Method for evaluating low-frequency oscillation stability of hybrid heterogeneous system of network-following construction network type equipment

Abstract

The invention discloses a low-frequency oscillation stability evaluation method for a hybrid heterogeneous system of network-following network-forming network type equipment. The method comprises the following steps: simplifying a hybrid heterogeneous system of a network construction type device to obtain an expanded admittance matrix, constructing a network construction type equivalent single-feed-in system, establishing a system matrix of the network construction type equivalent single-feed-in system, and further obtaining a power grid strength index and a critical value of the system; and based on the power grid strength index and the critical value thereof, judging the low-frequency oscillation stability of the hybrid heterogeneous system of the networking type equipment, and determining the low-frequency oscillation stability margin, thereby realizing low-frequency oscillation stability evaluation. According to the method disclosed by the invention, the interaction among a plurality of network-constructing and network-following devices and the difference of parameters and capacities among the devices are considered, the low-frequency oscillation stability of the series-parallel heterogeneous system can be quickly and effectively evaluated, and a powerful theoretical support is provided for planning and safe and stable operation of a novel power system.

Description

Technical Field

[0001] This invention relates to a method for evaluating the stability of grid-connected equipment, which relates to the field of power system stability analysis, and specifically to a method for evaluating the low-frequency oscillation stability of a hybrid heterogeneous system of grid-connected equipment. Background Technology

[0002] As the green and low-carbon transformation of the new power system accelerates, its "dual high" characteristics of high proportion of power electronics and high proportion of renewable energy are becoming increasingly prominent. Among them, converters are the main power electronic devices, and their large-scale integration has profoundly changed the dynamic characteristics of the system, posing challenges to the safe and stable operation of the system.

[0003] Currently, most converters employ grid-following (GFL) control. However, with the increasing penetration of renewable energy, many new power systems exhibit significant source-load asymmetry, meaning that large-scale renewable energy bases are often located far from load centers. Long-distance transmission and numerous small-capacity units further weaken grid strength, leading to small-disturbance synchronization stability problems dominated by phase-locked loops in grid-following converter-dominated systems, primarily manifested as sub-supersynchronous oscillations. To address this issue, grid-forming (GFM) converters have been proposed, possessing dynamic characteristics similar to voltage sources and capable of providing voltage and frequency support to the grid. Therefore, integrating grid-forming converters can enhance grid strength and alleviate stability problems associated with grid-following converters, making hybrid grid-following / grid-forming equipment systems a typical form of new power systems.

[0004] However, the introduction of grid-connected converters has also brought new challenges. Recent studies have shown that insufficient line impedance can lead to grid-dominated synchronous oscillations, and while grid-connected converters are effective in weak grids, they may induce low-frequency oscillations in strong grids. Therefore, when grid-connected converters are electrically close together, especially under strong grid conditions, the system is prone to low-frequency oscillation stability problems, thus affecting the safe and stable operation of the system. However, the interaction between grid-connected / grid-connected converters and the grid, along with the often different parameters and capacities among converters, makes the analysis of low-frequency oscillation stability problems difficult.

[0005] To address this problem, common methods include eigenvalue analysis, impedance analysis, and electromagnetic transient simulation. While effective, these methods are either computationally intensive, dependent on detailed models, or difficult to analyze stability mechanisms. Therefore, some studies have proposed faster and more efficient methods—simplifying the original system to an equivalent single-feed system and introducing the Generalized Short Circuit Ratio (gSCR) index, thus simplifying the analysis while possessing a better theoretical foundation and physical significance. However, this method primarily focuses on the small-disturbance synchronous stability problem dominated by grid-connected equipment. Due to the significant differences in control strategies and dynamic characteristics between grid-connected and grid-connected converters, these methods cannot directly assess the low-frequency oscillation stability problem caused by grid-connected converters. To address this, some studies have proposed the Generalized Grid Current Strength (gGCS) as an index for evaluating low-frequency oscillation stability, but this index does not consider the differences between grid-connected converters. Therefore, existing research still lacks an effective method for evaluating the low-frequency oscillation stability of heterogeneous systems with grid-connected / grid-connected equipment, while taking into account the interactions between multiple grid-connected and grid-connected converters as well as the differences between converters.

[0006] Since existing indicators and methods are insufficient to effectively analyze the low-frequency oscillation stability problem of hybrid heterogeneous systems with grid-connected / network-connected equipment, and thus cannot provide clear guidance for system planning, operation and control, there is an urgent need for a new low-frequency oscillation stability assessment method applicable to hybrid heterogeneous systems with grid-connected / network-connected equipment to address the shortcomings of existing technologies. Summary of the Invention

[0007] To address the problems existing in the background technology, this invention provides a method for evaluating the low-frequency oscillation stability of heterogeneous systems with grid-connected and grid-connected equipment. This invention solves the problem of low-frequency oscillation stability evaluation in such systems. Specifically, for the low-frequency oscillation stability problem of heterogeneous systems with grid-connected and grid-connected equipment, this invention proposes a simplified method that reduces the original complex multi-infeed system to a grid-connected equivalent single-infeed system, thus simplifying the analysis of the stability problem. Based on this, this invention proposes a grid strength index and its critical value for low-frequency oscillation stability, and further proposes an index-based low-frequency oscillation stability evaluation method. This method can determine the low-frequency oscillation stability of the system, quantify the stability margin, and provide theoretical support for the planning and safe and stable operation of new power systems. This invention is used for the low-frequency oscillation stability evaluation of heterogeneous systems with grid-connected / grid-connected equipment, determining the system's low-frequency oscillation stability, quantifying the stability margin, and providing reference and theoretical basis for the planning and safe and stable operation of new power systems.

[0008] The technical solution adopted in this invention is: The present invention relates to a method for evaluating the low-frequency oscillation stability of a hybrid heterogeneous system of grid-type equipment, comprising: Step 1) After simplifying the heterogeneous system of the hybrid network-type equipment, the extended admittance matrix is ​​obtained, and then the equivalent single-feed system of the network-type equipment is constructed and its system matrix is ​​established.

[0009] Step 2) Obtain the grid strength index based on the extended admittance matrix; obtain the critical value of the grid strength index based on the system matrix of the equivalent single-feed system of the grid structure.

[0010] Step 3) Based on the power grid strength index and its critical value, determine the low-frequency oscillation stability of the hybrid heterogeneous system with grid-connected equipment and determine the low-frequency oscillation stability margin, so as to realize the low-frequency oscillation stability assessment of the hybrid heterogeneous system with grid-connected equipment.

[0011] In step 1), the heterogeneous system with hybrid network-type equipment includes n Taiwan and network type equipment and m Taiwan-type network equipment, and the first to second units in a hybrid heterogeneous system of network-type network equipment. n Each node is connected to n Taiwan and network type equipment, the first n +1 to n + m Each node is connected to m Taiwan-based network equipment, the first n + m +1 to n + m + r The nth node is an intermediate passive node, and the nth node is... n + m + r +1 to n + m + r + a Each node is an infinite busbar; the hybrid heterogeneous system of grid-connected devices is simplified by treating each grid-connected device as an equivalent current source and performing Schur complement simplification. According to Schur complement theorem, the system matrix of the hybrid heterogeneous system of grid-connected devices is focused on the port of the grid-connected device; in addition, the rated capacity of the grid-connected devices is decoupled from the dynamics of the grid-connected devices, thereby constructing an equivalent single-feed system of the grid-connected device.

[0012] In step 1), the extended admittance matrix is ​​constructed. as follows: ; in, S Bm For mThe rated capacity of the table-type network equipment is a diagonal matrix with the main diagonal elements; B nn , B nm , B mn and B mm After simplification, only the four sub-matrices of the network Thevenin equivalent admittance matrix after dividing the network into blocks and retaining only the equipment buses of the heterogeneous system with network-connected devices are retained. These sub-matrices correspond to... n × n 3D matrix n × m 3D matrix m × n dimensional matrix and m × m 3D matrix.

[0013] In step 1), the system matrix of the network-type equivalent single-feed system is... as follows: ; ; in, Y GFMeq ( s The transfer function of the equivalent networked device is obtained by weighting all networked devices. s For the Laplace operator; λ m To extend the admittance matrix B eq The largest eigenvalue; A matrix used to characterize network dynamics; p mj For the first j Regarding the maximum eigenvalue of table-type network equipment m Participating factors p mj = x mj y mj , x mj and y mj These are the extended admittance matrices. B eq right eigenvector x m and left eigenvectors y m The j One element; Y GFMj ( s) is the first j The transfer function of a table-type network device based on its own rated capacity.

[0014] In step 2), the power grid strength index λ LFO as follows: ; in, To expand the maximum eigenvalue of the admittance matrix.

[0015] In step 2), the power grid strength index λ LFO critical value λ LFOc as follows: ; in, s d For a Laplace operator with a real part of 0, s d = jω d , ω d is the typical frequency of low-frequency oscillation; arg{} is used to find the roots of the equation; det() is the determinant of the matrix.

[0016] In step 3), when determining the low-frequency oscillation stability of the hybrid heterogeneous system with grid-type equipment, according to the low-frequency oscillation stability mechanism, when When, it is stable in a heterogeneous system mixed with network-type equipment; when When, the heterogeneous system of hybrid network-type equipment reaches critical stability; when At that time, the heterogeneous system of mixed connection with network-type equipment is unstable.

[0017] In step 3), the stability margin of low-frequency oscillations is determined based on the power grid strength index and its critical value. as follows: .

[0018] The electronic device of the present invention includes: a memory and a processor coupled to each other, wherein the memory stores program data, and the processor invokes the program data to execute the method described above.

[0019] The present invention provides a computer-readable storage medium having program data stored thereon, which, when executed by a processor, implements the method described above.

[0020] First, based on the closed-loop model of a hybrid heterogeneous system, this invention proposes a simplification method to reduce the original complex multi-infeed system to an equivalent single-infeed system connected to a single grid-connected device (referred to as "grid-connected equivalent single-infeed system"). Building upon this, this invention proposes a grid strength index and critical value for the low-frequency oscillation stability problem of hybrid heterogeneous systems connected to grids / grid-connected devices. Furthermore, it proposes an index-based low-frequency oscillation stability assessment method to determine the system's low-frequency oscillation stability, quantify the stability margin, and provide theoretical support for the planning and safe, stable operation of new power systems.

[0021] The beneficial effects of this invention are: This invention addresses the low-frequency oscillation stability problem in hybrid heterogeneous systems with grid-connected and interconnected equipment. It proposes a simplified method to reduce the original high-dimensional complex system to an equivalent single-feed system with grid-connected equipment, thus simplifying the stability analysis. Furthermore, this invention proposes a grid strength index and its critical value for low-frequency oscillation stability in hybrid heterogeneous systems, as well as a method for evaluating the system's low-frequency oscillation stability based on the index. This method can determine the system's low-frequency oscillation stability and quantify the stability margin. It considers the interactions between multiple grid-connected and interconnected equipment, as well as the differences in parameters and capacities among the equipment. This method can quickly and effectively evaluate the low-frequency oscillation stability of hybrid heterogeneous systems, providing strong theoretical support for the planning and safe and stable operation of new power systems. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of the method of the present invention; Figure 2 This is a schematic diagram of a heterogeneous hybrid system with grid-type equipment in a specific embodiment of the present invention; Figure 3 The system's dominant eigenvalue simulation results are an example of an embodiment of the present invention. Figure 4 The time-domain simulation waveform is an example of an implementation of the present invention. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1 As shown, the low-frequency oscillation stability assessment method for hybrid heterogeneous systems with network-connected devices of the present invention first obtains network and device information, among which the key requirement is the network's Thevenin equivalent admittance matrix. B The rated capacity S of each grid-type device Bj The transfer function of network-type equipment based on its rated capacity. Y GFMj ( s ), and the rated capacity of the network equipment SBi and transfer function Y GFLi ( s This can be obtained based on actual conditions and is not mandatory. This allows for the construction of broadband sensitivity transfer function matrices for both the power grid and equipment sides, forming the system matrix of the closed-loop system. Next, the original system matrix is ​​simplified, and then the extended admittance matrix is ​​calculated. B eq The largest eigenvalue and the corresponding right and left eigenvectors are denoted as follows: λ m , x m , y m Based on this, a grid-type equivalent single-infeed system is constructed. The grid strength index is obtained based on the grid-type equivalent single-infeed system. λ LFO and its critical value λ LFOc Based on this indicator, the low-frequency oscillation stability of the system is determined, and the stability margin is calculated. β This method achieves the stability assessment of low-frequency oscillations in the system. The specific method is as follows: Step 1) After simplifying the heterogeneous system of hybrid grid-type equipment, the extended admittance matrix is ​​obtained. Then, the equivalent single-feed system of the grid-type equipment is constructed, and its system matrix is ​​established. The heterogeneous system of hybrid grid-type equipment includes... n Taiwan and network type equipment and m Taiwan-type network equipment, and the first to second units in a hybrid heterogeneous system of network-type network equipment. n Each node is connected to n Taiwan and network type equipment, the first n +1 to n + m Each node is connected to m For tabletop network devices, the initial nodes have no order; the serial numbers are sorted according to the device number. n + m +1 to n + m + r The nth node is an intermediate passive node, and the nth node is... n + m + r +1 to n + m + r + aEach node is an infinite bus, and the resistance of all lines is much smaller than the inductance, which can be ignored. The heterogeneous system of hybrid interconnected grid-type equipment is simplified by treating each grid-type equipment as an equivalent current source and performing Schur complement simplification. According to Schur complement theorem, the system matrix of the hybrid interconnected heterogeneous system of grid-type equipment is focused on the port of the grid-type equipment. In addition, the rated capacity of the grid-type equipment is decoupled from its dynamic characteristics to reduce the differences in dynamic characteristics between the equipment, thereby constructing an equivalent single-feed system of grid-type equipment.

[0025] Constructed extended admittance matrix as follows: ; in, S Bm For m The rated capacity of the table-type network equipment is a diagonal matrix with the main diagonal elements; B nn , B nm , B mn and B mm After simplification, only the four sub-matrices of the network Thevenin equivalent admittance matrix after dividing the network into blocks and retaining only the equipment buses of the heterogeneous system with network-connected devices are retained. These sub-matrices correspond to... n × n 3D matrix n × m 3D matrix m × n dimensional matrix and m × m 3D matrix B nn ∈R n×n , B nm ∈R n×m , B mn ∈R m×n , B mm ∈R m×m .

[0026] Before establishing the extended admittance matrix and the system matrix of the equivalent single-feed system in a grid-connected configuration, a closed-loop model of the system must first be established. Based on network and equipment information, the broadband sensitivity transfer function matrices of the power grid and equipment sides of the heterogeneous system with grid-connected equipment are constructed to form the system matrix of the closed-loop system. The following steps are required: Obtain network information for heterogeneous systems with hybrid grid-type equipment, and determine the broadband sensitivity transfer function matrix on the grid side. Y N As shown in the following formula:

[0027] ,

[0028] Where, Δ I For the minute increment of current at the device port, Δ I =[Δ I 1, I 1Δ θ 1, …, Δ I v , I v Δ θ v , …,Δ I n+m , I n+m Δ θ n+m ] T Δ I v For the first v A small disturbance in the amplitude of the output current of the device. I v For the first v The current amplitude output by the device, Δ θ v For the first v The slight disturbance in the phase angle of the output current of the device. θ v For the first v The phase angle of the current output by the device is positive, with the current flowing out of the device being positive. v= 1,2…, n + m ; B The simplified network Thevenin equivalent admittance matrix, retaining only the equipment buses after Schul complement simplification; For Kronecker product; A matrix to characterize network dynamics, s For the Laplace operator; Δ U For the voltage increment at the device port, Δ U =[Δ U 1, U 1Δ δ 1, …, Δ U v , U v Δ δ v , …,Δ U n+m , U n+m Δ δn+m ] T Δ U v For the first v Minor disturbances in the voltage amplitude at the device port. U v For the first v The voltage amplitude at the port of the device, Δ δ v For the first v The small disturbance in the phase angle of the voltage at the device port. δ v For the first v The voltage phase angle at the device port; The broadband sensitivity transfer function matrix for the power grid side; ω 0 represents the synchronous speed of the AC power grid.

[0029] Obtain equipment information for heterogeneous systems with interconnected network-type equipment, and determine the broadband sensitivity transfer function matrix on the equipment side. Y IBR As shown in the following formula:

[0030] , ,

[0031] ,

[0032] in, S B For n Taiwan and network type equipment and m The rated capacity of the table-type network equipment is a diagonal matrix with the main diagonal elements; Y GFL ( s )and Y GFM ( s ) respectively with n Taiwan and network type equipment and m The transfer function of the table-type network device is a diagonal block matrix with main diagonal elements; The device-side broadband sensitivity transfer function matrix; S Bi and Y GFLi ( s ) are respectively the first i The rated capacity of the unit and network-type equipment and its transfer function based on its own rated capacity. i= 1,…, n ; S Bj andY GFMj ( s ) are respectively the first j The rated capacity of the table-type network equipment and its transfer function based on its rated capacity. j= 1,…, m ; is a two-dimensional identity matrix; diag(·) is a diagonal matrix.

[0033] By combining the broadband sensitivity transfer function matrices of the power grid and equipment sides, the system matrix of the closed-loop system is obtained. As shown in the following formula:

[0034] The system matrix of the closed-loop system can be obtained from the following. Y GFM ( s ).

[0035] The simplified system matrix can be obtained after system simplification. As shown in the following formula:

[0036] The extended admittance matrix is ​​obtained from the simplified system matrix. B eq .

[0037] The original system matrix is ​​simplified by equivalence, and then the largest eigenvalue and its right and left eigenvectors of the extended admittance matrix are used to construct a mesh-type equivalent single-feed system that approximates the low-frequency oscillation stability of the original system; the system matrix of the mesh-type equivalent single-feed system is... as follows: ; ; in, Y GFMeq ( s The transfer function of the equivalent networked device is obtained by weighting all networked devices. s For the Laplace operator; λ m To extend the admittance matrix B eq The largest eigenvalue; A matrix used to characterize network dynamics; p mj For the first j Regarding the maximum eigenvalue of table-type network equipment m Participating factors p mj = x mjy mj , x mj and y mj These are the extended admittance matrices. B eq right eigenvector x m and left eigenvectors y m The j One element; Y GFMj ( s ) is the first j The transfer function of a table-type network device based on its own rated capacity.

[0038] Based on the system matrix of the equivalent single-feed system of the network structure, .

[0039] Step 2) Obtain the grid strength index based on the extended admittance matrix; obtain the critical value of the grid strength index based on the system matrix of the equivalent single-feed system of the grid structure.

[0040] Power grid strength index λ LFO as follows: ;

[0041] in, To expand the maximum eigenvalue of the admittance matrix.

[0042] Power grid strength index λ LFO The equivalent grid strength of the system is equal to the short-circuit ratio of the equivalent single-infeed system in a grid-type configuration, which is also known as the extended admittance matrix. B eq The largest eigenvalue.

[0043] Power grid strength index λ LFO critical value λ LFOc as follows: ; in, s d For a Laplace operator with a real part of 0, s d = jω d , ω d is the typical frequency of low-frequency oscillation; arg{} is used to find the roots of the equation; det() is the determinant of the matrix.

[0044] According to the low-frequency oscillation stability mechanism, the stronger the power grid, the more prone the system is to low-frequency oscillation stability problems. Therefore, the power grid strength index... λ LFO The larger the value, the greater the power grid strength, and the more unstable the system. Based on this monotonic negative correlation, the power grid strength at which the system reaches a critical state is determined as the critical value of the power grid strength index.

[0045] It is worth mentioning that, in practical engineering, for ease of calculation, the critical value can be quickly obtained through methods such as approximate weighting. Specifically, the critical values ​​of the grid strength of all grid-type equipment can be calculated by weighted average, and the result can be used as an approximation of the critical value, as shown in the following formula; or, the minimum value among the critical values ​​of the grid strength of all grid-type equipment can be taken as a relatively conservative critical value.

[0046]

[0047] in, λ LFOcj For the first j Critical values ​​for grid strength of platform-type grid equipment.

[0048] The constructed grid-type equivalent single-feed system can approximate the low-frequency oscillation stability of the original system, thereby simplifying the analysis of the stability problem. Based on this, the grid strength index and its critical value are obtained, and then the low-frequency oscillation stability and stability margin of the system are evaluated.

[0049] Step 3) Based on the grid strength index and its critical values, determine the low-frequency oscillation stability of the hybrid heterogeneous system with grid-connected equipment and determine the low-frequency oscillation stability margin to achieve the low-frequency oscillation stability assessment of the hybrid heterogeneous system with grid-connected equipment. When determining the low-frequency oscillation stability of the hybrid heterogeneous system with grid-connected equipment, according to the low-frequency oscillation stability mechanism, when... When, it is stable in a heterogeneous system mixed with network-type equipment; when When, the heterogeneous system of hybrid network-type equipment reaches critical stability; when At this time, the heterogeneous system with mixed grid-type equipment becomes unstable. The stability margin for low-frequency oscillations is determined based on grid strength indicators and their critical values. as follows: .

[0050] Specific embodiments of the present invention are as follows: like Figure 2As shown, this invention constructs an electromagnetic transient simulation model of a five-machine system with hybrid heterogeneous grid-connected and grid-connected devices in the MATLAB / Simulink environment to verify the effectiveness of the proposed low-frequency oscillation stability assessment method for such systems. The system consists of three grid-connected devices and two grid-connected devices, comprising a total of 14 nodes. Nodes 1, 2, and 3 are connected to a photovoltaic generator, a wind turbine, and a new energy generator controlled by grid connection, respectively; nodes 4 and 5 are connected to a wind turbine and an energy storage system controlled by grid connection, respectively; node 6 is an infinite bus; and nodes 7 to 14 are intermediate passive nodes. Furthermore, the control parameters and rated capacities of the grid-connected devices are different. Based on this, the inductance values ​​of all lines are proportionally changed, with proportionality coefficients k=1, 0.9, 0.8, 0.7, 0.67, and 0.6, thus forming six calculation examples.

[0051] like Figure 3 As shown, the dominant eigenvalues ​​of the original system and the network-equivalent single-feed system are displayed under different scaling factors. The dominant eigenvalues ​​are complex numbers containing both real and imaginary parts. The coordinate system in the figure uses the real part of the eigenvalues ​​as the horizontal axis and the imaginary part as the vertical axis. It can be seen that in the low-frequency range, the dominant eigenvalues ​​of the two systems basically overlap, indicating that the network-equivalent single-feed system can effectively approximate the low-frequency oscillation stability of the original system.

[0052] Table 1 shows the low-frequency oscillation stability assessment results of the system under different scaling factors. The data shows that as the line impedance decreases, the grid strength index... λ LFO The gradual increase reflects the improvement in power grid strength; at the same time, the indicator is gradually approaching the critical value. λ LFOc This leads to a corresponding decrease in the system's stability margin; when k=0.6, λ LFO Exceed λ LFOc The system is unstable. The above assessment results are consistent with... Figure 3 The results obtained based on the location of the dominant eigenvalues ​​are consistent, which verifies the effectiveness of the proposed evaluation method.

[0053] Table 1 Simulation Results

[0054] Furthermore, at T=0.2s, a voltage drop is applied to the infinite bus of the system and quickly cleared, such as... Figure 4As shown, the time-domain simulation waveforms of the port voltage U of the network-type equipment after disturbance are presented under different scaling factors. It can be seen that the oscillating waveform initially converges, indicating system stability; as the line impedance decreases, the convergence rate gradually slows down, and at k=0.67, the system approaches constant amplitude oscillation, indicating a decrease in system stability margin; when k=0.6, the waveform diverges, indicating system instability. These results are consistent with... Figure 3 Consistent with the conclusions in Table 1, this further validates the effectiveness of the evaluation method.

[0055] 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, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented using various computer languages. This application is described with flowcharts of methods, systems, and computer program products according to embodiments of this application.

[0056] 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, this invention is intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0057] 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 these modifications and variations of this application fall within the scope of the equivalent technology of this invention, this application also intends to include these modifications and variations.

Claims

1. A method for evaluating the low-frequency oscillation stability of a heterogeneous system hybridized with grid-type equipment, characterized in that, include: Step 1) After simplifying the heterogeneous system of the hybrid network-type equipment, the extended admittance matrix is ​​obtained, and then the equivalent single-feed system of the network-type equipment is constructed and its system matrix is ​​established. Step 2) Obtain the grid strength index based on the extended admittance matrix; obtain the critical value of the grid strength index based on the system matrix of the equivalent single-feed system of the grid-type system; Step 3) Based on the power grid strength index and its critical value, determine the low-frequency oscillation stability of the hybrid heterogeneous system with grid-connected equipment and determine the low-frequency oscillation stability margin, so as to realize the low-frequency oscillation stability assessment of the hybrid heterogeneous system with grid-connected equipment.

2. The method for evaluating the low-frequency oscillation stability of a heterogeneous system with a mesh-type equipment as described in claim 1, characterized in that: In step 1), the heterogeneous system with hybrid network-type equipment includes n Taiwan and network type equipment and m Taiwan-type network equipment, and the first to second units in a hybrid heterogeneous system of network-type network equipment. n Each node is connected to n Taiwan and network type equipment, the first n +1 to n + m Each node is connected to m Taiwan-based network equipment, the first n + m +1 to n + m + r The nth node is an intermediate passive node, and the nth node is... n + m + r +1 to n + m + r + a Each node is an infinite bus; the hybrid heterogeneous system of grid-connected equipment is simplified by treating each grid-connected equipment as an equivalent current source and performing Schur complement simplification, focusing the system matrix of the hybrid heterogeneous system of grid-connected equipment to the port of the grid-connected equipment; in addition, the rated capacity of the grid-connected equipment is dynamically decoupled from the grid-connected equipment, thereby constructing an equivalent single-feed system of the grid-connected equipment.

3. The method for evaluating the low-frequency oscillation stability of a hybrid heterogeneous system with a mesh-type equipment as described in claim 2, characterized in that: In step 1), the extended admittance matrix is ​​constructed. as follows: ； in, S Bm For m The rated capacity of the table-type network equipment is a diagonal matrix with the main diagonal elements; B nn , B nm , B mn and B mm After simplification, only the four sub-matrices of the network Thevenin equivalent admittance matrix after dividing the network into blocks and retaining only the equipment buses of the heterogeneous system with network-connected devices are retained. These sub-matrices correspond to... n × n 3D matrix n × m 3D matrix m × n dimensional matrix and m × m 3D matrix.

4. The method for evaluating the low-frequency oscillation stability of a heterogeneous system with a mesh-type equipment as described in claim 2, characterized in that: In step 1), the system matrix of the network-type equivalent single-feed system is... as follows: ； ； in, Y GFMeq ( s The transfer function of the equivalent networked device is obtained by weighting all networked devices. s For the Laplace operator; λ m To extend the admittance matrix B eq The largest eigenvalue; A matrix used to characterize network dynamics; p mj For the first j Regarding the maximum eigenvalue of table-type network equipment m Participating factors p mj = x mj y mj , x mj and y mj These are the extended admittance matrices. B eq right eigenvector x m and left eigenvector y m The j One element; Y GFMj ( s ) is the first j The transfer function of a table-type network device based on its own rated capacity.

5. The method for evaluating the low-frequency oscillation stability of a heterogeneous system with a mesh-type equipment as described in claim 1, characterized in that: In step 2), the power grid strength index λ LFO as follows: ； in, To expand the maximum eigenvalue of the admittance matrix.

6. The method for evaluating the low-frequency oscillation stability of a heterogeneous system with a mesh-type equipment as described in claim 4, characterized in that: In step 2), the power grid strength index λ LFO critical value λ LFOc as follows: ； in, s d For a Laplace operator with a real part of 0, s d = jω d , ω d is the typical frequency of low-frequency oscillation; arg{} is used to find the roots of the equation; det() is the determinant of the matrix.

7. The method for evaluating the low-frequency oscillation stability of a heterogeneous system with a mesh-type equipment as described in claim 6, characterized in that: In step 3), when determining the low-frequency oscillation stability of the heterogeneous system with the grid-type equipment, when When, it is stable in a heterogeneous system mixed with network-type equipment; when When, the heterogeneous system of hybrid network-type equipment reaches critical stability; when At that time, the heterogeneous system of mixed connection with network-type equipment is unstable.

8. The method for evaluating the low-frequency oscillation stability of a heterogeneous system with a mesh-type equipment as described in claim 6, characterized in that: In step 3), the stability margin of low-frequency oscillations is determined based on the power grid strength index and its critical value. as follows: 。 9. An electronic device, characterized in that, include: A memory and a processor are coupled to each other, wherein the memory stores program data, and the processor invokes the program data to perform the method as described in any one of claims 1-8.

10. A computer-readable storage medium storing program data thereon, characterized in that, When the program data is executed by the processor, it implements the method as described in any one of claims 1-8.

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