Battery pack switching method, system, and vehicle

Abstract

This application provides a battery pack switching method, system, and vehicle. The method includes: in response to a battery pack switching request, determining the vehicle's operating conditions and target voltage requirements; under driving conditions, controlling the motor to make the DC bus current less than a first preset value, then switching the connection mode of multiple battery packs based on the target voltage requirements; after the switching is completed, if it is determined that the motor's back electromotive force matches the voltage of the switched battery pack, establishing a high-voltage connection between the switched battery pack and the bus capacitor; under parking conditions, discharging the bus capacitor to make its voltage less than a second preset value, then switching the connection mode of multiple battery packs based on the target voltage requirements; after the switching is completed, if it is determined that the voltage of the bus capacitor matches the voltage of the switched battery pack, establishing a high-voltage connection between the switched battery pack and the bus capacitor. This invention achieves adaptive switching of the battery pack based on operating conditions and target voltage.

Description

Technical Field

[0001] This application relates to battery management technology, and more particularly to a battery pack switching method, system, and vehicle. Background Technology

[0002] In new energy vehicles, multi-battery pack systems (e.g., including three or more battery packs) can achieve power supply flexibility and safety redundancy through series and parallel connections, ensuring that power is not lost when one battery pack fails. However, most existing multi-battery pack switching solutions can only be performed under parking conditions, and cannot achieve seamless switching during driving. Furthermore, the switching method is singular and difficult to flexibly adapt to different voltage requirements. Summary of the Invention

[0003] This application provides a battery pack switching method, system, and vehicle that can adaptively switch the connection mode of multiple battery packs under driving and parking conditions to flexibly adapt to different voltage requirements, and achieve seamless switching of battery packs under driving conditions and safe switching of battery packs under parking conditions.

[0004] The technical solution of this application embodiment is implemented as follows: This application provides a battery pack switching method applied to a vehicle including a battery pack switching circuit. The battery pack switching circuit includes multiple battery packs, a bus capacitor, and a motor. The method includes: In response to a battery pack switching request, the vehicle's operating conditions and target voltage requirements are determined. When the operating condition is the driving condition, the motor is controlled to make the DC bus current in the battery pack switching circuit less than a first preset value. Then, the connection mode of the multiple battery packs is switched based on the target required voltage. After the switching is completed, if it is determined that the back electromotive force of the motor matches the voltage of the switched battery pack, a high-voltage connection is established between the switched battery pack and the bus capacitor. When the operating condition is a parking condition, the bus capacitor is discharged so that the voltage of the bus capacitor is less than a second preset value. Then, the connection mode of the multiple battery packs is switched based on the target required voltage. After the switching is completed, if it is determined that the voltage of the bus capacitor matches the voltage of the switched battery pack, a high-voltage connection is established between the switched battery pack and the bus capacitor.

[0005] This application provides a battery pack switching system, including: an integrated power unit, a battery management system, and a vehicle controller, wherein the integrated power unit and the battery management system are both connected to the vehicle controller; The vehicle controller is used to respond to a battery pack switching request, determine the vehicle's operating conditions and target voltage requirements, and send control commands to the integrated power unit and the battery management system based on the operating conditions and target voltage requirements. The integrated power unit is used to control the motor according to the battery pack switching method provided in the embodiments of this application, based on the control commands sent by the vehicle controller. The battery management system is used to switch the connection mode of the multiple battery packs and establish a high-voltage connection between the switched battery pack and the bus capacitor based on the control commands sent by the vehicle controller, according to the battery pack switching method provided in the embodiments of this application.

[0006] This application provides a vehicle including a battery pack switching system as described in this application embodiment.

[0007] The embodiments of this application have the following beneficial effects: First, by responding to the battery pack switching request and determining the vehicle's operating conditions and target voltage requirements, the system then controls the motor to ensure the DC bus current is below a first preset value during driving, creating conditions for subsequent no-load switching and safe high-voltage connection establishment, thus avoiding high-voltage surges. Next, the system switches the battery pack connection method based on the target voltage requirements to flexibly adapt to different voltage needs. After switching, ensuring the motor back EMF matches the switched battery pack voltage, a high-voltage connection is established between the switched battery pack and the bus capacitor, achieving seamless switching without interrupted power or perceptible driving experience during driving. During parking, the system actively discharges the bus capacitor to reduce its voltage below a second preset value, then switches the battery pack connection method based on the target voltage requirements to flexibly adapt to different voltage needs. Finally, ensuring the bus capacitor voltage matches the switched battery pack voltage, a high-voltage connection is established between the switched battery pack and the bus capacitor, effectively achieving safe switching during parking. Attached Figure Description

[0008] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the specification, serve to explain the technical solutions of this application. Obviously, the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0009] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0010] Figure 1 This is a schematic flowchart of a battery pack switching method provided in an embodiment of this application; Figure 2 This is a schematic diagram of a battery pack switching process under driving conditions provided in an embodiment of this application; Figure 3 This is a schematic diagram of a battery pack switching process under parking conditions provided in an embodiment of this application; Figure 4 This is a schematic diagram of the topology of a battery pack switching circuit provided in an embodiment of this application; Figure 5 This is one of the interactive flow diagrams of a battery pack switching system provided in the embodiments of this application; Figure 6 This is a second schematic diagram of the interaction flow of a battery pack switching system provided in an embodiment of this application; Figure 7 This is the third interactive flowchart of a battery pack switching system provided in this application embodiment; Figure 8 This is the fourth interactive flowchart of a battery pack switching system provided in the embodiments of this application. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the specific technical solutions of this application will be further described in detail below with reference to the accompanying drawings of the embodiments of this application. The following embodiments are used to illustrate this application, but are not intended to limit the scope of this application.

[0012] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0013] In the following description, references to "some embodiments," "this embodiment," "this application embodiment," and examples, etc., describe a subset of all possible embodiments. However, it is understood that "some embodiments" may be the same subset or different subset of all possible embodiments and may be combined with each other without conflict.

[0014] The terms "first," "second," and "third" appearing in the embodiments of this application do not have a specific meaning (e.g., there is no order, nor does it indicate a special limitation on the number of devices in the embodiments of this application), but are merely for the purpose of clearly describing the embodiments of this application and do not constitute any limitation on the embodiments of this application. The term "multiple" appearing in the embodiments of this application refers to two or more integers.

[0015] To facilitate understanding of the technical solutions of the embodiments of this application, the relevant technologies or terms of the embodiments of this application are described below. The following related technologies or related terms are optional solutions and can be combined with the technical solutions of the embodiments of this application in any way, and all of them fall within the protection scope of the embodiments of this application.

[0016] In new energy vehicles, multi-core battery pack solutions (such as dividing the battery pack into areas A, B, and C, and using multiple (more than or equal to 2) 400V battery packs) have been applied. When a battery pack fails, the faulty pack can be immediately disconnected and other normal battery packs can be used to continue supplying power through series and parallel connection, thereby ensuring that the vehicle's power is not lost and achieving safety redundancy.

[0017] However, the inventors of this application found in their research and analysis that the multi-core battery pack solution still faces the problem of a single switching method in practical applications, which makes it difficult to meet the needs of vehicles for flexible adaptation to multiple voltage levels under actual operating conditions, and the switching process is subject to high voltage impact risk.

[0018] To address at least one of the aforementioned problems in related technologies, this application provides a battery pack switching method. This method is applied to a vehicle including a battery pack switching circuit, which comprises multiple battery packs, a bus capacitor, and a motor. The battery pack switching circuit is a high-voltage electrical topology for connecting multiple battery packs, the bus capacitor, and the motor. It can control the series and parallel connections between the multiple battery packs and the on / off switching between the multiple battery packs and the bus capacitor through components such as pre-charge relays, main relays, and a switch matrix, thereby achieving outputs at different voltage levels. The battery pack switching method provided in this application will be described in detail below with reference to the accompanying drawings.

[0019] Figure 1 This is a flowchart illustrating a battery pack switching method provided in an embodiment of this application; as shown... Figure 1 As shown, the method may include the following steps 101 to 103: Step 101: In response to the battery pack switching request, determine the vehicle's operating conditions and target required voltage.

[0020] It should be noted that a battery pack switching request refers to an event or command that triggers a battery pack switching process. A battery pack switching request can be triggered by changes in the vehicle's driving mode (such as switching from Sport mode to Eco mode), changes in charging demand (such as connecting to a charging station with a different voltage level), battery pack malfunctions, or voltage balancing management.

[0021] It should be noted that the vehicle's operating condition refers to its current working state, including driving condition (the vehicle is in motion) and parking condition (the vehicle is stationary, such as in P / N gear with electronic parking brake activated). The target required voltage refers to the desired output voltage determined based on the battery pack switching request, such as higher voltage required for sport mode or a matching voltage level required by the charging station.

[0022] In some embodiments, when the Vehicle Control Unit (VCU) or Battery Management System (BMS) detects an event requiring battery pack switching, it generates a battery pack switching request. The VCU determines whether the vehicle is in a driving or parked state based on information such as current vehicle speed and gear, and simultaneously determines the target required voltage based on the type of battery pack switching request. For example, when the driver switches from Eco mode to Sport mode, the VCU determines the target required voltage to be 800V (two 400V battery packs connected in series); when connected to a 400V charging station, the VCU determines the target required voltage to be 400V (battery packs connected in parallel).

[0023] Step 102: When the operating condition is the driving condition, the motor is controlled to make the DC bus current in the battery pack switching circuit less than a first preset value. Then, the connection mode of the multiple battery packs is switched based on the target required voltage. After the switching is completed, if it is determined that the back electromotive force of the motor matches the voltage of the switched battery pack, a high-voltage connection is established between the switched battery pack and the bus capacitor.

[0024] In some embodiments, the motor can be controlled to enter a zero-torque mode (quadrature-axis current Iq=0), making the motor output torque zero, thereby causing the DC bus current to approach zero or be less than a first preset value (e.g., 5A), creating conditions for subsequent no-load switching. The first preset value is the maximum limit of the relay load switch (typically 5A), used to ensure the relay operates under low-current conditions.

[0025] In some embodiments, the series and parallel connection relationship between multiple battery packs can be changed by controlling the relays in the switch matrix of the battery pack switching circuit to achieve different voltage level outputs, thereby adapting to different voltage requirements.

[0026] In some embodiments, under driving conditions, the VCU can send control commands to the Integrated Power Unit (IPU) to control the IPU to adjust the motor's quadrature-axis current Iq to 0, thereby reducing the motor's output torque to zero and gradually decreasing the DC bus current sensor's detected value Idc. When the IPU detects that Idc remains below a first preset value (e.g., 5A) for a preset duration (e.g., 10-50ms), it indicates that the DC bus current has approached or returned to zero. Subsequently, the BMS controls the relays in the switch matrix to perform topology reconfiguration on multiple battery packs based on the target demand voltage. For example, when the target demand voltage is 800V, the BMS switches two 400V battery packs to a series connection; when the target demand voltage is 400V, it switches them to a parallel connection; and when a faulty battery pack needs to be disconnected, only the normal battery packs are reconfigured. After the topology reconfiguration is completed, when the IPU detects that the back electromotive force of the motor matches the voltage of the switched battery pack (e.g., the voltage difference is less than a preset value (e.g., ±5%)), the BMS controls the main relay to close and the pre-charge relay to open, establishing a high-voltage connection between the switched battery pack and the bus capacitor, thus completing the seamless switching.

[0027] It should be noted that the switched battery pack refers to the combination of battery packs that actually participates in power supply and outputs electrical energy to the DC bus after the connection method between multiple battery packs is switched (topology reconfiguration). The switched battery pack voltage refers to the total voltage output by the switched battery pack combination to the DC bus.

[0028] Step 103: When the operating condition is the parking condition, the bus capacitor is discharged so that the voltage of the bus capacitor is less than the second preset value. Then, the connection mode of the multiple battery packs is switched based on the target required voltage. After the switching is completed, if it is determined that the voltage of the bus capacitor matches the voltage of the switched battery pack, a high-voltage connection is established between the switched battery pack and the bus capacitor.

[0029] In some embodiments, under parking conditions, the bus capacitor can be actively discharged through a discharge resistor or motor windings to reduce the bus capacitor voltage to below a second preset value (i.e., a safe voltage, such as 60V) to avoid the risk of high-voltage electric shock.

[0030] It should be noted that the second preset value is a preset safety voltage threshold. When the bus capacitor voltage drops below this threshold, it indicates that the discharge is complete and subsequent topology reconfiguration operations can proceed. By setting this safety threshold, arcing can be avoided when switching relays under high voltage conditions. The second preset value can be calibrated according to functional safety requirements and vehicle high-voltage safety standards; this application embodiment does not specifically limit it in this regard.

[0031] In some embodiments, the VCU first confirms that the vehicle is in a parked state (e.g., vehicle speed ≤ 1 km / h, gear in P / N, electronic parking brake activated). Then, the BMS controls the discharge circuit to actively discharge the bus capacitor, releasing the bus capacitor voltage to below a safe voltage (e.g., ≤ 60V) through a discharge resistor or motor windings. After discharge, the BMS controls the relays in the switch matrix to operate according to the target required voltage, performing topology reconfiguration on multiple battery packs. For example, when connected to a 400V charging station, the battery packs are switched to a parallel connection; when connected to an 800V charging station, the battery packs are switched to a series connection. After topology reconfiguration, the BMS controls the pre-charge relay to close, pre-charging the bus capacitor and the battery pack with the lower voltage in the switched battery packs through a pre-charge resistor. The BMS uses a high-precision voltage sensor to detect the voltage change rate β = |d(Vbus) / dt| of the pre-charged battery pack in real time. When β remains less than a preset value (e.g., 1V / ms) for a preset duration (e.g., 10-50ms), it indicates that the bus capacitor voltage and the switched battery pack voltage have basically matched, and pre-charging is complete. At this time, the BMS controls the main relay to close and the pre-charging relay to open, establishing a high-voltage connection between the switched battery pack and the bus capacitor, completing the safe switching under parking conditions.

[0032] In this embodiment, the vehicle's operating conditions and target voltage requirements are first determined in response to a battery pack switching request. Then, under driving conditions, the motor is controlled to reduce the DC bus current to a first preset value, creating conditions for subsequent no-load switching and safe high-voltage connection establishment, thus avoiding high-voltage surges. The battery pack connection method is then switched based on the target voltage requirements to flexibly adapt to different voltage needs. After switching, ensuring the motor back EMF matches the switched battery pack voltage, a high-voltage connection is established between the switched battery pack and the bus capacitor, achieving seamless switching without interrupted power or perceptible driving experience under driving conditions. Under parking conditions, the bus capacitor is actively discharged to reduce its voltage to a second preset value. The battery pack connection method is then switched based on the target voltage requirements to flexibly adapt to different voltage needs. Finally, ensuring the bus capacitor voltage matches the switched battery pack voltage, a high-voltage connection is established between the switched battery pack and the bus capacitor, effectively achieving safe switching under parking conditions.

[0033] In some embodiments, when the operating condition is a driving condition, after switching the connection mode of the plurality of battery packs based on the target required voltage, the method further includes: Control the motor to enter active short-circuit mode or freewheeling mode; After the motor enters the active short-circuit mode or the freewheeling mode, if the percentage difference between the back electromotive force of the motor and the voltage of the switched battery pack is less than a third preset value, it is determined that the back electromotive force of the motor matches the voltage of the switched battery pack.

[0034] It should be noted that Active Short Circuit (ASC) mode refers to controlling the upper or lower arm of the three-phase Insulated Gate Bipolar Transistor (IGBT) of the inverter to be simultaneously turned on, forming a short circuit loop in the three-phase windings of the motor. This converts the back EMF energy into heat dissipation inside the motor, thereby actively reducing the back EMF. Freewheeling (FW) mode refers to controlling all IGBT arms to be turned off, using freewheeling diodes to clamp the back EMF and avoid overvoltage surges.

[0035] It should be noted that the voltage difference percentage refers to the percentage of the absolute difference between the motor's back electromotive force and the switched battery pack voltage, relative to the switched battery pack voltage, and is used to measure the degree of voltage matching. The third preset value is a preset voltage difference percentage threshold (typically ±5%). When the voltage difference percentage is less than the third preset value, it indicates that the back electromotive force and the switched battery pack voltage are basically matched. The third preset value can be adaptively set based on actual applications, and this application embodiment does not specifically limit it in this way.

[0036] In some embodiments, under driving conditions, after the BMS switches the connection mode between multiple battery packs according to the target required voltage, the VCU sends a command to the IPU to control the motor to enter active short-circuit mode or freewheeling mode. After the motor enters active short-circuit or freewheeling mode, the IPU continuously monitors the motor's back electromotive force (Eback) and calculates the voltage difference percentage α = (|Eback| - Vbus) / Vbus × 100% in real time, where Vbus is the switched battery pack voltage. When α is continuously less than a third preset value (e.g., ±5%) within a preset time period, the IPU determines that the motor's back EMF matches the switched battery pack voltage and sends a matching completion flag to the VCU or BMS. After receiving the flag, the VCU or BMS can execute the subsequent high-voltage connection establishment steps.

[0037] It is understood that, under driving conditions, after the connection mode of multiple battery packs is switched, the motor is controlled to enter active short-circuit mode or freewheeling mode to actively adjust the back electromotive force of the motor so that it matches the voltage of the switched battery pack, thereby avoiding the generation of inrush current due to excessive voltage difference, creating conditions for the subsequent safe establishment of high-voltage connection, so as to achieve seamless switching during driving.

[0038] In some embodiments, controlling the motor to enter an active short-circuit mode or a freewheeling mode includes: If the back electromotive force of the motor is determined to be greater than the voltage of the battery pack after switching, the motor is controlled to enter the active short-circuit mode. If the back electromotive force of the motor is determined to be less than the voltage of the battery pack after switching, the motor is controlled to enter freewheeling mode.

[0039] In some embodiments, the VCU can acquire the motor's back electromotive force (EMF) Eback, calculated in real-time by the IPU, and compare it with the switched battery pack voltage Vbus. When Eback is greater than Vbus, the VCU instructs the IPU to control the motor to enter active short-circuit mode, i.e., control the upper or lower arm of the three-phase IGBTs of the inverter to conduct simultaneously, forming a short-circuit loop in the motor's three-phase windings. At this time, the motor's back EMF energy is converted into heat and dissipated within the windings through the short-circuit current, and the back EMF amplitude gradually decreases, thereby actively reducing the back EMF. When Eback is less than Vbus, the VCU instructs the IPU to control the motor to enter freewheeling mode, i.e., control all IGBT arms to turn off. At this time, the motor's back EMF forms a freewheeling loop through the freewheeling diodes. Since the back EMF is lower than the switched battery pack voltage, it will not cause an overvoltage surge to the bus capacitor, thus achieving clamping of the back EMF.

[0040] It is understood that this embodiment adaptively selects between active short-circuit mode and freewheeling mode by comparing the magnitude of the motor's back EMF with the voltage of the switched battery pack. When the back EMF is greater than the voltage of the switched battery pack, the motor is controlled to enter active short-circuit mode, actively consuming the back EMF energy through a three-phase winding short circuit to reduce the back EMF and prevent high-voltage backcharging. When the back EMF is less than the voltage of the switched battery pack, the motor is controlled to enter freewheeling mode, clamping the back EMF through IGBT full shutdown to prevent overvoltage surges. This adaptive selection mechanism ensures that regardless of whether the back EMF is too high or too low, it can be adjusted to a safe range matching the voltage of the switched battery pack, thereby eliminating voltage difference surges and ensuring the safe establishment of subsequent high-voltage connections.

[0041] In some embodiments, when the operating condition is a parking condition, after switching the connection mode of the plurality of battery packs based on the target required voltage, the method further includes: The pre-charge relay in the battery pack switching circuit is closed to pre-charge the bus capacitor and the battery pack with the lower voltage after switching. During the pre-charging process, if the voltage change rate of the pre-charged side is determined to be less than a fourth preset value, the voltage of the bus capacitor is determined to match the voltage of the switched battery pack.

[0042] It should be noted that the pre-charge relay and pre-charge resistor are connected in series to form the pre-charge branch, which is used to control the on / off state of the pre-charge circuit. When the pre-charge relay is closed, current flows through the pre-charge resistor, limiting the charging current and preventing surges. The lower voltage side refers to the lower voltage of the bus capacitor and the battery pack after switching. By pre-charging the lower voltage side, the voltages of the two can be made to approach equality. The voltage change rate refers to the rate of change of the voltage of the pre-charged side over time. During the pre-charge process, the voltage change rate gradually decreases, and when the change rate approaches zero, it indicates that the voltage has stabilized. The fourth preset value is a preset voltage change rate threshold (e.g., 1V / ms). When the voltage change rate of the pre-charged side is less than this threshold, it indicates that the voltage has stabilized and the bus capacitor voltage is basically matched with the battery pack voltage after switching.

[0043] In some embodiments, under parking conditions, after the BMS switches the connection mode between multiple battery packs according to the target required voltage, it needs to perform voltage matching between the bus capacitor and the switched battery pack. The BMS then controls the pre-charge relay to close, allowing current to flow through the pre-charge resistor to pre-charge the battery pack with the lower voltage. If the switched battery pack voltage is lower than the bus capacitor voltage, energy flows from the bus capacitor to the battery pack, i.e., "reverse pre-charge"; if the bus capacitor voltage is lower than the battery pack voltage, energy flows from the battery pack to the bus capacitor, i.e., "forward pre-charge". In either direction, the pre-charge resistor limits current to prevent inrush current. During pre-charge, the BMS uses a high-precision voltage sensor (such as Shunt) to monitor the voltage of the pre-charged battery pack in real time and calculates its voltage change rate β = |d(Vbus) / dt|. When β remains less than a fourth preset value (such as 1V / ms) for a preset time period (e.g., 10-50ms), it indicates that the voltage has stabilized and the bus capacitor voltage and the switched battery pack voltage are basically matched. At this point, the BMS determines that voltage matching is complete.

[0044] Understandably, in the parking condition, after switching the battery pack connection method, this embodiment of the application pre-charges the side with the lower voltage to ensure that the bus capacitor voltage matches the battery pack voltage, creating conditions for the safe establishment of a high-voltage connection and avoiding possible large current surges.

[0045] In some embodiments, controlling the motor to make the DC bus current in the battery pack switching circuit less than a first preset value includes: Adjust the quadrature axis current of the motor to zero so that the DC bus current is less than the first preset value.

[0046] It should be noted that in motor vector control, the quadrature-axis current (q-axis current) is directly proportional to the motor's output torque. Adjusting the quadrature-axis current to zero (i.e., Iq=0) will make the motor's output torque zero, thus putting the motor into zero-torque mode.

[0047] In some embodiments, the integrated power unit (IPU) responds to a battery pack switching request by setting the quadrature-axis current command value of the motor to zero (Iq_ref=0) using a vector control algorithm. The current regulator calculates the output voltage based on the error between the actual quadrature-axis current and the command value, and drives the inverter after space vector pulse width modulation (SVPWM) to make the actual quadrature-axis current of the motor approach zero, thereby making the motor output torque zero.

[0048] It should be noted that after the motor enters zero-torque mode, the DC bus current mainly consists of motor no-load losses, and theoretically approaches zero. In some embodiments, to avoid misjudgments caused by instantaneous current fluctuations, the IPU or BMS continuously monitors the DC bus current sensor's detection value for a preset duration (e.g., 10ms to 50ms, calibrated according to system requirements). When the DC bus current is consistently less than a first preset value (e.g., the maximum limit of 5A for relay load switching) within this preset duration, it is determined that the relay contacts meet the conditions for no-load or low-load switching.

[0049] It is understood that by adjusting the quadrature axis current of the motor to zero, the embodiment of this application enables the motor to enter a zero torque mode, thereby making the DC bus current less than the first preset value, thus creating reliable conditions for subsequent no-load switching.

[0050] In some embodiments, after the back electromotive force of the motor is determined to match the voltage of the switched battery pack, a high-voltage connection is established between the switched battery pack and the bus capacitor, including: After the switching is completed, if it is determined that the back electromotive force of the motor matches the voltage of the switched battery pack, and the voltage change rate of the switched battery pack is less than the fifth preset value, a high-voltage connection is established between the switched battery pack and the bus capacitor.

[0051] It should be noted that the battery pack voltage change rate after switching refers to the rate at which the battery pack voltage changes over time after the switching is completed. This rate of change reflects whether the battery pack voltage has stabilized after the switching. The fifth preset value is a preset voltage change rate threshold (typically 1V / ms), used to determine whether the battery pack voltage has stabilized after the switching, i.e., whether pre-charging is complete. When the voltage change rate is less than this threshold, it indicates that the voltage has stabilized, pre-charging is complete, and there will be no surge when the relay is closed.

[0052] In some embodiments, under driving conditions, after the IPU adjusts the motor's back electromotive force to match the switched battery pack voltage through active short-circuit mode or freewheeling mode, the BMS also needs to confirm whether the switched battery pack voltage has stabilized before a high-voltage connection can be safely established. Specifically, the BMS uses a high-precision voltage sensor (such as Shunt) to detect the switched battery pack bus voltage Vbus in real time and calculates its voltage change rate β=|d(Vbus) / dt|. When β is continuously less than a fifth preset value (such as 1V / ms) for a preset time period (such as 10-50ms), it indicates that the switched battery pack voltage has stabilized, pre-charging is complete, and no inrush current will be generated when the relay is closed due to voltage fluctuations.

[0053] In some embodiments, when it is determined that the back electromotive force of the motor matches the voltage of the switched battery pack, and the voltage change rate of the switched battery pack is less than a fifth preset value, the BMS controls the main relay to close and the pre-charge relay to open, thereby establishing a high-voltage connection between the switched battery pack and the bus capacitor.

[0054] It is understood that the embodiments of this application, through a dual judgment mechanism, not only ensure that the back electromotive force matches the voltage of the switched battery pack, but also ensure that the voltage of the switched battery pack is pre-charged, that is, the high-voltage connection is established only after the voltage is stable, which further improves the safety and reliability of the switching process and avoids the impact risk caused by voltage fluctuations.

[0055] In some embodiments, switching the connection mode of the plurality of battery packs based on the target required voltage includes: Based on the target required voltage, the connection method between at least some of the battery packs is switched to any one of the following topologies: full series connection, full parallel connection, or series-parallel hybrid connection, so that the absolute difference between the switched battery pack voltage and the target required voltage is less than a sixth preset value.

[0056] It should be noted that "at least some battery packs" refers to the battery packs participating in topology reconfiguration. This can be all battery packs or only some battery packs (e.g., in a fault isolation scenario, after removing a faulty battery pack, only the normal battery packs are reconfigured). Full series connection means all battery packs participating in the reconfiguration are connected end-to-end, and the output voltage is the sum of the voltages of each battery pack. This is suitable for scenarios requiring high voltage (e.g., sport mode, high-speed driving, or connection to a high-voltage charging station). Full parallel connection means all battery packs participating in the reconfiguration are connected positively and negatively, and the output voltage is equal to the voltage of a single battery pack. This is suitable for scenarios requiring high current (e.g., connection to a low-voltage charging station). Series-parallel hybrid connection means some battery packs are connected in series and then in parallel with other battery packs, or some battery packs are connected in parallel and then in series with other battery packs. This can achieve an intermediate voltage level output (e.g., three battery packs: two connected in series and then the third in parallel).

[0057] It should be noted that the sixth preset value is a preset absolute voltage difference threshold, which is used to determine whether the voltage of the switched battery pack can reach the allowable error range of the target required voltage.

[0058] In some embodiments, during the switching process, the BMS controls the relays in the switching matrix to perform topology reconfiguration on multiple battery packs based on the target demand voltage determined by the VCU.

[0059] For example, when the target voltage requirement is 1200V and three 400V battery packs are available, the BMS will switch the three battery packs to a fully series connection, so that the voltage of the switched battery packs is 400V×3=1200V, and the absolute difference between the voltage and the target voltage requirement is less than the sixth preset value (e.g., within ±5%).

[0060] For example, when the target voltage requirement is 400V and three 400V battery packs are available, the BMS will switch the three battery packs to a fully parallel connection so that the voltage of the switched battery packs is 400V, and the absolute difference between the voltage requirement and the target voltage is less than the sixth preset value.

[0061] For example, when the target voltage requirement is 800V and three 400V battery packs are available, the BMS can connect two of the battery packs in series (to obtain 800V), and disconnect or not participate in power supply for the third battery pack, so that the voltage of the switched battery pack is 800V, and the absolute difference between the voltage and the target voltage requirement is less than the sixth preset value. Alternatively, the BMS can also configure the three battery packs in a mixed series-parallel connection (e.g., two connected in series and then in parallel with the third, the output voltage is still 400V or 800V), selecting the optimal topology according to specific requirements.

[0062] In some embodiments, when a battery pack fails and needs to be isolated, the BMS only reassembles at least the normal battery packs. For example, if pack A fails, while packs B and C are normal, and the target voltage requirement is 800V, the BMS connects packs B and C in series so that the voltage of the switched battery pack is 800V, and the absolute difference between this voltage and the target voltage requirement is less than a sixth preset value.

[0063] It is understood that the embodiments of this application, through the topology reconfiguration mechanism, can flexibly configure the connection method of the battery pack according to the target required voltage, realize the output of multiple voltage levels, and meet the needs of different working conditions such as driving mode switching, charging pile matching, and fault isolation.

[0064] In some embodiments, the battery pack switching request is triggered by at least one of the following: change in driving mode, change in charging demand, battery pack failure, or voltage balancing management.

[0065] It's important to note that driving mode changes refer to the driver switching between different driving modes, such as Rampage, Sport, and Eco. Different driving modes have different requirements for vehicle power performance and voltage levels. For example, Sport mode requires a higher voltage to achieve greater power and torque output. Changing charging requirements refers to the vehicle connecting to charging stations with different voltage levels, such as 400V, 800V, 1000V, and 1200V. To match the charging station's output voltage, the battery pack connection method needs to be adjusted to ensure compatibility with charging equipment of different voltage levels. Battery pack failure refers to the malfunction of one or more battery packs (such as abnormal voltage, overheating, insulation failure, etc.). In this case, the faulty battery pack needs to be disconnected, and other normal battery packs should be connected in series or parallel to continue supplying power to maintain vehicle power. Voltage balancing management refers to the BMS actively managing the voltage balance of the battery packs. When there are significant voltage differences between battery packs, voltage balancing needs to be achieved by switching connection methods or adjusting charging and discharging strategies to extend battery pack life.

[0066] In some embodiments, during vehicle operation, the vehicle control unit (VCU) or battery management system (BMS) monitors various triggering conditions in real time, and generates a battery pack switching request when any of the following conditions are detected: (1) Driving mode change, for example, when the driver switches from Eco mode to Sport mode, the VCU detects the driving mode change and generates a battery pack switching request. This request indicates that the battery pack connection method needs to be switched from parallel (Eco mode, output voltage 400V) to series (Sport mode, output voltage 800V) to provide higher power and torque output. The VCU determines the target required voltage as 800V based on the request and executes the battery pack switching procedure under driving conditions; (2) Changes in charging demand, such as when a vehicle is connected to a charging pile, the VCU obtains the output voltage level of the charging pile (e.g., 400V or 800V) through the charging pile communication protocol. If the output voltage of the current battery pack connection method does not match the charging pile voltage, the VCU generates a battery pack switching request. For example, if the current battery pack is connected in series (output voltage 800V), but the connected charging pile is 400V, the VCU determines that the target voltage requirement is 400V and executes the battery pack switching process under parking conditions to switch the battery pack to a parallel connection to be compatible with the charging pile voltage; (3) Battery pack failure. For example, when the BMS detects a failure in a battery pack (such as abnormal voltage, excessive temperature, or decreased insulation resistance), it generates a battery pack switching request. For example, if battery pack A experiences thermal runaway, the BMS generates a switching request, indicating that the faulty battery pack A needs to be disconnected and that normal battery packs B and C can be used to continue power supply. The VCU executes the corresponding battery pack switching procedure based on the vehicle's current operating conditions and the status of the remaining normal battery packs. (4) Voltage equalization management. For example, when the BMS detects a large voltage difference between battery packs (e.g., battery pack A has a voltage of 420V, battery pack B has a voltage of 380V, and battery pack C has a voltage of 400V), the BMS generates a battery pack switching request, indicating that voltage equalization management is required. The VCU determines the target voltage requirement based on the equalization requirement and executes the corresponding battery pack switching process (usually performed under parking conditions). By adjusting the battery pack connection method, the voltage of each battery pack is made to be consistent.

[0067] It is understood that the embodiments of this application can adaptively trigger battery pack switching according to different situations such as changes in driving mode, changes in charging demand, battery pack failure, and voltage balance management, flexibly adapting to various actual working conditions and improving the intelligence level of the system and user experience.

[0068] For example, Figure 2 This is a schematic diagram of a battery pack switching process under driving conditions provided in an embodiment of this application, such as... Figure 2 As shown, the process includes steps 201 to 204: Step 201: Adjust the quadrature axis current of the motor to zero so that the DC bus current is less than the first preset value; Step 202: Switch the connection method of multiple battery packs based on the target required voltage; Step 203: If the back EMF of the motor is determined to be greater than the voltage of the battery pack after switching, control the motor to enter the active short-circuit mode; if the back EMF of the motor is determined to be less than the voltage of the battery pack after switching, control the motor to enter the freewheeling mode. Step 204: If the back electromotive force of the motor matches the voltage of the switched battery pack, and the voltage change rate of the switched battery pack is less than the fifth preset value, establish a high-voltage connection between the switched battery pack and the bus capacitor.

[0069] It should be noted that the descriptions of the same steps and contents as in other embodiments in this embodiment can be found in the descriptions in other embodiments, and will not be repeated here.

[0070] It is understood that this embodiment of the application creates conditions for subsequent no-load switching by adjusting the quadrature-axis current to zero so that the DC bus current is less than a first preset value; it flexibly reorganizes the battery pack topology based on the target required voltage to adapt to different voltage levels; it adaptively selects active short-circuit mode or freewheeling mode according to the relationship between the back electromotive force and the voltage of the switched battery pack, actively adjusting the back electromotive force to match the voltage of the switched battery pack; and it establishes a high-voltage connection after the voltage is matched and the voltage change rate is stable. In this way, a seamless and shock-free switching of the battery pack under driving conditions is achieved, effectively avoiding the risks of power interruption and high-voltage impact.

[0071] For example, Figure 3 This is a schematic diagram of a battery pack switching process under parking conditions provided in an embodiment of this application, as shown below. Figure 3 As shown, the process includes steps 301 to 304: Step 301: Discharge the bus capacitor so that the voltage of the bus capacitor is less than the second preset value; Step 302: Switch the connection method of multiple battery packs based on the target required voltage; Step 303: Control the pre-charge relay to close, so as to pre-charge the bus capacitor and the battery pack with the lower voltage after switching. Step 304: If the voltage change rate of the pre-charged side is less than the fourth preset value, and the voltage of the bus capacitor is determined to match the voltage of the switched battery pack, then a high-voltage connection is established between the switched battery pack and the bus capacitor.

[0072] It should be noted that the descriptions of the same steps and contents as in other embodiments in this embodiment can be found in the descriptions in other embodiments, and will not be repeated here.

[0073] It is understood that the embodiments of this application first actively discharge the bus capacitor to below a second preset value (i.e., a safe voltage), eliminating the risk of residual high voltage. Then, based on the target required voltage, the battery pack topology is flexibly reorganized to adapt to different voltage levels. Subsequently, the side with the lower voltage is pre-charged, and the completion of pre-charging or voltage matching is determined by monitoring the voltage change rate of the pre-charged side. Once pre-charging is complete or voltage matching is achieved, a high-voltage connection is established. In this way, safe and reliable switching of the battery pack is realized under parking conditions, effectively avoiding the risk of high-voltage shock and electric shock.

[0074] In some embodiments, the method further includes: If it is determined that the battery pack switching request is triggered by a fault in any battery pack, and the motor fails to enter the active short-circuit mode or freewheeling mode, the power output of the motor is limited based on the fault type of the battery pack.

[0075] It should be noted that the motor failing to enter the active short-circuit mode or freewheeling mode means that the IPU fails to complete the control action for the motor to enter the corresponding mode within the preset time (e.g., 100ms), or the feedback flag bit is not received after the timeout.

[0076] It should be noted that the fault type refers to the specific category of battery pack fault that triggers the battery pack switching request, including but not limited to collision faults, bottoming-out faults, and thermal runaway faults. Different fault types have different degrees of impact on vehicle safety, requiring differentiated protection strategies.

[0077] It should be noted that power limiting refers to restricting the motor's output torque or power to reduce vehicle power and prevent the fault from escalating or causing a safety accident. Depending on the severity of the fault, different levels of limiting measures may be taken, such as completely prohibiting output, derating to a certain percentage and then maintaining it, or gradually reducing the output to zero after derating.

[0078] For example, when a collision fault is detected in a battery pack (such as a collision sensor triggering, abnormal insulation resistance, voltage surge, etc.), it indicates that a serious accident may occur, posing a risk of high-voltage short circuit or electric shock. In this case, the VCU or BMS instructs the IPU to immediately disable the motor's torque output, linearly reducing the torque to 0%, causing the vehicle to lose power and preventing continued driving under dangerous conditions.

[0079] For example, when a battery pack is detected to have bottomed out (e.g., the chassis is impacted, causing deformation of the battery pack casing and a decrease in insulation resistance), it indicates that the battery pack may be damaged but has not yet experienced serious thermal runaway. In this case, the VCU or BMS instructs the IPU to reduce the output torque of the motor to 25% of the normal torque, limiting the vehicle's power output and allowing the vehicle to travel to a safe area at a lower speed.

[0080] For example, when a thermal runaway fault is detected in a battery pack (e.g., the battery temperature continues to rise, the rate of temperature rise exceeds a threshold, or the individual cell voltage drops abnormally), it indicates that the battery pack may be experiencing thermal runaway. At this time, the VCU or BMS instructs the IPU to control the motor's output torque to be dated to 15% of the normal torque, and after a preset time (e.g., 250 seconds), gradually reduce the output torque to 0%, that is, disable the motor's output torque.

[0081] It is understood that by setting differentiated power limiting strategies for different types of battery pack failures, the embodiments of this application can maximize the preservation of the vehicle's basic driving capability or provide sufficient emergency response time while ensuring safety.

[0082] The following examples illustrate possible implementation schemes of the battery pack switching method described in one or more of the above embodiments.

[0083] Figure 4 This is a schematic diagram of the topology of a battery pack switching circuit provided in an embodiment of this application, as shown below. Figure 4As shown, the battery pack switching circuit includes three battery packs (Block A, Block B, Block C), a bus capacitor C1, a discharge resistor R0, a pre-charge resistor R1, multiple fuses (F0, F1, F2, F3, F4), multiple current sensors (Shunt1, Shunt2, Shunt3), and multiple relays (k0 to k9). The positive terminal of each battery pack is connected to the positive terminal of the bus capacitor C1 via fuses and relays, and the negative terminal of each battery pack is connected to the negative terminal of the bus capacitor C1 via relays. The pre-charge relay k1 and the pre-charge resistor R1 are connected in series to form a pre-charge branch, which is connected in parallel with the main relay k0, used to pre-charge the bus capacitor C1 before high voltage is established. The discharge resistor R0 is connected in parallel across the bus capacitor C1 to actively discharge the residual energy of the bus capacitor C1 when the vehicle is parked. Each relay (k2 to k9) forms a switching matrix to control the series and parallel connection between the three battery packs, enabling outputs at different voltage levels (e.g., 400V, 800V, 1200V). The three-phase motor is connected to the bus capacitor C1 via an inverter (composed of IGBTs Q2, Q3, Q4, Q5, Q6, Q9 and anti-parallel diodes D1, D2, D3, D4, D5, D6) to drive the vehicle. This topology, through the coordinated control of the relays, allows for seamless and safe switching between driving and parking conditions.

[0084] This application embodiment also provides a battery pack switching system, including: an integrated power unit, a battery management system and a vehicle controller, wherein the integrated power unit and the battery management system are both connected to the vehicle controller; The vehicle controller is used to respond to a battery pack switching request, determine the vehicle's operating conditions and target voltage requirements, and send control commands to the integrated power unit and the battery management system based on the operating conditions and target voltage requirements. The integrated power unit is used to control the motor according to the battery pack switching method described in any of the above embodiments, based on the control commands sent by the vehicle controller. The battery management system is used to switch the connection mode of the multiple battery packs and establish a high-voltage connection between the switched battery pack and the bus capacitor according to the battery pack switching method described in any of the above embodiments, based on the control commands sent by the vehicle controller.

[0085] It should be noted that in this embodiment, the vehicle control unit (VCU) acts as the decision-making core, responsible for determining the operating conditions and target voltage requirements based on the battery pack switching request, and issuing control commands to the integrated power unit (IPU) and battery management system (BMS). The integrated power unit (IPU) acts as the motor control execution unit, responsible for executing motor-related control steps (such as zero-torque mode, active short-circuit mode, and freewheeling mode). The battery management system (BMS) acts as the high-voltage circuit control execution unit, responsible for executing steps such as switching the battery pack connection mode (i.e., battery pack topology reconfiguration), discharging and pre-charging the bus capacitor, and establishing high-voltage connections. Through the coordinated operation of the VCU, IPU, and BMS, this embodiment can achieve adaptive, seamless, and safe switching of the battery pack under driving and parking conditions.

[0086] In this solution, the VCU or BMS classifies and determines the current vehicle operating condition and issues a switching request. For example, (a) the driving mode changes (Rampage / Sport / Economy mode), requiring a change in voltage to alter power and torque; (b) charging demand changes, requiring a change in voltage to flexibly match charging to different voltage levels (e.g., 400V / 800V / 1000V / 1200V); (c) one or more battery packs malfunction and require isolation, thus requiring a change in voltage to maintain vehicle performance; (d) the BMS needs to actively manage battery pack voltage balancing, etc. When the condition is determined to be (a) or (c), the vehicle is in driving condition, and a switch to Mode 1 is requested; when the condition is determined to be (b) or (d), the vehicle is in parking condition, and a switch to Mode 2 is requested. Switching to Mode 1 may include steps S1 to S6, and switching to Mode 2 may include steps T1 to T6.

[0087] Step S1: The IPU receives a battery pack switching request from the BMS or VCU. By adjusting the d / q axis currents of the motor respectively, it enters a zero-torque control mode, making the quadrature axis current Iq=0, reducing the output torque to 0 N·m, and assisting in adjusting the direct axis current Id to weaken the magnetic field and reduce the bus voltage, so that the DC bus current sensor's detection value Idc is close to zero or meets the cut-off requirement value; the judgment condition is: within time t1, |Idc| < Ith. The threshold settings of t1 and Ith are determined according to system requirements. t1 is much smaller than the battery pack fault switching time, such as a typical value of 10 to 50 ms, and Ith is less than or equal to the maximum limit of the battery pack relay on / off under load (such as a typical value of 5A).

[0088] In step S2, under the condition that the DC bus current meets the above requirements, the pre-charge relay k1 first closes to maintain the connection of the high-voltage structure, and then disconnects the main positive relay k0 (the time interval between the closing of k1 and the opening of k0 is the difference in the mechanical action time of the relay, for example, 20ms). At the same time, the BMS operates the k2~k9 switch array according to the current fault or demand type (such as battery pack A being isolated and connected to battery pack B / battery pack C for power supply, then the mode combination corresponding to serial number 4 in Table 1 is selected) to complete the switching of the internal battery core group (i.e., battery pack). At this time, the bus capacitor C1 forms a pre-charge with the new multi-core battery pack through the pre-charge resistor R1 (the bus capacitor pre-charges the battery pack when the number of battery packs decreases, and the battery pack pre-charges the bus capacitor when the number of battery packs increases). The BMS sends the high-voltage pre-switching completion to the VCU.

[0089] Table 1

[0090] It should be noted that Table 1 lists the topology of the three battery packs (battery packs A, B, and C) and the relationship between the relay switch array and the battery packs. Adding one more battery pack in parallel to the dual-core architecture adds four relays, and the total number of relays for a multi-core battery pack with m additional battery packs is 6 + 4m; the overall control method and logic remain unchanged.

[0091] Among them, the A+B+C series mode combination is suitable for high-voltage charging / enhancing output capability; the (A+B) series / fault + C parallel mode combination is to cut off AB and leave only C for power supply / driving or low-voltage charging mode; the (A+B) series + C parallel / fault mode combination is to cut off C and leave only AB for power supply / driving or low-voltage charging mode; the A parallel / fault + (B+C) series mode combination is to cut off A and leave only BC for power supply / driving or low-voltage charging mode; the A parallel + (B+C) series / fault mode combination is to cut off BC and leave only A for power supply / driving or low-voltage charging mode; the (A+C) series + B parallel / fault mode combination is to cut off B and leave only AC for power supply / driving or low-voltage charging mode; the (A+C) series / fault + B parallel mode combination is to cut off AC and leave only B for power supply / driving or low-voltage charging mode.

[0092] It should be noted that in actual working conditions, two series and one parallel circuit cannot exist, as this will form a circulating short circuit. The only working conditions are when a single-core parallel branch fails or when two series-connected cores fail. Adding one battery pack adds four relays, so the total number of relays is 6 + 4m. Assuming one battery pack is 400V, it expands to 3 × 400 = 1200V, and m units are m × 400V.

[0093] Step S3: The IPU calculates the real-time back EMF Eback based on the current motor speed n and sends it to the VCU. The VCU identifies that if the back EMF Eback is less than the new multi-core battery pack voltage Vbus within time t2 (typically 10-50ms, adjustable), the VCU instructs the IPU to enter freewheeling mode, turn off all IGBT bridge arms, and clamp the back EMF. If the electric drive successfully enters freewheeling mode within time t_fw (e.g., 100ms), a flag signal is sent to the BMS / VCU. If it fails to enter freewheeling mode within the time limit, a failure flag is reported, and switching is prohibited. According to Table 2 below, based on the type of battery pack fault, the electric drive fault diagnosis strategy is used to perform graded power limiting output.

[0094] Table 2

[0095] If Eback is greater than the new multi-core battery pack voltage Vbus within time t3 (typically 10-50ms, adjustable), VCU sends a signal to IPU to control the motor to enter ASC mode, controlling the upper or lower arm of the three-phase IGBT to conduct simultaneously, creating a short circuit between the three-phase windings of the motor. Within time t_asc (e.g., 100ms), the electric drive enters ASC and simultaneously sends a flag signal indicating successful entry into this mode to BMS / VCU. If it fails to enter within the time limit, a failure flag is reported, and switching is prohibited. Power output is limited according to Table 2. The back EMF induced under high-speed vehicle rotation and the current generated on the windings are quickly converted into heat through the windings. During this process, IPU calculates the corresponding value of the back EMF at the current speed in real time. When the voltage difference percentage between the back EMF Eback and the new multi-core battery pack Vbus is α=[(|Eback|-Vbus) / Vbus]≤αth, such as the typical value αth=±5% (the threshold can also be adjusted according to the system functional safety requirements), it is used as one of the criteria for entering step S5.

[0096] In step S4, the BMS receives the mode signal from the IPU. At this time, the high-precision voltage sensor of Shunt detects whether the rate of change of the bus voltage of the new multi-core battery pack β=|d(Vbus) / dt| satisfies β≤βth within the time t4 (such as the typical value βth=1V / ms, the typical value of t4 is 10-50ms or other thresholds, depending on the high voltage safety requirements). If it satisfies the requirement, it indicates that the pre-charging of the bus capacitor and the new multi-core battery pack is completed (the voltage changes continuously during the pre-charging process. If the voltage gradually becomes constant, it indicates that the pre-charging is complete), and the next step can be started.

[0097] Step S5: Enter the power supply recovery phase of the new multi-core battery pack. At this time, the main positive relay k0 is closed, the pre-charge relay k1 is opened, the high-voltage circuit power supply is normal, and the high-voltage architecture recovery flag is sent to the VCU.

[0098] In step S6, the VCU confirms the switching is complete, the IPU exits ASC mode, and the Pulse Width Modulation (PWM) retransmits the waveform according to the current motor speed and bus voltage, and the electric drive system resumes torque or speed control mode.

[0099] In step T1, the IPU receives a battery pack switching request from the BMS or VCU. The IPU confirms that the vehicle speed is ≤1km / h, the gear is P or N, and the electronic parking brake is activated. The vehicle enters the high-voltage down-process. The IPU stops the Space Vector Pulse Width Modulation (SVPWM) control to stop power output, and the BMS disconnects the relevant relay switches in the current high-voltage circuit for subsequent reconfiguration.

[0100] In step T2, the IPU enters the discharge mode and begins the active discharge process. The bus capacitor C1 is discharged through the discharge resistor R0 or the electric drive winding. Within time t5 (typically 500ms to 1000ms), the capacitor voltage Vdc-C ≤ 60VDC, and a discharge completion flag is sent to the BMS / VCU.

[0101] Step T3: After receiving the discharge completion signal, the BMS performs topology reconfiguration of the battery pack according to the current fault type / operating condition requirements (if compatibility with 400V charging piles is required, battery packs A, B, and C need to be connected in parallel, so select the mode combination corresponding to serial number 8 in Table 1).

[0102] In step T4, after the topology mode is selected, the BMS begins to precharge the bus capacitor, closes the precharge relay k1, keeps the main positive relay k0 open, and then operates the corresponding relays according to the combination of k2~k9. At this time, the precharge condition between the new multi-core battery pack and the bus capacitor is formed.

[0103] In step T5, the BMS uses a shunt high-precision voltage sensor to detect whether the rate of change of the bus voltage β=|d(Vbus) / dt| of the pre-charged side of the new multi-core battery pack and the bus capacitor satisfies β≤βth within time t4 (such as typical value βth=1V / ms, typical value t4 10-500ms or other threshold, depending on high voltage safety requirements). If it satisfies the condition, it indicates that the pre-charge is complete.

[0104] In step T6, the BMS mode is restored. At this time, the main positive relay k0 is closed and the pre-charge relay k1 is opened, forming a high-voltage system connection. If the bus voltage Vbus∈(1±5%)×Vbus, the system will restore normal power supply in t6≤50ms and send the "high voltage restoration" flag bit to VCU. The system will enter standby mode to wait for charging or driving commands.

[0105] Understandably, this solution categorizes vehicle operating conditions to determine seamless switching during driving and safe switching during parking, and then operates the switch array according to different fault or demand types; it fully utilizes existing high-voltage architecture components in new energy vehicles to achieve safe switching under no load or low load. For seamless switching during driving (i.e., switching under driving conditions), the BMS selects a mode combination based on the fault or demand type. After receiving a battery pack switching request from the BMS or VCU, the IPU controls the electric drive system to bring the DC bus current to zero; the BMS controls the relay combination switch to pre-charge the bus capacitor with the new multi-core battery pack (i.e., the switched battery pack); the IPU enters ASC / FW mode to control the back EMF to drop to a safe range that matches the voltage of the new multi-core battery pack before restoring normal high-voltage connection; the IPU performs SVPWM torque control according to the voltage of the new multi-core battery pack. For safe switching while parked (i.e. switching under parking conditions), the BMS selects a combination of modes based on the type of fault or demand, controls the relay switch array to form a new multi-core battery pack, discharges the bus capacitor voltage through the motor windings or discharge resistor, then pre-charges, and then switches the relay to restore the high-voltage connection.

[0106] In this scheme, under driving conditions, (1) the motor and inverter are fully utilized as converters of controllable energy. By using zero torque mode, active short circuit ASC / freewheeling FW mode, etc., the bus voltage and current are independently adjusted during the battery pack disconnection process, creating conditions for the battery bus to be disconnected and restored under no load or low load, and eliminating the risk of high voltage impact; (2) the pre-charge resistor circuit is fully utilized to realize the dynamic balance between the DC bus capacitor and the voltage of the new multi-core battery pack, avoiding voltage and current impact, and the protection device achieves smooth switching. (3) during the entire switching process, the inverter accurately controls the back electromotive force and the slope of the bus voltage change, the closed-loop control of the active current component, and the control of the torque change rate, creating a good driving experience for the driver and passengers while switching without stopping. Under parking conditions, (1) make full use of the existing functional safety requirements and actively discharge the voltage of the bus capacitor through the motor winding or discharge resistor to avoid high voltage risks such as arcing, breakdown, and short circuit during the switching process; (2) make use of the original high voltage logic and recharge the bus capacitor to reach the safe range under the new multi-core battery pack state; (3) restore the normal high voltage connection.

[0107] Figure 5 This is one of the interactive flow diagrams of a battery pack switching system provided in this application embodiment. Figure 6 This is the second schematic diagram of the interaction flow of a battery pack switching system provided in this application embodiment. For example... Figure 5 and Figure 6As shown, the system includes the vehicle control unit (VCU), battery management system (BMS), integrated power unit (IPU), and high-voltage circuit HV_Bus (equivalent to the high-voltage DC bus in the battery pack switching circuit). The following section will discuss this further. Figure 5 and Figure 6 The interaction process of the system is explained in detail.

[0108] like Figure 5 As shown, in step S1, when a fault occurs in Block A and a switch to Block B / C is required, the vehicle controller (VCU) sends an ON·m torque command (i.e., a zero torque command) to the integrated power unit (IPU). The IPU responds to this command by entering zero torque control mode, causing the motor output torque to be zero, the DC bus current Idc to gradually decrease, and feeding back the electric drive zero torque mode flag. The BMS determines that |Idc| < Ith within time t1 and then proceeds to step S2.

[0109] In step S2, the BMS first sends a closing command to the pre-charge relay k1. After the k1 status feedback confirms the closing, it then sends a closing command to the main positive relay k0. After the k0 status feedback confirms the opening, the BMS controls the switch matrix (k2~k9) to operate, completing the battery pack topology reconfiguration (e.g., disconnecting the faulty Block A, and connecting Blocks B and C in series or parallel). After the reconfiguration is completed, the BMS sends a high-voltage pre-switching flag back to the VCU.

[0110] like Figure 6 As shown, in step S3, the IPU calculates the back electromotive force Eback in real time based on the current motor speed and feeds it back to the VCU. The VCU, based on the comparison between Eback and the switched battery pack voltage Vbus, sends a command to the IPU to enter either ASC or FW mode. After entering the corresponding mode, the IPU feeds back the ASC / FW flag to the BMS / VCU and calculates the voltage difference percentage α = [(|Eback|-Vbus) / Vbus] in real time. Once α ≤ αth, it feeds it back to the BMS.

[0111] In step S4, the voltage change rate β = |d(Vbus) / dt| is calculated, and it is determined whether β ≤ βth (e.g., 1V / ms) is satisfied within a preset time period t4. If satisfied, it is determined that the bus capacitor pre-charging is complete, indicating that the voltage has stabilized.

[0112] In step S5, the BMS sends a closing command to the main positive relay k0 and a closing command to the precharge relay k1. After the status feedback of k0 and k1 is confirmed, the BMS sends a high voltage switching completion flag to the VCU.

[0113] In step S6, after the VCU confirms the switching is complete, it sends an ASC exit command to the IPU and a torque control command. Responding to the command from the VCU, the IPU exits the active short-circuit or freewheeling mode, restores torque control via PWM ripple, and the electric drive system resumes normal operation.

[0114] Understandably, through methods such as Figure 5 and Figure 6 The interactive process shown in this application embodiment realizes precise timing coordination between IPU, BMS and VCU, and together completes seamless and shockless switching of multiple battery packs under driving conditions.

[0115] Figure 7 This is the third schematic diagram of the interaction flow of a battery pack switching system provided in this application embodiment. Figure 8 This is the fourth schematic diagram of the interaction flow of a battery pack switching system provided in this application embodiment. Figure 7 and Figure 8 As shown, the system includes the vehicle control unit (VCU), battery management system (BMS), integrated power unit (IPU), and high-voltage circuit HV_Bus (equivalent to the high-voltage DC bus in the battery pack switching circuit). The following section will discuss this further. Figure 7 and Figure 8 The interaction process of the system is explained in detail.

[0116] like Figure 7 As shown, in step T1, when a parking mode switch needs to be performed (e.g., connecting to a charging pile with a different voltage level), the VCU first sends an indication to the IPU that the vehicle is in a parking state, i.e., the vehicle speed is ≤1km / h, the gear is P or N, and the electronic parking brake is activated. After receiving this information, the IPU sends a stop output command to the high-voltage circuit HV_Bus. Then, the BMS sends a command to HV_Bus to disconnect the main positive relay k0 and related relay switches. After performing the disconnection operation, HV_Bus sends feedback on the status of k0 and related switches to the BMS.

[0117] In step T2, HV_Bus feeds back the current mode status to BMS and VCU, confirming that the parking switch preparation stage has begun. Then, the IPU enters active discharge mode, actively discharging the bus capacitor through a discharge resistor or motor windings. The BMS monitors the bus capacitor voltage Vdc-C and determines whether it has dropped below a safe voltage (e.g., ≤60VDC) within a preset time period t5. Once the condition is met, a discharge completion flag is sent to the VCU.

[0118] In step T3, the BMS selects the topology mode based on the operating conditions (including the target required voltage).

[0119] like Figure 8As shown, in step T4, the BMS operates the switch matrix (k2~k9) according to the selected topology mode and the topology array to complete the reconfiguration of the battery pack connection method. Simultaneously, the BMS closes the pre-charge relay k1 and opens the main positive relay k0, forming a pre-charge circuit. Then, the HV_Bus feeds back the status of k0~k9 to the BMS.

[0120] In step T5, the BMS uses a high-precision voltage sensor to detect the bus voltage Vbus in real time, calculates its voltage change rate β=|d(Vbus) / dt|, and determines whether β≤βth (e.g., 1V / ms) is satisfied within a preset time period t4. If satisfied, it is determined that the bus capacitor pre-charging is complete, indicating that the voltage has stabilized.

[0121] In step T6, the BMS closes the main positive relay k0 and opens the pre-charge relay k1, restoring the high-voltage circuit to normal connection. After receiving the k0 / k1 status feedback from the high-voltage circuit HV_Bus, the BMS sends a high-voltage recovery flag to the VCU. After the VCU confirms the high-voltage recovery, the system enters standby mode, waiting for charging or driving commands.

[0122] Understandably, through methods such as Figure 7 and Figure 8 The interactive process shown in this application embodiment realizes precise timing coordination between IPU, BMS and VCU, which together completes the safe switching of multiple battery packs under parking conditions, and realizes charging pile voltage adaptation and high voltage safety protection.

[0123] It is understandable that this solution can bring at least the following beneficial effects: 1. Seamless switching experience: Through calibration, the entire switching process can be seamless, with a switching time of less than 500ms, torque fluctuation of less than 5Nm, and acceleration change rate of less than 0.01g, so that the driver does not perceive it; 2. High electrical safety: The switch combination completely eliminates the risk of high-voltage surges to energy storage components, significantly improving system reliability; 3. Extend device lifespan: By adopting interactive logic, each relay switch can be switched under no load or low load, effectively extending the lifespan of relays and other devices; 4. High control precision: Capacitor energy consumption is achieved through multiple paths, and the bus voltage can be precisely matched with the target battery voltage.

[0124] 5. Highly adaptable and low-cost: It is suitable for various multi-core battery architectures and does not require any additional hardware costs.

[0125] It should be noted that although the steps of the method in this application are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps; or steps from different embodiments may be combined into a new technical solution.

[0126] This application also provides a vehicle including the battery pack switching system described in the above embodiments, which will not be repeated here for the sake of brevity.

[0127] This application also provides a computer-readable storage medium for storing a computer program, which causes a processor to execute various methods of this application embodiment. For the sake of brevity, these methods will not be described in detail here.

[0128] This application also provides a computer program product, including computer program instructions, which cause a processor to execute various methods of this application embodiment. For the sake of brevity, these will not be described in detail here.

[0129] This application also provides a computer program that, when run on a processor, causes the processor to execute various methods of this application embodiment. For the sake of brevity, these methods will not be described in detail here.

[0130] It should be noted that the descriptions of the vehicles, storage media, computer program products, and computer program embodiments above are similar to the descriptions of the method embodiments above, and have similar beneficial effects. For technical details not disclosed in the vehicle, storage media, computer program products, and computer program embodiments of this application, please refer to the descriptions of the method embodiments of this application for understanding.

[0131] It should be understood that the processor in the embodiments of this application may be an integrated circuit chip with signal processing capabilities. In implementation, the steps of the above method embodiments can be completed by integrated logic circuits in the processor's hardware or by instructions in software form. The processor described above can be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this application can be directly embodied in the execution of a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor. The software modules can be located in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. The storage medium is located in memory, and the processor reads information from the memory and, in conjunction with its hardware, completes the steps of the above method.

[0132] It is understood that the memory in the embodiments of this application can be volatile memory or non-volatile memory, or may include both volatile and non-volatile memory. The non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. The volatile memory can be random access memory (RAM), which is used as an external cache. By way of example, but not limitation, many forms of RAM are available, such as Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDR SDRAM), Enhanced Synchronous DRAM (ESDRAM), Synchlink DRAM (SLDRAM), and Direct Rambus RAM (DR RAM). It should be noted that the memory used in the systems and methods described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0133] It should be understood that the above-described memory is exemplary and not a limiting description. For example, the memory in the embodiments of this application may also be static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct memory bus RAM (DR RAM), etc. That is to say, the memory in the embodiments of this application is intended to include, but is not limited to, these and any other suitable types of memory.

[0134] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0135] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0136] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0137] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0138] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0139] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a vehicle to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0140] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A battery pack switching method, characterized in that, Applied to vehicles including a battery pack switching circuit, the battery pack switching circuit including multiple battery packs, a bus capacitor, and a motor, the method includes: In response to a battery pack switching request, the vehicle's operating conditions and target voltage requirements are determined. When the operating condition is the driving condition, the motor is controlled to make the DC bus current in the battery pack switching circuit less than a first preset value. Then, the connection mode of the multiple battery packs is switched based on the target required voltage. After the switching is completed, if it is determined that the back electromotive force of the motor matches the voltage of the switched battery pack, a high-voltage connection is established between the switched battery pack and the bus capacitor. When the operating condition is a parking condition, the bus capacitor is discharged so that the voltage of the bus capacitor is less than a second preset value. Then, the connection mode of the multiple battery packs is switched based on the target required voltage. After the switching is completed, if it is determined that the voltage of the bus capacitor matches the voltage of the switched battery pack, a high-voltage connection is established between the switched battery pack and the bus capacitor.

2. The method according to claim 1, characterized in that, When the operating condition is a driving condition, after switching the connection mode of the multiple battery packs based on the target required voltage, the method further includes: Control the motor to enter active short-circuit mode or freewheeling mode; After the motor enters the active short-circuit mode or the freewheeling mode, if the percentage difference between the back electromotive force of the motor and the voltage of the switched battery pack is less than a third preset value, it is determined that the back electromotive force of the motor matches the voltage of the switched battery pack.

3. The method according to claim 2, characterized in that, The control of the motor to enter active short-circuit mode or freewheeling mode includes: If the back electromotive force of the motor is determined to be greater than the voltage of the battery pack after switching, the motor is controlled to enter the active short-circuit mode. If the back electromotive force of the motor is determined to be less than the voltage of the battery pack after switching, the motor is controlled to enter freewheeling mode.

4. The method according to claim 1, characterized in that, When the operating condition is a parking condition, after switching the connection mode of the multiple battery packs based on the target required voltage, the method further includes: The pre-charge relay in the battery pack switching circuit is closed to pre-charge the bus capacitor and the battery pack with the lower voltage after switching. During the pre-charging process, if the voltage change rate of the pre-charged side is determined to be less than a fourth preset value, the voltage of the bus capacitor is determined to match the voltage of the switched battery pack.

5. The method according to claim 1, characterized in that, The step of controlling the motor to make the DC bus current in the battery pack switching circuit less than a first preset value includes: Adjust the quadrature axis current of the motor to zero so that the DC bus current is less than the first preset value.

6. The method according to claim 1, characterized in that, After the switching is completed and it is determined that the back electromotive force of the motor matches the voltage of the switched battery pack, a high-voltage connection is established between the switched battery pack and the bus capacitor, including: After the switching is completed, if it is determined that the back electromotive force of the motor matches the voltage of the switched battery pack, and the voltage change rate of the switched battery pack is less than the fifth preset value, a high-voltage connection is established between the switched battery pack and the bus capacitor.

7. The method according to claim 1, characterized in that, Switching the connection method of the multiple battery packs based on the target required voltage includes: Based on the target required voltage, the connection method between at least some of the battery packs is switched to any one of the following topologies: full series connection, full parallel connection, or series-parallel hybrid connection, so that the absolute difference between the switched battery pack voltage and the target required voltage is less than a sixth preset value.

8. The method according to any one of claims 1 to 7, characterized in that, The battery pack switching request is triggered by at least one of the following: change in driving mode, change in charging demand, battery pack failure, or voltage equalization management.

9. A battery pack switching system, characterized in that, include: The system integrates a power unit, a battery management system, and a vehicle controller, wherein both the integrated power unit and the battery management system are connected to the vehicle controller. The vehicle controller is used to respond to a battery pack switching request, determine the vehicle's operating conditions and target voltage requirements, and send control commands to the integrated power unit and the battery management system based on the operating conditions and target voltage requirements. The integrated power unit is used to control the motor according to the method described in any one of claims 1 to 8, based on the control commands sent by the vehicle controller. The battery management system is used to switch the connection mode of the plurality of battery packs and establish a high-voltage connection between the switched battery packs and the bus capacitor based on the control commands sent by the vehicle controller, according to the method described in any one of claims 1 to 8.

10. A vehicle, characterized in that, Includes the battery pack switching system as described in claim 9.

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