Liquid metal battery pack rapid equalization management system and control method

Abstract

The invention discloses a liquid metal battery pack rapid equalization management system and a control method, and belongs to the technical field of liquid metal batteries. Through control of two stages of equalization circuit units from a single battery to a module, energy transfer between the single battery / the module is quickly realized, so that the consistency of the single batteries in the battery pack is quickly improved, the available capacity attenuation of the battery pack in the cycle process is reduced, the cycle performance of the battery pack is improved, and the service life of the battery pack is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid metal batteries, and more specifically, relates to a rapid equalization management system and control method for a liquid metal battery pack. Background Art

[0002] Liquid metal batteries, as a new type of electrochemical battery, have a three-layer liquid structure design. They use inorganic molten salts and liquid metals as electrolytes and positive and negative electrodes, respectively. They have the characteristics of low cost, large capacity, and long life, and have broad application prospects in the field of large-scale energy storage. However, liquid metal battery cells have the characteristics of low voltage. In practical applications, compared with lithium-ion batteries, more battery cells need to be connected in series to achieve an increase in the voltage level of the energy storage system. During the operation of the liquid metal battery pack without external control, due to the inconsistency of the cells, the actual dischargeable capacity of the battery pack will continue to decrease as the cycle progresses, and the inconsistency of the cells will be further exacerbated. Since the number of liquid metal battery cells is larger, the actual dischargeable capacity of the battery pack will decrease more rapidly. In order to address the above problems, a balancing circuit will be added to the battery management system and the performance of the battery pack will be optimized through relevant balancing control methods to ensure its long-term stable and reliable operation.

[0003] To address the issue of discharge capacity decay during the cycling of liquid metal battery packs, existing technologies primarily consider battery balancing control, proposing related balancing circuit topologies and balancing control methods. However, these approaches often use voltage as the balancing variable and only actively balance with high currents at the end of the battery pack's charge and discharge cycles. This results in a limited effective balancing time and low balancing efficiency in practical applications. Furthermore, for liquid metal batteries with a wider voltage range, using voltage as the balancing variable does not produce ideal balancing results. Summary of the Invention

[0004] In view of the defects of the prior art, the purpose of the present invention is to provide a liquid metal battery pack rapid equalization management system and control method, aiming to solve the problems of decreased discharge capacity during the circulation of liquid metal battery packs and low equalization efficiency of existing methods.

[0005] To achieve the above objectives, the present invention provides, on one hand, a liquid metal battery pack balancing management system, comprising n intra-module balancing circuit units, one inter-module balancing circuit unit, a balancing control unit, a state monitoring unit, and a central processing unit. Each of the intra-module balancing circuit units includes a battery module, and the battery module includes m battery cells. The n intra-module balancing circuit units are connected in series and simultaneously perform balancing control on the battery pack with the inter-module balancing circuit unit, wherein m ≥ 3, n ≥ 2, and m and n are integers.

[0006] The status detection unit is connected to both ends of each battery cell, calculates the status information of each battery cell and battery module through the collected voltage and current information, and transmits the status information to the central processing unit; the central processing unit is used to receive the status information of each battery cell and send instruction information to the balancing control unit; the balancing control unit is used to receive the instruction information sent by the central processing unit and send corresponding control signals to the intra-module balancing circuit unit or inter-module balancing circuit unit connected to it.

[0007] Preferably, the intra-module balancing circuit unit is composed of one or more Buck-Boost circuits, each of which is composed of a transformer, a MOSFET, an ideal diode and an ideal inductor. The transformer operates in a fly-back mode to provide an energy transmission path between the first battery cell and the last battery cell in the intra-module balancing circuit unit.

[0008] Preferably, the inter-module balancing circuit unit has a substantially identical structure to the intra-module balancing circuit unit, and is composed of one or more Buck-Boost circuits. Each Buck-Boost balancing circuit is composed of a transformer, a MOSFET, an ideal diode, and an ideal inductor. The transformer operates in a fly-back mode, providing an energy transmission path between the first intra-module balancing circuit unit and the last intra-module balancing circuit unit.

[0009] Preferably, in the present invention, the battery cells in the battery pack are liquid metal batteries.

[0010] Preferably, the liquid metal battery pack battery cells are all obtained through consistency screening.

[0011] According to another aspect of the present invention, a control method for a liquid metal battery pack balancing management system is provided, comprising the following steps:

[0012] S1, collect the voltage and current information of the battery cells of the balancing unit in each module, and obtain the status information SOC1, SOC2, SOC3, ..., SOC m ;

[0013] S2, judging whether to start balancing based on the status information of each battery cell, if so, executing S3; otherwise, turning off the balancing control unit and disconnecting the external charging and discharging circuit;

[0014] S3, the balancing control unit receives the command signal from the central processing unit and outputs a PWM wave signal to the MOSFET of the balancing circuit unit in each module, turning on the active balancing of the battery cells in the balancing circuit unit in each module, and determines whether the maximum SOC difference of the battery cells in each module is less than 1%. If so, S4 is executed; otherwise, active balancing of the battery cells in the balancing circuit unit in each module is re-enabled.

[0015] S4, according to the status information SOC1, SOC2, SOC3, ..., SOC of the battery cells of the balancing circuit unit in each module, m Calculate the status information of each module MSOC1, MSOC2, MSOC3, ..., MSOC n The balancing control unit receives the command signal from the central processing unit, outputs a PWM wave signal to the MOSFET of the inter-module balancing circuit unit, turns on the active balancing of the inter-module balancing circuit unit, and judges whether the maximum SOC difference between the modules is <1%. If so, the balancing of the liquid metal battery pack ends; otherwise, the active balancing of the inter-module balancing circuit unit is restarted.

[0016] Beneficial effects: Automatically monitor the voltage of each cell in the battery pack and calculate the SOC of each battery. Based on the calculated SOC of each battery, determine the energy transfer method in the battery module, and output PWM signals to each MOSFET switch through the balancing control unit to achieve energy balancing of the battery cells / modules.

[0017] Preferably, step S3 includes the following steps:

[0018] S31, establish a distance matrix based on the status information of each battery cell Consider each battery cell as a node, where SOC i and SOC j They represent the monomer SOC of the i-th node and the j-th node, 1≤i≤m, 1≤j≤m, and c is a constant;

[0019] S32, establish a path matrix R(i,j)=j, with the first node as the intermediate point k, and the shortest path calculation formula is D(i,j)>D(i,k)+D(k,j). When this condition is met, the distance matrix D and the path matrix R are updated according to D(i,j)=D(i,k)+D(k,j) and R(i,j)=R(i,k). Otherwise, the distance matrix and the path matrix are not updated.

[0020] S33, checking the imbalance state of the battery, the number of batteries in series that need to be charged is stored in the state matrix, and the number of batteries in series that need to be discharged is stored in the state matrix;

[0021] S34, searches for the shortest equilibrium path using the Floyd-Warshall algorithm, and outputs a PWM signal according to the shortest path to drive the corresponding MOSFET to turn it on / off;

[0022] S35, the active balancing control in the module ends.

[0023] Preferably, step S4 includes the following steps:

[0024] S41, establish a distance matrix based on the status information of each battery module Consider each battery module as a node, where MSOC p and MSOC q They represent the module SOC of the p-th node and the q-th node, 1≤p≤n, 1≤q≤n, and c is a constant;

[0025] S42, establish a path matrix R(p,q)=q, with the first node as the intermediate point k, and the shortest path calculation formula is D(p,q)>D(p,k)+D(k,q). When this condition is met, the distance matrix D and the path matrix R are updated according to D(p,q)=D(p,k)+D(k,q) and R(p,q)=R(p,k). Otherwise, the distance matrix and the path matrix are not updated.

[0026] S43, checking the imbalance state of the battery modules, storing the number of battery modules that need to be charged in the state matrix, and storing the number of battery modules that need to be discharged in the state matrix;

[0027] S44, searching for the shortest equilibrium path using the Floyd-Warshall algorithm, and outputting a PWM signal according to the shortest path to drive the corresponding MOSFET to turn it on / off;

[0028] S45, the active balancing control between modules ends.

[0029] The present invention also provides an electronic device, comprising: a computer-readable storage medium and a processor;

[0030] The computer-readable storage medium is used to store executable instructions;

[0031] The processor is configured to read the executable instructions stored in the computer-readable storage medium and execute the above method.

[0032] The present invention also provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to execute the above method.

[0033] The present invention also provides a computer program product, comprising a computer program or instructions, wherein the computer program or instructions implement the above method when executed by a processor.

[0034] Compared with the prior art, the above technical solutions proposed by the present invention can achieve the following:

[0035] Beneficial effects:

[0036] (1) The present invention provides a rapid equalization management system and control method for a liquid metal battery pack. Through two-level control of the cell-to-module equalization circuit unit, the energy transfer between battery cells / modules is rapidly realized, thereby rapidly improving the consistency of cells within the group, reducing the attenuation of the battery pack's available capacity during the cycle process, improving the battery pack's cycle performance and extending its service life.

[0037] (2) The present invention proposes a method for finding the shortest balancing path, which improves the balancing speed and enables the balancing management system to quickly transfer energy between modules / within modules. Through the proposed balancing management system and its control method, the purpose of fast, efficient and accurate balancing of liquid metal battery packs can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a topological diagram of the liquid metal battery pack rapid balancing management system provided by the present invention;

[0039] Figure 2 A topological diagram of a balancing circuit unit within a liquid metal battery module provided by the present invention;

[0040] Figure 3 A schematic diagram of the balancing process of the balancing circuit unit in the liquid metal battery module provided by the present invention;

[0041] Figure 4 The voltage-SOC curve diagram of the liquid metal battery cell provided by the present invention;

[0042] Figure 5 This is a flow chart of the rapid equalization control method for liquid metal battery packs provided by the present invention;

[0043] Figure 6 It is a schematic diagram of the equalization effect of the liquid metal battery rapid equalization management system provided by the present invention. DETAILED DESCRIPTION

[0044] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0045] Figure 1 This is a topological diagram of the rapid balancing management system for liquid metal battery packs provided by the present invention. The balancing management system consists of multiple balancing circuit units (BCU1, BCU2, ..., BCU n ) and an inter-module balancing circuit unit (BCU). The intra-module BCU is used to achieve the balancing of battery cells within the module, and the inter-module balancing control module is used to achieve module balancing between modules.

[0046] Preferably, in this embodiment, n=4, that is, the battery pack is composed of 4 liquid metal battery modules.

[0047] Preferably, in this embodiment, m=4, that is, the battery module is composed of 4 liquid metal battery cells.

[0048] Figure 2 This is a topological diagram of the balancing circuit unit within the liquid metal battery module provided by the present invention. The balancing circuit unit is composed of m battery cells, each of which has two upper and lower MOSFETs and an ideal diode connected in parallel at both ends. A transformer is connected at the end to provide an energy transmission path between the first and last battery cells. When the MOSFET on the upper side of the cell is turned on, it serves as a battery discharge path, storing the battery discharge energy in the inductor and transformer; when the MOSFET on the lower side of the cell is turned on, it serves as a battery charging path, transferring the energy stored in the inductor and transformer to the battery cell. The ideal diode is used for clamping in the circuit.

[0049] Figure 3 Schematic diagram of the balancing process of the balancing circuit unit in the liquid metal battery pack module provided by the present invention. The battery status monitoring module monitors the status of the two batteries and inputs it to the central processing unit. After receiving the instruction, the post-balancing control module sends a PWM signal to the MOSFET to realize the charging and discharging of the battery cells. When the MOSFET on cell 1 is turned on and the MOSFET on cell 2 is turned off, cell 1 charges the inductor L and the energy is transferred to L; when the MOSFET on cell 1 is turned off and the MOSFET on cell 2 is turned on, the inductor L charges the cell 2 and the energy on the inductor L is transferred to cell 2. This constitutes the process of energy transfer from cell 1 to cell 2. Similarly, the energy transfer path between the remaining cells in the module is similar to the above process and will not be repeated.

[0050] Figure 4 This is a voltage-SOC curve for a liquid metal battery cell provided by the present invention. Because liquid metal batteries have a low and wide voltage plateau, to more effectively improve battery pack capacity utilization, both two-stage balancing control systems use SOC as the balancing variable. In this embodiment, an extended Kalman algorithm is used to accurately estimate SOC.

[0051] Figure 5 This is a flow chart of the rapid equalization control method for liquid metal battery packs provided by the present invention. It includes the following steps:

[0052] S1, the status monitoring module of the balancing unit in each module collects the voltage and current information of the battery cells and obtains the SOC1, SOC2, SOC3, ..., SOC m And each module status information MSOC1, MSOC2, MSOC3, ..., MSOC n ;

[0053] S2: After receiving the status information of each battery, the central processing unit makes a judgment and sends a command signal to each balancing control unit to perform intra-module / inter-module balancing;

[0054] S3, the module's internal balancing control unit receives the command signal from the central processing unit and outputs a PWM wave signal to each MOSFET to achieve active balancing of the monomers in each module;

[0055] S4, the inter-module balancing control unit receives the command signal from the central processing unit and outputs a PWM wave signal to each MOSFET to achieve active balancing between modules.

[0056] Preferably, step S3 includes the following steps:

[0057] S31, establish a distance matrix based on the status information of each battery cell Among them, SOC i and SOC j They represent the monomer SOC of the i-th node and the j-th node, 1≤i≤m, 1≤j≤m, and c is a constant;

[0058] S32, establish a path matrix R(i,j)=j, with the first node as the intermediate point k, and the shortest path calculation formula is D(i,j)>D(i,k)+D(k,j). When this condition is met, the distance matrix D and the path matrix R are updated according to D(i,j)=D(i,k)+D(k,j) and R(i,j)=R(i,k). Otherwise, the distance matrix and the path matrix are not updated.

[0059] S33, checking the imbalance state of the battery, the number of batteries in series that need to be charged is stored in the state matrix, and the number of batteries in series that need to be discharged is stored in the state matrix;

[0060] S34, searches for the shortest equilibrium path using the Floyd-Warshall algorithm, and outputs a PWM signal according to the shortest path to drive the corresponding MOSFET to turn it on / off;

[0061] S35, the active balancing control in the module ends.

[0062] Preferably, step S4 includes the following steps:

[0063] S41, establish a distance matrix based on the status information of each module Among them, MSOC p and MSOC q They represent the module SOC of the p-th node and the q-th node, 1≤p≤n, 1≤q≤n, and c is a constant;

[0064] S42, establish a path matrix R(p,q)=q, with the first node as the intermediate point k, and the shortest path calculation formula is D(p,q)>D(p,k)+D(k,q). When this condition is met, the distance matrix D and the path matrix R are updated according to D(p,q)=D(p,k)+D(k,q) and R(p,q)=R(p,k). Otherwise, the distance matrix and the path matrix are not updated.

[0065] S43, checking the imbalance state of the battery modules, storing the number of battery modules that need to be charged in the state matrix, and storing the number of battery modules that need to be discharged in the state matrix;

[0066] S44, searching for the shortest equilibrium path, and outputting a PWM signal according to the shortest path to drive the corresponding MOSFET to turn it on / off;

[0067] S35, the active balancing control between modules ends.

[0068] Figure 6 This is a schematic diagram of the balancing effect of the liquid metal battery rapid balancing management system provided by the present invention. It can be seen that in a simulation environment, under dynamic operating conditions, the energy of each battery cell is quickly and efficiently balanced after being controlled by the balancing management system, effectively improving the consistency of the liquid metal battery pack.

[0069] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A liquid metal battery pack balancing management system, characterized in that: include: n intra-module balancing circuit units, 1 inter-module balancing circuit unit, a balancing control unit, a state monitoring unit and a central processing unit, each of the intra-module balancing circuit units includes a battery module, the battery module includes m battery cells, the n intra-module balancing circuit units are connected in series with each other, and perform balancing control on the battery pack simultaneously with the inter-module balancing circuit unit, wherein m≥3, n≥2, and m and n are integers; The status detection unit is connected to both ends of each battery cell, and obtains the status information of each battery cell and the battery module by calculating the collected voltage and current information, and transmits the status information to the central processing unit; the central processing unit is used to receive the status information of each battery cell and send instruction information to the balancing control unit; the balancing control unit is used to receive the instruction information sent by the central processing unit, and send corresponding control signals to the intra-module balancing circuit unit or the inter-module balancing circuit unit connected to it.

2. The liquid metal battery pack balancing management system according to claim 1, characterized in that: The module-internal balancing circuit unit includes more than one group of Buck-Boost circuits, each group of the Buck-Boost circuits includes a transformer, a MOSFET, an ideal diode and an ideal inductor, and the transformer works in a fly-back mode to provide an energy transmission path between the first battery cell and the last battery cell in the module-internal balancing circuit unit.

3. The liquid metal battery pack balancing management system according to claim 1, characterized in that: The inter-module balancing circuit unit includes more than one group of Buck-Boost circuits, each group of the Buck-Boost circuits includes a transformer, a MOSFET, an ideal diode and an ideal inductor, and the transformer works in a fly-back mode to provide an energy transmission path between the first module intra-module balancing circuit unit and the last module intra-module balancing circuit unit.

4. The liquid metal battery pack balancing management system according to claim 1, characterized in that: The battery cell is a liquid metal battery.

5. A liquid metal battery pack balancing management method based on the liquid metal battery pack balancing management system according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, collect the voltage and current information of the battery cells of the balancing circuit unit in each module, and obtain the status information SOC1, SOC2, SOC3, ..., SOC m ; S2, judging whether to start balancing according to the status information of each battery cell, if yes, executing S3; otherwise, turning off the balancing control unit and cutting off the external charging and discharging circuit; S3, the balancing control unit receives the command signal from the central processing unit, outputs a PWM wave signal to the MOSFET of the balancing circuit unit in each module, turns on the active balancing of the battery cells in the balancing circuit unit in each module, and judges whether the maximum SOC difference of the single battery in each module is less than 1%. If so, execute S4; otherwise, restart the active balancing of the battery cells in the balancing circuit unit in each module; S4, according to the status information SOC1, SOC2, SOC3, ..., SOC m Calculate the status information of each module MSOC1, MSOC2, MSOC3, ..., MSOC n The balancing control unit receives the command signal from the central processing unit, outputs a PWM wave signal to the MOSFET of the inter-module balancing circuit unit, turns on the active balancing of the inter-module balancing circuit unit, and judges whether the maximum SOC difference between the modules is <1%. If so, the balancing of the liquid metal battery pack ends; otherwise, the active balancing of the inter-module balancing circuit unit is restarted.

6. The liquid metal battery pack equalization management method according to claim 5, characterized in that: The step S3 comprises the following steps: S31, establishing a distance matrix based on the status information of each battery cell Among them, SOC i and SOC j Represent the monomer SOC of the i-th node and the j-th node respectively, 1≤i≤m, 1≤j≤m, c is a constant; S32, establish a path matrix R(i,j)=j, take the first node as the middle point k, and the shortest path calculation formula is D(i,j)>D(i,k)+D(k,j). When this condition is met, the distance matrix D and the path matrix R are updated according to D(i,j)=D(i,k)+D(k,j) and R(i,j)=R(i,k), otherwise the distance matrix and the path matrix are not updated; S33, checking the unbalanced state of the battery, the number of batteries in series that need to be charged is stored in the state matrix, and the number of batteries in series that need to be discharged is stored in the state matrix; S34, searching for the shortest equilibrium path through the Floyd-Warshall algorithm, and outputting a PWM signal according to the shortest path to drive the corresponding MOSFET to turn it on / off; S35, the active balancing control in the module ends.

7. The liquid metal battery pack equalization management method according to claim 5, characterized in that: The step S4 comprises the following steps: S41, establish a distance matrix based on the status information of each module Among them, MSOC p and MSOC q They represent the module SOC of the p-th node and the q-th node, 1≤p≤n, 1≤q≤n, and c is a constant; S42, establish a path matrix R(p,q)=q, take the first node as the middle point k, and the shortest path calculation formula is D(p,q)>D(p,k)+D(k,q). When this condition is met, the distance matrix D and the path matrix R are updated according to D(p,q)=D(p,k)+D(k,q) and R(p,q)=R(p,k), otherwise the distance matrix and the path matrix are not updated; S43, checking the unbalanced state of the battery modules, the number of battery modules that need to be charged is stored in the state matrix, and the number of battery modules that need to be discharged is stored in the state matrix; S44, searching for the shortest equilibrium path through the Floyd-Warshall algorithm, and outputting a PWM signal according to the shortest path to drive the corresponding MOSFET to turn it on / off; S45, the active balancing control between modules ends.

8. An electronic device, characterized in that: include: A computer readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read the executable instructions stored in the computer-readable storage medium and execute the method according to any one of claims 1 to 7.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to execute the method according to any one of claims 1 to 7.

10. A computer program product comprising a computer program or instructions, characterized in that When the computer program or instruction is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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