A small disturbance stability evaluation method and device for a network-constructed new energy station

Abstract

The present application relates to the technical field of power system analysis, and specifically provides a small disturbance stability evaluation method and device for a grid-connected new energy station, comprising: establishing a nonlinear differential algebraic equation set of the station, and determining a steady-state equilibrium point through power flow calculation; establishing a multi-input multi-output small signal state space model based on the nonlinear differential algebraic equation set; determining a closed-loop sensitivity transfer function matrix of the grid-connected new energy station based on the small signal state space model; determining a stiffness index of the grid-connected new energy station based on the closed-loop sensitivity transfer function matrix, and evaluating the small disturbance stability of the grid-connected new energy station based on the stiffness index; the technical scheme provided by the present application quantitatively characterizes the voltage response sensitivity of the station to power disturbance in a wide frequency domain range, and realizes unified and quantifiable evaluation of the voltage stiffness of the station.

Description

Technical Field

[0001] This invention relates to the field of power system analysis technology, specifically to a method and apparatus for assessing the stability of grid-connected renewable energy power plants under small disturbances. Background Technology

[0002] With the large-scale integration of new energy power generation such as wind and solar power, the proportion of power electronic converters in power systems continues to rise, gradually replacing the rotational inertia and voltage support capabilities of traditional synchronous generators. Unlike grid-connected converters, grid-connected converters are essentially voltage sources, capable of actively establishing voltage and frequency, providing the grid with inertia and voltage support capabilities similar to those of traditional synchronous generators. Grid-connected energy storage, as a new form of energy storage, can provide active power support and actively form virtual synchronous machine characteristics, providing reactive power support and voltage support capabilities to the grid.

[0003] However, there is currently a lack of unified and effective quantitative methods for assessing the voltage stiffness of grid-connected renewable energy power plants. Traditional assessments mainly rely on the short-circuit ratio, but the short-circuit ratio only reflects the static strength at power frequency and cannot fully characterize the dynamic and wide-frequency coupling characteristics of converter controllers. This limitation is becoming increasingly prominent, especially in the context of dynamic interactions across multiple time scales in new power systems. Existing technologies include studies that propose constructing voltage support topologies using the "elastic mapping" theory and combining it with branch reactive power-voltage sensitivity for assessment. However, this method focuses on static network analysis and fails to consider the frequency-domain dynamic characteristics of converter controllers. Other studies have proposed a voltage dynamic support capability evaluation method based on the reactive power outer loop control strategy of grid-connected converters. However, this method only applies to single converter devices and is difficult to extend to the assessment of power plants involving multi-machine aggregation, and it also fails to establish a quantitative mapping relationship with system strength.

[0004] Therefore, there is an urgent need for a method to characterize the voltage stiffness of a station-level transformer that can comprehensively consider the dynamics of converter control, the multi-input multi-output coupling characteristics, and the wide frequency domain response, so as to make up for the shortcomings of existing technologies. Summary of the Invention

[0005] To overcome the above-mentioned shortcomings, this invention proposes a method and device for evaluating the small disturbance stability of grid-type renewable energy power stations.

[0006] Firstly, a method for assessing the small-disturbance stability of a grid-type renewable energy power station is provided, the method comprising: Collect system information on grid-type renewable energy power stations, establish a set of nonlinear differential-algebraic equations for the power stations, and determine the steady-state equilibrium point through power flow calculations; At the steady-state equilibrium point, the nonlinear differential-algebraic equations are linearized to establish a small-signal state-space model with multiple inputs and multiple outputs. The small-signal state-space model is transformed to the frequency domain by Laplace transform to obtain the open-loop transfer function matrix of the grid-type new energy power station, and the closed-loop sensitivity transfer function matrix of the grid-type new energy power station is determined based on the open-loop transfer function matrix. The stiffness index of the grid-type renewable energy power station is determined based on the closed-loop sensitivity transfer function matrix, and the small disturbance stability of the grid-type renewable energy power station is evaluated based on the stiffness index. The small-signal state-space model uses the active power disturbance and reactive power disturbance injected into the grid connection point of the power station as input vectors, and the voltage amplitude deviation and power angle deviation at the grid connection point as output vectors.

[0007] Preferably, the nonlinear differential-algebraic equation system is as follows:

[0008] In the above formula, The function values ​​are for nonlinear differential equations. It is a nonlinear differential equation. It is a nonlinear algebraic equation. These are state variables, including the virtual power angle, angular frequency, voltage inner loop integral state, current inner loop integral state, and phase-locked loop state of each converter. These are algebraic variables, including the voltage magnitude and phase angle at each node. The input variables include active power disturbances and reactive power disturbances.

[0009] Preferably, the small-signal state-space model is as follows:

[0010] In the above formula, for The derivative with respect to time, This is the offset vector of the state variables. The state matrix, and These are the direct influence coefficients of active and reactive disturbances on the derivatives of the state variables, respectively. and These are the active power disturbance and reactive power disturbance injected into the power station's grid connection point, respectively. and These are the voltage amplitude deviation and voltage phase angle deviation at the grid connection point, respectively. For voltage output matrix, The output matrix is ​​the power angle. for right Instantaneous gain, for right Instantaneous gain, for right Instantaneous gain, for right Instantaneous gain.

[0011] Preferably, the closed-loop sensitivity transfer function matrix is ​​as follows:

[0012] In the above formula, The closed-loop sensitivity transfer function matrix is... It is the identity matrix. The open-loop transfer function matrix is... Let be the closed-loop transfer function from active power disturbance to voltage amplitude output. This is the closed-loop transfer function from reactive power disturbance to voltage amplitude output. Let be the closed-loop transfer function from active power disturbance to power angle output. Let be the closed-loop transfer function from reactive power disturbance to power angle output. It is a complex frequency.

[0013] Furthermore, the stiffness indices include: voltage amplitude stiffness index, power angle stiffness index, and comprehensive stiffness index.

[0014] Furthermore, the voltage amplitude stiffness index is as follows: ,

[0015] In the above formula, This is a voltage amplitude stiffness index. This is the row vector in the closed-loop sensitivity transfer function matrix corresponding to the voltage amplitude output. It is an H∞ norm.

[0016] Furthermore, the work angle stiffness index is as follows: ,

[0017] In the above formula, This is a voltage amplitude stiffness index. This is the row vector in the closed-loop sensitivity transfer function matrix that corresponds to the power angle output.

[0018] Furthermore, the comprehensive stiffness index is as follows:

[0019] In the above formula, This is a comprehensive stiffness index.

[0020] Furthermore, the evaluation of the small disturbance stability of the grid-type new energy power station based on the stiffness index includes: when the voltage amplitude stiffness index, power angle stiffness index, and comprehensive stiffness index all do not exceed their corresponding thresholds, the small disturbance stability of the grid-type new energy power station is qualified.

[0021] Furthermore, the threshold values ​​corresponding to the voltage amplitude stiffness index, power angle stiffness index, and comprehensive stiffness index are 0.3, 0.7, and 0.2 rad, respectively.

[0022] Secondly, a small disturbance stability assessment device for a grid-type renewable energy power station is provided, the device comprising: The calculation module is used to collect system information of grid-type new energy power stations, establish a set of nonlinear differential-algebraic equations for the power stations, and determine the steady-state equilibrium point through power flow calculation. A module is established to linearize the nonlinear differential-algebraic equations at the steady-state equilibrium point and establish a small-signal state-space model with multiple inputs and multiple outputs. The determination module is used to transform the small-signal state-space model to the frequency domain through Laplace transform, obtain the open-loop transfer function matrix of the grid-type new energy power station, and determine the closed-loop sensitivity transfer function matrix of the grid-type new energy power station based on the open-loop transfer function matrix. The evaluation module is used to determine the stiffness index of the grid-type new energy power station based on the closed-loop sensitivity transfer function matrix, and to evaluate the small disturbance stability of the grid-type new energy power station based on the stiffness index. The small-signal state-space model uses the active power disturbance and reactive power disturbance injected into the grid connection point of the power station as input vectors, and the voltage amplitude deviation and power angle deviation at the grid connection point as output vectors.

[0023] Thirdly, a computer device is provided, comprising: one or more processors; The processor is used to store one or more programs; When the one or more programs are executed by the one or more processors, the small disturbance stability assessment method for grid-type new energy power stations is implemented.

[0024] Fourthly, a computer-readable storage medium is provided, on which a computer program is stored, wherein when the computer program is executed, the small disturbance stability assessment method for the grid-type new energy power station is implemented.

[0025] The above-described technical solutions of the present invention have at least one or more of the following beneficial effects: This invention provides a method and apparatus for assessing the small-disturbance stability of a grid-type renewable energy power station, comprising: collecting system information of the grid-type renewable energy power station; establishing a system of nonlinear differential-algebraic equations for the power station; and determining the steady-state equilibrium point through power flow calculation; linearizing the system of nonlinear differential-algebraic equations at the steady-state equilibrium point to establish a multi-input multi-output small-signal state-space model; transforming the small-signal state-space model to the frequency domain through Laplace transform to obtain the open-loop transfer function matrix of the grid-type renewable energy power station, and determining the closed-loop sensitivity transfer function matrix of the grid-type renewable energy power station based on the open-loop transfer function matrix; determining the stiffness index of the grid-type renewable energy power station based on the closed-loop sensitivity transfer function matrix, and assessing the small-disturbance stability of the grid-type renewable energy power station based on the stiffness index; the technical solution provided by this invention quantitatively characterizes the voltage response sensitivity of the power station to power disturbances over a wide frequency range, realizing a unified and quantifiable assessment of the power station-level voltage stiffness, specifically: This invention establishes a closed-loop sensitivity transfer function matrix and extracts the H∞ norm of the voltage row vector and the power angle row vector respectively, thereby achieving a unified characterization and independent quantization of voltage amplitude stiffness and power angle stiffness, filling a gap in the existing technology. This invention specifically models the virtual power angle dynamics of grid-type converters. The power angle stiffness index directly reflects the sensitivity of the power station to power angle fluctuations caused by active / reactive disturbances. It is a key quantitative indicator for measuring the synchronization stability between grid-type power stations and the power grid, and is of great significance for evaluating transient stability and small disturbance stability. This invention defines a comprehensive stiffness index, namely the H∞ norm of the entire closed-loop sensitivity matrix, which can comprehensively evaluate the voltage and power angle response capability of a power station to power disturbances, facilitating horizontal comparison and system-level evaluation between different power stations. This invention, by calculating the maximum singular value of the transfer function at all frequencies, can comprehensively capture the response characteristics of power plants to power disturbances at different frequencies. It is particularly suitable for analyzing broadband problems such as subsynchronous oscillations and hypersynchronous oscillations that may occur between grid-type converters and the power grid. Based on a detailed small-signal model, this invention fully preserves the dynamic characteristics of the active frequency loop, reactive voltage loop, virtual impedance, and dual closed-loop controller of the grid-type converter. Furthermore, it naturally handles the coupling effect between the active and reactive channels through a multi-input multi-output framework, overcoming the limitations of traditional decoupling analysis. The voltage stiffness index, power angle stiffness index, and comprehensive stiffness index proposed in this invention all have clear physical meanings—that is, the maximum response amplitude under worst-case power disturbance; the smaller the value, the stronger the system. These scalar indices facilitate horizontal comparisons between different power plants and can also provide intuitive quantitative basis for power plant planning, grid connection review, and operation scheduling. This invention provides a sensitivity analysis method for stiffness index on control parameters and enables multi-objective joint optimization, providing a quantitative tool for parameter design and site configuration of grid-type converters. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the main steps of the small disturbance stability assessment method for grid-type renewable energy power stations according to an embodiment of the present invention. Detailed Implementation

[0027] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

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

[0029] Example 1 See appendix Figure 1 , Figure 1 This is a schematic flowchart illustrating the main steps of a small-disturbance stability assessment method for a grid-type renewable energy power station according to an embodiment of the present invention. Figure 1 As shown, the small disturbance stability assessment method for grid-type renewable energy power stations in this embodiment of the invention mainly includes the following steps: Step S101: Collect system information of grid-type new energy power stations, establish a set of nonlinear differential-algebraic equations for the power stations, and determine the steady-state equilibrium point through power flow calculation; Step S102: Linearize the nonlinear differential-algebraic equations at the steady-state equilibrium point to establish a small-signal state-space model with multiple inputs and multiple outputs; Step S103: Transform the small-signal state-space model to the frequency domain using Laplace transform to obtain the open-loop transfer function matrix of the grid-type new energy power station, and determine the closed-loop sensitivity transfer function matrix of the grid-type new energy power station based on the open-loop transfer function matrix. Step S104: Determine the stiffness index of the grid-type new energy power station based on the closed-loop sensitivity transfer function matrix, and evaluate the small disturbance stability of the grid-type new energy power station based on the stiffness index. The small-signal state-space model uses the active power disturbance and reactive power disturbance injected into the grid connection point of the power station as input vectors, and the voltage amplitude deviation and power angle deviation at the grid connection point as output vectors.

[0030] In this embodiment, the collected system information of the grid-type new energy power stations includes: the power station network topology, collection line parameters, transformer parameters, load data, rated capacity and control parameters of each grid-type converter (including but not limited to virtual inertia coefficient, damping coefficient, reactive power-voltage droop coefficient, voltage and current dual closed-loop PI parameters, virtual impedance parameters, etc.), and grid equivalent impedance parameters.

[0031] In this embodiment, the nonlinear differential-algebraic equation system is as follows:

[0032] In the above formula, The function values ​​are for nonlinear differential equations. It is a nonlinear differential equation. It is a nonlinear algebraic equation. These are state variables, including the virtual power angle, angular frequency, voltage inner loop integral state, current inner loop integral state, and phase-locked loop state of each converter. These are algebraic variables, including the voltage magnitude and phase angle at each node. The input variables include active power disturbances and reactive power disturbances.

[0033] In this embodiment, the small-signal state-space model is as follows:

[0034] In the above formula, for The derivative with respect to time, i.e., the rate of change of the state offset. This is the offset vector of the state variables. The state matrix describes the dynamic coupling relationships between state variables and determines the eigenvalues ​​and stability of the system. and These are the direct influence coefficients of active and reactive disturbances on the derivatives of the state variables, respectively. and These are the active power disturbance and reactive power disturbance injected into the power station's grid connection point, respectively. and These are the voltage amplitude deviation and voltage phase angle deviation at the grid connection point, respectively, which are used as the system output quantities. The voltage output matrix describes the state variables. How does it affect voltage amplitude deviation? , The output matrix is ​​the power angle. for right Instantaneous gain, for right Instantaneous gain, for right Instantaneous gain, for right Instantaneous gain.

[0035] The small-signal model can be derived based on the detailed control structure of the grid-type converter, specifically including: an active frequency control loop (simulating the swing equation of a synchronous generator), a reactive voltage control loop (simulating excitation regulation characteristics), a virtual impedance control loop, and a voltage and current dual closed-loop control loop. For power plants containing multiple grid-type converters, the single-machine equivalent method or component connection method can be used to aggregate the subsystems to obtain equivalent single-machine or multi-machine small-signal models.

[0036] In this embodiment, the closed-loop sensitivity transfer function matrix is ​​as follows:

[0037] In the above formula, The closed-loop sensitivity transfer function matrix is... It is the identity matrix. The open-loop transfer function matrix is... Let be the closed-loop transfer function from active power disturbance to voltage amplitude output. This is the closed-loop transfer function from reactive power disturbance to voltage amplitude output. Let be the closed-loop transfer function from active power disturbance to power angle output. Let be the closed-loop transfer function from reactive power disturbance to power angle output. It is a complex frequency.

[0038] In one embodiment, the stiffness index includes: voltage amplitude stiffness index, power angle stiffness index, and comprehensive stiffness index.

[0039] In one embodiment, the voltage amplitude stiffness index is as follows: ,

[0040] In the above formula, This is a voltage amplitude stiffness index. This is the row vector in the closed-loop sensitivity transfer function matrix corresponding to the voltage amplitude output. It is an H∞ norm.

[0041] In one embodiment, the work angle stiffness index is as follows: ,

[0042] In the above formula, This is a voltage amplitude stiffness index. This is the row vector in the closed-loop sensitivity transfer function matrix that corresponds to the power angle output.

[0043] In one implementation, the overall stiffness index is as follows:

[0044] In the above formula, This is a comprehensive stiffness index.

[0045] In one embodiment, the evaluation of the small disturbance stability of the grid-type renewable energy power station based on the stiffness index includes: when the voltage amplitude stiffness index, power angle stiffness index, and comprehensive stiffness index all do not exceed their corresponding thresholds, the small disturbance stability of the grid-type renewable energy power station is qualified.

[0046] In one embodiment, the threshold values ​​corresponding to the voltage amplitude stiffness index, power angle stiffness index, and comprehensive stiffness index are 0.3, 0.7, and 0.2 rad, respectively.

[0047] In one specific implementation, the present invention can set multiple sets of thresholds, for example: Preset voltage amplitude stiffness grading threshold , Threshold for angular stiffness classification , and comprehensive stiffness grading threshold , The grading criteria are as follows: like Determine the voltage amplitude stiffness; if The voltage amplitude stiffness is determined to be moderate; if The voltage amplitude stiffness is determined to be weak.

[0048] like Determine the angular stiffness to be strong; if The stiffness at the angle of work is determined to be moderate; if The angular stiffness is determined to be weak.

[0049] like Determine the overall stiffness to be strong; if The overall stiffness is determined to be moderate; if The overall stiffness is determined to be weak.

[0050] Typical recommended threshold values ​​are: , ; (Approximately 11.5°) (Approximately 28.6°); , The specific threshold can be adjusted according to the actual system requirements.

[0051] In one application scenario, a grid-connected renewable energy power station comprises 10 grid-connected wind turbine generators with a rated capacity of 5MW each. Each generator is equipped with a full-power converter and employs a virtual synchronous generator (VSG) control strategy. The power station is connected to the regional power grid via a 35kV / 110kV step-up transformer, with an equivalent short-circuit capacity of 500MVA at the grid connection point. The power station's network topology is radial, with a total line length of approximately 15km and a line impedance of (0.12 + j0.35)Ω / km. The main control parameters for each grid-connected converter are: virtual inertia coefficient... Damping coefficient Reactive power-voltage droop coefficient Active-frequency droop coefficient Voltage loop proportionality coefficient Voltage loop integral coefficient Current loop proportionality coefficient Integral coefficient of current loop .

[0052] Based on the aforementioned site parameters, a system of nonlinear differential-algebraic equations was established in the MATLAB / Simulink platform, comprising an equivalent model of 10 grid-connected wind turbines and their collection network, a step-up transformer, and the power grid. The grid-connected converter employs a virtual synchronous generator (VSG) control strategy, and the active frequency loop simulates the swing equations of a synchronous generator.

[0053] in, For virtual angular frequency, The rated angular frequency, This is the mechanical torque (determined by the active power reference value). Electromagnetic torque. Virtual power angle. Depend on The result is obtained through integration. The reactive voltage loop employs reactive-voltage droop control, outputting a reference value for the internal potential amplitude.

[0054] Power flow calculations were performed under rated operating conditions (50MW active power output, 0Mvar reactive power output) to obtain the steady-state equilibrium point: grid connection point voltage. Virtual power angle At this equilibrium point, a first-order Taylor expansion of the nonlinear model is performed to obtain a small-signal state-space model. After aggregation and simplification, the state variable dimension of the equivalent single-machine model is 12th order.

[0055] Based on the above small-signal model, the closed-loop transfer function matrix is ​​derived in the frequency domain. The frequency domain expressions for each element are calculated (specific numerical values ​​are omitted). The gain is dominant in the low-frequency band, reflecting the main influence of reactive power on voltage; The gain is relatively large in the low-frequency band, reflecting the main influence of active power on the power angle, while there are also certain coupling terms.

[0056] The calculated voltage amplitude stiffness index, power angle stiffness index, and overall stiffness index are as follows: , and ; Calculated It falls within the middle range ( The voltage amplitude stiffness is determined to be moderate. It falls within the moderate to weak range. The angular stiffness is determined to be moderate. It falls within the middle range ( The overall stiffness is determined to be moderate. This station faces certain risks of voltage and power angle fluctuations; therefore, it is recommended to adjust the control parameters appropriately to improve stiffness.

[0057] To verify the effectiveness of the method of this invention, it was compared with the traditional short-circuit ratio evaluation method and existing evaluation methods that only consider voltage stiffness. When the system operating conditions change (such as the single-circuit line of the collection line being taken out of operation, or the equivalent short-circuit capacity of the power grid decreasing to 350MVA), the traditional short-circuit ratio method (SCR decreasing from 10 to 7) still determines it as a strong system, while the method that only considers voltage stiffness ( The value increased from 0.452 to 0.612, triggering a moderate warning. Simultaneously, this invention detected a significant deterioration in the work angle stiffness. The warning value increased from 0.281 rad to 0.452 rad, indicating a stronger risk of power angle instability. This demonstrates that the method of this invention can more comprehensively assess the actual operational risks of the station.

[0058] Example 2 Based on the same inventive concept, the present invention also provides a small disturbance stability assessment device for a grid-type renewable energy power station, the small disturbance stability assessment device for the grid-type renewable energy power station comprising: The calculation module is used to collect system information of grid-type new energy power stations, establish a set of nonlinear differential-algebraic equations for the power stations, and determine the steady-state equilibrium point through power flow calculation. A module is established to linearize the nonlinear differential-algebraic equations at the steady-state equilibrium point and establish a small-signal state-space model with multiple inputs and multiple outputs. The determination module is used to transform the small-signal state-space model to the frequency domain through Laplace transform, obtain the open-loop transfer function matrix of the grid-type new energy power station, and determine the closed-loop sensitivity transfer function matrix of the grid-type new energy power station based on the open-loop transfer function matrix. The evaluation module is used to determine the stiffness index of the grid-type new energy power station based on the closed-loop sensitivity transfer function matrix, and to evaluate the small disturbance stability of the grid-type new energy power station based on the stiffness index. The small-signal state-space model uses the active power disturbance and reactive power disturbance injected into the grid connection point of the power station as input vectors, and the voltage amplitude deviation and power angle deviation at the grid connection point as output vectors.

[0059] Preferably, the nonlinear differential-algebraic equation system is as follows:

[0060] In the above formula, The function values ​​are for nonlinear differential equations. It is a nonlinear differential equation. It is a nonlinear algebraic equation. These are state variables, including the virtual power angle, angular frequency, voltage inner loop integral state, current inner loop integral state, and phase-locked loop state of each converter. These are algebraic variables, including the voltage magnitude and phase angle at each node. The input variables include active power disturbances and reactive power disturbances.

[0061] Preferably, the small-signal state-space model is as follows:

[0062] In the above formula, for The derivative with respect to time, This is the offset vector of the state variables. The state matrix, and These are the direct influence coefficients of active and reactive disturbances on the derivatives of the state variables, respectively. and These are the active power disturbance and reactive power disturbance injected into the power station's grid connection point, respectively. and These are the voltage amplitude deviation and voltage phase angle deviation at the grid connection point, respectively. For voltage output matrix, The output matrix is ​​the power angle. for right Instantaneous gain, for right Instantaneous gain, for right Instantaneous gain, for right Instantaneous gain.

[0063] Preferably, the closed-loop sensitivity transfer function matrix is ​​as follows:

[0064] In the above formula, The closed-loop sensitivity transfer function matrix is... It is the identity matrix. The open-loop transfer function matrix is... Let be the closed-loop transfer function from active power disturbance to voltage amplitude output. This is the closed-loop transfer function from reactive power disturbance to voltage amplitude output. Let be the closed-loop transfer function from active power disturbance to power angle output. Let be the closed-loop transfer function from reactive power disturbance to power angle output. It is a complex frequency.

[0065] Furthermore, the stiffness indices include: voltage amplitude stiffness index, power angle stiffness index, and comprehensive stiffness index.

[0066] Furthermore, the voltage amplitude stiffness index is as follows: ,

[0067] In the above formula, This is a voltage amplitude stiffness index. This is the row vector in the closed-loop sensitivity transfer function matrix corresponding to the voltage amplitude output. It is an H∞ norm.

[0068] Furthermore, the work angle stiffness index is as follows: ,

[0069] In the above formula, This is a voltage amplitude stiffness index. This is the row vector in the closed-loop sensitivity transfer function matrix that corresponds to the power angle output.

[0070] Furthermore, the comprehensive stiffness index is as follows:

[0071] In the above formula, This is a comprehensive stiffness index.

[0072] Furthermore, the evaluation of the small disturbance stability of the grid-type new energy power station based on the stiffness index includes: when the voltage amplitude stiffness index, power angle stiffness index, and comprehensive stiffness index all do not exceed their corresponding thresholds, the small disturbance stability of the grid-type new energy power station is qualified.

[0073] Furthermore, the threshold values ​​corresponding to the voltage amplitude stiffness index, power angle stiffness index, and comprehensive stiffness index are 0.3, 0.7, and 0.2 rad, respectively.

[0074] Example 3 Based on the same inventive concept, this invention also provides a computer device, which includes a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the computer storage medium to realize the corresponding method flow or corresponding function, so as to realize the steps of the small disturbance stability assessment method for a grid-type new energy power station in the above embodiments.

[0075] Example 4 Based on the same inventive concept, this invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the small-disturbance stability assessment method for a grid-type renewable energy power station in the above embodiments.

[0076] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0077] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0078] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0079] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for assessing the small-disturbance stability of a grid-type renewable energy power station, characterized in that, The method includes: Collect system information on grid-type renewable energy power stations, establish a set of nonlinear differential-algebraic equations for the power stations, and determine the steady-state equilibrium point through power flow calculations; At the steady-state equilibrium point, the nonlinear differential-algebraic equations are linearized to establish a small-signal state-space model with multiple inputs and multiple outputs. The small-signal state-space model is transformed to the frequency domain by Laplace transform to obtain the open-loop transfer function matrix of the grid-type new energy power station, and the closed-loop sensitivity transfer function matrix of the grid-type new energy power station is determined based on the open-loop transfer function matrix. The stiffness index of the grid-type renewable energy power station is determined based on the closed-loop sensitivity transfer function matrix, and the small disturbance stability of the grid-type renewable energy power station is evaluated based on the stiffness index. The small-signal state-space model uses the active power disturbance and reactive power disturbance injected into the grid connection point of the power station as input vectors, and the voltage amplitude deviation and power angle deviation at the grid connection point as output vectors.

2. The method as described in claim 1, characterized in that, The nonlinear differential-algebraic equations are as follows: In the above formula, The function values ​​are for nonlinear differential equations. It is a nonlinear differential equation. It is a nonlinear algebraic equation. These are state variables, including the virtual power angle, angular frequency, voltage inner loop integral state, current inner loop integral state, and phase-locked loop state of each converter. These are algebraic variables, including the voltage magnitude and phase angle at each node. The input variables include active power disturbances and reactive power disturbances.

3. The method as described in claim 1, characterized in that, The small-signal state-space model is as follows: In the above formula, for The derivative with respect to time, This is the offset vector of the state variables. The state matrix, and These are the direct influence coefficients of active and reactive disturbances on the derivatives of the state variables, respectively. and These are the active power disturbance and reactive power disturbance injected into the power station's grid connection point, respectively. and These are the voltage amplitude deviation and voltage phase angle deviation at the grid connection point, respectively. For voltage output matrix, The output matrix is ​​the power angle. for right Instantaneous gain, for right Instantaneous gain, for right Instantaneous gain, for right Instantaneous gain.

4. The method as described in claim 1, characterized in that, The closed-loop sensitivity transfer function matrix is ​​as follows: In the above formula, The closed-loop sensitivity transfer function matrix is... It is the identity matrix. The open-loop transfer function matrix is... Let be the closed-loop transfer function from active power disturbance to voltage amplitude output. Let be the closed-loop transfer function from reactive power disturbance to voltage amplitude output. Let be the closed-loop transfer function from active power disturbance to power angle output. Let be the closed-loop transfer function from reactive power disturbance to power angle output. It is a complex frequency.

5. The method as described in claim 4, characterized in that, The stiffness indices include: voltage amplitude stiffness index, power angle stiffness index, and comprehensive stiffness index.

6. The method as described in claim 5, characterized in that, The voltage amplitude stiffness parameters are as follows: ， In the above formula, This is a voltage amplitude stiffness index. This is the row vector in the closed-loop sensitivity transfer function matrix corresponding to the voltage amplitude output. It is an H∞ norm.

7. The method as described in claim 6, characterized in that, The work angle stiffness parameters are as follows: ， In the above formula, This is a voltage amplitude stiffness index. This is the row vector in the closed-loop sensitivity transfer function matrix that corresponds to the power angle output.

8. The method as described in claim 7, characterized in that, The comprehensive stiffness index is as follows: In the above formula, This is a comprehensive stiffness index.

9. The method as described in claim 5, characterized in that, The evaluation of the small disturbance stability of the grid-type new energy power station based on the stiffness index includes: when the voltage amplitude stiffness index, power angle stiffness index and comprehensive stiffness index do not exceed their corresponding thresholds, the small disturbance stability of the grid-type new energy power station is qualified.

10. The method as described in claim 9, characterized in that, The threshold values ​​for the voltage amplitude stiffness index, power angle stiffness index, and comprehensive stiffness index are 0.3, 0.7, and 0.2 rad, respectively.

11. A small-disturbance stability assessment device for a grid-type renewable energy power station, characterized in that, The device includes: The calculation module is used to collect system information of grid-type new energy power stations, establish a set of nonlinear differential-algebraic equations for the power stations, and determine the steady-state equilibrium point through power flow calculation. A module is established to linearize the nonlinear differential-algebraic equations at the steady-state equilibrium point and establish a small-signal state-space model with multiple inputs and multiple outputs. The determination module is used to transform the small-signal state-space model to the frequency domain through Laplace transform, obtain the open-loop transfer function matrix of the grid-type new energy power station, and determine the closed-loop sensitivity transfer function matrix of the grid-type new energy power station based on the open-loop transfer function matrix. The evaluation module is used to determine the stiffness index of the grid-type new energy power station based on the closed-loop sensitivity transfer function matrix, and to evaluate the small disturbance stability of the grid-type new energy power station based on the stiffness index. The small-signal state-space model uses the active power disturbance and reactive power disturbance injected into the grid connection point of the power station as input vectors, and the voltage amplitude deviation and power angle deviation at the grid connection point as output vectors.

12. A computer device, characterized in that, include: One or more processors; The processor is used to execute one or more programs; When the one or more programs are executed by the one or more processors, the method for small disturbance stability assessment of grid-type renewable energy power stations as described in any one of claims 1 to 10 is implemented.

13. A computer-readable storage medium, characterized in that, It contains a computer program, which, when executed, implements the small disturbance stability assessment method for grid-type new energy power stations as described in any one of claims 1 to 10.

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