Power limiting method and system for preventing battery from being over-discharged and vehicle

Abstract

The invention discloses a power limiting method and system for preventing battery over-discharge and a vehicle, and belongs to the technical field of new energy vehicles. The method comprises the following steps: monitoring the discharge current and the charge state of a power battery in real time, and if the real-time discharge current of the power battery is greater than the allowable discharge current of the power battery for a certain time, entering a power limiting mode; in the mode, according to the real-time charge state of the power battery, calculating the limit power percentage; based on the target torque and the rotating speed of the current motor, the driving demand power is calculated; according to the product of the driving demand power and the limited power percentage, obtaining the limited motor output power; and if the current driving demand power is not greater than the allowable discharge power of the power battery, and the real-time discharge current of the power battery is not greater than a preset safety threshold value, and lasts for a preset time, exiting the power limiting mode. The output power can be dynamically limited, the battery utilization rate is maximized while the battery is prevented from being over-discharged, and the service life of the battery is prolonged.

Description

Technical Field

[0001] The present invention relates to a power limiting method, system and vehicle for preventing battery over-discharge, belonging to the technical field of new energy vehicles. Background Art

[0002] With the rapid development of new energy vehicles, power battery over-discharge protection strategies are gaining increasing attention. This brings with it the challenge of improving battery utilization while protecting the battery from over-discharge. Currently, over-discharge protection strategies used in the market include a combination of pre-undervoltage strategies and power limiting or cutting off. Specifically, when the minimum cell voltage falls below a certain threshold, the vehicle's output power is limited or cut off to protect the battery.

[0003] However, existing power battery over-discharge protection strategies have drawbacks. They employ a simple linear power reduction approach to limit vehicle output power. If the output power limit is too small, over-discharge protection may fail, reducing battery cell performance and service life. In severe cases, it may even cause battery cell failure, leading to serious consequences such as thermal runaway of the entire pack and vehicle fire. If the output power limit is too large, insufficient power may occur, significantly negatively impacting the driving experience. Furthermore, existing protection strategies fail to dynamically adjust to the real-time status of the battery cells, resulting in low battery utilization. Summary of the Invention

[0004] The purpose of the present invention is to provide a power limiting method, system and vehicle for preventing battery over-discharge, which can solve the technical problems of battery protection failure, sudden drop in power experience and low battery utilization caused by linear power reduction in existing battery over-discharge protection strategies.

[0005] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions.

[0006] In a first aspect, the present invention provides a power limiting method for preventing battery over-discharge, comprising: Real-time monitoring of the power battery's discharge current and state of charge. If the power battery's real-time discharge current exceeds the allowable discharge current for a certain period of time, the system will enter power limiting mode. In power limit mode, the power limit percentage is calculated based on the real-time state of charge of the power battery; Calculate the required drive power based on the current motor torque and speed; The limited motor output power is obtained based on the product of the required drive power and the limited power percentage; if the current required drive power of the motor is not greater than the allowable discharge power of the power battery, and the real-time discharge current of the power battery is not greater than the preset safety threshold and lasts for a preset time, the power limiting mode is exited.

[0007] In combination with the first aspect, further, calculating the limited power percentage according to the real-time state of charge of the power battery includes: Calculate the rated required power P of the vehicle accessories f The difference between the power battery's allowable discharge power P and the power margin Δ P ; Based on the power margin Δ P The ratio of the power factor k1 to the allowable discharge power P of the power battery is used to obtain the motor power coefficient k1; Compare the real-time state of charge (SOC) of the power battery with the preset safety threshold (SOC0), and calculate the limit power percentage based on the comparison result and the motor power coefficient (k1). α .

[0008] In combination with the first aspect, further, comparing the real-time state of charge SOC of the power battery with a preset safety threshold SOC0 includes: If the real-time state of charge (SOC) of the power battery is not less than a preset safety threshold value (SOC0), a first limited power percentage is obtained by multiplying the ratio of the power battery allowable discharge current (I) to the power battery real-time discharge current (i) by the motor power factor (k1); If the real-time state of charge (SOC) of the power battery is less than a preset safety threshold value (SOC0), the power battery allowable discharge power (P) is linearly limited to obtain a power battery discharge limit ratio (m1); The second limited power percentage is obtained by multiplying the ratio of the power battery allowed discharge current I to the power battery real-time discharge current by the motor power coefficient k1 and then by the power battery discharge limit ratio m1.

[0009] In combination with the first aspect, further, the calculation expression of the power battery discharge limit ratio m1 is: m1= a * SOC + b; Among them, m1 represents the power battery discharge limit ratio; a represents the power battery discharge limit ratio coefficient; SOC represents the real-time state of charge of the power battery; b represents the power battery discharge limit ratio constant.

[0010] In combination with the first aspect, further, the real-time discharge current of the power battery is not greater than a preset safety threshold, including: A safety factor k2 is set. When the real-time discharge current i of the power battery is not greater than the product of the safety factor k2 and the allowable discharge current I of the power battery, a safety state determination is initiated, specifically including: Synchronously monitor the relationship between the current motor drive demand power P0 and the power battery allowable discharge power P. If the following exit judgment conditions are met at the same time: (1) P0≤ P; (2) i ≤ k2* I; (3) last for a preset period of time; The power limiting mode is then exited and the normal output power of the motor is restored; if any one of the exit determination conditions is not met, the power limiting mode is maintained and the limiting strategy continues to be executed.

[0011] In combination with the first aspect, further, when the real-time discharge current i of the power battery is not greater than the product of the safety factor k2 and the allowable discharge current I of the power battery, the method further includes: When the real-time state of charge SOC of the power battery is less than a preset safety threshold SOC0, the safety factor k2 is optimized to obtain an optimized safety factor; When the real-time state of charge (SOC) of the power battery is not less than the preset safety threshold SOC0, the current default safety factor is maintained.

[0012] In combination with the first aspect, further, the optimized safety factor expression is: k2= a * SOC + b; Among them, k2 represents the safety factor; a represents the power battery discharge limit ratio coefficient; SOC represents the real-time state of charge of the power battery; b represents the power battery discharge limit ratio constant.

[0013] In combination with the first aspect, further, the calculation expression of the driving demand power is: P0= T0* n0 / k3; Among them, P0 represents the current driving power demand; T0 represents the motor torque at the current moment; n0 represents the motor speed; and k3 represents the conversion coefficient.

[0014] In a second aspect, a power limiting system for preventing battery over-discharge includes: The judgment module is used to monitor the discharge current and charge state of the power battery in real time. If the real-time discharge current of the power battery is greater than the allowable discharge current of the power battery and lasts for a certain period of time, the power limiting mode is entered; A first calculation module is used to calculate the limit power percentage according to the real-time state of charge of the power battery in the power limit mode; The second calculation module is used to calculate the required driving power of the motor based on the current torque and speed of the motor; The power limiting module obtains the limited motor output power based on the product of the drive demand power and the limited power percentage; wherein, if the current motor drive demand power is not greater than the allowable discharge power of the power battery, and the real-time discharge current of the power battery is not greater than a preset safety threshold, and continues for a preset time, the power limiting mode is exited.

[0015] In a third aspect, a vehicle is provided, characterized in that it is equipped with the power limiting system for preventing battery over-discharge according to claim 9, comprising: Power battery: used to provide driving energy; A vehicle controller, used to integrate the judgment module, the first calculation module, the second calculation module and the power control module; A motor controller, configured to receive the limited motor output power P1 output by the power control module and control the motor to operate according to P1; The battery management system is used to provide the vehicle controller with the power battery's allowable discharge current I, allowable discharge power P, and state of charge SOC in real time; Sensor set, including: Current sensor, used to collect the real-time discharge current i of the power battery; The motor torque / speed sensor is used to collect the motor torque T0 and speed n0 at the current moment.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The discharge current and state of charge of the power battery are monitored in real time. If the real-time discharge current of the power battery continuously exceeds the allowable discharge current for a preset period of time, the power limiting mode is triggered. In this mode, the limit power percentage is dynamically calculated based on the real-time state of charge of the power battery, and the current driving demand power is calculated based on the real-time torque and speed of the motor. By multiplying the driving demand power with the limit power percentage, the limited safe motor output power is generated in real time to ensure that the battery discharge current returns to the safe range. When the current driving demand power does not exceed the allowable discharge power of the battery and the real-time discharge current of the battery continues to be lower than the dynamically adjusted safety threshold for a preset time, the power limiting mode is exited.

[0017] This method uses multi-condition coordinated judgment and dynamic power limiting strategy to accurately prevent battery over-discharge while significantly improving battery utilization efficiency and avoiding power drops or protection failures caused by traditional linear power reduction. Combined with the state of charge layered control mechanism, it takes into account battery safety and basic vehicle power requirements under extreme working conditions, effectively extending battery life and optimizing the driving experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG2 is a flow chart of a power limiting method for preventing battery over-discharge provided by an embodiment of the present invention; Figure 2 Shown is a flow chart of limiting motor power provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0020] The term "and / or" simply describes a relationship between related objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. Additionally, the character " / " generally indicates an "or" relationship between the related objects. Example 1

[0021] See also Figure 1 This embodiment introduces a power limiting method for preventing battery over-discharge, including the following steps: Step S1: Real-time monitoring of the discharge current and state of charge of the power battery. If the real-time discharge current i of the power battery is greater than the allowable discharge current I of the power battery and lasts for a certain period of time, the power limiting mode is entered; By monitoring the real-time discharge current i of the power battery and comparing it with the allowable discharge current I of the power battery, if: 1) i>I; 2) Last for a certain period of time The battery is considered to be in an over-discharge state. This triggers the power limit mode based on the battery's current performance (such as the battery's state of charge (SOC) and state of health (SOH). For example, if the allowable discharge current I is 100A and the real-time current i reaches 120A for 5 seconds (this duration can be set based on the specific situation), the system will determine that power limit mode is necessary.

[0022] Step S3: In the power limiting mode, the power limiting percentage is calculated according to the real-time state of charge of the power battery; See also Figure 2 , calculate the limited power percentage based on the real-time state of charge of the power battery, including: Step S31: Calculate the rated required power P of the vehicle accessories f The difference between the power battery's allowable discharge power P and the power margin Δ P , whose expression is: Δ P = P-P f ; Among them, P represents the allowable discharge power of the power battery; P f Indicates the rated required power of the vehicle's accessories; Δ P Indicates the power margin.

[0023] Step S32: Based on the ratio of the power margin Δ P to the allowable discharge power P of the power battery, the motor power coefficient k1 is obtained, and its expression is: k1 = Δ P / P, 0 ≤ k 1 ≤ 1 where k1 represents the motor power coefficient.

[0024] Step S33: Compare the real-time state of charge SOC of the power battery with a preset safety threshold SOC0, and dynamically calculate the limited power percentage α .

[0025] Specifically, if the real-time state of charge SOC of the power battery is greater than or equal to the preset safety threshold SOC0 (SOC ≥ SOC0), then multiply the ratio of the allowable discharge current I of the power battery to the real-time discharge current i of the power battery by the motor power coefficient k1 to obtain the first limited power percentage, and its expression is: α 1 = k 1 * I / i; where, α 1 represents the first limited power percentage.

[0026] If the real-time state of charge SOC of the power battery is less than the preset safety threshold SOC0 (SOC < SOC0), then linearly limit the allowable discharge power of the power battery to obtain the power battery discharge limit ratio m1, and multiply the ratio of the allowable discharge current I of the power battery to the real-time discharge current by the motor power coefficient k1, and then multiply by the power battery discharge limit ratio m1 to obtain the second limited power percentage, and its expression is: α 2 = m 1 * k 1 * I / i; where, α 2 represents the second limited power percentage.

[0027] where the expression of the power battery discharge limit ratio m1 is: m1 = a * SOC + b; where m1 represents the power battery discharge limit ratio; a represents the power battery discharge limit ratio coefficient; SOC represents the real-time state of charge of the power battery; b represents the power battery discharge limit ratio constant.

[0028] According to the comparison between the real-time state of charge (SOC) of the above power battery and the preset safety threshold SOC0, when the battery current is low, the power output can be more finely controlled according to the real-time state of the battery to prevent over-discharge of the battery.

[0029] Step S4: Based on the current torque and speed of the motor, calculate the driving demand power of the current motor, and its calculation expression is: P0 = T0 * n0 / k3; Where, P0 represents the current driving demand power; T0 represents the motor torque at the current moment; n0 represents the motor speed; k3 represents the conversion coefficient, taking 9550.

[0030] Step S5: Obtain the restricted motor output power according to the product of the current driving demand power and the power limit percentage, and its expression is: P 1 = P 0 * α ; Where, P 1 represents the restricted motor output power.

[0031] Therefore, by adjusting the motor output power to the safety value P1 through the restriction strategy, it not only prevents over-discharge of the battery but also ensures the minimum power demand of the vehicle.

[0032] Furthermore, if the current driving demand power is less than or equal to the allowable discharge power of the power battery, and the real-time discharge current of the power battery is not greater than the preset safety threshold and lasts for the preset time, then exit the power limit mode.

[0033] The specific steps for exiting the power limit mode include the following: Step S51: Set the safety factor k2 (0 ≤ k 2 ≤ 1). When the real-time discharge current i of the power battery is less than or equal to the product of the safety factor k2 and the allowable discharge current I of the power battery, start the safety state determination; Specifically, when the real-time state of charge SOC of the power battery is less than the preset safety threshold SOC0 (SOC < SOC0), optimize the safety factor k2 to obtain the optimized safety factor, and its expression is: k2 = a * SOC + b; Where, k2 represents the safety factor.

[0034] When the real-time state of charge SOC of the power battery is greater than or equal to the preset safety threshold SOC0 (SOC ≥ SOC0), maintain the current default safety factor.

[0035] Step S52: synchronously monitor the relationship between the current driving demand power P0 and the power battery allowable discharge power P. If the following exit determination conditions are met at the same time: Condition 1: P0 ≤ P (the vehicle's current power requirement is within the battery's safe discharge range, the battery stress is relatively low, and the basic conditions for exiting power limit mode are met); Condition 2: i ≤ k2* I (further ensuring that the battery discharge current is at a safer level); Condition 3: Continuing for a preset time (e.g., no more than 5000ms); The power limit mode is then exited and the normal output power of the motor is restored; if any of the exit judgment conditions is not met, the power limit mode is maintained and the limitation strategy continues to be executed.

[0036] For example, the allowable discharge current I of the power battery is 100A, the safety factor k2 is 0.8, the allowable power P of the power battery is 50kW, the current motor output power P1 is 40kW, and the real-time discharge current i of the power battery is 70A.

[0037] Judgment: The motor output power P1 (40kW) is less than the power battery allowable power P (50kW); The real-time current i (70A) of the power battery is less than k2 times the allowable discharge current (0.8×100A=80A); If this state lasts for a certain period of time (such as 5 seconds), the system will exit the power limit mode and resume normal power output. Example 2

[0038] A power limiting system for preventing battery over-discharge, comprising: The judgment module is used to monitor the discharge current and charge state of the power battery in real time. If the real-time discharge current of the power battery is greater than the allowable discharge current of the power battery and lasts for a certain period of time, the power limiting mode is entered; A first calculation module is used to calculate the limit power percentage according to the real-time state of charge of the power battery in the power limit mode; A second calculation module is used to calculate the current driving power requirement based on the current torque and speed of the motor; The power limiting module obtains the limited motor output power based on the product of the current driving demand power and the limited power percentage; wherein, if the current driving demand power is not greater than the allowable discharge power of the power battery and the real-time discharge current of the power battery is not greater than a preset safety threshold and lasts for a preset time, the power limiting mode is exited. Example 3

[0039] A vehicle, characterized in that it is equipped with the power limiting system for preventing battery over-discharge according to claim 9, comprising: Power battery: used to provide driving energy; A vehicle controller unit (VCU), configured to integrate the monitoring module, the judgment module, the first calculation module, the second calculation module, and the power control module; a motor controller (MCU), configured to receive the limited motor output power P1 output by the power control module and control the motor to operate according to P1; The battery management system (BMS) is used to provide the VCU with the power battery's allowable discharge current I, allowable discharge power P, and state of charge SOC in real time; Sensor set, including: Current sensor, used to collect the real-time discharge current i of the power battery; The motor torque / speed sensor is used to collect the motor torque T0 and speed n0 at the current moment.

[0040] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which are all protected by the present invention.

Claims

1. A power limiting method for preventing battery over-discharge, characterized in that: include: Real-time monitoring of the power battery's discharge current and state of charge. If the power battery's real-time discharge current exceeds the allowable discharge current for a certain period of time, the system will enter power limiting mode. In power limit mode, the power limit percentage is calculated based on the real-time state of charge of the power battery; Calculate the required drive power based on the current motor's target torque and speed; The limited motor output power is obtained based on the product of the required drive power and the limited power percentage; if the current required drive power of the motor is not greater than the allowable discharge power of the power battery, and the real-time discharge current of the power battery is not greater than the preset safety threshold and lasts for a preset time, the power limiting mode is exited.

2. The power limiting method for preventing battery over-discharge according to claim 1, characterized in that: Calculate the power limit percentage based on the real-time state of charge of the power battery, including: Calculate the rated required power P of the vehicle accessories f The difference between the power battery's allowable discharge power P and the power margin Δ P ; Based on the power margin Δ P The ratio of the power factor k1 to the allowable discharge power P of the power battery is used to obtain the motor power coefficient k1; Compare the real-time state of charge (SOC) of the power battery with the preset safety threshold (SOC0), and dynamically calculate the limit power percentage based on the comparison result and the motor power coefficient (k1). α .

3. The power limiting method for preventing battery over-discharge according to claim 2, characterized in that: Compare the real-time state of charge (SOC) of the power battery with the preset safety threshold (SOC0), including: If the real-time state of charge (SOC) of the power battery is not less than a preset safety threshold value (SOC0), a first limited power percentage is obtained by multiplying the ratio of the power battery allowable discharge current (I) to the power battery real-time discharge current (i) by the motor power factor (k1); If the real-time state of charge (SOC) of the power battery is less than a preset safety threshold value (SOC0), the power battery allowable discharge power (P) is linearly limited to obtain a power battery discharge limit ratio (m1); The second limited power percentage is obtained by multiplying the ratio of the power battery allowed discharge current I to the power battery real-time discharge current by the motor power coefficient k1 and then by the power battery discharge limit ratio m1.

4. The power limiting method for preventing battery over-discharge according to claim 3, characterized in that: The calculation expression of the power battery discharge limit ratio m1 is: m1= a * SOC + b; Among them, m1 represents the power battery discharge limit ratio; a represents the power battery discharge limit ratio coefficient; SOC represents the real-time state of charge of the power battery; b represents the power battery discharge limit ratio constant.

5. The power limiting method for preventing battery over-discharge according to claim 1, characterized in that: The real-time discharge current of the power battery is not greater than a preset safety threshold, including: A safety factor k2 is set. When the real-time discharge current i of the power battery is not greater than the product of the safety factor k2 and the allowable discharge current I of the power battery, a safety state determination is initiated, specifically including: Synchronously monitor the relationship between the current motor drive demand power P0 and the power battery allowable discharge power P. If the following exit judgment conditions are met at the same time: (1) P0≤ P; (2) i ≤ k2* I; (3) last for a preset period of time; The power limiting mode is then exited and the normal output power of the motor is restored; if any one of the exit determination conditions is not met, the power limiting mode is maintained and the limiting strategy continues to be executed.

6. The power limiting method for preventing battery over-discharge according to claim 5, characterized in that: When the real-time discharge current i of the power battery is not greater than the product of the safety factor k2 and the allowable discharge current I of the power battery, the method further includes: When the real-time state of charge SOC of the power battery is less than a preset safety threshold SOC0, the safety factor k2 is optimized to obtain an optimized safety factor; When the real-time state of charge (SOC) of the power battery is not less than the preset safety threshold SOC0, the current default safety factor is maintained.

7. The power limiting method for preventing battery over-discharge according to claim 6, characterized in that: The optimized safety factor expression is: k2 = a * SOC + b; Among them, k2 represents the safety factor; a represents the power battery discharge limit ratio coefficient; SOC represents the real-time state of charge of the power battery; b represents the power battery discharge limit ratio constant.

8. The power limiting method for preventing battery over-discharge according to claim 1, characterized in that: The calculation expression of the driving demand power is: P0= T0* n0 / k3; Among them, P0 represents the current driving power demand; T0 represents the motor target torque at the current moment; n0 represents the motor target speed; and k3 represents the conversion coefficient.

9. A power limiting system for preventing battery over-discharge, characterized in that: include: The judgment module is used to monitor the discharge current and charge state of the power battery in real time. If the real-time discharge current of the power battery is greater than the allowable discharge current of the power battery and lasts for a certain period of time, the power limiting mode is entered; A first calculation module is used to calculate the limit power percentage according to the real-time state of charge of the power battery in the power limit mode; The second calculation module is used to calculate the required driving power of the motor based on the current torque and speed of the motor; The power limiting module obtains the limited motor output power based on the product of the drive demand power and the limited power percentage; wherein, if the current motor drive demand power is not greater than the allowable discharge power of the power battery, and the real-time discharge current of the power battery is not greater than a preset safety threshold, and continues for a preset time, the power limiting mode is exited.

10. A vehicle, characterized in that: The power limiting system for preventing battery over-discharge according to claim 9 comprises: Power battery: used to provide driving energy; A vehicle controller, used to integrate the judgment module, the first calculation module, the second calculation module and the power control module; A motor controller, configured to receive the limited motor output power P1 output by the power control module and control the motor to operate according to P1; The battery management system is used to provide the vehicle controller with the power battery's allowable discharge current I, allowable discharge power P, and state of charge SOC in real time; Sensor set, including: Current sensor, used to collect the real-time discharge current i of the power battery; The motor torque / speed sensor is used to collect the motor torque T0 and speed n0 at the current moment.

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