Transformer dynamic excitation simulation method based on reverse power flow of power system

Abstract

The invention discloses a dynamic excitation simulation method for a transformer based on reverse power flow of a power system, and the method comprises the steps: building a two-dimensional model of the transformer, and importing the two-dimensional model of the transformer into a coupling external circuit model of reverse flow of power flow of the power system; adding a slow start parameter in a double-exponential function form into the external excitation equation, and adjusting an excitation voltage waveform by using the external excitation equation; carrying out analogue simulation under power flow return of the novel power system, and calculating simulation results under different slow start parameters; according to the method, the input voltage waveform is adjusted by introducing the slow start parameter in a double-exponential function form, so that accurate simulation of the power transformer in a power flow reverse flow scene is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment simulation, and in particular to a transformer dynamic excitation simulation method based on power system reverse power flow. Background Art

[0002] In the power system, power transformers are core equipment for energy conversion and transmission. Their operating efficiency and stability are directly related to the safety and reliability of the entire power system. In recent years, with the significant increase in the proportion of renewable energy sources such as wind and solar power entering the grid, the power system is facing unprecedented changes. The intermittent, volatile, and uncertain nature of these renewable energy sources poses a huge challenge to the supply and demand balance of the power system. In particular, during certain periods of time, due to the surge in renewable energy generation, the demand side of the power system may experience excess reactive power or active power, causing the power flow to no longer flow unidirectionally from the power source to the load, but instead flow in the opposite direction toward the grid (i.e., the power source). This phenomenon is known as the "power system power flow reverse flow scenario."

[0003] In the reverse power flow scenario, the operating state of the power transformer will change significantly. The polarity changes of current and voltage, as well as the possible reverse flow of reactive power and active power, will have a significant impact on the transformer's core loss, hysteresis effect, eddy current loss, and temperature distribution. Traditional simulation methods, based on linear or simplified nonlinear models, are often unable to accurately capture these changes, resulting in a large deviation between the simulation results and the actual situation. In addition, when dealing with external excitation of the transformer, existing simulation methods usually use a fixed input voltage waveform, ignoring the impact of the DC component on the magnetic flux density that may exist in actual operation. This simplified processing method is particularly unsuitable in the reverse power flow scenario, because the DC component may cause magnetic flux density deviations, which in turn affects the performance and life of the transformer.

[0004] In related technology, patent application document CN110427687A proposes to accurately obtain the core loss distribution within the core by establishing a model and applying simulated electromagnetic and circuit simulations to the model. However, this solution is mainly applicable to the static distribution of core loss and cannot capture the changes in core loss during dynamic processes (such as harmonics, short circuits, and sudden load changes). At the same time, this solution does not consider the impact of power system reverse power flow on the transformer. Therefore, it is necessary to study the changes in the excitation characteristics of the transformer under reverse power flow (such as the access of distributed power generation) in view of the dynamic operation of the power system.

[0005] Patent application publication number CN118194798A combines electromagnetic transient simulation models with finite element simulation models to accurately simulate the electromagnetic characteristics of transformers. However, this approach primarily focuses on transformer simulation analysis and does not directly address the issue of reverse power flow in power systems after the integration of renewable energy sources. Therefore, it is limited in addressing the impact of reverse power flow on transformer simulation.

[0006] Therefore, in order to accurately simulate the operating state of power transformers under the reverse flow scenario of power system power flow, it is necessary to develop an improved simulation excitation method. Summary of the Invention

[0007] The technical problem to be solved by the present invention is how to accurately capture the changes in the working state of the transformer when simulating the power transformer in a reverse flow scenario of the power system power flow.

[0008] The present invention solves the above technical problems through the following technical means:

[0009] A transformer dynamic excitation simulation method based on power system reverse power flow is proposed, the method comprising:

[0010] Build a two-dimensional transformer model and import the two-dimensional transformer model into the coupled external circuit model of the reverse flow of power system power flow;

[0011] A slow start parameter in the form of a double exponential function is added to the external excitation equation, and the excitation voltage waveform is adjusted using the external excitation equation;

[0012] Conduct field-circuit joint simulation under the new power system power flow return, and calculate the simulation results under different slow start parameters.

[0013] Furthermore, the two-dimensional transformer model is constructed and the two-dimensional transformer model is imported into a coupled external circuit model of reverse power system power flow to obtain a field-circuit coupling model, including:

[0014] Build a deep two-dimensional transformer model and set the electrical characteristics of the transformer model based on the nonlinear characteristics of the iron core and the anisotropy of each component material. The transformer model includes the excitation coil, iron core, and test environment.

[0015] Constructing a coupled external circuit model for reverse power system power flow, wherein the coupled external circuit model enables the primary side of the transformer to satisfy the reactive power value less than 0 or the active power value less than 0;

[0016] The two-dimensional model of the transformer is introduced into a coupled external circuit model, and the coupled external circuit model applies an excitation voltage to the excitation coil.

[0017] Furthermore, the depth of the two-dimensional model of the transformer is the ratio of the cross-sectional area of a single limb of the iron core to the length of the iron core.

[0018] Furthermore, a capacitor group is provided in the coupled external circuit model, and the capacitor group is connected in parallel to the secondary side of the transformer two-dimensional model.

[0019] Furthermore, the formula of the external excitation equation is expressed as:

[0020]

[0021] Among them, V peak represents the peak value of the external excitation voltage, f is the operating frequency, g is the slow start parameter that changes with time t, V in_PhaseA is the external excitation voltage of phase A.

[0022] Furthermore, the slow start parameter g is gradually increased from a value of 1 during the simulation process, and the winding conduction deviation is kept less than 7%.

[0023] Furthermore, the simulation of the new power system under power flow return and calculation of simulation results under different slow start parameters include:

[0024] The simulation software ANSYS MAXWELL is used to simulate the two-dimensional model of the transformer, and the instantaneous flux density distribution and core loss distribution under different slow start parameters are calculated.

[0025] Furthermore, the core loss distribution in the simulation results is calculated using the core loss calculation model, which is expressed as follows:

[0026]

[0027] Where k h is the hysteresis loss, k c is the eddy current loss, k e For excessive loss, B m is the magnetic flux density of the core, f is the operating frequency of the transformer, and P is the core loss.

[0028] Furthermore, the hysteresis loss k h and the excessive loss k e The calculation formula is:

[0029]

[0030] In the formula, k1, k2 are solved by the least squares method The equivalent coefficient obtained, P vi is the transient iron loss determined by the core BP curve, B viis the magnetic flux density defined by the core BP curve, which is the nonlinear characteristic of the core.

[0031] Furthermore, the simulation of the new power system under power flow return and calculation of simulation results under different slow start parameters also include:

[0032] The thermal-magnetic coupling analysis method is used to simulate the temperature field effect during transformer operation.

[0033] The advantages of the present invention are:

[0034] (1) The present invention introduces a two-dimensional transformer model into a coupled external circuit model of reverse power system current flow, performs effective finite element simulation under the new power system current return, and designs a new external excitation equation, in which a slow start parameter in the form of a double exponential function is introduced to adjust the input excitation voltage waveform, so as to achieve accurate input of simulation excitation in special scenarios, greatly improve the convergence of finite element simulation, and significantly reduce computing resource consumption while ensuring high accuracy. The slow start parameter in the form of a double exponential function can more accurately simulate the excitation voltage waveform under actual working conditions, avoiding the magnetic flux density deviation caused by the DC component.

[0035] (2) The instantaneous magnetic flux density distribution, core loss distribution and temperature field influence are taken into account during the simulation, which significantly improves the accuracy and practicality of the simulation results and provides a reliable basis for the design and operation of transformers under uncertain flow direction in new power systems.

[0036] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a flow chart of a transformer dynamic excitation simulation method based on power system reverse power flow proposed in one embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the structure of a two-dimensional transformer model constructed in one embodiment of the present invention;

[0039] Figure 3 is a BH curve of the core material in one embodiment of the present invention;

[0040] Figure 4 is a BP curve of the core material in one embodiment of the present invention;

[0041] Figure 5 This is a schematic diagram of field-circuit coupling in one embodiment of the present invention;

[0042] Figure 61 is a schematic diagram of a slow start external excitation voltage curve in one embodiment of the present invention;

[0043] Figure 7 1 is a schematic diagram of flux deviation without slow start in one embodiment of the present invention;

[0044] Figure 8 1 is a schematic diagram of loss distribution without slow start in one embodiment of the present invention;

[0045] Figure 9 Schematic diagram of loss distribution under slow start excitation in one embodiment of the present invention. DETAILED DESCRIPTION

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0047] like Figure 1 As shown, an embodiment of the present invention provides a transformer dynamic excitation simulation method based on power system reverse power flow, the method comprising the following steps:

[0048] S10, constructing a two-dimensional transformer model, and importing the two-dimensional transformer model into a coupled external circuit model of reverse power system power flow;

[0049] Specifically, this embodiment establishes a three-dimensional transformer model in Ansys Electronics. To improve calculation speed, the three-dimensional model is converted into a two-dimensional model for simulation. An external circuit is built in Simplorer, and field-circuit joint simulation is performed using Ansys Electronics and Simplorer. Ansys Electronics is responsible for electromagnetic field analysis (such as core magnetic flux distribution and eddy current loss), while Simplorer is responsible for external circuit modeling (such as excitation power supply, load, and control logic). The two exchange data (such as voltage and current) in real time through an interface, realizing accurate simulation of the dynamic interaction between the transformer and the power system.

[0050] S20, adding a slow start parameter in the form of a double exponential function to the external excitation equation, and adjusting the excitation voltage waveform using the external excitation equation;

[0051] S30. Conduct simulation under the new power system power flow return and calculate simulation results under different slow start parameters.

[0052] It should be noted that this embodiment imports the two-dimensional transformer model into the coupled external circuit model of the reverse flow of the power system power flow, performs effective finite element simulation under the new power system power flow return, and designs a new external excitation equation, in which a slow start parameter in the form of a double exponential function is introduced to adjust the input excitation voltage waveform. The slow start parameter in the form of a double exponential function can more accurately simulate the excitation voltage waveform under actual working conditions and avoid the magnetic flux density deviation caused by the DC component.

[0053] As a further preferred technical solution, step S10: building a two-dimensional transformer model and importing the two-dimensional transformer model into a coupled external circuit model of reverse power system power flow to obtain a field-circuit coupling model, specifically includes the following steps:

[0054] S11. Build a deep two-dimensional transformer model, and set the electrical characteristics of the two-dimensional transformer model based on the nonlinear characteristics of the iron core and the anisotropy of the materials of each component. The two-dimensional transformer model includes an excitation coil, an iron core, and a test environment.

[0055] Specifically, if Figure 2 As shown in FIG, the transformer 2D model constructed in ANSYS MAXWELL in this embodiment is a 2D finite element analysis model. The transformer 2D model includes the excitation coil, the core, and the test environment, which takes into account the anisotropy of the material and the nonlinear characteristics of the core material, thickness, mass, density, and operating frequency. The nonlinear characteristics of the core material include the BH curve and the BP curve, as shown in FIG. Figure 3 and Figure 4 As shown, the BH curve and BP curve can reflect but are not limited to saturation effect, hysteresis effect, etc.

[0056] Furthermore, this embodiment uses interpolation to fit the BH and BP curves during transformer modeling. Interpolation generates continuous, smooth curves from a limited number of measured or discrete data points, ensuring accurate representation of magnetization intensity and loss coefficient at varying magnetic flux densities. Furthermore, the two-dimensional transformer model accounts for material anisotropy, i.e., differences in magnetization properties in different directions. This approach, through model dimensionality reduction and system-level coupling, expands simulation dimensionality and engineering applicability.

[0057] S12, constructing a coupled external circuit model for reverse flow of power system power, wherein the coupled external circuit model enables the primary side of the transformer to satisfy the value of the reactive power generated is less than 0 or the value of the active power generated is less than 0;

[0058] Specifically, this embodiment builds an external field model in Simplore to add a path calculation project. The built coupled external circuit model of the reverse flow of the power system flow is as follows: Figure 5As shown, the primary side of the power transformer is required to meet either the condition that the reactive power value generated is less than 0 or the active power value generated is less than 0, that is, to ensure that at least one of the reactive power or the active power flows in the reverse direction.

[0059] Then the finite element two-dimensional model is imported to realize transient field-circuit coupling, and a capacitor group is connected in parallel on the secondary side of the transformer to ensure that the reactive power flow direction is from the secondary side to the primary side of the transformer.

[0060] S13. Importing the transformer two-dimensional model into a coupled external circuit model, and applying an excitation voltage to the excitation coil by the coupled external circuit model.

[0061] As a further preferred technical solution, the depth of the two-dimensional model of the transformer is the ratio of the cross-sectional area of a single limb of the core to the length of the core, which more finely simulates the three-dimensional structural characteristics while maintaining the two-dimensional calculation efficiency.

[0062] Specifically, this embodiment adds the depth of the two-dimensional model to the two-dimensional simulation model of the transformer, which is obtained by the two-dimensional model depth equation. In this example, the cross-sectional area of a single core leg is 4960.992 mm2, the core length is 480 mm, and the two-dimensional model depth is 10.3354 mm. The two-dimensional model depth equation is as follows:

[0063]

[0064] The excitation coil is made of copper with a resistivity of 1.68×10-8Ω·m, the core conductivity σ is 2083300S / m, the mass density is 7650kg / m3, the thickness d is 0.27mm, and the nonlinear factor of the core is taken into account.

[0065] As a further preferred technical solution, in step S20, the designed external excitation equation is expressed as:

[0066]

[0067] Among them, V peak represents the peak value of the external excitation voltage, f is the transformer operating frequency, g is the slow start parameter that changes with time t, V in_PhaseA is the external excitation voltage of phase A.

[0068] It should be noted that this embodiment controls the time required for the external excitation voltage to reach a steady state by changing the value of the slow start parameter g. When g = 25, 50, 75, and 100, the external excitation voltage reaches a steady state within 0.04s, 0.06s, 0.08s, and 0.14s, respectively.

[0069] Furthermore, during the simulation process, the slow start parameter g is gradually increased from a value of 1, and the winding conduction deviation is kept less than 7%, thereby optimizing the balance between simulation accuracy and calculation efficiency.

[0070] As a further preferred technical solution, step S30: performing simulation under power flow return of the new power system and calculating simulation results under different slow start parameters specifically includes:

[0071] The simulation software ANSYS MAXWELL is used to simulate the two-dimensional model of the transformer, and the instantaneous flux density distribution and core loss distribution under different slow start parameters are calculated.

[0072] It should be noted that this embodiment uses the simulation software ANSYS MAXWELL to simulate the transformer and calculate the instantaneous magnetic flux density distribution and core loss distribution, specifically including:

[0073] (1) Adaptive meshing technology is used to mesh the two-dimensional transformer model. During the meshing process, the critical areas (such as the interface between the core and the air) are ensured to have a sufficiently high resolution. At the same time, a coarser mesh is used in non-critical areas to reduce the amount of calculation. The mesh size is about 0.5 mm inside the core and gradually increases to 2 mm outside the core.

[0074] (2) A transient solver is selected with a time step of 1e-6s to ensure that the rapidly changing magnetic field distribution is captured. A second-order time integration scheme is used in the solution process to improve the accuracy of the solution results.

[0075] (3) Periodic boundary conditions are applied to simulate the continuous operation state of the actual transformer, and non-reflection boundary conditions are applied to the external boundaries to prevent numerical reflection from affecting the simulation results.

[0076] (4) Set the initial magnetic flux density to zero to ensure that the simulation starts from the unbiased state, thereby accurately reflecting the excitation process.

[0077] (5) The output frequency is set to output data once every 1e-4s so as to record the changing trend of the entire simulation process in detail.

[0078] As a further preferred technical solution, the step S30 of performing simulation under power flow return of the new power system and calculating simulation results under different slow start parameters further includes:

[0079] The thermal-magnetic coupling analysis method is used to simulate the temperature field effect during transformer operation.

[0080] Specifically, this embodiment also considers the influence of the temperature field during transformer operation during the simulation process, and uses a thermal-magnetic coupling analysis method to ensure that the simulation results not only reflect the magnetic field distribution, but also consider the influence of temperature on material properties and losses. The specific process of thermal-magnetic coupling analysis is as follows:

[0081] A four-step iterative algorithm is used in the thermal-magnetic coupling analysis, where the temperature and magnetic fields are updated once in each iterative step. The temperature field calculation is based on the Fourier heat conduction equation, and the magnetic field calculation is based on Maxwell's equations. The coupled boundary conditions of the temperature and magnetic fields are ensured to be consistent, that is, at the end of each time step, the boundary conditions of the temperature and magnetic fields match each other.

[0082] As a further preferred technical solution, the core loss distribution in the simulation results is calculated using the core loss calculation model, which is expressed as follows:

[0083]

[0084] Where k h is the hysteresis loss, k c is the eddy current loss, k e For excessive loss, B m is the magnetic flux density of the core, f is the operating frequency of the transformer (taken as 50Hz), and P is the core loss.

[0085] It should be noted that the advantage of this calculation solution lies in the dynamic nonlinear correction and multi-physics field collaborative simulation capabilities.

[0086] Specifically, the classical eddy current loss coefficient can be written as σ is the conductivity of the iron core, and d is the thickness of the iron core.

[0087] As a further preferred technical solution, the hysteresis loss k h and the excessive loss k e The calculation formula is:

[0088]

[0089] In the formula, k1, k2 are solved by the least squares method The equivalent coefficient obtained, P vi is the transient iron loss determined by the core BP curve, B vi is the magnetic flux density defined by the core BP curve, which is the nonlinear characteristic of the core.

[0090] This embodiment achieves high-fidelity simulation of core loss under complex working conditions through dynamic, nonlinear kh and ke calculation models.

[0091] As a further preferred technical solution, this embodiment sets a three-phase symmetrical sinusoidal excitation voltage without slow start external excitation, such as Figure 6 As shown in the figure, the external excitation voltage is taken as 25, 50, 75, and 100 respectively, and the peak value of the excitation voltage is 301.64V. Figure 7 As shown in the figure, the simulation results without double exponential slow start external excitation show that the winding flux deviation is 75%. Under the proposed external excitation, the winding flux deviation is 0.387%, 0.312%, 1.043% and 5.87% when the slow start parameters are 25, 50, 75 and 100, respectively.

[0092] As a further preferred technical solution, this embodiment calculates the core loss simulation results under different slow start parameters, such as Figure 8 As shown in the figure, without slow start, the core loss is 2.4093kW, of which hysteresis loss accounts for 76.92% and eddy current loss accounts for 23.08; Figure 9 As shown, when the slow start parameter is 25, the core loss is 1.9479kW, of which hysteresis loss accounts for 62.30% and eddy current loss accounts for 37.70%. When the slow start parameter is 50, the core loss is 1.9345kW, of which hysteresis loss accounts for 61.85% and eddy current loss accounts for 38.15%. When the slow start parameter is 75, the core loss is 1.9773kW, of which hysteresis loss accounts for 62.48% and eddy current loss accounts for 37.52%. When the slow start parameter is 100, the core loss is 2.0012kW, of which hysteresis loss accounts for 62.91% and eddy current loss accounts for 37.09%.

[0093] It should be noted that this embodiment proposes a method for simulating transformer dynamic excitation based on reverse power flow in a power system. By constructing a two-dimensional finite element analysis model and a coupled external circuit model, it takes into account the nonlinear characteristics of the core material, the dynamic changes of external excitation, and the simulation of inrush current, and introduces a slow start parameter in the form of a double exponential function to adjust the input voltage waveform. This method achieves accurate simulation of power transformers in reverse power flow scenarios. It also takes into account the effects of instantaneous magnetic flux density distribution, core loss distribution, and temperature field, significantly improving the accuracy and practicality of the simulation results and providing a reliable basis for the design and operation of transformers in new power systems with uncertain power flow direction.

[0094] It should be noted that the logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing the logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device), or in conjunction with such instruction execution system, apparatus, or device. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transmit a program for use by an instruction execution system, apparatus, or device, or in conjunction with such instruction execution system, apparatus, or device. More specific examples (non-exhaustive list) of computer-readable media include the following: an electrical connection portion having one or more wires (electronic device), a portable computer disk cartridge (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and programmable read-only memory (EPROM or flash memory), fiber optic devices, and portable compact disc read-only memory (CDROM). Furthermore, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing it in another suitable manner if necessary, and then storing it in a computer memory.

[0095] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0096] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0097] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0098] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A transformer dynamic excitation simulation method based on power system reverse power flow, characterized in that: include: Build a two-dimensional transformer model and import the two-dimensional transformer model into the coupled external circuit model of the reverse flow of power system power flow; A slow start parameter in the form of a double exponential function is added to the external excitation equation, and the excitation voltage waveform is adjusted using the external excitation equation; Conduct simulations under the new power system power flow return and calculate simulation results under different slow start parameters.

2. The transformer dynamic excitation simulation method based on power system reverse power flow according to claim 1, characterized in that: The two-dimensional transformer model is constructed and introduced into a coupled external circuit model of reverse power system power flow to obtain a field-circuit coupling model, including: Build a deep two-dimensional transformer model and set the electrical characteristics of the transformer model based on the nonlinear characteristics of the iron core and the anisotropy of each component material. The transformer model includes the excitation coil, iron core, and test environment. Constructing a coupled external circuit model for reverse power system power flow, wherein the coupled external circuit model enables the primary side of the transformer to satisfy the reactive power value less than 0 or the active power value less than 0; The two-dimensional model of the transformer is introduced into a coupled external circuit model, and the coupled external circuit model applies an excitation voltage to the excitation coil.

3. The transformer dynamic excitation simulation method based on power system reverse power flow according to claim 2, characterized in that: The depth of the two-dimensional transformer model is the ratio of the cross-sectional area of a single limb of the core to the length of the core.

4. The transformer dynamic excitation simulation method based on power system reverse power flow according to claim 2, characterized in that: A capacitor group is provided in the coupled external circuit model, and the capacitor group is connected in parallel to the secondary side of the transformer two-dimensional model.

5. The transformer dynamic excitation simulation method based on power system reverse power flow according to claim 1, characterized in that: The formula of the external excitation equation is expressed as: Among them, V peak represents the peak value of the external excitation voltage, f is the operating frequency, g is the slow start parameter that changes with time t, V in_PhaseA is the external excitation voltage of phase A.

6. The transformer dynamic excitation simulation method based on power system reverse power flow according to claim 5, characterized in that: The slow start parameter g is gradually increased from a value of 1 during the simulation process, and the winding conduction deviation is kept less than 7%.

7. The transformer dynamic excitation simulation method based on power system reverse power flow according to claim 1, characterized in that: The simulation of the new power system under power flow return and calculation of simulation results under different slow start parameters include: The simulation software ANSYS MAXWELL is used to simulate the two-dimensional model of the transformer, and the instantaneous flux density distribution and core loss distribution under different slow start parameters are calculated.

8. The transformer dynamic excitation simulation method based on power system reverse power flow according to claim 1 or 7, characterized in that: The core loss distribution in the simulation results is calculated using the core loss calculation model, which is expressed as follows: Where k h is the hysteresis loss, k c is the eddy current loss, k e For excessive loss, B m is the magnetic flux density of the core, f is the operating frequency of the transformer, and P is the core loss.

9. The transformer dynamic excitation simulation method based on power system reverse power flow according to claim 8, characterized in that: The hysteresis loss k h and the excessive loss k e The calculation formula is: In the formula, k1, k2 are solved by the least squares method The equivalent coefficient obtained, P vi is the transient iron loss determined by the core BP curve, B vi is the magnetic flux density defined by the core BP curve, which is the nonlinear characteristic of the core.

10. The transformer dynamic excitation simulation method based on power system reverse power flow according to claim 1, characterized in that: The simulation of the new power system under power flow return and calculation of simulation results under different slow start parameters also include: The thermal-magnetic coupling analysis method is used to simulate the temperature field effect during transformer operation.

Images