Method for integrated equalization control of lithium-ion battery voltage and cells

Abstract

The present application relates to the technical field of lithium ion battery, especially to a kind of lithium ion battery voltage and cell integration equalization control method, first, the circuit structure of lithium ion battery voltage and cell integration equalization is designed;Second, the difference between the maximum and minimum of battery monomer voltage, the difference between the maximum and minimum of battery monomer SOC is taken as two input variables, input fuzzy logic controller and carry out operation, output two output variables of equalization current and duty cycle of field effect transistor, design fuzzy logic control rule;Finally, according to the current of two output variables control circuit and the conduction time of field effect transistor, so that different lithium ion battery monomer in the circuit has the same voltage and similar SOC, thereby realizing voltage and cell double equalization.The method can effectively adjust the size and equalization time of the equalization current between each battery monomer, take into account voltage equalization and cell equalization, maximize the cycle life of battery, fully reduce the damage of cell caused by overcharge and overdischarge and other failures.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery voltage and cell integrated equalization control method. BACKGROUND

[0002] Lithium ion batteries have been widely applied in various energy storage fields such as new energy vehicles and power storage power sources due to long cycle life, large rated capacity and high working voltage. In general, the battery needs to maintain two kinds of equalization of each single body in the working process, namely voltage equalization and cell equalization. The so-called voltage equalization is to transfer energy from a high-energy battery single body to a low-energy battery single body, thereby avoiding overcharging and overdischarging caused by voltage imbalance; and the cell equalization is to transfer the energy of a high-energy battery single body in a battery pack to a low-energy battery single body, so as to realize similar state of charge (SOC) of different battery single bodies, and avoid heating of the battery pack, thereby prolonging the cycle life of the lithium ion battery.

[0003] In the past research, there are generally two methods for voltage equalization: passive and active. The passive voltage equalization principle is simple, and can be realized only by discharging through a resistor, but the energy consumed by the resistor in the form of heat cannot be recovered, resulting in waste of energy. The active voltage equalization is to use power electronic switches as main devices, and to actively control the conduction and turn-off of the devices through a corresponding control algorithm, thereby realizing energy transfer. The active voltage equalization has good effect and high energy conversion efficiency, but also has problems of complex equalization circuit and large control difficulty.

[0004] The ultimate goal of cell equalization is to keep the SOC of each single battery in the battery pack similar. The cell equalization and the voltage equalization have the same passive and active two implementation methods, and the working principles of the two implementation methods are basically the same, only the implementation goals are different. In some researches, the same voltage amplitude is used as the test standard for whether the cell is equalized, this method often ignores the factors such as the change of the internal resistance of the battery and the polarization effect, and the relationship between the voltage and the SOC is a nonlinear relationship, so this method cannot fully reflect the actual state of the internal SOC of the battery, and is easy to cause over-equalization. In summary, it is urgent to design a lithium ion battery voltage and cell integrated equalization method. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the deficiencies in the prior art and provide a lithium ion battery voltage and cell integrated equalization control method.

[0006] The technical scheme adopted by the present application to solve the technical problem is: a lithium ion battery voltage and cell integrated equalization control method, comprising the following steps:

[0007] S1, constructing a lithium ion battery voltage and cell integrated equalization circuit structure;

[0008] S2, sequentially measuring the voltages of the three batteries to be equalized in step S1 to obtain the maximum voltage U max and the minimum voltage U min , calculating the voltage difference △U = U max -U min ; sequentially measuring the state of charge of the three batteries to be equalized in step S1 to obtain the maximum state of charge SOC max and the minimum state of charge SOC min , calculating the state of charge difference △SOC = SOC max -SOC min ; inputting the voltage difference △U and the state of charge difference △SOC as two input variables into the fuzzy logic controller, and obtaining two output variables, the equalization current I d and the duty cycle D of the MOS tube, through the fuzzy logic algorithm of the fuzzy logic controller;

[0009] S3, the battery management system adjusts the current of the circuit and the conduction time of the MOS tube in step S1 according to the two output variables in step S2, so that the voltages of the three batteries to be equalized are the same, and the state of charge is similar, realizing the double equalization of voltage and cell.

[0010] Further, the circuit in step S1 includes a battery to be equalized BT1, a battery to be equalized BT2, a battery to be equalized BT3, a MOS tube Q1, a MOS tube Q2, a MOS tube Q3, a MOS tube Q4, a MOS tube Q5, a MOS tube Q6 and an equalization capacitor C. The equalization capacitor C, the MOS tube Q1, the battery to be equalized BT1, the battery to be equalized BT2, the battery to be equalized BT3 and the MOS tube Q6 are connected in series to form a loop. One end of the MOS tube Q2 is connected between the equalization capacitor C and the MOS tube Q6, and the other end is connected between the battery to be equalized BT1 and the battery to be equalized BT2. One end of the MOS tube Q3 is connected between the equalization capacitor C and the MOS tube Q1, and the other end is connected between the battery to be equalized BT1 and the battery to be equalized BT2. One end of the MOS tube Q4 is connected between the equalization capacitor C and the MOS tube Q6, and the other end is connected between the battery to be equalized BT2 and the battery to be equalized BT3. One end of the MOS tube Q5 is connected between the equalization capacitor C and the MOS tube Q1, and the other end is connected between the battery to be equalized BT2 and the battery to be equalized BT3.

[0011] Further, the voltages of the batteries to be balanced in step S3 are the same, and need to be charged and discharged according to the voltage values of the first battery to be balanced BT1, the second battery to be balanced BT2 and the third battery to be balanced BT3, and are divided into 12 states, which are specifically as follows:

[0012] State 1: when U BT1 > U BT2 = U BT3 , first turn on Q1 and Q2, and charge BT1 to C, after the charging is completed, turn on Q3 and Q4, and charge C to BT2, after the charging is completed, turn on Q1 and Q2 again, and charge BT1 to C again, after the charging of C is completed, turn on Q5 and Q6, and charge C to BT3, and after several cycles, the voltages are balanced;

[0013] State 2: when U BT2 > U BT1 = U BT3 , first turn on Q3 and Q4, and charge BT2 to C, after the charging is completed, turn on Q1 and Q2, and charge C to BT1, after the charging is completed, turn on Q3 and Q4 again, and charge BT2 to C again, after the charging of C is completed, turn on Q5 and Q6, and charge C to BT3, and after several cycles, the voltages are balanced;

[0014] State 3: when U BT3 > U BT1 = U BT2 , first turn on Q5 and Q6, and charge BT3 to C, after the charging is completed, turn on Q1 and Q2, and charge C to BT1, after the charging is completed, turn on Q5 and Q6 again, and charge BT3 to C again, after the charging of C is completed, turn on Q3 and Q4, and charge C to BT2, and after several cycles, the voltages are balanced;

[0015] State 4: when U BT3 = U BT2 > U BT1 , first turn on Q5 and Q6, and charge BT3 to C, after the charging is completed, turn on Q1 and Q2, and charge C to BT1, after the charging is completed, turn on Q3 and Q4, and charge BT2 to C, after the charging of C is completed, turn on Q1 and Q2, and charge C to BT1, and after several cycles, the voltages are balanced;

[0016] State 5: when U BT1 = U BT3 > U BT2 , first turn on Q1 and Q2, and charge BT1 to C, after the charging is completed, turn on Q3 and Q4, and charge C to BT2, after the charging is completed, turn on Q5 and Q6 again, and charge BT3 to C, after the charging of C is completed, turn on Q3 and Q4, and charge C to BT2, and after several cycles, the voltages are balanced;

[0017] State 6: when UBT1 = U BT2 > U BT3 Q1 and Q2, BT1 charges C, after charging, Q5 and Q6 are turned on, C charges BT3, after charging, Q3 and Q4 are turned on, C charges BT2, at this time, it can jump to state 1 or state 5 or the voltage is directly balanced;

[0018] State 7: when U BT1 > U BT2 > U BT3 Q1 and Q2 are turned on, BT1 charges C, after charging, Q5 and Q6 are turned on, C charges BT3, at this time, it can jump to state 1 or state 6 or the voltage is directly balanced;

[0019] State 8: when U BT1 > U BT3 > U BT2 Q1 and Q2 are turned on, BT1 charges C, after charging, Q3 and Q4 are turned on, C charges BT2, at this time, it can jump to state 1 or state 5 or the voltage is directly balanced;

[0020] State 9: when U BT2 > U BT1 > U BT3 Q3 and Q4 are turned on, BT2 charges C, after charging, Q5 and Q6 are turned on, C charges BT3, at this time, it can jump to state 2 or state 6 or the voltage is directly balanced;

[0021] State 10: when U BT2 > U BT3 > U BT1 Q3 and Q4 are turned on, BT2 charges C, after charging, Q1 and Q2 are turned on, C charges BT1, at this time, it can jump to state 2 or state 4 or the voltage is directly balanced;

[0022] State 11: when U BT3 > U BT2 > U BT1 Q5 and Q6 are turned on, BT3 charges C, after charging, Q1 and Q2 are turned on, C charges BT1, at this time, it can jump to state 3 or state 4 or the voltage is directly balanced;

[0023] State 12: when U BT3 > U BT1 > U BT2 Q5 and Q6 are turned on, BT3 charges C, after charging, Q3 and Q4 are turned on, C charges BT1, at this time, it can jump to state 3 or state 5 or the voltage is directly balanced.

[0024] Further, the state of charge of each battery to be balanced in step S3 is similar, and needs to be charged and discharged according to the state of charge values of the first battery to be balanced BT1, the second battery to be balanced BT2 and the third battery to be balanced BT3, and is divided into 12 states, which are specifically as follows:

[0025] State 1: when SOC BT1 > SOC BT2 = SOC BT3 , first turn on Q1 and Q2, charge BT1 to C, after the charging is completed, turn on Q3 and Q4, charge C to BT2, after the charging is completed, turn on Q1 and Q2 again, charge BT1 to C again, after the charging of C is completed, turn on Q5 and Q6, charge C to BT3, and after several cycles, the battery cells are balanced;

[0026] State 2: when SOC BT2 > SOC BT1 = SOC BT3 , first turn on Q3 and Q4, charge BT2 to C, after the charging is completed, turn on Q1 and Q2, charge C to BT1, after the charging is completed, turn on Q3 and Q4 again, charge BT2 to C again, after the charging of C is completed, turn on Q5 and Q6, charge C to BT3, and after several cycles, the battery cells are balanced;

[0027] State 3: when SOC BT3 > SOC BT1 = SOC BT2 , first turn on Q5 and Q6, charge BT3 to C, after the charging is completed, turn on Q1 and Q2, charge C to BT1, after the charging is completed, turn on Q5 and Q6 again, charge BT3 to C again, after the charging of C is completed, turn on Q3 and Q4, charge C to BT2, and after several cycles, the battery cells are balanced;

[0028] State 4: when SOC BT3 = SOC BT2 > SOC BT1 , first turn on Q5 and Q6, charge BT3 to C, after the charging is completed, turn on Q1 and Q2, charge C to BT1, after the charging is completed, turn on Q3 and Q4 again, charge BT2 to C, after the charging of C is completed, turn on Q1 and Q2, charge C to BT1, and after several cycles, the battery cells are balanced;

[0029] State 5: when SOC BT1 = SOC BT3 > SOC BT2 , first turn on Q1 and Q2, charge BT1 to C, after the charging is completed, turn on Q3 and Q4, charge C to BT2, after the charging is completed, turn on Q5 and Q6 again, charge BT3 to C, after the charging of C is completed, turn on Q3 and Q4, charge C to BT2, and after several cycles, the battery cells are balanced;

[0030] State 6: when SOC BT1 > SOC BT2 > SOC BT3 , Q1 and Q2 are turned on, BT1 charges C, after charging is completed, Q5 and Q6 are turned on, C charges BT3, after charging is completed, Q3 and Q4 are turned on again, BT2 charges C, after C charging is completed, Q5 and Q6 are turned on, C charges BT3, after several cycles, until the battery cells are balanced;

[0031] State 7: when SOC BT1 > SOC BT2 > SOC BT3 , Q1 and Q2 are turned on, BT1 charges C, after charging is completed, Q5 and Q6 are turned on, C charges BT3, at this time, it can jump to state 1 or state 6 or the battery cells are directly balanced;

[0032] State 8: when SOC BT1 > SOC BT3 > SOC BT2 , Q1 and Q2 are turned on, BT1 charges C, after charging is completed, Q3 and Q4 are turned on, C charges BT2, at this time, it can jump to state 1 or state 5 or the battery cells are directly balanced;

[0033] State 9: when SOC BT2 > SOC BT1 > SOC BT3 , Q3 and Q4 are turned on, BT2 charges C, after charging is completed, Q5 and Q6 are turned on, C charges BT3, at this time, it can jump to state 2 or state 6 or the battery cells are directly balanced;

[0034] State 10: when SOC BT2 > SOC BT3 > SOC BT1 , Q3 and Q4 are turned on, BT2 charges C, after charging is completed, Q1 and Q2 are turned on, C charges BT1, at this time, it can jump to state 2 or state 4 or the battery cells are directly balanced;

[0035] State 11: when SOC BT3 > SOC BT2 > SOC BT1 , Q5 and Q6 are turned on, BT3 charges C, after charging is completed, Q1 and Q2 are turned on, C charges BT1, at this time, it can jump to state 3 or state 4 or the battery cells are directly balanced;

[0036] State 12: when SOC BT3 > SOC BT1 > SOC BT2When, Q5 and Q6 are turned on, BT3 charges C, after the charging is completed, Q3 and Q4 are turned on, C charges BT1, at this time, it can jump to state 3 or state 5 or the battery directly balances.

[0037] Further, the fuzzy logic algorithm of the fuzzy logic controller in the step S2 constructs a nonlinear mapping relationship between △U, △SOC and I b and D, and sets that the closer △U and △SOC are to 0, the more balanced the voltage and the battery are; the larger I b and D are, the faster the balancing speed is and the longer the balancing time is, and the better the balancing effect is.

[0038] Further, the logic rules from △U, △SOC to I b are set: △U, △SOC and I b have a proportional relationship, and the logic rules from △U, △SOC to D are set: △U, △SOC and D have a strict proportional relationship, that is, the larger △U and △SOC are, the larger I b is; the larger △U and △SOC are, the larger D is; conversely, the smaller △U and △SOC are, the smaller I b is; the smaller △U and △SOC are, the smaller D is.

[0039] Further, the fuzzy logic algorithm adopts four sub-membership functions, which are the sub-membership functions of △U, △SOC, I b and D; wherein, the value range of △U is [0, 0.5V], which is divided into six intervals of minimum UVL, small UL, relatively small UML, relatively large UMH, large UH and maximum UVH, and there is an intersection between each interval; the value range of △SOC is [0, 5%], which is divided into six intervals of S minimum VL, small SL, relatively small SML, relatively large SMH, large SH and maximum SVH, and there is an intersection between each interval; the value range of I b is [0, 2.5A], which is divided into six intervals of minimum IVL, small IL, relatively small IML, relatively large IMH, large IH and maximum IVH, and there is an intersection between each interval; the value range of D is [0.40, 0.65], which is divided into six intervals of minimum DVL, small DL, relatively small DML, relatively large DMH, large DH and maximum DVH, and there is an intersection between each interval; according to the four sub-membership functions, a suitable value is inferred from one value interval by using uncertainty and fuzziness.

[0040] The beneficial effects of the present application are: the present application realizes integrated voltage and cell balancing control based on the fuzzy logic algorithm of the fuzzy logic controller, which can effectively adjust the size of the balancing current and the length of the balancing time between each battery monomer, and takes into account the dual goals of voltage balancing and cell balancing, so that each battery monomer in the battery pack maintains the same voltage and similar SOC, thereby maximizing the cycle life of the battery and fully reducing the damage of the battery caused by overcharge and overdischarge. BRIEF DESCRIPTION OF DRAWINGS

[0041] The present application will be further described below in conjunction with the drawings and examples.

[0042] Figure 1 is a schematic diagram of the circuit structure of the present application.

[0043] Figure 2 is a control block diagram of the present application.

[0044] Figure 3 is a curve diagram of the membership function in the present application. DETAILED DESCRIPTION

[0045] The present application will now be further described in conjunction with the drawings and preferred embodiments. These drawings are all simplified schematic diagrams, and only illustrate the basic structure of the present application in a schematic manner, and therefore only show the components related to the present application.

[0046] An integrated voltage and cell balancing control method for lithium ion batteries, first, a circuit structure for integrated voltage and cell balancing of lithium ion batteries is designed; secondly, the difference between the maximum and minimum values of the battery monomer voltage and the difference between the maximum and minimum values of the battery monomer SOC are taken as two input variables, which are input into the fuzzy logic controller for operation, and two output variables, the balancing current and the duty cycle of the field effect transistor, are output, and the fuzzy logic control rule is designed; finally, the current of the circuit and the conduction time of the field effect transistor are controlled according to the two output variables, so that different lithium ion battery monomers in the circuit have the same voltage and similar SOC, thereby realizing dual balancing of voltage and cell.

[0047] As Figure 1As shown, the lithium ion battery voltage and the cell integration equalization circuit structure, the circuit provided by the embodiment includes a BT1 to be balanced battery, a BT2 to be balanced battery, a BT3 to be balanced battery, a MOS tube Q1, a MOS tube Q2, a MOS tube Q3, a MOS tube Q4, a MOS tube Q5, a MOS tube Q6 and an equalization capacitor C, the equalization capacitor C, the MOS tube Q1, the BT1 to be balanced battery, the BT2 to be balanced battery, the BT3 to be balanced battery and the MOS tube Q6 are connected in series to form a loop, one end of the MOS tube Q2 is connected between the equalization capacitor C and the MOS tube Q6, and the other end is connected between the BT1 to be balanced battery and the BT2 to be balanced battery, one end of the MOS tube Q3 is connected between the equalization capacitor C and the MOS tube Q1, and the other end is connected between the BT1 to be balanced battery and the BT2 to be balanced battery, one end of the MOS tube Q4 is connected between the equalization capacitor C and the MOS tube Q6, and the other end is connected between the BT2 to be balanced battery and the BT3 to be balanced battery, one end of the MOS tube Q5 is connected between the equalization capacitor C and the MOS tube Q1, and the other end is connected between the BT2 to be balanced battery and the BT3 to be balanced battery. Among them, the equalization capacitor C is used as an energy storage and transfer device, and the MOS tube is used as a switching device. In practical application, the number of batteries to be balanced is relatively large. A normal battery module is generally 6 or 12 batteries in a group, and there are several groups, and the battery balancing is carried out based on 3 batteries (minimum), and is expanded to a single battery group (6 or 12), and finally expanded to the entire battery module.

[0048] The voltage equalization working principle in the circuit is:

[0049] State 1: when U BT1 >U BT2 =U BT3 , first turn on Q1 and Q2, BT1 charges C, after charging, turn on Q3 and Q4, C charges BT2, after charging, turn on Q1 and Q2 again, BT1 charges C again, after C charging, turn on Q5 and Q6, C charges BT3, after several cycles, until the voltage is balanced;

[0050] State 2: when U BT2 >U BT1 =U BT3 , first turn on Q3 and Q4, BT2 charges C, after charging, turn on Q1 and Q2, C charges BT1, after charging, turn on Q3 and Q4 again, BT2 charges C again, after C charging, turn on Q5 and Q6, C charges BT3, after several cycles, until the voltage is balanced;

[0051] State 3: when U BT3 >U BT1 =UBT2 When charging, Q5 and Q6 are turned on first, BT3 charges C. After charging, Q1 and Q2 are turned on, C charges BT1. After charging, Q5 and Q6 are turned on again, BT3 charges C again. After C is charged, Q3 and Q4 are turned on, C charges BT2. This cycle repeats several times until the voltage is balanced.

[0052] State 4: When U BT3 =U BT2 >U BT1 When charging, first turn on Q5 and Q6, BT3 charges C, after charging is completed, turn on Q1 and Q2, C charges BT1, after charging is completed, turn on Q3 and Q4, BT2 charges C, after C is charged, turn on Q1 and Q2, C charges BT1, after several cycles, until the voltage is balanced;

[0053] State 5: When U BT1 =U BT3 >U BT2 When charging, first turn on Q1 and Q2, BT1 charges C, after charging is completed, turn on Q3 and Q4, C charges BT2, after charging is completed, turn on Q5 and Q6, BT3 charges C, after C is charged, turn on Q3 and Q4, C charges BT2, after several cycles, until the voltage is balanced;

[0054] State 6: When U BT1 =U BT2 >U BT3 When charging, first turn on Q1 and Q2, BT1 charges C, after charging is completed, turn on Q5 and Q6, C charges BT3, after charging is completed, turn on Q3 and Q4, BT2 charges C, after C is charged, turn on Q5 and Q6, C charges BT3, after several cycles, until the voltage is balanced;

[0055] State 7: When U BT1 >U BT2 >U BT3 When Q1 and Q2 are turned on, BT1 charges C. After charging is completed, Q5 and Q6 are turned on, and C charges BT3. At this time, the system can jump to state 1 or state 6 or directly balance the voltage.

[0056] State 8: When U BT1 >U BT3 >U BT2 When Q1 and Q2 are turned on, BT1 charges C. After charging is completed, Q3 and Q4 are turned on, and C charges BT2. At this time, the system can jump to state 1 or state 5 or the voltage can be directly balanced.

[0057] State 9: When U BT2 >U BT1 >U BT3When U > U, turn on Q3 and Q4, BT2 charges C, after charging, turn on Q1 and Q2, C charges BT1, at this time can jump to state 2 or state 4 or voltage direct balancing;

[0058] State 10: when U BT2 >U BT3 >U BT1 , turn on Q3 and Q4, BT2 charges C, after charging, turn on Q1 and Q2, C charges BT1, at this time can jump to state 2 or state 4 or voltage direct balancing;

[0059] State 11: when U BT3 >U BT2 >U BT1 , turn on Q5 and Q6, BT3 charges C, after charging, turn on Q1 and Q2, C charges BT1, at this time can jump to state 3 or state 4 or voltage direct balancing;

[0060] State 12: when U BT3 >U BT1 >U BT2 , turn on Q5 and Q6, BT3 charges C, after charging, turn on Q3 and Q4, C charges BT1, at this time can jump to state 3 or state 5 or voltage direct balancing.

[0061] The working principle of the cell equalization in the circuit is:

[0062] State 1: when SOC BT1 >SOC BT2 = SOC BT3 , first turn on Q1 and Q2, BT1 charges C, after charging, turn on Q3 and Q4, C charges BT2, after charging, turn on Q1 and Q2 again, BT1 charges C again, after C charging, turn on Q5 and Q6, C charges BT3, after several cycles, until the cell equalization;

[0063] State 2: when SOC BT2 >SOC BT1 = SOC BT3 , first turn on Q3 and Q4, BT2 charges C, after charging, turn on Q1 and Q2, C charges BT1, after charging, turn on Q3 and Q4 again, BT2 charges C again, after C charging, turn on Q5 and Q6, C charges BT3, after several cycles, until the cell equalization;

[0064] State 3: when SOC BT3 >SOC BT1 = SOC BT2When SOC

[0065] State 4: When SOC BT3 = SOC BT2 > SOC BT1 , first turn on Q5 and Q6, BT3 charges C, after charging is completed, turn on Q1 and Q2, C charges BT1, after charging is completed, turn on Q3 and Q4, BT2 charges C, after C is charged, turn on Q1 and Q2, C charges BT1, after several cycles, until the battery cells are balanced;

[0066] State 5: When SOC BT1 = SOC BT3 > SOC BT2 , first turn on Q1 and Q2, BT1 charges C, after charging is completed, turn on Q3 and Q4, C charges BT2, after charging is completed, turn on Q5 and Q6, BT3 charges C, after C is charged, turn on Q3 and Q4, C charges BT2, after several cycles, until the battery cells are balanced;

[0067] State 6: When SOC BT1 = SOC BT2 > SOC BT3 , first turn on Q1 and Q2, BT1 charges C, after charging is completed, turn on Q5 and Q6, C charges BT3, after charging is completed, turn on Q3 and Q4, BT2 charges C, after C is charged, turn on Q5 and Q6, C charges BT3, after several cycles, until the battery cells are balanced;

[0068] State 7: When SOC BT1 > SOC BT2 > SOC BT3 , turn on Q1 and Q2, BT1 charges C, after charging is completed, turn on Q5 and Q6, C charges BT3, at this time, it can jump to state 1 or state 6 or the battery cells are directly balanced;

[0069] State 8: When SOC BT1 > SOC BT3 > SOC BT2 , turn on Q1 and Q2, BT1 charges C, after charging is completed, turn on Q3 and Q4, C charges BT2, at this time, it can jump to state 1 or state 5 or the battery cells are directly balanced;

[0070] State 9: When SOC BT2 > SOC BT1>SOC BT3 When Q3 and Q4 are turned on, BT2 charges C. After charging is completed, Q5 and Q6 are turned on, and C charges BT3. At this time, the system can jump to state 2 or state 6 or balance the cells directly.

[0071] State 10: When SOC BT2 >SOC BT3 >SOC BT1 When charging is complete, Q3 and Q4 are turned on, and BT2 charges C. After charging is completed, Q1 and Q2 are turned on, and C charges BT1. At this time, the system can jump to state 2 or state 4, or the battery cells can be balanced directly.

[0072] State 11: When SOC BT3 >SOC BT2 >SOC BT1 When charging is complete, Q5 and Q6 are turned on, and BT3 charges C. After charging is completed, Q1 and Q2 are turned on, and C charges BT1. At this time, the system can jump to state 3 or state 4 or balance the cells directly.

[0073] State 12: When SOC BT3 >SOC BT1 >SOC BT2 When charging is complete, Q5 and Q6 are turned on, and BT3 charges C. After charging is completed, Q3 and Q4 are turned on, and C charges BT1. At this time, the system can jump to state 3 or state 5, or the battery cells can be balanced directly.

[0074] Figure 2 As shown, U max 、U min They represent the maximum and minimum values ​​of the battery cell voltage respectively, and △U is U max with U min Similarly, SOC max , SOC min They represent the maximum and minimum values ​​of the battery cell SOC respectively, and △SOC is the SOC max With SOC min The fuzzy logic controller adopts a dual-input-dual-output structure. In this embodiment, △U and △SOC are used as two input variables, and the balanced current I b The fuzzy logic controller uses the powerful artificial intelligence reasoning ability to construct the relationship between △U, △SOC and I b The nonlinear mapping relationship between ∆U and D. Therefore, the control target can be designed as follows: the closer ∆U and ∆SOC are to 0, the more balanced the voltage and battery cell are; I b The larger the and D are, the faster the balancing speed and the longer the balancing time are, thus the better the balancing effect is.

[0075] Figure 3As shown, the membership function is composed of 4 sub-membership functions, respectively △U, △SOC, I b and D. Figure 3 (a) is the △U sub-membership function, the value range of △U is [0, 0.5V], divided into UVL (minimum), UL (small), UML (smaller), UMH (larger), UH (large), UVH (maximum) 6 intervals, and there is intersection between each interval. Figure 3 (b) is the △SOC sub-membership function, the value range of △SOC is [0, 5%], divided into SVL (minimum), SL (small), SML (smaller), SMH (larger), SH (large), SVH (maximum) 6 intervals, and there is intersection between each interval. Figure 3 (c) is the I b sub-membership function, the value range of I b is [0, 2.5A], divided into IVL (minimum), IL (small), IML (smaller), IMH (larger), IH (large), IVH (maximum) 6 intervals, and there is intersection between each interval. Figure 3 (d) is the D sub-membership function, the value range of D is [0.40, 0.65], divided into DVL (minimum), DL (small), DML (smaller), DMH (larger), DH (large), DVH (maximum) 6 intervals, and there is intersection between each interval. From the membership function, it can be seen that △SOC, △U, I b and D are not accurate to a specific value during the value process, but use uncertainty and fuzziness to infer the appropriate value from a value interval, so that the robustness and adaptability of the control system are fully improved.

[0076] Table 1

[0077]

[0078] Table 2

[0079]

[0080] The logic rule consists of two parts, Table 1 is the logic rule of inferring I b from △U, △SOC, and Table 2 is the logic rule of inferring D from △U, △SOC. From the two tables, it is not difficult to see that there is a strict proportional relationship between △U, △SOC and I b , and △U, △SOC and D, that is: if △U and △SOC are larger, large current balancing is needed, then I b is larger; if △U and △SOC are larger, long-time balancing is needed, then D is larger. Conversely, if △U and △SOC are smaller, small current balancing is needed, then I bThe smaller the △U and the smaller the △SOC, the shorter the time needed for balancing, and the smaller the D.

[0081] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A method for integrated voltage and cell balancing control of a lithium-ion battery, characterized in that: The steps include: S1. Construct an integrated balancing circuit structure for lithium-ion battery voltage and battery cells; S2: Measure the voltage of the battery to be balanced in step S1 and obtain the maximum voltage U max and minimum voltage U min , calculate the voltage difference between the two △U=U max -U min ; Sequentially measure the state of charge of the battery to be balanced in step S1 to obtain the maximum state of charge SOC max and minimum state of charge SOC min , calculate the difference in state of charge between the two △SOC=SOC max -SOC min ; The voltage difference △U and the state of charge difference △SOC are input as two input variables to the fuzzy logic controller, and the balancing current I is obtained through the fuzzy logic algorithm of the fuzzy logic controller. d And the two output variables of the duty cycle D of the MOS tube; S3. The battery management system adjusts the current of the circuit and the on-time of the MOS tube in step S1 according to the two output variables in step S2, so that the voltages of the batteries to be balanced are the same and the states of charge are similar, thus achieving dual balancing of voltage and cells. The circuit in S1 includes a first battery to be balanced BT1, a second battery to be balanced BT2, a third battery to be balanced BT3, a MOS transistor Q1, a second MOS transistor Q2, a third MOS transistor Q3, a fourth MOS transistor Q4, a fifth MOS transistor Q5, a sixth MOS transistor Q6 and a balancing capacitor C. The balancing capacitor C, the first MOS transistor Q1, the first battery to be balanced BT1, the second battery to be balanced BT2, the third battery to be balanced BT3 and the sixth MOS transistor Q6 are connected in series to form a loop. One end of the second MOS transistor Q2 is connected between the balancing capacitor C and the sixth MOS transistor Q6, and the other end is connected to the balancing capacitor C. Between battery 1 BT1 and battery 2 to be balanced BT2, one end of MOS transistor 3 Q3 is connected between balancing capacitor C and MOS transistor 1 Q1, and the other end is connected between battery 1 BT1 to be balanced and battery 2 BT2 to be balanced. One end of MOS transistor 4 Q4 is connected between balancing capacitor C and MOS transistor 6 Q6, and the other end is connected between battery 2 BT2 to be balanced and battery 3 BT3 to be balanced. One end of MOS transistor 5 Q5 is connected between balancing capacitor C and MOS transistor 1 Q1, and the other end is connected between battery 2 BT2 to be balanced and battery 3 BT3 to be balanced. In step S3, the voltages of the batteries to be balanced are the same. Charge and discharge are performed according to the voltage values ​​of the first battery to be balanced BT1, the second battery to be balanced BT2, and the third battery to be balanced BT3. The charging and discharging are divided into 12 states, specifically: State 1: When U BT1 >U BT2 =U BT3 When charging, Q1 and Q2 are turned on first, BT1 charges C. After charging, Q3 and Q4 are turned on, C charges BT2. After charging, Q1 and Q2 are turned on again, BT1 charges C again. After C is charged, Q5 and Q6 are turned on, C charges BT3. This cycle repeats several times until the voltage is balanced. State 2: When U BT2 >U BT1 =U BT3 When charging, first turn on Q3 and Q4, BT2 charges C, after charging is completed, turn on Q1 and Q2, C charges BT1, after charging is completed, turn on Q3 and Q4, BT2 charges C again, after C is charged, turn on Q5 and Q6, C charges BT3, after several cycles, until the voltage is balanced; State 3: When U BT3 >U BT1 =U BT2 When charging, Q5 and Q6 are turned on first, BT3 charges C. After charging, Q1 and Q2 are turned on, C charges BT1. After charging, Q5 and Q6 are turned on again, BT3 charges C again. After C is charged, Q3 and Q4 are turned on, C charges BT2. This cycle repeats several times until the voltage is balanced. State 4: When U BT3 =U BT2 >U BT1 When charging, first turn on Q5 and Q6, BT3 charges C, after charging is completed, turn on Q1 and Q2, C charges BT1, after charging is completed, turn on Q3 and Q4, BT2 charges C, after C is charged, turn on Q1 and Q2, C charges BT1, after several cycles, until the voltage is balanced; State 5: When U BT1 = U BT3 >U BT2 When charging, first turn on Q1 and Q2, BT1 charges C, after charging is completed, turn on Q3 and Q4, C charges BT2, after charging is completed, turn on Q5 and Q6, BT3 charges C, after C is charged, turn on Q3 and Q4, C charges BT2, after several cycles, until the voltage is balanced; State 6: When U BT1 = U BT2 >U BT3 When charging, first turn on Q1 and Q2, BT1 charges C, after charging is completed, turn on Q5 and Q6, C charges BT3, after charging is completed, turn on Q3 and Q4, BT2 charges C, after C is charged, turn on Q5 and Q6, C charges BT3, after several cycles, until the voltage is balanced; State 7: When U BT1 >U BT2 >U BT3 When Q1 and Q2 are turned on, BT1 charges C. After charging is completed, Q5 and Q6 are turned on, and C charges BT3. At this time, the system can jump to state 1 or state 6 or directly balance the voltage. State 8: When U BT1 >U BT3 >U BT2 When Q1 and Q2 are turned on, BT1 charges C. After charging is completed, Q3 and Q4 are turned on, and C charges BT2. At this time, the system can jump to state 1 or state 5 or the voltage can be directly balanced. State 9: When U BT2 >U BT1 >U BT3 When Q3 and Q4 are turned on, BT2 charges C. After charging is completed, Q5 and Q6 are turned on, and C charges BT3. At this time, the system can jump to state 2 or state 6 or the voltage can be directly balanced. State 10: When U BT2 >U BT3 >U BT1 When Q3 and Q4 are turned on, BT2 charges C. After charging is completed, Q1 and Q2 are turned on, and C charges BT1. At this time, the system can jump to state 2 or state 4 or the voltage can be directly balanced. State 11: When U BT3 >U BT2 >U BT1 When Q5 and Q6 are turned on, BT3 charges C. After charging is completed, Q1 and Q2 are turned on, and C charges BT1. At this time, the system can jump to state 3 or state 4 or the voltage can be directly balanced. State 12: When U BT3 >U BT1 >U BT2 When Q5 and Q6 are turned on, BT3 charges C. After charging is completed, Q3 and Q4 are turned on, and C charges BT1. At this time, the system can jump to state 3 or state 5 or the voltage can be directly balanced. In step S3, the charge states of the batteries to be balanced are similar. Charging and discharging are performed according to the charge state values ​​of the first battery to be balanced BT1, the second battery to be balanced BT2, and the third battery to be balanced BT3. The charging and discharging are divided into 12 states, specifically: State 1: When SOC BT1 >SOC BT2 =SOC BT3 When charging, first turn on Q1 and Q2, BT1 charges C, after charging is completed, turn on Q3 and Q4, C charges BT2, after charging is completed, turn on Q1 and Q2 again, BT1 charges C again, after C is charged, turn on Q5 and Q6, C charges BT3, after several cycles, until the cells are balanced; State 2: When SOC BT2 >SOC BT1 =SOC BT3 When charging, first turn on Q3 and Q4, BT2 charges C, after charging is completed, turn on Q1 and Q2, C charges BT1, after charging is completed, turn on Q3 and Q4, BT2 charges C again, after C is charged, turn on Q5 and Q6, C charges BT3, after several cycles, until the cells are balanced; State 3: When SOC BT3 >SOC BT1 =SOC BT2 When charging, first turn on Q5 and Q6, BT3 charges C, after charging is completed, turn on Q1 and Q2, C charges BT1, after charging is completed, turn on Q5 and Q6, BT3 charges C again, after C is charged, turn on Q3 and Q4, C charges BT2, after several cycles, until the cells are balanced; State 4: When SOC BT3 =SOC BT2 >SOC BT1 When charging, first turn on Q5 and Q6, BT3 charges C, after charging is completed, turn on Q1 and Q2, C charges BT1, after charging is completed, turn on Q3 and Q4, BT2 charges C, after C is charged, turn on Q1 and Q2, C charges BT1, after several cycles, until the cells are balanced; State 5: When SOC BT1 =SOC BT3 >SOC BT2 When charging, first turn on Q1 and Q2, BT1 charges C, after charging is completed, turn on Q3 and Q4, C charges BT2, after charging is completed, turn on Q5 and Q6, BT3 charges C, after C is charged, turn on Q3 and Q4, C charges BT2, after several cycles, until the cells are balanced; State 6: When SOC BT1 =SOC BT2 >SOC BT3 When charging, first turn on Q1 and Q2, BT1 charges C, after charging is completed, turn on Q5 and Q6, C charges BT3, after charging is completed, turn on Q3 and Q4, BT2 charges C, after C is charged, turn on Q5 and Q6, C charges BT3, after several cycles, until the cells are balanced; State 7: When SOC BT1 >SOC BT2 >SOC BT3 When Q1 and Q2 are turned on, BT1 charges C. After charging is completed, Q5 and Q6 are turned on, and C charges BT3. At this time, the system can jump to state 1 or state 6 or balance the cells directly. State 8: When SOC BT1 >SOC BT3 >SOC BT2 When Q1 and Q2 are turned on, BT1 charges C. After charging is completed, Q3 and Q4 are turned on, and C charges BT2. At this time, the system can jump to state 1 or state 5 or balance the cells directly. State 9: When SOC BT2 >SOC BT1 >SOC BT3 When Q3 and Q4 are turned on, BT2 charges C. After charging is completed, Q5 and Q6 are turned on, and C charges BT3. At this time, the system can jump to state 2 or state 6 or balance the cells directly. State 10: When SOC BT2 >SOC BT3 >SOC BT1 When charging is complete, Q3 and Q4 are turned on, and BT2 charges C. After charging is completed, Q1 and Q2 are turned on, and C charges BT1. At this time, the system can jump to state 2 or state 4, or the battery cells can be balanced directly. State 11: When SOC BT3 >SOC BT2 >SOC BT1 When charging is complete, Q5 and Q6 are turned on, and BT3 charges C. After charging is completed, Q1 and Q2 are turned on, and C charges BT1. At this time, the system can jump to state 3 or state 4 or balance the cells directly. State 12: When SOC BT3 >SOC BT1 >SOC BT2 When charging is complete, Q5 and Q6 are turned on, and BT3 charges C. After charging is completed, Q3 and Q4 are turned on, and C charges BT1. At this time, the system can jump to state 3 or state 5, or the battery cells can be balanced directly.

2. The integrated balancing control method for lithium-ion battery voltage and battery cells according to claim 1, characterized in that: In S2, the fuzzy logic algorithm of the fuzzy logic controller is used to construct △U, △SOC and I b The nonlinear mapping relationship between ∆U and ∆SOC is set to 0, and the voltage and cell are more balanced. b The larger the sum D is, the faster the balancing speed is, the longer the balancing time is, and the better the balancing effect is.

3. The integrated balancing control method for lithium-ion battery voltage and battery cells according to claim 2, characterized in that: Set the inference from △U, △SOC to I b Logical rules: △U, △SOC and I b There is a proportional relationship, and the logical rule of inference from △U, △SOC to D is set: there is a strict proportional relationship between △U, △SOC and D, that is: if △U and △SOC are larger, large current balancing is required, then I b The larger the △U and △SOC are, the longer the balancing time is needed, and the larger D is. On the contrary, if △U and △SOC are smaller, small current balancing is required, then I b The smaller it is; if △U and △SOC are smaller, a shorter time is required for balancing, then D is smaller.

4. The integrated balancing control method for lithium-ion battery voltage and battery cells according to claim 3, characterized in that: The fuzzy logic algorithm uses a membership function composed of four sub-membership functions, which are △U, △SOC, I b and the sub-membership function of D; where the value range of △U is [0, 0.5V], which is divided into 6 intervals: minimum UVL, small UL, small UML, large UMH, large UH, and maximum UVH, and there is an intersection between each interval; the value range of △SOC is [0, 5%], which is divided into 6 intervals: minimum VL, small SL, small SML, large SMH, large SH, and maximum SVH, and there is also an intersection between each interval; I b The value range of is [0, 2.5A], which is divided into 6 intervals: minimum IVL, small IL, small IML, large IMH, large IH, and maximum IVH, and each interval has an intersection. The value range of D is [0.40, 0.65], which is divided into 6 intervals: minimum DVL, small DL, small DML, large DMH, large DH, and maximum DVH, and each interval also has an intersection. According to the four sub-membership functions, uncertainty and fuzziness are used to infer the appropriate value from a value interval.

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