Lithium battery discharge control method and system

Abstract

The invention relates to the technical field of energy storage charging and discharging, and provides a lithium battery discharging control method and system, and the method comprises the steps: collecting a voltage value V, a temperature value T, a cluster residual charge amount SOCRAACK, a cluster average residual charge amount SOCavg and a discharging state of a current single cell of a battery pack; setting a three-level alarm grade and a threshold value of under-voltage of the single battery cell; calculating a dynamic discharge step number S of the battery pack; calculating the variation delta V'of the dynamic step of the single voltage based on temperature correction; performing multistage threshold trigger control and dynamic step power reduction discharge on the battery pack based on results obtained in the step S3 and the step S4; and controlling the battery pack to perform constant-voltage current-limiting discharge until the discharge is ended. Through the method, the accuracy of discharge control of the energy storage lithium battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage charging and discharging, and in particular to a lithium battery discharge control method and system thereof. Background Art

[0002] In the new energy storage industry, battery discharge protection has always been a challenge in energy storage systems. Due to the chemical properties of lithium batteries, the cell voltage drops rapidly at the end of discharge. Traditional lithium battery discharge control uses a fixed voltage threshold to trigger protection, and this fixed threshold protection mechanism results in insufficient discharge capacity utilization. Furthermore, changes in chemical properties at the end of discharge trigger a voltage drop, lacking a dynamic response mechanism. Furthermore, stepped power regulation lacks dynamic correlation with battery capacity and environmental parameters. The energy storage inverter (PCS) enters protection mode, making it difficult to achieve constant voltage and current limiting for balanced discharge, resulting in a low actual system discharge capacity and inefficient efficiency. Currently, technologies using graded power reduction for charge and discharge control have emerged. For example, Chinese invention patent application CN116647009A, "A Battery Charging Protection Strategy Method in an Energy Storage System," discloses a battery charging protection strategy method in an energy storage system. By obtaining graded overvoltage alarm protection parameters from the BMS (Battery Management System), the EMS implements step-by-step power reduction and controlled equalization initiation during the charging process. This effectively slows the rate of voltage rise at the end of charge and ensures effective equalization by the PCS, thereby preventing single-cell overvoltage protection or the inability to achieve equalization. However, the above invention does not consider the nonlinear influence of the temperature-SOC coupling effect on the voltage change rate, which will cause the execution accuracy of the charge and discharge control strategy to be reduced and the effect to be poor. Summary of the Invention

[0003] The technical problem to be solved by the present invention is how to improve the accuracy of discharge control of energy storage lithium batteries.

[0004] The present invention solves the above technical problems through the following technical means:

[0005] The present invention provides a lithium battery discharge control method, comprising the following steps:

[0006] S1. Collect the current single cell voltage value V, temperature value T, and cluster remaining charge SOC of the battery pack RACK , cluster average residual charge SOC avg and discharge status;

[0007] S2. Set the three-level alarm level and threshold for single cell undervoltage. The alarm level decreases in severity from level 1 to level 3. The thresholds are Cell_Vol_Value_1, Cell_Vol_Value_2, and Cell_Vol_Value_3 respectively.

[0008] S3. Calculate the dynamic step number S of battery pack discharge;

[0009] S4. Calculate the change ΔV of the cell voltage dynamic step based on temperature correction ′ ;

[0010] S5. Based on the results obtained in step S3 and step S4, the battery pack is subjected to multi-level threshold trigger control and dynamic step-down power discharge.

[0011] S6. Control the battery pack to perform constant voltage and current limiting discharge until the discharge is terminated.

[0012] Furthermore, the calculation formula for the dynamic step number S of the battery pack discharge in step S3 is:

[0013]

[0014] Among them, Q is the total capacity of the energy storage battery; Q base is the energy storage battery benchmark capacity; floor[·] is the rounding function; S offset is the safety correction value, the maximum temperature of the battery cell T max >45℃ or battery health status SOH<80%, S offset =-1; in static state, S offset =0, in discharge correction mode, S offset =1.

[0015] Furthermore, step S4 includes the following steps:

[0016] S41. Calculate the dynamic step change ΔV of the discharge single-step cell voltage using the following formula:

[0017]

[0018] S42, calculating the corrected discharge single-step cell voltage dynamic step change ΔV ′ , the calculation formula is as follows:

[0019] ΔV ′ =ΔV+α(TT ref )+β(SOC avg -SOC rack )

[0020] Where T is the real-time temperature of the monomer, in °C; T ref is the reference temperature, in °C; α is the temperature correction coefficient, in V / °C; β is the SOC correction coefficient, in V / %; SOC avg is the average SOC of the current cluster; SOC RACK Current cluster SOC.

[0021] Furthermore, step S5 includes the following steps:

[0022] S51, continuously obtain the minimum voltage value V of the single battery during the battery pack discharge process min ;

[0023] S52, judge V min Is it less than or equal to the third-level alarm threshold Cell_Vol_Value_3? If so, continue to execute S53; otherwise, return to continue to execute S51;

[0024] S53, start the discharge control strategy, initialize the discharge step count COUNT_STEP=1, and execute the power reduction to the current power CURR_POWER for discharge; wherein CURR_POWER=reference power*(1-COUNT_STEP / S);

[0025] S54, judge V min Whether it decreases by an integer multiple of the corrected discharge single-step monomer dynamic step change amount ΔV'; if so, continue to execute S55; otherwise, return to continue to execute S54;

[0026] S55, add 1 to the discharge step count COUNT_STEP; determine whether COUNT_STEP is equal to S, if so, continue to execute S6; otherwise, execute power reduction to current power CURR_POWER for discharge, where CURR_POWER = reference power * (1-COUNT_STEP / S), and continue to execute S54.

[0027] Furthermore, the S6 includes the following steps:

[0028] S61, dynamically adjust the output current I out , where the output current is adjusted where K P is the proportional gain, fast response error; e is the voltage error, the calculation formula is e=V 目标恒压 -V 实际单体检测单体电压值 , K i is the integral gain, eliminating steady-state error;

[0029] S62. Obtain the current minimum voltage of the single cell and determine whether it is less than or equal to the undervoltage level 2 alarm or level 1 alarm threshold or the constant voltage and current limiting discharge mode stop condition. If so, discharge is terminated; otherwise, return to and continue to execute S61.

[0030] The present invention also provides a lithium battery discharge control system, which adopts the above method when the system is running, and includes the following modules:

[0031] The data acquisition module is used to collect the current single cell voltage value V, temperature value T, and cluster remaining charge SOC of the battery pack RACK , cluster average residual charge SOC avg and discharge status;

[0032] The undervoltage alarm setting module is used to set the three-level alarm level and threshold of single cell undervoltage. The alarm level decreases in severity from level 1 to level 3. The thresholds are Cell_Vol_Value_1, Cell_Vol_Value_2, and Cell_Vol_Value_3 respectively.

[0033] Dynamic step number calculation module, used to calculate the dynamic step number S of battery pack discharge;

[0034] Voltage change calculation module, used to calculate the change ΔV of the cell voltage dynamic step based on temperature correction ′ ;

[0035] The discharge control module is used to perform multi-level threshold trigger control and dynamic step-down power discharge of the battery pack based on the results obtained by the dynamic step number calculation module and the voltage change calculation module;

[0036] The constant voltage and current limiting control module is used to control the battery pack to perform constant voltage and current limiting discharge until the discharge is terminated.

[0037] Furthermore, the calculation formula of the dynamic step number calculation module for the battery pack discharge dynamic step number S is:

[0038]

[0039] Among them, Q is the total capacity of the energy storage battery; Q base is the benchmark capacity unit of the energy storage battery; floor[·] is the rounding function; S offset is the safety correction value, the maximum temperature of the battery cell T max >45℃ or battery health status SOH<80%, S offset =-1; in static state, S offset =0, in discharge correction mode, S offset =1.

[0040] Furthermore, the voltage variation calculation module includes the following units:

[0041] The dynamic step change unit is used to calculate the dynamic step change ΔV of the discharge single-step cell voltage. The calculation formula is as follows:

[0042]

[0043] Dynamic step change correction unit, used to calculate the corrected dynamic step change ΔV of the discharge single-step cell voltage′ , the calculation formula is as follows:

[0044] ΔV ′ =ΔV+α(TT ref )+β(SOC avg -SOC rack )

[0045] Where T is the real-time temperature of the monomer, in °C; T ref is the reference temperature, in °C; α is the temperature correction coefficient, in V / °C; β is the SOC correction coefficient, in V / %; SOC avg is the average SOC of the current cluster; SOC RACK Current stage cluster SOC.

[0046] Furthermore, the discharge control module is executed as follows:

[0047] (1) During the discharge process of the battery pack, the minimum voltage value V of the single battery is continuously obtained min ;

[0048] (2) Determine V min Is it less than or equal to the third-level alarm threshold Cell_Vol_Value_3? If so, continue to execute S53; otherwise, return to continue to execute (1);

[0049] (3) Start the discharge control strategy, initialize the discharge step count COUNT_STEP = 1, and execute the power reduction to the current power CURR_POWER discharge; where CURR_POWER = reference power * (1-COUNT_STEP / S);

[0050] (4) Determine V min Whether it decreases by an integer multiple of the corrected single-step discharge monomer dynamic step change ΔV'; if so, continue to execute (5); otherwise, return to continue to execute (4);

[0051] (5) The discharge step count COUNT_STEP is increased by 1; it is determined whether COUNT_STEP is equal to S. If so, the constant voltage and current limiting control module is continued to be executed; otherwise, the power is reduced to the current power CURR_POWER for discharge, where CURR_POWER = reference power * (1-COUNT_STEP / S), and the execution (4) is continued.

[0052] Furthermore, the constant voltage and current limiting control module is executed as follows:

[0053] (1) Dynamically adjust the output current I out , where the output current is adjusted where K Pis the proportional gain, fast response error; e is the voltage error, the calculation formula is e=V 目标恒压 -V 实际单体检测单体电压值 , K i is the integral gain, eliminating steady-state error;

[0054] (2) Obtain the current minimum value of the single cell voltage and determine whether it is less than or equal to the undervoltage level 2 alarm or level 1 alarm threshold or the constant voltage current limiting discharge mode stop condition. If so, discharge is terminated; otherwise, return to continue executing (1).

[0055] The advantages of the present invention are:

[0056] The present invention proposes a lithium battery discharge control system and method, which utilizes a temperature-SOC collaborative compensation calculation model to reduce voltage signal deviations and inconsistent cell aging caused by ambient temperature changes, increase the calculation accuracy of discharge step voltage differences, and thus improve the accuracy of discharge control of energy storage lithium batteries. At the same time, a dynamic mapping relationship between the dynamic step number S and the battery pack capacity Q is designed to avoid overregulation of small-capacity batteries and solve the problem of rapid cell voltage drop at the end of discharge. Finally, PI control is used to dynamically adjust the output current to achieve a constant voltage mode, maintain a constant voltage and current limiting discharge mode, solve the problem of premature undervoltage protection of single cells at the end of discharge caused by the chemical properties of the battery, and achieve efficient utilization of the discharge system capacity and maximize the benefits of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 The figure is a flow chart of a lithium battery discharge control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0059] Example 1

[0060] This embodiment assumes a 100MW / 200MWh energy storage power station with a single battery cluster capacity of 280kWh and uses 3.2V / 280Ah lithium iron phosphate cells, with a total of 160 cells connected in series (cluster voltage 512V). A lithium battery discharge control method is provided, such as Figure 1 As shown, the following steps are included:

[0061] S1. Collect the current single cell voltage value V, temperature value T, and cluster remaining charge SOC of the battery pack RACK, cluster average residual charge SOC avg and discharge status;

[0062] S2. Set the three-level alarm level and threshold for single cell undervoltage. The alarm levels decrease in severity from level 1 to level 3. The thresholds are Cell_Vol_Value_1, Cell_Vol_Value_2, and Cell_Vol_Value_3. In this embodiment, the alarm thresholds are set to 2.6V, 2.7V, and 2.8V respectively.

[0063] S3. Calculate the dynamic step number S of the battery pack discharge. The specific calculation formula is:

[0064]

[0065] Where Q is the total capacity of the energy storage battery; Qbase is the base capacity of the energy storage battery; floor[·] is the rounding function; S offset is the safety correction value, the maximum temperature of the battery cell T max >45℃ or battery health status SOH<80%, S offset =-1; in static state, S offset =0, in discharge correction mode, S offset =1.

[0066] S4. Calculate the change ΔV of the cell voltage dynamic step based on temperature correction ′ ; The specific implementation method includes the following steps:

[0067] S41. Calculate the dynamic step change ΔV of the discharge single-step cell voltage using the following formula:

[0068]

[0069] S42, calculating the corrected discharge single-step cell voltage dynamic step change ΔV ′ , the calculation formula is as follows:

[0070] ΔV ′ =ΔV+α(TT ref )+β(SOC avg -SOC rack )

[0071] Where T is the real-time temperature of the monomer, in °C; T ref is the reference temperature, in °C; α is the temperature correction coefficient, in V / °C; β is the SOC correction coefficient, in V / %; SOC avg is the average SOC of the current cluster; SOC RACK Current cluster SOC. The temperature compensation coefficient α is usually set to 0.003V / °C.

[0072] S5. Based on the results obtained in step S3 and step S4, the battery pack is subjected to multi-level threshold trigger control and dynamic step-down power discharge. The specific implementation includes the following steps:

[0073] S51, continuously obtaining the minimum voltage value Vmin of the single battery during the discharge process of the battery pack;

[0074] S52. Determine whether Vmin is less than or equal to the third-level alarm threshold Cell_Vol_Value_3; if so, continue to execute S53; otherwise, return to continue to execute S51;

[0075] S53, start the discharge control strategy, initialize the discharge step count COUNT_STEP=1, and execute the power reduction to the current power CURR_POWER for discharge; wherein CURR_POWER=reference power*(1-COUNT_STEP / S);

[0076] S54, determining whether Vmin decreases by an integer multiple of the corrected single-step discharge monomer dynamic step change ΔV'; if so, proceeding to S55; otherwise, returning to S54;

[0077] S55, add 1 to the discharge step count COUNT_STEP; determine whether COUNT_STEP is equal to S, if so, continue to execute S6; otherwise, execute power reduction to current power CURR_POWER for discharge, where CURR_POWER = reference power * (1-COUNT_STEP / S), and continue to execute S54.

[0078] S6: Control the battery pack to perform constant voltage and current limiting discharge until the discharge is terminated. The specific implementation includes the following steps:

[0079] S61, dynamically adjust the output current I out , where the output current is adjusted where K P is the proportional gain, fast response error; e is the voltage error, the calculation formula is e=V 目标恒压 -V 实际单体检测单体电压值 , K i is the integral gain, eliminating steady-state error;

[0080] S62. Obtain the current minimum voltage of the single cell and determine whether it is less than or equal to the undervoltage level 2 alarm or level 1 alarm threshold or the constant voltage and current limiting discharge mode stop condition. If so, discharge is terminated; otherwise, return to and continue to execute S61.

[0081] Example 2

[0082] This embodiment provides a lithium battery discharge control system. The system operates based on the method described in Example 1 and includes the following modules:

[0083] The data acquisition module is used to collect the current single cell voltage value V, temperature value T, and cluster remaining charge SOC of the battery pack RACK , cluster average residual charge SOC avg and discharge status;

[0084] The undervoltage alarm setting module is used to set the three-level alarm level and threshold of single cell undervoltage. The alarm level decreases in severity from level 1 to level 3. The thresholds are Cell_Vol_Value_1, Cell_Vol_Value_2, and Cell_Vol_Value_3 respectively.

[0085] The dynamic step number calculation module is used to calculate the dynamic step number S of the battery pack discharge. The calculation formula of the dynamic step number calculation module for the dynamic step number S of the battery pack discharge is:

[0086]

[0087] Among them, Q is the total capacity of the energy storage battery; Q base is the benchmark capacity unit of the energy storage battery; floor[·] is the rounding function; S offset is the safety correction value, the maximum temperature of the battery cell T max >45℃ or battery health status SOH<80%, S offset =-1; in static state, S offset =0, in discharge correction mode, S offset =1.

[0088] Voltage change calculation module, used to calculate the change ΔV of the cell voltage dynamic step based on temperature correction ′ The voltage variation calculation module includes the following units:

[0089] The dynamic step change unit is used to calculate the dynamic step change ΔV of the discharge single-step cell voltage. The calculation formula is as follows:

[0090]

[0091] Dynamic step change correction unit, used to calculate the corrected dynamic step change ΔV of the discharge single-step cell voltage ′ , the calculation formula is as follows:

[0092] ΔV ′ =ΔV+α(TT ref )+β(SOC avg -SOC rack )

[0093] Where T is the real-time temperature of the monomer, in °C; T ref is the reference temperature, in °C; α is the temperature correction coefficient, in V / °C; β is the SOC correction coefficient, in V / %; SOC avg is the average SOC of the current cluster; SOC RACK Current stage cluster SOC.

[0094] The discharge control module is used to perform multi-level threshold trigger control and dynamic step-down power discharge on the battery pack based on the results obtained by the dynamic step number calculation module and the voltage change calculation module. The execution method of the discharge control module is as follows:

[0095] (1) During the discharge process of the battery pack, the minimum voltage value V of the single battery is continuously obtained min ;

[0096] (2) Determine V min Is it less than or equal to the third-level alarm threshold Cell_Vol_Value_3? If so, continue to execute S53; otherwise, return to continue to execute (1);

[0097] (3) Start the discharge control strategy, initialize the discharge step count COUNT_STEP = 1, and execute the power reduction to the current power CURR_POWER discharge; where CURR_POWER = reference power * (1-COUNT_STEP / S);

[0098] (4) Determine V min Whether it decreases by an integer multiple of the corrected single-step discharge monomer dynamic step change ΔV'; if so, continue to execute (5); otherwise, return to continue to execute (4);

[0099] (5) The discharge step count COUNT_STEP is increased by 1; it is determined whether COUNT_STEP is equal to S. If so, the constant voltage and current limiting control module is continued to be executed; otherwise, the power is reduced to the current power CURR_POWER for discharge, where CURR_POWER = reference power * (1-COUNT_STEP / S), and the execution (4) is continued.

[0100] The constant voltage and current limiting control module is used to control the battery pack to perform constant voltage and current limiting discharge until the discharge is terminated. The execution mode of the constant voltage and current limiting control module is as follows:

[0101] (1) Dynamically adjust the output current I out , where the output current is adjusted where K P is the proportional gain, fast response error; e is the voltage error, the calculation formula is e=V 目标恒压 -V 实际单体检测单体电压值 , Ki is the integral gain, eliminating steady-state error;

[0102] (2) Obtain the current minimum value of the single cell voltage and determine whether it is less than or equal to the undervoltage level 2 alarm or level 1 alarm threshold or the constant voltage current limiting discharge mode stop condition. If so, discharge is terminated; otherwise, return to continue executing (1).

[0103] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A lithium battery discharge control method, characterized in that: The following steps are involved: S1. Collect the current single cell voltage value V, temperature value T, and cluster remaining charge SOC of the battery pack RACK , cluster average residual charge SOC avg and discharge status; S2. Set the three-level alarm level and threshold for single cell undervoltage. The alarm level decreases in severity from level 1 to level 3. The thresholds are Cell_Vol_Value_1, Cell_Vol_Value_2, and Cell_Vol_Value_3 respectively. S3. Calculate the dynamic step number S of battery pack discharge; S4. Calculate the change ΔV of the cell voltage dynamic step based on temperature correction ′ ; S5. Based on the results obtained in step S3 and step S4, the battery pack is subjected to multi-level threshold trigger control and dynamic step-down power discharge; S6. Control the battery pack to perform constant voltage and current limiting discharge until the discharge is terminated.

2. A lithium battery discharge control method according to claim 1, characterized in that: The calculation formula for the dynamic step number S of the battery pack discharge in step S3 is: Among them, Q is the total capacity of the energy storage battery; Q base is the energy storage battery benchmark capacity; floor[·] is the rounding function; S offset is the safety correction value, the maximum temperature of the battery cell T max >45℃ or battery health status SOH<80%, S offset =-1; in static state, S offset =0, in discharge correction mode, S offset =1.

3. A lithium battery discharge control method according to claim 1, characterized in that: The step S4 comprises the following steps: S41. Calculate the dynamic step change ΔV of the discharge single-step cell voltage using the following formula: S42, calculating the corrected discharge single-step cell voltage dynamic step change ΔV ′ , the calculation formula is as follows: ΔV ′ =ΔV+α(TT ref )+β(SOC avg -SOC rack ) Where T is the real-time temperature of the monomer, in °C; T ref is the reference temperature, in °C; α is the temperature correction coefficient, in V / °C; β is the SOC correction coefficient, in V / %; SOC avg is the average SOC of the current cluster; SOC RACK Current cluster SOC.

4. A lithium battery discharge control method according to claim 3, characterized in that: The step S5 comprises the following steps: S51, continuously obtain the minimum voltage value V of the single battery during the battery pack discharge process min ; S52, judge V min Is it less than or equal to the third-level alarm threshold Cell_Vol_Value_3? If so, continue to execute S53; otherwise, return to continue to execute S51; S53, start the discharge control strategy, initialize the discharge step count COUNT_STEP=1, and execute the power reduction to the current power CURR_POWER for discharge; wherein CURR_POWER=reference power*(1-COUNT_STEP / S); S54, judge V min Whether it decreases by an integer multiple of the corrected discharge single-step monomer dynamic step change amount ΔV'; if so, continue to execute S55; otherwise, return to continue to execute S54; S55, add 1 to the discharge step count COUNT_STEP; determine whether COUNT_STEP is equal to S, if so, continue to execute S6; otherwise, execute power reduction to current power CURR_POWER for discharge, where CURR_POWER = reference power * (1-COUNT_STEP / S), and continue to execute S54.

5. The lithium battery discharge control method according to claim 1, wherein: The S6 comprises the following steps: S61, dynamically adjust the output current I out , where the output current is adjusted where K P is the proportional gain, fast response error; e is the voltage error, the calculation formula is e=V 目标恒压 -V 实际单体检测单体电压值 , K i is the integral gain, eliminating steady-state error; S62. Obtain the current minimum voltage of the single cell and determine whether it is less than or equal to the undervoltage level 2 alarm or level 1 alarm threshold or the constant voltage and current limiting discharge mode stop condition. If so, discharge is terminated; otherwise, return to and continue to execute S61.

6. A lithium battery discharge control system, characterized in that: Includes the following modules: The data acquisition module is used to collect the current single cell voltage value V, temperature value T, cluster remaining charge SOCRACK, cluster average remaining charge SOCavg and discharge status of the battery pack; The undervoltage alarm setting module is used to set the three-level alarm level and threshold of single cell undervoltage. The alarm level decreases in severity from level 1 to level 3. The thresholds are Cell_Vol_Value_1, Cell_Vol_Value_2, and Cell_Vol_Value_3 respectively. Dynamic step number calculation module, used to calculate the dynamic step number S of battery pack discharge; Voltage change calculation module, used to calculate the change ΔV of the cell voltage dynamic step based on temperature correction ′ ; The discharge control module is used to perform multi-level threshold trigger control and dynamic step-down power discharge of the battery pack based on the results obtained by the dynamic step number calculation module and the voltage change calculation module; The constant voltage and current limiting control module is used to control the battery pack to perform constant voltage and current limiting discharge until the discharge is terminated.

7. A lithium battery discharge control system according to claim 6, characterized in that: The calculation formula of the dynamic step number calculation module for the battery pack discharge dynamic step number S is: Among them, Q is the total capacity of the energy storage battery; Q base is the benchmark capacity unit of the energy storage battery; floor[·] is the rounding function; S offset is the safety correction value, the maximum temperature of the battery cell T max >45℃ or battery health status SOH<80%, S offset =-1; in static state, S offset =0, in discharge correction mode, S offset =1.

8. A lithium battery discharge control system according to claim 6, characterized in that: The voltage variation calculation module includes the following units: The dynamic step change unit is used to calculate the dynamic step change ΔV of the discharge single-step cell voltage. The calculation formula is as follows: Dynamic step change correction unit, used to calculate the corrected dynamic step change ΔV of the discharge single-step cell voltage ′ , the calculation formula is as follows: ΔV ′ =ΔV+α(TT ref )+β(SOC avg -SOC rack ) Where T is the real-time temperature of the monomer, in °C; T ref is the reference temperature, in °C; α is the temperature correction coefficient, in V / °C; β is the SOC correction coefficient, in V / %; SOC avg is the average SOC of the current cluster; SOC RACK Current stage cluster SOC.

9. A lithium battery discharge control system according to claim 8, characterized in that: The discharge control module is executed as follows: (1) During the discharge process of the battery pack, the minimum voltage value V of the single battery is continuously obtained min ; (2) Determine V min Is it less than or equal to the third-level alarm threshold Cell_Vol_Value_3? If so, continue to execute S53; otherwise, return to continue to execute (1); (3) Start the discharge control strategy, initialize the discharge step count COUNT_STEP = 1, and execute the power reduction to the current power CURR_POWER discharge; where CURR_POWER = reference power * (1-COUNT_STEP / S); (4) Determine V min Whether it decreases by an integer multiple of the corrected single-step discharge monomer dynamic step change ΔV'; if so, continue to execute (5); otherwise, return to continue to execute (4); (5) The discharge step count COUNT_STEP is increased by 1; it is determined whether COUNT_STEP is equal to S. If so, the constant voltage and current limiting control module is continued to be executed; otherwise, the power is reduced to the current power CURR_POWER for discharge, where CURR_POWER = reference power * (1-COUNT_STEP / S), and the execution (4) is continued.

10. A lithium battery discharge control system according to claim 6, characterized in that: The execution mode of the constant voltage and current limiting control module is as follows: (1) Dynamically adjust the output current I out , where the output current is adjusted where K P is the proportional gain, fast response error; e is the voltage error, the calculation formula is e=V 目标恒压 -V 实际单体检测单体电压值 , K i is the integral gain, eliminating steady-state error; (2) Obtain the current minimum value of the single cell voltage and determine whether it is less than or equal to the undervoltage level 2 alarm or level 1 alarm threshold or the constant voltage current limiting discharge mode stop condition. If so, discharge is terminated; otherwise, return to continue executing (1).

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