CN117559600A - Balance control method for inter-group double-layer inductance in lithium battery pack - Google Patents
Balance control method for inter-group double-layer inductance in lithium battery pack Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0047—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with monitoring or indicating devices or circuits
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Abstract
The invention relates to a double-layer inductance balance control method between lithium battery packs, which is characterized in that the maximum voltage difference of battery cells in the battery packs and the voltage difference between the two battery packs are measured, then the maximum voltage difference of the battery cells in the battery packs and the voltage difference between the two battery packs are judged, and finally the energy transfer paths between the battery cells in the battery packs and the energy transfer paths between the two battery packs are respectively regulated by a fuzzy logic controller.
Description
Technical Field
The invention relates to the technical field of active equalization of lithium battery packs, in particular to a method for controlling inter-pack double-layer inductance equalization in a lithium battery pack.
Background
The current battery equalization techniques can be divided into two categories: one is energy dissipation type equalization, namely passive equalization, wherein the equalization mode dissipates the electric quantity of a battery with higher electric quantity in a resistance shunt mode, and the structure of the equalization mode is simple, but the electric energy is wasted; another approach is non-energy dissipative equalization, i.e., active equalization, which is also battery SOC equalization, battery capacity equalization, and battery voltage equalization, with higher active equalization efficiency, energy transfer from high to low batteries.
The selection of the balanced object, namely the battery index, can directly influence the speed efficiency of battery balancing, and the balanced object comprises the following components:
(1) Battery SOC equalization: the state of charge of the battery is the most direct index of equalization, and the residual quantity of the battery is directly reflected, and the SOC of the battery cell is taken as an equalization object, so that the SOC reaches a consistent level.
(2) Battery capacity equalization: in this method, the capacities of the battery cells are equalized, and the capacity of the entire battery pack is maximized.
(3) Cell voltage equalization: the voltage value of the battery cell is the most intuitive index for judging the external power supply capacity, and is strictly positively correlated with the state of charge of the battery.
Compared with the three active equalization control modes, the battery SOC equalization has high accuracy requirement on the algorithm, and the battery state of charge is difficult to directly measure; the battery capacity equalization is easy to overcharge the battery cells, and although equalization can be realized, the service life of the battery is damaged; the battery voltage equalization is simple to obtain and high in accuracy, overcharge and overdischarge of the battery can be avoided, and the charge state of the battery can be accurately reflected, so that in summary, the inventor chooses to equalize the index of the battery voltage, and provides a double-layer inductance equalization control method between the lithium battery packs.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a double-layer inductance balance control method between lithium battery packs, which has the advantages of good balance effect and the like and solves the problem of poor traditional balance effect.
In order to achieve the above purpose, the present invention provides the following technical solutions: a double-layer inductance balance control method between lithium battery packs comprises the following specific steps:
step 1: dividing 2n battery cells into two groups, wherein n is more than 1, n is a positive integer, and collecting the voltage of the battery cells through a voltage measuring element;
step 2: calculating according to the formula (1) and the formula (2) to obtain the maximum voltage difference of the battery cells in the battery packs and the voltage difference between the two battery packs:
Δv 1 ＝v max -v min (1)
Wherein v is max V is the highest voltage value of the voltage in the battery cell min V is the lowest voltage value of the voltage in the battery cell 1 To v n Is the voltage value of the battery cell in one battery pack, v n+1 To v 2n For the voltage value of the battery cell in another battery pack, deltav 1 Is the maximum voltage difference of the battery cells in the battery pack, deltav 2 Is the voltage difference between the two battery packs;
step 3: respectively judge Deltav 1 The value of (a) and Deltav 2 If the value of (2) is larger than the threshold voltage Xv, if not, the step 2 is entered, and if yes, the step 4 is entered;
step 4: when Deltav 1 When the value of (a) is larger than Xv, the fuzzy logic controller is utilized to adjust the energy transfer path among the battery cells in the battery pack, the battery cell with the highest voltage value in the battery pack is transferred to the other battery cells, and when Deltav 2 When the value of (2) is larger than Xv, the fuzzy logic controller is used for adjusting the energy transfer path between the two battery packs, and one group with higher voltage between the battery packs is transferred into one group with lower voltage between the battery packs.
Further, the structure of the inter-group double-layer inductance equalization circuit in the lithium battery pack in step 4 is as follows: battery cell B 1 -B 2n Are connected in series and divided into two groups,B 1 -B n for the first group, B n+1 -B 2n The number of the two groups of batteries is equal to that of the second group;
the circuit structure of the in-group equalization is as follows:
battery cell B 1 -B 2n Any battery cell B i And voltage measuring element V i In parallel, the battery cells B i Positive electrode of (c) and inductance element L i Is connected to one end of the inductance element L i The other end of (2) is connected with a switch tube Q i D pole and diode D of (2) i The diode D i Is connected with the battery cell B 1 Is a positive electrode of (a); the switch tube Q i The S pole of (C) is connected with the battery cell B i Is a negative electrode of (a); the inductance element L i One end of (a) is also connected with a switch tube Q i-1 An S pole of (2); wherein i is more than 1, i is a positive integer;
when i=2, the inductance element L 2 One end of (a) is connected with the inductance element L 1 Is arranged at the other end of the tube; the battery cell B 1 And voltage measuring element V 1 In parallel, the battery cells B 1 Positive electrode connection switch tube Q 1 D pole of said switching tube Q 1 S pole of (C) is connected with inductance element L 1 And diode D 1 Is the negative electrode of the diode D 1 Positive electrode of (a) and cell B 2n Is connected with the negative electrode of the battery;
the circuit structure of the inter-group equalization is as follows:
the battery cell B 1 Positive electrode connection switch tube Q 2n+1 D pole of said switching tube Q 2n+1 S pole of (C) and inductance L 2n+1 Is connected with one end of the connecting rod; the battery cell B n Negative electrode of (2) and switch tube Q 2n+2 S pole of the switch tube Q 2n+2 D pole of (c) is connected with inductance L 2n+1 Is connected with one end of the connecting rod; the inductance L 2n+1 Is connected with the battery cell B at the other end n+1 Positive electrode of (a) and cell B n Is a negative electrode of (a).
Further, the fuzzy logic controller input variables of step 4 include the maximum voltage difference Δv of the cells in the battery pack 1 And a voltage difference Deltav between the battery packs 2 The fuzzy logic controller is used for controlling the voltage difference Deltav of the single cells in the battery pack according to the maximum voltage difference Deltav of the single cells in the battery pack 1 And a voltage difference Deltav between the battery packs 2 Obtaining the frequency of an output variable switching tube;
maximum voltage difference Deltav of battery cells in the battery pack 1 And a voltage difference Deltav between the battery packs 2 The argument D of (1) is set to 0,0.5]Describing input variables through fuzzy languages, wherein the set of the fuzzy languages is of small (small), medium (middle) and large (large) 3 grades;
the switching tube frequency domain is set to be [0,5], the output variable is described through fuzzy language, and the set of the fuzzy language is small (small), medium (middle), large (large) and ultra-large (very large) 4 grades.
Further, the method for adjusting the energy transfer path between the battery cells in the battery pack by using the fuzzy logic controller in the step 4 comprises the following specific steps:
when the battery cell B 1 When the voltage is highest, and the difference of the maximum value of the battery cell voltage minus the minimum value of the battery cell voltage is more than 0.01v, the switch tube Q 1 Conduction, B 1 Energy storage inductance L 1 Charging is carried out, and after the charging is finished, the switching tube Q is turned off 1 Energy storage inductance L 1 To battery B 2 -B 2n Charging to finish energy transfer;
when in addition to B 1 Battery B other than i When the voltage is highest, and the difference of the maximum value of the battery cell voltage minus the minimum value of the battery cell voltage is more than 0.01v, the switch tube Q i Conduction, battery B i To energy storage inductance L i Charging is carried out, and after the charging is finished, the switching tube Q is turned off n Energy storage inductance L n To battery B 1 -B i-1 And charging to complete energy transfer.
Further, the method for adjusting the energy transfer path between two battery packs by using the fuzzy logic controller in the step 4 includes the following specific steps:
when the average voltage of the first group of cells is higher than that of the second group of cells and the difference between the average values is more than 0.01v, the switch tubeQ 2n+1 Conduction, first group battery pair inductance L 2n+1 Charging is carried out, and after the charging is finished, a switch tube Q 2n+1 Turn-off, switch tube Q 2n+2 Conduction and inductance L 2n+1 Charging the second group of batteries to finish energy transfer;
when the average voltage of the second group of cells is higher than that of the first group of cells and the difference between the average values is more than 0.01v, the switch tube Q 2n+2 Conduction, second group battery pair inductance L 2n+2 Charging is carried out, and after the charging is finished, a switch tube Q 2n+2 Turn-off, switch tube Q 2n+1 Conduction and inductance L 2n+1 And charging the first group of batteries to finish energy transfer.
Compared with the prior art, the technical scheme of the application has the following beneficial effects:
compared with the traditional single-layer lithium battery pack equalization circuit, the inter-group double-layer inductance equalization control method in the lithium battery pack can realize simultaneous voltage equalization operation in the battery pack and among the battery packs, can improve the equalization speed and the energy utilization rate of the battery pack, and reduces energy loss.
Drawings
FIG. 1 is a diagram of a double-layer inductance equalization circuit between lithium battery packs according to the present invention;
FIG. 2 shows the membership input function Deltav of the present invention 1 A figure;
FIG. 3 shows the membership input function Deltav of the present invention 2 A figure;
FIG. 4 is a graph showing the output of the membership input function of the present invention;
FIG. 5 is a diagram showing a specific experimental construction of the circuit of the present invention;
FIG. 6 is a schematic diagram of the inductance equalization circuit between the two-layer inner groups of the double-layer set according to the invention;
FIG. 7 is a diagram of the discharge equalization of the inductance equalization circuit between the two-layer inner groups of the double-layer set according to the present invention;
fig. 8 is a charge equalization diagram of an inter-group inductance equalization circuit in a double-layer group according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, a method for controlling inter-group double-layer inductance balance in a lithium battery pack according to the present embodiment includes the following steps:
step 1: dividing 2n battery cells into two groups, wherein n is more than 1, n is a positive integer, and collecting the voltage of the battery cells through a voltage measuring element;
step 2: calculating according to the formula (1) and the formula (2) to obtain the maximum voltage difference of the battery cells in the battery packs and the voltage difference between the two battery packs:
Δv 1 ＝v max -v min (1)
Wherein v is max V is the highest voltage value of the voltage in the battery cell min V is the lowest voltage value of the voltage in the battery cell 1 To v n Is the voltage value of the battery cell in one battery pack, v n+1 To v 2n For the voltage value of the battery cell in another battery pack, deltav 1 Is the maximum voltage difference of the battery cells in the battery pack, deltav 2 Is the voltage difference between the two battery packs;
step 3: respectively judge Deltav 1 The value of (a) and Deltav 2 If the value of (2) is larger than the threshold voltage Xv, if not, the step 2 is entered, and if yes, the step 4 is entered;
step 4: when Deltav 1 When the value of (a) is larger than Xv, the fuzzy logic controller is utilized to adjust the energy transfer path among the battery cells in the battery pack, the battery cell with the highest voltage value in the battery pack is transferred to the other battery cells, and when Deltav 2 When the value of (a) is larger than Xv, the fuzzy logic controller is utilized to regulate the space between two battery packsIs transferred from a group having a higher inter-battery voltage to a group having a lower inter-battery voltage.
Step 4, the inter-group double-layer inductance equalization circuit structure in the lithium battery pack is as follows: battery cell B 1 -B 2n Are connected in series and divided into two groups, B 1 -B n For the first group, B n+1 -B 2n The number of the two groups of batteries is equal to that of the second group;
the circuit structure of the in-group equalization is as follows:
battery cell B 1 -B 2n Any battery cell B i And voltage measuring element V i Parallel connection of battery cells B i Positive electrode of (c) and inductance element L i Is connected to one end of the inductance element L i The other end of (2) is connected with a switch tube Q i D pole and diode D of (2) i Positive electrode of diode D i Is connected with the battery cell B 1 Is a positive electrode of (a); switch tube Q i The S pole of (C) is connected with the battery cell B i Is a negative electrode of (a); inductance element L i One end of (a) is also connected with a switch tube Q i-1 An S pole of (2); wherein i is more than 1, i is a positive integer;
when i=2, the inductance element L 2 One end of (a) is connected with the inductance element L 1 Is arranged at the other end of the tube; battery cell B 1 And voltage measuring element V 1 Parallel connection of battery cells B 1 Positive electrode connection switch tube Q 1 D pole of (B), switch tube Q 1 S pole of (C) is connected with inductance element L 1 And diode D 1 Is the cathode of diode D 1 Positive electrode of (a) and cell B 2n Is connected with the negative electrode of the battery;
the circuit structure of the inter-group equalization is as follows:
battery cell B 1 Positive electrode connection switch tube Q 2n+1 D pole of (B), switch tube Q 2n+1 S pole of (C) and inductance L 2n+1 Is connected with one end of the connecting rod; battery cell B n Negative electrode of (2) and switch tube Q 2n+2 S pole of (C) is connected with a switch tube Q 2n+2 D pole of (c) is connected with inductance L 2n+1 Is connected with one end of the connecting rod; inductance L 2n+1 Is connected with the battery cell B at the other end n+1 Positive electrode of (a) and cell B n Is a negative electrode of (a).
Step 4 fuzzy logic controller input variables include the maximum voltage difference Deltav of the cells in the stack 1 And a voltage difference Deltav between the battery packs 2 The fuzzy logic controller is used for controlling the maximum voltage difference Deltav of the battery cells in the battery pack 1 And a voltage difference Deltav between the battery packs 2 The frequency of the output variable switching tube is obtained, and as the number of the input variables is two, three domains can be generated, but the domains of the two input variables are the same, so that the domains of the two input variables are combined;
maximum voltage difference Deltav of battery cells in battery pack 1 And a voltage difference Deltav between the battery packs 2 The argument D of (1) is set to 0,0.5]Describing input variables through fuzzy languages, wherein the set of the fuzzy languages is of small (small), medium (middle) and large (large) 3 grades;
the switching tube frequency is set to be [0,5], the output variable is described by fuzzy language, and the set of fuzzy languages is small (small), medium (middle), large (large) and oversized (verylarge) 4 grades.
Specifically, the inter-group double-layer inductance equalization circuit in the lithium battery pack realizes specific control by controlling the frequency of a switching tube through a fuzzy logic controller, the core of the fuzzy logic control is the fuzzy logic controller, and the fuzzy logic controller has the function of inputting natural language and outputting computer algorithm language required by a controlled object, wherein the specific steps are as follows: firstly, the controlled quantity is adopted by a computer, and then, the difference is made between the controlled quantity and a given value to obtain an error signal E; fuzzifying the error signal to become a fuzzy quantity, and further obtaining a subset E of a fuzzy language set of the error E; and finally combining the e and the fuzzy rule R to form a fuzzy decision to obtain a fuzzy control quantity u. In order to control the controlled object more accurately, the blurring amount u needs to be converted into an accurate value after defuzzification processing, and then the accurate value is sent to an executing mechanism to control the controlled object. The fuzzy control of the controlled object can be realized by continuously cycling the above processes.
If there is a number A (x) ∈ [0,1] corresponding to any element x in the argument D, then A is called the fuzzy set on U, and A (x) is called the membership of x to A. When x varies in U, A (x) is a function called the membership function of A. The membership A (x) is closer to 1, the degree that x belongs to A is higher, the degree that A (x) is closer to 0, the degree that x belongs to A is lower, common fuzzy value membership functions comprise a triangular function, a ladder function, a Gaussian function, a Z-shaped function and the like, the Gaussian function is selected as the membership function of fuzzy logic control input by the input function, the membership function is shown in fig. 2-4, the Gaussian function has good smoothness and symmetry compared with other membership functions, and no zero point in a graph has clear physical significance.
By the maximum voltage difference Deltav of the battery cells in the battery pack 1 And a voltage difference Deltav between the battery packs 2 The relation with the switching tube frequency can obtain 9 fuzzy control rules, which cover the voltage difference between all the battery cells and between the battery packs and the switching tube frequency corresponding to the voltage difference between all the battery cells and between the battery packs, as shown in the following table 1;
TABLE 1 fuzzy control rules
If and, then, mode represents the output variable, and M10, M20, M30, and M40 are the frequencies of the switching transistors, respectively, and the smaller the frequency of the switching transistor is, the greater the charging current is, so the fuzzy languages corresponding to M10, M20, M30, and M40 are "verylarge", "large", "middle", and "small", respectively.
According to the fuzzy control rule of table 1, the following fuzzy control rule table 2 can be obtained;
table 2 fuzzy rule control table
The fuzzy rule control table shows that the switching tube frequency is determined by the maximum voltage difference Deltav of the battery cells in the battery pack 1 And a voltage difference Deltav between the battery packs 2 Together, the maximum voltage difference Deltav of the battery cells in the battery pack 1 And a voltage difference Deltav between the battery packs 2 When the voltage difference is larger, the lower the switching tube frequency is, if the integral voltage difference between the batteries is larger; if the integral voltage difference between the batteries is smaller, the switching tube frequency is higher; when the maximum voltage difference Deltav of the battery cells in the battery pack 1 And a voltage difference Deltav between the battery packs 2 One hour, the whole voltage difference is moderate, and the switching tube frequency is moderate.
Step 4, the method for adjusting the energy transfer paths among the battery cells in the battery pack by using the fuzzy logic controller comprises the following specific steps:
when the battery cell B 1 When the voltage is highest, and the difference of the maximum value of the battery cell voltage minus the minimum value of the battery cell voltage is more than 0.01v, the switch tube Q 1 Conduction, B 1 Energy storage inductance L 1 Charging is carried out, and after the charging is finished, the switching tube Q is turned off 1 Energy storage inductance L 1 To battery B 2 -B 2n Charging to finish energy transfer;
when in addition to B 1 Battery B other than i When the voltage is highest, and the difference of the maximum value of the battery cell voltage minus the minimum value of the battery cell voltage is more than 0.01v, the switch tube Q i Conduction, battery B i To energy storage inductance L i Charging is carried out, and after the charging is finished, the switching tube Q is turned off n Energy storage inductance L n To battery B 1 -B i-1 And charging to complete energy transfer.
Step 4, the method for adjusting the energy transfer path between two battery packs by using the fuzzy logic controller comprises the following specific steps:
when the first group of batteriesWhen the average voltage of the second group of cells is higher than that of the second group of cells and the difference between the average values is more than 0.01v, the switching tube Q 2n+1 Conduction, first group battery pair inductance L 2n+1 Charging is carried out, and after the charging is finished, a switch tube Q 2n+1 Turn-off, switch tube Q 2n+2 Conduction and inductance L 2n+1 Charging the second group of batteries to finish energy transfer;
when the average voltage of the second group of cells is higher than that of the first group of cells and the difference between the average values is more than 0.01v, the switch tube Q 2n+2 Conduction, second group battery pair inductance L 2n+2 Charging is carried out, and after the charging is finished, a switch tube Q 2n+2 Turn-off, switch tube Q 2n+1 Conduction and inductance L 2n+1 And charging the first group of batteries to finish energy transfer.
Specific experimental structure of circuit (as shown in figure 5)
The experimental circuit diagram takes n=2, and then there are four batteries in total. Battery cell B 1 -B 4 Any battery cell and corresponding voltage measuring element V 1 -V 4 Parallel connection, the fuzzy logic controllers are respectively connected through pins S 1 -S 6 And switch tube Q 1 -Q 6 And the switching frequency of the switching tube is controlled by the output current.
Circuit equalization is divided into intra-and inter-group:
the in-group equalization circuit structure is as follows: battery cell B 1 Positive electrode connection switch tube Q 1 D pole of (B), switch tube Q 1 S pole of (C) is connected with inductance element L 1 And diode D 1 Is the cathode of diode D 1 Positive electrode of (a) and cell B 4 Is connected with the negative electrode of the inductance element L 2 One end of (a) is connected with the inductance element L 1 Is arranged at the other end of the tube; battery B 2 Positive electrode of L 2 One end of B 2 Is connected with Q by the negative electrode 2 S-pole diode D of (2) 2 Positive electrode connection inductance L 2 And Q and the other end of (2) 2 D pole of (2); battery B 3 Positive electrode of L 3 One end of B 3 Is connected with Q by the negative electrode 3 S-pole diode D of (2) 3 Positive electrode connection inductance L 3 And Q and the other end of (2) 3 D pole of (D), inductance L 3 Connected to the switching tube Q 2 S level of (2); battery B 4 Positive electrode of L 4 One end of B 4 Is connected with Q by the negative electrode 4 S-pole diode D of (2) 4 Positive electrode connection inductance L 4 And Q and the other end of (2) 4 D pole of (D), inductance L 4 Connected to the switching tube Q 3 Is a stage S of (2).
The inter-group equalization circuit structure is as follows: battery cell B 1 Positive electrode connection switch tube Q 5 D pole of (B), switch tube Q 5 S pole of (C) and inductance L 5 Is connected with one end of the connecting rod; battery cell B 2 Negative electrode of (2) and switch tube Q 6 S pole of (C) is connected with a switch tube Q 6 D pole of (c) is connected with inductance L 5 Is connected with one end of the connecting rod; inductance L 5 Is connected with the battery cell B at the other end 3 Positive electrode of (a) and cell B 2 Is a negative electrode of (a).
Static equilibrium experiment
In the static balancing experiment, the in-group synchronous balancing is adopted, the battery voltages are respectively 4v,3.5v,3v and 2.5v, and the in-group synchronous balancing is completed at 346s according to the simulation result (as shown in fig. 6).
Initial voltage U of four active equalization batteries start The method comprises the following steps:
U start ＝4v+3.5v+3v+2.5v＝13v
final equalizing voltage U of four active equalizing cells finish The method comprises the following steps:
U finish ＝3v+3v+3v+3v＝12v
the energy utilization of the active equalization was calculated according to the above equation to be 12v/13 v=92.31%.
Discharge equalization experiment
In the discharge balancing experiment, the same initial voltages as those of the batteries of the first group are adopted, the battery voltages are respectively 4v,3.5v,3v and 2.5v, and according to the simulation experiment result, the balancing of the inter-group double-layer inductance balancing circuit in the lithium battery group is completed at 358s, and the balancing voltage is 2.96v (shown in fig. 7).
Charge equalization experiments
In the charge equalization experiment, a battery equalization experiment for charging a battery pack is performed. According to the occurrence mechanism of thermal runaway during charging, the charging voltage and charging current of the unit cells must be controlled to control the thermal runaway, wherein the charging voltage and charging current are real-time voltages of the unit cells, and the functions and tasks of the battery balancing technology are realized through the adjustment of the voltages and the currents. When the shunt current meets the shunt requirement, the voltage and the heating value of the low-capacity battery can be effectively controlled, the requirement on the charge equalization capability of the battery pack is higher, and the absolute voltage and the relative voltage difference of each unit battery in the battery pack are closely related to the actual capacity distribution of each unit and are always in dynamic change.
In the charge equalization experiment, the same initial voltages as those of the batteries of the first group were adopted, and the voltages were 4v,3.5v,3v, and 2.5v, respectively. According to the simulation experiment result, the inter-group double-layer inductance balancing circuit in the lithium battery pack completes balancing at 343s, and the balancing voltage is 3.05v (shown in fig. 8).
Compared with the traditional single-layer lithium battery pack equalization circuit, the inter-group double-layer inductance equalization control method in the lithium battery pack can realize simultaneous voltage equalization operation in the battery pack and among the battery packs, can improve the equalization speed and the energy utilization rate of the battery pack, and reduces energy loss.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (5)
1. The method for controlling the balance of the inter-group double-layer inductance in the lithium battery pack is characterized by comprising the following specific steps:
step 1: dividing 2n battery cells into two groups, wherein n is more than 1, n is a positive integer, and collecting the voltage of the battery cells through a voltage measuring element;
step 2: calculating according to the formula (1) and the formula (2) to obtain the maximum voltage difference of the battery cells in the battery packs and the voltage difference between the two battery packs:
Δv 1 ＝v max -v min (1)
Wherein v is max V is the highest voltage value of the voltage in the battery cell min V is the lowest voltage value of the voltage in the battery cell 1 To v n Is the voltage value of the battery cell in one battery pack, v n+1 To v 2n For the voltage value of the battery cell in another battery pack, deltav 1 Is the maximum voltage difference of the battery cells in the battery pack, deltav 2 Is the voltage difference between the two battery packs;
step 3: respectively judge Deltav 1 The value of (a) and Deltav 2 If the value of (2) is larger than the threshold voltage Xv, if not, the step 2 is entered, and if yes, the step 4 is entered;
step 4: when Deltav 1 When the value of (a) is larger than Xv, the fuzzy logic controller is utilized to adjust the energy transfer path among the battery cells in the battery pack, the battery cell with the highest voltage value in the battery pack is transferred to the other battery cells, and when Deltav 2 When the value of (a) is larger than Xv, the fuzzy logic controller is utilized to regulate the space between two battery packsIs transferred from a group having a higher inter-battery voltage to a group having a lower inter-battery voltage.
2. The method for controlling balance of inter-group double-layer inductance in a lithium battery pack according to claim 1, wherein the method comprises the following steps: and step 4, the inter-group double-layer inductance equalization circuit structure in the lithium battery pack is as follows: battery cell B 1 -B 2n Are connected in series and divided into two groups, B 1 -B n For the first group, B n+1 -B 2n The number of the two groups of batteries is equal to that of the second group;
the circuit structure of the in-group equalization is as follows:
battery cell B 1 -B 2n Any battery cell B i And voltage measuring element V i In parallel, the battery cells B i Positive electrode of (c) and inductance element L i Is connected to one end of the inductance element L i The other end of (2) is connected with a switch tube Q i D pole and diode D of (2) i The diode D i Is connected with the battery cell B 1 Is a positive electrode of (a); the switch tube Q i The S pole of (C) is connected with the battery cell B i Is a negative electrode of (a); the inductance element L i One end of (a) is also connected with a switch tube Q i-1 An S pole of (2); wherein i is more than 1, i is a positive integer;
when i=2, the inductance element L 2 One end of (a) is connected with the inductance element L 1 Is arranged at the other end of the tube; the battery cell B 1 And voltage measuring element V 1 In parallel, the battery cells B 1 Positive electrode connection switch tube Q 1 D pole of said switching tube Q 1 S pole of (C) is connected with inductance element L 1 And diode D 1 Is the negative electrode of the diode D 1 Positive electrode of (a) and cell B 2n Is connected with the negative electrode of the battery;
the circuit structure of the inter-group equalization is as follows:
the battery cell B 1 Positive electrode connection switch tube Q 2n+1 D pole of said switching tube Q 2n+1 S pole of (C) and inductance L 2n+1 Is connected with one end of the connecting rod; the battery cell B n Negative electrode of (2) and switch tube Q 2n+2 S pole of the switch tube Q 2n+2 D pole of (c) is connected with inductance L 2n+1 Is connected with one end of the connecting rod; the inductance L 2n+1 Is connected with the battery cell B at the other end n+1 Positive electrode of (a) and cell B n Is a negative electrode of (a).
3. The method for controlling balance of inter-group double-layer inductance in a lithium battery pack according to claim 2, wherein the method comprises the steps of: the fuzzy logic controller input variables in step 4 include the maximum voltage difference Deltav of the battery cells in the battery pack 1 And a voltage difference Deltav between the battery packs 2 The fuzzy logic controller is used for controlling the voltage difference Deltav of the single cells in the battery pack according to the maximum voltage difference Deltav of the single cells in the battery pack 1 And a voltage difference Deltav between the battery packs 2 Obtaining the frequency of an output variable switching tube;
maximum voltage difference Deltav of battery cells in the battery pack 1 And a voltage difference Deltav between the battery packs 2 The argument D of (1) is set to 0,0.5]Describing input variables through fuzzy languages, wherein the set of the fuzzy languages is of small (small), medium (middle) and large (large) 3 grades;
the switching tube frequency domain is set to be [0,5], the output variable is described through fuzzy language, and the set of the fuzzy language is small (small), medium (middle), large (large) and ultra-large (very large) 4 grades.
4. The method for controlling balance of inter-group double-layer inductance in a lithium battery pack according to claim 3, wherein: the method for adjusting the energy transfer path between the battery cells in the battery pack by using the fuzzy logic controller in the step 4 comprises the following specific steps:
when the battery cell B 1 When the voltage is highest, and the difference of the maximum value of the battery cell voltage minus the minimum value of the battery cell voltage is more than 0.01v, the switch tube Q 1 Conduction, B 1 Energy storage inductance L 1 Charging is carried out, and after the charging is finished, the switching tube Q is turned off 1 Energy storage inductance L 1 To battery B 2 -B 2n Charging to finish energy transfer;
when in addition to B 1 Other than electricPool B i When the voltage is highest, and the difference of the maximum value of the battery cell voltage minus the minimum value of the battery cell voltage is more than 0.01v, the switch tube Q i Conduction, battery B i To energy storage inductance L i Charging is carried out, and after the charging is finished, the switching tube Q is turned off n Energy storage inductance L n To battery B 1 -B i-1 And charging to complete energy transfer.
5. The method for controlling balance of inter-group double-layer inductance in a lithium battery pack according to claim 4, wherein: the method for adjusting the energy transfer path between two battery packs by using the fuzzy logic controller in the step 4 comprises the following specific steps:
when the average voltage of the first group of cells is higher than that of the second group of cells and the difference between the average values is more than 0.01v, the switch tube Q 2n+1 Conduction, first group battery pair inductance L 2n+1 Charging is carried out, and after the charging is finished, a switch tube Q 2n+1 Turn-off, switch tube Q 2n+2 Conduction and inductance L 2n+1 Charging the second group of batteries to finish energy transfer;
when the average voltage of the second group of cells is higher than that of the first group of cells and the difference between the average values is more than 0.01v, the switch tube Q 2n+2 Conduction, second group battery pair inductance L 2n+2 Charging is carried out, and after the charging is finished, a switch tube Q 2n+2 Turn-off, switch tube Q 2n+1 Conduction and inductance L 2n+1 And charging the first group of batteries to finish energy transfer.
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