Inductive active balancing strategy and system

Abstract

The embodiment of the present invention provides an inductive active balancing strategy and system, which belongs to the technical field of battery charge balancing. The balancing strategy includes: obtaining a circuit diagram model of an active balancing circuit; constructing a bond graph model according to the circuit diagram model; determining the state equation of the active balancing circuit according to the bond graph model; determining the corresponding output equation according to the active balancing circuit; establishing a cost function equation according to the output equation; traversing the allowable value of the inductor current reference value to obtain the minimum value of the cost function equation; obtaining the inductor current reference value of each inductor in the active balancing circuit according to the minimum value of the cost function equation; performing active balancing operation according to the actual value of the inductor current and the inductor current reference value. The balancing strategy and system derive the state equation of the system by constructing a bond graph model, accurately describe the working condition of the system, and realize model prediction and control based on the state equation, thereby improving the efficiency of battery balancing.

Description

Technical Field

[0001] The present invention relates to the technical field of battery charge balancing, and in particular to an inductive active balancing strategy and system. Background Art

[0002] Series cell balancing can improve the reliability of battery charging and discharging and extend battery life. Series cell balancing places higher demands on the battery management system (BMS). Inductor-based battery balancing solutions have the advantages of simple topology and control strategy. These inductor-based battery balancing solutions are most common in industrial applications. However, in most inductor-based battery balancing solutions, the inductor can only transfer energy between adjacent batteries, and the speed of inductor-based battery balancing solutions is low. Summary of the invention

[0003] The purpose of the present invention is to provide an inductive active balancing strategy and system, which derives the state equation of the system by constructing a bond graph model, accurately describes the working conditions of the system, and realizes model prediction and control based on the state equation, thereby improving the efficiency of battery balancing.

[0004] In order to achieve the above object, an embodiment of the present invention provides an inductive active balancing strategy, including:

[0005] Obtaining a circuit diagram model of an active equalization circuit;

[0006] constructing a bonding graph model according to the circuit graph model;

[0007] Determining a state equation of the active balancing circuit according to the bond graph model;

[0008] Determine an output equation corresponding to the active equalization circuit;

[0009] Establishing a cost function equation according to the output equation;

[0010] Traverse the allowable values ​​of the inductor current reference value to obtain the minimum value of the cost function equation;

[0011] Obtaining an inductor current reference value of each inductor in the active balancing circuit according to the minimum value of the cost function equation;

[0012] An active balancing operation is performed according to the actual value of the inductor current and the reference value of the inductor current.

[0013] Optionally, determining a state equation of the active balancing circuit according to the bond graph model includes:

[0014] According to formula (1), the input variables of the bond graph model are determined.

[0015] , (1)

[0016] in, is the input variable, For the The switching signal corresponding to each single cell, For the current moment, is an integer number, is the number of single cells.

[0017] Optionally, determining a state equation of the active balancing circuit according to the bond graph model includes:

[0018] According to formula (2), the state variables of the bond graph model are determined.

[0019] , (2)

[0020] in, is the state variable, For the An inductor flux.

[0021] Optionally, determining a state equation of the active balancing circuit according to the bond graph model includes:

[0022] According to formula (3) and formula (4), the inductor voltage and inductor current of the bond graph model are determined.

[0023] , (3)

[0024] , (4)

[0025] in, For the The inductor voltage, For the The first differential of the inductor flux, For the The inductor current, For the A balancing inductor.

[0026] Optionally, determining a state equation of the active balancing circuit according to the bond graph model includes:

[0027] The state equation of the active balancing circuit is determined according to formula (5):

[0028] , (5)

[0029] in, is the first differential of the state variable, For the The terminal voltage of each battery cell, , is the coefficient matrix.

[0030] Optionally, determining a state equation of the active balancing circuit according to the bond graph model includes:

[0031] Determine the coefficient matrix according to formula (6) and formula (7) and ,

[0032] , (6)

[0033] , (7).

[0034] Optionally, determining a corresponding output equation according to the active equalization circuit includes:

[0035] According to formula (8), the active equalization circuit determines the corresponding output equation:

[0036] , (8)

[0037] in, is the output variable, For the Single cell battery , For the The capacity of a single battery.

[0038] Optionally, establishing a cost function equation according to the output equation includes:

[0039] According to formula (9), the cost function equation is established:

[0040] , (9)

[0041] in, For array No. The value of the row, is the predicted output variable, is the cost function value.

[0042] Optionally, obtaining the minimum value of the cost function equation includes:

[0043] Discretize formula (5) to obtain formula (10):

[0044] , (10)

[0045] in, For the The corresponding state variable for the calculation is For the The predicted value of the state variable at the next moment in the calculation, To participate in The input variables of the calculation are An integer number.

[0046] On the other hand, the present invention further provides an inductive active balancing system, the balancing system comprising a processor for executing any of the above balancing strategies.

[0047] Through the above technical scheme, the present invention provides an inductive active balancing strategy and system, which obtains the circuit diagram model of the active balancing circuit, constructs a bond graph model according to the circuit diagram model, determines the state equation and the corresponding output equation of the active balancing circuit according to the bond graph model, establishes a cost function equation according to the output equation, traverses the allowable value of the inductor current reference value, obtains the minimum value of the cost function equation, obtains the inductor current reference value of each inductor in the active balancing circuit according to the minimum value of the cost function equation, and controls the actual value of the inductor current to be equal to the inductor current reference value according to the actual value of the inductor current and the inductor current reference value, thereby performing active balancing operation on the battery pack. The balancing strategy and system derives the state equation of the system by constructing a bond graph model, accurately describes the working condition of the system, and realizes model prediction and control based on the state equation, thereby improving the efficiency of battery balancing.

[0048] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings:

[0050] Figure 1 is a flow chart of an inductive active balancing strategy according to an embodiment of the present invention;

[0051] Figure 2 is a bonding graph model of an inductive active balancing circuit according to an embodiment of the present invention;

[0052] Figure 3 is a circuit diagram model of an inductive active balancing circuit according to an embodiment of the present invention;

[0053] Figure 4 It is a flow chart for determining the state equation of the active balancing circuit in the inductive active balancing strategy according to one embodiment of the present invention. DETAILED DESCRIPTION

[0054] The specific implementation of the embodiment of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the embodiment of the present invention, and is not used to limit the embodiment of the present invention.

[0055] like Figure 1 FIG. 1 is a flow chart of an inductive active balancing strategy according to an embodiment of the present invention. Figure 2 FIG. 1 is a bonding graph model of an inductive active balancing circuit according to an embodiment of the present invention. Figure 3 FIG. 1 is a circuit diagram model of an inductive active balancing circuit according to an embodiment of the present invention. Figure 1 In the example, the balancing strategy may include:

[0056] In step S10, a circuit diagram model of an active equalization circuit is obtained;

[0057] In step S20, a bonding graph model is constructed according to the circuit graph model;

[0058] In step S30, a state equation of the active equalization circuit is determined according to the bond graph model;

[0059] In step S40, an output equation corresponding to the active equalization circuit is determined;

[0060] In step S50, a cost function equation is established according to the output equation;

[0061] In step S60, the allowable values ​​of the inductor current reference value are traversed to obtain the minimum value of the cost function equation;

[0062] In step S70, the inductor current reference value of each inductor in the active balancing circuit is obtained according to the minimum value of the cost function equation;

[0063] In step S80 , an active balancing operation is performed according to the actual value of the inductor current and the reference value of the inductor current.

[0064] In step S10 to step S80, the circuit diagram model of the active balancing circuit is first obtained, and a bond graph model is constructed according to the circuit diagram model. The state equation of the active balancing circuit can be determined through the bond graph model, and the output equation corresponding to the active balancing circuit is determined. The cost function equation is established through the output equation, and the allowable values ​​of the current inductance reference value are traversed to obtain the minimum value of the cost function equation. The inductor current reference value of each inductor in the active balancing circuit is obtained according to the minimum value of the cost function equation. According to the actual value of the inductor current and the inductor current reference value, the actual value of the inductor current is controlled to be equal to the inductor current reference value, thereby performing active balancing operation on the battery pack.

[0065] In this Figure 1In the method shown, step S10 can be used to obtain a circuit diagram model of the active equalization circuit. The circuit diagram model obtained in step S10 can be as follows: Figure 3 Step S20 can be used to construct a bonding graph model according to the circuit diagram model of FIG. 3 . The bonding graph model constructed in step S20 can be as follows: Figure 2 As shown. Figure 2 In the circuit, there are Battery cells and A balancing inductor, The node is a switch node, corresponding to Figure 3 In and The parallel structure of Figure 2 Take the top equalization unit in as an example, The keys of the nodes are 1-7 and 1-8 respectively, and their potential flow relationship can be expressed by formula (11):

[0066] , (11)

[0067] in, is the switch on-duty cycle, is the conduction duty cycle of the anti-parallel diode, is the current of the keys numbered 1-7, is the current of the keys numbered 1-8, is the voltage of the keys numbered 1-7, is the voltage of the keys numbered 1-8.

[0068] Step S30 may be used to determine the state equation of the active equalization circuit according to the bond graph model. The specific method for determining the state equation may be in various forms known to those skilled in the art. In one example of the present invention, the method for determining the state equation may include: Figure 4 The steps shown. Specifically:

[0069] In step S11, the input variables of the bond graph model are determined according to formula (1).

[0070] , (1)

[0071] in, is the input variable, For the The switching signal corresponding to each single cell, For the current moment, is an integer number, is the number of single cells.

[0072] Since all switches will not be turned on at the same time, so the formula (1) can be Dimensional data is reduced to dimensional, which corresponds to the dimension of the state equation, that is, formula (12):

[0073] , (12).

[0074] In step S12, the state variables of the bond graph model are determined according to formula (2):

[0075] , (2)

[0076] in, is the state variable, For the An inductor flux.

[0077] In step S13, the inductor voltage and inductor current of the bond graph model are determined according to formula (3) and formula (4).

[0078] , (3)

[0079] , (4)

[0080] in, For the The inductor voltage, For the The first differential of the inductor flux, For the The inductor current, For the A balancing inductor.

[0081] According to formula (3) and formula (4), the first differential of the state variable is determined according to formula (13):

[0082] , (13)

[0083] in, For the number The voltage of the key.

[0084] In step S14, the state equation of the active balancing circuit is determined according to formula (5):

[0085] , (5)

[0086] in, is the first differential of the state variable, For the The terminal voltage of each battery cell, , is the coefficient matrix.

[0087] In step S15, the coefficient matrix is ​​determined according to formula (6) and formula (7): and ,

[0088] , (6)

[0089] , (7).

[0090] Step S40 may be used to determine the output equation corresponding to the active equalization circuit. The specific method for determining the corresponding output equation may be in various forms known to those skilled in the art. In one example of the present invention, the output equation corresponding to the active equalization circuit may be determined according to formula (8):

[0091] , (8)

[0092] in, is the output variable, For the Single cell battery , For the The capacity of a single battery.

[0093] Step S50 can be used to establish a cost function equation according to the output equation. The specific method for establishing the cost function equation can be various forms known to those skilled in the art. In one example of the present invention, the cost function equation can be established according to formula (9):

[0094] , (9)

[0095] in, Represents an array No. The value of the row, is the predicted output variable, is the cost function value.

[0096] Step S60 can be used to traverse the allowable values ​​of the inductor current reference value to obtain the minimum value of the cost function equation. The specific method for obtaining the minimum value of the cost function equation can be a variety of forms known to those skilled in the art. In one example of the present invention, the minimum value of the cost function equation can be obtained by discretizing formula (5) to obtain formula (10),

[0097] , (10)

[0098] in, For the The corresponding state variable for the calculation is For the The predicted value of the state variable at the next moment in the calculation, To participate in The input variables of the calculation are An integer number.

[0099] According to the reference value of each inductor current, the first The corresponding state variables for the calculation , traverse the allowable values ​​of each inductor current reference value, and calculate the different The predicted value of the state variable at the next moment , substitute into the output equation formula (8) to calculate the output variable The value is then substituted into formula (9) to calculate the cost function value.

[0100] Step S70 can be used to obtain the inductor current reference value of each inductor in the active balancing circuit according to the minimum value of the cost function equation, that is, the optimal reference value of the balancing current value. Step S80 can be used to perform active balancing operation according to the actual value of the inductor current and the reference value of the inductor current, and control the actual value of the inductor current in the circuit to be equal to the reference value of the inductor current, thereby achieving efficient balancing of the battery pack.

[0101] On the other hand, the present invention further provides an inductive active balancing system, the balancing system comprising a processor for executing any of the above balancing strategies.

[0102] Through the above technical scheme, the present invention provides an inductive active balancing strategy and system, which obtains the circuit diagram model of the active balancing circuit, constructs a bond graph model according to the circuit diagram model, determines the state equation and the corresponding output equation of the active balancing circuit according to the bond graph model, establishes a cost function equation according to the output equation, traverses the allowable value of the inductor current reference value, obtains the minimum value of the cost function equation, obtains the inductor current reference value of each inductor in the active balancing circuit according to the minimum value of the cost function equation, and controls the actual value of the inductor current to be equal to the inductor current reference value according to the actual value of the inductor current and the inductor current reference value, thereby performing active balancing operation on the battery pack. The balancing strategy and system derives the state equation of the system by constructing a bond graph model, accurately describes the working condition of the system, and realizes model prediction and control based on the state equation, thereby improving the efficiency of battery balancing.

[0103] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0104] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0105] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0106] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0107] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0108] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0109] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0110] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0111] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. An inductive active balancing strategy, characterized in that: The balancing strategy includes: Obtain a circuit diagram model of an active equalization circuit; constructing a bonding graph model according to the circuit graph model; Determining a state equation of the active balancing circuit according to the bond graph model; Determine an output equation corresponding to the active equalization circuit; Establishing a cost function equation according to the output equation; Traverse the allowable values ​​of the inductor current reference value to obtain the minimum value of the cost function equation; Obtaining an inductor current reference value of each inductor in the active balancing circuit according to the minimum value of the cost function equation; Performing active balancing operation according to the inductor current reference value and the inductor current actual value; Determining a corresponding output equation according to the active equalization circuit includes: According to formula (8), the output equation corresponding to the active equalization circuit is determined: ，（8） in, is the output variable, For the Single cell battery , For the The capacity of a single battery, For the current moment, is an integer number, is the number of single cells, is the state variable, specifically the inductor flux.

2. The balancing strategy according to claim 1, characterized in that: Determining a state equation of the active balancing circuit according to the bond graph model includes: According to formula (1), the input variables of the bond graph model are determined. ，（1） in, is the input variable, For the The switching signal corresponding to each single battery.

3. The balancing strategy according to claim 2, characterized in that: Determining a state equation of the active balancing circuit according to the bond graph model includes: According to formula (2), the state variables of the bond graph model are determined. ，（2） in, For the An inductor flux.

4. The balancing strategy according to claim 3, characterized in that: Determining a state equation of the active balancing circuit according to the bond graph model includes: According to formula (3) and formula (4), the inductor voltage and inductor current of the bond graph model are determined. ，（3） ，（4） in, For the The inductor voltage, For the The first differential of the inductor flux, For the The inductor current, For the A balancing inductor.

5. The balancing strategy according to claim 4, characterized in that: Determining a state equation of the active balancing circuit according to the bond graph model includes: The state equation of the active balancing circuit is determined according to formula (5): ，（5） in, is the first differential of the state variable, For the The terminal voltage of each battery cell, , is the coefficient matrix.

6. The balancing strategy according to claim 5, characterized in that: Determining a state equation of the active balancing circuit according to the bond graph model includes: Determine the coefficient matrix according to formula (6) and formula (7) and , ，（6） ，（7）。 7. The balancing strategy according to claim 6, characterized in that: Establishing a cost function equation according to the output equation includes: According to formula (9), the cost function equation is established: ，（9） in, For array No. The value of the row, is the predicted output variable, is the cost function value.

8. The balancing strategy according to claim 5, characterized in that: Get the minimum value of the cost function equation, including: Discretize formula (5) to obtain formula (10): ，（10） in, For the The corresponding state variable for the calculation is For the The predicted value of the state variable at the next moment in the calculation, To participate in The input variables of the calculation are An integer number.

9. An inductive active balancing system, characterized in that: The balancing system comprises a processor, configured to execute the balancing strategy according to any one of claims 1 to 8.

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