CN116154924A - Active equalization system and method for lithium battery based on double-layer topology - Google Patents
Active equalization system and method for lithium battery based on double-layer topology Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/44—Methods for charging or discharging
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
- B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
- B60L58/18—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries of two or more battery modules
- B60L58/22—Balancing the charge of battery modules
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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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Abstract
The invention relates to a lithium battery active equalization system and method based on double-layer topology, which are applied to at least two battery packs, wherein each battery pack comprises two battery cells, the equalization system comprises at least two bottom equalization circuits and a top equalization circuit, the at least two bottom equalization circuits are connected with the at least two battery packs in a one-to-one correspondence manner, and the bottom equalization circuits are used for realizing equalization of the two battery cells in the battery packs; the top-layer equalization circuit is connected with at least two bottom-layer equalization circuits, and the top-layer equalization circuit is used for realizing inter-group equalization of at least two battery packs. The invention realizes the rapid and efficient equalization in the battery packs based on the double-layer topological structure, and the rapid and efficient equalization among any battery packs improves the equalization rate when the inconsistency of the battery packs is lower; and the equalization control method in the first group and the second group avoids repeated equalization, improves the equalization speed, and is superior to the traditional equalization mode in the aspects of equalization speed, equalization efficiency and equalization consistency.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a lithium battery active equalization system and method based on double-layer topology.
Background
The lithium battery has wide application in the fields of electric automobiles and the like due to the excellent characteristics of strong charge holding capacity, long recycling service life, small pollution and the like. The power battery pack of the electric automobile is formed by connecting a large number of lithium battery cells in series, and small differences in the production process or other factors easily cause inconsistency among the battery cells, and the different battery cells can generate problems of overcharge, overdischarge and the like in the charge and discharge process, so that the performance and the safety of the battery pack are seriously influenced, and the power battery pack has important significance in researching an equalization system among the lithium battery cells.
At present, the main equalization modes are divided into passive equalization and active equalization, the passive equalization is also called energy consumption type equalization, the working principle is mainly to utilize a resistance element to consume energy, a single body with high single body voltage in a lithium battery pack is connected with a resistor through a switch, and the switch is controlled to consume and discharge redundant energy, so that the equalization of the lithium battery is achieved, and the passive equalization is low in efficiency and has a certain danger. Active equalization is also called non-energy consumption equalization, and the main principle is that energy in a battery pack is transferred from a monomer with high energy to a monomer with low energy by using an energy storage element such as an inductor, a capacitor and the like, so that the equalization is high in efficiency and low in energy loss.
However, the existing active equalization system often has difficulty in achieving the effects of expansibility, equalization speed and equalization efficiency. For example, in the distributed capacitor topology structure shown in fig. 1, the capacitor is used as an intermediate carrier for energy transfer, and the opening and closing of the bidirectional switch are controlled between adjacent battery cells, so that the energy of the battery with high electric quantity can be transferred into the battery with low electric quantity, and finally the energy of all the batteries is consistent. When the topological structure is used, more switches and capacitors are needed when the number of the battery monomers is more, and each time, two adjacent battery monomers are balanced, so that the balancing time is long and the balancing efficiency is lower. For example, the centralized switched capacitor topology shown in fig. 2 uses only a single equalizing capacitor, and has a simpler circuit structure and lower hardware cost. The bridging structure of multiple switches is utilized, so that the one-time energy transfer of any two monomers is realized, the loss in the balancing process is less, and the balancing efficiency is higher. However, due to the centralized structure limitation, the system can only balance a single cell at a time, and when the inconsistency between batteries is smaller, the balancing speed becomes slower and the expandability is poorer due to the use of the capacitor as the balancing device. For example, the double-layer capacitor topology shown in fig. 3, which adds a layer of capacitor above a typical single-layer capacitor balancing topology, can realize that multiple batteries charge and discharge the capacitor at the same time. The equalization has a faster equalization speed than a typical single layer capacitance equalization topology. Theoretically, the equalization time can be shortened by one fourth by adding a layer of switch capacitor, but the problems are that the volume of the equalizer is increased and the cost is increased, and the equalization speed is reduced when the number of the batteries is large.
Accordingly, there is a strong need to provide an innovative active equalization system for lithium batteries based on a double-layer topology to overcome the above-mentioned technical drawbacks of the prior art.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to overcome the technical defects in the prior art, and a lithium battery active equalization system and method based on double-layer topology are provided, which are superior to the traditional equalization in equalization speed, equalization efficiency and equalization consistency.
In order to solve the technical problems, the invention provides a lithium battery active equalization system based on double-layer topology, which is applied to at least two battery packs, wherein each battery pack comprises two battery monomers, and the lithium battery active equalization system comprises:
the bottom equalization circuits are connected with at least two battery packs in a one-to-one correspondence manner and are used for realizing equalization of two battery monomers in the battery packs;
the top-layer equalization circuit is connected with at least two bottom-layer equalization circuits, and the top-layer equalization circuit is used for realizing inter-group equalization of at least two battery packs.
In one embodiment of the present invention, each of the bottom equalization circuits includes a first switching tube and a first inductor, a drain electrode of the first switching tube is connected to a positive electrode of a battery cell in the battery pack, a source electrode of the first switching tube is connected to the first inductor, the first inductor is connected to a negative electrode of the battery cell, and when the first switching tube is turned on, electric energy of the battery cell is transferred to the first inductor through the first switching tube.
In one embodiment of the present invention, each of the bottom equalization circuits includes a first diode connected in parallel with the first switching tube, wherein an anode of the first diode is connected to a source of the first switching tube, and a cathode of the first diode is connected to a drain of the first switching tube.
In one embodiment of the present invention, each of the bottom equalization circuits further includes a second switching tube, a drain electrode of the second switching tube is connected to the first inductor, the first inductor is connected to an anode of another battery cell in the battery pack, and a source electrode of the second switching tube is connected to a cathode of the battery cell.
In one embodiment of the present invention, each of the bottom equalization circuits further includes a second diode connected in parallel with the second switching tube, wherein an anode of the second diode is connected to a source of the second switching tube, and a cathode of the second diode is connected to a drain of the second switching tube.
In one embodiment of the invention, the on and off of the first and second switching tubes are controlled by PWM techniques.
In one embodiment of the invention, the top-layer equalization circuit comprises a switch array, a second inductor, a first power tube and a super capacitor, wherein the super capacitor is connected with the first power tube, the drain electrode of the first power tube is connected with the second inductor, the second inductor is connected with the positive electrode of the battery pack through the switch array, and the source electrode of the first power tube is connected with the negative electrode of the battery pack through the switch array.
In one embodiment of the present invention, the top-level equalization circuit further includes a third diode, the first power tube is connected in parallel with the third diode, an anode of the third diode is connected to a source of the first power tube, and a cathode of the third diode is connected to a drain of the first power tube.
In an embodiment of the present invention, the top-layer equalization circuit further includes a second power tube and a fourth diode, a drain electrode of the second power tube is connected to the super capacitor, a source electrode of the second power tube is connected to the second inductor, the fourth diode is connected in parallel to the second power tube, wherein an anode of the fourth diode is connected to the source electrode of the second power tube, and a cathode of the fourth diode is connected to the drain electrode of the second power tube.
In addition, the invention also provides a lithium battery active equalization method based on double-layer topology, which is realized based on the lithium battery active equalization system based on double-layer topology, and comprises the following steps:
acquiring a voltage value of each battery cell, and calculating an average voltage value of the battery pack according to the voltage value of each battery cell;
calculating a difference value between the maximum voltage value and the minimum voltage value based on the average voltage value of the battery pack;
judging whether the difference value is larger than a set top-layer inter-group equalization threshold value, if so, equalizing the battery group corresponding to the maximum voltage value and the battery group corresponding to the minimum voltage value; if not, entering the bottom layer group for equalization;
judging whether the difference value is smaller than or equal to a set top-layer inter-group balancing threshold value in real time in the inter-group balancing process, and if so, completing the top-layer inter-group balancing; if not, returning to the step of inter-group equalization;
after the balancing of the top layer is completed, solving to obtain the voltage difference of two battery monomers in the battery pack;
judging whether the voltage difference is larger than a set in-group equalization threshold value of the bottom layer, and if so, equalizing two battery monomers in the battery pack; if not, ending;
judging whether the voltage difference is smaller than or equal to a set in-group equalization threshold value of the bottom layer in real time in the in-group equalization process, and if so, completing in-group equalization of the bottom layer; if not, returning to the step of judging the voltage difference.
Compared with the prior art, the technical scheme of the invention has the following advantages:
according to the lithium battery active equalization system and method based on the double-layer topology, rapid and efficient equalization in battery packs is realized based on the double-layer topology structure, rapid and efficient equalization among any battery packs is realized, and the equalization rate when the inconsistency of the battery packs is low is improved; and the equalization control method in the first group and the second group avoids repeated equalization, improves the equalization speed, and is superior to the traditional equalization in the aspects of equalization speed, equalization efficiency and equalization consistency.
Drawings
In order that the invention may be more readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings.
Fig. 1 is a prior art distributed capacitance topology diagram.
Fig. 2 is a prior art topology of a centralized switched capacitor.
Fig. 3 is a prior art double layer capacitive topology.
Fig. 4 is a frame diagram of a lithium battery active equalization system based on a double-layer topology according to an embodiment of the present invention.
Fig. 5 is a topology structure diagram of a lithium battery active equalization system based on a double-layer topology according to an embodiment of the present invention.
Fig. 6 is a topology structure diagram of a bottom equalization circuit according to an embodiment of the present invention.
Fig. 7 is a topology structure diagram of a top-level equalization circuit according to an embodiment of the present invention.
Fig. 8 is an equivalent circuit diagram of the top-layer equalization circuit according to the embodiment of the present invention when the battery cell is connected to the supercapacitor through the switch.
Fig. 9 is a graph of DCM inductor current variation.
Fig. 10 is a graph of the conventional equalization of the voltage variation of each cell.
Fig. 11 is a diagram showing voltage changes of each battery balanced by a double-layer topology according to an embodiment of the present invention.
Fig. 12 is a flowchart of a lithium battery active equalization method based on a double-layer topology according to an embodiment of the present invention.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the invention and practice it.
Referring to fig. 4, an embodiment of the present invention provides a lithium battery active equalization system based on a double-layer topology, which is applied to at least two battery packs, wherein each battery pack includes two battery cells, the lithium battery active equalization system includes at least two bottom equalization circuits and a top equalization circuit, the at least two bottom equalization circuits are connected with the at least two battery packs in a one-to-one correspondence manner, and the bottom equalization circuits are used for equalizing the two battery cells in the battery packs; the top-layer equalization circuit is connected with at least two bottom-layer equalization circuits, and the top-layer equalization circuit is used for realizing inter-group equalization of at least two battery packs.
The lithium battery active equalization system based on the double-layer topology realizes rapid and efficient equalization in battery packs based on the double-layer topology structure, and rapid and efficient equalization among any battery packs is realized, so that the equalization rate of the battery packs when the inconsistency is lower is improved, and the equalization speed, the equalization efficiency and the equalization consistency are superior to those of the traditional equalization.
The overall topology of the lithium battery active equalization system based on the double-layer topology is shown in fig. 5, bidirectional Buck-Boost circuits are used for equalization in groups, and equalization is performed among groups through an improved centralized capacitance topology. The topology combines the advantages of two equalization circuits, the bottom layer takes two batteries as a group, the efficiency and the speed advantage of the Buck-Boost circuit are fully exerted, the top layer topology can realize the energy efficient exchange among any battery monomers, the number of battery packs required to be equalized on the top layer is effectively reduced by the layered structure, and the equalization rate is improved. The switch array greatly improves the expandability of the circuit and has more practical value.
The bottom equalization circuit adopts a bidirectional Buck-Boost topology, the topology of the bottom equalization circuit is shown in fig. 6, the bottom equalization circuit comprises a first switch tube Q1, a first inductor L1, a first diode D1, a second switch tube Q2 and a second diode D2, the drain electrode of the first switch tube Q1 is connected with the positive electrode of a battery cell B1 in a battery pack, the source electrode of the first switch tube Q1 is connected with the first inductor L1, the first inductor L1 is connected with the negative electrode of the battery cell B1, and when the first switch tube Q1 is conducted, the electric energy of the battery cell B1 is transferred into the first inductor L1 through the first switch tube Q1; the first diode D1 is connected in parallel with the first switching tube Q1, wherein an anode of the first diode D1 is connected with a source electrode of the first switching tube Q1, and a cathode of the first diode D1 is connected with a drain electrode of the first switching tube Q1; the drain electrode of the second switching tube Q2 is connected with the first inductor L1, the first inductor L1 is connected with the positive electrode of the other battery cell B2 in the battery pack, and the source electrode of the second switching tube Q2 is connected with the negative electrode of the battery cell B2; the second diode D2 is connected in parallel with the second switching tube Q2, where an anode of the second diode D2 is connected to a source of the second switching tube Q2, and a cathode of the second diode D2 is connected to a drain of the second switching tube Q2. The bottom equalization circuit mainly comprises an N-type MOS tube, a power inductor, a diode and two battery monomers, when the inconsistency of the two battery monomers in the battery pack is large, the N-type MOS tube is controlled to be conducted and closed through PWM signals, a charge-discharge loop based on the power inductor is formed, equalization between the two battery monomers is realized, and the topology is high in speed, high in efficiency and simpler in control when a small number of batteries are equalized.
The equalization principle of the bottom equalization circuit is as follows, and when the voltage of B1 is greater than the voltage of B2 and exceeds the equalization threshold, the PWM signals control Q1 and Q2 to be always turned off. When Q1 is on, a series loop B1-Q1-L1 is formed, B1 charges L1 through Q1, and B1 energy is reduced. When Q1 is turned off, the current in L1 does not generate abrupt change, a series loop B2-D2-L1 is formed, L1 charges B2 through D2, and energy transfer between adjacent battery monomers is realized. When the voltage of B2 is greater than the voltage of B1, the equalization process is similar. And when the voltage difference between the B1 and the B2 is smaller than the threshold value, the Q1 and the Q1 are simultaneously turned off, and the equalization is completed.
Therefore, the bidirectional Buck-Boost equalizing circuit is simple in structure and control, and has high efficiency and speed in the process of equalizing the two battery monomers. However, when the number of the battery cells connected in series is too large, since energy cannot be transmitted across the batteries, two battery cells far away from each other in an equalization manner need to pass through each battery cell in the middle, the equalization path is longer, and the transmission efficiency and the transmission rate are greatly reduced. Therefore, the bottom equalization circuit of the embodiment uses two battery monomers as a group, and fully plays the advantages of the bidirectional Buck-Boost equalization circuit.
The topology structure of the top-layer equalization circuit is shown in fig. 7, the top-layer equalization circuit includes switch arrays S1 and S2, a second inductor L0, a first power tube M1, a super capacitor CF, a third diode MD1, a second power tube M2 and a fourth diode MD2, the super capacitor CF is connected to the first power tube M1, a drain electrode of the first power tube M1 is connected to the second inductor L0, the second inductor L0 is connected to a positive electrode of the battery pack through the switch array S1, and a source electrode of the first power tube M1 is connected to a negative electrode of the battery pack through the switch array S2; the first power tube M1 is connected with the third diode MD1 in parallel, the positive electrode of the third diode MD1 is connected with the source electrode of the first power tube M1, and the negative electrode of the third diode MD1 is connected with the drain electrode of the first power tube M1; the drain electrode of the second power tube M2 is connected with the super capacitor CF, the source electrode of the second power tube M2 is connected with the second inductor L0, the fourth diode MD2 is connected with the second power tube M2 in parallel, the positive electrode of the fourth diode MD2 is connected with the source electrode of the second power tube M2, and the negative electrode of the fourth diode MD2 is connected with the drain electrode of the second power tube M2. The top-layer equalization circuit consists of a battery pack, a switch array, a bidirectional Buck-Boost converter and a super capacitor. The super capacitor is a novel energy storage element, has higher charge and discharge rate and high energy conversion efficiency, and can effectively reduce energy loss in the equalization process. When the single voltage maximum value and the single voltage minimum value in the battery pack are detected, the super capacitor is connected with the super capacitor by controlling the switch array, so that energy transfer is realized.
The circuit of the battery cell and the super capacitor CF can be equivalently shown in fig. 8 when the battery cell is connected with the super capacitor CF through a switch. If the voltage of b1 is the highest value, the PWM signal is used for controlling the on-off of M2, and M1 is continuously turned off. When M2 is conducted, b1-L0-M2 form a loop, b1 discharges, and the inductor converts electric energy into magnetic energy. When M2 is turned off, b1-L0-MD 1-CF forms a loop, the inductor and the battery charge the super capacitor CF at the same time, and the circuit works in Boost mode. When the difference between the voltage value b1 and the average voltage value is detected to be smaller than the threshold value, M2 and M1 are simultaneously turned off. If the voltage of b1 is the minimum value, M2 is continuously turned off in the same way, M1 is controlled by PWM signals, the circuit works in a Buck mode, and the super capacitor CF charges a battery to realize energy transfer. The top-layer equalization circuit adopts an improved centralized capacitance topological structure, so that high-efficiency energy exchange between any two battery monomers can be realized, and the addition of the bidirectional Buck-Boost converter improves the equalization rate when the inconsistency of the battery monomers is smaller. .
The working principle of the equalization circuit can be seen that the core of the bottom equalization circuit and the core of the top equalization circuit are both bidirectional Buck-Boost circuits, so that the determination of relevant parameters of the circuits is also particularly important. The Buck-Boost circuit uses the power inductor as an energy transfer carrier, so that the selection of the working mode of the power inductor has important significance. The inductor is selected to operate in Discontinuous Conduction Mode (DCM) in consideration of the problems of inductor magnetic saturation and control difficulty, namely, in a period of inductor current change, the current gradually increases from zero to peak value at the beginning of the period and gradually decreases to zero value before the period ends, and the inductor current change curve is shown in fig. 9.
Analyzing the current change period of one inductor of the bottom equalization circuit, and listing the formula (1) according to the relation of voltage in the process of charging the inductor by the battery cell B1 and converting electric energy into magnetic energy:
wherein, the liquid crystal display device comprises a liquid crystal display device,
for battery cell->
Voltage value of>
For the current through the inductance L1, +.>
For the equivalent internal resistance in the series circuit, the value is generally very small and can be ignored, L is the inductance value of the inductor L1, D is the duty ratio of the control signals of the MOS transistors Q1 and Q2, and T is the period of the control signals of the MOS transistors Q1 and Q2.
In the process of charging the battery cell B2 by the inductor and converting the magnetic energy into electric energy, the formula (2) can be listed according to the voltage relation:
wherein, the liquid crystal display device comprises a liquid crystal display device,
for the current value passing through the inductor L1, L is the inductance value of the inductor L1, +.>
For the equivalent internal resistance in the series circuit, the value is usually very small, negligible, +.>
For the conduction voltage drop of the freewheeling diodes D1 and D2, V B2 Is battery cell B 2 D is the duty ratio of the control signals of the MOS transistors Q1 and Q2, T is the period of the control signals of the MOS transistors Q1 and Q2, < >>
For the inductance current value->
Time of 0.
From the formulas (1) and (2), the inductor current at each time period can be deduced
The value is shown as formula (3)>
Wherein, the liquid crystal display device comprises a liquid crystal display device,
for the value of the current through the inductance L1, < >>
For the conduction voltage drop of the freewheeling diodes D1 and D2, V B1 Is battery cell B 1 Voltage value of V B2 Is battery cell B 2 D is the duty ratio of the control signals of the MOS transistors Q1 and Q2, T is the period of the control signals of the MOS transistors Q1 and Q2, < >>
For the inductance current value->
Time of 0. As can be deduced from equation (3), the peak inductor current is:
wherein i is peak For current passing through inductance
Peak value of V B1 Is battery cell B 1 L is the inductance value of the inductor L1, D is the duty ratio of the control signals of the MOS transistors Q1 and Q2, and T is the period of the control signals of the MOS transistors Q1 and Q2. From the following componentsWhen the inductor needs to operate in the intermittent conduction mode, the PWM signal for controlling the switch needs to be such that the inductor current is less than 0 when t=t, as shown in equation (5):
wherein, the liquid crystal display device comprises a liquid crystal display device,
for the value of the current through the inductance L1, < >>
For the conduction voltage drop of the freewheeling diodes D1 and D2, V B1 Is battery cell B 1 Voltage value of V B2 Is battery cell B 2 D is the duty ratio of the control signals of the MOS transistors Q1 and Q2, and T is the period of the control signals of the MOS transistors Q1 and Q2. It can be deduced that the duty cycle needs to satisfy equation (6):
wherein, the liquid crystal display device comprises a liquid crystal display device,
for the conduction voltage drop of the freewheeling diodes D1 and D2, V B1 Is battery cell B 1 Voltage value of V B2 Is battery cell B 2 D is the duty ratio of the control signals of the MOS transistors Q1 and Q2.
In order to test the equalization effect and feasibility of the double-layer equalization circuit, the invention builds a six-battery equalization model in Matlab/Simulink, and because the topology structure is simpler and the voltage value is adopted as an equalization variable, a capacitor is connected in series with a small resistor to be used as a lithium battery model. Six battery initial voltage values are set to 3.8V, 3.0V, 3.6V, 0.9V, 3.5V and 2.1V, inter-group equalization threshold
Set to 6mV, equalization threshold in group +.>
Set to 2mV. The voltage change curves of the traditional Buck-Boost topology simulation and the simulation of the double-layer topology structure are respectively shown in fig. 10 and 11. From the graph, the equalizing speed of the double-layer topological structure used by the invention is obviously faster than that of the traditional single-layer Buck-Boost equalizing circuit, and the equalizing speed is about 46 percent faster. The cell voltage values before and after equalization are listed in table 1.
Table 1 voltage values of each battery before and after equalization
Post-equalization variance using conventional equalization schemes
The variance after double-layer topology equalization is +.>
It can be seen that the consistency is higher after balancing using a double layer balancing topology. The voltage value after double-layer equalization is higher than the voltage value after traditional equalization, so that the traditional efficiency is higher. In summary, the double-layer topology equalization proposed by the present invention has advantages in all aspects.
The embodiment of the invention discloses a lithium battery active equalization method based on double-layer topology, and the lithium battery active equalization method based on double-layer topology and the lithium battery active equalization system based on double-layer topology described below can be referred to correspondingly.
Referring to fig. 12, the present invention further provides a lithium battery active equalization method based on double-layer topology, which includes:
step one: acquiring a voltage value of each battery cell, and calculating an average voltage value of the battery pack according to the voltage value of each battery cell;
step two: based on average voltage value of battery pack, voltage maximum value Vmax and voltage minimum value Vmin are calculated, and difference value between voltage maximum value Vmax and voltage minimum value Vmin is calculated
；
Step three: judging the difference value
Whether or not it is greater than the set inter-group equalization threshold of the top layer +.>
If yes, balancing the battery pack corresponding to the maximum voltage value and the battery pack corresponding to the minimum voltage value; if not, entering the bottom layer group for equalization;
step four: real-time difference determination during inter-group equalization
Whether or not is equal to or less than the set top level inter-group equalization threshold +.>
If yes, balancing among groups of the top layer; if not, returning to the step of inter-group equalization;
step five: after the balancing of the top layer is completed, solving to obtain the voltage difference of two battery monomers in the battery pack
；
Step six: judging the voltage difference
Whether or not it is greater than the set intra-group equalization threshold of the bottom layer +.>
If yes, balancing two battery monomers in the battery pack; if not, ending;
step seven: determining voltage differences in real time during intra-group equalization
Whether or not is equal to or less than the set intra-group equalization threshold +.>
If yes, the bottom layer in-group equalization is completed; if not, returning to the step of judging the voltage difference.
The lithium battery active equalization method based on double-layer topology uses an inter-group and intra-group equalization control method, avoids repeated equalization for multiple times, improves the equalization speed, and is superior to the traditional equalization in the aspects of equalization speed, equalization efficiency and equalization consistency.
The invention adopts a top-down control strategy in the groups after the groups. Since the bottom layer of one battery pack is composed of only two battery cells, the balancing of the bidirectional Buck-Boost circuit has extremely high efficiency. Therefore, the average value of the voltages of the two single batteries in the group can be approximately expressed as the voltage value of each battery after equalization, so that the equalization between groups can be carried out first, and the average value of the voltages in each group can be used as an equalization variable of the equalization between the battery groups. The equalization mode can effectively avoid the situation that the traditional equalization mode is repeated in groups before groups, and the equalization rate and the equalization efficiency are greatly improved.
The active equalization method for the lithium battery based on the double-layer topology is realized based on the active equalization system for the lithium battery based on the double-layer topology, so that the specific implementation of the method can be seen from the previous example part of the active equalization system for the lithium battery based on the double-layer topology, and therefore, the specific implementation of the method can be referred to the description of the corresponding examples of the parts and is not described herein.
In addition, since the active equalization method of the lithium battery based on the double-layer topology is implemented based on the active equalization system of the lithium battery based on the double-layer topology, the actions of the active equalization method of the lithium battery based on the double-layer topology correspond to those of the active equalization system of the lithium battery based on the double-layer topology, and the active equalization method is not repeated here.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations and modifications of the present invention will be apparent to those of ordinary skill in the art in light of the foregoing description. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (10)
1. A lithium battery active equalization system based on double-layer topology is characterized in that: be applied to at least two group battery, each group battery includes two battery monomers, and lithium cell initiative balanced system includes:
the bottom equalization circuits are connected with at least two battery packs in a one-to-one correspondence manner and are used for realizing equalization of two battery monomers in the battery packs;
the top-layer equalization circuit is connected with at least two bottom-layer equalization circuits, and the top-layer equalization circuit is used for realizing inter-group equalization of at least two battery packs.
2. The lithium battery active equalization system based on double-layer topology of claim 1, wherein: each bottom equalization circuit comprises a first switching tube and a first inductor, wherein the drain electrode of the first switching tube is connected with the positive electrode of a battery monomer in the battery pack, the source electrode of the first switching tube is connected with the first inductor, the first inductor is connected with the negative electrode of the battery monomer, and when the first switching tube is conducted, electric energy of the battery monomer is transferred into the first inductor through the first switching tube.
3. The lithium battery active equalization system based on double-layer topology of claim 2, wherein: each bottom equalization circuit comprises a first diode, the first diode is connected with the first switching tube in parallel, wherein the positive electrode of the first diode is connected with the source electrode of the first switching tube, and the negative electrode of the first diode is connected with the drain electrode of the first switching tube.
4. A lithium battery active equalization system based on a double layer topology as claimed in claim 3, wherein: each bottom equalization circuit further comprises a second switching tube, the drain electrode of the second switching tube is connected with the first inductor, the first inductor is connected with the positive electrode of another battery cell in the battery pack, and the source electrode of the second switching tube is connected with the negative electrode of the battery cell.
5. The lithium battery active equalization system based on double-layer topology according to claim 4, wherein: each bottom equalization circuit further comprises a second diode, the second diode is connected with the second switching tube in parallel, the positive electrode of the second diode is connected with the source electrode of the second switching tube, and the negative electrode of the second diode is connected with the drain electrode of the second switching tube.
6. The lithium battery active equalization system based on double-layer topology according to claim 4 or 5, wherein: the on and off of the first switching tube and the second switching tube are controlled by PWM signals.
7. The lithium battery active equalization system based on double-layer topology of claim 1, wherein: the top-layer equalization circuit comprises a switch array, a second inductor, a first power tube and a super capacitor, wherein the super capacitor is connected with the first power tube, a drain electrode of the first power tube is connected with the second inductor, the second inductor is connected with a positive electrode of the battery pack through the switch array, and a source electrode of the first power tube is connected with a negative electrode of the battery pack through the switch array.
8. The lithium battery active equalization system based on double-layer topology of claim 7, wherein: the top-layer equalization circuit further comprises a third diode, the first power tube is connected with the third diode in parallel, the positive electrode of the third diode is connected with the source electrode of the first power tube, and the negative electrode of the third diode is connected with the drain electrode of the first power tube.
9. The lithium battery active equalization system based on double-layer topology of claim 8, wherein: the top-layer equalization circuit further comprises a second power tube and a fourth diode, wherein the drain electrode of the second power tube is connected with the super capacitor, the source electrode of the second power tube is connected with the second inductor, the fourth diode is connected with the second power tube in parallel, the positive electrode of the fourth diode is connected with the source electrode of the second power tube, and the negative electrode of the fourth diode is connected with the drain electrode of the second power tube.
10. A lithium battery active equalization method based on double-layer topology is characterized in that: the method based on the implementation of a lithium battery active equalization system based on a double-layer topology as claimed in any of claims 1-9, comprising:
acquiring a voltage value of each battery cell, and calculating an average voltage value of the battery pack according to the voltage value of each battery cell;
calculating a difference value between the maximum voltage value and the minimum voltage value based on the average voltage value of the battery pack;
judging whether the difference value is larger than a set top-layer inter-group equalization threshold value, if so, equalizing the battery group corresponding to the maximum voltage value and the battery group corresponding to the minimum voltage value; if not, entering the bottom layer group for equalization;
judging whether the difference value is smaller than or equal to a set top-layer inter-group balancing threshold value in real time in the inter-group balancing process, and if so, completing the top-layer inter-group balancing; if not, returning to the step of inter-group equalization;
after the balancing of the top layer is completed, solving to obtain the voltage difference of two battery monomers in the battery pack;
judging whether the voltage difference is larger than a set in-group equalization threshold value of the bottom layer, and if so, equalizing two battery monomers in the battery pack; if not, ending;
judging whether the voltage difference is smaller than or equal to a set in-group equalization threshold value of the bottom layer in real time in the in-group equalization process, and if so, completing in-group equalization of the bottom layer; if not, returning to the step of judging the voltage difference.
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