Control method of multi-battery pack parallel operation system and battery packs

Abstract

The invention provides a control method of a multi-battery pack parallel operation system and battery packs, and is applied to the technical field of energy storage. The method comprises the following steps: when a non-electrified first battery pack branch exists in a discharge mode, acquiring a parallel operation voltage difference threshold value, a discharge current, a first voltage of the first battery pack branch and a second voltage of an electrified battery pack branch of a current multi-battery pack parallel operation system; according to the discharging current, the first voltage, the second voltage and a parallel operation voltage difference threshold value, the first battery pack branch is controlled to be powered on; when a non-electrified second battery pack branch exists in the charging mode, acquiring a parallel operation voltage difference threshold value and a charging current of the current multi-battery pack parallel operation system, a third voltage of the second battery pack branch and a fourth voltage of an electrified battery pack branch; and controlling the second battery pack branch to be electrified according to the charging current, the third voltage, the fourth voltage and a parallel operation voltage difference threshold. And safe and efficient parallel operation of the multiple battery pack branches under the condition that the voltage difference exists is realized.

Description

Technical Field

[0001] The present application belongs to the field of energy storage technology, and in particular, relates to a control method and a battery pack for a multi-battery pack parallel system. Background Art

[0002] With the promotion and development of household energy storage, in order to meet customers' demand for battery capacity expansion, the industry has widely adopted the solution of multi-branch battery parallel connection. Under this configuration, when multi-branch batteries are connected in parallel, due to the possible pressure difference between the branches, a circulation phenomenon will occur, that is, the branch with a high total pressure will charge the branch with a low total pressure. Excessive circulation will damage the battery cell. Therefore, when paralleling, it is necessary to ensure that the pressure difference between the branches is within a certain range to prevent excessive circulation. In the discharge condition, the system will give priority to the fault-free and higher voltage branch for power supply. In the charging condition, the fault-free and lower voltage branch will be given priority for charging.

[0003] When implementing the embodiments of the present application, the inventors found that in certain special cases, parallel connection may not be possible. For example, in a discharge condition, if a branch that has been temporarily disabled due to a fault is restored and its voltage is higher than the branch currently supplying power, and the voltage difference between the two exceeds the allowable threshold, then parallel connection cannot be performed at this time. Because the system cannot be interrupted when supplying power to the outside, it is impossible to cut off the power to the branch that is supplying power. As the discharge continues, the voltage difference between the branch that is not powered on and the branch that is supplying power will continue to increase, eventually resulting in the inability to parallel the entire discharge condition. Summary of the invention

[0004] The embodiments of the present application provide a control method and a battery pack for a multi-battery pack parallel system, which can realize parallel control of the multi-battery pack parallel system and realize safe and efficient parallel connection of multiple battery pack branches in the presence of voltage differences.

[0005] A first aspect provides a control method for a multi-battery pack parallel system, the method comprising: when there is a first battery pack branch that is not powered on in a discharge mode, obtaining a parallel voltage difference threshold of the current multi-battery pack parallel system, a first voltage of the first battery pack branch, a second voltage of the powered battery pack branch, and a discharge current of the multi-battery pack parallel system; controlling the powering on of the first battery pack branch according to the discharge current, the first voltage, the second voltage, and the parallel voltage difference threshold; when there is a second battery pack branch that is not powered on in a charging mode, obtaining a parallel voltage difference threshold of the current multi-battery pack parallel system, a third voltage of the second battery pack branch, a fourth voltage of the powered battery pack branch, and a charging current of the multi-battery pack parallel system; controlling the powering on of the second battery pack branch according to the charging current, the third voltage, the fourth voltage, and the parallel voltage difference threshold.

[0006] In the embodiment of the present application, when there is a first battery pack branch that is not powered on in the discharge mode, the first battery pack branch is powered on according to the discharge current, the first voltage, the second voltage, and the parallel voltage difference threshold, so that multiple battery pack branches can be safely and efficiently connected in parallel under different discharge current conditions when there is a voltage difference. When there is a second battery pack branch that is not powered on in the charging mode, the second battery pack branch is powered on according to the charging current, the third voltage, the fourth voltage, and the parallel voltage difference threshold, so that multiple battery pack branches can be safely and efficiently connected in parallel under different charging current conditions when there is a voltage difference.

[0007] In one possible implementation, controlling power-on of the first battery pack branch according to the discharge current, the first voltage, the second voltage and the parallel voltage difference threshold includes: when the first voltage is greater than the second voltage, and the voltage difference between the first voltage and the second voltage is greater than the parallel voltage difference threshold, detecting the discharge current; when the discharge current is greater than the first current threshold, and the duration for which the discharge current is greater than the first current threshold is greater than a first preset time, controlling power-on of the first battery pack branch.

[0008] In one possible implementation, controlling power-on of the first battery pack branch according to the discharge current, the first voltage, the second voltage and the parallel voltage difference threshold includes: when the discharge current is greater than the second current threshold, the first voltage is higher than the second voltage, and the voltage difference between the first voltage and the second voltage reaches the first voltage threshold, and the voltage difference between the first voltage and the second voltage is less than the parallel voltage difference threshold, controlling power-on of the first battery pack branch; when the discharge current is less than the second current threshold, and the voltage difference between the first voltage and the second voltage is less than or equal to the parallel voltage difference threshold, controlling power-on of the first battery pack branch.

[0009] In one possible implementation, controlling power-on of the second battery pack branch according to the charging current, the third voltage, the fourth voltage and the parallel voltage difference threshold includes: when the third voltage is less than the fourth voltage, the voltage difference between the third voltage and the fourth voltage is greater than the parallel voltage difference threshold, and there is a charging request for the second battery pack branch, limiting the charging current; within a second preset time after limiting the charging current, the voltage difference between the third voltage and the fourth voltage is less than or equal to the parallel voltage difference threshold, controlling power-on of the second battery pack branch; when the duration after limiting the charging current exceeds the second preset time, the voltage difference between the third voltage and the fourth voltage is greater than the parallel voltage difference threshold, controlling the powered-on battery pack branch to power off and controlling the second battery pack branch to power on.

[0010] In one possible implementation, controlling power-on of the second battery pack branch according to the charging current, the third voltage, the fourth voltage and the parallel voltage difference threshold also includes: when the third voltage is less than the fourth voltage, the voltage difference between the third voltage and the fourth voltage is greater than the parallel voltage difference threshold, and there is no charging request for the second battery pack branch, limiting the charging current; at a third preset time after limiting the charging current, the voltage difference between the third voltage and the fourth voltage is less than or equal to the parallel voltage difference threshold, controlling power-on of the second battery pack branch; at a third preset time after limiting the charging current, the voltage difference between the third voltage and the fourth voltage is greater than the parallel voltage difference threshold, and canceling limiting the charging current, wherein the third preset time is greater than the second preset time.

[0011] In one possible implementation, controlling power-on of the second battery pack branch according to the charging current, the third voltage, the fourth voltage and the parallel voltage difference threshold includes: when the charging current is greater than the second current threshold, the third voltage is less than the fourth voltage, and the voltage difference between the fourth voltage and the third voltage is greater than the first voltage threshold, and the voltage difference between the third voltage and the fourth voltage is less than or equal to the parallel voltage difference threshold, controlling power-on of the second battery pack branch; when the discharging current is less than the second current threshold, and the voltage difference between the third voltage and the fourth voltage is less than or equal to the parallel voltage difference threshold, controlling power-on of the second battery pack branch.

[0012] In one possible implementation, obtaining the parallel voltage difference threshold of the current multi-battery pack parallel system includes: obtaining the current temperature; determining the parallel voltage difference threshold of the current multi-battery pack parallel system based on the current temperature, wherein the parallel voltage difference threshold of the multi-battery pack parallel system is obtained based on the number of battery packs in the multi-battery pack parallel system and the parallel voltage difference threshold of one battery pack, wherein the parallel voltage difference threshold of one battery pack is obtained based on the number of battery cells in one battery pack and the parallel voltage difference threshold of one battery cell, wherein the parallel voltage difference threshold of one battery cell is obtained based on the minimum internal resistance of the battery cell at the current temperature and the allowable charging current of the battery cell at the current temperature.

[0013] In one possible implementation, the control method of a multi-battery pack parallel system further includes controlling a battery pack branch with the highest total voltage among the N unpowered battery pack branches to be powered on when there are N unpowered battery pack branches in a discharge mode, and two or more of the N unpowered battery pack branches have respective maximum single-cell voltages greater than a first threshold and a state of charge greater than or equal to a first preset threshold, wherein N is an integer greater than 1; and controlling other battery pack branches that meet the parallel voltage difference threshold to be powered on when the state of charge of a powered battery pack branch is less than the first preset threshold, or the maximum single-cell voltage of a powered battery pack branch is less than a second preset voltage value.

[0014] In one possible implementation, the control method of a multi-battery pack parallel system further includes: when there are N powered-on battery pack branches in a charging mode, determining a target battery pack branch in which the maximum single-cell voltage of each of the N-1 powered-on battery pack branches reaches a second voltage threshold; controlling the target battery pack branch to power off; when there is a powered-on battery pack branch in the charging mode, and the maximum single-cell voltage of the powered-on battery pack branch reaches a third voltage threshold, limiting the charging current of the powered-on battery pack branch to a preset current value, wherein the second voltage threshold is less than the third voltage threshold.

[0015] A second aspect provides a battery pack, which includes a processor and a memory, wherein the processor is used to implement any of the above control methods for a multi-battery pack parallel system when executing a computer program stored in the memory.

[0016] It can be understood that the battery pack provided in the above-mentioned second aspect corresponds to the method in the above-mentioned first aspect. Therefore, the beneficial effects or various implementation methods that can be achieved can be referred to above and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the application environment of the multi-battery pack parallel system provided in the embodiment of the present application.

[0018] Figure 2 A schematic diagram of the structure of a battery pack provided in an embodiment of the present application.

[0019] Figure 3 A schematic flow chart of a control method for a multi-battery pack parallel system provided in an embodiment of the present application.

[0020] Figure 4 A flowchart of another control method for a multi-battery pack parallel system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0021] It should be noted that the terms "first" and "second" in the specification, claims and drawings of this application are used to distinguish similar objects, rather than to describe a specific order or sequence. In the specification, claims and drawings of this application, unless otherwise specified, " / " means or, for example, A / B can mean A or B. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the term "plurality" in the specification, claims and drawings of this application refers to two or more than two.

[0022] It should also be noted that the method disclosed in the embodiments of the present application or the method shown in the flowchart includes one or more steps for implementing the method. Without departing from the scope of the claims, the execution order of multiple steps can be interchangeable with each other, and some of the steps can also be deleted.

[0023] Some embodiments will be described below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0024] The technical solution of the present application is further described in detail below in conjunction with the accompanying drawings.

[0025] See also Figure 1 , exemplarily introduces the application environment of the multi-battery pack parallel system provided in an embodiment of the present application, which includes a multi-battery pack parallel system 10 and a load 20.

[0026] In the embodiment of the present application, the multi-battery pack parallel system 10 includes two or more battery packs 11. The two or more battery packs 11 are electrically connected to the parallel end through power lines, and the power lines can be used to transmit electric energy, that is, each battery pack 11 outputs electric energy to the load 20 through the parallel end through the power line.

[0027] like Figure 1 As shown, the multi-battery pack parallel system provided in the embodiment of the present application is demonstrated by taking three battery packs 11 as an example. The branch where each battery pack is located is the battery pack branch corresponding to the battery pack, which includes three battery pack branches.

[0028] It can be understood that the embodiments of the present application do not limit the function and type of the power line.

[0029] In some embodiments, the two or more battery packs 11 can communicate with each other via a communication line.

[0030] In some embodiments, the two or more battery packs 11 are electrically connected to a power conversion device (not shown). The power conversion device integrates an AC-DC conversion circuit, a DC-AC conversion circuit, a DC-DC conversion circuit, etc. In this way, the multi-battery pack parallel system 10 can receive the power output of the power supply (not shown) through the power conversion device for charging; the multi-battery pack parallel system 10 can also discharge through the power conversion device to power the load 20.

[0031] Parallel control is required for parallel charging and discharging of multi-battery pack parallel systems. However, in the current parallel control, if a battery pack branch that has been temporarily disabled due to a fault is restored and its voltage is higher than the battery pack branch that is currently supplying power, and the voltage difference between the two exceeds the allowable threshold, then parallel connection is not possible at this time. Because the system cannot be interrupted when supplying power to the outside, it is impossible to cut off the power to the battery pack branch that is supplying power. As the discharge continues, the voltage difference between the unpowered battery pack branch and the battery pack branch that is supplying power will continue to increase, eventually making the entire discharge condition unable to be paralleled. Therefore, how to enable the multi-battery pack parallel system to complete parallel connection under special conditions has become an urgent problem to be solved.

[0032] In view of this, an embodiment of the present application provides a control method for a multi-battery pack parallel system to achieve parallel control of the multi-battery pack parallel system, to achieve safe and efficient parallel connection of multiple battery pack branches in the presence of voltage differences, and to solve the problem of being unable to connect in parallel under special working conditions.

[0033] It is understandable that in the multi-battery pack parallel system 10, each battery pack 11 includes a controller (not shown). In some embodiments, the controller is loaded with a battery management system BMS (Battery Management System) (not shown) for protecting and managing the corresponding battery pack 11. The multiple battery packs 11 in the multi-battery pack parallel system 10 can communicate with each other, for example, through a CAN (Controller Area Network) bus. One battery pack 11 in the multi-battery pack parallel system 10 serves as the master pack, and the other battery packs 11 serve as slave packs. The controller on the master pack is also loaded with an energy management system EMS (Energy Management System) for communicating with all BMSs in the multi-battery pack parallel system 10. EMS is used to execute the control method of the multi-battery pack parallel system provided in the present application, so as to achieve unified control of each battery pack in the multi-battery pack parallel system 10, including parallel control.

[0034] In the embodiment of the present application, each battery pack 11 includes a relay (not shown). Powering on the battery pack can be understood as: closing the relay of the battery pack to supply power to the outside. Powering off the battery pack can be understood as: disconnecting the relay of the battery pack.

[0035] In other embodiments, the BMS can be used to execute the control method of the multi-battery pack parallel system provided in the present application, thereby achieving unified control of each battery pack in the multi-battery pack parallel system 10, including parallel control.

[0036] Understandably, Figure 1The number of battery packs in the multi-battery pack parallel system 10 shown is only an example. In actual applications, the number of battery packs to be paralleled can be set according to actual needs, and this application does not make any specific limitations on this.

[0037] See also Figure 2 , the structure of the battery pack 11 provided in an embodiment of the present application is exemplarily introduced.

[0038] The battery pack 11 includes a processor 111 and a memory 112 . The processor 111 is connected to the memory 112 .

[0039] The processor 111 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc. For example, the processor 111 is the computing core and control center of the battery pack 11, and uses various interfaces and lines to connect various parts of the entire battery pack 11, and obtain the operating system of the battery pack 11 and various installed applications, program codes, etc.

[0040] It can be understood that the above-mentioned memory 112 mainly includes a program storage area and a data storage area. Among them, the program storage area can store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.), etc. In addition, the memory 112 can include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other non-volatile solid-state storage devices.

[0041] For example, the memory 112 may be an external memory and / or an internal memory of the battery pack 11. Furthermore, the memory 112 may be a memory in a physical form, such as a memory stick, a TF card (Trans-flash Card), and the like.

[0042] If the program code and various data in the memory 112 are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the present application implements all or part of the processes in the parallel control method provided in the embodiment of the present application, and can also be completed by instructing related hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and when the computer program is executed by the processor 111, the parallel control method provided in the embodiment of the present application can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc. Computer-readable media may include: any entity or device capable of carrying computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), etc.

[0043] It is understandable that the battery pack 11 may also include more functional modules or fewer functional modules, and this application does not make any specific limitation on this.

[0044] See also Figure 3 , a control method for a multi-battery pack parallel system provided by an embodiment of the present application is exemplarily introduced, the multi-battery pack parallel system includes a plurality of battery packs. The control method for the multi-battery pack parallel system includes steps S301 to S308.

[0045] Step S301, initializing the self-check state.

[0046] In the embodiment of the present application, after the battery pack is powered on, the self-test state is initialized.

[0047] Step S302: When the first condition is met, the multi-battery pack parallel system is controlled to enter a low energy consumption mode.

[0048] The first condition may include but is not limited to: the self-test passes or the time in the initialization state reaches a self-test time threshold.

[0049] Among them, the self-check time threshold can be 4s, 5s or 6s, and this application does not make any specific limitation on this.

[0050] In some embodiments, the first condition may include, but is not limited to: all battery packs pass self-test or the time the main pack is in the initialization state reaches a self-test time threshold.

[0051] When the first condition is met, the multi-battery pack parallel system is controlled to enter a low energy consumption (Standby) mode.

[0052] Step S303, when the second condition is met, the multi-battery pack parallel system is controlled to enter a discharge mode and execute related operations of the discharge mode.

[0053] The second condition may include but is not limited to: in the low energy consumption mode, the multi-battery pack parallel system has no system faults, and receives a power-on command from the inverter or triggers a black start. That is, the second condition may be that the inverter power-on command is valid or the black start command is valid, and there is no system fault.

[0054] In the embodiment of the present application, no system fault may mean that there is no fault in the system that affects power on or off. System faults may include, but are not limited to: the battery models of the two battery pack branches are different, and the inverter communication is lost. Correspondingly, no system fault may mean: the battery models of the two battery pack branches are the same and there is no inverter communication loss.

[0055] In some embodiments, no system fault may mean that the system is in a non-fault state, ie, there is no ongoing system fault or warning.

[0056] The black start may include but is not limited to: actively controlling the relay to close to supply power to the outside. In the normal state, power supply to the outside requires the power-on instruction of the inverter, while the black start can close the relay to supply power to the outside without the power-on instruction of the inverter.

[0057] When the second condition is met, the multi-battery pack parallel system is controlled to enter a discharge mode.

[0058] In the embodiment of the present application, in the discharge mode, the battery pack is controlled to supply power to the outside. First, it is determined whether the multi-battery pack parallel system meets any one of the following two conditions:

[0059] Condition 1: The multi-battery parallel system is in the state of being fully charged.

[0060] Condition 2: the maximum single cell voltage of two or more battery pack branches is greater than a first preset voltage value (such as 3336mv) and the state of charge (SOC) is greater than or equal to a first preset threshold value (such as 95%).

[0061] If any of the above conditions is met, in order to prevent two high-capacity battery pack branches from being connected in parallel and causing the single cell voltage of the battery pack branch with a low total voltage to be overcharged due to circulating current, only one battery pack branch with the highest total voltage is allowed to be powered on.

[0062] Among them, when the multi-battery pack parallel system is in a fully charged state, ChgFinsh==1. When the maximum single cell voltage of two or more battery pack branches is greater than the first preset voltage value and the SOC is greater than or equal to the first preset threshold, SysCellVolHigh==1. When ChgFinsh==1 or SysCellVolHIgh==1, after the battery pack branch with the highest total voltage is powered on, the power is discharged to an SOC less than the first preset threshold, or the maximum single cell voltage of the powered-on battery pack branch is less than the second preset voltage value (such as 3328mv), ChgFinsh is set to 0, SysCellVolHIgh is set to 0, and other battery pack branches that meet the parallel voltage difference threshold are allowed to power on.

[0063] Among them, the first preset voltage value can be 3336mv, etc., the first preset threshold can be 95%, etc., the second preset voltage value is less than the first preset voltage value, and the second preset voltage value can be 3328mv, etc. The embodiment of the present application does not make specific limitations on this.

[0064] Among them, ChgFinsh (charging completion mark) indicates that the system is fully charged. SysCellVolHIgh indicates that there are two or more battery pack branches, the maximum single cell voltage is greater than the first preset voltage value and the SOC is greater than or equal to the first preset threshold.

[0065] Specifically, determine whether the multi-battery pack parallel system is in a just-fully-charged state (ChgFinsh==1) or whether there are two or more battery pack branches with a maximum single cell voltage greater than 3336mv and SOC>=95% (SysCellVolHIgh==1). If any of the conditions are met, in order to prevent overvoltage caused by circulating current, only one battery pack branch with the highest total voltage is allowed to be powered on. When the power of the powered battery pack branch is discharged to an SOC less than 95% or the maximum single cell voltage of the powered battery pack branch is less than 3328mv, other battery pack branches that meet the parallel voltage difference threshold are allowed to be powered on.

[0066] Secondly, determine the SOC status of each branch:

[0067] The number a of battery clusters without faults and whose SOP allows power-on is screened out, and the number b of these clusters whose SOC is less than a second preset threshold (such as 10%). If the two numbers a and b are equal and greater than 0, BO_SOCLowflg is set to 1, otherwise BO_SOCLowflg is set to 0.

[0068] In some embodiments, the following operations are always performed in the discharge mode:

[0069] Step 1: Select the battery cluster that needs to be powered on.

[0070] When no battery pack branch is powered on (i.e., the number of powered-on branches is 0), the following two filters are performed:

[0071] Screening 1: Check all unpowered battery pack branches and check the number of battery pack branches that meet the following conditions: no system faults (such as no faults that affect power-on), the power state (State of Power, SOP) allows power-on, the maximum single cell voltage exceeds the first preset voltage value and the SOC is greater than or equal to the first preset threshold. When the number of battery pack branches that meet the above conditions exceeds 1, set SysCellVolHigh to 1.

[0072] The logic for allowing power on of the SOP may include but is not limited to:

[0073] SOP under discharge conditions allows power-on: (1) During the discharge process, batteries with a discharge current limit value (maximum current value allowed during discharge) that is not equal to 0 are preferentially selected for power-on. (2) If the discharge current limit values ​​of all fault-free batteries in the system are 0 (i.e., these batteries cannot provide effective current during discharge), batteries with a charge current limit value (maximum current value allowed during charge) that is not 0 are selected for power-on.

[0074] The SOP under charging conditions allows power-on: (1) During the charging process, batteries with a charge current limit value that is not equal to 0 are preferentially selected for power-on. (2) If the charge current limit values ​​of all non-faulty batteries in the system are 0 (i.e., these battery clusters cannot accept current during charging), batteries with a discharge current limit value that is not 0 are selected for power-on.

[0075] Screening 2: Screen the battery cluster with the highest total voltage.

[0076] Case 1: If there is a battery cluster whose SOC is greater than or equal to the second preset threshold, i.e., corresponding to BO_SOCLowflg=0, no fault, and SOP allows power-on, then the battery cluster A with the highest total voltage is selected and pre-powered on. However, if one of the following four conditions is met, the battery cluster with the highest total voltage is reselected for pre-powering: (1) the battery cluster A with the highest total voltage is faulty; (2) the SOP does not allow the battery cluster A with the highest total voltage to be powered on.

[0077] The second preset threshold is smaller than the first preset threshold, and the second preset threshold may be 10%, which is not specifically limited in the present application.

[0078] Case 2: If the SOC of all battery clusters is less than the second preset threshold, corresponding to BO_SOCLowflg=1, then directly select battery cluster A with no faults and the highest total voltage allowed by SOP for powering on. If battery cluster A fails, then reselect the battery cluster with the highest total voltage.

[0079] Step 2, discharge current monitoring.

[0080] If the multi-battery pack parallel system discharge current exceeds the first current threshold and the duration of the multi-battery pack parallel system discharge current exceeding the first current threshold reaches the first time threshold, Bo_KeepDchFlg is set to 1. When Bo_KeepDchFlg is 1 and the system discharge current drops to or below the first current threshold, Bo_KeepDchFlg is reset to 0.

[0081] Exemplarily, when the system discharge current is greater than 5 A and lasts for 3 seconds, Bo_KeepDchFlg is set to 1; when Bo_KeepDchFlg is equal to 1 and the system discharge current is less than or equal to 5 A, Bo_KeepDchFlg is set to 0.

[0082] The first current threshold may be 4A, 5A or 6A, which is not specifically limited in the embodiment of the present application. The first time threshold may be 3s, 4s or 5s, which is not specifically limited in the embodiment of the present application.

[0083] Step S304 , when there is a first battery pack branch that is not powered on in the discharge mode, a corresponding power-on operation is performed on the first battery pack branch.

[0084] In an embodiment of the present application, after step S303, when a battery pack branch in the multi-battery pack parallel system is not powered on, such as the battery pack branch is not powered on because the voltage difference does not meet the parallel voltage difference threshold, then the unpowered battery pack branch is the first battery pack branch.

[0085] In some embodiments, after step S303, when a battery pack branch in the multi-battery pack parallel system is not powered on (such as the battery pack branch is not powered on because the voltage difference does not meet the parallel voltage difference threshold), and ChgFinsh==0, and SysCellVolHIgh==0, and the battery pack branch itself has no faults, then the battery pack branch is the first battery pack branch.

[0086] In an embodiment of the present application, the corresponding power-on operation for the first battery pack branch may include: (1) if the discharge current of the current system is greater than the second current threshold, the voltage of the unpowered battery pack branch needs to be higher than the voltage of the powered battery pack branch to reach the first voltage threshold (such as the voltage of the unpowered battery pack branch needs to be 1V higher than the voltage of the powered battery pack branch), and the unpowered battery pack branch is powered on. Because before the unpowered battery pack branch is powered on, the discharge current needs to be limited to prevent the relay from closing and causing adhesion when there is a large current, and after the discharge current of the powered battery pack branch is limited, the voltage of the powered battery pack branch will increase, causing the voltage difference with the total voltage of the unpowered battery pack branch to increase, exceeding the allowable parallel voltage difference threshold. Among them, the second current threshold can be 1A, 2A or 3A, and the first voltage threshold can be 1V, 2V or 3V, which can be set according to actual conditions, and the present application does not make specific restrictions on this. (2) If the current system discharge current is less than the second current threshold, as long as the voltage difference between the unpowered battery pack branch and the powered battery pack branch is less than or equal to the parallel voltage difference threshold AllowVdealt, the unpowered battery pack branch will be powered on. (3) When the voltage of the unpowered battery pack branch is higher than the voltage of the powered battery pack branch, and the voltage difference between the unpowered battery pack branch and the powered battery pack branch is greater than the parallel voltage difference threshold AllowVdealt, and the system discharge current is greater than the first current threshold, and the duration of the discharge current being greater than the first current threshold is greater than or equal to the first time threshold, Bo_KeepDchFlg is set to 1, the system charging current is limited, and the unpowered battery pack branch is powered on. Among them, AllowVdealt is used to represent the voltage difference threshold allowed for parallel operation.

[0087] In some embodiments, if there is a battery pack branch whose relay is not closed due to voltage difference, the following real-time determination is performed:

[0088] The prerequisites must meet the following points at the same time: no fault, SOP allows power-on, SOC is greater than or equal to the second preset threshold, ChgFinsh is set to 0, SysCellVolHigh is set to 0, and the number of powered-on battery pack branches is greater than 0. After the above conditions are met, the following real-time pressure difference judgment is performed to determine whether any of the following three conditions are met.

[0089] Condition 1: When the absolute value of the system discharge current is greater than or equal to the second current threshold, if (the difference between the battery voltage of the unpowered branch and the voltage of battery cluster A with the highest total voltage) is greater than or equal to the first voltage threshold and less than or equal to the parallel voltage difference threshold AllowVdealt.

[0090] Exemplarily, condition 1 is that the absolute value of the system discharge current is greater than or equal to 1A, and the voltage difference obtained by subtracting the voltage of battery cluster A with the highest total voltage from the battery voltage of the unpowered branch is greater than or equal to 1V and less than or equal to AllowVdealt.

[0091] Condition 2: when the absolute value of the system discharge current is less than the second current threshold, if (the absolute value of the difference between the battery voltage of the non-powered branch and the voltage of battery cluster A with the highest total voltage) is less than or equal to the parallel voltage difference threshold AllowVdealt.

[0092] Exemplarily, condition 2 is that the absolute value of the system discharge current is less than 1 A, and the absolute value of the voltage difference obtained by subtracting the voltage of battery cluster A with the highest total voltage from the battery voltage of the non-powered branch is less than or equal to AllowVdealt.

[0093] Condition 3: If (the difference between the voltage of the battery in the non-powered branch and the voltage of the battery cluster A with the highest total voltage) is greater than the parallel voltage difference threshold AllowVdealt, and Bo_KeepDchFlg is equal to 1.

[0094] Exemplarily, condition 3 is that (the battery voltage of the non-powered branch minus the voltage of battery cluster A with the highest total voltage) is greater than AllowVdealt, and Bo_KeepDchFlg is equal to 1.

[0095] When any of the above three conditions is met, the battery is pre-powered, and the system will limit the total allowable charge and discharge current to 10A multiplied by the number of relay closure clusters. If the current total current is less than the threshold CloseCur, the system will send a power-on command to the unpowered battery. After the power-on is completed, the system will restore the SOP current limit value.

[0096] Wherein, CloseCur represents the current value that allows the battery pack to close the relay. 1. If the number of clusters of currently closed relays == 0, then CloseCur = 10A; otherwise, CloseCur = 20A*the number of clusters of currently closed relays.

[0097] It can be done immediately, the total allowed charge and discharge current can be limited, and CloseCur can be set according to actual conditions, and this application does not make specific limitations on this.

[0098] In the embodiments of the present application, there are two situations that require special handling for power-off current limiting: (1) If a powered-on battery pack fails or the SOP does not allow power-on, the total allowable charge and discharge current will be limited to 10A multiplied by the number of relay closure clusters, and then a power-off command will be sent. After the battery is powered off, the current limiting setting will be restored. (2) When the battery is discharged (such as the SOC is less than the second preset threshold value) and the number of relay closure clusters is greater than 1, the total allowable charge and discharge current will be limited to 10A multiplied by the number of relay closure clusters, the discharged battery will be disconnected, and the current limiting setting will be restored.

[0099] In the embodiment of the present application, in the discharge mode, when there is no powered-on battery pack branch, the branch with the highest total voltage is powered on first. If there is already a branch that has been powered on, the unpowered branch needs to meet any of the following conditions to be powered on: (1) The discharge current is small and within 1A. The voltage difference between the unpowered branch and the powered-on branch is within the allowable parallel voltage difference range before it can be powered on; (2) The discharge current exceeds 1A. The unpowered branch needs to have a total voltage 1V higher than that of the powered branch before it is allowed to be powered on; (3) When the voltage of the unpowered branch is higher than that of the powered branch and exceeds the allowable parallel voltage difference threshold, the discharge current needs to be greater than a certain threshold and last for a certain time (because when the system has a discharge current, the branch with a high voltage is connected, which will simultaneously supply power to the load and the branch with a low total voltage, so that the circulating current will be reduced) before it is allowed to be powered on.

[0100] In an embodiment of the present application, if the maximum single-cell voltage of two or more branches is greater than the first preset voltage value (e.g., 3336mv) and the SOC is greater than or equal to the first preset threshold value (e.g., SOC>=95%), only one branch is allowed to be powered on to prevent single-cell overvoltage due to circulating current during parallel operation. When the power of the powered branch is less than a certain value, other branches are allowed to be powered on.

[0101] Step S305, when the third condition is met, the multi-battery pack parallel system is controlled to enter a charging mode and execute related operations of the charging mode.

[0102] In the embodiment of the present application, when the charging current of the multi-battery pack parallel system is greater than the third current threshold, and the duration of the charging current being greater than the third current threshold is greater than or equal to the second time threshold, the third condition is met.

[0103] The third current threshold may be 0.4A, 0.5A or 0.6A, which is not specifically limited in the embodiment of the present application. The second time threshold may be 2s, 3s or 4s, which is not specifically limited in the embodiment of the present application.

[0104] The second time threshold may be the same as or different from the first time threshold.

[0105] In the embodiment of the present application, the related operations of the charging mode may include: giving priority to powering on the battery pack branch with a low total voltage. After screening the minimum voltage of the battery pack branch, sending a power-off instruction to the battery pack branch whose voltage difference with the minimum voltage exceeds the parallel voltage difference threshold AllowVdealt, and then powering on the battery pack branch with a low total voltage and a voltage difference within the parallel voltage difference threshold AllowVdealt.

[0106] In an embodiment of the present application, the relevant operations of the charging mode may include: Step 1, battery pack branch voltage screening: monitor the voltages of all battery pack branches, and screen out the battery pack branch with the lowest voltage. Step 2, perform voltage difference judgment: after determining the battery pack branch with the lowest voltage, further analyze the voltage difference between other battery pack branches and the battery pack branch with the lowest voltage. Step 3, send a power-off instruction: for the battery pack branch whose voltage difference exceeds the parallel voltage difference threshold in step 2, send a power-off instruction. Step 4, power-on operation: after completing the above-mentioned voltage difference adjustment, power on the battery pack branch with the lowest total voltage. At the same time, for other battery pack branches whose voltage difference with the lowest voltage battery pack branch is within the parallel voltage difference threshold, power-on operations will also be performed at the same time to ensure the charging balance and efficiency of the entire system. Step 5, monitoring and adjustment: during the entire charging process, continuously monitor the voltage and current of each battery pack branch, and adjust as needed. If it is found that the voltage or current of any battery pack branch is out of the normal range, the system will immediately take corresponding measures, such as reducing the charging power or interrupting charging, to ensure the safe and stable operation of the system.

[0107] In some embodiments, in the charging mode, in order to ensure the safety and effective charging of the system, the battery voltage needs to be screened. This process aims to find all batteries without faults, whose SOP allows power-on (and the charging current limit value is not 0), and determine the battery with the lowest voltage, which is recorded as B. Then, it is determined which batteries have a voltage difference with B within the parallel voltage difference threshold AllowVdealt, so as to determine which batteries meet the power-on conditions.

[0108] Specifically, all batteries are traversed to screen out batteries that are fault-free, whose SOP allows power-on (i.e., the system is ready to provide charging for the battery), and whose charging current limit value is not equal to 0. Secondly, the lowest voltage battery B is determined, and among the screened batteries, the battery with the lowest voltage is found, recorded as B. Then, the voltage difference judgment and pre-power-on instruction setting are performed, and for each screened battery, the voltage difference between its voltage and B is calculated. If the voltage difference between the battery's voltage and the voltage difference between B is within the parallel voltage difference threshold AllowVdealt, the battery is considered to meet the power-on condition, and its corresponding pre-power-on instruction is set to pre-power-on. If the voltage difference between the battery's voltage and the voltage difference between B exceeds the parallel voltage difference threshold AllowVdealt, the battery is considered to not meet the power-on condition, and the battery is set to an unpowered branch. Finally, by performing subsequent operations, the system can decide which batteries should be powered on and which batteries need to wait or perform other processing.

[0109] When the inverter power-on command or black start command is valid and there is no system fault, real-time fault judgment is performed to ensure safe operation. If a fault that requires power-off is found during the judgment process, or the SOP no longer allows power-on, the following operations will be performed: 1. Update the pre-power-on status: Set the batteries that are not allowed to be powered on due to faults or SOP as unpowered branches, indicating that these batteries do not currently meet the power-on conditions. 2. Send a power-off command: Send a power-off command to the battery clusters that are set as unpowered branches to ensure that these batteries are safely disconnected to prevent the fault from expanding or affecting other parts of the system. 3. Wait for power-off to be completed: Continuously monitor the status of the batteries that have been sent power-off commands and wait for all these batteries to be completely disconnected. This is to ensure that there are no potential safety hazards in the system before attempting to power on. 4. Send a power-on command: Once it is confirmed that all batteries that need to be powered off have been disconnected, check the batteries that are set to be powered on in advance. These batteries meet the power-on conditions, and send a power-on command to the batteries that are set to be powered on in advance, allowing them to safely connect to the system and start working.

[0110] Check whether the relays of all batteries that have been sent power-on commands are in the closed state. This indicates that these batteries are ready and safely connected to the high-voltage system. Check whether the relays of all batteries that have been sent power-off commands are in the disconnected state. This ensures that batteries that no longer need to work or have safety hazards have been safely disconnected from the system before continuing. If the above two conditions are met at the same time (that is, the relay states of the batteries that have sent power-on commands are all closed && the relays of the batteries that have sent power-off commands are all disconnected), or the system has remained in this state for more than 5 minutes, the system will automatically enter the battery balancing working state. The battery balancing working state is a special system operating mode that aims to balance the voltage and state between each battery through a series of operations to ensure the stability and performance of the entire system.

[0111] Step S306 , when there is a second battery pack branch that is not powered on in the charging mode, a corresponding power-on operation is performed on the second battery pack branch.

[0112] In the embodiment of the present application, in the charging mode, when a battery pack branch in the multi-battery pack parallel system is not powered on, the unpowered battery pack branch is the second battery pack branch.

[0113] In some embodiments, when a battery pack branch is not powered on, and the battery pack branch meets the conditions of no faults and SOP allows power-on and SOC<100% and the full charge flag of the battery pack branch is not set, that is, the battery pack branch is not in a fully charged state, further judgment is performed.

[0114] In the embodiment of the present application, if the following conditions are met: no fault, SOP allows power-on, SOC < 100%, and the battery pack branch full charge flag is not set, then a voltage difference judgment can be performed. Voltage difference judgment usually involves comparing the voltage differences between different battery pack branches or battery cells to ensure that the difference between them is within an acceptable range.

[0115] In the embodiment of the present application, when there is a second battery pack branch, the voltage difference determination can be performed according to the following steps:

[0116] Step 11, when the current charging current of the system is greater than the second current threshold (such as 1A), the charging current limiting measures will be implemented on the powered battery pack branch before power-on to avoid large current closing the relay and causing the relay to stick. This current limiting operation will cause the charging current of the powered battery pack branch to decrease, which will in turn cause the voltage to drop, thereby forming a large voltage difference with the unpowered battery pack branch. Therefore, the voltage of the powered battery pack branch is required to be at least the first voltage threshold higher than the voltage of the unpowered battery pack branch to ensure that the voltage difference does not exceed the allowable range.

[0117] Step 12: If the current charging current of the system is less than the second current threshold (such as 1A), determine whether the voltage difference is within the parallel voltage difference threshold. If it is within the parallel voltage difference threshold, the power-on operation is allowed.

[0118] Step 13, if the voltage of the unpowered battery pack branch is lower than the voltage of the currently powered battery pack branch, and the voltage difference exceeds the parallel voltage difference threshold AllowVdealt, the following measures will be taken: (1) If the unpowered battery pack branch has a charging request, the current limiting operation will be implemented first to reduce the charging current of the powered battery pack branch, thereby reducing the voltage difference. If the voltage difference drops to within the parallel voltage difference threshold, the battery pack branch is allowed to be powered on. If the voltage difference still does not meet the requirements after the current limiting continues for the second preset time (that is, the voltage difference still exceeds the parallel voltage difference threshold), the powered battery pack branch will be disconnected and the battery pack branch with a lower voltage will be allowed to be powered on. (2) For the battery pack branch whose voltage is lower than the powered battery pack branch and the voltage difference exceeds the parallel voltage difference threshold, if the battery pack branch has no charging request, the current limiting operation will also be implemented to reduce the voltage difference. If the voltage difference still does not meet the requirements after the current limiting continues for the third preset time (that is, the voltage difference still exceeds the parallel voltage difference threshold), the current limiting measure will be cancelled. It is worth noting that each time the charging mode is entered, each battery pack branch is only allowed to attempt the above operation once.

[0119] In some embodiments, if there is a battery whose relay is not closed due to voltage difference, and there is no fault and SOP allows power-on and SOC < 100%, and the maximum single cell voltage of the cluster has not exceeded ChgEndVol during this charging, real-time judgment of voltage difference can be performed:

[0120] First, if the absolute value of the system's charging current is greater than or equal to the second current threshold (such as 1A), when the voltage difference between the lowest voltage battery B and the battery voltage of the unpowered branch (i.e., power-off) is between 1V and AllowVdealt, and there is no response to the power-on fault, and the battery has not been fully charged, the battery is pre-powered (power-on is allowed), and the total allowed charge and discharge current is limited to 10A multiplied by the number of relay closure clusters. If the current total current is less than the threshold CloseCur, a power-on instruction is sent to the battery. After power-on is completed, the current limiting setting of the SOP is restored.

[0121] Exemplarily, the absolute value of the system's charging current is greater than or equal to 1A. When the voltage of the lowest voltage battery B is subtracted from the battery voltage of the unpowered branch to obtain the voltage difference A, the voltage difference A is greater than or equal to 1V and less than or equal to AllowVdealt, and there is no response to the power-on failure, and the current state has not been fully charged, then the battery is pre-powered on, and the total allowable charge and discharge current is limited to 10A*the number of relay closure clusters. The current total current is less than the threshold CloseCur, and a power-on command is sent to the battery. After the power-on is completed, the SOP current limiting is restored.

[0122] Second, if the absolute value of the system charging current is less than the second current threshold (such as 1A), when the absolute value of the difference between the voltage of the lowest voltage battery B and the battery voltage of the unpowered branch is less than or equal to AllowVdealt, and there is no response to the power-on fault, and the battery is not fully charged, the processing steps are similar to the first, except that it is no longer limited by the absolute value of the current being greater than or equal to 1A.

[0123] Exemplarily, the absolute value of the system's charging current is less than 1A. When the voltage of the lowest voltage battery B minus the battery voltage of the unpowered branch is used to obtain the voltage difference B, the absolute value of the voltage difference B is less than or equal to AllowVdealt, and there is no response to the power-on fault, and the battery has not been fully charged in this state, the battery is pre-powered on, and the total allowable charge and discharge current is limited to 10A*the number of relay closure clusters. The current total current is less than the threshold CloseCur, and a power-on command is sent to the battery. After the power-on is completed, the SOP current limiting is restored.

[0124] Third, if the difference between the voltage of the lowest voltage battery B and the battery voltage of the unpowered branch is greater than AllowVdealt: If there is no response to the power-on failure and there is a charge request, and the battery is not fully charged, it will try to send a 5-second current limit instruction. If the power-on is still not successful after 5 seconds, exit to the charging mode and allow the battery with a lower total voltage to power on. If there is no response to the power-on failure and there is no charge request, try to send a 20-second current limit instruction to reduce the voltage difference and try to power on. However, each battery cluster only attempts this operation once.

[0125] Exemplarily, when the voltage difference C is obtained by subtracting the voltage of the battery of the unpowered branch from the voltage of the lowest voltage battery B, and the voltage difference C is greater than AllowVdealt, and there is no response to the power-on fault and a charging request, and there is no full charge in this state, a 5s current limit is performed, and there is still no power-on after 5s, and the charging mode is exited to allow the low-voltage branch to be powered on. When the voltage difference C is obtained by subtracting the voltage of the battery of the unpowered branch from the voltage of the lowest voltage battery B, and the voltage difference C is greater than AllowVdealt, and there is no response to the power-on fault and no charging request, a 20s current limit is performed to reduce the voltage difference and try to power on. Each cluster can only be tried once.

[0126] Fourth, if the powered battery fails:

[0127] First, the total allowed charge and discharge current is limited to 10A multiplied by the number of relay closure clusters, and then a power-off command is sent to the faulty battery. After the faulty battery is powered off, the current limit setting is restored.

[0128] Fifth, when the maximum single cell voltage of a battery cluster exceeds the charging cut-off voltage ChgEndVol:

[0129] When the maximum cell voltage of a battery cluster exceeds ChgEndVol, the battery cluster is determined to be fully charged. If the number of battery clusters with closed relays is greater than 1, a current limiting instruction is sent to disconnect the fully charged battery and restore the current limiting setting. Otherwise, if this is the last cluster, charging continues until the current limiting current drops to 0A. At this point, the Main Battery Management Unit (MBMU) will perform a full charge SOC calibration, calibrate the SOC to 100%, and keep the relay closed to wait for the discharge condition.

[0130] In the embodiment of the present application, when the number of branches of the powered battery pack is greater than 1, the corresponding charging cut-off voltage ChgEndVol is greater than the corresponding charging cut-off voltage ChgEndVol when the number of branches of the powered battery pack is equal to 1.

[0131] Exemplarily, when the number of closed relay clusters is greater than 1, ChgEndVol=3580mv. When the number of closed relay clusters is equal to 1, ChgEndVol=3600mv.

[0132] It can be understood that ChgEndVol can be specifically set according to actual conditions, and this application does not make any specific limitation on this.

[0133] In the embodiment of the present application, in the charging mode, the charging cut-off voltage is divided into two levels. If the number of currently powered-on branches is greater than 1, the branch with the maximum single cell voltage reaching 3580mv (i.e., the second voltage threshold) in the powered-on branch is powered off, until the number of powered-on branches is equal to 1, the charging cut-off voltage is 3600mv (i.e., the third voltage threshold), the powered-on branch remains powered on, and the charging current of the powered-on branch is limited to a preset current value such as 0A. In the charging mode, the maximum single cell voltage is first allowed to reach 3580mv to power off, so that it has a certain rechargeable capacity to prevent single cell voltage overvoltage when paralleling.

[0134] Step S307: when the fourth condition is met, the multi-battery pack parallel system is controlled to enter a power-off mode, and a power-off operation of the power-off mode is executed.

[0135] In the embodiment of the present application, the fourth condition includes: the inverter or button sends a power-off command or there is a system failure that lasts for a certain period of time (such as 3 seconds) or the inverter is heated.

[0136] In an embodiment of the present application, when the inverter or button sends a power-off command, or the system detects a fault and lasts for more than 3 seconds, or the inverter triggers a protection mechanism due to overheating, the multi-battery pack parallel system is controlled to enter the power-off mode (PowerDown) mode, and a power-off command is sent to all battery clusters to ensure that all batteries are safely disconnected from the system.

[0137] Step S308, when the fifth condition is met, the multi-battery pack parallel system is controlled to enter a low energy consumption mode from a power-off mode.

[0138] In the embodiment of the present application, the fifth condition includes: the inverter power-on instruction is valid||the black start instruction is valid)&&there is no system fault&&the system is not in inverter heating.

[0139] In an embodiment of the present application, when the fifth condition is met, the power-off mode will be switched to the low-power mode. The fifth condition includes a startup condition and a safety condition. The startup conditions include: the inverter power-on command is valid: when the inverter receives a valid power-on command, this is a prerequisite for switching to the low-power mode. Or the black start command is valid: in some cases, if the system receives a valid black start command, it can also trigger the transition to the low-power mode. Safety conditions include: no system failure. The system is not in inverter heating: the inverter cannot be in an overheating state or heating mode to ensure that the system can safely and stably transition to the low-power mode. Once the above startup conditions and safety conditions are met, the system will start to transition from the power-off mode. During the transition process, the battery management system will perform a series of operations, such as shutting down unnecessary circuits, adjusting power management parameters, etc., to enter the low-power mode.

[0140] In some embodiments, when the sixth condition is met, the multi-battery pack parallel system is controlled to enter the discharge mode from the charging mode. The sixth condition is: the charging current is less than or equal to the fourth current threshold, and the time less than the fourth current threshold reaches the third time threshold. The fourth current threshold can be 0.1A, 0.2A or 0.3A, and the third time threshold can be 3s, 4s or 5s, which is not specifically limited in the embodiments of the present application. The first time threshold, the second time threshold, and the third time threshold can be the same or different.

[0141] In an embodiment of the present application, in order to ensure that when multiple battery pack branches are charged in parallel, they can reach a full charge state safely and effectively, while avoiding voltage imbalance problems caused by overcharging and parallel circulating current, a parallel full charge strategy is implemented.

[0142] In an embodiment of the present application, the parallel full charge strategy includes: charging cut-off voltage setting, multi-battery pack branch charging monitoring, single battery pack branch charging monitoring, and preventing single cell voltage overvoltage during parallel operation. Among them, charging cut-off voltage setting: In order to cope with different charging conditions and battery pack branch states, the charging cut-off voltage is divided into two levels. When the number of powered-on battery pack branches is greater than 1, in order to avoid overcharging of relatively low voltage battery pack branches due to small circulation currents during parallel operation, the charging cut-off voltage is set to 3580mv; and when the number of powered-on battery pack branches is equal to 1, since there is no risk of parallel circulation current, the charging cut-off voltage is set to a higher 3600mv. Among them, multi-battery pack branch charging monitoring: If the number of currently powered-on battery pack branches is greater than 1, the maximum single cell voltage in each powered-on battery pack branch is continuously monitored. When the maximum single cell voltage of a battery pack branch first reaches 3580mv, the battery pack branch is considered to be fully charged, the full charge flag (such as BO_BattChgFinsh[cnt]) will be set to 1, and the power-off operation of the battery pack branch will be triggered. After the power-off operation is completed, the battery pack branch will no longer participate in charging, but will remain in a monitored state to ensure its safety. Among them, single battery pack branch charging monitoring: If only one battery pack branch is currently powered on for charging, monitor the maximum single cell voltage of the battery pack branch. Once the maximum single cell voltage of the battery pack branch reaches the charging cut-off voltage of 3600mv, the full charge flag signal (such as ChgFinsh) of the entire system will be set to 1, indicating that the system is fully charged. Unlike the case of multiple battery pack branches, the last fully charged battery pack branch will remain powered on so that it can provide power output immediately when needed. To prevent single cell voltage overvoltage during parallel operation: under charging conditions, the battery pack branch with the maximum single cell voltage reaching 3580mv is powered off first, so that the battery pack branch maintains a certain rechargeability. During parallel operation, even if there is a small circulating current, the battery pack branch with a relatively low voltage will not be overcharged due to excessive voltage differences.

[0143] In the embodiment of the present application, when designing and implementing a multi-battery pack parallel system, it is crucial to determine an appropriate parallel voltage difference threshold. The setting of the parallel voltage difference threshold directly affects the system's operating performance, safety, and battery life. By measuring the minimum internal resistance of a new battery cell at different temperatures, and based on the charging current allowed by the battery at different temperatures, the two are multiplied to obtain the parallel voltage difference threshold of a battery cell. The parallel voltage difference threshold of a battery pack can be obtained based on the number of series-connected batteries in a battery pack, and then multiplied by the number of battery packs to obtain the parallel voltage difference threshold of the multi-battery pack parallel system at the current temperature; and through the actual system, different temperatures are set in the temperature box, and the voltage difference is verified, and the voltage difference of the parallel system is within the parallel voltage difference threshold, and the circulating current is in the normal charging and discharging range of the battery, thereby determining the allowable parallel voltage difference.

[0144] Specifically, the internal resistance of the battery cell is measured first: the minimum internal resistance of the new battery cell is measured under different temperature conditions. This is because the internal resistance of the battery cell changes with the temperature, and the size of the internal resistance directly affects the maximum voltage difference that the battery cell can withstand when connected in parallel. Then determine the allowable charging current of the battery: determine the allowable charging current of the battery at different temperatures. This parameter is usually provided by the battery manufacturer and reflects the safe charging capability of the battery at different temperatures. Then calculate the allowable parallel voltage difference of the battery cell: multiply the measured minimum internal resistance of the battery cell by the allowable charging current of the battery to obtain the parallel voltage difference threshold of the battery cell at the current temperature. This parallel voltage difference threshold represents the maximum voltage difference that the battery cell can safely withstand when connected in parallel. Then determine the allowable parallel voltage difference of the battery pack: according to the number of batteries connected in series in a battery pack, the parallel voltage difference threshold of a single battery cell is accumulated to obtain the parallel voltage difference threshold of the entire battery pack. The parallel voltage difference threshold of the battery pack is the maximum voltage difference that the battery pack can safely withstand when connected in parallel. Finally, determine the allowable voltage difference of the multi-battery pack parallel system: multiply the voltage difference threshold of the battery pack by the number of battery packs to obtain the voltage difference threshold of the entire multi-battery pack parallel system at the current temperature. The voltage difference threshold of the multi-battery pack parallel system is an important parameter that needs to be considered when designing the multi-battery pack parallel system.

[0145] In some embodiments, in an actual system, a parallel test is performed by setting different temperature and pressure difference conditions. It is verified whether the system's circulating current is within the normal battery charge and discharge range within the set parallel pressure difference threshold AllowVdealt threshold. This process can help us determine the rationality of the parallel pressure difference setting and make necessary adjustments based on the test results.

[0146] Exemplarily, the minimum temperatures are 0, 5, 15, 25, 38, 45, and 50 degrees Celsius, respectively, and the parallel voltage difference thresholds may be 0.8, 1, 1.8, 1.3, 1.3, 1.3, and 1.1 V, respectively.

[0147] See also Figure 4 , exemplarily introduces another control method for a multi-battery pack parallel system provided in an embodiment of the present application, the method comprising steps S41 to S44.

[0148] Step S41, when there is an unpowered first battery pack branch in the discharge mode, obtain the parallel voltage difference threshold of the current multi-battery pack parallel system, the first voltage of the first battery pack branch, the second voltage of the powered battery pack branch and the discharge current of the multi-battery pack parallel system.

[0149] Step S42, controlling the power-on of the first battery pack branch according to the discharge current, the first voltage, the second voltage and the parallel voltage difference threshold.

[0150] In an embodiment of the present application, controlling the power-on of the first battery pack branch according to the discharge current, the first voltage, the second voltage and the parallel voltage difference threshold includes: when the first voltage is greater than the second voltage, and the voltage difference between the first voltage and the second voltage is greater than the parallel voltage difference threshold, detecting the discharge current; when the discharge current is greater than the first current threshold, and the duration for which the discharge current is greater than the first current threshold is greater than a first preset time, controlling the power-on of the first battery pack branch.

[0151] In an embodiment of the present application, controlling power-on of the first battery pack branch according to the discharge current, the first voltage, the second voltage and the parallel voltage difference threshold also includes: when the discharge current is greater than the second current threshold, the first voltage is higher than the second voltage, and the voltage difference between the first voltage and the second voltage reaches the first voltage threshold, and the voltage difference between the first voltage and the second voltage is less than the parallel voltage difference threshold, controlling power-on of the first battery pack branch; when the discharge current is less than the second current threshold, and the voltage difference between the first voltage and the second voltage is less than or equal to the parallel voltage difference threshold, controlling power-on of the first battery pack branch.

[0152] Step S43, when there is an unpowered second battery pack branch in the charging mode, obtain the parallel voltage difference threshold of the current multi-battery pack parallel system, the third voltage of the second battery pack branch, the fourth voltage of the powered battery pack branch and the charging current of the multi-battery pack parallel system.

[0153] Step S44, controlling the power-on of the second battery pack branch according to the charging current, the third voltage, the fourth voltage and the parallel voltage difference threshold.

[0154] In an embodiment of the present application, controlling the power-on of the second battery pack branch according to the charging current, the third voltage, the fourth voltage and the parallel voltage difference threshold includes: when the third voltage is less than the fourth voltage, the voltage difference between the third voltage and the fourth voltage is greater than the parallel voltage difference threshold, and there is a charging request for the second battery pack branch, limiting the charging current; within a second preset time after limiting the charging current, the voltage difference between the third voltage and the fourth voltage is less than or equal to the parallel voltage difference threshold, and the power-on of the second battery pack branch is controlled; when the duration after limiting the charging current exceeds the second preset time, the voltage difference between the third voltage and the fourth voltage is greater than the parallel voltage difference threshold, the powered-on battery pack branch is controlled to be powered off and the second battery pack branch is controlled to be powered on.

[0155] In an embodiment of the present application, controlling power-on of the second battery pack branch according to the charging current, the third voltage, the fourth voltage and the parallel voltage difference threshold also includes: when the third voltage is less than the fourth voltage, the voltage difference between the third voltage and the fourth voltage is greater than the parallel voltage difference threshold, and there is no charging request for the second battery pack branch, limiting the charging current; at a third preset time after limiting the charging current, the voltage difference between the third voltage and the fourth voltage is less than or equal to the parallel voltage difference threshold, controlling power-on of the second battery pack branch; at a third preset time after limiting the charging current, the voltage difference between the third voltage and the fourth voltage is greater than the parallel voltage difference threshold, and canceling limiting the charging current, wherein the third preset time is greater than the second preset time.

[0156] In an embodiment of the present application, controlling power-on of the second battery pack branch according to the charging current, the third voltage, the fourth voltage and the parallel voltage difference threshold also includes: when the charging current is greater than the second current threshold, the third voltage is less than the fourth voltage, and the voltage difference between the fourth voltage and the third voltage is greater than the first voltage threshold, and the voltage difference between the third voltage and the fourth voltage is less than or equal to the parallel voltage difference threshold, controlling power-on of the second battery pack branch; when the discharging current is less than the second current threshold, and the voltage difference between the third voltage and the fourth voltage is less than or equal to the parallel voltage difference threshold, controlling power-on of the second battery pack branch.

[0157] In an embodiment of the present application, obtaining the parallel pressure difference threshold of the current multi-battery pack parallel system includes: obtaining the current temperature; determining the parallel pressure difference threshold of the current multi-battery pack parallel system based on the current temperature, wherein the parallel pressure difference threshold of the multi-battery pack parallel system is obtained based on the number of battery packs in the multi-battery pack parallel system and the parallel pressure difference threshold of a battery pack, wherein the parallel pressure difference threshold of a battery pack is obtained based on the number of battery cells in a battery pack and the parallel pressure difference threshold of a battery cell, wherein the parallel pressure difference threshold of a battery cell is obtained based on the minimum internal resistance of the battery cell at the current temperature and the charging current allowed by the battery cell at the current temperature.

[0158] In the embodiment of the present application, the parallel voltage difference threshold is determined by measuring the minimum internal resistance of the new battery cell at different temperatures and looking up a table to finely control the voltage difference at different temperatures, rather than roughly setting a fixed threshold. This allows the system circulation to maximize the allowable parallel voltage difference under the conditions allowed by battery charging and discharging, thereby allowing the system to enter the parallel state earlier.

[0159] In an embodiment of the present application, the method also includes: when there are N unpowered battery pack branches in the discharge mode, and two or more of the N unpowered battery pack branches have respective maximum single-cell voltages greater than a first threshold and a state of charge greater than or equal to a first preset threshold, controlling a battery pack branch with the highest total voltage among the N unpowered battery pack branches to be powered on, where N is an integer greater than 1; when the state of charge of a powered battery pack branch is less than the first preset threshold, or the maximum single-cell voltage of the powered battery pack branch is less than a second preset voltage value, controlling other battery pack branches that meet the parallel voltage difference threshold to be powered on.

[0160] In the embodiment of the present application, when there are N powered-on battery pack branches in the charging mode, determine the target battery pack branch whose maximum cell voltage of each of the N-1 powered-on battery pack branches reaches the second voltage threshold; control the target battery pack branch to power off; when there is one powered-on battery pack branch in the charging mode (i.e., there is only one powered-on battery pack branch in the charging mode), and the maximum cell voltage of the powered-on battery pack branch reaches the third voltage threshold, keep the powered-on battery pack branch powered on, and limit the charging current of the powered-on battery pack branch to a preset current value, wherein the second voltage threshold is less than the third voltage threshold. The preset current value is 0A.

[0161] It can be understood that when the maximum single-cell voltage of the powered-on battery pack branch reaches the third voltage threshold, the powered-on battery pack branch remains powered on, and the charging current of the powered-on battery pack branch is limited to a preset current value, the actual detected charging current of the powered-on battery pack branch can be 0.1A or 0.2A, or other values ​​close to 0A, and the present application does not make any specific limitations on this.

[0162] Among them, the second voltage threshold is the voltage value of a fully charged single cell, which can be 3580mv. The second voltage threshold can be a charging cut-off threshold during the charging process set according to actual conditions, and this application does not make any specific limitations on this.

[0163] Among them, the third voltage threshold may be, for example, 3600 mv. The third voltage threshold may be a charging cutoff threshold during the charging process set according to actual conditions, and this application does not make any specific limitation on this.

[0164] The second voltage threshold is different from the third voltage threshold. For example, the second voltage threshold may be a charge cut-off voltage of 3580 mv, and the third voltage threshold may be a charge cut-off voltage of 3600 mv.

[0165] The implementation of the embodiments of the present application has at least the following technical effects:

[0166] By limiting the current of the charging and discharging branch when the unpowered battery pack branch meets the power-on condition, the relay sticking caused by closing the relay under high current conditions is avoided. In the discharge mode of high current discharge, the voltage of the unpowered battery pack branch is limited to be higher than the voltage of the powered battery pack branch to reach a first voltage threshold such as 1V before powering on. This avoids the situation where the unpowered battery pack branch just meets the parallel voltage difference threshold, while the discharge current of the powered battery pack branch becomes smaller, causing the voltage of the powered battery pack branch to increase, so that the voltage difference between the unpowered battery pack branch and the powered battery pack branch exceeds the parallel voltage difference threshold. When the voltage of the unpowered battery pack branch is higher than the voltage of the powered battery pack branch, and the voltage difference between the unpowered battery and the powered battery exceeds the parallel voltage difference threshold, the battery is connected only when the discharge current is monitored to be greater than a certain threshold (such as the first current threshold) and lasts for a certain time (such as the first preset time). When the system is in a state of large current discharge, the high-voltage branch is connected, and the branch with a total high voltage will supply power to the load and the low-voltage branch at the same time, thereby reducing the circulating current and solving the problem that the unpowered branch in the discharge mode cannot be connected in parallel because the voltage difference exceeds the threshold compared with the powered branch.

[0167] In the charging mode, the charging cut-off voltage is controlled by setting two gears (the second voltage threshold and the third voltage threshold, respectively) to control the branch that reaches the second voltage threshold, such as 3580mv, to be powered off first, so that it retains a certain amount of rechargeable energy, and prevents the single cell voltage from being over-voltage due to circulating current when paralleling. When there is only one powered-on branch in the charging mode, and the maximum single cell voltage of the powered-on battery pack branch reaches the third voltage threshold, such as 3600mV, the powered-on battery pack branch is kept powered on, and the charging current of the powered-on battery pack branch is limited to the preset current value. In the discharge mode, if it is detected that the system is in a full state ChgFinsh==1 or (the number of branches with a maximum single cell greater than 3336mv and an SOC greater than 95% is greater than 1), only one branch is allowed to be powered on, to prevent the high power of each branch from being paralleled, and the low-voltage branch single cell from being over-charged due to circulating current charging.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the preferred embodiments, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present application.

Claims

1. A control method for a multi-battery pack parallel system, characterized in that: The method comprises: When there is an unpowered first battery pack branch in the discharge mode, obtaining a parallel voltage difference threshold of the current multi-battery pack parallel system, a first voltage of the first battery pack branch, a second voltage of the powered battery pack branch, and a discharge current of the multi-battery pack parallel system; Controlling power on the first battery pack branch according to the discharge current, the first voltage, the second voltage, and the parallel voltage difference threshold; When there is an unpowered second battery pack branch in the charging mode, obtaining a parallel voltage difference threshold of the current multi-battery pack parallel system, a third voltage of the second battery pack branch, a fourth voltage of the powered battery pack branch, and a charging current of the multi-battery pack parallel system; The second battery pack branch is powered on according to the charging current, the third voltage, the fourth voltage and the parallel voltage difference threshold.

2. The method according to claim 1, characterized in that The controlling the power-on of the first battery pack branch according to the discharge current, the first voltage, the second voltage, and the parallel voltage difference threshold comprises: When the first voltage is greater than the second voltage, and the voltage difference between the first voltage and the second voltage is greater than the parallel voltage difference threshold, detecting the discharge current; When the discharge current is greater than a first current threshold, and a duration in which the discharge current is greater than the first current threshold is greater than a first preset time, the first battery pack branch is controlled to be powered on.

3. The method according to claim 1, characterized in that The controlling the power-on of the first battery pack branch according to the discharge current, the first voltage, the second voltage, and the parallel voltage difference threshold comprises: When the discharge current is greater than a second current threshold, the first voltage is higher than the second voltage, the voltage difference between the first voltage and the second voltage reaches a first voltage threshold, and the voltage difference between the first voltage and the second voltage is less than a parallel voltage difference threshold, controlling the first battery pack branch to be powered on; When the discharge current is less than the second current threshold and the voltage difference between the first voltage and the second voltage is less than or equal to the parallel voltage difference threshold, the first battery pack branch is controlled to be powered on.

4. The method according to claim 1, characterized in that The controlling the power-on of the second battery pack branch according to the charging current, the third voltage, the fourth voltage and the parallel voltage difference threshold comprises: When the third voltage is lower than the fourth voltage, the voltage difference between the third voltage and the fourth voltage is greater than the parallel voltage difference threshold, and the second battery pack branch has a charging request, limiting the charging current; Within a second preset time after limiting the charging current, the voltage difference between the third voltage and the fourth voltage is less than or equal to the parallel voltage difference threshold, and the second battery pack branch is controlled to be powered on; When the duration after limiting the charging current exceeds the second preset time, the voltage difference between the third voltage and the fourth voltage is greater than the parallel voltage difference threshold, the powered-on battery pack branch is controlled to be powered off and the second battery pack branch is controlled to be powered on.

5. The method according to claim 4, characterized in that The controlling the power-on of the second battery pack branch according to the charging current, the third voltage, the fourth voltage and the parallel voltage difference threshold further includes: When the third voltage is lower than the fourth voltage, the voltage difference between the third voltage and the fourth voltage is greater than the parallel voltage difference threshold, and the second battery pack branch has no charging request, limiting the charging current; At a third preset time after limiting the charging current, the voltage difference between the third voltage and the fourth voltage is less than or equal to the parallel voltage difference threshold, and the second battery pack branch is controlled to be powered on; In the third preset time after limiting the charging current, the voltage difference between the third voltage and the fourth voltage is greater than the parallel voltage difference threshold, and limiting the charging current is cancelled, wherein the third preset time is greater than the second preset time.

6. The method according to claim 1, characterized in that The controlling the power-on of the second battery pack branch according to the charging current, the third voltage, the fourth voltage and the parallel voltage difference threshold comprises: When the charging current is greater than the second current threshold, the third voltage is less than the fourth voltage, and the voltage difference between the fourth voltage and the third voltage is greater than the first voltage threshold, and the voltage difference between the third voltage and the fourth voltage is less than or equal to the parallel voltage difference threshold, control the second battery pack branch to be powered on; When the discharge current is less than the second current threshold and the voltage difference between the third voltage and the fourth voltage is less than or equal to the parallel voltage difference threshold, the second battery pack branch is controlled to be powered on.

7. The method according to any one of claims 1 to 6, characterized in that The step of obtaining the parallel voltage difference threshold of the current multi-battery pack parallel system includes: Get the current temperature; The parallel pressure difference threshold of the current multi-battery pack parallel system is determined according to the current temperature, wherein the parallel pressure difference threshold of the multi-battery pack parallel system is obtained according to the number of battery packs in the multi-battery pack parallel system and the parallel pressure difference threshold of one battery pack, wherein the parallel pressure difference threshold of one battery pack is obtained according to the number of battery cells in one of the battery packs and the parallel pressure difference threshold of one battery cell, wherein the parallel pressure difference threshold of one battery cell is obtained according to the minimum internal resistance of the battery cell at the current temperature and the allowed charging current of the battery cell at the current temperature.

8. The method according to any one of claims 1 to 6, characterized in that The method further comprises: When there are N unpowered battery pack branches in the discharge mode, and two or more of the N unpowered battery pack branches have respective maximum single cell voltages greater than a first threshold and a state of charge greater than or equal to a first preset threshold, control a battery pack branch with the highest total voltage among the N unpowered battery pack branches to be powered on, where N is an integer greater than 1; When the state of charge of the powered-on battery pack branch is less than a first preset threshold, or the maximum single cell voltage of the powered-on battery pack branch is less than a second preset voltage value, other battery pack branches that meet the parallel voltage difference threshold are controlled to be powered on.

9. The method according to any one of claims 1 to 6, characterized in that The method further comprises: When there are N powered-on battery pack branches in the charging mode, determine a target battery pack branch whose maximum single-cell voltage of each of N-1 powered-on battery pack branches reaches a second voltage threshold; Controlling the target battery pack branch to power off; When there is a powered-on battery pack branch in the charging mode and the maximum single-cell voltage of the powered-on battery pack branch reaches a third voltage threshold, the charging current of the powered-on battery pack branch is limited to a preset current value, wherein the second voltage threshold is less than the third voltage threshold.

10. A battery pack, characterized in that: The battery pack includes a processor and a memory, and the processor is used to implement the control method of the multi-battery pack parallel system as described in any one of claims 1 to 9 when executing the computer program stored in the memory.

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