A method and system for modeling equivalent circuits of railway trains

Abstract

This invention discloses a method and system for modeling the equivalent circuit of a rail train, relating to the field of modeling technology. The method includes the following steps: combining the equivalent circuits of the carriage and connector, as well as the equivalent circuits of the rails below the carriage and connector, to obtain the equivalent circuit of the rail train; solving for the values ​​of each impedance at different frequencies in the corresponding equivalent circuits of the carriage, connector, and rails below the carriage using multiple impedance frequency responses, to obtain the frequency response of each impedance in the equivalent circuit of the rail train; fitting the frequency response of each impedance in the equivalent circuit of the rail train using the vector matching method, and representing the fitting result using an RLC circuit to obtain the equivalent circuit model of the rail train. This invention constructs an equivalent circuit model of the train and rails using the impedance frequency responses of the train and rails, which can reflect the impedance relationship between the train and rails at different frequencies, facilitating the analysis of the current path and magnitude after a large current is injected into the rails.

Description

Technical Field

[0001] This invention relates to the field of modeling technology, and in particular to a method and system for modeling equivalent circuits of railway trains. Background Technology

[0002] Currently, most equivalent circuit models for rail trains model the power supply path from pantograph to rooftop equipment to traction converter to traction motor to rail. This treats the traction power supply system (including traction substation, overhead contact line, and rails) as a whole with the train, establishing an equivalent circuit that includes the traction substation, rail impedance, and onboard power supply devices, while neglecting the train body itself. For the equivalent circuit of the car body, the impedance of the car body above the train's grounding resistance at DC or 50Hz power frequency is typically used. However, this approach introduces significant errors for high-frequency modeling and simulation.

[0003] When a high-frequency, high-current injection occurs in the rails (such as from lightning strikes, traction network short circuits, or electromagnetic pulse interference), the current in the rails flows through the train wheels to the car body, posing a hazard to passengers and onboard equipment. At this time, part of the current flows to the car body, while the other part continues to dissipate through the rails. The magnitudes of these two currents are significantly related to the impedance of the train and the rails. Existing equivalent circuits for railcars cannot accurately reflect the impedance relationship between the train and the rails at different frequencies, making it difficult to analyze the current path after a large current injection into the rails. Summary of the Invention

[0004] Based on the shortcomings of the existing technology, the present invention provides a method for modeling the equivalent circuit of a rail train, which solves the problem that the existing equivalent circuit of a rail train cannot well reflect the impedance relationship between the train and the rail at different frequencies, and it is difficult to analyze the current path after a large current is injected into the rail.

[0005] The present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for modeling the equivalent circuit of a railway train, comprising the following steps:

[0007] The equivalent circuits of the carriage and connector are established based on the impedances of the right, left, front and rear sides of the carriage and connector. The equivalent circuits of the rails below the carriage and the rails below the connector are established based on the self-impedance, impedance to ground and mutual impedance of the two rails, respectively.

[0008] The equivalent circuit of the railcar and connector is obtained by combining the equivalent circuits of the rails below the railcar and the rails below the connector.

[0009] The impedance frequency response of the carriage, connector and the rail under the carriage is obtained respectively. The values ​​of each impedance in the equivalent circuit of the carriage, connector and the rail under the carriage at different frequencies are solved by multiple impedance frequency responses to obtain the frequency response of each impedance in the equivalent circuit of the rail train.

[0010] The frequency response of each impedance in the equivalent circuit of the rail train is fitted using the vector matching method, and the fitting result is represented using an RLC circuit to obtain the equivalent circuit model of the rail train.

[0011] Preferably, the step of solving for the values ​​of each impedance at different frequencies in the equivalent circuits corresponding to the carriage, connector, and rail below the carriage through multiple impedance frequency responses includes:

[0012] The values ​​of each impedance in the equivalent circuit of the carriage at different frequencies are solved based on the first expression, which is shown below:

[0013] ;

[0014] In the formula, The impedance frequency response of the carriage. , , and These are the impedances on the right, left, front, and rear sides of the carriage, respectively.

[0015] The values ​​of each impedance in the equivalent circuit of the connector at different frequencies are solved according to the second expression, which is shown below:

[0016] ;

[0017] In the formula, This refers to the impedance frequency response of the connector. , , and These are the impedances on the right, left, front, and rear sides of the carriage, respectively.

[0018] The values ​​of various impedances in the equivalent circuit of the rails beneath the carriage at different frequencies are solved using a third expression, which is shown below:

[0019] ;

[0020] In the formula, The impedance frequency response of the rails beneath the carriage. and These are the self-impedances of the right and left rails, respectively. and These are the ground impedances of the right and left rails, respectively. This represents the mutual impedance between the right and left rails.

[0021] Preferably, the frequency response relationship of each impedance in the equivalent circuit of the rail below the carriage and the rail below the connector is as follows:

[0022] ;

[0023] In the formula, The length of the steel rail below the connector. The length of the rails beneath the carriage. The frequency response of the rail impedance below the connector;

[0024] The frequency response of each impedance in the equivalent circuit of the rail below the connector is solved using the above relationships.

[0025] Preferably, the step of fitting the frequency response of each impedance in the equivalent circuit of the rail train using the vector matching method and representing the fitting result using an RLC circuit specifically includes the following steps:

[0026] The frequency response of each impedance in the equivalent circuit of the rail train is inverted to obtain the corresponding admittance frequency response.

[0027] Each admittance frequency response is fitted to obtain the corresponding fitting expression;

[0028] The fitted expression is transformed by an RLC circuit to obtain the RLC circuit representation of each impedance.

[0029] Preferably, the fitting expression is as follows:

[0030] ;

[0031] In the formula, f For frequency, For the extreme point, To leave a residue s Represents complex variables in the complex plane. N The number of poles n As variables, d This is a constant term.

[0032] Preferably, the RLC circuit includes a resistor circuit, an RL series circuit, and an RLCG series-parallel circuit. The number of resistor circuits, RL series circuits, and RLCG series-parallel circuits in the RLC circuit representation of different impedances are different, and their resistance, inductance, capacitance, and conductance values ​​are different.

[0033] Preferably, the step of acquiring the multiple impedance frequency responses of the carriage, connector, and rail below the carriage includes the following steps:

[0034] The front and rear ports of the car are defined according to the wheel-rail contact points between the car and the rail. The front port includes the two wheel-rail contact points of the front wheelset, and the rear port includes the two wheel-rail contact points of the rear wheelset.

[0035] The impedance frequency response of the front and rear ports of the carriage is taken as the impedance frequency response of the carriage. The impedance frequency response of the rear port of the front carriage and the front port of the rear carriage in two adjacent carriages is taken as the impedance frequency response of the connector. The impedance frequency response of the two rails to the ground and the two rails is taken as the impedance frequency response of the rails under the carriage.

[0036] Preferred options also include:

[0037] If the first, second, or third expression has no exact solution, the equivalent circuit of the railcar is simplified using a two-port equivalent circuit to obtain a two-port T-type equivalent circuit.

[0038] The impedances of the two-port T-type equivalent circuit are solved using the fourth expression, which is shown below:

[0039] ;

[0040] In the formula, The impedance frequency response of the carriage, connector, or rail. , and These are the impedance parameters in a two-port T-type equivalent circuit.

[0041] Secondly, the present invention provides a railway train equivalent circuit modeling system, comprising:

[0042] A module is established to establish the equivalent circuit of the carriage and connector based on the impedance of the right, left, front and rear sides of the carriage and connector, and to establish the equivalent circuit of the rail below the carriage and the rail below the connector based on the self impedance, impedance to ground and mutual impedance of the two rails respectively.

[0043] The module is used to combine the equivalent circuits of the carriage and connector, as well as the equivalent circuits of the rails below the carriage and the rails below the connector, to obtain the equivalent circuit of the rail train.

[0044] The solution module is used to obtain the impedance frequency response of the carriage, connector and the rail under the carriage respectively. By using multiple impedance frequency responses, the values ​​of each impedance in the equivalent circuit of the carriage, connector and the rail under the carriage at different frequencies are solved to obtain the frequency response of each impedance in the equivalent circuit of the rail train.

[0045] The conversion module is used to fit the frequency response of each impedance in the equivalent circuit of the rail train using the vector matching method, and to represent the fitting result using an RLC circuit to obtain the equivalent circuit model of the rail train.

[0046] Compared with the prior art, the above-mentioned at least one technical solution adopted by the present invention can achieve the following beneficial effects:

[0047] This invention establishes equivalent circuits for the carriage and connector based on the impedances of the right, left, front, and rear sides of the carriage and connector. Equivalent circuits for the rails below the carriage and connector are established based on the self-impedance, impedance to ground, and mutual impedance of the two rails, respectively. Then, multiple impedance frequency responses for the carriage, connector, and rails below the carriage are obtained. Each impedance in the corresponding equivalent circuit is solved using different impedance frequency responses to obtain the frequency response of each impedance in the equivalent circuit of the railcar. Finally, the frequency response of each impedance in the equivalent circuit of the railcar is fitted using the vector matching method, and the fitting result is represented using an RLC circuit to obtain the equivalent circuit model of the railcar. This invention constructs equivalent circuit models of the train and rails based on their impedance frequency responses, reflecting the impedance relationship between the train and rails at different frequencies, facilitating the analysis of the current path and magnitude after a large current is injected into the rails. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is a schematic diagram of the wheel-rail contact point of the two carriages of the present invention;

[0050] Figure 2 This is a schematic diagram of the fifth, sixth, and seventh ports of the present invention;

[0051] Figure 3 This is the equivalent circuit diagram of the train in this invention;

[0052] in, Figure 3 (a): Equivalent circuit diagram of the first carriage. Figure 3 (b) Equivalent circuit diagram of the connector;

[0053] Figure 4 This is the equivalent circuit diagram of the rail in this invention;

[0054] Figure 5 This is an equivalent circuit diagram of a single carriage and the rail below it according to the present invention.

[0055] Figure 6 This is an equivalent circuit diagram of the two train sections and the rails below them according to the present invention;

[0056] Figure 7 This is the two-port equivalent circuit diagram of the present invention;

[0057] Figure 8 This is the simplified equivalent circuit of the two train cars and the rails below them according to the present invention;

[0058] Figure 9 This is a diagram of the RLC circuit implementation of the model of the present invention;

[0059] in, Figure 9 (a): constant term, Figure 9 (b): Real pole term, Figure 9 (c): Complex conjugate pole term;

[0060] Figure 10 This is a schematic diagram of the RLC equivalent circuit model of the rail train of the present invention;

[0061] Figure 11 This is a simplified RLC equivalent circuit model diagram of the rail train according to the present invention;

[0062] Figure 12 This is a flowchart of an equivalent circuit modeling method for a railcar according to the present invention.

[0063] In the diagram: 1-First port, 2-First port, 3-First port, 4-First port, 5-First carriage, 6-Second carriage, 7-Connector, 8-Grounding resistor, 9-Right rail, 10-Left rail, 11-Fifth port, 12-Sixth port, 13-Seventh port. Detailed Implementation

[0064] 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.

[0065] Based on the above problems, it is necessary to establish an equivalent circuit model of the rail system that covers a high frequency range, using the wheel-rail contact point as the port, to simulate the current flowing from the rail through the wheels to the train, thus providing technical support for protecting the safety of personnel and equipment on board. This invention provides a method for modeling the equivalent circuit of a rail train, referring to... Figure 12Specifically, it includes the following steps:

[0066] S1: Establish the equivalent circuit of the car and connector based on the impedance of the right, left, front and rear sides of the car and connector. Establish the equivalent circuit of the rail below the car and the rail below the connector based on the self impedance, impedance to ground and mutual impedance of the two rails respectively.

[0067] S2: Combine the equivalent circuits of the carriage and connector, as well as the equivalent circuits of the rails below the carriage and the rails below the connector, to obtain the equivalent circuit of the rail train.

[0068] S3: Obtain the impedance frequency response of the carriage, connector, and rail below the carriage respectively. Solve the values ​​of each impedance in the equivalent circuit of the carriage, connector, and rail below the carriage at different frequencies through multiple impedance frequency responses to obtain the frequency response of each impedance in the equivalent circuit of the rail train.

[0069] S4: Fit the frequency response of each impedance in the equivalent circuit of the rail train using the vector matching method, and represent the fitting result using an RLC circuit to obtain an equivalent circuit model of the rail train that satisfies the impedance frequency response within any frequency range.

[0070] The proposed method for modeling the equivalent circuit of a rail train uses the wheel-rail contact point as a terminal to establish a port, thus constructing an equivalent circuit model of the train and rail within an arbitrary frequency range. Taking two carriages as an example, the first carriage 5 and the second carriage 6 are connected by a connector 7. (Refer to...) Figure 1 and Figure 2 .

[0071] The front and rear ports of the car are defined according to the wheel-rail contact points between the car and the rail. The front port includes the two wheel-rail contact points of the front wheelset, and the rear port includes the two wheel-rail contact points of the rear wheelset.

[0072] The impedance frequency response of the front and rear ports of the carriage is taken as the impedance frequency response of the carriage. The impedance frequency response of the rear port of the front carriage and the front port of the rear carriage in two adjacent carriages is taken as the impedance frequency response of the connector. The impedance frequency response of the two rails to the ground and the two rails is taken as the impedance frequency response of the rails under the carriage.

[0073] The impedance frequency response of the first carriage 5, with port 1 and port 2 as its two ports, was measured using a network analyzer. The impedance frequency response of a connector with two ports, 2 and 3. The rail impedance frequency response with the fifth port 11, the sixth port 12, and the seventh port 13 as three ports. Specifically, the two contact points between the two front wheels of the first carriage 5 and the rails constitute the two ends of the first port 1; the two contact points between the two rear wheels of the first carriage 5 and the rails constitute the two ends of the second port 2; the two contact points between the two front wheels of the second carriage 6 and the rails constitute the two ends of the third port 3; and the two contact points between the two rear wheels of the second carriage 6 and the rails constitute the two ends of the fourth port 4. The right rail 9 and the ground constitute the two ends of the fifth port 11; the left rail 10 and the ground constitute the two ends of the sixth port 12; and the right rail 9 and the left rail 10 constitute the two ends of the seventh port.

[0074] use Figure 3 The equivalent circuits shown are used to equip the first carriage 5 and the connector 7 respectively, and the corresponding equivalent circuits are obtained. Figure 3 (a) is the first carriage 5, in which , , and Let be the impedances of the right, left, front, and rear sides of the first carriage 5. The impedance parameters of this equivalent circuit are shown in the first expression (1). Figure 3 (b) is connector 7, and connector 7 has the same equivalent circuit structure as the first carriage 5, therefore , , and Let be the impedances of the right, left, front, and rear sides of connector 7. The impedance parameters of this equivalent circuit are shown in the second expression (2). Let , The equivalent circuit of the first carriage can then be obtained. , , and The frequency response, and the equivalent circuit of connector 7 , , and The frequency response.

[0075] (1);

[0076] (2);

[0077] use Figure 4 The circuit shown is equivalent to the rails below the first carriage 5, wherein, and These are the self-impedances of the right rail 9 and the left rail 10, respectively. and These are the ground impedances of the right rail 9 and the left rail 10, respectively. Let be the mutual impedance between the right rail 9 and the left rail 10. The impedance parameters of this equivalent circuit are shown in the third expression (3), let The frequency response of each impedance in the equivalent circuit of the rail below the first carriage 5 can then be obtained.

[0078] (3);

[0079] In summary, the equivalent circuit of a single train car and the rails beneath it can be obtained as follows: Figure 5 As shown.

[0080] The impedance of the rail below connector 7 meets the following requirements:

[0081] (4);

[0082] in, The length of the rail below connector 7 is the distance between the rear wheel of the first carriage 5 and the front wheel of the second carriage 6. This refers to the length of the rails below the first carriage 5, which is the distance between the front and rear wheels of the first carriage 5. This represents the frequency response of the rail impedance below the connector.

[0083] After connecting two identical carriages via train connector 7, the equivalent circuit of the train and rails is obtained as follows: Figure 6 As shown. Among them, , , and These are the impedances for the right, left, front, and rear sides of a single carriage, respectively. and These are the self-impedances of the right rail 9 and the left rail 10 below each single carriage. and These are the ground impedances of the right rail 9 and the left rail 10, respectively. The mutual impedance between right rail 9 and left rail 10. , , and These are the impedances for the right, left, front, and rear sides of connector 7, respectively. and These are the self-impedances of the right rail 9 and the left rail 10 below connector 7, respectively. and These are the ground impedances of the right rail 9 and the left rail 10 below the train connector 7, respectively. The mutual impedance between the right rail 9 and the left rail 10 below the train connector 7.

[0084] If equations (1), (2), or (3) have no exact solution or the physical structure of the carriage and rails is not considered, then it is only necessary to ensure that the equivalent circuit satisfies the two-port external conditions. Figure 6 The equivalent circuit shown is simplified. The two-port circuit is then simplified. Figure 7The circuit shown is equivalent. Figure 7 The impedance parameters of the two-port equivalent circuit shown are given in the fourth expression (5). Let the left side of the equation in formula (5) be respectively... , or The equivalent circuits of the carriage, connector, and rail can then be obtained separately. Specifically, the impedance frequency response of the rail beneath the first carriage 5, with port 1 and port 2 as its two ports, is measured using a network analyzer. Similarly, according to equation (4), the train and rail can be adopted. Figure 8 The two-port T-type equivalent circuit shown in the figure represents this. , and The impedance of the equivalent circuit of the carriage. , and The impedance of the connector's equivalent circuit. , and Let be the impedance of the equivalent circuit of the rails beneath the carriage. , and This represents the impedance of the equivalent circuit of the rail below the connector.

[0085] (5);

[0086] In the formula, , and These are the impedance parameters in a two-port T-type equivalent circuit. This refers to the impedance frequency response of the carriage, connector, or rail.

[0087] After determining the equivalent circuit representation and calculating the frequency response of each impedance in the equivalent circuit, the first step is to inverse the frequency response of each impedance in the circuit to obtain the admittance frequency response of the impedance. Then, the admittance frequency response is fitted to an approximate functional expression. The rational function approximation used here is Equation (6):

[0088] (6);

[0089] in, f For frequency, For the first n Extreme points, For the first n Residual number, s Represents complex variables in the complex plane. N The number of poles d This is a constant term.

[0090] According to circuit synthesis theory, the constant term can be synthesized as follows: Figure 9 The resistor circuit shown in (a) has the following resistance values:

[0091] (7);

[0092] In the formula, R 1 represents the resistance of the resistive circuit.

[0093] For real pole terms, they can be comprehensively expressed as: Figure 9 The circuit shown in (b) is a series circuit of a resistor and an inductor (RL), where the values ​​of the resistor and the inductor are respectively:

[0094] (8);

[0095] (9);

[0096] In the formula, R 2 represents the resistance of the RL series circuit. L 2 represents the inductance of the RL series circuit.

[0097] For the complex conjugate pole term, it can be comprehensively expressed as: Figure 9 The RLCG series-parallel circuit shown in (c) has the following values: The values ​​of resistance, inductance, capacitance, and conductance are as follows:

[0098] (10);

[0099] (11);

[0100] (12);

[0101] (13);

[0102] In the formula, L 3 represents the inductance of the RLCG series-parallel circuit. R 3 represents the resistance of the RLCG series-parallel circuit. C 3 represents the capacitor in the RLCG series-parallel circuit. G 3 represents the conductance of the RLCG series-parallel circuit. and They are respectively a and c . conjugate.

[0103] In summary, by connecting the circuits represented by the constant terms, real pole terms, and complex conjugate pole terms in the fitted rational function in parallel, we obtain the equivalent circuit of the impedance. Figure 6 or Figure 8The frequency response of each impedance in the equivalent circuit of the track shown is rationally fitted using the method described above, resulting in an equivalent circuit model that can be expressed using an RLC circuit, as shown below. Figure 10 and Figure 11 As shown.

[0104] Based on the same concept, the present invention also provides an equivalent circuit modeling system for railway trains, including a modeling module, a combination module, a solution module, and a transformation module.

[0105] The module is used to establish the equivalent circuit of the carriage and connector based on the impedance of the right, left, front and rear sides of the carriage and connector. The equivalent circuit of the rail below the carriage and the rail below the connector is established based on the self impedance, impedance to ground and mutual impedance of the two rails, respectively.

[0106] The combination module is used to combine the equivalent circuits of the carriage and connector, as well as the equivalent circuits of the rails below the carriage and the rails below the connector, to obtain the equivalent circuit of the rail train.

[0107] The solver module is used to obtain the impedance frequency response of the carriage, connector, and rail under the carriage respectively. By using multiple impedance frequency responses, the values ​​of each impedance in the equivalent circuit of the carriage, connector, and rail under the carriage at different frequencies are solved to obtain the frequency response of each impedance in the equivalent circuit of the railcar.

[0108] The conversion module is used to fit the frequency response of each impedance in the equivalent circuit of the rail train using the vector matching method, and the fitting result is represented using an RLC circuit to obtain the equivalent circuit model of the rail train.

[0109] When a large current is injected into the rail, it may couple to the car body through the rail-wheel contact point, causing an abnormal rise in the car body potential. This threatens the insulation performance of onboard equipment or passenger safety. However, measuring the distribution of such transient currents is both costly and risky, and it is difficult to cover all operating conditions. The method proposed in this invention can accurately analyze the current shunting ratio between the rail and the car body through equivalent circuit modeling and simulation, reveal the impedance coupling mechanism of the critical path, and assess in advance whether the current component of the car body exceeds the safety threshold, thus avoiding equipment damage or electric shock accidents. Through parameter sensitivity analysis, parameters such as rail insulation and car body grounding resistance can be adjusted to suppress current intrusion, thereby guiding the optimization of the grounding system and overvoltage protection design. This method not only improves the reliability and safety of the high-speed rail traction power supply system, but also provides an efficient analysis tool for the car-rail coupling problem in complex electromagnetic environments.

[0110] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0111] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method of modeling an equivalent circuit of a rail vehicle, characterized in that, The method comprises the following steps: establishing an equivalent circuit of the car and the connector based on the impedance of the right side, the left side, the front side and the back side of the car and the connector, and establishing an equivalent circuit of the steel rail under the car and the steel rail under the connector based on the self-impedance, the ground impedance and the mutual impedance of the two steel rails; combining the equivalent circuit of the car and the connector and the equivalent circuit of the steel rail under the car and the steel rail under the connector to obtain an equivalent circuit of the rail train; obtaining the impedance frequency responses of the car, the connector and the steel rail under the car respectively, and solving the values of each impedance in the corresponding equivalent circuit of the car, the connector and the steel rail under the car at different frequencies through the multiple impedance frequency responses to obtain the frequency responses of each impedance in the equivalent circuit of the rail train; fitting the frequency responses of each impedance in the equivalent circuit of the rail train through the vector matching method, and representing the fitting results by using the RLC circuit to obtain the equivalent circuit model of the rail train; the solving of the values of each impedance in the corresponding equivalent circuit of the car, the connector and the steel rail under the car at different frequencies through the multiple impedance frequency responses comprises: solving the values of each impedance in the equivalent circuit of the car at different frequencies according to a first expression, and the first expression is specifically as follows: ； wherein is the impedance frequency response of the vehicle cabin, , , and are the impedances of the right, left, front and back sides of the vehicle cabin, respectively. solving the values of each impedance in the equivalent circuit of the connector at different frequencies according to a second expression, and the second expression is specifically as follows: ； wherein is the impedance frequency response of the connector, , , and are the impedances of the right, left, front and back sides of the vehicle cabin, respectively. solving the values of each impedance in the equivalent circuit of the steel rail under the car at different frequencies through a third expression, and the third expression is specifically as follows: ； wherein is the impedance frequency response of the rail below the car, and are the self-impedances of the right rail and the left rail, respectively, and are the ground impedances of the right rail and the left rail, respectively, is the mutual impedance between the right rail and the left rail. the relationship of the frequency responses of each impedance in the equivalent circuit of the steel rail under the car and the steel rail under the connector is as follows: ； wherein Lc is the length of the rail below the connector, Lc is the length of the rail below the connector, Lc is the length of the rail below the connector, solving the frequency responses of each impedance in the equivalent circuit of the steel rail under the connector through the above relationship.

2. The method of claim 1, wherein, the fitting of the frequency responses of each impedance in the equivalent circuit of the rail train through the vector matching method, and the representation of the fitting results by using the RLC circuit specifically comprises the following steps: inverting the frequency responses of each impedance in the equivalent circuit of the rail train to obtain the corresponding admittance frequency responses; fitting each admittance frequency response to obtain a corresponding fitting expression; converting the fitting expression through the RLC circuit to obtain the RLC circuit representation of each impedance.

3. A method of modeling the equivalent circuit of a railcar as recited in claim 2, wherein, the fitting expression is as follows: ； wherein f is the frequency, is the pole, is the residue, s represents a complex variable in the complex plane, N is the number of poles, n is the variable, d is the constant term.

4. The method of claim 2, wherein the equivalent circuit modeling of the railcar is performed by: the RLC circuit comprises a resistance circuit, an RL series circuit and an RLCG series-parallel circuit, the number of the resistance circuit, the RL series circuit and the RLCG series-parallel circuit in the RLC circuit representation of different impedances is different, and the values of the resistance, the inductance, the capacitance and the conductance are different.

5. The method of claim 1, wherein, the obtaining of the multiple impedance frequency responses of the car, the connector and the steel rail under the car comprises the following steps: defining the front port and the back port of the car according to the wheel-rail contact points of the car and the steel rail, wherein the front port comprises two wheel-rail contact points of the front wheel pair, and the back port comprises two wheel-rail contact points of the rear wheel pair; The impedance frequency response of the front port and the rear port of the car is taken as the impedance frequency response of the car, the impedance frequency response of the front port of the front car and the rear port of the rear car of the two adjacent cars is taken as the impedance frequency response of the connector, and the impedance frequency response of the two rails and the ground and the two rails is taken as the impedance frequency response of the rails under the car.

6. A method of modeling the equivalent circuit of a railcar as recited in claim 1, wherein, Also include: If the first expression, the second expression or the third expression has no exact solution, the equivalent circuit of the rail train is simplified by using a two-port equivalent circuit, and a two-port T equivalent circuit is obtained; The fourth expression is used to solve the impedance of the two-port T equivalent circuit, and the fourth expression is specifically as follows: ； wherein Z is the impedance frequency response of the car, the coupler or the rail, , and are the impedance parameters in the two-port T equivalent circuit, respectively.

7. A modeling system for a railcar equivalent circuit modeling method according to any one of claims 1-6, characterized by, Include: The establishment module is configured to establish the equivalent circuit of the car and the connector based on the impedance of the right side, the left side, the front side and the rear side of the car and the connector, and establish the equivalent circuit of the rails under the car and the rails under the connector based on the self-impedance, the ground impedance and the mutual impedance of the two rails; The combination module is configured to combine the equivalent circuit of the car and the connector and the equivalent circuit of the rails under the car and the rails under the connector to obtain the equivalent circuit of the rail train; The solving module is configured to obtain the impedance frequency response of the car, the connector and the rails under the car, respectively, and solve the value of each impedance in the corresponding equivalent circuit of the car, the connector and the rails under the car at different frequencies through the multiple impedance frequency responses to obtain the frequency response of each impedance in the equivalent circuit of the rail train; The conversion module is configured to fit the frequency response of each impedance in the equivalent circuit of the rail train by using the vector matching method, and represent the fitting result by using the RLC circuit to obtain the equivalent circuit model of the rail train.

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