A method for suppressing high voltage side of operation overvoltage of motor train unit

Abstract

This invention provides a method for suppressing high-voltage side overvoltage during operation in high-speed trains, belonging to the field of overvoltage suppression technology for high-speed trains. Starting from the propagation path of operational overvoltage, this invention studies a universal means to suppress operational overvoltage and designs and manufactures a suppression device based on an inductor through theoretical calculations. Impedance analysis of this device is also performed. This invention solves the problem that most current research on operational overvoltage suppression methods focuses on suppressing overvoltage in the low-voltage section under the train, but due to differences in the protective grounding methods of different train bodies, it is difficult to form a systematic and universal suppression method for operational overvoltage.

Description

Technical Field

[0001] This invention belongs to the field of overvoltage suppression technology for high-speed trains, and particularly relates to a method for suppressing high-voltage side overvoltage during high-speed train operation. Background Technology

[0002] my country's main railway transport capacity—high-speed trains—coexist with high-voltage, low-voltage, and various other electrical equipment. Most of these electrical systems treat the train car body as a common ground, leading to numerous electromagnetic compatibility (EMC) issues. Overvoltage, due to its propagation path, can cause instability in the common ground potential of the train body, resulting in serious interference problems for the equipment.

[0003] Numerous studies have been conducted on suppressing overvoltage. Japanese scholar Hatsukade S pointed out that AC vehicles can effectively suppress surge overvoltage by grounding with a low-impedance SiC grounding resistor. Yang Shuai et al. proposed that reducing the grounding resistor of the EMU can suppress surge overvoltage to a certain extent, and that a resistance value of 0.5 ohms is more reasonable for the EMU's grounding resistor. Maxime from the Faculty of Engineering at the University of Montreal, Canada... Berger constructed a surge simulation model for DC high-speed trains and analyzed the impact of surge overvoltage on the train's electronic devices based on the model. The team led by Gao Guoqiang at Southwest Jiaotong University studied the overvoltage characteristics of the car body where high-voltage cables are located and analyzed in depth the influence of factors such as the contact network voltage phase, traction transformer magnetizing inductance, and high-voltage cable distributed capacitance on the overvoltage characteristics during VCB disconnection. Shi Dan mainly studied the overvoltage characteristics of the high-voltage system during circuit breaker operation and proposed corresponding suppression schemes. Liang Jianying proposed measures to suppress car body overvoltage: setting protective grounding and surge devices that can discharge surge voltage on the lead car body. Zheng Yue analyzed the impact of the grounding system on car body overvoltage and concluded that increasing the grounding point can suppress car body overvoltage to a certain extent, and the suppression effect is most obvious in the car where the surge arrester is located. Shen Hanlin et al. analyzed the impact of parallel capacitance of the grounding resistor on overvoltage and concluded that as the capacitance value of the parallel capacitor increases, the peak overvoltage of the car body appears later, effectively suppressing the impact of overvoltage on the EMU.

[0004] It's easy to see that current research on overvoltage suppression methods mostly focuses on suppressing overvoltage in the low-voltage section under the vehicle. This includes modifying the protective grounding path and method to suppress overvoltage, and optimizing the distribution and impedance of protective grounding under the vehicle. However, these methods largely only optimize the overvoltage peak at the axle end, providing effective overvoltage suppression for devices with grounding points at the axle end, such as speed sensors. They fail to effectively suppress lateral overvoltages that affect numerous other onboard devices. This is because suppression methods in the low-voltage section under the vehicle do not address the overvoltage propagation path to the vehicle body, thus failing to suppress overvoltage propagation at its source. Furthermore, due to the large number of protective grounding points on the vehicle body and the differences in their methods, it's difficult to develop a systematic and universal suppression method for operational overvoltages. Summary of the Invention

[0005] To address the aforementioned shortcomings in the existing technology, this invention provides a method for suppressing high-voltage side overvoltage during operation of a high-speed train. This method solves the problem that most current research on overvoltage suppression methods focuses on suppressing overvoltage in the low-voltage section under the train. However, due to differences in the protective grounding methods of different train bodies, it is difficult to form a systematic and universal suppression method for overvoltage.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This solution provides a method for suppressing overvoltage on the high-voltage side of a high-speed train, including the following steps:

[0008] S1, Close the circuit breaker;

[0009] S2. Overvoltage is generated in the core wire of the high-voltage cable;

[0010] S3. The generated overvoltage is coupled to the shielding layer through the distributed capacitance of the high-voltage cable core;

[0011] S4. Transmit the overvoltage signal on the shielding layer to the vehicle body through the grounding wire between the shielding layer and the vehicle body.

[0012] S5. A suppression device is connected in series with the grounding wire, and the suppression device is used to share the overvoltage signal to complete the suppression of the high voltage side of the EMU operation overvoltage. The suppression device is connected in series with the car body, and the impedance of the suppression device is greater than the impedance of the car body.

[0013] The beneficial effects of this invention are as follows: This invention addresses overvoltage during operation in high-speed trains by starting from the high-voltage side and following the propagation path. An inductive suppression device is connected in series between the high-voltage cable shielding layer and the car body grounding wire, changing the grounding method from direct grounding to inductive grounding. This invention effectively suppresses lateral and axle-end overvoltages in the car body. The invention uses a spiral coil wound with a magnetic core as the main body of the suppression device. The coil is wound according to theoretically calculated parameters, and the magnetic core material is selected. Impedance analysis shows that the results match the theoretical calculations. This invention solves the problem that current research on overvoltage suppression methods mostly focuses on suppressing overvoltage in the low-voltage section under the car body. However, due to differences in the protective grounding methods of different car bodies, it is difficult to develop a systematic and universal suppression method for overvoltage during operation.

[0014] Furthermore, the design method of the suppression device is as follows:

[0015] A1. Collect vehicle body overvoltage data;

[0016] A2. Establish a simulation model and optimize the simulation model using the collected overvoltage data;

[0017] A3. Using the optimized simulation model, the parameters of the vehicle body, the grounding system impedance, and the distributed parameters of the contact wire to the vehicle body are obtained respectively.

[0018] A4. Based on the results obtained in step A3, set the inductance of the suppression device;

[0019] A5. Based on the inductance suppression device already in place, the suppression device, which is mainly composed of an inductor, is installed between the high-voltage cable shielding layer and the vehicle grounding wire.

[0020] A6. Utilize the installed suppression device to reduce the overvoltage of the vehicle body through voltage division;

[0021] A7. Simulate the installation of suppression devices on the vehicle body overvoltage;

[0022] A8. Compare the simulation results with the original vehicle body simulation data to confirm the effectiveness of the suppression device and select the inductance range of the suppression device.

[0023] A9. Based on the inductance range, design the actual suppression device and complete the design of the suppression device.

[0024] The beneficial effect of the above-described further solutions is that the present invention, through the above design, confirms the effectiveness of the suppression device.

[0025] Furthermore, the expression for the impedance of the suppression device is as follows:

[0026] Z L ≥Z C +Z G

[0027] Among them, Z L Z represents the impedance of the suppression device. C Z represents the vehicle body impedance. G This indicates the impedance of the grounding system.

[0028] The beneficial effect of the above-mentioned further scheme is that the impedance of the suppression device is an important parameter when dividing the voltage. In order to significantly reduce the overvoltage component on the vehicle body, the impedance of the suppression device should be greater than or equal to the impedance of the vehicle body and the grounding system.

[0029] Furthermore, step A4 includes the following steps:

[0030] A401. Based on the results obtained in step A3, calculate the distributed capacitance between the overhead contact line and the vehicle body;

[0031] A402. Based on the distributed capacitance and the impedance of the suppression device, the inductance of the suppression device is obtained.

[0032] Furthermore, the expression for the distributed capacitance is as follows:

[0033]

[0034]

[0035] Where C represents the capacitance of the capacitor with a spacing of dz, ∫ represents the integral from 0 to h over dz, ε represents the dielectric constant of air, S represents the planar area between the two plates of the distributed capacitance, dz represents the infinitesimal distance between the contact wire and the vehicle body, r represents the radius of the contact wire, h represents the distance from the contact wire to the roof of the vehicle, b represents the width of the vehicle body, a represents the length of the vehicle body, and l represents the length of the contact wire.

[0036] Furthermore, the main body of the suppression device is configured as a spiral coil wound around a magnetic core, wherein the inductance expression of the spiral coil is as follows:

[0037]

[0038] Where L0 represents the inductance of the spiral coil, μ0 represents the free permeability, and μ r The magnetic core has a relative permeability, N has the number of turns of the spiral coil, h has the core height, r1 has the outer radius of the core, and r2 has the inner radius of the core. Attached Figure Description

[0039] Figure 1 This is a circuit diagram and schematic diagram of the overvoltage propagation path in this embodiment.

[0040] Figure 2 This is a flowchart of the method of the present invention.

[0041] Figure 3 This is a schematic diagram illustrating the working principle of the suppression device in this embodiment.

[0042] Figure 4 This is a schematic diagram of the equivalent impedance of the vehicle body in this embodiment.

[0043] Figure 5 This is a schematic diagram of the equivalent impedance of the grounding system in this embodiment.

[0044] Figure 6 This is a schematic diagram of the equivalent impedance of the entire vehicle in this embodiment.

[0045] Figure 7 This is a schematic diagram of the overvoltage coupling path in this embodiment.

[0046] Figure 8 This is a schematic diagram of the integration region in this embodiment.

[0047] Figure 9 This is a schematic diagram of the overvoltage simulation circuit in this embodiment.

[0048] Figure 10 This is the equivalent circuit diagram of the inductor in this embodiment.

[0049] Figure 11 This is a schematic diagram of the main body model of the suppression device in this embodiment.

[0050] Figure 12 This is a schematic diagram of the inductance of the suppression device under different relative permeabilities of magnetic cores in this embodiment.

[0051] Figure 13 This is a schematic diagram showing the change in relative magnetic permeability of the iron powder core material with frequency in this embodiment.

[0052] Figure 14 This is a schematic diagram of the physical body of the suppression device in this embodiment.

[0053] Figure 15 This is a schematic diagram of a ground test to verify the parameters of the suppression device in this embodiment.

[0054] Figure 16 This is a schematic diagram of the impedance curve of the suppression device in this embodiment. Detailed Implementation

[0055] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0056] Example

[0057] This invention analyzes the generation mechanism of switching overvoltage and, starting from the propagation path of overvoltage, develops a universal switching overvoltage suppression method. During high-speed train operation, the main circuit breaker is frequently operated before and after phase breaks, and during the activation of the pantograph. When the circuit breaker operates, the state of the traction side circuit of the train changes drastically, generating overvoltages (switching overvoltages) in the high-voltage system, car body, and grounding system. When the circuit breaker is closed, the traction main transformer is also in an unloaded state, but at this time, the energy stored in the inductors and capacitors in the on-board high-voltage system is zero. When the circuit breaker is closed, the high-voltage system undergoes a zero-state response under the action of an external excitation source, resulting in a high-frequency oscillation process in the circuit, generating switching overvoltage. The magnitude of the switching overvoltage when the circuit breaker is closed is related to the phase angle at closing and the inductive and capacitive components in the circuit. The process of disconnecting the circuit breaker is similar to a common operation in power systems of disconnecting an unloaded transformer. Disconnecting an unloaded transformer involves interrupting a small current from an inductive load. This current is extremely small, allowing the circuit breaker's arc-extinguishing capability to reach its maximum, thus cutting off the no-load current before it crosses zero—a phenomenon known as current-cutting. This can generate a high overvoltage. The peak value of the disconnecting overvoltage is related to the current-cutting phase angle, the circuit resonant frequency, and the damping coefficient. Both types of operational overvoltages are negatively correlated with the equivalent distributed capacitance of the transformer and the high-voltage cable core to ground. Since the shielding layer of the high-voltage cable on the roof is connected to the vehicle body, the operational overvoltage can couple to the shielding layer through the distributed capacitance between the high-voltage cable core and the shielding layer, and then propagate to the vehicle body through the connection path between the shielding layer and the vehicle body. This process can be equivalent to the core passing through the distributed capacitance C between the core and the shielding layer. d A path is formed to discharge to the vehicle body. The shielding layer of the high-voltage cable is not continuous; each segment of the shielding layer is directly connected to a single point on the vehicle body. Therefore, the coupling path can be considered as multiple parallel circuit segments, such as... Figure 1 As shown.

[0058] like Figure 2 As shown, the present invention provides a method for suppressing high-voltage side overvoltage during operation of a high-speed train, the implementation method of which is as follows:

[0059] S1, Close the circuit breaker;

[0060] S2. Overvoltage is generated in the core wire of the high-voltage cable;

[0061] S3. The generated overvoltage is coupled to the shielding layer through the distributed capacitance of the high-voltage cable core;

[0062] S4. Transmit the overvoltage signal on the shielding layer to the vehicle body through the grounding wire between the shielding layer and the vehicle body.

[0063] S5. A suppression device is connected in series with the grounding wire, and the suppression device is used to share the overvoltage signal to complete the suppression of the high-voltage side of the EMU operation overvoltage. The suppression device is connected in series with the car body, and the impedance of the suppression device is greater than the impedance of the car body. The expression for the impedance of the suppression device is as follows:

[0064] Z L ≥Z C +Z G

[0065] Among them, Z L Z represents the impedance of the suppression device. C Z represents the vehicle body impedance. G This indicates the impedance of the grounding system.

[0066] In this embodiment, the design method of the suppression device is as follows:

[0067] A1. Collect vehicle body overvoltage data;

[0068] A2. Establish a simulation model and optimize the simulation model using the collected overvoltage data;

[0069] A3. Using the optimized simulation model, the parameters of the vehicle body, the grounding system impedance, and the distributed parameters of the contact wire to the vehicle body are obtained respectively.

[0070] A4. Based on the results obtained in step A3, set the inductance of the suppression device. The implementation method is as follows:

[0071] A401. Calculate the distributed capacitance between the overhead contact line and the vehicle body:

[0072]

[0073]

[0074] Where C represents the capacitance of the capacitor with a spacing of dz, ∫ represents the integral from 0 to h over dz, ε represents the dielectric constant of air, S represents the planar area between the two plates of the distributed capacitance, dz represents the infinitesimal distance between the contact wire and the vehicle body, r represents the radius of the contact wire, h represents the distance from the contact wire to the roof of the vehicle, b represents the width of the vehicle body, a represents the length of the vehicle body, and l represents the length of the contact wire.

[0075] A402. Based on the distributed capacitance and the impedance of the suppression device, the inductance of the suppression device is obtained;

[0076] A5. Based on the inductance suppression device already in place, the suppression device, which is mainly composed of an inductor, is installed between the high-voltage cable shielding layer and the vehicle grounding wire.

[0077] A6. Utilize the installed suppression device to reduce the overvoltage of the vehicle body through voltage division;

[0078] A7. Simulate the installation of suppression devices on the vehicle body overvoltage;

[0079] A8. Compare the simulation results with the original vehicle body simulation data to confirm the effectiveness of the suppression device and select the inductance range of the suppression device.

[0080] A9. Based on the inductance range, design a physical suppression device, completing the design of the suppression device. The main body of the suppression device is a helical coil wound around a magnetic core, wherein the inductance expression of the helical coil is as follows:

[0081]

[0082] Where L0 represents the inductance of the spiral coil, μ0 represents the free permeability, and μ r The magnetic core has a relative permeability, N has the number of turns of the spiral coil, h has the core height, r1 has the outer radius of the core, and r2 has the inner radius of the core.

[0083] The present invention will now be further described.

[0084] In this embodiment, the method for suppressing the effects of overvoltage addresses the three key elements of electromagnetic compatibility: reducing the interference source, suppressing the propagation path, and improving the immunity of sensitive equipment. However, considering the versatility of the suppression method and the distribution of high-voltage cables in high-speed trains, suppressing the propagation path is more easily applied in practical engineering. As described above, overvoltage couples to the shielding layer through the distributed capacitance between the high-voltage cable core and its shielding layer, and then propagates to the car body. Since the shielding layers of the high-voltage cables in different high-speed trains are all connected to the car body, developing a suppression method based on this path would be universally applicable.

[0085] In this embodiment, the operating overvoltage frequency is generally distributed between several hundred kHz and 2 MHz. Therefore, an inductor-based suppression device is considered to suppress the propagation of the overvoltage. Figure 3 As shown, its working principle can be equivalent to a series voltage divider, which reduces the overvoltage of the vehicle body and grounding system.

[0086] In this embodiment, the impedance of the suppression device is an important parameter during voltage division. To significantly reduce the overvoltage component on the vehicle body, the impedance of the suppression device should be greater than or equal to the impedance of the vehicle body and the grounding system, i.e., Z. L ≥Z C +Z G Z L To suppress device impedance, Z C Z is the vehicle body impedance. G This represents the impedance of the grounding system.

[0087] In this embodiment, the vehicle body impedance is divided into two parts, longitudinal and transverse, which can construct a quadrilateral network of vehicle body impedance, such as... Figure 4 As shown, the transverse direction of the car body refers to the direction along the end walls on both sides of the train, and the longitudinal direction of the car body refers to the direction from the top of the train to the underframe.

[0088] In this embodiment, the equivalent impedance of the grounding system is established based on the distribution location of the grounding axle ends of the standard EMU, such as... Figure 5 .

[0089] In this embodiment, taking the impedance of various parts of a standard EMU as an example, the equivalent impedance of the entire vehicle is constructed, such as... Figure 6 As shown, and with the overvoltage frequency recorded as 0.5-1.5MHz, a frequency sweep of the overvoltage band is performed on the vehicle impedance to obtain Z. C +Z G ≈47~143Ω, substituting the corresponding frequency, we can get L≥15μH.

[0090] In this embodiment, as Figure 7 As shown, Cn is the distributed capacitance of each core wire and shielding layer, Rn and Ln are the equivalent impedances of the vehicle body and grounding system, and there is also a distributed capacitance CT between the contact wire and the vehicle body. When the inductance of the introduced suppression device is large enough, the operating overvoltage will be forced to be discharged through the distributed capacitance between the contact wire and the vehicle body, which may break down the roof.

[0091] In this embodiment, the approximate algorithm for irregular capacitors from "Overvoltage Measurement in Power Systems" is used. The contact wire is considered as an infinitely long straight conductor, and the end effects and sag of the contact wire are ignored. The distributed capacitance between the contact wire and the vehicle body is calculated. Since the radius of the contact wire is r, it can be considered as a thin strip with a width of 2r and a length of l. The length of the vehicle body is taken as a and the width as b. Between the two plates, a plane parallel to the plates is taken, with a distance dz between the plane and the plates and an area of ​​S. According to the formula for calculating the capacitance of a single small parallel plate capacitor with a spacing of dz, the capacitance is:

[0092] dC=εS / dz

[0093] The distributed capacitance between the overhead contact line and the vehicle body can be considered as multiple small parallel-plate capacitors connected in series:

[0094]

[0095] Where z varies from 0 to h, and the integration region is as follows: Figure 8 As shown, this is the region within the line connecting the thin strip to the corresponding vertex of the vehicle body:

[0096]

[0097] In this embodiment, by substituting the aforementioned characteristic parameters of a standard high-speed train, the distributed capacitance C can be obtained. S ≈81pF, and Z L +Z C +Z G < <Z Cs Therefore, we take Z. L ≤Z Cs / 10, that is, L≤125μH, therefore 15μH≤L≤125μH.

[0098] In this embodiment, the inductance of the suppression device is set sequentially to 20μH, 50μH, and 100μH, and placed between the shielding layer of the high-voltage cable of vehicle 3-6 and the grounding wire of the vehicle body. Overvoltage simulation is then performed on the entire system. The simulation circuit is as follows: Figure 9 As shown, the simulation results of overvoltage at each car body and axle end are shown in Table 1 and Table 2. Table 1 shows the simulation results of overvoltage at the car body of cars 1-4 under different inductance values ​​of the suppression devices, and Table 2 shows the simulation results of overvoltage at the axle ends of cars 1-4 under different inductance values ​​of the suppression devices (a typical axle end is taken for each car).

[0099] Table 1

[0100] 0μH 20μH 50μH 100μH 1 car 3.01kV 2.71kV 2.08kV 1.51kV 2 cars 4.86kV 3.57kV 2.74kV 1.98kV 3 cars 3.95kV 2.88kV 2.19kV 1.58kV 4 cars 3.01kV 1.28kV 1.18kV 0.37kV

[0101] Table 2

[0102] 0μH 20μH 50μH 100μH 1 car, 1 axle 1.54kV 1.13kV 0.87kV 0.63kV 2 cars, 4 axles 0.85kV 0.65kV 0.51kV 0.37kV 3 cars and 1 axle 0.92kV 0.53kV 0.32kV 0.20kV 3 cars, 2 axles 2.46kV 1.82kV 1.41kV 1.03kV 4 cars and 1 axle 1.73kV 1.11kV 0.80kV 0.57kV

[0103] In this embodiment, simulation data shows that the suppression device has a suppressive effect on both vehicle body overvoltage and axle end overvoltage.

[0104] In this embodiment, the next step is to design the vehicle body overvoltage suppression device.

[0105] In this embodiment, based on the calculated inductance of the suppression device, the inductance is set to 50-100 μH. In practical applications, inductors are typically made by winding wires around a circular conductor cylinder, resulting in a loss resistance R. L and distributed capacitance C L Its equivalent circuit diagram is as follows: Figure 10 As shown.

[0106] In this embodiment, because the distributed capacitance C L The existence of this factor indicates that the suppression device has a self-resonant frequency. To ensure the suppression device operates normally within the overvoltage frequency range, its self-resonant frequency f >> the overvoltage frequency F. For ease of calculation, the maximum overvoltage frequency F is set to 2MHz. From the equivalent circuit, the distributed capacitance C can be calculated. L <<127pF.

[0107] In this embodiment, the main body of the suppression device is set as a spiral coil wound magnetic core inductor, according to the spiral coil inductance calculation formula:

[0108]

[0109] Where r1 is the outer radius of the magnetic core, r2 is the inner radius of the magnetic core, h is the height of the magnetic core, μ0 is the permeability of free space, and μ r Where is the relative permeability of the magnetic core, and N is the number of turns in the coil.

[0110] In this embodiment, r1 is set to 40mm, r2 to 25mm, h to 50mm, and N to 20 turns. Given that μ0 = 4π × 10 -7 H / m gives 26.6 < μ r <53.2.

[0111] In this embodiment, simulation shows that at the overvoltage moment, the peak current through the 100μH coil is approximately 97A and the peak voltage is approximately 18.54kV, while the peak current through the 50μH coil is approximately 94A and the peak voltage is approximately 13.25kV. Based on the toroidal flux formula:

[0112]

[0113] Where I0 is the current through the coil.

[0114] In this embodiment, at the moment of overvoltage, the maximum magnetic induction intensity through the magnetic core is 0.31T-0.63T.

[0115] The main design of the suppression device is as follows Figure 11 As shown, its main parameters are shown in Table 3.

[0116] Table 3

[0117]

[0118] In this embodiment, modeling is performed in simulation software, and the relative permeability of the magnetic core is set to 30 and 50 to obtain the inductance corresponding to the relative permeability, such as... Figure 12 As shown.

[0119] In this embodiment, after selecting the core material based on the relative permeability and maximum magnetic flux, it was decided to use iron powder core material with a saturation magnetic induction intensity of 1.4T as the core material, and the winding is required to withstand a transient overvoltage of 20kV.

[0120] In this embodiment, the parameters of the suppression device were verified by the following experiments.

[0121] In this embodiment, iron powder core is used as the magnetic core material. The effective relative permeability of the iron powder core decreases with increasing frequency. Figure 13 As shown.

[0122] In this embodiment, the relative permeability decreases from 57 to 35 in the overvoltage distribution frequency band. The actual suppression device is shown below. Figure 14 As shown, its main parameters are shown in Table 4, which is a table of main parameters of the actual suppression device.

[0123] Table 4

[0124]

[0125] In this embodiment, an impedance analyzer TH2851-030 was used to perform a parameter scan of the suppression device from 100kHz to 10MHz, with a voltage of 500mV. The on-site setup is as follows. Figure 15 As shown, the impedance curve is as follows Figure 16 As shown.

[0126] In this embodiment, the impedance curve shows that the actual inductance of the suppression device decreases from 112μH to 67μH within the 100kHz-2MHz range, consistent with the theoretical prediction. The resonant point is at 6.8MHz, according to the resonance formula... The distributed capacitance C can be obtained. L =9.4pF, and all the above characteristic parameters meet the theoretical design.

[0127] This invention addresses the issue of overvoltage propagation from the high-voltage side of high-speed trains by connecting a suppression device, primarily composed of inductors, in series between the high-voltage cable shielding layer and the train's grounding wire. This changes the grounding method from direct grounding to inductive grounding, effectively suppressing lateral and axle-end overvoltages. The invention uses a helical coil wound around a magnetic core as the main body of the suppression device. The coil is wound according to theoretically calculated parameters, and the core material is selected. Impedance analysis reveals that the results match the theoretical calculations.

Claims

1. A method for suppressing high voltage side of EMU operation overvoltage, characterized in that, The method comprises the following steps: S1, closing the circuit breaker; S2, generating overvoltage in the high-voltage cable core; S3, coupling the generated overvoltage to the shielding layer through the distributed capacitance between the high-voltage cable core and the shielding layer; S4, transmitting the overvoltage signal on the shielding layer to the vehicle body through the grounding wire between the shielding layer and the vehicle body; S5, connecting the suppression device in series on the grounding wire, and sharing the overvoltage signal by using the suppression device to complete the suppression of the high-voltage side of the EMU operation overvoltage, wherein the suppression device is in series with the vehicle body, and the impedance of the suppression device is greater than the impedance of the vehicle body; The design method of the suppression device is as follows: A1, collecting vehicle body overvoltage data; A2, establishing a simulation model and optimizing the simulation model by using the collected overvoltage data; A3, using the optimized simulation model to obtain the parameters of the vehicle body, the impedance of the grounding system and the distribution parameters of the overhead contact system to the vehicle body, respectively; A4, setting the inductance of the suppression device according to the results obtained in step A3; The step A4 comprises the following steps: A401, calculating the distributed capacitance between the overhead contact system and the vehicle body according to the results obtained in step A3; The expression of the distributed capacitance is as follows: wherein, represents the capacitance of a capacitor with a distance of dz represents the integration of 0 to dz represents the dielectric constant of air, represents the planar area between the two plates of a distributed capacitance, represents the infinitesimal distance between the catenary and the car body, represents the radius of the catenary, represents the distance between the catenary and the roof of the car, represents the width of the car body, represents the length of the car body, represents the length of the catenary;​​​ A402, obtaining the inductance of the suppression device according to the distributed capacitance and the impedance of the suppression device; A5, installing the suppression device mainly composed of an inductor between the high-voltage cable shielding layer and the vehicle body grounding wire based on the suppression device with the set inductance; A6, reducing the overvoltage of the vehicle body in the form of voltage division by using the installed suppression device; A7, simulating the overvoltage of the vehicle body with the installed suppression device; A8, comparing the simulation results with the original vehicle body simulation data to confirm the effectiveness of the suppression device and select the inductance range of the suppression device; A9, designing the suppression device based on the inductance range to complete the design of the suppression device; The expression of the impedance of the suppression device is as follows: Z L ≥Z C +Z G wherein Z L represents the impedance of the suppression device, Z C represents the impedance of the vehicle body, Z G represents the impedance of the grounding system.

2. The method of claim 1, wherein the method is a method of suppressing a high voltage side of an EMU operating overvoltage, characterized by, The main body of the suppression device is a spiral coil wound magnetic core spiral ring inductor, wherein the inductance expression of the spiral coil is as follows: wherein, represents the inductance of the spiral coil, represents the vacuum permeability, represents the relative permeability of the magnetic core, represents the number of turns of the spiral coil, represents the height of the magnetic core, represents the outer radius of the magnetic core, represents the inner radius of the magnetic core.

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