A liquid cooling system for electric vehicle battery pack and a simple control method thereof

Abstract

The present invention discloses a liquid cooling system for an electric vehicle battery pack, comprising a battery pack (1), a liquid cooling plate (2), an adjustable speed water pump (3), a radiator (4), an adjustable speed fan (5), a controller (6) and a temperature acquisition module (7), wherein the liquid cooling plate (2) is tightly attached to the battery pack (1) and is used to cool the battery pack (1), the adjustable speed fan (5) is located near the radiator (4) and is used to promote the heat dissipation of the radiator (4) to the external environment, and the temperature acquisition module (7) is used to acquire the temperature values ​​of several positions on the surface of the battery pack (1). The present invention also discloses a simple control method based on the cooling system, comprising the steps of obtaining the maximum temperature of the battery pack in step S1, comparing the relationship between the maximum temperature of the battery pack and the upper limit value of the battery temperature and adjusting the speed, waiting and returning to step S1, etc. The cooling system has a simple structure and reliable operation, and the corresponding control method has good adaptability to the environment and working conditions, simple logic, high reliability and significant energy saving effect.

Description

Technical Field

[0001] The invention relates to an electric vehicle, and in particular to a liquid cooling system for a battery pack of an electric vehicle and a simple control method thereof. Background Art

[0002] Electric vehicles have been rapidly developed due to their advantages such as being green, environmentally friendly, comfortable and efficient. Electric vehicles are usually powered by lithium-ion power battery packs. During operation, lithium-ion battery packs generate a lot of heat and cause their own temperature to rise, so heat dissipation measures need to be taken to prevent the temperature of the battery pack from being too high, otherwise the performance of the battery pack will be reduced and even bring safety hazards. At present, mainstream electric vehicles generally use liquid cooling to dissipate heat for battery packs. Among them, the liquid cooling method of economical electric vehicles is that the coolant flows through the liquid cooling plate to exchange heat with the battery pack. The coolant after the temperature rises flows into the radiator, and the heat is dissipated to the outside air with the help of the fan. The cooled coolant returns to the liquid cooling plate to continue circulating.

[0003] Among the currently known electric vehicle cooling technologies, there are many technical solutions for the structure and operation control of the cooling system, but most of them ignore the energy consumption of the cooling system itself, which also has a great impact on the cruising range of electric vehicles. During the working process of the electric vehicle liquid cooling system, the power equipment such as the water pump and fan also consumes a lot of electricity. The power of the water pump is usually hundreds of watts, and the power of the fan is tens of watts. Moreover, the power of these power equipment increases sharply with the increase of its speed. In most of the speed range, the power ratio of the same power equipment is roughly equal to the cube of its speed ratio. Generally speaking, when other conditions remain unchanged, increasing the speed of a certain power equipment will help to strengthen the cooling of the battery pack. However, under different environments and working conditions, the degree of improvement in the cooling capacity of the battery pack brought about by increasing the speed of a certain power equipment by a certain percentage is different. Therefore, it is necessary to perform better online cooling control on the battery pack according to the actual situation, so as to achieve the cooling effect of the battery pack and reduce the energy consumption of the cooling system itself as much as possible. Summary of the invention

[0004] The purpose of the present invention is to provide an electric vehicle battery pack cooling system with simple structure and reliable operation, and to provide an electric vehicle battery pack cooling control method with good adaptability to corresponding environments and working conditions, simple logic, high reliability and significant energy-saving effect.

[0005] To achieve the above-mentioned purpose, the technical solution provided by the present invention is as follows: According to one aspect of the present invention, a liquid cooling system for an electric vehicle battery pack is provided, comprising a battery pack, a liquid cooling plate, an adjustable speed water pump, a radiator, an adjustable speed fan, a controller and a temperature acquisition module, wherein the liquid cooling plate is tightly attached to the battery pack and is used to cool the battery pack, the adjustable speed fan is located near the radiator and is used to promote the flow of ambient air to achieve heat dissipation from the radiator to the ambient environment, and the temperature acquisition module comprises a plurality of temperature sensors fixed on the surface of the battery pack to collect temperature values ​​at a plurality of positions on the surface of the battery pack; the liquid cooling plate is connected to the adjustable speed water pump and the radiator in sequence through a pipeline to form a loop, and the loop is filled with a coolant; the controller is electrically connected to the adjustable speed water pump, the adjustable speed fan and the temperature acquisition module respectively, and is used to obtain the temperature values ​​collected by the temperature points of each sensor in the temperature acquisition module and adjust the rotation speeds of the adjustable speed water pump and the adjustable speed fan.

[0006] According to another aspect of the present invention, a simple control method for the liquid cooling system of the battery pack of the electric vehicle is provided, wherein the upper limit value Tc of the battery temperature in the battery pack is determined by consulting the design data; the minimum permissible speed value M of the adjustable speed water pump is determined; min and the maximum permissible speed value M max , determine the minimum permissible speed value N of the adjustable speed fan min and the maximum permissible speed value N max ; Determine the single speed adjustment range ΔM and ΔN of the adjustable speed water pump and adjustable speed fan respectively, where ΔM=(M max -M min ) / m, ΔN=(N max -N min ) / n, m and n are both integers greater than 5; at the initial moment of battery pack startup, set the speed of the adjustable speed water pump M=M min , set the speed of the adjustable fan to N = N min ;After the battery pack is started, control it according to the following steps:

[0007] Step S1, reading the battery pack temperature values ​​collected by each sensor temperature point in the temperature collection module, and comparing to obtain the maximum value T;

[0008] Step S2, read the current speed M of the adjustable speed water pump and the speed N of the adjustable speed fan, and compare the relationship between the maximum battery pack temperature T and the upper battery temperature limit Tc obtained in step S1:

[0009] (1) If T≤Tc and M>M min , then the speed M of the adjustable speed water pump is reduced by ΔM;

[0010] (2) If T≤Tc, M=M min And N>N min, then the speed N of the adjustable speed fan is reduced by ΔN;

[0011] (3) If T≤Tc, M=M min And N = N min , then no operation is performed;

[0012] (4) If T>Tc and N <N max , then the speed N of the adjustable speed fan is increased by ΔN;

[0013] (5) If T>Tc, N=N max And M <M max , then the speed M of the adjustable speed water pump is increased by ΔM;

[0014] (6) If T>Tc, M=M max And N = N max , then no operation is performed;

[0015] Step S3, waiting for a time of Δt, and then returning to step S1, wherein Δt is between 20 seconds and 120 seconds.

[0016] The beneficial effects of the present invention are as follows: the electric vehicle battery pack liquid cooling system has a simple structure and reliable operation, and only includes a battery pack, a liquid cooling plate, an adjustable speed water pump, a radiator, an adjustable speed fan, a controller and a temperature acquisition module, wherein the liquid cooling plate is connected to the adjustable speed water pump and the radiator in sequence through pipes to form a loop, and the power equipment of the entire liquid cooling system has only one adjustable speed water pump and one adjustable speed fan, without complex valve structures and precise and expensive electronic components. The simple control method of the electric vehicle battery pack liquid cooling system has good adaptability to the environment and working conditions, simple logic, high reliability, and significant energy-saving effect. The control method only relies on the temperature acquisition module for measurement, and the execution only includes the speed adjustment of the adjustable speed water pump and the adjustable speed fan, and fully considers the fact that the energy consumption of the water pump operation is much higher than the energy consumption of the fan operation within the normal speed range. When the maximum temperature of the battery pack is less than or equal to the upper temperature limit, the speed of the water pump with a higher energy consumption level is reduced first, and the fan speed is reduced only when the speed of the water pump drops to its minimum allowable value; when the maximum temperature of the battery pack is greater than the upper temperature limit, the speed of the fan with a lower energy consumption level is increased first, and the speed of the water pump is increased only when the fan speed reaches its maximum allowable value; after the speed adjustment is performed, wait for a fixed time interval to allow the adjustment means to play a certain role before the next temperature comparison and speed adjustment cycle is performed. Since a control cycle takes less time, it can be adjusted flexibly and quickly according to actual conditions during the operation of the battery pack liquid cooling system; the speed adjustment range of the water pump or fan is constant each time, so even if a single adjustment action is not adjusted in place, it will quickly enter the next control cycle to continue adjustment until the temperature reaches the requirement or the speed of the water pump and fan are adjusted to their limit allowable values. Therefore, even if there is a certain hysteresis in the adjustment control, since each control cycle takes a short time, sufficient speed adjustment can still be obtained through multiple dynamic adjustments in a short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Attached Figure 1 Schematic diagram of the structure of the liquid cooling system of the electric vehicle battery pack in an embodiment of the present invention.

[0018] Attached Figure 2 Flow chart of a simplified control method for an electric vehicle battery pack in an embodiment of the present invention. Example

[0019] The present invention will be further described below with reference to specific embodiments in conjunction with the accompanying drawings.

[0020] As attached Figure 1As shown, a liquid cooling system for an electric vehicle battery pack comprises a battery pack 1, a liquid cooling plate 2, an adjustable speed water pump 3, a radiator 4, an adjustable speed fan 5, a controller 6 and a temperature acquisition module 7, wherein the liquid cooling plate 2 is closely attached to the battery pack 1 and is used to cool the battery pack 1, the adjustable speed fan 5 is located near the radiator 4 and is used to promote the flow of ambient air to achieve heat dissipation from the radiator 4 to the ambient environment, and the temperature acquisition module 7 comprises a plurality of temperature sensors fixed on the surface of the battery pack 1 to collect temperature values ​​at a plurality of positions on the surface of the battery pack 1; the liquid cooling plate 2 is connected to the adjustable speed water pump 3 and the radiator 4 in sequence through a pipeline to form a loop, and the loop is filled with a coolant; the controller 6 is electrically connected to the adjustable speed water pump 3, the adjustable speed fan 5 and the temperature acquisition module 7 respectively, and is used to obtain the temperature values ​​collected by the temperature points of each sensor in the temperature acquisition module 7 and adjust the rotation speeds of the adjustable speed water pump 3 and the adjustable speed fan 5.

[0021] The simple control method applied to the liquid cooling system of the battery pack of the electric vehicle is to determine the upper limit value Tc of the battery temperature in the battery pack by consulting the design data; determine the minimum allowable speed value M of the adjustable speed water pump 3 min and the maximum permissible speed value M max , determine the minimum permissible speed value N of the adjustable speed fan 5 min and the maximum permissible speed value N max ; Determine the single speed adjustment range ΔM and ΔN of the adjustable speed water pump 3 and the adjustable speed fan 5, respectively, where ΔM=(M max -M min ) / m, ΔN=(N max -N min ) / n, m and n are both integers greater than 5; Figure 2 As shown, at the initial moment when the battery pack is started, the speed of the adjustable speed water pump 3 is set to M = M min , set the speed of adjustable fan 5 to N = N min After the battery pack is started, control is performed according to the following steps:

[0022] Step S1, reading the battery pack temperature values ​​collected by each sensor temperature point in the temperature collection module 7, and comparing to obtain the maximum value T;

[0023] Step S2, read the current speed M of the adjustable speed water pump 3 and the speed N of the adjustable speed fan 5, and compare the relationship between the maximum battery pack temperature T and the upper battery temperature limit Tc obtained in step S1:

[0024] (1) If T≤Tc and M>M min , then the speed M of the adjustable speed water pump 3 is reduced by ΔM;

[0025] (2) If T≤Tc, M=M min And N>Nmin , then the speed N of the adjustable speed fan 5 is reduced by ΔN;

[0026] (3) If T≤Tc, M=M min And N = N min , then no operation is performed;

[0027] (4) If T>Tc and N <N max , the speed N of the adjustable speed fan 5 is increased by ΔN;

[0028] (5) If T>Tc, N=N max And M <M max , then the speed M of the adjustable speed water pump 3 is increased by ΔM;

[0029] (6) If T>Tc, M=M max And N = N max , then no operation is performed;

[0030] Step S3, waiting for a time of Δt, and then returning to step S1, wherein Δt is between 20 seconds and 120 seconds.

[0031] Specifically, in this embodiment, the battery pack is composed of 1 parallel 96 series ternary cells, with a rated capacity of 150Ah and a rated voltage of 350V. The coolant flowing through the liquid cooling plate 2 is an ethylene glycol solution. The upper limit value of the battery temperature in the battery pack is Tc=40°C. The minimum permissible speed value M of the adjustable speed water pump 3 is min =1000r / min, maximum permissible speed value M max =8000r / min, the minimum permissible speed value N of the adjustable speed fan 5 min =1000r / min, maximum permissible speed value N max =9000r / min, m=7, n=8, then the single speed adjustment range of the adjustable speed water pump 3 ΔM=(M max -M min ) / m=(8000-1000) / 7=1000r / min, the single speed adjustment range of the adjustable speed fan 5 ΔN=(N max -N min ) / n=(9000-1000) / 8=1000r / min, the temperature acquisition module 7 acquires the temperature values ​​of 5 different positions inside the battery pack and transmits them to the controller 6 to calculate the maximum temperature T of the battery pack. During the operation of the battery pack, the control process waiting time Δt=30s. The operating power of the adjustable speed fan 5 is constant at 60W. The operating power of the adjustable speed water pump 3 and the adjustable speed fan 5 is the highest at their maximum allowable speed, which are 400W and 60W respectively.

[0032] In this embodiment, at the initial moment of battery pack startup, i.e., t=0, the speed of the adjustable speed water pump 3 is set to M=1000r / min, and the speed of the adjustable speed fan 5 is set to N=1000r / min. After the battery pack is started, the maximum value of the battery pack temperature T=36°C is read at t=0. Since T≤Tc, M=M min And N = N min , then no operation is performed and waits for Δt = 30s.

[0033] When t = Δt = 30s, the maximum battery pack temperature is read as T = 39°C. Since T ≤ Tc, M = M min And N = N min , then no operation is performed and waits for Δt = 30s.

[0034] When t = 2Δt = 60s, the maximum battery pack temperature is read as T = 41°C. Since T>Tc and N <N max , then the speed N of the adjustable speed fan 5 is increased by ΔN, so that N=N min +ΔN=2000r / min, then wait for Δt=30s.

[0035] After that, in the range of t = 3Δt = 90s to t = 9Δt = 270s, T>Tc and N <N max , the speed N of the adjustable speed fan 5 is increased by ΔN each time, and then a time of Δt=30s is waited.

[0036] When t=10Δt=300s, the maximum battery pack temperature is read as T=41.5℃. Since T>Tc, N=N max And M <M max , then the speed M of the adjustable speed water pump 3 is increased by ΔM, so that M=M min +ΔM=2000r / min, then wait for Δt=30s.

[0037] When t=11Δt=330s, the maximum battery pack temperature is read as T=40.5℃. Since T>Tc, N=N max And M <M max , then increase the speed M of the adjustable speed water pump 3 by ΔM, so that M = 3000r / min, and then wait for Δt = 30s.

[0038] When t=12Δt=360s, the maximum battery pack temperature is read as T=39℃. Since T≤Tc and M>M min , then the speed M of the adjustable speed water pump 3 is reduced by ΔM to make M = 2000r / min, and then wait for Δt = 30s.

[0039] Thereafter, in this embodiment, the rotation speed M of the adjustable speed water pump 3 and the rotation speed N of the adjustable speed fan 5 are always in dynamic adjustment, wherein M is basically maintained in the range of 1000-4000 r / min, and N is basically maintained in the range of 7000-9000 r / min. On the premise that the maximum temperature of the battery pack is lower than its upper temperature limit, the water pump speed is maintained as low as possible, thereby achieving the purpose of saving energy consumption.

[0040] The electric vehicle battery pack liquid cooling system provided in this embodiment has a simple structure and reliable operation. It only includes a battery pack, a liquid cooling plate, an adjustable speed water pump, a radiator, an adjustable speed fan, a controller and a temperature acquisition module, wherein the liquid cooling plate is connected to the adjustable speed water pump and the radiator in sequence through pipes to form a loop. The power equipment of the entire liquid cooling system has only one adjustable speed water pump and one adjustable speed fan, without complex valve structures and precise and expensive electronic components. The corresponding simple control method of the battery pack liquid cooling system has good adaptability to the environment and working conditions, simple logic, high reliability, and significant energy-saving effect. The control method only relies on the temperature acquisition module for measurement, and the execution only includes the speed adjustment of the adjustable speed water pump and the adjustable speed fan, and fully considers the fact that the energy consumption of the water pump operation is much higher than the energy consumption of the fan operation within the normal speed range. When the maximum temperature of the battery pack is less than or equal to the upper temperature limit, the speed of the water pump with a higher energy consumption level is reduced first, and the fan speed is reduced only when the speed of the water pump drops to its minimum allowable value; when the maximum temperature of the battery pack is greater than the upper temperature limit, the speed of the fan with a lower energy consumption level is increased first, and the speed of the water pump is increased only when the fan speed reaches its maximum allowable value; after the speed adjustment is performed, wait for a fixed time interval to allow the adjustment means to play a certain role before the next temperature comparison and speed adjustment cycle is performed. Since a control cycle takes less time, it can be adjusted flexibly and quickly according to actual conditions during the operation of the battery pack liquid cooling system; the speed adjustment range of the water pump or fan is constant each time, so even if a single adjustment action is not adjusted in place, it will quickly enter the next control cycle to continue adjustment until the temperature reaches the requirement or the speed of the water pump and fan are adjusted to their limit allowable values. Therefore, even if there is a certain hysteresis in the adjustment control, since each control cycle takes a short time, sufficient speed adjustment can still be obtained through multiple dynamic adjustments in a short time.

Claims

1. A simple control method for a liquid cooling system of an electric vehicle battery pack, characterized in that: The simple control method is based on the liquid cooling system of the electric vehicle battery pack. The electric vehicle battery pack liquid cooling system is characterized by comprising a battery pack (1), a liquid cooling plate (2), an adjustable speed water pump (3), a radiator (4), an adjustable speed fan (5), a controller (6) and a temperature acquisition module (7), wherein the liquid cooling plate (2) is closely attached to the battery pack (1) and is used to cool the battery pack (1), the adjustable speed fan (5) is located near the radiator (4) and is used to promote the flow of ambient air to achieve heat dissipation from the radiator (4) to the ambient environment, and the temperature acquisition module (7) comprises a plurality of The temperature sensor on the surface of the battery pack (1) collects temperature values ​​at several positions on the surface of the battery pack (1); the liquid cooling plate (2) is connected to the adjustable speed water pump (3) and the radiator (4) in sequence through a pipeline to form a loop, and the loop is filled with a coolant; the controller (6) is electrically connected to the adjustable speed water pump (3), the adjustable speed fan (5) and the temperature collection module (7) respectively, and is used to obtain the temperature values ​​collected by each sensor temperature point in the temperature collection module (7) and adjust the rotation speed of the adjustable speed water pump (3) and the adjustable speed fan (5); In a normal speed range, the operating energy consumption of the adjustable speed water pump (3) is much higher than the operating energy consumption of the adjustable speed fan (5); The simple control method is to determine the upper limit value Tc of the battery temperature in the battery pack by consulting the design data; determine the minimum allowable speed value M of the adjustable speed water pump (3); min and the maximum permissible speed value M max , determine the minimum permissible speed value N of the adjustable speed fan (5) min and the maximum permissible speed value N max ; respectively determine the single speed adjustment amplitudes ΔM and ΔN of the adjustable speed water pump (3) and the adjustable speed fan (5), where ΔM = (M max -M min ) / m, ΔN=(N max -N min ) / n, m and n are both integers greater than 5; at the initial moment of battery pack startup, the speed of the adjustable speed water pump (3) is set to M = M min , set the speed of the adjustable speed fan (5) to N = N min ;After the battery pack is started, control it according to the following steps: Step S1, reading the battery pack temperature values ​​collected by each sensor temperature point in the temperature collection module (7), and comparing to obtain the maximum value T; Step S2, read the current speed M of the adjustable speed water pump (3) and the speed N of the adjustable speed fan (5), and compare the relationship between the maximum value T of the battery pack temperature obtained in step S1 and the upper limit Tc of the battery temperature: (1) If T≤Tc and M>M min , then the speed M of the adjustable speed water pump (3) is reduced by ΔM; (2) If T≤Tc, M=M min And N>N min , the speed N of the adjustable speed fan (5) is decreased by ΔN; (3) If T≤Tc, M=M min And N = N min , then no operation is performed; (4) If T>Tc and N <N max , the speed N of the adjustable speed fan (5) is increased by ΔN; (5) If T>Tc, N=N max And M <M max , the speed M of the adjustable speed water pump (3) is increased by ΔM; (6) If T>Tc, M=M max And N = N max , then no operation is performed; Step S3, waiting for a time of Δt, and then returning to step S1, wherein Δt is between 20 seconds and 120 seconds.

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