CN109037802B - Battery system and electric automobile - Google Patents

Battery system and electric automobile Download PDF

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CN109037802B
CN109037802B CN201810838058.1A CN201810838058A CN109037802B CN 109037802 B CN109037802 B CN 109037802B CN 201810838058 A CN201810838058 A CN 201810838058A CN 109037802 B CN109037802 B CN 109037802B
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battery
resistance value
adjusting unit
switch
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CN109037802A (en
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齐军
刘小德
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Zhejiang Yinglun Automobile Co ltd
Zhejiang Geely Holding Group Co Ltd
Zhejiang Geely New Energy Commercial Vehicle Co Ltd
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Zhejiang Yinglun Automobile Co ltd
Zhejiang Geely Holding Group Co Ltd
Zhejiang Geely New Energy Commercial Vehicle Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4207—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells for several batteries or cells simultaneously or sequentially
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B13/00—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion
    • G05B13/02—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric
    • G05B13/04—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric involving the use of models or simulators
    • G05B13/042—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric involving the use of models or simulators in which a parameter or coefficient is automatically adjusted to optimise the performance
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M2010/4271—Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

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  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Health & Medical Sciences (AREA)
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  • Physics & Mathematics (AREA)
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  • Automation & Control Theory (AREA)
  • Secondary Cells (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)

Abstract

The embodiment of the invention provides a battery system and an electric automobile, and relates to the technical field of battery application. The battery system comprises at least two battery branches and a controller, wherein each battery branch comprises a battery and an adjusting unit, the battery branches are connected in parallel, the battery in each battery branch is connected in series with the adjusting unit in each battery branch, and the controller is electrically connected with the adjusting unit in each battery branch; the controller is used for adjusting the resistance value of the adjusting unit in each battery branch according to a pre-established mathematical model, and then adjusting the output current of each battery branch. By adopting the battery system and the electric automobile provided by the embodiment of the invention, the problem of unbalanced distribution of the output current of each branch of the battery system can be solved.

Description

Battery system and electric automobile
Technical Field
The invention relates to the technical field of battery application, in particular to a battery system and an electric automobile.
Background
With the rapid development of the new energy automobile industry, higher requirements are put forward on the high-voltage power battery technology for the automobile. The new energy automobile has complex operation condition and large power demand variation range, and in order to obtain a battery combination with larger capacity, a battery parallel connection mode is generally adopted, namely a plurality of batteries are connected in parallel to increase the capacity of the battery. In practical application, however, when batteries are used in parallel, the phenomena of circulation and non-uniform current can be generated, and the batteries can be seriously damaged.
Disclosure of Invention
The invention aims to provide a battery system and an electric automobile, and solves the problem of unbalanced distribution of output current of each battery branch of the battery system.
In order to achieve the above purpose, the embodiment of the present invention adopts the following technical solutions:
in a first aspect, an embodiment of the present invention provides a battery system, including at least two battery branches and a controller, where each battery branch includes a battery and an adjusting unit, the battery branches are connected in parallel, the battery in each battery branch is connected in series with the adjusting unit in each battery branch, and the controller is electrically connected to the adjusting unit in each battery branch; the controller is used for adjusting the resistance value of the adjusting unit in each battery branch according to a pre-established mathematical model so as to adjust the output current of each battery branch; the pre-established mathematical model represents the corresponding relation between the output current of each battery branch and the resistance value of each battery branch, and the resistance value of each battery branch is the sum of the internal resistance of the battery in each battery branch and the resistance value of the regulating unit in each battery branch.
In a second aspect, an embodiment of the present invention provides an electric vehicle, including a battery system, where the battery system includes at least two battery branches and a controller, each battery branch includes a battery and an adjusting unit, the battery branches are connected in parallel, the battery in each battery branch is connected in series with the adjusting unit in each battery branch, and the controller is electrically connected to the adjusting unit in each battery branch; the controller is used for adjusting the resistance value of the adjusting unit in each battery branch according to a pre-established mathematical model so as to adjust the output current of each battery branch; the pre-established mathematical model represents the corresponding relation between the output current of each battery branch and the resistance value of each battery branch, and the resistance value of each battery branch is the sum of the internal resistance of the battery in each battery branch and the resistance value of the regulating unit in each battery branch.
According to the battery system and the electric automobile provided by the embodiment of the invention, the resistance value of each battery branch is adjusted through the controller according to the pre-established mathematical model, and then the output current of each battery branch is adjusted, so that the output current of each battery branch is uniformly distributed under the regulation and control of the controller, and the problem of circulation and non-uniform current generated when batteries are used in parallel is solved. Compared with the existing mathematical model, the mathematical model established by the method has the advantages of high precision and small calculated amount.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 is a schematic circuit diagram of a battery system according to an embodiment of the present invention;
FIG. 2 is a graph illustrating the output current distribution versus the actual current distribution of a mathematical model provided by an embodiment of the present invention;
FIG. 3 illustrates a circuit schematic of a first current detector and a second current detector provided by an embodiment of the present invention;
fig. 4 is a schematic circuit diagram of another first current detector and a second current detector provided in an embodiment of the present invention.
Icon: 1-a battery system; 10-a first battery; 20-a second battery; 30-a first regulating unit; 31-a first switch; 32-a first resistance; 40-a second regulating unit; 41-a second switch; 42-a second resistance; 50-a first current detector; 60-a second current detector; 70-a controller; 80-a first branch; 90-second branch.
Detailed Description
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 only a part of the embodiments of the present invention, and not all of the embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present invention, the terms "first", "second", and the like are used only for distinguishing the description, and are not to be construed as indicating or implying relative importance.
As shown in fig. 1, a battery system 1 according to an embodiment of the present invention is applied to an electric vehicle, and the electric vehicle using the battery system 1 has high power and can solve the problems of circular current and non-uniform current generated when batteries are used in parallel.
The battery system 1 comprises at least two battery branches and a controller 70, each battery branch comprises a battery and an adjusting unit, the battery branches are connected in parallel, the battery in each battery branch is connected in series with the adjusting unit in each battery branch, and the controller 70 is electrically connected with the adjusting unit in each battery branch.
The controller 70 is configured to adjust a resistance value of the adjusting unit in each battery branch according to a pre-established mathematical model, so as to adjust an output current of each battery branch; the pre-established mathematical model represents the corresponding relation between the output current of each battery branch and the resistance value of each battery branch, and the resistance value of each battery branch is the sum of the internal battery resistance of each battery branch and the resistance value of the regulating unit in each battery branch.
The at least two battery branches include a first branch 80 and a second branch 90, the first branch 80 includes a first battery 10 and a first adjusting unit 30, the second branch 90 includes a second battery 20 and a second adjusting unit 40, the first branch 80 is connected in parallel with the second branch 90, the first battery 10 is connected in series with the first adjusting unit 30, the second battery 20 is connected in series with the second adjusting unit 40, the first adjusting unit 30 and the second adjusting unit 40 are connected in series with the controller 70 electrically.
The controller 70 is configured to adjust the resistance value of the first adjusting unit 30 and the resistance value of the second adjusting unit 40 according to a pre-established mathematical model, so as to adjust the output current of the first branch 80 and the output current of the second branch 90; the pre-established mathematical model represents a corresponding relationship between the output current of the first branch circuit 80 and the resistance values of the first branch circuit 80 and the second branch circuit 90, and a corresponding relationship between the output current of the second branch circuit 90 and the resistance values of the first branch circuit 80 and the second branch circuit 90, the resistance value of the first branch circuit 80 is a sum of the internal resistance of the first battery 10 and the resistance value of the first adjusting unit 30, and the resistance value of the second branch circuit 90 is a sum of the internal resistance of the second battery 20 and the resistance value of the second adjusting unit 40.
The pre-established mathematical model is as follows:
Figure BDA0001744924350000051
wherein t is time, i1(t) is the output current of the first branch 80 at time t, i2(t) is the output current of the second branch 90 at time t, t0As an initial time, i1(t0) For the initial output current of the first branch 80,i is the output current of the battery system 1, Δ E is the potential difference between the open circuit voltages of the first branch 80 and the second branch 90, and k1Is a fitting coefficient, k, of the first cell 102Is a fitting coefficient, Z, of the second cell 201(t0) Is the initial depth of discharge, Z, of the first battery 102(t0) Is an initial depth of discharge, R, of the second battery 201Is the resistance value, R, of the first branch 802Is the resistance value, Q, of the second branch 901Is the capacity, Q, of the first battery 102Is the capacity of the second battery 20.
In this embodiment, the mathematical model is obtained from the Unnewehr cell model, and the Unnewehr cell model of the first branch 80 is:
y1＝E01-i1R1-k1Z1
wherein, y1Is the terminal voltage of the first branch 80, said E01Is the open circuit voltage, i, of the first branch 801Is the output current of the first branch 80, R1Is the resistance value, Z, of the first branch 801Is the depth of discharge of the first cell 10, wherein E01、R1And k1Can be obtained using a least squares fit.
In this embodiment, the unnnewehr cell model for the second leg 90 is:
y2＝E02-i2R2-k2Z2
wherein, y2Terminal voltage of the second branch 90, E02Is the open circuit voltage, i, of the second branch 902Is the output current, R, of the second branch 902Is the resistance value, Z, of the second branch 902Is the depth of discharge of the second battery 20, wherein E02、R2And k2Can be obtained using a least squares fit.
In the present embodiment, the following combination relationship is obtained from the unnnewehr cell model of the first branch 80 and the unnnewehr cell model of the first branch 80 according to kirchhoff's law:
Figure BDA0001744924350000071
in the present embodiment, the depth of discharge Z of the first battery 10 in the above-described combination relation is set1Expressed by a defined expansion, and the depth of discharge Z of the second cell 20 in the above-described combined relation2Expressed by the definition expansion, the following integral relation is obtained:
Figure BDA0001744924350000072
where Δ E is the difference between the open circuit voltage of the first branch 80 and the open circuit voltage of the second branch 90, Q1Is the capacity, Q, of the first battery 102Is the capacity of the second battery 20.
In this embodiment, the following differential relation can be obtained by differentiating the equation of the integral relation with time and combining the combined relation:
Figure BDA0001744924350000073
in this embodiment, the differential relational expressions are collated to obtain the following relational expressions:
Figure BDA0001744924350000074
wherein the content of the first and second substances,
Figure BDA0001744924350000075
in this embodiment, kirchhoff's law processing is performed on the unnnewehr cell model of the first branch 80 and the unnnewehr cell model of the second branch 90 to obtain a combined relation, and then calculus processing is performed on the combined relation to establish the mathematical model, so that a corresponding relation between the output current of the first branch 80 and the resistance value of the second branch 90, and a corresponding relation between the output current of the second branch 90 and the resistance value of the first branch 80 and the resistance value of the second branch 90 are obtained.
As shown in fig. 2, a comparison graph of the output current distribution and the actual current distribution of the mathematical model provided in the embodiment of the present invention is shown, and compared with the actual output current, the current error between the output current of the first branch circuit 80 and the output current of the second branch circuit 90 obtained through simulation by the mathematical model is less than 1A, so the simulation accuracy of the mathematical model is very high.
In this embodiment, the first adjusting unit 30 includes a first switch 31 and a first resistor 32, the second adjusting unit 40 includes a second switch 41 and a second resistor 42, the first switch 31 is connected in parallel with the first resistor 32, the second switch 41 is connected in parallel with the second resistor 42, and both the first switch 31 and the second switch 41 are electrically connected to the controller 70.
The controller 70 is configured to control an open time or a close time of the first switch 31 or the second switch 41 according to the pre-established mathematical model, so as to adjust a resistance value of the first adjusting unit 30 or the second adjusting unit 40 to decrease or increase.
The controller 70 is configured to output a first control signal to the first switch 31 according to the pre-established mathematical model, and control an open time or a close time of the first switch 31 by adjusting a duty ratio of the first control signal, so as to adjust a resistance value of the first adjusting unit 30 to decrease or increase.
In this embodiment, if the first switch 31 is turned off, the resistance of the first adjusting unit 30 is the resistance of the first resistor 32; if the first switch 31 is closed, the internal resistance of the first switch 31 is connected in parallel with the first resistor 32, and the resistance value of the first adjusting unit 30 is a fixed value smaller than that of the first resistor 32.
In this embodiment, it can be understood that, if the period of the first control signal is 10us, the duty ratio of the first control signal is 60%, the closing time of the first switch 31 in this period is 6us, and the opening time of the first switch 31 is 4us, the resistance value of the first adjusting unit 30 in this period is 4us, and the resistance value of the first adjusting unit 30 in this period is 6us, which is a fixed value time smaller than that of the first resistor 32. Therefore, the effective resistance values of the first adjusting unit 30 in the periods where the duty ratios of the first control signals are different, the resistance value of the first adjusting unit 30 is smaller as the duty ratio of the first control signal is larger, and the resistance value of the first adjusting unit 30 is larger as the duty ratio of the first control signal is smaller.
The controller 70 is configured to output a second control signal to the second switch 41 according to the pre-established mathematical model, and control the open time or the close time of the second switch 41 by adjusting the duty ratio of the second control signal, so as to adjust the resistance value of the second adjusting unit 40 to decrease or increase.
In this embodiment, if the second switch 41 is turned off, the resistance of the second adjusting unit 40 is the resistance of the second resistor 42; if the second switch 41 is closed, the internal resistance of the second switch 41 is connected in parallel with the second resistor 42, and the resistance value of the second adjusting unit 40 is a fixed value smaller than that of the second resistor 42.
In this embodiment, the duty ratio of the second control signal controls the open time or the close time of the second switch 41, which may be understood as that, if the period of the second control signal is 10us, the duty ratio of the second control signal is 60%, the close time of the second switch 41 in this period is 6us, and the open time of the second switch 41 is 4us, the resistance value of the second adjusting unit 40 in this period is 4us, and the resistance value of the second adjusting unit 40 in this period is 6us which is smaller than the resistance value of the second resistor 42. Therefore, the effective resistance values of the second adjusting unit 40 in the periods where the duty ratios of the second control signals are different, the resistance value of the second adjusting unit 40 is smaller as the duty ratio of the second control signal is larger, and the resistance value of the second adjusting unit 40 is larger as the duty ratio of the second control signal is smaller.
In this embodiment, the first switch 31 and the second switch 41 may both adopt MOS transistors, the gate of the first switch 31 and the gate of the second switch 41 are both electrically connected to the controller 70, the source and the drain of the first switch 31 are connected in parallel to the first resistor 32, and the source and the drain of the second switch 41 are connected in parallel to the second resistor 42.
Further, in this embodiment, the battery system 1 further includes at least two current detectors, the number of the at least two current detectors is the same as the number of the at least two battery branches, and each current detector is disposed on each corresponding battery branch.
Each current detector is used for detecting the real-time output current of each corresponding battery branch circuit; the controller 70 is configured to adjust a current resistance value of the adjusting unit in each battery branch to a target resistance value according to the real-time output current of each battery branch, the set output current, and the pre-established mathematical model; the controller 70 is configured to adjust the resistance value of the adjusting unit in each battery branch from the current resistance value to the target resistance value, so that the output current of each battery branch is the set output current.
In the present embodiment, the at least two current detectors include a first current detector 50 and a second current detector 60, and the first current detector 50 and the second current detector 60 have two arrangements.
As shown in fig. 3, which is a schematic circuit diagram of an arrangement of the first current detector 50 and the second current detector 60, the first current detector 50 is disposed on the first branch 80, and the second current detector 60 is disposed on the second branch 90.
The first current detector 50 is used for detecting the real-time output current of the first branch 80; the second current detector 60 is used for detecting the real-time output current of the second branch 90; the controller 70 is configured to adjust a first current resistance value of the first adjusting unit 30 to reach a first target resistance value and adjust a second current resistance value of the second adjusting unit 40 to reach a second target resistance value according to the real-time output current of the first branch 80, the real-time output current of the second branch 90, the first set output current of the first branch 80, the second set output current of the second branch 90, and the pre-established mathematical model; the controller 70 is configured to adjust the resistance value of the first adjusting unit 30 from the first current resistance value to the first target resistance value, so that the output current of the first branch 80 is the first set output current, and adjust the resistance value of the second adjusting unit 40 from the second current resistance value to the second target resistance value, so that the output current of the second branch 90 is the second set output current.
In this embodiment, the first target resistance value and the second target resistance value are calculated in such a way that, if the real-time output current of the first branch 80 is smaller than the first set output current, the first switch 31 is kept closed, that is, the duty ratio of the first control signal output by the controller 70 is 1, and the second switch 41 adjusts the on-off time according to the duty ratio of the second control signal to adjust the resistance of the second branch 90. If the real-time output current of the first branch 80 is greater than the first set output current, the first control signal controls the duty ratio of the first switch 31 to adjust the resistance of the first branch 80, and meanwhile, the second switch 41 remains closed. The duty cycle of the first branch 80 or the second branch 90 is calculated according to a pre-established mathematical model, determined by the following system of equations:
Figure BDA0001744924350000111
discretizing the equation set to obtain the following discrete equation set:
Figure BDA0001744924350000121
and solving the discrete equation set.
The duty ratio solving process is described by taking the example that the real-time output current of the first branch 80 is smaller than the first set output current. Since the real-time output current of the first branch 80 is smaller than the first set output current, the first switch 31 remains closed, that is, the duty ratio of the first control signal output by the controller 70 is 1, and then the equivalent resistance R of the second branch 90 is calculated according to the above discrete equation set2According to the equivalent resistance R of the second branch 902 *A second target resistance value of the second adjusting unit 40 is obtained, and the controller 70 obtains the duty ratio of the second control signal according to the second target resistance value of the second adjusting unit 40.
As shown in fig. 4, which is a schematic circuit diagram of another arrangement of the first current detector 50 and the second current detector 60, the first current detector 50 is disposed on the first branch 80, and the second current detector 60 is electrically connected to both the first branch 80 and the second branch 90.
The first current detector 50 is used for detecting the real-time output current of the first branch 80; the second current detector 60 is used for detecting the real-time output current of the battery system 1; the controller 70 is configured to obtain a real-time output current of the second branch circuit 90 according to the real-time output current of the first branch circuit 80 and the real-time output current of the battery system 1, adjust a first current resistance value of the first adjusting unit 30 and a second current resistance value of the second adjusting unit 40 according to the real-time output current of the first branch circuit 80, the real-time output current of the second branch circuit 90 and the pre-established mathematical model, and adjust a first target resistance value of the first adjusting unit 30 and a second target resistance value of the second adjusting unit 40 according to a first set output current of the first branch circuit 80, a second set output current of the second branch circuit 90 and the pre-established mathematical model; the controller 70 is configured to adjust the resistance value of the first adjusting unit 30 from the first current resistance value to the first target resistance value, so that the output current of the first branch 80 is the first set output current, and adjust the resistance value of the second adjusting unit 40 from the second current resistance value to the second target resistance value, so that the output current of the second branch 90 is the second set output current.
In the present embodiment, each of the current detectors may employ, but is not limited to, a hall sensor or a shunt.
In this embodiment, the at least two battery branches may employ the same battery material, for example, the at least two battery branches may each employ, but are not limited to, a lithium iron phosphate material or a lithium titanate material.
In this embodiment, the at least two battery branches may adopt different battery materials, for example, one of the at least two battery branches may adopt a lithium iron phosphate material, and the other branches of the at least two battery branches may adopt a lithium titanate material, the lithium titanate battery is better than the rate capability of the lithium iron phosphate battery and has a long service life, but the lithium titanate battery is better than the energy density of the lithium iron phosphate battery is low, and the lithium titanate battery and the lithium iron phosphate battery are connected in parallel for use, so that the advantages of high energy density and good rate capability of the lithium iron phosphate battery can be simultaneously exerted.
In this embodiment, the number of the batteries in each battery branch may be at least one.
In summary, in the battery system and the electric vehicle provided in this embodiment, the controller of the battery system adjusts the first current resistance value of the first adjusting unit to reach the first target resistance value and adjusts the second current resistance value of the second adjusting unit to reach the second target resistance value according to the real-time output current of the first branch detected by the first current detector, the real-time output current of the second branch detected by the second current detector, the first set output current of the first branch, the second set output current of the second branch, and the pre-established mathematical model, so that the output current of the first branch is the first set output current and the output current of the second branch is the second set output current. The output current of the first branch circuit and the output current of the second branch circuit are balanced and distributed under the regulation and control of the controller, and therefore the problem that circulating current and uneven current are generated when batteries are connected in parallel for use is solved. Compared with the existing mathematical model, the mathematical model established by the method has the advantages of high precision and small calculated amount.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

Claims (8)

1. When the at least two battery branches comprise a first branch and a second branch, the first branch comprises a first battery and a first adjusting unit, the second branch comprises a second battery and a second adjusting unit, the first branch is connected with the second branch in parallel, the first battery is connected with the first adjusting unit in series, the second battery is connected with the second adjusting unit in series, and the first adjusting unit and the second adjusting unit are both electrically connected with the controller;
the controller is used for adjusting the resistance value of the first adjusting unit and the resistance value of the second adjusting unit according to a pre-established mathematical model so as to adjust the output current of the first branch circuit and the output current of the second branch circuit;
the pre-established mathematical model represents a corresponding relationship between the output current of the first branch and the resistance value of the second branch, and a corresponding relationship between the output current of the second branch and the resistance value of the first branch and the resistance value of the second branch, the resistance value of the first branch is a sum of the internal resistance of the first battery and the resistance value of the first adjusting unit, the resistance value of the second branch is a sum of the internal resistance of the second battery and the resistance value of the second adjusting unit, and the pre-established mathematical model is as follows:
Figure 338511DEST_PATH_IMAGE001
wherein, t is the time,
Figure 537411DEST_PATH_IMAGE002
for the output current of the first branch at time t,
Figure 268607DEST_PATH_IMAGE003
for the output current of the second branch at time t,
Figure 261971DEST_PATH_IMAGE004
for the purpose of the initial time, the time of the start,
Figure 16300DEST_PATH_IMAGE005
is the initial output current of the first branch, I is the output current of the battery system,
Figure 753312DEST_PATH_IMAGE006
is a potential difference of the open circuit voltages of the first branch and the second branch,
Figure 339014DEST_PATH_IMAGE007
is the fitting coefficient of the first cell,
Figure 768858DEST_PATH_IMAGE008
is the fitting coefficient of the second cell,
Figure 10484DEST_PATH_IMAGE009
is the initial depth of discharge of the first battery,
Figure 347924DEST_PATH_IMAGE010
is the initial depth of discharge, R, of the second cell1Is the resistance value, R, of the first branch2Is the resistance value of the second branch circuit,
Figure 991395DEST_PATH_IMAGE011
is the capacity of the first battery and is,
Figure 326562DEST_PATH_IMAGE012
is the capacity of the second battery.
2. The battery system of claim 1, wherein the first regulating unit comprises a first switch and a first resistor, the second regulating unit comprises a second switch and a second resistor, the first switch and the first resistor are connected in parallel, the second switch and the second resistor are connected in parallel, and the first switch and the second switch are both electrically connected to the controller;
the controller is used for controlling the opening time or the closing time of the first switch or the second switch according to the pre-established mathematical model, and further adjusting the resistance value of the first adjusting unit or the second adjusting unit to be reduced or increased.
3. The battery system of claim 2, wherein the controller is configured to output a first control signal to the first switch according to the pre-established mathematical model, and control an open time or a close time of the first switch by adjusting a duty ratio of the first control signal, so as to adjust a resistance value of the first adjusting unit to decrease or increase.
4. The battery system of claim 2, wherein the controller is configured to output a second control signal to the second switch according to the pre-established mathematical model, and control an open time or a close time of the second switch by adjusting a duty ratio of the second control signal, so as to adjust a resistance value of the second adjusting unit to decrease or increase.
5. The battery system of claim 2, wherein the first switch and the second switch are MOS transistors, the gate of the first switch and the gate of the second switch are electrically connected to the controller, the source and the drain of the first switch are connected in parallel to the first resistor, and the source and the drain of the second switch are connected in parallel to the second resistor.
6. The battery system of claim 1, further comprising at least two current detectors, the number of the at least two current detectors being the same as the number of the at least two battery branches, each current detector being disposed on each corresponding battery branch;
each current detector is used for detecting the real-time output current of each corresponding battery branch circuit;
the controller is used for adjusting the current resistance value of the adjusting unit in each battery branch to reach a target resistance value according to the real-time output current of each battery branch, the set output current and the pre-established mathematical model;
the controller is used for adjusting the resistance value of the adjusting unit in each battery branch circuit from the current resistance value to the target resistance value, so that the output current of each battery branch circuit is the set output current.
7. The battery system of claim 1 wherein the batteries in each battery branch are of the same battery material.
8. An electric vehicle characterized by comprising the battery system according to any one of claims 1 to 6.
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