CN114043901B - Protection method for lithium battery and lithium battery - Google Patents
Protection method for lithium battery and lithium battery Download PDFInfo
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- CN114043901B CN114043901B CN202111322351.0A CN202111322351A CN114043901B CN 114043901 B CN114043901 B CN 114043901B CN 202111322351 A CN202111322351 A CN 202111322351A CN 114043901 B CN114043901 B CN 114043901B
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 29
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 29
- 238000000034 method Methods 0.000 title claims abstract description 20
- 238000012544 monitoring process Methods 0.000 claims abstract description 41
- 230000002159 abnormal effect Effects 0.000 claims abstract description 11
- 238000010438 heat treatment Methods 0.000 claims description 67
- 238000012937 correction Methods 0.000 claims description 35
- 238000007599 discharging Methods 0.000 claims description 27
- 238000004891 communication Methods 0.000 claims description 13
- 239000000178 monomer Substances 0.000 claims description 6
- 238000005070 sampling Methods 0.000 claims description 6
- 238000001514 detection method Methods 0.000 claims description 5
- 239000006185 dispersion Substances 0.000 claims description 4
- 238000009825 accumulation Methods 0.000 claims 1
- 230000003247 decreasing effect Effects 0.000 claims 1
- 230000007547 defect Effects 0.000 abstract description 3
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000005856 abnormality Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011217 control strategy Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000004781 supercooling Methods 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
- B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
- B60L58/12—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries responding to state of charge [SoC]
-
- 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
- B60L3/00—Electric devices on electrically-propelled vehicles for safety purposes; Monitoring operating variables, e.g. speed, deceleration or energy consumption
- B60L3/0023—Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train
- B60L3/0046—Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train relating to electric energy storage systems, e.g. batteries or capacitors
-
- 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
- B60L2240/00—Control parameters of input or output; Target parameters
- B60L2240/40—Drive Train control parameters
- B60L2240/54—Drive Train control parameters related to batteries
- B60L2240/545—Temperature
-
- 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
- B60L2240/00—Control parameters of input or output; Target parameters
- B60L2240/40—Drive Train control parameters
- B60L2240/54—Drive Train control parameters related to batteries
- B60L2240/547—Voltage
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Secondary Cells (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
Abstract
A protection method for lithium battery and lithium battery, comprising: the sub-monitoring system detects state values of each independent battery pack, including battery cell voltage, battery cell temperature and current data of the battery pack during operation, and meanwhile, the sub-control system sends the data to the main control system; according to the collected battery state data received by the sub-control system, calculating a protection threshold value of the abnormal state of the battery; establishing a voltage U protection condition according to the calculated protection threshold value; and establishing a temperature T protection condition according to the calculated protection threshold value. The invention overcomes the defects of the prior art, and ensures the real-time performance and the effectiveness of the protection threshold by adopting the protection threshold calculation scheme. And the fault judgment triggering calculation scheme is adopted, so that the running stability of the system is ensured, and misjudgment caused by external interference is avoided.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a protection method for a lithium battery and the lithium battery.
Background
Industrial vehicle power sources are becoming more popular worldwide when transforming from traditional energy sources to new energy sources, and electric industrial vehicles in the future will take the dominant market in China from the increasing speed of new energy forklifts in recent years. Meanwhile, as an important branch of industrial vehicles, an airport tractor power supply lithium battery will acquire a new opportunity. The power supply vehicle of the airplane is a very important airport special vehicle. Along with the great improvement of the performance of the lithium battery, the application range is also expanded from the civil consumption field to the aerospace field.
In order to co-build a green airport, the application of airport related equipment in new energy sources is enhanced, wherein the foremost is to realize the comprehensive electric drive of airport ground vehicles. The special lithium iron phosphate battery for the airport tractor brings cleanness, green, environmental protection and wisdom into an airport design scheme, has great advantages in the aspects of high-efficiency output, good performance at high temperature, excellent cycle life, quick charge, low cost and the like, and can meet the high requirements of the application of a power battery system on safety functions such as electric, mechanical, thermal, electromagnetic compatibility, environment and the like. The special lithium iron phosphate battery is customized and developed for airport equipment, complete matching is realized, and airport ground vehicles are propelled to change oil into electricity.
Because of the complex use environment of the airport, compared with the use condition of the traditional industrial vehicle, the method has higher requirements on the reliability of the special lithium iron phosphate battery for the airport tractor. In short, when a certain battery cell unit of the lithium battery fails, the system can be positioned in time, and meanwhile, part of battery strings can be actively cut off without affecting the normal operation of other battery packs, so that the airport tractor can be ensured to continue to be used.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a protection method for the use of a lithium battery and the lithium battery, which overcome the defects of the prior art, not only can accurately position a fault source of the lithium battery, but also can put the use reliability of a battery pack in a first position, and can cut off part of battery loops while accurately positioning the fault source, thereby ensuring the safety of a system.
In order to achieve the above purpose, the invention is realized by the following technical scheme:
a protection method for lithium battery includes the following steps:
step S1: the sub-monitoring system detects state values of each independent battery pack, including battery cell voltage, battery cell temperature and current data of the battery pack during operation, and meanwhile, the sub-control system sends the data to the main control system;
step S2: according to the voltage value U of each single cell of the sub-battery pack CELL Calculating average single voltage value U of sub-battery pack AVG The method comprises the steps of carrying out a first treatment on the surface of the According to the temperature value T of each monomer of the sub-battery pack CELL Calculating the average monomer temperature value T of the sub-battery pack AVG ；
Step S3: according to the collected battery state data received by the sub-control system, calculating a protection threshold value of the abnormal state of the battery;
step S4: establishing a voltage U protection condition according to the calculated protection threshold value;
step S5: and establishing a temperature T protection condition according to the calculated protection threshold value.
Preferably, the calculating the protection threshold value of the abnormal state of the battery in step S3 specifically includes:
voltage protection threshold function U:
U＝U p *(1+U a +U b )
wherein U is p A basic threshold value for protecting the voltage of the battery cell;
wherein U is a ＝(U CELL /U AVG -1) a, substitutionCorrecting the voltage protection threshold under the condition of different average voltages of the battery cells, reducing the voltage protection threshold correction value when the voltage value of the battery pack is not large in discreteness, and increasing the protection threshold correction value when the discreteness is increased, wherein a is the correction coefficient multiplied value;
wherein U is b ＝(I p I) b, representing the correction of the protection threshold for different discharge currents, I p The voltage protection threshold value is used for protecting the battery cell voltage, when the discharge current is closer to the current base threshold value, the voltage protection threshold value correction value is reduced, when the discharge current is further away from the current base threshold value, the voltage protection threshold value correction value is increased, and b is a correction coefficient multiplied value;
temperature protection threshold function T:
T＝T p *(1+T a )
wherein T is p Basic threshold value for protecting battery cell temperature
Wherein T is a ＝(T CELL /T AVG -1) c, representing the correction of the temperature protection threshold under the condition of different cell average temperatures, wherein the temperature protection threshold correction value is reduced when the temperature value of the battery pack is not large in variability, and the protection threshold correction value is increased when the variability is increased, and c is the correction coefficient multiplied value.
Preferably, the voltage unprotected condition established in step S4 is specifically:
wherein t is the unit time interval of the lowest sampling period;
wherein U is max And U min Calculating upper and lower limit protection thresholds for the voltage protection threshold function U;
wherein U (k) is the accumulated value of the battery cell voltage exceeding the upper limit threshold value in unit time, and U (n) is the accumulated value of the battery cell voltage being lower than the lower limit threshold value in unit timeThe value of U (k) accumulated value is greater than the protection accumulated threshold U (k) in unit time T max The system will trigger overvoltage protection, and similarly when the U (n) accumulated value in unit time T is greater than the protection accumulated threshold U (n) min The system will trigger under-voltage protection.
Preferably, the establishing temperature T protection condition in step S5 is specifically:
wherein t is the unit time interval of the lowest sampling period;
wherein T is max And T min Calculating upper and lower limit protection thresholds for the temperature protection threshold function T;
wherein T (k) is an accumulated value of the battery core temperature exceeding an upper limit threshold value in unit time, T (N) is an accumulated value of the battery core temperature being lower than a lower limit threshold value in unit time, and when the accumulated value of T (k) in unit time N is larger than a protection accumulated threshold value T (k) max The system will trigger overvoltage protection, and likewise when the T (N) accumulated value in unit time N is greater than the protection accumulated threshold T (N) min The system will trigger under-voltage protection.
The invention also discloses a lithium battery applied to the protection method, which comprises the following steps: the system comprises at least two sub-battery packs and a main monitoring system, wherein the sub-battery packs are connected in parallel; each sub-battery pack comprises a sub-monitoring system, a battery pack and a control unit, and the sub-monitoring system, the battery pack and the control unit independently operate; the word monitoring system is used for detecting the current, the temperature and the voltage of the battery pack corresponding to the word monitoring system, and the control unit is used for controlling the current on-off of the battery pack corresponding to the word monitoring system and the external equipment piece; the main monitoring system is in communication connection with the sub-monitoring system;
the positive electrode output end and the negative electrode output end of the sub-battery pack are respectively connected in parallel to form a discharge positive electrode and a discharge negative electrode; the positive and negative discharge electrodes are arranged in pairs and can be multiple, a first discharge current sensor and a second discharge current sensor are further arranged between the positive and negative discharge electrodes in parallel, and the first and second discharge current sensors are used for detecting currents when the positive and negative discharge electrodes discharge outwards and inputting detection results into the BMS.
Preferably, a first discharging relay and a second discharging relay are respectively connected in series on the circuit of each discharging anode, and the first discharging relay and the second discharging relay are respectively used for controlling the current on-off of a circuit connected with the first discharging relay and the second discharging relay in series, so that the on-off of the current released by each discharging anode outwards is controlled.
Preferably, the circuit of the discharging anode and the circuit of the discharging cathode are respectively and electrically connected with the circuit of the charging anode and the circuit of the charging cathode, and the circuit of the charging anode is also sequentially connected with a charging fuse and a charging relay in series, so that the charging fuse has the function of overload fusing; the charging relay is used for controlling the current on-off of the charging positive electrode circuit, and the initial state of the charging relay is a closed state; the control end of the charging relay is in communication connection with the signal end of the main monitoring system.
Preferably, the sub-battery pack comprises a battery pack, a battery management unit and a current sensor, wherein the battery management unit is used for detecting the voltage and the temperature of the battery pack; the power supply circuit of the battery pack is connected in series with a current sensor, the current sensor is used for detecting the magnitude of the current of the battery pack for supplying power outwards and transmitting signals to the battery management unit, the power supply circuit of the battery pack is connected in series with an output relay, and the output relay is in a closed state in the initial state and is used for cutting off the circuit of the battery pack for outputting the current outwards; the control end of the output relay is in communication connection with the signal end of the battery management unit; the battery management unit collects and analyzes the running state of the battery pack in real time and sends state data to the main control system.
Preferably, a fuse is connected in series to the line for supplying power to the battery pack, and the fuse is in overload fusing.
Preferably, a heating film is arranged in the sub-battery pack, and the heating film releases heat after being electrified; the heating film is powered by the battery pack, a heating film relay is connected in series on a power supply circuit of the heating film, the heating film relay is used for controlling the on-off of the heating film current, and the heating film relay is in an off state in the initial state; the control end of the heating film relay is in communication connection with the signal end of battery management;
the current access end of the heating film relay is also respectively and electrically connected with the connection end of the first discharging relay and the connection end of the second discharging relay, so that the heating film relay can be powered when either the connection end of the first discharging relay or the second discharging relay is closed;
the positive electrode power-on end of the heating film or the power-off end of the heating film relay is electrically connected with the power-off end of the heating relay, and the power-on end of the heating relay is directly or indirectly electrically connected with the charging positive electrode; the access end of the heating relay is connected with the heating fuse in series and then is electrically connected with the charging anode.
The invention provides a protection method for a lithium battery and the lithium battery. The beneficial effects are as follows: by adopting the protection threshold calculation scheme, the real-time performance and the effectiveness of the protection threshold are ensured. And the fault judgment triggering calculation scheme is adopted, so that the running stability of the system is ensured, and misjudgment caused by external interference is avoided.
Each sub-battery pack is collected and controlled by adopting an independent BMU, and is cut off by an independent controllable relay, if an abnormality occurs in a single sub-battery pack, the sub-battery pack can be cut off independently, and other sub-battery packs can still continue to operate.
The heating system under the battery working mode controlled by the independent BMU can independently judge the temperature and heat, so that the temperature of the battery pack in the use process is kept, and the service life of the battery is ensured. Different heating control strategies are adopted in the charging mode and the discharging mode, so that the reliability and the efficiency of battery heating are fully ensured. And adopt the double current sensor mode in the return circuit that discharges, guarantee the overcurrent capacity of electric connection and current collection precision, and adopt independent current collection mode respectively in every sub-battery package, can guarantee that the system can accurately collect the running current of every battery package, guarantee system safety.
Drawings
In order to more clearly illustrate the invention or the technical solutions in the prior art, the drawings used in the description of the prior art will be briefly described below.
FIG. 1 is a schematic diagram of a system framework of the present invention.
Fig. 2 is a schematic diagram of a battery architecture of the present invention.
Fig. 3 is a schematic diagram of a sub-battery pack system architecture according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings.
Example 1
A protection method for lithium battery includes the following steps:
step S1: the sub-monitoring system detects state values of each independent battery pack, including battery cell voltage, battery cell temperature and current data of the battery pack during operation, and meanwhile, the sub-control system sends the data to the main control system; the battery cell voltage value is a real-time data acquisition value, the battery cell temperature is a real-time data acquisition value, and the battery pack discharge current value is a real-time data acquisition value.
Step S2: according to the voltage value U of each single cell of the sub-battery pack CELL Calculating average single voltage value U of sub-battery pack AVG The method comprises the steps of carrying out a first treatment on the surface of the According to the temperature value T of each monomer of the sub-battery pack CELL Calculating the average monomer temperature value T of the sub-battery pack AVG ；
Step S3: according to the collected battery state data received by the sub-control system, calculating a protection threshold value of the abnormal state of the battery;
step S4: establishing a voltage U protection condition according to the calculated protection threshold value;
step S5: and establishing a temperature T protection condition according to the calculated protection threshold value.
The sub-control system automatically cuts off the output of the sub-battery pack control unit according to the running state of the sub-battery pack when the battery pack is abnormal or fails, so that the sub-battery pack is in an open state, and the safety of the battery pack is fully ensured on the premise that the running of the whole battery pack is not influenced.
Specifically, the protection threshold for calculating the abnormal state of the battery in step S3 specifically includes:
voltage protection threshold function U:
U＝U p *(1+U a +U b )
wherein U is p A basic threshold value for protecting the voltage of the battery cell;
wherein U is a ＝(U CELL /U AVG -1) a, representing the correction of the voltage protection threshold under the condition of different cell average voltages, when the voltage value of the battery pack is not large in dispersion, the voltage protection threshold correction value is reduced, when the dispersion is increased, the protection threshold correction value is increased, and a is the correction coefficient multiplied value;
wherein U is b ＝(I p I) b, representing the correction of the protection threshold for different discharge currents, I p The voltage protection threshold value is used for protecting the battery cell voltage, when the discharge current is closer to the current base threshold value, the voltage protection threshold value correction value is reduced, when the discharge current is further away from the current base threshold value, the voltage protection threshold value correction value is increased, and b is a correction coefficient multiplied value;
temperature protection threshold function T:
T＝T p *(1+T a )
wherein T is p Basic threshold value for protecting battery cell temperature
Wherein T is a ＝(T CELL /T AVG -1) c, representing the correction of the temperature protection threshold under the condition of different cell average temperatures, wherein the temperature protection threshold correction value is reduced when the temperature value of the battery pack is not large in variability, and the protection threshold correction value is increased when the variability is increased, and c is the correction coefficient multiplied value.
Specifically, the conditions for establishing the voltage unprotected U in step S4 are specifically:
wherein t is the unit time interval of the lowest sampling period;
wherein U is max And U min Calculating upper and lower limit protection thresholds for the voltage protection threshold function U;
wherein U (k) is an accumulated value of the battery cell voltage exceeding an upper limit threshold value in unit time, U (n) is an accumulated value of the battery cell voltage being lower than a lower limit threshold value in unit time, and when the accumulated value of U (k) in unit time T is larger than a protection accumulated threshold value U (k) max The system will trigger overvoltage protection, and similarly when the U (n) accumulated value in unit time T is greater than the protection accumulated threshold U (n) min The system will trigger under-voltage protection.
Specifically, the conditions for establishing the temperature T protection in step S5 are specifically:
wherein t is the unit time interval of the lowest sampling period;
wherein T is max And T min Calculating upper and lower limit protection thresholds for the temperature protection threshold function T;
wherein T (k) is an accumulated value of the battery core temperature exceeding an upper limit threshold value in unit time, T (N) is an accumulated value of the battery core temperature being lower than a lower limit threshold value in unit time, and when the accumulated value of T (k) in unit time N is larger than a protection accumulated threshold value T (k) max The system will trigger overvoltage protection, and likewise when the T (N) accumulated value in unit time N is greater than the protection accumulated threshold T (N) min The system will trigger under-voltage protection.
In practical application of the embodiment, an 80V912Ah lithium iron phosphate battery is adopted, and the battery pack is formed by combining 4 independent 80V228Ah sub-battery packs in parallel. Actual simulated fault conditions occur: when 1 independent sub-battery pack is abnormal, the control system actively cuts off the control unit corresponding to the output, and the rest 3 sub-batteries continue to work, so that the target tractor can be smoothly moved to a designated area, and the whole process does not influence the running and use of the vehicle. Compared with the traditional battery pack scheme, when a fault occurs, the whole battery pack output is switched, and the reliability of the vehicle in the using process can be greatly improved by adopting the new system architecture scheme.
The protection method adopts the protection threshold calculation scheme, so that the instantaneity and the effectiveness of the protection threshold are ensured. And the fault judgment triggering calculation scheme is adopted, so that the running stability of the system is ensured, and misjudgment caused by external interference is avoided.
Example two
As shown in fig. 1-3, the present invention also discloses a lithium battery applied to the protection method, which includes: a plurality of sub-battery packs with the same voltage and a main monitoring system BMS are connected in parallel; each sub-battery pack comprises a sub-monitoring system, a battery pack and a control unit, and the sub-monitoring system, the battery pack and the control unit independently operate; the word monitoring system is used for detecting the current, the temperature and the voltage of the battery pack corresponding to the word monitoring system, and the control unit is used for controlling the current on-off of the battery pack corresponding to the word monitoring system and the external equipment piece;
the main monitoring system BMS is in communication connection with the sub-monitoring system; the sub-monitoring system and the main monitoring system BMS form a complete battery control construction; if the sub-monitoring system finds that the corresponding detected battery pack is abnormal, the corresponding output control unit is cut off, and the main monitoring system is notified; after the independent battery pack output control unit is cut off, the remaining battery packs continue to work, so that the safety and the continuity of equipment use are ensured.
In this embodiment, the sub-battery pack system has a certain logic control autonomy, and when a fault condition is detected, the battery management unit BMU will actively disconnect the output relay K1 to cut off the sub-battery pack output. Meanwhile, the sub-battery pack system is provided with an independent heating control system, and the battery management unit BMU detects and calculates according to real-time temperature, and when the sub-battery pack system has a heating requirement, the heating film relay K2 is closed to heat the sub-battery pack system.
Referring to fig. 2, the whole battery comprises 4 sub-battery PACKs PACK01-04, and positive electrode output ends and negative electrode output ends of the four sub-battery PACKs PACK01-04 are respectively connected in parallel to finally form a discharge positive electrode and a discharge negative electrode; the discharge anodes and the discharge cathodes are arranged in pairs and can be multiple, a first discharge relay K5 and a second discharge relay K6 are respectively connected in series on the circuit of each discharge anode, and the first discharge relay K5 and the second discharge relay K6 are respectively used for controlling the current on-off of a circuit connected with the first discharge relay K5 and the second discharge relay K6 in series, so that the on-off of the current released by each discharge anode outwards is controlled.
The circuit of the discharging anode and the circuit of the discharging cathode are respectively and electrically connected with the circuit of the charging anode and the circuit of the charging cathode, and the circuit of the charging anode is also sequentially connected with a charging fuse F2 and a charging relay K3 in series, and the charging fuse F2 plays a role of overload fusing; the charging relay K3 is used for controlling the current on-off of the charging positive electrode circuit, and the initial state of the charging relay K3 is a closed state; the control end of the charging relay K3 is in communication connection with the signal end of the main monitoring system BSM, so that the on-off of the charging relay K3 can be controlled through the main monitoring system BSM to control the on-off of charging current to the sub-battery packs, and overcharge is prevented.
A first discharge current sensor S2 and a second discharge current sensor S3 are also arranged in parallel between the discharge anode and the discharge cathode, and the first discharge current sensor S2 and the second discharge current sensor S3 are used for detecting the currents of the discharge anode and the discharge cathode when the discharge anode and the discharge cathode discharge outwards and inputting the detection results into a main monitoring system BMS; the main monitoring system BMS adds the detection results of the first discharge current sensor S2 and the second discharge current sensor S3 to obtain an integral discharge current value, and the mode is mainly used for improving the detection precision; and then combining the discharge current of each sub-battery pack, so as to judge the current loss of the whole circuit and the battery pack with abnormal current.
Referring to fig. 3, the sub-battery pack includes a battery CELL, a battery management unit BMU, and a current sensor S1, where the battery management unit BMU is configured to detect a voltage and a temperature of the battery CELL; the power supply circuit of the battery pack CELL is also connected in series with a current sensor S1, the current sensor S1 is used for detecting the magnitude of current supplied by the battery pack CELL outwards and transmitting signals to a battery management unit BMU, the power supply circuit of the battery pack CELL outwards is also connected in series with an output relay K1 and a fuse F1 in sequence, and the output relay K1 is in a closed state in the initial state and is used for cutting off a circuit for outputting the current outwards by the battery pack CELL; the fuse F1 is used for preventing current overload, and when the current overload occurs, the fuse is fused, so that the battery CELL is protected; the control end of the output relay K1 is in communication connection with the signal end of the battery management unit BMU, so that the battery management unit BMU can control the opening and closing of the output relay K1. And the battery management unit BMU collects and analyzes the running state of the battery pack CELL in real time and sends state data to the main control system BMS.
Preferably, a heating film R1 is installed in the sub-battery pack, and the heating film R1 releases heat after being electrified, so as to heat the battery CELL and corresponding parts, so as to ensure attenuation caused by supercooling of the battery CELL. The heating film R1 is powered by a battery pack CELL, a heating film relay K2 is connected in series on a power supply circuit of the heating film R1, the heating film relay K2 is used for controlling the on-off of the current of the heating film R1, and the heating film relay K2 is in an off state in the initial state; the control end of the heating film relay K2 is in communication connection with the signal end of the battery management unit BMU, so that the opening and closing of the heating film relay K2 can be controlled through the battery management unit BMU. When the battery pack CELL temperature control device is used, once the temperature of the battery pack CELL is lower than a preset threshold value, the battery management unit BMU controls the heating film relay K2 to be closed, and the heating film R1 is electrified, so that the sub-battery pack, namely the battery pack CELL, is heated, and normal operation of the battery pack CELL is guaranteed.
Preferably, the current inlet end of the heating film relay is further electrically connected with the outlet end of the first discharging relay K5 and the outlet end of the second discharging relay K6 respectively, so that when any one of the outlet end of the first discharging relay K5 and the second discharging relay K6 is closed, the heating film relay can be powered, and at the moment, the heating film can be powered by the current and the voltage output by the whole battery, so that the heating film works.
More preferably, the positive electrode power connection end of the heating film or the power connection end of the heating film relay is electrically connected with the power connection end of the heating relay K4, and the power connection end of the heating relay K4 is electrically connected with the charging positive electrode after being connected with the heating fuse F3 in series. In the charged state, the heating relay K4 is closed, so that the heating film can be directly supplied with the charging current to realize heating, and the mode is mainly used for ensuring that the battery pack is in a proper temperature range, so that the charging efficiency is improved. The heating fuse F3 is used for fusing when current is overloaded, and plays a role in protection. The control end of the heating relay K4 is in communication connection with the signal end of the main monitoring system BMS, so that the heating relay K4 can be controlled to be closed through the main monitoring system BMS.
In actual use, the main monitoring system BMS may directly transmit a control instruction to the battery management unit BMU, thereby controlling the corresponding operation of the sub-battery pack.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (7)
1. The protection method for the lithium battery is characterized by comprising the following steps of:
step S1: the sub-monitoring system detects state values of each independent battery pack, including battery cell voltage, battery cell temperature and current data of the battery pack during operation, and meanwhile, the sub-control system sends the data to the main control system;
step S2: according to the voltage value U of each single cell of the sub-battery pack CELL Calculating average single of sub-battery packsBulk voltage value U AVG The method comprises the steps of carrying out a first treatment on the surface of the According to the temperature value T of each monomer of the sub-battery pack CELL Calculating the average monomer temperature value T of the sub-battery pack AVG ；
Step S3: according to the collected battery state data received by the sub-control system, calculating a protection threshold value of the abnormal state of the battery;
step S4: establishing a voltage U protection condition according to the calculated protection threshold value;
step S5: according to the calculated protection threshold value, establishing a temperature T protection condition;
the step S3 of calculating the protection threshold value of the abnormal state of the battery specifically includes:
voltage protection threshold function U:
U＝U p *(1+U a +U b )
wherein U is p A basic threshold value for protecting the voltage of the battery cell;
wherein U is a ＝(U CELL /U AVG -1) a, representing the correction of the voltage protection threshold under the condition of different cell average voltages, when the voltage value of the battery pack is not large in dispersion, the voltage protection threshold correction value is reduced, when the dispersion is increased, the protection threshold correction value is increased, and a is the correction coefficient multiplied value;
wherein U is b ＝(I p I) b, representing the correction of the protection threshold for different discharge currents, I p The voltage protection threshold value is used for protecting the battery cell voltage, when the discharge current is closer to the current base threshold value, the voltage protection threshold value correction value is reduced, when the discharge current is further away from the current base threshold value, the voltage protection threshold value correction value is increased, and b is a correction coefficient multiplied value;
temperature protection threshold function T:
T＝T p *(1+T a )
wherein T is p Basic threshold value for protecting battery cell temperature
Wherein T is a ＝(T CELL /T AVG -1) c, representing the correction of the temperature protection threshold value in the case of different cell average temperatures, the correction value of the temperature protection threshold value decreasing when the variability of the temperature values of the battery pack is not greatWhen the discreteness is increased, the protection threshold correction value is increased, and c is the correction coefficient multiplied value;
in step S4, the conditions for establishing the voltage U protection are specifically:
where dt is the unit time interval of the lowest sampling period;
wherein U is max And U min Calculating upper and lower limit protection thresholds for the voltage protection threshold function U;
wherein U (k) is an accumulated value of the battery cell voltage exceeding an upper limit threshold value in unit time, U (n) is an accumulated value of the battery cell voltage being lower than a lower limit threshold value in unit time, and when the accumulated value of U (k) in unit time T is larger than a protection accumulated threshold value U (k) max The system will trigger overvoltage protection, and similarly when the U (n) accumulated value in unit time T is greater than the protection accumulated threshold U (n) min The system will trigger under-voltage protection;
the temperature T protection condition established in step S5 is specifically:
where dt is the unit time interval of the lowest sampling period;
wherein T is max And T min Calculating upper and lower limit protection thresholds for the temperature protection threshold function T;
wherein T (k) is the accumulated value of the battery cell temperature exceeding the upper limit threshold value in unit time, T (N) is the accumulated value of the battery cell temperature being lower than the lower limit threshold value in unit time, and T (k) is accumulated in unit time NThe added value is larger than the protection accumulation threshold value T (k) max The system will trigger overvoltage protection, and likewise when the T (N) accumulated value in unit time N is greater than the protection accumulated threshold T (N) min The system will trigger under-voltage protection.
2. A lithium battery applied to the protection method for the lithium battery of claim 1, characterized in that: comprising the following steps: the system comprises at least two sub-battery packs and a main monitoring system, wherein the sub-battery packs are connected in parallel; each sub-battery pack comprises a sub-monitoring system, a battery pack and a control unit, and the sub-monitoring system, the battery pack and the control unit independently operate; the sub-monitoring system is used for detecting the current, the temperature and the voltage of the battery pack corresponding to the sub-monitoring system, and the control unit is used for controlling the current on-off of the battery pack corresponding to the sub-monitoring system and the external equipment piece; the main monitoring system is in communication connection with the sub-monitoring system;
the positive electrode output end and the negative electrode output end of the sub-battery pack are respectively connected in parallel to form a discharge positive electrode and a discharge negative electrode; the positive and negative discharge electrodes are arranged in pairs and can be multiple, a first discharge current sensor and a second discharge current sensor are further arranged between the positive and negative discharge electrodes in parallel, and the first and second discharge current sensors are used for detecting currents when the positive and negative discharge electrodes discharge outwards and inputting detection results into the BMS.
3. A lithium battery according to claim 2, wherein: the circuit of each discharge positive electrode is respectively connected with a first discharge relay and a second discharge relay in series, and the first discharge relay and the second discharge relay are respectively used for controlling the current on-off of a circuit connected with the first discharge relay and the second discharge relay in series, so that the on-off of the current released by each discharge positive electrode outwards is controlled.
4. A lithium battery according to claim 2, wherein: the circuit of the discharging anode and the circuit of the discharging cathode are respectively and electrically connected with the circuit of the charging anode and the circuit of the charging cathode, and the circuit of the charging anode is also sequentially connected with a charging fuse and a charging relay in series, so that the charging fuse has the function of overload fusing; the charging relay is used for controlling the current on-off of the charging positive electrode circuit, and the initial state of the charging relay is a closed state; the control end of the charging relay is in communication connection with the signal end of the main monitoring system.
5. A lithium battery according to claim 2, wherein: the sub-battery pack comprises a battery pack, a battery management unit and a current sensor, wherein the battery management unit is used for detecting the voltage and the temperature of the battery pack; the power supply circuit of the battery pack is connected in series with a current sensor, the current sensor is used for detecting the magnitude of the current of the battery pack for supplying power outwards and transmitting signals to the battery management unit, the power supply circuit of the battery pack is connected in series with an output relay, and the output relay is in a closed state in the initial state and is used for cutting off the circuit of the battery pack for outputting the current outwards; the control end of the output relay is in communication connection with the signal end of the battery management unit; the battery management unit collects and analyzes the running state of the battery pack in real time and sends state data to the main control system.
6. A lithium battery according to claim 5, wherein: and a fuse is also connected in series on a circuit for supplying power to the battery pack, and the fuse is fused in an overload way.
7. A lithium battery according to claim 5, wherein: a heating film is arranged in the sub-battery pack, and the heating film releases heat after being electrified; the heating film is powered by the battery pack, a heating film relay is connected in series on a power supply circuit of the heating film, the heating film relay is used for controlling the on-off of the heating film current, and the heating film relay is in an off state in the initial state; the control end of the heating film relay is in communication connection with the signal end of battery management;
the current access end of the heating film relay is also respectively and electrically connected with the connection end of the first discharging relay and the connection end of the second discharging relay, so that the heating film relay can be powered when either the connection end of the first discharging relay or the second discharging relay is closed;
the positive electrode power-on end of the heating film or the power-off end of the heating film relay is electrically connected with the power-off end of the heating relay, and the power-on end of the heating relay is directly or indirectly electrically connected with the charging positive electrode; the access end of the heating relay is connected with the heating fuse in series and then is electrically connected with the charging anode.
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