Power disturbance-based network configuration type converter transient stability evaluation method and system

Abstract

The present application belongs to the field of power electronics, and provides a network configuration type converter transient stability evaluation method and system based on power disturbance, which forms an angle difference by applying disturbance to active power control of the network configuration type converter and obtaining corresponding power angle change; based on the power angle difference, active power reference, reactive power reference and disturbance amount of the active power, a power angle curve is fitted, and according to the power angle curve, the transient stability transmission boundary of the reactive power or the active power under the current active power or reactive power reference condition is determined; based on the transient stability transmission boundary, the current transient stability of the network configuration type converter is determined. The present application can directly calculate the converter transient stability boundary, thereby avoiding obtaining system parameters such as grid voltage, and realizing accurate evaluation of the transient stability of the network configuration type converter.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, specifically relating to a method and system for evaluating the transient stability of a grid-type converter based on power disturbances. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] As the penetration rate of new energy sources in power systems continues to increase, power systems face stability challenges. Traditional grid-connected converters, heavily reliant on grid voltage and frequency, struggle to adapt to the changing stability requirements of new power systems. Grid-connected converters, on the other hand, can independently construct voltage, actively providing inertia support, oscillation damping, and rapid voltage recovery for the grid. Therefore, grid-connected converters have become a key supporting technology for building new power systems.

[0004] Compared to grid-connected converters, grid-connected converters can support stable grid operation. However, they may still experience transient instability under significant disturbances, leading to oscillations or even system collapse. Therefore, the transient stability of grid-connected converters has become a hot research topic. Existing research indicates that maintaining the transient stability of grid-connected converters is crucial to limiting the input active and reactive power references within a specific range. However, calculating this range relies on several system parameters that are difficult to obtain accurately in real time, such as grid voltage amplitude and line inductance between the converter and the grid. Due to the uncertainty and time-varying nature of these parameters, it is difficult to reliably assess the transient stability of grid-connected converters in practical engineering applications. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a method and system for evaluating the transient stability of grid-connected converters based on power disturbances. This invention can directly calculate the transient stability boundary of the converter, thereby avoiding the need to obtain system parameters such as grid voltage, and achieving accurate evaluation of the transient stability of grid-connected converters.

[0006] According to some embodiments, the present invention adopts the following technical solution:

[0007] A transient stability assessment method for a grid-type converter based on power perturbation includes the following steps:

[0008] A disturbance is applied to the active power control of the grid-type converter and the corresponding power angle change is obtained, thus forming a power angle difference;

[0009] Based on the power angle difference, active power reference, reactive power reference, and the disturbance applied by the active power, a power angle curve is fitted, and the transient stable transmission boundary of reactive power or active power under the current active power or reactive power reference conditions is determined according to the power angle curve.

[0010] Based on the transient stability transmission boundary, the current transient stability of the grid-type converter is determined.

[0011] As an alternative implementation, the active power control adopts a droop control strategy.

[0012] As an alternative implementation method, a PI control strategy is adopted for reactive power control of the grid-type converter.

[0013] As an alternative implementation, the process of determining the transient stability transmission boundary of reactive power or active power under the current active power or reactive power reference conditions includes:

[0014] Based on the active power reference signal, a power disturbance Δ is applied to the active power control. p And ensure that the system is transiently stable at this time, obtain the change in power angle Δ of the active power control output. d 1;

[0015] Based on the obtained Δ p Δ d 1. Seek A cos(2) d A is the amplitude. d For the angle of attack;

[0016] Apply a power disturbance –Δ to active power control p And ensure that the system is transiently stable at this time, obtain the change in the power angle of the output – Δ d 2;

[0017] Based on the obtained –Δ p , –Δ d 2. Find A cos(2) d );

[0018] The average of the two results is used for fitting the work angle curve, and let... c This is the average of the two results.

[0019] based on c Using the active power reference signal, calculate the amplitude of the fitted curve;

[0020] Plot the fitted power angle curve based on the relationship between the amplitude of the fitted curve and the power angle.

[0021] When the reactive power reference is fixed and the reactive power reference is greater than the set value, the maximum active power transmission value that ensures the transient stability of the system under this condition is calculated.

[0022] When the active power reference is fixed, let Δ p The value is zero, and the minimum reactive power transmission value that guarantees the transient stability of the system under this condition is calculated.

[0023] As a further defined implementation method, the maximum active power transmission value p max for:

[0024] ;

[0025] Where A is the amplitude of the fitted curve, and q ref For reactive power reference;

[0026] Minimum reactive power transmission value q min :

[0027] ;

[0028] p ref This is for active power reference.

[0029] A transient stability evaluation system for grid-type converters based on power perturbation includes:

[0030] The active power control module is used to apply disturbances to the active power control of the grid-type converter and obtain the corresponding power angle changes, thus forming a power angle difference.

[0031] The stability boundary calculation module is used to fit the power angle curve based on the power angle difference, active power reference, reactive power reference, and the disturbance applied by the active power. Based on the power angle curve, it determines the transient stability transmission boundary of reactive power or active power under the current active power or reactive power reference conditions. Based on the transient stability transmission boundary, it determines the current transient stability of the grid-type converter.

[0032] As an optional implementation, it also includes a power calculation module, a reactive power control module, and a voltage control module, wherein:

[0033] The power calculation module is used to generate a virtual signal orthogonal to the input signal through a second-order generalized integrator, establish a two-phase stationary coordinate system based on the virtual signal, realize the power calculation of the single-phase converter, and provide the dq component of the converter capacitor voltage to the voltage control module through dq transformation.

[0034] The reactive power control module is used to achieve zero steady-state error tracking of actual reactive power to reactive power reference using PI control. The input is the reactive power reference value and the actual value, and the output is the d-axis voltage reference value, which provides input to the voltage control module.

[0035] The voltage control module is used to achieve zero steady-state error tracking of the actual output voltage of the converter to the voltage reference using PI control. It performs PI control on both the d and q axes respectively, with the output of the reactive power control module serving as the d-axis reference and 0 serving as the q-axis reference. The dq component of the actual capacitor voltage of the converter serves as the feedback quantity, and the reference value of the converter capacitor voltage in the dq coordinate system is output. After inverse transformation, it is used for PWM modulation.

[0036] As an optional implementation, the active power control module is used to adjust the active power output of the converter using droop control. When there is no power disturbance, the input to the active power control module is the active power reference value and the actual value, and the output phase reference provides a phase reference for the dq transformation in the power calculation module and the inverse dq transformation before PWM modulation. When a power disturbance is applied, the power angle output by the active power control module changes accordingly Δ under the influence of the disturbance. d That is, the output power angle after the disturbance has a power angle difference compared with the original power angle. The active power reference of the active power control module, the disturbance amount, and the power angle difference after the disturbance are used as inputs to the stability boundary calculation module.

[0037] As an alternative implementation, the stability boundary calculation module is designed based on the transient stability mechanism of the converter when the reactive power control strategy is PI control and the active power control strategy is droop control.

[0038] As an alternative implementation, the stability boundary calculation module is configured as follows:

[0039] Based on the active power reference signal, a power disturbance Δ is applied to the active power control. p And ensure that the system is transiently stable at this time, obtain the change in power angle Δ of the active power control output. d 1;

[0040] Based on the obtained Δ p Δ d 1. Seek A cos(2) d A is the amplitude. d For the angle of attack;

[0041] Apply a power disturbance –Δ to active power control p And ensure that the system is transiently stable at this time, obtain the change in the power angle of the output – Δ d 2;

[0042] Based on the obtained –Δp , –Δ d 2. Find A cos(2) d );

[0043] The average of the two results is used for fitting the work angle curve, and let... c This is the average of the two results.

[0044] based on c Using the active power reference signal, calculate the amplitude of the fitted curve;

[0045] Plot the fitted power angle curve based on the relationship between the amplitude of the fitted curve and the power angle.

[0046] When the reactive power reference is fixed and the reactive power reference is greater than the set value, the maximum active power transmission value that ensures the transient stability of the system under this condition is calculated.

[0047] When the active power reference is fixed, let Δ p The value is zero, and the minimum reactive power transmission value that guarantees the transient stability of the system under this condition is calculated.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0049] This invention obtains the power angle change by adding a power disturbance to the active power control, and fits the power angle curve based on the power disturbance and the power angle change, thereby obtaining the key parameters for calculating the transient stability boundary. It can directly calculate the transient stability boundary of the converter, thus avoiding the need to obtain system parameters such as grid voltage, and achieving accurate assessment of the transient stability of grid-connected converters.

[0050] The present invention is simple to implement and has low computational requirements for hardware, and solves the problem that the transient stable state of the system cannot be determined due to the difficulty in obtaining power grid parameters.

[0051] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0052] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0053] Figure 1 This is a block diagram of a grid-type converter system provided in one embodiment;

[0054] Figure 2 This is a schematic diagram of a power calculation module structure provided in one embodiment;

[0055] Figure 3 This is a schematic diagram of a reactive power control module provided in one embodiment;

[0056] Figure 4 This is a schematic diagram of the active power control module structure provided in one embodiment;

[0057] Figure 5 This is a schematic diagram of a voltage control module structure provided in one embodiment;

[0058] Figure 6 This is a schematic diagram of a stable boundary calculation module provided in one embodiment;

[0059] Figure 7 This is a flowchart illustrating the operation of a stability boundary calculation module provided in one embodiment.

[0060] Figure 8 This is a schematic diagram of a fitted work angle curve provided in one embodiment. Detailed Implementation

[0061] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0062] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0063] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0064] Where there is no conflict, the embodiments and features described in this application may be combined with each other.

[0065] Example 1

[0066] A transient stability assessment method for a grid-type converter based on power perturbation includes the following steps:

[0067] A disturbance is applied to the active power control of the grid-type converter and the corresponding power angle change is obtained, thus forming a power angle difference;

[0068] Based on the power angle difference, active power reference, reactive power reference, and the disturbance applied by the active power, a power angle curve is fitted, and the transient stable transmission boundary of reactive power or active power under the current active power or reactive power reference conditions is determined according to the power angle curve.

[0069] Based on the transient stability transmission boundary, the current transient stability of the grid-type converter is determined.

[0070] In this embodiment, the active power control adopts a droop control strategy.

[0071] In this embodiment, a PI control strategy is adopted for reactive power control of the grid-type converter.

[0072] In this embodiment, the process of determining the transient stable transmission boundary of reactive power or active power under the current active power or reactive power reference conditions includes:

[0073] Based on the active power reference signal, a power disturbance Δ is applied to the active power control. p And ensure that the system is transiently stable at this time, obtain the change in power angle Δ of the active power control output. d 1;

[0074] Based on the obtained Δ p Δ d 1. Seek A cos(2) d A is the amplitude. d For the angle of attack;

[0075] Apply a power disturbance –Δ to active power control p And ensure that the system is transiently stable at this time, obtain the change in the power angle of the output – Δ d 2;

[0076] Based on the obtained –Δ p , –Δ d 2. Find A cos(2) d );

[0077] The average of the two results is used for fitting the work angle curve, and let... c This is the average of the two results.

[0078] based on c Using the active power reference signal, calculate the amplitude of the fitted curve;

[0079] Plot the fitted power angle curve based on the relationship between the amplitude of the fitted curve and the power angle.

[0080] When the reactive power reference is fixed and the reactive power reference is greater than the set value, the maximum active power transmission value that ensures the transient stability of the system under this condition is calculated.

[0081] When the active power reference is fixed, let Δ p The value is zero, and the minimum reactive power transmission value that guarantees the transient stability of the system under this condition is calculated.

[0082] Preferred maximum active power transmission value p max for:

[0083] ;

[0084] Where A is the amplitude of the fitted curve, and q ref For reactive power reference;

[0085] Minimum reactive power transmission value q min :

[0086] ;

[0087] p ref This is for active power reference.

[0088] Example 2

[0089] A transient stability assessment system for grid-connected converters based on power disturbances can calculate the transient stability boundary of the system without obtaining grid voltage and line impedance parameters. That is, given a determined active (reactive) power reference, it can obtain the reactive (active) power reference range that guarantees the transient stability of the system.

[0090] like Figure 1 As shown, the grid-type converter system used in this system consists of a DC power supply, a single-phase half-bridge inverter, and... LCL Filters, power grids v s and its line impedance L s Composition. Among them... LCL The filter consists of an inverter-side inductor. L gi Filter capacitor C gf , grid-side inductor L gg composition.

[0091] A transient stability assessment system for grid-type converters based on power perturbations, such as... Figure 1 As shown, it includes a power calculation module, a reactive power control module, an active power control module, a voltage control module, and a stability boundary calculation module.

[0092] The power calculation module generates a virtual signal orthogonal to the input signal (converter capacitor voltage and line current) through a second-order generalized integrator (SOGI), thereby establishing a two-phase stationary coordinate system to realize the power calculation of the single-phase converter. At the same time, it provides the dq component of the converter capacitor voltage to the voltage control module through dq transformation.

[0093] The reactive power control module uses PI control to achieve zero steady-state error tracking of the actual reactive power to the reactive power reference. The inputs are the reactive power reference value and the actual value, and the output is the d-axis voltage reference value, which provides input to the voltage control module.

[0094] The active power control module uses droop control to adjust the converter's active power output. Under normal power conditions (Δ... p = 0 W), the module takes the active power reference value and the actual value as input, and the output phase reference provides a phase reference for the dq transformation in the power calculation module and the inverse dq transformation before PWM modulation. When a power disturbance is applied (Δ p (≠ 0 W), under the influence of power disturbances, the power angle output by this module will change accordingly Δ. d This means that the output power angle after the disturbance has a power angle difference compared to the original power angle. The active power reference, the disturbance amount, and the power angle difference after the disturbance are used as inputs to the stability boundary calculation module.

[0095] The voltage control module employs PI control to achieve zero steady-state error tracking of the actual output voltage of the converter to a voltage reference. This module performs PI control on both the d-axis and q-axis, with the output of the reactive power control module serving as the d-axis reference and 0 as the q-axis reference. The dq component of the actual capacitor voltage of the converter is used as feedback. Finally, the reference value of the converter capacitor voltage in the dq coordinate system is output, and after inverse transformation, it is used for PWM modulation.

[0096] The stability boundary calculation module is designed based on the transient stability mechanism of the converter when the reactive power control strategy is PI control and the active power control strategy is droop control. Its inputs are active and reactive power references, active power disturbance, and the power angle difference of the output after the disturbance. Based on the input information, it can perform... p-d Curve fitting is performed to obtain the amplitude of the curve. By performing corresponding algebraic operations on the obtained amplitude, the reactive (active) boundary that guarantees the transient stability of the system under the current active (reactive) power reference conditions can be obtained.

[0097] The following is a detailed introduction to each module.

[0098] like Figure 2 As shown, the power calculation module input is the converter capacitor voltage. v gf Fundamental angular frequency oh Line current i s Reference phase angle i ref Based on the input information, a second-order generalized integrator (SOGI) can be used to establish information about... v gf and i s of α-β Coordinate system, based on this i ref After performing dq transformation and low-pass filtering, the dq components of the capacitor voltage and line current are obtained as follows: v gf_dq and i s_dq ,in v gf_dq This will be used as the input to the voltage control module. Based on the instantaneous reactive power theory, the expressions for active power and reactive power can be obtained as follows:

[0099] ;

[0100] ;

[0101] like Figure 3 As shown, the input to the reactive power control module is the reactive power reference. q ref and the actual reactive power output of the converter q g After normalizing the deviation between the two values, PI control is applied, and the module outputs the d-axis voltage reference value. (See figure) S 0 is the baseline value used for per-unit scaling; 311 is the ideal grid voltage amplitude. Proportional coefficient. K p = 0.08, integral coefficient K i = 1.2.

[0102] like Figure 4 As shown, the input to the active power control module is the active power reference. p ref The actual active power output of the converter p g and active power disturbance Δ p When the module does not apply a power disturbance, Δ p = 0 W. p ref and p g The difference is used as the input for droop control, and the output is added to 1 and then integrated to output the reference phase angle. iref When the module adds power disturbance, Δ p ≠ 0 W. At this point, the frequency increment obtained after droop control can be directly integrated to output the power angle difference information Δ under the current conditions. d This provides the conditions for the stability boundary calculation module. When Δ p = 0 W and p g = p ref At that time, the output power angle d and p ref Corresponding. When Δ p When ≠ 0 W, the output power angle d + Δ d and p ref + Δ p Corresponding. Due to Δ d This can be obtained, therefore this module provides the work angle change Δ to the stability boundary calculation module. d In the diagram, the control parameters K droop = 0.05.

[0103] like Figure 5 As shown, the d-axis of the voltage control module is output by the reactive power control module. v ref_d For reference, the q-axis is referenced to 0. Both are respectively correlated with the dq component of the actual output capacitor voltage of the converter. v d and v q By taking the difference and then applying PI control to the obtained deviation, zero steady-state error tracking can be achieved. Adding a feedforward of 311 to the d-axis can avoid inrush current. v dc This represents the DC voltage amplitude, with a gain of 1 / 2 derived from the single-phase half-bridge structure. The final output capacitor voltage is the reference value in the dq coordinate system. v gf_ref_dq0 In the diagram, both PI control parameters are... K p = 0.1, K i = 0.5.

[0104] like Figure 6 As shown, the stability boundary calculation module aims to avoid transient instability of the grid-connected converter. Under steady-state conditions, the power exchange between the grid-connected converter and the grid can be expressed as:

[0105] ;

[0106] ;

[0107] in, X s = oh ( L gg + L s () represents the line inductive reactance. Under the condition that active power uses droop control and reactive power uses PI control, v gf and d The following relationship exists:

[0108] ;

[0109] in, k d = ohK droop / S 0. k p = 311 K p / S 0, k i = 311 K i / S 0. From the above equation, the condition for the system to be transiently stable can be derived as follows:

[0110] ;

[0111] Furthermore, given a defined active (reactive) power reference, the boundary expression for reactive (active) power can be derived as follows:

[0112] ;

[0113] ;

[0114] As can be seen from the above equation, the prerequisite for the transient stability of the grid converter is... q ref >–( v s ) 2 / (8) X s ).when q ref When = 0 Var, v gf = v s cos d To find the stable equilibrium point, substituting it into the conditions for transient stability of the system, we get:

[0115] ;

[0116] At this moment, the angle of attack p g -d The curve is a standard sine function with an amplitude of A = ( v s ) 2 / (4) X s ).

[0117] The function of the stable boundary calculation module is to... p g -d Curve fitting to obtain A Then, the power reference boundary in the reactive (active) power boundary expression is solved through algebraic operations. p max and q min The specific process is as follows: Figure 7 As shown.

[0118] The first step is to input the active power control module. q ref = 0 Var, p ref = p 0 (0 < p 0 < ( v s ) 2 / (0.4) oh ), used here v s (This is an estimated value for the grid voltage). p ref The information is then input into the stability boundary calculation module.

[0119] The second step involves applying a power disturbance Δ to the active power control module based on the input conditions from the first step. p And ensure that the system is transiently stable at this time, obtain the change in its output power angle Δ. d 1. Δ p Δ d 1. Input to the stability boundary calculation module.

[0120] The third step is to use the obtained Δ p Δ d 1. Seek A cos(2) d ), and make c 1= A cos(2) d );

[0121] ;

[0122] The fourth step is to apply a power disturbance – Δ – to the active power control module. p And ensure that the system is transiently stable at this time, obtain the change in its output power angle – Δ d 2. (The remaining text appears to be incomplete and contains errors. A more accurate translation would require the full context.) p 、–Δ d 2. Input to the stability boundary calculation module.

[0123] Fifth step, based on the obtained –Δ p , –Δ d 2. Find A cos(2) d ), and make c 2= A cos(2) d );

[0124] ;

[0125] Step 6, take c 1 and c The average value of 2 is used for the work angle curve fitting, and let c = ( c 1+ c 2) / 2.

[0126] Step 7: Calculate the amplitude of the fitted curve. A .

[0127] ;

[0128] Step 8, based on amplitude A and the relationship between the work angle p g = A sin(2) d Plot the fitted work angle curve p g -d .

[0129] Step 9: When the reactive power reference is fixed, the following conditions must be met. q ref >–( v s ) 2 / (8) X s The maximum active power transmission value that guarantees transient stability of the system under this condition can be calculated. p max :

[0130] ;

[0131] Step 10: When the active power reference is fixed, let Δ p = 0 W, the minimum reactive power transmission value that guarantees transient stability of the system under this condition can be calculated. q min :

[0132] ;

[0133] Through the above steps, this module can calculate the reactive (active) power transmission boundary to ensure the transient stability of the system based on the currently determined active (reactive) power reference.

[0134] Figure 8 This is a schematic diagram of the proposed fitted power angle curve, which illustrates the relationship between grid voltage and power angle. v s = 100 V, q ref = 0 Var, p ref = 400 W, Δ p The power angle curve fitted by the stability boundary calculation module under simulation conditions of 100 W. At this point, the curve amplitude... A This refers to the maximum active power transmission value that ensures the transient stability of the system. p max = 880 W. The actual maximum active power transmission value derived from theory is 884 W. Therefore, the proposed transient stability assessment system has high feasibility and accuracy.

[0135] 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 one or more computer-usable storage media (including, but not limited to, disk storage, etc.) containing computer-usable program code. CD - ROM It takes the form of a computer program product implemented on (such as optical memory, etc.).

[0136] 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 oneOne or more processes and / or boxes Figure one A device that provides the functions specified in one or more boxes.

[0137] 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 one One or more processes and / or boxes Figure one The function specified in one or more boxes.

[0138] 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 one One or more processes and / or boxes Figure one The steps of the function specified in one or more boxes.

[0139] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art without creative effort within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for power-perturbation-based network configuration type converter transient stability assessment, characterized in that, The method comprises the following steps: A disturbance is applied to active power control of the grid-forming converter, and a corresponding power angle change is obtained to form a power angle difference; Based on the power angle difference, an active power reference, a reactive power reference, and a disturbance amount applied by the active power, a power angle curve is fitted, and based on the power angle curve, a transient stability transmission boundary of the reactive power or the active power under the current active power or reactive power reference condition is determined; Based on the transient stability transmission boundary, the current transient stability of the grid-forming converter is determined; The process of determining the transient stability transmission boundary of reactive power or active power under the condition of current active power or reactive power reference includes: based on the active power reference signal, applying a power disturbance Δ to the active power control p and ensuring the transient stability of the system at this time, obtaining the power angle change amount Δ of the active power control output When the reactive power reference is fixed and the reactive power reference is greater than a set value, a maximum active power transmission value under the condition of ensuring the transient stability of the system is calculated; 1; according to the obtained Δ p , Δ The active power control adopts a droop control strategy. 1 A cos (2 The reactive power control of the grid-forming converter adopts a PI control strategy. ), A is the amplitude, The method comprises: is the power angle, and let c 1= A cos (2 An active power control module is configured to apply a disturbance to active power control of the grid-forming converter and obtain a corresponding power angle change to form a power angle difference; ); wherein p ref is the active power reference; Applying power disturbance - Δ to active power control p and ensuring the system transient stability at this time, obtaining the output power angle variation - Δ A stability boundary calculation module is configured to fit a power angle curve based on the power angle difference, an active power reference, a reactive power reference, and a disturbance amount applied by the active power, and determine a transient stability transmission boundary of the reactive power or the active power under the current active power or reactive power reference condition according to the power angle curve; based on the transient stability transmission boundary, the current transient stability of the grid-forming converter is determined; 2; According to the acquired -Δ p , -Δ When the reactive power reference is fixed and the reactive power reference is greater than a set value, a maximum active power transmission value under the condition of ensuring the transient stability of the system is calculated; 2 is calculated A cos(2 The method further comprises a power calculation module, a reactive power control module, and a voltage control module, wherein: ), and let c 2= A cos(2 The power calculation module is configured to generate a virtual signal orthogonal to an input signal through a second-order generalized integrator, establish a two-phase stationary coordinate system according to the virtual signal, realize power calculation of a single-phase converter, and provide dq components of a converter capacitor voltage for the voltage control module through dq transformation; ); ； The average of the two results is taken for the power angle curve fitting, and let c be the average of the two results, c = ( c 1+ c 2) / 2; based on c and the active power reference signal, calculating a fitted curve amplitude A , ; According to the amplitude of the fitted curve A and the power angle relationship p g = A sin(2 The reactive power control module is configured to realize zero-static error tracking of an actual reactive power on a reactive power reference through PI control, input the reactive power reference value and the actual value, and output a d-axis voltage reference value to provide input for the voltage control module; ) to draw a fitted power angle curve p g The voltage control module is configured to realize zero-static error tracking of an actual output voltage of the converter on a voltage reference through PI control, and perform PI control on the d-axis and the q-axis respectively, wherein the output of the reactive power control module is used as the d-axis reference, 0 is used as the q-axis reference, the dq components of the actual capacitor voltage of the converter are used as feedback, and the reference value of the capacitor voltage of the converter in the dq coordinate system is output to be used for PWM modulation after inverse transformation. ; The stability boundary calculation module is designed based on the transient stability mechanism of the converter when the reactive power control strategy is PI control and the active control strategy is droop control. When the active power reference is fixed, let Δ p be zero, the minimum reactive power transmission value is calculated to ensure the transient stability of the system under this condition.

2. The method of claim 1, wherein the method further comprises: ​ 3. The method of claim 1, wherein the method further comprises: ​ 4. The method of claim 1, wherein the method further comprises: Maximum active power transfer value p max is: ； where A is the amplitude of the fitted curve, q ref is the reactive power reference; Minimum reactive power transfer value q min : ； where p ref is the active power reference.

5. A power-perturbation-based network configuration type converter transient stability assessment system, characterized in that, ​ ​ ​ The stable boundary calculation module is configured to impose a power disturbance Δ on the active power control based on an active power reference signal p and ensure that the system is transiently stable at this time, and obtain a power angle change amount Δ of the active power control output ​ 1; according to the obtained Δ p , Δ ​ 1 is calculated A cos (2 ​ ), A is an amplitude, ​ is a power angle, and let c 1= A cos (2 ​ ); wherein p ref is the active power reference; Applying power disturbance - Δ to active power control p and ensuring the system transient stability at this time, obtaining the output power angle variation - Δ ​ 2; According to the acquired -Δ p , -Δ ​ 2 is calculated A cos(2 ​ ), and let c 2= A cos(2 ​ ); ； The average of the two results is taken for the power angle curve fitting, and let c be the average of the two results, c = ( c 1+ c 2) / 2; based on c and the active power reference signal, calculating a fitted curve amplitude A , ; According to the amplitude of the fitted curve A and the power angle relationship p g = A sin(2 ​ ) to draw a fitted power angle curve p g ​ ; ​ When the active power reference is fixed, let Δ p be zero, the minimum reactive power transmission value is calculated to ensure the transient stability of the system under this condition.

6. The power-perturbation-based networked transformer transient stability assessment system of claim 5, wherein, ​ ​ ​ ​ 7. The power-perturbation-based networked transformer transient stability assessment system of claim 6, wherein, The active power control module is configured to adjust the active power output of the converter by using droop control. When there is no reactive power disturbance, the input of the active power control module is an active power reference value and an actual value, and the phase reference output provides a phase reference for dq transformation in the power calculation module and dq inverse transformation before PWM modulation. When a power disturbance is applied, the power angle output by the active power control module changes by a corresponding change Δ ​ , i.e., there is a power angle difference between the output power angle after the disturbance and the original power angle. The active power reference of the active power control module, the disturbance amount, and the power angle difference output after the disturbance are used as inputs of the stable boundary calculation module.

8. The power-perturbation-based networked transformer transient stability assessment system of claim 5, wherein, ​

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