METHOD AND DEVICE FOR SWITCHING TO ACTIVE SHORT CIRCUIT WHEN CONTROLLING A VEHICLE, CARRIER AND VEHICLE

Abstract

Provided in the present disclosure is an active short circuit switching control method for a vehicle. The method comprises: acquiring the current maximum allowable recharge power of a traction battery, and a default limp-home speed; on the basis of the maximum allowable recharge power, determining the maximum allowable switching speed; on the basis of the maximum allowable switching speed and the default limp-home speed, determining a switching threshold value; and when a vehicle needs to perform active short circuit switching, on the basis of the switching threshold value, controlling the vehicle to perform active short circuit switching.

Description

Vehicle active short circuit switching control method, device, program product, medium and vehicle

[0001] Cross Reference to Related Applications

[0002] The present disclosure claims priority to Chinese Patent Application No. 2024108633769, filed on June 29, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure belongs to the technical field of vehicle control, and particularly relates to a vehicle active short circuit switching control method, device, program product, medium and vehicle. BACKGROUND

[0004] The electric drive system is one of the core systems of a new energy vehicle. When an electric drive system fault occurs, ensuring stable limp home at high speed or no secondary damage is a key problem for the vehicle.

[0005] In related technologies, vehicle control is performed by controlling the vehicle to switch into an active short circuit mode. However, the switching of the active short circuit mode in related technologies often leads to vehicle faults, which has great safety hazards.

[0006] SUMMARY

[0007] The problem of improving vehicle faults and improving safety is solved by using one or more embodiments of the present disclosure.

[0008] Other characteristics and advantages of the present disclosure will become apparent from the following detailed description, or will be learned by practice of the present disclosure.

[0009] According to a first aspect of an embodiment of the present disclosure, a vehicle active short circuit switching control method is provided. The method includes: obtaining a current maximum allowed regenerative power of a power battery and a default limp home speed; confirming a maximum allowed switching speed according to the maximum allowed regenerative power; confirming a switching threshold according to the maximum allowed switching speed and the default limp home speed; and when the vehicle needs to perform active short circuit switching, controlling the vehicle to perform active short circuit switching according to at least the switching threshold.

[0010] According to a second aspect of an embodiment of the present disclosure, a vehicle active short circuit switching control device is provided. The device can include: an obtaining unit configured to obtain a current maximum allowed regenerative power of a power battery and a default limp home speed; a speed confirming unit configured to confirm a maximum allowed switching speed according to the maximum allowed regenerative power; a threshold confirming unit configured to confirm a switching threshold according to the maximum allowed switching speed and the default limp home speed; and a switching unit configured to, when the vehicle needs to perform active short circuit switching, control the vehicle to perform active short circuit switching according to at least the switching threshold.

[0011] According to a third aspect of the embodiments of the present disclosure, a computer program product is provided, which can include computer instructions stored in a computer readable storage medium and adapted to be read and executed by a processor to enable a computer device having the processor to perform the method according to any of the embodiments of the first aspect.

[0012] According to a fourth aspect of the embodiments of the present disclosure, a computer readable storage medium is provided, which stores at least one computer program instruction, the at least one computer program instruction is loaded and executed by a processor to implement the operations performed by the method according to any of the embodiments of the first aspect.

[0013] According to a fifth aspect of the embodiments of the present disclosure, a vehicle is provided, which can include one or more processors and one or more memories, the one or more memories store at least one computer program instruction, the at least one computer program instruction is loaded and executed by the one or more processors to implement the method according to any of the embodiments of the first aspect.

[0014] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and are not limiting of the present disclosure.

[0015] BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and serve to explain the principles of the present disclosure. It is readily apparent to one of ordinary skill in the art that the accompanying drawings only illustrate some embodiments of the present disclosure, and other drawings can be obtained by one of ordinary skill in the art without creative effort based on the accompanying drawings. In the drawings:

[0017] FIG. 1 shows a schematic diagram of active short circuit switching in the related art;

[0018] FIG. 2 shows a flowchart of a vehicle active short circuit switching control method according to some embodiments of the present disclosure.

[0019] FIG. 3 shows a detailed flowchart of a vehicle active short circuit switching control method according to some embodiments of the present disclosure.

[0020] FIG. 4 shows a detailed flowchart of a vehicle active short circuit switching control method according to some embodiments of the present disclosure.

[0021] FIG. 5 schematically shows an electromotive force speed curve diagram of the present disclosure.

[0022] FIG. 6 is an actual measurement schematic diagram of an electric drive according to an example of the present disclosure.

[0023] FIG. 7 shows a detailed flow chart of a vehicle active short circuit switching control method according to some embodiments of the present disclosure.

[0024] FIG. 8 shows a flow chart of a vehicle active short circuit switching control method according to some embodiments of the present disclosure.

[0025] FIG. 9 shows a block diagram of a vehicle active short circuit switching control device according to some embodiments of the present disclosure; and

[0026] FIG. 10 shows a structural schematic diagram of a vehicle according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments of the present disclosure. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present disclosure.

[0028] In addition, the described features, structures or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, many specific details are provided to give a full understanding of the embodiments of the present disclosure. However, those skilled in the art will realize that the technical solutions of the present disclosure can be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. can be used. In other cases, well-known methods, devices, implementations or operations are not shown or described in detail to avoid obscuring the aspects of the present disclosure.

[0029] The block diagrams shown in the drawings are only functional entities, which do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0030] The flow charts shown in the drawings are only exemplary illustrations, which do not necessarily include all contents and operations / steps, and are not necessarily executed in the described order. For example, some operations / steps can be further decomposed, and some operations / steps can be combined or partially combined, so that the actual execution order can be changed according to the actual situation.

[0031] In the description of the present disclosure, it should be understood that the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can be explicitly or implicitly included one or more features. In the description of the present disclosure, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0032] In order for those skilled in the art to better understand the present disclosure, first, the application scenario related to the present disclosure is simply described.

[0033] The electric drive system is one of the core systems of new energy vehicles. Due to the complexity of the working environment, electric drive failures occur from time to time. And after the failure occurs, it shows that the power is lost and the vehicle is stranded, which seriously threatens the safety of the driver and the reputation of the manufacturer. Therefore, how to ensure that after the electric drive failure occurs, the vehicle can still guarantee high-speed stable limp or no secondary damage is a key technical issue of new energy vehicles.

[0034] In the related art, the vehicle sets active short circuit protection ASC and full-off protection FW modes, and uses the switching of the two modes to ensure that after the electric drive failure occurs, the vehicle can still guarantee high-speed stable limp or no secondary damage.

[0035] As shown in FIG. 1, FIG. 1 shows a schematic diagram of active short circuit switching in the related art. The intersection of the negative torque (switching threshold) generated by the vehicle motor is ①. And after the electric drive failure occurs, the motor speed is continuously monitored, if the current speed is less than speed ①, the vehicle controller (hereinafter referred to as MCU) enters the full-off protection FW mode; if the current speed is greater than speed ①, the MCU enters the active short circuit protection ASC mode.

[0036] In some embodiments, the FW mode (free wheeling) and the ASC mode (active short circuit) are two safe states of the drive motor system, the purpose is to avoid unexpected torque or deceleration of the motor or the vehicle.

[0037] The FW mode is the full-off protection mode (hereinafter referred to as FW mode), the implementation principle is to realize by full-off of the upper and lower bridge arms of the inverter circuit. The ASC mode is the three-phase active short circuit protection function (hereinafter referred to as ASC mode), the implementation principle is to realize by full-on of the upper bridge arm and full-off of the lower bridge arm or full-off of the upper bridge arm and full-on of the lower bridge arm.

[0038] The above scheme can meet the ideal environment under normal temperature and normal working condition, and the vehicle motor can normally perform ASC / FW switching after a three-level serious fault occurs, that is, the vehicle is in ASC mode at high speed, and the vehicle is in FW mode at medium and low speed, and the negative torque always remains in a reasonable state.

[0039] However, the above scheme has a problem that the negative torque generated in the ASC / FW mode is an inherent property of the motor, so the intersection ① is always a fixed value and cannot adaptively change with the current state of the vehicle. This leads to a problem that the ASC / FW switching using the fixed negative torque has a large problem in the actual complex environment, which easily causes vehicle failure and has a large safety hazard.

[0040] To solve the above problem, the present disclosure discloses the following technical scheme.

[0041] Referring to FIG. 2, FIG. 2 shows a flowchart of a vehicle active short circuit switching control method in an embodiment of the present disclosure, which can be executed by a device with computing processing function. Specifically, it can be executed by the controller (hereinafter referred to as MCU) of the vehicle, which is the control center of the vehicle and can control the vehicle by obtaining various states of the vehicle, including obtaining the motor speed of the vehicle and then controlling various modes of the vehicle or obtaining the fault condition of the vehicle and then controlling the vehicle, etc.

[0042] Referring to FIG. 1, the vehicle active short circuit switching control method at least includes steps 110 to 140, which are described in detail as follows:

[0043] In step 110, the maximum allowed charging power of the power battery at present and the default limp home speed are obtained.

[0044] The power battery of the vehicle itself has a BMS, which can obtain the maximum allowed charging power of the power battery at present in real time, and then send it to the MCU, so that the MCU can obtain the maximum allowed charging power of the power battery at present.

[0045] The default limp home speed is a characteristic of the vehicle, which can be obtained through the vehicle specifications.

[0046] In step 120, the maximum allowed switching speed is confirmed according to the maximum allowed charging power.

[0047] After the MCU obtains the maximum allowed charging power, the maximum allowed switching speed can be confirmed according to the maximum allowed charging power.

[0048] Specifically, in an embodiment of the present disclosure, based on the foregoing scheme, the method for confirming the maximum allowed switching speed according to the maximum allowed charging power can include steps 310-330.

[0049] Step 310: calculating the maximum allowed regenerative charging current according to the maximum allowed regenerative charging power.

[0050] When the MCU obtains the maximum allowed regenerative charging power of the power battery through the BMS, the maximum allowed regenerative charging current can be calculated by using the maximum allowed regenerative charging power.

[0051] Specifically, as shown in FIG. 4, in an embodiment of the present disclosure, the method for calculating the maximum allowed regenerative charging current according to the maximum allowed regenerative charging power can include steps 410-420.

[0052] Step 410: obtaining the bus voltage currently controlled by the vehicle.

[0053] The power battery of the vehicle is connected with the motor of the vehicle, and the motor is provided with energy by the power battery. In some embodiments, in order to control the stable operation of the motor of the vehicle, a bus can be directly arranged on the power battery and the motor. Therefore, the bus voltage currently controlled by the vehicle can be obtained in step 410 of the present disclosure, so that the voltage currently received by the motor can be known.

[0054] Step 420: dividing the maximum allowed regenerative charging power by the bus voltage to obtain the maximum allowed regenerative charging current.

[0055] Then, the maximum allowed regenerative charging current is obtained by dividing the maximum allowed regenerative charging power by the bus voltage. The maximum allowed regenerative charging current calculated here can be used for subsequent judgment. In some embodiments, the maximum allowed regenerative charging power and the maximum allowed regenerative charging current of the present disclosure can be used to determine the maximum allowed regenerative charging capacity of the power battery. The allowed regenerative charging capacity of the battery is not the same in different states. For example, in the case of extremely low temperature, the allowed regenerative charging power of the battery is 0. If an uncontrollable regenerative charging current is generated in the FW mode at this time, lithium ions in the battery will be precipitated, resulting in battery failure and irreversible loss of capacity.

[0056] Therefore, when the vehicle active short circuit switching is performed, the maximum allowed regenerative charging power is combined as a step for judgment to avoid the precipitation of lithium ions in the battery, resulting in battery failure and irreversible loss of capacity, thereby improving the safety hazard.

[0057] The maximum allowed regenerative charging current is calculated in the above steps, and step 320 is continued.

[0058] Step 320: confirming the maximum allowed potential difference according to the maximum allowed regenerative charging current.

[0059] After obtaining the maximum allowed regenerative charging current, the maximum allowed potential difference can be confirmed according to the maximum allowed regenerative charging current in the present disclosure.

[0060] In some embodiments of the present disclosure, based on the foregoing scheme, before step 120, the method of the present disclosure can further include steps 510-520.

[0061] Step 510: Control the vehicle to switch to the full-off tube protection mode.

[0062] When the motor enters the FW mode at a high speed, a large induced back electromotive force will be generated. When there is a difference between the voltage of the power battery of the vehicle and the induced back electromotive force of the motor of the vehicle, an adverse braking torque and a back charging current will be generated, and the greater the difference, the greater the impact. In order to reduce the impact of the back charging current, the present disclosure measures the correlation between the induced back electromotive force and the corresponding back charging current value through steps 510-520 of the present disclosure. Therefore, step 510 of the present disclosure needs to control the vehicle to switch to the full-off tube protection mode.

[0063] Step 520: Stepwise adjust the input voltage to change the potential difference between the induced back electromotive force and the input voltage, record the current back charging current value, fit the potential difference value and the back charging current value to form a potential difference current curve.

[0064] When the vehicle of the present disclosure switches to the full-off tube protection mode, the input voltage is stepwise adjusted to change the potential difference between the induced back electromotive force and the input voltage, and the current back charging current value is recorded. For example, the stepwise adjustment is performed by gradually increasing the voltage by 1V, and finally the corresponding back charging current size under the potential difference from 0 to the maximum potential difference can be obtained. Then, by fitting the potential difference value and the back charging current value, a potential difference current curve is formed. In this way, step 320 can be performed through the potential difference current curve.

[0065] Steps 510-520 of the present disclosure can effectively measure the relationship between the potential difference value and the back charging current value by pre-testing the corresponding back charging current value under different potential difference values. In some embodiments, steps 510-520 of the present disclosure can be performed at any step before step 320, and the present disclosure does not limit this.

[0066] After the potential difference current curve is formed in steps 510-520, step 320 of the present disclosure for confirming the maximum allowed potential difference according to the maximum allowed back charging current can include:

[0067] According to the potential difference current curve, the maximum allowed potential difference corresponding to the maximum allowed back charging current is determined.

[0068] That is, by determining the maximum allowed potential difference corresponding to the back charging current on the potential difference current curve, the maximum allowed potential difference can be obtained. For example, the back charging current is the horizontal coordinate, and the corresponding maximum allowed potential difference is the vertical coordinate.

[0069] After the maximum allowable potential difference is determined, step 330 is continued.

[0070] Step 330: Determine the maximum allowable switching speed using the maximum allowable potential difference.

[0071] In some embodiments of the present disclosure, based on the foregoing scheme, before step 120, the method of the present disclosure can further include the following steps.

[0072] The motor of the vehicle is controlled to rotate at different speeds, and the induced back electromotive force of the motor at different speeds is recorded, and an electromotive force speed curve is generated.

[0073] In the project development process of the present disclosure, the induced back electromotive force of the motor at different speeds is simulated and bench tested. Through simulation and testing, the corresponding different induced back electromotive forces at different speeds can be obtained. In some embodiments, the maximum allowable potential difference of the vehicle is the difference between the induced back electromotive force of the motor of the vehicle and the voltage of the power battery.

[0074] As shown in FIG. 5, FIG. 5 schematically shows the electromotive force speed curve of the present disclosure. As can be seen from FIG. 5, the induced back electromotive force of the DC bus and the speed generally present a positive proportional relationship.

[0075] In some embodiments, the above steps of the present disclosure can be performed at any step before step 330, and the present disclosure does not limit this.

[0076] After the electromotive force speed curve is obtained through the above steps, the method for determining the maximum allowable switching speed using the maximum allowable potential difference in step 330 of the present disclosure can include:

[0077] According to the electromotive force speed curve, the maximum allowable switching speed corresponding to the maximum allowable potential difference is determined.

[0078] The process of this determination can be obtained by adding the maximum allowable potential difference to the voltage of the power battery to obtain the induced back electromotive force of the motor of the vehicle, and then through FIG. 5, the speed corresponding to the horizontal coordinate of the induced back electromotive force of the motor of the vehicle as the vertical coordinate is the maximum allowable switching speed.

[0079] The maximum allowable switching speed can be determined through the above steps, and step 130 is continued.

[0080] In step 130: Confirm the switching threshold according to the maximum allowable switching speed and the default limp-home speed.

[0081] In some embodiments of the present disclosure, based on the foregoing scheme, the method for confirming the switching threshold according to the maximum allowable switching speed and the default limp-home speed in step 130 of the present disclosure can include:

[0082] When the maximum allowable switching speed is greater than or equal to the default limp-home speed, the switching threshold is equal to the default limp-home speed plus a preset value;

[0083] When the maximum allowable switching speed is less than the default limp-home speed, the switching threshold is equal to the maximum allowable switching speed.

[0084] The present disclosure compares the maximum allowable switching speed with the default limp-home speed, so that the switching threshold always remains a large value when the conditions are met, avoiding the problem that the maximum limp-home speed of the vehicle is limited because the switching threshold is too small. For a four-wheel drive vehicle, after the single electric drive experiences a three-level serious fault, the other electric drive can still work normally, i.e., enters the limp-home state to avoid the vehicle breaking down. Since the electric drive cannot be in the ASC state for a long time, this mode is only suitable for use when the vehicle needs to be quickly reduced in speed after the electric drive fails; if the vehicle needs to run in the limp-home state for a long time, it must be switched to the FW state first. Therefore, if it is necessary to ensure a larger limp-home speed of the vehicle, a higher ASC / FW switching threshold needs to be set. The present disclosure combines the default limp-home speed of the vehicle, and when the maximum allowable switching speed is less than the default limp-home speed, the switching threshold is equal to the maximum allowable switching speed. According to step 140 of the present disclosure, since the current speed is less than the switching threshold when the maximum allowable switching speed is less than the default limp-home speed, the switching threshold is equal to the maximum allowable switching speed, so that the vehicle can be automatically switched to the FW state when the current speed of the vehicle is less than the default limp-home speed, ensuring a larger limp-home speed of the vehicle. If the maximum allowable switching speed is greater than or equal to the default limp-home speed, it means that the default limp-home speed has not reached the maximum allowable switching speed, so the switching threshold can be increased, i.e., the switching threshold is equal to the default limp-home speed plus a preset value. In some embodiments, this preset value can be adjusted according to actual conditions, for example, it can be 500 rpm.

[0085] Therefore, by using the above scheme, the switching threshold can be obtained according to the real-time situation of the vehicle, and a larger value is maintained as much as possible under the condition that the conditions are met, avoiding the situation that the vehicle is in the FW state at high speed, and improving the safety.

[0086] The switching threshold is determined through the above steps, and step 140 is continued.

[0087] In step 140, when the vehicle needs to be actively short-circuited, the vehicle is controlled to be actively short-circuited according to at least the switching threshold.

[0088] In some embodiments of the present disclosure, based on the foregoing scheme, the method of controlling the vehicle to be actively short-circuited according to the switching threshold in step 140 can include steps 610-630.

[0089] Step 610: Obtain the current rotating speed of the vehicle motor.

[0090] The MCU can obtain the current rotating speed of the vehicle motor, and use the current rotating speed and the switching threshold value determined in step 130 to make subsequent judgments.

[0091] Step 620: When the current rotating speed is greater than or equal to the switching threshold value, control the vehicle to enter the active short-circuit protection mode.

[0092] Step 630: When the current rotating speed is less than the switching threshold value, control the vehicle to enter the full-off protection mode.

[0093] In some embodiments, the active short-circuit switching of the present disclosure when the vehicle needs to be performed can mean that the vehicle has occurred a three-level fault of the electric drive, which corresponds to a more serious fault, for example, a fault that needs to be parked. For example, the controller has overcurrent or overvoltage phenomenon; 2. Internal components of the drive motor are damaged or faulty; 3. The battery voltage is too low or too high, causing the controller to fail; 4. Electronic system failure or communication anomaly and the like. In some embodiments, the MCU can obtain the current state of the vehicle, thereby obtaining these faults.

[0094] If no three-level fault is obtained, it means that active short-circuit switching is not needed, and at this time, active short-circuit switching can not be performed.

[0095] The above introduces step 140 of the present disclosure, and the present disclosure can further perform the following method after step 140.

[0096] As shown in FIG. 7, FIG. 7 shows a detailed flowchart of the vehicle active short-circuit switching control method in the embodiments of the present disclosure; in some embodiments of the present disclosure, based on the foregoing scheme, the method of the present disclosure can further include steps 710-720.

[0097] Step 710: Confirm the actual limp-home speed according to the maximum allowable switching rotating speed and the default limp-home speed.

[0098] In some embodiments of the present disclosure, based on the foregoing scheme, the method of confirming the actual limp-home speed according to the maximum allowable switching rotating speed and the default limp-home speed in step 710 can include:

[0099] When the maximum allowable switching rotating speed is greater than or equal to the default limp-home speed, the actual limp-home speed is equal to the default limp-home speed;

[0100] When the maximum allowable switching rotating speed is less than the default limp-home speed, the actual limp-home speed is equal to the maximum allowable switching rotating speed minus a preset value.

[0101] After the actual limp-home speed is determined, step 720 is performed

[0102] Step 720: control the vehicle to travel at the actual limp-home speed.

[0103] The steps 710-720 of the present disclosure determine the actual limp-home speed through the relationship between the maximum allowable switching speed and the default limp-home speed. When the maximum allowable switching speed is greater than or equal to the default limp-home speed, it means that the vehicle continues to travel at the default limp-home speed at this time, and there is no risk of exceeding the maximum allowable switching speed, so the corresponding battery failure and irreversible loss of capacity can be avoided, and therefore the actual limp-home speed at this time is equal to the default limp-home speed. When the maximum allowable switching speed is less than the default limp-home speed, it means that if the vehicle travels at the default limp-home speed at this time, there is a risk, for example, it may cause battery failure, so the actual limp-home speed at this time is equal to the maximum allowable switching speed minus the preset value. In some embodiments, the preset value here is the same as the preset value in step 130, for example, both can be 500 rpm. In some embodiments, this preset value can be adjusted according to the actual situation.

[0104] Therefore, the steps 710-720 of the present disclosure can ensure that the vehicle travels at the actual limp-home speed without causing battery failure and irreversible loss of capacity, further ensuring safety.

[0105]

[0106] The present disclosure actively controls the short-circuit switching of the vehicle through the above method, and the effect of the present disclosure will be further described below in combination with specific application examples.

[0107] The scheme in the related art uses the negative torque generated by the vehicle motor as the switching threshold. If the current speed is less than the negative torque, the vehicle controller (hereinafter referred to as MCU) enters the full-off protection FW mode; if the current speed is greater than the negative torque, the MCU enters the active short-circuit protection ASC mode. However, using this method, since the negative torque is a fixed switching threshold regardless of the actual environment, it cannot cope with complex and variable environments. The present disclosure analyzes that the factors that most affect the switching of the two modes of the vehicle are: 1, the comparison relationship between the power battery voltage and the motor induced back electromotive force; 2, the maximum allowable recharging capacity of the power battery; 3, the negative impact in the long ASC state. The influence of these three factors on the active short-circuit protection switching of the vehicle will be introduced one by one.

[0108] 1, the comparison relationship between the power battery voltage and the motor induced back electromotive force

[0109] When the motor enters the FW mode at a high speed, a large induced back electromotive force is generated. In the case where the voltage of the power battery is lower than the induced back electromotive force of the motor, there is a potential difference between the power battery and the motor, and the existence of the MCU freewheeling diode can cause uncontrollable passive rectification, which not only generates negative torque, but also generates uncontrollable back charging current; and the greater the potential difference, the greater the negative torque and back charging current generated.

[0110] For example, when a certain electric drive is tested on a bench, it is found that when the motor speed reaches 4500 rpm, the induced back electromotive force in the FW mode is 210.5V, which is higher than the minimum voltage 200V of the power battery.

[0111] Table 1 below is a table of the relationship between the motor speed (rpm) and the induced back electromotive force (V).

[0112] Table 1

[0113] Through the above bench test, when the motor speed reaches 6400 rpm, the electric drive enters the FW state, and at this time the induced back electromotive force of the motor is 296.5V. At the same time, the voltage of the input power supply cabinet is gradually reduced during the test, and the test results are as follows:

[0114] (1) When the input voltage is reduced to 296V, braking torque begins to be generated.

[0115] (2) When the input voltage is further reduced to 225V, the braking torque at the motor end is about 100Nm, and the back charging current at the DC end is about 356A.

[0116] (3) When the input voltage is kept at 225V and the speed is gradually reduced to 5000 rpm, the braking torque at the motor end is 8.8Nm, and the back charging current at the DC end is about 15A.

[0117] Through the above test, it can be seen that when there is a difference between the voltage of the power battery of the vehicle and the induced back electromotive force of the motor of the vehicle, adverse braking torque and back charging current will be generated, and the greater the difference, the greater the impact. Therefore, if the fixed negative torque is directly used as the switching threshold, it will result in a large error in the actual switching result. In some embodiments, there are two methods to solve the above problem: 1. Increase the input voltage; 2. Reduce the speed of entering the FW. Since the input voltage (power battery voltage) is the actual state of the vehicle and cannot be modified artificially, the speed of entering the FW can be reduced for optimization.

[0118] 2. Maximum allowable back charging capacity of power battery

[0119] The amount of charge allowed to be recharged by the battery is not the same in different states. For example, in the case of extremely low temperature, the battery allows 0 recharging power. If an uncontrollable recharging current is generated in the FW mode at this time, lithium ions will be precipitated inside the battery, causing battery failure and irreversible loss of capacity.

[0120] Therefore, the current battery BMS system generally has a battery safety operation program (SOP) algorithm. The "recharge peak" and "recharge sustain" are defined, and the allowed recharging capacity is fed back to the MCU and the electric drive system.

[0121] Recharge peak: The recharge peak refers to the maximum charging power or charging current that the battery can accept during charging. It represents the highest charging rate that the battery can withstand. When the charging power or charging current exceeds the recharge peak, it may cause the battery to overheat, damage or other safety problems.

[0122] Recharge sustain: The recharge sustain refers to the longest charging time or charging capacity that the battery can sustain during charging. It represents the time or capacity that the battery can maintain a safe state during charging. When the charging time or charging capacity exceeds the recharge sustain, it may have a negative impact on the performance and life of the battery.

[0123] The recharge peak and recharge sustain are important parameters in the battery management system (Battery Management System, hereinafter referred to as BMS) for controlling the charging process. When charging the battery, the BMS will limit the charging power or charging current according to the characteristics and design parameters of the battery, to ensure that the charging is within the recharge peak and sustain value range, to avoid overloading, overheating or other safety problems to the battery. In some embodiments, the size of the SOP coefficient of the battery is related to the following parameters: battery SOC, battery temperature, battery voltage and battery current limiting fault.

[0124] Therefore, if the current environment does not consider the allowed recharging power of the battery, directly using a fixed motor to generate negative torque for switching control may cause uncontrollable recharging current in the FW mode, which may cause lithium ions to precipitate inside the battery, causing battery failure and irreversible loss of capacity. Therefore, we need to consider the allowed recharging power of the battery in the current environment when performing active short circuit switching.

[0125] 3. Negative effects of long ASC state

[0126] The first two points illustrate the influence of high back electromotive force generated by FW mode on power battery at high speed, so the switching threshold of ASC / FW mode needs to be reduced. However, the switching threshold cannot be reduced indefinitely, and too low threshold will cause the electric drive to be in ASC mode for a long time, and a series of negative effects will be generated, so the switching threshold needs to be set to be greater than the limp speed in actual application.

[0127] The negative effects include at least:

[0128] 1) The threshold is too low, and the vehicle is in ASC for a long time, and the electric drive is rapidly heated

[0129] When the electric drive enters ASC mode at high speed, the motor and MCU are rapidly heated, and if the switching threshold is too low, the vehicle will be in ASC for a long time during the process of gradually reducing the speed from high speed, which will cause the MCU and motor to be overheated and burned out, and this problem has been a fault case on previous vehicle models.

[0130] As shown in FIG. 6, FIG. 6 is a measured schematic diagram of an electric drive according to an example of the present disclosure. For example, according to the measured data of a certain electric drive, if the switching threshold is 6400 rpm, the MCU is heated by 31℃ and the motor is heated by 52℃ in 1 min when entering ASC; and the temperature of the motor will continue to rise, and the temperature of the motor will be heated by 110℃ in 3 min. Therefore, if the switching threshold is set too low, the vehicle will be in ASC for a long time, the electric drive will be rapidly heated, and there will be a great safety hazard.

[0131] 2) The threshold is too low, and the maximum limp speed of the vehicle is limited

[0132] For a four-wheel drive vehicle, after the single electric drive occurs a serious fault of level three, the other electric drive can still work normally, that is, the vehicle enters the limp state to avoid breaking down. Since the electric drive cannot be in ASC state for a long time, this mode is only suitable for use when the vehicle needs to be rapidly reduced in speed after the electric drive fails; if the vehicle needs to be in the limp state for a long time, it must be switched to the FW state.

[0133] Therefore, if the vehicle needs to have a larger limp speed, a higher ASC / FW switching threshold needs to be set.

[0134] Therefore, in summary of the above three contents, if the vehicle actively switches at high speed, for example, the electric drive needs to enter ASC or FW mode after a serious fault of level three occurs, the following factors need to be considered when selecting the two modes:

[0135] 1. When the motor enters the FW mode at high speed, a large induced back electromotive force will be generated. In the case that the voltage of the power battery is lower than the induced back electromotive force of the motor, there is a potential difference between the power battery and the motor, and the existence of the MCU freewheeling diode will cause uncontrollable passive rectification.

[0136] 2、When the power battery allows a small recharging capacity due to environmental or vehicle state, etc., but the ASC / FW switching threshold is high at this time, it will cause the uncontrollable recharging current generated by the high potential difference to exceed the allowed value of the power battery, causing BMS overcharge failure or cell damage.

[0137] 3、When the switching threshold is set too low, the electric drive will be in ASC mode for a long time after failure, causing rapid temperature rise; at the same time, the low threshold will also affect the setting of the limp home speed of the vehicle, affecting the safety of driving.

[0138] The present disclosure confirms the maximum allowed switching speed according to the maximum allowed recharging power, confirms the switching threshold according to the maximum allowed switching speed and the default limp home speed, and controls the vehicle to actively switch to short circuit according to the switching threshold when the vehicle needs to actively switch to short circuit.

[0139] In some embodiments, the present disclosure considers the state of the power battery to set the maximum allowed switching speed. In the related art, the high speed of the motor entering the FW mode and generating a large induced back electromotive force are not fully considered. In the case where the voltage of the power battery is lower than the induced back electromotive force of the motor, there is a recharging current caused by the potential difference between the power battery and the motor; if the power battery allows a small recharging capacity at this time, the motor recharging current will exceed the allowed value of the power battery, causing BMS overcharge failure or cell damage. In step 120 of the present disclosure, the maximum allowed switching speed is confirmed according to the maximum allowed recharging power, which can to some extent avoid the vehicle entering the FW mode at high speed, prevent the actual recharging current from exceeding the battery recharging capacity, and avoid BMS failure and cell damage. Therefore, the method of the present disclosure can improve safety.

[0140] At the same time, the present disclosure also considers the limp home speed, and sets the ASC / FW switching threshold in combination with the limp home speed. Specifically, the present disclosure confirms the switching threshold according to the maximum allowed switching speed and the default limp home speed, and since the switching threshold is related to the default limp home speed, it is avoided that the electric drive will be in ASC mode for a long time after failure, causing rapid temperature rise. Especially in single motor mode, the vehicle can still run at high speed after single motor failure.

[0141] Further, the present disclosure further combines the relationship between the actual limp home speed and the maximum allowed switching speed after the vehicle actively switches to short circuit control, avoids the uncontrollable recharging current generated in the FW mode, which will cause lithium ions to precipitate inside the battery, leading to battery failure and irreversible loss of capacity.

[0142] Therefore, by the method of the present disclosure, the active short circuit switching is flexibly controlled according to the actual environment, the above problems are solved, the vehicle failure is effectively reduced, and the safety factor is high.

[0143] The active short circuit switching control method of the present disclosure is introduced above. A specific embodiment is listed below to further illustrate the content of the present disclosure.

[0144] As shown in FIG. 8, FIG. 8 shows a flowchart of the vehicle active short circuit switching control method in the embodiment of the present disclosure. The present disclosure can include steps S801-S809.

[0145] Step S801: The power battery feeds back the maximum allowed recharge power.

[0146] Corresponding to step 110 of the present disclosure, the current maximum allowed recharge power of the power battery is obtained.

[0147] Step S802: The electric drive calculates the maximum allowed recharge current.

[0148] This step corresponds to steps 410-420 of the present disclosure.

[0149] Step S803: The recharge current looks up the maximum allowed potential difference.

[0150] This step corresponds to the determination of the maximum allowed potential difference corresponding to the maximum allowed recharge current according to the potential difference-current curve of the present disclosure.

[0151] Step S804: The maximum allowed induced back electromotive force = power battery voltage + maximum allowed potential difference.

[0152] Step S805: The induced back electromotive force looks up the maximum allowed switching speed

[0153] Corresponding to the determination of the maximum allowed switching speed corresponding to the maximum allowed potential difference according to the electromotive force-speed curve of the present disclosure.

[0154] Step S806: Is the maximum allowed switching speed ≥ default limp-home speed?

[0155] This step corresponds to the content of step 130 of the present disclosure.

[0156] Step S807: If yes, switching threshold = default limp-home speed + TBD; actual limp-home speed = default limp-home speed.

[0157] Step S808: If no, switching threshold = maximum allowed switching speed; actual limp-home speed = maximum allowed switching speed - TBD.

[0158] Step S809: Control the vehicle FW / ASC according to the switching threshold.

[0159] This step corresponds to step 140 of the present disclosure.

[0160] In summary, based on the scheme of the present disclosure, the present disclosure sets the maximum allowable switching speed by considering the state of the power battery, and sets the ASC / FW switching threshold by considering the limp-home speed. With the method of the present disclosure, since the switching threshold is determined according to the maximum allowable switching speed and the default limp-home speed, and the maximum allowable switching speed is determined according to the current maximum allowable recharging power of the power battery, the switching threshold of the present disclosure is not a fixed value, but is obtained in real time according to the current maximum allowable recharging power of the power battery through the steps of the present disclosure, avoiding the problem that the fixed threshold based on the active short circuit switching in the related art cannot adapt to the complex and changeable actual environment in actual application, and further causing vehicle failure and safety hazards.

[0161] Specifically, the present disclosure determines the maximum allowable switching speed according to the maximum allowable recharging power, which can to some extent avoid the vehicle entering the FW mode at a high speed, prevent the actual recharging current from exceeding the battery recharging capacity, and avoid BMS failure and cell damage. At the same time, the present disclosure also considers the limp-home speed, and determines the switching threshold according to the maximum allowable switching speed and the default limp-home speed, which can improve the switching threshold of ASC / FW, thereby avoiding the problem that the electric drive fails and stays in the ASC mode for a long time, causing rapid temperature rise.

[0162] Moreover, the method of the present disclosure is only software strategy optimization, without involving hardware changes and costs, and is convenient for import and implementation.

[0163] After the scheme of the present disclosure is implemented, the recharging current of different potential differences is calibrated in advance, and the allowable recharging current of the power battery is identified in real time on the whole vehicle, which can avoid the problem that the motor recharging current exceeds the allowable value of the power battery, causing BMS overcharging failure or cell damage.

[0164] After the scheme of the present disclosure is implemented, the real-time calculation strategy of the maximum allowable switching speed can improve the switching threshold of ASC / FW, and accordingly the default limp-home speed can also be improved, so as to achieve the effect that the whole vehicle can still drive at high speed after single motor failure.

[0165] Therefore, the scheme of the present disclosure can effectively reduce vehicle failure and has high safety factor.

[0166] The device embodiment of the present disclosure is introduced below, which can be used to execute the vehicle active short circuit switching control method in the above-mentioned embodiments of the present disclosure. For details not disclosed in the device embodiment of the present disclosure, please refer to the above-mentioned embodiments of the vehicle active short circuit switching control method of the present disclosure.

[0167] Referring to FIG. 9, a block diagram of a vehicle active short circuit switching control device in an embodiment of the present disclosure is shown. The device can include: an acquisition unit 901 configured to acquire a current maximum allowed recharge power of a power battery and a default limp-home speed; a rotational speed confirmation unit 902 configured to confirm a maximum allowed switching rotational speed according to the maximum allowed recharge power; a threshold confirmation unit 903 configured to confirm a switching threshold according to the maximum allowed switching rotational speed and the default limp-home speed; and a switching unit 904 configured to control the vehicle to perform active short circuit switching according to at least the switching threshold when the vehicle needs to perform active short circuit switching.

[0168] In some embodiments, the device further comprises:

[0169] a travel control unit configured to confirm an actual limp-home speed according to the maximum allowed switching rotational speed and the default limp-home speed;

[0170] control the vehicle to travel at the actual limp-home speed.

[0171] In some embodiments, the travel control unit is specifically configured to

[0172] when the maximum allowed switching rotational speed is greater than or equal to the default limp-home speed, the actual limp-home speed is equal to the default limp-home speed;

[0173] when the maximum allowed switching rotational speed is less than the default limp-home speed, the actual limp-home speed is equal to the maximum allowed switching rotational speed minus a preset value.

[0174] In some embodiments, the rotational speed confirmation unit is specifically configured to

[0175] calculate a maximum allowed recharge current according to the maximum allowed recharge power;

[0176] confirm a maximum allowed potential difference according to the maximum allowed recharge current; and

[0177] determine the maximum allowed switching rotational speed using the maximum allowed potential difference.

[0178] In some embodiments, the device further comprises:

[0179] a data fitting unit configured to control the vehicle to switch to a full-off battery protection mode;

[0180] step-adjust an input voltage to change a potential difference between an induced back electromotive force and the input voltage, record a current recharge current value, fit the potential difference value and the recharge current value to form a potential difference-current curve;

[0181] the rotational speed confirmation unit is specifically configured to acquire a current bus voltage controlled by the vehicle.

[0182] divide the maximum allowed regenerative power by the bus voltage to obtain a maximum allowed regenerative current; and

[0183] determine, according to the potential difference current curve, a maximum allowed potential difference corresponding to the maximum allowed regenerative current.

[0184] In some embodiments, the apparatus further comprises:

[0185] a curve generating unit configured to control the vehicle motor to rotate at different rotating speeds, record the induced back electromotive force of the motor at different rotating speeds, and generate an electromotive force rotating speed curve;

[0186] The rotating speed confirming unit is configured to determine, according to the electromotive force rotating speed curve, a maximum allowed switching rotating speed corresponding to the maximum allowed potential difference.

[0187] In some embodiments, the threshold confirming unit is configured to, when the maximum allowed switching rotating speed is greater than or equal to the default limp-home speed, set the switching threshold to be equal to the default limp-home speed plus the preset value; and when the maximum allowed switching rotating speed is less than the default limp-home speed, set the switching threshold to be equal to the maximum allowed switching rotating speed.

[0188] In some embodiments, the switching unit is configured to

[0189] obtain a current rotating speed of the vehicle motor;

[0190] when the current rotating speed is greater than or equal to the switching threshold, control the vehicle to enter an active short-circuit protection mode; and

[0191] when the current rotating speed is less than the switching threshold, control the vehicle to enter a full-off protection mode.

[0192] The various units described above (such as the obtaining unit 901, the rotating speed confirming unit 902, the threshold confirming unit 903, the switching unit 904, etc.) can be configured in one controller or CPU, or in multiple controllers or CPUs, and are not limited herein.

[0193] Based on the same inventive concept, the embodiments of the disclosure further provide a computer program product. The computer program product comprises computer instructions stored in a computer readable storage medium and adapted to be read and executed by a processor, so as to enable a computer device having the processor to perform the method described above.

[0194] Based on the same inventive concept, embodiments of this disclosure provide a computer-readable storage medium storing at least one computer program instruction, which is loaded and executed by a processor to perform the operations described above.

[0195] Based on the same inventive concept, this disclosure also provides a vehicle. Referring to FIG10, a structural schematic diagram of the vehicle in this disclosure is shown. The vehicle includes one or more memories 1004, one or more processors 1002, and at least one computer program (computer program instruction) stored on the memory 1004 and executable on the processor 1002. When the processor 1002 executes the computer program, it implements the method described above.

[0196] In some embodiments, as shown in FIG. 10, a bus architecture (represented by bus 1000) may be included. Bus 1000 may include any number of interconnected buses and bridges, linking various circuits including one or more processors represented by processor 1002 and memory represented by memory 1004. Bus 1000 may also link various other circuits such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and therefore will not be described further herein. Bus interface 1005 provides an interface between bus 1000 and receiver 1001 and transmitter 1003. Receiver 1001 and transmitter 1003 may be the same element, i.e., a transceiver, providing a unit for communicating with various other devices over a transmission medium. Processor 1002 is responsible for managing bus 1000 and general processing, while memory 1004 may be used to store data used by processor 1002 during operation.

[0197] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored as one or more instructions or codes on or transmitted via a computer-readable medium. Other examples and embodiments are within the scope and spirit of this disclosure and the appended claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hardwired, or any combination thereof. Furthermore, the functional units may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit.

[0198] In several embodiments provided by the present disclosure, it should be understood that the disclosed technology can be implemented in other ways. Among them, the above-mentioned device embodiments are only schematic, for example, the division of the units can be a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units or modules shown or discussed can be indirect coupling or communication connection through some interface, unit or module, and can be electrical or other forms.

[0199] The units described as separate components can or can not be physically separated, and the components of the control device can or can not be physical units, i.e. can be located in one place or can be distributed to multiple units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.

[0200] The integrated unit, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present disclosure essentially or the part that contributes to the related art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a number of instructions for causing a computer device (which can be a personal computer, a server or a network device, etc.) to execute all or part of the steps of the method described in the various embodiments of the present disclosure. The aforementioned storage medium includes: a U disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a mobile hard disk, a magnetic disk or an optical disk, and various computer program instruction storage media.

[0201] The above only describes the embodiments of the present disclosure and does not limit the present disclosure. For those skilled in the art, the present disclosure can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present disclosure shall be included in the scope of the claims of the present disclosure.

Claims

1. A method for switching to an active short circuit when driving a vehicle, including obtaining the current maximum permissible recharging power of the traction battery and the default emergency mode driving speed; determination of the maximum permissible rotation speed when switching according to the maximum permissible recharging power; determining the switching threshold according to the maximum permissible rotation speed during switching and the default emergency mode driving speed; and controlling the vehicle by performing a switch to an active short circuit according to the switching threshold when it is necessary for the vehicle to perform a switch to an active short circuit.

2. The method according to paragraph 1, characterized in that after determining the maximum permissible rotation speed during switching according to the maximum permissible recharge power, the method additionally includes determining the practical emergency running speed according to the maximum permissible switching speed and the default emergency running speed; and driving a vehicle while ensuring movement at practical speed in emergency mode.

3. The method according to paragraph 2, characterized in that the determination of the practical speed of movement in emergency mode according to the maximum permissible rotation speed during switching and the speed of movement in emergency mode by default provides for the following: when the maximum allowable switching speed is greater than or equal to the default emergency running speed, the practical emergency running speed is equal to the default emergency running speed; and When the maximum permissible switching speed is less than the default emergency running speed, the practical emergency running speed is equal to the maximum permissible switching speed minus the set value.

4. The method according to any one of paragraphs 1-3, characterized in that determining the maximum permissible rotation speed during switching according to the maximum permissible recharge power includes Calculation of the maximum permissible recharge current according to the maximum permissible recharge power; determination of the maximum permissible potential difference according to the maximum permissible recharging current; and determination of the maximum permissible switching speed using the maximum permissible potential difference.

5. The method according to paragraph 4, characterized in that before determining the maximum permissible rotation speed during switching according to the maximum permissible recharge power, the method additionally includes vehicle control with switching to free rotation mode; stepwise adjusting the input voltage to change the potential difference value between the induced reverse electromotive force and the input voltage and recording the current value of the recharging current; and adjusting the potential difference value and the recharging current value to form a potential difference and current curve; in this case, the calculation of the maximum permissible recharging current according to the maximum permissible recharging power includes: obtaining real-time bus voltage from the vehicle's engine control unit; dividing the maximum allowable recharge power by the bus voltage to obtain the maximum allowable recharge current; and in this case, the determination of the maximum permissible potential difference according to the maximum permissible recharging current includes: determination according to the curve of potential difference and current of the maximum permissible potential difference corresponding to the maximum permissible recharge current.

6. The method according to paragraph 4, characterized in that before determining the maximum permissible rotation speed during switching according to the maximum permissible recharge power, the method additionally includes controlling the engine of a vehicle to rotate at different rotation speeds and recording the induced back electromotive forces of the engine at different rotation speeds; and obtaining a curve of the electromotive force and rotation speed; Determination of the maximum permissible switching speed using the maximum permissible potential difference includes: determination, according to the curve of electromotive force and rotation speed, of the maximum permissible rotation speed during switching, corresponding to the maximum permissible potential difference.

7. The method according to any one of paragraphs 1-6, characterized in that the determination of the switching threshold according to the maximum permissible rotation speed during switching and the speed of movement in emergency mode by default provides for the following: when the maximum allowable switching speed is greater than or equal to the default emergency running speed, the switching threshold is equal to the sum of the default emergency running speed and the set value; and When the maximum allowable shift speed is less than the default emergency running speed, the shift threshold is equal to the maximum allowable shift speed.

8. The method according to any one of paragraphs 1-7, characterized in that the control of the vehicle with the execution of switching to an active short circuit according to the switching threshold includes obtaining the current engine speed of the vehicle; controlling the vehicle to enter the active short circuit protection mode when the current rotation speed is greater than or equal to the switching threshold; and control the vehicle to enter freewheel mode when the current rotation speed is less than the switching threshold.

9. A device for switching to an active short circuit when driving a vehicle, comprising a receiving unit configured to receive the current maximum permissible recharging power of the traction battery and the default emergency mode travel speed; a rotation speed determination unit configured to determine the maximum permissible rotation speed when switching according to the maximum permissible recharge power; a threshold determination unit configured to determine a switching threshold according to the maximum permissible rotation speed during switching and the default emergency mode driving speed; and a switching unit configured to control the vehicle to perform switching to an active short circuit according to a switching threshold when the vehicle needs to perform switching to an active short circuit.

10. The device according to paragraph 9, characterized in that it additionally contains a movement control unit configured to determine a practical emergency travel speed according to a maximum permissible switching speed and a default emergency travel speed; and control of a vehicle to move at practical speed in emergency mode.

11. The device according to item 10, characterized in that the movement control unit, in particular, is designed so that when the maximum allowable switching speed is greater than or equal to the default emergency running speed, the practical emergency running speed is equal to the default emergency running speed; and When the maximum permissible switching speed is less than the default emergency running speed, the practical emergency running speed is equal to the maximum permissible switching speed minus the set value.

12. A device according to any one of paragraphs 9-12, characterized in that the rotation speed determination unit, in particular, is designed with the possibility calculation of the maximum permissible recharge current according to the maximum permissible recharge power; determining the maximum permissible potential difference according to the maximum permissible recharging current; and determining the maximum permissible switching speed by using the maximum permissible potential difference.

13. The device according to paragraph 12, characterized in that it additionally contains a data fitting unit configured to control the vehicle to switch to a free rotation mode; stepwise adjusting the input voltage to change the value of the potential difference between the induced reverse electromotive force and the input voltage and recording the current value of the recharging current; and adjusting the value of the potential difference and the value of the recharging current to form a curve of the potential difference and the current; wherein the rotation speed determination unit, in particular, is configured to obtain the bus voltage in real time from the engine control unit of the vehicle; dividing the maximum allowable recharge power by the bus voltage to obtain the maximum allowable recharge current; and determination according to the curve of potential difference and current of the maximum permissible potential difference corresponding to the maximum permissible recharge current.

14. The device according to paragraph 13, characterized in that it additionally contains a curve obtaining unit configured to control the vehicle engine to rotate at different rotation speeds and record the induced reverse electromotive forces of the engine at different rotation speeds; and to obtain a curve of the electromotive force and rotation speed; wherein the rotation speed determination unit is configured to determine, according to the curve of the electromotive force and rotation speed, the maximum permissible rotation speed during switching, corresponding to the maximum permissible potential difference.

15. The device according to any one of paragraphs. 9-14, characterized in that the threshold determination unit is designed so that when the maximum permissible rotation speed during switching is greater than or equal to the default emergency mode speed, the switching threshold is equal to the default emergency mode speed plus a predetermined value; and when the maximum permissible rotation speed during switching is less than the default emergency mode speed, the switching threshold is equal to the maximum permissible rotation speed during switching.

16. A device according to any one of paragraphs 9-15, characterized in that the switching unit is designed with the possibility obtaining the current engine speed of the vehicle; control the vehicle to enter the active short circuit protection mode when the current rotation speed is greater than or equal to the switching threshold; and vehicle control to enter freewheel mode when the current rotation speed is less than the switching threshold.

17. A vehicle comprising: a processor and a memory device, wherein the memory device stores a computer program command executed by the processor, and the processor, when executing the computer program command, implements the command for the method according to any of paragraphs 1-8.

18. A machine-readable data carrier on which at least one program code is stored, wherein the loading and execution of at least one program code is ensured by a processor for performing the operation of the method according to any of paragraphs 1-8.