A method, device and medium for judging the stability of power system with small disturbance

Abstract

The present invention discloses a method, device, and medium for determining the stability of a power system under small disturbances. The method includes: constructing a state matrix of the power system by equating a grid-type converter in the power system to the nearest synchronous generator; equating all synchronous generators at the supply and receiving ends of the power system to equivalent synchronous generators at the supply and receiving ends, respectively, wherein all synchronous generators include the synchronous generators equivalent to the grid-type converter; using the partial inertia center method, based on the state matrix, respectively constructing the third-order state matrices of the equivalent synchronous generators at the supply and receiving ends; and using the integral current method to reduce the order of the third-order state matrix to determine the second-order state matrix of the equivalent synchronous generators at the supply and receiving ends; constructing a damping ratio calculation equation for the power system based on the second-order state matrix; calculating the damping ratio of the power system based on the control parameters of the power system and the damping ratio calculation equation, and determining whether the power system is stable based on the damping ratio.

Description

Technical Field

[0001] The present invention relates to the technical field of power system stability determination, and more particularly to a method, device and medium for determining small-disturbance stability of a power system. Background Art

[0002] With the construction of new power systems, the proportion of renewable energy in these systems continues to increase. This integration of renewable energy replaces some thermal power units, reducing system inertia and posing challenges to the dynamic frequency stability of the power grid. To ensure frequency stability, renewable energy units often employ additional virtual inertia control and virtual damping to strengthen inertia support. However, the introduction of virtual inertia control and virtual damping can lead to small-disturbance stability issues.

[0003] The introduction of new state variables in the control of grid-following converters makes the directly listed state matrix too complex, making it difficult to directly solve the relationship between the damping ratio of the inter-regional oscillation mode and the control parameters of each renewable energy unit by reducing the order of the state matrix. Therefore, in large-scale power systems, the problem of low-frequency oscillation between regions is difficult to directly analyze through functions, and it is also difficult to directly suppress the low-frequency oscillation between regions by optimizing the control parameters of renewable energy units through functions.

[0004] Previous strategies for analyzing the small-disturbance stability of inter-regional oscillations have rarely considered the effects of all thermal power units and grid-following converters. Most have directly analyzed the inter-regional oscillation mode by solving the state matrix and selecting the oscillation mode with the lowest oscillation frequency. However, this strategy is computationally expensive in large power systems, and the state matrix is ​​complex, making it difficult to adjust control parameters and unable to quantify the inter-regional low-frequency oscillation problem. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method, device and medium for determining the small-disturbance stability of an electric power system.

[0006] According to one aspect of the present invention, a method for determining small-disturbance stability of a power system is provided, comprising:

[0007] The state matrix of the power system is constructed by equating the grid-connected converters in the power system to the nearest synchronous generators;

[0008] Equivalently convert all synchronous generators at the supply and receiving ends of the power system into equivalent synchronous generators at the supply and receiving ends, respectively, wherein all synchronous generators include synchronous generators equivalent to grid-type converters;

[0009] The partial inertia center method is used to construct the third-order state matrices of the equivalent synchronous generators at the supply and receiving ends according to the state matrix. The third-order state matrices are reduced by the integral flow method to determine the second-order state matrices of the equivalent synchronous generators at the supply and receiving ends.

[0010] According to the second-order state matrix, the damping ratio calculation equation of the power system is constructed;

[0011] The damping ratio of the power system is calculated according to the control parameters of the power system and the damping ratio calculation equation, and whether the power system is stable is judged according to the damping ratio.

[0012] Optionally, the state matrix is:

[0013]

[0014] Where a ij is the parameter of the state equation corresponding to the state matrix, Δδ i is the change in the potential phase angle of the i-th synchronous generator after a small disturbance, Δω i is the change in angular velocity at the node of the i-th synchronous generator after a small disturbance, Δδ i , and Δω i are all state variables.

[0015] Optionally, the third-order state matrix is:

[0016]

[0017] Where M A is the equivalent power grid inertia at the supply end, M B is the equivalent receiving-end grid inertia, D A is the equivalent power grid damping at the supply end, D B is the equivalent receiving-end grid damping, Δδ AB is the change in the power angle difference between the equivalent supply-side synchronous generator and the equivalent receiving-side synchronous generator after a small disturbance, Δω A is the change in angular velocity at the node of the synchronous generator at the supply end after a small disturbance, Δω B is the change in angular velocity at the node of the synchronous generator at the receiving end after a small disturbance.

[0018] Optionally, the second-order state matrix is:

[0019]

[0020]

[0021] Where D A is the equivalent power grid damping at the supply end, M B is the equivalent receiving-end grid inertia, DB is the equivalent receiving-end grid damping, K BB is the synchronous power factor of the receiving grid, and w0 is the rotation angular velocity at the rated frequency of the grid.

[0022] Optionally, based on the second-order state matrix, a damping ratio calculation equation for the power system is constructed, including:

[0023] According to the second-order state matrix, the state equation of the equivalent power system is constructed, and the state equation is solved to determine the solution of the state equation of the power system;

[0024] According to the solution of the state equation, the damping ratio calculation equation is constructed.

[0025] Optionally, the equation of state is:

[0026]

[0027] The solution of the state equation is:

[0028]

[0029]

[0030] Where M A is the equivalent power grid inertia at the supply end, M B is the equivalent receiving-end grid inertia, D A is the equivalent power grid damping at the supply end, D B is the equivalent receiving-end grid damping, λ=-σ±jω is the conjugate characteristic root of the state equation under the inter-regional oscillation mode, K AA is the synchronous power factor at the supply-side grid, K BB is the synchronous power factor of the receiving grid, -σ is the real part of the eigenvalue λ, ±jω is the imaginary part of the eigenvalue λ, and w0 is the rotation angular velocity at the rated frequency of the grid.

[0031] Optionally, the damping ratio calculation equation is:

[0032]

[0033] According to another aspect of the present invention, a device for determining small-disturbance stability of a power system is provided, comprising:

[0034] The first building module is used to construct a state matrix of the power system after equating the grid-connected converter in the power system to the nearest synchronous generator;

[0035] An equivalent module is used to convert all synchronous generators at the supply and receiving ends of the power system into equivalent synchronous generators at the supply and receiving ends, respectively, where all synchronous generators include synchronous generators equivalent to grid-type converters;

[0036] The order reduction module is used to construct the third-order state matrices of the equivalent synchronous generators at the supply and receiving ends respectively according to the state matrix using the partial inertia center method, and reduce the order of the third-order state matrices using the integral flow method to determine the second-order state matrices of the equivalent synchronous generators at the supply and receiving ends;

[0037] The second building module is used to construct a damping ratio calculation equation of the power system according to the second-order state matrix;

[0038] The calculation module is used to calculate the damping ratio of the power system according to the control parameters of the power system and the damping ratio calculation equation, and to judge whether the power system is stable according to the damping ratio.

[0039] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein the storage medium stores a computer program, and the computer program is used to execute the method according to any one of the above aspects of the present invention.

[0040] According to another aspect of the present invention, an electronic device is provided, comprising: a processor; a memory for storing instructions executable by the processor; and the processor for reading the executable instructions from the memory and executing the instructions to implement the method described in any one of the above aspects of the present invention.

[0041] Therefore, this application, based on the partial inertia center method and the integral flow method, reduces the high-order state matrix to make the relationship between the damping ratio of the inter-regional oscillation mode and the control parameters of the renewable energy unit explicit. This provides a reference for adjusting the control parameters of renewable energy units to improve the small-disturbance stability of the power system. The calculated damping ratio can effectively support the operation mode formulation and unit scheduling of power grid companies, ensuring the stability of the power grid under small-disturbance conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0043] Figure 1 1 is a flow chart of a method for determining small-disturbance stability of a power system provided by an exemplary embodiment of the present invention;

[0044] Figure 2a 、 Figure 2b They are respectively a control block diagram of a machine-side converter and a control block diagram of a grid-side converter provided by an exemplary embodiment of the present invention;

[0045] Figure 3a 、 Figure 3b They are respectively a control block diagram of a machine-side converter and a control block diagram of a grid-side converter provided by an exemplary embodiment of the present invention;

[0046] Figure 41 is a schematic diagram of a grid-connected model of a grid-following converter and a synchronous generator or a grid-following converter and a grid-connecting converter provided by an exemplary embodiment of the present invention;

[0047] Figure 5 1 is a schematic diagram of an aggregate equivalent model of a grid-following converter and a synchronous generator or a grid-following converter and a grid-forming converter provided by an exemplary embodiment of the present invention;

[0048] Figure 6 is a schematic diagram of a two-region power system model provided by an exemplary embodiment of the present invention;

[0049] Figure 7 This is a schematic diagram of an equivalent model of a supply and a receiving end provided by an exemplary embodiment of the present invention;

[0050] Figure 8 1 is a schematic structural diagram of a device for determining small-disturbance stability of a power system provided by an exemplary embodiment of the present invention;

[0051] Figure 9 This is a structure of an electronic device provided by an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0052] Below, the exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0053] It should be noted that the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

[0054] Those skilled in the art will understand that the terms "first" and "second" in the embodiments of the present invention are only used to distinguish different steps, devices or modules, and neither represent any specific technical meaning nor indicate the necessary logical order between them.

[0055] It should also be understood that, in the embodiments of the present invention, “a plurality of” may refer to two or more than two, and “at least one” may refer to one, two or more than two.

[0056] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more, unless explicitly limited or otherwise indicated in the context.

[0057] In addition, the term "and / or" in this invention merely describes an association relationship between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Furthermore, the character " / " in this invention generally indicates that the related objects are in an "or" relationship.

[0058] It should also be understood that the description of the various embodiments of the present invention focuses on the differences between the various embodiments, and the same or similar aspects thereof can be referenced with each other. For the sake of brevity, they will not be described one by one.

[0059] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0060] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0061] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0062] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0063] Embodiments of the present invention can be applied to electronic devices such as terminal devices, computer systems, and servers, and can operate in conjunction with numerous other general-purpose or specialized computing system environments or configurations. Examples of well-known terminal devices, computing systems, environments, and / or configurations suitable for use with terminal devices, computer systems, servers, and other electronic devices include, but are not limited to, personal computer systems, server computer systems, thin clients, thick clients, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network personal computers, minicomputer systems, mainframe computer systems, and distributed cloud computing technology environments including any of the above.

[0064] Electronic devices such as terminal devices, computer systems, and servers can be described in the general context of computer system-executable instructions (such as program modules) executed by a computer system. Generally, program modules can include routines, programs, object programs, components, logic, data structures, etc., which perform specific tasks or implement specific abstract data types. Computer systems / servers can be implemented in a distributed cloud computing environment, where tasks are performed by remote processing devices linked via a communication network. In a distributed cloud computing environment, program modules can be located on local or remote computing system storage media, including storage devices.

[0065] Exemplary Methods

[0066] Figure 1 FIG. 1 is a flow chart of a method for determining the stability of a power system with small disturbances provided by an exemplary embodiment of the present invention. This embodiment can be applied to electronic devices, such as Figure 1 As shown, the method 100 for determining the stability of a power system with small disturbances includes the following steps:

[0067] Step 101: Equilibrium the grid-connected converters in the power system to the nearest synchronous generators and then construct a state matrix of the power system;

[0068] Step 102: Equivalent all synchronous generators at the supply and receiving ends of the power system to equivalent synchronous generators at the supply and receiving ends, respectively, wherein all synchronous generators include synchronous generators equivalent to the grid-type converter;

[0069] Step 103: Using the partial inertia center method, the third-order state matrices of the equivalent synchronous generators at the supply and receiving ends are constructed based on the state matrices, and the third-order state matrices are reduced using the integral flow method to determine the second-order state matrices of the equivalent synchronous generators at the supply and receiving ends.

[0070] Step 104: construct a damping ratio calculation equation for the power system based on the second-order state matrix;

[0071] Step 105 : Calculate the damping ratio of the power system according to the control parameters of the power system and the damping ratio calculation equation, and determine whether the power system is stable according to the damping ratio.

[0072] Specifically, the damping ratio is the key indicator for determining the small-disturbance stability of a power system, which can be obtained by solving the system state equation. However, since it is difficult to establish an explicit direct relationship between the frequency regulation control parameters of renewable energy units and the damping ratios of the various oscillation modes in the system state-space equation, and the influence of the control parameters on the damping ratio is uncertain, there is no effective method for optimizing the frequency regulation control parameters of renewable energy units to improve the system's small-disturbance stability. Furthermore, in the high-dimensional state matrix of a multi-machine power system, the relationship between the control parameters and the damping ratio is even more complex, making it difficult to adjust the coefficients for the virtual inertia control and droop control of renewable energy units.

[0073] To address the above issues, this patent proposes an explicit expression of the damping ratio of the inter-regional oscillation mode and the control parameters of new energy sources, and then uses the system parameters to calculate the damping ratio to judge the small disturbance stability of the power system. First, the partial inertia center method is used to equate the supply-end power grid and the receiving-end power grid to a synchronous generator set, reducing the high-order state matrix to a fourth-order state matrix; after selecting the reference node, the state matrix is ​​reduced to a third-order state matrix; then, the integral flow method is used to reduce the third-order state matrix to a second-order state matrix. The second-order state matrix can be used to solve a set of conjugate eigenvalues, i.e., the eigenvalues ​​of the inter-regional oscillation mode, and solve its corresponding damping ratio. This patent solves the problem that the control parameters and damping ratio cannot be optimized due to non-explicitness, and provides an effective method and basis for control parameter tuning to enhance the small disturbance stability of multi-machine power systems after the integration of new energy sources.

[0074] The present invention proposes a method for explicitly expressing the damping ratio of inter-regional oscillation modes and the control parameters of renewable energy sources, including (1) deriving the differential algebraic equations of a multi-machine power system containing renewable energy units and establishing a state matrix; (2) using the partial inertia center method to equate the supply and receiving power systems to a synchronous generator, and reconstructing the state matrix after selecting a reference node; (3) using the integral flow method to reduce the third-order state matrix to a second-order state matrix, and directly solving the function of each control parameter and the damping ratio from the second-order state matrix. The specific technical solution is as follows:

[0075] (1) Derive the differential algebraic equations of a multi-machine power system containing renewable energy units and establish the state matrix.

[0076] The state matrix of the inter-area oscillation of the power system is the coefficient matrix of the state variables of the state equation composed of the rotor motion equation of the synchronous generator, the differential equation of the rotor motion equation of the grid-type converter with additional virtual inertia control and virtual damping control, the influence of the grid-type converter on the synchronous generator and the grid-type converter, and the algebraic equation of the power flow equation. The control logic of the grid-type converter is as follows: Figure 2a and 2b shown.

[0077] The external characteristics of the grid-type converter are the same as the rotor motion equation of the synchronous generator, and it has the ability to actively support the system frequency and system voltage. If the synchronous generator only considers the second-order rotor motion equation, there is no difference in the external characteristics of the grid-type converter and the synchronous generator.

[0078] The differential equations of the synchronous generator rotor motion equation and the rotor motion equations of the grid-type converter with additional virtual inertia control and virtual damping control are defined as follows: j The sum of the response and damping D to the rate of change of the j-node frequency j The response to the change in the frequency of node j consists of:

[0079]

[0080] Where P mj is the mechanical power of the jth synchronous generator, P emj is the electromagnetic power of the jth synchronous generator, f j is the frequency of the jth synchronous generator, f0 is the rated frequency of the system, M j is the inertia time constant of the jth synchronous generator, D j is the damping coefficient of the jth synchronous generator.

[0081] The control strategy of grid-following converter is as follows: Figure 3a and 3b As shown, the frequency at the grid connection point is controlled by a phase-locked loop and has no ability to actively support the grid frequency. The virtual inertia control coefficient K Hi Differential control and droop control coefficient K for the i-th node frequency Di The proportional control response to the i-th node frequency consists of:

[0082]

[0083] Where P refi is the reference active power of the ith grid-type converter, P opti is the actual active power output of the ith grid-type converter, f i is the terminal frequency measured by the phase-locked loop of the i-th grid-type converter, K Hi is the virtual inertia control coefficient of the i-th grid-following converter, K Di is the droop control coefficient of the i-th grid-type converter.

[0084] The influence of the grid-following converter on the synchronous generator and the grid-forming converter refers to selecting the grid-connected point of the grid-following converter and the synchronous generator or the grid-forming converter as the reference node, such as Figure 4 As shown, its equivalent inertia and equivalent damping can be derived as follows:

[0085]

[0086] Where P ∑ is the total active power of the grid-following converter and synchronous generator to the grid connection point, P G is the actual active power output of the synchronous generator at the grid connection point, U0 is the voltage at the reference node, U1 is the voltage at the grid connection point between the grid-following converter and the synchronous generator, E' is the internal potential of the synchronous generator, θ E is the phase difference between the internal potential of the synchronous generator and the reference node, θ1 is the phase difference between the internal potential of the synchronous generator and the grid connection point, z1 is the impedance from the internal potential of the synchronous generator to the grid connection point, and z2 is the impedance from the grid connection point to the reference node.

[0087] Linear analysis of equations (2) and (3) yields:

[0088]

[0089]

[0090] ΔP ∑ -ΔP G =ΔP D (6)

[0091] The combined equations (4-6) yield:

[0092]

[0093] Assume parameter a as shown in formula (8):

[0094]

[0095] Combining equations (7) and (8), we can get:

[0096]

[0097] According to the equivalence of the power balance equation at the grid connection point under small signal analysis, the grid-following converter and synchronous generator, grid-following converter and grid-forming converter can be equivalent to a synchronous generator set. Figure 4 Equivalent to Figure 5 As shown:

[0098] The state equations are obtained by linearizing the rotor motion equations of the synchronous generator set and the new energy generator set at the equilibrium point:

[0099]

[0100] Where E j is the internal potential of the equivalent synchronous generator set, θ jk is the power angle difference between the voltages at the i-th node and the k-th node.

[0101] The state matrix of is composed of the coefficient matrix of the state variables:

[0102]

[0103] Where a ij is the parameter of the state equation corresponding to the state matrix.

[0104] Furthermore, the specific state matrix A is obtained according to the set virtual inertia control coefficient and droop control coefficient.

[0105] (2) Reduction of the state matrix of the power supply and receiving end systems.

[0106] The partial inertia center method is a method that reduces the order of the multi-rotor motion equation of the power system to the motion equation of only one rotor at the supply and receiving ends, that is, the multiple inertia centers are equivalent to the inertia centers of the supply and receiving ends, such as Figure 6 Equivalent to Figure 7 shown.

[0107] The partial inertia center method, where the supply and receiving end groups are equivalent to a generator set, is derived as follows:

[0108]

[0109]

[0110]

[0111] Where M A is the equivalent power grid inertia at the supply end, M B is the equivalent receiving-end grid inertia, D A is the equivalent power grid damping at the supply end, D B is the equivalent receiving-end grid damping, ΣΔP GA is the active power of the generator set on the supply side after the disturbance, ΣΔP GB is the active power of the receiving grid generator set after the disturbance, Δθ A is the power angle difference of the supply-side grid, Δθ B is the power angle difference of the receiving grid.

[0112] According to the principle that the power of the tie line before and after the equivalence remains unchanged, the above formula can be equivalent to:

[0113]

[0114]

[0115] The synchronous power coefficient on the tie line can also be equivalent to:

[0116]

[0117] Where K AA is the synchronous power factor at the supply-side grid, K BB is the synchronous power factor of the receiving grid.

[0118] Selecting end B as the reference node, the high-order state equation can be simplified to:

[0119]

[0120] At this time, the state matrix is ​​third order according to the state equation:

[0121]

[0122] Furthermore, the third-order state matrix can be further simplified and reduced in order.

[0123] (3) Reduction of the third-order state matrix.

[0124] The integral flow method reduces the third-order state matrix to the second-order. First, the synchronous power coefficients of the supply and receiving ends can be written according to the equivalent model:

[0125]

[0126] Where U A is the voltage amplitude at the grid connection point of the equivalent power supply end, U B is the voltage amplitude at the equivalent receiving grid connection point, G AB is the conductivity between the supply and receiving ends, B AB is the electrical admittance between the supply and receiving ends.

[0127] Assume infinitesimal quantity

[0128] Substituting formula (21) into formula (18) yields:

[0129]

[0130] At the same time, let Δω B is Δδ AB , Δω A 、ε composite function:

[0131] Δω B =h(Δδ AB ,Δω A ,ε) (23)

[0132] Taylor expansion of the above infinitesimal quantities yields:

[0133]

[0134] Solving equation (24) yields:

[0135]

[0136] The combined equations (23-25) yield:

[0137]

[0138] Therefore, the state matrix can be simplified as follows:

[0139]

[0140] The state equation can be written from the state matrix:

[0141]

[0142] The conjugate characteristic roots of the inter-regional oscillation mode are obtained as follows:

[0143]

[0144] Where -σ is the real part of the eigenvalue λ, and ±jω is the imaginary part of the eigenvalue λ.

[0145]

[0146]

[0147] The damping ratio of the inter-regional oscillation mode is obtained by combining equations (30) and (31):

[0148]

[0149] The damping ratio has different stability standards in different regions. For example, in the North China power grid, the strong damping system requires a damping ratio greater than 0.02, in the East China power grid, the strong damping system requires a damping ratio greater than 0.03, and in the Northwest power grid, the strong damping system requires a damping ratio greater than 0.05.

[0150] By utilizing the high-order state matrix reduction method, the inter-area oscillation mode and the virtual inertia and virtual damping control parameters of each grid-type converter and grid-forming converter are explicitly functionalized, so that the control parameters can be adjusted according to the objective function to improve the small disturbance stability of the power system.

[0151] Therefore, this application, based on the partial inertia center method and the integral flow method, reduces the high-order state matrix to make the relationship between the damping ratio of the inter-regional oscillation mode and the control parameters of the renewable energy unit explicit. This provides a reference for adjusting the control parameters of renewable energy units to improve the small-disturbance stability of the power system. The calculated damping ratio can effectively support the operation mode formulation and unit scheduling of power grid companies, ensuring the stability of the power grid under small-disturbance conditions.

[0152] Exemplary devices

[0153] Figure 8 FIG. 1 is a schematic diagram of a structure of a device for determining the stability of a power system with small disturbances provided by an exemplary embodiment of the present invention. Figure 8 As shown, the apparatus 800 includes:

[0154] The first constructing module 810 is used to construct a state matrix of the power system by equating the grid-connected converters in the power system to the nearest synchronous generators;

[0155] An equivalent module 820 is used to convert all synchronous generators at the supply and receiving ends of the power system into equivalent synchronous generators at the supply and receiving ends, respectively, wherein all synchronous generators include synchronous generators equivalent to grid-type converters;

[0156] The order reduction module 830 is used to construct the third-order state matrices of the equivalent synchronous generators at the supply and receiving ends respectively according to the state matrices using the partial center of inertia method, and reduce the order of the third-order state matrices using the integral flow method to determine the second-order state matrices of the equivalent synchronous generators at the supply and receiving ends;

[0157] A second construction module 840 is configured to construct a damping ratio calculation equation for the power system according to the second-order state matrix;

[0158] The calculation module 850 is used to calculate the damping ratio of the power system according to the control parameters of the power system and the damping ratio calculation equation, and to determine whether the power system is stable according to the damping ratio.

[0159] Optionally, the state matrix is:

[0160]

[0161] Where a ij is the parameter of the state equation corresponding to the state matrix, Δδ i is the change in the potential phase angle of the i-th synchronous generator after a small disturbance, Δω i is the change in angular velocity at the node of the i-th synchronous generator after a small disturbance, Δδ i , and Δω i are all state variables.

[0162] Optionally, the third-order state matrix is:

[0163]

[0164] Where M A is the equivalent power grid inertia at the supply end, M B is the equivalent receiving-end grid inertia, D A is the equivalent power grid damping at the supply end, DB is the equivalent receiving-end grid damping, Δδ AB is the change in the power angle difference between the equivalent supply-side synchronous generator and the equivalent receiving-side synchronous generator after a small disturbance, Δω A is the change in angular velocity at the node of the synchronous generator at the supply end after a small disturbance, Δω B is the change in angular velocity at the node of the synchronous generator at the receiving end after a small disturbance.

[0165] Optionally, the second-order state matrix is:

[0166]

[0167]

[0168]

[0169] Where D A is the equivalent power grid damping at the supply end, M B is the equivalent receiving-end grid inertia, D B is the equivalent receiving-end grid damping, K BB is the synchronous power factor of the receiving grid, and w0 is the rotation angular velocity at the rated frequency of the grid.

[0170] Optionally, based on the second-order state matrix, a damping ratio calculation equation for the power system is constructed, including:

[0171] According to the second-order state matrix, the state equation of the equivalent power system is constructed, and the state equation is solved to determine the solution of the state equation of the power system;

[0172] According to the solution of the state equation, the damping ratio calculation equation is constructed.

[0173] Optionally, the state equation is:

[0174]

[0175] The solution of the state equation is:

[0176]

[0177]

[0178] Where M A is the equivalent power grid inertia at the supply end, M B is the equivalent receiving-end grid inertia, D A is the equivalent power grid damping at the supply end, D B is the equivalent receiving-end grid damping, λ=-σ±jω is the conjugate characteristic root of the state equation under the inter-regional oscillation mode, K AAis the synchronous power factor at the supply-side grid, K BB is the synchronous power factor of the receiving grid, -σ is the real part of the eigenvalue λ, ±jω is the imaginary part of the eigenvalue λ, and w0 is the rotation angular velocity at the rated frequency of the grid.

[0179] Optionally, the damping ratio calculation equation is:

[0180]

[0181] Exemplary electronic devices

[0182] Figure 9 This is the structure of an electronic device provided by an exemplary embodiment of the present invention. Figure 9 As shown, the electronic device 90 includes one or more processors 91 and a memory 92 .

[0183] The processor 91 may be a central processing unit (CPU) or other forms of processing units having data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0184] The memory 92 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may, for example, include random access memory (RAM) and / or cache memory (cache), etc. The non-volatile memory may, for example, include read-only memory (ROM), a hard disk, a flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 91 may execute the program instructions to implement the methods of the software programs of the various embodiments of the present invention described above and / or other desired functions. In one example, the electronic device may further include: an input device 93 and an output device 94, which are interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0185] In addition, the input device 93 may also include, for example, a keyboard, a mouse, and the like.

[0186] The output device 94 can output various information to the outside. The output device 94 can include, for example, a display, a speaker, a printer, a communication network and a remote output device connected thereto.

[0187] Of course, to simplify, Figure 9 Only some of the components related to the present invention in the electronic device are shown, and components such as a bus, an input / output interface, etc. are omitted. In addition, the electronic device may further include any other appropriate components according to specific application conditions.

[0188] Exemplary computer program products and computer-readable storage media

[0189] In addition to the above-mentioned methods and devices, an embodiment of the present invention may also be a computer program product, which includes computer program instructions, which, when executed by a processor, enable the processor to perform the steps of the method according to various embodiments of the present invention described in the above "Exemplary Method" section of this specification.

[0190] The computer program product may be written in any combination of one or more programming languages ​​to implement the operations of embodiments of the present invention, including object-oriented programming languages ​​such as Java, C++, and conventional procedural programming languages ​​such as C or similar programming languages. The program code may be executed entirely on the user's computing device, partially on the user's computing device, as a stand-alone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0191] In addition, an embodiment of the present invention may also be a computer-readable storage medium having computer program instructions stored thereon, which, when executed by a processor, enable the processor to execute the steps of the method according to various embodiments of the present invention described in the above "Exemplary Method" section of this specification.

[0192] The computer-readable storage medium can adopt any combination of one or more readable media. The readable medium can be a readable signal medium or a readable storage medium. The readable storage medium can, for example, include but is not limited to a system, system or device of electricity, magnetism, light, electromagnetic, infrared, or semiconductor, or any combination thereof. More specific examples (non-exhaustive list) of readable storage media include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof.

[0193] The basic principles of the present invention have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in the present invention are merely illustrative and non-limiting, and should not be construed as necessarily possessed by each embodiment of the present invention. Furthermore, the specific details disclosed above are provided for illustrative purposes and to facilitate understanding, and are not intended to be limiting. These details do not necessarily limit the present invention to being implemented using these specific details.

[0194] Each embodiment in this specification is described in a progressive manner, with each embodiment focusing on its differences from the other embodiments. References to the same or similar parts between the various embodiments are sufficient. For system embodiments, since they largely correspond to method embodiments, their description is relatively simple. For relevant parts, references to the description of the method embodiments are sufficient.

[0195] The block diagrams of the devices, systems, equipment, and systems involved in the present invention are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these devices, systems, equipment, and systems can be connected, arranged, or configured in any manner. Words such as "including," "comprising," "having," and the like are open-ended words, meaning "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and can be used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

[0196] The method and system of the present invention may be implemented in many ways. For example, the method and system of the present invention may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above sequence of steps for the method is for illustration only, and the steps of the method of the present invention are not limited to the sequence specifically described above, unless otherwise specified. In addition, in some embodiments, the present invention may also be implemented as a program recorded in a recording medium, which includes machine-readable instructions for implementing the method according to the present invention. Thus, the present invention also covers recording media that store programs for executing the method according to the present invention.

[0197] It should also be noted that, in the system, device and method of the present invention, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be regarded as equivalent schemes of the present invention. The above description of the disclosed aspects is provided to enable any technician in this field to make or use the present invention. Various modifications to these aspects will be very obvious to those skilled in the art, and the general principles defined here can be applied to other aspects without departing from the scope of the present invention. Therefore, the present invention is not intended to be limited to the aspects shown here, but according to the widest scope consistent with the principles disclosed here and novel features.

[0198] The above description has been presented for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the present invention to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for determining the stability of a power system with small disturbances, characterized in that: include: Equivalently equate the grid-connected converters in the power system to the nearest synchronous generators and construct a state matrix of the power system; Equivalently converting all synchronous generators at the supply and receiving ends of the power system into equivalent synchronous generators at the supply and receiving ends, respectively, wherein all synchronous generators include synchronous generators equivalent to grid-type converters; Using the partial inertia center method, according to the state matrix, the third-order state matrices of the equivalent synchronous generators at the supply and receiving ends are respectively constructed, and the third-order state matrices are reduced by using the integral flow method to determine the second-order state matrices of the equivalent synchronous generators at the supply and receiving ends; Constructing a damping ratio calculation equation for the power system according to the second-order state matrix; Calculating the damping ratio of the power system according to the control parameters of the power system and the damping ratio calculation equation, and determining whether the power system is stable according to the damping ratio; The state matrix is: Where a ij is the parameter of the state equation corresponding to the state matrix, Δδ j is the change in the potential phase angle of the jth synchronous generator after a small disturbance, Δω j is the change in angular velocity at the node of the jth synchronous generator after a small disturbance, Δδ j , and Δω j All are state variables; is the derivative of the change in the potential phase angle of the jth synchronous generator after being subjected to a small disturbance; is the derivative of the change in angular velocity at the node of the jth synchronous generator after a small disturbance; The third-order state matrix is: Where M A is the equivalent power grid inertia at the supply end, M B is the equivalent receiving-end grid inertia, D A is the equivalent power grid damping at the supply end, D B is the equivalent receiving-end grid damping, Δδ AB is the change in the power angle difference between the equivalent synchronous generator at the supply end and the equivalent synchronous generator at the receiving end after a small disturbance, Δω A is the change in angular velocity at the node of the synchronous generator at the supply end after a small disturbance, Δω B K is the change in angular velocity at the receiving end synchronous generator node after a small disturbance. AA is the synchronous power factor at the supply-side grid, K BB is the synchronous power factor of the receiving grid, is the derivative of the change in the power angle difference between the equivalent supply-side synchronous generator and the equivalent receiving-side synchronous generator after a small disturbance, is the derivative of the change in angular velocity at the node of the synchronous generator at the supply end after a small disturbance, is the derivative of the change in angular velocity at the node of the receiving synchronous generator after a small disturbance; The second-order state matrix is: Where D A is the equivalent power grid damping at the supply end, M B is the equivalent receiving-end grid inertia, D B is the equivalent receiving-end grid damping, K BB is the synchronous power factor of the receiving grid, and w0 is the rotation angular velocity at the rated frequency of the grid.

2. The method according to claim 1, characterized in that According to the second-order state matrix, a damping ratio calculation equation of the power system is constructed, including: constructing an equivalent state equation of the power system according to the second-order state matrix, and solving the state equation to determine a solution to the state equation of the power system; The damping ratio calculation equation is constructed based on the solution of the state equation.

3. The method according to claim 2, characterized in that The state equation is: The solution of the state equation is: Where M A is the equivalent power grid inertia at the supply end, M B is the equivalent receiving-end grid inertia, D A is the equivalent power grid damping at the supply end, D B is the equivalent receiving-end grid damping, λ=-σ±jω is the conjugate characteristic root of the state equation under the inter-regional oscillation mode, K AA is the synchronous power factor at the supply-side grid, K BB is the synchronous power factor of the receiving grid, -σ is the real part of the eigenvalue λ, ±jω is the imaginary part of the eigenvalue λ, and w0 is the rotation angular velocity at the rated frequency of the grid.

4. The method according to claim 3, characterized in that The damping ratio calculation equation is:

5. A device for determining the stability of a power system with small disturbances, characterized in that: include: A first building module is used to construct a state matrix of the power system after equating the grid-connected converter in the power system to the nearest synchronous generator; An equivalent module, configured to convert all synchronous generators at the supply and receiving ends of the power system into equivalent synchronous generators at the supply and receiving ends, respectively, wherein all synchronous generators include synchronous generators equivalent to grid-type converters; an order reduction module, configured to construct, based on the state matrix, the third-order state matrices of the equivalent synchronous generators at the supply and receiving ends respectively by using a partial center of inertia method, and reduce the order of the third-order state matrices by using an integral flow method to determine the second-order state matrices of the equivalent synchronous generators at the supply and receiving ends; A second construction module is configured to construct a damping ratio calculation equation for the power system according to the second-order state matrix; a calculation module, configured to calculate the damping ratio of the power system according to the control parameters of the power system and the damping ratio calculation equation, and determine whether the power system is stable according to the damping ratio; The state matrix is: Where a ij is the parameter of the state equation corresponding to the state matrix, Δδ j is the change in the potential phase angle of the jth synchronous generator after a small disturbance, Δω j is the change in angular velocity at the node of the jth synchronous generator after a small disturbance, Δδ j , and Δω j All are state variables; is the derivative of the change in the potential phase angle of the jth synchronous generator after being subjected to a small disturbance; is the derivative of the change in angular velocity at the node of the jth synchronous generator after a small disturbance; The third-order state matrix is: Where M A is the equivalent power grid inertia at the supply end, M B is the equivalent receiving-end grid inertia, D A is the equivalent power grid damping at the supply end, D B is the equivalent receiving-end grid damping, Δδ AB is the change in the power angle difference between the equivalent supply-side synchronous generator and the equivalent receiving-side synchronous generator after a small disturbance, Δω A is the change in angular velocity at the node of the synchronous generator at the supply end after a small disturbance, Δω B K is the change in angular velocity at the receiving end synchronous generator node after a small disturbance. AA is the synchronous power factor at the supply-side grid, K BB is the synchronous power factor of the receiving grid, is the derivative of the change in the power angle difference between the equivalent supply-side synchronous generator and the equivalent receiving-side synchronous generator after a small disturbance, is the derivative of the change in angular velocity at the node of the synchronous generator at the supply end after a small disturbance, is the derivative of the change in angular velocity at the node of the receiving synchronous generator after a small disturbance; The second-order state matrix is: Where D A is the equivalent power grid damping at the supply end, M B is the equivalent receiving-end grid inertia, D B is the equivalent receiving-end grid damping, K BB is the synchronous power factor of the receiving grid, and w0 is the rotation angular velocity at the rated frequency of the grid.

6. A computer-readable storage medium, characterized in that The storage medium stores a computer program, and the computer program is used to execute the method according to any one of claims 1 to 4.

7. An electronic device, characterized in that: The electronic device comprises: processor; a memory for storing instructions executable by the processor; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method of claim 1-4.

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