A liquid metal battery pack rapid equalization management system and control method

Abstract

The application discloses a liquid metal battery pack quick equalization management system and a control method, and belongs to the technical field of liquid metal batteries. The application realizes the energy transfer between the battery monomers and the modules quickly through the control of the two-stage equalization circuit units from the monomers to the modules, thereby quickly improving the consistency of the monomers in the group, reducing the available capacity attenuation of the battery pack in the cycle process, improving the cycle performance of the battery pack, and prolonging the service life of the battery pack.

Description

Technical Field

[0001] This invention belongs to the field of liquid metal battery technology, and more specifically, relates to a rapid equalization management system and control method for liquid metal battery packs. Background Technology

[0002] Liquid metal batteries, as a novel type of electrochemical battery, feature a three-layer liquid structure design. They utilize inorganic molten salt and liquid metal as the electrolyte and positive and negative electrodes, respectively, offering advantages such as low cost, large capacity, and long lifespan, making them promising for large-scale energy storage applications. However, individual liquid metal battery cells exhibit low voltage. In practical applications, compared to lithium-ion batteries, more cells need to be connected in series to achieve higher voltage levels in the energy storage system. During uncontrolled operation of liquid metal battery packs, due to cell inconsistency, the actual discharge capacity of the pack decreases continuously with cycling, further exacerbating this inconsistency. Because liquid metal battery packs have a larger number of cells, the actual discharge capacity decreases even more rapidly. To address these issues, battery management systems incorporate balancing circuits and employ relevant balancing control methods to optimize battery pack performance, ensuring long-term stable and reliable operation.

[0003] To address the capacity decay issue in liquid metal battery packs during cycling, current technologies primarily focus on battery equalization control, proposing relevant equalization circuit topologies and control methods. However, these methods often use voltage as the equalization variable and only employ high current for active equalization at the end of the charge / discharge cycle, resulting in limited effective equalization time and low equalization efficiency in practical applications. Furthermore, for liquid metal batteries with a wider voltage platform, using voltage as the equalization variable does not yield ideal equalization results. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a fast equalization management system and control method for liquid metal battery packs, which aims to solve the problems of reduced discharge capacity during the cycling process of liquid metal battery packs and low equalization efficiency of existing methods.

[0005] To achieve the above objectives, the present invention provides a liquid metal battery pack equalization management system, comprising n intra-module equalization circuit units, 1 inter-module equalization circuit unit, an equalization control unit, a status monitoring unit, and a central processing unit. Each intra-module equalization circuit unit includes one battery module, and the battery module includes m individual battery cells. The n intra-module equalization circuit units are connected in series and simultaneously perform equalization control on the battery pack with the inter-module equalization 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. It calculates the status information of each battery cell and battery module by collecting 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 equalization control unit. The equalization control unit is used to receive the instruction information sent by the central processing unit and send corresponding control signals to the equalization circuit unit within the module or the equalization circuit unit between modules connected to it.

[0007] Preferably, the equalization circuit unit within the module consists of one or more Buck-Boost circuits. Each Buck-Boost equalization circuit consists of a transformer, a MOSFET, an ideal diode, and an ideal inductor. The transformer operates in a fly-back mode, providing an energy transfer path between the first and last battery cells within the equalization circuit unit of a module.

[0008] Preferably, the inter-module equalization circuit unit has a structure that is basically the same as the intra-module equalization circuit unit, and is composed of one or more Buck-Boost circuits. Each Buck-Boost equalization circuit consists of a transformer, a MOSFET, an ideal diode, and an ideal inductor. The transformer operates in a fly-back mode and provides an energy transfer path between the first intra-module equalization circuit unit and the last intra-module equalization circuit unit.

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

[0010] Preferably, the individual cells of the liquid metal battery pack are obtained through a consistency screening process.

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

[0012] S1, Collect the voltage and current information of the battery cells in each module's equalization unit to obtain the state information of each battery cell: SOC1, SOC2, SOC3, ..., SOC m ;

[0013] S2, determine whether to enable equalization based on the status information of each battery cell; if yes, proceed to S3; otherwise, shut down the equalization control unit and disconnect the external charging and discharging circuit.

[0014] S3, the equalization control unit receives the instruction signal from the central processing unit, outputs the PWM wave signal to the MOSFET of the equalization circuit unit in each module, turns on the active equalization of the battery cells in the equalization circuit unit in each module, and determines that the maximum SOC difference of the battery cells in each module is <1%. If so, then execute S4; otherwise, turn on the active equalization of the battery cells in the equalization circuit unit in each module again.

[0015] S4, based on the state information of the individual battery cells in the equalization circuit unit within each module, SOC1, SOC2, SOC3, ..., SOC m The status information of each module, MSOC1, MSOC2, MSOC3, ..., MSOC, is calculated. n The equalization control unit receives the instruction signal from the central processing unit and outputs the PWM wave signal to the MOSFET of the inter-module equalization circuit unit to enable the active equalization of the inter-module equalization circuit unit. It determines that the maximum SOC difference between each module is <1%. If so, the liquid metal battery pack equalization ends; otherwise, the active equalization of the inter-module equalization circuit unit is restarted.

[0016] Beneficial effects: Automatically monitors the voltage of each cell in the battery pack and calculates the SOC of each cell. Based on the calculated SOC of each cell, it determines the energy transfer mode in the battery module and outputs PWM signals to each MOSFET switch through the equalization control unit to achieve energy balance of the cell / module.

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

[0018] S31, Establish a distance matrix based on the state information of each battery cell. Each battery cell is considered a node, where SOC i and SOC j Let SOC represent the individual nodes of the i-th node and the j-th node respectively, where 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. 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, check the battery imbalance state. The number of batteries that need to be charged in series is stored in the state matrix, and the number of batteries that need to be discharged in series is stored in the state matrix.

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

[0022] S35, active balancing control within 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. Each battery module is considered as a node, where MSOC p and MSOC q Let SOC represent the modules of the p-th node and the q-th node respectively, where 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. 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, check the imbalance 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.

[0027] S44 searches for the shortest equalization path using the Floyd-Warshall algorithm and outputs a PWM signal based on the shortest path to drive the corresponding MOSFET to turn it on / off.

[0028] S45, inter-module active balancing control 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 used to read executable instructions stored in the computer-readable storage medium and execute the above-described method.

[0032] The present invention also provides a computer-readable storage medium storing computer instructions for causing a processor to perform the above-described method.

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

[0034] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following results.

[0035] Beneficial effects:

[0036] (1) This invention provides a fast equalization management system and control method for liquid metal battery packs. Through the control of two-level equalization circuit units from individual cells to modules, the energy transfer between individual cells / modules is quickly realized, thereby rapidly improving the consistency of individual cells within the pack, reducing the decay of the available capacity of the battery pack during the cycle, improving the cycle performance of the battery pack and extending its service life.

[0037] (2) This 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 / within modules. Through the proposed balancing management system and its control method, the goal of fast, efficient and accurate balancing of liquid metal battery packs can be achieved. Attached Figure Description

[0038] Figure 1 A schematic diagram of the topology of the liquid metal battery pack rapid equalization management system provided by the present invention;

[0039] Figure 2 A schematic diagram of the topology of the equalization circuit unit within the liquid metal battery module provided by this invention;

[0040] Figure 3 A schematic diagram of the equalization process of the equalization circuit unit within the liquid metal battery module provided by the present invention.

[0041] Figure 4 The liquid metal battery cell voltage-SOC curve provided by this invention;

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

[0043] 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. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be 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 illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0045] Figure 1 This is a schematic diagram of the topology of the fast equalization management system for liquid metal battery packs provided by the present invention. The equalization management system consists of multiple equalization circuit units within each module (BCU1, BCU2, ..., BCU...). n It consists of two levels: a module equalization circuit unit (BCU) and an inter-module equalization control module. The BCU within the module is used to achieve equalization of individual battery cells within the module, while the inter-module equalization control module is used to achieve equalization between modules.

[0046] Preferably, in this embodiment, n=4, that is, the battery pack consists 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 comprises m battery cells. Each battery cell has two MOSFETs (upper and lower) and an ideal diode connected in parallel across its terminals. A transformer is connected at the end to provide an energy transfer path between the first and last battery cells. When the upper MOSFET 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 lower MOSFET 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 This is a schematic diagram of the balancing process within the balancing circuit unit of the liquid metal battery pack module provided by the present invention. The battery state monitoring module monitors the state of the two batteries and inputs the data to the central processing unit. The balancing control module then receives the command and sends a PWM signal to the MOSFETs to realize the charging and discharging of the individual battery cells. When the MOSFET on cell 1 is turned on and the MOSFET on cell 2 is turned off, cell 1 charges inductor L, and energy is transferred to L. When the MOSFET on cell 1 is turned off and the MOSFET on cell 2 is turned on, inductor L charges cell 2, and energy is transferred from inductor L to cell 2. This constitutes the process of energy transfer from cell 1 to cell 2. Similarly, the energy transfer paths between the remaining cells in the module are similar to the above process and will not be described in detail.

[0050] Figure 4 This invention provides a voltage-SOC curve for a single liquid metal battery cell. Because liquid metal batteries have a low and wide voltage plateau, both stages of the equalization control system use SOC as the equalization variable to more effectively improve the battery pack capacity utilization. In this embodiment, an extended Kalman algorithm is used to estimate the accurate SOC value.

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

[0052] S1, the state monitoring module of the equalization unit in each module collects the voltage and current information of the individual battery cells to obtain the SOC1, SOC2, SOC3, ..., SOC of each cell. m and the status information of each module 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 equalization control unit to perform equalization within / between modules;

[0054] S3, the equalization control unit in the module receives the instruction signal from the central processing unit and outputs the PWM wave signal to each MOSFET to realize the active equalization of each unit in the module;

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

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

[0057] S31, Establish a distance matrix based on the state information of each battery cell. SOC i and SOC j Let SOC represent the individual nodes of the i-th node and the j-th node respectively, where 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. 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, check the battery imbalance state. The number of batteries that need to be charged in series is stored in the state matrix, and the number of batteries that need to be discharged in series is stored in the state matrix.

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

[0061] S35, active balancing control within 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. MSOC p and MSOC q Let SOC represent the modules of the p-th node and the q-th node respectively, where 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. 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, check the imbalance 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.

[0066] S44 searches for the shortest equalization path and outputs a PWM signal based on the shortest path to drive the corresponding MOSFET to turn it on / off.

[0067] S35, inter-module active balancing control ends.

[0068] Figure 6 This is a schematic diagram illustrating the balancing effect of the rapid balancing management system for liquid metal batteries provided by this invention. It can be seen that in the simulation environment, under dynamic operating conditions, the energy of each battery cell achieves rapid and efficient balancing after being managed by the balancing management system, effectively improving the consistency of the liquid metal battery pack.

[0069] Those skilled in the art will readily understand 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 within the scope of protection of the present invention.

Claims

1. A liquid metal battery pack balancing management method based on a liquid metal battery pack balancing management system, wherein the liquid metal battery pack balancing management system includes 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 intra-module balancing circuit unit includes one battery module, and the battery module includes m individual battery cells. The n intra-module balancing circuit units are connected in series and simultaneously perform balancing control of the battery pack with the inter-module balancing circuit unit. m≥3, n≥2, and m and n are integers; the state detection unit is connected to both ends of each battery cell, calculates the state information of each battery cell and battery module by collecting voltage and current information, and transmits the state information to the central processing unit; the central processing unit is used to receive the state information of each battery cell and send instruction information to the equalization control unit; the equalization control unit is used to receive the instruction information sent by the central processing unit and send corresponding control signals to the equalization circuit unit within the module or the equalization circuit unit between modules connected to it; characterized by including the following steps: S1: Collect the voltage and current information of the battery cells in the equalization circuit unit of each module to obtain the state information of each battery cell: SOC1, SOC2, SOC3, ..., SOC m ; S2, determine whether to enable equalization based on the status information of each battery cell; if yes, proceed to S3; otherwise, shut down the equalization control unit and disconnect the external charging and discharging circuit. S3, the equalization control unit receives the instruction signal from the central processing unit, outputs the PWM wave signal to the MOSFET of the equalization circuit unit in each module, turns on the active equalization of the battery cells in the equalization circuit unit in each module, and determines that the maximum SOC difference of the battery cells in each module is <1%. If so, proceed to S4; otherwise, turn on the active equalization of the battery cells in the equalization circuit unit in each module again. This includes the following steps: S31, Establish a distance matrix based on the state information of each battery cell. ,in and Let SOC represent the individual nodes i and j, respectively, where 1 ≤ i ≤ m and 1 ≤ j ≤ m. c It is a constant; S32, Establish the path matrix With the first node as the intermediate point k, the shortest path calculation formula is: When this condition is met, the distance matrix D and the path matrix R are determined according to... and Update the matrix; otherwise, do not update the distance matrix and path matrix. S33, check the battery imbalance state. The number of batteries that need to be charged in series is stored in the state matrix, and the number of batteries that need to be discharged in series is stored in the state matrix. S34 searches for the shortest equalization path using the Floyd-Warshall algorithm and outputs a PWM signal based on the shortest path to drive the corresponding MOSFET to turn it on / off. S35, Intra-module active balancing control ends; S4, based on the state information of the individual battery cells in the equalization circuit unit within each module, SOC1, SOC2, SOC3, ..., SOC m The status information of each module, MSOC1, MSOC2, MSOC3, ..., MSOC, is calculated. n The equalization control unit receives a command signal from the central processing unit and outputs a PWM wave signal to the MOSFET of the inter-module equalization circuit unit to activate the active equalization of the inter-module equalization circuit unit. It determines whether the maximum SOC difference between each module is less than 1%. If so, the liquid metal battery pack equalization ends; otherwise, the active equalization of the inter-module equalization circuit unit is restarted. This includes the following steps: S41, Establish a distance matrix based on the status information of each module. ,in and Let SOC represent the modules of the p-th node and the q-th node, respectively, where 1 ≤ p ≤ n and 1 ≤ q ≤ n. c It is a constant; S42, Establish the path matrix With the first node as the intermediate point k, the shortest path calculation formula is: When this condition is met, the distance matrix D and the path matrix R are determined according to... and Update the matrix; otherwise, do not update the distance matrix and path matrix. S43, check the imbalance 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 searches for the shortest equalization path using the Floyd-Warshall algorithm and outputs a PWM signal based on the shortest path to drive the corresponding MOSFET to turn it on / off. S45, inter-module active balancing control ends.

2. An electronic device, characterized in that, include: Computer-readable storage media and processors; The computer-readable storage medium is used to store executable instructions; The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the method as described in claim 1.

3. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that cause a processor to perform the method as described in claim 1.

4. A computer program product, comprising a computer program or instructions, characterized in that, When the computer program or instructions are executed by the processor, they implement the method as described in claim 1.

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