Non-current-sharing control method, control device, control equipment and energy storage system

Abstract

The invention provides a non-current-sharing control method, a non-current-sharing control device, a non-current-sharing control device and an energy storage system. The problem of non-current sharing of a battery pack can be solved. The control method comprises the following steps: acquiring the DCR of the battery pack; and according to the DCR of the plurality of battery packs, determining whether the plurality of battery packs are non-uniform in current. By acquiring the DCR of the battery pack and according to the difference between the DCR of the plurality of battery packs connected in parallel, the non-uniform current among the plurality of battery packs connected in parallel can be found and prevented in time, so that the charging and discharging performance of the whole energy storage system is improved.

Description

Methods, devices, equipment, and energy storage systems for controlling uneven flow

[0001] This application claims priority to Chinese Patent Application No. 202311814038.8, filed on December 26, 2023, entitled "Overcurrent Control Method and Apparatus, BMS, EMS and Energy Storage System", and to Chinese Patent Application No. 202311811317.9, filed on December 26, 2023, entitled "Overcurrent Control Method and Apparatus, Battery Management System and Energy Storage System", the entire contents of which are incorporated herein by reference.

[0002] This application relates to the field of batteries, and in particular to a method, device, equipment and energy storage system for controlling uneven current.

[0003] Energy storage systems typically require high voltage and large capacity. Therefore, they need numerous batteries connected in series and parallel to form products such as power cabinets or containers, and then interact with the grid through a power conversion system (PCS). Battery packs in an energy storage system can be connected in parallel. If uneven current distribution occurs among these battery packs, it can lead to two problems: firstly, the uneven current distribution can cause the entire energy storage system to prematurely stop charging and discharging, affecting its overall capacity and energy output; secondly, excessively high current from a battery pack may exceed the charging capacity window of individual battery cells, affecting their safety performance and lifespan. Therefore, it is necessary to address the problem of uneven current distribution among battery packs.

[0004] Summary of the Invention

[0005] This application provides a method, device, equipment, and energy storage system for controlling uneven current distribution, which can solve the problem of uneven current distribution in battery packs.

[0006] In a first aspect, a method for controlling uneven current distribution is provided, the method comprising: acquiring the current distribution coefficient (DCR) of a battery pack; and determining, based on the DCR of multiple battery packs, whether there is uneven current distribution among the multiple battery packs.

[0007] In this embodiment, the DCR of the battery pack is obtained, and based on the difference between the DCRs of multiple parallel battery packs, uneven current between multiple parallel battery packs is detected and prevented in a timely manner, thereby improving the charging and discharging performance of the entire battery pack.

[0008] In one possible implementation, obtaining the DCR of the battery pack includes: obtaining a state parameter set of the battery pack, the state parameter set including at least two state parameters of the battery pack; determining a first DCR of the battery pack based on the state parameter set of the battery pack and a preset correspondence between multiple state parameter sets 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 is established that includes the correspondence between the battery pack's state parameter set and the DCR. This database is used to determine the battery pack's DCR under the current state parameters. The state parameter set includes various state parameters that may affect the battery pack's DCR. Since the influence of different state parameters on the battery pack's DCR is fully considered, the accuracy of the DCR can be improved.

[0010] In one possible implementation, the state parameter set 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 charging / discharging direction of the battery pack, the charging / discharging time of the battery pack, and the health status of the battery pack. This comprehensively considers the impact of different influencing factors on the DCR of the battery pack.

[0011] In one possible implementation, determining the second DCR of the battery pack based on 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 DCR detection, or, after obtaining the DCR of the battery pack, the first DCR of the battery pack can be calibrated by an appropriate calibration coefficient, and the resulting second DCR can be used as the result of DCR detection. This calibration coefficient can improve the inconsistency between the initial DCRs of different battery cells in the battery pack, thus improving the accuracy of DCR.

[0013] In one possible implementation, the method further includes: obtaining a set of state parameters of the battery pack at a target time after the current time; and determining the DCR of the battery pack at the target time based on the set of state parameters of the battery pack at the target time and the correspondence.

[0014] In this implementation, 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 determined in advance whether uneven current may occur between battery packs, and appropriate strategies can be determined and responded in a timely manner, thereby reducing the risk caused by excessive differences in DCR between battery packs.

[0015] In one 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 based on the information about the voltage and / or current.

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

[0017] In one possible implementation, obtaining the voltage and / or current information of the battery pack includes: obtaining the open-circuit voltage of the battery pack; 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 information about the current OCV, voltage, and current of the battery pack. Because this DCR detection method utilizes the current voltage and current of the battery pack, as well as its current static OCV, it is independent of the initial voltage of the battery pack and will not be affected by the instability of the initial voltage, thus exhibiting high accuracy. Furthermore, it enables dynamic testing of the DCR, allowing for rapid and accurate acquisition of the battery pack's DCR.

[0019] In one possible implementation, obtaining the open-circuit voltage of the battery pack includes: obtaining the state of charge (SOC) of the battery pack; and determining the open-circuit voltage of the battery pack based on the SOC of the battery pack and a preset correspondence between the open-circuit voltage and the SOC.

[0020] In this implementation, the relationship curve between the battery pack's OCV and SOC can be pre-built into the BMS software to facilitate the acquisition of the battery pack's current OCV. When detecting the battery pack's DCR, the OCV corresponding to the current SOC can be determined based on the battery pack's current SOC and the relationship curve between OCV and SOC. This OCV is then used as the battery pack's current OCV 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 the voltage difference between the voltage of the battery pack and the open-circuit voltage of the battery pack; determining the 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 between the difference and the current current of the battery pack can be calculated. This ratio is then used as the current DCR of the battery pack. Since this method of calculating DCR only uses the current voltage and current of the battery pack, as well as the current static OCV of the battery pack, and does not depend on the initial voltage of the battery pack, it has high accuracy and can perform dynamic testing of DCR.

[0023] In one possible implementation, acquiring the voltage and / or current information of the battery pack includes: controlling a PCS connected to the battery pack to charge and discharge the battery pack; acquiring the voltage and current information 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 the change in the voltage of the battery pack within a target time period.

[0024] In this implementation, the battery pack is charged and discharged by controlling the PCS, and the voltage and current information of the battery pack during the charging and discharging process can be used to dynamically obtain the DCR of the battery pack.

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

[0026] Within a target duration, the battery pack is charged and discharged using a PCS. Based on the battery pack's current and voltage changes within that target duration, the battery pack's DCR can be effectively calculated, enabling online testing of the battery pack's DCR.

[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 a target duration includes: determining the ratio between the change in the voltage of the battery pack and the current of the battery pack within the target duration as the target DCR of the battery pack.

[0028] In one possible implementation, determining whether there is uneven current distribution among the multiple battery packs based on the difference in DCR among the multiple battery packs includes: determining uneven current distribution among the multiple battery packs if the ratio between the DCR of the first battery pack and the DCR of the second battery pack is greater than a preset DCR threshold, wherein the first battery pack is the battery pack with the largest DCR among the multiple battery packs, and the second battery pack is the battery pack with the smallest DCR among the multiple battery packs.

[0029] In this implementation, 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 current regulation (DCR) between the battery packs will cause a difference in current between the battery packs, resulting in uneven current distribution among the battery packs and affecting their capacity and charge. Therefore, by detecting the difference in DCR between the parallel-connected battery packs, it is possible to determine whether uneven current distribution has occurred among the battery packs, so as to promptly detect and prevent uneven current distribution among the parallel-connected 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 grid's power demand, and the output power of the corresponding PCS is determined based on the overcurrent state of the target battery pack. This allows for dynamic adjustment of the charging and discharging power of the battery packs under each PCS from the perspective of the entire substation, reducing the probability of overcurrent in the battery packs while meeting the grid's demands.

[0032] In one possible implementation, determining the target battery pack for charging and discharging with the power grid based on the power grid's demand includes: determining that the target battery pack comprises all or part of multiple battery packs, wherein the multiple battery packs are connected in parallel to the power grid through multiple power control systems.

[0033] In this implementation, since the power demand of the power grid varies at different times, it is determined whether all battery packs need to participate in charging and discharging 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 optimal resource allocation can be achieved.

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

[0035] In this implementation, if uneven current occurs among multiple battery packs connected in parallel, it may cause overcurrent in the battery pack with higher current. In this case, current limiting information can be applied to the battery pack based on the degree of overcurrent, which can effectively improve the overcurrent situation.

[0036] In one possible implementation, the current limiting of the battery pack includes: determining overcurrent information of the battery pack; sending overcurrent indication information to the energy management system, the overcurrent indication information including the overcurrent information, the overcurrent indication information being 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 the overcurrent indication information carrying the overcurrent level to the EMS. Based on the overcurrent indication information and the current operating conditions, the EMS determines whether to limit the current of the battery pack. 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 of the battery pack and the overcurrent duration; wherein the overcurrent ratio is the ratio between the current of the battery pack and its allowable current.

[0039] In this implementation, the overcurrent rating of the battery pack is related to the proportion by which the battery pack's current exceeds its allowable current. Therefore, the overcurrent rating of the battery pack can be determined based on the overcurrent ratio, which is quite intuitive. Furthermore, the overcurrent rating can also be determined by combining the duration of the overcurrent.

[0040] For example, determining the overcurrent level of the battery pack based on its overcurrent ratio and overcurrent duration includes: determining the overcurrent level of the battery pack as the first overcurrent level when the overcurrent ratio of the battery pack reaches the overcurrent ratio corresponding to the first overcurrent level and lasts for a first duration, or when the battery pack is at the second overcurrent level for a second duration, wherein the overcurrent ratio corresponding to the first overcurrent level is greater than the overcurrent ratio corresponding to the second overcurrent level. This considers not only the degree of overcurrent but also the duration of overcurrent, making the determination of the overcurrent level more consistent with reality.

[0041] In one possible implementation, the current limiting of the battery pack includes: determining current limiting information corresponding to the overcurrent level based on the overcurrent level, wherein the overcurrent indication information further 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. This 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 according to 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, a corresponding current adjustment ratio can be set for different overcurrent levels. Based on the initial value of the battery pack's allowable current and the corresponding current adjustment ratio, the target value of the allowable current can be determined, so that the current limiting of the battery pack matches its overcurrent level, thereby improving the effect of current limiting.

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

[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 situation of the battery pack.

[0047] In one possible implementation, adjusting the allowable current of the battery pack according to the overcurrent 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 and the allowable current of the battery pack both reach the corresponding threshold, it can be considered that the battery pack has experienced overcurrent, thereby adjusting the allowable current of the battery pack.

[0049] In one possible implementation, adjusting the allowable current of the battery pack includes: calculating the allowable current value of the battery pack with the smallest allowable current among the N parallel battery packs, and multiplying it by 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; and determining that the adjusted allowable current of the battery pack is equal to the ratio between the difference and N.

[0050] In this implementation, according to I a '=(I min The adjusted allowable current value I of the battery pack is calculated using *ND*k) / N. a ', where I min This refers to the allowable current value of the battery pack with the lowest allowable current among multiple battery packs connected in parallel, including this battery pack. N is the number of battery packs connected in parallel, D is the current difference between the actual current of this battery pack and its allowable current, and k is a preset coefficient. The adjusted allowable current I for this battery pack is calculated based on the current difference D between the actual current and the allowable current of each individual battery pack. a ', and the allowable current I of the battery pack a The adjustment will not affect the current of other battery packs connected in parallel, thus reducing the impact on the charging and discharging process of the entire system.

[0051] In one 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 if at least one of the multiple batteries is overcurrent.

[0052] In this implementation, it is possible to first determine whether multiple batteries in the battery pack are overcurrent, and if at least one of the batteries is overcurrent, determine whether the entire battery pack is overcurrent, thereby determining the overcurrent information of the battery pack in the case of overcurrent.

[0053] In one possible implementation, the control method further includes: acquiring the temperature of a first battery system and a second battery system in a plurality of battery systems, wherein the first battery system includes at least one battery cluster and the second battery system includes at least one battery cluster; 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, wherein 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.

[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 temperature 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, solving problems such as impedance and current imbalance of the battery system caused by poor temperature consistency, and reducing the probability of the high current battery system being prematurely charged or discharged, which is conducive to improving the conversion efficiency of the battery product.

[0055] In one possible implementation, the battery pack is a battery cluster or a cabinet, or the battery pack is a container, wherein the container includes multiple cabinets connected in series and / or in parallel, the battery cluster or cabinet includes multiple boxes connected in series and / or in parallel, and the boxes include multiple individual battery cells connected in series and / or in parallel.

[0056] Secondly, a non-uniform current control device is provided, the control device comprising: a detection module for acquiring the DCR of a battery pack; and a processing module for determining whether there is non-uniform current among the multiple battery packs based on the DCR of the multiple battery packs.

[0057] Thirdly, a non-uniform flow control device is provided, comprising a processor and a memory, the memory for storing instructions, and the processor for executing the instructions to implement the non-uniform flow control method described in the first aspect or any possible implementation thereof.

[0058] Fourthly, 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 thereof.

[0059] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0060] Figure 1 is a schematic diagram of a possible energy storage system according to an embodiment of this application.

[0061] Figure 2 is a schematic diagram of a possible battery cluster according to an embodiment of this application.

[0062] Figure 3 is a schematic diagram of a possible electrical box according to an embodiment of this application.

[0063] Figure 4 is a schematic diagram of a possible energy storage system according to an embodiment of this application.

[0064] Figure 5 is a schematic flowchart of the uneven flow control method according to an embodiment of this application.

[0065] Figure 6 is a schematic flowchart of a method for detecting DCR according to an embodiment of this application.

[0066] Figure 7 is a schematic diagram of the DCR calculation principle.

[0067] Figure 8 is a schematic diagram of one possible specific implementation of the method shown in Figure 6.

[0068] Figure 9 is a schematic diagram of a possible test method for the initial DCR of a single battery cell.

[0069] Figure 10 is a schematic diagram of a possible specific implementation of the method shown in Figure 6.

[0070] Figure 11 is a schematic diagram of a possible specific implementation of the method shown in Figure 6.

[0071] Figure 12 is a schematic flowchart of a method for detecting DCR according to another embodiment of this application.

[0072] Figure 13 is a schematic diagram of the relationship curve between the OCV and SOC of the battery pack.

[0073] Figure 14 is a schematic diagram of one possible specific implementation of the method shown in Figure 12.

[0074] Figures 15 and 16 are schematic flowcharts of a method for detecting DCR according to another embodiment of this application.

[0075] Figure 17 is a schematic diagram of the architecture of an energy storage system according to an embodiment of this application.

[0076] Figure 18 is a flowchart of one possible specific implementation of the method shown in Figures 15 and 16.

[0077] Figure 19 is a schematic diagram of a possible specific implementation of the method shown in Figures 15 and 16.

[0078] Figure 20 is a schematic flowchart of a power control method according to an embodiment of this application.

[0079] Figure 21 is a schematic diagram of an energy storage system according to an embodiment of this application.

[0080] Figure 22 is a schematic diagram of the power demand of the power grid at different times.

[0081] Figure 23 is a schematic diagram of one possible specific implementation of the method shown in Figure 20.

[0082] Figure 24 is a schematic flowchart of the overcurrent determination method according to an embodiment of this application.

[0083] Figure 25 is a schematic diagram of one possible specific implementation of the method shown in Figure 24.

[0084] Figure 26 is a schematic flowchart of the end-point current limiting method according to an embodiment of this application.

[0085] Figure 27 is a flowchart of one possible implementation of the method shown in Figure 26.

[0086] Figure 28 is a schematic flowchart of the adaptive rate limiting method according to an embodiment of this application.

[0087] Figure 29 is a flowchart of one possible implementation of the method shown in Figure 28.

[0088] Figure 30 is a schematic flowchart of a temperature control method according to an embodiment of this application.

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

[0090] Figure 33 is a flowchart of one possible implementation of the method shown in Figure 30.

[0091] Figure 34 is a schematic block diagram of the control device of DCR according to an embodiment of this application.

[0092] Figure 35 is a schematic block diagram of the control device of DCR according to an embodiment of this application.

[0093] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0094] Since energy storage systems typically require high voltage and large capacity, a large number of batteries need to be connected in series and parallel to form products such as power cabinets or containers. These systems interact with the power grid through a power grid control system (PCS), which is used to convert the AC signal from the power grid to the DC signal from the energy storage system.

[0095] As an example, as shown in Figure 1, battery pack 1 includes N battery clusters, namely battery clusters R1 to RN, where N is a positive integer. Battery clusters R1 to RN are connected in parallel and are charged or discharged to the power grid through the PCS. Each battery cluster includes multiple boxes. For example, as shown in Figure 2, each battery cluster from R1 to RN includes M boxes, namely boxes B1 to BM, where M is a positive integer. The M boxes are connected in series; or, some of the M 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 box is assembled from K battery cells. For example, as shown in Figure 3, each box from B1 to BM includes K battery cells connected in series and / or in parallel, namely battery cells C1 to 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 for charging or discharging with the grid. The battery pack can be, for example, a battery cabinet or a container. The cabinet can be considered a battery product formed from battery clusters; therefore, the battery cluster shown in Figure 1 can also be called a cabinet. Multiple cabinets can be assembled to form battery products such as containers. 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 manufacturing process, the direct current resistance (DCR) of individual battery cells is affected by various factors, resulting in differences in DCR between different cells. This, in turn, leads to significant differences in the DCR of battery packs assembled from these cells, such as electrical cabinets or containers. After the battery packs are connected in parallel to the power grid via a pre-installed circuit (PCS), the differences in DCR among the battery packs on the parallel branches cause current differences in each branch, resulting in uneven current distribution among the multiple parallel battery packs.

[0098] Therefore, this application provides a solution for uneven current, which aims to detect and prevent uneven current between multiple battery packs in parallel by detecting the DCR of the battery pack and based on the differences in the DCR between the multiple battery packs connected in parallel, thereby improving the charging and discharging performance of the entire battery pack.

[0099] Figure 5 illustrates a schematic flow of the uneven flow control method according to an embodiment of this application. The control method may be executed by a battery management system (BMS) and / or an energy management system (EMS). The BMS may include 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, based on the DCR of the multiple battery packs, it is determined whether there is uneven current flow among the multiple battery packs.

[0102] By detecting the DCR of the battery pack and based on the differences in the DCRs between multiple parallel battery packs, uneven current distribution between multiple parallel battery packs can be detected and prevented in a timely manner, thereby improving the charging and discharging performance of the entire battery pack.

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

[0104] First, referring to Figures 6 to 19, the method for obtaining the DCR of the battery pack in step 110 is described. This application provides two methods for detecting the DCR of the battery pack, which are described below.

[0105] Method 1

[0106] In Method 1, a database is established that includes the correspondence between the state parameter group of the battery pack and the DCR. The DCR of the battery pack under the current state parameters is determined using this database. The state parameter group includes a variety of 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 FIG6, step 110 may include steps 111 and 112.

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

[0109] In step 112, the first DCR of the battery pack is determined based on the state parameter group of the battery pack and the pre-set correspondence between multiple state parameter groups and multiple DCRs.

[0110] In step 113, the second DCR of the battery pack is determined based on the first DCR of the battery pack.

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

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

[0113] Due to their electrochemical characteristics, the internal resistance of a battery can be affected by multiple factors. To more accurately detect the discharge resistance (DCR) of a battery pack, it is first necessary to identify the influencing factors associated with the DCR. This application provides several influencing factors that may affect the DCR of a battery pack, including the state of charge (SOC), temperature (T), current (I), charging / discharging direction, charging / discharging time (Time), and state of equilibrium (SOH). For either the charging or discharging state, the DCR of the battery pack is defined as f(SOC, SOH, I, Time, T, charging / discharging direction), where f represents the relationship between these state parameters and the DCR, i.e., the correspondence between the aforementioned multiple state parameter sets and multiple DCR values.

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

[0115] After identifying the various state parameters that may affect the battery's discharge rate (DCR), the values ​​for each state parameter during the DCR test can be designed. For example, as shown in Table 1, reasonable value ranges matching the actual operating conditions of the battery can be set for various state parameters that may affect DCR, including State of Charge (SOC), temperature, current, charging / discharging direction, charging / discharging time, and State of Harshness (SOH). Here, we only take a charging time range of 5s-60s and a charging current range of 120A-180A as an example. In practical applications, a longer charging time range and / or a larger current range can be set.

[0116] Table 1

[0117] During the testing process, the controlled 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 individually, and a series of DCR tests were performed for each state parameter.

[0118] For example, a fresh battery cell is used as the test object, with 100% SOH, an ambient temperature of 25°C, and a constant charging current of 140A during charging. Under these conditions, the DCR of the battery cell is tested at different SOC values, including 0%, 5%, 10%, 15%, ..., 95%, and 100%.

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

[0120] Table 2

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

[0122] In Table 2, U0 is the initial voltage, i.e., the static voltage. Therefore, the DCR of a single battery cell at 0 seconds of charging is DCR. 01 The DCR of a single battery cell after 5 seconds of charging 02= (U5-U0) / I, the DCR of a single battery cell after 10 seconds of charging. 03 =(U 10 -U0) / I, DCR of a single battery cell after 15 seconds of charging 04 =(U 15 -U0) / I, DCR of a single battery cell after 20 seconds of charging 05 =(U 20 -U0) / I, ..., DCR of a single battery cell after 55 seconds of charging 06 =(U 55 -U0) / I, DCR of a single battery cell after 60 seconds of charging 07 =(U 60 -U0) / I, where I = 140A.

[0123] Thus, we can obtain the relationship between charging time and DCR under the conditions of 100% SOH, test environment temperature of 25℃, constant charging current of 140A during charging, and SOC of 0%, as shown in Table 3.

[0124] Table 3

[0125] Secondly, by adjusting the SOC of the battery cell to 5% and conducting the test as described above, a relationship between charging time and DCR can be obtained similar to that shown in Table 3, under the conditions of 100% SOH, ambient temperature of 25℃, constant charging current of 140A during charging, and SOC of 5%.

[0126] Sequentially, the SOC of each battery cell is adjusted at 5% SOC intervals, and DCR tests are performed according to the above procedures. This yields a DCR mapping table under the following conditions: 100% SOH, ambient temperature 25℃, 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 correspondence between the state parameter group consisting of charging time and SOC and the DCR.

[0127] Table 4

[0128] Using the same approach, the remaining state parameters, such as temperature, current, and SOH, were changed sequentially. A series of DCR tests were conducted for each of these state parameters using a single-factor controlled variable method. The DCR data for all state parameters at different values ​​were then compiled to obtain the correspondence between the state parameter group (SOC, temperature, current, charge / discharge direction, charge / discharge time, and SOH) and the DCR, thereby establishing a multi-dimensional, full-lifecycle DCR database for the battery.

[0129] The DCR database includes the correspondence between multiple state parameter groups and DCRs. This DCR database can be written into BMS software, for example. In practical applications, the state parameter groups of the battery pack can be collected, including parameters such as SOC, temperature, current, charging / discharging direction, charging / discharging time, and SOH. The DCR corresponding to the parameter values ​​of each state parameter in the state parameter group of the battery pack can be found from the DCR database stored in the BMS.

[0130] The correspondence between the various state parameters in the state parameter group and the DCR can be implemented in various forms. For example, the correspondence can be a table showing the mapping relationship between the values ​​of each state parameter and the DCR; it can also be a curve or formula representing the correspondence between the various state parameters in the state parameter group and the DCR, such as DCR = f(SOC, SOH, I, Time, T, charging / discharging direction); or other forms that can represent the correspondence between the various state parameters in the state parameter group and the DCR. Tables 1 to 4 are examples of mapping tables, storing the mapping relationship between the various state parameters in the state parameter group and the DCR in the BMS.

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

[0132] In another implementation, in step 112, for parameter values ​​located between adjacent values ​​in the DCR database, the DCR corresponding to the parameter value can be calculated using an interpolation algorithm, such as a linear interpolation algorithm. Assume 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, among the multiple values ​​of the first state parameter in the correspondence, a first value and a second value that are closest to the parameter value of the first state parameter of the battery pack can be found, and the DCR corresponding to the first value and the second value can be determined. Thus, the first DCR corresponding to the parameter value of the first state parameter of the battery pack can be obtained through an interpolation algorithm.

[0133] Specifically, in step 112, among the multiple values ​​of the first state parameter in the DCR database, a first value and a second value that are closest to the parameter value of the first state parameter of the battery pack can be determined; based on the first value, the second value, and the correspondence between the first parameter value and the DCR in the DCR database, the DCR corresponding to the first value and the DCR corresponding to the second value are determined; based on the DCR corresponding to the first value and the DCR corresponding to the second value, the DCR corresponding to the parameter value of the first state parameter of the battery pack is determined using an interpolation algorithm; 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 following parameters are present in the current state parameter group of the battery pack: SOH is 100%, ambient temperature is 25℃, charging current is constant at 140A, charging time is 60s, and SOC is 8%. If the DCR database shows SOC values ​​in 5% increments, including 0%, 5%, 10%, 15%, ..., 95%, and 100%, then the closest SOC values ​​to 8% are 5% and 10%. We can then look up the DCR under the conditions of SOH 100%, ambient temperature 25℃, charging current constant at 140A, charging time 60s, and SOC 5%, and the DCR under the conditions of SOH 100%, ambient temperature 25℃, charging current constant at 140A, charging time 60s, and SOC 10%.

[0135] Assume the DCR values ​​corresponding to 5% SOC and 10% SOC are respectively DCR 16 and DCR 26Therefore, based on the linear interpolation algorithm, we can obtain the DCR = DCR under the following conditions: SOH = 100%, ambient temperature = 25℃, charging current = 140A, charging time = 60s, and SOC = 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 current regulation (DCR) between the battery packs will cause a difference in current between the battery packs, resulting in uneven current distribution among the battery packs and affecting the overall capacity and charge of the battery pack. Therefore, in some embodiments, method 100 may further include: determining whether there is uneven current distribution among the multiple battery packs based on the DCR of the multiple battery packs connected in parallel. That is, by detecting the DCR of the multiple battery packs connected in parallel, it is possible to determine whether there is uneven current distribution among the multiple battery packs, so as to detect and prevent uneven current distribution among the parallel battery packs in a timely manner.

[0137] Optionally, it can be determined whether there is uneven current distribution among multiple battery packs based on the difference in DCR between the multiple battery packs connected in parallel, such as the difference in DCR between the first battery pack and the second battery pack in the battery pack, wherein the first battery pack is the battery pack with the largest DCR among the multiple battery packs, and the second battery pack is the battery pack with the smallest DCR among the multiple battery packs.

[0138] For example, if the ratio between the DCR of the first battery pack and the DCR of the second battery pack is greater than the corresponding DCR threshold, uneven current distribution among the multiple battery packs can be determined; or, for another example, if the difference between the DCR of the first battery pack and the DCR of the second battery pack is greater than the corresponding DCR threshold, uneven current distribution among the multiple battery packs can be determined.

[0139] In this way, by analyzing the difference in DCR between the battery pack with the highest DCR and the battery pack with the lowest DCR, uneven current distribution among multiple battery packs can be detected in a timely manner.

[0140] As an example, the DCR detection process shown in Figure 8 takes the battery pack as an example. In this process, the SBMU of each battery cluster is responsible for the management of the corresponding battery cluster and uploads the 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 Figure 8, in step 1101, it is determined that the battery cluster is in the operating condition, that is, the battery cluster is currently charging or discharging.

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

[0143] For example, this state parameter group includes parameters such as SOC, temperature, current, charging / discharging direction, charging / discharging 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 current state parameters in the battery cluster's current state parameter group are in the DCR database.

[0146] If the DCR database includes the parameter value of the status parameter, proceed to step 1105; if the DCR database does not include the parameter value of the status parameter, proceed to step 1106.

[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 it as the first DCR of the battery cluster.

[0149] Among them, the SBMU can report the first DCR of the corresponding battery cluster to the MBMU.

[0150] In step 1107, the MBMU calculates the inter-cluster internal resistance difference based on the first DCR of the multiple parallel battery clusters.

[0151] For example, this internal resistance difference can be represented by DCRmax / DCRmin, where DCRmax and DCRmin represent the largest and smallest DCRs among the first DCRs of multiple battery clusters, respectively.

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

[0153] If the inter-cluster internal resistance difference DCRmax / DCRmin is greater than the DCR threshold x%, i.e., DCRmax / DCRmin > x%, proceed to step 1109; if the inter-cluster internal resistance difference DCRmax / DCRmin is less than or equal to the DCR threshold x%, i.e., DCRmax / DCRmin ≤ x%, continue to detect the first DCR of the battery cluster.

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

[0155] This uneven current strategy can be built into the BMS software to reduce the degree of uneven current between multiple battery clusters connected in parallel. For example, it can reduce the current of some or all battery clusters based on certain strategies.

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

[0157] In other words, 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 can be calibrated using an appropriate calibration coefficient, and the resulting second DCR can be used as the result of DCR detection.

[0158] Since the DCR database is established based on the DCR test results of a few standard battery cells, and in reality, the initial DCRs of different battery cells exhibit a certain distribution pattern, a DCR database based on some of these cells cannot be accurately applied to the DCR testing of other battery packs. By processing the first DCR obtained from the DCR database using this calibration coefficient, a calibrated second DCR is obtained. This improves the inconsistency between the initial DCRs of different battery cells in the battery pack, thus enhancing the accuracy of the DCR.

[0159] As an example, Figure 9 shows one possible testing method for the initial DCR of a battery cell. The initial DCR of a battery cell typically refers to the DCR obtained by testing the battery cell on the production line. As shown in Figure 9, battery cells on the production line usually need to undergo processes such as formation, aging, room temperature coefficient measurement (K), DCR testing, capacity testing, and DCR grouping. In the DCR testing process, a battery cell with a certain SOC can be charged for a certain period of time, for example, it can be charged at a constant current for 30 seconds when the battery cell is at 20% SOC. Based on the DCR testing principle shown in Figure 6, for example, the DCR of the battery cell is calculated, and this DCR can be used as the initial DCR of the battery cell.

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

[0161] In this embodiment, the initial DCR of a battery cell can refer to the initial DCR after temperature correction. The initial DCR of the battery cell can 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 DCR between different battery cells, the initial DCR of different battery cells is not the same. It is not possible to directly call the data in the DCR standard library that is based on tests of only some of the battery cells. Therefore, it is necessary to set appropriate calibration coefficients in order to reduce or eliminate the differences in the initial DCR between different battery cells to a certain extent.

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

[0164] The standard battery cell is used to establish a correspondence between the battery cells. The initial DCR of the standard battery cell is obtained by testing the initial DCR of multiple battery cells in the battery pack 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 the production line, such as the constant current charging for 30 seconds under the 20% SOC condition mentioned above.

[0166] The calibration coefficient can be specific to this battery pack. Different battery packs may have the same or different calibration coefficients.

[0167] The calibration coefficient is determined by using the initial DCR of a standard battery cell and the initial DCR of multiple battery cells in the 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] Optionally, the calibration factor can be equal to the ratio between the average initial DCR of multiple cells in the battery pack and the initial DCR of a standard cell.

[0169] In some embodiments, in step 113, the product of the first DCR and the calibration coefficient can be determined as the second DCR, thereby enabling simple and quick calibration of the first DCR of the battery pack to obtain the calibrated second DCR.

[0170] Taking Figures 1 to 3 as examples, N battery clusters are assembled to form battery products such as cabinets or containers. 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 initial DCR R of the M*K battery cells in that battery cluster. mean And the initial DCR of a standard battery cell. For example, if the initial DCR of a standard battery cell used to establish the DCR database is 0.7 mΩ, then the calibration coefficient corresponding to that battery cluster can be set to equal R. mean / 0.7mΩ.

[0171] In actual production, the Data Criteria (DCR) at different levels, such as the battery cell level, battery box level, battery cluster or cabinet level, and container level, can be recorded for production control. Using the DCR testing process shown in Figure 7, the initial DCR of a battery cell is obtained. The identification information corresponding to that battery cell, such as a barcode, can be used as its identity label, and the corresponding initial DCR is entered into the MES system. When assembling multiple battery cells into a battery box, if the battery box is not the object of DCR testing, the DCR of the battery box can be calculated based on the initial DCRs of the multiple battery cells within it when generating the corresponding barcode. Similarly, the DCR of a battery cluster or cabinet level can be calculated based on the DCRs of the multiple battery boxes included in the battery cluster or cabinet, and the calculated DCR of the cabinet is then embedded into the corresponding SBMU (Battery Storage Unit). The DCR of a container level can be calculated based on the DCRs of the multiple battery boxes included in the container, and the calculated DCR of the container is then embedded into the corresponding MBMU (Battery Management Unit). The DCR values ​​of the electrical cabinets or containers can be stored in a local database or uploaded to a cloud server. After the DCR of the electrical cabinets or containers is detected online in a subsequent manner, the DCR data in the local database or cloud server can be updated.

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

[0173] Based on the average initial DCR of each cell in the battery cluster and the initial DCR of the standard cells used to establish the DCR database, the calibration coefficient corresponding to the battery cluster can be determined. For example, the average initial DCR R of each cell in the battery cluster can be used as the calibration coefficient. max The ratio between the initial DCR of the battery cluster and that of a standard individual 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, it is read, and the first DCR corresponding to the state parameter group of the battery cluster, which is found in the DCR database, is multiplied by the calibration coefficient to obtain the calibrated second DCR. The second DCR is used as the actual DCR of the battery cluster under the state parameter group for subsequent operations such as uneven current detection.

[0174] When multiple battery packs are connected to the power grid in parallel, because the voltages of the battery packs are the same, the difference in current regulation (DCR) between them, based on Ohm's law, will cause current imbalances among the battery packs, affecting the overall capacity and charge of the battery pack. Therefore, the presence of current imbalance among the parallel battery packs can be determined by measuring the second DCR of the parallel battery packs. In other words, by detecting the second DCR of the parallel battery packs, it is possible to determine whether current imbalance occurs among them, so as to promptly detect and prevent such imbalances.

[0175] Optionally, it can be determined whether there is uneven current distribution among multiple battery packs based on the difference between the second DCRs of the multiple battery packs connected in parallel, such as the difference between the second DCRs of the first battery pack and the second battery pack, wherein the first battery pack is the battery pack with the largest second DCR among the multiple battery packs, and the second battery pack is the battery pack with the smallest second DCR among the multiple battery packs.

[0176] For example, uneven current distribution among multiple battery packs can be determined if the ratio between the second DCR of the first battery pack and the second DCR of the second battery pack is greater than the corresponding DCR threshold; or, for another example, uneven current distribution among multiple battery packs can be determined if the difference between the second DCR of the first battery pack and the second DCR of the second battery pack is greater than the corresponding DCR threshold.

[0177] In this way, by analyzing the difference in DCR between the battery pack with the highest DCR and the battery pack with the lowest DCR, uneven current distribution among multiple battery packs can be detected in a timely manner.

[0178] As an example, the DCR detection process shown in Figure 10 takes the battery pack as an example. In this process, the SBMU of each battery cluster is responsible for the management of the corresponding battery cluster and uploads the 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 Figure 10, in step 1201, it is determined that the battery cluster is in operating condition, that is, the battery cluster is currently charging or discharging.

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

[0181] For example, this state parameter group includes parameters such as SOC, temperature, current, charging / discharging direction, charging / discharging time, and SOH.

[0182] In step 1203, the SBMU determines the 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 coefficients corresponding to the battery cluster.

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

[0185] Among them, the SBMU can report the second DCR of the corresponding battery cluster to the MBMU.

[0186] In step 1206, the MBMU calculates the inter-cluster internal resistance difference based on the DCR of the multiple parallel battery clusters.

[0187] For example, this internal resistance difference can be represented by DCRmax / DCRmin, where DCRmax and DCRmin represent the largest and smallest second DCRs among multiple battery clusters, respectively.

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

[0189] If the inter-cluster internal resistance difference DCRmax / DCRmin is greater than the DCR threshold x%, i.e., DCRmax / DCRmin > x%, proceed to step 1208; if the inter-cluster internal resistance difference DCRmax / DCRmin is less than or equal to the DCR threshold x%, i.e., DCRmax / DCRmin ≤ x%, continue to detect the DCR of the battery cluster.

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

[0191] This uneven current strategy can be built into the BMS software to reduce the degree of uneven current between multiple battery clusters connected in parallel. For example, it can reduce the current of some or all battery clusters based on certain strategies.

[0192] The aforementioned DCR database can also be used to predict the DCR of a battery pack. For example, in some embodiments, the state parameter set of the battery pack at a target time after the current time can be obtained; and the DCR of the battery pack at the target time can be determined based on the state parameter set of the battery pack at the target time and the correspondence between multiple preset state parameter sets and multiple DCRs.

[0193] By establishing a DCR database that includes the correspondence between battery pack state parameters and DCR, the DCR of the battery pack at any given time can be determined. For example, knowing the battery pack state parameters 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 instance, it is possible to determine in advance whether uneven current distribution may occur between battery packs, determine appropriate strategies in a timely manner, and take corresponding responses, thereby reducing the risks caused by excessive differences in DCR between battery packs.

[0194] The target time for the battery pack after the current time can refer to any time after the current time when 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 can be predicted if the state parameters in the battery pack's state parameter set change.

[0195] The battery pack's temperature, state of equilibrium (SOH), and current state of charge (SOC) can be calculated by the battery management system (BMS), and the probability of changes in battery pack temperature and SOH within a short period is low. Therefore, changes in state parameters mainly include changes in battery pack current, including changes in current magnitude, direction, and duration. In some embodiments, the energy management system (EMS) can send new current information to the BMS. The BMS receives the battery pack current information at the target time from the EMS, such as current magnitude, duration, and direction, and determines the battery pack's SOC at the target time based on the current, duration, and direction at the target time, as well as the battery pack's current SOC at the current moment.

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

[0197] In other words, the SOC of the battery pack at the target time can be calculated based on the current and its direction, as well as the charging and discharging time, at that time. The battery pack receives a new current I from the EMS, the duration T of this current I, and the charging / discharging direction (positive or negative) of current I. Assuming charging begins from the current time with the new current I, the charging / discharging capacity of the battery pack based on current I within the time T is ΔQ = I*T / Q, where T is the duration of charging / discharging based on current I from the current time to the target time, and Q is the battery pack's capacity, such as its 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 SOC of the battery pack at the current time, and SOC2 is the SOC value of the battery pack 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 SOC of the battery pack at the current time, and SOC3 is the SOC value of the battery pack at the target time.

[0198] Then, 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 and used as the DCR of the battery pack at the target time.

[0199] Optionally, the BMS can predict the DCR of the battery pack under changed state parameters, such as current-related parameters, when it is determined that the state parameters of the battery pack have changed. For example, knowing that the current will charge and discharge based on a new current I from the current moment until a target moment, the BMS can determine the SOC of the battery pack at the target moment based on the current SOC and the current-related parameters, and predict the DCR of the battery pack at the target moment by combining other state parameters at the target moment. In other embodiments, the BMS can 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 operating condition information at the target time in advance, including updated current, its duration, and direction. This allows the battery pack's SOC at the target time to be determined based on the current SOC and the updated current, duration, and direction sent by the EMS. Then, combined with the values ​​of other state parameters at the target time, the DCR of the battery pack at the target time is determined from a DCR database containing the correspondence 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, the difference in current regulation (DCR) between the battery packs, based on Ohm's law, will cause a difference in current between the battery packs, resulting in uneven current distribution among the battery packs and affecting the capacity and charge of the battery clusters. Therefore, in some embodiments, method 100 may further include: determining whether there is uneven current distribution among the multiple battery packs based on their DCR at a target time. That is, by detecting the DCR of the multiple battery packs in parallel at a target time, it is possible to predict whether uneven current distribution may occur among the multiple battery packs at the target time, so as to detect and prevent uneven current distribution among the parallel battery packs in a timely manner.

[0202] Optionally, it can be determined whether there is uneven current distribution among multiple battery packs based on the difference in DCR between multiple battery packs connected in parallel at a target time, such as the difference in DCR between the first battery pack and the second battery pack. Here, the first battery pack is the battery pack with the largest DCR among the multiple battery packs, and the second battery pack is the battery pack with the smallest DCR among the multiple battery packs.

[0203] For example, if the ratio between the DCR of the first battery pack and the DCR of the second battery pack is greater than the corresponding DCR threshold, uneven current distribution among the multiple battery packs can be determined; or, for another example, if the difference between the DCR of the first battery pack and the DCR of the second battery pack is greater than the corresponding DCR threshold, uneven current distribution among the multiple battery packs can be determined.

[0204] In this way, by analyzing the difference in DCR between the battery pack with the highest DCR and the battery pack with the lowest DCR, uneven current distribution among multiple battery packs can be detected in a timely manner.

[0205] As an example, the DCR detection process shown in Figure 11 takes the battery pack as an example. The SBMU of each battery cluster is responsible for the management of the corresponding battery cluster and uploads the 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 Figure 11, in step 1301, it is determined that the battery cluster is in the operating condition, that is, the battery cluster is currently charging or discharging.

[0207] In step 1302, the MBMU receives the current information at the target time sent by the EMS, including 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, as well as 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; or, if the DCR database does not include the parameter value of a certain state parameter at the target time, the value adjacent to the parameter value can be selected in the DCR database, and the DCR corresponding to the parameter value can be calculated by interpolation algorithm and used as the actual DCR of the battery cluster at the target time.

[0212] Among them, the SBMU can report the DCR of the corresponding battery cluster at the target time to the MBMU.

[0213] In step 1306, the MBMU calculates the inter-cluster internal resistance difference at the target time based on the DCR of the multiple parallel battery clusters at the target time.

[0214] For example, this internal resistance difference can be represented by DCRmax / DCRmin, where DCRmax and DCRmin represent the maximum and minimum DCRs among the multiple battery clusters at the target time, respectively.

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

[0216] If the inter-cluster internal resistance difference DCRmax / DCRmin is greater than the DCR threshold x%, i.e., DCRmax / DCRmin > x%, proceed to step 1308; if the inter-cluster internal resistance difference DCRmax / DCRmin is less than or equal to the DCR threshold x%, i.e., DCRmax / DCRmin ≤ x%, continue to detect the DCR of the battery cluster.

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

[0218] This uneven current strategy can be built into the BMS software to reduce the degree of uneven current between multiple battery clusters connected in parallel. For example, it can reduce the current of some or all battery clusters based on certain strategies.

[0219] Based on the above description, it can be seen that in Method 1, by establishing a database that includes the correspondence between the state parameter group of the battery pack and the DCR, the DCR of the battery pack under the current state parameters is determined using this database. The state parameter group includes a variety of 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 may occur between battery packs, determine appropriate strategies in time, and respond accordingly, thereby reducing the risk caused by excessive differences in DCR between battery packs.

[0221] After obtaining the DCR of the battery pack, the DCR of the battery pack can be calibrated by using an appropriate calibration factor. This calibration factor can improve the inconsistency between the initial DCRs of different battery cells in the battery pack, thus improving the accuracy of the DCR.

[0222] Method 2

[0223] In Method 2, the voltage and / or current of the battery pack are detected, and the DCR of the battery pack is determined based on the information of the voltage and / or current, thereby realizing dynamic detection of the DCR.

[0224] As a method for dynamically detecting DCR, for example as shown in Figure 12, step 110 may include steps 114 and 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 based on 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, including charging or discharging.

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

[0230] In some embodiments, step 114 may further include: obtaining the SOC of the battery pack, and determining the OCV of the battery pack based on the SOC of the battery pack and a preset correspondence between OCV and 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 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 showing the mapping relationship 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 a battery pack.

[0233] As an example, Figure 13 shows the OCV-SOC curve of a battery. The correspondence between the battery's SOC and OCV is represented by this OCV-SOC curve. As shown in Figure 13, during the charging and discharging process, the battery's OCV changes as the internal chemical reactions continue. Optionally, under the battery's operating conditions, the battery's SOC can be adjusted at certain intervals, and the battery can be allowed to stand for a certain period to eliminate polarization before collecting the battery voltage. For example, a suitable battery cell can be selected and charged with a current of 0.05C. After each 5% SOC is charged, the cell can be allowed to stand for 2 or 3 hours to eliminate polarization, and the voltage of the battery cell can be collected after standing. This yields multiple sets of corresponding SOC and OCV data. By fitting these multiple sets of corresponding SOC and OCV data, an OCV-SOC curve, also known as a static OCV curve, can be plotted. Similarly, during the discharge process, the corresponding OCV-SOC curve can also be obtained in the same way.

[0234] The OCV-SOC curve of the battery pack can be pre-built into the BMS software to facilitate the acquisition of the current OCV of the battery pack. When detecting the current DCR of the battery pack, the OCV corresponding to the current SOC of the battery pack can be determined based on the current SOC and the OCV-SOC curve, and this OCV can be used as the current OCV of the battery pack to calculate the DCR of the battery pack.

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

[0236] According to the principle of electrochemical polarization of batteries, during the charging and discharging process of a 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, as well as the real-time collected voltage and current information.

[0238] Wherein, the DCR of the battery pack is (U-OCV) / I, where 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 current SOC obtained from the OCV-SOC curve based on the current SOC of the battery pack.

[0239] As can be seen, the difference between the current voltage of the battery pack and the OCV is calculated, and the ratio between this difference and the current current of the battery pack is used as the current DCR of the battery pack. This method of calculating DCR only uses the current voltage and current information of 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, the difference in current regulation (DCR) between the battery packs, based on Ohm's law, will cause a difference in current between the battery packs, resulting in uneven current distribution and affecting the overall capacity and charge of the battery pack. Therefore, in some embodiments, method 100 may further include: determining whether there is uneven current distribution among the multiple battery packs based on the DCR of the multiple battery packs connected in parallel. That is, by detecting the DCR of the multiple battery packs connected in parallel, it is possible to determine whether there is uneven current distribution among the multiple battery packs, so as to detect and prevent uneven current distribution among the parallel battery packs in a timely manner.

[0241] Optionally, it can be determined whether there is uneven current distribution among multiple battery packs based on the difference in DCR between the multiple battery packs connected in parallel, such as the difference in DCR between the first battery pack and the second battery pack. The first battery pack is the battery pack with the largest DCR among the multiple battery packs, and the second battery pack is the battery pack with the smallest DCR among the multiple battery packs.

[0242] For example, if the ratio between the DCR of the first battery pack and the DCR of the second battery pack is greater than the corresponding DCR threshold, uneven current distribution among the multiple battery packs can be determined; or, for another example, if the difference between the DCR of the first battery pack and the DCR of the second battery pack is greater than the corresponding DCR threshold, uneven current distribution among the multiple battery packs can be determined.

[0243] In this way, by analyzing the difference in DCR between the battery pack with the highest DCR and the battery pack with the lowest DCR, uneven current distribution among multiple battery packs can be detected in a timely manner.

[0244] As an example, the DCR detection process shown in Figure 14 takes the battery pack as an example. In this process, the SBMU of each battery cluster is responsible for the management of the corresponding battery cluster and uploads the 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 Figure 14, in step 1401, it is determined that the battery cluster is in operating condition, 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 a battery cluster can be calculated based on its current, charging and discharging time, and charging and discharging direction. For instance, the SOC of a battery cluster is calculated as I*T / Q, where T is the charging time and Q is the capacity of the battery cluster, such as its rated capacity or maximum capacity.

[0249] In step 1404, the SBMU extracts the corresponding OCV from the OCV-SOC curve based on the SOC of the battery cluster.

[0250] In step 1405, the SBMU calculates the DCR of the battery cluster as (U-OCV) / I based on the OCV, voltage U, and current I of the battery cluster.

[0251] Among them, the SBMU can report the DCR of the corresponding battery cluster to the MBMU.

[0252] In step 1406, the MBMU calculates the inter-cluster internal resistance difference based on the DCR of the multiple parallel battery clusters.

[0253] For example, this internal resistance difference can be represented by DCRmax / DCRmin, where DCRmax and DCRmin represent the maximum and minimum DCRs among multiple battery clusters, respectively.

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

[0255] If the inter-cluster internal resistance difference DCRmax / DCRmin is greater than the DCR threshold x%, i.e., DCRmax / DCRmin > x%, proceed to step 1408; if the inter-cluster internal resistance difference DCRmax / DCRmin is less than or equal to the DCR threshold x%, i.e., DCRmax / DCRmin ≤ x%, continue to detect the DCR of the battery cluster.

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

[0257] This uneven current strategy can be built into the BMS software to reduce the degree of uneven current between multiple battery clusters connected in parallel. For example, it can reduce the current of some or all battery clusters based on certain strategies.

[0258] Based on the above description, it can be seen that the DCR of the battery pack can be detected by using 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 will not affect the DCR detection results due to the instability of the initial voltage. It has high accuracy and can perform dynamic testing of DCR, thereby quickly and accurately obtaining the DCR of the battery pack.

[0259] As another way to dynamically detect DCR, the detection of DCR in step 110 can be implemented by EMS and / or 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, and the DCR detection method shown in Figure 16 can be performed by a battery pack BMS. Of course, where feasible, the BMS can perform some of the operations performed by the EMS, and vice versa.

[0261] As shown in Figure 15, EMS can perform steps 116 and 117.

[0262] In step 116, it is determined that the DCR of the battery pack will be tested.

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

[0264] Here, charging and discharging can refer to the power grid charging the battery pack through the PCS, or the battery pack discharging to the power grid through the PCS.

[0265] For example, when the EMS determines that the DCR of the battery pack needs to be detected, it controls the PCS connected to the battery pack to charge and discharge the battery pack. During the charging and discharging process, the voltage and current information of the battery pack are used to determine the target DCR of the battery pack.

[0266] As shown in Figure 16, the BMS can execute steps 118 and 119.

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

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

[0269] For example, during the charging and discharging process of the battery pack by the PCS, the BMS collects information on the voltage and current of the battery pack and determines the target DCR of the battery pack based on this information. Optionally, the EMS can issue commands to instruct the BMS to collect voltage and current and calculate the DCR.

[0270] In this way, by controlling the PCS to charge and discharge the battery pack, and by utilizing 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 power control system (PCS) acts as a medium connecting the alternating current (AC) side of the power grid and the direct current (DC) side of the battery pack. For example, it may include a bidirectional AC / DC converter. As an example, in the energy storage system architecture shown in Figure 17, battery packs 1, 2, ..., n are connected to the PCS via corresponding power units 1, 2, ..., n. These power units include switches to enable DC input and output. The energy of the entire system is regulated and controlled by the battery management system (BMS), PCS, and energy management system (EMS). Furthermore, other modules, such as a display module, can be configured to implement corresponding functions. In this embodiment, the PCS is controlled to charge and discharge the battery packs. Specifically, the battery packs are charged and discharged via the PCS during specific periods of actual use, such as idle periods. The voltage and current information of the battery packs during charging and discharging enables online detection of the current rating (DCR). Optionally, the DCR detection results can be uploaded to a local database or cloud server via communication methods such as Wi-Fi, Bluetooth, 4G, and 5G for storage and updating of the battery pack's DCR.

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

[0273] The target duration is used to detect the DCR of the battery pack. For example, it can be the duration for the PCS to charge and discharge the battery pack. Within this target duration, the battery pack is charged and discharged using the PCS, and the DCR of the battery pack can be effectively calculated based on the change in the battery pack current and voltage within this target duration, thus realizing online testing of the battery pack's DCR.

[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 current I to reach the target duration ΔT. At the beginning of charging, the voltage of the battery pack is U0. After the target duration ΔT is reached, the voltage of the battery pack is U. The change in voltage of the battery pack during the target duration ΔT is ΔU = U - U0. Based on the change in voltage ΔU and current I, the target DCR of the battery pack is determined as ΔU / I = (U - U0) / I.

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

[0276] The battery pack is in a quiescent state, or in a static operating condition, meaning there is no demand for charging and discharging between the power grid and the battery pack. In this case, the control PCS charges and discharges the battery pack to perform DCR (Discharge Rate Reduction) detection. This avoids affecting the normal charging and discharging process of the battery pack to meet grid demands, reducing the impact of DCR detection on the ongoing charging and discharging process between the power grid and the battery pack.

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

[0278] In other words, in step 117, if the battery pack is in a static state for a duration greater than or equal to the target duration, the EMS controls the PCS to charge and discharge the battery pack.

[0279] Since it is necessary to utilize the voltage change of the battery pack within the target duration, sufficient time, i.e., the target duration, needs to be reserved for DCR detection of the battery pack. Therefore, before performing DCR detection, it is necessary to determine whether the battery pack can be in a static state for a duration greater than or equal to the target duration, so as to facilitate DCR detection of the battery pack using PCS, thereby reducing the interruption of DCR detection caused by sudden charging and discharging processes 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. These state parameters include, for example, at least one of the battery pack's state of charge (SOC), state of equilibrium (SOH), and temperature. This allows for more accurate detection of the battery pack's drain cascade (DCR) under these state parameters, improving the accuracy of the detection results.

[0281] Typically, this target duration can be set to within one minute. Optionally, the target duration can be determined based on the battery pack's SOC, SOH, and current temperature. For example, for a battery pack at 25°C, with a SOC of 25% and BCL SOH, the battery pack is discharged for 30 seconds using a PCS (Power Control System). The DCR of the battery pack is determined based on the ratio of the voltage change to the discharge current during these 30 seconds. Similarly, for a battery pack at 25°C, with a SOC of 25% and EOL SOH of 70%, the battery pack is discharged for 30 seconds using a PCS. The DCR of the battery pack is determined based on the ratio of the voltage change to the discharge current during these 30 seconds. Generally, the DCR of a battery pack with 100% BOL SOH is less than that of a battery pack with 70% EOL SOH. For battery packs with these state parameters, the DCR is approximately in the milliohm range.

[0282] Optionally, the BMS can determine the target duration when the battery pack is in a static state 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 in a static state is greater than or equal to the target duration, and then determines whether to perform DCR detection 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 the target duration for DCR detection.

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

[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 duration of the battery pack being in a quiescent state is greater than or equal to the target duration.

[0289] In step 1505, if the battery pack is in a static state for a duration greater than or equal to the target duration, the EMS controls the PCS to charge and discharge the battery pack.

[0290] In step 1506, the BMS acquires information about the voltage and current of the battery pack during the charging and discharging process of the battery pack by the PCS.

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

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

[0293] Specifically, when the EMS determines that the battery pack is in a resting state, the BMS determines the target duration required for DCR testing. The BMS sends this target duration information to the EMS so that the EMS can determine whether the power grid has a charging / discharging requirement within that target duration. If the EMS determines, or the user determines, that the power grid does not have a charging / discharging requirement within the target duration, the test conditions are met, and the DCR of the battery pack can be tested using the above method. In other words, it is first determined whether there is sufficient time to test the battery pack's DCR to reduce the possibility of the power grid forcing charging / discharging during the DCR test. If there is sufficient time to test the battery pack's DCR, then the DCR test is performed within that predetermined time. At this time, the EMS can control the PCS to charge or discharge the battery pack with a certain current. During this process, the BMS detects the voltage change and current of the battery pack within the target duration and calculates the battery pack's DCR based on the voltage change and current.

[0294] In this embodiment, the EMS determines whether the battery pack's resting time exceeds the target duration in two ways. Firstly, the EMS can determine if the power grid has charging / discharging demand within the target duration. Secondly, the EMS can provide the target duration to the user through a human-machine interface system for confirmation. For example, the EMS can access a display interface and, in response to user actions on that interface, determine whether the battery pack's resting time is greater than or equal to the target duration. The user can inform the EMS whether the battery pack can remain idle for more than the target duration by performing corresponding actions on the display interface, such as confirming or canceling.

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

[0296] In other words, the DCR of the battery pack can be calibrated by combining historical DCR data, 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 target DCR can be used as the final detection result, for example, as a criterion for judging uneven current distribution. If the database or cloud platform stores the battery pack's historical DCR, then the historical DCR data and the target DCR can be used for corresponding data processing to obtain an updated DCR as the final detection result, for example, as a criterion for judging uneven current distribution.

[0298] By combining historical DCR data, it is possible to effectively determine whether the target DCR detected online has become outlier, allowing for timely detection of deviations from the normal range caused by environmental factors or forced charging and discharging by the power grid. Alternatively, the target DCR can be adjusted based on historical DCR trends to compensate for the impact of battery pack usage and environmental factors on DCR.

[0299] Historical DCR includes the initial DCR of the battery pack and / or the DCR of the battery pack detected over a historical period. The DCR of the battery pack detected over a historical period can, for example, be the target DCR of the battery pack obtained by charging and discharging the battery pack using a PCS over a historical period. The initial DCR of the battery pack can, for example, be calculated based on the initial DCR of each individual battery cell in the battery pack, where the initial DCR of the individual battery cell can be the DCR obtained by the individual battery cell during the DCR testing process on the production line.

[0300] As shown in Figure 9 above, the initial DCR of a battery cell typically refers to the DCR obtained from testing the battery cell on the production line. Battery cells on the production line usually undergo processes such as formation, aging, room temperature coefficient measurement (K), DCR testing, capacity testing, and DCR grouping. In the DCR testing process, a battery cell with a certain SOC can be charged for a certain period of time, for example, constant current charging for 30 seconds at a SOC of 20%. Based on a principle similar to that in 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 illustrates a possible specific implementation of the DCR control method according to an embodiment of this application. The method shown in Figure 8 can be executed by EMS and BMS.

[0302] As shown in Figure 19, in step 1601, the EMS determines whether the battery pack is in a static state.

[0303] In step 1602, with the battery pack in a quiescent state, the BMS determines the target 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 a longer period than the target duration, the DCR detection begins.

[0305] In step 1604, the EMS controls the PCS to charge and discharge the battery pack at 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 period ΔT, and calculates the target DCR.

[0307] For example, the target DCR = △U / I.

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

[0309] In step 1607, EMS determines whether the database contains historical DCRs for the battery pack.

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

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

[0312] BMS can use the target DCR as the final detection result, for example, as a criterion for judging uneven flow.

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

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

[0315] BMS can use the corrected DCR as the final detection result, for example, as a criterion for judging uneven flow.

[0316] It is evident that in the actual application of batteries, during the idle time when there is no demand for charging and discharging from the power grid, the PCS is used to charge and discharge the battery pack. Based on the voltage and current information of the battery pack during the charging and discharging process, the target DCR of the battery pack is determined. Furthermore, the target DCR can be processed by combining historical DCR data to obtain a 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, by using the current OCV, voltage, and current information of the battery pack to obtain the DCR, it does not depend on the initial voltage of the battery pack and will not be affected by the instability of the initial voltage, thus having high accuracy. As 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, it will not affect the normal operating conditions of the battery pack.

[0318] After obtaining the DCR of the battery pack, it is possible to determine whether uneven current distribution may occur among the multiple battery packs connected in parallel based on their DCRs. In this embodiment, the following three solutions are also provided to address the overcurrent problem in the battery pack caused by uneven current distribution.

[0319] The following, with reference to Figures 20 to 29, describes in detail how to suppress overcurrent in the parallel battery packs.

[0320] Figure 20 illustrates a power control method 200 according to an embodiment of this application. Method 200 can be executed by an EMS, for example. As shown in Figure 20, method 200 includes some or all of the following steps.

[0321] In step 210, a target battery pack for charging and discharging with the power grid is determined based on the power demand of the power grid.

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

[0323] Referring to Figure 21, the PCS (Power Control System) is used to convert the AC signal from the power grid to the DC signal from the energy storage system. Each PCS can connect to one or more battery packs, and multiple battery packs are connected in parallel to the power grid through the PCS, thereby enabling charging or discharging with the power grid. As shown in Figure 21, taking two battery packs connected to each PCS as an example, the battery pack can be a battery product such as an electrical cabinet or a container. The electrical cabinet can be regarded as a battery product formed by battery clusters, so the electrical cabinet described in this embodiment can also be called a battery cluster. Multiple electrical cabinets can be assembled to form battery products such as containers. 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 manufacturing process, the direct current recoil (DCR) of individual battery cells is affected by various factors, leading to differences in DCR between different cells. This, in turn, results in significant differences in the DCR of battery packs assembled from these cells, such as electrical cabinets or containers. When battery packs are connected to the grid in parallel via a power distribution system (PCS), even if each battery pack is allocated the same power, the differences in DCR among the battery packs on the parallel branches cause current differences in each branch. This leads to uneven current distribution among the multiple parallel battery packs, resulting in overcurrent in some battery packs.

[0325] In method 200, a target battery pack for charging and discharging with the grid is determined based on the grid's power demand, and the output power of the corresponding PCS is determined based on the overcurrent state of the target battery pack. This allows for dynamic adjustment of the charging and discharging power of the battery packs under each PCS at the whole-station level, reducing the probability of overcurrent in the battery packs while meeting grid demands.

[0326] In some embodiments, in step 210, the target battery pack may be determined to include all or part of the battery packs in a plurality of battery packs, based on the power demand of the power grid. These plurality of battery packs are connected to the power grid in parallel via multiple PCS (Power Control System). Here, the battery pack may be, for example, a battery cabinet or a container; correspondingly, the plurality of battery packs may be multiple cabinets or multiple containers. For example, each cabinet may include one or more cabinets connected to the power grid in parallel via the same PCS; similarly, each container may include one or more containers connected to the power grid in parallel via the same PCS.

[0327] In other words, it is necessary to determine whether all battery packs need to participate in charging and discharging 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 above a threshold, the target battery pack can be determined as all battery packs in a group of battery packs; when the power demand of the power grid is low, such as below a threshold, the target battery pack can be determined as some battery packs in a group of battery packs.

[0329] Each battery pack is connected to the power grid through a corresponding PCS. For example, as shown in Figure 21, the energy storage system includes n PCSs and 2n battery packs. Each PCS connects two battery packs. Battery pack 1 and battery pack 2 are connected to the power grid through PCS1; battery pack 3 and battery pack 4 are connected to the power grid through PCS2; ...; battery pack 2n-1 and battery pack 2n are connected to the power grid through PCSn.

[0330] Taking Figure 21 as an example, the target battery pack can include all battery packs connected to PCS1 to PCSn, i.e., battery pack 1 to battery pack 2n; or, the target battery pack can include some of the battery packs connected to PCS1 to PCSn. The power demand of the power grid varies over different time periods. For example, as shown in Figure 22, the power demand of the power grid varies over 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 pack, the differences in the DCR of the battery packs on the parallel branches may lead to current differences in each branch, thus causing uneven current distribution in the parallel system. Therefore, optionally, based on the power demand of the power grid, all battery packs, i.e., battery packs 1 to battery pack 2n, can be fully charged and discharged during time period 1, while only some of the battery packs, such as battery pack 1 and battery pack 2 corresponding to PCS1, can be fully charged and discharged during time period 2.

[0331] The following describes in detail the power distribution method when the target battery pack includes all battery packs, as well as when it includes only a portion of the battery packs.

[0332] Case 1

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

[0334] At this point, in step 220, the overcurrent state of the multiple battery packs is determined when the output power of the multiple PCS is at full load power, and based on the overcurrent state of the multiple battery packs, it is determined whether to adjust the output power of the multiple PCS from full load power to the 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 of high power demand from the power grid, 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 state 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 state. This takes into account both the power grid demand and the overcurrent situation of the battery packs, and reduces the probability of overcurrent in the battery packs while meeting the power demand of the power grid.

[0337] In this embodiment, the overcurrent state includes, for example, overcurrent and no overcurrent. It should be understood that, here, overcurrent refers to a risk of overcurrent, and no overcurrent refers to no overcurrent risk or a low overcurrent risk. Optionally, the presence of overcurrent risk in the battery pack can be determined based on factors such as the battery pack's DCR, temperature, and SOC. If there is no overcurrent risk or the overcurrent risk is low, the battery pack's overcurrent state is considered to be no overcurrent; if there is an overcurrent risk, the battery pack's overcurrent state is considered to be overcurrent.

[0338] In one implementation, in step 220, if none of the multiple battery packs are experiencing overcurrent, the output power of the multiple PCS is determined to be the full-load power. In this case, the multiple battery packs connected to the multiple PCS respectively charge and discharge with the power grid based on the 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 experiences overcurrent, it is determined whether the output power of the multiple PCSs, when equal to the target power, meets the grid's power demand. In this case, if the grid's power demand is met, reducing the output power of the PCS can be considered to mitigate the impact of individual battery pack overcurrent on the entire energy storage system.

[0340] Furthermore, if it is determined that the output power of multiple PCSs meets the grid's demand when the target power is reached, then the output power of the multiple PCSs will be adjusted from full-load power to this target power. That is, the output power of the PCSs will be reduced. In this way, without significantly impacting grid demand, the output power of the PCSs can be reduced, 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 of overcurrent in individual battery packs on the entire energy storage system.

[0341] If the output power of multiple PCS (Power Control Systems) cannot meet the grid's power demand when the target power is reached, then the output power of the multiple PCS is determined to be at full load. Since the grid's power demand cannot be met, the output power of the multiple PCS should be maintained at full load. However, even with the output power of multiple PCS at full load, some battery packs may still face overcurrent risks. Optionally, the BMS (Battery Management System) for these battery packs can implement appropriate current limiting strategies within the battery packs based on factors such as the degree of overcurrent in each battery pack, to reduce the probability of overcurrent in these battery packs.

[0342] Case 2

[0343] The target battery pack identified in step 210 for charging and discharging with the power grid includes a portion of the battery packs among multiple battery packs connected to the power grid.

[0344] At this point, in step 220, it can be determined that the overcurrent state of the battery pack is when the output power of the PCS connected to the battery pack is at full load, and the output power of the PCS connected to the battery pack is 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 to reduce power waste. In this case, 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. Based on this overcurrent state, the output power of the corresponding PCS is determined. This approach considers both grid demand and the battery pack overcurrent situation, reducing the probability of battery pack overcurrent while meeting the grid's power demand.

[0346] In one implementation, in step 220, if none of the battery packs experience overcurrent, the output power of the target PCS is determined to be the 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 issues.

[0347] In another implementation, in step 220, if at least one battery pack in this portion of the battery pack experiences an overcurrent, the output power of the PCS connected to that portion of the battery pack is determined to be 0. Here, the output power of the PCS being 0 can mean that the battery pack corresponding to that PCS is not currently being used; for example, the branch corresponding to that PCS can be disconnected. In this case, to reduce the impact of overcurrent in individual battery packs on the entire energy storage system, the output power of the PCS corresponding to this portion of the battery pack can be adjusted to 0. That is, during this period, this portion of the battery pack is not used for charging and discharging with the grid. Optionally, the battery packs used for charging and discharging with the grid can be determined from among the other battery packs besides this portion of the battery pack.

[0348] Taking Figure 21 as an example, if battery packs 1 and 2 corresponding to PCS1 are initially selected as target battery packs for charging and discharging within the current time period, but battery packs 1 and 2 may have overcurrent risk under full load power, then other battery packs corresponding to PCS can be selected sequentially as target battery packs and their overcurrent risk can be assessed until a battery pack without overcurrent risk is selected for charging and discharging within the current time 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 overcurrent risk, then battery packs 3 and 4 will charge and discharge within the current time period based on full load power to meet the power demand of the power grid.

[0349] Figure 23 is a schematic flowchart of one possible specific implementation of method 200. The process shown in Figure 23 can, for example, be executed by EMS.

[0350] As shown in Figure 6, in step 2101, the EMS determines whether all parallel battery packs need to be charged and discharged during the current time 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 as shown in Figure 22, and the power demand of the power grid is high, then in step 2101, the EMS determines that all battery packs need to be charged and discharged, and executes step 2103; if the current time period is time period 2 as shown in Figure 22, then in step 2101, the EMS determines that only some 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 BMS of all battery packs to participate in charging and discharging.

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

[0355] That is, determine the overcurrent state of each battery pack under full-load charging and discharging conditions. If there is no overcurrent risk in all battery packs under full-load charging and discharging conditions, proceed to step 2105; if there may be overcurrent risk in some battery packs under full-load charging and discharging conditions, proceed to step 2106.

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

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

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

[0359] If reducing the output power of the PCS can meet the power demand of the power grid, then proceed to step 2107; if reducing the output power of the PCS can no longer meet the power demand of the power grid, then proceed to step 2108.

[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 full load power, and the battery pack with overcurrent risk executes the corresponding current limiting strategy.

[0362] Of course, the number of times the power is reduced is not limited in the embodiments of this application. For example, if the power demand of the power grid can still be met when the output power of the PCS is reduced to a power lower than the target power, then the output power of the PCS can be further reduced to that other power to reduce the overcurrent of the battery pack.

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

[0364] In step 2102, the EMS determines whether the charging and discharging of only battery pack 1 and battery pack 2 corresponding to PCS1 can meet the power demand of the power grid.

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

[0366] That is, determine the overcurrent state of battery pack 1 and battery pack 2 under full-load power charging and discharging conditions. If there is no overcurrent risk for battery pack 1 and battery pack 2 under full-load power charging and discharging conditions, proceed to step 2105; if there is an overcurrent risk for battery pack 1 and battery pack 2 under full-load power charging and discharging conditions, proceed to step 2106.

[0367] In step 2110, the EMS determines that battery pack 1 and battery pack 2 corresponding to PCS1 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] As can be seen from the process shown in Figure 23, the EMS can dynamically adjust the output power of each PCS, thereby reducing the probability of uneven current between multiple parallel battery packs while meeting the grid demand, and thus reducing the probability of overcurrent in the battery packs.

[0370] In this embodiment of the application, in addition to executing the aforementioned power control method 200 to control the power of the battery pack from the perspective of the entire station to improve the overcurrent of the battery pack, the following two current limiting strategies can also be used to solve the overcurrent problem of the battery pack. Both of the following schemes execute the corresponding current limiting strategies within the battery pack.

[0371] Before describing these two current limiting strategies, firstly, let's refer to the overcurrent judgment method 300 provided in the embodiments of this application, as described in conjunction with Figures 24 and 25. Method 300 can be executed by, for example, the BMS, to determine whether an overcurrent has occurred in the battery pack. In the event of an overcurrent in the battery pack, the BMS of the battery pack executes a corresponding current limiting strategy for that battery pack.

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

[0373] In other words, it is possible to first determine whether multiple batteries in the battery pack are overcurrent, and if at least one battery is overcurrent, determine whether the entire battery pack is overcurrent, thereby determining the overcurrent information of the battery pack in the case of overcurrent. The battery, for example, can be a single battery cell.

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

[0375] In step 310, the BMS determines whether multiple batteries in the battery pack are overcurrent based on the first power mapping table.

[0376] In step 320, if at least one of the multiple batteries is overcurrent, the BMS determines whether the battery pack is overcurrent according to the second power mapping table.

[0377] In this situation, when the battery pack experiences overcurrent, the BMS implements an appropriate current-limiting strategy based on the difference between the actual current and the allowable current of the battery pack. The allowable current of the battery pack can be, for example, the permitted current or the rated current of the battery pack.

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

[0379] Using the first power mapping table, it can be determined whether the batteries in the battery pack are overcurrent. When the overcurrent level of a certain battery in the battery pack is significantly higher than that of other batteries, it can be considered whether the battery is faulty, and the cause of the overcurrent can be found in time.

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

[0381] As can be seen, the first and second power mapping tables can be used to determine the overcurrent situation of the battery pack simply and efficiently. The first power mapping table includes the allowable power values ​​of the battery at different SOCs and temperatures. If the actual power of the battery exceeds the allowable power value corresponding to the current SOC and temperature in the first power mapping table, the battery is considered to be overcurrent. The second power mapping table includes the allowable power values ​​of the battery pack at different SOCs and temperatures. If the actual power of the battery pack exceeds the allowable power value corresponding to the current SOC and temperature in the second power mapping table, the battery pack is considered to be overcurrent. Separate power mapping tables can be set for overcurrent detection during charging and discharging.

[0382] Taking a single battery cell in a battery pack as an example, assuming the current temperature of the cell is 25°C and its state of charge (SOC) is 95%, a first power value corresponding to 25°C and 95% SOC can be obtained from a first power mapping table. If the actual power value calculated based on the current and voltage of the cell is greater than the first power value, the cell is considered to be overcurrent.

[0383] If a certain number of battery cells in the battery pack experience overcurrent (this number can be one or more), the overcurrent status of the battery pack is determined according to the second power mapping table. Assuming the current temperature of the battery pack is 25°C and the state of charge (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 current current and voltage of the battery pack is greater than the second power value, the battery pack is considered to be overcurrent.

[0384] If it is determined that the battery pack has experienced overcurrent, an appropriate current limiting strategy is implemented for the battery pack based on the difference between the actual current and its allowable current.

[0385] Figure 25 illustrates one possible implementation for determining whether a battery pack is overcurrent. The method shown in Figure 25 can be executed by the battery pack's BMS. The battery pack charges or discharges with the grid based on the EMS's requirements.

[0386] As shown in Figure 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, the direction of the current, i.e. whether the current sign is positive or negative, can be used to determine whether it is charging or discharging.

[0389] If the battery pack is charging, proceed to steps 3103 to 3106; if the battery pack is discharging, proceed to steps 3107 to 3131.

[0390] In step 3103, the first power mapping table corresponding to the charging process is used to determine whether the individual battery cells in the battery pack are overcurrent.

[0391] If at least one battery cell in the battery pack experiences an overcurrent, proceed to steps 3105 and 3106; otherwise, proceed to step 3104.

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

[0393] In step 3105, it is determined whether the battery pack has experienced overcurrent based on the second power mapping table corresponding to the charging process.

[0394] If the battery pack is not overcurrent, proceed to step 3104; if the battery pack is overcurrent, proceed to step 3106.

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

[0396] In step 3107, the first power mapping table corresponding to the discharge process is used to determine whether the individual battery cells in the battery pack are overcurrent.

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

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

[0399] In step 3109, it is determined whether the battery pack has experienced overcurrent based on the second power mapping table corresponding to the discharge process.

[0400] If the battery pack is not overcurrent, proceed to step 3108; if the battery pack is overcurrent, proceed to step 3110.

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

[0402] Once it is determined that the battery pack has experienced an overcurrent, the current can be limited.

[0403] The following describes two methods for current limiting of battery packs provided in the embodiments of this application.

[0404] Method 1

[0405] The BMS determines the appropriate overcurrent level based on the overcurrent condition of the battery pack and reports it to the EMS. The EMS then determines whether to limit the current of the battery pack based on the current operating conditions. This can improve the overcurrent situation of the battery pack while ensuring that the current operating conditions are not affected.

[0406] Figure 26 illustrates an overcurrent control method 400 according to an embodiment of this application. Method 400 can be executed, for example, by an EMS and / or a BMS. Of course, where possible, the BMS can perform some of the operations performed by the EMS, and the EMS can also perform some of the operations performed by the BMS.

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

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

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

[0410] The overcurrent indication information includes the battery pack's overcurrent information, which is used to request 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 based on the overcurrent indication information.

[0413] Here, 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] This overcurrent information could be, for example, the overcurrent level or overcurrent capacity of the battery pack, which characterizes the degree of overcurrent in the battery pack.

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

[0416] The overcurrent control method of this application embodiment is described in detail below, taking the use of overcurrent information to represent the overcurrent level of a battery pack as an example. The overcurrent level can be replaced with other overcurrent information, such as overcurrent flow rate.

[0417] In some embodiments, in step 410, the BMS can determine the overcurrent level of the battery pack based on 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 extent to which the battery pack's current exceeds its allowable current. Therefore, the overcurrent rating of the battery pack can be determined based on the overcurrent ratio, which is quite intuitive. Assume the current of the battery pack is Ir, and the allowable current of the battery pack is Ia. When an overcurrent occurs, Ir > Ia. In this case, the overcurrent ratio of the battery pack is the ratio between current Ir and current Ia, i.e., Ir / Ia.

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

[0420] Multiple overcurrent levels correspond to multiple overcurrent ratios. For example, the overcurrent levels of the battery pack can be set from high to low as follows: first overcurrent level, second overcurrent level, third overcurrent level, and fourth overcurrent level. Assuming that the higher the overcurrent level, the higher its 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, second, third, and fourth overcurrent levels are x1%, x2%, x3%, and x4%, respectively. When Ir / Ia > x4%, the battery pack's overcurrent level can be considered to have reached the fourth overcurrent level; when Ir / Ia > x4%, the battery pack's overcurrent level can be considered to have reached the third overcurrent level; when Ir / Ia > x2%, the battery pack's overcurrent level can be considered to have reached the second overcurrent level; and when Ir / Ia > x1%, the battery pack's overcurrent level can be considered to have reached the first overcurrent level. Where x4 < x3 < x2 < x1.

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

[0423] Furthermore, optionally, the overcurrent level can also be determined by combining the overcurrent duration. That is, the overcurrent level of the battery pack is determined based on the overcurrent ratio and the overcurrent duration of the battery pack.

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

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

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

[0427] For example, if the overcurrent ratio of the battery pack reaches the overcurrent ratio corresponding to the fourth overcurrent level and lasts for a duration of 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 can be at least partially the same or all different. Optionally, T1 < T2, T3 < T4, and T5 < T6 can be set.

[0429] In this way, not only is the overcurrent level of the battery pack relative to the allowable current taken into account, but also the duration of the overcurrent, making the determination of the overcurrent level more in line with the actual situation.

[0430] As an example, Table 5 shows the correspondence between overcurrent levels and their corresponding overcurrent ratios. Each overcurrent level's overcurrent condition includes information such as the overcurrent ratio and overcurrent duration. The 10A in the overcurrent condition is determined based on the minimum current detection accuracy; 10A is used as an example here, but it can be replaced with other current values ​​in practical applications.

[0431] Table 5

[0432] In some embodiments, as shown in FIG27, method 400 may further include step 460.

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

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

[0435] At this point, the EMS can 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 can be set for each of the multiple overcurrent levels. The BMS can determine the desired current limiting information based on the overcurrent level of the battery pack. This 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 for the allowable current of the battery pack. The BMS can determine the target value based on an initial value of its allowable current and a current adjustment ratio corresponding to its overcurrent level. For example, the initial value can be multiplied by the current adjustment ratio to obtain the target value. The current adjustment ratio can be a pre-set ratio between the 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. When the battery pack's overcurrent level reaches the fourth level, the allowable current can be limited to the target value y4*Ia. When y4 = 1, the allowable current of the battery pack is not limited, i.e., the current adjustment ratio is 1. When the battery pack's overcurrent level reaches the third level, the allowable current can be limited to the target value y3*Ia. When the battery pack's overcurrent level reaches the second level, the allowable current can be limited to the target value y2*Ia. When the battery pack's overcurrent level reaches the first level, other risks may arise, so the allowable current can be limited to the target value y1*Ia. When y1 = 0, the current adjustment ratio is 0, and the BMS can request a high voltage, at which point the overcurrent level can be cleared. Where y1 < y2 < y3 < y4 < Ia.

[0439] By setting corresponding current adjustment ratios for different overcurrent levels, 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 and improves the effect of current limiting.

[0440] It's understandable that the target allowable current value in this current limiting information represents the allowable current value that the BMS expects the battery pack to achieve, i.e., it hopes the battery pack will reach an allowable current value that matches the current overcurrent level, thereby improving its overcurrent situation. However, whether the battery pack can actually limit its allowable 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 corresponding current limiting information, i.e., the target value. After receiving the overcurrent indication information, the EMS can determine whether to limit the current of the battery pack, i.e., whether to allow the battery pack's allowable current to be limited to the target value, 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 grid and / or the current sharing situation among multiple parallel battery packs, to determine whether to allow the battery pack to limit its allowable current, and by how much.

[0442] This application does not impose specific restrictions on how the EMS decides whether to reduce the battery pack's power. The EMS needs to consider the current actual operating conditions to determine whether to respond to the overcurrent indication information reported by the battery pack. For example, when the power demand of the grid is high, the EMS can, depending on the overcurrent level of the battery pack, choose not to limit the battery pack's allowable current, or limit the battery pack's allowable current but cannot limit it to the target value carried in the overcurrent indication information; when the power demand of the grid is low, the EMS can, depending on the overcurrent level of the battery pack, allow limiting the battery pack's allowable current, specifically, limiting the allowable current to the target value carried in the overcurrent indication information or to other current values.

[0443] Optionally, the EMS can also consider the current sharing among multiple battery packs connected in parallel. If limiting the allowable current of a battery pack can compensate for the reduced charging and discharging power of the battery pack by other battery packs connected in parallel, then the EMS can 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 connected in parallel, then the EMS may also not allow the battery pack to limit its allowable current.

[0444] It is 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 be other current limiting information determined by the EMS for the BMS, such as other current values.

[0445] If the EMS determines that it does not need to limit the current of the battery pack, it may not respond to the overcurrent indication information sent by the BMS. If the EMS determines that it needs to limit the current of the battery pack, it may optionally send a current limiting indication information, which is used to indicate that the current of the battery pack should be limited based on the corresponding current limiting information.

[0446] It is understandable that, since the current of the battery pack is typically controlled by a PCS connected between the battery pack and the grid, the EMS can send a current-limiting instruction to the BMS. Based on this instruction, the BMS controls the PCS to limit the battery pack current according to the current-limiting information corresponding to the current overcurrent level. Alternatively, the EMS can directly send the current-limiting instruction to the PCS to control it to limit the battery pack current according to the current-limiting information corresponding to the current overcurrent level. After receiving the current-limiting instruction from the BMS or EMS, the PCS limits the allowable current of the battery pack to the target value or another current value allowed by the EMS.

[0447] For example, as shown in Figure 26, in step 450, the EMS sends a flow limiting indication message.

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

[0449] In some embodiments, as shown in FIG27, method 400 further includes steps 470 and 480.

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

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

[0452] For example, if the battery pack reaches the overcurrent cancellation condition, the BMS can instruct the PCS to restore the battery pack's allowable current to its initial value.

[0453] In this way, if the current of the battery pack meets the overcurrent cancellation condition, the allowable current of the battery pack can be restored, allowing the battery pack to resume normal charging and discharging.

[0454] Optionally, the overcurrent cancellation condition includes: the battery pack current Ir is less than or equal to the initial value of the allowable current Ia; or, the battery pack current Ir is less than or equal to the initial value Ia and the difference between it 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 < Ia and this condition persists for a certain duration, 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 duration; then, in step 470, the BMS determines whether the battery pack has reached the overcurrent cancellation condition after the predetermined duration.

[0457] In other words, the BMS can continuously send overcurrent indication information to the EMS for a predetermined period of time, and determine whether the overcurrent cancellation condition has been met after the predetermined period of time. 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 limiting the battery pack's allowable current, it can control the PCS to limit the battery pack's allowable current by sending a current-limiting indication message to the BMS or to the PCS connected between the battery pack and the grid, thereby reducing the battery pack's charging and discharging power. However, even if the allowable current is limited, the battery pack's overcurrent situation may not improve significantly. The BMS still needs to monitor its current in real time to determine if 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 it meets the overcurrent cancellation condition and restores its allowable current. If the battery pack consistently fails to meet the overcurrent cancellation condition, the battery pack will be powered down after its overcurrent level rises to the highest 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 degree of overcurrent, thereby improving the overcurrent situation of the battery pack.

[0461] Figure 28 illustrates another overcurrent control method 500 according to an embodiment of this application. Method 500 may be executed by a BMS, for example. As shown in Figure 28, method 500 includes some or all of the following steps.

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

[0463] The overcurrent includes the current difference and / or current ratio between the battery pack's current and its allowable current. Assuming the current of the battery pack is Ir and its allowable current is Ia, the overcurrent 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 this application embodiment can be, for example, an electrical box, an electrical cabinet, or a container, or other parallel units connected to the power grid in parallel via PCS. These parallel units can all be overcurrent controlled by the method 500 in this application embodiment to improve their overcurrent situation.

[0466] Typically, for multiple battery packs connected in parallel to the grid, if one or more of these packs experience overcurrent, the allowable current of all parallel battery packs will be limited. This reduces the current of battery packs that are not experiencing overcurrent, thus affecting the charging and discharging process of the entire system. However, this embodiment of the application performs overcurrent control on a single battery pack, adjusting its allowable current based on the overcurrent of that battery pack. This does not affect the current of other battery packs connected in parallel, reducing the impact on the charging and discharging process of the entire system. Furthermore, because the adjustment of the allowable current is adapted to the overcurrent of that battery pack, the impact on the charging and discharging process of that battery pack itself is further reduced, achieving adaptive current reduction for a single battery pack.

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

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

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

[0470] Assume 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 ratio between the actual current and the allowable current of the battery pack are |Ir-Ia| or Ir / Ia, respectively. Specifically, if |Ir-Ia| is greater than or equal to a first threshold (e.g., |Ir-Ia| ≥ 1A), and Ir / Ia is greater than or equal to a second threshold (e.g., Ir / Ia ≥ 105%), the BMS adjusts the allowable current of the battery pack according to the overcurrent.

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

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

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

[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 current corresponding to the multiple parallel branches is multiplied by the number of parallel branches N to obtain the first product. The overcurrent of a single branch, such as the current difference D, is multiplied by a preset coefficient to obtain the 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 The adjusted allowable current value of the battery pack is calculated using *ND*k) / N, where Ia' is the adjusted allowable current value of the battery pack, I minIt 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, where 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] It can be seen that the larger D is, the smaller Ia' is. In other words, the larger the overcurrent, the smaller the allowable current value needs to be adjusted. Since the adjustment of the allowable current is adapted to the overcurrent of the battery pack, the impact on the charging and discharging process of the battery pack is further reduced, and adaptive current reduction of the individual battery pack is achieved.

[0477] Since the adjusted allowable current value Ia' for a battery pack is calculated based on the current difference D between the actual current and the allowable current of a single battery pack, 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, thus reducing the impact on the charging and discharging process of the entire system.

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

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

[0480] The preset value can be set according to the actual operating 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] In this embodiment, the BMS adjusts the allowable current of the battery pack, for example, by controlling the PCS to adjust the allowable current of the battery pack. When current limiting is required, the BMS can instruct the PCS to adjust the allowable current of the battery pack from the initial value Ia to Ia', where Ia' < Ia; when the battery pack reaches the overcurrent cancellation condition, the BMS can instruct the PCS to restore the allowable current of the battery pack to the initial value Ia.

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

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

[0484] For example, the excess flow rate is the current difference |Ir-Ia| between the actual current Ir of the battery pack and the allowable 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] Specifically, if |Ir-Ia|≥1A and Ir / Ia≥105%, steps 5103 and 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 met the 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, then step 5105 is executed; if the overcurrent cancellation condition is still not met, then 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, tests are conducted on actual battery packs, for example, on 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.

[0494] Table 6 shows the actual current Ir and allowable current Ia of each battery pack. The actual current and allowable current of battery pack 1 are -141.4 and -132.7, respectively; the actual current and allowable current of battery pack 2 are -141.5 and -132.4, respectively; the actual current and allowable current of battery pack 3 are -141.0 and -132.3, respectively; the actual current and allowable current of battery pack 4 are -141.9 and -132.6, respectively; and the actual current and allowable current of battery pack 5 are -142.0 and -132.2, respectively.

[0495] Table 6

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

[0497] The current difference between the actual current and the allowable current of battery pack 1 is |(-141.4)-(-132.7)|=8.7>1A, and the actual current exceeds 105% of the allowable current value, that is, |-141.4|>|(-132.7)*105%|=|-139.9|. Therefore, the allowable 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 allowable current of battery pack 2 is |(-141.5)-(-132.4)|=9.1>1A, and the actual current exceeds 105% of the allowable current value, that is, |-141.5|>|(-132.4)*105%|=|-139.0|. Therefore, the allowable 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 allowable current of battery pack 3 is |(-141.0)-(-132.3)|=8.7>1A, and the actual current exceeds 105% of the allowable current value, that is, |-141.0|>|(-132.3)*105%|=|-138.9|. Therefore, the allowable 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 allowable current of battery pack 4 is |(-141.9)-(-132.6)|=9.3>1A, and the actual current exceeds 105% of the allowable current value, that is, |-141.9|>|(-132.6)*105%|=|-139.2|. Therefore, the allowable 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 allowable current of battery pack 5 is |(-142.0)-(-132.2)|=9.8>1A, and the actual current exceeds 105% of the allowable current value, that is, |-142.0|>|(-132.2)*105%|=|-138.8|. Therefore, the allowable current of battery pack 5 can be adjusted to [(-132.2)*5-(-9.8)*1] / 20=-130.2.

[0502] Table 7

[0503] Based on the adjusted allowable current value Ia' shown in Table 7, current limiting of the battery pack yields the results shown in Table 8. Table 8 shows the actual current Ir of the battery pack after current limiting and the overcurrent cancellation condition, taking the overcurrent cancellation condition of Ir≤Ia-10A as an example.

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

[0505] Table 8

[0506] As can be seen from Tables 6 to 8, the overcurrent control scheme adopted in the embodiments of this application can effectively improve the overcurrent situation of the battery pack.

[0507] It is understandable 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 experiencing overcurrent. This allows the EMS to adjust the power allocated to each branch of the battery pack based on the current operating conditions, such as the power demand of the power grid, the current sharing among multiple battery packs, and the degree of overcurrent of the battery pack, thereby covering up the overcurrent situation of the battery pack.

[0508] The overcurrent control methods described in Methods 1 and 2 above can improve the overcurrent situation of battery packs when uneven current distribution among multiple parallel battery packs causes overcurrent.

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

[0510] Figure 30 illustrates a temperature control method 600 according to an embodiment of this application. Method 600 can be executed by a BMS or other control modules. As shown in Figure 30, method 600 includes some or all of the following steps.

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

[0512] In step 620, the 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, when the aforementioned battery pack is a cabinet or battery cluster, the battery system may include at least one cabinet or battery cluster; when 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, Figure 31 shows a one-to-two architecture, where each PCS connects 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 shows an example of two battery systems in parallel in container A, with the first and second battery systems connected in parallel. The first battery system includes five parallel battery clusters, designated as clusters 1 to 5; the second battery system includes five parallel battery clusters, designated as clusters 6 to 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 this application can be liquid cooling components, such as water-cooled units. Compared with air-cooled components, liquid cooling components provide more uniform temperature control, making it easier to keep the battery system at a suitable temperature, which is beneficial to improving the lifespan of battery products.

[0518] Based on the architecture shown in Figure 31, taking the first and second thermal management components as water-cooled units as examples, as shown in Figure 32, each water-cooled unit includes 5 water pumps, each water pump corresponds to one water-cooled pipe, and each water-cooled pipe connects to the corresponding battery cluster shown in Figure 31. Each battery cluster has independent inlet and outlet pipes. The 5 water pumps in the first water-cooled unit are connected to water-cooled pipes R1#, R2#, R3#, R4#, and R5#, respectively. Water-cooled pipes R1#, R2#, R3#, R4#, and R5# are connected to battery clusters 1, 2, 3, 4, and 5 shown in Figure 31, respectively. The 5 water pumps in the second water-cooled unit are connected to water-cooled pipes R6#, R7#, R8#, R9#, and R10#, respectively. Water-cooled pipes R6#, R7#, R8#, R9#, and R10# are connected to battery clusters 6, 7, 8, 9, and 10 shown in Figure 31, respectively. Each water chiller also includes a temperature management system (TMS) to control the operating mode of the five water-cooled pipes in the chiller.

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

[0520] Optionally, in step 610, in addition to acquiring the temperatures of the first battery system and the second battery system, the highest and / or lowest temperatures of multiple battery clusters in the first battery system can also be acquired. The highest and / or lowest temperatures of the multiple battery clusters in the first battery system can, for example, be used to determine whether there are any battery clusters in the first battery system with outlier temperatures, and thus determine whether the temperature change of the first battery system is caused by such a battery cluster, thereby better controlling the temperature of the first battery system.

[0521] Similarly, in step 610, in addition to acquiring the temperature of the second battery system, the highest and / or lowest temperatures of multiple battery clusters in the second battery system can also be acquired. The highest and / or lowest temperatures of the multiple battery clusters in the second battery system can, for example, be used to determine whether there are any battery clusters with outlier temperatures in the second battery system, and thus determine whether the temperature change of the second battery system is caused by that battery cluster, thereby better controlling the temperature of the second battery system.

[0522] The operating modes of the first and second thermal management components include, for example, cooling mode, heating mode, self-circulation mode, or a shutdown mode. Cooling mode is used to lower the battery system temperature, heating mode is used to raise the battery system temperature, and self-circulation mode can also be considered a heat preservation mode or a self-heating mode. Switching between different modes requires a transition; for example, switching from heating mode to cooling mode requires switching from heating mode to self-circulation mode and then back to cooling mode, and vice versa.

[0523] The first battery system and the second battery system can be any two battery systems from multiple battery systems connected to the PCS, such as two battery systems connected in parallel among the multiple battery systems. The two battery systems can be arranged adjacently or not adjacently. 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, the method 600 in this embodiment can solve the problem of temperature consistency of the battery system caused by different thermal management components.

[0524] Based on the temperature difference between the first and second battery systems, the BMS determines the operating modes of the first and second thermal management components. These components then control the temperatures of the first and second battery systems respectively, improving temperature consistency and resolving imbalances in impedance and current caused by poor temperature consistency. This reduces the probability of premature charging or discharging of high-current battery systems, thereby improving the RTE (Recovery Time Efficiency) of the battery product.

[0525] In some embodiments, in step 620, if 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] In other words, it can be determined 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 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] When the first thermal management component and the second thermal management component have the same initial operating mode, it indicates that the temperature difference between the first battery system and the second battery system is not significant. Therefore, optionally, the operating modes of the first thermal management component and the second thermal management component do not need to be adjusted; the first thermal management component and the second thermal management component can simply 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; similarly, 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 individual battery cells within that cluster, for example, by taking the average temperature of the multiple individual battery cells in the cluster as the temperature of the cluster.

[0529] Here, the initial operating mode of the first thermal management component and the second thermal management component is the operating mode used before adjusting to the target operating mode. 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 further determined whether the initial operating mode needs to be adjusted based on the temperature of the first battery system and the temperature of the second battery system.

[0530] In some embodiments, in step 620, the target operating mode of the first thermal management component and / or the second thermal management component can be determined based on the 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 can 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 can be determined.

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

[0533] Taking the first and second battery systems shown in Figures 31 and 32 as examples, assuming that the temperatures of battery clusters 1, 2, 3, 4, and 5 in the first battery system are T1, T2, T3, T4, and T5 respectively, and the temperatures of battery clusters 6, 7, 8, 9, and 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, where T is the average temperature of multiple battery clusters in the second battery system. B = (T6+T7+T8+T9+T10) / 20, the temperature difference ΔT between the first battery system and the second battery system is |T A -T B Where 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 cooling mode or self-circulation mode, and / or the operating mode of the thermal management component of the low-temperature battery system can be adjusted to heating mode or self-circulation mode.

[0534] The temperature of a battery system is related to its state; therefore, the current state of the battery system can also be considered when determining the target operating mode of the first thermal management component and / or the second thermal management component. The state of the battery system includes, for example, a resting state and a charge / discharge state, wherein the charge / discharge state includes a charging state and a discharging state.

[0535] In some embodiments, in step 620, if 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 states of the first battery system and the second battery system.

[0536] In one scenario, where the first and second battery systems are in a static state, the target operating mode of the thermal management component of the battery system with the higher temperature in the first and second battery systems can be determined to be the cooling mode.

[0537] Specifically, in most cases, the thermal management component operates in self-circulation mode when stationary. Self-circulation mode often results in high-temperature outliers. Since it is easy to keep the battery system warm when stationary, and heat dissipation can only rely on the cooling of the thermal management component, the target operating mode of the thermal management component of the higher-temperature battery system in the first and second battery systems can be adjusted to cooling mode to reduce the temperature of the higher-temperature battery system as quickly as possible.

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

[0539] It is understandable that, since not all thermal management components in a static state are in static mode, it is still necessary to add the above steps, namely, to determine whether to adjust the operating mode of the first thermal management component and / or the second thermal management component based on whether the initial operating 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 static state. Assume that the temperature difference ΔT between the temperatures of the first battery system and the second battery system is greater than a first temperature threshold, and the temperature T of the first battery system is... A Temperature T below the second battery system B That is, T A <T B Therefore, the target operating mode of the second thermal management component can be selected as the cooling mode, so that it continuously forces the second battery system to cool down.

[0541] Of course, when the first and second battery systems are in a quiescent state, the target operating modes of the first thermal management component and / or the second thermal management component can be adjusted to other operating modes that can reduce the temperature difference between the first and second battery systems. For example, the target operating mode of the thermal management component of the lower-temperature battery system can be adjusted to a heating mode; or, simultaneously, the target operating mode of the thermal management component of the higher-temperature battery system can be adjusted to a cooling mode, and the target operating mode of the thermal management component of the lower-temperature battery system can be adjusted to a heating mode, in order to reduce the temperature difference between the two battery systems more quickly. However, since most battery systems in a quiescent state rely on the thermal management components for cooling, adjusting the operating mode of the thermal management component of the higher-temperature battery system to a cooling mode for continuous 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 practical applications.

[0542] In another scenario, where the first and second battery systems are in a charging / discharging state, it can be determined that the thermal management components of the battery system with the lower temperature in the first and second battery systems will stop working.

[0543] Specifically, when the first battery system and the second battery system are in a charging and discharging state, the battery system itself will also heat up. Therefore, the thermal management component of the lower-temperature battery system in 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 lower-temperature battery system to instruct the TMS to be turned off, so that the lower-temperature battery system can increase its own temperature through the charging and discharging process.

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

[0545] For example, the first battery system and the second battery system are in a charging and discharging state. Assume that the temperature difference ΔT between the temperatures of the first battery system and the second battery system is greater than a first temperature threshold, and the temperature T of the first battery system is... A Temperature T below the second battery system B That is, T A <T B Therefore, the first thermal management component can be turned off, allowing the first battery system to raise its own temperature through the charging and discharging process.

[0546] Of course, when the first and second battery systems are in a charging / discharging state, the target operating mode of the first thermal management component and / or the second thermal management component can be adjusted to other operating modes that can reduce the temperature difference between the first and second battery systems. For example, the target operating mode of the thermal management component of the battery system with the higher temperature in the first and second battery systems can be adjusted to a cooling mode; or, simultaneously, the thermal management components of the battery system with the lower temperature in the first and second battery systems can be adjusted to be off, and the target operating mode of the thermal management component of the battery system with the higher temperature can be adjusted to a cooling mode, so as to reduce the temperature difference between the two battery systems more quickly. However, since the battery system with the lower temperature in the charging / discharging state can achieve self-heating through the charging / discharging 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 practical application conditions.

[0547] In some embodiments, if 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, the first thermal management component and the second thermal management component are determined to be adjusted to the same operating mode to maintain temperature consistency.

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

[0549] Figure 33 shows a flowchart of one possible specific implementation of method 600. As shown in Figure 33, the process can be executed by BMS and TMS. It can be understood that TMS1 of the first thermal management component and TMS2 of the second thermal management component can both refer to the steps executed by TMS as shown in Figure 33.

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

[0551] If the BMS self-test confirms that it is normal, then proceed to step 6003.

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

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

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

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

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

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

[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 acquires the temperatures of multiple battery clusters in the first battery system and the temperatures of multiple battery clusters in the second battery system.

[0561] In addition, the BMS can also obtain the highest and / or lowest temperatures of multiple individual cells in each battery cluster.

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

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

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

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

[0566] If TMS1 and TMS2 have the same operating mode, proceed to step 6011; if TMS1 and TMS2 have different operating modes, proceed to step 6012.

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

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

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

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

[0571] In step 6014, the BMS determines whether the battery system is in a resting state or a charging / discharging state.

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

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

[0574] In step 6016, it is determined that the thermal management components of the battery system with low temperature stop working.

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

[0576] It is evident that by adjusting the operating modes of the first thermal management component and the second thermal management component according to the temperature relationship between the first battery system and the second battery system, the temperature consistency between the first battery system and the second battery system can be effectively improved.

[0577] The above describes in detail the non-uniform flow control method of the embodiments of this application, including, for example, the DCR control method, the non-uniform flow judgment method, the overcurrent judgment method, the current limiting method, etc. The non-uniform flow control device of the embodiments of this application is described in detail below with reference to FIG34 and FIG35. The technical features described in the method embodiments are applicable to the following device embodiments.

[0578] Figure 34 is a schematic block diagram of a non-uniform flow control device according to an embodiment of this application. As shown in Figure 34, 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; the processing module 720 is used to determine whether there is uneven current distribution among the multiple battery packs based on the DC resistance of the multiple battery packs.

[0580] In some embodiments, the detection module 710 is specifically used to: acquire a set of state parameters of the battery pack, the set of state parameters including at least two state parameters of the battery pack; determine a first DC resistance of the battery pack based on the set of state parameters of the battery pack and the correspondence between a plurality of preset state parameter sets and a plurality of DC resistances; and determine a second DC resistance of the battery pack based on the first DC resistance of the battery pack.

[0581] In some embodiments, 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 charging and discharging direction of the battery pack, the charging and discharging time of the battery pack, and the health status of the battery pack.

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

[0583] In some embodiments, the detection module 710 is further configured to acquire a set of state parameters 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 set of state parameters of the battery pack at the target time and the corresponding relationship.

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

[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 information of the voltage and / or the current 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 acquire the state of charge of the battery pack; and determine the open-circuit voltage of the battery pack based on the state of charge of the battery pack and the preset correspondence between the open-circuit voltage and the state of charge.

[0587] In some embodiments, the detection module 710 is specifically configured 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 configured to control the PCS connected to the battery pack to charge and discharge the battery pack; acquire information on the voltage and current of the battery pack during the charging and discharging process; and determine the target DC resistance of the battery pack based on the current of the battery pack and the amount of change in the voltage of the battery pack within a target duration.

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

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

[0591] In some embodiments, the processing module 720 is further configured to acquire the temperature of the first battery system and the temperature of the second battery system in the plurality of battery systems; and 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, wherein 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 is overcurrent; and in the case of overcurrent in the battery pack, to limit the current of the battery pack according to the degree of overcurrent in the battery pack.

[0593] In some embodiments, the processing module 720 is specifically configured to determine the overcurrent of the battery pack, the overcurrent including the current difference and / or current ratio between the current of the battery pack and its allowable current; and adjust the allowable current of the battery pack according to the overcurrent.

[0594] In some embodiments, the processing module 720 is specifically configured to adjust 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.

[0595] In some embodiments, the processing module 720 is specifically configured to: calculate the allowable current value of the battery pack with the smallest allowable current among the N parallel battery packs, and multiply it by N, wherein the N battery packs include the battery packs 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 that the adjusted allowable current of the battery pack is equal to the ratio between the difference and N.

[0596] In some embodiments, the processing module 720 is specifically configured to: determine the overcurrent information of the battery pack; send overcurrent indication information to the energy management system, the overcurrent indication information including the overcurrent information, the overcurrent indication information being 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 represent the overcurrent level of the battery pack. 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 of the battery pack and the overcurrent duration; wherein the overcurrent ratio is the ratio between the current of the battery pack and its allowable current.

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

[0599] In some embodiments, the processing module 720 is specifically configured to determine 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.

[0600] In some embodiments, the processing module 720 is further configured to determine whether a plurality of batteries in the battery pack are overcurrent; and if at least one of the plurality of batteries is overcurrent, determine whether the battery pack is overcurrent.

[0601] In some embodiments, the control device 700 further includes a control module for determining a target battery pack for charging and discharging with the power grid based on the power demand of the power grid; and for 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.

[0602] In some embodiments, the control module is specifically configured 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, wherein 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 a power cabinet, or the battery pack is a container, wherein the container includes a plurality of power cabinets connected in series and / or in parallel, the battery cluster or the power cabinet includes a plurality of power boxes connected in series and / or in parallel, and the power box includes a plurality of battery cells connected in series and / or in parallel.

[0604] It should be understood that the specific method by which the control device 700 performs temperature control and the beneficial effects thereof can be found in the relevant descriptions in the method embodiments, and will not be repeated here for the sake of simplicity.

[0605] This application also provides a computer-readable storage medium for storing a computer program that, when executed by a computing device, causes the computing device to implement the temperature control method 600 described in any of the above embodiments. Optionally, the computer program may be a computer program in a BMS.

[0606] This application embodiment also provides a non-uniform 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 this 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] Optionally, as shown in Figure 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, it may send information, data, or instructions to other devices, or receive information, data, or instructions sent by other devices.

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

[0609] It should be understood that the processor in the embodiments of this application may be an integrated circuit chip with signal processing capabilities. In implementation, the steps of the above method embodiments can be completed by integrated logic circuits in the processor's hardware or by instructions in software form. The processor described above can 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 devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. A general-purpose processor can be a microprocessor or any conventional processor, etc. The steps of the methods disclosed in the embodiments of this application can be directly embodied as being executed by a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor. The software modules can be located in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. This storage medium is located in memory, and the processor reads information from the memory and, in conjunction with its hardware, completes the steps of the above method.

[0610] It is understood that the memory in the embodiments of this application can be volatile memory or non-volatile memory, or a combination of both. The non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. The volatile memory can be random access memory (RAM), which is used as an external cache. By way of example, but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous linked dynamic random access memory (SLDRAM), and direct rambus RAM (DR RAM). It should be noted that the memory used in 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, without conflict, the various embodiments and / or technical features described in this application can be arbitrarily combined with each other, and the resulting technical solutions should also fall within the protection scope of this application.

[0612] In the embodiments of this application, the order of the steps does not imply the order of execution. The execution order 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 this application.

[0613] Those skilled in the art will recognize that the units and algorithm steps of the various examples 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 implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art 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, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0615] The units described as separate components may or may not be physically separate. 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 can be selected to achieve the purpose of the embodiments of this application, depending on actual needs.

[0616] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

A method for controlling uneven flow, characterized in that, The control method includes: acquiring the DC resistance of the battery pack; and determining whether there is uneven current distribution among the multiple battery packs based on their DC resistances. The control method according to claim 1 is characterized in that, The step of obtaining the DC resistance of the battery pack includes: obtaining a set of state parameters of the battery pack, the set of state parameters including at least two state parameters of the battery pack; determining a first DC resistance of the battery pack based on the set of state parameters of the battery pack and a preset correspondence between multiple sets of state parameters and multiple DC resistances; and determining a second DC resistance of the battery pack based on the first DC resistance of the battery pack. The control method according to claim 2 is characterized in that, 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 charging and discharging direction of the battery pack, the charging and discharging time of the battery pack, and the health status of the battery pack. The control method according to claim 2 or 3 is characterized in that, Determining the second DC resistance of the battery pack based on 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. The control method according to any one of claims 2 to 4 is characterized in that, The method further includes: obtaining a set of state parameters of the battery pack at a target time after the current time; and determining the DC resistance of the battery pack at the target time based on the set of state parameters of the battery pack at the target time and the corresponding relationship. The control method according to claim 1 is characterized in that, The step of obtaining the DC resistance of the battery pack includes: obtaining information on the voltage and / or current of the battery pack; and determining the DC resistance of the battery pack based on the voltage and / or current information. The control method according to claim 6 is characterized in that, The step of obtaining the voltage and / or current information of the battery pack includes: obtaining the open-circuit voltage of the battery pack; the step of 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. The control method according to claim 7 is characterized in that, The step of 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 based on the state of charge of the battery pack and a preset correspondence between the open-circuit voltage and the state of charge. The control method according to claim 7 or 8 is characterized in that, Determining the DC resistance of the battery pack based on the open-circuit voltage, 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 between the voltage difference and the current of the battery pack; and determining the ratio as the DC resistance of the battery pack. The control method according to claim 6 is characterized in that, The step of acquiring the voltage and / or current information of the battery pack includes: controlling the PCS connected to the battery pack to charge and discharge the battery pack; acquiring the voltage and current information of the battery pack during the charging and discharging process; and determining the DC resistance of the battery pack based on the voltage and / or current information includes: determining 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 a target time period. The control method according to claim 10 is characterized in that, Determining 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 duration includes: determining the target DC resistance of the battery pack as the ratio between the change in the voltage of the battery pack and the current of the battery pack within the target duration. The control method according to any one of claims 1 to 11 is characterized in that, The step of determining whether there is uneven current distribution among the multiple battery packs based on the difference in DC resistance among the multiple battery packs includes: determining uneven current distribution among the multiple battery packs when the ratio between the DC resistance of the first battery pack and the DC resistance of the second battery pack is greater than a preset DC resistance threshold, wherein 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. The control method according to any one of claims 1 to 12 is characterized in that, The control method further includes: determining whether the battery pack is overcurrent; and, if the battery pack is overcurrent, limiting the current of the battery pack according to the degree of overcurrent. The control method according to claim 13 is characterized in that, The current limiting of the battery pack includes: determining the overcurrent of the battery pack, the overcurrent including the current difference and / or current ratio between the current of the battery pack and its allowable current; and adjusting the allowable current of the battery pack according to the overcurrent. The control method according to claim 14 is characterized in that, The step of adjusting the allowable current of the battery pack according to the overflow 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. The control method according to claim 15 is characterized in that, The adjustment of the allowable current of the battery pack includes: calculating the allowable current value of the battery pack with the smallest allowable current among the N parallel battery packs, and multiplying it by 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; and determining that the adjusted allowable current of the battery pack is equal to the ratio between the difference and N. The control method according to any one of claims 13 to 16 is characterized in that, 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, wherein 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. The control method according to claim 17 is characterized in that, 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 based on the overcurrent ratio of the battery pack; or, determining the overcurrent level based on the overcurrent ratio of the battery pack and the overcurrent duration; wherein the overcurrent ratio is the ratio between the current of the battery pack and its allowable current. The control method according to claim 18 is characterized in that, The current limiting of the battery pack includes: determining current limiting information corresponding to the overcurrent level based on the overcurrent level, wherein the overcurrent indication information further includes current limiting information corresponding to the overcurrent level. The control method according to claim 19 is characterized in that, The current limiting information includes the target value of the allowable current of the battery pack. Determining the current limiting information corresponding to the overcurrent level according to 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. The control method according to any one of claims 13 to 20 is characterized in that, 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 if at least one of the multiple batteries is overcurrent. The control method according to any one of claims 1 to 21 is characterized in that, The control method further includes: determining a target battery pack for charging and discharging with the power grid based on the power grid's demand; 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. The control method according to claim 22 is characterized in that, The step of determining the target battery pack for charging and discharging with the power grid based on the power grid's demand includes: determining that the target battery pack includes all or part of multiple battery packs, wherein the multiple battery packs are connected in parallel to the power grid through multiple power control systems. The control method according to any one of claims 1 to 23 is characterized in that, The control method further includes: acquiring the temperature of a first battery system and the temperature of a second battery system in a plurality of battery systems, wherein the first battery system includes at least one battery cluster and the second battery system includes at least one battery cluster; 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, wherein 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. The control method according to any one of claims 1 to 24 is characterized in that, The battery pack is a battery cluster or a power cabinet, or the battery pack is a container, wherein the container includes multiple power cabinets connected in series and / or in parallel, the battery cluster or the power cabinet includes multiple power boxes connected in series and / or in parallel, and the power box includes multiple battery cells connected in series and / or in parallel. A control device for uneven flow, characterized in that, The control device includes: a detection module for acquiring the DC resistance of the battery pack; and a processing module for determining whether there is uneven current distribution among the multiple battery packs based on their DC resistances. A control device for uneven flow, characterized in that, It includes a processor and a memory, the memory being used to store instructions, and the processor being used to execute the instructions to implement the non-uniform flow control method according to any one of claims 1 to 25. An energy storage system, characterized in that, include: Multiple battery packs, wherein the multiple battery packs are connected in parallel; And the non-uniform flow control device as described in claim 27.

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