Power-up control method, system and vehicle for a traction system

Abstract

The present disclosure relates to a power-on control method and system of a traction system and a vehicle, comprising: the traction system receiving a power-on instruction; a first traction unit controlling a pre-charging contactor to be closed; after the first traction unit and the second traction unit both confirm that the pre-charging contactor is successfully closed, pre-charging a first bus capacitor and a second bus capacitor; after the first traction unit confirms that the pre-charging of the first bus capacitor is completed and the second traction unit confirms that the pre-charging of the second bus capacitor is completed, the first traction unit and the second traction unit cooperatively control a main contactor to be closed; and after the first traction unit and the second traction unit both confirm that the main contactor is successfully closed, the first traction unit controls the pre-charging contactor to be disconnected. The control method of the traction system in the present application has a fast power-on speed, and the main contactor is cooperatively controlled by multiple traction units, so that the power-on process of the traction system is safe and reliable.

Description

Technical Field

[0001] This disclosure relates to the field of traction inverter power-on control technology, and in particular to a power-on control method, system and vehicle for a traction system. Background Technology

[0002] The traction inverter is a core component of a vehicle. Its main function is to convert grid voltage into variable voltage and variable frequency AC power to provide power to the motor, meet the requirements of traction and braking performance, and thus drive the motor to drive the vehicle. Therefore, the performance of the traction inverter directly affects the vehicle's operating condition.

[0003] In existing technologies, the commonly used pre-charge control method for traction inverters involves one traction inverter controlling one corresponding pre-charge circuit or multiple traction inverters sharing one pre-charge circuit. When multiple traction inverters share a pre-charge circuit, a separate control unit is required to control the pre-charge and high-voltage power-on processes, and this unit needs to exchange information with the traction inverters via network messages. Furthermore, for road electric vehicles, the pre-charge process of their drive system is generally controlled by the BMS (Battery Management System). The drive system cannot control the pre-charge process independently, and the success of pre-charge is determined by the BMS through messages received from the motor controller. Therefore, this approach has the following drawbacks: a separate control unit is required to control the pre-charge process, and information exchange and judgment via network messages introduce waiting time, thus increasing the pre-charge time. Additionally, pre-charge and power-on functions cannot be achieved in the event of a network failure. Summary of the Invention

[0004] To overcome the problems existing in related technologies, this disclosure provides a power-on control method, system, and vehicle for an ignition system.

[0005] According to a first aspect of the present disclosure, a power-on control method for a traction system is provided. The traction system includes at least a first traction unit and a second traction unit. The first traction unit includes a first bus capacitor, and the second traction unit includes a second bus capacitor. The first traction unit is connected to a high-voltage bus via a pre-charging unit. The pre-charging unit includes a main contactor and a pre-charging module. The main contactor is disposed on the high-voltage bus, and the pre-charging module is connected in parallel with the main contactor. The pre-charging module includes a pre-charging contactor and a pre-charging resistor. The second traction unit is connected in parallel with the first traction unit. The method includes:

[0006] The traction system receives a power-on command;

[0007] The first traction unit controls the pre-charge contactor to close;

[0008] After both the first traction unit and the second traction unit confirm that the pre-charge contactor has been successfully closed, the first bus capacitor and the second bus capacitor are pre-charged.

[0009] After the first traction unit confirms that the pre-charging of the first bus capacitor is complete and the second traction unit confirms that the pre-charging of the second bus capacitor is complete, the first traction unit and the second traction unit jointly control the main contactor to close.

[0010] After both the first traction unit and the second traction unit confirm that the main contactor has been successfully closed, the first traction unit controls the precharge contactor to open.

[0011] In some embodiments, before precharging the first bus capacitor and the second bus capacitor after both the first traction unit and the second traction unit have confirmed that the precharge contactor has been successfully closed, the method further includes:

[0012] The first traction unit determines whether the pre-charge contactor is closed within a first preset time period;

[0013] If so, the first traction unit confirms that the pre-charge contactor has been successfully closed; otherwise, it exits the power-on process of the traction system.

[0014] The second traction unit determines whether the pre-charge contactor is closed within a second preset time period;

[0015] If so, the second traction unit confirms that the pre-charge contactor has been successfully closed; otherwise, it exits the power-on process of the traction system.

[0016] In some embodiments, after the first traction unit confirms that the pre-charging of the first bus capacitor is complete and the second traction unit confirms that the pre-charging of the second bus capacitor is complete, and before the first traction unit and the second traction unit jointly control the main contactor to close, the method further includes:

[0017] The first traction unit determines whether the difference between the bus voltage and the terminal voltage of the first bus capacitor is less than or equal to the first preset voltage within a third preset time and whether the duration reaches a fourth preset time.

[0018] If so, the first traction unit confirms that the first bus capacitor has been pre-charged; otherwise, it exits the power-on process of the traction system.

[0019] The second traction unit determines whether the difference between the bus voltage and the terminal voltage of the second bus capacitor is less than or equal to the first preset voltage within a third preset time and whether the duration reaches a fourth preset time.

[0020] If so, the second traction unit confirms that the second bus capacitor is pre-charged; otherwise, it exits the power-on process of the traction system.

[0021] Furthermore, the third preset time is determined based on the size of the pre-charge resistor, the size of the first bus capacitor, and the size of the second bus capacitor.

[0022] In some embodiments, the first traction unit and the second traction unit cooperate to control the closing of the main contactor, including:

[0023] The first traction unit outputs a high-level signal to one end of the inductor coil of the main contactor, and the second traction unit outputs a low-level signal to the other end of the inductor coil of the main contactor. The inductor coil is energized to close the main contactor.

[0024] In some embodiments, before the first traction unit controls the precharge contactor to open after both the first traction unit and the second traction unit have confirmed that the main contactor has been successfully closed, the method further includes:

[0025] Within a fourth preset time period, the first traction unit determines whether the main contactor is closed;

[0026] If so, the first traction unit confirms that the main contactor has been successfully closed; otherwise, it exits the power-on process of the traction system.

[0027] During the fourth preset time period, the second traction unit determines whether the main contactor is closed;

[0028] If so, the second traction unit confirms that the main contactor has been successfully closed; otherwise, it exits the power-on process of the traction system.

[0029] In some embodiments, after the first traction unit controls the precharge contactor to disconnect, the system further includes:

[0030] Within a fifth preset time period, the first traction unit determines whether the pre-charge contactor is disconnected;

[0031] If so, the first traction unit is successfully powered on; otherwise, the power-on process of the traction system is exited.

[0032] Within a sixth preset time period, the second traction unit determines whether the pre-charge contactor is disconnected;

[0033] If so, the second traction unit is successfully powered on; otherwise, the power-on process of the traction system is exited.

[0034] In some embodiments, before the first traction unit controls the precharge contactor to close, the method further includes:

[0035] The first traction unit and the second traction unit each perform self-tests;

[0036] If both the first traction unit and the second traction unit pass the self-test, the power-on process of the traction system will begin.

[0037] According to a second aspect of the present disclosure, a traction system is provided, the traction system comprising at least a first traction unit and a second traction unit, the first traction unit comprising a first bus capacitor, the second traction unit comprising a second bus capacitor, the first traction unit being connected to a high-voltage bus via a pre-charging unit, the pre-charging unit comprising a main contactor and a pre-charging module, the main contactor being disposed on the high-voltage bus, the pre-charging module being connected in parallel with the main contactor, the pre-charging module comprising a pre-charging contactor and a pre-charging resistor, the second traction unit being connected in parallel with the first traction unit, the traction system specifically used for:

[0038] The traction system receives a power-on command;

[0039] The first traction unit controls the pre-charge contactor to close;

[0040] After both the first traction unit and the second traction unit confirm that the pre-charge contactor has been successfully closed, the first bus capacitor and the second bus capacitor are pre-charged.

[0041] After the first traction unit confirms that the pre-charging of the first bus capacitor is complete and the second traction unit confirms that the pre-charging of the second bus capacitor is complete, the first traction unit and the second traction unit jointly control the main contactor to close.

[0042] After both the first traction unit and the second traction unit confirm that the main contactor has been successfully closed, the first traction unit controls the precharge contactor to open.

[0043] According to a third aspect of the present disclosure, a vehicle is provided, including the traction system as described in the second aspect.

[0044] The technical solutions provided by the embodiments of this disclosure can include the following beneficial effects: the pre-charging circuit is jointly detected and controlled by multiple control units. Each traction inverter can only close the main contactor after pre-charging is completed. This ensures that each traction inverter can be fully pre-charged and avoids voltage surges caused by insufficient pre-charging, which could lead to contactor burning, adhesion, or unsuccessful pre-charging. Furthermore, multiple control units simultaneously detect the status of a contactor, avoiding detection errors caused by a fault in a single control unit or its detection circuit, resulting in more reliable detection results. Compared to the prior art requiring a separate control unit, this application requires no additional hardware, resulting in lower costs. Moreover, in this application, the main contactor can be closed immediately after all traction inverters have completed pre-charging, eliminating the need for information exchange and judgment via network messages as in the prior art, thus shortening the pre-charging time. The power-on process does not require network message exchange; it can be achieved solely through its own status detection information. Even in the event of a network failure, the pre-charging and high-voltage power-on functions can still be achieved upon receiving the power-on command.

[0045] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0046] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0047] Figure 1 This is a flowchart illustrating an energization control method for a traction system according to an exemplary embodiment.

[0048] Figure 2 This is a schematic diagram of a traction system according to an exemplary embodiment.

[0049] Figure 3 This is a control principle diagram illustrating the pre-charging and high-voltage power-on of a traction system according to an exemplary embodiment. Detailed Implementation

[0050] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0051] Figure 1This is a flowchart illustrating a power-on control method for a traction system according to an exemplary embodiment. The traction system includes at least a first traction unit and a second traction unit. The first traction unit includes a first bus capacitor, and the second traction unit includes a second bus capacitor. The first traction unit is connected to a high-voltage bus via a pre-charging unit. The pre-charging unit includes a main contactor and a pre-charging module. The main contactor is disposed on the high-voltage bus, and the pre-charging module is connected in parallel with the main contactor. The pre-charging module includes a pre-charging contactor and a pre-charging resistor. The second traction unit is connected in parallel with the first traction unit. The method includes the following steps:

[0052] In step S101, the traction system receives a power-on command.

[0053] Specifically, when the traction system needs to be powered on, it needs to receive a power-on command to execute subsequent power-on operations.

[0054] In step S102, the first traction unit controls the pre-charge contactor to close.

[0055] Specifically, such as Figure 2 As shown, KM1 is the main contactor of the pre-charging circuit, KM2 is the pre-charging contactor, and R1 is the pre-charging resistor, located on the high-voltage positive terminal of the system. The remaining symbols and devices are as follows: traction inverter 1 (first traction unit) and traction inverter 2 (second traction unit), with their corresponding control units TCU1 and TCU2 respectively; V1, V2, and V3 are voltage measurement sensors; A1, A2, and A3 are current measurement sensors; L1 and L2 are reactors, forming LC filter circuits with bus capacitors C1 and C2 respectively; R2 and R3 are passive discharge resistors, which dissipate the energy of the bus capacitor through R1 and R2 after the main circuit is de-energized; D1 and D2 are DC-AC power devices; and M1 and M2 are drive motors.

[0056] like Figure 3As shown, to achieve control and status monitoring of the high-voltage system from the low-voltage system, a low-voltage relay inductor coil is needed to control the opening and closing of the high-voltage contactor, and a separate linkage low-voltage switch is set up to detect the closed state of the contactor. Q1 and Q2 are the control contactor inductors of the main contactor KM1 and the pre-charge contactor KM2, respectively, and K1 and K2 are the status detection switches for KM1 and KM2, respectively. The inductor coil Q2 of KM2 is controlled by TCU1, with its positive and negative terminals connected to control interfaces 4 and 5 of TCU1, respectively. When interfaces 4 and 5 receive different level signals, inductor coil Q2 is energized, and KM2 closes. The inductor coil Q1 of KM1 is jointly controlled by TCU1 and TCU2, with its positive and negative terminals connected to control interface 1 of TCU1 and control interface 8 of TCU2, respectively. When interface 1 is at a high level and interface 2 is at a low level, inductor coil Q1 is energized, and KM1 closes. The status detection switch K1 of KM1 is connected to detection interface 2 of TCU1 and detection interface 7 of TCU2. The status detection switch K2 of KM2 is connected to the detection interface 3 of TCU1 and the detection interface 6 of TCU2 respectively.

[0057] Combination Figure 2 and Figure 3 When the traction system receives the power-on command, TCU1, i.e. the first traction unit, controls the inductor coil Q2 to be energized, which in turn attracts the pre-charge contactor KM2 and begins the pre-charge process.

[0058] In some embodiments, before the first traction unit controls the precharge contactor to close, the method further includes:

[0059] The first traction unit and the second traction unit each perform self-tests;

[0060] If both the first traction unit and the second traction unit pass the self-test, the power-on process of the traction system will begin.

[0061] Specifically, when TCU1 (the first traction unit) and TCU2 (the second traction unit) receive the high-voltage power-on command, they perform a self-check to confirm that the status is normal (including confirming that the status of KM1 and KM2 is normal) and the front-end voltage is within the set range (confirming that the front end has been powered on by high voltage), i.e., U1≤U≤U2, they enter the pre-charging process; otherwise, they report "pre-charging failed". The values ​​of U1 and U2 are 500V-900V or 1000V-1800V.

[0062] In step S103, after both the first traction unit and the second traction unit confirm that the pre-charge contactor has been successfully closed, the first bus capacitor and the second bus capacitor are pre-charged.

[0063] Specifically, after both the first traction unit TCU1 and the second traction unit TCU2 confirm that the pre-charge contactor has been successfully closed, the first bus capacitor C1 and the second bus capacitor C2 are pre-charged.

[0064] In some embodiments, before precharging the first bus capacitor and the second bus capacitor after both the first traction unit and the second traction unit have confirmed that the precharge contactor has been successfully closed, the method further includes:

[0065] The first traction unit determines whether the pre-charge contactor is closed within a first preset time period;

[0066] If so, the first traction unit confirms that the pre-charge contactor has been successfully closed; otherwise, it exits the power-on process of the traction system.

[0067] The second traction unit determines whether the pre-charge contactor is closed within a second preset time period;

[0068] If so, the second traction unit confirms that the pre-charge contactor has been successfully closed; otherwise, it exits the power-on process of the traction system.

[0069] Specifically, TCU1 controls the inductor coil Q2 to be energized, which engages the pre-charge contactor KM2, initiating pre-charging. After a waiting time t1 (the first preset time), if TCU1 detects that K2 is closed, it confirms that the pre-charge contactor KM2 is closed and pre-charging has begun. TCU1's status feedback changes from "not pre-charging" to "pre-charging in progress." Otherwise, it controls the disconnection of KM2, exiting the high-voltage power-on process, and the status feedback is "pre-charging failed," ending the power-on process. Similarly, after receiving the high-voltage power-on command, if TCU2 detects that KM2 is closed at t6 (the second preset time), its status feedback changes from "not pre-charging" to "pre-charging in progress." Otherwise, it exits the high-voltage power-on process, and the status feedback is "pre-charging failed," ending the power-on process. K1 and K2 are the status detection switches for KM1 and KM2, respectively. t1 = 500ms, t6 = 3s.

[0070] In step S104, after the first traction unit confirms that the first bus capacitor has been pre-charged and the second traction unit confirms that the second bus capacitor has been pre-charged, the first traction unit and the second traction unit jointly control the main contactor to close.

[0071] In some embodiments, the first traction unit and the second traction unit cooperate to control the closing of the main contactor, including:

[0072] The first traction unit outputs a high-level signal to one end of the inductor coil of the main contactor, and the second traction unit outputs a low-level signal to the other end of the inductor coil of the main contactor. The inductor coil is energized to close the main contactor.

[0073] Specifically, after TCU1 determines that the pre-charging is complete, it outputs a high level through control interface 1. After TCU2 determines that the pre-charging is complete, it outputs a low level through control interface 8, which energizes the inductor coil Q1 and completes the closing of the main contactor KM1 command.

[0074] In some embodiments, after the first traction unit confirms that the pre-charging of the first bus capacitor is complete and the second traction unit confirms that the pre-charging of the second bus capacitor is complete, and before the first traction unit and the second traction unit jointly control the main contactor to close, the method further includes:

[0075] The first traction unit determines whether the difference between the bus voltage and the terminal voltage of the first bus capacitor is less than or equal to the first preset voltage within a third preset time and whether the duration reaches a fourth preset time.

[0076] If so, the first traction unit confirms that the first bus capacitor has been pre-charged; otherwise, it exits the power-on process of the traction system.

[0077] The second traction unit determines whether the difference between the bus voltage and the terminal voltage of the second bus capacitor is less than or equal to the first preset voltage within a third preset time and whether the duration reaches a fourth preset time.

[0078] If so, the second traction unit confirms that the second bus capacitor is pre-charged; otherwise, it exits the power-on process of the traction system.

[0079] Specifically, TCU1 and TCU2 continuously monitor the voltage across the bus capacitor and simultaneously time the pre-charging process. If, within the third preset time t3, the voltage difference across the first bus capacitor C1 is ≤ U3 (the first preset voltage), and the duration is not less than t2 (the fourth preset time), then the pre-charging voltage meets the requirements, and the status feedback is updated to "Pre-charging complete." Otherwise, TCU1 controls the disconnection of KM2, exiting the high-voltage power-on process, and the status feedback is "Pre-charging failed." Similarly, if, within the third preset time t3, the voltage difference across the second bus capacitor C2 is ≤ U3 (the first preset voltage), and the duration is not less than t2 (the fourth preset time), then the pre-charging voltage meets the requirements, and the status feedback is updated to "Pre-charging complete." Otherwise, TCU2 controls the disconnection of KM2, exiting the high-voltage power-on process, and the status feedback is "Pre-charging failed," ending the power-on process. Here, U3 is 50V, and t2 = 1s.

[0080] Furthermore, the third preset time is determined based on the size of the pre-charge resistor, the size of the first bus capacitor, and the size of the second bus capacitor.

[0081] Specifically, the third preset time t3 is calculated based on the values ​​of the bus capacitors C1 and C2 and the pre-charge resistor R1, with a certain margin.

[0082] In step S105, after both the first traction unit and the second traction unit confirm that the main contactor has been successfully closed, the first traction unit controls the precharge contactor to open.

[0083] Specifically, after both the first traction unit and the second traction unit confirm that the main contactor has been successfully closed, the first traction unit controls the pre-charge contactor KM2 to open, thus completing the process of simultaneously powering on multiple traction systems.

[0084] In some embodiments, before the first traction unit controls the precharge contactor to open after both the first traction unit and the second traction unit have confirmed that the main contactor has been successfully closed, the method further includes:

[0085] Within a fourth preset time period, the first traction unit determines whether the main contactor is closed;

[0086] If so, the first traction unit confirms that the main contactor has been successfully closed; otherwise, it exits the power-on process of the traction system.

[0087] During the fourth preset time period, the second traction unit determines whether the main contactor is closed;

[0088] If so, the second traction unit confirms that the main contactor has been successfully closed; otherwise, it exits the power-on process of the traction system.

[0089] Specifically, if TCU1 detects that KM1 is closed within time t4 (the fourth preset time), the status feedback is updated to "Pre-charge successful"; otherwise, KM2 and KM1 are disconnected, the high-voltage power-on process is exited, and the status feedback is "Pre-charge failed". Similarly, if TCU2 detects that KM1 is closed within time t4, the status feedback is updated to "Pre-charge successful"; otherwise, KM1 is disconnected, the high-voltage power-on process is exited, and the status feedback is "Pre-charge failed". Here, t4 = 2 seconds.

[0090] In some embodiments, after the first traction unit controls the precharge contactor to disconnect, the system further includes:

[0091] Within a fifth preset time period, the first traction unit determines whether the pre-charge contactor is disconnected;

[0092] If so, the first traction unit is successfully powered on; otherwise, the power-on process of the traction system is exited.

[0093] Within a sixth preset time period, the second traction unit determines whether the pre-charge contactor is disconnected;

[0094] If so, the second traction unit is successfully powered on; otherwise, the power-on process of the traction system is exited.

[0095] Specifically, after KM1 is closed, TCU1 controls the opening of KM2. If, within time t5 (the fifth preset time), TCU1 detects that KM2 is in an open state, the status feedback is updated to "Power-on successful"; otherwise, it controls the opening of both KM2 and KM1, and the status feedback is "Power-on failed". TCU2 only needs to detect the status of KM2 for judgment. If, within time t7 (the sixth preset time), TCU2 detects that KM2 is in an open state, the status feedback is updated to "Power-on successful"; otherwise, it controls the opening of KM1, and the status feedback is "Power-on failed". Here, t5 = t7 = 200ms.

[0096] This application also discloses a traction system, which includes at least a first traction unit and a second traction unit. The first traction unit includes a first bus capacitor, and the second traction unit includes a second bus capacitor. The first traction unit is connected to a high-voltage bus via a pre-charging unit. The pre-charging unit includes a main contactor and a pre-charging module. The main contactor is disposed on the high-voltage bus, and the pre-charging module is connected in parallel with the main contactor. The pre-charging module includes a pre-charging contactor and a pre-charging resistor. The second traction unit is connected in parallel with the first traction unit. The traction system is specifically used for:

[0097] The traction system receives a power-on command;

[0098] The first traction unit controls the pre-charge contactor to close;

[0099] After both the first traction unit and the second traction unit confirm that the pre-charge contactor has been successfully closed, the first bus capacitor and the second bus capacitor are pre-charged.

[0100] After the first traction unit confirms that the pre-charging of the first bus capacitor is complete and the second traction unit confirms that the pre-charging of the second bus capacitor is complete, the first traction unit and the second traction unit jointly control the main contactor to close.

[0101] After both the first traction unit and the second traction unit confirm that the main contactor has been successfully closed, the first traction unit controls the precharge contactor to open.

[0102] The specific manner of executing the operation method in the above embodiments has been described in detail in the embodiments related to the method, and will not be elaborated here.

[0103] This application also discloses a vehicle comprising: a traction system as described in the second aspect, wherein the traction system described in the second aspect performs the power-on control method of the traction system as described in the first aspect.

[0104] In summary, the pre-charging circuit is jointly detected and controlled by multiple control units. Each traction inverter must complete pre-charging before closing the main contactor. This ensures sufficient pre-charging for each traction inverter and avoids voltage surges caused by insufficient pre-charging, which could lead to contactor burnout, adhesion, or unsuccessful pre-charging. Furthermore, the simultaneous detection of a contactor's status by multiple control units prevents errors caused by faults in a single control unit or its detection circuit, resulting in more reliable detection results. Compared to existing technologies requiring a separate control unit, this application requires no additional hardware, resulting in lower costs. Moreover, this application allows for immediate main contactor closure after all traction inverters have completed pre-charging, eliminating the need for network message interaction and judgment as in existing technologies, thus shortening pre-charging time. The power-on process also eliminates the need for network message interaction, relying solely on its own status detection information. Even in the event of a network failure, the pre-charging and high-voltage power-on functions can still be achieved upon receiving the power-on command.

[0105] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0106] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method of power-on control of a traction system, characterized in that, The traction system includes at least a first traction unit and a second traction unit. The first traction unit includes a first bus capacitor, and the second traction unit includes a second bus capacitor. The first traction unit is connected to a high-voltage bus via a pre-charging unit. The pre-charging unit includes a main contactor and a pre-charging module. The main contactor is disposed on the high-voltage bus, and the pre-charging module is connected in parallel with the main contactor. The pre-charging module includes a pre-charging contactor and a pre-charging resistor. The second traction unit is connected in parallel with the first traction unit. The method includes: The traction system receives the power-on command; The first traction unit controls the pre-charge contactor to close; After both the first traction unit and the second traction unit confirm that the pre-charge contactor has been successfully closed, the first bus capacitor and the second bus capacitor are pre-charged. After the first traction unit confirms that the first bus capacitor is pre-charged and the second traction unit confirms that the second bus capacitor is pre-charged, the first traction unit outputs a high-level signal to one end of the inductor coil of the main contactor, and the second traction unit outputs a low-level signal to the other end of the inductor coil of the main contactor. The inductor coil is energized to close the main contactor. After both the first traction unit and the second traction unit confirm that the main contactor has been successfully closed, the first traction unit controls the precharge contactor to open.

2. The power-up control method of a traction system according to claim 1, characterized in that, After both the first traction unit and the second traction unit confirm that the pre-charge contactor has been successfully closed, but before pre-charging the first bus capacitor and the second bus capacitor, the method further includes: The first traction unit determines whether the pre-charge contactor is closed within a first preset time period; If so, the first traction unit confirms that the pre-charge contactor has been successfully closed; otherwise, it exits the power-on process of the traction system. The second traction unit determines whether the pre-charge contactor is closed within a second preset time period; If so, the second traction unit confirms that the pre-charge contactor has been successfully closed; otherwise, it exits the power-on process of the traction system.

3. The power-up control method of a towing system according to claim 1, characterized in that, After the first traction unit confirms that the pre-charging of the first bus capacitor is complete and the second traction unit confirms that the pre-charging of the second bus capacitor is complete, before the first traction unit and the second traction unit jointly control the main contactor to close, the following steps are included: The first traction unit determines whether the difference between the bus voltage and the terminal voltage of the first bus capacitor is less than or equal to the first preset voltage within a third preset time and whether the duration reaches a fourth preset time. If so, the first traction unit confirms that the first bus capacitor has been pre-charged; otherwise, it exits the power-on process of the traction system. The second traction unit determines whether the difference between the bus voltage and the terminal voltage of the second bus capacitor is less than or equal to the first preset voltage within a third preset time and whether the duration reaches a fourth preset time. If so, the second traction unit confirms that the second bus capacitor is pre-charged; otherwise, it exits the power-on process of the traction system.

4. The power-up control method of a traction system according to claim 3, characterized in that, The third preset time is determined based on the size of the pre-charge resistor, the size of the first bus capacitor, and the size of the second bus capacitor.

5. The power-up control method of a towing system according to claim 1, characterized in that, After both the first traction unit and the second traction unit confirm that the main contactor has been successfully closed, and before the first traction unit controls the pre-charge contactor to open, the process further includes: Within a fourth preset time period, the first traction unit determines whether the main contactor is closed; If so, the first traction unit confirms that the main contactor has been successfully closed; otherwise, it exits the power-on process of the traction system. During the fourth preset time period, the second traction unit determines whether the main contactor is closed; If so, the second traction unit confirms that the main contactor has been successfully closed; otherwise, it exits the power-on process of the traction system.

6. The power-up control method of a towing system according to claim 1, characterized in that, After the first traction unit controls the precharge contactor to disconnect, it further includes: Within a fifth preset time period, the first traction unit determines whether the pre-charge contactor is disconnected; If so, the first traction unit is successfully powered on; otherwise, the power-on process of the traction system is exited. Within a sixth preset time period, the second traction unit determines whether the pre-charge contactor is disconnected; If so, the second traction unit is successfully powered on; otherwise, the power-on process of the traction system is exited.

7. The power-up control method of a towing system according to any one of claims 1-6, characterized in that, Before the first traction unit controls the pre-charge contactor to close, the following is also included: The first traction unit and the second traction unit each perform self-tests; If both the first traction unit and the second traction unit pass the self-test, the power-on process of the traction system will begin.

8. A traction system characterized in that, The traction system includes at least a first traction unit and a second traction unit. The first traction unit includes a first bus capacitor, and the second traction unit includes a second bus capacitor. The first traction unit is connected to a high-voltage bus via a pre-charging unit. The pre-charging unit includes a main contactor and a pre-charging module. The main contactor is disposed on the high-voltage bus, and the pre-charging module is connected in parallel with the main contactor. The pre-charging module includes a pre-charging contactor and a pre-charging resistor. The second traction unit is connected in parallel with the first traction unit. The traction system is specifically used for: The traction system receives a power-on command; The first traction unit controls the pre-charge contactor to close; After both the first traction unit and the second traction unit confirm that the pre-charge contactor has been successfully closed, the first bus capacitor and the second bus capacitor are pre-charged. After the first traction unit confirms that the first bus capacitor is pre-charged and the second traction unit confirms that the second bus capacitor is pre-charged, the first traction unit outputs a high-level signal to one end of the inductor coil of the main contactor, and the second traction unit outputs a low-level signal to the other end of the inductor coil of the main contactor. The inductor coil is energized to close the main contactor. After both the first traction unit and the second traction unit confirm that the main contactor has been successfully closed, the first traction unit controls the precharge contactor to open.

9. A vehicle characterized by comprising: include: The traction system according to claim 8.

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