CN115923586A - Over-current protection method for battery system and vehicle - Google Patents
Over-current protection method for battery system and vehicle Download PDFInfo
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Abstract
The invention provides a battery system overcurrent protection method and a vehicle, and belongs to the field of vehicle battery safety protection. Because the current battery system of the vehicle can not realize the overcurrent protection in the full current stage, the overcurrent protection method of the battery system can compare the real-time charging current with the preset charging current standard when the whole vehicle is in a charging state by detecting the current in the high-voltage circuit in real time when the high-voltage circuit connected with the battery system has abnormal current, and execute a breaking instruction to disconnect the charging high-voltage circuit connecting the battery system and a charger if the charging current meets the charging fault breaking condition; when the whole vehicle is in a driving state, the real-time discharge current of the battery system is compared with a preset discharge current standard, if the discharge current meets a driving fault breaking condition, a breaking instruction is executed, a discharge high-voltage loop connecting the battery system and a load is disconnected, and the safety of the battery system is ensured.
Description
Technical Field
The invention relates to a battery system overcurrent protection method and a vehicle, and belongs to the field of vehicle battery safety protection.
Background
With the continuous development of new energy technology, the safety problem of the battery system has become the focus of attention in the industry, the safety protection of the battery system not only depends on the improvement of the safety performance of the single battery, but also focuses on the improvement of the safety performance of the battery system, and not only active protection but also passive protection are provided. The active protection mode by means of contactors and the passive protection mode by means of fuses do not allow the full protection of the battery system, in particular the consideration of commercial vehicles based on standard platform products. As shown in fig. 1, a battery system of an existing new energy vehicle is generally implemented in a multi-branch parallel connection manner, so that the protection of the battery system is more complex, and a certain protection blind area exists, so that effective protection of the battery system cannot be achieved.
The short-circuit protection of the traditional fuse can not meet the protection requirement of a battery system, and the main problem is that if the specification of a matched hot-melt fuse is too large, the battery can not be rapidly and effectively protected when the battery system is short-circuited, so that the thermal runaway of a battery pack is caused, and further, a fire disaster or explosion is caused; if the matched specification of the hot-melt fuse is too small, the short-time current impact and continuous charging and discharging processes in the driving process of the vehicle often exceed the impact resistance of the fuse, and the reliability of long-term use has risks; and the thermal fuse can not be safely disconnected when the overload current below 5 times of rated current appears under the condition of rated voltage.
The mode that battery system mostly adopted contactor and fuse cooperation protection in the trade realizes at present, under the heavy current short circuit condition, relies on hot melt fuse protection, relies on abnormal signal to detect under the undercurrent condition, through the unusual return circuit of external control contactor disconnection, this kind of protection mode has following problem: firstly, the protection range of the contactor and the fuse is limited, the fuse needs to meet the requirements of short-time current impact in the normal use process of a vehicle and temperature rise in the continuous charging and discharging process, and the short-circuit protection current which can be generally realized is more than 3000A; the contactor adopts a magnetic quenching mode, and the breaking current is generally less than 2000A due to the influence of volume and temperature, so that a protection blind area exists for the protection of a battery system; secondly, when the vehicle is in an abnormal state such as collision, the low-voltage power supply of the contactor is possibly failed, and under the condition, the contactor loses control, a fault loop of abnormal current below 2000A cannot be cut off in time, and the safety failure risk exists; thirdly, the current detection sensor equipped in the current battery system mainly estimates the electric quantity of the battery system, and can not effectively detect the abnormal current of more than 1000A; fourthly, the existing vehicle can not realize that the high-voltage loop is quickly cut off after the vehicle is collided, thereby effectively protecting the whole vehicle and a battery system.
In summary, when an overcurrent fault occurs in a battery system of an existing vehicle, a high-voltage circuit connected with the battery system cannot be safely and effectively disconnected.
Disclosure of Invention
The invention aims to provide a battery system overcurrent protection method and a vehicle, which are used for solving the problem that the battery system is difficult to be effectively protected when the battery system has an overcurrent fault.
In order to achieve the above object, the present invention provides a battery system overcurrent protection method, including the steps of:
1) Acquiring a vehicle state, wherein the vehicle state comprises a driving state;
2) When the vehicle is in a driving state, the control module acquires a discharge current passing through the high-voltage loop through the current detection module; the current detection module is connected between the battery system and the high-voltage loop in series;
3) When the discharge current is larger than a first set value, acquiring the real-time speed of the vehicle, and if the real-time speed is smaller than the set speed, sending a breaking instruction to an execution module; if the real-time vehicle speed is greater than the set vehicle speed, sending an alarm instruction for reducing the vehicle speed to a driver or controlling the vehicle to reduce the vehicle speed;
the execution module comprises a conductive plate which is connected between the battery system and the high-voltage loop in series; the control module is connected with the execution module in a control mode, and the execution module disconnects the conductive plate when receiving a breaking instruction.
Acquiring the discharge current of a battery system of a vehicle in a driving state, detecting the real-time speed of the vehicle if the discharge current is greater than a preset current standard, and disconnecting the power supply of the battery system to a high-voltage loop if the speed is less than a preset reference speed; when the vehicle speed is high, the battery system is disconnected from supplying power to the high-voltage loop, secondary accidents of the vehicle are easily caused, and therefore if the real-time vehicle speed is higher than the set vehicle speed, an alarm instruction for reducing the vehicle speed is sent to a driver or the vehicle is controlled to reduce the vehicle speed.
Further, in the method, in the step 3), when the discharge current is greater than the first set value, the real-time speed of the vehicle is obtained;
when the real-time vehicle speed is less than the set vehicle speed, if the duration time of the discharge current is more than the tolerance time corresponding to the first set value, sending a breaking instruction to an execution module; if the duration time of the discharge current is less than the tolerance time corresponding to the first set value, continuing waiting until the duration time of the discharge current is greater than the tolerance time corresponding to the first set value, and sending a breaking instruction to an execution module;
the tolerance time corresponding to the first set value is obtained by a corresponding relationship between the discharge current and the tolerance time obtained in advance.
Further, in the method, in step 3), after a set time elapses after the alarm command is sent, the vehicle speed is detected again, if the real-time vehicle speed is less than the set vehicle speed, the discharge current passing through the high-voltage loop is detected again, and if the discharge current is greater than a first set value, an interruption command is sent to the execution module.
After the alarm instruction is sent for a set period of time, the vehicle speed is detected again, the real-time vehicle speed is smaller than the set vehicle speed, the vehicle meets the breaking condition, breaking can be executed, the discharge current passing through the high-voltage loop is detected again, if the discharge current is larger than a first set value, a breaking instruction is sent to an execution module, the power supply of the battery system to the high-voltage loop is disconnected, and if the discharge current is smaller than the first set value, the fault is considered to be eliminated, and breaking is not required.
Further, in the above method, the first set value is also adjusted periodically; and acquiring the real-time temperature of the battery system during adjustment, and increasing the first set value if the real-time temperature is greater than the preset temperature.
The tolerance capacity of the battery system is related to the internal resistance of the battery system, the internal resistance of the battery system is related to the temperature, when the temperature increases, the internal resistance of the battery system decreases, the current increases, the heat production of the battery system increases, and the tolerance capacity of the battery system is poor.
Further, in the above method, the method of adjusting the first setting value includes: acquiring real-time internal resistance corresponding to real-time temperature according to a relation of internal resistance of a battery system measured in advance along with temperature change; the nominal internal resistance of the battery system is also obtained, and the ratio of the real-time internal resistance to the nominal internal resistance is used as a correction coefficient; and taking the ratio of the original first set value to the modification coefficient as a new first set value.
Obtaining the internal resistance of the battery system at the current temperature according to the relation of the internal resistance of the battery system, which is measured in advance when the battery system leaves a factory, along with the temperature change, comparing the internal resistance with the nominal internal resistance of the battery system when the battery system leaves the factory, obtaining a trimming coefficient by a quantitative calculation method, adjusting a first set value according to the trimming coefficient, and improving the adjustment reliability; the ratio of the real-time internal resistance to the nominal internal resistance is used as a correction coefficient, the calculation is simple and convenient, and the power consumption of the control module is reduced.
Further, in the above method, the tolerance time corresponding to the new first setting value is acquired as the new setting time according to the previously measured tolerance times of the battery system at different tolerance currents.
Under different withstand currents, the battery system can insist on different withstand times, and after the first set value is adjusted, the set time is also adjusted, so that the reliability of protection of the battery system is improved.
Further, in the above method, the vehicle state further includes a charging state, when the vehicle is in the charging state, the control module obtains a charging current passing through the high-voltage loop through the current detection module, and if the duration time is longer than the tolerance time corresponding to the current charging current under the current charging current, sends a breaking instruction to the execution module; the tolerance time corresponding to the current charging current is obtained through the corresponding relation between the charging current and the tolerance time obtained in advance.
And detecting the charging current of the battery system during charging, and if the duration time is longer than the tolerance time corresponding to the current charging current under the current charging current, which indicates that the input current of the battery system during charging is too large and exceeds the tolerance capacity of the battery system, so that the battery system is easy to cause a fault, sending a breaking instruction to an execution module, and disconnecting the charging current of the high-voltage loop to the battery system.
Further, in the method, a power supply is further included, and the power supply is connected with the current detection module, the control module and the execution module.
And an independent power supply is adopted to supply power to the current detection module, the control module and the execution module, so that the failure loop can be timely disconnected when the battery system has abnormal faults under the condition of low-voltage power supply failure.
The invention also provides a vehicle adopting the over-current protection method of the battery system.
Drawings
FIG. 1 is an electrical schematic diagram of a prior art multiple parallel battery system;
FIG. 2 is a schematic structural diagram of a battery system configured with an activated fuse protector in an embodiment of the present invention;
FIG. 3 is a flow chart of a method for over-current protection of a battery system according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a withstand current-withstand time of a battery system of a vehicle at the time of shipment according to an embodiment of the present invention;
fig. 5 is a schematic diagram of an internal resistance-temperature decay characteristic of a battery system in an embodiment of the invention;
fig. 6 is a schematic diagram of the withstand current of the battery system at different SOCs according to the embodiment of the invention.
In the figure: 1 is an excitation fusing protection device; 2 is a current detection module; 3 is an execution module; and 4, a control module.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments.
The method comprises the following steps:
the over-current protection method for the battery system can detect the current in the high-voltage loop and the temperature of a battery pack in the battery system in real time when the high-voltage loop connected with the battery system has abnormal current, compare the real-time charging current with a preset charging current standard when the whole vehicle is in a charging state, and execute a breaking instruction to disconnect the charging high-voltage loop connected with the battery system and a charger if the charging current meets a charging fault breaking condition; when the whole vehicle is in a running state, the real-time discharge current of the battery system is compared with a preset discharge current standard, if the discharge current meets a running fault breaking condition, a breaking instruction is executed, a discharge high-voltage loop connecting the battery system and a load is disconnected, and the safety of the battery system is ensured.
In the present embodiment, overcurrent protection is performed on the battery system by using the activation fuse protector 1 shown in fig. 2. The device comprises a current detection module 2, an execution module 3 and a control module 4. The current detection module 2 and the execution module 3 are arranged on the charge-discharge loop and are connected with the battery system in series, the control module 4 is connected with the current detection module 2 to detect the charge-discharge current of the charge-discharge loop in real time, and is also connected with the execution module 3 to disconnect the charge-discharge loop when the charge fault breaking condition or the driving fault breaking condition is met.
In this embodiment, the execution module 3 is a switching device for breaking a charging and discharging high-voltage circuit, for example, an excitation fuse integrated with an arc-extinguishing melt described in CN212257338U is adopted, and when the control module 4 sends a breaking instruction to the execution module 3, an ignition explosion device of the excitation fuse is activated to push a piston to act on a conductive plate, so that the conductive plate is broken, thereby realizing breaking of a fault current. In another embodiment, the execution block 3 may be a fuse that is actively blown by a large input current, and the fuse may be blown by applying a driving voltage to both ends of the fuse.
In this embodiment, the control module 4 is a separately arranged controller, and is connected to an independently arranged power supply, and the power supply is further electrically connected to the current detection module 2 and the execution module 3, so that it can be ensured that a breaking instruction can still be executed under the condition that the low-voltage power supply of the whole vehicle fails, and the execution module 3 can normally operate. As another embodiment, the control module 4 may be a vehicle control unit or a BMS. The control module 4 can periodically detect the execution module 3 to reduce the risk that the circuit cannot be cut off in time when the circuit needs to be cut off actively.
In this embodiment, the control module 4 further obtains the temperature of the battery system, and may collect the temperature through a temperature sensor (not shown in the figure) arranged in the battery system, where the temperature sensor may be a thermistor temperature sensor, and specifically, the thermistor temperature sensor may be connected to a connection line that connects the single batteries in series and in parallel, so as to obtain the temperature of the battery system by detecting a resistance value of the thermistor temperature sensor. The temperature of the battery system may also be obtained from the battery management system BMS, which is the real-time temperature of the battery pack in the battery system. As another embodiment, the temperature of each electrical device in the charge and discharge circuit, such as a battery, a connector, a connection busbar, a contactor, a fuse, etc., may be obtained after mathematical statistical analysis by detecting the temperature of each electrical device.
In addition, the control module 4 is connected with a collision detection unit (not shown in the figure), when a vehicle collides, once a collision fault reaches a critical trigger value of a collision sensor, the control module 4 can send a breaking instruction to drive the execution module 3 to act, so that a high-voltage loop of the whole vehicle is cut off, high-voltage short circuit caused by insulation failure of a high-voltage line or breakage of a liquid pipeline due to collision of the whole vehicle is prevented, and unexpected safety accidents are avoided. The collision detection unit can be a pressure sensor in an air bag of the vehicle, can also be an accelerometer for detecting the instantaneous acceleration of the whole vehicle, and can also be an electronic rubber strip for detecting the collision state of the vehicle.
The overcurrent protection method for the battery system of the embodiment adopts the flow shown in fig. 3, and includes the following steps:
1) The excitation fusing protection device is subjected to power-on self-test, if the control module 4 detects that the excitation fuse (namely the execution module 3) works abnormally, fault alarm information is sent to a battery management system BMS, the BMS forwards the fault alarm information to a vehicle control unit, and the vehicle control unit transmits the fault alarm information to a background monitoring network in a wireless transmission mode for pushing and troubleshooting faults; if the excitation fuse works normally, a normal working instruction is sent to the BMS and the vehicle control unit, and when the BMS and the vehicle control unit receive the normal working instruction of the excitation fusing protection device, the vehicle state is sent to the control module 4, wherein the vehicle state comprises a charging state and a driving state.
2) After the self-checking is finished, a real-time current and temperature detection process is carried out, the control module 4 collects the temperature of the battery system and the current passing through the high-voltage loop, and meanwhile, detected current and temperature data are transmitted to a background monitoring network in a wireless transmission mode through the BMS and the vehicle control unit so as to realize the real-time monitoring of the vehicle.
3) And after the control module 4 acquires the state of the whole vehicle, fault diagnosis is carried out according to the detected current and temperature. If the vehicle state received by the control module 4 is a charging state, fault judgment is carried out according to fault breaking conditions in the charging state, and corresponding control is carried out; and if the vehicle state received by the control module 4 is the driving state, judging whether the fault occurs according to the fault breaking condition in the driving state, and performing corresponding control.
The fault breaking condition of the charging state is set according to the charging tolerance of a charging circuit connected with a battery system, and the characteristics of components such as a battery pack, a connecting bus bar, a charging contactor, a charging socket, a charging plug, a charger, a fuse and the like in the charging circuit need to be considered when the charging tolerance is set. In this embodiment, the charging state fault breaking condition is obtained by comparing the charging withstand current of the battery system with the charging current detected in real time. As another embodiment, the withstand voltage or the withstand temperature of the charging circuit may be used as a reference for comparison.
The fault breaking condition of the driving state is set according to the discharge tolerance of a discharge circuit connecting the battery system and the load, and the characteristics of components such as a battery pack, a connecting bus bar, a discharge contactor, a connector and a fuse in the discharge circuit need to be considered when the discharge tolerance is set. In this embodiment, the fault breaking condition of the driving state is obtained by comparing the discharge withstand current of the battery system with the discharge current detected in real time. In another embodiment, the withstand voltage or withstand temperature of the discharge circuit may be used as a standard for comparison.
When the state of the whole vehicle is a charging state, the control module 4 compares the charging current detected in real time with a preset charging tolerance current standard, if the charging current is larger than the charging tolerance current, it indicates that the charging current exceeds the bearing capacity of some electric device in the charging loop, which may damage the charging loop, cause overload fault, cause short circuit or open circuit risk, and even cause fire or explosion, and at this moment, it is considered that the fault breaking condition of the charging state is satisfied, the control module 4 sends a breaking instruction to the excitation fuse, the excitation fuse executes breaking operation, and the high-voltage charging loop is disconnected. Meanwhile, the control module 4 sends overload fault alarm information to the vehicle control unit through the BMS, and the vehicle control unit gives a fault alarm through the alarm device to remind a charging operator to perform maintenance processing in time; in addition, the overload fault alarm instruction is transmitted to a background monitoring network in a wireless transmission mode for statistical analysis of fault information.
If the charging current is smaller than the charging tolerance current, the fault breaking condition of the charging state is not satisfied, and the control module 4 continues to cyclically detect the charging current for the next round of judgment. In this embodiment, the control module 4 collects the charging current in the charging loop at a certain time interval, so as to reduce the power consumption of the control module and prolong the detection time. As another embodiment, the charging current may be collected without interruption to reduce the risk of failure of the over-current protection of the battery system.
When the vehicle state is a driving state, the control module 4 compares the detected discharge current with a preset discharge withstand current standard, and if the discharge current is smaller than the discharge withstand current, the discharge current is smaller than the maximum bearing capacity of each electric device in the discharge loop, so that an overload fault cannot be caused, and at this time, the control module 4 determines that the fault breaking condition of the driving state is not satisfied, and continues to cyclically detect the discharge current.
If the discharge current is greater than or equal to the discharge withstand current, the discharge current exceeds the bearing capacity of a certain electric device in the discharge loop, the discharge loop is damaged, an overload fault is caused, the risk of short circuit or open circuit is caused, even a fire or explosion is caused, the fault breaking condition of the driving state is considered to be met at the moment, if the fault breaking condition is directly broken at the moment, under the conditions of high speed and high load operation, the secondary accidents of steering failure, motor inverter explosion and the like of a vehicle with high-voltage steering can be caused, so that the vehicle is not controlled or directly ablated, and a greater risk is caused. Therefore, when the fault breaking condition in the driving state is met, the control module sends fault information to the whole vehicle to give an alarm to remind a driver of reducing the vehicle speed.
When the fault breaking condition in the driving state is met, if the vehicle is provided with low-voltage steering or high-low-voltage double steering or the motor inverter has an anti-explosion function, the high-voltage discharge circuit can be directly broken at the moment.
In this embodiment, when the fault breaking condition in the driving state is satisfied, the control module 4 obtains the real-time speed of the vehicle from the vehicle controller through the BMS to make a further determination, so as to ensure the safety of the personnel and the vehicle. If the real-time vehicle speed V is less than or equal to the reference vehicle speed Vref, the vehicle speed is smaller or the driver controls the vehicle to decelerate, the discharging current is detected again at the moment and compared with the discharging tolerant current, if the discharging current is more than or equal to the discharging tolerant current at the moment and the lasting time of the discharging current reaches the tolerant time standard corresponding to the discharging tolerant current, the fault still exists, the control module 4 sends a breaking execution instruction to the excitation fuse, the excitation fuse executes breaking operation, and the high-voltage discharging loop is disconnected; if the discharge current detected this time is smaller than the discharge tolerant current, or the duration time of the discharge current does not reach the tolerance time standard corresponding to the discharge tolerant current, the fault is indicated as false alarm or is solved by other methods, and the high-voltage discharge loop does not need to be disconnected.
If the real-time vehicle speed V is greater than the reference vehicle speed Vref, in order to prevent the battery system from breaking the high-voltage discharge loop within the limited time, which causes the battery system to continuously over-current to cause the battery failure, the damage of a protection device or the circuit ablation, the discharge current is detected again after the interval set time, if the discharge current is still greater than the discharge tolerant current at the moment, which indicates that the discharge current is longer in the discharge loop and can cause the great damage to the battery system and the vehicle, the control module 4 sends a breaking instruction to the excitation fuse, the excitation fuse executes the breaking operation, and the high-voltage discharge loop is broken; if the duration of the detected discharge current is less than the set time standard, the fault is false alarm or eliminated, and therefore the waiting is continued until the duration of the detected discharge current exceeding the discharge tolerance current reaches the tolerance time standard, the alarm is given out and the breaking control is executed.
In the present embodiment, the charge withstand current in the charged state and the discharge withstand current in the driving state of the battery system are set according to the withstand current-withstand time characteristic curve shown in fig. 4. Because the internal resistance of the battery system is increased due to aging of the battery system, the withstand current of the battery system is gradually reduced along with the time, and a system failure curve shown in the figure shows that the charging and discharging current of the battery system cannot exceed the corresponding current on the curve, and if the charging and discharging current exceeds the corresponding current, the battery system is damaged; the system safety curve shows that if the charging and discharging current of the battery system is close to the tolerance current standard corresponding to the curve, the battery system is subjected to overcurrent protection, and the battery system cannot be damaged. And formulating a charging tolerance current standard of the battery system in a charging state and a discharging tolerance current standard of the battery system in a discharging state according to the system safety curve, and respectively corresponding to a charging protection curve and a driving protection curve in the graph.
4) The control module 4 detects whether the vehicle collides through the collision detection unit, and if the vehicle collides, the control module directly cuts off the execution module of the excitation fuse, disconnects the high-voltage discharge loop and records fault information.
In the embodiment, in order to improve the accuracy of the charging withstand current and the discharging withstand current, an internal resistance-temperature attenuation model is adopted according to the temperature and the internal resistance of the battery system to improve the internal resistance of the battery system due to the fact that the temperature of the battery system is higher during charging or discharging.
Specifically, as shown in fig. 5, as the temperature of the battery system changes, the internal resistance of the battery system also changes, and generally, the internal resistance is large at low temperature and small at high temperature, and both the open-circuit current and the current-withstanding capability of the battery system change under the condition that the terminal voltage of the battery system is not changed. Therefore, the battery internal resistance-temperature attenuation model is determined according to the change rule of the battery internal resistance of the battery at different temperatures, the voltage of the battery system is combined, the tolerance current value of the battery system is pre-judged according to the ohm law, and then a new tolerance current standard is issued to the control module through the BMS, so that the overcurrent protection of the battery system is more accurate.
In fig. 5, the abscissa is the temperature of the battery system, the ordinate is the ratio of the internal resistance R of the battery to the nominal internal resistance R0 of the battery, and the nominal internal resistance of the battery is the internal resistance of the battery system at 25 ℃ at an SOC of 0%. When the withstand current-withstand time curve in fig. 4 is modified by using the ratio of the internal resistance R of the battery to the nominal internal resistance R0 of the battery as a modification coefficient, the withstand current should change as shown in fig. 6.
For example, at T ℃, the internal resistance of the battery system is R1, which is k times (k = R1/R0) the nominal internal resistance R0 of the battery system, and the withstand capability of the battery system is weakened while the terminal voltage of the battery system is not changed, as shown in fig. 6, the withstand current of the battery system is changed to 1/k, and the charge withstand current and the discharge withstand current of the battery system are changed to 1/k accordingly. The control module determines a new battery endurance standard according to the modification coefficient k, and can realize the full utilization and effective protection of the battery system.
The method comprises the steps that a battery system is gradually aged along with the increase of the service time of the vehicle battery system, the maximum charging capacity of the battery system is reduced, and the tolerance capacity of the battery system is weakened, so that the tolerance current value of the battery system is pre-judged according to ohm's law by combining a battery internal resistance-temperature attenuation model determined by the change rule of the battery internal resistance at different temperatures according to the change rule of the internal resistance in the whole life cycle of the battery.
The embodiment of the vehicle is as follows:
the vehicle of the present invention adopts the circuit structure and the overcurrent protection method described in the method embodiment to protect the battery system, and includes the following steps:
1) Exciting the protection device for self-checking, if a fault occurs, giving an alarm, and if no fault occurs, performing the step 2);
2) Acquiring a vehicle state and detecting the current of a charge-discharge loop in real time;
3) When the vehicle is in a charging state, if the charging current is detected to be larger than a preset charging tolerance current standard, the charging loop is disconnected; when the vehicle is in a driving state, if the discharging current is detected to be larger than a preset discharging tolerance current standard, performing fault alarm to remind a driver to reduce the vehicle speed, and when the vehicle speed is detected to be smaller than a preset reference vehicle speed, detecting the discharging current again, comparing the discharging current with the preset discharging tolerance current, and if the discharging current is smaller than the discharging tolerance current standard, indicating that no fault exists; if the discharge current is larger than the discharge tolerance current standard and the duration time of the discharge current reaches the tolerance time standard corresponding to the discharge tolerance current, breaking the discharge loop; if the duration time of the discharge current does not reach the tolerance time corresponding to the discharge tolerance current, continuing waiting until the duration time of the discharge current reaches the tolerance time corresponding to the first set value, and sending a breaking instruction to an execution module; and when the detected vehicle speed is greater than the preset reference vehicle speed, judging the time that the discharge current is greater than the discharge tolerance current, if the time exceeds the set time, breaking the discharge loop, and if the time is less than the set time, continuing to detect and judge.
4) And acquiring collision information of the vehicle, and breaking a high-voltage loop when the vehicle collides to ensure the safety of a battery system.
5) The withstand current standard is corrected according to the temperature of the battery system.
It is clear that the implementation of the method has already been described in the method embodiments and is not described here in detail.
Claims (9)
1. An over-current protection method for a battery system, comprising the steps of:
1) Acquiring a vehicle state, wherein the vehicle state comprises a driving state;
2) When the vehicle is in a driving state, the control module acquires a discharge current passing through the high-voltage loop through the current detection module; the current detection module is connected between the battery system and the high-voltage loop in series;
3) When the discharge current is larger than a first set value, acquiring the real-time speed of the vehicle, and if the real-time speed is smaller than the set speed, sending a breaking instruction to an execution module; if the real-time vehicle speed is greater than the set vehicle speed, sending an alarm instruction for reducing the vehicle speed to a driver or controlling the vehicle to reduce the vehicle speed;
the execution module comprises a conductive plate connected in series between the battery system and the high-voltage loop; the control module controls the connection execution module, and when the execution module receives a breaking instruction, the conducting plate is disconnected.
2. The battery system overcurrent protection method according to claim 1, wherein in step 3), when the discharge current is greater than a first set value, a real-time vehicle speed of the vehicle is obtained;
when the real-time vehicle speed is less than the set vehicle speed, if the duration time of the discharge current is more than the tolerance time corresponding to the first set value, sending a breaking instruction to an execution module; if the duration time of the discharge current is less than the tolerance time corresponding to the first set value, continuing waiting until the duration time of the discharge current is greater than the tolerance time corresponding to the first set value, and sending a breaking instruction to an execution module;
the tolerance time corresponding to the first set value is obtained by a corresponding relationship between the discharge current and the tolerance time obtained in advance.
3. The overcurrent protection method for the battery system according to claim 1, wherein in step 3), the vehicle speed is detected again after a set time elapses after the alarm command is sent, the discharging current through the high-voltage circuit is detected again if the real-time vehicle speed is less than the set vehicle speed, and the disconnection command is sent to the execution module if the discharging current is greater than the first set value.
4. The battery system overcurrent protection method according to claim 2 or 3, characterized in that the first set value is also adjusted periodically; and acquiring the real-time temperature of the battery system during adjustment, and increasing the first set value if the real-time temperature is greater than the preset temperature.
5. The battery system overcurrent protection method according to claim 4, wherein the method for adjusting the first set value is: acquiring real-time internal resistance corresponding to real-time temperature according to a relation of internal resistance of a battery system measured in advance along with temperature change; the nominal internal resistance of the battery system is also obtained, and the ratio of the real-time internal resistance to the nominal internal resistance is used as a correction coefficient; and taking the ratio of the original first set value to the modification coefficient as a new first set value.
6. The battery system overcurrent protection method according to claim 3, wherein a withstand time corresponding to the new first set value is acquired as a new set time based on a previously measured withstand time of the battery system at different withstand currents.
7. The battery system overcurrent protection method according to claim 1, wherein the vehicle state further includes a charging state, when the vehicle is in the charging state, the control module obtains a charging current passing through the high-voltage loop through the current detection module, and if the duration of the current charging current is longer than the tolerance time corresponding to the current charging current, sends a breaking instruction to the execution module; the tolerance time corresponding to the current charging current is obtained through the corresponding relation between the charging current and the tolerance time which is obtained in advance.
8. The battery system overcurrent protection method according to claim 1, further comprising a power supply, wherein the power supply is connected to the current detection module, the control module, and the execution module.
9. A vehicle characterized in that the battery system overcurrent protection method according to any one of claims 1 to 8 is employed.
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| CN117465222A (en) * | 2023-12-25 | 2024-01-30 | 合众新能源汽车股份有限公司 | Fault early warning method and fault early warning system of power battery |
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