Lithium battery charge and discharge equalization control method and charge and discharge equalization control system

Abstract

The invention relates to the technical field of battery management, in particular to a lithium battery charge-discharge equalization control method and system, and the method comprises the steps: collecting the charge states of a plurality of lithium batteries to be charged and discharged, and calculating a charge difference value; and when the charge difference value exceeds the charge difference threshold value, performing charge equalization or discharge equalization according to the charge and discharge states. The problems that traditional passive equalization is low in equalization efficiency and wastes energy are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery management, and particularly to a lithium battery charge and discharge equalization control method and a charge and discharge equalization control system. Background Art

[0002] As the core energy unit in fields such as electric vehicles and energy storage systems, a lithium battery pack is usually composed of multiple single cells connected in series and parallel; however, due to differences in manufacturing processes, operating temperatures, aging degrees, etc. of single cells, parameters such as voltage, capacity, and internal resistance of each single cell in the battery pack often show significant inconsistencies; in long-term charge and discharge cycles, this inconsistency will lead to an accelerated decline in the effective capacity of the battery pack, a shortened cycle life, and even cause local overcharge or over-discharge, resulting in safety hazards such as thermal runaway; therefore, how to achieve dynamic energy balance inside the battery pack has become a key technical challenge for improving the performance and safety of the battery system.

[0003] To solve the above problems, lithium battery equalizers are generally used in the prior art to regulate the energy of single cells; traditional equalization technologies can be divided into two categories: passive equalization and active equalization: passive equalization dissipates the energy of high-voltage single cells through a parallel resistor. Although it has the advantage of a simple circuit structure, it has defects such as low equalization efficiency, significant energy waste, and serious heating, and it is difficult to meet the actual requirements especially in high-voltage and large-capacity battery packs; active equalization technology constructs a lithium battery energy transfer path based on energy storage elements such as capacitors, inductors, or transformers; in recent years, with the increasing demand for the intelligence of the battery management system (BMS), the industry has begun to explore hybrid equalization topologies and multi-mode control algorithms. Summary of the Invention

[0004] Aiming at the deficiencies of the existing methods, the present invention combines a flyback transformer and a buck converter to design a new type of equalization topology circuit and proposes a corresponding equalization strategy to achieve fast and efficient equalization of the energy of the lithium battery pack.

[0005] The technical solution adopted by the present invention is that the lithium battery charge and discharge equalization control method includes the following steps:

[0006] Step 1: Collect the state of charge of several lithium batteries to be charged and discharged, and calculate the charge difference;

[0007] As a preferred embodiment of the present invention, the charge difference is the maximum state of charge of the lithium battery - the minimum state of charge of the lithium battery.

[0008] Step 2: When the charge difference exceeds the charge difference threshold, perform charge equalization or discharge equalization according to the charge and discharge state;

[0009] As a preferred embodiment of the present invention, the process of charge equalization includes:

[0010] First, select the lithium battery corresponding to the maximum state of charge among the lithium batteries to be charged as the charge equalization source battery;

[0011] Secondly, within the first duty cycle period, use the charge equalization source battery to charge the flyback transformer;

[0012] Next, within the second duty cycle period, use the flyback transformer to charge all the lithium batteries to be charged.

[0013] As a preferred embodiment of the present invention, when the state of charge of a certain charge equalization source battery does not exceed the average state of charge of all the lithium batteries to be charged, perform the next round of selection of the charge equalization source battery;

[0014] Otherwise, continue to perform charge equalization for the next charging cycle of this charge equalization source battery until the state of charge of this charge equalization source battery does not exceed the average state of charge of all the lithium batteries to be charged;

[0015] When the maximum state of charge difference is less than the state of charge difference threshold, end the charge equalization.

[0016] As a preferred embodiment of the present invention, the process of discharge equalization includes:

[0017] First, calculate the average state of charge of the lithium batteries to be discharged in each lithium battery pack and the average state of charge of all the lithium batteries to be discharged;

[0018] Secondly, when the average state of charge of a certain lithium battery pack is less than the average state of charge of all the lithium batteries to be discharged, set this lithium battery pack as the discharge equalization source battery pack;

[0019] Next, simultaneously obtain the lithium battery with the lowest state of charge in several discharge equalization source battery packs and set it as the discharge equalization source battery of this discharge equalization source battery pack;

[0020] Next, within the third duty cycle period, use the auxiliary battery corresponding to the lithium battery pack to charge the energy storage unit corresponding to the lithium battery pack and the discharge equalization source battery;

[0021] Finally, within the fourth duty cycle period, use the energy storage unit of the discharge equalization source battery pack to continue charging the discharge equalization source battery.

[0022] As a preferred embodiment of the present invention, when the state of charge of the discharge equalization source battery in a certain lithium battery pack exceeds the average state of charge of all the lithium batteries to be charged, perform the next round of discharge equalization;

[0023] Otherwise, continue to perform discharge equalization for the next discharge cycle of this discharge equalization source battery until the state of charge of this discharge equalization source battery exceeds the average state of charge of all the lithium batteries to be charged;

[0024] When the maximum charge difference is less than the charge difference threshold, the discharge equalization ends.

[0025] As a preferred embodiment of the present invention, the first duty cycle satisfies the constraint condition:

[0026]

[0027] Wherein, U Celli represents the voltage of the charging equalization source battery, U pack is the voltage of all lithium battery packs to be charged, U di1 is the forward voltage drop of the diode in the charging equalization source battery circuit; U d2 is the forward voltage drop of the MOSFET in the charging equalization source battery circuit.

[0028] As a preferred embodiment of the present invention, the inductor of the energy storage unit of the discharge equalization source battery pack satisfies the constraint condition:

[0029]

[0030] Wherein, D'3 is the third duty cycle, U m,BL is the auxiliary battery voltage of the m-th lithium battery pack, T2 is the discharge period, and i m,LC is the average value of the circuit critical current of the m-th lithium battery pack.

[0031] As a preferred embodiment of the present invention, the charging equalization control system of the lithium battery charge and discharge equalization control method includes:

[0032] A charging energy storage transmission unit, a lithium battery pack, a MOS transistor K, a first MOSFET unit, and a second MOSFET unit;

[0033] The charging energy storage transmission unit is used to store the charge of the charging equalization source battery of a certain lithium battery pack and charge all the lithium batteries to be charged with this charge;

[0034] The first MOSFET unit and the second MOSFET unit are used to control the charging equalization source battery circuit;

[0035] The MOS transistor K is used to control the charging circuits of all the lithium batteries to be charged.

[0036] As a preferred embodiment of the present invention, the discharge equalization control system of the lithium battery charge and discharge equalization control method includes:

[0037] A discharge energy storage transmission unit, a lithium battery pack, a first MOSFET unit, and a second MOSFET unit;

[0038] The discharge energy storage transmission unit provides energy for discharge equalization and controls the discharge equalization circuit of the energy storage unit;

[0039] The first MOSFET unit and the second MOSFET unit are used to control the discharge equalization source battery circuit.

[0040] Advantages of the present invention:

[0041] 1. During the charging process, a flyback transformer is used for battery cell to battery pack equalization, and during the discharging process, multiple buck circuits and auxiliary batteries are used to simultaneously equalize multiple low-energy batteries;

[0042] 2. In terms of the equalization strategy, the present invention adopts a hybrid control strategy with SOC as the equalization variable. This strategy enables the balancing circuit to flexibly adjust the equalization method, compensate for the disadvantages of each equalization type, and keep the battery pack in the best working state;

[0043] 3. The present invention can achieve synchronous equalization of multiple batteries, improving the balancing speed and efficiency of the battery pack. Brief Description of the Drawings

[0044] Figure 1 is the flyback-buck hybrid equalization topology circuit for rapid equalization of lithium batteries of the present invention;

[0045] Figure 2 is a schematic diagram of the charging equalization process when Cell2 is the highest-energy battery of the present invention;

[0046] Figure 3 is a timing diagram of the switches and equalization current during the charging equalization process when Cell2 is the highest-energy battery of the present invention;

[0047] Figure 4 is a schematic diagram of the discharging equalization process when Cell4 is the lowest-energy battery of the present invention;

[0048] Figure 5 is a timing diagram of the switches, inductors and diodes during the discharging equalization process when Cell4 is the lowest-energy battery of the present invention;

[0049] Figure 6 is the flow chart of the flyback-buck hybrid equalization strategy for rapid equalization of lithium batteries of the present invention;

[0050] Figure 7 is a simulation diagram of the charging equalization process of the present invention;

[0051] Figure 8 is a simulation diagram of the discharging equalization process of the present invention. Detailed Embodiments

[0052] The present invention will be further described below with reference to the drawings and embodiments. This figure is a simplified schematic diagram, which only illustrates the basic structure of the present invention in a schematic manner. Therefore, it only shows the components related to the present invention.

[0053] As Figure 6 shown, the lithium battery charge and discharge equalization control method includes the following steps:

[0054] Step 1: Collect the state of charge of several lithium batteries to be charged and discharged, and calculate the maximum state of charge difference;

[0055] The formula for the maximum state of charge difference ΔSOC is:

[0056] ΔSOC = SOC max - SOC min (1)

[0057] where SOC max is the maximum state of charge of the lithium battery, and SOC min is the minimum state of charge of the lithium battery.

[0058] As Figure 1 in, there are m lithium battery packs. Taking m = 2 as an example, find SOC max and SOC min among the lithium batteries cell1 - cell8 to be charged and discharged in the first and second lithium battery packs.

[0059] Step 2: When the state of charge difference exceeds the state of charge difference threshold, perform charge equalization or discharge equalization according to the charge and discharge state.

[0060] The charge and discharge state can be determined according to whether the lithium battery is in the charging state or the load discharge state; for example, when the lithium battery pack is connected to an external charging power supply, it is in the charging state; when the lithium battery pack is connected to a load, it is in the discharge state;

[0061] When charge and discharge equalization is required, the state of charge difference exceeds the state of charge difference threshold; that is, ΔSOC > φ; φ is the state of charge difference threshold.

[0062] When charge and discharge equalization is not required, ΔSOC ≤ φ;

[0063] The process of charge equalization includes:

[0064] First, select the lithium battery corresponding to SOC max in the lithium batteries to be charged as the charge equalization source battery;

[0065] Secondly, within the first duty cycle D’1, use the charge equalization source battery to charge the flyback transformer;

[0066] Finally, within the second duty cycle D’2, use the flyback transformer to charge all the lithium batteries to be charged;

[0067] When the state of charge SOC i of the charge equalization source battery does not exceed the average state of charge SOC of all the lithium batteries to be chargedaverage When the battery is equalized, the next round of charge equalization source battery selection is performed;

[0068] Otherwise, continue to charge and balance the charge balancing source battery in the next charging cycle until the charge SOC of the charge balancing source battery reaches i Not exceeding the average SOC of all lithium batteries to be charged average ; The next charging cycle is a switching process between the first duty cycle and the second duty cycle;

[0069] When ΔSOC≤φ, charge balancing ends.

[0070] like Figure 1 As shown, the charging and discharging balancing control system of the lithium battery includes: a charging energy storage transmission unit, a lithium battery pack, a first MOSFET unit, and a second MOSFET unit;

[0071] Lithium battery includes: cell1 to cell n ; n is the number of lithium batteries;

[0072] The first MOSFET unit includes: n+1 MOS tubes and n+1 diodes D;

[0073] The second MOSFET unit includes: n+1 MOS tubes and n+1 diodes D;

[0074] The charging energy storage transmission unit includes: a flyback transformer T and a MOS tube K;

[0075] like Figure 2 As shown, taking lithium battery cell2 as the charge balancing source battery as an example, that is, i=2, the red arrow shows the charge balancing source battery circuit. In the first duty cycle D'1, MOS tubes Q4 and Q5 are turned on first, and other MOS tubes are all turned off; at this time, cell2 is used to charge the flyback transformer T; when the flyback transformer T is charged, the second duty cycle D'2 is executed, as shown in FIG. Figure 2 As shown in the charging circuit of all the lithium batteries to be charged by the blue arrows, in the second duty cycle period D'2, all the MOS tubes of the first MOSFET unit and the second MOSFET unit are disconnected, and the MOS tube K is turned on, and the flyback transformer T is used to charge all the lithium batteries to be charged; it is judged whether the SOC of Cell2 does not exceed SOC average , SOC average That is, all lithium battery cells to be charged n If it exceeds, repeat the above process, that is, continue to charge and balance Cell2; if it does not exceed, select other charging and balancing source batteries for the next round; continue to cycle until the power of all lithium batteries to be charged is equal;

[0076] Figure 2 The charging equalization source battery circuit of the red arrow is the charging circuit for the primary coil of the flyback transformer T by flowing from the positive electrode to the negative electrode of the lithium battery of Cell2.

[0077] Figure 2 The charging circuits of all lithium batteries to be charged of the blue arrow are the charging circuits for all lithium batteries to be charged by flowing from the positive electrode to the negative electrode of the secondary coil of the flyback transformer T.

[0078] The process of discharge equalization includes:

[0079] First, calculate the average state of charge SOC of the lithium batteries to be discharged in each lithium battery pack m,average and the average state of charge SOC of all lithium batteries to be discharged average ;

[0080] Taking Figure 1 where m = 4 as an example, there are 4 lithium batteries in each lithium battery pack. Then, for the first lithium battery pack, SOC m,average = SOC 1,1-4 , that is, calculate the average value of cell1 - cell4 in the first lithium battery pack; the number of lithium batteries in the lithium battery pack can be equal or unequal; when they are equal, the differential impact on the auxiliary battery BZ is the smallest and the performance is the best; SOC average is the average state of charge of all lithium batteries to be discharged;

[0081] Second, when the average state of charge SOC m,average of a certain lithium battery pack is less than the average state of charge SOC average of all lithium batteries to be discharged, set this lithium battery pack as the discharge equalization source battery pack;

[0082] Third, simultaneously obtain the SOC of the lithium battery with the lowest state of charge in several discharge equalization source battery packs m,min , and set it as the discharge equalization source battery of this discharge equalization source battery pack; the number of discharge equalization source battery packs < m;

[0083] For example Figure 4 , taking the first lithium battery pack as the discharge equalization source battery pack as an example, cell4 in the first group of lithium battery packs is the discharge equalization source battery; if there are two lithium battery packs as the discharge equalization source battery packs, then respectively select the discharge equalization source batteries in their respective lithium battery packs and calculate the SOC of their respective smallest lithium batteries m,min ;

[0084] Third, in the third duty cycle D'3, use the auxiliary battery BZ corresponding to the lithium battery pack to charge the energy storage unit and the discharge equalization source battery corresponding to the lithium battery pack;

[0085] For example Figure 4The red arrow represents the discharge equalization source battery circuit. The switch SW1 of the first lithium battery pack is closed, and the MOS transistors Q7 and Q10 in this lithium battery pack are turned on, while the other MOS transistors in this lithium battery pack are turned off. The auxiliary battery BZ1 is used to charge the energy storage unit L1 and the discharge equalization source battery Cell4. Similarly, if the second lithium battery pack also meets the condition: SOC 2,average <SOC average , and Cell5 meets the minimum lithium battery SOC 2,min , then the switches SW2 are respectively closed, and Q9 and Q 12 are turned on; and so on;

[0086] Finally, in the fourth duty cycle D’4, the energy storage unit of the discharge equalization source battery pack is used to continue charging the discharge equalization source battery;

[0087] As Figure 4 shown, the blue arrow represents the energy storage unit discharge equalization circuit. The switch SW1 is turned off, and the MOS transistors Q7 and Q9 in this lithium battery pack are turned on, while the other MOS transistors are turned off. The inductor L1 is used to continue charging the discharge equalization source battery Cell4;

[0088] When the state of charge SOC j of the discharge equalization source battery in a certain lithium battery pack exceeds the average state of charge SOC average of all the lithium batteries to be charged, the next round of discharge equalization is executed;

[0089] Otherwise, the discharge equalization of the next discharge cycle is carried out until the state of charge SOC j of this discharge equalization source battery exceeds the average state of charge SOC average of all the lithium batteries to be charged; the next discharge cycle is the third duty cycle and the fourth duty cycle;

[0090] When ΔSOC≤φ, the discharge equalization discharge cycle ends.

[0091] Figure 4 For the discharge equalization source battery circuit with the red arrow, the auxiliary battery flows from the positive electrode to the capacitor of the energy storage unit and the positive electrode of the discharge equalization source battery, and then flows from the negative electrode of the discharge equalization source battery to the negative electrode of the auxiliary battery;

[0092] Figure 4 For the energy storage unit discharge equalization circuit with the blue arrow, that is, the inductor L1 is the charging circuit from the positive electrode to the negative electrode of Cell4; C1 is used for the acceleration mutation of L1 and voltage stabilization of L1.

[0093] It should be noted that the discharge equalization is a judgment for all lithium battery packs that meet SOC m,average <SOC average to execute a discharge cycle simultaneously, which is beneficial to improving the discharge equalization efficiency.

[0094] As shown Figure 1 in the figure, the discharge equalization control system of the lithium battery charge and discharge equalization control system includes: a discharge energy storage and transmission unit, a lithium battery pack, a first MOSFET unit, and a second MOSFET unit;

[0095] The lithium battery pack includes: cell1 to cell n ;

[0096] The first MOSFET unit includes: n + 1 MOS transistors and n + 1 diodes D;

[0097] The second MOSFET unit includes: n + 1 MOS transistors and n + 1 diodes D;

[0098] The discharge energy storage and transmission unit includes: an energy storage unit BZ m and a buck converter; wherein, the buck converter includes: a switch SW m an inductor L m a capacitor C m a diode DI m ;

[0099] In this embodiment, the diode D is used to limit the current to avoid short - circuit, and all MOS transistors use NMOS transistors.

[0100] As shown Figure 2 Figure 3 in the figure, Cell2 is the lithium - battery monomer with the highest energy among all battery packs. During t0 to t1, Q4 and Q5 are turned on, and Cell2 transfers energy to the primary side of the flyback transformer T, and i w1 increases linearly;

[0101]

[0102] Among them, U Cell2 represents the voltage of Cell2; U d1 is the forward voltage drop of the diode in the circuit; U d2 is the forward voltage drop of the MOSFET in the circuit; L T is the magnetizing inductance of the transformer.

[0103] The forward voltage drops of diodes D4 and D5 are equal, and the forward voltage drops of MOS transistors Q4 and Q5 are equal;

[0104] At the moment t = t1, the balancing current i W1 increases to the maximum value i W1,max , and the formula is:

[0105]

[0106] Among them, D’1 represents the first duty cycle; T1 is the charging equalization period; f1 is the charging equalization frequency.

[0107] Q4 and Q5 are disconnected, and the energy of the flyback transformer T is released through the secondary side of the transformer. The current generated on the secondary side of the transformer decreases linearly, transferring energy to all lithium battery packs to be charged, i w2 decreases linearly, and the formula is:

[0108]

[0109] Among them, U pack is the voltage of all lithium battery packs to be charged, t is the current moment, and t1 is the moment when the first stage of equalization ends.

[0110] At the moment t = t2, the equalization current i W2 decreases to the minimum value i W2,min , and the formula is:

[0111]

[0112] Among them, D’2 is the second duty cycle.

[0113] When the value of the equalization period T1 is fixed, the smaller the value of D’1 and the larger the value of D’2, the longer the discharge process time of the battery, resulting in a reduction in the charging time of the battery pack. This will cause the transformer not to complete the discharge process completely, affecting the efficiency of battery equalization. The duty cycle constraint is adjusted to D’1 + D’2 ≤ 1, so the first duty cycle needs to meet the condition:

[0114]

[0115] As Figure 4 , 5 shown, assume that Cell4 is the battery monomer with the lowest energy in the group; during t0 - t1, close the switch SW1, and Q7 and Q9 are turned on to charge Cell4; the inductor L1 stores energy, and i L increases linearly; during t1 - t2, SW1 is disconnected, and Q7 and Q9 still remain turned on; the energy stored in L1 flows freely to Cell4.

[0116] In the discharge equalization, the balance current can be adjusted by adjusting the duty cycle of the switch SW1, thereby adjusting the energy within a single cycle of the adjustment switch SW1; the duty cycles of the adjustment switch SW1 are the third duty cycle D’3 and the fourth duty cycle D’4, and the third duty cycle and the fourth duty cycle are user-defined parameters; it is only necessary to satisfy D’3 + D’4 ≤ 1.

[0117] The voltage (U BL ) required by the auxiliary battery BZm is determined by the output voltage equation, and the formula is:

[0118] U BL = D'3 * U cell (6)

[0119] where D’3 is the third duty cycle; U cell is the voltage of a single lithium battery cell;

[0120] When the inductance value in the circuit reaches the critical state, the current i of the inductor Lm L and the inductor current ripple Δi L are:

[0121]

[0122] where f2 is the frequency of discharge equalization, T2 is the period of discharge equalization; L is the value of the inductor.

[0123] Then the average value i of the critical current of the circuit LC is:

[0124]

[0125] In a buck converter, too small an inductance value will cause an increase in current ripple, affecting the stability of the output voltage. At the same time, the peak current may exceed the saturation current of the inductor, causing the magnetic core to saturate and fail; too large an inductance value will reduce the dynamic response speed and lead to a decrease in efficiency and an increase in cost due to an increase in volume and resistance; in addition, the inductor needs to meet the rated current to avoid the risk of over-temperature rise and thermal damage. Therefore, it is necessary to reasonably constrain the value of L to optimize the contradiction among ripple, efficiency, and heat dissipation.

[0126] To meet the limit conditions of the circuit: the average current is greater than or equal to the average value of the critical current, the inductor L needs to meet the conditions:

[0127]

[0128] Figure 7 and Figure 8 are respectively the simulation waveform diagrams of the fast equalization of lithium batteries in two working modes of charging and discharging. Different colors represent four lithium batteries in the lithium battery pack; it can be seen that the voltage inconsistency of the battery pack can be reduced in both working states of the two equalization strategies, verifying the feasibility of the equalization scheme.

[0129] Inspired by the above ideal embodiments based on the present invention, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A lithium battery charge and discharge balance control method, characterized in that: The following steps are involved: Step 1: Collect the charge states of several lithium batteries to be charged and discharged, and calculate the maximum charge difference; Step 2: When the maximum charge difference exceeds the charge difference threshold, charge balancing or discharge balancing is performed according to the charge and discharge status of the lithium battery pack.

2. The lithium battery charge and discharge balance control method according to claim 1, characterized in that: The charge equalization process includes: First, the lithium battery corresponding to the maximum charge among the lithium batteries to be charged is selected as the charge balancing source battery; Secondly, in the first duty cycle, the flyback transformer is charged by using the charge balancing source battery; Secondly, in the second duty cycle, the flyback transformer is used to charge all the lithium batteries to be charged.

3. The lithium battery charge and discharge balance control method according to claim 2, characterized in that: When the charge of the charge balancing source battery does not exceed the average charge of all the lithium batteries to be charged, the next round of charge balancing source battery selection is performed; Otherwise, continue to perform charge balancing on the charge balancing source battery in the next charging cycle; When the maximum charge difference is less than the charge difference threshold, charge balancing ends.

4. The lithium battery charge and discharge balance control method according to claim 1, characterized in that: The discharge equalization process includes: First, the average charge of the to-be-discharged lithium batteries of each lithium battery group and the average charge of all to-be-discharged lithium batteries are calculated; Secondly, when the average charge of a lithium battery group is less than the average charge of all lithium batteries to be discharged, the lithium battery group is set as the discharge balancing source battery group; Secondly, simultaneously obtain the lithium batteries with the smallest charge in several discharge balancing source battery groups, and set them as the discharge balancing source batteries of the discharge balancing source battery group; Secondly, in the third duty cycle, the auxiliary battery is used to charge the corresponding energy storage unit and the discharge balancing source battery; Finally, in the fourth duty cycle, the energy storage unit is used to continue charging the discharge balancing source battery.

5. The lithium battery charge and discharge balance control method according to claim 4, characterized in that: When the charge of the discharge balancing source battery in a lithium battery pack exceeds the average charge of all lithium batteries to be charged, the next round of discharge balancing is performed; Otherwise, the discharge balancing source battery continues to be discharged in the next discharge cycle; When the maximum charge difference is less than the charge difference threshold, discharge balancing ends.

6. The lithium battery charge and discharge balance control method according to claim 2, characterized in that: The first duty cycle satisfies the constraint: Among them, U Celli Indicates the voltage of the charge equalization source battery, U pack is the voltage of all lithium battery packs to be charged, U di1 U is the forward voltage drop of the diode in the charging balancing source battery loop; d2 It is the forward voltage drop of the MOSFET in the charge balancing source battery loop.

7. The lithium battery charge and discharge balance control method according to claim 4, characterized in that: The inductance of the energy storage unit satisfies the following constraints: Among them, D ’ 3 is the third duty cycle, U m,BL is the auxiliary battery voltage of the mth lithium battery pack, T2 is the discharge cycle, i m,LC is the average value of the circuit critical current of the mth lithium battery pack.

8. The lithium battery charge and discharge balance control method according to claim 1, characterized in that: The charge difference is the maximum charge of the lithium battery minus the minimum charge of the lithium battery.

9. A charging equalization control system using the lithium battery charging and discharging equalization control method according to any one of claims 1, 2, 3, and 6, characterized in that: include: Charging energy storage transmission unit, lithium battery pack, MOS tube K, first MOSFET unit, second MOSFET unit; The charging energy storage transmission unit is used to store the charge of the charging equalization source battery of a lithium battery pack, and use the charge to charge all lithium batteries to be charged; The first MOSFET unit and the second MOSFET unit are used to control the charge balancing source battery loop; MOS tube K is used to control the charging circuit of all lithium batteries to be charged.

10. A discharge balancing control system using the lithium battery charge and discharge balancing control method according to any one of claims 1, 4, 5, and 7, characterized in that: include: Discharge energy storage transmission unit, lithium battery pack, first MOSFET unit, second MOSFET unit; The discharge energy storage transmission unit provides energy for discharge equalization and controls the energy storage unit discharge equalization loop; The first MOSFET unit and the second MOSFET unit are used to control the discharge balancing source battery loop.

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