Method and system for calculating traction network impedance of three-phase alternating-current traction power supply system

Abstract

The invention discloses a traction network impedance calculation method and system for a three-phase alternating-current traction power supply system, and the method comprises the steps: selecting a left contact rail, a right contact rail and a walking rail as three-phase conductors according to the requirements of a vehicle power receiving system, and determining the materials and electrical parameters of each conductor; determining the installation position of the three-phase conductor according to the power receiving requirement of a vehicle; the contact rail and the steel rail are equivalent to cylindrical conductors, and geometric parameters of the equivalent cylindrical conductors are determined; constructing an overhead line model of an equivalent cylindrical conductor, and respectively calculating conductor self-impedance and mutual impedance between conductors according to an electromagnetic theory and a Carcon ground loop impedance model; respectively calculating the voltage drop of the contact rail and the voltage drop of the running rail according to the calculated impedance values of the self-impedance of the conductors and the mutual impedance between the conductors; through a standardized impedance calculation process, standardized design and evaluation of the traction power supply system are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of urban rail transit traction power supply, and particularly to a method and system for calculating the impedance of a traction network in a three-phase AC traction power supply system. Background Art

[0002] At present, the power supply systems of rail transit traction networks mainly include DC 1500V, 750V DC power supply, and single-phase AC 25kV, 15kV power supply. Among them, the DC power supply system generally uses catenary (contact rail) for power supply, and the running rail or special rail for return; the AC power supply system usually uses catenary for power supply, and the running rail and return line for return. Whether it is the DC power supply system or the AC power supply system, its traction network can be regarded as a two-wire system.

[0003] However, there are many problems in the existing power supply systems. The DC 1500V and 750V power supply systems will generate stray currents, which will cause long-term electrochemical corrosion and damage to underground metal pipelines and steel structures, seriously threatening the life and safety of urban underground facilities, and its long-term losses are immeasurable. In addition, the braking regenerative energy of vehicles cannot be directly utilized in the DC power supply system, and additional inverter equipment needs to be added, which undoubtedly increases the investment cost.

[0004] The single-phase AC 25kV power supply system will generate negative sequence currents, which will have a greater impact on the power system and pose higher requirements for its power supply capacity. In order to reduce the unbalanced impact on the power system, it is usually necessary to set up electrical neutral sections at the outlet of the traction substation and between adjacent traction substations. However, the existence of electrical neutral sections will affect the safe operation and efficiency of trains. At the same time, the single-phase AC 15kV and 25kV catenaries require a large safety distance. Compared with low-voltage power supply, this will increase the cross-section of the rail transit tunnel section, and thus increase the civil engineering investment.

[0005] To solve the above problems, an AC 3kV three-phase traction power supply system has emerged. This system not only avoids the problem of stray current corrosion in the DC system, but also solves the negative sequence problem caused by three-phase imbalance. Moreover, the electrical safety distance required for the AC 3kV voltage level is equivalent to that of the DC system, which is 225mm smaller than that of the single-phase AC 25kV traction power supply system, thus reducing the requirement for the tunnel clearance and directly reducing the civil engineering investment.

[0006] Among the measurement indicators of power supply capacity, voltage deviation is an important reference factor, and voltage deviation is significantly affected by the impedance of the traction network. For DC 750V and 1500V traction power supply systems and single-phase AC 25kV traction power supply systems, since they adopt a double-wire system, the currents in the catenary and the running rail (return rail) are equal in magnitude and opposite in direction, so the calculation methods for their impedance and voltage drop have been relatively mature. Accurate impedance calculation helps to predict and reduce power losses in the system, extend the equipment life, and reduce maintenance costs caused by equipment failures. However, for three-phase traction power supply systems, the magnitudes of their three-phase currents are equal and the phase angle difference is 120°, which makes the calculation methods for their impedance and voltage drop yet to be further improved. Summary of the Invention

[0007] The present invention aims to provide a calculation method and system for the impedance of the traction network of a three-phase AC traction power supply system. By equivalenting the contact rail and the steel rail to cylindrical conductors and constructing an overhead line model based on the Carson ground loop impedance model accordingly, accurate calculation of the self-impedance and mutual impedance of the conductors is achieved. This method comprehensively considers the conductivity of the earth and the electromagnetic interaction between conductors, thus significantly improving the accuracy of the calculation results. In addition, the present invention particularly considers the influence of the earth conductivity on impedance calculation, effectively reducing the electromagnetic interference caused by electromagnetic coupling between conductors. This enables our system to adapt to diverse geological environments, enhancing electromagnetic compatibility and system adaptability. By accurately predicting, calculating, and controlling the voltage drop, this method can evaluate the voltage stability, power loss, and overall efficiency of the traction power supply system, providing a solid theoretical basis for the optimal design of the system. By optimizing the design of the traction power supply system, the safety of the system can be improved, and the risks of faults and accidents can be reduced. By establishing an accurate circuit model and impedance calculation formula, accurate evaluation of the traction network impedance is achieved; and through a standardized impedance calculation process, the standardized design and evaluation work of the traction power supply system are promoted. The present invention provides an innovative impedance calculation method for the AC 3kV three-phase traction power supply system, which not only improves the calculation accuracy and system adaptability, but also provides important support for the safety, economy, and standardized design of the system.

[0008] In view of the above defects or improvement requirements of the prior art, according to the first aspect of the present invention, the present invention provides a calculation method for the impedance of the traction network of a three-phase AC traction power supply system, where the power supply voltage level of the three-phase traction power supply system is AC 3kV, including:

[0009] S1: According to the requirements of the vehicle power receiving system, select the left contact rail, the right contact rail, and the running rail as the three-phase conductors, and determine the materials and electrical parameters of each conductor; the electrical parameters include cross-sectional area, perimeter, and resistance per unit length;

[0010] S2: Determine the installation positions of the three-phase conductors according to the power receiving requirements of the vehicle, ensuring that the horizontal and vertical distances between each contact rail and the rail meet the design requirements;

[0011] S3: Equivalent the contact rail and the rail as cylindrical conductors respectively, and determine the geometric parameters of the equivalent cylindrical conductors; construct an overhead line model of the equivalent cylindrical conductors, and calculate the self-impedance of the conductors and the mutual impedance between the conductors according to the electromagnetic theory and the Carcon ground loop impedance model respectively;

[0012] S4: Calculate the voltage drops of the contact rail and the running rail respectively according to the impedance values of the self-impedance of the conductors and the mutual impedance between the conductors obtained by calculation.

[0013] Furthermore, the geometric parameters of the equivalent cylindrical conductors determined in step S3 include:

[0014] Select the equivalent principle according to the cross-sectional characteristics of the contact rail and the rail; determine the radius of the equivalent cylinder using the area equivalence or perimeter equality principle;

[0015] Set the length of the equivalent cylindrical conductors according to the actual laying lengths of the contact rail and the rail.

[0016] Furthermore, the construction of the overhead line model of the equivalent cylindrical conductors in step S3 includes:

[0017] Equivalent the contact rail and the rail as overhead cylindrical conductors;

[0018] Regard the equivalent cylindrical conductors as an overhead line model, ignoring their actual laying positions, and only considering the relative positions and spacings between the conductors;

[0019] Determine the horizontal and vertical distances between the contact rail and the rail, and the spacing between the rails according to the actual laying situation.

[0020] Furthermore, the calculation of the self-impedance of the conductors and the mutual impedance between the conductors according to the electromagnetic theory and the Carcon ground loop impedance model respectively in step S3 includes:

[0021] S31: Calculate the effective resistance per unit length of the rail according to the magnetic saturation coefficient of the steel conductor, the resistivity of the steel conductor, and the cross-sectional area of the steel conductor;

[0022] S32: Calculate the self-impedance of a single running rail, the mutual impedance between two rails, and the equivalent self-impedance of the running rail respectively according to the effective resistance per unit length of the rail, the depth of the equivalent ground loop conductor, the equivalent radius of the rail, and the spacing between two rails;

[0023] S33: Calculate the self-impedance of the contact rail, the mutual impedance between the contact rails, and the mutual impedance between the contact rail and the rail respectively according to the effective resistance per unit length of the contact rail, the equivalent radius of the contact rail, the depth of the equivalent ground loop conductor, the spacing between two contact rails, and the spacing between the contact rail and the rail.

[0024] Furthermore, the effective resistance r per unit length of the rail in step S31 g is calculated by Equation (1):

[0025]

[0026] where β is the magnetic saturation coefficient of the steel conductor; ρ is the resistivity of the steel conductor at a working temperature of 20 °C, taking 0.147×10 -4 Ω·mm; S is the cross-sectional area of the steel conductor, mm 2 .

[0027] Furthermore, the self-impedance of a single running rail in step S32 is calculated by Equation (4):

[0028]

[0029] In the formula, Z g is the self-impedance of the rail (Ω / km); r g is the effective resistance per unit length of the rail (Ω / km); D g is the depth of the equivalent ground return conductor (mm); R g is the equivalent radius of the rail (mm); j is a complex number;

[0030] The mutual impedance of two rails is calculated by Equation (5):

[0031]

[0032] In the formula, Z gg is the mutual impedance of two rails (Ω / km); d gg is the distance between two rails (mm); D g is the depth of the equivalent ground return conductor (mm);

[0033] The equivalent self-impedance Z of the running rail G is calculated by Equation (6):

[0034]

[0035] Furthermore, the self-impedance of the contact rail in step S33 is calculated according to Equation (7):

[0036]

[0037] where Z j is the self-impedance of the contact rail, (Ω / km); r j is the effective resistance per unit length of the contact rail (Ω / km), approximately taking the DC resistance of the aluminum conductor; R j is the equivalent radius of the contact rail (mm);

[0038] The mutual impedance of the contact rail is calculated by Equation (8):

[0039]

[0040] Among them, Z jj is the mutual impedance of the contact rail, (Ω / km); d jj is the distance between contact rails (mm);

[0041] The mutual impedance Z between the contact rail and the steel rail jG is calculated by Equation (9):

[0042]

[0043] Among them, d jg1 is the distance between the contact rail and one of the steel rails (mm); d jg2 is the distance between the contact rail and the other steel rail (mm);

[0044] Furthermore, the voltage drop of the contact rail is calculated by Equation (10):

[0045] ΔU j = I a Z j1 + I b Z jj1 + I c Z jG1 (10)

[0046] Among them, ΔU j represents the voltage drop on the contact rail; I a , I b , I c : respectively represent the phase A, phase B, and phase C currents in the three-phase current; Z j1 represents the self-impedance of the contact rail through which the phase A current I a flows, and is calculated by Equation (7); Z jj1 represents the self-impedance of the contact rail through which the phase B current I b flows, and is calculated by Equation (8); Z jG1 represents the mutual impedance between the contact rail through which the phase C current I c flows and the running rail, and is calculated by Equation (9);

[0047] The voltage drop of the running rail is calculated by Equation (11):

[0048] ΔU g = I c Z G1 + I a Z jG2 + I b Z jG2 (11)

[0049] Among them, ΔU grepresents the voltage drop on the running rail; Z G1 represents the self-impedance of the running rail through which the current of phase C flows, calculated by Equation (6); Z jG2 represents the current of phase A, I a and the current of phase B, I b represents the mutual impedance between the contact rail and the running rail through which the currents flow, calculated by Equation (9); Z jG2 and Z jG1 represent the same mutual impedance.

[0050] As a second aspect of the present invention, the present invention provides a traction network impedance calculation system for a three-phase AC traction power supply system, which is used to implement the above calculation method, including a parameter determination module, a mounting position determination module for three-phase conductors, an impedance calculation module, and a voltage drop calculation module;

[0051] The parameter determination module is used to select the left contact rail, the right contact rail, and the running rail as three-phase conductors according to the requirements of the vehicle power receiving system, and determine the materials and electrical parameters of each conductor;

[0052] The mounting position determination module for three-phase conductors is used to determine the mounting positions of the three-phase conductors according to the vehicle power receiving requirements, and ensure that the horizontal and vertical distances between each contact rail and the rail meet the design requirements;

[0053] The impedance calculation module is used to equivalently regard the contact rail and the rail as cylindrical conductors, determine the geometric parameters of the equivalent cylindrical conductors; construct an overhead line model of the equivalent cylindrical conductors, and calculate the conductor self-impedance and the mutual impedance between conductors respectively according to electromagnetic theory and the Carcon ground loop impedance model;

[0054] The voltage drop calculation module is used to calculate the voltage drops of the contact rail and the running rail respectively according to the impedance values of the conductor self-impedance and the mutual impedance between conductors obtained by calculation.

[0055] As a third aspect of the present invention, the present invention also provides an electronic device, which is characterized in that it includes a processor and a memory, and the processor and the memory are connected to each other;

[0056] The memory is used to store a computer program;

[0057] The processor is configured to execute any step of the above-mentioned traction network impedance calculation method for a three-phase AC traction power supply system when calling the computer program.

[0058] Generally speaking, compared with the prior art by the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0059] (1) The traction network impedance calculation method of the three-phase AC traction power supply system of the present invention realizes the accurate calculation of the self-impedance and mutual impedance of conductors by equivalenting the contact rail and the steel rail into cylindrical conductors and constructing an overhead line model based on the Carson ground loop impedance model. This method comprehensively considers the conductivity of the earth and the electromagnetic interaction between conductors, thus significantly improving the accuracy of the calculation results. In addition, the present invention particularly considers the influence of the earth conductivity on impedance calculation, effectively reducing the electromagnetic interference caused by electromagnetic coupling between conductors. This enables our system to adapt to diverse geological environments, enhancing electromagnetic compatibility and system adaptability. By accurately predicting, calculating, and controlling the voltage drop, this method can evaluate the voltage stability, power loss, and overall efficiency of the traction power supply system, providing a solid theoretical basis for the optimal design of the system. By optimizing the design of the traction power supply system, the safety of the system can be improved, and the risks of faults and accidents can be reduced.

[0060] (2) The traction network impedance calculation method of the three-phase AC traction power supply system of the present invention simplifies the design process of the traction power supply system and reduces the design complexity by equivalenting the geometric parameters of cylindrical conductors and the overhead line model and using mature electromagnetic theory for simplified calculation.

[0061] (3) The traction network impedance calculation method of the three-phase AC traction power supply system of the present invention can be applied to different operating frequencies and conductor geometries. By selecting appropriate equivalent principles (such as the area equivalence or perimeter equality principle), the electromagnetic characteristics of conductors under actual operating conditions can be more accurately reflected.

[0062] (4) The traction network impedance calculation method of the three-phase AC traction power supply system of the present invention can optimize material selection, reduce material waste, and lower system costs by accurately calculating the impedance of conductors. For example, the most suitable materials and dimensions can be selected according to the impedance characteristics of different conductors.

[0063] (5) The traction network impedance calculation method of the three-phase AC traction power supply system of the present invention realizes the standardized design and evaluation of the traction power supply system through a standardized impedance calculation process; this method is not only applicable to a specific 3 kV three-phase AC traction power supply system, but also has good adaptability and can be extended to other voltage levels and types of traction power supply systems. Description of the Drawings

[0064] Figure 1 is the flowchart of the traction network impedance calculation method of the three-phase AC traction power supply system according to the embodiment of the present invention;

[0065] Figure 2 is the position distribution diagram of the three-phase conductors according to the embodiment of the present invention;

[0066] Figure 3In the embodiment of the present invention, the contact rail and the steel rail are both equivalent to cylindrical conductors, and the schematic diagram of the conductor distribution structure after equivalence;

[0067] Figure 4 It is a schematic diagram of a typical Carcon ground loop impedance model;

[0068] Figure 5 It is a schematic diagram of the curve of μ=f(H) of steel with different carbon contents in the embodiment of the present invention;

[0069] Figure 6 It is a schematic diagram of the structure of the traction network impedance calculation system of the three-phase AC traction power supply system in the embodiment of the present invention;

[0070] Figure 7 It is a schematic diagram of the structure of an electronic device in the embodiment of the present invention. Detailed implementation manners

[0071] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0072] As Figure 1 shown, one aspect of the present invention provides a method for calculating the traction network impedance of a three-phase AC traction power supply system. The power supply voltage level of the three-phase traction power supply system is 3 kV AC. The method includes:

[0073] S1: According to the requirements of the vehicle power receiving system, select the left contact rail, the right contact rail and the running rail as the three-phase conductors, and determine the materials and electrical parameters of each conductor; the electrical parameters include cross-sectional area, perimeter and resistance per unit length;

[0074] Specifically, in accordance with the principle of minimizing the changes to the power receiving systems such as the vehicle and the contact rail, the left contact rail, the right contact rail and the running rail are selected as the three-phase conductors. Among them, the A-phase conductor uses a left steel-aluminum composite rail, with an aluminum rail area of 4775 mm 2 , a perimeter of 239 mm, and a DC resistance of 7.141 mΩ / km (20 °C); the B-phase conductor uses a right steel-aluminum composite rail, with an aluminum rail area of 4775 mm2, a perimeter of 239 mm, and a DC resistance of 7.141 mΩ / km (20 °C); the C-phase conductor uses two P60 steel rails, with a single-rail cross-sectional area of 7745 mm2, a perimeter of 706 mm, and a resistivity of 0.147×10-5 Ω·cm (20 °C);

[0075] S2: Determine the installation positions of the three-phase conductors according to the power receiving requirements of the vehicle, and ensure that the horizontal and vertical distances between each contact rail and the rail meet the design requirements; Figure 2 is the position distribution diagram of the three-phase conductors;

[0076] Specifically, the horizontal distance between the contact rail and the rail is 715 mm, and the vertical distance is 360 mm; the distance between the left and right rail bars is 1510 mm;

[0077] S3: Equivalent the contact rail and the rail into cylindrical conductors respectively, and determine the geometric parameters of the equivalent cylindrical conductors; construct an overhead line model of the equivalent cylindrical conductors, and calculate the self-impedance of the conductors and the mutual impedance between the conductors according to the electromagnetic theory and the Carcon earth loop impedance model respectively;

[0078] S4: Calculate the voltage drops of the contact rail and the running rail respectively according to the impedance values of the conductor self-impedance and the mutual impedance between the conductors obtained by calculation.

[0079] Furthermore, in step S3, the overhead line model is a simplified method that equivalent the actual conductors (such as contact rails, rails, etc.) into overhead conductors. This model assumes that the conductors are cylindrical, which is convenient for calculating their electromagnetic characteristics. For conductors with non-circular cross-sections (such as rails), they are transformed into cylindrical conductors for calculation by the method of equivalent radius;

[0080] The Carson model is a classic impedance calculation method used to calculate the self-impedance and mutual impedance of overhead conductors in the earth loop. It takes into account the conductivity of the earth and the electromagnetic coupling between the conductors. The core idea of this model is to divide the impedance of the conductor into two parts: the internal impedance, which is related to the material and cross-section characteristics of the conductor itself; the external impedance, which is related to the relative positions between the conductors, the conductivity of the earth, and the distribution of the electromagnetic field;

[0081] Furthermore, in step S3, both the contact rail and the rail are equivalent to cylindrical conductors, and the distribution structure of the conductors after equivalence is as Figure 3 shown;

[0082] Determining the geometric parameters of the equivalent cylindrical conductors includes:

[0083] Select the equivalent principle according to the cross-section characteristics of the contact rail and the rail; use the principle of equal area or equal perimeter to determine the radius of the equivalent cylinder;

[0084] Set the length of the equivalent cylindrical conductor according to the actual laying lengths of the contact rail and the rail;

[0085] Furthermore, the cross-sectional shape of the actual conductor is complex (such as the I-shaped cross-section of a rail), and it is very complex to directly calculate its electromagnetic characteristics. By equivalent to a cylindrical conductor, mature electromagnetic theories (such as the Carson model) can be used for simplified calculations; the equivalent principle can ensure consistency with the actual conductor in key electromagnetic characteristics (such as resistance, inductance, or impedance), thus ensuring the accuracy of the calculation results; different equivalent principles are applicable to different operating frequencies, and choosing the appropriate equivalent principle can more accurately reflect the electromagnetic characteristics of the conductor under actual operating conditions; the core of the equivalent principle is to simplify the actual conductor cross-section (such as rectangular, I-shaped, or other complex shapes) into a circular cross-section while ensuring consistency with the original conductor in specific electromagnetic characteristics (such as resistance, inductance, or impedance). Which equivalent principle to specifically choose depends on the operating frequency and the geometric shape of the conductor: the operating frequency includes low-frequency and high-frequency cases; the geometric shape of the conductor includes rectangular cross-section and complex cross-section;

[0086] Low-frequency cases (such as direct current or power frequency 50 Hz): The current is mainly evenly distributed within the conductor cross-section. At this time, the area equivalent principle is usually adopted; High-frequency cases (such as in the megahertz range): Due to the skin effect, the current is mainly concentrated on the surface of the conductor. At this time, the perimeter equal principle is usually adopted;

[0087] For a rectangular cross-section (such as a contact rail), the equivalent radius can be selected according to its cross-sectional area or perimeter; For a complex cross-section (such as a rail), it is necessary to perform the equivalent in combination with the actual current distribution;

[0088] Furthermore, the overhead line model for constructing the equivalent cylindrical conductor in step S3 includes:

[0089] Equivalent the contact rail and the rail to an overhead cylindrical conductor;

[0090] Regard the equivalent cylindrical conductor as an overhead line model, ignoring its actual laying position, and only considering the relative position and spacing between the conductors;

[0091] According to the actual laying situation, determine the horizontal and vertical distances between the contact rail and the rail, as well as the spacing between the rails;

[0092] Furthermore, Figure 4 is a schematic diagram of a typical Carcon ground loop impedance model; The Carcon ground loop impedance model includes the ground, a conductor located above the ground, and an equivalent ground loop conductor located inside the ground; Among them, the height of the center of the conductor from the ground surface is h, and the depth of the equivalent ground loop conductor is D g ; In step S3, calculate the self-impedance of the conductor and the mutual impedance between the conductors according to the electromagnetic theory and the Carcon ground loop impedance model respectively; including:

[0093] S31: Calculate the effective resistance per unit length of the rail according to the magnetic saturation coefficient of the steel conductor, the resistivity of the steel conductor, and the cross-sectional area of the steel conductor;

[0094] S32: Calculate the self-impedance of a single running rail, the mutual impedance between two rails, and the equivalent self-impedance of the running rail according to the effective resistance per unit length of the rail, the depth of the equivalent ground return conductor, the equivalent radius of the rail, and the distance between two rails respectively;

[0095] S33: Calculate the self-impedance of the contact rail, the mutual impedance between contact rails, and the mutual impedance between the contact rail and the rail according to the effective resistance per unit length of the contact rail, the equivalent radius of the contact rail, the depth of the equivalent ground return conductor, the distance between two contact rails, and the distance between the contact rail and the rail respectively;

[0096] Further, the effective resistance per unit length of the rail r in step S31 g is calculated by Equation (1):

[0097]

[0098] where β is the magnetic saturation coefficient of the steel conductor; ρ is the resistivity of the steel conductor at a working temperature of 20°C, taking 0.147×10 -4 Ω·mm; S is the cross-sectional area of the steel conductor, in mm 2 ;

[0099] The magnetic saturation coefficient β of the steel conductor is calculated by Equation (2):

[0100]

[0101] where p is the perimeter of the steel conductor, in mm; f is (Hz), 50 Hz; μ is the relative magnetic permeability of the steel conductor, and its value is related to the magnetic field strength H; as Figure 5 shown, it is a schematic diagram of the μ=f(H) curve for steel of different carbon contents;

[0102] The relationship between the relative magnetic permeability μ of the steel conductor and the magnetic field strength H is expressed by Equation (3):

[0103]

[0104] where I is the current passing through the steel conductor, in A;

[0105] Further, the self-impedance of a single running rail in step S32 is calculated by Equation (4):

[0106]

[0107] In the formula, Z g is the self-impedance of the rail (Ω / km); r g is the effective resistance per unit length of the rail (Ω / km); D gis the depth of the equivalent ground return conductor (mm); R g is the equivalent radius of the rail (mm); j is the imaginary unit;

[0108] The depth D of the equivalent ground return conductor g The depth of the equivalent ground return conductor is calculated according to the earth conductivity and frequency, and is expressed by Equation (12):

[0109]

[0110] In the formula, f is the frequency (Hz), taking 50 Hz; σ is the earth conductivity (1 / Ω·cm), generally taking 10 -4 / Ω·cm for multi-rock geology;

[0111] The mutual impedance between two rails is calculated by Equation (5):

[0112]

[0113] In the formula, Z gg is the mutual impedance between two rails (Ω / km); d gg is the distance between two rails (mm); D g is the depth of the equivalent ground return conductor (mm);

[0114] The self-impedance Z of the running rail G is calculated by Equation (6):

[0115]

[0116] Furthermore, the self-impedance of the contact rail in step S33 is calculated according to Equation (7):

[0117]

[0118] Among them, Z j is the self-impedance of the contact rail, (Ω / km); r j is the effective resistance per unit length of the contact rail (Ω / km), approximately taking the DC resistance of the aluminum conductor; R j is the equivalent radius of the contact rail (mm);

[0119] The mutual impedance of the contact rail is calculated by Equation (8):

[0120]

[0121] Among them, Z jj is the mutual impedance of the contact rail, (Ω / km); d jj is the distance between the contact rails (mm);

[0122] The mutual impedance Z between the contact rail and the rail jG is calculated by Equation (9):

[0123]

[0124] where d jg1 is the distance (mm) between the contact rail and one of the steel rails; d jg2 is the distance (mm) between the contact rail and the other steel rail;

[0125] Furthermore, in step S4, the voltage drop is the voltage loss caused by the impedance of the conductor to the current when the current flows through the conductor. In a three-phase AC system, the current in each phase will generate a voltage drop on its corresponding conductor. At the same time, due to the electromagnetic coupling between the conductors, the currents in different phases may also generate additional voltage drops (caused by mutual impedance) on other conductors. These voltage drops are very important parameters for analyzing and designing power systems, especially traction power supply systems.

[0126] In a three-phase AC system, calculating the voltage drop usually requires considering the self-impedance generated when the current in each phase flows through its corresponding conductors (such as the contact rail and the running rail), as well as the mutual impedance between the currents in different phases. The calculation method of the voltage drop can be divided into the following steps:

[0127] Step 1: Determine the self-impedance and mutual impedance of each phase conductor; these parameters can be obtained through experimental measurements or calculated using electromagnetic field theory;

[0128] Step 2: Calculate the voltage drop generated by the current in each phase on the conductor;

[0129] Step 3: Consider the influence of the mutual impedance and calculate the contribution of the mutual impedance to the voltage drop;

[0130] In a three-phase system, the current in one phase not only affects the voltage drop of this phase, but may also affect the voltage drops of other phases through the mutual impedance. Therefore, it is necessary to calculate the contribution of the mutual impedance to the voltage drop;

[0131] Step 4: Calculate the total voltage drop; for each conductor (such as the contact rail and the running rail), its total voltage drop is the vector sum of the voltage drops generated by all phase currents.

[0132] Furthermore, the contact rail voltage drop is calculated by Equation (10):

[0133] ΔU j =I a Z j1 +I b Z jj1 +I c Z jG1 (10)

[0134] where ΔU j represents the voltage drop on the contact rail; I a , I b, I c : respectively represent the phase A, phase B, and phase C currents in the three-phase current; Z j1 represents the self-impedance of the contact rail through which the phase A current I a flows, and is calculated by Equation (7); Z jj1 represents the self-impedance of the contact rail through which the phase B current I b flows, and is calculated by Equation (8); Z jG1 represents the mutual impedance between the contact rail and the running rail through which the phase C current I c flows, and is calculated by Equation (9);

[0135] The voltage drop of the running rail is calculated by Equation (11):

[0136] ΔU g = I c Z G1 + I a Z jG2 + I b Z jG2 (11)

[0137] Among them, ΔU g represents the voltage drop on the running rail; Z G1 represents the self-impedance of the running rail through which the phase C current flows, and is calculated by Equation (6); Z jG2 represents the phase A current I a and the phase B current I b flows through the mutual impedance between the contact rail and the running rail, and is calculated by Equation (9); Z jG2 and Z jG1 represent the same mutual impedance.

[0138] As Figure 6 shown, the second aspect of the present invention provides a traction network impedance calculation system for a three-phase AC traction power supply system, which is used to implement the above design method, including a parameter determination module, a mounting position determination module for three-phase conductors, an impedance calculation module, and a voltage drop calculation module;

[0139] The parameter determination module is used to select the left contact rail, the right contact rail, and the running rail as the three-phase conductors according to the requirements of the vehicle power receiving system, and determine the materials and electrical parameters of each conductor;

[0140] The mounting position determination module for three-phase conductors is used to determine the mounting positions of the three-phase conductors according to the vehicle power receiving requirements, and ensure that the horizontal and vertical distances between each contact rail and the rail meet the design requirements;

[0141] An impedance calculation module, which is used to equivalently regard the contact rail and the steel rail as cylindrical conductors, determine the geometric parameters of the equivalent cylindrical conductors; construct an overhead line model of the equivalent cylindrical conductors, and calculate the self-impedance of the conductors and the mutual impedance between the conductors respectively according to the electromagnetic theory and the Carcon earth loop impedance model;

[0142] A voltage drop calculation module, which is used to calculate the voltage drops of the contact rail and the running rail respectively according to the impedance values of the self-impedance of the conductors and the mutual impedance between the conductors obtained by calculation.

[0143] It should be noted that the traction network impedance calculation system of the three-phase AC traction power supply system provided in this embodiment can be a computer program (including program code) running in a computer device. For example, the traction network impedance calculation system of the three-phase AC traction power supply system is an application software; the traction network impedance calculation system of the three-phase AC traction power supply system can be used to execute the corresponding steps in the above method provided in the embodiments of the present application.

[0144] In some feasible implementation manners, the traction network impedance calculation system of the three-phase AC traction power supply system provided in this embodiment can be implemented in a combination of software and hardware. As an example, the traction network impedance calculation system of the three-phase AC traction power supply system provided in the embodiments of the present application can be a processor in the form of a hardware decoding processor, which is programmed to execute the traction network impedance calculation method of the three-phase AC traction power supply system provided in the embodiments of the present application. For example, the processor in the form of a hardware decoding processor can adopt one or more application-specific integrated circuits (ASICs, Application Specific Integrated Circuits), digital signal processors (DSPs, digital signal processors), programmable logic devices (PLDs, Programmable Logic Devices), complex programmable logic devices (CPLDs, Complex Programmable Logic Devices), field programmable gate arrays (FPGAs, Field-Programmable Gate Arrays) or other electronic components.

[0145] In some feasible implementation manners, the traction network impedance calculation system of the three-phase AC traction power supply system provided in this embodiment can be implemented in a software manner. It can be software in the form of programs and plugins, etc., and includes a series of modules to implement the traction network impedance calculation method of the three-phase AC traction power supply system provided in the embodiments of the present invention.

[0146] The traction network impedance calculation system of the three-phase AC traction power supply system provided in this embodiment realizes the accurate calculation of the self-impedance and mutual impedance of conductors by equivalent the contact rail and the steel rail as cylindrical conductors and constructing an overhead line model based on the Carson ground loop impedance model. This method comprehensively considers the conductivity of the earth and the electromagnetic interaction between conductors, thus significantly improving the accuracy of the calculation results. In addition, the present invention particularly considers the influence of the earth conductivity on impedance calculation, effectively reducing the electromagnetic interference caused by electromagnetic coupling between conductors. This enables our system to adapt to diverse geological environments, enhancing the electromagnetic compatibility and the adaptability of the system. By accurately predicting, calculating, and controlling the voltage drop, this method can evaluate the voltage stability, power loss, and overall efficiency of the traction power supply system, providing a solid theoretical basis for the optimal design of the system. By optimizing the design of the traction power supply system, the safety of the system can be improved, and the risk of faults and accidents can be reduced.

[0147] The third aspect of the present invention also provides an electronic device, Figure 7 which is a schematic structural diagram of the electronic device of this embodiment, as Figure 7 shown, the electronic device 1000 in this embodiment may include: a processor 1001, a network interface 1004, and a memory 1005. In addition, the above-mentioned electronic device 1000 may further include: a user interface 1003, and at least one communication bus 1002. Among them, the communication bus 1002 is used to realize the connection and communication between these components. Among them, the user interface 1003 may include a display screen (Display), a keyboard (Keyboard), and optionally the user interface 1003 may further include a standard wired interface, a wireless interface. The network interface 1004 may optionally include a standard wired interface, a wireless interface (such as a WI-FI interface). The memory 1005 may be a high-speed RAM memory, or a non-volatile memory, for example, at least one disk memory. The memory 1005 may optionally be at least one storage device located far from the aforementioned processor 1001. As Figure 7 shown, the memory 1005, as a computer-readable storage medium, may include an operating system, a network communication module, a user interface module, and a device control application program.

[0148] As Figure 7 shown in the electronic device 1000, the network interface 1004 can provide network communication functions; while the user interface 1003 is mainly used to provide an input interface for users; and the processor 1001 can be used to call the device control application program stored in the memory 1005 to achieve:

[0149] According to the requirements of the vehicle power receiving system, select the left contact rail, the right contact rail, and the running rail as the three-phase conductors, and determine the materials and electrical parameters of each conductor; the electrical parameters include cross-sectional area, perimeter, and resistance per unit length;

[0150] According to the vehicle power receiving requirements, determine the installation positions of the three-phase conductors to ensure that the horizontal and vertical distances between each contact rail and the rail meet the design requirements;

[0151] Equivalent the contact rail and the rail to cylindrical conductors respectively, and determine the geometric parameters of the equivalent cylindrical conductors; construct an overhead line model of the equivalent cylindrical conductors, and calculate the self-impedance of the conductors and the mutual impedance between the conductors respectively according to electromagnetic theory and the Carcon earth loop impedance model;

[0152] According to the impedance values of the conductor self-impedance and the mutual impedance between the conductors obtained by calculation, calculate the voltage drops of the contact rail and the running rail respectively.

[0153] It should be understood that in some feasible implementation manners, the above-mentioned processor 1001 may be a central processing unit (CPU), and this processor may also be other general-purpose processors, DSPs, ASICs, FPGAs or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or this processor may also be any conventional processor, etc. The memory may include a read-only memory and a random access memory, and provide instructions and data to the processor. A part of the memory may also include a non-volatile random access memory. For example, the memory may also store information about the device type.

[0154] In specific implementation, the above-mentioned electronic device 1000 can execute the implementation manners provided in each step as described above through its built-in various functional modules. For specific details, refer to the implementation manners provided in each step as described above, which will not be elaborated here. Figure 1

[0155] ​The electronic device provided in this embodiment realizes the accurate calculation of the self-impedance and mutual impedance of conductors by equivalenting the contact rail and the steel rail to cylindrical conductors and constructing an overhead line model based on the Carson ground loop impedance model. This method comprehensively considers the conductivity of the earth and the electromagnetic interaction between conductors, thus significantly improving the accuracy of the calculation results. In addition, the present invention particularly considers the influence of the earth conductivity on impedance calculation, effectively reducing the electromagnetic interference caused by electromagnetic coupling between conductors. This enables our system to adapt to diverse geological environments, enhancing the electromagnetic compatibility and the adaptability of the system. By accurately predicting, calculating, and controlling the voltage drop, this method can evaluate the voltage stability, power loss, and overall efficiency of the traction power supply system, providing a solid theoretical basis for the optimal design of the system. By optimizing the design of the traction power supply system, the safety of the system can be improved, and the risks of faults and accidents can be reduced.

[0156] The embodiment of the present application also provides a computer-readable storage medium, which stores a computer program and is executed by a processor to implement Figure 1 the methods provided in each step, and for the specific implementation, reference may be made to the implementation manners provided in each of the above steps, which will not be elaborated herein.

[0157] The computer-readable storage medium provided in this embodiment realizes the accurate calculation of the self-impedance and mutual impedance of conductors by equivalenting the contact rail and the steel rail to cylindrical conductors and constructing an overhead line model based on the Carson ground loop impedance model. This method comprehensively considers the conductivity of the earth and the electromagnetic interaction between conductors, thus significantly improving the accuracy of the calculation results. In addition, the present invention particularly considers the influence of the earth conductivity on impedance calculation, effectively reducing the electromagnetic interference caused by electromagnetic coupling between conductors. This enables our system to adapt to diverse geological environments, enhancing the electromagnetic compatibility and the adaptability of the system. By accurately predicting, calculating, and controlling the voltage drop, this method can evaluate the voltage stability, power loss, and overall efficiency of the traction power supply system, providing a solid theoretical basis for the optimal design of the system. By optimizing the design of the traction power supply system, the safety of the system can be improved, and the risks of faults and accidents can be reduced.

[0158] Any reference to memory, storage, database, or other media used in the embodiments provided by this application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct rambus dynamic RAM (DRDRAM), and rambus dynamic RAM (RDRAM), among others.

[0159] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A calculation method for the impedance of a traction network in a three-phase AC traction power supply system, characterized in that, Including: S1: According to the requirements of the vehicle power receiving system, select the left contact rail, right contact rail and running rail as three-phase conductors, and determine the materials and electrical parameters of each conductor; the electrical parameters include cross-sectional area, perimeter and resistance per unit length; S2: According to the vehicle power receiving requirements, determine the installation positions of the three-phase conductors to ensure that the horizontal and vertical distances between each contact rail and the rail meet the design requirements; S3: Equivalent the contact rail and the rail as cylindrical conductors respectively, and determine the geometric parameters of the equivalent cylindrical conductors; construct an overhead line model of the equivalent cylindrical conductors, and calculate the self-impedance of the conductors and the mutual impedance between the conductors respectively according to electromagnetic theory and the Carcon earth loop impedance model; S4: According to the impedance values of the conductor self-impedance and the mutual impedance between the conductors obtained by calculation, calculate the voltage drops of the contact rail and the running rail respectively.

2. The traction network impedance calculation method of a three-phase AC traction power supply system according to claim 1, characterized in that The geometric parameters of the equivalent cylindrical conductors determined in step S3 include: According to the cross-sectional characteristics of the contact rail and the rail, select the equivalent principle; use the principle of equal area or equal perimeter to determine the radius of the equivalent cylinder; According to the actual laying length of the contact rail and the rail, set the length of the equivalent cylindrical conductor.

3. A traction network impedance calculation method for a three-phase AC traction power supply system according to claim 1, characterized in that The construction of the overhead line model of the equivalent cylindrical conductors in step S3 includes: Equivalent the contact rail and the rail as overhead cylindrical conductors; Regard the equivalent cylindrical conductors as an overhead line model, ignore their actual laying positions, and only consider the relative positions and spacings between the conductors; According to the actual laying situation, determine the horizontal and vertical distances between the contact rail and the rail, and the spacing between the rails.

4. A method for calculating the impedance of a traction network in a three-phase AC traction power supply system according to claim 1, characterized in that, In step S3, calculate the self-impedance of the conductors and the mutual impedance between the conductors respectively according to electromagnetic theory and the Carcon earth loop impedance model; including: S31: Calculate the effective resistance per unit length of the rail according to the magnetic saturation coefficient of the steel conductor, the resistivity of the steel conductor and the cross-sectional area of the steel conductor; S32: Calculate the self-impedance of a single running rail, the mutual impedance between two rails and the equivalent self-impedance of the running rail respectively according to the effective resistance per unit length of the rail, the depth of the equivalent earth loop conductor, the equivalent radius of the rail and the spacing between two rails; S33: Calculate the self-impedance of the contact rail, the mutual impedance between the contact rails and the mutual impedance between the contact rail and the rail respectively according to the effective resistance per unit length of the contact rail, the equivalent radius of the contact rail, the depth of the equivalent earth loop conductor, the spacing between two contact rails and the spacing between the contact rail and the rail.

5. A method for calculating the impedance of a traction network in a three-phase AC traction power supply system according to claim 4, characterized in that The effective resistance r per unit length of the rail in step S31 g is calculated by formula (1): Among them, β is the magnetic saturation coefficient of the steel conductor; ρ is the resistivity of the steel conductor at a working temperature of 20°C, taking 0.147×10 -4 Ω·mm; S is the cross-sectional area of the steel conductor, in mm 2 .

6. The traction network impedance calculation method for a three-phase AC traction power supply system according to claim 5, characterized in that, The self-impedance of a single running rail in step S32 is calculated by formula (4): where Z g is the self-impedance of the rail (Ω / km); r g is the effective resistance per unit length of the rail (Ω / km); D g is the depth of the equivalent ground return conductor (mm); R g is the equivalent radius of the rail (mm); j is a complex number; The mutual impedance between two rails is calculated by formula (5): where Z gg is the mutual impedance between two rails (Ω / km); d gg is the distance between two rails (mm); D g is the depth of the equivalent ground return conductor (mm). Self-impedance Z of running rail G Calculated by Equation (6):

7. A method for calculating the impedance of a traction network in a three-phase AC traction power supply system according to claim 6, characterized in that The self-impedance of the contact rail in step S33 is calculated according to formula (7): Among them, Z j is the self-impedance of the contact rail, (Ω / km); r j is the effective resistance per unit length of the contact rail (Ω / km), approximately taking the DC resistance of the aluminum conductor; R j is the equivalent radius of the contact rail (mm); The mutual impedance between the contact rails is calculated by formula (8): Among them, Z jj is the mutual impedance of the contact rails, (Ω / km); d jj is the distance between the contact rails (mm); Mutual impedance Z between the contact rail and the steel rail jG Calculated by equation (9): Among them, d jg1 is the distance (mm) between the contact rail and one of the steel rails; d jg2 is the distance (mm) between the contact rail and the other steel rail; 8. A calculation method for the traction network impedance of a three-phase AC traction power supply system according to claim 7, characterized in that, The voltage drop of the contact rail is calculated by formula (10): ΔU j = I a Z j1 + I b Z jj1 + I c Z jG1 (10) Among them, ΔU j represents the voltage drop on the contact rail; I a , I b , I c : respectively represent the phase A, phase B, and phase C currents in the three-phase current; Z j1 represents the self-impedance of the contact rail through which the phase A current I a flows, and is calculated by Equation (7); Z jj1 represents the self-impedance of the contact rail through which the phase B current I b flows, and is calculated by Equation (8); Z jG1 represents the mutual impedance between the contact rail through which the phase C current I c flows and the running rail, and is calculated by Equation (9); The voltage drop of the running rail is calculated by formula (11): ΔU g = I c Z G1 + I a Z jG2 + I b Z jG2 (11) Among them, ΔU g represents the voltage drop on the running rail; Z G1 represents the self-impedance of the running rail through which the current of phase C flows, and is calculated by Equation (6); Z jG2 represents the mutual impedance between the contact rail and the running rail through which the current I a of phase A and the current I b of phase B flow, and is calculated by Equation (9); Z jG2 and Z kG1 represent the same mutual impedance.

9. A traction network impedance calculation system for a three-phase AC traction power supply system, used to implement the calculation method described in any one of claims 1-8, including a parameter determination module, a three-phase conductor installation position determination module, an impedance calculation module and a voltage drop calculation module; The parameter determination module is used to select the left contact rail, right contact rail and running rail as three-phase conductors according to the requirements of the vehicle power receiving system, and determine the materials and electrical parameters of each conductor; The installation position determination module of the three-phase conductor is used to determine the installation position of the three-phase conductor according to the power receiving requirements of the vehicle, ensuring that the horizontal and vertical distances between each contact rail and the rail meet the design requirements; The impedance calculation module is used to equivalently regard the contact rail and the rail as cylindrical conductors, determine the geometric parameters of the equivalent cylindrical conductors; construct an overhead line model of the equivalent cylindrical conductors, and calculate the self-impedance of the conductors and the mutual impedance between the conductors respectively according to the electromagnetic theory and the Carcon ground loop impedance model; The voltage drop calculation module is used to calculate the voltage drops of the contact rail and the running rail respectively according to the impedance values of the conductor self-impedance and the mutual impedance between the conductors obtained by calculation.

10. An electronic device, characterized in that, It includes a processor and a memory, and the processor and the memory are connected to each other; The memory is used to store computer programs; The processor is configured to execute the traction network impedance calculation method of the three-phase AC traction power supply system according to any one of claims 1 to 8 when calling the computer program.

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