Transient stability limit evaluation method and system for new energy through flexible direct transmission system

Abstract

The present disclosure provides a transient stability limit evaluation method and system of a new energy through flexible direct transmission system, relates to the technical field of transient stability quantitative evaluation of a new energy power system, and comprises the following steps: establishing a transient linearization model of new energy, flexible direct transmission and multiple devices, and a nonlinear model of the system; constructing a system state matrix according to the linearization model, screening a type one balance point through the state matrix, and calculating a first-order parameter matrix of a hyperplane of each target type one balance point; calculating a Hessian matrix according to the nonlinear model, and calculating a second-order parameter matrix of the hyperplane of each target type one balance point by using the Hessian matrix; constructing a corresponding hyperplane equation according to the first-order parameter matrix and the second-order parameter matrix, determining the intersection point of a trajectory and the hyperplane in combination with a fault trajectory, calculating a fault limit cutting time, and evaluating the transient stability margin of the system. The present disclosure can accurately calculate the fault cutting time of the system under different types of faults, and accurately evaluate the transient stability of the new energy through flexible direct transmission system.

Description

Technical Field

[0001] This disclosure relates to the field of transient stability quantitative evaluation technology for new energy power systems, specifically to a transient stability limit evaluation method and system for new energy systems transmitted via flexible direct transmission. Background Technology

[0002] The statements in this section are merely background information relating to this disclosure and do not necessarily constitute prior art.

[0003] Under the current trend of vigorously promoting clean energy power generation such as hydropower, photovoltaic, and wind power, the construction of integrated clean energy power generation bases combining hydropower, photovoltaic, and wind power is an important measure in the energy and power sector. With the rapid growth of new energy sources represented by wind power and photovoltaics, the penetration rate of new energy in the power grid is constantly increasing. Since large-scale new energy bases are far from load centers, developing ultra-high voltage (UHV) long-distance power transmission technology is a strategic choice for power development to meet the urgent need for long-distance power transmission from these bases. Among these technologies, flexible direct current (DC) transmission systems have significant advantages in areas such as power grid interconnection and large-capacity long-distance transmission. Large-scale new energy transmission via flexible DC will be the main technical solution adopted for new energy bases in remote areas and desert regions. However, large-scale new energy transmission via flexible DC has a high penetration rate of power electronic equipment, strong interaction, and small transient stability margin, making it prone to transient instability accidents, which seriously threaten the safe operation of the sending-end power grid and the reliable consumption of new energy.

[0004] Currently, various methods have been used to analyze the transient stability of single-new-energy grid-connected systems, such as EAC analysis, Lyapunov function method, energy function method, sum of squares (SOS) estimation method, phase diagram analysis, and bifurcation analysis. However, due to the significant difference between the dynamic characteristics of new-energy power electronic equipment and synchronous machines, the energy function construction method based on the mathematical equations and dynamic characteristics of synchronous machines is difficult to apply. Therefore, directly applying existing synchronous machine-based analysis methods to the transient stability evaluation of systems with multiple power electronic equipment presents a significant challenge. On the other hand, some studies have proposed transient stability analysis and evaluation methods based on artificial intelligence and numerical simulation. However, compared to theoretical analysis methods, numerical simulation methods are time-consuming and cannot provide operators with relevant indicators such as transient stability margin. Therefore, the transient stability evaluation methods for new energy systems with multiple power electronic equipment via flexible direct current transmission remain incomplete. Summary of the Invention

[0005] To address the aforementioned issues, this disclosure proposes a transient stability limit evaluation method and system for new energy transmission via flexible direct current transmission systems. Based on second-order estimation, it achieves quantitative evaluation of the transient stability of new energy transmission via flexible direct current transmission systems. Simultaneously, considering the conditions of new energy and flexible direct current equipment, it quantitatively calculates the limit cut-off time to ensure system stability after a transient large disturbance fault occurs, guiding the parameter settings of control and protection devices for large-scale new energy base transmission via flexible direct current transmission systems.

[0006] According to some embodiments, the present disclosure adopts the following technical solutions:

[0007] The transient stability limit evaluation method for new energy transmission systems via flexible direct power transmission includes:

[0008] Obtain the primary wiring topology of the new energy transmission system via flexible direct current transmission, and establish a linearized model of transient order reduction for new energy equipment, a linearized model of transient order reduction for multiple flexible direct current transmission devices, and a nonlinear model of the new energy transmission system via flexible direct current transmission based on the primary wiring topology.

[0009] The system state matrix is ​​constructed based on the linearized model. A set of type I equilibrium points is initially determined based on the nonlinearized model. The target type I equilibrium points are selected from the set of type I equilibrium points using the system state matrix, and the first-order parameter matrix of the hypertangent surface of each target type I equilibrium point is calculated.

[0010] The Hessian matrix is ​​calculated based on the nonlinear model, and the second-order parameter matrix of the hypertangent surface of the equilibrium point of each target is calculated using the Hessian matrix.

[0011] Construct the corresponding hypertangent equation based on the first-order and second-order parameter matrices. Construct the corresponding hypertangent equation based on the fault trajectory and the first-order and second-order parameter matrices. Determine the intersection point between the fault trajectory and the hypertangent equation. Take the minimum value among all the obtained intersection points as the limit clearance time of the fault.

[0012] According to some embodiments, the present disclosure adopts the following technical solutions:

[0013] The transient stability limit evaluation system for new energy transmission systems includes:

[0014] The model building module is used to obtain the primary wiring topology of the new energy transmission system via flexible direct current transmission, and to establish a transient order reduction linearization model of the new energy equipment, a transient order reduction linearization model of the flexible direct current equipment, and a nonlinearization model of the new energy transmission system via flexible direct current transmission based on the primary wiring topology.

[0015] The first-order parameter determination module is used to construct the system state matrix based on the linearized model, initially determine a set of type I equilibrium points based on the nonlinearized model, filter each target type I equilibrium point from the set of type I equilibrium points through the system state matrix, and calculate the first-order parameter matrix of the hypertangent surface of each target type I equilibrium point.

[0016] The second-order parameter determination module is used to calculate the Hessian matrix based on the nonlinear model, and to calculate the second-order parameter matrix of the hypertangent surface of each target type-I equilibrium point using the Hessian matrix.

[0017] The quantitative evaluation module is used to construct the corresponding hypertangent equation based on the first-order and second-order parameter matrices, construct the corresponding hypertangent equation based on the fault trajectory and the first-order and second-order parameter matrices, determine the intersection point of the fault trajectory and the hypertangent equation, and take the minimum value among all the obtained intersection points as the limit clearance time of the fault.

[0018] According to some embodiments, the present disclosure adopts the following technical solutions:

[0019] A non-transitory computer-readable storage medium is provided for storing computer instructions, which, when executed by a processor, implement the transient stability limit evaluation method of the new energy transmission system via flexible direct transmission.

[0020] According to some embodiments, the present disclosure adopts the following technical solutions:

[0021] An electronic device includes a processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to enable the electronic device to perform the transient stability limit evaluation method for the new energy transmission system via flexible direct transmission.

[0022] Compared with the prior art, the beneficial effects of this disclosure are as follows:

[0023] The transient stability limit evaluation method for new energy transmission systems via flexible direct transmission disclosed herein provides high accuracy in the limit clearing time under various fault conditions. This method is beneficial for the online identification and judgment of transient stability limit conditions of large-scale new energy base transmission systems via flexible direct transmission, timely fault isolation, and prevention of cascading faults. It can also be used to study the influence of factors such as network connection structure, system operating conditions, and controller parameters on the system fault limit clearing time. Overall, it can improve the accuracy of fault limit clearing time calculation and stability evaluation of large-scale new energy base transmission systems via flexible direct transmission.

[0024] The transient stability limit evaluation method for new energy transmission systems disclosed herein uses a simple model, requires low numerical calculation, is applicable to both symmetrical and asymmetrical faults, and is easy to apply to large-scale new energy base transmission systems via flexible direct transmission.

[0025] The transient stability limit evaluation method for new energy systems via flexible direct transmission disclosed herein can accurately calculate the system fault clearing time under different types of faults, realize the quantitative assessment of transient stability, and further study the influence of factors such as network connection structure, system operating conditions, and controller parameters on the system fault limit clearing time. The calculation process is simple, the calculation method is clear, and the calculation results are easy to use, which facilitates the field application of existing large-scale new energy systems via flexible direct transmission. It has significant advantages in the quantitative evaluation of transient stability and the planning and design that takes transient stability into account. Attached Figure Description

[0026] The accompanying drawings, which form part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute an undue limitation of this disclosure.

[0027] Figure 1 This is a flowchart of the transient stability limit evaluation method for a new energy transmission system via flexible direct transmission, according to an embodiment of this disclosure.

[0028] Figure 2 This is a schematic diagram of the network topology of the new energy transmission system via flexible direct transmission according to an embodiment of this disclosure. Detailed Implementation

[0029] The present disclosure will be further described below with reference to the accompanying drawings and embodiments.

[0030] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this disclosure. 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 disclosure pertains.

[0031] 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 exemplary embodiments according to this disclosure. 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.

[0032] Example 1

[0033] One embodiment of this disclosure provides a transient stability limit evaluation method for a new energy system via flexible direct transmission. This method is also a quantitative evaluation method for the transient stability of a new energy system via flexible direct transmission based on second-order estimation. It includes four steps: linear and nonlinear modeling of the system, determination of the first-order equilibrium point and calculation of first-order parameters, calculation of second-order parameters, and determination of the limit cut-off time. Figure 1 As shown, the specific process steps include:

[0034] Step 1: Obtain the primary wiring topology of the new energy transmission system via flexible direct current transmission, and establish a transient linearized model of the new energy and flexible direct current transmission multiple devices, as well as a nonlinear model of the new energy transmission system via flexible direct current transmission, based on the primary wiring topology.

[0035] Step 2: Construct the system state matrix based on the linearized model, initially determine a set of type I equilibrium points based on the nonlinearized model, select target type I equilibrium points from the set of type I equilibrium points through the system state matrix, and calculate the first-order parameter matrix of the hypertangent surface of each target type I equilibrium point.

[0036] Step 3: Calculate the Hessian matrix based on the nonlinear model, and use the Hessian matrix to calculate the second-order parameter matrix of the hypertangent surface of each target's type-I equilibrium point;

[0037] Step 4: Construct the corresponding hypertangent equation based on the first-order and second-order parameter matrices. Determine the intersection point between the fault trajectory and the hypertangent equation. Take the minimum value among all the obtained intersection time points as the limit clearance time, thereby obtaining the limit clearance time of the fault.

[0038] As one embodiment, to accurately determine the transient limit conditions under new energy equipment failure and to facilitate computer implementation and field engineering applications, the specific implementation process of the transient stability limit evaluation method for a new energy system via flexible direct transmission disclosed herein is as follows:

[0039] Step 1: Establish linearized and nonlinear models of the system

[0040] Specifically, by acquiring basic data such as controller parameters and system operating conditions of new energy and flexible DC equipment, a transient order-reduced nonlinear model (nonlinear equation) and a linear model (linearized state equation) for new energy and flexible DC equipment are established.

[0041] by Figure 2 Taking the system shown as an example, the sending-end system connects the new energy source to the main power grid, and simultaneously transmits part of the power through flexible DC transmission equipment. Here, the new energy source and the flexible DC transmission are nodes, described using nonlinear / linear differential equations; the power transmission lines are a network, described using algebraic equations (admittance matrix or impedance matrix).

[0042] Furthermore, when establishing the transient order reduction linearization model for new energy equipment, only the phase-locked loop (PLL) dynamics are considered. The new energy equipment exhibits current source characteristics externally. The transient order reduction linearization model for the new energy equipment consists of differential equations and input / output interface equations, namely:

[0043]

[0044] The first sub-equation in the above equation is the input equation, where u is the input variable of the new energy node. tq The terminal voltage U is determined by the network topology. t The imaginary part is denoted by Im(), which represents taking the real part. The differential equation represents the dynamics of the PLL. x pll k represents the PLL angle and the integrator variable, respectively. p,pll ,k i,pll For the PI controller parameters of the PLL; i dref i qref These represent the reference values ​​for the d-axis and q-axis currents of new energy equipment, respectively. The angle representing the reference values ​​of the d-axis and q-axis currents is equal to arctan(i qref / i dref ). j is the imaginary unit. The fourth sub-formula is the output equation representing the characteristics of the controlled current source in the new energy equipment. Simultaneously, the linearized model of the new energy equipment can be obtained as follows:

[0045]

[0046] Furthermore, when establishing the transient order reduction linearization model of the flexible DC-DC equipment, only the virtual synchronous control loop is considered. The flexible DC-DC equipment exhibits voltage source characteristics externally. The transient order reduction linearization model of the flexible DC-DC equipment consists of differential equations and input / output interface equations, specifically:

[0047]

[0048] The first small formula is the input equation, where the input variable of the flexible straight node is the electromagnetic power P. e Re() indicates taking the real part. State variables δ and ω represent the angle and frequency of the virtual synchronous generator (VSG) control, J and D are the inertia and damping control parameters of the VSG control, and P... e For input electromagnetic power, P ref The power reference value is for VSG control. The fourth formula is the output equation, where the amplitude of the output voltage E of the flexible DC device is the given voltage reference value E. ref The phase δ is determined by VSG control. e is the natural constant, ejθ This represents a complex number with an amplitude of 1 and an angle of θ. Simultaneously, the linearized model of the flexible straight-line device can be obtained as follows:

[0049]

[0050] The system state matrix is ​​constructed based on the linearization model, which includes: combining the linearization model of transient order reduction of new energy equipment, the linearization model of transient order reduction of flexible DC equipment, and the network equation (algebraic equation of transmission line) to obtain the system state matrix.

[0051] A nonlinear model of the renewable energy transmission system via flexible DC power transmission is established based on the primary wiring topology. This includes establishing the nonlinear models of the renewable energy equipment and the flexible DC power transmission equipment, as well as the network equations, to obtain the nonlinear model of the renewable energy transmission system via flexible DC power transmission. The nonlinear equations of the nodes (flexible DC power transmission equipment and renewable energy equipment) and the algebraic equations of the network (power transmission lines) constitute the nonlinear equations of the system; the linear equations of the nodes (flexible DC power transmission equipment and renewable energy equipment) and the algebraic equations of the network (power transmission lines) constitute the linear model of the system.

[0052] Step 2: Determining the equilibrium point and calculating the first-order parameter matrix;

[0053] Specifically, a set of type-1 equilibrium points is initially determined based on the nonlinear equations, including:

[0054] Based on the nonlinear model, a set of type I equilibrium points is initially determined, including: according to the definition that a type I equilibrium point has only one unstable characteristic root, the unstable characteristic root of the nonlinear model is initially calculated and used as the type I equilibrium point.

[0055] Then, according to the definition of a Type I equilibrium point (i.e., having only one unstable eigenvalue), target Type I equilibrium points are selected from a set of Type I equilibrium points using the system state matrix, and the first-order parameter matrix of the hypertangent surface of each target Type I equilibrium point is calculated. This includes: selecting the initially obtained Type I equilibrium points using the system state matrix; calculating eigenvalues ​​from the initially determined Type I equilibrium points based on the system state matrix to determine the target Type I equilibrium point; and calculating the left eigenvectors corresponding to the unstable eigenvalues ​​of the Type I equilibrium point to obtain the first-order parameter matrix of the hypertangent surface equation.

[0056] Specifically, the obtained system state matrix is ​​used to screen the initially determined Type I equilibrium points. From the initially determined Type I equilibrium points, those that meet the definition are selected (by calculating eigenvalues ​​based on the aforementioned system state matrix) to determine the target Type I equilibrium point. Simultaneously, the left eigenvector corresponding to the unstable eigenvalue of the Type I equilibrium point is calculated to obtain the first-order parameter matrix K of the hypertangent. i ,Right now:

[0057]

[0058] Among them, y i T Let be the left eigenvector corresponding to the unstable eigenvalue of the i-th type I equilibrium point.

[0059] Step 3: Calculation of the second-order parameter matrix

[0060] Specifically, based on the system's nonlinear equations and the definition of the Hessian matrix (i.e., a square matrix composed of the second-order partial derivatives of a multivariable function), the calculated Hessian matrix H... i for:

[0061]

[0062] Using the Hessian matrix, the second-order parameter matrix of the hypertangent surface at the equilibrium point of each target satisfies:

[0063]

[0064] in, The symbol V represents the Kronecker tensor product. c For column stack mapping operations of the matrix, I is the inverse operation of the column stack mapping operation of a matrix. n Represents an n-dimensional identity matrix. Coefficient matrices C and H are intermediate calculation matrices, respectively. J is the system state matrix. H i Let y be the Hessian matrix. i Let μ be the left eigenvector corresponding to the unstable eigenvalue of the i-th type I equilibrium point, and μ be the value of the corresponding unstable eigenvalue.

[0065] Step 4: Determine the optimal resection time;

[0066] Specifically, based on the first-order and second-order parameter matrices of the hypertangent, the hypertangent equation F corresponding to the i-th type I equilibrium point is... i (x) can be represented as:

[0067]

[0068] Where x is the state variable fault trajectory, x u,i Let y be the i-th type I equilibrium point, which is a row vector. i T It is the transpose of the left eigenvector corresponding to the unstable eigenvalue of the i-th type I equilibrium point.

[0069] Simultaneously, based on the fault trajectory, the first-order parameter matrix, and the second-order parameter matrix, the corresponding hypertangent equation is constructed, and the intersection point of the fault trajectory and the hypertangent equation is determined, including: substituting the fault trajectory into any hypertangent equation, when the function F of the hypertangent equation... iWhen the sign of the value changes, the fault trajectory is considered to have crossed this hypertangent plane, i.e., satisfying:

[0070]

[0071] Among them, t i Let be the time corresponding to the intersection of the i-th target type-I equilibrium point and the fault trajectory in the hypercut surface equation, and Δt be the time step of the fault trajectory. Therefore, the minimum value among the times corresponding to all obtained intersection points is taken as the limit cut-off time, which satisfies:

[0072] t c =min(t1,t2,...,t) i )

[0073] Among them, t c The final determined fault clearing time, t, is used as one of the evaluation metrics for system stability to assess the margin of system transient stability. c The larger the value of t, the better the stability and the greater the stability margin. c The smaller the value, the worse the system stability and the smaller the stability margin.

[0074] Simulation Experiment

[0075] This disclosure uses equivalent grid voltage dips, three-phase short-circuit faults, and two-phase short-circuit faults to test the effectiveness of the method described herein. The accuracy of the method is verified by comparing the limit clearing time / angle calculated using the method with the time-domain simulation results. Taking a voltage dip fault as an example, when the bus voltage drops from 1.0 pu to 0.68 pu and then recovers to 1.0 pu, the fault limit clearing time obtained from numerical simulation is 0.157 s. The limit clearing time obtained using the overcutting plane method considering only the first-order linear term is 0.161 s, with a relative error of 2.55%. The limit clearing time obtained using the method described herein, which considers second-order coefficients, is 0.158 s, with a relative error of 1.27%. When a three-phase short-circuit fault occurs at the common connection point of the system, the fault clearance time obtained from numerical simulation is 0.070 s. The clearance time obtained using the overtangent plane method considering only the first-order linear term is 0.074 s, with a relative error of 5.71%. The clearance time obtained using the method described in this disclosure, which considers the second-order coefficients, is 0.073 s, with a relative error of 4.29%. For other faults, the method described in this disclosure and the simulation calculation results are shown in Tables 1 and 2. The calculation results show that the method described in this disclosure can obtain relatively accurate results under different fault types.

[0076] Table 1 Comparison of ultimate cutoff times obtained by different methods during voltage drop.

[0077]

[0078] Table 2 Comparison of ultimate clearing times obtained by different methods under short-circuit faults.

[0079]

[0080] In summary, the method disclosed herein can accurately calculate the system fault clearing time under different types of faults, achieving a quantitative assessment of transient stability. Furthermore, it allows for further research into the impact of factors such as network connection structure, system operating conditions, and controller parameters on the system fault clearance time. The calculation process described in this invention is simple, the calculation method is clear, and the calculation results are easy to use, facilitating field applications in existing large-scale new energy transmission systems via flexible direct transmission. It has significant advantages in both quantitative evaluation of transient stability and planning and design considering transient stability. This invention also provides a method for quantitative evaluation of the transient stability of new energy transmission systems via flexible direct transmission based on second-order estimation, which is used to implement the aforementioned method for assessing the transient fault clearance time of new energy transmission systems via flexible direct transmission.

[0081] Example 2

[0082] One embodiment of this disclosure provides a transient stability limit evaluation system for a new energy transmission system via flexible direct transmission, comprising:

[0083] The model building module is used to obtain the primary wiring topology of the new energy transmission system via flexible direct current transmission, and to establish a transient order reduction linearization model of the new energy equipment, a transient order reduction linearization model of the flexible direct current equipment, and a nonlinearization model of the new energy transmission system via flexible direct current transmission based on the primary wiring topology.

[0084] The first-order parameter determination module is used to construct the system state matrix based on the linearized model, initially determine a set of type I equilibrium points based on the nonlinearized model, select each target type I equilibrium point from the set of type I equilibrium points through the system state matrix, and calculate the first-order parameter matrix of the hypertangent surface of each target type I equilibrium point.

[0085] The second-order parameter determination module is used to calculate the Hessian matrix based on the nonlinear model, and to calculate the second-order parameter matrix of the hypertangent surface of each target type-I equilibrium point using the Hessian matrix.

[0086] The quantitative evaluation module is used to construct the corresponding hypertangent equation based on the first-order and second-order parameter matrices, construct the corresponding hypertangent equation based on the fault trajectory and the first-order and second-order parameter matrices, determine the intersection point of the fault trajectory and the hypertangent equation, and take the minimum value among all the obtained intersection points as the limit clearance time of the fault.

[0087] Example 3

[0088] One embodiment of this disclosure provides a non-transitory computer-readable storage medium for storing computer instructions. When the computer instructions are executed by a processor, they implement the transient stability limit evaluation method of the new energy transmission system via flexible direct transmission.

[0089] Example 4

[0090] One embodiment of this disclosure provides an electronic device, including a processor, a memory, and a computer program; wherein the processor is connected to the memory, and the computer program is stored in the memory. When the electronic device is running, the processor executes the computer program stored in the memory to enable the electronic device to perform the transient stability limit evaluation method for the new energy transmission system via flexible direct transmission.

[0091] This disclosure is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this disclosure. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine 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.

[0092] 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.

[0093] While the specific embodiments of this disclosure have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of this disclosure. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of this disclosure are still within the scope of protection of this disclosure.

Claims

1. A transient stability limit evaluation method for a new energy transmission system via flexible direct power transmission, characterized in that, include: Obtain the primary wiring topology of the new energy transmission system via flexible direct current transmission, and establish a linearized model of transient order reduction for the new energy equipment, a linearized model of transient order reduction for the flexible direct current equipment, and a nonlinear model of the new energy transmission system via flexible direct current transmission based on the primary wiring topology. The system state matrix is ​​constructed based on the linearized model. A set of type I equilibrium points is initially determined based on the nonlinearized model. The target type I equilibrium points are selected from the set of type I equilibrium points using the system state matrix, and the first-order parameter matrix of the hypertangent surface of each target type I equilibrium point is calculated. The Hessian matrix is ​​calculated based on the nonlinear model, and the second-order parameter matrix of the hypertangent surface of the equilibrium point of each target is calculated using the Hessian matrix. Using the Hessian matrix, the second-order parameter matrix of the hypertangent surface at the equilibrium point of each target satisfies: Where Q is a second-order parameter matrix, The symbol V represents the Kronecker tensor product. c Vc represents the column stack mapping operation of a matrix, and V-1 is the inverse operation of the column stack mapping operation of a matrix. n represent n The system is a 3D identity matrix, with coefficient matrices C and H being intermediate calculation matrices, J being the system state matrix, and H... i For Hessian matrix, y i For the first i The left eigenvectors corresponding to the non-stable eigenvalues ​​of each objective type-1 equilibrium point. μ The value of the corresponding unstable eigenvalue; Construct the corresponding hypertangent equation based on the first-order and second-order parameter matrices. Construct the corresponding hypertangent equation based on the fault trajectory and the first-order and second-order parameter matrices. Determine the intersection point between the fault trajectory and the hypertangent equation. Take the minimum value among all the obtained intersection points as the limit clearance time of the fault.

2. The transient stability limit evaluation method for a new energy transmission system via flexible direct transmission as described in claim 1, characterized in that, A transient order reduction linearization model for multiple new energy and flexible DC power devices is established based on a primary wiring topology. This includes: acquiring all basic data on the controller parameters and system operating conditions of the new energy and flexible DC power devices, and establishing transient order reduction linearization models for the new energy and flexible DC power devices based on the acquired basic data. Specifically, when establishing the transient order reduction linearization model for the new energy devices, only the phase-locked loop dynamics are considered, exhibiting current source characteristics externally. The transient order reduction linearization model for the new energy devices consists of differential equations and input / output interface equations. Similarly, when establishing the transient order reduction linearization model for the flexible DC power devices, only the virtual synchronous control loop is considered, exhibiting voltage source characteristics externally. The transient order reduction linearization model for the flexible DC power devices consists of differential equations and input / output interface equations.

3. The transient stability limit evaluation method for a new energy transmission system via flexible direct transmission as described in claim 1, characterized in that, The system state matrix is ​​constructed based on the linearization model, including: combining the linearization model of transient order reduction of new energy equipment, the linearization model of transient order reduction of flexible DC equipment, and the network equations to obtain the system state matrix.

4. The transient stability limit evaluation method for a new energy transmission system via flexible direct transmission as described in claim 1, characterized in that, The nonlinear model of the new energy transmission system via flexible direct current includes: establishing a nonlinear model of the new energy transmission system via flexible direct current based on the primary wiring topology, including: combining the nonlinear models of the new energy equipment, the flexible direct current equipment, and the network equations to obtain the nonlinear model of the new energy transmission system via flexible direct current.

5. The transient stability limit evaluation method for a new energy transmission system via flexible direct transmission as described in claim 1, characterized in that, Based on the nonlinear model, a set of type I equilibrium points is initially determined, including: according to the definition that a type I equilibrium point has only one unstable eigenvalue, the unstable eigenvalue of the nonlinear model is initially calculated, and the calculated unstable eigenvalue of the nonlinear model is taken as the type I equilibrium point.

6. The transient stability limit evaluation method for a new energy transmission system via flexible direct transmission as described in claim 4, characterized in that, The process involves selecting target Type I equilibrium points from a set of Type I equilibrium points using the system state matrix, and calculating the first-order parameter matrix of the hypertangent surface of each target Type I equilibrium point. This includes: selecting the initially determined Type I equilibrium points from the preliminary selection using the system state matrix; calculating eigenvalues ​​based on the system state matrix to determine the target Type I equilibrium points; calculating the left eigenvectors corresponding to the unstable eigenvalues ​​of the target Type I equilibrium points; and using the left eigenvectors corresponding to the unstable eigenvalues ​​of each target Type I equilibrium point as the first-order parameter matrix of the hypertangent surface equation of each target Type I equilibrium point.

7. The transient stability limit evaluation method for a new energy transmission system via flexible direct transmission as described in claim 1, characterized in that, Based on the first-order and second-order parameter matrices, the corresponding hypertangent equation is constructed as follows: Where x is the state variable fault trajectory, x u,i For the first i One target is a type-I equilibrium point; Q is a second-order parameter matrix; F i (x) is the equation of the hypertangent surface. y i For the first i The transpose of the left eigenvectors corresponding to the non-stable eigenvalues ​​of a target type-I equilibrium point.

8. The transient stability limit evaluation method for a new energy transmission system via flexible direct transmission as described in claim 7, characterized in that, Construct the corresponding hypertangent equation based on the fault trajectory, first-order parameter matrix, and second-order parameter matrix. Determine the intersection point between the fault trajectory and the hypertangent equation, including: substituting the fault trajectory into any hypertangent equation; when the function of the hypertangent equation... F i When the sign of the value changes, the fault trajectory is considered to have crossed this hypertangent plane, i.e., satisfying: in, t i The first in the hyper-tangent equation i The time corresponding to the intersection of the target type-1 equilibrium point and the fault trajectory, Δ t Let be the time step of the fault trajectory. Therefore, the minimum value among the times corresponding to all the obtained intersection points is taken as the limit removal time, which satisfies: in, t c This represents the fault clearance limit time.

9. A transient stability limit evaluation system for a new energy transmission system via flexible direct transmission, characterized in that, include: The model building module is used to obtain the primary wiring topology of the new energy transmission system via flexible direct current transmission, and to establish a transient order reduction linearization model of the new energy equipment, a transient order reduction linearization model of the flexible direct current equipment, and a nonlinearization model of the new energy transmission system via flexible direct current transmission based on the primary wiring topology. The first-order parameter determination module is used to construct the system state matrix based on the linearized model, initially determine a set of type I equilibrium points based on the nonlinearized model, select each target type I equilibrium point from the set of type I equilibrium points through the system state matrix, and calculate the first-order parameter matrix of the hypertangent surface of each target type I equilibrium point. The second-order parameter determination module is used to calculate the Hessian matrix based on the nonlinear model, and to calculate the second-order parameter matrix of the hypertangent surface of each target type-I equilibrium point using the Hessian matrix. In the second-order parameter determination module, the second-order parameter matrix of the hypertangent surface of each target's type-I equilibrium point is calculated using the Hessian matrix, satisfying the following: Where Q is a second-order parameter matrix, The symbol V represents the Kronecker tensor product. c Vc represents the column stack mapping operation of a matrix, and V-1 is the inverse operation of the column stack mapping operation of a matrix. n represent n The system is a 3D identity matrix, with coefficient matrices C and H being intermediate calculation matrices, J being the system state matrix, and H... i For Hessian matrix, y i For the first i The left eigenvectors corresponding to the non-stable eigenvalues ​​of each objective type-1 equilibrium point. μ The value of the corresponding unstable eigenvalue; The quantitative evaluation module is used to construct the corresponding hypertangent equation based on the first-order and second-order parameter matrices, construct the corresponding hypertangent equation based on the fault trajectory and the first-order and second-order parameter matrices, determine the intersection point of the fault trajectory and the hypertangent equation, and take the minimum value among all the obtained intersection points as the limit clearance time of the fault.

10. The transient stability limit evaluation system for a new energy transmission system via flexible direct transmission as described in claim 9, characterized in that, In the model construction module, a transient order reduction linearization model for multiple new energy and flexible DC power devices is established based on the primary wiring topology. This includes: the primary wiring topology being all basic data on the controller parameters of the new energy and flexible DC power devices and the system operating conditions; acquiring all basic data on the controller parameters of the new energy and flexible DC power devices and the system operating conditions; and establishing transient order reduction linearization models for the new energy and flexible DC power devices based on the acquired basic data. Specifically, when establishing the transient order reduction linearization model for the new energy devices, only the phase-locked loop dynamics are considered, exhibiting current source characteristics externally. The transient order reduction linearization model for the new energy devices consists of differential equations and input / output interface equations. When establishing the transient order reduction linearization model for the flexible DC power devices, only the virtual synchronous control loop is considered, exhibiting voltage source characteristics externally. The transient order reduction linearization model for the flexible DC power devices consists of differential equations and input / output interface equations.

11. The transient stability limit evaluation system for a new energy transmission system via flexible direct transmission as described in claim 10, characterized in that, The nonlinear model of the new energy transmission system via flexible direct current includes: establishing a nonlinear model of the new energy transmission system via flexible direct current based on the primary wiring topology, including: combining the nonlinear models of the new energy equipment, the flexible direct current equipment, and the network equations to obtain the nonlinear model of the new energy transmission system via flexible direct current.

12. The transient stability limit evaluation system for a new energy transmission system via flexible direct transmission as described in claim 9, characterized in that, In the first-order parameter determination module, a set of type I equilibrium points is initially determined based on the nonlinear model, including: according to the definition that a type I equilibrium point has only one unstable eigenvalue, the unstable eigenvalue of the nonlinear model is initially calculated, and the calculated unstable eigenvalue of the nonlinear model is used as the type I equilibrium point.

13. The transient stability limit evaluation system for a new energy transmission system via flexible direct transmission as described in claim 12, characterized in that, The process involves selecting target Type I equilibrium points from a set of Type I equilibrium points using the system state matrix, and calculating the first-order parameter matrix of the hypertangent surface of each target Type I equilibrium point. This includes: selecting the initially determined Type I equilibrium points using the system state matrix; calculating eigenvalues ​​based on the system state matrix to determine the target Type I equilibrium points; calculating the left eigenvectors corresponding to the unstable eigenvalues ​​of each target Type I equilibrium point; and using the left eigenvectors corresponding to the unstable eigenvalues ​​of each target Type I equilibrium point as the first-order parameter matrix of the hypertangent surface equation of each target Type I equilibrium point.

14. The transient stability limit evaluation system for a new energy transmission system via flexible direct transmission as described in claim 9, characterized in that, In the quantitative evaluation module, the corresponding hypertangent equation is constructed based on the first-order parameter matrix and the second-order parameter matrix as follows: Where x is the state variable fault trajectory, x u,i For the first i One target is a type-I equilibrium point; Q is a second-order parameter matrix; F i (x) is the equation of the hypertangent surface. y i For the first i The transpose of the left eigenvectors corresponding to the non-stable eigenvalues ​​of a target type-I equilibrium point.

15. The transient stability limit evaluation system for a new energy transmission system via flexible direct transmission as described in claim 14, characterized in that, Construct the corresponding hypertangent equation based on the fault trajectory, first-order parameter matrix, and second-order parameter matrix. Determine the intersection point between the fault trajectory and the hypertangent equation, including: substituting the fault trajectory into any hypertangent equation; when the function of the hypertangent equation... F i When the sign of the value changes, the fault trajectory is considered to have crossed this hypertangent plane, i.e., satisfying: in, t i The first in the hyper-tangent equation i The time corresponding to the intersection of the target type-1 equilibrium point and the fault trajectory, Δ t Let be the time step of the fault trajectory. Therefore, the minimum value among the times corresponding to all the obtained intersection points is taken as the limit removal time, which satisfies: in, t c This represents the fault clearance limit time.

16. A non-transitory computer-readable storage medium, characterized in that, The non-transitory computer-readable storage medium is used to store computer instructions, which, when executed by a processor, implement the transient stability limit evaluation method for a new energy system via flexible direct transmission as described in any one of claims 1-8.

17. An electronic device, characterized in that, include: The device includes a processor, a memory, and a computer program; wherein the processor is connected to the memory, and the computer program is stored in the memory. When the electronic device is running, the processor executes the computer program stored in the memory to enable the electronic device to perform the transient stability limit evaluation method for the new energy flexible direct transmission system as described in any one of claims 1-8.

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