A method and device for determining the limit transmission power of a power transmission line, a terminal device and a storage medium

Abstract

The application discloses a kind of limit transmission power determination method, device, terminal equipment and storage medium of transmission line, according to the frequency data of each load point in transmission line and each operating index in power system, system stability model for describing the stability characteristics of power system is constructed;And by repeatedly executing critical value evaluation operation to determine limit transmission power, and in each evaluation, the current frequency value and operating index value of each load point and power system are obtained, then the application can adapt to the real-time change of power system operating state, the frequency and operating index value monitored in real time are substituted into system stability model to solve, so as to continuously evaluate the stability performance of power system, adjust generator according to evaluation result, to obtain limit transmission power, then the limit transmission power finally obtained can accurately reflect the stability operating characteristics of power system, avoid system instability or overload phenomenon.

Description

Technical Field

[0001] This invention relates to the field of power transmission line operation and processing technology, and in particular to a method, apparatus, terminal equipment and storage medium for determining the limit transmission power of a power transmission line. Background Technology

[0002] The maximum transmission capacity of a transmission line is one of the key factors in ensuring the stable operation of a power system. It determines the maximum power that a transmission line can safely transmit without causing system instability. Accurate determination of the maximum transmission capacity is crucial for the planning, design, and operation management of power systems. It helps operators rationally schedule power generation and transmission, avoiding overload and instability, thereby ensuring the safe and stable operation of the power system.

[0003] In traditional technologies, determining the ultimate transmission power of transmission lines typically relies on empirical formulas or static analysis, such as using fixed power thresholds or empirical power limits. This lacks flexibility and accuracy, failing to adapt to real-time changes in the power system's operating state and failing to assess the power system's stability performance. Consequently, traditional methods of determining ultimate transmission power may not accurately reflect the stable operation of the power system, leading to system instability or overload. Summary of the Invention

[0004] This invention provides a method, apparatus, terminal equipment, and storage medium for determining the ultimate transmission power of a power transmission line. It can substitute real-time monitored frequency and operating index values ​​into a system stability model for solution, thereby ensuring that the obtained ultimate transmission power can still maintain the stable operation of the power system by continuously evaluating the stability performance of the power system. It can effectively solve the problem in the prior art that the ultimate transmission power that cannot accurately reflect the stable operation of the power system is not obtained, which leads to system instability or overload.

[0005] An embodiment of the present invention provides a method for determining the maximum transmission power of a power transmission line, comprising:

[0006] Based on the frequency data of each load point in the transmission line and various operating indicators of the power system, a system stability model is constructed to describe the stability characteristics of the power system.

[0007] Repeat the following critical value evaluation operation until it is determined that the critical value is not less than a preset critical threshold, and the difference between the critical value and the preset critical threshold is not greater than a preset difference threshold. Then, the current time corresponding to the critical value not being less than the preset critical threshold and the difference between the critical value and the preset critical threshold being not greater than the preset difference threshold is taken as the target time. Then, the power of the transmission line corresponding to the target time is taken as the limit transmission power of the transmission line.

[0008] Obtain the current frequency value of each load point at the current moment, as well as the current operating index values ​​of the power system at the current moment;

[0009] After substituting each current frequency value and each current operating index value into the system stability model, the system stability model is solved. When the function value of the system stability model is minimized, the minimum function value is taken as the critical value.

[0010] If the critical value is determined to be less than a preset critical threshold, the power of each generator in the transmission line is reduced; otherwise, it is determined whether the difference between the critical value and the preset critical threshold is greater than a preset difference threshold. If the difference is determined to be greater than the preset difference threshold, the power of each generator in the transmission line is increased.

[0011] Update the current time and perform the next critical value evaluation operation.

[0012] Preferably, the operating indicators of the power system include: the angular velocity of the generator, the rotor angle between the generator and the reference generator, the steady-state rotor angle value used to characterize the rotor angle between the generator and the reference generator when the power system is in a stable operating state, the susceptance of each branch in the power system's transmission network, the internal electromotive force corresponding to the generator, the internal electromotive force corresponding to the load point, and the angular velocity of the preset reference generator.

[0013] Frequency data corresponding to each load point includes: frequency coefficient, frequency, and steady-state frequency value used to characterize the frequency of the load point when the power system is in a stable operating state;

[0014] The process of constructing a system stability model to describe the stability characteristics of the power system based on frequency data from various load points in the transmission line and various operating indicators of the power system includes:

[0015] Based on the frequency coefficient corresponding to each load point, the susceptance of each branch in the power system's transmission network, the internal electromotive force of the generator, the internal electromotive force corresponding to the load point, the rotor angle difference between any two different generators, the steady-state rotor angle difference between any two different generators, and the angular velocity of a preset reference generator, a first function is generated to characterize the generator's operating characteristics.

[0016] Based on the frequency coefficient corresponding to each load point, the susceptance of each branch in the power system's transmission network, the internal electromotive force of the generator, the internal electromotive force corresponding to the load point, the frequency difference between any two different load points, the steady-state frequency difference between any two different load points, and the angular velocity of a preset reference generator, a second function is generated to characterize the operating characteristics of the load point.

[0017] Based on the deviation between the rotor angle and steady-state rotor angle of each generator, the deviation between the frequency of each load point and steady-state frequency, and the angular velocity of each generator, a target state vector is generated to characterize the operating state of the power system.

[0018] Based on the first function, the second function, the target state vector, the preset system connection matrix for representing the network structure of the power system, and the trigonometric function for generating nonlinear terms, a third function for describing the dynamic operation of the power system in the state space is generated; wherein, the third function includes: a nonlinear feedback term for describing the nonlinear dynamic behavior of the power system, and a linear term for describing the nonlinear dynamic behavior of the power system.

[0019] Based on the preset functional expression used to describe the stability of the nonlinear dynamic system and the third functional expression, generate the analytical expression of the preset functional expression;

[0020] The analytical expression of the preset function is used as a system stability model to describe the stability characteristics of the power system.

[0021] Preferably, the step of generating a target state vector characterizing the power system operating state based on the deviation between the rotor angle and the steady-state rotor angle value of each generator, the deviation between the frequency of each load point and the steady-state frequency value, and the angular velocity of each generator includes:

[0022] For each generator, a first state vector is generated based on the deviation between the rotor angle and the steady-state rotor angle value;

[0023] A second state vector is generated based on the angular velocity of each generator;

[0024] For each load point, a third state vector is generated based on the deviation between the frequency and the steady-state frequency value;

[0025] The first state vector, the second state vector, and the third state vector are aggregated to generate a target state vector that characterizes the operating state of the power system.

[0026] Preferably, the third function includes:

[0027]

[0028] Where x is the target state vector, A is the matrix corresponding to the linear term, and B is the matrix corresponding to the nonlinear feedback term; φ(Cx) is the linear term corresponding to the transformed target state vector after transformation based on trigonometric functions; when i is the i-th generator, then δ ij The rotor angle difference between any two different generators in the branch circuit. Let be the steady-state rotor angle difference between any two different generators in the branch; when i is the i-th load point, then δ ij The frequency difference between any two different load points. δ represents the steady-state frequency difference between any two different load points; E is the preset system connection matrix, and δ 1n The rotor angle between the generator and the reference generator. δ is the steady-state rotor angle value used to characterize the rotor angle between the generator and the reference generator when the power system is in a stable operating state. (n+m)n The frequency corresponding to the load point. Let ε be the steady-state frequency value corresponding to the load point, which characterizes the frequency of the load point when the power system is in a stable operating state, and let ε be the set of branches in the power system's transmission network.

[0029] Preferably, generating the analytical expression of the preset functional expression based on the preset functional expression used to describe the stability of the nonlinear dynamic system and the third functional expression includes:

[0030] Based on the preset functional expression used to describe the stability of the nonlinear dynamic system and the third functional expression, a fourth functional expression containing the target state vector and reflecting the stability of the power system is generated.

[0031] Substituting the third function into the derivative of the fourth function generates the linear matrix inequality corresponding to the third function.

[0032] Solve the linear matrix inequality to generate an analytical expression for the preset function.

[0033] Preferably, the constraints of the system stability model include: nonlinear constraints characterizing the nonlinear relationship between operating indicators and the stability of the power system, and nonconvex constraints characterizing the nonconvexity of the transient stability domain of the system stability model.

[0034] Solving the system stability model, and taking the minimum function value as the critical value when the function value of the system stability model is minimized, includes:

[0035] Under nonlinear and nonconvex constraints, the system stability model is iteratively solved until the function value of the system stability model is minimized, and the minimum function value is taken as the critical value.

[0036] Preferably, the step of using the power of the transmission line at the target time as the ultimate transmission power of the transmission line includes:

[0037] The sum of the output power of all generators connected to the first node of the transmission line is taken as the maximum transmission power of the transmission line.

[0038] Based on the above method embodiments, the present invention provides corresponding apparatus embodiments.

[0039] One embodiment of the present invention provides a device for determining the maximum transmission power of a transmission line, comprising: a model building module and a maximum transmission power determination module;

[0040] The model building module is used to build a system stability model to describe the stability characteristics of the power system based on the frequency data of each load point in the transmission line and various operating indicators of the power system.

[0041] The limit transmission power determination module is used to repeatedly perform the following critical value evaluation operation until it is determined that the critical value is not less than a preset critical threshold, and the difference between the critical value and the preset critical threshold is not greater than a preset difference threshold. Then, the current time corresponding to the critical value not being less than the preset critical threshold and the difference between the critical value and the preset critical threshold being not greater than the preset difference threshold is taken as the target time. Subsequently, the power of the transmission line corresponding to the target time is taken as the limit transmission power of the transmission line.

[0042] Obtain the current frequency value of each load point at the current moment, as well as the current operating index values ​​of the power system at the current moment;

[0043] After substituting each current frequency value and each current operating index value into the system stability model, the system stability model is solved. When the function value of the system stability model is minimized, the minimum function value is taken as the critical value.

[0044] If the critical value is determined to be less than a preset critical threshold, the power of each generator in the transmission line is reduced; otherwise, it is determined whether the difference between the critical value and the preset critical threshold is greater than a preset difference threshold. If the difference is determined to be greater than the preset difference threshold, the power of each generator in the transmission line is increased.

[0045] Update the current time and perform the next critical value evaluation operation.

[0046] Based on the above method embodiments, the present invention provides corresponding terminal device embodiments.

[0047] Another embodiment of the present invention provides a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements a method for determining the maximum transmission power of a power transmission line as described in the above-described embodiment of the invention.

[0048] Based on the above method embodiments, the present invention provides corresponding storage medium embodiments.

[0049] Another embodiment of the present invention provides a storage medium, the computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to execute the method for determining the maximum transmission power of a transmission line as described in the above-described embodiment of the invention.

[0050] The following benefits can be obtained by implementing the present invention:

[0051] This invention provides a method, apparatus, terminal equipment, and storage medium for determining the ultimate transmission power of a power transmission line. First, a system stability model describing the stability characteristics of the power system is constructed based on frequency data from various load points along the transmission line and different operating indicators of the power system. Next, the invention determines the ultimate transmission power by repeatedly performing a critical value evaluation operation. In each evaluation, the current frequency value and operating indicator value of each load point and the power system are obtained and substituted into the system stability model for solution. When the function value of the system stability model is minimized, this function value is taken as the critical value. Then, based on the comparison between the critical value and a preset critical threshold, the power of each generator in the transmission line is adjusted, and the current time is updated for the next evaluation. This process continues until the difference between the critical value and the preset critical threshold is no greater than a preset difference threshold. The power corresponding to this point is the ultimate transmission power of the transmission line. Compared with existing technologies, this invention, by monitoring the frequency and operating index values ​​of the power system in real time, can adapt to the real-time changes in the operating state of the power system. By substituting the real-time monitored frequency and operating index values ​​into the system stability model for solution, the stability performance of the power system can be continuously evaluated. Based on the evaluation results, the power output of the generator is adjusted to ensure that the obtained limit transmission power can still keep the power system operating stably. This ensures that the final obtained limit transmission power can accurately reflect the stability operating characteristics of the power system, avoid system instability or overload, and ensure the safe and stable operation of the power system. Attached Figure Description

[0052] Figure 1 This is a flowchart illustrating a method for determining the maximum transmission power of a power transmission line according to an embodiment of the present invention.

[0053] Figure 2 This is a schematic diagram of the structure of a power system comprising n synchronous generators and m frequency loads according to an embodiment of the present invention.

[0054] Figure 3 This is a flowchart of a method for determining the maximum transmission power provided in another embodiment of the present invention.

[0055] Figure 4 This is an embodiment of the present invention providing projection of power adjustment before and after onto δ. 21 -δ 31 A schematic diagram of the stability region estimation results for the plane.

[0056] Figure 5 This is an embodiment of the present invention providing projection of power adjustment before and after onto δ. 21 -δ 41 A schematic diagram of the stability region estimation results for the plane.

[0057] Figure 6 This is a schematic diagram of a device for determining the maximum transmission power of a power transmission line according to an embodiment of the present invention. Detailed Implementation

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] like Figure 1 The diagram shown is a flowchart illustrating a method for determining the maximum transmission power of a power transmission line according to an embodiment of the present invention. The method for determining the maximum transmission power of a power transmission line includes:

[0060] Step S1: Based on the frequency data of each load point in the transmission line and various operating indicators of the power system, construct a system stability model to describe the stability characteristics of the power system.

[0061] Step S2: Repeat the following critical value evaluation operation until it is determined that the critical value is not less than the preset critical threshold, and the difference between the critical value and the preset critical threshold is not greater than the preset difference threshold. Then, take the current time corresponding to the critical value not being less than the preset critical threshold and the difference between the critical value and the preset critical threshold being not greater than the preset difference threshold as the target time, and then take the power of the transmission line corresponding to the target time as the limit transmission power of the transmission line:

[0062] Obtain the current frequency value of each load point at the current moment, as well as the current operating index values ​​of the power system at the current moment;

[0063] After substituting each current frequency value and each current operating index value into the system stability model, the system stability model is solved. When the function value of the system stability model is minimized, the minimum function value is taken as the critical value.

[0064] If the critical value is determined to be less than a preset critical threshold, the power of each generator in the transmission line is reduced; otherwise, it is determined whether the difference between the critical value and the preset critical threshold is greater than a preset difference threshold. If the difference is determined to be greater than the preset difference threshold, the power of each generator in the transmission line is increased.

[0065] Update the current time and perform the next critical value evaluation operation.

[0066] For step S1, the present invention can analyze the stability of the power system based on the frequency data of each load point in the transmission line and different operating indicators of the power system, thereby constructing a system stability model. This system stability model can comprehensively consider multiple operating indicators and the frequency data of the load points, thus more accurately reflecting the actual operating state of the power system. It can then more precisely predict the stability of the power system based on the current frequency value of the load points and the current operating indicator values, and determine the maximum transmission power of the transmission line accordingly.

[0067] In a preferred embodiment, the operating parameters of the power system include: the angular velocity of the generator, the rotor angle between the generator and the reference generator, the steady-state rotor angle value used to characterize the rotor angle between the generator and the reference generator when the power system is in a stable operating state, the susceptance of each branch in the power system's transmission network, the internal electromotive force corresponding to the generator, the internal electromotive force corresponding to the load point, and the angular velocity of the preset reference generator.

[0068] Frequency data corresponding to each load point includes: frequency coefficient, frequency, and steady-state frequency value used to characterize the frequency of the load point when the power system is in a stable operating state;

[0069] When constructing a system stability model to describe the stability characteristics of a power system based on the above parameters and data, the specific steps include:

[0070] Based on the frequency coefficient corresponding to each load point, the susceptance of each branch in the power system's transmission network, the internal electromotive force of the generator, the internal electromotive force corresponding to the load point, the rotor angle difference between any two different generators, the steady-state rotor angle difference between any two different generators, and the angular velocity of a preset reference generator, a first function is generated to characterize the generator's operating characteristics.

[0071] Based on the frequency coefficient corresponding to each load point, the susceptance of each branch in the power system's transmission network, the internal electromotive force of the generator, the internal electromotive force corresponding to the load point, the frequency difference between any two different load points, the steady-state frequency difference between any two different load points, and the angular velocity of a preset reference generator, a second function is generated to characterize the operating characteristics of the load point.

[0072] Based on the deviation between the rotor angle and steady-state rotor angle of each generator, the deviation between the frequency of each load point and steady-state frequency, and the angular velocity of each generator, a target state vector is generated to characterize the operating state of the power system.

[0073] Based on the first function, the second function, the target state vector, the preset system connection matrix for representing the network structure of the power system, and the trigonometric function for generating nonlinear terms, a third function for describing the dynamic operation of the power system in the state space is generated; wherein, the third function includes: a nonlinear feedback term for describing the nonlinear dynamic behavior of the power system, and a linear term for describing the nonlinear dynamic behavior of the power system.

[0074] Based on the preset functional expression used to describe the stability of the nonlinear dynamic system and the third functional expression, generate the analytical expression of the preset functional expression;

[0075] The analytical expression of the preset function is used as a system stability model to describe the stability characteristics of the power system.

[0076] It is understood that this invention can construct a mathematical model to measure the stability characteristics of a power system based on key indicators that reflect the operating state and load point characteristics of the power system, so as to accurately reflect the actual operating state of the power system and provide a scientific basis for subsequently determining the limit transmission power of transmission lines.

[0077] In a preferred embodiment, generating a target state vector characterizing the power system operating state based on the deviation between the rotor angle and steady-state rotor angle of each generator, the deviation between the frequency of each load point and steady-state frequency, and the angular velocity of each generator includes:

[0078] For each generator, a first state vector is generated based on the deviation between the rotor angle and the steady-state rotor angle value;

[0079] A second state vector is generated based on the angular velocity of each generator;

[0080] For each load point, a third state vector is generated based on the deviation between the frequency and the steady-state frequency value;

[0081] The first state vector, the second state vector, and the third state vector are aggregated to generate a target state vector that characterizes the operating state of the power system.

[0082] Indicatively, by aggregating the first state vector (generator rotor angle deviation), the second state vector (generator angular velocity), and the third state vector (load point frequency deviation), the target state vector can comprehensively and accurately reflect the current operating state of the power system.

[0083] The target state vector serves as a key input to the system stability model, making stability analysis more intuitive and convenient. After generating a third function to describe the dynamic operation of the power system in the state space based on the first function, the second function, the target state vector, the preset system connection matrix representing the network structure of the power system, and the trigonometric function used to generate nonlinear terms, the solution and analysis of the third function can determine whether the power system is trending towards stability or whether there are potential unstable factors by analyzing the changes in the state vector.

[0084] In a preferred embodiment, the third function includes:

[0085]

[0086] Where x is the target state vector, A is the matrix corresponding to the linear term, and B is the matrix corresponding to the nonlinear feedback term; φ(Cx) is the linear term corresponding to the transformed target state vector after transformation based on trigonometric functions; when i is the i-th generator, then δ ij The rotor angle difference between any two different generators in the branch circuit. Let be the steady-state rotor angle difference between any two different generators in the branch; when i is the i-th load point, then δ ij The frequency difference between any two different load points. δ represents the steady-state frequency difference between any two different load points; E is the preset system connection matrix, and δ 1n The rotor angle between the generator and the reference generator. δ is the steady-state rotor angle value used to characterize the rotor angle between the generator and the reference generator when the power system is in a stable operating state. (n+m)n The frequency corresponding to the load point. Let ε be the steady-state frequency value corresponding to the load point, which characterizes the frequency of the load point when the power system is in a stable operating state, and let ε be the set of branches in the power system's transmission network.

[0087] Indicative, such as Figure 2As shown, this embodiment provides a power system structure diagram including n synchronous generators. The source side includes n synchronous generators, numbered 1 to n; the load side includes m frequency loads, numbered 2n+1 to 2n+m; and the grid side includes n nodes. Then, according to... Figure 2 The power system structure diagram shown constructs a system stability model containing n synchronous generators and m frequency loads. Furthermore, network shrinkage can eliminate the number of generations, and using relative angles as state variables can eliminate equilibrium manifolds, thereby reducing the number of nodes and branches to be considered in the model and thus lowering its dimensionality. Using relative angles (such as the rotor angle difference between generators) as state variables eliminates equilibrium manifolds, i.e., constraints that keep the system unchanged under certain conditions, making the system stability model in this embodiment of the invention more concise while preserving key information about the system's dynamic behavior.

[0088] Furthermore, the generator of this invention is a synchronous generator, and the reference generator is the nth synchronous generator. The frequency load of each load point is a function of the angular frequency. Therefore, the functional model of the power system with relative angle as the state variable after network shrinkage can be expressed as:

[0089]

[0090] Among them, S ij =E i E j B ij δ in ω represents the angle of synchronous generator i, or frequency load i, relative to the reference machine. i ω represents the rotor angular velocity of synchronous generator i. n E is the rotor angular velocity of the reference machine. i E represents the internal electromotive force of synchronous generator i at frequency i, which is the internal electromotive force of load i. i Keep constant, M i D i Let B represent the inertial constant and damping coefficient of synchronous generator i, respectively. ij Let d represent the susceptance of branch {i,j} in the shrinking network, where {i,j}∈ε, and ε is the set of all branches in the shrinking network; i P di d represents the constant frequency coefficient of frequency load i and the power consumed by frequency load i in steady state, respectively. i >0.

[0091] Furthermore, the present invention can represent the above-mentioned power system function model as a Lure-type system, then:

[0092] Define a state vector x = [x1; x2; x3], which includes a vector consisting of the deviations between the angles of the synchronous generator and their steady-state values. Angular velocity vector of a synchronous generator The vector formed by the deviation between the frequency load angle and its steady-state value. Define matrix E as the graph of the shrinking network, then we have

[0093] Using vectors composed of trigonometric functions By representing the nonlinear terms, the linear and nonlinear terms of the power system's function model can be separated, and the power system's function model in state space can be represented in the following form:

[0094]

[0095] In the formula: T1=[I (n-1)×(n-1) [,-e1] is the coefficient matrix, T2 is an (n-1)-dimensional column vector with all elements equal to 1, where I is the identity matrix; T2 = [O m×(n-1) [,-e2] is the coefficient matrix, Let M be an m-dimensional column vector with all elements equal to 1, and O be a zero matrix; M = diag(M1,…,M) n M is a diagonal matrix consisting of the inertial constants of all synchronous generators. n Let D be the inertial constant of synchronous generator n; D = diag(D1,…,D n Let D be a diagonal matrix consisting of the damping coefficients of all synchronous generators. n S1 = [M] is the damping coefficient of synchronous generator n; -1 O n×m [O] is the coefficient matrix containing the inverse matrix corresponding to the synchronous generator inertia constant matrix; S2 = [O] m×n ,d -1 ] is the coefficient matrix containing the inverse matrix corresponding to the constant frequency coefficient matrix, d = diag(d1,…,d m Let d be a diagonal matrix consisting of the constant frequency coefficients of all frequency loads. m The constant frequency coefficient of the frequency load m; S = diag(S ij ) {i,j}∈ε S is a diagonal matrix. ij =E i E i B ij E i E represents the internal electromotive force of the synchronous generator i / frequency load i. i Keep constant, B ij Let ε represent the susceptance of branch {i,j} in the shrinking network, and let ε be the set of all branches in the shrinking network.

[0096] The functional model of the power system can then be represented in state space as a Lure-type system, as shown below. This allows for the generation of a third functional expression to describe the dynamic operation of the power system in state space:

[0097]

[0098] In the formula: matrices A and B are respectively:

[0099]

[0100]

[0101] In the formula: |ε| represents the number of branches.

[0102] In this embodiment of the invention, relative angles are used as state variables to represent the functional model of the power system, including the angle and angular velocity of the synchronous generator, and the deviation between the frequency load angle and its steady-state value. Furthermore, the functional model of the power system can be represented as a Lure-type system, defining a state vector x, including the angle, angular velocity, and frequency load angle of the synchronous generator, etc. Nonlinear terms are represented by a vector constructed using trigonometric functions, thus separating linear and nonlinear terms and better handling the complex dynamic behavior of the power system.

[0103] Based on the Lure-type system representation, a third function is obtained, including the definition and specific form of matrices A and B. It can accurately describe the dynamic operation of the power system in the state space, thereby enabling the analysis and prediction of the power system's stability, dynamic response, etc.

[0104] Furthermore, after obtaining the third functional expression, an analytical expression for the preset functional expression can be generated based on the preset functional expression used to describe the stability of the nonlinear dynamic system and the third functional expression, specifically as follows:

[0105] Based on the preset functional expression used to describe the stability of the nonlinear dynamic system and the third functional expression, a fourth functional expression containing the target state vector and reflecting the stability of the power system is generated.

[0106] Substituting the third function into the derivative of the fourth function generates the linear matrix inequality corresponding to the third function.

[0107] Solve the linear matrix inequality to generate an analytical expression for the preset function.

[0108] Schematic: First, based on the preset function used to describe the stability of the nonlinear dynamic system and the third function, a fourth function containing the target state vector and reflecting the stability of the power system can be generated. By constructing the fourth function, the stability of the power system under different operating states can be analyzed, such as the stability of the power system under different generator power levels, thus deriving the limit transmission power of the transmission line. Further, substituting the third function into the derivative of the fourth function allows the dynamic model of the power system to be combined with the stability analysis function, resulting in a derivative expression for the power system state. Then, based on this derivative expression, a linear matrix inequality is generated.

[0109] In a preferred embodiment, the preset function may be a Lyapunov function, and the Lyapunov function is a quadratic Lyapunov function. Q is a positive definite matrix, and the linear matrix inequality to be solved is:

[0110]

[0111] Let K1=kI |ε|×|ε| K2 = I |ε|×|ε| Then the above formula can be further transformed into:

[0112]

[0113] Using Schur's theorem, this can be further transformed into the following linear matrix inequality, that is, the linear matrix inequality corresponding to the third function is:

[0114]

[0115] In the formula:

[0116] By solving the linear matrix inequalities, we can obtain the positive definite matrix Q and the Lyapunov function. The analytical expression can be generated from the preset functional expression.

[0117] This invention can derive an analytical expression for the stability of a power system, which can be used to evaluate the stability of the power system. By utilizing the transformation process of linear matrix inequalities, this invention transforms the complex nonlinear dynamic system stability problem into a solvable linear problem. The generated analytical expression can then be used as a system stability model to describe the stability characteristics of the power system, thereby analyzing the stability of the power system under different operating conditions. This ensures that the obtained limit transmission power can still enable the power system to maintain stable operation, and that the final obtained limit transmission power can accurately reflect the stable operating characteristics of the power system.

[0118] For step S2, in a preferred embodiment, the present invention continuously adjusts and evaluates the operating state of the power system until a power level that meets the stability requirements is found, that is, the transmission line can maintain stable operation when it does not exceed the power level, and then the limit transmission power of the transmission line can be determined.

[0119] This invention can gradually approach the limit transmission power of the transmission line by gradually adjusting the power of the generator and re-evaluating the stability of the system. Since it can take into account the impact of small changes in the operating state of the power system on stability, the final limit transmission power can accurately reflect the stable operating characteristics of the power system.

[0120] During each critical value assessment operation, this invention can reduce or increase the power of each generator in the transmission line, obtain the current frequency value of each load point at the current moment, and the current operating index value of the power system at the current moment, and then substitute the current frequency value and the current operating index value into the system stability model to solve the model, and obtain the target time corresponding to the difference not being greater than the preset difference threshold, so as to determine the limit transmission power of the transmission line.

[0121] In a preferred embodiment, the constraints of the system stability model include: nonlinear constraints characterizing the nonlinear relationship between operating indicators and the stability of the power system, and nonconvex constraints characterizing the nonconvexity of the transient stability domain of the system stability model.

[0122] Solving the system stability model, and taking the minimum function value as the critical value when the function value of the system stability model is minimized, includes:

[0123] Under nonlinear and nonconvex constraints, the system stability model is iteratively solved until the function value of the system stability model is minimized, and the minimum function value is taken as the critical value.

[0124] As an illustration, since the relationships between many key variables in a power system are often nonlinear and the stability domain of the system is nonconvex, the embodiments of the present invention can more realistically reflect the actual operating characteristics of the power system by considering nonlinear and nonconvex constraints. Furthermore, through iterative solutions, the actual operating state of the system can be gradually approximated, thereby obtaining more accurate critical values.

[0125] In a preferred embodiment, the present invention can estimate the critical value corresponding to the Lyapunov function (i.e., the analytical expression of the preset function) based on the transient stability criterion, and the set formed by the Lyapunov function and the obtained critical value is the estimated stability region.

[0126] The transient stability criterion is:

[0127]

[0128] Among them, polyhedron The definition of polyhedron The boundary is divided into inflow boundary. Outflow boundary Taking a certain branch {i,j} as an example, simultaneously satisfying and Called the inflow boundary Simultaneously satisfy and This is called the outflow boundary. but

[0129] Therefore, the critical value V min The calculation can be transformed into the following two optimization problems:

[0130]

[0131]

[0132] Indicative and These are nonlinear constraints and nonconvex constraints, respectively.

[0133] It is understood that the Lyapunov function is a predefined function used to evaluate the stability of a system, and its value changing over time reflects the stability state of the system. In embodiments of the present invention, the minimum value (i.e., the critical value V) of the Lyapunov function can be estimated. min This is used to define the stability region of the system.

[0134] Transient stability criteria provide conditions for evaluating system stability, such as polyhedral boundary conditions, including inflow and outflow boundaries. The critical value V can then be derived from the inflow and outflow boundaries in the transient stability criteria. min .

[0135] Schematic, optimization problem 1 can be: minimizing the Lyapunov function under nonlinear constraints, with the aim of finding the minimum value of the Lyapunov function that satisfies the nonlinear stability condition.

[0136] Optimization problem 2 can be: under non-convex constraints, minimize the Lyapunov function, which takes into account the non-convexity of the system's stability domain, and find the minimum value of the Lyapunov function that satisfies the non-convexity stability condition.

[0137] For optimization problem 1, due to the presence of nonlinear constraints, this invention can employ optimization algorithms capable of handling nonlinear problems, such as gradient descent or interior point methods. For optimization problem 2, due to the nonconvexity of the stability region, this invention can employ algorithms capable of handling nonconvex optimization problems, such as global optimization algorithms (e.g., branch and bound, Monte Carlo simulation), aiming to find the global optimum, or employing local optimization algorithms combined with a multi-starting-point search strategy to increase the probability of finding the global optimum.

[0138] After the solution is completed, based on the obtained critical value V min With the corresponding Lyapunov function values, an estimated stability region can be constructed. This stability region represents the range of parameters within which the system can maintain stable operation under given conditions. Therefore, the solution function under nonlinear and nonconvex constraints can be expressed as:

[0139]

[0140] The estimate of the stability region is then:

[0141] In a preferred embodiment, the step of using the power of the transmission line at the target time as the ultimate transmission power of the transmission line includes:

[0142] The sum of the output power of all generators connected to the first node of the transmission line is taken as the maximum transmission power of the transmission line.

[0143] Schematic representation: When determining the critical value, the difference between the critical value and the preset critical threshold should not exceed the preset difference threshold, which can be expressed as: V min -V thre ≤V e V thre As a preset critical threshold, V e It is a sufficiently small positive number.

[0144] It is understood that the determination process of the present invention is as follows: if the estimated critical value is less than the critical value threshold, the output power of the generator is reduced, and the critical value evaluation operation is repeated until the estimated critical value is slightly greater than the critical value threshold; if the estimated critical value is much greater than the critical value threshold, the output power of the generator is increased, and the following critical value evaluation operation is repeated.

[0145] Until the estimated critical value is slightly greater than the critical value threshold (i.e., the difference between the critical value and the preset critical value threshold is not greater than the preset difference threshold), the sum of the output power of all generators connected to the first node of the target line is recorded, which is the limit transmission power of the target line.

[0146] In a preferred embodiment, such as Figure 3The flowchart shown illustrates the steps of the transmission line limit power calculation method of the present invention:

[0147] Step S1: Construct a transient stability analysis model of the power system containing n synchronous generators and m frequency loads, eliminate the number of generations by network contraction, and eliminate the equilibrium manifold by using relative angles as state variables;

[0148] Step S2: Represent the transient stability analysis model of the power system as a Lure-type system;

[0149] Step S3: Set candidate Lyapunov functions and obtain the analytical expressions of candidate Lyapunov functions by solving linear matrix inequalities;

[0150] Step S4: Estimate the critical value corresponding to the Lyapunov function based on the transient stability criterion. The set consisting of the Lyapunov function and the obtained critical value is the estimate of the stability region.

[0151] Step S5: If the estimated critical value is less than the critical value threshold, reduce the generator output power and repeat steps S1-S4 until the estimated critical value is slightly greater than the critical value threshold; if the estimated critical value is much greater than the critical value threshold, increase the generator output power and repeat steps S1-S4 until the estimated critical value is slightly greater than the critical value threshold.

[0152] Step S6: Record the sum of the output power of all generators connected to the first node of the target line at this time, which is the limit transmission power of the target line.

[0153] To illustrate, if the estimated critical value is less than the critical threshold, it indicates that the current power system lacks stability and is at risk of instability. Therefore, it is necessary to reduce the output power of all generators connected to the head node of the target line. Subsequently, the critical value assessment operation is repeated to observe whether the adjusted system stability improves. This process will continue until the estimated critical value is slightly greater than the critical threshold, indicating that the system stability has reached an acceptable level.

[0154] If the estimated critical value is significantly larger than the critical threshold, it indicates that the current power system is too stable and has the potential to further increase transmission power. Therefore, it is necessary to increase the output power of all generators connected to the head node of the target line. Similarly, the critical value assessment operation is repeated to monitor how system stability changes after the power is increased. This process will continue until the estimated critical value is slightly larger than the critical threshold to maintain system stability and maximize transmission power.

[0155] When the difference between the estimated critical value and the critical value threshold is no greater than the preset difference threshold, the system is considered to have reached a stable and efficient operating state. At this time, the sum of the output power of all generators connected to the first node of the target line is recorded; this value is the limit transmission power of the target line.

[0156] Therefore, the determination process of the present invention can accurately determine the limit transmission power of the target line by continuously adjusting the output power of the generator and repeatedly performing the critical value evaluation operation, and calculate the limit transmission power of the line from the perspective of transient stability, thus solving the problem of transient instability caused by excessively high power transmission levels, thereby ensuring the safe and stable operation of the power system.

[0157] In a preferred embodiment, Figure 4 , Figure 5 The sum of the total output power of generators SG1 and SG2 (the power transmitted by the line between nodes 7 and 8) is represented by P0 = P m1 +P m2 P max =1.8(P) m1 +P m2 The corresponding optimal transient stability region is in δ 21 -δ 31 plane, δ 21 -δ 41 The projection onto the plane. The area enclosed by the solid red line represents the optimal transient stability region when the power transmitted by the line between nodes 7 and 8 is P0, and the area enclosed by the dashed blue line represents the region when the power transmitted by the line between nodes 7 and 8 is P. max The optimal transient stability region corresponding to the time.

[0158] Then, when the critical threshold is V thre =1, V e Taking a value of 0.01, when the power transmitted by the line between nodes 7 and 8 is P0, the estimated critical value is 1.52; when the power transmitted by the line between nodes 7 and 8 is P... max At that time, the estimated critical value was 1.01, corresponding to the power P. max This is the maximum transmission power of line 7-8.

[0159] In this example, when the power transmitted by the line between nodes 7 and 8 is Pmax = 1.8(Pm1 + Pm2), the estimated critical value decreases but still meets the stability requirements, and the power is at its maximum at this time. Therefore, Pmax is determined as the limit transmission power of line 7-8.

[0160] Therefore, by studying the transient stability region and critical value of the system under different power levels, this invention can derive the limit transmission power that meets the stability requirements, thereby ensuring that the system remains stable under various operating scenarios.

[0161] like Figure 6 As shown, based on the embodiments of the above-mentioned methods for determining the maximum transmission power of various transmission lines, the present invention provides corresponding embodiments of the apparatus.

[0162] One embodiment of the present invention provides a device for determining the maximum transmission power of a transmission line, comprising: a model building module and a maximum transmission power determination module;

[0163] The model building module is used to build a system stability model to describe the stability characteristics of the power system based on the frequency data of each load point in the transmission line and various operating indicators of the power system.

[0164] The limit transmission power determination module is used to repeatedly perform the following critical value evaluation operation until it is determined that the critical value is not less than a preset critical threshold, and the difference between the critical value and the preset critical threshold is not greater than a preset difference threshold. Then, the current time corresponding to the critical value not being less than the preset critical threshold and the difference between the critical value and the preset critical threshold being not greater than the preset difference threshold is taken as the target time. Subsequently, the power of the transmission line corresponding to the target time is taken as the limit transmission power of the transmission line.

[0165] Obtain the current frequency value of each load point at the current moment, as well as the current operating index values ​​of the power system at the current moment;

[0166] After substituting each current frequency value and each current operating index value into the system stability model, the system stability model is solved. When the function value of the system stability model is minimized, the minimum function value is taken as the critical value.

[0167] If the critical value is determined to be less than a preset critical threshold, the power of each generator in the transmission line is reduced; otherwise, it is determined whether the difference between the critical value and the preset critical threshold is greater than a preset difference threshold. If the difference is determined to be greater than the preset difference threshold, the power of each generator in the transmission line is increased.

[0168] Update the current time and perform the next critical value evaluation operation.

[0169] It should be noted that the device embodiments described above are merely illustrative. The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules; they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided by this invention, the connection relationships between modules indicate that they have communication connections, which can be specifically implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0170] Those skilled in the art will clearly understand that, for convenience and simplicity, the specific working process of the device described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0171] Based on the embodiments of the above-mentioned methods for determining the maximum transmission power of various transmission lines, the present invention provides corresponding embodiments for terminal equipment.

[0172] One embodiment of the present invention provides a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements a method for determining the maximum transmission power of a power transmission line as described in any embodiment of the present invention.

[0173] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0174] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the terminal device, connecting all parts of the terminal device via various interfaces and lines.

[0175] The memory can be used to store the computer program. The processor implements various functions of the terminal device by running or executing the computer program stored in the memory and calling data stored in the memory. The memory may mainly include a program storage area and a data storage area. The program storage area may store the operating system, at least one application program required for a function, etc.; the data storage area may store data created based on the use of the mobile phone, etc. In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as hard disk, RAM, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0176] Based on the embodiments of the above-mentioned methods for determining the maximum transmission power of various transmission lines, the present invention provides corresponding embodiments for storage media.

[0177] One embodiment of the present invention provides a storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to execute a method for determining the maximum transmission power of a transmission line as described in any embodiment of the present invention.

[0178] The storage medium is a computer-readable storage medium, and the computer program is stored in the computer-readable storage medium. When executed by a processor, the computer program can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0179] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method of determining a limit transmission power of a power transmission line, characterized by, The method comprises the following steps: According to the frequency data of each load point in the power transmission line and each operating index in the power system, a system stability model for describing the stability characteristics of the power system is constructed; The critical value evaluation operation is repeatedly performed until it is determined that the critical value is not less than the preset critical threshold value and the difference between the critical value and the preset critical threshold value is not greater than the preset difference threshold value, at which time the current time corresponding to the critical value being not less than the preset critical threshold value and the difference between the critical value and the preset critical threshold value being not greater than the preset difference threshold value is taken as the target time, and then the power of the power transmission line at the target time is taken as the limit transmission power of the power transmission line: The current frequency values of each load point at the current time and each current operating index value of the power system at the current time are obtained; After substituting each current frequency value and each current operating index value into the system stability model, the system stability model is solved, and the minimum function value is taken as the critical value when the function value of the system stability model is at the minimum; When it is determined that the critical value is less than the preset critical threshold value, the power of each generator in the power transmission line is reduced, otherwise, it is determined whether the difference between the critical value and the preset critical threshold value is greater than the preset difference threshold value, and when it is determined that the difference is greater than the preset difference threshold value, the power of each generator in the power transmission line is increased; The current time is updated, and the next critical value evaluation operation is performed.

2. A method of determining a power transfer limit of a power transmission line as claimed in claim 1, wherein, The operating indexes of the power system include the angular velocity of the generator, the rotor angle between the generator and the reference generator, the steady-state rotor angle value for representing the rotor angle between the generator and the reference generator when the power system is in a stable operating state, the susceptance of each branch in the transmission network of the power system, the internal potential of the generator, the internal potential of the load point, and the angular velocity of the preset reference generator; The frequency data corresponding to each load point includes the frequency coefficient, the frequency, and the steady-state frequency value for representing the frequency of the load point when the power system is in a stable operating state; The system stability model for describing the stability characteristics of the power system is constructed according to the frequency data of each load point in the power transmission line and each operating index in the power system, which comprises: According to the frequency coefficient corresponding to each load point, the susceptance of each branch in the transmission network of the power system, the internal potential of the generator, the internal potential of the load point, the rotor angle difference between any two different generators, the steady-state rotor angle difference between any two different generators, and the angular velocity of the preset reference generator, a first functional expression for representing the operating characteristics of the generator is generated; According to the frequency coefficient corresponding to each load point, the susceptance of each branch in the transmission network of the power system, the internal potential of the generator, the internal potential of the load point, the frequency difference between any two different load points, the steady-state frequency difference between any two different load points, and the angular velocity of the preset reference generator, a second functional expression for representing the operating characteristics of the load point is generated; generating a target state vector for representing an operating state of the power system according to a deviation between a rotor angle of each generator and a steady-state rotor angle value, a deviation between a frequency of each load point and a steady-state frequency value, and an angular velocity of each generator; generating a third function for describing an operating dynamic of the power system in a state space according to the first function, the second function, the target state vector, a preset system connection matrix for representing a network structure of the power system, and a trigonometric function for generating a nonlinear term, wherein the third function comprises a nonlinear feedback term for describing a nonlinear dynamic behavior of the power system, and a linear term for describing the nonlinear dynamic behavior of the power system; generating an analytical expression of a preset function according to the preset function for describing stability of a nonlinear dynamic system and the third function; taking the analytical expression of the preset function as a system stability model for describing a stability characteristic of the power system.

3. A method of determining a power limit of a power transmission line according to claim 2, wherein, The generating a target state vector for representing an operating state of the power system according to a deviation between a rotor angle of each generator and a steady-state rotor angle value, a deviation between a frequency of each load point and a steady-state frequency value, and an angular velocity of each generator, comprises: for each generator, generating a first state vector according to a deviation between a rotor angle and a steady-state rotor angle value; generating a second state vector according to an angular velocity of each generator; for each load point, generating a third state vector according to a deviation between a frequency and a steady-state frequency value; aggregating the first state vector, the second state vector, and the third state vector to generate the target state vector for representing the operating state of the power system.

4. A method of determining a power limit of a power transmission line according to claim 3, wherein, The third function comprises: wherein x is a target state vector, A is a matrix corresponding to a linear term, B is a matrix corresponding to a nonlinear feedback term; φ(Cx) is a linear term corresponding to the target state vector after the target state vector is converted based on a trigonometric function; when i is the i th generator, then δ ij is a rotor angle difference between any two different generators in a branch, is a steady-state rotor angle difference between any two different generators in a branch; when i is the i th load point, then δ ij is a frequency difference between any two different load points, is a steady-state frequency difference between any two different load points; E is a preset system connection matrix, δ 1n is a rotor angle between a generator and a reference generator, is a steady-state rotor angle value used to represent the rotor angle between the generator and the reference generator when the power system is in a stable operation state, δ (n+m)n is a frequency corresponding to a load point, is a steady-state frequency value used to represent the frequency of the load point when the power system is in a stable operation state, and ε is a branch set in a transmission network of the power system.

5. A method of determining a power limit of a power transmission line according to claim 4, wherein, The generating an analytical expression of a preset function according to the preset function for describing stability of a nonlinear dynamic system and the third function, comprises: generating a fourth function containing the target state vector and reflecting stability of the power system according to the preset function for describing stability of the nonlinear dynamic system and the third function; substituting the third function into a derivative corresponding to the fourth function to generate a linear matrix inequality corresponding to the third function; solving the linear matrix inequality to generate the analytical expression of the preset function.

6. A method of determining a power transfer limit of a power transmission line according to claim 1, wherein, The constraint condition of the system stability model comprises a nonlinear constraint for representing a nonlinear relationship between an operating index and stability of the power system, and a non-convex constraint for representing that a transient stability region of the system stability model has non-convexity; The solving the system stability model comprises: taking a minimum function value as a critical value when the function value of the system stability model is minimum; and The solving the system stability model comprises: iteratively solving the system stability model under the nonlinear constraint and the non-convex constraint until the function value of the system stability model is minimum, and taking the minimum function value as the critical value.

7. A method of determining a power limit of a power transmission line according to claim 6, wherein, The taking the power corresponding to the transmission line at the target time as the limit transmission power of the transmission line, comprises: taking a sum of output powers of all generators connected with a first end node of the transmission line as the limit transmission power of the transmission line.

8. A device for determining the maximum transmission power of a power transmission line, characterized in that, The method comprises the following steps: The model construction module is configured to construct a system stability model for describing stability characteristics of the power system according to frequency data of each load point in the power transmission line and each operation index in the power system. The limit transmission power determination module is configured to repeatedly perform the following critical value evaluation operation until the difference between the critical value and the preset critical threshold is not greater than the preset difference threshold, and then take the current time corresponding to the condition that the difference is not greater than the preset difference threshold as a target time, and take the power of the power transmission line corresponding to the target time as the limit transmission power of the power transmission line: Obtain current frequency values of each load point at a current time and each current operation index value of the power system at the current time; After substituting each current frequency value and each current operation index value into the system stability model, solve the system stability model, and take the minimum function value as the critical value when the function value of the system stability model is at the minimum; If the critical value is less than the preset critical threshold, reduce the power of each generator in the power transmission line, or if the difference between the critical value and the preset critical threshold is greater than the preset difference threshold, increase the power of each generator in the power transmission line; Update the current time and perform the next critical value evaluation operation. The storage medium comprises a stored computer program, wherein the computer program controls the device where the storage medium is located to perform the limit transmission power determination method of the power transmission line according to any one of claims 1 to 7 when the computer program is running.

9. A terminal device, comprising: The storage medium comprises a stored computer program, wherein the computer program controls the device where the storage medium is located to perform the limit transmission power determination method of the power transmission line according to any one of claims 1 to 7 when the computer program is running.

10. A storage medium, characterized by ​

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