CN113851757A

CN113851757A - Power battery thermal management method and device

Info

Publication number: CN113851757A
Application number: CN202111121840.XA
Authority: CN
Inventors: 任庆鑫
Original assignee: Jingwei Hengrun Tianjin Research And Development Co ltd
Current assignee: Jingwei Hengrun Tianjin Research And Development Co ltd
Priority date: 2021-09-24
Filing date: 2021-09-24
Publication date: 2021-12-28
Anticipated expiration: 2041-09-24
Also published as: CN113851757B

Abstract

The invention provides a power battery thermal management method and a device, which are applied to the technical field of automobiles. The forced cooling device is started before the target driving moment, so that the forced cooling device cools the power battery in advance, the performance requirement on the forced cooling device can be effectively reduced, and the overall cost control of the vehicle is facilitated.

Description

Power battery thermal management method and device

Technical Field

The invention belongs to the technical field of automobiles, and particularly relates to a power battery heat management method and device.

Background

In recent years, power batteries used by new energy vehicles are continuously developed towards high energy density, the high energy density power batteries are necessarily accompanied with high heat output during working, and in order to ensure that the power batteries are in a proper working temperature range during working, the new energy vehicles need to adopt a corresponding heat management method to control heat generation, particularly a heat dissipation process of the new energy vehicles.

The existing power battery thermal management method generally obtains the maximum temperature Tmax of the power battery according to the monitoring of a battery management system, and determines which management measure is taken according to the size relation between the maximum temperature Tmax and a preset temperature threshold. For example, if the maximum temperature Tmax of the power battery is greater than or equal to a preset temperature threshold T1, the forced cooling device is started to perform forced cooling on the power battery; if the maximum temperature Tmax of the power battery is larger than or equal to a preset temperature threshold T2 which is higher than T1, in order to ensure the safety of the power battery and the vehicle, the output power of the power battery is limited forcibly, and the battery is prevented from further generating a large amount of heat.

The conventional thermal management method is realized based on the actual temperature of the power battery, when the actual temperature of the power battery reaches a preset temperature threshold value T1, the power battery is actually in a higher temperature state, more importantly, the power battery still generates heat continuously, forced cooling is performed at the moment, the temperature of the power battery can be rapidly reduced in a short time by the forced cooling device with sufficient cooling capacity, the performance requirement on the forced cooling device is high, and the overall cost control of a vehicle is not facilitated.

Further, if the cooling capacity of the forced cooling device is insufficient, the battery temperature is greater than or equal to the preset temperature threshold T2, and a power limiting measure is triggered, so that the vehicle cannot effectively respond to the driving demand, and the driving experience of the user is affected.

Disclosure of Invention

In view of the above, the present invention provides a method and a device for thermal management of a power battery, which predict a temperature of the power battery, and start a forced cooling device before the power battery reaches a maximum temperature, so that the power battery has enough time to cool down, thereby solving the problems in the prior art, and the specific scheme is as follows:

in a first aspect, the invention provides a power battery thermal management method, which includes:

acquiring reference driving data of a vehicle, and taking the reference driving data as target driving data;

determining the running duration of the vehicle and a first mapping relation according to the target running data; the first mapping relation records the corresponding relation between the output current and the running time of a power battery of the vehicle in the running time;

determining a second mapping relation based on a power battery heat balance equation and the first mapping relation;

the second mapping relation records the corresponding relation between the working temperature of the power battery and the running time under the condition that the power battery is controlled to work according to the first mapping relation and a natural cooling mode is adopted;

acquiring the highest working temperature recorded in the second mapping relation and the target driving time corresponding to the highest working temperature;

and if the maximum working temperature is greater than or equal to a preset temperature threshold value, starting a forced cooling device before the target driving moment.

Optionally, the turning on the forced cooling device before the target driving time includes:

acquiring a preset starting time of the forced cooling device;

determining the target forced cooling starting time within the candidate duration;

wherein the candidate duration is a duration between a starting time of the running duration and the target running time, and the candidate duration does not include the target running time;

the target forced cooling starting time is the running time corresponding to the preset temperature threshold value when the working temperature of the power battery in the running time is smaller than the preset temperature threshold value;

and controlling the forced cooling device to be started at the target forced cooling starting moment and continuously operating for the preset starting duration.

Optionally, the determining the target forced cooling start time within the candidate duration includes:

selecting at least one driving moment in the candidate duration as a first candidate forced cooling starting moment;

respectively determining a third mapping relation corresponding to each first candidate strong cold starting moment based on a power battery heat balance equation and the first mapping relation;

the third mapping relation records the corresponding relation between the working temperature of the power battery and the running time under the condition that the power battery is controlled to work according to the first mapping relation and the forced cooling device is controlled to be started at the first candidate strong cold starting time and continuously run for the preset starting time;

if at least one third mapping relation meets a first preset screening condition, determining a target forced cooling starting time in first candidate forced cooling starting times corresponding to all third mapping relations meeting the first preset screening condition;

wherein the first preset screening condition comprises: and any working temperature of the power battery recorded in the third mapping relation is smaller than the preset temperature threshold.

Optionally, the determining a target forced cooling start time in the first candidate forced cooling start times corresponding to the third mapping relationships that satisfy the first preset screening condition includes:

taking a third mapping relation meeting the first preset screening condition as a target third mapping relation;

respectively calculating the average value of the working temperature recorded in each target third mapping relation to obtain a corresponding temperature average value;

and taking the first candidate forced cooling starting time corresponding to the target third mapping relation with the minimum temperature mean value as the target forced cooling starting time.

screening a second candidate strong cold starting moment in the candidate duration based on a power battery heat balance equation and a dichotomy, and recording a fourth mapping relation;

the fourth mapping relation records a corresponding relation between the working temperature of the power battery and the driving time under the condition that the power battery is controlled to work according to the first mapping relation and the forced cooling device is controlled to be started at the second candidate strong cold starting time and continuously operates for the preset starting time, and any working temperature of the power battery recorded in the fourth mapping relation is smaller than the preset temperature threshold value;

and determining a target strong cold starting time in the second candidate strong cold starting time.

Optionally, the power battery thermal management method provided by the first aspect of the present invention further includes:

in the process of screening a second candidate strong cold starting time within a candidate duration based on a dichotomy, if the second candidate strong cold starting time meeting a second preset screening condition exists, determining the second candidate strong cold starting time corresponding to the second preset screening condition as a target strong cold starting time, and stopping screening;

the second preset screening condition includes: and under the conditions that the power battery is controlled to work according to the first mapping relation, and the forced cooling device is controlled to be started at the second candidate strong cold starting moment and continuously run for the preset starting duration, the average value of the working temperature of the power battery is smaller than the service life temperature threshold, and the service life temperature threshold is smaller than the preset temperature threshold.

in the process of screening the second candidate strong cold starting time in the candidate duration based on the dichotomy, if the condition is met

Stopping temperature screening; wherein, Δ t is a preset time duration, n is a set value, Y is a candidate time duration, and p is the number of times that the screening has been executed.

Optionally, if the target forced cooling starting time is not determined in the candidate time, increasing the preset starting time, and returning to execute the step of determining the target forced cooling starting time in the candidate time.

calculating the average value of the actual output current of the power battery in the target duration to obtain the actual measurement current average value;

calculating the average value of the output current of the power battery under the condition that the power battery is controlled to work according to the first mapping relation in the target duration to obtain a predicted current average value;

if the difference value between the actually measured current mean value and the predicted current mean value exceeds a preset current range, taking actual driving data of the vehicle as the target driving data;

and returning to the step of determining the running time of the vehicle and the first mapping relation according to the target running data.

In a second aspect, the present invention provides a power battery thermal management device, including:

a first acquisition unit configured to acquire reference travel data of a vehicle and to use the reference travel data as target travel data;

the first determining unit is used for determining the running time of the vehicle and a first mapping relation according to the target running data;

the first mapping relation records the corresponding relation between the output current and the running time of a power battery of the vehicle in the running time;

the second determining unit is used for determining a second mapping relation based on the power battery heat balance equation and the first mapping relation;

a second obtaining unit configured to obtain a maximum operating temperature described in the second mapping relationship and a target travel time corresponding to the maximum operating temperature;

and the control unit is used for starting a forced cooling device before the target driving moment if the highest working temperature is greater than or equal to a preset temperature threshold value.

According to the power battery thermal management method and device provided by the invention, after reference driving data of a vehicle are obtained and the obtained reference driving data are taken as target driving data, the driving duration and the first mapping relation of the vehicle are determined according to the target driving data, and the second mapping relation is further determined based on the power battery thermal balance equation and the first mapping relation, wherein the first mapping relation records the corresponding relation between the output current and the driving time of the power battery of the vehicle during the driving duration; and recording the corresponding relation between the working temperature of the power battery and the driving time under the condition that the power battery is controlled to work according to the first mapping relation and a natural cooling mode is adopted by the second mapping relation, namely, finishing the prediction of the working temperature of the power battery at each driving time within the driving time through the first mapping relation and the second mapping relation, then obtaining the highest working temperature recorded in the second mapping relation and the target driving time corresponding to the highest working temperature, and if the obtained highest working temperature is more than or equal to a preset temperature threshold value, starting the forced cooling device before the target driving time.

According to the thermal management method and device provided by the invention, the working temperature of the power battery is predicted based on the reference driving data, if the highest working temperature in the prediction result is greater than or equal to the preset temperature threshold, forced cooling is necessary, the forced cooling device is started before the target driving moment corresponding to the highest working temperature, so that the forced cooling device cools the power battery in advance.

Furthermore, as the power battery is cooled in advance, the temperature of the power battery cannot be further increased, and then a protective measure for limiting power output cannot be triggered, so that the driving requirement of the vehicle can be effectively responded, and the driving experience of a user is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a flowchart of a power battery thermal management method according to an embodiment of the present invention;

FIG. 2 is a flow chart of another method for thermal management of a power battery according to an embodiment of the present invention;

FIG. 3 is a flow chart of a method for thermal management of a power battery according to another embodiment of the present invention;

fig. 4 is a structural block diagram of a power battery thermal management device according to an embodiment of the present invention;

fig. 5 is a block diagram of another power battery thermal management device according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in 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 derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The power battery thermal management method provided by each embodiment of the invention can be applied to a controller of a battery management system in a finished automobile, can also be applied to other controllers which can acquire various driving data, execute a preset control program and control the output of a power battery in the finished automobile, and can also be applied to a server on a network side under certain conditions.

Referring to fig. 1, fig. 1 is a flowchart of a power battery thermal management method according to an embodiment of the present invention, and as shown in fig. 1, the flowchart may include:

and S100, acquiring reference running data of the vehicle, and taking the reference running data as target running data.

In the method for thermal management of a power battery provided by the embodiment, the reference driving data mainly refers to parameters which can be used for determining the driving time length of the vehicle and the output current change condition of the power battery in the driving time length during the driving process of the vehicle, particularly during a determined driving cycle. Since the parameters acquired in S100 are prepared for determining the travel time period and the first mapping relationship in S110, which parameters are specifically acquired in this step is relevant to the specific method of determining the travel time period and the first mapping relationship in S110.

In practical applications, the reference driving data may include a departure point, a destination point, a current SOC (State of Charge) value, a current SOE (State of Energy) value, historical data of output current of the power battery, road condition information from the departure point to the destination point, road network change information, traffic signal setting conditions, and the like, which are not listed one by one herein.

It should be noted that the method provided by the embodiment of the present invention is started after the vehicle is started in most cases, that is, the reference driving data herein is mostly obtained or predicted directly based on the history data and the current state of the vehicle, so in this step, the reference driving data is first used as the target driving data for the subsequent control process, if it is found that the deviation between the control based on the reference driving data and the actual situation is large in the actual driving process, the method provided by the present invention will change to the subsequent management process based on the actual driving data of the vehicle, that is, the actual driving data is used as the target driving data, thereby achieving a better management effect.

As to how to judge whether the target driving data needs to be switched, detailed descriptions will be provided in the following text, and will not be described in detail here.

And S110, determining the running time of the vehicle and the first mapping relation according to the target running data.

First, it is conceivable that, in the present embodiment, the driving duration of the vehicle refers to the driving duration in the current driving cycle, that is, if the vehicle does not shut down on the way from the departure point to the destination, the whole process is one driving cycle, and if the vehicle stops on several times on the way from the departure point to the destination, the driving cycle can be theoretically divided into a plurality of driving cycles, and in such a case, the management method provided by the present invention needs to be executed in each driving cycle.

Further, in the first mapping relationship according to the embodiment of the present invention, a corresponding relationship between the output current and the driving time of the power battery of the vehicle during the driving period, that is, a change relationship of the output current of the power battery with time during the driving cycle, is mainly recorded.

The specific embodiment of the first mapping relationship may be a functional relationship between the output current of the power battery and the driving time, that is, expressed by a specific functional expression, or may be a curve in which the output current varies with the driving time, or may be a set of data pairs, each data pair recording a driving time and the output current corresponding to the driving time.

The specific determination process for the first mapping relationship may be implemented by combining the prior art, for example:

1. and the pre-estimation of the first mapping relation is realized by combining a vehicle-mounted or mobile phone navigation system. For example, the destination input on the vehicle or mobile phone navigation can directly predict the arrival time, namely the driving time through calculation, the prediction of the arrival time is comprehensively calculated according to a scientific data model system and a navigation system tested by a large number of users for years, and factors such as big data accumulation, real-time road condition study and judgment, road network road condition evolution trend estimation, road historical operation data comparison and the like, and even the number of traffic lights in a road and the waiting time can be predicted, so that the change condition of the output current of the power battery in a long time during driving can be obtained.

2. Based on historical driving data of a user recorded by a vehicle BMS (Battery Management System), and in combination with SOC or SOE calculated by the BMS, the change condition of the output current of the power Battery is estimated when the vehicle runs to a driving time corresponding to the SOC or SOE being 0.

3. And (3) taking the working condition of the NEDC (New European Driving Cycle) as the estimation of the working condition of the Driving current, and estimating the change condition of the output current of the power battery in the Driving time period corresponding to the running of the NEDC working condition to the SOC or SOE as 0 by combining the SOC or SOE calculated by the BMS.

In practical application, of course, other methods may be adopted to obtain the change condition of the output current of the power battery within the estimated driving time, which are not listed here.

And S120, determining a second mapping relation based on the power battery heat balance equation and the first mapping relation.

The heat balance equation of the power battery designed in the embodiment and the subsequent embodiments of the invention is as follows:

Q_p，n-Q_n，n-Q_c，n＝C_bm_b(T_n+1-T_n)

wherein Q is_p，nThe heat generated by the power battery in the running time corresponding to the running time n + 1; q_n，nThe heat dissipated by the power battery in a natural cooling mode in the running time period corresponding to the running time n + 1; q_c，nQ is the heat dissipated by the power battery in a forced cooling mode in the running time period corresponding to the running time n +1, and under the condition of adopting a natural cooling mode_c，n＝0；C_bThe specific heat capacity of the power battery; m is_bIs the mass of the power battery; t is_n+1The temperature of the power battery corresponding to the driving time n + 1; t is_nAs the time of traveln corresponds to the temperature of the power cell.

The following describes the method of obtaining each parameter term involved in the above-described heat balance equation.

For Q_p，nThe embodiment of the invention is realized by adopting a Bernadi heat production model, and the expression of the model is as follows:

wherein the content of the first and second substances,

is t_nAt the moment, the heat-generating power of the power battery is assumed to be t_n+1-t_nA smaller time period, the time period can be considered as the time period

Keeping the same; i is the working current of the power battery estimated based on the first mapping relation; the OCV is the open-circuit voltage of the power battery and is related to the SOC value of the power battery and the battery temperature T; u is the actual working voltage of the power battery; f is the temperature of the power battery, it should be noted that the parameter T is the measured temperature of the power battery at the initial time of the driving cycle, and in the subsequent application, is the predicted temperature.

I (OCV-U) calculating to obtain joule heat caused by internal resistance of the battery and polarization heat caused by mass transfer loss;

and calculating to obtain the reaction heat of the anode and the cathode of the power battery.

When the power battery leaves the factory, the battery manufacturer measures the OCV in detail, and can obtain the corresponding OCV and the OCV for actual products

And (4) information.

For Q_n，nThe calculation of (2) can be realized based on Newton's cooling law, which has the following relation:

wherein, T_e，nThe ambient temperature outside the power battery pack (namely the power battery) at the moment n; r_nThe thermal resistance is the heat transfer convection resistance between the power battery pack and the external environment.

In practical application, R_nThe value of (c) is influenced by the relative velocity Ve between the power cell pack and the surrounding air, and can therefore be determined as follows:

placing the power battery pack to be tested in a wind tunnel or a temperature box, adjusting the temperature of the wind tunnel or the temperature box to be the maximum temperature Tmax allowed by the power battery pack, and standing until the temperature of all battery monomers in the battery pack is Tmax +/-1 ℃. Starting the test, adjusting the temperature of the wind tunnel or the incubator to Te (Te is less than Tmax, which is the environment temperature in which the vehicle may run, for example, the temperature range is-30 to 50 ℃, then the temperature can be selected by taking 10 ℃ as the gradient, the smaller the gradient, the R obtained by measurement_nThe more accurate) and controlling the wind speed in the incubator to be Ve (for example, the possible speed interval of the vehicle is 0-120 km/h, then 10km/h can be selected as a gradient, the smaller the gradient, the R obtained by measurement_nThe more accurate) until the temperature of all the battery cells in the battery pack stabilizes to Te +/-1 ℃, and stopping the test. And in the test process, recording the battery temperature at different moments. R is obtained according to the test procedure_nThe following were used:

wherein R is_nIs at ambient temperature T_eThe thermal resistance of convective heat transfer at n moments under the condition of the relative speed Ve between the power battery pack and the ambient air,T_mand T_m+1The temperature of the power battery pack to be tested during the test is shown. According to the above test, the battery temperature T can be obtained_bAmbient temperature T_eR related to the relative velocity Ve between the battery pack and the surrounding air_nValue of (a) can be used to calculate Q_n，nThe preparation is used.

Further, for Q_c，nThe calculation of (2) can also be realized according to Newton's cooling law:

wherein, T_c，mThe temperature is the cooling temperature of the forced cooling mode at the moment m, if the temperature is liquid cooling, the temperature is the cooling liquid temperature, and if the temperature is direct cooling, the temperature is the refrigerant evaporation temperature; r_c，nAnd heat transfer resistance is provided for the power battery pack and the forced cooling device.

Wherein R is_c，nThe value of (A) can be determined as follows:

the power battery pack is placed in a wind tunnel or a warm box, the temperature of the wind tunnel or the warm box is adjusted to be the highest temperature Tmax allowed by the power battery pack, and the power battery pack is placed until the temperature of all battery monomers in the power battery pack is Tmax +/-1 ℃. Starting the test, adjusting the temperature of the wind tunnel or the incubator to T_c，mStarting forced cooling until all the battery monomers in the battery pack are stabilized to T_c，mThe test was stopped at + -1 ℃. And in the test process, recording the battery temperature at different moments. R is obtained according to the test procedure_c，nThe following were used:

it is conceivable that the above-described acquisition process of the relevant parameters is performed between the actual application of the power battery to the entire vehicle, and after the corresponding parameters are obtained, the parameters can be directly applied to the use process of the power battery, and it is not necessary to repeatedly measure the above-described parameters during the use process of the vehicle. Based on the above, in combination with Q_p，n-Q_n，n-Q_c，n＝C_bm_b(T_n+1-T_n) And the corresponding relation between the output current of the power battery and the driving time recorded in the first mapping relation can obtain the change relation of the working temperature of the power battery along with the driving time.

In this step, since it is necessary to first obtain the corresponding relationship between the operating temperature of the power battery under the self-cooling condition and the driving time, it is necessary to use Q in the aforementioned thermal balance equation of the power battery_c，nAnd zero is taken, so that the corresponding relation between the working temperature of the power battery and the running time, namely the second mapping relation can be obtained under the condition that the power battery is controlled to work according to the first mapping relation and a natural cooling mode is adopted. Correspondingly, the forced cooling is started in the control process to obtain the corresponding Q_c，nAnd obtaining the corresponding relation between the working temperature of the power battery and the driving time of the power battery in the forced cooling mode.

And S130, acquiring the maximum working temperature recorded in the second mapping relation and the target running time corresponding to the maximum working temperature.

As described above, the second mapping relation records the operating temperature of the power battery at each driving time within the driving time period, and therefore, the operating temperature corresponding to any driving time can be obtained by querying the second mapping relation. Based on this, the highest operating temperature recorded therein and the target travel time corresponding to the highest operating temperature can be obtained by traversing the second mapping relationship.

S140, judging whether the highest working temperature is greater than or equal to a preset temperature threshold value, and if so, executing S150.

The preset temperature threshold mentioned in the embodiment of the invention can be set based on the allowable highest temperature of the power battery in practical application, and the specific value of the preset temperature threshold is not limited in the embodiment of the invention, and can be flexibly selected according to the actual control and protection requirements.

After the maximum working temperature is obtained, judging the magnitude relation between the obtained maximum working temperature and a preset temperature threshold, wherein as can be seen from the foregoing, the maximum working temperature mentioned herein is obtained under a self-cooling condition, so that if the maximum working temperature is less than the preset temperature threshold, it indicates that the working temperature of the power battery does not exceed the preset temperature threshold in a natural cooling mode of the vehicle within the whole driving duration, and it can be further determined that the forced cooling device does not need to be started in the current driving cycle, and the current management process can be temporarily exited; correspondingly, if the obtained maximum working temperature is greater than or equal to the preset temperature threshold, it indicates that the forced cooling device needs to be started in the current driving cycle, and then S150 is continuously executed.

And S150, starting the forced cooling device before the target running time.

In specific application, the time and duration for starting the forced cooling device are determined according to a preset temperature threshold, and the maximum working temperature of the power battery can be smaller than the preset temperature threshold by starting the forced cooling device.

In the management method provided by the embodiment of the invention, in order to reduce the performance requirement on the forced cooling device and provide a better operating environment for the power battery, after the target driving time needing the highest working temperature is determined, the forced cooling device is started when the driving time reaches the target driving time, and the temperature of the power battery is reduced in advance.

In summary, according to the thermal management method provided in the embodiment of the present invention, the operating temperature of the power battery is predicted based on the reference driving data, and if the maximum operating temperature in the prediction result is greater than or equal to the preset temperature threshold, it is determined that forced cooling is necessary, the forced cooling device is started before the target driving time corresponding to the maximum operating temperature, so that the forced cooling device cools the power battery in advance.

Based on the above, it is conceivable that the key to achieving the above management object is how to determine at which time before the target driving time the forced cooling device is turned on, and for this reason, the embodiment of the present invention provides a more specific embodiment, and develops a specific implementation manner of S150 in the above-described embodiment.

Optionally, referring to fig. 2, fig. 2 is a flowchart of another power battery thermal management method according to an embodiment of the present invention, and based on the flowchart shown in fig. 1, a specific process of starting the forced cooling device before the target driving time may include:

and S200, acquiring the preset starting time of the forced cooling device.

In practical applications, the preset opening time may be set based on the minimum opening time of the forced cooling device, and in general, the preset opening time may be set as the minimum opening time of the forced cooling device, and of course, other time longer than the minimum opening time may be selected.

And S210, determining the target forced cooling starting time in the candidate duration.

Specifically, the candidate time period mentioned in the embodiment of the invention is the time period between the start time of the aforementioned running time period and the target running time, and it is conceivable that the candidate time period does not include the target running time because the forced cooling device is to be turned on before the target running time. Correspondingly, the target forced cooling starting time is the running time corresponding to the preset temperature threshold value, so that the working temperature of the power battery in the running time is lower than the running time corresponding to the preset temperature threshold value, namely if the forced cooling device is started at the target forced cooling starting time and the running time is maintained for the preset starting time, the working temperature of the power battery in the current driving cycle can be ensured not to be higher than the preset temperature threshold value any more.

Alternatively, referring to fig. 3, fig. 3 is a flowchart of another power battery management method according to an embodiment of the present invention, where the method for determining the target forced cooling start time is mainly provided, and specifically,

s300, selecting at least one driving moment in the candidate duration as a first candidate strong cold starting moment.

Firstly, the number of the first candidate strong cold starting time is selected, a plurality of the first candidate strong cold starting times can be simultaneously selected in the candidate duration, and the subsequent steps are respectively executed aiming at each first candidate strong cold starting time, so that the processing mode needs a processor with strong computing capability and high requirements on equipment hardware; correspondingly, only one first candidate strong cold starting time can be selected each time, and the subsequent operation steps are executed aiming at the first candidate strong cold starting time, so that the requirement on the hardware performance of the processor can be obviously reduced.

Secondly, for the specific selection of the candidate forced cooling starting time, any time in the candidate duration can be used as the first candidate forced cooling starting time in a traversal mode.

And S310, respectively determining a third mapping relation corresponding to each first candidate strong cold starting moment based on the power battery heat balance equation and the first mapping relation.

As mentioned above, in the case that the power battery adopts the natural cooling mode, the Q in the power battery heat balance equation can be adjusted_c，nTaking zero, correspondingly, starting forced cooling in the control process to obtain corresponding Q_c，nAnd obtaining the corresponding relation between the working temperature of the power battery and the driving time of the power battery in the forced cooling mode. The main purpose of this step is to obtain the relevant data of the power battery under the forced cooling condition, therefore, in the heat balance equation of the power battery mentioned in this step, Q_c，nAnd needs to participate in a specific calculation process.

Based on the definition of the second mapping relationship, the third mapping relationship mentioned in this embodiment refers to a corresponding relationship between the operating temperature of the power battery and the driving time recorded when the power battery is controlled to operate according to the first mapping relationship and the forced cooling device is controlled to be turned on at the first candidate strong cold start time and continuously operated for the preset turn-on duration.

That is, through the foregoing steps, the corresponding relationship between the output current of the power battery and the driving time, that is, the first mapping relationship, and the first candidate strong cold start time and the preset start time of the forced cooling device, are already obtained, and in this step, it is necessary to further obtain the corresponding relationship between the operating temperature of the power battery and the driving time in the case where the output current of the power battery is controlled according to the first mapping relationship, the forced cooling device is controlled to be started at the first candidate strong cold start time and continuously operated for the preset start time.

It should be noted that, for each first candidate strong cold start time, a corresponding third mapping relationship needs to be obtained, that is, one first candidate strong cold start time corresponds to one third mapping relationship, and for the obtaining process of each third mapping relationship, the obtaining process of the second mapping relationship may be implemented by referring to the obtaining process of the second mapping relationship, which is not described herein again.

And S320, judging whether at least one third mapping relation meets a first preset screening condition, and if so, executing S330.

Optionally, the first preset screening condition is: and any working temperature of the power battery recorded in the third mapping relation is smaller than a preset temperature threshold value.

If at least one third mapping relation meets the first preset screening condition, it indicates that at least one management process exists, the working temperature of the power battery in the whole running duration can be smaller than the preset temperature threshold, and the expected control target can be reached, in which case, S330 is continuously executed.

If any third mapping relation does not meet the first preset screening condition, it indicates that the current preset opening time of the forced cooling is difficult to meet the cooling requirement, the preset opening time needs to be further increased, and the control flow provided by the embodiment shown in fig. 2 is executed again until at least one third mapping relation meeting the first preset screening condition is determined. The specific content of increasing the preset opening time length will be expanded in the following, and will not be detailed here.

S330, determining a target forced cooling starting time in the first candidate forced cooling starting times corresponding to all the third mapping relations meeting the first preset screening condition.

Specifically, if only one third mapping relationship satisfying the first preset screening condition exists, the first candidate strong cold start time corresponding to the third mapping relationship is taken as the target strong cold start time, and if the third mapping relationships satisfying the first preset screening condition include a plurality of third mapping relationships, one of the plurality of third mapping relationships satisfying the first preset screening condition needs to be selected.

Optionally, when the number of the third mapping relationships meeting the first preset screening condition is multiple, the third mapping relationships meeting the first preset screening condition may be used as target third mapping relationships, the average value of the working temperatures recorded in each target third mapping relationship is respectively calculated to obtain a corresponding temperature average value, and then the first candidate forced cooling start time corresponding to the target third mapping relationship with the smallest temperature average value is used as the target forced cooling start time.

It is conceivable that the target third mapping relation determined according to the above process may minimize the operating temperature of the power battery, which is more beneficial to prolonging the service life of the power battery.

Optionally, in practical applications, it is possible that the running time is very long, so that the range of the candidate time is also relatively large, the whole process of determining the target forced cooling start time takes a long time, and the computing capability and the computing time of the processor are greatly challenged.

In order to determine the target forced cooling starting time in a short time, it may be further determined whether at least one third mapping relationship satisfies a second preset screening condition, and the target forced cooling starting time is determined in the first candidate forced cooling starting time corresponding to each third mapping relationship satisfying the second preset screening condition.

The second preset screening condition in this embodiment is: the average value of the working temperatures of the power batteries recorded in the third mapping relation is smaller than the service life temperature threshold, and the service life temperature threshold is smaller than the preset temperature threshold.

Specifically, the life temperature threshold mentioned in this embodiment refers to an average temperature of the power battery allowed by the power battery reaching the required service life, and if the average temperature of the power battery in the whole working process is not greater than this value, it indicates that the service life of the power battery is not damaged by the current driving cycle.

Of course, if there are a plurality of third mapping relationships that satisfy the second preset screening condition, the target third mapping relationship may also be selected according to the temperature mean value of the power battery corresponding to each third mapping relationship, and details thereof are not repeated here.

And S220, controlling the forced cooling device to be started at the target forced cooling starting moment and continuously operating for a preset starting duration.

After the target strong cold starting time is determined, the forced cooling device can be controlled to be started at the target strong cold starting time and continuously run for a preset starting time, and under the condition, the working temperature of the power battery in the whole driving cycle cannot exceed a preset temperature threshold value, so that the normal use of the power battery is ensured.

Alternatively, if the target forced cooling start time is not determined within the candidate time period according to the method provided by the embodiment shown in fig. 3, which indicates that the on-time period of the forced cooling device is not long enough to effectively reduce the temperature of the power battery, in this case, it is necessary to increase the preset on-time period, that is, the time for controlling the forced cooling device to start is longer, and then to execute the method provided by the embodiment shown in fig. 3 again, of course, it can also be understood that the step S210 in the embodiment shown in fig. 2 is executed again until the target forced cooling start time is obtained.

Optionally, there are various specific ways to increase the preset opening duration, for example, the preset opening duration may be increased in multiple according to a preset multiple, or the preset opening duration may be increased according to a preset amplification ratio, which are all preferable, and on the premise of not exceeding the scope of the core idea of the present invention, the present invention also falls within the protection scope of the present invention.

In summary, the present embodiment provides a method for determining when to specifically start a forced cooling device, according to the method provided in the present embodiment, not only can the forced cooling device be started in advance, and the hardware requirement for the forced cooling device is reduced, but also it can be ensured that the operating temperature of the power battery in the whole driving cycle does not exceed the preset temperature threshold, which is helpful for prolonging the service life of the power battery.

Based on the method for determining the target forced cooling start time provided by the embodiment shown in fig. 3, if the number of the first candidate forced cooling start times is large, and it is very likely that the preset start time needs to be continuously adjusted, a longer time is consumed in the process of determining the target forced cooling start time, which not only occupies a large amount of hardware resources, but also affects the thermal management effect of the power battery, and even affects the service life of the power battery. Therefore, the embodiment of the invention also provides a method for determining the target forced cooling starting time based on the dichotomy and the power battery heat balance equation.

Specifically, when the target strong cold starting time is determined in the candidate duration, a second candidate strong cold starting time is screened in the candidate duration based on a power battery thermal balance equation and a dichotomy, and a fourth mapping relation is recorded. The fourth mapping relation mentioned in this embodiment records a corresponding relation between the operating temperature of the power battery and the driving time when the power battery is controlled to operate according to the first mapping relation and the forced cooling device is controlled to be turned on at the second candidate strong cold start time and continuously operated for a preset turn-on duration, and any operating temperature of the power battery recorded in the fourth mapping relation is smaller than a preset temperature threshold. Then, in each second candidate strong cold start time, a target strong cold start time is determined.

The implementation process of the above embodiment is specifically described below with reference to a specific dichotomy:

assuming that the maximum working temperature occurs at the time Y within the candidate time period, the driving time period is Z, and the preset opening time period of the forced cooling device is Δ t, then:

the temperature of the target strong cooling starting moment is estimated for the 1 st time in a 0-Z time period by a dichotomy, and the process is as follows:

during the time period of 0-Y/2, T is calculated according to the following formula_n+1：

During the time period of Y/2-Y/2 + delta T, T is calculated according to the following formula_n+1：

During the time period of Y/2+ delta T-Z, T is calculated according to the following formula_n+1：

Judging whether the fourth mapping relation obtained by the temperature estimation meets the preset screening condition or not, and if so, recording that the fourth mapping relation is T (t) 1. Wherein, the preset screening conditions comprise: and under the conditions that the power battery is controlled to work according to the first mapping relation, and the forced cooling device is controlled to continuously run at the starting moment determined according to the bisection method for the preset starting duration, any working temperature of the power battery is smaller than the preset temperature threshold.

According to the preset opening duration delta t, carrying out temperature estimation for the 2 nd time at the target forced cooling opening time within the time periods of 0-Y/2 and Y/2-Y by a dichotomy respectively, namely, starting the forced cooling device within the time periods of Y/4-Y/4 + delta t and 3Y/4-3Y/4 + delta t in sequence, temporarily recording the obtained fourth mapping relations as T (t)11 and T (t)12 respectively, and respectively judging whether the corresponding fourth mapping relations meet the preset screening conditions:

if T (t)11 meets the preset screening condition and T (t)12 does not meet the preset screening condition, recording T (t)11 as T (t)2 when the fourth mapping relation obtained by the 1 st temperature estimation meets the preset screening condition, recording T (t)11 as T (t)1 when the fourth mapping relation obtained by the 1 st temperature estimation does not meet the preset screening condition, and neglecting the cooling starting interval of the forced cooling starting time estimation scheme of the T (t)12 in the subsequent dichotomy temperature estimation, namely not continuously predicting the forced cooling starting and stopping time in the Y/2-Y time period;

if T (t)12 meets the preset screening condition and T (t)11 does not meet the preset screening condition, recording T (t)12 as T (t)2 when the fourth mapping relation obtained by the 1 st temperature estimation meets the first preset screening condition, recording T (t)12 as T (t)1 when the fourth mapping relation obtained by the 1 st temperature estimation does not meet the preset screening condition, and neglecting the cooling opening interval of the forced cooling opening time estimation scheme for obtaining T (t)11 in the subsequent dichotomy temperature estimation, namely not continuously predicting the forced cooling opening and closing time within the time period of 0-Y/2;

if both T (t)11 and T (t)12 meet the preset screening condition, comparing the temperature mean values of T (t)11 and T (t)12, recording the smaller of the T (t)11 and T (t)12 when the fourth mapping relation obtained by the 1 st temperature estimation meets the preset screening condition as T (t)2, recording the smaller of the T (t)1 when the fourth mapping relation obtained by the 1 st temperature estimation does not meet the preset screening condition, neglecting the larger of the obtained temperature mean values of T (t)11 and T (t)12 in the subsequent dichotomy temperature prediction, and not continuously predicting the forced cooling start-stop time in the corresponding time period;

if the T (t)11 and the T (t)12 do not meet the preset screening condition, the fourth mapping relation is not recorded, and the cooling opening interval of the cooling forced cooling opening time estimation scheme for obtaining the T (t)11 and the T (t)12 is reserved, namely the forced cooling start-stop time estimation is continued in the corresponding time period.

By analogy, the ith reserved fourth mapping relation is recorded as t (t) i, where i is 1, 2, 3 … …; when the temperature is estimated next time, estimating the start-stop time of the continuous forced cooling in the reserved time period, starting the forced cooling device in the corresponding time period, temporarily recording the obtained fourth mapping relations as T (t) i1 and T (t) i2 respectively, and respectively judging whether the corresponding fourth mapping relations meet the preset screening conditions:

if T (t) i1 meets the preset screening condition and T (t) i2 does not meet the preset screening condition, recording T (t) i1 as T (t) i +1, and neglecting a cooling opening interval of the forced cooling opening time estimation scheme for obtaining T (t) i2 in the subsequent dichotomy temperature prediction;

if T (t) i2 meets the preset screening condition and T (t) i1 does not meet the preset screening condition, recording T (t) i2 as T (t) i +1, and neglecting a cooling opening interval of the forced cooling opening time estimation scheme for obtaining T (t) i1 in the subsequent dichotomy temperature prediction;

if both T (t) i1 and T (t) i2 meet the preset screening condition, comparing the temperature mean values of T (t) i1 and T (t) i2, recording the smaller of the temperature mean values as T (t) i +1, in the subsequent dichotomy temperature prediction, neglecting the larger of the temperature mean values of T (t) i1 and T (t) i2, and not continuously predicting the forced cooling start-stop time in the corresponding time period;

if the T (t) i1 and the T (t) i2 do not meet the preset screening condition, reserving a cooling opening interval of the cooling forced cooling opening time estimation scheme for obtaining the T (t) i1 and the T (t) i2, namely estimating the start-stop time of continuous forced cooling in a corresponding time period;

optionally, in the process of screening the second candidate strong cold start time within the candidate duration based on the dichotomy, if the condition is met

Stopping temperature screening; wherein, Δ t is a preset duration, Y is a candidate duration, and q is the number of times that the screening has been performed.

In another alternative scheme, in the process of screening the second candidate strong cold starting time within the candidate duration based on the dichotomy, if the condition is met

Stopping temperature screening; wherein, Δ t is a preset time duration, n is a set value, Y is a candidate time duration, and p is the number of times that the screening has been executed. In practical application, n can be determined according to the position of the controllerThe physical ability is flexibly determined. The larger n, the shorter the screening time, but the optimal forced cooling on time may be missed.

If the target forced cooling starting time is estimated according to the preset starting time of the initial forced cooling device until the fourth mapping relation meeting the preset screening condition does not exist even when the forced cooling device stops, the preset starting time is reset to be m delta t (m is 2, 3, 4 …), the steps from the first step to the third step are carried out again until the fourth mapping relation meeting the screening condition exists, and the target forced cooling starting time is obtained.

Optionally, on the basis of the above embodiment, the present invention further provides a method for quickly ending the screening process of the target strong cold start time, that is, in the process of screening the second candidate strong cold start time within the candidate duration based on the bisection method, if there is a second candidate strong cold start time satisfying the second preset screening condition, determining the second candidate strong cold start time corresponding to the second preset screening condition as the target strong cold start time, and stopping the screening;

wherein the second preset screening condition comprises: under the conditions that the power battery is controlled to work according to the first mapping relation, and the forced cooling device is controlled to be started at the second candidate strong cold start time and continuously run for the preset start time, the average value of the working temperature of the power battery is smaller than the service life temperature threshold, and of course, the service life temperature threshold mentioned here is smaller than the preset temperature threshold.

Optionally, in any of the above embodiments, the predictions of the second mapping relationship, the third mapping relationship and the fourth mapping relationship are obtained based on the first mapping relationship, and if a current output condition of the vehicle in an actual driving process significantly deviates from the first mapping relationship, it is necessary to correct the first mapping relationship, and perform a subsequent management process based on the corrected first mapping relationship.

Specifically, calculating an average value of actual output current of the power battery in a target duration to obtain an actual measurement current average value; and the average value of the output current of the power battery under the condition that the power battery works is controlled according to a first mapping relation (obtained by taking the reference running data as the target running data) in the target time length, so that the predicted current average value is obtained. Then, calculating the difference between the actual measured current mean value and the predicted current mean value, if the difference between the actual measured current mean value and the predicted current mean value exceeds the preset current range, it can be considered that the first mapping relation obtained by using the reference running data as the target running data is no longer accurate, the angle deviation occurs between the first mapping relation and the actual situation of the vehicle, the actual running data of the vehicle needs to be used as the target running data, and the step of determining the running time length of the vehicle and the first mapping relation according to the target running data and the subsequent steps are returned to be executed in S110.

Specifically, the calculation can be performed according to the following formula:

wherein the content of the first and second substances,

representing the mean value of the measured current;

representing a predicted current mean value;

a is a preset coefficient and is used for adjusting the size of a preset current range.

In summary, the management method provided in the embodiment of the present invention firstly determines and manages whether the power battery is higher than the preset temperature threshold in the driving cycle according to the estimated corresponding relationship between the output current and the driving time, that is, the first mapping relationship, and if the deviation between the actual output current and the estimated output current is large in the actual use of the vehicle, the second mapping relationship and the third mapping relationship are confirmed again based on the actual condition of the power battery, so as to correct the timing for turning on the forced cooling device, thereby ensuring that the working temperature of the power battery is not higher than the preset temperature threshold, which is beneficial to prolonging the service life of the power battery.

The power battery thermal management device provided by the embodiment of the invention is introduced below, and the power battery thermal management device described below can be regarded as a functional module architecture which needs to be arranged in central equipment to realize the power battery thermal management method provided by the embodiment of the invention; the following description may be cross-referenced with the above.

Optionally, referring to fig. 4, fig. 4 is a structural block diagram of a power battery thermal management device provided in an embodiment of the present invention, where the power battery thermal management device provided in this embodiment includes:

a first acquisition unit 10 for acquiring reference travel data of the vehicle and taking the reference travel data as target travel data;

a first determination unit 20, configured to determine a driving duration of the vehicle and a first mapping relationship according to the target driving data;

the first mapping relation records the corresponding relation between the output current and the driving time of a power battery of the vehicle within the driving time;

a second determining unit 30, configured to determine a second mapping relationship based on the power battery thermal balance equation and the first mapping relationship;

a second obtaining unit 40 configured to obtain a maximum operating temperature described in the second mapping relationship and a target travel time corresponding to the maximum operating temperature;

and the control unit 50 is used for starting the forced cooling device before the target driving moment if the highest working temperature is greater than or equal to a preset temperature threshold value.

Optionally, the control unit 50 is configured to turn on the forced cooling device before the target driving time, and includes:

acquiring a preset starting time of the forced cooling device;

the candidate duration is the duration between the starting time of the running duration and the target running time, and the candidate duration does not include the target running time;

the target forced cooling starting time is the running time corresponding to the preset temperature threshold value when the working temperature of the power battery in the running time is lower than the preset temperature threshold value;

and controlling the forced cooling device to be started at the target forced cooling starting moment and continuously operating for a preset starting duration.

Optionally, the control unit 50 is configured to determine the target forced cooling start time within the candidate duration, and includes:

if at least one third mapping relation meets a first preset screening condition, determining a target forced cooling starting time in first candidate forced cooling starting times corresponding to all the third mapping relations meeting the first preset screening condition;

wherein, the first preset screening condition comprises: and any working temperature of the power battery recorded in the third mapping relation is smaller than a preset temperature threshold value.

Optionally, the control unit 50 is configured to determine a target forced cooling start time in first candidate forced cooling start times corresponding to respective third mapping relationships that satisfy the first preset screening condition, and includes:

respectively calculating the average value of the working temperature recorded in the third mapping relation of each target to obtain the corresponding temperature average value;

the fourth mapping relation records the corresponding relation between the working temperature of the power battery and the driving time under the condition that the power battery is controlled to work according to the first mapping relation and the forced cooling device is controlled to be started at the second candidate strong cold starting time and continuously run for the preset starting time, and any working temperature of the power battery recorded in the fourth mapping relation is smaller than the preset temperature threshold value;

and determining the target strong cold starting time in the second candidate strong cold starting time.

Optionally, the control unit 50 is configured to increase the preset starting time if the target strong cooling starting time is not determined within the candidate time, and return to the step of determining the target strong cooling starting time within the candidate time.

Optionally, in the process of screening the second candidate strong cold start time within the candidate duration based on the dichotomy, if there is a second candidate strong cold start time meeting a second preset screening condition, the control unit 50 determines the second candidate strong cold start time corresponding to the second preset screening condition as the target strong cold start time, and stops the screening;

the second preset screening condition includes: and under the conditions that the power battery is controlled to work according to the first mapping relation, and the forced cooling device is controlled to be started at the second candidate strong cold starting moment and continuously run for a preset starting duration, the average value of the working temperature of the power battery is smaller than the service life temperature threshold, and the service life temperature threshold is smaller than the preset temperature threshold.

Optionally, the control unit 50 is configured to, in the process of screening the second candidate strong cold start time within the candidate duration based on the dichotomy, if a condition is met

Optionally, referring to fig. 5, fig. 5 is a block diagram of another power battery thermal management device provided in the embodiment of the present invention, and on the basis of the embodiment shown in fig. 4, the device further includes:

the calculating unit 60 is configured to calculate an average value of actual output currents of the power battery within the target time duration to obtain an actually measured current average value, and calculate an average value of output currents of the power battery within the target time duration under the condition that the power battery is controlled to work according to the first mapping relationship to obtain a predicted current average value;

and the updating unit 70 is configured to take the actual driving data of the vehicle as the target driving data and trigger the first determining unit 20 if the difference between the measured current mean value and the predicted current mean value exceeds the preset current range.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.

Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power battery thermal management method is characterized by comprising the following steps:

2. The power battery thermal management method according to claim 1, wherein the turning on a forced cooling device before the target driving moment comprises:

acquiring a preset starting time of the forced cooling device;

3. The power battery thermal management method according to claim 2, wherein the determining a target forced cold turn-on time within a candidate duration comprises:

4. The power battery heat management method according to claim 3, wherein the determining a target strong cold start time in the first candidate strong cold start times corresponding to the third mapping relations satisfying the first preset screening condition includes:

5. The power battery thermal management method according to claim 2, wherein the determining a target forced cold turn-on time within a candidate duration comprises:

6. The power battery thermal management method according to claim 5, further comprising:

7. The power battery thermal management method according to claim 5, further comprising:

8. The power battery heat management method according to claim 2, wherein if the target forced cooling starting time is not determined in the candidate time period, the preset starting time period is increased, and the step of determining the target forced cooling starting time in the candidate time period is executed in a return mode.

9. The power battery thermal management method according to any one of claims 1-7, further comprising:

10. A power battery thermal management device, comprising: