A general numerical aggregation method and system for frequency-coupled admittance / impedance

Abstract

The application discloses a universal numerical aggregation method and system for frequency coupling admittance / impedance, and the method comprises the following steps: determining a frequency coupling admittance model of a converter; acquiring complementary frequency sums in the frequency coupling admittance model; splitting an original network of the converter into a first network and a second network corresponding to the complementary frequency sums respectively; connecting the frequency coupling admittance model to the first network and the second network respectively, and generating a first admittance matrix and a second admittance matrix corresponding to the first network and the second network; merging the first admittance matrix and the second admittance matrix into an extended node admittance matrix; and performing coupling frequency admittance calculation on specified network nodes based on the extended node admittance matrix.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy power generation, more particularly, to a universal numerical aggregation method and system for frequency coupling admittance / impedance. BACKGROUND

[0002] Currently, renewable energy is gradually replacing traditional fossil energy, and in the future, new energy power generation will become the main source of final energy demand. With the increasing proportion of new energy power generation, the power system is gradually developing towards high proportion of new energy and high proportion of power electronic equipment. The internal control links of new energy power generation and power electronic equipment system are coupled with each other, forming a complex multi-time scale high-order nonlinear system, which is easy to cause sub / super synchronous oscillation problems when interacting with the power grid, becoming one of the important problems affecting the safe and stable operation of the power grid.

[0003] Currently, there are many research results on the sub / super synchronous oscillation characteristics of converter grid-connected systems. The research methods mainly include time domain simulation of electromagnetic transient model, eigenvalue analysis of state space model, admittance / impedance model analysis and Nyquist stability criterion. However, the research is mainly for single converter grid-connected systems, and the above methods are difficult to apply to the oscillation characteristic analysis of new energy collection systems containing numerous grid-connected converters. Impedance / admittance network modeling is a feasible method to study the oscillation characteristics of multi-converter network, but in the sub / super synchronous frequency range, the converter has a coupling frequency effect, and single structure network modeling cannot reflect this coupling characteristic. Using coupled impedance series-parallel aggregation is difficult to apply to general programmatic analysis of the sub / super synchronous oscillation characteristics of complex networks containing multiple converters. The impedance / admittance of the converter adopts the explicit transfer function form, and if the number of network nodes reaches hundreds or thousands, the explicit high-order node admittance transfer function matrix is difficult to directly perform inverse operation and matrix characteristic analysis. In addition, it is also difficult to obtain the white box model of the grid-connected unit in the actual new energy collection system accessing a large number of different types of grid-connected units. The black box model can be simulated in time domain or real-time simulation with actual controller in the loop to obtain the frequency coupling admittance curve data of the grid-connected converter unit. Therefore, numerical calculation at each frequency point is more suitable for the sub / super synchronous oscillation analysis of large-scale new energy collection system networks, which can calculate the aggregated coupling admittance curve data of the access point of the converter (station) to be researched, and facilitate further analysis of the stability of the system.

[0004] The prior art analyzes the network resonance point through admittance network modeling, but in the sub / super synchronous frequency range, the converter has a coupling frequency effect, and single structure network modeling cannot reflect this coupling characteristic;

[0005] The frequency coupling impedance series-parallel aggregation in the prior art is not easy to apply to general programmatic analysis of the sub / super synchronous oscillation characteristics of complex networks containing multiple converters.

[0006] The prior art is difficult to directly perform inverse operation and matrix characteristic analysis on the high-order node admittance transfer function matrix of a network with a node number reaching hundreds of thousands.

[0007] Therefore, a technology is needed to realize general numerical aggregation calculation of frequency coupling admittance / impedance of a multi-converter network. SUMMARY

[0008] The technical scheme of the present application 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 of a multi-converter network.

[0009] To solve the above problem, the present application provides a general numerical aggregation method for frequency coupling admittance / impedance, which comprises:

[0010] determining a frequency coupling admittance model of a converter, and obtaining complementary frequencies and in the frequency coupling admittance model;

[0011] splitting the original network of the converter into a first network and a second network corresponding to the complementary frequencies and respectively;

[0012] connecting the frequency coupling admittance model into 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;

[0013] merging 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.

[0014] Preferably, the determination of the frequency coupling admittance model of the converter comprises:

[0015] applying a disturbance voltage with a frequency of at the grid-connected point of the converter, and determining the harmonic voltage on the valve side of the converter as:

[0016] (1)

[0017] wherein the variable with superscript d is a variable corresponding to the complementary frequency , the variable with superscript c is a variable corresponding to the complementary frequency , the asterisk is a conjugate, , is a disturbance voltage phasor on the valve side of the converter, , is a disturbance voltage phasor at the point of common coupling (PCC). , is the conjugate of the disturbance voltage phasor at the connection point PCC, , is the disturbance current phasor of the converter, , is the conjugate of the disturbance current phasor of the converter, , , , , , , , is the coefficient transfer function, S d is a complex variable corresponding to the disturbance frequency , S C is a complex variable corresponding to the disturbance frequency ;

[0018] The frequency coupled admittance model of the converter is determined by the above equation as:

[0019] (2)

[0020] wherein , , , are the frequency coupled admittance matrix elements of the converter.

[0021] Preferably, the original network of the converter is split into a first network and a second network corresponding to the complementary frequencies and respectively, wherein the node Kirchhoff law KCL equations of the first network and the second network corresponding to node k are:

[0022] (3)

[0023] wherein , are the disturbance voltage phasors of node k at the complementary frequencies and respectively, , are the disturbance voltage phasors of node i at the complementary frequencies and respectively, , are the L non-converter element admittances of node k at the complementary frequencies and respectively, , are the L non-converter element admittances of node i at the complementary frequencies and the I non-variator element admittances between node k and other nodes, , the M variator currents of node k at complementary frequencies and , the J current sources of node k at complementary frequencies and the frequency of node k.

[0024] Preferably, the coupling of the frequency-admittance model into 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, comprises the node Kirchhoff's law (KCL) equation of the coupling of the frequency-admittance model into 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:

[0025] (4)

[0026] wherein, , , , the i-th variator frequency-admittance model element of node k at complementary frequencies and the conjugate of the L ground non-variator element admittances of node k at complementary frequencies the conjugate of the I non-variator element admittances between node k and other nodes at complementary frequencies the conjugate of the disturbance voltage phasor of node k at complementary frequencies the conjugate of the disturbance voltage phasor of node i at complementary frequencies the conjugate of the J current sources of node k at complementary frequencies

[0027] Preferably, the merging of the first admittance matrix and the second admittance matrix into an extended node admittance matrix, based on the extended node admittance matrix, comprises:

[0028] For an N-node network, the corresponding extended node admittance matrix is , and the node voltage phasor is:

[0029] (5) ​​​​​​​​

[0030] wherein, is the N-node voltage phasor of the network at the perturbation frequency, is the conjugate of the N-node voltage phasor of the network at the coupling frequency, T is the phasor transposition symbol;

[0031] the (k, m)th element of the extended node admittance matrix corresponds to the KCL of the kth node of the first network, the (k, m)th element of the extended node admittance matrix corresponds to the KCL of the kth node of the second network;

[0032] Suppose a grid-connected converter is connected to the kth node of the original network, and its coupling frequency admittance model is:

[0033] (6)

[0034] wherein, , are the port current response phasor of the converter connected to the kth node at the perturbation frequency, the conjugate of the port current response phasor at the coupling frequency, respectively, , are the admittance coefficients of the port voltage phasor at the perturbation frequency corresponding to the perturbation frequency current phasor, the admittance coefficients of the port voltage phasor at the coupling frequency corresponding to the conjugate of the coupling frequency current phasor, respectively, , are the admittance coefficients of the port voltage phasor at the perturbation frequency corresponding to the perturbation frequency current phasor, the admittance coefficients of the port voltage phasor at the coupling frequency corresponding to the conjugate of the coupling frequency current phasor, respectively;

[0035] The contribution of the grid-connected converter to the extended node admittance matrix is calculated as follows: the (k, m)th element of the extended node admittance matrix is added by the (k, m)th element of the extended node admittance matrix, , , , , , , , ;

[0036] The transmission line or transformer branch connected between the kth node and the mth node in the original network, which has no coupling admittance model between the first network and the second network, is:

[0037] (7)

[0038] wherein, , are the perturbation frequency current phasor and the conjugate of the coupling frequency current phasor of the element branch between the kth node and the mth node, respectively,​​ , are the element at the disturbance frequency admittance, the coupling frequency admittance conjugate value, respectively; is the voltage phasor of the node m of the first network at the frequency is the voltage phasor conjugate of the node m of the second network at the frequency

[0039] The contribution of the power transmission line, transformer branch to the extended node admittance matrix is calculated as: the , element of the extended admittance matrix plus , , element minus , , element plus , , element minus .

[0040] Preferably, the coupling admittance aggregation calculation of the specified network node based on the extended node admittance matrix comprises:

[0041] Inject two sets of complementary frequency and current sources at the specified node J of the network in turn, wherein, , are the i-th disturbance frequency current source phasor injected at node J, the coupling frequency current source conjugate phasor, respectively, is the disturbance frequency, coupling frequency current source phasor injected at node J, is the disturbance frequency, coupling frequency current source matrix injected at node J;

[0042] The Kirchhoff's law KCL equation of the network extended node admittance matrix is used to calculate the two sets of aggregation node J voltage , wherein, , are the disturbance frequency response voltage phasor of node J, the coupling frequency voltage conjugate phasor, respectively, is the response voltage matrix of node J;

[0043] (8)

[0044] (9)

[0045] Let the aggregation frequency coupling admittance of node J be:

[0046] (10)​​

[0047] wherein, , are the admittance coefficients of the port voltage phasors at the disturbance frequency corresponding to the disturbance frequency current phasor, the port voltage phasors at the coupling frequency corresponding to the coupling frequency current conjugate phasor, 、 are the admittance coefficients of the port voltage phasors at the disturbance frequency corresponding to the disturbance frequency current phasor, the port voltage phasors at the coupling frequency corresponding to the coupling frequency current conjugate phasor;

[0048] Substitute the two groups of voltage and current into , and the coupling frequency admittance of the node J is obtained as:

[0049] (11)

[0050] Based on another aspect of the present application, the present application provides a universal numerical aggregation system of frequency coupling admittance / impedance, which comprises:

[0051] An initial unit is configured to determine a frequency coupling admittance model of a converter, and obtain complementary frequencies and in the frequency coupling admittance model;

[0052] A splitting unit is configured to split an original network of the converter into a first network and a second network corresponding to the complementary frequencies and respectively;

[0053] A generating unit is configured to connect the frequency coupling admittance model into 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;

[0054] An expanding unit is configured to combine the first admittance matrix and the second admittance matrix into an expanded node admittance matrix, and perform coupling frequency admittance calculation of a specified network node based on the expanded node admittance matrix.

[0055] Preferably, the initial unit configured to determine the frequency coupling admittance model of the converter is further configured to:

[0056] apply a disturbance voltage with a frequency of at a grid-connected point of the converter, and determine a harmonic voltage at a valve side of the converter as:

[0057] (1)

[0058] wherein, the variable with superscript d is a variable corresponding to the complementary frequency , and the variable with superscript c is a variable corresponding to the complementary frequency the conjugate of the disturbance voltage phasor at the point of connection PCC, , the disturbance voltage phasor at the converter valve side, , the disturbance voltage phasor at the point of connection PCC, , the conjugate of the disturbance voltage phasor at the point of connection PCC, , the disturbance current phasor at the converter, , the conjugate of the disturbance current phasor at the converter, , , , , , , , the coefficient transfer function, S d the complex variable corresponding to the disturbance frequency , S C the complex variable corresponding to the disturbance frequency ;

[0059] The frequency coupled admittance model of the converter is determined by the above equation as:

[0060] (2)

[0061] wherein, , , , are the frequency coupled admittance matrix elements of the converter.

[0062] Preferably, the splitting unit is configured to split the original network of the converter into a first network and a second network corresponding to the complementary frequencies and respectively, wherein the node Kirchhoff's law KCL equations of the first network and the second network corresponding to node k are:

[0063] (3)

[0064] wherein, , are the disturbance voltage phasors of node k at the complementary frequencies and respectively, , are the disturbance voltage phasors of node i at the complementary frequencies and respectively, , 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.

[0065] Preferably, 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, including 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 a first admittance matrix and a second admittance matrix corresponding to the first network and the second network:

[0066] (4)

[0067] 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 phasor conjugate of node i. complementary frequencies The J current sources at node k are conjugate.

[0068] Preferably, the expansion unit is configured 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, is further configured to:

[0069] For an N-node network, its corresponding extended node admittance matrix is , and the node voltage phasor is

[0070] (5)

[0071] wherein is the N-node voltage phasor of the network at the corresponding perturbation frequency, is the conjugate of the N-node voltage phasor of the network at the corresponding coupling frequency, T is the phasor transposition symbol;

[0072] the kth row of the extended node admittance matrix corresponds to the kth node Kirchhoff's Current Law (KCL) of the first network, and the kth row of the extended node admittance matrix corresponds to the kth node Kirchhoff's Current Law (KCL) of the second network; Suppose a grid-connected converter is connected to the kth node of the original network, and its coupling frequency admittance model is:

[0073] (6)

[0074] wherein ,

[0075] are the port current response phasor of the converter connected to the kth node at the perturbation frequency and the conjugate of the port current response phasor at the coupling frequency, respectively, , are the port voltage phasor at the perturbation frequency corresponding to the perturbation frequency current phasor and the admittance coefficient of the port voltage phasor at the coupling frequency, respectively, , are the port voltage phasor at the perturbation frequency corresponding to the conjugate of the coupling frequency current phasor and the admittance coefficient of the port voltage phasor at the coupling frequency, respectively;

[0076] The contribution of the grid-connected converter to the extended node admittance matrix is calculated as follows: the element of the extended node admittance matrix is added by , , , , , , , ;

[0077] The power transmission line and transformer branch connected between the kth node and the mth node in the original network have no coupling admittance model between the first network and the second network, and are as follows:

[0078] ​​ (7)

[0079] wherein, , are the disturbance frequency current phasor and the conjugate of the coupling frequency current phasor of the branch between node k and node m respectively, , are the disturbance frequency admittance and the conjugate of the coupling frequency admittance of the element respectively; is the voltage phasor of node m of the first network at the disturbance frequency; is the voltage phasor of node m of the second network at the coupling frequency; is the conjugate of the voltage phasor of node m of the second network at the disturbance frequency; The contribution of the transmission line, transformer branch to the extended node admittance matrix is calculated as:

[0080] , , , , , , , , , , , , .

[0081] Preferably, the extension unit is configured to perform the coupling admittance aggregation calculation for the specified network node based on the extended node admittance matrix, and is further configured to:

[0082] Inject two sets of complementary frequency current sources and at the specified node J of the network in turn, where, , , are the disturbance frequency current source phasor and the conjugate of the coupling frequency current source phasor injected at node J respectively, is the disturbance frequency and the coupling frequency current source phasor injected at node J, is the disturbance frequency and the coupling frequency current source matrix injected at node J;

[0083] The Kirchhoff's law KCL equation of the network extended node admittance matrix is used to calculate the voltage of the two sets of aggregation nodes J, where, , are the disturbance frequency response voltage phasor and the conjugate of the coupling frequency voltage of node J respectively, is the response voltage matrix of node J;

[0084] (8)

[0085] (9)

[0086] Let the aggregated frequency coupling admittance of node J be:

[0087] (10)

[0088] wherein, , and are the admittance coefficients of the port voltage phasor at the perturbation frequency corresponding to the perturbation frequency current phasor, and the port voltage phasor at the coupling frequency corresponding to the coupling frequency current conjugate phasor, respectively; , and are the admittance coefficients of the port voltage phasor at the perturbation frequency corresponding to the perturbation frequency current phasor, and the port voltage phasor at the coupling frequency corresponding to the coupling frequency current conjugate phasor, respectively;

[0089] Substitute the two sets of voltage and current into , and obtain the coupling frequency admittance of node J as:

[0090] (11)

[0091] Based on another aspect of the present application, the present application provides a computer readable storage medium, which stores a computer program, and the program is executed by a processor to realize the steps of the above-mentioned universal numerical aggregation method of frequency coupling admittance / impedance.

[0092] Based on another aspect of the present application, the present application provides an electronic device, comprising:

[0093] The above-mentioned computer readable storage medium; and

[0094] One or more processors for executing the program in the computer readable storage medium.

[0095] The technical scheme of the present application provides a universal numerical aggregation method and system of frequency coupling admittance / impedance, wherein the method comprises: determining a frequency coupling admittance model of a converter, obtaining complementary frequencies and in the frequency coupling admittance model; and splitting the original network of the converter into two networks respectively corresponding to the complementary frequencies and The corresponding first network and second network; the frequency coupling admittance model is respectively accessed to the first network and the second network, and the first admittance matrix and the second admittance matrix corresponding to the first network and the second network are generated; the first admittance matrix and the second admittance matrix are combined into an extended node admittance matrix, and the coupling frequency admittance calculation of the specified network node is carried out based on the extended node admittance matrix. The technical scheme of the present application proposes a general program frequency coupling admittance / impedance numerical calculation aggregation method and system, and the extended companion network of any network structure corresponding to the coupling frequency is based on the extended node admittance matrix to realize the general program numerical calculation aggregation of the coupling frequency admittance of the multi-converter network, which is equivalent to a single-converter grid-connected system, and is convenient for subsequent stability analysis of the system. BRIEF DESCRIPTION OF DRAWINGS

[0096] The exemplary embodiments of the present application can be more completely understood in reference to the following drawings:

[0097] Figure 1 A general numerical aggregation method of frequency coupling admittance / impedance according to the preferred embodiment of the present application is shown in the flow chart;

[0098] Figure 2 A multi-converter network frequency coupling admittance / impedance aggregation flow chart based on the extended node admittance matrix according to the preferred embodiment of the present application is shown in the flow chart;

[0099] Figure 3 A grid-connected converter coupling frequency circuit schematic diagram according to the preferred embodiment of the present application is shown in the schematic diagram;

[0100] Figure 4 A coupling frequency companion network schematic diagram according to the preferred embodiment of the present application is shown in the schematic diagram;

[0101] Figure 5 A VSC1-VSC3 grid-connected system structure diagram according to the preferred embodiment of the present application is shown in the structure diagram;

[0102] Figure 6 A VSC1-VSC3 coupling admittance (35kV side) diagram according to the preferred embodiment of the present application is shown in the diagram;

[0103] Figure 7 A node 4 aggregated frequency coupling admittance calculation value and time domain simulation analysis comparison schematic diagram according to the preferred embodiment of the present application is shown in the schematic diagram;

[0104] Figure 8 A general numerical aggregation system structure diagram of frequency coupling admittance / impedance according to the preferred embodiment of the present application is shown in the structure diagram. DETAILED DESCRIPTION

[0105] Reference will now be made to the drawings to describe the exemplary embodiments of the present application in greater detail. The present application can be variously embodied and is not limited to the embodiments described herein, which are provided for the purposes of explanation and thoroughness in disclosing the present application and to fully convey the scope of the present application to those skilled in the art. The terminology used in the description of the exemplary embodiments presented in the accompanying drawings is not intended to limit the present application. In the drawings, the same elements / elements are denoted by the same reference numerals.

[0106] Unless otherwise defined, the terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0107] Figure 1 A general numerical aggregation method of frequency-coupled admittance / impedance according to a preferred embodiment of the present application is shown in the flowchart.

[0108] The present application relates to a frequency-coupled admittance / impedance aggregation method based on a network containing new energy and power electronic devices. The new energy collection network contains a large number of grid-connected converters. In the sub-synchronous / super-synchronous 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 mode, and the model is a port frequency-coupled admittance / impedance; (2) there are many converters in the new energy collection network, and the influence of other converters in the network needs to be considered when analyzing the sub-synchronous / super-synchronous stability of the grid-connected converter to be studied. The present application proposes a general programmatic frequency-coupled admittance / impedance numerical calculation aggregation method: based on the extended node admittance matrix, the general programmatic numerical calculation aggregation of the coupling frequency admittance of the multi-converter network corresponding to the extended companion network of any network structure is realized, which is equivalent to a single-converter grid-connected system, facilitating subsequent stability analysis of the system.

[0109] In view of the lack of a general programmatic aggregation analysis method for a multi-converter network, the present application first analyzes the frequency-coupled admittance model of the converter; then, in the sub-synchronous / super-synchronous frequency range, the network is divided into two networks corresponding to a pair of coupling frequencies, and a general programmatic frequency-coupled admittance numerical calculation aggregation method based on the extended node admittance matrix is proposed, which retains the dynamic characteristics of the grid-connected converter and the network, is equivalent to a single-converter grid-connected system, and facilitates the analysis of the sub-synchronous / super-synchronous oscillation stability of a complex multi-converter network.

[0110] As shown in Figure 1 The present application provides a general numerical aggregation method of frequency-coupled admittance / impedance, characterized in that the method comprises:

[0111] Step 101: Determine the frequency coupling admittance model of the converter and obtain the complementary frequencies in the frequency coupling admittance model. and ;

[0112] Preferably, determining the frequency coupling admittance model of the converter includes:

[0113] At the grid connection point of the converter, a frequency of... Disturbance voltage The harmonic voltage on the valve side of the converter is determined as follows:

[0114] (1)

[0115] 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 For the corresponding disturbance frequency Complex variables, S C For the corresponding disturbance frequency Complex variables;

[0116] The frequency coupling admittance model of the converter is determined by the above equation as follows:

[0117] (2)

[0118] in, , , , These are the frequency coupling admittance matrix elements of the converter.

[0119] This invention first determines the frequency coupling model of the converter's sub-supersynchronous frequency:

[0120] If the grid is disturbed, resulting in the appearance of a positive sequence voltage disturbance component with frequency at the grid-connected point of the converter, a beat frequency component with frequency ( is the system fundamental frequency) appears in the DC side voltage of the converter, the difference frequency component of appears in the angle output by the phase-locked loop, the PCC voltage and the dq variables of the converter current in the controller, and the difference frequency component appears in the valve side dq voltage reference value output by the outer loop and the inner loop. 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 after pulse width modulation (PWM), generates a positive sequence disturbance component with two frequencies ( and ) coupling in the AC voltage at the valve side of the converter, as shown in Figure 3 , the corresponding frequency current disturbance component is generated in the AC circuit at the AC side of the converter.

[0121] The present application adopts the method of harmonic linearization, by adding a small signal disturbance voltage with harmonic frequency in the PCC steady-state power frequency voltage of the VSC, according to the disturbance voltage and current phase, through PARK transformation, transmission path in the controller, PARK inverse transformation and PWM modulation, the harmonic voltage at the valve side of the VSC is obtained as:

[0122] (1)

[0123] In the formula: the superscript d is the variable corresponding to the frequency , the superscript c is the variable corresponding to the frequency , the asterisk is the conjugate, , is the disturbance voltage phase of the converter valve side, , is the PCC disturbance voltage phase, , is the disturbance current phase of the converter, , , , , , , , is the coefficient transfer function.

[0124] From the above formula, the frequency coupling admittance model of the VSC is:

[0125] (2)

[0126] In the formula: 、 、 、 is the frequency coupling admittance matrix element of the converter.

[0127] The converter frequency coupling admittance model features are as follows:

[0128] (1) Two complementary frequencies (f d and 2f1-f d ) voltage, current coupling effect exists;

[0129] (2) Conjugate property: the main diagonal element admittance is conjugate, the off-diagonal element admittance is conjugate; The coupling frequency voltage and current in the model are in the form of conjugate.

[0130] (3) The converter circuit port is the coupling frequency voltage and current, which cannot be directly connected with the coupling frequency model (conjugate quantity) (node KCL equation).

[0131] Step 102: split the original network of the converter into a first network and a second network corresponding to the complementary frequencies and respectively;

[0132] Preferably, the original network of the converter is split into a first network and a second network corresponding to the complementary frequencies and respectively, wherein the node Kirchhoff's law KCL equation of the first network and the second network corresponding to node k is:

[0133] (3)

[0134] wherein, 、 are the disturbance voltage phasors of node k at the complementary frequencies and respectively, 、 are the disturbance voltage phasors of node i at the complementary frequencies and respectively, 、 are the L non-converter element admittances of node k at the complementary frequencies and respectively, 、 are the I non-converter element admittances between node k and other nodes at the complementary frequencies and respectively, 、 are the I non-converter element admittances between node k and other nodes at the 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.

[0135] This invention extends the network node admittance matrix:

[0136] 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:

[0137] (3)

[0138] In the formula: , Let be the perturbation voltage phasors for nodes k and i. The admittance of L non-converter elements to ground at node k is given. The admittance of I non-converter elements connecting node k to other nodes. For the M converter currents connected to node k, Let J be the current sources injected into node k.

[0139] 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;

[0140] 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.

[0141] (4)

[0142] wherein, , , , are the i-th converter frequency coupling admittance model elements of node k with complementary frequencies and are the L non-converter element admittance conjugates of node k with complementary frequencies are the I non-converter element admittance conjugates between node k and other nodes with complementary frequencies are the perturbation voltage phasor conjugates of node k with complementary frequencies are the perturbation voltage phasor conjugates of node i with complementary frequencies are the J current source conjugates of node k with complementary frequencies

[0143] The present application takes the conjugate of the second equation of formula (3), substitutes the converter frequency coupling admittance model, and transforms the above formula into:

[0144] (4)

[0145] In the formula: , , , are the i-th converter frequency coupling admittance model elements of node k.

[0146] From the above formula, the first equation is the KCL of the original network node k with corresponding frequency , denoted as network ( ), and the second equation is the conjugate equation of the KCL of the original network node k with corresponding frequency , denoted as the adjoint network ( ). As shown in Figure 4 , the voltage and of the non-converter access node in network ( ) and adjoint network ( ) are independent of each other, and the voltage and of the grid-connected converter access node are the coupling variables between the two networks.

[0147] Step 104: Merge the first admittance matrix and the second admittance matrix into an extended node admittance matrix, and based on the extended node admittance matrix, perform the coupling frequency admittance calculation of the specified network node. ​​​​​​

[0148] Preferably, the first admittance matrix and the second admittance matrix are combined into an extended node admittance matrix, based on which, including:

[0149] For an N-node network, its corresponding extended node admittance matrix is , and the node voltage phasor is:

[0150] (5)

[0151] wherein, is the N-node voltage phasor of the network at the corresponding disturbance frequency, is the conjugate of the N-node voltage phasor of the network at the corresponding coupling frequency, T is the phasor transposition symbol;

[0152] The first row of the extended node admittance matrix corresponds to the KCL of the kth node of the first network, and the first row of the extended node admittance matrix corresponds to the KCL of the kth node of the second network;

[0153] Suppose the grid-connected converter is connected to the kth node of the original network, and its coupling frequency admittance model is:

[0154] (6)

[0155] wherein, , are the port current response phasor of the converter connected to the kth node at the disturbance frequency and the conjugate of the port current response phasor at the coupling frequency, respectively, , are the port voltage phasor at the disturbance frequency and the admittance coefficient of the port voltage phasor at the coupling frequency corresponding to the disturbance frequency current phasor, respectively, , are the port voltage phasor at the disturbance frequency and the admittance coefficient of the port voltage phasor at the coupling frequency corresponding to the conjugate of the coupling frequency current phasor, respectively;

[0156] The contribution of the grid-connected converter to the extended node admittance matrix is calculated as follows: the element of the extended node admittance matrix is added by , the element is added by , the element is added by ;

[0157] The transmission line and transformer branch between the connected nodes k and m in the original network, the uncoupled admittance model between the first network and the second network is:

[0158] (7)

[0159] wherein, , are the perturbation frequency current phasor and the coupling frequency current conjugate phasor of the element branch between the nodes k and m, , are the perturbation frequency admittance and the coupling frequency admittance conjugate value of the element; is the voltage phasor of the node m in the first network at the frequency; is the voltage phasor conjugate of the node m in the second network at the frequency; The contribution of the transmission line and transformer branch to the extended node admittance matrix is calculated as follows: the , elements of the extended admittance matrix are added by , , elements are subtracted by , , elements are added by , , elements are subtracted by .

[0160] Preferably, based on the extended node admittance matrix, the coupling admittance aggregation calculation of the specified network node is carried out, including:

[0161] Inject two groups of complementary frequency and current sources at the specified node J of the network in turn, wherein, , are the i-th perturbation frequency current source phasor and the coupling frequency current source conjugate phasor injected at the node J, is the perturbation frequency and the coupling frequency current source phasor injected at the node J, is the perturbation frequency and the coupling frequency current source matrix injected at the node J;

[0162] The Kirchhoff's law KCL equation of the network extended node admittance matrix is used to calculate the two groups of voltage of the aggregation node J, wherein, , are the perturbation frequency response voltage phasor and the coupling frequency voltage conjugate phasor of the node J, is the response voltage matrix of the node J;

[0163] (8)

[0164] (9)

[0165] Let the aggregation frequency coupling admittance of node J be:

[0166] (10)

[0167] 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.

[0168] Substitute the two sets of voltages and currents into The coupling frequency admittance of node J is obtained as follows:

[0169] (11)

[0170] 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 phasors are:

[0171] (5)

[0172] The first of the extended node admittance matrix Line correspondence network ( The k-th node KCL of the extended admittance matrix is ​​the k-th node of the extended admittance matrix. Line-to-line companion network ( The k-th node KCL of the grid-connected converter is given. The coupled frequency admittance model of the grid-connected converter connected to the k-th node of the original network is:

[0173] (6)

[0174] The contribution of the grid-connected converter to the extended node admittance matrix is: [Extended admittance matrix] Element plus , Element plus , Element plus , Element plus The branch between the connected node k and node m in the original network, the transmission line, the transformer and the like, in the network (1000) and the accompanying network (2000) have no coupling terms, and the admittance model is:

[0175] (7)

[0176] The branch of the transmission line / transformer and the like contributes to the extended node admittance matrix as follows: the , element of the extended admittance matrix is added by , , element is subtracted by , , element is added by , , element is subtracted by .

[0177] The present application carries out node frequency coupling admittance aggregation:

[0178] As shown in Figure 4 , two groups of are injected into the node J of the network to be studied in turn, and the KCL equation of the extended node admittance matrix of the network is calculated to obtain the voltage of the two groups of aggregated node J.

[0179] (8)

[0180] (9)

[0181] Let the aggregated frequency coupling admittance of node J be:

[0182] (10)

[0183] Substitute the two groups of voltage and current into , and the aggregated frequency coupling admittance of node J is

[0184] (11)

[0185] From the above analysis process, it can be seen that the network element model is not reduced and simplified in the aggregation calculation based on the extended node admittance matrix, therefore, the sub / super synchronous frequency range dynamic characteristics of all grid-connected converters and network branches are retained in the aggregated frequency coupling admittance model of the node to be studied, and the sub / super synchronous oscillation characteristics of the converter connected to the node to be studied can be accurately analyzed.

[0186] The accompanying matrix corresponding to the coupling frequency is: ​​

[0187] The port voltage and current of a pair of coupling frequencies exist in the converter coupling frequency model simultaneously, two network models with the same topology corresponding to different frequencies are needed to interface with the converter model; and the conjugate quantity of the coupling frequency voltage and current is included in the converter coupling frequency model, therefore, the adjoint matrix corresponding to the network of the coupling frequency is needed to be constructed to complete the interconnection relationship with the converter coupling frequency model.

[0188] The present application is based on the frequency coupling admittance / impedance numerical calculation aggregation of the network expansion node admittance matrix:

[0189] The port voltage and current of a pair of coupling frequencies exist in the converter coupling frequency model simultaneously, and need to be solved in the numerical calculation of each corresponding frequency point of the model, the network expansion node admittance matrix is constructed, the network corresponding to a pair of coupling frequencies is in a node admittance matrix, and the equivalent coupling frequency admittance / impedance of the frequency point by frequency point numerical calculation of the specified node can be aggregated and calculated based on the expansion matrix.

[0190] The following illustrates the embodiments of the present application:

[0191] At present, a large amount of research work has been carried out on the oscillation problem, and fruitful research results have been obtained, mainly focusing on the modeling, mechanism analysis and suppression of subsynchronous / ultrasynchronous oscillation of single or a small number of new energy equipment grid-connected systems.

[0192] However, with the continuous increase of the scale of domestic new energy grid connection, the subsynchronous / ultrasynchronous oscillation problem has occurred many times in new energy gathering areas. At present, the analysis method based on single converter grid-connected system cannot analyze the subsynchronous / ultrasynchronous oscillation characteristics of the multi-new energy station gathering and sending out system: in the subsynchronous / ultrasynchronous frequency range, the converter has a coupling frequency effect, and the single structure network modeling cannot reflect this coupling characteristic, and the subsynchronous / ultrasynchronous oscillation risk assessment has a large deviation; due to the existence of many types of network structures and numerous operation modes in new energy gathering areas, if the coupled impedance series-parallel aggregation analysis method is used, the research work is huge, therefore, it is urgent to develop a general programmatic analysis method for the subsynchronous / ultrasynchronous oscillation characteristics of the complex network containing multiple converters.

[0193] The application firstly analyzes the coupling frequency effect of the converter and the converter frequency coupling admittance model, further considers that the conventional elements such as the power transmission line and the transformer almost do not exist the sub / super synchronous frequency coupling effect, therefore, the network corresponding to a pair of sub / super synchronous coupling frequencies is considered respectively, the network structure is the same, the element admittance / impedance value is determined by the coupling frequency, the network is split into two networks corresponding to a pair of coupling frequencies, the converter frequency coupling admittance model is connected to the two networks respectively, and the node admittance matrix of the two networks is combined into an extended node admittance matrix, therefore, for the network containing multiple converters, the equivalent frequency coupling admittance aggregation calculation and analysis can be carried out at the specified node.

[0194] With the considerable scale of wind power and photovoltaic new energy distributed in the desert and Gobi regions, the power grid is mostly a weak system; the new energy grid-connected unit is mostly a converter, and a large number of converters are gathered, so that the sub / super synchronous oscillation problem is prone to occur. The application is aimed at the sub / super synchronous oscillation characteristic analysis of the multi-converter network, therefore, has wide application prospect.

[0195] The flow chart of the multi-converter network frequency coupling admittance / impedance aggregation method based on the extended node admittance matrix is as follows: starting to read the frequency coupling admittance 2*2 matrix model parameters of each grid-connected converter, each element is a frequency-admittance curve data, and the data is stored in the memory; then reading the network topology and the model parameters of the conventional elements such as the power transmission line and the transformer in the network, determining the order of the extended node admittance matrix as according to the set frequency calculation step (such as 1 Hz), at each frequency point, sequentially traversing the nodes in the network, first considering the contribution of the coupling frequency admittance model of each grid-connected converter to the corresponding access node number element of the extended node admittance matrix at the calculation frequency point, then sequentially considering the contribution of each conventional element in the network to the corresponding access node number element of the extended node admittance matrix; forming the extended node admittance matrix at the current calculation frequency point, injecting the frequency coupling current at the aggregation node, solving the extended node admittance matrix equation, obtaining the aggregation node voltage value, and further calculating the aggregation node frequency coupling admittance value at the current calculation frequency point, continuing the calculation process at the next frequency point, and obtaining the aggregation frequency coupling admittance model of the specified node.

[0196] As shown in Figure 5 , three grid-connected converters form a 4-node 35kV network.

[0197] In the figure, the element parameters of branches 1-4 are , , , 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.

[0198] 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.

[0199] 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.

[0200] like Figure 8 As shown, this invention provides a general numerical aggregation system for frequency-coupled admittance / impedance, the system comprising:

[0201] 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 ;

[0202] Preferably, the initial unit 801 is used to determine the frequency coupling admittance model of the converter, and is also used for:

[0203] At the grid connection point of the converter, a frequency of... Disturbance voltage The harmonic voltage on the valve side of the converter is determined as follows:

[0204] (1)

[0205] 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 For the corresponding disturbance frequency Complex variables, S C For the corresponding disturbance frequency Complex variables;

[0206] The frequency coupling admittance model of the converter is determined by the above equation as follows:

[0207] (2)

[0208] in, , , , These are the frequency coupling admittance matrix elements of the converter.

[0209] 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;

[0210] 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:

[0211] (3)

[0212] in, , complementary frequencies and The perturbation voltage phasor at node k. , complementary frequencies and the disturbance voltage phasor of node i, , the L non-converter element admittances of node k at complementary frequencies and , , the I non-converter element admittances between node k and other nodes at complementary frequencies and , , the M converter currents of node k at complementary frequencies and , , the J current sources of node k at complementary frequencies and , the frequency of node k.

[0213] The generating unit 803 is configured to input the frequency coupling admittance model into 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.

[0214] Preferably, the generating unit 803 is configured to input the frequency coupling admittance model into 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, including inputting the node Kirchhoff law KCL equation of the frequency coupling admittance model into the first network and the second network respectively, and generating a first admittance matrix and a second admittance matrix corresponding to the first network and the second network:

[0215] (4)

[0216] wherein, , , , the i-th converter frequency coupling admittance model element of node k at complementary frequencies and , the conjugate of the L non-converter element admittances of node k at complementary frequencies , the conjugate of the I non-converter element admittances between node k and other nodes at complementary frequencies , the conjugate of the disturbance voltage phasor of node k at complementary frequencies , the conjugate of the disturbance voltage phasor of node i at complementary frequencies , complementary frequency of node k.

[0217] The extension unit 804 is configured to combine the first admittance matrix and the second admittance matrix into an extended node admittance matrix, and perform the coupling frequency admittance calculation of the specified network node based on the extended node admittance matrix.

[0218] Preferably, the extension unit 804 is configured to combine the first admittance matrix and the second admittance matrix into an extended node admittance matrix, and based on the extended node admittance matrix, further configured to:

[0219] For an N-node network, the corresponding extended node admittance matrix is , and the node voltage phasor is:

[0220] (5)

[0221] wherein, is the network N-node voltage phasor corresponding to the perturbation frequency, is the conjugate of the network N-node voltage phasor corresponding to the coupling frequency, T is the phasor transposition symbol;

[0222] The first row of the extended node admittance matrix corresponds to the Kirchhoff's Current Law (KCL) of the kth node of the first network, and the first row of the extended node admittance matrix corresponds to the Kirchhoff's Current Law (KCL) of the kth node of the second network.

[0223] Suppose that the grid-connected converter is connected to the kth node of the original network, and the coupling frequency admittance model of the grid-connected converter is:

[0224] (6)

[0225] wherein, , are the port current response phasor of the converter connected to the kth node at the perturbation frequency and the conjugate of the port current response phasor at the coupling frequency, respectively, , are the port voltage phasor at the perturbation frequency corresponding to the perturbation frequency current phasor and the admittance coefficient of the port voltage phasor at the coupling frequency, respectively, , are the port voltage phasor at the perturbation frequency corresponding to the conjugate of the coupling frequency current phasor and the admittance coefficient of the port voltage phasor at the coupling frequency, respectively;

[0226] The contribution of the grid-connected converter to the extended node admittance matrix is: Element plus , Element plus , Element plus , Element plus ;

[0227] The transmission lines and transformer branches connecting nodes k and m in the original network, with no coupling admittance model between the first and second networks, are as follows:

[0228] (7)

[0229] 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. For node m in the first network Voltage phasors at frequency; For node m in the second network Voltage phasor conjugate at frequency;

[0230] 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 .

[0231] 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, and is also used for:

[0232] 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 perturbation frequency and coupling frequency current source phasor into node J, injecting a disturbance frequency, a coupling frequency current source matrix at node J;

[0233] The Kirchhoff's law KCL equation of the admittance matrix of the network expansion node is extended, and the voltages of two groups of aggregated nodes J are calculated wherein, , are a disturbance frequency response voltage phasor and a coupling frequency voltage conjugate phasor of node J respectively, is a response voltage matrix of node J;

[0234] (8)

[0235] (9)

[0236] Supposing that the aggregated frequency coupling admittance of node J is:

[0237] (10)

[0238] wherein, , are a disturbance frequency lower port voltage phasor corresponding to a disturbance frequency current phasor and a coupling frequency lower port voltage phasor corresponding to a coupling frequency current conjugate phasor respectively, , are a disturbance frequency lower port voltage phasor corresponding to a disturbance frequency current conjugate phasor and a coupling frequency lower port voltage phasor corresponding to a coupling frequency current phasor respectively;

[0239] two groups of voltages and currents are substituted into , and the coupling frequency admittance of node J is obtained as:

[0240] (11)

[0241] The application provides a computer readable storage medium, which stores a computer program, and the program is executed by a processor to realize steps of a general numerical aggregation method of frequency coupling admittance / impedance.

[0242] The application provides an electronic device, which comprises:

[0243] The computer readable storage medium described above; and

[0244] One or more processors are used to execute the program in the computer readable storage medium.

[0245] Those skilled in the art will appreciate that embodiments of the present application can be readily used as software, hardware, or a combination of software and hardware. In a software embodiment, the methods can be tangibly embodied in a machine-readable storage medium having stored thereon instructions that can be used to program a computer to perform any of the methods. The software implementation can be initialized by loading and executing a set of instructions arranged to perform one of the methods into the computer's memory. Alternatively, hard-wired circuitry can be used in place of, or in combination with, software instructions. Thus, the

[0246] The present application is described in reference to the flowchart and / or block diagrams of the methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each block of the flowchart and / or block diagrams, and combinations of blocks in the flowchart 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, create means for implementing the functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in one or more of the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in one or more of the flowchart and / or block diagram block or blocks.

[0247] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in one or more of the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in one or more of the flowchart and / or block diagram block or blocks.

[0248] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in one or more of the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in one or more of the flowchart and / or block diagram block or blocks.

[0249] While preferred embodiments of the application have been described, modifications and alterations thereto will occur to those skilled in the art upon reading the preceding description. In particular, it will be apparent to those skilled in the art that parts can be added to, or substituted for, parts of the described embodiment. It is therefore contemplated that the claims be construed to include all such alterations and modifications as fall within the true spirit and scope of the application. Accordingly, while the preferred embodiment of the application has been described above, it will be recognized and understood that many additions, modifications, and substitutions can be made to the above description by one of ordinary skill in the art, in light of the foregoing, without departing from the spirit and scope of the application.

[0250] Obviously, numerous modifications and variations of the present application are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, and their equivalents, the application can be practiced otherwise than as specifically described.

[0251] The present application has been described in terms of particular embodiments. However, the specific embodiments are not intended to limit the scope of the present application, which is defined solely by the claims below, and equivalents thereof. Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the present application disclosed herein.

[0252] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the [device, component, etc.] are to be interpreted openly as referring to at least one instance of the referenced device, component, etc., unless otherwise indicated. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

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. 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 phasors are: （5） in, Let N be the voltage phasors of the network nodes at the corresponding disturbance frequency. This represents the conjugate of the voltage phasors of the N nodes in the network at the corresponding coupling frequency. T This is the symbol for phasor 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. , complementary frequencies and The perturbation voltage phasor at node k; complementary frequencies The perturbation voltage phasor conjugate at node k; 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. For node m in the first network Voltage phasors at frequency; For node m in the second network Voltage phasor conjugation at frequency; 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 .

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... Disturbance voltage The harmonic voltage on the valve side of the converter is determined 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 For the corresponding disturbance frequency Complex variables, S C For the corresponding disturbance frequency Complex variables; 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 non-converter elements at node k to ground. complementary frequencies The admittance conjugate of node k with other nodes is I non-converter element. complementary frequencies The perturbation voltage phasor conjugate at node k. complementary frequencies The perturbation voltage phasor conjugate of node i. complementary frequencies The J current sources at node k are conjugate.

5. The method according to claim 1, 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 perturbation frequency and coupling frequency current source phasor into 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）。 6. 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. 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. The expansion unit is configured to merge the first admittance matrix and the second admittance matrix into an expanded node admittance matrix, and calculate the coupling frequency admittance of a specified network node based on the expanded node admittance matrix; the expansion unit is further configured to: merge the first admittance matrix and the second admittance matrix into an expanded node admittance matrix, and calculate the coupling frequency admittance of a specified network node based on the expanded node admittance matrix. For an N-node network, its corresponding extended node admittance matrix is: The node voltage phasors are: （5） in, Let N be the voltage phasors of the network nodes at the corresponding disturbance frequency. This represents the conjugate of the voltage phasors of the N nodes in the network at the corresponding coupling frequency. T This is the symbol for phasor 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. For node m in the first network Voltage phasors at frequency; For node m in the second network Voltage phasor conjugation at frequency; 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 .

7. The system according to claim 6, 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... Disturbance voltage The harmonic voltage on the valve side of the converter is determined 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 For the corresponding disturbance frequency Complex variables, S C For the corresponding disturbance frequency Complex variables; 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.

8. The system according to claim 7, characterized in that, 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.

9. The system according to claim 8, characterized in that, 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, including 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 a first admittance matrix and a 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 non-converter elements at node k to ground. complementary frequencies The admittance conjugate of node k with other nodes is I non-converter element. complementary frequencies The perturbation voltage phasor conjugate at node k. complementary frequencies The perturbation voltage phasor conjugate of node i. complementary frequencies The J current sources at node k are conjugate.

10. The system according to claim 6, characterized in that, The extended unit is used to perform coupled admittance aggregation calculation of a specified network node based on the extended node admittance matrix, and is also used for: 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 perturbation frequency and coupling frequency current source phasor into 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）。 11. 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 1-5.

12. An electronic device, characterized in that, include: The computer-readable storage medium as described in claim 11; and one or more processors for executing the program in the computer-readable storage medium.

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