CN112865232A - Active battery pack equalization circuit and control method - Google Patents
Active battery pack equalization circuit and control method Download PDFInfo
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- CN112865232A CN112865232A CN202110048952.0A CN202110048952A CN112865232A CN 112865232 A CN112865232 A CN 112865232A CN 202110048952 A CN202110048952 A CN 202110048952A CN 112865232 A CN112865232 A CN 112865232A
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- 230000002457 bidirectional effect Effects 0.000 claims abstract description 91
- 238000012544 monitoring process Methods 0.000 claims abstract description 59
- 238000005070 sampling Methods 0.000 claims abstract description 30
- 238000007599 discharging Methods 0.000 claims abstract description 14
- 239000003990 capacitor Substances 0.000 claims description 48
- 238000012546 transfer Methods 0.000 claims description 32
- 238000012163 sequencing technique Methods 0.000 claims description 6
- 238000004146 energy storage Methods 0.000 abstract description 8
- 230000010354 integration Effects 0.000 description 8
- 238000010586 diagram Methods 0.000 description 5
- 230000009286 beneficial effect Effects 0.000 description 4
- 230000007547 defect Effects 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
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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
- H02J7/0013—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
- H02J7/0019—Circuits for equalisation of charge between batteries using switched or multiplexed charge circuits
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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
-
- 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
- H02J7/005—Detection of state of health [SOH]
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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
- H02J7/007—Regulation of charging or discharging current or voltage
- H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
- H02J7/007182—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters in response to battery voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33584—Bidirectional converters
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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
- H02J2207/00—Indexing scheme relating to details of circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J2207/20—Charging or discharging characterised by the power electronics converter
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Medical Informatics (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
Abstract
The invention discloses an active battery pack equalization circuit and a control method, the active battery pack equalization circuit comprises a voltage monitoring circuit, a current monitoring circuit, a switch array, a bidirectional DC-DC converter, an equalization bus and a control circuit, wherein a microcontroller is used for judging the charge state of each single battery in a battery pack according to sampling values of the voltage monitoring circuit and the current monitoring circuit, and a drive circuit is used for controlling the switch array to gate unbalanced batteries in the battery pack to the input end of the bidirectional DC-DC converter and controlling the bidirectional DC-DC converter to alternately work in a charging state and a discharging state so as to realize energy exchange between the unbalanced batteries and the whole battery pack. The invention obviously reduces the switch number and the energy storage elements of the whole equalizing system, and has the advantages of simple structure, flexible control, easy expansion and higher efficiency.
Description
Technical Field
The invention relates to the technical field of battery equalization, in particular to an active battery pack equalization circuit and a control method.
Background
In order to meet the voltage and power requirements of high-power applications such as electric vehicles, lithium ion batteries are generally connected in series and in parallel to form a battery pack. While the cells in a battery pack typically have performance differences and these differences can expand as the cells age. This will result in a reduction in the capacity and life of the battery pack, and even cause a fire or explosion. Therefore, the battery equalization technology is adopted to realize the equalization management of the battery pack, the existing potential of the battery is fully exerted, the service life of the battery is prolonged, and the safe and reliable work of the battery pack is guaranteed.
The traditional battery equalization method can realize equalization only by adopting a large number of switches and energy storage elements, and has the defects of low integration level, poor reliability and high cost.
Disclosure of Invention
The invention mainly aims to provide an active battery pack equalization circuit and a control method, aiming at improving the integration level and reliability of an equalization system and solving the problem of low cost, small volume and long series battery pack equalization.
In order to achieve the above object, the present invention provides an active battery pack equalization circuit, which includes a voltage monitoring circuit, a current monitoring circuit, a switch array, a bidirectional DC-DC converter, an equalization bus, and a control circuit, where the control circuit includes a microcontroller and a driving circuit connected to the microcontroller, the battery pack is connected to the microcontroller through the voltage monitoring circuit and the current monitoring circuit, the microcontroller is connected to the switch array and the bidirectional DC-DC converter through the driving circuit, a single battery in the battery pack is connected to an input end of the bidirectional DC-DC converter through the switch array, and an output end of the bidirectional DC-DC converter is connected to the entire battery pack;
the microcontroller is used for judging the charge state of each single battery in the battery pack according to the sampling values of the voltage monitoring circuit and the current monitoring circuit, and the driving circuit is used for controlling the switch array to gate the unbalanced battery in the battery pack to the input end of the bidirectional DC-DC converter and controlling the bidirectional DC-DC converter to alternately work in a charging state and a discharging state, so that energy exchange between the unbalanced battery and the whole battery pack is realized.
The further technical scheme of the invention is that the battery pack comprises n single batteries connected in series, the switch array comprises n +1 switch tubes, and the bidirectional DC-DC converter comprises six switch tubes, an inductor, a capacitor C1, a balanced bus capacitor C2 and a transformer; four switching tubes in the DC-DC converter form two bridge arms, and the capacitor C1 is connected with the inductor L1 in series, then is connected with the midpoints of the two bridge arms respectively, and then is connected with the balanced bus capacitor C2 in parallel; the other two switching tubes in the DC-DC converter and the transformer form a bidirectional flyback converter, the input end of the bidirectional flyback converter is connected with the balanced bus capacitor C2, and the output end of the bidirectional flyback converter is connected with the whole battery pack.
The further technical scheme of the invention is that the switch array can only gate one battery at the same time, and the voltage polarities of the odd-numbered single batteries and the even-numbered single batteries which are connected to the input end of the bidirectional DC-DC converter through the switch array are different.
The further technical scheme of the invention is that the bidirectional DC-DC converter can enable the balanced current to work in a continuously adjustable state.
The active battery pack equalization circuit has the beneficial effects that: according to the technical scheme, the battery pack comprises a voltage monitoring circuit, a current monitoring circuit, a switch array, a bidirectional DC-DC converter, a balance bus and a control circuit, wherein the control circuit comprises a microcontroller and a driving circuit connected with the microcontroller, the battery pack is connected to the microcontroller through the voltage monitoring circuit and the current monitoring circuit, the microcontroller is connected with the switch array and the bidirectional DC-DC converter through the driving circuit, a single battery in the battery pack is connected to the input end of the bidirectional DC-DC converter through the switch array, and the output end of the bidirectional DC-DC converter is connected with the whole battery pack; the microcontroller is used for judging the charge state of each single battery in the battery pack according to the sampling values of the voltage monitoring circuit and the current monitoring circuit, the driving circuit is used for controlling the switch array to gate the unbalanced battery in the battery pack to the input end of the bidirectional DC-DC converter and controlling the bidirectional DC-DC converter to alternately work in a charging state and a discharging state, so that energy exchange is realized between the unbalanced battery and the whole battery pack, the switch number and energy storage elements of the whole balancing system are obviously reduced, and the battery pack balancing system has the advantages of simple structure, flexible control, easiness in expansion and high efficiency; in addition, the equalizing circuit can work in a continuously adjustable state, has excellent rapid equalizing performance of a single battery, improves the integration level and reliability of an equalizing system, and solves the problem of low cost, small volume and long series battery pack equalization.
In order to achieve the above object, the present invention further provides an active battery pack equalization circuit control method, which is applied to the active battery pack equalization circuit described above, and the method includes the following steps:
the microcontroller acquires a sampling value of the voltage monitoring circuit and a sampling value of the current monitoring circuit;
calculating the SOC value of each single battery in the battery pack according to the sampling value of the voltage monitoring circuit and the sampling value of the current monitoring circuit;
acquiring a difference value between the SOC value of each single battery and the average SOC value of the battery pack according to the SOC value of each single battery;
comparing the difference value with a preset maximum equalization threshold value and a preset minimum equalization threshold value;
and when the difference value is larger than the maximum equalization threshold value or smaller than the minimum equalization threshold value, controlling the active battery pack equalization circuit to perform equalization operation on the battery pack.
A further technical solution of the present invention is that the step of controlling the active battery pack balancing circuit to perform balancing operation on the battery pack includes:
the microcontroller performs balanced sequencing on the unbalanced batteries according to the sequence of the difference values from large to small;
sequentially conducting switch tubes corresponding to all unbalanced batteries in the switch array through a driving circuit according to a balanced sequence, and sequentially gating the unbalanced batteries to the input end of the bidirectional DC-DC converter;
and acquiring a difference value between the SOC value of each single battery and the average SOC value of the battery pack according to the SOC value of each single battery, and controlling the working state of the bidirectional DC-DC converter so as to perform balancing operation on the battery pack.
According to a further technical scheme of the invention, the step of sequentially conducting the switch tubes corresponding to the unbalanced batteries in the switch array through the driving circuit according to the balanced sequence comprises the following steps:
judging whether the unbalanced battery is an odd number or an even number;
obtaining corresponding working modes according to the judgment result and the difference value, wherein the working modes comprise an odd number battery mode for balancing overvoltage, an even number battery mode for balancing overvoltage, an odd number battery mode for balancing undervoltage and an even number battery mode for balancing undervoltage;
the step of conducting the switch tubes corresponding to the unbalanced batteries in the switch array in sequence through the driving circuit according to the balanced sequence further comprises:
and sequentially conducting the switch tubes corresponding to the unbalanced batteries in the switch array through a driving circuit according to the balance sequencing and the working mode.
A further technical solution of the present invention is that the step of obtaining a difference between the SOC value of each single battery and the average SOC value of the battery pack according to the SOC value of each single battery, and controlling the operating state of the bidirectional DC-DC converter to perform the balancing operation on the battery pack includes:
when the difference value between the SOC value of the odd-numbered battery or the even-numbered battery and the average SOC value of the battery pack is larger than the maximum balance threshold value, adopting a corresponding overvoltage balancing odd-numbered battery mode or overvoltage balancing even-numbered battery mode to control the bidirectional DC-DC converter to work in a discharging state;
and when the difference value between the SOC value of the odd battery or the even battery and the average SOC value of the battery pack is smaller than the minimum equalization threshold value, controlling the bidirectional DC-DC converter to work in a charging state by adopting a corresponding odd battery mode for equalizing under voltage or an even battery mode for equalizing under voltage.
A further technical solution of the present invention is that, when the difference is greater than the maximum equalization threshold, the step of controlling the active battery pack equalization circuit to perform equalization operation on the battery pack includes:
when the difference value is larger than the maximum equalization threshold value, controlling the overvoltage battery to transfer energy to the equalization bus capacitor C2;
and controlling the equalizing bus capacitor C2 to transfer energy to the whole battery pack.
A further technical solution of the present invention is that, when the difference is smaller than the minimum equalization threshold, the step of controlling the active battery pack equalization circuit to perform equalization operation on the battery pack includes:
when the difference is smaller than the minimum equalization threshold value, controlling the whole battery pack to transfer energy to the equalization bus capacitor C2;
and controlling the equalizing bus capacitor C2 to transfer energy to the undervoltage battery.
The active battery pack equalization circuit control method has the beneficial effects that: according to the technical scheme, the microcontroller acquires the sampling value of the voltage monitoring circuit and the sampling value of the current monitoring circuit, calculates the SOC value of each single battery in the battery pack according to the sampling value of the voltage monitoring circuit and the sampling value of the current monitoring circuit, acquires the difference value between the SOC value of each single battery and the average SOC value of the battery pack according to the SOC value of each single battery, compares the difference value with a preset maximum equalization threshold value and a preset minimum equalization threshold value, and controls the active equalization circuit of the battery pack to perform equalization operation on the battery pack when the difference value is greater than the maximum equalization threshold value or less than the minimum equalization threshold value, so that the number of switches and energy storage elements of the whole equalization system are obviously reduced, and the system has the advantages of simple structure, flexibility in control, easiness in expansion and high efficiency; in addition, the equalizing circuit can work in a continuously adjustable state, has excellent rapid equalizing performance of a single battery, improves the integration level and reliability of an equalizing system, and solves the problem of low cost, small volume and long series battery pack equalization.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a system diagram of an active battery equalization circuit according to a preferred embodiment of the present invention;
FIG. 2 is an equivalent circuit diagram when the cells of odd number of overvoltage are equalized;
fig. 3 is an equivalent circuit diagram when an even number of cells of overvoltage are equalized;
FIG. 4 is an equivalent circuit diagram when undervoltage odd cells are equalized;
FIG. 5 is an equivalent circuit diagram when an even number of undervoltage batteries are equalized;
fig. 6 is a flowchart illustrating a control method for an active battery equalization circuit according to a preferred embodiment of the present invention.
The objects, features and advantages of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that, if directional indications (such as up, down, left, right, front, and back … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative positional relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.
In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and/or" appearing throughout includes three juxtapositions, exemplified by "A and/or B" including either A or B or both A and B. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
Aiming at the defects that the battery pack equalization circuit in the prior art can realize equalization only by adopting a large number of switches and energy storage elements, and has low integration level, poor reliability and high cost, the invention provides the active battery pack equalization circuit, which can obviously reduce the number of switches and energy storage elements of the whole equalization system and has the advantages of simple structure, flexible control, easy expansion and higher efficiency; in addition, the equalizing current can work in a continuously adjustable state, so that the active battery pack equalizing circuit has excellent rapid equalizing performance of single battery.
Specifically, referring to fig. 1, a preferred embodiment of the active battery pack equalization circuit of the present invention includes a voltage monitoring circuit, a current monitoring circuit, a switch array, a bidirectional DC-DC converter, an equalization bus, and a control circuit, where the control circuit includes a microcontroller and a driving circuit connected to the microcontroller, the battery pack is connected to the microcontroller through the voltage monitoring circuit and the current monitoring circuit, the microcontroller is connected to the switch array and the bidirectional DC-DC converter through the driving circuit, a single battery in the battery pack is connected to an input terminal of the bidirectional DC-DC converter through the switch array, and an output terminal of the bidirectional DC-DC converter is connected to the entire battery pack.
The microcontroller is used for judging the charge state of each single battery in the battery pack according to the sampling values of the voltage monitoring circuit and the current monitoring circuit, and the driving circuit is used for controlling the switch array to gate the unbalanced battery in the battery pack to the input end of the bidirectional DC-DC converter and controlling the bidirectional DC-DC converter to alternately work in a charging state and a discharging state, so that energy exchange between the unbalanced battery and the whole battery pack is realized.
Wherein, in one embodiment, the battery pack comprises n single batteries connected in series, the switch array comprises n +1 switch tubes, and the bidirectional DC-DC converter comprises six switch tubes, an inductor, a capacitor C1, a balanced bus capacitor C2 and a transformer; four switching tubes in the DC-DC converter form two bridge arms, and the capacitor C1 is connected with the inductor L1 in series, then is connected with the midpoints of the two bridge arms respectively, and then is connected with the balanced bus capacitor C2 in parallel; the other two switching tubes in the DC-DC converter and the transformer form a bidirectional flyback converter, the input end of the bidirectional flyback converter is connected with the balanced bus capacitor C2, and the output end of the bidirectional flyback converter is connected with the whole battery pack.
It can be understood that, in this embodiment, the switch array can only gate one battery at a time, and the polarities of the voltages of the odd-numbered single batteries and the even-numbered single batteries connected to the input end of the bidirectional DC-DC converter through the switch array are different.
The bidirectional DC-DC converter can enable the equalizing current to work in a continuously adjustable state. By adjusting the magnitude of the equalizing current, the active battery pack equalizing circuit of the embodiment has excellent rapid equalizing performance of a single battery.
The structure and operation of the active battery equalization circuit of the present invention will be further described in detail with reference to fig. 1 to 5.
The active battery pack equalization circuit comprises a voltage monitoring circuit, a battery pack, a switch array, a bidirectional DC-DC converter, an equalization bus and a control circuit. The battery pack is connected to the control circuit through the voltage and current monitoring circuit, the microcontroller in the control circuit is connected with the switch array and the bidirectional DC-DC converter through the driving circuit, a single battery in the battery pack is connected to the input end of the bidirectional DC-DC converter through the switch array, and the output end of the bidirectional DC-DC converter is connected with the whole battery pack.
As shown in FIG. 1, for a battery pack formed by connecting n batteries in series, the switch array only comprises n +1 switch tubes Sc1-Scn + 1. The bidirectional DC-DC converter comprises 6 switching tubes S1-S6, an inductor L1, two capacitors C1-C2 and a transformer Tr. The four switching tubes S1-S4 form two bridge arms, an input capacitor C1 is connected with an inductor L1 in series and then is connected with the midpoints of the two bridge arms respectively, and then the input capacitor C1 is connected with a balanced bus capacitor C2 in parallel. The switching tubes S5-S6 and the transformer Tr form a bidirectional flyback converter, the input end of the bidirectional flyback converter is connected with the balanced bus capacitor C2, and the output end of the bidirectional flyback converter is connected with the whole battery pack. As can be seen from fig. 1, the present invention significantly reduces the number of switches of the entire equalization system, has the advantages of simple structure, easy expansion, and high efficiency, and improves the integration level and reliability of the equalization system.
In the active battery pack balancing circuit, a microcontroller in a control circuit judges the state of charge (SOC) of each single battery according to sampling values of a voltage and current monitoring circuit, controls a switch array through a driving circuit to gate an unbalanced battery in the battery pack to the input end of a bidirectional DC-DC converter, and controls the bidirectional DC-DC converter to alternately work in a charging state and a discharging state through the driving circuit, so that energy exchange between the unbalanced battery and the whole battery pack is realized.
The microcontroller calculates the state of charge (SOC) of each single battery in the battery pack according to the sampling values of the voltage and the current, and sequences the balance sequence of the unbalanced batteries according to the difference value of the SOC value of each single battery and the average SOC of the battery pack. When the difference value between the SOC value of the single battery and the average SOC of the battery pack is larger than the set maximum balance threshold value, the converter works in a discharging state to release the energy in the overvoltage battery to the whole battery pack; when the difference value between the SOC value of the single battery and the average SOC of the battery pack is smaller than the set minimum equalization threshold value, the converter works in a charging state to release the energy in the whole battery pack to the undervoltage battery.
In the active battery pack equalization circuit, the switch array can only gate one battery at the same time, the voltage polarities of the odd-numbered batteries and the even-numbered batteries which are connected to the input end of the bidirectional DC-DC converter through the switch array are different, and the equivalent circuits of the unbalanced single batteries during equalization are shown in fig. 3 to fig. 6. In addition, the bidirectional DC-DC can enable the equalizing current to work in a continuously adjustable state, and the invention has excellent rapid equalizing performance of a single battery by adjusting the magnitude of the equalizing current.
The specific working process of the active battery pack equalization circuit is as follows:
(1) the microcontroller receives the sampling values of the voltage monitoring circuit and the current monitoring circuit through data communication.
(2) And the microcontroller calculates the state of charge (SOC) of each single battery in the battery pack according to the voltage and current sampling values.
(3) And the microcontroller calculates the difference between the SOC value of each single battery and the average SOC of the battery pack, and when the difference is greater than the set maximum balance threshold or less than the set minimum balance threshold, the unbalanced batteries need to be balanced, and the balance sequence of the unbalanced batteries is sorted according to the balance difference from large to small.
(4) And the microcontroller sequentially conducts the switch tubes corresponding to the unbalanced batteries in the switch array through the driving circuit according to the balance sequence determined in real time, and sequentially gates the unbalanced batteries to the input end of the bidirectional DC-DC converter. And determining the working state (charging state or discharging state) of the bidirectional DC-DC converter according to the difference value of the SOC value of the unbalanced battery and the average SOC value of the battery pack.
(5) The polarities of the voltages of the odd-numbered batteries and the even-numbered batteries connected to the input end of the bidirectional DC-DC converter through the switch array are different. And the microcontroller divides four working modes of the equalizing circuit according to the voltage polarity and the working state of the bidirectional DC-DC converter. Respectively as follows: the battery pack comprises odd batteries for balancing overvoltage, even batteries for balancing overvoltage, odd batteries for balancing undervoltage and even batteries for balancing undervoltage.
The specific operation of these four modes will be described in turn.
1. And balancing the odd batteries with overvoltage:
when the difference value between the SOC value of the odd-numbered batteries and the average SOC value of the battery pack is larger than the set maximum equalization threshold value, the bidirectional DC-DC converter works in a discharging state to release the energy in the overvoltage battery to the whole battery pack. The process of transferring energy from the overvoltage battery to the battery pack is divided into two stages, wherein the first stage is that the overvoltage battery transfers energy to the equalizing bus capacitor C2, and the second stage is that the equalizing bus capacitor C2 transfers energy to the whole battery pack.
As shown in fig. 2, in the first stage of energy transfer, the switching tubes S2 and S4 are first closed, and the overvoltage battery discharges energy to the inductor L1; next, the switching tubes S1 and S4 close and the overvoltage battery and inductor L1 discharges energy to the equalizing bus capacitor C2. In the second stage of energy transfer, the equalizing bus capacitor C2 transfers energy to the battery pack through the bidirectional flyback converter composed of the switching tubes S5, S6 and the transformer Tr, and the bidirectional flyback converter operates in the same manner for the odd-numbered and even-numbered batteries.
2. Even number of cells to equalize overvoltage:
when the difference value between the SOC value of the even number of batteries and the average SOC value of the battery pack is larger than the set maximum equalization threshold value, the bidirectional DC-DC converter works in a discharging state to release the energy in the overvoltage battery to the whole battery pack. The process of transferring energy from the overvoltage battery to the battery pack is divided into two stages, wherein the first stage is that the overvoltage battery transfers energy to the equalizing bus capacitor C2, and the second stage is that the equalizing bus capacitor C2 transfers energy to the whole battery pack.
As shown in fig. 3, in the first stage of energy transfer, the switching tubes S2 and S4 are first closed, and the overvoltage battery discharges energy to the inductor L1; next, the switching tubes S2 and S3 are closed and the overvoltage battery and inductor L1 discharges energy to the equalizing bus capacitor C2. In the second stage of energy transfer, the equalizing bus capacitor C2 transfers energy to the battery pack through the bidirectional flyback converter composed of the switching tubes S5, S6 and the transformer Tr, and the bidirectional flyback converter operates in the same manner for the odd-numbered and even-numbered batteries.
3. Balancing the odd number of batteries with undervoltage:
when the difference value between the SOC value of the odd batteries and the average SOC value of the battery pack is smaller than the set minimum equalization threshold value, the bidirectional DC-DC converter works in a charging state to release the energy in the whole battery pack to the undervoltage battery. The process of transferring energy from the battery pack to the undervoltage battery is divided into two stages, wherein the first stage is that the whole battery pack transfers energy to the balance bus capacitor C2, and the second stage is that the balance bus capacitor C2 transfers energy to the undervoltage battery.
As shown in fig. 4, in the first stage of energy transfer, the battery pack transfers energy to the balanced bus capacitor C2 through the bidirectional flyback converter formed by the switching tubes S5 and S6 and the transformer Tr, and the bidirectional flyback converter operates in the same manner for the odd-numbered and even-numbered cells. In the second stage of energy transfer, firstly, the switching tubes S1 and S4 are closed, and the balanced bus capacitor C2 releases energy to the inductor L1 and the undervoltage battery; then the switch tubes S2 and S4 are closed and the inductor L1 releases energy to the under-voltage battery.
4. Even number of cells balancing undervoltage:
when the difference value between the SOC value of the even number of batteries and the average SOC value of the battery pack is smaller than the set minimum equalization threshold value, the bidirectional DC-DC converter works in a charging state to release the energy in the whole battery pack to the undervoltage battery. The process of transferring energy from the battery pack to the undervoltage battery is divided into two stages, wherein the first stage is that the whole battery pack transfers energy to the balance bus capacitor C2, and the second stage is that the balance bus capacitor C2 transfers energy to the undervoltage battery.
As shown in fig. 5, in the first stage of energy transfer, the battery pack transfers energy to the balanced bus capacitor C2 through the bidirectional flyback converter formed by the switching tubes S5 and S6 and the transformer Tr, and the bidirectional flyback converter operates in the same manner for the odd-numbered and even-numbered cells. In the second stage of energy transfer, firstly, the switching tubes S2 and S3 are closed, and the balanced bus capacitor C2 releases energy to the inductor L1 and the undervoltage battery; then the switch tubes S2 and S4 are closed and the inductor L1 releases energy to the under-voltage battery.
The active battery pack equalization circuit has the beneficial effects that: according to the technical scheme, the battery pack comprises a voltage monitoring circuit, a current monitoring circuit, a switch array, a bidirectional DC-DC converter, a balance bus and a control circuit, wherein the control circuit comprises a microcontroller and a driving circuit connected with the microcontroller, the battery pack is connected to the microcontroller through the voltage monitoring circuit and the current monitoring circuit, the microcontroller is connected with the switch array and the bidirectional DC-DC converter through the driving circuit, a single battery in the battery pack is connected to the input end of the bidirectional DC-DC converter through the switch array, and the output end of the bidirectional DC-DC converter is connected with the whole battery pack; the microcontroller is used for judging the charge state of each single battery in the battery pack according to the sampling values of the voltage monitoring circuit and the current monitoring circuit, the driving circuit is used for controlling the switch array to gate the unbalanced battery in the battery pack to the input end of the bidirectional DC-DC converter and controlling the bidirectional DC-DC converter to alternately work in a charging state and a discharging state, so that energy exchange is realized between the unbalanced battery and the whole battery pack, the switch number and energy storage elements of the whole balancing system are obviously reduced, and the battery pack balancing system has the advantages of simple structure, flexible control, easiness in expansion and high efficiency; in addition, the equalizing circuit can work in a continuously adjustable state, has excellent rapid equalizing performance of a single battery, improves the integration level and reliability of an equalizing system, and solves the problem of low cost, small volume and long series battery pack equalization.
To achieve the above object, the present invention further provides a method for controlling an active battery pack equalization circuit, the method is applied to the active battery pack equalization circuit according to the above embodiment, as shown in fig. 6, a preferred embodiment of the method for controlling an active battery pack equalization circuit according to the present invention includes the following steps:
in step S10, the microcontroller obtains the sampling value of the voltage monitoring circuit and the sampling value of the current monitoring circuit.
And step S20, calculating the SOC value of each single battery in the battery pack according to the sampling value of the voltage monitoring circuit and the sampling value of the current monitoring circuit.
And step S30, acquiring the difference value between the SOC value of each single battery and the average SOC value of the battery pack according to the SOC value of each single battery.
And step S40, comparing the difference value with a preset maximum equalization threshold value and a preset minimum equalization threshold value.
And step S50, when the difference is greater than the maximum equalization threshold or less than the minimum equalization threshold, controlling the active battery pack equalization circuit to perform equalization operation on the battery pack.
As an embodiment, the step of controlling the active battery pack balancing circuit to perform the balancing operation on the battery pack includes the following steps:
and the microcontroller performs balanced sequencing on the unbalanced batteries according to the sequence of the difference values from large to small.
And sequentially conducting the switch tubes corresponding to the unbalanced batteries in the switch array through the driving circuit according to the balanced sequence, and sequentially gating the unbalanced batteries to the input end of the bidirectional DC-DC converter.
And acquiring a difference value between the SOC value of each single battery and the average SOC value of the battery pack according to the SOC value of each single battery, and controlling the working state of the bidirectional DC-DC converter so as to perform balancing operation on the battery pack.
Wherein, according to balanced rank order through the step preceding of the corresponding switch tube of each unbalanced battery of drive circuit conduction switch array in proper order include:
and judging whether the unbalanced battery is an odd number or an even number.
And acquiring corresponding working modes according to the judgment result and the difference value, wherein the working modes comprise an odd number battery mode for balancing overvoltage, an even number battery mode for balancing overvoltage, an odd number battery mode for balancing undervoltage and an even number battery mode for balancing undervoltage.
The step of conducting the switch tubes corresponding to the unbalanced batteries in the switch array in sequence through the driving circuit according to the balanced sequence further comprises:
and sequentially conducting the switch tubes corresponding to the unbalanced batteries in the switch array through a driving circuit according to the balance sequencing and the working mode.
The step of obtaining the difference value between the SOC value of each single battery and the average SOC value of the battery pack according to the SOC value of each single battery, controlling the working state of the bidirectional DC-DC converter and executing the balancing operation on the battery pack comprises the following steps:
and when the difference value between the SOC value of the odd-numbered battery or the even-numbered battery and the average SOC value of the battery pack is larger than the maximum equalization threshold value, controlling the bidirectional DC-DC converter to work in a discharging state by adopting a corresponding overvoltage-balanced odd-numbered battery mode or overvoltage-balanced even-numbered battery mode.
And when the difference value between the SOC value of the odd battery or the even battery and the average SOC value of the battery pack is smaller than the minimum equalization threshold value, controlling the bidirectional DC-DC converter to work in a charging state by adopting a corresponding odd battery mode for equalizing under voltage or an even battery mode for equalizing under voltage.
When the difference value is greater than the maximum equalization threshold value, the step of controlling the active battery pack equalization circuit to perform equalization operation on the battery pack comprises the following steps:
and when the difference value is larger than the maximum equalization threshold value, controlling the overvoltage battery to transfer energy to the equalization bus capacitor C2.
And controlling the equalizing bus capacitor C2 to transfer energy to the whole battery pack.
When the difference value is smaller than the minimum equalization threshold value, the step of controlling the active battery pack equalization circuit to perform equalization operation on the battery pack comprises the following steps:
and when the difference value is smaller than the minimum equalization threshold value, controlling the whole battery pack to transfer energy to the equalization bus capacitor C2.
And controlling the equalizing bus capacitor C2 to transfer energy to the undervoltage battery.
The active battery pack equalization circuit control method has the beneficial effects that: according to the technical scheme, the microcontroller acquires the sampling value of the voltage monitoring circuit and the sampling value of the current monitoring circuit, calculates the SOC value of each single battery in the battery pack according to the sampling value of the voltage monitoring circuit and the sampling value of the current monitoring circuit, acquires the difference value between the SOC value of each single battery and the average SOC value of the battery pack according to the SOC value of each single battery, compares the difference value with a preset maximum equalization threshold value and a preset minimum equalization threshold value, and controls the active equalization circuit of the battery pack to perform equalization operation on the battery pack when the difference value is greater than the maximum equalization threshold value or less than the minimum equalization threshold value, so that the number of switches and energy storage elements of the whole equalization system are obviously reduced, and the system has the advantages of simple structure, flexibility in control, easiness in expansion and high efficiency; in addition, the equalizing circuit can work in a continuously adjustable state, has excellent rapid equalizing performance of a single battery, improves the integration level and reliability of an equalizing system, and solves the problem of low cost, small volume and long series battery pack equalization.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. An active battery pack equalization circuit is characterized by comprising a voltage monitoring circuit, a current monitoring circuit, a switch array, a bidirectional DC-DC converter, an equalization bus and a control circuit, wherein the control circuit comprises a microcontroller and a driving circuit connected with the microcontroller, the battery pack is connected to the microcontroller through the voltage monitoring circuit and the current monitoring circuit, the microcontroller is connected with the switch array and the bidirectional DC-DC converter through the driving circuit, a single battery in the battery pack is connected to the input end of the bidirectional DC-DC converter through the switch array, and the output end of the bidirectional DC-DC converter is connected with the whole battery pack;
the microcontroller is used for judging the charge state of each single battery in the battery pack according to the sampling values of the voltage monitoring circuit and the current monitoring circuit, and the driving circuit is used for controlling the switch array to gate the unbalanced battery in the battery pack to the input end of the bidirectional DC-DC converter and controlling the bidirectional DC-DC converter to alternately work in a charging state and a discharging state, so that energy exchange between the unbalanced battery and the whole battery pack is realized.
2. The active battery pack equalization circuit of claim 1 wherein the battery pack comprises n series connected single cells, the switch array comprises n +1 switching tubes, the bi-directional DC-DC converter comprises six switching tubes, an inductor, a capacitor C1, an equalization bus capacitor C2, and a transformer; four switching tubes in the DC-DC converter form two bridge arms, and the capacitor C1 is connected with the inductor L1 in series, then is connected with the midpoints of the two bridge arms respectively, and then is connected with the balanced bus capacitor C2 in parallel; the other two switching tubes in the DC-DC converter and the transformer form a bidirectional flyback converter, the input end of the bidirectional flyback converter is connected with the balanced bus capacitor C2, and the output end of the bidirectional flyback converter is connected with the whole battery pack.
3. The active battery pack equalization circuit of claim 1 wherein the switch array can only gate one battery at a time, and wherein the odd and even numbered cells have different polarities of voltage connected to the input of the bi-directional DC-DC converter through the switch array.
4. The active battery pack equalization circuit of claim 1, wherein the bi-directional DC-DC converter enables equalization current operation in a continuously adjustable state.
5. An active battery equalization circuit control method, applied to the active battery equalization circuit according to any one of claims 1 to 4, the method comprising the steps of:
the microcontroller acquires a sampling value of the voltage monitoring circuit and a sampling value of the current monitoring circuit;
calculating the SOC value of each single battery in the battery pack according to the sampling value of the voltage monitoring circuit and the sampling value of the current monitoring circuit;
acquiring a difference value between the SOC value of each single battery and the average SOC value of the battery pack according to the SOC value of each single battery;
comparing the difference value with a preset maximum equalization threshold value and a preset minimum equalization threshold value;
and when the difference value is larger than the maximum equalization threshold value or smaller than the minimum equalization threshold value, controlling the active battery pack equalization circuit to perform equalization operation on the battery pack.
6. The active battery pack equalization circuit control method of claim 5, wherein the step of controlling the active battery pack equalization circuit to perform equalization operations on the battery pack is preceded by the steps of:
the microcontroller performs balanced sequencing on the unbalanced batteries according to the sequence of the difference values from large to small;
sequentially conducting switch tubes corresponding to all unbalanced batteries in the switch array through a driving circuit according to a balanced sequence, and sequentially gating the unbalanced batteries to the input end of the bidirectional DC-DC converter;
and acquiring a difference value between the SOC value of each single battery and the average SOC value of the battery pack according to the SOC value of each single battery, and controlling the working state of the bidirectional DC-DC converter so as to perform balancing operation on the battery pack.
7. The active battery pack equalization circuit control method of claim 6, wherein the step of sequentially turning on the switching tubes corresponding to the unbalanced batteries in the switch array through the driving circuit according to the equalization sequence comprises:
judging whether the unbalanced battery is an odd number or an even number;
obtaining corresponding working modes according to the judgment result and the difference value, wherein the working modes comprise an odd number battery mode for balancing overvoltage, an even number battery mode for balancing overvoltage, an odd number battery mode for balancing undervoltage and an even number battery mode for balancing undervoltage;
the step of conducting the switch tubes corresponding to the unbalanced batteries in the switch array in sequence through the driving circuit according to the balanced sequence further comprises:
and sequentially conducting the switch tubes corresponding to the unbalanced batteries in the switch array through a driving circuit according to the balance sequencing and the working mode.
8. The active battery pack equalization circuit control method according to claim 7, wherein the step of obtaining a difference between the SOC value of each single battery and the average SOC value of the battery pack according to the SOC value of each single battery, and controlling the operating state of the bidirectional DC-DC converter to perform equalization operation on the battery pack comprises:
when the difference value between the SOC value of the odd-numbered battery or the even-numbered battery and the average SOC value of the battery pack is larger than the maximum balance threshold value, adopting a corresponding overvoltage balancing odd-numbered battery mode or overvoltage balancing even-numbered battery mode to control the bidirectional DC-DC converter to work in a discharging state;
and when the difference value between the SOC value of the odd battery or the even battery and the average SOC value of the battery pack is smaller than the minimum equalization threshold value, controlling the bidirectional DC-DC converter to work in a charging state by adopting a corresponding odd battery mode for equalizing under voltage or an even battery mode for equalizing under voltage.
9. The active battery pack equalization circuit control method of claim 5, wherein the step of controlling the active battery pack equalization circuit to perform equalization operations on the battery pack when the difference is greater than the maximum equalization threshold comprises:
when the difference value is larger than the maximum equalization threshold value, controlling the overvoltage battery to transfer energy to the equalization bus capacitor C2;
and controlling the equalizing bus capacitor C2 to transfer energy to the whole battery pack.
10. The active battery pack equalization circuit control method of claim 5, wherein the step of controlling the active battery pack equalization circuit to perform equalization operations on the battery pack when the difference is less than the minimum equalization threshold value comprises:
when the difference is smaller than the minimum equalization threshold value, controlling the whole battery pack to transfer energy to the equalization bus capacitor C2;
and controlling the equalizing bus capacitor C2 to transfer energy to the undervoltage battery.
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