CN112054571A - Lithium battery energy storage system SOC consistency balancing method - Google Patents

Lithium battery energy storage system SOC consistency balancing method Download PDF

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CN112054571A
CN112054571A CN202010806670.8A CN202010806670A CN112054571A CN 112054571 A CN112054571 A CN 112054571A CN 202010806670 A CN202010806670 A CN 202010806670A CN 112054571 A CN112054571 A CN 112054571A
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charge
soc
integral
equalization
lithium battery
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CN112054571B (en
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凡绍桂
张强
巩冰
游江
孟繁荣
张敬南
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Harbin Engineering University
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Harbin Engineering University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0047—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with monitoring or indicating devices or circuits
    • H02J7/0048—Detection of remaining charge capacity or state of charge [SOC]
    • 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
    • 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

Abstract

The invention discloses a method for balancing the SOC consistency of a lithium battery energy storage system, which provides a method for constructing virtual capacity by charging and discharging a lithium battery by adopting an active voltage balancing system. The SOC consistency balancing method based on the virtual capacity is adopted, so that the phenomenon of under-balancing or over-balancing caused by low SOC estimation precision in the voltage platform period is avoided, and the accurate and rapid SOC consistency balancing strategy in the voltage platform period of the lithium battery is realized. The dependence degree of the voltage plateau period on the SOC is reduced, and the SOC balance precision of the lithium battery voltage plateau period is improved.

Description

Lithium battery energy storage system SOC consistency balancing method
Technical Field
The invention relates to a lithium battery energy storage system SOC consistency balancing method, in particular to a lithium battery energy storage system SOC consistency balancing method based on virtual capacity, and belongs to the field of energy storage system balancing.
Background
The lithium battery energy storage system is composed of a large number of lithium battery monomers in series-parallel connection, although before grouping, certain initial capacity difference still exists through strict capacity matching, in the using process, due to the fact that the monomer temperature and the manufacturing process have difference, capacity attenuation in the using process is inconsistent, the inconsistent phenomenon that the monomer capacity in the energy storage system cannot be eliminated exists, and the problems that a battery pack has safety risks and the monomer capacity utilization rate is low are caused.
The overcharge and overdischarge of the lithium battery can cause irreversible capacity fading, and the overcharge can also bring about the safety hazard of combustion and even explosion. In order to prevent overcharge or overdischarge of a lithium battery, a charge cut-off voltage and a discharge cut-off voltage are generally set. When the low-capacity monomer is charged/discharged to the cut-off voltage, the charging/discharging is stopped, and the high-capacity monomer does not reach the cut-off voltage, so that the capacity of the energy storage system of the lithium battery is limited by the low-capacity monomer, and the capacity of each monomer in the battery pack cannot be fully utilized. In the application occasions with serious monomer capacity inconsistency, such as the echelon utilization of the power battery, the capacity of the energy storage system is greatly reduced due to the inconsistency of the monomer capacity. The voltage balancing system can improve the safety of the lithium battery energy storage system and the utilization rate of the single capacity.
At present, in the aspect of a balancing topology, an active balancing topology with single charging and discharging capability can complete a task of a balancing system, and in the aspect of a balancing strategy, a State of charge (SOC) consistency balancing strategy can be suitable for more application occasions. The lithium battery has a voltage plateau, and when the lithium battery is in the voltage plateau, the Open Circuit Voltage (OCV) changes less with the SOC. An article, "lithium iron phosphate battery SOC estimation method research", of article introduces a lithium iron phosphate battery with a capacity of 20A.h, and after charging 3.5A.h in a voltage plateau period, the voltage changes by only 0.01V, and the open-circuit voltage and state-of-charge curve is shown in fig. 1. During the lithium battery voltage platform period, the voltage change caused by the charge quantity change is small, the measurement noise can be submerged, the estimation accuracy of the lithium battery OCV is influenced, and the estimation accuracy of the voltage platform period SOC is far lower than that of the non-voltage platform period. Due to the fact that SOC estimation accuracy is low during a lithium battery voltage platform, difficulty is brought to implementation of a traditional SOC consistency balancing strategy depending on SOC estimation accuracy of single batteries, and the phenomenon of under-balancing or over-balancing can occur, so that a balancing circuit can act repeatedly.
By adopting an advanced SOC estimation algorithm, the SOC estimation precision is improved, and the problem of SOC consistency balance in a lithium battery voltage platform period can be solved to a certain extent. In an article research on an SOC estimation scheme of a lithium ion battery for a pure electric vehicle, by authors such as Liuhao, Betula lack, Jiang Jiuchun and the like, an SOC value calculated by an ampere-hour integration method is corrected by an observed voltage value while an extended Kalman filtering algorithm (EKF) is adopted, and the estimation precision is improved. Ephrem C, Phillip J.K, Matthias P, and the like, in an article of Long Short-Term Memory Networks for Accurate states-of-Charge Estimation of Li-ion Batteries, the authors adopt a neural network to estimate the SOC of the lithium battery, thereby improving the Estimation accuracy. However, the experimental effects of the methods are based on the laboratory environment, the adopted measuring instruments have high precision, and some algorithms are complex and are not suitable for the on-line estimation of the SOC of the single body. In a patent CN201710562904.7, a lithium battery pack balance control method and system for dynamically correcting SOC, a lithium battery is divided into a use period and a rest period, an ampere-hour integration method is used in the use period, and an open-circuit voltage method is used in the rest period to correct the ampere-hour integration method, but the battery needs to be left for a long time to obtain an open-circuit voltage, and the method has few applications. In consideration of the practical application environment, the sampling precision is generally about 5mV, the voltage change caused by the charge quantity change is small in the lithium battery voltage plateau period, the small voltage change quantity can be submerged by measurement noise, the estimation precision of the lithium battery OCV is influenced, and the SOC estimation precision in the voltage plateau period is far lower than that in the non-voltage plateau period.
The invention fully recognizes the problem of low SOC estimation precision of the lithium battery in the voltage platform period, provides a method for charging and discharging the lithium battery by adopting an active voltage equalization system to construct virtual capacity, the SOC estimation precision is lower in the voltage platform period, the equalization is carried out by adopting a virtual capacity equalization method, the SOC estimation precision is higher in the non-voltage platform period, and the equalization result of the virtual capacity is corrected.
Disclosure of Invention
Aiming at the prior art, the technical problem to be solved by the invention is to provide a battery energy storage system SOC consistency balancing method for improving the SOC estimation precision of a lithium battery voltage platform period and the SOC balancing precision of the lithium battery voltage platform period, and solve the problem that a single SOC consistency balancing strategy cannot be accurately realized due to low SOC estimation precision of the lithium battery voltage platform period.
In order to solve the technical problem, the invention provides a lithium battery energy storage system SOC uniformity balancing method, wherein a lithium battery energy storage system is formed by connecting lithium battery monomers in series, and the method comprises the following steps:
s1: initializing sampling period T of voltage, current and temperaturesInitializing n, every nTsPeriodically executing an equalization method, wherein an initialization counter t is equal to 0, and k is initialized and represents the k-th sampling;
s2: collecting output voltage Vo(k) Input current Iall(k) And temperature T (k), input current IallIs a current I and an equalizing current IBSumming, integrating the battery current I to obtain the battery charge QR(k)；
S3: according to the output voltage Vo(k) Input current Iall(k) And temperature T (k) and battery charge QR(k) Obtaining estimated value of SOC of kth sampling by adopting Karl diffusion filter algorithm
Figure BDA0002629387660000021
And obtaining an estimated value of the k-th sampling OCV according to the relation curve of the SOC-OCV
Figure BDA0002629387660000022
S4: judging whether the counter t is equal to n, executing step S4 when t is equal to n, otherwise, making t equal to t +1, k equal to k +1 and returning to S2;
s5: according to
Figure BDA0002629387660000023
Judging whether the energy storage monomer is in a voltage plateau period, if so, executing S6, otherwise, executing S7;
s6: setting the switching amount ω to 1, and then performing S8;
s7: setting the switching amount ω to 0, and then performing S9;
s8: calculating the charge variation amount DeltaQR(k)，ΔQR(k)＝QR(k)-QR(k-n) and then calculating the equilibrium charge Δ QV(k)，ΔQV(k)＝ΔQV1(k)，ΔQV1(k)＝KΔQR(k) K is the estimated charge coefficient, and then S10 is performed;
s9: calculating SOC deviation value
Figure BDA0002629387660000031
Wherein
Figure BDA0002629387660000032
Is the average value of SOC estimated values of each cell when
Figure BDA0002629387660000033
Less than SOHTHWhen the SOC balance reaches a stable stage, stopping the balance; when Δ SOC is greater than SOHTHWhile, the equilibrium charge Δ Q is calculatedV(k)，ΔQV(k)＝ΔQV2(k)，
Figure BDA0002629387660000034
QRNFactory rated capacity, SOH, of lithium battery cellTHFor a given hysteresis width, then S10 is performed;
s10: to obtain an equalized charge DeltaQV(k)＝ωΔQV1(k)+(1-ω)ΔQV2(k) Then, charge equalization is performed by using an active equalization circuit, and the process returns to S2 with t being equal to 0.
The invention also includes:
the method for estimating the charge coefficient K in the S8 specifically comprises the following steps:
s8.1: judging satisfaction
Figure BDA0002629387660000035
Whether the number of the equalization cycles is larger than m, wherein m is a set constant, if so, executing S8.2, otherwise, executing S8.1;
s8.2: for equalizing charge QVAnd battery charge amount QRIntegrating to obtain an integral quantity QV_integral、QR_integralAre all zero, QV_integral＝QV_integral+ΔQV2(k)，QR_integral＝QR_integral+ΔQR(k) The integral equalization period count value d is d +1, and then S8.3 is performed;
s8.3: judging whether D is more than or equal to D, wherein D is a set constant for ensuring enough integration time, and executing the step S8.4 when D is equal to D, otherwise executing the step S8.1;
s8.4: estimating the charge coefficient K, K-QV_integral/QR_integral，d、QV_integralAnd QR_integralAnd (6) clearing.
Δ Q according to the equalizing charge in S10V(k) The active equalization circuit for performing charge equalization specifically includes: equalizing charge Δ Q generated for each cycleV(k) Summing to obtain total balanced charge quantity delta QV∑. For the equalizing current IBIntegration yields the amount of charge Δ Q that has been performedB，ΔQV∑Subtracting the already performed charge quantity Δ QBWhen the balance charges to be output are in a set range in a continuous a balance periods, a is a given value, the charge balance is completed, the balance circuit is closed, and the delta Q is adjustedV∑And Δ QBClearing; otherwise, the equalization circuit is started to continue equalization.
The invention has the beneficial effects that: compared with the prior art, the SOC consistency balancing method based on the virtual capacity is adopted in the voltage platform period of the lithium battery, so that the phenomenon of under-balancing or over-balancing caused by low SOC estimation precision in the voltage platform period is avoided, and the accurate and rapid SOC consistency balancing strategy in the voltage platform period of the lithium battery is realized. The dependence degree of the voltage plateau period on the SOC is reduced, and the SOC balance precision of the lithium battery voltage plateau period is improved.
Drawings
FIG. 1 is a graph of open circuit voltage versus state of charge for a lithium iron phosphate battery;
FIG. 2 is a schematic block diagram of a SOC consistency balancing strategy based on "virtual capacity";
FIG. 3 is a block diagram of SOC consistency balancing policy enforcement based on "virtual capacity";
FIG. 4 is a flow chart of charge coefficient K estimation;
fig. 5 is a logic block diagram of an implementation of the equalization circuit.
Detailed Description
The following further describes the embodiments of the present invention with reference to the drawings.
The purpose of the invention is realized as follows:
the essence of the cell SOC uniformity balance is that the apparent capacities of the cells are equal, but the actual capacities of the cells are not uniform, and a balance circuit is required to charge/discharge the cells to achieve uniformity of the apparent capacities. The amount of increase or decrease in the apparent capacity of the active equalization system for a cell is referred to as the "virtual capacity" of the cell. Assuming that all monomers have a performance capacity of QNAnd then the relation between the actual capacity of the battery cell and the virtual capacity satisfies the formula (1). When the actual charge variation of the battery is delta QRCorresponding change amount of equalizing charge Δ QVAs shown in formula (2). When k is>At 1, the charge coefficient K is negative; when k is<At 1, the charge coefficient K is positive. Actual charge variation Δ QRThe equalization charge required for SOC equalization can be obtained by integrating the battery current, if the charge factor K is known.
QN＝QR+QV＝kQN+(1-k)QN (1)
In the formula QR＝kQNTo actual capacity, QV＝(1-k)QNFor "virtual capacity", k is a proportionality coefficient 0.8 ≦ k ≦ 1.2 (assuming that there is a ± 20% capacity inconsistency for the battery cells in the energy storage system).
Figure BDA0002629387660000041
Where K is (1-K)/K is the charge coefficient, K is 0.8. ltoreq. k.ltoreq.1.2, -0.167. ltoreq. K.ltoreq.0.25, and Δ QRThe charge variation of the lithium battery.
The equalization strategy based on the virtual capacity according to the charge coefficient K belongs to open loop equalization, and the equalization accuracy depends on the accuracy degree of the virtual capacity, namely the accuracy of the K value. After the voltage platform is exited, the accuracy of the single SOC estimation is high, and the balance effect of the open loop balance strategy based on the virtual capacity can be corrected by adopting an SOC closed loop balance strategy. Since the actual capacity of the battery cell varies with temperature and the degree of degradation, it is desirable that the charge coefficient K can be corrected online. In consideration of the equalization of the SOC and the online correction of the K value, a schematic block diagram of an equalization strategy is made as shown in FIG. 2.
As shown in FIG. 2, the input values of the actual lithium battery are current I and balance current IBThe sum of the two currents is IallThe output quantity is the output voltage VoAnd a charge amount Q, etc. Will Vo、Q、IallAnd the temperature T is used for obtaining an estimated value of the SOC through an SOC online estimation algorithm
Figure BDA0002629387660000051
Equalizing charge quantity Δ QVThe method is obtained by two methods, namely a virtual capacity equalization algorithm in a voltage platform period and a real-time estimated SOC value in a non-voltage platform period, and the two SOC values are switched by a switching value omega. When omega is 1, adopting a balancing strategy of virtual capacity; when ω is 0, the equalization charge is derived from the SOC closed loop equalization strategy. The whole equalization strategy is carried out in cycles, and the amount of the equalized electric charge is adjusted once in each cycle.
The balance algorithm based on the virtual capacity is obtained according to the formula (2), and the charge variation delta QRSampling value Q by twice battery charge quantityRAre subtracted to obtain QRFrom the battery current integral. Change amount of charge Δ QRMultiplying with charge coefficient K to obtain balanced charge delta QV1. SOC real-time estimation value by SOC closed-loop equalization strategy
Figure BDA0002629387660000052
And the average value of the SOC estimated values of the individual units
Figure BDA0002629387660000053
Making a difference to obtain an SOC difference value
Figure BDA0002629387660000054
Will be provided with
Figure BDA0002629387660000055
Multiplied by the battery factory rated capacity QRNThe equilibrium charge delta Q can be obtainedV2. In order to reduce the action times of the equalizing circuit, one is arranged
Figure BDA00026293876600000513
Width of hysteresis of
Figure BDA0002629387660000056
And when the value is smaller, the equalization is stopped in a hysteresis range. Final equalizing charge Δ QVSelected by the switching value ω, Δ Q when ω is 1V＝ΔQV1(ii) a When ω is 0, Δ QV＝ΔQV2。
The balancing strategy based on the virtual capacity has the balancing precision depending on the accuracy of the K value. The algorithm for realizing the accurate identification of the K value is as follows: in the non-voltage plateau period, the SOC adopts a closed-loop balancing strategy, and the balanced charges still satisfy the formula (2). Selecting a period of time t during the SOC closed loop equalization periods～teAnd recording the charge variation and the balance charge of the battery in the time period to obtain the K value shown as the formula (3). The time period is selected in a stable stage of SOC closed loop balance, and a dynamic adjustment period is avoided.
Figure BDA0002629387660000057
In the formula,. DELTA.QVFor equalizing charge, Δ QRIs the amount of change in battery charge, tsTo select the starting moment of the time period, teThe end time of the time period is selected.
The implementation block diagram of the lithium battery SOC consistency balancing strategy based on the virtual capacity is shown in FIG. 3. The sampling period of voltage, current and temperature is TsThe k-th sampling values are respectively Vo(k)、Iall(k) And t (k) and the amount of charge is calculated as q (k) by integrating the current. Then, estimating the estimated value of the SOC of the monomer by adopting a Carl diffuse filter algorithm or combining the Carl diffuse filter algorithm and an ampere-hour integration method according to the measured value
Figure BDA0002629387660000058
To obtain a monomer
Figure BDA0002629387660000059
Later, the SOC-OCV relationship can be obtained
Figure BDA00026293876600000510
Value is corresponded to
Figure BDA00026293876600000511
The values, SOC and OCV calculated by the k-th sampling are SOC (k) and OCV (k), respectively. Balancing strategy nTsThe period is executed once, the counter t is made to be 0 after each time of executing the equalization strategy, is made to be t +1 after each time of sampling period, and the equalization strategy is executed once when t is n.
When the equalization strategy is executed, firstly, the estimated open circuit voltage value is used
Figure BDA00026293876600000512
And judging whether the energy storage monomer is in a voltage platform period, if so, adopting a SOC consistency balancing method of virtual capacity, and if not, adopting an SOC closed loop balancing strategy. When the SOC consistency balancing method of virtual capacity is adopted, the charge variation quantity delta Q is firstly calculatedR(k) Then, the equalizing charge quantity DeltaQ is calculatedV1(k) Finally, an active equalization circuit is used to perform the equalization of the charge amount.
When an SOC closed loop equalization strategy is adopted, the SOC real-time estimation value is obtained
Figure BDA0002629387660000061
And the average value of SOC values of the respective units
Figure BDA0002629387660000062
Making a difference to obtain an SOC deviation value
Figure BDA0002629387660000063
Wherein
Figure BDA0002629387660000064
Collecting SOC estimated values of all monomers by a system master controller
Figure BDA0002629387660000065
Summing and averaging. In order to reduce the action times of the equalizing circuit, one is arranged
Figure BDA0002629387660000066
Hysteresis width SOHTHWhen is coming into contact with
Figure BDA0002629387660000067
Less than SOHTHWhen the SOC balance reaches a stable stage, the balance can be stopped; when in use
Figure BDA0002629387660000068
Greater than SOHTHThen, the monomer is polymerized
Figure BDA0002629387660000069
And the average SOC value of the cell
Figure BDA00026293876600000610
Difference is made and multiplied by the factory rated capacity Q of the lithium batteryRNThe equilibrium charge delta Q can be obtainedV2(k) In that respect The amount of charge is then equalized using an active equalization circuit. And estimating the charge coefficient K in the SOC closed-loop equalization strategy process.
The process of estimating the charge factor K is shown in fig. 4. In the stable stage of SOC closed loop equalization, starting the estimation of the charge coefficient K, wherein the judgment basis of the stable stage is as follows: satisfy the requirement of
Figure BDA00026293876600000611
Whether the number of equalization cycles of (2) is greater than m, m being a set constant. If a stable condition is reached, the equalizing charge Q can be appliedVAnd battery charge amount QRIntegrating to obtain an integral quantity QV_integral、QR_integralThe initial values of (a) are all zero. The number of integrating equalization cycles is recorded by D, and the calculation of the value of K can be started when D is equal to or greater than D, which is a constant set to ensure sufficient integration time. When the integration time is up to the requirement, the value K can be calculated, and K is QV_integral/QR_integral. After the charge coefficient K is calculated, d and Q are calculatedV_integralAnd QR_integralAnd (6) clearing.
To obtain an equalized charge DeltaQV(k) After the command, the equalization circuit starts equalization, and the equalization circuit needs to be active and have bidirectional equalization current capability. A logic block diagram of the equalization circuit performing equalization of charge is shown in fig. 5. The received equalizing charge instructions of each period are superposed to obtain the total equalizing charge quantity delta QV∑. For the equalizing current IBIntegration yields the amount of charge Δ Q that has been performedB，ΔQV∑Subtracting the already performed charge quantity Δ QBAnd obtaining the balance charge needing to be output. When the balance charge to be output is within a set range in a continuous a (a is a given value) balance cycles, if the balance charge is-0.01% QRN～0.01％QRN(QRNSingle rated capacity) indicating that equalization charge has been performed by the equalization topology, charge equalization is complete, the equalization circuit is turned off, and Δ Q is adjustedV∑And Δ QBZero clearing is carried out to prevent error accumulation; otherwise, the equalization circuit is started to continue equalization.

Claims (3)

1. A lithium battery energy storage system SOC uniformity balancing method is characterized by comprising the following steps of:
s1: initializing sampling period T of voltage, current and temperaturesInitializing n, every nTsPeriodically executing an equalization method, wherein an initialization counter t is equal to 0, and k is initialized and represents the k-th sampling;
s2: collecting output voltage Vo(k) Input current Iall(k) And temperature T (k), input current IallIs a current I and an equalizing current IBSumming, integrating the battery current I to obtain the battery charge QR(k)；
S3: according to the output voltage Vo(k) Input current Iall(k) And temperature T (k) and battery charge QR(k) Obtaining estimated value of SOC of kth sampling by adopting Karl diffusion filter algorithm
Figure FDA0002629387650000011
And obtaining an estimated value of the k-th sampling OCV according to the relation curve of the SOC-OCV
Figure FDA0002629387650000012
S4: judging whether the counter t is equal to n, executing step S4 when t is equal to n, otherwise, making t equal to t +1, k equal to k +1 and returning to S2;
s5: according to
Figure FDA0002629387650000013
Judging whether the energy storage monomer is in a voltage plateau period, if so, executing S6, otherwise, executing S7;
s6: setting the switching amount ω to 1, and then performing S8;
s7: setting the switching amount ω to 0, and then performing S9;
s8: calculating the charge variation amount DeltaQR(k)，ΔQR(k)＝QR(k)-QR(k-n) and then calculating the equilibrium charge Δ QV(k)，ΔQV(k)＝ΔQV1(k)，ΔQV1(k)＝KΔQR(k) K is the estimated charge coefficient, and then S10 is performed;
s9: calculating SOC deviation value
Figure FDA0002629387650000014
Figure FDA0002629387650000015
Wherein
Figure FDA0002629387650000016
Is the average value of SOC estimated values of each cell when
Figure FDA0002629387650000017
Less than SOHTHWhen the SOC balance reaches a stable stage, stopping the balance; when Δ SOC is greater than SOHTHWhile, the equilibrium charge Δ Q is calculatedV(k)，ΔQV(k)＝ΔQV2(k)，
Figure FDA0002629387650000018
QRNFactory rated capacity, SOH, of lithium battery cellTHFor a given hysteresis width, then S10 is performed;
s10: to obtain an equalized charge DeltaQV(k)＝ωΔQV1(k)+(1-ω)ΔQV2(k) Then, charge equalization is performed by using an active equalization circuit, and the process returns to S2 with t being equal to 0.
2. The method for equalizing the SOC consistency of the energy storage system of the lithium battery according to claim 1, wherein the method comprises the following steps: s8 the method for estimating the charge coefficient K specifically includes:
s8.1: judging satisfaction
Figure FDA0002629387650000021
Whether the number of the equalization cycles is larger than m, wherein m is a set constant, if so, executing S8.2, otherwise, executing S8.1;
s8.2: for equalizing charge QVAnd battery charge amount QRIntegrating to obtain an integral quantity QV_integral、QR_integralAre all zero, QV_integral＝QV_integral+ΔQV2(k)，QR_integral＝QR_integral+ΔQR(k) Integral balance period count value dD +1, then S8.3 is performed;
s8.3: judging whether D is more than or equal to D, wherein D is a set constant for ensuring enough integration time, and executing the step S8.4 when D is equal to D, otherwise executing the step S8.1;
s8.4: estimating the charge coefficient K, K-QV_integral/QR_integral，d、QV_integralAnd QR_integralAnd (6) clearing.
3. The method for equalizing the SOC consistency of the energy storage system of the lithium battery according to claim 1 or 2, wherein the method comprises the following steps: s10 according to the equalizing charge DeltaQV(k) The active equalization circuit for performing charge equalization specifically includes: equalizing charge Δ Q generated for each cycleV(k) Summing to obtain total balanced charge quantity delta QV∑. For the equalizing current IBIntegration yields the amount of charge Δ Q that has been performedB，ΔQV∑Subtracting the already performed charge quantity Δ QBWhen the balance charges to be output are in a set range in a continuous a balance periods, a is a given value, the charge balance is completed, the balance circuit is closed, and the delta Q is adjustedV∑And Δ QBClearing; otherwise, the equalization circuit is started to continue equalization.
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US20220324350A1 (en) * 2021-04-13 2022-10-13 Hyundai Motor Company Method for equalizing states of charge (socs) of battery packs in electric vehicle
CN116315187A (en) * 2023-05-19 2023-06-23 杭州协能科技股份有限公司 Battery equalization control method and system and electronic equipment

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