An excitation fuse protection method for a battery system and a vehicle

Abstract

The present invention provides an excitation fuse protection method and vehicle for a battery system, and belongs to the field of vehicle safety protection technology. The current flowing between the battery system and the high-voltage circuit is obtained by a current detection module and sent to a control module. The control module compares the current with a first set value. If the current is greater than the first set value, the detection is continued. If the duration of the current exceeds the set time standard, it is considered that the actual working condition of the battery system exceeds the tolerance of the battery system, and the control module sends a disconnection instruction to the execution module. The execution module includes a conductive plate, which is connected in series between the battery system and the high-voltage circuit. When the disconnection instruction is received, the conductive plate is disconnected, and the power supply between the battery system and the high-voltage system can be disconnected to protect the safety of the battery system. The control module can also compare the current with a second set value. If the current is greater than the second set value, a segmentation instruction is sent to the execution module to achieve disconnection.

Description

Technical Field

[0001] The invention relates to an excitation fusing protection method for a battery system and a vehicle, belonging to the technical field of vehicle safety protection. Background Art

[0002] With the continuous development of new energy technologies, the safety of battery systems has become the focus of attention in the industry. The safety protection of battery systems not only relies on the improvement of the safety performance of single batteries, but also focuses on the improvement of the safety performance of the battery system level, which includes both active protection and passive protection. The active protection method of the contactor and the passive protection method of the fuse cannot achieve full range protection of the battery system, especially for commercial vehicles based on standard platform products. The battery system adopts a multi-branch parallel connection method, which makes the protection of the battery system more complicated, and there are certain protection blind spots, which cannot achieve effective protection of the battery system.

[0003] The short-circuit protection of traditional fuses can no longer meet the protection requirements of battery systems. The main problem is that if the matching thermal cutout is too large, it will not be able to quickly and effectively protect the battery when a short circuit occurs in the battery system, causing thermal runaway of the battery pack; if the matching thermal cutout is too small, the short-term current shock and continuous charging and discharging process during vehicle driving will exceed the fuse's impact tolerance capacity, and there will be risks to long-term reliability; and the thermal cutout cannot safely disconnect overload currents below 5 times the rated current under rated voltage conditions.

[0004] At present, most battery systems in the industry are implemented by the combination of contactors and fuses for protection. In the case of high current short circuit, they rely on thermal fuses for protection, and in the case of low current, they rely on abnormal signal detection. The abnormal circuit is disconnected by external control contactors. This protection method has the following problems: First, the protection range of contactors and fuses is limited. Fuses need to meet the short-term current shocks during normal use of the vehicle and the temperature rise requirements during continuous charging and discharging. The generally achievable short-circuit protection current is greater than 3000A; while the contactor adopts the method of magnetic arc extinguishing. Due to the influence of volume and temperature, the breaking current is generally less than 2000A. Therefore, there is a blind spot for battery system protection; second, in abnormal conditions such as vehicle collision, the low-voltage power supply of the contactor may fail. In this case, the contactor loses control and cannot cut off the fault circuit of abnormal current below 2000A in time, which poses a risk of safety failure; third, the current detection sensors currently equipped in the battery system are mainly used to estimate the battery system power, and cannot effectively detect abnormal currents above 1000A.

[0005] Therefore, it is difficult for current new energy vehicles to achieve safe and effective protection when a battery system failure occurs. Summary of the invention

[0006] The object of the present invention is to provide an excitation fuse protection method and a vehicle for a battery system, so as to solve the problem that the battery system is difficult to disconnect safely when an overcurrent fault occurs.

[0007] In order to achieve the above object, the present invention provides an excitation fuse protection method for a battery system, comprising the following steps:

[0008] 1) The control module obtains the current passing through the high-voltage circuit through the current detection module; the current detection module is connected in series between the battery system and the high-voltage circuit;

[0009] 2) If the current passing through the high-voltage circuit is greater than the first set value, and the duration of the current exceeds the set time corresponding to the first set value, a disconnection instruction is sent to the execution module; the set time corresponding to the first set value is obtained by the correspondence between the charging current and the tolerance time obtained in advance;

[0010] If the current passing through the high-voltage circuit is greater than the second set value, a disconnection instruction is sent to the execution module;

[0011] The first set value is less than the second set value;

[0012] The execution module includes a conductive plate, which is connected in series between the battery system and the high-voltage circuit; the control module controls the connection execution module, and when the execution module receives a disconnection instruction, the conductive plate is disconnected.

[0013] The current flowing between the battery system and the high-voltage circuit is obtained through the current detection module and sent to the control module. The control module uses the first set value and the set time as the standard for measuring the tolerance of the battery system. The control module compares the current with the first set value. If the current is greater than the first set value, the detection continues. If the duration of the current exceeds the set time standard, it is considered that the actual working condition of the battery system exceeds the tolerance of the battery system, and the control module sends a disconnection instruction to the execution module. The execution module includes a conductive plate, which is connected in series between the battery system and the high-voltage circuit. When the disconnection instruction is received, the conductive plate is disconnected, and the power supply between the battery system and the high-voltage system can be disconnected to protect the safety of the battery system. The control module also uses the second set value as the standard for measuring the tolerance of the battery system. The control module compares the current with the second set value. If the current is greater than the second set value, a segmentation instruction is sent to the execution module to disconnect the conductive plate, thereby achieving disconnection.

[0014] Furthermore, in the above method, the first set value and the second set value are also adjusted regularly; during the adjustment, the real-time temperature of the battery system is obtained, and if the real-time temperature is greater than the preset temperature, the first set value and the second set value are increased.

[0015] The tolerance of the battery system is related to the internal resistance of the battery system, and the internal resistance of the battery system is related to temperature. When the temperature increases, the internal resistance of the battery system decreases, the short-circuit current increases, and the heat generation of the battery system increases, resulting in the deterioration of the tolerance of the battery system. Therefore, the first and second set values ​​are adjusted according to the temperature. When the temperature is greater than the preset temperature value, the first and second set values ​​are increased to improve the comparison standard and reduce safety hazards.

[0016] Furthermore, in the above method, the method for adjusting the first set value and the second set value is: according to the relationship between the internal resistance of the battery system and the temperature measured in advance, the real-time internal resistance corresponding to the real-time temperature is obtained; the nominal internal resistance of the battery system is also obtained, and the correction coefficient is calculated according to the real-time internal resistance and the nominal internal resistance, and the first set value and the second set value are adjusted according to the correction coefficient.

[0017] According to the relationship between the internal resistance of the battery system and the temperature measured in advance before leaving the factory, the internal resistance of the battery system at the current temperature is obtained and compared with the nominal internal resistance of the battery system when leaving the factory. The correction coefficient is calculated by a quantitative calculation method, and the first set value and the second set value are adjusted according to the correction coefficient to improve the reliability of the adjustment.

[0018] Furthermore, in the above method, the ratio of the real-time internal resistance to the nominal internal resistance is used as the correction coefficient;

[0019] The ratio of the original first setting value to the revised coefficient is used as the new first setting value, and the ratio of the original second setting value to the revised coefficient is used as the new second setting value.

[0020] A relatively simple calculation method is adopted, and the ratio of the real-time internal resistance to the nominal internal resistance is used as the correction coefficient, which saves the amount of calculation and reduces the power consumption of the control module.

[0021] Furthermore, in the above method, the nominal internal resistance is the internal resistance value of the battery system at 25° C. and 0% SOC.

[0022] Furthermore, in the above method, according to the pre-measured tolerance time of the battery system at different tolerance currents, the tolerance time corresponding to the new first setting value is obtained as the new setting time.

[0023] Under different tolerance currents, the battery system can maintain different tolerance times. When the first set value is adjusted, the set time is also adjusted to improve the reliability of the protection of the battery system.

[0024] Furthermore, in the above method, the control module also detects the state of the execution module, and sends an alarm message to the entire vehicle if the execution module does not disconnect the high-voltage circuit after receiving the disconnection instruction.

[0025] After sending the disconnection command to the execution module, the control module also checks the status of the execution module to prevent the conductive plate of the execution module from not being disconnected in time, causing the vehicle fault to continue and thus causing an accident.

[0026] Furthermore, in the above method, it is characterized in that it also includes a power supply, and the power supply is connected to the current detection module, the control module, and the execution module.

[0027] An independent power supply is used to power the current detection module, control module, and execution module to ensure that in the event of a low-voltage power supply failure, the failure circuit can be disconnected in time when an abnormal fault occurs in the battery system.

[0028] The present invention also provides a vehicle, which adopts the above-mentioned excitation fuse protection method of the battery system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the battery system structure in an embodiment of the present invention;

[0030] Figure 2 The electrical schematic diagram of the vehicle power supply in the embodiment of the present invention;

[0031] Figure 3 Flow chart of a battery system excitation fuse protection method according to an embodiment of the present invention;

[0032] Figure 4 It is a schematic diagram of the broken line of the initial withstand current of the battery system changing with time in an embodiment of the present invention;

[0033] Figure 5 A schematic diagram of a broken line showing changes in the correction coefficient with temperature in an embodiment of the present invention;

[0034] Figure 6 It is a broken line diagram showing the variation of the withstand current with temperature in an embodiment of the present invention.

[0035] In the figure: 1 is an excitation protection unit, 2 is a control module, 3 is a current detection module, and 4 is an execution module. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0037] Method Example:

[0038] like Figure 1As shown, an excitation fuse protection method for a battery system of this embodiment uses an excitation protection unit to achieve overcurrent safety protection. Specifically, the battery system includes a vehicle power supply and an excitation protection unit 1. The excitation protection unit 1 is arranged on a high-voltage circuit connecting the vehicle power supply and the load to achieve overcurrent protection for the battery system. Figure 2 As shown, a battery module is composed of multiple single batteries connected in series, and multiple battery modules are connected in parallel and in series with the high-voltage circuit. A fuse is set on the line connecting each battery module to the main circuit. When the current output or input of the vehicle power exceeds the specified value, the fuse of the fuse will be blown, thereby disconnecting the circuit, which can effectively protect the circuit. The excitation protection unit 1 can replace the fuse, or be connected in series with the fuse to form a more reliable battery system and vehicle protection circuit. A manual maintenance switch (MSD) is set on the high-voltage circuit to quickly disconnect the high-voltage connection between the battery system and the load when the vehicle maintenance personnel are repairing the vehicle, thereby reducing the occurrence of safety accidents.

[0039] In this embodiment, the excitation protection unit 1 includes a control module 2, a current detection module 3 and an execution module 4. Among them, the current detection module 3 is set on the high-voltage circuit connecting the vehicle power supply and the load, and is used to detect all fault currents in the battery system. It usually adopts a Hall current sensor or a high-precision resistor, etc., and the general detection range is -8000A to 8000A. The current detection range of the current detection module 3 can be adjusted according to actual use requirements, and a current detection device with a detection range of -3000A to 3000A is preferably used. When the detection range of the current detection module 3 is -3000A to 3000A, circuit protection with a short-circuit current below 3000A can be achieved. At this time, a fuse is still set in the circuit to achieve circuit protection with a short-circuit current above 3000A; if the detection range of the current detection module 3 is greater than -3000A to 3000A, the fuse can be set without setting, and the circuit is only protected by the excitation protection unit 1. The current detection module 3 is connected to the control module 2 and sends the detected fault current information to the control module 2.

[0040] The execution module 4 is a switch device for disconnecting the high-voltage circuit. It is arranged on the high-voltage circuit, connected in series with the vehicle power supply, and is also connected to the control module 2. It is used to receive the disconnection command sent by the control module 2, disconnect the high-voltage circuit, and ensure that the battery can be protected to the maximum extent when an abnormal current appears in the battery system. For example, the execution module 4 can adopt an excitation fuse with an integrated arc-extinguishing fuse as described in the announcement number CN212257338U. When the control module 2 sends a disconnection command to the execution module 4, the ignition explosion device of the excitation fuse is activated, pushing the piston to act on the conductive plate, disconnecting the conductive plate, thereby realizing the disconnection of the fault current. As another embodiment, the execution module 4 can also be a fuse that uses a larger input current for active melting, and the fuse is melted by applying a driving voltage to both ends of the fuse.

[0041] In this embodiment, the control module 2 is an independently arranged controller. As other implementation modes, the control module may directly adopt a vehicle controller or a battery management system.

[0042] When the vehicle is in an abnormal state such as a collision, the low-voltage power supply of the contactor in the battery system may fail. At this time, the contactor loses control and cannot cut off the power supply circuit with abnormal current in time, which poses a safety hazard. Therefore, an independent power supply is used to power the excitation protection unit 1. When the external contactor cannot cut off the fault circuit in time, it can still ensure that the battery system can disconnect the failed circuit in time when a current fault occurs, thereby ensuring the safety of the battery system and the vehicle.

[0043] In this embodiment, the power supply has a backup power function. In the event of an abnormal external power supply, it can continuously provide backup power for the excitation protection unit 1 for more than 10 minutes, ensuring that when the low-voltage power supply fails, the failure circuit can be disconnected in time when an abnormal fault occurs in the battery system.

[0044] The control module 2 receives the current information sent by the current detection module 3, performs graded judgment processing, and outputs different judgment results to the execution module 4, thereby realizing the excitation fuse protection method of the battery system. According to the different fault levels, the action time of the execution module 4 is different. The process of the excitation fuse protection method is as follows Figure 3 As shown, the following steps are included:

[0045] 1) The power supply supplies power to the excitation protection unit, and the excitation protection unit performs self-check. If a fault is detected in the control module, current detection module or execution module, the fault information is sent to the entire vehicle through the CAN communication network to warn; if no fault is detected, proceed to step 2).

[0046] 2) The current detection module detects the current passing through the high-voltage circuit in real time, including the input current of the battery system during charging and the output current of the battery system during driving, and sends the input / output current information to the control module. The control module receives the input / output current information and compares it with the preset tolerance current standard to complete the fault classification judgment.

[0047] like Figure 4 As shown, the battery system has different tolerance currents in different states, and the tolerance time that can sustain the tolerance current is different. The system failure curve shown in the figure shows that the greater the current passing through the battery system, the shorter the tolerance time of the battery system. If it is detected that the duration of the battery system under a certain input / output current exceeds the failure time standard corresponding to the system failure curve, it indicates that the battery system has a high risk of failure. Therefore, a set of tolerance times under different currents that are less than the failure time standard is selected as the safety time, and the system safety curve is fitted, indicating that as long as the tolerance time of the battery system under a certain input / output current is less than the safety time, the battery system will not be dangerous. Therefore, different tolerance currents and corresponding tolerance time standards are set in different current segments.

[0048] When the input / output current is greater than the first set threshold, it is considered that the battery system has a first-level overload fault. Considering that the battery system can continue to work for a period of time under the input / output current, the test is performed again after a set time interval. If the input / output current is still greater than the first set threshold, the input / output current of the battery system is tested again after a set time interval t, until the time when the input / output current exceeds the first set threshold reaches the set time standard T, the control module sends a fault message to the vehicle through CAN communication to warn, and at the same time, the control module sends a disconnection instruction to drive the execution module to disconnect the high-voltage circuit. The control module also automatically records the fault current, fault current duration and fault occurrence time for statistical analysis of fault information. In this embodiment, the set time standard T is not greater than the tolerance time of the first-level overload fault of the battery system.

[0049] If the input / output current detected in real time is less than the first set threshold, or the time the input / output current exceeds the first set threshold is less than T, it is considered that the battery system has no fault, and the protection unit is stimulated to perform the next round of judgment.

[0050] During the charging period, the first level overload fault corresponds to Figure 4 Charging protection curve in; During driving period, the first level overload fault corresponds to Figure 4Driving protection curve in. Specifically, if it is detected that the input current of the battery system is greater than the first tolerance current standard corresponding to the charging protection curve during the charging period, and the duration of the input current exceeds the tolerance time standard of the battery system that can withstand the tolerance current, it indicates that the charging current of the battery system during the charging period exceeds the tolerance capacity of the battery system, and it is necessary to cut off the charging high-voltage circuit in time. At this time, the controller sends a disconnection instruction to control the execution module to disconnect the charging high-voltage circuit; if it is detected that the input current is greater than the second tolerance current standard corresponding to the charging protection curve, and the duration of the input current exceeds the tolerance time standard of the battery system that can withstand the second tolerance current, it indicates that the charging current of the battery system during the charging period exceeds the tolerance capacity of the battery system, and it is necessary to cut off the charging high-voltage circuit in time. At this time, the controller sends a disconnection instruction to control the execution module to disconnect the charging high-voltage circuit.

[0051] Similarly, if it is detected during the driving period that the output current of the battery system is greater than the first tolerance current standard corresponding to the driving protection curve, and the duration of the output current exceeds the tolerance time standard that the battery system can withstand under the tolerance current, it indicates that the discharge current of the battery system during the driving period exceeds the tolerance capacity of the battery system, and the discharge high-voltage circuit needs to be cut off in time; if it is detected that the output current is greater than the second tolerance current standard corresponding to the driving protection curve, and the duration of the output current exceeds the tolerance time standard that the battery system can withstand under the second tolerance current, it indicates that the discharge current of the battery system during the discharge period exceeds the tolerance capacity of the battery system, and the discharge high-voltage circuit needs to be cut off in time.

[0052] When the input / output current detected by the control module exceeds the second set threshold, it is considered that the battery system has a secondary overload fault. At this time, the control module directly sends fault information to the entire vehicle for alarm. At the same time, the control module sends a disconnection instruction to drive the execution module to disconnect the high-voltage circuit of the battery system. The control module also automatically records the fault current, fault current duration and fault occurrence time for statistical analysis of fault information.

[0053] Overload secondary fault corresponding Figure 4 The system safety curve in the figure indicates that the input / output current exceeds the safety range of the battery system, and the risk of battery system failure is very high. Therefore, when a secondary overload fault occurs, the excitation fuse must be immediately executed to disconnect the high-voltage circuit.

[0054] The control module monitors the working status of the execution module in real time. If the execution module fails and cannot disconnect the high-voltage circuit in time, a disconnection abnormality will be sent to the entire vehicle.

[0055] 3) As the temperature of the battery system rises during the charging and discharging process, the resistance of the battery system will gradually increase. When the terminal voltage of the battery system remains unchanged, the battery's tolerance will be weakened. Therefore, according to the change law of the internal resistance of the battery system at different temperatures, the internal resistance-temperature attenuation model of the battery system is determined, and then combined with the voltage of the battery system, the tolerance current value of the battery system is predicted according to Ohm's law.

[0056] In this embodiment, appropriate temperature sampling points are selected at the power poles, connector terminals, connecting busbars, contactors and other parts of the vehicle power supply in the battery system, and temperature sensors are set at the temperature sampling points to detect the temperature of the battery system. The battery management system performs a comprehensive analysis based on the current value monitored by the current detection module in the excitation protection unit and the sampling data of each temperature point, and regularly calculates the correction coefficient of the battery system overcurrent protection through the temperature-current mathematical model. The change trend of the battery system tolerance capacity is determined based on the correction coefficient. After two comprehensive analysis verifications and background confirmations by the battery management system, the final correction coefficient is determined and sent to the control module in the excitation protection unit for adjustment.

[0057] like Figure 5 As shown, the horizontal axis is the temperature of the battery system. When the battery system is at different temperatures, the internal resistance is different. According to the relationship between the internal resistance and time measured in the laboratory before leaving the factory, the internal resistance R of the battery system at the current temperature is obtained. The vertical axis is the ratio of the battery internal resistance R to the nominal internal resistance R0 of the battery. The nominal internal resistance of the battery is the internal resistance of the battery system at 25°C and SOC is 0%. The ratio of the battery internal resistance R to the nominal internal resistance R0 of the battery is used as the correction coefficient. Figure 4 When modifying the withstand current-withstand time curve in the Figure 6 Changes shown.

[0058] For example, at T℃, the internal resistance of the battery system is R1, then the correction coefficient K=R1 / R0, indicating that the internal resistance of the battery system at T℃ changes to K times of the original. When the terminal voltage of the battery system remains unchanged, its withstand current should become 1 / K of the original, thereby obtaining the new first set threshold and the second set threshold. Figure 4 When the tolerance current-tolerance time variation curve shown in the figure is revised, since the corresponding failure current and safety current of the battery system are changed to 1 / K of the original, the first set threshold and the second set threshold are also changed to 1 / K of the original, and a new tolerance time can be obtained. According to the tolerance current-tolerance time curve, a new overload first-level fault standard and overload second-level fault standard are formulated, so that when the tolerance capacity changes due to the use time and temperature during the use of the battery system, the excitation fuse protection method can be adjusted in time, thereby enhancing the overcurrent protection capability of the battery system.

[0059] Vehicle Example:

[0060] The vehicle of this embodiment adopts the excitation fuse protection method of the battery system in the method embodiment. The steps for implementing the method are clearly described in the method embodiment and will not be repeated here.

Claims

1. An excitation fuse protection method for a battery system, characterized in that: The steps include: 1) The control module obtains the current passing through the high-voltage circuit through the current detection module; the current detection module is connected in series between the battery system and the high-voltage circuit; 2) If the current passing through the high-voltage circuit is greater than the first set value, and the duration of the current exceeds the set time corresponding to the first set value, a disconnection instruction is sent to the execution module; the set time corresponding to the first set value is obtained by the correspondence between the charging current and the tolerance time obtained in advance; If the current passing through the high-voltage circuit is greater than the second set value, a disconnection instruction is sent to the execution module; The first set value is less than the second set value; The execution module includes a conductive plate, which is connected in series between the battery system and the high-voltage circuit; the control module controls the connection execution module, and when the execution module receives a disconnection instruction, the conductive plate is disconnected; The first set value and the second set value are also adjusted regularly; during the adjustment, the real-time temperature of the battery system is obtained, and if the real-time temperature is greater than the preset temperature, the first set value and the second set value are increased; The method for adjusting the first set value and the second set value is: according to the relationship between the internal resistance of the battery system and the temperature measured in advance, the real-time internal resistance corresponding to the real-time temperature is obtained; the nominal internal resistance of the battery system is also obtained, and the correction coefficient is calculated according to the real-time internal resistance and the nominal internal resistance, and the first set value and the second set value are adjusted according to the correction coefficient.

2. The excitation fuse protection method of the battery system according to claim 1, characterized in that: The ratio of the real-time internal resistance to the nominal internal resistance is used as the correction coefficient; The ratio of the original first setting value to the revised coefficient is used as the new first setting value, and the ratio of the original second setting value to the revised coefficient is used as the new second setting value.

3. The excitation fuse protection method of the battery system according to claim 2, characterized in that: The nominal internal resistance is the internal resistance value of the battery system at 25°C and 0% SOC.

4. The excitation fuse protection method of the battery system according to claim 1, characterized in that: According to the pre-measured tolerance time of the battery system at different tolerance currents, the tolerance time corresponding to the new first setting value is obtained as the new setting time.

5. The excitation fuse protection method of the battery system according to claim 1, characterized in that: The control module also detects the status of the execution module. If the execution module does not disconnect the high-voltage circuit after receiving the disconnection command, an alarm message is sent to the entire vehicle.

6. The excitation fuse protection method of the battery system according to claim 1, characterized in that: It also includes a power supply, which is connected to the current detection module, the control module, and the execution module.

7. A vehicle, characterized in that: An excitation fusing protection method for a battery system according to any one of claims 1 to 6 is adopted.

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