New energy and nuclear power transmission limit evaluation method and system through extra-high voltage power transmission

Abstract

The present application belongs to the technical field of power system, and particularly relates to a new energy and nuclear power transmission limit evaluation method and system through extra-high voltage power transmission. The method comprises the following steps: simulating and constructing a provincial power grid example; constructing a set of provincial power grid operation modes with different transmission power values, and identifying a set of key transmission section lines; constructing an instability scenario and performing time-domain simulation, and determining an instability generator group according to the clustering of the synchronous machine rotor angle curve in the simulation results; setting a blocking fault for a direct current simulating the transmission power from the outside to the provincial power grid, constructing a first set of expected fault scenarios, and estimating the new energy and nuclear power transmission limit through extra-high voltage power transmission considering the static stability constraint; simulating a short-circuit fault of the extra-high voltage line in the key transmission section, constructing a second set of expected fault scenarios, and estimating the new energy and nuclear power transmission limit through extra-high voltage power transmission considering the transient stability constraint. The present application establishes a double-constraint comprehensive evaluation system of static stability constraint and transient stability constraint, and the evaluation conclusion is more comprehensive and reliable.

Description

Technical Field

[0001] This invention belongs to the field of power system technology, and in particular relates to a method and system for assessing the limits of new energy and nuclear power transmission via ultra-high voltage transmission. Background Technology

[0002] Ultra-high voltage (UHV) AC transmission technology has significant advantages in ensuring the efficient absorption of large-scale new energy and nuclear power. However, with the integration of high proportions of renewable energy and power electronic equipment, the stability mechanism of the power system has undergone profound changes, and safety and stability characteristics such as power angle and frequency have changed significantly. The assessment of the transmission limits of UHV AC faces unprecedented challenges.

[0003] In the complex scenario of transmitting new energy and nuclear power via ultra-high voltage (UHV) AC transmission, the transmission limit is no longer solely constrained by the thermal stability capacity of the line or the traditional static voltage stability boundary. Instead, it is subject to both static and transient stability constraints, with a strong nonlinear coupling between the two. Existing research on the transmission limits of new energy and nuclear power via UHV transmission only considers static or transient stability constraints, resulting in incomplete conclusions. Furthermore, there is a lack of in-depth research on comprehensive quantitative analysis methods for transmission limits, particularly in the comprehensive assessment of the impact of the diversity and complexity of the dynamic behavior of new energy units on system stability. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a method and system for assessing the limits of new energy and nuclear power transmission via ultra-high voltage. It considers static and transient stability constraints and establishes a comprehensive assessment system with dual constraints of static and transient stability constraints, overcoming the limitation of the prior art that only considers a single constraint, and the assessment conclusions are more comprehensive and reliable.

[0005] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: The first aspect of this invention provides a method for assessing the transmission limits of new energy sources and nuclear power via ultra-high voltage transmission.

[0006] The method for assessing the transmission limits of new energy and nuclear power via ultra-high voltage transmission includes the following steps: Simulation constructs a provincial power grid example that includes both sending-end and receiving-end power grids for the transmission of new energy and nuclear power. Construct a set of provincial power grid operation modes with different power output values, disable AC lines in the provincial power grid one by one, and identify the set of key transmission section lines. By combining the key transmission section line set, an instability scenario is constructed and time-domain simulation is performed. The instability group is determined based on the clustering of the synchronous machine rotor angle curve in the simulation results. By simulating the DC setting blocking fault for power transmission from the outside to the provincial power grid, a first set of expected fault scenarios is constructed. Based on whether there are instability scenarios in the first set of expected fault scenarios, the transmission limit of new energy and nuclear power UHV transmission considering static stability constraints is estimated. By simulating short-circuit faults in key transmission sections of ultra-high voltage lines, a second set of anticipated fault scenarios is constructed. Based on whether there are instability scenarios in the second set of anticipated fault scenarios, the transmission limits of new energy and nuclear power ultra-high voltage lines considering transient stability constraints are estimated.

[0007] The second aspect of this invention provides a limit assessment system for the transmission of new energy and nuclear power via ultra-high voltage power transmission.

[0008] A limit assessment system for transmitting new energy and nuclear power via ultra-high voltage transmission includes: The power grid simulation module is configured to: simulate and construct a provincial power grid simulation involving the transmission of new energy and nuclear power, including both sending-end and receiving-end power grids; The operation mode construction and section search module is configured to: construct a set of provincial power grid operation modes with different power output values, disable AC lines in the provincial power grid one by one, and identify the set of key transmission section lines; The instability scenario construction and cluster determination module is configured to: construct instability scenarios and perform time-domain simulations by combining the set of key transmission section lines, and determine the unstable clusters based on the clustering of the synchronous machine rotor angle curves in the simulation results; The static limit calculation module is configured to: construct a first set of anticipated fault scenarios by simulating a DC blocking fault for power transmission from the outside to the provincial power grid; and estimate the transmission limits of new energy and nuclear power UHV power transmission considering static stability constraints based on whether there are instability scenarios in the first set of anticipated fault scenarios. The transient limit calculation module is configured to: construct a second set of anticipated fault scenarios by simulating short-circuit faults in UHV lines at key transmission sections; and estimate the transmission limits of new energy and nuclear power UHV lines considering transient stability constraints based on whether there are instability scenarios in the second set of anticipated fault scenarios.

[0009] The above one or more technical solutions have the following beneficial effects: This invention provides a method and system for assessing the transmission limits of new energy and nuclear power plants via ultra-high voltage (UHV) transmission. By establishing a comprehensive assessment system with both static and transient stability constraints, it overcomes the limitations of existing technologies that only consider a single constraint, resulting in more comprehensive and reliable assessment conclusions. Specifically, this invention assesses the transmission limits under static stability constraints by simulating DC blocking faults and assesses the transmission limits under transient stability constraints by simulating short-circuit faults on UHV lines. Static and transient instability criteria are established respectively, enabling accurate identification of two different instability modes. Compared to existing technologies that only consider transient stability limits or stability control limits, this invention simultaneously considers static and transient stability constraints, establishing a comprehensive assessment system with both constraints. The assessment results are more comprehensive and accurate, providing a more scientific and reliable basis for power grid planning and operation.

[0010] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0011] 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.

[0012] Figure 1 This is a flowchart of the method in Example 1.

[0013] Figure 2 This is a schematic diagram of the process for identifying provincial power grid zones and key transmission sections in Example 1.

[0014] Figure 3 This is a rotor angle curve of the synchronous machine under the steady-state transmission power of 39.2 million kilowatts in Example 1.

[0015] Figure 4 This is a rotor angle curve of the synchronous machine under the steady-state transmission power of 39.1 million kilowatts in Example 1.

[0016] Figure 5 This is a cross-sectional line power curve diagram under the steady-state transmission power of 39.1 million kilowatts in the first embodiment.

[0017] Figure 6 This is a rotor angle curve of the synchronous machine under the steady-state transmission power of 31.9 million kilowatts in Example 1.

[0018] Figure 7 This is a rotor angle curve of the synchronous machine under the steady-state transmission power of 32 million kilowatts in Example 1. Detailed Implementation

[0019] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration 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.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0021] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0022] Example 1 To address the shortcomings of existing research on the transmission limits of new energy and nuclear power via ultra-high voltage (UHV) power transmission, which fails to simultaneously consider static and transient stability constraints and lacks a comprehensive quantitative analysis method for transmission limits, this invention proposes a method for assessing the transmission limits of new energy and nuclear power via UHV power transmission that considers both static and transient stability constraints. By constructing a provincial power grid example involving large-scale centralized transmission of new energy and nuclear power, and creating corresponding instability scenarios, the method comprehensively considers both static and transient stability constraints to calculate the transmission limits of new energy and nuclear power via UHV power transmission.

[0023] like Figure 1 As shown, the limit assessment method for transmitting new energy and nuclear power via ultra-high voltage transmission includes the following steps: Simulation constructs a provincial power grid example containing both sending-end and receiving-end power grids for the transmission of new energy and nuclear power; Construct a set of provincial power grid operation modes with different power output values, disable AC lines in the provincial power grid one by one, and identify the set of key transmission section lines. By combining the key transmission section line set, an instability scenario is constructed and time-domain simulation is performed. The instability group is determined based on the clustering of the synchronous machine rotor angle curve in the simulation results. By simulating the DC setting blocking fault for power transmission from the outside to the provincial power grid, a first set of expected fault scenarios is constructed. Based on whether there are instability scenarios in the first set of expected fault scenarios, the transmission limit of new energy and nuclear power UHV transmission considering static stability constraints is estimated. By simulating short-circuit faults in key transmission sections of ultra-high voltage lines, a second set of anticipated fault scenarios is constructed. Based on whether there are instability scenarios in the second set of anticipated fault scenarios, the transmission limits of new energy and nuclear power ultra-high voltage lines considering transient stability constraints are estimated.

[0024] The technical solution of this embodiment will be explained in detail below.

[0025] (i) Provincial power grid zoning method including large-scale new energy and nuclear power centralized transmission.

[0026] Using the STEPS (Simulation Toolkit for Electrical Power Systems) power system simulation software package, based on a regional interconnected 10,000-node power grid case, and according to the provincial power grid planning scheme for densely populated areas of new energy and nuclear power, a provincial power grid case involving large-scale centralized transmission of new energy and nuclear power is constructed. The specific steps are as follows: ① In the regional interconnection of 10,000 nodes in the power grid example, the scope of the provincial power grid is determined according to the bus ID, and the regional label is set to 37; according to the provincial power grid planning scheme for densely populated areas of new energy and nuclear power, high-voltage and ultra-high-voltage lines, thermal power and nuclear power units, and new energy units are added to expand the example.

[0027] ② In the extended example, the main nodes with region number 37 (i.e., nodes of 500kV and above in the provincial power grid) are traversed, the main nodes of the sending-end power grid (i.e., the dense area of ​​new energy and nuclear power in the provincial power grid) are located and the region number is set to 1. The remaining main nodes are the main nodes of the receiving-end power grid and the region number is set to 2.

[0028] ③The main node sets of the sending-end and receiving-end power grids within the provincial power grid, respectively. B Based on this, following the search path of "transformer-transmission line-transformer," the area labels for each voltage level node are assigned progressively in descending order of node voltage level. Specifically: (1) Search for connections to the main node b i All transformers T , will be through T Connected to b i All nodes c i Form a set C , c i Set the region label to the primary node b i Corresponding area label; c i The meaning is through a transformer T Connected to b i The i-th node; (2) Using nodes c i Starting from this point, the search links to... c i All transmission lines L c , obtain through L c Connected toc i All nodes d i Form a set D , d i Set the region label as the starting node c i Corresponding area label; d i The meaning is through power transmission lines L c Connect to c i The i-th node; (3) Repeat step (2) twice more to obtain the sets respectively. E , F By performing the same operation on each node and prohibiting the resetting of nodes that have already been assigned area labels, it can be ensured that... c i The area labels of all nodes of the same voltage level can be completely covered and set without exceeding the area boundaries specified in the plan; E The meaning is to d i Starting from the power line, the search finds nodes connected via transmission lines. d i The set of all nodes; F The meaning is the i-th node in set E. e i Starting from the power line, the search finds nodes connected via transmission lines. e i The set of all nodes; (4) The union of the sets obtained in steps (2) and (3) G Nodes in g i Starting from this point, repeat step (1) to ensure that the area labels of all low-voltage level nodes in the area are completely covered. G The meaning is the union of sets E and F obtained in step three.

[0029] It can be understood that in this embodiment, the i in the subscript position represents the index of the i-th node.

[0030] (II) Construction method of provincial power grid operation mode for new energy and nuclear power transmitted via ultra-high voltage transmission.

[0031] In provincial power grids that have been differentiated by regional designation, the capacity of various power sources at both the sending and receiving ends of the power grid is determined. M i With the proportion of output p iPower injected into the power grid from high-voltage direct current sources outside the provincial power grid. P HVDCi The total power emitted within the region was calculated. P total The calculation formula is: (1) Where n source This indicates the total number of various power sources in the sending and receiving power grids; n HVDC This indicates the total amount of high-voltage direct current (HVDC) power injected into the provincial power grid from outside the provincial power grid.

[0032] Given the target power surplus of the sending and receiving end power grids P surplus ,according to P surplus and P total Determine the target total active power load within the region. P L The calculation formula is: (2) Traverse all active loads within the region P Li0 Then sum them up to obtain the current total active power load. P L0 Calculations yielded P L and P L0 The ratio is used to proportionally scale up the active load values ​​of each load model. P Li The calculation formula is: (3) Among them, P Li0 P represents the initial active load of the i-th load model in the sending-end and receiving-end power grids; Li This represents the proportionally scaled-up active load of the i-th load model in the sending and receiving power grids; n load This indicates the total number of load models in the sending and receiving power grids.

[0033] Adjust the operating mode until the power flow calculation converges: Solve the power flow problem, traverse and output the per-unit values ​​of the main nodes and DC landing point voltages of the provincial power grid, and increase reactive power compensation if the voltage is too low. Read the log file output by STEPS to obtain the location where the maximum power imbalance occurs (generally the node where the new energy unit is located and is in the PV-PQ transition state), and add reactive power compensation or parallel reactors according to the reactive power output of the unit.

[0034] Repeat the above steps to ensure that the per-unit voltage values ​​obtained from the main nodes fall within the interval [0.98, 1.02], and minimize the number of units with AC nodes in the PV-PQ transition state, until the power flow solutions converge after two consecutive calculations. This yields the initial operating mode. O C0 Under this operating mode, the power transmitted from the sending-end grid to the receiving-end grid within the provincial power grid is P T = | P surplus |

[0035] The PV-PQ transition state refers to a type of AC node in STEPS power flow calculation. It is an intermediate state in which the AC node changes from PV type to PQ type, and is used to prevent oscillation or divergence in AC power flow iteration due to hard node type switching.

[0036] PV stands for: a type of AC node in power flow calculation, where the given quantities for this type of node are active power and voltage amplitude.

[0037] PQ stands for: A type of AC node in power flow calculation, where the given quantities for this type of node are active power and reactive power.

[0038] Based on the initial running mode O C0 By using Python to call the STEPS interface, we can batch construct provincial power grid operation modes with different power output values, including large-scale centralized transmission of new energy and nuclear power. O Ci This forms a set of operating modes. X OC : Obtain the sending and receiving end power grids within the provincial power grid. P L0 Increase or decrease (or decrease or increase) the same amount of load, respectively. ΔP L Construct a transmission power of P Ti New operating mode O Ci Among them, P L0 This represents the initial total active power load of the sending and receiving end power grids; ΔP L P represents the change in the total active power load of the sending and receiving power grids; Ti This represents the active power transmitted from the sending-end grid to the receiving-end grid.

[0039] (III) Strategies for finding key transmission sections of provincial power grids.

[0040] like Figure 2The diagram shows a flowchart for locating key transmission sections in a provincial power grid. Specifically, it describes the operational mode constructed using the aforementioned method. O Ci The 500kV and above AC lines within the provincial power grid were banned one by one. A comparison was made of the data before and after the bans for each of the 500kV and above AC lines within the power grid. i Change in active power ΔP i ,Will ΔP i With preset threshold ΔP threshold After comparison, the lines that were previously disabled were identified. l The set of lines that form a parallel connection, which then includes the disabled lines. l This refers to the set of key transmission sections corresponding to this line. L l i This represents the i-th line among all 500kV and above AC lines in the power grid; ΔP i This indicates that the disabled line is disabled. l The i-th line before and after i The change in active power; l This indicates that the line is disabled.

[0041] The specific steps are as follows: ①Based on operating mode O Ci Solve the initial power flow and obtain the initial power on all transmission lines of the provincial power grid. P li0 ; P li0 Indicates the i-th line l i Initial power; ② Select 500kV and above AC lines as the target set for prohibited lines. L trip ; ③ For the target set L trip One of the lines l Obtain the initial power on the line P l0 ; ④ Disable the line and resolve the power flow to obtain the new power on all transmission lines of the provincial power grid. P li ; P li This indicates that a certain line is disabled. l The new power on the i-th line; ⑤ Order L trip China's various routesl i New power P li Subtract initial power P li0 To obtain the change in active power Δ P i The calculation formula is: (4) ⑥If ΔP i ≥ΔP threshold Determine the route l i Initial power and disabled lines l initial power P l0 The directions are the same; then, determine whether the two ends of the line belong to different areas within the power grid; if they are determined to belong to different areas, then the line... l i With the disabled line l Belonging to the same cross section; ⑦ Repeat steps ③ to ⑥. The union of the selected lines is the set of key transmission sections of the provincial power grid. L .

[0042] (iv) Method for setting up instability scenarios.

[0043] The selected fault types are line short-circuit fault and DC blocking fault.

[0044] For a three-phase short-circuit fault: Select a target line and the other line in the corresponding double-circuit line. First, set the target line to a three-phase short-circuit fault. After running for a period of time, clear the fault on the line and trip the line. At the same time, trip the other line in the corresponding double-circuit line to simulate the line protection action logic.

[0045] For DC blockage faults: In a single simulation, select a target DC project. Simulate the DC blockage fault by forcibly blocking the target DC project using the manual blockage DC interface in STEPS.

[0046] (v) Method for constructing provincial power grid instability scenarios involving large-scale centralized transmission of new energy and nuclear power.

[0047] ① Construct a simulated fault scenario for a provincial power grid, including large-scale centralized transmission of new energy and nuclear power, by simulating line short-circuit faults. S i1 : The set of key transmission section lines is obtained based on the aforementioned method. L For each line within the setl target : Obtain the bus numbers of the sending and receiving ends of the line, and iterate through the remaining lines in the set. l iother If the line l iother Sending bus number and line l target If the sending-end bus numbers are equal, then these two lines constitute a sending-end line pair. c si If the line l iother Receiving bus number and line l target If the receiving bus numbers are the same, then these two lines constitute a receiving-end line pair. c ri The line pair is used to simulate the line protection action logic of a double-circuit line in a line short-circuit fault.

[0048] Based on the aforementioned method, STEPS is used to simulate three-phase short-circuit faults in the line set of key transmission sections to construct instability scenarios. S i1 : Obtain all line pairs, if the simulation is set to allow for line fault distances. x If ∈(0,0.5], then iterate through all sending line pairs and perform a process for each sending line pair. c si In a single simulation, the first line to be aligned with the line. l 1. Set up a three-phase short-circuit fault with a fault distance of [missing information]. x .exist l 1. After 0.1 seconds of fault detection, clear the fault and disconnect the line pair. c si The two lines in the simulation. Similarly, if the simulation sets the line fault distance... x If ∈(0.5,1), then iterate through all sending line pairs and perform a check on the receiving line pairs. c ri Perform the same operation.

[0049] ② Construct a simulated fault scenario for a provincial power grid, including large-scale centralized transmission of new energy and nuclear power, by simulating DC blocking faults. S i2 : Acquire all HVDC projects with inverter-side converter stations located within the provincial power grid to form a target-blocked HVDC project set. X HVDC Using STEPS collections X HVDC Simulate DC bipolar blockage faults within a certain range to construct instability scenarios: In a single simulation, within the set X HVDCSelect a high-voltage direct current project HVDC i Forced locking using manual locking DC interface HVDC i The positive and negative terminals; if HVDC i If the inverter-side converter station adopts a hierarchical access method, then all DC converters should be locked out.

[0050] ③ Construct scenarios according to the methods described above. S i After performing time-domain simulation, S i This represents the set consisting of scenarios Si1 and Si2 constructed according to the above method; based on the simulation result output file, the power curves, synchronous machine speed curves, rotor angle curves, and the terminal voltage and power curves of the new energy units are plotted on the provincial power grid cross-section lines. If the power curves on the cross-section lines and the terminal voltage and power curves of the new energy units exhibit equal-amplitude or increasing-amplitude oscillations, and the synchronous machine speed curves and rotor angle curves are clearly divided into multiple clusters, then the scenario is determined to be... S i This is a scenario of power grid instability in a province that includes large-scale centralized transmission of new energy and nuclear power.

[0051] (vi) Rapid determination method for different unstable generator groups within a provincial power grid.

[0052] Get Scene S i The time-domain simulation results file is used to extract the rotor angle data of the synchronous machine within the provincial power grid, and the rotor angle curve of the synchronous machine is plotted. If the rotor angle curve of the synchronous machine is clearly divided into... n If clusters are arranged in a specific pattern, the number of unstable generator clusters within the provincial power grid will increase. n It equals the number of clusters of rotor angle curves.

[0053] Under high-power transmission conditions within a provincial power grid, if instability occurs, the synchronous machine rotor angle curve will clearly diverge into multiple clusters, often exhibiting an overall increasing or decreasing divergent trend. Therefore, the following method is used to identify different unstable machine groups: ① Extract the synchronous machine rotor angle data from the results file δ i ( t k ), i=1,2,…, Ng, N g This represents the total number of synchronous generator units; k =1,2,…, N t k represents the index number of the time point in the time series. N tThe time series length is specified. The inertial constants of each synchronizer are obtained, with equal weighting assumed by default. Inertial center transformation is used to eliminate overall system frequency drift and balance relative power angles. It only reflects the relative sway between units: (5) in, The power angle of the system's center of inertia is the weighted average power angle with the inertial constants of each synchronizer as the weights, representing the "average motion" of the entire system. Let represent the inertial constant of the i-th synchronous machine; This represents the rotor angle data of the i-th synchronous machine; Let represent the relative work angle of the i-th synchronizing machine with respect to the center of inertia.

[0054] ② For any two synchronous machines Calculate the Pearson correlation coefficient of the relative work angle sequence. ρ αβ : (6) in ρ αβ ∈[-1,1], the closer to 1, the more similar the swing patterns of the two machines. α and β represent the index numbers of the two different synchronizers, used to distinguish them; This indicates that the α-th synchronizing machine is at time t. k The relative angle of work; This indicates that the relative power angle of the α-th synchronous machine is within all N... t The time average value at each sampling point; This indicates that the β-th synchronizer is at time t. k The relative angle of work; This indicates that the relative power angle of the β-th synchronous machine is among all N... t The time average value at each sampling point; ③ Set the coherence threshold ρ th Define an undirected graph G =( V , E ): (7) Two synchronous machines α , β If the correlation coefficient is not lower than the threshold ρ th Then connect the edges in the graph. G represents an undirected graph describing the connection relationships between all synchronizers based on swing similarity. V represents the set of nodes in graph G, with each node corresponding to a synchronizer; E represents the set of edges in graph G.

[0055] Homology threshold ρ th The threshold used to describe the similarity of the swing of two synchronous machines is used; only machines with a correlation coefficient higher than this value are considered to be electrically closely connected.

[0056] Calculation graph G Connected components: (8) C represents the set of connected components of the graph, where C1, C2, C3, C4, C5, C6, C7, C8, C9 ... M Let Cp and Cq represent the 1st, 2nd, and Mth homology groups (i.e., connected components), respectively; let Cp and Cq represent any two distinct connected components in set C, where p represents and q represents; and m represents the index number of each connected component in set C.

[0057] Each connected component of graph G is a maximal subset of nodes that satisfies the following conditions: there is a path between any two nodes in the subset consisting of edges from set E, and no node outside the subset is connected to any node in the subset by any edge.

[0058] Each connected component is a homology group, whose internal units maintain a highly similar oscillation throughout the entire observation window.

[0059] ④ For homology groups C m Define the relative work angle of its weighted center of inertia: (9) C m Let m be the m-th homology group (i.e., the connected component) in set C.

[0060] For any two homology groups p,q Define relative angle difference: (10) and Let Cp and Cq represent the relative work angles of the centers of inertia of the homology groups Cp and Cq, respectively. The relative work angle difference between two homology groups is represented by p; p and q represent the index numbers of the two homology groups, used to distinguish between them.

[0061] Set two instability detection parameters: angle separation threshold. θ sep Sum-end divergence slope threshold ε If the following conditions are met simultaneously: (11) This represents the relative work angle difference between two homology groups at the last time t. end The first time derivative of time.

[0062] Then it is believed C p and C q Those belonging to different unstable clusters (whose relative angles have widened sufficiently and are still diverging) are considered unstable clusters; otherwise, they belong to the same unstable cluster. The unseparated clusters are merged using a disjoint-set data structure to obtain the final unstable cluster classification. u 1,…, u k u1、u k Let represent the 1st and kth unstable groups obtained in the end, respectively.

[0063] The disjoint-set data structure merges non-separated groups, which specifically means dynamically merging all initial homogeneous groups that do not exhibit sustained divergence of work angles into a final unstable group.

[0064] If the number of homology groups equals m This proves that the data processing results are correct and corroborate the rotor angle curve. Compared to clustering, this method does not require pre-specifying the number of groups, the distance metric (correlation coefficient) has a clear physical meaning, and directly reflects the consistency of swaying; the computation of graph connected components is extremely fast and iterative; compared to the EEAC / complementary group inertia center method, it only relies on time-domain simulation trajectories, does not require constructing equivalent energy functions, and can naturally handle multi-group instability. EEAC refers to the extended equal area criterion, which is a classic quantitative method in power system transient stability analysis.

[0065] (vii) Calculation method for the transmission limit of new energy and nuclear power UHV transmission considering static stability constraints.

[0066] Estimate the ultra-high voltage power transmission limit for new energy and nuclear power plants considering static stability constraints. P Tmax0 This is used to determine the target power surplus of the sending-end and receiving-end power grids within the provincial power grid. P surplus Area X Ps The method for constructing a provincial power grid based on a case study involving large-scale centralized transmission of new energy and nuclear power is determined according to the scope. X Ps and accuracy ΔP (i.e., load variation within the region) Δ P L Construct a set of operating modes that consider static stability constraints. X OC1 .

[0067] For sets X OC1 Operating mode in OCi1 Based on the method for constructing provincial power grid instability scenarios, this paper constructs an operation mode by simulating a DC setting blocking fault for external power transmission to the provincial power grid. O Ci1 The following set of anticipated fault scenarios for provincial power grids with large-scale centralized transmission of new energy and nuclear power, considering static stability constraints. X Si1 This is called the first set of anticipated failure scenarios; If the set X Si1 In cases of instability, this operating mode... O Ci1 Corresponding transmission power P Ti1 (i.e., the first power) is higher than the ultra-high voltage transmission limit of new energy and nuclear power considering static stability constraints. P Tmax Conversely, it is lower than P Tmax .

[0068] When the transmission power is P Ti1 Operating scenarios O Ci1 The corresponding set of first anticipated failure scenarios X Si1 There are no unstable scenarios in the middle, but the transmission power is P Ti1 +ΔP Operating scenarios O Cj The corresponding set of anticipated failure scenarios X Sj If an instability scenario exists, and the overall results of the instability cluster determination meet the criteria of "the rotor angle curve of the sending-end grid cluster swings upward at an accelerating rate, the rotor angle curve of the receiving-end grid cluster swings downward, and each curve cluster contains multiple units," then the operating mode is... O Ci1 Corresponding transmission power P Ti1 For this power grid at the current accuracy ΔP The limit of ultra-high voltage power transmission for new energy and nuclear power considering static stability constraints P Tmax .

[0069] The above O Cj This indicates that the transmission power is the first power. P Ti1 + accuracy ΔP The operating scenario; X Sj Indicates the running scenario OCj The corresponding set of anticipated failure scenarios.

[0070] (viii) Calculation method for the transmission limit of new energy and nuclear power UHV power transmission considering transient stability constraints.

[0071] After obtaining the ultra-high voltage transmission limit for new energy and nuclear power considering static stability constraints, a lower value is used to estimate the ultra-high voltage transmission limit for new energy and nuclear power considering transient stability constraints. P Tmax0 ， This is used to determine the target power surplus of the sending-end and receiving-end power grids within the provincial power grid. P surplus Area X Ps The method for constructing a provincial power grid based on a case study involving large-scale centralized transmission of new energy and nuclear power is determined according to the scope. X Ps and accuracy ΔP (i.e., load variation within the region) ΔP L Construct a set of operating modes considering transient stability constraints. X OC2 .

[0072] For sets X OC2 Operating mode in O Ci2 Based on the method for constructing provincial power grid instability scenarios, the operation mode is constructed by simulating line short-circuit faults. O Ci2 Considering transient stability constraints, this paper proposes potential fault scenarios for provincial power grids involving large-scale centralized transmission of new energy and nuclear power, and selects a set of potential fault scenarios that include 1000kV ultra-high voltage lines. X Si2 This is called the second set of anticipated failure scenarios; If the set X Si2 In cases of instability, this operating mode... O Ci2 Corresponding transmission power P Ti2 (i.e., the second power) exceeds the ultra-high voltage transmission limit of new energy and nuclear power considering transient stability constraints. P Tmax ， Conversely, it is lower than P Tmax ， .

[0073] When the transmission power is P Ti2 Operating scenariosO Ci2 The corresponding set of anticipated failure scenarios X Si2 There are no unstable scenarios in the middle, but the transmission power is P Ti2 +ΔP Operating scenarios O Cj ， The corresponding set of anticipated failure scenarios X Sj ， If an instability scenario exists, and the instability group determination result meets the condition that "at least one unit's rotor angle curve is significantly deflected," then... P Ti2 For this power grid at the current accuracy ΔP The transmission limit of new energy and nuclear power ultra-high voltage power transmission under transient stability constraints P Tmax ， .

[0074] The above O Cj ， This indicates that the transmission power is the second power. P Ti2 + accuracy ΔP The operating scenario; X Sj ， Indicates the running scenario O Cj ， The corresponding set of anticipated failure scenarios.

[0075] Since the obtained static stability limit is usually higher than or equal to the transient stability limit, the calculation result of the static stability limit defines the upper bound of the search for the transient stability limit, improving computational efficiency. If the transient stability limit is significantly lower than the static stability limit, it indicates that transient stability is the key factor limiting the transmission capacity.

[0076] The actual UHV transmission limit of the power grid must simultaneously satisfy both static and transient stability constraints. After obtaining the static stability limit and the transient stability limit respectively, the smaller of the two values ​​is taken as the final transmission limit.

[0077] The embodiments of the present invention have the following technical advantages: 1. This invention overcomes the limitations of existing technologies that only consider a single constraint by establishing a comprehensive evaluation system that combines static and transient stability constraints, resulting in more comprehensive and reliable evaluation conclusions. Specifically, this invention assesses the transmission limit under static stability constraints by simulating DC blocking faults and assesses the transmission limit under transient stability constraints by simulating UHV line short-circuit faults, establishing static and transient instability criteria respectively, which can accurately identify two different instability modes. Compared to existing technologies that only consider transient stability limits or control limits, this invention simultaneously considers static and transient stability constraints, establishing a comprehensive evaluation system with dual constraints. The evaluation results are more comprehensive and accurate, providing a more scientific and reliable basis for power grid planning and operation.

[0078] 2. This invention proposes a method for determining unstable machine groups based on Pearson correlation coefficient, graph connected components, angle separation threshold, and end divergence slope threshold. Compared to traditional methods, this method does not require pre-specifying the number of groups or constructing an equivalent energy function, offering significant technical advantages. Specifically, this invention calculates the Pearson correlation coefficient of the relative power angle sequences of any two machines, defines an undirected graph, and calculates the connected components of the graph to obtain homology groups. Then, it uses the angle separation threshold and end divergence slope threshold to determine whether different homology groups belong to different unstable machine groups. Finally, it obtains the final unstable group classification by using a disjoint-set data structure to identify groups that have not separated. Compared to traditional clustering methods, this method does not require pre-specifying the number of groups, the distance metric has clear physical meaning, directly reflects the consistency of swaying, and the graph connected component calculation is extremely fast and iterative. Compared to the EEAC / complementary group inertia center method, it only relies on time-domain simulated trajectories, does not require constructing an equivalent energy function, and can naturally handle multi-group instability, demonstrating significant technical advantages.

[0079] 3. This invention proposes a critical transmission section identification strategy based on line disabling and power change, which can accurately identify critical transmission sections and provide an accurate basis for subsequent instability scenario construction and transmission limit calculation. Specifically, this invention disables 500kV and above AC lines one by one, compares the change in active power on each line before and after disabling, and combines preset thresholds and power direction judgment to identify the set of lines that form a parallel relationship with the disabled lines, thereby determining the set of critical transmission section lines. Compared with the traditional method of dividing transmission section segments based on voltage stability and power angle stability sensitivity, this method can more accurately identify the critical lines with the greatest impact on transmission limits, avoid missing critical transmission channels, and provide an accurate basis for subsequent instability scenario construction and transmission limit calculation.

[0080] 4. This invention constructs a complete technical chain from provincial power grid zoning to dual-constraint transmission limit calculation. The technical solution is highly systematic and operable, and can be directly applied to actual power grid planning and operation. Specifically, this invention includes core steps such as provincial power grid zoning, operation mode construction, key transmission section identification, instability scenario construction, instability cluster determination, static stability constraint transmission limit calculation, and transient stability constraint transmission limit calculation. The logical relationships between each step are clear, and the technical connections are close, forming a complete technical chain. This technical chain is highly systematic and operable, and can be directly applied to actual power grid planning and operation, providing a scientific basis for power grid dispatching departments, helping planning departments to rationally determine the scale of new energy and nuclear power integration and transmission channel capacity, and improving the safe and stable operation level of the power grid.

[0081] (ix) Specific applications.

[0082] Using the ultra-high voltage (UHV) transmission limit assessment of new energy and nuclear power in a provincial power grid as a specific application scenario, the effectiveness of the proposed method for assessing the UHV transmission limit of new energy and nuclear power considering static and transient stability constraints is verified.

[0083] Based on the proposed method for constructing a provincial power grid example involving large-scale centralized transmission of new energy and nuclear power, the power transmitted from the sending-end grid to the receiving-end grid within the provincial power grid is constructed as follows: P T0 =40 million kilowatts initial operating mode O C0 .

[0084] To calculate the transmission limits of new energy and nuclear power UHV transmission considering static stability constraints in a provincial power grid, based on O C0 With precision ΔP =100,000 kilowatts P Ti1 The set of construction and operation modes for ∈[3800,4200] MW. X OC1 , P Ti1 This represents the transmission power corresponding to each operating mode in the operating mode set Xoc1; and based on the proposed method for constructing provincial power grid instability scenarios involving large-scale centralized transmission of new energy and nuclear power, it is used to... X OC1 Each operating mode in O Ci1 Construct a set of anticipated fault scenarios for DC bipolar blocking in the provincial power grid X Si1 .

[0085] Figure 3The figure shown is the rotor angle curve of the synchronous machine under the steady-state transmission power of 39.2 million kilowatts. Figure 4 The figure shown is the rotor angle curve of the synchronous machine under the steady-state transmission power of 39.1 million kilowatts. Figure 5 The figure shown is a cross-sectional line power curve under the steady-state transmission power of 39.1 million kilowatts.

[0086] Figure 3 In the figure, the horizontal axis represents the simulation time, and the vertical axis represents the rotor angle of the synchronous machine. The curves of different colors represent the trend of the rotor angle of each synchronous machine unit in the provincial power grid as a function of time under the operating scenario of steady-state transmission power of 39.2 million kilowatts. Figure 4 In the figure, the horizontal axis represents the simulation time, and the vertical axis represents the rotor angle of the synchronous machine. The curves of different colors represent the trend of the rotor angle of each synchronous machine unit in the provincial power grid as a function of time under the operating scenario of steady-state transmission power of 39.1 million kilowatts. Figure 5 In the figure, the horizontal axis represents the simulation time, and the vertical axis represents the active power flowing through the AC line. The curves of different colors represent the trend of AC power flowing through each AC line of the key section of the provincial power grid with time under the operating scenario of steady-state transmission power of 39.1 million kilowatts.

[0087] The above Figure 3 , Figure 4 and Figure 5 The curve shown represents a hypothetical fault in a high-voltage direct current (HVDC) project, specifically a bipolar blocking fault. When the steady-state transmission power at the critical section reaches 39.3 million kilowatts, this HVDC project's blocking fault will be the first to cause instability in the provincial power grid. A synchronization threshold is set. ρ th The value is 0.95. According to the instability group judgment results, this DC bipolar blocking will cause the sending-end and receiving-end power grid groups within the provincial power grid to lose synchronization. In the figure, the first cluster of upward-sloping rotor angle curves corresponds to the synchronous generator units in the sending-end power grid that are far from the node where the cross-section line is located; the second cluster of three rotor angle curves that first decline and then rise corresponds to the three nuclear power units in the plan that are connected to the 1000kV node where the cross-section line is located via a 1000kV line; the third cluster of rotor angle curves corresponds to the synchronous generator units in the receiving-end power grid within the scenario, which is consistent with the instability group judgment results. The maximum power transmission capacity of new energy and nuclear power UHV for this provincial power grid, considering static stability constraints, is 39.2 million kilowatts.

[0088] To calculate the ultra-high voltage transmission limits of new energy and nuclear power in a provincial power grid, considering transient stability constraints, based on O C0 With precision ΔP =100,000 kilowatts P Ti2The set of construction and operation modes for ∈[3100,3800] MW. X OC2 , P Ti2 This represents the transmission power corresponding to each operating mode in the Xoc2 operating mode set; and based on the proposed method for constructing provincial power grid instability scenarios involving large-scale centralized transmission of new energy and nuclear power, it is used to... X OC2 Each operating mode in O Ci2 Construct a set of anticipated three-phase short-circuit fault scenarios for key sections of ultra-high voltage lines in the provincial power grid. X Si2 .

[0089] Figure 6 The synchronous machine rotor angle curve is shown under the steady-state transmission power of 31.9 million kilowatts. Figure 7 The synchronous machine rotor angle curve is shown under the steady-state transmission power of 32 million kilowatts.

[0090] Figure 6 In the figure, the horizontal axis represents the simulation time, and the vertical axis represents the rotor angle of the synchronous machine. The curves of different colors represent the trend of the rotor angle of each synchronous machine unit in the provincial power grid as a function of time under the operating scenario of steady-state transmission power of 31.9 million kilowatts. Figure 7 In the figure, the horizontal axis represents the simulation time, and the vertical axis represents the rotor angle of the synchronous machine. The curves of different colors represent the trend of the rotor angle of each synchronous machine unit in the provincial power grid as a function of time under the operating scenario of steady-state transmission power of 32 million kilowatts.

[0091] Figure 6 and Figure 7 The curve shown represents a scenario where the anticipated fault is a three-phase short-circuit fault on a critical section of a 1000kV AC UHV line in a provincial power grid. The fault location is 1% of the line length from the busbar of the receiving-end power grid to which the line is connected. The line cooperating with the fault is another 1000kV AC UHV line connected to the aforementioned receiving-end power grid busbar. When the steady-state transmission power of the critical section reaches 32 million kilowatts, a synchronization threshold is set. ρ th The value is 0.95. Analysis of the unstable generator group judgment results shows that a three-phase short-circuit fault on the selected 1000kV AC UHV line will be the first to cause instability in the provincial power grid, and the unstable generator is a nuclear power unit belonging to the sending-end grid. Therefore, the transmission limit of new energy and nuclear power UHV for this grid, considering transient stability constraints, is 31.9 million kilowatts.

[0092] Example 2 This embodiment discloses a limit assessment system for transmitting new energy and nuclear power via ultra-high voltage transmission.

[0093] A limit assessment system for transmitting new energy and nuclear power via ultra-high voltage transmission includes: The power grid simulation module is configured to: simulate and construct a provincial power grid simulation involving the transmission of new energy and nuclear power, including the sending-end power grid and the receiving-end power grid; The operation mode construction and section search module is configured to: construct a set of provincial power grid operation modes with different power output values, disable AC lines in the provincial power grid one by one, and identify the set of key transmission section lines; The instability scenario construction and cluster determination module is configured to: construct instability scenarios and perform time-domain simulations by combining the set of key transmission section lines, and determine the unstable clusters based on the clustering of the synchronous machine rotor angle curves in the simulation results; The static limit calculation module is configured to: construct a first set of anticipated fault scenarios by simulating a DC blocking fault for power transmission from the outside to the provincial power grid; and estimate the transmission limits of new energy and nuclear power UHV power transmission considering static stability constraints based on whether there are instability scenarios in the first set of anticipated fault scenarios. The transient limit calculation module is configured to: construct a second set of anticipated fault scenarios by simulating short-circuit faults in UHV lines at key transmission sections; and estimate the transmission limits of new energy and nuclear power UHV lines considering transient stability constraints based on whether there are instability scenarios in the second set of anticipated fault scenarios.

[0094] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.

[0095] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. 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 the present invention are still within the scope of protection of the present invention.

Claims

1. A method for assessing the limits of transmitting new energy and nuclear power via ultra-high voltage transmission, characterized in that: Includes the following steps: Simulation constructs a provincial power grid example that includes both sending-end and receiving-end power grids for the transmission of new energy and nuclear power. Construct a set of provincial power grid operation modes with different power output values, disable AC lines in the provincial power grid one by one, and identify the set of key transmission section lines. By combining the key transmission section line set, an instability scenario is constructed and time-domain simulation is performed. The instability group is determined based on the clustering of the synchronous machine rotor angle curve in the simulation results. By simulating the DC setting blocking fault for power transmission from the outside to the provincial power grid, a first set of expected fault scenarios is constructed. Based on whether there are instability scenarios in the first set of expected fault scenarios, the transmission limit of new energy and nuclear power UHV transmission considering static stability constraints is estimated. By simulating short-circuit faults in key transmission sections of ultra-high voltage lines, a second set of anticipated fault scenarios is constructed. Based on whether there are instability scenarios in the second set of anticipated fault scenarios, the transmission limits of new energy and nuclear power ultra-high voltage lines considering transient stability constraints are estimated.

2. The method for assessing the transmission limits of new energy and nuclear power via ultra-high voltage transmission as described in claim 1, characterized in that, Also includes: The ultra-high voltage power transmission limit of new energy and nuclear power, considering static stability constraints, is taken as the static stability limit. The ultra-high voltage transmission limit of new energy and nuclear power, which takes into account transient stability constraints, is taken as the transient stability limit; The smaller value between the static stability limit and the transient stability limit is taken as the final output limit; or, Simulations are constructed to build a provincial power grid example for transmitting new energy and nuclear power, including sending-end and receiving-end power grids. In the regional interconnected power grid example, high-voltage and ultra-high-voltage lines, thermal power and nuclear power units, and new energy units are added to expand the example; In the expanded example, the main nodes of the sending-end and receiving-end power grids within the provincial power grid are located; Based on the main node sets of the sending-end and receiving-end power grids respectively, and following the search path of transformer-transmission line-transformer, the area labels of each voltage level node are set in descending order of node voltage level.

3. The method for assessing the transmission limits of new energy and nuclear power via ultra-high voltage transmission as described in claim 2, characterized in that, Set the area labels for each voltage level node step by step, including: Search for all transformers connected to the main node, and set the area labels of all nodes connected to the main node through transformers to the area label corresponding to the main node. Starting from the node connected to the main node via a transformer, search for all transmission lines connected to the starting point, and set the area labels of all nodes connected to the starting point via transmission lines as the area labels corresponding to the starting node.

4. The method for assessing the transmission limits of new energy and nuclear power via ultra-high voltage transmission as described in claim 1, characterized in that, Construct a set of provincial power grid operation modes with different power output values, including: The capacity and output ratio of various power sources in the sending-end and receiving-end power grids are determined respectively, as well as the power injected into the current power grid from various high-voltage DC sources outside the provincial power grid, and the total power generated in the region is calculated. Given the target power surplus of the sending-end grid and the receiving-end grid, the target total active load in the region is determined based on the target power surplus and the total power generated in the region. Traverse all active loads within the region and sum them to obtain the current total active load. Calculate the ratio of the target total active load to the current total active load, and proportionally enlarge the active load values ​​of each load model. Adjust the operating mode until the power flow calculation converges to obtain the initial operating mode; Based on the initial operating mode, new operating modes with different output power values ​​are constructed in batches to form a set of operating modes.

5. The method for assessing the transmission limits of new energy and nuclear power via ultra-high voltage transmission as described in claim 4, characterized in that, Identify the set of key transport sections, including: Based on the new operating mode in the set of operating modes, the initial power flow is solved to obtain the initial power on all transmission lines of the provincial power grid; AC lines of 500 kV and above were selected as the target set for prohibited lines; Disable a line in the target set, re-solve the power flow, and obtain the new power on all transmission lines of the provincial power grid; Subtract the initial power from the new power on each line in the target set to obtain the change in active power; If the change in active power is greater than or equal to a preset threshold, it is determined that the initial power of the current line is in the same direction as the initial power of the disabled line; then it is further determined whether the two ends of the current line belong to different areas within the power grid. If they are determined to belong to different areas, then the current line and the disabled line belong to the same cross section. Repeat the above steps, and the union of the selected lines is the set of key transmission sections of the provincial power grid.

6. The method for assessing the transmission limits of new energy and nuclear power via ultra-high voltage transmission as described in claim 1, characterized in that, Construct instability scenarios, including constructing a line short-circuit fault scenario and a DC blocking fault scenario, wherein: Constructing line short-circuit fault scenarios, specifically including: For each line within the set of key transmission sections, obtain the bus number at the sending end and the bus number at the receiving end of the line; Traverse the remaining lines in the set of key transmission sections. If the sending bus number of the remaining lines is equal to the sending bus number of the current line, then these two lines form a sending line pair; if the receiving bus number of the remaining lines is equal to the receiving bus number of the current line, then these two lines form a receiving line pair. If the line fault distance set in the simulation is between 0 and 0.5, then all sending line pairs are traversed. For each sending line pair, in a single simulation, a three-phase short-circuit fault is set on the first line in the line pair. After the first line fault occurs for 0.1 seconds, the fault is cleared and the two lines in the line pair are disconnected. If the simulation-set line fault distance is between 0.5 and 1, then iterate through all receiving-end line pairs and perform the same operation on each receiving-end line pair. Constructing DC blocking fault scenarios, specifically including: Acquire all high-voltage direct current (HVDC) projects with inverter-side converter stations located within the provincial power grid, and construct a target-blocked HVDC project set. In a single simulation, a high-voltage direct current (HVDC) project is selected from the set of target-locked HVDC projects, and the positive and negative terminals of the selected HVDC project are forcibly locked.

7. The method for assessing the transmission limits of new energy and nuclear power via ultra-high voltage transmission as described in claim 1, characterized in that, Determining an unstable cluster includes: Extract the rotor angle data of the synchronous machine within the provincial power grid from the results file, and plot the rotor angle curve of the synchronous machine; If the rotor angle curve of the synchronous machine is divided into multiple clusters, then the number of unstable machine groups in the provincial power grid is equal to the number of clusters of rotor angle curves. or, Determining whether they belong to the same unstable cluster includes: The inertial constants of each synchronizing machine are obtained, and the center of inertia is transformed so that the relative power angle reflects only the relative sway between the units. For any two synchronous machines, calculate the Pearson correlation coefficient of their relative power angle sequences; Set a homology threshold and define an undirected graph. If the Pearson correlation coefficient of two synchronizing machines is not lower than the homology threshold, then connect the top edge in the undirected graph and calculate the connected components of the undirected graph. Each connected component is a homology group. For homology groups, define the relative work angle of the weighted inertia centers; for any two homology groups, define the relative angle difference. Set an angle separation threshold and an end divergence slope threshold. If the maximum value of the relative angle difference is greater than the angle separation threshold, and the absolute value of the rate of change of the relative angle difference at the end of the simulation is greater than the end divergence slope threshold, then the two homology groups are considered to belong to different unstable machine groups; otherwise, the two homology groups belong to the same unstable machine group.

8. The method for assessing the transmission limits of new energy and nuclear power via ultra-high voltage transmission as described in claim 1, characterized in that, Estimate the transmission limits of ultra-high voltage power transmission from new energy sources and nuclear power plants, taking into account static stability constraints, including: Determine the range of target power surplus for the sending and receiving power grids within the provincial power grid, and construct a set of operating modes considering static stability constraints based on the target power surplus range and accuracy. For a certain operating mode with a transmission power of the first power value in the set of operating modes considering static stability constraints, a set of first anticipated fault scenarios is constructed by simulating the DC setting blocking fault of power transmission from the outside to the provincial power grid. If the first set of anticipated fault scenarios includes an unstable scenario, then the first power value is higher than the ultra-high voltage transmission limit of new energy and nuclear power considering static stability constraints. If there is no instability scenario in the first set of anticipated fault scenarios, but there is an instability scenario in the set of anticipated fault scenarios corresponding to the operation scenario with transmission power equal to the first power value plus precision, and the instability group determination result meets the following conditions: the rotor angle curve of the sending-end grid group accelerates upward, the rotor angle curve of the receiving-end grid group swings downward, and each curve cluster contains multiple units, then the first power value is the limit of new energy and nuclear power UHV transmission under the current precision considering static stability constraints.

9. The method for assessing the transmission limits of new energy and nuclear power via ultra-high voltage transmission as described in claim 1, characterized in that, Estimate the ultra-high voltage transmission limits for new energy and nuclear power plants considering transient stability constraints, including: Determine the range of target power surplus for the sending and receiving power grids within the provincial power grid, and construct a set of operating modes that consider transient stability constraints based on the target power surplus range and accuracy. For a certain operating mode with a transmission power of the second power value in the set of operating modes considering transient stability constraints, a second set of anticipated fault scenarios is constructed by simulating a line short-circuit fault. If an instability scenario exists in the second set of anticipated fault scenarios, then the second power value is higher than the ultra-high voltage transmission limit of new energy and nuclear power considering transient stability constraints. If there is no instability scenario in the second set of anticipated fault scenarios, but there is an instability scenario in the set of anticipated fault scenarios corresponding to the operation scenario with transmission power equal to the second power value plus precision, and the instability group determination result is that at least one unit's rotor angle curve is significantly spread out, then the second power value is the limit of new energy and nuclear power UHV transmission under the current precision considering transient stability constraints.

10. A limit assessment system for transmitting new energy and nuclear power via ultra-high voltage transmission, characterized in that: include: The power grid simulation module is configured to: simulate and construct a provincial power grid simulation involving the transmission of new energy and nuclear power, including the sending-end power grid and the receiving-end power grid; The operation mode construction and section search module is configured to: construct a set of provincial power grid operation modes with different power output values, disable AC lines in the provincial power grid one by one, and identify the set of key transmission section lines; The instability scenario construction and cluster determination module is configured to: construct instability scenarios and perform time-domain simulations by combining the set of key transmission section lines, and determine the unstable clusters based on the clustering of the synchronous machine rotor angle curves in the simulation results; The static limit calculation module is configured to: construct a first set of anticipated fault scenarios by simulating a DC blocking fault for power transmission from the outside to the provincial power grid; and estimate the transmission limits of new energy and nuclear power UHV power transmission considering static stability constraints based on whether there are instability scenarios in the first set of anticipated fault scenarios. The transient limit calculation module is configured to: construct a second set of anticipated fault scenarios by simulating short-circuit faults in UHV lines at key transmission sections; and estimate the transmission limits of new energy and nuclear power UHV lines considering transient stability constraints based on whether there are instability scenarios in the second set of anticipated fault scenarios.

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