Control method for preventing over-temperature of new energy commercial vehicle

Abstract

The invention relates to the technical field of new energy vehicle over-temperature control, in particular to a new energy commercial vehicle over-temperature prevention control method which comprises the following steps: S1, a VCU monitors the temperature of a motor and a battery in real time; s2, the VCU sets different external characteristic limit curves for realizing independent pre-control of motor and battery over-temperature; s3, when the temperature of the battery is higher than the threshold value, on the premise that the dynamic property of the whole vehicle is guaranteed, the external characteristic capacity of the motor starts to be limited step by step; and S4, multiplying the external characteristic coefficient of the battery by the external characteristic coefficient of the motor, setting an amplitude limiting lower limit, and when the double-superposed limiting coefficient is lower than the amplitude limiting lower limit, furthest restraining the temperature rise trend of the motor and the battery on the premise of ensuring the driving dynamic property of the vehicle by taking the amplitude limiting lower limit as a criterion, so that the motor and the battery work in a normal temperature interval, and the driving dynamic property of the vehicle is ensured. Core parts such as the battery and the motor are protected, and diversified vehicle using requirements of different users in different scenes are better met.

Description

Technical Field

[0001] The present invention relates to the technical field of over-temperature control of new energy vehicles, and in particular to a method for preventing over-temperature of new energy commercial vehicles. Background Art

[0002] New energy commercial vehicles operate in various complex working conditions. Among them, there are many users who drive fully loaded vehicles through extremely high temperature environments. During the high temperature period in summer every year, some vehicles may experience overheating of the motor or battery due to factors such as continuous extreme driving by the driver, or large and long road slopes.

[0003] If the motor temperature exceeds 150℃, the motor controller MCU will control the motor to limit the current linearly. After the current is limited, the torque output of the motor will be limited, and it will not be able to respond normally to the driver's driving intention analyzed by the vehicle control unit VCU, causing the vehicle to be unable to drive normally, affecting the user's normal use of the vehicle. If the battery temperature exceeds 60℃, the battery management system BMS will linearly reduce the battery's discharge capacity. After the VCU receives the discharge capacity reduction from the BSM, in order to protect the battery from over-discharge, it will control the power consumption of the vehicle end such as the drive to not exceed the battery's allowable discharge capacity. As the battery's allowable discharge capacity decreases, it will also affect the motor's torque output. Therefore, when the motor and battery are overheated, it will seriously affect the driving of the vehicle. Summary of the invention

[0004] The present invention provides a method for preventing new energy commercial vehicles from overheating. The real-time temperature of the motor and the battery is continuously monitored. When the motor or the battery shows an overheating trend, the VCU actively performs pre-control. Under the premise of ensuring the driving dynamics of the vehicle, the temperature rise trend of the motor and the battery is curbed to the maximum extent, so that the motor and the battery can work in a normal temperature range, which not only protects core components such as the battery and the motor, but also better meets the diverse vehicle use needs of different users in different scenarios.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: a method for preventing overheating of a new energy commercial vehicle, which specifically includes the following steps:

[0006] Step S1, the VCU monitors the temperature of the motor and the battery in real time. When the temperature of the motor or the battery may exceed a set temperature threshold, the VCU starts to limit the external characteristic torque of the drive motor;

[0007] Step S2, the VCU sets different external characteristic limit curves for independent pre-control of motor and battery over-temperature. The motor external characteristic limit curve is obtained by looking up the table according to the motor speed and the real-time motor temperature, and the battery external characteristic limit curve is directly obtained by looking up the table according to the maximum temperature of the battery cell and the motor speed.

[0008] Step S3, by comprehensively analyzing the heating conditions of the motor at different speeds, the external characteristics of the motor at different speeds are differentiated and restricted. When the battery temperature is higher than a threshold, the external characteristic capacity of the motor is gradually restricted while ensuring the power of the vehicle;

[0009] Step S4, obtain the battery external characteristic coefficient and the motor external characteristic coefficient by looking up the table, multiply the battery external characteristic coefficient and the motor external characteristic coefficient, set the lower limit, and when the double superimposed limit coefficient is lower than the lower limit, the lower limit shall prevail.

[0010] It is further defined that in step S2, the external characteristics of the motor and the battery both have external characteristic coefficients, and the external characteristic limitation coefficient refers to limiting processing of the external characteristics of the motor, which has the advantage of being able to differentiate and limit the peak torque capacity of the motor at different speeds.

[0011] It is further defined that for the plug-in charging condition, when the battery is charging, the opening thresholds of the water pump and the cooling fan of the battery cooling circuit are all advanced, and the temperature thresholds of the temperature range of the duty cycle control of the water pump and the fan of the battery cooling circuit are overall shifted to the left and adjusted locally.

[0012] It is further limited that under extreme working conditions, when both the motor and the battery show an over-temperature trend, the battery external characteristic coefficient and the motor external characteristic coefficient are calibrated, the calibrated values ​​are multiplied, and a lower limit is set. When the double superimposed limit coefficient is lower than the lower limit, the lower limit shall prevail; when the double superimposed limit coefficient is higher than the lower limit, the actual value shall prevail.

[0013] It is further defined that the motor external characteristic coefficient and the battery external characteristic coefficient are control actions performed before the motor and the battery body limit their own capabilities. When the battery and the motor overheat under extreme working conditions and cause the BMS or MCU to begin to limit their own capabilities, the VCU needs to exit the relevant restrictions and focus on the limitations of the components themselves to prevent the VCU limitations from overlapping with the BMS or MCU, resulting in overlapping restrictions that affect the power of the entire vehicle.

[0014] It is further defined that when only one of the motor or the battery exceeds the temperature threshold, the triggered motor external characteristic limitation coefficient is independently multiplied with the motor external characteristic torque set in the VCU. If the limitation is triggered at the same time, the external characteristic limitation coefficients of the battery and the motor are multiplied as described in step S4, and then the lower limit is limited and multiplied with the motor external characteristic torque set in the VCU.

[0015] Further restrictions, when the motor or battery overheats and reports an over-temperature fault, the VCU will limit the speed of the entire vehicle. When the motor and battery temperatures are lower than the over-temperature threshold, that is, the over-temperature fault reported by the motor or battery is cured, the VCU will not immediately release the fault processing, and the power must be turned off and then on again to lift the restriction.

[0016] The beneficial effects of adopting the above technical solution are:

[0017] 1. The control strategy of the plug-in charging condition in the present invention can allow the water pump and the fan to intervene earlier in a lower temperature range and operate at a relatively higher speed to more effectively dissipate heat for the battery under the plug-in charging condition. In this way, after the battery is charged, it can be "traveled light" at a relatively lower temperature, which can better prevent and control the overheating of the battery.

[0018] 2. The control strategy for extreme working conditions in the present invention can ensure that the temperature of the battery and the motor can be more effectively controlled when they both show an over-temperature trend, and at the same time, the power performance of the entire vehicle will not be affected by the tightening of external characteristic restrictions.

[0019] 3. By continuously monitoring the real-time temperature of the motor and battery, when the motor or battery shows an overheating trend, the VCU will actively perform pre-control. Under the premise of ensuring the vehicle's driving dynamics, it will maximize the containment of the temperature rise trend of the motor and battery, allowing the motor and battery to operate in a normal temperature range. This not only protects core components such as batteries and motors, but also better meets the diverse vehicle use needs of different users in different scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The overall control architecture diagram of the present invention is

[0021] Figure 2 The overall control strategy flow chart of the present invention is DETAILED DESCRIPTION

[0022] The specific implementation methods of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and facilitating its implementation.

[0023] The present invention is a control method for preventing new energy commercial vehicles from overheating. The real-time temperature of the motor and the battery is continuously monitored. When the motor or the battery shows an overheating trend, the VCU actively performs pre-control. Under the premise of ensuring the driving dynamics of the vehicle, the temperature rise trend of the motor and the battery is curbed to the maximum extent, so that the motor and the battery can work in a normal temperature range, which not only protects core components such as the battery and the motor, but also better meets the diverse vehicle use needs of different users in different scenarios.

[0024] Specifically, Figure 1 and Figure 2 As shown, the specific steps include:

[0025] Step S1, the VCU monitors the temperature of the motor and the battery in real time. Under extreme working conditions, when the hardware cooling system of the motor and the battery reaches its maximum capacity and cannot effectively reduce the temperature of the motor and the battery, the temperature of the motor or the battery may exceed the set temperature threshold, and the VCU begins to limit the external characteristic torque of the drive motor;

[0026] Step S2, the VCU sets different external characteristic limit curves for realizing independent pre-control of over-temperature of the motor and the battery. The external characteristic limit curve of the motor is obtained by looking up the table according to the motor speed and the real-time temperature of the motor, and the external characteristic limit curve of the battery is directly obtained by looking up the table according to the maximum temperature of the battery cell and the motor speed. The external characteristics of the motor and the battery have external characteristic coefficients. The external characteristic limit coefficient refers to the restriction processing of the external characteristics of the motor. The advantage is that the peak torque capacity of the motor at different speeds can be differentiated and restricted. For example, the external characteristic capacity below the inflection point speed of the motor can be relatively slightly restricted or not restricted, while for the constant power operation range of the motor, it is necessary to gradually strengthen the restriction as the motor speed increases;

[0027] When the motor is running at low speed, it works in the constant torque range, and the motor stator winding current corresponding to the external characteristic torque reaches the maximum. According to Joule's law, the heat generated by the motor stator winding also reaches the maximum. Therefore, in theory, the external characteristics of the motor when running at low speed should also be restricted to a certain extent. However, considering the actual vehicle usage scenarios of users, especially the long and steep slopes in Yunnan, Guizhou, Sichuan and Chongqing, if the external characteristic capacity in the constant torque range is restricted too much, it may affect the heavy-load climbing ability of the vehicle. Therefore, in order to take into account the climbing power of the whole vehicle and the control of motor overheating, below the motor inflection point, if the motor shows an overheating trend, a method of slightly restricting the external characteristics is adopted for overall control;

[0028] When the motor operates at medium and high speeds, the external characteristic torque decreases. When the motor operates in a constant power range, the stator winding current gradually decreases as the motor speed increases. Therefore, when the motor operates at medium and high speeds, the copper loss of the motor decreases, but the proportion of iron loss of the motor increases. The iron loss of the motor is mainly related losses generated by the rotor, including hysteresis loss and eddy current loss. Hysteresis loss is the energy dissipated in the iron core due to repeated magnetization and demagnetization of ferromagnetic materials, while eddy current loss is caused by the induced current heating generated by the alternating magnetic field in the rotor core. The higher the rotor speed, the higher the frequency of magnetization and demagnetization of ferromagnetic materials, the higher the loss energy, and the higher the average value of the induced current in the iron core. Therefore, the heat generated by the rotor part is also greater. Therefore, the external characteristic capabilities of the motor in the constant power range must be restricted, and at the same time, the vehicle's power must meet driving requirements.

[0029] Step S3, by comprehensively analyzing the heating conditions of the motor at different speeds and distinguishing and limiting the external characteristics of the motor at different speeds, the temperature of the motor can be controlled more specifically and effectively, and the motor temperature control under extreme vehicle conditions is more effective. The motor external characteristic limit table for preventing the motor from overheating is calibrated as follows:

[0030]

[0031]

[0032] The temperature of the battery changes slowly compared to the motor, and once the temperature starts to rise, the temperature rise may show a certain lag. The reason for the battery overheating is that the user continues to use the car and charges and discharges the battery uninterruptedly. After several cycles, sometimes heavy-load climbing conditions are superimposed, which eventually causes the battery temperature to exceed the normal level. In order to protect the battery, the BMS will report a battery overtemperature fault when the battery temperature is higher than the threshold. Therefore, for the battery temperature pre-control, it is necessary to start from the battery discharge source under driving conditions, and also focus on the thermal management control strategy in the battery plug-in charging scenario.

[0033] For driving conditions, the largest electricity consumer of the vehicle is the drive motor. Under driving conditions, the battery discharges a large current due to the large discharge power of the drive motor. According to Joule's law, the heat generated by the battery will naturally increase. Therefore, when the motor continues to output high power, it is more likely to cause the battery to overheat under driving conditions. Therefore, when the battery temperature is higher than the threshold, the external characteristic capacity of the motor is gradually limited while ensuring the power of the vehicle. When the external characteristics of the motor decrease, the mechanical work output by the motor decreases, so the discharge power will also decrease, thereby curbing the "culprit" that causes the battery to overheat during driving at the power source. The motor external characteristic limit table for battery overheating prevention is calibrated as follows:

[0034]

[0035]

[0036] For the plug-in charging condition, considering that the driver will continue to drive after the battery is charged, if the subsequent driving conditions are relatively severe, then if the ambient temperature is high, the battery temperature will be relatively high after the plug-in charging is completed, which will more easily cause the battery to overheat. Therefore, considering the driving continuity scenario during actual vehicle use, when the battery is charging, the opening thresholds of the water pump and the cooling fan of the battery cooling circuit are all advanced, and the temperature thresholds of the temperature range of the duty cycle control of the water pump and the fan of the battery cooling circuit are shifted to the left as a whole and adjusted locally. That is, the water pump and the fan are intervened earlier in a lower temperature range and at a relatively higher operating speed to provide more powerful heat dissipation for the battery under the plug-in charging condition. In this way, after the battery is charged, it can be "lightly loaded on the road" at a relatively lower temperature, which can better prevent and control the overheating of the battery.

[0037] Step S4, for extreme working conditions, when both the motor and the battery show an over-temperature trend, in order to more effectively control the temperature of the two core components, it is necessary to consider the control method in this scenario, calibrate the battery external characteristic coefficient and the motor external characteristic coefficient, and obtain the battery external characteristic coefficient of 0.8 and the motor external characteristic coefficient of 0.7 by looking up the table. Multiplying the calibrated values, the limit coefficient is reduced to 0.56. Compared with the single limit, the limit strength is superimposed, which may cause insufficient power of the whole vehicle. Therefore, the lower limit is set to 0.6. When the double superimposed limit coefficient RatiototalRaw is lower than the lower limit of 0.6, 0.6 is used as the standard. This can ensure that when both the battery and the motor show an over-temperature trend, their temperatures can be more effectively controlled, and at the same time, the power of the whole vehicle will not be affected by the tightening of the external characteristic restrictions.

[0038] The motor external characteristic coefficient and the battery external characteristic coefficient are both control actions executed before the motor and battery body limit their own capabilities. In extreme working conditions, when the battery and motor overheat and cause the BMS or MCU to start limiting its own capabilities, the VCU needs to exit the relevant restrictions and focus on the limitations of the components themselves to prevent the VCU restrictions from overlapping with the BMS or MCU, resulting in overlapping restrictions and affecting the power of the entire vehicle. If only one of the motor or the battery exceeds the temperature threshold, the triggered motor external characteristic limitation coefficient is independently multiplied by the motor external characteristic torque set in the VCU. If the restrictions are triggered at the same time, the battery and motor external characteristic limitation coefficients are multiplied as described in step S4, and then the lower limit is limited and multiplied by the motor external characteristic torque set in the VCU.

[0039] When the motor or battery overheats and reports an overtemperature fault, the VCU will limit the speed of the entire vehicle. For driving safety reasons, when the temperature of the motor and battery is lower than the overtemperature threshold, that is, after the overtemperature fault reported by the motor or battery is cured, the VCU will not immediately release the fault processing, and the power must be turned off and then on before the restriction can be lifted. This mechanism takes into account that after the fault is reported, the VCU limits the vehicle speed. At this time, if the fault is cured, the vehicle speed is near the speed limit, and the driver presses the accelerator pedal deeply. If the restriction is lifted directly, the battery and / or motor capabilities have returned to normal, and the vehicle may accelerate beyond the driver's expectations. At this time, the vehicle in front is close, which may cause dangerous situations such as rear-end collisions. Therefore, from the perspective of functional safety, the fault state needs to be locked to fully protect the driver's driving safety.

[0040] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above-mentioned concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for preventing overheating of a new energy commercial vehicle, characterized in that: The specific steps include: Step S1, the VCU monitors the temperature of the motor and the battery in real time. When the temperature of the motor or the battery may exceed a set temperature threshold, the VCU starts to limit the external characteristic torque of the drive motor; Step S2, the VCU sets different external characteristic limit curves for independent pre-control of motor and battery over-temperature. The motor external characteristic limit curve is obtained by looking up the table according to the motor speed and the real-time motor temperature, and the battery external characteristic limit curve is directly obtained by looking up the table according to the maximum temperature of the battery cell and the motor speed. Step S3, by comprehensively analyzing the heating conditions of the motor at different speeds, the external characteristics of the motor at different speeds are differentiated and restricted. When the battery temperature is higher than a threshold, the external characteristic capacity of the motor is gradually restricted while ensuring the power of the vehicle; Step S4, obtain the battery external characteristic coefficient and the motor external characteristic coefficient by looking up the table, multiply the battery external characteristic coefficient and the motor external characteristic coefficient, set the lower limit, and when the double superimposed limit coefficient is lower than the lower limit, the lower limit shall prevail.

2. A method for preventing overheating of a new energy commercial vehicle according to claim 1, characterized in that: In step S2, the external characteristics of the motor and the battery both have external characteristic coefficients. The external characteristic limiting coefficient refers to limiting processing of the external characteristics of the motor. Its advantage is that it can differentiate and limit the peak torque capacity of the motor at different speeds.

3. A method for preventing overheating of a new energy commercial vehicle according to claim 1, characterized in that: For plug-in charging conditions, when the battery is charging, the opening thresholds of the water pump and the cooling fan of the battery cooling circuit are all advanced, and the temperature thresholds of the temperature range of the duty cycle control of the water pump and the fan of the battery cooling circuit are overall shifted to the left and adjusted locally.

4. A method for preventing overheating of a new energy commercial vehicle according to claim 1, characterized in that: Under extreme working conditions, when both the motor and the battery show an over-temperature trend, the battery external characteristic coefficient and the motor external characteristic coefficient are calibrated, the calibrated values ​​are multiplied, and the lower limit is set. When the double superimposed limit coefficient is lower than the lower limit, the lower limit shall prevail. When the double superimposed limit coefficient is higher than the lower limit, the actual value shall prevail.

5. A method for preventing overheating of a new energy commercial vehicle according to claim 3, characterized in that: The motor external characteristic coefficients and battery external characteristic coefficients are control actions performed before the motor and battery body limit their own capabilities. When the battery and motor overheat under extreme working conditions and cause the BMS or MCU to begin to limit their own capabilities, the VCU needs to exit the relevant restrictions and focus on the limitations of the components themselves to prevent the VCU limitations from overlapping with the BMS or MCU, resulting in overlapping restrictions that affect the power of the entire vehicle.

6. A method for preventing overheating of a new energy commercial vehicle according to claim 1, characterized in that: When only one of the motor or the battery exceeds the temperature threshold, the triggered motor external characteristic limitation coefficient is independently multiplied with the motor external characteristic torque set in the VCU. If the limitation is triggered at the same time, the external characteristic limitation coefficients of the battery and the motor are multiplied as described in step S4, and then the lower limit is limited and multiplied with the motor external characteristic torque set in the VCU.

7. A method for preventing overheating of a new energy commercial vehicle according to claim 1, characterized in that: When the motor or battery overheats and reports an overtemperature fault, the VCU will limit the speed of the entire vehicle. When the motor and battery temperatures are lower than the overtemperature threshold, that is, the overtemperature fault reported by the motor or battery is cured, the VCU will not immediately release the fault processing. The restriction can only be lifted after the power is turned off and then on again.

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