Dynamic analysis method, identification method and analysis system for asymmetric faults in power systems

Abstract

The present invention discloses a method for dynamic analysis of asymmetric faults in a power system, an analysis system and a method for identifying fault characteristics. The method comprises: constructing a rotating vector matrix relationship between a power source and a fault point according to a circuit matrix relationship of three-phase electrical quantities between the power source and the fault point, and a conversion relationship between three-phase electrical quantities and rotating vectors, and obtaining an equivalent network of each rotating vector; traversing the fault type of the fault point, and for each type of fault, connecting the equivalent networks of each rotating vector into a composite network according to vector boundary conditions, and calculating the rotating vector of the fault point under the corresponding fault type according to the composite network, and then obtaining the rotating vector of any node in the system under different fault types, and analyzing the fault characteristics of any node in the system under different fault types. The method can analyze the transient fault process of any three-phase power supply signal acting on an asymmetric fault network, and provide a theoretical basis for subsequent relay protection.

Description

Technical Field

[0001] The present invention belongs to the technical field of power system fault analysis, and more specifically, relates to a power system asymmetric fault dynamic analysis method, a fault feature identification method and an analysis system. 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 faults in the power grid have occurred at home and abroad, destroying 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, and system fault analysis is the basis of relay protection. Therefore, the power system needs to implement asymmetric fault analysis based on asymmetric fault analysis methods to provide a theoretical basis for relay protection configuration.

[0003] The typical asymmetric fault analysis method at present is the symmetrical component method. The mathematical basis of this method is that the amplitude and frequency of the electrical quantity in the system are constant. Based on this, the phasor model of the electrical quantity and the impedance model of the network are established, and the asymmetric three-phase phasor is further converted into a symmetrical three-sequence phasor. The positive, negative, and zero-sequence impedance network is established, and the asymmetric fault problem of the three-phase network is converted into a problem of coupling of the three-sequence network only at the fault point for algebraic solution. However, during the period when an asymmetric fault occurs in a power system dominated by power electronic power supply, 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, it is impossible to establish the phasor model of the electrical quantity and the impedance model of the network. The symmetrical component method is no longer applicable to the asymmetric fault problem of the power system dominated by power electronic power supply. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a dynamic analysis method, identification method and analysis system for asymmetric faults in an electric power system, whose purpose is to analyze the asymmetric fault problems of the electric power system without being affected by the time-varying amplitude and frequency of the electrical quantities in the system.

[0005] To achieve the above object, according to one aspect of the present invention, a method for dynamic analysis of asymmetric faults in a power system is provided, comprising:

[0006] According to the circuit matrix relationship of the three-phase electrical quantity between the power source and the fault point, and the conversion relationship between the three-phase electrical quantity and the rotating vector, the rotating vector matrix relationship between the power source and the fault point is constructed;

[0007] According to the rotation vector matrix relationship, an equivalent network of each rotation vector is obtained;

[0008] Traversing the fault types of the fault point, for each type of fault, constructing the vector boundary conditions of the rotating vector according to the boundary conditions of the three-phase electrical quantity, connecting the equivalent networks of each rotating vector into a composite network according to the vector boundary conditions, and calculating the rotating vector of the fault point under the corresponding fault type according to the composite network;

[0009] According to the rotation vector of the fault point, the rotation vector of any node in the system under different fault types is obtained, and the fault characteristics of any node in the system under different fault types are analyzed.

[0010] In one embodiment, the circuit matrix relationship of the three-phase electrical quantities between the power supply and the fault point includes the circuit matrix relationship between the three-phase voltage of the power supply, the three-phase voltage of the fault point and the three-phase current on the line.

[0011] In one embodiment, a single-ended single-branch topology is used between the power source and the fault point, and the circuit matrix relationship of the three-phase electrical quantity between the power source and the fault point is:

[0012]

[0013] Among them, u fa 、u fb 、u fc is the three-phase voltage at the fault point, u ta 、u tb 、u tc is the three-phase voltage of the power supply, i ta 、i tb 、i tc is the three-phase current on the line, L s is the self-inductance parameter of the line between the power source and the fault point, L m is the mutual inductance parameter of the line from the power source to the fault point, p is the differential operator, which means

[0014] In one of the embodiments, the rotating vector includes a forward rotating vector, a reverse rotating vector and a pulsation vector.

[0015] In one embodiment, the three-phase electrical quantity is converted into a rotating vector by a transformation matrix C, wherein the transformation matrix C is:

[0016]

[0017] The transformation relationship of three-phase electrical quantity into rotating vector is:

[0018]

[0019]

[0020] Among them, Uαβ is the forward rotating voltage vector, is the reverse rotating voltage vector, U α′β′ is the pulsating voltage vector, I αβ is the positive rotating current vector, is the counter-rotating current vector, I α′β′ is the pulsating current vector, u a 、u b 、u c is the three-phase voltage, i a 、i b 、i c is the three-phase current.

[0021] In one embodiment, the fault type of the fault point includes a phase A grounding fault, a BC two-phase short circuit fault, and a BC two-phase metallic short circuit followed by a grounding fault;

[0022] Define u fa 、u fb 、u fc is the three-phase voltage at the fault point, i fa 、i fb 、i fc is the three-phase current of the fault branch, where

[0023] The boundary conditions of the three-phase electrical quantities of phase A grounding fault are: Among them, R f1 is the grounding resistance corresponding to the fault;

[0024] The boundary conditions of the three-phase electrical quantities of the BC two-phase short circuit fault are: Among them, R f2 is the short-circuit resistance corresponding to the fault;

[0025] The boundary conditions of the three-phase electrical quantities of the ground fault after the BC two-phase metallic short circuit are: Among them, R f3 is the ground resistance corresponding to the fault.

[0026] In one embodiment, the rotation vectors of each node in the system under different fault types are obtained according to the rotation vector of the fault point, including:

[0027] Determine any node m in the system, calculate the ratio of the distance from point m to the fault point to the distance from the power source to the fault point, and calculate the rotation vector of point m under the corresponding fault type based on the ratio and the rotation vector of the fault point under the corresponding fault type.

[0028] According to another aspect of the present invention, there is provided a method for identifying asymmetric faults in a power system, comprising:

[0029] According to the power system network topology, the fault characteristics of the current node under different fault types are obtained according to the above-mentioned power system asymmetric fault dynamic analysis method;

[0030] The electrical quantity of the current node is sampled, and the sampling result is matched with the fault characteristics of the current node under each fault type, so that the fault type that is successfully matched is determined as the fault occurring in the current branch.

[0031] According to another aspect of the present invention, there is provided a power system asymmetric fault dynamic analysis system, comprising:

[0032] A rotating vector matrix relationship building unit, used to build a rotating vector matrix relationship between the power source and the fault point according to a circuit matrix relationship of three-phase electrical quantities between the power source and the fault point, and a conversion relationship between the three-phase electrical quantities and the rotating vector;

[0033] An equivalent network construction unit, used to obtain an equivalent network of each rotation vector according to the rotation vector matrix relationship;

[0034] A fault point rotating vector calculation unit, for constructing the vector boundary conditions of the rotating vector according to the boundary conditions of the three-phase electrical quantity for each type of fault at the fault point, connecting the equivalent networks of the rotating vectors into a composite network according to the vector boundary conditions, and calculating the rotating vector of the fault point under the corresponding fault type according to the composite network;

[0035] The fault characteristic analysis unit is used to obtain the rotation vector of any node in the system under different fault types according to the rotation vector of the fault point, and analyze the fault characteristics of any node in the system under different fault types.

[0036] In one embodiment, the fault feature analysis unit includes a node rotation vector calculation subunit and an analysis subunit, wherein:

[0037] The node rotation vector calculation subunit is used to select any node m in the system, calculate the ratio of the distance from point m to the fault point to the distance from the power source to the fault point, and calculate the rotation vector of point m under the corresponding fault type according to the ratio and the rotation vector of the fault point under the corresponding fault type;

[0038] The analysis subunit is used to analyze the fault characteristics under different fault types according to the rotation vector of any node under the corresponding fault type.

[0039] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0040] According to the asymmetric fault analysis method of the power system of the present invention, during the calculation, no simplification or assumption is made to the electrical quantities after the fault, and a conjugate vector method is proposed for asymmetric fault analysis. The method constructs a relationship matrix of corresponding rotating vectors according to the electrical quantity relationship matrix and the conversion relationship between the electrical quantity and the rotating vector, and then obtains the equivalent network of each rotating vector, and integrates the equivalent network of each rotating vector based on the boundary conditions of different fault types. Based on the integrated composite network, the rotating vector of the fault point under each fault type can be calculated. The method is not affected by the time-varying power supply amplitude and frequency, and can analyze the electrical quantity relationship of any three-phase power supply acting on the asymmetric fault network under various fault types, and then analyzes the fault transient process, providing a theoretical basis for subsequent relay protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a flowchart of the steps of a method for dynamic analysis of asymmetric faults in a power system in an embodiment;

[0042] FIG2( a ) is a single-ended single-branch power system network topology structure in one embodiment;

[0043] FIG2( b ) is a double-terminal single-branch power system network topology structure in one embodiment;

[0044] FIG. 3( a ) is a forward rotation vector equivalent network in one embodiment;

[0045] FIG3( b ) is a reverse rotation vector equivalent network in one embodiment;

[0046] FIG3( c ) is a pulse vector equivalent network in one embodiment;

[0047] Figure 4 is a schematic diagram of a composite network constructed according to a phase A ground fault boundary condition in an embodiment;

[0048] Figure 5 is a schematic diagram of a composite network constructed according to a BC two-phase short-circuit fault boundary condition in an embodiment;

[0049] Figure 6 It is a schematic diagram of a composite network constructed according to the boundary condition of a ground fault after a metallic short circuit between two phases BC in an embodiment;

[0050] Figure 7 It is a block diagram of a power system asymmetric fault dynamic analysis system in one embodiment. DETAILED DESCRIPTION

[0051] 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.

[0052] like Figure 1 The figure shows a flow chart of the steps of the dynamic analysis method of asymmetric faults in a power system, which includes:

[0053] Step S100: construct a rotating vector matrix relationship between the power source and the fault point according to the circuit matrix relationship of the three-phase electrical quantities between the power source and the fault point, and the conversion relationship between the three-phase electrical quantities and the rotating vector.

[0054] First, the circuit matrix relationship of the three-phase electrical quantities between the power source and the fault point is determined according to the power system network topology. The circuit matrix relationship of the three-phase electrical quantities includes the circuit matrix relationship between the three-phase voltage of the power source, the three-phase voltage of the fault point, and the three-phase current on the line. Among them, the fault point is the location where the fault may occur that is determined in advance.

[0055] Figure 2(a) shows the network topology of a single-ended single-branch power system, where m represents any point between the power source and the fault point, f represents the fault point, and u t (t) represents the three-phase voltage of the amplitude-frequency time-varying voltage source in the form of instantaneous value, which is a 3×1 matrix; L s It represents the self-inductance parameter of the line between the voltage source and the fault point, L m represents the mutual inductance parameter of the line from the voltage source to the fault point, i t (t) represents the instantaneous value of the three-phase current on the line between the voltage source and the fault point, 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. According to the network topology shown in Figure 2, the circuit relationship of the three-phase electrical quantities from the power supply to the fault point is listed, and the formula is shown in formula (1):

[0056]

[0057] Among them, u ta ,u tb ,u tc Respectively represent the instantaneous values ​​of the A-phase, B-phase, and C-phase voltages of the amplitude-frequency time-varying voltage source; u fa ,u fb ,u fcRespectively represent the instantaneous values ​​of the A phase, B phase, and C phase voltages at the fault point; i ta ,i tb ,i tc They represent the instantaneous current values ​​of phase A, phase B, and phase C on the line between the voltage source and the fault point respectively; p is a differential operator, which represents

[0058] Figure 2(b) shows the network topology of a two-terminal single-branch power system, where f represents the fault point; u 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,

[0059] 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, 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, 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.

[0060] List the circuit relationship of the three-phase electrical quantities between power supply t1 and the fault point

[0061]

[0062] List the circuit relationship of the three-phase electrical quantities between power source t2 and the fault point

[0063]

[0064] The three-phase current at the fault point satisfies the following relationship

[0065]

[0066] 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; u fa ,u fb ,u fc Respectively represent the instantaneous values ​​of the A phase, B phase, and C phase voltages at the fault point; i t1a ,i t1b ,i t1c Respectively represent the instantaneous current values ​​of phase A, phase B, and phase C on the line between the voltage source t1 and the fault point; i t2a ,i t2b ,i t2c They represent the instantaneous current values ​​of phase A, phase B, and phase C on the line between the voltage source t1 and the fault point; p is a differential operator, which represents

[0067] It should be noted that different network topologies have different circuit matrix relationships, which can be directly derived from the network topology and are not limited here. After determining the circuit matrix relationship, the electrical quantities in the matrix are converted into rotating vectors according to the conversion relationship between the electrical quantities and the rotating vectors, thereby obtaining the rotating vector matrix relationship between the power supply and the fault point. Converting electrical quantities into rotating vectors is conducive to the decoupling of subsequent equivalent networks.

[0068] In one embodiment, a group of rotating vectors is a forward rotating vector, a reverse rotating vector and a pulsating vector. 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, the forward rotating vector and the reverse rotating vector are both on the first complex plane, and the rotation direction of the reverse rotating vector is always opposite to that of the forward 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, and its zero axis component can be regarded as an AC signal whose real axis is not 0 and the imaginary axis is always 0. The AC signal is a vector pulsating on the real axis of the second complex plane, which is called a pulsating vector, that is, the real axis component of the pulsating 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.

[0069] Specifically, the transformation matrix C is introduced to transform the three-phase electrical quantity into a rotating vector. The transformation relationship is shown in equations (2) and (3):

[0070]

[0071]

[0072] In formula (2), Uαβ is the forward rotating voltage vector, is the reverse rotating voltage vector, U α′β′ is the pulsating voltage vector, and the transformation matrix C is a vector transformation matrix describing the transformation of the three-phase instantaneous value into three rotating vectors. Its inverse transformation matrix C -1 As shown in formula (4).

[0073]

[0074] In formula (3), I αβ is the positive rotating current vector, is the counter-rotating current vector, I α′β′ is the pulsating current vector.

[0075] Continuing with the topology shown in Figure 2(a) as an example, substituting the above equations (2) and (3) into equation (1) to obtain equation (5):

[0076]

[0077] Thus, the rotation vector matrix relationship between the power source and the fault point is obtained.

[0078] Step S200: Obtaining an equivalent network of each rotation vector according to the rotation vector matrix relationship.

[0079] The rotation vector matrix is ​​decoupled to obtain the equivalent network of each rotation vector. For example, the matrix of formula (5) is decoupled to obtain:

[0080] This corresponds to the forward rotation vector equivalent network shown in Figure 3(a);

[0081] This corresponds to the reverse rotation vector shown in Figure 3(b);

[0082] This corresponds to the pulse vector equivalent network shown in Figure 3(c).

[0083] Step S300: traverse the fault types of the fault point, for each type of fault, construct the vector boundary conditions of the rotating vector according to the boundary conditions of the three-phase electrical quantities, connect the equivalent networks of each rotating vector into a composite network according to the vector boundary conditions, and calculate the rotating vector of the fault point under the corresponding fault type according to the composite network.

[0084] There may be multiple types of faults occurring at the fault point, so the present invention analyzes each type of fault. Specifically, three scenarios are taken as examples: A-phase grounding fault, BC two-phase short circuit fault, and BC two-phase metallic short circuit followed by grounding fault.

[0085] When a phase A ground fault occurs at the fault point, the ground resistance is R f1 , write the boundary conditions satisfied by the three-phase electrical quantities as shown in formula (6)

[0086]

[0087] According to the conversion relationship between electrical quantity and rotating vector (such as equation (2) and equation (3)), the above boundary conditions are converted into the conditions satisfied by the rotating vector, as shown in equation (7):

[0088]

[0089] According to the relationship in formula (7), Figure 3(a) to Figure 3(c) The equivalent network graphs represented by are connected into a composite network, such as Figure 4 As shown, according to Figure 4 The circuit relationship and the mathematical relationship between equation (5) and equation (7) can be calculated as follows:

[0090] The fault branch current rotation vector is shown in equation (8):

[0091]

[0092] The three voltage rotation vectors at the fault point are shown in equation (9):

[0093]

[0094] When a BC two-phase short circuit occurs at the fault point, the short circuit resistance is R f2 , write the boundary conditions satisfied by the three-phase electrical quantities as shown in formula (10)

[0095]

[0096] After conversion to a rotation vector, it satisfies equation (11):

[0097]

[0098] According to the relationship in formula (11), Figure 3(a) to Figure 3(c) The equivalent network graphs represented by are connected into a composite network, such as Figure 5 As shown. Figure 5 The circuit relationship and the mathematical relationship between equations (5) and (11) can be used to calculate the fault branch current rotation vector as shown in equation (12):

[0099]

[0100] The three voltage rotation vectors at the fault point are shown in equation (13):

[0101]

[0102] When a ground fault occurs after a metallic short circuit between the two phases BC at the fault point, the grounding resistance is R f3 , write the boundary conditions satisfied by the three-phase electrical quantities as shown in formula (14)

[0103]

[0104] After conversion to a rotation vector, it satisfies equation (15):

[0105]

[0106] According to the relationship in formula (15), Figure 3(a) to Figure 3(c) The equivalent network graphs represented by are connected into a composite network, such as Figure 6 As shown. Figure 6 The circuit relationship and the mathematical relationship between equations (5) and (15) can be used to calculate the fault branch current rotation vector as shown in equation (16):

[0107]

[0108] The three voltage rotation vectors at the fault point are shown in equation (17):

[0109]

[0110] By referring to the above method, the rotation vector of the fault point under different fault types can be obtained.

[0111] Step S400: According to the rotation vector of the fault point, the rotation vector of any node in the system under different fault types is obtained, and the fault characteristics of any node in the system under different fault types are analyzed.

[0112] Specifically, determine any node m in the system.

[0113] For the current rotation vector at point m, there is a certain relationship between the current at any node m and the current at the fault point. For example, for the structure in Figure 2, there is a current relationship as shown in equation (18):

[0114]

[0115] That is, the current rotating vector in the system is equal to the current rotating vector at the fault point.

[0116] For the voltage rotation vector at point m, the percentage of the distance from point m to the fault point to the distance from the power source to the fault point is calculated as k. The calculation formula for the voltage rotation vector at point m is shown in formula (19):

[0117]

[0118] in, They are the forward rotating voltage vector, reverse rotating voltage vector and pulsating voltage vector at point m respectively.

[0119] After obtaining the rotating vector of any node in the system, the rotating vector can be analyzed. Specifically, the rotating vector can be analyzed directly, or the rotating vector can be converted into an electrical quantity and then analyzed to obtain fault characteristics under different faults.

[0120] Specifically, the instantaneous value i of the three-phase current of the branch between point m and the fault point can be calculated by equation (18), equation (3) and equation (4): ma ,i mb ,i mc , the calculation formula is shown in formula (20)

[0121]

[0122] The instantaneous value u of the three-phase voltage at point m can be calculated by equation (19), equation (3) and equation (4): ma ,u mb ,u mc , the calculation formula is shown in formula (21)

[0123]

[0124] The instantaneous value i of the three-phase current at point m is obtained. ma ,i mb ,i mc And the instantaneous value of three-phase voltage u ma ,u mb ,u mc After that, different types of asymmetric faults can be dynamically analyzed to obtain the fault characteristics under different fault types.

[0125] It should be noted that the calculation formulas listed above are only for specific embodiments. Different power system network topologies are different, and the expression of the calculation formulas will be different, but the processing process and method are the same as those of the above embodiments, and will not be described in detail here.

[0126] Accordingly, the present application also relates to a method for identifying asymmetric faults in a power system, which comprises:

[0127] Step A: According to the power system network topology, the fault characteristics of the current node under different fault types are obtained, and the fault characteristics are obtained according to the power system asymmetric fault dynamic analysis method introduced above;

[0128] Step B: Sample the electrical quantity of the current node, and match the sampling result with the fault characteristics of the current node under each fault type, so as to determine the fault type that matches successfully as the fault occurring in the current branch.

[0129] Accordingly, the present application also relates to a power system asymmetric fault dynamic analysis system, such as Figure 7 As shown, it includes:

[0130] A rotating vector matrix relationship building unit, used to build a rotating vector matrix relationship between the power source and the fault point according to a circuit matrix relationship of three-phase electrical quantities between the power source and the fault point, and a conversion relationship between the three-phase electrical quantities and the rotating vector;

[0131] An equivalent network construction unit is used to obtain an equivalent network of each rotation vector according to the rotation vector matrix relationship;

[0132] A fault point rotating vector calculation unit is used to construct a vector boundary condition of the rotating vector according to the boundary conditions of the three-phase electrical quantity for each type of fault at the fault point, connect the equivalent networks of each rotating vector into a composite network according to the vector boundary conditions, and calculate the rotating vector of the fault point under the corresponding fault type according to the composite network;

[0133] The fault characteristic analysis unit is used to obtain the rotation vector of any node in the system under different fault types according to the rotation vector of the fault point, and analyze the fault characteristics of any node in the system under different fault types.

[0134] Specifically, the fault feature analysis unit includes a node rotation vector calculation subunit and an analysis subunit, wherein:

[0135] The node rotation vector calculation subunit is used to select any node m in the system, calculate the ratio of the distance from point m to the fault point to the distance from the power source to the fault point, and calculate the rotation vector of point m under the corresponding fault type according to the ratio and the rotation vector of the fault point under the corresponding fault type;

[0136] The analysis subunit is used to analyze the fault characteristics under different fault types according to the rotation vector of any node under the corresponding fault type.

[0137] In summary, according to the asymmetric fault analysis method of the power system of the present invention, during the calculation, no simplification or assumption is made to the electrical quantities after the fault, and a conjugate vector method is proposed for asymmetric fault analysis. This method constructs a relationship matrix of corresponding rotating vectors based on the electrical quantity relationship matrix and the conversion relationship between the electrical quantity and the rotating vector, and then obtains the equivalent network of each rotating vector, and integrates the equivalent network of each rotating vector based on the boundary conditions of different fault types. Based on the integrated composite network, the rotating vector of the fault point under each fault type can be calculated. This method is not affected by the time-varying power supply amplitude and frequency, and can analyze the relationship between electrical quantities of any three-phase power supply acting on the asymmetric fault network under various fault types, and then analyzes the fault transient process, providing a theoretical basis for subsequent relay protection.

[0138] It will be easily understood by those skilled in the art that the above are only preferred embodiments of the present invention and are 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 dynamic analysis of asymmetric faults in a power system, characterized in that: include: According to the circuit matrix relationship of the three-phase electrical quantity between the power supply and the fault point, and the conversion relationship between the three-phase electrical quantity and the rotating vector, the rotating vector matrix relationship between the power supply and the fault point is constructed, and the rotating vector includes a forward rotating vector, a reverse rotating vector and a pulsation vector, wherein the conversion relationship of the three-phase electrical quantity to the rotating vector is: Where U αβ is the forward rotating voltage vector, is the reverse rotating voltage vector, U α′β′ is the pulsating voltage vector, I αβ is the positive rotating current vector, is the counter-rotating current vector, I α′β′ is the pulsating current vector, u a 、u b 、u c is the three-phase voltage, i a 、i b 、i c is the three-phase current; According to the rotation vector matrix relationship, an equivalent network of each rotation vector is obtained; Traversing the fault types of the fault point, for each type of fault, according to the transformation relationship of converting the three-phase electrical quantity into the rotating vector, the boundary conditions of the three-phase electrical quantity under the corresponding fault are converted into the vector boundary conditions of the rotating vector, according to the vector boundary conditions, the equivalent networks of each rotating vector are connected into a composite network, and the rotating vector of the fault point under the corresponding fault type is calculated according to the composite network; According to the rotation vector of the fault point, the rotation vector of any node in the system under different fault types is obtained, and the fault characteristics of any node in the system under different fault types are analyzed.

2. The method for dynamic analysis of asymmetric faults in a power system according to claim 1, characterized in that: The circuit matrix relationship of the three-phase electrical quantities between the power supply and the fault point includes the circuit matrix relationship between the three-phase voltage of the power supply, the three-phase voltage of the fault point and the three-phase current on the line.

3. The method for dynamic analysis of asymmetric faults in a power system according to claim 2, characterized in that: The topology between the power supply and the fault point is single-ended single-branch. The circuit matrix relationship of the three-phase electrical quantities between the power supply and the fault point is: Among them, u fa 、u fb 、u fc is the three-phase voltage at the fault point, u ta 、u tb 、u tc is the three-phase voltage of the power supply, i ta 、i tb 、i tc is the three-phase current on the line, L s is the self-inductance parameter of the line between the power source and the fault point, L m is the mutual inductance parameter of the line from the power source to the fault point, p is the differential operator, which means 4. The method for dynamic analysis of asymmetric faults in a power system according to claim 1, characterized in that: The fault types of the fault point include A-phase grounding fault, BC two-phase short circuit fault, BC two-phase metallic short circuit followed by grounding fault; Define u fa 、u fb 、u fc is the three-phase voltage at the fault point, i fa 、i fb 、i fc is the three-phase current of the fault branch, where The boundary conditions of the three-phase electrical quantities of phase A grounding fault are: Among them, R f1 is the grounding resistance corresponding to the fault; The boundary conditions of the three-phase electrical quantities of the BC two-phase short circuit fault are: Among them, R f2 is the short-circuit resistance corresponding to the fault; The boundary conditions of the three-phase electrical quantities of the ground fault after the BC two-phase metallic short circuit are: Among them, R f3 is the ground resistance corresponding to the fault.

5. The method for dynamic analysis of asymmetric faults in a power system according to claim 1, characterized in that: According to the rotation vector of the fault point, the rotation vectors of each node in the system under different fault types are obtained, including: Determine any node m in the system, calculate the ratio of the distance from point m to the fault point to the distance from the power source to the fault point, and calculate the rotation vector of point m under the corresponding fault type based on the ratio and the rotation vector of the fault point under the corresponding fault type.

6. A method for identifying asymmetric faults in a power system, characterized in that: include: According to the power system network topology, the fault characteristics of the current node under different fault types are obtained, wherein the fault characteristics are obtained by the power system asymmetric fault dynamic analysis method according to any one of claims 1 to 5; The electrical quantity of the current node is sampled, and the sampling result is matched with the fault characteristics of the current node under each fault type, so that the fault type that is successfully matched is determined as the fault occurring in the current branch.

7. A power system asymmetric fault dynamic analysis system, characterized in that: include: The rotating vector matrix relationship construction unit is used to construct the rotating vector matrix relationship between the power supply and the fault point according to the circuit matrix relationship of the three-phase electrical quantity between the power supply and the fault point, and the conversion relationship between the three-phase electrical quantity and the rotating vector, wherein the rotating vector includes a forward rotating vector, a reverse rotating vector and a pulsation vector, wherein the conversion relationship of the three-phase electrical quantity into the rotating vector is: Where U αβ is the forward rotating voltage vector, is the reverse rotating voltage vector, Uα ′β′ is the pulsating voltage vector, I αβ is the positive rotating current vector, is the counter-rotating current vector, I α′β′ is the pulsating current vector, u a 、u b 、u c is the three-phase voltage, i a 、i b 、i c is the three-phase current; An equivalent network construction unit, used to obtain an equivalent network of each rotation vector according to the rotation vector matrix relationship; A fault point rotating vector calculation unit is used for converting the boundary conditions of the three-phase electrical quantities under the corresponding fault into the vector boundary conditions of the rotating vector according to the transformation relationship of converting the three-phase electrical quantities into the rotating vector for each type of fault at the fault point, connecting the equivalent networks of the rotating vectors into a composite network according to the vector boundary conditions, and calculating the rotating vector of the fault point under the corresponding fault type according to the composite network; The fault characteristic analysis unit is used to obtain the rotation vector of any node in the system under different fault types according to the rotation vector of the fault point, and analyze the fault characteristics of any node in the system under different fault types.

8. The power system asymmetric fault dynamic analysis system according to claim 7, characterized in that: The fault feature analysis unit includes a node rotation vector calculation subunit and an analysis subunit, wherein: The node rotation vector calculation subunit is used to select any node m in the system, calculate the ratio of the distance from point m to the fault point to the distance from the power source to the fault point, and calculate the rotation vector of point m under the corresponding fault type according to the ratio and the rotation vector of the fault point under the corresponding fault type; The analysis subunit is used to analyze the fault characteristics under different fault types according to the rotation vector of any node under the corresponding fault type.

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