Post-fault system frequency balance point determination method considering detailed dynamic element model

Abstract

The invention provides a post-fault system frequency balance point determination method considering a detailed dynamic element model. Comprising the following steps: carrying out load flow calculation on a system before a fault to obtain a load flow calculation result, and determining a balance point state variable steady-state value and a balance point algebraic variable steady-state value of the system under a given operation condition according to the load flow calculation result; determining a whole system model according to the element model of the system, the balance point state variable steady-state value and the balance point algebraic variable steady-state value; the phase reference node selection equation is used for determining phase reference nodes, the initial iteration condition of the system is determined according to the fault type of the system, the whole system model is solved according to the initial iteration condition, and the frequency balance point of the system after the fault is determined through the phase reference node selection equation. The problems that in the prior art, after-fault frequency balance point solving depends on system time domain simulation, and after-fault system behavior analysis is slow due to the fact that the online application time domain simulation process is slow are solved.

Description

Technical Field

[0001] The present application relates to the technical field of determining a frequency balance point of a system after a fault, and in particular, to a method, device, computer-readable storage medium and electronic device for determining a frequency balance point of a system after a fault taking into account a detailed dynamic component model. Background Art

[0002] Power flow calculation is the basis of power system planning, operation and stability analysis. In conventional power flow calculation, a slack node is usually selected and it is assumed that the unbalanced power generated by the system interference is balanced by this node. In actual process, faults or operations such as line disconnection, machine shedding and load shedding often cause the system to generate large unbalanced power, resulting in changes in system frequency. The regulation relationship between unbalanced power and system frequency is often the result of the joint action of the generator sets involved in frequency regulation in the system. The static power flow calculation cannot accurately calculate the actual operation of the system after the fault. The existing stability analysis of post-fault systems is often based on time-domain simulation software. By analyzing the system equations of various dynamic components and selecting appropriate simulation steps, the change curves of various state variables of the system under different disturbances are obtained. Due to the solving characteristics of algebraic-differential equations, the time-domain solution of thousands of nonlinear differential equations in actual-scale power systems is very computationally intensive and requires a considerable amount of time to complete. The analysis method of simplifying the frequency regulation effect of each generator and speed regulation system in the system through the dynamic power flow method can better reflect the equilibrium state of the actual system after a fault than traditional power flow calculations, but there are also problems such as inaccurate generator models, large errors between DC single-pole locking and simulation results, and poor convergence.

[0003] The mathematical essence of the power system flow calculation process is still to solve a set of multivariate nonlinear equations, which are mainly solved by iterative methods. In order to more accurately reflect the distribution of unbalanced power in the system dynamic components, it is considered to introduce the system frequency as a state variable and establish a detailed model of dynamic components for solving the frequency balance point. At present, the solution of the frequency balance point after a fault depends on the system time domain simulation. For online applications, the slow time domain simulation process is not conducive to the rapid analysis of the system behavior after the fault. Therefore, it is necessary to obtain a fast solution method for the frequency balance point considering the detailed dynamic component model of the system.

[0004] In actual simulation, it is found that the behavior of the power system after a fault can be obtained by calculating and analyzing the balance point after the fault. Different fault types and different configurations of the power system will lead to different system behaviors. The solution of the frequency balance point after the fault can not only understand whether the system is capable of reaching equilibrium after the disturbance before the fault, thereby evaluating the system stability, but also know the potential problems of the system, thereby optimizing the system operation mode and providing a reference for the planning and operation of the system. And with the expansion of the scale of the power system and the increase in the proportion of renewable energy, the uncertainty of system operation increases and the reliability decreases, and the types and number of potential faults in the system increase, so it is of great significance to make accurate judgments on the behavior of the system after the fault. Summary of the invention

[0005] The main purpose of the present application is to provide a method, device, computer-readable storage medium and electronic device for determining the frequency balance point of a post-fault system taking into account a detailed dynamic component model, so as to at least solve the problem that the solution of the post-fault frequency balance point in the prior art relies on system time domain simulation, and the slow time domain simulation process for online applications leads to slow analysis of the post-fault system behavior.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a method for determining the frequency balance point of a system after a fault considering a detailed dynamic component model is provided, comprising: performing a power flow calculation on the system before the fault to obtain a power flow calculation result, and determining the steady-state value of the balance point state variable and the steady-state value of the balance point algebraic variable of the system under a given operating condition according to the power flow calculation result; determining the full system model according to the component model of the system, the steady-state value of the balance point state variable and the steady-state value of the balance point algebraic variable, the full system model including a power supply model, a load model and a network equation; constructing a phase reference node selection equation, wherein the phase reference node selection equation is used to determine the phase reference node, and the phase reference node is the node that is least affected by the disturbance voltage and power parameter changes for different disturbed points; determining the initial iteration condition of the system according to the fault type of the system, and solving the full system model and the phase reference node selection equation according to the initial iteration condition to determine the frequency balance point of the system after the fault.

[0007] Optionally, determining a power supply model in the whole system model according to the component model of the system, the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable includes:

[0008] According to the first set of equations:

[0009]

[0010] Determine the power model of the full system model, where X d With X qRespectively represent the d-axis and q-axis synchronous reactance, V x With V y Represent the voltage at the x-terminal and y-terminal of the generator, R a is the stator resistance, I Gx and I Gy are the components of the power supply injection current on the x-axis and y-axis respectively, K is the regulator gain coefficient, K A is the regulator gain, K V is the proportional integral, V ref is the excitation voltage reference value, R C is the load compensation resistance component, X C is the load compensation reactance component, D is the damping coefficient, F is the system frequency after the fault, and Y ref is the reference value of the valve opening, K GW is the speed magnification factor, b p is the proportion of constant current load, and δ is the power angle.

[0011] Optionally, determining a load model in the whole system model according to the component model of the system, the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable includes:

[0012] According to the second set of equations:

[0013]

[0014] Determine the load model of the full system model, where V 0 is the initial steady-state voltage, P L0 and Q L0 is the power absorbed by the load at the initial steady-state voltage and frequency, a P and a Q 、b P and b Q 、c P and c Q are the proportions of constant impedance load, constant current load and constant power load respectively, F is the system frequency after the fault, L DP is the active frequency factor, L DQ is the reactive frequency factor, I Lx and I Ly are the components of the load injected current on the x-axis and y-axis respectively.

[0015] Optionally, determining the network equations in the whole system model according to the component model of the system, the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable includes:

[0016] According to the first formula:

[0017] Determine the network equations of the full system model, where i=1, 2, ..., n, is the injection current of the power supply, Inject current into the load, Y ij is the mutual admittance between node i and node j, The voltage at node j.

[0018] Optionally, a phase reference node selection equation is constructed, including:

[0019] According to the second formula: Construct the phase reference node selection equation, where V kx and V ky are the components of the voltage at the reference node k on the x-axis and y-axis, θ k0 is the voltage phase of node k.

[0020] Optionally, determining the initial iteration condition of the system according to the fault type of the system includes: determining a base state disturbance value according to the fault type of the system, and determining whether the base state disturbance value is greater than a preset disturbance value, wherein the base state disturbance value is determined according to the voltage, frequency and power of the fault node of the system; when the base state disturbance value is less than or equal to the preset disturbance value, adopting the initial iteration condition of the system's pre-fault equilibrium point as the initial iteration condition of the post-fault equilibrium point.

[0021] Optionally, after determining whether the base state disturbance value is greater than a preset disturbance value, the method further includes:

[0022] When it is determined that the base state disturbance value is greater than the preset disturbance value, according to the third formula: Determine the initial iteration condition, where: is the modified initial value of iteration, x( 0 ) is the initial iteration point before correction, p is the fault parameter, p 0 is the initial value of the fault parameter, h p is the partial derivative of the fault parameter p, h x is the partial derivative with respect to the state variable x.

[0023] According to another aspect of the present application, a device for determining a frequency balance point of a system after a fault taking into account a detailed dynamic component model is provided, comprising: a first determination unit, for performing power flow calculation on the system before the fault to obtain a power flow calculation result, and determining the steady-state value of the balance point state variable and the steady-state value of the balance point algebraic variable of the system under a given operating condition according to the power flow calculation result; a second determination unit, for determining a full system model according to the component model of the system, the steady-state value of the balance point state variable and the steady-state value of the balance point algebraic variable, wherein the full system model includes a power supply model, a load model and a network equation; a construction unit, for constructing a phase reference node selection equation, wherein the phase reference node selection equation is used to determine a phase reference node, and the phase reference node is a node that is least affected by the disturbance voltage and power parameter changes for different disturbed points; a third determination unit, for determining an initial iteration condition of the system according to the fault type of the system, and solving the full system model and the phase reference node selection equation according to the initial iteration condition to determine the frequency balance point of the system after the fault.

[0024] According to another aspect of the present application, a computer-readable storage medium is provided, the computer-readable storage medium comprising a stored program, wherein when the program is running, the device where the computer-readable storage medium is located is controlled to execute any one of the methods for determining the frequency balance point of a post-fault system considering a detailed dynamic component model.

[0025] According to another aspect of the present application, an electronic device is provided, comprising: one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and the one or more programs include methods for executing any one of the methods for determining the frequency balance point of a post-fault system considering a detailed dynamic element model.

[0026] Applying the technical solution of the present application, the power flow calculation is performed on the system before the fault, and the power flow calculation result is obtained. According to the power flow calculation result, the steady-state value of the system's balance point state variable and the steady-state value of the balance point algebraic variable under a given operating condition are determined; the whole system model is determined according to the system's component model, the steady-state value of the balance point state variable and the steady-state value of the balance point algebraic variable, and the whole system model includes a power supply model, a load model and a network equation; a phase reference node selection equation is constructed, wherein the phase reference node selection equation is used to determine the phase reference node, and the phase reference node is the node with the least influence on different disturbed points, disturbed voltage and power parameter changes; the initial iteration condition of the system is determined according to the fault type of the system, and the whole system model and the phase reference node selection equation are solved according to the initial iteration condition to determine the frequency balance point of the system after the fault. The problem that the solution of the frequency balance point after the fault in the prior art depends on the system time domain simulation and the slow analysis of the system behavior after the fault due to the slow online application of the time domain simulation process is solved, and the frequency balance point of the system after the fault can be efficiently calculated. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings constituting part of the present application are used to provide a further understanding of the present application. The exemplary embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0028] Figure 1 A hardware structure block diagram of a mobile terminal for executing a method for determining a frequency balance point of a system after a fault considering a detailed dynamic component model provided in an embodiment of the present application is shown;

[0029] Figure 2 A flow chart of a method for determining a frequency balance point of a system after a fault considering a detailed dynamic component model is shown according to an embodiment of the present application;

[0030] Figure 3 A schematic diagram of a specific power system post-fault balance point calculation process provided in accordance with an embodiment of the present application is shown;

[0031] Figure 4 A block diagram of an FV type excitation system provided according to an embodiment of the present application is shown;

[0032] Figure 5 A block diagram of a GM type regulation system provided according to an embodiment of the present application is shown;

[0033] Figure 6 A block diagram of a GA type electro-hydraulic servo system provided according to an embodiment of the present application is shown;

[0034] Figure 7 A block diagram of a TW type water turbine system provided according to an embodiment of the present application is shown;

[0035] Figure 8 A structural block diagram of a device for determining a frequency balance point of a post-fault system taking into account a detailed dynamic component model provided according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0038] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0039] As introduced in the background technology, the solution of the post-fault frequency balance point in the prior art relies on the system time domain simulation. The time domain simulation process for online application is slow, resulting in a slow analysis of the post-fault system behavior. In order to solve the problem that the solution of the post-fault frequency balance point in the prior art relies on the system time domain simulation. The time domain simulation process for online application is slow, resulting in a slow analysis of the post-fault system behavior. The embodiments of the present application provide a method, device, computer-readable storage medium and electronic device for determining the frequency balance point of the post-fault system considering a detailed dynamic component model.

[0040] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0041] The method embodiments provided in the embodiments of the present application can be executed in a mobile terminal, a computer terminal or a similar computing device. Taking running on a mobile terminal as an example, Figure 11 is a hardware structure block diagram of a mobile terminal of a method for determining a system frequency balance point after a fault considering a detailed dynamic component model according to an embodiment of the present invention. Figure 1 As shown, the mobile terminal may include one or more ( Figure 1 Only one is shown in the figure) a processor 102 (the processor 102 may include but is not limited to a processing device such as a microprocessor MCU or a programmable logic device FPGA) and a memory 104 for storing data, wherein the mobile terminal may also include a transmission device 106 and an input / output device 108 for communication functions. It can be understood by those skilled in the art that Figure 1 The structure shown is only for illustration and does not limit the structure of the mobile terminal. Figure 1 More or fewer components as shown, or with Figure 1 Different configurations are shown.

[0042] The memory 104 can be used to store computer programs, for example, software programs and modules of application software, such as the computer program corresponding to the method for determining the frequency balance point of the system after a fault considering the detailed dynamic component model in the embodiment of the present invention. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, that is, to implement the above method. The memory 104 may include a high-speed random access memory, and may also include a non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some examples, the memory 104 may further include a memory remotely arranged relative to the processor 102, and these remote memories can be connected to the mobile terminal via a network. Examples of the above network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof. The transmission device 106 is used to receive or send data via a network. The specific example of the above network may include a wireless network provided by a communication provider of the mobile terminal. In one example, the transmission device 106 includes a network adapter (Network Interface Controller, referred to as NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 106 may be a radio frequency (RF) module, which is used to communicate with the Internet wirelessly.

[0043] In this embodiment, a method for determining the frequency balance point of a post-fault system considering a detailed dynamic component model is provided, which runs on a mobile terminal, a computer terminal or a similar computing device. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0044] Figure 2 FIG. 1 is a flow chart of a method for determining a frequency balance point of a system after a fault considering a detailed dynamic component model according to an embodiment of the present application. Figure 2 As shown, the method comprises the following steps:

[0045] Step S201, performing power flow calculation on the system before the fault to obtain power flow calculation results, and determining the steady-state values ​​of the equilibrium point state variables and the steady-state values ​​of the equilibrium point algebraic variables of the system under a given operating condition according to the power flow calculation results;

[0046] Specifically, according to the power flow calculation of the power grid system before the fault, the steady-state value of the state variable of the equilibrium point and the steady-state value of the algebraic variable of the equilibrium point when the system is in a steady state can be determined according to the calculation results.

[0047] Step S202, determining a full system model according to the system component model, the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable, wherein the full system model includes a power supply model, a load model and a network equation;

[0048] Among them, the component models of the power grid system include generators, transformers, transmission lines, loads, and switchgear. These components are interconnected, and the normal operation of the power grid system and the supply of power are achieved through the transmission and distribution of electric energy. The generator is the energy source of the power grid system. The transformer increases or decreases the voltage of the electric energy generated by the generator, and then transmits the electric energy to loads in different regions through transmission lines. Finally, the flow and distribution of electric energy are controlled by switchgear. The operation of the entire power grid system is completed by the coordination and cooperation of these components.

[0049] Specifically, the power supply model and load model expressions for solving the equilibrium point in steady state are derived based on the component model of the system, and the full system model for solving the equilibrium point is further formed in combination with the network equation.

[0050] Step S203, constructing a phase reference node selection equation, wherein the phase reference node selection equation is used to determine a phase reference node, and the phase reference node is a node least affected by the disturbance voltage and power parameter changes for different disturbed points;

[0051] Specifically, for the selection of phase reference nodes, for different disturbed points, selecting nodes that are less affected by changes in parameters such as disturbance voltage and power as phase reference nodes can effectively avoid the situation where the initial value deviates from the convergence domain. This is reflected in the network topology, that is, the nodes that are electrically far away from the disturbed points can be quantitatively calculated through the equivalent impedance between nodes.

[0052] Step S204, determining the initial iteration condition of the system according to the fault type of the system, and solving the whole system model and the phase reference node selection equation according to the initial iteration condition to determine the frequency balance point of the system after the fault.

[0053] Specifically, for the determination of the initial iteration conditions of the base state, most of the base state disturbances can directly use the pre-fault equilibrium point as the initial iteration condition of the post-fault equilibrium point. For some base state disturbances that have a significant impact on the stability margin and can cause obvious local power flow in the power grid, the tangent method can be directly considered to obtain the initial iteration conditions. For serious faults, the continuous method is used to select an appropriate step size to track the post-fault equilibrium point.

[0054] Through this embodiment, the power flow calculation is performed on the system before the fault to obtain the power flow calculation result, and the steady-state value of the balance point state variable and the steady-state value of the balance point algebraic variable of the system under a given operating condition are determined according to the power flow calculation result; the whole system model is determined according to the component model of the system, the steady-state value of the balance point state variable and the steady-state value of the balance point algebraic variable, and the whole system model includes a power supply model, a load model and a network equation; a phase reference node selection equation is constructed, wherein the phase reference node selection equation is used to determine the phase reference node, and the phase reference node is the node with the least influence on the disturbance voltage and power parameter changes for different disturbed points; the initial iteration condition of the system is determined according to the fault type of the system, and the whole system model and the phase reference node selection equation are solved according to the initial iteration condition to determine the frequency balance point of the system after the fault. The problem that the solution of the frequency balance point after the fault in the prior art depends on the system time domain simulation and the slow analysis of the system behavior after the fault due to the slow online application time domain simulation process is solved, and the frequency balance point of the system after the fault can be efficiently calculated.

[0055] In the specific implementation process, the power supply model in the whole system model is determined according to the component model of the system, the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable, including:

[0056] According to the first set of equations:

[0057]

[0058] Determine the power model of the full system model, where X d With X q Respectively represent the d-axis and q-axis synchronous reactance, V x With Vy Represent the voltage at the x-terminal and y-terminal of the generator, R a is the stator resistance, I Gx and I Gy are the components of the power supply injection current on the x-axis and y-axis respectively, K is the regulator gain coefficient, K A is the regulator gain, K V is the proportional integral, V ref is the excitation voltage reference value, R C is the load compensation resistance component, X C is the load compensation reactance component, D is the damping coefficient, F is the system frequency after the fault, and Y ref is the reference value of the valve opening, K GW is the speed magnification factor, b p is the proportion of constant current load, and δ is the power angle.

[0059] This method first needs to model the power supply, such as the commonly used four-winding synchronous generator model, whose stator side voltage steady-state balance equation is:

[0060]

[0061] Among them, X d and X q Respectively represent the d-axis and q-axis synchronous reactance; V d and V q Indicates the d-axis and q-axis voltages. The voltage and current involved in equation (1) satisfy the dq-xy coordinate transformation relationship with the voltage and current in the network. The coordinate transformation equation taking into account the voltage and current is:

[0062]

[0063]

[0064] For excitation, taking a simple FV type excitation system as an example, considering the existence of the PSS DC isolation link, the steady-state additional excitation input is zero, and the equation under steady state is derived as follows:

[0065] E fq =K FV (V ref -V C ) (4)

[0066] Where V ref is the excitation voltage reference value, K FV is the proportionality coefficient, V C To measure the compensation voltage, the terminal voltage V x and V y The relationship between them is:

[0067]

[0068] In the formula, R C , X C The resistance and reactance components of the load are compensated.

[0069] Consider the rotor motion equation of the synchronous generator, with the frequency F of the system after disturbance S =F N F redefines the frequency reference,

[0070]

[0071] Among them, P m ,P e ,D and T J They are respectively the prime mover mechanical power, prime mover electromagnetic power, rotor damping coefficient and rotor inertia time constant of the generator; F is the system frequency after the fault. Synchronous generator electromagnetic power P e The expression is given by the grid point equation:

[0072]

[0073] For the prime mover and its speed control system, taking a simple GM-GA-TW turbine and its speed control system as an example, the equation under steady state is derived as follows:

[0074]

[0075] Where Y ref is the reference value of the valve opening, K W and b p are the regulator gain coefficient and the difference coefficient respectively. Substituting equations (2) to (5) into equation (1), and equations (7) and (8) into equation (6), we can get the power model of the whole system model of the synchronous generator set after the disturbance.

[0076] Specifically, the load model in the whole system model is determined according to the component model of the system, the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable, including:

[0077] According to the second set of equations:

[0078]

[0079] Determine the load model of the whole system model, where V 0 is the initial steady-state voltage, P L0 and Q L0 is the power absorbed by the load at the initial steady-state voltage and frequency, a P and a Q 、bP and b Q 、c P and c Q are the proportions of constant impedance load, constant current load and constant power load respectively, F is the system frequency after the fault, L DP is the active frequency factor, L DQ is the reactive frequency factor, I Lx and I Ly are the components of the load injected current on the x-axis and y-axis respectively.

[0080] For the load model, this method selects the ZIP model that considers voltage and frequency characteristics, which is:

[0081]

[0082] Among them, V 0 is the initial steady-state voltage, P L0 and Q L0 is the power absorbed by the load at the initial steady-state voltage and frequency, a P and a Q ,b P and b Q ,c P and c Q are the proportions of constant impedance load, constant current load and constant power load respectively, K P and K Q is the load change factor relative to the system frequency. Also consider the grid connection point equation:

[0083]

[0084] Substituting equation (11) into equation (10), we can obtain the load model of the whole system model after the disturbance.

[0085] More specifically, the network equations in the whole system model are determined according to the component model of the system, the steady-state values ​​of the equilibrium point state variables and the steady-state values ​​of the equilibrium point algebraic variables, including:

[0086] According to the first formula:

[0087] Determine the network equations of the full system model, where i = 1, 2, ..., n, is the injection current of the power supply, Inject current into the load, Y ij is the mutual admittance between node i and node j, The voltage at node j.

[0088] The method forms a whole system model of the system by the power supply model, load model and network equations mentioned above.

[0089] Furthermore, a phase reference node selection equation is constructed, including:

[0090] According to the second formula: Construct the phase reference node selection equation, where V kx and V ky are the components of the voltage at the reference node k on the x-axis and y-axis, θ k0 is the voltage phase of node k.

[0091] For the selection of phase reference nodes, this method selects nodes that are less affected by changes in parameters such as disturbance voltage and power as phase reference nodes for different disturbed points. This can effectively avoid the situation where the initial value deviates from the convergence domain. This is reflected in the network topology, that is, the nodes that are electrically far away from the disturbed points can be quantitatively calculated through the equivalent impedance between nodes.

[0092] Furthermore, the initial iteration conditions of the system are determined according to the fault type of the system, including:

[0093] Determine a base state disturbance value according to the fault type of the system, and determine whether the base state disturbance value is greater than a preset disturbance value, wherein the base state disturbance value is determined according to the voltage, frequency and power of the fault node of the system;

[0094] When the base state disturbance value is less than or equal to the preset disturbance value, the initial iteration condition of the system's pre-fault equilibrium point is used as the initial iteration condition of the post-fault equilibrium point.

[0095] Specifically, after determining whether the base state disturbance value is greater than a preset disturbance value, the method further includes:

[0096] When it is determined that the ground state disturbance value is greater than the preset disturbance value, according to the third formula: Determine the initial iteration conditions, where is the modified initial value of iteration, x( 0) is the initial iteration point before correction, p is the fault parameter, and p 0 is the initial value of the fault parameter, h p is the partial derivative of the fault parameter p, h x is the partial derivative with respect to the state variable x.

[0097] This method obtains the initial iteration conditions of the base state. For most base state disturbances, the pre-fault equilibrium point can be directly used as the initial iteration condition of the post-fault equilibrium point. For some base state disturbances that have a significant impact on the stability margin and can cause obvious local power flow in the power grid, the tangent method can be directly used to obtain the initial iteration conditions. For more complex and serious faults, the continuous method is used to select the appropriate step size to track the post-fault equilibrium point.

[0098] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the implementation process of the method for determining the frequency balance point of a system after a fault considering a detailed dynamic component model of the present application will be described in detail below in combination with specific embodiments.

[0099] This embodiment relates to a specific method for determining a frequency balance point of a system after a fault by considering a detailed dynamic component model, such as Figure 3 As shown, the following steps are included:

[0100] 1) Calculate the system power flow before the fault, and use the power flow calculation results to back-calculate the values ​​of various variables under the initial operating conditions to obtain the initial steady-state values ​​of the equilibrium point state variables and algebraic variables;

[0101] 2) Based on the component model of the system, the power supply model and load model expressions for solving the equilibrium point in steady state are derived, and combined with the network equation to further form the full system model for solving the equilibrium point;

[0102] 3) The nonlinear equations are well-posed by selecting the phase reference node;

[0103] 4) Modify the parameters of the iterative equation group according to different fault types and form the initial value of the iteration. For the base state disturbance, the tangent method can be used to predict the initial value of the equilibrium point iteration at the equilibrium point before the disturbance. For severe faults, the continuous method is used to select the appropriate step size to track the equilibrium point after the fault;

[0104] 5) Iterate and solve the problem and analyze the stability at the equilibrium point.

[0105] In the required step 2), a full system model for equilibrium point solution is required. A typical full system equilibrium point solution modeling example is given below. For convenience of representation, the subscript of the i-th node is ignored in the derivation.

[0106] First, the power supply needs to be modeled. For example, the commonly used four-winding synchronous generator model has a stator side voltage steady-state balance equation as follows:

[0107]

[0108] Among them, X d and X q Respectively represent the d-axis and q-axis synchronous reactance; V d and V q Indicates the d-axis and q-axis voltages. The voltage and current involved in equation (1) satisfy the dq-xy coordinate transformation relationship with the voltage and current in the network. The coordinate transformation equation taking into account the voltage and current is:

[0109]

[0110] For excitation, taking a simple FV type excitation system as an example, the transfer function block diagram is as follows Figure 4 As shown, considering the existence of the PSS DC isolation link, the steady-state additional excitation input is zero, and the equation in the steady state is derived as follows:

[0111] E fq =K FV (V ref -V C ) (4)

[0112] Where V ref is the excitation voltage reference value, K FV is the proportionality coefficient, V C To measure the compensation voltage, the terminal voltage V x and V y The relationship between them is:

[0113]

[0114] In the formula, R C , X C The resistance and reactance components of the load compensation.

[0115] Consider the rotor motion equation of the synchronous generator, with the frequency F of the system after disturbance S =F N F redefines the frequency reference as follows:

[0116]

[0117] Among them, P m ,P e ,D and T J They are respectively the prime mover mechanical power, prime mover electromagnetic power, rotor damping coefficient and rotor inertia time constant of the generator; F is the system frequency after the fault. Synchronous generator electromagnetic power P e The expression is given by the grid point equation:

[0118]

[0119] For the prime mover and its speed control system, take a simple GM-GA-TW turbine and its speed control system as an example. The GM control system block diagram in the transfer function block diagram is as follows: Figure 5 As shown in the figure, the block diagram of GA type electro-hydraulic servo system is as follows Figure 6 As shown in the figure and the TW type prime mover block diagram as shown in Figure 7 As shown, the equation under steady state is derived as follows:

[0120]

[0121] Where, is the reference value of the valve opening, and are the regulator gain coefficient and difference coefficient respectively. Substituting equations (2) to (5) into equation (1), and equations (7) and (8) into equation (6), the steady-state equation of the synchronous generator set after the disturbance can be obtained:

[0122]

[0123] Then, for the load model, the ZIP model considering voltage and frequency characteristics is selected, and:

[0124]

[0125] Among them, V 0 is the initial steady-state voltage, P L0 and Q L0 is the power absorbed by the load at the initial steady-state voltage and frequency, a P and a Q ,b P and b Q ,c P and c Q are the proportions of constant impedance load, constant current load and constant power load respectively, K P and K Q is the load change factor relative to the system frequency. Also consider the grid connection point equation:

[0126]

[0127] Substituting equation (11) into equation (10), we can obtain the steady-state equation of the load after the disturbance:

[0128]

[0129] Finally, the communication network is characterized as:

[0130]

[0131] In the formula, is the injection current of the power supply, Inject current into the load.

[0132] Above, equations (9), (12) and (13) together constitute the full system model for calculating the equilibrium point of a specified system.

[0133] In the required step 3), for the selection of the phase reference node, for different disturbed points, selecting the node that is less affected by the change of parameters such as the disturbance voltage and power as the phase reference node can effectively avoid the situation where the initial value deviates from the convergence domain. This is reflected in the network topology, that is, the nodes that are electrically far away from the disturbed point can be quantitatively calculated by the equivalent impedance between the nodes. The equivalent impedance between nodes ij is numerically equal to the voltage difference between nodes i and j after the unit current is injected into node i:

[0134]

[0135] According to the superposition principle, equation (12) is transformed into:

[0136] Z ij,equ =(Z ii -Z ij )-(Z ij -Z jj ) (15)

[0137] Among them, Z ii ,Z jj and Z ij They represent the self-impedance of node i, the self-impedance of node j, and the mutual impedance of node ij respectively. The larger the equivalent impedance between the node and the fault node, and the farther the electrical distance from the fault point, the more suitable it is as a phase reference node.

[0138] After selecting the phase reference node based on this, the equation corresponding to the supplementary phase reference node in the nonlinear equation group is calculated at the equilibrium point composed of equations (9), (12) and (13):

[0139]

[0140] Where k is the phase reference node number, and the voltage phase at this point is θ k0 The x-axis and y-axis components of the voltage are V kx and V ky At this point, the number of unknowns is equal to the number of equations, and the system of equations is well-posed.

[0141] In the required step 4), the initial iteration conditions of the base state are obtained. For most base state disturbances, the pre-fault equilibrium point can be directly used as the initial iteration condition of the post-fault equilibrium point. For some base state disturbances that have a significant impact on the stability margin and can cause obvious local power flow in the power grid, the tangent method can be directly used to obtain the initial iteration conditions. The active load at the load node i is P L0,i Change to P L1,i Take this as an example, and replace the load model in the equilibrium point solution equation group with:

[0142]

[0143] Assuming that the whole system equation is extended to h(x,u)=0, the modified initial iteration condition is obtained:

[0144]

[0145] For more complex and serious faults, the equilibrium point solution process can be divided into a continuous process, with the active output of the synchronous machine at node a being Y G0,a Change to Y G1,a , line bc is cut off after a short circuit occurs, and the active load at load node d is P L0,d Change to P L1,d The reactive load is Q L0,d Change to Q L1,d At the same time, as an example, the fault scalar parameter λ is introduced to describe the continuous change process of the fault, and the iterative equation group is modified according to different fault types as follows:

[0146]

[0147] in, are the parameterized prime mover valve opening of node a, the self-impedance of nodes b and c and the mutual impedance between nodes b and c, the initial load active power and initial load reactive power of node d, λ is a scalar parameter describing the continuous change of fault and λ∈[0,1].

[0148] Substituting the corresponding elements in the equilibrium point solution equation into the variable form in equation (18), we get h(x,λ)=0, and then the tangent vector at the equilibrium point is formed by the following equation:

[0149]

[0150] And estimate according to the following formula:

[0151]

[0152] Where h is the step size, which needs to be corrected according to the curvature of the curve formed by the continuation method to ensure that the approximate solution falls within the convergence domain while having a larger step size.

[0153] The correction equation is:

[0154]

[0155] In the formula, x k is a continuous parameter.

[0156] In the required step 5), the error is finally calculated by comparing with the transient simulation result and judging whether the equilibrium point exists to analyze the universality of the solution method.

[0157] The relative error percentage between the calculation result and the transient simulation is determined by the following formula:

[0158]

[0159] Among them, F S represents the transient simulation results, F C Indicates the calculation result.

[0160] Compared with the prior art, the advantages of this embodiment are:

[0161] First: The accuracy of the model considered is basically the same as that of the transient simulation software. For the equilibrium point problem after a fault, it has an accuracy that cannot be achieved by conventional power flow calculation methods and dynamic power flow calculation methods.

[0162] Second: Compared with the transient simulation process, the method of this embodiment greatly reduces the computational complexity of solving the post-fault equilibrium point, and has obvious advantages in both computational speed and storage space.

[0163] Third: The gradient initial iteration condition proposed in this embodiment can form the initial value of the iteration with a smaller amount of calculation for different faults, and the continuous method can give an exact conclusion on whether the equilibrium point exists after the fault, providing guidance for the stability analysis of the system after the fault, and has a wide range of application scenarios in actual power grid safety analysis and dispatching accident handling.

[0164] In order to verify the accuracy and computational efficiency of the method for determining the frequency balance point of the system after a fault considering the detailed dynamic component model in this embodiment, programming and simulation are carried out on an Intel(R)Core(TM)i5-7400@3.00GHz personal computer equipped with 8.00GBRAM based on MATLAB R2021a and DSP 2.3.33.1 software platforms. The modeling method in Chapter 2 and the calculation and analysis methods in Chapter 3 are verified by using a 39-node system and the Hainan power grid system as the test system.

[0165] Various types of ground state perturbations are considered, and the specific perturbations are described in Table 1.

[0166] Table 1

[0167]

[0168] It should be noted that for faults 1 to 6, the initial value of the balance point iteration is directly obtained by using the system balance point before the fault, while for faults 7 and 8, the system balance point before the fault cannot converge. At this time, the tangent method is used to correct the balance point before the fault as the initial value of the iteration. The comparison of the voltage deviation changes before and after correction with the transient simulation results is shown in Table 2, where the iteration convergence error is selected as ε = 10 -5 .

[0169] Table 2

[0170]

[0171] Considering a variety of basic disturbance types, the comparison results of system frequency calculation after various disturbances in Table 1 are shown in Table 3. In order to obtain accurate and stable simulation values ​​of the system equilibrium point after disturbance, the time domain simulation step in the table is set to 0.25 cycles, the total simulation time of disturbances 1 to 4, 7 to 8 is set to 200s, and the total simulation time of disturbances 5 to 6 is set to 80s.

[0172] Table 3

[0173]

[0174] Since the stability of a stable system is not easy to change after suffering from various basic disturbances, in this case, the direct calculation method of the equilibrium point in this paper combines the advantages of fast calculation speed of the power flow method and the accuracy of time domain simulation solution, and usually consumes less computing resources, including CPU, memory, etc., to obtain the equilibrium point of the system after the disturbance more conveniently and accurately. The time and accuracy meet the requirements of real-time monitoring of the steady-state characteristics of the system, and can further provide guidance for monitoring the behavior of the system after the disturbance and optimizing the power grid operation strategy.

[0175] Considering various serious fault types, the fault information is shown in Table 4, where the numbers after G, L and B represent the number of generators with faulty generators, the number of lines cut off after three-phase short circuit and the number of loads with faults. The comparison table of balance point calculation results and simulation results is shown in Table 5.

[0176] Table 4

[0177]

[0178] Through the calculation results of the balance points of the above serious faults, it can be seen that the existence of the balance point of the system after the fault is the premise for the system to maintain stability. The fault that causes the non-existence of the balance point will cause some nodes of the system to break through the voltage stability margin. At this time, the system voltage is unstable, which is manifested as voltage monotonic instability, corresponding to fault 11; and when the balance point exists, there are two situations. If the system has sufficient damping, the fluctuation amplitude of the variables caused by the system fault can be gradually reduced, and the system reaches stability, corresponding to fault 9; the second system has insufficient damping. At this time, the fluctuation amplitude caused by the fault cannot be reduced, and the node voltage, frequency, etc. of the system remain in an oscillating state for a long time or even lose step. It shows that the calculation results of this method have good performance in the prediction of transient stability of the system after the fault, and are very suitable for transient stability judgment and online safety assessment of the system after the fault. Of course, the above discussion on the balance point problem is based on the fault removal time being less than the maximum removal time. When the fault removal time is large, the system cannot reach stability even if the balance point exists, and the discussion on the balance point problem loses its meaning.

[0179] The embodiment of the present application also provides a device for determining the frequency balance point of a system after a fault taking into account a detailed dynamic component model. It should be noted that the device for determining the frequency balance point of a system after a fault taking into account a detailed dynamic component model of the embodiment of the present application can be used to execute the method for determining the frequency balance point of a system after a fault taking into account a detailed dynamic component model provided in the embodiment of the present application. The device is used to implement the above-mentioned embodiments and preferred implementation modes, and those that have been described will not be repeated. As used below, the term "module" can implement a combination of software and / or hardware for a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0180] The following is an introduction to a device for determining a frequency balance point of a system after a fault taking into account a detailed dynamic component model provided in an embodiment of the present application.

[0181] Figure 8 Schematic diagram of a device for determining a frequency balance point of a system after a fault considering a detailed dynamic component model according to an embodiment of the present application. Figure 8 As shown, the device comprises:

[0182] The first determining unit 81 is used to perform power flow calculation on the system before the fault, obtain the power flow calculation result, and determine the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable of the system under a given operating condition according to the power flow calculation result;

[0183] A second determining unit 82 is used to determine a full system model according to the system component model, the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable, wherein the full system model includes a power supply model, a load model and a network equation;

[0184] A construction unit 83 is used to construct a phase reference node selection equation, wherein the phase reference node selection equation is used to determine a phase reference node, and the phase reference node is a node that is least affected by the disturbance voltage and power parameter changes for different disturbed points;

[0185] The third determination unit 84 is used to determine the initial iteration condition of the system according to the fault type of the system, and solve the whole system model and the phase reference node selection equation according to the initial iteration condition to determine the frequency balance point of the system after the fault.

[0186] In this embodiment, the first determination unit is used to perform power flow calculation on the system before the fault, obtain the power flow calculation result, and determine the steady-state value of the balance point state variable and the steady-state value of the balance point algebraic variable of the system under a given operating condition according to the power flow calculation result; the second determination unit is used to determine the whole system model according to the component model of the system, the steady-state value of the balance point state variable and the steady-state value of the balance point algebraic variable, and the whole system model includes a power supply model, a load model and a network equation; the construction unit is used to construct a phase reference node selection equation, wherein the phase reference node selection equation is used to determine the phase reference node, and the phase reference node is the node with the least influence on different disturbed points, disturbed voltage and power parameter changes; the third determination unit is used to determine the initial iteration condition of the system according to the fault type of the system, and solve the whole system model and the phase reference node selection equation according to the initial iteration condition to determine the frequency balance point of the system after the fault. The problem that the solution of the frequency balance point after the fault in the prior art depends on the system time domain simulation and the slow analysis of the system behavior after the fault due to the slow online application time domain simulation process is solved, and the frequency balance point of the system after the fault can be efficiently calculated.

[0187] As an optional solution, the second determination unit includes a first determination module, which is used to determine the following according to the first set of equations:

[0188]

[0189] Determine the power model of the full system model, where X d With X q Respectively represent the d-axis and q-axis synchronous reactance, V x With V y Represent the voltage at the x-terminal and y-terminal of the generator, R a is the stator resistance, I Gx and I Gy are the components of the power supply injection current on the x-axis and y-axis respectively, K is the regulator gain coefficient, K A is the regulator gain, K V is the proportional integral, V ref is the excitation voltage reference value, R C is the load compensation resistance component, X C is the load compensation reactance component, D is the damping coefficient, F is the system frequency after the fault, and Y ref is the reference value of the valve opening, K GW is the speed magnification factor, b p is the proportion of constant current load, and δ is the power angle.

[0190] In an optional solution, the second determination unit includes a second determination module, which is used to determine the load model in the whole system model according to the component model of the system, the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable, including: according to the second equation group:

[0191]

[0192] Determine the load model of the whole system model, where V 0 is the initial steady-state voltage, P L0 and Q L0 is the power absorbed by the load at the initial steady-state voltage and frequency, a P and a Q 、b P and b Q 、c P and c Q are the proportions of constant impedance load, constant current load and constant power load respectively, F is the system frequency after the fault, L DP is the active frequency factor, L DQ is the reactive frequency factor, I Lx and I Ly are the components of the load injected current on the x-axis and y-axis respectively.

[0193] In an optional solution, the second determining unit includes a third determining module, configured to determine, according to the first formula: Determine the network equations of the full system model, where i = 1, 2, ..., n, is the injection current of the power supply, Inject current into the load, Y ij is the mutual admittance between node i and node j, The voltage at node j.

[0194] In an optional solution, the building unit includes a building module for building according to the second formula: Construct the phase reference node selection equation, where V kx and V ky are the components of the voltage at the reference node k on the x-axis and y-axis, θ k0 is the voltage phase of node k.

[0195] An optional scheme, the third determination unit includes a fourth determination module and an adoption module, the fourth determination module is used to determine the base state disturbance value according to the fault type of the system, and determine whether the base state disturbance value is greater than a preset disturbance value, wherein the base state disturbance value is determined according to the voltage, frequency and power of the fault node of the system; the adoption module is used to adopt the initial iteration condition of the system's pre-fault equilibrium point as the initial iteration condition of the post-fault equilibrium point when the base state disturbance value is less than or equal to the preset disturbance value.

[0196] In an optional solution, the third determination unit further includes a fifth determination module, which is used to determine, when it is determined that the base state disturbance value is greater than the preset disturbance value, according to the third formula: Determine the initial iteration conditions, where is the modified initial value of iteration, x( 0 ) is the initial iteration point before correction, p is the fault parameter, p 0 is the initial value of the fault parameter, h p is the partial derivative of the fault parameter p, h x is the partial derivative with respect to the state variable x.

[0197] The apparatus for determining the frequency balance point of a system after a fault considering a detailed dynamic component model includes a processor and a memory, wherein the first determining unit, the second determining unit, the constructing unit, the third determining unit, etc. are all stored in the memory as program units, and the processor executes the program units stored in the memory to implement corresponding functions. The modules are all located in the same processor; or, the modules are located in different processors in any combination.

[0198] The processor includes a kernel, which retrieves the corresponding program unit from the memory. One or more kernels can be set, and the kernel parameters can be adjusted to solve the problem that the solution of the frequency balance point after the fault in the prior art depends on the system time domain simulation, and the slow time domain simulation process for online applications leads to a slow analysis of the system behavior after the fault.

[0199] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM, and the memory includes at least one memory chip.

[0200] An embodiment of the present invention provides a computer-readable storage medium, which includes a stored program, wherein when the program is running, the device where the computer-readable storage medium is located is controlled to execute the above-mentioned method for determining the frequency balance point of the post-fault system considering the detailed dynamic component model.

[0201] An embodiment of the present invention provides a processor, which is used to run a program, wherein the program executes the above-mentioned method for determining a frequency balance point of a system after a fault considering a detailed dynamic component model when running.

[0202] An embodiment of the present invention provides a device, the device includes a processor, a memory, and a program stored in the memory and executable on the processor, and when the processor executes the program, the steps of the method for determining the frequency balance point of a system after a fault considering at least the above-mentioned detailed dynamic component model are implemented. The device in this article can be a server, a PC, a PAD, a mobile phone, etc.

[0203] The present application also provides a computer program product, which, when executed on a data processing device, is suitable for executing a program for initializing at least the steps of the method for determining a frequency balance point of a post-fault system considering a detailed dynamic component model.

[0204] Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0205] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0206] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0207] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0208] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0209] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0210] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0211] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0212] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0213] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for determining the frequency equilibrium point of a post-fault system considering a detailed dynamic component model, characterized in that: include: Performing power flow calculation on the system before the fault to obtain power flow calculation results, and determining the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable of the system under a given operating condition according to the power flow calculation results; Determine a full system model according to the component model of the system, the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable, wherein the full system model includes a power supply model, a load model and a network equation; Constructing a phase reference node selection equation, wherein the phase reference node selection equation is used to determine a phase reference node, and the phase reference node is a node that is least affected by disturbance voltage and power parameter changes for different disturbed points; The initial iteration condition of the system is determined according to the fault type of the system, and the full system model and the phase reference node selection equation are solved according to the initial iteration condition to determine the frequency balance point of the system after the fault.

2. The method according to claim 1, characterized in that Determining a power supply model in the whole system model according to the component model of the system, the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable includes: According to the first set of equations: 0=V x sinδ-V y cosδ+R a (I Gx sinδ-I Gy cosδ)-X q (I Gx cosδ+I Gy sinδ) Determine the power model of the full system model, where X d With X q Respectively represent the d-axis and q-axis synchronous reactance, V x With V y Represent the voltage at the x-terminal and y-terminal of the generator, R a is the stator resistance, I Gx and I Gy are the components of the power supply injection current on the x-axis and y-axis respectively, K is the regulator gain coefficient, K A is the regulator gain, K V is the proportional integral, V ref is the excitation voltage reference value, R C is the load compensation resistance component, X C is the load compensation reactance component, D is the damping coefficient, F is the system frequency after the fault, and Y ref is the reference value of the valve opening, K GW is the speed magnification factor, b p is the proportion of constant current load, and δ is the power angle.

3. The method according to claim 1, characterized in that: Determining a load model in the whole system model according to the component model of the system, the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable includes: According to the second set of equations: Determine the load model of the whole system model, where V0 is the initial steady-state voltage, P L0 and Q L0 is the power absorbed by the load at the initial steady-state voltage and frequency, a P and a Q 、b P and b Q 、c P and c Q are the proportions of constant impedance load, constant current load and constant power load respectively, F is the system frequency after the fault, L DP is the active frequency factor, L DQ is the reactive frequency factor, I Lx and I Ly are the components of the load injected current on the x-axis and y-axis respectively.

4. The method according to claim 1, characterized in that: Determining the network equations in the whole system model according to the component model of the system, the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable includes: According to the first formula: Determine the network equations of the full system model, where i=1, 2, ..., n, is the injection current of the power supply, Inject current into the load, Y ij is the mutual admittance between node i and node j, The voltage at node j.

5. The method according to claim 1, characterized in that Construct the phase reference node selection equation, including: According to the second formula: Construct the phase reference node selection equation, where V kx and V ky are the components of the voltage at the reference node k on the x-axis and y-axis, θ k0 is the voltage phase of node k.

6. The method according to claim 1, characterized in that Determining an initial iteration condition of the system according to a fault type of the system includes: Determine a base state disturbance value according to the fault type of the system, and determine whether the base state disturbance value is greater than a preset disturbance value, wherein the base state disturbance value is determined according to the voltage, frequency and power of the fault node of the system; In the case that the base state disturbance value is less than or equal to the preset disturbance value, the initial iteration condition of the system's pre-fault equilibrium point is used as the initial iteration condition of the post-fault equilibrium point.

7. The method according to claim 6, characterized in that After determining whether the base state disturbance value is greater than a preset disturbance value, the method further includes: When it is determined that the base state disturbance value is greater than the preset disturbance value, according to the third formula: Determine the initial iteration condition, where: is the modified initial value of iteration, x( 0 ) is the initial iteration point before correction, p is the fault parameter, p0 is the initial value of the fault parameter, h p is the partial derivative of the fault parameter p, h x is the partial derivative with respect to the state variable x.

8. A device for determining the frequency balance point of a post-fault system considering a detailed dynamic component model, characterized in that: include: A first determining unit is used to perform power flow calculation on the system before the fault to obtain a power flow calculation result, and determine a steady-state value of a state variable of a balance point and a steady-state value of algebraic variable of a balance point of the system under a given operating condition according to the power flow calculation result; A second determining unit is used to determine a full system model according to the component model of the system, the steady-state value of the equilibrium point state variable and the steady-state value of the equilibrium point algebraic variable, wherein the full system model includes a power supply model, a load model and a network equation; A construction unit, used for constructing a phase reference node selection equation, wherein the phase reference node selection equation is used for determining a phase reference node, and the phase reference node is a node least affected by a disturbance voltage and a power parameter change for different disturbed points; The third determination unit is used to determine the initial iteration condition of the system according to the fault type of the system, and solve the full system model and the phase reference node selection equation according to the initial iteration condition to determine the frequency balance point of the system after the fault.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute the method for determining the frequency balance point of a post-fault system considering a detailed dynamic component model as described in any one of claims 1 to 7.

10. An electronic device, characterized in that: include: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and the one or more programs include a method for executing the method for determining the frequency balance point of a post-fault system considering a detailed dynamic element model as described in any one of claims 1 to 7.

Images