A bidirectional interface method and system for multi-rate electromechanical transient models and AC system models

Abstract

This invention discloses a bidirectional interface method and system for a multi-rate electromechanical transient model and an AC system model. When the electromechanical transient calculation system is running, the AC power grid is solved with a large time step. The system equivalent model of the AC grid interface location is passed to the complex topology DC multi-rate electromechanical transient model through the DC grid interface. After the complex topology DC multi-rate electromechanical transient model completes the small-step integration solution with the system equivalent model, the DC grid interface location is returned to the system model through the AC grid interface according to the type of converter transformer. The system model performs calculations with the DC equivalent model. Through the above alternating iteration, the accuracy, calculation efficiency and stability of power system electromechanical transient simulation are improved.

Description

Technical Field

[0001] This invention relates to the field of electromechanical transient simulation technology for large-scale AC / DC hybrid power systems, specifically to a bidirectional interface method and system for a multi-rate electromechanical transient model and an AC system model. Background Technology

[0002] This technology comprises two technical backgrounds: first, an electromechanical transient simulation interface for multi-rate complex topology DC transmission systems; and second, an electromechanical transient simulation method for complex topology DC transmission systems.

[0003] First, simulations include three types: electromechanical transient simulation, electromagnetic transient simulation, and hybrid electromechanical-electromagnetic transient simulation. This invention falls under the category of electromechanical transient simulation. In the field of simulation, system models and component models are solved simultaneously. When a large disturbance occurs in the system or component, the nonlinear response process of the system or component is simulated, depicting the process of arbitrary variables in the system changing with the curve. This process is called power system transient stability simulation. In the field of pure electromechanical transient simulation, the system model refers to the mathematical description of the transmission or distribution network, including static loads. Mathematically, it is represented by an algebraic equation model and is solved in decoupled with three-sequence components: positive sequence, negative sequence, and zero sequence. The component model refers to components with dynamic effects, mathematically represented by differential equations.

[0004] There are two methods for simultaneously solving system and component models: simultaneous solution and modular solution. The simultaneous solution method does not require discussion of the interface between the component model and the system model, and is not within the scope of this invention. Existing commercial electromechanical transient simulation software (PSASP / PSSE / PSD, etc.) all employ a modular solution method. Modular solution refers to the process of solving the system model and component model separately, and then iteratively calculating alternately to obtain a feasible simultaneous solution. During this alternating calculation process, a numerical relationship needs to be established between the two, also known as the interface. This invention discusses the interface method and computational system between the system model and component model.

[0005] What is a multi-rate model? Taking a complex topology DC multi-rate model as an example, generally, transient stable system models and component models are solved block by block using a consistent time step. However, AC grids and complex topology DC systems do not use a consistent simulation step size during block simulation because the primary and secondary systems of complex topology DC systems have response speeds much higher than the system model. Such component models are called multi-rate models. If a large simulation step size is used overall, it cannot accurately reflect the characteristics of rapid regulation of converter station controllers and high-speed switching of converter valves in flexible DC transmission systems; if a small simulation step size is used overall, the calculation speed decreases significantly and the calculation time increases. In fact, electromechanical equipment in AC grids has a large time constant, and using too small a simulation step size will waste computational resources. Based on this, multi-rate simulation technology using different simulation step sizes on both AC and DC sides is widely used in flexible DC electromechanical transient models. The concept of multi-rate simulation has been widely applied in electromechanical transients and electromechanical-electromagnetic hybrid simulation technology for AC / DC hybrid grids.

[0006] The bidirectional interface method between the complex topology DC multi-rate electromechanical transient model and the AC system model is described as follows: the AC network interface position and the DC network interface position are defined during the calculation of the multi-rate complex topology DC model.

[0007] AC network interface location: Pass the system model's location variable to the solution of the complex topology DC multi-rate model.

[0008] DC network interface location: This location variable of the complex topology DC multi-rate model is passed to the system model for solution.

[0009] In solving multi-rate complex topology DC models, the system provides the DC network interface voltage vector to the model, effectively treating the AC system as a constant voltage source. In solving the system model, the complex topology DC model injects system current into the AC network interface, treating the DC network as a current source. This interface method neglects the influence of system impedance on the multi-rate complex topology DC model during solution, and ignores the influence of certain characteristics of the complex topology DC model on the system during system model solution. This results in two main problems: firstly, the neglect of individual interface characteristics can lead to divergent and inaccurate calculation results; secondly, this approach significantly increases the number of iterations when alternating between component and system model solutions, leading to a decrease in overall computational efficiency. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention provides a bidirectional interface method between a multi-rate electromechanical transient model and an AC system model, comprising:

[0011] By combining the DC multi-rate electromechanical transient model and the AC system model, a combined three-order algebraic equation is obtained.

[0012] Solving the three-order algebraic equations, if the difference between the obtained system voltage vector magnitude and the steady-state calculation result voltage magnitude is less than or equal to the preset error, then initialization is successful, and the electromechanical transient stability calculation process begins; let the current calculation time be... T The system voltage vector obtained during initialization is T The calculation results for the time step show that the system voltage vector for the next large time step is equal to... T Voltage vector at time step;

[0013] The AC system model at the next large time step AC network interface position is input into the DC multi-rate electromechanical transient model through the DC network interface; the DC multi-rate electromechanical transient model performs a differentiation operation once to obtain the DC equivalent model for the next time step;

[0014] By combining the DC equivalent model with the AC system model and solving the combined algebraic equations, the system three-sequence node voltage vector for the next large time step can be obtained.

[0015] If the magnitude of the system's three-sequence node voltage vector is compared with the voltage magnitude of the system's power flow calculation, and the difference is greater than a preset error, then at the current time step... T Without shifting, return to the step of transferring the AC system model at the next major time step's AC network interface position to the DC multi-rate electromechanical transient model via the DC network interface; if the difference is less than a preset error, then set the system voltage vector of the next major time step equal to the voltage vector calculated in this time step, and then advance the current time step to the next major time step, i.e. , For the next large time step, return to the step of transferring the AC system model at the AC network interface position of the next large time step into the DC multi-rate electromechanical transient model via the DC network interface.

[0016] Furthermore, before the step of merging the DC multi-rate electromechanical transient model and the AC system model, the following steps are also included:

[0017] Based on the power flow calculation results, the state variables of the AC system model are calculated, and the AC system model is returned. and DC multi-rate electromechanical transient model .

[0018] Furthermore, by simultaneously establishing the DC multi-rate electromechanical transient model and the AC system model, the simultaneous three-order algebraic equations are obtained, including:

[0019] By simultaneously solving the DC multi-rate electromechanical transient model and the AC system model, and obtaining the simultaneous three-order algebraic equations, we arrive at the following results.

[0020]

[0021] in, , , Provides node positive-sequence, negative-sequence, and zero-sequence injection currents for DC multi-rate electromechanical transient models and AC system models, respectively; , , These are the positive-sequence, negative-sequence, and zero-sequence admittance matrices of the AC system model, including static load and fault equivalent impedance. , , These are the positive-sequence, negative-sequence, and zero-sequence voltage vectors of the system nodes, respectively.

[0022] Furthermore, it also includes:

[0023] If the difference between the obtained system voltage vector magnitude and the steady-state calculation result voltage magnitude exceeds the preset error, the initialization will fail.

[0024] Furthermore, let the current computation time be... T The system voltage vector obtained during initialization is T The calculation results for the time step show that the system voltage vector for the next large time step is equal to... T The voltage vector at each time step includes:

[0025] Let the current computation time be T = 0.0 s The system voltage vector obtained during initialization is T= 0.0 s The calculation results for the time step show that the system voltage vector for the next large time step is equal to... T= 0.0 s Voltage vector at time step.

[0026] Furthermore, if the difference is less than a preset error, then the current time step is a large time step, including:

[0027] If the difference is less than the preset error, then let , For the great time to take steps.

[0028] Furthermore, it also includes:

[0029] like T If the simulation time exceeds the preset time, the simulation will end and the results will be output.

[0030] This invention also provides a bidirectional interface system for a multi-rate electromechanical transient model and an AC system model, comprising:

[0031] The algebraic equation acquisition module is used to combine the DC multi-rate electromechanical transient model and the AC system model to obtain the combined three-order algebraic equations.

[0032] The stability calculation module is used to solve the three-order algebraic equations. If the difference between the obtained system voltage vector magnitude and the steady-state calculation result voltage magnitude is less than or equal to a preset error, the initialization is successful, and the electromechanical transient stability calculation process begins. Let the current calculation time be... T The system voltage vector obtained during initialization is T The calculation results for the time step show that the system voltage vector for the next large time step is equal to... T Voltage vector at time step;

[0033] The DC equivalent model acquisition module is used to input the AC system model at the next large time step AC network interface position into the DC multi-rate electromechanical transient model through the DC network interface; the DC multi-rate electromechanical transient model performs a differentiation operation once to obtain the DC equivalent model for the next time step;

[0034] The three-sequence node voltage vector acquisition module is used to combine the DC equivalent model with the AC system model, and obtain the system three-sequence node voltage vector for the next large time step by solving the combined algebraic equations.

[0035] The voltage amplitude comparison module is used to compare the amplitude of the three-sequence node voltage vector of the system with the voltage amplitude of the system power flow calculation result. If the difference is greater than the preset error, the current time step... T If no shift is made, the process returns to the step of transferring the AC system model at the next large time step AC network interface position to the DC multi-rate electromechanical transient model via the DC network interface; if the difference is less than the preset error, then the current time step is a large time step, and the process returns to the step of transferring the AC system model at the next large time step AC network interface position to the DC multi-rate electromechanical transient model via the DC network interface.

[0036] Furthermore, it also includes:

[0037] The power flow calculation module is used to calculate the state variables of the AC system model based on the power flow calculation results, and return the AC system model. , ,

[0038] and DC multi-rate electromechanical transient model .

[0039] Furthermore, it also includes:

[0040] The initialization module is used to prevent initialization from failing if the difference between the obtained system voltage vector magnitude and the steady-state calculation result voltage magnitude exceeds a preset error.

[0041] This invention provides a bidirectional interface method and system for a multi-rate electromechanical transient model and an AC system model. During the operation of the electromechanical transient calculation system, the AC power grid is solved using large time steps. The system equivalent model at the AC grid interface location is input into the complex topology DC multi-rate electromechanical transient model via the DC grid interface. After the complex topology DC multi-rate electromechanical transient model completes the small-time step integration solution with the system equivalent model, the AC grid interface returns the DC grid interface location, based on the converter transformer type, to the system model. The system model then performs calculations with the DC equivalent model. This iterative process improves the accuracy, computational efficiency, and stability of power system electromechanical transient simulation. Attached Figure Description

[0042] Figure 1 This is a flowchart illustrating a bidirectional interface method between a multi-rate electromechanical transient model and an AC system model provided by the present invention.

[0043] Figure 2 This invention relates to the interaction structure of complex topology DC and system models;

[0044] Figure 3 This invention relates to a system model solution structure diagram;

[0045] Figure 4 This invention relates to a structural diagram of a solution for a complex topology DC electromechanical transient model.

[0046] Figure 5 This invention relates to a multi-rate simulation principle diagram of an AC / DC hybrid power grid;

[0047] Figure 6 This is a schematic diagram of the system structure of a bidirectional interface between a multi-rate electromechanical transient model and an AC system model provided by the present invention. Detailed Implementation

[0048] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0049] Example 1

[0050] This invention modifies the current bidirectional interface method between complex topology DC multi-rate electromechanical transient models and AC system models, ultimately forming a related interface method and computing system. The complex topology DC multi-rate electromechanical transient model refers to an AC power grid using a large time step... DC uses hourly steps The method of simulation, , The set is positive integers. During calculation, the AC grid is solved using large time steps. The system equivalent model (originally a constant voltage source) at the AC grid interface location is passed to the complex topology DC multi-rate electromechanical transient model via the DC grid interface. After the complex topology DC multi-rate electromechanical transient model completes the small-time step integration with the system equivalent model, the AC grid interface returns the DC equivalent model (originally a current source) at the DC grid interface location, based on the converter transformer type, to the system model. The system model then performs calculations with the DC equivalent model. Finally, the above iterative process ensures accuracy. The overall simulation principle is shown in the attached figure. Figure 5 As shown. The execution steps of the method are as follows. Figure 1 As shown, it includes:

[0051] Step S101: Combine the DC multi-rate electromechanical transient model and the AC system model to obtain the combined three-order algebraic equations.

[0052] Based on the power flow calculation results, the state variables of the AC system model are calculated, and the AC system model is returned. and DC multi-rate electromechanical transient model .

[0053] The admittance matrix of the system model is formed. The DC multi-rate electromechanical transient model and the AC system model are simultaneously solved, and the simultaneous three-order algebraic equations are obtained.

[0054]

[0055] in, , , Provides node positive-sequence, negative-sequence, and zero-sequence injection currents for DC multi-rate electromechanical transient models and AC system models, respectively; , , These are the positive-sequence, negative-sequence, and zero-sequence admittance matrices of the AC system model, including static load and fault equivalent impedance. , , These are the positive-sequence, negative-sequence, and zero-sequence voltage vectors of the system nodes, respectively.

[0056] Step S102: Solve the three-order algebraic equations. If the difference between the obtained system voltage vector magnitude and the steady-state calculation result voltage magnitude is less than or equal to the preset error, the initialization is successful, and the electromechanical transient stability calculation process begins. Let the current calculation time be... T The system voltage vector obtained during initialization is T The calculation results of the time step show that the system voltage vector of the next large time step is equal to the voltage vector of time step T.

[0057] Let the current computation time be T =0.0 s The system voltage vector obtained during initialization is T= 0.0 s The calculation results for the time step show that the system voltage vector for the next large time step is equal to... T= 0.0 s Voltage vector at time step.

[0058] If the difference between the obtained system voltage vector magnitude and the steady-state calculation result voltage magnitude exceeds the preset error, the initialization will fail.

[0059] Step S103: The AC system model at the next large time step AC network interface position is transmitted to the DC multi-rate electromechanical transient model through the DC network interface; the DC multi-rate electromechanical transient model performs a differential operation once to obtain the DC equivalent model for the next time step.

[0060] Step S104: Combine the DC equivalent model with the AC system model, and obtain the system three-sequence node voltage vector for the next large time step by solving the combined algebraic equations.

[0061] Step S105: If the magnitude of the system's three-sequence node voltage vector is compared with the voltage magnitude of the system power flow calculation result, and the difference is greater than the preset error, then the current time step... T If no further steps are taken, the process returns to the step of transmitting the AC system model at the next large time step AC network interface position to the DC multi-rate electromechanical transient model via the DC network interface.

[0062] If the difference is less than the preset error, then the system voltage vector of the next major time step is set equal to the voltage vector calculated in this time step, and the current time step is advanced to the next major time step. , For large time steps, return to the step of transferring the AC system model at the next large time step AC network interface position to the DC multi-rate electromechanical transient model via the DC network interface. If T is greater than the preset simulation time, the simulation ends and the results are output.

[0063] Example 2

[0064] The execution steps for alternately solving the system model and the multi-rate model are described below:

[0065] 1. Initialization: Calculate the state variables of the component model based on the steady-state calculation results (power flow calculation results). This requires inputting the voltage vector, active power, and reactive power at the AC grid interface location into the component model via the DC grid interface. After the component model calculation is completed, return the component equivalent model (originally a current source). and complex topology DC equivalent models .

[0066] 2. System Model Solution: Form the admittance matrix of the system model, and solve the simultaneous three-order algebraic equations by combining the component equivalent models with the system model.

[0067]

[0068] 3. Initialization result verification: The magnitude of the system voltage vector obtained from the system model solution is compared one by one with the voltage magnitude of the steady-state calculation result (power flow calculation result). If the maximum difference exceeds the set error, the initialization fails and the program terminates.

[0069] 4. If initialization passes, the electromechanical transient stability calculation process begins. Let the current calculation time be... T = 0.0 s The system voltage vector obtained during initialization is T = 0.0 s The calculation results for the next time step show that the system voltage vector for the next large time step is equal to... T = 0.0 s Voltage vector at time step.

[0070] 5. The equivalent system model (previously a constant voltage source) at the next large time step AC network interface location is transferred to the component model via the DC network interface. The component model performs a differentiation operation once (if it is a multi-rate model, use a small time step). Perform differentiation operations Each hourly equivalent model is used to obtain the DC equivalent model for the next major time step by taking the system equivalent model at the AC network interface position of the current time step and the next major time step (the system equivalent model is taken linearly according to the time step).

[0071] 6. Solve the simultaneous algebraic equations of the DC equivalent model and the system model to solve the system model and obtain the system three-sequence node voltage vector for the next large time step.

[0072] 7. Compare the system voltage vector magnitude obtained from the system model solution with the resulting voltage magnitude (power flow calculation result). If the maximum difference exceeds the set error, then the current time step... T Without further action, return to step 5. If the maximum difference result is less than the set error, then let... Return to step 5. If T is greater than the set simulation time, exit the program and output the results.

[0073] In the above steps, steps 5 and 6 can respectively introduce disturbances within the system or component model at specified large time steps. The specific implementation steps of the bidirectional interface method between the complex topology DC multi-rate electromechanical transient model and the AC system model in this invention are described below. First, the interaction structure between the complex topology DC and the system model is shown in the attached figure. Figure 2 As shown, the structure diagram when the system model is solved individually is as follows: Figure 3As shown in the attached figure, the structure of the complex topology DC electromechanical transient model when solved alone is as follows. Figure 4 As shown.

[0074] The method for forming the DC equivalent model is as follows:

[0075] From the appendix Figure 3 It can be seen that the DC equivalent model formed by this invention is not only a current source, but also incorporates an equivalent impedance. During the initialization in step 1, the equivalent impedance of the model is calculated, and the voltage vector, active power, and reactive power at the AC grid interface location are respectively... The method for calculating the equivalent impedance is as follows:

[0076]

[0077] The DC equivalent model in step 5 No recalculation or further changes are required. The calculation method for the injected current source in the DC equivalent model in steps 1 and 5 is as follows: Let the injected current source calculated by the DC equivalent model at the DC grid interface location before the improvement be... (The method for calculating the differential of the component model is not protected in this invention; the focus is on the interface method. The final result of the differential of the component model is always a current source.) Therefore, in the new interface, the injected current source obtained by the model calculation is:

[0078]

[0079] The DC system has multiple interface locations, and each interface location is used to create a DC equivalent model in the manner described above. (Corresponding to the appendix...) Figure 3 In Ultimately, it forms at the DC grid interface location. , The DC equivalent model, after being connected in parallel, is input into the system model and calculated together with the system model. The above describes the formation method of the positive-sequence DC equivalent model. The negative-sequence and zero-sequence equivalent models remain consistent with the model before the improvement, that is, only the negative-sequence and zero-sequence injection currents are provided, without calculating the equivalent admittances of the negative-sequence and zero-sequence.

[0080] The method for forming the system equivalent model is as follows:

[0081] The system equivalent model consists of an equivalent voltage source. After the equivalent impedance matrix of the series system is constructed, it is then fed into the complex topology DC multi-rate model and used together for hourly step calculations. In step 5, the calculation of the system equivalent model requires first extracting the positive sequence voltage source vector at the AC grid interface position before the current time step improvement and setting it as... The injected current vector obtained by the differential calculation of the time-step model is: Positive-sequence equivalent impedance The calculation method is described as follows:

[0082] First, obtain the positive-order admittance matrix of the system. The positive-sequence admittance matrix is ​​incorporated into the DC equivalent model. Admittance of equivalent models for other components When considering system failures, a fault impedance is added to the system model, generating a positive-sequence admittance matrix for system equivalence. .

[0083] The dimension is the number of interface locations on the communication network, set to Now describing The calculation method for the i-th row corresponding to the i-th interface. First, solve the following equation:

[0084]

[0085] In the formula, The standard vector is the admittance matrix corresponding to the i-th interface position, with each row position set to 1 and the others set to zero.

[0086] This is the solution vector corresponding to the i-th interface obtained by solving equation (X). All locations corresponding to the China Central Television (CCTV) interface Composed of elements The i-th row corresponds to the i-th interface. Repeat the above steps to calculate all rows in sequence. Each interface ultimately forms a complete system. The above solution process can be understood as obtaining the... The process of finding the equivalent Thevenin impedance matrix at the AC network interface location of the system admittance matrix.

[0087] Similarly, , , By replacing them with negative-sequence and zero-sequence, we can obtain the equivalent impedance matrices of the AC network in negative-sequence and zero-sequence formats. , Thus, an appendix was formed. Figure 4 The equivalent impedance part of the system. If the system admittance matrix does not change during the transient stability integration, then the equivalent impedance matrix of the AC network... , , The values ​​remain unchanged, therefore, there is no need to recalculate the three equivalent impedance values.

[0088] Appendix Figure 4 The method for calculating the equivalent voltage of the system is as follows:

[0089]

[0090] Note: To perform decoupling calculations for each DC converter, the equivalent impedance matrix of the AC grid can be ignored. , , The off-diagonal elements form the system model.

[0091] Appendix Figure 2 middle, , , The component models in the system provide node positive sequence, negative sequence, and zero sequence injection currents to the system model, respectively. , , These are the positive-sequence, negative-sequence, and zero-sequence admittance matrices of the system model, including static load and fault equivalent impedance. , , These represent the positive-sequence, negative-sequence, and zero-sequence voltage vectors of the system nodes, respectively. The types of converters in complex topology DC systems include line commutated converters (LCCs) and voltage source converters (VSCs). Both are devices that convert alternating current (AC) to direct current (DC) in a DC system. These devices, along with the DC grid, collectively generate the complex topology DC model.

[0092] Appendix Figure 3 middle, , The impedances and injected currents generated by the equivalent models of other components are incorporated into the admittance matrix of the system model, forming the final network model, which is an algebraic equation model of the system step size.

[0093] Based on the same inventive concept, this invention also provides a bidirectional interface system 600 for a multi-rate electromechanical transient model and an AC system model, such as... Figure 6 As shown, it includes:

[0094] The algebraic equation acquisition module 610 is used to combine the DC multi-rate electromechanical transient model and the AC system model to obtain the combined three-order algebraic equations.

[0095] The stability calculation module 620 is used to solve the three-sequence algebraic equations. If the difference between the obtained system voltage vector amplitude and the steady-state calculation result voltage amplitude is less than or equal to a preset error, the initialization is successful, and the electromechanical transient stability calculation process begins. Let the current calculation time be... T The system voltage vector obtained during initialization is T The calculation results of the time step show that the system voltage vector of the next large time step is equal to the voltage vector of time step T.

[0096] The DC equivalent model acquisition module 630 is used to input the AC system model at the next large time step AC network interface position into the DC multi-rate electromechanical transient model through the DC network interface; the DC multi-rate electromechanical transient model performs a differential operation once to obtain the DC equivalent model for the next time step;

[0097] The three-sequence node voltage vector acquisition module 640 is used to combine the DC equivalent model with the AC system model, and obtain the system three-sequence node voltage vector for the next large time step by solving the combined algebraic equations.

[0098] The voltage amplitude comparison module 650 is used to compare the amplitude of the three-sequence node voltage vector of the system with the voltage amplitude of the system power flow calculation result. If the difference is greater than the preset error, then at the current time step... T Without shifting, the AC system model at the next large time step AC network interface position is re-introduced into the DC multi-rate electromechanical transient model through the DC network interface; if the difference is less than the preset error, the current time step is a large time step, and the AC system model at the next large time step AC network interface position is re-introduced into the DC multi-rate electromechanical transient model through the DC network interface.

[0099] Furthermore, it also includes:

[0100] The power flow calculation module is used to calculate the state variables of the AC system model based on the power flow calculation results, and return the AC system model. , ,

[0101] and DC multi-rate electromechanical transient model .

[0102] Furthermore, it also includes:

[0103] The initialization module is used to prevent initialization from failing if the difference between the obtained system voltage vector magnitude and the steady-state calculation result voltage magnitude exceeds a preset error.

[0104] The traditional bidirectional interface method between the multi-rate electromechanical transient model and the AC system model for complex topology DC systems neglects the influence of system impedance on the multi-rate complex topology DC model when solving it. This approach can lead to divergence in the final calculation results and significantly increases the number of iterations when alternately solving the component and system models, resulting in a decrease in the overall efficiency of the computational system.

[0105] When solving the system model, the DC model does not provide impedance to the system, which can easily cause the Jacobian matrix of the linear equations of the system model to be singular, leading to numerical problems in solving the system model.

[0106] The interface and computing system provided by this invention theoretically solve the above problems and effectively improve the robustness of the overall computing system.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A bidirectional interface method between a multi-rate electromechanical transient model and an AC system model, characterized in that, include: By simultaneously establishing the DC multi-rate electromechanical transient model and the AC system model, the simultaneous three-order algebraic equations are obtained, including: simultaneously establishing the DC multi-rate electromechanical transient model and the AC system model, solving the simultaneous three-order algebraic equations, and obtaining... in, Provides node positive sequence injection current for DC multi-rate electromechanical transient models and AC system models. Provides nodal negative sequence injection current for DC multi-rate electromechanical transient models and AC system models. Provide node zero-sequence injection current for DC multi-rate electromechanical transient models and AC system models; , , These are the positive-sequence, negative-sequence, and zero-sequence admittance matrices of the AC system model, including static load and fault equivalent impedance. , , These are the positive-sequence, negative-sequence, and zero-sequence voltage vectors of the system nodes, respectively. Solving the three-order algebraic equations, if the difference between the obtained system voltage vector magnitude and the steady-state calculation result voltage magnitude is less than or equal to the preset error, then initialization is successful, and the electromechanical transient stability calculation process begins; let the current calculation time be... T The system voltage vector obtained during initialization is T The calculation results for the time step show that the system voltage vector for the next large time step is equal to... T Voltage vector at time step; The AC system model at the next large time step AC network interface position is input into the DC multi-rate electromechanical transient model through the DC network interface; the DC multi-rate electromechanical transient model performs a differentiation operation once to obtain the DC equivalent model for the next time step; By combining the DC equivalent model with the AC system model and solving the combined algebraic equations, the system three-sequence node voltage vector for the next large time step can be obtained. The magnitude of the system's three-sequence node voltage vector is compared with the voltage magnitude of the system's power flow calculation results. If the difference is greater than a preset error, then the current time step... T Without shifting, return to the step of transferring the AC system model at the next major time step's AC network interface position to the DC multi-rate electromechanical transient model via the DC network interface; if the difference is less than a preset error, then set the system voltage vector of the next major time step equal to the voltage vector calculated in this time step, and then advance the current time step to the next major time step, i.e. , For the next large time step, return to the step of transferring the AC system model at the AC network interface position of the next large time step into the DC multi-rate electromechanical transient model via the DC network interface.

2. The method according to claim 1, characterized in that, Before the step of merging the DC multi-rate electromechanical transient model and the AC system model, the following steps are also included: Based on the power flow calculation results, the state variables of the AC system model are calculated, and the AC system model is returned. and DC multi-rate electromechanical transient model .

3. The method according to claim 1, characterized in that, Also includes: If the difference between the obtained system voltage vector magnitude and the steady-state calculation result voltage magnitude exceeds the preset error, the initialization will fail.

4. The method according to claim 1, characterized in that, Let the current computation time be T The system voltage vector obtained during initialization is T The calculation results of the time steps show that the system voltage vector of the next large time step is equal to the voltage vector of time step T, including: Let the current computation time be T = 0.0 s The system voltage vector obtained during initialization is T= 0.0 s The calculation results for the time step show that the system voltage vector for the next large time step is equal to... T= 0.0 s Voltage vector at time step.

5. The method according to claim 1, characterized in that, If the difference is less than the preset error, then the current time step is a large time step, including: If the difference is less than the preset error, then let , For the great time to take steps.

6. The method according to claim 1 or 4, characterized in that, Also includes: like T If the simulation time exceeds the preset time, the simulation will end and the results will be output.

7. A bidirectional interface system for a multi-rate electromechanical transient model and an AC system model, characterized in that, include: The algebraic equation acquisition module is used to simultaneously solve the DC multi-rate electromechanical transient model and the AC system model to obtain the simultaneous three-order algebraic equations. This includes: simultaneously solving the DC multi-rate electromechanical transient model and the AC system model to obtain the simultaneous three-order algebraic equations. in, Provides node positive sequence injection current for DC multi-rate electromechanical transient models and AC system models. Provides nodal negative sequence injection current for DC multi-rate electromechanical transient models and AC system models. Provide node zero-sequence injection current for DC multi-rate electromechanical transient models and AC system models; , , These are the positive-sequence, negative-sequence, and zero-sequence admittance matrices of the AC system model, including static load and fault equivalent impedance. , , These are the positive-sequence, negative-sequence, and zero-sequence voltage vectors of the system nodes, respectively. The stability calculation module is used to solve the three-order algebraic equations. If the difference between the obtained system voltage vector magnitude and the steady-state calculation result voltage magnitude is less than or equal to a preset error, the initialization is successful, and the electromechanical transient stability calculation process begins. Let the current calculation time be... T The system voltage vector obtained during initialization is T The calculation results for the time step show that the system voltage vector for the next large time step is equal to... T Voltage vector at time step; The DC equivalent model acquisition module is used to input the AC system model at the next large time step AC network interface position into the DC multi-rate electromechanical transient model through the DC network interface; the DC multi-rate electromechanical transient model performs a differentiation operation once to obtain the DC equivalent model for the next time step; The three-sequence node voltage vector acquisition module is used to combine the DC equivalent model with the AC system model, and obtain the system three-sequence node voltage vector for the next large time step by solving the combined algebraic equations. The voltage amplitude comparison module compares the amplitude of the three-sequence node voltage vectors of the system with the voltage amplitude of the system power flow calculation results. If the difference is greater than a preset error, the current time step... T Without shifting, return to the step of transferring the AC system model at the next major time step's AC network interface position to the DC multi-rate electromechanical transient model via the DC network interface; if the difference is less than a preset error, then set the system voltage vector of the next major time step equal to the voltage vector calculated in this time step, and then advance the current time step to the next major time step, i.e. , For the next large time step, return to the step of transferring the AC system model at the AC network interface position of the next large time step into the DC multi-rate electromechanical transient model via the DC network interface.

8. The system according to claim 7, characterized in that, Also includes: The power flow calculation module is used to calculate the state variables of the AC system model based on the power flow calculation results, and return the AC system model. , , and DC multi-rate electromechanical transient model .

9. The system according to claim 7, characterized in that, Also includes: The initialization module is used to prevent initialization from failing if the difference between the obtained system voltage vector magnitude and the steady-state calculation result voltage magnitude exceeds a preset error.

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