Double-shaft excitation synchronous generator short circuit fault magnetic field intensity simulation analysis method

Abstract

The invention relates to the field of motor design and simulation analysis, and discloses a double-shaft excitation synchronous generator short circuit fault magnetic field intensity simulation analysis method, which comprises the following steps: S1, establishing and correcting a high-protection simulation model; s101, carrying out preliminary modeling; s102, correcting and calibrating the model; s2, setting a short-circuit fault simulation working condition; s3, running simulation and performing magnetic field intensity comparative analysis; s4, collaborative optimization feedback is carried out; s201, building an external circuit; s202, simulating a short circuit switch; s203, setting a fault time sequence; and S204, excitation current is set. In the step S1, a mode of manufacturing a physical model machine and acquiring actual measurement data is adopted to ensure the establishment of a high-fidelity simulation model, and in the step S3, the magnetic field intensity cloud atlas and the magnetic induction line distribution map under the three key states before, during and after the short circuit fault are extracted and compared and analyzed to obtain the high-fidelity simulation model. And the complex electromagnetic dynamic process in the generator during the short-circuit fault period can be visually and deeply revealed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor design and simulation analysis, in particular to a short-circuit fault magnetic field strength simulation analysis method for a dual-axis field synchronous generator. BACKGROUND

[0002] The dual-axis field synchronous generator can realize decoupled regulation of active power and reactive power due to independent control of d-axis and q-axis field excitation, and has shown significant advantages in improving transient stability of power systems. It is a new type of generator that has attracted much attention in modern power systems. However, when the generator is connected to the grid, it will inevitably face short-circuit faults caused by lightning strikes, line insulation damage, etc. The huge current generated by the short-circuit fault will cause a strong electromagnetic impact on the generator, which can lead to loss of synchronization or even damage to the generator. Therefore, accurate analysis and optimization design of the transient performance of the generator under short-circuit fault are crucial to ensure its safe and stable operation.

[0003] In the prior art, the analysis of the fault characteristics of synchronous generators usually relies on mathematical models or equivalent circuit models established by analytical methods. These methods can preliminarily estimate the external characteristics of the generator, but due to a large number of simplifications, they cannot accurately account for the complex nonlinear magnetic saturation effects, magnetic circuit harmonics, and complex spatial distribution of armature reactions inside the generator. This leads to a large deviation between the calculation results and the actual situation when analyzing severe transient processes (such as severe short-circuit), and cannot provide reliable guidance for detailed design.

[0004] With the development of computer technology, finite element simulation analysis methods have been introduced into the field of motor design. However, existing simulation applications mostly remain at the level of one-way verification of a fixed design scheme, i.e., after the design is completed, the performance is "seen" through simulation to see if it meets the standards. This analysis process is linear and open-loop, lacking an effective mechanism to feed back the internal physical field diagnostic information during the fault process to the early design stage. Designers often have difficulty obtaining directional improvement basis for structure or control strategy from simulation results, leading to a disconnect between design and analysis processes. The structural design of the generator and the optimization of the excitation control strategy are usually treated as two independent steps, lacking a systematic method that can closely integrate the two and use fault simulation results for collaborative iterative optimization, which makes the development process rely on trial and error, long cycle, and difficult to achieve optimal matching of the overall performance. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a short-circuit fault magnetic field strength simulation analysis method for a dual-axis field synchronous generator, which solves the problem of insufficient accuracy in analyzing short-circuit faults in the prior art.

[0006] In order to achieve the above object, the present application is realized by the following technical scheme: a double-shaft field excitation synchronous generator short-circuit fault magnetic field strength simulation analysis method, comprising the following steps: S1, establishing and correcting a high-fidelity simulation model: before carrying out the double-shaft field excitation synchronous generator short-circuit simulation, a simulation model highly consistent with the actual prototype characteristics must be obtained first; S2, setting a short-circuit fault simulation working condition: on the basis of the high-fidelity simulation model corrected in step S1, a single-phase short-circuit fault is simulated by building an external circuit to form a fault simulation scene; S3, running simulation and performing magnetic field strength comparative analysis: the fault simulation scene set in step S2 is run, and after the simulation converges and ends, the magnetic field strength nephogram and magnetic induction line distribution graph of the double-shaft field excitation synchronous generator in the three key states of pre-short-circuit, short-circuit and post-short-circuit injected q-axis current are extracted and analyzed to reveal the fault mechanism and the role of q-axis excitation, so as to obtain the short-circuit fault magnetic field strength simulation analysis result and provide physical diagnosis basis for the subsequent steps; S4, cooperative optimization feedback: based on the magnetic field strength nephogram and magnetic induction line distribution graph obtained in step S3 as the diagnosis basis, the structure parameters of the high-fidelity simulation model established in step S1 and the excitation current and fault timing in the fault simulation scene set in step S2 are feedback corrected through iterative optimization.

[0007] Preferably, in step S1, the simulation model establishing step specifically comprises: S101, preliminary modeling: a simulation model is established in the design software according to the design parameters of the double-shaft field excitation synchronous generator, and the simulation model comprises: a two-dimensional finite element model of the double-shaft field excitation synchronous generator; S102, model correction and calibration: a physical prototype is manufactured and tested, the measured data of the tested physical prototype under different working conditions are obtained, the obtained measured data are compared with the output data of the simulation model in step S101, the key parameters of the simulation model are adjusted based on the measured data, the output data of the simulation model are made substantially consistent with the measured data, and finally the corrected high-fidelity simulation model is obtained.

[0008] Preferably, in step S2, the external circuit is built to simulate a single-phase short-circuit fault to form a fault simulation scene, specifically comprising: S201, building an external circuit: an external circuit is built for the double-shaft field excitation synchronous generator model in the design software, an external circuit is built for the high-fidelity double-shaft field excitation synchronous generator model established in step S1, and the external circuit comprises a load element simulating a power grid or an actual working condition; S202, simulate short-circuit switch: in the external circuit built in step S201, a voltage-controlled switch is connected in parallel across the load element connected to the stator A-phase winding, which is used to simulate the occurrence and duration of a short-circuit fault. Specifically, when the voltage-controlled switch is closed, the current will bypass the load and directly form a ground or inter-phase short circuit of the A-phase winding. S203, set fault timing: a square wave signal source is used to accurately control the on-off timing of the voltage-controlled switch in step S202, thereby defining the occurrence time and duration of the short-circuit fault. S204, set excitation current: in order to study the effect of dual-axis excitation during a fault, an excitation current is applied to the d-axis and q-axis excitation windings respectively.

[0009] Preferably, in step S101, the parameters of the dual-axis excitation synchronous generator include prototype machine parameters, stator structure, and rotor topology.

[0010] Preferably, in step S102, the measured data under different operating conditions include: performing no-load excitation experiments at rated speed; conducting pure resistive load experiments and variable load experiments; and measuring and recording the terminal voltage, output current, and excitation current data of the dual-axis excitation synchronous generator in the above two groups of experiments.

[0011] Preferably, in step S102, the adjustment of the key parameters of the simulation model based on the measured data includes: repeatedly modifying the BH curve of the rotor silicon steel sheet in the simulation model, and checking the number of turns of the excitation winding, so that the calculated values of the simulation model under corresponding operating conditions are highly consistent with the measured values of the physical prototype.

[0012] Preferably, in step S201, the design software includes: the circuit editor embedded in the ANSYS Maxwell software suite, referred to as Maxwell Circuit Editor, which is responsible for connecting a two-dimensional or three-dimensional finite element electromagnetic model as a circuit element with an external lumped parameter circuit to realize field-circuit coupled co-simulation. The external lumped parameter circuit includes: an external lumped parameter circuit.

[0013] Preferably, in step S204, the purpose and method of applying an excitation current to the d-axis and q-axis excitation windings respectively include: d-axis excitation setting: a constant rated excitation current is applied to the d-axis excitation winding, which is used to simulate the normal and stable operating state of the dual-axis excitation synchronous generator before a fault occurs, and to establish a reference main magnetic field; Q-axis excitation setting: the current is accessed in time through the piecewise linear function built in Maxwell software, a timed trigger excitation current is set for the q-axis excitation winding, the purpose is to simulate the control behavior of the control system injecting excitation current into the q-axis to suppress the fault impact after the fault occurs, specifically: after a period of time after the short-circuit fault occurs, the q-axis excitation current is started to be applied, so as to compare and analyze the influence of the intervention of the q-axis current on the fault process.

[0014] Preferably, in step S4, the feedback correction of the structure parameters of the high-fidelity simulation model established in step S1 and the excitation current and fault timing in the fault simulation scene set in step S2 by iterative optimization is specifically: S401, excitation strategy optimization based on magnetic field analysis: based on the comparison result of analysis point two and analysis point three in step S3, the preset q-axis excitation setting in step S204 is evaluated, specifically the injection time and amplitude of the excitation current, the effectiveness of suppressing the direct-axis armature reaction demagnetizing effect revealed by analysis point two; S402, rotor structure optimization based on fault mechanism: according to the magnetic field distribution graph revealed by analysis point two in step S3, the specific physical area where the magnetic density on the rotor d-axis decreases most significantly or the magnetic circuit distortion is most serious under short-circuit impact is accurately positioned, and the area is identified as a weak link of the magnetic circuit structure in the two-dimensional finite element model established in step S101, then, based on the positioning of the above weak link, return to step S101 to perform directional correction on the rotor topology structure in the two-dimensional finite element model of the double-axis excitation synchronous generator, and after the model structure in step S101 is corrected, return to step S2 to rebuild the fault simulation scene based on the high-fidelity simulation model after the structure optimization, and execute step S3, finally, through the comparison and analysis of the magnetic field intensity before and after the structure correction in step S3, the effectiveness of the rotor topology structure improvement in improving the short-circuit resistance is quantitatively evaluated, so as to realize the directional optimization design of the generator structure.

[0015] The application provides a short-circuit fault magnetic field strength simulation analysis method for a double-axis excitation synchronous generator. 1、The application can intuitively and deeply reveal the complex electromagnetic dynamic process inside the generator during the short-circuit fault by extracting and comparing the magnetic field strength cloud diagram and the magnetic induction line distribution diagram under three key states before, during and after the short-circuit fault in step S3.

[0016] 2. By setting up a collaborative optimization feedback loop in step S4, this invention transforms the simulation analysis from a traditional one-way verification process into a closed-loop, iterative optimization design flow. Using the analysis results from step S3, the excitation control strategy in step S2 or the rotor topology in step S1 can be optimized in a targeted manner, further improving the accuracy of the short-circuit fault magnetic field strength simulation analysis.

[0017] 3. In step S1, the present invention uses the method of manufacturing a physical prototype and obtaining measured data to repeatedly correct and calibrate the key parameters in the simulation model, ensuring the establishment of a high-fidelity simulation model. This allows the subsequent short-circuit fault simulation analysis to be based on a reliable foundation that closely matches the actual working conditions, greatly improving the accuracy of the simulation results and the engineering application value. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a flowchart of step S2 in the present invention; Figure 3 This is a diagram of the magnetic field strength before the short circuit of the present invention; Figure 4 This is a diagram of the magnetic field lines before the short circuit of the present invention; Figure 5 This is a diagram of the magnetic field strength during a short circuit according to the present invention; Figure 6 This is a diagram of the magnetic induction lines during a short circuit according to the present invention; Figure 7 This is a diagram showing the magnetic field strength of the q-axis current after short-circuiting according to the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see the appendix Figure 1 - Appendix Figure 7 This invention provides a method for simulating and analyzing the magnetic field intensity during a short-circuit fault in a dual-shaft excitation synchronous generator, comprising the following steps: S1. Establish and calibrate a high-fidelity simulation model: Before performing short-circuit simulation of a dual-shaft excitation synchronous generator, a simulation model that highly matches the characteristics of the actual prototype must be obtained. The specific steps for establishing the simulation model are as follows: S101. Preliminary Modeling: Based on the design parameters of the dual-shaft excitation synchronous generator, a simulation model is established in the design software. The simulation model includes a two-dimensional finite element model of the dual-shaft excitation synchronous generator. The parameters of the dual-shaft excitation synchronous generator include: prototype parameters, stator structure, and rotor topology; S102, Model Correction and Calibration: Manufacture and test a physical prototype, obtain measured data of the physical prototype under different working conditions, compare the obtained measured data with the output data of the simulation model in step S101, and adjust the key parameters of the simulation model based on the measured data so that the output data of the simulation model is basically consistent with the measured data, and finally obtain the corrected high-fidelity simulation model. The measured data under different operating conditions include: Under rated speed, an unloaded excitation test was conducted; Experiments with purely resistive loads and variable loads; In the two sets of experiments mentioned above, the terminal voltage, output current and excitation current data of the dual-shaft excitation synchronous generator were measured and recorded. The adjustment of key parameters of the simulation model based on measured data includes: iteratively modifying the BH curve of the rotor silicon steel lamination in the simulation model and checking the number of turns of the excitation winding so that the calculated values ​​of the simulation model under the corresponding working conditions are highly consistent with the measured values ​​of the test physical prototype. S2. Set up short-circuit fault simulation conditions: Based on the high-fidelity simulation model after correction in step S1, simulate a single-phase short-circuit fault by building an external circuit to form a fault simulation scenario. S201. Building an external circuit: Building an external circuit for the dual-shaft excitation synchronous generator model in the design software. An external circuit is built for the high-fidelity dual-shaft excitation synchronous generator model established in step S1. The external circuit includes load elements that simulate the power grid or actual working conditions. The design software includes the circuit editor embedded in the ANSYS Maxwell2 software suite, referred to as MaxwellCircuitEditor, which is responsible for connecting a two-dimensional or three-dimensional finite element electromagnetic model as a circuit element to an external lumped parameter circuit to achieve field-circuit coupling co-simulation. The external lumped parameter circuit includes: external lumped parameter circuit. S202, Simulated short-circuit switch: In the external circuit built in step S201, a voltage-controlled switch is connected in parallel across the load element connected to the stator A-phase winding. The voltage-controlled switch is used to simulate the occurrence and duration of a short-circuit fault. Specifically, when the voltage-controlled switch is closed, the current will bypass the load and directly form a short circuit to ground or between phases of the A-phase winding. S203. Set fault timing: Use a square wave signal source to precisely control the on / off timing of the voltage-controlled switch in step S202, thereby defining the occurrence time and duration of the short-circuit fault. Example: The square wave signal is set to transition from low to high level 0.2 seconds after the simulation begins, triggering the voltage-controlled switch to close, thus short-circuiting the load in phase A. This high level lasts for 0.2 seconds before returning to low, causing the switch to open and clearing the fault. The specific timing parameters can be adjusted according to the analysis requirements. S204. Setting the excitation current: To study the effect of biaxial excitation during a fault, it is necessary to apply current excitation to the excitation windings of the d-axis and q-axis respectively. The purpose and method of setting this current include: d-axis excitation setting: A constant rated excitation current is applied to the d-axis excitation winding. The purpose is to simulate the normal and stable operating state of the dual-axis excitation synchronous generator before a fault occurs and to establish a reference main magnetic field. Q-axis excitation setting: The current is timed by using the piecewise linear function built into Maxwell software. A timed excitation current is set for the q-axis excitation winding. The purpose is to simulate the control behavior of the control system injecting excitation current into the q-axis to suppress the fault impact after a fault occurs. Specifically, the q-axis excitation current is applied after a period of time after the short-circuit fault occurs, so as to compare and analyze the impact of the intervention of the q-axis current on the fault process. The time following the occurrence of the short-circuit fault includes: 50ms and 100ms. S3. Run the simulation and perform magnetic field strength comparison analysis: Run the fault simulation scenario set in step S2. After the simulation converges and ends, focus on extracting and analyzing the magnetic field strength cloud map and magnetic induction line distribution map of the dual-axis excitation synchronous generator under three key states: before, during, and after the short circuit when q-axis current is injected. This will reveal the fault mechanism and the role of q-axis excitation, obtain the simulation analysis results of the short-circuit fault magnetic field strength, and provide a physical diagnostic basis for subsequent steps, including but not limited to the following analysis points: Analysis Point 1: The magnetic field under normal operating conditions before the short circuit: Extract the magnetic field intensity diagram and magnetic induction line diagram of the dual-shaft excitation synchronous generator during stable operation. Please refer to the attached diagram for details. Figure 3 and attached Figure 4 ; Analysis results show that the magnetic field is concentrated on the d-axis, the magnetic flux density is reasonably distributed, there is no large-scale saturation, and the dual-shaft excitation synchronous generator exhibits a normal 4-pole motor magnetic field configuration. Analysis point two: During a short circuit, the magnetic field is in a state where no q-axis current is applied. Extract the magnetic field intensity diagram and magnetic field line diagram at the instant of the short circuit in phase A. Please refer to the attached diagram for details.Figure 5 and attached Figure 6 ; Analysis results show that: the short circuit generates a huge short circuit current, and the resulting direct-axis armature reaction magnetic field is opposite to the direction of the rotor main magnetic field, producing a strong demagnetizing effect, which leads to a significant reduction in the magnetic flux density of the rotor d-axis. At the same time, the d-axis magnetic circuit is significantly distorted. Analysis Point 3: After a short circuit, the magnetic field of the applied q-axis excitation current: Extract the magnetic field strength diagram after applying the q-axis excitation current during the short circuit process. Please refer to the attached diagram for details. Figure 7 ; Analysis results show that applying q-axis current enhances the magnetic field of rotor d-axis, effectively counteracting part of the armature reaction demagnetization effect caused by short circuit, thereby stabilizing the operating state of the dual-shaft excitation synchronous generator and lowering the power angle. S4. Collaborative Optimization Feedback: Based on the magnetic field intensity cloud map and magnetic induction line distribution map obtained in step S3 as diagnostic criteria, the structural parameters of the high-fidelity simulation model established in step S1 and the excitation current and fault timing in the fault simulation scenario set in step S2 are corrected through iterative optimization. The specific steps include: S401. Optimization of excitation strategy based on magnetic field analysis: Based on the comparison results of analysis point two and analysis point three in step S3, evaluate the effectiveness of the preset q-axis excitation settings in step S204, specifically the injection time and amplitude of the excitation current, in suppressing the demagnetizing effect of the direct-axis armature reaction revealed by analysis point two. If the evaluation results show that the demagnetizing effect is not sufficiently suppressed or there is overcompensation, adjust the q-axis excitation setting parameters in step S204, and then return to step S2 to reconstruct the fault simulation scenario with the updated parameters, and execute step S3 again to run the simulation and perform magnetic field strength comparison analysis. It should be noted that by repeatedly performing the above iterative cycle of analysis, adjustment, and reanalysis until the analysis results of step S3 show that the generator's power angle is effectively stabilized and the decrease in d-axis magnetic flux density during the fault is within the optimal acceptable range, the optimal q-axis excitation control strategy that matches the electromagnetic characteristics of the high-fidelity simulation model determined in step S1 is obtained. The q-axis excitation setting parameters include: the injection time and amplitude of the excitation current; S402. Rotor structure optimization based on fault mechanism: Based on the magnetic field distribution map revealed in analysis point two in step S3, accurately locate the specific physical region on the rotor d-axis where the magnetic flux density decreases most significantly or the magnetic circuit distortion is most severe under short-circuit impact. Identify this region as the weak link in the magnetic circuit structure of the two-dimensional finite element model established in step S101. Then, based on the location of the weak link, return to step S101 to perform directional correction on the rotor topology in the two-dimensional finite element model of the dual-shaft excitation synchronous generator. After the model structure in step S101 is corrected, return to step S2. Based on this structure-optimized high-fidelity simulation model, rebuild the fault simulation scenario and execute step S3. Finally, by comparing the simulation results before and after the structure correction in step S3 and performing magnetic field strength comparison analysis, quantitatively evaluate the effectiveness of rotor topology improvement in enhancing short-circuit resistance, thereby achieving directional optimization design of the generator body structure. The return step S101, which involves directional correction of the rotor topology in the two-dimensional finite element model of the dual-shaft excitation synchronous generator, includes adjusting the shape and size of the magnetic barrier in the weak link region or adding local magnetic bridges.

Claims

1. A method for simulation analysis of magnetic field intensity in short-circuit fault of a two-axis field excitation synchronous generator, characterized in that, The method comprises the following steps: S1, establishing and correcting a high-fidelity simulation model: before simulating the short-circuit of the double-shaft field synchronous generator, a high-fidelity simulation model highly consistent with the characteristics of the actual prototype must be obtained; S2, setting a short-circuit fault simulation condition: on the basis of the high-fidelity simulation model corrected in step S1, an external circuit is built to simulate a single-phase short-circuit fault, thereby forming a fault simulation scene; S3, running the simulation and performing a magnetic field strength comparison and analysis: the fault simulation scene set in step S2 is run, and after the simulation converges and ends, the magnetic field strength cloud diagram and the magnetic induction line distribution diagram of the double-shaft field synchronous generator in the three key states of pre-short-circuit, during short-circuit and post-short-circuit injection of the q-axis current are extracted and analyzed, so as to reveal the fault mechanism and the role of q-axis excitation, obtain the simulation analysis result of the short-circuit fault magnetic field strength, and provide a physical diagnosis basis for the subsequent steps; S4, cooperative optimization feedback: based on the magnetic field strength cloud diagram and the magnetic induction line distribution diagram obtained in step S3 as a diagnosis basis, the structure parameters of the high-fidelity simulation model established in step S1 and the excitation current and the fault timing in the fault simulation scene set in step S2 are feedback corrected through iterative optimization.

2. The short-circuit fault magnetic field strength simulation analysis method of a two-shaft field excitation synchronous generator according to claim 1, characterized in that, In step S1, the simulation model establishing step specifically comprises: S101, preliminary modeling: a simulation model is established in a design software according to the design parameters of the double-shaft field synchronous generator, and the simulation model comprises a two-dimensional finite element model of the double-shaft field synchronous generator; S102, model correction and calibration: a physical prototype is manufactured and tested, the measured data of the tested physical prototype under different conditions are obtained, the measured data obtained are compared with the output data of the simulation model in step S101, the key parameters of the simulation model are adjusted based on the measured data, the output data of the simulation model are made substantially consistent with the measured data, and finally a corrected high-fidelity simulation model is obtained.

3. The short-circuit fault magnetic field strength simulation analysis method of a two-shaft field excitation synchronous generator according to claim 1, characterized in that, In step S2, the external circuit is built to simulate a single-phase short-circuit fault, thereby forming a fault simulation scene, specifically comprising: S201, building an external circuit: an external circuit is built for the double-shaft field synchronous generator model in a design software, an external circuit is built for the high-fidelity double-shaft field synchronous generator model established in step S1, and the external circuit comprises load elements simulating a power grid or actual conditions; S202, simulating a short-circuit switch: in the external circuit built in step S201, a voltage-controlled switch is connected in parallel at both ends of the load elements connected to the stator A-phase winding, and the voltage-controlled switch is used to simulate the occurrence and duration of a short-circuit fault, specifically: when the voltage-controlled switch is closed, the current bypasses the load and directly forms a short circuit of the A-phase winding to ground or between phases; S203, setting a fault timing: a square wave signal source is used to accurately control the on-off timing of the voltage-controlled switch in step S202, thereby defining the occurrence time and duration of the short-circuit fault; S204, setting an excitation current: in order to study the role of double-shaft excitation during the fault, an excitation current needs to be applied to the d-axis and q-axis excitation windings respectively.

4. The short-circuit fault magnetic field strength simulation analysis method of a two-shaft field excitation synchronous generator according to claim 2, characterized in that, In step S101, the parameters of the double-shaft field synchronous generator comprise prototype parameters, stator structure and rotor topology.

5. The short-circuit fault magnetic field strength simulation analysis method of a two-shaft field excitation synchronous generator according to claim 2, characterized in that, In step S102, the measured data under different working conditions include: conducting no-load excitation experiment at rated speed; conducting pure resistance load experiment and variable load experiment; and measuring and recording the terminal voltage, output current and excitation current data of the double-shaft excitation synchronous generator in the above two groups of experiments.

6. The short-circuit fault magnetic field strength simulation analysis method of a two-shaft field excitation synchronous generator according to claim 2, characterized in that, In step S102, the adjustment of the key parameters of the simulation model based on the measured data includes: repeatedly modifying the BH curve of the rotor silicon steel sheet punching in the simulation model, and checking the excitation winding turns, so that the calculation value of the simulation model under the corresponding working condition is highly consistent with the measured value of the test physical prototype.

7. The short-circuit fault magnetic field strength simulation analysis method of a two-shaft field excitation synchronous generator according to claim 3, characterized in that, In step S201, the design software includes: MaxwellCircuitEditor, an embedded circuit editor in the ANSYS Maxwell software suite, which is responsible for connecting a two-dimensional or three-dimensional finite element electromagnetic model as a circuit element with an external lumped parameter circuit to realize field-circuit coupled co-simulation. The external lumped parameter circuit includes: an external lumped parameter circuit.

8. The short-circuit fault magnetic field strength simulation analysis method of a two-shaft field excitation synchronous generator according to claim 3, characterized in that, In step S204, the purpose and method of setting the excitation current of the d-axis and q-axis excitation windings respectively include: d-axis excitation setting: a constant rated excitation current is applied to the d-axis excitation winding, which aims to simulate the normal and stable operation state of the double-shaft excitation synchronous generator before the fault occurs, and establish a benchmark main magnetic field; q-axis excitation setting: a timed access of current is realized through the built-in piecewise linear function of Maxwell software, and a timed trigger excitation current is set for the q-axis excitation winding, which aims to simulate the control behavior of the control system injecting excitation current into the q-axis to suppress the fault impact after the fault occurs. Specifically, after a period of time after the short-circuit fault occurs, the q-axis excitation current is applied again to compare and analyze the influence of the intervention of the q-axis current on the fault process.

9. The short circuit fault magnetic field strength simulation analysis method of a two-shaft field excitation synchronous generator according to claim 1, characterized in that, In step S4, the feedback correction of the structure parameters of the high-fidelity simulation model established in step S1 and the excitation current and fault timing in the fault simulation scene set in step S2 through iterative optimization is specifically: S401, excitation strategy optimization based on magnetic field analysis: based on the comparison results of analysis point two and analysis point three in step S3, the preset q-axis excitation setting in step S204 is evaluated, specifically the injection time and amplitude of the excitation current, for the effectiveness of suppressing the direct-axis armature reaction demagnetizing effect revealed by analysis point two; S402, rotor structure optimization based on fault mechanism: according to the magnetic field distribution map disclosed in step S3, the specific physical area where the magnetic density on the rotor d-axis decreases most significantly or the magnetic circuit distortion is most serious under short circuit impact is accurately positioned, and the area is identified as the weak link of the magnetic circuit structure in the two-dimensional finite element model established in step S101, then, based on the positioning of the above weak link, step S101 is returned to, the rotor topology structure in the two-dimensional finite element model of the double-shaft excitation synchronous generator is corrected, and after the model structure in step S101 is corrected, step S2 is returned to, the fault simulation scene is re-established based on the high-fidelity simulation model after the structure optimization, and step S3 is executed, finally, the effectiveness of the improvement of the rotor topology structure on improving the short circuit resistance is quantitatively evaluated by comparing and analyzing the magnetic field strength comparison results before and after the structure correction in step S3 running simulation, so as to realize the directional optimization design of the generator structure.

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