Simplified stability judgment method for amplitude-phase characteristics of key modal impedance, terminal equipment and storage medium

Abstract

The invention discloses a simplified stability judgment method for amplitude-phase characteristics of key modal impedance, terminal equipment and a storage medium, a resonance mode of a system can be identified according to a Bode diagram of the key modal impedance, and whether the resonance mode is in a positive damping state or a negative damping state is judged. Compared with an existing method, the method has the advantages that determinant zero point solving of a high-order s-domain node admittance matrix is avoided, the amplitude-phase characteristic of the key modal impedance can be obtained through frequency scanning, and the complexity of frequency domain modal analysis of the multi-node multi-type new energy grid-connected system is reduced.

Description

Simplified stability assessment method for amplitude and phase characteristics of critical mode impedance, terminal equipment and storage media Technical Field

[0001] This invention relates to the field of new energy power generation, and in particular to a simplified method for determining the stability of the amplitude and phase characteristics of key mode impedance, a terminal device, and a storage medium. Background Technology

[0002] In recent years, with the rapid development of new energy sources such as wind power and photovoltaics, the penetration rate of power electronic equipment in power systems has been increasing. The broadband oscillation problem caused by the interaction of large-scale power electronic equipment seriously endangers the safe and stable operation of new energy grid-connected systems and is one of the key issues restricting the reliable transmission and efficient consumption of new energy. Impedance analysis, which analyzes system stability through the terminal characteristics of converters, has advantages such as clear physical meaning, high modularity and scalability, measurable impedance models, and strong practicality, and is widely used in the broadband oscillation mechanism analysis of new energy grid-connected systems. However, the traditional impedance analysis method based on the Nyquist stability criterion is sensitive to the "source-load" subsystem division point, limiting its application in multi-machine grid-connected systems. Frequency domain modal analysis, on the other hand, determines the small-disturbance stability of the system by analyzing the zero-point distribution of the determinant of the system's s-domain node admittance matrix. It can not only assess the interaction stability between the grid-connected system and the grid, but also identify the interaction stability between various nodes within the system, showing significant advantages in the small-disturbance stability analysis of multi-machine grid-connected systems. However, when the number of system nodes is large, solving for the zeros of the determinant of the node admittance matrix becomes extremely difficult, and it typically relies on analytical functional admittance models (white-box mechanism modeling or black-box identification modeling), making it impossible to directly analyze using discrete admittance models obtained from black-box measurements. This limits the application of frequency domain modal analysis in practical power systems containing large-scale power electronic equipment. Therefore, avoiding the need for solving for the zeros of the determinant of the higher-order s-domain node admittance matrix, exploring simplified stability criteria that can directly use black-box measurement models, and enabling frequency domain modal analysis of complex renewable energy grid-connected systems with multiple nodes and multiple unit types (grid-connected / interconnected) to assess the system's small-disturbance stability and locate damping weaknesses are of great significance for the safe operation and stable control of renewable energy grid-connected systems.

[0003] Existing technologies determine the small-disturbance stability of a system by analyzing the distribution of zeros in the determinant of the s-domain node admittance matrix. For large-scale, multi-node renewable energy grid-connected systems, the determinant of the s-domain node admittance matrix is ​​generally a high-order polynomial, and solving for its zeros is usually very complex. Furthermore, solving for the zeros of the s-domain node admittance matrix determinant typically requires presenting an analytical polynomial power electronic device admittance model (white-box mechanism modeling or black-box identification modeling). Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a simplified stability assessment method, terminal equipment and storage medium for the amplitude and phase characteristics of key modal impedances, which addresses the shortcomings of existing technologies. This reduces the complexity of frequency domain modal analysis of multi-power electronic device grid-connected systems and enables rapid and accurate assessment of small-disturbance stability of large-scale heterogeneous multi-machine new energy grid-connected systems.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a simplified stability determination method for the amplitude and phase characteristics of key mode impedance, comprising the following steps:

[0006] S1. Based on the frequency coupling sequence admittance model of the power electronic equipment in the new energy grid-connected system to be analyzed, as well as the parameters of passive components and the grid structure, establish the s-domain node admittance matrix Y of the new energy grid-connected system considering the frequency coupling characteristics. N (s);

[0007] S2. Set the starting frequency f of the analysis band. s Step size Δf, termination frequency f e At each frequency point f p ,make According to Y N (s p )=R(s p )Λ(s p )L(s p ) The admittance matrix Y of the s-domain nodes N (s p Decomposed into left and right eigenvector matrices L(s) p ) and R(s p ), and the eigenvalue diagonal matrix Here, n represents the number of nodes in the new energy grid-connected system to be analyzed, and j represents the imaginary unit;

[0008] S3, at each frequency point f p Calculate the minimum eigenvalue λ min (s p )=min(λ1(s p ), λ2(s p ), …, λ n (s p Define the critical mode impedance. ;

[0009] S4. Draw the analysis frequency band [f] s f e Internal critical mode impedance Z m (s p Bode plots were used to identify the resonant modes of the renewable energy grid-connected system based on simplified stability criteria, and the system's small disturbance stability was determined. The participation factor P of mode k was also used. kAssess the degree of participation of each node in the resonant mode k and locate the weak damping node of the system; if the power electronic equipment is a white box model, analyze the sensitivity of the control parameter x of the converter connected to the weak damping node to the resonant mode based on the relative magnitude of the parameter relative sensitivity Rsen(x).

[0010] The proposed solution does not require complex zero-point solutions to the determinant of the s-domain nodal admittance matrix. It only requires the amplitude and phase information of the critical modal impedance to obtain the system's resonant mode information, thereby determining the system's small-disturbance stability. Furthermore, the critical modal impedance can be obtained simply by decomposing the s-domain nodal admittance matrix, thus avoiding reliance on analytical admittance models. Frequency domain modal analysis can be directly performed using the power electronic equipment measurement admittance model obtained through frequency scanning, significantly reducing the complexity of small-disturbance stability analysis for large-scale multi-node renewable energy grid-connected systems and facilitating engineering applications.

[0011] The s-domain node admittance matrix Y of a new energy grid-connected system considering frequency coupling characteristics N The expression for (s) is:

[0012] ;

[0013] Among them, Y 11 and Y 22 Y is the positive-order and negative-order admittance matrix. 12 and Y 21 The coupling admittance matrix is... , Y11 ii and Y22 ii are the positive and negative order self-admittances of node i, respectively; Y11 ij and Y22 ij are the positive and negative order mutual admittances between node i and node j, respectively; Y12 ii and Y21 ii are the coupled self-admittances of node i, i=1,2,…n, j=1,2,…n, j≠i;

[0014] The specific implementation process of identifying the resonant modes of a new energy grid-connected system based on simplified stability criteria and determining the system's small disturbance stability includes: when Z m (s p When the amplitude-frequency response of Z shows a resonance peak, if Z m (s p The phase frequency characteristic of ) is that the phase change near the resonant frequency is Within the range, the modal damping is positive; if Z m (s p The phase frequency characteristics of ) occur near the resonant frequency. If the phase jump occurs within a certain range, the modal damping is negative, and the system oscillation frequency is the frequency corresponding to the phase jump point.

[0015] Participation factor P of mode k kThe calculation formula is: Among them, R jk The right eigenvector matrix R(s) p The element in the j-th row and k-th column of ) is L kj The left eigenvector matrix L(s) p The element in the k-th row and j-th column of ).

[0016] The formula for calculating the relative sensitivity Rsen(x) is:

[0017] ;

[0018] Where x0 and x p Let x be the initial value and disturbance value of the control parameter, and Z be the disturbance value. m_0 (s p ) and Z m_p (s p ) represent the control parameter x at x0 and x... p The key modal impedance obtained under the given conditions; the larger the relative sensitivity Rsen(x), the higher the sensitivity of the control parameter x of the converter connected to the weak damping node to the resonant mode.

[0019] As an inventive concept, the present invention also provides a terminal device, including a memory, a processor, and a computer program stored in the memory; the processor executes the computer program to implement the steps of the above method.

[0020] As an inventive concept, the present invention also provides a computer-readable storage medium having a computer program / instructions stored thereon; when the computer program / instructions are executed by a processor, they implement the steps of the above-described method.

[0021] Compared with existing technologies, the advantages of this invention are as follows: This invention establishes the s-domain node admittance matrix of the system based on a sequence admittance model considering frequency coupling, and proposes a simplified stability criterion based on the amplitude and phase characteristics of key mode impedances. The resonant modes of the system can be identified based on the Bode plot of the key mode impedances, and it can be determined whether the resonant modes are in a positively or negatively damped state. Compared with existing methods, this invention avoids solving for the zeros of the determinant of the high-order s-domain node admittance matrix, and the amplitude and phase characteristics of the key mode impedances can be obtained through frequency scanning, reducing the complexity of frequency domain modal analysis for multi-node, multi-type renewable energy grid-connected systems. Through the frequency domain modal analysis method proposed in this invention, the small-disturbance stability of renewable energy grid-connected systems can be quickly and accurately evaluated. Furthermore, by identifying the damping weak nodes of the system through participation factors, the key control links that play a dominant role in the resonant modes in the control loop of the converter connected to that node can be determined based on parameter sensitivity. This provides a favorable method for small-disturbance stability analysis of large-scale heterogeneous multi-machine renewable energy grid-connected systems. Attached Figure Description

[0022] Figure 1 is a flowchart of a simplified stability determination method for the amplitude and phase characteristics of key mode impedances according to an embodiment of the present invention;

[0023] Figure 2 is a topology diagram of a hybrid renewable energy power station based on a grid / network structure according to an embodiment of the present invention;

[0024] Figure 3 shows the key modal impedance Bode plots of the system under different operating conditions according to the embodiment of the present invention.

[0025] Figure 4 shows the participation factor diagram of each node for different resonant modes in the embodiments of the present invention;

[0026] Figure 5 shows the sensitivity distribution of key converter parameters to different resonant modes in an embodiment of the present invention;

[0027] Figure 6 shows the power waveforms of different nodes of the system under different operating conditions according to an embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] Figure 1 illustrates a simplified stability determination method for the amplitude and phase characteristics of the key mode impedance in Embodiment 1 of the present invention, comprising the following steps:

[0031] 1) Establish the frequency-coupled sequence admittance model Y of the power electronic equipment in the new energy grid-connected system to be analyzed through theoretical modeling (white box) or admittance measurement (black box) methods. Ci (s);

[0032] 2) Based on the parameters of passive components such as transmission lines and transformers in the new energy grid-connected system to be analyzed, and considering the frequency coupling characteristics of the grid structure, the s-domain node admittance matrix Y of the system is established. N (s);

[0033] 3) Set the starting frequency f of the analysis band. s Step size Δf, termination frequency f e At each frequency point f p make , where j represents the imaginary unit, and according to Y N (s p )=R(s p )Λ(sp )L(s p ) The admittance matrix Y of the s-domain nodes N (s p Decomposed into left and right eigenvector matrices L(s) p ) and R(s p ), and the eigenvalue diagonal matrix Here, n represents the eigenvalues, and n is the number of nodes in the system to be analyzed.

[0034] 4) At each frequency point f p Calculate the minimum eigenvalue λ min (s p )=min(λ1(s p ), λ2(s p ), …, λ n (s p Define the critical mode impedance. ;

[0035] 5) Draw the analysis frequency band [f] s f e Internal critical mode impedance Z m (s p Bode plot of ) is used to identify the system's resonant modes and determine the system's stability under small disturbances based on simplified stability criteria;

[0036] 6) Based on the participation factor P of mode k k Assess the degree of participation of each node in the resonant mode k, and locate the weak damping node of the system;

[0037] 7) If the equipment is a white-box model, the sensitivity of the control parameter x of the converter connected to the weak damping node to the resonant mode is analyzed based on the relative magnitude of the parameter relative sensitivity Rsen(x), providing theoretical guidance for converter parameter optimization.

[0038] Step 1) The established sequence admittance model Y of the power electronic equipment considering frequency coupling Ci (s) = [Y11 Ci(s), Y12 Ci(s); Y21 Ci(s), Y22 Ci(s)], where Y11 Ci(s) and Y22 Ci(s) are the positive and negative order admittances of the power electronic device, Y12 Ci(s) and Y21 Ci(s) are the coupled order admittances of the power electronic device, s is the Laplace operator, and Ci is the number of the power electronic device.

[0039] Step 2) The s-domain nodal admittance matrix Y considering frequency coupling characteristics is constructed. N (s) The specific structure can be represented as:

[0040]

[0041] Where Y 11 and Y 22 Y is the positive-order and negative-order admittance matrix. 12 and Y 21 This is the coupling admittance matrix. Specifically:

[0042]

[0043]

[0044] Where Y11 ii and Y22 ii (i=1,2,…n) are the positive and negative order self-admittances of node i, respectively, and Y11 ij and Y22 ij (i=1,2,…n, j=1,2,…n & j≠i) are the positive and negative order mutual admittances between node i and node j, respectively. Y12 ii and Y21 ii (i=1,2,…n) are the coupled self-admittances of node i.

[0045] Step 5) The simplified stability criterion proposed is: when Z m (s p When the amplitude-frequency response of Z exhibits a resonant peak, the system possesses a resonant mode at the corresponding frequency. m (s p The phase frequency characteristic of ) is that the phase change near the resonant frequency is Within the range, the modal damping is positive; if Z m (s p The phase frequency characteristics of ) occur near the resonant frequency. If the phase jump occurs within a certain range, the modal damping is negative, and the system oscillation frequency is the frequency corresponding to the phase jump point.

[0046] Step 6) Participating factor P k The calculation method is as follows:

[0047]

[0048] Among them, R jk The right eigenvector matrix R(s) p The element in the j-th row and k-th column of ) is L kj The left eigenvector matrix L(s) p The element in the k-th row and j-th column of the given array. It has the largest participation factor P for mode k with minimum damping or negative damping. k The node that is weak in damping is the node of the system.

[0049] The method for calculating the relative sensitivity Rsen(x) in step 7) is as follows:

[0050]

[0051] Where x0 and x p Let x be the initial value and disturbance value of the control parameter, and Z be the disturbance value. m_0 (s p ) and Z m_p (s p ) represents the control parameter x at x0 and x p The key modal impedance is obtained under the given conditions. The larger the relative sensitivity Rsen(x), the higher the sensitivity of the control parameter x of the converter connected to the weakly damped node to the resonant mode.

[0052] Figure 2 is a topology diagram of a 16-unit-34-node hybrid grid-following / grid-forming renewable energy power station according to Embodiment 1 of the present invention. This power station includes three 35kV feeders, each connecting five grid-following (GFL) renewable energy units, and is equipped with one grid-forming (GFM) centralized energy storage unit connected to the power station's 35kV bus. The GFM / GFL converter port voltage is 690V, connected to the power station's 35kV network via a 0.69V / 35kV connection, and then connected to the grid via a 35kV / 110kV main transformer. In the figure, Line represents a transmission line, Y... g This represents the grid admittance. The numbering rules for each node in the substation are as follows: Node 1 is the connection point between the main transformer and the grid; Node 2 is the 35kV feeder bus; Nodes 3-17 are the nodes where the 0.69V / 35kV transformers of the new energy units are connected to the feeder; Nodes 18-32 are the grid connection points for GFL type converters; and Nodes 33 and 34 are the connection points for the 0.69V / 35kV transformers of the energy storage units and the grid connection points for the GFM converters, respectively.

[0053] First, using the white-box mechanism admittance modeling method, sequence admittance models considering frequency coupling characteristics are established for the GFL converter and GFM converter within the power station:

[0054]

[0055]

[0056] In the formula, U p and U p1 These are the positive and negative sequence disturbance voltages, I p and I p1 These are the positive and negative sequence response currents, Y GFL (s) represents the GFL converter sequence admittance matrix, Y GFM(s) represents the GFM converter sequence admittance matrix, where Y11 x(s) and Y22 x(s) are the positive and negative sequence admittances, respectively, and Y12 x(s) and Y21 x(s) are the coupling term admittances.

[0057] The injection frequency at each node of the site is f. p The positive sequence current I p Then, based on the power station topology and Kirchhoff's current law, the positive-sequence and negative-sequence node network equations of the new energy power station were established:

[0058]

[0059] in, Inject current vectors into nodes. This is the positive-sequence node response voltage vector. Y is the negative-sequence node response voltage vector. 11 (s) and Y 22 (s) are the positive-order and negative-order s-domain admittance matrices, Y 12 (s) and Y 21 (s) represents the positive-order and negative-order s-domain admittance matrices. The individual admittance matrices are as follows:

[0060]

[0061]

[0062] Among them, the positive-order and negative-order s-domain admittance matrices Y 11 and Y 22 In the matrix, each element Y11 ii and Y22 ii (i=1,2,…n) represents the positive and negative self-admittances of node i, respectively, and Y11 ij and Y22 ij (i=1,2,…n, j=1,2,…n & j≠i) represent the positive and negative mutual admittances between nodes i and j, respectively. The coupling admittance matrix Y... 12 and Y 21 It is a diagonal matrix, and Y12 ii and Y21 ii (i=1,2,…n) are the coupled self-admittances of node i. If node i is a passive node without a converter connected, then Y12 ii and Y21 ii are both 0.

[0063] Substituting the negative-order network equation into the positive-order network equation yields the s-domain node network equation for new energy power plants considering frequency coupling characteristics:

[0064]

[0065] Where Y N(s) is the admittance matrix of the nodes in the s-domain.

[0066] Figure 3 shows the Bode plots of the key modal impedances of the system under different operating conditions according to an embodiment of the present invention. In this embodiment, the starting frequency f of the analysis band is... s =0Hz, step size Δf=0.1Hz, stop frequency f e =3000Hz. The multi-station short-circuit ratios (MRSCR1) of the new energy power plant grid connection points under four operating conditions are 9.57, 4.70, 3.04, and 2.15, respectively. From the figure, it can be seen that the amplitude-frequency characteristic of the critical mode impedance has 6 resonant peaks, but the 20Hz and 70Hz resonant peaks represent the same oscillation mode. Therefore, the system should have 5 oscillation modes, labeled S1 to S5 from low frequency to high frequency. When the system is under operating condition 1: MRSCR1 = 9.57, the phase-frequency characteristic of S1 changes. Phase transition, the phase transition from S2 to S5 is in Within the range. According to the stability criterion proposed in this paper, only the modal damping of oscillation mode S1 is negative, the system becomes unstable under small disturbances, and the oscillation frequency is 43.02Hz. As the grid strength decreases, the phase jump of the phase frequency characteristic of oscillation mode S1 decreases to Within the range, and the resonance peak gradually decreases, it means that the modal damping changes from negative to positive and gradually increases. However, the resonance peak of the amplitude-frequency characteristic of the oscillation mode S3 increases with the decrease of grid strength, that is, the modal damping gradually decreases, and in operating condition 4: MRSCR1=2.15, the phase-frequency characteristic of S3 changes. A phase jump occurs, the modal damping changes from positive to negative, the system becomes unstable under small disturbances, and the oscillation frequency is 268.8 Hz.

[0067] Figure 4 shows the participation factors of each node for different resonant modes in an embodiment of the present invention. Under operating condition 4: MRSCR1=2.15, the participation factors of system resonant modes S1~S5 are calculated. It can be seen from the figure that the participation factor of the GFM converter grid-connected node Bus34 for resonant modes S1 and S5 is much larger than that of other nodes, while resonant modes S2~S4 are mainly affected by the GFL converter grid-connected nodes, and the nodes with larger GFL converter capacities have even larger participation factors. Furthermore, it can be observed that nodes closer to the end of the feeder on the same feeder have larger participation factors for resonant modes S2~S4; therefore, Bus30 is the node with the largest participation factor for resonant modes S2~S4. When the damping of resonant modes S1~S5 is negative or small, the node with the largest participation factor for the resonant modes is the weakly damped node of the system.

[0068] Figure 5 shows the sensitivity distribution of key converter parameters to different resonant modes in an embodiment of the present invention. After locating the weak damping node of the system, the parameter sensitivity of the converter connected to that node is further calculated. This allows us to determine the control loops and control parameters that have a significant impact on resonant modes S1 to S5, thereby guiding the optimization of converter parameters or improvement of control to enhance the damping of the resonant modes. Based on the parameter sensitivity of resonant modes S1 to S5 to the GFM converter connected to Bus34, it can be seen that the power loop, voltage loop, and virtual impedance of the GFM converter have a significant impact on resonant mode S1, while resonant mode S5 is mainly affected by the voltage loop and current loop. Based on the parameter sensitivity of resonant modes S1 to S5 to the GFL converter connected to Bus30, it can be found that the voltage loop parameters of the GFL converter have a high sensitivity to resonant mode S2, while the phase-locked loop parameters have the highest sensitivity to resonant mode S3.

[0069] Figure 6 shows the power waveforms of different nodes of the system under different operating conditions according to the embodiment of the present invention. It can be seen from the figure that the system can operate stably under operating conditions 2 and 3. Under operating condition 1, the system experienced a power oscillation of 7.5 Hz, corresponding to oscillation frequencies of 42.5 Hz and 52.5 Hz in the abc coordinate system, and this oscillation is mainly related to Bus34. Under operating condition 4, the system experienced a power oscillation of 202.5 Hz, corresponding to oscillation frequencies of 252.5 Hz and 152.5 Hz in the abc coordinate system, consistent with the theoretical analysis results in Figure 3.

[0070] Example 2

[0071] Embodiment 2 of the present invention provides a terminal device corresponding to Embodiment 1 above. The terminal device can be a processing device for a client, such as a mobile phone, a laptop, a tablet computer, a desktop computer, etc., to execute the method of the above embodiments.

[0072] The terminal device in this embodiment includes a memory, a processor, and a computer program stored in the memory; the processor executes the computer program in the memory to implement the steps of the method in Embodiment 1 described above.

[0073] In some implementations, the memory may be high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device.

[0074] In other implementations, the processor can be any type of general-purpose processor, such as a central processing unit (CPU) or a digital signal processor (DSP), and there is no limitation here.

[0075] Example 3

[0076] Embodiment 3 of the present invention provides a computer-readable storage medium corresponding to Embodiment 1 above, on which a computer program / instructions are stored. When the computer program / instructions are executed by a processor, they implement the steps of the method of Embodiment 1 above.

[0077] A computer-readable storage medium can be a tangible device that holds and stores instructions for use by an instruction execution device. A computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination thereof.

[0078] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application 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 this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0079] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. 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, create means for implementing the functions specified in one or more blocks of the flowchart illustrations and / or one or more blocks of the block diagrams.

[0080] These computer program instructions may 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 functions specified in one or more flowcharts and / or one or more block diagrams.

[0081] Although preferred embodiments of this application 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 the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0082] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A simplified stability determination method for the amplitude and phase characteristics of critical mode impedance, characterized in that, Includes the following steps: S1. Based on the frequency coupling sequence admittance model of the power electronic equipment in the new energy grid-connected system to be analyzed, as well as the parameters of passive components and the grid structure, establish the s-domain node admittance matrix Y of the new energy grid-connected system considering the frequency coupling characteristics. N (s); S2, Set the starting frequency f of the analysis band s Step size Δf, termination frequency f e At each frequency point f p ,make According to Y N (s p )=R(s p )Λ(s p )L(s p ) The admittance matrix Y of the s-domain nodes N (s p The eigenvector matrix L(s) is decomposed into left and right eigenvector matrices. p ) and R(s p ), and the eigenvalue diagonal matrix S3, at each frequency point f p Calculate the minimum eigenvalue λ min (s p )=min(λ1(s p ), λ2(s p ), …, λ n (s p Define the critical mode impedance. S4. Draw the analysis frequency band [f] s f e Internal critical mode impedance Z m (s p Bode plots were used to identify the resonant modes of the renewable energy grid-connected system based on simplified stability criteria, and the system's small disturbance stability was determined. The participation factor P of mode k was also used. k Assess the degree of participation of each node in the resonant mode k and locate the weak damping node of the system; if the power electronic equipment is a white box model, analyze the sensitivity of the control parameter x of the converter connected to the weak damping node to the resonant mode based on the relative magnitude of the parameter relative sensitivity Rsen(x).

2. The simplified stability determination method for the amplitude and phase characteristics of the critical mode impedance according to claim 1, characterized in that, The s-domain node admittance matrix Y of a new energy grid-connected system considering frequency coupling characteristics N The expression for (s) is: ; where Y 11 and Y 22 Y is the positive-order and negative-order admittance matrix. 12 and Y 21 The coupling admittance matrix is... ， Y11 ii and Y22 ii are the positive and negative order self-admittances of node i, respectively; Y11 ij and Y22 ij are the positive and negative order mutual admittances between node i and node j, respectively; Y12 ii and Y21 ii are the coupled self-admittances of node i, i=1,2,…n, j=1,2,…n, j≠i.

3. The simplified stability determination method for the amplitude and phase characteristics of the critical mode impedance according to claim 1, characterized in that, The specific implementation process of identifying the resonant modes of a new energy grid-connected system based on simplified stability criteria and determining the system's small disturbance stability includes: when Z m (s p When the amplitude-frequency response of Z shows a resonance peak, if Z m (s p The phase frequency characteristic of ) is that the phase change near the resonant frequency is Within the range, the modal damping is positive; if Z m (s p The phase frequency characteristics of ) occur near the resonant frequency. If the phase jump occurs within a certain range, the modal damping is negative, and the system oscillation frequency is the frequency corresponding to the phase jump point.

4. The simplified stability determination method for the amplitude and phase characteristics of the critical mode impedance according to claim 1, characterized in that, Participation factor P of mode k k The calculation formula is: Among them, R jk The right eigenvector matrix R(s) p The element in the j-th row and k-th column of ) is L kj The left eigenvector matrix L(s) p The element in the k-th row and j-th column of ).

5. The simplified stability determination method for the amplitude and phase characteristics of the critical mode impedance according to claim 1, characterized in that, The formula for calculating the relative sensitivity Rsen(x) is: ;where x0 and x p Let x be the initial value and disturbance value of the control parameter, and Z be the disturbance value. m_0 (s p ) and Z m_p (s p ) represent the control parameter x at x0 and x... p The key modal impedance obtained under the given conditions; the larger the relative sensitivity Rsen(x), the higher the sensitivity of the control parameter x of the converter connected to the weak damping node to the resonant mode.

6. A terminal device, comprising a memory, a processor, and a computer program stored in the memory; characterized in that, The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 5.

7. A computer-readable storage medium having a computer program / instructions stored thereon; characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method according to any one of claims 1 to 5.

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