Multi-stage discharge control system and control method for energy storage lithium battery

Abstract

The invention discloses a multistage discharge control system and control method for an energy storage lithium battery in the technical field of energy storage charge and discharge, and the method comprises the steps: collecting the voltage and temperature of a single cell in a battery cluster in real time, and obtaining the residual SOC of the battery cluster; calculating a discharge dynamic step number; calculating a discharge single-step monomer voltage variation, and performing correction based on the multi-stage under-voltage alarm threshold and the temperature-SOC cooperative compensation model to obtain a compensated discharge single-step monomer voltage variation; when the minimum voltage value of the single battery cells in the battery cluster reaches a preset alarm condition, executing a multi-stage dynamic step power reduction discharge process; after all dynamic step power reduction is completed, entering a constant-voltage current-limiting discharge stage; when a discharge stop condition is satisfied, the discharge process is terminated. According to the invention, the problem of rapid voltage drop of the discharge end cell and the problem of early protection of discharge end monomer under-voltage caused by chemical properties of the battery are solved, and efficient capacity utilization of the discharge system and benefit maximization of the energy storage system are realized.

Description

Technical Field

[0001] This invention belongs to the field of energy storage charging and discharging technology, and more specifically, relates to a multi-stage discharge control system and control method for energy storage lithium batteries. Background Technology

[0002] Currently, battery discharge protection remains a significant challenge in the new energy storage industry. Due to the chemical characteristics of lithium batteries, the cell voltage drops rapidly at the end of discharge. Traditional lithium battery discharge control uses fixed voltage threshold triggering protection, failing to consider the nonlinear impact of temperature-SOC (state of charge) coupling on the voltage change rate. Furthermore, the fixed threshold protection mechanism leads to insufficient discharge capacity utilization. Simultaneously, the sudden voltage drop caused by changes in chemical characteristics at the end of discharge lacks a dynamic response mechanism. Secondly, the stepped power regulation lacks dynamic correlation with battery capacity and environmental parameters. When the energy storage inverter's PCS enters protection mode, it struggles to achieve constant voltage and current-limited balanced discharge, resulting in a smaller actual system discharge capacity and lower efficiency. Summary of the Invention

[0003] The purpose of this invention is to address the above-mentioned shortcomings by providing a multi-stage discharge control system and method for energy storage lithium batteries, solving the problems of rapid voltage drop at the end of discharge and premature protection due to undervoltage of individual cells at the end of discharge caused by battery chemistry, thereby achieving efficient utilization of discharge system capacity and maximizing the benefits of energy storage system.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0005] In a first aspect, the present invention provides a multi-stage discharge control method for an energy storage lithium battery, comprising:

[0006] Real-time acquisition of voltage and temperature of individual cells in the battery cluster, and acquisition of the remaining SOC of the battery cluster;

[0007] Calculate the discharge dynamic step number S based on the capacity of the battery cluster;

[0008] The single-step voltage change ΔV of the discharge cell is calculated and corrected based on the preset multi-level undervoltage alarm threshold and temperature-SOC collaborative compensation model to obtain the compensated single-step voltage change ΔV' of the discharge cell.

[0009] When the minimum voltage of a single cell in the battery cluster reaches the preset alarm condition, a multi-stage dynamic step power reduction discharge process is executed based on the discharge dynamic step number S and the compensated discharge single-step voltage change ΔV'.

[0010] After completing all dynamic step power reduction, it enters the constant voltage and current limiting discharge stage;

[0011] The discharge process terminates when the discharge stop condition is met.

[0012] The above technical solution constructs a three-stage control architecture of threshold detection, dynamic step reduction, and constant voltage holding. The transition conditions of each stage are clear. By introducing discharge dynamic step number and temperature-SOC collaborative compensation, the control accuracy at the discharge end is effectively improved. At the same time, the constant voltage current limiting discharge mode is maintained, which solves the problem of premature protection caused by voltage drop and significantly improves the discharge capacity utilization rate.

[0013] Furthermore, the formula for calculating the discharge dynamic step number S is as follows:

[0014] ;

[0015] Where Q is the total capacity of the battery cluster; Q base This is the reference capacity of the battery cell; S offset For safety correction, where: when the real-time temperature T of a single cell is greater than 45℃ or the state of health (SOH) of a single cell is less than 80%, S offset =-1; When static, S offset =0; In discharge correction mode, S offset =1.

[0016] In the above technical solution, an adaptive dynamic mapping relationship between the dynamic step number S and the total capacity of the battery cluster is established, which enables the control strategy to be flexibly adjusted according to the battery size. A safety correction amount based on temperature and SOH is introduced to avoid over-adjustment of small-capacity battery packs, solve the problem of rapid voltage drop of cells at the end of discharge, and enhance the robustness and safety of the system under different health conditions.

[0017] Furthermore, the preset multi-level undervoltage alarm thresholds include a single cell undervoltage level one alarm threshold Cell_Vol_Value_1, a single cell undervoltage level two alarm threshold Cell_Vol_Value_2, and a single cell undervoltage level three alarm threshold Cell_Vol_Value_3, wherein Cell_Vol_Value_1 > Cell_Vol_Value_2 > Cell_Vol_Value_3.

[0018] In the above technical solution, a clear, tiered voltage warning system is established by setting three levels of undervoltage alarm thresholds, which provides precise triggering conditions for subsequent multi-level power reduction control and achieves a seamless transition from warning to protection.

[0019] Furthermore, the formula for calculating the single-step voltage change ΔV during discharge is as follows:

[0020] ;

[0021] The formula for calculating the compensated single-step voltage change ΔV' of the discharge cell is as follows:

[0022] ;

[0023] Where T represents the real-time temperature of a single battery cell, in °C; T ref The reference temperature is typically 25°C; α is the temperature correction factor in V / °C; β is the SOC correction factor in V / %; SOC avg The current cluster average SOC, SOC RACK The current stage is cluster SOC.

[0024] The above technical solution provides a specific voltage compensation calculation formula that integrates the dual influencing factors of temperature and SOC. This model significantly reduces the voltage measurement deviation caused by changes in ambient temperature and inconsistencies in cell aging, thereby improving the calculation accuracy of step voltage changes.

[0025] Furthermore, the preset alarm condition is the minimum voltage V of a single battery cell. min The cell has reached the three-level undervoltage alarm threshold Cell_Vol_Value_3.

[0026] The above technical solution clearly uses a three-level alarm threshold as the starting condition for the dynamic step power reduction process, which ensures that the system intervenes in time when the voltage begins to enter the rapid decline range. This prevents premature action from affecting the output and avoids undervoltage protection caused by late action.

[0027] Furthermore, the multi-stage dynamic step power reduction discharge process, based on the discharge dynamic step number S and the compensated single-step voltage change, includes:

[0028] The formula for calculating the current discharge power is: Current discharge power = Base power × (1 - COUNT_STEP / S); where COUNT_STEP is the current step count;

[0029] The multi-stage dynamic step-drop power discharge process includes:

[0030] Set the initial value of COUNT_STEP to 1, and reduce the power to the current discharge power for discharge;

[0031] When the voltage of a single cell in the battery cluster reaches its minimum value V min The voltage drops to the minimum value after dynamic step correction of the single-step discharge cell voltage (V). min If -ΔV'), then COUNT_STEP will be incremented by 1, the current discharge power will be updated, and the power will be reduced to the updated current discharge power for discharge.

[0032] Repeat the above process until COUNT_STEP equals the dynamic step number S.

[0033] The above technical solution provides a specific and quantified step power reduction execution process. Through a cycle of monitoring-judgment-increment-update, it achieves a smooth and step-by-step decrease in power, effectively slowing down the rate of change of cell voltage at the end of discharge and creating conditions for switching to constant voltage mode.

[0034] Furthermore, in the constant voltage and current limiting discharge stage, a PI controller is used to dynamically adjust the output current I. out The calculation formula is as follows:

[0035] ;

[0036] Among them, K p ε is the proportional gain, used for fast response error; e is the voltage error, calculated using the following formula: ;K i This is the integral gain, used to eliminate steady-state error (cumulative historical error).

[0037] In the above technical solution, a PI controller is introduced in the constant voltage and current limiting stage. By utilizing the fast response of its proportional element and the characteristics of its integral element in eliminating steady-state errors, the output current is accurately and smoothly adjusted, ensuring that a stable voltage output can be maintained at the end of the discharge, and further tapping the potential of the battery.

[0038] Furthermore, the discharge stop conditions include: the minimum voltage of the individual cell reaches the single cell undervoltage level one alarm threshold or the single cell undervoltage level two alarm threshold, or the constant voltage current limiting discharge reaches its own stop condition. The self-stop condition refers to the energy storage system charge and discharge cutoff conditions, such as cutoff voltage, charge and discharge SOC threshold, etc.

[0039] The above technical solution sets clear and multiple discharge termination conditions, forming a multi-protection mechanism. This design ensures that the system can reliably stop after reaching the safety boundary or completing constant voltage discharge, preventing over-discharge damage to the battery and ensuring the safe operation of the system.

[0040] In a second aspect, the present invention also provides a multi-stage discharge control system for energy storage lithium batteries, used to implement the multi-stage discharge control method for energy storage lithium batteries described in the first aspect, comprising:

[0041] A battery cluster containing several battery packs;

[0042] The battery slave is used to collect the voltage, temperature and SOC values ​​of individual cells in the battery cluster.

[0043] A battery host is used to calculate the remaining SOC value of the battery cluster;

[0044] The battery management unit, connected to the battery slave and battery master, is used to acquire the voltage and temperature values ​​of individual cells and the SOC data of the battery cluster, generate a discharge control strategy, and output discharge commands.

[0045] The energy management system is used to set the undervoltage alarm level and threshold of individual cells, receive discharge commands from the battery management unit, and send them to the discharge execution module.

[0046] The discharge execution module is an energy storage inverter, used to adjust the discharge power and output current according to the discharge command.

[0047] In the above technical solution, the system constructs the physical foundation for realizing the aforementioned method through the coordinated work of the battery slave, master, management unit, energy management system and energy storage inverter; each module has a clear division of labor, and the data flow and control flow are clear, which together realize efficient and intelligent multi-level discharge control.

[0048] Furthermore, the system also includes a power grid, and the energy management system is connected to the power grid to receive dispatch instructions from the power grid side.

[0049] The aforementioned technical solution clarifies the connection architecture between the system and the power grid, establishing the ultimate value of this system in grid-connected energy storage applications. By receiving grid dispatch instructions through the energy management system, the discharge control process can actively respond to the actual needs of the power grid, achieving intelligent interaction with the grid. Simultaneously, the direct connection between the energy storage inverter and the power grid provides an efficient and reliable feed-in channel for the released electrical energy after optimized control using this method. This architecture enables the energy storage system to truly serve the power grid's peak shaving and valley filling and stable operation, enhancing its economic efficiency and practicality.

[0050] Thirdly, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the multi-stage discharge control method for energy storage lithium batteries as described in the first aspect.

[0051] In the above technical solution, by converting the multi-stage discharge control method into a computer program stored in a medium, the control strategy can be deployed and run in various battery management systems in software form. This achieves automation and precision in the discharge control process, reduces manual intervention, and improves the consistency and reliability of system response. Simultaneously, the software format facilitates reuse and iteration across different hardware platforms and energy storage projects, enhancing the applicability and scalability of the control method.

[0052] Fourthly, the present invention also provides an apparatus comprising:

[0053] Memory, used to store instructions;

[0054] A processor is configured to execute the instructions, causing the device to perform operations implementing the multi-stage discharge control method for energy storage lithium batteries as described in the first aspect.

[0055] The device defined in the above technical solution executes stored instructions through a processor, enabling the implementation of the multi-level discharge control method in a real hardware environment. This allows the battery cluster to perform real-time and precise temperature-SOC coordinated compensation and dynamic step adjustment during discharge, thereby effectively delaying voltage drop and improving discharge capacity utilization. Such devices can be directly integrated into energy storage systems, providing them with stable and intelligent discharge control capabilities, ensuring the long-term economic efficiency and safety of the system.

[0056] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0057] This invention constructs a complete five-stage closed-loop control logic encompassing acquisition, calculation, judgment, execution, and termination. This control method reduces voltage signal deviations caused by ambient temperature changes and inconsistent cell aging through a temperature-SOC collaborative compensation calculation model, increasing the accuracy of discharge step voltage difference calculations. Simultaneously, it employs a dynamic mapping relationship between the dynamic step number S and the battery pack capacity Q to avoid over-adjustment of small-capacity batteries and address the problem of rapid cell voltage drop at the end of discharge. By establishing a three-level voltage warning system and its mapping relationship with the dynamic step number S, it achieves step-wise power reduction discharge, slowing down the voltage change rate. Finally, it uses PI control to dynamically adjust the output current, achieving a constant voltage mode and maintaining a constant voltage current-limiting discharge mode. This solves the problem of premature protection due to undervoltage of individual cells at the end of discharge caused by battery chemistry, achieving efficient utilization of the discharge system capacity and maximizing the benefits of the energy storage system. Attached Figure Description

[0058] Figure 1 A system architecture topology diagram of a multi-stage discharge control system for energy storage lithium batteries provided in an embodiment of the present invention;

[0059] Figure 2 This is a flowchart of a multi-stage discharge control method for energy storage lithium batteries provided in an embodiment of the present invention. Detailed Implementation

[0060] Preferred embodiments of the present invention will now be described in more detail with reference to the accompanying drawings and specific examples.

[0061] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments in order to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments may be practiced without one or more of these specific details. In other instances, well-known apparatuses, structures, and techniques associated with this application may not have been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0062] Unless the context requires otherwise, throughout the specification and claims, the word “comprising” and its variations, such as “including” and “having”, shall be understood to have an open, inclusive meaning, that is, to be interpreted as “including, but not limited to”.

[0063] Throughout this specification, references to "an embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Therefore, the appearance of "in an embodiment" or "an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic may be combined in any manner in one or more embodiments.

[0064] The singular forms “a” and “the” used in this specification and the appended claims include plural references unless otherwise expressly stated herein. It should be noted that the term “or” is generally used to mean “and / or” unless otherwise expressly stated herein.

[0065] Example 1

[0066] This embodiment provides a multi-stage discharge control method for energy storage lithium batteries with coordinated compensation and dynamic step adjustment. The method consists of... Figure 1 The multi-stage discharge control system for energy storage lithium batteries shown is implemented, such as... Figure 1 As shown, the control system includes a battery cluster, a battery slave unit (BMU), a battery master unit (BCMU), a battery management module (EMU), an energy management system (EMS), an energy storage inverter (PCS), and a power grid.

[0067] Figure 2 This is a flowchart of the multi-stage discharge control method for energy storage lithium batteries with coordinated compensation and dynamic step adjustment described in this embodiment. This flowchart only illustrates the logical sequence of the method described in this embodiment. Provided there are no conflicts, different methods may be used in other possible embodiments of the invention. Figure 2 Complete the steps shown or described in the indicated order. Participate Figure 2 The method in this embodiment specifically includes the following steps:

[0068] S101: System Initialization and Parameter Configuration

[0069] The battery slave unit (BMU) collects the voltage (V), temperature (T), and state of charge (SOC) values ​​of individual cells from the battery pack of the battery cluster; the battery master unit (BCMU) calculates the remaining SOC value of the battery cluster and the minimum voltage (Vmin) of the individual cells in the battery cluster; these values ​​can be uploaded to the battery management module (EMU), and then uploaded by the battery management module (EMU) to the energy management system (EMS).

[0070] The Energy Management System (EMS) sets multi-level undervoltage alarm thresholds for individual battery cells. In this embodiment, three levels of undervoltage alarm thresholds are configured. The first-level undervoltage alarm threshold for individual battery cells is Cell_Vol_Value_1 = 2.8V, the second-level undervoltage alarm threshold is Cell_Vol_Value_2 = 2.7V, and the third-level undervoltage alarm threshold is Cell_Vol_Value_3 = 2.6V.

[0071] S102: The battery management module EMU obtains the dischargeable state of the energy storage system, that is, the energy storage system is fault-free and can be charged and discharged; it determines the undervoltage alarm level of individual cells in the battery cluster based on the individual cell voltage value V.

[0072] S103: Calculation of the number of dynamic step steps

[0073] The Energy Management System (EMS) obtains the total capacity Q and baseline capacity Q of the battery cluster in real time. base Given the individual cell voltage V, temperature T, and state of health (SOH) of the individual cell, calculate the discharge dynamic step number S using the following formula:

[0074] ;

[0075] Where Q is the total capacity of the battery cluster; Q base The base capacity of the battery cell is determined based on the selected cell model; S offset For safety correction, where: when the real-time temperature T of a single cell is greater than 45℃ or the state of health (SOH) of a single cell is less than 80%, S offset =-1; When static, S offset =0; In discharge correction mode, S offset =1.

[0076] In this embodiment, the total capacity of the battery cluster is Q = 1300Wh, and the base capacity is Q base =314Ah, initial safety correction factor S offset =1, and the calculated discharge dynamic step number S=4, that is, the preset discharge step number is 4.

[0077] S104: Calculate the single-step voltage change

[0078] The battery management module (EMU) calculates the single-step voltage change ΔV during discharge, and then calculates the single-step voltage change ΔV' after temperature-SOC co-compensation.

[0079] The formula for calculating the single-step voltage change ΔV of the discharge cell is as follows:

[0080] ;

[0081] The formula for calculating the compensated single-step voltage change ΔV' of the discharge cell is as follows:

[0082] ;

[0083] Where T represents the real-time temperature of a single battery cell, in °C; T ref The reference temperature is artificially determined and obtained through laboratory simulation data, typically 25℃; α is the temperature correction factor, in V / ℃; β is the SOC correction factor, in V / %; SOC avg The current cluster average SOC, SOC RACK The current stage is cluster SOC.

[0084] In this embodiment, the battery management module EMU temperature correction coefficient α = 0.003V / ℃ and the SOC correction coefficient β = 0.005V / %. Substituting these values ​​into the above formula, the voltage difference ΔV' after the target compensation is calculated.

[0085] S105: The Battery Management Module (EMU) obtains the minimum voltage V of the individual cells in the battery cluster, calculated by the Battery Host Module (BCMU). min .

[0086] S106: The battery management module (EMU) determines that the minimum voltage of a single battery cell has reached the level three alarm range, i.e., V. min If ∈[Cell_Vol_Value_3, Cell_Vol_Value_2), then proceed to step 107; otherwise, loop through step 106.

[0087] S107: The Battery Management Module (EMU) initiates the discharge control strategy. Simultaneously, the Energy Management System (EMS) initializes the discharge step count COUNT_STEP = 1, and the EMU issues a power reduction discharge command, which is uploaded to the EMS and the Energy Storage Inverter (PCS). After receiving the power reduction discharge command, the EMS issues a command to the PCS to reduce the power to the current power CURR_POWER. The formula for calculating the current discharge power is: Current discharge power = Base power × (1 - COUNT_STEP / S); that is, CURR_POWER1 = 0.75 * Base power.

[0088] S108: Battery Management Unit (EMU) determines the minimum voltage V of a single battery cell. min Has it dropped to the minimum value V after dynamic step correction of the single-step discharge cell voltage? min -ΔV', if reached, proceed to S109, otherwise loop in S108;

[0089] S109: COUNT_STEP is incremented by 1, updating the current discharge power, i.e., CURR_POWER2 = 0.5 * base power. The battery management module EMU sends a power reduction command to the energy management system EMS and the energy storage inverter PCS; the energy storage inverter PCS executes the updated current power CURR_POWER2 to discharge.

[0090] S110: Following the method in S109, COUNT_STEP is incremented by 1 step by step to perform power reduction discharge. The battery management module EMU checks whether COUNT_STEP is equal to 4. If yes, proceed to S111; otherwise, loop through S110.

[0091] S111: The Battery Management Unit (EMU) uploads constant voltage and current limiting commands to the Energy Management System (EMS) and the Energy Storage Inverter (PCS). The EMS can also control and issue equalization discharge commands to the PCS. The PCS uses a PI controller to dynamically adjust the output current I. out This enables dual protection operation;

[0092] The output current I out The calculation formula is:

[0093] ;

[0094] Among them, K p ε is the proportional gain, used for fast response error; e is the voltage error, calculated using the following formula: ;K i This is the integral gain, used to eliminate steady-state error (cumulative historical error).

[0095] S112: The battery management module (EMU) determines the minimum voltage V of a single battery cell. min Has the voltage reached the level 1 undervoltage alarm range for a single battery cell (V)? min ∈[Cell_Vol_Value_2, Cell_Vol_Value_1)) or the undervoltage secondary alarm range of a single cell (V min ≥Cell_Vol_Value_1), or constant voltage current limiting discharge reaches its own stopping condition, that is, the charging and discharging medium conditions of the energy storage system, such as cutoff voltage, charging and discharging SOC threshold, etc.; if it enters S113, otherwise it cycles in S112.

[0096] S113, the battery management module (EMU) sends a discharge completion command.

[0097] Example 2

[0098] This embodiment provides a multi-stage discharge control system for energy storage lithium batteries with coordinated compensation and dynamic step adjustment, which can implement the control method described in Embodiment 1.Figure 1 As shown, the control system described in this embodiment is divided into 7 modules, including a battery cluster containing several battery packs; module 2 is the battery slave unit (BMU); module 3 is the battery master unit (BCMU); module 4 is the battery management unit (EMU); module 5 is the energy management system (EMS); module 6 is the energy storage inverter (PCS); and module 7 is the grid side.

[0099] In this embodiment, the battery cluster includes several battery packs; the battery slave unit (BMU) is connected to both the battery cluster and the battery master unit (BCMU). The battery slave unit (BMU) is used to collect the voltage, temperature, and SOC values ​​of individual cells in the battery cluster, while the battery master unit (BCMU) is used to calculate the remaining SOC value of the battery cluster.

[0100] In this embodiment, the Battery Management Unit (EMU) is connected to the Battery Host Unit (BCMU) and the Energy Management System (EMS) to acquire the voltage and temperature values ​​of individual cells and the SOC data of the battery cluster, generate a discharge control strategy, and output discharge commands. The Energy Management System (EMS) is used to set the undervoltage alarm level and threshold of individual cells, receive the power reduction discharge command from the Battery Management Unit (EMU), and send it to the Energy Storage Inverter (PCS). The Energy Storage Inverter (PCS) is connected to the Energy Management System (EMS) and is used to adjust the discharge power and output current according to the discharge command.

[0101] In this embodiment, the energy management system (EMS) is connected to the power grid and receives dispatch instructions from the power grid side; the AC output terminal of the energy storage inverter (PCS) is connected to the power grid and feeds the electrical energy released by the battery clusters into the power grid.

[0102] The specific functions of each module described above are explained in the relevant content of the method in Embodiment 1, and will not be repeated here.

[0103] Example 3

[0104] This embodiment provides a computer-readable storage medium storing a computer program thereon. When the computer program is executed by a processor, it implements the multi-stage discharge control method for energy storage lithium batteries as described in Embodiment 1.

[0105] Example 4

[0106] This embodiment provides a device, including:

[0107] Memory, used to store instructions;

[0108] A processor is configured to execute the instructions, causing the device to perform operations that implement the multi-stage discharge control method for energy storage lithium batteries as described in Example 1.

[0109] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and principles of the described embodiments, and these modifications and variations should also be considered within the scope of protection of the present invention.

Claims

1. A multi-stage discharge control method for energy storage lithium batteries, characterized in that, include: Real-time acquisition of voltage and temperature of individual cells in the battery cluster, and acquisition of the remaining SOC of the battery cluster; Calculate the discharge dynamic step number S based on the capacity of the battery cluster; The single-step voltage change ΔV of the discharge cell is calculated and corrected based on the preset multi-level undervoltage alarm threshold and temperature-SOC collaborative compensation model to obtain the compensated single-step voltage change ΔV' of the discharge cell. When the minimum voltage of a single cell in the battery cluster reaches the preset alarm condition, a multi-stage dynamic step power reduction discharge process is executed based on the discharge dynamic step number S and the compensated discharge single-step voltage change ΔV'. After completing all dynamic step power reduction, it enters the constant voltage and current limiting discharge stage; The discharge process terminates when the discharge stop condition is met.

2. The multi-stage discharge control method for energy storage lithium batteries according to claim 1, characterized in that, The formula for calculating the discharge dynamic step number S is as follows: ； Where Q is the total capacity of the battery cluster; Q base This is the reference capacity of the battery cell; S offset For safety correction, where: when the real-time temperature T of a single cell is greater than 45℃ or the state of health (SOH) of a single cell is less than 80%, S offset =-1; When static, S offset =0; In discharge correction mode, S offset =1.

3. The multi-stage discharge control method for energy storage lithium batteries according to claim 1, characterized in that, The preset multi-level undervoltage alarm thresholds include a single cell undervoltage level 1 alarm threshold Cell_Vol_Value_1, a single cell undervoltage level 2 alarm threshold Cell_Vol_Value_2, and a single cell undervoltage level 3 alarm threshold Cell_Vol_Value_3, wherein Cell_Vol_Value_1 > Cell_Vol_Value_2 > Cell_Vol_Value_3.

4. The multi-stage discharge control method for energy storage lithium batteries according to claim 3, characterized in that, The formula for calculating the single-step voltage change ΔV of the discharge cell is as follows: ； The formula for calculating the compensated single-step voltage change ΔV' of the discharge cell is as follows: ； Where T represents the real-time temperature of a single battery cell, in °C; T ref The reference temperature is α, the temperature correction factor is in V / ℃, and β is the SOC correction factor is in V / %; SOC avg The current cluster average SOC, SOC RACK The current stage is cluster SOC.

5. The multi-stage discharge control method for energy storage lithium batteries according to claim 3, characterized in that, The preset alarm condition is the minimum voltage V of a single battery cell. min The cell has reached the three-level undervoltage alarm threshold Cell_Vol_Value_3.

6. The multi-stage discharge control method for energy storage lithium batteries according to claim 1, characterized in that, The process of performing a multi-stage dynamic step power reduction discharge based on the discharge dynamic step number S and the compensated single-step voltage change includes: The formula for calculating the current discharge power is: Current discharge power = Base power × (1 - COUNT_STEP / S); where COUNT_STEP is the current step count; The multi-stage dynamic step-drop power discharge process includes: Set the initial value of COUNT_STEP to 1, and reduce the power to the current discharge power for discharge; When the voltage of a single cell in the battery cluster reaches its minimum value V min The voltage drops to the minimum value after dynamic step correction of the single-step discharge cell voltage (V). min If -ΔV'), then COUNT_STEP will be incremented by 1, the current discharge power will be updated, and the power will be reduced to the updated current discharge power for discharge. Repeat the above process until COUNT_STEP equals the dynamic step number S.

7. The multi-stage discharge control method for energy storage lithium batteries according to claim 1, characterized in that, During the constant voltage and current limiting discharge stage, a PI controller is used to dynamically adjust the output current I. out The calculation formula is as follows: ； Among them, K p Here, e represents the proportional gain; e is the voltage error, calculated using the following formula: ;K i This is the integral gain.

8. The multi-stage discharge control method for energy storage lithium batteries according to claim 3, characterized in that, The discharge stop conditions include: the minimum voltage of the individual cell reaches the single cell undervoltage level 1 alarm threshold or the single cell undervoltage level 2 alarm threshold, or the constant voltage current limiting discharge reaches its own stop condition.

9. A multi-stage discharge control system for an energy storage lithium battery, used to implement the multi-stage discharge control method for an energy storage lithium battery according to any one of claims 1 to 8, characterized in that, include: A battery cluster containing several battery packs; The battery slave is used to collect the voltage, temperature and SOC values ​​of individual cells in the battery cluster. A battery host is used to calculate the remaining SOC value of the battery cluster; The battery management unit is used to acquire the voltage and temperature values ​​of individual battery cells and the SOC data of the battery cluster, generate a discharge control strategy, and output discharge commands. The energy management system is used to set the undervoltage alarm level and threshold of individual cells, receive discharge commands from the battery management unit, and send them to the discharge execution module. The discharge execution module is an energy storage inverter, used to adjust the discharge power and output current according to the discharge command.

10. The multi-stage discharge control system for energy storage lithium batteries according to claim 9, characterized in that, It also includes the power grid, The energy management system is connected to the power grid and receives dispatch instructions from the power grid side; The AC output terminal of the energy storage inverter is connected to the power grid, feeding the electrical energy released by the battery cluster into the power grid.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the multi-stage discharge control method for energy storage lithium batteries as described in any one of claims 1 to 8.

12. A device, characterized in that, include: Memory, used to store instructions; A processor is configured to execute the instructions, causing the device to perform operations that implement the multi-stage discharge control method for energy storage lithium batteries as described in any one of claims 1 to 8.

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