Current distribution method and device for parallel batteries in energy storage system and storage medium

Abstract

The invention relates to a current distribution method and device for parallel batteries in an energy storage system and a storage medium, and belongs to the technical field of energy storage systems, and the method comprises the steps: obtaining at least two battery parameters of each battery module in a plurality of battery modules; determining a sub-weight of each battery parameter based on each battery parameter of each battery module; determining a weighting coefficient of the sub-weight of each battery parameter of each battery module; based on the sub-weight of each battery parameter of each battery module and the weighting coefficient of the sub-weight of each battery parameter, determining the current distribution weight of the battery module; dividing the current total load demand current according to the current distribution weight of each battery module to obtain a target output current corresponding to each battery module; controlling the battery module to supply power to the load according to the target output current; the service life of the energy storage system can be prolonged, the reliability of current distribution is enhanced, and the problems of low precision and poor reliability of a traditional current balancing method can be solved.

Description

TECHNICAL FIELD

[0001] The application relates to a current distribution method, device and storage medium for parallel batteries in an energy storage system, and belongs to the technical field of energy storage systems. BACKGROUND

[0002] An energy storage system is used to store and release electric energy. With the increasing demand for energy storage, the energy storage system needs to be expanded by connecting multiple battery modules in parallel. Each battery module includes at least one battery cell. However, due to differences in characteristics (such as capacity, internal resistance, aging degree, etc.) between different battery cells or between different battery modules, uneven current distribution may occur when the battery modules are connected in parallel. Uneven current distribution can cause circulating current in the energy storage system, local overheating, reduce energy storage efficiency, shorten battery life, and affect the safety of the energy storage system.

[0003] Currently, the current distribution method for parallel batteries in an energy storage system includes: by simulating the droop characteristics of a traditional power grid, each battery module adjusts its output power according to the deviation of its output voltage from the voltage of the common bus (or the locally measured output current). Each battery module sets different virtual impedance (usually represented by the voltage-current droop coefficient) to achieve current sharing.

[0004] However, when adjusting the output power based on the voltage-current droop characteristics, the dynamic response is slow and the current sharing accuracy is limited. SUMMARY

[0005] The application provides a current distribution method, device and storage medium for parallel batteries in an energy storage system, which can solve the problems of low accuracy and poor reliability of traditional current balancing methods. The application provides the following technical solutions: In a first aspect, a current distribution method for parallel batteries in an energy storage system is provided, the energy storage system including a plurality of battery modules connected in parallel, the method comprising: obtaining at least two battery parameters of each battery module in the plurality of battery modules; determining a sub-weight of each battery parameter based on each battery parameter of each battery module; determining a weighting coefficient of the sub-weight of each battery parameter of each battery module; determining a current distribution weight of the battery module based on the sub-weight of each battery parameter of each battery module and the weighting coefficient of the sub-weight of each battery parameter; wherein the weighting coefficient is used to indicate the importance of the sub-weight of the corresponding battery parameter in determining the current distribution weight; dividing the current distribution weight of each battery module into the current demand of the total load to obtain the target output current corresponding to each battery module; control the battery modules to supply power to the load according to the target output current.

[0006] Optionally, the at least two battery parameters include an actual available capacity and a state of health (SOH); correspondingly, The determining of the weighting coefficients of each battery parameter of each battery module includes: determining a capacity utilization rate of each battery module, the capacity utilization rate being used to indicate a ratio of the actual available capacity to a rated capacity of each battery module; determining the weighting coefficient of the actual available capacity and the weighting coefficient of the SOH based on the capacity utilization rate and a total proportion of the weighting coefficients of the actual available capacity and the SOH.

[0007] Optionally, the determining of the capacity utilization rate of each battery module includes: obtaining a state of charge (SOC) of each battery module; determining a product of the SOC and the SOH of each battery module to obtain the capacity utilization rate.

[0008] Optionally, the at least two battery parameters further include a temperature factor and an internal resistance factor; the temperature factor and the internal resistance factor respectively correspond to preset weighting coefficients, and the total proportion of the weighting coefficients is 1 minus the weighting coefficients respectively corresponding to the temperature factor and the internal resistance factor.

[0009] Optionally, the obtaining of the at least two battery parameters of each battery module in the plurality of battery modules includes: in a case where the energy storage system is in a charging state, determining a product of the rated capacity, the SOH and the difference between 1 and the SOC of each battery module to obtain the actual available capacity; or, in a case where the energy storage system is in a discharging state, determining a product of the rated capacity, the SOH and the SOC of each battery module to obtain the actual available capacity.

[0010] Optionally, the obtaining of the at least two battery parameters of each battery module in the plurality of battery modules includes: obtaining a battery temperature of each battery module; determining a temperature factor of each battery module based on a mapping relationship between the battery temperature and the temperature factor.

[0011] Optionally, the mapping relationship includes: in a case where the battery temperature is greater than a first temperature threshold and less than a second temperature threshold, the temperature factor corresponding to the battery temperature is 0; wherein the first temperature threshold is greater than the second temperature threshold; In a case that the battery temperature is less than or equal to a first temperature threshold, greater than or equal to a second temperature threshold, and not equal to a preset standard temperature, a temperature factor corresponding to the battery temperature is negatively correlated with a difference between the battery temperature and the standard temperature. In a case that the battery temperature is equal to the standard temperature, the temperature factor corresponding to the battery temperature is 1.

[0012] Optionally, the obtaining of the at least two battery parameters of each battery module in the plurality of battery modules comprises: obtaining a battery internal resistance of each battery module; determining an internal resistance factor of each battery module based on the battery internal resistance; the internal resistance factor is negatively correlated with the battery internal resistance.

[0013] Optionally, the determining of the sub-weight of each battery parameter based on each battery parameter of each battery module comprises: determining a sum of the battery parameter of each battery module for each battery parameter; determining a ratio of the battery parameter of each battery module to the sum of the battery parameter, to obtain the sub-weight of the battery parameter of each battery module.

[0014] Optionally, the controlling of the battery module to supply power to the load according to the target output current further comprises: obtaining an actual output current of each battery module; determining whether a difference between the actual output current and the target output current exceeds a preset error range; in a case that the difference exceeds the preset error range, triggering the step of obtaining the at least two battery parameters of each battery module in the plurality of battery modules and the steps thereafter.

[0015] In a second aspect, a current distribution device for parallel-connected batteries in an energy storage system is provided, the device comprising a processor and a memory; the memory stores a program which is loaded and executed by the processor to implement the current distribution method for parallel-connected batteries in an energy storage system according to the first aspect.

[0016] In a third aspect, a computer-readable storage medium is provided, the storage medium stores a program which is loaded and executed by the processor to implement the current distribution method for parallel-connected batteries in an energy storage system according to the first aspect.

[0017] The beneficial effects of the present application are: by acquiring at least two battery parameters of each battery module in a plurality of battery modules; determining a sub-weight of each battery parameter based on each battery parameter of each battery module; determining a weighting coefficient of the sub-weight of each battery parameter of each battery module; determining a current distribution weight of the battery module based on the sub-weight of each battery parameter of each battery module and the weighting coefficient of the sub-weight of each battery parameter; wherein the weighting coefficient is used to indicate the importance of the sub-weight of the corresponding battery parameter to the determination of the current distribution weight; dividing the current total load demand according to the current distribution weight of each battery module to obtain a target output current corresponding to each battery module; controlling the battery module to supply power to the load according to the target output current; can make the battery module with better state (such as high remaining capacity and low aging degree) bear more output current, and the battery module with poor state (such as low remaining capacity and high aging degree) bear less output current, delay the overall aging speed of the battery module, prolong the service life of the energy storage system, enhance the reliability of current distribution, and solve the problems of low precision and poor reliability of the traditional current equalization method. At the same time, only the calculation based on the battery parameters is needed to realize the current distribution, and the output power based on the voltage-current droop characteristic is not needed, which can improve the response speed.

[0018] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, and can be implemented according to the content of the description, the following is a preferred embodiment of the present application and the detailed description of the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a structure diagram of a current distribution system of parallel batteries in an energy storage system provided by an embodiment of the present application; Figure 2 is a flow chart of a current distribution method of parallel batteries in an energy storage system provided by an embodiment of the present application; Figure 3 is a block diagram of a current distribution device of parallel batteries in an energy storage system provided by an embodiment of the present application; Figure 4 is a block diagram of a current distribution device of parallel batteries in an energy storage system provided by an embodiment of the present application. DETAILED DESCRIPTION

[0020] The specific embodiments of the present application will be further described in detail below in combination with the drawings and examples. The following examples are used to illustrate the present application, but not to limit the scope of the present application.

[0021] Figure 1 is a structure diagram of an energy storage system provided by an embodiment of the present application, such as Figure 1As shown, the system at least includes: a plurality of battery modules 110 connected in parallel, a battery management system (BMS) 120, and a DC / DC converter 130.

[0022] The battery module 110 is a device for storing electrical energy in the energy storage system, and each battery module 110 includes at least one battery cell, which is a rechargeable battery.

[0023] The BMS 120 is an electronic control system for monitoring, controlling and managing the battery module 110. The BMS 120 is used to ensure the safe operation of the battery module 110, optimize the performance of the battery module 110, and prolong the service life of the battery.

[0024] The DC / DC converter 130 is a power electronic conversion device and is used to convert the voltage of a DC power supply from one level to another level.

[0025] In a conventional energy storage system, the control of the BMS 120 and the DC / DC converter 130 is usually independent of each other. The BMS 120 is only responsible for monitoring and protecting the battery cell, and the DC / DC converter 130 only completes voltage conversion. The two do not work together to achieve current balancing.

[0026] In one possible implementation, the parallel current sharing of the energy storage system can be achieved based on the cooperation of the BMS 120 and the DC / DC converter 130. Specifically, in the present embodiment, the BMS 120 is integrated with a battery state management unit, a dynamic current sharing decision unit, and a DC / DC adaptive adjustment unit.

[0027] In the present embodiment, the battery state management unit is configured to obtain at least two battery parameters of each battery module 110 in the plurality of battery modules 110.

[0028] The dynamic current sharing decision unit is configured to determine a sub-weight of each battery parameter based on each battery parameter of each battery module 110; determine a weighting coefficient of the sub-weight of each battery parameter of each battery module 110; and determine a current distribution weight of the battery module 110 based on the sub-weight of each battery parameter of each battery module 110 and the weighting coefficient of the sub-weight of each battery parameter.

[0029] The weighting coefficient is used to indicate the importance of the sub-weight of the corresponding battery parameter in determining the current distribution weight.

[0030] The DC / DC adaptive adjustment unit is configured to divide a current total load demand according to the current distribution weight of each battery module 110 to obtain a target output current corresponding to each battery module 110; and control the battery module 110 to supply power to the load according to the target output current.

[0031] Specifically, the DC / DC adaptive adjustment unit is configured to send an adjustment instruction to the DC / DC converter 130, and the DC / DC converter 130 is configured to adjust the system bus voltage and control the charging and discharging power of the battery module 110 accordingly.

[0032] Optionally, the BMS 120 further comprises a closed-loop feedback unit configured to acquire an actual output current of each battery module 110, determine whether a difference between the actual output current and the target output current exceeds a preset error range, and send an error compensation instruction to the dynamic current sharing decision unit in a case where the difference exceeds the preset error range, the error compensation instruction being configured to trigger the dynamic current sharing decision unit to determine the current distribution weight again to re-determine the target output current.

[0033] Optionally, the BMS 120 can further control the DC / DC converter 130 in other manners, and the control content includes but is not limited to: start-stop, setting of output voltage / current limit, etc. The present embodiment does not limit the control content of the BMS 120 on the DC / DC converter 130.

[0034] To sum up, the present application can interactively send adjustment instructions between the BMS and the DC / DC converter, realize current distribution of parallel-connected batteries in an energy storage system, and solve the problems of circulating current and uneven service life in a multi-module parallel system. The present application can improve the accuracy, efficiency and reliability of current equalization, and is suitable for large-scale energy storage and power battery systems.

[0035] Hereinafter, the current distribution method for parallel-connected batteries in an energy storage system provided by the present application is taken as an example to be applied to the BMS. In other embodiments, the method can also be applied to other control components in communication with the BMS and the DC / DC converter. The present embodiment does not limit the application scenarios of the method.

[0036] Figure 2 is a flowchart of the current distribution method for parallel-connected batteries in an energy storage system provided by an embodiment of the present application. The energy storage system comprises a plurality of parallel-connected battery modules. The method comprises at least the following steps: Step 201: Acquire at least two battery parameters of each battery module in the plurality of battery modules.

[0037] The battery parameters are parameters that can affect the current output capability of the battery module. Exemplarily, the at least two battery parameters include but are not limited to: actual available capacity, state of health (SOH), temperature factor and internal resistance factor.

[0038] wherein the actual available capacity is determined in combination with a State of Charge (SOC) and a SOH of the battery module. Since a battery module with a higher SOC or a larger capacity should bear more discharge current when the energy storage system is in a discharging state, and a battery module with a lower SOC or a smaller capacity should bear more charging current when the energy storage system is in a charging state, in order to ensure that the current distribution is proportional to the actual available capacity, in one example, at least two battery parameters (specifically, the actual available capacity) of each battery module in the plurality of battery modules are obtained, including: In the case that the energy storage system is in a charging state, the product of the rated capacity, the SOH and the difference between 1 and the SOC of each battery module is determined to obtain the actual available capacity; or in the case that the energy storage system is in a discharging state, the product of the rated capacity, the SOH and the SOC of each battery module is determined to obtain the actual available capacity.

[0039] That is, in the case that the energy storage system is in a charging state, the actual available capacity can be represented by the following formula: ; In the case that the energy storage system is in a discharging state, the actual available capacity can be represented by the following formula: ; wherein C_avl_i represents the actual available capacity of the i-th battery module, SOC_i represents the SOC of the i-th battery module; C_rated_i represents the rated capacity of the i-th battery module, and the rated capacity of each battery module is pre-stored in the energy storage system; SOH_i represents the SOH of the i-th battery module.

[0040] SOC represents the percentage of the current available capacity of each battery module to its current maximum available capacity. It reflects the “remaining power” or “charge level” of the battery. SOC_i can be obtained by inputting the electrical energy parameters of the i-th battery module into a pre-set SOC estimation model, wherein the electrical energy parameters include but are not limited to: output voltage, output current, battery temperature, battery impedance; and the SOC estimation model includes but is not limited to: Coulomb counting algorithm, extended Kalman filtering algorithm, artificial intelligence model, etc., and the implementation of the electrical energy parameters and the SOC estimation model is not limited in the present embodiment.

[0041] SOH represents an index of the performance degradation of each battery module relative to its initial state. It quantifies the aging degree and the remaining potential life of the battery. SOH_i can be obtained by inputting the electrical energy parameters of the i-th battery module into a preset SOH estimation model, wherein the electrical energy parameters include but are not limited to: output voltage, output current, battery temperature, battery impedance; the SOH estimation model includes but is not limited to: internal resistance reduction algorithm, data-driven algorithm, etc., and the implementation of the electrical energy parameters and the SOH estimation model is not limited herein.

[0042] The temperature factor is used to indicate the battery temperature of each battery module, which is determined based on the battery temperature of each battery module. In one example, at least two battery parameters (specifically, the temperature factor) of each battery module in the plurality of battery modules are obtained, including: obtaining the battery temperature of each battery module; determining the temperature factor of each battery module based on the mapping relationship between the battery temperature and the temperature factor.

[0043] Exemplarily, the mapping relationship includes: in the case that the battery temperature is greater than a first temperature threshold and less than a second temperature threshold, the temperature factor corresponding to the battery temperature is 0; wherein the first temperature threshold is greater than the second temperature threshold; in the case that the battery temperature is less than or equal to the first temperature threshold, greater than or equal to the second temperature threshold, and not equal to a preset standard temperature, the temperature factor corresponding to the battery temperature is in a negative correlation with the difference between the battery temperature and the standard temperature; in the case that the battery temperature is equal to the standard temperature, the temperature factor corresponding to the battery temperature is 1.

[0044] For example: the first temperature threshold is 60℃, the second temperature threshold is -20℃, and the standard temperature is 25℃, then the mapping relationship includes: T_i=25℃, ; -20℃≤T_i≤60℃, ; -20℃>T_i or T_i>60℃, ; wherein T_i represents the battery temperature of the i-th battery module; invT_i represents the temperature factor corresponding to T_i; |·| represents the absolute value. Wherein the battery temperature indicates the temperature of the battery module, which can be collected by a temperature sensor. The temperature sensor can be arranged on the outer surface or inside of the battery module, or outside the battery module, and the implementation of the temperature sensor is not limited herein.

[0045] In actual implementation, the values of the first temperature threshold, the second temperature threshold and the standard temperature can also be other values, and the negative correlation between the temperature factor and the difference between the battery temperature and the standard temperature can also be other implementation forms, and the implementation is not limited herein.

[0046] The internal resistance factor is used to indicate the battery internal resistance of each battery module, and the battery internal resistance refers to the energy efficiency impedance of the device inside the battery module that can hinder the instantaneous change of current. The internal resistance factor is determined based on the battery internal resistance of each battery module. Obtaining at least two battery parameters (specifically, the internal resistance factor) of each battery module in the plurality of battery modules includes: obtaining the battery internal resistance of each battery module; determining the internal resistance factor of each battery module based on the battery internal resistance.

[0047] Wherein, the internal resistance factor and the battery internal resistance are in a negative correlation relationship. For example: the internal resistance factor is represented by the following formula: ; Wherein, invR_i represents the internal resistance factor of the i-th battery module, and R_i represents the battery internal resistance of the i-th battery module.

[0048] Optionally, the battery internal resistance can be measured based on an alternating current injection method or a direct current discharge method, and the embodiment does not limit the acquisition method of the battery internal resistance.

[0049] In one example, to obtain at least two battery parameters, the BMS (specifically, the battery state management unit in the BMS) collects the SOC, SOH, battery temperature and battery internal resistance of each battery module; the collected data is preprocessed; and at least two battery parameters are determined based on the preprocessed SOC, SOH, battery temperature and battery internal resistance. Wherein, the pre-processing method includes but is not limited to filtering, calibration, etc., and the embodiment does not limit the pre-processing method.

[0050] Step 202, based on each battery parameter of each battery module, determine the sub-weight of each battery parameter.

[0051] In one example, based on each battery parameter of each battery module, the sub-weight of each battery parameter is determined, including: for each battery parameter, determining the sum of the battery parameters of each battery module; determining the ratio of the battery parameter of each battery module to the sum of the battery parameters, to obtain the sub-weight of the battery parameter of each battery module.

[0052] Taking the battery parameters including the actual available capacity, SOH, temperature factor and internal resistance factor as an example, the sub-weight of the actual available capacity can be represented as: ; The sub-weight of SOH can be represented as: ; The sub-weight of the temperature factor can be represented as: ; The sub-weight of the internal resistance factor can be represented as: ; wherein N represents the total number of battery modules, w cap i represents a sub-weight of the actual available capacity of the i th battery module, C avl i represents the actual available capacity of the i th battery module; w soh i represents a sub-weight of the SOH of the i th battery module; SOH i represents the SOH of the i th battery module; w temp i represents a sub-weight of the temperature factor of the i th battery module; invT i represents the temperature factor of the i th battery module; w r i represents a sub-weight of the internal resistance factor of the i th battery module; invR i represents the internal resistance factor of the i th battery module.

[0053] In step 203, a weighting coefficient of the sub-weight of each battery parameter of each battery module is determined.

[0054] The weighting coefficient is used to indicate the importance of the sub-weight of the corresponding battery parameter to determining the current distribution weight. The sum of the weighting coefficients of the sub-weights of various battery parameters is 1.

[0055] Optionally, step 203 can be executed after step 202; or, step 203 can also be executed before step 202; or, step 203 can also be executed synchronously with step 202, and the embodiment does not limit the execution order of steps 203 and 202.

[0056] In one example, the at least two battery parameters include: the actual available capacity and the state of health (SOH) of the battery; accordingly, determining the weighting coefficient of the sub-weight of each battery parameter of each battery module includes: determining the capacity utilization rate of each battery module; determining the weighting coefficient of the actual available capacity and the weighting coefficient of the SOH based on the capacity utilization rate and the total proportion of the weighting coefficients of the actual available capacity and the SOH.

[0057] wherein the capacity utilization rate is used to indicate the ratio of the actual available capacity to the rated capacity of each battery module. Exemplarily, the capacity utilization rate can be represented by the following formula: ; wherein CUR i represents the capacity utilization rate of the i th battery module, C avl i represents the actual available capacity of the i th battery module; C rated i represents the rated capacity of the i th battery module; SOC i represents the SOC of the i th battery module; SOH i represents the SOH of the i th battery module. According to the above formula, the capacity utilization rate of the i th battery module can be obtained by determining the product of the SOC and the SOH of the i th battery module; accordingly, determining the capacity utilization rate of each battery module includes: obtaining the SOC of each battery module; determining the product of the SOC and the SOH of each battery module to obtain the capacity utilization rate.

[0058] Correspondingly, the weighted coefficient of the actual available capacity and the weighted coefficient of the SOH can be represented by the following formula: ; ; wherein a represents the weighted coefficient of the actual available capacity of the i th battery module, b represents the weighted coefficient of the SOH of the i th battery module, and S represents the total proportion of the weighted coefficients of the actual available capacity and the SOH.

[0059] Optionally, in the case that the at least two battery parameters further include a temperature factor and an internal resistance factor, the temperature factor and the internal resistance factor correspond to preset weighted coefficients respectively, and the total proportion S of the weighted coefficients is 1 minus the weighted coefficients corresponding to the temperature factor and the internal resistance factor respectively.

[0060] For example, the weighted coefficient corresponding to the temperature factor is 0.2, and the weighted coefficient corresponding to the internal resistance factor is 0.1, so the total proportion S of the weighted coefficients is 1-0.2-0.1=0.7. In actual implementation, the weighted coefficients corresponding to the temperature factor and the internal resistance factor can also be set to other values, and the embodiment does not limit the values of the weighted coefficients corresponding to the temperature factor and the internal resistance factor.

[0061] In the embodiment, by dynamically setting the weighted coefficient of the actual available capacity and the weighted coefficient of the SOH, the weighted coefficients can be adjusted according to the actual state of the battery module, thereby improving the adaptability of the weighted coefficients to the battery module.

[0062] In step 204, the current distribution weight of the battery module is determined based on the sub-weight of each battery parameter of each battery module and the weighted coefficient of the sub-weight of each battery parameter.

[0063] Specifically, for each battery module, the product of the sub-weight of each battery parameter of the battery module and the weighted coefficient of the sub-weight is determined, and the sum of the products corresponding to various battery parameters is determined to obtain the current distribution weight of the battery module. Taking the case that the battery parameters include the actual available capacity, the SOH, the temperature factor and the internal resistance factor as an example, the sum of the products corresponding to various battery parameters of each battery module can be represented by the following formula: ; wherein w_i' represents the sum of the products of the various battery parameters of the i th battery module, a represents the weighted coefficient of the actual available capacity of the i th battery module, b represents the weighted coefficient of the SOH of the i th battery module, c represents the weighted coefficient of the temperature factor of the i th battery module, d represents the weighted coefficient of the internal resistance factor of the i th battery module, w_cap_i represents the sub-weight of the actual available capacity of the i th battery module; w_soh_i represents the sub-weight of the SOH of the i th battery module; w_temp_i represents the sub-weight of the temperature factor of the i th battery module; and w_r_i represents the sub-weight of the internal resistance factor of the i th battery module.

[0064] Optionally, after determining the sum of the products of the various battery parameters, the sum of the products can be normalized to ensure that the sum of the products of each battery module is added to 1, and the normalized sum of the products is the current distribution weight of the battery module. Correspondingly, the current distribution weight of each battery module can be represented by the following formula: ; wherein N represents the total number of battery modules, and w_i represents the current distribution weight of the i th battery module.

[0065] Step 205, dividing the current total load demand current according to the current distribution weight of each battery module to obtain the target output current corresponding to each battery module.

[0066] Optionally, the current total load demand current can be sent by other devices or estimated based on the state data of the energy storage system, and the present embodiment does not limit the acquisition method of the current total load demand current.

[0067] The target output current can be represented by the following formula: ; wherein I_out_i represents the target output current of the i th battery module, w_i represents the current distribution weight of the i th battery module, and I_total represents the current total load demand current of the energy storage system.

[0068] Step 206, controlling the battery module to supply power to the load according to the target output current.

[0069] Specifically, the BMS sends an adjustment instruction to the DC / DC converter to drive the power device of the DC / DC converter to control the battery module output current according to the target output current, and the adjustment instruction indicates the current value of the target output current.

[0070] Optionally, after the step of controlling the battery modules to supply power to the load according to the target output current, the method further comprises: obtaining an actual output current of each battery module; determining whether a difference between the actual output current and the target output current exceeds a preset error range; in a case where the difference exceeds the preset error range, triggering the step of obtaining the at least two battery parameters of each battery module in the plurality of battery modules and the steps following the step.

[0071] The step of obtaining the actual output current of each battery module comprises: collecting a branch current of the branch in which each battery module is located by means of a current collection component (such as a high-precision Hall sensor); and processing the branch current, and determining the actual output current of each battery module based on the processed branch current. Optionally, the processing of the branch current comprises ADC conversion processing and digital filtering processing, and the processing manner of the direct current is not limited in the embodiment.

[0072] In summary, the current distribution method for parallel batteries in the energy storage system provided in the embodiment comprises: obtaining at least two battery parameters of each battery module in a plurality of battery modules; determining a sub-weight of each battery parameter of each battery module based on each battery parameter of each battery module; determining a weighting coefficient of the sub-weight of each battery parameter of each battery module; determining a current distribution weight of the battery module based on the sub-weight of each battery parameter of each battery module and the weighting coefficient of the sub-weight of each battery parameter; wherein the weighting coefficient is used to indicate the importance of the sub-weight of the corresponding battery parameter to the determination of the current distribution weight; dividing a current demand of a total load according to the current distribution weight of each battery module to obtain a target output current corresponding to each battery module; and controlling the battery module to supply power to the load according to the target output current. This can make the battery module in a better state (such as high remaining capacity and low aging degree) bear more output current, and the battery module in a poor state (such as low remaining capacity and high aging degree) bear less output current, thereby delaying the overall aging speed of the battery module, prolonging the service life of the energy storage system, enhancing the reliability of current distribution, and solving the problems of low precision and poor reliability of the traditional current equalization method.

[0073] In addition, by cooperating the BMS and the DC / DC converter, parallel current equalization of the energy storage system is achieved, which can avoid the problem that the current equalization will fail once the battery module serving as the master module is abnormal in the traditional current distribution based on the master-slave control method, and further ensures the reliability of current distribution.

[0074] In addition, by dynamically setting the weighting coefficient of the actual available capacity and the weighting coefficient of the SOH, the weighting coefficients can be adjusted according to the actual state of the battery module, and the adaptability of the weighting coefficients to the battery module is improved.

[0075] In order to more clearly understand the current distribution method of the parallel battery in the energy storage system provided in the present application, the current distribution method is exemplified below with the battery parameters including the actual available capacity, SOH, temperature factor and internal resistance factor. It is assumed that the energy storage system includes three parallel battery modules, i.e. N=3 in the above embodiment, the current total load demand current I_total=100A, and the SOC_i, SOH_i, battery temperature T_i, battery internal resistance R_i and rated capacity C_rated_i of each battery module i are shown in Table One below.

[0076] Table One:

[0077] According to the above Table One and the calculation method of the sub-weight of each battery parameter in the above embodiment, it can be determined that: I. For the sub-weight corresponding to the actual available capacity: The actual available capacity C_avl_1 of the battery module 1 is 0.8x100x0.95=76; The actual available capacity C_avl_2 of the battery module 2 is 0.5x120x0.85=51; The actual available capacity C_avl_3 of the battery module 3 is 0.8x150x0.80=96; Correspondingly, The sub-weight w_cap_1 of the actual available capacity of the battery module 1 is 76 / (76+51+96)=76 / 223≈0.3408; The sub-weight w_cap_2 of the actual available capacity of the battery module 2 is 51 / (76+51+96)=51 / 223≈0.2287; The sub-weight w_cap_3 of the actual available capacity of the battery module 3 is 96 / (76+51+96)=96 / 223≈0.4305.

[0078] II. For the sub-weight of SOH: The sub-weight w_soh_1 of SOH of the battery module 1 is 95 / (95+85+80)=95 / 260≈0.3654; The sub-weight w_soh_2 of SOH of the battery module 2 is 85 / (95+85+80)=85 / 260≈0.3269; The sub-weight w_soh_3 of SOH of the battery module 3 is 80 / (95+85+80)=80 / 260≈0.3077.

[0079] III. For the sub-weight of the temperature factor: Temperature factor of battery module 1: 1 / |T_1-25|=1 / 5=0.2; Temperature factor of battery module 2: 1 / |T_2-25|=1 / 10=0.1 ; Temperature factor of battery module 3: 1 / |T_3-25|=1 / 15≈0.0667 ; Sum=0.2+0.1+0.0667=0.3667; Sub-weight of temperature factor of battery module 1: w_temp_1=0.2 / 0.3667≈0.5454; Sub-weight of temperature factor of battery module 2: w_temp_2=0.1 / 0.3667≈0.2727; Sub-weight of temperature factor of battery module 3: w_temp_3=0.0667 / 0.3667≈0.1819.

[0080] Four, sub-weight of internal resistance factor: Internal resistance factor of battery module 1: 1 / R_1=1 / 10=0.1000; Internal resistance factor of battery module 2: 1 / R_2=1 / 15≈0.0667; Internal resistance factor of battery module 3: 1 / R_3=1 / 12≈0.0833; Sum=0.1000+0.0667+0.0833=0.2500; Sub-weight of internal resistance factor of battery module 1: w_r_1=0.1000 / 0.2500=0.4000; Sub-weight of internal resistance factor of battery module 2: w_r_2=0.0667 / 0.2500≈0.2668; Sub-weight of internal resistance factor of battery module 3: w_r_3=0.0833 / 0.2500≈0.3332.

[0081] Assuming the weighting coefficient c of the sub-weight of the temperature factor is 0.2, and the weighting coefficient d of the sub-weight of the internal resistance factor is 0.1, which is a fixed preset value, the remaining 0.7 is allocated to the weighting coefficient a of the sub-weight of the actual available capacity and the weighting coefficient b of the sub-weight of the SOH, which is dynamically allocated by calculating the capacity utilization rate CUR_i of each battery module i.

[0082] Capacity utilization rate of battery module 1: CUR_1=0.8×0.95=0.76; The ratio of a and b is calculated as: a_1=0.7×0.76=0.532; b_1=0.7-(0.7×0.76) =0.168.

[0083] Calculate w_1' = (a_1 w_cap_1) + (b_1 w_soh_1) + (c w_temp_1) + (d w_r_1) = (0.532 x 0.3408) + (0.168 x 0.3654) + (0.2 x 0.5455) + (0.1 x 0.4000) = 0.1813 + 0.0614 + 0.1091 + 0.0400 = 0.3918.

[0084] CUR_2 of battery module 2 = 0.5 x 0.85 = 0.425; Calculate the ratio of a and b: a_2 = 0.7 x 0.425 ≈ 0.298; b_2 = 0.7 - (0.7 x 0.425) = 0.402.

[0085] Calculate w_2' = (0.2975 x 0.2287) + (0.4025 x 0.3269) + (0.2 x 0.2727) + (0.1 x 0.2668) = 0.0680 + 0.1316 + 0.0545 + 0.0267 = 0.2808.

[0086] CUR_3 of battery module 3 = 0.8 x 0.80 = 0.64; Calculate the ratio of a and b: a_3 = 0.7 x 0.64 = 0.448; b_3 = 0.7 - (0.7 x 0.64) = 0.252.

[0087] Calculate w_3' = (0.448 x 0.4305) + (0.252 x 0.3077) + (0.2 x 0.1818) + (0.1 x 0.3332) = 0.1929 + 0.0775 + 0.0364 + 0.0333 = 0.3401.

[0088] Normalization processing: Check w_1' + w_2' + w_3' = 0.3918 + 0.2808 + 0.3401 = 1.0127 not equal to 1, so normalization processing is needed, and we get: The current distribution weight w_1 of the battery module 1 is 0.3918 / 1.0127≈0.3869; The current distribution weight w_2 of the battery module 2 is 0.2808 / 1.0127≈0.2772; The current distribution weight w_3 of the battery module 3 is 0.3401 / 1.0127≈0.3359.

[0089] The distribution current (I_out_i) is calculated as follows: The target output current of the battery module 1 ; The target output current of the battery module 2 ; The target output current of the battery module 3 .

[0090] In this embodiment, by synthesizing the target output current, SOH, temperature factor, and sub-weight of the internal resistance factor of the battery module 2, the current distribution weight is dynamically adjusted according to the real-time state of the battery module, and the weight sum of all battery modules is ensured to be 1, so that the total load current can be fully distributed, the overall aging speed of the battery module can be slowed down, the service life of the energy storage system can be prolonged, and the reliability of current distribution can be enhanced.

[0091] Figure 3 is a block diagram of a current distribution device for parallel batteries in an energy storage system provided by an embodiment of the present application. In this embodiment, the device is applied to the BMS of the energy storage system shown in Figure 1 , which includes a plurality of parallel battery modules. The device includes at least the following modules: a parameter acquisition module 310, a sub-weight determination module 320, a coefficient determination module 330, a weight determination module 340, a current distribution module 350, and a battery control module 360.

[0092] The parameter acquisition module 310 is configured to acquire at least two battery parameters of each battery module in the plurality of battery modules. The sub-weight determination module 320 is configured to determine a sub-weight of each battery parameter based on each battery parameter of each battery module. The coefficient determination module 330 is configured to determine a weighting coefficient of the sub-weight of each battery parameter of each battery module. The weight determination module 340 is configured to determine a current distribution weight of the battery module based on the sub-weight of each battery parameter of each battery module and the weighting coefficient of the sub-weight of each battery parameter. The weighting coefficient is used to indicate the importance of the sub-weight of the corresponding battery parameter in determining the current distribution weight. The current distribution module 350 is configured to divide the current demand of the total load according to the current distribution weight of each battery module, to obtain a target output current corresponding to each battery module; The battery control module 360 is configured to control the battery modules to supply power to the load according to the target output current.

[0093] Optionally, the at least two battery parameters include an actual available capacity and a state of health (SOH), and the coefficient determination module 330 is configured to: determine a capacity utilization rate of each battery module, the capacity utilization rate being used to indicate a ratio of the actual available capacity to a rated capacity of each battery module; determine a weighted coefficient of the actual available capacity and a weighted coefficient of the SOH based on the capacity utilization rate and a total proportion of the weighted coefficients of the actual available capacity and the SOH.

[0094] Optionally, the coefficient determination module 330 is specifically configured to: obtain a state of charge (SOC) of each battery module; determine a product of the SOC and the SOH of each battery module to obtain the capacity utilization rate.

[0095] Optionally, the at least two battery parameters further include a temperature factor and an internal resistance factor, the temperature factor and the internal resistance factor respectively corresponding to preset weighted coefficients, and the total proportion of the weighted coefficients being 1 minus the weighted coefficients corresponding to the temperature factor and the internal resistance factor.

[0096] Optionally, the parameter acquisition module 310 is configured to: in a case where the energy storage system is in a charging state, determine a product of the rated capacity, the SOH and the difference between 1 and the SOC of each battery module to obtain the actual available capacity; or, in a case where the energy storage system is in a discharging state, determine a product of the rated capacity, the SOH and the SOC of each battery module to obtain the actual available capacity.

[0097] Optionally, the parameter acquisition module 310 is configured to: obtain a battery temperature of each battery module; determine the temperature factor of each battery module based on a mapping relationship between the battery temperature and the temperature factor.

[0098] Optionally, the mapping relationship includes: in a case where the battery temperature is greater than a first temperature threshold and less than a second temperature threshold, the temperature factor corresponding to the battery temperature is 0, and the first temperature threshold is greater than the second temperature threshold. In a case where the battery temperature is less than or equal to a first temperature threshold, greater than or equal to a second temperature threshold, and not equal to a preset standard temperature, a temperature factor corresponding to the battery temperature is negatively correlated with a difference between the battery temperature and the standard temperature. In a case where the battery temperature is equal to the standard temperature, the temperature factor corresponding to the battery temperature is 1.

[0099] Optionally, the parameter obtaining module 310 is configured to: obtain a battery internal resistance of each battery module; determine an internal resistance factor of each battery module based on the battery internal resistance; the internal resistance factor is negatively correlated with the battery internal resistance.

[0100] Optionally, the sub-weight determining module 320 is configured to: for each battery parameter, determine a sum of the battery parameter of each battery module; determine a ratio of the battery parameter of each battery module to the sum of the battery parameter, to obtain a sub-weight of the battery parameter of each battery module.

[0101] Optionally, after the control of the battery module to supply power to the load according to the target output current, the method further comprises a current obtaining module and an error determining module.

[0102] The current obtaining module is configured to obtain an actual output current of each battery module; The error determining module is configured to determine whether a difference between the actual output current and the target output current exceeds a preset error range; The parameter obtaining module 310 is further configured to trigger the execution of the steps of obtaining at least two battery parameters of each battery module in the plurality of battery modules and the subsequent steps in a case where the difference exceeds the preset error range.

[0103] For related details, refer to the above method embodiments.

[0104] It should be noted that: when the current distribution device for parallel battery in the energy storage system provided in the above embodiments performs current distribution of the parallel battery in the energy storage system, only the division of the above functional modules is exemplified, and in actual application, the above functions can be completed by different functional modules according to needs, that is, the internal structure of the current distribution device for parallel battery in the energy storage system is divided into different functional modules to complete all or part of the above described functions. In addition, the current distribution device for parallel battery in the energy storage system provided in the above embodiments and the method embodiment of current distribution for parallel battery in the energy storage system belong to the same concept, and the specific implementation process is shown in the method embodiment, which will not be repeated here.

[0105] Figure 4 is a block diagram of a current distribution device for parallel batteries in an energy storage system provided by an embodiment of the present application, which can be a BMS in an energy storage system as shown in Figure 1 The device at least includes a processor 401 and a memory 402.

[0106] The processor 401 can include one or more processing cores, such as a 4-core processor, a 4-core processor, etc. The processor 401 can be implemented in at least one of a hardware form of a DSP (Digital Signal Processing), an FPGA (Field-Programmable Gate Array), a PLA (Programmable Logic Array). The processor 401 can also include a main processor and a coprocessor, the main processor is a processor for processing data in an awake state, also known as a CPU (Central Processing Unit); the coprocessor is a low-power processor for processing data in a standby state. In some embodiments, the processor 401 can be integrated with a GPU (Graphics Processing Unit), which is responsible for rendering and drawing the content required to be displayed by the display screen. In some embodiments, the processor 401 can also include an AI (Artificial Intelligence) processor, which is used to process computing operations related to machine learning.

[0107] The memory 402 can include one or more computer-readable storage media, which can be non-transitory. The memory 402 can also include a high-speed random access memory, and a non-volatile memory such as one or more disk storage devices, flash storage devices. In some embodiments, the non-transitory computer-readable storage medium in the memory 402 is used to store at least one instruction for being executed by the processor 401 to implement the current distribution method for parallel batteries in an energy storage system provided by the method embodiment of the present application.

[0108] In some embodiments, the current distribution device for parallel batteries in an energy storage system can also optionally include a peripheral device interface and at least one peripheral device. The processor 401, the memory 402 and the peripheral device interface can be connected through a bus or a signal line. Each peripheral device can be connected to the peripheral device interface through a bus, a signal line or a circuit board. Illustratively, the peripheral device includes but is not limited to a radio frequency circuit, a touch display screen, an audio circuit, a power supply, etc.

[0109] Of course, the current distribution device of parallel batteries in the energy storage system can also include fewer or more components, and the present embodiment is not limited thereto.

[0110] Optionally, the present application also provides a computer readable storage medium, wherein a program is stored in the computer readable storage medium, and the program is loaded and executed by a processor to implement the current distribution method of parallel batteries in the energy storage system according to the above method embodiment.

[0111] Optionally, the present application also provides a computer product, which comprises a computer readable storage medium, wherein a program is stored in the computer readable storage medium, and the program is loaded and executed by a processor to implement the current distribution method of parallel batteries in the energy storage system according to the above method embodiment.

[0112] The technical features of the above embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above embodiments are described, but as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present disclosure.

[0113] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method of current distribution among parallel connected batteries in an energy storage system, characterized by, The energy storage system includes a plurality of battery modules in parallel, and the method comprises: obtaining at least two battery parameters of each battery module in the plurality of battery modules; determining a sub-weight of each battery parameter of each battery module based on each battery parameter of each battery module; determining a weighting coefficient of the sub-weight of each battery parameter of each battery module; determining a current distribution weight of the battery module based on the sub-weight of each battery parameter of each battery module and the weighting coefficient of the sub-weight of each battery parameter; wherein the weighting coefficient is used to indicate the importance of the sub-weight of the corresponding battery parameter to the determination of the current distribution weight; dividing the current total load demand according to the current distribution weight of each battery module to obtain a target output current corresponding to each battery module; controlling the battery module to supply power to the load according to the target output current.

2. The method of claim 1, wherein, The at least two battery parameters include actual available capacity and state of health (SOH); accordingly, The determination of the weighting coefficient of the sub-weight of each battery parameter of each battery module comprises: determining the capacity utilization rate of each battery module, which is used to indicate the ratio of the actual available capacity to the rated capacity of each battery module; determining the weighting coefficient of the actual available capacity and the weighting coefficient of the SOH based on the capacity utilization rate and the total proportion of the weighting coefficients of the actual available capacity and the SOH.

3. The method of claim 2, wherein, The determination of the capacity utilization rate of each battery module comprises: obtaining the state of charge (SOC) of each battery module; determining the product of the SOC and the SOH of each battery module to obtain the capacity utilization rate.

4. The method of claim 2, wherein, The at least two battery parameters further include a temperature factor and an internal resistance factor; the temperature factor and the internal resistance factor correspond to preset weighting coefficients respectively, and the total proportion of the weighting coefficients is 1 minus the weighting coefficients corresponding to the temperature factor and the internal resistance factor respectively.

5. The method of claim 2, wherein, The obtaining of the at least two battery parameters of each battery module in the plurality of battery modules comprises: in the case that the energy storage system is in a charging state, determining the product of the rated capacity, the SOH and the difference between 1 and the SOC of each battery module to obtain the actual available capacity; or, in the case that the energy storage system is in a discharging state, determining the product of the rated capacity, the SOH and the SOC of each battery module to obtain the actual available capacity.

6. The method of claim 4, wherein, The obtaining of the at least two battery parameters of each battery module in the plurality of battery modules comprises: obtaining the battery temperature of each battery module; determining the temperature factor of each battery module based on the mapping relationship between the battery temperature and the temperature factor.

7. The method of claim 6, wherein, The mapping relationship comprises: in the case that the battery temperature is greater than a first temperature threshold and less than a second temperature threshold, the temperature factor corresponding to the battery temperature is 0; wherein the first temperature threshold is greater than the second temperature threshold; in the case that the battery temperature is less than or equal to the first temperature threshold, greater than or equal to the second temperature threshold, and not equal to a preset standard temperature, the temperature factor corresponding to the battery temperature is negatively correlated with the difference between the battery temperature and the standard temperature. In a case that the battery temperature equals to the standard temperature, the temperature factor corresponding to the battery temperature is 1.

8. The method of claim 4, wherein, The acquiring the at least two battery parameters of each battery module in the plurality of battery modules comprises: acquiring a battery internal resistance of each battery module; determining an internal resistance factor of each battery module based on the battery internal resistance; the internal resistance factor is in a negative correlation with the battery internal resistance.

9. The method according to any one of claims 1 to 8, characterized in that, The determining the sub-weight of each battery parameter based on each battery parameter of each battery module comprises: determining a sum of the battery parameter of each battery module for each battery parameter; determining a ratio of the battery parameter of each battery module to the sum of the battery parameter, to obtain the sub-weight of the battery parameter of each battery module.

10. The method according to any one of claims 1 to 8, characterized in that, The controlling the battery module to supply power to the load according to the target output current further comprises: acquiring an actual output current of each battery module; determining whether a difference between the actual output current and the target output current exceeds a preset error range; in a case that the difference exceeds the preset error range, triggering the step of acquiring the at least two battery parameters of each battery module in the plurality of battery modules and the steps thereafter.

11. A current distribution apparatus for parallel connected batteries in an energy storage system, characterized by The device comprises a processor and a memory; the memory stores a program, the program is loaded and executed by the processor to realize the current distribution method of the parallel battery in the energy storage system according to any one of claims 1 to 10.

12. A computer-readable storage medium, characterized in that, The storage medium stores a program, the program is executed by the processor to realize the current distribution method of the parallel battery in the energy storage system according to any one of claims 1 to 10.

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