a flowchart of the steps of a method for selecting a phase for a power system fault based on an electrical quantity vector model according to an embodiment of the present invention. The method for selecting a phase includes:

[0082] Step S100: determining a power supply route for supplying power to the fault point, wherein a relay protection device is arranged on the power supply route, and calculating the three-phase load current components on the power supply route according to the circuit matrix relationship of the three-phase electrical quantities of the power supply route.

[0083] Figure 2 A schematic diagram of a power system network topology provided in an embodiment of the present invention, Figure 2Where f represents the fault point, and the power supply route for supplying power to the fault point is determined. The power supply route can be a section of the power supply route in the entire power system, and the two ends of the power supply route can be equivalent to two voltage sources with time-varying amplitude and frequency, such as Figure 2 As shown; t1 (t) represents the three-phase voltage of the amplitude-frequency time-varying voltage source t1 in the form of instantaneous value, which is a 3×1 matrix; u t2 (t) represents the three-phase voltage of the amplitude-frequency time-varying voltage source t2 in the form of instantaneous value, which is a 3×1 matrix; R 1s +L 1s p represents the self-resistance operator of the line between the voltage source t1 and the fault point, R 1m +L 1m p represents the mutual resistance operator of the line between the voltage source t1 and the fault point; R 2s +L 2s p represents the self-resistance operator of the line between the voltage source t2 and the fault point, R 2m +L 2m p represents the mutual resistance operator of the line between the voltage source t2 and the fault point; i t1 (t) represents the instantaneous value of the three-phase current on the line between the voltage source t1 and the fault point, that is, the instantaneous value of the three-phase current measured at t1, which is a 3×1 matrix; i t2 (t) represents the instantaneous value of the three-phase current on the line between the voltage source t2 and the fault point, that is, the instantaneous value of the three-phase current measured at t2, which is a 3×1 matrix; u f (t) represents the instantaneous value of the three-phase voltage at the fault point, which is a 3×1 matrix; i f (t) represents the instantaneous value of the three-phase current on the fault branch at the fault point, which is a 3×1 matrix. p is a differential operator, which represents

[0084] According to the circuit matrix relationship of the three-phase electrical quantities of the power supply route, that is, according to the three-phase voltages on both sides of the power supply route and the line parameters, the three-phase load current components on the power supply route are calculated. Specifically, according to Figure 2 The network topology is shown in Figure 1, and the relationship between the load current component and the voltage on both sides of the line is written out. The formula is shown in formula (1):

[0085]

[0086] In the above formula, u t1a ,u t1b ,u t1c Respectively represent the instantaneous values ​​of the voltages of phase A, phase B, and phase C of the amplitude-frequency time-varying voltage source t1; u t2a ,u t2b ,u t2c Respectively represent the instantaneous values ​​of the voltages of phase A, phase B, and phase C of the amplitude-frequency time-varying voltage source t2; it1La ,i t1Lb ,i t1Lc Respectively represent the instantaneous values ​​of the load current components A, B, and C from the voltage source t1 to the voltage source t2; R s +L s p represents the self-resistance operator of the line between voltage source t1 and voltage source t2, which is the sum of the self-resistance operator of the line between voltage source t1 and the fault point and the self-resistance operator of the line between voltage source t2 and the fault point, satisfying the relationship shown in formula (2); R m +L m p represents the mutual resistance operator of the line between voltage source t1 and voltage source t2, which is the sum of the mutual resistance operator of the line between voltage source t1 and the fault point and the mutual resistance operator of the line between voltage source t2 and the fault point, satisfying the relationship shown in formula (3);

[0087] R s +L s p=(R 1s +R 2s )+(L 1s +L 2s )p (2)

[0088] R m +L m p=(R 1m +R 2m )+(L 1m +L 2m )p (3)

[0089] Step S200: Collect the three-phase total current flowing through the relay protection device, and subtract the three-phase load current component from the three-phase total current to obtain the three-phase fault current component flowing into the fault point in the three-phase total current.

[0090] like Figure 2 As shown, t1 (t) is the instantaneous value of the three-phase current on the line between the voltage source t1 and the fault point, that is, the total three-phase current flowing through the relay protection device, which can be directly collected. This current is divided into two parts, such as Figure 1 Part of it is the three-phase load current component flowing to the opposite voltage source t2, and the other part is the fault current component flowing to the fault branch. In this scheme, it is necessary to solve the fault current component at the relay protection device. According to the superposition principle, the three-phase fault current component is calculated as follows:

[0091]

[0092] In the above formula, i t1Fa ,i t1Fb ,i t1FcThey respectively represent the calculated instantaneous values ​​of the fault current components of phase A, phase B, and phase C flowing from the voltage source t1 to the fault point.

[0093] Step S300: converting three-phase fault current components into vector parameters, where the vector parameters include a forward rotating vector, a reverse rotating vector and a pulsation vector.

[0094] The three-phase instantaneous electrical quantity can be transformed into α-axis component, β-axis component and zero-axis component through Clarke transformation.

[0095] The complex plane formed by the α axis as the real axis and the β axis as the imaginary axis is defined as the first complex plane. Both the positive rotating vector and the reverse rotating vector are on the first complex plane, and the rotation direction of the reverse rotating vector is always opposite to that of the positive rotating vector. The α′ axis and the β′ axis are taken to form the second complex plane, and the α′ axis coincides with the zero axis. Its zero axis component can be regarded as an AC signal whose real axis is not 0 and whose imaginary axis is always 0. This AC signal is a vector pulsating on the real axis of the second complex plane, which is called a pulse vector. That is, the real axis component of the pulse vector is equal to the zero axis component obtained by Clarke transformation of the three-phase instantaneous electrical quantity, and its imaginary axis component is 0. By transforming the three-phase electrical quantity into the above vector parameters and analyzing the fault characteristics through vectors, without any simplification or assumption of the electrical quantity after the fault, it can be applied to the fault phase selection problem under the condition of time-varying amplitude and frequency, and the phase selection result is not affected by the short circuit / grounding resistance at the fault point.

[0096] Among them, the transformation of electrical quantities and vectors can be performed through the transformation matrix, and the transformation matrix is:

[0097]

[0098] Specifically, the electrical quantity is transformed into a vector to obtain vector parameters based on different reference phases.

[0099] Among them, the positive rotation vector of phase A is taken as the reference phase. Reverse Rotation Vector and pulse vector The vector transformation formula is

[0100]

[0101] The positive rotation vector with phase B as the reference phase Reverse Rotation Vector and pulse vector The vector transformation formula is

[0102]

[0103] Positive rotation vector with C phase as the reference phase Reverse Rotation Vector and pulse vector The vector transformation formula is

[0104]

[0105] Step S400: Determine the fault phase under the current vector parameters according to the logical relationship between different fault phases and vector parameters.

[0106] The logical relationship between different fault phases and vector parameters is determined in advance through analysis. Therefore, after obtaining the value of the vector parameter through the above steps, the corresponding fault phase can be determined by judging which logical relationship the vector parameter satisfies.

[0107] Specifically, the fault phase may include a two-phase short circuit fault, a three-phase short circuit fault, a single-phase grounding fault, and a two-phase short circuit grounding fault. For these faults, the research and development team has analyzed and obtained multiple fault indicators for fault judgment.

[0108] Among them, the ground fault indicator is the pulse vector Can be Any one of .

[0109] The single-phase grounding fault indicators are:

[0110]

[0111] The two-phase short-circuit grounding fault indicators are:

[0112]

[0113] Among them, the real() function means taking the real part of the complex number.

[0114] The two-phase short-circuit fault indicators are:

[0115]

[0116] Based on the above fault indicators, the fault logic analyzed specifically includes:

[0117] Ground fault logic: When The corresponding fault type is non-ground fault; when The corresponding fault type is ground fault.

[0118] Two-phase short circuit fault logic: When And I t1bc ,I t1ac ,I t1ab If any of the items is 0, the corresponding fault type is a two-phase short circuit fault.

[0119] When I t1bc=0, the corresponding fault type is BC short circuit fault;

[0120] When I t1ac =0, the corresponding fault type is AC short circuit fault;

[0121] When I t1ab =0, the corresponding fault type is AB short circuit fault.

[0122] Three-phase short circuit fault logic: And I t1bc ,I t1ac I t1ab When both are not 0, the corresponding fault type is a three-phase short circuit fault.

[0123] Single-phase ground fault logic: When And I t1ag ,I t1bg ,I t1cg If any of the items is 0, the corresponding fault type is a single-phase grounding fault.

[0124] When I t1ag =0, the corresponding fault type is phase A grounding fault;

[0125] When I t1bg =0, the corresponding fault type is phase B grounding fault;

[0126] When I t1cg =0, the corresponding fault type is phase C ground fault.

[0127] Two-phase short circuit ground fault logic: When I t1ag ,I t1bg ,I t1cg Both are not 0 and I t1bcg ,I t1acg ,I t1abg If any of the items is 0, the corresponding fault type is a two-phase short-circuit grounding fault.

[0128] When I t1bcg =0, the corresponding fault type is BC short circuit grounding fault;

[0129] When I t1acg =0, the corresponding fault type is AC short circuit grounding fault;

[0130] When I t1abg =0, the corresponding fault type is AB short circuit grounding fault.

[0131] Based on the above fault logic, such as Figure 3 As shown, the following process can be adopted for specific operation:

[0132] First, determine the pulsating current vector Whether it is 0.

[0133] like If it is 0, a non-ground fault occurs in the system; on this basis, the two-phase short-circuit fault index I is judged. t1bc ,I t1ac ,I t1ab Is there a situation where it is always 0? If I t1bc is 0, then the system has a BC two-phase short circuit fault. If I t1ac is 0, then the system has an AC two-phase short circuit fault. If I t1ab If the two-phase short-circuit fault indicators are not 0, a three-phase short-circuit fault occurs in the system.

[0134] like If it is not 0, a ground fault occurs in the system; on this basis, the single-phase ground fault index I is judged. t1ag ,I t1bg ,I t1cg Is there a situation where it is always 0? If I t1ag If I t1bg is 0, then the system has a phase B ground fault. If I t1cg If the single-phase grounding fault index is not 0, a two-phase short-circuit grounding fault occurs in the system. t1bcg is 0, then the system has a BC two-phase short circuit grounding fault. If I t1acg is 0, then the system has an AC two-phase short circuit grounding fault. If I t1abg If it is 0, a two-phase AB short-circuit grounding fault occurs in the system.

[0135] After completing the fault phase selection, the relay protection device can be controlled to perform corresponding relay protection operations.

[0136] Accordingly, the present invention also relates to a power system fault phase selection system based on an electrical quantity vector model, such as Figure 4 As shown, it includes:

[0137] A three-phase load current component calculation unit, used to calculate the three-phase load current components on the power supply route according to the circuit matrix relationship of the three-phase electrical quantities of the power supply route supplying power to the fault point when a fault occurs;

[0138] A three-phase fault current component calculation unit is used to obtain the collected three-phase total current flowing through the relay protection device, and to subtract the three-phase load current component from the three-phase total current to obtain the three-phase fault current component flowing into the fault point in the three-phase total current;

[0139] A vector conversion unit, used for converting the three-phase fault current into vector parameters, wherein the vector parameters include a forward rotating vector, a reverse rotating vector and a pulsation vector, wherein the imaginary axis component of the pulsation vector is zero and the real axis component is equal to the zero axis component obtained by Clarke transformation of the three-phase fault current;

[0140] The phase selection unit is used to determine the fault phase under the current vector parameters according to the logical relationship between different fault phases and vector parameters.

[0141] The phase selection system is compatible with the above-mentioned phase selection method and is used to execute the relevant steps in the above-mentioned phase selection method. For specific details, please refer to the above introduction and will not be repeated here.

[0142] In summary, the present invention realizes fault phase selection of the power system through a vector model, first calculates the fault current component flowing through the relay protection device and converts it into a forward rotating vector, a reverse rotating vector and a pulsation vector, and quickly determines the fault phase under the current vector parameters according to the logical relationship between the vector parameters and different fault types, wherein the logical relationship between the vector parameters and different fault types is obtained in advance through the analysis of multiple groups of measurement data. This method does not make any simplifications or assumptions on the electrical quantities after the fault, and can be applied to the fault phase selection problem under the condition of time-varying amplitude and frequency, and the phase selection result is not affected by the short circuit / grounding resistance at the fault point.

[0143] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for selecting phases for power system faults based on an electrical quantity vector model, characterized in that: include: Determine a power supply route for supplying power to the fault point, the power supply route being provided with a relay protection device, and calculate the three-phase load current components on the power supply route according to the circuit matrix relationship of the three-phase electrical quantities of the power supply route; Collecting a three-phase total current flowing through the relay protection device, and subtracting the three-phase load current component from the three-phase total current to obtain a three-phase fault current component flowing into the fault point in the three-phase total current; The electrical quantity and vector are transformed by the transformation matrix to convert the three-phase fault current components into vector parameters. The transformation matrix is: The vector parameters include a forward rotating vector, a reverse rotating vector and a pulsation vector, wherein the imaginary axis component of the pulsation vector is zero and the real axis component is equal to the zero axis component obtained by Clarke transformation of the three-phase fault current component; According to the logical relationship between different fault phases and vector parameters, the fault phase under the current vector parameters is determined.

2. The method for selecting a fault phase in a power system based on an electrical quantity vector model according to claim 1, characterized in that: The power supply route has a voltage source t1 and a voltage source t2 located on both sides of the fault point, and the relay protection device is located between the voltage source t1 and the fault point; The circuit matrix relationship of the three-phase electrical quantities of the power supply route is: Among them, u t1a ,u t1b ,u t1c Respectively represent the instantaneous values ​​of the A-phase, B-phase, and C-phase voltages of the voltage source t1; u t2a ,u t2b ,u t2c Respectively represent the instantaneous values ​​of the A-phase, B-phase, and C-phase voltages of the voltage source t2; i t1La ,i t1Lb ,i t1Lc They represent the instantaneous values ​​of phase A, phase B, and phase C of the load current component flowing from the voltage source t1 to the voltage source t2, respectively. s , R m , L s , L m They represent the self-resistance, mutual resistance, self-inductance and mutual inductance of the power supply line between voltage source t1 and voltage source t2 respectively, and p is a differential operator, which represents The three-phase fault current components are: Among them, i t1Fa ,i t1Fb ,i t1Fc They represent the instantaneous values ​​of phase A, phase B, and phase C of the three-phase fault current components flowing from voltage source t1 to the fault point, respectively. t1a ,i t1b ,i t1c They respectively represent the instantaneous values ​​of phase A, phase B and phase C in the three-phase total current flowing through the relay protection device.

3. The method for selecting a fault phase in a power system based on an electrical quantity vector model according to claim 1, characterized in that: The following transformation formula is used to convert the three-phase fault current components into vector parameters with any one of phases A, B, and C as the reference phase: Among them, the positive rotation vector of phase A is taken as the reference phase. Reverse Rotation Vector and pulse vector The vector transformation formula is In the formula, i t1Fa ,i t1Fb ,i t1Fc Indicates the instantaneous values ​​of phase A, phase B, and phase C in the three-phase fault current components flowing to the fault point; The positive rotation vector with phase B as the reference phase Reverse Rotation Vector and pulse vector The vector transformation formula is Positive rotation vector with C phase as the reference phase Reverse Rotation Vector and pulse vector The vector transformation formula is 4. The method for selecting a fault phase in a power system based on an electrical quantity vector model according to claim 1, characterized in that: The logical relationship between different fault phases and vector parameters includes one or more of the following: Ground fault logic: When The corresponding fault type is non-ground fault; when The corresponding fault type is ground fault; among them, is the pulse vector; Two-phase short circuit fault logic: When And I t1bc ,I t1ac ,I t1ab If any of the items is 0, the corresponding fault type is a two-phase short circuit fault; t1bc ,I t1ac ,I t1ab is the fault index of two-phase short circuit, and the calculation formula is: or or or In the formula, are the positive rotation vectors with phase A, phase B and phase C as the reference phase, are the reverse rotating vectors taking phase A, phase B and phase C as the reference phases respectively; Three-phase short circuit fault logic: And I t1bc ,I t1ac I t1ab When both are not 0, the corresponding fault type is a three-phase short circuit fault; Single-phase ground fault logic: When And I t1ag ,I t1bg ,I t1cg If any of the items is 0, the corresponding fault type is a single-phase grounding fault. t1cg ,I t1bg ,I t1cg is the fault index of single-phase grounding, and the calculation formula is: In the formula, are the pulse vectors with phase A, phase B and phase C as reference phases respectively; Two-phase short circuit ground fault logic: When I t1ag ,I t1bg ,I t1cg Both are not 0 and I t1bcg ,I t1acg ,I t1abg If any of the items is 0, the corresponding fault type is a two-phase short-circuit grounding fault; t1bcg ,I t1acg ,I t1abg It is the fault index of two-phase short circuit grounding; calculation formula or or or 5. The method for selecting a fault phase in a power system based on an electrical quantity vector model according to claim 4, characterized in that: In the two-phase short-circuit fault logic, I t1bc ,I t1ac ,I t1ab They are the fault indicators of BC short circuit, AC short circuit and AB short circuit respectively. when When the I t1bc ,I t1ac ,I t1ab If any of the items is 0, the corresponding fault type is a two-phase short circuit fault, including: When I t1bc =0, the corresponding fault type is BC short circuit fault; When I t1ac =0, the corresponding fault type is AC short circuit fault; When I t1ab =0, the corresponding fault type is AB short circuit fault.

6. The method for selecting a fault phase in a power system based on an electrical quantity vector model according to claim 4, characterized in that: In the single-phase ground fault logic, I t1ag ,I t1bg ,I t1cg They are the fault indicators of phase A grounding, phase B grounding and phase C grounding respectively; when When the I t1ag ,I t1bg ,I t1cg If any of the items is 0, the corresponding fault type is a single-phase grounding fault, including: When I t1ag =0, the corresponding fault type is phase A grounding fault; When I t1bg =0, the corresponding fault type is phase B grounding fault; When I t1cg =0, the corresponding fault type is phase C ground fault.

7. The method for selecting a fault phase in a power system based on an electrical quantity vector model according to claim 4, characterized in that: In the two-phase short-circuit ground fault logic, I t1bcg , I t1acg , I t1abg They are the fault indicators of BC short circuit to ground, AC short circuit to ground, and AB short circuit to ground; when I t1ag , I t1bg , I t1cg When both are not 0, the I t1bcg , I t1acg , I t1abg If any of the items is 0, the corresponding fault type is a two-phase short-circuit grounding fault, including: When I t1bcg =0, the corresponding fault type is BC short circuit grounding fault; When I t1acg =0, the corresponding fault type is AC short circuit grounding fault; When I t1abg =0, the corresponding fault type is AB short circuit grounding fault.

8. The method for selecting a fault phase in a power system based on an electrical quantity vector model according to claim 4, characterized in that: According to the logical relationship between different fault phases and vector parameters, the fault phase under the current vector parameters is determined, including: Step S41: Determination Is it 0? If yes, go to step S42; if no, go to step S44; Step S42: Determination I t1bc , I t1ac , I t1ab Is there an indicator of 0 in the logic? If not, the fault type is determined to be a three-phase short circuit fault logic; if so, it is determined to be a two-phase short circuit fault and step S43 is executed; Step S43: Identification I t1bc , I t1ac , I t1ab The index is 0, when I t1bc =0, the fault type is determined to be a BC short circuit fault; when I t1ac =0, it is determined to be an AC short circuit fault; when I t1ab =0, it is judged as AB short circuit fault; Step S44: Determination I t1ag , I t1bg , I t1cg Whether there is an indicator of 0 in the logic, if not, the fault type is determined to be a two-phase short circuit grounding fault and the process jumps to step S45; if so, it is determined to be a single-phase grounding fault and the process jumps to step S46; Step S45: Identification I t1bcg , I t1acg , I t1abg The index is 0, when I t1bcg =0, the fault type is determined to be a BC short-circuit grounding fault; when I t1acg =0, it is determined to be an AC short circuit grounding fault; when I t1abg =0, it is determined to be an AB short-circuit grounding fault; Step S46: Identification I t1ag , I t1bg , I t1cg The index is 0, when I t1ag =0, the corresponding fault type is phase A ground fault; when I t1bg =0, the corresponding fault type is phase B grounding fault; when I t1cg =0, the corresponding fault type is phase C ground fault.

9. The method for selecting a fault phase in a power system based on an electrical quantity vector model according to claim 2, characterized in that: The voltage source t1 and the voltage source t2 are both equivalent voltage sources.

10. A power system fault phase selection system based on an electrical quantity vector model, characterized in that include: A three-phase load current component calculation unit, used to calculate the three-phase load current components on the power supply route according to the circuit matrix relationship of the three-phase electrical quantities of the power supply route supplying power to the fault point when a fault occurs; A three-phase fault current component calculation unit is used to obtain the collected three-phase total current flowing through the relay protection device, and to subtract the three-phase load current component from the three-phase total current to obtain the three-phase fault current component flowing into the fault point in the three-phase total current; The vector conversion unit is used to convert the electrical quantity and the vector through the transformation matrix to convert the three-phase fault current into a vector parameter. The transformation matrix is The vector parameters include a forward rotating vector, a reverse rotating vector and a pulsation vector, wherein the imaginary axis component of the pulsation vector is zero and the real axis component is equal to the zero axis component obtained by Clarke transformation of the three-phase fault current; The phase selection unit is used to determine the fault phase under the current vector parameters according to the logical relationship between different fault phases and vector parameters.

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