CN117040064A - Balancing method for battery energy storage - Google Patents

Balancing method for battery energy storage Download PDF

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Publication number
CN117040064A
CN117040064A CN202311026937.1A CN202311026937A CN117040064A CN 117040064 A CN117040064 A CN 117040064A CN 202311026937 A CN202311026937 A CN 202311026937A CN 117040064 A CN117040064 A CN 117040064A
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China
Prior art keywords
battery
capacity
equalization
battery cell
cell
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CN202311026937.1A
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Chinese (zh)
Inventor
赵伟
初广前
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Shandong Jiaotong University
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Shandong Jiaotong University
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Priority to CN202311026937.1A priority Critical patent/CN117040064A/en
Publication of CN117040064A publication Critical patent/CN117040064A/en
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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
    • 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
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • 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
    • H01M10/441—Methods for charging or discharging for several batteries or cells simultaneously or sequentially
    • 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
    • H02J7/0016—Circuits for equalisation of charge between batteries using shunting, discharge or bypass circuits
    • 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
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M2010/4271—Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)

Abstract

The invention provides a battery energy storage equalization method. The method comprises the following steps: at least one equalization constant current device and at least one equalization charger are arranged in each battery pack of the battery cabinet, a plurality of battery cores connected in series are arranged in one battery pack, and at least one battery core is connected to the equalization constant current device and the equalization charger; when the battery cabinet is charged, for the battery core with the capacity smaller than the set target capacity, an equalizing constant current device is used for bypassing the battery core, and discharging equalization is carried out; when discharging the battery cabinet, for the battery core with the capacity smaller than the set target capacity, an equalization charger is used to be connected in parallel with the battery core, and charge equalization is carried out. The method can achieve the use of the battery capacity of the whole battery cabinet. When the battery cabinet is charged, the capacities of all the battery packs are different but are connected in series, and the method saves a part of circuits and energy storage devices which are needed for storing electric energy for the battery packs with small capacities when the battery cabinet is charged, so that the devices are fewer, and the cost is saved.

Description

Balancing method for battery energy storage
Technical Field
The invention relates to the technical field of battery energy storage management, in particular to a battery energy storage equalization method.
Background
The battery is widely applied in the energy storage industry, and particularly the lithium battery has the advantages of high energy density, high charge and discharge speed, light weight, long service life, no environmental pollution and the like, and is increasingly applied in energy storage. However, the main problem of the lithium ion battery is that the battery has fire and explosion hazards in the overcharge and overdischarge states, so that the battery is required to be matched with a good BMS (Battery Management System ).
The battery cells used for storing energy have individual capacity differences; even if the capacities of the electric cores are generally consistent before leaving the factory, under the difference of working conditions and the potential difference of the electric cores, the problem that the capacities of the electric cores are different in a battery pack formed by a plurality of electric cores can occur after the electric cores work for a period of time; there is also a difference in capacity between battery packs between a plurality of battery packs of the same specification; the battery cell has a charge-discharge limit voltage, which results in the decrease of the system capacity. In order to maximize the energy storage capacity of the system, the corresponding battery cells need to be subjected to equalization processing.
The lithium battery energy storage industry needs proprietary BMS, and BMS can automatically improve consistency among battery monomers through an equalizing circuit and an equalizing strategy, so that output capacity of a system is improved, and economic benefit is improved.
At present, the processing procedure of the battery energy storage equalization method in the prior art comprises the following steps:
passive equalization: each cell is provided with a controllable discharge resistor in an attempt to discharge the high voltage cell to achieve uniformity of cell voltage.
Active equalization in battery packs: the method is divided into two types, wherein when the voltage of a certain battery cell in a battery pack is higher, the battery cell discharges to charge the whole battery string in the battery pack, and when the voltage of the certain battery cell in the battery pack is lower, the energy of the battery string in the battery pack is taken to charge the battery cell; alternatively, the higher voltage cells in the battery pack charge the lower voltage cells in the battery pack.
Active equalization with auxiliary power supply: when the voltage of a certain cell is lower, an external power supply charges the cell; when a certain cell is low, the cell is discharged through a resistor.
Drawbacks of the above-described prior art equalization method for battery energy storage include:
the passive equalization method pursues the consistency of the voltage of the battery core, reduces the electric energy of the battery core with high capacity through resistance discharge, wastes the electric energy and cannot improve the whole storage capacity.
The active equalization method in the battery packs ignores the difference among the battery packs, the energy storage cabinet is formed by connecting a plurality of battery packs in series, and the pack with the lowest capacity in the battery packs is a short plate of a wooden barrel of the energy storage cabinet.
The active equalization method of the auxiliary power supply is adopted, when the battery cabinet is charged, the small-capacity battery core needs to be discharged through the resistor, so that the large-capacity battery core is ensured to be charged fully, and the waste of electric energy is caused.
Disclosure of Invention
The embodiment of the invention provides a battery energy storage equalization method, which is used for effectively improving the charge and discharge capacity of a whole battery cabinet.
In order to achieve the above purpose, the present invention adopts the following technical scheme.
A method of equalizing energy stored by a battery, comprising:
at least one equalization constant current device and at least one equalization charger are arranged in each battery pack of the battery cabinet, a plurality of battery cores connected in series are arranged in one battery pack, and at least one battery core is connected to the equalization constant current device and the equalization charger;
when the battery cabinet is charged, for the battery core with the capacity smaller than the set target capacity, an equalizing constant current device is used for bypassing the battery core, and discharging equalization is carried out; when discharging the battery cabinet, for the battery core with the capacity smaller than the set target capacity, an equalization charger is used to be connected in parallel with the battery core, and charge equalization is carried out.
Preferably, at least one cell is provided with an equalizing constant current device and an equalizing charger in the battery pack, and the parallel connection of the certain cell and the equalizing constant current device or the equalizing charger is realized through the switch array.
Preferably, the equalizing constant current device is composed of an inductor, a capacitor, a switching device, a current sensor, an operational amplifier circuit and a logic circuit, wherein the switching device comprises K1, K2, K3 and K4;
in the initial stage, K1 and K2 are closed, the current passing through the inductor is changed from small to large and then from large to small, when the current approaches zero, the output of the D trigger is reversed through the operational amplifier, the comparator and the D trigger, so that K1, K2 are opened, K3 and K4 are closed, the current passing through the sensor is changed from small to large and then from large to small, when the current approaches zero, the control circuit enables K3 and K4 to be opened, K1 and K2 are connected, and the cycle is repeated in this way, and before the other battery is replaced after the connected battery is disconnected, an externally controlled discharging circuit is adopted for discharging for a period of time so as to realize that the voltage on the capacitor is smaller than the voltage of the battery.
Preferably, when the battery cabinet is charged, for the battery cells with the capacity smaller than the set target capacity, the equalizing constant current device is used for bypassing the battery cells, and discharging equalization is performed, including:
collecting the voltage value and the current value of each battery cell in real time when the battery cabinet is charged and discharged each time, calculating the capacity of the battery cell when the voltage of the battery cell reaches a limit value, and calculating the charge balance time or the discharge balance time required by the battery cell according to the capacity of the battery cell and the target capacity of the battery cell when the battery cabinet is charged and discharged next time; cell capacity (Ah) =battery current (a) x time of use;
when the battery cabinet is charged, the capacity of a certain battery cell is set to be smaller than the set target capacity, an equalizing constant current device is bypassed for the battery cell, a part Ibc of the charging current Ic from top to bottom passes through the equalizing constant current bypass, and the charging current of the battery cell is reduced to be Isc, isc=ic-Ibc.
Preferably, when discharging the battery cabinet, for the battery cell with the capacity smaller than the set target capacity, an equalizing charger is used in parallel with the battery cell, and charge equalization is performed, including:
collecting the voltage value and the current value of each battery cell in real time when the battery cabinet is charged and discharged each time, calculating the capacity of the battery cell according to the previous data, calculating the target capacity of the battery cell according to the charging and discharging current, and calculating the charge balance time or the discharge balance time required by the battery cell according to the capacity of the battery cell and the target capacity of the battery cell;
when the battery cabinet is discharged, the capacity of a certain battery cell is set to be smaller than the set target capacity, an equalization charger is connected to the battery cell in parallel, a part Ibd of the discharging current Id to the lower side is provided by the equalization charger, and the discharging current of the battery cell is reduced to be Isd, and isd=Id-Ibd.
Preferably, the method further comprises:
the switch is arranged at two ends of the capacitor, the positive and negative connection of the capacitor is controlled, when the current is detected to be reduced from large to small and approaches zero, the positive and negative connection of the capacitor is reversed, and under the condition that a plurality of electric cores share one balanced constant current device, the balanced constant current device is disconnected from one electric core, then the capacitor is discharged in the forward direction, and when the capacitor is charged in the reverse direction, the capacitor is not discharged.
Preferably, the method further comprises: and according to the total cell capacity of the battery cabinet, the control system makes a target capacity according to an equalization strategy, and the cells with the capacity lower than the target capacity are subjected to capacity supplementation by using the constant current device and the charger.
The technical scheme provided by the embodiment of the invention can show that the battery energy storage equalization method can reduce the charging current of a single battery core according to the capacity of the individual battery core when the battery string is charged; during discharging, an external power supply provides additional discharging current for the small-capacity battery cell.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a block diagram of a battery pack according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a working process of an equalizing constant current device according to an embodiment of the present invention;
fig. 3 is a schematic diagram of a working process of an equalizing charger according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a parallel connection between a certain cell and an equalization galvanostat or an equalization charger through a switch array according to an embodiment of the present invention;
fig. 5 is a schematic diagram of an equalizing constant current device and an equalizing charger for each cell according to an embodiment of the present invention;
fig. 6 is a schematic diagram of a parallel connection between a certain cell and an equalization galvanostat or an equalization charger through a bus switch array according to an embodiment of the present invention;
fig. 7 is a schematic flow chart of an equalization strategy according to an embodiment of the present invention;
fig. 8 is a schematic diagram of an implementation principle of an equalization galvanostat according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of an example implementation of a specific device for equalizing a constant current transformer according to an embodiment of the present invention;
fig. 10 is a schematic diagram of a simulation result of current balancing of a constant current device according to an embodiment of the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only for explaining the present invention and are not to be construed as limiting the present invention.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless expressly stated otherwise, as understood by those skilled in the art. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or coupled. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
For the purpose of facilitating an understanding of the embodiments of the invention, reference will now be made to the drawings of several specific embodiments illustrated in the drawings and in no way should be taken to limit the embodiments of the invention.
The invention provides a battery energy storage balancing method for an energy storage system based on a balancing constant current device and a balancing charger, which achieves the aims of not wasting electric energy and maximizing the capacity of a battery cabinet.
Fig. 1 is a block diagram of a battery pack according to an embodiment of the present invention, and as shown in fig. 1, at least one equalization constant current device and at least one equalization charger are disposed in each battery pack of a battery cabinet. A plurality of cells connected in series are arranged in one battery pack, and at least one cell is connected to the equalization constant current device and the equalization charger. When the battery cabinet is charged, for a battery core with small capacity, an equalizing constant current device is used for bypassing the battery core so as to reduce the charging current of the battery core; when discharging the battery cabinet, for the small-capacity battery cell, an equalizing charger is used in parallel connection with the battery cell so as to reduce the discharge current of the battery cell. Thereby achieving the maximum energy storage capacity of the whole battery cabinet.
Fig. 2 is a schematic diagram of a working process of an equalizing constant current device according to an embodiment of the present invention, as shown in fig. 2, if a certain cell capacity is relatively small during charging of a battery cabinet, an equalizing constant current device is bypassed to the cell, so that a part Ibc of charging current Ic from top to bottom passes through the equalizing constant current bypass, and thus the charging current of the cell is reduced to Isc, isc=ic-Ibc, so that the charging current of the whole battery string is not reduced, and the battery string is not fully charged in advance due to the small cell capacity.
Fig. 3 is a schematic diagram of an operation process of an equalizing charger according to an embodiment of the present invention, as shown in fig. 3, when a battery cabinet discharges, if a certain battery cell has a relatively small capacity, an equalizing charger is connected in parallel to the battery cell, so that a part Ibd of a discharge current Id going up to the bottom is provided by the equalizing charger, and thus the discharge current of the battery cell is reduced to Isd, isd=id-Ibd, so that the discharge current of the whole battery string is not reduced, and the battery cell is not discharged to the limit in advance due to the small capacity of the battery cell.
As shown in fig. 4, a certain cell may be connected in parallel with an equalization galvanostat or an equalization charger in the battery pack through a switch array. As shown in fig. 5, each cell may also be provided with an equalization galvanostat and an equalization charger, and the galvanostat or equalization galvanostat may be turned on as necessary. As shown in fig. 6, a certain cell may be connected in parallel with an equalization galvanostat or an equalization charger in a battery pack through a bus type switch array.
The equalization strategy flow of the equalization method for battery energy storage provided by the embodiment of the invention is shown in fig. 7, the voltage value and the current value of each battery cell are collected in real time when the battery cabinet is charged and discharged each time, and the capacity of a certain battery cell is calculated according to the previous data. As the basis for the next equalization. And according to the total cell capacity of the battery cabinet, a target capacity is made by the control system according to an equalization strategy. Such as: the current capacity of the constant current device, the current capacity of the charge equalizer, the capacity attenuation condition and the capacity difference condition of all the battery cells of the whole cabinet are comprehensively considered to formulate the target capacity of the battery cells. And then the battery core with the capacity lower than the target capacity is subjected to capacity supplementation by using a constant current device and a charger.
And calculating the working time length of the balance constant current device or the balance charger according to the capacity, the charging current or the discharging current of the battery cell. Cell capacity (Ah) =battery current (a) ×time of use (hours)). When the battery cabinet is charged and discharged each time, collecting the voltage value and the current value of each battery cell in real time, and calculating the charge balance time or the discharge balance time required by the battery cell according to the capacity of the battery cell and the target capacity of the battery cell; cell capacity (Ah) =battery current (a) x time of use.
When the battery cabinet is charged, the capacity of a certain battery cell is set to be smaller than the set target capacity, an equalizing constant current device is bypassed for the battery cell, a part Ibc of the charging current Ic from top to bottom passes through the equalizing constant current bypass, and the charging current of the battery cell is reduced to be Isc, isc=ic-Ibc.
Switches are arranged at two ends of a capacitor in the equalizing constant current device to control positive and negative connection of the capacitor; the positive and negative connection of the capacitor is reversed when the approach of the current from large to small is detected. Under the condition that a plurality of electric cores share one equalizing constant current device, after the equalizing constant current device is disconnected from one electric core, the capacitor needs to be positively discharged, and a unidirectional current discharging method is used.
Fig. 8 is a schematic diagram of an implementation principle of an equalization galvanostat according to an embodiment of the present invention, and fig. 9 is a schematic diagram of a specific device for use of the equalization galvanostat according to an embodiment of the present invention.
The equalizing constant current device consists of an inductor, a capacitor, a switching device, a current sensor, an operational amplifier circuit and a logic circuit. In addition, when another cell is switched in practical application, the voltage of the capacitor in the forward working process is ensured to be lower than the voltage of the cell, and a unidirectional discharge circuit is required to be added. The working principle of the equalization constant current device is as follows: at first, K1 and K2 are closed, the current passing through the inductor is changed from small to large and then from large to small, when the current approaches zero, the output of the D trigger is reversed through the operational amplifier, the comparator and the D trigger, so that K1, K2 are opened, K3 and K4 are closed, the current passing through the sensor is changed from small to large and then from large to small, and when the current approaches zero, the control circuit enables K3, K4 to be opened and K1 and K2 to be closed. And the process is repeated in a circulating way. After the connected cell is disconnected and before another cell is replaced, an externally controlled discharging circuit is adopted to discharge for a period of time so as to ensure that the balanced constant current device can work according to the envisaged state when being connected.
Fig. 10 is a schematic diagram of a simulation result of current balancing of a constant current device according to an embodiment of the present invention. The switching of the balancing galvanostat can be implemented by MOSFETs as shown in fig. 8, K1, K2, K3, K4, which require a boost circuit.
In order to reduce current fluctuation, a plurality of equalizing constant current devices can be used in parallel and the phases are staggered.
The selection of a certain cell switch matrix may also be implemented with a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The MOSFET may be driven by the node voltage of the string of cells in the battery pack. In conjunction with a widely used BMS (Battery Management System ) chip, the passive equalization control pins thereon are utilized to control the turning on or off of the MOSFETs of the switch array. The switch array may also be implemented with an optical solid state relay.
In summary, the method of the embodiment of the invention can achieve the use of the battery capacity of the whole battery cabinet. When the battery cabinet is charged, the capacities of all the battery packs are different but are connected in series, and the method saves a part of circuits and energy storage devices which are needed for storing electric energy for the battery packs with small capacities when the battery cabinet is charged, so that the devices are fewer, and the cost is saved.
When the battery cabinet is charged, the method for charging the whole battery string to full capacity is realized by reducing the small-capacity battery core current in the battery string in a parallel connection mode of the balanced constant current device. When the battery cabinet discharges, the battery core with small capacity in the battery string is supplemented by external electric energy to achieve the maximum discharge capacity of the whole battery string. When the current transformer is used for carrying out direct current charging on the battery cabinet, the external voltage of the battery core is reduced when the constant current transformer is used, so that even if the current of the current transformer is unchanged, the voltage is reduced, the whole power is reduced, and the electric energy is saved.
Those of ordinary skill in the art will appreciate that: the drawing is a schematic diagram of one embodiment and the modules or flows in the drawing are not necessarily required to practice the invention.
In this specification, each embodiment is described in a progressive manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments. In particular, for apparatus or system embodiments, since they are substantially similar to method embodiments, the description is relatively simple, with reference to the description of method embodiments in part. The apparatus and system embodiments described above are merely illustrative, wherein the elements illustrated as separate elements may or may not be physically separate, and the elements shown as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art will understand and implement the present invention without undue burden.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims (7)

1. A method for equalizing energy stored in a battery, comprising:
at least one equalization constant current device and at least one equalization charger are arranged in each battery pack of the battery cabinet, a plurality of battery cores connected in series are arranged in one battery pack, and at least one battery core is connected to the equalization constant current device and the equalization charger;
when the battery cabinet is charged, for the battery core with the capacity smaller than the set target capacity, an equalizing constant current device is used for bypassing the battery core, and discharging equalization is carried out; when discharging the battery cabinet, for the battery core with the capacity smaller than the set target capacity, an equalization charger is used to be connected in parallel with the battery core, and charge equalization is carried out.
2. The method of claim 1, wherein at least one cell is provided with an equalization galvanostat and an equalization charger within the battery pack, and wherein the parallel connection of a cell to the equalization galvanostat or equalization charger is accomplished by an array of switches.
3. The method of claim 1, wherein the balancing constant current device is composed of an inductance, a capacitance, a switching device, a current sensor, an operational amplifier circuit, and a logic circuit, the switching device including K1, K2, K3, and K4;
in the initial stage, K1 and K2 are closed, the current passing through the inductor is changed from small to large and then from large to small, when the current approaches zero, the output of the D trigger is reversed through the operational amplifier, the comparator and the D trigger, so that K1, K2 are opened, K3 and K4 are closed, the current passing through the sensor is changed from small to large and then from large to small, when the current approaches zero, the control circuit enables K3 and K4 to be opened, K1 and K2 are connected, and the cycle is repeated in this way, and before the other battery is replaced after the connected battery is disconnected, an externally controlled discharging circuit is adopted for discharging for a period of time so as to realize that the voltage on the capacitor is smaller than the voltage of the battery.
4. A method according to claim 3, wherein said bypassing the battery cells having a capacity less than the set target capacity with the equalization galvanostat and performing discharge equalization when charging the battery cell comprises:
collecting the voltage value and the current value of each battery cell in real time when the battery cabinet is charged and discharged each time, calculating the capacity of the battery cell when the voltage of the battery cell reaches a limit value, and calculating the charge balance time or the discharge balance time required by the battery cell according to the capacity of the battery cell and the target capacity of the battery cell when the battery cabinet is charged and discharged next time; cell capacity (Ah) =battery current (a) x time of use;
when the battery cabinet is charged, the capacity of a certain battery cell is set to be smaller than the set target capacity, an equalizing constant current device is bypassed for the battery cell, a part Ibc of the charging current Ic from top to bottom passes through the equalizing constant current bypass, and the charging current of the battery cell is reduced to be Isc, isc=ic-Ibc.
5. A method according to claim 3, wherein the step of using an equalization charger in parallel with the battery cells having a capacity smaller than the set target capacity and performing charge equalization when discharging the battery cell comprises:
collecting the voltage value and the current value of each battery cell in real time when the battery cabinet is charged and discharged each time, calculating the capacity of the battery cell according to the previous data, calculating the target capacity of the battery cell according to the charging and discharging current, and calculating the charge balance time or the discharge balance time required by the battery cell according to the capacity of the battery cell and the target capacity of the battery cell;
when the battery cabinet is discharged, the capacity of a certain battery cell is set to be smaller than the set target capacity, an equalization charger is connected to the battery cell in parallel, a part Ibd of the discharging current Id to the lower side is provided by the equalization charger, and the discharging current of the battery cell is reduced to be Isd, and isd=Id-Ibd.
6. The method of claim 1, wherein the method further comprises:
the switch is arranged at two ends of the capacitor, the positive and negative connection of the capacitor is controlled, when the current is detected to be reduced from large to small and approaches zero, the positive and negative connection of the capacitor is reversed, and under the condition that a plurality of electric cores share one balanced constant current device, the balanced constant current device is disconnected from one electric core, then the capacitor is discharged in the forward direction, and when the capacitor is charged in the reverse direction, the capacitor is not discharged.
7. The method of claim 1, wherein the method further comprises: and according to the total cell capacity of the battery cabinet, the control system makes a target capacity according to an equalization strategy, and the cells with the capacity lower than the target capacity are subjected to capacity supplementation by using the constant current device and the charger.
CN202311026937.1A 2023-08-15 2023-08-15 Balancing method for battery energy storage Pending CN117040064A (en)

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