Current imbalance control method, control apparatus and control device, and energy storage system

Abstract

Provided in the present application are a current imbalance control method, control apparatus and control device, and an energy storage system, which can solve the problem of current imbalance among battery packs. The control method comprises: acquiring DCR of battery packs; and on the basis of the DCR of a plurality of battery packs, determining whether there is current imbalance among the plurality of battery packs. By means of acquiring the DCR of the battery packs and on the basis of the difference between the DCR of the plurality of battery packs connected in parallel, the current imbalance among the plurality of battery packs connected in parallel can be detected and prevented in a timely manner, thereby improving the charging and discharging performance of the entire energy storage system.

Description

Unbalanced flow control method, control device, control equipment and energy storage system

[0001] This application claims priority to the invention patent application filed with the Patent Office of China on December 26, 2023, with application number 202311814038.8, and with the invention name “Overcurrent control method and device, BMS, EMS and energy storage system”, as well as the invention patent application filed with the Patent Office of China on December 26, 2023, with application number 202311811317.9, and with the invention name “Overcurrent control method and device, battery management system and energy storage system”. The entire contents of both applications are incorporated herein by reference. Technical Field

[0002] The present application relates to the field of batteries, and in particular to a method for controlling uneven flow, a control device, a control equipment, and an energy storage system. Background Art

[0003] Energy storage systems typically require high voltage and large capacity. To this end, they require a large number of batteries connected in series and parallel to form cabinets or containers, interacting with the power grid through a power conversion system (PCS). Battery packs in an energy storage system can be connected in parallel. If current imbalance occurs between multiple battery packs, this can lead to premature charge and discharge terminations for the entire energy storage system, impacting its capacity and power utilization. Furthermore, battery packs with excessive current can exceed the battery cell's charging window, impacting its safety and service life. Therefore, addressing this issue of battery pack current imbalance is crucial.

[0004] Summary of the Invention

[0005] The embodiments of the present application provide a method for controlling uneven current, a control device, a control equipment, and an energy storage system, which can solve the problem of uneven current in a battery pack.

[0006] In a first aspect, a method for controlling uneven current is provided, the method comprising: obtaining a DCR of a battery pack; and determining whether there is uneven current between the multiple battery packs according to the DCRs of the multiple battery packs.

[0007] In the embodiment of the present application, the DCR of the battery pack is obtained, and according to the difference between the DCRs of the multiple battery packs connected in parallel, the uneven current between the multiple battery packs connected in parallel is promptly discovered and prevented, thereby improving the charge and discharge performance of the entire battery pack.

[0008] In one possible implementation, obtaining the DCR of the battery pack includes: obtaining a state parameter group of the battery pack, the state parameter group including at least two state parameters of the battery pack; determining a first DCR of the battery pack based on the state parameter group of the battery pack and a preset correspondence between multiple state parameter groups and multiple DCRs; and determining a second DCR of the battery pack based on the first DCR of the battery pack.

[0009] In this implementation, a database including the correspondence between the state parameter group of the battery pack and the DCR is established, and the DCR of the battery pack under the current state parameters is determined using the database, where the state parameter group includes multiple state parameters that may affect the DCR of the battery pack. Since the influence of different state parameters on the DCR of the battery pack is fully considered, the accuracy of the DCR can be improved.

[0010] In one possible implementation, the state parameter group includes at least two of the following state parameters: the state of charge of the battery pack, the temperature of the battery pack, the current of the battery pack, the charge and discharge direction of the battery pack, the charge and discharge time of the battery pack, and the health status of the battery pack. This fully considers the impact of different influencing factors on the DCR of the battery pack.

[0011] In a possible implementation, determining the second DCR of the battery pack according to the first DCR of the battery pack includes: determining the first DCR as the second DCR; or calibrating the first DCR according to a preset calibration coefficient to obtain the calibrated second DCR of the battery pack.

[0012] In this implementation, the first DCR can be directly used as the result of the DCR detection. Alternatively, after obtaining the DCR of the battery pack, the first DCR of the battery pack is calibrated using an appropriate calibration coefficient, and the obtained second DCR is used as the result of the DCR detection. The calibration coefficient can improve the inconsistency between the initial DCRs of different battery cells in the battery pack, thereby improving the accuracy of the DCR.

[0013] In a possible implementation, the method further includes: acquiring a state parameter group of the battery pack at a target time after the current time; and determining a DCR of the battery pack at the target time based on the state parameter group of the battery pack at the target time and the corresponding relationship.

[0014] In this implementation, when the state parameters of the battery pack under future operating conditions are known, the DCR database can be used to predict the DCR of the battery pack under future operating conditions, and risk prediction can be performed based on the DCR. For example, it can be determined in advance whether uneven current may occur between battery packs, and appropriate strategies can be determined and responded to in a timely manner, thereby reducing the risks caused by excessive differences in DCR between battery packs.

[0015] In a possible implementation, obtaining the DCR of the battery pack includes: obtaining information about the voltage and / or current of the battery pack; and determining the DCR of the battery pack according to the information about the voltage and / or current.

[0016] In this implementation, the voltage and / or current of the battery pack may be detected, and the DCR of the battery pack may be determined based on information about the voltage and / or current, thereby achieving dynamic detection of the DCR.

[0017] In one possible implementation, obtaining the information of the voltage and / or current of the battery pack includes: obtaining the open-circuit voltage of the battery pack; and determining the DCR of the battery pack based on the voltage and / or current information includes: determining the DCR of the battery pack based on the open-circuit voltage of the battery pack, the voltage of the battery pack, and the current of the battery pack.

[0018] In this implementation, the DCR of the battery pack is detected using the current OCV, voltage, and current information of the battery pack. Because this DCR detection method uses the current voltage and current of the battery pack, as well as the current static OCV of the battery pack, it does not rely on the initial voltage of the battery pack and will not be affected by the instability of the initial voltage. Therefore, it has high accuracy and can perform dynamic testing of the DCR, thereby quickly and accurately obtaining the DCR of the battery pack.

[0019] In a possible implementation, obtaining the open circuit voltage of the battery pack includes: obtaining the state of charge of the battery pack; and determining the open circuit voltage of the battery pack according to the state of charge of the battery pack and a preset correspondence between the open circuit voltage and the state of charge.

[0020] In this implementation, a curve between the battery pack's OCV and SOC can be pre-built into the BMS software to facilitate obtaining the battery pack's current OCV. When testing the battery pack's DCR, the OCV corresponding to the current SOC and the curve between OCV and SOC can be determined. This OCV is then used as the current OCV of the battery pack to calculate the battery pack's DCR.

[0021] In one possible implementation, determining the DCR of the battery pack based on the open-circuit voltage of the battery pack, the voltage of the battery pack, and the current of the battery pack includes: determining a voltage difference between the voltage of the battery pack and the open-circuit voltage of the battery pack; determining a ratio between the voltage difference and the current of the battery pack; and determining the ratio as the DCR of the battery pack.

[0022] In this implementation, the current voltage of the battery pack can be subtracted from the OCV of the battery pack, and the ratio of the difference to the current current of the battery pack can be calculated, so that the ratio is used as the current DCR of the battery pack. Since this DCR calculation method only uses the current voltage and current of the battery pack and the current static OCV of the battery pack, it does not depend on the initial voltage of the battery pack. Therefore, it has higher accuracy and can perform dynamic testing of DCR.

[0023] In one possible implementation, obtaining information about the voltage and / or current of the battery pack includes: controlling a PCS connected to the battery pack to charge and discharge the battery pack; obtaining information about the voltage and current of the battery pack during the charging and discharging process; and determining the DCR of the battery pack based on the voltage and / or current information includes: determining the target DCR based on the current of the battery pack and a change in the voltage of the battery pack within a target duration.

[0024] In this implementation, the DCR of the battery pack can be dynamically obtained by controlling the PCS to charge and discharge the battery pack and utilizing the voltage and current information of the battery pack during the charging and discharging process.

[0025] In some possible implementations, determining the target DCR of the battery pack based on the voltage information and current information of the battery pack includes: determining the target DCR based on the current of the battery pack and a change in the voltage of the battery pack within a target duration.

[0026] The battery pack is charged and discharged through the PCS within the target time, and the DCR of the battery pack can be effectively calculated based on the current of the battery pack and the change in the voltage of the battery pack within the target time, thereby realizing online testing of the DCR of the battery pack.

[0027] For example, determining the target DCR based on the current of the battery pack and the change in the voltage of the battery pack within the target duration includes: determining the target DCR of the battery pack as a ratio between the change in the voltage of the battery pack within the target duration and the current of the battery pack.

[0028] In one possible implementation, determining whether there is unequal current distribution among the multiple battery groups based on the difference between the DCRs of the multiple battery groups includes: determining that there is unequal current distribution among the multiple battery groups when a ratio between the DCR of a first battery group and the DCR of a second battery group among the multiple battery groups is greater than a preset DCR threshold, wherein the first battery group is the battery group with the largest DCR among the multiple battery groups, and the second battery group is the battery group with the smallest DCR among the multiple battery groups.

[0029] In this implementation, when multiple battery packs are connected to the grid in parallel, since the voltages of the multiple battery packs are the same, differences in the DCRs between the multiple battery packs, based on Ohm's law, will cause current differences between the battery packs, resulting in uneven current flow between the multiple battery packs, affecting the capacity and charge of the battery packs. Therefore, by detecting the differences in the DCRs of the multiple parallel battery packs, it is possible to determine whether uneven current flow occurs between the multiple battery packs, thereby facilitating the timely detection and prevention of uneven current flow between the parallel battery packs.

[0030] In one possible implementation, the control method further includes: determining a target battery pack for charging and discharging with the power grid based on the power demand of the power grid; and determining the output power of a power control system connected between the power grid and the target battery pack based on the overcurrent state of the target battery pack.

[0031] In this implementation, the target battery pack for charging and discharging with the grid is determined based on the power demand of the grid, and the output power of the corresponding PCS is determined based on the overcurrent status of the target battery pack. From the perspective of the entire station level, the charging and discharging power of the battery pack under each PCS can be dynamically adjusted to reduce the probability of overcurrent in the battery pack while meeting the grid demand.

[0032] In one possible implementation, determining a target battery group for charging and discharging with the power grid based on the power demand of the power grid includes: determining that the target battery group includes all or part of a plurality of battery groups based on the power demand of the power grid, and the plurality of battery groups are respectively connected in parallel to the power grid through a plurality of power control systems.

[0033] In this implementation, since the power demand of the power grid changes in different time periods, it is determined whether all battery packs need to participate in charging and discharging in order to meet the power demand of the power grid. In this way, while meeting the power demand of the power grid, power waste can be reduced and the optimal allocation of resources can be achieved.

[0034] In a possible implementation, the control method further includes: determining whether the battery pack has an overcurrent; and if the battery pack has an overcurrent, limiting the current of the battery pack according to the degree of the overcurrent of the battery pack.

[0035] In this implementation, if uneven current occurs in multiple battery packs connected in parallel, it may cause overcurrent in the battery pack with higher current. At this time, current limiting information is provided to the battery pack according to the degree of overcurrent, which can effectively improve its overcurrent situation.

[0036] In one possible implementation, the current limiting of the battery pack includes: determining the overcurrent information of the battery pack; sending overcurrent indication information to the energy management system, the overcurrent indication information including the overcurrent information, and the overcurrent indication information is used to request the energy management system to determine whether to limit the current of the battery pack.

[0037] In this implementation, the BMS determines the overcurrent level of the battery pack and reports overcurrent indication information carrying the overcurrent level to the EMS. The EMS determines whether to limit the current of the battery pack based on the overcurrent indication information and the current operating conditions. In this way, the overcurrent situation of the battery pack can be improved while ensuring that the current operating conditions are not affected.

[0038] In one possible implementation, the overcurrent information is used to represent the overcurrent level of the battery pack, and determining the overcurrent information of the battery pack includes: determining the overcurrent level of the battery pack based on the overcurrent ratio of the battery pack; or, determining the overcurrent level based on the overcurrent ratio and overcurrent duration of the battery pack; wherein the overcurrent ratio is the ratio between the current of the battery pack and its allowable current.

[0039] In this implementation, the battery pack's overcurrent level is associated with the percentage by which the battery pack's current exceeds its allowable current. Therefore, the battery pack's overcurrent level can be determined based on the battery pack's overcurrent percentage, which is relatively straightforward. Furthermore, the overcurrent level can also be determined based on the duration of the overcurrent.

[0040] For example, determining the overcurrent level of the battery pack based on the overcurrent ratio and overcurrent duration of the battery pack includes: when the overcurrent ratio of the battery pack reaches an overcurrent ratio corresponding to a first overcurrent level and persists for a first duration, or when the battery pack is at a second overcurrent level for a second duration, determining that the overcurrent level of the battery pack is the first overcurrent level, and the overcurrent ratio corresponding to the first overcurrent level is greater than the overcurrent ratio corresponding to the second overcurrent level. In this way, not only the degree of overcurrent but also the duration of overcurrent are taken into account, making the determination of the overcurrent level more consistent with actual conditions.

[0041] In a possible implementation, the current limiting of the battery pack includes: determining current limiting information corresponding to the overcurrent level according to the overcurrent level, wherein the overcurrent indication information also includes current limiting information corresponding to the overcurrent level.

[0042] In this implementation, the BMS can determine its desired current limiting information based on the overcurrent level of the battery pack. The current limiting information can be carried in the overcurrent indication information for the EMS to use as a reference to determine whether to reduce the power of the battery pack.

[0043] In one possible implementation, the current limiting information includes a target value of the allowable current of the battery pack, and determining the current limiting information corresponding to the overcurrent level based on the overcurrent level includes: determining the target value based on the initial value of the allowable current and the current adjustment ratio corresponding to the overcurrent level, wherein the current adjustment ratio is the ratio between the target value and the initial value of the allowable current.

[0044] In this implementation, corresponding current adjustment ratios can be set for different overcurrent levels, so that the target value of the allowable current can be determined based on the initial value of the allowable current of the battery pack and the corresponding current adjustment ratio, so that the current limiting of the battery pack matches its overcurrent level, thereby improving the effect of the current limiting.

[0045] In one possible implementation, the current limiting of the battery pack includes: determining an overflow of the battery pack, the overflow including a current difference and / or a current ratio between the current of the battery pack and its allowed current; and adjusting the allowed current of the battery pack according to the overflow.

[0046] In this implementation, the allowable current of the battery pack is adjusted according to the overcurrent of the battery pack, so that the allowable current of the battery pack can be adaptively adjusted based on the overcurrent, thereby improving the overcurrent condition of the battery pack.

[0047] In a possible implementation, adjusting the allowable current of the battery pack according to the excess current includes adjusting the allowable current of the battery pack when the current difference is greater than or equal to a first threshold, and / or the current ratio is greater than or equal to a second threshold.

[0048] In this implementation, when the difference and ratio between the actual current of the battery pack and the allowed current both reach corresponding thresholds, it can be considered that an overcurrent has occurred in the battery pack, and the allowed current of the battery pack is adjusted.

[0049] In one possible implementation, adjusting the allowable current of the battery pack includes: calculating a first product between the allowable current value of the battery pack with the smallest allowable current among N battery packs connected in parallel and N, wherein the N battery packs include the battery pack and N is a positive integer; calculating a second product between the current difference and a preset coefficient; calculating the difference between the first product and the second product; and determining the allowable current of the adjusted battery pack, which is equal to the ratio between the difference and N.

[0050] In this implementation, according to I a '=(I min *ND*k) / N to calculate the allowed current value of the adjusted battery pack I a ', where I min The allowed current value of the battery pack with the smallest allowed current among the multiple battery packs connected in parallel, including the battery pack, is calculated based on the difference D between the actual current of the battery pack and its allowed current. a ', and the allowable current I a Adjustments will not affect the current of other battery packs connected in parallel, reducing the impact on the charging and discharging process of the entire system.

[0051] In a possible implementation, determining whether the battery pack is overcurrent includes: determining whether multiple batteries in the battery pack are overcurrent; and determining whether the battery pack is overcurrent when at least one battery among the multiple batteries is overcurrent.

[0052] In this implementation, it is possible to prioritize whether multiple batteries in a battery pack have overcurrent, and when at least one of the batteries has overcurrent, determine whether the battery pack has overcurrent, thereby determining the overcurrent information of the battery pack when the battery pack has overcurrent.

[0053] In one possible implementation, the control method further includes: obtaining the temperature of a first battery system and a second battery system among multiple battery systems, the first battery system including at least one battery cluster, and the second battery system including at least one battery cluster; and determining a target operating mode of a first thermal management component and / or a second thermal management component based on the temperature of the first battery system and the temperature of the second battery system, the first thermal management component being used to control the temperature of the first battery system, and the second thermal management component being used to control the temperature of the second battery system.

[0054] In this implementation, the operating modes of the first thermal management component and the second thermal management component are determined based on the temperature information of the first battery system and the second battery system, so that the first thermal management component and the second thermal management component can effectively control the temperatures of the first battery system and the second battery system respectively, thereby improving the temperature consistency between the first battery system and the second battery system, and solving problems such as imbalance in impedance, current, etc. of the battery system caused by poor temperature consistency, thereby reducing the probability of large-current battery systems being filled or discharged prematurely, which is beneficial to improving the conversion efficiency of battery products.

[0055] In one possible implementation, the battery pack is a battery cluster or an electrical cabinet, or the battery pack is a container, wherein the container includes a plurality of electrical cabinets connected in series and / or in parallel, the battery cluster or electrical cabinet includes a plurality of electrical boxes connected in series and / or in parallel, and the electrical box includes a plurality of battery cells connected in series and / or in parallel.

[0056] In a second aspect, a control device for uneven current is provided, the control device comprising: a detection module for obtaining a DCR of a battery pack; and a processing module for determining whether there is uneven current between the multiple battery packs according to the DCRs of the multiple battery packs.

[0057] In a third aspect, a device for controlling uneven flow is provided, comprising a processor and a memory, wherein the memory is used to store instructions, and the processor is used to execute the instructions to implement the uneven flow control method described in the first aspect or any possible implementation of the first aspect.

[0058] In a fourth aspect, an energy storage system is provided, comprising: a plurality of battery packs connected in parallel; and a battery management system as described in the third aspect or any possible implementation of the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0060] FIG1 is a schematic diagram of a possible energy storage system according to an embodiment of the present application.

[0061] FIG. 2 is a schematic diagram of a possible battery cluster according to an embodiment of the present application.

[0062] FIG3 is a schematic diagram of a possible electrical box according to an embodiment of the present application.

[0063] FIG4 is a schematic diagram of a possible energy storage system according to an embodiment of the present application.

[0064] FIG5 is a schematic flow chart of a method for controlling uneven flow according to an embodiment of the present application.

[0065] FIG6 is a schematic flowchart of a method for detecting DCR according to an embodiment of the present application.

[0066] FIG7 is a schematic diagram of the DCR calculation principle.

[0067] FIG8 is a schematic diagram of a possible specific implementation of the method shown in FIG6 .

[0068] FIG9 is a schematic diagram of a possible method for testing the initial DCR of a battery cell.

[0069] FIG10 is a schematic diagram of a possible specific implementation of the method shown in FIG6 .

[0070] FIG11 is a schematic diagram of a possible specific implementation of the method shown in FIG6 .

[0071] FIG12 is a schematic flowchart of a method for detecting DCR according to another embodiment of the present application.

[0072] FIG13 is a schematic diagram of a relationship curve between OCV and SOC of a battery pack.

[0073] FIG14 is a schematic diagram of a possible specific implementation of the method shown in FIG12 .

[0074] 15 and 16 are schematic flow charts of a method for detecting DCR according to yet another embodiment of the present application.

[0075] FIG17 is a schematic diagram of the architecture of the energy storage system according to an embodiment of the present application.

[0076] FIG18 is a flow chart of a possible specific implementation of the method shown in FIG15 and FIG16 .

[0077] FIG19 is a schematic diagram of a possible specific implementation of the method shown in FIG15 and FIG16 .

[0078] FIG20 is a schematic flowchart of a power control method according to an embodiment of the present application.

[0079] FIG21 is a schematic diagram of an energy storage system according to an embodiment of the present application.

[0080] FIG22 is a schematic diagram of the power demand of the power grid in different time periods.

[0081] FIG23 is a schematic diagram of a possible specific implementation of the method shown in FIG20 .

[0082] FIG24 is a schematic flowchart of the method for overcurrent determination according to an embodiment of the present application.

[0083] FIG25 is a schematic diagram of a possible specific implementation of the method shown in FIG24 .

[0084] FIG26 is a schematic flow chart of the terminal current limiting method according to an embodiment of the present application.

[0085] FIG27 is a flow chart of a possible implementation of the method shown in FIG26 .

[0086] FIG28 is a schematic flowchart of the adaptive current limiting method according to an embodiment of the present application.

[0087] FIG29 is a flow chart of a possible implementation of the method shown in FIG28 .

[0088] FIG30 is a schematic flow chart of a temperature control method according to an embodiment of the present application.

[0089] 31 and 32 are schematic diagrams of the architecture of the thermal management component according to an embodiment of the present application.

[0090] FIG33 is a flow chart of a possible implementation of the method shown in FIG30 .

[0091] FIG34 is a schematic block diagram of a DCR control device according to an embodiment of the present application.

[0092] FIG35 is a schematic block diagram of a DCR control device according to an embodiment of the present application. DETAILED DESCRIPTION

[0093] The following detailed description of the embodiments of the present application is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present application, but are not intended to limit the scope of the present application, i.e., the present application is not limited to the described embodiments.

[0094] Since energy storage systems usually have requirements such as high voltage and large capacity, a large number of batteries are required in the energy storage system to be connected in series and parallel to form products such as electrical cabinets or containers, and energy interaction with the power grid is carried out through PCS. Among them, PCS is used to realize the conversion between the AC power signal of the power grid and the DC power signal of the energy storage system.

[0095] As an example, as shown in FIG1 , the battery pack 1 includes N battery clusters, namely, battery cluster R1 to battery cluster RN, where N is a positive integer. Battery clusters R1 to battery cluster RN are connected in parallel with each other, and are charged or discharged with the power grid through the PCS. Each battery cluster includes multiple electrical boxes. For example, as shown in FIG2 , each battery cluster in battery cluster R1 to battery cluster RN includes M electrical boxes, namely, electrical boxes B1 to electrical boxes BM, where M is a positive integer. The M electrical boxes are connected in series; or, some of the M electrical boxes are first connected in parallel to form parallel units, and then multiple parallel units are connected in series to form a battery cluster. Each electrical box is assembled from K battery cells. For example, as shown in FIG3 , each electrical box in electrical boxes B1 to electrical boxes BM includes K battery cells connected in series and / or in parallel, namely, battery cells C1 to battery cells CK.

[0096] As an example, as shown in Figure 4, each PCS can connect to one or more battery packs. Multiple battery packs are connected in parallel to the power grid via the PCS, allowing charging or discharging with the grid. The battery pack can be, for example, a battery product such as a cabinet or container. The cabinet can be considered a battery product consisting of a battery cluster. Therefore, the battery cluster shown in Figure 1 can also be called a cabinet. Multiple cabinets can be assembled to form a battery product such as a container. For example, cabinets R1 to RN shown in Figure 1 can be connected in parallel to form a container. Multiple containers can be connected in parallel to the power grid via the PCS.

[0097] During the production process, the direct current resistance (DCR) of battery cells is affected by various factors, resulting in differences in DCR between individual cells. This, in turn, leads to significant differences in DCR in battery packs assembled from these cells, such as in electrical cabinets or containers. After the battery packs are connected in parallel to the grid through the PCS, the differences in DCR of the battery packs in the parallel branches lead to current differences in each branch, resulting in uneven current distribution among the multiple parallel battery packs.

[0098] To this end, the present application provides a solution to uneven current flow, which aims to detect the DCR of the battery pack and, based on the differences between the DCRs of multiple parallel battery packs, promptly detect and prevent uneven current flow between multiple parallel battery packs, thereby improving the charge and discharge performance of the entire battery pack.

[0099] Figure 5 shows a schematic flow chart of an uneven flow control method according to an embodiment of the present application. The control method may be executed, for example, by a battery management system (BMS) and / or an energy management system (EMS). The BMS may include, for example, a master battery management unit (MBMU) and / or a sub-battery management unit (SBMU). As shown in Figure 5 , method 100 may include some or all of the following steps.

[0100] In step 110 , the DCR of the battery pack is obtained.

[0101] In step 120 , it is determined whether current is not balanced among the battery packs according to the DCRs of the battery packs.

[0102] By detecting the DCR of the battery pack and based on the difference between the DCRs of multiple parallel battery packs, it is possible to promptly detect and prevent uneven current between multiple parallel battery packs, thereby improving the charge and discharge performance of the entire battery pack.

[0103] The battery pack described in the embodiments of the present application may be, for example, a battery cluster or an electrical cabinet, or a container. The container includes a plurality of electrical cabinets connected in series and / or in parallel, the battery cluster or the electrical cabinet includes a plurality of electrical boxes connected in series and / or in parallel, and each electrical box includes a plurality of battery cells connected in series and / or in parallel. Of course, there may also be uneven current flow between other units in the energy storage system that need to be connected in parallel, and the problem of uneven current flow of these parallel units can also be solved by the method 100 described in the embodiments of the present application.

[0104] First, referring to Figures 6 to 19 , the following describes how to obtain the DCR of a battery pack in step 110. This application provides two methods for detecting the DCR of a battery pack, which are described below respectively.

[0105] Method 1

[0106] In method 1, a database including the correspondence between the state parameter group of the battery pack and the DCR is established, and the DCR of the battery pack under the current state parameters is determined using the database, where the state parameter group includes multiple state parameters that may affect the DCR of the battery pack. Since the influence of different state parameters on the DCR of the battery pack is fully considered, the accuracy of DCR detection can be improved.

[0107] In some embodiments, as shown in FIG. 6 , step 110 may include step 111 and step 112 .

[0108] In step 111 , a state parameter group of the battery pack is obtained.

[0109] In step 112 , a first DCR of the battery pack is determined according to the state parameter group of the battery pack and a preset correspondence relationship between a plurality of state parameter groups and a plurality of DCRs.

[0110] In step 113 , a second DCR of the battery pack is determined according to the first DCR of the battery pack.

[0111] The state parameter group includes at least one state parameter of the battery pack, for example, at least one of the following state parameters: the state of charge (SOC) of the battery pack, the temperature of the battery pack, the current of the battery pack, the charge and discharge direction of the battery pack, the charge and discharge time of the battery pack, and the state of health (SOH) of the battery pack, etc., which may affect the DCR of the battery pack.

[0112] Among them, SOC can, for example, represent the percentage of the remaining capacity of the battery, that is, the ratio between the current remaining capacity of the battery and its maximum capacity or rated capacity; SOH can, for example, represent the percentage between the capacity of the battery and the factory capacity, which is used to measure the aging state of the battery, that is, the degree of performance degradation of the battery during use; the charge and discharge direction of the battery pack includes charging and discharging, that is, the positive or negative current; the charge and discharge time can, for example, refer to the duration of the current.

[0113] Due to its electrochemical characteristics, the internal resistance of the battery may be affected by multiple factors. In order to more accurately detect the DCR of the battery pack, it is first necessary to identify the influencing factors associated with the DCR of the battery pack. The embodiments of the present application provide multiple influencing factors that may affect the DCR of the battery pack, including the SOC of the battery pack, the temperature T of the battery pack, the current I of the battery pack, the charge and discharge direction of the battery pack, the charge and discharge time Time of the battery pack, and the SOH of the battery pack. Among them, for the charge state or discharge state, the DCR of the battery pack = f(SOC, SOH, I, Time, T, charge and discharge direction), where f is the relationship between these state parameters and DCR, that is, the corresponding relationship between the above-mentioned multiple state parameter groups and multiple DCRs.

[0114] The following describes in detail the process of establishing the correspondence between multiple state parameter groups and multiple DCRs.

[0115] After determining the various state parameters that may affect the battery's DCR, the values ​​for each state parameter during the DCR test can be designed. For example, as shown in Table 1, for the various state parameters that may affect DCR, including SOC, temperature, current, charge and discharge direction, charge and discharge time, and SOH, reasonable value ranges are set to match the actual operating conditions of the battery. This example uses a charging time range of 5s-60s and a charging current range of 120A-180A. In actual applications, longer charging time ranges and / or larger current ranges can be set.

[0116] Table 1

[0117] During the test, the control variable method was used. According to the value requirements described in Table 1, the value of each of the six state parameters in Table 1 was changed separately, and a series of DCR tests were performed under the state parameter.

[0118] For example, a fresh battery cell is taken as the test object, with 100% SOH, a test environment temperature of 25°C, and a constant charging current of 140A in the charging state. Under these conditions, the DCR of the battery cell is tested at different SOCs, and the SOC values ​​include 0%, 5%, 10%, 15%, ..., 95%, and 100%.

[0119] First, for the DCR test with an SOC of 0%, the battery cell's SOC is adjusted to 0%, and the battery is left to rest for a sufficient period of time, such as 2 hours. The battery cell is then charged at a current of 140A for 60 seconds, and the battery cell voltage is recorded at multiple times. For example, as shown in Table 2, when the SOC is 0%, the battery cell voltage is recorded at 5-second intervals from 5 seconds to 60 seconds of charging time.

[0120] Table 2

[0121] Based on Table 2, the DCR of a battery cell can be calculated for different charging times. As an example, the DCR test principle shown in Figure 7 can be used to calculate the DCR of a battery cell. As shown in Figure 7, after charging a battery cell at a constant current I for a certain time ΔT, the DCR of the battery cell can be determined based on the battery cell voltage U and current I at the time after ΔT, as well as the battery cell's initial voltage U0. Where DCR = (U - U0) / I.

[0122] In Table 2, U0 is the initial voltage, i.e., the static voltage. Then, the DCR of the battery cell at 0s of charging is DCR 01 , DCR of battery cell when charging for 5s 02 =(U5-U0) / I, DCR of the battery cell when charging for 10s03 =(U 10 -U0) / I, DCR of battery cell when charging for 15s 04 =(U 15 -U0) / I, DCR of battery cell when charging for 20s 05 =(U 20 -U0) / I, ..., DCR of battery cell when charging for 55s 06 =(U 55 -U0) / I, DCR of battery cell when charging for 60s 07 =(U 60 -U0) / I, where I=140A.

[0123] In this way, the corresponding relationship between charging time and DCR under the conditions of 100% SOH, test environment temperature of 25°C, constant charging current of 140A in charging state, and SOC of 0% can be obtained as shown in Table 3.

[0124] Table 3

[0125] Secondly, the SOC of the battery cell was adjusted to 5%, and the test was performed according to the above operation. The corresponding relationship between charging time and DCR was similar to that shown in Table 3 under the conditions of 100% SOH, test environment temperature of 25°C, constant charging current of 140A in the charging state, and SOC of 5%.

[0126] By adjusting the SOC of each battery cell at 5% SOC intervals and performing DCR tests according to the above procedure, we can obtain a DCR mapping table for the following conditions: 100% SOH, a test environment temperature of 25°C, a constant charging current of 140A, SOCs of 0%, 5%, 10%, 15%, ..., 95%, 100%, and charging times of 0s, 5s, 15s, ..., 60s. For example, Table 4 shows the corresponding relationship between the state parameter group consisting of charging time and SOC and DCR.

[0127] Table 4

[0128] Using the same approach, the remaining state parameters, such as temperature, current, and SOH, are sequentially varied. Using the single-factor control variable method, DCR tests are performed for a range of values ​​under these other state parameters. The DCR data for all state parameters at different values ​​are summarized to obtain the corresponding relationship between the state parameter group consisting of SOC, temperature, current, charge / discharge direction, charge / discharge time, and SOH, thereby establishing a multi-dimensional DCR database for the entire battery life cycle.

[0129] The DCR database includes mappings between multiple state parameter groups and DCRs. This DCR database can be written into the BMS software, for example. In actual use, a battery pack state parameter group, including parameters such as the battery pack's SOC, temperature, current, charge / discharge direction, charge / discharge time, and SOH, can be collected. The DCR corresponding to each state parameter value in the battery pack's state parameter group can then be searched from the DCR database stored in the BMS.

[0130] The correspondence between each state parameter in the state parameter group and DCR can be implemented in various forms. For example, the correspondence between each state parameter in the state parameter group and DCR can be a table of mapping relationships between the values ​​of each state parameter and DCR; it can also be a curve or formula used to represent the correspondence between each state parameter in the state parameter group and DCR, such as DCR = f (SOC, SOH, I, Time, T, charge and discharge direction); or other forms that can represent the correspondence between each state parameter in the state parameter group and DCR. Among them, Tables 1 to 4 are in the form of mapping tables as examples. The mapping relationships between each state parameter in the state parameter group and DCR are stored in the BMS in the form of mapping tables.

[0131] In one implementation, in step 112 , the DCR corresponding to the state parameter group of the battery pack among the multiple DCRs in the DCR database may be directly determined as the first DCR of the battery pack, thereby simply and quickly obtaining the DCR of the battery pack.

[0132] In another implementation, in step 112, for parameter values ​​between adjacent values ​​in the DCR database, an interpolation algorithm, such as a linear interpolation algorithm, may be used to calculate the DCR corresponding to the parameter value. Assume that the state parameter group includes a first state parameter, and the DCR database includes multiple values ​​of the first state parameter corresponding to multiple DCRs. If the parameter value of the first state parameter in the state parameter group of the battery pack is not equal to any of the multiple values ​​of the first state parameter in the DCR database, then the multiple values ​​of the first state parameter in the corresponding relationship may be searched for a first value and a second value that are closest to the parameter value of the first state parameter of the battery pack, and the DCR corresponding to the first value and the second value may be determined, thereby obtaining a first DCR corresponding to the parameter value of the first state parameter of the battery pack through the interpolation algorithm.

[0133] Specifically, in step 112, a first value and a second value closest to the parameter value of the first state parameter of the battery pack can be determined from multiple values ​​of the first state parameter in the DCR database; a DCR corresponding to the first value and a DCR corresponding to the second value are determined based on the first value, the second value, and the correspondence between the first parameter value and the DCR in the DCR database; a DCR corresponding to the parameter value of the first state parameter of the battery pack is determined based on an interpolation algorithm based on the DCR corresponding to the first value and the DCR corresponding to the second value; and the DCR corresponding to the parameter value of the first state parameter of the battery pack is determined as the first DCR of the battery pack.

[0134] Taking SOC as an example, assume the values ​​of the various state parameters in the current state parameter group of the battery pack are as follows: SOC 100%, test ambient temperature 25°C, constant charging current 140A, charging time 60s, and SOC 8%. If the DCR database lists SOC values ​​in 5% intervals, including DCRs corresponding to SOCs of 0%, 5%, 10%, 15%, ..., 95%, and 100%, then the SOC values ​​closest to 8% are 5% and 10%. The DCR values ​​for the conditions of 100% SOC, 25°C test ambient temperature, constant charging current 140A, charging time 60s, and SOC 5% can be found, as well as the DCR values ​​for the conditions of 100% SOC, 25°C test ambient temperature, constant charging current 140A, charging time 60s, and SOC 10%.

[0135] Assume that the DCR values ​​corresponding to 5% SOC and 10% SOC are DCR 16 and DCR 26 Then, according to the linear interpolation algorithm, we can get DCR = DCR under the conditions of SOH of 100%, test environment temperature of 25℃, constant charging current of 140A, charging time of 60s, and SOC of 8%. 16 +(DCR 26 -DCR 16 )*(8%-5%) / (10%-5%)=DCR 16 +3(DCR 26 -DCR 16 ) / 20.

[0136] When multiple battery packs are connected to the power grid in parallel, since the voltages of the multiple battery packs are the same, according to Ohm's law, the difference in DCR between the multiple battery packs will cause current differences between the battery packs, resulting in uneven current flow between the multiple battery packs, affecting the capacity and power of the entire battery pack. Therefore, in some embodiments, method 100 may further include: determining whether there is uneven current flow between the multiple battery packs based on the DCR of the multiple battery packs in parallel. In other words, by detecting the DCR of the multiple battery packs in parallel, it is determined whether there is uneven current flow between the multiple battery packs, so as to promptly detect and prevent uneven current flow between the parallel battery packs.

[0137] Optionally, whether the multiple battery groups are current-unbalanced can be determined based on the difference between the DCRs of the multiple battery groups connected in parallel, for example, the difference between the DCR of the first battery group and the DCR of the second battery group in the battery group, where the first battery group is the battery group with the largest DCR among the multiple battery groups, and the second battery group is the battery group with the smallest DCR among the multiple battery groups.

[0138] For example, when the ratio between the DCR of a first battery group and the DCR of a second battery group in the multiple battery groups is greater than the corresponding DCR threshold, it can be determined that the current is not balanced among the multiple battery groups; for another example, when the difference between the DCR of the first battery group and the DCR of the second battery group is greater than the corresponding DCR threshold, it can be determined that the current is not balanced among the multiple battery groups.

[0139] In this way, according to the DCR difference between the battery pack with the largest DCR and the battery pack with the smallest DCR among the multiple battery packs, the uneven current distribution among the multiple battery packs can be discovered in time.

[0140] As an example, the DCR detection process shown in Figure 8 takes the battery pack as a battery cluster. The SBMU of each battery cluster is responsible for managing the corresponding battery cluster and uploading relevant data to the MBMU. The MBMU is responsible for the operation and management of the entire system formed by multiple battery clusters and can interact with external devices.

[0141] As shown in FIG8 , in step 1101 , it is determined that the battery cluster is in an operating state, that is, the battery cluster is currently charging or discharging.

[0142] In step 1102 , parameter values ​​of a plurality of state parameters in a state parameter group of a battery cluster are obtained.

[0143] For example, the state parameter group includes parameters such as SOC, temperature, current, charge and discharge direction, charge and discharge time, and SOH.

[0144] In step 1103 , the SBMU determines the DCR of the battery cluster based on the current state parameter group of the battery cluster and the correspondence between multiple state parameter groups and multiple DCRs in the DCR database.

[0145] In step 1104 , the SBMU determines whether the parameter values ​​of the status parameters in the current status parameter group of the battery cluster are in the DCR database.

[0146] If the DCR database includes the parameter value of the state parameter, step 1105 is executed; if the DCR database does not include the parameter value of the state parameter, step 1106 is executed.

[0147] In step 1105 , the SBMU determines the DCR corresponding to the parameter value of the state parameter as the first DCR of the battery cluster.

[0148] In step 1106 , the SBMU selects a value adjacent to the parameter value in the DCR database, calculates the DCR corresponding to the parameter value through an interpolation algorithm, and uses the DCR as the first DCR of the battery cluster.

[0149] The SBMU may report the first DCR of the corresponding battery cluster to the MBMU.

[0150] In step 1107 , the MBMU calculates the internal resistance difference between the multiple battery clusters connected in parallel based on the first DCRs of the multiple battery clusters.

[0151] For example, the internal resistance difference may be represented by DCRmax / DCRmin, where DCRmax and DCRmin respectively represent the maximum DCR and the minimum DCR among the first DCRs of the plurality of battery clusters.

[0152] In step 1108 , the MBMU determines whether the inter-cluster internal resistance difference DCRmax / DCRmin is greater than a preset DCR threshold, where the DCR threshold is, for example, x%, where x is a preset value.

[0153] When the inter-cluster internal resistance difference DCRmax / DCRmin is greater than the DCR threshold x%, that is, DCRmax / DCRmin>x%, step 1109 is executed; when the inter-cluster internal resistance difference DCRmax / DCRmin is less than or equal to the DCR threshold x%, that is, DCRmax / DCRmin≤x%, the first DCR of the battery cluster continues to be detected.

[0154] In step 1109 , the uneven flow strategy is executed.

[0155] The uneven current strategy may be built into the BMS software, for example, to reduce the degree of uneven current between multiple battery clusters connected in parallel. For example, the current of some or all battery clusters may be reduced based on a certain strategy.

[0156] In some embodiments, in step 113 , the first DCR may be determined as the second DCR; or the first DCR may be calibrated according to a preset calibration coefficient to obtain a calibrated second DCR of the battery pack.

[0157] That is, the first DCR can be directly used as the result of DCR detection, thereby reducing the complexity of DCR detection; or, after obtaining the DCR of the battery pack, the first DCR of the battery pack is calibrated using an appropriate calibration coefficient, and the obtained second DCR is used as the result of DCR detection.

[0158] Because the DCR database is built based on the DCR test results of a few standard battery cells, and in reality, the initial DCRs of different battery cells have certain distribution patterns, the DCR database built based on some of these battery cells cannot be accurately applied to DCR testing of other battery packs. By using this calibration coefficient to process the first DCR obtained from the DCR database to obtain a calibrated second DCR, it can reduce the inconsistency between the initial DCRs of different battery cells in the battery pack, thereby improving the accuracy of the DCR.

[0159] As an example, a possible test method for the initial DCR of a battery cell is shown in FIG9 . The initial DCR of a battery cell may generally refer to the DCR obtained by testing the battery cell on the production line. As shown in FIG9 , the battery cells on the production line generally need to undergo processes such as formation, aging, coefficient K measurement at room temperature, DCR test and capacity test, and DCR grouping. In the DCR test process, a battery cell with a certain SOC can be charged for a certain period of time. For example, a constant current charge of 30s can be performed when the battery cell has an SOC of 20%. Based on the DCR test principle shown in FIG6 , for example, the DCR of the battery cell is calculated, and the DCR can be used as the initial DCR of the battery cell.

[0160] Of course, the ambient temperature when performing the DCR test process shown in Figure 9 is different. Therefore, optionally, the DCR of the battery cell can be temperature-corrected according to its current temperature to correct it to the DCR of the battery cell at 25°C. For example, the relationship between temperature and DCR can be used, such as f(T) = 0.007T 2-0.0627T+1.8401, the initial DCR of the battery cell is corrected to obtain the corrected initial DCR=[f(25) / f(T)]*DCR before correction.

[0161] In this embodiment, the initial DCR of the battery cell may refer to the initial DCR after temperature correction. The initial DCR of the battery cell may be stored, for example, by uploading the initial DCR of the battery cell to a manufacturing execution system (MES).

[0162] Due to the differences in the initial DCRs of different battery cells, the initial DCRs of different battery cells are not the same. It is impossible to directly call the data in the DCR standard library based on the testing of only some of the battery cells. Therefore, it is necessary to set an appropriate calibration coefficient to reduce or eliminate the differences in the initial DCRs of different battery cells to a certain extent.

[0163] In some embodiments, the method 100 further includes: obtaining initial DCRs of multiple battery cells in the battery pack; obtaining initial DCRs of standard battery cells; and determining the calibration coefficient based on the initial DCRs of the standard battery cells and the initial DCRs of multiple battery cells in the battery pack.

[0164] The standard battery cell is a battery cell used to establish a corresponding relationship, and the initial DCR of the standard battery cell and the initial DCR of multiple battery cells in the battery pack are tested under the same state parameters.

[0165] The same state parameters refer to the state parameters used when testing the initial DCR of a battery cell on a production line, such as the constant current charging for 30 seconds under the aforementioned 20% SOC condition.

[0166] The calibration coefficient may be a calibration coefficient for the battery pack, and the calibration coefficients corresponding to different battery packs may be the same or different.

[0167] The calibration coefficient is determined using the initial DCR of a standard battery cell and the initial DCRs of multiple battery cells in a battery pack, so that the calibration coefficient can effectively improve the inconsistency between the initial DCRs of different battery cells in the battery pack.

[0168] Alternatively, the calibration coefficient may be equal to a ratio between an average of the initial DCRs of the plurality of battery cells in the battery pack and an initial DCR of a standard battery cell.

[0169] At this time, in some embodiments, in step 113, the product of the first DCR and the calibration coefficient can be determined as the second DCR, so that the first DCR of the battery pack can be calibrated simply and quickly to obtain the calibrated second DCR.

[0170] Taking Figures 1 to 3 as an example, N battery clusters are assembled to form a battery product such as a cabinet or container. Each of the N battery clusters includes M battery boxes, and each of the M battery boxes includes K battery cells. Therefore, each battery cluster includes M*K battery cells. When determining the calibration coefficient corresponding to the battery cluster, it is necessary to obtain the average value R of the initial DCR of the M*K battery cells in the battery cluster. mean , and the initial DCR of the standard battery cell. For example, the initial DCR of the standard battery cell used to establish the DCR database is 0.7mΩ, then the calibration coefficient corresponding to the battery cluster can be set equal to R mean / 0.7mΩ.

[0171] In the actual production process, the DCRs of different levels, such as the battery cell level, the electrical box level, the battery cluster or electrical cabinet level, and the container level, can all be recorded to facilitate production control. The initial DCR of the battery cell is obtained by using the DCR test process shown in Figure 7, and the identification information corresponding to the battery cell, such as a barcode, can be used as its identity tag to enter the corresponding initial DCR into the MES system. When multiple battery cells are assembled to form an electrical box, if the electrical box is not the object of the DCR test, then when generating the barcode corresponding to the electrical box, the DCR of the electrical box can be calculated based on the initial DCRs of the multiple battery cells in the electrical box. Similarly, the DCR of the battery cluster or electrical cabinet level can be calculated based on the DCRs of the multiple electrical boxes included in the battery cluster or electrical cabinet, and the calculated DCR of the electrical cabinet is implanted into the SBMU corresponding to the electrical cabinet; the DCR of the container level can be calculated based on the DCRs of the multiple electrical cabinets included in the container, and the calculated DCR of the container is implanted into the MBMU corresponding to the container. The DCR value of the switch cabinet or container can be stored in a local database or uploaded to a cloud server. After the DCR of the switch cabinet or container is subsequently detected online, the DCR data in the local database or cloud server can be updated.

[0172] When multiple electrical boxes are assembled to form a battery cluster, the barcode scanning device can automatically identify the barcodes of the multiple electrical boxes in the battery cluster. Through the MES system, the barcode of the battery cell in each electrical box can be traced back, as well as the initial DCR of the battery cell obtained after the DCR test on the production line, and the average initial DCR of each battery cell in the battery cluster can be calculated.

[0173] According to the average of the initial DCR of each battery cell in the battery cluster and the initial DCR of the standard battery cell used to establish the DCR database, the calibration coefficient corresponding to the battery cluster can be determined. For example, the average of the initial DCR of each battery cell in the battery cluster R max The ratio of the initial DCR of the battery cell to the initial DCR of a standard battery cell is used as the calibration coefficient. The calibration coefficient corresponding to the battery cluster can be stored in the BMS software of the battery cluster. When the calibration coefficient is needed later, the calibration coefficient is read and the first DCR corresponding to the battery cluster's state parameter set found in the DCR database is multiplied by the calibration coefficient to obtain a calibrated second DCR. The second DCR is used as the actual DCR of the battery cluster under the state parameter set for subsequent operations such as uneven current detection.

[0174] When multiple battery packs are connected to the power grid in parallel, since the voltages of the multiple battery packs are the same, based on Ohm's law, the differences in DCR between the multiple battery packs will cause current differences between the battery packs, resulting in uneven current flow between the multiple battery packs, affecting the capacity and power of the entire battery pack. Therefore, it is possible to determine whether there is uneven current flow between the multiple battery packs based on the second DCR of the multiple battery packs connected in parallel. In other words, by detecting the second DCR of the multiple battery packs connected in parallel, it is possible to determine whether there is uneven current flow between the multiple battery packs, so as to promptly detect and prevent uneven current flow between the parallel battery packs.

[0175] Optionally, whether the multiple battery groups are current-unbalanced can be determined based on the difference between the second DCRs of the multiple battery groups connected in parallel, for example, the difference between the second DCR of the first battery group and the second DCR of the second battery group in the battery group, where the first battery group is the battery group with the largest second DCR among the multiple battery groups, and the second battery group is the battery group with the smallest second DCR among the multiple battery groups.

[0176] For example, when the ratio between the second DCR of the first battery group and the second DCR of the second battery group in the multiple battery groups is greater than the corresponding DCR threshold, it can be determined that the current is not balanced among the multiple battery groups; for another example, when the difference between the second DCR of the first battery group and the second DCR of the second battery group is greater than the corresponding DCR threshold, it can be determined that the current is not balanced among the multiple battery groups.

[0177] In this way, according to the DCR difference between the battery pack with the largest DCR and the battery pack with the smallest DCR among the multiple battery packs, the uneven current distribution among the multiple battery packs can be discovered in time.

[0178] As an example, the DCR detection process shown in Figure 10 takes the battery pack as a battery cluster. The SBMU of each battery cluster is responsible for managing the corresponding battery cluster and uploading relevant data to the MBMU. The MBMU is responsible for the operation and management of the entire system formed by multiple battery clusters and can interact with external devices.

[0179] As shown in FIG10 , in step 1201 , it is determined that the battery cluster is in an operating state, that is, the battery cluster is currently charging or discharging.

[0180] In step 1202 , parameter values ​​of a plurality of state parameters in a state parameter group of a battery cluster are obtained.

[0181] For example, the state parameter group includes parameters such as SOC, temperature, current, charge and discharge direction, charge and discharge time, and SOH.

[0182] In step 1203 , the SBMU determines a first DCR of the battery cluster based on the current state parameter group of the battery cluster and the correspondence between multiple state parameter groups and multiple DCRs in the DCR database.

[0183] In step 1204 , the SBMU obtains the calibration coefficient corresponding to the battery cluster.

[0184] In step 1205, the SBMU calibrates the first DCR according to the calibration coefficient to obtain a second DCR.

[0185] The SBMU may report the second DCR of the corresponding battery cluster to the MBMU.

[0186] In step 1206 , the MBMU calculates the internal resistance difference between the clusters based on the DCRs of the multiple battery clusters connected in parallel.

[0187] For example, the internal resistance difference may be represented by DCRmax / DCRmin, where DCRmax and DCRmin respectively represent the maximum second DCR and the minimum second DCR among the second DCRs of the plurality of battery clusters.

[0188] In step 1207 , the MBMU determines whether the inter-cluster internal resistance difference DCRmax / DCRmin is greater than a preset DCR threshold, where the DCR threshold is, for example, x%, where x is a preset value.

[0189] When the inter-cluster internal resistance difference DCRmax / DCRmin is greater than the DCR threshold value x%, that is, DCRmax / DCRmin>x%, step 1208 is executed; when the inter-cluster internal resistance difference DCRmax / DCRmin is less than or equal to the DCR threshold value x%, that is, DCRmax / DCRmin≤x%, the DCR of the battery cluster continues to be detected.

[0190] In step 1208, the uneven flow strategy is executed.

[0191] The uneven current strategy may be built into the BMS software, for example, to reduce the degree of uneven current between multiple battery clusters connected in parallel. For example, the current of some or all battery clusters may be reduced based on a certain strategy.

[0192] The above-mentioned DCR database can also be used to predict the DCR of the battery pack. For example, in some embodiments, a state parameter group of the battery pack at a target moment after the current moment can be obtained; and based on the state parameter group of the battery pack at the target moment and the correspondence between multiple preset state parameter groups and multiple DCRs, the DCR of the battery pack at the target moment is determined.

[0193] By establishing a DCR database that includes the correspondence between battery pack state parameter groups and DCR, the DCR of the battery pack at any moment can be determined if the battery pack state parameters at that moment are known. For example, if the battery pack state parameters under future operating conditions are known, the DCR database can be used to predict the battery pack's DCR under future operating conditions. Based on this DCR, risk prediction can be performed, such as determining in advance whether uneven current distribution between battery packs is likely, and determining appropriate strategies and responses in a timely manner, thereby reducing the risks caused by excessive DCR differences between battery packs.

[0194] The target time after the current time of the battery pack may refer to any time after the current time at which the DCR of the battery pack needs to be predicted. For example, the DCR of the battery pack at the target time after the current time may be predicted when it is determined that a state parameter in the state parameter group of the battery pack has changed.

[0195] The temperature, SOH, and current SOC of the battery pack can be calculated by the BMS itself, and the probability of the battery pack temperature and SOH changing in a short period of time is low. Therefore, the change in state parameters mainly includes the change in the current of the battery pack, including changes in parameters such as the magnitude, direction, and duration of the current. At this time, in some embodiments, the EMS can send new current information to the BMS, and the BMS receives the current information of the battery pack at the target moment sent by the EMS, such as the magnitude of the current, the duration of the current, and the direction of the current, and determines the SOC of the battery pack at the target moment based on the current of the battery pack at the target moment, the duration of the current, the direction of the current, and the SOC of the battery pack at the current moment.

[0196] For example, the charge and discharge capacity of the battery pack from the current moment to the target moment can be determined based on the current, current duration, and current direction of the battery pack at the target moment, and the SOC of the battery pack at the target moment can be determined based on the SOC of the battery pack at the current moment and the charge and discharge capacity.

[0197] In other words, the battery pack's SOC at the target time can be calculated based on the battery pack's current flow, direction, and charge / discharge time at the target time. The battery pack receives the new current I, the duration T of this current I, and the charge / discharge direction (i.e., whether it is positive or negative) sent by the EMS. Assuming charging begins at the current I, the battery pack's charge / discharge capacity (ΔQ) based on current I over time T is calculated as ΔQ = I*T / Q, where T is the duration of charge / discharge based on current I between the current and the target time, and Q is the battery pack's capacity, such as the rated capacity or maximum capacity. If the battery pack is charged to the target time, then SOC2 = SOC1 + ΔQ = SOC1 + I*T / Q, where SOC1 is the battery pack's SOC at the current time and SOC2 is the battery pack's SOC at the target time. If the battery pack is discharged to the target time, then SOC3 = SOC1 - ΔQ = SOC1 - I*T / Q, where SOC1 is the battery pack's SOC at the current time and SOC3 is the battery pack's SOC at the target time.

[0198] Afterwards, based on SOC2 or SOC3 and other state parameters of the battery pack at the target time, such as temperature and SOH, the DCR corresponding to these state parameters is searched in the DCR database as the DCR of the battery pack at the target time.

[0199] Optionally, upon determining that a state parameter of the battery pack, such as a parameter related to current, has changed, the BMS may predict the DCR of the battery pack under the changed state parameter. For example, if it is known that the current will be charged and discharged based on a new current I from the current moment and continue until the target moment, the BMS may determine the SOC of the battery pack at the target moment based on the SOC of the battery pack at the current moment and parameters related to current I, and, in combination with other state parameters at the target moment, predict the DCR of the battery pack at the target moment. In other embodiments, the BMS may also predict the DCR of the battery pack at the target moment based on a certain period.

[0200] As can be seen, the EMS sends the target time's operating condition information in advance, such as the updated current, duration, and direction. Therefore, the battery pack's SOC at the target time can be determined based on the battery pack's current SOC and the updated current, duration, and direction sent by the EMS. Combined with the values ​​of other state parameters at the target time, the battery pack's DCR at the target time is determined from a DCR database that includes correspondences between multiple state parameter groups and multiple DCRs.

[0201] When multiple battery packs are connected to the power grid in parallel, since the voltages of the multiple battery packs are the same, based on Ohm's law, the difference in DCR between the multiple battery packs will cause current differences between the battery packs, resulting in uneven current flow between the multiple battery packs, affecting the capacity and power of the battery cluster. Therefore, in some embodiments, method 100 may further include: determining whether there is uneven current flow between the multiple battery packs based on the DCR of the multiple battery packs in parallel at the target time. In other words, by detecting the DCR of the multiple battery packs in parallel at the target time, it is predicted whether there may be uneven current flow between the multiple battery packs at the target time, so as to promptly detect and prevent uneven current flow between the parallel battery packs.

[0202] Optionally, whether the multiple battery groups are not current-balanced can be determined based on the difference between the DCRs of the multiple battery groups connected in parallel at the target moment, for example, the difference between the DCR of the first battery group and the DCR of the second battery group among the multiple battery groups, where the first battery group is the battery group with the largest DCR among the multiple battery groups, and the second battery group is the battery group with the smallest DCR among the multiple battery groups.

[0203] For example, when the ratio between the DCR of a first battery group and the DCR of a second battery group in the multiple battery groups is greater than the corresponding DCR threshold, it can be determined that the current is not balanced among the multiple battery groups; for another example, when the difference between the DCR of the first battery group and the DCR of the second battery group is greater than the corresponding DCR threshold, it can be determined that the current is not balanced among the multiple battery groups.

[0204] In this way, according to the DCR difference between the battery pack with the largest DCR and the battery pack with the smallest DCR among the multiple battery packs, the uneven current distribution among the multiple battery packs can be discovered in time.

[0205] As an example, the DCR detection process shown in Figure 11 takes the battery pack as a battery cluster. The SBMU of each battery cluster is responsible for managing the corresponding battery cluster and uploading relevant data to the MBMU. The MBMU is responsible for the operation and management of the entire system formed by multiple battery clusters and can interact with external devices.

[0206] As shown in FIG11 , in step 1301 , it is determined that the battery cluster is in an operating state, that is, the battery cluster is currently charging or discharging.

[0207] In step 1302 , the MBMU receives the current information at the target moment sent by the EMS, including, for example, the magnitude, direction, and duration T of the current I, and sends the current information to the SBMU.

[0208] In step 1303 , the SBMU calculates the SOC of the battery cluster at the target time based on the current information and the current SOC of the battery cluster.

[0209] In step 1304 , the SBMU determines the SOH and temperature of the battery cluster at the target time.

[0210] In step 1305 , the SBMU determines the actual DCR of the battery cluster at the target time based on the SOH, SOC, temperature, and current information of the battery cluster at the target time, such as the magnitude, direction, and duration of the current, and the DCR database.

[0211] For example, the DCR found in the DCR database can be used as the actual DCR of the battery cluster at the target time. Alternatively, if the DCR database does not include the parameter value of a certain state parameter at the target time, a value adjacent to the parameter value is selected from the DCR database, and the DCR corresponding to the parameter value is calculated using an interpolation algorithm and used as the actual DCR of the battery cluster at the target time.

[0212] The SBMU may report the DCR of the corresponding battery cluster at the target time to the MBMU.

[0213] In step 1306 , the MBMU calculates the internal resistance difference between the clusters at the target time based on the DCRs of the multiple battery clusters connected in parallel at the target time.

[0214] For example, the internal resistance difference may be represented by DCRmax / DCRmin, where DCRmax and DCRmin respectively represent the maximum DCR and the minimum DCR among the DCRs of the plurality of battery clusters at the target moment.

[0215] In step 1307 , the MBMU determines whether the inter-cluster internal resistance difference DCRmax / DCRmin is greater than a preset DCR threshold, where the DCR threshold is, for example, x%, where x is a preset value.

[0216] When the inter-cluster internal resistance difference DCRmax / DCRmin is greater than the DCR threshold x%, that is, DCRmax / DCRmin>x%, step 1308 is executed; when the inter-cluster internal resistance difference DCRmax / DCRmin is less than or equal to the DCR threshold x%, that is, DCRmax / DCRmin≤x%, the DCR of the battery cluster continues to be detected.

[0217] In step 1308 , the uneven flow strategy to be adopted is prepared in advance.

[0218] The uneven current strategy may be built into the BMS software, for example, to reduce the degree of uneven current between multiple battery clusters connected in parallel. For example, the current of some or all battery clusters may be reduced based on a certain strategy.

[0219] Based on the above description, it can be seen that in method 1, a database including the correspondence between the state parameter group of the battery pack and the DCR is established, and the DCR of the battery pack under the current state parameters is determined using the database, wherein the state parameter group includes multiple state parameters that may affect the DCR of the battery pack. Since the influence of different state parameters on the DCR of the battery pack is fully considered, the accuracy of the DCR can be improved.

[0220] Furthermore, knowing the state parameters of the battery pack under future operating conditions, the DCR database can be used to predict the DCR of the battery pack under future operating conditions, and risk prediction can be performed based on the DCR. For example, it can be used to determine in advance whether uneven current flow may occur between battery packs, determine appropriate strategies and respond in a timely manner, and thus reduce the risks caused by excessive differences in DCR between battery packs.

[0221] After obtaining the DCR of the battery pack, the DCR of the battery pack may be calibrated using a suitable calibration coefficient. The calibration coefficient can improve the inconsistency between the initial DCRs of different battery cells in the battery pack, thereby improving the accuracy of the DCR.

[0222] Method 2

[0223] In the second approach, the voltage and / or current of the battery pack is detected, and the DCR of the battery pack is determined based on the voltage and / or current information, thereby achieving dynamic detection of the DCR.

[0224] As a way of dynamically detecting DCR, for example, as shown in FIG12 , step 110 may include step 114 and step 115 .

[0225] In step 114 , the open circuit voltage (OCV) of the battery pack is obtained.

[0226] In step 115 , the DCR of the battery pack is determined according to the OCV of the battery pack, the voltage of the battery pack, and the current of the battery pack.

[0227] The OCV of a battery pack refers to the terminal voltage of the battery pack in an open circuit state. It is a physical quantity of the battery under static conditions and can be regarded as the static voltage of the battery pack.

[0228] The voltage and current of a battery pack refer to the voltage and current of the battery pack under actual operating conditions, which include charging or discharging of the battery pack.

[0229] In this embodiment, the DCR of the battery pack is obtained using information about the current OCV, voltage, and current of the battery pack. This method does not depend on the initial voltage of the battery pack and will not affect the detection result of the DCR due to the instability of the initial voltage. Therefore, it has high accuracy and can perform dynamic testing on the DCR, thereby quickly and accurately obtaining the DCR of the battery pack.

[0230] In some embodiments, step 114 may further include: acquiring the SOC of the battery pack, and determining the OCV of the battery pack according to the SOC of the battery pack and a preset correspondence between the OCV and the SOC.

[0231] For example, the OCV corresponding to the SOC of the battery pack is determined as the OCV of the battery pack, and is used to determine the DCR of the battery pack in the subsequent step 115 .

[0232] The correspondence between OCV and SOC can be realized in various forms. For example, the correspondence between OCV and SOC can be a table of mapping relationships between multiple OCV values ​​and multiple SOC values; it can also be a curve or formula used to represent the correspondence between OCV and SOC; or other forms that can represent the correspondence between OCV and SOC of the battery pack.

[0233] As an example, the OCV-SOC curve of a battery shown in Figure 13 represents the corresponding relationship between the battery's SOC and OCV. As shown in Figure 13, during the battery's charge and discharge process, the battery's OCV will also change as the chemical reactions within the battery continue. Optionally, under the battery's operating conditions, the battery's SOC can be adjusted at regular intervals and the battery can be left to rest for a certain period of time to eliminate polarization before the battery voltage is collected. For example, a suitable battery cell can be selected and charged at a current of 0.05C. After each charge of 5% SOC, the cell is left to rest for 2 or 3 hours to eliminate polarization. The voltage of the cell is then collected after the rest period to obtain multiple sets of corresponding SOC and OCV. By fitting the data of the multiple sets of corresponding SOC and OCV, an OCV-SOC curve, also known as a static OCV curve, can be plotted. Similarly, during the discharge process, a corresponding OCV-SOC curve can also be obtained using the above method.

[0234] The battery pack's OCV-SOC curve can be pre-built into the BMS software to facilitate obtaining the battery pack's current OCV. When detecting the battery pack's current DCR, the OCV corresponding to the battery pack's current SOC and the OCV-SOC curve can be determined. This OCV is then used as the battery pack's current OCV to calculate the battery pack's DCR.

[0235] In some embodiments, in step 115 , a voltage difference between the voltage of the battery pack and the OCV of the battery pack may be determined, and a ratio of the voltage difference to the current of the battery pack may be determined, thereby determining the ratio of the voltage difference to the current of the battery pack as the DCR of the battery pack.

[0236] According to the electrochemical polarization principle of the battery, during the charge and discharge process of the battery pack, the dynamic voltage U of the battery is equal to the product of the real-time current I of the battery system and the dynamic polarization internal resistance R of the battery pack, and the sum of the static OCV of the battery pack, that is, U = OCV + I*R.

[0237] Based on this, we can obtain R = (U - OCV) / I. Therefore, the DCR of the battery pack can be calculated using the static voltage of the battery pack and the voltage and current information collected in real time.

[0238] Among them, the DCR of the battery pack = (U-OCV) / I, U is the current voltage value of the battery pack, I is the current current value of the battery pack, and OCV is the static OCV value corresponding to the SOC captured from the OCV-SOC curve based on the current SOC of the battery pack.

[0239] It can be seen that the current voltage of the battery pack is subtracted from the OCV, and the ratio of the difference to the current current of the battery pack is calculated, so that the ratio is used as the current DCR of the battery pack. This DCR calculation method only uses the voltage and current information currently collected by the battery pack and the static OCV corresponding to the current SOC of the battery pack. It does not depend on the initial voltage of the battery pack, so it has high accuracy and can perform dynamic testing of DCR.

[0240] When multiple battery packs are connected to the power grid in parallel, since the voltages of the multiple battery packs are the same, based on Ohm's law, the difference in DCR between the multiple battery packs will cause current differences between the battery packs, resulting in uneven current flow between the multiple battery packs, affecting the capacity and power of the entire battery pack. Therefore, in some embodiments, method 100 may further include: determining whether there is uneven current flow between the multiple battery packs based on the DCR of the multiple battery packs in parallel. In other words, by detecting the DCR of the multiple battery packs in parallel, it is determined whether there is uneven current flow between the multiple battery packs, so as to promptly detect and prevent uneven current flow between the parallel battery packs.

[0241] Optionally, whether the multiple battery groups are current-unbalanced can be determined based on the difference between the DCRs of the multiple battery groups connected in parallel, for example, the difference between the DCR of the first battery group and the DCR of the second battery group in the multiple battery groups, where the first battery group is the battery group with the largest DCR among the multiple battery groups, and the second battery group is the battery group with the smallest DCR among the multiple battery groups.

[0242] For example, when the ratio between the DCR of a first battery group and the DCR of a second battery group in the multiple battery groups is greater than the corresponding DCR threshold, it can be determined that the current is not balanced among the multiple battery groups; for another example, when the difference between the DCR of the first battery group and the DCR of the second battery group is greater than the corresponding DCR threshold, it can be determined that the current is not balanced among the multiple battery groups.

[0243] In this way, according to the DCR difference between the battery pack with the largest DCR and the battery pack with the smallest DCR among the multiple battery packs, the uneven current distribution among the multiple battery packs can be discovered in time.

[0244] As an example, the DCR detection process shown in Figure 14 takes the battery pack as a battery cluster. The SBMU of each battery cluster is responsible for managing the corresponding battery cluster and uploading relevant data to the MBMU. The MBMU is responsible for the operation and management of the entire system formed by multiple battery clusters and can interact with external devices.

[0245] As shown in FIG14 , in step 1401 , it is determined that the battery cluster is in an operating state, that is, the battery cluster is currently charging or discharging.

[0246] In step 1402 , the voltage U and current I of the battery cluster are collected.

[0247] In step 1403 , the SBMU calculates the SOC of the battery cluster based on the current I.

[0248] For example, the SOC of the battery cluster can be calculated based on the current, charge and discharge time, and charge and discharge direction of the battery cluster, such as SOC of the battery cluster = I*T / Q, where T is the charging time and Q is the capacity of the battery cluster, such as the rated capacity or maximum capacity.

[0249] In step 1404 , the SBMU captures the corresponding OCV from the OCV-SOC curve according to the SOC of the battery cluster.

[0250] In step 1405 , the SBMU calculates the DCR of the battery cluster according to the OCV, voltage U, and current I of the battery cluster: DCR=(U−OCV) / I.

[0251] The SBMU may report the DCR of the corresponding battery cluster to the MBMU.

[0252] In step 1406 , the MBMU calculates the internal resistance difference between the clusters based on the DCRs of the multiple battery clusters connected in parallel.

[0253] For example, the internal resistance difference may be represented by DCRmax / DCRmin, where DCRmax and DCRmin represent the maximum DCR and the minimum DCR, respectively, among the DCRs of the plurality of battery clusters.

[0254] In step 1407 , the MBMU determines whether the inter-cluster internal resistance difference DCRmax / DCRmin is greater than a preset DCR threshold value x%.

[0255] When the inter-cluster internal resistance difference DCRmax / DCRmin is greater than the DCR threshold x%, that is, DCRmax / DCRmin>x%, step 1408 is executed; when the inter-cluster internal resistance difference DCRmax / DCRmin is less than or equal to the DCR threshold x%, that is, DCRmax / DCRmin≤x%, the DCR of the battery cluster continues to be detected.

[0256] In step 1408, the uneven flow strategy is executed.

[0257] The uneven current strategy may be built into the BMS software, for example, to reduce the degree of uneven current between multiple battery clusters connected in parallel. For example, the current of some or all battery clusters may be reduced based on a certain strategy.

[0258] Based on the above description, it can be seen that the DCR of the battery pack is detected through the current OCV, voltage and current information of the battery pack. The test process does not depend on the initial voltage of the battery pack, and the DCR test result will not be affected by the instability of the initial voltage. It has high accuracy and can perform dynamic testing on the DCR, so as to quickly and accurately obtain the DCR of the battery pack.

[0259] As another way to dynamically detect DCR, the detection of DCR in step 110 may be implemented by an EMS and / or a BMS.

[0260] For example, as shown in Figures 15 and 16, the DCR detection method shown in Figure 15 can be performed by an EMS, for example, and the DCR detection method shown in Figure 16 can be performed by a BMS of a battery pack, for example. Of course, where possible, the BMS can perform some of the operations performed by the EMS below, and the EMS can also perform some of the operations performed by the BMS below.

[0261] As shown in FIG. 15 , the EMS may perform steps 116 and 117 .

[0262] In step 116 , it is determined to detect the DCR of the battery pack.

[0263] In step 117 , the PCS connected to the battery pack is controlled to charge and discharge the battery pack.

[0264] The charging and discharging here may mean that the grid charges the battery pack through the PCS, or the battery pack discharges the grid through the PCS.

[0265] For example, when the EMS determines to detect the DCR of a battery pack, it controls the PCS connected to the battery pack to charge and discharge the battery pack. The voltage and current information of the battery pack during the charge and discharge process is used to determine the target DCR of the battery pack.

[0266] As shown in FIG. 16 , the BMS may perform steps 118 and 119 .

[0267] In step 118 , during the process of charging and discharging the battery pack through the PCS, information on the voltage and current of the battery pack is obtained.

[0268] In step 119 , a target DCR of the battery pack is determined based on the information of the voltage and current of the battery pack.

[0269] For example, the BMS collects voltage and current information from the battery pack while the PCS is charging and discharging the battery pack. Based on this information, the BMS determines the target DCR for the battery pack. Alternatively, the EMS can issue instructions to the BMS to collect voltage and current and calculate DCR.

[0270] In this way, by controlling the PCS to charge and discharge the battery pack and using the voltage and current information of the battery pack during the charging and discharging process, the DCR of the battery pack can be dynamically obtained.

[0271] The PCS serves as a medium between the alternating current (AC) side of the power grid and the direct current (DC) side of the battery pack, and may include, for example, a bidirectional AC / DC converter. As an example, in the architecture of the energy storage system shown in Figure 17, battery pack 1, battery pack 2, ..., battery pack n are respectively connected to the PCS through corresponding power units 1, power units 2, ..., power units n, and the power units include switches, etc., to realize the switching in and out of the DC side, and to mobilize and control the energy of the entire system through the BMS, PCS and EMS. In addition, other modules such as display modules can be configured to realize corresponding functions. In an embodiment of the present application, the battery pack is charged and discharged by controlling the PCS, that is, the battery pack is charged and discharged by the PCS during the corresponding period of actual use, such as the idle period, and the voltage and current information of the battery pack during the charging and discharging process is used to realize online detection of DCR. Optionally, the detection result of DCR can also be uploaded to a local database or cloud server through communication methods such as WIFI, Bluetooth, 4G and 5G to store and update the DCR of the battery pack.

[0272] In some embodiments, in step 119, the BMS may determine a target DCR for the battery pack based on the battery pack current and the change in battery pack voltage within the target duration. For example, the BMS may determine the target DCR for the battery pack as the ratio of the change in battery pack voltage to the battery pack current within the target duration.

[0273] The target duration is used to detect the DCR of the battery pack. For example, it can be the duration used by the PCS to charge and discharge the battery pack. During the target duration, the PCS charges and discharges the battery pack, and based on the battery pack current and the change in the battery pack voltage during the target duration, the DCR of the battery pack can be effectively calculated, thereby achieving online DCR testing of the battery pack.

[0274] For example, as shown in Figure 7, the EMS controls the PCS to charge or discharge the battery pack. Taking the charging of the battery pack as an example, the PCS charges the battery pack with a current I for a target time △T. The voltage of the battery pack at the start of charging is U0. After charging reaches the target time △T, the voltage of the battery pack is U. The change in the voltage of the battery pack within the target time △T is △U = U-U0. Based on the voltage change △U and the current I, the target DCR of the battery pack is determined as △U / I = (U-U0) / I.

[0275] Since this embodiment requires the battery pack to be charged or discharged for a target duration by the PCS, in some embodiments, in step 117 , it is necessary to control the PCS to charge and discharge the battery pack when the battery pack is in a stationary state.

[0276] The battery pack is in a static state, or in a static operating condition, meaning there is no demand for charging or discharging between the grid and the battery pack. During this time, the PCS is controlled to charge and discharge the battery pack to perform DCR testing. This ensures that the battery pack's normal charging and discharging processes to meet grid demand are not affected, minimizing the impact of DCR testing on the ongoing charging and discharging process between the grid and the battery pack.

[0277] Optionally, in step 116, the EMS may determine whether the rest time of the battery pack, i.e., the time the battery pack is in a rest state, is greater than or equal to the target time, and determine to detect the DCR of the battery pack if the time the battery pack is in a rest state is greater than or equal to the target time.

[0278] That is, in step 117 , when the time period during which the battery pack is in the static state is greater than or equal to the target time period, the EMS controls the PCS to charge and discharge the battery pack.

[0279] Since the voltage change of the battery pack within the target duration needs to be utilized, a sufficient duration, namely the target duration, needs to be reserved to detect the DCR of the battery pack. Therefore, before performing the DCR detection, it is necessary to determine whether the duration that the battery pack can be in a static state is greater than or equal to the target duration, so as to facilitate the use of the PCS to detect the DCR of the battery pack, thereby reducing the possibility of DCR detection interruption caused by the sudden start of the charging and discharging process between the grid and the battery pack.

[0280] In some embodiments, the BMS can determine the target duration based on the battery pack's state parameters, which may include, for example, at least one of the battery pack's state of charge (SOC), state of hydration (SOH), and temperature. This allows for more accurate detection of the battery pack's DCR under these state parameters, improving the accuracy of the test results.

[0281] Typically, the target duration can be set to less than one minute. Optionally, the target duration can be determined based on, for example, the battery pack's SOC, SOH, and current temperature. For example, for a battery pack at 25°C, a 25% SOC, and a BCL SOH, the battery pack is discharged for 30 seconds via the PCS. The DCR of the battery pack is determined based on the ratio between the change in the battery pack voltage during the 30-second discharge and the battery pack's discharge current. For another example, for a battery pack at 25°C, a 25% SOC, and a 70% EOL SOH, the battery pack is discharged for 30 seconds via the PCS. The DCR of the battery pack is determined based on the ratio between the change in the battery pack voltage during the 30-second discharge and the battery pack's discharge current. Typically, the DCR of a battery pack with a 100% BOL SOH is smaller than that of a battery pack with a 70% EOL SOH. For battery packs with the aforementioned state parameters, the DCR is approximately in the milliohm range.

[0282] Optionally, the BMS can determine the target duration when the battery pack is at rest and send the target duration to the EMS. Accordingly, the EMS receives the target duration sent by the BMS and determines whether the duration of the battery pack being at rest is greater than or equal to the target duration, and then determines whether to perform a DCR test on the battery pack.

[0283] For example, the process interaction diagram between EMS and BMS is shown in Figure 18.

[0284] In step 1501 , the BMS determines a target duration for DCR detection.

[0285] For example, the target duration is determined based on the current state parameters of the battery pack, such as SOC, SOH, and temperature, or a pre-set target duration is directly used.

[0286] In step 1502 , the BMS sends the target duration to the EMS.

[0287] In step 1503, the EMS receives the target duration.

[0288] In step 1504 , the EMS determines whether the time period during which the battery pack has been in the rest state is greater than or equal to a target time period.

[0289] In step 1505 , when the time period during which the battery pack is in the static state is greater than or equal to the target time period, the EMS controls the PCS to charge and discharge the battery pack.

[0290] In step 1506 , the BMS obtains information on the voltage and current of the battery pack while the PCS is charging and discharging the battery pack.

[0291] In step 1507 , the BMS determines a target DCR of the battery pack based on the voltage and current information of the battery pack.

[0292] It is understandable that the EMS determines whether the time the battery pack is in the static state is greater than or equal to the target time in order to ensure that the battery pack can currently be static for a sufficient time to perform DCR detection. The sufficient time should be greater than or equal to the target time.

[0293] Specifically, after the EMS determines that the battery pack is in a static state, the BMS determines the target duration required for DCR testing. The BMS transmits this target duration information to the EMS, allowing it to determine whether there is grid demand for charging or discharging within the target duration. If the EMS or the user determines that there is no grid demand for charging or discharging within the target duration, the test conditions are met, and the battery pack's DCR can be tested using the aforementioned method. Specifically, a determination is first made as to whether sufficient time is available for testing the battery pack's DCR to minimize the possibility of the grid forcing charging or discharging during the DCR test. If sufficient time is available for testing the battery pack's DCR, the DCR test is performed within the predetermined timeframe. The EMS then controls the PCS to charge or discharge the battery pack at a specific current. During this process, the BMS detects the battery pack's voltage change and current within the target duration and calculates the battery pack's DCR based on these changes.

[0294] In this embodiment, the EMS determines whether the length of time the battery pack has been in a static state is greater than the target duration in two ways. On the one hand, the EMS can determine whether the power grid has a charge or discharge demand within the target duration; or, on the other hand, the EMS can provide the target duration to the user, for example, through a human-computer interaction system, for user confirmation. For example, the EMS can obtain a display interface and, in response to user operations on the display interface, determine whether the length of time the battery pack has been in a static state is greater than or equal to the target duration. The user can inform the EMS whether the battery pack can currently remain in a static state for more than the target duration by performing corresponding operations on the display interface, such as confirming or canceling.

[0295] In some embodiments, the method 100 may further include: obtaining a historical DCR of the battery pack; and correcting the target DCR of the battery pack obtained in the above step according to the historical DCR of the battery pack to obtain a corrected DCR of the battery pack.

[0296] That is to say, the DCR detected online can be corrected in combination with the historical DCR data of the battery pack, which can improve the accuracy of DCR detection.

[0297] If the database or cloud platform does not store the battery pack's historical DCR, the battery pack's target DCR can be used as the final test result, for example, as a criterion for determining uneven current flow. If the database or cloud platform stores the battery pack's historical DCR, corresponding data processing can be performed based on the historical DCR data and the target DCR to obtain an updated DCR as the final test result, for example, as a criterion for determining uneven current flow.

[0298] Combined with historical DCR, it is possible to effectively determine whether the target DCR obtained from online testing is outliers. This allows for timely detection of deviations from the normal target DCR range due to environmental factors or forced charging and discharging by the grid. Alternatively, the target DCR can be adjusted based on historical DCR trends to compensate for the effects of battery pack usage and environmental factors on DCR.

[0299] The historical DCR includes the battery pack's initial DCR and / or the DCR of the battery pack tested historically. The DCR of the battery pack tested historically can be, for example, the target DCR of the battery pack obtained by charging and discharging the battery pack using a PCS during the historical period. The initial DCR of the battery pack can be, for example, calculated based on the initial DCR of each battery cell in the battery pack. The initial DCR of a battery cell can be the DCR of the battery cell obtained through a DCR test process on the production line.

[0300] As shown in Figure 9 above, the initial DCR of a battery cell can generally refer to the DCR obtained by testing the battery cell on the production line. Battery cells on the production line generally need to undergo processes such as formation, aging, constant temperature coefficient K measurement, DCR testing and capacity testing, and DCR grouping. In the DCR test process, a battery cell with a certain SOC can be charged for a certain period of time. For example, a constant current charge can be performed for 30 seconds when the battery cell has an SOC of 20%. Based on a principle similar to that of Figure 5, the DCR of the battery cell is calculated, and this DCR can be used as the initial DCR of the battery cell.

[0301] Figure 19 is a possible specific implementation of the DCR control method of the embodiment of the present application. The method shown in Figure 8 can be executed by the EMS and the BMS.

[0302] As shown in FIG. 19 , in step 1601 , the EMS pre-determines whether the battery pack is in a stationary state.

[0303] In step 1602 , when the battery pack is in a stationary state, the BMS determines a target time duration ΔT for detecting DCR.

[0304] In step 1603 , the BMS sends the target duration ΔT to the EMS, and after the EMS or the user confirms that the battery pack has been in a static state for longer than the target duration, the DCR detection is started.

[0305] In step 1604 , the EMS controls the PCS to charge and discharge the battery pack according to a certain charge and discharge rate.

[0306] In step 1605 , the BMS detects the voltage change ΔU and current I of the battery pack within the target time ΔT and calculates the target DCR.

[0307] For example, target DCR = ΔU / I.

[0308] In step 1606 , the BMS uploads the target DCR to the EMS.

[0309] In step 1607, the EMS determines whether there is a historical DCR of the battery pack in the database.

[0310] If the target DCR of the battery pack is not stored in the database, step 1608 is executed; if the target DCR of the battery pack is stored in the database, step 1609 is executed.

[0311] In step 1608, the detection result is determined to be a target DCR.

[0312] The BMS can use the target DCR as the final detection result, for example, as a judgment condition for uneven current flow.

[0313] In step 1609 , the target DCR is processed according to the historical DCR of the battery pack to obtain a corrected DCR.

[0314] In step 1610 , the EMS determines that the detection result is the corrected DCR and may feed back the corrected DCR to the BMS.

[0315] The BMS can use the corrected DCR as the final detection result, for example, as a judgment condition for uneven current flow.

[0316] It can be seen that in the actual application of the battery, during the idle time when the grid has no charging or discharging demand, the PCS is used to charge and discharge the battery pack, and the target DCR of the battery pack is determined based on the voltage and current information of the battery pack during the charging and discharging process. The target DCR can be processed in combination with historical DCR data to obtain the corrected DCR, thereby accurately realizing online detection of DCR.

[0317] Based on the above description, it can be seen that in method 2, the DCR of the battery pack can be dynamically obtained based on the voltage and / or current information of the battery pack. For example, the DCR of the battery pack is obtained by using the current OCV, voltage and current information of the battery pack. This does not depend on the initial voltage of the battery pack and will not be affected by the instability of the initial voltage on the DCR detection result, so it has higher accuracy. For another example, by controlling the PCS to charge and discharge the battery pack, and using the voltage and current information of the battery pack during the charging and discharging process to obtain the DCR of the battery pack, it will not affect the normal working condition of the battery pack.

[0318] After obtaining the DCR of the battery pack, it is possible to determine whether there is a possibility of uneven current in the multiple battery packs based on the DCR of the multiple battery packs connected in parallel. In the embodiment of the present application, the following three solutions are also provided to solve the overcurrent problem of the battery pack caused by uneven current.

[0319] Hereinafter, how to suppress overcurrent of each battery pack connected in parallel will be described in detail with reference to FIG. 20 to FIG. 29 .

[0320] FIG20 is a power control method 200 according to an embodiment of the present application. The method 200 may be executed by an EMS, for example. As shown in FIG20 , the method 200 includes some or all of the following steps.

[0321] In step 210 , a target battery group for charging and discharging with the grid is determined according to the power demand of the grid.

[0322] In step 220 , the output power of the PCS connected to the target battery pack is determined according to the overcurrent state of the target battery pack.

[0323] Referring to Figure 21, the PCS is used to realize the conversion between the AC power signal of the power grid and the DC power signal of the energy storage system. Each PCS can be connected to one or more battery packs, and multiple battery packs are connected in parallel to the power grid through the PCS, so as to charge or discharge with the power grid. As shown in Figure 21, each PCS is connected to two battery packs as an example, wherein the battery pack can be, for example, a battery product such as an electrical cabinet or a container. The electrical cabinet can be regarded as a battery product formed by a battery cluster. Therefore, the electrical cabinet described in this embodiment can also be called a battery cluster, and multiple electrical cabinets can be assembled to form a battery product such as a container. Each electrical cabinet includes multiple electrical boxes connected in series and / or in parallel, and each electrical box includes multiple battery cells connected in series and / or in parallel.

[0324] During the production process, the DCR of battery cells is affected by various factors, resulting in differences in DCR between individual cells. This, in turn, leads to significant differences in the DCR of battery packs assembled from these cells, such as in cabinets or containers. After battery packs are connected in parallel to the grid through the PCS, if each pack receives the same power, the differences in DCR of the battery packs in the parallel branches will cause current differences between the branches, leading to uneven current distribution among the multiple parallel battery packs and causing overcurrent in some packs.

[0325] In method 200, the target battery pack for charging and discharging with the grid is determined based on the required power of the grid, and the output power of the corresponding PCS is determined based on the overcurrent status of the target battery pack. The charging and discharging power of the battery packs under each PCS can be dynamically adjusted at the entire station level, reducing the probability of overcurrent in the battery pack while meeting the grid demand.

[0326] In some embodiments, in step 210, a determination can be made as to whether the target battery group includes all or a portion of the multiple battery groups based on the power demand of the power grid, wherein the multiple battery groups are connected in parallel to the power grid via multiple PCSs. Here, the battery group may be, for example, a battery product such as a cabinet or a container, and accordingly, the multiple battery groups may be multiple cabinets or containers. For example, each cabinet group may include one or more cabinets, and these cabinets are connected in parallel to the power grid via the same PCS; or, for another example, each container group may include one or more containers, and these containers are connected in parallel to the power grid via the same PCS.

[0327] In other words, it is necessary to determine whether all battery packs need to be charged and discharged in order to meet the power demand of the power grid, thereby reducing power waste and achieving optimal resource allocation while meeting the power demand of the power grid.

[0328] For example, when the power demand of the power grid is high, such as higher than a threshold, the target battery group can be determined to be all the battery groups in the multiple battery groups; when the power demand of the power grid is low, such as lower than a threshold, the target battery group can be determined to be some of the battery groups in the multiple battery groups.

[0329] Each battery pack is connected to the grid via its corresponding PCS. For example, as shown in Figure 21, the energy storage system includes n PCSs, which in turn include 2n battery packs. Each PCS connects two battery packs. Battery packs 1 and 2 form a group connected to the grid via PCS 1; battery packs 3 and 4 form a group connected to the grid via PCS 2; and finally, battery packs 2n-1 and 2n form a group connected to the grid via PCS n.

[0330] Taking Figure 21 as an example, the target battery group can include all battery groups connected to PCSs 1 through 2n, that is, battery groups 1 through 2n; alternatively, the target battery group can include battery groups connected to some of the PCSs from 1 through 2n. The power demand of the power grid varies during different time periods. For example, Figure 22 shows the power variation of the power grid during different time periods, with the horizontal axis representing time and the vertical axis representing power. During time period 1, the power demand of the power grid is higher, while during time period 2, the power demand is lower. If the same power is allocated to each battery group, the differences in the DCR of the battery groups in the parallel branches may lead to current differences between the branches, thus causing uneven current distribution in the parallel system. Therefore, optionally, based on the power demand of the power grid, all battery groups, that is, battery groups 1 through 2n, can be fully charged and discharged during time period 1, while only some of the battery groups, such as battery groups 1 and 2 corresponding to PCS 1, can be fully charged and discharged during time period 2.

[0331] The following describes in detail the power distribution method when the target battery group includes all battery groups and when the target battery group includes some battery groups.

[0332] Case 1

[0333] The target battery pack for charging and discharging with the power grid determined in step 210 includes all battery packs in the multiple battery packs under the power grid.

[0334] At this time, in step 220, the overcurrent status of the multiple battery packs when the output power of the multiple PCSs is full load power is determined, and according to the overcurrent status of the multiple battery packs, it is determined whether to adjust the output power of the multiple PCSs from full load power to target power.

[0335] The full load power is, for example, the rated power or the maximum power. The target power is less than the full load power, for example, the annual target power is between 70% and 90%, such as 70%, 75%, 80%, 85%, 90% or 95%.

[0336] During periods when the power demand of the power grid is high, such as period 1 shown in Figure 22, all battery packs connected in parallel to the power grid need to participate in charging and discharging. At this time, the overcurrent status of these battery packs is determined when the output power of each PCS is at full load power, and the output power of each PCS is determined based on the overcurrent status. At the same time, the power grid demand and the overcurrent status of the battery pack are taken into consideration. While meeting the power demand of the power grid, the probability of overcurrent in the battery pack is reduced.

[0337] The overcurrent status in this embodiment includes, for example, overcurrent and non-current. It should be understood that, here, overcurrent refers to the presence of an overcurrent risk, while non-current refers to the absence of an overcurrent risk or a low overcurrent risk. Alternatively, whether the battery pack has an overcurrent risk can be determined based on the battery pack's DCR, temperature, SOC, and other factors. If there is no overcurrent risk or the overcurrent risk is low, the battery pack's overcurrent status is considered non-current; if there is an overcurrent risk, the battery pack's overcurrent status is considered overcurrent.

[0338] In one implementation, in step 220, if none of the multiple battery packs are flowing current, the output power of the multiple PCSs is determined to be full load power. In this case, the multiple battery packs connected to the multiple PCSs are charged and discharged with the power grid based on full load power to meet the current high power demand of the power grid.

[0339] In another implementation, in step 220, if at least one of the multiple battery packs has an overcurrent, a determination is made as to whether the output power of the multiple PCSs, while being at the target power, meets the power requirement of the power grid. In this case, if the power requirement of the power grid is met, consideration may be given to reducing the output power of the PCSs to mitigate the impact of the overcurrent of the individual battery pack on the entire energy storage system.

[0340] Furthermore, if it is determined that the output power of multiple PCSs meets the power demand of the grid at the target power, the output power of the multiple PCSs is adjusted from full load power to the target power. In other words, the output power of the PCSs is reduced. This allows the PCS output power to be reduced without significantly impacting grid demand, allowing multiple battery packs to participate in the over-discharge process with the grid, thereby meeting the current high power demand of the grid and reducing the impact on the entire energy storage system caused by overcurrent in individual battery packs.

[0341] If it is determined that the output power of multiple PCSs cannot meet the power demand of the power grid when the output power is at the target power, the output power of the multiple PCSs is determined to be full load power. Since the power demand of the power grid cannot be met, the output power of the multiple PCSs should be maintained at full load power. However, if the output power of multiple PCSs is still at full load power, some battery packs may be at risk of overcurrent. Optionally, the BMS of these battery packs can implement corresponding current limiting strategies within the battery packs based on factors such as the overcurrent level of the corresponding battery packs to reduce the probability of overcurrent in these battery packs.

[0342] Case 2

[0343] The target battery pack for charging and discharging with the power grid determined in step 210 includes some battery packs among the multiple battery packs under the power grid.

[0344] At this time, in step 220, the overcurrent state of the battery pack can be determined when the output power of the PCS connected to the battery pack is full load power, and the output power of the PCS connected to the battery pack can be determined based on the overcurrent state of the battery pack.

[0345] During periods of low grid power demand, such as period 2 shown in Figure 22, only a portion of the battery packs connected in parallel to the grid need to participate in charging and discharging, reducing power waste. At this time, the overcurrent state of the battery packs is determined when the output power of the PCS connected to these battery packs is at full load power. The output power of the corresponding PCS is determined based on this overcurrent state. This takes into account both the grid demand and the overcurrent condition of the battery packs. This reduces the probability of overcurrent in the battery packs while still meeting the grid's power demand.

[0346] In one implementation, in step 220, if none of the battery packs are overcurrent-producing, the output power of the target PCS is determined to be full-load power. In this case, the battery packs can charge and discharge with the grid based on the full-load power to meet the grid's power requirements without worrying about overcurrent.

[0347] In another implementation, in step 220, when at least one of the battery packs in the portion has an overcurrent, the output power of the PCS connected to the portion of the battery packs is determined to be 0. Here, the output power of the PCS being 0 may mean that the battery pack corresponding to the PCS may not be used at the moment, for example, the branch corresponding to the PCS may be disconnected. In this case, in order to reduce the impact of the overcurrent of an individual battery pack on the entire energy storage system, the output power of the PCS corresponding to this portion of the battery packs may be adjusted to 0. That is, during this period of time, this portion of the battery packs is not used for charging and discharging with the power grid. At this time, optionally, a battery pack used for charging and discharging with the power grid may be determined from among the battery packs other than this portion of the battery packs in the plurality of battery packs.

[0348] Taking Figure 21 as an example, if battery packs 1 and 2 corresponding to PCS1 are first selected as target battery packs for charging and discharging with the battery packs during the current period, but battery packs 1 and 2 may have an overcurrent risk at full load power, then battery packs corresponding to other PCSs can be selected as target battery packs in sequence and their overcurrent risk determined until a battery pack without overcurrent risk is selected for charging and discharging with the battery packs during the current period. For example, a polling method can be used to continue selecting battery packs 3 and 4 corresponding to PCS2. If battery packs 3 and 4 do not have an overcurrent risk, battery packs 3 and 4 will charge and discharge with the battery packs based on full load power during the current period to meet the power demand of the grid.

[0349] Fig. 23 is a schematic flow chart of a possible specific implementation of method 200. The process shown in Fig. 23 may be executed by an EMS, for example.

[0350] As shown in FIG6 , in step 2101 , the EMS determines whether all parallel-connected battery packs need to be charged or discharged in the current period.

[0351] Taking the architecture and scenario shown in Figures 21 and 22 as an example, if the current time period is time period 1 shown in Figure 22 and the power demand of the power grid is high, then in step 2101 the EMS determines that all current battery packs need to be charged and discharged, and executes step 2103; if the current time period is time period 2 shown in Figure 22, then in step 2101 the EMS determines that only some of the current battery packs need to participate in charging and discharging, and executes step 2102.

[0352] In one case, steps 2103 to 2108 are performed.

[0353] In step 2103 , the EMS notifies the BMSs of all battery packs to participate in charging and discharging.

[0354] In step 2104, the EMS determines whether there are any battery packs that are at risk of overcurrent.

[0355] That is, the overcurrent status of each battery pack is determined when charging or discharging at full power. If all battery packs are free of overcurrent risk when charging or discharging at full power, step 2105 is executed; if some battery packs may be at risk of overcurrent when charging or discharging at full power, step 2106 is executed.

[0356] In step 2105 , the EMS determines that all battery packs are charged and discharged at full power.

[0357] In step 2106 , the EMS determines whether the power requirement of the grid is met when the output power of each PCS is reduced to the target power.

[0358] The target power is less than the full load power and may be, for example, 90% of the rated power.

[0359] If the power requirement of the power grid can be met after the output power of the PCS is reduced, step 2107 is executed; if the power requirement of the power grid cannot be met after the output power of the PCS is reduced, step 2108 is executed.

[0360] In step 2107 , the EMS controls the output power of the PCS to decrease to the target power.

[0361] In step 2108 , the EMS controls the output power of the PCS to be full load power, and the battery pack with overcurrent risk executes a corresponding current limiting strategy inside.

[0362] Of course, the number of times the power is reduced is not limited in the embodiment of the present application. For example, when the output power of the PCS is reduced to another power that is less than the target power, the power demand of the power grid can still be met. In this case, the output power of the PCS can be further reduced to the other power to reduce the overcurrent level of the battery pack.

[0363] In another case, step 2102, step 2109, step 2121 and step 2111 are performed.

[0364] In step 2102 , the EMS determines whether the power demand of the power grid can be met if only battery group 1 and battery group 2 corresponding to PCS 1 participate in charging and discharging.

[0365] In step 2109 , the EMS determines whether battery pack 1 and battery pack 2 corresponding to PCS1 have overcurrent risks.

[0366] That is, the overcurrent status of battery pack 1 and battery pack 2 when charging and discharging at full power is determined. If there is no overcurrent risk for battery pack 1 and battery pack 2 when charging and discharging at full power, step 2105 is executed; if there is an overcurrent risk for battery pack 1 and battery pack 2 when charging and discharging at full power, step 2106 is executed.

[0367] In step 2110 , the EMS determines that battery pack 1 and battery pack 2 corresponding to PCS 1 participate in charging and discharging.

[0368] In step 2111 , the EMS reselects a group of battery packs without overcurrent risk to participate in charging and discharging.

[0369] It can be seen that based on the process shown in Figure 23, the EMS can dynamically adjust the output power of each PCS, reducing the probability of uneven current between multiple parallel battery packs while meeting the grid demand, thereby reducing the probability of overcurrent in the battery pack.

[0370] In an embodiment of the present application, in addition to executing the aforementioned power control method 200 and controlling the power of the battery pack from the perspective of the entire station to improve the overcurrent of the battery pack, the overcurrent problem of the battery pack can also be solved by the following two current limiting strategies. The following two solutions both execute corresponding current limiting strategies within the battery pack.

[0371] Before describing these two current limiting strategies, we first describe an overcurrent determination method 300 provided in accordance with an embodiment of the present application, described in conjunction with FIG. 24 and FIG. 25 . This method 300 can be executed, for example, by a battery management system (BMS) to determine whether a battery pack has an overcurrent. If an overcurrent occurs in a battery pack, the BMS executes a corresponding current limiting strategy for the battery pack.

[0372] In some embodiments, method 300 further includes determining whether multiple batteries in the battery pack have overcurrent, and determining whether the battery pack has overcurrent if at least one of the multiple batteries has overcurrent. In this case, if the battery pack is determined to have overcurrent, in step 310, the BMS determines overcurrent information of the battery pack, such as an overcurrent level, based on the difference between the actual current of the battery pack and its allowed current.

[0373] That is, it is possible to prioritize whether multiple batteries in a battery pack have overcurrent, and if at least one of the batteries has overcurrent, determine whether the battery pack has overcurrent, and thereby determine the overcurrent information of the battery pack if the battery pack has overcurrent. The batteries may be, for example, battery cells.

[0374] For example, as shown in FIG. 24 , method 300 may include some or all of the following steps.

[0375] In step 310 , the BMS determines whether a plurality of batteries in the battery pack have overcurrent according to a first power mapping table.

[0376] In step 320 , when at least one battery among the plurality of batteries has an overcurrent, the BMS determines whether the battery pack has an overcurrent according to the second power mapping table.

[0377] At this time, in the case of battery pack overcurrent, the BMS implements a corresponding current limiting strategy for the battery pack based on the difference between the actual current of the battery pack and its allowed current. The allowed current of the battery pack can be, for example, the allowable current or rated current of the battery pack.

[0378] The first power mapping table includes allowable power values ​​of battery cells at different SOCs and different temperatures, and the second power mapping table includes allowable power values ​​of battery packs at different SOCs and different temperatures.

[0379] The first power mapping table can be used to determine whether the batteries in the battery pack are overcurrent. When the overcurrent level of a battery in the battery pack is significantly higher than that of other batteries, it can be considered whether the battery is faulty, so that the cause of the overcurrent can be found in time.

[0380] When it is determined according to the first power mapping table that a battery in the battery pack has an overcurrent, the battery pack may not necessarily have an overcurrent because the parallel batteries may achieve automatic current balancing. In this case, it is necessary to determine whether the battery pack has an overcurrent according to the second power mapping table.

[0381] As can be seen, using the first power mapping table and the second power mapping table, it is possible to simply and efficiently determine battery pack overcurrent conditions. The first power mapping table includes allowable power values ​​for batteries at different SOCs and temperatures. If the actual power of a battery exceeds the allowable power value corresponding to the current SOC and temperature in the first power mapping table, the battery is considered to have an overcurrent. The second power mapping table includes allowable power values ​​for battery packs at different SOCs and temperatures. If the actual power of a battery pack exceeds the allowable power value corresponding to the current SOC and temperature in the second power mapping table, the battery is considered to have an overcurrent. Separate power mapping tables can be set for overcurrent determination during charging and for overcurrent determination during discharging.

[0382] For example, if a battery cell in a battery pack is currently at a temperature of 25°C and a SOC of 95%, a first power value corresponding to 25°C and 95% SOC can be obtained based on a first power mapping table. If the actual power value calculated based on the current current and voltage of the battery cell is greater than the first power value, the battery cell is considered to be overcurrent.

[0383] If a certain number of battery cells in a battery pack (which can be one or more) experience overcurrent, the battery pack is determined to have overcurrent based on a second power mapping table. Assuming the battery pack's current temperature is 25°C and its SOC is 90%, the second power value corresponding to 25°C and 90% SOC can be obtained from the second power mapping table. If the actual power value calculated based on the battery pack's current current and voltage is greater than the second power value, the battery pack is considered to have overcurrent.

[0384] When it is determined that an overcurrent has occurred in the battery pack, a corresponding current limiting strategy is executed on the battery pack according to the difference between the actual current of the battery pack and the allowed current.

[0385] Figure 25 shows a possible implementation method for determining whether a battery pack has overcurrent. The method shown in Figure 25 can be executed by the battery pack's BMS. The battery pack charges or discharges with the power grid based on the needs of the EMS.

[0386] As shown in FIG. 25 , in step 3101 , the BMS detects information such as the current and voltage of the battery pack.

[0387] In step 3102 , the BMS determines whether the battery pack is currently charging or discharging based on the current.

[0388] For example, charging or discharging can be determined based on the direction of the current, that is, whether the current sign is positive or negative.

[0389] If the battery pack is being charged, then execute steps 3103 to 3106 ; if the battery pack is being discharged, then execute steps 3107 to 3131 .

[0390] In step 3103 , it is determined whether the battery cells in the battery pack have overcurrent according to the first power mapping table corresponding to the charging process.

[0391] If at least one battery cell in the battery pack has an overcurrent, execute step 3105 and step 3106 ; otherwise, execute step 3104 .

[0392] In step 3104, the battery pack continues to charge.

[0393] In step 3105, it is determined whether an overcurrent occurs in the battery pack according to the second power mapping table corresponding to the charging process.

[0394] If the battery pack does not have an overcurrent, execute step 3104 ; if the battery pack has an overcurrent, execute step 3106 .

[0395] In step 3106, an overcurrent level for charging of the battery pack is determined.

[0396] In step 3107 , it is determined whether the battery cells in the battery pack have overcurrent according to the first power mapping table corresponding to the discharge process.

[0397] If at least one battery cell in the battery pack has an overcurrent, execute step 3109 ; otherwise, execute step 3108 .

[0398] In step 3108, the battery pack continues to discharge.

[0399] In step 3109, it is determined whether an overcurrent occurs in the battery pack according to the second power mapping table corresponding to the discharge process.

[0400] If the battery pack does not have an overcurrent, execute step 3108 ; if the battery pack has an overcurrent, execute step 3110 .

[0401] In step 3110, an overcurrent level of discharge of the battery pack is determined.

[0402] After determining that an overcurrent has occurred in the battery pack, the current of the battery pack may be limited.

[0403] The following describes two methods for current limiting a battery pack provided in an embodiment of the present application, which are described separately below.

[0404] Method 1

[0405] The BMS determines the corresponding overcurrent level based on the overcurrent degree of the battery pack and reports it to the EMS. The EMS determines whether to limit the current of the battery pack based on the current operating conditions. The overcurrent condition of the battery pack can be improved while ensuring that the current operating conditions are not affected.

[0406] FIG26 shows an overcurrent control method 400 according to an embodiment of the present application. The method 400 may be performed by, for example, an EMS and / or a BMS. Of course, where feasible, the BMS may perform some of the following operations performed by the EMS, and the EMS may also perform some of the following operations performed by the BMS.

[0407] As shown in FIG. 26 , method 400 includes some or all of the following steps.

[0408] In step 410 , the BMS determines overcurrent information of the battery pack.

[0409] In step 420 , the BMS sends overcurrent indication information to the EMS.

[0410] The overcurrent indication information includes overcurrent information of the battery pack, and the overcurrent indication information is used to request the EMS to determine whether to limit the current of the battery pack.

[0411] In step 430 , the EMS receives the overcurrent indication information sent by the BMS.

[0412] In step 440 , the EMS determines whether to limit the current of the battery pack according to the overcurrent indication information.

[0413] Here, the current limiting refers to, for example, limiting the allowable current of the battery pack, that is, reducing the allowable current of the battery pack.

[0414] The overcurrent information may be, for example, an overcurrent level or an overcurrent flow rate of the battery pack, or other information used to characterize the degree of overcurrent of the battery pack.

[0415] The overcurrent level indicates the extent to which the battery pack's current exceeds its allowable current. The overcurrent level can be the difference or ratio between the battery pack's current current and its allowable current. The BMS determines the battery pack's overcurrent information and reports overcurrent indication information containing the battery pack's overcurrent information to the EMS. Based on this overcurrent indication information and the current operating conditions, the EMS determines whether to limit the battery pack's current. This improves the battery pack's overcurrent situation while ensuring that the current operating conditions are not affected.

[0416] The following describes in detail the overcurrent control method of the embodiment of the present application, taking the overcurrent information used to represent the overcurrent level of the battery pack as an example, wherein the overcurrent level can be replaced by other overcurrent information such as the overcurrent flow rate.

[0417] In some embodiments, in step 410 , the BMS may determine the overcurrent level of the battery pack according to the overcurrent ratio of the battery pack, wherein the overcurrent ratio is the ratio between the current of the battery pack and its allowable current.

[0418] The overcurrent rating of a battery pack is related to the degree to which the current exceeds its allowable current. Therefore, the overcurrent rating of a battery pack can be determined intuitively based on the overcurrent ratio. Assume that the current of the battery pack is Ir and the allowable current of the battery pack is Ia. In the event of an overcurrent, Ir>Ia. In this case, the overcurrent ratio of the battery pack is the ratio between the current Ir and the current Ia, that is, Ir / Ia.

[0419] Of course, the overcurrent level of the battery pack may also be determined based on the difference |Ir-Ia| between Ir and Ia, and this application does not limit this.

[0420] Multiple overcurrent levels correspond to multiple overcurrent ratios respectively. As an example, the overcurrent levels of the battery pack can be set from high to low to include the first overcurrent level, the second overcurrent level, the third overcurrent level and the fourth overcurrent level. It is assumed that the higher the overcurrent level, the higher the corresponding overcurrent ratio, that is, the overcurrent ratio corresponding to the first overcurrent level is greater than the overcurrent ratio corresponding to the second overcurrent level, the overcurrent ratio corresponding to the second overcurrent level is greater than the overcurrent ratio corresponding to the third overcurrent level, and the overcurrent ratio corresponding to the third overcurrent level is greater than the overcurrent ratio corresponding to the fourth overcurrent level.

[0421] Assume that the overcurrent ratio thresholds corresponding to the first overcurrent level, the second overcurrent level, the third overcurrent level, and the fourth overcurrent level are x1%, x2%, x3%, and x4%, respectively. If Ir / Ia>x4%, the battery pack's overcurrent level can be considered to have reached the fourth overcurrent level; if Ir / Ia>x4%, the battery pack's overcurrent level can be considered to have reached the third overcurrent level; if Ir / Ia>x2%, the battery pack's overcurrent level can be considered to have reached the second overcurrent level; and if Ir / Ia>x1%, the battery pack's overcurrent level can be considered to have reached the first overcurrent level. Here, x4<x3<x2<x1.

[0422] It can be understood that the overcurrent information described in the embodiments of the present application can be identification information used to indicate the overcurrent level of the battery pack, or it can be the overcurrent ratio threshold corresponding to the overcurrent level, such as the above-mentioned first overcurrent threshold, second overcurrent threshold, third overcurrent threshold or fourth overcurrent threshold, or it can be other information that can indicate the overcurrent level.

[0423] Furthermore, optionally, the overcurrent level may be determined in combination with the duration of the overcurrent, that is, the overcurrent level of the battery pack may be determined based on the overcurrent ratio and the duration of the overcurrent.

[0424] For example, when the overcurrent ratio of the battery pack reaches the overcurrent ratio corresponding to the first overcurrent level and lasts for a period of T1, or when the battery pack is in the second overcurrent level for a period of T2, the overcurrent level of the battery pack is determined to be the first overcurrent level.

[0425] For another example, when the overcurrent ratio of the battery pack reaches the overcurrent ratio corresponding to the second overcurrent level and lasts for a period of T3, or when the battery pack is in the third overcurrent level for a period of T4, the overcurrent level of the battery pack is determined to be the second overcurrent level.

[0426] For another example, when the overcurrent ratio of the battery pack reaches the overcurrent ratio corresponding to the third overcurrent level and lasts for a period of T5, or when the battery pack is in the fourth overcurrent level for a period of T6, the overcurrent level of the battery pack is determined to be the third overcurrent level.

[0427] For another example, when the overcurrent ratio of the battery pack reaches the overcurrent ratio corresponding to the fourth overcurrent level and lasts for a time period T7, the overcurrent level of the battery pack is determined to be the fourth overcurrent level.

[0428] The durations T1, T2, T3, T4, T5, T6, and T7 may be at least partially the same or all different. Optionally, T1 < T2, T3 < T4, and T5 < T6 may be set.

[0429] In this way, not only the overcurrent degree of the battery pack relative to the allowable current is considered, but also the duration of the overcurrent is considered, so that the determination of the overcurrent level is more in line with the actual situation.

[0430] As an example, Table 5 shows the relationship between overcurrent levels and their corresponding overcurrent ratios. The overcurrent condition for each overcurrent level includes information such as the overcurrent ratio and overcurrent duration. The 10A value in the overcurrent condition is based on the minimum current detection accuracy. While 10A is used as an example here, other current values ​​can be substituted in actual applications.

[0431] Table 5

[0432] In some embodiments, as shown in FIG. 27 , method 400 may further include step 460 .

[0433] In step 460 , the BMS determines current limiting information corresponding to the overcurrent level according to the overcurrent level of the battery pack, wherein the overcurrent indication information also includes the current limiting information corresponding to the overcurrent level.

[0434] The current limiting information is information used when limiting the current of the battery pack, and includes, for example, information such as a target value of the desired adjusted allowable current.

[0435] At this time, the EMS may consider the current limiting information corresponding to the overcurrent level of the battery pack carried in the overcurrent indication information, and determine whether to limit the current of the battery pack based on the current limiting information corresponding to the overcurrent level.

[0436] The desired current limiting information corresponding to multiple overcurrent levels can be set. The BMS can determine its desired current limiting information based on the overcurrent level of the battery pack. The current limiting information can be carried in the overcurrent indication information for the EMS to use as a reference to determine whether to reduce the power of the battery pack.

[0437] In some embodiments, the current limiting information includes a target value of the battery pack's allowable current, wherein the BMS may determine the target value based on the initial value of the allowable current and a current adjustment ratio corresponding to the overcurrent level thereof, for example, by multiplying the initial value by the current adjustment ratio to obtain the target value. The current adjustment ratio may be a ratio between a predetermined target value to which the allowable current is expected to be adjusted and its initial value.

[0438] For example, as shown in Table 5, the current adjustment ratios corresponding to the first, second, third, and fourth overcurrent levels are y1, y2, y3, and y4, respectively. If the battery pack's overcurrent level reaches the fourth overcurrent level, the battery pack's allowable current can be limited to the target value y4*Ia. If y4 = 1, the battery pack's allowable current can be unrestricted, meaning the current adjustment ratio is 1. If the battery pack's overcurrent level reaches the third overcurrent level, the battery pack's allowable current can be limited to the target value y3*Ia. If the battery pack's overcurrent level reaches the second overcurrent level, the battery pack's allowable current can be limited to the target value y2*Ia. If the battery pack's overcurrent level reaches the first overcurrent level, other risks may arise, so the battery pack's allowable current can be limited to the target value y1*Ia. If y1 = 0, the current adjustment ratio is 0, the BMS can request a high voltage reduction, and the overcurrent level can be cleared. Here, y1 < y2 < y3 < y4 < Ia.

[0439] Corresponding current adjustment ratios are set for different overcurrent levels, so that the target value of the allowable current is determined according to the initial value of the allowable current of the battery pack and the corresponding current adjustment ratio, so that the current limiting of the battery pack matches its overcurrent level, thereby improving the effect of the current limiting.

[0440] It's understood that the target current value in this current-limiting information represents the current value the BMS expects the battery pack to achieve. Specifically, the BMS hopes the battery pack will achieve a current value that matches the current overcurrent level, thereby improving the overcurrent situation. However, whether the battery pack can actually limit its current to this target value requires the EMS to consider various factors.

[0441] The overcurrent indication information sent by the BMS to the EMS can carry the overcurrent level and the current limiting information corresponding to the overcurrent level, that is, the target value. After receiving the overcurrent indication information, the EMS can determine whether to limit the current of the battery pack, that is, whether to allow the allowable current of the battery pack to be limited to the target value based on the information carried in the overcurrent indication information. The EMS needs to determine whether to allow the battery pack to limit its allowable current and to what extent its allowable current can be reduced based on the information carried in the overcurrent indication information reported by the battery pack, such as the overcurrent level and / or the corresponding current limiting information, and in combination with factors such as the current power demand of the power grid and / or the current sharing between multiple parallel battery packs.

[0442] The embodiment of the present application does not impose any specific restrictions on how the EMS decides whether to reduce the power of the battery pack. The EMS needs to determine whether to respond to the overcurrent indication information reported by the battery pack in combination with the current actual working conditions. For example, when the power demand of the power grid is high, the EMS may, based on the overcurrent level of the battery pack, choose not to limit the allowable current of the battery pack, or limit the allowable current of the battery pack but cannot limit the allowable current to the target value carried in the overcurrent indication information; when the power demand of the power grid is not high, the EMS may, based on the overcurrent level of the battery pack, allow the allowable current of the battery pack to be limited, specifically, the allowable current may be limited to the target value carried in the overcurrent indication information or to other current values.

[0443] Optionally, the EMS may also consider the current sharing between multiple battery packs in parallel. If, after limiting the allowable current of the battery pack, the reduced charge and discharge power of the battery pack can be compensated by other battery packs in parallel, then the EMS may allow the battery pack to limit its allowable current to improve the overcurrent situation of the battery pack; if the overcurrent of the battery pack can achieve current balance between the battery pack and other battery packs in parallel, then the EMS may not allow the battery pack to limit its allowable current.

[0444] It can be understood that in step 440, the EMS determines whether to limit the current of the battery pack. The current limiting information mentioned here may refer to the current limiting information carried in the overcurrent indication information, such as the target value, or the current limiting information may also be other current limiting information determined by the EMS for the BMS, such as other current values.

[0445] If the EMS determines that the battery pack is not to be current limited, it may not respond to the overcurrent indication information sent by the BMS. If the EMS determines that the battery pack is to be current limited, it may optionally send current limiting indication information, which is used to instruct the battery pack to be current limited based on the corresponding current limiting information.

[0446] It is understood that since the current of the battery pack is usually controlled by the PCS connected between the battery pack and the power grid, the EMS can send current limiting instruction information to the BMS. The BMS controls the PCS to limit the current of the battery pack based on the current limiting information corresponding to the current overcurrent level according to the current limiting instruction information. Alternatively, the EMS can directly send the current limiting instruction information to the PCS to control the PCS to limit the current of the battery pack based on the current limiting information corresponding to the current overcurrent level. After receiving the current limiting instruction information from the BMS or EMS, the PCS limits the allowable current of the battery pack to be equal to the target value or other current value allowed by the EMS.

[0447] For example, as shown in FIG. 26 , in step 450 , the EMS sends current limiting indication information.

[0448] The current limiting indication information is used to indicate whether to current limit the battery pack based on the current limiting information corresponding to the battery pack's overcurrent level. If the EMS determines to current limit the battery pack but cannot allow current limiting of the battery pack based on the current limiting information corresponding to the battery pack, the current limiting indication information may also carry another current value to indicate that the allowable current of the battery pack needs to be limited to the other current value.

[0449] In some embodiments, as shown in FIG. 27 , method 400 further includes steps 470 and 480 .

[0450] In step 470 , the BMS determines whether the battery pack reaches an overcurrent cancellation condition.

[0451] In step 480 , when the battery pack reaches the overcurrent cancellation condition, the BMS restores the allowable current of the battery pack to the initial value.

[0452] For example, in the event that the battery pack reaches an overcurrent cancellation condition, the BMS may instruct the PCS to restore the allowed current of the battery pack to an initial value.

[0453] In this way, when the current of the battery pack meets the overcurrent cancellation condition, the allowable current of the battery pack can be restored, so that the battery pack can resume normal current for charging and discharging.

[0454] Optionally, the overcurrent cancellation condition includes: the current Ir of the battery pack is less than or equal to the initial value Ia of the allowed current; or, the current Ir of the battery pack is less than or equal to the initial value Ia and the difference between the current Ir and the initial value Ia |Ir-Ia| is less than a preset value; or, the overcurrent level is cleared.

[0455] As an example, as shown in Table 5, when Ir is less than Ia and lasts for a certain period of time, such as T0, the allowable current of the battery pack is restored from the corresponding target value to the initial value Ia; or, when the overcurrent level is cleared after the battery pack is powered off, the allowable current of the battery pack is restored from the corresponding target value to the initial value Ia.

[0456] In some embodiments, in step 420 , the BMS may send overcurrent indication information to the EMS for a predetermined period of time; in this case, in step 470 , the BMS determines whether the battery pack reaches an overcurrent cancellation condition after the predetermined period of time.

[0457] That is, the BMS can continuously send overcurrent indication information to the EMS within a predetermined time period, and determine whether the overcurrent cancellation condition has been met after the predetermined time period. If the EMS does not respond to the BMS's overcurrent indication information, the BMS continues to monitor its current until it reaches the highest overcurrent level, such as the first overcurrent level in Table 5, and then shuts down. If the EMS responds to the BMS's overcurrent indication information but the battery pack still meets the overcurrent cancellation condition, the BMS can continue to send overcurrent indication information.

[0458] If the EMS responds to the overcurrent indication information reported by the battery pack, meaning the EMS allows the battery pack's allowable current to be limited, the EMS can send a current limit indication to the BMS or to the PCS connected between the battery pack and the power grid to control the PCS to limit the battery pack's allowable current, thereby reducing the battery pack's charge and discharge power. However, even if the battery pack's allowable current is limited, the overcurrent condition may not significantly improve. The BMS still needs to monitor the current in real time to determine whether the overcurrent cancellation condition has been met. If the overcurrent cancellation condition has not been met, the BMS can continue to report overcurrent indication information until the overcurrent cancellation condition is met, at which point the allowable current can be restored. If the battery pack still fails to meet the overcurrent cancellation condition, the battery pack will be powered off after its overcurrent level rises to the highest overcurrent level, such as the first overcurrent level in Table 5, to reduce unnecessary risks caused by the battery pack's overcurrent.

[0459] Method 2

[0460] The BMS limits the allowable current of the battery pack to a corresponding degree according to the overcurrent level of the battery pack, thereby improving the overcurrent situation of the battery pack.

[0461] FIG28 shows another overcurrent control method 500 according to an embodiment of the present application. The method 500 may be executed by a BMS, for example. As shown in FIG28 , the method 500 includes some or all of the following steps.

[0462] In step 510 , the overcurrent of the battery pack is determined.

[0463] The overcurrent flow rate includes the current difference and / or current ratio between the battery pack current and its allowable current. Assuming that the current current of the battery pack is Ir and the allowable current of the battery pack is Ia, the overcurrent flow rate of the battery pack can be |Ir-Ia| and / or Ir / Ia.

[0464] In step 520 , the allowable current of the battery pack is adjusted according to the overcurrent of the battery pack.

[0465] The battery pack in the embodiment of the present application can be, for example, an electrical box, an electrical cabinet or a container, or other parallel units connected to the power grid in parallel through PCS. These parallel units can all be subjected to overcurrent control through method 500 of the embodiment of the present application to improve their overcurrent conditions.

[0466] Typically, for multiple battery packs connected in parallel to the power grid, if one or more of the battery packs experiences an overcurrent, the allowable current of all the battery packs in parallel will be limited. This will also reduce the current of the battery packs that are not experiencing an overcurrent, thereby affecting the charging and discharging of the entire system. However, in the embodiments of the present application, overcurrent control is performed for a single battery pack, and its allowable current is adjusted based on the overcurrent of the battery pack. This does not affect the current of other battery packs connected in parallel, thereby reducing the impact on the charging and discharging process of the entire system. Furthermore, because the adjustment of the allowable current is compatible with the overcurrent of the battery pack, the impact on the charging and discharging process of the battery pack itself is further reduced, achieving adaptive current reduction for a single battery pack.

[0467] In some embodiments, conditions for adjusting the allowed current can be set. For example, in step 520, the allowed current of the battery pack is adjusted when the current difference between the actual current of the battery pack and the allowed current is greater than or equal to a first threshold, and / or the current ratio between the actual current of the battery pack and the allowed current is greater than or equal to a second threshold.

[0468] That is to say, the allowable current of the battery pack is adjusted only when the overcurrent level is large enough, that is, the current difference between the actual current of the battery pack and the allowable current is greater than or equal to the first threshold, and / or the current ratio between the actual current of the battery pack and the allowable current is greater than or equal to the second threshold.

[0469] The first threshold and the second threshold can be set according to actual working conditions. For example, the first threshold can be set to 1A, and the second threshold can be set to 105%.

[0470] Assume that the current of the battery pack is Ir and the allowable current of the battery pack is Ia. In the event of an overcurrent in the battery pack, Ir>Ia. In this case, the current difference and current ratio between the actual current of the battery pack and the allowable current are |Ir-Ia| or Ir / Ia, respectively. When |Ir-Ia| is greater than or equal to a first threshold, for example, |Ir-Ia|≥1A, and Ir / Ia is greater than or equal to a second threshold, for example, Ir / Ia≥105%, the BMS adjusts the allowable current of the battery pack based on the overcurrent.

[0471] In some embodiments, step 520 may include: calculating a first product between the allowable current value of the battery pack with the smallest allowable current among the N battery packs connected in parallel and N; calculating a second product between the current difference of the battery pack and a preset coefficient; calculating the difference between the first product and the second product; and determining that the adjusted allowable current of the battery pack is equal to the ratio between the difference and N.

[0472] The N battery packs include a battery pack that currently requires current limiting, where N is a positive integer.

[0473] The preset coefficient is used to adjust the degree of current limiting of the battery pack. The preset coefficient can be set to be equal to 1 or not equal to 1.

[0474] In other words, since multiple battery packs are connected to the power grid in parallel, in steps 121 to 124, the minimum value of the allowable currents corresponding to the multiple parallel branches is multiplied by the number of parallel branches N to obtain a first product, and the overflow of a single branch, such as the current difference D, is multiplied by a preset coefficient to obtain a second product. The difference between the first product and the second product is divided by the number of parallel branches N to obtain the adjusted allowable current value of the single branch.

[0475] Formula I can be used a '=(I min *ND*k) / N to calculate the allowed current value of the adjusted battery pack, where Ia' is the allowed current value of the adjusted battery pack, I min is the allowable current value of the battery pack with the smallest allowable current among multiple battery packs connected in parallel, including this battery pack; N is the number of the multiple battery packs connected in parallel; D is the current difference between the actual current of the battery pack and its allowable current; and k is a preset coefficient.

[0476] As can be seen, the larger D is, the smaller Ia' is. In other words, the greater the overflow, the smaller the allowable current value needs to be adjusted. Because the adjustment of the allowable current is compatible with the battery pack's overflow, the impact on the battery pack's charge and discharge processes is further reduced, achieving adaptive current reduction for individual battery packs.

[0477] Since the adjusted allowable current value Ia' for a single battery pack is calculated based on the current difference D between the actual current of the battery pack and its allowable current, and the allowable current of the battery pack is adjusted based on Ia', the allowable current of other battery packs connected in parallel with it is not affected, thereby reducing the impact on the charging and discharging process of the entire system.

[0478] In some embodiments, the method 500 further includes determining whether the battery pack reaches an overcurrent cancellation condition, and restoring the allowable current of the battery pack to an initial value if the battery pack reaches the overcurrent cancellation condition.

[0479] For example, the overcurrent cancellation condition may include that the current Ir of the battery pack is less than or equal to the initial value Ia of the allowed current, that is, Ir≤Ia; for another example, the overcurrent cancellation condition may include that the current Ir of the battery pack is less than or equal to the initial value Ia, and the difference between the current Ir of the battery pack and the initial value Ia |Ia-Ir| is less than a preset value, that is, Ir≤Ia-b, where b is a preset value.

[0480] The preset value can be set according to actual working conditions. For example, the preset value can be set to 10A. In this way, when the current Ir of the battery pack satisfies Ir≤Ia-10A, the allowable current value of the battery pack is restored to its initial value Ia.

[0481] The BMS in this embodiment adjusts the battery pack's allowable current. For example, the BMS can adjust the battery pack's allowable current by controlling the PCS. When current limiting is required, the BMS can instruct the PCS to adjust the battery pack's allowable current from an initial value Ia to Ia', where Ia' < Ia. When the battery pack reaches an overcurrent cancellation condition, the BMS can instruct the PCS to restore the battery pack's allowable current to the initial value Ia.

[0482] Figure 29 shows a flowchart of a possible specific implementation of method 500. Multiple battery packs are connected in parallel to the power grid through the PCS and are charged or discharged with the power grid. The method shown in Figure 29 can be executed by the BMS corresponding to each battery pack.

[0483] As shown in FIG. 29 , in step 5101 , the overflow flow of the corresponding battery pack is calculated.

[0484] For example, the overcurrent is the current difference |Ir-Ia| between the actual current Ir of the battery pack and the allowed current Ia, and the current ratio Ir / Ia.

[0485] In step 5102, it is determined whether the allowable current of the battery pack needs to be adjusted.

[0486] If |Ir-Ia|≥1A and Ir / Ia≥105%, step 5103 and step 5104 are executed; otherwise, the allowable current of the battery pack does not need to be adjusted and its initial value Ia can be maintained.

[0487] In step 5103, the allowable current of the battery pack is adjusted to Ia'.

[0488] Among them, I a '=(I min *ND*k) / N.

[0489] In step 5104, it is determined whether the battery pack has reached an overcurrent cancellation condition.

[0490] The overcurrent cancellation condition is Ir≤Ia-10A.

[0491] After limiting the allowable current of the battery pack to Ia', if the overcurrent of the battery pack is improved and the overcurrent cancellation condition is met, step 5105 is executed; if the overcurrent cancellation condition is still not met, the current of the battery pack is continuously monitored.

[0492] In step 5105, the allowable current of the battery pack is restored to the initial value Ia.

[0493] Based on the above process, actual battery packs are tested. For example, multiple battery packs connected in parallel as shown in Tables 6 to 8, namely, battery pack 1, battery pack 2, battery pack 3, battery pack 4, and battery pack 5, are tested.

[0494] As shown in Table 6, the actual current Ir and the allowed current Ia of each battery group are: the actual current and the allowed current of battery group 1 are -141.4 and -132.7 respectively; the actual current and the allowed current of battery group 2 are -141.5 and -132.4 respectively; the actual current and the allowed current of battery group 3 are -141.0 and -132.3 respectively; the actual current and the allowed current of battery group 4 are -141.9 and -132.6 respectively; the actual current and the allowed current of battery group 5 are -142.0 and -132.2 respectively.

[0495] Table 6

[0496] As shown in Table 7, taking the first threshold value of 1A, the second threshold value of 105%, and the preset coefficient equal to 1 as an example, the current difference |Ir-Ia| between the actual current and the allowed current of each battery pack, the proportional relationship Ir / Ia between the actual current and the allowed current, and the adjusted allowed current value Ia' are respectively shown.

[0497] Among them, the current difference between the actual current of battery pack 1 and the allowed current is |(-141.4)-(-132.7)|=8.7>1A, and the actual current exceeds 105% of the allowed current value, that is, |-141.4|>|(-132.7)*105%|=|-139.9|. Therefore, the allowed current of battery pack 1 can be adjusted to [(-132.2)*5-(-8.7)*1] / 20=-130.5.

[0498] The current difference between the actual current and the allowed current of battery pack 2 is |(-141.5)-(-132.4)|=9.1>1A, and the actual current exceeds 105% of the allowed current value, that is, |-141.5|>|(-132.4)*105%|=|-139.0|, so the allowed current of battery pack 2 can be adjusted to [(-132.2)*5-(-9.1)*1] / 20=-130.4.

[0499] The current difference between the actual current and the allowed current of battery pack 3 is |(-141.0)-(-132.3)|=8.7>1A, and the actual current exceeds 105% of the allowed current value, that is, |-141.0|>|(-132.3)*105%|=|-138.9|, so the allowed current of battery pack 3 can be adjusted to [(-132.2)*5-(-8.7)*1] / 20=-130.5.

[0500] The current difference between the actual current and the allowed current of battery pack 4 is |(-141.9)-(-132.6)|=9.3>1A, and the actual current exceeds 105% of the allowed current value, that is, |-141.9|>|(-132.6)*105%|=|-139.2|, so the allowed current of battery pack 4 can be adjusted to [(-132.2)*5-(-9.3)*1] / 20=-130.3.

[0501] The current difference between the actual current and the allowed current of the battery pack 5 is |(-142.0)-(-132.2)|=9.8>1A, and the actual current exceeds 105% of the allowed current value, that is, |-142.0|>|(-132.2)*105%|=|-138.8|, therefore, the allowed current of the battery pack 5 can be adjusted to [(-132.2)*5-(-9.8)*1] / 20=-130.2.

[0502] Table 7

[0503] By limiting the battery pack's current according to the adjusted allowable current value Ia' shown in Table 7, the results shown in Table 8 are obtained. Table 8 shows the actual battery pack current Ir after current limiting and the overcurrent cancellation condition, using the overcurrent cancellation condition of Ir ≤ Ia - 10A as an example.

[0504] As shown in Table 8, the current value of battery group 1 is -122.4, which is less than -132.7-(-10)=-122.7; the current value of battery group 2 is -122.4, which is equal to -132.4-(-10)=-122.4; the current value of battery group 3 is -122.1, which is less than -132.3-(-10)=-122.3; the current value of battery group 4 is -122.4, which is less than -132.6-(-10)=-122.6; and the current value of battery group 5 is -122.0, which is less than -132.2-(-10)=-122.2.

[0505] Table 8

[0506] It can be seen from Tables 6 to 8 that the overcurrent control solution of the embodiment of the present application can effectively improve the overcurrent condition of the battery pack.

[0507] It can be understood that by limiting the current of the battery pack, that is, reducing the allowable current value of the battery pack, it is equivalent to informing the EMS that the battery pack is currently overcurrent, so that the EMS can adjust the power allocated to the battery pack on each branch based on the current operating conditions, such as the power demand of the power grid, the current sharing between multiple battery packs, the overcurrent degree of the battery pack, etc., so as to cover the overcurrent of the battery pack.

[0508] By using the overcurrent control methods described in the above-mentioned methods 1 and 2, when an overcurrent of the battery pack is caused by uneven current distribution among multiple battery packs connected in parallel, the overcurrent condition of the battery pack can be improved.

[0509] As mentioned above, the DCR of the battery pack is affected by temperature, so the temperature of the battery pack needs to be controlled.

[0510] 30 shows a temperature control method 600 according to an embodiment of the present application, which may be executed by a BMS or other control modules, etc. As shown in FIG30 , the method 600 includes some or all of the following steps.

[0511] In step 610 , the temperature of the first battery system and the temperature of the second battery system are acquired.

[0512] In step 620 , a target operating mode of the first thermal management component and / or the second thermal management component is determined based on the temperature of the first battery system and the temperature of the second battery system.

[0513] The first thermal management component is used to control the temperature of the first battery system, and the second thermal management component is used to control the temperature of the second battery system.

[0514] The first battery system includes at least one battery cluster, and the second battery system includes at least one battery cluster. As an example, if the aforementioned battery pack is a cabinet or battery cluster, the battery system may include at least one cabinet or battery cluster; if the aforementioned battery pack is a container, the battery system may include at least some of the cabinets or battery clusters within the container.

[0515] As an example, consider the one-to-two architecture shown in Figure 31, where each PCS connects to two containers, namely, container A and container B. Container A includes two battery systems, and container B includes two battery systems. The first battery system and the second battery system can be two containers in different containers or two containers in the same container. Figure 31 uses the first battery system and the second battery system as two battery systems connected in parallel in container A as an example. The first battery system includes five parallel battery clusters, namely, battery cluster 1 to battery cluster 5; the second battery system includes five parallel battery clusters, namely, battery cluster 6 to battery cluster 10.

[0516] As shown in Figure 31, the first battery system and the second battery system are temperature-managed by the first thermal management component and the second thermal management component in container A respectively. The first thermal management component is used to control the temperature of the first battery system, and the second thermal management component is used to control the temperature of the second battery system.

[0517] Optionally, the first and second thermal management components in the embodiments of the present application may be liquid cooling components, such as water cooling units. Compared to air cooling components, liquid cooling components provide more uniform temperature control, making it easier to maintain the battery system at an appropriate temperature, thereby improving the lifespan of the battery product.

[0518] Based on the architecture shown in Figure 31, taking the first and second thermal management components as water cooling units as an example, as shown in Figure 32, each water cooling unit includes five water pumps, each corresponding to a water cooling pipe. Each water cooling pipe is connected to a corresponding battery cluster shown in Figure 31, and each battery cluster is equipped with independent inlet and outlet pipes. The five water pumps in the first water cooling unit are connected to water cooling pipes R1#, R2#, R3#, R4#, and R5#, respectively. Water cooling pipes R1#, R2#, R3#, R4#, and R5# are connected to battery clusters 1, 2, 3, 4, and 5, respectively, shown in Figure 31. The five water pumps in the second water cooling unit are connected to water cooling pipes R6#, R7#, R8#, R9#, and R10#, respectively. Water cooling pipes R6#, R7#, R8#, R9#, and R10# are connected to battery clusters 6, 7, 8, 9, and 10, respectively, shown in Figure 31. Each water cooling unit also includes a temperature management system (TMS) for controlling the working modes of the five water cooling pipes in the water cooling unit.

[0519] Similarly, the temperature of the second battery system can be determined based on the temperatures of multiple battery clusters in the second battery system, for example, by taking the average temperature of the multiple battery clusters in the second battery system as the temperature of the second battery system. The temperature of each battery cluster can be determined based on the temperatures of multiple battery cells in the battery cluster, for example, by taking the average temperature of the multiple battery cells in the battery cluster as the temperature of the battery cluster.

[0520] Optionally, in addition to obtaining the temperature of the first battery system and the temperature of the second battery system, in step 610, the maximum temperature and / or minimum temperature of multiple battery clusters in the first battery system may also be obtained. The maximum temperature and / or minimum temperature of multiple battery clusters in the first battery system may be used, for example, to determine whether there is a battery cluster with an outlier temperature in the first battery system, and further determine whether the temperature change of the first battery system is caused by the battery cluster, thereby better controlling the temperature of the first battery system.

[0521] Similarly, in step 610, in addition to obtaining the temperature of the second battery system and the temperature of the second battery system, the maximum temperature and / or minimum temperature of multiple battery clusters in the second battery system may also be obtained. The maximum temperature and / or minimum temperature of multiple battery clusters in the second battery system may be used, for example, to determine whether there is a battery cluster with an outlier temperature in the second battery system, and further determine whether the temperature change of the second battery system is caused by the battery cluster, thereby better controlling the temperature of the second battery system.

[0522] The working modes of the first thermal management component and the second thermal management component include, for example, a cooling mode, a heating mode, a self-circulation mode, or a stop mode. Among them, the cooling mode is used to reduce the temperature of the battery system, the heating mode is used to increase the temperature of the battery system, and the self-circulation mode can also be regarded as a heat preservation mode or a self-heating mode. Switching between different modes requires a transition. For example, switching from the heating mode to the cooling mode requires switching from the heating mode to the self-circulation mode and switching from the self-circulation mode to the cooling mode. Switching from the cooling mode to the heating mode requires switching from the cooling mode to the self-circulation mode and switching from the self-circulation mode to the heating mode.

[0523] The first battery system and the second battery system can be any two battery systems among multiple battery systems connected to the PCS, for example, two battery systems arranged in parallel among the multiple battery systems. The two battery systems can be arranged adjacent to each other or not. Two corresponding thermal management components, namely, a first thermal management component and a second thermal management component, are provided for the first battery system and the second battery system, respectively, to control the temperature of the first battery system and the second battery system. In other words, method 600 in this embodiment can solve the problem of temperature consistency of the battery system caused by different thermal management components.

[0524] The BMS determines the operating modes of the first thermal management component and the second thermal management component based on the temperature difference between the first battery system and the second battery system, thereby controlling the temperatures of the first battery system and the second battery system respectively through the first thermal management component and the second thermal management component to improve the temperature consistency between the first battery system and the second battery system, solving the problems of impedance, current and other imbalances in the battery system caused by poor temperature consistency, thereby reducing the probability of premature filling or discharge of the high-current battery system and improving the RTE of the battery product.

[0525] In some embodiments, in step 620, when the initial operating modes of the first thermal management component and the second thermal management component are different, the target operating mode of the first thermal management component and / or the second thermal management component can be determined based on the temperature of the first battery system and the temperature of the second battery system.

[0526] That is to say, it is possible to determine whether the initial operating modes of the first thermal management component and the second thermal management component are the same. Since the initial operating modes of the first thermal management component and the second thermal management component are different, it indicates that there is a temperature inconsistency problem between the first battery system and the second battery system. At this time, the target operating mode of the first thermal management component and / or the second thermal management component can be determined based on the temperature of the first battery system and the temperature of the second battery system, thereby adjusting the first thermal management component and / or the second thermal management component from the initial operating mode to the target operating mode.

[0527] If the initial operating modes of the first thermal management assembly and the second thermal management assembly are the same, this indicates that the temperature difference between the first battery system and the second battery system is not significant. Therefore, the operating modes of the first thermal management assembly and the second thermal management assembly may be left unchanged, and the first thermal management assembly and the second thermal management assembly may maintain their respective initial operating modes.

[0528] The initial operating mode of the first thermal management component can be determined, for example, based on the temperatures of multiple battery clusters in the first battery system; the initial operating mode of the second thermal management component can be determined, for example, based on the temperatures of multiple battery clusters in the second battery system. The temperature of each battery cluster in the first and second battery systems can be determined based on the temperatures of multiple battery cells in the battery cluster, for example, by taking the average temperature of the multiple battery cells in the battery cluster as the temperature of the battery cluster.

[0529] Here, the initial operating modes of the first thermal management component and the second thermal management component are the operating modes used before they are adjusted to the target operating modes. For example, after determining the initial operating modes of the first thermal management component and the second thermal management component, if the initial operating modes of the first thermal management component and the second thermal management component are different, it is determined whether the initial operating mode needs to be adjusted in combination with the temperature of the first battery system and the temperature of the second battery system.

[0530] In some embodiments, in step 620 , a target operating mode of the first thermal management component and / or the second thermal management component may be determined based on a temperature difference between the temperature of the first battery system and the temperature of the second battery system.

[0531] For example, a first temperature threshold may be set, and when the temperature difference between the first battery system and the second battery system is greater than or equal to the first temperature threshold, the target operating mode of the first thermal management component and / or the second thermal management component is determined.

[0532] The first temperature threshold may be set based on actual conditions. For example, the first temperature threshold may be between 1°C and 3°C, such as 1°C, 2°C or 3°C.

[0533] Taking the first battery system and the second battery system shown in Figures 31 and 32 as an example, assuming that the temperatures of battery cluster 1, battery cluster 2, battery cluster 3, battery cluster 4, and battery cluster 5 in the first battery system are T1, T2, T3, T4, and T5 respectively, and the temperatures of battery cluster 6, battery cluster 7, battery cluster 8, battery cluster 9, and battery cluster 10 in the second battery system are T6, T7, T8, T9, and T10 respectively, then the average temperature T of the multiple battery clusters in the first battery system is A=(T1+T2+T3+T4+T5) / 20, the average temperature of the plurality of battery clusters in the second battery system T B =(T6+T7+T8+T9+T10) / 20, the temperature difference between the temperature of the first battery system and the temperature of the second battery system ΔT=|T A -T B When the temperature difference ΔT is greater than or equal to a preset first temperature threshold, the operating mode of the first thermal management component and / or the second thermal management component can be adjusted to reduce the temperature difference ΔT. For example, the operating mode of the thermal management component of the high-temperature battery system can be adjusted to a cooling mode or a self-circulation mode, and / or the operating mode of the thermal management component of the low-temperature battery system can be adjusted to a heating mode or a self-circulation mode.

[0534] The temperature of the battery system is associated with its state. Therefore, when determining the target operating mode of the first thermal management component and / or the second thermal management component, the current state of the battery system may also be considered. The battery system state includes, for example, a stationary state and a charge / discharge state, where the charge / discharge state includes a charge state and a discharge state.

[0535] In some embodiments, in step 620, when the temperature difference between the temperature of the first battery system and the temperature of the second battery system is greater than a first temperature threshold, the target operating mode of the first thermal management component and / or the second thermal management component can be determined based on the status of the first battery system and the second battery system.

[0536] In one case, ie, when the first battery system and the second battery system are in a stationary state, it can be determined that the target operating mode of the thermal management component of the battery system with a higher temperature among the first battery system and the second battery system is the cooling mode.

[0537] Specifically, in most cases, the working mode of the thermal management component in the static state is the self-circulation mode, and the situations caused by the self-circulation mode are mostly high-temperature outliers. Since the battery system is easy to keep warm in the static state, and heat dissipation can basically only rely on the cooling of the thermal management component, therefore, the target working mode of the thermal management component of the battery system with a higher temperature among the first battery system and the second battery system can be adjusted to the cooling mode to reduce the temperature of the battery system with a higher temperature as soon as possible.

[0538] At this time, the operating mode of the thermal management component of the battery system with the lower temperature among the first and second battery systems may remain unchanged, that is, the target operating mode of the thermal management component of the battery system with the lower temperature remains the same as its initial operating mode.

[0539] It can be understood that since not all thermal management components in a static state are in static mode, it is still necessary to add the above steps, that is, to determine whether to adjust the working mode of the first thermal management component and / or the second thermal management component based on whether the initial working modes of the first thermal management component and the second thermal management component are the same.

[0540] For example, the first battery system and the second battery system are in a stationary state. Assume that the temperature difference ΔT between the temperature of the first battery system and the temperature of the second battery system is greater than a first temperature threshold, and the temperature of the first battery system T A Lower than the temperature T of the second battery system B That is T A <T B , then, the target operating mode of the second thermal management component can be selected as the cooling mode, so that it can continuously force the second battery system to cool down.

[0541] Of course, when the first battery system and the second battery system are in a stationary state, the target operating mode of the first thermal management component and / or the second thermal management component can also be adjusted to other operating modes that can reduce the temperature difference between the first battery system and the second battery system. For example, the target operating mode of the thermal management component of the battery system with the lower temperature in the first battery system and the second battery system is adjusted to a heating mode; or, the target operating mode of the thermal management component of the battery system with the higher temperature in the first battery system and the second battery system is adjusted to a cooling mode, and the target operating mode of the thermal management component of the battery system with the lower temperature is adjusted to a heating mode at the same time, so as to more quickly reduce the temperature difference between the two battery systems. However, since most battery systems in a stationary state need to rely on thermal management components for cooling to achieve temperature reduction, adjusting the operating mode of the thermal management component of the battery system with the higher temperature to a cooling mode for continuous cooling or forced cooling can effectively reduce the temperature of the high-temperature battery system and reduce unnecessary system power consumption, which is more in line with actual application conditions.

[0542] In another case, that is, when the first battery system and the second battery system are in a charge and discharge state, it can be determined that the thermal management component of the battery system with the lower temperature among the first battery system and the second battery system stops working.

[0543] Specifically, when the first battery system and the second battery system are in the charging and discharging state, the battery system itself will also heat up. Therefore, the thermal management component of the battery system with a lower temperature among the first battery system and the second battery system can be turned off. For example, a stop command can be sent to the TMS of the thermal management component of the battery system with a lower temperature to instruct the TMS to shut down, so that the battery system with a lower temperature can rely on the charging and discharging process to increase its own temperature.

[0544] At this time, the operating mode of the thermal management component of the battery system with higher temperature among the first and second battery systems may remain unchanged, that is, the target operating mode of the thermal management component of the battery system with higher temperature remains the same as its initial operating mode.

[0545] For example, the first battery system and the second battery system are in a charge-discharge state. Assume that the temperature difference ΔT between the temperature of the first battery system and the temperature of the second battery system is greater than the first temperature threshold, and the temperature T A Lower than the temperature T of the second battery system B That is T A <T B , then, the first thermal management component can be turned off, so that the first battery system can increase its own temperature by relying on the charging and discharging process.

[0546] Of course, when the first battery system and the second battery system are in the charge and discharge state, the target operating mode of the first thermal management component and / or the second thermal management component can also be adjusted to other operating modes that can reduce the temperature difference between the first battery system and the second battery system. For example, the target operating mode of the thermal management component of the battery system with the higher temperature among the first battery system and the second battery system is adjusted to the cooling mode; or, at the same time, the thermal management component of the battery system with the lower temperature among the first battery system and the second battery system is adjusted to be turned off and the target operating mode of the thermal management component of the battery system with the higher temperature is adjusted to the cooling mode, so as to more quickly reduce the temperature difference between the two battery systems. However, since the battery system with a lower temperature in the charge and discharge state can achieve self-heating through the charge and discharge process, turning off the thermal management component of the battery system can effectively increase the temperature of the low-temperature battery system and reduce unnecessary system power consumption, which is more in line with actual application conditions.

[0547] In some embodiments, when the temperature difference between the temperature of the first battery system and the temperature of the second battery system is less than or equal to a preset second temperature threshold, it is determined that the first thermal management component and the second thermal management component are adjusted to the same operating mode to maintain temperature consistency.

[0548] The second temperature threshold may be the same as or different from the first temperature threshold. The second temperature threshold may be set based on actual conditions. For example, the second temperature threshold may be between 1°C and 3°C, such as 1°C, 2°C or 3°C.

[0549] FIG33 is a flowchart of a possible specific implementation of method 600. As shown in FIG33 , the process can be executed by a BMS and a TMS. It is understood that both TMS1 of the first thermal management component and TMS2 of the second thermal management component can refer to the steps executed by the TMS shown in FIG33 .

[0550] In step 6001, the BMS performs a self-test.

[0551] If the BMS self-checks and determines that it is normal, step 6003 is executed.

[0552] In step 6002, TMS1 and TMS2 perform self-test.

[0553] If the self-test result is a fault, a fault signal is sent to the BMS.

[0554] In step 6003 , the BMS detects whether a fault signal is received.

[0555] If the BMS receives a fault signal, step 6004 is executed; if the BMS does not receive a fault signal, step 6005 is executed.

[0556] In step 6004, the fault is processed.

[0557] For example, reporting fault signals, determining whether to control the thermal management component to shut down based on the fault level, etc.

[0558] In step 6005 , TMS1 and TMS2 collect the ambient temperature and send it to the BMS.

[0559] In step 6006 , the BMS collects the ambient temperatures of the first battery system and the second battery system.

[0560] In step 6007 , the BMS obtains the temperatures of the multiple battery clusters in the first battery system and the temperatures of the multiple battery clusters in the second battery system.

[0561] In addition, the BMS can also obtain the maximum temperature and / or minimum temperature of multiple battery cells in each battery cluster.

[0562] In step 6008 , the BMS determines the operating modes of TMS1 and TMS2 based on the temperature information acquired in step 6007 .

[0563] For example, the operating mode of the thermal management component of each battery system can be determined as self-circulation mode, cooling mode or heating mode based on the temperature of each battery cluster in each battery system and the relevant temperature threshold, and the operating mode can be indicated to the TMS of the thermal management component.

[0564] In step 6009, the corresponding working mode is started according to the instruction of the BMS.

[0565] In step 6010 , the BMS determines whether the operation modes of TMS1 and TMS2 are the same.

[0566] If the operating modes of TMS1 and TMS2 are the same, step 6011 is executed; if the operating modes of TMS1 and TMS2 are different, step 6012 is executed.

[0567] In step 6011 , TMS1 and TMS2 continue to operate in the working mode in step 6009 .

[0568] In step 6012 , the BMS obtains a temperature difference ΔT between the first battery system and the second battery system.

[0569] In step 6013, it is determined whether ΔT exceeds a first temperature threshold.

[0570] If ΔT does not exceed the first temperature threshold, step 6011 is executed; if ΔT exceeds the first temperature threshold, step 6014 is executed.

[0571] In step 6014, the BMS determines whether the battery system is in a rest state or a charge / discharge state.

[0572] If the battery system is in a static state, execute step 6015; if the battery system is in a charging or discharging state, execute step 6016.

[0573] In step 6015 , the operating mode of the thermal management component of the battery system determined to have a high temperature is adjusted to a cooling mode.

[0574] In step 6016, the thermal management components of the battery system that are determined to be at a low temperature are deactivated.

[0575] In step 6017 , when the temperature difference ΔT between the first battery system and the second battery system is lower than a second temperature threshold, it is determined that the first thermal management component and the second thermal management component operate in the same operating mode.

[0576] It can be seen that adjusting the operating modes of the first thermal management component and the second thermal management component according to the relationship between the temperatures of the first battery system and the second battery system can effectively improve the temperature consistency between the first battery system and the second battery system.

[0577] The above describes in detail the uneven flow control method of the embodiment of the present application, such as the DCR control method, the uneven flow judgment method, the overcurrent judgment method, the current limiting method, etc. The uneven flow control device of the embodiment of the present application is described in detail in combination with Figures 34 and 35. The technical features described in the method embodiment are applicable to the following device embodiments.

[0578] FIG34 is a schematic block diagram of a control device for uneven flow according to an embodiment of the present application. As shown in FIG34 , the control device 700 includes a detection module 710 and a processing module 720 .

[0579] The detection module 710 is used to obtain the DC resistance of the battery pack; and the processing module 720 is used to determine whether the current is unevenly distributed among the multiple battery packs according to the DC resistance of the multiple battery packs.

[0580] In some embodiments, the detection module 710 is specifically used to obtain a state parameter group of the battery pack, wherein the state parameter group includes at least two state parameters of the battery pack; determine the first DC resistance of the battery pack based on the state parameter group of the battery pack and the correspondence between multiple preset state parameter groups and multiple DC resistances; and determine the second DC resistance of the battery pack based on the first DC resistance of the battery pack.

[0581] In some embodiments, the status parameter group includes at least two of the following status parameters: the state of charge of the battery pack, the temperature of the battery pack, the current of the battery pack, the charge and discharge direction of the battery pack, the charge and discharge time of the battery pack, and the health status of the battery pack.

[0582] In some embodiments, the detection module 710 is specifically configured to determine the first DC resistance as the second DC resistance; or, calibrate the first DC resistance according to a preset calibration coefficient to obtain a calibrated second DC resistance of the battery pack.

[0583] In some embodiments, the detection module 710 is also used to obtain a state parameter group of the battery pack at a target time after the current time; and determine the DC resistance of the battery pack at the target time based on the state parameter group of the battery pack at the target time and the corresponding relationship.

[0584] In some embodiments, the detection module 710 is specifically configured to obtain information about the voltage and / or current of the battery pack; and determine the DC resistance of the battery pack based on the voltage and / or current information.

[0585] In some embodiments, the detection module 710 is specifically used to obtain the open circuit voltage of the battery pack; determining the DC resistance of the battery pack based on the voltage and / or current information includes: determining the DC resistance of the battery pack based on the open circuit voltage of the battery pack, the voltage of the battery pack, and the current of the battery pack.

[0586] In some embodiments, the detection module 710 is specifically used to obtain the state of charge of the battery pack; and determine the open circuit voltage of the battery pack according to the state of charge of the battery pack and a preset correspondence between the open circuit voltage and the state of charge.

[0587] In some embodiments, the detection module 710 is specifically used to determine the voltage difference between the voltage of the battery pack and the open circuit voltage of the battery pack; determine the ratio between the voltage difference and the current of the battery pack; and determine the ratio as the DC resistance of the battery pack.

[0588] In some embodiments, the detection module 710 is specifically used to control the PCS connected to the battery pack to charge and discharge the battery pack; during the charging and discharging process, obtain information on the voltage and current of the battery pack; and determine the target DC resistance of the battery pack based on the current of the battery pack and the change in the voltage of the battery pack within the target time.

[0589] In some embodiments, the detection module 710 is specifically configured to determine a ratio between a change in the voltage of the battery pack within the target duration and a current of the battery pack as a target DC resistance of the battery pack.

[0590] In some embodiments, the processing module 720 is specifically used to determine that there is uneven current distribution among the multiple battery groups when the ratio between the DC resistance of the first battery group and the DC resistance of the second battery group among the multiple battery groups is greater than a preset DC resistance threshold, wherein the first battery group is the battery group with the largest DC resistance among the multiple battery groups, and the second battery group is the battery group with the smallest DC resistance among the multiple battery groups.

[0591] In some embodiments, the processing module 720 is also used to obtain the temperature of the first battery system and the temperature of the second battery system among the multiple battery systems; determine the target operating mode of the first thermal management component and / or the second thermal management component based on the temperature of the first battery system and the temperature of the second battery system, the first thermal management component is used to control the temperature of the first battery system, and the second thermal management component is used to control the temperature of the second battery system.

[0592] In some embodiments, the processing module 720 is further configured to determine whether the battery pack has an overcurrent; and if the battery pack has an overcurrent, limit the current of the battery pack according to the degree of the overcurrent of the battery pack.

[0593] In some embodiments, the processing module 720 is specifically used to determine the overflow of the battery pack, where the overflow includes the current difference and / or current ratio between the current of the battery pack and its allowed current; and adjust the allowed current of the battery pack according to the overflow.

[0594] In some embodiments, the processing module 720 is specifically configured to adjust the allowed current of the battery pack when the current difference is greater than or equal to a first threshold, and / or the current ratio is greater than or equal to a second threshold.

[0595] In some embodiments, the processing module 720 is specifically used to calculate the first product between the allowable current value of the battery pack with the smallest allowable current among the N battery packs connected in parallel and N, wherein the N battery packs include the battery pack and N is a positive integer; calculate the second product between the current difference and a preset coefficient; calculate the difference between the first product and the second product; and determine the adjusted allowable current of the battery pack, which is equal to the ratio between the difference and N.

[0596] In some embodiments, the processing module 720 is specifically used to determine the overcurrent information of the battery pack; send overcurrent indication information to the energy management system, the overcurrent indication information includes the overcurrent information, and the overcurrent indication information is used to request the energy management system to determine whether to limit the current of the battery pack.

[0597] In some embodiments, the overcurrent information is used to indicate the overcurrent level of the battery pack, and the processing module 720 is specifically used to determine the overcurrent level of the battery pack based on the overcurrent ratio of the battery pack; or, to determine the overcurrent level based on the overcurrent ratio and overcurrent duration of the battery pack; wherein the overcurrent ratio is the ratio between the current of the battery pack and its allowed current.

[0598] In some embodiments, the processing module 720 is specifically configured to determine, based on the overcurrent level, current limiting information corresponding to the overcurrent level, wherein the overcurrent indication information further includes the current limiting information corresponding to the overcurrent level.

[0599] In some embodiments, the processing module 720 is specifically used to determine the target value based on the initial value of the allowed current and the current adjustment ratio corresponding to the overcurrent level, wherein the current adjustment ratio is the ratio between the target value and the initial value of the allowed current.

[0600] In some embodiments, the processing module 720 is further configured to determine whether multiple batteries in the battery pack have overcurrent; and determine whether the battery pack has overcurrent when at least one battery in the multiple batteries has overcurrent.

[0601] In some embodiments, the control device 700 also includes a control module for determining a target battery group for charging and discharging with the power grid based on the required power of the power grid; and determining the output power of the power control system connected between the power grid and the target battery group based on the overcurrent state of the target battery group.

[0602] In some embodiments, the control module is specifically used to determine, based on the power demand of the power grid, that the target battery pack includes all or part of a plurality of battery packs, and the plurality of battery packs are connected in parallel to the power grid through a plurality of power control systems.

[0603] In some embodiments, the battery pack is a battery cluster or an electrical cabinet, or the battery pack is a container, wherein the container includes a plurality of the electrical cabinets connected in series and / or in parallel, the battery cluster or the electrical cabinet includes a plurality of electrical boxes connected in series and / or in parallel, and the electrical box includes a plurality of battery cells connected in series and / or in parallel.

[0604] It should be understood that the specific manner in which the control device 700 performs temperature control and the beneficial effects produced can be found in the relevant description in the method embodiment, and for the sake of simplicity, they will not be repeated here.

[0605] The present application also provides a computer-readable storage medium for storing a computer program. When the computer program is executed by a computing device, the computing device implements the temperature control method 600 described in any of the above embodiments. Optionally, the computer program can be a computer program in a BMS.

[0606] The present application also provides an uneven flow control device 800, which may include, for example, a BMS and / or an EMS. As shown in FIG35 , the control device 800 includes a processor 810 and a memory 820, wherein the memory 820 is used to store instructions, and the processor 810 is used to read the instructions and execute the methods described in the various embodiments of the present application based on the instructions. The memory 820 may be a separate device independent of the processor 810, or it may be integrated into the processor 810.

[0607] 35 , the temperature control device 800 may further include a transceiver 830, and the processor 810 may control the transceiver 830 to communicate with other devices, for example, to send information, data, or instructions to other devices, or to receive information, data, or instructions sent by other devices.

[0608] The present application also provides an energy storage system, which includes multiple battery packs and the uneven current control device described in any of the above embodiments. The multiple battery packs can be connected in parallel, for example.

[0609] It should be understood that the processor in the embodiments of the present application may be an integrated circuit chip with signal processing capabilities. During implementation, each step of the above-mentioned method embodiment may be completed by hardware integrated logic circuits in the processor or by software instructions. The above-mentioned processor may be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic device, or discrete hardware component. It can implement or execute the various methods, steps, and logic block diagrams disclosed in the embodiments of the present application. The general-purpose processor may be a microprocessor or any conventional processor. The steps of the method disclosed in the embodiments of the present application may be directly implemented and executed by a hardware decoding processor, or by a combination of hardware and software modules in the decoding processor. The software module may be located in a storage medium well-known in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, etc. The storage medium is located in the memory, and the processor reads the information in the memory and, in conjunction with its hardware, completes the steps of the above-mentioned method.

[0610] It is understood that the memory in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), and direct RAM bus RAM (DR RAM). It should be noted that the memory of the systems and methods described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0611] It should be noted that, under the premise of no conflict, the various embodiments and / or the technical features in each embodiment described in this application can be arbitrarily combined with each other, and the technical solution obtained after the combination should also fall within the scope of protection of this application.

[0612] In the embodiments of the present application, the size of the serial numbers of each step does not mean the order of execution. The order of execution of each step should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0613] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0614] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0615] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solutions of the embodiments of the present application.

[0616] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A control method for non-uniform current flow, characterized in that, The control method includes: Obtaining the DC resistance of the battery pack; Determining whether there is uneven current sharing among the multiple battery packs according to the DC resistances of the multiple battery packs.

2. The control method according to claim 1, characterized in that The obtaining of the DC resistance of the battery pack includes: Obtaining a set of state parameters of the battery pack, where the set of state parameters includes at least two state parameters of the battery pack; Determining a first DC resistance of the battery pack according to the set of state parameters of the battery pack and a corresponding relationship between a preset multiple sets of state parameters and multiple DC resistances; Determining a second DC resistance of the battery pack according to the first DC resistance of the battery pack.

3. The control method according to claim 2, characterized in that, The set of state parameters includes at least two of the following state parameters: The state of charge of the battery pack, the temperature of the battery pack, the current of the battery pack, the charge and discharge direction of the battery pack, the charge and discharge time of the battery pack, and the health state of the battery pack.

4. The control method according to claim 2 or 3, characterized in that The determining of the second DC resistance of the battery pack according to the first DC resistance of the battery pack includes: Determining the first DC resistance as the second DC resistance; or, Calibrating the first DC resistance according to a preset calibration coefficient to obtain the calibrated second DC resistance of the battery pack.

5. The control method according to any one of claims 2 to 4, characterized in that, The method further includes: Obtaining a set of state parameters of the battery pack at a target moment after the current moment; Determining the DC resistance of the battery pack at the target moment according to the set of state parameters of the battery pack at the target moment and the corresponding relationship.

6. The control method according to claim 1, characterized in that The obtaining of the DC resistance of the battery pack includes: Obtaining information on the voltage and / or current of the battery pack; Determining the DC resistance of the battery pack according to the information on the voltage and / or the current.

7. The control method according to claim 6, characterized in that, The obtaining of the information on the voltage and / or current of the battery pack includes: Obtaining the open-circuit voltage of the battery pack; The determining of the DC resistance of the battery pack according to the information on the voltage and / or the current includes: Determining the DC resistance of the battery pack according to the open-circuit voltage of the battery pack, the voltage of the battery pack, and the current of the battery pack.

8. The control method according to claim 7, wherein The obtaining of the open-circuit voltage of the battery pack includes: Obtaining the state of charge of the battery pack; Determining the open-circuit voltage of the battery pack according to the state of charge of the battery pack and a corresponding relationship between the open-circuit voltage and the state of charge.

9. The control method according to claim 7 or 8, characterized in that The determining of the DC resistance of the battery pack according to the open-circuit voltage of the battery pack, the voltage of the battery pack, and the current of the battery pack includes: Determining the voltage difference between the voltage of the battery pack and the open-circuit voltage of the battery pack; Determining the ratio of the voltage difference to the current of the battery pack; Determining the ratio as the DC resistance of the battery pack.

10. The control method according to claim 6, characterized in that The obtaining of the information on the voltage and / or current of the battery pack includes: Controlling the PCS connected to the battery pack to charge and discharge the battery pack; During the charging and discharging process, obtaining the information on the voltage and current of the battery pack; The determining of the DC resistance of the battery pack according to the information on the voltage and / or the current includes: Determining the target DC resistance of the battery pack according to the current of the battery pack and the change amount of the voltage of the battery pack within a target duration.

11. The control method according to claim 10, characterized in that, Determining the target DC resistance of the battery pack according to the current of the battery pack and the change amount of the voltage of the battery pack within a target duration includes: Determining the ratio between the change amount of the voltage of the battery pack within the target duration and the current of the battery pack as the target DC resistance of the battery pack.

12. The control method according to any one of claims 1 to 11, characterized in that, Determining whether the multiple battery packs are unevenly current-sharing according to the difference between the DC resistances of the multiple battery packs includes: When the ratio between the DC resistance of the first battery pack and the DC resistance of the second battery pack among the multiple battery packs is greater than a preset DC resistance threshold, determining that the multiple battery packs are unevenly current-sharing, where the first battery pack is the battery pack with the largest DC resistance among the multiple battery packs, and the second battery pack is the battery pack with the smallest DC resistance among the multiple battery packs.

13. The control method according to any one of claims 1 to 12, characterized in that, The control method further includes: Determining whether the battery pack is overcurrent; When the battery pack is overcurrent, limiting the current of the battery pack according to the overcurrent degree of the battery pack.

14. The control method according to claim 13, wherein Limiting the current of the battery pack includes: Determining the overcurrent amount of the battery pack, where the overcurrent amount includes the current difference and / or current ratio between the current of the battery pack and its allowed current; Adjusting the allowed current of the battery pack according to the overcurrent amount.

15. The control method according to claim 14, characterized in that, Adjusting the allowed current of the battery pack according to the overcurrent amount includes: When the current difference is greater than or equal to a first threshold, and / or the current ratio is greater than or equal to a second threshold, adjusting the allowed current of the battery pack.

16. The control method according to claim 15, characterized in that, Adjusting the allowed current of the battery pack includes: Calculating the first product between the allowed current value of the battery pack with the smallest allowed current among N parallel-connected battery packs and N, where the N battery packs include the battery pack and N is a positive integer; Calculating the second product between the current difference and a preset coefficient; Calculating the difference between the first product and the second product; Determining that the adjusted allowed current of the battery pack is equal to the ratio between the difference and N.

17. The control method according to any one of claims 13 to 16, characterized in that, Limiting the current of the battery pack includes: Determining the overcurrent information of the battery pack; Sending overcurrent indication information to the energy management system, where the overcurrent indication information includes the overcurrent information, and the overcurrent indication information is used to request the energy management system to determine whether to limit the current of the battery pack.

18. The control method according to claim 17, wherein The overcurrent information is used to represent the overcurrent level of the battery pack. Determining the overcurrent information of the battery pack includes: Determining the overcurrent level of the battery pack according to the overcurrent ratio of the battery pack; or, Determining the overcurrent level according to the overcurrent ratio and overcurrent duration of the battery pack; where the overcurrent ratio is the ratio between the current of the battery pack and its allowed current.

19. The control method according to claim 18, wherein, Limiting the current of the battery pack includes: Determining the current-limiting information corresponding to the overcurrent level according to the overcurrent level, where the overcurrent indication information further includes the current-limiting information corresponding to the overcurrent level.

20. The control method according to claim 19, wherein The current-limiting information includes the target value of the allowed current of the battery pack. Determining the current-limiting information corresponding to the overcurrent level according to the overcurrent level includes: Determine the target value according to the initial value of the allowed current and the current adjustment ratio corresponding to the overcurrent level, where the current adjustment ratio is the ratio between the target value and the initial value of the allowed current.

21. The control method according to any one of claims 13 to 20, characterized in that, The determining whether the battery pack is overcurrent includes: Determine whether multiple batteries in the battery pack are overcurrent; When at least one of the multiple batteries is overcurrent, determine whether the battery pack is overcurrent.

22. The control method according to any one of claims 1 to 21, characterized in that, The control method further includes: Determine a target battery pack for charging and discharging with the power grid according to the required power of the power grid; Determine the output power of the power control system connected between the power grid and the target battery pack according to the overcurrent state of the target battery pack.

23. The control method according to claim 22, wherein The determining a target battery pack for charging and discharging with the power grid according to the required power of the power grid includes: Determine that the target battery pack includes all or part of a plurality of battery packs according to the required power of the power grid, and the plurality of battery packs are respectively connected in parallel to the power grid through a plurality of power control systems.

24. The control method according to any one of claims 1 to 23, characterized in that, The control method further includes: Obtain the temperature of a first battery system and the temperature of a second battery system in a plurality of battery systems, where the first battery system includes at least one battery cluster and the second battery system includes at least one battery cluster; According to the temperature of the first battery system and the temperature of the second battery system, determine the target operating mode of a first thermal management component and / or a second thermal management component, where the first thermal management component is used to control the temperature of the first battery system and the second thermal management component is used to control the temperature of the second battery system.

25. The control method according to any one of claims 1 to 24, characterized in that, The battery pack is a battery cluster or an electric cabinet, or the battery pack is a container, where the container includes a plurality of the electric cabinets connected in series and / or in parallel, the battery cluster or the electric cabinet includes a plurality of electric boxes connected in series and / or in parallel, and the electric box includes a plurality of battery cells connected in series and / or in parallel.

26. A control device for uneven flow, characterized in that, The control device includes: A detection module for obtaining the DC resistance of the battery pack; A processing module for determining whether there is uneven current sharing between the multiple battery packs according to the DC resistances of the multiple battery packs.

27. A control device for uneven flow, characterized in that, It includes a processor and a memory, where the memory is used to store instructions, and the processor is used to execute the instructions to implement the uneven current sharing control method according to any one of claims 1 to 25.

28. A energy storage system, characterized in that, It includes: A plurality of battery packs connected in parallel; And, The uneven current sharing control device according to claim 27.

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