阅读说明：本技术 车辆动力电池系统的控制方法、程序产品和动力电池系统 (Control method for vehicle power battery system, program product, and power battery system ) 是由 胡晓玮 张琦 于 2021-08-09 设计创作，主要内容包括：本发明涉及一种用于车辆的动力电池系统(100)的控制方法,所述动力电池系统具有至少两个电池子系统(11、12),所述控制方法至少包括以下步骤：检测所述动力电池系统(100)的荷电状态；根据所述荷电状态调节所述至少两个电池子系统(11、12)之间的连接状态,其中,当所述荷电状态等于或高于规定值时,使所述至少两个电池子系统(11、12)并联连接,当所述荷电状态低于所述规定值时,使所述至少两个电池子系统(11、12)串联连接。本发明还涉及一种相应的计算机程序产品和一种相应的动力电池系统。能够在荷电状态低时优化地满足车辆的功率需求。(The invention relates to a control method for a power battery system (100) of a vehicle, having at least two battery subsystems (11, 12), comprising at least the following steps: detecting a state of charge of the power battery system (100); -adjusting the connection state between the at least two battery subsystems (11, 12) in dependence of the state of charge, wherein the at least two battery subsystems (11, 12) are connected in parallel when the state of charge is equal to or above a prescribed value, and the at least two battery subsystems (11, 12) are connected in series when the state of charge is below the prescribed value. The invention also relates to a corresponding computer program product and a corresponding power battery system. The power requirement of the vehicle can be optimally met when the state of charge is low.)

1. A control method for a power battery system (100) of a vehicle, the power battery system having at least two battery subsystems (11, 12), the control method comprising at least the steps of:

s1: detecting a state of charge of the power battery system (100);

s2: -adjusting the connection state between the at least two battery subsystems (11, 12) in dependence of the state of charge, wherein the at least two battery subsystems (11, 12) are connected in parallel when the state of charge is equal to or above a prescribed value, and the at least two battery subsystems (11, 12) are connected in series when the state of charge is below the prescribed value.

2. The control method according to claim 1, wherein the prescribed value is calculable based on a variation curve between the state of charge and an output voltage of the power battery system (100), a current limit of the vehicle, and a required power of the vehicle.

3. The control method according to claim 1 or 2, wherein the at least two battery subsystems (11, 12) have the same number of individual cells in series with each other and have substantially the same output voltage.

4. The control method according to any one of the preceding claims, wherein in step S1 the state of charge of each of the at least two battery subsystems (11, 12) is detected separately.

5. The control method according to claim 4, wherein one of the at least two battery subsystems (11, 12) is deactivated when its state of charge is below a state of charge threshold.

6. The control method according to any one of the preceding claims, wherein additionally a voltage of each individual cell in the power cell system (100) is detected, wherein a system equalization function is initiated when a difference between a maximum value and a minimum value of the voltage of the individual cell exceeds a voltage threshold value.

7. A control method according to any one of the preceding claims, wherein a battery backup subsystem is provided, which is connected in series with the at least two battery subsystems (11, 12) when the state of charge is below the prescribed value.

8. The control method according to any one of the preceding claims, wherein a plurality of relays (21, 22, 23) are arranged between the at least two battery subsystems (11, 12) for controlling the connection state of the at least two battery subsystems (11, 12).

9. A computer program product comprising computer program instructions, wherein the computer program instructions, when executed by one or more processors, enable the processors to perform the control method of any one of claims 1-8.

10. A power battery system (100) for a vehicle, the power battery system comprising at least:

-at least two battery subsystems (11, 12) configured to be adapted to be connected in series or in parallel;

-a state of charge detection device (50, 60) configured and adapted to detect a state of charge of the power battery system (100);

-a controller (40) configured to be able to adjust the connection state of the at least two battery subsystems (11, 12) according to the state of charge using the computer program product according to claim 9, wherein the at least two battery subsystems (11, 12) are connected in parallel when the state of charge is equal to or above a prescribed value and the at least two battery subsystems (11, 12) are connected in series when the state of charge is below the prescribed value.

Technical Field

The invention relates to a control method for a power battery system of a vehicle, in particular of an electric vehicle. The invention further relates to a corresponding computer program product and a corresponding power battery system for a vehicle.

Background

In recent years, along with the increasing prominence of the problem of environmental pollution and the development of battery technology, electric vehicles have advantages of no pollution, low noise and the like as travel tools and are increasingly favored.

The power battery is a core component of the electric vehicle, and the working performance of the power battery influences the charging time, the driving mileage and the power performance of the vehicle to a certain extent. To extend the maximum range of a vehicle and improve overall drivability, power battery systems having multiple battery subsystems are commonly used. However, for the current power battery system, the series-parallel scheme of the battery subsystem is determined according to technical indexes of the whole vehicle, such as a voltage platform, required power and allowable charge and discharge current, at the initial stage of system design, and the series-parallel connection state of the battery subsystem is not changed under different use conditions. However, the overall voltage, the charging and discharging current and other performances of the power battery system as an energy storage device show different characteristics according to the state of charge of the power battery system and the using environment, and the power requirement of the vehicle does not change according to the state of charge of the power battery system. Therefore, with the series-parallel connection of the battery subsystems remaining unchanged, the power battery systems in different states of charge have different output powers and the output powers do not always optimally meet the power requirements of the vehicle. For example, when the charge or state of charge of the power battery system decreases, the overall output voltage of the power battery system decreases, which results in a corresponding decrease in the output power of the power battery system, and when the output power decreases to a certain extent, the power requirement of the vehicle cannot be met, so that the driveability of the vehicle and the operability of the electrical consumers are adversely affected.

Disclosure of Invention

The object of the present invention is therefore to provide an improved control method for a power battery system of a vehicle, in particular of an electric vehicle, by means of which the output power of the power battery system can be varied by switching the series-parallel connection state of the battery subsystems of the power battery system in the event of different states of charge of the vehicle, so that the supply electrical energy of the power battery system is utilized fully and the power requirement of the vehicle is met optimally, and adverse effects such as reduced driveability of the vehicle and an electrical load not operating properly are avoided, so that the driving safety of the vehicle is ensured. The invention also aims to provide a corresponding computer program product and a corresponding power battery system for a vehicle.

According to a first aspect of the present invention, a control method for a power battery system of a vehicle is provided, the power battery system having at least two battery subsystems, the control method comprising at least the following steps:

s1: detecting a state of charge of the power battery system;

s2: adjusting a connection state between the at least two battery subsystems according to the state of charge, wherein when the state of charge is equal to or higher than a prescribed value, the at least two battery subsystems are connected in parallel, and when the state of charge is lower than the prescribed value, the at least two battery subsystems are connected in series.

Compared with the prior art, the control method for the power battery system of the vehicle can detect the charge state of the power battery system of the vehicle during the running of the vehicle, and switches the series-parallel connection state between at least two battery subsystems of the power battery system according to the charge state so as to control the output voltage and the output power of the power battery system, thereby meeting the power requirement and the working performance of the running of the vehicle. For example, when the state of charge of the power battery system is lower than a predetermined value, the output voltage of the power battery system is increased by connecting the at least two battery subsystems in series, so that a large output power, which corresponds to the power requirement of the vehicle, can be achieved without exceeding the current limit of the vehicle, thereby ensuring that the vehicle can run normally and the electrical loads of the vehicle can work normally. Particularly, under the condition of excessively low charge state, traffic accidents caused by the failure of electric consumers of the vehicles can be avoided.

Within the framework of the present invention, "state of charge" is understood to be the ratio of the residual charge capacity or residual charge of the power cell system after a period of use to the charge capacity or charge in the fully charged state, expressed as a percentage and taking values between 0 and 1. A state of charge of 1 indicates that the power battery system is fully charged, and a state of charge of 0 indicates that the power battery system is fully discharged.

Within the framework of the present invention, an "electrical load" is understood to be an electrical component of a vehicle, which is operated by supplying electrical energy via a power battery system, such as a steering assistance device, a brake assistance device, an air conditioner, etc.

According to an exemplary embodiment of the invention, the defined value can be calculated on the basis of a curve of change between the state of charge and the output voltage of the power battery system, a current limit of the vehicle and a power demand of the vehicle.

According to an exemplary embodiment of the invention, the at least two battery subsystems have the same number of individual cells connected in series with one another and have substantially the same output voltage.

According to an exemplary embodiment of the present invention, in step S1, the state of charge of each of the at least two battery subsystems is detected separately.

According to an exemplary embodiment of the invention, one of the at least two battery subsystems is deactivated when its state of charge is below a state of charge threshold.

According to an exemplary embodiment of the invention, the voltage of each individual cell in the power cell system is additionally detected, wherein a system equalization function is initiated when the difference between the maximum and minimum value of the voltage of the individual cell exceeds a voltage threshold value.

According to an exemplary embodiment of the invention, a backup battery subsystem is provided, which is connected in series with the at least two battery subsystems when the state of charge is below the prescribed value.

According to an exemplary embodiment of the invention, a plurality of relays are arranged between the at least two battery subsystems for controlling the connection state of the at least two battery subsystems.

A second aspect of the invention proposes a computer program product comprising computer program instructions, wherein said computer program instructions, when executed by one or more processors, are capable of executing the control method for a power battery system of a vehicle according to the invention.

A third aspect of the invention proposes a power battery system for a vehicle, said power battery system comprising at least:

-at least two battery subsystems configured to be adapted to be connected in series or in parallel;

-a state of charge detection device configured and adapted to detect a state of charge of the power battery system;

-a controller configured to enable adjusting the connection state of the at least two battery subsystems according to the state of charge using the computer program product according to the invention, wherein the at least two battery subsystems are connected in parallel when the state of charge is equal to or above a prescribed value and in series when the state of charge is below the prescribed value.

Drawings

The principles, features and advantages of the present invention may be better understood by describing the invention in more detail below with reference to the accompanying drawings. The drawings comprise:

FIG. 1 shows a flow chart of a control method for a power battery system of a vehicle according to an exemplary embodiment of the present invention;

fig. 2 shows a circuit diagram of a power battery system for a vehicle according to an exemplary embodiment of the present invention.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and exemplary embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of the invention.

It is to be understood that, herein, the expressions "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance, nor are they to be construed as implicitly indicating the number of technical features indicated. A feature defined as "first" or "second" may be explicitly or implicitly indicated as including at least one of the feature.

Fig. 1 shows a flow chart of a control method of a power battery system 100 for a vehicle according to an exemplary embodiment of the present invention. In this case, the vehicle is in particular an electric vehicle which is completely supplied with energy by the power battery system and is driven by the electric motor in an electric-only mode. However, a hybrid vehicle driven by both the electric motor and the engine is also conceivable. The power battery system 100 is configured here as an exemplary power lithium battery system.

Here, the power battery system 100 comprises at least two battery subsystems. Of course more, for example three or four, battery subsystems are also contemplated. Each battery subsystem has a plurality of series-connected individual cells, the sum of the voltages of which is the output voltage of the battery subsystem.

In this case, the individual cells have different nominal voltages depending on the different electrode materials of the individual cells. During the discharge process of the individual cells, the individual cells are not kept discharged at the nominal voltage, and the actual output voltage of the individual cells depends on the actual capacity of the individual cells. Illustratively, the voltage of the cell ranges from 2.5V to 4.2V, the voltage is 4.2V when the cell is fully charged, and the voltage is 2.5V after the cell is discharged, and the variation curve between the charge capacity and the voltage during the whole discharging process appears like a parabola, that is, the voltage gradually decreases from 4.2V in the initial stage of discharging, then gradually enters a discharging plateau stage, the voltage is approximately kept at the nominal voltage in the discharging plateau stage, and finally the voltage rapidly decreases to 2.5V in the final stage of discharging, wherein the discharging plateau stage occupies about three quarters of the total discharging time and the cell maintains discharging at the nominal voltage in the discharging plateau stage. Within the framework of the present invention, "nominal voltage" is understood to mean the potential difference between the positive and negative electrodes when the battery is operating under the conditions specified in the standard and is determined by the electrode potential of the plate material and the concentration of the internal electrolyte, also referred to as nominal voltage.

The voltage of the individual cells here likewise depends on the electrode material used. Illustratively, the lithium iron phosphate monomer cell has a full electric voltage of 3.65V and a nominal voltage of 3.2V, while the lithium cobaltate monomer cell has a full electric voltage of 4.2V and a nominal voltage of 3.7V, the lithium manganate monomer cell has a full electric voltage of 4.2V and a nominal voltage of 3.8V, and the lithium nickel cobalt manganese ternary monomer cell has a nominal voltage of 3.5-3.7V. Generally, the full-electric voltage does not exceed 4.2V for material and safety of use. The nominal voltage can thereby identify or indicate the battery type to some extent.

For example, the at least two battery subsystems of the power battery system 100 have the same number of individual cells, for example 100, connected in series with one another and have substantially the same output voltage. Within the framework of the present invention, "substantially identical" is to be understood to mean that the difference between the output voltages of the at least two battery subsystems is in the range of 5%, in particular in the range of 1%. Of course, other numbers of individual cells connected in series with one another are also conceivable. For example, the at least two battery subsystems each have an output voltage of 420V when fully charged or at 100% state of charge, an output voltage of 370V during the discharge plateau, and an output voltage of 250V when low, for example at 5% state of charge.

As shown in fig. 1, the control method at least includes the following steps:

s1: detecting a state of charge of the power battery system 100;

s2: adjusting a connection state between the at least two battery subsystems according to the state of charge, wherein when the state of charge is equal to or higher than a prescribed value, the at least two battery subsystems are connected in parallel, and when the state of charge is lower than the prescribed value, the at least two battery subsystems are connected in series.

The state of charge of the power cell system 100 reflects the state of charge of each of the at least two battery subsystems, which are both in a low state of charge when the power cell system 100 is in a low state of charge. The state of charge of the power cell system 100 can be detected, for example, by voltage testing, battery modeling, or coulometry.

By way of example, it is assumed that the power battery system 100 has two battery subsystems, each battery subsystem having 100 individual cells connected in series with one another, which have a nominal voltage of 3.7V and a minimum voltage of 2.5V, so that each battery subsystem has a nominal output voltage of 370V and a minimum output voltage of 250V, a required power of 60kw for the vehicle, and a current limit of 200A for the vehicle, which is derived from the overcurrent capacity of the electric motor and the load. Other values which are considered to be significant by the person skilled in the art can of course also be considered for the individual parameters.

When the state of charge of the power battery system 100 is equal to or higher than a defined value, for example 50%, both battery subsystems of the power battery system 100 have an output voltage of 370V, and the two battery subsystems form a total output voltage of 370V of the power battery system 100 in the parallel connected state. It follows that from the power demand and the total output voltage of the power battery system 100, a total output current of 162A for the power battery system 100 and a current of 81A through the individual cells of each battery subsystem can be calculated, see table 1. Therefore, the required power of the vehicle can be satisfied while ensuring that both the total output voltage and the total output current of the power battery system 100 are within the prescribed limit ranges.

TABLE 1

When the state of charge of the power battery system 100 is below a specified value, for example 4%, both battery subsystems of the power battery system 100 have an output voltage of 250V, for example. If the two battery subsystems are still connected in parallel, the total output voltage of the power battery system 100 is 250V, at which time the total output current of the power battery system 100 is 200A and the output current of each battery subsystem is 100A due to the current limitation of the vehicle, in which case the output power of the power battery system 100 is 50kw, which is lower than the required power of the vehicle, which can adversely affect the drivability of the vehicle and the operability of the electrical consumers, and in the severe case can lead to safety accidents. Conversely, if two battery subsystems are connected in series, the total output voltage of the power battery system 100 is 500V, and the total output current of the power battery system 100, which is still within the current limits of the vehicle, can be calculated as 120A from the power demand, see table 2. Therefore, by changing the connection state of the two battery subsystems of the power battery system 100, it is possible to supply the required power of the vehicle and to operate the vehicle normally while satisfying the current limit of the vehicle even when the state of charge is low.

TABLE 2

For example, the specified value for the state of charge of the power battery system 100 can be calculated on the basis of a curve of the state of charge of the power battery system and the output voltage, a current limit of the vehicle and a power demand of the vehicle. Here, when the state of charge of the power battery system 100 is lower than a predetermined value, the output voltage of the battery subsystem of the power battery system 100 rapidly decreases. The prescribed value is illustratively 5%. It is of course also conceivable to estimate the defined value using empirical formulas or experimental data.

Illustratively, in step S1, the state of charge of each of the at least two battery subsystems is detected. The state of charge of the entire power cell system 100 and of each cell subsystem can thus be determined more precisely.

Illustratively, one of the at least two battery subsystems is deactivated when its state of charge is below a state of charge threshold. Here, the state of charge threshold is, for example, 1%. During the actual use of the power battery system, the states of charge of the battery subsystems may be different, and if the battery subsystems continue to discharge in a state in which the states of charge are lower than a state of charge threshold, the single cells in the battery subsystems are irreversibly damaged due to overdischarge, and the battery life is shortened. The performance of the battery subsystem can be protected by deactivating battery subsystems having a state of charge below a state of charge threshold.

In an exemplary embodiment, a backup battery subsystem is also provided in power battery system 100, and is connected in series with the at least two battery subsystems when the state of charge is below the predetermined value. The power output of the power battery system 100 can thereby be ensured more fully.

For example, the voltage of each individual cell in the power cell system 100 is additionally detected, wherein, when the difference between the maximum and minimum values of the voltage of the individual cell exceeds a voltage threshold value, a system equalization function is initiated, by means of which it is ensured that the differential pressure of the cell remains within a certain range, thereby eliminating inconsistencies between the battery subsystems 11, 12 and protecting the life and safety of the cell. Here, the system balancing function may be implemented by the battery management system and have both active and passive balancing schemes.

Fig. 2 shows a circuit diagram of a power battery system 100 for a vehicle according to an exemplary embodiment of the present invention.

As shown in fig. 2, the power battery system 100 includes two battery subsystems, namely a first battery subsystem 11 and a second battery subsystem 12. In this case, the first battery subsystem 11 and the second battery subsystem 12 have the same number of individual cells connected in series with one another and have substantially the same output voltage.

As shown in fig. 2, a plurality of relays 21, 22, 23 are arranged between the first battery subsystem 11 and the second battery subsystem 12, and the series-parallel connection state of the first battery subsystem 11 and the second battery subsystem 12 can be controlled accordingly by opening and closing these relays. Specifically, the cathode of the first battery subsystem 11 is connected to the anode of the second battery subsystem 12 through the first relay 21, the cathode of the first battery subsystem 11 is connected to the cathode of the second battery subsystem 12 through the second relay 22, and the anode of the first battery subsystem 11 is connected to the anode of the second battery subsystem 12 through the third relay 23. In addition, the positive pole of the first battery subsystem 11 is connected to the overall positive pole 31 of the power battery system 100, while the negative pole of the second battery subsystem 12 is connected to the overall negative pole 32 of the power battery system 100, with a terminal or overall output voltage of the power battery system 100 being established between the overall positive pole 31 and the overall negative pole 32. When the first relay 21 is closed and the second and third relays 22 and 23 are open, the first and second battery subsystems 11 and 12 are connected in series and the terminal voltage of the power battery system 100 is the sum of the two battery subsystems, thereby providing a high voltage platform; when the first relay 21 is open and the second relay 22 and the third relay 23 are closed, the first battery subsystem 11 and the second battery subsystem 12 are connected in parallel and the terminal voltage of the power battery system 100 is equal to the output voltage of the first battery subsystem 11 and the second battery subsystem 12.

As shown in fig. 2, the power cell system 100 has a controller 40 which controls the opening and closing of the relays 21, 22, 23 as a function of the state of charge of the power cell system 100 and thus sets the series-parallel connection state of the first battery subsystem 11 and the second battery subsystem 12. Here, the controller 40 has a computer program product comprising computer program instructions, wherein the processor is capable of performing the control method according to the invention when the computer program instructions are executed by one or more processors.

As shown in fig. 2, the power battery system 100 also illustratively has state of charge detection devices 50, 60 configured and adapted to detect the state of charge of each battery subsystem individually and communicate the state of charge to the controller 40. Of course, it is also conceivable to detect the state of charge of the entire power cell system 100 by a common state of charge detection device.

Illustratively, the controller 40 and the state of charge detection devices 50, 60 are each integrated into a battery management module 70 of the power cell system 100, which is configured to monitor the status of the power cell system 100 as a whole and the battery subsystems and individual cells. Here, the battery management module also optionally implements a system balancing function for eliminating inconsistencies between battery subsystems.

The preceding explanations of embodiments describe the invention only in the framework of said examples. Of course, the individual features of the embodiments can be freely combined with one another as far as technically expedient, without departing from the framework of the invention.

Other advantages and alternative embodiments of the present invention will be apparent to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative structures, and illustrative examples shown and described. On the contrary, various modifications and substitutions may be made by those skilled in the art without departing from the basic spirit and scope of the invention.