Broadband oscillation analysis method, system and medium based on source-network impedance equivalence

Abstract

The present invention relates to the technical field of power systems, and in particular to a broadband oscillation analysis method, system and medium based on source-network impedance equivalence. The method comprises: obtaining converter control protection parameters and operation modes, and establishing a converter impedance model; retaining key converter grid-connected nodes to perform grid dimension reduction, solving within a wide frequency band, and obtaining an equivalent network impedance model of a regional power grid; generating a frequency sequence according to a target frequency range, obtaining converter impedance and equivalent network impedance, constructing an equivalent circuit model of the entire system, constructing its differential-algebraic equation according to the topological connection relationship of each element in the equivalent circuit, and forming a state space and its linearized state matrix; calculating eigenvalues ​​of the linearized state matrix of different frequencies one by one, selecting key eigenvalues ​​from the relationship between the real and imaginary parts of the eigenvalues, calculating risk modal participation factors, and obtaining converter correlation information corresponding to the key eigenvalues, so as to realize high oscillation risk section identification.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a broadband oscillation analysis method, system and medium based on source-grid impedance equivalence. Background Art

[0002] With the development of power technology, the power grid is undergoing a transformation from traditional large-inertia power generation systems such as thermal power and hydropower to distributed new energy, namely power electronic systems. Large-scale power electronic systems bring corresponding challenges to the power quality and stability of the power grid, such as wide-band harmonic oscillations.

[0003] Impedance analysis is a commonly used method for analyzing the grid-connected stability of converters. In this method, the stability of the power system is evaluated by establishing an equivalent impedance model between the converter and the power network. The equivalent impedance model regards the converter as an impedance and matches it with the impedance of the power network to analyze their interaction and the impact on the stability of the system. The impedance analysis method separates the system into a power subsystem and a load subsystem from the source side and the grid side of the key section, and uses the classic / generalized Nyquist criterion to realize the closed-loop system stability analysis. It has clear physical meaning and supports multi-element "black / gray box" system impedance aggregation. It is suitable for large-scale engineering applications and hardware-in-the-loop frequency sweeping, and plays an important role in wide-band oscillation analysis.

[0004] However, the existing impedance analysis method is mostly suitable for stability analysis of single-input and single-output systems. In scenarios with multiple converters connected, there are problems such as difficulty in tracing the source of oscillations and insufficient analysis theory, making it difficult to analyze and locate oscillation risks in systems with multiple converters connected.

[0005] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0006] The present invention provides a broadband oscillation analysis method, device, equipment and medium based on source-network impedance equivalence, thereby effectively solving the problems in the background technology.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: a broadband oscillation analysis method based on source-network impedance equivalence, comprising the following steps:

[0008] Obtain the converter control and protection parameters and power system operation mode in the target area power grid, perform impedance analysis, and establish a converter impedance model;

[0009] The grid dimension is reduced by retaining the key converter grid-connected nodes, and the equivalent network impedance model of the regional power grid is obtained by solving the problem in a wide frequency band.

[0010] Generate a frequency sequence according to the target frequency range, obtain the converter impedance and equivalent network impedance of any frequency in the frequency sequence, construct an equivalent circuit model of the whole system of any frequency in the frequency sequence, construct its differential-algebraic equation according to the topological connection relationship of each element in the equivalent circuit, and form a state space and its linearized state matrix;

[0011] According to the frequency sequence, the eigenvalues ​​of the linearized state matrix of different frequencies are calculated one by one, the key eigenvalues ​​are screened out from the relationship between the real and imaginary parts of the eigenvalues, the risk modal participation factors are calculated, and the converter correlation information corresponding to the key eigenvalues ​​is obtained to realize the identification of high oscillation risk sections.

[0012] Furthermore, when performing impedance analysis, obtaining the impedance response characteristics of the grid-connected node looking at the converter port includes the following steps:

[0013] Construct a broadband disturbance injection circuit in the electromagnetic transient simulation environment, select the voltage source / current source disturbance injection circuit according to the grid-connected characteristics and control strategy of the converter, and simulate the normal operating conditions of the converter;

[0014] Adjust the converter operating conditions according to the analysis requirements, set the harmonic voltage source / current source disturbance injection frequency according to the frequency sequence, and collect the converter port current / voltage steady-state response data, including the three-phase AC voltage AC Current

[0015] Convert the AC electrical quantity into positive and negative sequence components, solve the positive sequence impedance, and obtain the converter impedance model Z C (f):

[0016]

[0017] In the formula, is the positive sequence impedance at different frequencies.

[0018] Furthermore, the voltage source / current source disturbance injection circuit is selected according to the grid-connected characteristics and control strategy of the converter, including:

[0019] For the grid-connected converter, a voltage source disturbance injection circuit is used, and the disturbance source is set to be an ideal power frequency voltage source connected in series with a harmonic voltage source. The relevant parameters of the ideal power frequency voltage source are consistent with the rated voltage of the grid-connected port. The amplitude of the harmonic voltage source is 1% to 5% of the ideal power frequency voltage source. During the harmonic injection period, the converter is in a stable operating state.

[0020] For grid-connected converters, a current source disturbance injection circuit is used. The disturbance source is set to an ideal power frequency current source and a harmonic current source in parallel. The relevant parameters of the ideal power frequency current source are consistent with the rated current of the grid-connected port. The amplitude of the harmonic current source is 1% to 5% of the ideal power frequency current source. The converter is in a stable operating state during the harmonic injection period.

[0021] Furthermore, the grid near the converter grid-connected node is modeled using detailed distributed parameters, including:

[0022] Looking at the power grid from the grid-connected port of the converter, select the detailed distributed parameter modeling range of the nearby power grid, and select the distributed parameter modeling of the overhead lines and transformers in the selected area.

[0023] Furthermore, the retaining of key converter grid-connected nodes to perform grid dimension reduction comprises the following steps:

[0024] For the power grid to be analyzed, the admittance matrix Y(f) of the physical parameter power grid is first formed, and the nodes are divided into converter nodes B according to whether they are connected to the converter. C (f) With conventional Node B G (f), partition Y(f) according to the corresponding sequence number of the node:

[0025]

[0026] Y CC The order of (f) is n C ×n C , Y CG The order of (f) is n C ×n G , Y GC The order of (f) is n G ×n C , Y GG The order of (f) is n G ×n G , retain converter node B C (f), the grid equivalent admittance matrix is:

[0027]

[0028] Y G The order of (f) is n C ×n C , describes the equivalent physical properties of the system, and forms the equivalent impedance of the power grid based on its parameters, specifically:

[0029] The equivalent branch impedance of any branch is z G,ij (f) = -1 / y G,ij (f), y G,ij (f) is Y G(f) The jth element in the i-th row (i≠j); the equivalent impedance to ground of any node is:

[0030]

[0031] In the formula, y G,ij (f) is Y G (f) The i-th element in the i-th row.

[0032] Furthermore, the construction of an equivalent circuit model of the entire system at any frequency in the frequency sequence includes:

[0033] For the grid-connected converter z at port i C,i (f k )=r C,i (f k )+jx C,i (f k ),u C,i (f k ) and i C,i (f k ) are the node voltage and node injection current respectively;

[0034] If x C,i (f k )<0, then at frequency f k The converter behaves as a capacitive, x C,i (f k )=1 / (2πf k C C,i (f k ))The corresponding differential equation is abbreviated as:

[0035]

[0036] If x C,i (f k )≥0, then at frequency f k The converter behaves as an inductive device, x C,i (f k )=2πf k L C,i (f k ) Its corresponding differential equation is abbreviated as:

[0037]

[0038] For the branch between node i and node j, z G,ij (f) = r G,ij (f k )+jx G,ij (f k ),u C,i (f k ) and uC,j (f k ) are the voltages of the two nodes of the branch, i C,ij (f k ) is the branch current;

[0039] If x G,ij (f k )<0, then at frequency f k The converter behaves as a capacitive, x G,ij (f k )=1 / (2πf k C G,ij (f k ))The corresponding differential equation is abbreviated as:

[0040]

[0041] If x G,ij (f k )≥0, then at frequency f k The converter behaves as an inductive device, x G,ij (f k )=2πf k L G,ij (f k ) Its corresponding differential equation is abbreviated as:

[0042]

[0043] For the equivalent grid grounding branch z at port i G,ii (f k )=r G,ii (f k )+jx G,ii (f k ),u C,i (f k ) are the node voltage and node injection current;

[0044] If x G,ii (f k )<0, then at frequency f k The converter behaves as a capacitive, x G,ii (f k )=1 / (2πf k C G,ii (f k ))The corresponding differential equation is abbreviated as:

[0045]

[0046] If x G,ii (f k )≥0, then at frequency f k The converter behaves as an inductive device, x G,ii(f k )=2πf k L G,ii (f k ) Its corresponding differential equation is abbreviated as:

[0047]

[0048] Furthermore, constructing the differential-algebraic equation according to the topological connection relationship of each element in the equivalent circuit to form the state space and its linearized state matrix includes the following steps:

[0049] The equivalent grid node voltage U C , node injection current I C , branch current I L As a state quantity, the number of equivalent network branches Number of nodes n C , formed according to the branch information The state vector X(f k ),make

[0050]

[0051] In the formula, Indicates the voltage of equivalent network nodes; Indicates the amount of current injected into an equivalent network node; Indicates the current of equivalent network branches;

[0052] Write down the equivalent grid differential equations:

[0053] According to the equivalent circuit model, the differential equations for the converter, the differential equations for the equivalent grid interconnection and the differential equations for the equivalent grid grounding branch are established, and the following equations are obtained:

[0054]

[0055] Where A1(f k ) and A2(f k ) are both n X ×n X If it is a full rank square matrix of order, then:

[0056]

[0057] Let A(f k )=A1 -1 (f k )A2(f k ), and get the frequency f k The linearized state matrix of .

[0058] Furthermore, the step of calculating the eigenvalues ​​of the linearized state matrices of different frequencies one by one according to the frequency sequence includes:

[0059] Calculate A(f k )The eigenvalue sequence of the matrix Combine all frequency eigenvalue sequences into n X ×n f Matrix of order

[0060] Furthermore, the step of selecting key eigenvalues ​​from the relationship between the real part and the imaginary part of the eigenvalues ​​and calculating the risk modal participation factor includes:

[0061] First call the steady-state operation criterion and determine the frequency f according to the properties of all eigenvalues k Does the system have a steady-state operating point when:

[0062] Traverse all elements of D(f), if the element λ in row i and column k i (f k ) is a positive real number, then the system is determined to be at frequency f k There is no stable operating point; the system can operate stably in the entire frequency band if and only if the real parts of all elements of D(f) are less than or equal to zero;

[0063] Next, the disturbance response criterion is called to determine the frequency f according to the real part of all complex eigenvalues. k Whether the system has negative damping to the disturbance when :

[0064] Traverse all elements of D(f), if the element λ in row i and column k i (f k ) is a complex number, then the column of the matrix must have its conjugate eigenvalue λ j (f k ), and denote them as λ ij (f k )=α ij (f k )±jβ ij (f k );

[0065] The damping ratio is defined as:

[0066]

[0067] If ij (f k )≥-0.03 or α ij (f k )>ξ set , then the system is judged at frequency f k After being disturbed, there is a negative damping response, where ξ setTo set the threshold; the corresponding eigenvalue is marked as the key eigenvalue;

[0068] Finally, the coupling self-excitation criterion is called to determine whether the system has a multi-frequency self-excitation oscillation risk based on the frequency coupling characteristics between the complex eigenvalues:

[0069] Filter all negatively damped response eigenvalues ​​from all elements of D(f) to form a set:

[0070]

[0071] Where n- is the number of eigenvalues ​​of the negatively damped response; its corresponding frequency set is defined as:

[0072]

[0073] With set D (-) The elements in the equation correspond one to one; the corresponding eigenvalue imaginary part frequency set is defined as:

[0074]

[0075] With set D (-) The elements in the equation correspond one to one, and the solution is:

[0076]

[0077] If there exists a set D (-) A non-empty subset of Correspondingly F (-) With F (O) The elements in the set form a subset of and and The system has self-oscillation; if If the number of elements in is greater than or equal to 2, the system has coupled self-oscillation, and the corresponding eigenvalue is marked as the key eigenvalue;

[0078] On the contrary, there is no non-empty subset that satisfies the above conditions. Then the system does not have the conditions for coupled self-excitation.

[0079] Further, the obtaining of converter correlation information corresponding to the key characteristic value includes:

[0080] For any key characteristic value at any frequency, if the coupled self-excitation criterion If the number of elements is 1, or only the negative damping disturbance response criterion is met, the power electronic converter correlation ratio of the eigenvalue is calculated:

[0081] Let the key eigenvalue λ i (f k ) has a left eigenvector of The right eigenvector is The correlation factor of the eigenvalue to the jth state quantity is calculated as:

[0082]

[0083] The relevant ratio of the power electronic converter is calculated as:

[0084]

[0085] By i (f k ) numerically determines the degree of participation of the power electronic converter in the negative damping mode. If ρ i (f k )>ε set , then the negative damping mode is determined to be dominated by the power electronic converter, otherwise it is determined that the negative damping mode is a strong grid-related mode; where ε set To set the threshold;

[0086] If the coupled self-excitation criterion If the number of elements is greater than 1, the power electronic converter correlation ratio of each eigenvalue should be analyzed one by one and calculated according to the threshold ε set Determine its attributes as power electronic converter-dominated or grid-strongly related mode.

[0087] Furthermore, the high oscillation risk section identification includes:

[0088] For the dominant mode λ of the power electronic converter i (f k ), filter state quantity X C (f k )=[U C (f k )|I C (f k )] and its state quantity related factors Yes | C (f k )| Sort, select the significantly larger items, and mark the section as a high-risk section;

[0089] For the strongly correlated power grid mode, the state quantities are divided according to the real part signs of the left eigenvectors of each key eigenvalue.

[0090] The present invention also includes a power electronic power system stability analysis device, using the above method, including:

[0091] A converter impedance model building unit is used to obtain converter control and protection parameters and power system operation mode in the target area power grid, perform impedance analysis, and establish a converter impedance model;

[0092] The equivalent network impedance model modeling unit is used to retain the key converter grid-connected nodes to reduce the grid dimension, solve within a wide frequency band, and obtain the equivalent network impedance model of the regional power grid;

[0093] The state space unit is used to generate a frequency sequence according to the target frequency range, obtain the converter impedance and equivalent network impedance of any frequency in the frequency sequence, construct an equivalent circuit model of the whole system of any frequency in the frequency sequence, construct its differential-algebraic equation according to the topological connection relationship of each element in the equivalent circuit, and form a state space and its linearized state matrix;

[0094] The analysis unit is used to calculate the eigenvalues ​​of the linearized state matrix of different frequencies one by one according to the frequency sequence, screen out the key eigenvalues ​​from the relationship between the real and imaginary parts of the eigenvalues, calculate the risk mode participation factor, and obtain the converter correlation information corresponding to the key eigenvalues, so as to realize the identification of high oscillation risk sections.

[0095] The present invention also includes a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method described above is implemented.

[0096] The present invention also includes a storage medium on which a computer program is stored. When the computer program is executed by a processor, the method described above is implemented.

[0097] The beneficial effects of the present invention are as follows: the present invention constructs a system equivalent impedance network model at each frequency point, establishes a differential-algebraic equation group of the system equivalent circuit at a specific frequency, and uses pattern analysis technology to analyze and screen the system characteristic values ​​at the frequency, and further expands to all frequency points to propose steady-state operation criteria, disturbance response criteria and coupled self-excitation criteria to identify system resonance risks, and realize risk section identification, which can be applicable to multi-converter grid-connected systems, has clear and intuitive physical meanings, and is convenient for automated analysis through software programming. BRIEF DESCRIPTION OF THE DRAWINGS

[0098] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0099] Figure 1 is a flow chart of the method in Example 1;

[0100] Figure 2 It is a structural schematic diagram of the device in Example 1;

[0101] Figure 3 is a flow chart of the method in Example 2;

[0102] Figure 4 This is the current source frequency sweep circuit diagram;

[0103] Figure 5 It is the circuit diagram of voltage source frequency sweep;

[0104] Figure 6 It is a schematic diagram of flexible direct impedance;

[0105] Figure 7 It is the impedance diagram of doubly-fed wind turbine;

[0106] Figure 8 A schematic diagram of the structure of a computer device. DETAILED DESCRIPTION

[0107] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0108] Embodiment 1:

[0109] like Figure 1 As shown: A broadband oscillation analysis method based on source-network impedance equivalence includes the following steps:

[0110] Obtain the converter control and protection parameters and power system operation mode in the target area power grid, perform impedance analysis, and establish a converter impedance model;

[0111] The grid dimension is reduced by retaining the key converter grid-connected nodes, and the equivalent network impedance model of the regional power grid is obtained by solving the problem in a wide frequency band.

[0112] Generate a frequency sequence according to the target frequency range, obtain the converter impedance and equivalent network impedance of any frequency in the frequency sequence, construct an equivalent circuit model of the whole system of any frequency in the frequency sequence, construct its differential-algebraic equation according to the topological connection relationship of each element in the equivalent circuit, and form a state space and its linearized state matrix;

[0113] According to the frequency sequence, the eigenvalues ​​of the linearized state matrix of different frequencies are calculated one by one, the key eigenvalues ​​are screened out from the relationship between the real and imaginary parts of the eigenvalues, the risk modal participation factors are calculated, and the converter correlation information corresponding to the key eigenvalues ​​is obtained to realize the identification of high oscillation risk sections.

[0114] By constructing the system equivalent impedance network model at each frequency point, the differential-algebraic equation group of the system equivalent circuit at a specific frequency is established, and the pattern analysis technology is used to analyze and screen the system characteristic values ​​at this frequency. It is further expanded to all frequency points to propose steady-state operation criteria, disturbance response criteria and coupled self-excitation criteria to identify the system resonance risk and realize risk section identification. It can be applied to multi-converter grid-connected systems, has clear and intuitive physical meaning, and is convenient for automated analysis through software programming.

[0115] In this embodiment, when performing impedance analysis, obtaining the impedance response characteristics of the grid-connected node looking at the converter port includes the following steps:

[0116] Construct a broadband disturbance injection circuit in the electromagnetic transient simulation environment, select the voltage source / current source disturbance injection circuit according to the grid-connected characteristics and control strategy of the converter, and simulate the normal operating conditions of the converter;

[0117] Adjust the converter operating conditions according to the analysis requirements, set the harmonic voltage source / current source disturbance injection frequency according to the frequency sequence, and collect the converter port current / voltage steady-state response data, including the three-phase AC voltage AC Current

[0118] Convert the AC electrical quantity into positive and negative sequence components, solve the positive sequence impedance, and obtain the converter impedance model Z C (f):

[0119]

[0120] In the formula, is the positive sequence impedance at different frequencies.

[0121] The voltage source / current source disturbance injection circuit is selected according to the grid-connected characteristics and control strategy of the converter, including:

[0122] For the grid-connected converter, a voltage source disturbance injection circuit is used. The disturbance source is set to be an ideal power frequency voltage source connected in series with a harmonic voltage source. The relevant parameters of the ideal power frequency voltage source are consistent with the rated voltage of the grid-connected port. The amplitude of the harmonic voltage source is 1% to 5% of the ideal power frequency voltage source. During the harmonic injection period, the converter is in a stable operating state.

[0123] For grid-connected converters, a current source disturbance injection circuit is used. The disturbance source is set to an ideal power frequency current source in parallel with a harmonic current source. The relevant parameters of the ideal power frequency current source are consistent with the rated current of the grid-connected port. The amplitude of the harmonic current source is 1% to 5% of the ideal power frequency current source. The converter is in a stable operating state during the harmonic injection period.

[0124] The grid near the converter grid-connected node adopts detailed distributed parameter modeling, including:

[0125] Looking at the power grid from the grid-connected port of the converter, select the detailed distributed parameter modeling range of the nearby power grid, and select the distributed parameter modeling of the overhead lines and transformers in the selected area.

[0126] Retaining key converter grid-connected nodes to reduce grid dimension includes the following steps:

[0127] For the power grid to be analyzed, the admittance matrix Y(f) of the physical parameter power grid is first formed, and the nodes are divided into converter nodes B according to whether they are connected to the converter. C (f) With conventional Node B G (f), partition Y(f) according to the corresponding sequence number of the node:

[0128]

[0129] Y CC The order of (f) is n C ×n C , Y CG The order of (f) is n C ×n G , Y GC The order of (f) is n G ×n C , Y GG The order of (f) is n G ×n G , retain converter node B C (f), the grid equivalent admittance matrix is:

[0130]

[0131] Y G The order of (f) is n C ×n C , describes the equivalent physical properties of the system, and forms the equivalent impedance of the power grid based on its parameters, specifically:

[0132] The equivalent branch impedance of any branch is z G,ij (f) = -1 / y G,ij (f), y G,ij (f) is Y G (f) The jth element in the i-th row (i≠j); the equivalent impedance to ground of any node is:

[0133]

[0134] In the formula, y G,ij (f) is Y G (f) The i-th element in the i-th row.

[0135] In this embodiment, an equivalent circuit model of the entire system at any frequency in the frequency sequence is constructed, including:

[0136] For the grid-connected converter z at port i C,i (f k )=r C,i (f k )+jx C,i (f k ),u C,i (f k ) and i C,i (f k ) are the node voltage and node injection current respectively;

[0137] If x C,i (f k )<0, then at frequency f k The converter behaves as a capacitive, x C,i (f k )=1 / (2πf k C C,i (f k ))The corresponding differential equation is abbreviated as:

[0138]

[0139] If x C,i (f k )≥0, then at frequency f k The converter behaves as an inductive device, x C,i (f k )=2πf k L C,i (f k ) Its corresponding differential equation is abbreviated as:

[0140]

[0141] For the branch between node i and node j, z G,ij (f) = r G,ij (f k )+jx G,ij (f k ),u C,i (f k ) and u C,j (f k ) are the voltages of the two nodes of the branch, i C,ij (f k ) is the branch current;

[0142] If x G,ij (f k )<0, then at frequency f k The converter behaves as a capacitive, x G,ij(f k )=1 / (2πf k C G,ij (f k ))The corresponding differential equation is abbreviated as:

[0143]

[0144] If x G,ij (f k )≥0, then at frequency f k The converter behaves as an inductive device, x G,ij (f k )=2πf k L G,ij (f k ) Its corresponding differential equation is abbreviated as:

[0145]

[0146] For the equivalent grid grounding branch z at port i G,ii (f k )=r G,ii (f k )+jx G,ii (f k ),u C,i (f k ) are the node voltage and node injection current;

[0147] If x G,ii (f k )<0, then at frequency f k The converter behaves as a capacitive, x G,ii (f k )=1 / (2πf k C G,ii (f k ))The corresponding differential equation is abbreviated as:

[0148]

[0149] If x G,ii (f k )≥0, then at frequency f k The converter behaves as an inductive device, x G,ii (f k )=2πf k L G,ii (f k ) Its corresponding differential equation is abbreviated as:

[0150]

[0151] As a preferred embodiment of the above, constructing the differential-algebraic equations of the components in the equivalent circuit according to the topological connection relationship to form the state space and its linearized state matrix includes the following steps:

[0152] The equivalent grid node voltage U C , node injection current I C , branch current I L As a state quantity, the number of equivalent network branches Number of nodes n C , formed according to the branch information The state vector X(f k ),make

[0153]

[0154] In the formula, Indicates the voltage of equivalent network nodes; Indicates the amount of current injected into an equivalent network node; Indicates the current of equivalent network branches;

[0155] Write down the equivalent grid differential equations:

[0156] According to the equivalent circuit model, the differential equations for the converter, the differential equations for the equivalent grid interconnection and the differential equations for the equivalent grid grounding branch are established, and the following equations are obtained:

[0157]

[0158] Where A1(f k ) and A2(f k ) are both n X ×n X If it is a full rank square matrix of order, then:

[0159]

[0160] Let A(f k )=A1 -1 (f k )A2(f k ), and get the frequency f k The linearized state matrix of .

[0161] Among them, according to the frequency sequence, the eigenvalues ​​of the linearized state matrix of different frequencies are calculated one by one, including:

[0162] Calculate A(f k )The eigenvalue sequence of the matrix Combine all frequency eigenvalue sequences into n X ×n f Matrix of order

[0163] The key eigenvalues ​​are selected from the relationship between the real and imaginary parts of the eigenvalues, and the risk modal participation factors are calculated, including:

[0164] First call the steady-state operation criterion and determine the frequency f according to the properties of all eigenvalues k Does the system have a steady-state operating point when:

[0165] Traverse all elements of D(f), if the element λ in row i and column k i (f k ) is a positive real number, then the system is determined to be at frequency f k There is no stable operating point; the system can operate stably in the entire frequency band if and only if the real parts of all elements of D(f) are less than or equal to zero;

[0166] Next, the disturbance response criterion is called to determine the frequency f according to the real part of all complex eigenvalues. k Whether the system has negative damping to the disturbance when :

[0167] Traverse all elements of D(f), if the element λ in row i and column k i (f k ) is a complex number, then the column of the matrix must have its conjugate eigenvalue λ j (f k ), and denote them as λ ij (f k )=α ij (f k )±jβ ij (f k );

[0168] The damping ratio is defined as:

[0169]

[0170] If ij (f k )≥-0.03 or α ij (f k )>ξ set , then the system is judged at frequency f k After being disturbed, there is a negative damping response, where ξ set To set the threshold; the corresponding eigenvalue is marked as the key eigenvalue;

[0171] Finally, the coupling self-excitation criterion is called to determine whether the system has a multi-frequency self-excitation oscillation risk based on the frequency coupling characteristics between the complex eigenvalues:

[0172] Filter all negatively damped response eigenvalues ​​from all elements of D(f) to form a set:

[0173]

[0174] Where n- is the number of eigenvalues ​​of the negatively damped response; its corresponding frequency set is defined as:

[0175]

[0176] With set D (-) The elements in the equation correspond one to one; the corresponding eigenvalue imaginary part frequency set is defined as:

[0177]

[0178] With set D (-) The elements in the equation correspond one to one, and the solution is:

[0179]

[0180] If there exists a set D (-) A non-empty subset of Correspondingly F (-) With F (O) The elements in the set form a subset of and and The system has self-oscillation; if If the number of elements in is greater than or equal to 2, the system has coupled self-oscillation, and the corresponding eigenvalue is marked as the key eigenvalue;

[0181] On the contrary, there is no non-empty subset that satisfies the above conditions. Then the system does not have the conditions for coupled self-excitation.

[0182] In this embodiment, the converter correlation information corresponding to the key characteristic value is obtained, including:

[0183] For any key characteristic value at any frequency, if the coupled self-excitation criterion If the number of elements is 1, or only the negative damping disturbance response criterion is met, the power electronic converter correlation ratio of the eigenvalue is calculated:

[0184] Let the key eigenvalue λ i (f k ) has a left eigenvector of The right eigenvector is The correlation factor of the eigenvalue to the jth state quantity is calculated as:

[0185]

[0186] Calculate the relevant ratio of the power electronic converter as:

[0187]

[0188] By i (f k ) numerically determines the degree of participation of the power electronic converter in the negative damping mode. If ρ i (f k )>ε set , then the negative damping mode is determined to be dominated by the power electronic converter, otherwise it is determined that the negative damping mode is a strong grid-related mode; where ε set To set the threshold;

[0189] If the coupled self-excitation criterion If the number of elements is greater than 1, the power electronic converter correlation ratio of each eigenvalue should be analyzed one by one and calculated according to the threshold ε set Determine its attributes as power electronic converter-dominated or grid-strongly related mode.

[0190] Identification of high oscillation risk sections includes:

[0191] For the dominant mode λ of the power electronic converter i (f k ), filter state quantity X C (f k )=[U C (f k )|I C (f k )] and its state quantity related factors Yes | C (f k )| Sort, select the significantly larger items, and mark the section as a high-risk section;

[0192] For the strongly correlated power grid mode, the state quantities are divided according to the real part signs of the left eigenvectors of each key eigenvalue.

[0193] like Figure 2 As shown, this embodiment also includes a power electronic power system stability analysis device, using the above method, including:

[0194] A converter impedance model building unit is used to obtain converter control and protection parameters and power system operation mode in the target area power grid, perform impedance analysis, and establish a converter impedance model;

[0195] The equivalent network impedance model modeling unit is used to retain the key converter grid-connected nodes to reduce the grid dimension, solve within a wide frequency band, and obtain the equivalent network impedance model of the regional power grid;

[0196] The state space unit is used to generate a frequency sequence according to the target frequency range, obtain the converter impedance and equivalent network impedance of any frequency in the frequency sequence, construct an equivalent circuit model of the whole system of any frequency in the frequency sequence, construct its differential-algebraic equation according to the topological connection relationship of each element in the equivalent circuit, and form a state space and its linearized state matrix;

[0197] The analysis unit is used to calculate the eigenvalues ​​of the linearized state matrix of different frequencies one by one according to the frequency sequence, screen out the key eigenvalues ​​from the relationship between the real and imaginary parts of the eigenvalues, calculate the risk mode participation factor, and obtain the converter correlation information corresponding to the key eigenvalues ​​to realize the identification of high oscillation risk sections.

[0198] Embodiment 2:

[0199] The present embodiment is further described in detail below with reference to the accompanying drawings. Figure 3 As shown, this embodiment includes a broadband oscillation analysis method based on source-network impedance equivalence, including:

[0200] Power electronic converter impedance model acquisition:

[0201] Obtain the impedance response characteristics of the grid-connected point looking toward the converter port, taking the flexible DC converter as an example:

[0202] Step 1: Construct a broadband disturbance injection circuit in the electromagnetic transient simulation environment, select the voltage source / current source disturbance injection circuit according to the grid-connected characteristics and control strategy of the converter, and simulate the normal operating conditions of the converter.

[0203] Use a current source disturbance injection circuit, such as Figure 4 As shown, the disturbance source is set to an ideal power frequency current source and a harmonic current source in parallel, wherein the relevant parameters of the ideal power frequency current source are consistent with the rated current of the grid-connected port, and the amplitude of the harmonic current source is 1% to 5% of the ideal power frequency voltage source. During the harmonic injection period, the converter is in a stable operating state.

[0204] Use a voltage source disturbance injection circuit, such as Figure 5 As shown, the disturbance source is set to be an ideal power frequency voltage source and a harmonic voltage source in series, wherein the relevant parameters of the ideal power frequency voltage source are consistent with the rated voltage of the grid-connected port, the amplitude of the harmonic voltage source is 1% to 5% of the ideal power frequency voltage source, and the converter is in a stable operating state during the harmonic injection period.

[0205] Step 2: Adjust the converter operating conditions according to the analysis requirements, and follow the frequency sequence [f1,f2,…,f N ]Set the harmonic voltage source / current source disturbance injection frequency and collect the converter port current / voltage steady-state response data, including three-phase AC voltage, AC current, etc.

[0206] Step 3: Convert AC electrical quantities into positive and negative sequence components and solve for the positive sequence impedance

[0207]

[0208] The soft impedance characteristic curve is as follows: Figure 6 As shown in Figure 2, the impedance characteristic curve of the doubly fed wind turbine is as follows: Figure 7 shown.

[0209] Calculation of equivalent network impedance model of regional power grid:

[0210] Looking at the grid from the grid-connected port of the power electronic converter, the detailed distributed parameter modeling range of the near-area grid is selected, and the distributed parameter modeling of the overhead lines, transformers and other equipment in the selected area can be used. Considering the distributed parameter characteristics of the transformer and AC transmission line near the converter station, the frequency range is 1 to 3000Hz, and the impedance matrix formed contains 9×9×3000 elements.

[0211] Power grid dimensionality reduction method:

[0212] For the power grid to be analyzed, the input system operation mode information includes but is not limited to the power network parameter information (including the parameters of primary equipment such as overhead lines, cables, transformers, etc.), startup mode information, load access information, and power flow analysis results. First, the admittance matrix Y(f) of the physical parameter power grid is formed, and the nodes are divided into converter nodes B according to whether they are connected to power electronic converters. C (f) With conventional Node B G (f), partition Y(f) according to the corresponding sequence number of the node:

[0213]

[0214] Y CC The order of (f) is n C ×n C , Y CG The order of (f) is n C ×n G , Y GC The order of (f) is n G ×n C , Y GG The order of (f) is n G ×n G , retain converter node B C (f), the grid equivalent admittance matrix is:

[0215]

[0216] Y G The order of (f) is n C ×nC , describes the equivalent physical properties of the system, and forms the equivalent impedance of the power grid based on its parameters, specifically:

[0217] The equivalent branch impedance of any branch is z G,ij (f) = -1 / y G,ij (f), y G,ij (f) is Y G (f) The jth element in the i-th row (i≠j); the equivalent impedance to ground of any node is y G,ij (f) is Y G (f) The i-th element in the i-th row.

[0218] Equivalent circuit model construction:

[0219] 1) Converter branch

[0220] For the grid-connected converter z at port i C,i (f k )=r C,i (f k )+jx C,i (f k ),u C,i (f k ) and i C,i (f k ) are the node voltage and node injection current respectively.

[0221] If x C,i (f k )<0, then at frequency f k The converter behaves as a capacitive, x C,i (f k )=1 / (2πf k C C,i (f k ))The corresponding differential equation can be simplified as

[0222]

[0223] If x C,i (f k )≥0, then at frequency f k The converter behaves as an inductive device, x C,i (f k )=2πf k L C,i (f k ) The corresponding differential equation can be simplified as

[0224]

[0225] 2) Equivalent grid interconnection branches

[0226] For the branch between node i and node j, z G,ij (f) = r G,ij (f k )+jx G,ij (f k ),u C,i (f k ) and u C,j (f k ) are the voltages of the two nodes of the branch, i C,ij (f k ) is the branch current.

[0227] If x G,ij (f k )<0, then at frequency f k The converter behaves as a capacitive, x G,ij (f k )=1 / (2πf k C G,ij (f k ))The corresponding differential equation can be simplified as

[0228]

[0229] If x G,ij (f k )≥0, then at frequency f k The converter behaves as an inductive device, x G,ij (f k )=2πf k L G,ij (f k ) The corresponding differential equation can be simplified as

[0230]

[0231] 3) Equivalent grid grounding branch

[0232] For the equivalent grid grounding branch z at port i G,ii (f k )=r G,ii (f k )+jx G,ii (f k ),u C,i (f k ) are the node voltage and node injection current.

[0233] If x G,ii (f k )<0, then at frequency f k The converter behaves as a capacitive, x G,ii (f k )=1 / (2πf k CG,ii (f k ))The corresponding differential equation can be simplified as

[0234]

[0235] If x G,ii (f k )≥0, then at frequency f k The converter behaves as an inductive device, x G,ii (f k )=2πf k L G,ii (f k ) The corresponding differential equation can be abbreviated as

[0236]

[0237] The state space is formed according to the electrical network equation and the dynamic equation of the converter grid connection point:

[0238] Step 1: Equivalent grid node voltage U C , node injection current I C , branch current I L As a state quantity, the number of equivalent network branches Number of nodes n C , formed according to the branch information The state vector X(f k ),make

[0239]

[0240] In the formula, Indicates the voltage of equivalent network nodes; Indicates the amount of current injected into an equivalent network node; Indicates the current of equivalent network branches;

[0241] Step 2 Write the equivalent power grid differential equations

[0242] According to equations (4) to (5), the differential equations for the converter branches are established. According to equations (6) to (7), the differential equations for the equivalent grid interconnection branches are established. According to equations (8) to (9), the differential equations for the equivalent grid grounding branches are established. The following forms are obtained:

[0243]

[0244] Where A1(f k ) and A2(f k ) are both n X ×n X If a square matrix of full rank is

[0245]

[0246] Let A(f k )=A1 -1 (f k )A2(f k ), and get the frequency f k The linearized state matrix of .

[0247] Eigenvalue calculation and key eigenvalue screening:

[0248] Form the matrix:

[0249] Calculate A(f k )The eigenvalue sequence of the matrix Combine all frequency eigenvalue sequences into n X ×n f Matrix of order The calculation methods include but are not limited to the existing mature QR method, BR method, Arnoldi method, etc.

[0250] The risk characteristic values ​​are screened out by integrating steady-state operation criteria, coupled self-excitation criteria and disturbance response criteria, including:

[0251] 1) First, call the steady-state operation criterion and determine the frequency f according to the properties of all eigenvalues k Does the system have a steady-state operating point?

[0252] 2) Then, the disturbance response criterion is called to determine the frequency f according to the real part of all complex eigenvalues. k Whether the system has negative damping to disturbances;

[0253] 3) Finally, the coupling self-excitation criterion is called to determine whether the system has the risk of multi-frequency self-oscillation based on the frequency coupling characteristics between the complex eigenvalues.

[0254] Steady-state operation criteria:

[0255] Traverse all elements of D(f), if the element λ in row i and column k i (f k ) is a positive real number, then the system is determined to be at frequency f k There is no stable operating point; the system can operate stably over the entire frequency band if and only if the real parts of all elements of D(f) are less than or equal to zero.

[0256] Disturbance response criterion:

[0257] Traverse all elements of D(f), if the element λ in row i and column k i (f k ) is a complex number, then the column of the matrix must have its conjugate eigenvalue λ j (fk ), and denote them as λ ij (f k )=α ij (f k )±jβ ij (f k ). The damping ratio is defined as

[0258]

[0259] If ij (f k )≥-0.03 or α ij (f k )>ξ set , then the system is judged at frequency f k After being disturbed, there is a negative damping response, where ξ set For setting the threshold, a reference value of -0.1 can be selected. The corresponding eigenvalues ​​are marked as key eigenvalues.

[0260] Coupled self-excitation criterion:

[0261] According to the disturbance response criterion, all negative damping response eigenvalues ​​are selected from all elements of D(f) to form a set Where n- is the number of eigenvalues ​​of the negative damping response; its corresponding frequency set is defined as With set D (-) The elements in the equation correspond one to one; the corresponding eigenvalue imaginary part frequency set is defined as With set D (-) The elements in the equation correspond one to one, and the solution is:

[0262]

[0263] If there exists a set D (-) A non-empty subset of Correspondingly F (-) With F (O) The elements in the set form a subset of and and The system has self-oscillation; if If the number of elements in is greater than or equal to 2, the system has coupled self-oscillation. The corresponding eigenvalues ​​are marked as key eigenvalues.

[0264] On the contrary, there is no non-empty subset that satisfies the above conditions. Then the system does not have the conditions for coupled self-excitation.

[0265] Analysis of relevant information of power electronic converter:

[0266] For any key characteristic value at any frequency, if the coupled self-excitation criterion If the number of elements is 1, or only the negative damping disturbance response criterion is met, the power electronic converter correlation ratio of the eigenvalue is calculated:

[0267] Let the key eigenvalue λ i (f k ) has a left eigenvector of The right eigenvector is Calculate the correlation factor of the eigenvalue to the jth state quantity:

[0268]

[0269] Calculate the relevant ratio of the power electronic converter as

[0270]

[0271] By i (f k ) value can determine the degree of participation of the power electronic converter in the negative damping mode. If ρ i (f k )>ε set , then the negative damping mode is determined to be dominated by the power electronic converter, otherwise it is determined that the negative damping mode is a strong grid-related mode. set To set the threshold, a reference value of 0.5 may be selected.

[0272] If the coupled self-excitation criterion If the number of elements is greater than 1, the power electronic converter correlation ratio of each eigenvalue should be analyzed one by one and calculated according to the threshold ε set Determine its attributes as power electronic converter-dominated or grid-strongly related mode.

[0273] Identification of resonant sections with high oscillation risk:

[0274] For the dominant mode λ of the power electronic converter i (f k ), filter state quantity X C (f k )=[U C (f k )|I C (f k )] and its state quantity related factors Yes | C (f k )|Sort, select the significantly larger items, and mark the section as a high-risk section.

[0275] For the strongly correlated power grid mode, the state quantities should be divided according to the real part sign of the left eigenvector of each key eigenvalue.

[0276] See also Figure 8A computer device 400 provided in an embodiment of the present application includes: a processor 410 and a memory 420, wherein the memory 420 stores a computer program executable by the processor 410, and when the computer program is executed by the processor 410, the above method is executed.

[0277] The embodiment of the present application further provides a storage medium 430 on which a computer program is stored. When the computer program is run by the processor 410, the above method is executed.

[0278] Among them, the storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable red-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, disk or optical disk.

[0279] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0280] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0281] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0282] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0283] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic devices), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0284] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0285] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0286] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A broadband oscillation analysis method based on source-network impedance equivalence, characterized in that: The steps include: Obtain the converter control and protection parameters and power system operation mode in the target area power grid, perform impedance analysis, and establish a converter impedance model; The grid dimension is reduced by retaining the key converter grid-connected nodes, and the equivalent network impedance model of the regional power grid is obtained by solving the problem in a wide frequency band. Generate a frequency sequence according to the target frequency range, obtain the converter impedance and equivalent network impedance of any frequency in the frequency sequence, construct an equivalent circuit model of the whole system of any frequency in the frequency sequence, construct its differential-algebraic equation according to the topological connection relationship of each element in the equivalent circuit, and form a state space and its linearized state matrix; According to the frequency sequence, the eigenvalues ​​of the linearized state matrix of different frequencies are calculated one by one, the key eigenvalues ​​are screened out from the relationship between the real and imaginary parts of the eigenvalues, the risk mode participation factor is calculated, and the converter correlation information corresponding to the key eigenvalues ​​is obtained to realize the identification of high oscillation risk sections; The step of calculating the eigenvalues ​​of the linearized state matrices of different frequencies one by one according to the frequency sequence comprises: Calculate A(f k )The eigenvalue sequence of the matrix Combine all frequency eigenvalue sequences into n X ×n f Matrix of order The step of selecting key eigenvalues ​​from the relationship between the real part and the imaginary part of the eigenvalues ​​and calculating the risk modal participation factor includes: First call the steady-state operation criterion and determine the frequency f according to the properties of all eigenvalues k Does the system have a steady-state operating point when: Traverse all elements of D(f), if the element λ in row i and column k i (f k ) is a positive real number, then the system is determined to be at frequency f k There is no stable operating point; the system can operate stably in the entire frequency band if and only if the real parts of all elements of D(f) are less than or equal to zero; Next, the disturbance response criterion is called to determine the frequency f according to the real part of all complex eigenvalues. k Whether the system has negative damping to the disturbance when : Traverse all elements of D(f), if the element λ in row i and column k i (f k ) is a complex number, then the column of the matrix must have its conjugate eigenvalue λ j (f k ), and denote them as λ ij (f k )=α ij (f k )±jβ ij (f k ); The damping ratio is defined as: If ij (f k )≥-0.03 or α ij (f k )>ξ set , then the system is judged at frequency f k After being disturbed, there is a negative damping response, where ξ set To set the threshold; the corresponding eigenvalue is marked as the key eigenvalue; Finally, the coupling self-excitation criterion is called to determine whether the system has a multi-frequency self-excitation oscillation risk based on the frequency coupling characteristics between the complex eigenvalues: Filter all negatively damped response eigenvalues ​​from all elements of D(f) to form a set: Where n- is the number of eigenvalues ​​of the negatively damped response; its corresponding frequency set is defined as: With set D (-) The elements in the equation correspond one to one; the corresponding eigenvalue imaginary part frequency set is defined as: With set D (-) The elements in the equation correspond one to one, and the solution is: If there exists a set D (-) A non-empty subset of Correspondingly F (-) With F (O) The elements in the set form a subset of and and The system has self-oscillation; if If the number of elements in is greater than or equal to 2, the system has coupled self-oscillation, and the corresponding eigenvalue is marked as the key eigenvalue; On the contrary, there is no non-empty subset that satisfies the above conditions. Then the system does not have the conditions for coupled self-excitation.

2. The broadband oscillation analysis method based on source-network impedance equivalence according to claim 1, characterized in that: When performing impedance analysis, obtaining the impedance response characteristics of the grid-connected node looking at the converter port includes the following steps: Construct a broadband disturbance injection circuit in the electromagnetic transient simulation environment, select the voltage source / current source disturbance injection circuit according to the grid-connected characteristics and control strategy of the converter, and simulate the normal operating conditions of the converter; Adjust the converter operating conditions according to the analysis requirements, set the harmonic voltage source / current source disturbance injection frequency according to the frequency sequence, and collect the converter port current / voltage steady-state response data, including the three-phase AC voltage AC Current Convert the AC electrical quantity into positive and negative sequence components, solve the positive sequence impedance, and obtain the converter impedance model Z C (f): In the formula, is the positive sequence impedance at different frequencies.

3. The broadband oscillation analysis method based on source-network impedance equivalence according to claim 2, characterized in that: The voltage source / current source disturbance injection circuit is selected according to the grid-connected characteristics and control strategy of the converter, including: For the grid-connected converter, a voltage source disturbance injection circuit is used, and the disturbance source is set to be an ideal power frequency voltage source connected in series with a harmonic voltage source. The relevant parameters of the ideal power frequency voltage source are consistent with the rated voltage of the grid-connected port. The amplitude of the harmonic voltage source is 1% to 5% of the ideal power frequency voltage source. During the harmonic injection period, the converter is in a stable operating state. For grid-connected converters, a current source disturbance injection circuit is used. The disturbance source is set to an ideal power frequency current source and a harmonic current source in parallel. The relevant parameters of the ideal power frequency current source are consistent with the rated current of the grid-connected port. The amplitude of the harmonic current source is 1% to 5% of the ideal power frequency current source. The converter is in a stable operating state during the harmonic injection period.

4. The broadband oscillation analysis method based on source-network impedance equivalence according to claim 2, characterized in that: The grid near the converter grid-connected node is modeled using detailed distributed parameters, including: Looking at the power grid from the grid-connected port of the converter, select the detailed distributed parameter modeling range of the nearby power grid, and select the distributed parameter modeling of the overhead lines and transformers in the selected area.

5. The broadband oscillation analysis method based on source-network impedance equivalence according to claim 1, characterized in that: The method of retaining key converter grid-connected nodes to perform grid dimension reduction includes the following steps: For the power grid to be analyzed, the admittance matrix Y(f) of the physical parameter power grid is first formed, and the nodes are divided into converter nodes B according to whether they are connected to the converter. C (f) With conventional Node B G (f), partition Y(f) according to the corresponding sequence number of the node: Y CC The order of (f) is n C ×n C , Y CG The order of (f) is n C ×n G , Y GC The order of (f) is n G ×n C , Y GG The order of (f) is n G ×n G , retain converter node B C (f), the grid equivalent admittance matrix is: Y G The order of (f) is n C ×n C , describes the equivalent physical properties of the system, and forms the equivalent impedance of the power grid based on its parameters, specifically: The equivalent branch impedance of any branch is z G,ij (f) = -1 / y G,ij (f), y G,ij (f) is Y G (f) The jth element in the i-th row (i≠j); the equivalent impedance to ground of any node is: In the formula, y G,ij (f) is Y G (f) The i-th element in the i-th row.

6. The broadband oscillation analysis method based on source-network impedance equivalence according to claim 1, characterized in that: The equivalent circuit model of the whole system at any frequency under the constructed frequency sequence includes: For the grid-connected converter z at port i C,i (f k )=r C,i (f k )+jx C,i (f k ),u C,i (f k ) and i C,i (f k ) are the node voltage and node injection current respectively; If x C,i (f k )<0, then at frequency f k The converter behaves as a capacitive, x C,i (f k )=1 / (2πf k C C,i (f k ))The corresponding differential equation is abbreviated as: If x C,i (f k )≥0, then at frequency f k The converter behaves as an inductive device, x C,i (f k )=2πf k L C,i (f k ) Its corresponding differential equation is abbreviated as: For the branch between node i and node j, z G,ij (f) = r G,ij (f k )+jx G,ij (f k ),u C,i (f k ) and u C,j (f k ) are the voltages of the two nodes of the branch, i C,ij (f k ) is the branch current; If x G,ij (f k )<0, then at frequency f k The converter behaves as a capacitive, x G,ij (f k )=1 / (2πf k C G,ij (f k ))The corresponding differential equation is abbreviated as: If x G,ij (f k )≥0, then at frequency f k The converter behaves as an inductive device, x G,ij (f k )=2πf k L G,ij (f k ) Its corresponding differential equation is abbreviated as: For the equivalent grid grounding branch z at port i G,ii (f k )=r G,ii (f k )+jx G,ii (f k ),u C,i (f k ) are the node voltage and node injection current; If x G,ii (f k )<0, then at frequency f k The converter behaves as a capacitive, x G,ii (f k )=1 / (2πf k C G,ii (f k ))The corresponding differential equation is abbreviated as: If x G,ii (f k )≥0, then at frequency f k The converter behaves as an inductive device, x G,ii (f k )=2πf k L G,ii (f k ) Its corresponding differential equation is abbreviated as:

7. The broadband oscillation analysis method based on source-network impedance equivalence according to claim 6, characterized in that: The method of constructing the differential-algebraic equation according to the topological connection relationship of each element in the equivalent circuit to form the state space and its linearized state matrix includes the following steps: The equivalent grid node voltage U C , Node injection current I C , branch current I L As a state quantity, the number of equivalent network branches Number of nodes n C , formed according to the branch information The state vector X(f k ),make In the formula, Indicates the voltage of equivalent network nodes; Indicates the amount of current injected into an equivalent network node; Indicates the current of equivalent network branches; Write down the equivalent grid differential equations: According to the equivalent circuit model, the differential equations for the converter, the differential equations for the equivalent grid interconnection and the differential equations for the equivalent grid grounding branch are established, and the following equations are obtained: Where A1(f k ) and A2(f k ) are both n X ×n X If it is a full rank square matrix of order, then: Let A(f k )=A1 -1 (f k )A2(f k ), and get the frequency f k The linearized state matrix of .

8. The broadband oscillation analysis method based on source-network impedance equivalence according to claim 1, characterized in that: The converter correlation information corresponding to the key characteristic value is obtained, including: For any key characteristic value at any frequency, if the coupled self-excitation criterion If the number of elements is 1, or only the negative damping disturbance response criterion is met, the power electronic converter correlation ratio of the eigenvalue is calculated: Let the key eigenvalue λ i (f k ) has a left eigenvector of The right eigenvector is The correlation factor of the eigenvalue to the jth state quantity is calculated as: The relevant ratio of the power electronic converter is calculated as: By i (f k ) numerically determines the degree of participation of the power electronic converter in the negative damping mode. If ρ i (f k )>ε set , then the negative damping mode is determined to be dominated by the power electronic converter, otherwise it is determined that the negative damping mode is a strong grid-related mode; where ε set To set the threshold; If the coupled self-excitation criterion If the number of elements is greater than 1, the power electronic converter correlation ratio of each eigenvalue should be analyzed one by one, and the threshold ε set Determine its attributes as power electronic converter-dominated or grid-strongly related mode.

9. The broadband oscillation analysis method based on source-network impedance equivalence according to claim 8, characterized in that: The high oscillation risk section identification includes: For the dominant mode λ of the power electronic converter i (f k ), filter state quantity and its state quantity related factors Yes | C (f k )| Sort, select the significantly larger items, and mark the section as a high-risk section; For the strongly correlated power grid mode, the state quantities are divided according to the real part signs of the left eigenvectors of each key eigenvalue.

10. A power electronic power system stability analysis device, characterized in that: Use of the method according to any one of claims 1 to 9, comprising: A converter impedance model building unit is used to obtain converter control and protection parameters and power system operation mode in the target area power grid, perform impedance analysis, and establish a converter impedance model; The equivalent network impedance model modeling unit is used to retain the key converter grid-connected nodes to reduce the grid dimension, solve within a wide frequency band, and obtain the equivalent network impedance model of the regional power grid; The state space unit is used to generate a frequency sequence according to the target frequency range, obtain the converter impedance and equivalent network impedance of any frequency in the frequency sequence, construct an equivalent circuit model of the whole system of any frequency in the frequency sequence, construct its differential-algebraic equation according to the topological connection relationship of each element in the equivalent circuit, and form a state space and its linearized state matrix; The analysis unit is used to calculate the eigenvalues ​​of the linearized state matrix of different frequencies one by one according to the frequency sequence, screen out the key eigenvalues ​​from the relationship between the real and imaginary parts of the eigenvalues, calculate the risk mode participation factor, and obtain the converter correlation information corresponding to the key eigenvalues, so as to realize the identification of high oscillation risk sections.

11. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 9 is implemented.

12. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 9 is implemented.

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