Multi-rate simulation method and system based on improved dynamic simulation method of power system

Abstract

The invention relates to the technical field of power system dynamic simulation, in particular to a multi-rate simulation method and system based on a power system improved dynamic simulation method. According to the characteristics of the power system, establishing a simulation model by adopting a differential algebraic equation DAE; adopting implicit integration and a Newton method to solve the model, and setting a simulation strategy; and performing dynamic simulation calculation according to a simulation strategy to realize data exchange among different simulation modules. The system is divided into a plurality of subsystems, and a multi-rate simulation strategy is adopted, so that the problem of low efficiency caused by the fact that the whole system adopts the minimum step length is avoided. In the simulation process, a data exchange mechanism between the subsystems ensures time synchronization and data consistency of the system, and the stability problem caused by extrapolation calculation is avoided. According to the multi-rate simulation method, the simulation efficiency is remarkably improved while high simulation precision is kept, the simulation time is far shorter than that of a traditional method especially in a large-scale electric power system, and good practical value and application prospects are shown.

Description

Technical Field

[0001] The present invention relates to the technical field of power system dynamic simulation, and in particular to a multi-rate simulation method and system based on an improved dynamic simulation method of a power system. Background Art

[0002] With the large-scale access of distributed devices and power electronic devices, modern power systems present multi-time scale, broadband and nonlinear dynamic characteristics. The simulation of systems containing power electronic devices requires a microsecond time step, while the dynamic response of synchronous generators and other devices in traditional power systems is slow, which leads to different time constants of various components of the entire system. The former usually requires a simulation time step of microseconds or even nanoseconds. However, if all large-scale systems are simulated with small steps, the simulation efficiency will be low; on the contrary, the latter generally uses a millisecond simulation time step, which has high simulation efficiency but cannot accurately capture the dynamic characteristics of power electronic devices. Therefore, a multi-rate simulation method is proposed. This method involves using different simulation time steps for network areas with different time constants in the joint simulation, and connecting different areas through appropriate interfaces. Through this method, not only the efficiency of the large-scale power system simulation process can be improved, but also the accuracy of the simulation results can be guaranteed. Summary of the invention

[0003] In view of the above problems existing in the prior art, the present invention is proposed.

[0004] Therefore, the present invention provides a multi-rate simulation method based on an improved dynamic simulation method for a power system, which can solve the stability problem caused by extrapolation calculation in the traditional multi-rate simulation method and the low efficiency problem during large-scale system simulation. By flexibly configuring the time step and serial simulation, the extrapolation calculation is avoided, while ensuring the accuracy and efficiency of the simulation results, and improving the simulation speed, especially in the application of large-scale power systems.

[0005] To solve the above technical problems, the present invention provides the following technical solutions, which are multi-rate simulation methods based on improved dynamic simulation methods of power systems, including: according to the characteristics of the power system, using differential algebraic equations (DAE) to establish a simulation model; using implicit integration and Newton's method to solve the model and set a simulation strategy; performing dynamic simulation calculations according to the simulation strategy to achieve data exchange between different simulation modules.

[0006] As a preferred solution of the multi-rate simulation method based on the improved dynamic simulation method of the power system described in the present invention, the differential algebraic equation DAE includes dividing the system into two subsystems, subsystem 1 and subsystem 2, each subsystem is described by a differential algebraic equation, and the formula is expressed as follows:

[0007]

[0008] 0=g1(x1,y1,u10

[0009] Among them, x1 is the state variable of subsystem 1, y1 is the algebraic variable of subsystem 1, u1 is the system input of subsystem 1, f1 and g1 are the differential equation and algebraic equation of subsystem 1 respectively, and dx1 / dt is the rate of change of state variable x1 with respect to time t;

[0010]

[0011] 0=g2(x2,y2,u2)

[0012] Among them, x2 is the state variable of subsystem 2, y2 is the algebraic variable of subsystem 2, u2 is the system input of subsystem 2, f2 and g2 are the differential equation and algebraic equation of subsystem 2 respectively, and dx2 / dt is the rate of change of state variable x2 with respect to time t.

[0013] As a preferred solution of the multi-rate simulation method based on the improved dynamic simulation method of the power system described in the present invention, wherein: the simulation model includes the result of the power flow calculation used for system initialization, and the initial value formula for dynamic simulation of each subsystem is expressed as:

[0014] x1(0)=x 1,init ,y1(0)=y 1,init

[0015] x2(0)=x 2,init ,y2(0)=y 2,init

[0016] Among them, x1(0) and y1(0) are the initial values ​​of the state variables and algebraic variables of the preliminary dynamic simulation of subsystem 1, respectively. 1,init ,y 1,init are the initial values ​​of the state variables and algebraic variables obtained by the power flow calculation of subsystem 1, x2(0) and y2(0) are the initial values ​​of the state variables and algebraic variables of the preliminary dynamic simulation of subsystem 2, respectively. 2,init ,y 2,init The initialization values ​​of state variables and algebraic variables are obtained by power flow calculation for subsystem 2 respectively.

[0017] As a preferred solution of the multi-rate simulation method based on the improved dynamic simulation method of the power system described in the present invention, the method of solving the model using implicit integration and Newton's method includes converting the differential equation into algebraic form using the implicit integration formula, and the differential equation and the algebraic equation constitute a nonlinear equation group, which is expressed as follows:

[0018]

[0019] 0=g1(x1(t+Δt),y1(t+Δt))

[0020]

[0021] 0 = g2(x2(t+Δt),y2(t+Δt))

[0022] in, are the independent functions of the implicit integration method for subsystem 1 and subsystem 2, respectively, and Δt is the time step;

[0023] Considering that the equations are in nonlinear form, Newton's method is used to solve them. The formula is expressed as:

[0024]

[0025]

[0026] Among them, Δx(i), Δy (i are the i-th iteration updates of state variables and algebraic variables respectively, is the matrix of the i-th iteration associated with the Jacobian matrix, x(i) and y(i) are the state variables and algebraic variables of the i-th iteration, respectively. g (i) are the independent functions and algebraic equations of the i-th iteration respectively;

[0027] In the trapezoidal method, The formula is:

[0028]

[0029]

[0030] in, is the identity matrix of the same dimension as the DAE equation, are the partial derivatives of the ith iterative differential equation f with respect to x and y, respectively. are the partial derivatives of the algebraic equation g with respect to x and y for the i-th iteration, respectively, and f (i) is the differential equation of the i-th iteration.

[0031] As a preferred solution of the multi-rate simulation method based on the improved dynamic simulation method of the power system described in the present invention, wherein: the setting simulation strategy includes in the improved dynamic simulation method, starting from the second inter-system electrical data exchange, the subsystem does not need to perform the initialization operation, the interface data is exchanged in the interface program, the node k of subsystem 1 is connected with the node m of subsystem 2, during the second exchange, subsystem 1 cancels the initialization process, calls the interface data initially exchanged by subsystem 2, the state variables and algebraic variables remain consistent with the initial simulation results, and subsystem 1 performs the second simulation;

[0032] When subsystem 2 transmits electrical data to subsystem 1, the power flow equation is used to update the power data exchanged last time. The data is substituted into the nonlinear equation group to update the state variables and algebraic variables of the system. The power flow equation is expressed as:

[0033]

[0034]

[0035] in, are the active powers transmitted by interfaces k and m in the i-th iteration, are the reactive powers transmitted by interfaces k and m in the i-th iteration, Δt1 and Δt2 are the time steps of subsystem 1 and subsystem 2, respectively;

[0036] Subsystem 1 transfers the node voltage amplitude and phase angle of the connection node to subsystem 2, and the formula is expressed as:

[0037] V m (i) (t+Δt2)=V k (i+1) (t+Δt1)

[0038] θ m (i) (t+Δt2)=θ k (i+1) (t+Δt1)

[0039] Among them, V m (i) ,θ m (i) are the voltage amplitude and voltage phase angle of interface m at the i-th iteration, V k (i+1) ,θ k (i+1) are the voltage amplitude and voltage phase angle of interface k in the i+1th iteration respectively.

[0040] As a preferred solution of the multi-rate simulation method based on the improved dynamic simulation method of the power system described in the present invention, wherein: the dynamic simulation calculation includes consideration of the need to avoid extrapolation calculation, and in the data exchange of the multi-rate interface, the time synchronization selection configures the simulation time and time step provided by the simulation software, and the simulation process is a serial process. After the simulation of subsystem 1 is completed, subsystem 1 is paused and suspended, and subsystem 2 reduces the time step to complete the simulation, ensuring that the data exchange mechanism in the simulation software is carried out along two independent paths, and information exchange only occurs at the coupling point between the two systems. When the system is stable, the efficiency of the simulation is improved by reducing the order of the system matrix.

[0041] As a preferred solution of the multi-rate simulation method based on the improved dynamic simulation method of the power system described in the present invention, wherein: the multi-rate simulation includes using data exchange to ensure information interaction between subsystems, two subsystems are connected to run simulation strategies with different step sizes, when subsystem 1 is simulated independently, subsystem 2 is a PQ load, and when subsystem 2 is simulated independently, subsystem 1 is a Thevenin equivalent voltage source;

[0042] Subsystem 1 runs a dynamic simulation at the time step of subsystem 1 to obtain an output file, extracts the voltage amplitude and phase angle from the output file, and inputs the data into the Slack node in the input file of subsystem 2. Subsystem 2 uses the input file to run a dynamic simulation at the time step of subsystem 2 to obtain the output file of subsystem 2, and provides the injected active and reactive power of the node to subsystem 1;

[0043] For subsystem 1, the improved dynamic simulation TDS program is TDS1, and for subsystem 2, the improved TDS program is TDS2. The node power of the output file of subsystem 2 is injected into subsystem 1, and the voltage amplitude and phase angle remain the same as the previous step. All variables are used for dynamic simulation in TDS1, and the amplitude and phase angle of the interface node voltage are output;

[0044] Subsystem 2 receives the node voltage transmitted by subsystem 1, runs TDS2 in the dynamic simulation, runs iteratively, obtains the results of multi-rate simulation, and compares them with the simulation of single step size.

[0045] Another object of the present invention is to provide a multi-rate simulation system based on an improved dynamic simulation method for an electric power system, wherein the electric power system is divided into a plurality of subsystems, each subsystem is represented by a differential algebraic equation (DAE), and state variables and algebraic variables are initialized by power flow calculation. Implicit integration and Newton's method are used to solve the nonlinear equations, and during the simulation process, each subsystem is simulated alternately and data is exchanged to ensure time synchronization and data consistency. By flexibly configuring the time step, different subsystems are simulated with different step sizes to avoid extrapolation calculations and improve simulation efficiency and accuracy.

[0046] As a preferred solution of the multi-rate simulation system based on the improved dynamic simulation method of the power system described in the present invention, it includes: a simulation model establishment module, a simulation strategy module and a multi-rate simulation module;

[0047] The simulation model building module divides the system into multiple subsystems and describes each subsystem using differential algebraic equations to build a simulation model;

[0048] The simulation strategy module adopts implicit integration and Newton's method to solve the model, converts the differential equation into algebraic form through implicit integration formula, combines Newton's method to solve the nonlinear equation system, and sets the policy strategy;

[0049] The multi-rate simulation module realizes data exchange and information synchronization between subsystems during the simulation process by configuring the simulation time and time step of the simulation software.

[0050] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and is characterized in that when the processor executes the computer program, the steps of any one of the methods described in the multi-rate simulation method based on the improved dynamic simulation method of the power system are implemented.

[0051] A computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the steps of any one of the methods in a multi-rate simulation method based on an improved dynamic simulation method for an electric power system are implemented.

[0052] Beneficial effects of the present invention: The method of the present invention effectively improves the efficiency and accuracy of power system simulation. By dividing the system into multiple subsystems and adopting a multi-rate simulation strategy, the simulation can select a suitable time step according to the dynamic characteristics of each subsystem, thereby avoiding the inefficiency problem caused by the minimum step size of the whole system. During the simulation process, the data exchange mechanism between subsystems ensures the time synchronization and data consistency of the system, and avoids the stability problems caused by extrapolation calculations. Experimental results show that the multi-rate simulation method of the present invention significantly improves the simulation efficiency while maintaining high simulation accuracy, especially in large-scale power systems, the simulation time is much lower than the traditional method, showing good practical value and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0054] Figure 1A topology diagram of an IEEE 14 and 33 node integrated system based on a multi-rate simulation method of an improved dynamic simulation method for a power system provided by an embodiment of the present invention.

[0055] Figure 2 A platform unit outlet voltage curve diagram of a multi-rate simulation method based on an improved dynamic simulation method for a power system provided by an embodiment of the present invention.

[0056] Figure 3 A PSS / E unit outlet voltage curve diagram of a multi-rate simulation method based on an improved dynamic simulation method for a power system provided by an embodiment of the present invention.

[0057] Figure 4 A platform unit speed curve diagram of a multi-rate simulation method based on an improved dynamic simulation method for an electric power system provided by an embodiment of the present invention.

[0058] Figure 5 A PSS / E unit speed curve diagram of a multi-rate simulation method based on an improved dynamic simulation method for a power system provided by an embodiment of the present invention.

[0059] Figure 6 An output power curve diagram of a multi-rate simulation method based on an improved dynamic simulation method for an electric power system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0060] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0061] Example 1, reference Figure 1 , which is the first embodiment of the present invention, provides a multi-rate simulation method based on an improved dynamic simulation method for a power system, comprising:

[0062] S1: According to the characteristics of the power system, the simulation model is established using differential algebraic equations (DAE).

[0063] Before describing the embodiments of the present application in detail, some related concepts are first explained for the sake of clarity.

[0064] Dynamic simulation of power system: English name: Dynamic simulation of distribution networks, refers to the simulation of the dynamic process of distribution networks by applying simulation tools through mathematical methods in order to study the transient stability of distribution networks.

[0065] Multi-rate simulation: English name: Multi-rate simulation, refers to a method of simulating different systems on different time scales according to their dynamic characteristics, while maintaining the simulation accuracy and improving the efficiency of system simulation as much as possible.

[0066] Data exchange interface: English name: Data exchange interface, refers to the mechanism or platform for data exchange between different simulation components or systems in multi-rate simulation. This interface allows different simulation modules, running at different rates, to effectively exchange information and data.

[0067] DAE equation: English name: Differential algebraic equation, DAE, refers to differential equations and algebraic equations used to describe the dynamic behavior of power systems.

[0068] It should be noted that, assuming there are two subsystems, namely subsystem 1 and subsystem 2, each subsystem is described by differential algebraic equations, and the formula is expressed as follows:

[0069]

[0070] 0=g1(x1,y1,u1)

[0071] Among them, x1 is the state variable of subsystem 1, y1 is the algebraic variable of subsystem 1, u1 is the system input of subsystem 1, f1 and g1 are the differential equation and algebraic equation of subsystem 1 respectively, and dx1 / dt is the rate of change of state variable x1 with respect to time t;

[0072]

[0073] 0=g2(x2,y2,u2)

[0074] Among them, x2 is the state variable of subsystem 2, y2 is the algebraic variable of subsystem 2, u2 is the system input of subsystem 2, f2 and g2 are the differential equation and algebraic equation of subsystem 2 respectively, and dx2 / dt is the rate of change of state variable x2 with respect to time t.

[0075] In the traditional power system dynamic simulation method, system initialization is usually realized by the results of power flow calculation. The state variables of each generator and variables such as voltage and phase angle of each node will be initialized and given an initial value for dynamic simulation. The initial value formula for dynamic simulation of each subsystem is expressed as:

[0076] x1(0)=x 1,init ,y1(0)=y 1,init

[0077] x2(0)=x 2,init ,y2(0)=y 2,init

[0078] Among them, x1(0) and y1(0) are the initial values ​​of the state variables and algebraic variables of the preliminary dynamic simulation of subsystem 1, respectively. 1,init ,y 1,init are the initial values ​​of the state variables and algebraic variables obtained by the power flow calculation of subsystem 1, x2(0) and y2(0) are the initial values ​​of the state variables and algebraic variables of the preliminary dynamic simulation of subsystem 2, respectively. 2,init ,y 2,init The initialization values ​​of state variables and algebraic variables are obtained by power flow calculation for subsystem 2 respectively.

[0079] S2: Use implicit integration and Newton's method to solve the model and set the simulation strategy.

[0080] It should be noted that the numerical solution adopted by the present invention is a simultaneous solution, that is, firstly, a set of differential equations is converted into algebraic form using an implicit integral formula, these equations together with a set of algebraic equations constitute a nonlinear equation system, and the Newton method is used to solve the nonlinear equation system, thereby avoiding repeated alternating solutions of differential equations and algebraic equations. The formula of the nonlinear equation system is expressed as:

[0081]

[0082] 0=g1(x1(t+Δt),y1(t+Δt))

[0083]

[0084] 0 = g2(x2(t+Δt),y2(t+Δt))

[0085] in, are the independent functions of the implicit integration method for subsystem 1 and subsystem 2, respectively, and Δt is the time step;

[0086] Considering the equation system is nonlinear, therefore, Δx (i) , Δy (i)In order to be continuously updated, Newton's method is used to solve it, and the formula is expressed as:

[0087]

[0088]

[0089] Where Δx (i) , Δy (i) are the i-th iteration updates of state variables and algebraic variables respectively, is the matrix of the i-th iteration associated with the Jacobian matrix, x (i) ,y (i) are the state variables and algebraic variables of the i-th iteration, respectively. g (i) are the independent functions and algebraic equations of the i-th iteration respectively;

[0090] In the trapezoidal method, The formula is:

[0091]

[0092]

[0093] in, is the identity matrix of the same dimension as the DAE equation, are the partial derivatives of the ith iterative differential equation f with respect to x and y, respectively. are the partial derivatives of the algebraic equation g with respect to x and y for the i-th iteration, respectively, and f (i) is the differential equation of the i-th iteration.

[0094] It should be noted that, assuming that node k of subsystem 1 is connected to node m of subsystem 2, in the improved dynamic simulation method, starting from the second inter-system electrical data exchange, the two power systems do not need to perform initialization operations, but directly exchange interface data in the interface program. For example, during the second exchange, subsystem 1 cancels the initialization process and calls the interface data exchanged by subsystem 2 for the first time. Other state variables and algebraic variables remain consistent with the first simulation results. Then, subsystem 1 continues the second simulation. This ensures that the results of the second simulation are based on the first one, while maintaining the stability and efficiency of the simulation.

[0095] When subsystem 2 transmits electrical data to subsystem 1, the power flow equation is used to update the power data exchanged last time. The data is substituted into the nonlinear equation group to update the state variables and algebraic variables of the system. The power flow equation is expressed as:

[0096]

[0097]

[0098] in, are the active powers transmitted by interfaces k and m in the i-th iteration, are the reactive powers transmitted by interfaces k and m in the i-th iteration, Δt1 and Δt2 are the time steps of subsystem 1 and subsystem 2, respectively;

[0099] Similarly, subsystem 1 transfers the node voltage amplitude and phase angle of the connected node to subsystem 2, which can be expressed as:

[0100] V m (i) (t+Δt2)=V k (i+1) (t+Δt1)

[0101] θ m (i) (t+Δt2)=θ k (i+1) (t+Δt1)

[0102] Among them, V m (i) ,θ m (i) are the voltage amplitude and voltage phase angle of interface m at the i-th iteration, V k (i+1) ,θ k (i+1) are the voltage amplitude and voltage phase angle of interface k in the i+1th iteration respectively.

[0103] Generally, in the multi-rate simulation method applied in power system analysis, these simulation software provide the function of customizing the simulation step size for each subsystem. Therefore, the step size of the integral differential equation can be selected according to the dynamic characteristics of each subsystem, thereby improving the simulation efficiency.

[0104] S3: Perform dynamic simulation calculations according to the simulation strategy to achieve data exchange between different simulation modules.

[0105] It should be noted that time synchronization is a key factor to be considered in data exchange on multi-rate interfaces. However, the proposed method is different from the traditional multi-rate method because it avoids the need for extrapolated approximate calculations. The essence of this method lies in the flexible configuration of simulation time and time step provided by the simulation software. Specifically, once the simulation of subsystem 1 is completed, it can be temporarily paused to allow subsystem 2 to complete its simulation with a finer time step. In other words, the simulation process of the proposed method is serial, which ensures the accuracy of the simulation while reducing a certain degree of simulation efficiency. Therefore, this method ensures that the data exchange mechanism in the simulation software is carried out along two independent paths, and information exchange only occurs at the coupling point between the two systems. It is worth noting that once the system stability is guaranteed, the efficiency of the simulation can be improved by reducing the order of the system matrix. For example, if an order of (2n) 2 The matrix is ​​divided into two subsystems, whose orders are (0.5n) 2 and (1.5n) 2 , then since the serial process is completely dependent on 2.25n 2 The simulation efficiency is significantly improved.

[0106] Furthermore, based on the improved TDS method, multi-rate simulation also needs to consider the data exchange method to ensure information interaction between subsystems. Assume that subsystem 1 is a fast dynamic system and subsystem 2 is a slow dynamic system. The two subsystems are connected at a certain node and run TDS at different steps. The present invention assumes that the data exchanged between the fast and slow dynamic systems include the amplitude and phase angle of the node voltage, as well as the active and reactive power injected at the node. That is, when subsystem 1 is simulated independently, subsystem 2 is regarded as a PQ load; and when subsystem 2 is simulated independently, subsystem 1 is regarded as a Thevenin equivalent voltage source.

[0107] The steps of data exchange are as follows:

[0108] (1) In general simulation software, the dynamic simulation program is called TDS (time domain simulation). The fast dynamic system (subsystem 1) runs the dynamic simulation with a larger step size of 10ms. Assume that a short circuit fault occurs at 1.0s and lasts until 1.01s, and a simulation is performed to obtain an output file. The amplitude and phase angle of the voltage are extracted from the output file and input into the Slack node in the slow dynamic system input file. The slow dynamic system (subsystem 2) then uses this input file to run the dynamic simulation with a smaller step size of 1ms. This input file contains a small disturbance to simulate the dynamic impact from subsystem 1. Similarly, another output file is obtained, which provides the injected active and reactive power of the node to subsystem 1.

[0109] (2) The improved TDS procedure is called TDS1 for subsystem 1 and TDS2 for subsystem 2. The node power from the output file of the previous step is injected into subsystem 1, while other variables remain the same as in the previous step. On this basis, all variables are used in the second step of dynamic simulation in TDS1, and the amplitude and phase angle of the interface node voltage are output.

[0110] (3) Subsystem 2 receives the node voltage transmitted by subsystem 2, and then runs TDS2 in the subsequent dynamic simulation.

[0111] (4) Repeat steps (2) and (3) to obtain all the results of the multi-rate simulation and compare them with the single-step simulation.

[0112] The above is a schematic scheme of the multi-rate simulation method based on the improved dynamic simulation method of the electric power system of this embodiment. It should be noted that the technical scheme of the system of multi-rate simulation based on the improved dynamic simulation method of the electric power system and the technical scheme of the multi-rate simulation method based on the improved dynamic simulation method of the electric power system mentioned above belong to the same concept. For the details not described in detail in the technical scheme of the multi-rate simulation system based on the improved dynamic simulation method of the electric power system in this embodiment, please refer to the description of the technical scheme of the multi-rate simulation method based on the improved dynamic simulation method of the electric power system mentioned above.

[0113] The multi-rate simulation system based on the improved dynamic simulation method of the power system in this embodiment includes: a simulation model establishment module, a simulation strategy module and a multi-rate simulation module;

[0114] The simulation model building module divides the system into multiple subsystems and describes each subsystem using differential algebraic equations to build a simulation model;

[0115] The simulation strategy module adopts implicit integration and Newton's method to solve the model, converts the differential equation into algebraic form through implicit integration formula, combines Newton's method to solve the nonlinear equation system, and sets the policy strategy;

[0116] The multi-rate simulation module realizes data exchange and information synchronization between subsystems during the simulation process by configuring the simulation time and time step of the simulation software.

[0117] The above-mentioned unit modules may be embedded in or independent of the processor in the computer device in the form of hardware, or may be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above-mentioned modules.

[0118] This embodiment also provides a computing device suitable for multi-rate simulation based on the improved dynamic simulation method of the power system, including: the present invention can be implemented with the help of software and necessary general-purpose hardware, and of course it can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as a computer's floppy disk, read-only memory (ReadOnly, Memory, ROM), random access memory (Random Access Memory, RAM), flash memory (FLASH), hard disk or optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, server, or network device, etc.) to execute the methods of various embodiments of the present invention.

[0119] Example 2, reference Figure 2-Figure 6 , which is the second embodiment of the present invention, provides a multi-rate simulation method based on an improved dynamic simulation method of a power system. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through experiments.

[0120] The present invention takes IEEE14 and IEEE33 systems as examples and performs simulation comparison and verification in python software.

[0121] The topology diagram of the IEEE 14 and 33 node integrated system is as follows: Figure 2 As shown in the figure, the generators in the IEEE14 node system are all synchronous generators, and the generators in the IEEE33 node system are all distributed photovoltaics. The head of the IEEE33 node is connected to the 11th node of the IEEE14 node, and the IEEE33 node is regarded as a small dynamic load of the IEEE14 node.

[0122] The data of each load node of the IEEE14 and IEEE33 node integrated system are shown in Table 1, the output power of each generator node is shown in Table 2, and the static and dynamic parameters of the 8 generators in the system are shown in Tables 3-5.

[0123] Table 1. System node parameter table

[0124]

[0125]

[0126]

[0127] Table 2. Generator static parameters

[0128] Node number Active power (pu) Reactive power (pu) 2 0.4 0.15 3 0.4 0.15 6 0.3 0.1 8 0.35 0.1 27 0.008 0.006 33 0.002 0.008 37 0.004 0.004 40 0.008 0.004

[0129] Table 3. Generator dynamic parameters

[0130]

[0131] Table 4. Distributed photovoltaic dynamic parameters table a

[0132] Serial number node Sn dq fdbd ddn ialim vt0 vt1 vt2 vt3 1 27 1 0 0.06 -1 -0.017 5 1.2 0.88 0.9 2 33 1 0 0.06 -1 -0.017 5 1.2 0.88 0.9 3 37 1 0 0.06 -1 -0.017 5 1.2 0.88 0.9 4 40 1 0 0.06 -1 -0.017 5 1.2 0.88 0.9

[0133] Table 5. Distributed photovoltaic dynamic parameters table b

[0134] Serial number node ft0 ft1 ft2 ft3 ft0 ft1 ft2 1 27 49.5 49.7 50.3 50.5 8 0.03 0.4 2 33 49.5 49.7 50.3 50.5 8 0.03 0.4 3 37 49.5 49.7 50.3 50.5 8 0.03 0.4 4 40 49.5 49.7 50.3 50.5 8 0.03 0.4

[0135] The simulation step sizes of the two systems are 10ms and 1ms respectively, and the total simulation time is 10s. In the simulation, a fault is imposed on the system, and a three-phase short circuit occurs at node 13 at 1s, which lasts for 0.1s.

[0136] from Figure 2-Figure 6 From the results in Table 6, it can be seen that the multi-rate simulation results of this method are very close to the dynamic simulation results obtained by the integrated system simulation, but the multi-rate simulation time is much lower than the integrated system simulation. This shows that while meeting the simulation accuracy, the method provided by the present invention can significantly improve the simulation efficiency by running multi-rate simulation.

[0137] Table 6. Dynamic simulation time table in different scenarios

[0138] Scenario T / s Small step length 3.4051 Long stride 142.0161 Multi-rate 66.7128

[0139] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A multi-rate simulation method based on an improved dynamic simulation method of a power system, characterized in that: include, According to the characteristics of the power system, the simulation model is established using differential algebraic equations (DAE); Use implicit integration and Newton's method to solve the model and set the simulation strategy; Perform dynamic simulation calculations according to the simulation strategy to achieve data exchange between different simulation modules.

2. The multi-rate simulation method based on the improved dynamic simulation method of the power system according to claim 1, characterized in that: The differential algebraic equation DAE includes dividing the system into two subsystems, subsystem 1 and subsystem 2, and each subsystem is described by a differential algebraic equation, which is expressed as follows: 0=g1(x1,y1,u1) Among them, x1 is the state variable of subsystem 1, y1 is the algebraic variable of subsystem 1, u1 is the system input of subsystem 1, f1 and g1 are the differential equation and algebraic equation of subsystem 1 respectively, and dx1 / dt is the rate of change of state variable x1 with respect to time t; 0=g2(x2,y2,u2) Among them, x2 is the state variable of subsystem 2, y2 is the algebraic variable of subsystem 2, u2 is the system input of subsystem 2, f2 and g2 are the differential equation and algebraic equation of subsystem 2 respectively, and dx2 / dt is the rate of change of state variable x2 with respect to time t.

3. The multi-rate simulation method based on the improved dynamic simulation method of the power system according to claim 2, characterized in that: The simulation model includes the results of the power flow calculation used for system initialization. The initial value formula for dynamic simulation of each subsystem is expressed as: x1(0)=x 1,init ,y1(0)=y 1,init x2(0)=x 2,init ,y2(0)=y 2,init Among them, x1(0) and y1(0) are the initial values ​​of the state variables and algebraic variables of the preliminary dynamic simulation of subsystem 1, respectively. 1,init ,y 1,init are the initial values ​​of the state variables and algebraic variables obtained by the power flow calculation of subsystem 1, x2(0) and y2(0) are the initial values ​​of the state variables and algebraic variables of the preliminary dynamic simulation of subsystem 2, respectively. 2,init ,y 2,init The initialization values ​​of state variables and algebraic variables are obtained by power flow calculation for subsystem 2 respectively.

4. The multi-rate simulation method based on the improved dynamic simulation method of the power system according to claim 3, characterized in that: The method of solving the model by using implicit integration and Newton's method includes converting the differential equation into algebraic form by using the implicit integration formula. The differential equation and the algebraic equation constitute a nonlinear equation system, which is expressed as follows: 0=g1(x1(t+Δt),y1(t+Δt)) 0 = g2(x2(t+Δt),y2(t+Δt)) in, are the independent functions of the implicit integration method for subsystem 1 and subsystem 2, respectively, and Δt is the time step; Considering that the equations are in nonlinear form, Newton's method is used to solve them. The formula is expressed as: Among them, Δx(i), Δy (i) are the i-th iteration updates of state variables and algebraic variables respectively, is the matrix of the i-th iteration associated with the Jacobian matrix, x (i) ,y (i) are the state variables and algebraic variables of the i-th iteration, respectively. g (i) are the independent functions and algebraic equations of the i-th iteration respectively; In the trapezoidal method, The formula is: in, is the identity matrix of the same dimension as the DAE equation, are the partial derivatives of the ith iterative differential equation f with respect to x and y, respectively. are the partial derivatives of the algebraic equation g with respect to x and y for the i-th iteration, respectively, and f (i) is the differential equation of the i-th iteration.

5. The multi-rate simulation method based on the improved dynamic simulation method of the power system according to claim 4, characterized in that: The setting simulation strategy includes in the improved dynamic simulation method, starting from the second electrical data exchange between systems, the subsystems do not need to perform initialization operations, the interface data are exchanged in the interface program, the node k of subsystem 1 is connected to the node m of subsystem 2, during the second exchange, subsystem 1 cancels the initialization process, calls the interface data preliminarily exchanged by subsystem 2, the state variables and algebraic variables remain consistent with the preliminary simulation results, and subsystem 1 performs the second simulation; When subsystem 2 transmits electrical data to subsystem 1, the power flow equation is used to update the power data exchanged last time. The data is substituted into the nonlinear equation group to update the state variables and algebraic variables of the system. The power flow equation is expressed as: in, are the active powers transmitted by interfaces k and m in the i-th iteration, are the reactive powers transmitted by interfaces k and m in the i-th iteration, Δt1 and Δt2 are the time steps of subsystem 1 and subsystem 2, respectively; Subsystem 1 transfers the node voltage amplitude and phase angle of the connection node to subsystem 2, and the formula is expressed as: V m (i) (t+Δt2)=V k (i+1) (t+Δt1) i m (i) (t+Δt2)=θ k (i+1) (t+Δt1) Among them, V m (i0 ,θ m (i) are the voltage amplitude and voltage phase angle of interface m at the i-th iteration, V k (i+10 ,θ k (i+10 are the voltage amplitude and voltage phase angle of interface k in the i+1th iteration respectively.

6. The multi-rate simulation method based on the improved dynamic simulation method of the power system according to claim 5, characterized in that: The dynamic simulation calculation includes consideration of the need to avoid extrapolation calculation. In the data exchange of the multi-rate interface, the time synchronization selection configures the simulation time and time step provided by the simulation software. The simulation process is a serial process. After the simulation of subsystem 1 is completed, subsystem 1 is paused and suspended, and subsystem 2 reduces the time step to complete the simulation, ensuring that the data exchange mechanism in the simulation software is carried out along two independent paths. Information exchange only occurs at the coupling point between the two systems. When the system is stable, the efficiency of the simulation is improved by reducing the order of the system matrix.

7. The multi-rate simulation method based on the improved dynamic simulation method of the power system according to claim 6, characterized in that: The multi-rate simulation includes using data exchange to ensure information interaction between subsystems, two subsystems are connected to run simulation strategies with different step sizes, when subsystem 1 is simulated independently, subsystem 2 is a PQ load, and when subsystem 2 is simulated independently, subsystem 1 is a Thevenin equivalent voltage source; Subsystem 1 runs a dynamic simulation at the time step of subsystem 1 to obtain an output file, extracts the voltage amplitude and phase angle from the output file, and inputs the data into the Slack node in the input file of subsystem 2. Subsystem 2 uses the input file to run a dynamic simulation at the time step of subsystem 2 to obtain the output file of subsystem 2, and provides the injected active and reactive power of the node to subsystem 1; For subsystem 1, the improved dynamic simulation TDS program is TDS1, and for subsystem 2, the improved TDS program is TDS2. The node power of the output file of subsystem 2 is injected into subsystem 1, and the voltage amplitude and phase angle remain the same as the previous step. All variables are used for dynamic simulation in TDS1, and the amplitude and phase angle of the interface node voltage are output; Subsystem 2 receives the node voltage transmitted by subsystem 1, runs TDS2 in the dynamic simulation, runs iteratively, obtains the results of multi-rate simulation, and compares them with the simulation of single step size.

8. A system based on the multi-rate simulation method based on the improved dynamic simulation method of the power system according to any one of claims 1 to 7, characterized in that: It includes simulation model building module, simulation strategy module and multi-rate simulation module; The simulation model building module divides the system into multiple subsystems and describes each subsystem using differential algebraic equations to build a simulation model; The simulation strategy module adopts implicit integration and Newton's method to solve the model, converts the differential equation into algebraic form through implicit integration formula, combines Newton's method to solve the nonlinear equation system, and sets the policy strategy; The multi-rate simulation module realizes data exchange and information synchronization between subsystems during the simulation process by configuring the simulation time and time step of the simulation software.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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