A ternary lithium-lithium iron phosphate hybrid battery pack balancing method

Abstract

The invention discloses a ternary lithium-lithium iron phosphate hybrid battery pack balancing method: step 1, setting voltage thresholds for batteries of two systems; step 2, when the sum of the charging voltages of the battery monomers is respectively greater than or equal to the voltage thresholds of each system, calculating the charging current integral of the monomer until charging is completed, and obtaining the charging power corresponding to each battery monomer; step 3, selecting the monomers with the smallest charging power in the battery respectively, making a difference in the corresponding charging power, obtaining the charging power difference of the special-shaped battery cells, performing charging power difference iteration, and obtaining an iteration result; step 4, taking the iteration result as the target balanced discharge power; step 5, feeding back the estimation of the charging power difference of the special-shaped battery cells, and judging whether the charging power difference of the special-shaped battery cells increases or decreases due to natural evolution; step 6, performing difference iteration on the target balanced discharge power and the discharge balanced power; step 7, judging whether the battery pack performs a special-shaped battery cell balancing operation according to the comparison between the difference and the set value.

Description

Technical Field

[0001] The present invention relates to the technical field of battery management systems, and in particular to a ternary lithium-lithium iron phosphate hybrid battery pack equalization method. Background Art

[0002] Lithium iron phosphate cells, which can be reused, are more sustainable, and have lower manufacturing carbon emissions, will be further widely used in electric vehicles and grid energy storage. However, compared with ternary lithium batteries, lithium iron phosphate batteries still have shortcomings in energy density and low-temperature performance, and current battery packs are all composed of a single cell, which cannot fully utilize the advantages of each system battery. However, under reasonable configuration matching and management, ternary lithium-lithium iron phosphate hybrid battery packs can effectively reduce the risk of heat spread, reconcile cost and energy density, and comprehensively utilize the respective advantages of the two cells, so they are expected to replace the two pure battery packs.

[0003] However, it is worth noting that the battery cells of the two different systems have different characteristics such as self-discharge rate and aging rate. If corresponding corrective measures are not taken, during the long-term use of the hybrid battery pack, its configuration will change due to the difference in power between the different-shaped battery cells, resulting in the attenuation of the available energy of the hybrid battery pack, seriously affecting the user experience.

[0004] To this end, a heterogeneous difference state observer is proposed to target the differences in heterogeneous battery cells. By providing long-term intermittent feedback on the charging capacity differences of heterogeneous battery cells in the hybrid battery pack and combining it with a balancing algorithm to adjust the capacity and capacity matching of the configuration, stable or less attenuated energy output expectations can be achieved. Summary of the invention

[0005] The present invention is made to solve the above-mentioned problem, and its purpose is to provide a method for equalizing a ternary lithium-lithium iron phosphate hybrid battery pack.

[0006] The present invention provides a ternary lithium-lithium iron phosphate hybrid battery pack balancing method, which has the following characteristics: the hybrid battery pack comprises N ternary lithium battery cells and N lithium iron phosphate battery cells, the ternary lithium battery cells and the lithium iron phosphate battery cells are connected in series, and the method comprises the following steps: step 1, during the charging process, setting voltage thresholds U for the batteries of the two systems respectively T_NCM and U T_LFP ; Step 2, when the charging voltage U of each single cell of the two system batteries NCM，i and U LFP，i Respectively greater than or equal to the voltage threshold U of each system T_NCM and U T_LFP When the charging current integral of the single cell is calculated, the charging current integral of each single cell of the two systems is obtained until the charging is completed. NCM，i and Q LFP，iStep 3: Select the cells with the smallest charge capacity in the two system batteries respectively, and make their corresponding charge capacity Q NCM，i and Q LFP，i Difference is made to obtain the difference in charging capacity Q of different-shaped cells. D , and use it as the control target for the balancing of heterogeneous cells in the hybrid battery pack, and iterate the charging power difference at the end of the next charging to obtain the iteration result; Step 4, use the iteration result as the target balanced discharge power Q E Step 5: Feedback the charging capacity difference Q of the heterogeneous battery cells based on the heterogeneous difference state observer D Estimate the difference in charge capacity Q between the different-shaped cells and determine whether the difference is caused by natural evolution. D Increase or decrease; Step 6, set the target balanced discharge power Q E The balancing resistor of the corresponding battery system performs difference iteration at the discharge balancing capacity of each sampling period Δt; Step 7, according to the difference and the set value Q d By comparing the data of the hybrid battery pack, it is determined whether the hybrid battery pack is performing a balancing operation on the special-shaped cells, thereby controlling the opening or closing of the balancing controller.

[0007] The ternary lithium-lithium iron phosphate hybrid battery pack balancing method provided by the present invention may also have the following characteristics: wherein, in step 1, when setting the voltage threshold U T_NCM and U T_LFP When charging, due to the different upper and lower cut-off voltage ranges of the two systems' battery cells, it is necessary to monitor the charging voltage of each system's cells separately. Therefore, part of the charging voltage curve is selected for the ternary lithium battery and lithium iron phosphate battery respectively, and the setting standard for the lithium iron phosphate battery system is after the plateau period.

[0008] The ternary lithium-lithium iron phosphate hybrid battery pack balancing method provided by the present invention may also have the following characteristics: wherein, in step 2, the charging power Q is estimated by current integration. NCM，i and Q LFP，i ; If the ternary lithium monomer in the hybrid battery pack reaches the threshold when the battery pack is charged, it is expressed as:

[0009]

[0010] If the lithium iron phosphate monomer in the hybrid battery pack reaches the threshold value when the battery pack is charged, it is expressed as:

[0011]

[0012] Where I is the battery pack charging current, t e The end time of charging the hybrid battery pack, t N，s ,t L，s are the moments corresponding to the voltage thresholds of ternary lithium and lithium iron phosphate, respectively, Q NCM，iis the charge capacity of the ternary lithium monomer, Q LFP，i is the charging capacity of the i-th lithium iron phosphate monomer.

[0013] The ternary lithium-lithium iron phosphate hybrid battery pack balancing method provided by the present invention may also have the following characteristics: wherein, in step 3, the balancing type of the hybrid battery pack includes balancing of the same type of cells and balancing of the different type of cells.

[0014] The balancing method for the ternary lithium-lithium iron phosphate hybrid battery pack provided by the present invention may also have the following characteristics: for balancing the same type of cells, a balancing algorithm with consistent remaining charge capacity is used to control the balancing channel.

[0015] The ternary lithium-lithium iron phosphate hybrid battery pack balancing method provided by the present invention may also have the following characteristics: wherein, for the balancing of heterogeneous cells, the control process is: respectively selecting the cells with the smallest charge capacity in the two system batteries, so that their corresponding charge capacity Q NCM，i and Q LFP，i The difference is expressed as:

[0016] Q D =min(Q LFP，i )-min(Q NCM，i )

[0017] In the formula, min(Q LFP，i ) is the lithium iron phosphate monomer with the smallest charge capacity in the hybrid battery pack, min(Q NCM，i ) is the ternary lithium monomer with the smallest charge capacity in the hybrid battery pack, Q D It is the difference in charging capacity of different-shaped batteries.

[0018] The ternary lithium-lithium iron phosphate hybrid battery pack balancing method provided by the present invention may also have the following characteristics: wherein the process of iterating the charging power difference of the heterogeneous battery cells is expressed as:

[0019] Q e =Q D，0 -Q D，i

[0020] In the formula, Q D，0 is the difference in initial charge capacity of heterogeneous cells under the original configuration of the hybrid battery pack, Q D，i is the difference in charge capacity recorded at the end of the i-th charge between cells of different shapes, Q e is the theoretical target balanced power of special-shaped cells. To prevent over-balancing, the over-balancing coefficient K should be selected, and K < 1, that is, the target balanced discharge power Q E for:

[0021] Q E =KQe .

[0022] In the ternary lithium-lithium iron phosphate hybrid battery pack balancing method provided by the present invention, it can also have the following characteristics: wherein, in step 5, it naturally evolves into: in actual situations, since the power changes of each monomer in the series hybrid battery pack are not completely consistent, and the self-discharge rate, aging rate and other characteristics of the ternary lithium battery system and the lithium iron phosphate battery system are different, the batteries of each system show different attenuation rates, resulting in a difference in charging power Q between the heterogeneous cells. D Increase or decrease.

[0023] In the ternary lithium-lithium iron phosphate hybrid battery pack balancing method provided by the present invention, it can also have the following characteristics: wherein, in step 5, it is determined whether the charging power difference Q of the heterogeneous battery cell is caused by natural evolution. D In the process of increasing or decreasing, the main consideration is the cell attenuation caused by the self-discharge rate.

[0024] The ternary lithium-lithium iron phosphate hybrid battery pack balancing method provided by the present invention may also have the following characteristics: wherein, in step 6, the target balanced discharge power Q E The difference between the discharge balance capacity of the corresponding battery system's balance resistor in each sampling period Δt is expressed as:

[0025] Q E，i+1 =Q E，i -I E ·Δt

[0026] In the formula, Q E，i is the target balanced charge between heterogeneous cells in the battery pack in the i-th sampling cycle, I E is the vector composed of the balanced current of each monomer, Δt is the duration of each sampling cycle, Q E，i+1 It is the target balanced power among the heterogeneous cells in the i+1th sampling period.

[0027] Functions and Effects of the Invention

[0028] According to the ternary lithium-lithium iron phosphate hybrid battery pack balancing method involved in the present invention, the specific process is as follows: Step 1, during the charging process, the voltage thresholds U are set for the batteries of the two systems respectively. T_NCM and U T_LFP ; Step 2, when the charging voltage U of each single cell of the two system batteries NCM，i and U LFP，i Respectively greater than or equal to the voltage threshold U of each system T_NCM and U T_LFP When the charging current integral of the single cell is calculated, the charging current integral of each single cell of the two systems is obtained until the charging is completed. NCM，i and QLFP，i Step 3: Select the cells with the smallest charge capacity in the two system batteries respectively, and make their corresponding charge capacity Q NCM，i and Q LFP，i Difference is made to obtain the difference in charging capacity Q of different-shaped cells. D , and use it as the control target for the balancing of heterogeneous cells in the hybrid battery pack, and iterate the charging power difference at the end of the next charging to obtain the iteration result; Step 4, use the iteration result as the target balanced discharge power Q E Step 5: Feedback the charging capacity difference Q of the heterogeneous battery cells based on the heterogeneous difference state observer D Estimate the difference in charge capacity Q between the different-shaped cells and determine whether the difference is caused by natural evolution. D Increase or decrease; Step 6, set the target balanced discharge power Q E The discharge balance capacity of the corresponding battery system is iterated at each sampling period Δt by the balance resistor; Step 7, according to the difference and the set value Q d By comparing the data of the hybrid battery pack, it is determined whether the hybrid battery pack is performing a balancing operation on the special-shaped cells, thereby controlling the opening or closing of the balancing controller.

[0029] Therefore, on the basis of achieving consistent charging capacity balance of the same-type battery cells, the present invention further proposes the charging capacity difference of different-type battery cells as the control target of the balancing of different-type battery cells, judges the attenuation state of each system battery, and then adopts a balancing algorithm to ensure the stability of the charging capacity difference of different-type battery cells.

[0030] Furthermore, the present invention dynamically adjusts the available capacity and power ranges of different battery systems by intermittently feeding back the charging power differences of different-shaped battery cells over a long period, thereby maintaining a stable hybrid battery pack energy output under different attenuation levels, fully utilizing the configuration advantages of the ternary lithium-lithium iron phosphate hybrid battery pack, and obtaining an excellent user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart of a ternary lithium-lithium iron phosphate hybrid battery pack equalization method in an embodiment of the present invention;

[0032] Figure 2 Schematic diagram of the configuration of a ternary lithium-lithium iron phosphate battery pack in an embodiment of the present invention;

[0033] Figure 3 is a schematic diagram of charging current integration of a ternary lithium battery system in an embodiment of the present invention;

[0034] Figure 4 is a schematic diagram of charging current integration of a lithium iron phosphate battery system in an embodiment of the present invention;

[0035] Figure 5Schematic diagram of balancing correction of special-shaped cells in an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the following embodiments and accompanying drawings specifically illustrate a ternary lithium-lithium iron phosphate hybrid battery pack equalization method of the present invention.

[0037] In this embodiment, a ternary lithium-lithium iron phosphate hybrid battery pack balancing method is provided.

[0038] Figure 1 It is a flow chart of a ternary lithium-lithium iron phosphate hybrid battery pack balancing method in an embodiment of the present invention.

[0039] like Figure 1 As shown, the hybrid battery pack includes N ternary lithium battery cells and N lithium iron phosphate battery cells, and the ternary lithium battery cells and the lithium iron phosphate battery cells are connected in series. In this embodiment, the battery pack includes 4 ternary lithium battery cells and 4 lithium iron phosphate battery cells. The ternary lithium-lithium iron phosphate hybrid battery pack balancing method involved in this embodiment includes the following steps:

[0040] Step S1: During the charging process, the voltage thresholds U are set for the batteries of the two systems. T_NCM and U T_LFP .

[0041] When setting the voltage threshold U T_NCM and U T_LFP When the upper and lower cut-off voltage ranges of the two system battery cells are different, it is necessary to monitor the charging voltage of each system cell separately. Therefore, the ternary lithium battery and the lithium iron phosphate battery select part of the charging voltage curve respectively. The setting standard of the lithium iron phosphate battery system is after the plateau period. In this embodiment, U T_NCM =3.75V (volts) and U T_LFP =3.35V (volts).

[0042] Step S2, when the charging voltage U NCM，i and U LFP，i Respectively greater than or equal to the voltage threshold U of each system T_NCM and U T_LFP When the charging current integral of the single cell is calculated, the charging current integral of each single cell of the two systems is obtained until the charging is completed. NCM，i and Q LFP，i .

[0043] Figure 2 It is a schematic diagram of the configuration of a ternary lithium-lithium iron phosphate battery pack in an embodiment of the present invention.

[0044] Since the upper and lower cut-off voltage ranges of the two systems’ battery cells are different, it is necessary to monitor the charging voltage of each system’s cells separately. Figure 2 As shown, the charge and discharge termination states of the ternary lithium-lithium iron phosphate hybrid battery pack are respectively recorded as the charge termination state S PN，F and discharge cut-off state S PL，E In the original configuration of this example, the ternary lithium battery and the lithium iron phosphate battery respectively control the emptying and full charging states of the battery pack.

[0045] However, in the actual use of the hybrid battery pack, the charging current is not always fixed and sometimes changes with the working conditions. Therefore, it is more accurate to estimate the charging capacity by integrating the current.

[0046] Figure 3 It is a schematic diagram of charging current integration of a ternary lithium battery system in an embodiment of the present invention.

[0047] like Figure 3 As shown in the figure, the partial charging voltage curve of the four ternary lithium monomers in the ternary lithium-lithium iron phosphate battery pack adopts the constant current charging method. If the battery pack is charged, then the threshold value of the ternary lithium monomer in the hybrid battery pack at the end of charging can be expressed as:

[0048]

[0049] Figure 4 It is a schematic diagram of charging current integration of a lithium iron phosphate battery system in an embodiment of the present invention.

[0050] like Figure 4 As shown in Figure 1, the partial charging voltage curve of the four lithium iron phosphate monomers in the ternary lithium-lithium iron phosphate battery pack adopts a constant current charging method. If the battery pack is charged, then the lithium iron phosphate monomer in the hybrid battery pack reaches the threshold value at the end of charging, which can be expressed as:

[0051]

[0052] Where I is the battery pack charging current, t e The end time of charging the hybrid battery pack, t N，s , t L，s are the moments corresponding to the voltage thresholds of ternary lithium and lithium iron phosphate, respectively, Q NCM，i is the charge capacity of the ternary lithium monomer, Q LFP，i is the charging capacity of the i-th lithium iron phosphate monomer.

[0053] Step S3, respectively select the cells with the smallest charge capacity in the two system batteries, and make their corresponding charge capacity Q NCM，i and Q LFP，i Difference is made to obtain the difference in charging capacity Q of different-shaped cells. D, and use it as the control target for balancing the heterogeneous cells of the hybrid battery pack, and iterate the charging power difference at the end of the next charge to obtain the iterative result.

[0054] In addition, the ternary lithium-lithium iron phosphate hybrid battery components are divided into the same type of battery cell balancing and the different type of battery cell balancing. For the same type of battery cell balancing, the balancing algorithm with the same remaining charge capacity is used to control the balancing channel. This embodiment mainly discusses the different type of battery cell balancing, specifically:

[0055] Select the monomer with the smallest charge in the two systems as the difference, and its value can be expressed as:

[0056] Q D =min(Q LFP，i )-min(Q NCM，i )

[0057] In the formula, min(Q LFP，i ) is the lithium iron phosphate monomer with the smallest charge capacity in the hybrid battery pack, min(Q NCM，i ) is the ternary lithium monomer with the smallest charge capacity in the hybrid battery pack, Q D It is the difference in charging capacity of different-shaped batteries.

[0058] The difference in charging capacity of heterogeneous cells can be expressed as follows:

[0059] Q e =Q D，0 -Q D，i

[0060] In the formula, Q D，0 is the difference in initial charge capacity of heterogeneous cells under the original configuration of the hybrid battery pack, Q D，i is the difference in charge capacity recorded at the end of the i-th charge between cells of different shapes, Q e It is the theoretical target balanced charge of special-shaped batteries.

[0061] To prevent over-balancing, the over-balancing coefficient K should be selected, and K < 1, that is, the target balanced discharge power Q E for:

[0062] Q E =KQ e .

[0063] Step S4: taking the iteration result as the target balanced discharge power Q E .

[0064] Step S5: Feedback the charging power difference Q of the heterogeneous cells according to the heterogeneous difference state observer D Estimate the difference in charge capacity Q between the different-shaped cells and determine whether the difference is caused by natural evolution. D Increase or decrease.

[0065] In actual situations, since the charge changes of each monomer in the series hybrid battery pack are not completely consistent, and the self-discharge rate, aging rate and other characteristics of the ternary lithium battery system and the lithium iron phosphate battery system are different, the batteries of each system show different attenuation rates, resulting in a difference in charging capacity Q between different-shaped cells. D In this embodiment, the cell attenuation caused by self-discharge is mainly considered.

[0066] Figure 5 Schematic diagram of balancing correction of special-shaped cells in an embodiment of the present invention.

[0067] like Figure 5 As shown in the figure, in the hybrid battery pack, if the attenuation of the ternary lithium battery system is greater than that of the lithium iron phosphate battery system, the discharge cut-off state S of the ternary lithium battery system PN，E Compared with the original configuration, it shifts upward; the charging cut-off state S of the lithium iron phosphate battery system PL，F Compared with the original configuration, it shifts downward, resulting in a difference in charging capacity Q between different-shaped cells. D On the contrary, if the attenuation of the lithium iron phosphate battery system is greater than that of the ternary lithium battery system, the discharge cut-off state S of the ternary lithium battery system PN，E Compared with the original configuration, it shifts downward. The charging cut-off state S of the lithium iron phosphate battery system PL，F Compared with the original configuration, it shifts upward, resulting in a difference in charging capacity Q between different-shaped cells. D If no equalization correction is made to maintain a stable charge difference Q D , which will reduce the output energy of the hybrid battery pack, resulting in a significant reduction in the mileage of pure electric vehicles.

[0068] Step S6: Set the target balanced discharge capacity Q E The difference between the discharge balance capacity of the corresponding battery system and the balance resistance in each sampling period Δt is iterated.

[0069] Among them, the target balanced discharge capacity Q E The difference between the discharge balance capacity of the corresponding battery system's balance resistor in each sampling period Δt is expressed as:

[0070] Q E，i+1 =Q E，i -I E ·Δt

[0071] In the formula, Q E，i is the target balanced power between heterogeneous cells in the battery pack in the i-th sampling cycle, I E is the vector of balanced currents of each monomer, Δt is the duration of each sampling cycle, Q E，i+1It is the target balanced power among the heterogeneous cells in the i+1th sampling period.

[0072] Step S7, based on the difference and the set value Q d , and judge whether the hybrid battery pack performs the balancing operation of the heterogeneous cells, thereby controlling the opening or closing of the balancing controller. d Take 5mAh

[0073] According to the ternary lithium-lithium iron phosphate hybrid battery pack balancing method of an embodiment of the present invention, after the hybrid battery pack performs balancing of the heterogeneous battery cells, the available capacity and power range of the heterogeneous battery cell configuration is readjusted, and the power difference between the heterogeneous battery cells is maintained, thereby stabilizing or less attenuating the energy output expectation of the hybrid battery pack.

[0074] Functions and Effects of the Embodiments

[0075] According to the ternary lithium-lithium iron phosphate hybrid battery pack balancing method involved in this embodiment, the specific process is as follows: Step 1, during the charging process, the voltage thresholds U are set for the batteries of the two systems respectively. T_NCM and U T_LFP ; Step 2, when the charging voltage U of each single cell of the two system batteries NCM，i and U LFP，i Respectively greater than or equal to the voltage threshold U of each system T_NCM and U T_LFP When the charging current integral of the single cell is calculated, the charging current integral of each single cell of the two systems is obtained until the charging is completed. NCM，i and Q LFP，i Step 3: Select the cells with the smallest charge capacity in the two system batteries respectively, and make their corresponding charge capacity Q NCM，i and Q LFP，i Difference is made to obtain the difference in charging capacity Q of different-shaped cells. D , and use it as the control target for the balancing of heterogeneous cells in the hybrid battery pack, and iterate the charging power difference at the end of the next charging to obtain the iteration result; Step 4, use the iteration result as the target balanced discharge power Q E Step 5: Feedback the charging capacity difference Q of the heterogeneous battery cells based on the heterogeneous difference state observer D Estimate the difference in charge capacity Q between the different-shaped cells and determine whether the difference is caused by natural evolution. D Increase or decrease; Step 6, set the target balanced discharge power Q E The discharge balance capacity of the corresponding battery system is iterated at each sampling period Δt by the balance resistor; Step 7, according to the difference and the set value Q d By comparing the data of the hybrid battery pack, it is determined whether the hybrid battery pack is performing a balancing operation on the special-shaped cells, thereby controlling the opening or closing of the balancing controller.

[0076] Therefore, the above-mentioned embodiment, on the basis of achieving the consistency and balance of the charging capacity of the same-type battery cells, further proposes the difference in charging capacity of different-type battery cells, takes this as the control target of the balancing of different-type battery cells, judges the attenuation state of the batteries in each system, and then adopts a balancing algorithm to ensure the stability of the difference in charging capacity of different-type battery cells.

[0077] Furthermore, this embodiment dynamically adjusts the available capacity and power ranges of different battery systems through long-term intermittent feedback of the charging power differences of different-shaped battery cells, thereby maintaining a stable hybrid battery pack energy output under different attenuation levels, fully utilizing the configuration advantages of the ternary lithium-lithium iron phosphate hybrid battery pack, and obtaining an excellent user experience.

[0078] The above-mentioned embodiments are preferred examples of the present invention and are not intended to limit the protection scope of the present invention.

Claims

1. A ternary lithium-lithium iron phosphate hybrid battery pack equalization method, characterized in that: The hybrid battery pack comprises N ternary lithium battery cells and N lithium iron phosphate battery cells, wherein the ternary lithium battery cells and the lithium iron phosphate battery cells are connected in series, and comprises the following steps: Step 1: during the charging process, set a voltage threshold U for the ternary lithium battery cell. T_NCM , set a voltage threshold U for the lithium iron phosphate battery cell T_LFP ; Step 2, when the charging voltage U NCM,i Greater than or equal to its voltage threshold U T_NCM , and the charging voltage U of the lithium iron phosphate battery cell LFP.i Greater than or equal to its voltage threshold U T_LFP When the charging current integral of the ternary lithium battery cell and the lithium iron phosphate battery cell is calculated, the charging current integral of the ternary lithium battery cell and the lithium iron phosphate battery cell is calculated until the charging is completed, and the charging power Q of the ternary lithium battery cell at this time is obtained. NCM , i and the charging capacity Q of the lithium iron phosphate battery cell LFP,i ; Step 3: The charging power Q corresponding to the cell with the smallest charging power among the N ternary lithium battery cells is NCM,i Denoted as min(Q NCM,i ), the charging power Q corresponding to the cell with the smallest charging power among the N lithium iron phosphate battery cells LFP，i Denoted as min(Q LFP，i ), charging capacity difference of different-shaped batteries Q D =min(Q NCM,i )-min(Q LFP,i ), Q D As the control target of the balancing of heterogeneous cells in the hybrid battery pack, the charging power difference is iterated at the end of the next charging to obtain the iterative result; Step 4: Using the iteration result as the target balanced discharge capacity Q E ; Step 5: Feedback the charging power difference Q of the heterogeneous battery cells according to the heterogeneous difference state observer D Estimate the difference in charge capacity Q between the different-shaped cells and determine whether the difference is caused by natural evolution. D increase or decrease; Step 6: Set the target balanced discharge capacity Q E Perform difference iteration with the discharge balance capacity of the corresponding battery system’s balance resistor in each sampling period Δt; Step 7, according to the difference and the set value Q d By comparing the data of the hybrid battery pack, it is determined whether the hybrid battery pack is performing a balancing operation on the special-shaped cells, thereby controlling the opening or closing of the balancing controller.

2. The ternary lithium-lithium iron phosphate hybrid battery pack equalization method according to claim 1, characterized in that: in, In step 1, the voltage threshold U is set T_NCM and U T_LFP When charging, due to the different upper and lower cut-off voltage ranges of the two systems' battery cells, it is necessary to monitor the charging voltage of each system's cells separately. Therefore, part of the charging voltage curve is selected for the ternary lithium battery and lithium iron phosphate battery respectively, and the setting standard for the lithium iron phosphate battery system is after the plateau period.

3. The ternary lithium-lithium iron phosphate hybrid battery pack equalization method according to claim 1, characterized in that: in, In step 2, the charging quantity Q is estimated by current integration. NCM,i and Q LFP,i : If the ternary lithium monomer in the hybrid battery pack reaches the threshold value when the battery pack is charged, it is expressed as: If the lithium iron phosphate monomer in the hybrid battery pack reaches the threshold value when the battery pack is charged, it is expressed as: Where I is the battery pack charging current, t e The end time of charging the hybrid battery pack, t N,s ,t L,s are the moments corresponding to the voltage thresholds of ternary lithium and lithium iron phosphate, respectively, Q NCM,i is the charge capacity of the ternary lithium monomer, Q LFP,i is the charging capacity of the i-th lithium iron phosphate monomer.

4. The ternary lithium-lithium iron phosphate hybrid battery pack equalization method according to claim 1, characterized in that: in, In step 3, the balancing types of the hybrid battery pack include balancing of the same type of cells and balancing of the different type of cells.

5. The ternary lithium-lithium iron phosphate hybrid battery pack equalization method according to claim 4, characterized in that: in, For the balancing of the same type of cells, a balancing algorithm with consistent remaining charge capacity is used to control the balancing channel.

6. The ternary lithium-lithium iron phosphate hybrid battery pack equalization method according to claim 1, characterized in that: in, The process of iterating the charging capacity difference of the heterogeneous battery cells is expressed as: Q e =Q D，0 -Q D，a In the formula, Q D，0 is the difference in initial charge capacity of heterogeneous cells under the original configuration of the hybrid battery pack, Q D，a is the difference in charge capacity recorded at the end of the ath charge between cells of different shapes, Q e It is the theoretical target balanced charge of special-shaped batteries. To prevent over-balancing, the over-balancing coefficient K should be selected, and K < 1, that is, the target balanced discharge power Q E for: Q E =KQ e 。 7. The ternary lithium-lithium iron phosphate hybrid battery pack equalization method according to claim 1, characterized in that: in, In step 5, the natural evolution is: In actual situations, since the charge changes of each monomer in the series hybrid battery pack are not completely consistent, and the self-discharge rate and aging rate of the ternary lithium battery system and the lithium iron phosphate battery system are different, the batteries of each system show different attenuation rates, which leads to the difference in charging capacity Q between different-shaped cells. D Increase or decrease.

8. The ternary lithium-lithium iron phosphate hybrid battery pack equalization method according to claim 7, characterized in that: in, In step 5, the determination of whether the charging capacity difference Q of the special-shaped battery cell is caused by natural evolution D During the process of increasing or decreasing, at least the cell attenuation caused by the self-discharge rate is taken into consideration.

9. The ternary lithium-lithium iron phosphate hybrid battery pack equalization method according to claim 1, characterized in that: in, In step 6, the target balanced discharge capacity Q E The difference between the discharge balance capacity of the corresponding battery system's balance resistor in each sampling period Δt is expressed as: Q E,b+1 =Q E,b -I E ·Δt In the formula, Q E,b is the target balanced power between heterogeneous cells in the battery pack in the bth sampling cycle, I E is the vector composed of the balanced current of each monomer, Δt is the duration of each sampling cycle, Q E,b+1 It is the target balanced power among the special-shaped cells in the b+1th sampling period.

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