CN116512990A - Battery thermal management system in high-temperature environment in pure electric vehicle and control method thereof - Google Patents

Battery thermal management system in high-temperature environment in pure electric vehicle and control method thereof Download PDF

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CN116512990A
CN116512990A CN202310486152.6A CN202310486152A CN116512990A CN 116512990 A CN116512990 A CN 116512990A CN 202310486152 A CN202310486152 A CN 202310486152A CN 116512990 A CN116512990 A CN 116512990A
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battery
vehicle
port
temperature
lithium ion
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李蒙
高游游
徐兴
何帆
李勇
廉玉波
凌和平
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Jiangsu University
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Jiangsu University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
    • B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
    • B60L58/24—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries for controlling the temperature of batteries
    • B60L58/26—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries for controlling the temperature of batteries by cooling
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2111/00—Details relating to CAD techniques
    • G06F2111/04—Constraint-based CAD
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/08—Thermal analysis or thermal optimisation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

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Abstract

The invention discloses a battery thermal management system under a medium-high temperature environment of a pure electric vehicle and a control method thereof, wherein a front vehicle driving characteristic parameter is compared with a real-time driving characteristic parameter of the vehicle to obtain an instantaneous speed weight and an average speed weight which change along with the driving of the vehicle, so as to determine the future driving working condition of the vehicle; determining the influence of the future driving working condition of the vehicle on the charge and discharge current in the battery reaction process, further determining the battery temperature corresponding to the future driving working condition of the vehicle, comparing the battery temperature with a threshold value, and judging whether the battery enters a radiator cooling mode or a chiller cooling mode; and taking the minimum difference value between the temperature of the lithium ion battery and the target temperature and the optimal energy consumption of an actuator of the thermal management system as optimization targets, and solving the optimal output rotating speeds of the water pump and the fan in the cooling mode. The invention considers the energy consumption of the actuator and the switching among different modes, has higher control precision and reduces the energy consumption.

Description

Battery thermal management system in high-temperature environment in pure electric vehicle and control method thereof
Technical Field
The invention belongs to the technical field of heat management of new energy automobiles, and particularly relates to a battery heat management system in a high-temperature environment of a pure electric automobile and a control method thereof.
Background
With the development of the automobile industry level in China, the sales volume of the automobile industry is continuously increased. The automotive industry has a series of environmental and energy problems as well as economic growth. The battery is used as a power source of the pure electric vehicle, and the temperature of the battery has important influence on the safety and reliability of the pure electric vehicle.
According to researches, the optimal working temperature of the battery is 15-35 ℃, once the optimal working temperature exceeds the range, the diffusion speed of lithium ions in the battery is increased, the reaction speed in the battery is increased, the capacity of the battery is slightly increased, but some side reaction speeds are increased correspondingly, and the SEI film thickness of the battery is increased, so that the aging rate of the battery is increased. As heat is generated inside the battery is accumulated, the temperature of the battery is continuously increased, eventually leading to thermal runaway of the battery. When the gas caused by the side reaction of the battery is continuously accumulated in the battery, an explosion is caused when the gas exceeds a certain value, and the problem of thermal safety is caused.
At present, commonly used battery cooling optimization methods can be divided into a classical control method and an intelligent optimization method. The classical control method mainly establishes a battery cooling optimization strategy based on rules, such as segmented control, proportional-integral-derivative (PID) control, fuzzy control and the like; these methods have the advantages of simple design and easy realization, but the control rules are mostly obtained from practical experience, and when the experience is insufficient, it is difficult to achieve a satisfactory cooling effect, and no accurate energy consumption evaluation standard is given. In order to make up for the deficiency of the classical control algorithm, the intelligent optimization algorithm is gradually applied to the battery cooling system; in the battery cooling process, the intelligent optimization algorithm does not consider the energy consumption of the actuator and does not consider the switching between different modes, so that the control precision is lower and the energy consumption is higher.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a battery thermal management system in a high-temperature environment in a pure electric vehicle and a control method thereof.
The present invention achieves the above technical object by the following means.
A control method of a battery thermal management system in a high-temperature environment in a pure electric vehicle comprises the following steps:
comparing the driving characteristic parameter of the front vehicle with the real-time driving characteristic parameter of the host vehicle to obtain the instant speed weight which changes along with the driving of the host vehicleAnd average speed weight +.>Based on the weights, by the formula +.>Acquiring a driving characteristic parameter value of the next state of the vehicle, and further determining the future driving condition of the vehicle; wherein v is t+1,1n An instantaneous speed, v, representing the next state of the nth target preceding vehicle t+1,2n Representing the average speed of the next state of the nth target front vehicle;
determining the influence of the future driving working condition of the vehicle on a battery thermal management system, in particular to the influence on charge and discharge current in the reaction process of the lithium ion battery; the charge and discharge current and the lithium ion battery temperature in the lithium ion battery reaction process meet a lithium ion battery centralized thermal model under the liquid cooling condition, so that the lithium ion battery temperature corresponding to the future driving working condition of the vehicle is determined, the lithium ion battery temperature is compared with a battery working temperature threshold value, and the battery is judged to enter a radiator cooling mode or a chiller cooling mode;
and taking the minimum difference value between the temperature of the lithium ion battery and the target temperature and the optimal energy consumption of an actuator of the thermal management system as optimization targets, and solving the optimal output rotating speeds of the water pump and the fan in the cooling mode.
Further, the instantaneous speed weightAnd average speed weight +.>The following respectively satisfy:wherein: v 1n V is the instantaneous speed of the preceding vehicle 2n For the average speed of the preceding vehicles, n=1, 2 … … m, n represents the n-th target preceding vehicle, m represents the total number of preceding vehicles; v 1 V is the instantaneous speed of the vehicle 2 Is the average speed of the host vehicle.
Further, the influence of the future driving condition of the vehicle on the charge and discharge current in the reaction process of the lithium ion battery is specifically as follows:
wherein: i is charge-discharge current in the reaction process of the lithium ion battery, U 0 R is the open circuit voltage of a lithium ion battery 0 P is the sum of ohmic internal resistance and polarization internal resistance of lithium ion battery p Is the traction power of the electric automobile, P s Power of thermal management system of electric automobile, V v For the running speed of the vehicle F r For rolling resistance of vehicle, F a For vehicle air resistance, M v Is the total mass of the vehicle eta s For traction efficiency, deltaV v Is the vehicle running speed variation.
Further, the heat model in the lithium ion battery set under the liquid cooling condition is as follows:
wherein: delta T b T is the temperature variation of the lithium ion battery b Is the temperature of the lithium ion battery, m b C, concentrating the mass of the battery b For specific heat capacity of battery, A b G is the contact area between the lithium ion battery and the cooling liquid 1 Is of intermediate quantity G l T is the mass flow of the cooling liquid l Is the temperature of the cooling liquid.
Further, when T b low ≤T b ≤T b high The battery enters a radiator cooling mode: the second port (2032) of the three-way valve is closed, the first port (2031) of the three-way valve is communicated with the third port (2033) of the three-way valve, the fan (301) is started, and the water pump (201) is started; when T is b ＞T b high The battery enters a cooling mode of the water chiller: the first port (2031) of the three-way valve is closed, the second port (2032) of the three-way valve is communicated with the third port (2033) of the three-way valve, the fan (301) is closed, and the water pump (201) is opened.
Further, the objective function corresponding to the optimization objective is:
wherein: o (O) 1 With O 2 Is weight, T br For the target temperature, N p Representing a prediction time domain and a control time domain, and P s ＝N pump T pump η pump +N fan T fan η fan Wherein T is pump Represents the torque, eta of the water pump pump Indicating the efficiency of the water pump, T fan Represents fan torque, eta fan Indicating fan efficiency.
Further, the constraint conditions met by the battery temperature, the water pump rotation speed and the fan rotation speed are as follows:
T b 1 ≤T b ≤T b 2
wherein T is b 1 Is the lower limit of the optimal operating temperature of the battery; t (T) b 2 Is the lower limit of the optimal operating temperature of the battery;is the minimum value of the rotation speed of the water pump, < >>Is the maximum value of the rotation speed of the water pump; />Is the minimum value of the rotation speed of the fan, < >>Is the maximum value of the rotational speed of the fan.
The battery thermal management system in the high-temperature environment of the pure electric vehicle comprises a water chiller, a water pump, a power battery, a three-way valve, a radiator and a fan, wherein a first port of the water chiller and a second port of the water chiller are respectively communicated with a refrigerant loop, a fourth port of the water chiller is communicated with a second port of the three-way valve, a third port of the three-way valve is communicated with a first port of the power battery, a second port of the power battery is communicated with a first port of the water pump, a second port of the water pump is communicated with an end point A, the end point A is also communicated with a third port of the water chiller and a first port of the radiator, and the second port of the radiator is communicated with the first port of the three-way valve; the fan is disposed at the heat sink.
The beneficial effects of the invention are as follows:
(1) The method has real-time property by estimating the weight of the front vehicle driving characteristic parameter of the future driving condition of the vehicle, and determines the influence of the future driving condition of the vehicle on the cooling process of the lithium ion battery, so that the control precision can be improved;
(2) According to the invention, the model predictive control is utilized, the minimum difference between the temperature of the lithium ion battery and the target temperature and the optimal energy consumption of the actuator of the thermal management system are used as target functions, the temperature tracking and the energy consumption optimizing are carried out, the switching of two working modes of cooling a battery radiator and cooling a cold water machine is considered, and the thermal safety of the battery in a medium-high temperature environment is ensured.
Drawings
FIG. 1 is a block diagram of a battery thermal management system in a medium-high temperature environment according to the present invention;
FIG. 2 is a schematic diagram of a method for optimizing a thermal management system of a battery in a medium-high temperature environment according to the present invention;
FIG. 3 is a flowchart of a control method of a battery thermal management system in a medium-high temperature environment according to the present invention;
in the figure: 100-battery thermal management system, 101-chiller, 201-water pump, 202-power battery, 203-three-way valve, 204-radiator, 301-fan, 1011-chiller first port, 1012-chiller second port, 1013-chiller third port, 1014-chiller fourth port, 2011-water pump first port, 2012-water pump second port, 2021-power battery first port, 2022-power battery second port, 2031-three-way valve first port, 2032-three-way valve second port, 2033-three-way valve third port, 2041-radiator first port, 2042-radiator second port.
Detailed Description
The invention will be further described with reference to the drawings and the specific embodiments, but the scope of the invention is not limited thereto.
Fig. 1 is a block diagram of a battery thermal management system 100 of the present application, the battery thermal management system 100 including a chiller 101, a water pump 201, a power battery 202, a three-way valve 203, a radiator 204, and a fan 301, the fan 301 being disposed at the radiator 204; the first port 1011 of the chiller communicates with a refrigerant circuit (e.g., an electronic expansion valve), the second port 1012 of the chiller communicates with a refrigerant circuit (e.g., a gas-liquid separator), the refrigerant circuit is not illustrated, and is only indicated by a dashed line; the fourth port 1014 of the chiller is in communication with the second port 2032 of the three-way valve, the third port 2033 of the three-way valve is in communication with the first port 2021 of the power battery, the second port 2022 of the power battery is in communication with the first port 2011 of the water pump, the second port 2012 of the water pump is in communication with the endpoint a, the endpoint a is also in communication with the third port 1013 of the chiller, the first port 2041 of the radiator, and the second port 2042 of the radiator is in communication with the first port 2031 of the three-way valve; in fig. 1, a solid line represents a coolant circuit, and a broken line represents a refrigerant circuit. In this embodiment, the power battery 202 is composed of a plurality of lithium ion unit batteries.
The battery thermal management system comprises two working modes, namely battery radiator cooling and battery water chiller cooling. In a medium-temperature environment, the environment temperature is suitable, the heat generated by the battery is not large, and the battery can radiate heat by using the radiator, so that the load of the compressor is reduced, and the function of reducing the energy consumption of the compressor is achieved; in this mode, the three-way valve second port 2032 is closed, the three-way valve first port 2031 and the three-way valve third port 2033 are communicated, and heat is radiated by the radiator to ensure thermal safety of the battery in a medium-temperature environment, and achieve the effect of reducing heat management energy consumption. In a high-temperature environment, the battery high-temperature cooling liquid cannot exchange heat with ambient air through a radiator, so that the battery high-temperature cooling liquid needs to be cooled through a water chiller; in this mode, the three-way valve first port 2031 is closed, the three-way valve second port 2032 is communicated with the three-way valve third port 2033, the battery thermal management high-temperature coolant exchanges heat with the low-temperature refrigerant through the chiller 101, and the low-temperature coolant is formed at the outlet of the chiller third port 1013, so that the battery is cooled in a high-temperature environment, the battery chiller solves the problem of insufficient heat dissipation of the battery radiator during cooling at a high temperature, and the thermal safety of the battery is ensured.
Fig. 2 is a schematic diagram of a method for optimizing a battery thermal management system in a medium-high temperature environment according to the present application, and fig. 3 is a flowchart of a method for controlling a battery thermal management system in a medium-high temperature environment according to the present invention. When the electric automobile is in a working state, driving characteristic parameter information of the electric automobile and a front automobile is obtained in real time based on an Internet of vehicles system, and future driving conditions are predicted; then, according to the predicted future driving working condition, determining the influence of the future driving working condition on the battery thermal management system; then consider the cooling of the battery radiator and cooling of the chiller to switch over two models; and finally, by using a model predictive control method, taking the target temperature of the battery as an optimized target value, taking the minimum difference value between the actual temperature of the battery and the target temperature and the optimal energy consumption of an actuator of a thermal management system as an optimized target, solving the optimal output rotating speed of the actuator, and realizing the aim of cooling and optimizing the battery in a medium-high temperature environment.
The optimization method of the battery thermal management system in the medium-high temperature environment is specifically designed as follows:
1. predicting future driving condition of host vehicle
Calling driving characteristic parameter information of the vehicle and the front vehicle through the vehicle networking system, comprising: the method comprises the steps of carrying out interaction of driving characteristic parameter information on an own vehicle and a front vehicle through a vehicle networking system, and storing the driving characteristic parameter information of the own vehicle and the front vehicle in the vehicle networking system.
Based on the obtained front-vehicle driving characteristic parameter and the own-vehicle driving characteristic parameter, the following formula is determinedThe weight of each driving characteristic parameter of each front vehicle is shown, and the driving information of the pure electric vehicle changes in real time along with time, so that the weight of each driving characteristic parameter of each front vehicle has real-time performance, and the driving characteristic parameter v of the front vehicle is taken 1n And v 2n Where n=1, 2 … … m, n represents the nth target preceding vehicle, and m represents the total number of preceding vehicles; comparing the driving characteristic parameters with the real-time driving characteristic parameters of the vehicle to obtain the instantaneous speed weight which changes along with the driving of the vehicle>And average speed weight +.> Wherein v is 1 Indicating the instantaneous speed of the vehicle, v 2 Indicating the average speed of the host vehicle.
Determining the characteristic parameters of the future driving conditions of the vehicle according to the obtained influence weights of each characteristic parameter of each preceding vehicleThereby determining the driving condition. The driving characteristic parameter value of the next state of the vehicle can be obtained by multiplying and summing the driving characteristic parameter value of the next state of each preceding vehicle with the obtained weight, and the formula is as followsShown, v t+1,1n And v t+1,2n Driving characteristic parameter value representing next state of nth target preceding vehicle, +.>And->The influence weight of the nth target preceding vehicle is expressed, and the driving characteristic parameter value of the next state of the vehicle can be determined, so that the future driving condition sequence V is determined v (k+i)，i＝1:N p K represents the kth moment of vehicle operation, i represents the driving condition prediction horizon N p I-th driving condition predicted time node of (c).
2. Establishing a battery thermal management system model
The invention uses a cooling structure, which comprises a battery side cooling liquid circulation loop and a heat pump air conditioner refrigerant circulation loop. Based on the above structure, in order to realize the optimal solution of the cooling process, a prediction model needs to be established to simulate the electrothermal characteristics of the battery and the heat exchange characteristics of each actuator.
(1) Battery heat collecting model
During running of the new energy automobile, the lithium ion battery works to output current with a certain discharge rate, so that the lithium ion battery generates certain heat in unit time, and the temperature of the lithium ion battery is increased. The heat generation in the lithium ion battery is mainly composed of joule heat, polarized heat, reaction heat and side reaction heat, wherein the side reaction heat is small, so that the heat generation is neglected.
The chemical reaction process of the lithium ion battery under charge and discharge is as follows:
the chemical reactions occurring inside a lithium ion battery are reversible, and the thermodynamic equation of a lithium ion battery can be expressed as:
ΔG＝ΔH-T b ΔS＝-nFU 0
wherein ΔG is the energy released by the lithium ion battery in the chemical reaction process, ΔH is the enthalpy change of the lithium ion battery in the chemical reaction process, T b Delta S is entropy change of the lithium ion battery in the chemical reaction process, n is charge number related to the chemical reaction of the lithium ion battery, F is Faraday constant, U 0 Is the open circuit voltage of the lithium ion battery.
Reaction heat Q of lithium ion battery chemical reaction process r The method comprises the following steps:
wherein I is charge and discharge current in the reaction process of the lithium ion battery.
The sum of the ohmic internal resistance and the polarization internal resistance of the lithium ion battery is R 0 Then the sum of the joule heat and the polarized heat of the lithium ion battery can be obtained as:
Q j +Q p ＝I 2 R 0
in summary, the relationship between the heat generated by the lithium ion battery and the charge and discharge current in the reaction process of the lithium ion battery is as follows:
the heat dissipation modes of the lithium ion battery are divided into heat conduction, heat convection and heat radiation.
In the running process of the vehicle, the heat transferred by the lithium ion battery to the surrounding cooling liquid is as follows:
Q s ＝hA b (T b -T l )
wherein Q is s The heat dissipated by the lithium ion battery is transferred by hCoefficient A b T is the contact area between the lithium ion battery and the cooling liquid b Is the temperature of the lithium ion battery, T l Is the temperature of the cooling liquid; the heat transfer coefficient h is:
h＝g 1 G l
wherein the intermediate amountρ l For density of cooling liquid, pr f Is a dimensionless constant, mu, of the Plandter number representing the heat exchange in the fluid flow f Dynamic viscosity, mu, derived for average temperature of coolant in the pipe ω The dynamic viscosity obtained for the temperature of the cooling liquid wall surface in the pipeline, G l Is the mass flow of the cooling liquid.
The relationship between the heat change per unit time of the lithium ion battery and the temperature of the lithium ion battery is as follows:
Q b ＝c b m b ΔT b
wherein DeltaT b Represents the temperature change quantity, m of the lithium ion battery b C, concentrating the mass of the battery b Is the specific heat capacity of the battery.
Heat change per unit time Q of lithium battery b It can also be expressed as:
Q b ＝Q c -Q s
therefore, the thermal model of the lithium ion battery collection under the liquid cooling condition can be obtained:
wherein, the model input is charging and discharging current I and temperature T of cooling liquid in the reaction process of the lithium ion battery l The output is the temperature change delta T of the lithium ion battery b 。
(2) Cold water machine model
At the water chiller, the heat exchange amount of the refrigerant and the cooling liquid is:
Q e ＝h e A e ΔT e ＝G com q k
wherein h is e A is the heat exchange coefficient of the cooling liquid and the refrigerant at the water chiller e Is the heat transfer area of the water chiller, G com For refrigerant flow, q k Is the heat generation per unit mass, deltaT e The average heat transfer temperature difference variation of the water chiller is expressed as:
wherein T is e T is the average heat transfer temperature difference of the water chiller lei Is the temperature of cooling liquid at the inlet of the water chiller, T leo The temperature of the cooling liquid at the outlet of the water chiller.
By the law of thermodynamic equilibrium, the average heat transfer temperature difference of the water chiller is equal to the variation of the temperature of the cooling liquid at the inlet and the outlet of the water chiller, so that the temperature of the cooling liquid at the outlet of the water chiller is as follows:
wherein c l Is the specific heat capacity of the cooling liquid.
(3) Water pump model
In the battery cooling loop, the water pump provides power required by the flow of cooling liquid, and the rotating speed of the water pump is as follows:
wherein V is pump Is the displacement of the water pump, eta pump For water pump efficiency ρ l Is the density of the cooling liquid.
(4) Radiator model
The heat exchange amount of the radiator is as follows:
Q rad ＝|T rad,a,i -T rad,a,out |·G air ·c air ＝|T rad,l,i -T rad,l,o |·G l ·c l
wherein,,Q rad heat exchange amount of radiator, T rad,a,i For the air inlet temperature of the radiator, T rad,a,out For the air outlet temperature of the radiator, T rad,l,i For radiator coolant inlet (i.e. radiator second port 2042) temperature, T rad,l,o For radiator cooling outlet (i.e. radiator first port 2041) temperature, G air For air mass flow, c air Is the specific heat capacity of air.
(5) Fan model
Air volume V of fan fan The method comprises the following steps:
wherein A is fan For fan blade area, N fan Fan speed, eta fan For fan efficiency, P fan Fan pressure.
3. Influence of driving conditions on battery thermal management system
In the running process of the electric automobile, the heat generation of the battery changes along with the change of the driving working condition of the automobile, so that the driving working condition can have a certain influence on the cooling of the battery; the power output of the battery mainly depends on traction power required by the operation of the electric automobile and power required by the thermal management of a system, and the expression of charge and discharge current in the reaction process of the lithium ion battery and power is related to the expression:
wherein P is p Is the traction power of the electric automobile,V v for the running speed of the vehicle F r For rolling resistance of vehicle, F a For vehicle air resistance, M v Is the total mass of the vehicle eta s For traction efficiency, P s The power of the electric automobile thermal management system is delta V v The vehicle running speed variation is used;
further:
from this, it can not only influence the change of the charge-discharge current in the lithium ion battery reaction process to see that the change of driving condition, and then influence the heat production of battery, can also influence air mass flow, and then influence the radiator cooling.
4. Battery radiator cooling and chiller cooling mode switching
When the environment temperature is proper and the heat generated by the battery is not large, the battery can be cooled by using the radiator, so that the load of the compressor is reduced, and the effect of reducing the energy consumption of the system is achieved. When the ambient temperature is higher, the battery high-temperature cooling liquid cannot exchange heat with ambient air through the radiator, so that the battery high-temperature cooling liquid needs to be cooled by the water chiller, and the thermal safety of the battery is ensured. Therefore, it is necessary to switch the two modes in consideration of the driving condition and the lithium ion battery temperature. Since the vehicle driving conditions have some impact on battery thermal management, battery temperature and driving conditions are taken into account simultaneously during mode switching. And inputting the acquired driving working condition and battery temperature information into a vehicle controller, determining the temperature of the lithium ion battery corresponding to the driving working condition, comparing the temperature with a battery working temperature threshold value, and judging that the battery enters a radiator cooling mode or a water chiller cooling mode according to a comparison result. As shown in fig. 3, T b low 、T b high Respectively corresponding to the minimum temperature value and the maximum temperature value of the battery at the cooling moment of the radiator, when T b ＜T b low The battery enters a heating mode; when T is b low ≤T b ≤T b high The battery enters a radiator cooling mode: the three-way valve second port 2032 is closed, the three-way valve first port 2031 is communicated with the three-way valve third port 2033, the fan 301 is started, the water pump 201 is started, and the working mode ensures the thermal comfort of the cabin and the thermal management safety of the battery at medium and high temperature, and the heat of the battery is dissipatedThe cooling of the device avoids the extra compressor load and energy consumption caused by cooling of the battery water chiller; when T is b ＞T b high The battery enters a cooling mode of the water chiller: the three-way valve first port 2031 is closed, the three-way valve second port 2032 is communicated with the three-way valve third port 2033, the fan 301 is turned off, the water pump 201 is turned on, the thermal comfort of the cabin at high temperature and the thermal management safety of the battery are guaranteed by the working mode, and the problem of insufficient heat dissipation of the battery radiator at high temperature is solved by cooling of the battery chiller.
5. Model predictive control method design
The heat generation of the battery can change along with the change of driving conditions, if the heat generation of the battery can be predicted, and the corresponding control quantity is solved according to the target temperature of the battery, the temperature of the battery can be well close to the designed target temperature value of the battery, and meanwhile, the energy consumption of a battery thermal management system can be correspondingly improved.
The invention adopts a state space equation form to construct a model prediction controller, the model is required to be discretized, and other external interference factors are considered for the system, and the discretized state space model of the system is expressed as follows:
wherein x (k+1), x (k), u (k), r (k), y (k) represent the state quantity at time k+1 and the state variable, control variable, measurable disturbance variable and output variable at time k, respectively, A, B u 、B d The invention regards the state space equation of the battery thermal management system as a black box model, namely, a matrix A and a matrix B as unknown parameters, and a matrix C as an identity matrix.
For the battery thermal management system of the present invention, the state variables are:
x＝[T b T l T leo Q rad ]
the system control variables are:
u＝[N pump N fan ]
the input disturbance quantity of the battery thermal management system model change is the driving working condition of the vehicle, namely:
r＝[V v ]
the target of the controlled object is the battery temperature, and the system output value is as follows:
y＝[T b P s ]
the objective of the optimization of the objective function is to minimize the function value of the cost function:
min[J(z k )]
the objective function is:
wherein: o (O) 1 With O 2 Is the weight; p (P) s To evaluate the energy consumption index of the battery during cooling, specifically P s The power of the electric automobile thermal management system can be expressed as the rotation speed N of a water pump pum And fan rotation speed N fan Function of (i.e. P) s ＝N pump T pump η pump +N fan T fan η fan Wherein T is pump Represents the torque, eta of the water pump pump Indicating the efficiency of the water pump, T fan Represents fan torque, eta fan Indicating fan efficiency; both the prediction time domain and the control time domain are set to N p The first term of the objective function is expressed as the lithium ion battery temperature and the target temperature T br The smaller the difference in value, the more the battery operates near the optimal temperature; the second term represents battery thermal management system cooling power consumption, with smaller values representing lower actuator power consumption during battery cooling. According to the difference between the actual temperature of the battery and the target temperature of the battery, the energy consumption of the two actuators of the water pump and the fan is considered, so that the corresponding control quantity of the objective function is solved.
In addition, the battery temperature, the water pump rotating speed and the fan rotating speed are controlled in a reasonable range, so that the restraint is imposed:
T b 1 ≤T b ≤T b 2
wherein T is b 1 Is the lower limit of the optimal operating temperature of the battery; t (T) b 2 Is the lower limit of the optimal operating temperature of the battery;is the minimum value of the rotation speed of the water pump, < >>Is the maximum value of the rotation speed of the water pump; />Is the minimum value of the rotation speed of the fan, < >>Is the maximum value of the rotational speed of the fan.
The examples are preferred embodiments of the present invention, but the present invention is not limited to the above-described embodiments, and any obvious modifications, substitutions or variations that can be made by one skilled in the art without departing from the spirit of the present invention are within the scope of the present invention.

Claims (10)

1. A control method of a battery thermal management system in a high-temperature environment in a pure electric automobile is characterized by comprising the following steps of:
comparing the driving characteristic parameter of the front vehicle with the real-time driving characteristic parameter of the host vehicle to obtain the instant speed weight which changes along with the driving of the host vehicleAnd average speed weight +.>Based on the weights, by the formula +.>Acquiring a driving characteristic parameter value of the next state of the vehicle, and further determining the future driving condition of the vehicle; wherein v is t+1,1n An instantaneous speed, v, representing the next state of the nth target preceding vehicle t+1,2n Representing the average speed of the next state of the nth target front vehicle;
determining the influence of the future driving working condition of the vehicle on a battery thermal management system, in particular to the influence on charge and discharge current in the reaction process of the lithium ion battery; the charge and discharge current and the lithium ion battery temperature in the lithium ion battery reaction process meet a lithium ion battery centralized thermal model under the liquid cooling condition, so that the lithium ion battery temperature corresponding to the future driving working condition of the vehicle is determined, the lithium ion battery temperature is compared with a battery working temperature threshold value, and the battery is judged to enter a radiator cooling mode or a chiller cooling mode;
and taking the minimum difference value between the temperature of the lithium ion battery and the target temperature and the optimal energy consumption of an actuator of the thermal management system as optimization targets, and solving the optimal output rotating speeds of the water pump and the fan in the cooling mode.
2. The control method of claim 1, wherein the instantaneous speed weightSatisfy the following requirementsWherein: v 1n For the instantaneous speed of the preceding vehicle, n=1, 2 … … m, n denotes the n-th target preceding vehicle, m denotes the total number of preceding vehicles, v 1 Is the instant speed of the vehicle.
3. The control method according to claim 1, characterized in that the average speed weightSatisfy the following requirementsWherein: v 2n For the average speed of the preceding vehicles, n=1, 2 … … m, n denotes the n-th target preceding vehicle, m denotes the total number of preceding vehicles, v 2 Is the average speed of the host vehicle.
4. The control method according to claim 1, wherein the influence of the future driving condition of the host vehicle on the charge-discharge current in the reaction process of the lithium ion battery is specifically:
wherein: i is charge-discharge current in the reaction process of the lithium ion battery, U 0 R is the open circuit voltage of a lithium ion battery 0 P is the sum of ohmic internal resistance and polarization internal resistance of lithium ion battery p Is the traction power of the electric automobile, P s Power of thermal management system of electric automobile, V v For the running speed of the vehicle F r For rolling resistance of vehicle, F a For vehicle air resistance, M v Is the total mass of the vehicle eta s For traction efficiency, deltaV v Is the vehicle running speed variation.
5. The control method according to claim 4, wherein the lithium ion battery integrated thermal model under the liquid cooling condition is:
wherein:ΔT b t is the temperature variation of the lithium ion battery b Is the temperature of the lithium ion battery, m b C, concentrating the mass of the battery b For specific heat capacity of battery, A b G is the contact area between the lithium ion battery and the cooling liquid 1 Is of intermediate quantity G l T is the mass flow of the cooling liquid l Is the temperature of the cooling liquid.
6. The control method according to claim 1, wherein whenThe battery enters a radiator cooling mode: the second port (2032) of the three-way valve is closed, the first port (2031) of the three-way valve is communicated with the third port (2033) of the three-way valve, the fan (301) is started, and the water pump (201) is started; wherein: />For the minimum temperature value of the battery at the moment of cooling of the radiator, is->The maximum temperature value of the battery at the time of cooling the radiator.
7. The control method according to claim 1, wherein whenThe battery enters a cooling mode of the water chiller: the first port (2031) of the three-way valve is closed, the second port (2032) of the three-way valve is communicated with the third port (2033) of the three-way valve, the fan (301) is closed, and the water pump (201) is opened; wherein->The maximum temperature value of the battery at the time of cooling the radiator.
8. The control method according to claim 4, wherein the objective function corresponding to the optimization objective is:
wherein: o (O) 1 With O 2 Is weight, T br For the target temperature, N p Representing a prediction time domain and a control time domain, and P s ＝N pump T pump η pump +N fan T fan η fan Wherein T is pump Represents the torque, eta of the water pump pump Indicating the efficiency of the water pump, T fan Represents fan torque, eta fan Indicating fan efficiency.
9. The control method according to claim 8, wherein the constraints satisfied by the battery temperature, the water pump rotation speed, and the fan rotation speed are:
wherein,,is the lower limit of the optimal operating temperature of the battery; />Is the lower limit of the optimal operating temperature of the battery; />Is the minimum value of the rotation speed of the water pump, < >>Is the maximum value of the rotation speed of the water pump; />Is the minimum value of the rotation speed of the fan, < >>Is the maximum value of the rotational speed of the fan.
10. A battery thermal management system implementing the control method according to any one of claims 1 to 9, characterized by comprising a chiller (101), a water pump (201), a power battery (202), a three-way valve (203), a radiator (204) and a fan (301), a chiller first port (1011) and a chiller second port (1012) being respectively in communication with the refrigerant circuit, a chiller fourth port (1014) being in communication with a three-way valve second port (2032), a three-way valve third port (2033) being in communication with the power battery first port (2021), the power battery second port (2022) being in communication with the water pump first port (2011), the water pump second port (2012) being in communication with an end point a, the end point a also being in communication with the chiller third port (1013), the radiator first port (2041), the radiator second port (2042) being in communication with the three-way valve first port (2031); the fan (301) is arranged at the radiator (204).
CN202310486152.6A 2023-04-28 2023-04-28 Battery thermal management system in high-temperature environment in pure electric vehicle and control method thereof Pending CN116512990A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117117397A (en) * 2023-10-25 2023-11-24 宁德时代新能源科技股份有限公司 Battery thermal management simulation method, device, system and storage medium
CN117691253A (en) * 2023-12-13 2024-03-12 北京卡文新能源汽车有限公司 Energy management method of efficient liquid cooling system and vehicle

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117117397A (en) * 2023-10-25 2023-11-24 宁德时代新能源科技股份有限公司 Battery thermal management simulation method, device, system and storage medium
CN117117397B (en) * 2023-10-25 2024-03-19 宁德时代新能源科技股份有限公司 Battery thermal management simulation method, device, system and storage medium
CN117691253A (en) * 2023-12-13 2024-03-12 北京卡文新能源汽车有限公司 Energy management method of efficient liquid cooling system and vehicle

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