Control method for suppressing high pulse current of hybrid electric vehicle battery in low-temperature environment

Abstract

The invention relates to the technical field of new energy automobiles, in particular to a control method for inhibiting pulse large current of a hybrid electric vehicle battery in a low-temperature environment, which comprises the following steps: establishing an energy management system taking an HCU as a core, and realizing multi-component information interaction through CAN communication; after the vehicle is powered on, the HCU identifies a cold and hot machine mode according to the charging and discharging power and the temperature of the battery; a gear shifting sequence (a cold engine mode D gear is fixed, and a hot engine mode dynamically shifts gears) is planned according to the mode and engine working requirements; calculating the maximum allowable driving / braking torque of an EM2 motor by combining the charging and discharging power of the battery, the power of the EM1 motor and the consumed power of the electric accessory; and controlling the torque of the EM2 motor to be within a limit value, and limiting the power of the battery to be within an allowable range. Instantaneous overcharge and overdischarge of the battery during low-temperature gear shifting can be thoroughly eliminated, the service life and safety of the battery are protected, power and driving smoothness are both considered, and the method is suitable for hybrid vehicle battery control in the low-temperature environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy vehicles, and particularly relates to a control method for inhibiting large-current pulses of a battery of a hybrid vehicle in a low-temperature environment. BACKGROUND

[0002] A hybrid vehicle combines the advantages of a traditional fuel vehicle and an electric vehicle, and can work in an electric mode or a hybrid mode according to a working scene and power demand, so as to improve problems such as high fuel consumption and large emission pollution in an urban area, and has no range anxiety, and can achieve optimal energy distribution in different scenes. A multi-gear power split hybrid transmission carried by a certain type of hybrid vehicle realizes power split by using a single planetary gear set, and realizes speed regulation and torque regulation by using an AMT with a 2x2 combined gear, so that the oil-saving capability and power advantage of the hybrid system are fully exerted.

[0003] However, in a low-temperature environment (lower than minus 5 DEG C), when gear shifting is performed during vehicle driving, over-discharge (exceeding the maximum allowable available discharge power of the battery) and over-charge (exceeding the maximum allowable available charge power of the battery) of the power battery are caused due to the effects of shift torque compensation and motor speed regulation, and a pulse current generated in the process of gear shifting has a great influence on the performance and service life of the battery. Specifically, compared with a fuel vehicle, a hybrid vehicle is additionally provided with a power battery as an energy storage unit, the performance of the power battery is significantly affected by temperature, in a low-temperature environment, due to the decrease of lithium ion activity, the increase of electrode liquid viscosity, and the increase of internal resistance of the battery, if the power use of the battery is not limited, the battery capacity will be attenuated, and risks such as internal short circuit will be caused.

[0004] Further, when a certain type of vehicle equipped with a 2x2 combined AMT power split hybrid transmission drives in a low temperature environment and performs gear shifting, there are two typical power overrun scenarios: the first is ICE-AMT shift discharge power overrun. To avoid power interruption during engine shifting, EM2 motor needs to increase the power output of the engine before shifting to compensate for the torque. Meanwhile, during engine shifting and speed regulation, EM1 motor participates in the speed regulation process of the planetary gear set, which is in the process of electric power consumption. The superposition of these two power usage requirements causes the actual power of the battery to exceed the maximum allowable discharge power of the battery. The second is EM2-AMT shift charging power overrun. When EM2 motor shifts, EM2 does not participate in vehicle driving. To ensure that the power of the vehicle does not decrease, the power output of the engine needs to be increased. However, after the engine power is increased, due to the effect of power splitting, the power generation of EM1 motor is also increased. When entering the synchronization speed regulation phase of shifting, EM2 motor is in the state of braking and power generation, which will generate a large amount of pulse charging power. The superposition of these two charging powers causes the actual power of the battery to exceed the maximum allowable charging power of the battery. In the above two scenarios, the battery is in a state of instantaneous overcharging and overdischarging, and the instantaneous overrun power is more than 10kW, which poses a serious risk to the life and safe use of the battery.

[0005] Therefore, due to the factors such as the limited performance of the battery in a low temperature environment and the small limit of the usable charging and discharging power, it is necessary to have a control method for inhibiting the pulse large current of the battery of a hybrid vehicle in a low temperature environment to protect the battery power from being used excessively. SUMMARY

[0006] The present application aims to overcome the shortcomings of the prior art and provides a control method for inhibiting the pulse large current of the battery of a hybrid vehicle in a low temperature environment to solve the technical problem that in the prior art, in a low temperature environment (lower than minus 5℃), the performance of the battery is limited, and when the hybrid vehicle equipped with a 2x2 combined AMT power split hybrid transmission shifts, due to the shift torque compensation and motor speed regulation, the battery is in a state of overcharging and overdischarging (the instantaneous overrun power is more than 10kW), which affects the life and safe use of the battery. By intelligently identifying the cold and hot engine modes of the vehicle, planning the optimal shift sequence and controlling the torque limit of EM2 motor, the real-time use of the battery power is strictly controlled within the allowable charging and discharging power range, and the battery is protected from being used excessively.

[0007] The above object is achieved by the following technical solution: A control method for inhibiting the pulse large current of the battery of a hybrid vehicle in a low temperature environment, applied to a hybrid vehicle equipped with a multi-gear power split hybrid transmission, the multi-gear power split hybrid transmission realizes power splitting with a single planetary gear set, and an AMT with a 2x2 combined gear is configured to realize speed regulation and torque regulation, the control method comprising the following steps: Step (1): build an energy management system with the vehicle controller HCU as the control core, the energy management system includes the battery and the battery management system BMS, the engine and the engine management system EMS, the motor and the motor controller PEU, and the electrical accessories; the vehicle controller HCU realizes information interaction with the battery management system BMS, the engine management system EMS, the motor controller PEU and the electrical accessories through CAN communication; Step (2): after the vehicle low voltage is powered on and the CAN network is normally communicated, the vehicle controller HCU receives the battery maximum allowable discharge power, the maximum allowable charging power and the battery temperature information sent by the battery management system BMS, and identifies the cold and hot engine mode of the vehicle; if the battery maximum allowable discharge power and the maximum allowable charging power are lower than the set threshold, or the battery temperature is lower than the set threshold, the vehicle enters the cold engine mode; if the battery maximum allowable discharge power and the maximum allowable charging power are higher than the set threshold, or the battery temperature is higher than the set threshold, the vehicle enters the hot engine mode; Step (3): the vehicle controller HCU autonomously plans and decides the corresponding shift sequence according to the identified cold and hot engine mode; Step (4): the vehicle controller HCU receives the battery maximum allowable discharge power, the maximum allowable charging power sent by the battery management system BMS, and the consumption power of the electrical accessories and the actual power of the EM1 motor, respectively calculates the maximum allowable driving torque and the maximum allowable braking torque of the EM2 motor; Step (5): the vehicle controller HCU controls the driving torque of the EM2 motor not to exceed the maximum allowable driving torque, and controls the braking torque of the EM2 motor not to exceed the maximum allowable braking torque, and limits the real-time use power of the battery within the allowable charging and discharging power range of the battery.

[0008] Preferably, the cold engine mode and the hot engine mode in step (2) can be switched to each other; in the cold engine mode, if the battery maximum allowable discharge power and the maximum allowable charging power are higher than the set threshold, or the battery temperature is higher than the set threshold, the vehicle is switched from the cold engine mode to the hot engine mode; after the vehicle low voltage is powered off, the cold engine mode or the hot engine mode is switched to the initialization state.

[0009] Preferably, the initialization state in step (2) is the initial state before the vehicle low voltage is powered on; after the vehicle low voltage is powered on, the vehicle controller HCU first enters the initialization state, and then enters the cold engine mode or the hot engine mode according to the battery parameters.

[0010] Preferably, in step (3), when the vehicle is in the cold mode, the gear shifting sequence is divided into a cold mode-pure electric gear sequence and a cold mode-hybrid gear sequence according to whether there is engine operation demand; the cold mode-pure electric gear sequence is N0-D4-N0-R4-N0; and the cold mode-hybrid gear sequence is N0-N4-D4-N4-R4-N4-N0.

[0011] Preferably, in step (3), when the vehicle is in the hot mode, the gear shifting sequence is divided into a hot mode-pure electric gear sequence and a hot mode-hybrid gear sequence according to whether there is engine operation demand; the hot mode-pure electric gear sequence is N0-D1-D3-D4-D3-D1-N0-R1-N0; and the hot mode-hybrid gear sequence is N0-N1-D1-D3-D4-D3-D1-N1-R1-N1-N0.

[0012] Preferably, in step (4), the specific process of calculating the maximum allowable driving torque of the EM2 motor is as follows: first, the maximum available discharge power of the EM2 motor is calculated according to the maximum allowable discharge power of the battery, the actual power of the EM1 motor and the consumed power of the electrical accessories, and the calculation formula is: EM2 motor maximum available discharge power = battery maximum allowable discharge power - (EM1 motor actual power + electrical accessory consumed power); second, the maximum allowable driving torque of the EM2 motor is converted from the maximum available discharge power of the EM2 motor in combination with the motor efficiency and angular velocity of the EM2 motor.

[0013] Preferably, in step (4), the specific process of calculating the maximum allowable braking torque of the EM2 motor is as follows: first, the maximum available charging power of the EM2 motor is calculated according to the maximum allowable charging power of the battery, the actual power of the EM1 motor and the consumed power of the electrical accessories, and the calculation formula is: EM2 motor maximum available charging power = battery maximum allowable charging power + (EM1 motor actual power + electrical accessory consumed power); second, the maximum allowable braking torque of the EM2 motor is converted from the maximum available charging power of the EM2 motor in combination with the power generation efficiency and angular velocity of the EM2 motor.

[0014] Preferably, the electrical accessories include a DCDC converter, an air conditioning compressor EAC and an electric air pump APC; and the vehicle control unit HCU receives the working voltage and working current of the DCDC converter, the air conditioning compressor EAC and the electric air pump APC to calculate the consumed power of the electrical accessories.

[0015] Preferably, the actual power of the EM1 motor reflects the power generation power of the engine; the vehicle controller HCU receives the operating speed and torque of the EM1 motor and the EM2 motor, as well as the operating speed and torque of the engine, and calculates the required power of the engine and the required power of the EM2 motor in combination with the driving power requirements of the vehicle, and converts the required power into required torque and required speed, and sends them to the engine management system EMS and the motor controller PEU through CAN communication.

[0016] Preferably, the low-temperature environment is an environment with a temperature below -5°C; in the low-temperature environment, if the control method is not executed, when the vehicle shifts gears, the battery will experience instantaneous overcharging or over-discharging, and the instantaneous over-limit power will reach more than 10kW.

[0017] This invention provides a control method for suppressing high-current pulses in hybrid vehicle batteries at low temperatures. This method effectively solves the problem of battery overcharging and over-discharging (instantaneous over-limit power exceeding 10kW) during gear shifting in hybrid vehicles at low temperatures (below -5°C). By identifying hot and cold engine modes, planning the shifting sequence, and controlling the torque of the EM2 motor, the battery power is limited to an allowable range, protecting the battery from degradation and short circuits, extending its lifespan, reducing safety risks, and also considering the overall vehicle power and driving smoothness. Specific beneficial effects are as follows: 1. Completely eliminate battery pulse high current: By fixing the D gear in cold mode (without performing gear shifting), the power superposition caused by "torque compensation + motor speed regulation" during gear shifting is avoided from the root, eliminating the triggering conditions for instantaneous overcharging and over-discharging of the battery; at the same time, through EM2 motor torque limit control in all modes, it is further ensured that the real-time power of the battery does not exceed the allowable range, completely solving the problem of instantaneous over-limit power of the battery exceeding 10kW during low-temperature gear shifting.

[0018] 2. Protecting battery life and safety: In response to the characteristics of reduced lithium-ion activity, increased electrode fluid viscosity, and increased internal resistance in low-temperature environments, the battery charging and discharging power is strictly controlled to effectively avoid risks such as battery capacity decay and internal short circuits. This significantly extends the service life of the power battery in low-temperature environments and reduces the vehicle safety hazards caused by battery failures.

[0019] 3. Balancing power needs and smoothness: In cold engine mode, the vehicle operates in a fixed gear, avoiding the problem of large torque fluctuations caused by low power limits, which leads to poor driving smoothness; in warm engine mode, dynamic shifting is restored, giving full play to the torque output capability and fuel-saving advantages of the 2x2 AMT multi-gear power split hybrid transmission; at the same time, the switching between cold and warm engine modes and gear adjustment are automatically executed based on real-time parameters, and the EM2 motor torque gradual control avoids power fluctuations and driving jerks, ensuring the smoothness of the entire vehicle's driving.

[0020] 4. Strong system coordination: With the vehicle controller HCU as the core, it realizes information interaction and coordinated control of BMS, EMS, PEU and electrical accessories through CAN communication. It has comprehensive data acquisition, rapid decision response and can dynamically adjust the control strategy according to battery status, ambient temperature and vehicle power demand, making it highly adaptable. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a multi-gear power split hybrid system in a certain type of vehicle, which is part of the control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions as described in this invention. In the diagram, ICE-AMT (engine-AMT transmission), EM2-AMT (EM2 motor-AMT transmission), EMS (engine management system), PEU (motor controller), SAU (shift actuator controller), HCU (vehicle controller), CAN (controller area network), and Out (transmission output). Figure 2 This is a schematic diagram illustrating the excessive discharge power during engine gear shifting at low temperatures in the control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature environments, as described in this invention. The diagram shows torque reduction (engine torque reduction phase), disengagement speed adjustment (engine disengagement speed adjustment phase), gear engagement torque recovery (engine engagement torque recovery phase), target gear (engine target gear), actual gear (engine actual gear), throttle opening (driver's throttle input), and over-discharge power (battery power exceeding the maximum permissible discharge value). Figure 3 This is a schematic diagram illustrating the charging power exceeding the limit during the TM gear shifting process at low temperatures in the control method for suppressing pulsed high current in hybrid vehicle batteries under low-temperature environments, as described in this invention. The diagram shows: torque reduction (EM2 motor torque reduction stage), disengagement speed adjustment (EM2 motor disengagement speed adjustment stage), gear engagement torque recovery (EM2 motor gear engagement torque recovery stage), target gear (EM2 motor target gear), actual gear (EM2 motor actual gear), and overcharging power (the power value of the battery exceeding the maximum allowable charging value). Figure 4 The diagram shows the topology of the vehicle energy management system in the control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions, as described in this invention. The components in the diagram are: BMS (Battery Management System), EMS (Engine Management System), HCU (Vehicle Controller), PEU (Motor Controller), DCDC (DC-CDC Converter), EAC (Air Conditioning Compressor), and APC (Electric Air Pump). Figure 5This is a schematic diagram illustrating the principle of cold / hot engine state recognition in the control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature environments, as described in this invention. In the diagram, Init (initialization state), Cold (cold engine mode), Warm (hot engine mode), value A (maximum allowable discharge power threshold of the battery), value B (maximum allowable charging power threshold of the battery), value C (battery temperature threshold, triggered by cold engine mode), value D (maximum allowable discharge power threshold of the battery, triggered by hot engine mode), value E (maximum allowable charging power threshold of the battery, triggered by hot engine mode), and value F (battery temperature threshold, triggered by hot engine mode). Figure 6 This is a schematic diagram of the gear sequence in the control method for suppressing large pulse current of hybrid vehicle battery in low temperature environment according to the present invention; in the figure, N0 (neutral initial position), N1 (hybrid mode neutral 1), N4 (hybrid mode neutral 4), D1 (forward gear 1), D3 (forward gear 3), D4 (forward gear 4), R1 (reverse gear 1), R4 (reverse gear 4). Figure 7 This is a schematic diagram illustrating the calculation principle of the maximum allowable driving torque of the EM2 motor in the control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions as described in this invention. Figure 8 This is a schematic diagram illustrating the calculation principle of the maximum allowable braking torque of the EM2 motor in the control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions, as described in this invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. The described embodiments are merely some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] like Figures 1-8 As shown, this solution provides a control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions. It is applied to hybrid vehicles equipped with a multi-gear power-split hybrid transmission. The multi-gear power-split hybrid transmission uses a single planetary gear set to achieve power splitting and is configured with a 2x2 AMT (Automated Manual Transmission) for speed and torque adjustment. The control method specifically includes the following steps: Step (1) Build an energy management system An energy management system is established with the vehicle controller (HCU) as the control core. This energy management system also includes a battery and battery management system (BMS), an engine and engine management system (EMS), a motor and motor controller (PEU), and electrical accessories (including a DC-DC converter, an air conditioning compressor (EAC), and an electric air pump (APC). The HCU communicates with the BMS, EMS, PEU, and electrical accessories via CAN (Controller Area Network). Specifically, the HCU receives data from the BMS regarding the battery's maximum allowable discharge power, maximum allowable charging power, operating current, and voltage; the operating voltage and current of the electrical accessories (DC-DC converter, EAC, and APC); the operating speed and torque of motors EM1 and EM2; and the operating speed and torque of the engine. Simultaneously, the HCU can transmit the calculated engine torque and speed requirements, as well as the EM2 motor's torque and speed requirements, to the EMS and PEU via CAN communication to control the engine and motor responses.

[0024] Step (2) Identify the heating / cooling mode like Figure 5 and Figure 6 As shown, after the vehicle is powered on at low voltage and the CAN network is communicating normally, the vehicle controller (HCU) first enters the initialization state, and then receives the maximum allowable discharge power, maximum allowable charging power, and battery temperature information sent by the battery management system (BMS). Based on the above information, it identifies the vehicle's hot / cold engine mode. If the maximum allowable discharge power and maximum allowable charging power of the battery are lower than the set threshold, or if the battery temperature is lower than the set threshold, the vehicle will enter the cold engine mode from the initialization state. If the maximum allowable discharge power and maximum allowable charging power of the battery are higher than the set threshold, or if the battery temperature is higher than the set threshold, the vehicle will enter the warm-up mode from the initialization state.

[0025] Furthermore, the cold engine mode and the hot engine mode can be switched between each other: in the cold engine mode, if the maximum allowable discharge power and the maximum allowable charging power of the battery are higher than the set threshold, or if the battery temperature is higher than the set threshold, the vehicle switches from the cold engine mode to the hot engine mode; after the vehicle is powered off at low voltage, both the cold engine mode and the hot engine mode switch to the initialization state.

[0026] Step (3) Planning the shift sequence The vehicle control unit (HCU) autonomously plans and decides on the corresponding shift sequence based on the identified engine cold / hot mode, and the shift sequence is further subdivided according to whether there is an engine operating requirement: Shift sequence in cold mode: If the engine does not need to work (pure electric mode), the cold engine mode - pure electric gear sequence is used: N0-D4-N0-R4-N0; under this sequence, the vehicle will always remain in D4 gear when driving in D gear, and no gear shifting will be performed; If the engine needs to operate (hybrid mode), the cold engine mode hybrid gear sequence is used: N0-N4-D4-N4-R4-N4-N0; under this sequence, the vehicle will always remain in D4 gear when driving in D gear, and no gear shifting will be performed.

[0027] Shift sequence in warm-up mode: If the engine does not need to work (pure electric mode), the warm engine mode - pure electric gear sequence is used: N0-D1-D3-D4-D3-D1-N0-R1-N0; under this sequence, when the vehicle is driving in D gear, the gear shift can be performed from D1 to D3 to D4 to D3 to D1. If the engine needs to operate (hybrid mode), the hot engine mode hybrid gear sequence is used: N0-N1-D1-D3-D4-D3-D1-N1-R1-N1-N0; under this sequence, when the vehicle is driving in D gear, the gear shift can be performed as D1→D3→D4→D3→D1.

[0028] Step (4) Calculate the torque limit of EM2 motor The vehicle controller (HCU) receives the maximum permissible discharge power and maximum permissible charging power of the battery from the battery management system (BMS), as well as the power consumption of the electrical accessories (calculated based on the operating voltage and current of the electrical accessories) and the actual power of the EM1 motor (the power of the EM1 motor actually reflects the generator power of the engine). It then calculates the maximum permissible drive torque and maximum permissible braking torque of the EM2 motor. like Figure 7 As shown, calculate the maximum allowable drive torque of the EM2 motor: First, based on the maximum allowable discharge power of the battery, the actual power of the EM1 motor, and the power consumed by the electrical accessories, calculate the maximum usable discharge power of the EM2 motor. The calculation formula is: Maximum usable discharge power of the EM2 motor = Maximum allowable discharge power of the battery - (Actual power of the EM1 motor + Power consumed by the electrical accessories). Secondly, combining the efficiency and angular velocity of the EM2 motor (calculated based on the operating speed of the EM2 motor), the maximum usable discharge power of the EM2 motor is converted into the maximum allowable driving torque of the EM2 motor. The specific conversion relationship satisfies: power = torque × angular velocity ÷ efficiency, that is, torque = power × electric efficiency ÷ angular velocity.

[0029] like Figure 8 As shown, calculate the maximum permissible braking torque of the EM2 motor: First, based on the maximum allowable charging power of the battery, the actual power of the EM1 motor, and the power consumed by the electrical accessories, calculate the maximum available charging power of the EM2 motor. The calculation formula is: Maximum available charging power of EM2 motor = maximum allowable charging power of the battery + (actual power of EM1 motor + power consumed by electrical accessories). Secondly, combining the efficiency and angular velocity of the EM2 motor, the maximum available charging power of the EM2 motor is converted into the maximum allowable braking torque of the EM2 motor. The conversion relationship also satisfies: Torque = Power × Power generation efficiency ÷ angular velocity.

[0030] Step (5) Control the EM2 motor torque and battery power The vehicle controller HCU controls the EM2 motor to ensure that its driving torque does not exceed the maximum allowable driving torque and its braking torque does not exceed the maximum allowable braking torque, based on the calculated maximum allowable driving torque and maximum allowable braking torque. Simultaneously, the vehicle controller HCU calculates the required power of the engine and the EM2 motor based on the vehicle's driving power requirements, converting the required power into required torque and required speed, and sends this information to the engine management system (EMS) and the motor controller (PEU) via CAN communication. Ultimately, this strictly limits the real-time power consumption of the battery within the battery's allowable charging and discharging power range, preventing overcharging or over-discharging of the battery.

[0031] As a specific embodiment of this solution, the implementation process is as follows: Application Scenario 1: Cold Engine Mode - Hybrid Driving After the vehicle is powered on at low voltage, the vehicle control unit (HCU) identifies that the vehicle is in cold engine mode based on battery power limits and ambient temperature. It selects the shift sequence for cold engine mode and, based on thermal management's requirements for starting the engine, ultimately selects the cold engine mode hybrid shift sequence: N0-N4-D4-N4-R4. After high voltage power is applied, the gear shift first moves from N0 to N4, where the engine starts and operates. When the driver shifts the gear lever into D, the gear shifts from N4 to D4 and remains in D4 without any further shifting. Compared to the warm engine shift sequence (D1-D3-D4), the cold engine shift sequence maintains a fixed gear without shifting, thus eliminating the large pulse current generated during shifting. By driving in a fixed gear, it avoids instantaneous overcharging and over-discharging of the battery. After the vehicle stops, the driver shifts the gear lever into reverse (R), then from D4 to N4 and finally to R4, maintaining this position while reversing. Simultaneously, the EM2 motor's torque demand is limited to the calculated [EM2 motor maximum available braking torque, EM2 motor maximum available driving torque] limits, and the battery's charging and discharging power is not exceeded.

[0032] Application Scenario 2: Switching from Cold Mode to Hot Mode After the vehicle is powered on at low voltage, the vehicle control unit (HCU) identifies that the vehicle is in cold engine mode based on the battery power limit and ambient temperature. It selects the shift sequence for cold engine mode and, considering the engine starting requirements for thermal management, ultimately selects the cold engine mode-hybrid shift sequence: N0-N4-D4-N4-R4. After the vehicle has been running in D4 gear for a period of time, with the support of thermal management, the battery power limit returns to normal, and the vehicle mode changes from cold engine mode to hot engine mode. D4 gear changes to D4 gear in hot engine mode, and the shift sequence becomes: N0-N1-D1-D3-D4-D3-D1-N1-R1. During the process of the vehicle slowing down to a stop and shifting into reverse (R), the shift route is: D4-D3-D1-N1-R1. During the switching from cold mode to hot mode and the switching of various gears, the torque required by the EM2 motor is always limited within the calculated torque limits of [EM2 motor maximum available braking torque, EM2 motor maximum available driving torque], while the charging and discharging power of the battery is not exceeded.

[0033] Application Scenario 3: Switching from hot mode to cold mode After the vehicle is powered on at low voltage, the vehicle control unit (HCU) identifies that the vehicle is in hot engine mode based on battery power limits and ambient temperature. It selects the gear sequence for hot engine mode. At this time, the engine is faulty and cannot operate, so the vehicle can only operate in pure electric mode. The final selected gear sequence for hot engine mode - pure electric mode is: N0-D1-D3-D4-D3-D1-N0-R1. When driving in D gear, the gear shift route is: D1-D3-D4-D3-D1. Due to the engine's inability to operate, limited thermal management functions, and continuously decreasing battery power, the vehicle mode changes from hot engine mode to cold engine mode. The gear shift sequence changes to the cold engine mode - pure electric mode sequence: N0-D4-N0-R4. The D4 gear has now become the D4 gear in cold engine mode. During the process of the vehicle slowing down to a stop and shifting into R gear, the gear shift route is: D4-N0-R4. During the switching from hot mode to cold mode and the switching of various gears, the torque demand of the EM2 motor is always limited within the calculated torque limits of [EM2 motor maximum available braking torque, EM2 motor maximum available driving torque], while the charging and discharging power of the battery is not exceeded.

[0034] The above description is merely illustrative of the embodiments of the present invention and is not intended to limit the present invention. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions, characterized in that, Includes the following steps: Step (1): Build an energy management system with the vehicle controller HCU as the control core. The energy management system includes a battery and battery management system (BMS), an engine and engine management system (EMS), a motor and motor controller (PEU), and electrical accessories. The vehicle controller HCU communicates with the battery management system (BMS), the engine management system (EMS), the motor controller (PEU), and the electrical accessories via CAN communication. Step (2): After the vehicle is powered on at low voltage and the CAN network is communicating normally, the vehicle controller HCU receives the maximum allowable discharge power, maximum allowable charging power and battery temperature information sent by the battery management system BMS, and identifies the cold or hot engine mode of the vehicle; if the maximum allowable discharge power and maximum allowable charging power of the battery are lower than the set threshold, or the battery temperature is lower than the set threshold, the vehicle enters the cold engine mode; if the maximum allowable discharge power and maximum allowable charging power of the battery are higher than the set threshold, or the battery temperature is higher than the set threshold, the vehicle enters the hot engine mode. Step (3): The vehicle controller HCU autonomously plans and decides on the corresponding shift sequence based on the identified hot and cold engine modes; Step (4): The vehicle controller HCU receives the maximum allowable discharge power and maximum allowable charging power of the battery, as well as the power consumption of the electrical accessories and the actual power of the EM1 motor, sent by the battery management system BMS, and calculates the maximum allowable driving torque and maximum allowable braking torque of the EM2 motor respectively. Step (5): The vehicle controller HCU controls the driving torque of the EM2 motor to not exceed the maximum allowable driving torque, and controls the braking torque of the EM2 motor to not exceed the maximum allowable braking torque, thereby limiting the real-time power consumption of the battery to within the allowable charging and discharging power range of the battery.

2. The control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions according to claim 1, characterized in that, The cold engine mode and the hot engine mode in step (2) can be switched to each other; in the cold engine mode, if the maximum allowable discharge power and the maximum allowable charging power of the battery are higher than the set threshold, or the battery temperature is higher than the set threshold, the vehicle switches from the cold engine mode to the hot engine mode; after the vehicle is powered off at low voltage, both the cold engine mode and the hot engine mode switch to the initialization state.

3. The control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions according to claim 1, characterized in that, The initialization state mentioned in step (2) is the initial state before the vehicle is powered on at low voltage. After the vehicle is powered on at low voltage, the vehicle controller HCU first enters the initialization state, and then determines whether to enter the cold engine mode or the hot engine mode based on the battery parameters.

4. The control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions according to claim 1, characterized in that, In step (3), when the vehicle is in cold engine mode, the shift sequence is divided into cold engine mode-pure electric gear sequence and cold engine mode-hybrid gear sequence according to whether there is an engine working requirement; the cold engine mode-pure electric gear sequence is N0-D4-N0-R4-N0; the cold engine mode-hybrid gear sequence is N0-N4-D4-N4-R4-N4-N0.

5. A control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions according to claim 1 or 4, characterized in that, In step (3), when the vehicle is in hot engine mode, the shift sequence is divided into hot engine mode-pure electric gear sequence and hot engine mode-hybrid gear sequence according to whether there is an engine working requirement; the hot engine mode-pure electric gear sequence is N0-D1-D3-D4-D3-D1-N0-R1-N0; the hot engine mode-hybrid gear sequence is N0-N1-D1-D3-D4-D3-D1-N1-R1-N1-N0.

6. The control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions according to claim 1, characterized in that, The specific process for calculating the maximum allowable driving torque of the EM2 motor in step (4) is as follows: First, based on the maximum allowable discharge power of the battery, the actual power of the EM1 motor, and the power consumed by the electrical accessories, the maximum usable discharge power of the EM2 motor is calculated. The calculation formula is: Maximum usable discharge power of the EM2 motor = maximum allowable discharge power of the battery - (actual power of the EM1 motor + power consumed by the electrical accessories); Second, combined with the electric efficiency and angular velocity of the EM2 motor, the maximum usable discharge power of the EM2 motor is converted into the maximum allowable driving torque of the EM2 motor.

7. The control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions according to claim 1, characterized in that, The specific process for calculating the maximum allowable braking torque of the EM2 motor in step (4) is as follows: First, based on the maximum allowable charging power of the battery, the actual power of the EM1 motor, and the power consumed by the electrical accessories, the maximum available charging power of the EM2 motor is calculated. The calculation formula is: Maximum available charging power of the EM2 motor = maximum allowable charging power of the battery + (actual power of the EM1 motor + power consumed by the electrical accessories); Second, combined with the power generation efficiency and angular velocity of the EM2 motor, the maximum available charging power of the EM2 motor is converted into the maximum allowable braking torque of the EM2 motor.

8. The control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions according to claim 1, characterized in that, The electrical accessories include a DC-DC converter, an air conditioning compressor (EAC), and an electric air pump (APC); the vehicle controller (HCU) receives the operating voltage and current of the DC-DC converter, the air conditioning compressor (EAC), and the electric air pump (APC) to calculate the power consumption of the electrical accessories.

9. The control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions according to claim 1, characterized in that, The actual power of the EM1 motor reflects the power output of the engine. The vehicle controller HCU receives the operating speed and torque of the EM1 and EM2 motors, as well as the operating speed and torque of the engine. Combining the vehicle's driving power requirements, it calculates the required power of the engine and the required power of the EM2 motor, and converts the required power into required torque and required speed. These are then sent to the engine management system EMS and the motor controller PEU via CAN communication.

10. The control method for suppressing large pulse currents in hybrid vehicle batteries under low-temperature conditions according to claim 1, characterized in that, The low-temperature environment is an environment with a temperature below -5°C. In the low-temperature environment, if the control method is not executed, when the vehicle shifts gears, the battery will experience instantaneous overcharging or over-discharging, with instantaneous over-limit power exceeding 10kW.

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