General numerical aggregation method and system for frequency coupling admittance / impedance

Abstract

The invention discloses a universal numerical aggregation method and system for frequency coupling admittance / impedance, and the method comprises the steps: determining a frequency coupling admittance model of a converter, and obtaining a complementary frequency sum in the frequency coupling admittance model; splitting an original network of the converter into a first network and a second network which respectively correspond to the complementary frequency; respectively accessing the frequency coupling admittance model to the first network and the second network, and generating a first admittance matrix and a second admittance matrix corresponding to the first network and the second network; and combining the first admittance matrix and the second admittance matrix into an extended node admittance matrix, and performing coupling frequency admittance calculation of a specified network node based on the extended node admittance matrix.

Description

Technical Field

[0001] This invention relates to the field of new energy power generation technology, and more specifically, to a general numerical aggregation method and system for frequency coupling admittance / impedance. Background Technology

[0002] Currently, renewable energy is gradually replacing traditional fossil fuels, and in the future, new energy power generation will become the main source of final energy demand. As the proportion of new energy power generation gradually increases, the power system is gradually developing towards a high proportion of new energy and a high proportion of power electronic equipment. The internal multiple control links of new energy power generation and power electronic equipment systems are coupled, forming a complex multi-timescale high-order nonlinear system. Its interaction with the power grid easily causes subsynchronous / supersynchronous oscillations, becoming one of the important issues affecting the safe and stable operation of the power grid.

[0003] Currently, significant research has been achieved on the subsynchronous / supersynchronous oscillation characteristics of converter grid-connected systems. The main research methods include time-domain simulation of electromagnetic transient models, eigenvalue analysis of state-space models, admittance / impedance model analysis, and the Nyquist stability criterion. However, most studies focus on single-converter grid-connected systems, and these methods are difficult to apply to the oscillation characteristic analysis of renewable energy aggregation systems containing numerous grid-connected converters. Impedance / admittance network modeling is a feasible method for studying the oscillation characteristics of multi-converter networks. However, in the subsynchronous / supersynchronous frequency range, converters exhibit coupling frequency effects, and single-structure network modeling cannot reflect this coupling characteristic. Furthermore, using coupled impedance series-parallel aggregation is difficult to apply to generalized procedural analysis of the subsynchronous / supersynchronous oscillation characteristics of complex networks containing multiple converters. The impedance / admittance of converters is expressed as explicit transfer functions. If the number of network nodes reaches hundreds or thousands, it is difficult to directly perform inversion operations and matrix characteristic analysis on the explicit high-order node admittance transfer function matrix. Furthermore, real-world renewable energy aggregation systems connect a large number of different types of converter grid-connected units, making it difficult to obtain white-box models of these units. Instead, time-domain simulation or real-time controller-in-the-loop simulation of the actual controller can be performed on the black-box model to obtain the frequency coupling admittance curve data of the grid-connected converter units. Therefore, numerical calculation at each frequency point is more suitable for analyzing subsynchronous / supersynchronous oscillations in large-scale renewable energy aggregation system networks. It can solve for the aggregated coupling admittance curve data of the converter (station) connection point under study, facilitating further analysis of system stability.

[0004] Existing technologies analyze network resonance points by modeling admittance networks, but in the subsynchronous / supersynchronous frequency range, converters exhibit coupling frequency effects, and modeling with a single-structure network cannot reflect this coupling characteristic. The existing frequency-coupled impedance series-parallel aggregation method is not easily applicable to general programmatic analysis of the subsynchronous / supersynchronous oscillation characteristics of complex networks containing multiple converters.

[0005] For networks with hundreds or thousands of nodes, existing technologies make it difficult to directly perform inversion operations and matrix characteristic analysis on high-order node admittance transfer function matrices.

[0006] Therefore, a technique is needed to enable universal numerical aggregation calculations of frequency coupling admittance / impedance for multi-converter networks. Summary of the Invention

[0007] The present invention provides a general numerical aggregation method and system for frequency coupling admittance / impedance to solve the problem of how to calculate the general numerical aggregation of frequency coupling admittance / impedance for multi-converter networks.

[0008] To address the aforementioned problems, this invention provides a general numerical aggregation method for frequency-coupled admittance / impedance, the method comprising: Determine the frequency coupling admittance model of the converter and obtain the complementary frequencies in the frequency coupling admittance model. and ; The original network of the converter is split into two parts, one with a complementary frequency. and The corresponding first and second networks; The frequency-coupled admittance model is connected to the first network and the second network respectively to generate a first admittance matrix and a second admittance matrix corresponding to the first network and the second network. The first admittance matrix and the second admittance matrix are merged into an extended node admittance matrix. Based on the extended node admittance matrix, the coupling frequency admittance of the specified network node is calculated.

[0009] Preferably, determining the frequency coupling admittance model of the converter includes: At the grid connection point of the converter, a frequency of... The disturbance voltage is used to determine the harmonic voltage on the valve side of the converter as follows: (1) Among them, the variables with the superscript d are the corresponding complementary frequencies. The variable with superscript 'c' represents the corresponding complementary frequency. The variable is represented by an asterisk (*) for conjugation. , This refers to the phasor of the disturbance voltage on the valve side of the converter. , For the PCC disturbance voltage phasor at the connection point, , The conjugate of the PCC disturbance voltage phasor at the connection point. , For converter disturbance current phasor , It is the conjugate of the converter disturbance current phasor. , , , , , , , For coefficient transfer functions, S d , S C For the corresponding perturbation frequency, complementary frequencies The Laplace operator; The frequency coupling admittance model of the converter is determined by the above equation as follows: (2) in, , , , These are the frequency coupling admittance matrix elements of the converter.

[0010] Preferably, the original network of the converter is split into two groups, each with a complementary frequency. and The corresponding first and second networks, where node K corresponds to the node Kirchhoff's law KCL equation in the first and second networks, are as follows: (3) in, , complementary frequencies and The perturbation voltage phasor at node k. , complementary frequencies and The perturbation voltage phasor of node i. , complementary frequencies and The admittance of L non-converter elements at node k to ground. , complementary frequencies and The admittance of node k between other nodes and I non-converter elements. , complementary frequencies and The current of the M converters at node k, , complementary frequencies and J current sources at node k, Let k be the frequency of node k.

[0011] Preferably, the step of connecting the frequency-coupled admittance model to the first network and the second network respectively, and generating the first admittance matrix and the second admittance matrix corresponding to the first network and the second network, includes connecting the frequency-coupled admittance model to the node Kirchhoff's law KCL equations of the first network and the second network respectively, and generating the first admittance matrix and the second admittance matrix corresponding to the first network and the second network: (4) in, , , , complementary frequencies and The i-th converter frequency coupling admittance model element at node k. complementary frequencies The admittance conjugate of the L ground-connected non-converter elements at node k. complementary frequencies The admittance conjugate of node k with other nodes is I for non-converter elements. complementary frequencies The perturbation voltage phasor conjugate at node k. complementary frequencies The perturbation voltage phasors of nodes k and i are conjugate. complementary frequencies The J current sources at node k are conjugate.

[0012] Preferably, the step of merging the first admittance matrix and the second admittance matrix into an extended node admittance matrix, based on the extended node admittance matrix, includes: For an N-node network, its corresponding extended node admittance matrix is: The node voltage vector is: (5) in, Let N be the voltage phasors of the network nodes corresponding to the perturbation frequency. This represents the conjugate of the voltage vectors of the N nodes in the network at the corresponding coupling frequency. T The symbol for vector transpose; The first of the extended node admittance matrix The row corresponds to Kirchhoff's law KCL at the k-th node of the first network, and the row of the extended node admittance matrix is... The row corresponds to Kirchhoff's law KCL at the k-th node of the second network; Suppose that the grid-connected converter is connected to the k-th node of the original network, and its coupled frequency admittance model is: (6) in, , These are the phasors of the port current response at the disturbance frequency and the conjugate of the port current response at the coupling frequency for the converter connected to node k. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current phasor at the corresponding disturbance frequency. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current conjugate phasor at the corresponding coupling frequency. The contribution of the grid-connected converter to the extended node admittance matrix is ​​calculated as follows: [Equation of extended node admittance matrix]. Element plus , Element plus , Element plus , Element plus ; The transmission lines and transformer branches connecting nodes k and m in the original network have the following uncoupled admittance model between the first network and the second network: (7) in, , These are the disturbance frequency current phasor and the coupling frequency current conjugate phasor of the component branch between node k and node m, respectively. , These are the conjugate values ​​of the component's admittance at the disturbance frequency and the admittance at the coupling frequency, respectively. The contribution of transmission lines and transformer branches to the extended node admittance matrix is ​​calculated as follows: (The extended admittance matrix is...) , Element plus , , Subtraction of elements , , Element plus , , Subtraction of elements .

[0013] Preferably, based on the extended node admittance matrix, the coupled admittance aggregation calculation of a specified network node is performed, including: Two sets of complementary frequencies are sequentially injected into a designated node J in the network. and Current source ,in, , Injecting the i-th perturbation frequency current source phasor and the conjugate of the coupled frequency current source into node J, respectively. To inject the disturbance frequency and coupling frequency current source vector at node J, To inject the disturbance frequency and coupling frequency current source matrix at node J; By applying Kirchhoff's law KCL equation to the network extended node admittance matrix, the voltages of the two sets of aggregation nodes J are calculated. ,in, , These are the voltage phasor of the perturbation frequency response at node J and the voltage conjugate of the coupling frequency, respectively. Let J be the response voltage matrix of node J; (8) (9) Let the aggregation frequency coupling admittance of node J be: (10) in, , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current phasor at the corresponding disturbance frequency. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current conjugate phasor at the corresponding coupling frequency. Substitute the two sets of voltages and currents into The coupling frequency admittance of node J is obtained as follows: (11)

[0014] Based on another aspect of the present invention, the present invention provides a general numerical aggregation system for frequency-coupled admittance / impedance, the system comprising: An initial unit is used to determine the frequency coupling admittance model of the converter and obtain the complementary frequencies in the frequency coupling admittance model. and ; Splitting units are used to split the original converter network into units that are complementary to the frequency. and The corresponding first and second networks; The generation unit is used to connect the frequency-coupled admittance model to the first network and the second network respectively, and generate a first admittance matrix and a second admittance matrix corresponding to the first network and the second network. An extension unit is used to merge the first admittance matrix and the second admittance matrix into an extended node admittance matrix, and to calculate the coupling frequency admittance of a specified network node based on the extended node admittance matrix.

[0015] Preferably, the initial unit, used to determine the frequency coupling admittance model of the converter, is also used for: At the grid connection point of the converter, a frequency of... The disturbance voltage is used to determine the harmonic voltage on the valve side of the converter as follows: (1) Among them, the variables with the superscript d are the corresponding complementary frequencies. The variable with superscript 'c' represents the corresponding complementary frequency. The variable is represented by an asterisk (*) for conjugation. , This refers to the phasor of the disturbance voltage on the valve side of the converter. , For the PCC disturbance voltage phasor at the connection point, , The conjugate of the PCC disturbance voltage phasor at the connection point. , For converter disturbance current phasor , It is the conjugate of the converter disturbance current phasor. , , , , , , , For coefficient transfer functions, S d , S C For the corresponding perturbation frequency, complementary frequencies The Laplace operator; The frequency coupling admittance model of the converter is determined by the above equation as follows: (2) in, , , , These are the frequency coupling admittance matrix elements of the converter.

[0016] Preferably, the splitting unit is used to split the original network of the converter into units with complementary frequencies. and The corresponding first and second networks, where node K corresponds to the node Kirchhoff's law KCL equation in the first and second networks, are as follows: (3) in, , complementary frequencies and The perturbation voltage phasor at node k. , complementary frequencies and The perturbation voltage phasor of node i. , complementary frequencies and The admittance of L non-converter elements at node k to ground. , complementary frequencies and The admittance of node k between other nodes and I non-converter elements. , complementary frequencies and The current of the M converters at node k, , complementary frequencies and J current sources at node k, Let k be the frequency of node k.

[0017] Preferably, the generation unit, in the step of connecting the frequency-coupled admittance model to the first network and the second network respectively, and generating the first admittance matrix and the second admittance matrix corresponding to the first network and the second network, includes connecting the frequency-coupled admittance model to the node Kirchhoff's law KCL equations of the first network and the second network respectively, and generating the first admittance matrix and the second admittance matrix corresponding to the first network and the second network: (4) in, , , , complementary frequencies and The i-th converter frequency coupling admittance model element at node k. complementary frequencies The admittance conjugate of the L ground-connected non-converter elements at node k. complementary frequencies The admittance conjugate of node k with other nodes is I for non-converter elements. complementary frequencies The perturbation voltage phasor conjugate at node k. complementary frequencies The perturbation voltage phasors of nodes k and i are conjugate. complementary frequencies The J current sources at node k are conjugate.

[0018] Preferably, the expansion unit merges the first admittance matrix and the second admittance matrix into an expanded node admittance matrix, and based on the expanded node admittance matrix, includes: For an N-node network, its corresponding extended node admittance matrix is: The node voltage vector is: (5) in, Let N be the voltage phasors of the network nodes corresponding to the perturbation frequency. This represents the conjugate of the voltage vectors of the N nodes in the network at the corresponding coupling frequency. T The symbol for vector transpose; The first of the extended node admittance matrix The row corresponds to Kirchhoff's law KCL at the k-th node of the first network, and the row of the extended node admittance matrix is... The row corresponds to Kirchhoff's law KCL at the k-th node of the second network; Suppose that the grid-connected converter is connected to the k-th node of the original network, and its coupled frequency admittance model is: (6) in, , These are the phasors of the port current response at the disturbance frequency and the conjugate of the port current response at the coupling frequency for the converter connected to node k. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current phasor at the corresponding disturbance frequency. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current conjugate phasor at the corresponding coupling frequency. The contribution of the grid-connected converter to the extended node admittance matrix is ​​calculated as follows: [Equation of extended node admittance matrix]. Element plus , Element plus , Element plus , Element plus ; The transmission lines and transformer branches connecting nodes k and m in the original network have the following uncoupled admittance model between the first network and the second network: (7) in, , These are the disturbance frequency current phasor and the coupling frequency current conjugate phasor of the component branch between node k and node m, respectively. , These are the conjugate values ​​of the component's admittance at the disturbance frequency and the admittance at the coupling frequency, respectively. The contribution of transmission lines and transformer branches to the extended node admittance matrix is ​​calculated as follows: (The extended admittance matrix is...) , Element plus , , Subtraction of elements , , Element plus , , Subtraction of elements .

[0019] Preferably, the extended unit, wherein the coupled admittance aggregation calculation of the specified network nodes based on the extended node admittance matrix includes: Two sets of complementary frequencies are sequentially injected into a designated node J in the network. and Current source ,in, , Injecting the i-th perturbation frequency current source phasor and the conjugate of the coupled frequency current source into node J, respectively. To inject the disturbance frequency and coupling frequency current source vector at node J, To inject the disturbance frequency and coupling frequency current source matrix at node J; By applying Kirchhoff's law KCL equation to the network extended node admittance matrix, the voltages of the two sets of aggregation nodes J are calculated. ,in, , These are the voltage phasor of the perturbation frequency response at node J and the voltage conjugate of the coupling frequency, respectively. Let J be the response voltage matrix of node J; (8) (9) Let the aggregation frequency coupling admittance of node J be: (10) in, , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current phasor at the corresponding disturbance frequency. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current conjugate phasor at the corresponding coupling frequency. Substitute the two sets of voltages and currents into The coupling frequency admittance of node J is obtained as follows: (11)

[0020] According to another aspect of the present invention, the present invention provides a computer-readable storage medium having a computer program stored thereon, characterized in that, when the program is executed by a processor, it implements the steps of the general numerical aggregation method for frequency coupling admittance / impedance as described above.

[0021] According to another aspect of the present invention, the present invention provides an electronic device, characterized in that it comprises: A computer-readable storage medium that is easy to describe; and One or more processors for executing a program in the computer-readable storage medium.

[0022] This invention provides a general numerical aggregation method and system for frequency coupling admittance / impedance, wherein the method includes: determining the frequency coupling admittance model of the converter, and obtaining the complementary frequencies in the frequency coupling admittance model. and The original network of the converter is split into two parts, one for each complementary frequency. and The corresponding first and second networks are used; the frequency coupling admittance model is connected to the first and second networks respectively, generating a first admittance matrix and a second admittance matrix corresponding to the first and second networks; the first admittance matrix and the second admittance matrix are merged into an extended node admittance matrix, and the coupling frequency admittance of the specified network nodes is calculated based on the extended node admittance matrix. This invention proposes a general programmed numerical calculation aggregation method and system for frequency coupling admittance / impedance, corresponding to an extended adjoint network of arbitrary network structure at the coupling frequency. Based on the extended node admittance matrix, a general programmed numerical calculation aggregation of coupling frequency admittance for multi-converter networks is achieved, equivalent to a single-converter grid-connected system, facilitating subsequent system stability analysis. Attached Figure Description

[0023] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures: Figure 1 This is a flowchart of a general numerical aggregation method for frequency-coupled admittance / impedance according to a preferred embodiment of the present invention; Figure 2 This is a flowchart of frequency coupling admittance / impedance aggregation for a multi-converter network based on an extended node admittance matrix according to a preferred embodiment of the present invention. Figure 3 This is a schematic diagram of the coupling frequency circuit of a grid-connected converter according to a preferred embodiment of the present invention. Figure 4 This is a schematic diagram of a coupling frequency adjoint network according to a preferred embodiment of the present invention; Figure 5 This is a structural diagram of the VSC1-VSC3 grid-connected system according to a preferred embodiment of the present invention; Figure 6 This is a diagram of the VSC1-VSC3 coupling admittance (35kV side) according to a preferred embodiment of the present invention; Figure 7 This is a schematic diagram comparing the calculated value of the aggregation frequency coupling admittance of node 4 with the time-domain simulation analysis according to a preferred embodiment of the present invention; Figure 8 This is a structural diagram of a general numerical aggregation system for frequency-coupled admittance / impedance according to a preferred embodiment of the present invention. Detailed Implementation

[0025] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0026] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0027] Figure 1 This is a flowchart of a general numerical aggregation method for frequency-coupled admittance / impedance according to a preferred embodiment of the present invention; This invention relates to a frequency coupling admittance / impedance aggregation method based on a network containing new energy sources and power electronic equipment. The new energy aggregation network contains numerous grid-connected converters. In the subsynchronous / supersynchronous frequency range, the converter model has the following characteristics: (1) There is a coupling frequency effect in the small-signal model of the converter based on the phase-locked loop synchronization method, and its model is port frequency coupling admittance / impedance; (2) There are many converters in the new energy aggregation network, and the analysis of the subsynchronous / supersynchronous stability of the grid-connected converter under study needs to consider the influence of other converters in the network. This invention proposes a general programmed frequency coupling admittance / impedance numerical calculation aggregation method: an extended adjoint network corresponding to any network structure of the coupling frequency, and a general programmed numerical calculation aggregation of the coupling frequency admittance of the multi-converter network based on the extended node admittance matrix, which is equivalent to a single-converter grid-connected system, which facilitates the subsequent stability analysis of the system.

[0028] To address the lack of a universal, programmed aggregation analysis method for multi-converter networks, this invention first analyzes the frequency coupling admittance model of the converter. Then, considering the subsynchronous / supersynchronous frequency range, it splits the network into two networks corresponding to a pair of coupling frequencies and proposes a universal, programmed, frequency-point-by-frequency numerical aggregation calculation method for frequency coupling admittance based on the extended node admittance matrix. This method preserves the dynamic characteristics of the grid-connected converter and the network, effectively transforming it into a single-converter grid-connected system, which facilitates the analysis of the subsynchronous / supersynchronous oscillation stability of complex multi-converter networks.

[0029] like Figure 1 As shown, this invention provides a general numerical aggregation method for frequency-coupled admittance / impedance, characterized in that the method includes: Step 101: Determine the frequency coupling admittance model of the converter and obtain the complementary frequencies in the frequency coupling admittance model. and ; Preferably, determining the frequency coupling admittance model of the converter includes: At the grid connection point of the converter, a frequency of... The disturbance voltage is used to determine the harmonic voltage on the valve side of the converter as follows: (1) Among them, the variables with the superscript d are the corresponding complementary frequencies. The variable with superscript 'c' represents the corresponding complementary frequency. The variable is represented by an asterisk (*) for conjugation. , This refers to the phasor of the disturbance voltage on the valve side of the converter. , For the PCC disturbance voltage phasor at the connection point, , The conjugate of the PCC disturbance voltage phasor at the connection point. , For converter disturbance current phasor , It is the conjugate of the converter disturbance current phasor. , , , , , , , For coefficient transfer functions, S d , S C For the corresponding perturbation frequency, complementary frequencies The Laplace operator; The frequency coupling admittance model of the converter is determined by the above equation as follows: (2) in, , , , These are the frequency coupling admittance matrix elements of the converter.

[0030] This invention first determines the frequency coupling model of the converter's sub-supersynchronous frequency: When a converter using phase-locked loop synchronous control is connected to the power grid, if a disturbance occurs in the power grid, causing a frequency of [unspecified frequency] to appear in the voltage at the converter's grid connection point... If the positive sequence voltage disturbance component appears, then the frequency of its occurrence in the DC side voltage of the converter is... beat frequency components ( (This refers to the system fundamental frequency), and the dq variables of the phase-locked loop output angle, PCC voltage, and converter current in the controller all appear in the system fundamental frequency. The difference frequency component appears in the converter valve-side dq voltage reference value after passing through the outer and inner loops. Due to the asymmetry of the dq-axis control structure, the valve-side dq voltage reference value, after transformation from the dq coordinate system to the abc coordinate system and pulse width modulation (PWM), generates two frequencies in the converter valve-side AC voltage. and Coupled positive-sequence perturbation components, such as Figure 3 As shown, current disturbance components of the corresponding frequency are generated in the AC side circuit of the converter.

[0031] This invention employs a harmonic linearization method. By adding a small-signal harmonic frequency disturbance voltage to the steady-state power frequency voltage of the VSC's PCC, and based on the disturbance voltage and current phasor through PARK transformation, the transmission path in the controller, PARK inverse transformation, and PWM modulation, the harmonic voltage on the VSC valve side is obtained as follows: (1) In the formula: the superscript d represents the corresponding frequency. The variable, with the superscript c representing the corresponding frequency. The variable is represented by an asterisk (*) for conjugation. , This refers to the phasor of the disturbance voltage on the valve side of the converter. , For PCC disturbance voltage phasor , For converter disturbance current phasor , , , , , , , Let be the coefficient transfer function.

[0032] From the above equation, the frequency coupling admittance model of VSC can be obtained as follows: (2) in, , , , These are the frequency coupling admittance matrix elements of the converter.

[0033] The converter frequency coupling admittance model has the following characteristics: (1) Two complementary frequencies ( and Voltage and current exhibit coupling effects; (2) Conjugate characteristics: the admittances of the main diagonal elements are conjugate to each other, and the admittances of the off-diagonal elements are conjugate to each other; the coupling frequency voltage and current in the model are in conjugate form.

[0034] (3) The converter circuit port is a coupled frequency voltage and current, which cannot be directly connected to the coupled frequency model (conjugate quantity) (node ​​KCL equation).

[0035] Step 102: Split the original network of the converter into two parts, one with a complementary frequency. and The corresponding first and second networks; Preferably, the original network of the converter is split into two groups, each with a complementary frequency. and The corresponding first and second networks, where node K corresponds to the node Kirchhoff's law KCL equation in the first and second networks, are as follows: (3) in, , complementary frequencies and The perturbation voltage phasor at node k. , complementary frequencies and The perturbation voltage phasor of node i. , complementary frequencies and The admittance of L non-converter elements at node k to ground. , complementary frequencies and The admittance of node k between other nodes and I non-converter elements. , complementary frequencies and The current of the M converters at node k, , complementary frequencies and J current sources at node k, Let k be the frequency of node k.

[0036] This invention extends the network node admittance matrix: When studying the subsynchronous / supersynchronous oscillation characteristics of a grid-connected converter under study in a network containing multiple converters, the aggregated frequency coupling admittance (impedance) at the connection point of the converter under study and on the system side needs to take into account the influence of other grid-connected converters. The converter frequency coupling admittance model simultaneously contains complementary frequencies (…). and The port voltage and current of the transmission lines and transformers in the network are relatively constant, while non-converter components such as transmission lines and transformers have almost no frequency coupling effect. Therefore, this invention splits all nodes in the network into two nodes, forming two networks with the same topology as the original network. The admittances of components such as transmission lines and transformers in the network correspond to the frequencies of the transmission lines and transformers. and For node k in the network, list the corresponding frequencies. and The nodal KCL equations are: (3) in, , complementary frequencies and The perturbation voltage phasor at node k. , complementary frequencies and The perturbation voltage phasor of node i. , complementary frequencies and The admittance of L non-converter elements at node k to ground. , complementary frequencies and The admittance of node k between other nodes and I non-converter elements. , complementary frequencies and The current of the M converters at node k, , complementary frequencies and J current sources at node k, Let k be the frequency of node k.

[0037] Step 103: Connect the frequency-coupled admittance model to the first network and the second network respectively, and generate the first admittance matrix and the second admittance matrix corresponding to the first network and the second network; Preferably, the frequency-coupled admittance model is connected to the first network and the second network respectively to generate the first admittance matrix and the second admittance matrix corresponding to the first network and the second network. This includes connecting the frequency-coupled admittance model to the node Kirchhoff's law KCL equations of the first network and the second network respectively to generate the first admittance matrix and the second admittance matrix corresponding to the first network and the second network. (4) in, , , , complementary frequencies and The i-th converter frequency coupling admittance model element at node k. complementary frequencies The admittance conjugate of the L ground-connected non-converter elements at node k. complementary frequencies The admittance conjugate of node k with other nodes is I for non-converter elements. complementary frequencies The perturbation voltage phasor conjugate at node k. complementary frequencies The perturbation voltage phasors of nodes k and i are conjugate. complementary frequencies The J current sources at node k are conjugate.

[0038] This invention takes the conjugate of both sides of the second equation in (3), substitutes the converter frequency coupling admittance model into it, and the above equation is transformed into: (4) In the formula: , , , The frequency coupling admittance model element of the i-th converter at access node k.

[0039] From the above equation, we can obtain that the first equation corresponds to the frequency. The KCL of the original network node k is denoted as network ( The second equation is the conjugate equation of the KCL for the original network node k at the corresponding frequency, denoted as the adjoint network ( ).like Figure 4 As shown, the network ( ) and companion networks ( Voltage at nodes without converters and Independent of each other, the voltage of the grid-connected converter at the node is and This represents the coupling variable between the two networks.

[0040] Step 104: Merge the first admittance matrix and the second admittance matrix into an extended node admittance matrix, and calculate the coupling frequency admittance of the specified network node based on the extended node admittance matrix.

[0041] Preferably, the first admittance matrix and the second admittance matrix are merged into an extended node admittance matrix, and based on the extended node admittance matrix, the following are included: For an N-node network, its corresponding extended node admittance matrix is: The node voltage vector is: (5) in, Let N be the voltage phasors of the network nodes corresponding to the perturbation frequency. This represents the conjugate of the voltage vectors of the N nodes in the network at the corresponding coupling frequency. T The symbol for vector transpose; The first of the extended node admittance matrix The row corresponds to Kirchhoff's law KCL at the k-th node of the first network, and the row of the extended node admittance matrix is... The row corresponds to Kirchhoff's law KCL at the k-th node of the second network; Suppose that the grid-connected converter is connected to the k-th node of the original network, and its coupled frequency admittance model is: (6) in, , These are the phasors of the port current response at the disturbance frequency and the conjugate of the port current response at the coupling frequency for the converter connected to node k. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current phasor at the corresponding disturbance frequency. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current conjugate phasor at the corresponding coupling frequency. The contribution of the grid-connected converter to the extended node admittance matrix is ​​calculated as follows: (The extended node admittance matrix is...) Element plus , Element plus , Element plus , Element plus ; The transmission lines and transformer branches connecting nodes k and m in the original network have the following uncoupled admittance model between the first network and the second network: (7) in, , These are the disturbance frequency current phasor and the coupling frequency current conjugate phasor of the component branch between node k and node m, respectively. , These are the conjugate values ​​of the component's admittance at the disturbance frequency and the admittance at the coupling frequency, respectively. The contribution of transmission lines and transformer branches to the extended node admittance matrix is ​​calculated as follows: (The extended admittance matrix is...) , Element plus , , Subtraction of elements , , Element plus , , Subtraction of elements .

[0042] Preferably, based on the extended node admittance matrix, the coupled admittance aggregation calculation of a specified network node is performed, including: Two sets of complementary frequencies are sequentially injected into a designated node J in the network. and Current source ,in, , Injecting the i-th perturbation frequency current source phasor and the conjugate of the coupled frequency current source into node J, respectively. To inject the disturbance frequency and coupling frequency current source vector at node J, To inject the disturbance frequency and coupling frequency current source matrix at node J; By applying Kirchhoff's law KCL equation to the network extended node admittance matrix, the voltages of the two sets of aggregation nodes J are calculated. ,in, , These are the voltage phasor of the perturbation frequency response at node J and the voltage conjugate of the coupling frequency, respectively. Let J be the response voltage matrix of node J; (8) (9) Let the aggregation frequency coupling admittance of node J be: (10) in, , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current phasor at the corresponding disturbance frequency. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current conjugate phasor at the corresponding coupling frequency. Substitute the two sets of voltages and currents into The coupling frequency admittance of node J is obtained as follows: (11)

[0043] This invention integrates networks ( ) and companion networks ( The node admittance matrices of N nodes are merged into a single extended admittance matrix. For an N-node network, the dimension of the corresponding extended admittance matrix is... The node voltage vector is: (5) The first of the extended node admittance matrix Line correspondence network ( Kirchhoff's law KCL at the k-th node, and the extended node admittance matrix at the k-th node. Line-to-line companion network ( Kirchhoff's law KCL at the k-th node; (6) The contribution of the grid-connected converter to the extended node admittance matrix is: [Extended node admittance matrix] Element plus , Element plus , Element plus , Element plus ; In the original network, the power transmission lines, transformers, and other branches connecting nodes k and m are... ) and companion networks ( There are no coupling terms between them, and its admittance model is: (7) The contribution of the transmission line, transformer, and other branches to the extended node admittance matrix is: [Extended admittance matrix] , Element plus , , Subtraction of elements , , Element plus , , Subtraction of elements .

[0044] This invention performs node frequency coupling admittance aggregation: like Figure 4 As shown, two sets of data are sequentially injected into the node J to be studied in the network. By applying Kirchhoff's law KCL equation to the network extended node admittance matrix, the voltage of two sets of aggregate nodes J is calculated. .

[0045] (8) (9) Let the aggregation frequency coupling admittance of node J be: (10) Substitute the two sets of voltages and currents into The coupling frequency admittance of node J is obtained as follows: (11)

[0046] As can be seen from the above analysis, the network element model was not simplified by reducing its order in the aggregation calculation based on the extended node admittance matrix. Therefore, the dynamic characteristics of the subsynchronous / supersynchronous frequency range of all grid-connected converters and network branches are retained in the aggregation frequency coupling admittance model of the node under study, which can accurately analyze the subsynchronous / supersynchronous oscillation characteristics of the converter connected to the node under study.

[0047] The adjoint matrix corresponding to the coupling frequency: The converter coupling frequency model contains a pair of port voltages and currents with coupling frequencies. It requires two networks with the same topology but different frequencies to interface with the converter model. The converter coupling frequency model contains the conjugate quantities of coupling frequency voltage and current. Therefore, it is necessary to construct the adjoint matrix of the corresponding coupling frequency network to complete the interconnection relationship with the converter coupling frequency model.

[0048] This invention is based on the aggregation of frequency-coupled admittance / impedance numerical calculations using the admittance matrix of network extended nodes: In the converter coupling frequency model, there are simultaneously a pair of coupling frequencies of port voltage and current. These need to be solved in the numerical calculation of each corresponding frequency point in the model. A network extended node admittance matrix is ​​constructed. The networks corresponding to a pair of coupling frequencies are all in a node admittance matrix. Based on this extended matrix, the equivalent coupling frequency admittance / impedance of a specified node can be calculated by aggregating the frequency-by-frequency numerical calculation.

[0049] The following are examples illustrating embodiments of the present invention: Extensive research has been conducted on oscillation problems, yielding fruitful results. The main focus is on the modeling, mechanism analysis, and suppression of subsynchronous / supersynchronous oscillations in grid-connected systems of single or a few new energy devices.

[0050] However, with the continuous increase in the scale of new energy grid connection in China, subsynchronous / supersynchronous oscillations have occurred repeatedly in areas where new energy sources are concentrated. Current analysis methods based on single-converter grid-connected systems are insufficient for analyzing the subsynchronous / supersynchronous oscillation characteristics of multiple new energy power plants converging and transmitting power. Within the subsynchronous / supersynchronous frequency range, converters exhibit coupling frequency effects, and single-structure network modeling cannot reflect this coupling characteristic, leading to significant biases in subsynchronous / supersynchronous oscillation risk assessments. Furthermore, given the diverse network structures and operating modes in new energy converging areas, employing a series-parallel coupling impedance aggregation analysis method would require an enormous workload. Therefore, a general, procedural analysis method for the subsynchronous / supersynchronous oscillation characteristics of complex networks involving multiple converters is urgently needed.

[0051] This invention first analyzes the coupling frequency effect of converters and the converter frequency coupling admittance model. Further considering that conventional components such as transmission lines and transformers almost do not exhibit subsynchronous / supersynchronous frequency coupling effects, it considers two networks corresponding to a pair of subsynchronous / supersynchronous coupling frequencies. These networks have identical structures, and the component admittance / impedance values ​​are determined by the coupling frequency. The network is split into two networks corresponding to the pair of coupling frequencies, and the converter frequency coupling admittance model is connected to these two networks respectively. The node admittance matrices of these two networks are merged into an extended node admittance matrix. Therefore, for networks containing multiple converters, equivalent frequency coupling admittance aggregation calculations and analyses can be performed at specified nodes. The theoretical basis of this invention is the fundamental theory of electrical networks—the node admittance equation. Therefore, it can analyze and calculate any network structure to assess the subsynchronous / supersynchronous oscillation risk of the grid-connected converter under study.

[0052] With a significant amount of wind and solar power being distributed in desert and Gobi regions, the grid connections are mostly weak systems. Furthermore, the grid-connected units for these new energy sources are primarily converters, and the aggregation of numerous converters easily leads to subsynchronous / supersynchronous oscillations. This invention analyzes the subsynchronous / supersynchronous oscillation characteristics of multi-converter networks, thus possessing broad application prospects.

[0053] The flowchart of the frequency coupling admittance / impedance aggregation method for multi-converter networks based on the extended node admittance matrix of this invention is shown in the figure below. It begins by reading the 2×2 matrix model parameters of the frequency coupling admittance of each grid-connected converter. Each element represents a frequency-admittance curve data, which is stored in memory. Then, it reads the model parameters of the network topology and conventional components such as transmission lines and transformers in the network. Based on the number of network nodes N, the order of the extended node admittance matrix is ​​determined. Following a set frequency calculation step size (e.g., 1Hz), at each frequency point, the nodes in the network are traversed sequentially. First, the contribution of each grid-connected converter's coupled frequency admittance model to the corresponding access node number element of the extended node admittance matrix at the calculation frequency point is considered. Then, the contribution of each conventional component in the network to the corresponding access node number element of the extended node admittance matrix is ​​sequentially included. This forms the extended node admittance matrix for the current calculation frequency point. Frequency coupling current is injected into the aggregation node, and the extended node admittance matrix equation is solved to obtain the aggregation node voltage value. Then, the aggregation node frequency coupling admittance value for the current calculation frequency point is calculated. The calculation process continues to the next frequency point to obtain the aggregation frequency coupling admittance model for the specified node.

[0054] like Figure 5 As shown, three grid-connected converters form a 4-node 35kV network.

[0055] In the diagram: the component parameters for branches 1-4 are as follows: , , , The VSC parameters are shown in the appendix; VSC4 has the same parameters as VSC1. Time-domain simulations of individual VSC grid-connected systems were performed, using a frequency scanning method with an added series disturbance voltage to obtain the frequency coupling admittance values ​​of the three VSCs, as follows: Figure 6 As shown.

[0056] First consideration Figure 5 Without connecting equivalent power sources Vs and VSC4, the extended node admittance matrix of the network is established. Within the

[3100] Hz range, according to the set calculation frequency step size (e.g., 1 Hz), two sets of frequency coupling currents with different amplitudes are injected into node 4. Through calculation and analysis of the extended node admittance matrix, the two sets of frequency coupling node voltages can be obtained. From equation (9), the aggregate frequency coupling admittance of node 4 corresponding to the injected current frequency can be obtained. Then, the network is further processed... Figure 5 The system undergoes time-domain simulation, sequentially applying a series of frequency-coupled perturbation voltages at the same frequency between node 4 and the equivalent power source. DFT analysis yields the aggregated frequency-coupled admittance of node 4. For example... Figure 7 As shown, the calculated value of the node-aggregated frequency coupling admittance based on the extended node admittance matrix is ​​consistent with the value of the time-domain simulation analysis, verifying the correctness and accuracy of the node-frequency coupling admittance aggregation method based on the extended node admittance matrix.

[0057] Figure 8 This is a structural diagram of a general numerical aggregation system for frequency-coupled admittance / impedance according to a preferred embodiment of the present invention.

[0058] like Figure 8 As shown, this invention provides a general numerical aggregation system for frequency-coupled admittance / impedance, the system comprising: Initial unit 801 is used to determine the frequency coupling admittance model of the converter and obtain the complementary frequencies in the frequency coupling admittance model. and ; Preferably, the initial unit 801 is used to determine the frequency coupling admittance model of the converter, and is also used for: At the grid connection point of the converter, a frequency of... The disturbance voltage is used to determine the harmonic voltage on the valve side of the converter as follows: (1) Among them, the variables with the superscript d are the corresponding complementary frequencies. The variable with superscript 'c' represents the corresponding complementary frequency. The variable is represented by an asterisk (*) for conjugation. , This refers to the phasor of the disturbance voltage on the valve side of the converter. , For the PCC disturbance voltage phasor at the connection point, , The conjugate of the PCC disturbance voltage phasor at the connection point. , For converter disturbance current phasor , It is the conjugate of the converter disturbance current phasor. , , , , , , , For coefficient transfer functions, S d , S C For the corresponding perturbation frequency, complementary frequencies The Laplace operator; The frequency coupling admittance model of the converter is determined by the above equation as follows: (2) in, , , , These are the frequency coupling admittance matrix elements of the converter.

[0059] Splitting unit 802 is used to split the original network of the converter into two parts respectively with complementary frequencies. and The corresponding first and second networks; Preferably, the splitting unit 802 is used to split the original network of the converter into units with complementary frequencies. and The corresponding first and second networks, where node K corresponds to the node Kirchhoff's law KCL equation in the first and second networks, are as follows: (3) in, , complementary frequencies and The perturbation voltage phasor at node k. , complementary frequencies and The perturbation voltage phasor of node i. , complementary frequencies and The admittance of L non-converter elements at node k to ground. , complementary frequencies and The admittance of node k between other nodes and I non-converter elements. , complementary frequencies and The current of the M converters at node k, , complementary frequencies and J current sources at node k, Let k be the frequency of node k.

[0060] The generation unit 803 is used to connect the frequency-coupled admittance model to the first network and the second network respectively, and generate the first admittance matrix and the second admittance matrix corresponding to the first network and the second network. Preferably, the generation unit 803 is used to connect the frequency-coupled admittance model to the first network and the second network respectively, and generate the first admittance matrix and the second admittance matrix corresponding to the first network and the second network, including connecting the frequency-coupled admittance model to the node Kirchhoff's law KCL equation of the first network and the second network respectively, and generating the first admittance matrix and the second admittance matrix corresponding to the first network and the second network: (4) in, , , , complementary frequencies and The i-th converter frequency coupling admittance model element at node k. complementary frequencies The admittance conjugate of the L ground-connected non-converter elements at node k. complementary frequencies The admittance conjugate of node k with other nodes is I for non-converter elements. complementary frequencies The perturbation voltage phasor conjugate at node k. complementary frequencies The perturbation voltage phasors of nodes k and i are conjugate. complementary frequencies The J current sources at node k are conjugate.

[0061] The extension unit 804 is used to merge the first admittance matrix and the second admittance matrix into an extended node admittance matrix, and to calculate the coupling frequency admittance of a specified network node based on the extended node admittance matrix.

[0062] Preferably, the expansion unit 804 is used to merge the first admittance matrix and the second admittance matrix into an expanded node admittance matrix, and based on the expanded node admittance matrix, includes: For an N-node network, its corresponding extended node admittance matrix is: The node voltage vector is: (5) in, Let N be the voltage phasors of the network nodes corresponding to the perturbation frequency. This represents the conjugate of the voltage vectors of the N nodes in the network at the corresponding coupling frequency. T The symbol for vector transpose; The first of the extended node admittance matrix The row corresponds to Kirchhoff's law KCL at the k-th node of the first network, and the row of the extended node admittance matrix is... The row corresponds to Kirchhoff's law KCL at the k-th node of the second network; Suppose that the grid-connected converter is connected to the k-th node of the original network, and its coupled frequency admittance model is: (6) in, , These are the phasors of the port current response at the disturbance frequency and the conjugate of the port current response at the coupling frequency for the converter connected to node k. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current phasor at the corresponding disturbance frequency. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current conjugate phasor at the corresponding coupling frequency. The contribution of the grid-connected converter to the extended node admittance matrix is ​​calculated as follows: [Equation of extended node admittance matrix]. Element plus , Element plus , Element plus , Element plus ; The transmission lines and transformer branches connecting nodes k and m in the original network have the following uncoupled admittance model between the first network and the second network: (7) in, , These are the disturbance frequency current phasor and the coupling frequency current conjugate phasor of the component branch between node k and node m, respectively. , These are the conjugate values ​​of the component's admittance at the disturbance frequency and the admittance at the coupling frequency, respectively. The contribution of transmission lines and transformer branches to the extended node admittance matrix is ​​calculated as follows: (The extended admittance matrix is...) , Element plus , , Subtraction of elements , , Element plus , , Subtraction of elements .

[0063] Preferably, the extension unit 804 is used to perform coupled admittance aggregation calculation of a specified network node based on the extended node admittance matrix, including: Two sets of complementary frequencies are sequentially injected into a designated node J in the network. and Current source ,in, , Injecting the i-th perturbation frequency current source phasor and the conjugate of the coupled frequency current source into node J, respectively. To inject the disturbance frequency and coupling frequency current source vector at node J, To inject the disturbance frequency and coupling frequency current source matrix at node J; By applying Kirchhoff's law KCL equation to the network extended node admittance matrix, the voltages of the two sets of aggregation nodes J are calculated. ,in, , These are the voltage phasor of the perturbation frequency response at node J and the voltage conjugate of the coupling frequency, respectively. Let J be the response voltage matrix of node J; (8) (9) Let the aggregation frequency coupling admittance of node J be: (10) in, , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current phasor at the corresponding disturbance frequency. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current conjugate phasor at the corresponding coupling frequency. Substitute the two sets of voltages and currents into The coupling frequency admittance of node J is obtained as follows: (11)

[0064] The present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a general numerical aggregation method for frequency-coupled admittance / impedance.

[0065] This invention provides an electronic device, comprising: The aforementioned computer-readable storage medium; and One or more processors for executing a program in a computer-readable storage medium.

[0066] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0067] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0068] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0069] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0070] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0071] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A general numerical aggregation method for frequency-coupled admittance / impedance, characterized in that, The method includes: Determine the frequency coupling admittance model of the converter and obtain the complementary frequencies in the frequency coupling admittance model. and ; The original network of the converter is split into two parts, one with a complementary frequency. and The corresponding first and second networks; The frequency-coupled admittance model is connected to the first network and the second network respectively to generate a first admittance matrix and a second admittance matrix corresponding to the first network and the second network. The first admittance matrix and the second admittance matrix are merged into an extended node admittance matrix. Based on the extended node admittance matrix, the coupling frequency admittance of the specified network node is calculated.

2. The method according to claim 1, characterized in that, The frequency coupling admittance model for determining the converter includes: At the grid connection point of the converter, a frequency of... The disturbance voltage is used to determine the harmonic voltage on the valve side of the converter as follows: （1） Among them, the variables with the superscript d are the corresponding complementary frequencies. The variable with superscript 'c' represents the corresponding complementary frequency. The variable is represented by an asterisk (*) for conjugation. , This refers to the phasor of the disturbance voltage on the valve side of the converter. , For the PCC disturbance voltage phasor at the connection point, , The conjugate of the PCC disturbance voltage phasor at the connection point. , For converter disturbance current phasor , It is the conjugate of the converter disturbance current phasor. , , , , , , , For coefficient transfer functions, S d , S C For the corresponding perturbation frequency, complementary frequencies The Laplace operator; The frequency coupling admittance model of the converter is determined by the above equation as follows: （2） in, , , , These are the frequency coupling admittance matrix elements of the converter.

3. The method according to claim 2, characterized in that, The original network of the converter is split into complementary frequencies. and The corresponding first and second networks, where node K corresponds to the node Kirchhoff's law KCL equation in the first and second networks, are as follows: （3） in, , complementary frequencies and The perturbation voltage phasor at node k. , complementary frequencies and The perturbation voltage phasor of node i. , complementary frequencies and The admittance of L non-converter elements at node k to ground. , complementary frequencies and The admittance of node k between other nodes and I non-converter elements. , complementary frequencies and The current of the M converters at node k, , complementary frequencies and J current sources at node k, Let k be the frequency of node k.

4. The method according to claim 3, characterized in that, The step of connecting the frequency-coupled admittance model to the first network and the second network respectively, and generating the first admittance matrix and the second admittance matrix corresponding to the first network and the second network, includes connecting the frequency-coupled admittance model to the node Kirchhoff's law KCL equations of the first network and the second network respectively, and generating the first admittance matrix and the second admittance matrix corresponding to the first network and the second network: （4） in, , , , complementary frequencies and The i-th converter frequency coupling admittance model element at node k. complementary frequencies The admittance conjugate of the L ground-connected non-converter elements at node k. complementary frequencies The admittance conjugate of node k with other nodes is I for non-converter elements. complementary frequencies The perturbation voltage phasor conjugate at node k. complementary frequencies The perturbation voltage phasors of nodes k and i are conjugate. complementary frequencies The J current sources at node k are conjugate.

5. The method according to claim 4, characterized in that, The step of merging the first admittance matrix and the second admittance matrix into an extended node admittance matrix, based on the extended node admittance matrix, includes: For an N-node network, its corresponding extended node admittance matrix is: The node voltage vector is: （5） in, Let N be the voltage phasors of the network nodes corresponding to the perturbation frequency. This represents the conjugate of the voltage vectors of the N nodes in the network at the corresponding coupling frequency. T The symbol for vector transpose; The first of the extended node admittance matrix The row corresponds to Kirchhoff's law KCL at the k-th node of the first network, and the row of the extended node admittance matrix is... The row corresponds to Kirchhoff's law KCL at the k-th node of the second network; Suppose that the grid-connected converter is connected to the k-th node of the original network, and its coupled frequency admittance model is: （6） in, , These are the phasors of the port current response at the disturbance frequency and the conjugate of the port current response at the coupling frequency for the converter connected to node k. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current phasor at the corresponding disturbance frequency. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current conjugate phasor at the corresponding coupling frequency. The contribution of the grid-connected converter to the extended node admittance matrix is ​​calculated as follows: [Equation of extended node admittance matrix]. Element plus , Element plus , Element plus , Element plus ; The transmission lines and transformer branches connecting nodes k and m in the original network have the following uncoupled admittance model between the first network and the second network: （7） in, , These are the disturbance frequency current phasor and the coupling frequency current conjugate phasor of the component branch between node k and node m, respectively. , These are the conjugate values ​​of the component's admittance at the disturbance frequency and the admittance at the coupling frequency, respectively. The contribution of transmission lines and transformer branches to the extended node admittance matrix is ​​calculated as follows: (The extended admittance matrix is...) , Element plus , , Subtraction of elements , , Element plus , , Subtraction of elements .

6. The method according to claim 5, characterized in that, The calculation of coupled admittance aggregation for a specified network node based on the extended node admittance matrix includes: Two sets of complementary frequencies are sequentially injected into a designated node J in the network. and Current source ,in, , Injecting the i-th perturbation frequency current source phasor and the conjugate of the coupled frequency current source into node J, respectively. To inject the disturbance frequency and coupling frequency current source vector at node J, To inject the disturbance frequency and coupling frequency current source matrix at node J; By applying Kirchhoff's law KCL equation to the network extended node admittance matrix, the voltages of the two sets of aggregation nodes J are calculated. ,in, , These are the voltage phasor of the perturbation frequency response at node J and the voltage conjugate of the coupling frequency, respectively. Let J be the response voltage matrix of node J; （8） （9） Let the aggregation frequency coupling admittance of node J be: （10） in, , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current phasor at the corresponding disturbance frequency. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current conjugate phasor at the corresponding coupling frequency. Substitute the two sets of voltages and currents into The coupling frequency admittance of node J is obtained as follows: （11）。 7. A general numerical aggregation system for frequency-coupled admittance / impedance, characterized in that, The system includes: An initial unit is used to determine the frequency coupling admittance model of the converter and obtain the complementary frequencies in the frequency coupling admittance model. A splitting unit is used to split the original network of the converter into a first network and a second network, which are respectively associated with complementary frequencies. The generation unit is used to connect the frequency-coupled admittance model to the first network and the second network respectively, and generate a first admittance matrix and a second admittance matrix corresponding to the first network and the second network. An extension unit is used to merge the first admittance matrix and the second admittance matrix into an extended node admittance matrix, and to calculate the coupling frequency admittance of a specified network node based on the extended node admittance matrix.

8. The system according to claim 7, characterized in that, The initial element is used to determine the frequency coupling admittance model of the converter, and also for: At the grid connection point of the converter, a frequency of... The disturbance voltage is used to determine the harmonic voltage on the valve side of the converter as follows: （1） Among them, the variables with the superscript d are the corresponding complementary frequencies. The variable with superscript 'c' represents the corresponding complementary frequency. The variable is represented by an asterisk (*) for conjugation. , This refers to the phasor of the disturbance voltage on the valve side of the converter. , For the PCC disturbance voltage phasor at the connection point, , The conjugate of the PCC disturbance voltage phasor at the connection point. , For converter disturbance current phasor , It is the conjugate of the converter disturbance current phasor. , , , , , , , For coefficient transfer functions, S d , S C For the corresponding perturbation frequency, complementary frequencies The Laplace operator; The frequency coupling admittance model of the converter is determined by the above equation as follows: （2） in, , , , These are the frequency coupling admittance matrix elements of the converter.

9. The system according to claim 8, characterized in that, The original network of the converter is split into complementary frequencies. and The corresponding first and second networks, where node K corresponds to the node Kirchhoff's law KCL equation in the first and second networks, are as follows: （3） in, , complementary frequencies and The perturbation voltage phasor at node k. , complementary frequencies and The perturbation voltage phasor of node i. , complementary frequencies and The admittance of L non-converter elements at node k to ground. , complementary frequencies and The admittance of node k between other nodes and I non-converter elements. , complementary frequencies and The current of the M converters at node k, , complementary frequencies and J current sources at node k, Let k be the frequency of node k.

10. The system according to claim 9, characterized in that, The step of connecting the frequency-coupled admittance model to the first network and the second network respectively, and generating the first admittance matrix and the second admittance matrix corresponding to the first network and the second network, includes connecting the frequency-coupled admittance model to the node Kirchhoff's law KCL equations of the first network and the second network respectively, and generating the first admittance matrix and the second admittance matrix corresponding to the first network and the second network: （4） in, , , , complementary frequencies and The i-th converter frequency coupling admittance model element at node k. complementary frequencies The admittance conjugate of the L ground-connected non-converter elements at node k. complementary frequencies The admittance conjugate of node k with other nodes is I for non-converter elements. complementary frequencies The perturbation voltage phasor conjugate at node k. complementary frequencies The perturbation voltage phasors of nodes k and i are conjugate. complementary frequencies The J current sources at node k are conjugate.

11. The system according to claim 9, characterized in that, The step of merging the first admittance matrix and the second admittance matrix into an extended node admittance matrix, based on the extended node admittance matrix, includes: For an N-node network, its corresponding extended node admittance matrix is: The node voltage vector is: （5） in, Let N be the voltage phasors of the network nodes corresponding to the perturbation frequency. This represents the conjugate of the voltage vectors of the N nodes in the network at the corresponding coupling frequency. T The symbol for vector transpose; The first of the extended node admittance matrix The row corresponds to Kirchhoff's law KCL at the k-th node of the first network, and the row of the extended node admittance matrix is... The row corresponds to Kirchhoff's law KCL at the k-th node of the second network; Suppose that the grid-connected converter is connected to the k-th node of the original network, and its coupled frequency admittance model is: （6） in, , These are the phasors of the port current response at the disturbance frequency and the conjugate of the port current response at the coupling frequency for the converter connected to node k. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current phasor at the corresponding disturbance frequency. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current conjugate phasor at the corresponding coupling frequency. The contribution of the grid-connected converter to the extended node admittance matrix is ​​calculated as follows: [Equation of extended node admittance matrix]. Element plus , Element plus , Element plus , Element plus ; The transmission lines and transformer branches connecting nodes k and m in the original network have the following uncoupled admittance model between the first network and the second network: （7） in, , These are the disturbance frequency current phasor and the coupling frequency current conjugate phasor of the component branch between node k and node m, respectively. , These are the conjugate values ​​of the component's admittance at the disturbance frequency and the admittance at the coupling frequency, respectively. The contribution of transmission lines and transformer branches to the extended node admittance matrix is ​​calculated as follows: (The extended admittance matrix is...) , Element plus , , Subtraction of elements , , Element plus , , Subtraction of elements .

12. The system according to claim 11, characterized in that, The calculation of coupled admittance aggregation for a specified network node based on the extended node admittance matrix includes: Two sets of complementary frequencies are sequentially injected into a designated node J in the network. and Current source ,in, , Injecting the i-th perturbation frequency current source phasor and the conjugate of the coupled frequency current source into node J, respectively. To inject the disturbance frequency and coupling frequency current source vector at node J, To inject the disturbance frequency and coupling frequency current source matrix at node J; By applying Kirchhoff's law KCL equation to the network extended node admittance matrix, the voltages of the two sets of aggregation nodes J are calculated. ,in, , These are the voltage phasor of the perturbation frequency response at node J and the voltage conjugate of the coupling frequency, respectively. Let J be the response voltage matrix of node J; （8） （9） Let the aggregation frequency coupling admittance of node J be: （10） in, , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current phasor at the corresponding disturbance frequency. , These are the admittance coefficients of the port voltage phasor at the disturbance frequency and the port voltage phasor at the coupling frequency, respectively, for the current conjugate phasor at the corresponding coupling frequency. Substitute the two sets of voltages and currents into The coupling frequency admittance of node J is obtained as follows: （11）。 13. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the method as described in any one of claims 1-6.

14. An electronic device, characterized in that, include: The computer-readable storage medium as described in claim 13; as well as One or more processors for executing a program in the computer-readable storage medium.

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