Transient simulation modeling method and system for intermediate frequency oscillation of converter station

Abstract

The invention provides a transient simulation modeling method and system for intermediate frequency oscillation of a converter station, and belongs to the technical field of transient simulation and modeling of a power system. Comprising the steps that an alternating current filter bank model is established, and an arc channel Cassie-Mayr model in the breakdown process is introduced; based on the geometric parameters of the converter station grounding network, calculating the port impedance characteristics of the converter station grounding network in a middle frequency band, and constructing a lumped parameter equivalent circuit consistent with the impedance characteristics in the middle frequency band as the intermediate frequency grounding network equivalent model; in the electromagnetic transient simulation platform, connecting the alternating-current filter bank model, the intermediate-frequency grounding network equivalent model, the converter transformer and the alternating-current power grid model by using a connecting conductor to obtain a transient simulation model of the intermediate-frequency oscillation of the converter station; and performing simulation by using the transient simulation model of the converter station intermediate frequency oscillation, performing model verification and correction by combining measured data, and enabling a difference value between a simulation result and the measured data to be within a preset error range by adjusting parameters.

Description

Technical Field

[0001] This invention relates to the field of power system transient simulation and modeling technology, and in particular to a transient simulation modeling method and system for intermediate frequency oscillations in converter stations. Background Technology

[0002] In high-voltage direct current (HVDC) transmission systems, converter stations are a core component. To filter out the characteristic harmonics generated by the converters, multiple AC filters are typically installed on the AC bus side of the converter station. In actual operation, especially during transient processes such as filter switching and system disturbances, medium-frequency oscillations with frequencies ranging from hundreds to thousands of hertz have been observed within the converter station (particularly in ungrounded or high-impedance grounded systems).

[0003] Such intermediate-frequency oscillations can lead to overvoltage and overcurrent, seriously threatening the safety of critical equipment such as AC filter banks and transformers, and even causing protection malfunctions and DC system shutdown. Existing electromagnetic transient simulation models (such as those in PSCAD / EMTDC and RTDS) typically focus on accurate simulation of power frequency or characteristic harmonic frequencies. Their simulation accuracy is insufficient for intermediate-frequency oscillations generated by the coupling between filter banks and the complex grounding network within the station. The main reasons are: existing models do not adequately consider the frequency characteristics of AC filter components, neglecting the parasitic parameters and stray capacitance of capacitors and reactors in the kHz frequency band; the large grounding network of converter stations is usually treated with simple equivalent resistance or ideal grounding, ignoring its inductive characteristics and complex network structure in the intermediate-frequency range, making it impossible to accurately simulate the electromagnetic coupling resonance between the grounding network and the filter; therefore, it is difficult to predict, analyze, and formulate suppression strategies in advance in engineering. Summary of the Invention

[0004] In view of this, the present invention provides a transient simulation modeling method and system for intermediate frequency oscillations in converter stations, which improves the simulation accuracy of intermediate frequency oscillations. During the design phase or before operation of the DC transmission system, it accurately simulates the inductive impedance characteristics of the grounding grid in the intermediate frequency range and its electromagnetic coupling resonance with the filter network, and accurately predicts the risk of intermediate frequency oscillations.

[0005] The technical solution adopted by the embodiments of the present invention to solve its technical problem is as follows:

[0006] A transient simulation modeling method for intermediate frequency oscillations in a converter station includes:

[0007] Step S1: Establish an AC filter bank model and introduce the Cassie-Mayr model of the arc channel during the breakdown process;

[0008] Step S2, construct the equivalent model of the intermediate frequency grounding network: Based on the geometric parameters of the converter station grounding network, calculate the port impedance characteristics of the converter station grounding network in the intermediate frequency band, and construct a lumped parameter equivalent circuit consistent with the impedance characteristics in the intermediate frequency band as the equivalent model of the intermediate frequency grounding network;

[0009] Step S3: In the electromagnetic transient simulation platform, the AC filter bank model, the equivalent model of the intermediate frequency grounding network, the converter transformer and the AC power grid model are connected, and the distributed parameters and electromagnetic coupling of the connecting conductors are considered to obtain the transient simulation model of the intermediate frequency oscillation of the converter station.

[0010] Step S4: Simulate using the transient simulation model of intermediate frequency oscillation in the converter station, and verify and correct the model by combining it with measured data. Adjust the parameters so that the difference between the simulation results and the measured data is within the preset error range.

[0011] Preferably, step S1 includes:

[0012] By introducing the equivalent series inductance and equivalent series resistance of the filter capacitor, a high-frequency equivalent circuit model of the filter capacitor is established.

[0013] By incorporating the frequency-varying characteristics of the inter-turn distributed capacitance and core loss of the filter reactor, a high-frequency variable impedance model is established.

[0014] For discharge coils, current transformers and auxiliary equipment, stray capacitance and frequency-dependent resistance should be considered;

[0015] A high-frequency equivalent model of the AC filter bank is established, and the Cassie-Mayr model of the arc path during the breakdown process is introduced: ;

[0016] in It is the instantaneous conductance of the electric arc, and t is time. It is the rate of change of arc conductivity over time. It is the arc time constant. It is the instantaneous voltage of the electric arc. It is the instantaneous current of the electric arc. It refers to heat dissipation power.

[0017] Preferably, step S2 includes:

[0018] Based on the grounding grid design drawings of the converter station, the topology and geometric parameters of the grounding conductors are extracted;

[0019] Based on the geometric parameters of the converter station grounding grid, its port impedance characteristics in the target mid-frequency band are calculated.

[0020] By applying the field-circuit coupling method, the port impedance frequency characteristics of the grounding grid in the target mid-frequency band are calculated, and a lumped parameter equivalent circuit with the same impedance characteristics in the target mid-frequency band is constructed.

[0021] An RLC network synthesis method is used to construct a lumped-parameter equivalent circuit that matches the actual impedance frequency characteristics of the grounding grid within the target frequency band; the impedance function in the lumped-parameter equivalent circuit is expressed using Foster's first-type method. : ;

[0022] in Corresponding to a series inductor, This corresponds to a series resistor; For a parallel LC resonant circuit, the total number of N nodes is: Is The parallel capacitor at point ω, where s is the complex frequency and ω is the cutoff frequency. This is the impedance function.

[0023] Preferably, step S3 includes:

[0024] Step S31: In the electromagnetic transient simulation platform, connect the refined AC filter model, the equivalent model of the intermediate frequency grounding network, the converter transformer, and the AC power grid model.

[0025] Step S32: Simulate the spatial location and length of the connecting conductor between the high-voltage side of the filter bank and the grounding grid, and model the connecting conductor as a transmission line model with distributed parameters.

[0026] Preferably, step S4 includes:

[0027] Step S41: Obtain actual waveform data from the field, including the AC bus voltage and filter branch current waveforms when intermediate frequency oscillation occurs;

[0028] Step S42: Reproduce the same operating conditions as the recorded waveform data in the simulation model, perform transient simulation, and iteratively correct the high-frequency parameters in the model: Objective function: ; Parameter update: ;

[0029] Indicates in The on-site measured value at any given time is the amplitude of the oscillating current or the waveform of the voltage. This includes the set of all high-frequency parameters that need to be corrected, including the equivalent series inductance of the capacitor, the equivalent series resistance of the capacitor, and the inter-turn distributed capacitance of the reactor. Indicates in parameter set In the model, Simulation calculation values ​​at any given time; Indicates in Time error; This represents the weight coefficient, where i is the time point index, and α is the learning rate. objective function At point The gradient at point N; N is the total number of time points;

[0030] Step S43: Compare the simulated intermediate frequency oscillation waveform (including oscillation frequency, amplitude, and damping) with the field recorded waveform data. If the error exceeds the allowable range, fine-tune the high-frequency parameters for iterative correction until the difference between the simulation result and the measured data is within the preset error range. The intermediate frequency oscillation waveform data includes oscillation frequency, amplitude, and damping. The high-frequency parameters include stray capacitance and ESL.

[0031] A transient simulation modeling system for intermediate frequency oscillations in a converter station, used to implement the aforementioned method, the system comprising:

[0032] The model building module is used to build an AC filter bank model, introducing the Cassie-Mayr model of the arc path during the breakdown process; constructing an equivalent model of the intermediate frequency grounding network: based on the geometric parameters of the converter station grounding network, the port impedance characteristics of the converter station grounding network in the intermediate frequency band are calculated, and a lumped parameter equivalent circuit with the same impedance characteristics in the intermediate frequency band is constructed as the equivalent model of the intermediate frequency grounding network; in the electromagnetic transient simulation platform, the AC filter bank model, the equivalent model of the intermediate frequency grounding network, the converter transformer and the AC power grid model are connected, and the distributed parameters and electromagnetic coupling of the connecting conductors are considered to obtain the transient simulation model of the intermediate frequency oscillation of the converter station;

[0033] The model training module is used to perform simulations using a transient simulation model of intermediate frequency oscillations in converter stations, and to verify and correct the model by combining it with measured data. By adjusting the parameters, the difference between the simulation results and the measured data is kept within a preset error range.

[0034] As can be seen from the above technical solutions, the transient simulation modeling method and system for intermediate frequency oscillation of converter stations provided by the embodiments of the present invention.

[0035] This invention discloses a transient simulation model and method capable of accurately simulating intermediate frequency oscillations in converter stations. The simulation model is based on a PSCCD simulation model. The modeling method includes: establishing an AC filter bank model and introducing the Cassie-Mayr model for the arc path during breakdown; constructing an equivalent model of the intermediate frequency grounding network: based on the geometric parameters of the converter station grounding network, calculating the port impedance characteristics of the converter station grounding network in the intermediate frequency band, and constructing a lumped parameter equivalent circuit consistent with the impedance characteristics in the intermediate frequency band as the equivalent model of the intermediate frequency grounding network; in an electromagnetic transient simulation platform, connecting the AC filter bank model, the equivalent model of the intermediate frequency grounding network, the converter transformer, and the AC power grid model, and considering the distributed parameters and electromagnetic coupling of the connecting conductors, to obtain a transient simulation model of the intermediate frequency oscillations in the converter station; performing simulation using the transient simulation model of the intermediate frequency oscillations in the converter station, and verifying and correcting the model by combining it with measured data, adjusting the parameters to ensure that the difference between the simulation results and the measured data is within a preset error range. This invention can improve the accuracy of intermediate frequency oscillation simulation. During the design phase or before operation of a DC transmission system, it can accurately simulate the inductive impedance characteristics of the grounding grid in the intermediate frequency range and its electromagnetic coupling resonance with the filter network, and accurately predict the risk of intermediate frequency oscillation. Attached Figure Description

[0036] Figure 1 This invention relates to a transient simulation modeling method for intermediate frequency oscillations in converter stations.

[0037] Figure 2 The high-frequency equivalent circuit model diagram is shown.

[0038] Figure 3 This is a diagram showing the actual operation on site.

[0039] Figure 4 This is a diagram of the measured voltage waveform. Detailed Implementation

[0040] The technical solution and effects of the present invention will be further described in detail below with reference to the accompanying drawings.

[0041] A transient simulation modeling method for intermediate frequency oscillations in a converter station includes:

[0042] Step S1: Establish an AC filter bank model and introduce the Cassie-Mayr model of the arc channel during the breakdown process;

[0043] Step S2, construct the equivalent model of the intermediate frequency grounding network: Based on the geometric parameters of the converter station grounding network, calculate the port impedance characteristics of the converter station grounding network in the intermediate frequency band, and construct a lumped parameter equivalent circuit consistent with the impedance characteristics in the intermediate frequency band as the equivalent model of the intermediate frequency grounding network;

[0044] Step S3: In the electromagnetic transient simulation platform, the AC filter bank model, the equivalent model of the intermediate frequency grounding network, the converter transformer and the AC power grid model are connected, and the distributed parameters and electromagnetic coupling of the connecting conductors are considered to obtain the transient simulation model of the intermediate frequency oscillation of the converter station.

[0045] Step S4: Simulate using the transient simulation model of intermediate frequency oscillation in the converter station, and verify and correct the model by combining it with measured data. Adjust the parameters so that the difference between the simulation results and the measured data is within the preset error range.

[0046] Furthermore, the preparation of the composite flexible piezoelectric material in step S1 includes:

[0047] By introducing the equivalent series inductance (ESL) and equivalent series resistance (ESR) of the filter capacitor, a high-frequency equivalent circuit model of the filter capacitor is established.

[0048] The frequency-varying characteristics of the inter-turn distributed capacitance and core loss of the filter reactor are introduced, and a "wideband model" that can reflect its high-frequency impedance characteristics is adopted.

[0049] For discharge coils, current transformers and auxiliary equipment, stray capacitance and frequency-dependent resistance should be considered;

[0050] A high-frequency equivalent model of the AC filter bank is established. To accurately reproduce the discharge process that may be triggered by the filter bank in actual operation, a Cassie-Mayr model of the arc channel during the breakdown process is introduced based on the above topology: ;

[0051] in It is the instantaneous conductance of the electric arc, and t is time. It is the rate of change of arc conductivity over time. It is the arc time constant. It is the instantaneous voltage of the electric arc. It is the instantaneous current of the electric arc. It refers to heat dissipation power.

[0052] Preferably, step S2 includes:

[0053] Based on the grounding grid design drawings of the converter station, the topology and geometric parameters of the grounding conductors are extracted;

[0054] Based on the geometric parameters of the converter station grounding grid, its port impedance characteristics in the target mid-frequency band are calculated.

[0055] By applying the field-circuit coupling method, the port impedance frequency characteristics of the grounding grid in the target mid-frequency band are calculated, and a lumped parameter equivalent circuit with the same impedance characteristics in the target mid-frequency band is constructed.

[0056] Using the RLC network synthesis method, a lumped-parameter equivalent circuit with the same frequency characteristics as the actual grounding grid impedance within the target frequency band is constructed. This equivalent circuit is a π-type or T-type network containing multiple nodes, and its parameters vary with frequency in a manner consistent with the real grounding grid. The impedance function in the lumped-parameter equivalent circuit is expressed using Foster's first-type method. : ;

[0057] in Corresponding to a series inductor, This corresponds to a series resistor; For a parallel LC resonant circuit, the total number of N nodes is: Is The parallel capacitor at point ω, where s is the complex frequency and ω is the cutoff frequency. This is the impedance function.

[0058] Preferably, step S3 includes:

[0059] Step S31: In the electromagnetic transient simulation platform, connect the refined AC filter model, the equivalent model of the intermediate frequency grounding network, the converter transformer, and the AC power grid model.

[0060] Step S32: Simulate the spatial location and length of the connecting conductor between the high-voltage side of the filter bank and the grounding grid, and model the connecting conductor as a transmission line model with distributed parameters to consider the electromagnetic coupling effect between it and the grounding grid.

[0061] Preferably, step S4 includes:

[0062] Step S41: Obtain actual waveform data from the field, including the AC bus voltage and filter branch current waveforms when intermediate frequency oscillation occurs;

[0063] Step S42: Reproduce the same operating conditions as the recorded waveform data in the simulation model, perform transient simulation, and iteratively correct the high-frequency parameters in the model: Objective function: ; Parameter update: ;

[0064] Here It is a vector representing all the high-frequency parameters that need to be corrected (such as the equivalent series inductance of a capacitor, the equivalent series resistance of a capacitor, and the inter-turn distributed capacitance of a reactor). The objective function, also known as the loss function, measures the performance of the current parameter set. Below is the overall error between the simulation results and the measured data; Indicates in The on-site measured value at any given time is the amplitude of the oscillating current or the waveform of the voltage. This includes the set of all high-frequency parameters that need to be corrected, including the equivalent series inductance of the capacitor, the equivalent series resistance of the capacitor, and the inter-turn distributed capacitance of the reactor. Indicates in parameter set In the model, Simulation calculation values ​​at any given time; Indicates in Time error; This represents the weight coefficient, where i is the time point index, allowing for the assignment of higher weights to certain key time points; then, the squared errors of the N time points are summed, and α is the learning rate, a positive number that determines the magnitude of parameter adjustment in each iteration; objective function At point The gradient at point N; N is the total number of time points;

[0065] Step S43: Compare the simulated intermediate frequency oscillation waveform (including oscillation frequency, amplitude, and damping) with the field recorded waveform data. If the error exceeds the allowable range, fine-tune the high-frequency parameters (such as stray capacitance, ESL value, etc.) for iterative correction until the difference between the simulation result and the measured data is within the preset error range, i.e., minJ enters the allowable range, and the iteration stops.

[0066] A transient simulation modeling system for intermediate frequency oscillations in a converter station, used to implement the aforementioned method, the system comprising:

[0067] The model building module is used to build an AC filter bank model, introducing the Cassie-Mayr model of the arc path during the breakdown process; constructing an equivalent model of the intermediate frequency grounding network: based on the geometric parameters of the converter station grounding network, the port impedance characteristics of the converter station grounding network in the intermediate frequency band are calculated, and a lumped parameter equivalent circuit with the same impedance characteristics in the intermediate frequency band is constructed as the equivalent model of the intermediate frequency grounding network; in the electromagnetic transient simulation platform, the AC filter bank model, the equivalent model of the intermediate frequency grounding network, the converter transformer and the AC power grid model are connected, and the distributed parameters and electromagnetic coupling of the connecting conductors are considered to obtain the transient simulation model of the intermediate frequency oscillation of the converter station;

[0068] The model training module is used to perform simulations using a transient simulation model of intermediate frequency oscillations in converter stations, and to verify and correct the model by combining it with measured data. By adjusting the parameters, the difference between the simulation results and the measured data is kept within a preset error range.

[0069] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, taking a 1500Hz intermediate frequency oscillation that once occurred in a ±500kV converter station as an example:

[0070] S1: Modeling the HP3 / 36 AC filter used at this station. Using the manufacturer's datasheet and impedance analyzer measurements, the ESL of the filter capacitor at 1.5kHz was found to be 0.5μH, and the ESR was 10mΩ. The reactor was modeled using a frequency-varying impedance model based on the measured data.

[0071] S2: Based on the grounding grid drawings of the station, a detailed model was established. Calculations showed that the port impedance exhibited inductive behavior near 1.5kHz, with a distinct resonant peak. A third-order equivalent circuit was synthesized using an RLC network, ensuring that the impedance curve in the 1kHz-2kHz frequency band had an error of less than 5% compared to the detailed model calculations.

[0072] S3: Build the entire simulation platform in PSCAD and connect the refined filter model, the equivalent model of the grounding grid, and the converter transformer (using its high-frequency model) through a 30-meter-long distributed parameter bus model;

[0073] S4: Simulate the operation of "putting on the HP3 / 36 filter" on-site. The initial simulation result showed an oscillation frequency of 1400Hz, with insufficient damping. By fine-tuning the parallel stray capacitance value of the reactor, the final simulation yielded an oscillation frequency of 1480Hz. The amplitude and attenuation trend were highly consistent with the on-site waveform data, verifying the effectiveness of the model. Using this corrected model, the suppression effect of adding a small-capacity damping resistor at the filter neutral point was successfully evaluated, providing a theoretical basis for on-site modifications.

[0074] The beneficial effects of this invention are as follows:

[0075] (1) By introducing parasitic parameters and frequency-varying characteristics such as the equivalent series inductance / resistance of the capacitor and the inter-turn distributed capacitance of the reactor when modeling the AC filter, the limitations of the traditional power frequency model in the high-frequency band are overcome, so that the simulation results can more realistically reflect the dynamic response of the system in the frequency band of hundreds to thousands of hertz, and significantly improve the simulation accuracy of intermediate frequency oscillation.

[0076] (2) Achieved accurate equivalent modeling of complex grounding networks: For the first time, a lumped parameter equivalent circuit for grounding networks in the mid-frequency band was proposed, replacing the traditional simple resistor or ideal grounding model. This can accurately simulate the inductive impedance characteristics of the grounding network in the mid-frequency range and its electromagnetic coupling resonance with the filter network, fundamentally solving the problem of inaccurate modeling of the critical path that induces mid-frequency oscillations.

[0077] (3) Enhanced the realism and scene coverage of the model: The Cassie-Mayr model of the arc channel was introduced into the AC filter model, which enabled the simulation model to accurately reproduce the nonlinear transient processes such as breakdown discharge that may be triggered in actual operation (such as switching and faults) of the filter bank, greatly expanding the applicability and accuracy of the model under complex fault conditions.

[0078] (4) A complete and closed-loop modeling and verification method has been formed: it provides a complete process from fine-grained modeling of components, system connection considering electromagnetic coupling, to finally comparing with field waveform data and performing parameter iterative correction. This method ensures the verifiability and reliability of the established model and provides a standardized tool that can be directly applied to predict, analyze and suppress intermediate frequency oscillations in engineering.

[0079] (5) The model established by the present invention can accurately predict the risk of intermediate frequency oscillation during the design stage or before operation of DC transmission system, thereby optimizing filter design and protection strategy, effectively avoiding equipment damage, protection malfunction and system shutdown caused by oscillation, ensuring power grid safety, and having significant economic and safety benefits.

[0080] (6) By introducing the high-frequency characteristics of the components and the frequency-varying equivalent model of the grounding grid, the problem that the traditional model cannot simulate the intermediate frequency oscillation is fundamentally solved, and the simulation accuracy is significantly improved.

[0081] (7) It provides a complete process from modeling to verification, which is highly practical for engineering and can be directly used to guide the design and operation of DC engineering.

[0082] (8) Using this model, the risk of intermediate frequency oscillation can be predicted in the early stage of engineering construction or when a new filter design scheme is proposed, and the filter parameters and grounding grid design can be optimized to avoid the occurrence of oscillation from the source and save huge costs of later modification.

[0083] (9) It provides a reliable digital twin platform for analyzing the intermediate frequency oscillation problem of the converter station that has been put into operation, evaluating equipment stress and verifying the effectiveness of suppression measures (such as adding damping resistors and changing control strategies), thus ensuring the safe and stable operation of the power grid.

[0084] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A transient simulation modeling method for intermediate frequency oscillations in a converter station, characterized in that, include: Step S1: Establish an AC filter bank model and introduce the Cassie-Mayr model of the arc channel during the breakdown process; Step S2, construct the equivalent model of the intermediate frequency grounding network: Based on the geometric parameters of the converter station grounding network, calculate the port impedance characteristics of the converter station grounding network in the intermediate frequency band, and construct a lumped parameter equivalent circuit consistent with the impedance characteristics in the intermediate frequency band as the equivalent model of the intermediate frequency grounding network; Step S3: In the electromagnetic transient simulation platform, the AC filter bank model, the equivalent model of the intermediate frequency grounding network, the converter transformer and the AC power grid model are connected, and the distributed parameters and electromagnetic coupling of the connecting conductors are considered to obtain the transient simulation model of the intermediate frequency oscillation of the converter station. Step S4: Simulate using the transient simulation model of the intermediate frequency oscillation of the converter station, verify and correct the model by combining it with the measured data, and adjust the parameters so that the difference between the simulation results and the measured data is within the preset error range.

2. The transient simulation modeling method for intermediate frequency oscillations in converter stations as described in claim 1, characterized in that, Step S1 includes: By introducing the equivalent series inductance and equivalent series resistance of the filter capacitor, a high-frequency equivalent circuit model of the filter capacitor is established. By incorporating the frequency-varying characteristics of the inter-turn distributed capacitance and core loss of the filter reactor, a high-frequency variable impedance model is established. For discharge coils, current transformers and auxiliary equipment, stray capacitance and frequency-dependent resistance should be considered; A high-frequency equivalent model of the AC filter bank is established, and the Cassie-Mayr model of the arc path during the breakdown process is introduced: ； in It is the instantaneous conductance of the electric arc, and t is time. It is the rate of change of arc conductivity over time. It is the arc time constant. It is the instantaneous voltage of the electric arc. It is the instantaneous current of the electric arc. It refers to heat dissipation power.

3. The transient simulation modeling method for intermediate frequency oscillations in converter stations as described in claim 2, characterized in that, Step S2 includes: Based on the grounding grid design drawings of the converter station, the topology and geometric parameters of the grounding conductors are extracted; Based on the geometric parameters of the converter station grounding grid, its port impedance characteristics in the target mid-frequency band are calculated. By applying the field-circuit coupling method, the port impedance frequency characteristics of the grounding grid in the target mid-frequency band are calculated, and a lumped parameter equivalent circuit with the same impedance characteristics in the target mid-frequency band is constructed. An RLC network synthesis method is used to construct a lumped-parameter equivalent circuit that matches the actual impedance frequency characteristics of the grounding grid within the target frequency band; the impedance function in the lumped-parameter equivalent circuit is expressed using Foster's first-type method. : ； in Corresponding to a series inductor, This corresponds to a series resistor; For a parallel LC resonant circuit, the total number of N nodes is: Is The parallel capacitor at point ω, where s is the complex frequency and ω is the cutoff frequency. This is the impedance function.

4. The transient simulation modeling method for intermediate frequency oscillations in converter stations as described in claim 3, characterized in that, Step S3 includes: Step S31: In the electromagnetic transient simulation platform, connect the refined AC filter model, the equivalent model of the intermediate frequency grounding network, the converter transformer, and the AC power grid model. Step S32: Simulate the spatial location and length of the connecting conductor between the high-voltage side of the filter bank and the grounding grid, and model the connecting conductor as a transmission line model with distributed parameters.

5. The transient simulation modeling method for intermediate frequency oscillations in converter stations as described in claim 4, characterized in that, Step S4 includes: Step S41: Obtain actual waveform data from the field, including the AC bus voltage and filter branch current waveforms when intermediate frequency oscillation occurs; Step S42: Reproduce the same operating conditions as the recorded waveform data in the simulation model, perform transient simulation, and iteratively correct the high-frequency parameters in the model: Objective function: ; Parameter update: ; Indicates in The on-site measured value at any given time is the amplitude of the oscillating current or the waveform of the voltage. This includes the set of all high-frequency parameters that need to be corrected, including the equivalent series inductance of the capacitor, the equivalent series resistance of the capacitor, and the inter-turn distributed capacitance of the reactor. Indicates in parameter set In the model, Simulation calculation values ​​at any given time; Indicates in Error in time; This represents the weight coefficient, where i is the time point index, and α is the learning rate. objective function At point The gradient at point N; N is the total number of time points; Step S43: Compare the simulated intermediate frequency oscillation waveform (including oscillation frequency, amplitude, and damping) with the field recorded waveform data. If the error exceeds the allowable range, fine-tune the high-frequency parameters for iterative correction until the difference between the simulation result and the measured data is within the preset error range. The intermediate frequency oscillation waveform data includes oscillation frequency, amplitude, and damping. The high-frequency parameters include stray capacitance and ESL.

6. A transient simulation modeling system for intermediate frequency oscillations in a converter station, characterized in that, The system for implementing the method according to any one of claims 1-5 comprises: The model building module is used to build an AC filter bank model, introducing the Cassie-Mayr model of the arc path during the breakdown process; constructing an equivalent model of the intermediate frequency grounding network: based on the geometric parameters of the converter station grounding network, the port impedance characteristics of the converter station grounding network in the intermediate frequency band are calculated, and a lumped parameter equivalent circuit with the same impedance characteristics in the intermediate frequency band is constructed as the equivalent model of the intermediate frequency grounding network; in the electromagnetic transient simulation platform, the AC filter bank model, the equivalent model of the intermediate frequency grounding network, the converter transformer and the AC power grid model are connected, and the distributed parameters and electromagnetic coupling of the connecting conductors are considered to obtain the transient simulation model of the intermediate frequency oscillation of the converter station; The model training module is used to perform simulation using the transient simulation model of the intermediate frequency oscillation of the converter station, and to verify and correct the model by combining it with measured data. The parameters are adjusted so that the difference between the simulation results and the measured data is within a preset error range.

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