A power battery protection system and control method thereof

Abstract

The present invention provides a protection system for a power battery and a control method thereof, and relates to the technical field of power battery protection. Among them, the protection system includes a battery assembly, a nitrogen assembly, and a first connecting assembly. The battery assembly includes a battery pack with a built-in cavity, a power battery arranged in the cavity, and a first air pressure sensor and an oxygen concentration sensor arranged in the battery pack. The nitrogen assembly includes a nitrogen gas cylinder provided with an inflation port and a third air pressure sensor arranged in the nitrogen gas cylinder. The first connecting assembly is used to connect the nitrogen gas cylinder and the cavity. The first connecting assembly includes a one-way valve and a first solenoid valve arranged in series. The power battery is wrapped by the battery pack, and the inert gas nitrogen is filled into the battery pack through the nitrogen assembly and the first connecting assembly. Thereby effectively preventing the power battery from catching fire. It has great practical significance.

Description

Technical Field

[0001] The present invention relates to the technical field of power battery protection, and in particular to a power battery protection system and a control method thereof. Background Art

[0002] With the development and popularization of new energy vehicles, the safety requirements of new energy vehicles are constantly increasing. As a key component of new energy vehicles, the safety of power batteries has received special attention from users. The power batteries of electric buses use lithium-ion batteries with advantages such as high energy density, energy storage and release, and long life. Power battery fire accidents are major accidents of new energy buses, which greatly affect the promotion and use of new energy buses.

[0003] In actual application, there are still many problems with the safety of lithium-ion batteries. Spontaneous combustion and fire incidents of new energy vehicles are common, and each accident has attracted much attention from the society. In response to the safety issues of lithium-ion batteries, relevant departments and enterprises have invested a lot of manpower and material resources in research and testing, and have made great breakthroughs in improving the safety of lithium-ion power batteries. Despite this, lithium-ion batteries are still not absolutely safe, and safety hazards of electric bus power batteries still exist. How to prevent the occurrence of power battery fires has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present invention provides a power battery protection system and a control method thereof, aiming to improve the problem that the prior art cannot effectively prevent power battery fires.

[0005] First,

[0006] In order to solve the above technical problems, the present invention provides a power battery protection system, which includes a battery assembly, a nitrogen assembly, and a first connecting assembly.

[0007] The battery assembly includes a battery pack with a built-in cavity, a power battery arranged in the cavity, and a first air pressure sensor and an oxygen concentration sensor arranged in the battery pack. The nitrogen assembly includes a nitrogen gas cylinder provided with a charging port and a third air pressure sensor arranged in the nitrogen gas cylinder. The first connecting assembly is used to connect the nitrogen gas cylinder and the cavity. The first connecting assembly includes a one-way valve and a first solenoid valve arranged in series.

[0008] Optionally, the first connecting assembly further includes a pressure reducing valve for connecting the nitrogen gas cylinder and the first solenoid valve, and a second air pressure sensor disposed between the pressure reducing valve and the first solenoid valve.

[0009] Optionally, the battery assembly further includes a safety valve and a back pressure valve configured in the battery pack.

[0010] Optionally, the nitrogen assembly further comprises a manual valve for connecting the interior of the nitrogen storage cylinder and the charging port.

[0011] Optionally, the protection system further includes

[0012] The air component comprises an air reservoir, a fourth air pressure sensor arranged on the air reservoir, and an air compressor connected to the air reservoir.

[0013] The second connecting assembly is used to connect the air storage cylinder and the first connecting assembly. The second connecting assembly includes a molecular sieve and a second electromagnetic valve arranged in series.

[0014] Optionally, the second connecting assembly further comprises a filter and an air filter which are arranged in series with the molecular sieve and the second solenoid valve.

[0015] The filter, the second solenoid valve, the air filter and the molecular sieve are connected in sequence. A one-way valve is arranged between the second connecting component and the first connecting component, and between the second connecting component and the air storage cylinder.

[0016] Optionally, a one-way valve is provided between the air compressor and the air storage cylinder.

[0017] Optionally, the pressure of the safety valve is 40 kPa to 60 kPa, and the pressure of the back pressure valve is 10 kPa to 20 kPa.

[0018] Second,

[0019] The embodiment of the present invention provides a control method of a power battery protection system, which is used to control the protection system as described in the first aspect. The method comprises: when replacing the air in the cavity with nitrogen, the method comprises the following steps:

[0020] S01. Acquire a first air pressure value detected by a first air pressure sensor, an oxygen concentration value detected by an oxygen concentration sensor, and a second air pressure value detected by a second air pressure sensor.

[0021] S02. Determine whether the pressure difference between the second air pressure value and the first air pressure value exceeds the first pressure difference.

[0022] S03. When it is determined that the pressure difference between the second air pressure value and the first air pressure value exceeds the first pressure difference, the first solenoid valve is opened to allow the nitrogen in the nitrogen storage cylinder to enter the cavity.

[0023] S04. When the oxygen concentration value is less than the first concentration value, close the first solenoid valve.

[0024] Optionally, step S03 further includes: opening the first solenoid valve, and while the nitrogen in the nitrogen gas storage cylinder enters the cavity, gradually increasing the pressure of the back pressure valve until reaching a first pressure value.

[0025] Optionally, after S04, the method further includes:

[0026] S05: Determine whether the first air pressure value decreases by more than a first leakage value after a first preset time period.

[0027] S06: When it is determined that the first air pressure value drops to exceed the first leakage value, an alarm message is issued.

[0028] Optionally, the first pressure difference is 1 kPa, the first concentration value is 4%, the first pressure value is 10 kPa, the first leakage value is 50 Pa, and the first preset time length is 60 seconds.

[0029] Optionally, after the air in the cavity is replaced with nitrogen, the following steps are further included:

[0030] S11. Determine whether the first air pressure value exceeds a first preset value.

[0031] S12: When the first air pressure value does not exceed the first preset value, determine whether the difference between the second air pressure value and the first air pressure value is not less than a second pressure difference.

[0032] S13, when it is determined that the difference between the second air pressure value and the first air pressure value is not less than the second pressure difference, the first solenoid valve is opened, and nitrogen is delivered to the cavity by the nitrogen component. Otherwise, the second solenoid valve and the first solenoid valve are opened, and nitrogen is delivered to the cavity by the air component.

[0033] S14: Determine whether the first air pressure value is not less than a second preset value.

[0034] S15. When it is determined that the first air pressure value is not less than the second preset value, determine whether the oxygen concentration value is greater than a second concentration value.

[0035] S16: When it is determined that the oxygen concentration value is greater than the second concentration value, an alarm message is issued. Otherwise, all electromagnetic valves are closed to stop the nitrogen filling.

[0036] Optionally, step S13 specifically includes:

[0037] S131: when it is determined that the difference between the second air pressure value and the first air pressure value is not less than the second pressure difference, the first solenoid valve is opened, and nitrogen is delivered into the cavity by the nitrogen assembly.

[0038] S132: When it is determined that the difference between the second air pressure value and the first air pressure value is not less than the second pressure difference, determine whether the fourth air pressure value detected by the fourth air pressure sensor is less than a third preset value.

[0039] S133: When the fourth air pressure value is less than the third preset value, start the air compressor to increase the pressure until the fourth air pressure value is not less than the third preset value, and then open the second solenoid valve. Otherwise, directly open the second solenoid valve.

[0040] S134: Determine whether the difference between the second air pressure value and the first air pressure value is less than a third pressure difference.

[0041] S135. When the difference between the second air pressure value and the first air pressure value is not less than a third pressure difference, the first solenoid valve is opened to allow the air component to deliver nitrogen into the cavity.

[0042] Optionally, the first preset value is 3 kPa, the second pressure difference is 10 kPa, the second preset value is 6 kPa, the second concentration value is 4%, the third preset value is 600 kPa, and the third pressure difference is 1 kPa.

[0043] Optionally, step S16 specifically includes:

[0044] S161. When it is determined that the oxygen concentration value is greater than the second concentration value, continue to inject nitrogen into the cavity until the oxygen concentration value is no greater than the second concentration value.

[0045] S162: Determine whether the duration of continuous nitrogen injection exceeds a second preset duration, and issue an alarm message when the duration exceeds the second preset duration.

[0046] S163: When it is determined that the oxygen concentration value is not greater than the second concentration value, close all electromagnetic valves and stop filling with nitrogen.

[0047] Optionally, the second preset duration is 30 minutes.

[0048] By adopting the above technical solution, the present invention can achieve the following technical effects:

[0049] The power battery is wrapped by the battery pack, and the inert gas nitrogen is filled into the battery pack through the nitrogen assembly and the first connecting assembly. This effectively prevents the power battery from catching fire. This has great practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0051] Figure 1 is a schematic structural diagram of a power battery protection system provided by a first embodiment of the present invention;

[0052] Figure 2 is a schematic diagram of electrical connections of a power battery protection system provided by a first embodiment of the present invention;

[0053] Figure 3 is a logic diagram of ventilation of the control method provided by the second embodiment of the present invention;

[0054] Figure 4 It is a logic diagram of the pressure maintaining control method provided by the second embodiment of the present invention.

[0055] Markings in the figure: 1-air compressor, 2-fourth air pressure sensor, 3-air storage cylinder, 4-filter, 5-second solenoid valve, 6-air filter, 7-molecular sieve, 8-tee, 9-pressure reducing valve, 10-second air pressure sensor, 11-first solenoid valve, 12-third air pressure sensor, 13-nitrogen storage cylinder, 14-manual valve, 15-charging port, 16-first air pressure sensor, 17-oxygen concentration sensor, 18-battery pack, 19-power battery, 20-safety valve, 21-back pressure valve. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0057] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0058] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0059] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0061] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0062] Embodiment 1

[0063] Depend on Figure 1 , Figure 2 As shown, an embodiment of the present invention provides a power battery protection system, which includes a battery assembly, a nitrogen assembly, and a first connection assembly.

[0064] The battery assembly includes a battery pack 18 with a built-in cavity, a power battery 19 arranged in the cavity, and a first air pressure sensor 16 and an oxygen concentration sensor 17 arranged in the battery pack 18. The nitrogen assembly includes a nitrogen gas cylinder 13 provided with a charging port 15 and a third air pressure sensor 12 arranged in the nitrogen gas cylinder 13. The first connecting assembly is used to connect the nitrogen gas cylinder 13 and the cavity. The first connecting assembly includes a one-way valve and a first solenoid valve 11 arranged in series.

[0065] Specifically, the power battery pack (i.e., battery assembly) usually includes a battery cell (i.e., power battery 19), a battery management module, a battery box (i.e., battery pack 18) and corresponding accessories (cooling components, connecting cables, etc.). Currently, the outer casing can achieve IP68 protection level, that is, the sealing effect is very good.

[0066] In the prior art, early warning is often provided through battery temperature or smoke particle concentration. Judging whether there is a fire by temperature is not accurate and is prone to misjudgment, which affects customer use. Some fire accidents are ignited instantly, and it is difficult to detect an impending fire through temperature detection. Smoke particle and gas composition detection is a sign that the lithium battery has caught fire, and it cannot prevent fire in advance.

[0067] In the embodiment of the present invention, the power battery is wrapped by the battery pack 18, and the inert gas nitrogen is filled into the battery pack 18 through the nitrogen assembly and the first connecting assembly. A layer of inert gas protection is provided to isolate the power battery 19 from contact with oxygen, thereby preventing the power battery 19 from catching fire and burning. This has good practical significance.

[0068] like Figure 1 As shown, based on the above embodiment, in an optional embodiment of the present invention, the first connecting assembly further includes a pressure reducing valve 9 for connecting the nitrogen gas storage cylinder 13 and the first solenoid valve 11, and a second air pressure sensor 10 disposed between the pressure reducing valve 9 and the first solenoid valve 11. The nitrogen can be reduced to a more reasonable pressure through the pressure reducing valve 9, and then input into the cavity through the first solenoid valve 11, so as to prevent the inflation speed from being too fast and causing the problem of excessive pressure in the cavity.

[0069] like Figure 1As shown, on the basis of the above embodiment, in an optional embodiment of the present invention, the battery assembly also includes a safety valve 20 and a back pressure valve 21 configured in the battery pack 18. Optionally, the pressure of the safety valve 20 is 40kPa to 60kPa, and the pressure of the back pressure valve 21 is 10kPa to 20kPa. Preferably, the pressure of the safety valve 20 is set to 50kPa, and the pressure of the back pressure valve 21 is set to 15kPa. Through the back pressure valve 21, the gas pressure in the cavity can be well controlled. When ventilating, the pressure of the back pressure valve 21 is lowered, and as much air as possible can be discharged. After the ventilation is completed, the pressure of the back pressure valve 21 is increased to ensure that the nitrogen in the cavity has a certain pressure to prevent air from entering the cavity again. The safety valve 20 can quickly reduce the air pressure in the cavity to a safe air pressure when the pressure in the cavity is too high, so as to prevent the battery pack 18 from exploding, which has great practical significance.

[0070] like Figure 1 As shown, based on the above embodiment, in an optional embodiment of the present invention, the nitrogen assembly further includes a manual valve 14 for connecting the interior of the nitrogen gas storage cylinder 13 and the charging port 15. In other embodiments, a one-way valve can be provided at the charging port 15, which can also have the effect of closing the charging port 15.

[0071] like Figure 1 As shown, based on the above embodiment, in an optional embodiment of the present invention, the protection system further includes an air component and a second connection component.

[0072] The air component includes an air reservoir 3, a fourth air pressure sensor 2 disposed in the air reservoir 3, and an air compressor 1 connected to the air reservoir 3. The second connecting component is used to connect the air reservoir 3 and the first connecting component. The second connecting component includes a molecular sieve 7 and a second solenoid valve 5 arranged in series.

[0073] The air component is the whole vehicle air source of the bus. The whole vehicle air source of the new energy bus is from the vehicle's air compressor 1, which compresses the air and stores it in the whole vehicle air reservoir 3. The air reservoir 3 outputs the air source to the brake system, the door switch, etc. to provide the air source as a driving energy source. The vehicle instrument will collect the air pressure sensor on the air reservoir, determine the state of the stored air source, and then feedback the air source state to the air compressor 1 inverter through CAN communication. The general control strategy is to start the air compressor 1 to inflate the air reservoir when the air pressure is lower than 600kPa, and when the air pressure is greater than 800kPa, the air compressor 1 stops working.

[0074] The oxygen in the air is filtered out by molecular sieve 7, and most of the remaining gas is inert gas, especially nitrogen. Therefore, when the air pressure of the nitrogen component is insufficient, the air component can provide stable nitrogen to the battery component to prevent the battery component from catching fire.

[0075] like Figure 1 As shown, based on the above embodiment, in an optional embodiment of the present invention, the second connecting component also includes a filter 4 and an air filter 6 which are arranged in series with the molecular sieve 7 and the second solenoid valve 5. The filter 4, the second solenoid valve 5, the air filter 6 and the molecular sieve 7 are connected in sequence. A one-way valve is arranged between the second connecting component and the first connecting component, and between the second connecting component and the air reservoir 3. A one-way valve is arranged between the air compressor 1 and the air reservoir 3.

[0076] Specifically, the filter 4 can filter out moisture and oil stains in the air, the air filter 6 can filter out impurities, and the molecular sieve 7 can filter out oxygen. By connecting the filter 4, the second solenoid valve 5, the air filter 6 and the molecular sieve 7 in sequence, the service life of each component can be guaranteed. The one-way valve can prevent the gas in the air storage cylinder 3 from flowing back to the air compressor 1 when the air compressor 1 is not working.

[0077] like Figure 1 As shown, the first connecting component is connected with a pressure reducing valve 9, a second air pressure sensor 10, a first solenoid valve 11, and a one-way valve in sequence. The second connecting component is connected with a one-way valve, a filter 4, a second solenoid valve 5, an air filter 6, a molecular sieve 7, and a one-way valve in sequence. The first connecting component, the second connecting component, and the nitrogen component are connected through a three-way valve 8.

[0078] When the first embodiment of the present invention is installed on a bus, the vehicle instrument collects the pressure of the vehicle air storage cylinder 3 through the fourth air pressure sensor 2, and then sends it to the controller through the CAN network of the vehicle. The controller collects the pressure of the nitrogen storage cylinder 13 through the third air pressure sensor 12, the intake pressure of the power battery pack through the second air pressure sensor 10, the gas pressure of the power battery pack through the first air pressure sensor 16, and the oxygen concentration in the power battery pack through the oxygen concentration sensor 17. The second battery valve is controlled by controlling the second solenoid valve 5 relay, and the first solenoid valve 11 is controlled by controlling the first solenoid valve 11 relay. The operator inputs the control requirements through the human-machine interface and sets the corresponding control parameters of the system. The controller feeds back the air pressure status, oxygen concentration status, and fault information of each collection point to the human-machine interface display. The controller sends the demand for the gas source of the whole vehicle to the air compressor inverter through the vehicle CAN network. The air compressor inverter intelligently turns on the air compressor according to the state of the vehicle to ensure the stability of the gas source of the whole vehicle.

[0079] Embodiment 2

[0080] like Figure 3 and Figure 4As shown, an embodiment of the present invention provides a control method for a power battery protection system, which is used to control the protection system as described in the first aspect. The method comprises: when replacing the air in the cavity with nitrogen, the method comprises the following steps:

[0081] S01, obtaining a first air pressure value P1 detected by a first air pressure sensor, an oxygen concentration value detected by an oxygen concentration sensor, and a second air pressure value P2 detected by a second air pressure sensor.

[0082] S02. Determine whether the pressure difference between the second air pressure value and the first air pressure value exceeds the first pressure difference.

[0083] S03. When it is determined that the pressure difference between the second air pressure value and the first air pressure value exceeds the first pressure difference, the first solenoid valve is opened to allow the nitrogen in the nitrogen storage cylinder to enter the cavity.

[0084] On the basis of the above embodiment, in an optional embodiment of the present invention, step S03 further includes: opening the first solenoid valve, while the nitrogen in the nitrogen gas storage cylinder enters the cavity, gradually increasing the pressure of the back pressure valve until reaching a first pressure value.

[0085] S04. When the oxygen concentration value is less than the first concentration value, close the first solenoid valve.

[0086] During vehicle offline commissioning and regular vehicle maintenance, the power battery pack needs to be replaced with nitrogen. Fill the nitrogen cylinder with nitrogen through its filling port, then start the manual replacement mode through the human-machine interface, open the first solenoid valve, and manually adjust the pressure of the back pressure valve to gradually replace the air in the power battery pack with nitrogen. Determine whether the replacement is complete by judging the oxygen concentration in the power battery pack, and determine whether the power battery pack is well sealed by judging the gas pressure decay rate of the power battery pack.

[0087] like Figure 3 As shown, based on the above embodiment, in an optional embodiment of the present invention, after step S04, the following further includes:

[0088] S05: Determine whether the first air pressure value decreases by more than a first leakage value after a first preset time period.

[0089] S06: When it is determined that the first air pressure value drops to exceed the first leakage value, an alarm message is issued.

[0090] Optionally, the first pressure difference is 1 kPa, the first concentration value is 4%, the first pressure value is 10 kPa, the first leakage value is 50 Pa, and the first preset time length is 60 seconds.

[0091] The manual replacement mode is the mode used for vehicle offline debugging and regular vehicle maintenance. The operator first fills the nitrogen gas cylinder with nitrogen, that is, the third air pressure value P3 of the third air pressure sensor is filled to 800kPa. Then select the replacement mode on the human-machine interface to replace the power battery pack with nitrogen. After turning on the replacement, manually adjust the back pressure valve pressure on the power battery pack during the replacement process, gradually increase it, and slowly discharge the oxygen in the power battery pack. When the oxygen concentration in the power battery pack is less than 4%, it is considered that the oxygen discharge is basically completed, and then the pressure is maintained for 60S to ensure that the power battery pack is sealed. After the replacement is completed, the back pressure valve pressure is set to a relatively high pressure of 10kPa.

[0092] When the vehicle is powered off and parked, the nitrogen in the nitrogen tank can be used to maintain the nitrogen demand of the power battery pack. During the factory commissioning and regular vehicle maintenance, the nitrogen tank is filled with nitrogen through the filling port to ensure the nitrogen supply to the power battery pack.

[0093] A safety pressure relief valve (50kPa) is installed on the power battery pack. When a system failure occurs and the pressure limit in the power battery pack is abnormally high, the pressure is automatically released to ensure the safety of the air pressure in the power battery pack. A back pressure valve (15kPa) is installed. During the air replacement process, the pressure value of the back pressure valve can be adjusted to discharge as much air as possible from the power battery pack.

[0094] like Figure 4 As shown, based on the above embodiment, in an optional embodiment of the present invention, after the air in the cavity is replaced with nitrogen, the following steps are also included:

[0095] S11. Determine whether the first air pressure value exceeds a first preset value.

[0096] Specifically, after the power battery pack completes nitrogen replacement, the back pressure valve pressure is set to 10kPa. When the power battery pack pressure P1≤3kPa, nitrogen needs to be injected into the power battery pack to ensure the amount of nitrogen in the power battery pack. The following control step is entered by judging the pressure difference between the second air pressure value (i.e., intake pressure) P2 and the first air pressure value P1 of the power battery pack.

[0097] S12: When the first air pressure value does not exceed the first preset value, determine whether the difference between the second air pressure value and the first air pressure value is not less than the second pressure difference.

[0098] S13, when it is determined that the difference between the second air pressure value and the first air pressure value is not less than the second pressure difference, the first solenoid valve is opened, and the nitrogen component is used to deliver nitrogen into the cavity. Otherwise, the second solenoid valve and the first solenoid valve are opened, and the air component is used to deliver nitrogen into the cavity. Step S13 specifically includes S131 to S135:

[0099] S131: when it is determined that the difference between the second air pressure value and the first air pressure value is not less than the second pressure difference, the first solenoid valve is opened, and nitrogen is delivered into the cavity by the nitrogen assembly.

[0100] S132: When it is determined that the difference between the second air pressure value and the first air pressure value is not less than the second pressure difference, determine whether the fourth air pressure value P4 detected by the fourth air pressure sensor is less than a third preset value.

[0101] S133: When the fourth air pressure value is less than the third preset value, start the air compressor to increase the pressure until the fourth air pressure value is not less than the third preset value, and then open the second solenoid valve. Otherwise, directly open the second solenoid valve.

[0102] S134: Determine whether the difference between the second air pressure value and the first air pressure value is less than the third pressure difference.

[0103] S135. When the difference between the second air pressure value and the first air pressure value is not less than the third pressure difference, the first solenoid valve is opened, and nitrogen is delivered into the cavity by the air component.

[0104] It is understandable that when P2-P1≥10kPa, only the first battery valve is opened to inject nitrogen into the power battery pack through the nitrogen gas cylinder. When P2-P1<10kPa, first determine the vehicle's air source pressure P4. If the vehicle's air source pressure is insufficient, send the air source demand to the vehicle's air compressor inverter, and the compressor inverter controls the compressor to provide air source to the vehicle. When the vehicle's air source pressure P4≥600kPa, open the second solenoid valve, and the vehicle's air source passes through the filter, air filter, and molecular plug to filter out moisture, oil stains, oxygen and other substances. The remaining nitrogen is injected into the nitrogen gas cylinder. When the intake pressure is greater than the power battery pack pressure by 1kPa, open the first solenoid valve to inject nitrogen into the power battery pack.

[0105] S14: Determine whether the first air pressure value is not less than a second preset value.

[0106] S15. When it is determined that the first air pressure value is not less than the second preset value, determine whether the oxygen concentration value is greater than the second concentration value.

[0107] When the power battery pack pressure P1 ≥ 6kPa, it is judged that the oxygen concentration is less than or equal to 4%, the solenoid valve is closed to stop injecting nitrogen. If the oxygen concentration is greater than 4%, the nitrogen injection is continued.

[0108] S16: When it is determined that the oxygen concentration value is greater than the second concentration value, an alarm message is issued. Otherwise, all solenoid valves are closed to stop filling with nitrogen. Step S16 specifically includes S161 to S163:

[0109] S161. When it is determined that the oxygen concentration value is greater than the second concentration value, continue to inject nitrogen into the cavity until the oxygen concentration value is no greater than the second concentration value.

[0110] S162, determining whether the duration of continuous nitrogen injection exceeds a second preset duration, and issuing an alarm message when the duration exceeds the second preset duration. Optionally, the second preset duration is 1 to 60 minutes. Preferably, the second preset duration is 30 minutes.

[0111] S163. When it is determined that the oxygen concentration value is not greater than the second concentration value, all solenoid valves are closed to stop filling with nitrogen.

[0112] When the gas pressure in the power battery pack is greater than the back pressure valve set pressure of 10kPa, it will automatically enter nitrogen replacement. This process will add a 30-minute time limit. If it exceeds 30 minutes, it is judged that the system has a fault and there may be a leak in the system.

[0113] Specifically, when the vehicle is powered on and operated, nitrogen is prepared using the vehicle's gas source to maintain the nitrogen balance requirement of the power battery pack. The air in the vehicle's air storage cylinder passes through the filter to remove moisture and oil stains in the air, then passes through the second solenoid valve, and then passes through the air filter to filter out impurities, and then is sent to the molecular sieve to filter out oxygen, and then passes through the pressure reducing valve and is injected into the battery pack through the first solenoid valve.

[0114] When the gas supply of the whole vehicle is relatively sufficient, the second solenoid valve can be opened to prepare nitrogen in advance and store it in the nitrogen storage cylinder.

[0115] Optionally, the first preset value is 2kPa to 4kPa, the second pressure difference is 9kPa to 11kPa, the second preset value is 5kPa to 7kPa, the second concentration value is 3% to 5%, the third preset value is 500kPa to 700kPa, and the third pressure difference is 0.9kPa to 1.1kPa. Preferably, the first preset value is 3kPa, the second pressure difference is 10kPa, the second preset value is 6kPa, the second concentration value is 4%, the third preset value is 600kPa, and the third pressure difference is 1kPa.

[0116] The technical solution of the present invention, starting from isolating oxygen among the three elements of combustion, uses inert gas nitrogen to provide a protective layer for the power battery, effectively solving safety accidents such as power battery fire and explosion caused by thermal runaway of the power battery. It is conducive to the application and promotion of new energy buses and has high safety application benefits for new energy buses.

[0117] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A control method for a power battery protection system, characterized in that: The power battery protection system comprises: A battery assembly, comprising a battery pack (18) having a built-in cavity, a power battery (19) disposed in the cavity, and a first air pressure sensor (16) and an oxygen concentration sensor (17) disposed in the battery pack (18); A nitrogen assembly comprises a nitrogen gas storage cylinder (13) provided with a charging port (15) and a third air pressure sensor (12) arranged on the nitrogen gas storage cylinder (13); A first connecting assembly, used to connect the nitrogen gas storage cylinder (13) and the cavity; the first connecting assembly comprises a one-way valve and a first solenoid valve (11) arranged in series; The first connecting assembly further comprises a pressure reducing valve (9) for connecting the nitrogen gas storage cylinder (13) and the first solenoid valve (11), and a second air pressure sensor (10) arranged between the pressure reducing valve (9) and the first solenoid valve (11); The battery assembly further comprises a safety valve (20) and a back pressure valve (21) arranged on the battery pack (18); The nitrogen assembly further comprises a manual valve (14) for connecting the interior of the nitrogen storage cylinder (13) and the charging port (15); The protection system also includes An air component comprises an air storage cylinder (3), a fourth air pressure sensor (2) arranged on the air storage cylinder (3); and an air compressor (1) connected to the air storage cylinder (3); A second connecting assembly, used to connect the air storage cylinder (3) and the first connecting assembly; the second connecting assembly comprises a molecular sieve (7) and a second solenoid valve (5) arranged in series; The control method comprises: When replacing the air in the chamber with nitrogen: Acquire a first air pressure value detected by a first air pressure sensor, an oxygen concentration value detected by an oxygen concentration sensor, and a second air pressure value detected by a second air pressure sensor; determining whether a pressure difference between the second air pressure value and the first air pressure value exceeds a first pressure difference; When it is determined that the pressure difference between the second air pressure value and the first air pressure value exceeds the first pressure difference, opening the first solenoid valve to allow the nitrogen in the nitrogen storage cylinder to enter the cavity; When the oxygen concentration value is less than a first concentration value, closing the first solenoid valve; After replacing the air in the chamber with nitrogen, it also includes: Determining whether the first air pressure value exceeds a first preset value; When the first air pressure value does not exceed the first preset value, determining whether the difference between the second air pressure value and the first air pressure value is not less than a second pressure difference; When it is determined that the difference between the second air pressure value and the first air pressure value is not less than the second pressure difference, the first solenoid valve is opened, and the nitrogen component is used to deliver nitrogen into the cavity; otherwise, the second solenoid valve and the first solenoid valve are opened, and the air component is used to deliver nitrogen into the cavity; Determining whether the first air pressure value is not less than a second preset value; When it is determined that the first air pressure value is not less than the second preset value, determining whether the oxygen concentration value is greater than a second concentration value; When it is determined that the oxygen concentration value is greater than the second concentration value, an alarm message is issued; otherwise, all electromagnetic valves are closed to stop filling with nitrogen.

2. A control method for a power battery protection system according to claim 1, characterized in that: The second connection assembly further comprises a filter (4) and an air filter (6) which are arranged in series with the molecular sieve (7) and the second solenoid valve (5); The filter (4), the second solenoid valve (5), the air filter (6) and the molecular sieve (7) are connected in sequence; a one-way valve is provided between the second connecting component and the first connecting component, and between the second connecting component and the air storage cylinder (3); A one-way valve is provided between the air compressor (1) and the air storage cylinder (3).

3. The control method of a power battery protection system according to claim 1, characterized in that: The pressure of the safety valve (20) is 40 kPa to 60 kPa, and the pressure of the back pressure valve (21) is 10 kPa to 20 kPa.

4. The control method of a power battery protection system according to claim 1, characterized in that: The first solenoid valve is opened, and the nitrogen in the nitrogen gas storage cylinder enters the cavity, while the pressure of the back pressure valve is gradually increased until the first pressure value is reached; When the oxygen concentration value is less than a first preset value, after closing the first solenoid valve, the method further includes: Determine whether the first air pressure value decreases by more than a first leakage value after a first preset time period; When it is determined that the first air pressure value drops to more than the first leakage value, an alarm message is issued; The first pressure difference is 1 kPa, the first concentration value is 4%, the first pressure value is 10 kPa, the first leakage value is 50 Pa, and the first preset time length is 60 seconds.

5. The control method of a power battery protection system according to claim 1, characterized in that: When it is determined that the difference between the second air pressure value and the first air pressure value is not less than a second pressure difference, the first solenoid valve is opened, and nitrogen is delivered into the cavity by the nitrogen component; Otherwise, the second solenoid valve and the first solenoid valve are opened, and nitrogen is delivered into the cavity by the air component, specifically including: When it is determined that the difference between the second air pressure value and the first air pressure value is not less than the second pressure difference, determining whether the fourth air pressure value detected by the fourth air pressure sensor is less than a third preset value; When the fourth air pressure value is less than the third preset value, the air compressor is started to pressurize the air until the fourth air pressure value is not less than the third preset value, and the second solenoid valve is opened; otherwise, the second solenoid valve is directly opened; determining whether a difference between the second air pressure value and the first air pressure value is less than a third pressure difference; When the difference between the second air pressure value and the first air pressure value is not less than a third pressure difference, the first solenoid valve is opened, and nitrogen is delivered into the cavity by the air component; The first preset value is 3 kPa, the second pressure difference is 10 kPa, the second preset value is 6 kPa, the second concentration value is 4%, the third preset value is 600 kPa, and the third pressure difference is 1 kPa.

6. The control method of a power battery protection system according to claim 1, characterized in that: When it is determined that the oxygen concentration value is greater than the second concentration value, an alarm message is issued, specifically: When it is determined that the oxygen concentration value is greater than the second concentration value, continuously injecting nitrogen into the cavity until the oxygen concentration value is no greater than the second concentration value; Determining whether the duration of continuous nitrogen injection exceeds a second preset duration, and issuing an alarm message when the duration exceeds the second preset duration; The second preset duration is 30 minutes.

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