Method for online balancing SOC of energy storage battery

Abstract

The invention provides a method for online balancing the SOC of an energy storage battery, and relates to the technical field of energy storage battery management. The method comprises the following steps: S1, collecting data in a battery pack; s2, calculating the SOC value of the battery; s3, classifying the batteries according to the SOC values; s4, sequential pairing is carried out, and the electric quantity of the batteries in the high SOC group is transferred to the low SOC group; s5, when a transfer stopping condition is met, stopping the transfer; s6, when the electric quantity transfer is finished, classifying the single batteries of which the SOC values meet the conditions of the middle SOC group in the high SOC group and the low SOC group into the middle SOC group; s7, repeating the steps S4-S6, and processing according to conditions; and S8, re-grouping the batteries, and repeating the steps S4-S7 until the equalization condition is met. The method has the beneficial effects that the grouping threshold can be selected more reasonably, and the equalization efficiency is improved; balancing operation is performed on the battery pack in a step-by-step balancing mode, so that the probability of repeated balancing of the single batteries can be effectively reduced; multi-battery equalization can be simultaneously carried out through grouping and pairing, and the equalization efficiency is further improved.

Description

Technical Field

[0001] This invention relates to the field of energy storage battery management technology, and more specifically to a method for online balancing of the state of charge (SOC) of an energy storage battery. Background Technology

[0002] Energy dissipation-type equalization management is a passive, individual cell equalization method. This method has a long equalization period, sometimes taking several months to equalize all the individual cells in an entire battery string.

[0003] Therefore, researchers have conducted in-depth studies on online balancing. Group balancing can improve the balancing rate, but it suffers from insufficient adaptability due to a fixed threshold. The problem with a fixed threshold is that it is difficult to cope with the impact of dynamic factors such as battery aging and temperature changes on the SOC balancing requirements. Summary of the Invention

[0004] The main objective of this invention is to provide a method for online balancing of the State of Charge (SOC) of energy storage batteries, which uses an adaptive variable threshold grouping approach to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for online balancing of the state of charge (SOC) of an energy storage battery, comprising the following steps: S1. Collect data on the voltage, current, and temperature of each battery in the battery pack; S2. Calculate the SOC value of each battery; S3. Classify the batteries according to their SOC values ​​into high SOC group, medium SOC group and low SOC group; S4. Pair the batteries in the high SOC group with the batteries in the low SOC group in sequence, and transfer the power of the batteries in the high SOC group to the low SOC group. S5. When the individual cells in the battery pack reach the transfer stop condition, the transfer is terminated. S6. When all the batteries in the battery pack have finished transferring power, the individual cells whose SOC values ​​meet the conditions of the medium SOC group in the high SOC group and low SOC group will be classified into the medium SOC group. S7. Repeat steps S4~S6, and the following three situations will occur: Scenario 1: All individual cells are classified into the medium SOC group; Scenario 2: Most of the individual cells belong to the medium SOC group, and a small portion belong to the low SOC group. The medium SOC group and the low SOC group are matched sequentially, and the energy of the cells in the medium SOC group is transferred to the low SOC group. Finally, all the individual cells are classified into the medium SOC group. Scenario 3: Most of the individual cells belong to the medium SOC group, and a small portion belong to the high SOC group. The medium SOC group and the high SOC group are matched sequentially, and the energy of the cells in the high SOC group is transferred to the medium SOC group. Finally, all the individual cells are classified into the medium SOC group. S8. Re-divide all batteries into high SOC group, medium SOC group and low SOC group according to SOC value, and repeat steps S4 to S7 until the equalization condition is met.

[0006] Furthermore, the battery grouping steps are as follows: S201. Determine the initial values ​​of the grouping thresholds SOC1 and SOC2; S202. The threshold is adjusted based on the average temperature of the battery pack and the number of charge cycles. The adjustment process is as follows: (1); Among them, SOC x SOC is the grouping threshold. x 0 is the initial value for the grouping threshold. k 1. k 2 is the correction factor. This represents the normalized error between the real-time temperature and the set temperature. This represents the number of loop iterations. S203. When the SOC value of a single cell is less than SOC1, it is classified into the low SOC group; when the SOC value of a single cell is greater than or equal to SOC1 and less than or equal to SOC2, it is classified into the medium SOC group; when the SOC value of a single cell is greater than SOC2, it is classified into the high SOC group.

[0007] Furthermore, the aforementioned The expression is: (2); in, T r This is the real-time temperature value. T 0 represents the standard temperature value; The The expression is: (3); in, C r The number of loops. C 0 is the baseline value for the number of iterations.

[0008] Furthermore, the sequential pairing process is as follows: the corresponding group numbers for the high, medium, and low groups are set to 3, 2, and 1; For any two paired groups, compare their group numbers. Groups with larger group numbers are sorted in descending order of SOC value, and groups with smaller group numbers are sorted in ascending order of SOC value. Individual cells in the two groups are paired one by one according to the sorting order. Individual cells that are left over due to the difference in the number of cells in the two groups are not processed.

[0009] Furthermore, in step S5, the transfer stopping condition is: In the high SOC group, the SOC value of the battery drops to SOC2, or in the low SOC group, the SOC value of the battery rises to SOC1.

[0010] Furthermore, in scenario 2, the power transfer process is as follows: Batteries in the medium SOC group and low SOC group are paired according to the sequential pairing principle. When the SOC value of a single cell in the medium SOC group drops to (SOC1+SOC2) / 2 or the SOC value of a cell in the low SOC group rises to SOC1, the transfer stops. When the transfer of all single cells is completed, the single cells in the low SOC group that meet the conditions are transferred to the medium SOC group. Repeat the above process until all batteries in the low SOC group are transferred to the medium SOC group. In scenario 3, the power transfer process is as follows: Batteries in the medium SOC group and high SOC group are paired according to the sequential pairing principle. When the SOC value of a single cell in the medium SOC group rises to (SOC1+SOC2) / 2 or the SOC value of a battery in the high SOC group drops to SOC12, the power transfer is stopped. When the transfer of all single cells is completed, the single cells in the high SOC group that meet the conditions are transferred to the medium SOC group. Repeat the above process until all batteries in the high SOC group are reassigned to the medium SOC group.

[0011] Furthermore, in step S8, the regrouping method is as follows: Determine the iteration coefficients β The value of is used to iteratively update the grouping threshold: (4); The batteries were reclassified into low SOC, medium SOC, and high SOC groups based on the updated grouping thresholds.

[0012] Furthermore, the equilibrium condition is: the difference between the maximum and minimum SOC values ​​of the batteries in the battery pack is less than the equilibrium threshold.

[0013] Furthermore, the energy storage battery, during charging, preferentially charges individual cells in the low SOC group. During discharge, individual cells in the high SOC group are discharged preferentially.

[0014] The present invention also provides an online equalization energy storage battery SOC management system to implement the steps in the above method, including: a control module, a charging module, an equalization module, a data acquisition module, a power calculation module, and a communication module; The data acquisition module is connected to the power calculation module and is used to collect the battery's voltage, current, and temperature data, and send the data to the power calculation module. The power calculation module calculates the SOC value of the batteries in the battery pack based on the data sent by the data acquisition module, and sends the data to the control module. The charging module is connected to the control module and charges the battery pack according to the instructions of the control module. Before charging, the charging module will first perform initialization and self-test to determine whether it is working properly and at the same time check whether the current conditions meet the charging requirements. The control module is connected to the equalization module. It determines the battery equalization scheme based on the SOC value data and sends the control signal to the equalization module. The equalization module turns the equalization switch on and off according to the control signal from the control module to achieve battery pack equalization. The communication module is used to enable communication and data transmission between the various modules.

[0015] Beneficial effects: The beneficial effects of this invention are as follows: (1) Set the grouping threshold to adapt to changes in battery temperature and cycle number, taking into account the effects of battery temperature and battery aging, so that the selection of the grouping threshold is more reasonable and the balancing efficiency is improved. (2) Iteratively update the grouping threshold and perform equalization operation on the battery pack in a step-by-step equalization method, which can effectively reduce the probability of repeated equalization of individual cells. (3) Group pairing can perform multi-battery equalization simultaneously, further improving equalization efficiency. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a flowchart of the method steps of the present invention; Figure 2 This is a system structure diagram of the present invention. Detailed Implementation

[0017] Example 1 like Figure 1 As shown, a method for online balancing of the state of charge (SOC) of an energy storage battery includes the following steps: S1. Collect data on the voltage, current, and temperature of each battery in the battery pack.

[0018] S2. The SOC value of each battery can be calculated using the Kalman filter method or the ampere-hour integration method.

[0019] S3. Classify the batteries according to their SOC values ​​into high SOC, medium SOC, and low SOC groups, corresponding to group numbers 3, 2, and 1. Taking a battery pack with 10 individual cells as an example, the SOC values ​​of individual cells 1 to 10 are 20%, 24%, 46%, 35%, 78%, 56%, 67%, 32%, 26%, and 68%, respectively. The grouping process is as follows: A1. Determine the initial values ​​of the grouping thresholds SOC1 and SOC2 to be 36% and 64%, respectively; A2. Adjust the threshold based on the average temperature of the battery pack and the number of charge cycles. The adjustment process is as follows: (1); Among them, SOC x SOC is the grouping threshold. x 0 is the initial value for the grouping threshold. k 1. k 2 is a correction factor; values ​​of 0.02 and 0.0002 are preferable. This represents the normalized error between the real-time temperature and the set temperature. This represents the number of loop iterations. The The expression is: (2); in, T r The real-time temperature is 42 degrees Celsius. T 0 represents the standard temperature value, which is 35 degrees Celsius. The The expression is: (3); in, C r The loop count is 200. C 0 represents the base number of iterations, which is 500. Therefore, SOC1 = 36% - 0.4% = 35.6%; SOC2 = 64% - 0.4% = 63.6%; A3. When the SOC value of a single cell is less than SOC1, it is classified into the low SOC group. When the SOC value of a single cell is greater than or equal to SOC1 and less than or equal to SOC2, it is classified into the medium SOC group. When the SOC value of a single cell is greater than SOC2, it is classified into the high SOC group. The low SOC group includes cells 1, 2, 4, 8, and 9; the medium SOC group includes cells 3 and 6; and the high SOC group includes cells 5, 7, and 10.

[0020] S4. Sequentially pair the batteries in the high SOC group with the batteries in the low SOC group. The specific process for sequential pairing is as follows: Compare the serial numbers of the high SOC group and the low SOC group. Since 3 > 1, arrange the individual cells in the high SOC group in descending order as 5, 10, 7, and arrange them in ascending order as 1, 2, 9, 8, 4. Pair cells 5 with 1, 10 with 2, and 7 with 9. Do not operate on cells 8 and 4. The energy is transferred from the high SOC group to the low SOC group. The SOC value after the transfer is determined by the transfer efficiency. Taking single cell 5 and 1 as an example, let the SOC value of cell 5 after the conversion be... a The SOC value after conversion of battery 1 is b The conversion formula is: (4); in, φ For conversion efficiency.

[0021] S5. When the individual cells in the battery pack reach the transfer stop condition, the transfer is terminated. The conditions for terminating the transfer are: the SOC value of the battery in the high SOC group drops to SOC2 or the SOC value of the battery in the low SOC group rises to SOC1; S6. When all the batteries in the battery pack have finished transferring power, the individual cells whose SOC values ​​meet the conditions of the medium SOC group in the high SOC group and low SOC group will be classified into the medium SOC group. S7. Repeat steps S4~S6, and the following three situations will occur: Scenario 1: All individual cells are classified into the medium SOC group; Scenario 2: Most of the individual cells belong to the medium SOC group, and a small portion belong to the low SOC group. The medium SOC group and the low SOC group are matched sequentially, and the energy of the cells in the medium SOC group is transferred to the low SOC group. Finally, all the individual cells are classified into the medium SOC group. Batteries in the medium SOC group and low SOC group are paired according to the sequential pairing principle. When the SOC value of a single cell in the medium SOC group drops to (SOC1+SOC2) / 2 or the SOC value of a cell in the low SOC group rises to SOC1, the transfer stops. When the transfer of all single cells is completed, the single cells in the low SOC group that meet the conditions are transferred to the medium SOC group. Repeat the above process until all batteries in the low SOC group are transferred to the medium SOC group. Scenario 3: Most of the individual cells belong to the medium SOC group, and a small portion belong to the high SOC group. The medium SOC group and the high SOC group are matched sequentially, and the energy of the cells in the high SOC group is transferred to the medium SOC group. Finally, all the individual cells are classified into the medium SOC group. Batteries in the medium SOC group and high SOC group are paired according to the sequential pairing principle. When the SOC value of a single cell in the medium SOC group rises to (SOC1+SOC2) / 2 or the SOC value of a battery in the high SOC group drops to SOC2, the power transfer is stopped. When the transfer of all single cells is completed, the single cells in the high SOC group that meet the conditions are transferred to the medium SOC group. Repeat the above process until all batteries in the high SOC group are reassigned to the medium SOC group.

[0022] S8. Re-divide all batteries into high SOC group, medium SOC group and low SOC group according to their SOC value. Repeat steps S4 to S7 until the balance condition is met: the difference between the maximum and minimum SOC values ​​of the batteries in the battery group is less than the balance threshold, which is 1.5%. The regrouping method is as follows: Determine the iteration coefficients β The value of is used to iteratively update the grouping threshold: (4); Based on the updated grouping thresholds, the batteries are reclassified into low SOC, medium SOC, and high SOC groups. The iteration coefficients are reselected after each update to adapt to the actual SOC of the batteries.

[0023] During charging, the aforementioned energy storage battery pack prioritizes charging individual cells in the low SOC group. During discharge, individual cells in the high SOC group are discharged preferentially.

[0024] Example 2 like Figure 2 As shown in the figure, in conjunction with Embodiment 1, an online equalization energy storage battery SOC management system is used to implement the steps in the above method, including: a control module, a charging module, an equalization module, a data acquisition module, a power calculation module, and a communication module; The data acquisition module is connected to the power calculation module and is used to collect the battery's voltage, current, and temperature data, and send the data to the power calculation module. The power calculation module calculates the SOC value of the batteries in the battery pack based on the data sent by the data acquisition module, and sends the data to the control module. The charging module is connected to the control module and charges the battery pack according to the instructions of the control module. Before charging, the charging module will first perform initialization and self-test to determine whether it is working properly and at the same time check whether the current conditions meet the charging requirements. The control module is connected to the equalization module. It determines the battery equalization scheme based on the SOC value data and sends the control signal to the equalization module. The equalization module turns the equalization switch on and off according to the control signal from the control module to achieve battery pack equalization. The communication module is used to enable communication and data transmission between the various modules.

[0025] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for online balancing of the State of Charge (SOC) of an energy storage battery, characterized in that: Includes the following steps: S1. Collect data on the voltage, current, and temperature of each battery in the battery pack; S2. Calculate the SOC value of each battery; S3. Classify the batteries according to their SOC values ​​into high SOC group, medium SOC group and low SOC group; S4. Pair the batteries in the high SOC group with the batteries in the low SOC group in sequence, and transfer the power of the batteries in the high SOC group to the low SOC group. S5. When the individual cells in the battery pack reach the transfer stop condition, the transfer is terminated. S6. When all the batteries in the battery pack have finished transferring power, the individual cells whose SOC values ​​meet the conditions of the medium SOC group in the high SOC group and low SOC group will be classified into the medium SOC group. S7. Repeat steps S4~S6, and the following three situations will occur: Scenario 1: All individual cells are classified into the medium SOC group; Scenario 2: Most of the individual cells belong to the medium SOC group, and a small portion belong to the low SOC group. The medium SOC group and the low SOC group are matched sequentially, and the energy of the cells in the medium SOC group is transferred to the low SOC group. Finally, all the individual cells are classified into the medium SOC group. Scenario 3: Most of the individual cells belong to the medium SOC group, and a small portion belong to the high SOC group. The medium SOC group and the high SOC group are matched sequentially, and the energy of the cells in the high SOC group is transferred to the medium SOC group. Finally, all the individual cells are classified into the medium SOC group. S8. Re-divide all batteries into high SOC group, medium SOC group and low SOC group according to SOC value, and repeat steps S4 to S7 until the equalization condition is met.

2. The method for online balancing of the state of charge (SOC) of an energy storage battery according to claim 1, characterized in that: The steps for battery grouping are as follows: S201. Determine the initial values ​​of the grouping thresholds SOC1 and SOC2; S202. The threshold is adjusted based on the average temperature of the battery pack and the number of charge cycles. The adjustment process is as follows: （1）； Among them, SOC x SOC is the grouping threshold. x 0 is the initial value for the grouping threshold. k 1. k 2 is the correction factor. This represents the normalized error between the real-time temperature and the set temperature. This represents the number of loop iterations. S203. When the SOC value of a single cell is less than SOC1, it is classified into the low SOC group; when the SOC value of a single cell is greater than or equal to SOC1 and less than or equal to SOC2, it is classified into the medium SOC group; when the SOC value of a single cell is greater than SOC2, it is classified into the high SOC group.

3. The method for online balancing of the state of charge (SOC) of an energy storage battery according to claim 2, characterized in that: The The expression is: （2）； in, T r This is the real-time temperature value. T 0 represents the standard temperature value; The The expression is: （3）； in, C r The number of loops. C 0 is the baseline value for the number of iterations.

4. The method for online balancing of the state of charge (SOC) of an energy storage battery according to claim 1, characterized in that: The sequential pairing process is as follows: set the corresponding group numbers for the high, medium, and low groups to 3, 2, and 1; For any two paired groups, compare their group numbers. Groups with larger group numbers are sorted in descending order of SOC value, and groups with smaller group numbers are sorted in ascending order of SOC value. Individual cells in the two groups are paired one by one according to the sorting order. Individual cells that are left over due to the difference in the number of cells in the two groups are not processed.

5. The method for online balancing of the state of charge (SOC) of an energy storage battery according to claim 1, characterized in that: In step S5, the transfer stopping condition is: In the high SOC group, the SOC value of the battery drops to SOC2, or in the low SOC group, the SOC value of the battery rises to SOC1.

6. The method for online balancing of the state of charge (SOC) of an energy storage battery according to claim 4, characterized in that: In scenario 2, the power transfer process is as follows: Batteries in the medium SOC group and low SOC group are paired according to the sequential pairing principle. When the SOC value of a single cell in the medium SOC group drops to (SOC1+SOC2) / 2 or the SOC value of a cell in the low SOC group rises to SOC1, the transfer stops. When the transfer of all single cells is completed, the single cells in the low SOC group that meet the conditions are transferred to the medium SOC group. Repeat the above process until all batteries in the low SOC group are transferred to the medium SOC group. In scenario 3, the power transfer process is as follows: Batteries in the medium SOC group and high SOC group are paired according to the sequential pairing principle. When the SOC value of a single cell in the medium SOC group rises to (SOC1+SOC2) / 2 or the SOC value of a battery in the high SOC group drops to SOC12, the power transfer is stopped. When the transfer of all single cells is completed, the single cells in the high SOC group that meet the conditions are transferred to the medium SOC group. Repeat the above process until all batteries in the high SOC group are reassigned to the medium SOC group.

7. The method for online balancing of the state of charge (SOC) of an energy storage battery according to claim 1, characterized in that: In step S8, the regrouping method is as follows: Determine the iteration coefficients β The value of is used to iteratively update the grouping threshold: （4）； The batteries were reclassified into low SOC, medium SOC, and high SOC groups based on the updated grouping thresholds.

8. The method for online balancing of the state of charge (SOC) of an energy storage battery according to claim 1, characterized in that: The equilibrium condition is: the difference between the maximum and minimum SOC values ​​of the batteries in the battery pack is less than the equilibrium threshold.

9. The method for online balancing of the state of charge (SOC) of an energy storage battery according to claim 1, characterized in that: The energy storage battery, when being charged, prioritizes charging individual cells in the low SOC group. During discharge, individual cells in the high SOC group are discharged preferentially.

10. An online equalization energy storage battery SOC management system, used to implement the steps of the method described in any one of claims 1 to 9, characterized in that: include: Control module, charging module, equalization module, data acquisition module, power calculation module, and communication module; The data acquisition module is connected to the power calculation module and is used to collect the battery's voltage, current, and temperature data, and send the data to the power calculation module. The power calculation module calculates the SOC value of the batteries in the battery pack based on the data sent by the data acquisition module, and sends the data to the control module. The charging module is connected to the control module and charges the battery pack according to the instructions of the control module. Before charging, the charging module will first perform initialization and self-test to determine whether it is working properly and at the same time check whether the current conditions meet the charging requirements. The control module is connected to the equalization module. It determines the battery equalization scheme based on the SOC value data and sends the control signal to the equalization module. The equalization module turns the equalization switch on and off according to the control signal from the control module to achieve battery pack equalization. The communication module is used to enable communication and data transmission between the various modules.

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