TRAIN CONTROL SYSTEM

Abstract

Provided in the present disclosure is a train control system, comprising: a traction transformer, which is located outside a train, and an auxiliary traction converter, which is located in the train, the auxiliary traction converter at least comprising a rectifier module, a direct-current module and an inverter module, wherein the rectifier module is located in a loop where a secondary winding of the traction transformer is located; the rectifier module is connected to the direct-current module by means of a connecting piece; the direct-current module is connected to the inverter module by means of a connecting piece; the rectifier module is configured to receive a first alternating current input by the traction transformer, and convert the first alternating current into a first direct current; the direct-current module is configured to receive the first direct current and input the first direct current into the inverter module; and the inverter module is configured to receive the first direct current, and convert the first direct current into a second alternating current. Functional components are modularly designed, and modules are connected to each other by means of connecting pieces, so that good levels of maintainability and reliability are achieved.

Description

Train control system

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure is based on the Chinese patent application with application number 202311825148.4 and application date of December 27, 2023, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby incorporated into this application by introduction. Technical Field

[0003] The present disclosure relates to rail transportation technology, and in particular to a train control system. Background Art

[0004] In the relevant technologies, the main-auxiliary integrated converter is the key development direction of rail transit vehicle equipment. When adding an auxiliary converter device on the basis of the traction converter, it is necessary to consider the auxiliary main circuit topology and the impact of the increase in the intermediate DC circuit capacity on the intermediate capacitor capacity. The circuit topology of the locomotive converter device that draws power from the secondary side of the transformer is complex, with a large number of components, and is not suitable for miniaturization requirements. In the design scheme of adding a separate capacitor to the front end of the auxiliary converter power module, the size of the capacitor capacitance needs to be considered in conjunction with the traction capacitor and the line stray inductance. Generally speaking, the capacitance of the auxiliary front end is relatively small and the capacitance of the traction support capacitor is large, which easily forms a large circulating current between the two capacitors. There is currently no effective solution to this problem. Summary of the Invention

[0005] In view of this, an embodiment of the present application provides a train control system, aiming to effectively improve the maintainability and reliability of the train control system.

[0006] The technical solution of the embodiment of the present application is implemented as follows:

[0007] An embodiment of the present application provides a train control system, comprising a traction transformer located outside the train and a traction auxiliary converter located inside the train, wherein the traction auxiliary converter comprises at least a rectifier module, a DC module, and an inverter module;

[0008] The rectifier module is located in the loop where the secondary winding of the traction transformer is located; the rectifier module is connected to the DC module via a connector; the DC module is connected to the inverter module via a connector;

[0009] The rectifier module is configured to receive the first alternating current input by the traction transformer and convert the first alternating current into a first direct current;

[0010] The DC module is configured to receive the first DC power and input the first DC power into the inverter module;

[0011] The inverter module is configured to receive the first direct current and convert the first direct current into a second alternating current.

[0012] In the above solution, the rectifier module includes at least one group of first bridge arm components; the connecting member includes a first composite busbar; the two ends of the first bridge arm component are connected to the first composite busbar, and the first composite busbar is connected to the two ends of the DC module.

[0013] In the above solution, the inverter module includes at least one group of second bridge arm components; the connecting member includes a second composite busbar; the two ends of the second bridge arm components are connected to the second composite busbar, and the second composite busbar is connected to the two ends of the inverter module.

[0014] In the above solution, the DC module at least includes a supporting capacitor, and the capacitance of the supporting capacitor is determined at least according to the first power and rated voltage of the DC module.

[0015] In the above solution, the inverter module is connected to at least one motor; the first power is determined based on at least the second power of the motor and the third power of the rectifier module.

[0016] In the above scheme, the inductance value of the DC module is determined based on at least the first inductance of the rectifier module, the second inductance of the DC module, the third inductance of the inverter module and the connection inductance; wherein the connection inductance includes at least the inductance of the connection between the rectifier module and the DC module and the inductance of the connection between the DC module and the inverter module.

[0017] In the above solution, the DC module includes at least a first submodule and a second submodule; the connection inductor also includes an inductor connecting the first submodule and the second submodule.

[0018] In the above solution, the traction auxiliary converter further includes an auxiliary inverter module; the auxiliary inverter module is connected to the DC module via a connector;

[0019] The DC module is configured to receive the first DC power and input the first DC power to the auxiliary inverter module;

[0020] The auxiliary inverter module is configured to receive the first direct current and convert the first direct current into a third alternating current.

[0021] In the above solution, the auxiliary inverter module includes at least one group of third bridge arm components; the connecting member includes a third composite busbar; the two ends of the third bridge arm components are connected to the third composite busbar, and the third composite busbar is connected to the two ends of the DC module.

[0022] In the above solution, the inductance value of the DC module is also determined based on the fourth inductance of the auxiliary inverter module.

[0023] An embodiment of the present application provides a train control system, comprising a traction transformer located outside the train and a traction auxiliary converter located inside the train. The traction auxiliary converter comprises at least a rectifier module, a DC module, and an inverter module. The rectifier module is located in the loop of the secondary winding of the traction transformer. The rectifier module is connected to the DC module via a connector. The DC module is connected to the inverter module via a connector. The rectifier module is configured to receive a first alternating current (AC) input from the traction transformer and convert the first AC into a first DC. The DC module is configured to receive the first DC and input the first DC into the inverter module. The inverter module is configured to receive the first DC and convert the first DC into a second AC. Using the technical solution of the embodiment of the present application, the components with rectifier functions, components with DC input and output functions, and components with inverter functions are modularized, and the modules are connected via connectors, effectively improving the maintainability and reliability of the train control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 is a schematic diagram of the structure of a train control system provided by an embodiment of the present disclosure;

[0025] FIG2 is a schematic diagram of a train control system in an application example of the first embodiment of the present disclosure;

[0026] FIG3 is a schematic diagram of a train control system in another application example of the embodiment of the present disclosure;

[0027] FIG4 is a schematic diagram of the structural layout of a train control system in an application example of the first embodiment of the present disclosure;

[0028] FIG5 is a schematic diagram of voltage and current waveforms of an intermediate DC circuit of a train control system in an application example of the first embodiment of the present disclosure;

[0029] FIG6 is a schematic diagram of voltage and current analysis of the intermediate DC circuit of a train control system in an application example of the first embodiment of the present disclosure. DETAILED DESCRIPTION

[0030] To make the purpose, technical solutions and advantages of the embodiments of the present disclosure more clear, the specific technical solutions disclosed will be further described in detail below in conjunction with the drawings in the embodiments of the present disclosure. The following embodiments are used to illustrate the present disclosure, but are not intended to limit the scope of the present disclosure.

[0031] In related technologies, locomotive auxiliary converter topologies are categorized by input circuitry into two types: transformer secondary-side power generation and intermediate DC circuit power generation. When adding auxiliary converters to traction converters, the front-end capacitors of the auxiliary power modules are typically considered separately.

[0032] The power supply method in the relevant technology includes: the auxiliary circuit for power supply from the secondary side of the transformer is mainly composed of a pre-charging circuit, a four-quadrant rectifier power module, an intermediate DC detection circuit, an inverter power module, and an output contactor, wherein the pre-charging circuit is composed of a pre-charging contactor, a pre-charging resistor, a short-circuit contactor, and an input current sensor. The four-quadrant rectifier module is composed of four half-bridge insulated gate bipolar transistors (IGBT) to form a full-bridge rectifier circuit. The intermediate DC detection circuit is composed of a supporting capacitor, a grounding resistor, a grounding voltage sensor, a grounding capacitor, a discharge resistor, a voltage sensor, a chopper resistor, and a chopper current sensor. The inverter power module is composed of six IGBTs to form a three-phase inverter circuit.

[0033] Related technologies also include powering an auxiliary circuit from the traction intermediate DC circuit, primarily composed of auxiliary support capacitors, voltage sensors, and inverter power modules. Designs that add separate capacitors to the front end of the auxiliary converter power module require careful consideration of the capacitance, balancing the traction capacitors and line stray inductance. Smaller auxiliary front-end capacitance and larger traction support capacitance can easily create significant circulating currents between the two capacitors.

[0034] To effectively improve the maintainability and reliability of a train control system, an embodiment of the present application provides a train control system. As shown in FIG1 , the train control system includes a traction transformer 110 located outside the train and a traction auxiliary converter 120 located inside the train. The traction auxiliary converter 120 includes at least a rectifier module 121, a DC module 122, and an inverter module 123.

[0035] The rectifier module 121 is located in the loop where the secondary winding of the traction transformer 110 is located; the rectifier module 121 is connected to the DC module 122 via a connector; the DC module 122 is connected to the inverter module 123 via a connector;

[0036] The rectifier module 121 is configured to receive the first alternating current input by the traction transformer 110 and convert the first alternating current into a first direct current.

[0037] The DC module 122 is configured to receive the first DC power and input the first DC power to the inverter module 123;

[0038] The inverter module 123 is configured to receive the first direct current and convert the first direct current into a second alternating current.

[0039] Exemplarily, the train control system may be a control system for a high-power freight electric locomotive; the traction auxiliary converter 120 may be a traction converter cabinet; the main circuit of the traction auxiliary converter 120 may include at least one independent traction circuit, specifically, two independent traction circuits; each traction circuit may include a rectifier module 121, a DC module 122, and an inverter module 123. Rectifier module 121 may be a rectifier, specifically, a four-quadrant power module; DC module 122 may be an intermediate DC circuit; and inverter module 123 may be a three-phase traction inverter. The three-phase traction inverter modulates the intermediate DC voltage (i.e., the first DC power) and converts it into a three-phase AC power supply with variable voltage and frequency to control the characteristics of the traction motor. Specifically, inverter module 123 may be an inverter-chopper power module or a traction inverter power module.

[0040] It can be understood that the four-quadrant power module and the traction inverter power module are of a unified design and are both equipped with the same number of half-bridge circuits. Each power module is rectified or inverted through the same half-bridge circuit, so that the power modules in the traction auxiliary converter are unified and interchangeable with each other, effectively reducing the types of power modules used in the traction auxiliary converter, facilitating the functional partitioning and component layout design of the converter, and benefiting the improvement of user inspection and maintenance efficiency.

[0041] In some embodiments, each traction circuit may further include a pre-charging circuit located in the circuit where the secondary winding of the traction transformer 110 is located; the pre-charging circuit is connected to the rectifier module 121, wherein the pre-charging circuit may be a pre-charging circuit. It is understood that the secondary winding of the traction transformer 110 may be a secondary winding or a secondary winding.

[0042] In some embodiments, high-speed sampling and computation circuits can be added to the existing control unit architecture to enable early identification of component performance. Specifically, sensors are added to the control system nodes, most commonly voltage, current, and speed sensors. The sensor signal lines are directly connected to a prognostics and health management (PHM) device, which is implemented using high-speed sampling and computation circuits and ultimately outputs the computational results.

[0043] For ease of understanding, an example is given here. Two traction circuits are installed in the traction converter cabinet, as shown in Figure 2. Each traction circuit includes a pre-charging circuit 201, a four-quadrant power module 202, an intermediate DC circuit 203, and an inverter-chopper power module 204.

[0044] The traction auxiliary converter of the embodiment of the present application can be modularly expanded as needed. For example, it can be expanded to three traction circuits, and the cooling system can be a shared water cooling system or an independent water cooling system.

[0045] The four-quadrant power module and the inverter-chopper power module share the same design, both featuring four parallel IGBT circuits. When used as a four-quadrant power module, the first and second half-bridges are connected in parallel, with their midpoints connected to the AC input terminal on the main contactor side of the pre-charging circuit, which serves as one end of the traction transformer's secondary winding. The third and fourth half-bridges are connected in parallel, with their midpoints connected to the other end of the traction transformer's secondary winding. The DC external terminals on both ends of the half-bridges connect to intermediate circuit components. When used as an inverter-chopper power module, one half-bridge functions as part of the chopper circuit, with the midpoint connected to a chopper resistor. Three of the half-bridges function as a three-phase AC inverter connected to the permanent magnet motor. Each traction circuit is powered by two power modules: a four-quadrant power module and an inverter-chopper power module. The DC side of the power modules is connected, while the AC side is wired according to specific functions.

[0046] The intermediate DC circuit adopts a circuit without secondary filtering. The rated DC voltage of the intermediate DC circuit is 1800V±5%. The power of the applicable permanent magnet motor is 1200kW. Considering the voltage ripple index requirements of the intermediate DC circuit and the total power of the intermediate DC circuit with auxiliary power, the total capacitance parameters of the supporting capacitor in the intermediate DC circuit are selected based on the considerations.

[0047] In an optional embodiment of the present disclosure, the rectifier module includes at least one group of first bridge arm components; the connecting member includes a first composite busbar; the two ends of the first bridge arm component are connected to the first composite busbar, and the first composite busbar is connected to the two ends of the DC module.

[0048] In an optional embodiment of the present disclosure, the inverter module includes at least one group of second bridge arm components; the connecting member includes a second composite busbar; the two ends of the second bridge arm components are connected to the second composite busbar, and the second composite busbar is connected to the two ends of the inverter module.

[0049] It can be understood that the support capacitors in the DC module are placed side by side with the first bridge arm assembly in the rectifier module, connected to the support capacitors via a first composite busbar. The support capacitors are also placed side by side with the second bridge arm assembly in the inverter module, connected to the support capacitors via a second composite busbar. This reduces stray inductance in the intermediate circuit; and the fact that each power module is equipped with a support capacitor allows the support capacitors to absorb peak overvoltages generated by the IGBT during turn-on and turn-off, helping to extend its service life.

[0050] In an optional embodiment of the present disclosure, the DC module includes at least a supporting capacitor, and the capacitance of the supporting capacitor is determined according to at least the first power and rated voltage of the DC module.

[0051] For example, the support capacitor can smooth and filter the output voltage of the rectifier module in the inverter circuit; absorb the high-amplitude pulsating current requested by the inverter module from the support capacitor, prevent it from generating a high-amplitude pulsating voltage on the impedance of the support capacitor, and keep the voltage fluctuation on the DC bus within the allowable range; prevent the voltage overshoot and transient overvoltage from the support capacitor from affecting the IGBT.

[0052] It is understandable that the distribution of support capacitors inside the converter cabinet should be determined taking into account the number of power modules, ensuring that the distance between the capacitors and the power modules is as short as possible and that the stray inductance between the power modules and the capacitors is as small as possible.

[0053] For example, the first power of the DC module can be the maximum power of the intermediate DC circuit, i.e., the total output power of the rectifier module; the rated voltage can be the rated operating voltage of the intermediate DC circuit. The capacitance of the support capacitor can also be determined based on the second harmonic frequency, the fluctuation value of the DC voltage, and the cosine value of the angle between the voltage and current of the secondary winding of the traction transformer.

[0054] For ease of understanding, an example is given here to illustrate that when selecting and calculating the capacitance of the intermediate DC circuit support capacitor, the sum of the auxiliary capacitance and the traction capacitance needs to be considered. The calculation method for the capacitance of the support capacitor is shown in formula (1):

[0055] In formula (1), C FC is the capacitance of the supporting capacitor of the intermediate DC circuit; P max_BUS is the maximum power of the intermediate DC circuit (i.e., the total output power of the four-quadrant power module), in watts (W); f is the second harmonic frequency (100 Hz), in hertz (Hz); λ is the fluctuation of the DC voltage (generally less than 5%); is the cosine value of the angle between the voltage and current of the secondary winding of the traction transformer; U dc It is the rated working voltage of the intermediate DC circuit, in volts (V).

[0056] In an optional embodiment of the present disclosure, the inverter module is connected to at least one motor; and the first power is determined based on at least the second power of the motor and the third power of the rectifier module.

[0057] Exemplarily, at least one motor may be a traction motor, specifically, a permanent magnet motor or an AC asynchronous motor (axle controlled). It is understood that the train control system may drive at least one motor.

[0058] For example, the second power of the motor can be the motor shaft power; the third power of the rectifier module can be the input power from the rectifier module to the DC module. The first power can also be determined based on the number of motor shafts, the power of the traction auxiliary converter, the efficiency of the motor, the efficiency of the gearbox in the train control system, the efficiency of the traction inverter, and the efficiency of the traction auxiliary converter.

[0059] For ease of understanding, an example is given here to illustrate the calculation method of the first power as shown in formula (2):

[0060] In formula (2), P max_BUS is the first power; P total_axle_power is the motor (shaft) power, unit is watt (W); N is the number of motors (shafts); P auxilary is the power of the traction auxiliary converter, in watts (W); η motor is the efficiency of the motor; η gearbox is the efficiency of the gearbox; η inverter is the efficiency of the traction inverter; η aux is the efficiency of the traction auxiliary converter.

[0061] It is understood that the selection of the support capacitor in the above calculations has fully taken into account the capacity of the traction auxiliary converter. Therefore, there is no need to add additional support capacitors at the front end of the traction auxiliary converter. This is to avoid the situation where the capacitance at the front end of the traction auxiliary converter is relatively small and the capacitance of the traction support capacitor is large, which can easily form a large circulating current between the two capacitors.

[0062] In an optional embodiment of the present disclosure, the inductance value of the DC module is determined based on at least the first inductance of the rectifier module, the second inductance of the DC module, the third inductance of the inverter module and the connection inductance; wherein the connection inductance includes at least the inductance of the connection between the rectifier module and the DC module and the inductance of the connection between the DC module and the inverter module.

[0063] Exemplarily, the first inductor of the rectifier module may include a first internal inductor and a first front-end inductor; the second inductor of the DC module may include a second internal inductor and a second front-end inductor; and the third inductor of the inverter module may include a third internal inductor and a third front-end inductor.

[0064] Exemplarily, the inductance value of the DC module may be the sum of the first inductance of the rectifier module, the second inductance of the DC module, the third inductance of the inverter module, and the connection inductance.

[0065] It is understood that the first, second, and third internal inductors may be the inductors of the module's internal composite busbar, where the module's internal composite busbar refers to a composite busbar integrated into the power module and serves as the circuit connecting the power devices within the power module to the module's external interfaces. The first, second, and third internal inductors may be the inductors of the module's front-end composite busbar, where the module's front-end composite busbar serves as the circuit connecting the module's interface to other electrical components within the converter cabinet.

[0066] In an optional embodiment of the present disclosure, the DC module includes at least a first submodule and a second submodule; the connecting inductor further includes an inductor connecting the first submodule and the second submodule.

[0067] For example, the first submodule can be the first set of support capacitors in the DC module, and the second submodule can be the second set of support capacitors in the DC module. It is understood that considering that the support capacitors are connected to the power modules via a composite busbar to reduce line stray inductance, and that the positioning of the support capacitors and the power modules facilitates the operation of the power modules, two sets of support capacitors are selected, evenly distributed below the four-quadrant power modules and the traction inverter power module, and connected via the same composite busbar to reduce stray inductance in the lines from the capacitors to the power modules.

[0068] In some embodiments, the connecting inductor also includes an inductor connecting the first submodule and the second submodule. It can be understood that the first submodule and the second submodule are respectively connected to a composite busbar, and the composite busbar connected to the first submodule is connected to the composite busbar connected to the second submodule.

[0069] In some embodiments, each of the two groups of support capacitors may include two support capacitors, and a group of support capacitors is formed by the two support capacitors and connected to the four-quadrant power module or the traction inverter power module.

[0070] In an optional embodiment of the present disclosure, the traction auxiliary converter further includes an auxiliary inverter module; the auxiliary inverter module is connected to the DC module via a connector;

[0071] a DC module, configured to receive a first DC power and input the first DC power to the auxiliary inverter module;

[0072] The auxiliary inverter module is configured to receive the first direct current and convert the first direct current into a third alternating current.

[0073] For ease of understanding, an example is provided here. As shown in Figure 3, the voltage of the secondary winding of the traction transformer is connected to the four-quadrant power module 302 via a pre-charging circuit 301. The four-quadrant power module 302 performs rectification, converting the single-phase AC power into DC power and outputting it to the intermediate DC circuit 303. The traction inverter power module 304 inverts the DC power into three-phase AC power and outputs it to the traction motor. The auxiliary inverter power module 305 is connected to the intermediate DC circuit 303 via a composite busbar, inverting the DC power into three-phase AC power and outputting it to the auxiliary filter cabinet and auxiliary load. In terms of inductance control of the auxiliary input DC circuit, the auxiliary power module and the intermediate support capacitor are connected via a composite busbar. The support capacitor can be used to reduce the peak voltage of the auxiliary inverter power module switch.

[0074] In an optional embodiment of the present disclosure, the auxiliary inverter module includes at least one group of third bridge arm components; the connecting member includes a third composite busbar; the two ends of the third bridge arm component are connected to the third composite busbar, and the third composite busbar is connected to the two ends of the DC module.

[0075] In this embodiment, the two ends of the third bridge arm assembly are connected to the third composite busbar. The connection between the third composite busbar and the two ends of the DC module can refer to the description of the two ends of the first bridge arm assembly being connected to the first composite busbar, and the first composite busbar being connected to the two ends of the DC module in the above embodiment; or the two ends of the second bridge arm assembly being connected to the second composite busbar, and the second composite busbar being connected to the two ends of the inverter module, which will not be repeated here.

[0076] In an optional embodiment of the present disclosure, the inductance value of the DC module is also determined according to the fourth inductance of the auxiliary inverter module.

[0077] Exemplarily, the fourth inductor of the auxiliary inverter module may include a fourth internal inductor and a fourth front-end inductor. The fourth internal inductor and the fourth front-end inductor in this embodiment can refer to the description of the first internal inductor and the first front-end inductor in the above embodiment and are not further described here. In some embodiments, the connection inductor also includes an inductor connecting the auxiliary inverter module to the DC module.

[0078] This application designs a traction converter device and a low-inductance DC circuit design method suitable for heavy-load freight locomotives, providing a design idea for the miniaturization and low-cost design of the main and auxiliary integrated converter.

[0079] As shown in Figure 4, one traction circuit in the train control system's product structure includes a pre-charge resistor 401, a pre-charge contactor 402, and a main contactor 406, forming a pre-charge circuit; a support capacitor 404 and a chopper resistor 408, forming an intermediate DC circuit; and a four-quadrant power module 403, a support capacitor 404, and an inverter power module 405. The four-quadrant power module 403 is connected to the pre-charge circuit, and the support capacitor 404 is connected to the four-quadrant power module 403 and the inverter power module 405, respectively, via a composite busbar. Another traction circuit in the train control system's product structure also includes an auxiliary inverter power module 407, which is connected to the support capacitor 404 via a composite busbar. The train control system's product structure also includes an expansion water tank 409, a water-cooling resistor 410, and a water pump 411. In some embodiments, the train control system also includes an environmental control device, an automatic transmission control unit (TCU), and an automated-driving control unit (ACU).

[0080] When designing a low-inductance intermediate DC circuit, the following points must be considered: 1. The inductance of the composite busbars within the four-quadrant power modules, traction inverter power modules, and auxiliary power modules; 2. The inductance of the composite busbars located in front of the auxiliary inverter power modules, four-quadrant power modules, and inverter power modules; 3. The internal inductance of the support capacitors and the inductance of the composite busbars located in front of the inverter power modules; and 4. The stray inductance of the connections. The sum of these inductances constitutes the total inductance of the intermediate DC circuit.

[0081] During the design process, it is necessary to consider that the inductance of the total stray inductance on the line from the IGBT to the capacitor inside the power module must be less than the limit value, and the inductance of each part can be controlled by the design of the composite busbar. In this solution, the sum of the inductances from the IGBT of the auxiliary inverter module to the supporting capacitor is considered, and electrical simulation and comparative calculations are performed on the capacitors directly connected in parallel at the front end of the auxiliary module to obtain the inverter output UV line voltage, the inverter output U-phase current, the transformer secondary side UV line voltage and the LC (inductor capacitor) filter output side UV line voltage. The specific results are shown in Figures 5 and 6. According to the auxiliary DC input current amplitude spectrum, the DC component and the AC component at 2 times the switching frequency in the current account for the main components. It was finally confirmed that the capacitor can be eliminated at the front end of the auxiliary power module involved in the disclosed solution, so as to achieve lightweight and low cost in the overall solution design.

[0082] The above description is merely a specific embodiment of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this disclosure should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. A train control system comprising traction transformer located outside the train; a traction auxiliary converter (TAC) located inside the train and comprising at least a rectifier module, a direct current (DC) module and an inverter module, wherein the rectifier module is placed in a circuit in which the secondary side winding of the traction transformer is placed, the rectifier module is connected to the direct current module via a first connecting element, and the direct current module is connected to the inverter module via a second connecting element, the rectifier module is configured to receive a first alternating current (AC) power supplied by the traction transformer and to convert the first AC power into a first direct current power, the direct current module is configured to receive the first direct current power and supply the first direct current power to the inverter module, the inverter module is configured to receive the first direct current power and convert the first direct current power into a second alternating current power.

2. The system of claim 1, wherein the rectifier module comprises at least one set of first bridge arm components, the first connecting element comprises a first composite busbar, two ends of each set of first bridge arm components are connected to the first composite busbar, and the first composite busbar is connected to two ends of the DC module.

3. The system of claim 1, wherein the inverter module comprises at least one set of components of the second bridge arm, the second connecting element comprises a second composite busbar, two ends of each set of components of the second bridge arm are connected to the second composite busbar, and the second composite busbar is connected to two ends of the DC module.

4. The system of claim 1, wherein the DC module comprises at least a reference capacitor, and the capacitance of the reference capacitor is determined at least in accordance with the first power and the nominal voltage of the DC module.

5. The system of claim 4, wherein the inverter module is connected to at least one motor, and the first power is determined at least in accordance with the second power of the motor and the third power of the rectifier module.

6. The system of claim 1, wherein the inductance value of the DC module is determined at least in accordance with the first inductance of the rectifier module, the second inductance of the DC module, the third inductance of the inverter module, and the coupling inductance, wherein the coupling inductance includes at least the inductance of the coupling between the rectifier module and the DC module and the inductance of the coupling between the DC module and the inverter module.

7. The system of claim 6, wherein the DC module comprises at least a first submodule and a second submodule, and the coupling inductance further also includes a coupling inductance between the first submodule and the second submodule.

8. The system of claim 1, wherein the traction auxiliary converter further comprises an auxiliary inverter module connected to the DC module via a third connecting element, the DC module is configured to receive the first DC power and supply the first DC power to the auxiliary inverter module, the auxiliary inverter module is configured to receive the first direct current power and convert the first direct current power into a third alternating current power.

9. The system of claim 8, wherein the auxiliary inverter module comprises at least one set of components of the third bridge arm, the third connecting element comprises a third composite busbar, two ends of each set of components of the third bridge arm are connected to the third composite busbar, and the third composite busbar is connected to two ends of the DC module.

10. The system of claim 8, wherein the inductance value of the DC module is also determined in accordance with the fourth inductance of the auxiliary inverter module.