CN113103872A

CN113103872A - Protection system of power battery and control method thereof

Info

Publication number: CN113103872A
Application number: CN202110466314.0A
Authority: CN
Inventors: 肖红千; 林剑健; 康燕语; 陈子元; 卢启水; 王世利
Original assignee: Xiamen Golden Dragon Bus Co Ltd
Current assignee: Xiamen Golden Dragon Bus Co Ltd
Priority date: 2021-04-28
Filing date: 2021-04-28
Publication date: 2021-07-13

Abstract

The invention provides a protection system of a power battery and a control method thereof, and relates to the technical field of power battery protection. Wherein the protection system comprises a battery assembly, a nitrogen assembly, and a first connection assembly. The battery pack comprises 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 component comprises a nitrogen gas storage cylinder provided with an inflation inlet and a third air pressure sensor arranged on the nitrogen gas storage cylinder. The first connecting component is used for communicating the nitrogen gas storage cylinder and the cavity. The first connecting assembly comprises a check valve and a first solenoid valve which are arranged in series. The power battery is wrapped by the battery pack, and inert gas nitrogen is filled into the battery pack through the nitrogen component and the first connecting component. Thereby the power battery of effectual house catches fire. Has good practical significance.

Description

Protection system of power battery and control method thereof

Technical Field

The invention relates to the technical field of power battery protection, in particular to a protection system of a power battery and a control method thereof.

Background

With the development and popularization of new energy automobiles, the safety requirements of the new energy automobiles are continuously improved. The safety of the power battery, which is a key part of the new energy automobile, is particularly concerned by users. The power battery of the electric motor coach adopts a lithium ion battery with the advantages of high energy density, energy storage and release, long service life and the like. The power battery fire accident is a major accident of the new energy passenger car, and the popularization and the use of the new energy passenger car are greatly influenced.

In the practical application process, the safety of the lithium ion battery still has many problems, the events of spontaneous combustion and ignition of new energy vehicles are frequent, and each accident is paid social attention. Aiming at the safety problem of the lithium ion battery, relevant departments and enterprises have invested a great deal of manpower and material resources to carry out research and test, and great breakthrough is made in the aspect of improving the safety of the lithium ion power battery. Nevertheless, lithium ion battery is still not absolute safety, and the potential safety hazard of [ electric ] motor coach power battery still exists. How to prevent the power battery fire from happening becomes a technical problem which needs to be solved urgently.

Disclosure of Invention

The invention provides a power battery protection system and a control method thereof, aiming at solving the problem that the prior art can not effectively prevent the power battery from being on fire.

The first aspect,

In order to solve the technical problem, the invention provides a protection system of a power battery, which comprises a battery assembly, a nitrogen assembly and a first connecting assembly.

The battery pack comprises 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 which are arranged in the battery pack. The nitrogen component comprises a nitrogen gas storage cylinder provided with an inflation inlet and a third air pressure sensor arranged on the nitrogen gas storage cylinder. The first connecting assembly is used for communicating the nitrogen gas storage cylinder with the cavity. The first connecting assembly comprises a one-way valve and a first electromagnetic valve which are arranged in series.

Optionally, the first connection assembly further comprises a pressure reducing valve for communicating the nitrogen gas cylinder with the first solenoid valve, and a second air pressure sensor disposed between the pressure reducing valve and the first solenoid valve.

Optionally, the battery assembly further comprises a safety valve and a back pressure valve disposed in the battery pack.

Optionally, the nitrogen assembly further comprises a manual valve for communicating the inside of the nitrogen gas cylinder with the inflation port.

Optionally, the protection system further comprises

And the air assembly comprises an air storage cylinder and a fourth air pressure sensor arranged on the air storage cylinder. And an air compressor communicated with the air storage cylinder.

And the second connecting component is used for communicating the air cylinder with the first connecting component. The second connecting assembly comprises a molecular sieve and a second electromagnetic valve which are arranged in series.

Optionally, the second connection assembly further comprises a filter and an air cleaner disposed in series with the molecular sieve and the second solenoid valve.

The filter, the second electromagnetic valve, the air filter and the molecular sieve are connected in sequence. The second coupling assembling with between the first coupling assembling, and the second coupling assembling with all be provided with the check valve between the air receiver.

Optionally, a one-way valve is provided between the air compressor and the air reservoir.

Optionally, the pressure of the relief valve is 40 to 60kPa and the pressure of the back pressure valve is 10 to 20 kPa.

The second aspect,

An embodiment of the present invention provides a control method for a power battery protection system, so as to control the protection system according to the first aspect. It includes: when the air in the cavity is replaced by the nitrogen, the method comprises the following steps:

s01, acquiring a first air pressure value detected by the first air pressure sensor, an oxygen concentration value detected by the oxygen concentration sensor and a second air pressure value detected by the second air pressure sensor.

And S02, judging whether the pressure difference between the second air pressure value and the first air pressure value exceeds a first pressure difference.

And S03, when the pressure difference between the second air pressure value and the first air pressure value is judged to exceed the first pressure difference, opening a first electromagnetic valve to enable nitrogen in the nitrogen gas storage cylinder to enter the cavity.

S04, when the oxygen concentration value is smaller than the first concentration value, closing the first electromagnetic valve.

Optionally, step S03 further includes: and opening the first electromagnetic valve, and gradually increasing the pressure of the backpressure valve until the pressure reaches a first pressure value while nitrogen in the nitrogen gas storage cylinder enters the cavity.

Optionally, after S04, the method further includes:

s05, judging whether the first air pressure value is reduced to exceed the first leakage value after the first preset time.

And S06, when the first air pressure value is judged to be reduced and exceeds the first leakage value, sending alarm information.

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

Optionally, after replacing the air in the cavity with nitrogen, the method further comprises the following steps:

and S11, judging whether the first air pressure value exceeds a first preset value.

And S12, when the first air pressure value is not more than the first preset value, judging whether the difference value between the second air pressure value and the first air pressure value is not less than a second pressure difference.

And S13, opening the first electromagnetic valve when the difference value between the second air pressure value and the first air pressure value is judged to be not less than the second pressure difference, and conveying nitrogen to the cavity by the nitrogen component. Otherwise, opening the second electromagnetic valve and the first electromagnetic valve, and conveying nitrogen to the cavity by the air assembly.

And S14, judging whether the first air pressure value is not less than a second preset value.

S15, when the first air pressure value is judged to be not less than the second preset value, judging whether the oxygen concentration value is greater than a second concentration value.

And S16, when the oxygen concentration value is judged to be larger than the second concentration value, sending out alarm information. Otherwise, all the electromagnetic valves are closed to stop filling the nitrogen.

Optionally, step S13 specifically includes:

s131, when the difference value between the second air pressure value and the first air pressure value is judged to be not less than the second pressure difference, the first electromagnetic valve is opened, and nitrogen is conveyed into the cavity from the nitrogen component

S132, when the difference value between the second air pressure value and the first air pressure value is not smaller than the second pressure difference, whether a fourth air pressure value detected by a fourth air pressure sensor is smaller than a third preset value is judged.

And S133, when the fourth air pressure value is smaller than a third preset value, starting the air compressor to pressurize, and opening the second electromagnetic valve until the fourth air pressure value is not smaller than the third preset value. Otherwise, the second electromagnetic valve is directly opened.

S134, judging whether the difference value of the second air pressure value and the first air pressure value is smaller than a third pressure difference.

And S135, when the difference value between the second air pressure value and the first air pressure value is not less than a third pressure difference, opening a first electromagnetic valve, and conveying nitrogen to the cavity by the air assembly.

Optionally, 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 1 kPa.

Optionally, step S16 specifically includes:

s161, when the oxygen concentration value is judged to be larger than the second concentration value, continuously injecting nitrogen into the cavity until the oxygen concentration value is not larger than the second concentration value.

And S162, judging whether the duration of continuously injecting the nitrogen gas exceeds a second preset duration, and sending out alarm information when the duration exceeds the second preset duration.

S163, when the oxygen concentration value is judged not to be larger than the second concentration value, closing all the electromagnetic valves and stopping filling the nitrogen gas

Optionally, the second preset time period is 30 minutes.

By adopting the technical scheme, the invention can obtain the following technical effects:

the power battery is wrapped by the battery pack, and inert gas nitrogen is filled into the battery pack through the nitrogen component and the first connecting component. Thereby effectively preventing the power battery from being ignited. Has good practical significance.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

Fig. 1 is a schematic structural diagram of a protection system for a power battery according to a first embodiment of the present invention;

fig. 2 is an electrical connection schematic diagram of a protection system for a power battery provided in a first embodiment of the present invention;

FIG. 3 is a logic diagram of ventilation in accordance with a second embodiment of the present invention;

fig. 4 is a logic diagram of the pressure holding in the control method according to the second embodiment of the present invention.

The labels in the figure are: 1-air compressor, 2-fourth air pressure sensor, 3-air cylinder, 4-filter, 5-second electromagnetic valve, 6-air filter, 7-molecular sieve, 8-tee joint, 9-pressure reducing valve, 10-second air pressure sensor, 11-first electromagnetic valve, 12-third air pressure sensor, 13-nitrogen gas cylinder, 14-manual valve, 15-inflation inlet, 16-first air pressure sensor, 17-oxygen concentration sensor, 18-battery pack, 19-power battery, 20-safety valve and 21-back pressure valve.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the equipment or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

The invention is described in further detail below with reference to the following detailed description and accompanying drawings:

the first embodiment,

As shown in fig. 1 and fig. 2, the embodiment of the invention provides a protection system for a power battery, which comprises a battery assembly, a nitrogen assembly, and a first connecting assembly.

The battery assembly includes a battery pack 18 having a cavity therein, a power battery 19 disposed in the cavity, and a first pressure sensor 16 and an oxygen concentration sensor 17 disposed in the battery pack 18. The nitrogen assembly includes a nitrogen gas cylinder 13 provided with a gas filling port 15 and a third pressure sensor 12 disposed at the nitrogen gas cylinder 13. The first connecting component is used for communicating the nitrogen gas storage cylinder 13 and the cavity. The first connection assembly comprises a non-return valve and a first solenoid valve 11 arranged in series.

Specifically, a power battery pack (i.e., a battery assembly) generally includes a battery cell (i.e., a power battery 19), a battery management module, a battery box (i.e., a battery pack 18), and corresponding accessories (a cooling component, a connection cable, etc.), and at present, the casing can achieve the IP68 protection level, i.e., the sealing effect is good.

In the prior art, early warning is often performed by the temperature of the battery or the concentration of smoke particles. Whether a fire disaster exists or not is judged through the temperature, the accuracy is not high, misjudgment is easy, and the use of a client is influenced. Some fire accidents are instantaneous ignition, and the impending fire is difficult to detect through temperature detection. Smoke particle and gas composition detection is a sign that a lithium battery has been on fire and cannot prevent fire in advance.

In the embodiment of the 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 component and the first connecting component. An inert gas protective layer is provided to isolate the power cells 19 from oxygen, thereby preventing the power cells 19 from igniting. Has good practical significance.

As shown in fig. 1, on the basis of the above embodiment, in an alternative embodiment of the present invention, the first connection assembly further includes a pressure reducing valve 9 for communicating the nitrogen gas cylinder 13 with 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. Can drop to a comparatively reasonable pressure with nitrogen gas through relief pressure valve 9, the rethread first solenoid valve 11 is inputed to the cavity in, prevents that gas filled speed is too fast, arouses the too big problem of cavity internal pressure.

As shown in fig. 1, in an alternative embodiment of the present invention, the battery pack further includes a safety valve 20 and a back pressure valve 21 disposed in the battery pack 18. Alternatively, the pressure of the relief valve 20 is 40kPa to 60kPa, and the pressure of the backpressure valve 21 is 10kPa to 20 kPa. Preferably, the pressure of the relief valve 20 is set to 50kPa and the pressure of the back pressure valve 21 is set to 15 kPa. The back pressure valve 21 can control the gas pressure in the cavity well, and when in ventilation, the pressure of the back pressure valve 21 is adjusted to be low, and air can be exhausted as much as possible. After the air exchange is finished, the pressure of the backpressure valve 21 is increased, so that the nitrogen in the cavity can be ensured to have certain pressure, and air is prevented from entering the cavity again. The safety valve 20 can rapidly 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, and has good practical significance.

As shown in fig. 1, in an alternative embodiment of the present invention, based on the above embodiment, the nitrogen gas assembly further includes a manual valve 14 for communicating the inside of the nitrogen gas cylinder 13 with the gas charging port 15. In other embodiments, a one-way valve may be provided at the inflation port 15, which also has the effect of closing the inflation port 15.

As shown in fig. 1, on the basis of the above embodiment, in an alternative embodiment of the present invention, the protection system further includes an air component and a second connecting component.

The air assembly comprises an air reservoir 3 and a fourth air pressure sensor 2 arranged on the air reservoir 3. And an air compressor 1 communicated with the air reservoir 3. The second connecting assembly is used for communicating the air cylinder 3 with the first connecting assembly. The second connection assembly comprises a molecular sieve 7 and a second solenoid valve 5 arranged in series.

The air assembly is a whole bus air source of the bus. The air compressor 1 of the vehicle compresses air and stores the air in the air storage cylinder 3 of the whole vehicle, and the air storage cylinder 3 outputs an air source to a brake system, a vehicle door switch and the like to provide the air source as a driving energy source. The vehicle instrument CAN gather the baroceptor on the gas receiver, judges the air supply state of storing, and the rethread CAN communication feeds back the air supply state to air compressor 1 converter, and general control strategy is to open air compressor 1 when atmospheric pressure is low 600kPa and aerify for the gas receiver, and when atmospheric pressure was greater than 800kPa, air compressor 1 stopped working.

The oxygen in the air is filtered out by the molecular sieve 7, and the rest gas is mostly inert gas, especially the proportion of nitrogen is more. Therefore, when the air pressure of the nitrogen component is insufficient, stable nitrogen is provided for the battery component through the air component. Preventing the battery pack from being ignited.

In an alternative embodiment of the present invention, as shown in fig. 1, based on the above embodiment, the second connecting assembly further comprises a filter 4 and an air cleaner 6, which are arranged in series with the molecular sieve 7 and the second solenoid valve 5. The filter 4, the second electromagnetic valve 5, the air filter 6 and the molecular sieve 7 are connected in sequence. And one-way valves are arranged between the second connecting component and the first connecting component and between the second connecting component and the air cylinder 3. A one-way valve is arranged between the air compressor 1 and the air storage cylinder 3.

Specifically, the filter 4 can filter out moisture and oil stain in the air, the air filter 6 can filter out impurities, and the molecular sieve 7 can filter out oxygen. The filter 4, the second electromagnetic valve 5, the air filter 6 and the molecular sieve 7 are connected in sequence, so that the service life of each part can be ensured. The check valve can prevent the gas in the air cylinder 3 from flowing back to the air compressor 1 when the air compressor 1 is not in operation.

As shown in fig. 1, the first connection assembly is connected with a pressure reducing valve 9, a second air pressure sensor 10, a first electromagnetic valve 11 and a one-way valve in sequence. The second connecting component is sequentially connected with a one-way valve, a filter 4, a second electromagnetic valve 5, an air filter 6, a molecular sieve 7 and the one-way valve. The first connecting assembly, the second connecting assembly and the nitrogen assembly are communicated through a three-way 8-valve.

When the first embodiment of the invention is installed on a bus, a vehicle instrument acquires the pressure of the air storage cylinder 3 of the whole bus through the fourth air pressure sensor 2 and then sends the pressure to the controller through the CAN network of the whole bus. The controller gathers the pressure of nitrogen gas receiver 13 through third baroceptor 12, gathers the inlet pressure of power battery package through second baroceptor 10, gathers the gas pressure of power battery package through first baroceptor 16, gathers the oxygen concentration of power battery package the inside through oxygen concentration sensor 17, controls opening and closing of second battery valve through controlling second solenoid valve 5 relay, controls opening and closing of first solenoid valve 11 through controlling first solenoid valve 11 relay. And an operator inputs control requirements through a human-computer interface and sets corresponding control parameters of the system. And the controller feeds back the air pressure state, the oxygen concentration state and the fault information of each acquisition point to a human-computer interface for display. The controller sends the requirement of the whole vehicle air source to the air compressor frequency converter through the whole vehicle CAN network, and the air compressor frequency converter intelligently opens the air compressor according to the state of the vehicle to ensure the stability of the whole vehicle air source.

Example II,

As shown in fig. 3 and 4, an embodiment of the present invention provides a control method for a power battery protection system, so as to control the protection system according to the first aspect. It includes: when the air in the cavity is replaced by the nitrogen, the method comprises the following steps:

s01, acquiring a first air pressure value P1 detected by the first air pressure sensor, an oxygen concentration value detected by the oxygen concentration sensor and a second air pressure value P2 detected by the second air pressure sensor.

And S02, judging whether the pressure difference between the second air pressure value and the first air pressure value exceeds the first pressure difference.

And S03, when the pressure difference between the second air pressure value and the first air pressure value exceeds the first pressure difference, opening the first electromagnetic valve to enable the nitrogen in the nitrogen air storage cylinder to enter the cavity.

On the basis of the foregoing embodiment, in an optional embodiment of the present invention, step S03 further includes: and opening the first electromagnetic valve, and gradually increasing the pressure of the backpressure valve until the pressure reaches a first pressure value while nitrogen in the nitrogen gas storage cylinder enters the cavity.

S04, when the oxygen concentration value is less than the first concentration value, the first electromagnetic valve is closed.

During vehicle offline debugging and vehicle regular maintenance, need carry out the nitrogen gas replacement with the power battery package, fill the nitrogen gas receiver with nitrogen gas through the filler of nitrogen gas receiver, then open manual replacement mode through human-computer interface, open first solenoid valve, the pressure of manual regulation back pressure valve gradually replaces the air of power battery package into nitrogen gas. Whether replacement is completed or not is determined by judging the concentration of oxygen in the power battery pack, and whether the sealing performance of the power battery pack is good or not is determined by judging the gas pressure attenuation speed of the power battery pack.

As shown in fig. 3, on the basis of the foregoing embodiment, in an alternative embodiment of the present invention, after step S04, the method further includes:

The manual replacement mode is used when the vehicle is debugged off line and the vehicle is periodically maintained. The operator first fills the nitrogen gas cylinder with nitrogen gas, i.e., the third pressure value P3 of the third pressure sensor is filled to 800 kPa. And then, performing nitrogen replacement on the power battery pack by selecting a replacement mode on a human-computer interface. After the replacement is started, the pressure of a backpressure valve on the power battery pack is manually adjusted in the replacement process, the backpressure valve is gradually increased, and oxygen in the power battery pack is slowly discharged. And when the oxygen concentration in the power battery pack is less than 4%, the discharge of the oxygen is considered to be basically finished, and the pressure maintaining is carried out 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 10 kPa.

When the vehicle is powered off and stops, the nitrogen of the nitrogen gas storage cylinder can be used for maintaining the nitrogen requirement of the power battery pack. When the vehicle leaves factory and is debugged and the vehicle is maintained regularly, the nitrogen gas storage cylinder is filled with nitrogen gas through the filling port, so that the nitrogen gas supply quantity of the power battery pack is ensured.

The power battery pack is provided with 1 safety relief valve (50kPa), and when the system fails and the pressure limit in the power battery pack is abnormal and overlarge, the pressure is automatically relieved, so that the air pressure safety of the power battery pack is ensured. 1 backpressure valve (15kPa) is installed, and in the air replacement process, the pressure value of backpressure valve is adjusted to discharge the air in the power battery pack as much as possible.

As shown in fig. 4, on the basis of the above embodiment, in an alternative embodiment of the present invention, after replacing the air in the cavity with the nitrogen gas, the method further includes the following steps:

s11, judging whether the first air pressure value exceeds a first preset value.

Specifically, after the power battery pack completes the nitrogen replacement, the backpressure valve pressure is set to 10 kPa. When the pressure P1 of the power battery pack is less than or equal to 3kPa, nitrogen needs to be injected into the power battery pack to ensure the nitrogen amount 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 air pressure) P2 and the first air pressure value P1 of the power battery pack.

And S12, when the first air pressure value is not more than the first preset value, judging whether the difference value between the second air pressure value and the first air pressure value is not less than the second pressure difference.

And S13, opening the first electromagnetic valve when the difference value between the second air pressure value and the first air pressure value is judged to be not less than the second pressure difference, and conveying nitrogen to the cavity by the nitrogen component. Otherwise, the second electromagnetic valve and the first electromagnetic valve are opened, and the air assembly conveys nitrogen to the cavity. Step S13 specifically includes S131 to S135:

s131, when the difference value between the second air pressure value and the first air pressure value is judged to be not less than the second pressure difference, the first electromagnetic valve is opened, and the nitrogen component conveys nitrogen to the cavity

And S132, when the difference value between the second air pressure value and the first air pressure value is not smaller than the second pressure difference, judging whether a fourth air pressure value P4 detected by the fourth air pressure sensor is smaller than a third preset value.

And S133, when the fourth air pressure value is smaller than the third preset value, starting the air compressor to pressurize, and opening the second electromagnetic valve until the fourth air pressure value is not smaller than the third preset value. Otherwise, the second electromagnetic valve is directly opened.

And S135, when the difference value between the second air pressure value and the first air pressure value is not less than the third pressure difference, opening the first electromagnetic valve, and conveying nitrogen to the cavity by the air assembly.

It can be understood that when the pressure is greater than or equal to 10kPa from P2 to P1, only the first battery valve is opened, and nitrogen is injected into the power battery pack through the nitrogen gas storage cylinder. When P2-P1 is less than 10kPa, firstly, the air source pressure P4 of the whole vehicle is judged, if the air source pressure of the whole vehicle is insufficient, an air source demand is sent to a frequency converter of an air compressor of the vehicle, and the frequency converter of the compressor controls the compressor to work to provide air source for the whole vehicle. When the air pressure P4 of the whole vehicle air source is larger than or equal to 600kPa, the second electromagnetic valve is opened, the whole vehicle air source filters out moisture, oil stain, oxygen and other substances through a filter, an air filter and a molecular plug, the nitrogen is remained and injected into the nitrogen storage cylinder, and when the air inlet pressure is larger than the pressure of the power battery pack by 1kPa, the first electromagnetic valve is opened, and the nitrogen is injected into the power battery pack.

And S14, judging whether the first air pressure value is not less than the second preset value.

S15, when the first air pressure value is not less than the second preset value, judging whether the oxygen concentration value is greater than the second concentration value.

And when the pressure P1 of the power battery pack is more than or equal to 6kPa, judging that the oxygen concentration is less than or equal to 4%, closing the electromagnetic valve and stopping injecting the nitrogen. If the oxygen concentration is greater than 4%, the nitrogen injection is continued.

And S16, when the oxygen concentration value is judged to be larger than the second concentration value, sending out alarm information. Otherwise, all the electromagnetic valves are closed to stop filling the nitrogen. Step S16 specifically includes S161 to S163:

And S162, judging whether the duration of continuously injecting the nitrogen gas exceeds a second preset duration or not, and sending out alarm information when the duration exceeds the second preset duration. Optionally, the second preset time period is 1 to 60 minutes. Preferably, the second market preset is 30 minutes.

And S163, closing all the electromagnetic valves and stopping filling the nitrogen when the oxygen concentration value is judged to be not greater than the second concentration value.

When the gas pressure in the power battery pack is greater than the set pressure of the backpressure valve by 10kPa, nitrogen replacement is automatically carried out, 1 time limit of 30min is added in the process, and if the time limit exceeds 30min, system failure is judged, and leakage possibly exists in the system.

Specifically, when the vehicle is powered on and operated, the nitrogen balance requirement of the power battery pack is maintained by preparing nitrogen from the air source of the whole vehicle, the air of the air storage cylinder of the whole vehicle is filtered to remove moisture and oil stains in the air after passing through the filter, impurities are filtered by the air filter through the second electromagnetic valve, oxygen is filtered by the molecular sieve, and the oxygen is injected into the battery pack through the first electromagnetic valve after passing through the pressure reducing valve.

When the air source of the whole vehicle is sufficient, the second electromagnetic valve can be opened, and nitrogen gas is prepared in advance and stored in the nitrogen gas storage cylinder.

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 1.1 kPa. 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 1 kPa.

According to the technical scheme, the inert gas nitrogen is adopted to provide a protective layer for the power battery from the principle of oxygen isolation in three elements of combustion, so that safety accidents of ignition, explosion and the like of the power battery caused by thermal runaway of the power battery are effectively solved. The application and popularization of the new energy passenger car are facilitated, and the novel energy passenger car has high safety application benefits.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A protection system for a power battery, comprising:

the battery pack comprises 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) which are arranged on the battery pack (18);

the nitrogen assembly comprises a nitrogen gas storage cylinder (13) provided with an inflation inlet (15) and a third air pressure sensor (12) arranged on the nitrogen gas storage cylinder (13);

the first connecting assembly is used for communicating the nitrogen gas storage cylinder (13) with the cavity; the first connecting assembly comprises a check valve and a first solenoid valve (11) which are arranged in series.

2. The protection system according to claim 1, characterized in that said first connection assembly further comprises a pressure reducing valve (9) for communicating said nitrogen gas cylinder (13) with said first solenoid valve (11), and a second air pressure sensor (10) arranged between said pressure reducing valve (9) and said first solenoid valve (11);

the battery pack further includes a safety valve (20) and a back pressure valve (21) disposed in the battery pack (18);

the nitrogen assembly further comprises a manual valve (14) used for communicating the interior of the nitrogen gas storage cylinder (13) with the inflation port (15).

3. The protection system of claim 1, further comprising

The air assembly comprises an air storage cylinder (3) and a fourth air pressure sensor (2) arranged on the air storage cylinder (3); and an air compressor (1) communicated with the air storage cylinder (3);

a second connection assembly for communicating the air reservoir (3) with the first connection assembly; the second connecting assembly comprises a molecular sieve (7) and a second electromagnetic valve (5) which are arranged in series.

4. The protection system according to claim 3, characterized in that said second connection assembly further comprises a filter (4) and an air filter (6) arranged in series with said molecular sieve (7) and said second solenoid valve (5);

the filter (4), the second electromagnetic valve (5), the air filter (6) and the molecular sieve (7) are connected in sequence; one-way valves are arranged between the second connecting assembly and the first connecting assembly, and between the second connecting assembly and the air cylinder (3);

a one-way valve is arranged between the air compressor (1) and the air storage cylinder (3).

5. Protection system according to claim 2, characterized in that the pressure of the safety valve (20) is 40 to 60kPa and the pressure of the back pressure valve (21) is 10 to 20 kPa.

6. A control method of a power battery protection system for controlling the protection system of claim 3, wherein, when the air in the cavity is replaced by nitrogen gas:

acquiring 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;

judging whether the pressure difference between the second air pressure value and the first air pressure value exceeds a first pressure difference;

when the pressure difference between the second air pressure value and the first air pressure value is judged to exceed the first pressure difference, a first electromagnetic valve is opened so that nitrogen in the nitrogen air storage cylinder enters the cavity;

closing the first solenoid valve when the oxygen concentration value is less than a first concentration value.

7. The control method according to claim 6, wherein the first electromagnetic valve is opened, and the pressure of the back pressure valve is gradually increased until the first pressure value is reached while the nitrogen in the nitrogen gas cylinder enters the cavity;

when the oxygen concentration value is smaller than a first preset value, after the first electromagnetic valve is closed, the method further comprises the following steps:

judging whether the first air pressure value is reduced to exceed a first leakage value after the first preset time length;

when the first air pressure value is judged to be reduced and exceed the first leakage value, alarm information is sent out;

the first pressure difference is 1kPa, the first concentration value is 4%, the first pressure value is 10kPa, the first leakage value is 50Pa, and the first preset time period is 60 seconds.

8. The method of claim 6, wherein after displacing air from the chamber with nitrogen, further comprising:

judging whether the first air pressure value exceeds a first preset value or not;

when the first air pressure value does not exceed the first preset value, judging whether the difference value between the second air pressure value and the first air pressure value is not less than a second pressure difference;

when the difference value between the second air pressure value and the first air pressure value is judged to be not less than a second pressure difference, the first electromagnetic valve is opened, and nitrogen is conveyed into the cavity by the nitrogen component; otherwise, opening the second electromagnetic valve and the first electromagnetic valve, and conveying nitrogen to the cavity by the air assembly;

judging whether the first air pressure value is not less than a second preset value or not;

when the first air pressure value is judged to be not smaller than the second preset value, judging whether the oxygen concentration value is larger than a second concentration value;

when the oxygen concentration value is judged to be larger than the second concentration value, sending out alarm information; otherwise, all the electromagnetic valves are closed to stop filling the nitrogen.

9. The control method according to claim 8, wherein when the difference between the second air pressure value and the first air pressure value is judged to be not less than a second pressure difference, the first electromagnetic valve is opened, and nitrogen is conveyed into the cavity by the nitrogen component; otherwise, open second solenoid valve with first solenoid valve, by air component to cavity internal transportation nitrogen gas, specifically include:

when the difference value between the second air pressure value and the first air pressure value is judged to be not smaller than the second pressure difference, whether a fourth air pressure value detected by a fourth air pressure sensor is smaller than a third preset value or not is judged;

when the fourth air pressure value is smaller than a third preset value, starting an air compressor to pressurize, and opening a second electromagnetic valve when the fourth air pressure value is not smaller than the third preset value; otherwise, directly opening the second electromagnetic valve;

judging whether the difference value between the second air pressure value and the first air pressure value is smaller than a third pressure difference;

when the difference value between the second air pressure value and the first air pressure value is not less than a third pressure difference, a first electromagnetic valve is opened, and nitrogen is conveyed into the cavity by the air assembly;

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 1 kPa.

10. The control method according to claim 8, wherein when it is determined that the oxygen concentration value is greater than the second concentration value, an alarm message is sent, specifically:

when the oxygen concentration value is judged to be larger than the second concentration value, continuously injecting nitrogen into the cavity until the oxygen concentration value is not larger than the second concentration value;

judging whether the duration of continuously injecting the nitrogen gas exceeds a second preset duration or not, and sending out alarm information when the duration exceeds the second preset duration;

the second preset time period is 30 minutes.