Control method for detecting vehicle speed before power failure during running of new energy vehicle

Abstract

The invention provides a control method for detecting the vehicle speed before power failure in the running process of a new energy vehicle, and aims to judge the power failure opportunity by detecting the rotating speed of a motor and the current of a battery so as to avoid damage of high-voltage impact to system elements. The method comprises the four steps of fault detection, fault type judgment, power-off condition judgment and a delayed power-off mechanism: when a battery management system detects a non-limit fault, if the battery current is lower than 20A and the rotating speed of a motor is lower than 300rpm, executing power-off operation; if the fault is a limit fault (such as collision or thermal runaway), the power is directly cut off. And if the power-off condition of the non-limit fault is not achieved, the system is forcibly powered off after delaying for 50 seconds. According to the method, the safety of the high-voltage system is ensured, and the stability and reliability of the new energy automobile in sudden failures are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicle control, and more specifically to a control method for detecting vehicle speed before power failure during driving of a new energy vehicle. Background Art

[0002] With the rapid development of new energy vehicles, the application of battery electrification drive has gradually become mainstream. However, electric vehicles are easily affected by various factors such as battery status and power system failure during driving. In particular, the performance and safety of core components such as battery packs, control systems, and motors have become particularly important. Under normal driving conditions, the battery management system (BMS) can achieve real-time control of the power system by monitoring parameters such as battery status, temperature, and current. However, when new energy vehicles encounter failures or emergencies (such as collisions or battery thermal runaway), the BMS usually needs to quickly cut off the high-voltage system to ensure the safety of the vehicle and passengers.

[0003] The traditional power-off strategy is to immediately cut off the power supply to isolate the faulty components in an emergency, but this method may induce strong back electromotive force when the motor is running at high speed. In the case of high-speed power off, the back electromotive force will generate instantaneous high voltage, causing the high-voltage components to be overloaded and may even break down the MCU (motor control unit) and other key components. Especially when the battery cannot absorb or buffer the instantaneous high voltage, the power bus will experience a voltage surge, posing a major threat to the safety of the high-voltage system.

[0004] Most existing power-off control schemes use an "immediate power-off" method, that is, once a fault is detected and the power is off, the main relay will be cut off immediately regardless of whether the motor is running at high speed. This solution is simple and direct, but due to the lack of judgment on the motor speed and current conditions, it is easy to cause high-voltage shocks and increase the risk of damage to system components. At the same time, in the case of non-emergency faults (such as increased battery temperature or excessive current), a simple power off may also interrupt the normal driving of the vehicle and affect the user experience.

[0005] Therefore, a new power-off control method is urgently needed, which can evaluate the motor speed and current when encountering non-limit faults, and perform power-off operations after ensuring that the system parameters are within the safe range. This can not only protect high-voltage components from impact, but also avoid driving interruptions caused by unnecessary power outages, and improve the durability and safety of the system. In addition, in the case of extreme faults, it is still necessary to ensure the rapid responsiveness of power outages, thereby improving the emergency response capabilities of new energy vehicles in various scenarios. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a control method for determining whether to disconnect the main relay by detecting the motor speed and battery current when a new energy vehicle encounters a fault or other situations requiring power off during driving. The method can perform the power-off operation when the motor speed and current meet the safety conditions, avoid the high-voltage system from suffering from instantaneous high-voltage shock, and improve the safety and reliability of new energy vehicles during driving.

[0007] To achieve the above object, the present invention provides the following technical solution, which mainly includes:

[0008] A control method for detecting vehicle speed before power failure of a new energy vehicle during driving, by detecting the motor speed and battery current conditions when the power system of the new energy vehicle encounters a fault or needs to be powered off, and controlling the disconnection of the main relay, thereby preventing high-voltage shock from damaging high-voltage components. The method comprises the following steps:

[0009] (1) Fault detection: The battery management system continuously monitors the vehicle's driving status and starts the power-off process when a fault is detected;

[0010] (2) Fault type determination: If it is a critical fault, the main relay is disconnected immediately; if it is a non-critical fault, the condition determination process is entered;

[0011] (3) Power-off condition determination: When the battery current is less than 20A and lasts for 100 milliseconds, and the motor speed is less than 300 rpm, the main relay is disconnected;

[0012] (4) Delayed power-off mechanism: If the power-off condition is not met within 50 seconds, the main relay will be forcibly disconnected.

[0013] Preferably, the fault detection step monitors the battery current, motor speed of the power system, vehicle speed and other status data of the new energy vehicle in real time through the battery management system, and enters the fault warning state when an abnormality is detected.

[0014] Preferably, the fault type determination step includes identification of extreme faults and non-extreme faults, wherein extreme faults include collision or battery thermal runaway, and after detecting the extreme fault, the system immediately disconnects the main relay to ensure the safety of the high voltage system.

[0015] Preferably, in the power-off condition determination step, the battery management system determines the battery current and when the battery current is less than 20A and lasts for more than 100 milliseconds, the power-off current condition is met.

[0016] Preferably, in the power-off condition determination step, the battery management system determines the motor speed including satisfying the power-off speed condition when the motor speed is less than 300 rpm.

[0017] Preferably, when the power-off condition is not met, the delayed power-off mechanism detects the current and speed parameters at regular intervals and continuously determines whether the power-off condition is met within 50 seconds.

[0018] Preferably, if the current and speed conditions for power failure are not met within 50 seconds, the battery management system forcibly disconnects the main relay to prevent the system from being in a fault state for a long time and affecting the stability of the system.

[0019] Preferably, after detecting a fault state requiring power off, the battery management system simultaneously shuts down the torque output of the motor control unit and the working state of the DCDC module to reduce the system load and control the rapid release of high voltage.

[0020] Preferably, the control method is executed based on the automatic control logic of the battery management system, and automatically determines and executes the corresponding power-off strategy after the vehicle enters the power-off process.

[0021] Preferably, when the power-off condition is met, the battery management system first confirms the state of the main relay before disconnecting the main relay, and ensures that the power-off of the high-voltage system is completed through the relay's disconnection confirmation signal, so as to improve system safety and reliability.

[0022] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) Improve system security:

[0024] The present invention determines whether the system has reached a safe state before power failure by detecting the motor speed and battery current, effectively avoiding the impact of the back electromotive force generated by power failure when the motor is running at high speed on the high-voltage components of the system, and improving the stability of the high-voltage system.

[0025] (2) Extend the service life of components:

[0026] Under non-limit fault conditions, the present invention reduces the damage to the MCU and other high-voltage components caused by instantaneous high voltage by reasonably controlling the power-off timing, reduces the loss of key components, prevents high voltage from breaking through power devices, and thus extends the service life of components.

[0027] (3) Enhance the flexibility of fault handling:

[0028] The present invention distinguishes between extreme faults and non-extreme faults. Through condition determination and delayed power-off mechanism, the power supply will not be cut off immediately when a non-emergency fault occurs, but the power will be cut off when the system parameters meet the safety requirements, thereby improving the flexibility and intelligence of fault handling.

[0029] (4) Improving emergency response capabilities:

[0030] The present invention can quickly perform a power-off operation in the event of extreme faults such as a collision or battery thermal runaway, ensuring that the high-voltage system is quickly isolated in an emergency, reducing safety risks, and helping to protect the safety of passengers and the stability of the entire vehicle.

[0031] (5) Improve driving experience:

[0032] In non-extreme fault situations, by avoiding unnecessary power outages, the present invention improves the continuous operation capability of new energy vehicles, reduces the probability of system erroneous shutdown, and thus improves the user's driving experience.

[0033] (6) Reduce maintenance costs:

[0034] Since the present invention effectively protects the high-voltage components and the motor control unit of the system, the risk of damage caused by failure is reduced, thereby reducing the cost of repair and maintenance and improving the overall reliability of the vehicle.

[0035] (7) Enhance the stability of the high-voltage system:

[0036] By determining the current and speed conditions before power failure, the power failure operation is ensured to be carried out in a stable system state, which helps to maintain the safety state of the high-voltage system and improve the overall stability and durability of the system.

[0037] (8) Meeting the application requirements of multiple scenarios:

[0038] The present invention can realize delayed power off in general driving failures and instant power off in emergency situations, and is therefore suitable for a variety of application scenarios, improving the adaptability of new energy vehicles in various environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0040] Figure 1 This is the first part of the flow chart of the present invention.

[0041] Figure 2 This is the flow chart of the second part of the present invention.

[0042] Figure 3 This is the flow chart of the third part of the present invention. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example

[0045] A control strategy for the vehicle when driving is now formulated. When encountering a related high-voltage disconnection state fault, in order to prevent the vehicle from immediately disconnecting the high-voltage relay, the motor reverse thrust generates high voltage and is released to the high-voltage circuits such as the motor controller (MCU), causing damage to related high-voltage components. Now, it can be controlled and judged whether the relay should be disconnected according to the current motor speed. When the motor speed is reduced to a certain speed, the motor reverse thrust is not very large. At this time, the relay can be disconnected. Generally, the motor speed is reduced to 300rpm / min, and the vehicle BMS can judge that disconnecting the relay at this time will not cause the related reverse thrust voltage to be related. In addition, the disconnection of the relay needs to judge the current state and the current value passing through the relay. If the current is too large, it may cause the disconnected relay to be in a sticking state. The BMS determines in real time whether the allowable current of the relay needs to be met by detecting the output current of the battery pack. The relay can be disconnected when the current is less than 20A. By judging the above state, it is determined whether the relay at that time meets the relay disconnection situation. For extreme fault states (collision, thermal runaway), it is not necessary to judge the motor speed, battery pack current and other states.

[0046] A: The vehicle model is in normal driving condition;

[0047] B: The power system encounters a fault;

[0048] C: BMS determines the current fault state, extreme fault or high voltage disconnection state;

[0049] D: Extreme fault, disconnect the relay immediately;

[0050] E: Other fault states that require power off;

[0051] 1) Determine whether the current battery pack current is less than 20A;

[0052] 2) Determine whether the current motor speed is less than 300rpm / min;

[0053] F: If the state 1) is met, the relay can be disconnected if the state 2) is met. If not, wait for the speed to be less than 300rpm / min to disconnect the relay. Otherwise, after 50S, the main relay is forcibly disconnected.

[0054] G: If the state 2) is met, the relay can be disconnected if the state 1) is met. If not, the relay needs to be disconnected forcibly after 50 seconds.

[0055] H: If the conditions 1) and 2) are not met, it is necessary to continue to judge whether the conditions are met. If they are not met, the relay will be forced to disconnect after 50 seconds.

[0056] The specific process is as follows Figures 1 to 3 shown.

[0057] Example 1: Power-off control for non-critical faults

[0058] During the driving of new energy vehicles, the battery management system (BMS) continuously monitors the vehicle's motor speed and battery current. When it detects that the battery temperature in the power system has risen and reached the fault warning state but has not yet reached the limit state (such as overcurrent or overheating), the system enters the non-limit fault mode and does not immediately perform a power-off, but enters the power-off condition determination process.

[0059] 1.Conditional judgment

[0060] The BMS detects that the battery pack output current is 15A and lasts for more than 100 milliseconds, meeting the current conditions for power outage.

[0061] Subsequently, the BMS detected the motor speed and found that the current speed was 280rpm, which was lower than the speed threshold of 300rpm and met the speed condition for power off.

[0062] 2. Power off execution

[0063] After the above current and speed conditions are met, the BMS controls the main relay to disconnect and complete the safe power-off operation.

[0064] Through this control process, power is cut off when the motor speed decreases and the current reaches a safe range, avoiding the impact of the motor's back electromotive force on the high-voltage system, thereby effectively protecting the system's high-voltage components and ensuring the stability of the system in the event of a fault.

[0065] Example 2: Emergency power off for extreme faults

[0066] The vehicle was in high-speed driving and a collision occurred. The BMS detected the collision signal and the system determined it to be a critical fault and immediately performed an emergency power-off operation:

[0067] 1. Extreme fault identification

[0068] The BMS detects the impact signal caused by the collision and enters the extreme fault mode. It directly triggers the emergency power-off process without further judging the current and speed conditions.

[0069] 2. Power off execution

[0070] The BMS quickly controls the main relay to disconnect, isolating the battery pack from the power system, ensuring the safety of the motor and power system after a collision.

[0071] This embodiment achieves rapid isolation of the high-voltage system by directly disconnecting the main relay, preventing the back electromotive force generated after the collision from affecting other components of the power system, and ensuring the safety and reliability of the system under extreme conditions.

[0072] Example 3: Delayed power-off mechanism for non-critical faults

[0073] During vehicle driving, the battery management system detects battery voltage fluctuations and determines that it is not a critical fault, but the motor speed and battery current have not yet reached the power-off condition. The BMS adopts a delay mechanism to wait for the system to reach the power-off condition:

[0074] 1.Conditional judgment

[0075] The BMS detects that the battery pack output current is 25A, which does not reach the power-off current threshold.

[0076] At the same time, the motor speed is 320rpm, which does not reach the speed condition for power failure (below 300rpm).

[0077] 2. Delay mechanism

[0078] The BMS starts the delayed power-off mechanism and continuously monitors the current and speed, repeating the detection at regular intervals.

[0079] After a 50-second delay, if the power-off conditions of current less than 20A and speed less than 300rpm are still not met, the BMS will forcibly disconnect the main relay.

[0080] 3. Power off execution

[0081] After a delay of 50 seconds, the BMS forcibly disconnects the main relay to complete safe power off.

[0082] This embodiment ensures that even when the current and speed safety conditions are not met, the system can still be forced to power off within a reasonable time, thereby preventing the long-term existence of non-limit faults from posing risks to the system.

[0083] Example 4: Power failure recovery during normal driving

[0084] When the new energy vehicle completes the power-off operation during normal driving, the system can perform a reset operation through the BMS status detection:

[0085] 1. Normal status detection

[0086] If the BMS does not detect any fault condition (battery temperature is normal, current is normal, and speed meets driving standards), the vehicle's power status can be restored.

[0087] 2. Recovery Operation

[0088] The BMS reactivates the main relay and restores the power system connection, ensuring that the vehicle can drive normally.

[0089] This embodiment illustrates that after the fault is eliminated or the system is reset, the vehicle can be restored through BMS control to provide the user with a normal driving experience.

[0090] In summary, all the above embodiments demonstrate the control strategies of the present invention under different fault scenarios, and ensure the safety and stability of new energy vehicles under various driving conditions through condition determination, delay mechanism, emergency power off and system reset.

[0091] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0092] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for detecting vehicle speed before power failure during driving of a new energy vehicle, characterized in that: The method detects the motor speed and battery current conditions and controls the disconnection of the main relay when the power system of the new energy vehicle encounters a fault or needs to be powered off, thereby preventing the high-voltage impact from damaging the high-voltage components. The method includes the following steps: (1) Fault detection: The battery management system continuously monitors the vehicle's driving status and starts the power-off process when a fault is detected; (2) Fault type determination: If it is a critical fault, the main relay is disconnected immediately; if it is a non-critical fault, the condition determination process is entered; (3) Power-off condition determination: When the battery current is less than 20A and lasts for 100 milliseconds, and the motor speed is less than 300 rpm, the main relay is disconnected; (4) Delayed power-off mechanism: If the power-off condition is not met within 50 seconds, the main relay will be forcibly disconnected.

2. A control method for detecting vehicle speed before power failure during driving of a new energy vehicle according to claim 1, characterized in that: The fault detection step monitors the battery current, motor speed of the power system, vehicle speed and other status data of the new energy vehicle in real time through the battery management system, and enters the fault warning state when an abnormality is detected.

3. The control method for detecting vehicle speed before power failure of a new energy vehicle during driving according to claim 1 is characterized in that: The fault type determination step includes identification of extreme faults and non-extreme faults, wherein extreme faults include collision or battery thermal runaway. After detecting an extreme fault, the system immediately disconnects the main relay to ensure the safety of the high voltage system.

4. The control method for detecting vehicle speed before power failure of a new energy vehicle during driving according to claim 1 is characterized in that: In the power-off condition determination step, the battery management system determines the battery current and when the battery current is less than 20A and lasts for more than 100 milliseconds, the power-off current condition is met.

5. The control method for detecting vehicle speed before power failure of a new energy vehicle during driving according to claim 1 is characterized in that: In the power-off condition determination step, the battery management system determines the motor speed, including when the motor speed is less than 300 rpm, the power-off speed condition is met.

6. A control method for detecting vehicle speed before power failure during driving of a new energy vehicle according to claim 1, characterized in that: When the power-off condition is not met, the delayed power-off mechanism detects the current and speed parameters at regular intervals and continuously determines whether the power-off condition is met within 50 seconds.

7. A control method for detecting vehicle speed before power failure during driving of a new energy vehicle according to claim 1, characterized in that: If the current and speed conditions for power failure are not met within 50 seconds, the battery management system will forcibly disconnect the main relay to prevent the system from being in a fault state for a long time and affecting system stability.

8. A control method for detecting vehicle speed before power failure during driving of a new energy vehicle according to any one of claims 1 to 7, characterized in that: After detecting a fault condition that requires power off, the battery management system simultaneously shuts down the torque output of the motor control unit and the working state of the DCDC module to reduce the system load and control the rapid release of high voltage.

9. A control method for detecting vehicle speed before power failure during driving of a new energy vehicle according to any one of claims 1 to 8, characterized in that: The control method is executed based on the automatic control logic of the battery management system, and automatically determines and executes the corresponding power-off strategy after the vehicle enters the power-off process.

10. A control method for detecting vehicle speed before power failure during driving of a new energy vehicle according to any one of claims 1 to 9, characterized in that: When the power-off conditions are met, the battery management system confirms the status of the main relay before disconnecting the main relay, and ensures that the power-off of the high-voltage system is completed through the relay's disconnection confirmation signal to improve system safety and reliability.

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