Shunting locomotive traction converter double-auxiliary power supply system and fan starting method

Abstract

The invention provides a shunting locomotive traction converter double-auxiliary power supply system and a fan starting method, in the system, a converter cooling fan is connected with an external electric load of a constant-frequency constant-voltage branch or a port of a garage power supply through a contactor, and is connected with an external electric load port of a variable-frequency variable-voltage branch through another contactor; when the locomotive is in a traction, braking or standby working condition, the converter cooling fan is disconnected with the constant-frequency and constant-voltage branch and is communicated with the variable-frequency and variable-voltage branch, and when the locomotive is in a garage charging working condition, the converter cooling fan is disconnected with the variable-frequency and variable-voltage branch and is intermittently communicated with the constant-frequency and constant-voltage branch. The invention has the technical effects of energy conservation and noise reduction.

Description

Technical Field

[0001] The present invention relates to the technical field of heat dissipation and cooling of locomotive converters, and in particular to a dual auxiliary power supply system of a shunting locomotive traction converter with a built-in cooling fan, and a cooling fan starting method suitable for the dual auxiliary power supply system. Background Art

[0002] The auxiliary power supply system of the locomotive can provide power for the control battery, air compressor, air conditioner, motor cooling fan and life load of the locomotive, and is an indispensable power component of the locomotive. When a serious fault occurs in the auxiliary power supply system, the locomotive will be unable to operate. In order to improve the redundancy and reliability of the auxiliary power supply system, locomotives generally use a two-way auxiliary power supply system (also called a dual auxiliary power supply system). In this two-way auxiliary power supply system, when one of the auxiliary power supplies fails, the other auxiliary power supply can still work normally, thereby realizing redundant power supply. The loads of this two-way auxiliary power supply system are usually hung on two different power supply branches according to different types: one is a constant frequency and constant voltage branch (for example, 400V / 50Hz or 440V / 60Hz), which is usually used to control the battery charger, water pump, air compressor, air conditioner and other loads; the other is a variable frequency and voltage branch (for example, 80V / 10Hz~440V / 60Hz), which is usually used to power the motor cooling fan, converter cooling fan, transformer cooling fan and the like. Among them, the voltage output by the frequency conversion and voltage conversion branch can be adjusted according to the output power of the locomotive (the amount of heat generated by the motor, transformer, and converter), so as to achieve the effect of saving energy and reducing noise.

[0003] In addition, with the continuous development of technology, a large number of locomotives have begun to introduce traction batteries, so that locomotives can still work normally in areas without power grids. In order to use the power supply of the locomotive shed to charge the traction battery, the auxiliary power supply system of the locomotive needs to add corresponding functions: convert the voltage of the three-phase AC power supply in the locomotive shed into a DC voltage suitable for charging the traction battery. To this end, it is necessary to connect the voltage of the three-phase AC power supply in the locomotive shed (mostly 380V / 50Hz) to the constant frequency and constant voltage branch of the locomotive auxiliary power supply system, and then convert the three-phase AC voltage into DC voltage through the auxiliary transformer and the three-phase inverter in the converter, and then chop it into a lower DC voltage in the converter to provide it to the traction battery for charging.

[0004] If the locomotive uses an auxiliary power supply system, the converter cooling fan (integrated inside the converter, used to dissipate heat from the power module of the traction converter and heating devices such as the auxiliary transformer) is usually connected to the auxiliary power supply circuit (constant frequency and constant voltage branch), and the cooling fan will always be started and running. In particular, when the locomotive is in low power or standby operation, or when the locomotive is charging in the depot, the working noise of the cooling fan is too loud.

[0005] If the locomotive uses a two-way auxiliary power supply system, the converter cooling fan is usually connected to the variable frequency transformer branch of the two auxiliary power supplies. When the locomotive is charging in the depot, the variable frequency transformer branch needs to be started to start the cooling fan. In this case, the charging current in the depot is limited, which will affect the charging efficiency of the traction battery. In addition, if the transformer temperature is high, the speed of the cooling fan needs to be increased to increase the cooling speed, but the working noise of the cooling fan will also increase. Summary of the invention

[0006] In view of the above problems, an embodiment of the present invention provides a dual auxiliary power supply system for a traction converter of a shunting locomotive and a cooling fan starting method applicable to the dual auxiliary power supply system.

[0007] In a first aspect, an embodiment of the present invention provides a dual auxiliary power supply system for a traction converter of a shunting locomotive, characterized in that it includes a constant frequency and constant voltage branch, a variable frequency and voltage branch, a converter cooling fan, and two contactors, wherein:

[0008] The converter cooling fan is connected to the port of the external power load or garage power supply of the constant frequency and constant voltage branch through one of the two contactors, and is connected to the port of the external power load of the variable frequency and voltage branch through the other of the two contactors;

[0009] The two contactors are configured to operate according to the operating conditions of the locomotive, so that when the locomotive is in traction, braking or standby conditions, the converter cooling fan can be disconnected from the constant frequency and constant voltage branch and connected to the variable frequency and voltage branch; and when the locomotive is in a garage charging condition, the converter cooling fan can be disconnected from the variable frequency and voltage branch and intermittently connected to the constant frequency and constant voltage branch.

[0010] According to an embodiment of the present invention, the variable frequency and voltage transformation branch and the constant frequency and voltage branch are composed of a rectifier, a DC chopper, an intermediate DC circuit, two three-phase inverters, and two filter components, wherein:

[0011] One end of the rectifier is externally connected to a power transformer, and the other end is connected to the intermediate DC circuit, so as to rectify the single-phase AC voltage on the secondary side of the power transformer into a DC voltage and provide it to the intermediate DC circuit;

[0012] One end of the DC chopper is externally connected to a power battery pack, and the other end is connected to the intermediate DC circuit, so as to increase the DC voltage output by the power battery pack to the intermediate DC circuit, or reduce the DC voltage of the intermediate DC circuit to the power battery pack;

[0013] The intermediate DC circuit is used to support the DC voltage;

[0014] One end of one of the two three-phase inverters is connected to the intermediate DC circuit, and the other end is connected to an external power load or a garage power supply through a filter component, and is used to convert the DC voltage provided by the intermediate DC circuit into a PWM voltage, and then filter it into a sine wave, and provide it to the power load, or convert the AC voltage provided by the garage power supply into a DC voltage, and provide it to the intermediate DC circuit;

[0015] One end of the other three-phase inverter of the two three-phase inverters is connected to the intermediate DC circuit, and the other end is externally connected to an electrical load through another filtering component, for converting the DC voltage provided by the intermediate DC circuit into a PWM voltage, which is then filtered into a sine wave and provided to the electrical load.

[0016] According to an embodiment of the present invention, the ports of the two three-phase inverters connected to the filter components are further connected via a switch contactor.

[0017] According to an embodiment of the present invention, the intermediate DC circuit includes a capacitor.

[0018] According to an embodiment of the present invention, the filtering component includes an isolation transformer and a filtering capacitor.

[0019] In a second aspect, the present invention further provides a fan starting method applied to the dual auxiliary power supply system of the traction converter of the shunting locomotive, characterized in that it comprises the following steps:

[0020] When the locomotive is in traction, braking or standby conditions, the two contactors are driven to operate, so that the converter cooling fan is disconnected from the constant frequency and constant voltage branch and connected to the variable frequency and voltage branch.

[0021] According to an embodiment of the present invention, the above-mentioned fan starting method further includes the following steps:

[0022] When the locomotive is in traction, braking or standby conditions, the operating voltage of the converter cooling fan is regulated according to the temperature of the auxiliary voltage device, the temperature of the converter cooling water and the temperature of the transformer in the dual auxiliary power supply system.

[0023] In a third aspect, the present invention further provides a fan starting method applied to the dual auxiliary power supply system of the traction converter of the shunting locomotive, characterized in that it comprises the following steps:

[0024] When the locomotive is in a charging state in the garage, the two contactors are driven to operate so that the converter cooling fan can be disconnected from the variable frequency and voltage branch and intermittently connected to the constant frequency and constant voltage branch.

[0025] According to an embodiment of the present invention, when the locomotive is in a garage charging condition, the converter cooling fan is intermittently connected to the constant frequency and constant voltage branch according to the temperature of the auxiliary voltage device and the temperature of the converter cooling water in the dual auxiliary power supply system.

[0026] According to an embodiment of the present invention, when the locomotive is in a garage charging condition, the converter cooling fan is intermittently connected to the constant frequency and constant voltage branch according to the temperature of the auxiliary voltage device and the temperature of the converter cooling water in the dual auxiliary power supply system, comprising the following steps:

[0027] Disconnecting the converter cooling fan from the variable frequency and voltage branch and the constant frequency and voltage branch;

[0028] Connecting the dual auxiliary power supply system to a garage power supply to charge the power battery pack;

[0029] Monitor the temperature of the auxiliary voltage device and the temperature of the converter cooling water in the dual auxiliary power supply system. When the temperature of the auxiliary voltage device or the temperature of the converter cooling water rises above a first temperature threshold, connect the converter cooling fan to the constant frequency and constant voltage branch. When the temperature of the auxiliary voltage device and the temperature of the converter cooling water drop below a second temperature threshold, disconnect the converter cooling fan from the constant frequency and constant voltage branch.

[0030] Compared with the prior art, the above technical solution of the present invention has the following beneficial effects:

[0031] 1. The present invention provides a new dual auxiliary power supply system for traction converter of shunting locomotive, which enables the converter cooling fan to cleverly switch between the constant frequency and constant voltage branch and the variable frequency and variable voltage branch by adding two contactors, so as to meet the working requirements under different locomotive working conditions;

[0032] 2. A new dual auxiliary power supply system for traction converter of shunting locomotive provided by the present invention starts converter cooling fan in an intermittent manner by controlling two contactors, thereby effectively reducing energy loss and fan noise, and achieving the technical effect of energy saving and noise reduction;

[0033] 3. The present invention provides a new dual auxiliary power supply system for traction converter of shunting locomotive, in which the start timing of converter cooling fan can be set and adjusted according to different requirements (for example, by selecting temperature threshold), with high flexibility and strong applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 It is a schematic diagram of the circuit topology structure of the existing dual auxiliary power supply system of the traction converter of the shunting locomotive;

[0036] Figure 2 Schematic diagram of the circuit topology structure of the dual auxiliary power supply system of the traction converter of the shunting locomotive provided by the embodiment of the present invention;

[0037] Figure 3 The embodiment of the present invention is applied to Figure 2 Schematic diagram of the fan starting method of the dual auxiliary power supply system shown. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] like Figure 1 The figure shows a circuit structure topology diagram of a dual auxiliary power supply system used in locomotives in the prior art. In this figure:

[0040] Main circuit breaker 1, used to connect and disconnect the contact network. This figure shows a 25kV power grid;

[0041] Traction battery 2, used to provide power to the locomotive when there is no electricity;

[0042] Power transformer 3, used to step down the 25kV grid to the converter input voltage;

[0043] The chopper reactor 4 is used for energy storage and freewheeling, and works together with the DC chopper to realize DC step-up and step-down;

[0044] Rectifier 5, used to rectify the single-phase AC on the secondary side of the power transformer into DC;

[0045] The DC chopper 6 controls the IGBT to turn on and off, and works together with the chopper reactor to achieve DC voltage step-up and step-down;

[0046] An intermediate DC circuit 7, used to support an intermediate DC voltage;

[0047] Three-phase inverter 8, controls IGBT on and off, and outputs PWM voltage pulse width;

[0048] The filter component 9 includes an auxiliary transformer and a filter capacitor, which filters the PWM voltage into a sine wave after isolation;

[0049] The functional components 5 to 9 mentioned above, as well as a converter cooling fan and a charger are integrated in the traction converter 10 .

[0050] As mentioned above, for the dual auxiliary power supply system of the traction inverter of the shunting locomotive, the inverter cooling fan is connected to the variable frequency and voltage branch of the two auxiliary power supplies. When the locomotive is charging in the depot, it is necessary to start the variable frequency and voltage branch to start the cooling fan. In this case, since the charging current in the depot is limited, it will affect the charging efficiency of the traction battery. In addition, if the temperature of the transformer is high, the speed of the cooling fan needs to be increased to increase the cooling speed, but the working noise of the cooling fan will also increase.

[0051] In order to solve the above problems, the present invention proposes a new dual auxiliary power supply system for traction converter of shunting locomotive. Figure 2 The circuit structure of the dual auxiliary power supply system of the traction converter of the shunting locomotive of the present invention is shown as an example. In this system, the converter cooling fan is connected to the port of the external power load or the garage power supply of the constant frequency and constant voltage branch through the first contactor 11, and at the same time, the converter cooling fan is also connected to the port of the external power load of the variable frequency and voltage branch through the second contactor 12. Among them, the first contactor 11 and the second contactor 12 are connected to the controller of the converter (not shown in the figure) to act according to the instructions sent by the controller.

[0052] In order to achieve the purpose of energy saving and noise reduction, it is necessary to set a control logic to control the closing of the first contactor 11 and the second contactor 12, so as to start the inverter cooling fan. In particular, when the locomotive is in traction, braking or standby conditions, the inverter cooling fan can be disconnected from the constant frequency and constant voltage branch and connected to the variable frequency and voltage branch; and when the locomotive is in the garage charging condition, the inverter cooling fan can be disconnected from the variable frequency and voltage branch and intermittently connected to the constant frequency and constant voltage branch.

[0053] To this end, the present invention also provides a fan starting strategy applied to the dual auxiliary power supply system of the traction converter of the shunting locomotive. Figure 3 As shown, different starting methods are used to start the converter cooling fan according to different locomotive operating conditions.

[0054] The specific contents are as follows:

[0055] When the locomotive is in traction / braking / standby mode, the first contactor 11 is disconnected and the second contactor 12 is closed, so that the converter cooling fan is connected to the variable frequency and voltage branch of the auxiliary transformer power supply system to maintain continuous operation. During this period, the power supply voltage of the converter cooling fan can be adjusted by comprehensively considering multiple factors such as the temperature of the auxiliary transformer, the temperature of the converter cooling water and the temperature of the transformer;

[0056] When the locomotive is in the working condition of charging in the depot, the second contactor 12 is disconnected, and the second contactor 11 is intermittently closed or disconnected, so that the converter cooling fan is intermittently connected to the constant frequency and constant voltage branch of the auxiliary transformer power supply system. During this period, the power supply voltage of the converter cooling fan is provided by the power supply in the depot, and can be adjusted according to various factors such as the temperature of the auxiliary transformer and the temperature of the converter cooling water. The specific steps of the regulation are:

[0057] The first contactor 11 and the second contactor 12 are disconnected, and the traction converter is connected to the power supply in the depot, so that the traction battery is charged by the power supply in the depot. During the charging period, the temperature of the power unit of the traction converter and the temperature of the auxiliary transformer will gradually increase;

[0058] When the temperature of the auxiliary transformer or the temperature of the converter cooling water rises and exceeds the first temperature threshold, the first contactor 11 is closed and the converter cooling fan is started to dissipate heat, so that the temperature of the auxiliary transformer and the temperature of the converter cooling water are rapidly reduced. When the temperature of the auxiliary transformer or the temperature of the converter cooling water is reduced and falls below the second temperature threshold, the first contactor 11 is disconnected to stop the converter cooling fan.

[0059] In this way, the converter cooling fan operates intermittently until the traction battery is fully charged.

[0060] The above-mentioned dual auxiliary power supply system of the traction inverter of the shunting locomotive is equipped with two contactors, so that the inverter cooling fan can cleverly switch between the constant frequency and constant voltage branch and the variable frequency and voltage branch, meeting the working requirements under different locomotive operating conditions; and the starting timing of the inverter cooling fan can also be flexibly set and adjusted according to different needs (for example, through the selection of temperature thresholds). This intermittent way of starting the inverter cooling fan effectively reduces energy loss and fan noise, achieves the technical effect of energy saving and noise reduction, and has significant progressiveness.

[0061] It should be noted that those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0062] The devices, equipment, systems, modules or units described in the above embodiments may be implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer. Specifically, the computer may be, for example, a personal computer, a laptop computer, a vehicle-mounted human-computer interaction device, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0063] Although the present invention provides method operation steps as described in the embodiments or flow charts, more or fewer operation steps may be included based on conventional or non-creative means. The order of steps listed in the embodiments is only one way of executing the order of many steps and does not represent the only execution order. When the device or terminal product in practice is executed, it can be executed in sequence or in parallel according to the method shown in the embodiments or the drawings (for example, in a parallel processor or multi-threaded processing environment, or even in a distributed data processing environment).

[0064] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0065] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0066] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0067] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0068] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device, electronic device, and readable storage medium embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A dual auxiliary power supply system for traction converter of shunting locomotive, characterized in that: It includes a constant frequency and constant voltage branch, a variable frequency and voltage branch, a converter cooling fan, and two contactors, among which: The converter cooling fan is connected to the port of the external power load or garage power supply of the constant frequency and constant voltage branch through one of the two contactors, and is connected to the port of the external power load of the variable frequency and voltage branch through the other of the two contactors; The two contactors are configured to operate according to the operating conditions of the locomotive, so that when the locomotive is in traction, braking or standby conditions, the converter cooling fan can be disconnected from the constant frequency and constant voltage branch and connected to the variable frequency and voltage branch; and when the locomotive is in a garage charging condition, the converter cooling fan can be disconnected from the variable frequency and voltage branch and intermittently connected to the constant frequency and constant voltage branch.

2. The dual auxiliary power supply system for traction converter of shunting locomotive according to claim 1, characterized in that: The variable frequency and voltage conversion branch and the constant frequency and voltage branch are composed of a rectifier, a DC chopper, an intermediate DC circuit, two three-phase inverters, and two filter components, wherein: One end of the rectifier is externally connected to a power transformer, and the other end is connected to the intermediate DC circuit, so as to rectify the single-phase AC voltage on the secondary side of the power transformer into a DC voltage and provide it to the intermediate DC circuit; One end of the DC chopper is externally connected to a power battery pack, and the other end is connected to the intermediate DC circuit, so as to increase the DC voltage output by the power battery pack to the intermediate DC circuit, or reduce the DC voltage of the intermediate DC circuit to the power battery pack; The intermediate DC circuit is used to support the DC voltage; One end of one of the two three-phase inverters is connected to the intermediate DC circuit, and the other end is connected to an external power load or a garage power supply through a filter component, and is used to convert the DC voltage provided by the intermediate DC circuit into a PWM voltage, and then filter it into a sine wave, and provide it to the power load, or convert the AC voltage provided by the garage power supply into a DC voltage, and provide it to the intermediate DC circuit; One end of the other three-phase inverter of the two three-phase inverters is connected to the intermediate DC circuit, and the other end is externally connected to an electrical load through another filtering component, for converting the DC voltage provided by the intermediate DC circuit into a PWM voltage, which is then filtered into a sine wave and provided to the electrical load.

3. The dual auxiliary power supply system for traction converter of shunting locomotive according to claim 2, characterized in that: The ports of the two three-phase inverters connected to the filter components are also connected via a switch contactor.

4. The fan starting method of the dual auxiliary power supply system of the traction converter of the shunting locomotive according to claim 3 is characterized in that: The intermediate DC circuit includes a capacitor.

5. The fan starting method of the dual auxiliary power supply system of the traction converter of the shunting locomotive according to claim 4 is characterized in that: The filtering component includes an isolation transformer and a filtering capacitor.

6. A fan starting method applied to the dual auxiliary power supply system of the traction converter of a shunting locomotive as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: When the locomotive is in traction, braking or standby conditions, the two contactors are driven to operate, so that the converter cooling fan is disconnected from the constant frequency and constant voltage branch and connected to the variable frequency and voltage branch.

7. The fan starting method according to claim 6, characterized in that: The following steps are also included: When the locomotive is in traction, braking or standby conditions, the operating voltage of the converter cooling fan is regulated according to the temperature of the auxiliary voltage device, the temperature of the converter cooling water and the temperature of the transformer in the dual auxiliary power supply system.

8. A fan starting method applied to the dual auxiliary power supply system of the traction converter of a shunting locomotive as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: When the locomotive is in a charging state in the garage, the two contactors are driven to operate so that the converter cooling fan can be disconnected from the variable frequency and voltage branch and intermittently connected to the constant frequency and constant voltage branch.

9. The fan starting method according to claim 8, characterized in that: The converter cooling fan is intermittently connected to the constant frequency and constant voltage branch according to the temperature of the auxiliary voltage device and the temperature of the converter cooling water in the dual auxiliary power supply system.

10. The fan starting method according to claim 9, characterized in that: The method of intermittently connecting the converter cooling fan to the constant frequency and constant voltage branch according to the temperature of the auxiliary voltage device and the temperature of the converter cooling water in the dual auxiliary power supply system comprises the following steps: Disconnecting the converter cooling fan from the variable frequency and voltage branch and the constant frequency and voltage branch; Connecting the dual auxiliary power supply system to a garage power supply to charge the power battery pack; Monitor the temperature of the auxiliary voltage device and the temperature of the converter cooling water in the dual auxiliary power supply system. When the temperature of the auxiliary voltage device or the temperature of the converter cooling water rises above a first temperature threshold, connect the converter cooling fan to the constant frequency and constant voltage branch. When the temperature of the auxiliary voltage device and the temperature of the converter cooling water drop below a second temperature threshold, disconnect the converter cooling fan from the constant frequency and constant voltage branch.

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