CN107733007B - Dual-target direct equalization circuit and equalization method for battery pack - Google Patents
Dual-target direct equalization circuit and equalization method for battery pack Download PDFInfo
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- CN107733007B CN107733007B CN201710894144.XA CN201710894144A CN107733007B CN 107733007 B CN107733007 B CN 107733007B CN 201710894144 A CN201710894144 A CN 201710894144A CN 107733007 B CN107733007 B CN 107733007B
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- 238000000034 method Methods 0.000 title claims description 37
- 238000004146 energy storage Methods 0.000 claims abstract description 24
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 9
- 229910001416 lithium ion Inorganic materials 0.000 claims description 9
- 238000001514 detection method Methods 0.000 claims description 7
- 230000021715 photosynthesis, light harvesting Effects 0.000 claims description 3
- 238000010586 diagram Methods 0.000 description 9
- 239000000178 monomer Substances 0.000 description 7
- 238000011217 control strategy Methods 0.000 description 6
- 238000012546 transfer Methods 0.000 description 6
- 239000003990 capacitor Substances 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- 230000002457 bidirectional effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
Classifications
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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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L53/00—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
- B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
- B60L58/18—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries of two or more battery modules
- B60L58/22—Balancing the charge of battery modules
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- H02J7/0026—
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- H02J7/0027—
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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
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/0036—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using connection detecting 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
- H02J7/0068—Battery or charger load switching, e.g. concurrent charging and load supply
-
- 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
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/00302—Overcharge protection
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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
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/00306—Overdischarge protection
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- 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
-
- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/7072—Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
-
- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02T90/10—Technologies relating to charging of electric vehicles
- Y02T90/14—Plug-in electric vehicles
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
- Secondary Cells (AREA)
Abstract
The invention discloses a battery pack double-target direct equalization circuit. The series battery pack comprises at least three single batteries, and is divided into an upper part and a lower part, each single battery is connected with an equalization sub-circuit, the equalization sub-circuit consists of two MOSFETs and an energy storage inductor, the series battery pack and the equalization sub-circuit are connected between VCC and GND in a bridging way, and each equalization sub-circuit is connected with a control circuit to realize direct equalization of an equalization target. The control circuit takes the terminal voltage and the SOC of the single battery as balance indexes at the same time, balances the terminal voltage and the SOC of the single battery in stages in one balance period, and realizes double-target balance of the terminal voltage and the SOC of the single battery by controlling the on-off of two MOSFETs of the balance sub-circuit and utilizing the energy storage effect of the energy storage inductor. The equalization circuit and the equalization strategy are suitable for an equalization management system of an energy storage device in a hybrid electric vehicle, a pure electric vehicle or an energy storage power station.
Description
Technical Field
The invention relates to a double-target direct equalization technology and an equalization method for a series battery pack, which are suitable for a battery management system of an energy storage device in a hybrid electric vehicle, a pure electric vehicle or an energy storage power station.
Background
Because the single battery has limited capacity and low single voltage, the power battery pack is generally formed by connecting a plurality of single batteries in series and parallel so as to meet the use requirement. Because of unavoidable inconsistency among the single batteries of the same model, the service life of the battery pack is seriously affected, and overcharge and overdischarge phenomena are easily caused. After a plurality of charge and discharge cycles, the distribution of the residual capacities of the single batteries of the series battery pack approximately shows three conditions: the residual capacity of the individual single batteries is higher; the residual capacity of the individual single batteries is lower; the remaining capacity of the individual unit cells is high and the remaining capacity of the individual unit cells is low.
Aiming at the situation, students at home and abroad propose own solutions. As for the case where the residual capacity of the individual unit cells is high, there has been proposed a parallel resistance shunt method which consumes energy of the battery module having the high residual capacity through the resistors by controlling the corresponding switching devices, which wastes energy and generates a large amount of heat during the balancing process, increasing the thermal management load of the battery. Researchers have also proposed equalization circuits such as a bidirectional DC-DC equalization method and a coaxial transformer equalization method, which use transformers, and increase the cost of the equalization circuit.
The current lithium ion battery pack balance control method can be divided into two main types, namely energy dissipation type and energy non-dissipation type according to the energy consumption condition of a circuit in the balance process; according to the equalization function classification, charge equalization, discharge equalization and dynamic equalization can be classified. The charge equalization refers to equalization in the charging process, and is generally started when the cell voltage of the battery pack reaches a set value, and overcharge is prevented by reducing the charging current; discharge equalization means equalization in the discharge process, and prevents overdischarge by supplementing energy to a cell having low remaining energy; the dynamic equalization mode combines the advantages of charge equalization and discharge equalization, and means equalization of the battery pack in the whole charge and discharge process. A number of equalization topologies and control strategies have been proposed today. For research on control strategies of an equalization circuit, kobzev, tae-hoon Kim and the like are used for equalizing a battery pack by taking battery terminal voltage as an equalization index, however, the quality of battery performance cannot be measured only by the voltage, the terminal voltage of a battery with low capacity in the battery pack can be higher than that of other batteries during or after charging, and if the equalization method is adopted, the equalization result is that the battery with low capacity supplements energy for the battery with high capacity, so that the difference of the capacities of the batteries in the battery pack is increased. Danielson, huang W et al consider that the advantage of using SOC as an equalization variable is that when current suddenly changes under different working conditions, the state of charge of the battery is not fluctuated, so that the equalization target changes more stably, and the influence of equalization oscillation on the battery is reduced, but the equalization method only solves the problem that the performance of the battery with larger capacity in the battery pack is reduced due to insufficient long-term charging, and cannot reduce or eliminate the difference of the actual capacities of the batteries. In general, current research on equalization control strategies mostly uses a single terminal voltage or a single SOC as an equalization index.
Disclosure of Invention
The invention aims to adopt an equalization circuit in a battery management system of a series battery pack to ensure that the single batteries in the battery pack are not overcharged and overdischarged in the charging and discharging processes, improve the imbalance phenomenon of the series battery pack, improve the available capacity of the battery pack, reduce the maintenance and replacement period of the series battery pack, prolong the service life of the battery pack and reduce the running cost of a hybrid electric vehicle, an electric vehicle and an energy storage power station. In the charging process, when the energy of any one monomer in the battery pack is too high, the energy of the monomer can be balanced to all other residual monomers in the battery pack; during discharge, when the energy of any one cell in the battery pack is too low, the energy of all other remaining cells in the battery pack can be balanced to the cell with the too low energy. And the SOC and the terminal voltage are used as equalization indexes to formulate an equalization control strategy, and the uniformity of the single battery of the power battery pack is improved essentially by equalizing the SOC and the terminal voltage in stages.
In order to achieve the above object, the present invention is achieved by the following technical solutions.
The battery pack double-target direct equalization circuit consists of a series battery pack and an equalization sub-circuit. The series battery pack is divided into an upper part and a lower part, wherein the upper part of single batteries are upper batteries, and the lower part of single batteries are lower batteries; when the total number of the single batteries n is even, the numbers of the single batteries at the upper part and the lower part are (n/2), and when the total number of the single batteries n is odd, the number of the single batteries at the upper part is [ (n+1)/2]The number of the lower single batteries is [ (n-1)/2]The method comprises the steps of carrying out a first treatment on the surface of the The single batteries are respectively named as B from top to bottom 1 、B 2 、B 3 、……B n ，B 1 Positive electrode of (B) is connected with VCC n The negative electrode of (2) is connected with GND. Each single battery is connected with an equalization sub-circuit.
The single battery can be a secondary battery such as a lead-acid battery, a lithium ion battery, a nickel-hydrogen battery, a super capacitor and the like.
Preferably, each equalization sub-circuit is composed of two MOSFETs with freewheeling diodes and an energy storage inductor L, and the MOSFET of the upper bridge arm is Q u The MOSFET of the lower bridge arm is Q d ，Q u Source and Q of (2) d The drain electrode of the capacitor is connected with one end of the energy storage inductor L; q (Q) u Is taken as the drain electrode of the output terminal a, Q u Gate of (2) as output terminal b, Q d Gate of (c) as output terminal c, Q d The other end of L is used as an output end e; the output ends b and c are connected with the control circuit, so that the on and off of the MOSFET is controlled by the control circuit; the equalization sub-circuit is connected with the upper single battery, the end a is connected with the anode of the corresponding single battery, the end e is connected with the cathode of the corresponding single battery, and the end d is connected with GND; the equalization sub-circuit is connected with the lower single battery, the e end is connected with the anode of the corresponding single battery, the d end is connected with the cathode of the corresponding single battery, and the a end is connected with VCC; the total equalization subcircuit a is terminated with VCC, d is terminated with GND, e is terminated with the common point k of the upper and lower batteries.
The principle of operation of the equalizer subcircuit is as follows.
In the charge and discharge process, if the monomer B is positioned above the k point i Discharge equalization is required by controlling S i Upper bridge arm switch tube Q of (2) ui Conduction, B i Discharge is L i Storing energy; q (Q) ui Turn off after a certain time of turn-on, when the current passes through B i Corresponding equalization subcircuit lower bridge arm switch tube Q di Freewheel diode, L i B (B) i+1 、B i+2 ……B n ，L i Releasing energy to B i+1 、B i+2 ……B n Realizing energy from B i To B i+1 、B i+2 ……B n Is transferred from the first to the second transfer station. If the monomer B is located below the k-point j Discharge equalization is required to make B in one PWM period j Corresponding equalization subcircuit lower bridge arm MOSFET Q dj On, the current passes through Q dj 、B j Corresponding equalization subcircuit energy storage inductance L j B, B j ，B j Discharge is L j Storing energy; q (Q) dj Turn on oneAfter a certain time, turn off the current passing through B j Corresponding equalization subcircuit upper bridge arm MOSFET Q uj Freewheel diode, L j B (B) 1 、B 2 ……B i-1 ，L j Releasing energy to B 1 、B 2 ……B i-1 Realizing energy from B j To B 1 、B 2 ……B i-1 Is transferred from the first to the second transfer station.
If the monomer B is located above the k point i Charge equalization is required by controlling S i Lower bridge arm switch tube Q of (2) di Conduction, B i+1 、B i+2 ……B n Discharge is L i Storing energy; q (Q) di Turn off after a certain time of turn-on, when the current passes through B i Corresponding upper bridge arm switch tube Q of equalization subcircuit ui Freewheel diode, L i B (B) i+1 、B i+2 ……B n ，L i Releasing energy to B i Realizing energy from B i+1 、B i+2 ……B n To B i Is transferred from the first to the second transfer station. If the monomer B is located below the k-point i Charge equalization is required to be performed, and B is caused to occur in one PWM period j Corresponding equalization subcircuit upper bridge arm MOSFET Q uj On, the current passes through Q uj 、B j Corresponding equalization subcircuit energy storage inductance L j B, B 1 、B 2 ……B j-1 ，B 1 、B 2 ……B j-1 Discharge is L j Storing energy; q (Q) uj Turn off after a certain time of turn-on, when the current passes through B j Corresponding equalization subcircuit lower bridge arm MOSFET Q dj Freewheel diode, L j B (B) j ，L j Releasing energy to B j Realizing energy from B 1 、B 2 ……B j-1 To B j Is transferred from the first to the second transfer station.
And (3) establishing equalization indexes based on the SOC and the terminal voltage, and equalizing the equalization indexes in stages in one equalization period, so that the consistency of the SOC and the terminal voltage of each single battery in the battery pack is finally realized, and the design requirement is met.
The specific equalization control strategy comprises the following contents:
s1, setting an equalization index: judging whether the inconsistency of the SOC and the terminal voltage of each battery meets the working condition of an equalizing circuit or not by a detection circuit; if the equalization condition is met, the equalization circuit starts to work; if the equalization condition is not satisfied, the equalization circuit does not operate.
And S2, the equalization process comprises a plurality of equalization periods, wherein each equalization period is used for voltage equalization by T/2 time, and each equalization period is used for SOC equalization by T/2 time.
S3, after each equalization period is finished, the detection circuit re-detects and judges whether the SOC and the terminal voltage of each battery meet equalization conditions;
s4, repeating the step S2 until the inconsistency of the single batteries does not meet the working condition of the equalization circuit, stopping the operation of the equalization circuit, and ending the equalization process.
Furthermore, the control circuit controls the equalization sub-circuit by outputting a control signal, wherein the frequency of the control signal is determined according to the inductance value of the energy storage inductor of the equalization sub-circuit, the switching loss of the MOSFET, the battery terminal voltage of the single battery and the single capacity of the single battery.
Further, the duty ratio of the control signal output by the control circuit can enable the energy storage inductor to reset in each signal period, namely, the current of the energy storage inductor firstly rises from zero and finally falls to zero.
Further, in step S2, during the operation of the equalization circuit, the open-circuit voltage of the unit cell corresponding to the maximum SOC value is reduced, and the terminal voltage of the unit cell corresponding to the minimum terminal voltage is increased, so thatAnd the battery pack consistency index is gradually met. When each single battery in the battery pack/>When the dynamic performance of the single batteries is consistent, the consistency of the dynamic performance of the single batteries can be realized.
The equalization method of the lithium ion battery provided by the invention can be applied to various energy dissipation type equalization circuits and energy non-dissipation type equalization circuits.
The circuit is also applicable to a capacitance type equalization circuit, a converter type equalization circuit and a transformer type equalization circuit.
The invention adopts the equalization technology in the battery management system of the series battery pack, so that each battery is ensured not to be overcharged and overdischarged in the charging and discharging processes, and meanwhile, the battery terminal voltage and the SOC are used as inconsistent indexes, so that the consistency of single batteries in the battery pack can be essentially improved; through staged equalization, terminal voltage and SOC double-target equalization is realized simultaneously on the premise of not increasing program operand and control complexity. The control strategy method is reliable, has small on-line operation amount, can obviously improve the safety and reliability of the battery, improve the energy utilization rate of the battery, prolong the service life of the battery and reduce the cost of the storage battery energy storage system in the hybrid electric vehicle, the electric vehicle and the power station.
Drawings
Fig. 1 is a schematic diagram of an equalization circuit in the present invention.
Fig. 2 is a schematic diagram of an equalization sub-circuit in the present invention.
Fig. 3 is a schematic diagram of an equalization strategy in the present invention.
Fig. 4 is a schematic diagram of the operation of the equalization circuit during charging of a four-cell series battery.
Fig. 5 is a schematic diagram of the operation of the equalization circuit during discharge of the four-cell series battery.
Detailed Description
The following detailed description of specific embodiments of the invention refers to the accompanying drawings.
Fig. 1 is a schematic diagram of an equalization circuit. The series battery pack is divided into an upper part and a lower part, wherein the upper part of single batteries are upper batteries, and the lower part of single batteries are lower batteries; when a sheet isWhen the total number of the body batteries n is even, the numbers of the upper and lower part single batteries are (n/2), and when the total number of the single batteries n is odd, the number of the upper single batteries is [ (n+1)/2]The number of the lower single batteries is [ (n-1)/2]The method comprises the steps of carrying out a first treatment on the surface of the The single batteries are respectively named as B from top to bottom 1 、B 2 、B 3 、……B n ，B 1 Positive electrode of (B) is connected with VCC n The negative electrode of (2) is connected with GND. Each single battery is connected with an equalization sub-circuit.
Fig. 2 is a schematic diagram of an equalization sub-circuit. Each equalization subcircuit is composed of two MOSFETs with freewheeling diodes and an energy storage inductor L, and the MOSFET of the upper bridge arm is Q u The MOSFET of the lower bridge arm is Q d ，Q u Source and Q of (2) d The drain electrode of the capacitor is connected with one end of the energy storage inductor L; q (Q) u Is taken as the drain electrode of the output terminal a, Q u Gate of (2) as output terminal b, Q d Gate of (c) as output terminal c, Q d The other end of L is used as an output end e; the output ends b and c are connected with the control circuit, so that the on and off of the MOSFET is controlled by the control circuit; the equalization sub-circuit is connected with the upper single battery, the end a is connected with the anode of the corresponding single battery, the end e is connected with the cathode of the corresponding single battery, and the end d is connected with GND; and the end e of the equalization sub-circuit is connected with the anode of the corresponding single battery, the end d of the equalization sub-circuit is connected with the cathode of the corresponding single battery, and the end a is connected with VCC.
Fig. 3 is a schematic diagram of a dual-objective staged equalization strategy. The double targets are that SOC and terminal voltage are simultaneously used as equalization indexes, thereby realizingTo ensure the consistency of the working state of each single battery of the battery pack. The grading is that in each balancing period, half period is used for realizing terminal voltage balancing, and the process is realized by carrying out charge balancing on the single battery with the lowest terminal voltage; there is a half cycle for achieving SOC equalization, i.e., open circuit voltage equalization, by discharging equalization of the cell with the highest open circuit voltage. Judging whether the inconsistency of the SOC and the terminal voltage of each battery meets the working condition of an equalizing circuit or not by a detection circuit; if the equilibrium condition is satisfiedThe equalization circuit starts to work; if the equalization condition is not satisfied, the equalization circuit does not operate.
And (3) after each equalization period, the detection circuit re-detects and judges whether the SOC and the terminal voltage of each battery meet the working conditions of the equalization circuit. And (3) ending an equalization period, if the SOC and the terminal voltage of each single battery meet the working conditions of the equalization circuit, continuing to work the equalization circuit, and if the SOC and the terminal voltage of each single battery do not meet the working conditions of the equalization circuit, stopping the operation of the equalization circuit, and ending the equalization process.
Fig. 4 and 5 are schematic diagrams of the working principle of the equalization circuit in the charge-discharge process, taking the number of single batteries n=4 as an example,
FIG. 4 is pair B 1 Performing discharge equalization to make B in one PWM period 1 Corresponding equalization subcircuit upper bridge arm MOSFET Q u1 On, current i u1 Through Q u1 、B 1 Corresponding equalization subcircuit energy storage inductance L 1 B, B 1 ，B 1 Discharge is L 1 Storing energy; q (Q) u1 Turn off after a certain time of turn-on, when the current passes through B 1 Corresponding equalization subcircuit lower bridge arm MOSFET Q d1 Freewheel diode, L 1 B (B) 2 、B 3 、B 4 ，L 1 Releasing energy to B 2 、B 3 、B 4 Realizing energy from B 1 To B 2 、B 3 、B 4 Is transferred from the first to the second transfer station.
FIG. 5 is pair B 3 Charge equalization is performed by making B in one PWM period 3 Corresponding equalization subcircuit upper bridge arm MOSFET Q u3 On, the current passes through Q u3 、B 3 Corresponding equalization subcircuit energy storage inductance L 3 B, B 1 、B 2 ，B 1 、B 2 Discharge is L 3 Storing energy; q (Q) u3 Turn off after a certain time of turn-on, when the current passes through B 3 Corresponding equalization subcircuit lower bridge arm MOSFET Q d3 Flywheel diode of (a)Tube, L 3 B (B) 3 ，L 3 Releasing energy to B 3 Realizing energy from B 1 、B 2 To B 3 Is transferred from the first to the second transfer station.
Claims (5)
1. A balancing method of a lithium ion battery pack is characterized by comprising the following steps of: the lithium ion battery pack is balanced according to the battery pack double-target direct balancing circuit,
the battery pack double-target direct equalization circuit comprises a series battery pack formed by connecting a plurality of single batteries in series, equalization sub-circuits and a control circuit, wherein the number of the single batteries is not less than 3, each single battery is connected with one equalization sub-circuit, and each equalization sub-circuit is connected with the control circuit; the series battery pack is divided into an upper part and a lower part, and the number of the single batteries of the upper part is the same as or more than that of the single batteries of the lower part by 1; the equalization subcircuit connected with the single batteries at the upper part is connected with the GND end of the series battery pack, and the equalization subcircuit connected with the single batteries at the lower part is connected with the VCC end of the series battery pack; the equalization sub-circuit is formed by connecting two MOSFETs with freewheeling diodes and an energy storage inductor, and the control circuit is connected with the grid electrodes of the two MOSFETs; the positive and negative ends of the single battery are respectively connected with the second end of the drain electrode of one MOSFET and the second end of the energy storage inductor; the source electrode of the other MOSFET is connected with the GND end or the VCC end of the series battery pack; the single battery is a secondary battery;
the equalization method comprises the following steps:
s1, connecting an equalization circuit with a detection circuit, and setting equalization indexes: judging whether the inconsistency of the SOC and the terminal voltage of each battery meets the working condition of an equalizing circuit or not by a detection circuit; if the equalization condition is met, the equalization circuit starts to work; if the equalization condition is not satisfied, the equalization circuit does not operate,
setting the average open-circuit voltage of each single battery of the battery pack as U oc_are The average terminal voltage of each single battery is U L_aw And (3) making:
D i ＝U oc_j -U L_i (1)
U oc_i ＝f(soc i ) (2)
D max ＝U oc_max -U L_min | (3)
D ave ＝U oc_aw -U L_aw (4)
the working judgment conditions of the equalizing circuit are as follows: d (D) max -D ave ＞v ref ，v ref The reference voltage value is an equalizing circuit reference voltage value;
s2, the equalization process comprises a plurality of equalization periods T, the battery terminal voltage is equalized in the first half period T/2 of the equalization period T, the battery SOC is equalized in the second half period T/2 of the equalization period T,
in the charge-discharge process, if D max -D ave ≤v ref The equalization circuit does not work if D max -D ave ＞v ref The equalization circuit starts to operate, and the first half period pair U of each equalization period oc_max The corresponding single battery performs discharge equalization to ensure U oc_max The last half period of each equalization period is reduced to U I_min Corresponding single batteries are charged and balanced, so that U L_min Increase, resulting in D max Reduce, finally make D max -D aw ≤v ref Establishment;
s3, after each equalization period is finished, the detection circuit re-detects and judges whether the inconsistency of the battery terminal voltage and the battery SOC of each single battery meets the equalization condition;
and S4, the operation is repeated until the inconsistency of the single batteries does not meet the working condition of the equalization circuit, and the equalization circuit stops working.
2. The equalization method of a lithium ion battery pack of claim 1, wherein: the control circuit controls the equalization sub-circuit by outputting a control signal, wherein the frequency of the control signal is determined according to the inductance value of the energy storage inductor of the equalization sub-circuit, the switching loss of the MOSFET, the battery terminal voltage of the single battery and the single capacity of the single battery.
3. The equalization method of a lithium ion battery pack according to claim 2, wherein: the duty cycle of the control signal output by the control circuit can enable the energy storage inductor to reset in each signal period.
4. The equalization method of a lithium ion battery pack of claim 1, wherein: the equalization method is applied to an energy dissipation type equalization circuit and an energy non-dissipation type equalization circuit.
5. The equalization method of a lithium ion battery pack of claim 1, wherein: the equalization method is applied to a capacitance type equalization circuit, a converter type equalization circuit and a transformer type equalization circuit.
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| CN111435791A (en) * | 2019-01-11 | 2020-07-21 | 河南理工大学 | Double-voltage self-adaptive equalization control method for series battery pack |
| CN109638922A (en) * | 2019-01-11 | 2019-04-16 | 河南理工大学 | A kind of direct balance control method of series-connected cell group twin voltage |
| CN109768595A (en) * | 2019-01-11 | 2019-05-17 | 河南理工大学 | A kind of series-connected cell group twin voltage mixed equilibrium control method |
| CN110758179B (en) * | 2019-11-11 | 2020-11-24 | 河南理工大学 | LC-L-based series battery pack equalization circuit and equalization method |
| CN111180811B (en) * | 2020-01-06 | 2022-03-25 | 宁波吉利汽车研究开发有限公司 | Method and device for acquiring actual SOC of vehicle power storage battery pack |
| CN111200306B (en) * | 2020-01-11 | 2023-06-13 | 国网辽宁省电力有限公司电力科学研究院 | Novel battery pack equalization circuit topology and equalization strategy |
| CN112510774B (en) * | 2020-11-24 | 2022-06-03 | 东风汽车集团有限公司 | Equalization method of battery pack |
| CN115946572B (en) * | 2022-11-21 | 2023-06-30 | 上海玫克生储能科技有限公司 | Battery module capacity calculation and compensation control method, system, equipment and medium |
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